1.
Life
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Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. The criteria can at times be ambiguous and may or may not define viruses, viroids, biology is the primary science concerned with the study of life, although many other sciences are involved. The definition of life is controversial, the current definition is that organisms maintain homeostasis, are composed of cells, undergo metabolism, can grow, adapt to their environment, respond to stimuli, and reproduce. However, many other definitions have been proposed, and there are some borderline cases. Modern definitions are more complex, with input from a diversity of scientific disciplines, biophysicists have proposed many definitions based on chemical systems, there are also some living systems theories, such as the Gaia hypothesis, the idea that the Earth itself is alive. Another theory is that life is the property of systems, and yet another is elaborated in complex systems biology. Abiogenesis describes the process of life arising from non-living matter. Properties common to all organisms include the need for certain chemical elements to sustain biochemical functions. Life on Earth first appeared as early as 4.28 billion years ago, soon after ocean formation 4.41 billion years ago, Earths current life may have descended from an RNA world, although RNA-based life may not have been the first. The mechanism by which began on Earth is unknown, though many hypotheses have been formulated and are often based on the Miller–Urey experiment. The earliest known forms are microfossils of bacteria. In July 2016, scientists reported identifying a set of 355 genes believed to be present in the last universal ancestor of all living organisms. Since its primordial beginnings, life on Earth has changed its environment on a time scale. To survive in most ecosystems, life must often adapt to a range of conditions. Some microorganisms, called extremophiles, thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth, Aristotle was the first person to classify organisms. Later, Carl Linnaeus introduced his system of nomenclature for the classification of species. Eventually new groups and categories of life were discovered, such as cells and microorganisms, cells are sometimes considered the smallest units and building blocks of life. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many such as proteins
2.
Biological agent
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In addition to these living and/or replicating pathogens, biological toxins are also included among the bio-agents. More than 1,200 different kinds of potentially weaponizable bio-agents have been described and studied to date, Biological agents have the ability to adversely affect human health in a variety of ways, ranging from relatively mild allergic reactions to serious medical conditions, including death. Many of these organisms are ubiquitous in the environment where they are found in water, soil, plants. Bio-agents may be amenable to weaponization to render them easier to deploy or disseminate, genetic modification may enhance their incapacitating or lethal properties, or render them imprevious to conventional treatments or preventives. Since many bio-agents reproduce rapidly and require minimal resources for propagation, the Biological Weapons Convention is an international treaty banning the use or stockpiling of bio-agents, as of February 2015 there were 171 state signatories. Bio-agents are, however, widely studied for defensive purposes under various biosafety levels, in 2008, according to a U. S. The former US biological warfare program categorized its weaponized anti-personnel bio-agents as either Lethal Agents or Incapacitating Agents, since 1997, United States law has declared a list of bio-agents designated by the U. S. Department of Health and Human Services or the U. S. Select agents are divided into HHS select agents and toxins, USDA select agents and toxins and Overlap select agents, centers for Disease Control and Prevention breaks biological agents into three categories, Category A, Category B, and Category C. Category A agents pose the greatest threat to the U. S, Category A agents include anthrax, botulism, plague, smallpox, tularemia, and viral hemorrhagic fevers. The following pathogens and toxins were weaponized by one nation or another at some time, NATO abbreviations are included where applicable. Additionally, the Soviet Union is known to have weaponized Marburg virus in the 1970s and 80s, simulants are organisms or substances which mimic physical or biological properties of real biological agents, without being pathogenic. They are used to study the efficiency of various dissemination techniques or the risks caused by the use of agents in bioterrorism. The typical size of simulants enables it to buildings with closed windows and doors. This bears a sigificant health risk, even if the agent is normally not pathogenic
3.
Fungus
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A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from the other eukaryotic life kingdoms of plants, a characteristic that places fungi in a different kingdom from plants, bacteria and some protists, is chitin in their cell walls. Similar to animals, fungi are heterotrophs, they acquire their food by absorbing dissolved molecules, growth is their means of mobility, except for spores, which may travel through the air or water. Fungi are the principal decomposers in ecological systems and this fungal group is distinct from the structurally similar myxomycetes and oomycetes. The discipline of biology devoted to the study of fungi is known as mycology, in the past, mycology was regarded as a branch of botany, although it is now known fungi are genetically more closely related to animals than to plants. Abundant worldwide, most fungi are inconspicuous because of the size of their structures. Fungi include symbionts of plants, animals, or other fungi and they may become noticeable when fruiting, either as mushrooms or as molds. Fungi perform a role in the decomposition of organic matter and have fundamental roles in nutrient cycling. Since the 1940s, fungi have been used for the production of antibiotics, Fungi are also used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, the fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies. Fungi can break down manufactured materials and buildings, and become significant pathogens of humans, losses of crops due to fungal diseases or food spoilage can have a large impact on human food supplies and local economies. The fungus kingdom encompasses a diversity of taxa with varied ecologies, life cycle strategies. However, little is known of the biodiversity of Kingdom Fungi. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, which is divided into one subkingdom, seven phyla, and ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace, a group of all the fungi present in a particular area or geographic region is known as mycobiota, e. g. the mycobiota of Ireland. Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies. The fungi are now considered a kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago. Fungi have membrane-bound cytoplasmic organelles such as mitochondria, sterol-containing membranes and they have a characteristic range of soluble carbohydrates and storage compounds, including sugar alcohols, disaccharides, and polysaccharides
4.
Bacteria
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Bacteria constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods, Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only half of the bacterial phyla have species that can be grown in the laboratory. The study of bacteria is known as bacteriology, a branch of microbiology, There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a millilitre of fresh water. There are approximately 5×1030 bacteria on Earth, forming a biomass which exceeds that of all plants, Bacteria are vital in many stages of the nutrient cycle by recycling nutrients such as the fixation of nitrogen from the atmosphere. The nutrient cycle includes the decomposition of bodies and bacteria are responsible for the putrefaction stage in this process. In March 2013, data reported by researchers in October 2012, was published and it was suggested that bacteria thrive in the Mariana Trench, which with a depth of up to 11 kilometres is the deepest known part of the oceans. Other researchers reported related studies that microbes thrive inside rocks up to 580 metres below the sea floor under 2.6 kilometres of ocean off the coast of the northwestern United States. According to one of the researchers, You can find microbes everywhere—theyre extremely adaptable to conditions, the vast majority of the bacteria in the body are rendered harmless by the protective effects of the immune system, though many are beneficial particularly in the gut flora. However several species of bacteria are pathogenic and cause diseases, including cholera, syphilis, anthrax, leprosy. The most common fatal diseases are respiratory infections, with tuberculosis alone killing about 2 million people per year. In developed countries, antibiotics are used to treat infections and are also used in farming, making antibiotic resistance a growing problem. Once regarded as constituting the class Schizomycetes, bacteria are now classified as prokaryotes. Unlike cells of animals and other eukaryotes, bacterial cells do not contain a nucleus and these evolutionary domains are called Bacteria and Archaea. The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, for about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. In 2008, fossils of macroorganisms were discovered and named as the Francevillian biota, however, gene sequences can be used to reconstruct the bacterial phylogeny, and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. Bacteria were also involved in the second great evolutionary divergence, that of the archaea, here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea
5.
Unicellular organism
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A unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell, unlike a multicellular organism that consists of more than one cell. Historically, simple unicellular organisms have been referred to as monads, though this term is used more specifically to describe organisms of the genus Monas. The main groups of organisms are bacteria, archaea, protozoa, unicellular algae. Unicellular organisms fall into two categories, prokaryotic organisms and eukaryotic organisms. Unicellular organisms are thought to be the oldest form of life, prokaryotes, most Protista, and some fungi are unicellular. Although some of these live in colonies, they dont exhibit specialization. These organisms live together, and each cell in the colony is the same, however, each individual cell must carry out all life processes to survive. In contrast, even the simplest multicellular organisms have cells that depend on each other to survive, most multicellular organisms have a unicellular life-cycle stage. Gametes, for example, are reproductive unicells for multicellular organisms, additionally, multicellularity appears to have evolved independently many times in the history of life. Some organisms are partially uni- and multicellular, like Dictyostelium discoideum, additionally, unicellular organisms can be multinucleate, like Myxogastria and Plasmodium. Candidatus Magnetoglobus multicellular, related to Deltaproteobacteria, is a multicellular prokaryote and it is neither unicellular, nor a colony. Primitive cells, often referred to as protocells, are the precursors to todays unicellular organisms, the RNA world hypothesis assumes that RNA molecules could form in abiotic conditions, which would require nucleic acids and ribose to be present. Theoretical and experimental findings show that nucleic acids and sugars could have been synthesized in early prebiotic conditions, compartmentalization was necessary for chemical reactions to be more likely as well as to differentiate reactions with the external environment. For example, an early RNA replicator ribozyme may have replicated other replicator ribozymes of different RNA sequences if not kept separate, when amphiphiles like lipids are placed in water, the hydrophobic tails aggregate to form micelles and vesicles, with the hydrophilic ends facing outwards. Primitive cells likely used self-assembling fatty-acid vesicles to separate chemical reactions, because of their simplicity and ability to self-assemble in water, its likely that these simple membranes predated other forms of early biological molecules. Prokaryotes lack membrane-bound organelles, such as mitochondria or a nucleus, instead, most prokaryotes have an irregular region that contains DNA, known as the nucleoid. Most prokaryotes have a single, circular chromosome, which is in contrast to eukaryotes, nutritionally, prokaryotes have the ability to utilize a wide range of organic and inorganic material for use in metabolism, including sulfur, cellulose, ammonia, or nitrite. Prokaryotes as a whole are ubiquitous in the environment and exist in extreme environments as well, bacteria are one of the world’s oldest forms of life, and are found virtually everywhere in nature
6.
Eukaryote
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A eukaryote is any organism whose cells contain a nucleus and other organelles enclosed within membranes. Eukaryotes belong to the taxon Eukarya or Eukaryota, the presence of a nucleus gives eukaryotes their name, which comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, in addition, plants and algae contain chloroplasts. Eukaryotic organisms may be unicellular or multicellular, only eukaryotes form multicellular organisms consisting of many kinds of tissue made up of different cell types. Eukaryotes can reproduce asexually through mitosis and sexually through meiosis and gamete fusion. In mitosis, one cell divides to produce two identical cells. In meiosis, DNA replication is followed by two rounds of division to produce four daughter cells each with half the number of chromosomes as the original parent cell. These act as sex cells resulting from genetic recombination during meiosis, the domain Eukaryota appears to be monophyletic, and so makes up one of the three domains of life. The two other domains, Bacteria and Archaea, are prokaryotes and have none of the above features, eukaryotes represent a tiny minority of all living things. However, due to their larger size, eukaryotes collective worldwide biomass is estimated at about equal to that of prokaryotes. Eukaryotes first developed approximately 1. 6–2.1 billion years ago, in 1905 and 1910, the Russian biologist Konstantin Mereschkowsky argued three things about the origin of nucleated cells. Firstly, plastids were reduced cyanobacteria in a symbiosis with a non-photosynthetic host, secondly, the host had earlier in evolution formed by symbiosis between an amoeba-like host and a bacteria-like cell that formed the nucleus. Thirdly, plants inherited photosynthesis from cyanobacteria, the split between the prokaryotes and eukaryotes was introduced in the 1960s. The concept of the eukaryote has been attributed to the French biologist Edouard Chatton, the terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch-American microbiologist C. B. van Niel in 1962. In his 1938 work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes. However he mentioned this in one paragraph, and the idea was effectively ignored until Chattons statement was rediscovered by Stanier. In 1967, Lynn Margulis provided microbiological evidence for endosymbiosis as the origin of chloroplasts and mitochondria in cells in her paper. In the 1970s, Carl Woese explored microbial phylogenetics, studying variations in 16S ribosomal RNA and this helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organelles, mitochondria and chloroplasts
7.
Plasmodium
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Plasmodium is a genus of parasitic alveolates, many of which cause malaria in their hosts. The parasite always has two hosts in its cycle, a Dipteran insect host and a vertebrate host. Sexual reproduction always occurs in the insect, making it the definitive host, the life-cycles of Plasmodium species involve several different stages both in the insect and the vertebrate host. These stages include sporozoites, which are injected by the vector into the vertebrate hosts blood. Sporozoites infect the host liver, giving rise to merozoites and hypnozoites and these move into the blood where they infect red blood cells. In the red cells, the parasites can either form more merozoites to infect more red blood cells. In the insect host, gametocytes merge to sexually reproduce, after sexual reproduction, parasites grow into new sporozoites, which move to the insects salivary glands, from which they can infect a vertebrate host bitten by the insect. The genus Plasmodium was first described in 1885 and it now contains about 200 species, which are spread across the world where both the insect and vertebrate hosts are present. Five species regularly infect humans, while many others infect birds, reptiles, rodents, Plasmodium was first identified when Charles Louis Alphonse Laveran described parasites in the blood of malaria patients in 1880. He named the parasite Oscillaria malariae, the fact that several species may be involved in causing different forms of malaria was first recognized by Camillo Golgi in 1886. Soon thereafter, Giovanni Batista Grassi and Raimondo Filetti named the parasites causing two different types of human malaria Plasmodium vivax and Plasmodium malariae, in 1897, William Welch identified and named Plasmodium falciparum. This was followed by the recognition of the two species of Plasmodium which infect humans, Plasmodium ovale and Plasmodium knowlesi. The contribution of insect hosts to the Plasmodium life cycle was described in 1897 by Ronald Ross and in 1899 by Giovanni Batista Grassi, Amico Bignami, the life cycle of Plasmodium involves several distinct stages in the insect and vertebrate hosts. In infected mosquitoes, parasites in the gland are called sporozoites. When the mosquito bites a vertebrate host, sporozoites are injected into the host with the saliva, from there, the sporozoites enter the bloodstream and are transported to the liver, where they invade and replicate within hepatocytes. At this point, some species of Plasmodium can form a dormant stage called a hypnozoite which can remain in the liver for many years. The parasites that emerge from infected hepatocytes are called merozoites, within the red blood cells, the merozoites grow first to a ring-shaped form and then to a larger form called a trophozoite. Trophozoites then mature to schizonts which divide several times to produce new merozoites, the infected red blood cell eventually bursts, allowing the new merozoites to travel within the bloodstream to infect new red blood cells
8.
Growth medium
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A growth medium or culture medium is a solid or liquid or semi-solid designed to support the growth of microorganisms or cells, or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells, the most common growth media for microorganisms are nutrient broths and agar plates, specialized media are sometimes required for microorganism and cell culture growth. Some organisms, termed fastidious organisms, require specialized environments due to nutritional requirements. Viruses, for example, are intracellular parasites and require a growth medium containing living cells. The most common media for microorganisms are nutrient broths or LB medium. Liquid media are often mixed with agar and poured via a media dispenser into Petri dishes to solidify. These agar plates provide a medium on which microbes may be cultured. They remain solid, as very few bacteria are able to decompose agar, bacteria grown in liquid cultures often form colloidal suspensions. In the case of cells, this difficulty is often addressed by the addition of blood serum or a synthetic serum replacement to the medium. In the case of microorganisms, no such limitations exist, as they are often unicellular organisms. One other major difference is that cells in culture are often grown on a flat surface to which they attach, and the medium is provided in a liquid form. In contrast, bacteria such as Escherichia coli may be grown on solid or in liquid media, an important distinction between growth media types is that of defined versus undefined media. A defined medium will have known quantities of all ingredients, for microorganisms, they consist of providing trace elements and vitamins required by the microbe and especially defined carbon and nitrogen sources. Glucose or glycerol are used as carbon sources, and ammonium salts or nitrates as inorganic nitrogen sources. An undefined medium has some complex ingredients, such as yeast extract or casein hydrolysate, undefined media are sometimes chosen based on price and sometimes by necessity – some microorganisms have never been cultured on defined media. A good example of a medium is the wort used to make beer. The wort contains all the nutrients required for yeast growth, and under anaerobic conditions, when the fermentation process is complete, the combination of medium and dormant microbes, now beer, is ready for consumption. Minimal media can also be used to select for or against recombinants or exconjugants and this supplementation allows for the culturing of specific lines of auxotrophic recombinants
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Heat
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In physics, heat is the amount of energy flowing from one body to another spontaneously due to their temperature difference, or by any means other than through work or the transfer of matter. Thus, energy exchanged as heat during a process changes the energy of each body by equal. The sign of the quantity of heat can indicate the direction of the transfer, for example from system A to system B, negation indicates energy flowing in the opposite direction. While heat flows spontaneously from hot to cold, it is possible to construct a heat pump or refrigeration system that does work to increase the difference in temperature between two systems, conversely, a heat engine reduces an existing temperature difference to do work on another system. Heat is a consequence of the motion of particles. When heat is transferred between two objects or systems, the energy of the object or systems particles increases, as this occurs, the arrangement between particles becomes more and more disordered. In other words, heat is related to the concept of entropy, historically, many energy units for measurement of heat have been used. The standards-based unit in the International System of Units is the joule, Heat is measured by its effect on the states of interacting bodies, for example, by the amount of ice melted or a change in temperature. The quantification of heat via the change of a body is called calorimetry. In calorimetry, sensible heat is defined with respect to a specific chosen state variable of the system, sensible heat causes a change of the temperature of the system while leaving the chosen state variable unchanged. Heat transfer that occurs at a constant system temperature but changes the state variable is called latent heat with respect to the variable, for infinitesimal changes, the total incremental heat transfer is then the sum of the latent and sensible heat. Physicist James Clerk Maxwell, in his 1871 classic Theory of Heat, was one of many who began to build on the established idea that heat has something to do with matter in motion. This was the idea put forth by Benjamin Thompson in 1798. One of Maxwells recommended books was Heat as a Mode of Motion, Maxwell outlined four stipulations for the definition of heat, It is something which may be transferred from one body to another, according to the second law of thermodynamics. It is a quantity, and so can be treated mathematically. It cannot be treated as a substance, because it may be transformed into something that is not a material substance. Heat is one of the forms of energy and this was the way of the historical pioneers of thermodynamics. Maxwell writes that convection as such is not a purely thermal phenomenon, in thermodynamics, convection in general is regarded as transport of internal energy
10.
Chemical substance
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A chemical substance is a form of matter that has constant chemical composition and characteristic properties. It cannot be separated into components by physical methods, i. e. without breaking chemical bonds. Chemical substances can be chemical elements, chemical compounds, ions or alloys, Chemical substances are often called pure to set them apart from mixtures. A common example of a substance is pure water, it has the same properties. Other chemical substances commonly encountered in pure form are diamond, gold, table salt, however, in practice, no substance is entirely pure, and chemical purity is specified according to the intended use of the chemical. Chemical substances exist as solids, liquids, gases, or plasma, Chemical substances may be combined or converted to others by means of chemical reactions. Forms of energy, such as light and heat, are not matter, a chemical substance may well be defined as any material with a definite chemical composition in an introductory general chemistry textbook. According to this definition a chemical substance can either be a chemical element or a pure chemical compound. But, there are exceptions to this definition, a substance can also be defined as a form of matter that has both definite composition and distinct properties. The chemical substance index published by CAS also includes several alloys of uncertain composition, in geology, substances of uniform composition are called minerals, while physical mixtures of several minerals are defined as rocks. Many minerals, however, mutually dissolve into solid solutions, such that a rock is a uniform substance despite being a mixture in stoichiometric terms. Feldspars are an example, anorthoclase is an alkali aluminium silicate. In law, chemical substances may include both pure substances and mixtures with a composition or manufacturing process. For example, the EU regulation REACH defines monoconstituent substances, multiconstituent substances and substances of unknown or variable composition, the latter two consist of multiple chemical substances, however, their identity can be established either by direct chemical analysis or reference to a single manufacturing process. For example, charcoal is a complex, partially polymeric mixture that can be defined by its manufacturing process. Therefore, although the chemical identity is unknown, identification can be made to a sufficient accuracy. The CAS index also includes mixtures, polymers almost always appear as mixtures of molecules of multiple molar masses, each of which could be considered a separate chemical substance. However, the polymer may be defined by a precursor or reaction
11.
Filtration
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Filtration is any of various mechanical, physical or biological operations that separate solids from fluids by adding a medium through which only the fluid can pass. The fluid that passes through is called the filtrate, in physical filters oversize solids in the fluid are retained and in biological filters particulates are trapped and ingested and metabolites are retained and removed. However, the separation is not complete, solids will be contaminated with some fluid, Filtration occurs both in nature and in engineered systems, there are biologic, geologic, and industrial forms. Filtration is used to separate particles and fluid in a suspension, where the fluid can be a liquid, depending on the application, either one or both of the components may be isolated. Filtration, as an operation is very important in chemistry for the separation of materials of different chemical composition. A solvent is chosen which dissolves one component, while not dissolving the other, by dissolving the mixture in the chosen solvent, one component will go into the solution and pass through the filter, while the other will be retained. This is one of the most important techniques used by chemists to purify compounds, Filtration is also important and widely used as one of the unit operations of chemical engineering. It may be combined with other unit operations to process the feed stream, as in the biofilter. Filtration differs from sieving, where separation occurs at a single perforated layer, in sieving, particles that are too big to pass through the holes of the sieve are retained. In filtration, a multilayer lattice retains those particles that are unable to follow the tortuous channels of the filter, oversize particles may form a cake layer on top of the filter and may also block the filter lattice, preventing the fluid phase from crossing the filter. Filtration differs from adsorption, where it is not the size of particles that causes separation. Some adsorption devices containing activated charcoal and ion exchange resin are commercially called filters, Filtration differs from removal of magnetic contaminants from fluids with magnets, because there is no filter medium. Commercial devices called magnetic filters are sold, but the name reflects their use, the remainder of this article focuses primarily on liquid filtration. There are many different methods of filtration, all aim to attain the separation of substances, separation is achieved by some form of interaction between the substance or objects to be removed and the filter. The substance that is to pass through the filter must be a fluid, methods of filtration vary depending on the location of the targeted material, i. e. whether it is dissolved in the fluid phase or suspended as a solid. There are several filtration techniques depending on the desired outcome namely, hot, cold, some of the major purposes of getting a desired outcome are, for the removal of impurities from a mixture or, for the isolation of solids from a mixture. Hot filtration method is used to separate solids from a hot solution. This is done in order to prevent crystal formation in the filter funnel, one of the most important measure to prevent the formation of crystals in the funnel and to undergo effective hot filtration is the use stemless filter funnel
12.
Disinfectant
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Disinfectants are antimicrobial agents that are applied to the surface of non-living objects to destroy microorganisms that are living on the objects. Disinfectants are different from other agents such as antibiotics, which destroy microorganisms within the body, and antiseptics. Disinfectants are also different from biocides — the latter are intended to destroy all forms of life, Disinfectants work by destroying the cell wall of microbes or interfering with the metabolism. Sanitizer are substances that simultaneously clean and disinfect, Disinfectants are frequently used in hospitals, dental surgeries, kitchens, and bathrooms to kill infectious organisms. Bacterial endospores are most resistant to disinfectants, but some viruses, an alternative term used in the sanitation sector for disinfection of waste streams, sewage sludge or fecal sludge is sanitisation or sanitization. A perfect disinfectant would also complete and full microbiological sterilisation, without harming humans and useful form of life, be inexpensive. However, most disinfectants are also, by nature, potentially harmful to humans or animals, most modern household disinfectants contain Bitrex, an exceptionally bitter substance added to discourage ingestion, as a safety measure. Those that are used indoors should never be mixed with other cleaning products as chemical reactions can occur, the choice of disinfectant to be used depends on the particular situation. Some disinfectants have a spectrum, while others kill a smaller range of disease-causing organisms but are preferred for other properties. There are arguments for creating or maintaining conditions that are not conducive to survival and multiplication. Bacteria can increase in very quickly, which enables them to evolve rapidly. Should some bacteria survive an attack, they give rise to new generations composed completely of bacteria that have resistance to the particular chemical used. Under a sustained attack, the surviving bacteria in successive generations are increasingly resistant to the chemical used. For this reason, some question the wisdom of impregnating cloths, cutting boards, air disinfectants are typically chemical substances capable of disinfecting microorganisms suspended in the air. Disinfectants are generally assumed to be limited to use on surfaces, in 1928, a study found that airborne microorganisms could be killed using mists of dilute bleach. An air disinfectant must be dispersed either as an aerosol or vapour at a sufficient concentration in the air to cause the number of infectious microorganisms to be significantly reduced. In principle, these substances are ideal air disinfectants because they have both high lethality to microorganisms and low mammalian toxicity. The engineering challenge associated with creating a sufficient concentration of the glycol vapours in the air have not to date been sufficiently addressed, Alcohols are most effective when combined with distilled water to facilitate diffusion through the cell membrane, 100% alcohol typically denatures only external membrane proteins
13.
Pasteurization
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Pasteurization or pasteurisation is a process that kills microbes in food and drink, such as milk, juice, canned food, and others. It was invented by French scientist Louis Pasteur during the nineteenth century, in 1864 Pasteur discovered that heating beer and wine was enough to kill most of the bacteria that caused spoilage, preventing these beverages from turning sour. The process achieves this by eliminating pathogenic microbes and lowering microbial numbers to prolong the quality of the beverage, today, pasteurization is used widely in the dairy industry and other food processing industries to achieve food preservation and food safety. Unlike sterilization, pasteurization is not intended to kill all microorganisms in the food, instead, it aims to reduce the number of viable pathogens so they are unlikely to cause disease. Commercial-scale sterilization of food is not common because it affects the taste. Certain foods, such as products, may be superheated to ensure pathogenic microbes are destroyed. The process of heating wine for preservation purposes has been known in China since 1117, much later, in 1768, an Italian priest and scientist Lazzaro Spallanzani proved experimentally that heat killed bacteria, and that they do not reappear if the product is hermetically sealed. He placed the food in glass jars, sealed them with cork and sealing wax, in that same year, the French military offered a cash prize of 12,000 francs for a new method to preserve food. After some 14 or 15 years of experimenting, Appert submitted his invention and won the prize in January 1810, later that year, Appert published LArt de conserver les substances animales et végétales. This was the first cookbook of its kind on modern food preservation methods, la Maison Appert, in the town of Massy, near Paris, became the first food-bottling factory in the world, preserving a variety of food in sealed bottles. Apperts method was to fill thick, large-mouthed glass bottles with produce of every description, ranging from beef and fowl to eggs, milk and his greatest success for publicity was an entire sheep. He left air space at the top of the bottle, the bottle was then wrapped in canvas to protect it, while it was dunked into boiling water and then boiled for as much time as Appert deemed appropriate for cooking the contents thoroughly. Appert patented his method, sometimes called appertisation, in his honor, Apperts method was so simple and workable that it quickly became widespread. In 1810, British inventor and merchant Peter Durand, also of French origin, patented his own method, in 1812, Englishmen Bryan Donkin and John Hall purchased both patents and began producing preserves. Just a decade later, Apperts method of canning had made its way to America, Apperts preservation by boiling involved heating the food to an unnecessarily high temperature, and for an unnecessarily long time, which could destroy some of the flavor of the preserved food. A less aggressive method was developed by the French chemist Louis Pasteur during an 1864 summer holiday in Arbois, in honour of Pasteur, the process became known as pasteurization. Pasteurization was originally used as a way of preventing wine and beer from souring, in the United States in the 1870s, it was common for milk to contain substances intended to mask spoilage before milk was regulated. Milk is an excellent medium for growth, and when stored at ambient temperature bacteria
14.
Nicolas Appert
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Nicolas Appert, was the French inventor of airtight food preservation. Appert, known as the father of canning, was a confectioner, Appert was a confectioner and chef in Paris from 1784 to 1795. In 1795, he began experimenting with ways to preserve foodstuffs, succeeding with soups, vegetables, juices, dairy products, jellies, jams and he placed the food in glass jars, sealed them with cork and sealing wax and placed them in boiling water. In 1795 the French military offered a prize of 12,000 francs for a new method to preserve food. This was the first cookbook of its kind on modern food preservation methods, la Maison Appert, in the town of Massy, near Paris, became the first food bottling factory in the world, years before Louis Pasteur proved that heat killed bacteria. Appert patented his invention and established a business to preserve a variety of food in sealed bottles, apperts method was to fill thick, large-mouthed glass bottles with produce of every description, ranging from beef, fowl, eggs, milk, and prepared dishes. His greatest success for publicity was an entire sheep and he left air space at the top of the bottle, and the cork would then be sealed firmly in the jar by using a vise. The bottle was then wrapped in canvas to protect it, while it was dunked into boiling water, in honor of Appert, canning is sometimes called appertisation, but should be distinguished from pasteurization. Apperts method was so simple and workable that it became widespread. In 1810, British inventor and merchant Peter Durand also of French origin, patented his own method, in 1812 Englishmen Bryan Donkin and John Hall purchased both patents and began producing preserves. Just a decade later, the Appert method of canning had made its way to America, in 1991, a monumental statue of Appert, a work in bronze by the artist Jean-Robert Ipousteguy, was erected in Châlons-en-Champagne. A plaque was affixed to his birthplace in 1986, in 1999, busts of Appert by Richard Bruyère were erected in Institute of Food Technologists I. F. T. Chicago, Massy, and Museum of Fine Arts in Châlons-en-Champagne, in 2010, a statue of Appert by Roger Marion was erected in Malataverne. There are 72 streets named after Nicolas Appert in France, there is a high school named after Nicolas Appert in Orvault, France. In 1955 a French postal stamp commemorated him,2010 was declared Nicolas Appert Year, a national celebration, by the French ministry of culture. The Principality of Monaco issued a stamp featuring Appert. An exhibition entitled Mise en boîte was held at the Musée des Beaux-Arts et dArchéologie de Châlons-en-Champagne, since 1942, each year the Chicago Section of the Institute of Food Technologists awards the Nicholas Appert Award, recognizing lifetime achievement in food technology. The student association of the Food Technology education at Wageningen University is called Nicolas Appert, since 1972 this association has focused on improving the courses related to food technology education and organises several events each year for students and alumni
15.
Canning
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Canning is a method of preserving food in which the food contents are processed and sealed in an airtight container. Canning provides a shelf life ranging from one to five years. A freeze-dried canned product, such as canned dried lentils, could last as long as 30 years in an edible state. In 1974, samples of canned food from the wreck of the Bertrand, although appearance, smell and vitamin content had deteriorated, there was no trace of microbial growth and the 109-year-old food was determined to be still safe to eat. The larger armies of the period required increased and regular supplies of quality food, limited food availability was among the factors limiting military campaigns to the summer and autumn months. In 1809, Nicolas Appert, a French confectioner and brewer, observed that food cooked inside a jar did not spoil unless the seals leaked, Appert was awarded the prize in 1810 by Count Montelivert, a French minister of the interior. The reason for lack of spoilage was unknown at the time, unfortunately for Appert, the factory which he had built with his prize money was razed in 1814 by Allied soldiers when they entered France. Following the end of the Napoleonic Wars, the process was gradually employed in other European countries. Durand did not pursue food canning himself, selling his patent in 1811 to Bryan Donkin and John Hall, Bryan Donkin developed the process of packaging food in sealed airtight cans, made of tinned wrought iron. Initially, the process was slow and labour-intensive, as each large can had to be hand-made. The main market for the food at this stage was the British Army, by 1817 Donkin recorded that he had sold £3000 worth of canned meat in six months. In 1824 Sir William Edward Parry took canned beef and pea soup with him on his voyage to the Arctic in HMS Fury, in 1829, Admiral Sir James Ross also took canned food to the Arctic, as did Sir John Franklin in 1845. Some of his stores were found by the expedition led by Captain Leopold McLintock in 1857. One of these cans was opened in 1939, and was edible and nutritious, throughout the mid-19th century, canned food became a status symbol amongst middle-class households in Europe, being something of a frivolous novelty. Increasing mechanization of the process, coupled with a huge increase in urban populations across Europe. Demand for canned food greatly increased during wars, urban populations in Victorian Britain demanded ever-increasing quantities of cheap, varied, quality food that they could keep at home without having to go shopping daily. In response, companies such as Underwood, Nestlé, Heinz, in particular, Crosse and Blackwell took over the concern of Donkin Hall and Gamble. Shortages of canned food in the British Army in 1917 led to the government issuing cigarettes and amphetamines to soldiers to suppress their appetites, after the war, companies that had supplied military canned food improved the quality of their goods for civilian sale
16.
Foodborne illness
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Symptoms vary depending on the cause, and are described below in this article. A few broad generalizations can be made, e. g, the incubation period ranges from hours to days, depending on the cause and on how much was consumed. The incubation period tends to cause sufferers to not associate the symptoms with the item consumed, symptoms often include vomiting, fever, and aches, and may include diarrhea. Some types of microbes stay in the intestine, some produce a toxin that is absorbed into the bloodstream, Foodborne illness usually arises from improper handling, preparation, or food storage. Good hygiene practices before, during, and after food preparation can reduce the chances of contracting an illness, there is a consensus in the public health community that regular hand-washing is one of the most effective defenses against the spread of foodborne illness. The action of monitoring food to ensure that it will not cause illness is known as food safety. Foodborne disease can also be caused by a variety of toxins that affect the environment. Foodborne illness can also be caused by pesticides or medicines in food, bacteria are a common cause of foodborne illness. In the United Kingdom during 2000, the bacteria involved were the following, Campylobacter jejuni 77. 3%, Salmonella 20. 9%, Escherichia coli O157, H71. 4%. In the past, bacterial infections were thought to be prevalent because few places had the capability to test for norovirus. Toxins from bacterial infections are delayed because the bacteria need time to multiply, as a result, symptoms associated with intoxication are usually not seen until 12–72 hours or more after eating contaminated food. However, in cases, such as Staphylococcal food poisoning. Most common bacterial foodborne pathogens are, Campylobacter jejuni which can lead to secondary Guillain–Barré syndrome and periodontitis Clostridium perfringens, enterotoxins can produce illness even when the microbes that produced them have been killed. Symptom appearance varies with the toxin but may be rapid in onset and this causes intense vomiting including or not including diarrhea, and staphylococcal enterotoxins are the most commonly reported enterotoxins although cases of poisoning are likely underestimated. The CDC has estimated about 240,000 cases per year in the United States, many foodborne illnesses remain poorly understood. In August 2006, the United States Food and Drug Administration approved Phage therapy which involves spraying meat with viruses that infect bacteria and this has raised concerns, because without mandatory labelling consumers would not be aware that meat and poultry products have been treated with the spray. At home, prevention mainly consists of food safety practices. Many forms of bacterial poisoning can be prevented by cooking it sufficiently, many toxins, however, are not destroyed by heat treatment
17.
Food irradiation
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Food irradiation is the process of exposing foodstuffs to ionizing radiation. Ionizing radiation is energy that can be transmitted without direct contact to the source of the energy capable of freeing electrons from their bonds in the targeted food. This treatment is used to food, reduce the risk of food borne illness, prevent the spread of invasive pests. Irradiated food does not become radioactive, the radiation can be emitted by a radioactive substance or generated electrically. Irradiation is also used for applications, such as medical devices. Although consumer perception of foods treated with irradiation is more negative than those processed by other means, one family of chemicals are uniquely formed by irradiation, and this product is nontoxic. When irradiating food, all other chemicals occur in a lower or comparable frequency to other processing techniques. Food irradiation is permitted by over 60 countries, with about 500,000 metric tons of food annually processed worldwide, the regulations that dictate how food is to be irradiated, as well as the food allowed to be irradiated, vary greatly from country to country. Irradiation is used to reduce or eliminate the risk of food born illnesses, prevent or slow down spoilage, arrest maturation or sprouting and as a treatment against pests. Depending on the dose, some or all of the organisms, microorganisms, bacteria. In this respect it is similar to pasteurization, Irradiation is used to create safe foods for people at high risk of infection or for conditions where food must be stored for long periods of time and or proper storage conditions are not available. Foods that can tolerate irradiation at sufficient doses are treated to ensure that the product is completely sterilized and this is most commonly done with rations for astronauts, special diets for hospital patients. Irradiation is used to create shelf stable products, since irradiation reduces the populations of spoilage microorganisms and because pre-packed food can be irradiated, the packaging prevents recontamination into the final product. Irradiation is used to reduce post harvest losses and it reduces populations of spoilage micro-organisms in the food and can slow down the speed at which enzymes change the food and therefore slows spoilage, ripening, and inhibits sprouting. Food is also irradiated to prevent the spread of invasive pest species through trade in vegetables and fruits. The pests are sterilized when the food is treated by low doses of irradiation, in general the higher doses required to destroy pests such as insects, mealybugs, mites, moths and butterflies either affect the look or taste or cannot be tolerated by fresh produce. Low dosage treatments enables trade across quarantine boundaries and may help reduce spoilage. Irradiation has been approved by many countries, for example in the US the FDA has approved food irradiation for over 50 years and this phytosanitary irradiation aims to render any hitch-hiking pest incapable of breeding
18.
Joseph Lister
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Joseph Lister, 1st Baron Lister, OM PC PRS, known between 1883 and 1897 as Sir Joseph Lister, Bt. was a British surgeon and a pioneer of antiseptic surgery. He promoted the idea of sterile portable ports while working at the Glasgow Royal Infirmary, Lister successfully introduced carbolic acid to sterilise surgical instruments and to clean wounds. Applying Louis Pasteurs advances in microbiology, Lister championed the use of acid as an antiseptic. He first suspected it would prove an adequate disinfectant because it was used to ease the stench from fields irrigated with sewage waste and he presumed it was safe because fields treated with carbolic acid produced no apparent ill-effects on the livestock that later grazed upon them. Listers work led to a reduction in post-operative infections and made safer for patients. Lister came from a prosperous Quaker home in West Ham, Essex, England, a son of Joseph Jackson Lister, at school, he became a fluent reader of French and German. A young Joseph Lister attended Benjamin Abbotts Isaac Brown Academy, a Quaker school in Hitchin, as a teenager, Lister attended Grove House School Tottenham, studying mathematics, natural science, and languages. He attended University College, London, one of only a few institutions which accepted Quakers at that time and he initially studied botany and obtained a bachelor of Arts degree in 1847. He registered as a student and graduated with honours as Bachelor of Medicine. In 1854, Lister became both first assistant to and friend of surgeon James Syme at the University of Edinburgh, Edinburgh Royal Infirmary in Scotland. There he joined the Royal Medical Society and presented two dissertations, in 1855 and 1871, which are still in the possession of the Society today and he subsequently left the Quakers, joined the Scottish Episcopal Church, and eventually married Symes daughter, Agnes. On their honeymoon, they spent 3 months visiting leading medical institutes in France, by this time, Agnes was enamoured of medical research and was Listers partner in the laboratory for the rest of her life. Before Listers studies of surgery, most people believed that damage from exposures to bad air was responsible for infections in wounds. Hospital wards were occasionally aired out at midday as a precaution against the spread of infection via miasma, a surgeon was not required to wash his hands before seeing a patient because such practices were not considered necessary to avoid infection. Despite the work of Ignaz Semmelweis and Oliver Wendell Holmes, Sr. hospitals practiced surgery under unsanitary conditions, Surgeons of the time referred to the good old surgical stink and took pride in the stains on their unwashed operating gowns as a display of their experience. Pasteur suggested three methods to eliminate the micro-organisms responsible, filtration, exposure to heat, or exposure to solution/chemical solutions, Lister confirmed Pasteurs conclusions with his own experiments and decided to use his findings to develop antiseptic techniques for wounds. As the first two suggested by Pasteur were dangerous and unsafe for the treatment of human tissue, Lister experimented with the third idea. In 1834, Friedlieb Ferdinand Runge discovered phenol, also known as carbolic acid, upon hearing that creosote had been used for treating sewage, Lister began to test the efficacy of carbolic acid when applied directly to wounds
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Antiseptic
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Antiseptic are antimicrobial substances that are applied to living tissue/skin to reduce the possibility of infection, sepsis, or putrefaction. Disinfectants do not kill bacterial spores e. g. on surgical instruments, even sterilization may not destroy prions. Some antibiotics are true germicides, capable of destroying microbes, while others are bacteriostatic, antibacterials are antiseptics that have the proven ability to act against bacteria. Microbicides which destroy virus particles are called viricides or antivirals, antisepsis was recommended by Hungarian physician Ignaz Semmelweis in 1847 but, tragically, he was ignored. In this paper, Lister advocated the use of acid as a method of ensuring that any germs present were killed. Some of this work was anticipated by, Ancient Greek physicians Galen and Hippocrates and their theories were bitterly opposed by Galenist Guy de Chauliac and others trained in the classical tradition. Joseph Smith alluded to the use of alcohol as an antiseptic in February 1833, specifically, verse 7 states, And, again, strong drinks are not for the belly, but for the washing of your bodies. More commonly, 3% solutions of hydrogen peroxide have been used in household first aid for scrapes, however, the strong oxidization causes scar formation and increases healing time during fetal development. Iodine is usually used in a solution or as Lugols iodine solution as a pre-. Some people do not recommend disinfecting minor wounds with iodine because of concern that it may induce scar tissue formation, however, concentrations of 1% iodine or less have not been shown to increase healing time and are not otherwise distinguishable from treatment with saline. Polyhexanide is a compound suitable for clinical use in critically colonized or infected acute. The physicochemical action on the bacterial envelope prevents or impedes the development of resistant bacterial strains, balsam of Peru is a mild antiseptic. By continued exposure to antibiotics, bacteria may evolve to the point where they are no longer harmed by these compounds, bacteria can also develop a resistance to antiseptics, but the effect is generally less pronounced. The mechanism by which bacteria evolve may vary in response to different antiseptics, low concentrations of an antiseptic may encourage growth of a bacterial strain that is resistant to the antiseptic, where a higher concentration of the antiseptic would simply kill the bacteria. In addition, use of a high concentration of an antiseptic may cause tissue damage or slow the process of wound healing
20.
Scalpel
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A scalpel, or lancet, is a small and extremely sharp bladed instrument used for surgery, anatomical dissection, and various arts and crafts. Scalpels may be disposable or re-usable. Re-usable scalpels can have permanently attached blades that can be sharpened or, more commonly, disposable scalpels usually have a plastic handle with an extensible blade and are used once, then the entire instrument is discarded. Scalpel blades are usually packed in sterile pouches but are also offered non-sterile. Double-edged scalpels are referred to as lancets, scalpel blades are usually made of hardened and tempered steel, stainless steel, or high carbon steel, in addition, titanium, ceramic, diamond and even obsidian knives are not uncommon. For example, when performing surgery under MRI guidance, steel blades are unusable, historically, the preferred material for surgical scalpels was silver, on account of its antimicrobial properties. Scalpel blades are also offered by manufacturers with a zirconium nitride-coated edge to improve sharpness. Others manufacture blades that are coated to enhance lubricity during a cut. Alternatives to scalpels in surgical applications include electrocautery and lasers, Surgical scalpels consist of two parts, a blade and a handle. The handles are often reusable, with the blades being replaceable, in medical applications, each blade is only used once. The handle is known as a B. P. handle, named after Charles Russell Bard and Morgan Parker. The handle of medical scalpels come in two basic types, the first is a flat handle used in the #3 and #4 handles. The #7 handle is more like a writing pen, rounded at the front. A #4 handle is larger than a #3, blades are manufactured with a corresponding fitment size so that they fit on only one size handle. The following table of blades is incomplete and some blades listed may work with handles not specified here, also called the dinner knife grip. This grip is best for initial incisions and larger cuts, best used for more accurate cuts with smaller blades and the #7 handle. The scalpel is held with the tips of the first and second fingers, care should be taken not to allow the handle to rest too far along the index finger as this promotes an unstable grip and cramped fingers. Graphical and model-making scalpels tend to have handles, with textured grips
21.
Hypodermic needle
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A hypodermic needle, also called a sharp, is a very thin, hollow tube with a sharp tip which contains a small opening at the pointed end. It is commonly used with a syringe, a device with a plunger. They are used to take samples from the body, for example taking blood from a vein in venipuncture. Large bore hypodermic intervention is useful in catastrophic blood loss or treating shock. A hypodermic needle is used for delivery of liquids, or when the injected substance cannot be ingested, either because it would not be absorbed. There are many routes for an injection, with the arm being a common location. The hypodermic needle also serves an important role in research environments where sterile conditions are required, the hypodermic needle significantly reduces contamination during inoculation of a sterile substrate. The ancient Greeks and Romans knew injection as a method of delivery from observations of snakebites. There are also references to anointing and inunction in the Old Testament as well as the works of Homer, christopher Wren performed the earliest confirmed experiments with crude hypodermic needles, performing intravenous injection into dogs in 1656. These experiments consisted of using animal bladders and goose quills to administer drugs such as opium intravenously to dogs, Wren and others’ main interest was to learn if medicines traditionally administered orally would be effective intravenously. Elsholtz of Berlin were the first to experiment with injections in humans and these early experiments were generally ineffective and in some cases fatal. Injection fell out of favor for two centuries, the 19th century saw the development of medicines that were effective in small doses, such as opiates and strychnine. This spurred a renewed interest in direct, controlled application of medicine, some controversy surrounds the question of priority in hypodermic medication. Dr. Francis Rynd is generally credited with the first successful injection in 1844, Dr. Alexander Wood’s main contribution was the all-glass syringe in 1851, which allowed the user to estimate dosage based on the levels of liquid observed through the glass. Wood used hypodermic needles and syringes primarily for the application of localized, subcutaneous injection, simultaneous to Wood’s work in Edinburgh, Dr. Charles Pravaz of Lyon also experimented with sub-dermal injections in sheep using a syringe of his own design. Pravaz designed a syringe measuring 3 cm long and 5 mm in diameter, Dr. Charles Hunter, a London surgeon, is credited with the coining of the term hypodermic to describe subcutaneous injection in 1858. The name originates from two Greek words, hypo, under, and derma, skin, Hunter and Wood were involved in lengthy legal disputes over not only the origin of the modern hypodermic needle, but also because of their disagreement to the medicine’s effect once administered. Dr. Wood can be credited with the popularization and acceptance of injection as a medical technique, as well as the widespread use
22.
Planetary protection
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There are two types of interplanetary contamination. Forward contamination is the transfer of organisms from Earth to another celestial body. A major goal of protection is to preserve the planetary record of natural processes by preventing introduction of Earth-originated life. Back contamination is the transfer of organisms, if such exist. The potential problem of lunar and planetary contamination was first raised at the International Astronautical Federation VIIth Congress in Rome in 1956, Mars and possibly Venus need to remain uncontaminated only until study by manned ships becomes possible”. In 1959, planetary protection was transferred to the newly formed Committee on Space Research, COSPAR in 1964 issued Resolution 26 affirming that, In 1967, the US, USSR, and UK ratified the United Nations Outer Space Treaty. The legal basis for planetary protection lies in Article IX of this treaty, another 24 have signed but not ratified. All the current space-faring nation states have signed and ratified it. Amongst nations with space faring aspirations, some have not yet ratified, the provisions of the Outer Space Treaty are therefore binding on all states, even those who have neither signed nor ratified it. For forward contamination, the phrase to be interpreted is harmful contamination, two legal reviews came to differing interpretations of this clause. However the currently accepted interpretation is that “any contamination which would result in harm to a state’s experiments or programs is to be avoided”, NASA policy states explicitly that “the conduct of scientific investigations of possible extraterrestrial life forms, precursors, and remnants must not be jeopardized”. The Committee on Space Research meets every two years, in a gathering of 2000 to 3000 scientists, and one of its tasks is to develop recommendations for avoiding interplanetary contamination and its legal basis is Article IX of the Outer Space Treaty. Its recommendations depend on the type of mission and the celestial body explored. COSPAR categorizes the missions into 5 groups, Category I, Any mission to locations not of direct interest for chemical evolution or the origin of life, examples include the Moon, Venus, and comets. Requires simple documentation only, primarily to outline intended or potential impact targets, requires more involved documentation than Category II. Other requirements, depending on the mission, may include trajectory biasing, clean room assembly, bioburden reduction, Category IV, Lander or probe missions to the same locations as Category III. Measures to be applied depend on the body and the planned operations. For other landers and rovers, the requirements would be for decontamination, missions to Mars in category IV are subclassified further, Category IVa
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Planetary habitability
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Planetary habitability is the measure of a planets or a natural satellites potential to have habitable environments hospitable to life. Habitable environments do not need to contain life, Life may develop directly on a planet or satellite or be transferred to it from another body, a hypothetical process known as panspermia. Research and theory in this regard is a component of planetary science, in determining the habitability potential of a body, studies focus on its bulk composition, orbital properties, atmosphere, and potential chemical interactions. Stellar characteristics of importance include mass and luminosity, stable variability, the idea that planets beyond Earth might host life is an ancient one, though historically it was framed by philosophy as much as physical science. The late 20th century saw two breakthroughs in the field, the discovery of extrasolar planets, beginning in the early 1990s and accelerating thereafter, has provided further information for the study of possible extraterrestrial life. These findings confirm that the Sun is not unique among stars in hosting planets, the chemistry of life may have begun shortly after the Big Bang,13.8 billion years ago, during a habitable epoch when the Universe was only 10–17 million years old. According to the hypothesis, microscopic life—distributed by meteoroids, asteroids. Nonetheless, Earth is the place in the Universe known to harbor life. 11 billion of these planets may be orbiting Sun-like stars. The nearest such planet may be 12 light-years away, according to the scientists, an understanding of planetary habitability begins with the host star. Under the auspices of SETIs Project Phoenix, scientists Margaret Turnbull and Jill Tarter developed the HabCat in 2002. According to research published in August 2015, very large galaxies may be favorable to the formation and development of habitable planets than smaller galaxies. The spectral class of a star indicates its photospheric temperature, which correlates to overall mass, the appropriate spectral range for HabStars is considered to be late F or G, to mid-K. This corresponds to temperatures of a more than 7,000 K down to a little more than 4,000 K, the Sun. This spectral range probably accounts for between 5% and 10% of stars in the local Milky Way galaxy, middle-class stars of this sort have a number of characteristics considered important to planetary habitability, They live at least a few billion years, allowing life a chance to evolve. More luminous main-sequence stars of the O, B, and A classes usually live less than a billion years and they emit enough high-frequency ultraviolet radiation to trigger important atmospheric dynamics such as ozone formation, but not so much that ionisation destroys incipient life. Liquid water may exist on the surface of planets orbiting them at a distance that does not induce tidal locking, k-type stars may be able to support life far longer than the Sun. Gliese 581 c, a super-Earth, has been found orbiting in the zone of a red dwarf
24.
Temperature
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A temperature is an objective comparative measurement of hot or cold. It is measured by a thermometer, several scales and units exist for measuring temperature, the most common being Celsius, Fahrenheit, and, especially in science, Kelvin. Absolute zero is denoted as 0 K on the Kelvin scale, −273.15 °C on the Celsius scale, the kinetic theory offers a valuable but limited account of the behavior of the materials of macroscopic bodies, especially of fluids. Temperature is important in all fields of science including physics, geology, chemistry, atmospheric sciences, medicine. The Celsius scale is used for temperature measurements in most of the world. Because of the 100 degree interval, it is called a centigrade scale.15, the United States commonly uses the Fahrenheit scale, on which water freezes at 32°F and boils at 212°F at sea-level atmospheric pressure. Many scientific measurements use the Kelvin temperature scale, named in honor of the Scottish physicist who first defined it and it is a thermodynamic or absolute temperature scale. Its zero point, 0K, is defined to coincide with the coldest physically-possible temperature and its degrees are defined through thermodynamics. The temperature of zero occurs at 0K = −273. 15°C. For historical reasons, the triple point temperature of water is fixed at 273.16 units of the measurement increment, Temperature is one of the principal quantities in the study of thermodynamics. There is a variety of kinds of temperature scale and it may be convenient to classify them as empirically and theoretically based. Empirical temperature scales are historically older, while theoretically based scales arose in the middle of the nineteenth century, empirically based temperature scales rely directly on measurements of simple physical properties of materials. For example, the length of a column of mercury, confined in a capillary tube, is dependent largely on temperature. Such scales are only within convenient ranges of temperature. For example, above the point of mercury, a mercury-in-glass thermometer is impracticable. A material is of no use as a thermometer near one of its phase-change temperatures, in spite of these restrictions, most generally used practical thermometers are of the empirically based kind. Especially, it was used for calorimetry, which contributed greatly to the discovery of thermodynamics, nevertheless, empirical thermometry has serious drawbacks when judged as a basis for theoretical physics. Theoretically based temperature scales are based directly on theoretical arguments, especially those of thermodynamics, kinetic theory and they rely on theoretical properties of idealized devices and materials
25.
Water activity
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Water activity or aw is the partial vapor pressure of water in a substance divided by the standard state partial vapor pressure of water. In the field of science, the standard state is most often defined as the partial vapor pressure of pure water at the same temperature. Using this particular definition, pure distilled water has an activity of exactly one. As temperature increases, aw typically increases, except in some products with crystalline salt or sugar, higher aw substances tend to support more microorganisms. Bacteria usually require at least 0.91, and fungi at least 0.7, water migrates from areas of high aw to areas of low aw. For example, if honey is exposed to air, the honey absorbs water from the air. If salami is exposed to dry air, the salami dries out, definition of aw, a w ≡ p / p ∗ where p is the vapor pressure of water in the solution, and p*₀ is the vapor pressure of pure water at the same temperature. Alternate definition, a w ≡ l w x w where lw is the activity coefficient of water, relationship to relative humidity, The relative humidity of air in equilibrium with a sample is called the Equilibrium Relative Humidity. Food designers use water activity to formulate shelf-stable food, if a product is kept below a certain water activity, then mold growth is inhibited. This results in a shelf life. Water activity values can help limit moisture migration within a food product made with different ingredients. Food formulators use water activity to predict how much moisture migration affects their product, water activity is used in many cases as a critical control point for Hazard Analysis and Critical Control Points programs. Samples of the product are periodically taken from the production area. Measurements can be made in as little as five minutes, and are regularly in most major food production facilities. For many years, researchers tried to equate bacterial growth potential with water content and they found that the values were not universal, but specific to each food product. W. J. Scott first established that bacterial growth correlated with activity, not water content. It is firmly established that growth of bacteria is inhibited at specific water activity values, U. S. Food and Drug Administration regulations for intermediate moisture foods are based on these values. Lowering the water activity of a product should not be seen as a kill step
26.
PH
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In chemistry, pH is a numeric scale used to specify the acidity or basicity of an aqueous solution. It is approximately the negative of the base 10 logarithm of the concentration, measured in units of moles per liter. More precisely it is the negative of the logarithm to base 10 of the activity of the hydrogen ion, solutions with a pH less than 7 are acidic and solutions with a pH greater than 7 are basic. Pure water is neutral, at pH7, being neither an acid nor a base, contrary to popular belief, the pH value can be less than 0 or greater than 14 for very strong acids and bases respectively. The pH scale is traceable to a set of standard solutions whose pH is established by international agreement, the pH of aqueous solutions can be measured with a glass electrode and a pH meter, or an indicator. In the first papers, the notation had the H as a subscript to the p, as so. The exact meaning of the p in pH is disputed, but according to the Carlsberg Foundation and it has also been suggested that the p stands for the German Potenz, others refer to French puissance. Another suggestion is that the p stands for the Latin terms pondus hydrogenii, potentia hydrogenii and it is also suggested that Sørensen used the letters p and q simply to label the test solution and the reference solution. Currently in chemistry, the p stands for decimal cologarithm of, PH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution. P H = − log 10 = log 10 For example and this definition was adopted because ion-selective electrodes, which are used to measure pH, respond to activity. For H+ number of electrons transferred is one and it follows that electrode potential is proportional to pH when pH is defined in terms of activity. The reference electrode may be a silver chloride electrode or a calomel electrode, the hydrogen-ion selective electrode is a standard hydrogen electrode. Reference electrode | concentrated solution of KCl || test solution | H2 | Pt Firstly, the cell is filled with a solution of hydrogen ion activity. Then the emf, EX, of the cell containing the solution of unknown pH is measured. PH = pH + E S − E X z The difference between the two measured emf values is proportional to pH and this method of calibration avoids the need to know the standard electrode potential. The proportionality constant, 1/z is ideally equal to 12.303 R T / F the Nernstian slope, to apply this process in practice, a glass electrode is used rather than the cumbersome hydrogen electrode. A combined glass electrode has a reference electrode. It is calibrated against buffer solutions of hydrogen ion activity
27.
Celsius
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Celsius, also known as centigrade, is a metric scale and unit of measurement for temperature. As an SI derived unit, it is used by most countries in the world and it is named after the Swedish astronomer Anders Celsius, who developed a similar temperature scale. The degree Celsius can refer to a temperature on the Celsius scale as well as a unit to indicate a temperature interval. Before being renamed to honour Anders Celsius in 1948, the unit was called centigrade, from the Latin centum, which means 100, and gradus, which means steps. The scale is based on 0° for the point of water. This scale is widely taught in schools today, by international agreement the unit degree Celsius and the Celsius scale are currently defined by two different temperatures, absolute zero, and the triple point of VSMOW. This definition also precisely relates the Celsius scale to the Kelvin scale, absolute zero, the lowest temperature possible, is defined as being precisely 0 K and −273.15 °C. The temperature of the point of water is defined as precisely 273.16 K at 611.657 pascals pressure. This definition fixes the magnitude of both the degree Celsius and the kelvin as precisely 1 part in 273.16 of the difference between absolute zero and the point of water. Thus, it sets the magnitude of one degree Celsius and that of one kelvin as exactly the same, additionally, it establishes the difference between the two scales null points as being precisely 273.15 degrees. In his paper Observations of two persistent degrees on a thermometer, he recounted his experiments showing that the point of ice is essentially unaffected by pressure. He also determined with precision how the boiling point of water varied as a function of atmospheric pressure. He proposed that the point of his temperature scale, being the boiling point. This pressure is known as one standard atmosphere, the BIPMs 10th General Conference on Weights and Measures later defined one standard atmosphere to equal precisely 1013250dynes per square centimetre. On 19 May 1743 he published the design of a mercury thermometer, in 1744, coincident with the death of Anders Celsius, the Swedish botanist Carolus Linnaeus reversed Celsiuss scale. In it, Linnaeus recounted the temperatures inside the orangery at the University of Uppsala Botanical Garden, since the 19th century, the scientific and thermometry communities worldwide referred to this scale as the centigrade scale. Temperatures on the scale were often reported simply as degrees or. More properly, what was defined as centigrade then would now be hectograde.2 gradians, for scientific use, Celsius is the term usually used, with centigrade otherwise continuing to be in common but decreasing use, especially in informal contexts in English-speaking countries
28.
Food and Drug Administration
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The Food and Drug Administration is a federal agency of the United States Department of Health and Human Services, one of the United States federal executive departments. As of 2017, 3/4th of the FDA budget is funded by the pharmaceutical companies due to the Prescription drug user fee act and these include regulating lasers, cellular phones, condoms and control of disease on products ranging from certain household pets to sperm donation for assisted reproduction. The FDA is led by the Commissioner of Food and Drugs, appointed by the President with the advice, the Commissioner reports to the Secretary of Health and Human Services. Dr. Robert M. Califf, MD is the current commissioner, who took over in February 2016 for Dr. Stephen Ostroff, the FDA has its headquarters in unincorporated White Oak, Maryland. The agency also has 223 field offices and 13 laboratories located throughout the 50 states, the United States Virgin Islands, in 2008, the FDA began to post employees to foreign countries, including China, India, Costa Rica, Chile, Belgium, and the United Kingdom. The site was renamed from the White Oak Naval Surface Warfare Center to the Federal Research Center at White Oak, the first building, the Life Sciences Laboratory, was dedicated and opened with 104 employees on the campus in December 2003. Only one original building from the facility was kept. All other buildings are new construction, the project is slated to be completed by 2017, assuming future Congressional funding While most of the Centers are located in the Washington, D. C. The Office of Regulatory Affairs is considered the eyes and ears of the agency, the Office of Regulatory Affairs is divided into five regions, which are further divided into 20 districts. Districts are based roughly on the divisions of the federal court system. Each district comprises a main office and a number of Resident Posts. ORA also includes the Agencys network of laboratories, which analyze any physical samples taken. Though samples are usually food-related, some laboratories are equipped to analyze drugs, cosmetics, the Office of Criminal Investigations was established in 1991 to investigate criminal cases. Unlike ORA Investigators, OCI Special Agents are armed, and dont focus on aspects of the regulated industries. In many cases, OCI pursues cases involving Title 18 violations, OCI Special Agents often come from other criminal investigations backgrounds, and work closely with the Federal Bureau of Investigation, Assistant Attorney General, and even Interpol. OCI receives cases from a variety of sources—including ORA, local agencies, OCI is a smaller branch, comprising about 200 agents nationwide. The FDA frequently works with federal agencies, including the Department of Agriculture, Drug Enforcement Administration, Customs and Border Protection. Often local and state government agencies also work with the FDA to provide regulatory inspections, the FDA regulates more than US$1 trillion worth of consumer goods, about 25% of consumer expenditures in the United States
29.
Autoclave
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An autoclave is a pressure chamber used to carry out industrial processes requiring elevated temperature and pressure different from ambient air pressure. Autoclaves are used in applications to perform sterilization and in the chemical industry to cure coatings and vulcanize rubber. They are also used in applications, especially regarding composites. Many autoclaves are used to sterilize equipment and supplies by subjecting them to saturated steam at 121 °C for around 15–20 minutes depending on the size of the load. The autoclave was invented by Charles Chamberland in 1879, although a precursor known as the steam digester was created by Denis Papin in 1679, the name comes from Greek auto-, ultimately meaning self, and Latin clavis meaning key, thus a self-locking device. Sterilization autoclaves are used in microbiology, medicine, podiatry, tattooing, body piercing, veterinary medicine, mycology, funeral homes, dentistry. They vary in size and function depending on the media to be sterilized, typical loads include laboratory glassware, other equipment and waste, surgical instruments, and medical waste. A notable recent and increasingly popular application of autoclaves is the treatment and sterilization of waste material. A new generation of waste converters is capable of achieving the effect without a pressure vessel to sterilize culture media, rubber material, gowns, dressings, gloves. It is particularly useful for materials which cannot withstand the temperature of a hot air oven. Autoclaves are also used to cure composites and in the vulcanization of rubber. The high heat and pressure that autoclaves allow help to ensure that the best possible properties are repeatable. The aerospace industry and sparmakers have autoclaves well over 50 feet long, other types of autoclave are used to grow crystals under high temperatures and pressures. Synthetic quartz crystals used in the industry are grown in autoclaves. Packing of parachutes for specialist applications may be performed under vacuum in an autoclave and it is very important to ensure that all of the trapped air is removed from the autoclave before activation, as trapped air is a very poor medium for achieving sterility. Steam at 134 °C can achieve in three minutes the same sterility that hot air at 160 °C can take two hours to achieve. Methods of air removal include, Downward displacement, As steam enters the chamber and this process compresses the air to the bottom, forcing it out through a drain which often contains a temperature sensor. Only when air evacuation is complete does the discharge stop, flow is usually controlled by a steam trap or a solenoid valve, but bleed holes are sometimes used, often in conjunction with a solenoid valve
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Spore
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In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavorable conditions. Spores form part of the cycles of many plants, algae, fungi. Bacterial spores are not part of a sexual cycle but are resistant structures used for survival under unfavourable conditions, spores are usually haploid and unicellular and are produced by meiosis in the sporangium of a diploid sporophyte. Under favourable conditions the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, two gametes fuse to form a zygote which develops into a new sporophyte. This cycle is known as alternation of generations, the term spore derives from the ancient Greek word σπορά spora, meaning seed, sowing, related to σπόρος sporos, sowing, and σπείρειν speirein, to sow. Spores germinate to give rise to haploid gametophytes, while seeds germinate to give rise to diploid sporophytes, vascular plant spores are always haploid. Vascular plants are either homosporous or heterosporous, plants that are homosporous produce spores of the same size and type. Spores can be classified in several ways, In fungi and fungus-like organisms, spores are often classified by the structure in which meiosis, since fungi are often classified according to their spore-producing structures, these spores are often characteristic of a particular taxon of the fungi. Sporangiospores, spores produced by a sporangium in many such as zygomycetes. Zygospores, spores produced by a zygosporangium, characteristic of zygomycetes, ascospores, spores produced by an ascus, characteristic of ascomycetes. Basidiospores, spores produced by a basidium, characteristic of basidiomycetes, aeciospores, spores produced by an aecium in some fungi such as rusts or smuts. Urediniospores, spores produced by a uredinium in some such as rusts or smuts. Teliospores, spores produced by a telium in some such as rusts or smuts. Oospores, spores produced by an oogonium, characteristic of oomycetes, carpospores, spores produced by a carposporophyte, characteristic of red algae. Tetraspores, spores produced by a tetrasporophyte, characteristic of red algae, chlamydospores, thick-walled resting spores of fungi produced to survive unfavorable conditions. Parasitic fungal spores may be classified into internal spores, which germinate within the host, meiospores, spores produced by meiosis, they are thus haploid, and give rise to a haploid daughter cell or a haploid individual. Examples are the cells of gametophytes of seed plants found in flowers or cones. Microspores, meiospores that give rise to a male gametophyte, megaspores, meiospores that give rise to a female gametophyte
31.
Scrapie
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Scrapie is a fatal, degenerative disease that affects the nervous systems of sheep and goats. It is one of several transmissible spongiform encephalopathies, which are related to bovine spongiform encephalopathy, like other spongiform encephalopathies, scrapie is caused by a prion. Scrapie has been known since 1732, and does not appear to be transmissible to humans, the name scrapie is derived from one of the clinical signs of the condition, wherein affected animals will compulsively scrape off their fleeces against rocks, trees, or fences. The disease apparently causes a sensation in the animals. Other clinical signs include excessive lip smacking, altered gaits, Scrapie is infectious and transmissible among conspecifics, so one of the most common ways to contain it is to quarantine and destroy those affected. However, scrapie tends to persist in flocks and can also arise spontaneously in flocks that have not previously had cases of the disease. The mechanism of transmission between animals and other aspects of the biology of the disease are only poorly understood, recent studies suggest prions may be spread through urine and persist in the environment for decades. Scrapie usually affects sheep around three to five years of age, the potential for transmission at birth and from contact with placental tissues is apparent. No evidence indicates scrapie is infectious to humans, the protein enters through the intestines or through cuts in the skin. The prions cause normal proteins of the sheep to fold into the wrong shape and these proteins are gradually accumulated in the body, especially in nerve cells, which subsequently die. When the prions are absorbed through the intestines, they first appear in the lymph nodes, an experiment has shown lambs risk being infected through milk from infected ewes, but the lambs in the experiment also infected each other, making the risk of infection difficult to assess. The experiment did not continue long enough to show if the lambs developed symptoms, changes are mild at first, slight behavioural changes and an increase in chewing movements may occur. Ataxia and neurological signs develop, and affected sheep struggle to keep up with the flock. Some sheep scratch excessively and show patches of wool loss and lesions on the skin, scratching sheep over the rump area may lead to a nibbling reflex, which is characteristic for the condition. Signs of a systemic disease appear later, with weight loss, anorexia, lethargy. Post mortem examination is important for the diagnosis of scrapie, histology of tissues shows accumulation of prions in the central nervous system, and immunohistochemical staining and ELISA can also be used to demonstrate the protein. No treatment is available for affected sheep, a test performed by sampling a small amount of lymphatic tissue from the third eyelid is now available. In the United Kingdom, the government has put in place a National Scrapie Plan and this is intended to eventually reduce the incidence of the disease in the UK sheep population
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Bovine spongiform encephalopathy
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BSE has a long incubation period, of 2.5 to 5 years, usually affecting adult cattle at a peak age onset of four to five years. BSE is caused by a misfolded protein—a prion, in the United Kingdom, the country worst affected by an epidemic in 1986–1998, more than 180,000 cattle were infected and 4.4 million slaughtered during the eradication program. The disease may be most frequently transmitted to humans by eating food contaminated with the brain, spinal cord, however, the infectious agent, although most highly concentrated in nervous tissue, can be found in virtually all tissues throughout the body, including blood. Between 460,000 and 482,000 BSE-infected animals had entered the food chain before controls on high-risk offal were introduced in 1989. The epidemic was probably accelerated by the recycling of infected bovine tissues prior to the recognition of BSE, the origin of the disease itself remains unknown. The infectious agent is distinctive for the temperatures at which it remains viable. This contributed to the spread of the disease in the United Kingdom, another contributory factor was the feeding of infected protein supplements to very young calves. Symptoms are not seen immediately in cattle due to the extremely long incubation period. Some cattle have been observed to have an abnormal gait, changes in behavior, tremors, hindlimb ataxia affects the animal’s gait and occurs when muscle control is lost. This results in poor balance and coordination, behavioural changes may include aggression, anxiety relating to certain situations, nervousness, frenzy or an overall change in temperament. Some rare but previously observed symptoms also include persistent pacing, rubbing or licking, additionally, nonspecific symptoms have also been observed which include weight loss, decreased milk production, lameness, ear infections and teeth grinding due to pain. Some animals may show a combination of symptoms, while others may only be observed demonstrating one of the many reported. Once clinical symptoms arise, they typically get worse over the weeks and months, eventually leading to recumbency, coma. The infectious agent in BSE is a type of misfolded protein called a prion. Prions can be transmitted to humans by eating food contaminated with them, Prions are not destroyed even if the beef or material containing them is cooked or heat-treated. Prion proteins carry the disease between individuals and cause deterioration of the brain, transmission can occur when healthy animals come in contact with tainted tissues from others with the disease. In the brain, these proteins cause native cellular prion protein to deform into the infectious state, Different hypotheses exist for the origin of prion proteins in cattle. In the 5th century BC, Hippocrates described a similar illness in cattle and sheep, publius Flavius Vegetius Renatus recorded cases of a disease with similar characteristics in the fourth and fifth centuries AD
33.
Laboratory mouse
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The laboratory mouse is a small mammal of the order Rodentia which is bred and used for scientific research. Laboratory mice are usually of the species Mus musculus and they are the most commonly used mammalian research model and are used for research in genetics, psychology, medicine and other scientific disciplines. Mice belong to the Euarchontoglires clade, which includes humans, the laboratory mouse genome has been sequenced and many mouse genes have human homologues. Other mouse species sometimes used in research include the American white-footed mouse. During the 18th Century Joseph Priestley and Antoine Lavoisier both used mice to study respiration, in the early part of the 20th century Clarence Cook Little, a Harvard undergraduate was conducting studies on mouse genetics in the laboratory of William Ernest Castle. Together they generated the DBA inbred mouse strain and initiated the systematic generation of inbred strains, the mouse has since been used extensively as a model organism and is associated with many important biological discoveries of the 20th and 21st Centuries. The Jackson laboratory in Bar Harbor, Maine is currently one of the worlds largest suppliers of laboratory mice, the laboratory is also the worlds source for more than 8,000 strains of genetically defined mice and is home of the Mouse Genome Informatics database. Breeding onset occurs at about 50 days of age in females and males, although females may have their first estrus at 25–40 days. Mice are polyestrous and breed year round, ovulation is spontaneous, the duration of the estrous cycle is 4–5 days and lasts about 12 hours, occurring in the evening. Vaginal smears are useful in timed matings to determine the stage of the estrous cycle, mating can be confirmed by the presence of a copulatory plug in the vagina up to 24 hours post-copulation. The presence of sperm on a smear is also a reliable indicator of mating. The average gestation period is 20 days, a fertile postpartum estrus occurs 14–24 hours following parturition, and simultaneous lactation and gestation prolongs gestation by 3–10 days owing to delayed implantation. The average litter size is 10–12 during optimum production, but is highly strain-dependent, as a general rule, inbred mice tend to have longer gestation periods and smaller litters than outbred and hybrid mice. The young are called pups and weigh 0. 5–1.5 g at birth, are hairless, pups are weaned at 3 weeks of age when they weigh about 10–12 g. If the female does not mate during the postpartum estrus, she resumes cycling 2–5 days post-weaning, newborn males are distinguished from newborn females by noting the greater anogenital distance and larger genital papilla in the male. This is best accomplished by lifting the tails of littermates and comparing perineums, Mice are mammals of the Glires clade, which means they are amongst the closest relatives of humans along with lagomorphs, treeshrews, flying lemurs and other primates. Laboratory mice are the species as the house mouse, however, they are often very different in behaviour. There are hundreds of established inbred, outbred, and transgenic strains, a strain, in reference to rodents, is a group in which all members are as nearly as possible genetically identical
34.
Brain
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The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
35.
Logarithm
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In mathematics, the logarithm is the inverse operation to exponentiation. That means the logarithm of a number is the exponent to which another fixed number, in simple cases the logarithm counts factors in multiplication. For example, the base 10 logarithm of 1000 is 3, the logarithm of x to base b, denoted logb, is the unique real number y such that by = x. For example, log2 =6, as 64 =26, the logarithm to base 10 is called the common logarithm and has many applications in science and engineering. The natural logarithm has the e as its base, its use is widespread in mathematics and physics. The binary logarithm uses base 2 and is used in computer science. Logarithms were introduced by John Napier in the early 17th century as a means to simplify calculations and they were rapidly adopted by navigators, scientists, engineers, and others to perform computations more easily, using slide rules and logarithm tables. The present-day notion of logarithms comes from Leonhard Euler, who connected them to the function in the 18th century. Logarithmic scales reduce wide-ranging quantities to tiny scopes, for example, the decibel is a unit quantifying signal power log-ratios and amplitude log-ratios. In chemistry, pH is a measure for the acidity of an aqueous solution. Logarithms are commonplace in scientific formulae, and in measurements of the complexity of algorithms and they describe musical intervals, appear in formulas counting prime numbers, inform some models in psychophysics, and can aid in forensic accounting. In the same way as the logarithm reverses exponentiation, the logarithm is the inverse function of the exponential function applied to complex numbers. The discrete logarithm is another variant, it has uses in public-key cryptography, the idea of logarithms is to reverse the operation of exponentiation, that is, raising a number to a power. For example, the power of 2 is 8, because 8 is the product of three factors of 2,23 =2 ×2 ×2 =8. It follows that the logarithm of 8 with respect to base 2 is 3, the third power of some number b is the product of three factors equal to b. More generally, raising b to the power, where n is a natural number, is done by multiplying n factors equal to b. The n-th power of b is written bn, so that b n = b × b × ⋯ × b ⏟ n factors, exponentiation may be extended to by, where b is a positive number and the exponent y is any real number. For example, b−1 is the reciprocal of b, that is, the logarithm of a positive real number x with respect to base b, a positive real number not equal to 1, is the exponent by which b must be raised to yield x
36.
Bioindicator
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A bioindicator is any species or group of species whose function, population, or status can reveal the qualitative status of the environment. For example, copepods and other small crustaceans that are present in many water bodies can be monitored for changes that may indicate a problem within their ecosystem. Bioindicators can tell us about the effects of different pollutants in the ecosystem and about how long a problem may have been present. A biological monitor, or biomonitor, can be defined as an organism that provides information on the quality of the environment around it. Therefore, a good biomonitor will indicate the presence of the pollutant and also attempt to provide information about the amount. A bioindicator is an organism or biological response that reveals the presence of the pollutants by the occurrence of typical symptoms or measurable responses, and is therefore more qualitative. The use of a biomonitor is described as biological monitoring and is the use of the properties of an organism to obtain information on aspects of the biosphere. Biomonitoring of air pollutants can be passive or active, passive methods observe plants growing naturally within the area of interest. Active methods detect the presence of air pollutants by placing test plants of known response, bioaccumulative indicators are frequently regarded as biomonitors. Depending on the selected and their use, there are several types of bio-indicators. The presence or absence of plant or other vegetative life in an ecosystem can provide important clues about the health of the environment. There are several types of plant and fungi biomonitors, including mosses, lichens, tree bark, bark pockets, tree rings, leaves, lichens are organisms comprising both fungi and algae. They are found on rocks and tree trunks, and they respond to changes in forests, including changes in forest structure – conservation biology, air quality. The disappearance of lichens in a forest may indicate environmental stresses, such as levels of sulfur dioxide, sulfur-based pollutants. The composition and total biomass of species in aquatic systems serves as an important metric for organic water pollution and nutrient loading such as nitrogen. An increase or decrease in a population may indicate damage to the ecosystem caused by pollution. For example, if pollution causes the depletion of important food sources, animal species dependent upon these food sources will also be reduced in number, overpopulation can be the result of opportunistic species growth. Microorganisms can be used as indicators of aquatic or terrestrial ecosystem health, found in large quantities, microorganisms are easier to sample than other organisms
This article incorporates text from this source, which is in the public domain.
. PMID 20509961.
This article incorporates text from this source, which is in the 