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The Portlethen Moss is an acidic bog nature reserve located to the west of the town of Portlethen, Aberdeenshire in Scotland. Like other mosses, this wetland area supports a variety of plant and animal species, even though it has been subject to certain development and agricultural degradation pressures. For example, the Great Crested Newt was found here prior to the expansion of the town of Portlethen. Many acid-loving vegetative species occur in Portlethen Moss, and the habitat is monitored by the Scottish Wildlife Trust. Portlethen Moss is the location of considerable prehistoric, Middle Ages and seventeenth century history, largely due to a ridge near the bog which was the route of early travellers. By at least the Middle Ages, this trackway was more formally constructed with raised stonework and called the Causey Mounth. Without this drovers' road, travel through the Portlethen Moss and several nearby bogs would have been impossible between Aberdeen and coastal points to the south. == History == Prehistoric man inhabited the Portlethen Moss area as evidenced by well-preserved Iron Age stone circles and other excavated artifacts nearby. Only the outcrops and ridge areas would have been habitable, but the desirability of primitive habitation would have been enhanced by proximity to the sea and natural defensive protection of the moss to impede intruders. From Tacitus accounts of the Roman general Agricola, it is known that the Romans were daunted by Portlethen Moss, Netherley Red Moss, Cookney Moss and other local bogs that hindered travel. This is also evidenced by the Roman Camp of Raedykes having been established immediately south of this cluster of mosses; the Romans, not being able to progress further north, turned inland toward Netherley. The Portlethen Moss is near the Grampian Mountains. The ancient Causey Mounth passage specifically connected the Bridge of Dee to
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the town of Stonehaven. This route was used to access the historic meeting of the Covenanters at Muchalls Castle in the year 1638 AD as they opposed the Bishops of Aberdeen. The route was also that taken by William Keith, 7th Earl Marischal and James Graham, 1st Marquess of Montrose when they led a Covenanter army of 9000 men in the biggest battle of the Bishops' Wars in 1639 Further to the east of Portlethen Moss lie three original coastal fishing villages: Findon, Portlethen Village and Downies. In the period from 1960 to 2005, Portlethen has developed as a dormitory town to Aberdeen and a location for retail superstores. == Conservation status == The Portlethen Moss is a recognised nature preserve by the Scottish Wildlife Trust (with designation PLM076) and the Aberdeenshire Council. While peat cutting was conducted in prehistoric and Middle Ages times, there has been no harvesting of peat in the modern era. There is some ongoing loss of moss habitat from cattle grazing, but the most significant threat is from ongoing land development pressure; in fact, half of the Portlethen Moss has been lost to urban (low-density) land development by the town of Portlethen during the period 1985 to 2005. Trampling is considered an insignificant threat due to the small animal or human presence in the existing nature reserve area; furthermore, cattle grazing, while ongoing, is deemed a much lesser current threat than population expansion pressure. Enrichment (addition of grazing animal manure) is not a major issue due to the low density of animals. As a net result, damage to the primordial moss is considered extensive and widespread by the Scottish Wildlife Trust. The raised bog habitat of the Portlethen Moss is also protected by the United Kingdom Biodiversity Action Plan. == Topography and meteorology == Portlethen
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Moss is considered a raised bog, because its general situation is on higher ground, at the edge of the Mounth, a coastal mountain spur of the Grampian Mountains overlooking the North Sea. There are rock outcrops and strewn boulders relict from the glacial age at this site. Elevations within the Portlethen Moss range from approximately 35 to 60 metres above sea level. Formation of this moss has occurred due to extensive sets of depressions in the underlying rock formations of Old Red Sandstone. The entire water composition of the bog thus has been provided by precipitation with no source of surface runoff, since the topography reduces to lower elevations in every direction. Due to the high winds, moderate precipitation and cool temperatures that generally prevail, conditions are favourable for the formation of an acid bog, since water stagnates, but eventually evaporates with ensuing acidity enhancement of decaying organic matter. There was virtually no drainage outlet in prehistoric times, and little drainage even in modern times. == Evolution of Portlethen Moss == Many coastal mosses were initiated by the process of glaciation, which sheared rock formations to a generally level terrain, while also gouging moderate-sized craters that would pond. This description fits the fundamental situation of Portlethen Moss, where sphagnum would have flourished over millennia of evaporation, further intensifying the soil acidity, fueled by organic matter decaying, with little drainage outlet. A layer of sphagnum moss would have developed at the benthic level of the bog, and additional sphagnum layers floated in mats atop the bog. At an intermediate level of evolution, thick peat layers formed from the decay and carbonisation of the rotting sphagnum. Generations of Carex and Juncus flourished, leading to further decay of these materials and eventual heightening of the organic mass. Finally, secondary vegetation took root in
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the spongy sphagnum mats, adding greater biomass to the bog. In some cases, the heavily saturated organic layers could rupture, spilling large volumes of mud and organic debris into surrounding fields, thus enabling a bed for further spatial expansion of the entire bog. Ultimately, the colour of the moss waters became blood red from the successive organic decay and stagnation. Only in times associated with cattle grazing and significant human presence (probably the late Iron Age) would this process reverse and the bog reduce in size. == Vegetation == A wide variety of sphagnum, sedges, rushes and other characteristic bog species inhabit Portlethen Moss. Sometimes, insectivorous plants reside in mosses, since the soils are generally nutrient-poor. The heath also serves as a food source for the area roe deer, while Corydalis claviculata is an attractive host for numerous butterfly larvae. Representative plant species found in this nature reserve include: == Relation to other mosses == There are numerous mosses or bog habitats in Scotland, many of them situated also in Aberdeenshire, including the Cookney Moss, Leuchar Moss and Red Moss of Netherley nearby. Many other shires within Scotland that contain mosses such as Fife, Angus, Morayshire and Lanarkshire. Some of these are lowland bogs and others, like Portlethen Moss, are raised bogs. There are other similar acidic peat bogs in the northern part of North America, Russia and northern Europe, but in those locations, they are usually called "bogs". == See also == Acid rain Fen Haraldskær Woman Surface runoff == References == == External links == Portlethen Moss: Comparison of historic to modern conditions
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Nicole Oresme (; French: [nikɔl ɔʁɛm]; 1 January 1325 – 11 July 1382), also known as Nicolas Oresme, Nicholas Oresme, or Nicolas d'Oresme, was a French philosopher of the later Middle Ages. He wrote influential works on economics, mathematics, physics, astrology, astronomy, philosophy, and theology. He was Bishop of Lisieux, a translator, a counselor of King Charles V of France, and one of the most original thinkers of 14th-century Europe. == Life == Nicole Oresme was born c. 1320–1325 in the village of Allemagnes (today's Fleury-sur-Orne) in the vicinity of Caen, Normandy, in the diocese of Bayeux. Practically nothing is known concerning his family. The fact that Oresme attended the royally sponsored and subsidised College of Navarre, an institution for students too poor to pay their expenses while studying at the University of Paris, makes it probable that he came from a peasant family. Oresme studied the "arts" in Paris, together with Jean Buridan (the so-called founder of the French school of natural philosophy), Albert of Saxony and perhaps Marsilius of Inghen, and there received the Magister Artium. He was already a regent master in arts by 1342, during the crisis over William of Ockham's natural philosophy. In 1348, he was a student of theology in Paris. In 1356, he received his doctorate and in the same year he became grand master (grand-maître) of the College of Navarre. In 1364, he was appointed dean of the Cathedral of Rouen. Around 1369, he began a series of translations of Aristotelian works at the request of Charles V, who granted him a pension in 1371 and, with royal support, was appointed bishop of Lisieux in 1377. In 1382, he died in Lisieux. == Scientific work == === Cosmology === In his Livre du ciel et du monde Oresme discussed a range of
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evidence for and against the daily rotation of the Earth on its axis. From astronomical considerations, he maintained that if the Earth were moving and not the celestial spheres, all the movements that we see in the heavens that are computed by the astronomers would appear exactly the same as if the spheres were rotating around the Earth. He rejected the physical argument that if the Earth were moving the air would be left behind causing a great wind from east to west. In his view the Earth, Water, and Air would all share the same motion. As to the scriptural passage that speaks of the motion of the Sun, he concludes that "this passage conforms to the customary usage of popular speech" and is not to be taken literally. He also noted that it would be more economical for the small Earth to rotate on its axis than the immense sphere of the stars. Nonetheless, he concluded that none of these arguments were conclusive and "everyone maintains, and I think myself, that the heavens do move and not the Earth." === Critiques of astrology === In his mathematical work, Oresme developed the notion of incommensurate fractions, fractions that could not be expressed as powers of one another, and made probabilistic, statistical arguments as to their relative frequency. From this, he argued that it was very probable that the length of the day and the year were incommensurate (irrational), as indeed were the periods of the motions of the moon and the planets. From this, he noted that planetary conjunctions and oppositions would never recur in quite exactly the same way. Oresme maintained that this disproves the claims of astrologers who, thinking "they know with punctual exactness the motions, aspects, conjunctions and oppositions… [judge] rashly and erroneously about future events."
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Oresme's critique of astrology in his Livre de divinacions treats it as having six parts. The first, essentially astronomy, the movements of heavenly bodies, he considers good science but not precisely knowable. The second part deals with the influences of the heavenly bodies on earthly events at all scales. Oresme does not deny such influence, but states, in line with a commonly held opinion, that it could either be that arrangements of heavenly bodies signify events, purely symbolically, or that they actually cause such events, deterministically. Mediaevalist Chauncey Wood remarks that this major elision "makes it very difficult to determine who believed what about astrology". The third part concerns predictiveness, covering events at three different scales: great events such as plagues, famines, floods and wars; weather, winds and storms; and medicine, with influences on the humours, the four Aristotelian fluids of the body. Oresme criticizes all of these as misdirected, though he accepts that prediction is a legitimate area of study, and argues that the effect on the weather is less well known than the effect on great events. He observes that sailors and farmers are better at predicting weather than astrologers, and specifically attacks the astrological basis of prediction, noting correctly that the zodiac has moved relative to the fixed stars (because of precession of the equinoxes) since the zodiac was first described in ancient times. These first three parts are what Oresme considers the physical influences of the stars and planets (including sun and moon) on the earth, and while he offers critiques of them, he accepts that effects exist. The last three parts are what Oresme considers to concern (good or bad) fortune. They are interrogations, meaning asking the stars when to do things such as business deals; elections, meaning choosing the best time to do things
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such as getting married or fighting a war and nativities, meaning the natal astrology with birth charts that forms much of modern astrological practice. Oresme classifies interrogations and elections as "totally false" arts, but his critique of nativities is more measured. He denies that any path is predetermined by the heavenly bodies, because humans have free will, but he accepts that the heavenly bodies can influence behaviour and habitual mood, via the combination of humours in each person. Overall, Oresme's skepticism is strongly shaped by his understanding of the scope of astrology. He accepts things a modern skeptic would reject, and rejects some things — such as the knowability of planetary movements, and effects on weather — that are accepted by modern science. === Sense perception === In discussing the propagation of light and sound, Oresme adopted the common medieval doctrine of the multiplication of species, as it had been developed by optical writers such as Alhacen, Robert Grosseteste, Roger Bacon, John Pecham, and Witelo. Oresme maintained that these species were immaterial, but corporeal (i.e., three-dimensional) entities. === Mathematics === Oresme's most important contributions to mathematics are contained in Tractatus de configurationibus qualitatum et motuum. In a quality, or accidental form, such as heat, he distinguished the intensio (the degree of heat at each point) and the extensio (as the length of the heated rod). These two terms were often replaced by latitudo and longitudo. For the sake of clarity, Oresme conceived the idea of visualizing these concepts by plane figures, approaching what we would now call rectangular coordinates. The intensity of the quality was represented by a length or latitudo proportional to the intensity erected perpendicular to the base at a given point on the base line, which represents the longitudo. Oresme proposed that the geometrical form of such
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a figure could be regarded as corresponding to a characteristic of the quality itself. Oresme defined a uniform quality as that which is represented by a line parallel to the longitude, and any other quality as difform. Uniformly varying qualities are represented by a straight line inclined to the axis of the longitude, while he described many cases of nonuniformly varying qualities. Oresme extended this doctrine to figures of three dimensions. He considered this analysis applicable to many different qualities such as hotness, whiteness, and sweetness. Significantly for later developments, Oresme applied this concept to the analysis of local motion where the latitudo or intensity represented the speed, the longitudo represented the time, and the area of the figure represented the distance travelled. He shows that his method of figuring the latitude of forms is applicable to the movement of a point, on condition that the time is taken as longitude and the speed as latitude; quantity is, then, the space covered in a given time. In virtue of this transposition, the theorem of the latitudo uniformiter difformis became the law of the space traversed in case of uniformly varied motion; thus Oresme published what was taught over two centuries prior to Galileo's making it famous. Diagrams of the velocity of an accelerating object against time in On the Latitude of Forms by Oresme have been cited to credit Oresme with the discovery of "proto bar charts". In De configurationibus Oresme introduces the concept of curvature as a measure of departure from straightness, for circles he has the curvature as being inversely proportional to radius and attempts to extend this to other curves as a continuously varying magnitude. Significantly, Oresme developed the first proof of the divergence of the harmonic series. His proof, requiring less advanced mathematics than current standard
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tests for divergence (for example, the integral test), begins by noting that for any n that is a power of 2, there are n/2 − 1 terms in the series between 1/(n/2) and 1/n. Each of these terms is at least 1/n, and since there are n/2 of them they sum to at least 1/2. For instance, there is one term 1/2, then two terms 1/3 + 1/4 that together sum to at least 1/2, then four terms 1/5 + 1/6 + 1/7 + 1/8 that also sum to at least 1/2, and so on. Thus the series must be greater than the series 1 + 1/2 + 1/2 + 1/2 + ..., which does not have a finite limit. This proves that the harmonic series must be divergent. This argument shows that the sum of the first n terms grows at least as fast as ( 1 / 2 ) log 2 n {\displaystyle (1/2)\log _{2}n} . (See also Harmonic series) Oresme was the first mathematician to prove this fact, and (after his proof was lost) it was not proven again until the 17th century by Pietro Mengoli. He also worked on fractional powers, and the notion of probability over infinite sequences, ideas which would not be further developed for the next three and five centuries, respectively.: 142–3 === On local motion === Oresme, like many of his contemporaries such as John Buridan and Albert of Saxony, shaped and critiqued Aristotle's and Averroes's theories of motion to their own liking. Taking inspiration from the theories of forma fluens and fluxus formae, Oresme would suggest his own descriptions for change and motion in his commentary of Physics. Forma fluens is described by William of Ockham as "Every thing that is moved is moved by a mover," and fluxus formae
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as "Every motion is produced by a mover." Buridan and Albert of Saxony each subscribed to the classic interpretation of flux being an innate part of an object, but Oresme differs from his contemporaries in this aspect. Oresme agrees with fluxus formae in that motion is attributed to an object, but that an object is “set into” motion, rather than “given” motion, denying a distinction between a motionless object and an object in motion. To Oresme, an object moves, but it is not a moving object. Once an object begins movement through the three dimensions it has a new “modus rei” or “way of being,” which should only be described through the perspective of the moving object, rather than a distinct point. This line of thought coincides with Oresme's challenge to the structure of the universe. Oresme's description of motion was not popular, although it was thorough. A Richard Brinkley is thought to be an inspiration for the modus-rei description, but this is uncertain. === Political thought === Oresme provided the first modern vernacular translations of Aristotle's moral works that are still extant today. Between 1371 and 1377 he translated Aristotle's Ethics, Politics and Economics (the last of which is nowadays considered to be pseudo-Aristotelian) into Middle French. He also extensively commented on these texts, thereby expressing some of his political views. Like his predecessors Albert the Great, Thomas Aquinas and Peter of Auvergne (and quite unlike Aristotle), Oresme favours monarchy as the best form of government. His criterion for good government is the common good. A king (by definition good) takes care of the common good, whereas a tyrant works for his own profit. A monarch can ensure the stability and durability of his reign by letting the people participate in government. This has rather confusingly and anachronistically been
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called popular sovereignty. Like Albert the Great, Thomas Aquinas, Peter of Auvergne and especially Marsilius of Padua, whom he occasionally quotes, Oresme conceives of this popular participation as rather restrictive: only the multitude of reasonable, wise and virtuous men should be allowed political participation by electing and correcting the prince, changing the law and passing judgement. Oresme, however, categorically denies the right of rebellion since it endangers the common good. Unlike earlier commentators, however, Oresme prescribes the law as superior to the king's will. It must only be changed in cases of extreme necessity. Oresme favours moderate kingship, thereby negating contemporary absolutist thought, usually promoted by adherents of Roman law. Furthermore, Oresme doesn't comply to contemporary conceptions of the French king as sacred, as promoted by Évrart de Trémaugon in his Songe du vergier or Jean Golein in his Traité du sacre. Although he heavily criticises the Church as corrupt, tyrannical and oligarchical, he never fundamentally questions its necessity for the spiritual well-being of the faithful. It has traditionally been thought that Oresme's Aristotelian translations had a major influence on King Charles V's politics: Charles' laws concerning the line of succession and the possibility of a regency for an underage king have been accredited to Oresme, as has the election of several high-ranking officials by the king's council in the early 1370s. Oresme may have conveyed Marsilian and conciliarist thought to Jean Gerson and Christine de Pizan. === Economics === With his Treatise on the origin, nature, law, and alterations of money (De origine, natura, jure et mutationibus monetarum), one of the earliest manuscripts devoted to an economic matter, Oresme brings an interesting insight on the medieval conception of money. Oresme's viewpoints of theoretical architecture are outlined in Part 3 and 4 of his work from De moneta, which he
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completed between 1356 and 1360. His belief is that humans have a natural right to own property; this property belongs to the individual and community. In Part 4, Oresme provides a solution to a political problem as to how a monarch can be held accountable to put the common good before any private affairs. Though the monarchy rightfully has claims on all money given an emergency, Oresme states that any ruler that goes through this is a “Tyrant dominating slaves”. Oresme was one of the first medieval theorists that did not accept the right of the monarch to have claims on all money as well as “his subjects’ right to own private property.” === Psychology === Oresme was known to be a well rounded psychologist. He practiced the technique of “inner senses” and studied the perception of the world. Oresme contributed to 19th and 20th century psychology in the fields of cognitive psychology, perception psychology, psychology of consciousness, and psychophysics. Oresme discovered the psychology of unconscious and came up with the theory of unconscious conclusion of perception. He developed many ideas beyond quality, quantity, categories and terms which were labeled “theory of cognition”. == Posthumous reputation == Oresme's economic thought remained well regarded centuries after his death. In a 1920 Essay on Medieval Economic Teaching, Irish economist George O'Brien summed up the favorable academic consensus over Oresme's Treatise on the origin, nature, law, and alterations of money: The merits of this work have excited the unanimous admiration of all who have studied it. Roscher says that it contains 'a theory of money, elaborated in the fourteenth century, which remains perfectly correct to-day, under the test of the principles applied in the nineteenth century, and that with a brevity, a precision, a clarity, and a simplicity of language which is a
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striking proof of the superior genius of its author.' According to Brants, 'the treatise of Oresme is one of the first to be devoted ex professo to an economic subject, and it expresses many ideas which are very just, more just than those which held the field for a long period after him, under the name of mercantilism, and more just than those which allowed of the reduction of money as if it were nothing more than a counter of exchange.' 'Oresme's treatise on money,' says Macleod, 'may be justly said to stand at the head of modern economic literature. This treatise laid the foundations of monetary science, which are now accepted by all sound economists.' 'Oresme's completely secular and naturalistic method of treating one of the most important problems of political economy,' says Espinas, 'is a signal of the approaching end of the Middle Ages and the dawn of the Renaissance.' Dr. Cunningham adds his tribute of praise: 'The conceptions of national wealth and national power were ruling ideas in economic matters for several centuries, and Oresme appears to be the earliest of the economic writers by whom they were explicitly adopted as the very basis of his argument…. A large number of points of economic doctrine in regard to coinage are discussed with much judgment and clearness.' Endemann alone is inclined to quarrel with the pre-eminence of Oresme; but on this question, he is in a minority of one. == Selected works in English translation == Nicole Oresme's De visione stellarum (On seeing the stars): a critical edition of Oresme's treatise on optics and atmospheric refraction, translated by Dan Burton, (Leiden; Boston: Brill, 2007, ISBN 9789004153707) Nicole Oresme and the marvels of nature: a study of his De causis mirabilium, translated by Bert Hansen, (Toronto: Pontifical Institute of
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Mediaeval Studies, 1985, ISBN 9780888440686) Questiones super quatuor libros meteororum, in SC McCluskey, ed, Nicole Oresme on Light, Color and the Rainbow: An Edition and Translation, with introduction and critical notes, of Part of Book Three of his Questiones super quatuor libros meteororum (PhD dissertation, University of Wisconsin, 1974, Google Books) Nicole Oresme and the kinematics of circular motion: Tractatus de commensurabilitate vel incommensurabilitate motuum celi, translated by Edward Grant, (Madison: University of Wisconsin Press, 1971) Nicole Oresme and the medieval geometry of qualities and motions: a treatise on the uniformity and difformity of intensities known as Tractatus de configurationibus qualitatum et motuum, translated by Marshall Clagett, (Madison: University of Wisconsin Press, 1971, OCLC 894) Le Livre du ciel et du monde. A. D. Menut and A. J. Denomy, ed. and trans. (Madison: University of Wisconsin Press, 1968, ISBN 9780783797878) De proportionibus proportionum and Ad pauca respicientes. Edward Grant, ed. and trans. (Madison: University of Wisconsin Press, 1966, ISBN 9780299040000) The De moneta of N. Oresme, and English Mint documents, translated by C. Johnson, (London, 1956) == See also == List of multiple discoveries Science in the Middle Ages Oresme (crater) List of Roman Catholic scientist-clerics == Notes == == References == Clagett, Marshall (1970). "Nicole Oresme" (PDF). In Gillispie, Charles (ed.). Dictionary of Scientific Biography. Vol. 10. New York: Scribner & American Council of Learned Societies. pp. 223–240. ISBN 978-0-684-10114-9. Clagett, Marshall (1968). Nicole Oresme and the Medieval Geometry of Qualities and Motions: A Treatise on the Uniformity and Difformity of Intensities Known as Tractatus de configurationibus qualitatum at motuum. Madison: University of Wisconsin Press. Grant, Edward (1971). Nicole Oresme and the Kinematics of Circular Motion. Madison: University of Wisconsin Press. ISBN 0-299-05830-1. Hansen, Bert (1985). Nicole Oresme and the Marvels of Nature: A Study of his De causis
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mirabilium with Critical Edition, Translation, and Commentary. Pontifical Institute of Medieval Studies. ISBN 0-88844-068-5. Mäkeler, Hendrik (2003). "Nicolas Oresme und Gabriel Biel: Zur Geldtheorie im späten Mittelalter". Scripta Mercaturae: Zeitschrift für Wirtschafts- und Sozialgeschichte. 37 (1): 56–94. (covers Oresme's monetary theory). Wood, Chauncey (1970). Chaucer and the Country of the Stars: Poetical Uses of Astrological Imagery. Princeton: Princeton University Press. ISBN 0-691-06172-6. Labellarte, Alberto (a cura di) (2016). Nicola Oresme. Trattato sull'origine, la natura, il diritto e i cambiamenti del denaro. Testo latino a fronte. Bari: Stilo Editrice. ISBN 978-88-6479-158-6. == External links == Works by or about Nicole Oresme at the Internet Archive (SPC) MSS BH 100 COCH Volume of works by Nicole Oresme, Maffeo Vegio, and Jordanus von Osnabrück at OPenn Kirschner, Stefan (2021). "Nicole Oresme". Stanford Encyclopedia of Philosophy.. O'Connor, John J.; Robertson, Edmund F., "Nicole Oresme", MacTutor History of Mathematics Archive, University of St Andrews Oresme biography Article on Oresme's monetary theory The De Moneta of Nicholas Oresme and English Mint Documents (pdf) Tractatus de Origine, Natura, Jure et Mutationibus Monetarum (Latin)
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This is a list of plasma physics topics. == A == == B == == C == == D == == E == == F == == G == == H == == I == == J == Jellium, uniform electron gas, homogeneous electron gas Jet (particle physics) Jet quenching Joint European Torus == K == == L == == M == == N == == O == Ohmic contact Onset of deconfinement Optode Optoelectric nuclear battery Orbitrap Outer space == P == == Q == == R == == S == == T == == U == U-HID, Ultra High Intensity Discharge UMIST linear system Undulator Upper hybrid oscillation Upper-atmospheric lightning == V == == W == == X == XANES, X-ray Absorption Near Edge Structure Xenon arc lamp X-ray transient X-ray astronomy X-shaped radio galaxy == Y == == Z == Zakharov system Zero-point energy ZETA (fusion reactor) Zonal and poloidal Zonal flow (plasma) Z Pulsed Power Facility == References ==
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"page_id": 33820413,
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Titanium chloride may refer to: Titanium tetrachloride (titanium(IV) chloride), TiCl4 Titanium trichloride (titanium(III) chloride), TiCl3 Titanium dichloride (titanium(II) chloride), TiCl2
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Flora Londinensis is a folio sized book that described the flora found in the London region of the mid 18th century. The Flora was published by William Curtis in six large volumes. The descriptions of the plants included hand-coloured copperplate plates by botanical artists such as James Sowerby, Sydenham Edwards and William Kilburn. The full title is Flora Londinensis: or, plates and descriptions of such plants as grow wild in the environs of London: with their places of growth, and times of flowering, their several names according to Linnæus and other authors: with a particular description of each plant in Latin and English. To which are added, their several uses in medicine, agriculture, rural œconomy and other arts. The first volume was produced in 1777 and the final one, containing a title and an index, was published in 1798. A binary name is given for each species in the survey; common and other names are also provided. Previous works on the flora of Britain had been intended for scientists, apothecaries, and herbalists, while Flora Londinensis was written for the general reader. The appealing plates also provided botanical details which could assist in the identification of a species. Curtis was praefectus horti (Director, Society of Apothecaries) at the Chelsea Physic Garden and a botanist with a broad knowledge of exotic species. However, Flora Londinensis covered the territory most familiar to him -- the flowering species within a 10-mile radius of London. He commissioned several painters to produce hand-coloured copper engravings to accompany the pages. Curtis wrote the descriptions and managed the publishing and sales of the volumes, producing six fascicles of twelve issues, each containing six plates. The final survey eventually came to include many species found in southern England and a few others. The Subscriber's List in Volume I records
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"page_id": 12521217,
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}
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321 names who between them subscribed for 331 complete copies. Plates were also sold individually, either coloured or plain. For such an expensive and high quality work this was a surprisingly large output, a reflection of the esteem in which William Curtis was held. His The Botanical Magazine would be a greater financial success. James Sowerby, who helped to publish this work and provided over 70 of the plates, went on to produce natural history publications in a similar format, most notably, English Botany comprising 36 volumes published over 23 years commencing in November 1790. The work was effectively enlarged by the botanical illustrator William Hooker (1779-1832) (sometimes confused with Sir William Jackson Hooker) who from 1805 to 1807 published The Paradisus Londinensis: or coloured figures of plants cultivated in the vicinity of the metropolis. == References == == External links == https://www.biodiversitylibrary.org/bibliography/62570#/summary Flora Londinensis at the BioDiversity Heritage Library == See also == English Botany
|
{
"page_id": 12521217,
"source": null,
"title": "Flora Londinensis"
}
|
== Annual Sales (USD Millions) == == Notes ==
|
{
"page_id": 24448768,
"source": null,
"title": "Annual pharmaceutical drug sales"
}
|
A radiobinding assay is a method of detecting and quantifying antibodies targeted toward a specific antigen. As such, it can be seen as the inverse of radioimmunoassay, which quantifies an antigen by use of corresponding antibodies. == Technique == The corresponding antigen is radiolabeled and mixed with the fluid that may contain the antibody, such as blood serum from a person. Presence of antibodies causes precipitation of antibody-antigen complexes that can be collected by centrifugation into pellets. The amount of antibody is proportional to the radioactivity of the pellet, as determined by gamma counting. == Uses == It is used to detect most autoantibodies seen in latent autoimmune diabetes. == References ==
|
{
"page_id": 30674691,
"source": null,
"title": "Radiobinding assay"
}
|
Small Cajal body-specific RNAs (scaRNAs) are a class of small nucleolar RNAs (snoRNAs) that specifically localise to the Cajal body, a nuclear organelle (cellular sub-organelle) involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs or snurps). ScaRNAs guide the modification (methylation and pseudouridylation) of RNA polymerase II transcribed spliceosomal RNAs U1, U2, U4, U5 and U12. The first scaRNA identified was U85. It is unlike typical snoRNAs in that it is a composite C/D box and H/ACA box snoRNAs and can guide both pseudouridylation and 2′-O-methylation. Not all scaRNAs are composite C/D and H/ACA box snoRNA and most scaRNAs are structurally and functionally indistinguishable from snoRNAs, directing ribosomal RNA (rRNA) modification in the nucleolus. == Drosophila scaRNAs == Several studies identified scaRNAs in Drosophila. One of the studies showed that several Drosophila scaRNAs could function equally well in the nucleoplasm of mutant flies that lack Cajal bodies. Further investigation showed that scaRNA pugU6-40 targets U6 snRNA, whose modification occurs in the nucleolus not CB and that pugU1-6 and pug U2-55 guide 2 RNAs: snRNA and 28s rRNA. == Small Cajal body-specific RNA 1 == In molecular biology, Small Cajal body-specific RNA 1 (also known as SCARNA1 or ACA35) is a small nucleolar RNA found in Cajal bodies and believed to be involved in the pseudouridylation of U2 spliceosomal RNA at residue U89. scaRNA1 is a non-coding RNA, which are functional products of genes not translated into proteins. Such RNA molecules usually contain important secondary structure or ligand-binding motifs and are involved in many important biological processes in the cell. scaRNA1 belongs to the H/ACA box class of snoRNAs, as it has the predicted hairpin-hinge-hairpin-tail structure, conserved H/ACA-box motifs, and is found associated with GAR1 protein. == References == == External links == snoRNAbase: human H/ACA and C/D box snoRNA database
|
{
"page_id": 12324611,
"source": null,
"title": "Small Cajal body-specific RNA"
}
|
Page for Small Cajal body-specific RNA at Rfam
|
{
"page_id": 12324611,
"source": null,
"title": "Small Cajal body-specific RNA"
}
|
Magnetofossils are the fossil remains of magnetic particles produced by magnetotactic bacteria (magnetobacteria) and preserved in the geologic record. The oldest definitive magnetofossils formed of the mineral magnetite come from the Cretaceous chalk beds of southern England, while magnetofossil reports, not considered to be robust, extend on Earth to the 1.9-billion-year-old Gunflint Chert; they may include the four-billion-year-old Martian meteorite ALH84001. Magnetotactic organisms are prokaryotic, with only one example of giant magnetofossils, likely produced by eukaryotic organisms, having been reported. Magnetotactic bacteria, the source of the magnetofossils, are magnetite (Fe3O4) or greigite (Fe3S4) producing bacteria found in both freshwater and marine environments. These magnetite bearing magnetotatic bacteria are found in the oxic-anoxic transition zone where conditions are such that oxygen levels are less than those found in the atmosphere (microaerophilic). Compared to the magnetite producing magnetotactic bacteria and subsequent magnetofossils, little is known about the environments in which greigite magnetofossils are created and the magnetic properties of the preserved greigite particles. Existence of magnetotactic bacteria was first suggested in the 1960s, when Salvatore Bellini of the University of Pavia discovered bacteria in a bog that appeared to align themselves with the magnetic field lines of the Earth. Following this discovery researchers began to think of the effect of magnetotactic bacteria on the fossil record and magnetization of sedimentary layers. Most of the research concentrated on marine environments, although it has been suggested that these magnetofossils can be found in terrestrial sediments (derived from terrestrial sources). These magnetofossils can be found throughout the sedimentary record, and therefore are influenced by deposition rate. Episodes of high sedimentation, not correlating with an increase in magnetobacterial and thus magnetofossil production, can decrease magnetofossil concentrations vastly, although this is not always the case. An increase in sedimentation normally coincides with an increase of land erosion,
|
{
"page_id": 14290695,
"source": null,
"title": "Magnetofossil"
}
|
and therefore an increase in iron abundance and nutrient supply. == Magnetization == Within the magnetotactic bacteria, magnetite and greigite crystals are biosynthesized (biomineralized) within organelles called magnetosomes. These magnetosomes form chains within the bacterial cell and in doing so, provide the organism with a permanent magnetic dipole. The organism uses it for geomagnetic navigation, to align itself with the Earth's geomagnetic field (magnetotaxis) and to reach the optimal position along vertical chemical gradients. When an organism dies the magnetosomes become trapped in sediments. Under the right conditions, primarily if the redox conditions are correct, the magnetite can then be fossilized and therefore stored in the sedimentary record. The fossilization of the magnetite (magnetofossils) within sediments contributes largely to the natural remanent magnetization of the sediment layers. The natural remanent magnetization is the permanent magnetism remaining in a rock or sediment after it has formed. == Paleoindicators == Magnetotactic bacteria use iron to create magnetite in magnetosomes. As a result of this process, increased iron levels correlate with increased production of magnetotactic bacteria. Increases in iron levels have been long associated with hyperthermal (period of warming, usually between 4-8 degrees Celsius) periods in the Earth's history. These hyperthermal events, such as the Palaeocene-Eocene Thermal Maximum or the Holocene Warm Period (HWP), stimulated increased productivity in planktonic and benthic foraminifera, which in turn, resulted in higher levels of sedimentation. Furthermore, an increase in temperature (like the one in the HWP) may also be associated with a wet period. These warm and wet conditions were favourable for magnetofossil production due to an increased nutrient supply in a period of post-glacial warming during the HWP. As a result, this period shows an increase in magnetofossil concentration. Using this increase in concentration, researchers can use magnetofossils as an indicator of a period of relatively
|
{
"page_id": 14290695,
"source": null,
"title": "Magnetofossil"
}
|
high (or low) temperatures in Earth's history. Dating of these rocks can provide information about the time period of this climate change and can be correlated to other rock formations or depositional environments in which the Earth's climate at that time may not have been as clear. Sediment aging and dissolution or alteration of magnetite present problems with providing useful measurements as the crystals structural integrity may not be preserved. Magnetofossils are not only being studied for their paleoenvironmental or paleoclimatic indicators. As mentioned above, magnetofossils hold a remanent magnetization when they are formed. That is, the magnetite (or greigite) aligns in the direction of the geomagnetic field. The magnetite crystals can be thought of as being a simple magnet with a north and south pole, this north–south orientation aligns with the north–south magnetic poles of the Earth. These fossils are then buried within the rock record. Researchers can examine these rock samples in a remanent magnetometer where the effects of Earth's current magnetic field is removed, to determine the remanent, or initial, magnetization of the rock sample when it was formed. In knowing the orientation of the rock in-situ and the remanent magnetization, researchers can determine the Earth's geomagnetic field at the time the rock was formed. This can be used as an indicator of magnetic field direction, or reversals in the Earth's magnetic field, where the Earth's north and south magnetic poles switch (which happen on average every 450,000 years). == Research == There are many methods for detecting and measuring magnetofossils, although there are some issues with the identification. Current research is suggesting that the trace elements found in the magnetite crystals formed in magnetotactic bacteria differ from crystals formed by other methods. It has also been suggested that calcium and strontium incorporation can be used to
|
{
"page_id": 14290695,
"source": null,
"title": "Magnetofossil"
}
|
identify magnetite inferred from magnetotactic bacteria. Other methods such as transmission electron microscopy (TEM) of samples from deep boreholes and ferromagnetic resonance (FMR) spectroscopy are being used. FMR spectroscopy of chains of cultured magnetotactic bacteria compared to sediment samples are being used to infer magnetofossil preservation over geological time frames. Research suggests that magnetofossils retain their remanent magnetization at deeper burial depths, although this is not entirely confirmed. FMR measurements of saturation isothermal remanent magnetization (SIRM) in some samples, compared with FMR and rainfall measurements taken over the past 70 years, have shown that magnetofossils can retain a record of paleorainfall variations on a shorter time-scale (hundreds of years), making a very useful recent history paleoclimate indicator. == Summary == The process of magnetite and greigite formation from magnetotactic bacteria and the formation of magnetofossils are well understood, although the more specific relationships, like those between the morphology of these fossils and the effect on the climate, nutrient availability and environmental availability would require more research. This however, does not alter the promise of better insight into the Earth's microbial ecology and geomagnetic variations over a large time scale presented by magnetofossils. Unlike some other methods used to provide information of the Earth's history, magnetofossils normally have to be seen in large abundances to provide useful information of Earth's ancient history. Although lower concentrations can tell their own story of the more recent paleoclimate, paleoenvironmental and paleoecological history of the Earth. == References ==
|
{
"page_id": 14290695,
"source": null,
"title": "Magnetofossil"
}
|
The Melchett Award is an honour awarded by the Energy Institute for outstanding contributions to the science of fuel and energy. It was created by and named for Alfred Moritz Mond, 1st Baron Melchett, the 20th century businessman and philanthropist. == Winners == Source: == See also == List of chemistry awards == References ==
|
{
"page_id": 45158152,
"source": null,
"title": "Melchett Medal"
}
|
The molecular formula C11H13NO6 (molar mass: 255.23 g/mol, exact mass: 255.0743 u) may refer to: Caramboxin Diroximel fumarate
|
{
"page_id": 42012426,
"source": null,
"title": "C11H13NO6"
}
|
An oleaginous microorganism is a type of microbe that accumulates lipid as a normal part of its metabolism. Oleaginous microbes may accumulate an array of different lipid compounds, including polyhydroxyalkanoates, triacylglycerols, and wax esters. Various microorganisms, including bacteria, fungi, and yeast, are known to accumulate lipids. These organisms are often researched for their potential use in producing fuels from waste products. == Function == For a typical bacteria, polar lipids such as phospholipids are synthesized to maintain the cell membrane. However, in oleaginous organisms, lipids can be synthesized and accumulated within the cell to act as energy storage in nutrient deprived conditions. Lipid accumulation can also serve secondary purposes such as acting as a water source in water stressed conditions, and to prevent oxidative stress from the formation of reactive oxygen species as a result of ultraviolet radiation. Lipid accumulation occurs as a storage of energy and nutrients, which appears to be triggered by inadequate environmental conditions. Bacteria such as Methylobacterium rhodesianum strain MB126 have been observed to accumulate poly-β-hydroxybutyrate when grown under phosphorus-, nitrogen-, and carbon-deficient conditions. Similarly, other organisms such as oleaginous Rhodococcus species like R. opacus are known to accumulate triacylglycerols instead, with the fatty acid content of these compounds varying by organism and environmental conditions. Lipid accumulation is proposed to be advantageous to oleaginous microbes as it provides a source of energy and nutrients when they are absent from the environment. It allows the organisms to survive through 'feast and famine' conditions, to prevent die offs before a new source of energy and nutrients may be provided to the population. The specific conditions causing triacylglycerol synthesis and accumulation have been studied in order to develop processes where its intracellular content is maximized. The carbon to nitrogen ratio has been identified as being particularly important for the
|
{
"page_id": 73600781,
"source": null,
"title": "Oleaginous microorganism"
}
|
accumulation of lipids. Conditions with low nitrogen and excess carbon content have been observed to cause increased lipogenesis in bacteria in the genus Rhodococcus. Lipid accumulation may also provide benefits to organisms in water stressed conditions. The metabolism of triacylglycerols and wax esters have the potential to produce 1.4 molecules of water for each molecule of lipid processed, while poly-β-hydroxybutyrate has a return of 0.5 molecules of water for each molecule of lipid metabolism. Another analysis determined that 107.1g of water can be harvested from 100g of microbial lipids, which is higher than the same amount of carbohydrate storage molecules. This means that oleaginous organisms can rely on lipid storage to reduce water stress and prevent desiccation in arid environments. Another way that lipid accumulation supports oleaginous microbes survival is the tempering of oxidative stress caused by reactive oxygen species. In environments where ultraviolet radiation is intense, such as deserts or polar regions, microbes can be damaged by the formation of reactive oxygen species from water molecules that interact with the cell's DNA, cellular components, or metabolic processes. Osmolytes such as glycerol – a component of triacylglycerol – stabilize the intracellular water and prevent the formation of reactive oxygen species, preventing cell damage and lysis as a result of ultraviolet radiation. The genetic component of triacylglycerol biosynthesis has been investigated. Its biosynthesis is catalyzed by the wax ester/acyl-CoA:diacylglycerol acyltransferase enzymes, which is associated with the atf genes, A study investigating the atf genes determines that out of the 10 atf genes identified in R. opacus PD630, only atf1 and aft2 had significant impacts on the activity of the enzymes and the resulting synthesis and accumulation of triacylglycerol. == Source of biofuels == Oleaginous microbes have attracted attention for their potential as sources for biofuels such as biodiesel. Instead of using
|
{
"page_id": 73600781,
"source": null,
"title": "Oleaginous microorganism"
}
|
nonrenewable fuel sources such as petroleum and natural gas, biodiesel has the potential to produce fuel sources from other forms of waste such as agricultural waste or wastewater. Oleaginous microbes have the ability to degrade various different materials into polyhydroxyalkanoates, which may have the potential to form bioplastics, and triacylglycerols, which may have the potential to form biodiesel. Microbes can be integrated into existing processes or waste streams such as wastewater treatment to harvest resources from the waste. Currently, many biofuels are made using plant oils, but products such as single cell oil utilizing microbial lipids require less land and have shorter time constraints compared to the processing of plant oils. Considering both the use of waste as a substrate, the integration into established processes, and the low resource investment, using oleaginous microbes as a source of biofuel is attractive to many researchers. == References ==
|
{
"page_id": 73600781,
"source": null,
"title": "Oleaginous microorganism"
}
|
An autoimmune disease is a condition that results from an anomalous response of the adaptive immune system, wherein it mistakenly targets and attacks healthy, functioning parts of the body as if they were foreign organisms. It is estimated that there are more than 80 recognized autoimmune diseases, with recent scientific evidence suggesting the existence of potentially more than 100 distinct conditions. Nearly any body part can be involved. Autoimmune diseases are a separate class from autoinflammatory diseases. Both are characterized by an immune system malfunction which may cause similar symptoms, such as rash, swelling, or fatigue, but the cardinal cause or mechanism of the diseases are different. A key difference is a malfunction of the innate immune system in autoinflammatory diseases, whereas in autoimmune diseases there is a malfunction of the adaptive immune system. Symptoms of autoimmune diseases can significantly vary, primarily based on the specific type of the disease and the body part that it affects. Symptoms are often diverse and can be fleeting, fluctuating from mild to severe, and typically comprise low-grade fever, fatigue, and general malaise. However, some autoimmune diseases may present with more specific symptoms such as joint pain, skin rashes (e.g., urticaria), or neurological symptoms. The exact causes of autoimmune diseases remain unclear and are likely multifactorial, involving both genetic and environmental influences. While some diseases like lupus exhibit familial aggregation, suggesting a genetic predisposition, other cases have been associated with infectious triggers or exposure to environmental factors, implying a complex interplay between genes and environment in their etiology. Some of the most common diseases that are generally categorized as autoimmune include coeliac disease, type 1 diabetes, Graves' disease, inflammatory bowel diseases (such as Crohn's disease and ulcerative colitis), multiple sclerosis, alopecia areata, Addison's disease, pernicious anemia, psoriasis, rheumatoid arthritis, and systemic lupus erythematosus. Diagnosing
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
autoimmune diseases can be challenging due to their diverse presentations and the transient nature of many symptoms. Treatment modalities for autoimmune diseases vary based on the type of disease and its severity. Therapeutic approaches primarily aim to manage symptoms, reduce immune system activity, and maintain the body's ability to fight diseases. Nonsteroidal anti-inflammatory drugs (NSAIDs) and immunosuppressants are commonly used to reduce inflammation and control the overactive immune response. In certain cases, intravenous immunoglobulin may be administered to regulate the immune system. Despite these treatments often leading to symptom improvement, they usually do not offer a cure and long-term management is often required. In terms of prevalence, a UK study found that 10% of the population were affected by an autoimmune disease. Women are more commonly affected than men. Autoimmune diseases predominantly begin in adulthood, although they can start at any age. The initial recognition of autoimmune diseases dates back to the early 1900s, and since then, advancements in understanding and management of these conditions have been substantial, though much more is needed to fully unravel their complex etiology and pathophysiology. == Signs and symptoms == Autoimmune diseases represent a vast and diverse category of disorders that, despite their differences, share some common symptomatic threads. These shared symptoms occur as a result of the body's immune system mistakenly attacking its own cells and tissues, causing inflammation and damage. However, due to the broad range of autoimmune diseases, the specific presentation of symptoms can significantly vary based on the type of disease, the organ systems affected, and individual factors such as age, sex, hormonal status, and environmental influences. An individual may simultaneously have more than one autoimmune disease (known as polyautoimmunity), further complicating the symptomatology. === Common symptoms === Symptoms that are commonly associated with autoimmune diseases include: fatigue. This is
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
the most common complaint of people with autoimmune disease. A 2015 US survey found that 98% of people with autoimmune diseases experienced fatigue, 89% said it was a "major issue", 68% said "fatigue is anything but normal. It is profound and prevents [them] from doing the simplest everyday tasks." and 59% said it was "probably the most debilitating symptom of having an [autoimmune disease]." low-grade fever malaise (a general feeling of discomfort or unease) muscle aches joint pain skin rashes Autoimmune diseases can present a diverse array of symptoms. For instance, some people may experience dry mouth or dry eyes, tingling or numbness in various body parts, unexpected changes in weight, and diarrhea. === Patterns of symptom occurrence === These symptoms often reflect the body's systemic inflammatory response. However, their occurrence and intensity can fluctuate over time, leading to periods of heightened disease activity, referred to as flare-ups, and periods of relative inactivity, known as remissions. The specific presentation of symptoms largely depends on the location and type of autoimmune response. For instance, in rheumatoid arthritis, an autoimmune disease primarily affecting the joints, symptoms typically include joint pain, swelling, and stiffness. On the other hand, type 1 diabetes, which results from an autoimmune attack on the insulin-producing cells of the pancreas, primarily presents with symptoms related to high blood sugar, such as increased thirst, frequent urination, and unexplained weight loss. === Commonly affected body areas === Commonly affected areas in autoimmune diseases include blood vessels, connective tissues, joints, muscles, red blood cells, skin, and endocrine glands such as the thyroid gland (in diseases like Hashimoto's thyroiditis and Graves' disease) and the pancreas (in type 1 diabetes). The impacts of these diseases can range from localized damage to certain tissues, alteration in organ growth and function, to more systemic effects when
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
multiple tissues throughout the body are affected. === Value of tracking symptom occurrence === The appearance of these signs and symptoms can not only provide clues for the diagnosis of an autoimmune condition, often in conjunction with tests for specific biological markers, but also help monitor disease progression and response to treatment. Ultimately, due to the diverse nature of autoimmune diseases, a multidimensional approach is often needed for the management of these conditions, taking into consideration the variety of symptoms and their impacts on individuals' lives. == Types == While it is estimated that over 80 recognized types of autoimmune diseases exist, this section provides an overview of some of the most common and well-studied forms. === Coeliac disease === Coeliac disease is an immune reaction to eating gluten, a protein found in wheat, barley, and rye. For those with the disease, eating gluten triggers an immune response in the small intestine, leading to damage on the villi, small fingerlike projections that line the small intestine and promote nutrient absorption. This explains the increased risk of gastrointestinal cancers, as the gastrointestinal tract includes the esophagus, stomach, small intestine, large intestine, rectum, and anus, all areas that the ingested gluten would traverse in digestion. The incidence of gastrointestinal cancer can be partially reduced or eliminated if a patient removes gluten from their diet. Additionally, coeliac disease is correlated with lymphoproliferative disorders. === Graves' disease === Graves' disease is a condition characterized by development of autoantibodies to thyroid-stimulating hormone receptors. The binding of the autoantibodies to the receptors results in unregulated production and release of thyroid hormone, which can lead to stimulatory effects such as rapid heart rate, weight loss, nervousness, and irritability. Other symptoms more specific to Graves' disease include bulging eyes and swelling of the lower legs. === Inflammatory bowel
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
disease === Inflammatory bowel disease encompasses conditions characterized by chronic inflammation of the digestive tract, including Crohn's disease and ulcerative colitis. In both cases, individuals lose immune tolerance for normal bacteria present in the gut microbiome. Symptoms include severe diarrhea, abdominal pain, fatigue, and weight loss. Inflammatory bowel disease is associated with cancers of the gastrointestinal tract and some lymphoproliferative cancers. === Multiple sclerosis === Multiple sclerosis (MS) is a neurodegenerative disease in which the immune system attacks myelin, a protective covering of nerve fibers in the central nervous system, causing communication problems between the brain and the rest of the body. Symptoms can include fatigue, difficulty walking, numbness or tingling, muscle weakness, and problems with coordination and balance. MS is associated with an increased risk of central nervous system cancer, primarily in the brain. === Rheumatoid arthritis === Rheumatoid arthritis (RA) primarily targets the joints, causing persistent inflammation that results in joint damage and pain. It is often symmetrical, meaning that if one hand or knee has it, the other one does too. RA can also affect the heart, lungs, and eyes. Additionally, the chronic inflammation and over-activation of the immune system creates an environment that favors further malignant transformation of other cells, perhaps explaining the associations with cancer of the lungs and skin as well as the increased risk of other hematologic cancers, none of which are directly affected by the inflammation of joints. === Psoriasis and psoriatic arthritis === Psoriasis is a skin condition characterized by the rapid buildup of skin cells, leading to scaling on the skin's surface. Inflammation and redness around the scales is common. Some individuals with psoriasis also develop psoriatic arthritis, which causes joint pain, stiffness, and swelling. === Sjögren's syndrome === Sjögren syndrome is a long-term autoimmune disease that affects the body's
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
moisture-producing glands (lacrimal and salivary), and often seriously affects other organ systems, such as the lungs, kidneys, and nervous system. === Systemic lupus erythematosus === Systemic lupus erythematosus, referred to simply as lupus, is a systemic autoimmune disease that affects multiple organs, including the skin, joints, kidneys, and the nervous system. It is characterized by a widespread loss of immune tolerance. The disease is characterized by periods of flares and remissions, and symptoms range from mild to severe. Women, especially those of childbearing age, are disproportionately affected. === Type 1 diabetes === Type 1 diabetes is a condition resulting from the immune system attacking insulin-producing beta cells in the pancreas, leading to high blood sugar levels. Symptoms include increased thirst, frequent urination, and unexplained weight loss. It is most commonly diagnosed in children and young adults. === Undifferentiated connective tissue disease === Undifferentiated connective tissue disease occurs when people have features of connective tissue disease, such as blood test results and external characteristics, but do not fulfill the diagnostic criteria established for any one connective tissue disease. Some 30–40% transition to a specific connective tissue disease over time. == Causes == The exact causes of autoimmune diseases remain largely unknown; however, research has suggested that a combination of genetic, environmental, and hormonal factors, as well as certain infections, may contribute to the development of these disorders. The human immune system is equipped with several mechanisms to maintain a delicate balance between defending against foreign invaders and protecting its own cells. To achieve this, it generates both T cells and B cells, which are capable of reacting with self-proteins. However, in a healthy immune response, self-reactive cells are generally either eliminated before they become active, rendered inert via a process called anergy, or their activities are suppressed by regulatory cells. ===
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
Genetics === A familial tendency to develop autoimmune diseases suggests a genetic component. Some conditions, like lupus and multiple sclerosis, often occur in several members of the same family, indicating a potential hereditary link. Additionally, certain genes have been identified that increase the risk of developing specific autoimmune diseases. ==== Genetic predisposition ==== Evidence suggests a strong genetic component in the development of autoimmune diseases. For instance, conditions such as lupus and multiple sclerosis frequently appear in multiple members of the same family, signifying a potential hereditary link. Furthermore, certain genes have been identified that augment the risk of developing specific autoimmune diseases. Experimental methods like genome-wide association studies have proven instrumental in pinpointing genetic risk variants potentially responsible for autoimmune diseases. For example, these studies have been used to identify risk variants for diseases such as type 1 diabetes and rheumatoid arthritis. In twin studies, autoimmune diseases consistently demonstrate a higher concordance rate among identical twins compared with fraternal twins. For instance, the rate in multiple sclerosis is 35% in identical twins compared to 6% in fraternal twins. ==== Balancing infection and autoimmunity ==== There is increasing evidence that certain genes selected during evolution offer a balance between susceptibility to infection and the capacity to avoid autoimmune diseases. For example, variants in the ERAP2 gene provide some resistance to infection even though they increase the risk of autoimmunity (positive selection). In contrast, variants in the TYK2 gene protect against autoimmune diseases but increase the risk of infection (negative selection). This suggests the benefits of infection resistance may outweigh the risks of autoimmune diseases, particularly given the historically high risk of infection. Several experimental methods such as the genome-wide association studies have been used to identify genetic risk variants that may be responsible for diseases such as type 1 diabetes
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
and rheumatoid arthritis. === Environmental factors === A significant number of environmental factors have been implicated in the development and progression of various autoimmune diseases, either directly or as catalysts. Current research suggests that up to seventy percent of autoimmune diseases could be attributed to environmental influences, which encompass an array of elements such as chemicals, infectious agents, dietary habits, and gut dysbiosis. However, a unifying theory that definitively explains the onset of autoimmune diseases remains elusive, emphasizing the complexity and multifaceted nature of these conditions. Various environmental triggers are identified, some of which include: Impaired oral tolerance Gut dysbiosis Increased gut permeability Heightened immune reactivity Chemicals, which are either a part of the immediate environment or found in drugs, are key players in this context. Examples of such chemicals include hydrazines, hair dyes, trichloroethylene, tartrazines, hazardous wastes, and industrial emissions. Ultraviolet radiation has been implicated as a potential causative factor in the development of autoimmune diseases, such as dermatomyositis. Furthermore, exposure to pesticides has been linked with an increased risk of developing rheumatoid arthritis. Vitamin D, on the other hand, appears to play a protective role, particularly in older populations, by preventing immune dysfunctions. Infectious agents are also being increasingly recognized for their role as T cell activators — a crucial step in triggering autoimmune diseases. The exact mechanisms by which they contribute to disease onset remain to be fully understood. For instance, certain autoimmune conditions like Guillain-Barre syndrome and rheumatic fever are thought to be triggered by infections. Furthermore, analysis of large-scale data has revealed a significant link between SARS-CoV-2 infection (the causative agent of COVID-19) and an increased risk of developing a wide range of new-onset autoimmune diseases. === Sex === Women typically make up some 80% of autoimmune disease patients. Whilst many proposals have been made
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
}
|
for the cause of this high weighting, no clear explanation is available. A possible role for hormonal factors has been suggested. For example, some autoimmune diseases tend to flare during pregnancy (possibly as an evolutionary mechanism to increase health protection for the child), when hormone levels are high, and improve after menopause, when hormone levels decrease. Women may also naturally have autoimmune disease trigger events in puberty and pregnancy. Under-reporting by men may also be a factor, as men may interact less with the health system than women. === Infections === Certain viral and bacterial infections have been linked to autoimmune diseases. For instance, research suggests that the bacterium that causes strep throat, Streptococcus pyogenes, might trigger rheumatic fever, an autoimmune response affecting the heart. Similarly, some studies propose a link between the Epstein–Barr virus, responsible for mononucleosis, and the subsequent development of multiple sclerosis or lupus. === Dysregulated immune response === Another area of interest is the immune system's ability to distinguish between self and non-self, a function that is compromised in autoimmune diseases. In healthy individuals, immune tolerance prevents the immune system from attacking the body's own cells. When this process fails, the immune system may produce antibodies against its own tissues, leading to an autoimmune response. === Negative selection and the role of the thymus === The elimination of self-reactive T cells occurs primarily through a mechanism known as "negative selection" within the thymus, an organ responsible for the maturation of T cells. This process serves as a key line of defense against autoimmunity. If these protective mechanisms fail, a pool of self-reactive cells can become functional within the immune system, contributing to the development of autoimmune diseases. === Molecular mimicry === Some infectious agents, like Campylobacter jejuni, bear antigens that resemble, but are not identical to,
|
{
"page_id": 19468046,
"source": null,
"title": "Autoimmune disease"
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the body's self-molecules. This phenomenon, known as molecular mimicry, can lead to cross-reactivity, where the immune response to such infections inadvertently results in the production of antibodies that also react with self-antigens. An example of this is Guillain–Barré syndrome, in which antibodies generated in response to a C. jejuni infection also react with the gangliosides in the myelin sheath of peripheral nerve axons. == Diagnosis == Diagnosing autoimmune disorders can be complex due to the wide range of diseases within this category and their often overlapping symptoms. Accurate diagnosis is crucial for determining appropriate treatment strategies. Generally, the diagnostic process involves a combination of medical history evaluation, physical examination, laboratory tests, and, in some cases, imaging or biopsies. === Medical history and examination === The first step in diagnosing autoimmune disorders typically involves a thorough evaluation of the patient's medical history and a comprehensive physical examination. Clinicians often pay close attention to the patient's symptoms, family history of autoimmune diseases, and any exposure to environmental factors that might trigger an autoimmune response. The physical examination can reveal signs of inflammation or organ damage, which are common features of autoimmune disorders. === Laboratory tests === Laboratory testing plays a pivotal role in the diagnosis of autoimmune diseases. These tests can identify the presence of certain autoantibodies or other immune markers that indicate a self-directed immune response. Autoantibody testing: Many autoimmune diseases are characterized by the presence of autoantibodies. Blood tests can identify these antibodies, which are directed against the body's own tissues. For example, antinuclear antibody (ANA) testing is commonly used in the diagnosis of systemic lupus erythematosus and other autoimmune diseases. Complete Blood Count: Blood counts can provide valuable information about the number and characteristics of different blood cells, which can be affected in some autoimmune diseases. C-Reactive Protein and
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Erythrocyte Sedimentation Rate: These tests measure the levels of inflammation in the body, which is often elevated in autoimmune disorders. Organ-specific tests: Certain autoimmune diseases target specific organs, so tests to evaluate the function of these organs can aid in diagnosis. For example, thyroid function tests are used in diagnosing autoimmune thyroid disorders, while a biopsy can diagnose coeliac disease by identifying damage to the small intestine. === Imaging studies === In some cases, imaging studies may be used to assess the extent of organ involvement and damage. For example, chest x-rays or CT scans can identify lung involvement in diseases like rheumatoid arthritis or systemic lupus erythematosus, while an MRI can reveal inflammation or damage in the brain and spinal cord in multiple sclerosis. === Differential diagnosis === Given the variety and nonspecific nature of symptoms that can be associated with autoimmune diseases, differential diagnosis—determining which of several diseases with similar symptoms is causing a patient's illness—is an important part of the diagnostic process. This often involves ruling out other potential causes of symptoms, such as infections, malignancies, or genetic disorders. === Multidisciplinary approach === Given the systemic nature of many autoimmune disorders, a multidisciplinary approach may be necessary for their diagnosis and management. This can involve rheumatologists, endocrinologists, gastroenterologists, neurologists, dermatologists, and other specialists, depending on the organs or systems affected by the disease. In summary, the diagnosis of autoimmune disorders is a complex process that requires a thorough evaluation of clinical, laboratory, and imaging data. Due to the diverse nature of these diseases, an individualized approach, often involving multiple specialists, is crucial for an accurate diagnosis. == Treatment == Treatment depends on the type and severity of the condition. The majority of the autoimmune diseases are chronic and there is no definitive cure, but symptoms can be
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alleviated and controlled with treatment. Standard treatment methods include: Vitamin or hormone supplements for what the body is lacking due to the disease (insulin, vitamin B12, thyroid hormone, etc.) Blood transfusions if the disease is blood related Physical therapy if the disease impacts bones, joints, or muscles Pharmaceutical treatment options include immunosuppressant drugs to reduce the immune response against the body's own tissues, such as: Non-steroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation Glucocorticoids to reduce inflammation Disease-modifying anti-rheumatic drugs (DMARDs) to decrease the damaging tissue and organ effects of the inflammatory autoimmune response Because immunosuppressants weaken the overall immune response, relief of symptoms must be balanced with preserving the patient's ability to combat infections, which could potentially be life-threatening. Non-traditional treatments are being researched, developed, and used, especially when traditional treatments fail. These methods aim to either block the activation of pathogenic cells in the body, or alter the pathway that suppresses these cells naturally. These treatments aim to be less toxic to the patient and have more specific targets. Such options include: Monoclonal antibodies that can be used to block pro-inflammatory cytokines Antigen-specific immunotherapy which allows immune cells to specifically target the abnormal cells that cause autoimmune disease Co-stimulatory blockade that works to block the pathway that leads to the autoimmune response Regulatory T cell therapy that utilizes this special type of T cell to suppress the autoimmune response Thymoquinone, a compound found in the flower Nigella sativa, has been studied for potential in treating several autoimmune diseases due to its effects on inflammation. == Epidemiology == The first estimate of US prevalence for autoimmune diseases as a group was published in 1997 by Jacobson, et al. They reported US prevalence to be around 9 million, applying prevalence estimates for 24 diseases to a US population of 279 million.
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Jacobson's work was updated by Hayter & Cook in 2012. This study used Witebsky's postulates, as revised by Rose & Bona, to extend the list to 81 diseases and estimated overall cumulative US prevalence for the 81 autoimmune diseases at 5.0%, with 3.0% for males and 7.1% for females. The estimated community prevalence, which takes into account the observation that many people have more than one autoimmune disease, was 4.5% overall, with 2.7% for males and 6.4% for females. A 2024 estimate was that 1 in 15 people in the U.S. had at least one autoimmune disease. == Research == In both autoimmune and inflammatory diseases, the condition arises through aberrant reactions of the human adaptive or innate immune systems. In autoimmunity, the patient's immune system is activated against the body's own proteins. In chronic inflammatory diseases, neutrophils and other leukocytes are constitutively recruited by cytokines and chemokines, resulting in tissue damage. Mitigation of inflammation by activation of anti-inflammatory genes and the suppression of inflammatory genes in immune cells is a promising therapeutic approach. There is a body of evidence that once the production of autoantibodies has been initialized, autoantibodies have the capacity to maintain their own production. === Stem-cell therapy === Stem cell transplantation is being studied and has shown promising results in certain cases. Medical trials to replace the pancreatic β cells that are destroyed in type 1 diabetes are in progress. === Altered glycan theory === According to this theory, the effector function of the immune response is mediated by the glycans (polysaccharides) displayed by the cells and humoral components of the immune system. Individuals with autoimmunity have alterations in their glycosylation profile such that a proinflammatory immune response is favored. It is further hypothesized that individual autoimmune diseases will have unique glycan signatures. === Hygiene hypothesis
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=== According to the hygiene hypothesis, high levels of cleanliness expose children to fewer antigens than in the past, causing their immune systems to become overactive and more likely to misidentify own tissues as foreign, resulting in autoimmune or allergic conditions such as asthma. === Vitamin D influence on immune response === Vitamin D is known as an immune regulator that assists in the adaptive and innate immune response. A deficiency in vitamin D, from hereditary or environmental influence, can lead to a more inefficient and weaker immune response and seen as a contributing factor to the development of autoimmune diseases. With vitamin D present, vitamin D response elements are encoded and expressed via pattern recognition receptors responses and the genes associated with those responses. The specific DNA target sequence expressed is known as 1,25-(OH)2D3. The expression of 1,25-(OH)2D3 can be induced by macrophages, dendritic cells, T-cells, and B-cells. In the presence of 1,25-(OH)2D3, the immune system's production of inflammatory cytokines are suppressed and more tolerogenic regulatory T-cells are expressed. This is due to vitamin D's influence on cell maturation, specifically T-cells, and their phenotype expression. Lack of 1,25-(OH)2D3 expression can lead to less tolerant regulatory T-cells, larger presentation of antigens to less tolerant T-cells, and increased inflammatory response. == See also == Epigenetics of autoimmune disorders List of autoimmune diseases Immune dysregulation == References == == Further reading == == External links == Media related to Autoimmune diseases and disorders at Wikimedia Commons
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A nucleic acid sequence is a succession of bases within the nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. This succession is denoted by a series of a set of five different letters that indicate the order of the nucleotides. By convention, sequences are usually presented from the 5' end to the 3' end. For DNA, with its double helix, there are two possible directions for the notated sequence; of these two, the sense strand is used. Because nucleic acids are normally linear (unbranched) polymers, specifying the sequence is equivalent to defining the covalent structure of the entire molecule. For this reason, the nucleic acid sequence is also termed the primary structure. The sequence represents genetic information. Biological deoxyribonucleic acid represents the information which directs the functions of an organism. Nucleic acids also have a secondary structure and tertiary structure. Primary structure is sometimes mistakenly referred to as "primary sequence". However there is no parallel concept of secondary or tertiary sequence. == Nucleotides == Nucleic acids consist of a chain of linked units called nucleotides. Each nucleotide consists of three subunits: a phosphate group and a sugar (ribose in the case of RNA, deoxyribose in DNA) make up the backbone of the nucleic acid strand, and attached to the sugar is one of a set of nucleobases. The nucleobases are important in base pairing of strands to form higher-level secondary and tertiary structures such as the famed double helix. The possible letters are A, C, G, and T, representing the four nucleotide bases of a DNA strand – adenine, cytosine, guanine, thymine – covalently linked to a phosphodiester backbone. In the typical case, the sequences are printed abutting one another without gaps, as in the sequence AAAGTCTGAC, read left to right in the 5' to 3'
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direction. With regards to transcription, a sequence is on the coding strand if it has the same order as the transcribed RNA. One sequence can be complementary to another sequence, meaning that they have the base on each position in the complementary (i.e., A to T, C to G) and in the reverse order. For example, the complementary sequence to TTAC is GTAA. If one strand of the double-stranded DNA is considered the sense strand, then the other strand, considered the antisense strand, will have the complementary sequence to the sense strand. === Notation === While A, T, C, and G represent a particular nucleotide at a position, there are also letters that represent ambiguity which are used when more than one kind of nucleotide could occur at that position. The rules of the International Union of Pure and Applied Chemistry (IUPAC) are as follows: For example, W means that either an adenine or a thymine could occur in that position without impairing the sequence's functionality. These symbols are also valid for RNA, except with U (uracil) replacing T (thymine). Apart from adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytidine (m5C). In RNA, there are many modified bases, including pseudouridine (Ψ), dihydrouridine (D), inosine (I), ribothymidine (rT) and 7-methylguanosine (m7G). Hypoxanthine and xanthine are two of the many bases created through mutagen presence, both of them through deamination (replacement of the amine-group with a carbonyl-group). Hypoxanthine is produced from adenine, and xanthine is produced from guanine. Similarly, deamination of cytosine results in uracil. Example of comparing and determining the % difference between two nucleotide sequences AATCCGCTAG AAACCCTTAG Given the two
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10-nucleotide sequences, line them up and compare the differences between them. Calculate the percent difference by taking the number of differences between the DNA bases divided by the total number of nucleotides. In this case there are three differences in the 10 nucleotide sequence. Thus there is a 30% difference. == Biological significance == In biological systems, nucleic acids contain information which is used by a living cell to construct specific proteins. The sequence of nucleobases on a nucleic acid strand is translated by cell machinery into a sequence of amino acids making up a protein strand. Each group of three bases, called a codon, corresponds to a single amino acid, and there is a specific genetic code by which each possible combination of three bases corresponds to a specific amino acid. The central dogma of molecular biology outlines the mechanism by which proteins are constructed using information contained in nucleic acids. DNA is transcribed into mRNA molecules, which travel to the ribosome where the mRNA is used as a template for the construction of the protein strand. Since nucleic acids can bind to molecules with complementary sequences, there is a distinction between "sense" sequences which code for proteins, and the complementary "antisense" sequence, which is by itself nonfunctional, but can bind to the sense strand. == Sequence determination == DNA sequencing is the process of determining the nucleotide sequence of a given DNA fragment. The sequence of the DNA of a living thing encodes the necessary information for that living thing to survive and reproduce. Therefore, determining the sequence is useful in fundamental research into why and how organisms live, as well as in applied subjects. Because of the importance of DNA to living things, knowledge of a DNA sequence may be useful in practically any biological research. For
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example, in medicine it can be used to identify, diagnose and potentially develop treatments for genetic diseases. Similarly, research into pathogens may lead to treatments for contagious diseases. Biotechnology is a burgeoning discipline, with the potential for many useful products and services. RNA is not sequenced directly. Instead, it is copied to a DNA by reverse transcriptase, and this DNA is then sequenced. Current sequencing methods rely on the discriminatory ability of DNA polymerases, and therefore can only distinguish four bases. An inosine (created from adenosine during RNA editing) is read as a G, and 5-methyl-cytosine (created from cytosine by DNA methylation) is read as a C. With current technology, it is difficult to sequence small amounts of DNA, as the signal is too weak to measure. This is overcome by polymerase chain reaction (PCR) amplification. === Digital representation === Once a nucleic acid sequence has been obtained from an organism, it is stored in silico in digital format. Digital genetic sequences may be stored in sequence databases, be analyzed (see Sequence analysis below), be digitally altered and be used as templates for creating new actual DNA using artificial gene synthesis. == Sequence analysis == Digital genetic sequences may be analyzed using the tools of bioinformatics to attempt to determine its function. === Genetic testing === The DNA in an organism's genome can be analyzed to diagnose vulnerabilities to inherited diseases, and can also be used to determine a child's paternity (genetic father) or a person's ancestry. Normally, every person carries two variations of every gene, one inherited from their mother, the other inherited from their father. The human genome is believed to contain around 20,000–25,000 genes. In addition to studying chromosomes to the level of individual genes, genetic testing in a broader sense includes biochemical tests for the possible
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presence of genetic diseases, or mutant forms of genes associated with increased risk of developing genetic disorders. Genetic testing identifies changes in chromosomes, genes, or proteins. Usually, testing is used to find changes that are associated with inherited disorders. The results of a genetic test can confirm or rule out a suspected genetic condition or help determine a person's chance of developing or passing on a genetic disorder. Several hundred genetic tests are currently in use, and more are being developed. === Sequence alignment === In bioinformatics, a sequence alignment is a way of arranging the sequences of DNA, RNA, or protein to identify regions of similarity that may be due to functional, structural, or evolutionary relationships between the sequences. If two sequences in an alignment share a common ancestor, mismatches can be interpreted as point mutations and gaps as insertion or deletion mutations (indels) introduced in one or both lineages in the time since they diverged from one another. In sequence alignments of proteins, the degree of similarity between amino acids occupying a particular position in the sequence can be interpreted as a rough measure of how conserved a particular region or sequence motif is among lineages. The absence of substitutions, or the presence of only very conservative substitutions (that is, the substitution of amino acids whose side chains have similar biochemical properties) in a particular region of the sequence, suggest that this region has structural or functional importance. Although DNA and RNA nucleotide bases are more similar to each other than are amino acids, the conservation of base pairs can indicate a similar functional or structural role. Computational phylogenetics makes extensive use of sequence alignments in the construction and interpretation of phylogenetic trees, which are used to classify the evolutionary relationships between homologous genes represented in the genomes
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of divergent species. The degree to which sequences in a query set differ is qualitatively related to the sequences' evolutionary distance from one another. Roughly speaking, high sequence identity suggests that the sequences in question have a comparatively young most recent common ancestor, while low identity suggests that the divergence is more ancient. This approximation, which reflects the "molecular clock" hypothesis that a roughly constant rate of evolutionary change can be used to extrapolate the elapsed time since two genes first diverged (that is, the coalescence time), assumes that the effects of mutation and selection are constant across sequence lineages. Therefore, it does not account for possible differences among organisms or species in the rates of DNA repair or the possible functional conservation of specific regions in a sequence. (In the case of nucleotide sequences, the molecular clock hypothesis in its most basic form also discounts the difference in acceptance rates between silent mutations that do not alter the meaning of a given codon and other mutations that result in a different amino acid being incorporated into the protein.) More statistically accurate methods allow the evolutionary rate on each branch of the phylogenetic tree to vary, thus producing better estimates of coalescence times for genes. === Sequence motifs === Frequently the primary structure encodes motifs that are of functional importance. Some examples of sequence motifs are: the C/D and H/ACA boxes of snoRNAs, Sm binding site found in spliceosomal RNAs such as U1, U2, U4, U5, U6, U12 and U3, the Shine-Dalgarno sequence, the Kozak consensus sequence and the RNA polymerase III terminator. === Sequence entropy === In bioinformatics, a sequence entropy, also known as sequence complexity or information profile, is a numerical sequence providing a quantitative measure of the local complexity of a DNA sequence, independently of the direction
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of processing. The manipulations of the information profiles enable the analysis of the sequences using alignment-free techniques, such as for example in motif and rearrangements detection. == See also == Gene structure Nucleic acid structure determination Quaternary numeral system Single-nucleotide polymorphism (SNP) == References == == External links == A bibliography on features, patterns, correlations in DNA and protein texts
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The Apostles of Linnaeus were a group of students who carried out botanical and zoological expeditions throughout the world that were either devised or approved by botanist Carl Linnaeus. The expeditions took place during the latter half of the 18th century and the students were designated 'apostles' by Linnaeus. Many apostles began their journey from Sweden. Some would act as chaplains or doctors aboard a Swedish East India Company ship. The expeditions were often dangerous. Seven of the seventeen apostles never came home. The first apostle, Christopher Tärnström, died of a tropical fever on Côn Sơn Island in 1746. Tärnström's widow was angry with Linnaeus for making her children fatherless. After this incident, Linnaeus sent only unmarried men. Linnaeus remained involved in most expeditions. He often left notes for the apostles and outlined what they should look for during their journeys, and the apostles sent letters and botanical samples to Linnaeus. Upon their return, it was usual to give Linnaeus a selection of anything collected. However, Daniel Rolander elected not to transfer his collection and was criticised by Linnaeus. Many newly discovered plants, animals and insects were named and catalogued by Linnaeus and apostles. As a result, the apostles' expeditions helped spread the Linnaean taxonomy, a system for classifying organisms. Additionally, one of Linnaeus' admirers, the English botanist Joseph Banks, was inspired to begin the tradition for all British research ships to have a naturalist aboard. Thus the apostles had a direct influence on future expeditions such as Charles Darwin's expedition aboard HMS Beagle. == Origins == Carl Linnaeus was born in Råshult, Småland, Sweden on 23 May 1707. Linnaeus enrolled at Uppsala University to study botany and medicine in 1728. Following his studies, he went to the Netherlands to study medicine. While in the Netherlands, he published Systema Naturae
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that describes a new system for classifying plants. Linnaeus returned to Sweden in May 1741 and was appointed Professor of Medicine at Uppsala University. Nine years later he became the university's rector, starting a period where natural sciences were held in the greatest esteem. One contribution Linnaeus made during his time in Uppsala was as a teacher. His lectures were normally full and often held in the Botanical Garden. The Saturday botanical excursions during summer were more popular than his lectures. Linnaeus and students explored the flora and fauna in the vicinity of Uppsala. Additionally, he let some of the best students live with him at his house. Among Linnaeus' notable students, the most promising and committed ones made botanical expeditions to various places in the world, often with the help of their professor. These seventeen adventurers were referred to as Linnaeus' apostles. The amount of this help varied; sometimes he used his influence as Rector to grant his apostles a place on an expedition or a scholarship. Most apostles were given instructions of what to find during their journeys. The apostles collected, organised and classified new plants, animals and minerals according to Linnaeus' classification system. Most gave their collections to Linnaeus when their journey finished. == The Apostles == === Christopher Tärnström, China (1746) === Christopher Tärnström (1703–1746) was the first apostle. Linnaeus permitted Tärnström to conduct a botanical expedition in China. In early 1746, Tärnström received free passage on the Swedish East India Company ship Calmar to China. He took a list, written by Linnaeus, of things to collect which included plants, animals and insects. However, Calmar stopped sailing beyond Côn Sơn Island (off the modern-day Vietnamese coast) because it had been forced to find a winter berth. On 4 December 1746, Tärnström died of a tropical fever
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without a botanical or zoological specimen having been sent to Sweden. His widow blamed Linnaeus for making her children fatherless. Following the death of Tärnström, Linnaeus allowed only unmarried men to become his apostles. === Pehr Kalm, North America (1747–1751) === Pehr Kalm (1715–1779) was born in Sweden to Finnish parents and became a student of Linnaeus in December 1740. He proposed to Linnaeus that he travel to North America on a botanical expedition. Linnaeus concurred and in November 1747 Kalm began his journey to North America sponsored by the universities in Uppsala and Turku. After a long stay in England, on the way he reached Philadelphia in autumn 1748. Once there, he stayed in North America for two and a half years, visiting the states of Pennsylvania, New Jersey, New York and southern Canada. He then returned to Sweden. Kalm is one of the few apostles who actually lived up to Linnaeus' hopes; bringing with him a large collection of pressed plants and seeds. His travel experience was later published in a three-volume book, En resa til Norra America. === Fredric Hasselquist, Izmir, Egypt etc. (1749–1752) === Fredric Hasselquist (1722–1752) heard Linnaeus talking about the botanically unexplored Eastern Mediterranean and he was inspired to travel there. Hasselquist was poor and to make the expedition possible, he relied on sponsorships from Linnaeus and Olof Celsius. On 7 August 1749, Hasselquist sailed from Stockholm to Izmir (a city in Turkey) where he spent the winter. Subsequently, he sailed to Egypt where stayed for ten months before returning. On the way he passed: Syria; Cyprus; Rhodes; and Chios. He returned to Izmir with a rich collection of botanical and zoological findings and also minerals. On 9 February 1752, he died before returning to Sweden. During his expedition he accumulated a large debt
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and Linnaeus was informed that Hasselquist's collections and manuscripts would not be sent home until the debt was paid. Swedish Queen Louisa Ulrika paid the debt and Linnaeus received Hasselquist's findings. In 1757, Linnaeus published Iter Palaestinium based on Hasselquist's collections and manuscripts. === Olof Torén, Surat and Guangzhou (1750) === Olof Torén (1718–1753) travelled to Surat and India as a priest with the Swedish East India Company in 1750. He continued to Guangzhou (Canton) and China before returning to Sweden. During his journey, he corresponded with Linnaeus; these letters were published posthumously as an appendix in the travelogue of another apostle, Pehr Osbeck. He fell ill during his journey and died shortly after his return in 1753. He returned with a large collection of specimens. === Pehr Osbeck, China (1750–1752) === Pehr Osbeck (1723–1805) sailed from Gothenburg to China in 1750 on ship Prins Carl. His primary task was to collect a tea plant for Linnaeus. He spent four months in Guangzhou where he collected many plants, but not the tea plant. He returned to Sweden in June 1752 with his collection and several other objects which he gave to Linnaeus. === Pehr Löfling, Spain and Venezuela (1751–1756) === Pehr Löfling (1729–1756) was recommended by Linnaeus when the Spanish ambassador in Stockholm asked for help exploring Spanish flora. Löfling travelled to Madrid in 1751 where he stayed for approximately two years. He explored the flora and fauna and regularly sent plants to Linnaeus. In 1754 the Spanish organised an expedition to South America and Löfling was invited to join them. They first stopped in the Canary Islands, staying for a short time before continuing to Venezuela. In Venezuela, Löfling collected plants with the help of his two assistants. Löfling stayed in South America until his death on 22 February
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1756 in Guyana. === Daniel Rolander, Suriname (1755) === Daniel Rolander (1725–1793) followed Linnaeus' acquaintance, Carl Gustav Dahlberg, to Suriname in 1755. Although he became ill on the way, he had almost recovered by the time he arrived. In Suriname he tried to explore the rainforests but disliked the climate. He developed an alcohol addiction and his health began to decline. He stayed for seven months and then returned with a collection containing plants and insects. He did not, however, give anything from his collection to Linnaeus. This is reported to have made Linnaeus "furious". Linnaeus, determined to acquire parts of Rolander's collection, broke into Rolander's home and reportedly stole a Sauvagesia plant. This incident ended the relationship between the two men and Linnaeus was heard to speak ill of Rolander on several occasions. === Anton Rolandsson Martin, Spitsbergen (1758) === Anton Rolandsson Martin (1729–1785) was born in what is now Estonia and later came to Sweden to be taught by Linnaeus. Linnaeus helped Martin get a small grant from Sweden's Royal Academy of Sciences to go to Spitsbergen, an island in the Arctic Ocean. In 1758, Martin joined a whaling expedition to the island but was only able to get ashore a few hours. He managed to bring back mosses and lichen. Despite how few samples he was able to bring back, Martin's expedition gained Linnaeus' praise. === Carl Fredrik Adler, East Indies, China and Java (c. 1761) === Carl Fredrik Adler (1720–1761) sailed to the East Indies in 1761 on a Swedish East India Company ship. He also visited China and Java on the same expedition. His journey was short. He died later in the year of his departure while still in Java. However, before his death he had succeeded in sending some samples back to Linnaeus from
|
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China. === Pehr Forsskål, Egypt and Yemen (1761–1763) === Pehr Forsskål (1732–1763) was born in Finland and became a student of Linnaeus when he was 18 years old. Forsskål was asked if he wanted to join a Danish expedition, commissioned by the Danish King Frederick V, to the Middle East. He consulted Linnaeus and was given permission to go. Although it was a Danish expedition, King Frederick V stated that the findings would not be placed in Copenhagen until several international botanists, including Linnaeus, had studied them. Forsskål and the expedition sailed in the winter of 1761. Their first stop was Alexandria, Egypt. Forsskål made many findings at Suez and was one of the first to describe the flora and fauna of the Red Sea. The expedition reached Yemen in April 1763 where Forsskål found a Commiphora which Linnaeus was particularity interested in. However, Forsskål died of malaria on 11 July 1763 before he could deliver Commiphora to Linnaeus. Forsskål worked on Flora Aegyptiaco-Arabica and Descriptiones Animalis during the expedition. His works were published posthumously in 1775 by another expedition member. Carsten Niebuhr. === Göran Rothman, Tunisia and Libya (1773–1776) === Göran Rothman (1739–1778) studied medicine at Uppsala University and carried out his dissertation with Linnaeus as his supervisor. In 1773 Rothman travelled to North Africa that was commissioned by the Swedish Academy of Sciences. He visited Libya and Tunisia but was unable to go as far inland as he wished due to local unrest. He returned to Sweden in 1776 with very few findings. === Johan Peter Falk, Russia (1768–1774) === Johan Peter Falk (1732–1774) arrived in Uppsala University in 1751 and became an apostle. He followed Linnaeus on his expedition to the island province Gotland and later became a tutor to Linnaeus' son, Carl. In 1760, Linnaeus encouraged
|
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Falk to follow apostle Forsskål on the Danish expedition to Egypt but Falk did not gain approval from the Danes. In 1768, the Russian Academy of Sciences created several expeditions to explore eastern Russia. Thanks to Linnaeus, Falk was given responsibility for one of the expeditions and headed out the same year. The expedition explored many places in Russia, including Volgograd and the steppes. Falk explored and described native customs as well as both flora and fauna. During the journey Falk became addicted to opium and caused him to suffer depression throughout the expedition. In 1774 the expedition reached Kazan where Falk committed suicide. Following his death, his collections and journals were sent to Saint Petersburg to be later completed and published as Beyträga zur topografischen Kenntniss des Russichen Reichs in 1785–86 by Samuel Georg Gmelin. === Daniel Solander, Australia etc. (1768–1771) and Iceland (1772) === Daniel Solander (1733–1782) was living in Linnaeus's house during his time as a student in Uppsala. Linnaeus was fond of him, promising Solander his eldest daughter's hand in marriage and telling Solander that he would become his successor. Based on Linnaeus's recommendation, Solander travelled to England in 1760 where he spread the Linnaean taxonomy. Two years later Linnaeus got Solander a position as professor in botany in Saint Petersburg. Linnaeus was surprised and disappointed when Solander answered that he had decided to stay in England. This damaged their relationship and thereafter Linnaeus was heard to refer to "the ungrateful Solander." In 1768 Solander was employed by the English botanist Joseph Banks to follow James Cook on his first journey to the Pacific Ocean aboard the Endeavour. The Endeavour sailed to Australia, Asia, Africa and several other places where Solander and Banks made many natural sciences discoveries. About a year after the expedition, in 1772,
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Solander and Banks made another botanical journey to Iceland. He never sent anything from his collection home to Linnaeus, but continued to organise his samples according to Linnaeus's system. === Anders Sparrman, China (1765–1767), South Africa (1771–1772 and 1775) Oceania etc. (1772–1775) Senegal (1787) === Even before he became an apostle, Anders Sparrman (1748–1820) had made a two-year-long journey to China as a surgeon on a Swedish East India Company ship. In 1771, he sailed to South Africa as one of Linnaeus' apostles where he tutored and explored the flora and fauna. The next year he was asked to join Cook's second expedition on Resolution. On the journey, he visited and studied plants in various locations including Oceania and South America. He returned to South Africa two years later having made many botanical findings. He stayed there for another eight months before returning to Uppsala in 1776. In 1787, he travelled to Senegal on an expedition to find land for colonisation. He published his travel diary Resa till Goda Hopps-Udden, södra Polkretsen och omkring Jordklotet, samt till Hottentott- och Caffer-Landen Åren 1772-1776 in three volumes, 1783-1818. === Carl Peter Thunberg, South Africa, Japan etc. (1770–1779) === Just like Linnaeus, Carl Peter Thunberg (1743–1828) arrived in Uppsala at the age of 18. Having completed his dissertation in 1770, he travelled to Paris. On the way back to Sweden he met Linnaeus' friend Johannes Burman in Amsterdam. With Burman's influence, Thunberg became a surgeon in the Dutch East India Company. He joined an expedition heading to Japan, which at that time was only open for Dutch ships. The expedition stopped in South Africa in 1772 where it remained for three years. During this time Thunberg found 300 new plant species and sent many of his findings to Linnaeus. In 1775, the expedition
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continued to Java and then to Japan. All foreigners in Japan were forced to stay on the Dejima island, outside Nagasaki, so it was difficult for Thunberg to study the mainland flora. However, he got many translators to bring him some mainland specimens to add to those plants he found in the gardens of Dejima. The only time Thunberg could explore the Japanese landscape was when he visited the shōgun in Edo. After 15 months, he returned to Sweden, passing Sri Lanka on the way. From his findings in Japan, Thunberg published Flora Japonica. From his findings in South Africa, he published Flora Capensis. === Andreas Berlin, Guinea (1773) === Andreas Berlin (1746–1773) studied in Uppsala University with Linnaeus as his student before travelling to London to find a botanical expedition he could join. In 1773 he travelled to Guinea with the English naturalist Henry Smeathman. The purpose of the expedition was to explore the central parts of Africa but prior to reaching the mainland, Berlin died of a stomach illness while on the Îles de Los. Before his death, Berlin managed to send a few plants to Linnaeus. === Adam Afzelius, Sierra Leone (1792–1796) === Adam Afzelius (1750–1837) joined an English expedition to Sierra Leone in 1792 after studying and lecturing in Uppsala. He returned in 1796 having found many new samples, which he described in some of his botanical writings. He also published Linnaeus' autobiography. == References == === Notes === === Bibliography === Blunt, Wilfrid (2004). Linnaeus: the compleat naturalist. London: Frances Lincoln Limited. ISBN 0-7112-2362-9. Frängsmyr, Tore; Lindroth, Sten; Eriksson, Gunnar; Broberg, Gunnar (1983). Linnaeus, the man and his work. Berkeley and Los Angeles: University of California Press. ISBN 0-7112-1841-2. Fagerstedt, Otto; Sörlin, Sverker (2004). Linné och hans apostlar (in Swedish). Örebro: Natur & Kultur. ISBN
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{
"page_id": 27070227,
"source": null,
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|
91-27-35590-X. Gribbin, Mary; Gribbin, John (2008). Flower hunters. Oxford: Oxford University Press. ISBN 978-0-19-956182-7. Stöver, Dietrich Johann Heinrich (1794). Joseph Trapp (ed.). The life of Sir Charles Linnæus. London: Library of Congress. ISBN 0-19-850122-6. {{cite book}}: ISBN / Date incompatibility (help) Hansen, Lars (editor-in-chief), The Linnaeus Apostles – Global Science & Adventure. 8 vols. 11 books. London & Whitby: The IK Foundation & Company, 2007–2011. ISBN 978-1-904145-26-4.
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"page_id": 27070227,
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The Bio21 Institute of Molecular Science and Biotechnology, abbreviated as the Bio21 Institute, is an Australian scientific research institute that focuses on basic science and applied biotechnology. The Bio21 Institute is based at the University of Melbourne on Flemington Road in Parkville, Melbourne, Victoria. The institute is managed by the University of Melbourne and is supported by funding from the Victorian Government. == History == In September 2006, Bio21 formed a partnership with Australian-based global bio-pharmaceutical company CSL Limited. 50 scientists from CSL were relocated to participate in activities at the Bio21. The goal of the partnership was for Bio21 to gain the expertise of industry professionals and for CSL to gain access to state-of-the-art equipment. == See also == Health in Australia == References == == External links == Official website
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"page_id": 3280662,
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"title": "Bio21 Institute"
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Valence shell electron pair repulsion (VSEPR) theory ( VESP-ər,: 410 və-SEP-ər) is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm. The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other. The greater the repulsion, the higher in energy (less stable) the molecule is. Therefore, the VSEPR-predicted molecular geometry of a molecule is the one that has as little of this repulsion as possible. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion. The insights of VSEPR theory are derived from topological analysis of the electron density of molecules. Such quantum chemical topology (QCT) methods include the electron localization function (ELF) and the quantum theory of atoms in molecules (AIM or QTAIM). == History == The idea of a correlation between molecular geometry and number of valence electron pairs (both shared and unshared pairs) was originally proposed in 1939 by Ryutaro Tsuchida in Japan, and was independently presented in a Bakerian Lecture in 1940 by Nevil Sidgwick and Herbert Powell of the University of Oxford. In 1957, Ronald Gillespie and Ronald Sydney Nyholm of University College London refined this concept into a more detailed theory, capable of choosing between various alternative geometries. == Overview == VSEPR theory is used to predict the arrangement of electron pairs around central atoms in molecules, especially simple and symmetric molecules. A central atom is defined in this theory as an atom which is bonded to two or more other atoms, while a terminal atom is bonded to only one other atom.:
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398 For example, in the molecule methyl isocyanate (H3C-N=C=O), the two carbons and one nitrogen are central atoms, and the three hydrogens and one oxygen are terminal atoms.: 416 The geometry of the central atoms and their non-bonding electron pairs in turn determine the geometry of the larger whole molecule. The number of electron pairs in the valence shell of a central atom is determined after drawing the Lewis structure of the molecule, and expanding it to show all bonding groups and lone pairs of electrons.: 410–417 In VSEPR theory, a double bond or triple bond is treated as a single bonding group. The sum of the number of atoms bonded to a central atom and the number of lone pairs formed by its nonbonding valence electrons is known as the central atom's steric number. The electron pairs (or groups if multiple bonds are present) are assumed to lie on the surface of a sphere centered on the central atom and tend to occupy positions that minimize their mutual repulsions by maximizing the distance between them.: 410–417 The number of electron pairs (or groups), therefore, determines the overall geometry that they will adopt. For example, when there are two electron pairs surrounding the central atom, their mutual repulsion is minimal when they lie at opposite poles of the sphere. Therefore, the central atom is predicted to adopt a linear geometry. If there are 3 electron pairs surrounding the central atom, their repulsion is minimized by placing them at the vertices of an equilateral triangle centered on the atom. Therefore, the predicted geometry is trigonal. Likewise, for 4 electron pairs, the optimal arrangement is tetrahedral.: 410–417 As a tool in predicting the geometry adopted with a given number of electron pairs, an often used physical demonstration of the principle of minimal
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electron pair repulsion utilizes inflated balloons. Through handling, balloons acquire a slight surface electrostatic charge that results in the adoption of roughly the same geometries when they are tied together at their stems as the corresponding number of electron pairs. For example, five balloons tied together adopt the trigonal bipyramidal geometry, just as do the five bonding pairs of a PCl5 molecule. === Steric number === The steric number of a central atom in a molecule is the number of atoms bonded to that central atom, called its coordination number, plus the number of lone pairs of valence electrons on the central atom. In the molecule SF4, for example, the central sulfur atom has four ligands; the coordination number of sulfur is four. In addition to the four ligands, sulfur also has one lone pair in this molecule. Thus, the steric number is 4 + 1 = 5. === Degree of repulsion === The overall geometry is further refined by distinguishing between bonding and nonbonding electron pairs. The bonding electron pair shared in a sigma bond with an adjacent atom lies further from the central atom than a nonbonding (lone) pair of that atom, which is held close to its positively charged nucleus. VSEPR theory therefore views repulsion by the lone pair to be greater than the repulsion by a bonding pair. As such, when a molecule has 2 interactions with different degrees of repulsion, VSEPR theory predicts the structure where lone pairs occupy positions that allow them to experience less repulsion. Lone pair–lone pair (lp–lp) repulsions are considered stronger than lone pair–bonding pair (lp–bp) repulsions, which in turn are considered stronger than bonding pair–bonding pair (bp–bp) repulsions, distinctions that then guide decisions about overall geometry when 2 or more non-equivalent positions are possible.: 410–417 For instance, when 5 valence
|
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electron pairs surround a central atom, they adopt a trigonal bipyramidal molecular geometry with two collinear axial positions and three equatorial positions. An electron pair in an axial position has three close equatorial neighbors only 90° away and a fourth much farther at 180°, while an equatorial electron pair has only two adjacent pairs at 90° and two at 120°. The repulsion from the close neighbors at 90° is more important, so that the axial positions experience more repulsion than the equatorial positions; hence, when there are lone pairs, they tend to occupy equatorial positions as shown in the diagrams of the next section for steric number five. The difference between lone pairs and bonding pairs may also be used to rationalize deviations from idealized geometries. For example, the H2O molecule has four electron pairs in its valence shell: two lone pairs and two bond pairs. The four electron pairs are spread so as to point roughly towards the apices of a tetrahedron. However, the bond angle between the two O–H bonds is only 104.5°, rather than the 109.5° of a regular tetrahedron, because the two lone pairs (whose density or probability envelopes lie closer to the oxygen nucleus) exert a greater mutual repulsion than the two bond pairs.: 410–417 A bond of higher bond order also exerts greater repulsion since the pi bond electrons contribute. For example, in isobutylene, (H3C)2C=CH2, the H3C−C=C angle (124°) is larger than the H3C−C−CH3 angle (111.5°). However, in the carbonate ion, CO2−3, all three C−O bonds are equivalent with angles of 120° due to resonance. == AXE method == The "AXE method" of electron counting is commonly used when applying the VSEPR theory. The electron pairs around a central atom are represented by a formula AXmEn, where A represents the central atom and always
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has an implied subscript one. Each X represents a ligand (an atom bonded to A). Each E represents a lone pair of electrons on the central atom.: 410–417 The total number of X and E is known as the steric number. For example, in a molecule AX3E2, the atom A has a steric number of 5. When the substituent (X) atoms are not all the same, the geometry is still approximately valid, but the bond angles may be slightly different from the ones where all the outside atoms are the same. For example, the double-bond carbons in alkenes like C2H4 are AX3E0, but the bond angles are not all exactly 120°. Likewise, SOCl2 is AX3E1, but because the X substituents are not identical, the X–A–X angles are not all equal. Based on the steric number and distribution of Xs and Es, VSEPR theory makes the predictions in the following tables. === Main-group elements === For main-group elements, there are stereochemically active lone pairs E whose number can vary from 0 to 3. Note that the geometries are named according to the atomic positions only and not the electron arrangement. For example, the description of AX2E1 as a bent molecule means that the three atoms AX2 are not in one straight line, although the lone pair helps to determine the geometry. === Transition metals (Kepert model) === The lone pairs on transition metal atoms are usually stereochemically inactive, meaning that their presence does not change the molecular geometry. For example, the hexaaquo complexes M(H2O)6 are all octahedral for M = V3+, Mn3+, Co3+, Ni2+ and Zn2+, despite the fact that the electronic configurations of the central metal ion are d2, d4, d6, d8 and d10 respectively.: 542 The Kepert model ignores all lone pairs on transition metal atoms, so that the
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geometry around all such atoms corresponds to the VSEPR geometry for AXn with 0 lone pairs E.: 542 This is often written MLn, where M = metal and L = ligand. The Kepert model predicts the following geometries for coordination numbers of 2 through 9: == Examples == The methane molecule (CH4) is tetrahedral because there are four pairs of electrons. The four hydrogen atoms are positioned at the vertices of a tetrahedron, and the bond angle is cos−1(−1⁄3) ≈ 109° 28′. This is referred to as an AX4 type of molecule. As mentioned above, A represents the central atom and X represents an outer atom.: 410–417 The ammonia molecule (NH3) has three pairs of electrons involved in bonding, but there is a lone pair of electrons on the nitrogen atom.: 392–393 It is not bonded with another atom; however, it influences the overall shape through repulsions. As in methane above, there are four regions of electron density. Therefore, the overall orientation of the regions of electron density is tetrahedral. On the other hand, there are only three outer atoms. This is referred to as an AX3E type molecule because the lone pair is represented by an E.: 410–417 By definition, the molecular shape or geometry describes the geometric arrangement of the atomic nuclei only, which is trigonal-pyramidal for NH3.: 410–417 Steric numbers of 7 or greater are possible, but are less common. The steric number of 7 occurs in iodine heptafluoride (IF7); the base geometry for a steric number of 7 is pentagonal bipyramidal. The most common geometry for a steric number of 8 is a square antiprismatic geometry.: 1165 Examples of this include the octacyanomolybdate (Mo(CN)4−8) and octafluorozirconate (ZrF4−8) anions.: 1165 The nonahydridorhenate ion (ReH2−9) in potassium nonahydridorhenate is a rare example of a compound with a steric
|
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number of 9, which has a tricapped trigonal prismatic geometry.: 254 Steric numbers beyond 9 are very rare, and it is not clear what geometry is generally favoured. Possible geometries for steric numbers of 10, 11, 12, or 14 are bicapped square antiprismatic (or bicapped dodecadeltahedral), octadecahedral, icosahedral, and bicapped hexagonal antiprismatic, respectively. No compounds with steric numbers this high involving monodentate ligands exist, and those involving multidentate ligands can often be analysed more simply as complexes with lower steric numbers when some multidentate ligands are treated as a unit.: 1165, 1721 == Exceptions == There are groups of compounds where VSEPR fails to predict the correct geometry. === Some AX2E0 molecules === The shapes of heavier Group 14 element alkyne analogues (RM≡MR, where M = Si, Ge, Sn or Pb) have been computed to be bent. === Some AX2E2 molecules === One example of the AX2E2 geometry is molecular lithium oxide, Li2O, a linear rather than bent structure, which is ascribed to its bonds being essentially ionic and the strong lithium-lithium repulsion that results. Another example is O(SiH3)2 with an Si–O–Si angle of 144.1°, which compares to the angles in Cl2O (110.9°), (CH3)2O (111.7°), and N(CH3)3 (110.9°). Gillespie and Robinson rationalize the Si–O–Si bond angle based on the observed ability of a ligand's lone pair to most greatly repel other electron pairs when the ligand electronegativity is greater than or equal to that of the central atom. In O(SiH3)2, the central atom is more electronegative, and the lone pairs are less localized and more weakly repulsive. The larger Si–O–Si bond angle results from this and strong ligand-ligand repulsion by the relatively large -SiH3 ligand. Burford et al. showed through X-ray diffraction studies that Cl3Al–O–PCl3 has a linear Al–O–P bond angle and is therefore a non-VSEPR molecule. === Some AX6E1
|
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and AX8E1 molecules === Some AX6E1 molecules, e.g. xenon hexafluoride (XeF6) and the Te(IV) and Bi(III) anions, TeCl2−6, TeBr2−6, BiCl3−6, BiBr3−6 and BiI3−6, are octahedral, rather than pentagonal pyramids, and the lone pair does not affect the geometry to the degree predicted by VSEPR. Similarly, the octafluoroxenate ion (XeF2−8) in nitrosonium octafluoroxenate(VI): 498 is a square antiprism with minimal distortion, despite having a lone pair. One rationalization is that steric crowding of the ligands allows little or no room for the non-bonding lone pair; another rationalization is the inert-pair effect.: 214 === Square planar ML4 complexes === The Kepert model predicts that ML4 transition metal molecules are tetrahedral in shape, and it cannot explain the formation of square planar complexes.: 542 The majority of such complexes exhibit a d8 configuration as for the tetrachloroplatinate (PtCl2−4) ion. The explanation of the shape of square planar complexes involves electronic effects and requires the use of crystal field theory.: 562–4 === Complexes with strong d-contribution === Some transition metal complexes with low d electron count have unusual geometries, which can be ascribed to d subshell bonding interaction. Gillespie found that this interaction produces bonding pairs that also occupy the respective antipodal points (ligand opposed) of the sphere. This phenomenon is an electronic effect resulting from the bilobed shape of the underlying sdx hybrid orbitals. The repulsion of these bonding pairs leads to a different set of shapes. The gas phase structures of the triatomic halides of the heavier members of group 2, (i.e., calcium, strontium and barium halides, MX2), are not linear as predicted but are bent, (approximate X–M–X angles: CaF2, 145°; SrF2, 120°; BaF2, 108°; SrCl2, 130°; BaCl2, 115°; BaBr2, 115°; BaI2, 105°). It has been proposed by Gillespie that this is also caused by bonding interaction of the ligands with the
|
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d subshell of the metal atom, thus influencing the molecular geometry. === Superheavy elements === Relativistic effects on the electron orbitals of superheavy elements is predicted to influence the molecular geometry of some compounds. For instance, the 6d5/2 electrons in nihonium play an unexpectedly strong role in bonding, so NhF3 should assume a T-shaped geometry, instead of a trigonal planar geometry like its lighter congener BF3. In contrast, the extra stability of the 7p1/2 electrons in tennessine are predicted to make TsF3 trigonal planar, unlike the T-shaped geometry observed for IF3 and predicted for AtF3; similarly, OgF4 should have a tetrahedral geometry, while XeF4 has a square planar geometry and RnF4 is predicted to have the same. == Odd-electron molecules == The VSEPR theory can be extended to molecules with an odd number of electrons by treating the unpaired electron as a "half electron pair"—for example, Gillespie and Nyholm: 364–365 suggested that the decrease in the bond angle in the series NO+2 (180°), NO2 (134°), NO−2 (115°) indicates that a given set of bonding electron pairs exert a weaker repulsion on a single non-bonding electron than on a pair of non-bonding electrons. In effect, they considered nitrogen dioxide as an AX2E0.5 molecule, with a geometry intermediate between NO+2 and NO−2. Similarly, chlorine dioxide (ClO2) is an AX2E1.5 molecule, with a geometry intermediate between ClO+2 and ClO−2. Finally, the methyl radical (CH3) is predicted to be trigonal pyramidal like the methyl anion (CH−3), but with a larger bond angle (as in the trigonal planar methyl cation (CH+3)). However, in this case, the VSEPR prediction is not quite true, as CH3 is actually planar, although its distortion to a pyramidal geometry requires very little energy. == See also == Bent's rule (effect of ligand electronegativity) Comparison of software for molecular mechanics modeling
|
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Linear combination of atomic orbitals Molecular geometry Molecular modelling Molecular Orbital Theory (MOT) Thomson problem Valence Bond Theory (VBT) Valency interaction formula == References == == Further reading == Lagowski, J. J., ed. (2004). Chemistry: Foundations and Applications. Vol. 3. New York: Macmillan. pp. 99–104. ISBN 978-0-02-865721-9. == External links == VSEPR AR—3D VSEPR Theory Visualization with Augmented Reality app 3D Chem—Chemistry, structures, and 3D molecules Indiana University Molecular Structure Center (IUMSC)
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A scratch drive actuator (SDA) is a microelectromechanical system device that converts electrical energy into one-dimensional motion. == Description == The actuator component can come in many shapes and sizes, depending on the fabrication method used. It can be visualised as an 'L'. The smaller end is called the 'bushing'. The actuator sits on top of a substrate that has a thin insulating dielectric layer on top. A voltage is applied between the actuator and the substrate, and the resulting potential pulls the body of the actuator downwards. When this occurs, the brush is pushed forwards by a small amount, and energy is stored in the strained actuator. When the voltage is removed, the actuator springs back into shape while the bushing remains in its new position. By applying a pulsed voltage, the SDA can be made to move forward. The voltage is usually applied to the actuator by means of a 'tether'. This can consist of a rigid connector or a rail which the SDA follows. The size of an SDA is typically measured on the μm scale. == References ==
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{
"page_id": 1183515,
"source": null,
"title": "Scratch drive actuator"
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The Physics of Basketball is a non-fiction book by John Fontanella first published on November 15, 2006 that explores the scientific side of basketball. It is written from the perspective of a fan of the game and then through the eyes of a physicist. John Fontanella has been a physics professor at the United States Naval Academy since 1971 and was a college basketball player for Westminster College in New Wilmington, PA. As a senior in 1967, he was a NAIA First Team All-American. He then earned an NCAA postgraduate scholarship to Case Western Reserve where he earned his Ph.D. in Physics. He is currently focusing his research on naval applications of dielectrics. == References == == External links == Johns Hopkins' Book Site John Fontanella's site
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"page_id": 9244444,
"source": null,
"title": "The Physics of Basketball"
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|
Global Census of Marine Life on Seamounts (commonly CenSeam) is a global scientific initiative, launched in 2005, that is designed to expand the knowledge base of marine life at seamounts. Seamounts are underwater mountains, not necessarily volcanic in origin, which often form subsurface archipelagoes and are found throughout the world's ocean basins, with almost half in the Pacific. There are estimated to be as many as 100,000 seamounts at least one kilometer in height, and more if lower rises are included. However, they have not been explored very much—in fact, only about half of one percent have been sampled—and almost every expedition to a seamount discovers new species and new information. There is evidence that seamounts can host concentrations of biologic diversity, each with its own unique local ecosystem; they seem to affect oceanic currents, resulting among other things in local concentration of plankton which in turn attracts species that graze on it, and indeed are probably a significant overall factor in biogeography of the oceans. They also may serve as way stations in the migration of whales and other pelagic species. Despite being poorly studied, they are heavily targeted by commercial fishing, including dredging. In addition they are of interest to potential seabed mining. The overall goal of CenSeam is "to determine the role of seamounts in the biogeography, biodiversity, productivity, and evolution of marine organisms, and to evaluate the effects of human exploitation on seamounts." To this effect, the group organizes and contributes to various research efforts about seamount biodiversity. Specifically, the project aims to act as a standardized scaffold for future studies and samplings, citing inefficiency and incompatibility between individual research efforts in the past. To give a scale of their mission, there are an estimated 100,000 seamounts in the ocean, but only 350 of them have
|
{
"page_id": 22023966,
"source": null,
"title": "Global Census of Marine Life on Seamounts"
}
|
been sampled, and only about 100 sampled thoroughly. Although sampling all 100,000 seamounts is infeasible, major seamounts can be sampled in such a way. CenSeam is a subdivision of the Census of Marine Life program. Organisationally, the components of CenSeam consist of a secretariat (Malcolm Clark, Mireille Consalvey, Ashley Rowden and Karen Stocks) which is hosted by the National Institute of Water and Atmospheric Research in Wellington, New Zealand; an international steering committee; a taxonomic advisory panel; and two working groups, Data Analysis and Standardisation. In 2008 CenSeam began collaborating with the International Seabed Authority to study effects of seabed mining on seamount ecosystems. == See also == Seamount § Conservation Bowie Seamount Davidson Seamount Monterey Bay Aquarium Research Institute == External links == SenSeam website Seamounts Online Archived 20 February 2012 at the Wayback Machine, SenSeam's ecological sampling database. Encyclopedia of Earth entry Archived 11 July 2010 at the Wayback Machine == References ==
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{
"page_id": 22023966,
"source": null,
"title": "Global Census of Marine Life on Seamounts"
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Protonympha is a form genus for problematic fossils of Devonian age in New York. It has been of special interest because of its morphological similarity with the iconic Ediacaran fossil Spriggina, and may have been a late surviving vendobiont. == Description == Protonympha is a flat, quilted fossil, which has previously been compared with the arm of a starfish or an annelid worm, but lacks a segmented carapace or stereom. Its preservation in sandstone is similar to Ediacaran type preservations. A less-accepted hypothesis claims the organisms were terrestrial fossils like lichen, with hypothetically interpreted rhizoid-like extensions as possible evidence it may have lived on land or in shallow pools. == References ==
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{
"page_id": 56168223,
"source": null,
"title": "Protonympha"
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Melting curve analysis is an assessment of the dissociation characteristics of double-stranded DNA during heating. As the temperature is raised, the double strand begins to dissociate leading to a rise in the absorbance intensity, hyperchromicity. The temperature at which 50% of DNA is denatured is known as the melting temperature. Measurement of melting temperature can help us predict species by just studying the melting temperature. This is because every organism has a specific melting curve. The information gathered can be used to infer the presence and identity of single-nucleotide polymorphisms (SNP). This is because G-C base pairing have 3 hydrogen bonds between them while A-T base pairs have only 2. DNA with mutations from either A or T to either C or G will create a higher melting temperature. The information also gives vital clues to a molecule's mode of interaction with DNA. Molecules such as intercalators slot in between base pairs and interact through pi stacking. This has a stabilizing effect on DNA's structure which leads to a raise in its melting temperature. Likewise, increasing salt concentrations helps diffuse negative repulsions between the phosphates in the DNA's backbone. This also leads to a rise in the DNA's melting temperature. Conversely, pH can have a negative effect on DNA's stability which may lead to a lowering of its melting temperature. == Implementation == The energy required to break the base-base hydrogen bonding between two strands of DNA is dependent on their length, GC content and their complementarity. By heating a reaction-mixture that contains double-stranded DNA sequences and measuring dissociation against temperature, these attributes can be inferred. Originally, strand dissociation was observed using UV absorbance measurements, but techniques based on fluorescence measurements are now the most common approach. The temperature-dependent dissociation between two DNA-strands can be measured using a DNA-intercalating fluorophore
|
{
"page_id": 16453417,
"source": null,
"title": "Melting curve analysis"
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such as SYBR green, EvaGreen or fluorophore-labelled DNA probes. In the case of SYBR green (which fluoresces 1000-fold more intensely while intercalated in the minor groove of two strands of DNA), the dissociation of the DNA during heating is measurable by the large reduction in fluorescence that results. Alternatively, juxtapositioned probes (one featuring a fluorophore and the other, a suitable quencher) can be used to determine the complementarity of the probe to the target sequence. The graph of the negative first derivative of the melting-curve may make it easier to pin-point the temperature of dissociation (defined as 50% dissociation), by virtue of the peaks thus formed. SYBR Green enabled product differentiation in the LightCycler in 1997. Hybridization probes (or FRET probes) were also demonstrated to provide very specific melting curves from the single-stranded (ss) probe-to-amplicon hybrid. Idaho Technology and Roche have done much to popularize this use on the LightCycler instrument. == Applications == Since the late 1990s product analysis via SYBR Green, other double-strand specific dyes, or probe-based melting curve analysis has become nearly ubiquitous. The probe-based technique is sensitive enough to detect single-nucleotide polymorphisms (SNP) and can distinguish between homozygous wildtype, heterozygous and homozygous mutant alleles by virtue of the dissociation patterns produced. Without probes, amplicon melting (melting and analysis of the entire PCR product) was not generally successful at finding single base variants through melting profiles. With higher resolution instruments and advanced dyes, amplicon melting analysis of one base variants is now possible with several commercially available instruments. For example: Applied Biosystems 7500 Fast System and the 7900HT Fast Real-Time PCR System, Idaho Technology's LightScanner (the first plate-based high resolution melting device), Qiagen's Rotor-Gene instruments, and Roche's LightCycler 480 instruments. Many research and clinical examples exist in the literature that show the use of melting curve analysis
|
{
"page_id": 16453417,
"source": null,
"title": "Melting curve analysis"
}
|
to obviate or complement sequencing efforts, and thus reduce costs. While most quantitative PCR machines have the option of melting curve generation and analysis, the level of analysis and software support varies. High Resolution Melt (known as either Hi-Res Melting, or HRM) is the advancement of this general technology and has begun to offer higher sensitivity for SNP detection within an entire dye-stained amplicon. It is less expensive and simpler in design to develop probeless melting curve systems. However, for genotyping applications, where large volumes of samples must be processed, the cost of development may be less important than the total throughput and ease of interpretation, thus favoring probe-based genotyping methods. Digital High Resolution Melting (dHRM) is also used in conjunction with digital PCR (dPCR) to improve quantitative power by providing additional information on the melting behavior of the amplified DNA, which can help in distinguishing between different genetic variants and in ensuring the accuracy of the quantification. dHRM is enabled by the use of sensitive DNA-binding dyes and digital PCR instrumentation, which allows for the collection of high-density data points to generate detailed melt profiles. These profiles can be used to identify even subtle differences in nucleic acid sequences, making dHRM a powerful tool for genotyping, mutation scanning, and methylation analysis dHRM is an advanced molecular technique used for the analysis of genetic variations, such as single nucleotide polymorphisms (SNPs), mutations, and methylations, by monitoring the melting behavior of double-stranded DNA. It is a post-PCR method that involves the gradual heating of PCR-amplified DNA in the presence of intercalating dyes that fluoresce when bound to double-stranded DNA. As the DNA melts, the fluorescence decreases, and the changes in fluorescence are monitored in real-time with digital PCR system. The resulting melting curves are then analyzed to detect genetic differences based
|
{
"page_id": 16453417,
"source": null,
"title": "Melting curve analysis"
}
|
on the melting temperatures of the DNA fragments. The technique has been further advanced by its application on digital microfluidics platforms, which can facilitate the analysis of single-nucleotide polymorphisms (SNPs) with high accuracy and sensitivity. Additionally, massively parallel dHRM has been developed to enable rapid and absolutely quantitative sequence profiling, which can be particularly useful in clinical and industrial settings where accurate quantification of nucleic acids is critical. == See also == High Resolution Melt analysis Microscale thermophoresis, a method to determine the stability, the length, the conformation and the modifications of DNA and RNA Nucleic acid thermodynamics == References == == External links == Ririe, KM; Rasmussen, RP; Wittwer, CT (1997). "Product differentiation by analysis of DNA melting curves during the polymerase chain reaction". Anal Biochem. 245 (2): 154–160. doi:10.1006/abio.1996.9916. PMID 9056205. Lo, Patcick C. H. (2014-10-21). "The Moments: Melting Curve Analysis". BioTechniques. Retrieved 2014-10-21.
|
{
"page_id": 16453417,
"source": null,
"title": "Melting curve analysis"
}
|
In physiology, serous fluid or serosal fluid (originating from the Medieval Latin word serosus, from Latin serum) is any of various body fluids resembling serum, that are typically pale yellow or transparent and of a benign nature. The fluid fills the inside of body cavities. Serous fluid originates from serous glands, with secretions enriched with proteins and water. Serous fluid may also originate from mixed glands, which contain both mucous and serous cells. A common trait of serous fluids is their role in assisting digestion, excretion, and respiration. In medical fields, especially cytopathology, serous fluid is a synonym for effusion fluids from various body cavities. Examples of effusion fluid are pleural effusion and pericardial effusion. There are many causes of effusions which include involvement of the cavity by cancer. Cancer in a serous cavity is called a serous carcinoma. Cytopathology evaluation is recommended to evaluate the causes of effusions in these cavities. == Examples == Saliva consists of mucus and serous fluid; the serous fluid contains the enzyme amylase, which is important for the digestion of carbohydrates. Minor salivary glands of von Ebner present on the tongue secrete the lipase. The parotid gland produces purely serous saliva. The other major salivary glands produce mixed (serous and mucus) saliva. Another type of serous fluid is secreted by the serous membranes (serosa), two-layered membranes which line the body cavities. Serous membrane fluid collects on microvilli on the outer layer and acts as a lubricant and reduces friction from muscle movement. This can be seen in the lungs, with the pleural cavity. Pericardial fluid is a serous fluid secreted by the serous layer of the pericardium into the pericardial cavity. The pericardium consists of two layers, an outer fibrous layer and the inner serous layer. This serous layer has two membranes which enclose
|
{
"page_id": 3542825,
"source": null,
"title": "Serous fluid"
}
|
the pericardial cavity into which is secreted the pericardial fluid. Blood serum is the component of blood that is neither a blood cell nor a clotting factor. Blood serum and blood plasma are similar, but serum does not contain any clotting factors such as fibrinogen, prothrombin, thromboplastin and many others. Serum includes all proteins not used in coagulation (clotting) and all the electrolytes, antibodies, antigens, hormones and any exogenous substances, such as drugs and microorganisms. == See also == Seroma == References ==
|
{
"page_id": 3542825,
"source": null,
"title": "Serous fluid"
}
|
Gravitaxis (or geotaxis) is a form of taxis characterized by the directional movement of an organism in response to gravity. There are a few different causes for gravitaxis. Many microorganisms have receptors like statocysts that allow them to sense the direction of gravity and to adjust their orientation accordingly. However, gravitaxis can result also from a purely physical mechanism so that organs for sensing the direction of gravity are not necessary. An example is given by microorganisms with a center of mass that is shifted to one end of the organism. Similar to a buoy, such mass-anisotropic microorganisms orient upwards under gravity. It has been shown that even an asymmetry in the shape of microorganisms can be sufficient to cause gravitaxis. Gravitaxis is different from gravitropism in a way that the latter is more about the growth response of an organism to gravity. == Taxis == Taxis is a behavioral response of a cell or an organism to an external stimulus. The movement is characteristically directional. The movement may be positive or negative. A positive taxis is one in which the organism or a cell gravitates towards the source of stimulation (attraction). A negative taxis is when the organism or a cell moves away from the source of stimulation (repulsion). == Examples == It can be seen in many microorganisms including Euglena. The response of planktonic larvae of Lithodes aequispinus (king crab) to gravity is another example of gravitaxis. They show both positive and negative gravitaxis responses in a way that they move either upward (negative) or downward (positive). Gravitaxis can also be observed in Drosophila. == Etymology == The term is coined from gravi- meaning gravity, and taxis or the movement of an organism in response to a stimulus. == See also == Animal locomotion Haptotaxis Mechanotaxis Optomotor response
|
{
"page_id": 22810412,
"source": null,
"title": "Gravitaxis"
}
|
Tropism == References == == External links == The dictionary definition of gravitaxis at Wiktionary
|
{
"page_id": 22810412,
"source": null,
"title": "Gravitaxis"
}
|
FEMS Microbiology Ecology is one of the seven FEMS, peer-reviewed scientific journals, which covers all aspects of microbial ecology. According to the Journal Citation Reports, the journal has a 2023 impact factor of 3.5. The editor-in-chief is Max Häggblom. == References == == External links == Official website
|
{
"page_id": 42340141,
"source": null,
"title": "FEMS Microbiology Ecology"
}
|
A recognition sequence is a DNA sequence to which a structural motif of a DNA-binding domain exhibits binding specificity. Recognition sequences are palindromes. The transcription factor Sp1 for example, binds the sequences 5'-(G/T)GGGCGG(G/A)(G/A)(C/T)-3', where (G/T) indicates that the domain will bind a guanine or thymine at this position. The restriction endonuclease PstI recognizes, binds, and cleaves the sequence 5'-CTGCAG-3'. A recognition sequence is different from a recognition site. A given recognition sequence can occur one or more times, or not at all, on a specific DNA fragment. A recognition site is specified by the position of the site. For example, there are two PstI recognition sites in the following DNA sequence fragment, starting at base 9 and 31 respectively. A recognition sequence is a specific sequence, usually very short (less than 10 bases). Depending on the degree of specificity of the protein, a DNA-binding protein can bind to more than one specific sequence. For PstI, which has a single sequence specificity, it is 5'-CTGCAG-3'. It is always the same whether at the first recognition site or the second in the following example sequence. For Sp1, which has multiple (16) sequence specificity as shown above, the two recognition sites in the following example sequence fragment are at 18 and 32, and their respective recognition sequences are 5'-GGGGCGGAGC-3' and 5'-TGGGCGGAAC-3'. 5'-AACGTTAGCTGCAGTCGGGGCGGAGCTAGGCTGCAGGAATTGGGCGGAACCT-3' == See also == DNA-binding domain Transcription factor#Classes, for more examples == References ==
|
{
"page_id": 6754094,
"source": null,
"title": "Recognition sequence"
}
|
Linalool () refers to two enantiomers of a naturally occurring terpene alcohol found in many flowers and spice plants. Together with geraniol, nerol, citronellol, linalool is one of the rose alcohols. Linalool has multiple commercial applications, the majority of which are based on its pleasant scent (floral, with a touch of spiciness). A colorless oil, linalool is classified as an acyclic monoterpenoid. In plants, it is a metabolite, a volatile oil component, an antimicrobial agent, and an aroma compound. Linalool has uses in manufacturing of soaps, fragrances, food additives as flavors, household products, and insecticides. Esters of linalool are referred to as linalyl, e.g. linalyl pyrophosphate, an isomer of geranyl pyrophosphate. The word linalool is based on linaloe (a type of wood) and the suffix -ol. In food manufacturing, it may be called coriandrol. == Occurrence == Both enantiomeric forms are found in nature: (S)-linalool is found, for example, as a major constituent of the essential oils of coriander (Coriandrum sativum L.), cymbopogon (Cymbopogon martini var. martinii), and sweet orange (Citrus sinensis) flowers. (R)-linalool is present in lavender (Lavandula officinalis), bay laurel (Laurus nobilis), and sweet basil (Ocimum basilicum), among others. Each enantiomer evokes distinct neural responses in humans, so each is classified as possessing distinct scents. (S)-(+)-Linalool is perceived as sweet, floral, petitgrain-like (odor threshold 7.4 ppb) and the (R)-form as more woody and lavender-like (odor threshold 0.8 ppb). Over 200 species of plants produce linalool, notably from the families Lamiaceae (mint and other herbs), Lauraceae (laurels, cinnamon, rosewood), and Rutaceae (citrus fruits), but also birch trees and other plants, from tropical to boreal climate zones. Aniba rosaeodora Lavandula Cinnamomum tamala Cannabis sativa Basil Solidago (goldenrod) Artemisia vulgaris (mugwort) Humulus lupulus (hop) It was first synthesized in the laboratory of Leopold Ružička in 1919. == Production == Linalool is
|
{
"page_id": 1380144,
"source": null,
"title": "Linalool"
}
|
produced commercially from several terpenes and terpenoid precursors, which are often components of terpentine. 2-Pinanol, derived from pinene, gives linalool upon pyrolysis. === Biosynthesis === In higher plants linalool is formed by rearrangement of geranyl pyrophosphate (GPP). With the aid of linalool synthase (LIS), water attacks to form the chiral center. LIS appears to show a limonene synthase-type catalysis through a simplified "metal-cofactor-binding domain [where the majority] of the residues involved in substrate...binding [are] in the C-terminal part of the protein" suggesting stereoselectivity and the reasoning behind why some plants have varying levels of each enantiomer. == Odor and flavor == Linalool has complex odor and flavor properties. Its odor is similar to floral, spicy wood, somewhat resembling French lavender plants, bergamot oil or lily of the valley. It has a light, citrus-like flavor, sweet with a spicy tropical accent. Linalool is used as a scent in perfumed hygiene products and cleaning agents, including soaps, detergents, shampoos, and lotions. It exhibits antimicrobial and antifungal properties. == Chemical derivatives == Linalool is hydrogenated to give dihydro- and tetrahydrolinalool, which are fragrances that are more resilient toward oxidants, as might be found in household cleaning products. Linalyl acetate, a popular scent, is produced by esterification of linalool (as well as occurring naturally). Isomerization of linalool gives geraniol and nerol. == Safety == Linalool can be absorbed by inhalation of its aerosol and by oral intake or skin absorption, potentially causing irritation, pain and allergic reactions. Some 7% of people undergoing patch testing in Europe were found to be allergic to the oxidized form of linalool. The US Food and Drug Administration (FDA) lists linalool in the Code of Federal Regulations under substances generally recognized as safe, synthetic flavoring substances and adjuvants. == See also == Lavender oil == References == == External
|
{
"page_id": 1380144,
"source": null,
"title": "Linalool"
}
|
links == Comprehensive data sheet Linalool in the Consumer Product Information Database
|
{
"page_id": 1380144,
"source": null,
"title": "Linalool"
}
|
Hypomyces lactifluorum, or the lobster mushroom, is a parasitic ascomycete fungus that grows on certain species of mushrooms, turning them a reddish orange color that resembles the outer shell of a cooked lobster. Contrary to its common name, the species itself is neither a lobster nor a mushroom. == Description == H. lactifluorum specifically attacks members of the genera Lactarius and Lactifluus (milk-caps), and Russula (brittlegills), such as Russula brevipes and Lactifluus piperatus in North America. At maturity, the reddish orange H. lactifluorum thoroughly covers its host, rendering it unidentifiable. As it ages, its color can go from the entire sporocarp surface and lamella to the margin of the mushroom. The species produces a white spore print. === Similar species === Similar species include Hypomyces cervinigenus, H. chrysospermus, and H. luteovirens. Turbinellus floccosus has a similarly colored cap, but its underside has fine wrinkles rather than wavy gills. White, pink, and yellow molds could be toxic lookalike species. === Habitat === Hypomyces lactifluorum is found in wooded areas, often near Russula brevipes or Lactarius growing in conifer forests, in particular under ponderosa pine in the American Southwest and the Pacific Northwest. Its range in the woods has been described as "solitary, scattered or gregarious" depending on location. == Uses == Lobster mushrooms are widely eaten and enjoyed freshly foraged and cooked. They are commercially marketed and sometimes found in grocery stores; they have been made available at markets in Oregon. They have a seafood-like flavor and a firm, dense texture. While edible, field guides note the hypothetical possibility that H. lactifluorum could parasitize a toxic host and that individuals should avoid consuming lobster mushrooms with unknown hosts, although no instances of toxicity have been recorded. During the course of infection, the chemicals get converted into other more flavorful compounds, making
|
{
"page_id": 2101048,
"source": null,
"title": "Hypomyces lactifluorum"
}
|
lobster mushrooms more edible. Lactarius piperatus has a spicy, hot flavor but that flavor is counteracted by the parasite H. lactifluorum, making it more edible and delicious. One author notes that he has personally never experienced any trouble from consuming them and another notes that there have been no reports of poisoning in hundreds of years of consumption. === Research === A study from Quebec found that an infected R. brevipes mushroom mostly contained lobster mushroom DNA, with only trace amounts from the original species. This study also measured intermediate products of chemical reactions, or metabolites, in infected and non-infected mushrooms. Metabolites help determine how fungi look and taste, and whether they are fit to eat. They found that through the course of its infection, the parasitic fungus completely alters the diversity and amount of metabolites in R. brevipes. == References == == External links == Media related to Hypomyces lactifluorum at Wikimedia Commons A lobster mushroom article on Tom's Fungi AmericanMushrooms.com: Lobster Mushroom Lobster mushroom on mykoweb
|
{
"page_id": 2101048,
"source": null,
"title": "Hypomyces lactifluorum"
}
|
Digital microfluidics (DMF) is a platform for lab-on-a-chip systems that is based upon the manipulation of microdroplets. Droplets are dispensed, moved, stored, mixed, reacted, or analyzed on a platform with a set of insulated electrodes. Digital microfluidics can be used together with analytical analysis procedures such as mass spectrometry, colorimetry, electrochemical, and electrochemiluminescense. == Overview == In analogy to digital microelectronics, digital microfluidic operations can be combined and reused within hierarchical design structures so that complex procedures (e.g. chemical synthesis or biological assays) can be built up step-by-step. And in contrast to continuous-flow microfluidics, digital microfluidics works much the same way as traditional bench-top protocols, only with much smaller volumes and much higher automation. Thus a wide range of established chemical procedures and protocols can be seamlessly transferred to a nanoliter droplet format. Electrowetting, dielectrophoresis, and immiscible-fluid flows are the three most commonly used principles, which have been used to generate and manipulate microdroplets in a digital microfluidic device. A digital microfluidic (DMF) device set-up depends on the substrates used, the electrodes, the configuration of those electrodes, the use of a dielectric material, the thickness of that dielectric material, the hydrophobic layers, and the applied voltage. A common substrate used in this type of system is glass. Depending if the system is open or closed, there would be either one or two layers of glass. The bottom layer of the device contains a patterned array of individually controllable electrodes. When looking at a closed system, there is usually a continuous ground electrode found through the top layer made usually of indium tin oxide (ITO). The dielectric layer is found around the electrodes in the bottom layer of the device and is important for building up charges and electrical field gradients on the device. A hydrophobic layer is applied to the
|
{
"page_id": 331579,
"source": null,
"title": "Digital microfluidics"
}
|
top layer of the system to decrease the surface energy where the droplet will actually we be in contact with. The applied voltage activates the electrodes and allows changes in the wettability of droplet on the device’s surface. In order to move a droplet, a control voltage is applied to an electrode adjacent to the droplet, and at the same time, the electrode just under the droplet is deactivated. By varying the electric potential along a linear array of electrodes, electrowetting can be used to move droplets along this line of electrodes. Modifications to this foundation can also be fabricated into the basic design structure. One example of this is the addition of electrochemiluminescence detectors within the indium tin oxide layer (the ground electrode in a closed system) which aid in the detection of luminophores in droplets. In general, different materials may also be used to replace basic components of a DMF system such as the use of PDMS instead of glass for the substrate. Liquid materials can be added, such as oil or another substance, to a closed system to prevent evaporation of materials and decrease surface contamination. Also, DMF systems can be compatible with ionic liquid droplets with the use of an oil in a closed device or with the use of a catena (a suspended wire) over an open DMF device. Digital microfluidics can be light-activated. Optoelectrowetting can be used to transport sessile droplets around a surface containing patterned photoconductors. The photoelectrowetting effect can also be used to achieve droplet transport on a silicon wafer without the necessity of patterned electrodes. == Working principle == Droplets are formed using the surface tension properties of a liquid. For example, water placed on a hydrophobic surface such as wax paper will form spherical droplets to minimize its contact with
|
{
"page_id": 331579,
"source": null,
"title": "Digital microfluidics"
}
|
the surface. Differences in surface hydrophobicity affect a liquid’s ability to spread and ‘wet’ a surface by changing the contact angle. As the hydrophobicity of a surface increases, the contact angle increases, and the ability of the droplet to wet the surface decreases. The change in contact angle, and therefore wetting, is regulated by the Young-Lippmann equation. cos ( θ ) = cos ( θ 0 ) + ε 0 ε r V 2 2 γ d {\displaystyle \cos(\theta )=\cos(\theta {_{0}})+{\frac {\varepsilon {_{0}}\varepsilon {_{r}}V^{2}}{{2\gamma }d}}} where θ {\displaystyle \theta } is the contact angle with an applied voltage V {\displaystyle V} ; θ 0 {\displaystyle \theta {_{0}}} is the contact angle with no voltage; ε r {\displaystyle \varepsilon {_{r}}} is the relative permittivity of the dielectric; ε 0 {\displaystyle \varepsilon {_{0}}} is the permittivity of free space; γ {\displaystyle \gamma } is the liquid/filler media surface tension; d {\displaystyle d} is the dielectric thickness. In some cases, the hydrophobicity of a substrate can be controlled by using electrical fields. This refers to the phenomenon Electrowetting On Dielectric (EWOD).[3][4] For example, when no electric field is applied to an electrode, the surface will remain hydrophobic and a liquid droplet will form a more spherical droplet with a greater contact angle. When an electric field is applied, a polarized hydrophilic surface is created. The water droplet then becomes flattened and the contact angle decreases. By controlling the localization of this polarization, we can create an interfacial tension gradient that allows controlled displacement of the droplet across the surface of the DMF device. == Droplet formation == There are two ways to make new droplets with a digital microfluidic device. Either an existing droplet can be split in two, or a new droplet can be made from a reservoir of material.
|
{
"page_id": 331579,
"source": null,
"title": "Digital microfluidics"
}
|
Both processes are only known to work in closed devices, though this often is not a problem as the top plates of DMF devices are typically removable, so an open device can be made temporarily closed should droplet formation be necessary. === From an existing droplet === A droplet can be split by charging two electrodes on opposite sides of a droplet on an uncharged electrode. In the same way a droplet on an uncharged electrode will move towards an adjacent, charged electrode, this droplet will move towards both active electrodes. Liquid moves to either side, which causes the middle of the droplet to neck. For a droplet of the same size as the electrodes, splitting will occur approximately when R n e c k / R e n d = − 1 {\displaystyle R_{neck}/R_{end}=-1} , as the neck will be at its thinnest. R n e c k {\displaystyle R_{neck}} is the radius of curvature of the menisci at the neck, which is negative for a concave curve, and R e n d {\displaystyle R_{end}} is the radius of curvature of the menisci at the elongated ends of the droplet. This process is simple and consistently results in two droplets of equal volume. The conventional method of splitting an existing droplet by simply turning the splitting electrodes on and off produces new droplets of relatively equal volume. However, the new droplets formed by the conventional method show considerable difference in volume. This difference is caused by local perturbations due to the rapid mass transport. Even though the difference is negligible in some applications, it can still pose a problem in applications that are highly sensitive to variations in volume, such as immunoassays and DNA amplification. To overcome the limitation of the conventional method, an existing droplet can be split
|
{
"page_id": 331579,
"source": null,
"title": "Digital microfluidics"
}
|
by gradually changing the potential of the electrodes at the splitting region instead of simply switching them on and off. Using this method, a noticeable improvement in droplet volume variation, from around 10% variation in volume to less than 1% variation in volume, has been reported. === From a reservoir === Creating a new droplet from a reservoir of liquid can be done in a similar fashion to splitting a droplet. In this case, the reservoir remains stationary while a sequence of electrodes are used to draw liquid out of the reservoir. This drawn liquid and the reservoir form a neck of liquid, akin to the neck of a splitting droplet but longer, and the collapsing of this neck forms a dispensed droplet from the drawn liquid. In contrast to splitting, though, dispensing droplets in this manner is inconsistent in scale and results. There is no reliable distance liquid will need to be pulled from the reservoir for the neck to collapse, if it even collapses at all. Because this distance varies, the volumes of dispensed droplets will also vary within the same device. Due to these inconsistencies, alternative techniques for dispensing droplets have been used and proposed, including drawing liquid out of reservoirs in geometries that force a thinner neck, using a continuous and replenishable electrowetting channel, and moving reservoirs into corners so as to cut the reservoir down the middle. Multiple iterations of the latter can produce droplets of more manageable sizes. == Droplet manipulation == === Droplet merging === As an existing droplet can be split to form discrete droplets using electrodes (see From an existing droplet), droplets can be merged into one droplet by electrodes as well. Utilizing the same concept applied for creating new droplets through splitting an existing droplet with electrodes, an aqueous droplet
|
{
"page_id": 331579,
"source": null,
"title": "Digital microfluidics"
}
|
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