Characteristics.

The gaur is a strong and massively built bovid with a high convex ridge on the forehead between the horns, which protrudes anteriorly, causing a deep hollow in the profile of the upper part of the head. There is a prominent ridge on the back. The ears are very large; the tail only just reaches the hocks, and in old bulls the hair becomes very thin on the back. The adult male is dark brown, approaching black in very old individuals. The upper part of the head, from above the eyes to the nape of the neck, is ashy grey, or occasionally dirty white. The muzzle is pale coloured, and the lower part of the legs are pure white or tan. The cows and young bulls are paler, and in some instances have a rufous tinge, which is most marked in groups inhabiting dry and open areas. The tail is shorter than in the typical oxen, reaching only to the hocks. They have a distinct ridge running from the shoulders to the middle of the back; the shoulders may be as much as higher than the rump. This ridge is caused by the great length of the spinous processes of the vertebrae of the fore-part of the trunk as compared with those of the loins. The hair is short, fine and glossy; the hooves are narrow and pointed.  The gaur does not have a distinct dewlap on the throat and chest. Both sexes have horns, which grow from the sides of the head, curving upwards. Between the horns is a high convex ridge on the forehead. At their bases they present an elliptical cross-section, a characteristic that is more strongly marked in bulls than in cows. The horns are decidedly flattened at the base and regularly curved throughout their length, and are bent inward and slightly backward at their tips. The colour of the horns is some shade of pale green or yellow throughout the greater part of their length, but the tips are black. The horns, of medium size by large bovid standards, grow to a length of. The cow is considerably lighter in colour than the bull. Her horns are more slender and upright, with more inward curvature, and the frontal ridge is scarcely perceptible. In young animals, the horns are smooth and polished. In old bulls they are rugged and dented at the base.  The gaur is one of the largest wild bovids alive today. It has a head-and-body length of with a long tail, and is high at the shoulder, averaging about in females and in males. At the top of its muscular hump just behind its shoulder, an average adult male is just under tall and the male's girth at its midsection (behind its shoulders) averages about. Males are about one-fourth larger and heavier than females. Body mass can range widely from in adult females and in adult males. In general measurements are derived from gaurs surveyed in India. Indian gaur males averaged about (in a sample of 13) and females weigh a median of approximately. Body masses elsewhere suggest gaurs outside of India can grow larger. In China, males weigh or more. The Seladang, or Malayasian subspecies, ("B. g. hubbacki") appears to be larger on average than the nominate race from India, but sample sizes as known are small. According to some sources, seladang bulls weigh on average, which if accurate indicates these animals are on average more than 20% more massive than the gaurs of India.

Distribution and habitat.

Gaur historically occurred throughout mainland South and Southeast Asia, including Vietnam, Cambodia, Laos, Thailand, Peninsular Malaysia, Myanmar, India, Bangladesh, Bhutan, China and Nepal. Today, the range of the species is seriously fragmented, and it is regionally extinct in Sri Lanka.  Gaur are largely confined to evergreen forests or semi-evergreen and moist deciduous forests, but also occur in deciduous forest areas at the periphery of their range. Gaur habitat is characterized by large, relatively undisturbed forest tracts, hilly terrain below an altitude of, availability of water, and an abundance of forage in the form of grasses, bamboo, shrubs, and trees. Their apparent preference for hilly terrain may be partly due to the earlier conversion of most of the plains and other low-lying areas to croplands and pastures. They occur from sea level to an altitude of at least. Low-lying areas seem to comprise optimal habitat.  In Nepal, the gaur population was estimated to be 250–350 in the mid-1990s, with the majority in Chitwan National Park and the adjacent Parsa National Park. These two parks are connected by a chain of forested hills. Population trends appeared to be relatively stable. The Chitwan population has increased from 188 to 368 animals in the years 1997 to 2016. Census conducted in Parsa National Park confirmed the presence of 112 gaur in the same period.  In India, the population was estimated to be 12,000–22,000 in the mid-1990s. The Western Ghats and their outflanking hills in southern India constitute one of the most extensive extant strongholds of gaur, in particular in the Wayanad – Nagarhole – Mudumalai – Bandipur complex. The populations in India, Bhutan and Bangladesh are estimated to comprise 23,000–34,000 individuals. Major populations of about 2,000 individuals have been reported in both Nagarahole and Bandipur National Parks, over 1,000 individuals in Tadoba Andhari Tiger Project, 500–1000 individuals in both Periyar Tiger Reserve and Silent Valley and adjoining forest complexes, and over 800 individuals in Bhadra Wildlife Sanctuary.  In Bhutan, they apparently persist all over the southern foothill zone, notably in Royal Manas National Park, Phibsoo Wildlife Sanctuary and Khaling Wildlife Sanctuary.  In Bangladesh, a few gaur occur in the Chittagong Hill Tracts, mostly in Banderban district. During a camera trap project, few gaur were recorded indicating that the population is fragmented and probably declining. Gaurs are hunted by local tribal people in Sangu Matamuhari reserve forest although hunting is prohibited in Bangladesh.  In Thailand, gaur were once found throughout the country, but fewer than 1,000 individuals were estimated to have remained in the 1990s. In the mostly semi-evergreen Dong Phayayen – Khao Yai Forest Complex, they were recorded at low density at the turn of the century, with an estimated total of about 150 individuals.  In Vietnam, several areas in Đắk Lắk Province were known to contain gaur in 1997. Several herds persist in Cát Tiên National Park and in adjacent state forest enterprises. The current status of the gaur population is poorly known; they may be in serious decline.  In Cambodia, gaur declined considerably in the period from the late 1960s to the early 1990s. The most substantial population of the country remained in Mondulkiri Province, where up to 1000 individuals may have survived in a forested landscape of over. Results of camera trapping carried out in 2009 suggested a globally significant population of gaur in the Mondulkiri Protected Forest and the contiguous Phnom Prich Wildlife Sanctuary.  In Laos, up to 200 individuals were estimated to inhabit protected area boundaries in the mid–1990s. They were reported discontinuously distributed in low numbers. Overhunting had reduced the population, and survivors occurred mainly in remote sites. Fewer than six National Biodiversity Conservation Areas held more than 50 individuals. Areas with populations likely to be nationally important included the Nam Theun catchment and the adjoining plateau. Subsequent surveys carried out a decade later using fairly intensive camera trapping did not record any gaur any more, indicating a massive decline of the population.  In China, gaur occur in heavily fragmented populations in Yunnan and southeastern Tibet. By the 1980s, they were extirpated in Lancang County, and the remaining animals were split into two populations, viz. in Xishuangbanna–Simao and Cangyuan. In the mid-1990s, a population of 600–800 individuals may have lived in Yunnan Province, with the majority occurring in Xishuangbanna National Nature Reserve.

Ecology and behaviour.

Where gaur have not been disturbed, they are basically diurnal. In other areas, they have become largely nocturnal due to forest molestation caused by humans. In central India, they are most active at night, and are rarely seen in the open after 8 o'clock in the morning. During the dry season, herds congregate and remain in small areas, dispersing into the hills with the arrival of the monsoon. While gaur depend on water for drinking, they do not seem to bathe or wallow.  In January and February, gaur live in small herds of eight to 11 individuals, one of which is a bull. In April or May, more bulls may join the herd for mating, and individual bulls may move from herd to herd, each mating with many cows. In May or June, they leave the herd and may form herds of bulls only or live alone. Herds wander each day. Each herd has a nonexclusive home range, and sometimes herds may join in groups of 50 or more.  Gaur herds are led by an old adult female, the matriarch. Adult males may be solitary. During the peak of the breeding season, unattached males wander widely in search of receptive females. No serious fighting between males has been recorded, with size being the major factor in determining dominance. Males make a mating call of clear, resonant tones which may carry for more than. Gaur have also been known to make a whistling snort as an alarm call, and a low, cow-like moo.  In some regions in India where human disturbance is minor, the gaur is very timid and shy despite their great size and power. When alarmed, gaur crash into the jungle at a surprising speed. However, in Southeast Asia and South India, where they are used to the presence of humans, gaur are said by locals to be very bold and aggressive. They are frequently known to go into fields and graze alongside domestic cattle, sometimes killing them in fights. Gaur bulls may charge without provocation, especially during summer, when the intense heat and parasitic insects make them more short-tempered than usual. To warn other members of its herd of approaching danger, the gaur lets out a high whistle for help.

Feeding ecology.

Wild gaur graze and browse on a wider variety of plants than any other ungulate species of India, with a preference for the upper portions of plants, such as leaf blades, stems, seeds and flowers of grass species, including "kadam".  During a survey in the Bhagwan Mahaveer Sanctuary and Mollem National Park, 32 species of plants were identified as food for gaur. They consume herbs, young shoots, flowers, fruits of elephant apple ("Dillenia" ssp.) with a high preference for leaves. Food preference varies by season. In winter and monsoon, they feed on preferably fine and fresh grasses and herb species of the legume family, such as tick clover ("Desmodium triflorum"), but also browse on leaves of shrub species such as karvy ("Strobilanthes callosus"), Indian boxwood ("Gardenia latifolia"), mallow-leaved crossberry ("Grewia abutifolia"), East-Indian screw tree ("Helicteres" ssp.) and the chaste tree ("Vitex negundo"). In summer, they also feed on bark of teak ("Tectona grandis"), on fruit of golden shower tree ("Cassia fistula"), and on the bark and fruit of cashew ("Anacardium occidentale"). Gaur spent most of their daily time feeding. Peak feeding activity was observed between 6:30 and 8:30 am and between 5:30 and 6:45 pm. During the hottest hours of the day, 1:30 to 3:30 pm, they rest in the shade of big trees.  They may debark trees due to shortages of preferred food, and of minerals and trace elements needed for their nutrition, or for maintaining an optimum fiber/protein ratio for proper digestion of food and better assimilation of nutrients. They may turn to available browse species and fibrous teak bark in summer as green grass and herbaceous resources dry up. High concentrations of calcium (22400 ppm) and phosphorus (400 ppm) have been reported in teak bark, so consumption of teak bark may help animals to satisfy both mineral and other food needs. Long-term survival and conservation of these herbivores depend on the availability of preferred plant species for food. Hence, protection of the historically preferred habitats used by gaur is a significant factor in conservation biology.

Reproduction.

Sexual maturity occurs in the gaur's second or third year. Females have one calf, rarely two, after a gestation period of about 275 days, a few days less than domestic cattle. Calves are typically weaned after seven to 12 months. Breeding takes place year-round, but typically peaks between December and June. The lifespan of a gaur in captivity is up to 30 years.

Natural predators.

Due to their formidable size and power, gaur have few natural predators besides humans. Leopards, dhole packs and large mugger crocodiles occasionally attack unguarded calves or unhealthy animals. Only tiger and saltwater crocodile have been reported to kill adult gaur. However, the habitat and distribution of gaur and saltwater crocodile seldom overlaps in recent times due to the decreasing range of both species. A crocodile likely would need to be a mature adult male, more than and, to make a successful attack on healthy adult gaurs.  Tigers hunt young or infirm gaur, but have also been reported to have killed healthy bulls weighing at least. A video of a tiger killing a female gaur was recorded in the Bandipur Tiger Reserve in October 2013. When confronted by a tiger, the adult members of a gaur herd often form a circle surrounding the vulnerable young and calves, shielding them from the big cat. As tigers rely on ambush attacks when taking on prey as large as a gaur, they will almost always abandon a hunt if detected and met in this manner. A herd of gaur in Malaysia encircled a calf killed by a tiger and prevented it from approaching the carcass. Gaurs are capable of defending against, chasing off and killing tigers. An old tigress in Navegaon Nagzira Tiger Reserve appears to have died after being wounded by a gaur.  Gaur are not as aggressive toward humans as wild water buffaloes.

Threats.

In Laos, gaurs are highly threatened by poaching for trade to supply international markets, but also by opportunistic hunting, and specific hunting for home consumption. In the 1990s, they were particularly sought by Vietnamese poachers for their commercial value.  In Thailand, gaurs are highly threatened by poaching for commercial trade in meat and trophies.

Conservation.

"Bos gaurus" is listed in CITES Appendix I, and is legally protected in all range states. Cryoconservation of animal genetic resources have been put into place in order to help reinforce the Gaur population.

In captivity.

On 8 January 2001, the first cloned gaur was born at Trans Ova Genetics in Sioux Center, Iowa. The calf was carried and brought successfully to term by a surrogate mother, a domestic cow ("Bos taurus"). While healthy at birth, the calf died within 48 hours of a common dysentery, most likely unrelated to cloning.

Taxonomy.

"Bison gaurus" was the scientific name proposed by Charles Hamilton Smith in 1827. Later authors subordinated the species under either "Bos" or "Bibos".  In 2003, the International Commission on Zoological Nomenclature has fixed the first available specific name based on a wild population that the name for this wild species is valid by virtue of its being antedated by a name based on a domestic form. Most authors have adopted the binomial "Bos gaurus" for the wild species as valid for the taxon.  Traditionally, three gaur subspecies have been recognized:  In recognition of phenotypic differences between Indian and Southeast Asian specimens, the trinominals "Bos gaurus gaurus" and "Bos gaurus laosiensis" are provisionally accepted pending further morphometric and genetic study.

Etymology.

The Sanskrit word गौर gaura means white, yellowish, reddish. The Sanskrit word "gaur-mriga" means a kind of buffalo.  The Hindi word गौर gaur means fair-skinned, fair, white.

The gaur (), "Bos gaurus", also called the Indian bison, is one of the largest extant bovines. It is native to South and Southeast Asia and has been listed as Vulnerable on the IUCN Red List since 1986. The global population has been estimated at maximum 21,000 mature individuals by 2016. It declined by more than 70% during the last three generations, and is extinct in Sri Lanka and probably also in Bangladesh. In well-protected areas, it is stable and increasing.

Gaur ("Bos gaurus") je nejmohutnějším ze všech žijících turů. U samců překračuje kohoutková výška 2 metry, samice jsou o něco menší (kolem 170 cm). Dosahuje hmotnosti 700–1000 kg. Hlava gaurů je ozdobena mohutnými rohy dorůstajícími až 115 cm. U dospělých samců pozorujeme dvoudílný kožní lalok – na bradě a na krku. Konce končetin jsou vždy bílé.


Principles.

Turbofans were invented to circumvent the undesirable characteristic of turbojets being inefficient for subsonic flight. To raise the efficiency of a turbojet, the obvious approach would be to increase the burner temperature, to give better Carnot efficiency and fit larger compressors and nozzles. However, while that does increase thrust somewhat, the exhaust jet leaves the engine with even higher velocity, which at subsonic flight speeds, takes most of the extra energy with it, wasting fuel.  Instead, a turbofan can be thought of as a turbojet being used to drive a ducted fan, with both of those contributing to the thrust. Whereas all the air taken in by a turbojet passes through the turbine (through the combustion chamber), in a turbofan some of that air bypasses the turbine.  Because the turbine has to additionally drive the fan, the turbine is larger and has larger pressure and temperature drops, and so the nozzles are smaller. This means that the exhaust velocity of the core is reduced. The fan also has lower exhaust velocity, giving much more thrust per unit energy (lower specific thrust). The overall effective exhaust velocity of the two exhaust jets can be made closer to a normal subsonic aircraft's flight speed. In effect, a turbofan emits a large amount of air more slowly, whereas a turbojet emits a smaller amount of air quickly, which is a far less efficient way to generate the same thrust (see efficiency section below).  The ratio of the mass-flow of air bypassing the engine core compared to the mass-flow of air passing through the core is referred to as the bypass ratio. The engine produces thrust through a combination of these two portions working together; engines that use more jet thrust relative to fan thrust are known as "low-bypass turbofans", conversely those that have considerably more fan thrust than jet thrust are known as "high-bypass". Most commercial aviation jet engines in use today are of the high-bypass type, and most modern military fighter engines are low-bypass. Afterburners are not used on high-bypass turbofan engines but may be used on either low-bypass turbofan or turbojet engines.

Bypass ratio.

The "bypass ratio (BPR)" of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.  Turbofan engines are usually described in terms of BPR, which together with overall pressure ratio, turbine inlet temperature and fan pressure ratio are important design parameters. In addition BPR is quoted for turboprop and unducted fan installations because their high propulsive efficiency gives them the overall efficiency characteristics of very high bypass turbofans. This allows them to be shown together with turbofans on plots which show trends of reducing specific fuel consumption (SFC) with increasing BPR. BPR can also be quoted for lift fan installations where the fan airflow is remote from the engine and doesn't flow past the engine core.  A higher BPR provides a lower

Efficiency.

Propeller engines are most efficient for low speeds, turbojet engines - for high speeds, and turbofan engines - between the two. Turbofans are the most efficient engines in the range of speeds from about, the speed at which most commercial aircraft operate. Turbofans retain an efficiency edge over pure jets at low supersonic speeds up to roughly.  In a zero-bypass (turbojet) engine the high temperature and high pressure exhaust gas is accelerated by expansion through a propelling nozzle and produces all the thrust. The compressor absorbs all the mechanical power produced by the turbine. In a bypass design extra turbines drive a ducted fan that accelerates

Thrust.

While a turbojet engine uses all of the engine's output to produce thrust in the form of a hot high-velocity exhaust gas jet, a turbofan's cool low-velocity bypass air yields between 30% and

Nozzles.

The cold duct and core duct's nozzle systems are relatively complex due to there being two exhaust flows.  In high bypass engines the fan is generally situated in a short duct near the front of the engine and typically has a convergent cold nozzle, with the tail

Noise.

Most of the air flow through a high-bypass turbofan is lower velocity bypass flow: even when combined with the much higher velocity engine exhaust, the average exhaust velocity is considerably lower than in a pure turbojet. Turbojet engine noise is predominately jet noise from the high exhaust velocity, therefore turbofan engines are significantly quieter than a pure-jet of the same thrust, and jet noise is no longer the predominant source. Turbofan engine noise propagates both upstream via the inlet and downstream via the primary nozzle and the by-pass duct. Other noise sources are the fan, compressor and turbine.  Modern commercial aircraft employ high-bypass-ratio (HBPR) engines with separate flow, non-mixing, short-duct exhaust systems. Their noise is due to the speed, temperature, and pressure of the exhaust jet, especially during high thrust conditions such as those required for takeoff.

Common types.

Low-bypass turbofan.

A high-specific-thrust/low-bypass-ratio turbofan normally has a multi-stage fan, developing a relatively high pressure ratio and, thus, yielding a high (mixed or cold) exhaust velocity. The core airflow needs to be large enough to give sufficient core power to drive the fan. A smaller core flow/higher bypass ratio cycle can be achieved by raising the high-pressure (HP) turbine rotor inlet temperature.  To illustrate one aspect of how a turbofan differs from a turbojet, they may be compared, as in a re-engining assessment, at the same airflow (to keep a common intake for example) and the same net thrust (i.e. same specific

Afterburning turbofan.

Since the 1970s, most jet fighter engines have been low/medium bypass turbofans with a mixed exhaust, afterburner and variable area final nozzle. An afterburner is a combustor located downstream of the turbine blades and directly upstream of the nozzle, which burns fuel from afterburner-specific fuel injectors. When lit, prodigious amounts of fuel are burnt in the afterburner, raising the temperature of exhaust gases by a significant degree, resulting in a higher exhaust velocity/engine specific thrust. The variable geometry nozzle must open to a larger throat area to accommodate the extra volume flow when the afterburner is lit. Afterburning is often designed to give a significant thrust boost for take off, transonic acceleration and combat maneuvers, but is very fuel intensive. Consequently, afterburning can be used only for short portions of a mission.  Unlike the main combustor, where the downstream turbine blades must not be damaged by high temperatures, an afterburner can operate at the

High-bypass turbofan.

To boost fuel economy and reduce noise, almost all of today's jet airliners and most military transport aircraft (e.g., the C-17) are powered by low-specific-thrust/high-bypass-ratio turbofans. These engines evolved from the high-specific-thrust/low-bypass-ratio turbofans used in such aircraft in the 1960s. (Modern combat aircraft tend to use low-bypass ratio turbofans, and some military transport aircraft use turboprops.)  Low specific thrust is achieved by replacing the multi-stage fan with a single-stage unit. Unlike some military engines, modern civil turbofans lack stationary inlet guide vanes in front of the fan rotor. The fan is scaled to achieve the desired

Turbofan configurations.

Turbofan engines come in a variety of engine configurations. For a given engine cycle (i.e., same airflow, bypass ratio, fan pressure ratio, overall pressure ratio and HP turbine rotor inlet temperature), the choice of turbofan configuration has little impact upon the design point performance (e.g., net thrust, SFC), as long as overall component performance is maintained. Off-design performance and stability is, however, affected by engine configuration.  The basic element of a turbofan is a spool, a single combination of fan/compressor, turbine and shaft rotating at a single speed. For a given pressure ratio, the surge margin can be increased by two different design paths:  Most modern western civil turbofans employ a relatively high-pressure-ratio high-pressure (HP) compressor, with many rows of variable stators to control surge margin at low rpm. In the three-spool RB211/Trent the core compression system is split into two, with the IP compressor, which supercharges the HP compressor, being on a different coaxial shaft and driven by a separate (IP) turbine. As the HP compressor has a modest pressure ratio its speed can be reduced surge-free, without employing variable geometry. However, because a shallow IP compressor working line is inevitable, the IPC has one stage of variable geometry on all variants except the -535, which has none.

Single-shaft turbofan.

Although far from common, the single-shaft turbofan is probably the simplest configuration, comprising a fan and high-pressure compressor driven by a single turbine unit, all on

Aft-fan turbofan.

One of the earliest turbofans was a derivative of the General Electric J79 turbojet, known as the CJ805-23, which featured an integrated aft fan/low-pressure (LP) turbine unit located in the turbojet exhaust jetpipe. Hot gas from the turbojet

Basic two-spool.

Many turbofans have at least basic two-spool configuration where the fan is on a separate low pressure (LP) spool, running concentrically with the compressor or high pressure (HP) spool; the LP spool runs at a lower

Boosted two-spool.

Higher overall pressure ratios can be achieved by either raising the HP compressor pressure ratio or adding compressor (non-bypass) stages or T-stages to the LP spool, between the fan and the HP compressor, to boost the latter. All of the large

Three-spool.

Rolls-Royce chose a three-spool configuration for their large civil turbofans (i.e. the RB211 and Trent families), where the T-stages of the boosted two-spool configuration are separated into a separate intermediate pressure (IP) spool, driven by its own turbine. The first three-spool engine was the earlier Rolls-Royce

Geared fan.

As bypass ratio increases, the fan blade tip speed increases relative to the LPT blade speed. This will reduce the LPT blade speed, requiring more turbine stages to extract enough energy to drive the

Military turbofans.

Most of the configurations discussed above are used in

High-pressure turbine.

Most civil turbofans use a high-efficiency, 2-stage HP turbine to drive the HP compressor. The CFM International CFM56 uses an alternative approach: a single-stage, high-work unit. While this approach is probably less efficient, there

Low-pressure turbine.

Modern civil turbofans have multi-stage LP turbines (anywhere from 3 to 7). The number of stages required depends on the engine cycle bypass ratio and

Overall performance.

Cycle improvements.

Consider a mixed turbofan with a fixed bypass ratio and airflow. Increasing the overall pressure ratio of the compression system raises the combustor entry temperature. Therefore, at a fixed fuel flow there is an increase in (HP) turbine rotor inlet temperature. Although the higher temperature rise across the compression system implies a larger temperature drop over the turbine system, the mixed nozzle temperature is unaffected, because the same amount of heat is being added to the system. There is, however, a rise in nozzle pressure, because overall pressure ratio increases faster than the turbine expansion ratio, causing an increase in the hot mixer entry pressure. Consequently, net thrust increases, whilst specific fuel consumption (fuel flow/net thrust) decreases. A similar trend occurs with unmixed turbofans.  So turbofans can be made more fuel efficient by raising overall pressure ratio and turbine

Thrust growth.

Thrust growth is obtained by increasing core power. There are two basic routes available:  Both routes require an increase in the combustor fuel flow and, therefore, the heat energy added to the core stream.  The hot route may require changes in turbine blade/vane materials or better blade/vane cooling. The cold route can be obtained by one of the following:  all of

Early turbofans.

Early turbojet engines were not very fuel-efficient because their overall pressure ratio and turbine inlet temperature were severely limited by the technology available at the time.  The first turbofan engine, which was only run on a test bed, was the German Daimler-Benz DB 670, designated the 109-007 by the Nazi Ministry of Aviation, with a first run date of 27 May 1943, after the testing of the turbomachinery using an electric motor, which had been undertaken on 1 April 1943. Development of the engine was abandoned, with its problems unsolved, as the war situation worsened for Germany.  Later in 1943, the British ground tested the Metrovick F.3 turbofan, which used the Metrovick F.2 turbojet as a gas generator with the exhaust discharging into a close-coupled aft-fan module comprising a contra-rotating LP turbine system driving two co-axial contra-rotating fans.  Improved materials, and the introduction of twin compressors, such as in the Bristol Olympus, and Pratt & Whitney JT3C

Improvements.

Aerodynamic modelling.

Aerodynamics is a mix of subsonic, transonic and supersonic airflow on a single fan/gas compressor blade in a modern turbofan. The airflow past the blades has to be maintained within close angular limits to keep the air flowing against an increasing pressure. Otherwise the air will come back out of

Blade technology.

A 100 g turbine blade is subjected to 1,700 °C/3100 °F, at 17 bars/250 Psi and a centrifugal force of 40 kN/ 9,000 lbf, well above the point of plastic deformation and even above the melting point. Exotic alloys, sophisticated air cooling schemes and special mechanical design are needed to keep the physical stresses within the strength of the material. Rotating seals must withstand harsh conditions for 10 years, 20,000 missions and rotating at 10–20,000 rpm.  The high-temperature performance of fan blades has increased through developments in the casting manufacturing process, the cooling design, thermal barrier coatings, and alloys. Cycle-wise,

Fan blades.

Fan blades have been growing as jet engines have been getting bigger: each fan blade carries the equivalent of nine double-decker buses and swallows the volume of a squash court every second. Advances in computational fluid dynamics (CFD) modelling have permitted complex, 3D curved shapes with very wide chord, keeping the fan capabilities while minimizing the

Future progress.

Engine cores are shrinking as they are operating at higher pressure ratios and becoming more efficient, and become smaller compared to the fan as bypass ratios increase. Blade tip clearances are harder to maintain at the exit of the high-pressure compressor where blades are high or less, backbone bending further affects clearance control as the core is proportionately longer and thinner and the fan to low-pressure turbine driveshaft is in constrained space within the core.  For Pratt & Whitney VP technology and environment Alan Epstein "Over the history of commercial aviation, we have gone from 20% to 40% [cruise efficiency], and there is a consensus among the engine community that we can probably get to 60%". Geared turbofans and further fan pressure ratio reductions will continue to improve propulsive efficiency. The second phase of the FAA's

Manufacturers.

The turbofan engine market is dominated by General Electric, Rolls-Royce plc and Pratt & Whitney, in order of market share. General Electric and SNECMA of France have a joint venture, CFM International. Pratt & Whitney also have a joint venture, International Aero Engines with Japanese Aero Engine Corporation and MTU Aero Engines of Germany, specializing in engines for the Airbus A320 family. Pratt & Whitney and General Electric have a joint venture, Engine Alliance selling a range of engines for aircraft such as the Airbus

Extreme bypass jet engines.

In the 1970s, Rolls-Royce/SNECMA tested a M45SD-02 turbofan fitted with variable pitch fan blades to improve handling at ultra low fan pressure ratios and to provide thrust reverse down to zero aircraft speed. The engine was aimed at ultra quiet STOL aircraft operating from city centre airports.  In a bid for increased efficiency with speed, a development of the "turbofan" and "turboprop" known as a propfan engine was created that had an unducted fan. The fan blades are situated outside of the duct, so that it appears like a turboprop with wide scimitar-like blades. Both General Electric and Pratt & Whitney/Allison demonstrated propfan engines in the 1980s. Excessive cabin noise and relatively cheap jet fuel prevented the engines being put into service. The Progress D-27 propfan, developed in the U.S.S.R., was the only propfan engine equipped on a production aircraft.

The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the "turbo" portion refers to a gas turbine engine which achieves mechanical energy from combustion, and the "fan", a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine (through the combustion chamber), in a turbofan some of that air bypasses the turbine. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust.

Dvouproudový motor (také turbodmychadlový) je druh leteckého motoru, který pracuje na podobném principu jako proudový motor, tedy na principu zákona o akci a reakci. Oproti proudovému motoru obsahuje navíc dmychadlo (ventilátor, angl. "fan") a nízkotlaký kompresor, poháněné další turbínou.


Description.

Variometers measure the rate of change of altitude by detecting the change in air pressure (static pressure) as altitude changes. A simple variometer can be constructed by adding a large reservoir (a thermos bottle) to augment the storage capacity of a common aircraft rate-of-climb instrument. In its simplest electronic form, the instrument consists of an air bottle connected to the external atmosphere through a sensitive air flow meter. As the aircraft changes altitude, the atmospheric pressure outside the aircraft changes and air flows into or out of the air bottle to equalise the pressure inside the bottle and outside the aircraft. The rate and direction of flowing air is measured by the cooling of one of two self-heating thermistors and the difference between the thermistor resistances will cause a voltage difference; this is amplified and displayed to the pilot. The faster the aircraft is ascending (or descending), the faster the air flows. Air flowing out of the bottle indicates that the altitude of the aircraft is increasing. Air flowing into the bottle indicates that the aircraft is descending.  Newer variometer designs directly measure the static pressure of the atmosphere using a pressure sensor and detect changes in altitude directly from the change in air pressure instead of by measuring air flow. These designs tend to be smaller as they do not need the air bottle. They are more reliable as there is no bottle to be affected by changes in temperature and less chances for leaks to occur in the connecting tubes.  The designs described above, which measure the rate of change of altitude by automatically detecting the change in static pressure as the aircraft changes altitude are referred to as "uncompensated" variometers. The term "vertical speed indicator" or "VSI" is most often used for the instrument when it is installed in a powered aircraft. The term "variometer" is most often used when the instrument is installed in a glider or sailplane.  An "Inertial-lead" or "Instantaneous" VSI (IVSI) uses accelerometers to provide a quicker response to changes in vertical speed.

Purpose.

Human beings, unlike birds and other flying animals, are not able directly to sense climb and sink rates. Before the invention of the variometer, sailplane pilots found it very hard to soar. Although they could readily detect abrupt "changes" in vertical speed ("in the seat of the pants"), their senses did not allow them to distinguish lift from sink, or strong lift from weak lift. The "actual" climb/sink rate could not even be guessed at, unless there was some clear fixed visual reference nearby. Being near a fixed reference means being near to a hillside, or to the ground. Except when hill-soaring (exploiting the lift close to the up-wind side of a hill), these are generally very unprofitable positions for glider pilots to be in. The most useful forms of lift (thermal and wave lift) are found at higher altitudes and it is very hard for a pilot to detect or exploit them without the use of a variometer. After the variometer was invented in 1929 by Alexander Lippisch and Robert Kronfeld, the sport of gliding moved into a new realm.  Variometers also became important in foot-launch hang gliding, where the open-to-air pilot hears the wind but needs the variometer to help him or her to detect regions of rising or sinking air. In early hang gliding, variometers were not needed for the short flights or flights close to ridge lift. But the variometer became key as pilots began making longer flights. The first portable variometer for use in hang gliders was the Colver Variometer by Colver Soaring Instruments which served to extend the sport into cross-country thermal flying.

Total energy compensation.

As the sport of gliding developed, however, it was found that these very simple "uncompensated" instruments had their limitations. The information that glider pilots really need to soar is the total change in energy experienced by the glider, including both altitude and speed. An uncompensated variometer will simply indicate vertical speed of the glider, giving rise to the possibility of a "stick thermal," i.e., a change in altitude caused by stick input only. If a pilot pulls back on the stick, the glider will rise, but also slow down as well. But if a glider is rising without the speed changing, this is an indication of real lift, not "stick lift."  Compensated variometers also include information about the speed of the aircraft, so the total energy (potential and kinetic) is used, not just the change in altitude. For example, if a pilot pushes forward on the stick, speeding up as the plane dives, an uncompensated variometer only indicates that altitude is being lost. But the pilot could pull back on the stick, trading the extra speed for altitude again. A compensated variometer uses both speed and altitude to indicate the change in total energy. So the pilot that pushes the stick forward, diving to gain speed, and then pulls back again to regain altitude will notice no change in total energy on a compensated variometer (neglecting energy loss due to drag).  Most modern sailplanes are equipped with "Total Energy compensated" variometers.

Total energy compensation in theory.

The total energy of the aircraft is:  1. formula_1  where formula_2 is the potential energy, and formula_3 is the kinetic energy. So the change in total energy is:  2. formula_4  Since  3. Potential Energy is proportional to Height  formula_5  where m is the glider mass and g the acceleration of gravity  and  4. Kinetic Energy is proportional to Velocity squared,  formula_6  then from 2:  5. formula_7  6. Typically, this is converted to an effective altitude change by dividing by the acceleration of gravity, and the mass of the aircraft, so:  <math>{\Delta E_{tot} \over m g}= \Delta h +

A variometer – also known as a rate of climb and descent indicator (RCDI), rate-of-climb indicator, vertical speed indicator (VSI), or vertical velocity indicator (VVI) – is one of the flight instruments in an aircraft used to inform the pilot of the rate of descent or climb. It can be calibrated in metres per second, feet per minute (1 ft/min = 0.00508 m/s) or knots (1 kn ≈ 0.514 m/s), depending on country and type of aircraft. It is typically connected to the aircraft's external static pressure source.

Variometr je přístroj, který se používá zejména na palubách letadel pro indikaci rychlosti, jakou letoun mění výšku. Pilot s jeho pomocí zjistí například, že letoun v dané chvíli klesá rychlostí 5 m/s, nebo že okamžitá rychlost stoupání je 3 m/s. V anglosaských zemích a v civilním letectví se používají jednotky ft/min (stopy za minutu).


History.

In 1888, George Nuttall found that sheep blood serum had mild killing activity against the bacterium that causes anthrax. The killing activity disappeared when he heated the blood. In 1891, Hans Ernst August Buchner, noting the same property of blood in his experiments, named the killing property "alexin", which means "to ward off" in Greek. By 1894, several laboratories had demonstrated that serum from guinea pigs that had recovered from cholera killed the cholera bacterium "in vitro". Heating the serum destroyed its killing activity. Nevertheless, the heat-inactivated serum, when injected into guinea pigs exposed to the cholera bacteria, maintained its ability to protect the animals from illness. Jules Bordet, a young Belgian scientist in Paris at the Pasteur Institute, concluded that this principle has two components, one that maintained a "sensitizing" effect after being heated and one (alexin) whose toxic effect was lost after being heated. The heat-stable component was responsible for immunity against specific microorganisms, whereas the heat-sensitive component was responsible for the non-specific antimicrobial activity conferred by all normal sera. In 1899, Paul Ehrlich renamed the heat-sensitive component "complement."  Ehrlich introduced the term "complement" as part of his larger theory of the immune system. According to this theory, the immune system consists of cells that have specific receptors on their surface to recognize antigens. Upon immunisation with an antigen, more of these receptors are formed, and they are then shed from the cells to circulate in the blood. Those receptors, which we now call "antibodies", were called by Ehrlich "amboceptors" to emphasise their bifunctional binding capacity: They recognise and bind to a specific antigen, but they also recognise and bind to the heat-labile antimicrobial component of fresh serum. Ehrlich, therefore, named this heat-labile component "complement", because it is something in the blood that "complements" the cells of the immune system. Ehrlich believed that each antigen-specific amboceptor has its own specific complement, whereas Bordet believed that there is only one type of complement. In the early 20th century, this controversy was resolved when it became understood that complement can act in combination with specific antibodies, or on its own in a non-specific way.

Functions.

Complement triggers the following immune functions:

Overview.

Most of the proteins and glycoproteins that constitute the complement system are synthesized by hepatocytes. But significant amounts are also produced by tissue macrophages, blood monocytes, and epithelial cells of the genitourinary system and gastrointestinal tract. The three pathways of activation all generate homologous variants of the protease C3-convertase. The classical complement pathway typically requires antigen-antibody complexes for activation (specific immune response), whereas the alternative pathway can be activated by spontaneous complement component 3 (C3) hydrolysis, foreign material, pathogens, or damaged cells. The mannose-binding lectin pathway can be activated by C3 hydrolysis or antigens without the presence of antibodies (non-specific immune response). In all three pathways, C3-convertase cleaves and activates component C3, creating C3a and C3b, and causes a cascade of further cleavage and activation events. C3b binds to the surface of pathogens, leading to greater internalization by phagocytic cells by opsonization.  In the alternative pathway, C3b binds to Factor B. Factor D releases Factor Ba from Factor B bound to C3b. The complex of C3b(2)Bb is a protease which cleaves C5 into C5b and C5a. C5 convertase is also formed by the classical pathway when C3b binds C4b and C2b. C5a is an important chemotactic protein, helping recruit inflammatory cells. C3a is the precursor of an important cytokine (adipokine) named ASP (although this is not universally accepted ) and is usually rapidly cleaved by carboxypeptidase B. Both C3a and C5a have anaphylatoxin activity, directly triggering degranulation of mast cells as well as increasing vascular permeability and smooth muscle contraction. C5b initiates the membrane attack pathway, which results in the membrane attack complex (MAC), consisting of C5b, C6, C7, C8, and polymeric C9. MAC is the cytolytic endproduct of the complement cascade; it forms a transmembrane channel, which causes osmotic lysis of the target cell. Kupffer cells and other macrophage cell types help clear complement-coated pathogens. As part of the innate immune system, elements of the complement cascade can be found in species earlier than vertebrates; most recently in the protostome horseshoe crab species, putting the origins of the system back further than was previously thought.

Classical pathway.

The classical pathway is triggered by activation of the C1-complex. The C1-complex is composed of 1 molecule of C1q, 2 molecules of C1r and 2 molecules of C1s, or "C1qrs". This occurs when C1q binds to IgM or IgG complexed with antigens. A single pentameric IgM can initiate the pathway, while several, ideally six, IgGs are needed. This also occurs when C1q binds directly to the surface of the pathogen. Such binding leads to conformational changes in the C1q molecule, which leads to the activation of two C1r molecules. C1r is a serine protease. They then cleave C1s (another serine protease). The C1rs component now splits C4 and then C2, producing C4a, C4b, C2a, and C2b (historically, the larger fragment of C2 was called C2a but is now referred to as C2b). C4b and C2a bind to form the classical pathway C3-convertase (C4b2a complex), which promotes cleavage of C3 into C3a and C3b. C3b later joins with C4b2a to make C5 convertase (C4b2a3b complex).

Alternative pathway.

The alternative pathway is continuously activated at a low level, analogous to a car engine at idle, as a result of spontaneous C3 hydrolysis due to the breakdown of the internal thioester bond (C3 is mildly unstable in aqueous environment). The alternative pathway does not rely on pathogen-binding antibodies like the other pathways. C3b that is generated from C3 by a C3 convertase enzyme complex in the fluid phase is rapidly inactivated by factor H and factor I, as is the C3b-like C3 that is the product of spontaneous cleavage of the internal thioester. In contrast, when the internal thioester of C3 reacts with a hydroxyl or amino group of a molecule on the surface of a cell or pathogen, the C3b that is now covalently bound to the surface is protected from factor H-mediated inactivation. The surface-bound C3b may now bind factor B to form C3bB. This complex in the presence of factor D will be cleaved into Ba and Bb. Bb will remain associated with C3b to form C3bBb, which is the alternative pathway C3 convertase.  The C3bBb complex is stabilized by binding oligomers of factor P (properdin). The stabilized C3 convertase, C3bBbP, then acts enzymatically to cleave much more C3, some of which becomes covalently attached to the same surface as C3b. This newly bound C3b recruits more B, D and P activity and greatly amplifies the complement activation. When complement is activated on a cell surface, the activation is limited by endogenous complement regulatory proteins, which include CD35, CD46, CD55 and CD59, depending on the cell. Pathogens, in general, don't have complement regulatory proteins (there are many exceptions, which reflect adaptation of microbial pathogens to vertebrate immune defenses). Thus, the alternative complement pathway is able to distinguish self from non-self on the basis of the surface expression of complement regulatory proteins. Host cells don't accumulate cell surface C3b (and the proteolytic fragment of C3b called iC3b) because this is prevented by the complement regulatory proteins, while foreign cells, pathogens and abnormal surfaces may be heavily decorated with C3b and iC3b. Accordingly, the alternative complement pathway is one element of innate immunity.  Once the alternative C3 convertase enzyme is formed on a pathogen or cell surface, it may bind covalently another C3b, to form C3bBbC3bP, the C5 convertase. This enzyme then cleaves C5 to C5a, a potent anaphylatoxin, and C5b. The C5b then recruits and assembles C6, C7, C8 and multiple C9 molecules to assemble the membrane attack complex. This creates a hole or pore in the membrane that can kill or damage the pathogen or cell.

Lectin pathway.

The lectin pathway is homologous to the classical pathway, but with the opsonin, mannose-binding lectin (MBL), and ficolins, instead of C1q. This pathway is activated by binding of MBL to mannose residues on the pathogen surface, which activates the MBL-associated serine proteases, MASP-1, and MASP-2 (very similar to C1r and C1s, respectively), which can then split C4 into C4a and C4b and C2 into C2a and C2b. C4b and C2b then bind together to form the classical C3-convertase, as in the classical pathway. Ficolins are homologous to MBL and function via MASP in a similar way. Several single-nucleotide polymorphisms have been described in M-ficolin in humans, with effect on ligand-binding ability and serum levels. Historically, the larger fragment of C2 was named C2a, but it is now referred to as C2b. In invertebrates without an adaptive immune system, ficolins are expanded and their binding specificities diversified to compensate for the lack of pathogen-specific recognition molecules.

Complement protein fragment nomenclature.

Immunology textbooks have used different naming assignments for the smaller and larger fragments of C2 as C2a and C2b. The preferred assignment appears to be that the smaller fragment be designated as C2a: as early as 1994, a well known textbook recommended that the larger fragment of C2 should be designated C2b. However, this was amplified in their 1999 4th edition, to say that: "It is also useful to be aware that the larger active fragment of C2 was originally designated C2a, and is still called that in some texts and research papers. Here, for consistency, we shall call all large fragments of complement b, so the larger fragment of C2 will be designated C2b. In the classical and lectin pathways the C3 convertase enzyme is formed from membrane-bound C4b with C2b."  This nomenclature is used in another literature: "(Note that, in older texts, the smaller fragment is often called C2b, and the larger one is called C2a for historical reason.)" The assignment is mixed in the latter literature, though. Some sources designate the larger and smaller fragments as C2a and C2b respectively while other sources apply the converse. However, due to the widely established convention, C2b here is the larger fragment, which, in the classical pathway, forms C4b2b (classically C4b2a). It may be noteworthy that, in a series of editions of Janeway's book, 1st to 7th, in the latest edition they withdraw the stance to indicate the larger fragment of C2 as C2b.

Viral inhibition.

Fixation of the MBL protein on viral surfaces has also been shown to enhance neutralization of viral pathogens.

Activation of complements by antigen-associated antibody.

In the classical pathway, C1 binds with its C1q subunits to Fc fragments (made of CH2 region) of IgG or IgM, which has formed a complex with antigens. C4b and C3b are also able to bind to antigen-associated IgG or IgM, to its Fc portion.  Such immunoglobulin-mediated binding of the complement may be interpreted as that the complement uses the ability of the immunoglobulin to detect and bind to non-self antigens as its guiding stick. The complement itself can bind non-self pathogens after detecting their pathogen-associated molecular patterns (PAMPs), however, utilizing specificity of the antibody, complements can detect non-self enemies much more specifically.  Some components have a variety of binding sites. In the classical pathway, C4 binds to Ig-associated C1q and C1rs enzyme cleaves C4 to C4b and 4a. C4b binds to C1q, antigen-associated Ig (specifically to its Fc portion), and even to the microbe surface. C3b binds to antigen-associated Ig and to the microbe surface. Ability of C3b to bind to antigen-associated Ig would work effectively against antigen-antibody complexes to make them soluble.

Regulation.

The complement system has the potential to be extremely damaging to host tissues, meaning its activation must be tightly regulated. The complement system is regulated by complement control proteins, which are present at a higher concentration in the blood plasma than the complement proteins themselves. Some complement control proteins are present on the membranes of self-cells preventing them from being targeted by complement. One example is CD59, also known as protectin, which inhibits C9 polymerisation during the formation of the membrane attack complex. The classical pathway is inhibited by C1-inhibitor, which binds to C1 to prevent its activation.  C3-convertase can be inhibited by Decay accelerating factor (DAF), which is bound to erythrocyte plasma membranes via a GPI anchor.

Role in disease.

Complement deficiency.

It is thought that the complement system might play a role in many diseases with an immune component, such as Barraquer–Simons Syndrome, asthma, lupus erythematosus, glomerulonephritis, various forms of arthritis, autoimmune heart disease, multiple sclerosis, inflammatory bowel disease, paroxysmal nocturnal hemoglobinuria, atypical hemolytic uremic syndrome and ischemia-reperfusion injuries, and rejection of transplanted organs.  The complement system is also becoming increasingly implicated in diseases of the central nervous system such as Alzheimer's disease and other neurodegenerative conditions such as spinal cord injuries.  Deficiencies of the terminal pathway predispose to both autoimmune disease and infections (particularly Neisseria meningitidis, due to the role that the membrane attack complex ("MAC") plays in attacking Gram-negative bacteria).  Infections with "N. meningitidis" and "N. gonorrhoeae" are the only conditions known to be associated with deficiencies in the MAC components of complement. 40–50% of those with MAC deficiencies experience recurrent infections with "N. meningitidis".

Deficiencies in complement regulators.

Mutations in the complement regulators factor H and membrane cofactor protein have been associated with atypical hemolytic uremic syndrome. Moreover, a common single nucleotide polymorphism in factor H (Y402H) has been associated with the common eye disease age-related macular degeneration. Polymorphisms of complement component 3, complement factor B, and complement factor I, as well as deletion of complement factor H-related 3 and complement factor H-related 1 also affect a person's risk of developing age-related macular degeneration. Both of these disorders are currently thought to be due to aberrant complement activation on the surface of host cells.  Mutations in the C1 inhibitor gene can cause hereditary angioedema, a genetic condition resulting from reduced regulation of bradykinin by C1-INH.  Paroxysmal nocturnal hemoglobinuria is caused by complement breakdown of RBCs due to an inability to make GPI. Thus the RBCs are not protected by GPI anchored proteins such as DAF.

Diagnostic tools.

Diagnostic tools to measure complement activity include the total complement activity test.  The presence or absence of complement fixation upon a challenge can indicate whether particular antigens or antibodies are present in the blood. This is the principle of the complement fixation test.

Modulation by infections.

Recent research has suggested that the complement system is manipulated during HIV/AIDS, in a way that further damages the body.

The complement system, also known as complement cascade, is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. It is part of the innate immune system, which is not adaptable and does not change during an individual's lifetime. The complement system can, however, be recruited and brought into action by antibodies generated by the adaptive immune system.

Komplement (komplementový soubor, zkratka C) je soubor asi 40 sérových a membránových glykoproteinů, které slouží jako humorální složka nespecifické imunity (spolu s interferony a dalšími plazmatickými proteiny).


Biography.

Early years.

Kydland grew up as the eldest of six siblings at the family farm in Søyland, Gjesdal, which is located in the Jæren farming region in Rogaland county, southwestern Norway. He recalls having had a liberal upbringing, his parents not imposing many limitations on their children. Finn Kydland became interested in mathematics and economics as a young adult, after he did some bookkeeping at a friend's mink farm.  With a freshly awakened interest in theoretical economics, Kydland earned a BSc from NHH in 1968 and a Ph.D. in economics from Carnegie Mellon in 1973, dissertation: "Decentralized Macroeconomic Planning", supervised by Edward C. Prescott. After his Ph.D. he returned to NHH as an assistant professor. In 1978 he moved back to Carnegie Mellon as an associate professor. He has been living in the United States since then.

Scholarship.

Kydland's areas of expertise are economics in general and political economy. His main areas of teaching and interest are business cycles, monetary and fiscal policy and labor economics. He joined the faculty of Carnegie Mellon University in 1977, where he served as a Professor of Economics until 2004, when he became a faculty member of the University of California, Santa Barbara and founded the Laboratory for Aggregate Economics and Finance (LAEF) at this same institution. He is a Research Associate for the Federal Reserve Banks of Dallas, Cleveland and St. Louis, and a Fellow at the IC2 Institute at the University of Texas at Austin. He is also an Adjunct Professor at the NHH, and has held visiting scholar and professor positions at, among other places, the Hoover Institution and the Universidad Torcuato di Tella in Buenos Aires, Argentina.

Personal life.

Kydland was married to Liv Kjellevold in 1968 with whom he had four children; sons, Eirik, Jon Martin, and daughters, Camilla and Kari. He is now married to Tonya Schooler.

Finn Erling Kydland (born 1 December 1943) is a Norwegian economist known for his contributions to business cycle theory. He is the Henley Professor of Economics at the University of California, Santa Barbara. He also holds the Richard P. Simmons Distinguished Professorship at the Tepper School of Business of Carnegie Mellon University, where he earned his Ph.D., and a part-time position at the Norwegian School of Economics (NHH). Kydland was a co-recipient of the 2004 Nobel Memorial Prize in Economics, with Edward C. Prescott, "for their contributions to dynamic macroeconomics: the time consistency of economic policy and the driving forces behind business cycles."

Finn Erling Kydland (* 1. prosince 1943) je norský ekonom. V současné době je profesorem ekonomie na Kalifornské univerzitě v Santa Barbaře. Spolu s Američanem Edwardem C. Prescottem získal roku 2004 Nobelovu cenu za ekonomii za teorii hospodářských cyklů a ekonomické politiky, časové konzistence ekonomické politiky a zkoumání sil, které řídí výkyvy hospodářského cyklu.


Script.

Most hypotheses about the Linear A script and Minoan language start with Linear B.  Linear A has hundreds of signs, believed to represent syllabic, ideographic, and semantic values in a manner similar to Linear B. While many of those assumed to be syllabic signs are similar to ones in Linear B, approximately 80% of Linear A's logograms are unique; the difference in sound values between Linear A and Linear B signs ranges from 9% to 13%. It primarily appears in the left-to-right direction, but occasionally appears as a right-to-left or boustrophedon script.  Linear A may be divided into four categories: Numbers follow a decimal system, units are represented by vertical dashes, tens by horizontal dashes, hundreds by circles, and thousands by circles with rays. Specific signs that coincide with numerals are regarded as fractions.  An interesting feature is the recording of numbers in the script: The highest number recorded in known Linear A texts is 3000, but there are special symbols to indicate fractions and weights.

Corpus.

Linear A has been unearthed chiefly on Crete, but also at other sites in Greece, as well as Turkey and Israel. The extant corpus, comprising some 1,427 specimens totalling 7,362 to 7,396 signs, if scaled to standard type, would fit easily on two sheets of paper. Linear A has been written on various media, such as stone offering tables, gold and silver hairpins, and ceramics. The earliest inscriptions of Linear A come from Phaistos, in a layer dated at the end of the Middle Minoan II period: that is, no later than c. 1700 BC. Linear A texts have been found throughout the island of Crete and also on some Aegean islands (Kythera, Kea, Thera, Melos), in mainland Greece (Ayos Stephanos), on the west coast of Asia Minor (Miletos, Troy), and in the Levant (Tel Haror).

Crete.

The main discoveries of Linear A tablets have been at three sites on Crete:  Discoveries have been made at the following locations on Crete:

Outside Crete.

Until 1973, only one Linear A tablet had been found outside Crete (on Kea). Since then, other locations have yielded inscriptions.  Most—if not all—inscriptions found outside Crete appear to have been made locally, as indicated by the composition of the substrate and other indications. Also, close analysis of the inscriptions found outside Crete indicates the use of a script that is somewhere between Linear A and Linear B, combining elements from both.

Chronology.

Linear A became prominent during the Middle Minoan Period, specifically from 1625–1450 BC. It was contemporary with and possibly derived from Cretan hieroglyphs, and is an ancestor of Linear B. The sequence and the geographical spread of Cretan hieroglyphs, Linear A, and Linear B, the three overlapping but distinct writing systems on Bronze Age Crete and the Greek mainland, can be summarized as follows:

Discovery.

Archaeologist Arthur Evans named the script "Linear" because its characters consisted simply of lines inscribed in clay, in contrast to the more pictographic characters in Cretan hieroglyphs that were used during the same period.  Several tablets inscribed in signs similar to Linear A were found in the Troad in northwestern Anatolia. While their status is disputed, they may be imports, as there is no evidence of Minoan presence in the Troad. Classification of these signs as a unique Trojan script (proposed by contemporary Russian linguist Nikolai Kazansky) is not accepted by other linguists.

Egyptian evidence.

Egyptian evidence related to the Keftiu (Cretan/Crete) language consists of a spell against Asian chickenpox and a writing name exercise called Keftiu. The spell, probably originated from the reign of Amenhotep III (1390–1352 BC), evolves as follows: "sntÈk|pwpyw| yÈymantÈÈrk|k|r", or, in the vocal transliteration adopted by Wolfgang Helck: "santaka pupiwa ya’ayamantarakú ka ra".  Egyptian writing of Keftiu (Cretan/Crete) names such as mÈd|d|m, or "mi-da" is evidence for the language of the Keftiu, essentially indicating that it contains Semitic vocabulary. (see below).

Linear A and Linear B comparison.

In 1945, E. Pugliese Carratelli first introduced the classification of Linear A and Linear B parallels. However, in 1961 W.C. Brice modified the Carratelli system that was based on a wider range of Linear A sources, but Brice did not suggest Linear B equivalents to the Linear A signs. Louis Godart and Jean-Pierre Olivier introduced in the 1985 "Recueil des inscriptions en linéaire A (GORILA)," based on E.L Bennett's standard numeration of the signs of Linear B, introduced a joint numeration of the Linear A and B signs. The Egyptian exercise in writing the names of Keftiu even informs us of another Minoan ethnic identity in the form of mÈd|d|m whose first element cannot be associated with the name Midas, since it was already labeled by a linearly inscribed Hagia Triada (or HT 41.4) dating to c. 1350 BC. This Egyptian evidence of the Keftiu language essentially indicates that words in its vocabulary are Semitic, but in the language predominantly of the Luwians. One might conclude from this that a Semitic language was used in Minoan Crete as a lingua franca for a largely Luwian population.

Phonetic.

The majority of signs in the Linear A script appear to have graphical equivalents in the Linear B syllabary. Comparison of the Hagia Triada tablets HT 95 and HT 86 shows that they contain identical lists of words and some kind of phonetic alteration. Scholars that approached Linear A with the phonetic values of Linear B produced a series of identical words. The Linear B–Linear A parallels: ku-ku-da-ra, pa-i-to, ku-mi-na, di-de-ro →di-de-ru, qa-qa-ro→qa-qa-ru, a-ra-na-ro→a-ra-na-re.

Theories regarding language.

It is difficult to evaluate a given analysis of Linear A as there is little point of reference for reading its inscriptions. The simplest approach to decipherment may be to presume that the values of Linear A match more or less the values given to the deciphered Linear B script, used for Mycenaean Greek.  A characteristic of Minoan consonance is the lack of distinction between voice and voiceless in the velar and labial series. The distinction t / d reflected in the Linear A, Linear B and Cypriot is an example of speech stops.

Greek.

In 1957, Bulgarian scholar Vladimir I. Georgiev published his "Le déchiffrement des inscriptions crétoises en linéaire A" ("The decipherment of Cretan inscriptions in Linear A") stating that Linear A contains Greek linguistic elements. Georgiev then published another work in 1963, titled "Les deux langues des inscriptions crétoises en linéaire A" ("The two languages of Cretan inscriptions in Linear A"), suggesting that the language of the Hagia Triada tablets was Greek but that the rest of the Linear A corpus was in Hittite-Luwian. In December 1963, Gregory Nagy of Harvard University developed a list of Linear A and Linear B terms based on the assumption "that signs of identical or similar shape in the two scripts will represent similar or identical phonetic values"; Nagy concluded that the language of Linear A bears "Greek-like" and Indo-European elements. Michael Ventris' decipherment of Linear B in 1952 suggests an old form of Greek: it is derived from Linear A. Therefore, we can assume that the signs related to the Linear A express the same value as the Linear B. In all Linear B values for related words give a large number of identical forms or identical root forms, but alternate with the final vowel, or almost identical forms among linear texts, mainly those of Hagia Triada.  Extracting conclusions or arguments from a simple morphology can hardly be considered methodologically satisfactory. Yves Duhoux in the "Linear A as Greek" discussion at AEGEANET in March 1998:I would like to remind you of some basic facts related to the Greekness of Linear A's language: (1) The word for "total" is different in Linear A and in Linear B: LB "to - so(- de)"; LA > B "ku-ro." (2) The Linear B language is significantly less "prefixing" than Linear A. (3) Votive Linear A texts, where we are pretty sure to have variant forms of the same "word", show morphological (I mean: grammatical) features totally different from Linear B. The conclusion must be that even if one can find some casual resemblances between words in both languages (remember this MUST statistically happen: e.g. English and Persian use the same word "bad" to express the meaning of BAD, although it is proven that both words have no genetic relation at all), they are probably structurally different.

Anatolian languages.

Since the late 1950s, some scholars have suggested that the Linear A language could be an Anatolian language.

Luwian.

Palmer (1958) put forward a theory, based on Linear B phonetic values, suggesting that Linear A language could be related closely to Luwian. The theory, however, failed to gain universal support for the following reasons:  There are recent works focused on the Luwian connection, not in terms of the Minoan language being Anatolian, but rather in terms of possible borrowings from Luwian, including the origin of the writing system itself.

Lycian.

In an article from 2001, Margalit Finkelberg, Professor of Classics emerita at Tel Aviv University, demonstrated a "high degree of correspondence between the phonological and morphological system of Minoan and that of Lycian" and proposed that "the language of Linear A is either the direct ancestor of Lycian or a closely related idiom."

Semitic languages.

Cyrus H. Gordon first proposed in 1966–1969 that the texts contained Semitic vocabulary that was based on the lexical items such as "kull -." meaning 'all' (Akkadian "kalu, kullatu," Hebrew "kol"). Gordon uses morphological evidence to suggest that "u-" serves as a prefix in Linear A like Semitic copula "u-". However, Gordon's copula "u-" is based on an incomplete word, and even if some of Gordon's identifications were true, a complete case for a Semitic language has not yet been built.

Phoenician.

In 2001, the journal "Ugarit-Forschungen" published the article "The First Inscription in Punic – Vowel Differences in Linear A and B" by Jan Best, claiming to demonstrate how and why Linear A notates an archaic form of Phoenician. This was a continuation of attempts by Cyrus Gordon in finding connections between Minoan and West Semitic languages.

Indo-Iranian.

Another recent interpretation, based on the frequencies of the syllabic signs and on complete palaeographic comparative studies, suggests that the Minoan Linear A language belongs to the Indo-Iranian family of Indo-European languages. Studies by Hubert La Marle include a presentation of the morphology of the language, avoid the complete identification of phonetic values between Linear A and B, and also avoid comparing Linear A with Cretan hieroglyphs. La Marle uses the frequency counts to identify the type of syllables written in Linear A, and takes into account the problem of loanwords in the vocabulary.  However, La Marle's interpretation of Linear A has been subject to some criticism; it was rejected by John Younger of the University of Kansas who showed that La Marle had invented at will erroneous and arbitrary new transcriptions, based on resemblances with many different script systems (as Phoenician, Hieroglyphic Egyptian, Hieroglyphic Hittite, Ethiopian, Cypro-Minoan, etc.), ignoring established evidence and internal analysis, while for some words La Marle proposes religious meanings inventing names of gods and rites. La Marle made a rebuttal in "An answer to John G. Younger's remarks on Linear A" in 2010.

Ugric.

A 2019 journal article by Peter Revesz argues that archaeogenetics points to a Danube Basin and western Black Sea littoral origin for the Minoans, with connections to present populations there. The same researcher proposes that the Minoan language belongs to a novel West-Ugric language subfamily, which would also include Hattic and Hungarian. He also proposes a decipherment of twenty-eight Linear A documents.

Tyrrhenian.

Italian scholar Giulio M. Facchetti attempted to link Linear A to the Tyrrhenian language family comprising Etruscan, Rhaetic, and Lemnian. This family is reasoned to be a pre-Indo-European Mediterranean substratum of the 2nd millennium BC, sometimes referred to as Pre-Greek. Facchetti proposed some possible similarities between the Etruscan language and ancient Lemnian, and other Aegean languages like Minoan.  Michael Ventris who (with John Chadwick) successfully deciphered Linear B also believed in a link between Minoan and Etruscan. The same perspective is supported by S. Yatsemirsky in Russia.

A distinct, otherwise unknown branch of Indo-European.

According to Gareth Alun Owens, Linear A represents the Minoan language, which Owens classifies as a distinct branch of Indo-European potentially related to Greek, Sanskrit, Hittite, Latin, etc. At "The Cretan Literature Centre", Owens stated:Beginning our research with inscriptions in Linear A carved on offering tables found in the many peak sanctuaries on the mountains of Crete, we recognise a clear relationship between Linear A and Sanskrit, the ancient language of India. There is also a connection to Hittite and Armenian. This relationship allows us to place the Minoan language among the so-called Indo-European languages, a vast family that includes modern Greek and the Latin of Ancient Rome. The Minoan and Greek languages are considered to be different branches of Indo-European. The Minoans probably moved from Anatolia to the island of Crete about 10,000 years ago. There were similar population movements to Greece. The relative isolation of the population which settled in Crete resulted in the development of its own language, Minoan, which is considered different to Mycenaean. In the Minoan language (Linear A), there are no purely Greek words, as is the case in Mycenaean Linear B; it contains only words also found in Greek, Sanskrit, and Latin, i.e. sharing the same Indo-European origin.

Attempts at decipherment of single words.

Some researchers suggest that a few words or word elements may be recognized, without (yet) enabling any conclusion about relationship with other languages. In general, they use analogy with Linear B in order to propose phonetic values of the syllabic sounds. John Younger, in particular, thinks that place names usually appear in certain positions in the texts, and notes that the proposed phonetic values often correspond to known place names as given in Linear B texts (and sometimes to modern Greek names). For example, he proposes that three syllables, read as "KE-NI-SO", might be the indigenous form of Knossos. Likewise, in Linear A, "MA+RU" is suggested to mean "wool", and to correspond both to a Linear B pictogram with this meaning, and to the classical Greek word μαλλός with the same meaning (in that case a loan word from Minoan).

Unicode.

The Linear A alphabet (U+10600–U+1077F) was added to the Unicode Standard in June 2014 with the release of version 7.0.

Linear A is a writing system used by the Minoans (Cretans) from 1800 to 1450 BC to write the hypothesized Minoan language. Linear A was the primary script used in palace and religious writings of the Minoan civilization. It was discovered by archaeologist Sir Arthur Evans. It was succeeded by Linear B, which was used by the Mycenaeans to write an early form of Greek. No texts in Linear A have been deciphered.

Lineární písmo A (anglicky: Linear A) je nerozluštěné písmo používané v letech 2500 až 1450 před n.l. v starověké Krétě (spolu s ním také krétské hieroglyfy). Je podobné lineárnímu písmu B, které bylo rozluštěno v 50. letech 20. století Michaelem Ventrisem a bylo používáno k zapisování starověké řečtiny.