A drought or drouth is a natural disaster of below-average precipitation in a given region, resulting in prolonged shortages in the water supply, whether atmospheric, surface water or ground water. A drought may be declared after as few as 15 days, it can have a substantial impact on the ecosystem and agriculture of the affected region and harm to the local economy. Annual dry seasons in the tropics increase the chances of a drought developing and subsequent bush fires. Periods of heat can worsen drought conditions by hastening evaporation of water vapour. Many plant species, such as those in the family Cactaceae, have drought tolerance adaptations like reduced leaf area and waxy cuticles to enhance their ability to tolerate drought; some others survive dry periods as buried seeds. Semi-permanent drought produces arid biomes such as grasslands. Prolonged droughts have caused humanitarian crisis. Most arid ecosystems have inherently low productivity; the most prolonged drought in the world in recorded history occurred in the Atacama Desert in Chile.
Mechanisms of producing precipitation include convective and orographic rainfall. Convective processes involve strong vertical motions that can cause the overturning of the atmosphere in that location within an hour and cause heavy precipitation, while stratiform processes involve weaker upward motions and less intense precipitation over a longer duration. Precipitation can be divided into three categories, based on whether it falls as liquid water, liquid water that freezes on contact with the surface, or ice. Droughts occur in areas where normal levels of rainfall are, in themselves, low. If these factors do not support precipitation volumes sufficiently to reach the surface over a sufficient time, the result is a drought. Drought can be triggered by a high level of reflected sunlight and above average prevalence of high pressure systems, winds carrying continental, rather than oceanic air masses, ridges of high pressure areas aloft can prevent or restrict the developing of thunderstorm activity or rainfall over one certain region.
Once a region is within drought, feedback mechanisms such as local arid air, hot conditions which can promote warm core ridging, minimal evapotranspiration can worsen drought conditions. Within the tropics, distinct and dry seasons emerge due to the movement of the Intertropical Convergence Zone or Monsoon trough; the dry season increases drought occurrence, is characterized by its low humidity, with watering holes and rivers drying up. Because of the lack of these watering holes, many grazing animals are forced to migrate due to the lack of water in search of more fertile lands. Examples of such animals are zebras and wildebeest; because of the lack of water in the plants, bushfires are common. Since water vapor becomes more energetic with increasing temperature, more water vapor is required to increase relative humidity values to 100% at higher temperatures. Periods of warmth quicken the pace of fruit and vegetable production, increase evaporation and transpiration from plants, worsen drought conditions.
Drier and hotter weather occurs in parts of the Amazon River Basin and Central America during El Niño events. Winters during the El Niño are warmer and drier than average conditions in the Northwest, northern Midwest, northern Mideast United States, so those regions experience reduced snowfalls. Conditions are drier than normal from December to February in south-central Africa in Zambia, Zimbabwe and Botswana. Direct effects of El Niño resulting in drier conditions occur in parts of Southeast Asia and Northern Australia, increasing bush fires, worsening haze, decreasing air quality dramatically. Drier-than-normal conditions are in general observed in Queensland, inland Victoria, inland New South Wales, eastern Tasmania from June to August; as warm water spreads from the west Pacific and the Indian Ocean to the east Pacific, it causes extensive drought in the western Pacific. Singapore experienced the driest February in 2014 since records began in 1869, with only 6.3 mm of rain falling in the month and temperatures hitting as high as 35 °C on 26 February.
The years 2005 had the next driest Februaries, when 8.4 mm of rain fell. Human activity can directly trigger exacerbating factors such as over farming, excessive irrigation and erosion adversely impact the ability of the land to capture and hold water. In arid climates, the main source of erosion is wind. Erosion can be the result of material movement by the wind; the wind can cause small particles to be therefore moved to another region. Suspended particles within the wind may impact on solid objects causing erosion by abrasion. Wind erosion occurs in areas with little or no vegetation in areas where there is insufficient rainfall to support vegetation. Loess is a homogeneous nonstratified, friable coherent calcareous, fine-grained, pale yellow or buff, windblown sediment, it occurs as a widespread blanket deposit that covers areas of hundreds of square kilometers and tens of meters thick. Loess stands in either steep or vertical faces. Loess tends to develop into rich soils. Under appropriate climatic conditions, areas with loess are among the most agriculturally productive in the world.
Loess deposits are geologically unstable by nature, will erode readily. Therefore, windbreaks are planted by farmers to reduce the wind erosion of loess. Wind erosion
A stair riser is the near-vertical element in a set of stairs, forming the space between one step and the next. It is sometimes inclined from the vertical so that its top is closer than its base to the person climbing the stairs; the horizontal edge of the stair is called the nosing, whereas the surface on which a person's whole foot makes contact is called the tread. Decorated stair risers were used extensively in the Greco-Buddhist art of Gandhara, to form the pedestal to small devotional stupas, they were adorned with friezes, fantastic animals and decorations. A flight of stairs with decorated stair risers from the Chakhil-i-Ghoundi Stupa has been fully restored and can now be seen at the Guimet Museum in Paris. Archaeological research by the Italian IsMEO at the Butkara Stupa suggests that small decorative stairs were adjoined to Buddhist stupas at the time of the Indo-Greek Kingdom, that they were decorated with Buddhist scenes
Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels, marmots, flying squirrels, prairie dogs amongst other rodents. Squirrels are indigenous to the Americas and Africa, were introduced by humans to Australia; the earliest known squirrels date from the Eocene period and are most related to the mountain beaver and to the dormouse among other living rodent families. The word "squirrel", first attested in 1327, comes from the Anglo-Norman esquirel, from the Old French escurel, the reflex of a Latin word sciurus; this Latin word was borrowed from the Ancient Greek word σκίουρος, which means shadow-tailed, referring to the bushy appendage possessed by many of its members. The native Old English word for the squirrel, ācweorna, survived only into Middle English before being replaced; the Old English word is of Common Germanic origin, cognates of which are still used in other Germanic languages, including the German Eichhörnchen, the Norwegian ikorn/ekorn, the Dutch eekhoorn, the Swedish ekorre and the Danish egern.
Squirrels are small animals, ranging in size from the African pygmy squirrel at 7–10 cm in length and just 10 g in weight, to the Laotian giant flying squirrel at 1.08 m in length and the Alpine marmot, which weighs from 5 to 8 kg. Squirrels have slender bodies with bushy tails and large eyes. In general, their fur is silky, though much thicker in some species than others; the coat color of squirrels is variable between—and even within—species. In most squirrel species, the hind limbs are longer than the fore limbs, while all species have either four or five toes on each paw; the paws, which include an poorly developed thumb, have soft pads on the undersides and versatile, sturdy claws for grasping and climbing. Tree squirrels, unlike most mammals, can descend a tree head-first, they do so by rotating their ankles 180 degrees, enabling the hind paws to point backward and thus grip the tree bark from the opposite direction. Squirrels live in every habitat, from tropical rainforest to semiarid desert, avoiding only the high polar regions and the driest of deserts.
They are predominantly herbivorous, subsisting on seeds and nuts, but many will eat insects and small vertebrates. As their large eyes indicate, squirrels have an excellent sense of vision, important for the tree-dwelling species. Many have a good sense of touch, with vibrissae on their limbs as well as their heads; the teeth of sciurids follow the typical rodent pattern, with large incisors that grow throughout life, cheek teeth that are set back behind a wide gap, or diastema. The typical dental formula for sciurids is 184.108.40.206.0.1.3. Many juvenile squirrels die in the first year of life. Adult squirrels can have a lifespan of 5 to 10 years in the wild; some can survive 10 to 20 years in captivity. Premature death may be caused when a nest falls from the tree, in which case the mother may abandon her young if their body temperature is not correct. Many such baby squirrels have been rescued and fostered by a professional wildlife rehabilitator until they could be safely returned to the wild, although the density of squirrel populations in many places and the constant care required by premature squirrels means that few rehabilitators are willing to spend their time doing this and such animals are euthanized instead.
Squirrels mate either once or twice a year and, following a gestation period of three to six weeks, give birth to a number of offspring that varies by species. The young are altricial, being born naked and blind. In most species of squirrel, the female alone looks after the young, which are weaned at six to ten weeks and become sexually mature by the end of their first year. In general, the ground-dwelling squirrel species are social living in well-developed colonies, while the tree-dwelling species are more solitary. Ground squirrels and tree squirrels are either diurnal or crepuscular, while the flying squirrels tend to be nocturnal—except for lactating flying squirrels and their young, which have a period of diurnality during the summer; because squirrels cannot digest cellulose, they must rely on foods rich in protein and fats. In temperate regions, early spring is the hardest time of year for squirrels because the nuts they buried are beginning to sprout, while many of the usual food sources have not yet become available.
During these times, squirrels rely on the buds of trees. Squirrels, being herbivores, eat a wide variety of plants, as well as nuts, conifer cones, fruits and green vegetation; some squirrels, however consume meat when faced with hunger. Squirrels have been known to eat small birds, young snakes, smaller rodents, as well as bird eggs and insects. Indeed, some tropical squirrel species have shifted entirely to a diet of insects. Predatory behavior has been observed in various species of ground squirrels, in particular the thirteen-lined ground squirrel. For example, Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken. Wistrand reported seeing this same species eating a freshly killed snake. Whitaker examined the stomachs of 139 thirteen-lined ground squirrels and found bird flesh in four of the specimens and the remains of a short-tailed shrew in one.
Trichomes, from the Greek τρίχωμα meaning "hair", are fine outgrowths or appendages on plants, algae and certain protists. They are of diverse function. Examples are hairs, glandular hairs and papillae. A covering of any kind of hair on a plant is an indumentum, the surface bearing them is said to be pubescent. Certain filamentous, algae have the terminal cell produced into an elongate hair-like structure called a trichome; the same term is applied to such structures in some cyanobacteria, such as Spirulina and Oscillatoria. The trichomes of cyanobacteria may be unsheathed, as in Oscillatoria, or sheathed, as in Calothrix; these structures play an important role in preventing soil erosion in cold desert climates. The filamentous sheaths form a persistent sticky network. Trichomes on plants are epidermal outgrowths of various kinds; the terms emergences or prickles refer to outgrowths. This distinction is not always applied. There are nontrichomatous epidermal cells that protrude from the surface. A common type of trichome is a hair.
Plant hairs may be multicellular, branched or unbranched. Multicellular hairs may have several layers of cells. Branched hairs can be tufted, or stellate, as in Arabidopsis thaliana. Another common type of trichome is the scale or peltate hair, that has a plate or shield-shaped cluster of cells attached directly to the surface or borne on a stalk of some kind. Common examples are the leaf scales of bromeliads such as the pineapple and sea buckthorn. Any of the various types of hairs may be glandular, producing some kind of secretion, such as the essential oils produced by mints and many other members of the family Lamiaceae. In describing the surface appearance of plant organs, such as stems and leaves, many terms are used in reference to the presence and appearance of trichomes; the most basic terms used are glabrous—lacking hairs— and pubescent—having hairs. Details are provided by: glabrous, glabrate -- lacking trichomes. Several basic functions or advantages of having surface hairs can be listed.
It is that in many cases, hairs interfere with the feeding of at least some small herbivores and, depending upon stiffness and irritability to the palate, large herbivores as well. Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells. In windy locations, hairs break up the flow of air across the plant surface. Dense coatings of hairs reflect sunlight, protecting the more delicate tissues underneath in hot, open habitats. In addition, in locations where much of the available moisture comes from fog drip, hairs appear to enhance this process by increasing the surface area on which water droplets can accumulate. Both trichomes and root hairs, the rhizoids of many vascular plants, are lateral outgrowths of a single cell of the epidermal layer. Root hairs form from the hair-forming cells on the epidermis of a plant root. Root hairs vary between 5 and 17 micrometres in diameter, 80 to 1,500 micrometres in length. Root hairs can survive for two to three weeks and die off.
At the same time new root hairs are continually being formed at the top of the root. This way, the root hair coverage stays the same, it is therefore understandable that repotting must be done with care, because the root hairs are being pulled off for the most part. This is; the genetic control of patterning of trichomes and roots hairs shares similar control mechanisms. Both processes involve a core of related transcription factors that control the initiation and development of the epidermal outgrowth. Activation of genes that encode specific protein transcription factors are the major regulators of cell fate to produce trichomes or root hairs; when these genes are activated in a leaf epidermal cell, the formation of a trichrome is initiated within that cell. GL1, GL3. and TTG1 activate negative regulators, which serve to inhibit trichrome formation in neighboring cells. This system controls the spacing of trichomes on the leaf surface. Once trichome are developed they may branch. In contrast, root hairs only branch.
During the formation of trichomes and root hairs, many enzymes are regulated. For example, just prior to the root hair development, there is a point of elevated phosphorylase activity; the type and absence and location of trichomes are important diagnostic characters in plant identification and plant taxonomy. In forensic examination, plants such as Cannabis sativa can be identified by microscopic examination of the trichomes. Althoug
Cattle—colloquially cows—are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, are most classified collectively as Bos taurus. Cattle are raised as livestock for meat, for milk, for hides, which are used to make leather, they are used as riding animals and draft animals. Another product of cattle is dung, which can be used to create fuel. In some regions, such as parts of India, cattle have significant religious meaning. Cattle small breeds such as the Miniature Zebu, are kept as pets. Around 10,500 years ago, cattle were domesticated from as few as 80 progenitors in central Anatolia, the Levant and Western Iran. According to an estimate from 2011, there are 1.4 billion cattle in the world. In 2009, cattle became one of the first livestock animals to have a mapped genome; some consider cattle the oldest form of wealth, cattle raiding one of the earliest forms of theft. Cattle were identified as three separate species: Bos taurus, the European or "taurine" cattle.
The aurochs is ancestral to both taurine cattle. These have been reclassified as one species, Bos taurus, with three subspecies: Bos taurus primigenius, Bos taurus indicus, Bos taurus taurus. Complicating the matter is the ability of cattle to interbreed with other related species. Hybrid individuals and breeds exist, not only between taurine cattle and zebu, but between one or both of these and some other members of the genus Bos – yaks and gaur. Hybrids such as the beefalo breed can occur between taurine cattle and either species of bison, leading some authors to consider them part of the genus Bos, as well; the hybrid origin of some types may not be obvious – for example, genetic testing of the Dwarf Lulu breed, the only taurine-type cattle in Nepal, found them to be a mix of taurine cattle and yak. However, cattle cannot be hybridized with more distantly related bovines such as water buffalo or African buffalo; the aurochs ranged throughout Europe, North Africa, much of Asia. In historical times, its range became restricted to Europe, the last known individual died in Mazovia, Poland, in about 1627.
Breeders have attempted to recreate cattle of similar appearance to aurochs by crossing traditional types of domesticated cattle, creating the Heck cattle breed. The noun cattle encompasses both sexes; the singular, technically means the female, the male being bull. The plural form cows is sometimes used colloquially to refer to both sexes collectively, as e.g. in a herd, but that usage can be misleading as the speaker's intent may indeed be just the females. The bovine species per se is dimorphic. Cattle did not originate as the term for bovine animals, it was borrowed from Anglo-Norman catel, itself from medieval Latin capitale'principal sum of money, capital', itself derived in turn from Latin caput'head'. Cattle meant movable personal property livestock of any kind, as opposed to real property; the word is a variant of chattel and related to capital in the economic sense. The term replaced earlier Old English feoh ` property', which survives today as fee; the word "cow" came via Anglo-Saxon cū, from Common Indo-European gʷōus = "a bovine animal", compare Persian: gâv, Sanskrit: go-, Welsh: buwch.
The plural cȳ became ki or kie in Middle English, an additional plural ending was added, giving kine, but kies and others. This is the origin of the now archaic English plural, "kine"; the Scots language singular is coo or cou, the plural is "kye". In older English sources such as the King James Version of the Bible, "cattle" refers to livestock, as opposed to "deer" which refers to wildlife. "Wild cattle" may refer to undomesticated species of the genus Bos. Today, when used without any other qualifier, the modern meaning of "cattle" is restricted to domesticated bovines. In general, the same words are used in different parts of the world, but with minor differences in the definitions; the terminology described here contrasts the differences in definition between the United Kingdom and other British-influenced parts of the world such as Canada, New Zealand and the United States. An "intact" adult male is called a bull. A wild, unmarked bull is known as a micky in Australia. An unbranded bovine of either sex is called a maverick in the Canada.
An adult female that has had a calf is a cow. A young female before she has had a calf of her own and is under three years of age is called a heifer. A young female that has had only one calf is called a first-calf heifer. Young cattle of both sexes are called calves until they are weaned weaners until they are a year old in some areas. After that, they are referred to as stirks if between one and two years of age. A castrated male is called a steer in the United States.
Rodents are mammals of the order Rodentia, which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents, they are the most diversified mammalian order and live in a variety of terrestrial habitats, including human-made environments. Species can be fossorial, or semiaquatic. Well-known rodents include mice, squirrels, prairie dogs, chinchillas, beavers, guinea pigs, hamsters and capybaras. Other animals such as rabbits and pikas, whose incisors grow continually, were once included with them, but are now considered to be in a separate order, the Lagomorpha. Nonetheless and Lagomorpha are sister groups, sharing a most recent common ancestor and forming the clade of Glires. Most rodents are small animals with robust bodies, short limbs, long tails, they use their sharp incisors to gnaw food, excavate burrows, defend themselves. Most eat seeds or other plant material, they tend to be social animals and many species live in societies with complex ways of communicating with each other.
Mating among rodents can vary from monogamy, to polygyny, to promiscuity. Many have litters of altricial young, while others are precocial at birth; the rodent fossil record dates back to the Paleocene on the supercontinent of Laurasia. Rodents diversified in the Eocene, as they spread across continents, sometimes crossing oceans. Rodents reached both South America and Madagascar from Africa and were the only terrestrial placental mammals to reach and colonize Australia. Rodents have been used as food, for clothing, as pets, as laboratory animals in research; some species, in particular, the brown rat, the black rat, the house mouse, are serious pests and spoiling food stored by humans and spreading diseases. Accidentally introduced species of rodents are considered to be invasive and have caused the extinction of numerous species, such as island birds isolated from land-based predators; the distinguishing feature of the rodents is their pairs of continuously growing, razor-sharp, open-rooted incisors.
These incisors little enamel on the back. Because they do not stop growing, the animal must continue to wear them down so that they do not reach and pierce the skull; as the incisors grind against each other, the softer dentine on the rear of the teeth wears away, leaving the sharp enamel edge shaped like the blade of a chisel. Most species have up to 22 teeth with no canines or anterior premolars. A gap, or diastema, occurs between the cheek teeth in most species; this allows rodents to suck in their cheeks or lips to shield their mouth and throat from wood shavings and other inedible material, discarding this waste from the sides of their mouths. Chinchillas and guinea pigs have a high-fiber diet. In many species, the molars are large, intricately structured, cusped or ridged. Rodent molars are well equipped to grind food into small particles; the jaw musculature is strong. The lower jaw is pulled backwards during chewing. Rodent groups differ in the arrangement of the jaw muscles and associated skull structures, both from other mammals and amongst themselves.
The Sciuromorpha, such as the eastern grey squirrel, have a large deep masseter, making them efficient at biting with the incisors. The Myomorpha, such as the brown rat, have enlarged temporalis muscles, making them able to chew powerfully with their molars; the Hystricomorpha, such as the guinea pig, have larger superficial masseter muscles and smaller deep masseter muscles than rats or squirrels making them less efficient at biting with the incisors, but their enlarged internal pterygoid muscles may allow them to move the jaw further sideways when chewing. The cheek pouch is a specific morphological feature used for storing food and is evident in particular subgroups of rodents like kangaroo rats, hamsters and gophers which have two bags that may range from the mouth to the front of the shoulders. True mice and rats do not contain this structure but their cheeks are elastic due to a high degree of musculature and innervation in the region. While the largest species, the capybara, can weigh as much as 66 kg, most rodents weigh less than 100 g.
The smallest rodent is the Baluchistan pygmy jerboa, which averages only 4.4 cm in head and body length, with adult females weighing only 3.75 g. Rodents have wide-ranging morphologies, but have squat bodies and short limbs; the fore limbs have five digits, including an opposable thumb, while the hind limbs have three to five digits. The elbow gives the forearms great flexibility; the majority of species are plantigrade, walking on both the palms and soles of their feet, have claw-like nails. The nails of burrowing species tend to be long and strong, while arboreal rodents have shorter, sharper nails. Rodent species use a wide variety of methods of locomotion including quadrupedal walking, burrowing, bipedal hopping and gliding. Scaly-tailed squirrels and flying squirrels, although not related, can both glide from tree to tree using parachute-like membranes that stretch from the fore to the hind limbs; the agouti is antelope-like, being digitigrade and having hoof-like nails. The majority of rodents have tails, which can be of many shapes and siz
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition. Fire is hot because the conversion of the weak double bond in molecular oxygen, O2, to the stronger bonds in the combustion products carbon dioxide and water releases energy. At a certain point in the combustion reaction, called the ignition point, flames are produced; the flame is the visible portion of the fire. Flames consist of carbon dioxide, water vapor and nitrogen. If hot enough, the gases may become ionized to produce plasma. Depending on the substances alight, any impurities outside, the color of the flame and the fire's intensity will be different. Fire in its most common form can result in conflagration, which has the potential to cause physical damage through burning. Fire is an important process; the positive effects of fire include maintaining various ecological systems.
The negative effects of fire include hazard to life and property, atmospheric pollution, water contamination. If fire removes protective vegetation, heavy rainfall may lead to an increase in soil erosion by water; when vegetation is burned, the nitrogen it contains is released into the atmosphere, unlike elements such as potassium and phosphorus which remain in the ash and are recycled into the soil. This loss of nitrogen caused by a fire produces a long-term reduction in the fertility of the soil, which only recovers as nitrogen is "fixed" from the atmosphere by lightning and by leguminous plants such as clover. Fire has been used by humans in rituals, in agriculture for clearing land, for cooking, generating heat and light, for signaling, propulsion purposes, forging, incineration of waste, as a weapon or mode of destruction. Fires start when a flammable or a combustible material, in combination with a sufficient quantity of an oxidizer such as oxygen gas or another oxygen-rich compound, is exposed to a source of heat or ambient temperature above the flash point for the fuel/oxidizer mix, is able to sustain a rate of rapid oxidation that produces a chain reaction.
This is called the fire tetrahedron. Fire can not exist in the right proportions. For example, a flammable liquid will start burning only if the fuel and oxygen are in the right proportions; some fuel-oxygen mixes may require a catalyst, a substance, not consumed, when added, in any chemical reaction during combustion, but which enables the reactants to combust more readily. Once ignited, a chain reaction must take place whereby fires can sustain their own heat by the further release of heat energy in the process of combustion and may propagate, provided there is a continuous supply of an oxidizer and fuel. If the oxidizer is oxygen from the surrounding air, the presence of a force of gravity, or of some similar force caused by acceleration, is necessary to produce convection, which removes combustion products and brings a supply of oxygen to the fire. Without gravity, a fire surrounds itself with its own combustion products and non-oxidizing gases from the air, which exclude oxygen and extinguish the fire.
Because of this, the risk of fire in a spacecraft is small. This does not apply. Fire can be extinguished by removing any one of the elements of the fire tetrahedron. Consider a natural gas flame, such as from a stove-top burner; the fire can be extinguished by any of the following: turning off the gas supply, which removes the fuel source. In contrast, fire is intensified by increasing the overall rate of combustion. Methods to do this include balancing the input of fuel and oxidizer to stoichiometric proportions, increasing fuel and oxidizer input in this balanced mix, increasing the ambient temperature so the fire's own heat is better able to sustain combustion, or providing a catalyst, a non-reactant medium in which the fuel and oxidizer can more react. A flame is a mixture of reacting gases and solids emitting visible and sometimes ultraviolet light, the frequency spectrum of which depends on the chemical composition of the burning material and intermediate reaction products. In many cases, such as the burning of organic matter, for example wood, or the incomplete combustion of gas, incandescent solid particles called soot produce the familiar red-orange glow of "fire".
This light has a continuous spectrum. Complete combustion of gas has a dim blue color due to the emission of single-wavelength radiation from various electron transitions in the excited molecules formed in the flame. Oxygen is involved, but hydrogen burning in chlorine produces a flame, producing hydrogen chloride. Other possible combinations producing flames, amongst many, are fluorine and hydrogen, hydrazine and nitrogen tetroxide. Hydrogen and hydrazine/UDMH flames are