Biosynthesis and metabolism.

Many eukaryotes have the ability to synthesize carnitine, including humans. Humans synthesize carnitine from the substrate TML (6-"N"-trimethyllysine), which is in turn derived from the methylation of the amino acid lysine. TML is then hydroxylated into hydroxytrimethyllysine (HTML) by trimethyllysine dioxygenase, requiring the presence of ascorbic acid and iron. HTML is then cleaved by HTML aldolase (a pyridoxal phosphate requiring enzyme), yielding 4-trimethylaminobutyraldehyde (TMABA) and glycine. TMABA is then dehydrogenated into gamma-butyrobetaine in an NAD-dependent reaction, catalyzed by TMABA dehydrogenase. Gamma-butyrobetaine is then hydroxylated by gamma butyrobetaine hydroxylase (a zinc binding enzyme) into -carnitine, requiring iron in the form of Fe.  Carnitine is involved in transporting fatty acids across the mitochondrial membrane, by forming a long chain acetylcarnitine ester and being transported by carnitine palmitoyltransferase I and carnitine palmitoyltransferase II. Carnitine also plays a role in stabilizing Acetyl-CoA and coenzyme A levels through the ability to receive or give an acetyl group.

Tissue distribution of carnitine-biosynthetic enzymes.

The tissue distribution of carnitine-biosynthetic enzymes in humans indicates TMLD to be active in the liver, heart, muscle, brain and highest in kidney. HTMLA activity is found primarily in the liver. The rate of TMABA oxidation is greatest in the liver, with considerable activity also in the kidney.

Carnitine shuttle system.

The free-floating fatty acids, released from adipose tissues to the blood, bind to carrier protein molecule known as serum albumin that carry the fatty acids to the cytoplasm of target cells such as the heart, skeletal muscle, and other tissue cells, where they are used for fuel. But before the target cells can use the fatty acids for ATP production and β oxidation, the fatty acids with chain lengths of 14 or more carbons must be activated and subsequently transported into mitochondrial matrix of the cells in three enzymatic reactions of the carnitine shuttle.  The first reaction of the carnitine shuttle is a two-step process catalyzed by a family of isozymes of acyl-CoA synthetase that are found in the outer mitochondrial membrane, where they promote the activation of fatty acids by forming a thioester bond between the fatty acid carboxyl group and the thiol group of coenzyme A to yield a fatty acyl–CoA.  In the first step of the reaction, acyl-CoA synthetase catalyzes the transfer of adenosine monophosphate group (AMP) from an ATP molecule onto the fatty acid generating a fatty acyl–adenylate intermediate and a pyrophosphate group (PP). The pyrophosphate, formed from the hydrolysis of the two high-energy bonds in ATP, is immediately hydrolyzed to two molecule of P by inorganic pyrophosphatase. This reaction is highly exergonic which drives the activation reaction forward and makes it more favorable. In the second step, the thiol group of a cytosolic coenzyme A attacks the acyl-adenylate, displacing AMP to form thioester fatty acyl-CoA.  In the second reaction, acyl-CoA is transiently attached to the hydroxyl group of carnitine to form fatty acyl–carnitine. This transesterification is catalyzed by an enzyme found in the outer membrane of the mitochondria known as carnitine acyltransferase 1 (also called carnitine palmitoyltransferase 1, CPT1).  The fatty acyl–carnitine ester formed then diffuses across the intermembrane space and enters the matrix by facilitated diffusion through carnitine-acylcarnitine translocase (CACT) located on inner mitochondrial membrane. This antiporter return one molecule of carnitine from the matrix to the intermembrane space for every one molecule of fatty acyl–carnitine that moves into the matrix.  In the third and final reaction of the carnitine shuttle, the fatty acyl group is transferred from fatty acyl-carnitine to coenzyme A, regenerating fatty acyl–CoA and a free carnitine molecule. This reaction takes place in the mitochondrial matrix and is catalyzed by carnitine acyltransferase 2 (also called carnitine palmitoyltransferase 2, CPT2), which is located on the inner face of the inner mitochondrial membrane. The carnitine molecule formed is then shuttled back into the intermembrane space by the same cotransporter (CACT) while the fatty acyl-CoA enters β-oxidation.

Regulation of fatty acid β oxidation.

The carnitine-mediated entry process is a rate-limiting factor for fatty acid oxidation and is an important point of regulation.

Inhibition.

The liver starts actively making triglycerides from excess glucose when it is supplied with glucose that cannot be oxidized or stored as glycogen. This increases the concentration of malonyl-CoA, the first intermediate in fatty acid synthesis, leading to the inhibition of carnitine acyltransferase 1, thereby preventing fatty acid entry into the mitochondrial matrix for β oxidation. This inhibition prevents fatty acid breakdown while synthesis occurs.

Activation.

Carnitine shuttle activation occurs due to a need for fatty acid oxidation which is required for energy production. During vigorous muscle contraction or during fasting, ATP concentration decreases and AMP concentration increases leading to the activation of AMP-activated protein kinase (AMPK). AMPK phosphorylates acetyl-CoA carboxylase, which normally catalyzes malonyl-CoA synthesis. This phosphorylation inhibits acetyl-CoA carboxylase, which in turn lowers the concentration of malonyl-CoA. Lower levels of malonyl-CoA disinhibits carnitine acyltransferase 1, allowing fatty acid import to the mitochondria, ultimately replenishing the supply of ATP.

Transcription factors.

Peroxisome proliferator-activated receptor alpha (PPAR"α") is a nuclear receptor that functions as a transcription factor. It acts in muscle, adipose tissue, and liver to turn on a set of genes essential for fatty acid oxidation, including the fatty acid transporters carnitine acyltransferases 1 and 2, the fatty acyl–CoA dehydrogenases for short, medium, long, and very long acyl chains, and related enzymes.  PPAR"α" functions as a transcription factor in two cases; as mentioned before when there is an increased demand for energy from fat catabolism, such as during a fast between meals or long-term starvation. Besides that, the transition from fetal to neonatal metabolism in the heart. In the fetus, fuel sources in heart muscle are glucose and lactate, but in the neonatal heart, fatty acids are the main fuel which require the PPAR"α" to be activated so it is able in turn to activate the genes essential for fatty acid metabolism in this stage.

Metabolic defects of fatty acids oxidation.

More than 20 human genetic defects in fatty acid transport or oxidation have been identified. In case of Fatty acid oxidation defects, acyl-carnitines accumulate in mitochondria and are transferred into the cytosol, and then into the blood. Plasma levels of acylcarnitine in newborn infants can be detected in a small blood sample by tandem mass spectrometry.  When "β" oxidation is defective because of either mutation or deficiency in carnitine, the ω oxidation of fatty acids becomes more important in mammals. Actually, the ω Oxidation of Fatty Acids is another pathway for F-A degradation in some species of vertebrates and mammals that occurs in the endoplasmic reticulum of liver and kidney, it is the oxidation of the ω (omega) carbon—the carbon most far from the carboxyl group (in contrast to formula_1 oxidation which occurs at the carboxyl end of fatty acid, in the mitochondria).

Physiological effects.

As an example of normal synthesis, a person would produce 11–34 mg of carnitine per day. Adults eating mixed diets of red meat and other animal products ingest some 60–180 mg of carnitine per day, while vegans consume about 10–12 mg per day. Most (54–86%) carnitine obtained from the diet is absorbed in the small intestine before entering the blood. The total body content of carnitine is about in a person weighing, with nearly all of it contained within skeletal muscle cells. Carnitine metabolizes at rates of about 400 μmol per day, an amount less than 1% of total body stores.

Deficiency.

Carnitine deficiency does not exist in healthy people without metabolic disorders, indicating that most people have normal, adequate levels of carnitine normally produced through fatty acid metabolism. Even vegans show no signs of carnitine deficiency. Infants, especially premature infants, have low stores of carnitine, necessitating use of carnitine-fortified infant formulas as a replacement for breast milk, if necessary.  Two types of carnitine deficiency states exist. Primary carnitine deficiency is a genetic disorder of the cellular carnitine-transporter system that typically appears by the age of five with symptoms of cardiomyopathy, skeletal-muscle weakness, and hypoglycemia. Secondary carnitine deficiencies may happen as the result of certain disorders, such as chronic kidney failure, or under conditions that reduce carnitine absorption or increase its excretion, such as use of antibiotics, malnutrition, and poor absorption following digestion.

Supplementation.

Carnitine has been studied in various cardiometabolic conditions, indicating its use as an adjunct in heart disease and diabetes, among numerous other disorders. Carnitine has no effect on preventing mortality associated with cardiovascular diseases, and has no significant effect on blood lipids. Carnitine has no effect on most parameters in end-stage kidney disease, although it may lower c-reactive protein.  Despite widespread interest among athletes to use carnitine for improvement of exercise performance, inhibit muscle cramps, or enhance recovery from physical training, the quality of research for these possible benefits has been low, prohibiting any conclusion of effect. At supplement amounts of per day over a month, there was no consistent evidence that carnitine affected exercise or physical performance. Carnitine supplements do not improve oxygen consumption or metabolic functions when exercising, nor do they increase the amount of carnitine in muscle.

Male infertility.

The carnitine content of seminal fluid is directly related to sperm count and motility, suggesting that the compound might be of value in treating male infertility. One study concluded that carnitine supplementation may improve sperm quality, and the reported benefits may relate to increased mitochondrial fatty-acid oxidation (providing more energy for sperm) and reduced cell death in the testes of mice subjected to physical stress to the testes.

Cardiovascular and peripheral arterial diseases.

Several studies have approved the effectiveness of supplemental carnitine in the management of cardiac ischemia (restriction of blood flow to the heart) and peripheral arterial disease. In fact, levels of carnitine are low in the failing heart muscle, supplemental amounts might counteract the toxic effects of free fatty acids and improve carbohydrate metabolism. Carnitine has had anti-ischemic properties when given orally and by injection.

Atherosclerosis.

Koeth et al., from the Cleveland Clinic reported that carnitine from animal flesh (four times as much in red meat as in fish or chicken), as well as phosphatidylcholine from egg yolk, are converted by intestinal bacteria to trimethylamine (the compound that causes uremic breath to smell fishy). Trimethylamine is oxidized in the liver to trimethylamine "N"-oxide (TMAO), which causes atherosclerosis in animal models. Patients in the top quartile of TMAO had a 2.5-fold increase in the 3-year risk of stroke, death, or myocardial infarction.  A key issue is that vegans who consumed -carnitine did not produce TMAO because they did not have the intestinal bacteria that produce TMA from carnitine.

Diabetes mellitus type 2.

Type 2 diabetes which is marked by insulin resistance may be associated with a defect in fatty acid oxidation in muscle. Several studies suggest that carnitine supplementation may have a beneficial effect on glucose utilization and reduce diabetic neuropathy.

AIDS and HIV.

Generally HIV infected patients accumulate fat in some areas of the body and lose fat in other areas, besides having high blood levels of fats (hyperlipidemia) and insulin resistance which is known as the lipdystrophy syndrome. This syndrome causes a deficiency in -carnitine which causes defects in fat metabolism in mitochondria. Supplementation with carnitine in HIV-infected individuals may slow the death of lymphocytes, reduce neuropathy and favorably affect blood lipid levels.

End stage renal disease and hemodialysis.

The kidneys contribute to overall homeostasis in the body, including carnitine levels. In the case of renal impairment, urinary elimination of carnitine increasing, endogenous synthesis decreasing, and poor nutrition as a result of disease-induced anorexia can result in carnitine deficiency. Carnitine blood levels and muscle stores can become very low, which may contribute to anemia, muscle weakness, fatigue, altered levels of blood fats, and heart disorders. Some studies have shown that supplementation of high doses of -carnitine (often injected) may aid in anemia management.

Sources.

The form present in the body is -carnitine, which is also the form present in food. Food sources rich in -carnitine are animal products, particularly beef and pork. Redder meats tend to have higher levels of -carnitine. Adults eating diverse diets that contain animal products attain about 60–180 mg of carnitine per day. Vegans get noticeably less (about 10–12 mg) since their diets lack these carnitine-rich animal-derived foods. Approximately 54% to 86% of dietary carnitine is absorbed in the small intestine, then enters the blood. Even carnitine-poor diets have little effect on total carnitine content, as the kidneys conserve carnitine. In general, omnivorous humans each day consume between 2 and 12 μmol kg of body weight, accounting for 75% of carnitine in the body. Humans endogenously produce 1.2 μmol kg of body weight of carnitine on a daily basis, accounting for 25% of the carnitine in the body. Strict vegetarians obtain little carnitine from dietary sources (0.1 μmol kg of body weight daily), as it is mainly found in animal-derived foods.

Recommended intakes of carnitine.

In 1989, the Food and Nutrition Board concluded that carnitine wasn't an essential nutrient as healthy human liver and kidneys synthesize sufficient quantities of carnitine from lysine and methionine to meet up with daily body requirements without the need of consuming it from supplements or food. Also, the FNB has not established Dietary Reference Intakes (DRIs) for carnitine.

Supplemental sources of carnitine.

-carnitine, acetyl--carnitine, and propionyl--carnitine are available in dietary supplement pills or powders. It is also a drug approved by the Food and Drug Administration to treat primary and certain secondary carnitine-deficiency syndromes.

Drug interactions and adverse effects.

Carnitine interacts with pivalate-conjugated antibiotics such as pivampicillin. Chronic administration of these antibiotics increases the excretion of pivaloyl-carnitine, which can lead to carnitine depletion. Treatment with the anticonvulsants valproic acid, phenobarbital, phenytoin, or carbamazepine significantly reduces blood levels of carnitine.  When used in about per day, carnitine may cause nausea, vomiting, abdominal cramps, diarrhea, and body odor smelling like fish. Other possible adverse effects include skin rash, muscle weakness, or seizures in people with epilepsy.

History.

Levocarnitine was approved by the U.S. Food and Drug Administration as a new molecular entity under the brand name Carnitor on December 27, 1985.

Carnitine (β-hydroxy-γ-"N"-trimethylaminobutyric acid, 3-hydroxy-4-"N","N","N"-trimethylaminobutyrate) is a quaternary ammonium compound involved in metabolism in most mammals, plants, and some bacteria. In support of energy metabolism, carnitine transports long-chain fatty acids into mitochondria to be oxidized for energy production, and also participates in removing products of metabolism from cells. Given its key metabolic roles, carnitine is concentrated in tissues like skeletal and cardiac muscle that metabolize fatty acids as an energy source. Healthy individuals, including strict vegetarians, synthesize enough L-carnitine in vivo to not require supplementation.

Karnitin je kvarterní amoniová sloučenina a derivát aminokyselin lysinu a methioninu. Má důležitou roli v transportu mastných kyselin do mitochondrií.


Latin.

On the Latin stage the prologue was often more elaborate than it was in Athens, and in the careful composition of the poems which Plautus prefixes to his plays we see what importance he gave to this portion of the entertainment; sometimes, as in the preface to the "Rudens", Plautus rises to the height of his genius in his adroit and romantic prologues, usually placed in the mouths of persons who make no appearance in the play itself.  Molière revived the Plautian prologue in the introduction to his "Amphitryon". Racine introduced Piety as the speaker of a prologue which opened his choral tragedy of Esther.  The tradition of the ancients vividly affected our own early dramatists. Not only were the mystery plays and miracles of the Middle Ages begun by a homily, but when the drama in its modern sense was inaugurated in the reign of Elizabeth, the prologue came with it, directly adapted from the practice of Euripides and Terence. Sackville, Lord Buckhurst, prepared a sort of prologue in dumb show for his "Gorboduc" of 1562; and he also wrote a famous Induction, which is, practically, a prologue, to a miscellany of short romantic epics by diverse hands.

Elizabethan.

Prologues of Renaissance drama often served a specific function of transition and clarification for the audience. A direct address made by one actor, the prologue acted as an appeal to the audience's attention and sympathy, providing historical context, a guide to themes of the play, and occasionally, a disclaimer. In this mode, a prologue, like any scripted performance, would exist as the text, the actor who speaks that text, and the presentation of the language as it is spoken. In ushering the audience from the reality into the world of the play, the prologue straddles boundaries between audience, actors, characters, playwrights—basically, it creates a distinction between the imaginary space within the play and the outside world. Ben Jonson has often been noted as using the prologue to remind the audience of the complexities between themselves and all aspects of the performance.  The actor reciting the prologue would appear dressed in black, a stark contrast to the elaborate costumes used during the play. The prologue removed his hat and wore no makeup. He may have carried a book, scroll, or a placard displaying the title of the play. He was introduced by three short trumpet calls, on the third of which he entered and took a position downstage. He made three bows in the current fashion of the court, and then addressed the audience. The Elizabethan prologue was unique in incorporating aspects of both classical and medieval traditions. In the classical tradition, the prologue conformed to one of four subgenres: the "sustatikos", which recommends either the play or the poet; the "epitimetikos", in which a curse is given against a rival, or thanks given to the audience; "dramatikos", in which the plot of the play is explained; and mixtos, which contains all of these things. In the medieval tradition, expressions of morality and modesty are seen, as well as a meta-theatrical self-consciousness, and an unabashed awareness of the financial contract engaged upon by paid actors and playwrights, and a paying audience.

Use in fiction.

Prologues have long been used in non-dramatic fiction, since at least the time of Geoffrey Chaucer's "Canterbury Tales", although Chaucer had prologues to many of the tales, rather than one at the front of the book.  The Museum of Eterna's Novel by Argentine writer Macedonio Fernandez has over 50 prologues by the author. Their style varies between metaphysical, humoristic, psychological, discussions about the art of the Novel, etc.

A prologue or prolog (from Greek πρόλογος "prologos", from πρό "pro", "before" and λόγος "logos", "word") is an opening to a story that establishes the context and gives background details, often some earlier story that ties into the main one, and other miscellaneous information. The Ancient Greek "prólogos" included the modern meaning of "prologue", but was of wider significance, more like the meaning of preface. The importance, therefore, of the prologue in Greek drama was very great; it sometimes almost took the place of a romance, to which, or to an episode in which, the play itself succeeded.

Prolog (řecky πρόλογος "prologos" < πρό před + λόγος slovo, řeč) je úvodní část spisu, která má obvykle za úkol uvést drama. V širším smyslu se však používá pro předmluvu jakéhokoli druhu (podobně jako latinské "praefatio").


Overview.

Tropical rainforests can be characterized in two words: hot and wet. Mean monthly temperatures exceed during all months of the year. Average annual rainfall is no less than and can exceed although it typically lies between and. This high level of precipitation often results in poor soils due to leaching of soluble nutrients in the ground.  Tropical rainforests exhibit high levels of biodiversity. Around 40% to 75% of all biotic species are indigenous to the rainforests. Rainforests are home to half of all the living animal and plant species on the planet. Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called the "world's largest pharmacy", because over one quarter of natural medicines have been discovered within them. It is likely that there may be many millions of species of plants, insects and microorganisms still undiscovered in tropical rainforests.  Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation as a result of human activity. Habitat fragmentation caused by geological processes such as volcanism and climate change occurred in the past, and have been identified as important drivers of speciation. However, fast human driven habitat destruction is suspected to be one of the major causes of species extinction. Tropical rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, and the area covered by rainforests around the world is rapidly shrinking.

History.

Tropical rainforests have existed on earth for hundreds of millions of years. Most tropical rainforests today are on fragments of the Mesozoic era supercontinent of Gondwana. The separation of the landmass resulted in a great loss of amphibian diversity while at the same time the drier climate spurred the diversification of reptiles. The division left tropical rainforests located in five major regions of the world: tropical America, Africa, Southeast Asia, Madagascar, and New Guinea, with smaller outliers in Australia. However, the specifics of the origin of rainforests remain uncertain due to an incomplete fossil record.

Other types of tropical forest.

Several biomes may appear similar-to, or merge via ecotones with, tropical rainforest:  Moist seasonal tropical forests receive high overall rainfall with a warm summer wet season and a cooler winter dry season. Some trees in these forests drop some or all of their leaves during the winter dry season, thus they are sometimes called "tropical mixed forest". They are found in parts of South America, in Central America and around the Caribbean, in coastal West Africa, parts of the Indian subcontinent, and across much of Indochina.  These are found in cooler-climate mountainous areas, becoming known as cloud forests at higher elevations. Depending on latitude, the lower limit of montane rainforests on large mountains is generally between 1500 and 2500 m while the upper limit is usually from 2400 to 3300 m.  Tropical freshwater swamp forests, or "flooded forests", are found in Amazon basin (the Várzea) and elsewhere.

Forest structure.

Rainforests are divided into different strata, or layers, with vegetation organized into a vertical pattern from the top of the soil to the canopy. Each layer is a unique biotic community containing different plants and animals adapted for life in that particular strata. Only the emergent layer is unique to tropical rainforests, while the others are also found in temperate rainforests.

Forest floor.

The forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks, swamps and clearings, where dense undergrowth is found, the forest floor is relatively clear of vegetation because of the low sunlight penetration. This more open quality permits the easy movement of larger animals such as: ungulates like the okapi ("Okapia johnstoni"), tapir ("Tapirus" sp.), Sumatran rhinoceros ("Dicerorhinus sumatrensis"), and apes like the western lowland gorilla ("Gorilla gorilla"), as well as many species of reptiles, amphibians, and insects. The forest floor also contains decaying plant and animal matter, which disappears quickly, because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay the animal and plant waste.

Understory layer.

The understory layer lies between the canopy and the forest floor. The understory is home to a number of birds, small mammals, insects, reptiles, and predators. Examples include leopard ("Panthera pardus"), poison dart frogs ("Dendrobates" sp.), ring-tailed coati ("Nasua nasua"), boa constrictor ("Boa constrictor"), and many species of Coleoptera. The vegetation at this layer generally consists of shade-tolerant shrubs, herbs, small trees, and large woody vines which climb into the trees to capture sunlight. Only about 5% of sunlight breaches the canopy to arrive at the understory causing true understory plants to seldom grow to 3 m (10 feet). As an adaptation to these low light levels, understory plants have often evolved much larger leaves. Many seedlings that will grow to the canopy level are in the understory.

Canopy layer.

The canopy is the primary layer of the forest forming a roof over the two remaining layers. It contains the majority of the largest trees, typically 30–45 m in height. Tall, broad-leaved evergreen trees are the dominant plants. The densest areas of biodiversity are found in the forest canopy, as it often supports a rich flora of epiphytes, including orchids, bromeliads, mosses and lichens. These epiphytic plants attach to trunks and branches and obtain water and minerals from rain and debris that collects on the supporting plants. The fauna is similar to that found in the emergent layer, but more diverse. It is suggested that the total arthropod species richness of the tropical canopy might be as high as 20 million. Other species habituating this layer include many avian species such as the yellow-casqued wattled hornbill ("Ceratogymna elata"), collared sunbird ("Anthreptes collaris"), grey parrot ("Psitacus erithacus"), keel-billed toucan ("Ramphastos sulfuratus"), scarlet macaw ("Ara macao") as well as other animals like the spider monkey ("Ateles" sp.), African giant swallowtail ("Papilio antimachus"), three-toed sloth ("Bradypus tridactylus"), kinkajou ("Potos flavus"), and tamandua ("Tamandua tetradactyla").

Emergent layer.

The emergent layer contains a small number of very large trees, called "emergents", which grow above the general canopy, reaching heights of 45–55 m, although on occasion a few species will grow to 70–80 m tall. Some examples of emergents include: "Balizia elegans", "Dipteryx panamensis", "Hieronyma alchorneoides", "Hymenolobium mesoamericanum", "Lecythis ampla" and "Terminalia oblonga". These trees need to be able to withstand the hot temperatures and strong winds that occur above the canopy in some areas. Several unique faunal species inhabit this layer such as the crowned eagle ("Stephanoaetus coronatus"), the king colobus ("Colobus polykomos"), and the large flying fox ("Pteropus vampyrus").  However, stratification is not always clear. Rainforests are dynamic and many changes affect the structure of the forest. Emergent or canopy trees collapse, for example, causing gaps to form. Openings in the forest canopy are widely recognized as important for the establishment and growth of rainforest trees. It is estimated that perhaps 75% of the tree species at La Selva Biological Station, Costa Rica are dependent on canopy opening for seed germination or for growth beyond sapling size, for example.

Ecology.

Climates.

Tropical rainforests are located around and near the equator, therefore having what is called an equatorial climate characterized by three major climatic parameters: temperature, rainfall, and dry season intensity. Other parameters that affect tropical rainforests are carbon dioxide concentrations, solar radiation, and nitrogen availability. In general, climatic patterns consist of warm temperatures and high annual rainfall. However, the abundance of rainfall changes throughout the year creating distinct moist and dry seasons. Tropical forests are classified by the amount of rainfall received each year, which has allowed ecologists to define differences in these forests that look so similar in structure. According to Holdridge's classification of tropical ecosystems, true tropical rainforests have an annual rainfall greater than 2 m and annual temperature greater than 24 degrees Celsius, with a potential evapotranspiration ratio (PET) value of <0.25. However, most lowland tropical forests can be classified as tropical moist or wet forests, which differ in regards to rainfall. Tropical forest ecology- dynamics, composition, and function- are sensitive to changes in climate especially changes in rainfall.

Soils.

Soil types.

Soil types are highly variable in the tropics and are the result of a combination of several variables such as climate, vegetation, topographic position, parent material, and soil age. Most tropical soils are characterized by significant leaching and poor nutrients, however there are some areas that contain fertile soils. Soils throughout the tropical rainforests fall into two classifications which include the ultisols and oxisols. Ultisols are known as well weathered, acidic red clay soils, deficient in major nutrients such as calcium and potassium. Similarly, oxisols are acidic, old, typically reddish, highly weathered and leached, however are well drained compared to ultisols. The clay content of ultisols is high, making it difficult for water to penetrate and flow through. The reddish color of both soils is the result of heavy heat and moisture forming oxides of iron and aluminium, which are insoluble in water and not taken up readily by plants.  Soil chemical and physical characteristics are strongly related to above ground productivity and forest structure and dynamics. The physical properties of soil control the tree turnover rates whereas chemical properties such as available nitrogen and phosphorus control forest growth rates. The soils of the eastern and central Amazon as well as the Southeast Asian Rainforest are old and mineral poor whereas the soils of the western Amazon (Ecuador and Peru) and volcanic areas of Costa Rica are young and mineral rich. Primary productivity or wood production is highest in western Amazon and lowest in eastern Amazon which contains heavily weathered soils classified as oxisols. Additionally, Amazonian soils are greatly weathered, making them devoid of minerals like phosphorus, potassium, calcium, and magnesium, which come from rock sources. However, not all tropical rainforests occur on nutrient poor soils, but on nutrient rich floodplains and volcanic soils located in the Andean foothills, and volcanic areas of Southeast Asia, Africa, and Central America.  Oxisols, infertile, deeply weathered and severely leached, have developed on the ancient Gondwanan shields. Rapid bacterial decay prevents the accumulation of humus. The concentration of iron and aluminium oxides by the laterization process gives the oxisols a bright red color and sometimes produces minable deposits (e.g., bauxite). On younger substrates, especially of volcanic origin, tropical soils may be quite fertile.

Nutrient recycling.

This high rate of decomposition is the result of phosphorus levels in the soils, precipitation, high temperatures and the extensive microorganism communities. In addition to the bacteria and other microorganisms, there are an abundance of other decomposers such as fungi and termites that aid in the process as well. Nutrient recycling is important because below ground resource availability controls the above ground biomass and community structure of tropical rainforests. These soils are typically phosphorus limited, which inhibits net primary productivity or the uptake of carbon. The soil contains microbial organisms such as bacteria, which break down leaf litter and other organic matter into inorganic forms of carbon usable by plants through a process called decomposition. During the decomposition process the microbial community is respiring, taking up oxygen and releasing carbon dioxide. The decomposition rate can be evaluated by measuring the uptake of oxygen. High temperatures and precipitation increase decomposition rate, which allows plant litter to rapidly decay in tropical regions, releasing nutrients that are immediately taken up by plants through surface or ground waters. The seasonal patterns in respiration are controlled by leaf litter fall and precipitation, the driving force moving the decomposable carbon from the litter to the soil. Respiration rates are highest early in the wet season because the recent dry season results in a large percentage of leaf litter and thus a higher percentage of organic matter being leached into the soil.

Buttress roots.

A common feature of many tropical rainforests is the distinct buttress roots of trees. Instead of penetrating to deeper soil layers, buttress roots create a widespread root network at the surface for more efficient uptake of nutrients in a very nutrient poor and competitive environment. Most of the nutrients within the soil of a tropical rainforest occur near the surface because of the rapid turnover time and decomposition of organisms and leaves. Because of this, the buttress roots occur at the surface so the trees can maximize uptake and actively compete with the rapid uptake of other trees. These roots also aid in water uptake and storage, increase surface area for gas exchange, and collect leaf litter for added nutrition. Additionally, these roots reduce soil erosion and maximize nutrient acquisition during heavy rains by diverting nutrient rich water flowing down the trunk into several smaller flows while also acting as a barrier to ground flow. Also, the large surface areas these roots create provide support and stability to rainforests trees, which commonly grow to significant heights. This added stability allows these trees to withstand the impacts of severe storms, thus reducing the occurrence of fallen trees.

Forest succession.

Succession is an ecological process that changes the biotic community structure over time towards a more stable, diverse community structure after an initial disturbance to the community. The initial disturbance is often a natural phenomenon or human caused event. Natural disturbances include hurricanes, volcanic eruptions, river movements or an event as small as a fallen tree that creates gaps in the forest. In tropical rainforests, these same natural disturbances have been well documented in the fossil record, and are credited with encouraging speciation and endemism. Human land use practices have led to large-scale deforestation. In many tropical countries such as Costa Rica these deforested lands have been abandoned and forests have been allowed to regenerate through ecological succession. These regenerating young successional forests are called secondary forests or second-growth forests.

Biodiversity and speciation.

Tropical rainforests exhibit a vast diversity in plant and animal species. The root for this remarkable speciation has been a query of scientists and ecologists for years. A number of theories have been developed for why and how the tropics can be so diverse.

Interspecific competition.

Interspecific competition results from a high density of species with similar niches in the tropics and limited resources available. Species which "lose" the competition may either become extinct or find a new niche. Direct competition will often lead to one species dominating another by some advantage, ultimately driving it to extinction. Niche partitioning is the other option for a species. This is the separation and rationing of necessary resources by utilizing different habitats, food sources, cover or general behavioral differences. A species with similar food items but different feeding times is an example of niche partitioning.

Pliestocene refugia.

The theory of Pleistocene refugia was developed by Jürgen Haffer in 1969 with his article "Speciation of Amazonian Forest Birds". Haffer proposed the explanation for speciation was the product of rainforest patches being separated by stretches of non-forest vegetation during the last glacial period. He called these patches of rainforest areas refuges and within these patches allopatric speciation occurred. With the end of the glacial period and increase in atmospheric humidity, rainforest began to expand and the refuges reconnected. This theory has been the subject of debate. Scientists are still skeptical of whether or not this theory is legitimate. Genetic evidence suggests speciation had occurred in certain taxa 1–2 million years ago, preceding the Pleistocene.

Human dimensions.

Habitation.

Tropical rainforests have harboured human life for many millennia, with many Indian tribes in South- and Central America, who belong to the Indigenous peoples of the Americas, the Congo Pygmies in Central Africa, and several tribes in South-East Asia, like the Dayak people and the Penan people in Borneo. Food resources within the forest are extremely dispersed due to the high biological diversity and what food does exist is largely restricted to the canopy and requires considerable energy to obtain. Some groups of hunter-gatherers have exploited rainforest on a seasonal basis but dwelt primarily in adjacent savanna and open forest environments where food is much more abundant. Other people described as rainforest dwellers are hunter-gatherers who subsist in large part by trading high value forest products such as hides, feathers, and honey with agricultural people living outside the forest.

Indigenous peoples.

A variety of indigenous people live within the rainforest as hunter-gatherers, or subsist as part-time small scale farmers supplemented in large part by trading high-value forest products such as hides, feathers, and honey with agricultural people living outside the forest. Peoples have inhabited the rainforests for tens of thousands of years and have remained so elusive that only recently have some tribes been discovered. These indigenous peoples are greatly threatened by loggers in search for old-growth tropical hardwoods like Ipe, Cumaru and Wenge, and by farmers who are looking to expand their land, for cattle(meat), and soybeans, which are used to feed cattle in Europe and China. On 18 January 2007, FUNAI reported also that it had confirmed the presence of 67 different uncontacted tribes in Brazil, up from 40 in 2005. With this addition, Brazil has now overtaken the island of New Guinea as the country having the largest number of uncontacted tribes. The province of Irian Jaya or West Papua in the island of New Guinea is home to an estimated 44 uncontacted tribal groups.  The pygmy peoples are hunter-gatherer groups living in equatorial rainforests characterized by their short height (below one and a half meters, or 59 inches, on average). Amongst this group are the Efe, Aka, Twa, Baka, and Mbuti people of Central Africa. However, the term pygmy is considered pejorative so many tribes prefer not to be labeled as such.  Some notable indigenous peoples of the Americas, or Amerindians, include the Huaorani, Ya̧nomamö, and Kayapo people of the Amazon. The traditional agricultural system practiced by tribes in the Amazon is based on swidden cultivation (also known as slash-and-burn or shifting cultivation) and is considered a relatively benign disturbance. In fact, when looking at the level of individual swidden plots a number of traditional farming practices are considered beneficial. For example, the use of shade trees and fallowing all help preserve soil organic matter, which is a critical factor in the maintenance of soil fertility in the deeply weathered and leached soils common in the Amazon.  There is a diversity of forest people in Asia, including the Lumad peoples of the Philippines and the Penan and Dayak people of Borneo. The Dayaks are a particularly interesting group as they are noted for their traditional headhunting culture. Fresh human heads were required to perform certain rituals such as the Iban "kenyalang" and the Kenyah "mamat". Pygmies who live in Southeast Asia are, amongst others, referred to as "Negrito".

Resources.

Cultivated foods and spices.

Yam, coffee, chocolate, banana, mango, papaya, macadamia, avocado, and sugarcane all originally came from tropical rainforest and are still mostly grown on plantations in regions that were formerly primary forest. In the mid-1980s and 1990s, 40 million tons of bananas were consumed worldwide each year, along with 13 million tons of mango. Central American coffee exports were worth US$3 billion in 1970. Much of the genetic variation used in evading the damage caused by new pests is still derived from resistant wild stock. Tropical forests have supplied 250 cultivated kinds of fruit, compared to only 20 for temperate forests. Forests in New Guinea alone contain 251 tree species with edible fruits, of which only 43 had been established as cultivated crops by 1985.

Ecosystem services.

In addition to extractive human uses, rain forests also have non-extractive uses that are frequently summarized as ecosystem services. Rain forests play an important role in maintaining biological diversity, sequestering and storing carbon, global climate regulation, disease control, and pollination. Half of the rainfall in the Amazon area is produced by the forests. The moisture from the forests is important to the rainfall in Brazil, Paraguay, Argentina Deforestation in the Amazon rainforest region was one of the main reason that cause the severe Drought of 2014-2015 in Brazil For the last three decades, the amount of carbon absorbed by the world’s intact tropical forests has fallen, according to a study published in 2020 in the journal Nature. In 2019 they took up a third less carbon than they did in the 1990s, due to higher temperatures, droughts and deforestation. The typical tropical forest may become a carbon source by the 2060s.

Tourism.

Despite the negative effects of tourism in the tropical rainforests, there are also several important positive effects.

Conservation.

Threats.

Deforestation.

Mining and drilling.

Deposits of precious metals (gold, silver, coltan) and fossil fuels (oil and natural gas) occur underneath rainforests globally. These resources are important to developing nations and their extraction is often given priority to encourage economic growth. Mining and drilling can require large amounts of land development, directly causing deforestation. In Ghana, a West African nation, deforestation from decades of mining activity left about 12% of the country's original rainforest intact.

Conversion to agricultural land.

With the invention of agriculture, humans were able to clear sections of rainforest to produce crops, converting it to open farmland. Such people, however, obtain their food primarily from farm plots cleared from the forest and hunt and forage within the forest to supplement this. The issue arising is between the independent farmer providing for his family and the needs and wants of the globe as a whole. This issue has seen little improvement because no plan has been established for all parties to be aided.  Agriculture on formerly forested land is not without difficulties. Rainforest soils are often thin and leached of many minerals, and the heavy rainfall can quickly leach nutrients from area cleared for cultivation. People such as the Yanomamo of the Amazon, utilize slash-and-burn agriculture to overcome these limitations and enable them to push deep into what were previously rainforest environments. However, these are not rainforest dwellers, rather they are dwellers in cleared farmland that make forays into the rainforest. Up to 90% of the typical Yanamomo diet comes from farmed plants.  Some action has been taken by suggesting fallow periods of the land allowing secondary forest to grow and replenish the soil. Beneficial practices like soil restoration and conservation can benefit the small farmer and allow better production on smaller parcels of land.

Climate change.

The tropics take a major role in reducing atmospheric carbon dioxide. The tropics (most notably the Amazon rainforest) are called carbon sinks. As major carbon reducers and carbon and soil methane storages, their destruction contributes to increasing global energy trapping, atmospheric gases. Climate change has been significantly contributed to by the destruction of the rainforests. A simulation was performed in which all rainforest in Africa were removed. The simulation showed an increase in atmospheric temperature by 2.5 to 5 degrees Celsius.

Protection.

Efforts to protect and conserve tropical rainforest habitats are diverse and widespread. Tropical rainforest conservation ranges from strict preservation of habitat to finding sustainable management techniques for people living in tropical rainforests. International policy has also introduced a market incentive program called Reducing Emissions from Deforestation and Forest Degradation (REDD) for companies and governments to outset their carbon emissions through financial investments into rainforest conservation.

Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as "lowland equatorial evergreen rainforest". True rainforests are typically found between 10 degrees north and south of the equator (see map); they are a sub-set of the tropical forest biome that occurs roughly within the 28-degree latitudes (in the equatorial zone between the Tropic of Cancer and Tropic of Capricorn). Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest (or tropical wet forest) that also includes the more extensive seasonal tropical forests.

Tropický deštný les, též tropický deštný prales, je zalesněný biom s trvale teplým a vlhkým podnebím. Nevznikl působením člověka. Obvykle se uvádí jako dolní hranice celoročních srážek 2000 mm (v různých pojetích 1700–2500 mm). Podmínkou je, aby klima bylo vlhké skutečně celoročně, tzn. aby i v nejsušších měsících spadlo minimálně 60 mm srážek. Tento biom nalezneme zejména v rovníkových oblastech Země, byť některé okrajové enklávy mohou díky místním specifikům zasahovat až do subtropů. Nejrozsáhlejší je Amazonský deštný prales, dále Konžský deštný prales a pralesy na poloostrovech a ostrovech Přední a Zadní Indie. Krom nich ještě existují menší ostrovní pralesy v Karibiku, Indickém oceánu a rovníkové oblasti Pacifiku. Vlhkost vzduchu bývá až 100 %. Časté deště vše zvlhčují a rychlý bakteriální rozklad, kterému klima přeje, vykoná zbytek. Koncentrace oxidů železa a hliníku procesem laterizace způsobuje světlečervenou barvu oxisolí a někdy produkuje těžitelná ložiska (např. bauxitu, železa atd..). Na mladších substrátech, zvlášť vulkanického původu, mohou být tropické půdy relativně úrodné.


Biography.

Early life.

A native of Montefano, a small village near Macerata and Loreto he was the son of Ricardo Cervini who was the Apostolic Treasurer in Ancona. The family originated in Tuscany, in the town of Montepulciano, which had once been subject to Siena, but later was under the control of Florence. Marcello had two half-brothers, Alexander and Romulus. One of his sisters, Cinzia Cervini, married Vincenzo Bellarmino, and was the mother of Roberto Bellarmine.  Marcello was educated locally, and at Siena and Florence, where he became proficient in writing Latin, Greek, and Italian. He also received instruction in jurisprudence, philosophy, and mathematics. His father had an interest in astrology and upon discovering that his son's horoscope presaged high ecclesiastical honours, Riccardo set the young Cervini on a path to the priesthood.

Priesthood.

After his period of study at Siena, Cervini traveled to Rome in the company of the Delegation sent by Florence to congratulate the new Pope on his election. His father and Pope Clement VII were personal friends, and Marcello was made "Scrittore Apostolico". He was set to work on astronomical and calendar studies, a project which was intended to bring the year back into synchronization with the seasons. In 1527, he fled home after the Sack of Rome, but eventually returned and was taken into the household of Cardinal Alessandro Farnese "senior". Cervini was ordained a priest in 1535.

Cardinalate.

In 1534, after Farnese had become pope Pope Paul III, Cervini was appointed a papal secretary (1534–49) and served as a close advisor to the pope's nephew Alessandro Farnese. He was made a papal Protonotarius. He travelled in the suite of the Pope during the papal visit to Nice, where Paul III was promoting a truce between François I and Charles V. He then accompanied the young Cardinal Farnese on a trip to Spain, France and the Spanish Netherlands to help implement the terms of the truce. Paul III later appointed him bishop of Nicastro, Italy in 1539. Cervini was not, however, consecrated bishop until the day he himself was elected pope. While he was still on the embassy to the Netherlands, Paul III created him the Cardinal-Priest of "Santa Croce in Gerusalemme" on 19 December 1539.  When, almost immediately after, Cardinal Farnese was recalled to Rome, Cervini stayed on as Nuntius. Over the course of next decade Cervini also became the apostolic administrator of the dioceses of Reggio and Gubbio. His house in Rome became a center of Renaissance culture, and he himself corresponded with most of the leading humanists  During the Council of Trent he was elected one of the council's three presidents, along with fellow cardinals Reginald Pole and Giovanni Maria Ciocchi del Monte (the future Pope Julius III). He continued to serve in that role throughout the remainder of Paul III's papacy after which he was replaced to placate the Holy Roman Emperor Charles V (1519–56). He was credited not only with defending orthodoxy and Church discipline, but also the universal claims of the Papacy in spiritual and temporal affairs, and with such vigor that the Emperor was affronted. In 1548 (or 1550) he was granted the supervision of the Vatican Library, with the title of "Protettore della Biblioteca Apostolica".  The Apostolic Brief of his appointment, however, came from the new pope, Julius III, on 24 May 1550, and he was named not Vatican Librarian, but "Bibliothecarius Sanctae Romanae Ecclesiae" because he was the first cardinal to be in charge of the library. During his administration, he employed the services of Marcello and Sirleto, as well as Onuphrio Panvinio (who was especially consulted in matters of Christian archaeology). He added more than 500 codices to the holdings of the Library, including 143 Greek codices, as his own entry book (which still survives as "Vaticanus Latinus" 3963) testifies. In the conclave of 1549–50 to elect a successor to Paul III, fifty-one cardinals, including Marcello Cervini, participated at the opening on 3 December 1549. The initial candidates included Cardinals Pole, Sfondrati, Carpi and Ridolfi (who died on the night of 31 January). Pole, the favorite of the Emperor Charles V, came within two votes of being elected in the first scrutinies, but he could not attract any additional votes. Juan Álvarez de Toledo (Bishop of Burgos), another Imperial favorite, was proposed, and he too failed, because of strong opposition from the faction of Cardinal Alessandro Farnese, nephew of the late Pope Paul III and from the French.  On 12 December, five more French voters arrived, and though they could not advance the candidacy of their favorite, Ippolito d' Este, they did have Cardinal Cervini on their list of possible candidates. Farnese and his faction were also positively inclined toward him. Unfortunately, the Imperial faction was not. Worst of all, on 22 December, Cardinal Cervini left the Conclave, suffering from a quartan fever. Finally, on 7 February 1550, the cardinals chose Giovanni Maria Ciocchi del Monte, who took the name Julius III.

Papal election.

The first conclave of 1555, following the death of Julius III (1550–55), involved a struggle between French interests in Italy (which had been favored by Julius III) and Imperial interests, which were intent on Church reform through a Church council, but with the Emperor controlling the outcome. On 9 April 1555, on the evening of the fourth day of the papal conclave, Cervini was "adored" as Pope, despite efforts by cardinals loyal to the Emperor Charles V to block his election. Next morning, a formal vote was taken in the Capella Paolina, in which all of the votes cast were for Cardinal Cervini except his own, which he cast for the Dean of the Sacred College of Cardinals, Giampietro Carafa.  The new Pope chose to retain his birth name, the most recent Pope to do so, reigning as Marcellus II. He was both ordained [consecrated] as a bishop and crowned Pope on the next day in a subdued ceremony on account of it falling during the Lenten season.

Papacy.

Though Marcellus II desired to reform many of the inner workings of the church, his feeble constitution succumbed to the fatigues of the conclave, the exhausting ceremonies connected with his ascension, the anxieties arising from his high office, and overexertion in his performance of the pontifical functions of the Holy Week and Easter. He quickly fell ill.  He was bled, and appeared to begin to recover. In an audience he gave to the Cardinals, who wanted him to sign the Electoral Capitulations from the conclave and to guarantee that he would make no more cardinals than those agreements allowed, he refused to sign, stating that he would show his intent by deeds not words. In his first audience with the Ambassadors of France and Spain, he warned the Ambassadors that their monarchs should keep the peace that had been agreed upon, and that if they did not, not only would they be sent Nuncios and Legates, but that the Pope himself would come and admonish them. He wrote letters to the Emperor, to Queen Mary I of England, and to Cardinal Reginald Pole (in which he confirmed Pole's Legateship in England). When the Spanish Ambassador asked for pardon for having killed a man, the Pope replied that he did not want to start his reign with such auspices as absolution from homicide, and ordered the appropriate tribunals to observe the law.  He did not want his relatives descending on Rome, nor did he want them to be enriched beyond the station of a member of the nobility, and he did not allow his two nephews, Riccardo and Herennius (sons of his half-brother Alexander), who lived in Rome under his care, to have formal visits. He instituted immediate economies in Vatican expenditures. On 28 April, he was able to receive the Duke of Urbino in audience, and on 29 April, the Duke of Ferrara. He also gave audience to four cardinals, Farnese, D'Este, Louis de Guise and Ascanio Sforza, the leaders of the French faction in the recent conclave. That night he had difficulty sleeping. On the morning of the 30th he suffered a stroke ("hora XII apoplexi correptus") and slipped into a coma. That night he died, on the 22nd day after his election.

Legacy.

Palestrina's "Missa Papae Marcelli" (dating from 1565 or before), one of the glories of polyphonic sacred choral music, is traditionally believed to have been composed in his memory, ca. 1562. Having reigned for just 22 calendar days, Pope Marcellus II ranks sixth on the list of 10 shortest-reigning Popes. His successor was Giampietro Carafa, Dean of the Sacred College of Cardinals, who reigned as Pope Paul IV (1555–59).

Pope Marcellus II (6 May 1501 – 1 May 1555), born Marcello Cervini degli Spannochi, was head of the Catholic Church and ruler of the Papal States from 9 April 1555 until his death 22 days later on 1 May 1555.

Marcellus II. (Marcel II.) (vlastním jménem "Marcello Cervini degli Spannochi") (6. května 1501, Montefano – 1. května 1555, Řím) byl papežem v roce 1555. Aktivně se zúčastnil Tridentského koncilu a jako papež se pokusil reformovat církev a napravit světský životní styl mnoha duchovních.


History.

Ancient philosophers as far back as Thales of Miletus 550 BCE had inklings of the conservation of some underlying substance of which everything is made. However, there is no particular reason to identify their theories with what we know today as "mass-energy" (for example, Thales thought it was water). Empedocles (490–430 BCE) wrote that in his universal system, composed of four roots (earth, air, water, fire), "nothing comes to be or perishes"; instead, these elements suffer continual rearrangement. Epicurus ( 350 BCE) on the other hand believed everything in the universe to be composed of indivisible units of matter - the ancient precursor to 'atoms' - and he too had some idea of the necessity of conservation, stating that "the sum total of things was always such as it is now, and such it will ever remain".  In 1605, Simon Stevinus was able to solve a number of problems in statics based on the principle that perpetual motion was impossible.  In 1639, Galileo published his analysis of several situations—including the celebrated "interrupted pendulum"—which can be described (in modern language) as conservatively converting potential energy to kinetic energy and back again. Essentially, he pointed out that the height a moving body rises is equal to the height from which it falls, and used this observation to infer the idea of inertia. The remarkable aspect of this observation is that the height to which a moving body ascends on a frictionless surface does not depend on the shape of the surface.  In 1669, Christiaan Huygens published his laws of collision. Among the quantities he listed as being invariant before and after the collision of bodies were both the sum of their linear momenta as well as the sum of their kinetic energies. However, the difference between elastic and inelastic collision was not understood at the time. This led to the dispute among later researchers as to which of these conserved quantities was the more fundamental. In his "Horologium Oscillatorium", he gave a much clearer statement regarding the height of ascent of a moving body, and connected this idea with the impossibility of a perpetual motion. Huygens' study of the dynamics of pendulum motion was based on a single principle: that the center of gravity of a heavy object cannot lift itself. The fact that kinetic energy is scalar, unlike linear momentum which is a vector, and hence easier to work with did not escape the attention of Gottfried Wilhelm Leibniz. It was Leibniz during 1676–1689 who first attempted a mathematical formulation of the kind of energy which is connected with "motion" (kinetic energy). Using Huygens' work on collision, Leibniz noticed that in many mechanical systems (of several masses, "m" each with velocity "v"),  was conserved so long as the masses did not interact. He called this quantity the "vis viva" or "living force" of the system. The principle represents an accurate statement of the approximate conservation of kinetic energy in situations where there is no friction. Many physicists at that time, such as Newton, held that the conservation of momentum, which holds even in systems with friction, as defined by the momentum:  was the conserved "vis viva". It was later shown that both quantities are conserved simultaneously, given the proper conditions such as an elastic collision.  In 1687, Isaac Newton published his "Principia", which was organized around the concept of force and momentum. However, the researchers were quick to recognize that the principles set out in the book, while fine for point masses, were not sufficient to tackle the motions of rigid and fluid bodies. Some other principles were also required.  The law of conservation of vis viva was championed by the father and son duo, Johann and Daniel Bernoulli. The former enunciated the principle of virtual work as used in statics in its full generality in 1715, while the latter based his "Hydrodynamica", published in 1738, on this single conservation principle. Daniel's study of loss of vis viva of flowing water led him to formulate the Bernoulli's principle, which relates the loss to be proportional to the change in hydrodynamic pressure. Daniel also formulated the notion of work and efficiency for hydraulic machines; and he gave a kinetic theory of gases, and linked the kinetic energy of gas molecules with the temperature of the gas.  This focus on the vis viva by the continental physicists eventually led to the discovery of stationarity principles governing mechanics, such as the D'Alembert's principle, Lagrangian, and Hamiltonian formulations of mechanics.  Émilie du Châtelet (1706 – 1749) proposed and tested the hypothesis of the conservation of total energy, as distinct from momentum. Inspired by the theories of Gottfried Leibniz, she repeated and publicized an experiment originally devised by Willem's Gravesande in 1722 in which balls were dropped from different heights into a sheet of soft clay. Each ball's kinetic energy - as indicated by the quantity of material displaced - was shown to be proportional to the square of the velocity. The deformation of the clay was found to be directly proportional to the height from which the balls were dropped, equal to the initial potential energy. Earlier workers, including Newton and Voltaire, had all believed that "energy" (so far as they understood the concept at all) was not distinct from momentum and therefore proportional to velocity. According to this understanding, the deformation of the clay should have been proportional to the square root of the height from which the balls were dropped. In classical physics the correct formula is formula_3, where formula_4 is the kinetic energy of an object, formula_5 its mass and formula_6 its speed. On this basis, du Châtelet proposed that energy must always have the same dimensions in any form, which is necessary to be able to relate it in different forms (kinetic, potential, heat...).  Engineers such as John Smeaton, Peter Ewart,, Gustave-Adolphe Hirn and Marc Seguin recognized that conservation of momentum alone was not adequate for practical calculation and made use of Leibniz's principle. The principle was also championed by some chemists such as William Hyde Wollaston. Academics such as John Playfair were quick to point out that kinetic energy is clearly not conserved. This is obvious to a modern analysis based on the second law of thermodynamics, but in the 18th and 19th centuries the fate of the lost energy was still unknown.  Gradually it came to be suspected that the heat inevitably generated by motion under friction was another form of "vis viva". In 1783, Antoine Lavoisier and Pierre-Simon Laplace reviewed the two competing theories of "vis viva" and caloric theory. Count Rumford's 1798 observations of heat generation during the boring of cannons added more weight to the view that mechanical motion could be converted into heat, and (as importantly) that the conversion was quantitative and could be predicted (allowing for a universal conversion constant between kinetic energy and heat). "Vis viva" then started to be known as "energy", after the term was first used in that sense by Thomas Young in 1807.  The recalibration of "vis viva" to  which can be understood as converting kinetic energy to work, was largely the result of Gaspard-Gustave Coriolis and Jean-Victor Poncelet over the period 1819–1839. The former called the quantity "quantité de travail" (quantity of work) and the latter, "travail mécanique" (mechanical work), and both championed its use in engineering calculation.  In a paper "Über die Natur der Wärme"(German "On the Nature of Heat/Warmth"), published in the "Zeitschrift für Physik" in 1837, Karl Friedrich Mohr gave one of the earliest general statements of the doctrine of the conservation of energy in the words: "besides the 54 known chemical elements there is in the physical world one agent only, and this is called "Kraft" [energy or work]. It may appear, according to circumstances, as motion, chemical affinity, cohesion, electricity, light and magnetism; and from any one of these forms it can be transformed into any of the others."

Mechanical equivalent of heat.

A key stage in the development of the modern conservation principle was the demonstration of the "mechanical equivalent of heat". The caloric theory maintained that heat could neither be created nor destroyed, whereas conservation of energy entails the contrary principle that heat and mechanical work are interchangeable.  In the middle of the eighteenth century, Mikhail Lomonosov, a Russian scientist, postulated his corpusculo-kinetic theory of heat, which rejected the idea of a caloric. Through the results of empirical studies, Lomonosov came to the conclusion that heat was not transferred through the particles of the caloric fluid.  In 1798, Count Rumford (Benjamin Thompson) performed measurements of the frictional heat generated in boring cannons, and developed the idea that heat is a form of kinetic energy; his measurements refuted caloric theory, but were imprecise enough to leave room for doubt.  The mechanical equivalence principle was first stated in its modern form by the German surgeon Julius Robert von Mayer in 1842. Mayer reached his conclusion on a voyage to the Dutch East Indies, where he found that his patients' blood was a deeper red because they were consuming less oxygen, and therefore less energy, to maintain their body temperature in the hotter climate. He discovered that heat and mechanical work were both forms of energy and in 1845, after improving his knowledge of physics, he published a monograph that stated a quantitative relationship between them.  Meanwhile, in 1843, James Prescott Joule independently discovered the mechanical equivalent in a series of experiments. In the most famous, now called the "Joule apparatus", a descending weight attached to a string caused a paddle immersed in water to rotate. He showed that the gravitational potential energy lost by the weight in descending was equal to the internal energy gained by the water through friction with the paddle.  Over the period 1840–1843, similar work was carried out by engineer Ludwig A. Colding, although it was little known outside his native Denmark.  Both Joule's and Mayer's work suffered from resistance and neglect but it was Joule's that eventually drew the wider recognition.  In 1844, William Robert Grove postulated a relationship between mechanics, heat, light, electricity and magnetism by treating them all as manifestations of a single "force" ("energy" in modern terms). In 1846, Grove published his theories in his book "The Correlation of Physical Forces". In 1847, drawing on the earlier work of Joule, Sadi Carnot and Émile Clapeyron, Hermann von Helmholtz arrived at conclusions similar to Grove's and published his theories in his book "Über die Erhaltung der Kraft" ("On the Conservation of Force", 1847). The general modern acceptance of the principle stems from this publication.  In 1850, William Rankine first used the phrase "the law of the conservation of energy" for the principle.  In 1877, Peter Guthrie Tait claimed that the principle originated with Sir Isaac Newton, based on a creative reading of propositions 40 and 41 of the "Philosophiae Naturalis Principia Mathematica". This is now regarded as an example of Whig history.

Mass–energy equivalence.

Matter is composed of atoms and what makes up atoms. It has "intrinsic" or "rest" mass. In the limited range of recognized experience of the nineteenth century it was found that such rest mass is conserved. Einstein's 1905 theory of special relativity showed that it corresponds to an equivalent amount of "rest energy". This means that it can be converted to or from equivalent amounts of "other" (non-material) forms of energy, for example kinetic energy, potential energy, and electromagnetic radiant energy. When this happens, as recognized in twentieth century experience, rest mass is not conserved, unlike the "total" mass or "total" energy. All forms of energy contribute to the total mass and total energy.  For example, an electron and a positron each have rest mass. They can perish together, converting their combined rest energy into photons having electromagnetic radiant energy, but no rest mass. If this occurs within an isolated system that does not release the photons or their energy into the external surroundings, then neither the total "mass" nor the total "energy" of the system will change. The produced electromagnetic radiant energy contributes just as much to the inertia (and to any weight) of the system as did the rest mass of the electron and positron before their demise. Likewise, non-material forms of energy can perish into matter, which has rest mass.  Thus, conservation of energy ("total", including material or "rest" energy), and conservation of mass ("total", not just "rest"), each still holds as an (equivalent) law. In the 18th century these had appeared as two seemingly-distinct laws.

Conservation of energy in beta decay.

The discovery in 1911 that electrons emitted in beta decay have a continuous rather than a discrete spectrum appeared to contradict conservation of energy, under the then-current assumption that beta decay is the simple emission of an electron from a nucleus. This problem was eventually resolved in 1933 by Enrico Fermi who proposed the correct description of beta-decay as the emission of both an electron and an antineutrino, which carries away the apparently missing energy.

First law of thermodynamics.

For a closed thermodynamic system, the first law of thermodynamics may be stated as:  where formula_10 is the quantity of energy added to the system by a heating process, formula_11 is the quantity of energy lost by the system due to work done by the system on its surroundings and formula_12 is the change in the internal energy of the system.  The δ's before the heat and work terms are used to indicate that they describe an increment of energy which is to be interpreted somewhat differently than the formula_12 increment of internal energy (see Inexact differential). Work and heat refer to kinds of process which add or subtract energy to or from a system, while the internal energy formula_14 is a property of a particular state of the system when it is in unchanging thermodynamic equilibrium. Thus the term "heat energy" for formula_10 means "that amount of energy added as the result of heating" rather than referring to a particular form of energy. Likewise, the term "work energy" for formula_11 means "that amount of energy lost as the result of work". Thus one can state the amount of internal energy possessed by a thermodynamic system that one knows is presently in a given state, but one cannot tell, just from knowledge of the given present state, how much energy has in the past flowed into or out of the system as a result of its being heated or cooled, nor as the result of work being performed on or by the system.  Entropy is a function of the state of a system which tells of limitations of the possibility of conversion of heat into work.  For a simple compressible system, the work performed by the system may be written:  where formula_18 is the pressure and formula_19 is a small change in the volume of the system, each of which are system variables. In the fictive case in which the process is idealized and infinitely slow, so as to be called "quasi-static", and regarded as reversible, the heat being transferred from a source with temperature infinitesimally above the system temperature, then the heat energy may be written  where formula_21 is the temperature and formula_22 is a small change in the entropy of the system. Temperature and entropy are variables of state of a system.  If an open system (in which mass may be exchanged with the environment) has several walls such that the mass transfer is through rigid walls separate from the heat and work transfers, then the first law may be written:  where formula_24 is the added mass and formula_25 is the internal energy per unit mass of the added mass, measured in the surroundings before the process.

Noether's theorem.

The conservation of energy is a common feature in many physical theories. From a mathematical point of view it is understood as a consequence of Noether's theorem, developed by Emmy Noether in 1915 and first published in 1918. The theorem states every continuous symmetry of a physical theory has an associated conserved quantity; if the theory's symmetry is time invariance then the conserved quantity is called "energy". The energy conservation law is a consequence of the shift symmetry of time; energy conservation is implied by the empirical fact that the laws of physics do not change with time itself. Philosophically this can be stated as "nothing depends on time per se". In other words, if the physical system is invariant under the continuous symmetry of time translation then its energy (which is canonical conjugate quantity to time) is conserved. Conversely, systems which are not invariant under shifts in time (an example, systems with time dependent potential energy) do not exhibit conservation of energy – unless we consider them to exchange energy with another, external system so that the theory of the enlarged system becomes time invariant again. Conservation of energy for finite systems is valid in such physical theories as special relativity and quantum theory (including QED) in the flat space-time.

Relativity.

With the discovery of special relativity by Henri Poincaré and Albert Einstein, energy was proposed to be one component of an energy-momentum 4-vector. Each of the four components (one of energy and three of momentum) of this vector is separately conserved across time, in any closed system, as seen from any given inertial reference frame. Also conserved is the vector length (Minkowski norm), which is the rest mass for single particles, and the invariant mass for systems of particles (where momenta and energy are separately summed before the length is calculated—see the article on invariant mass).  The relativistic energy of a single massive particle contains a term related to its rest mass in addition to its kinetic energy of motion. In the limit of zero kinetic energy (or equivalently in the rest frame) of a massive particle, or else in the center of momentum frame for objects or systems which retain kinetic energy, the total energy of particle or object (including internal kinetic energy in systems) is related to its rest mass or its invariant mass via the famous equation formula_26.  Thus, the rule of "conservation of energy" over time in special relativity continues to hold, so long as the reference frame of the observer is unchanged. This applies to the total energy of systems, although different observers disagree as to the energy value. Also conserved, and invariant to all observers, is the invariant mass, which is the minimal system mass and energy that can be seen by any observer, and which is defined by the energy–momentum relation.  In general relativity, energy–momentum conservation is not well-defined except in certain special cases. Energy-momentum is typically expressed with the aid of a stress–energy–momentum pseudotensor. However, since pseudotensors are not tensors, they do not transform cleanly between reference frames. If the metric under consideration is static (that is, does not change with time) or asymptotically flat (that is, at an infinite distance away spacetime looks empty), then energy conservation holds without major pitfalls. In practice, some metrics such as the Friedmann–Lemaître–Robertson–Walker metric do not satisfy these constraints and energy conservation is not well defined. The theory of general relativity leaves open the question of whether there is a conservation of energy for the entire universe.

Quantum theory.

In quantum mechanics, energy of a quantum system is described by a self-adjoint (or Hermitian) operator called the Hamiltonian, which acts on the Hilbert space (or a space of wave functions) of the system. If the Hamiltonian is a time-independent operator, emergence probability of the measurement result does not change in time over the evolution of the system. Thus the expectation value of energy is also time independent. The local energy conservation in quantum field theory is ensured by the quantum Noether's theorem for energy-momentum tensor operator. Due to the lack of the (universal) time operator in quantum theory, the uncertainty relations for time and energy are not fundamental in contrast to the position-momentum uncertainty principle, and merely holds in specific cases (see Uncertainty principle). Energy at each fixed time can in principle be exactly measured without any trade-off in precision forced by the time-energy uncertainty relations. Thus the conservation of energy in time is a well defined concept even in quantum mechanics.

In physics and chemistry, the law of conservation of energy states that the total energy of an isolated system remains constant; it is said to be "conserved" over time. This law, first proposed and tested by Émilie du Châtelet, means that energy can neither be created nor destroyed; rather, it can only be transformed or transferred from one form to another. For instance, chemical energy is converted to kinetic energy when a stick of dynamite explodes. If one adds up all forms of energy that were released in the explosion, such as the kinetic energy and potential energy of the pieces, as well as heat and sound, one will get the exact decrease of chemical energy in the combustion of the dynamite. Classically, conservation of energy was distinct from conservation of mass; however, special relativity showed that mass is related to energy and vice versa by "E = mc", and science now takes the view that mass–energy as a whole is conserved. Theoretically, this implies that any object with mass can itself be converted to pure energy, and vice versa, though this is believed to be possible only under the most extreme of physical conditions, such as likely existed in the universe very shortly after the Big Bang or when black holes emit Hawking radiation.

Zákon zachování energie je jeden ze základních a nejčastěji používaných fyzikálních zákonů. Tento zákon (zjednodušeně řečeno) konstatuje, že energii nelze vyrobit ani zničit, ale pouze přeměnit na jiný druh energie.


Etymology and meaning.

"Duḥkha" (Sanskrit; Pali "dukkha") is a term found in ancient Indian literature, meaning anything that is "uneasy, uncomfortable, unpleasant, difficult, causing pain or sadness". It is also a concept in Indian religions about the nature of life that innately includes the "unpleasant", "suffering", "pain", "sorrow", "distress", "grief" or "misery." The term "duḥkha" does not have a one-word English translation, and embodies diverse aspects of unpleasant human experiences. It is opposed to the word "sukha", meaning "happiness," "comfort" or "ease."  The word is commonly explained as a derivation from Aryan terminology for an axle hole, referring to an axle hole which is not in the center and leads to a bumpy, uncomfortable ride. According to Winthrop Sargeant,  Joseph Goldstein, American vipassana teacher and writer, explains the etymology as follows: However, according to Monier Monier-Williams, the actual roots of the Pali term "dukkha" appear to be Sanskrit दुस्- ("dus-", "bad") + स्था ("stha", "to stand"). Regular phonological changes in the development of Sanskrit into the various Prakrits led to a shift from "dus-sthā" to "duḥkha" to "dukkha".

Buddhism.

Contemporary translators of Buddhist texts use a variety of English words to convey the aspects of "duḥkha". Early Western translators of Buddhist texts (before the 1970s) typically translated the Pali term "dukkha" as "suffering." Later translators have emphasized that "suffering" is too limited a translation for the term duḥkha, and have preferred to either leave the term untranslated or to clarify that translation with terms such as anxiety, distress, frustration, unease, unsatisfactoriness, etc. Many contemporary teachers, scholars, and translators have used the term "unsatisfactoriness" to emphasize the subtlest aspects of dukkha. Contemporary translators have used a variety of English words to translate the term "duḥkha", and many translators prefer to leave the term untranslated.  Within the Buddhist sutras, duḥkha is divided in three categories:  Various sutras sum up how life in this "mundane world" is regarded to be "duḥkha", starting with "samsara", the ongoing process of death and rebirth itself:  "Duḥkha" is one of the three marks of existence, namely "duḥkha" ("suffering"), "anatman" (not-self), "anitya" ("impermanence").  The Buddhist tradition emphasizes the importance of developing insight into the nature of "duḥkha", the conditions that cause it, and how it can be overcome. This process is formulated in the teachings on the Four Noble Truths.

Hinduism.

In Hindu literature, the earliest Upaniads — the and the — in all likelihood predate the advent of Buddhism. In these scriptures of Hinduism, the Sanskrit word "dukha" (दुःख) appears in the sense of "suffering, sorrow, distress", and in the context of a spiritual pursuit and liberation through the knowledge of Atman (soul/self).  The verse 4.4.14 of the states:  The verse 7.26.2 of the states: The concept of sorrow and suffering, and self-knowledge as a means to overcome it, appears extensively with other terms in the pre-Buddhist Upanishads. The term "Duhkha" also appears in many other middle and later post-Buddhist Upanishads such as the verse 6.20 of Shvetashvatara Upanishad, as well as in the Bhagavada Gita, all in the context of moksha. The term also appears in the foundational Sutras of the six schools of Hindu philosophy, such as the opening lines of "Samkhya karika" of the Samkhya school.

Comparison of Buddhism and Hinduism.

Both Hinduism and Buddhism emphasize that one overcomes "dukha" through the development of understanding. However, the two religions widely differ in the nature of that understanding. Hinduism emphasizes the understanding and acceptance of Atman (self, soul) and Brahman, while Buddhism emphasizes the understanding and acceptance of Anatta (Anatman, non-self, non-soul) as each discusses the means to liberation from "Duḥkha".

Pyrrhonism.

According to the Silk Road philologist, Christopher I. Beckwith, the ancient Greek philosopher, Pyrrho, based his new philosophy, Pyrrhonism, on elements of Early Buddhism, most particularly the Buddhist three marks of existence. Pyrrho accompanied Alexander the Great on his Indian campaign, spending about 18 months in Taxila studying Indian philosophy. Diogenes Laërtius' biography of Pyrrho reports that Pyrrho based his philosophy on what he learned there: ...he even went as far as the Gymnosophists, in India, and the Magi. Owing to which circumstance, he seems to have taken a noble line in philosophy, introducing the doctrine of acatalepsy (incomprehensibility), and of the necessity of epoche (suspending one's judgment)...  A summary of Pyrrho's philosophy was preserved by Eusebius, quoting Aristocles, quoting Pyrrho's student Timon, in what is known as the "Aristocles passage."  "Whoever wants to live well (eudaimonia) must consider these three questions: First, how are "pragmata" (ethical matters, affairs, topics) by nature? Secondly, what attitude should we adopt towards them? Thirdly, what will be the outcome for those who have this attitude?" Pyrrho's answer is that "As for "pragmata" they are all adiaphora (undifferentiated by a logical differentia), "astathmēta" (unstable, unbalanced, not measurable), and "anepikrita" (unjudged, unfixed, undecidable). Therefore, neither our sense-perceptions nor our "doxai" (views, theories, beliefs) tell us the truth or lie; so we certainly should not rely on them. Rather, we should be "adoxastoi" (without views), "aklineis" (uninclined toward this side or that), and "akradantoi" (unwavering in our refusal to choose), saying about every single one that it no more is than it is not or it both is and is not or it neither is nor is not.  According to Beckwith's analysis of the Aristocles Passage, Pyrrho translated "dukkha" into Greek as "astathmēta". This gives insight into what "dukkha" meant in Early Buddhism. ...although the sense of duḥkha in Normative Buddhism is traditionally given as ‘suffering’, that and similar interpretations are highly unlikely for Early Buddhism. Significantly, Monier-Williams himself doubts the usual explanation of duḥkha and presents an alternative one immediately after it, namely: duḥ-stha “‘standing badly,’ unsteady, disquieted (lit. and fig.); uneasy,” and so on. This form is also attested, and makes much better sense as the opposite of the Rig Veda sense of sukha, which Monier-Williams gives in full as “(said to be fr. 5. su + 3. kha, and to mean originally ‘having a good axle-hole’; possibly a Prakrit form of su-stha37 q.v.; cf. duḥkha) running swiftly or easily (only applied to cars or chariots, superl[ative] sukhátama), easy”... The most important point here is that duḥ + stha literally means ‘dis-/ bad- + stand-’, that is, ‘badly standing, unsteady’ and is therefore virtually identical to the literal meaning of Greek astathmēta, from a- + sta- ‘not- + stand’, both evidently meaning ‘unstable’. This strongly suggests that Pyrrho’s middle term is in origin a simple calque.

Duḥkha (; Sanskrit:दुःख; Pāli: dukkha) is an important concept in Hinduism and Buddhism, commonly translated as "suffering", "unhappiness", "pain", "unsatisfactoriness" or "stress". It refers to the fundamental unsatisfactoriness and painfulness of mundane life. It is the first of the Four Noble Truths and it is one of the three marks of existence. The term also appears in scriptures of Hinduism, such as the Upanishads, in discussions of moksha (spiritual liberation).

Dukkha (pálí), duḥkha (दुःख - sanskrt) se skládá ze dvou slov, duḥ = obtíž, nesnáz + kha = snést, vydržet, zvládnout. Tedy překlad může být strast, nepříjemnost, neuspokojivost, neklid ve významu nepohodlí, frustrace a nesouladu se skutečností.