1.
ChEMBL
–
ChEMBL or ChEMBLdb is a manually curated chemical database of bioactive molecules with drug-like properties. It is maintained by the European Bioinformatics Institute, of the European Molecular Biology Laboratory, based at the Wellcome Trust Genome Campus, Hinxton, the database, originally known as StARlite, was developed by a biotechnology company called Inpharmatica Ltd. later acquired by Galapagos NV. The data was acquired for EMBL in 2008 with an award from The Wellcome Trust, resulting in the creation of the ChEMBL chemogenomics group at EMBL-EBI, the ChEMBL database contains compound bioactivity data against drug targets. Bioactivity is reported in Ki, Kd, IC50, and EC50, data can be filtered and analyzed to develop compound screening libraries for lead identification during drug discovery. ChEMBL version 2 was launched in January 2010, including 2.4 million bioassay measurements covering 622,824 compounds and this was obtained from curating over 34,000 publications across twelve medicinal chemistry journals. ChEMBLs coverage of available bioactivity data has grown to become the most comprehensive ever seen in a public database, in October 2010 ChEMBL version 8 was launched, with over 2.97 million bioassay measurements covering 636,269 compounds. ChEMBL_10 saw the addition of the PubChem confirmatory assays, in order to integrate data that is comparable to the type, ChEMBLdb can be accessed via a web interface or downloaded by File Transfer Protocol. It is formatted in a manner amenable to computerized data mining, ChEMBL is also integrated into other large-scale chemistry resources, including PubChem and the ChemSpider system of the Royal Society of Chemistry. In addition to the database, the ChEMBL group have developed tools and these include Kinase SARfari, an integrated chemogenomics workbench focussed on kinases. The system incorporates and links sequence, structure, compounds and screening data, the primary purpose of ChEMBL-NTD is to provide a freely accessible and permanent archive and distribution centre for deposited data. July 2012 saw the release of a new data service, sponsored by the Medicines for Malaria Venture. The data in this service includes compounds from the Malaria Box screening set, myChEMBL, the ChEMBL virtual machine, was released in October 2013 to allow users to access a complete and free, easy-to-install cheminformatics infrastructure. In December 2013, the operations of the SureChem patent informatics database were transferred to EMBL-EBI, in a portmanteau, SureChem was renamed SureChEMBL. 2014 saw the introduction of the new resource ADME SARfari - a tool for predicting and comparing cross-species ADME targets
2.
ChemSpider
–
ChemSpider is a database of chemicals. ChemSpider is owned by the Royal Society of Chemistry, the database contains information on more than 50 million molecules from over 500 data sources including, Each chemical is given a unique identifier, which forms part of a corresponding URL. This is an approach to develop an online chemistry database. The search can be used to widen or restrict already found results, structure searching on mobile devices can be done using free apps for iOS and for the Android. The ChemSpider database has been used in combination with text mining as the basis of document markup. The result is a system between chemistry documents and information look-up via ChemSpider into over 150 data sources. ChemSpider was acquired by the Royal Society of Chemistry in May,2009, prior to the acquisition by RSC, ChemSpider was controlled by a private corporation, ChemZoo Inc. The system was first launched in March 2007 in a release form. ChemSpider has expanded the generic support of a database to include support of the Wikipedia chemical structure collection via their WiChempedia implementation. A number of services are available online. SyntheticPages is an interactive database of synthetic chemistry procedures operated by the Royal Society of Chemistry. Users submit synthetic procedures which they have conducted themselves for publication on the site and these procedures may be original works, but they are more often based on literature reactions. Citations to the published procedure are made where appropriate. They are checked by an editor before posting. The pages do not undergo formal peer-review like a journal article. The comments are moderated by scientific editors. The intention is to collect practical experience of how to conduct useful chemical synthesis in the lab, while experimental methods published in an ordinary academic journal are listed formally and concisely, the procedures in ChemSpider SyntheticPages are given with more practical detail. Comments by submitters are included as well, other publications with comparable amounts of detail include Organic Syntheses and Inorganic Syntheses
3.
European Chemicals Agency
–
ECHA is the driving force among regulatory authorities in implementing the EUs chemicals legislation. ECHA helps companies to comply with the legislation, advances the safe use of chemicals, provides information on chemicals and it is located in Helsinki, Finland. The Agency, headed by Executive Director Geert Dancet, started working on 1 June 2007, the REACH Regulation requires companies to provide information on the hazards, risks and safe use of chemical substances that they manufacture or import. Companies register this information with ECHA and it is freely available on their website. So far, thousands of the most hazardous and the most commonly used substances have been registered, the information is technical but gives detail on the impact of each chemical on people and the environment. This also gives European consumers the right to ask whether the goods they buy contain dangerous substances. The Classification, Labelling and Packaging Regulation introduces a globally harmonised system for classifying and labelling chemicals into the EU. This worldwide system makes it easier for workers and consumers to know the effects of chemicals, companies need to notify ECHA of the classification and labelling of their chemicals. So far, ECHA has received over 5 million notifications for more than 100000 substances, the information is freely available on their website. Consumers can check chemicals in the products they use, Biocidal products include, for example, insect repellents and disinfectants used in hospitals. The Biocidal Products Regulation ensures that there is information about these products so that consumers can use them safely. ECHA is responsible for implementing the regulation, the law on Prior Informed Consent sets guidelines for the export and import of hazardous chemicals. Through this mechanism, countries due to hazardous chemicals are informed in advance and have the possibility of rejecting their import. Substances that may have effects on human health and the environment are identified as Substances of Very High Concern 1. These are mainly substances which cause cancer, mutation or are toxic to reproduction as well as substances which persist in the body or the environment, other substances considered as SVHCs include, for example, endocrine disrupting chemicals. Companies manufacturing or importing articles containing these substances in a concentration above 0 and they are required to inform users about the presence of the substance and therefore how to use it safely. Consumers have the right to ask the retailer whether these substances are present in the products they buy, once a substance has been officially identified in the EU as being of very high concern, it will be added to a list. This list is available on ECHA’s website and shows consumers and industry which chemicals are identified as SVHCs, Substances placed on the Candidate List can then move to another list
4.
International Chemical Identifier
–
Initially developed by IUPAC and NIST from 2000 to 2005, the format and algorithms are non-proprietary. The continuing development of the standard has supported since 2010 by the not-for-profit InChI Trust. The current version is 1.04 and was released in September 2011, prior to 1.04, the software was freely available under the open source LGPL license, but it now uses a custom license called IUPAC-InChI Trust License. Not all layers have to be provided, for instance, the layer can be omitted if that type of information is not relevant to the particular application. InChIs can thus be seen as akin to a general and extremely formalized version of IUPAC names and they can express more information than the simpler SMILES notation and differ in that every structure has a unique InChI string, which is important in database applications. Information about the 3-dimensional coordinates of atoms is not represented in InChI, the InChI algorithm converts input structural information into a unique InChI identifier in a three-step process, normalization, canonicalization, and serialization. The InChIKey, sometimes referred to as a hashed InChI, is a fixed length condensed digital representation of the InChI that is not human-understandable. The InChIKey specification was released in September 2007 in order to facilitate web searches for chemical compounds and it should be noted that, unlike the InChI, the InChIKey is not unique, though collisions can be calculated to be very rare, they happen. In January 2009 the final 1.02 version of the InChI software was released and this provided a means to generate so called standard InChI, which does not allow for user selectable options in dealing with the stereochemistry and tautomeric layers of the InChI string. The standard InChIKey is then the hashed version of the standard InChI string, the standard InChI will simplify comparison of InChI strings and keys generated by different groups, and subsequently accessed via diverse sources such as databases and web resources. Every InChI starts with the string InChI= followed by the version number and this is followed by the letter S for standard InChIs. The remaining information is structured as a sequence of layers and sub-layers, the layers and sub-layers are separated by the delimiter / and start with a characteristic prefix letter. The six layers with important sublayers are, Main layer Chemical formula and this is the only sublayer that must occur in every InChI. The atoms in the formula are numbered in sequence, this sublayer describes which atoms are connected by bonds to which other ones. Describes how many hydrogen atoms are connected to each of the other atoms, the condensed,27 character standard InChIKey is a hashed version of the full standard InChI, designed to allow for easy web searches of chemical compounds. Most chemical structures on the Web up to 2007 have been represented as GIF files, the full InChI turned out to be too lengthy for easy searching, and therefore the InChIKey was developed. With all databases currently having below 50 million structures, such duplication appears unlikely at present, a recent study more extensively studies the collision rate finding that the experimental collision rate is in agreement with the theoretical expectations. Example, Morphine has the structure shown on the right, as the InChI cannot be reconstructed from the InChIKey, an InChIKey always needs to be linked to the original InChI to get back to the original structure
5.
Chemical formula
–
These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, the simplest types of chemical formulas are called empirical formulas, which use letters and numbers indicating the numerical proportions of atoms of each type. Molecular formulas indicate the numbers of each type of atom in a molecule. For example, the formula for glucose is CH2O, while its molecular formula is C6H12O6. This is possible if the relevant bonding is easy to show in one dimension, an example is the condensed molecular/chemical formula for ethanol, which is CH3-CH2-OH or CH3CH2OH. For reasons of structural complexity, there is no condensed chemical formula that specifies glucose, chemical formulas may be used in chemical equations to describe chemical reactions and other chemical transformations, such as the dissolving of ionic compounds into solution. A chemical formula identifies each constituent element by its chemical symbol, in empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound, as ratios to the key element. For molecular compounds, these numbers can all be expressed as whole numbers. For example, the formula of ethanol may be written C2H6O because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of compounds, however, cannot be written with entirely whole-number empirical formulas. An example is boron carbide, whose formula of CBn is a variable non-whole number ratio with n ranging from over 4 to more than 6.5. When the chemical compound of the consists of simple molecules. These types of formulas are known as molecular formulas and condensed formulas. A molecular formula enumerates the number of atoms to reflect those in the molecule, so that the formula for glucose is C6H12O6 rather than the glucose empirical formula. However, except for very simple substances, molecular chemical formulas lack needed structural information, for simple molecules, a condensed formula is a type of chemical formula that may fully imply a correct structural formula. For example, ethanol may be represented by the chemical formula CH3CH2OH
6.
Density
–
The density, or more precisely, the volumetric mass density, of a substance is its mass per unit volume. The symbol most often used for density is ρ, although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume, ρ = m V, where ρ is the density, m is the mass, and V is the volume. In some cases, density is defined as its weight per unit volume. For a pure substance the density has the numerical value as its mass concentration. Different materials usually have different densities, and density may be relevant to buoyancy, purity, osmium and iridium are the densest known elements at standard conditions for temperature and pressure but certain chemical compounds may be denser. Thus a relative density less than one means that the floats in water. The density of a material varies with temperature and pressure and this variation is typically small for solids and liquids but much greater for gases. Increasing the pressure on an object decreases the volume of the object, increasing the temperature of a substance decreases its density by increasing its volume. In most materials, heating the bottom of a results in convection of the heat from the bottom to the top. This causes it to rise relative to more dense unheated material, the reciprocal of the density of a substance is occasionally called its specific volume, a term sometimes used in thermodynamics. Density is a property in that increasing the amount of a substance does not increase its density. Archimedes knew that the irregularly shaped wreath could be crushed into a cube whose volume could be calculated easily and compared with the mass, upon this discovery, he leapt from his bath and ran naked through the streets shouting, Eureka. As a result, the term eureka entered common parlance and is used today to indicate a moment of enlightenment, the story first appeared in written form in Vitruvius books of architecture, two centuries after it supposedly took place. Some scholars have doubted the accuracy of this tale, saying among other things that the method would have required precise measurements that would have been difficult to make at the time, from the equation for density, mass density has units of mass divided by volume. As there are units of mass and volume covering many different magnitudes there are a large number of units for mass density in use. The SI unit of kilogram per metre and the cgs unit of gram per cubic centimetre are probably the most commonly used units for density.1,000 kg/m3 equals 1 g/cm3. In industry, other larger or smaller units of mass and or volume are often more practical, see below for a list of some of the most common units of density
7.
Aqueous solution
–
An aqueous solution is a solution in which the solvent is water. It is usually shown in chemical equations by appending to the relevant chemical formula, for example, a solution of table salt, or sodium chloride, in water would be represented as Na+ + Cl−. The word aqueous means pertaining to, related to, similar to, as water is an excellent solvent and is also naturally abundant, it is a ubiquitous solvent in chemistry. Substances that are hydrophobic often do not dissolve well in water, an example of a hydrophilic substance is sodium chloride. Acids and bases are aqueous solutions, as part of their Arrhenius definitions, the ability of a substance to dissolve in water is determined by whether the substance can match or exceed the strong attractive forces that water molecules generate between themselves. If the substance lacks the ability to dissolve in water the molecules form a precipitate, reactions in aqueous solutions are usually metathesis reactions. Metathesis reactions are another term for double-displacement, that is, when a cation displaces to form a bond with the other anion. The cation bonded with the latter anion will dissociate and bond with the other anion, aqueous solutions that conduct electric current efficiently contain strong electrolytes, while ones that conduct poorly are considered to have weak electrolytes. Those strong electrolytes are substances that are ionized in water. Nonelectrolytes are substances that dissolve in water yet maintain their molecular integrity, examples include sugar, urea, glycerol, and methylsulfonylmethane. When writing the equations of reactions, it is essential to determine the precipitate. To determine the precipitate, one must consult a chart of solubility, soluble compounds are aqueous, while insoluble compounds are the precipitate. Remember that there may not always be a precipitate, when performing calculations regarding the reacting of one or more aqueous solutions, in general one must know the concentration, or molarity, of the aqueous solutions. Solution concentration is given in terms of the form of the prior to it dissolving. Metal ions in aqueous solution Solubility Dissociation Acid-base reaction theories Properties of water Zumdahl S.1997, 4th ed. Boston, Houghton Mifflin Company
8.
Solubility
–
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent. The solubility of a substance depends on the physical and chemical properties of the solute and solvent as well as on temperature, pressure. The solubility of a substance is a different property from the rate of solution. Most often, the solvent is a liquid, which can be a substance or a mixture. One may also speak of solid solution, but rarely of solution in a gas, the extent of solubility ranges widely, from infinitely soluble such as ethanol in water, to poorly soluble, such as silver chloride in water. The term insoluble is often applied to poorly or very poorly soluble compounds, a common threshold to describe something as insoluble is less than 0.1 g per 100 mL of solvent. Under certain conditions, the solubility can be exceeded to give a so-called supersaturated solution. Metastability of crystals can also lead to apparent differences in the amount of a chemical that dissolves depending on its form or particle size. A supersaturated solution generally crystallises when seed crystals are introduced and rapid equilibration occurs, phenylsalicylate is one such simple observable substance when fully melted and then cooled below its fusion point. Solubility is not to be confused with the ability to dissolve a substance, for example, zinc dissolves in hydrochloric acid as a result of a chemical reaction releasing hydrogen gas in a displacement reaction. The zinc ions are soluble in the acid, the smaller a particle is, the faster it dissolves although there are many factors to add to this generalization. Crucially solubility applies to all areas of chemistry, geochemistry, inorganic, physical, organic, in all cases it will depend on the physical conditions and the enthalpy and entropy directly relating to the solvents and solutes concerned. By far the most common solvent in chemistry is water which is a solvent for most ionic compounds as well as a range of organic substances. This is a factor in acidity/alkalinity and much environmental and geochemical work. According to the IUPAC definition, solubility is the composition of a saturated solution expressed as a proportion of a designated solute in a designated solvent. Solubility may be stated in units of concentration such as molarity, molality, mole fraction, mole ratio, mass per volume. Solubility occurs under dynamic equilibrium, which means that solubility results from the simultaneous and opposing processes of dissolution, the solubility equilibrium occurs when the two processes proceed at a constant rate. The term solubility is used in some fields where the solute is altered by solvolysis
9.
Safety data sheet
–
A safety data sheet, material safety data sheet, or product safety data sheet is an important component of product stewardship, occupational safety and health, and spill-handling procedures. SDS formats can vary from source to source within a country depending on national requirements, SDSs are a widely used system for cataloging information on chemicals, chemical compounds, and chemical mixtures. SDS information may include instructions for the use and potential hazards associated with a particular material or product. The SDS should be available for reference in the area where the chemicals are being stored or in use, there is also a duty to properly label substances on the basis of physico-chemical, health and/or environmental risk. Labels can include hazard symbols such as the European Union standard symbols, a SDS for a substance is not primarily intended for use by the general consumer, focusing instead on the hazards of working with the material in an occupational setting. It is important to use an SDS specific to country and supplier, as the same product can have different formulations in different countries. The formulation and hazard of a product using a name may vary between manufacturers in the same country. Safety data sheets have made an integral part of the system of Regulation No 1907/2006. The SDS must be supplied in a language of the Member State where the substance or mixture is placed on the market. The 16 sections are, SECTION1, Identification of the substance/mixture, relevant identified uses of the substance or mixture and uses advised against 1.3. Details of the supplier of the safety data sheet 1.4, Emergency telephone number SECTION2, Hazards identification 2.1. Classification of the substance or mixture 2.2, Other hazards SECTION3, Composition/information on ingredients 3.1. Mixtures SECTION4, First aid measures 4.1, Description of first aid measures 4.2. Most important symptoms and effects, both acute and delayed 4.3, indication of any immediate medical attention and special treatment needed SECTION5, Firefighting measures 5.1. Special hazards arising from the substance or mixture 5.3, advice for firefighters SECTION6, Accidental release measure 6.1. Personal precautions, protective equipment and emergency procedures 6.2, methods and material for containment and cleaning up 6.4. Reference to other sections SECTION7, Handling and storage 7.1, conditions for safe storage, including any incompatibilities 7.3. Specific end use SECTION8, Exposure controls/personal protection 8.1, Exposure controls SECTION9, Physical and chemical properties 9.1
10.
Fluorescence
–
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
11.
Rhodamine
–
Rhodamine /ˈroʊdəmiːn/ is a family of related chemical compounds, fluorone dyes. Examples are Rhodamine 6G and Rhodamine B and they are used as dyes and as dye laser gain media. They are often used as a tracer dye within water to determine the rate and direction of flow, Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with instruments called fluorometers. Rhodamine dyes are used extensively in biotechnology applications such as microscopy, flow cytometry, fluorescence correlation spectroscopy. Rhodamine dyes are generally toxic, and are soluble in water, the laser dye rhodamine 123 is also used in biochemistry to inhibit mitochondrion function. Rhodamine 123 seems to bind to the membranes and inhibit transport processes, especially the electron transport chain. It is a substrate of P-glycoprotein, which is overexpressed in cancer cells. Recent reports indicate that rhodamine 123 may be also a substrate of multidrug resistance-associated protein, or more specifically, TRITC is the base rhodamine molecule functionalized with an isothiocyanate group, replacing a hydrogen atom on the bottom ring of the structure. This derivative is reactive towards amine groups on proteins inside cells, a succinimidyl-ester functional group attached to the rhodamine core, creating NHS-rhodamine, forms another common amine-reactive derivative
12.
Dye
–
A dye is a colored substance that has an affinity to the substrate to which it is being applied. The dye is applied in an aqueous solution, and may require a mordant to improve the fastness of the dye on the fiber. Both dyes and pigments are colored because they absorb some wavelengths of light more than others, in contrast to dyes, pigments are insoluble and have no affinity for the substrate. Some dyes can be precipitated with a salt to produce a lake pigment. The majority of natural dyes are from plant sources, roots, berries, bark, leaves, and wood, fungi, textile dyeing dates back to the Neolithic period. Throughout history, people have dyed their textiles using common, locally available materials, scarce dyestuffs that produced brilliant and permanent colors such as the natural invertebrate dyes Tyrian purple and crimson kermes were highly prized luxury items in the ancient and medieval world. Plant-based dyes such as woad, indigo, saffron, and madder were raised commercially and were important trade goods in the economies of Asia, across Asia and Africa, patterned fabrics were produced using resist dyeing techniques to control the absorption of color in piece-dyed cloth. Dyes from the New World such as cochineal and logwood were brought to Europe by the Spanish treasure fleets, dyed flax fibers have been found in the Republic of Georgia in a prehistoric cave dated to 36,000 BP. Archaeological evidence shows that, particularly in India and Phoenicia, dyeing has been carried out for over 5,000 years. The dyes were obtained from animal, vegetable or mineral origin, by far the greatest source of dyes has been from the plant kingdom, notably roots, berries, bark, leaves and wood, but only a few have ever been used on a commercial scale. The discovery of synthetic dyes late in the 19th century ended the large-scale market for natural dyes. These dyes are made from synthetic resources such as petroleum by-products, the first human-made organic aniline dye, mauveine, was discovered serendipitously by William Henry Perkin in 1856, the result of a failed attempt at the total synthesis of quinine. Other aniline dyes followed, such as fuchsine, safranine, many thousands of synthetic dyes have since been prepared. These may be natural or synthetic, other than pigmentation, they have a range of applications including organic dye lasers, optical media and camera sensors. This is the basic classification Dyes are classified according to their solubility, acid dyes are water-soluble anionic dyes that are applied to fibers such as silk, wool, nylon and modified acrylic fibers using neutral to acid dye baths. Attachment to the fiber is attributed, at least partly, to salt formation between anionic groups in the dyes and cationic groups in the fiber, acid dyes are not substantive to cellulosic fibers. Most synthetic food colors fall in this category, basic dyes are water-soluble cationic dyes that are mainly applied to acrylic fibers, but find some use for wool and silk. Usually acetic acid is added to the dye bath to help the uptake of the dye onto the fiber, basic dyes are also used in the coloration of paper
13.
Tracer dye
–
Dye tracing is tracking and tracing various flows using dye added to the liquid in question. That is, it uses dye as a flow tracer, the purpose of tracking may be an analysis of the flow itself, of the transport of something by the flow of the objects that convey the flow. It is an evolution of the ages-known float tracing method, which consists of throwing a buoyant object into a waterflow to see where it goes or where it emerges. Dye tracking may be qualitative, i. e. the presence of particular flow and its estimate, or quantitative. Fluorescein is among the first fluorescent dyes, developed in 1871 and its disodium salt under the trademark Uranine was developed several years later and still remains among the best tracer dyes. Other popular tracer dyes are rhodamine, pyranine and sulforhodamine, carbon sampling was the first method of technology-assisted dye tracing that was based on the absorption of dye in charcoal. Charcoal packets may be placed along the route of the flow, later the collected dye may be chemically extracted. Filter fluorometers were the first devices that could detect dye concentrations beyond human eye sensitivity, spectrofluorometers developed in the mid-1980s made it possible to perform advanced analysis of fluorescence. Filter fluorometers and spectrofluorometers identify the intensity of fluorscence that is present in a liquid sample, different dyes and chemicals produce a distinctive wavelength that is determined during analysis. Water flows, differentiated by the environment, possess certain factors that can affects how a dye performs, natural fluorescence in a water flow can interfere with certain dyes. Presence of organics, other chemicals, and sunlight can influence the intensity of dyes, each sampling area is analyzed by a quantitative instrument to test the background fluorescence. Each dye has significant performance factors that distinguish it in different settings and these factors influence how each dye interacts and is affected by each environment. Therefore, one dye can be useful in one environment. For example, fluorescent angiography, a technique of analysis of circulation in retina is used for diagnosing various eye diseases, with modern fluorometers, capable of tracking single fluorescent molecules, it is possible to track migrations of single cells tagged by a fluorescent molecule. For example, the fluorescent-activated cell sorting in flow makes it possible to sort out the cells with attached fluorescent molecules from a flow. Fluorescence microscope FLEX mission Fluorescent green pig Float tracking
14.
Fluorometer
–
A fluorometer or fluorimeter is a device used to measure parameters of fluorescence, its intensity and wavelength distribution of emission spectrum after excitation by a certain spectrum of light. These parameters are used to identify the presence and the amount of molecules in a medium. Modern fluorometers are capable of detecting fluorescent molecule concentrations as low as 1 part per trillion, Fluorescence analysis can be orders of magnitude more sensitive than other techniques. Applications include chemistry/biochemistry, medicine, environmental monitoring, for instance, they are used to measure chlorophyll fluorescence to investigate plant physiology. Typically fluorometers utilize a double beam and these two beams work in tandem to decrease the noise created from radiant power fluctuations. The upper beam is passed through a filter or monochromator and passes through the sample, the lower beam is passed through an attenuator and adjusted to try and match the fluorescent power given off from the sample. Light from the fluorescence of the sample and the lower, attenuated beam are detected by separate transducers, within the machine the transducer that detects fluorescence created from the upper beam is located a distance away from the sample and at a 90-degree angle from the incident, upper beam. The machine is constructed like this to decrease the light from the upper beam that may strike the detector. The optimal angle is 90 degrees, there are two different approaches to handling the selection of incident light that gives way to different types fluorometers. If filters are used to select wavelengths of light, the machine is called a fluorometer, while a spectrofluorometer will typically use two monochromators, some spectrofluorometers may use one filter and one monochromator. Light sources for fluorometers are often dependent on the type of sample being tested, among the most common light source for fluorometers is the low-pressure mercury lamp. This provides many excitation wavelengths, making it the most versatile, however, this lamp is not a continuous source of radiation. The xenon arc lamp is used when a source of radiation is needed. Both of these provide a suitable spectrum of ultraviolet light that induces chemiluminescence. These are just two of the possible light sources. Glass and silica cells are often the vessels in which the sample is placed, the scientist must be very careful to not leave fingerprints or any other sort of mark on the outside of the cell. Fluorimetry is widely used by the industry to verify whether pasteurization has been successful. This is done using a reagent which is hydrolysed to a fluorophore, if pasteurization has been successful then alkaline phosphatase will be entirely denatured and the sample will not fluoresce
15.
Fluorescence microscope
–
The specimen is illuminated with light of a specific wavelength which is absorbed by the fluorophores, causing them to emit light of longer wavelengths. The illumination light is separated from the much weaker emitted fluorescence through the use of an emission filter. Typical components of a microscope are a light source, the excitation filter, the dichroic mirror. The filters and the dichroic beamsplitter are chosen to match the spectral excitation and emission characteristics of the used to label the specimen. In this manner, the distribution of a fluorophore is imaged at a time. Multi-color images of types of fluorophores must be composed by combining several single-color images. Most fluorescence microscopes in use are epifluorescence microscopes, where excitation of the fluorophore and these microscopes are widely used in biology and are the basis for more advanced microscope designs, such as the confocal microscope and the total internal reflection fluorescence microscope. The majority of fluorescence microscopes, especially used in the life sciences, are of the epifluorescence design shown in the diagram. Light of the wavelength is focused on the specimen through the objective lens. Fluorescence microscopy requires intense, near-monochromatic, illumination which some widespread light sources, four main types of light source are used, including xenon arc lamps or mercury-vapor lamps with an excitation filter, lasers, supercontinuum sources, and high-power LEDs. In order for a sample to be suitable for fluorescence microscopy it must be fluorescent, there are several methods of creating a fluorescent sample, the main techniques are labelling with fluorescent stains or, in the case of biological samples, expression of a fluorescent protein. Alternatively the intrinsic fluorescence of a sample can be used, as a result, there is a diverse range of techniques for fluorescent staining of biological samples. Many fluorescent stains have been designed for a range of biological molecules, some of these are small molecules which are intrinsically fluorescent and bind a biological molecule of interest. Major examples of these are nucleic acid stains like DAPI and Hoechst and DRAQ5 and DRAQ7 which all bind the minor groove of DNA, others are drugs or toxins which bind specific cellular structures and have been derivatised with a fluorescent reporter. A major example of class of fluorescent stain is phalloidin which is used to stain actin fibres in mammalian cells. Immunofluorescence is a technique which uses the specific binding of an antibody to its antigen in order to label specific proteins or other molecules within the cell. A sample is treated with an antibody specific for the molecule of interest. A fluorophore can be conjugated to the primary antibody
16.
Flow cytometry
–
It allows simultaneous multiparametric analysis of the physical and chemical characteristics of up to thousands of particles per second. Flow cytometry is used in the diagnosis of health disorders, especially blood cancers. A common variation is to physically sort particles based on their properties, the first impedance-based flow cytometry device, using the Coulter principle, was disclosed in U. S. Patent 2,656,508, issued in 1953, to Wallace H. Coulter, mack Fulwyler was the inventor of the forerunner to todays flow cytometers - particularly the cell sorter. Fulwyler developed this in 1965 with his publication in Science, at that time, absorption methods were still widely favored by other scientists over fluorescence methods. The first label-free high-frequency impedance flow cytometer based on a patented microfluidic lab-on-chip, the original name of the fluorescence-based flow cytometry technology was pulse cytophotometry, based on the first patent application on fluorescence-based flow cytometry. Modern flow cytometers are able to analyze several thousand particles every second, in real time, a flow cytometer is similar to a microscope, except that, instead of producing an image of the cell, flow cytometry offers high-throughput automated quantification of set parameters. To analyze solid tissues, a single-cell suspension must first be prepared, the process of collecting data from samples using the flow cytometer is termed acquisition. Acquisition is mediated by a physically connected to the flow cytometer. Early flow cytometers were, in general, experimental devices, due to these developments, a considerable market for instrumentation, analysis software, as well as the reagents used in acquisition such as fluorescently labeled antibodies has developed. Modern instruments usually have multiple lasers and fluorescence detectors, the current record for a commercial instrument is ten lasers and 30 fluorescence detectors. Increasing the number of lasers and detectors allows for multiple antibody labeling, certain instruments can even take digital images of individual cells, allowing for the analysis of fluorescent signal location within or on the surface of cells. The data generated by flow-cytometers can be plotted in a dimension, to produce a histogram. The regions on these plots can be separated, based on fluorescence intensity, by creating a series of subset extractions. Specific gating protocols exist for diagnostic and clinical purposes especially in relation to hematology, the plots are often made on logarithmic scales. Because different fluorescent dyes emission spectra overlap, signals at the detectors have to be compensated electronically as well as computationally, once the data is collected, there is no need to stay connected to the flow cytometer and analysis is most often performed on a separate computer. This is especially necessary in core facilities where usage of these machines is in high demand, recent progress on automated population identification using computational methods has offered an alternative to traditional gating strategies. Automated identification systems could potentially help findings of rare and hidden populations, representative automated methods include FLOCK in Immunology Database and Analysis Portal, SamSPECTRAL and flowClust in Bioconductor, and FLAME in GenePattern
17.
Fluorescence correlation spectroscopy
–
Fluorescence correlation spectroscopy is a correlation analysis of fluctuation of the fluorescence intensity. The analysis provides parameters of the physics under the fluctuations, one of the interesting applications of this is an analysis of the concentration fluctuations of fluorescent particles in solution. In this application, the fluorescence emitted from a tiny space in solution containing a small number of fluorescent particles is observed. The fluorescence intensity is fluctuating due to Brownian motion of the particles, in other words, the number of the particles in the sub-space defined by the optical system is randomly changing around the average number. The analysis gives the number of fluorescent particles and average diffusion time. Eventually, both the concentration and size of the particle are determined, both parameters are important in biochemical research, biophysics, and chemistry. FCS is such an analytical tool because it observes a small number of molecules in a small volume. In contrast to other methods FCS has no physical separation process, instead, furthermore, FCS enables observation of fluorescence-tagged molecules in the biochemical pathway in intact living cells. This opens a new area, in situ or in vivo biochemistry, tracing the biochemical pathway in intact cells, commonly, FCS is employed in the context of optical microscopy, in particular Confocal microscopy or two-photon excitation microscopy. In these techniques light is focused on a sample and the fluorescence intensity fluctuations are analyzed using the temporal autocorrelation. FCS is in a way the fluorescent counterpart to dynamic light scattering, with the development of sensitive detectors such as avalanche photodiodes the detection of the fluorescence signal coming from individual molecules in highly dilute samples has become practical. With this emerged the possibility to conduct FCS experiments in a variety of specimens. The advent of engineered cells with genetically tagged proteins has made FCS a common tool for studying molecular dynamics in living cells, signal-correlation techniques were first experimentally applied to fluorescence in 1972 by Magde, Elson, and Webb, who are therefore commonly credited as the inventors of FCS. The technique was developed in a group of papers by these and other authors soon after, establishing the theoretical foundations. See Thompson for a review of that period, since then, there has been a renewed interest in FCS, and as of August 2007 there have been over 3,000 papers using FCS found in Web of Science. See Krichevsky and Bonnet for a recent review, the typical FCS setup consists of a laser line, which is reflected into a microscope objective by a dichroic mirror. The laser beam is focused in the sample, which contains fluorescent particles in such high dilution, when the particles cross the focal volume, they fluoresce. The resulting electronic signal can be stored directly as an intensity versus time trace to be analyzed at a later point
18.
Butanol
–
These are n-butanol,2 stereoisomers of 2-butanol, tert-butanol, and isobutanol. Butanol is primarily used as a solvent, as an intermediate in chemical synthesis and it is sometimes also called biobutanol when produced biologically. The unmodified term usually refers to the straight chain isomer with the alcohol functional group at the terminal carbon. The straight chain isomer with the alcohol at an internal carbon is sec-butanol or 2-butanol, the branched isomer with the alcohol at a terminal carbon is isobutanol or 2-methyl-1-propanol, and the branched isomer with the alcohol at the internal carbon is tert-butanol or 2-methyl-2-propanol. The butanol isomers have different melting and boiling points, n-butanol and isobutanol have limited solubility, sec-butanol has substantially greater solubility, while tert-butanol is fully miscible with water above tert-butanols melting point. The hydroxyl group makes the molecule polar, promoting solubility in water, while the hydrocarbon chain mitigates the polarity. Like many alcohols, butanol is considered toxic and it has shown low order of toxicity in single dose experiments to laboratory animals. And is considered enough for use in cosmetics. Brief, repeated overexposure with the skin can result in depression of the nervous system. Exposure may also cause eye irritation and moderate skin irritation. The main dangers are from prolonged exposure to fumes, in extreme cases this includes suppression of the central nervous system and even death. Under most circumstances, butanol is quickly metabolized to carbon dioxide and it has not been shown to damage DNA or cause cancer. Butanol is considered as a potential biofuel, Butanol can also be added to diesel fuel to reduce soot emissions. Butanol is used as a solvent for a variety of chemical and textile processes, in organic synthesis. It is also used as a paint thinner and a solvent in other coating applications where a relatively slow evaporating latent solvent is preferable, as with lacquers and it is also used as a component of hydraulic and brake fluids. Butanol is used in the synthesis of 2-butoxyethanol, a major application for butanol is as a reactant with acrylic acid to produce butyl acrylate, a primary ingredient of water based acrylic paint. It is also used as a base for perfumes, but on its own has a highly alcoholic aroma, salts of butanol are chemical intermediates, for example, alkali metal salts of tert-butanol are tert-butoxides. Since the 1950s, most butanol in the United States is produced commercially from fossil fuels, the most common process starts with propene, which is put through a hydroformylation reaction to form butyraldehyde, which is then reduced with hydrogen to 1-butanol and/or 2-butanol
19.
Ethanol
–
Ethanol, also called alcohol, ethyl alcohol, and drinking alcohol, is the principal type of alcohol found in alcoholic beverages. It is a volatile, flammable, colorless liquid with a characteristic odor. Its chemical formula is C 2H 6O, which can be written also as CH 3-CH 2-OH or C 2H 5-OH, ethanol is mostly produced by the fermentation of sugars by yeasts, or by petrochemical processes. It is a psychoactive drug, causing a characteristic intoxication. It is widely used as a solvent, as fuel, and as a feedstock for synthesis of other chemicals, the eth- prefix and the qualifier ethyl in ethyl alcohol originally come from the name ethyl assigned in 1834 to the group C 2H 5- by Justus Liebig. He coined the word from the German name Aether of the compound C 2H 5-O-C 2H5, according to the Oxford English Dictionary, Ethyl is a contraction of the Ancient Greek αἰθήρ and the Greek word ύλη. The name ethanol was coined as a result of a resolution that was adopted at the International Conference on Chemical Nomenclature that was held in April 1892 in Geneva, Switzerland. The term alcohol now refers to a class of substances in chemistry nomenclature. The Oxford English Dictionary claims that it is a loan from Arabic al-kuḥl, a powdered ore of antimony used since aniquity as a cosmetic. The use of alcohol for ethanol is modern, first recorded 1753, the systematic use in chemistry dates to 1850. Ethanol is used in medical wipes and most common antibacterial hand sanitizer gels as an antiseptic, ethanol kills organisms by denaturing their proteins and dissolving their lipids and is effective against most bacteria and fungi, and many viruses. However, ethanol is ineffective against bacterial spores, ethanol may be administered as an antidote to methanol and ethylene glycol poisoning. Ethanol, often in high concentrations, is used to dissolve many water-insoluble medications, as a central nervous system depressant, ethanol is one of the most commonly consumed psychoactive drugs. The amount of ethanol in the body is typically quantified by blood alcohol content, small doses of ethanol, in general, produce euphoria and relaxation, people experiencing these symptoms tend to become talkative and less inhibited, and may exhibit poor judgment. Ethanol is commonly consumed as a drug, especially while socializing. The largest single use of ethanol is as a fuel and fuel additive. Brazil in particular relies heavily upon the use of ethanol as an engine fuel, gasoline sold in Brazil contains at least 25% anhydrous ethanol. Hydrous ethanol can be used as fuel in more than 90% of new gasoline fueled cars sold in the country, Brazilian ethanol is produced from sugar cane and noted for high carbon sequestration
20.
Diethylene glycol
–
Diethylene glycol is an organic compound with the formula 2O. It is a colorless, practically odorless, poisonous, and hygroscopic liquid with a sweetish taste and it is miscible in water, alcohol, ether, acetone, and ethylene glycol. DEG is a widely used solvent and it can be a contaminant in consumer products, this has resulted in numerous epidemics of poisoning since the early 20th century. DEG is produced by the hydrolysis of ethylene oxide. Depending on the conditions, varying amounts of DEG and related glycols are produced, the resulting product is two ethylene glycol molecules joined by an ether bond. Diethylene glycol is derived as a co-product with ethylene glycol and triethylene glycol, the industry generally operates to maximize MEG production. Ethylene glycol is by far the largest volume of the products in a variety of applications. Availability of DEG will depend on demand for derivatives of the product, ethylene glycol. Diethylene glycol is one of several glycols derived from ethylene oxide, diethylene glycol is used in the manufacture of unsaturated polyester resins, polyurethanes, and plasticizers. DEG is used as a block in organic synthesis, e. g. of morpholine and 1. It is a solvent for nitrocellulose, resins, dyes, oils and it is a humectant for tobacco, cork, printing ink, and glue. It is also a component in brake fluid, lubricants, wallpaper strippers, artificial fog solutions, in personal care products, DEG is often replaced by selected diethylene glycol ethers. A dilute solution of diethylene glycol can also be used as a cryoprotectant, however, most ethylene glycol antifreeze contains a few percent diethylene glycol, present as an byproduct of ethylene glycol production. Despite the discovery of DEG’s toxicity in 1937 and its involvement in mass poisonings around the world, because of its adverse effects on humans, diethylene glycol is not allowed for use in food and drugs. The U. S. Code of Federal Regulations allows no more than 0. 2% of diethylene glycol in polyethylene glycol when the latter is used as a food additive. The Australian government does not allow DEG as a food additive, diethylene glycol has moderate acute toxicity in animal experiments. The LD50 for small mammals has been tested at between 2 and 25 g/kg, less toxic than its relative ethylene glycol, but still capable of causing toxicity in humans and it appears diethylene glycol is more hazardous to humans than implied by oral toxicity data in laboratory animals. Dermal absorption is low, unless it is administered on broken or damaged skin
21.
Triethylene glycol
–
Triethylene glycol, TEG, or triglycol is a colorless odorless viscous liquid with molecular formula HOCH2CH2OCH2CH2OCH2CH2OH. It is used as a plasticizer for vinyl and it is also used in air sanitizer products, such as Oust or Clean and Pure. When aerosolized it acts as a disinfectant, glycols are also used as liquid desiccants for natural gas and in air conditioning systems. It is an additive for hydraulic fluids and brake fluids and is used as a base for smoke machine fluid in the entertainment industry, triethylene glycol is a member of a homologous series of dihydroxy alcohols. It is a colorless, odorless and stable liquid with high viscosity, apart from its use as a raw material in the manufacture and synthesis of other products, TEG is known for its hygroscopic quality and its ability to dehumidify fluids. This liquid is miscible with water, and at a pressure of 101.325 kPa has a point of 286.5 degrees Celsius. It is also soluble in ethanol, acetone, acetic acid, glycerine, pyridine, aldehydes, slightly soluble in diethyl ether, TEG is used by the oil and gas industry to dehydrate natural gas. It may also be used to other gases, including CO2, H2S. It is necessary to dry natural gas to a point, as humidity in natural gas can cause pipelines to freeze. Triethylene glycol is placed into contact with gas, and strips the water out of the gas. Triethylene glycol is heated to a temperature and put through a condensing system. The waste TEG produced by this process has found to contain enough benzene to be classified as hazardous waste. Triethylene glycol is well established as a mild disinfectant toward a variety of bacteria. The ability of triethylene glycol to inactivate Streptococcus pneumoniae, Streptococcus pyogenes, further, the inactivation of H1N1 influenza A virus on surfaces has been demonstrated. The latter investigation suggests that triethylene glycol may prove to be a potent weapon against future influenza epidemics and pandemics
22.
Isopropyl alcohol
–
Isopropyl alcohol, also called isopropanol or dimethyl carbinol, is a compound with the chemical formula C3H8O or C3H7OH or CH3CHOHCH3. It is a colorless, flammable chemical compound with a strong odor, as a propyl group linked to a hydroxyl group, it is the simplest example of a secondary alcohol, where the alcohol carbon atom is attached to two other carbon atoms, sometimes shown as 2CHOH. It is an isomer of 1-propanol. It has a variety of industrial and household uses. Isopropyl alcohol is miscible in water, ethanol, ether, and it will dissolve ethyl cellulose, polyvinyl butyral, many oils, alkaloids, gums and natural resins. Unlike ethanol or methanol, isopropyl alcohol is not miscible with salt solutions, the process is colloquially called salting out, and causes concentrated isopropyl alcohol to separate into a distinct layer. Isopropyl alcohol forms an azeotrope with water, which gives a point of 80.37 °C. Water-isopropyl alcohol mixtures have depressed melting points and it has a slightly bitter taste, and is not safe to drink. Isopropyl alcohol becomes increasingly viscous with decreasing temperature will freeze at −89 °C, Isopropyl alcohol has a maximum absorbance at 205 nm in an ultraviolet-visible spectrum. Isopropyl alcohol can be oxidized to acetone, which is the corresponding ketone, Isopropyl alcohol may be converted to 2-bromopropane using phosphorus tribromide, or dehydrated to propene by heating with sulfuric acid. Like most alcohols, isopropyl alcohol reacts with metals such as potassium to form alkoxides that can be called isopropoxides. The reaction with aluminium is used to prepare the catalyst aluminium isopropoxide, in 1994,1.5 million tonnes of isopropyl alcohol was produced in the United States, Europe, and Japan. This compound is produced by combining water and propene in a hydration reaction. It is also produced by hydrogenating acetone, there are two routes for the hydration process, indirect hydration using the sulfuric acid process, and direct hydration. The former process, which can use low-quality propene, predominates in the USA while the latter process and these processes give predominantly isopropyl alcohol rather than 1-propanol because the addition of water or sulfuric acid to propene follows Markovnikovs rule. The indirect process reacts propene with sulfuric acid to form a mixture of sulfate esters, subsequent hydrolysis of these esters by steam produces isopropyl alcohol, which is distilled. Diisopropyl ether is a significant by-product of this process, it is recycled back to the process, direct hydration reacts propene and water, either in gas phase or in liquid phase, at high pressures in the presence of solid or supported acidic catalysts. Higher-purity propylene tends to be required for this type of process, both processes require that the isopropyl alcohol be separated from water and other by-products by distillation
23.
Ethoxyethanol
–
2-Ethoxyethanol, also known by the trademark Cellosolve or ethyl cellosolve, is a solvent used widely in commercial and industrial applications. It is a clear, colorless, nearly odorless liquid that is miscible with water, ethanol, diethyl ether, acetone, 2-Ethoxyethanol can be manufactured by the reaction of ethylene oxide with ethanol. As with other glycol ethers, 2-ethoxyethanol has the property of being able to dissolve chemically diverse compounds. It will dissolve oils, resins, grease, waxes, nitrocellulose and this is an ideal property as a multi-purpose cleaner, and, therefore, 2-ethoxyethanol is used in products, such as varnish removers and degreasing solutions. CDC - NIOSH Pocket Guide to Chemical Hazards
24.
Methoxyethanol
–
2-Methoxyethanol, or methyl cellosolve, is an organic compound with formula C 3H 8O2 that is used mainly as a solvent. It is a clear, colorless liquid with an ether-like odor and it is also used as an additive in airplane deicing solutions. In organometallic chemistry it is used for the synthesis of Vaskas complex. During these reactions the alcohol acts as a source of hydride, 2-Methoxyethanol is toxic to the bone marrow and testicles. Workers exposed to high levels are at risk for granulocytopenia, macrocytic anemia, oligospermia, the methoxyethanol is converted by alcohol dehydrogenase into methoxyacetic acid which is the substance which causes the harmful effects. Both ethanol and acetate have a protecting effect, the methoxyacetate can enter the Krebs cycle where it forms methoxycitrate
25.
Dipropylene glycol
–
Dipropylene glycol is a mixture of three isomeric chemical compounds, 4-oxa-2, 6-heptandiol, 2--propan-1-ol, and 2--propan-1-ol. It is a colorless, nearly odorless liquid with a boiling point. Dipropylene glycol finds many uses as a plasticizer, an intermediate in chemical reactions, as a polymerization initiator or monomer. Its low toxicity and solvent properties make it an ideal additive for perfumes and skin and it is also a common ingredient in commercial fog fluid, used in entertainment industry fog machines
26.
Polyethylene glycol
–
Polyethylene glycol is a polyether compound with many applications from industrial manufacturing to medicine. PEG is also known as polyethylene oxide or polyoxyethylene, depending on its molecular weight, the structure of PEG is commonly expressed as H−n−OH. PEG, PEO, and POE refer to an oligomer or polymer of ethylene oxide, the three names are chemically synonymous, but historically PEG is preferred in the biomedical field, whereas PEO is more prevalent in the field of polymer chemistry. PEG and PEO are liquids or low-melting solids, depending on their molecular weights, PEGs are prepared by polymerization of ethylene oxide and are commercially available over a wide range of molecular weights from 300 g/mol to 10,000,000 g/mol. Lower-molecular-weight PEGs are also available as purer oligomers, referred to as monodisperse, uniform, very high purity PEG has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray diffraction. Since purification and separation of pure oligomers is difficult, the price for this type of quality is often 10–1000 fold that of polydisperse PEG, PEGs are also available with different geometries. Branched PEGs have three to ten PEG chains emanating from a core group. Star PEGs have 10 to 100 PEG chains emanating from a core group. Comb PEGs have multiple PEG chains normally grafted onto a polymer backbone, most PEGs include molecules with a distribution of molecular weights. The size distribution can be characterized statistically by its weight average molecular weight and its number average molecular weight, MW and Mn can be measured by mass spectrometry. PEGylation is the act of covalently coupling a PEG structure to another molecule, for example, a therapeutic protein. PEGylated interferon alfa-2a or −2b are commonly used injectable treatments for hepatitis C infection, PEG is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. It is coupled to hydrophobic molecules to produce non-ionic surfactants, PEGs contain potential toxic impurities, such as ethylene oxide and 1, 4-dioxane. Ethylene Glycol and its ethers are nephrotoxic if applied to damaged skin, polyethylene glycol and related polymers are often sonicated when used in biomedical applications. However, as reported by Murali et al, PEG is very sensitive to sonolytic degradation and PEG degradation products can be toxic to mammalian cells. It is, thus, imperative to assess potential PEG degradation to ensure that the material does not contain undocumented contaminants that can introduce artifacts into experimental results. PEGs and methoxypolyethylene glycols are manufactured by Dow Chemical under the tradename Carbowax for industrial use and they vary in consistency from liquid to solid, depending on the molecular weight, as indicated by a number following the name. Some specific groups are lauromacrogols, nonoxynols, octoxynols, and poloxamers, macrogol, used as a laxative, is a form of polyethylene glycol
27.
Laser dye
–
Laser dyes are large organic molecules with molecular weights of a few hundred mu. When one of organic molecules is dissolved in a suitable liquid solvent it can be used as laser medium in a dye laser. Laser dye solutions absorb at shorter wavelengths and emit at longer wavelengths, successful laser dyes include the coumarins and the rhodamines. Coumarin dyes emit in the region of the spectrum while rhodamine dyes are used for emission in the yellow-red. The color emitted by the laser dyes depend upon the medium i. e. the medium in which they are dissolved. However, there are dozens of laser dyes that can be used to span continuously the emission spectrum from the ultraviolet to the near infrared. Laser dyes are used to dope solid-state matrices, such as poly. Coumarin DCM Fluorescein polyphenyl Rhodamine 6G Rhodamine B Rhodamine 123 Umbelliferone Dye laser Organic laser Solid state dye lasers
28.
Active laser medium
–
The active laser medium is the source of optical gain within a laser. The gain results from the emission of electronic or molecular transitions to a lower energy state from a higher energy state previously populated by a pump source. g. Liquids, in the form of dye solutions as used in dye lasers, in order to fire a laser, the active gain medium must be in a nonthermal energy distribution known as a population inversion. The preparation of this requires an external energy source and is known as laser pumping. Pumping may be achieved with electrical currents or with light, generated by discharge lamps or by other lasers, more exotic gain media can be pumped by chemical reactions, nuclear fission, or with high-energy electron beams. A universal model valid for all laser types does not exist, the simplest model includes two systems of sub-levels, upper and lower. Within each sub-level system, the fast transitions ensure that equilibrium is reached quickly. The upper level is assumed to be metastable, also, gain and refractive index are assumed independent of a particular way of excitation. For good performance of the medium, the separation between sub-levels should be larger than working temperature, then, at pump frequency ω p. In the case of amplification of signals, the lasing frequency is called signal frequency. However, the term is used even in the laser oscillators. The model below seems to work well for most optically-pumped solid-state lasers, the simple medium can be characterized with effective cross-sections of absorption and emission at frequencies ω p and ω s. Have N be concentration of active centers in the solid-state lasers, have N1 be concentration of active centers in the ground state. Have N2 be concentration of excited centers, in many cases the gain medium works in a continuous-wave or quasi-continuous regime, causing the time derivatives of populations to be negligible. The steady-state solution can be written, n 2 = W u W u + W d, n 1 = W d W u + W d. The dynamic saturation intensities can be defined, I p o = ℏ ω p τ, I s o = ℏ ω s τ, the absorption at strong signal, A0 = N D σ a s + σ e s. The gain at strong pump, G0 = N D σ a p + σ e p, gain never exceeds value G0, and absorption never exceeds value A0 U. The following identities take place, U − V =1, A / A0 + G / G0 =1, the state of gain medium can be characterized with a single parameter, such as population of the upper level, gain or absorption
29.
Dye laser
–
A dye laser is a laser which uses an organic dye as the lasing medium, usually as a liquid solution. Compared to gases and most solid state lasing media, a dye can usually be used for a wider range of wavelengths. The wide bandwidth makes them suitable for tunable lasers and pulsed lasers. The dye rhodamine 6G, for example, can be tuned from 635 nm to 560 nm, dye lasers were independently discovered by P. P. Sorokin and F. P. Schäfer in 1966. In addition to the liquid state, dye lasers are also available as solid state dye lasers. SSDL use dye-doped organic matrices as gain medium, a dye laser uses a gain medium consisting of an organic dye, which is a carbon-based, soluble stain that is often fluorescent, such as the dye in a highlighter pen. The dye is mixed with a solvent, allowing the molecules to diffuse evenly throughout the liquid. The dye solution may be circulated through a dye cell, or streamed through open air using a dye jet, a high energy source of light is needed to pump the liquid beyond its lasing threshold. A fast discharge flashtube or a laser is usually used for this purpose. Mirrors are also needed to oscillate the light produced by the dye’s fluorescence, the output mirror is normally around 80% reflective, while all other mirrors are usually more than 99. 9% reflective. The dye solution is circulated at high speeds, to help avoid triplet absorption. A prism or diffraction grating is usually mounted in the beam path, because the liquid medium of a dye laser can fit any shape, there are a multitude of different configurations that can be used. A Fabry–Pérot laser cavity is used for flashtube pumped lasers. The dye cell is often a tube approximately equal in length to the flashtube. The dye cell is usually side-pumped, with one or more flashtubes running parallel to the dye cell in a reflector cavity, the reflector cavity is often water cooled, to prevent thermal shock in the dye caused by the large amounts of near-infrared radiation which the flashtube produces. Axial pumped lasers have a hollow, annular-shaped flashtube that surrounds the dye cell, which has lower inductance for a shorter flash, and improved transfer efficiency. Coaxial pumped lasers have an annular dye cell that surrounds the flashtube, for even better transfer efficiency, flash pumped lasers can be used only for pulsed output applications. A ring laser design is chosen for continuous operation, although a Fabry–Pérot design is sometimes used
30.
Nitrogen laser
–
A nitrogen laser is a gas laser operating in the ultraviolet range using molecular nitrogen as its gain medium, pumped by an electrical discharge. The wall-plug efficiency of the laser is low, typically 0. 1% or less. The nitrogen laser is a three-level laser, in contrast to more typical four-level lasers, the upper laser level of nitrogen is directly pumped, imposing no speed limits on the pump. Pumping is normally provided by electron impact, the electrons must have sufficient energy. Typically reported optimum values are in the range of 80 to 100 eV per Torr·cm pressure of nitrogen gas, there is a 40 ns upper limit of laser lifetime at low pressures and the lifetime becomes shorter as the pressure increases. The lifetime is only 1 to 2 ns at 1 atmosphere, in general t =361 +12.8 ∗ p. The strongest lines are at 337.1 nm wavelength in the ultraviolet, other lines have been reported at 357.6 nm, also ultraviolet. This information refers to the second system of molecular nitrogen. No vibration of the two atoms is involved, because the atom-atom distance does not change with the electronic transition. The rotation needs to change to deliver the angular momentum of the photon, there are also lines in the far-red and infrared from the first positive system, and a visible blue laser line from the molecular nitrogen positive ion. The metastable lower level lifetime is 40 μs, thus, the laser self-terminates and this type of self-termination is sometimes referred to as bottlenecking in the lower level. Several organic dyes with upper level lifetimes of less than 10 ns have been used in continuous mode, the Nd, YAG laser has an upper level lifetime of 230 µs, yet it also supports 100 ps pulses. Repetition rates can range as high as a few kHz, provided adequate gas flow, there are also, apparently, issues involving ions remaining in the laser channel. Air, which is 78% nitrogen, can be used, for a 10 mm wide gain volume diffraction comes into play after 30 m along the gain medium, a length which is unheard of. Thus this laser does not need a concave lens or refocusing lenses, the height of the pumped volume may be as small as 1 mm, needing a refocusing lens already after 0.3 m. A simple solution is to use rounded electrodes with a large radius, the gain medium is usually pumped by a transverse electrical discharge. When the pressure is at 1013 mbar, the configuration is called a TEA laser Transverse Electrical discharge in gas at Atmospheric pressure, in a strong external electric field this electron creates an electron avalanche in the direction of the electric field lines. Diffusion of electrons and elastic scattering at a gas molecule spreads the avalanche perpendicular to the field
31.
Ion laser
–
An ion laser is a gas laser that uses an ionized gas as its lasing medium. Like other gas lasers, ion lasers feature a sealed cavity containing the laser medium, unlike helium–neon lasers, the energy level transitions that contribute to laser action come from ions. A small air-cooled ion laser might produce, for example,130 mW of light with a current of 10 A at 105 V. This is a total power draw over 1 kW, which translates into an amount of heat that must be dissipated. A krypton laser is an ion laser using krypton ions as a gain medium, krypton lasers are used for scientific research, or when krypton is mixed with argon, for creation of white-light lasers, useful for laser light shows. Krypton lasers are used in medicine, for manufacture of security holograms. Krypton lasers emit at several wavelengths through the spectrum, at 406.7 nm,413.1 nm,415.4 nm,468.0 nm,476.2 nm,482.5 nm,520.8 nm,530.9 nm,568.2 nm,647.1 nm,676.4 nm. The argon-ion laser was invented in 1964 by William Bridges at Hughes Aircraft and is one of a family of ion lasers that use a gas as the active medium. Argon-ion lasers are used for retinal phototherapy, lithography, and pumping other lasers, common argon and krypton lasers are capable of emitting continuous-wave output of several milliwatts to tens of watts. Their tubes are made from nickel end bells, kovar metal-to-ceramic seals, beryllium oxide ceramics. The earliest tubes were simple quartz, followed by quartz with graphite disks, in comparison with the helium–neon lasers that require just a few milliamperes, the current used for pumping the krypton laser is several amperes, as the gas has to be ionized. The ion laser tube produces a lot of heat and requires active cooling. The typical noble-gas ion-laser plasma consists of a high-current-density glow discharge in a gas in the presence of a magnetic field. Ar/Kr, A mix of argon and krypton can result in a laser with output wavelengths that appear as white light, helium–cadmium, blue laser emission at 442 nm and ultraviolet at 325 nm. Copper vapor, yellow and green emission at 578 nm and 510 nm, xenon Iodine Oxygen Confocal laser scanning microscopy Surgical. Direct write high density PCB lithography, long coherence length models can be used for holography. Laser List of laser types List of plasma articles
32.
Rhodamine B
–
Rhodamine B /ˈroʊdəmiːn/ is a chemical compound and a dye. It is often used as a tracer dye within water to determine the rate and direction of flow, Rhodamine dyes fluoresce and can thus be detected easily and inexpensively with instruments called fluorometers. Rhodamine dyes are used extensively in biotechnology applications such as microscopy, flow cytometry, fluorescence correlation spectroscopy. Rhodamine B is used in biology as a fluorescent dye, sometimes in combination with auramine O, as the auramine-rhodamine stain to demonstrate acid-fast organisms. Rhodamine B is tunable around 610 nm when used as a laser dye and its luminescence quantum yield is 0.65 in basic ethanol,0.49 in ethanol,1.0, and 0.68 in 94% ethanol. The fluorescence yield is temperature dependent, the solubility of rhodamine B in water is ~15 g/L. However, the solubility in acid solution is ~400 g/L. Chlorinated tap water decomposes rhodamine B, Rhodamine B solutions adsorb to plastics and should be kept in glass. Rhodamine B is being tested for use as a biomarker in oral rabies vaccines for wildlife, such as raccoons, the rhodamine is incorporated into the animals whiskers and teeth. It is also mixed with herbicides to show where they have been used. Rhodamine B is mixed with Quinacridone Magenta to make the bright pink watercolor known as Opera Rose, in California, rhodamine B is suspected to be carcinogenic and thus products containing it must contain a warning on its label. Cases of economically motivated adulteration, where it has illegally used to impart a red color to chili powder, have come to the attention of food safety regulators. Dye laser Laser dyes Rhodamine Rhodamine 6G
33.
F. J. Duarte
–
Francisco Javier Frank Duarte is a Chilean-born laser physicist and author/editor of several well-known books on tunable lasers and quantum optics. He introduced the generalized multiple-prism dispersion theory, has discovered various multiple-prism grating oscillator laser configurations, duartes research has mainly focused on physical and laser optics and has taken place at a number of institutions in the academic, industrial, and defense sectors. Duarte and Piper introduced the multiple-prism near-grazing-incidence grating cavities originally disclosed as copper-laser-pumped narrow-linewidth tunable laser oscillators and he then introduced multiple-prism grating configurations to high-power CO2 laser oscillators. Duarte also developed the theories for narrow-linewidth dispersive laser oscillators, and multiple-prism laser pulse compression, the tunable narrow-linewidth laser oscillator configurations, introduced by Duarte and Piper, were adopted by various research groups working on uranium atomic vapor laser isotope separation. This work was supported by the Australian Atomic Energy Commission, during the course of this research, Duarte writes that he did approach the then federal minister for energy, Sir John Carrick, to advocate for the introduction of an AVLIS facility in Australia. In 2002, he participated in research that led to the separation of lithium using narrow-linewidth tunable diode lasers. From the mid-1980s to early 1990s Duarte and scientists from the US Army Missile Command developed ruggedized narrow-linewidth laser oscillators tunable directly in the visible spectrum and this constituted the first disclosure, in the open literature, of a tunable narrow-linewidth laser tested on a rugged terrain. This research led to experimentation with polymer gain media and in 1994 Duarte reported on the first narrow-linewidth tunable solid state dye laser oscillators and these dispersive oscillator architectures were then refined to yield single-longitudinal-mode emission limited only by Heisenbergs uncertainty principle. In 2005, Duarte and colleagues were the first to demonstrate directional coherent emission from an electrically excited organic semiconductor and these experiments utilized a tandem OLED within an interferometric configuration. In the late 1980s, Duarte invented the N-slit laser interferometer and applied Dirac’s notation to describe quantum mechanically its interferometric, Duarte also derived the cavity linewidth equation, for dispersive laser oscillators, using quantum mechanical principles. More recently, Duarte and colleagues have developed very large N-slit laser interferometers to generate and propagate interferometric characters for secure free-space optical communications, interferometric characters is a term coined in 2002 to link interefometric signals to alphanumerical characters. Duarte provides a description of quantum optics, almost entirely via Diracs notation, in this book he derives the probability amplitude for quantum entanglement, | ψ ⟩ =12 which he calls the Pryce-Ward probability amplitude, from an N-slit interferometric perspective. Duarte also emphasizes a pragmatic approach to quantum mechanics. At Macquarie University, Duarte studied quantum physics under John Clive Ward and his PhD research was on laser physics and his supervisor was James A. Piper. In the area of university politics, he established and led the successful Macquarie science reform movement, macquaries science reform, was widely supported by local scientists including physicists R. E. Aitchison, R. E. B. Makinson, A. W. Pryor, and J. C. Ward, in 1980, Duarte was elected as one of the Macquarie representatives to the Australian Union of Students from where he was expelled, and then reinstated, for running over the tables. Following completion of his PhD work, Duarte did post doctoral research, with B. J. Orr at the University of New South Wales, in 1983, Duarte traveled to the United States to assume a physics professorship at the University of Alabama. In 1985 he joined the Imaging Research Laboratories, at the Eastman Kodak Company, while at Kodak he was chairman of Lasers 87 and subsequent conferences in this series
34.
International Standard Serial Number
–
An International Standard Serial Number is an eight-digit serial number used to uniquely identify a serial publication. The ISSN is especially helpful in distinguishing between serials with the same title, ISSN are used in ordering, cataloging, interlibrary loans, and other practices in connection with serial literature. The ISSN system was first drafted as an International Organization for Standardization international standard in 1971, ISO subcommittee TC 46/SC9 is responsible for maintaining the standard. When a serial with the content is published in more than one media type. For example, many serials are published both in print and electronic media, the ISSN system refers to these types as print ISSN and electronic ISSN, respectively. The format of the ISSN is an eight digit code, divided by a hyphen into two four-digit numbers, as an integer number, it can be represented by the first seven digits. The last code digit, which may be 0-9 or an X, is a check digit. Formally, the form of the ISSN code can be expressed as follows, NNNN-NNNC where N is in the set, a digit character. The ISSN of the journal Hearing Research, for example, is 0378-5955, where the final 5 is the check digit, for calculations, an upper case X in the check digit position indicates a check digit of 10. To confirm the check digit, calculate the sum of all eight digits of the ISSN multiplied by its position in the number, the modulus 11 of the sum must be 0. There is an online ISSN checker that can validate an ISSN, ISSN codes are assigned by a network of ISSN National Centres, usually located at national libraries and coordinated by the ISSN International Centre based in Paris. The International Centre is an organization created in 1974 through an agreement between UNESCO and the French government. The International Centre maintains a database of all ISSNs assigned worldwide, at the end of 2016, the ISSN Register contained records for 1,943,572 items. ISSN and ISBN codes are similar in concept, where ISBNs are assigned to individual books, an ISBN might be assigned for particular issues of a serial, in addition to the ISSN code for the serial as a whole. An ISSN, unlike the ISBN code, is an identifier associated with a serial title. For this reason a new ISSN is assigned to a serial each time it undergoes a major title change, separate ISSNs are needed for serials in different media. Thus, the print and electronic versions of a serial need separate ISSNs. Also, a CD-ROM version and a web version of a serial require different ISSNs since two different media are involved, however, the same ISSN can be used for different file formats of the same online serial
verify (what is 
?)
