The melting point of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium; the melting point of a substance depends on pressure and is specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point; because of the ability of some substances to supercool, the freezing point is not considered as a characteristic property of a substance. When the "characteristic freezing point" of a substance is determined, in fact the actual methodology is always "the principle of observing the disappearance rather than the formation of ice", that is, the melting point. For most substances and freezing points are equal. For example, the melting point and freezing point of mercury is 234.32 kelvins. However, certain substances possess differing solid-liquid transition temperatures.
For example, agar melts at 85 °C and solidifies from 31 °C. The melting point of ice at 1 atmosphere of pressure is close to 0 °C. In the presence of nucleating substances, the freezing point of water is not always the same as the melting point. In the absence of nucleators water can exist as a supercooled liquid down to −48.3 °C before freezing. The chemical element with the highest melting point is tungsten, at 3,414 °C; the often-cited carbon does not melt at ambient pressure but sublimes at about 3,726.85 °C. Tantalum hafnium carbide is a refractory compound with a high melting point of 4215 K. At the other end of the scale, helium does not freeze at all at normal pressure at temperatures arbitrarily close to absolute zero. Many laboratory techniques exist for the determination of melting points. A Kofler bench is a metal strip with a temperature gradient. Any substance can be placed on a section of the strip, revealing its thermal behaviour at the temperature at that point. Differential scanning calorimetry gives information on melting point together with its enthalpy of fusion.
A basic melting point apparatus for the analysis of crystalline solids consists of an oil bath with a transparent window and a simple magnifier. The several grains of a solid are placed in a thin glass tube and immersed in the oil bath; the oil bath is heated and with the aid of the magnifier melting of the individual crystals at a certain temperature can be observed. In large/small devices, the sample is placed in a heating block, optical detection is automated; the measurement can be made continuously with an operating process. For instance, oil refineries measure the freeze point of diesel fuel online, meaning that the sample is taken from the process and measured automatically; this allows for more frequent measurements as the sample does not have to be manually collected and taken to a remote laboratory. For refractory materials the high melting point may be determined by heating the material in a black body furnace and measuring the black-body temperature with an optical pyrometer. For the highest melting materials, this may require extrapolation by several hundred degrees.
The spectral radiance from an incandescent body is known to be a function of its temperature. An optical pyrometer matches the radiance of a body under study to the radiance of a source, calibrated as a function of temperature. In this way, the measurement of the absolute magnitude of the intensity of radiation is unnecessary. However, known temperatures must be used to determine the calibration of the pyrometer. For temperatures above the calibration range of the source, an extrapolation technique must be employed; this extrapolation is accomplished by using Planck's law of radiation. The constants in this equation are not known with sufficient accuracy, causing errors in the extrapolation to become larger at higher temperatures. However, standard techniques have been developed to perform this extrapolation. Consider the case of using gold as the source. In this technique, the current through the filament of the pyrometer is adjusted until the light intensity of the filament matches that of a black-body at the melting point of gold.
This establishes the primary calibration temperature and can be expressed in terms of current through the pyrometer lamp. With the same current setting, the pyrometer is sighted on another black-body at a higher temperature. An absorbing medium of known transmission is inserted between this black-body; the temperature of the black-body is adjusted until a match exists between its intensity and that of the pyrometer filament. The true higher temperature of the black-body is determined from Planck's Law; the absorbing medium is removed and the current through the filament is adjusted to match the filament intensity to that of the black-body. This establishes a second calibration point for the pyrometer; this step is repeated to carry the calibration to hi
The Jmol applet, among other abilities, offers an alternative to the Chime plug-in, no longer under active development. While Jmol has many features that Chime lacks, it does not claim to reproduce all Chime functions, most notably, the Sculpt mode. Chime requires plug-in installation and Internet Explorer 6.0 or Firefox 2.0 on Microsoft Windows, or Netscape Communicator 4.8 on Mac OS 9. Jmol operates on a wide variety of platforms. For example, Jmol is functional in Mozilla Firefox, Internet Explorer, Google Chrome, Safari. Chemistry Development Kit Comparison of software for molecular mechanics modeling Jmol extension for MediaWiki List of molecular graphics systems Molecular graphics Molecule editor Proteopedia PyMOL SAMSON Official website Wiki with listings of websites and moodles Willighagen, Egon. "Fast and Scriptable Molecular Graphics in Web Browsers without Java3D". Doi:10.1038/npre.2007.50.1
Dirofilaria immitis, the heartworm or dog heartworm, is a parasitic roundworm, a type of filarial worm, a small thread-like worm, that causes dirofilariasis. It is spread from host to host through the bites of mosquitoes; the definitive host is the dog, but it can infect cats, coyotes, jackals and other animals, such as ferrets, seals, sea lions and, under rare circumstances, humans. Dirofilaria immitis is called the "heartworm". Adult heartworms migrate to the right heart and the great veins in heavy infestations. Heartworm infection may result in serious disease for the host, with death as the result of congestive heart failure. Although at one time confined to the southern United States, heartworm has now spread to nearly all locations where its mosquito vector is found. Transmission of the parasite occurs in all of the United States, the warmer regions of Canada; the highest infection rates are found within 150 miles of the coast from Texas to New Jersey, along the Mississippi River and its major tributaries.
It has been found in South America, southern Europe,Southeast Asia, the Middle East, Australia and Japan. Heartworms go through several life stages before they become adults infecting the pulmonary artery of the host animal; the worms require the mosquito as an intermediate stage to complete their lifecycles. The rate of development in the mosquito is temperature-dependent, requiring about two weeks of temperature at or above 27 °C. Below a threshold temperature of 14 °C, development cannot occur, the cycle is halted; as a result, transmission is limited to warm weather, duration of the transmission season varies geographically. The period between the initial infection when the dog is bitten by a mosquito and the maturation of the worms into adults living in the pulmonary arteries takes six to seven months in dogs and is known as the "prepatent period". After infection, the third-stage larval heartworms deposited by the mosquito grow for a week or two and molt to the fourth larval stage under the skin at the site of the mosquito bite.
They migrate to the muscles of the chest and abdomen, 45 to 60 days after infection, molt to the fifth stage. Between 75 and 120 days after infection, these immature heartworms enter the bloodstream and are carried through the heart to reside in the pulmonary artery. Over the next three to four months, they increase in size; the female adult worm is about 30 cm in length, the male is about 23 cm, with a coiled tail. By seven months after infection, the adult worms have mated and the females begin giving birth to live young, called microfilariae; the microfilariae circulate in the bloodstream for as long as two years, waiting for the next stage in their lifecycles in the gut of a bloodsucking mosquito. When ingested by a mosquito, the microfilariae undergo a series of molts to the infective third larval stage, migrate to the salivary glands of the mosquito, where they wait to infect another host; the incubation period required to reach the stage where the microfilariae become transmittable to another host can be as little as two weeks or as long as six weeks, depending on the warmth of the climate, the larval lifecycle ceases if the ambient temperature drops below 14 °C.
Hosts of Dirofilaria immitis include: Dogs show no indication of heartworm infection during the six-month prepatent period prior to the worms' maturation, current diagnostic tests for the presence of microfilariae or antigens cannot detect prepatent infections. Migrating heartworm larvae get "lost" and end up in unusual sites, such as the eye, brain, or an artery in the leg, which results in unusual symptoms such as blindness and lameness, but until the larvae mature and congregate inside the heart, they produce no symptoms or signs of illness. Many dogs show little or no sign of infection after the worms become adults; these animals have only a light infection and live a sedentary lifestyle. However, active dogs and those with heavier infections may show the classic signs of heartworm disease. Early signs include a cough on exercise and early exhaustion upon exercise. In the most advanced cases where many adult worms have built up in the heart without treatment, signs progress to severe weight loss, coughing up blood, congestive heart failure.
Wolbachia pipientis is an intracellular bacterium, an endosymbiont of D. immitis. All heartworms are thought to be infected with Wolbachia to some degree; the inflammation occurring at the die-off of adult heartworms or larvae is in part due to the release of Wolbachia bacteria or protein into the tissues. This may be significant in cats, in which the disease seems to be more related to larval death than living adult heartworms. Treating heartworm-positive animals with an antibiotic such as doxycycline to remove Wolbachia may prove to be beneficial, but further studies are necessary. Three methods can be used for the diagnosis: Microfilarial detection was accomplished most in the past by the microscopic identification of microfilariae on a direct blood smear, above the buffy coat in a microhematocrit tube, using the modified Knott test, or after millipore filtration; the accuracy of these tests used for routine screening or diagnosis of heartworm infection, is improved by multiple testing. The modified Knott test and millipore filtratio
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, separate from the other eukaryotic life kingdoms of plants and animals. A characteristic that places fungi in a different kingdom from plants and some protists is chitin in their cell walls. Similar to animals, fungi are heterotrophs. Fungi do not photosynthesize. Growth is their means of mobility, except for spores, which may travel through the water. Fungi are the principal decomposers in ecological systems; these and other differences place fungi in a single group of related organisms, named the Eumycota, which share a common ancestor, an interpretation, strongly supported by molecular phylogenetics. This fungal group 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 related to animals than to plants.
Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, their cryptic lifestyles in soil or on dead matter. Fungi include symbionts of plants, animals, or other fungi and parasites, they may become noticeable when fruiting, either as molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient cycling and exchange in the environment, they have long been used in the form of mushrooms and truffles. Since the 1940s, fungi have been used for the production of antibiotics, more various enzymes produced by fungi are used industrially and in detergents. Fungi are used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, that are toxic to animals including humans; 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, become significant pathogens of humans and other animals. 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 an enormous diversity of taxa with varied ecologies, life cycle strategies, morphologies ranging from unicellular aquatic chytrids to large mushrooms. However, little is known of the true biodiversity of Kingdom Fungi, estimated at 2.2 million to 3.8 million species. Of these, only about 120,000 have been described, with over 8,000 species known to be detrimental to plants and at least 300 that can be pathogenic to humans. Since the pioneering 18th and 19th century taxonomical works of Carl Linnaeus, Christian Hendrik Persoon, Elias Magnus Fries, fungi have been classified according to their morphology or physiology. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, which has sometimes challenged the historical groupings based on morphology and other traits.
Phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, divided into one subkingdom, seven phyla, ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace and Pliny; this in turn is derived from the Greek word sphongos, which refers to the macroscopic structures and morphology of mushrooms and molds. The word mycology is derived from the Greek logos, it denotes the scientific study of fungi. The Latin adjectival form of "mycology" appeared as early as 1796 in a book on the subject by Christiaan Hendrik Persoon; the word appeared in English as early as 1824 in a book by Robert Kaye Greville. In 1836 the English naturalist Miles Joseph Berkeley's publication The English Flora of Sir James Edward Smith, Vol. 5. Refers to mycology as the study of fungi. A group of all the fungi present in a particular area or geographic region is known as mycobiota, e.g. "the mycobiota of Ireland". Before the introduction of molecular methods for phylogenetic analysis, taxonomists considered fungi to be members of the plant kingdom because of similarities in lifestyle: both fungi and plants are immobile, have similarities in general morphology and growth habitat.
Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies, which sometimes resemble plants such as mosses. The fungi are now considered a separate kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago; some morphological and genetic features are shared with other organisms, while others are unique to the fungi separating them from the other kingdoms: Shared features: With other euka
Western flower thrips
The western flower thrips is an invasive pest insect in agriculture. This species of thrips is native to the Southwestern United States but has spread to other continents, including Europe and South America via transport of infested plant material, it has been documented to feed on over 500 different species of host plants, including a large number of fruit and ornamental crops. The adult male is about 1 mm long. Most western flower thrips are reproduce by arrhenotokous parthenogenesis. Males are rare, are always pale yellow, while females vary in color by season, from red to yellow to dark brown; each adult is thin, with two pairs of long wings. The eggs are oval or kidney-shaped and about 0.2 mm long. The nymph is yellowish in color with red eyes; the lifecycle of the western flower thrips varies in length due to temperature, with the adult living from two to five or more weeks, the nymph stage lasting from five to 20 days. Each female may lay 40 to over 100 eggs in the tissues of the plant in the flower, but in the fruit or foliage.
The newly hatched nymph feeds on the plant for two of its instars falls off the plant to complete its other two instar stages. The insect damages the plant in several ways; the major damage is caused by the adult ovipositing in the plant tissue. The plant is injured by feeding, which leaves holes and areas of silvery discoloration when the plant reacts to the insect's saliva. Nymphs feed on new fruit just beginning to develop from the flower; the western flower thrips is the major vector of tomato spotted wilt virus, a serious plant disease. Western flower thrips are less destructive during wet weather. Damage can be reduced by growing barriers of nonhost plants around crops and by eliminating reservoir plants, plants to which the thrips are attracted, such as jimson weed; the thrips' natural enemies include pirate bugs of genus Orius. Other agents show promise as biological pest control, including the fungus Metarhizium anisopliae, the mirid Dicyphus hesperus. Flower-feeding thrips are attracted to bright floral colors white and yellow, will land and attempt to feed.
Some flower thrips will "bite" humans wearing clothing with such bright colors, though no species feed on blood. WFT fact sheet Hawaii fact sheet UC Davis IPM Close up photo PaDIL diagnostic photos CISR: Center for Invasive Species Research Fact Sheet on Western Flower Thrips
Veterinary medicine is the branch of medicine that deals with the prevention and treatment of disease and injury in non-human animals. The scope of veterinary medicine is wide, covering all animal species, both domesticated and wild, with a wide range of conditions which can affect different species. Veterinary medicine is practiced, both with and without professional supervision. Professional care is most led by a veterinary physician, but by paraveterinary workers such as veterinary nurses or technicians; this can be augmented by other paraprofessionals with specific specialisms such as animal physiotherapy or dentistry, species relevant roles such as farriers. Veterinary science helps human health through the monitoring and control of zoonotic disease, food safety, indirectly through human applications from basic medical research, they help to maintain food supply through livestock health monitoring and treatment, mental health by keeping pets healthy and long living. Veterinary scientists collaborate with epidemiologists, other health or natural scientists depending on type of work.
Ethically, veterinarians are obliged to look after animal welfare. Archeological evidence, in the form of a cow skull upon which trepanation had been performed, shows that people were performing veterinary procedures in the Neolithic; the Egyptian Papyrus of Kahun is the first extant record of veterinary medicine. The Shalihotra Samhita, dating from the time of Ashoka, is an early Indian veterinary treatise; the edicts of Asoka read: "Everywhere King Piyadasi made two kinds of medicine available, medicine for people and medicine for animals. Where there were no healing herbs for people and animals, he ordered that they be bought and planted."Hippiatrica is a Byzantine compilation of hippiatrics, dated to the 5th or 6th century. The first attempts to organize and regulate the practice of treating animals tended to focus on horses because of their economic significance. In the Middle Ages, farriers combined their work in horseshoeing with the more general task of "horse doctoring"; the Arabic tradition of Bayṭara, or Shiyāt al-Khayl, originates with the treatise of Ibn Akhī Hizām.
In 1356, the Lord Mayor of London, concerned at the poor standard of care given to horses in the city, requested that all farriers operating within a seven-mile radius of the City of London form a "fellowship" to regulate and improve their practices. This led to the establishment of the Worshipful Company of Farriers in 1674. Meanwhile, Carlo Ruini's book Anatomia del Cavallo, was published in 1598, it was the first comprehensive treatise on the anatomy of a non-human species. The first veterinary school was founded in France in 1762 by Claude Bourgelat. According to Lupton, after observing the devastation being caused by cattle plague to the French herds, Bourgelat devoted his time to seeking out a remedy; this resulted in his founding a veterinary school in Lyon in 1761, from which establishment he dispatched students to combat the disease. The school received immediate international recognition in the eighteenth century and its pedagogical model drew on the existing fields of human medicine, natural history, comparative anatomy.
The Odiham Agricultural Society was founded in 1783 in England to promote agriculture and industry, played an important role in the foundation of the veterinary profession in Britain. A founding member, Thomas Burgess, began to take up the cause of animal welfare and campaign for the more humane treatment of sick animals. A 1785 Society meeting resolved to "promote the study of Farriery upon rational scientific principles." The physician James Clark wrote a treatise entitled Prevention of Disease in which he argued for the professionalization of the veterinary trade, the establishment of veterinary colleges. This was achieved in 1790, through the campaigning of Granville Penn, who persuaded the Frenchman, Benoit Vial de St. Bel to accept the professorship of the newly established Veterinary College in London; the Royal College of Veterinary Surgeons was established by royal charter in 1844. Veterinary science came of age in the late 19th century, with notable contributions from Sir John McFadyean, credited by many as having been the founder of modern Veterinary research.
In the United States, the first schools were established in the early 19th century in Boston, New York and Philadelphia. In 1879, Iowa Agricultural College became the first land grant college to establish a school of veterinary medicine. Veterinary care and management is led by a veterinary physician; this role is the equivalent of a doctor in human medicine, involves post-graduate study and qualification. In many countries, the local nomenclature for a vet is a protected term, meaning that people without the prerequisite qualifications and/or registration are not able to use the title, in many cases, the activities that may be undertaken by a vet are restricted only to those people who are registered as vet. For instance, in the United Kingdom, as in other jurisdictions, animal treatment may only be performed by registered vets, it is illegal for any person, not registered to call themselves a vet or perform any treatment. Most vets work in clinical s
Flea, the common name for the order Siphonaptera, includes 2,500 species of small flightless insects that survive as external parasites of mammals and birds. Fleas live from their hosts. Adult fleas grow to about 3 mm or.12 in long, are brown, have bodies that are "flattened" sideways, or narrow, enabling them to move through their host's fur or feathers. They have strong claws preventing them from being dislodged, they are able to leap a distance of some 50 times their body length, a feat second only to jumps made by another group of insects, the superfamily of froghoppers. Fleas' larvae are worm-like with no limbs; the Siphonaptera are most related to the snow scorpionflies, or snow fleas in the UK, formally the Boreidae, placing them within the Endopterygote insect order Mecoptera. Fleas arose in the early Cretaceous, most as ectoparasites of mammals, before moving on to other groups including birds; each species of flea is more or less a specialist with respect to its host animal species: many species never breed on any other host, though some are less selective.
Some families of fleas are exclusive to a single host group. The oriental rat flea, Xenopsylla cheopis, is a vector of Yersinia pestis, the bacterium which causes bubonic plague; the disease was spread by rodents such as the black rat, which were bitten by fleas that infected humans. Major outbreaks included the Plague of Justinian, c. 540 and the Black Death, c. 1350, both of which killed a sizeable fraction of the world's population. Fleas appear in human culture in such diverse forms as flea circuses, poems like John Donne's erotic The Flea, works of music such as by Modest Mussorgsky, a film by Charlie Chaplin. Fleas are wingless insects, 1/16 to 1/8-inch long, that are agile dark colored, with a proboscis, or stylet, adapted to feeding by piercing the skin and sucking their host's blood through their epipharynx. Flea legs end in strong claws. Unlike other insects, fleas do not possess compound eyes but instead only have simple eyespots with a single biconvex lens, their bodies are laterally compressed, permitting easy movement through the hairs or feathers on the host's body.
The flea body is covered with hard plates called sclerites. These sclerites are covered with many hairs and short spines directed backward, which assist its movements on the host; the tough body is able to withstand great pressure an adaptation to survive attempts to eliminate them by scratching. Fleas lay tiny, oval eggs; the larvae are small and pale, have bristles covering their worm-like bodies, lack eyes, have mouth parts adapted to chewing. The larvae feed on organic matter the feces of mature fleas, which contain dried blood. Adults feed only on fresh blood, their legs are long, the hind pair well adapted for jumping. The flea jump is so rapid and forceful that it exceeds the capabilities of muscle, instead of relying on direct muscle power, fleas store muscle energy in a pad of the elastic protein named resilin before releasing it rapidly. Before the jump, muscles contract and deform the resilin pad storing energy which can be released rapidly to power leg extension for propulsion. To prevent premature release of energy or motions of the leg, the flea employs a "catch mechanism".
Early in the jump, the tendon of the primary jumping muscle passes behind the coxa-trochanter joint, generating a torque which holds the joint closed with the leg close to the body. To trigger jumping, another muscle pulls the tendon forward until it passes the joint axis, generating the opposite torque to extend the leg and power the jump by release of stored energy; the actual take off has been shown by high-speed video to be from the tibiae and tarsi rather than from the trochantera. Fleas are holometabolous insects, going through the four lifecycle stages of egg, larva and imago. In most species, neither female nor male fleas are mature when they first emerge but must feed on blood before they become capable of reproduction; the first blood meal triggers the maturation of the ovaries in females and the dissolution of the testicular plug in males, copulation soon follows. Some species breed all year round while others synchronise their activities with their hosts' life cycles or with local environmental factors and climatic conditions.
Flea populations consist of 50% eggs, 35% larvae, 10% pupae, 5% adults. The number of eggs laid depends with batch sizes ranging from two to several dozen; the total number of eggs produced in a female's lifetime varies from around one hundred to several thousand. In some species, the flea lives in the nest or burrow and the eggs are deposited on the substrate, but in others, the eggs are laid on the host itself and can fall off onto the ground; because of this, areas where the host rests and sleeps become one of the primary habitats of eggs and developing larvae. The eggs take around two days to two weeks to hatch. Experiments have show