The blood vessels are the part of the circulatory system that transports blood throughout the human body. The word vascular, meaning relating to the vessels, is derived from the Latin vas. A few structures do not contain blood vessels and are labeled, tunica media, circularly arranged elastic fiber, connective tissue, polysaccharide substances, the second and third layer are separated by another thick elastic band called external elastic lamina. The tunica media may be rich in smooth muscle, which controls the caliber of the vessel. Veins dont have the external elastic lamina, but only an internal one, tunica adventitia, entirely made of connective tissue. It contains nerves that supply the vessel as well as nutrient capillaries in the blood vessels. Capillaries consist of more than a layer of endothelium and occasional connective tissue. When blood vessels connect to form a region of diffuse vascular supply it is called an anastomosis, anastomoses provide critical alternative routes for blood to flow in case of blockages.
There is a layer of muscle surrounding the arteries and the veins which help contract and this creates enough pressure for blood to be pumped around the body. Blood vessels are part of the system, together with the heart. They are roughly grouped as arterial and venous, determined by whether the blood in it is flowing away from or toward the heart. The term arterial blood is used to indicate blood high in oxygen. This is because they are carrying the blood to and from the lungs, blood vessels do not actively engage in the transport of blood, but arteries—and veins to a degree—can regulate their inner diameter by contraction of the muscular layer. This changes the flow to downstream organs, and is determined by the autonomic nervous system. Vasodilation and vasoconstriction are used antagonistically as methods of thermoregulation, oxygen is the most critical nutrient carried by the blood. In all arteries apart from the artery, hemoglobin is highly saturated with oxygen. In all veins apart from the vein, the hemoglobin is desaturated at about 75%.
The blood pressure in blood vessels is traditionally expressed in millimetres of mercury, in the arterial system, this is usually around 120 mmHg systolic and 80 mmHg diastolic
Iron is a chemical element with symbol Fe and atomic number 26. It is a metal in the first transition series and it is by mass the most common element on Earth, forming much of Earths outer and inner core. It is the fourth most common element in the Earths crust, like the other group 8 elements and osmium, iron exists in a wide range of oxidation states, −2 to +6, although +2 and +3 are the most common. Elemental iron occurs in meteoroids and other low oxygen environments, but is reactive to oxygen, fresh iron surfaces appear lustrous silvery-gray, but oxidize in normal air to give hydrated iron oxides, commonly known as rust. Unlike the metals that form passivating oxide layers, iron oxides occupy more volume than the metal and thus flake off, Iron metal has been used since ancient times, although copper alloys, which have lower melting temperatures, were used even earlier in human history. Pure iron is soft, but is unobtainable by smelting because it is significantly hardened and strengthened by impurities, in particular carbon. A certain proportion of carbon steel, which may be up to 1000 times harder than pure iron.
Crude iron metal is produced in blast furnaces, where ore is reduced by coke to pig iron, further refinement with oxygen reduces the carbon content to the correct proportion to make steel. Steels and iron alloys formed with metals are by far the most common industrial metals because they have a great range of desirable properties. Iron chemical compounds have many uses, Iron oxide mixed with aluminium powder can be ignited to create a thermite reaction, used in welding and purifying ores. Iron forms binary compounds with the halogens and the chalcogens, among its organometallic compounds is ferrocene, the first sandwich compound discovered. Iron plays an important role in biology, forming complexes with oxygen in hemoglobin and myoglobin. Iron is the metal at the site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants. A human male of average height has about 4 grams of iron in his body and this iron is distributed throughout the body in hemoglobin, muscles, bone marrow, blood proteins, ferritin and transport in plasma.
The mechanical properties of iron and its alloys can be evaluated using a variety of tests, including the Brinell test, Rockwell test, the data on iron is so consistent that it is often used to calibrate measurements or to compare tests. An increase in the content will cause a significant increase in the hardness. Maximum hardness of 65 Rc is achieved with a 0. 6% carbon content, because of the softness of iron, it is much easier to work with than its heavier congeners ruthenium and osmium. Because of its significance for planetary cores, the properties of iron at high pressures and temperatures have been studied extensively
Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is commonly performed by examining cells and tissues under a microscope or electron microscope, the specimen having been sectioned, stained. Histological studies may be conducted using tissue culture, where human or animal cells are isolated and maintained in an artificial environment for various research projects. The ability to visualize or differentially identify microscopic structures is frequently enhanced through the use of histological stains, histology is an essential tool of biology and medicine. Trained physicians, frequently licensed pathologists, are the personnel who perform histopathological examination and their field of study is called histotechnology. In the 17th century, Italian Marcello Malpighi invented one of the first microscopes for studying tiny biological entities, Malpighi analysed several parts of the organs of bats and other animals under the microscope. Malpighi, while studying the structure of the lung, noticed its membranous alveoli and his discovery established how the oxygen we breathe enters the blood stream and serves the body.
In the 19th century, histology was a discipline in its own right. The French anatomist Bichat introduced the concept of tissue in anatomy in 1801, the 1906 Nobel Prize in Physiology or Medicine was awarded to histologists Camillo Golgi and Santiago Ramon y Cajal. They had dueling interpretations of the structure of the brain based in differing interpretations of the same images. Cajal won the prize for his theory and Golgi for the staining technique he invented to make it possible. There are four types of animal tissues, muscle tissue, nervous tissue, connective tissue. All tissue types are subtypes of these four basic tissue types and their structure is very different from animal tissues. The most common fixative for light microscopy is 10% neutral buffered formalin, for electron microscopy, the most commonly used fixative is glutaraldehyde, usually as a 2. 5% solution in phosphate buffered saline. These fixatives preserve tissues or cells mainly by irreversibly cross-linking proteins and this can be detrimental to certain histological techniques.
Further fixatives are often used for electron microscopy such as osmium tetroxide or uranyl acetate Formalin fixation leads to degradation of mRNA, miRNA and DNA in tissues, extraction and analysis of these nucleic acids from formalin-fixed, paraffin-embedded tissues is possible using appropriate protocols. Frozen section procedure is a way to fix and mount histology sections using a refrigeration device called a cryostat. It is often used after surgical removal of tumors to allow determination of margin
Keratin is one of a family of fibrous structural proteins. Keratin is the protein that protects cells from damage or stress. It is the key structural material making up the layer of human skin. Keratin monomers assemble into bundles to form filaments, which are tough and form strong unmineralized epidermal appendages found in reptiles, amphibians. The only other biological matter known to approximate the toughness of keratinized tissue is chitin, keratin derives from Greek κερατίνη from Greek keras meaning horn originating from the Proto-Indo-European *ḱer- of the same meaning. It is composed of horn like, i. e. kerato, to which the chemical suffix -in is appended, the Greek keras is used in many animal names, e. g. Rhinoceros, meaning nose with a horn. Keratin filaments are abundant in keratinocytes in the layer of the epidermis. In addition, keratin filaments are present in cells in general. For example, mouse thymic epithelial cells are known to react with antibodies for keratin 5, keratin 8 and these antibodies are used as fluorescent markers to distinguish subsets of TECs in genetic studies of the thymus.
The α-keratins in the hair, stratum corneum, nails and hooves of mammals, the harder β-keratins found in nails and in the scales and claws of reptiles, their shells, and in the feathers, claws of birds and quills of porcupines. The baleen plates of filter-feeding whales are made of keratin, keratins are polymers of type I and type II intermediate filaments, which have only been found in the genomes of chordates. Nematodes and many other animals seem to only have type VI intermediate filaments, lamins. The human genome encodes 54 functional keratin genes which are located in two clusters on chromosomes 12 and 17 and this suggests that they have originated from a series of gene duplications on these chromosomes. The first sequences of keratins were determined by Hanukoglu and Fuchs and these sequences revealed that there are two distinct but homologous keratin families which were named as Type I keratin and Type II keratins. This model has been confirmed by the determination of the structure of a helical domain of keratins.
Fibrous keratin molecules supercoil to form a stable, left-handed superhelical motif to multimerise. The major force that keeps the structure is hydrophobic interactions between apolar residues along the keratins helical segments. Limited interior space is the reason why the triple helix of the protein collagen, found in skin and bone
The Internet Archive launched the Wayback Machine in October 2001. It was set up by Brewster Kahle and Bruce Gilliat, and is maintained with content from Alexa Internet, the service enables users to see archived versions of web pages across time, which the archive calls a three dimensional index. Since 1996, the Wayback Machine has been archiving cached pages of websites onto its large cluster of Linux nodes and it revisits sites every few weeks or months and archives a new version. Sites can be captured on the fly by visitors who enter the sites URL into a search box, the intent is to capture and archive content that otherwise would be lost whenever a site is changed or closed down. The overall vision of the machines creators is to archive the entire Internet, the name Wayback Machine was chosen as a reference to the WABAC machine, a time-traveling device used by the characters Mr. Peabody and Sherman in The Rocky and Bullwinkle Show, an animated cartoon. These crawlers respect the robots exclusion standard for websites whose owners opt for them not to appear in search results or be cached, to overcome inconsistencies in partially cached websites, Archive-It.
Information had been kept on digital tape for five years, with Kahle occasionally allowing researchers, when the archive reached its fifth anniversary, it was unveiled and opened to the public in a ceremony at the University of California, Berkeley. Snapshots usually become more than six months after they are archived or, in some cases, even later. The frequency of snapshots is variable, so not all tracked website updates are recorded, Sometimes there are intervals of several weeks or years between snapshots. After August 2008 sites had to be listed on the Open Directory in order to be included. As of 2009, the Wayback Machine contained approximately three petabytes of data and was growing at a rate of 100 terabytes each month, the growth rate reported in 2003 was 12 terabytes/month, the data is stored on PetaBox rack systems manufactured by Capricorn Technologies. In 2009, the Internet Archive migrated its customized storage architecture to Sun Open Storage, in 2011 a new, improved version of the Wayback Machine, with an updated interface and fresher index of archived content, was made available for public testing.
The index driving the classic Wayback Machine only has a bit of material past 2008. In January 2013, the company announced a ground-breaking milestone of 240 billion URLs, in October 2013, the company announced the Save a Page feature which allows any Internet user to archive the contents of a URL. This became a threat of abuse by the service for hosting malicious binaries, as of December 2014, the Wayback Machine contained almost nine petabytes of data and was growing at a rate of about 20 terabytes each week. Between October 2013 and March 2015 the websites global Alexa rank changed from 162 to 208, in a 2009 case, Netbula, LLC v. Chordiant Software Inc. defendant Chordiant filed a motion to compel Netbula to disable the robots. Netbula objected to the motion on the ground that defendants were asking to alter Netbulas website, in an October 2004 case, Telewizja Polska USA, Inc. v. Echostar Satellite, No.02 C3293,65 Fed. 673, a litigant attempted to use the Wayback Machine archives as a source of admissible evidence, Telewizja Polska is the provider of TVP Polonia and EchoStar operates the Dish Network
Methyl blue is a chemical compound with the molecular formula C37H27N3Na2O9S3. It is used as a stain in histology, and stains blue in tissue sections. It can be used in differential staining techniques such as Mallorys connective tissue stain and Gömöri trichrome stain. Fungal cell walls are stained by methyl blue, methyl blue is available in mixture with water blue, under name Aniline Blue WS, Aniline blue, China blue, or Soluble blue. Potassium ferrocyanide Potassium ferricyanide Methylene blue Egyptian Blue Han Purple Gentian violet Fluorescein
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, acidic hot springs, radioactive waste, Bacteria 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, 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 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, 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 involved in the second great evolutionary divergence, that of the archaea, 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
Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered and its main use is as a purple dye for textiles and to give deep violet colors in paint and ink. Methyl violet 10B is known as violet and has medical uses. The term methyl violet encompasses three compounds that differ in the number of groups attached to the amine functional group. They are all soluble in water, diethylene glycol, methyl violet 2B is a green powder which is soluble in water in ethanol and water, but not in xylene. It appears yellow in solution of low pH and changes to violet with pH increasing toward 3.2, methyl violet 10B has six methyl groups. It is known in medicine as Gentian violet and is the ingredient in a Gram stain. It is used as a pH indicator, with a range between 0 and 1.6, the protonated form is yellow, turning blue-violet above pH levels of 1.6. Gentian violet destroys cells and can be used as a disinfectant, compounds related to methyl violet are potential carcinogens.
Methyl violet 10B inhibits the growth of many Gram positive bacteria, when used in conjunction with nalidixic acid, it can be used to isolate the streptococci bacteria for the diagnosis of an infection. Methyl violet is a mutagen and mitotic poison, therefore concerns exist regarding the impact of the release of methyl violet into the environment. Methyl violet has been used in vast quantities for textile and paper dyeing, numerous methods have been developed to treat methyl violet pollution. The three most prominent are chemical bleaching and photodegradation, chemical bleaching is achieved by oxidation or reduction. Oxidation can destroy the dye completely, e. g. through the use of sodium hypochlorite or hydrogen peroxide, reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite. Biodegradation has been investigated because of its relevance to sewage plants with specialized microorganisms. Two microorganisms that have studied in depth are the white rot fungus.
Light alone does not rapidly degrade methyl violet, but the process is accelerated upon the addition of large band-gap semiconductors, TiO2 or ZnO