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Non-stoichiometric compound

Non-stoichiometric compounds are chemical compounds always solid inorganic compounds, having elemental composition whose proportions cannot be represented by a ratio of small natural numbers. Contrary to earlier definitions, modern understanding of non-stoichiometric compounds view them as homogenous, not mixtures of stoichiometric chemical compounds. Since the solids are overall electrically neutral, the defect is compensated by a change in the charge of other atoms in the solid, either by changing their oxidation state, or by replacing them with atoms of different elements with a different charge. Many metal oxides and sulfides have non-stoichiometric examples; the type of equilibrium defects in non-stoichiometric compounds can vary with attendant variation in bulk properties of the material. Non-stoichiometric compounds exhibit special electrical or chemical properties because of the defects. Non-stoichiometric compounds have applications in ceramic and superconductive material and in electrochemical system designs.

Nonstoichiometry is pervasive for metal oxides when the metal is not in its highest oxidation state. For example, although wüstite has an ideal formula FeO, the actual stoichiometry is closer to Fe0.95O. The non-stoichiometry reflect the ease of oxidation of Fe2+ to Fe3+ replacing a small portion of Fe2+ with two thirds their number of Fe3+, thus for every three "missing" Fe2+ ions, the crystal contains two Fe3+ ions to balance the charge. The composition of a non-stoichiometric compound varies in a continuous manner over a narrow range. Thus, the formula for wüstite is written as Fe1−xO, where x is a small number representing the deviation from the "ideal" formula. Nonstoichiometry is important in solid, three-dimensional polymers that can tolerate mistakes. To some extent, entropy drives all solids to be non-stoichiometric, but for practical purposes, the term describes materials where the non-stoichiometry is measurable at least 1% of the ideal composition. The monosulfides of the transition metals are nonstoichiometric.

Best known is nominally iron sulfide with a composition Fe1−xS. The rare stoichiometric FeS endmember is known as the mineral troilite. Pyrrhotite is remarkable in that it has numerous polytypes, i.e. crystalline forms differing in symmetry and composition. These materials are always iron-deficient owing to the presence of lattice defects, namely iron vacancies. Despite those defects, the composition is expressed as a ratio of large numbers and the crystals symmetry is high; this means the iron vacancies are not randomly scattered over the crystal, but form certain regular configurations. Those vacancies affect the magnetic properties of pyrrhotite: the magnetism increases with the concentration of vacancies and is absent for the stoichiometric FeS. Palladium hydride is a nonstoichiometric material of the approximate composition PdHx; this solid conducts hydrogen by virtue of the mobility of the hydrogen atoms within the solid. It is sometimes difficult to determine if a material is non-stoichiometric or if the formula is best represented by large numbers.

The oxides of tungsten illustrate this situation. Starting from the idealized material tungsten trioxide, one can generate a series of related materials that are deficient in oxygen; these oxygen-deficient species can be described as WO3−x, but in fact they are stoichiometric species with large unit cells with the formulas WnO3n−2, where n = 20, 24, 25, 40. Thus, the last species can be described with the stoichiometric formula W40O118, whereas the non-stoichiometric description WO2.95 implies a more random distribution of oxide vacancies. At high temperatures, titanium sulfides present a series of non-stoichiometric compounds; the coordination polymer Prussian blue, nominally Fe718 and their analogs are well known to form in non-stoichiometric proportions. The non-stoichiometric phases exhibit useful properties vis-à-vis their ability to bind caesium and thallium ions. Many useful compounds are produced by the reactions of hydrocarbons with oxygen, a conversion, catalyzed by metal oxides; the process operates via the transfer of "lattice" oxygen to the hydrocarbon substrate, a step that temporarily generates a vacancy.

In a subsequent step, the missing oxygen is replenished by O2. Such catalysts rely on the ability of the metal oxide to form phases. An analogous sequence of events describes other kinds of atom-transfer reactions including hydrogenation and hydrodesulfurization catalysed by solid catalysts; these considerations highlight the fact that stoichiometry is determined by the interior of crystals: the surfaces of crystals do not follow the stoichiometry of the bulk. The complex structures on surfaces are described by the term "surface reconstruction"; the migration of atoms within a solid is influenced by the defects associated with non-stoichiometry. These defect sites provide pathways for atoms and ions to migrate through the otherwise dense ensemble of atoms that form the crystals. Oxygen sensors and solid state batteries are two applications. One example is

Walter J. C. Murray

Walter John Campbell Murray was born in Seaford, East Sussex 20 August 1900. During the First World War he spent time at sea as a radio officer in the Mercantile Marine and served in the R. A. F, he was a journalist in London for a short time before moving to Horam in Sussex to spend a year gathering and marketing wild herbs. Murray became a schoolmaster, in 1926 founded his own independent co-educational school of which he remained headmaster for forty years. Throughout his life he was a keen student of natural history, this took him to many remote corners and islands of the United Kingdom. Murray was well known as a nature photographer, as well as a television broadcaster, he died in January 1985. Nature's Undiscovered Kingdom, George Allen and Unwin Ltd, 1946 Copsford, George Allen and Unwin Ltd, 1948. ISBN 9781908213709 A Sanctuary Planted, Phoenix House Ltd, 1953 Romney Marsh, Robert Hale, 1953with L. Hugh Newman: Stand and Stare, Staples Press, 1950 Nature's Way: Questions and Answers on Animal Behaviour, Country Life, 1952 Wander and Watch, Staples Press, 1954'Copsford and Walter Murray' by Tom Wareham'Walter Murray: An Unacknowledged English Nature Mystic"Copsford: Walter Murray' by Mark Valentine The Cottage in the Weald: Walter Murray and Copsford by Tom Wareham

Uttarakhand Board of School Education

Uttarakhand Board of School Education abbr. UBSE is an agency of Government of Uttarakhand entrusted with the responsibilities of prescribing courses of instructions and text books and conducting examinations for secondary school students in Uttarakhand, it is responsible for result declaration of Board examination. It has its headquarters in Ramnagar. At present more than 10,000 schools are affiliated with the Board; the Board sets up over 1,300 examination centres for over 300,000 examinees every year. 9 February 1996: Regional office of the Uttar Pradesh Madhyamik Shiksha Parishad was established at Ramnagar, Uttarakhand. 1999: For the first time exams were conducted under the regional office at Ramnagar for Garhwal division and Kumaon division. 22 September 1996: Uttaranchal Shiksha Evam Pariksha Parishad was established followed by the foundation of new state Uttaranchal from erstwhile Uttar Pradesh. 2002: For the first time exams were conducted under Uttaranchal Shiksha Evam Pariksha Parishad.

22 April 2006: Uttaranchal Board of School Education was created by Uttaranchal School Education Act, 2006 enacted by the Uttaranchal Legislative Assembly. 11 December 2008: The institution was renamed Uttarakhand Board of School Education. Education in Uttarakhand List of institutions of higher education in Uttarakhand schooleducation.uk.gov.in

Ankita Raina

Ankita Ravinderkrishan Raina is an Indian professional tennis player and the current Indian No. 1 in both women’s singles and doubles. Raina has won one WTA Challenger in doubles, along with eleven singles and seventeen doubles titles on the ITF Women's Circuit. In April 2018, she entered the top 200 singles rankings for the first time, becoming only the fifth player representing India to achieve this feat. Raina has won gold medals in the women's singles and mixed-doubles events at the 2016 South Asian Games, won a bronze medal in singles at the 2018 Asian Games. Playing for India at the Fed Cup, Raina has a win-loss record of 18–14, she has notable wins over Yulia Putintseva, both at the 2018 Fed Cup. Raina was born to a Kashmiri Pandit family, her family hails from the town of Tral in Kashmir. Raina is fluent in Hindi and English. Raina had studied at Brihan Maharashtra. At the national events, Raina has represented her home state Gujarat, her idols growing up were Rafael Nadal, Serena Williams and Sania Mirza.

Raina trains at the Hemant Bendrey Tennis Academy at the PYC Hindu Gymkhana in Pune, is coached by Hemant Bendrey. Raina started playing tennis at the age of five. Following a promising junior career, Raina made her first professional appearance in 2009, at a small ITF tournament in Mumbai. In 2010, she continued to participate in local ITF events with limited success. Raina's 2011 season saw her advance to three ITF circuit finals in doubles, winning one with countrywoman Aishwarya Agrawal. In 2012, she won three more in doubles; this was followed by a few years of mediocre results on the ITF Women's Circuit. Raina won two matches at the 2017 Mumbai Open; this would turn out to be her breakthrough tournament. In April 2018, she reached a ranking of world No. 181 after winning a $25K ITF title, becoming the fifth Indian national to crack to the top-200 ladies singles rankings, following Nirupama Sanjeev, Sania Mirza, Shikha Uberoi, Sunitha Rao. In August 2018, Ankita won the bronze medal in the Asian Games at Jakarta, Indonesia in singles event.

Raina and Sania Mirza are the only players representing India to have won a singles medal at the Asian Games. At the 2019 Kunming Open, Raina got her first top-100 win, defeating Samantha Stosur, former US Open champion and top 10 player, scoring the biggest win of her career. In October 2019, Raina entered the top 150 doubles rankings for the first time, after reaching the finals of the 2019 Suzhou Ladies Open with partner Rosalie van der Hoek, she bettered this feat by winning two back-to-back ITF titles in Nonthaburi alongside Bibiane Schoofs. This gave Raina a new career-high raking of No. 123 in doubles. Raina is a steady baseliner who relies on her speed and counterpunching abilities to outlast her opponents, she hits with plenty of topspin on both her forehand and backhand, can hit in all directions comfortably. She uses the backhand slice quite as a way of varying the pattern of a rally. Raina is comfortable with volleying, approaches the net whenever she gets her opponent running or out of position.

She doesn't use the drop shot or lob too but brings them out as a surprise tactic. Raina's biggest strength is her baseline consistency, she can stay toe-to-toe with most players from the back of the court, can get a majority of shots back in play. Raina has a solid first serve, but it is her second serve that gives her an advantage at the start of a point, she can hit a good kick serve. Raina has a good return of serve, is capable of neutralizing most big serves by sending them back with precision, she is quite efficient at the net, can take the attack to the opponent on fast courts with her purposeful volleys. Raina's biggest weakness is the lack of firepower on her groundstrokes, she can't match the raw muscle strength of the top players, so is in danger of getting blown off the court. In her junior years, Raina was helped by Dishman Pharmaceuticals and Chemicals to participate in overseas junior tournaments. Since she has been supported by Bharat Forge and Lakshya. Most Raina has signed sponsorship deals with the Sports Authority of Gujarat, Yonex, is employed with ONGC.

Hence, Raina uses clothing. In 2013, Raina met Narendra Modi, India's then-future Prime Minister, was recognised under the Shaktidhoot scheme and hence became a part of India's goal of reaching Olympic podiums. Ankita Raina at the Women's Tennis Association Ankita Raina at the International Tennis Federation Ankita Raina at the Fed Cup Ankita Raina, Profile tennislive

Embalming cache

An embalming cache is a collection of material, used by the Ancient Egyptians in the mummification process and buried either with or separately from the body. It is believed that because the materials had come in contact with the body, they had absorbed part of it, needed to be buried in order for the body to be complete in the afterlife; the best known embalming cache is KV54, sometimes called the Embalming cache of Tutankhamun and excavated by Edward R. Ayrton in 1907. Theodore M. Davis showed the find to Herbert E. Winlock who could not see much in it at that time, so Davis donated the whole lot to the Metropolitan Museum of Art in 1909. In 1940 Winlock took the matter up again and bones from food in a storage jar were examined in the American Museum of Natural History as well as analysis of the bandages made; the hieratic and hieroglyfic inscriptions from the cache have been discussed by scholars of that time. Winlock presented the results 1942 in his book "Material used at the embalming of king Tut-Ankh-Amun".

Not so much a tomb as a pit, it contained about a dozen large sealed storage jars. Within them were contained pottery, bags of natron, animal bones, floral collars and linen containing text dated to the final years of the little-known 18th dynasty Pharaoh Tutankhamun, it was determined that that material not only contained material used in the embalming process, but the remains of food used in the funerary banquet held at the conclusion of the pharaoh's interment. When Tutankhamun's tomb was discovered in 1922, many small items similar to those found in the KV54 cache were found in the initial entryway, leading to the suggestion that following the initial robbery of the tomb, the embalming materials and burial party refuse were moved to KV54; the most excavated tomb in the Valley of the Kings, KV63, is thought by many to be another embalming cache. Like the KV54 cache, it contained no mummies, but its many jars contained similar materials, including natron, seeds, carbon, assorted pottery, small animal bones, papyrus fragments, mud trays, mud seals, pieces of twine or rope.

Not all embalming materials were kept separate from their owners. At least two non-royal interments in the Valley of the Kings, KV36, KV46, contained dozens of jars within their tombs holding embalming refuse

Metallosis

Metallosis is the putative medical condition involving deposition and build-up of metal debris in the soft tissues of the body. Metallosis has been hypothesized to occur when metallic components in medical implants joint replacements, abrade against one another. Metallosis has been observed in some patients either sensitive to the implant or for unknown reasons in the absence of malpositioned prosthesis. Though rare, metallosis has been observed at an estimated incidence of 5% of metal joint implant patients over the last 40 years. Women may be at higher risk than men. If metallosis occurs, it may involve the hip and knee joints, the shoulder, elbow joints, or spine. In the spine, the wear debris and resulting inflammatory reaction may result in a mass referred to as a "metalloma" in medical literature, which may lead to neurological impairment over time; the abrasion of metal components may cause metal ions to be solubilized. The hypothesis that the immune system identifies the metal ions as foreign bodies and inflames the area around the debris may be incorrect because of the small size of metal ions may prevent them from becoming haptens.

Poisoning from metallosis is rare. The involvement of the immune system in this putative condition has been theorized but has never been proven. Purported symptoms of metallosis include pain around the site of the implant, a noticeable rash that indicates necrosis; the damaged and inflamed tissue can contribute to loosening the implant or medical device. Metallosis can cause dislocation of non-cemented implants as the healthy tissue that would hold the implant in place is weakened or destroyed. Metallosis has been demonstrated to cause osteolysis. Women, those who are small in stature, the obese are at greater risk for metallosis because their body structure causes more tension on the implant, quickening the abrasion of the metal components and the subsequent build-up of metallic debris. Persons suffering from metallosis can experience any of the following symptoms: Extreme pain; as the grinding components cause metal flakes to shed from the system, the implant wears down. Metallosis results in numerous additional side effects: Confusion.

In August 2010, DePuy recalled its hip replacement systems ASR XL Acetabular Hip Replacement System and ASR Hip Resurfacing System due to failure rates and side effects including metallosis. The recalls triggered a large number of lawsuits against DePuy and its parent company Johnson & Johnson upon claims that the companies knew about the dangers of the implants before they went on the market in the United States. Tower, Stephen S. "Arthroprosthetic Cobaltism: Neurological and Cardiac Manifestations in Two Patients with Metal-on-Metal Arthroplasty". The Journal of Bone and Joint Surgery. American Volume. 92: 2847–2851. Doi:10.2106/JBJS. J.00125. ISSN 0021-9355. PMID 21037026. Retrieved 9 July 2017