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Parthenogenesis

Parthenogenesis is a natural form of asexual reproduction in which growth and development of embryos occur without fertilization by sperm. In animals, parthenogenesis means development of an embryo from an unfertilized egg cell. In plants parthenogenesis is a component process of apomixis. Parthenogenesis occurs in some plants, some invertebrate animal species and a few vertebrates; this type of reproduction has been induced artificially in a few species including fish and amphibians. Normal egg cells form after meiosis and are haploid, with half as many chromosomes as their mother's body cells. Haploid individuals, are non-viable, parthenogenetic offspring have the diploid chromosome number. Depending on the mechanism involved in restoring the diploid number of chromosomes, parthenogenetic offspring may have anywhere between all and half of the mother's alleles; the offspring having all of the mother's genetic material are called full clones and those having only half are called half clones. Full clones are formed without meiosis.

If meiosis occurs, the offspring will get only a fraction of the mother's alleles since crossing over of DNA takes place during meiosis, creating variation. Parthenogenetic offspring in species that use either the XY or the X0 sex-determination system have two X chromosomes and are female. In species that use the ZW sex-determination system, they have either two Z chromosomes or two W chromosomes, or they could have one Z and one W chromosome; some species reproduce by parthenogenesis, while others can switch between sexual reproduction and parthenogenesis. This is called facultative parthenogenesis; the switch between sexuality and parthenogenesis in such species may be triggered by the season, or by a lack of males or by conditions that favour rapid population growth. In these species asexual reproduction occurs either in summer or as long as conditions are favourable; this is because in asexual reproduction a successful genotype can spread without being modified by sex or wasting resources on male offspring who won't give birth.

In times of stress, offspring produced by sexual reproduction may be fitter as they have new beneficial gene combinations. In addition, sexual reproduction provides the benefit of meiotic recombination between non-sister chromosomes, a process associated with repair of DNA double-strand breaks and other DNA damages that may be induced by stressful conditions. Many taxa with heterogony have within them species that have lost the sexual phase and are now asexual. Many other cases of obligate parthenogenesis are found among polyploids and hybrids where the chromosomes cannot pair for meiosis; the production of female offspring by parthenogenesis is referred to as thelytoky while the production of males by parthenogenesis is referred to as arrhenotoky. When unfertilized eggs develop into both males and females, the phenomenon is called deuterotoky. Parthenogenesis can occur without meiosis through mitotic oogenesis; this is called apomictic parthenogenesis. Mature egg cells are produced by mitotic divisions, these cells directly develop into embryos.

In flowering plants, cells of the gametophyte can undergo this process. The offspring produced by apomictic parthenogenesis are full clones of their mother. Examples include aphids. Parthenogenesis involving meiosis is more complicated. In some cases, the offspring are haploid. In other cases, collectively called automictic parthenogenesis, the ploidy is restored to diploidy by various means; this is. In automictic parthenogenesis, the offspring differ from their mother, they are called half clones of their mother. Automixis is a term. Diploidy might be restored by the doubling of the chromosomes without cell division before meiosis begins or after meiosis is completed; this is referred to as an endomitotic cycle. This may happen by the fusion of the first two blastomeres. Other species restore their ploidy by the fusion of the meiotic products; the chromosomes may not separate at one of the two anaphases or the nuclei produced may fuse or one of the polar bodies may fuse with the egg cell at some stage during its maturation.

Some authors consider all forms of automixis sexual. Many others classify the endomitotic variants as asexual and consider the resulting embryos parthenogenetic. Among these authors, the threshold for classifying automixis as a sexual process depends on when the products of anaphase I or of anaphase II are joined together; the criterion for "sexuality" varies from all cases of restitutional meiosis, to those where the nuclei fuse or to only those where gametes are mature at the time of fusion. Those cases of automixis that are classified as sexual reproduction are compared to self-fertilization in their mechanism and consequences; the genetic composition of the offspring depends on. When endomitosis occurs before meiosis or when central fusion occurs, the offspring get all to more than half of the mother's genetic

Outer Mongolia

Outer Mongolia was a territory of the Manchu-led Qing dynasty. Its area was equivalent to that of the modern state of Mongolia, sometimes called "Outer Mongolia" in China today, plus the Russian republic of Tuva. While the administrative Outer Mongolia only consisted of the four Khalkha aimags, in the late Qing period "Outer Mongolia" was used to refer to Khalkha plus Oirat areas Khovd and the directly-ruled Tannu Uriankhai; the name "Outer Mongolia" is contrasted with South Mongolia, which corresponds to the autonomous region of Inner Mongolia in China. South Mongolia was given its name; the term ar mongol is sometimes used in Mongolian language to refer to North Mongolia when making a distinction with South Mongolia, so as to elide the history of Qing rule and rather imply a geographic unity or distinction of regions inhabited by Mongols in the Mongolian Plateau. There exists an English term Northern Mongolia, but with political connotations, it can be used to refer to Mongolia synchronically.

In the Mongolian language, the word ar refers to the back side of something, extended to mean the northern side of any spatial entity, e.g. a mountain or a yurt. The word öbür refers to the south side of a mountain. So the difference between South Mongolia and the Mongolian state is conceived of in the metaphor as at the backward northern side vs. the south side of a mountain. In contrast to Chinese: 漠北蒙古, there is Chinese: 漠南蒙古. Today, "Outer Mongolia" is sometimes still informally used to refer to Mongolia. "Outer Mongolia" is used quite in Taiwan. To avoid confusion between the sovereign nation of Mongolia and China's Inner Mongolia, but to recognize the sovereignty of Mongolia, media in China refer to the former as "State of Mongolia" instead of just "Mongolia", that could refer to the whole Mongolia area. Inner Mongolia Tannu Uriankhai Dzungaria Outer Northwest China Outer Manchuria

Cotesia

Cotesia is a genus of braconid wasps first described by Peter Cameron in 1891. Some species parasitize caterpillars of species considered as pests, thus they are used as biocontrol agents. Cotesia congregata parasitizes the tobacco hornworms. C. glomerata and C. rubecula feed on the cabbage other white butterfly caterpillars. C. gonopterygis and C. risilis parasitize the common brimstone. The wasp C. melanoscelus parasitizes the caterpillar of the gypsy moth. It, the gypsy moth, are native to Europe; the gypsy moth is an invasive species in North America, C. melanoscelus has been imported as a biocontrol of the moth. List of Cotesia species Preliminary evolutionary relationships within the parasitoid wasp genus Cotesia Moisset, Beatriz. "Genus Cotesia". BugGuide. Retrieved January 4, 2019. Hymenoptera Institute. U. Kentucky

Cross-drive steering transmission

A cross-drive steering transmission is a transmission, used in tracked vehicles to allow precise and energy efficient steering. It consists of the following main parts: Two identical single-stage planetary gearings a differential a hydraulic pump connected to the engine a hydraulic motor powered by the hydraulic pump hydraulic control valvesA steering transmission combines the two functions needed for a tracked vehicle transmission: a transmission to couple the constant engine speed to varying road speeds and a steering gearbox to drive the two output shafts at different speeds, thus steering the vehicle. Cross-drive transmissions developed after WWII, at a time when tanks were growing larger and heavier. A growing problem with earlier gearboxes had been the amount of heat dissipated in the brakes used for steering; as tanks grew heavier, a more efficient system was required not just for efficiency but to reduce the wasted power having to be disposed of through heat and wear in the steering brakes.

Cross-drive transmissions were developed from the earlier controlled-differential steering gearboxes. Their innovation was to cross-couple the two sides, so that excess power from the slow side of the gearbox could be supplied to the faster side; this reduced the power to be dissipated by braking and it increased the power available to drive the fast track. Implementing this was difficult for most transmissions as it required a varying gear ratio between the sides. Most gearboxes offered a single ratio, through fixed gears and clutches, which restricted steering to a single radius; the particular innovation of the cross-drive, over earlier attempts, was to use a torque converter in the cross shaft. This allowed a continuously variable ratio between the two sides and so more precise steering. Torque converters are easier to make for the high torques required in tank design, saving weight and cost. Cross-drive transmissions improved the drivability of the manual transmissions in use. Manual transmissions were heavy and tiring to drive, requiring skill and strength from the driver, frequent adjustments as the clutch plates wore.

The pre-selector gearbox had been used to simplify the driving task, but at the cost of mechanical complexity. The cross-drive transmissions offered a mechanically-actuated self-changing gearbox, where the ratio selection could be either manual, automatic, or by pre-selection; the control input for steering became lighter, allowing the use of a single hand-controlled joystick or'wobble stick', as used for the CD-850-1 transmission in the T44 Cargo Tractor of 1950. The construction of these transmissions integrated the transmission and steering gearbox functions into a single casing; this gave reduced overall weight and volume, reduced servicing times. A related development at this time was the'power pack' concept, where engine and transmission could be removed as a single unit; as size and complexity increased, fitter time became short but mechanical handling through mobile cranes became available in the field. It was now quicker and simpler to exchange one large unit than to dismantle and re-assemble more connections to remove a smaller component.

A design of cross-drive transmission, the Allison X1100, was used in the 1970s experimental US MBT-70 and XM1 tanks later adopted in the M1 Abrams. This adopts a different principle for the steering cross-coupling: instead of a hydro-dynamic torque converter, it uses a hydrostatic combination of a hydraulic pump and a hydraulic motor; the X1100 was designed as a modular system, allowing its easy adaption to vehicles with different power plants, ranging from diesels to gas turbines. The central module is matched to the engine driving it, the outer steering modules to the weight and speed of the vehicle

Bilohiria

Bilohiria is an urban-type settlement in the Khmelnytskyi Oblast of western Ukraine.. It serves as the administrative center of the Bilohiria Raion </ref>, housing the district's local administration buildings. The town's population was 5,592 as of the 2001 Ukrainian Census and 5,484 in 2012.. Nearby towns include Yampil and Kornytsya; the town is located on the banks of a tributary of the Prypyat. The town of Bilohiria administers the Bilohiria Settlement Council, whose jurisdiction covers the villages of Karasykha and Trostianka; the region surrounding Liakhivtsi was known to be settled by at least the 12th century, when residents of the Kiev area migrated west to Volhynia and beyond. The Mongol invasion of 1260 subjected the area to rule of the Mongol khan. Lithuanian control over the region took place in the 14th century; the settlement of Liakhivtsi was founded in 1441 on Bilohiria's modern-day territory. Yesiunin, Serhiy. "Bilohiria - pages through ancient history". Gazeta "Ye". Retrieved 20 May 2013.</ref>

Jews were allowed to return a few years later. The settlement received the Magdeburg rights in 1583. Polish influence increased over the 15th and 16th centuries, with Poland taking official control in 1569 with the Treaty of Lublin. Cultural life in Volhynia flourished under Polish rule, interrupted by the 1648 Chmielnicki Khmelnytsky_Uprising massacres, which killed many Jewish residents. Additional settlements formed in the 1660s. Volhynia was transferred to Polish control in 1793. In 1885, Liakhivtsi was the administrative center of the Liakhivtsi volost of the Ostroh povit. During that time, the settlement's population consisted of 2,368; the Russian Empire Census of 1897 reported the town's population as 5,401. At that time, 3,890 of the inhabitants belonged to the Eastern Orthodox faith, while 1,384 were of the Jewish faith. In the 20th century, the region was populated by both ethnic Ukrainians and Poles, whose populations struggled against each other. At the same time and the Soviet Union that were struggling for influence in the greater region.

World War II brought these conflicts to the forefront. Nazi Germany occupied the region in June 1941. World War II ended in tragedy for the Jews of Lechowitz. German forces invaded Russia in June 1941, within a year, murdered the entire Jewish population of Lechowitz. A memorial exists today in the forests outside of town, where 2,300 Jews from Lechowitz and nearby towns were murdered by German forces. A small number of Jews from Lechowitz survived World War II; the entire region fell under Soviet rule following the end of World War II. In August 1991, Ukraine became an independent state, Lechowitz is part of that state; the town was known by the name of Liakhivtsi until it was changed in 1949 when its status was upgraded to that of a rural settlement. In 1960, Bilohiria received the status of an urban-type settlement; the Yiddish version of the town name was לעחיוויץ. After World War II, the Russian government renamed the town to Belogor ` Belogoria; the Ukrainian version of the name is Bilohir ` Bilohiria.

There are other towns named Liakhivtsi, including one in called Lyakhavichy in Belarus, a town called Lachowice in Poland, one called Lechotice in the Czech Republic. _____________________________________________________________________________________________________________________ Yampil, the other urban-type settlement in the Bilohiria Raion Media related to Bilohiria at Wikimedia Commons

Shangri-La Hotel, Colombo

Shangri-La Colombo is a 5-star hotel in Colombo, Sri Lanka. Owned by Shangri-La Hotels, the property is part of the larger One Galle Face development project at the site of the Old Army Headquarters, it is the second Shangri-La hotel on the island and the 101st hotel of the chain of Shangri-La Hotels world-wide. The hotel was opened on 11 November 2017; the property has 500 rooms, has room to accommodate up to 2,000 conference guests. The Shangri-La was one of three sites of the 2019 Sri Lanka Easter bombings along with the Kingsbury and Cinnamon Grand Hotel. Sri Lankan celebrity chef Shantha Mayadunne and her daughter were among the fatalities. Sri Lankan cricketer Hasitha Boyagoda was having breakfast in the hotel, he escaped with only minor injuries. Three of the four children of Danish billionaire Anders Holch Povlsen were killed in the attack