1.
Chromium trioxide
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Chromium trioxide is an inorganic compound with the formula CrO3. It is the anhydride of chromic acid, and is sometimes marketed under the same name. This compound is a solid under anhydrous conditions, bright orange when wet. Millions of kilograms are produced annually, mainly for electroplating, Chromium trioxide is a powerful oxidiser and a suspected carcinogen. The solid consists of chains of tetrahedrally coordinated chromium atoms that share vertices, each chromium center, therefore, shares two oxygen centers with neighbors. Two oxygen atoms are not shared, giving an overall stoichiometry of 1,3, the structure of monomeric CrO3 has been calculated using density functional theory, and is predicted to be pyramidal rather than planar. In these oxidations, the Cr converts primary alcohols to the carboxylic acids. It is typically employed with additives that affect the plating process, the trioxide reacts with cadmium, zinc, and other metals to generate passivating chromate films that resist corrosion. It is also used in the production of synthetic rubies, Chromic acid solution is also used in applying types of anodic coating to aluminium, which are primarily used in aerospace applications. A Chromic Acid/ Phosphoric Acid solution is also the preferred stripping agent of anodic coatings of all types, Chromium trioxide is highly toxic, corrosive, and carcinogenic. It is the example of hexavalent chromium, an environmental hazard. The related chromium derivatives are not particularly dangerous, thus, reductants are used to destroy chromium samples, Chromium trioxide, being a powerful oxidizer, will ignite organic materials such as alcohols on contact. ATSDR Case Studies in Environmental Medicine, Chromium Toxicity U. S. Department of Health and Human Services Chromium Trioxide at The Periodic Table of Videos
2.
Chemical compound
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A chemical compound is an entity consisting of two or more atoms, at least two from different elements, which associate via chemical bonds. Many chemical compounds have a numerical identifier assigned by the Chemical Abstracts Service. For example, water is composed of two atoms bonded to one oxygen atom, the chemical formula is H2O. A compound can be converted to a different chemical composition by interaction with a chemical compound via a chemical reaction. In this process, bonds between atoms are broken in both of the compounds, and then bonds are reformed so that new associations are made between atoms. Schematically, this reaction could be described as AB + CD → AC + BD, where A, B, C, and D are each unique atoms, and AB, CD, AC, and BD are each unique compounds. A chemical element bonded to a chemical element is not a chemical compound since only one element. Examples are the diatomic hydrogen and the polyatomic molecule sulfur. Chemical compounds have a unique and defined chemical structure held together in a spatial arrangement by chemical bonds. Pure chemical elements are not considered chemical compounds, failing the two or more atom requirement, though they often consist of molecules composed of multiple atoms. There is varying and sometimes inconsistent nomenclature differentiating substances, which include truly non-stoichiometric examples, from chemical compounds, other compounds regarded as chemically identical may have varying amounts of heavy or light isotopes of the constituent elements, which changes the ratio of elements by mass slightly. Characteristic properties of compounds include that elements in a compound are present in a definite proportion, for example, the molecule of the compound water is composed of hydrogen and oxygen in a ratio of 2,1. In addition, compounds have a set of properties. The physical and chemical properties of compounds differ from those of their constituent elements, however, mixtures can be created by mechanical means alone, but a compound can be created only by a chemical reaction. Some mixtures are so combined that they have some properties similar to compounds. Other examples of compound-like mixtures include intermetallic compounds and solutions of metals in a liquid form of ammonia. Compounds may be described using formulas in various formats, for compounds that exist as molecules, the formula for the molecular unit is shown. For polymeric materials, such as minerals and many metal oxides, the elements in a chemical formula are normally listed in a specific order, called the Hill system
3.
Chromium
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Chromium is a chemical element with symbol Cr and atomic number 24. It is the first element in Group 6 and it is a steely-grey, lustrous, hard and brittle metal which takes a high polish, resists tarnishing, and has a high melting point. The name of the element is derived from the Greek word χρῶμα, chrōma, meaning color, Chromium metal is of high value for its high corrosion resistance and hardness. A major development was the discovery that steel could be highly resistant to corrosion and discoloration by adding metallic chromium to form stainless steel. Stainless steel and chrome plating together comprise 85% of the commercial use, trivalent chromium ion is an essential nutrient in trace amounts in humans for insulin, sugar and lipid metabolism, although the issue is debated. While chromium metal and Cr ions are not considered toxic, hexavalent chromium is toxic and carcinogenic, abandoned chromium production sites often require environmental cleanup. Chromium is remarkable for its properties, it is the only elemental solid which shows antiferromagnetic ordering at room temperature. Above 38 °C, it changes to paramagnetic, Chromium metal left standing in air is passivated by oxidation, forming a thin, protective, surface layer. This layer is a structure only a few molecules thick. It is very dense, and prevents the diffusion of oxygen into the underlying metal and this is different from the oxide that forms on iron and carbon steel, through which elemental oxygen continues to migrate, reaching the underlying material to cause incessant rusting. Passivation can be enhanced by short contact with oxidizing acids like nitric acid, passivated chromium is stable against acids. Passivation can be removed with a reducing agent that destroys the protective oxide layer on the metal. Chromium metal treated in this way readily dissolves in weak acids, Chromium, unlike such metals as iron and nickel, does not suffer from hydrogen embrittlement. However, it suffer from nitrogen embrittlement, reacting with nitrogen from air. Chromium is the 22nd most abundant element in Earths crust with a concentration of 100 ppm. Chromium compounds are found in the environment from the erosion of chromium-containing rocks, Chromium is mined as chromite ore. About two-fifths of the ores and concentrates in the world are produced in South Africa, while Kazakhstan, India, Russia. Untapped chromite deposits are plentiful, but geographically concentrated in Kazakhstan, although rare, deposits of native chromium exist
4.
Oxidation state
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The oxidation state, often called the oxidation number, is an indicator of the degree of oxidation of an atom in a chemical compound. This is never exactly true for real bonds, the term oxidation was first used by Lavoisier to signify reaction of a substance with oxygen. Much later, it was realized that the substance, upon being oxidized, loses electrons, oxidation states are typically represented by integers. In some cases, the oxidation state of an element is a fraction. It is predicted that even a +10 oxidation state may be achieveable by platinum in the platinum tetroxide dication, the increase in oxidation state of an atom, through a chemical reaction, is known as an oxidation, a decrease in oxidation state is known as a reduction. Such reactions involve the transfer of electrons, a net gain in electrons being a reduction. For pure elements, the state is zero. There are various methods for determining oxidation states, in inorganic nomenclature, the oxidation state is determined and expressed as an oxidation number, and is represented by a Roman numeral placed after the element name. In coordination chemistry, oxidation number is defined differently from oxidation state, a “Comprehensive definition of oxidation state ” has been published with free access. This article is a distillation of an IUPAC technical report Toward a comprehensive definition of oxidation state. Exceptions to this are that hydrogen has a state of −1 in hydrides of active metals, e. g. LiH. There are two different methods for determining the state of elements in chemical compounds. First a method based on the rules in the IUPAC definition, second, a method based on the relative electronegativity of the elements in the compound, where the more electronegative element is assumed to take the negative charge. Any pure element—even if it forms diatomic molecules like chlorine —has an oxidation state of zero, examples of this are Cu or O2. For monatomic ions, the state is the same as the charge of the ion. For example, the anion has an oxidation state of −2. The sum of oxidation states for all atoms in a molecule or polyatomic ion is equal to the charge of the molecule or ion, thus, the oxidation state of one element can be calculated from the oxidation states of the other elements. An application of this rule is that the sum of the states of all atoms in a neutral molecule must be zero
5.
Valence (chemistry)
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In chemistry, the valence or valency of an element is a measure of its combining power with other atoms when it forms chemical compounds or molecules. The concept of valence was developed in the half of the 19th century and was successful in explaining the molecular structure of inorganic and organic compounds. The combining power or affinity of an atom of an element was determined by the number of atoms that it combined with. In methane, carbon has a valence of 4, in ammonia, nitrogen has a valence of 3, in water, oxygen has a valence of 2, and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen, so phosphorus has a valence of 5 in phosphorus pentachloride, PCl5. Valence diagrams of a compound represent the connectivity of the elements, examples are, Valence only describes connectivity, it does not describe the geometry of molecular compounds, or what are now known to be ionic compounds or giant covalent structures. A line between atoms does not represent a pair of electrons as it does in Lewis diagrams and this definition differs from the IUPAC definition as an element can be said to have more than one valence. It is in manner, according to Frankland, that their affinities are best satisfied. Following these examples and postulates, Frankland declares how obvious it is that This “combining power” was afterwards called quantivalence or valency. In 1857 August Kekulé proposed fixed valences for many elements, such as 4 for carbon, and used them to propose structural formulas for many organic molecules, which are still accepted today. Most 19th-century chemists defined the valence of an element as the number of its bonds without distinguishing different types of valence or of bond. For main-group elements, in 1904 Richard Abegg considered positive and negative valences, in 1916, Gilbert N. Lewis explained valence and chemical bonding in terms of a tendency of atoms to achieve a stable octet of 8 valence-shell electrons. According to Lewis, covalent bonding leads to octets by the sharing of electrons, the term covalence is attributed to Irving Langmuir, who stated in 1919 that the number of pairs of electrons which any given atom shares with the adjacent atoms is called the covalence of that atom. The prefix co- means together, so that a co-valent bond means that the share a valence. Pauling also considered hypervalent molecules, in which main-group elements have apparent valences greater than the maximal of 4 allowed by the octet rule. Similar calculations on transition-metal molecules show that the role of p orbitals is minor, so that one s, for elements in the main groups of the periodic table, the valence can vary between 1 and 7. Many elements have a common valence related to their position in the periodic table, the Latin/Greek prefixes uni-/mono-, bi-/di-, ter-/tri-, quadri-/tetra- and quinque-/penta- are used to describe ions in the charge states 1,2,3,4,5 respectively. Polyvalence or multivalence refers to species that are not restricted to a number of valence bonds
6.
Salt (chemistry)
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In chemistry, a salt is an ionic compound that results from the neutralization reaction of an acid and a base. Salts are composed of related numbers of cations and anions so that the product is electrically neutral and these component ions can be inorganic, such as chloride, or organic, such as acetate, and can be monatomic, such as fluoride, or polyatomic, such as sulfate. There are several varieties of salts, salts that hydrolyze to produce hydroxide ions when dissolved in water are alkali salts, whilst those that hydrolyze to produce hydronium ions in water are acidic salts. Neutral salts are those salts that are neither acidic nor basic, zwitterions contain an anionic centre and a cationic centre in the same molecule, but are not considered to be salts. Examples of zwitterions include amino acids, many metabolites, peptides, usually, non-dissolved salts at standard conditions for temperature and pressure are solid, but there are exceptions. Molten salts and solutions containing dissolved salts are called electrolytes, as they are able to conduct electricity. As observed in the cytoplasm of cells, in blood, urine, plant saps and mineral waters, therefore, their salt content is given for the respective ions. Salts can appear to be clear and transparent, opaque, and even metallic, in many cases, the apparent opacity or transparency are only related to the difference in size of the individual monocrystals. Since light reflects from the boundaries, larger crystals tend to be transparent. The color of the salt is due to the electronic structure in the d-orbitals of transition elements or in the conjugated organic dye framework. Different salts can elicit all five basic tastes, e. g. salty, sweet, sour, bitter, and umami or savory. Salts of strong acids and strong bases are non-volatile and odorless and that slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts. Many ionic compounds can be dissolved in water or other similar solvents, the exact combination of ions involved makes each compound have a unique solubility in any solvent. The solubility is dependent on how well each ion interacts with the solvent, for example, all salts of sodium, potassium and ammonium are soluble in water, as are all nitrates and many sulfates – barium sulfate, calcium sulfate and lead sulfate are examples of exceptions. However, ions that bind tightly to each other and form highly stable lattices are less soluble, for example, most carbonate salts are not soluble in water, such as lead carbonate and barium carbonate. Some soluble carbonate salts are, sodium carbonate, potassium carbonate, solid salts do not conduct electricity. Moreover, solutions of salts also conduct electricity, the name of a salt starts with the name of the cation followed by the name of the anion. Salts are often referred to only by the name of the cation or by the name of the anion. g
7.
Sodium dichromate
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Sodium dichromate is the inorganic compound with the formula Na2Cr2O7. Usually, however, the salt is handled as its dihydrate Na2Cr2O7·2H2O, virtually all chromium ore is processed via conversion to sodium dichromate and virtually all compounds and materials based on chromium are prepared from this salt. In terms of reactivity and appearance, sodium dichromate and potassium dichromate are very similar, the sodium salt is, however, around twenty times more soluble in water than the potassium salt and its equivalent weight is also lower, which is often desirable. Sodium dichromate is generated on a scale from ores containing chromium oxides. At this stage, other components of the ore such as aluminium, in this way, many millions of kilograms of sodium dichromate are produced annually. Since chromium is toxic, especially as the dust, such factories are subject to stringent regulations, for example, effluent from such refineries is treated with reducing agents to return any chromium to chromium, which is less threatening to the environment. A variety of hydrates of this salt are known, ranging from the decahydrate below 19.5 °C as well as hexa-, tetra-, above 62 °C, these salts lose water spontaneously to give the anhydrous material. It is crystallised around 30 to 35 degrees C Dichromate and chromate salts are oxidizing agents, for the tanning of leather, sodium dichromate is first reduced with sulfur dioxide. In the area of synthesis, this compound oxidizes benzylic and allylic C-H bonds to carbonyl derivatives. For example,2,4, 6-trinitrotoluene is oxidized to the carboxylic acid. Similarly,2, 3-dimethylnaphthalene is oxidized by Na2Cr2O7 to 2, secondary alcohols are oxidized to the corresponding ketone, e. g. Like all hexavalent chromium compounds, sodium dichromate is considered hazardous and it is also a known carcinogen
8.
Chromate and dichromate
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Chromate salts contain the chromate anion, CrO2−4. Dichromate salts contain the anion, Cr 2O2−7. They are oxoanions of chromium in the oxidation state +6 and they are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible, chromates react with hydrogen peroxide giving products in which peroxide, O2−2, replaces one or more oxygen atoms. In acid solution the unstable blue peroxo complex Chromium oxide peroxide, CrO2, is formed, addition of pyridine results in the formation of the more stable complex CrO2py. In aqueous solution, chromate and dichromate anions exist in a chemical equilibrium,2 CrO2−4 +2 H+ ⇌ Cr 2O2−7 + H2O The predominance diagram shows that the position of the equilibrium depends on both pH and the analytical concentration of chromium. The chromate ion is the predominant species in solutions. Further condensation reactions can occur in acidic solution with the formation of trichromates, Cr 3O2−10. All polyoxyanions of chromium have structures made up of tetrahedral CrO4 units sharing corners, the chromate ion is a weak acid. HCrO−4 ⇌ CrO2−4 + H+, pKa ≈5.9 The hydrogen chromate ion,2 HCrO−4 ⇌ Cr 2O2−7 + H2O This equilibrium does not involve a change in hydrogen ion concentration, so should be independent of pH. The red line on the diagram is not quite horizontal due to the simultaneous equilibrium with the chromate ion. The hydrogenchromate ion may be protonated, with the formation of molecular chromic acid, H2CrO4, reported values vary between about −0.8 to 1.6. The dichromate ion is a weaker base than the chromate ion. HCr 2O−7 ⇌ Cr 2O2−7 + H+, pK =1.8 The pK value for this shows that it can be ignored at pH >4. The chromate and dichromate ions are fairly strong oxidizing agents, commonly three electrons are added to a chromium atom, reducing it to oxidation state +3. In acid solution the aquated Cr3+ ion is produced, Cr 2O2−7 +14 H3O+ +6 e− →2 Cr3+ +7 H2O ε0 =1.33 V In alkaline solution chromium hydroxide is produced. The redox potential shows that chromates are weaker oxidizing agent in alkaline solution than in acid solution. CrO2−4 +4 H 2O +3 e− → Cr 3 +5 OH− ε0 = −0.13 V Approximately 136,000 tonnes of hexavalent chromium, chromates and dichromates are used in chrome plating to protect metals from corrosion and to improve paint adhesion
9.
Chromate conversion coating
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Chromate conversion coating is a type of conversion coating used to passivate steel, aluminum, zinc, cadmium, copper, silver, magnesium, and tin alloys. It is primarily used as an inhibitor, primer, decorative finish. The process is named after the found in chromic acid, also known as hexavalent chromium. However, hexavalent chromium is toxic, thus, highly regulated, so new, Chromate conversion coatings are commonly applied to everyday items such as hardware and tools, and can usually be recognized by their distinctively iridescent, greenish-yellow color. Chromate conversion coatings on a substrate are known by the following terms, chemical film, yellow iridite. It is also used on aluminum alloy parts in the aircraft industry. Iridite NCP is a type of conversion coating for aluminium substrates. The most commonly referred-to standard for applying chromate conversion coating to aluminium is MIL-DTL-5541 in the US, Alodine may also refer to chromate-coating magnesium alloys. Chromate conversion coatings can be applied over phosphate conversion coatings used on ferrous substrates, the process is used to enhance the phosphate coating. Chromating is often performed on galvanized parts to them more durable. The chromate coating acts as paint does, protecting the zinc from white corrosion, thus making the part considerably more durable, steel and iron cannot be chromated directly. Chromating zinc plated steel does not enhance zincs cathodic protection of the steel from rust. The protective effect of chromate coatings on zinc is indicated by color, progressing from clear/blue to yellow, gold, olive drab, darker coatings generally provide more corrosion resistance. However, the color can also be changed with dyes. ISO4520 specifies chromate conversion coatings on electroplated zinc and cadmium coatings, ASTM B633 Type II and III specify zinc plating plus chromate conversion on iron and steel parts. The composition of chromate conversion solutions varies greatly, depending on the material to be coated, Iridite 14-2, a chromate conversion coating for aluminum, contains chromium oxide, barium nitrate, sodium silicofluoride and ferricyanide. Chromate coatings are soft and gelatinous when first applied, but harden, curing can be accelerated by heating up to 70 °C, but higher temperatures will gradually damage the coating. Yellow and green chromating chemistry on aluminium MIL-C-17711B, Chromate conversion coating specification for zinc and zinc alloy casting and hot dipped galvanized parts
10.
Chromic acid
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The term chromic acid is usually used for a mixture made by adding concentrated sulfuric acid to a dichromate, which may contain a variety of compounds, including solid chromium trioxide. This kind of acid may be used as a cleaning mixture for glass. Chromic acid may also refer to the species, H2CrO4 of which the trioxide is the anhydride. Chromic acid features chromium in a state of +6. It is a strong and corrosive oxidising agent, molecular chromic acid, H2CrO4, has much in common with sulfuric acid, H2SO4. Both are classified as acids, though only the first proton is lost easily. H2CrO4 ⇌ − + H+ The pKa for the equilibrium is not well characterized, reported values vary between about −0.8 to 1.6. The value at zero ionic strength is difficult to determine because half dissociation only occurs in acidic solution, at about pH0. A further complication is that the ion − has a tendency to dimerize, with the loss of a water molecule, to form the dichromate ion. Furthermore, the dichromate can be protonated, − ⇌ 2− + H+ pK =1.8 The pK value for this shows that it can be ignored at pH >4. Loss of the second occurs in the pH range 4–8. Molecular chromic acid could in principle be made by adding chromium trioxide to water, CrO3 + H2O ⇌ H2CrO4 but in practice the reverse reaction occurs when molecular chromic acid is dehydrated. This is what happens when concentrated sulfuric acid is added to a dichromate solution, at first the colour changes from orange to red and then deep red crystals of chromium trioxide precipitate from the mixture, without further colour change. The colours are due to LMCT transitions, Chromium trioxide is the anhydride of molecular chromic acid. It is a Lewis acid and can react with a Lewis base, dichromic acid, H2Cr2O7, is the fully protonated form of the dichromate ion and also can be seen as the product of adding chromium trioxide to molecular chromic acid. 2− + 2H+ ⇌ H2Cr2O7 ⇌ H2CrO4 + CrO3 It is probably present in chromic acid cleaning mixtures along with the mixed chromosulfuric acid H2CrSO7, chromic acid is an intermediate in chromium plating, and is also used in ceramic glazes, and colored glass. Because a solution of acid in sulfuric acid is a powerful oxidizing agent, it can be used to clean laboratory glassware. This application has declined due to environmental concerns, furthermore, the acid leaves trace amounts of paramagnetic chromic ions — Cr — that can interfere with certain applications, such as NMR spectroscopy
11.
Electroplate
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Electroplating is a process that uses electric current to reduce dissolved metal cations so that they form a thin coherent metal coating on an electrode. The term is used for electrical oxidation of anions onto a solid substrate. Electroplating is primarily used to change the properties of an object. The process used in electroplating is called electrodeposition and it is analogous to a galvanic cell acting in reverse. The part to be plated is the cathode of the circuit, in one technique, the anode is made of the metal to be plated on the part. Both components are immersed in a solution called an electrolyte containing one or more dissolved metal salts as well as other ions that permit the flow of electricity. A power supply supplies a direct current to the anode, oxidizing the metal atoms that it comprises, at the cathode, the dissolved metal ions in the electrolyte solution are reduced at the interface between the solution and the cathode, such that they plate out onto the cathode. The rate at which the anode is dissolved is equal to the rate at which the cathode is plated, in this manner, the ions in the electrolyte bath are continuously replenished by the anode. Other electroplating processes may use a non-consumable anode such as lead or carbon, in these techniques, ions of the metal to be plated must be periodically replenished in the bath as they are drawn out of the solution. The most common form of electroplating is used for creating coins such as pennies, the cations associate with the anions in the solution. These cations are reduced at the cathode to deposit in the metallic, for example, for copper plating, in an acid solution, copper is oxidized at the anode to Cu2+ by losing two electrons. The Cu2+ associates with the anion SO42− in the solution to form copper sulfate, at the cathode, the Cu2+ is reduced to metallic copper by gaining two electrons. The result is the transfer of copper from the anode source to a plate covering the cathode. The plating is most commonly a metallic element, not an alloy. However, some alloys can be electrodeposited, notably brass and solder, many plating baths include cyanides of other metals in addition to cyanides of the metal to be deposited. These free cyanides facilitate anode corrosion, help to maintain a constant metal ion level, additionally, non-metal chemicals such as carbonates and phosphates may be added to increase conductivity. When plating is not desired on certain areas of the substrate, typical stop-offs include tape, foil, lacquers, and waxes. The ability of a plating to cover uniformly is called throwing power, initially, a special plating deposit called a strike or flash may be used to form a very thin plating with high quality and good adherence to the substrate
12.
Carcinogen
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A carcinogen is any substance, radionuclide, or radiation that is an agent directly involved in causing cancer. This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes, several radioactive substances are considered carcinogens, but their carcinogenic activity is attributed to the radiation, for example gamma rays and alpha particles, which they emit. Common examples of non-radioactive carcinogens are inhaled asbestos, certain dioxins, although the public generally associates carcinogenicity with synthetic chemicals, it is equally likely to arise in both natural and synthetic substances. Carcinogens are not necessarily immediately toxic, thus their effect can be insidious, Cancer is any disease in which normal cells are damaged and do not undergo programmed cell death as fast as they divide via mitosis. Usually, severe DNA damage leads to apoptosis, but if the cell death pathway is damaged. Aflatoxin B1, which is produced by the fungus Aspergillus flavus growing on stored grains, nuts and peanut butter, is an example of a potent, certain viruses such as hepatitis B and human papilloma virus have been found to cause cancer in humans. The first one shown to cause cancer in animals is Rous sarcoma virus, other infectious organisms which cause cancer in humans include some bacteria and helminths. Dioxins and dioxin-like compounds, benzene, kepone, EDB, vinyl chloride, from which PVC is manufactured, is a carcinogen and thus a hazard in PVC production. Co-carcinogens are chemicals that do not necessarily cause cancer on their own, after the carcinogen enters the body, the body makes an attempt to eliminate it through a process called biotransformation. The purpose of these reactions is to make the carcinogen more water-soluble so that it can be removed from the body, however, in some cases, these reactions can also convert a less toxic carcinogen into a more toxic carcinogen. DNA is nucleophilic, therefore soluble carbon electrophiles are carcinogenic, because DNA attacks them, for example, some alkenes are toxicated by human enzymes to produce an electrophilic epoxide. DNA attacks the epoxide, and is bound permanently to it and this is the mechanism behind the carcinogenicity of benzopyrene in tobacco smoke, other aromatics, aflatoxin and mustard gas. Carcinogenicity of radiation depends on the type of radiation, type of exposure, for example, alpha radiation has low penetration and is not a hazard outside the body, but emitters are carcinogenic when inhaled or ingested. Low-level ionizing radiation may induce irreparable DNA damage leading to pre-mature aging, not all types of electromagnetic radiation are carcinogenic. Higher-energy radiation, including radiation, x-rays, and gamma radiation, generally is carcinogenic. For most people, ultraviolet radiations from sunlight is the most common cause of skin cancer, in Australia, where people with pale skin are often exposed to strong sunlight, melanoma is the most common cancer diagnosed in people aged 15–44 years. Substances or foods irradiated with electrons or electromagnetic radiation are not carcinogenic, in contrast, non-electromagnetic neutron radiation produced inside nuclear reactors can produce secondary radiation through nuclear transmutation. Chemicals used in processed and cured such as some brands of bacon, sausages
13.
European Union
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The European Union is a political and economic union of 28 member states that are located primarily in Europe. It has an area of 4,475,757 km2, the EU has developed an internal single market through a standardised system of laws that apply in all member states. Within the Schengen Area, passport controls have been abolished, a monetary union was established in 1999 and came into full force in 2002, and is composed of 19 EU member states which use the euro currency. The EU operates through a system of supranational and intergovernmental decision-making. The EU traces its origins from the European Coal and Steel Community, the community and its successors have grown in size by the accession of new member states and in power by the addition of policy areas to its remit. While no member state has left the EU or its antecedent organisations, the Maastricht Treaty established the European Union in 1993 and introduced European citizenship. The latest major amendment to the basis of the EU. The EU as a whole is the largest economy in the world, additionally,27 out of 28 EU countries have a very high Human Development Index, according to the United Nations Development Programme. In 2012, the EU was awarded the Nobel Peace Prize, through the Common Foreign and Security Policy, the EU has developed a role in external relations and defence. The union maintains permanent diplomatic missions throughout the world and represents itself at the United Nations, the World Trade Organization, the G7, because of its global influence, the European Union has been described as an emerging superpower. After World War II, European integration was seen as an antidote to the nationalism which had devastated the continent. 1952 saw the creation of the European Coal and Steel Community, the supporters of the Community included Alcide De Gasperi, Jean Monnet, Robert Schuman, and Paul-Henri Spaak. These men and others are credited as the Founding fathers of the European Union. In 1957, Belgium, France, Italy, Luxembourg, the Netherlands and West Germany signed the Treaty of Rome and they also signed another pact creating the European Atomic Energy Community for co-operation in developing nuclear energy. Both treaties came into force in 1958, the EEC and Euratom were created separately from the ECSC, although they shared the same courts and the Common Assembly. The EEC was headed by Walter Hallstein and Euratom was headed by Louis Armand, Euratom was to integrate sectors in nuclear energy while the EEC would develop a customs union among members. During the 1960s, tensions began to show, with France seeking to limit supranational power, Jean Rey presided over the first merged Commission. In 1973, the Communities enlarged to include Denmark, Ireland, Norway had negotiated to join at the same time, but Norwegian voters rejected membership in a referendum
14.
Genotoxicity
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In genetics, genotoxicity describes the property of chemical agents that damages the genetic information within a cell causing mutations, which may lead to cancer. While genotoxicity is often confused with mutagenicity, all mutagens are genotoxic, the alteration can have direct or indirect effects on the DNA, the induction of mutations, mistimed event activation, and direct DNA damage leading to mutations. The permanent, heritable changes can affect either somatic cells of the organism or germ cells to be passed on to future generations, cells prevent expression of the genotoxic mutation by either DNA repair or apoptosis, however, the damage may not always be fixed leading to mutagenesis. To assay for genotoxic molecules, researchers assay for DNA damage in cells exposed to the toxic substrates, the compromised integrity of the genetic material has been known to cause cancer. The genotoxic substances induce damage to the material in the cells through interactions with the DNA sequence. For example, the transition metal chromium interacts with DNA in its high-valent oxidation state so to incur DNA lesions leading to carcinogenesis, the metastable oxidation state Cr is achieved through reductive activation. The researchers performed an experiment to study the interaction between DNA with the carcinogenic chromium by using a Cr-Salen complex at the oxidation state. The interaction was specific to the nucleotide in the genetic sequence. In order to narrow the interaction between the Cr-Salen complex with the base, the researchers modified the bases to 8-oxo-G so to have site specific oxidation. The reaction between the two molecules caused DNA lesions, the two lesions observed at the base site were guanidinohydantoin and spiroiminodihydantoin. To further analyze the site of lesion, it was observed that polymerase stopped at the site, therefore, these lesions predominately contain G-->T transversions. Consequently, it shows how high-valent chromium can act as a carcinogen with 8-oxo-G forming xenobiotics, another example of a genotoxic substance causing DNA damage are pyrrolizidine alkaloids. These substances are mainly in plant species and are poisonous to animals, including humans, about half of them have been identified as genotoxic. The most common mutation within the genes ares G, C --> T, A tranversions, the pyrrolizidine alkaloids are mutagenic in vivo and in vitro and, therefore, responsible for the carcinogenesis prominently in the liver. Comfrey is an example of a plant species that contains fourteen different PAs, the active metabolites interact with DNA to cause DNA damage, mutation induction, and cancer development in liver endothelial cells and hepatocytes. The researchers discovered in the end that the comfrey is mutagenic in liver, the purpose of genotoxicity testing is to determine if a substrate will influence genetic material or may cause cancer. They can be performed in bacterial, yeast, and mammalian cells, with the knowledge from the tests, one can control early development of vulnerable organisms to genotoxic substances. The Bacterial Reverse Mutation Assay, also known as the Ames Assay, is used in laboratories to test for gene mutation, the technique uses many different bacterial strains in order to compare the different changes in the genetic material
15.
Sulfate
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The sulfate or sulphate ion is a polyatomic anion with the empirical formula SO2−4. Sulfate is the spelling recommended by IUPAC, but sulphate is used in British English, salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life, sulfates are salts of sulfuric acid and many are prepared from that acid. The sulfate anion consists of a sulfur atom surrounded by four equivalent oxygen atoms in a tetrahedral arrangement. The symmetry is the same as that of methane, the sulfur atom is in the +6 oxidation state while the four oxygen atoms are each in the state. The sulfate ion carries a charge of −2 and it is the conjugate base of the bisulfate ion, HSO−4. Organic sulfate esters, such as sulfate, are covalent compounds. The tetrahedral molecular geometry of the ion is as predicted by VSEPR theory. Later, Linus Pauling used valence bond theory to propose that the most significant resonance canonicals had two pi bonds involving d orbitals and his reasoning was that the charge on sulfur was thus reduced, in accordance with his principle of electroneutrality. The S−O bond length of 149 pm is shorter than the bond lengths in sulfuric acid of 157 pm for S−OH, the double bonding was taken by Pauling to account for the shortness of the S−O bond. Paulings use of d orbitals provoked a debate on the importance of π bonding. The outcome was a consensus that d orbitals play a role. A widely accepted description involving pπ – dπ bonding was initially proposed by D. W. J. Cruickshank, in this model, fully occupied p orbitals on oxygen overlap with empty sulfur d orbitals. However, in description, despite there being some π character to the S−O bonds. For sulfuric acid, computational analysis confirms a positive charge on sulfur. Therefore, the representation with four single bonds is the optimal Lewis structure rather than the one with two double bonds, in this model, the structure obeys the octet rule and the charge distribution is in agreement with the electronegativity of the atoms. However, the representation of Pauling for sulfate and other main group compounds with oxygen is still a common way of representing the bonding in many textbooks. On the other hand, in the structure with an ionic bond, exceptions include calcium sulfate, strontium sulfate, lead sulfate, and barium sulfate, which are poorly soluble
16.
Ascorbate
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Vitamin C, also known as ascorbic acid and L-ascorbic acid, is a vitamin found in food and used as a dietary supplement. As a supplement it is used to treat and prevent scurvy, evidence does not support use in the general population for the prevention of the common cold. It may be taken by mouth or by injection, large doses may cause gastrointestinal discomfort, headache, trouble sleeping, and flushing of the skin. Normal doses are safe during pregnancy, Vitamin C is an essential nutrient involved in the repair of tissue. Foods that contain vitamin C include citrus fruit, tomatoes, Vitamin C was discovered in 1912, isolated in 1928, and first made in 1933. It is on the World Health Organizations List of Essential Medicines, Vitamin C is available as a generic medication and over the counter. In 2015, the wholesale cost in the world was about 0.003 to 0.007 USD per tablet. In some countries, ascorbic acid may be added to such as breakfast cereal. A2012 Cochrane review found no effect of vitamin C supplementation on overall mortality, although rare in modern times, scurvy and its associated destabilization of collagen, connective tissue, and bone can be prevented by adequate vitamin C intake. A2014 review found that, Currently, the use of high-dose IV vitamin C cannot be recommended outside of a clinical trial, a 2013 Cochrane review found no evidence that vitamin C supplementation reduces the risk of lung cancer in healthy or high risk people. A2014 meta-analysis found that vitamin C intake might protect against lung cancer risk, a second meta-analysis found no effect on the risk of prostate cancer. Two meta-analyses evaluated the effect of vitamin C supplementation on the risk of colorectal cancer, one found a weak association between vitamin C consumption and reduced risk, and the other found no effect of supplementation. A2013 meta-analysis found no evidence that vitamin C supplementation reduces the risk of myocardial infarction, stroke, cardiovascular mortality, however, a second analysis found an inverse relationship between circulating vitamin C levels or dietary vitamin C and the risk of stroke. A meta-analysis of 44 clinical trials has shown a significant positive effect of vitamin C on endothelial function when taken at doses greater than 500 mg per day. The researchers noted that the effect of vitamin C supplementation appeared to be dependent on health status, a 2010 review found no role for vitamin C supplementation in the treatment of rheumatoid arthritis. Studies examining the effects of vitamin C intake on the risk of Alzheimers disease have reached conflicting conclusions, maintaining a healthy dietary intake is probably more important than supplementation for achieving any potential benefit. Vitamin C supplementation above the RDA has been used in trials to study a potential effect on preventing and slowing the progression of age-related cataract, however, no significant effects were found from the research. Vitamin Cs effect on the cold has been extensively researched
17.
Thiol
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In organic chemistry, a thiol is an organosulfur compound that contains a carbon-bonded sulfhydryl or sulphydryl group. Thiols are the analogue of alcohols, and the word is a portmanteau of thion + alcohol. The –SH functional group itself is referred to as either a group or a sulfhydryl group. Many thiols have strong odors resembling that of garlic or rotten eggs, thiols are used as odorants to assist in the detection of natural gas, and the smell of natural gas is due to the smell of the thiol used as the odorant. Thiols are sometimes referred to as mercaptans, thiols and alcohols have similar connectivity. Because sulfur is a larger element than oxygen, the C–S bond lengths, the C–S–H angles approach 90° whereas the angle for the C-O-H group are more open. In the solid or liquids, the hydrogen-bonding between individual groups is weak, the main cohesive force being van der Waals interactions between the highly polarizable divalent sulfur centers. Due to the lesser electronegativity difference between sulfur and hydrogen compared to oxygen and hydrogen, an S–H bond is less polar than the hydroxyl group, thiols have a lower dipole moment relative to the corresponding alcohol. There are several ways to name the alkylthiols, The suffix -thiol is added to the name of the alkane and this method is nearly identical to naming an alcohol and is used by the IUPAC. The word mercaptan replaces alcohol in the name of the equivalent alcohol compound, example, CH3SH would be methyl mercaptan, just as CH3OH is called methyl alcohol. The term sulfanyl or mercapto is used as a prefix, many thiols have strong odors resembling that of garlic. The odors of thiols, particularly those of low weight, are often strong. The spray of skunks consists mainly of low-molecular-weight thiols and derivatives and these compounds are detectable by the human nose at concentrations of only 10 parts per billion. Human sweat contains /-3-methyl-3-sulfanylhexan-1-ol, detectable at 2 parts per billion and having a fruity, methanethiol is a strong-smelling volatile thiol, also detectable at parts per billion levels, found in male mouse urine. Lawrence C. Katz and co-workers showed that MTMT functioned as a semiochemical, activating certain mouse olfactory sensory neurons, attracting female mice. Copper has been shown to be required by a specific mouse olfactory receptor, MOR244-3, thiols are also responsible for a class of wine faults caused by an unintended reaction between sulfur and yeast and the skunky odor of beer that has been exposed to ultraviolet light. Not all thiols have unpleasant odors, for example, furan-2-ylmethanethiol contributes to the aroma of roasted coffee, whereas grapefruit mercaptan, a monoterpenoid thiol, is responsible for the characteristic scent of grapefruit. The effect of the compound is present only at low concentrations
18.
Vitamin C
–
Vitamin C, also known as ascorbic acid and L-ascorbic acid, is a vitamin found in food and used as a dietary supplement. As a supplement it is used to treat and prevent scurvy, evidence does not support use in the general population for the prevention of the common cold. It may be taken by mouth or by injection, large doses may cause gastrointestinal discomfort, headache, trouble sleeping, and flushing of the skin. Normal doses are safe during pregnancy, Vitamin C is an essential nutrient involved in the repair of tissue. Foods that contain vitamin C include citrus fruit, tomatoes, Vitamin C was discovered in 1912, isolated in 1928, and first made in 1933. It is on the World Health Organizations List of Essential Medicines, Vitamin C is available as a generic medication and over the counter. In 2015, the wholesale cost in the world was about 0.003 to 0.007 USD per tablet. In some countries, ascorbic acid may be added to such as breakfast cereal. A2012 Cochrane review found no effect of vitamin C supplementation on overall mortality, although rare in modern times, scurvy and its associated destabilization of collagen, connective tissue, and bone can be prevented by adequate vitamin C intake. A2014 review found that, Currently, the use of high-dose IV vitamin C cannot be recommended outside of a clinical trial, a 2013 Cochrane review found no evidence that vitamin C supplementation reduces the risk of lung cancer in healthy or high risk people. A2014 meta-analysis found that vitamin C intake might protect against lung cancer risk, a second meta-analysis found no effect on the risk of prostate cancer. Two meta-analyses evaluated the effect of vitamin C supplementation on the risk of colorectal cancer, one found a weak association between vitamin C consumption and reduced risk, and the other found no effect of supplementation. A2013 meta-analysis found no evidence that vitamin C supplementation reduces the risk of myocardial infarction, stroke, cardiovascular mortality, however, a second analysis found an inverse relationship between circulating vitamin C levels or dietary vitamin C and the risk of stroke. A meta-analysis of 44 clinical trials has shown a significant positive effect of vitamin C on endothelial function when taken at doses greater than 500 mg per day. The researchers noted that the effect of vitamin C supplementation appeared to be dependent on health status, a 2010 review found no role for vitamin C supplementation in the treatment of rheumatoid arthritis. Studies examining the effects of vitamin C intake on the risk of Alzheimers disease have reached conflicting conclusions, maintaining a healthy dietary intake is probably more important than supplementation for achieving any potential benefit. Vitamin C supplementation above the RDA has been used in trials to study a potential effect on preventing and slowing the progression of age-related cataract, however, no significant effects were found from the research. Vitamin Cs effect on the cold has been extensively researched
19.
Nucleic acid
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Nucleic acids are biopolymers, or large biomolecules, essential to all known forms of life. They are composed of monomers, which are made of three components, a 5-carbon sugar, a phosphate group, and a nitrogenous base. If the sugar is a simple ribose, the polymer is RNA, if the sugar is derived from ribose as deoxyribose, Nucleic acids are arguably the most important of all biomolecules. They are found in abundance in all living things, where they function to create and encode, the encoded information is contained and conveyed via the nucleic acid sequence, which provides the ladder-step ordering of nucleotides within the molecules of RNA and DNA. Using amino acids and the known as protein synthesis, the specific sequencing in DNA of these nucleobase-pairs enables storing and transmitting coded instructions as genes. In RNA, base-pair sequencing provides for manufacturing new proteins that determine the frames and parts, Nucleic acids were discovered by Friedrich Miescher in 1869. In 1889 Richard Altmann discovered that nuclein has acidic properties, and it became called nucleic acid In 1938 Astbury, in 1953 Watson and Crick determined the structure of DNA. The term nucleic acid is the name for DNA and RNA, members of a family of biopolymers. Nucleic acids were named for their initial discovery within the nucleus, all living cells contain both DNA and RNA, while viruses contain either DNA or RNA, but usually not both. The basic component of nucleic acids is the nucleotide, each of which contains a pentose sugar, a phosphate group. Nucleic acids are generated within the laboratory, through the use of enzymes. The chemical methods also enable the generation of altered nucleic acids that are not found in nature, Nucleic acids are generally very large molecules. Indeed, DNA molecules are probably the largest individual molecules known, well-studied biological nucleic acid molecules range in size from 21 nucleotides to large chromosomes. In most cases, naturally occurring DNA molecules are double-stranded and RNA molecules are single-stranded, Nucleic acids are linear polymers of nucleotides. Each nucleotide consists of three components, a purine or pyrimidine nucleobase, a sugar, and a phosphate group. The substructure consisting of a nucleobase plus sugar is termed a nucleoside, Nucleic acid types differ in the structure of the sugar in their nucleotides–DNA contains 2-deoxyribose while RNA contains ribose. Also, the found in the two nucleic acid types are different, adenine, cytosine, and guanine are found in both RNA and DNA, while thymine occurs in DNA and uracil occurs in RNA. The sugars and phosphates in nucleic acids are connected to other in an alternating chain through phosphodiester linkages
20.
Protein
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Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, a linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide, short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides. The individual amino acid residues are bonded together by peptide bonds, the sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the code specifies 20 standard amino acids, however. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors, proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes. Once formed, proteins only exist for a period of time and are then degraded and recycled by the cells machinery through the process of protein turnover. A proteins lifespan is measured in terms of its half-life and covers a wide range and they can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly due to being targeted for destruction or due to being unstable. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms, many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized, digestion breaks the proteins down for use in the metabolism. Methods commonly used to study structure and function include immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance. Most proteins consist of linear polymers built from series of up to 20 different L-α-amino acids, all proteinogenic amino acids possess common structural features, including an α-carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this structure as it contains an unusual ring to the N-end amine group. The amino acids in a chain are linked by peptide bonds. Once linked in the chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen. The peptide bond has two forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar
21.
Hydroxyl radical
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The hydroxyl radical, •OH, is the neutral form of the hydroxide ion. Hydroxyl radicals are highly reactive and consequently short-lived, however, they form an important part of radical chemistry, most notably hydroxyl radicals are produced from the decomposition of hydroperoxides or, in atmospheric chemistry, by the reaction of excited atomic oxygen with water. In organic synthesis, hydroxyl radicals are most commonly generated by photolysis of 1-hydroxy-2-pyridinethione and it also has an important role in eliminating some greenhouse gases like methane and ozone. The rate of reaction with the hydroxyl radical often determines how long many pollutants last in the atmosphere, for instance methane, which reacts relatively slowly with hydroxyl radical, has an average lifetime of >5 years and many CFCs have lifetimes of 50 years or more. Pollutants, such as hydrocarbons, can have very short average lifetimes of less than a few hours. The first reaction with many organic compounds is the removal of a hydrogen atom, forming water. •OH + RH → H2O + R• The alkyl radical will react rapidly with oxygen forming a peroxy radical. R• + O2 → RO•2 The fate of this radical in the troposphere is dependent on such as the amount of sunlight, pollution in the atmosphere. Hydroxyl radicals can occasionally be produced as a byproduct of immune action, macrophages and microglia most frequently generate this compound when exposed to very specific pathogens, such as certain bacteria. The hydroxyl radical can damage all types of macromolecules, carbohydrates, nucleic acids, lipids. The hydroxyl radical has a short in vivo half-life of approximately 10−9 seconds. This makes it a very dangerous compound to the organism, unlike superoxide, which can be detoxified by superoxide dismutase, the hydroxyl radical cannot be eliminated by an enzymatic reaction. The hydroxyl •OH radical is one of the chemical species controlling the oxidizing capacity of the global Earth atmosphere. This oxidizing reactive species has an impact on the concentrations and distribution of greenhouse gases. It is the most widespread oxidizer in the troposphere, the lowest part of the atmosphere, understanding •OH variability is important to evaluating human impacts on the atmosphere and climate. The •OH species has a lifetime in the Earth atmosphere of less than one second, the lifetime of •OH radicals in the Earth atmosphere is very short, therefore •OH concentrations in the air are very low and very sensitive techniques are required for its direct detection. Global average hydroxyl radical concentrations have been measured indirectly by analyzing methyl chloroform present in the air and this small variability is consistent with measurements of methane and other trace gases primarily oxidized by •OH, as well as global photochemical model calculations. In 2014, researchers reported their discovery of a hole or absence of hydroxyl throughout the depth of the troposphere across a large region of the tropical West Pacific
22.
Hydrogen peroxide
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Hydrogen peroxide is a chemical compound with the formula H 2O2. In its pure form, it is a liquid, slightly more viscous than water. Hydrogen peroxide is the simplest peroxide and it is used as an oxidizer, bleaching agent and disinfectant. Concentrated hydrogen peroxide, or high-test peroxide, is an oxygen species and has been used as a propellant in rocketry. Its chemistry is dominated by the nature of its unstable peroxide bond, Hydrogen peroxide is unstable and slowly decomposes in the presence of base or a catalyst. Because of its instability, hydrogen peroxide is typically stored with a stabilizer in an acidic solution. Hydrogen peroxide is found in biological systems including the human body, enzymes that use or decompose hydrogen peroxide are classified as peroxidases. The boiling point of H 2O2 has been extrapolated as being 150.2 °C, in practice hydrogen peroxide will undergo potentially explosive thermal decomposition if heated to this temperature. It may be distilled at lower temperatures under reduced pressure. In aqueous solutions hydrogen peroxide differs from the material due to the effects of hydrogen bonding between water and hydrogen peroxide molecules. Hydrogen peroxide and water form a mixture, exhibiting freezing-point depression, pure water has a melting point of 0 °C. The boiling point of the same mixtures is also depressed in relation with the mean of both boiling points and this boiling point is 14 °C greater than that of pure water and 36.2 °C less than that of pure hydrogen peroxide. Hydrogen peroxide is a molecule with C2 symmetry. Although the O−O bond is a bond, the molecule has a relatively high rotational barrier of 2460 cm−1, for comparison. The increased barrier is ascribed to repulsion between the pairs of the adjacent oxygen atoms and results in hydrogen peroxide displaying atropisomerism. The molecular structures of gaseous and crystalline H 2O2 are significantly different and this difference is attributed to the effects of hydrogen bonding, which is absent in the gaseous state. Crystals of H 2O2 are tetragonal with the space group D4 4P4121, Hydrogen peroxide has several structural analogues with Hm−X−X−Hn bonding arrangements. It has the highest boiling point of this series, diphosphane and hydrogen disulfide exhibit only weak hydrogen bonding and have little chemical similarity to hydrogen peroxide
23.
Carcinogenesis
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Carcinogenesis or oncogenesis or tumorigenesis is the formation of a cancer, whereby normal cells are transformed into cancer cells. The process is characterized by changes at the cellular, genetic, Cell division is a physiological process that occurs in almost all tissues and under a variety circumstances. Normally the balance between proliferation and programmed cell death, in the form of apoptosis, is maintained to ensure the integrity of tissues and this results in uncontrolled cell division and the evolution of those cells by natural selection in the body. Only certain mutations lead to cancer whereas the majority of mutations do not, variants of inherited genes may predispose individuals to cancer. In addition, environmental factors such as carcinogens and radiation cause mutations that may contribute to the development of cancer, finally random mistakes in normal DNA replication may result in cancer causing mutations. A series of mutations to certain classes of genes is usually required before a normal cell will transform into a cancer cell. On average, for example,15 driver mutations and 60 passenger mutations are found in colon cancers, mutations in genes that regulate cell division, apoptosis, and DNA repair may result in uncontrolled cell proliferation and cancer. Cancer is fundamentally a disease of regulation of tissue growth, in order for a normal cell to transform into a cancer cell, genes that regulate cell growth and differentiation must be altered. There are two categories of genes that are affected by these changes. Oncogenes may be normal genes that are expressed at high levels. In either case, expression of these genes promotes the malignant phenotype of cancer cells, tumor suppressor genes are genes that inhibit cell division, survival, or other properties of cancer cells. Tumor suppressor genes are disabled by cancer-promoting genetic changes. Finally Oncovirinae, viruses that contain an oncogene, are categorized as oncogenic because they trigger the growth of tissues in the host. This process is referred to as viral transformation. There is a classification scheme for the various genomic changes that may contribute to the generation of cancer cells. Many of these changes are mutations, or changes in the sequence of genomic DNA. There are also many changes that alter whether genes are expressed or not expressed. Aneuploidy, the presence of a number of chromosomes, is one genomic change that is not a mutation
24.
Mouth
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It is also the cavity lying at the upper end of the alimentary canal, bounded on the outside by the lips and inside by the pharynx and containing in higher vertebrates the tongue and teeth. This cavity is known as the buccal cavity, from the Latin bucca. Some animal phyla, including vertebrates, have a digestive system, with a mouth at one end. Which end forms first in ontogeny is a used to classify animals into protostome and deuterostome. In the first multicellular animals there was probably no mouth or gut, the particles became enclosed in vacuoles into which enzymes were secreted and digestion took place intracellularly. The digestive products were absorbed into the cytoplasm and diffused into other cells, the vast majority of other multicellular organisms have a mouth and a gut, the lining of which is continuous with the epithelial cells on the surface of the body. A few animals which live parasitically originally had guts but have secondarily lost these structures, the original gut of multicellular organisms probably consisted of a simple sac with a single opening, the mouth. Indigestible waste is ejected through the mouth, in animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the formation of the gut. In deuterostomes, the blastopore becomes the anus while the gut tunnels through to make another opening. In the protostomes, it used to be thought that the formed the mouth while the anus formed later as an opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the slit-like blastopore close up in the middle, apart from sponges and placozoans, almost all animals have an internal gut cavity which is lined with gastrodermal cells. In less advanced invertebrates such as the sea anemone, the mouth also acts as an anus, circular muscles around the mouth are able to relax or contract in order to open or close it. A fringe of tentacles thrusts food into the cavity and it can gape widely enough to large prey items. Food passes first into a pharynx and digestion occurs extracellularly in the gastrovascular cavity, annelids have simple tube-like gets and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients. Many molluscs have a radula which is used to scrape microscopic particles off surfaces, in invertebrates with hard exoskeletons, various mouthparts may be involved in feeding behaviour. Insects have a range of mouthparts suited to their mode of feeding and these include mandibles, maxillae and labium and can be modified into suitable appendages for chewing, cutting, piercing, sponging and sucking. Decapods have six pairs of appendages, one pair of mandibles. Sea urchins have a set of five sharp calcareous plates which are used as jaws and are known as Aristotles lantern, in vertebrates, the first part of the digestive system is the buccal cavity, commonly known as the mouth
25.
Occupational Safety and Health Administration
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The Occupational Safety and Health Administration is an agency of the United States Department of Labor. Congress established the agency under the Occupational Safety and Health Act, OSHAs mission is to assure safe and healthful working conditions for working men and women by setting and enforcing standards and by providing training, outreach, education and assistance. The agency is charged with enforcing a variety of whistleblower statutes. OSHA is currently headed by Assistant Secretary of Labor David Michaels, OSHAs workplace safety inspections have been shown to reduce injury rates and injury costs without adverse effects to employment, sales, credit ratings, or firm survival. OSHA officially formed on April 28,1971, the date that the OSH Act became effective, george Guenther was appointed as the agencys first director. OSHA has a number of training, compliance assistance, and health, the OSHA Training Institute, which trains government and private sector health and safety personnel, began in 1972. In 1978, the agency began a program, now called the Susan Harwood Training Grant Program. OSHA started the Voluntary Protection Programs in 1982, which allow employers to apply as model workplaces to achieve special designation if they meet certain requirements. OSHA covers most private sector employers in all 50 states, the District of Columbia, state plans are OSHA-approved job safety and health programs operated by individual states instead of federal OSHA. Federal OSHA approves and monitors all state plans and provides as much as fifty percent of the funding for each program, state-run safety and health programs are required to be at least as effective as the federal OSHA program. Federal OSHA provides coverage to certain workplaces specifically excluded from a state’s plan — for example, workers at state and local government agencies are not covered by federal OSHA, but have OSH Act protections if they work in those states that have an OSHA-approved state program. OSHA rules also permit states and territories to develop plans that only public sector workers. In these cases, private sector workers and employers remain under federal OSHA jurisdiction. Five additional states and one U. S. territory have OSHA approved state plans that cover public sector only, Connecticut, Illinois, Maine, New Jersey, New York. OSHA’s protection applies to all federal agencies, section 19 of the OSH Act makes federal agency heads responsible for providing safe and healthful working conditions for their workers. OSHA conducts inspections of facilities in response to workers’ reports of hazards. Federal agencies must have a safety and health program that meets the standards as private employers. Under a 1998 amendment, the OSHA Act covers the U. S. Postal Service the same as any private sector employer, the self-employed, immediate family members of farm employers, and workplace hazards regulated by another federal agency
26.
United States Environmental Protection Agency
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The EPA was proposed by President Richard Nixon and began operation on December 2,1970, after Nixon signed an executive order. The order establishing the EPA was ratified by committee hearings in the House, the agency is led by its Administrator, who is appointed by the president and approved by Congress. The current administrator is Scott Pruitt, the EPA is not a Cabinet department, but the administrator is normally given cabinet rank. The EPA has its headquarters in Washington, D. C. regional offices for each of the ten regions. The agency conducts environmental assessment, research, and education and it has the responsibility of maintaining and enforcing national standards under a variety of environmental laws, in consultation with state, tribal, and local governments. It delegates some permitting, monitoring, and enforcement responsibility to U. S. states, EPA enforcement powers include fines, sanctions, and other measures. The agency also works with industries and all levels of government in a variety of voluntary pollution prevention programs. In 2016, the agency had 15,376 full-time employees, more than half of EPAs employees are engineers, scientists, and environmental protection specialists, other employees include legal, public affairs, financial, and information technologists. Beginning in the late 1950s and through the 1960s, Congress reacted to increasing concern about the impact that human activity could have on the environment. Senator James E. Murray introduced a bill, the Resources and Conservation Act of 1959, the 1962 publication of Silent Spring by Rachel Carson alerted the public about the detrimental effects on the environment of the indiscriminate use of pesticides. In the years following, similar bills were introduced and hearings were held to discuss the state of the environment, in the colloquium, some members of Congress expressed a continuing concern over federal agency actions affecting the environment. The National Environmental Policy Act of 1969 was modeled on RCA, President Nixon signed NEPA into law on January 1,1970. The law created the Council on Environmental Quality in the Executive Office of the President, NEPA required that a detailed statement of environmental impacts be prepared for all major federal actions significantly affecting the environment. The detailed statement would ultimately be referred to as an impact statement. On July 9,1970, Nixon proposed a reorganization that consolidated many environmental responsibilities of the federal government under one agency. After conducting hearings during that summer, the House and Senate approved the proposal, the agency’s first administrator, William Ruckelshaus, took the oath of office on December 4,1970. In May 2013, Congress renamed the EPA headquarters as the William Jefferson Clinton Federal Building, the EPA is led by an Administrator of the Environmental Protection Agency. As of 2017 Scott Pruitt is the 14th administrator, each EPA regional office is responsible within its states for implementing the Agencys programs, except those programs that have been specifically delegated to states
27.
Parts per Billion
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Parts Per Billion is a 2014 romantic drama written and directed by Brian Horiuchi. Erik, a musician who lives off his familys considerable wealth, clashes with his girlfriend, Anna. At the same time, Len and Mia, a married couple, Len, a depressed and unemployed writer, struggles to find direction in his life. He confesses to his sister, a nurse named Sarah, that he has taken his wife, Mia, Mia, an accomplished lawyer, has just successfully represented Andy, a scientist of some renown, from accusations of selling trade secrets to a research facility in the 1970s. Anna, worried about visions that she has had recently of an apocalypse that involve a young girl, confides in Rick, Lens best friend. Andy, Eriks grandfather, insists that he take more money, misunderstanding Eriks motives, Andy accuses Erik of being too good to take his money, as it was made through the production of biological weapons. Although Andy admits that he knew that the research was likely unethical, his wife, Esther, brushes off his guilt, meanwhile, the situation in the Middle East worsens considerably. Biological weapons are at first rumored to have deployed, then proven. Although the United States urges calm, Europe suffers massive casualties as trade winds blow the toxins westward, Andy, aware of the worst-case scenarios, urges Sarah to take appropriate precautions when she attends to him and his wife. Sarah in turn alerts Len, who takes Mia into their basement, as panic spreads through the country following loss of contact with the East Coast, Rick attempts to purchase a survival kit. When he comes up short of money, he grabs one and begs to be given a chance for survival, Andy and Esther survive through the use of oxygen tanks. Esther, an optimist, believes that Erik and Anna have survived somehow, but Andy, flashbacks interspersed with Andys and Esthers argument show Erik and Anna playfully flirting, having sex, and celebrating the news that Anna is pregnant. The flashbacks end with the apparent deaths of both Anna and Erik as they lie in bed, Andy and Esther set out to the local hospital to recover more oxygen tanks, where they discover Sarahs body. Discouraged, Esther begins to lose the will to live, at the same time, Len and Mia debate whether they should commit suicide together. Len is hurt by Mias admission that she failed to discourage a coworker from falling in love with her, Mia mocks Lens Adam and Eve scenario where they rebuild civilization, but Len begs her to stay with him, Mia tearfully pauses on the basement stairs. In the final scene, the girl that Anna saw in her visions earlier is depicted finding Annas ring and showing it to her mother. However, conflicting shooting schedules with another film, The Twilight Saga, New Moon, on December 12,2012, AKA/Bow Street Films announced that Teresa Palmer, Penn Badgley, Hill Harper and Alexis Bledel had joined the cast. Shooting was scheduled to begin in Detroit and last all through Christmas, also announced as cast members were Gena Rowlands, Frank Langella, Josh Hartnett, Molly Haskell, and Jennifer Levine
28.
Activated carbon
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Activated carbon, also called activated charcoal, is a form of carbon processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions. Activated is sometimes substituted with active, due to its high degree of microporosity, just one gram of activated carbon has a surface area in excess of 3,000 m2, as determined by gas adsorption. An activation level sufficient for useful application may be attained solely from high surface area, activated carbon is usually derived from charcoal and is sometimes utilized as biochar. Those derived from coal and coke are referred as activated coal, one major industrial application involves use of activated carbon in the metal finishing field. It is very widely employed for purification of electroplating solutions, for example, it is a main purification technique for removing organic impurities from bright nickel plating solutions. A variety of chemicals are added to plating solutions for improving their deposit qualities and for enhancing properties like brightness, smoothness, ductility. Due to passage of current and electrolytic reactions of anodic oxidation and cathodic reduction. Their excessive build up can adversely affect the quality and physical properties of deposited metal. Activated carbon treatment removes such impurities and restores plating performance to the desired level, activated carbon is used to treat poisonings and overdoses following oral ingestion. Tablets or capsules of activated carbon are used in countries as an over-the-counter drug to treat diarrhea, indigestion. However, it is ineffective for a number of poisonings including strong acids or alkali, cyanide, iron, lithium, arsenic, incorrect application results in pulmonary aspiration, which can sometimes be fatal if immediate medical treatment is not initiated. During early implementation of the 1974 Safe Drinking Water Act in the USA, activated carbon is also used for the measurement of radon concentration in air. Activated carbon is a substance used by organic farmers in both livestock production and wine making. In livestock production it is used as a pesticide, animal feed additive, processing aid, benefits in case of animal feed additive are questionable. In organic winemaking, activated carbon is allowed for use as an agent to absorb brown color pigments from white grape concentrates. Activated carbon filters can be used to filter vodka and whiskey of organic impurities which can affect color, taste, research is being done testing various activated carbons ability to store natural gas and hydrogen gas. The porous material acts like a sponge for different types of gases, the gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve bonding energies of 5–10 kJ per mol, the gas may then be desorbed when subjected to higher temperatures and either combusted to do work or in the case of hydrogen gas extracted for use in a hydrogen fuel cell
29.
University of Science, Malaysia
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University of Science, Malaysia is a publicly-funded Autonomous university in Malaysia. Founded on 10 June 1969, it is among the oldest institute of learning in Northern Malaysia. It has three campuses, a campus on the island of Penang, a health campus in Kelantan. There is offshore collaboration with KLE University, India offering the Doctor of Medicine undergraduate degree, USM plans to open a Global Campus located at Kuala Lumpur Education City. With around 28,300 postgraduate and undergraduate students in 2009, the number of lecturers is about 1,479, which leads to a student-lecturer ratio of around 19,1. The idea of a university in Penang was first mooted by D. S. Ramanathan in 1959 in the State Assembly, USM was established in 1969 as the second university in Malaysia. It was first known as Universiti Pulau Pinang, the university operated on borrowed premises at the Malayan Teachers Training College at Gelugor. In 1971, it moved to its present 239-hectare site at Minden in Gelugor,10 kilometres from the city of Georgetown. There are two other USM campuses, one at Kubang Kerian in Kelantan, known as the Health campus, the former houses the School of Medical Sciences, the School of Health Sciences and the School of Dental Sciences, while the latter houses the six engineering schools. USM offers courses at undergraduate and postgraduate levels to more than 28,000 students, USM has won the Asian Innovation Award in which USM emerged as the only winner from this country. There are three Deputy Vice-Chancellors led by the Vice-Chancellor, in August 2011 USM created a new role of Ombudsman to deal with staff issues and protect whistleblowers. The USM Ombudsman is Prof. Dato Seri Dr, salleh Yaapar, who is a former staff of the USM and is on a rolling 2-year contract. Twenty four academic schools,14 centres and 7 units have been established, the three liberal arts schools are Educational Studies, Humanities, and Social Sciences. There is offshore collaboration with KLE University, India offering the Doctor of Medicine undergraduate degree and this offshore five-year M. D. programme is conducted at the Jawaharlal Nehru Medical College, KLE University, Belgaum, India. In India, USM also has a collaboration with the James Lind Institute for conducting Translational Medicine programs, in December 1989, the School of Management was set up, having evolved from the Management program within the School of Social Sciences. As part of its expansion, the university established the School of Computer Sciences. In 2008, Professor Maqsudul Alam, set up the Centre for Chemical Biology where he became its first Chief Executive Officer and Director, there are research centres, namely the Centre for Policy Research, the Centre for Drug Research and the Centre for Marine and Coastal Studies. The distance education program offered through the School of Distance Education was adopted by the university in 1971, USM is one of six universities in Malaysia that have been identified as research-intensive universities, with the other being University of Malaya and Universiti Putra Malaysia
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Chitosan
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Chitosan /ˈkaɪtəsæn/ is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine. It is made by treating the chitin shells of shrimp and other crustaceans with an alkaline substance, chitosan has a number of commercial and possible biomedical uses. It can be used in agriculture as a treatment and biopesticide. In winemaking, it can be used as a fining agent, in industry, it can be used in a self-healing polyurethane paint coating. In medicine, it may be useful in bandages to reduce bleeding and as an antibacterial agent, more controversially, chitosan has been asserted to have use in limiting fat absorption, which would make it useful for dieting, but there is evidence against this. Other uses of chitosan that have been researched include use as a dietary fiber. Chitosan is produced commercially by deacetylation of chitin, which is the element in the exoskeleton of crustaceans. The degree of deacetylation can be determined by NMR spectroscopy, on average, the molecular weight of commercially produced chitosan is between 3800 and 20,000 Daltons. A common method for the synthesis of chitosan is the deacetylation of chitin using sodium hydroxide in excess as a reagent, the reaction occurs in two stages under first-order kinetic control. Activation energy for the first step is higher than the second and this reaction pathway, when allowed to go to completion yields up to 98% product. The amino group in chitosan has a pKa value of ~6.5, which leads to a protonation in acidic to neutral solution with a density dependent on pH. This makes chitosan water-soluble and a bioadhesive which readily binds to negatively charged surfaces such as mucosal membranes, chitosan enhances the transport of polar drugs across epithelial surfaces, and is biocompatible and biodegradable. It is not approved by FDA for drug delivery though, purified quantities of chitosans are available for biomedical applications. Chitosan and its derivatives, such as trimethylchitosan, have used in nonviral gene delivery. Oligomeric derivatives are relatively nontoxic and have good gene delivery properties, the cellular targets are the plasma membrane and nuclear chromatin. Subsequent changes occur in cell membranes, chromatin, DNA, calcium, MAP Kinase, oxidative burst, reactive species, callose pathogenesis-related genes. Since 1986, the United States Environmental Protection Agency has regulated chitosan for agricultural use, the natural biocontrol active ingredients, chitin/chitosan, are found in the shells of crustaceans, such as lobsters, crabs, and shrimp, and many other organisms, including insects and fungi. It is one of the most abundant biodegradable materials in the world, degraded molecules of chitin/chitosan exist in soil and water
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Ion
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An ion is an atom or a molecule in which the total number of electrons is not equal to the total number of protons, giving the atom or molecule a net positive or negative electrical charge. Ions can be created, by chemical or physical means. In chemical terms, if an atom loses one or more electrons. If an atom gains electrons, it has a net charge and is known as an anion. Ions consisting of only a single atom are atomic or monatomic ions, because of their electric charges, cations and anions attract each other and readily form ionic compounds, such as salts. In the case of ionization of a medium, such as a gas, which are known as ion pairs are created by ion impact, and each pair consists of a free electron. The word ion comes from the Greek word ἰόν, ion, going and this term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that goes from one electrode to the other through an aqueous medium. Faraday also introduced the words anion for a charged ion. In Faradays nomenclature, cations were named because they were attracted to the cathode in a galvanic device, arrhenius explanation was that in forming a solution, the salt dissociates into Faradays ions. Arrhenius proposed that ions formed even in the absence of an electric current, ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of charge to give neutral molecules or ionic salts. These stabilized species are commonly found in the environment at low temperatures. A common example is the present in seawater, which are derived from the dissolved salts. Electrons, due to their mass and thus larger space-filling properties as matter waves, determine the size of atoms. Thus, anions are larger than the parent molecule or atom, as the excess electron repel each other, as such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation contains no electrons, and thus consists of a single proton - very much smaller than the parent hydrogen atom. Since the electric charge on a proton is equal in magnitude to the charge on an electron, an anion, from the Greek word ἄνω, meaning up, is an ion with more electrons than protons, giving it a net negative charge. A cation, from the Greek word κατά, meaning down, is an ion with fewer electrons than protons, there are additional names used for ions with multiple charges
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Adsorption
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Adsorption is the adhesion of atoms, ions, or molecules from a gas, liquid, or dissolved solid to a surface. This process creates a film of the adsorbate on the surface of the adsorbent and this process differs from absorption, in which a fluid is dissolved by or permeates a liquid or solid, respectively. Adsorption is a process while absorption involves the whole volume of the material. The term sorption encompasses both processes, while desorption is the reverse of it, similar to surface tension, adsorption is a consequence of surface energy. In a bulk material, all the requirements of the constituent atoms of the material are filled by other atoms in the material. However, atoms on the surface of the adsorbent are not wholly surrounded by other adsorbent atoms, the exact nature of the bonding depends on the details of the species involved, but the adsorption process is generally classified as physisorption or chemisorption. It may also occur due to electrostatic attraction, pharmaceutical industry applications, which use adsorption as a means to prolong neurological exposure to specific drugs or parts thereof, are lesser known. The word adsorption was coined in 1881 by German physicist Heinrich Kayser, adsorption is usually described through isotherms, that is, the amount of adsorbate on the adsorbent as a function of its pressure or concentration at constant temperature. The quantity adsorbed is nearly always normalized by the mass of the adsorbent to allow comparison of different materials, to date,15 different isothem models were developed. The function is not adequate at very high pressure because in reality x / m has a maximum as pressure increases without bound. As the temperature increases, the k and n change to reflect the empirical observation that the quantity adsorbed rises more slowly. Irving Langmuir was the first to derive a scientifically based adsorption isotherm in 1918, the model applies to gases adsorbed on solid surfaces. It is a semi-empirical isotherm with a basis and was derived based on statistical thermodynamics. It is the most common isotherm equation to use due to its simplicity and it is based on four assumptions, All of the adsorption sites are equivalent and each site can only accommodate one molecule. The surface is energetically homogeneous and adsorbed molecules do not interact, at the maximum adsorption, only a monolayer is formed. Adsorption only occurs on localized sites on the surface, not with other adsorbates, the fourth condition is the most troublesome, as frequently more molecules will adsorb to the monolayer, this problem is addressed by the BET isotherm for relatively flat surfaces. The Langmuir isotherm is nonetheless the first choice for most models of adsorption, Langmuir suggested that adsorption takes place through this mechanism, A g + S ⇌ A S, where A is a gas molecule and S is an adsorption site. The direct and inverse rate constants are k and k−1, vmon is related to the number of adsorption sites through the ideal gas law
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Oxyanions
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An oxyanion or oxoanion is an ion with the generic formula AxOz−y. Oxoanions are formed by a majority of the chemical elements. The formulae of simple oxoanions are determined by the octet rule, the structures of condensed oxoanions can be rationalized in terms of AOn polyhedral units with sharing of corners or edges between polyhedra. The phosphate and polyphosphate esters adenosine monophosphate, adenosine diphosphate and adenosine triphosphate are important in biology, the formula of monomeric oxoanions, AOm−n, is dictated by the oxidation state of the element A and its position in the periodic table. Elements of the first row are limited to a coordination number of 4. However, none of the first row elements has a monomeric oxoanion with that coordination number, instead, carbonate and nitrate have a trigonal planar structure with π bonding between the central atom and the oxygen atoms. This π bonding is favoured by the similarity in size of the central atom, the oxoanions of second-row elements in the group oxidation state are tetrahedral. Tetrahedral SiO4 units are found in minerals, SiO4. Phosphate, sulfate, and perchlorate ions can be found as such in various salts, many oxoanions of elements in lower oxidation state obey the octet rule and this can be used to rationalize the formulae adopted. For example, chlorine has two valence electrons so it can accommodate three electron pairs from bonds with oxide ions, the charge on the ion is +5 −3 ×2 = −1, and so the formula is ClO−3. The structure of the ion is predicted by VSEPR theory to be pyramidal, in a similar way, the oxyanion of chlorine has the formula ClO−2, and is bent with two lone pairs and two bonding pairs. In the third and subsequent rows of the table, 6-coordination is possible. Thus molybdenum does not form MoO6−6, but forms the tetrahedral molybdate anion, moO6 units are found in condensed molybdates. Fully protonated oxoanions with a structure are found in such species as Sn2−6. The naming of monomeric oxoanions follows the following rules, the amount of order in the solution is decreased, releasing a certain amount of entropy which makes the Gibbs free energy more negative and favors the forward reaction. It is an example of a reaction with the monomeric oxoanion acting as a base. The reverse reaction is a reaction, as a water molecule. Further condensation may occur, particularly with anions of higher charge, the conversion of ATP to ADP is an hydrolysis reaction and is an important source of energy in biological systems
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Tobacco smoke
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Tobacco smoke is an aerosol produced by the incomplete combustion of tobacco during the smoking of cigarettes, pipes, or cigars. Temperatures in burning cigarettes range from about 400 ℃ between puffs to about 900 ℃ during a puff, during the burning of tobacco, thousands of chemical substances are generated by combustion, distillation, pyrolysis, and pyrosynthesis. Tobacco smoke is used as a fumigant and inhalant, the particles in tobacco smoke are liquid aerosol droplets, with a mass median aerodynamic diameter that is submicrometer. The droplets are present in high concentrations, tobacco smoke may be grouped into a particulate phase and a gas/vapor phase. Tar is mathematically determined by subtracting the weight of the nicotine, however, several components of tobacco smoke do not fit neatly into this rather arbitrary classification, because they are distributed among the solid, liquid and gaseous phases. The radioactive element polonium-210 is also known to occur in tobacco smoke, the chemical composition of smoke depends on puff frequency, intensity, volume, and duration at different stages of cigarette consumption. Between 1933 and the late 1940s, the yields from an average cigarette varied from 33 to 49 mg tar and from <1 to 3 mg nicotine. However, in the 1960s and 1970s, the yield from cigarettes in Western Europe. The development of lower tar and nicotine cigarettes has tended to yield products that lacked the taste components to which the smoker had become accustomed, in order to keep such products acceptable to the consumer, the manufacturers reconstitute aroma or flavor. The actual mechanisms by which smoking can cause so many diseases remain largely unknown, many attempts have been made to produce lung cancer in animals exposed to tobacco smoke by the inhalation route, without success. It is only by collecting the tar and repeatedly painting this on to mice that tumors are produced, tobacco smoke is associated with an increased risk of developing respiratory conditions such as bronchitis, pneumonia, and asthma. Tobacco smoke aerosols generated at temperatures below 400 ℃ did not test positive in the Ames assay, the shift over the years from higher- to lower-yield cigarettes may explain the change in the pathology of lung cancer. That is, the percentage of cancers that are adenocarcinomas has increased. In the United States, lung cancer incidence and mortality rates are high among African American men. Lung cancer tends to be most common in developed countries, particularly in North America and Europe, over 85% of all lung cancers are attributed to cigarette smoking, however, only a fraction of long-term cigarette smokers develop lung cancer. Cancer of the lung is occasionally observed among nonsmokers, indicating a genetic susceptibility in lung tumorigenesis, the incidence of lung cancer seems to have increased in dogs as well as in humans and cigarette smoking can hardly be incriminated. Tobacco polyphenols determine the taste and quality of the smoke, freshly cured tobacco leaf is unfit for use because of its pungent and irritating smoke. After fermentation and aging, the leaf delivers mild and aromatic smoke, plant smoke in general has a bacteriostatic effect and is one of the oldest methods of preserving meat
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Orica
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Founded in 1874, has a workforce of around 11,500 employees and contractors, servicing customers across more than 100 countries. Orica is listed on the Australian Securities Exchange, initially formed over 140 years ago as Jones, Scott and Co. a supplier of explosives during the Victorian gold rush, the company was bought by Nobel Industries. Nobel later merged with several British chemical manufacturers to form Imperial Chemical Industries, in 1928, Imperial Chemical Industries of Australia and New Zealand was incorporated to acquire and coordinate all the Australasian interests of ICI Plc. In July 1997, ICI Australia became an independent Australasian company after its parent company, ICI Plc, as a result of the selldown ICI Australia was required to change its name and on 2 February 1998 became known as Orica. In 2010, Orica successfully demerged Dulux Group leaving the company to focus on the provision of services to the mining, construction, in November 2014, Orica Limited announced the sale of its Chemicals business to the Blackstone Group. The sale was completed on 2 March 2015, and the Chemicals business now operates under the name Ixom. Oricas revenue in 2016 was AUD$5.1 billion and statutory net profit after tax attributable to the shareholders of Orica for the year ended 30 September 2016 was $343 million. Orica is a member of the Dow Jones Sustainability Index, the Australian SAM Sustainability Index and these Indexes provide a benchmark for the performance of investments in sustainable companies and funds. Orica releases an annual Sustainability Report that outlines performance against key sustainability metrics, registered Trademark for Hercules Inc. in 1967, but it is now owned by Orica Explosives Technology Pty Ltd. Minova is a member of the Orica Group, products and services include, Analysers PRO Service Data, Reporting & Analytics Sparge Training Orica is co-naming sponsor of the Orica–Scott men’s and women’s professional cycling team. In June 2016, Orica announced that it would be exiting its sponsorship of the men’s and women’s cycling teams at the end of the 2017 calendar year and it is one of the few post-war office buildings to be found on the Victorian Heritage Register. In March 2015 then CEO Ian Smith was ousted from the due to bullying of a female employee. During Smiths tenure as CEO, the majority of the leadership within the organization left for other companies. The main chemical contaminant found in groundwater around the old ICI site is EDC, Orica has built an A$167 million Groundwater Treatment Plant to achieve containment of this contamination and provide high quality industrial water to Botany Industrial Park. Water produced by Oricas GTP saves Sydneys potable water supply around 5 megalitres per day, residents in the area were banned from accessing the groundwater. Orica estimated in 2012 that the GTP had been in operation for seven years of its 30–year design life cycle, the Botany chemical plant released mercury vapour into the atmosphere on 27 September 2011, breaching environmental standards for nine hours. An air monitor located near residents at Banksmeadow detected the mercury vapour, dr Mariann Lloyd Smith, said the length of time the emissions last was extraordinary, Mercury is extremely toxic. It is recognised as one of the most important and most hazardous toxins that we deal with, the mercury vapour was associated with mercury which had polluted the soil on the Orica site, due to leaking pipes
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Ammonium nitrate
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Ammonium nitrate is a chemical compound, the nitrate salt of the ammonium cation. It has the chemical formula NH4NO3, simplified to N2H4O3 and it is a white crystal solid and is highly soluble in water. It is predominantly used in agriculture as a high-nitrogen fertilizer and its other major use is as a component of explosive mixtures used in mining, quarrying, and civil construction. It is the constituent of ANFO, a popular industrial explosive which accounts for 80% of explosives used in North America. Many countries are phasing out its use in consumer applications due to concerns over its potential for misuse, ammonium nitrate was mined there in the past, but virtually 100% of the chemical now used is synthetic. This reaction is violent owing to its exothermic nature. After the solution is formed, typically at about 83% concentration, the AN melt is then made into prills or small beads in a spray tower, or into granules by spraying and tumbling in a rotating drum. The prills or granules may be dried, cooled. These prills or granules are the typical AN products in commerce, the ammonia required for this process is obtained by the Haber process from nitrogen and hydrogen. Ammonia produced by the Haber process is oxidized to nitric acid by the Ostwald process, transformations of the crystal states due to changing conditions affect the physical properties of ammonium nitrate. Ammonium nitrate is an important fertilizer with the NPK rating 34-0-0 and it is less concentrated than urea, giving ammonium nitrate a slight transportation disadvantage. Ammonium nitrates advantage over urea is that it is more stable, during warm weather it is best to apply urea soon before rain is expected or to cover it with soil to minimize nitrogen loss. ANFO is a mixture of 94% ammonium nitrate and 6% fuel oil used as a bulk industrial explosive. Ammonium nitrate-based explosives were used in the Oklahoma City Bombing in 1995 and 2011 Delhi bombings, the 2013 Hyderabad blasts, due to these bans, Potassium chlorate — the stuff that makes matches catch fire — has surpassed fertilizer as the explosive of choice for insurgents. Ammonium nitrate is used in instant cold packs, as its dissolution in water is highly endothermic. Health and safety data are shown on the safety data available from suppliers. Heating or any ignition source may cause violent combustion or explosion, ammonium nitrate reacts with combustible and reducing materials as it is a strong oxidant. Although it is used for fertilizer, it can be used for explosives
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Stockton, New South Wales
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Stockton is a suburb of Newcastle, New South Wales, Australia, located 600 m from Newcastles central business district. It is the residential suburb of Newcastle that lies north of the Hunter River. Stockton is a peninsula, with the Hunter River at the south and south-west, on the eastern side are sand dunes and surfing beaches, with numerous shipwrecks at its north, while on the western side there are marshes, where many migratory birds can be spotted. There are numerous spots at Stockton suitable for recreational fishing, for many years, Stockton was linked to Newcastles Central Business District at the south by passenger and vehicular ferry services. While there is still a ferry service, vehicular traffic is now connected by the Stockton Bridge. Stockton was settled almost as soon as the foundation of Newcastle in 1797 and it was originally called Pirates Point as the result of escaped convicts being shipwrecked on the peninsula in 1800. The southern tip of the peninsula, near the breakwater is still known as Pirate Point. For much of the 19th century it served as an industrial, in 1896 tragedy struck the local colliery, in which a gas leak killed 11 people. It has become a dormitory suburb during the 20th century. Stocktonians are particularly proud of Dave Sands, a local resident, like the Colliery Disaster, the short life of Sands was commemorated by some of the numerous memorials across this seaside village. Stockton Beach is also known as the location of the 1989 rape and murder of Newcastle High School student, a play, Blackrock, and also a film of the same name, were inspired by this event. Despite being technically an inner-city suburb of Newcastle, Stockton has a country town atmosphere because of its isolation and it has its own shops, churches, two clubhouses, three pubs, a swimming pool, and a caravan park. It also has a residential unit for people with developmental disability, a public primary school. High school students catch the ferry or bus to go to schools in the city of Newcastle, Stockton was traditionally a working-class suburb. The Leigh Leigh murder caused irreparable damage to the community of Stockton. The crime has been described as a barely healed wound for Stockton, in recent years, however, the town has begun to re-invent itself with a push for young professionals to move in from other centres such as Sydney. This practice has led to an increase in real estate prices, Stockton includes a district cricket team. It also has a soccer club, the Stockton Sharks Soccer Club
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Prevailing winds
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Prevailing winds are winds that blow predominantly from a single general direction over a particular point on the Earths surface. The dominant winds are the trends in direction of wind with the highest speed over a point on the Earths surface. A regions prevailing and dominant winds acted by global patterns of movement in the Earths atmosphere, in general, easterly flow occurs at low and medium latitudes globally. In the mid-latitudes, westerly winds are the rule and their strength is determined by the polar cyclone. Highly elevated surfaces can induce a thermal low, which augments the environmental wind flow. Wind roses are used to determine the direction of the prevailing wind. Knowledge of the wind allows the development of prevention strategies for wind erosion of agricultural land. Sand dunes can orient themselves, or perpendicular to, the wind regime within coastal. Insects drift along with the wind, while birds are able to fly more independently of it. Prevailing winds in moun locations can lead to significant rainfall gradients within the topography, prevailing winds can have differences due to the uneven heating of the Earth. A wind rose is a tool used by meteorologists to give a succinct view of how wind speed. Presented in a coordinate grid, the wind rose shows the frequency of winds blowing from particular directions. The length of each spoke around the circle is related to the frequency that the blows from a particular direction per unit time. Each concentric circle represents a different frequency, emanating from zero at the center to increasing frequencies at the outer circles, a wind rose plot may contain additional information, in that each spoke is broken down into color-coded bands that show wind direction ranges. Wind roses typically use 8 or 16 cardinal directions, such as north, NNE, NE, the trade winds are the prevailing pattern of easterly surface winds found in the tropics near the Earths equator, equatorward of the subtropical ridge. These winds blow predominantly from the northeast in the Northern Hemisphere, the trade winds act as the steering flow for tropical cyclones that form over worlds oceans, guiding their path westward. Trade winds also steer African dust westward across the Atlantic Ocean into the Caribbean sea and these prevailing winds blow from the west to the east, and steer extra-tropical cyclones in this general manner. The winds are predominantly from the southwest in the Northern Hemisphere, the westerlies can be particularly strong, especially in the southern hemisphere, where there is less land in the middle latitudes to cause the flow pattern to amplify, which slows the winds down
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