A prescription is a health-care program implemented by a physician or other qualified health care practitioner in the form of instructions that govern the plan of care for an individual patient. The term refers to a health care provider's written authorization for a patient to purchase a prescription drug from a pharmacist; the format of a prescription falls in to seven parts. However, with modern prescribing habits, some are no longer applicable or included on an everyday basis. Definition: For such prescriptions to be accepted as a legal medical prescription, it needs to be filed by a qualified dentist, nurse, physician, veterinarian etc. which falls within their remit to prescribe such treatments. This is regardless of whether they included controlled substances or available over-the-counter treatments. Prescriptions may be entered into an electronic medical record system and transmitted electronically to a pharmacy. Alternatively, a prescription may be handwritten on preprinted prescription forms that have been assembled into pads, or printed onto similar forms using a computer printer or on plain paper according to the circumstance.
In some cases, a prescription may be transmitted from the physician to the pharmacist orally by telephone. The content of a prescription includes the name and address of the prescribing provider and any other legal requirement such as a registration number. Unique for each prescription is the name of the patient. In the United Kingdom and Ireland, the patient's name and address must be recorded; each prescription is dated and some jurisdictions may place a time limit on the prescription. In the past, prescriptions contained instructions for the pharmacist to use for compounding the pharmaceutical product but most prescriptions now specify pharmaceutical products that were manufactured and require little or no preparation by the pharmacist. Prescriptions contain directions for the patient to follow when taking the drug; these directions are printed on the label of the pharmaceutical product.'℞' is a symbol meaning "recipe". It is sometimes transliterated as "Rx" or just "Rx"; this symbol originated in medieval manuscripts as an abbreviation of the late Latin verb recipere the second person singular imperative form recipe meaning "take", thus: "take thou".
Abbreviated Rc, the c was simplified and written as a straight stroke making it look like an x in combination with the right "leg" of R. Medieval prescriptions invariably began with the command to "take" certain materials and compound them in specified ways. Folk theories about the origin of the symbol'℞' note its similarity to the Eye of Horus, or to the ancient symbol for Zeus or Jupiter, gods whose protection may have been sought in medical contexts; the word "prescription", from "pre-" and "script", refers to the fact that the prescription is an order that must be written down before a compound drug can be prepared. Those within the industry will call prescriptions "scripts". In certain states medical marijuana legislation has been drafted calling for a health care professional's written or oral "recommendation", in the belief that a written one would be distinguishable from a prescription, but since written advice to a patient is what a prescription is, that belief is mistaken. Jurisdictions may adopt a statutory definition of "prescription" that applies as a term of art only to the operation of that statute, but the general legal definition of the word is this broad one.
Many brand name drugs have cheaper generic drug substitutes that are therapeutically and biochemically equivalent. Prescriptions will contain instructions on whether the prescriber will allow the pharmacist to substitute a generic version of the drug; this instruction is communicated in a number of ways. In some jurisdictions, the preprinted prescription contains two signature lines: one line has "dispense as written" printed underneath; some have a preprinted box "dispense as written" for the prescriber to check off. Other jurisdictions the protocol is for the prescriber to handwrite one of the following phrases: "dispense as written", "DAW", "brand necessary", "do not substitute", "no substitution", "medically necessary", "do not interchange". In other jurisdictions they may use different languages, never mind a different formula of words. In some jurisdictions, it may be a legal requirement to include the age of child on the prescription. For pediatric prescriptions some advise the inclusion of the age of the child if the patient is less than twelve and the age and months if less than five.
Adding the weight of the child is helpful. Prescriptions have a "label" box; when checked, the pharmacist is instructed to label the medication and provide information about the prescription itself is given in addition to instructions on taking the medication. Otherwise, the patient is given the instructions; some prescribers further inform the patient and pharmacist by providing the indication for the medication. This assists the pharmacist in checking for errors as many common medications can be used for multiple medical conditions; some prescriptions will specify whether and how many "repeats" or "refills" are allowed. Regul
Recreational drug use
Recreational drug use is the use of a psychoactive drug to induce an altered state of consciousness for pleasure, by modifying the perceptions and emotions of the user. When a psychoactive drug enters the user's body, it induces an intoxicating effect. Recreational drugs are in three categories: depressants. Many people use prescribed and illegal opioids along with opiates and benzodiazepines. In popular practice, recreational drug use is a tolerated social behaviour, rather than perceived as the serious medical condition of self-medication. However, heavy use of some drugs is stigmatized. Recreational drugs include alcohol. What controlled substances are considered illegal drugs varies by country, but includes methamphetamines, cocaine, LSD, psilocybin mushrooms, MDMA and club drugs. In 2015, it was estimated that about 5% of people aged 15 to 65 had used illegal drugs at least once. Many researchers have explored the etiology of recreational drug use; some of the most common theories are: genetics, personality type, psychological problems, self-medication, age, instant gratification, basic human need, rebelliousness, a sense of belonging to a group and attachment issues, history of trauma, failure at school or work, socioeconomic stressors, peer pressure, juvenile delinquency, historical factors, or sociocultural influences.
There has not been agreement around any one single cause. Instead, experts tend to apply the biopsychosocial model. Any number of these factors are to influence an individual's drug use as they are not mutually exclusive. Regardless of genetics, mental health or traumatic experiences, social factors play a large role in exposure to and availability of certain types of drugs and patterns of drug use. According to addiction researcher Martin A. Plant, many people go through a period of self-redefinition before initiating recreational drug use, they tend to view using drugs as part of a general lifestyle that involves belonging to a subculture that they associate with heightened status and the challenging of social norms. Plant says, “From the user's point of view there are many positive reasons to become part of the milieu of drug taking; the reasons for drug use appear to have as much to do with needs for friendship and status as they do with unhappiness or poverty. Becoming a drug taker, to many people, is a positive affirmation rather than a negative experience.”
Anthropological research has suggested that humans "may have evolved to counter-exploit plant neurotoxins". The ability to use botanical chemicals to serve the function of endogenous neurotransmitters may have improved survival rates, conferring an evolutionary advantage. A restrictive prehistoric diet may have emphasised the apparent benefit of consuming psychoactive drugs, which had themselves evolved to imitate neurotransmitters. Chemical–ecological adaptations, the genetics of hepatic enzymes cytochrome P450, have led researchers to propose that "humans have shared a co-evolutionary relationship with psychotropic plant substances, millions of years old." Severity and type of risks that come with recreational drug use vary with the drug in question and the amount being used. There are many factors in the environment and within the user that interact with each drug differently. Overall, some studies suggest. However, studies which focus on a moderate level of alcohol consumption have concluded that there can be substantial health benefits from its use, such as decreased risk of cardiac disease and cognitive decline.
This claim has been disputed. Researcher David Nutt stated that these studies showing benefits for "moderate" alcohol consumption lacked control for the variable of what the subjects were drinking, beforehand. Experts in the UK have suggested that some drugs that may be causing less harm, to fewer users, include cannabis, psilocybin mushrooms, LSD, ecstasy; these drugs are not without their own particular risks. The concept of "responsible drug use" is that a person can use drugs recreationally or otherwise with reduced or eliminated risk of negatively affecting other aspects of one's life or other people's lives. Advocates of this philosophy point to the many well-known artists and intellectuals who have used drugs, experimentally or otherwise, with few detrimental effects on their lives. Responsible drug use becomes problematic only when the use of the substance interferes with the user's daily life. Responsible drug use advocates that users should not take drugs at the same time as activities such as driving, operating machinery, or other activities that are unsafe without a sober state.
Responsible drug use is emphasized as a primary prevention technique in harm-reduction drug policies. Harm-reduction policies were popularized in the late 1980s, although they began in the 1970s counter-culture, when cartoons explaining responsible drug use and the co
Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. In early days, electricity was considered as being not related to magnetism. On, many experimental results and the development of Maxwell's equations indicated that both electricity and magnetism are from a single phenomenon: electromagnetism. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others; the presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges produces a magnetic field; when a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. Thus, if that charge were to move, the electric field would be doing work on the electric charge, thus we can speak of electric potential at a certain point in space, equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is measured in volts.
Electricity is at the heart of many modern technologies, being used for: electric power where electric current is used to energise equipment. Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. Practical applications for electricity were few, it would not be until the late nineteenth century that electrical engineers were able to put it to industrial and residential use; the rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an limitless set of applications which include transport, lighting and computation. Electrical power is now the backbone of modern industrial society. Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", described them as the "protectors" of all other fish.
Electric fish were again reported millennia by ancient Greek and Arabic naturalists and physicians. Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by catfish and electric rays, knew that such shocks could travel along conducting objects. Patients suffering from ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them; the earliest and nearest approach to the discovery of the identity of lightning, electricity from any other source, is to be attributed to the Arabs, who before the 15th century had the Arabic word for lightning ra‘ad applied to the electric ray. Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.
Thales was incorrect in believing the attraction was due to a magnetic effect, but science would prove a link between magnetism and electricity. According to a controversial theory, the Parthians may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell, though it is uncertain whether the artifact was electrical in nature. Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber, he coined the New Latin word electricus to refer to the property of attracting small objects after being rubbed. This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646. Further work was conducted in the 17th and early 18th centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay.
In the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky. A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature, he explained the paradoxical behavior of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges. In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles. Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines used; the recognition of electromagnetism, the unity of electric
Urea known as carbamide, is an organic compound with chemical formula CO2. This amide has two –NH2 groups joined by a carbonyl functional group. Urea serves an important role in the metabolism of nitrogen-containing compounds by animals and is the main nitrogen-containing substance in the urine of mammals, it is a colorless, odorless solid soluble in water, non-toxic. Dissolved in water, it is neither alkaline; the body uses it in most notably nitrogen excretion. The liver forms it by combining two ammonia molecules with a carbon dioxide molecule in the urea cycle. Urea is used in fertilizers as a source of nitrogen and is an important raw material for the chemical industry. Friedrich Wöhler's discovery in 1828 that urea can be produced from inorganic starting materials was an important conceptual milestone in chemistry, it showed for the first time that a substance known only as a byproduct of life could be synthesized in the laboratory without biological starting materials thereby contradicting the held doctrine of vitalism.
More than 90% of world industrial production of urea is destined for use as a nitrogen-release fertilizer. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. Therefore, it has the lowest transportation costs per unit of nitrogen nutrient. Many soil bacteria possess the enzyme urease, which catalyzes conversion of urea to ammonia or ammonium ion and bicarbonate ion, thus urea fertilizers transform to the ammonium form in soils. Among the soil bacteria known to carry urease, some ammonia-oxidizing bacteria, such as species of Nitrosomonas, can assimilate the carbon dioxide the reaction releases to make biomass via the Calvin cycle, harvest energy by oxidizing ammonia to nitrite, a process termed nitrification. Nitrite-oxidizing bacteria Nitrobacter, oxidize nitrite to nitrate, mobile in soils because of its negative charge and is a major cause of water pollution from agriculture. Ammonium and nitrate are absorbed by plants, are the dominant sources of nitrogen for plant growth.
Urea is used in many multi-component solid fertilizer formulations. Urea is soluble in water and is therefore very suitable for use in fertilizer solutions, e.g. in'foliar feed' fertilizers. For fertilizer use, granules are preferred over prills because of their narrower particle size distribution, an advantage for mechanical application; the most common impurity of synthetic urea is biuret. Urea is spread at rates of between 40 and 300 kg/ha but rates vary. Smaller applications incur lower losses due to leaching. During summer, urea is spread just before or during rain to minimize losses from volatilization; because of the high nitrogen concentration in urea, it is important to achieve an spread. The application equipment must be calibrated and properly used. Drilling must not occur on contact with or close to seed, due to the risk of germination damage. Urea dissolves in water for application through irrigation systems. In grain and cotton crops, urea is applied at the time of the last cultivation before planting.
In high rainfall areas and on sandy soils and where good in-season rainfall is expected, urea can be side- or top-dressed during the growing season. Top-dressing is popular on pasture and forage crops. In cultivating sugarcane, urea is side-dressed after planting, applied to each ratoon crop. In irrigated crops, urea can be applied dry to the soil, or dissolved and applied through the irrigation water. Urea dissolves in its own weight in water, but becomes difficult to dissolve as the concentration increases. Dissolving urea in water is endothermic—the solution temperature falls when urea dissolves; as a practical guide, when preparing urea solutions for fertigation, dissolve no more than 3 g urea per 1 L water. In foliar sprays, urea concentrations of between 0.5% and 2.0% are used in horticultural crops. Low-biuret grades of urea are indicated. Urea absorbs moisture from the atmosphere and therefore is stored either in closed or sealed bags on pallets or, if stored in bulk, under cover with a tarpaulin.
As with most solid fertilizers, storage in a cool, well-ventilated area is recommended. Overdose or placing urea near seed is harmful. Urea is a raw material for the manufacture of two main classes of materials: urea-formaldehyde resins and urea-melamine-formaldehyde used in marine plywood. Urea can be used to make urea nitrate, a high explosive, used industrially and as part of some improvised explosive devices, it is a stabilizer in nitrocellulose explosives. Urea is used in SNCR and SCR reactions to reduce the NOx pollutants in exhaust gases from combustion from Diesel, dual fuel, lean-burn natural gas engines; the BlueTec system, for example, injects a water-based urea solution into the exhaust system. The ammonia produced by the hydrolysis of the urea reacts with the nitrogen oxide emissions and is converted into nitrogen and water within the catalytic converter. Trucks and cars using these catalytic converters need to carry a supply of diesel exhaust fluid, a solution of urea in water. Urea in concentrations up to 10 M is a powerful protein denaturant as it disrupts the noncovalent bonds in the proteins.
This property can be exploited to increase the solubility of some proteins. A mixture of urea and choline chloride is used as
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" sound in its physical properties, except that humans cannot hear it; this limit varies from person to person and is 20 kilohertz in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws. Industrially, ultrasound is used for cleaning and accelerating chemical processes. Animals such as bats and porpoises use ultrasound for locating prey and obstacles. Scientists are studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments.
Echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound, not vision. Francis Galton in 1893 invented the Galton whistle, an adjustable whistle that produced ultrasound, which he used to measure the hearing range of humans and other animals, demonstrating that many animals could hear sounds above the hearing range of humans; the first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917. The piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear. Auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear.
Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. An American cell phone company has used this to create ring signals that are only audible to younger humans, but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold; the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey, they can detect frequencies beyond 100 kHz up to 200 kHz. Many insects have good ultrasonic hearing, most of these are nocturnal insects listening for echolocating bats; these include many groups of moths, praying mantids and lacewings. Upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger a reflex action in the noctuid moth that causes it to drop in its flight to evade attack.
Tiger moths emit clicks which may disturb bats' echolocation, in other cases may advertise the fact that they are poisonous by emitting sound. Dogs and cats' hearing range extends into the ultrasound; the wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. A dog whistle is a whistle that emits ultrasound, used for calling dogs; the frequency of most dog whistles is within the range of 23 to 54 kHz. Toothed whales, including dolphins, can hear ultrasound and use such sounds in their navigational system to orient and to capture prey. Porpoises have the highest known upper hearing limit at around 160 kHz. Several types of fish can detect ultrasound. In the order Clupeiformes, members of the subfamily Alosinae have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies can hear only up to 4 kHz. Ultrasound generator/speaker systems are sold as electronic pest control devices, which are claimed to frighten away rodents and insects, but there is no scientific evidence that the devices work.
An ultrasonic level or sensing system requires no contact with the target. For many processes in the medical, pharmaceutical and general industries this is an advantage over inline sensors that may contaminate the liquids inside a vessel or tube or that may be clogged by the product. Both continuous wave and pulsed systems are used; the principle behind a pulsed-ultrasonic technology is that the transmit signal consists of short bursts of ultrasonic energy. After each burst, the electronics looks for a return signal within a small window of time corresponding to the time it takes for the energy to pass through the vessel. Only a signal received during this window will qualify for additional signal processing. A popular consumer application of ultrasonic ranging was the Polaroid SX-70 camera, which included a lightweight transducer system to focus the camera automatically. Polaroid licensed this ultrasound technology and it became the basis of a variety of ultrasonic products. A common ultrasound application is an automatic door opener, where an ultrasonic sensor detects a person's approach and opens the door.
Ultrasonic sensors are used to detect intruders. The flow in pipes or open channels can be measured by ultrasonic flowmeters, which measure the average veloci
Synthetic cannabinoids are a class of molecules that bind to cannabinoid receptors in the body. They are designer drugs that are sprayed onto plant matter and are smoked, although since 2016 they have been consumed in a concentrated liquid form in the US and UK, they have been marketed as herbal incense, or “herbal smoking blends” and sold under common names like K2, Synthetic Marijuana. They are labeled “not for human consumption” for liability defense; when the herbal blends went on sale in the early 2000s, it was thought that they achieved psychoactive effects from a mixture of natural herbs. Laboratory analysis in 2008 showed instead. Since 2016 synthetic cannabinoids are the most common new psychoactive substances. From 2008 to 2014, 142 synthetic cannabinoids were reported to the European Monitoring Centre for Drugs and Drug Addiction. A large and complex variety of synthetic cannabinoids are designed in an attempt to avoid legal restrictions on cannabis, making synthetic cannabinoids designer drugs.
Most synthetic cannabinoids are agonists of the cannabinoid receptors. They have been designed to be similar to THC, the natural cannabinoid with the strongest binding affinity to the CB1 receptor, linked to the psychoactive effects or "high" of marijuana; these synthetic analogs have greater binding affinity and greater potency to the CB1 receptors. There are several synthetic cannabinoid families classified based on the base structure. Reported user negative effects include palpitations, intense anxiety, vomiting, poor coordination, seizures. There have been reports of a strong compulsion to re-dose, withdrawal symptoms, persistent cravings. There have been several deaths linked to synthetic cannabinoids; the Centers for Disease Control and Prevention found that the number of deaths from synthetic cannabinoid use tripled between 2014 and 2015. In 2018 the United States Food and Drug Administration warned of significant health risks from synthetic cannabinoid products that contain the rat poison brodifacoum, added because it is thought to extend the duration of the drugs' effects.
Severe illnesses and death have resulted from this contamination. Many of the early synthetic cannabinoids that were synthesized for use in research were named after either the scientist who first synthesized them or the institution or company where they originated. For example, JWH compounds are named after John W. Huffman and AM compounds are named after Alexandros Makriyannis, the scientists who first synthesized those cannabinoids. HU compounds are named after Hebrew University in Jerusalem, the institution where they were first synthesized, CP compounds are named after Carl Pfizer, the company where they were first synthesized; some of the names of synthetic cannabinoids synthesized for recreational use were given names to help market the products. For example, AKB-48 is the name of a popular Japanese girl band. Now many synthetic cannabinoids are assigned names derived from their chemical names. For example, APICA comes from N--1-pentyl-1H-indole-3-carboxamide and APINACA comes from N--1-pentyl-1H-indazole-3-carboxamide.
Use of the term “synthetic marijuana” to describe products containing synthetic cannabinoids is controversial and, according to Dr. Lewis Nelson, a medical toxicologist at the NYU School of Medicine, a misnomer. Nelson claims that relative to marijuana, products containing synthetic cannabinoids “are quite different, the effects are much more unpredictable. It’s dangerous.” Since the term synthetic does not apply to the plant, but rather to the cannabinoid that the plant contains, the term synthetic cannabinoid is more appropriate. Synthetic cannabinoids are known by a number of brand names including K2, Black Mamba, Bombay Blue, Zohai, Banana Cream Nuke, Lava Red, many more. In some Spanish-speaking countries, such as Chile and Argentina, such preparations are referred to as "cripy", they are called “synthetic marijuana”, “natural herbs”, “herbal incense”, or “herbal smoking blends” and labeled “not for human consumption”. They are offered in e-cigarette form as "c-liquid" with brand names such as Kronic.
According to the Psychonaut Web Mapping Research Project, synthetic cannabinoids, sold under the brand name “Spice”, were first released in 2005 by the now-dormant company The Psyche Deli in London, UK. In 2006, the brand gained popularity. According to the Financial Times, the assets of The Psyche Deli rose from £65,000 in 2006 to £899,000 in 2007; the EMCDDA reported in 2009 that Spice products were identified in 21 of the 30 participating countries. Synthetic cannabinoids were made for cannabinoid research focusing on tetrahydrocannabinol, the main psychoactive and analgesic compound found in the cannabis plant. Synthetic cannabinoids were needed due to legal restrictions on natural cannabinoids, which make them difficult to obtain for research. Tritium-labelled cannabinoids such as CP-55,940 were instrumental in discovering the cannabinoid receptors in the early 1990s; some early synthetic cannabinoids were used clinically. Nabilone, a first generation synthetic THC analog, has been used as an antiemetic to combat vomiting and nausea, since 1981.
Synthetic THC has been used as an antiemetic since 1985 and an appetite stimulant since 1991. In the early 2000s, s
Lithium is a chemical element with symbol Li and atomic number 3. It is a silvery-white alkali metal. Under standard conditions, it is the lightest solid element. Like all alkali metals, lithium is reactive and flammable, is stored in mineral oil; when cut, it exhibits a metallic luster, but moist air corrodes it to a dull silvery gray black tarnish. It never occurs in nature, but only in compounds, such as pegmatitic minerals, which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride; the nucleus of the lithium atom verges on instability, since the two stable lithium isotopes found in nature have among the lowest binding energies per nucleon of all stable nuclides. Because of its relative nuclear instability, lithium is less common in the solar system than 25 of the first 32 chemical elements though its nuclei are light: it is an exception to the trend that heavier nuclei are less common.
For related reasons, lithium has important uses in nuclear physics. The transmutation of lithium atoms to helium in 1932 was the first man-made nuclear reaction, lithium deuteride serves as a fusion fuel in staged thermonuclear weapons. Lithium and its compounds have several industrial applications, including heat-resistant glass and ceramics, lithium grease lubricants, flux additives for iron and aluminium production, lithium batteries, lithium-ion batteries; these uses consume more than three quarters of lithium production. Lithium is present in biological systems in trace amounts. Lithium salts have proven to be useful as a mood-stabilizing drug in the treatment of bipolar disorder in humans. Like the other alkali metals, lithium has a single valence electron, given up to form a cation; because of this, lithium is a good conductor of heat and electricity as well as a reactive element, though it is the least reactive of the alkali metals. Lithium's low reactivity is due to the proximity of its valence electron to its nucleus.
However, molten lithium is more reactive than its solid form. Lithium metal is soft enough to be cut with a knife; when cut, it possesses a silvery-white color that changes to gray as it oxidizes to lithium oxide. While it has one of the lowest melting points among all metals, it has the highest melting and boiling points of the alkali metals. Lithium has a low density, comparable with pine wood, it is the least dense of all elements. Furthermore, apart from helium and hydrogen, it is less dense than any liquid element, being only two thirds as dense as liquid nitrogen. Lithium can float on the lightest hydrocarbon oils and is one of only three metals that can float on water, the other two being sodium and potassium. Lithium's coefficient of thermal expansion is twice that of aluminium and four times that of iron. Lithium is superconductive below 400 μK at standard pressure and at higher temperatures at high pressures. At temperatures below 70 K, like sodium, undergoes diffusionless phase change transformations.
At 4.2 K it has a rhombohedral crystal system. At liquid-helium temperatures the rhombohedral structure is prevalent. Multiple allotropic forms have been identified for lithium at high pressures. Lithium has a mass specific heat capacity of 3.58 kilojoules per kilogram-kelvin, the highest of all solids. Because of this, lithium metal is used in coolants for heat transfer applications. Lithium reacts with water but with noticeably less vigor than other alkali metals; the reaction forms hydrogen lithium hydroxide in aqueous solution. Because of its reactivity with water, lithium is stored in a hydrocarbon sealant petroleum jelly. Though the heavier alkali metals can be stored in more dense substances, such as mineral oil, lithium is not dense enough to be submerged in these liquids. In moist air, lithium tarnishes to form a black coating of lithium hydroxide, lithium nitride and lithium carbonate; when placed over a flame, lithium compounds give off a striking crimson color, but when it burns the flame becomes a brilliant silver.
Lithium will burn in oxygen when exposed to water or water vapors. Lithium is flammable, it is explosive when exposed to air and to water, though less so than the other alkali metals; the lithium-water reaction at normal temperatures is brisk but nonviolent because the hydrogen produced does not ignite on its own. As with all alkali metals, lithium fires are difficult to extinguish, requiring dry powder fire extinguishers. Lithium is one of the few metals. Lithium has a diagonal relationship with an element of similar atomic and ionic radius. Chemical resemblances between the two metals include the formation of a nitride by reaction with N2, the formation of an oxide and peroxide when burnt in O2, salts with similar solubilities, thermal instability of the carbonates and nitrides; the metal reacts with hy