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Barr body

A Barr body (named after discoverer Murray Barr) or X-chromatin is an inactive X chromosome. In species with XY sex-determination (including humans), females typically have two X chromosomes, and one is rendered inactive in a process called lyonization. Errors in chromosome separation can also result in male and female individuals with extra X chromosomes. The Lyon hypothesis states that in cells with multiple X chromosomes, all but one are inactivated early in embryonic development in mammals. The X chromosomes that become inactivated are chosen randomly, except in marsupials and in some extra-embryonic tissues of some placental mammals, in which the X chromosome from the sperm is always deactivated.

In humans with euploidy, a genotypical female (46, XX karyotype) has one Barr body per somatic cell nucleus, while a genotypical male (46, XY) has none. The Barr body can be seen in the interphase nucleus as a darkly staining small mass in contact with the nucleus membrane. Barr bodies can be seen in neutrophils at the rim of the nucleus.

In humans with more than one X chromosome, the number of Barr bodies visible at interphase is always one fewer than the total number of X chromosomes. For example, people with Klinefelter syndrome (47, XXY) have a single Barr body, and people with a 47, XXX karyotype have two Barr bodies.

Mechanism
Someone with two X chromosomes (such as the overwhelming majority of human females) has only one Barr body per somatic cell, while someone with one X chromosome (such as most human males) has none.

Mammalian X-chromosome inactivation is initiated from the X inactivation centre or Xic, usually found near the centromere. The center contains twelve genes, seven of which code for proteins, five for untranslated RNAs, of which only two are known to play an active role in the X inactivation process, Xist and Tsix. The centre also appears to be important in chromosome counting: ensuring that random inactivation only takes place when two or more X-chromosomes are present. The provision of an extra artificial Xic in early embryogenesis can induce inactivation of the single X found in male cells.

The roles of Xist and Tsix appear to be antagonistic. The loss of Tsix expression on the future inactive X chromosome results in an increase in levels of Xist around the Xic. Meanwhile, on the future active X Tsix levels are maintained; thus the levels of Xist remain low. This shift allows Xist to begin coating the future inactive chromosome, spreading out from the Xic. In non-random inactivation this choice appears to be fixed and current evidence suggests that the maternally inherited gene may be imprinted. Variations in Xi frequency have been reported with age, pregnancy, the use of oral contraceptives, fluctuations in menstrual cycle and neoplasia.

It is thought that this constitutes the mechanism of choice, and allows downstream processes to establish the compact state of the Barr body. These changes include histone modifications, such as histone H3 methylation (i.e. H3K27me3 by PRC2 which is recruited by Xist) and histone H2A ubiquitination, as well as direct modification of the DNA itself, via the methylation of CpG sites. These changes help inactivate gene expression on the inactive X-chromosome and to bring about its compaction to form the Barr body.

Reactivation of a Barr body is also possible, and has been seen in breast cancer patients. One study showed that the frequency of Barr bodies in breast carcinoma were significantly lower than in healthy controls, indicating reactivation of these once inactivated X chromosomes.

title: Barr body


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Smoking (cooking)

Smoking is the process of flavoring, browning, cooking, or preserving food by exposing it to smoke from burning or smoldering material, most often wood. Meat, fish, and lapsang souchong tea are often smoked.

In Europe, alder is the traditional smoking wood, but oak is more often used now, and beech to a lesser extent. In North America, hickory, mesquite, oak, pecan, alder, maple, and fruit tree woods, such as apple, cherry, and plum, are commonly used for smoking. Other biomass besides wood can also be employed, sometimes with the addition of flavoring ingredients. Chinese tea-smoking uses a mixture of uncooked rice, sugar, and tea, heated at the base of a wok.

Some North American ham and bacon makers smoke their products over burning corncobs. Peat is burned to dry and smoke the barley malt used to make Scotch whisky and some beers. In New Zealand, sawdust from the native manuka (tea tree) is commonly used for hot-smoking fish. In Iceland, dried sheep dung is used to cold-smoke fish, lamb, mutton, and whale.

Historically, farms in the Western world included a small building termed the "smokehouse", where meats could be smoked and stored. This was generally well separated from other buildings both because of fire danger and smoke emanations. The smoking of food may possibly introduce polycyclic aromatic hydrocarbons, which may lead to an increased risk of some types of cancer; however, this association is still being debated.

Smoking can be done in four ways: cold smoking, warm smoking, hot smoking, and through the employment of a smoke flavoring, such as liquid smoke. However, these methods of imparting smoke only affect the food surface, and are unable to preserve food, thus, smoking is paired with other microbial hurdles, such as chilling and packaging, to extend food shelf-life.

History
The smoking of food likely dates back to the paleolithic era. As simple dwellings lacked chimneys, these structures would probably have become very smoky. It is supposed that early humans would hang meat up to dry and out of the way of pests, thus accidentally becoming aware that meat that was stored in smoky areas acquired a different flavor, and was better preserved than meat that simply dried out. This process was later combined with pre-curing the food in salt or salty brine, resulting in a remarkably effective preservation process that was adapted and developed by numerous cultures around the world. Until the modern era, smoking was of a more "heavy duty" nature as the main goal was to preserve the food. Large quantities of salt were used in the curing process and smoking times were quite long, sometimes involving days of exposure.

The advent of modern transportation made it easier to transport food products over long distances and the need for the time and material intensive heavy salting and smoking declined. Smoking became more of a way to flavor than to preserve food. In 1939 a device called the Torry Kiln was invented at the Torry Research Station in Scotland. The kiln allowed for uniform mass-smoking and is considered the prototype for all modern large-scale commercial smokers. Although refinements in technique and advancements in technology have made smoking much easier, the basic steps involved remain essentially the same today as they were hundreds if not thousands of years ago.

Cold smoking
Cold smoking differs from hot smoking in that it does not cook anything; when cold smoking is finished, the food is still raw. Smokehouse temperatures for cold smoking are typically between 20 and 30 C. In this temperature range, foods take on a smoked flavor, but remain relatively moist. Since cold smoking does not cook foods, meats should be fully cured before cold smoking. Cold smoking can be used as a flavor enhancer for items such as cheese or nuts, along with meats such as chicken breasts, beef, pork chops, salmon, scallops, and steak. The item is often hung in a dry environment first to develop a pellicle; it can then be cold smoked up to several days to ensure it absorbs the smoke flavor. Some cold smoked foods are baked, grilled, steamed, roasted, or sautéed before eating.

Cold smoking meats should not be attempted at home, according to the US National Center for Home Food Preservation: "Most food scientists cannot recommend cold-smoking methods because of the inherent risks."

Cold smoking meats should only be attempted by personnel certified in HACCP [...] to ensure that it is safely prepared.

Warm smoking
Warm smoking exposes foods to temperatures of 25 –.

Hot smoking
Hot smoking cooks foods and simultaneously flavors them with smoke in a controlled environment such as a smoker oven or smokehouse. It requires consistent control of both the temperature of the food and the amount of smoke being applied to it. Some smokers have a heat source built into them, while others use the heat from a stove-top or oven. Like cold smoking, the item may be hung first to develop a pellicle; it is then smoked from 1 hour to as long as 24 hours. Although foods that have been hot smoked are often reheated or further cooked, they are typically safe to eat without further cooking. The temperature range for hot smoking is usually between 52 and 80 C. Foods smoked in this temperature range are usually fully cooked, but still moist and flavorful. At smoker temperatures hotter than 185 °F, foods can shrink excessively, buckle, or even split. Smoking at high temperatures also reduces yield, as both moisture and fat are cooked away.

Liquid smoke
Liquid smoke, a product derived from smoke compounds in water, is applied to foods through spraying or dipping.

Smoke roasting
Smoke-roasting refers to any process that has the attributes of both roasting and smoking. This smoking method is sometimes referred to as barbecuing or pit-roasting. It may be done in a smoke-roaster, a closed wood-fired oven, or a barbecue pit, any smoker that can reach above 121 C, or in a conventional oven by placing a pan filled with hardwood chips on the floor of the oven so that the chips can smolder and produce a smoke-bath. In North America, this smoking method is commonly referred to as "barbecuing", "pit baking", or "pit roasting".

Wood smoke

Hardwoods are made up mostly of three materials: cellulose, hemicellulose, and lignin. Cellulose and hemicellulose are the basic structural material of the wood cells; lignin acts as a kind of cell-bonding glue. Some softwoods, especially pines and firs, hold significant quantities of resin, which produces a harsh-tasting soot when burned; these woods are not often used for smoking.

Cellulose and hemicellulose are aggregate sugar molecules; when burnt, they effectively caramelize, producing carbonyls, which provide most of the color components and sweet, flowery, and fruity aromas. Lignin, a highly complex arrangement of interlocked phenolic molecules, also produces a number of distinctive aromatic elements when burnt, including smoky, spicy, and pungent compounds such as guaiacol, phenol, and syringol, and sweeter scents such as the vanilla-scented vanillin and clove-like isoeugenol. Guaiacol is the phenolic compound most responsible for the "smoky" taste, while syringol is the primary contributor to smoky aroma. Wood also contains small quantities of proteins, which contribute roasted flavors. Many of the odor compounds in wood smoke, especially the phenolic compounds, are unstable, dissipating after a few weeks or months.

A number of wood smoke compounds act as preservatives. Phenol and other phenolic compounds in wood smoke are both antioxidants, which slow rancidification of animal fats, and antimicrobials, which slow bacterial growth. Other antimicrobials in wood smoke include formaldehyde, acetic acid, and other organic acids, which give wood smoke a low pH—about 2.5. Some of these compounds are toxic to people as well, and may have health effects in the quantities found in cooking applications.

Since different species of trees have different ratios of components, various types of wood do impart a different flavor to food. Another important factor is the temperature at which the wood burns. High-temperature fires see the flavor molecules broken down further into unpleasant or flavorless compounds. The optimal conditions for smoke flavor are low, smoldering temperatures between 300 and 400 C. This is the temperature of the burning wood itself, not of the smoking environment, which uses much lower temperatures. Woods that are high in lignin content tend to burn hot; to keep them smoldering requires restricted oxygen supplies or a high moisture content. When smoking using wood chips or chunks, the combustion temperature is often raised by soaking the pieces in water before placing them on a fire.

Offset

The main characteristics of the offset smoker are that the cooking chamber is usually cylindrical in shape, with a shorter, smaller diameter cylinder attached to the bottom of one end for a firebox. To cook the meat, a small fire is lit in the firebox, where airflow is tightly controlled. The heat and smoke from the fire are drawn through a connecting pipe or opening into the cooking chamber.

The heat and smoke cook and flavor the meat before escaping through an exhaust vent at the opposite end of the cooking chamber. Most manufacturers' models are based on this simple but effective design, and this is what most people picture when they think of a "BBQ smoker". Even large capacity commercial units use this same basic design of a separate, smaller fire box and a larger cooking chamber.

Upright drum

The upright drum smoker (also referred to as an ugly drum smoker or UDS) is exactly what its name suggests: an upright steel drum that has been modified for the purpose of pseudo-indirect hot smoking. There are many ways to accomplish this, but the basics include the use of a complete steel drum, a basket to hold charcoal near the bottom, and a cooking rack (or racks) near the top, all covered by a vented lid of some sort. These smokers have been built using many different sizes of steel drums, such as 30 gal, 55 gal, and 85 gal, but the most popular size is the common 55-gallon drum.

This design is similar to smoking with indirect heat due to the distance between the coals and the cooking racks, which is typically 24 in. The temperature is controlled by limiting the air intake at the bottom of the drum, and allowing a similar amount of exhaust out of vents in the lid. UDSs use their fuel very efficiently, and are flexible in their ability to produce proper smoking conditions with or without the use of a water pan or drip pan.

Vertical water

A vertical water smoker (also referred to as a bullet smoker because of its shape) is a variation of the upright drum smoker. It uses charcoal or wood to generate smoke and heat, and contains a water bowl between the fire and the cooking grates. The water bowl serves to maintain optimal smoking temperatures and also adds humidity to the smoke chamber. It also creates an effect in which the water vapor and smoke condense together, which adds flavor to smoked foods. In addition, the bowl catches any drippings from the meat that may cause a flare-up. Vertical water smokers are extremely temperature stable and require very little adjustment once the desired temperature has been reached. Because of their relatively low cost and stable temperature, they are sometimes used in barbecue competitions where propane and electric smokers are not allowed.

Propane

A propane smoker is designed to allow the smoking of meat in a somewhat more temperature controlled environment. The primary differences are the sources of heat and of the smoke. In a propane smoker, the heat is generated by a gas burner directly under a steel or iron box containing the wood or charcoal that provides the smoke. The steel box has few vent holes, on the top of the box only. By starving the heated wood of oxygen, it smokes instead of burning. Any combination of woods and charcoal may used. This method uses much less wood but does require propane fuel.

Smoke box
This more traditional method uses a two-box system: a fire box and a food box. The fire box is typically adjacent or under the cooking box, and can be controlled to a finer degree. The heat and smoke from the fire box exhausts into the food box, where it is used to cook and smoke the meat. These may be as simple as an electric heating element with a pan of wood chips placed on it, although more advanced models have finer temperature controls.

Electric smokers

The most convenient of the various types of smokers are the insulated electric smokers. These devices house a heating element that can maintain temperatures ranging from that required for a cold smoke all the way up to 135 C with little to no intervention from the user. Although wood chunks, pellets, and even in some cases automatically fed wood pucks are used to generate smoke, the amount of flavor obtained is less than traditional wood or charcoal smokers.

Trench

In this method the firebox is a narrow trench cut down a slope pointing into the prevailing wind. The middle part of the trench is covered over to make it into a tunnel. At the upper end of the trench is a vertical framework covered to form a chimney within which is placed the rack of foodstuff. At the lower upwind end of the trench is lit a small smokey fire, and sustained day and night until the foodstuff is cured.

Commercial smokehouse
Commercial smokehouses, mostly made from stainless steel, have independent systems for smoke generation and cooking. Smoke generators use friction, an electric coil or a small flame to ignite sawdust on demand. Heat from steam coils or gas flames is balanced with live steam or water sprays to control the temperature and humidity. Elaborate air handling systems reduce hot or cold spots, to reduce variation in the finished product. Racks on wheels or rails are used to hold the product and facilitate movement.

Pellet smokers
A pellet smoker is a temperature controlled smoker that burns wood pellets made of dried-out sawdust, about an inch long and 1/4 inch wide. The wood pellets are stored in a gravity-fed hopper that feeds into a motor-controlled auger by the temperature regulator. This auger pushes the pellets into the fire pot. An ignition rod within the auger ignites the pellets where a combustion fan keeps them smouldering. The motor and the combustion fan regulate the temperature of the smoker by feeding it more pellets and increasing airflow in the auger. Above the auger is a heat shield to disperse the direct heat before it reaches the heat box to allow the wood smoke to keep the heat box at an even temperature throughout. The heat sensor inside the heat box relays the current temperature inside the box back to the temperature regulator that controls the fan speed and pellet hopper motor, which either increase or decrease the amount of pellets in the auger or the amount of air available to the fire to maintain the desired temperature for the cook.

The popularity of this type of smoker is on the rise after many BBQ pit-masters began using them in barbecue competitions.

Preservation

Smoke is both an antimicrobial and antioxidant, but it is insufficient for preserving food because it does not penetrate far into meat or fish; therefore, if the food is to be preserved, smoking is typically combined with salt-curing or drying.

Smoking is especially useful for oily fish, as its antioxidant properties inhibit surface fat rancidification and delay oxygen from reaching the interior fat and degrading it. Some heavily salted, long-smoked fish can keep without refrigeration for weeks or months.

Artificial smoke flavoring (such as liquid smoke) can be purchased to mimic smoking's flavor, but such products have no preservative qualities.

Competitive smoking
Competitive BBQ smoking is becoming increasingly popular, especially in the southern United States, where BBQ enthusiasts come together over a weekend to cook various cuts of meat such as a whole hog or a beef brisket.

Organisations such as Kansas City Barbeque Society run competitions all over America.

Health concerns
Regularly consuming smoked meats and fish may increase the risk of several types of cancer.

List of smoked foods and beverages

Some of the more common smoked foods and beverages include:
 * Beverages
 * Lapsang souchong tea leaves are smoked and dried over pine or cedar fires
 * Malt beverages
 * The malt used to make whisky
 * Rauchbier (smoked beer)
 * Grodziskie (smoked beer)
 * Maté, in the traditional preparation yerba mate leaves are smoked

 * Fruit and vegetables
 * Capsicums: chipotles (smoked, ripe jalapeños), paprika
 * Prunes (dried plums) can be smoked while drying
 * Wumei are smoked plum fruits
 * Iburi-gakko are a smoked daikon pickle from Akita Prefecture, Japan

 * Meat, fish, and cheese
 * Beef
 * Pastrami (pickled, spiced and smoked beef brisket)
 * Pork
 * Bacon
 * Ham
 * Bakkwa
 * Turkey
 * Chicken
 * Sausage
 * Salami
 * Jerky
 * Fish
 * Eel popular in eastern/northern Europe
 * Traditional Grimsby smoked fish (cod and haddock)
 * Haddock and Arbroath smokies (haddock)
 * Buckling, kippers and bloater (herring)
 * Salmon
 * Mackerel
 * Bivalves including oysters and mussels.
 * Egg (eggs and fish eggs)
 * Cheese
 * Adyghe Qwaye (Circassian)
 * Gouda
 * Gruyère
 * Oscypek
 * Other proteins
 * Nuts
 * Tofu

 * Spices
 * Paprika
 * Salt

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Smoking (cooking)


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Steaming

Steaming is a method of cooking using steam. This is often done with a food steamer, a kitchen appliance made specifically to cook food with steam, but food can also be steamed in a wok. In the American Southwest, steam pits used for cooking have been found dating back about 5,000 years. Steaming is considered a healthy cooking technique that can be used for many kinds of foods.

Because steaming can be achieved by heating less water or liquid, and because of the excellent thermodynamic heat transfer properties of steam, steaming can be as fast, or faster, than cooking in boiling water, as well as being more energy efficient.

History
Some of the world's earliest examples of steam cooking were found in China's Yellow River Valley; early steam cookers made of stoneware have been found dating back as far as 5,000 BCE. And also in Gunma Prefecture, Japan, created during the Stone Age. Some of the earliest examples of steam cooking have been found in Italy and Sardinia, created during the Bronze Age, and in Cochise County, Arizona, where steam pits were used for cooking about 10,000 years ago. From the eighth century CE, thin cypress strips were used to make steamers; today, their slatted bases are constructed from bamboo. The classic steamer has a chimney in the center, which distributes the steam among the tiers.

While steaming has not caught up in the west for assorted dishes, the technique has been heavily popularized worldwide by Chinese and East Asian cuisine. The two main classic steamers feature the ancient bamboo steamer as well as the modern metal (aluminium or stainless steel) steamer, with the difference being that the bamboo lid takes longer to heat up but absorbs excess moisture and allows heat to condense again over the delicate food. Other developments were the creation of microwaveable silicone steamers and plastic-hybrid steamers.

Method
Steaming works by boiling water continuously, causing it to vaporize into steam; the steam then carries heat to the nearby food, thus cooking the food. The food is kept separate from the boiling water but has direct contact with the steam, resulting in a moist texture to the food. This differs from double boiling, in which food is not directly exposed to steam, or pressure cooking, which uses a sealed vessel but is capable of pressure steaming or submerging.

Such cooking is most often done by placing the food in a food steamer, typically a circular container made of metal, wood, or bamboo. The steamer usually has a lid that is placed on top of the container during cooking to allow the steam to cook through the food. When a steamer is unavailable, food can be steamed inside a wok, supported over boiling water in the bottom of the wok by a metal frame. Some modern home microwave ovens include a structure to cook food with steam vapor produced in a separate water container, providing a similar result to being cooked on a stove. There are also specialized steam ovens available.

Steamed foods

In Japan, glutinous rice is steamed to prepare mochi rice cakes. Traditional Japanese sweets or wagashi making involves steaming rice or wheat dough for making mochigashi and manju.

In Western cooking, steaming is most often used to cook vegetables—it is rarely used to cook meats. However, steamed clams are prepared by steaming. With Chinese cuisine, vegetables are usually stir fried or blanched and seldom steamed. Seafood and meat dishes are steamed. For example: Steamed whole fish, steamed crab, steamed pork spare ribs, steamed ground pork or beef, steamed chicken and steamed goose.

Rice can be steamed too, although in Chinese cooking this is simply referred to as "cooking" rather than "steaming". In Thailand steaming is the definition of minimalist cooking. Wheat foods are steamed as well. Examples include buns and Chinese steamed cakes. Similarly, in Mexican and Central American cuisine, tamales are made by steaming a dough made from nixtamalized maize (called masa) in wrappers made from corn husks or banana leaves; the dough can be stuffed or left plain.

Steamed meat dishes (except fish and some dim sum) are less common in Chinese restaurants than in traditional home cooking, because meats usually require longer cooking times to steam than to stir fry. Commercially sold frozen foods (such as dim sum) formerly had instructions to reheat by steaming, until the rise in popularity of home microwave ovens, which have considerably shorter cooking times.

Chinese dishes

Staple foods
 * Mantou, steamed buns
 * Wotou, Chinese cornbread

Dim sum
 * Siu mai, meat dumplings
 * Har gao, shrimp dumplings
 * Baozi, filled buns
 * Lion's head meatballs
 * Steamed meatballs
 * Pearl meatballs, pork meatballs covered in sticky rice

Rice
 * Steamed rice with crab, Fujian cuisine called 蠘飯 (蟳飯)
 * Fenzhengrou (粉蒸肉): Steamed pork with rice flour

Seafood
 * Fish: Chinese perch, grouper, Japanese black porgy
 * Crab: Chinese mitten crab, Shanghai cuisine for the autumn

Soup
 * Weitang: Steamed pork rib soup, Jiangxi cuisine
 * Buddha Jumps Over the Wall: Fujian cuisine
 * Winter Melon Soup: Using a hollowed out and sculpted gourd as a vessel
 * Qi Guoji Steamed Chicken Soup: Chicken soup cook in a double steamer, Yunnan cuisine

Sweets
 * Double skin milk, said to be made in the 1850s in Daliang in Foshan, Guangdong
 * Guilinggao: also known as Turtle Jelly, a jelly-like Chinese medicine, also sold as a dessert

Others
 * Chinese steamed eggs similar to custard with local variety of ingredients and vessels.

Japanese dishes

 * Glutinous rice. Instead of boiling, glutinous rice is steamed to eat. Okowa (おこわ (強飯)) as it is called, receipts with ingredients and vessel chestnuts (kuri okowa) or wild herbs (sansai okowa) are popular.
 * Red rice (赤飯): served at festive occasions with azuki bean and color agent added to enhance red color.
 * Mochi: prepared with steamed rice and kneaded.

 * Chawanmushi: savory egg custard
 * Odamaki-mushi: udon in a cup of chawan-mushi. Osaka specialty.

There are recipes where sauce is added to the main ingredients, aiming to control smell or aroma, or keep moisture to the ingredients.
 * Awayukimushi: egg meringue over fish or seafood and keep moisture as well as retain aroma.
 * Kaburamushi: grated or shredded turnip covers crabs and fish to keep moisture.
 * Sakamushi: add sake to steam sea bream and clams which will reduce fishy smell.

Recipes named after the container.
 * Dobin-mushi: matsutake and fish in a pot together with dashi soup.
 * Yugama: yuzu citrus is hollowed out into a cup to hold and add zest to the food.
 * Sea bream milt steamed in yugama

Sweets: steaming is an important process in Japanese sweets making such as manjū, yōkan, uirō, karukan or suama.

Korean dishes

 * Gyeran-jjim, a custardy dish

Benefits
Overcooking or burning food is easily avoided when steaming it. Individuals preferring to avoid additional fat intake may prefer steaming to methods which require cooking oil.

A 2007 USDA comparison between steaming and boiling vegetables shows the most affected nutrients are folic acid and vitamin C. When compared to raw consumption, steaming reduces folic acid by 15%, and boiling reduces it by 35%. Steaming reduces vitamin C by 15%, and boiling reduces it by 25%.

Steaming, compared to boiling, showed 42% higher amount of glucosinolates in broccoli cooked for medium firmness. Phenolic compounds with antioxidant properties have been found to retain significantly better through steaming than through boiling or microwaving. Steaming compared to boiling retained β-carotene in carrots. The effect of cooking food may increase or decrease the nutrients.

title: Steaming


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Double steaming

Double steaming, sometimes called double boiling, is a Chinese cooking technique to prepare delicate food such as bird's nest soup and shark fin soup. The food is covered with water and put in a covered ceramic jar and the jar is then steamed for several hours. This technique ensures there is no loss of liquid or moisture (its essences) from the food being cooked, hence it is often used with expensive ingredients like Chinese herbal medicines.

In Cantonese, double steaming is called dun. The meaning of the Chinese character for dun in Cantonese is different from that in Mandarin, because dun means to simmer or stew in Mandarin. This technique is also common in Fujian, a neighbouring province of Guangdong (Canton).

Famous examples

Tong sui, or dessert soups, which contain medicinal herbs can be cooked using double steaming.

Cantonese cuisine is famous for its slow-cooked soup. One famous dish of this kind is called the winter melon urn (冬瓜盅). It is prepared by emptying the inside of a winter melon to make an urn. The outside of the winter melon is often carved with artistic patterns. The inside is then filled with soup ingredients, such as Chinese cured ham, and Chinese herbs. The whole urn, complete with its original melon lid, is double-steamed for at least four hours. The flavour of the soup is soaked into the flesh of the melon. The whole melon and its contents are brought to the dinner table. The soup is served by scooping out the liquid and the inside wall of the melon. In this case, the edible melon takes the place of the double steaming jar. This application is possible because winter melon has a waxy, and thus waterproof, rind. Winter melon is believed to be nourishing and it is seldom cooked with ingredients that are believed to be too yin or too yang.

A dessert dish called double-steamed frog ovaries in a coconut (椰青燉雪蛤膏) is traditionally prepared for women. Chinese medicinal ingredients (including hasma), spices, and rock sugar, are placed inside a young coconut to soak in the original coconut juice. The filled coconut is then double-steamed for several hours. The whole coconut is served whole at the table after dinner. The contents and the inside wall of the coconut are scooped out to be consumed.

title: Double steaming


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Phobos (moon)

Phobos (systematic designation: Mars I) is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall. It is named after Phobos, the Greek god of fear and panic, who is the son of Ares (Mars) and twin brother of Deimos.

Phobos is a small, irregularly shaped object with a mean radius of 11 km. Phobos orbits 6000 km from the Martian surface, closer to its primary body than any other known natural satellite to a planet. It orbits Mars much faster than Mars rotates and completes an orbit in just 7 hours and 39 minutes. As a result, from the surface of Mars it appears to rise in the west, move across the sky in 4 hours and 15 minutes or less, and set in the east, twice each Martian day.

Phobos is one of the least reflective bodies in the Solar System, with an albedo of 0.071. Surface temperatures range from about −4 C on the sunlit side to −112 C on the shadowed side. The notable surface feature is the large impact crater, Stickney, which takes up a substantial proportion of the moon's surface. The surface is also marked by many grooves, and there are numerous theories as to how these grooves were formed.

Images and models indicate that Phobos may be a rubble pile held together by a thin crust that is being torn apart by tidal interactions. Phobos gets closer to Mars by about 2 cm per year, and it is predicted that within 30 to 50 million years it will either collide with the planet or break up into a planetary ring.

Discovery
Phobos was discovered by astronomer Asaph Hall on 18 August 1877 at the United States Naval Observatory in Washington, D.C., at about 09:14 Greenwich Mean Time. (Contemporary sources, using the pre-1925 astronomical convention that began the day at noon, give the time of discovery as 17 August at 16:06 Washington mean time, meaning 18 August 04:06 in the modern convention.) Hall had discovered Deimos, Mars's other moon, a few days earlier on 12 August 1877 at about 07:48 UTC. The names, originally spelled Phobus and Deimus respectively, were suggested by Henry Madan (1838–1901), a science master at Eton College, based on Greek mythology, in which Phobos is a companion to the god, Ares.

Physical characteristics
Phobos has dimensions of 26 km × 23 km × 18 km, and retains too little mass to be rounded under its own gravity. Phobos does not have an atmosphere due to its low mass and low gravity. It is one of the least reflective bodies in the Solar System, with an albedo of about 0.071. Infrared spectra show that it has carbon-rich material found in carbonaceous chondrites, and its composition shows similarities to that of Mars' surface. Phobos's density is too low to be solid rock, and it is known to have significant porosity. These results led to the suggestion that Phobos might contain a substantial reservoir of ice. Spectral observations indicate that the surface regolith layer lacks hydration, but ice below the regolith is not ruled out.

Unlike Deimos, Phobos is heavily cratered, with one of the craters near the equator having a central peak despite the moon's small size. The most prominent of these is the crater Stickney, a large impact crater some 9 km in diameter, which takes up a substantial proportion of the moon's surface area. As with Mimas's crater Herschel, the impact that created Stickney must have nearly shattered Phobos.

Many grooves and streaks also cover the oddly shaped surface. The grooves are typically less than 30 m deep, 100 to 200 m wide, and up to 20 km in length, and were originally assumed to have been the result of the same impact that created Stickney. Analysis of results from the Mars Express spacecraft, however, revealed that the grooves are not radial to Stickney, but are centered on the leading apex of Phobos in its orbit (which is not far from Stickney). Researchers suspect that they have been excavated by material ejected into space by impacts on the surface of Mars. The grooves thus formed as crater chains, and all of them fade away as the trailing apex of Phobos is approached. They have been grouped into 12 or more families of varying age, presumably representing at least 12 Martian impact events. However, in November 2018, following further computational probability analysis, astronomers concluded that the many grooves on Phobos were caused by boulders, ejected from the asteroid impact that created Stickney crater. These boulders rolled in a predictable pattern on the surface of the moon.

Faint dust rings produced by Phobos and Deimos have long been predicted but attempts to observe these rings have, to date, failed. Recent images from Mars Global Surveyor indicate that Phobos is covered with a layer of fine-grained regolith at least 100 meters thick; it is hypothesized to have been created by impacts from other bodies, but it is not known how the material stuck to an object with almost no gravity.

The unique Kaidun meteorite that fell on a Soviet military base in Yemen in 1980 has been hypothesized to be a piece of Phobos, but this couldn't be verified because little is known about the exact composition of Phobos.

Shklovsky's "Hollow Phobos" hypothesis
In the late 1950s and 1960s, the unusual orbital characteristics of Phobos led to speculations that it might be hollow. Around 1958, Russian astrophysicist Iosif Samuilovich Shklovsky, studying the secular acceleration of Phobos's orbital motion, suggested a "thin sheet metal" structure for Phobos, a suggestion which led to speculations that Phobos was of artificial origin. Shklovsky based his analysis on estimates of the upper Martian atmosphere's density, and deduced that for the weak braking effect to be able to account for the secular acceleration, Phobos had to be very light—one calculation yielded a hollow iron sphere 16 km across but less than 6 cm thick. In a February 1960 letter to the journal Astronautics, Fred Singer, then science advisor to U.S. President Dwight D. Eisenhower, said of Shklovsky's theory: "If the satellite is indeed spiraling inward as deduced from astronomical observation, then there is little alternative to the hypothesis that it is hollow and therefore Martian made. The big 'if' lies in the astronomical observations; they may well be in error. Since they are based on several independent sets of measurements taken decades apart by different observers with different instruments, systematic errors may have influenced them."

Subsequently, the systematic data errors that Singer predicted were found to exist, the claim was called into doubt, and accurate measurements of the orbit available by 1969 showed that the discrepancy did not exist. Singer's critique was justified when earlier studies were discovered to have used an overestimated value of 5 cm/yr for the rate of altitude loss, which was later revised to 1.8 cm/yr. The secular acceleration is now attributed to tidal effects, which create drag on the moon and therefore cause it to spiral inward.

The density of Phobos has now been directly measured by spacecraft to be 1.887 g/cm3. Current observations are consistent with Phobos being a rubble pile. In addition, images obtained by the Viking probes in the 1970s clearly showed a natural object, not an artificial one. Nevertheless, mapping by the Mars Express probe and subsequent volume calculations do suggest the presence of voids and indicate that it is not a solid chunk of rock but a porous body. The porosity of Phobos was calculated to be 30% ± 5%, or a quarter to a third being empty.

Named geological features
Geological features on Phobos are named after astronomers who studied Phobos and people and places from Jonathan Swift's Gulliver's Travels.

Craters on Phobos
A number of craters have been named, and are listed in the following map and table.

Other named features
There is one named regio, Laputa Regio, and one named planitia, Lagado Planitia; both are named after places in Gulliver's Travels (the fictional Laputa, a flying island, and Lagado, imaginary capital of the fictional nation Balnibarbi). The only named ridge on Phobos is Kepler Dorsum, named after the astronomer Johannes Kepler.

Orbital characteristics
The orbital motion of Phobos has been intensively studied, making it "the best studied natural satellite in the Solar System" in terms of orbits completed. Its close orbit around Mars produces some unusual effects. With an altitude of 5989 km, Phobos orbits Mars below the synchronous orbit radius, meaning that it moves around Mars faster than Mars itself rotates. Therefore, from the point of view of an observer on the surface of Mars, it rises in the west, moves comparatively rapidly across the sky (in 4 h 15 min or less) and sets in the east, approximately twice each Martian day (every 11 h 6 min). Because it is close to the surface and in an equatorial orbit, it cannot be seen above the horizon from latitudes greater than 70.4°. Its orbit is so low that its angular diameter, as seen by an observer on Mars, varies visibly with its position in the sky. Seen at the horizon, Phobos is about 0.14° wide; at zenith, it is 0.20°, one-third as wide as the full Moon as seen from Earth. By comparison, the Sun has an apparent size of about 0.35° in the Martian sky. Phobos's phases, inasmuch as they can be observed from Mars, take 0.3191 days (Phobos's synodic period) to run their course, a mere 13 seconds longer than Phobos's sidereal period.

Solar transits
An observer situated on the Martian surface, in a position to observe Phobos, would see regular transits of Phobos across the Sun. Several of these transits have been photographed by the Mars Rover Opportunity. During the transits, Phobos casts a shadow on the surface of Mars; this event has been photographed by several spacecraft. Phobos is not large enough to cover the Sun's disk, and so cannot cause a total eclipse.

March 5, 2024: NASA released images of transits of the moon Deimos, the moon Phobos and the planet Mercury as viewed by the Perseverance rover on the planet Mars.

Predicted destruction
Tidal deceleration is gradually decreasing the orbital radius of Phobos by approximately two meters every 100 years, and with decreasing orbital radius the likelihood of breakup due to tidal forces increases, estimated in approximately 30–50 million years, or about 43 million years in  one study's estimate.

Phobos's grooves were long thought to be fractures caused by the impact that formed the Stickney crater. Other modelling suggested since the 1970s support the idea that the grooves are more like "stretch marks" that occur when Phobos gets deformed by tidal forces, but in 2015 when the tidal forces were calculated and used in a new model, the stresses were too weak to fracture a solid moon of that size, unless Phobos is a rubble pile surrounded by a layer of powdery regolith about 100 m thick. Stress fractures calculated for this model line up with the grooves on Phobos. The model is supported with the discovery that some of the grooves are younger than others, implying that the process that produces the grooves is ongoing.

Given Phobos's irregular shape and assuming that it is a pile of rubble (specifically a Mohr–Coulomb body), it will eventually break up due to tidal forces when it reaches approximately 2.1 Mars radii. When Phobos is broken up, it will form a planetary ring around Mars. This predicted ring may last from 1 million to 100 million years. The fraction of the mass of Phobos that will form the ring depends on the unknown internal structure of Phobos. Loose, weakly bound material will form the ring. Components of Phobos with strong cohesion will escape tidal breakup and will enter the Martian atmosphere.

Origin
The origin of the Martian moons has been disputed. Phobos and Deimos both have much in common with carbonaceous C-type asteroids, with spectra, albedo, and density very similar to those of C- or D-type asteroids. Based on their similarity, one hypothesis is that both moons may be captured main-belt asteroids. Both moons have very circular orbits which lie almost exactly in Mars's equatorial plane, and hence a capture origin requires a mechanism for circularizing the initially highly eccentric orbit, and adjusting its inclination into the equatorial plane, most probably by a combination of atmospheric drag and tidal forces, although it is not clear that sufficient time is available for this to occur for Deimos. Capture also requires dissipation of energy. The current Martian atmosphere is too thin to capture a Phobos-sized object by atmospheric braking. Geoffrey A. Landis has pointed out that the capture could have occurred if the original body was a binary asteroid that separated under tidal forces.

Phobos could be a second-generation Solar System object that coalesced in orbit after Mars formed, rather than forming concurrently out of the same birth cloud as Mars.

Another hypothesis is that Mars was once surrounded by many Phobos- and Deimos-sized bodies, perhaps ejected into orbit around it by a collision with a large planetesimal. The high porosity of the interior of Phobos (based on the density of 1.88 g/cm3, voids are estimated to comprise 25 to 35 percent of Phobos's volume) is inconsistent with an asteroidal origin. Observations of Phobos in the thermal infrared suggest a composition containing mainly phyllosilicates, which are well known from the surface of Mars. The spectra are distinct from those of all classes of chondrite meteorites, again pointing away from an asteroidal origin. Both sets of findings support an origin of Phobos from material ejected by an impact on Mars that reaccreted in Martian orbit, similar to the prevailing theory for the origin of Earth's moon.

Some areas of the surface are reddish in color, while others are bluish. The hypothesis is that gravity pull from Mars makes the reddish regolith move over the surface, exposing relatively fresh, unweathered and bluish material from the moon, while the regolith covering it over time has been weathered due to exposure of solar radiation. Because the blue rock differs from known Martian rock, it could contradict the theory that the moon is formed from leftover planetary material after the impact of a large object.

In February 2021, Amirhossein Bagheri (ETH Zurich), Amir Khan (ETH Zurich), Michael Efroimsky (US Naval Observatory) and their colleagues proposed a new hypothesis on the origin of the moons. By analyzing the seismic and orbital data from Mars InSight Mission and other missions, they proposed that the moons are born from disruption of a common parent body around 1 to 2.7 billion years ago. The common progenitor of Phobos and Deimos was most probably hit by another object and shattered to form both moons.

Launched missions
Phobos has been photographed in close-up by several spacecraft whose primary mission has been to photograph Mars. The first was Mariner 7 in 1969, followed by Mariner 9 in 1971, Viking 1 in 1977, Phobos 2 in 1989 Mars Global Surveyor in 1998 and 2003, Mars Express in 2004, 2008, 2010 and 2019, and Mars Reconnaissance Orbiter in 2007 and 2008. On 25 August 2005, the Spirit rover, with an excess of energy due to wind blowing dust off of its solar panels, took several short-exposure photographs of the night sky from the surface of Mars, and was able to successfully photograph both Phobos and Deimos.

The Soviet Union undertook the Phobos program with two probes, both launched successfully in July 1988. Phobos 1 was accidentally shut down by an erroneous command from ground control issued in September 1988 and lost while the craft was still en route. Phobos 2 arrived at the Mars system in January 1989 and, after transmitting a small amount of data and imagery shortly before beginning its detailed examination of Phobos's surface, the probe abruptly ceased transmission due either to failure of the onboard computer or of the radio transmitter, already operating on backup power. Other Mars missions collected more data, but no dedicated sample return mission has been successfully performed.

The Russian Space Agency launched a sample return mission to Phobos in November 2011, called Fobos-Grunt. The return capsule also included a life science experiment of The Planetary Society, called Living Interplanetary Flight Experiment, or LIFE. A second contributor to this mission was the China National Space Administration, which supplied a surveying satellite called "Yinghuo-1", which would have been released in the orbit of Mars, and a soil-grinding and sieving system for the scientific payload of the Phobos lander. However, after achieving Earth orbit, the Fobos–Grunt probe failed to initiate subsequent burns that would have sent it to Mars. Attempts to recover the probe were unsuccessful and it crashed back to Earth in January 2012.

On 1 July 2020, the Mars orbiter of the Indian Space Research Organisation was able to capture photos of the body from 4,200 km away.

Missions considered
In 1997 and 1998, the Aladdin mission was selected as a finalist in the NASA Discovery Program. The plan was to visit both Phobos and Deimos, and launch projectiles at the satellites. The probe would collect the ejecta as it performed a slow flyby (~1 km/s). These samples would be returned to Earth for study three years later. The Principal Investigator was Dr. Carle Pieters of Brown University. The total mission cost, including launch vehicle and operations was $247.7 million. Ultimately, the mission chosen to fly was MESSENGER, a probe to Mercury.

In 2007, the European aerospace subsidiary EADS Astrium was reported to have been developing a mission to Phobos as a technology demonstrator. Astrium was involved in developing a European Space Agency plan for a sample return mission to Mars, as part of the ESA's Aurora programme, and sending a mission to Phobos with its low gravity was seen as a good opportunity for testing and proving the technologies required for an eventual sample return mission to Mars. The mission was envisioned to start in 2016, was to last for three years. The company planned to use a "mothership", which would be propelled by an ion engine, releasing a lander to the surface of Phobos. The lander would perform some tests and experiments, gather samples in a capsule, then return to the mothership and head back to Earth where the samples would be jettisoned for recovery on the surface.

Proposed missions

In 2007, the Canadian Space Agency funded a study by Optech and the Mars Institute for an uncrewed mission to Phobos known as Phobos Reconnaissance and International Mars Exploration (PRIME). A proposed landing site for the PRIME spacecraft is at the "Phobos monolith", a prominent object near Stickney crater. The PRIME mission would be composed of an orbiter and lander, and each would carry 4 instruments designed to study various aspects of Phobos's geology.

In 2008, NASA Glenn Research Center began studying a Phobos and Deimos sample return mission that would use solar electric propulsion. The study gave rise to the "Hall" mission concept, a New Frontiers-class mission under further study as of 2010.

Another concept of a sample return mission from Phobos and Deimos is OSIRIS-REx II, which would use heritage technology from the first OSIRIS-REx mission.

As of January 2013, a new Phobos Surveyor mission is currently under development by a collaboration of Stanford University, NASA's Jet Propulsion Laboratory, and the Massachusetts Institute of Technology. The mission is currently in the testing phases, and the team at Stanford plans to launch the mission between 2023 and 2033.

In March 2014, a Discovery class mission was proposed to place an orbiter in Mars orbit by 2021 to study Phobos and Deimos through a series of close flybys. The mission is called Phobos And Deimos & Mars Environment (PADME). Two other Phobos missions that were proposed for the Discovery 13 selection included a mission called Merlin, which would flyby Deimos but actually orbit and land on Phobos, and another one is Pandora which would orbit both Deimos and Phobos.

The Japanese Aerospace Exploration Agency (JAXA) unveiled on 9 June 2015 the Martian Moons Exploration (MMX), a sample return mission targeting Phobos. MMX will land and collect samples from Phobos multiple times, along with conducting Deimos flyby observations and monitoring Mars's climate. By using a corer sampling mechanism, the spacecraft aims to retrieve a minimum 10 g amount of samples. NASA, ESA, DLR, and CNES are also participating in the project, and will provide scientific instruments. The U.S. will contribute the Neutron and Gamma-Ray Spectrometer (NGRS), and France the Near IR Spectrometer (NIRS4/MacrOmega). Although the mission has been selected for implementation and is now beyond proposal stage, formal project approval by JAXA has been postponed following the Hitomi mishap. Development and testing of key components, including the sampler, is currently ongoing. , MMX is scheduled to be launched in 2026, and will return to Earth five years later.

Russia plans to repeat Fobos-Grunt mission in the late 2020s, and the European Space Agency is assessing a sample-return mission for 2024 called Phootprint.

Human missions
Phobos has been proposed as an early target for a human mission to Mars. The teleoperation of robotic scouts on Mars by humans on Phobos could be conducted without significant time delay, and planetary protection concerns in early Mars exploration might be addressed by such an approach.

Phobos has been proposed as an early target for a crewed mission to Mars because a landing on Phobos would be considerably less difficult and expensive than a landing on the surface of Mars itself. A lander bound for Mars would need to be capable of atmospheric entry and subsequent return to orbit without any support facilities, or would require the creation of support facilities in-situ. A lander instead bound for Phobos could be based on equipment designed for lunar and asteroid landings. Furthermore, due to Phobos's very weak gravity, the delta-v required to land on Phobos and return is only 80% of that required for a trip to and from the surface of the Moon.

It has been proposed that the sands of Phobos could serve as a valuable material for aerobraking during a Mars landing. A relatively small amount of chemical fuel brought from Earth could be used to lift a large amount of sand from the surface of Phobos to a transfer orbit. This sand could be released in front of a spacecraft during the descent maneuver causing a densification of the atmosphere just in front of the spacecraft.

While human exploration of Phobos could serve as a catalyst for the human exploration of Mars, it could be scientifically valuable in its own right.

Space elevator base
Phobos has been proposed as a future site for space elevator construction. This would involve a pair of space elevators: one extending 6,000 km from the Mars-facing side to the edge of Mars' atmosphere, the other extending 6,000 km from the other side and away from Mars. A spacecraft launching from Mars' surface to the lower space elevator would only need a delta-v of 0.52 km/s, as opposed to the over 3.6 km/s needed to launch to low Mars orbit. The spacecraft could be lifted up using electrical power and then released from the upper space elevator with a hyperbolic velocity of 2.6 km/sec, enough to reach Earth and a significant fraction of the velocity needed to reach the asteroid belt. The space elevators could also work in reverse to help spacecraft enter the Martian system. The great mass of Phobos means that any forces from space elevator operation would have minimal effect on its orbit. Additionally, materials from Phobos could be used for space industry.

title: Phobos (moon)


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Stir frying

Stir frying is a cooking technique in which ingredients are fried in a small amount of very hot oil while being stirred or tossed in a wok. The technique originated in China and in recent centuries has spread into other parts of Asia and the West. It is similar to sautéing in Western cooking technique.

Wok frying may have been used as early as the Han dynasty (206 BC – 220 AD) for drying grain, not for cooking. It was not until the Ming dynasty (1368–1644) that the wok reached its modern shape and allowed quick cooking in hot oil. However, there is research indicating that metal woks and stir-frying of dishes were already popular in the Song dynasty (960–1279), and stir-frying as a cooking technique is mentioned in the 6th-century AD Qimin Yaoshu. Stir frying has been recommended as a healthy and appealing method of preparing vegetables, meats, and fish, provided calories are kept at a reasonable level.

The English-language term "stir-fry" was coined and introduced in Buwei Yang Chao, How to Cook and Eat in Chinese (1945) to translate the Chinese term chǎo 炒. Although using "stir-fry" as a noun is commonplace in English, in Chinese, chǎo is used as a verb or adjective only.

In China
The Chinese character 炒 is attested in inscriptions on bronze vessels from the Eastern Zhou period (771–256 BC), but not in the sense of stir frying. Dry stirring was used in the Han dynasty (206 BC – 220 AD) to parch grain. Although there are no surviving records of Han dynasty stir frying, archaeological evidence of woks and the tendency to slice food thinly indicate that the technique was likely used for cooking.

The term initially appears in the sense of "stir frying" in the Qimin Yaoshu (齊民要術), a sixth-century agricultural manual, including in a recipe for scrambled eggs. In sources from the Tang dynasty (618–907), chao refers not to a cooking technique, but to a method for roasting tea leaves. It reappears as a cooking method in a dozen recipes from the Song dynasty (960–1279). The Song period is when the Chinese started to use vegetable oil for frying instead of animal fats. Until then, vegetable oil had been used chiefly in lamps.

Historically, stir frying was not as important a technique as boiling or steaming, since the oil needed for stir frying was expensive. The technique became increasingly popular in the late Ming dynasty (1368–1644), in part because the wood and charcoal used to fire stoves were becoming increasingly expensive near urban centers, and stir-frying could cook food quickly without wasting fuel. "The increasingly commercial nature of city life" in the late Ming and Qing (1644–1912) periods also favored speedy methods. But even as stir frying became an important method in Chinese cuisine, it did not replace other cooking techniques. For instance, "only five or six of over 100 recipes recorded in the sixteenth-century novel Jin Ping Mei are stir fry recipes and wok dishes accounted for only 16 percent of the recipes in the most famous eighteenth century recipe book, the Suiyuan shidan".

By the late Qing, most Chinese kitchens were equipped with a wok range (chaozao 炒灶 or paotai zao 炮臺灶) convenient for stir-frying because it had a large hole in the middle to insert the bottom of a wok into the flames.

In the West
Stir frying was brought to America by early Chinese immigrants, and has been used in non-Asian cuisine.

The term "stir fry" as a translation for "chao" was coined in the 1945 book How To Cook and Eat in Chinese, by Buwei Yang Chao. The book told the reader:
 * Roughly speaking, ch'ao may be defined as a big-fire-shallow-fat-continual-stirring-quick-frying of cut-up material with wet seasoning. We shall call it 'stir-fry' or 'stir' for short. The nearest to this in western cooking is sauté. ... Because stir-frying has such critical timing and is done so quickly, it can be called 'blitz-cooking.'

Although using the term "stir-fry" as a noun is commonplace in English, in Chinese, the word 炒 (chǎo) is used as a verb or adjective only. In the West, stir frying spread from Chinese family and restaurant kitchens into general use. One popular cookbook noted that in the "health-conscious 1970s" suddenly it seemed that "everyone was buying a wok, and stir frying remained popular because it was quick." Many families had difficulty fitting a family dinner into their crowded schedules but found that stir-fried dishes could be prepared in as little as fifteen minutes.

Technique
Broadly speaking, there are two primary techniques: chao and bao. Both techniques use high heat, but chao adds a liquid and the ingredients are softer, whereas bao stir fries are more crispy because of the Maillard reaction.

Chao technique
The chao (炒) technique is similar to the Western technique of sautéing. There are regional variations in the amount and type of oil, the ratio of oil to other liquids, the combinations of ingredients, the use of hot peppers, and such, but the same basic procedure is followed in all parts of the country.

First the wok is heated to a high temperature, and just as or before it smokes, a small amount of cooking oil is added down the side of the wok (a traditional expression is 热锅冷油 "hot wok, cold oil") followed by dry seasonings such as ginger, garlic, scallions, or shallots. The seasonings are tossed with a spatula until they are fragrant, then other ingredients are added, beginning with the ones taking the longest to cook, such as meat or tofu. When the meat and vegetables are nearly cooked, combinations of soy sauce, vinegar, wine, salt, or sugar may be added, along with thickeners such as cornstarch, water chestnut flour, or arrowroot.

A single ingredient, especially a vegetable, may be stir-fried without the step of adding another ingredient, or two or more ingredients may be stir-fried to make a single dish. Although large leaf vegetables, such as cabbage or spinach, do not need to be cut into small pieces, for dishes which combine ingredients, they should all be cut to roughly the same size and shape.

Wok hei
Wok hei romanization is based on the Cantonese Chinese pronunciation of the phrase; when literally translated into English, it can be translated as "wok thermal radiation"  or, metaphorically, as the "breath of the wok". The phrase "breath of a wok" is a poetic translation Grace Young first coined in her cookbook The Wisdom of the Chinese Kitchen. In her book, The Breath of a Wok, Young further explores the ideas and concepts of wok hei. An essay called "Wok Hay: The Breath of a Wok" explains how the definition of wok hei varies from cook to cook and how difficult it is to translate the term. Some define it as the "taste of the wok," a "harmony of taste," etc.: "I think of wok hay as the breath of a wok—when a wok breathes energy into a stir-fry, giving foods a unique concentrated flavor and aroma."

When read in Mandarin, the second character is transliterated as qi (ch'i according to its Wade-Giles romanization, so wok hei is sometimes rendered as wok chi in Western cookbooks) is the flavour, tastes, and "essence" imparted by a hot wok on food during stir frying. Out of the Eight Culinary Traditions of China, wok hei is encountered the most in Cantonese cuisine, whereas it may not even be an accepted concept in some of the others.

To impart wok hei the traditional way, the food is cooked in a seasoned wok over a high flame while being stirred and tossed quickly. The distinct taste of wok hei is partially imbued into the metal of the wok itself from previous cooking sessions and brought out again when cooking over high heat. In practical terms, the flavour imparted by chemical compounds results from caramelization, Maillard reactions, and the partial combustion of oil that come from charring and searing of the food at very high heat in excess of 200 C. Aside from flavour, wok hei also manifests itself in the texture and smell of the cooked items.

Bao technique

In the eighteenth and nineteenth centuries, the bao technique of stir-frying on a high flame was typical of cuisine from the northern Chinese province of Shandong. The wok is first heated to a dull red glow over a high fire. The oil, seasonings, and meats are then added in rapid succession. The food is continually tossed, stopping only to add other ingredients such as broths, vegetables, or more seasonings. The purpose of bao is to highlight natural tastes, so minimal seasoning is added. Because of the high heat, bao is ideal for small amounts of food that cook quickly, so the juices do not flow out of the items. Meat is coated with egg white or starch in order to contain the juices. When the food is cooked it is poured and ladled out of the wok. The wok must then be quickly rinsed to prevent food residues from charring and burning to the wok bottom because of residual heat.

A larger amount of cooking fat with a high smoke point, such as refined plant oils, is often used in bao. The main ingredients are usually cut into smaller pieces to aid in cooking.

Effects on nutritional value

Writers extol the quick cooking at high heat for retaining color, texture, and nutritional value. One study compared the effects of boiling, steaming, and stir frying on bamboo shoots. Boiling and steaming decreased the amount of protein, soluble sugar, ash, and total free amino acids by more than one-third. Stir-frying bamboo shoots increased their fat content by 528.57% due to the addition of oil. With 78.9% retention, stir frying preserved significantly more vitamin C than boiling. Taking into consideration the total retention of nutrients, the study concluded that stir frying is the method best suited for bamboo shoots. Similar results were found for stir frying red peppers.

Another study examined the nutritional value of broccoli after five common cooking techniques: steaming, boiling, microwaving, stir-frying and stir-frying followed by deep frying. The study found that the two most common methods of home cooking in China, stir-frying and stir-frying combined with deep frying in soybean oil, resulted in a much greater loss of chlorophyll, soluble protein, soluble sugar and vitamin C. The method which affected these values the least was steaming. Stir frying for five minutes and stir frying combined with boiling caused the highest loss of glucosinolates, which according to this study are best preserved by steaming. A study performed by the Spanish National Research Counsel stir-fried the broccoli for only three minutes and thirty seconds and found that nutritional value of these broccoli samples varied depending on which cooking oil was used. Comparing these results to an uncooked sample, the study found that phenolics and vitamin C were reduced more than glucosinolates and minerals. Stir-frying with soybean, peanut, safflower or extra virgin olive oil did not reduce glucosinolates, and broccoli stir-fried with extra virgin olive oil or sunflower oil had vitamin C levels similar to uncooked broccoli. These levels were significantly lower with other edible oils.

Stir frying is not without health risks. Recent studies show that heterocyclic amines and polycyclic aromatic hydrocarbons are formed by stir frying meat at very high temperatures. These chemicals may cause DNA changes that may contribute to increased risk of cancer.

Uses in traditional medicine
The process of stir-frying is used in the preparation of some Chinese herbal medicines under the term 'dry-frying'. Stir frying a medical herb with honey is commonly used to increase its sweetness and therefore its spleen and stomach qi tonic effects. Stir frying in vinegar is typically used whenever one wants to direct the properties of an herb more to the liver based on the principle that the sour taste belongs to the liver. There is no scientific evidence for any of these medicinal claims.

title: Stir frying


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Iridium Communications

Iridium Communications Inc. (formerly Iridium Satellite LLC) is a publicly traded American company headquartered in McLean, Virginia, United States. Iridium operates the Iridium satellite constellation, a system of 75 satellites: 66 are active satellites and the remaining nine function as in-orbit spares. Iridium Satellites are used for worldwide voice and data communication from handheld satellite phones, satellite messenger communication devices and integrated transceivers, as well as for two-way satellite messaging service from supported conventional mobile phones. The nearly polar orbit and communication between satellites via inter-satellite links provide global service availability.

History
The Iridium communications service was launched on November 1, 1998, formerly known as Iridium SSC. The first Iridium call was made from Vice President of the United States Al Gore to Gilbert Grosvenor, the great-grandson of Alexander Graham Bell and chairman of the National Geographic Society. Motorola provided the technology and major financial backing. The logo of the company represents the Big Dipper. The company derives its name from the chemical element iridium, which has an atomic number of 77, equaling the initial number of satellites which were calculated to be required for global coverage. However, due to optimizations of orbit trajectories, technology updates and real-world conditions, only 66 are required for global coverage. A total of 95 satellites were launched in this constellation, with 66 active and the remaining 29 satellites operating as spares.

On August 13, 1999, nine months after the launch of the organization, the founding company went into Chapter 11 bankruptcy. The handsets could not operate as promoted until the entire constellation of satellites was in place, requiring a massive initial capital cost of billions of dollars. The cost of service dissuaded many potential users. Reception indoors was difficult and the handheld devices, when compared to terrestrial cellular mobile phones were bulkier and more expensive, both of which discouraged adoption among potential users.

Mismanagement is another major factor that was cited in the original program's failure. In 1999, CNN writer David Rohde detailed how he applied for Iridium service and was sent information kits, but was never contacted by a sales representative. He encountered programming problems on Iridium's website, and a "run-around" from the company's representatives. After Iridium filed bankruptcy, it cited "difficulty gaining subscribers."

The initial commercial failure of Iridium had a damping effect on other proposed commercial satellite constellation projects, including Teledesic. Other schemes (Orbcomm, ICO Global Communications, and Globalstar) followed Iridium into bankruptcy protection, while a number of other proposed schemes were never even constructed.

In August 2000, Motorola announced that the Iridium satellites would have to be deorbited. Despite this, they remained in orbit and operational. In December 2000, the US government stepped in to save Iridium by providing US$72 million in exchange for a two-year contract. They also approved the fire sale of the company from US bankruptcy court for $25 million in March 2001. This erased over $4 billion in debt.

Iridium service was restarted in 2001, by the newly founded Iridium Satellite LLC, which was owned by a group of private investors.

On February 10, 2009, the Iridium 33 satellite collided with a defunct Russian satellite, named Kosmos 2251, 800 km over Siberia. Two large debris clouds were created.

Iridium NEXT launch campaign
Iridium replaced its original constellation by sending 75 new Iridium satellites into space on SpaceX Falcon 9 rockets in a series of 8 launches. The campaign also consisted of upgrades to Iridium ground infrastructure.

The Iridium NEXT launch campaign was announced in 2007. Within three years, Iridium completed financing and began work on launching new satellites. In June 2010, Iridium announced a fixed-price contract with Thales Alenia Space for the design and construction of the next-generation satellites for the upgraded constellation. Two weeks later, Iridium announced a $492 million contract designating the Falcon 9 as a major provider of launch services for the Iridium NEXT campaign, becoming the largest single commercial launch deal ever signed (simultaneously representing a benchmark in cost-effective satellite delivery to space).

On January 14, 2017, 10 years after the campaign was first announced, the first of eight Iridium NEXT launches took place with SpaceX from Vandenberg Air Force Base in California. Over the next two years, Iridium sent an additional 65 satellites into low Earth orbit to completely replace the original satellite constellation. The final Iridium NEXT launch took place on January 11, 2019, less than two years after the first launch.

The Iridium NEXT network covers the entire Earth, including poles, oceans and airways, with 66 satellites, with the remaining nine acting as active backups, for a total of 75 launched. Six remain on the ground as spares for a total of 81 built.

Present status
Iridium Satellite LLC merged with a special-purpose acquisition company (GHQ) created by the investment bank Greenhill & Co. in September 2009 to create Iridium Communications Inc. The public company trades on NASDAQ under the symbol "IRDM". The company surpassed one million subscribers in March 2018. Revenue for the full year 2018 was $523.0 million with operational EBITDA of $302.0 million, a 14% increase from $265.6 million in the prior year.

Iridium manages several operations centers, including Tempe, Arizona and Leesburg, Virginia, United States.

The system is being used by the U.S. Department of Defense.

Matt Desch is the current CEO of Iridium LLC.

Hosted Payload Alliance
Iridium is a founding member of the Hosted Payload Alliance (HPA), a satellite industry alliance program. Membership in the HPA is open to satellite operators, satellite manufacturers, system integrators, and other interested parties.

Air safety communications
In July 2011, the Federal Aviation Administration (FAA) issued a ruling that approves the use of Iridium for Future Air Navigation System (FANS) data links, enabling satellite data links with air-traffic control for aircraft flying in the FANS environment, including areas not served by Inmarsat (above or below 70 degrees latitude) which includes polar routes.

Global Maritime Distress and Safety System
In January 2020, the Iridium constellation was certified for use in the Global Maritime Distress and Safety System (GMDSS). The certification ended a monopoly on the provision of maritime distress services that had previously been held by Inmarsat since the system became operational in 1999.

Adoption of standard-based solutions for cellphones
In 2023, Qualcomm and Iridium announced an agreement that was supposed to bring two-way satellite messaging service to Android smartphones. The service, called Snapdragon Satellite, should have been supported starting with devices that feature Snapdragon 8 Gen 2 chipsets, which was expected to be launched in the second half of 2023. The solution for smartphones was supposed to utilize Iridium's L Band spectrum for downlink and uplink.

On November 9, 2023, Iridium announced that Qualcomm had notified them about the end of their partnership due to a lack of interest in Qualcomm's and Iridium's proprietary solution by smartphone manufacturers. A Qualcomm spokesman stated "Smartphone makers have indicated a preference towards standards-based solutions for satellite-to-phone connectivity. We expect to continue to collaborate with Iridium on standards-based solutions while discontinuing efforts on the proprietary solution that was introduced earlier this year."

In 2024, Iridium introduceed Project Stardust, a 3GPP standard-based satellite-to-cellphone service focusing on messaging, emergency communications and IoT for devices like cars, smartphones, tablets and related consumer applications. The solution will be supported using a version of the NB-IoT standard for 5G non-terrestrial networks (NTN). Scheduled for launch in 2026, it won't replace the company’s proprietary solution for voice and high-speed data; instead it will co-exist with that offering on the Iridium's existing global low-earth orbit satellite network.

Russo-Ukrainian War
From 2015-2022, Iridium Satellite was selling navigation systems directly to its Russian subsidiary, Iridium Communications. In 2022, the Moscow-based subsidiary gave the National Guard of Russia access to the satellite constellation.

Following the 2022 Russian invasion of Ukraine, Iridium structured their operations to comply with US sanctions and stopped shipment of end-user equipment to Russia. Despite this, In 2023, Iridium Communications, via some unknown intermediaries, imported machines made by the American parent company for receiving and converting voice and images.

Iridium satellite constellation
The Iridium system requires 66 active satellites in low Earth orbit to complete its constellation and 9 spare satellites are kept in-orbit to serve in case of failure. The satellites are in six polar orbital planes at a height of approximately 485 mi. Satellites communicate with neighboring satellites via Ka band intersatellite links to relay communications to and from ground stations. The original constellation was launched in the late 1990s before the company went through bankruptcy. In January 2017, Iridium began to launch its next-generation satellites through its $3 billion launch campaign, Iridium NEXT. The new satellites were sent into space on SpaceX Falcon 9 launch vehicles from Vandenberg AFB Space Launch Complex 4 in California over the course of eight launches between January 2017 and January 2019. On January 14, 2017, SpaceX launched 10 of the new Iridium satellites into orbit. The second launch of Iridium NEXT satellites took place on June 25, 2017 on a SpaceX Falcon 9 rocket out of Vandenberg Air Force Base. This was the second of eight scheduled launches. The third launch of 10 NEXT satellites took place on October 9, 2017. On December 22, 2017, ten additional satellites were deployed after a successful launch on a SpaceX Falcon 9 rocket. On May 22, SpaceX successfully launched an additional five Iridium NEXT satellites from Vandenberg Air Force Base.

On January 11, 2019, the final ten satellites were placed in orbit by SpaceX.

Handsets
Iridium offers four satellite handsets: the 9555, 9575A (which is only available to US government customers), the Extreme, and the Extreme PTT.

Wi-Fi Hotspots
In 2014, Iridium began to offer the Iridium Go! hotspot, which can also be used as a distress beacon under certain circumstances. As of September 2020, Iridium's manufacturing contractor, Beam Communications, had built 50,000 of these devices.

One-way pagers
Two pagers were made for the Iridium network – the Motorola 9501 and Kyocera SP-66K. These are one-way devices that could receive messages sent in the form of SMS.

Messages are delivered to pre-selected "MDAs" which cover a certain geographic area. Three of these MDAs may be selected on a web-based portal or updated automatically if the paging service is bound to an Iridium phone. Each country has its own MDA based on its country code; some of the larger countries are divided into several MDAs, while separate MDAs exist for sections of ocean and common aeronautic routes.

Pagers are assigned with telephone numbers in area code 480 and can also be contacted using email, SMS and the web-based interface used to send messages to Iridium phones.

Two-way satellite messengers
In 2017, Garmin announced inReach SE+ and inReach Explorer+ satellite communicators, which use Iridium satellite network for global coverage. Garmin inReach mini, a satellite messenger, was announced a year later. These devices can send and receive text messages with any cell phone number, email address or another inReach device, as well as to provide location sharing, navigation and direct communication options to emergency services.

ZOLEO satellite communicator uses global Iridium network when cellular or Wi-Fi coverage is unavailable. It does so by means of Bluetooth connection to provide two-way messaging to connected smartphone or tablet devices.

Other satellite phones
Several other Iridium-based telephones exist, such as payphones, and equipment intended for installation on ships and aircraft. The DPL handset made by NAL Research combined with a 9522 transceiver is used for some of these products. This handset provides a user interface nearly identical to that of the 9505 series phones.

Standalone transceiver units
These can be used for data-logging applications in remote areas (as in data collection satellites). Some types of buoys, such as those used for the tsunami warning system, use Iridium satellites to communicate with their base. The remote device is programmed to call or send short burst data (SBD) messages to the base at specified intervals, or it can be set to accept calls in order for it to offload its collected data.

The following transceivers have been released over the years:

 * Iridium Core 9523 – Similar to the 9522B, a modular transceiver released in 2012
 * Iridium 9522B – A transceiver released in late 2008, is smaller than the 9522A and has similar features. It also supports Circuit-Switched Data (CSD), not just SBD.
 * Iridium 9522A – Based on the 9522, some variants have built in GPS and autonomous reporting functions. Supports SBD.
 * Motorola 9522 – Last Motorola transceiver, supports outgoing SMS but no SBD.
 * Motorola 9520 – Original transceiver module, does not support outgoing SMS or SBD. Designed for use in vehicles with accompanying handset

Short burst data modems
These devices support only SBD for Internet of things (IoT) services and do not use a SIM card.

 * Iridium 9601 – Supports only SBD, several tracking devices and other products have been built around this modem. It was an Iridium manufactured product designed as an OEM module for integration into applications that only use the Iridium Short Burst Data Service. Short Burst Data applications are supported through an RS-232 interface. Examples of these applications include maritime vessel tracking or automatic vehicle tracking.
 * Iridium 9602 – Smaller, cheaper version of 9601 (released in 2010).
 * Iridium 9603 – One-fourth the volume and half the footprint of 9602

Iridium OpenPort
Iridium OpenPort is a broadband satellite voice and data communications system for maritime vessels. The system is used for crew calling and e-mail services on sea vessels such as merchant fleets, government and navy vessels, fishing fleets and personal yachts.

Iridium operates at only 2.2 to 3.8 kbit/s, which requires very aggressive voice compression and decompression algorithms. (By comparison, AMR used in 3G phones requires a minimum of 4.75 kbit/s, G.729 requires 6.4 kbit/s, and iLBC requires 13.33 kbit/s.) Latency for data connections averages 1800 ms round-trip, with a mode of 1300 to 1400 ms and a minimum around 980 ms. Latency is highly variable depending on the path data takes through the satellite constellation as well the need for retransmissions due to errors, which may be around 2 to 3% for mobile originated packets under good conditions.

Iridium Certus
One of the Iridium NEXT services is Iridium Certus, a globally available satellite broadband which is capable of up to 704 Kbps of bandwidth across maritime, aviation, land mobile, government, and IoT applications. Terminals for the service are provided by Cobham, Intellian Technologies and Thales.

Iridium STL
Iridium is providing Satellite Time & Location (STL) service. It was developed by Satelles company, which was later acquired by Iridium Communications in April 2024.

According to the company, it is the only LEO satellite based commercial positioning, navigation, and timing (PNT) service (as of April 2024).

title: Iridium Communications