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108-526: The Tibetan antelope or chiru ( Pantholops hodgsonii ) ( Tibetan : གཙོད་ , Wylie : gtsod , pronounced [tsǿ] ; Chinese : 藏羚羊 ; pinyin : zànglíngyáng ) is a medium-sized bovid native to the northeastern Tibetan plateau . Most of the population live within the Chinese border, while some scatter across India and Bhutan in the high altitude plains, hill plateau and montane valley. Fewer than 150,000 mature individuals are left in

216-655: A doctored photograph of Tibetan antelope running near the Qinghai-Tibet Railway . Liu Weiqing, a 41-year-old photographer, was identified as the author of the work. He had reportedly camped on the Tibetan plateau since March 2007, as part of a series by the Daqing Evening News , to raise awareness regarding the Tibetan bovid. He was also under contract to provide images to Xinhua. He has since resigned from Daqing Evening News . Researchers of

324-400: A hydrocarbon . Benzene is a natural constituent of petroleum and is one of the elementary petrochemicals . Due to the cyclic continuous pi bonds between the carbon atoms, benzene is classed as an aromatic hydrocarbon . Benzene is a colorless and highly flammable liquid with a sweet smell, and is partially responsible for the aroma of gasoline . It is used primarily as a precursor to

432-410: A Hong Kong chemist and a senior forensic specialist looked at the material though a microscope. Using this method, they discovered shahtoosh contains coarser guard hairs unique to the species. By doing this, the duo had found a convenient way to prove this was poached material. In July 2006, the Chinese government inaugurated a new railway that bisects the chiru's feeding grounds on its way to Lhasa ,

540-421: A Lhasa Tibetan syllable is relatively simple; no consonant cluster is allowed and codas are only allowed with a single consonant. Vowels can be either short or long, and long vowels may further be nasalized . Vowel harmony is observed in two syllable words as well as verbs with a finite ending. Also, tones are contrastive in this language, where at least two tonemes are distinguished. Although

648-607: A Tibetan grammar in Hindi . Some of his other works on Tibetan were: In much of Tibet, primary education is conducted either primarily or entirely in the Tibetan language, and bilingual education is rarely introduced before students reach middle school . However, Chinese is the language of instruction of most Tibetan secondary schools . In April 2020, classroom instruction was switched from Tibetan to Mandarin Chinese in Ngaba , Sichuan. Students who continue on to tertiary education have

756-588: A collective or integral are often used after the tens, sometimes after a smaller number. In scientific and astrological works, the numerals, as in Vedic Sanskrit , are expressed by symbolical words. The written numerals are a variant of the Hindu–Arabic numeral system , forming a base-10 positional counting system that is attested early on in Classical Tibetan texts. Tibetan makes use of

864-594: A deliberate policy of extinguishing all that is Tibetan, including their own language in their own country" and he asserted a right for Tibetans to express themselves "in their mother tongue". However, Tibetologist Elliot Sperling has noted that "within certain limits the PRC does make efforts to accommodate Tibetan cultural expression" and "the cultural activity taking place all over the Tibetan plateau cannot be ignored." Some scholars also question such claims because most Tibetans continue to reside in rural areas where Chinese

972-415: A flat or rising-falling contour, the latter being a tone that rises to a medium level before falling again. It is normally safe to distinguish only between the two tones because there are very few minimal pairs that differ only because of contour. The difference occurs only in certain words ending in the sounds [m] or [ŋ]; for instance, the word kham ( Tibetan : ཁམ་ , "piece") is pronounced [kʰám] with

1080-419: A form of umlaut in the Ü/Dbus branch of Central Tibetan . In some unusual cases, the vowels /a/ , /u/ , and /o/ may also be nasalised. The Lhasa dialect is usually described as having two tones: high and low. However, in monosyllabic words, each tone can occur with two distinct contours. The high tone can be pronounced with either a flat or a falling contour, and the low tone can be pronounced with either

1188-499: A gasoline additive in some nations. In the United States , concern over its negative health effects and the possibility of benzene entering the groundwater has led to stringent regulation of gasoline's benzene content, with limits typically around 1%. European petrol specifications now contain the same 1% limit on benzene content. The United States Environmental Protection Agency introduced new regulations in 2011 that lowered

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1296-551: A gasoline additive, or routed through an extraction process to recover BTX aromatics (benzene, toluene and xylenes). Although of no commercial significance, many other routes to benzene exist. Phenol and halobenzenes can be reduced with metals. Benzoic acid and its salts undergo decarboxylation to benzene. The reaction of the diazonium compound derived from aniline with hypophosphorus acid gives benzene. Alkyne trimerisation of acetylene gives benzene. Complete decarboxylation of mellitic acid gives benzene. Benzene

1404-470: A high flat tone, whereas the word Khams ( Tibetan : ཁམས་ , "the Kham region") is pronounced [kʰâm] with a high falling tone. In polysyllabic words, tone is not important except in the first syllable. This means that from the point of view of phonological typology , Tibetan could more accurately be described as a pitch-accent language than a true tone language , in the latter of which all syllables in

1512-516: A lengthening of the vowel is also frequently substituted for the sounds [r] and [l] when they occur at the end of a syllable. The vowels /i/ , /y/ , /e/ , /ø/ , and /ɛ/ each have nasalized forms: /ĩ/ , /ỹ/ , /ẽ/ , /ø̃/ , and /ɛ̃/ , respectively. These historically result from /in/ , /un/ , /en/ , /on/ , /an/ , and are reflected in the written language. The vowel quality of /un/ , /on/ and /an/ has shifted, since historical /n/ , along with all other coronal final consonants, caused

1620-516: A method from LPG (mainly propane and butane) to aromatics. Toluene hydrodealkylation converts toluene to benzene. In this hydrogen-intensive process, toluene is mixed with hydrogen, then passed over a chromium , molybdenum , or platinum oxide catalyst at 500–650 °C and 20–60 atm pressure. Sometimes, higher temperatures are used instead of a catalyst (at the similar reaction condition). Under these conditions, toluene undergoes dealkylation to benzene and methane : This irreversible reaction

1728-424: A mixture of hydrocarbons with boiling points between 60 and 200 °C is blended with hydrogen gas and then exposed to a bifunctional platinum chloride or rhenium chloride catalyst at 500–525 °C and pressures ranging from 8–50 atm. Under these conditions, aliphatic hydrocarbons form rings and lose hydrogen to become aromatic hydrocarbons. The aromatic products of the reaction are then separated from

1836-776: A plural marker ཚོ <tsho> . Tibetan has been described as having six cases: absolutive , agentive , genitive , ablative , associative and oblique . These are generally marked by particles, which are attached to entire noun phrases, rather than individual nouns. These suffixes may vary in form based on the final sound of the root. Personal pronouns are inflected for number , showing singular, dual and plural forms. They can have between one and three registers . The Standard Tibetan language distinguishes three levels of demonstrative : proximal འདི <'di> "this", medial དེ <de> "that", and distal ཕ་གི <pha-gi> "that over there (yonder)". These can also take case suffixes. Verbs in Tibetan always come at

1944-488: A ring of six carbon atoms with alternating single and double bonds. The next year he published a much longer paper in German on the same subject. Kekulé used evidence that had accumulated in the intervening years—namely, that there always appeared to be only one isomer of any monoderivative of benzene, and that there always appeared to be exactly three isomers of every disubstituted derivative—now understood to correspond to

2052-461: A single bond (147 pm). This intermediate distance is caused by electron delocalization : the electrons for C=C bonding are distributed equally between each of the six carbon atoms. Benzene has 6 hydrogen atoms, fewer than the corresponding parent alkane , hexane , which has 14. Benzene and cyclohexane have a similar structure, only the ring of delocalized electrons and the loss of one hydrogen per carbon distinguishes it from cyclohexane. The molecule

2160-555: A special connector particle for the units above each multiple of ten. Between 100 and 199, the connective དང dang , literally "and", is used after the hundred portion. Above ས་ཡ saya million, the numbers are treated as nouns and thus have their multiples following the word. The numbers 1, 2, 3 and 10 change spelling when combined with other numerals, reflecting a change in pronunciation in combination. Tibetan numerals Tibetan numerals Tibetan numerals (1 Million) (1 Billion) Ordinal numbers are formed by adding

2268-488: A suffix to the cardinal number, པ ( -pa ), with the exception of the ordinal number "first", which has its own lexeme, དང་པོ ( dang po ). Tibetan is written with an Indic script , with a historically conservative orthography that reflects Old Tibetan phonology and helps unify the Tibetan-language area. It is also helpful in reconstructing Proto Sino-Tibetan and Old Chinese . Wylie transliteration

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2376-521: A symbol of wealth and status. Such demands resulted in massive illegal poaching in the second half of the 20th century. In consequence, the population of this species has suffered a severe decline from nearly a million (estimated) at the turn of the 20th century to less than 75,000 in the 1990s. Although formerly affected by poaching, it is now among the best safeguarded wildlife in the Tibetan Plateau, thanks to effective conservation efforts by

2484-401: A wider liquid range. Toluene is also processed into benzene. As a gasoline (petrol) additive, benzene increases the octane rating and reduces knocking . As a consequence, gasoline often contained several percent benzene before the 1950s, when tetraethyl lead replaced it as the most widely used antiknock additive. With the global phaseout of leaded gasoline, benzene has made a comeback as

2592-497: A word can carry their own tone. The Lhasa Tibetan verbal system distinguishes four tenses and three evidential moods. The three moods may all occur with all three grammatical persons, though early descriptions associated the personal modal category with European first-person agreement. In the 18th and 19th centuries several Western linguists arrived in Tibet: Indian indologist and linguist Rahul Sankrityayan wrote

2700-590: Is (1) to ensure that the worker can escape from a given contaminated environment in the event of failure of the respiratory protection equipment and (2) is considered a maximum level above which only a highly reliable breathing apparatus providing maximum worker protection is permitted. In September 1995, NIOSH issued a new policy for developing recommended exposure limits (RELs) for substances, including carcinogens. As benzene can cause cancer, NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding

2808-440: Is 5 ppm for 15 minutes. These legal limits were based on studies demonstrating compelling evidence of health risk to workers exposed to benzene. The risk from exposure to 1 ppm for a working lifetime has been estimated as 5 excess leukemia deaths per 1,000 employees exposed. (This estimate assumes no threshold for benzene's carcinogenic effects.) OSHA has also established an action level of 0.5 ppm to encourage even lower exposures in

2916-460: Is accompanied by an equilibrium side reaction that produces biphenyl (aka diphenyl) at higher temperature: If the raw material stream contains much non-aromatic components (paraffins or naphthenes), those are likely decomposed to lower hydrocarbons such as methane, which increases the consumption of hydrogen. A typical reaction yield exceeds 95%. Sometimes, xylenes and heavier aromatics are used in place of toluene, with similar efficiency. This

3024-414: Is associated with include: acute myeloid leukemia (AML), aplastic anemia, myelodysplastic syndrome (MDS), acute lymphoblastic leukemia (ALL), and chronic myeloid leukemia (CML). Carcinogenic activity of benzene was discovered by Swedish pharmacologist C. G. Santesson  [ se ] in 1897 on female workers of a tire-making factory. The American Petroleum Institute (API) stated in 1948 that "it

3132-586: Is caused by benzene. IARC rated benzene as "known to be carcinogenic to humans" ( Group 1 ). As benzene is ubiquitous in gasoline and hydrocarbon fuels that are in use everywhere, human exposure to benzene is a global health problem. Benzene targets the liver, kidney, lung, heart and brain and can cause DNA strand breaks and chromosomal damage, hence is teratogenic and mutagenic . Benzene causes cancer in animals including humans. Benzene has been shown to cause cancer in both sexes of multiple species of laboratory animals exposed via various routes. According to

3240-483: Is generally considered that the only absolutely safe concentration for benzene is zero". There is no safe exposure level; even tiny amounts can cause harm. The US Department of Health and Human Services (DHHS) classifies benzene as a human carcinogen. Long-term exposure to excessive levels of benzene in the air causes leukemia, a potentially fatal cancer of the blood-forming organs. In particular, acute myeloid leukemia or acute nonlymphocytic leukemia (AML & ANLL)

3348-407: Is hepatically metabolized and excreted in the urine . Measurement of air and water levels of benzene is accomplished through collection via activated charcoal tubes, which are then analyzed with a gas chromatograph . The measurement of benzene in humans can be accomplished via urine , blood , and breath tests ; however, all of these have their limitations because benzene is rapidly metabolized in

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3456-419: Is known as a calving ground for the Tibetan antelope. A special adaptation of the species to its high altitude habitat is the retention of the fetal version of hemoglobin even in adult animals, which provides higher oxygen affinity. The Tibetan antelope is the only species of mammal where this adaptation has been documented. The Tibetan antelope feeds on forbs , grasses , and sedges , often digging through

3564-479: Is often called "on-purpose" methodology to produce benzene, compared to conventional BTX (benzene-toluene-xylene) extraction processes. Toluene disproportionation ( TDP ) is the conversion of toluene to benzene and xylene . Given that demand for para -xylene ( p -xylene ) substantially exceeds demand for other xylene isomers, a refinement of the TDP process called Selective TDP (STDP) may be used. In this process,

3672-1004: Is often depicted with a circle inside a hexagonal arrangement of carbon atoms. Derivatives of benzene occur sufficiently often as a component of organic molecules, so much so that the Unicode Consortium has allocated a symbol in the Miscellaneous Technical block with the code U+232C (⌬) to represent it with three double bonds, and U+23E3 (⏣) for a delocalized version. Many important chemical compounds are derived from benzene by replacing one or more of its hydrogen atoms with another functional group . Examples of simple benzene derivatives are phenol , toluene , and aniline , abbreviated PhOH, PhMe, and PhNH 2 , respectively. Linking benzene rings gives biphenyl , C 6 H 5 –C 6 H 5 . Further loss of hydrogen gives "fused" aromatic hydrocarbons, such as naphthalene , anthracene , phenanthrene , and pyrene . The limit of

3780-401: Is planar. The molecular orbital description involves the formation of three delocalized π orbitals spanning all six carbon atoms, while the valence bond description involves a superposition of resonance structures . It is likely that this stability contributes to the peculiar molecular and chemical properties known as aromaticity . To reflect the delocalized nature of the bonding, benzene

3888-433: Is practiced on a large scale industrially. In the absence of the catalyst, benzene is impervious to hydrogen. Hydrogenation cannot be stopped to give cyclohexene or cyclohexadienes as these are superior substrates. Birch reduction , a non catalytic process, however selectively hydrogenates benzene to the diene. Benzene is an excellent ligand in the organometallic chemistry of low-valent metals. Important examples include

3996-590: Is rarely spoken, as opposed to Lhasa and other Tibetan cities where Chinese can often be heard. In the Texas Journal of International Law , Barry Sautman stated that "none of the many recent studies of endangered languages deems Tibetan to be imperiled, and language maintenance among Tibetans contrasts with language loss even in the remote areas of Western states renowned for liberal policies... claims that primary schools in Tibet teach Mandarin are in error. Tibetan

4104-505: Is sufficiently nucleophilic that it undergoes substitution by acylium ions and alkyl carbocations to give substituted derivatives. The most widely practiced example of this reaction is the ethylation of benzene. Approximately 24,700,000 tons were produced in 1999. Highly instructive but of far less industrial significance is the Friedel-Crafts alkylation of benzene (and many other aromatic rings) using an alkyl halide in

4212-565: Is the most common system of romanization used by Western scholars in rendering written Tibetan using the Latin alphabet (such as employed on much of this page), while linguists tend to use other special transliteration systems of their own. As for transcriptions meant to approximate the pronunciation, Tibetan pinyin is the official romanization system employed by the government of the People's Republic of China , while English language materials use

4320-485: Is used mainly as an intermediate to make other chemicals, above all ethylbenzene (and other alkylbenzenes ), cumene , cyclohexane , and nitrobenzene . In 1988 it was reported that two-thirds of all chemicals on the American Chemical Society 's lists contained at least one benzene ring. More than half of the entire benzene production is processed into ethylbenzene, a precursor to styrene , which

4428-538: Is used to make polymers and plastics like polystyrene . Some 20% of the benzene production is used to manufacture cumene, which is needed to produce phenol and acetone for resins and adhesives. Cyclohexane consumes around 10% of the world's benzene production; it is primarily used in the manufacture of nylon fibers, which are processed into textiles and engineering plastics. Smaller amounts of benzene are used to make some types of rubbers , lubricants , dyes , detergents , drugs , explosives , and pesticides . In 2013,

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4536-670: The Agency for Toxic Substances and Disease Registry (ATSDR) (2007), benzene is both a synthetically made and naturally occurring chemical from processes that include: volcanic eruptions, wild fires, synthesis of chemicals such as phenol , production of synthetic fibers , and fabrication of rubbers , lubricants , pesticides , medications, and dyes . The major sources of benzene exposure are tobacco smoke, automobile service stations, exhaust from motor vehicles, and industrial emissions; however, ingestion and dermal absorption of benzene can also occur through contact with contaminated water. Benzene

4644-507: The Central Tibetan branch (the other two being Khams Tibetan and Amdo Tibetan ). In terms of mutual intelligibility , speakers of Khams Tibetan are able to communicate at a basic level with Lhasa Tibetan, while Amdo speakers cannot. Both Lhasa Tibetan and Khams Tibetan evolved to become tonal and do not preserve the word-initial consonant clusters , which makes them very far from Classical Tibetan , especially when compared to

4752-651: The Chinese Academy of Sciences wrote in a 17 April 2008 letter to Nature , that despite the impression given by the faked photo, the antelopes are getting used to the railway. In the Karakoram regions of Pakistan-administered Kashmir it is listed as an endangered species. Standard Tibetan In the traditional "three-branched" classification of the Tibetic languages , the Lhasa dialect belongs to

4860-476: The Tibetan capital. In an effort to avoid harm to the animal, 33 special animal migration passages have been built beneath the railway. However, the railway will bring many more people, including potential poachers, closer to Tibetan antelope's breeding grounds and habitat. On 22 February 2008, The Wall Street Journal reported China's state-run news agency, Xinhua , issued a public apology for publishing

4968-481: The Universal Declaration of Human Rights in Tibetan, written in the Tibetan script : Benzene Benzene is an organic chemical compound with the molecular formula C 6 H 6 . The benzene molecule is composed of six carbon atoms joined in a planar hexagonal ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, benzene is classed as

5076-772: The World Conservation Union and the United States Fish and Wildlife Service due to commercial poaching for their underwool, competition with local domesticated herds, and the development of their rangeland for gold mining. Tibetan antelopes' underfur (down hair), being extremely soft, fine and warm, is known as shahtoosh and has traditionally been woven by craftsmen and women in Kashmir into shawls in high demand in India as girls' dowry and in Europe as

5184-539: The [ɛ̈] phone (resulting from /e/ in a closed syllable) and the [ɛ] phone (resulting from /a/ through the i-mutation ) are distinct or basically identical. Phonemic vowel length exists in Lhasa Tibetan but in a restricted set of circumstances. Assimilation of Classical Tibetan's suffixes, normally ' i (འི་), at the end of a word produces a long vowel in Lhasa Tibetan; the feature is sometimes omitted in phonetic transcriptions. In normal spoken pronunciation,

5292-440: The absolutive , remaining unmarked. Nonetheless, distinction in transitivity is orthogonal to volition; both the volitional and non-volitional classes contain transitive as well as intransitive verbs. The aspect of the verb affects which verbal suffixes and which final auxiliary copulae are attached. Morphologically, verbs in the unaccomplished aspect are marked by the suffix གི <gi> or its other forms, identical to

5400-421: The genitive case for nouns, whereas accomplished aspect verbs do not use this suffix. Each can be broken down into two subcategories: under the unaccomplished aspect, future and progressive /general; under the accomplished aspect, perfect and aorist or simple perfective . Evidentiality is a well-known feature of Tibetan verb morphology, gaining much scholarly attention, and contributing substantially to

5508-540: The 16th century via trade routes. An acidic material was derived from benzoin by sublimation , and named "flowers of benzoin", or benzoic acid. The hydrocarbon derived from benzoic acid thus acquired the name benzin, benzol, or benzene. Michael Faraday first isolated and identified benzene in 1825 from the oily residue derived from the production of illuminating gas, giving it the name bicarburet of hydrogen . In 1833, Eilhard Mitscherlich produced it by distilling benzoic acid (from gum benzoin ) and lime . He gave

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5616-575: The Chinese government since late 1990s. A 2009 assessment estimated an increased population of 150,000. The struggle to stop illegal antelope hunting was portrayed in the 2004 film, Kekexili: Mountain Patrol . In September 2016, Tibetan antelop has been reclassified on the International Union for Conservation of Nature (IUCN) Red list from Endangered to Near Threatened due to the increased population. To develop testing for shahtoosh ,

5724-481: The REL (10-hour) of 0.1 ppm. The NIOSH short-term exposure limit (STEL – 15 min) is 1 ppm. American Conference of Governmental Industrial Hygienists (ACGIH) adopted Threshold Limit Values (TLVs) for benzene at 0.5 ppm TWA and 2.5 ppm STEL. Several tests can determine exposure to benzene. Benzene itself can be measured in breath, blood or urine, but such testing is usually limited to the first 24 hours post-exposure due to

5832-512: The THL transcription system. Certain names may also retain irregular transcriptions, such as Chomolungma for Mount Everest . Tibetan orthographic syllable structure is (C 1 C 2 )C 3 (C 4 )V(C 5 C 6 ) Not all combinations are licit. The following summarizes the sound system of the dialect of Tibetan spoken in Lhasa , the most influential variety of the spoken language. The structure of

5940-546: The Tibetan antelope population. The Tibetan antelope is the sole species in the genus Pantholops , named after the Greek for "all antelope". It was formerly classified in the then-subfamily Antilopinae (now thought to be the tribe Antilopini), but morphological and molecular evidence led to it being placed in its own subfamily , Pantholopinae , closely allied to goat-antelopes of the then-subfamily Caprinae. However, this has been disputed, and most authorities now consider

6048-517: The Tibetan antelope to be a true member of the Caprinae, or the tribe Caprini. Phylogenetic evidence indicates that Pantholops is the most basal member of the Caprinae / Caprini, and belongs to its own tribe or subtribe, Pantholopini or Pantholopina . Although the genus Pantholops is currently monotypic, a fossil species, P. hundesiensis , is known from the Pleistocene of Tibet. It

6156-700: The behaviour typically seen in other antelope species, although males do commonly skim the thighs of females with a kick of their fore legs. Mothers give birth to a single calf in June or July, after a gestation period of about six months. The calves are precocial , being able to stand within 15 minutes of birth. They are fully grown within 15 months, and reach sexual maturity during their second or third year. Although females may remain with their mothers until they themselves give birth, males leave within 12 months, by which time their horns are beginning to grow. Males determine status by their relative horn length, with

6264-481: The benzene content in gasoline to 0.62%. In some European languages, the word for petroleum or gasoline is an exact cognate of "benzene". For instance in Catalan the word 'benzina' can be used for gasoline, though now it is relatively rare. The most common reactions of benzene involve substitution of a proton by other groups. Electrophilic aromatic substitution is a general method of derivatizing benzene. Benzene

6372-442: The benzene framework. Sulfonation of benzene involves the use of oleum , a mixture of sulfuric acid with sulfur trioxide . Sulfonated benzene derivatives are useful detergents . In nitration , benzene reacts with nitronium ions (NO 2 ), which is a strong electrophile produced by combining sulfuric and nitric acids. Nitrobenzene is the precursor to aniline . Chlorination is achieved with chlorine to give chlorobenzene in

6480-629: The biggest consumer country of benzene was China, followed by the USA. Benzene production is currently expanding in the Middle East and in Africa, whereas production capacities in Western Europe and North America are stagnating. Toluene is now often used as a substitute for benzene, for instance as a fuel additive. The solvent-properties of the two are similar, but toluene is less toxic and has

6588-686: The border in Ladakh , India. The westernmost population of Tibetan antelope is in Depsang Plains , where they are found at altitudes of up to 5500 m. Today, the majority are found within the Chang Tang Nature Reserve of northern Tibet. The first specimens to be described, in 1826, were from Nepal ; the species has apparently since been extirpated from the region. No subspecies are recognised. Zhuonai Lake (卓乃湖) in Hoh Xil

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6696-549: The compound the name benzin . In 1836, the French chemist Auguste Laurent named the substance "phène"; this word has become the root of the English word " phenol ", which is hydroxylated benzene, and " phenyl ", the radical formed by abstraction of a hydrogen atom from benzene. In 1845, Charles Blachford Mansfield , working under August Wilhelm von Hofmann , isolated benzene from coal tar . Four years later, Mansfield began

6804-492: The darker patterns on the face and legs. The males have long, curved-back horns that typically measure 54 to 60 cm (21 to 24 in) in length. The horns are slender, with ring-like ridges on their lower portions and smooth, pointed, tips. Although the horns are relatively uniform in length, there is some variation in their exact shape, so the distance between the tips can be quite variable, ranging from 19 to 46 cm ( 7 + 1 ⁄ 2 to 18 in). Unlike caprines ,

6912-503: The end of the clause . Verbs do not show agreement in person , number or gender in Tibetan. There is also no voice distinction between active and passive ; Tibetan verbs are neutral with regard to voice. Tibetan verbs can be divided into classes based on volition and valency . The volition of the verb has a major effect on its morphology and syntax . Volitional verbs have imperative forms, whilst non-volitional verbs do not: compare ལྟོས་ཤིག <ltos shig> "Look!" with

7020-404: The first industrial-scale production of benzene, based on the coal-tar method. Gradually, the sense developed among chemists that a number of substances were chemically related to benzene, comprising a diverse chemical family. In 1855, Hofmann was the first to apply the word " aromatic " to designate this family relationship, after a characteristic property of many of its members. In 1997, benzene

7128-483: The four tone analysis is favored by linguists in China, DeLancey (2003) suggests that the falling tone and the final [k] or [ʔ] are in contrastive distribution , describing Lhasa Tibetan syllables as either high or low. The vowels of Lhasa Tibetan have been characterized and described in several different ways, and it continues to be a topic of ongoing research. Tournadre and Sangda Dorje describe eight vowels in

7236-440: The fusion process is the hydrogen-free allotrope of carbon, graphite . In heterocycles , carbon atoms in the benzene ring are replaced with other elements. The most important variations contain nitrogen . Replacing one CH with N gives the compound pyridine , C 5 H 5 N. Although benzene and pyridine are structurally related, benzene cannot be converted into pyridine. Replacement of a second CH bond with N gives, depending on

7344-433: The horns do not grow throughout life. The ears are short and pointed, and the tail is also relatively short, at around 13 cm (5 in) in length. The fur of Tibetan antelopes is distinctive, and consists of long guard hairs and a silky undercoat of shorter fibres. The individual guard hairs are thicker than those of other goats, with unusually thin walls, and have a unique pattern of cuticular scales, said to resemble

7452-454: The human body. Exposure to benzene may lead progressively to aplastic anemia , leukaemia , and multiple myeloma . OSHA regulates levels of benzene in the workplace. The maximum allowable amount of benzene in workroom air during an 8-hour workday, 40-hour workweek is 1 ppm. As benzene can cause cancer , NIOSH recommends that all workers wear special breathing equipment when they are likely to be exposed to benzene at levels exceeding

7560-418: The late 1970s. Trace amounts of benzene are found in petroleum and coal. It is a byproduct of the incomplete combustion of many materials. For commercial use, until World War II , much of benzene was obtained as a by-product of coke production (or "coke-oven light oil") for the steel industry. However, in the 1950s, increased demand for benzene, especially from the growing polymers industry, necessitated

7668-534: The location of the second N, pyridazine , pyrimidine , or pyrazine . Four chemical processes contribute to industrial benzene production: catalytic reforming , toluene hydrodealkylation, toluene disproportionation, and steam cracking etc. According to the ATSDR Toxicological Profile for benzene, between 1978 and 1981, catalytic reformates accounted for approximately 44–50% of the total U.S. benzene production. In catalytic reforming,

7776-667: The long-term results of accidental exposure, have been reported on by news organizations such as The New York Times . For instance, a 2022 article stated that benzene contamination in the Boston metropolitan area caused hazardous conditions in multiple places, with the publication noting that the compound may eventually cause leukemia in some individuals. The word " benzene " derives from " gum benzoin " ( benzoin resin ), an aromatic resin known since ancient times in Southeast Asia, and later to European pharmacists and perfumers in

7884-400: The manufacture of chemicals with more complex structures, such as ethylbenzene and cumene , of which billions of kilograms are produced annually. Although benzene is a major industrial chemical , it finds limited use in consumer items because of its toxicity. Benzene is a volatile organic compound . Benzene is classified as a carcinogen . Its particular effects on human health , such as

7992-639: The maximum length being achieved at around three and a half years of age. Although the lifespan of Tibetan antelopes is not known with certainty, since so few have been kept in captivity, it is probably around 10 years. Since 1979, Tibetan antelope has had legal protection under the Convention on International Trade in Endangered Species (CITES) . Killing, harming or trading in the animal is illegal worldwide, as more than 160 countries are CITES signatories. It also used to be listed as Endangered by

8100-410: The molecule. The German chemist Wilhelm Körner suggested the prefixes ortho-, meta-, para- to distinguish di-substituted benzene derivatives in 1867; however, he did not use the prefixes to distinguish the relative positions of the substituents on a benzene ring. It was the German chemist Carl Gräbe who, in 1869, first used the prefixes ortho-, meta-, para- to denote specific relative locations of

8208-454: The more conservative Amdo Tibetan. Like many languages, Lhasa Tibetan has a variety of language registers : Tibetan is an ergative language , with what can loosely be termed subject–object–verb (SOV) word order . Grammatical constituents broadly have head-final word order: Tibetan nouns do not possess grammatical gender , although this may be marked lexically, nor do they inflect for number . However, definite human nouns may take

8316-400: The non-existent * མཐོང་ཤིག <mthong shig> "*See!". Additionally, only volitional verbs can take the egophoric copula ཡིན <yin> . Verbs in Tibetan can be split into monovalent and divalent verbs; some may also act as both, such as ཆག <chag> "break". This interacts with the volition of the verb to condition which nouns take the ergative case and which must take

8424-566: The option of studying humanistic disciplines in Tibetan at a number of minority colleges in China. This contrasts with Tibetan schools in Dharamsala , India, where the Ministry of Human Resource Development curriculum requires academic subjects to be taught in English from middle school. In February 2008, Norman Baker , a UK MP, released a statement to mark International Mother Language Day claiming, "The Chinese government are following

8532-587: The ortho, meta, and para patterns of arene substitution —to argue in support of his proposed structure. Kekulé's symmetrical ring could explain these curious facts, as well as benzene's 1:1 carbon-hydrogen ratio. The new understanding of benzene, and hence of all aromatic compounds, proved to be so important for both pure and applied chemistry that in 1890 the German Chemical Society organized an elaborate appreciation in Kekulé's honor, celebrating

8640-408: The parody was a lampoon of the snake anecdote, possibly already well known through oral transmission even if it had not yet appeared in print. Kekulé's 1890 speech in which this anecdote appeared has been translated into English. If the anecdote is the memory of a real event, circumstances mentioned in the story suggest that it must have happened early in 1862. In 1929, the cyclic nature of benzene

8748-485: The presence of a Lewis acid catalyst such as aluminium tri-chloride. Via hydrogenation , benzene and its derivatives convert to cyclohexane and derivatives. This reaction is achieved by the use of high pressures of hydrogen in the presence of heterogeneous catalysts , such as finely divided nickel . Whereas alkenes can be hydrogenated near room temperatures, benzene and related compounds are more reluctant substrates, requiring temperatures >100 °C. This reaction

8856-435: The presence of a strong Lewis acid catalyst. Similarly, the Friedel-Crafts acylation is a related example of electrophilic aromatic substitution . The reaction involves the acylation of benzene (or many other aromatic rings) with an acyl chloride using a strong Lewis acid catalyst such as aluminium chloride or Iron(III) chloride . Using electrophilic aromatic substitution, many functional groups are introduced onto

8964-440: The presence of horns and by black stripes on the legs, both of which the females lack. The coat is pale fawn to reddish-brown, with a whitish belly, and is particularly thick and woolly. The face is almost black in colour, with prominent nasal swellings that have a paler colour in males. In general, the colouration of males becomes more intense during the annual rut , with the coat becoming much paler, almost white, contrasting with

9072-484: The prevention of adverse effects, is zero benzene concentration in drinking water. The EPA requires that spills or accidental releases into the environment of 10 pounds (4.5 kg) or more of benzene be reported. The U.S. Occupational Safety and Health Administration (OSHA) has set a permissible exposure limit of 1 part of benzene per million parts of air (1 ppm) in the workplace during an 8-hour workday, 40-hour workweek. The short term exposure limit for airborne benzene

9180-613: The problem of how carbon atoms could bond to up to four other atoms at the same time. Curiously, a similar, humorous depiction of benzene had appeared in 1886 in a pamphlet entitled Berichte der Durstigen Chemischen Gesellschaft (Journal of the Thirsty Chemical Society), a parody of the Berichte der Deutschen Chemischen Gesellschaft , only the parody had monkeys seizing each other in a circle, rather than snakes as in Kekulé's anecdote. Some historians have suggested that

9288-399: The production of benzene from petroleum. Today, most benzene comes from the petrochemical industry , with only a small fraction being produced from coal. Benzene has been detected on Mars . X-ray diffraction shows that all six carbon-carbon bonds in benzene are of the same length, at 140 picometres (pm). The C–C bond lengths are greater than a double bond (135 pm) but shorter than

9396-556: The reaction mixture (or reformate) by extraction with any one of a number of solvents , including diethylene glycol or sulfolane , and benzene is then separated from the other aromatics by distillation. The extraction step of aromatics from the reformate is designed to produce aromatics with lowest non-aromatic components. Recovery of the aromatics, commonly referred to as BTX (benzene, toluene and xylene isomers), involves such extraction and distillation steps. In similar fashion to this catalytic reforming, UOP and BP commercialized

9504-467: The recommended (8-hour) exposure limit of 0.1 ppm. The United States Environmental Protection Agency has set a maximum contaminant level for benzene in drinking water at 0.005 mg/L (5 ppb), as promulgated via the U.S. National Primary Drinking Water Regulations. This regulation is based on preventing benzene leukemogenesis . The maximum contaminant level goal ( MCLG ), a nonenforceable health goal that would allow an adequate margin of safety for

9612-519: The relatively rapid removal of the chemical by exhalation or biotransformation. Most people in developed countries have measureable baseline levels of benzene and other aromatic petroleum hydrocarbons in their blood. In the body, benzene is enzymatically converted to a series of oxidation products including muconic acid , phenylmercapturic acid , phenol , catechol , hydroquinone and 1,2,4-trihydroxybenzene . Most of these metabolites have some value as biomarkers of human exposure, since they accumulate in

9720-518: The same sound as the one following it. The result is that the first is pronounced as an open syllable but retains the vowel typical of a closed syllable. For instance, ཞབས zhabs (foot) is pronounced [ɕʌp] and པད pad (borrowing from Sanskrit padma , lotus ) is pronounced [pɛʔ] , but the compound word, ཞབས་པད zhabs pad (lotus-foot, government minister) is pronounced [ɕʌpɛʔ] . This process can result in minimal pairs involving sounds that are otherwise allophones. Sources vary on whether

9828-505: The sandwich and half-sandwich complexes, respectively, Cr(C 6 H 6 ) 2 and [RuCl 2 (C 6 H 6 )] 2 . Benzene is classified as a carcinogen , which increases the risk of cancer and other illnesses, and is also a notorious cause of bone marrow failure . Substantial quantities of epidemiologic, clinical, and laboratory data link benzene to aplastic anemia, acute leukemia , bone marrow abnormalities and cardiovascular disease. The specific hematologic malignancies that benzene

9936-478: The shape of a benzene ring. Endemic to the Tibetan Plateau , the Tibetan antelope inhabits open alpine and cold steppe environments between 3,250 and 5,500 m (10,660 and 18,040 ft) elevation. They prefer flat, open terrain, with sparse vegetation cover. They are found almost entirely in China, where they inhabit Tibet , southern Xinjiang , and western Qinghai ; a few are also found across

10044-464: The snow to obtain food in winter. Their natural predators include wolves , lynx , snow leopards , and red foxes are known to prey on young calves. Tibetan antelope are gregarious, sometimes congregating in herds hundreds strong when moving between summer and winter pastures, although they are more usually found in much smaller groups, with no more than 20 individuals. The females migrate up to 300 km (200 mi) yearly to calving grounds in

10152-455: The standard language: Three additional vowels are sometimes described as significantly distinct: [ʌ] or [ə] , which is normally an allophone of /a/ ; [ɔ] , which is normally an allophone of /o/ ; and [ɛ̈] (an unrounded, centralised, mid front vowel), which is normally an allophone of /e/ . These sounds normally occur in closed syllables; because Tibetan does not allow geminated consonants , there are cases in which one syllable ends with

10260-688: The substituents on a di-substituted aromatic ring (viz, naphthalene). In 1870, the German chemist Viktor Meyer first applied Gräbe's nomenclature to benzene. In 1903, Ludwig Roselius popularized the use of benzene to decaffeinate coffee . This discovery led to the production of Sanka . This process was later discontinued. Benzene was historically used as a significant component in many consumer products such as liquid wrench , several paint strippers , rubber cements , spot removers, and other products. Manufacture of some of these benzene-containing formulations ceased in about 1950, although Liquid Wrench continued to contain significant amounts of benzene until

10368-446: The summer, where they usually give birth to a single calf, and rejoin the males at the wintering grounds in late autumn. The rutting season lasts from November to December. Males form harems of up to 12 females, although one to four is more common, and drive off other males primarily by making displays or chasing them with head down, rather than sparring directly with their horns. Courtship and mating are both brief, without most of

10476-434: The twenty-fifth anniversary of his first benzene paper. Here Kekulé spoke of the creation of the theory. He said that he had discovered the ring shape of the benzene molecule after having a reverie or day-dream of a snake biting its own tail (a symbol in ancient cultures known as the ouroboros ). This vision, he said, came to him after years of studying the nature of carbon-carbon bonds. This was seven years after he had solved

10584-498: The underfur of three to five adult antelopes to make one shawl. Despite strict controls on trade of shahtoosh products and CITES listing, there is still demand for these luxury items. Within India, shawls are worth $ 1,000–$ 5,000; internationally the price can reach as high as $ 20,000. In 1997 the Chinese government established the Hoh Xil National Nature Reserve (also known as Kekexili) solely to protect

10692-554: The understanding of evidentiality across languages. The evidentials in Standard Tibetan interact with aspect in a system marked by final copulae, with the following resultant modalities being a feature of Standard Tibetan, as classified by Nicolas Tournadre : Unlike many other languages of East Asia such as Burmese , Chinese , Japanese , Korean and Vietnamese , there are no numeral auxiliaries or measure words used in counting in Tibetan. However, words expressive of

10800-508: The urine in proportion to the extent and duration of exposure, and they may still be present for some days after exposure has ceased. The current ACGIH biological exposure limits for occupational exposure are 500 μg/g creatinine for muconic acid and 25 μg/g creatinine for phenylmercapturic acid in an end-of-shift urine specimen. Even if it is not a common substrate for metabolism, benzene can be oxidized by both bacteria and eukaryotes . In bacteria, dioxygenase enzyme can add an oxygen to

10908-463: The wild, but the population is currently thought to be increasing. In the 1980s and the 1990s, they had become endangered due to massive illegal poaching . They are hunted for their extremely soft, light and warm underfur which is usually obtained after death. This underfur, known as shahtoosh (a Persian word meaning "king of fine wools"), is used to weave luxury shawls. Shahtoosh shawls were traditionally given as wedding gifts in India and it takes

11016-704: The workplace. The U.S. National Institute for Occupational Safety and Health (NIOSH) revised the Immediately Dangerous to Life and Health (IDLH) concentration for benzene to 500 ppm. The current NIOSH definition for an IDLH condition, as given in the NIOSH Respirator Selection Logic, is one that poses a threat of exposure to airborne contaminants when that exposure is likely to cause death or immediate or delayed permanent adverse health effects or prevent escape from such an environment. The purpose of establishing an IDLH value

11124-470: The xylene stream exiting the TDP unit is approximately 90% p -xylene. In some systems, even the benzene-to-xylenes ratio is modified to favor xylenes. Steam cracking is the process for producing ethylene and other alkenes from aliphatic hydrocarbons . Depending on the feedstock used to produce the olefins, steam cracking can produce a benzene-rich liquid by-product called pyrolysis gasoline . Pyrolysis gasoline can be blended with other hydrocarbons as

11232-400: Was detected in deep space . The empirical formula for benzene was long known, but its highly polyunsaturated structure, with just one hydrogen atom for each carbon atom, was challenging to determine. Archibald Scott Couper in 1858 and Johann Josef Loschmidt in 1861 suggested possible structures that contained multiple double bonds or multiple rings, but in these years very little

11340-448: Was finally confirmed by the crystallographer Kathleen Lonsdale using X-ray diffraction methods. Using large crystals of hexamethylbenzene , a benzene derivative with the same core of six carbon atoms, Lonsdale obtained diffraction patterns. Through calculating more than thirty parameters, Lonsdale demonstrated that the benzene ring could not be anything but a flat hexagon, and provided accurate distances for all carbon-carbon bonds in

11448-545: Was known about aromatic chemistry, and so chemists were unable to adduce appropriate evidence to favor any particular formula. But many chemists had begun to work on aromatic substances, especially in Germany, and relevant data was coming fast. In 1865, the German chemist Friedrich August Kekulé published a paper in French (for he was then teaching in Francophone Belgium) suggesting that the structure contained

11556-709: Was slightly smaller than the living species, with a narrower skull. In addition, the fossil genus Qurliqnoria , from the Miocene of China, is thought to be an early member of the Pantholopini, which diverged from the goat-antelopes around this time. The Tibetan antelope is a medium-sized antelope, with a shoulder height of about 83 cm ( 32 + 1 ⁄ 2  in) in males, and 74 cm (29 in) in females. Males are significantly larger than females, weighing about 39 kg (86 lb), compared with 26 kg (57 lb), and can also be readily distinguished by

11664-443: Was the main language of instruction in 98% of TAR primary schools in 1996; today, Mandarin is introduced in early grades only in urban schools.... Because less than four out of ten TAR Tibetans reach secondary school, primary school matters most for their cultural formation." An incomplete list of machine translation software or applications that can translate Tibetan language from/to a variety of other languages. From Article 1 of

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