ratio of word probabilities predicted from brain for ant and refrigerator

ant	refrigerator
top 10 words in brain distribution (in article): animal species breed human hunt male plant bear population food	top 10 words in brain distribution (in article): light drink build house beer water store state design produce
top 10 words in brain distribution (not in article): cat wolf wild dog lion elephant tiger deer hybrid pet	top 10 words in brain distribution (not in article): city lamp wine material bottle wood street term town floor
times more probable under ant 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under refrigerator (words not in the model)
A phylogeny of the extant ant subfamilies. "'Ants'" are social insects of the family "'Formicidae'", and along with the related wasps and bees, they belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the mid-Cretaceous period between 110 and 130 million years ago and diversified after the rise of flowering plants. Today, more than 12,000 species are classified with upper estimates of about 14,000 species. They are easily identified by their elbowed antennae and a distinctive node-like structure that forms a slender waist. Ants form colonies that range in size from a few dozen predatory individuals living in small natural cavities to highly organised colonies which may occupy large territories and consist of millions of individuals. These larger colonies consist mostly of sterile wingless females forming castes of "workers", "soldiers", or other specialised groups. Ant colonies also have some fertile males called "drones" and one or more fertile females called "queens". The colonies are sometimes described as superorganisms because ants appear to operate as a unified entity, collectively working together to support the colony. Ants have colonised almost every landmass on Earth. The only places lacking indigenous ants are Antarctica and certain remote or inhospitable islands. Ants thrive in most ecosystems, and may form 15–25% of the terrestrial animal biomass. Their success has been attributed to their social organisation and their ability to modify habitats, tap resources, and defend themselves. Their long co-evolution with other species has led to mimetic, commensal, parasitic, and mutualistic relationships. Ant societies have division of labour, communication between individuals, and an ability to solve complex problems. These parallels with human societies have long been an inspiration and subject of study. Many human cultures make use of ants in cuisine, medication and rituals. Some species are valued in their role as biological pest control agents. However, their ability to exploit resources brings ants into conflict with humans, as they can damage crops and invade buildings. Some species, such as the red imported fire ant, are regarded as invasive species, since they have establish themselves in new areas where they may be accidentally introduced. Taxonomy and evolution. The family Formicidae belongs to the order Hymenoptera, which also includes sawflies, bees and wasps. Ants evolved from a lineage within the vespoid wasps. Phylogenetic analysis suggests that ants arose in the mid-Cretaceous period about 110 to 130 million years ago. After the rise of flowering plants about 100 million years ago they diversified and assumed ecological dominance around 60 million years ago. In 1966, E. O. Wilson and his colleagues identified the fossil remains of an ant ("Sphecomyrma freyi") that lived in the Cretaceous period. The specimen, trapped in amber dating back to more than 80 million years ago, has features of both ants and wasps. "Sphecomyrma" was probably a ground forager but some suggest on the basis of groups such as the Leptanillinae and Martialinae that primitive ants were likely to have been predators under the soil surface. During the Cretaceous period, only a few species of primitive ants ranged widely on the Laurasian super-continent (the northern hemisphere). They were scarce in comparison to other insects, representing about 1% of the insect population. Ants became dominant after adaptive radiation at the beginning of the Tertiary period. By the Oligocene and Miocene ants had come to represent 20–40% of all insects found in major fossil deposits. Of the species that lived in the Eocene epoch, approximately one in ten genera survive to the present. Genera surviving today comprise 56% of the genera in Baltic amber fossils (early Oligocene), and 92% of the genera in Dominican amber fossils (apparently early Miocene). Termites, though sometimes called "white ants", are not ants and belong to the order Isoptera. The termites are actually more closely related to cockroaches and mantids. The fact that ants and termites are both eusocial came about by Convergent evolution. Velvet ants look like large ants, but are wingless female wasps. Etymology. The word "ant" is derived from "ante" of Middle English which is derived from "æmette" and "emmett" of Old English and is related to the Old High German "āmeiza" from which comes "Ameise", the German word for ant. The family name "Formicidae" is derived from the Latin "formīca" ("ant") from which derived Portuguese "formiga", Spanish "hormiga", Romanian "furnică", French "fourmi", etc. Distribution and diversity. Ants are found on all continents except Antarctica and only a few large islands such as Greenland, Iceland, parts of Polynesia and the Hawaiian Islands lack native ant species. Ants occupy a wide range of ecological niches, and are able to exploit a wide range of food resources either as direct or indirect herbivores, predators and scavengers. Most species are omnivorous generalists but a few are specialist feeders. Their ecological dominance may be measured by their biomass, and estimates in different environments suggest that they contribute 15–20% (on average and nearly 25% in the tropics) of the total terrestrial animal biomass, which exceeds that of the vertebrates. Ants range in size from. Their colours vary; most are red or black, green is less common, and some tropical species have a metallic lustre. More than 12,000 species are currently known (with upper estimates of about 14,000), with the greatest diversity in the tropics. Taxonomic studies continue to resolve the classification and systematics of ants. Online databases of ant species, including AntBase and the Hymenoptera Name Server, help to keep track of the known and newly described species. The relative ease with which ants can be sampled and studied in ecosystems has made them useful as indicator species in biodiversity studies. Morphology. Ants are distinct in their morphology from other insects in having elbowed antennae, metapleural glands, and a strong constriction of their second abdominal segment into a node-like petiole. The head, mesosoma and metasoma or gaster are the three distinct body segments. The petiole forms a narrow waist between their mesosoma (thorax plus the first abdominal segment, which is fused to it) and gaster (abdomen less the abdominal segments in the petiole). The petiole can be formed by one or two nodes (the second alone, or the second and third abdominal segments). Like other insects, ants have an exoskeleton, an external covering that provides a protective casing around the body and a point of attachment for muscles, in contrast to the internal skeletons of humans and other vertebrates. Insects do not have lungs; oxygen and other gases like carbon dioxide pass through their exoskeleton through tiny valves called spiracles. Insects also lack closed blood vessels; instead, they have a long, thin, perforated tube along the top of the body (called the "dorsal aorta") that functions like a heart, and pumps haemolymph towards the head, thus driving the circulation of the internal fluids. The nervous system consists of a ventral nerve cord that runs the length of the body, with several ganglia and branches along the way reaching into the extremities of the appendages. An ant's head contains many sensory organs. Like most insects, ants have compound eyes made from numerous tiny lenses attached together. Ants' eyes are good for acute movement detection but do not give a high resolution. They also have three small ocelli (simple eyes) on the top of the head that detect light levels and polarisation. Compared to vertebrates, most ants have poor-to-mediocre eyesight and a few subterranean species are completely blind. Some ants such as Australia's bulldog ant, however, have exceptional vision. Two antennae ("feelers") are attached to the head; these organs detect chemicals, air currents and vibrations; they are also used to transmit and receive signals through touch. The head has two strong jaws, the mandibles, used to carry food, manipulate objects, construct nests, and for defence. In some species a small pocket (infrabuccal chamber) inside the mouth stores food, so it can be passed to other ants or their larvae. All six legs are attached to the mesosoma ("thorax"). A hooked claw at the end of each leg helps ants to climb and hang onto surfaces. Most queens and male ants have wings; queens shed the wings after the nuptial flight, leaving visible stubs, a distinguishing feature of queens. However, wingless queens (ergatoids) and males occur in a few species. The metasoma (the "abdomen") of the ant houses important internal organs, including those of the reproductive, respiratory (tracheae) and excretory systems. Workers of many species have their egg-laying structures modified into stings that are used for subduing prey and defending their nests. Polymorphism. In the colonies of a few ant species, there are physical castes—workers in distinct size-classes, called minor, median, and major workers. Often the larger ants have disproportionately larger heads, and correspondingly stronger mandibles. Such individuals are sometimes called "soldier" ants because their stronger mandibles make them more effective in fighting, although they are still workers and their "duties" typically do not vary greatly from the minor or median workers. In a few species the median workers are absent, creating a sharp divide between the minors and majors. Weaver ants, for example, have a distinct bimodal size distribution. Some other species show continuous variation in the size of workers. The smallest and largest workers in "Pheidologeton diversus" show nearly a 500-fold difference in their dry-weights. Workers cannot mate; however, because of the haplodiploid sex-determination system in ants, workers of a number of species can lay unfertilised eggs that become fully fertile haploid males. The role of workers may change with their age and in some species, such as honeypot ants, young workers are fed until their gasters are distended, and act as living food storage vessels. These food storage workers are called "repletes". This polymorphism in morphology and behaviour of workers was initially thought to be determined by environmental factors such as nutrition and hormones which led to different developmental paths; however, genetic differences between worker castes have been noted in "Acromyrmex" sp. These polymorphisms are caused by relatively small genetic changes; differences in a single gene of "Solenopsis invicta" can decide whether the colony will have single or multiple queens. The Australian jack jumper ant ("Myrmecia pilosula"), has only a single pair of chromosomes (males have just one chromosome as they are haploid), the lowest number known for any animal, making it an interesting subject for studies in the genetics and developmental biology of social insects. Development and reproduction. The life of an ant starts from an egg. If the egg is fertilised, the progeny will be female (diploid); if not, it will be male (haploid). Ants develop by complete metamorphosis with the larval stages passing through a pupal stage before emerging as an adult. The larva is largely immobile and is fed and cared for by workers. Food is given to the larvae by trophallaxis, a process in which an ant regurgitates liquid food held in its crop. This is also how adults share food, stored in the "social stomach", among themselves. Larvae may also be provided with solid food such as trophic eggs, pieces of prey and seeds brought back by foraging workers and may even be transported directly to captured prey in some species. The larvae grow through a series of moults and enter the pupal stage. The pupa has the appendages free and not fused to the body as in a butterfly pupa. The differentiation into queens and workers (which are both female), and different castes of workers (when they exist), is determined by the nutrition the larvae obtain. Larvae and pupae need to be kept at fairly constant temperatures to ensure proper development, and so are often moved around the various brood chambers within the colony. A new worker spends the first few days of its adult life caring for the queen and young. It then graduates to digging and other nest work, and later to defending the nest and foraging. These changes are sometimes fairly sudden, and define what are called temporal castes. An explanation for the sequence is suggested by the high casualties involved in foraging, making it an acceptable risk only for ants that are older and are likely to die soon of natural causes. Most ant species have a system in which only the queen and breeding females have the ability to mate. Contrary to popular belief, some ant nests have multiple queens while others can exist without queens. Workers with the ability to reproduce are called "gamergates" and colonies that lack queens are then called gamergate colonies; colonies with queens are said to be queen-right. The winged male ants, called drones, emerge from pupae along with the breeding females (although some species, like army ants, have wingless queens), and do nothing in life except eat and mate. During the short breeding period, the reproductives, excluding the colony queen, are carried outside where other colonies of similar species are doing the same. Then, all the winged breeding ants take flight. Mating occurs in flight and the males die shortly afterwards. Females of some species mate with multiple males. Mated females then seek a suitable place to begin a colony. There, they break off their wings and begin to lay and care for eggs. The females store the sperm they obtain during their nuptial flight to selectively fertilise future eggs. The first workers to hatch are weak and smaller than later workers, but they begin to serve the colony immediately. They enlarge the nest, forage for food and care for the other eggs. This is how new colonies start in most species. Species that have multiple queens may have a queen leaving the nest along with some workers to found a colony at a new site, a process akin to swarming in honeybees. Ant colonies can be long-lived. The queens can live for up to 30 years, and workers live from 1 to 3 years. Males, however, are more transitory, and survive only a few weeks. Ant queens are estimated to live 100 times longer than solitary insects of a similar size. Ants are active all year long in the tropics but, in cooler regions, survive the winter in a state of dormancy or inactivity. The forms of inactivity are varied and some temperate species have larvae going into the inactive state (diapause), while in others, the adults alone pass the winter in a state of reduced activity. Communication. Ants communicate with each other using pheromones. These chemical signals are more developed in ants than in other hymenopteran groups. Like other insects, ants perceive smells with their long, thin and mobile antennae. The paired antennae provide information about the direction and intensity of scents. Since most ants live on the ground, they use the soil surface to leave pheromone trails that can be followed by other ants. In species that forage in groups, a forager that finds food marks a trail on the way back to the colony; this trail is followed by other ants, these ants then reinforce the trail when they head back with food to the colony. When the food source is exhausted, no new trails are marked by returning ants and the scent slowly dissipates. This behaviour helps ants deal with changes in their environment. For instance, when an established path to a food source is blocked by an obstacle, the foragers leave the path to explore new routes. If an ant is successful, it leaves a new trail marking the shortest route on its return. Successful trails are followed by more ants, reinforcing better routes and gradually finding the best path. Ants use pheromones for more than just making trails. A crushed ant emits an alarm pheromone that sends nearby ants into an attack frenzy and attracts more ants from further away. Several ant species even use "propaganda pheromones" to confuse enemy ants and make them fight among themselves. Pheromones are produced by a wide range of structures including Dufour's glands, poison glands and glands on the hindgut, pygidium, rectum, sternum and hind tibia. Pheromones are also exchanged mixed with food and passed by trophallaxis, transferring information within the colony. This allows other ants to detect what task group ("e.g.", foraging or nest maintenance) other colony members belong to. In ant species with queen castes, workers begin to raise new queens in the colony when the dominant queen stops producing a specific pheromone. Some ants produce sounds by stridulation, using the gaster segments and their mandibles. Sounds may be used to communicate with colony members or with other species. Defence===. Ants attack and defend themselves by biting and, in many species, by stinging, often injecting or spraying chemicals like formic acid. Bullet ants ("Paraponera"), located in Central and South America, are considered to have the most painful sting of any insect, although it is usually not fatal to humans. This sting is given the highest rating on the Schmidt Sting Pain Index. The sting of Jack jumper ants can be fatal, and an antivenin has been developed. Fire ants, "Solenopsis" spp., are unique in having a poison sac containing piperidine alkaloids. Their stings are painful and can be dangerous to hypersensitive people. Trap-jaw ants of the genus "Odontomachus" are equipped with mandibles called trap-jaws, which snap shut faster than any other predatory appendages within the animal kingdom. One study of "Odontomachus bauri" recorded peak speeds of between 126 and 230 h (78 143 mph), with the jaws closing within 130 microseconds on average. The ants were also observed to use their jaws as a catapult to eject intruders or fling themselves backwards to escape a threat. Before the strike, the ant opens its mandibles extremely widely and locks them in this position by an internal mechanism. Energy is stored in a thick band of muscle and explosively released when triggered by the stimulation of sensory hairs on the inside of the mandibles. The mandibles also permit slow and fine movements for other tasks. Trap-jaws are also seen in the following genera: "Anochetus", "Orectognathus", and "Strumigenys", plus	A refrigerator'" (often called a "'fridge'" for short) is a cooling appliance comprising a thermally insulated compartment and a heat pump: a mechanism to transfer heat from it to the external environment, cooling the contents to a temperature below ambient. Refrigerators are extensively used to store foods which deteriorate at ambient temperatures; spoilage from bacterial growth and other processes is much slower at low temperatures. A device described as a "refrigerator" maintains a temperature a few degrees above the freezing point of water; a similar device which maintains a temperature below the freezing point of water is called a "'freezer'". The refrigerator is a relatively modern invention among kitchen appliances. It replaced the icebox, which had been a common household appliance for almost a century and a half prior. For this reason, a refrigerator is sometimes referred to as an "icebox". Freezers keep their contents frozen. They are used both in households and for commercial use. Most freezers operate around minus 18 °C (0 °F). Domestic freezers can be included as a compartment in a refrigerator, sharing the same mechanism or with a separate mechanism, or can be standalone units. Domestic freezers are generally upright units, resembling refrigerators, or chests, resembling upright units laid on their backs. Many modern freezers come with an icemaker. Commercial fridge and freezer units, which go by many other names, were in use for almost 40 years prior to the common home models. They used toxic ammonia gas systems, making them unsafe for home use. Practical household refrigerators were introduced in 1915 and gained wider acceptance in the United States in the 1930s as prices fell and non-toxic, non-flammable synthetic refrigerants such as Freon or R-12 were introduced. It is notable that while 60% of households in the US owned a refrigerator by the 1930s, it was not until 40 years later, in the 1970s, that the refrigerator achieved a similar level of penetration in the United Kingdom. History. Before the invention of the refrigerator, icehouses were used to provide cool storage for most of the year. Placed near freshwater lakes or packed with snow and ice during the winter, they were once very common. Using the environment to cool foodstuffs is still common today. On mountainsides, runoff from melting snow higher up is a convenient way to cool drinks, and during the winter months simply placing milk outside is sufficient to greatly extend its useful life. In the 11th century, the Persian physicist and chemist, Ibn Sina (Avicenna), invented the refrigerated coil, which condenses aromatic vapours. This was a breakthrough in distillation technology and he made use of it in his steam distillation process, which requires refrigerated tubing, to produce essential oils. The first known artificial refrigeration was demonstrated by William Cullen at the University of Glasgow in 1748. Between 1805, when Oliver Evans designed the first refrigeration machine that used vapor instead of liquid, and 1902 when Willis Haviland Carrier demonstrated the first air conditioner, scores of inventors contributed many small advances in cooling machinery. In 1850 or 1851, Dr. John Gorrie demonstrated an ice maker. In 1857, Australian James Harrison introduced vapor-compression refrigeration to the brewing and meat packing industries. Ferdinand Carré of France developed a somewhat more complex system in 1859. Unlike earlier compression-compression machines, which used air as a coolant, Carré's equipment contained rapidly expanding ammonia. The absorption refrigerator was invented by Baltzar von Platen and Carl Munters in 1922, while they were still students at the Royal Institute of Technology in Stockholm, Sweden. It became a worldwide success and was commercialized by Electrolux. Other pioneers included Charles Tellier, David Boyle, and Raoul Pictet. At the start of the 20th Century, about half of households in the United States relied on melting ice (in an icebox) to keep food cold, while the remaining half had no cooled storage at all. The ice used for household storage was expensive because ice had to be cut from winter ponds (or mechanically produced), stored centrally until needed, and delivered regularly. In a few exceptional cases, mechanical refrigeration systems had been adapted by the start of the 20th century for use in the homes of the very wealthy, and might be used for cooling both living and food storage areas. One early system was installed at the mansion of Walter Pierce, an oil company executive. Marcel Audiffren of France championed the idea of a refrigerating machine for cooling and preserving foods at home. His U.S. patents, issued in 1895 and 1908, were purchased by the American Audiffren Refrigerating Machine Company. Machines based on Audiffren's sulfur dioxide process were manufactured by General Electric in Fort Wayne, Indiana and marketed by the Johns-Manville company. The first unit was sold in 1911. Audiffren machines were expensive, selling for about $1,000 — about twice as much as the cost of an automobile at that time. General Electric sought to develop refrigerators of its own, and in 1915 the first "Guardian" unit was assembled in a back yard wash house as a predecessor to the Frigidaire. In 1916 Kelvinator and Servel introduced two units among a field of competing models. This number increased to 200 by 1920. In 1918, Kelvinator had a model with automatic controls. These home units usually required the installation of the mechanical parts, motor and compressor, in the basement or an adjacent room while the cold box was located in the kitchen. There was a 1922 model that consisted of a wooden cold box, water-cooled compressor, an ice cube tray and a 9 cubic foot compartment for $714. (A 1922 Model-T Ford cost about $450.) In 1923 Frigidaire introduced the first self-contained unit. About this same time porcelain covered metal cabinets began to appear. Ice cube trays were introduced more and more during the 1920s; up to this time freezing was not a function of the modern refrigerator. The first refrigerator to see widespread use was the General Electric "Monitor-Top" refrigerator introduced in 1927. The compressor assembly, which emitted a substantial amount of heat, was placed above the cabinet, and surrounded with a decorative ring. Over 1,000,000 units were produced. As the refrigerating medium, these refrigerators used either sulfur dioxide, which is corrosive to the eyes and may cause loss of vision, painful skin burns and lesions, or methyl formate, which is highly flammable, harmful to the eyes, and toxic if inhaled or ingested. Many of these units are still functional today. These cooling systems cannot be recharged with the hazardous original refrigerants if they leak or break down. The introduction of freon expanded the refrigerator market during the 1930s, and freezer units became more common during the 1940s. Home units did not go into mass production until after WWII. The 1950s and 1960s saw technical advances like automatic defrosting and automatic ice making. Developments of the 1970s and 80s brought about more efficient refrigerators, and environmental issues banned the use of CFC (freon) refrigerants used in sealed systems. Early refrigerator models (1916 and on) featured a cold compartment for ice cube trays. Successful processing of fresh vegetables through freezing began in the late 1920s by the Postum Company (the forerunner of General Foods) which had acquired the technology when it bought the rights to Clarence Birdseye's successful fresh freezing methods. The first successful example of the benefits of frozen foods occurred when General Foods heiress Marjorie Merriweather Post (then wife of Joseph E. Davies, United States Ambassador to the Soviet Union) deployed commercial-grade freezers to Spaso House, the US Embassy in Moscow in advance of the Davies’ arrival. Post, fearful of the food processing safety observed in the USSR, then fully stocked the freezers with products from General Foods' Birdseye unit. The frozen food stores allowed the Davies to lavishly entertain and serve fresh frozen foods that would otherwise be out of season. Upon returning from Moscow, Post (who resumed her maiden name after divorcing Davies) directed General Foods to market frozen product to upscale restaurants. Introduction of home freezer units occurred in the United States in 1940, and frozen foods began to make the transition from luxury to necessity. Design. Refrigerators work by the use of heat pumps operating in a refrigeration cycle. An industrial refrigerator is simply a refrigerator used in an industrial setting, usually in a restaurant or supermarket. It may consist of either a cooling compartment only (a larger refrigerator) or a freezing compartment only (a freezer) or both. The industry sometimes refers to such units as a “cold box” or a “walk-in.” The dual compartment was introduced commercially by General Electric in 1939. The vapor compression cycle is used in most household refrigerators. In this cycle, a circulating refrigerant such as R134a enters the compressor as a low-pressure vapor at its boiling point. The vapor is compressed and exits the compressor as a superheated high-pressure vapor. The superheated vapor travels through part of the condenser which removes the superheat by cooling the vapor. The vapor travels through the remainder of the condenser and is condensed into a liquid at its boiling point. Before the refrigerant leaves the condenser it will have been subcooled (i.e. below its boiling point). The subcooled liquid refrigerant passes through the metering (or throttling) device where its pressure abruptly decreases. The decrease in pressure results in the flash evaporation and auto-refrigeration of a portion of the liquid (typically, less than half of the liquid flashes). The cold and partially vaporized refrigerant travels through the coil or tubes in the evaporator. There, a fan circulates room air across the coil or tubes, and the refrigerant is totally vaporized, extracting heat from the air which is then returned to the food compartment. The refrigerant vapor, now slightly superheated, returns to the compressor inlet to continue the thermodynamic cycle. An absorption refrigerator works differently from a compressor refrigerator, using a source of heat, such as combustion of liquefied petroleum gas, or solar thermal energy. These heat sources are much quieter than the compressor motor in a typical refrigerator. The Peltier effect uses electricity directly to pump heat; refrigerators using this effect are sometimes used for camping, or where noise is not acceptable. They are totally silent, but less energy-efficient than other methods. Other uses of an absorption refrigerator (or "chiller") would include large systems used in office buildings or complexes such as hospitals and universities. These large systems are used to chill a brine solution that is circulated through the building. Other alternatives to the vapor-compression cycle but not in current use include thermionic, vortex tube, air cycle, magnetic cooling, Stirling cycle, Malone refrigeration, acoustic cooling, pulse tube and water cycle systems. Features. Early freezer units accumulated ice crystals around the freezing units. This was a result of humidity introduced into the units when the doors to the freezer were opened. This frost buildup required periodic thawing ("defrosting") of the units to maintain their efficiency. Advances in automatic defrosting eliminating the thawing task were introduced in the 1950s. Also, early units featured freezer compartments located within the larger refrigerator, and accessed by opening the refrigerator door, and then the smaller internal freezer door; units featuring entirely separate freezer compartment were introduced in the early 1960s, becoming the industry standard by the middle of that decade. Later advances included automatic ice units and self compartmentalized freezing units. An increasingly important environmental concern is the disposal of old refrigerators- initially because of the freon coolant damaging the ozone layer, but as the older generation of refrigerators disappears it is the destruction of CFC-bearing insulation which causes concern. Modern refrigerators usually use a refrigerant called HFC-134a (1,2,2,2-tetrafluoroethane), which has no ozone layer depleting properties, in place of freon. Disposal of discarded refrigerators is regulated, often mandating the removal of doors: children playing hide-and-seek have been asphyxiated while hiding inside a discarded refrigerator. This was particularly true for the older models that had latching doors. More modern units use a magnetic door gasket to hold the door sealed but can be pushed open from the inside. This gasket was invented by a man named Herman C. Ells Sr. Who didn't want children to lose their lives. He never gained recognition for his work, being a humble man only wanting to save lives. However, children can be unwittingly harmed by hiding inside any discarded refrigerator. Types of domestic refrigerators. Domestic refrigerators and freezers for food storage are made in a range of sizes. Among the smallest is a 4 L Peltier fridge advertised as being able to hold 6 cans of beer. A large domestic fridge stands as tall as a person and may be about 1 m wide with a capacity of 600 L. Some models for small households fit under kitchen work surfaces, usually about 86 cm high. Fridges may be combined with freezers, either stacked with fridge or freezer above, below, or side by side. A fridge without a true freezer may have a small compartment to make ice. Freezers may have drawers to store food in, or they may have no divisions (chest freezers). Fridges and freezers may be free-standing, or built into a kitchen. Refrigeration units for commercial and industrial applications can be made any size, shape or style to fit customer needs. Energy efficiency. An auto-defrost unit uses a blower fan to keep moisture out of the unit. It also has a heating coil beneath the evaporator that periodically heats the freezer compartment and melts any ice buildup. Some units also have heaters in the side of the door to keep the unit from "weeping." Manual defrost units are available in used-appliance shops or by special order. Refrigerators used to consume more energy than any other home appliance, but in the last twenty years great strides have been made to make refrigerators more energy efficient. In the early 1990s a competition was held among the major manufacturers to encourage energy efficiency. Current models that are Energy Star qualified use 50 percent less energy than models made before 1993. The most energy-efficient unit made in the US is designed to run on 12 or 110 volts, and consumes about half a kilowatt-hour per day. But even ordinary units are quite efficient; some smaller units use little more than one kilowatt-hour per day. Larger units, especially those with large freezers and icemakers, may use as much as 4 kWh per day. Among the different styles of refrigerators, top-freezer models are more efficient than bottom-freezer models of the same capacity, which are in turn more efficient than side-freezer models. Models with through-the-door ice units are less efficient than those without. Dr. Tom Chalko in Australia has developed an external thermostat to convert any chest freezer into a chest fridge using only about 0.1kWh per day--the amount of energy used by a 100 watt light bulb in one hour. Scientists at Oxford University have reconstructed a refrigerator invented in 1930 by Albert Einstein in their efforts to replace current technologies with energy efficient green technology. The Einstein refrigerator operates without electricity and uses no moving parts or greenhouse gases. Impact on lifestyle. The invention of the refrigerator has allowed the modern family to purchase, store, freeze, prepare and preserve food products in a fresh state for much longer periods of time than was previously possible. For the majority of families without a sizeable garden in which to grow vegetables and raise animals, the advent of the refrigerator along with the modern supermarket led to a vastly more varied diet and improved health resulting from improved nutrition. Dairy products, meats, fish, poultry and vegetables can be kept refrigerated in the same space within the kitchen (although raw meat should be kept separate from other foodstuffs for reasons of hygiene). The refrigerator allows families to consume more salads, fresh fruits and vegetables during meals without having to own a garden or an orchard. Exotic foodstuffs from far-off countries that have been imported by means of refrigeration can be enjoyed in the home because of the availability of domestic refrigeration. The luxury of freezing allows households to purchase more foods in bulk that can be eaten at leisure while the bulk purchase provides cost savings (see economies of scale). Ice cream, a popular commodity of the 20th century, was previously only available by traveling long distances to where the product was made fresh and had to be eaten on the spot. Now it is a common food item. Ice on-demand not only adds to the enjoyment of cold drinks, but is useful in first-aid applications, not to mention cold packs that can be kept frozen for picnics or in case of emergency. Temperature zones and ratings. Some refrigerators are now divided into four zones to store different types of food: The capacity of a refrigerator is measured in either litres or cubic feet (US). Typically the volume of a combined fridge-freezer is split to 100 litres (3.53 cubic feet) for the freezer and 140 litres (4.94 cubic feet) for the refrigerator, although these values are highly variable. Temperature settings for refrigerator and freezer compartments are often given arbitrary numbers (for example, 1 through 9, warmest to coldest) by manufacturers, but generally 2 to 8 °C (36 to 46 °F) is ideal for the refrigerator compartment and -18 °C (0 °F) for the freezer. Some refrigerators require a certain external temperature (60 °F) to run properly. This can be an issue when placing a refrigerator in an unfinished area such as a garage. European freezers, and refrigerators with a freezer compartment, have a four star rating system to grade freezers. Although both the three and four star ratings specify the same minimum temperature of -18°C, only a four star freezer is intended to be used for freezing fresh food. Three (or fewer) stars are used for frozen food compartments which are only suitable for storing frozen food; introducing fresh food into such a compartment is likely to result in unacceptable temperature rises.