Catalysis is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst, not consumed in the catalyzed reaction and can continue to act repeatedly. Because of this, only small amounts of catalyst are required to alter the reaction rate in principle. In general, chemical reactions occur faster in the presence of a catalyst because the catalyst provides an alternative reaction pathway with a lower activation energy than the non-catalyzed mechanism. In catalyzed mechanisms, the catalyst reacts to form a temporary intermediate, which regenerates the original catalyst in a cyclic process. A substance which provides a mechanism with a higher activation energy does not decrease the rate because the reaction can still occur by the non-catalyzed route. An added substance which does reduce the reaction rate is not considered a catalyst but a reaction inhibitor. Catalysts may be classified as either heterogeneous. A homogeneous catalyst is one whose molecules are dispersed in the same phase as the reactant's molecules.
A heterogeneous catalyst is one whose molecules are not in the same phase as the reactant's, which are gases or liquids that are adsorbed onto the surface of the solid catalyst. Enzymes and other biocatalysts are considered as a third category. In the presence of a catalyst, less free energy is required to reach the transition state, but the total free energy from reactants to products does not change. A catalyst may participate in multiple chemical transformations; the effect of a catalyst may vary due to the presence of other substances known as inhibitors or poisons or promoters. Catalyzed reactions have a lower activation energy than the corresponding uncatalyzed reaction, resulting in a higher reaction rate at the same temperature and for the same reactant concentrations. However, the detailed mechanics of catalysis is complex. Catalysts may bind to the reagents to polarize bonds, e.g. acid catalysts for reactions of carbonyl compounds, or form specific intermediates that are not produced such as osmate esters in osmium tetroxide-catalyzed dihydroxylation of alkenes, or cause dissociation of reagents to reactive forms, such as chemisorbed hydrogen in catalytic hydrogenation.
Kinetically, catalytic reactions are typical chemical reactions. The catalyst participates in this slowest step, rates are limited by amount of catalyst and its "activity". In heterogeneous catalysis, the diffusion of reagents to the surface and diffusion of products from the surface can be rate determining. A nanomaterial-based catalyst is an example of a heterogeneous catalyst. Analogous events associated with substrate binding and product dissociation apply to homogeneous catalysts. Although catalysts are not consumed by the reaction itself, they may be inhibited, deactivated, or destroyed by secondary processes. In heterogeneous catalysis, typical secondary processes include coking where the catalyst becomes covered by polymeric side products. Additionally, heterogeneous catalysts can dissolve into the solution in a solid–liquid system or sublimate in a solid–gas system; the production of most industrially important chemicals involves catalysis. Most biochemically significant processes are catalysed.
Research into catalysis is a major field in applied science and involves many areas of chemistry, notably organometallic chemistry and materials science. Catalysis is relevant to many aspects of environmental science, e.g. the catalytic converter in automobiles and the dynamics of the ozone hole. Catalytic reactions are preferred in environmentally friendly green chemistry due to the reduced amount of waste generated, as opposed to stoichiometric reactions in which all reactants are consumed and more side products are formed. Many transition metals and transition metal complexes are used in catalysis as well. Catalysts called. A catalyst works by providing an alternative reaction pathway to the reaction product; the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst. The disproportionation of hydrogen peroxide creates oxygen, as shown below. 2 H2O2 → 2 H2O + O2This reaction is preferable in the sense that the reaction products are more stable than the starting material, though the uncatalysed reaction is slow.
In fact, the decomposition of hydrogen peroxide is so slow that hydrogen peroxide solutions are commercially available. This reaction is affected by catalysts such as manganese dioxide, or the enzyme peroxidase in organisms. Upon the addition of a small amount of manganese dioxide, the hydrogen peroxide reacts rapidly; this effect is seen by the effervescence of oxygen. The manganese dioxide is not consumed in the reaction, thus may be recovered unchanged, re-used indefinitely. Accordingly, manganese dioxide catalyses this reaction. Catalytic activity is denoted by the symbol z and measured in mol/s, a unit, called katal and defined the SI unit for catalytic activity since 1999. Catalytic activity is not a kind of reaction rate, but a property of the catalyst under certain conditions, in relation to a specific chemical reaction. Catalytic activity of one katal of a catalyst means one mole of that catalyst will catalyse 1 mole of the reactant to product in one second. A catalyst may and will have different catalytic activity for di
Sweden the Kingdom of Sweden, is a Scandinavian Nordic country in Northern Europe. It borders Norway to the west and north and Finland to the east, is connected to Denmark in the southwest by a bridge-tunnel across the Öresund, a strait at the Swedish-Danish border. At 450,295 square kilometres, Sweden is the largest country in Northern Europe, the third-largest country in the European Union and the fifth largest country in Europe by area. Sweden has a total population of 10.2 million. It has a low population density of 22 inhabitants per square kilometre; the highest concentration is in the southern half of the country. Germanic peoples have inhabited Sweden since prehistoric times, emerging into history as the Geats and Swedes and constituting the sea peoples known as the Norsemen. Southern Sweden is predominantly agricultural, while the north is forested. Sweden is part of the geographical area of Fennoscandia; the climate is in general mild for its northerly latitude due to significant maritime influence, that in spite of this still retains warm continental summers.
Today, the sovereign state of Sweden is a constitutional monarchy and parliamentary democracy, with a monarch as head of state, like its neighbour Norway. The capital city is Stockholm, the most populous city in the country. Legislative power is vested in the 349-member unicameral Riksdag. Executive power is exercised by the government chaired by the prime minister. Sweden is a unitary state divided into 21 counties and 290 municipalities. An independent Swedish state emerged during the early 12th century. After the Black Death in the middle of the 14th century killed about a third of the Scandinavian population, the Hanseatic League threatened Scandinavia's culture and languages; this led to the forming of the Scandinavian Kalmar Union in 1397, which Sweden left in 1523. When Sweden became involved in the Thirty Years War on the Reformist side, an expansion of its territories began and the Swedish Empire was formed; this became one of the great powers of Europe until the early 18th century. Swedish territories outside the Scandinavian Peninsula were lost during the 18th and 19th centuries, ending with the annexation of present-day Finland by Russia in 1809.
The last war in which Sweden was directly involved was in 1814, when Norway was militarily forced into personal union. Since Sweden has been at peace, maintaining an official policy of neutrality in foreign affairs; the union with Norway was peacefully dissolved in 1905. Sweden was formally neutral through both world wars and the Cold War, albeit Sweden has since 2009 moved towards cooperation with NATO. After the end of the Cold War, Sweden joined the European Union on 1 January 1995, but declined NATO membership, as well as Eurozone membership following a referendum, it is a member of the United Nations, the Nordic Council, the Council of Europe, the World Trade Organization and the Organisation for Economic Co-operation and Development. Sweden maintains a Nordic social welfare system that provides universal health care and tertiary education for its citizens, it has the world's eleventh-highest per capita income and ranks in numerous metrics of national performance, including quality of life, education, protection of civil liberties, economic competitiveness, equality and human development.
The name Sweden was loaned from Dutch in the 17th century to refer to Sweden as an emerging great power. Before Sweden's imperial expansion, Early Modern English used Swedeland. Sweden is derived through back-formation from Old English Swēoþēod, which meant "people of the Swedes"; this word is derived from Sweon/Sweonas. The Swedish name Sverige means "realm of the Swedes", excluding the Geats in Götaland. Variations of the name Sweden are used in most languages, with the exception of Danish and Norwegian using Sverige, Faroese Svøríki, Icelandic Svíþjóð, the more notable exception of some Finnic languages where Ruotsi and Rootsi are used, names considered as referring to the people from the coastal areas of Roslagen, who were known as the Rus', through them etymologically related to the English name for Russia; the etymology of Swedes, thus Sweden, is not agreed upon but may derive from Proto-Germanic Swihoniz meaning "one's own", referring to one's own Germanic tribe. Sweden's prehistory begins in the Allerød oscillation, a warm period around 12,000 BC, with Late Palaeolithic reindeer-hunting camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania.
This period was characterised by small bands of hunter-gatherer-fishers using flint technology. Sweden is first described in a written source in Germania by Tacitus in 98 AD. In Germania 44 and 45 he mentions the Swedes as a powerful tribe with ships that had a prow at each end. Which kings ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC; as for literacy in Sweden itself, the runic script was in use among the south Scandinavian elite by at least the 2nd century AD, but all that has come down to the present from the Roman Period is curt inscriptions on artefacts of male names, demonstrating th
The Karolinska Institute is a research-led medical university in Solna within the Stockholm urban area of Sweden. It covers areas such as biochemistry, pharmacology, anatomy and medical microbiology, among others, it is recognised as Sweden's best university and one of the largest, most prestigious medical universities in the world. It is the highest ranked in all Scandinavia; the Nobel Assembly at the Karolinska Institute awards the Nobel Prize in Medicine. The assembly consists of fifty professors from various medical disciplines at the university; the current rector of Karolinska Institute is Ole Petter Ottersen, who took office in August 2017. The Karolinska Institute was founded in 1810 on the island of Kungsholmen on the west side of Stockholm. A second campus was established more in Flemingsberg, south of Stockholm; the Karolinska Institute is ranked among the top medical universities internationally in a number of ranking tables. The Karolinska Institute is Sweden's third oldest medical school, after Uppsala University and Lund University.
It is one of Sweden's largest centres for training and research, accounting for 30% of the medical training and more than 40% of all academic medical and life science research conducted in Sweden. The Karolinska University Hospital, located in Solna and Huddinge, is associated with the university as a research and teaching hospital. Together they form an academic health science centre. While most of the medical programs are taught in Swedish, the bulk of the Ph. D. projects are conducted in English. The institute's name is a reference to the Caroleans; the Karolinska Institute was founded by King Karl XIII on 13 December 1810 as an "academy for the training of skilled army surgeons" after one in three soldiers wounded in the Finnish War against Russia died in field hospitals. Indeed, a report of the time came to the conclusion that "the medical skills of the army barber-surgeons are manifestly inadequate, so Sweden needs to train surgeons in order to better prepare the country for future wars."
Just one year in 1811, the Karolinska Institute was granted license to train not only surgeons but medical practitioners in general. As one of KI's first professors, Jöns Jacob Berzelius laid the foundations of the newly inaugurated institute's scientific orientation, which in 1816 is granted the name Carolinska Institutet; this name, didn't make an impact at the time and so was expanded to Carolinska Medico Chirurgiska institutet, which proved more popular when preceded by the epithet Kongliga, as introduced in 1822. This original institute was situated in the Royal Bakery on Riddarholmen and within a just a couple of years had grown to encompass four professorships in anatomy, natural history and pharmacy, theoretical medicine and practical medicine. At around the same time Anders Johan Hagströmer, a professor of anatomy and surgery from the Collegium Medicum, was appointed the institute's first inspector, a post equivalent to today's president. In the same year, the institute moved to the old Glasbruk quarter on Norr Mälarstrand, beside what is now the City Hall.
The move across the waters of Riddarfjärden was accomplished with the help of barges, one of, said to have capsized, consigning parts of Hagströmer's collection of preparations to the lake bed. Despite this his library survives intact and today forms part of the KI-Swedish Society of Medicine museum at the institute's Hagströmer Library. In 1861 the institute reached a significant milestone in being awarded the right to confer its own degrees. This, in turn, led to an increase in the size of the student body, necessitating the demolition of the old building on the Glasbruk plot and its replacement with a new, larger one; this new institute building was built in stages during the 1880s and into the first decade of the 20th century. Although it had gained the right to confer general degrees, KI wasn't licensed to confer medical degrees until 1874. Though the institute could run courses in medicine, the right to confer medical degrees was exclusively that of Uppsala University. Following on from this change in the institute's status the first doctoral thesis was defended at KI by Alfred Levertin, on the subject of "Om Torpa Källa".
Just shortly thereafter the Medical Students' Union was formed. The next decade was one of firsts. By 1880 the Karolinska Institute had started to accept women and so it was in 1884 that Karolina Widerström became the first woman to obtain a bachelor's degree in medicine from the institute. Anna Stecksén became the first woman to obtain a doctorate from the university. Just five years following the death of Alfred Nobel in 1895, the Karolinska Institute received the right to select the recipient of the Nobel Prize in Physiology or Medicine. Since this assignment has given the Karolinska Institute a broad contact network in the field of medical science. Indeed, over the years, five of the institute's own researchers have been awarded the Nobel Prize in Physiology or Medicine. By 1930 the Swedish parliament had decided that a new teaching hospital was needed and
Uppsala University is a research university in Uppsala, is the oldest university in Sweden and all of the Nordic countries still in operation, founded in 1477. It ranks among the world's 100 best universities in several high-profile international rankings; the university embraces natural sciences. The university rose to pronounced significance during the rise of Sweden as a great power at the end of the 16th century and was given a relative financial stability with the large donation of King Gustavus Adolphus in the early 17th century. Uppsala has an important historical place in Swedish national culture and for the Swedish establishment: in historiography, literature and music. Many aspects of Swedish academic culture in general, such as the white student cap, originated in Uppsala, it shares some peculiarities, such as the student nation system, with Lund University and the University of Helsinki. Uppsala belongs to the Coimbra Group of European universities and to the Guild of European Research-Intensive Universities.
The university has nine faculties distributed over three "disciplinary domains". It has 2,300 doctoral students, it has a teaching staff of 1,800 out of a total of 6,900 employees. Twenty-eight per cent of the 716 professors at the university are women. Of its turnover of SEK 6.6 billion in 2016, 29% was spent on education at Bachelor's and Master's level, while 70% was spent on research and research programs. Architecturally, Uppsala University has traditionally had a strong presence in Fjärdingen, the neighbourhood around the cathedral on the western side of the River Fyris. Despite some more contemporary building developments further away from the centre, Uppsala's historic centre continues to be dominated by the presence of the university; as with most medieval universities, Uppsala University grew out of an ecclesiastical center. The archbishopric of Uppsala had been one of the most important sees in Sweden proper since Christianity first spread to this region in the ninth century. Uppsala had long been a hub for regional trade, had contained settlements dating back into the deep Middle Ages.
As was the case with most medieval universities, Uppsala had been chartered through a papal bull. Uppsala's bull, which granted the university its corporate rights, was issued by Pope Sixtus IV in 1477, established a number of provisions. Among the most important of these was that the university was given the same freedoms and privileges as the University of Bologna; this included the right to establish the four traditional faculties of theology, law and philosophy, to award the bachelor's, master's, doctoral degrees. The archbishop of Uppsala was named as the university's Chancellor, was charged with maintaining the rights and privileges of the university and its members; the turbulent period of the reformation of King Gustavus Vasa resulted in a drop in the relatively insignificant number of students in Uppsala, seen as a center of Catholicism and of potential disloyalty to the Crown. Swedish students travelled to one of the Protestant universities in Germany Wittenberg. There is some evidence of academic studies in Uppsala during the 16th century.
At the end of the century the situation had changed, Uppsala became a bastion of Lutheranism, which Duke Charles, the third of the sons of Gustavus Vasa to become king used to consolidate his power and oust his nephew Sigismund from the throne. The Meeting of Uppsala in 1593 established Lutheran orthodoxy in Sweden, Charles and the Council of state gave new privileges to the university on 1 August of the same year. Theology still had precedence, but in the privileges of 1593, the importance of a university to educate secular servants of the state was emphasized. Three of the seven professorial chairs which were established were in Theology. A fourth chair was given to Ericus Jacobi Skinnerus, appointed rector, but whose discipline was not mentioned in the charter. Of the professors, several were taken over from the Collegium Regium in Stockholm, functioning for a few years but closed in 1593. An eighth chair, in Medicine, received no appointee for several years. In 1599 the number of students was 150.
In 1600 the first post-reformation conferment of degrees took place. In the same year, the antiquarian and mystic Johannes Bureus designed and engraved the seal of the university, today used as part of the logotype; the medieval university had been a school for theology. The aspirations of the emergent new great power of Sweden demanded a different kind of learning. Sweden both grew through conquests and went through a complete overhaul of its administrative structure, it required a much larger class of civil educators than before. Preparatory schools, were founded during this period in various cathedral towns, notably Västerås in 1623. Beside Uppsala, new universities were founded in more distant parts of the Swedish Realm, the University of Dorpat in Estonia and the University of Åbo in Finland. Af
Cerium is a chemical element with symbol Ce and atomic number 58. Cerium is a soft and silvery-white metal that tarnishes when exposed to air, it is soft enough to be cut with a knife. Cerium is the second element in the lanthanide series, while it shows the +3 oxidation state characteristic of the series, it exceptionally has a stable +4 state that does not oxidize water, it is considered one of the rare-earth elements. Cerium has no biological role and is not toxic. Despite always occurring in combination with the other rare-earth elements in minerals such as those of the monazite and bastnäsite groups, cerium is easy to extract from its ores, as it can be distinguished among the lanthanides by its unique ability to be oxidized to the +4 state, it is the most common of the lanthanides, followed by neodymium and praseodymium. It is the 26th-most abundant element, making up 66 ppm of the Earth's crust, half as much as chlorine and five times as much as lead. Cerium was the first of the lanthanides to be discovered, in Bastnäs, Sweden by Jöns Jakob Berzelius and Wilhelm Hisinger in 1803, independently by Martin Heinrich Klaproth in Germany in the same year.
In 1839 Carl Gustaf Mosander became the first to isolate the metal. Today and its compounds have a variety of uses: for example, cerium oxide is used to polish glass and is an important part of catalytic converters. Cerium metal is used in ferrocerium lighters for its pyrophoric properties. Cerium-doped YAG phosphor is used in conjunction with blue light-emitting diodes to produce white light in most commercial white LED light sources. Cerium is the second element of the lanthanide series. In the periodic table, it appears between the lanthanides lanthanum to its left and praseodymium to its right, above the actinide thorium, it is a ductile metal with a hardness similar to that of silver. Its 58 electrons are arranged in the configuration 4f15d16s2, of which the four outer electrons are valence electrons. After lanthanum, the 4f orbitals contract and are lowered in energy to the point that they participate in chemical reactions. Most lanthanides can use only three electrons as valence electrons, as afterwards the remaining 4f electrons are too bound: cerium is an exception because of the stability of the empty f-shell in Ce4+ and the fact that it comes early in the lanthanide series, where the nuclear charge is still low enough until neodymium to allow the removal of the fourth valence electron by chemical means.
Four allotropic forms of cerium are known to exist at standard pressure, are given the common labels of α to δ: The high-temperature form, δ-cerium, has a bcc crystal structure and exists above 726 °C. The stable form below 726 °C to room temperature is γ-cerium, with an fcc crystal structure; the dhcp form β-cerium is the equilibrium structure from room temperature to −150 °C. The fcc form α-cerium is stable below about −150 °C. Other solid phases occurring only at high pressures are shown on the phase diagram. Both γ and β forms are quite stable at room temperature, although the equilibrium transformation temperature is estimated at around 75 °C. Cerium has a variable electronic structure; the energy of the 4f electron is nearly the same as that of the outer 5d and 6s electrons that are delocalized in the metallic state, only a small amount of energy is required to change the relative occupancy of these electronic levels. This gives rise to dual valence states. For example, a volume change of about 10% occurs when cerium is subjected to high pressures or low temperatures.
It appears that the valence changes from about 3 to 4 when it is compressed. At lower temperatures the behavior of cerium is complicated by the slow rates of transformation. Transformation temperatures are subject to substantial hysteresis and values quoted here are approximate. Upon cooling below −15 °C, γ-cerium starts to change to β-cerium, but the transformation involves a volume increase and, as more β forms, the internal stresses build up and suppress further transformation. Cooling below −160 °C will start formation of α-cerium but this is only from remaining γ-cerium. Β-cerium does not transform to α-cerium except in the presence of stress or deformation. At atmospheric pressure, liquid cerium is more dense than its solid form at the melting point. Occurring cerium is made up of four isotopes: 136Ce, 138Ce, 140Ce, 142Ce. All four are observationally stable, though the light isotopes 136Ce and 138Ce are theoretically expected to undergo inverse double beta decay to isotopes of barium, the heaviest isotope 142Ce is expected to undergo double beta decay to 142Nd or alpha decay to 138Ba.
Additionally, 140Ce would release energy upon spontaneous fission. None of these decay modes have yet been observed, though the double beta decay of 136Ce, 138Ce, 142Ce has been experimentally searched for; the current experimental limits for their half-lives are: 136Ce: >3.8×1016 y 138Ce: >1.5×1014 y 142Ce: >5×1016 yAll other cerium isotopes are synthetic and radioactive. The most stable of them are 144Ce with a half-life of 284.9 days, 139Ce with a half-life of 137.6 days, 143Ce with a half-life of 33.04 days, 141Ce with a half-life of 32.5 days. All other radioactive cerium isotopes have half-lives under four days, most of them have half-lives under ten minutes; the isotopes between 140Ce and 144Ce inclusive occur as fission products of uranium. The primary decay mode of the isotopes lighter than 140Ce is inverse bet
Wilhelm Hisinger was a Swedish physicist and chemist who in 1807, working in coordination with Jöns Jakob Berzelius, noted that in electrolysis any given substance always went to the same pole, that substances attracted to the same pole had other properties in common. This showed that there was at least a qualitative correlation between the chemical and electrical natures of bodies. In 1803, in separate laboratories, Martin Heinrich Klaproth in one, Berzelius and Hisinger in another, the element Cerium was discovered, named after the newly discovered asteroid, Ceres. Discovered nearly in two laboratories, though it was shown that Berzelius and Hisinger's cerium was a mixture of cerium, lanthanum and so-called didymium. Hisinger was elected a member of the Royal Swedish Academy of Sciences in 1804; the mineral hisingerite, an iron silicate, with the formula Fe3+2Si2O54·2H2O, is named after Hisinger. There is Aluminian Hisingerite, when one of the iron atoms is replaced by aluminum; the mountain of Hisingerfjellet in Nathorst Land at Spitsbergen, Svalbard, is named after him.
Bastnäs Wilhelm Hisinger in Nordisk familjebok Wilhelm Hisinger in Svenskt biografiskt handlexikon
Pehr Wilhelm Wargentin
Pehr Wilhelm Wargentin, Swedish astronomer and demographer. Wargentin was the son of the vicar of Sunne Wilhelm Wargentin and his spouse Christina Aroselia, the great grandson of Joachim Wargentin, a Lübeck-born burgher of Åbo in Finland; when Pehr Wargentin was 12 years old he observed a lunar eclipse which would spark his lifelong interest in Astronomy. During his tenure at Frösö trivialskola, his teacher deemed him advanced enough to continue directly to Uppsala University. However, Wargentin's father wanted him first to attend the gymnasium of Härnösand. According to his own account, Wargentin was unimpressed with the purely classical and theological curriculum and the lack of any education in the sciences and did not finish the fourth year. In 1735, Wargentin matriculated as a student at the University of Uppsala. Olof Hiorter was one of his instructors, he graduated with the degree of filosofie magister in 1743 and became a docent in astronomy in 1746 and an adjunct in 1748. He was called to Stockholm as secretary of the Royal Swedish Academy of Sciences in 1749 on the death of secretary Pehr Elvius, Jr. and stayed on this post until his death.
Wargentin therefore became the first long-serving secretary of the Academy, founded in 1739. He is seen as an important person in leading the Academy to its first golden era. Wargentin became the first director of the Stockholm Observatory founded by the Academy of Sciences on the initiative of his predecessor and completed in 1753. In 1756 Wargentin married Christina Magdalena Raab, a marriage that would produce three daughters until his wife's death due to a miscarriage in 1769, he was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1781. Wargentin made studies on the moons of Jupiter and published his first paper on the topic in 1741 in the Acta of the Royal Society of Sciences in Uppsala; the crater Wargentin on the Moon is named after him, as is the secondary school Wargentinsskolan in Östersund, Jämtland, with a historical continuity going back to the school Wargentin himself attended on Frösön. In his career, Wargentin's focus shifted from astronomy to demography.
The Swedish government decreed in 1736 that the clergy should maintain registers of all births and deaths in their parishes, the concept emerged in the Swedish Royal Academy of Sciences that these Parish data should be subjected to national analysis. Wargentin was assigned to lead this task nationally in 1754, subsequently published a number of demographic articles in the Transactions of the Swedish Royal Academy, in particular “Mortaliteten i Sverige, i anledning af Tabell-Verket”. Biography from Nordisk Familjebok, 2nd Ed.. Wargentins notes on his family and published in the journal Personhistorisk tidskrift 1904, pp. 28–38. Biographical article on Wargentin from the periodical Svenska Familj-Journalen 1879