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Natural science The field covers the chemistry, physics and engineering applications of materials including metals, ceramics, artificial polymers, and many others. The core of the field deals with relating structure of material with it properties. It is at the forefront of research in science and engineering. It is an important part of forensic engineering (the investigation of materials, products, structures or components that fail or do not operate or function as intended, causing personal injury or damage to property) and failure analysis, the latter being the key to understanding, for example, the cause of various aviation accidents. Many of the most pressing scientific problems that are faced today are due to the limitations of the materials that are available and, as a result, breakthroughs in this field are likely to have a significant impact on the future of technology. The basis of materials science involves studying the structure of materials, and relating them to their properties. Once a materials scientist knows about this structure-property correlation, they can then go on to study the relative performance of a material in a certain application. The major determinants of the structure of a material and thus of its properties are its constituent chemical elements and the way in which it has been processed into its final form. These characteristics, taken together and related through the laws of thermodynamics and kinetics, govern a material's microstructure, and thus its properties | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Some scholars trace the origins of natural science as far back as pre-literate human societies, where understanding the natural world was necessary for survival. People observed and built up knowledge about the behavior of animals and the usefulness of plants as food and medicine, which was passed down from generation to generation. These primitive understandings gave way to more formalized inquiry around 3500 to 3000 BC in the Mesopotamian and Ancient Egyptian cultures, which produced the first known written evidence of natural philosophy, the precursor of natural science. While the writings show an interest in astronomy, mathematics and other aspects of the physical world, the ultimate aim of inquiry about nature's workings was in all cases religious or mythological, not scientific. A tradition of scientific inquiry also emerged in Ancient China, where Taoist alchemists and philosophers experimented with elixirs to extend life and cure ailments. They focused on the yin and yang, or contrasting elements in nature; the yin was associated with femininity and coldness, while yang was associated with masculinity and warmth. The five phases – fire, earth, metal, wood and water – described a cycle of transformations in nature. Water turned into wood, which turned into fire when it burned. The ashes left by fire were earth | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Using these principles, Chinese philosophers and doctors explored human anatomy, characterizing organs as predominantly yin or yang and understood the relationship between the pulse, the heart and the flow of blood in the body centuries before it became accepted in the West. Little evidence survives of how Ancient Indian cultures around the Indus River understood nature, but some of their perspectives may be reflected in the Vedas, a set of sacred Hindu texts. They reveal a conception of the universe as ever-expanding and constantly being recycled and reformed. Surgeons in the Ayurvedic tradition saw health and illness as a combination of three humors: wind, bile and phlegm. A healthy life was the result of a balance among these humors. In Ayurvedic thought, the body consisted of five elements: earth, water, fire, wind and empty space. Ayurvedic surgeons performed complex surgeries and developed a detailed understanding of human anatomy. Pre-Socratic philosophers in Ancient Greek culture brought natural philosophy a step closer to direct inquiry about cause and effect in nature between 600 and 400 BC, although an element of magic and mythology remained. Natural phenomena such as earthquakes and eclipses were explained increasingly in the context of nature itself instead of being attributed to angry gods. Thales of Miletus, an early philosopher who lived from 625 to 546 BC, explained earthquakes by theorizing that the world floated on water and that water was the fundamental element in nature | https://en.wikipedia.org/wiki?curid=38890 |
Natural science In the 5th century BC, Leucippus was an early exponent of atomism, the idea that the world is made up of fundamental indivisible particles. Pythagoras applied Greek innovations in mathematics to astronomy, and suggested that the earth was spherical. Later Socratic and Platonic thought focused on ethics, morals and art and did not attempt an investigation of the physical world; Plato criticized pre-Socratic thinkers as materialists and anti-religionists. Aristotle, however, a student of Plato who lived from 384 to 322 BC, paid closer attention to the natural world in his philosophy. In his "History of Animals", he described the inner workings of 110 species, including the stingray, catfish and bee. He investigated chick embryos by breaking open eggs and observing them at various stages of development. Aristotle's works were influential through the 16th century, and he is considered to be the father of biology for his pioneering work in that science. He also presented philosophies about physics, nature and astronomy using inductive reasoning in his works "Physics" and "Meteorology". While Aristotle considered natural philosophy more seriously than his predecessors, he approached it as a theoretical branch of science. Still, inspired by his work, Ancient Roman philosophers of the early 1st century AD, including Lucretius, Seneca and Pliny the Elder, wrote treatises that dealt with the rules of the natural world in varying degrees of depth | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Many Ancient Roman Neoplatonists of the 3rd to the 6th centuries also adapted Aristotle's teachings on the physical world to a philosophy that emphasized spiritualism. Early medieval philosophers including Macrobius, Calcidius and Martianus Capella also examined the physical world, largely from a cosmological and cosmographical perspective, putting forth theories on the arrangement of celestial bodies and the heavens, which were posited as being composed of aether. Aristotle's works on natural philosophy continued to be translated and studied amid the rise of the Byzantine Empire and Abbasid Caliphate. In the Byzantine Empire John Philoponus, an Alexandrian Aristotelian commentator and Christian theologian, was the first who questioned Aristotle's teaching of physics. Unlike Aristotle who based his physics on verbal argument, Philoponus instead relied on observation, and argued for observation rather than resorting into verbal argument. He introduced the theory of impetus. John Philoponus' criticism of Aristotelian principles of physics served as inspiration for Galileo Galilei during the Scientific Revolution. A revival in mathematics and science took place during the time of the Abbasid Caliphate from the 9th century onward, when Muslim scholars expanded upon Greek and Indian natural philosophy. The words "alcohol", "algebra" and "zenith" all have Arabic roots | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Aristotle's works and other Greek natural philosophy did not reach the West until about the middle of the 12th century, when works were translated from Greek and Arabic into Latin. The development of European civilization later in the Middle Ages brought with it further advances in natural philosophy. European inventions such as the horseshoe, horse collar and crop rotation allowed for rapid population growth, eventually giving way to urbanization and the foundation of schools connected to monasteries and cathedrals in modern-day France and England. Aided by the schools, an approach to Christian theology developed that sought to answer questions about nature and other subjects using logic. This approach, however, was seen by some detractors as heresy. By the 12th century, Western European scholars and philosophers came into contact with a body of knowledge of which they had previously been ignorant: a large corpus of works in Greek and Arabic that were preserved by Islamic scholars. Through translation into Latin, Western Europe was introduced to Aristotle and his natural philosophy. These works were taught at new universities in Paris and Oxford by the early 13th century, although the practice was frowned upon by the Catholic church. A 1210 decree from the Synod of Paris ordered that "no lectures are to be held in Paris either publicly or privately using Aristotle's books on natural philosophy or the commentaries, and we forbid all this under pain of excommunication | https://en.wikipedia.org/wiki?curid=38890 |
Natural science " In the late Middle Ages, Spanish philosopher Dominicus Gundissalinus translated a treatise by the earlier Persian scholar Al-Farabi called "On the Sciences" into Latin, calling the study of the mechanics of nature "scientia naturalis", or natural science. Gundissalinus also proposed his own classification of the natural sciences in his 1150 work "On the Division of Philosophy". This was the first detailed classification of the sciences based on Greek and Arab philosophy to reach Western Europe. Gundissalinus defined natural science as "the science considering only things unabstracted and with motion," as opposed to mathematics and sciences that rely on mathematics. Following Al-Farabi, he then separated the sciences into eight parts, including physics, cosmology, meteorology, minerals science and plant and animal science. Later philosophers made their own classifications of the natural sciences. Robert Kilwardby wrote "On the Order of the Sciences" in the 13th century that classed medicine as a mechanical science, along with agriculture, hunting and theater while defining natural science as the science that deals with bodies in motion. Roger Bacon, an English friar and philosopher, wrote that natural science dealt with "a principle of motion and rest, as in the parts of the elements of fire, air, earth and water, and in all inanimate things made from them." These sciences also covered plants, animals and celestial bodies | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Later in the 13th century, a Catholic priest and theologian Thomas Aquinas defined natural science as dealing with "mobile beings" and "things which depend on a matter not only for their existence but also for their definition." There was wide agreement among scholars in medieval times that natural science was about bodies in motion, although there was division about the inclusion of fields including medicine, music and perspective. Philosophers pondered questions including the existence of a vacuum, whether motion could produce heat, the colors of rainbows, the motion of the earth, whether elemental chemicals exist and wherein the atmosphere rain is formed. In the centuries up through the end of the Middle Ages, natural science was often mingled with philosophies about magic and the occult. Natural philosophy appeared in a wide range of forms, from treatises to encyclopedias to commentaries on Aristotle. The interaction between natural philosophy and Christianity was complex during this period; some early theologians, including Tatian and Eusebius, considered natural philosophy an outcropping of pagan Greek science and were suspicious of it. Although some later Christian philosophers, including Aquinas, came to see natural science as a means of interpreting scripture, this suspicion persisted until the 12th and 13th centuries | https://en.wikipedia.org/wiki?curid=38890 |
Natural science The Condemnation of 1277, which forbade setting philosophy on a level equal with theology and the debate of religious constructs in a scientific context, showed the persistence with which Catholic leaders resisted the development of natural philosophy even from a theological perspective. Aquinas and Albertus Magnus, another Catholic theologian of the era, sought to distance theology from science in their works. "I don't see what one's interpretation of Aristotle has to do with the teaching of the faith," he wrote in 1271. By the 16th and 17th centuries, natural philosophy underwent an evolution beyond commentary on Aristotle as more early Greek philosophy was uncovered and translated. The invention of the printing press in the 15th century, the invention of the microscope and telescope, and the Protestant Reformation fundamentally altered the social context in which scientific inquiry evolved in the West. Christopher Columbus's discovery of a new world changed perceptions about the physical makeup of the world, while observations by Copernicus, Tyco Brahe and Galileo brought a more accurate picture of the solar system as heliocentric and proved many of Aristotle's theories about the heavenly bodies false. A number of 17th-century philosophers, including Thomas Hobbes, John Locke and Francis Bacon made a break from the past by rejecting Aristotle and his medieval followers outright, calling their approach to natural philosophy as superficial | https://en.wikipedia.org/wiki?curid=38890 |
Natural science The titles of Galileo's work "Two New Sciences" and Johannes Kepler's "New Astronomy" underscored the atmosphere of change that took hold in the 17th century as Aristotle was dismissed in favor of novel methods of inquiry into the natural world. Bacon was instrumental in popularizing this change; he argued that people should use the arts and sciences to gain dominion over nature. To achieve this, he wrote that "human life [must] be endowed with new discoveries and powers." He defined natural philosophy as "the knowledge of Causes and secret motions of things; and enlarging the bounds of Human Empire, to the effecting of all things possible." Bacon proposed scientific inquiry supported by the state and fed by the collaborative research of scientists, a vision that was unprecedented in its scope, ambition and form at the time. Natural philosophers came to view nature increasingly as a mechanism that could be taken apart and understood, much like a complex clock. Natural philosophers including Isaac Newton, Evangelista Torricelli and Francesco Redi conducted experiments focusing on the flow of water, measuring atmospheric pressure using a barometer and disproving spontaneous generation. Scientific societies and scientific journals emerged and were spread widely through the printing press, touching off the scientific revolution | https://en.wikipedia.org/wiki?curid=38890 |
Natural science Newton in 1687 published his "The Mathematical Principles of Natural Philosophy", or "Principia Mathematica", which set the groundwork for physical laws that remained current until the 19th century. Some modern scholars, including Andrew Cunningham, Perry Williams and Floris Cohen, argue that natural philosophy is not properly called a science, and that genuine scientific inquiry began only with the scientific revolution. According to Cohen, "the emancipation of science from an overarching entity called 'natural philosophy' is one defining characteristic of the Scientific Revolution." Other historians of science, including Edward Grant, contend that the scientific revolution that blossomed in the 17th, 18th and 19th centuries occurred when principles learned in the exact sciences of optics, mechanics and astronomy began to be applied to questions raised by natural philosophy. Grant argues that Newton attempted to expose the mathematical basis of nature – the immutable rules it obeyed – and in doing so joined natural philosophy and mathematics for the first time, producing an early work of modern physics. The scientific revolution, which began to take hold in the 17th century, represented a sharp break from Aristotelian modes of inquiry. One of its principal advances was the use of the scientific method to investigate nature. Data was collected and repeatable measurements made in experiments. Scientists then formed hypotheses to explain the results of these experiments | https://en.wikipedia.org/wiki?curid=38890 |
Natural science The hypothesis was then tested using the principle of falsifiability to prove or disprove its accuracy. The natural sciences continued to be called natural philosophy, but the adoption of the scientific method took science beyond the realm of philosophical conjecture and introduced a more structured way of examining nature. Newton, an English mathematician, and physicist, was the seminal figure in the scientific revolution. Drawing on advances made in astronomy by Copernicus, Brahe, and Kepler, Newton derived the universal law of gravitation and laws of motion. These laws applied both on earth and in outer space, uniting two spheres of the physical world previously thought to function independently of each other, according to separate physical rules. Newton, for example, showed that the tides were caused by the gravitational pull of the moon. Another of Newton's advances was to make mathematics a powerful explanatory tool for natural phenomena. While natural philosophers had long used mathematics as a means of measurement and analysis, its principles were not used as a means of understanding cause and effect in nature until Newton. In the 18th century and 19th century, scientists including Charles-Augustin de Coulomb, Alessandro Volta, and Michael Faraday built upon Newtonian mechanics by exploring electromagnetism, or the interplay of forces with positive and negative charges on electrically charged particles. Faraday proposed that forces in nature operated in "fields" that filled space | https://en.wikipedia.org/wiki?curid=38890 |
Natural science The idea of fields contrasted with the Newtonian construct of gravitation as simply "action at a distance", or the attraction of objects with nothing in the space between them to intervene. James Clerk Maxwell in the 19th century unified these discoveries in a coherent theory of electrodynamics. Using mathematical equations and experimentation, Maxwell discovered that space was filled with charged particles that could act upon themselves and each other and that they were a medium for the transmission of charged waves. Significant advances in chemistry also took place during the scientific revolution. Antoine Lavoisier, a French chemist, refuted the phlogiston theory, which posited that things burned by releasing "phlogiston" into the air. Joseph Priestley had discovered oxygen in the 18th century, but Lavoisier discovered that combustion was the result of oxidation. He also constructed a table of 33 elements and invented modern chemical nomenclature. Formal biological science remained in its infancy in the 18th century, when the focus lay upon the classification and categorization of natural life. This growth in natural history was led by Carl Linnaeus, whose 1735 taxonomy of the natural world is still in use. Linnaeus in the 1750s introduced scientific names for all his species. By the 19th century, the study of science had come into the purview of professionals and institutions. In so doing, it gradually acquired the more modern name of "natural science | https://en.wikipedia.org/wiki?curid=38890 |
Natural science " The term "scientist" was coined by William Whewell in an 1834 review of Mary Somerville's "On the Connexion of the Sciences". But the word did not enter general use until nearly the end of the same century. According to a famous 1923 textbook "Thermodynamics and the Free Energy of Chemical Substances" by the American chemist Gilbert N. Lewis and the American physical chemist Merle Randall, the natural sciences contain three great branches: Aside from the logical and mathematical sciences, there are three great branches of "natural science" which stand apart by reason of the variety of far reaching deductions drawn from a small number of primary postulates — they are mechanics, electrodynamics, and thermodynamics. Today, natural sciences are more commonly divided into life sciences, such as botany and zoology; and physical sciences, which include physics, chemistry, astronomy, and Earth sciences. | https://en.wikipedia.org/wiki?curid=38890 |
Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the entire Solar System, and has made important contributions to the understanding of a number of processes including mantle convection, the formation of planets and the origins of granite and basalt. The term "geochemistry" was first used by the Swiss-German chemist Christian Friedrich Schönbein in 1838: "a comparative geochemistry ought to be launched, before geochemistry can become geology, and before the mystery of the genesis of our planets and their inorganic matter may be revealed." However, for the rest of the century the more common term was "chemical geology", and there was little contact between geologists and chemists. emerged as a separate discipline after major laboratories were established, starting with the United States Geological Survey (USGS) in 1884, and began systematic surveys of the chemistry of rocks and minerals. The chief USGS chemist, Frank Wigglesworth Clarke, noted that the elements generally decrease in abundance as their atomic weights increase, and summarized the work on elemental abundance in "The Data of Geochemistry". The composition of meteorites was investigated and compared to terrestrial rocks as early as 1850. In 1901, Oliver C. Farrington hypothesised that, although there were differences, the relative abundances should still be the same | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry This was the beginnings of the field of cosmochemistry and has contributed much of what we know about the formation of the Earth and the Solar System. In the early 20th century, Max von Laue and William L. Bragg showed that X-ray scattering could be used to determine the structures of crystals. In the 1920s and 1930s, Victor Goldschmidt and associates at the University of Oslo applied these methods to many common minerals and formulated a set of rules for how elements are grouped. Goldschmidt published this work in the series "Geochemische Verteilungsgesetze der Elemente" [Geochemical Laws of the Distribution of Elements]. Some subfields of geochemistry are: The building blocks of materials are the chemical elements. These can be identified by their atomic number Z, which is the number of protons in the nucleus. An element can have more than one value for N, the number of neutrons in the nucleus. The sum of these is the mass number, which is roughly equal to the atomic mass. Atoms with the same atomic number but different neutron numbers are called isotopes. A given isotope is identified by a letter for the element preceded by a superscript for the mass number. For example, two common isotopes of chlorine are Cl and Cl. There are about 1700 known combinations of Z and N, of which only about 260 are stable. However, most of the unstable isotopes do not occur in nature. In geochemistry, stable isotopes are used to trace chemical pathways and reactions, while isotopes are primarily used to date samples | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry The chemical behavior of an atom – its affinity for other elements and the type of bonds it forms – is determined by the arrangement of electrons in orbitals, particularly the outermost (valence) electrons. These arrangements are reflected in the position of elements in the periodic table. Based on position, the elements fall into the broad groups of alkali metals, alkaline earth metals, transition metals, semi-metals (also known as metalloids), halogens, noble gases, lanthanides and actinides. Another useful classification scheme for geochemistry is the Goldschmidt classification, which places the elements into four main groups. "Lithophiles" combine easily with oxygen. These elements, which include Na, K, Si, Al, Ti, Mg and Ca, dominate in the Earth's crust, forming silicates and other oxides. "Siderophile" elements (Fe, Co, Ni, Pt, Re, Os) have an affinity for iron and tend to concentrate in the core. "Chalcophile" elements (Cu, Ag, Zn, Pb, S) form sulfides; and "atmophile" elements (O, N, H and noble gases) dominate the atmosphere. Within each group, some elements are refractory, remaining stable at high temperatures, while others are volatile, evaporating more easily, so heating can separate them. The chemical composition of the Earth and other bodies is determined by two opposing processes: differentiation and mixing | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry In the Earth's mantle, differentiation occurs at mid-ocean ridges through partial melting, with more refractory materials remaining at the base of the lithosphere while the remainder rises to form basalt. After an oceanic plate descends into the mantle, convection eventually mixes the two parts together. Erosion differentiates granite, separating it into clay on the ocean floor, sandstone on the edge of the continent, and dissolved minerals in ocean waters. Metamorphism and anatexis (partial melting of crustal rocks) can mix these elements together again. In the ocean, biological organisms can cause chemical differentiation, while dissolution of the organisms and their wastes can mix the materials again. A major source of differentiation is fractionation, an unequal distribution of elements and isotopes. This can be the result of chemical reactions, phase changes, kinetic effects, or radioactivity. On the largest scale, "planetary differentiation" is a physical and chemical separation of a planet into chemically distinct regions. For example, the terrestrial planets formed iron-rich cores and silicate-rich mantles and crusts. In the Earth's mantle, the primary source of chemical differentiation is partial melting, particularly near mid-ocean ridges. This can occur when the solid is heterogeneous or a solid solution, and part of the melt is separated from the solid | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry The process is known as "equilibrium" or "batch" melting if the solid and melt remain in equilibrium until the moment that the melt is removed, and "fractional" or "Rayleigh" melting if it is removed continuously. Isotopic fractionation can have mass-dependent and mass-independent forms. Molecules with heavier isotopes have lower ground state energies and are therefore more stable. As a result, chemical reactions show a small isotope dependence, with heavier isotopes preferring species or compounds with a higher oxidation state; and in phase changes, heavier isotopes tend to concentrate in the heavier phases. Mass-dependent fractionation is largest in light elements because the difference in masses is a larger fraction of the total mass. Ratios between isotopes are generally compared to a standard. For example, sulfur has four stable isotopes, of which the two most common are S and S. The ratio of their concentrations, , is reported as where is the same ratio for a standard. Because the differences are small, the ratio is multiplied by 1000 to make it parts per thousand (referred to as parts per mil). This is represented by the symbol . "Equilibrium fractionation" occurs between chemicals or phases that are in equilibrium with each other. In equilibrium fractionation between phases, heavier phases prefer the heavier isotopes. For two phases A and B, the effect can be represented by the factor In the liquid-vapor phase transition for water, at 20 degrees Celsius is 1.0098 for O and 1.084 for H | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry In general, fractionation is greater at lower temperatures. At 0 °C, the factors are 1.0117 and 1.111. When there is not equilibrium between phases or chemical compounds, "kinetic fractionation" can occur. For example, at interfaces between liquid water and air, the forward reaction is enhanced if the humidity of the air is less than 100% or the water vapor is moved by a wind. Kinetic fractionation generally is enhanced compared to equilibrium fractionation, and depends on factors such as reaction rate, reaction pathway and bond energy. Since lighter isotopes generally have weaker bonds, they tend to react faster and enrich the reaction products. Biological fractionation is a form of kinetic fractionation, since reactions tend to be in one direction. Biological organisms prefer lighter isotopes because there is a lower energy cost in breaking energy bonds. In addition to the previously mentioned factors, the environment and species of the organism can have a large effect on the fractionation. Through a variety of physical and chemical processes, chemical elements change in concentration and move around in what are called "geochemical cycles". An understanding of these changes requires both detailed observation and theoretical models. Each chemical compound, element or isotope has a concentration that is a function of position and time, but it is impractical to model the full variability | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Instead, in an approach borrowed from chemical engineering, geochemists average the concentration over regions of the Earth called "geochemical reservoirs". The choice of reservoir depends on the problem; for example, the ocean may be a single reservoir or be split into multiple reservoirs. In a type of model called a "box model", a reservoir is represented by a box with inputs and outputs. Geochemical models generally involve feedback. In the simplest case of a linear cycle, either the input or the output from a reservoir is proportional to the concentration. For example, salt is removed from the ocean by formation of evaporites, and given a constant rate of evaporation in evaporite basins, the rate of removal of salt should be proportional to its concentration. For a given component , if the input to a reservoir is a constant and the output is for some constant , then the "mass balance" equation is This expresses the fact that any change in mass must be balanced by changes in the input or output. On a time scale of , the system approaches a steady state in which . The "residence time" is defined as where and are the input and output rates. In the above example, the steady-state input and output rates are both equal to , so . If the input and output rates are nonlinear functions of , they may still be closely balanced over time scales much greater than the residence time; otherwise there will be large fluctuations in | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry In that case, the system is always close to a steady state and a lowest order expansion of the mass balance equation will lead to a linear equation like Equation (). In most systems, one or both of the input and output depend on , resulting in a feedback that tends to maintain the steady state. If an external forcing perturbs the system, it will return to the steady state on a time scale of . The composition of the Solar System is similar to that of many other stars, and aside from small anomalies it can be assumed to have formed from a solar nebula that had a uniform composition, and the composition of the Sun's photosphere is similar to that of the rest of the Solar System. The composition of the photosphere is determined by fitting the absorption lines in its spectrum to models of the Sun's atmosphere. By far the largest two elements by fraction of total mass are hydrogen (74.9%) and helium (23.8%), with all the remaining elements contributing just 1.3%. There is a general trend of exponential decrease in abundance with increasing atomic number, although elements with even atomic number are more common than their odd-numbered neighbors (the Oddo–Harkins rule). Compared to the overall trend, lithium, boron and beryllium are depleted and iron is anomalously enriched. The pattern of elemental abundance is mainly due to two factors. The hydrogen, helium, and some of the lithium were formed in about 20 minutes after the Big Bang, while the rest were created in the interiors of stars | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Meteorites come in a variety of compositions, but chemical analysis can determine whether they were once in planetesimals that melted or differentiated. Chondrites are undifferentiated and have round mineral inclusions called chondrules. With ages of 4.56 billion years, they date to the early solar system. A particular kind, the CI chondrite, has a composition that closely matches that of the Sun's photosphere, except for depletion of some volatiles (H, He, C, N, O) and a group of elements (Li, B, Be) that are destroyed by nucleosynthesis in the Sun. Because of the latter group, CI chondrites are considered a better match for the composition of the early Solar System. Moreover, the chemical analysis of CI chondrites is more accurate than for the photosphere, so it is generally used as the source for chemical abundance, despite their rareness (only five have been recovered on Earth). The planets of the Solar System are divided into two groups: the four inner planets are the terrestrial planets (Mercury, Venus, Earth and Mars), with relatively small sizes and rocky surfaces. The four outer planets are the giant planets, which are dominated by hydrogen and helium and have lower mean densities. These can be further subdivided into the gas giants (Jupiter and Saturn) and the ice giants (Uranus and Neptune) that have large icy cores. Most of our direct information on the composition of the giant planets is from spectroscopy. Since the 1930s, Jupiter was known to contain hydrogen, methane and ammonium | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry In the 1960s, interferometry greatly increased the resolution and sensitivity of spectral analysis, allowing the identification of a much greater collection of molecules including ethane, acetylene, water and carbon monoxide. However, Earth-based spectroscopy becomes increasingly difficult with more remote planets, since the reflected light of the Sun is much dimmer; and spectroscopic analysis of light from the planets can only be used to detect vibrations of molecules, which are in the infrared frequency range. This constrains the abundances of the elements H, C and N. Two other elements are detected: phosphorus in the gas phosphine (PH) and germanium in germane (GeH). The helium atom has vibrations in the ultraviolet range, which is strongly absorbed by the atmospheres of the outer planets and Earth. Thus, despite its abundance, helium was only detected once spacecraft were sent to the outer planets, and then only indirectly through collision-induced absorption in hydrogen molecules. Further information on Jupiter was obtained from the "Galileo" probe when it was sent into the atmosphere in 1995; and the final mission of the Cassini probe in 2017 was to enter the atmosphere of Saturn | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry In the atmosphere of Jupiter, He was found to be depleted by a factor of 2 compared to solar composition and Ne by a factor of 10, a surprising result since the other noble gases and the elements C, N and S were enhanced by factors of 2 to 4 (oxygen was also depleted but this was attributed to the unusually dry region that Galileo sampled). Spectroscopic methods only penetrate the atmospheres of Jupiter and Saturn to depths where the pressure is about equal to 1 bar, approximately Earth's atmospheric pressure at sea level. The Galileo probe penetrated to 22 bars. This is a small fraction of the planet, which is expected to reach pressures of over 40 Mbar. To constrain the composition in the interior, thermodynamic models are constructed using information on temperature from infrared emission spectra and equations of state for the likely compositions. High pressure experiments predict that hydrogen will be a metallic liquid in the interior of Jupiter and Saturn, while in Uranus and Neptune it remains in the molecular state. Estimates also depend on models for the formation of the planets. Condensation of the presolar nebula would result in a gaseous planet with the same composition as the Sun, but the planets could also have formed when a solid core captured nebular gas. In current models, the four giant planets have cores of rock and ice that are roughly the same size, but the proportion of hydrogen and helium decreases from about 300 Earth masses in Jupiter to 75 in Saturn and just a few in Uranus and Neptune | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Thus, while the gas giants are primarily composed of hydrogen and helium, the ice giants are primarily composed of heavier elements (O, C, N, S), primarily in the form of water, methane and ammonia. The surfaces are cold enough for molecular hydrogen to be liquid, so much of each planet is likely a hydrogen ocean overlaying one of heavier compounds. Outside the core, Jupiter has a mantle of liquid metallic hydrogen and an atmosphere of molecular hydrogen and helium. Metallic hydrogen does not mix well with helium, and in Saturn it may form a separate layer below the metallic hydrogen. Terrestrial planets are believed to have come from the same nebular material as the giant planets, but they have lost most of the lighter elements and have different histories. Planets closer to the Sun might be expected to have a higher fraction of refractory elements, but if their later stages of formation involved collisions of large objects with orbits that sampled different parts of the Solar System, there could be little systematic dependence on position. Direct information on Mars, Venus and Mercury largely comes from spacecraft missions. Using gamma-ray spectrometers, the composition of the crust of Mars has been measured by the Mars Odyssey orbiter, the crust of Venus by some of the Venera missions to Venus, and the crust of Mercury by the "MESSENGER" spacecraft | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Additional information on Mars comes from meteorites that have landed on Earth (the Shergottites, Nakhlites, and Chassignites, collectively known as SNC meteorites). Abundances are also constrained by the masses of the planets, while the internal distribution of elements is constrained by their moments of inertia. The planets condensed from the solar nebula, and much of the details of their composition are determined by fractionation as they cooled. The phases that condense fall into five groups. First to condense are materials rich in refractory elements such as Ca and Al. These are followed by nickel and iron, then magnesium silicates. Below about 700 kelvins (700 K), FeS and volatile-rich metals and silicates form a fourth group, and in the fifth group FeO enter the magnesium silicates. The compositions of the planets and the Moon are "chondritic", meaning that within each group the ratios between elements are the same as in carbonaceous chondrites. The estimates of planetary compositions depend on the model used. In the "equilibrium condensation" model, each planet was formed from a "feeding zone" in which the compositions of solids were determined by the temperature in that zone. Thus, Mercury formed at 1400 K, where iron remained in a pure metallic form and there was little magnesium or silicon in solid form; Venus at 900 K, so all the magnesium and silicon condensed; Earth at 600 K, so it contains FeS and silicates; and Mars at 450 K, so FeO was incorporated into magnesium silicates | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry The greatest problem with this theory is that volatiles would not condense, so the planets would have no atmospheres and Earth no atmosphere. In "chondritic mixing" models, the compositions of chondrites are used to estimate planetary compositions. For example, one model mixes two components, one with the composition of C1 chondrites and one with just the refractory components of C1 chondrites. In another model, the abundances of the five fractionation groups are estimated using an index element for each group. For the most refractory group, uranium is used; iron for the second; the ratios of potassium and thallium to uranium for the next two; and the molar ratio FeO/(FeO+MgO) for the last. Using thermal and seismic models along with heat flow and density, Fe can be constrained to within 10 percent on Earth, Venus and Mercury. U can be constrained within about 30% on Earth, but its abundance on other planets is based on "educated guesses". One difficulty with this model is that there may be significant errors in its prediction of volatile abundances because some volatiles are only partially condensed. The more common rock constituents are nearly all oxides; chlorides, sulfides and fluorides are the only important exceptions to this and their total amount in any rock is usually much less than 1%. By 1911, F. W. Clarke had calculated that a little more than 47% of the Earth's crust consists of oxygen | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry It occurs principally in combination as oxides, of which the chief are silica, alumina, iron oxides, and various carbonates (calcium carbonate, magnesium carbonate, sodium carbonate, and potassium carbonate). The silica functions principally as an acid, forming silicates, and all the commonest minerals of igneous rocks are of this nature. From a computation based on 1672 analyses of numerous kinds of rocks Clarke arrived at the following as the average percentage composition of the Earth's crust: SiO=59.71, AlO=15.41, FeO=2.63, FeO=3.52, MgO=4.36, CaO=4.90, NaO=3.55, KO=2.80, HO=1.52, TiO=0.60, PO=0.22, (total 99.22%). All the other constituents occur only in very small quantities, usually much less than 1%. These oxides combine in a haphazard way. For example, potash (potassium carbonate) and soda (sodium carbonate) combine to produce feldspars. In some cases they may take other forms, such as nepheline, leucite, and muscovite, but in the great majority of instances they are found as feldspar. Phosphoric acid with lime (calcium carbonate) forms apatite. Titanium dioxide with ferrous oxide gives rise to ilmenite. Part of the lime forms lime feldspar. Magnesium carbonate and iron oxides with silica crystallize as olivine or enstatite, or with alumina and lime form the complex ferro-magnesian silicates of which the pyroxenes, amphiboles, and biotites are the chief. Any excess of silica above what is required to neutralize the bases will separate out as quartz; excess of alumina crystallizes as corundum | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry These must be regarded only as general tendencies. It is possible, by rock analysis, to say approximately what minerals the rock contains, but there are numerous exceptions to any rule. Except in acid or siliceous igneous rocks containing greater than 66% of silica, known as felsic rocks, quartz is not abundant in igneous rocks. In basic rocks (containing 20% of silica or less) it is rare for them to contain as much silicon, these are referred to as mafic rocks. If magnesium and iron are above average while silica is low, olivine may be expected; where silica is present in greater quantity over ferro-magnesian minerals, such as augite, hornblende, enstatite or biotite, occur rather than olivine. Unless potash is high and silica relatively low, leucite will not be present, for leucite does not occur with free quartz. Nepheline, likewise, is usually found in rocks with much soda and comparatively little silica. With high alkalis, soda-bearing pyroxenes and amphiboles may be present. The lower the percentage of silica and alkali's, the greater is the prevalence of plagioclase feldspar as contracted with soda or potash feldspar. Earth's crust is composed of 90% silicate minerals and their abundance in the Earth is as follows: plagioclase feldspar (39%), alkali feldspar (12%), quartz (12%), pyroxene (11%), amphiboles (5%), micas (5%), clay minerals (5%); the remaining silicate minerals make up another 3% of Earth's crust | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Only 8% of the Earth is composed of non-silicate minerals such as carbonates, oxides, and sulfides. The other determining factor, namely the physical conditions attending consolidation, plays on the whole a smaller part, yet is by no means negligible. Certain minerals are practically confined to deep-seated intrusive rocks, e.g., microcline, muscovite, diallage. Leucite is very rare in plutonic masses; many minerals have special peculiarities in microscopic character according to whether they crystallized in depth or near the surface, e.g., hypersthene, orthoclase, quartz. There are some curious instances of rocks having the same chemical composition, but consisting of entirely different minerals, e.g., the hornblendite of Gran, in Norway, which contains only hornblende, has the same composition as some of the camptonites of the same locality that contain feldspar and hornblende of a different variety. In this connection we may repeat what has been said above about the corrosion of porphyritic minerals in igneous rocks. In rhyolites and trachytes, early crystals of hornblende and biotite may be found in great numbers partially converted into augite and magnetite. Hornblende and biotite were stable under the pressures and other conditions below the surface, but unstable at higher levels. In the ground-mass of these rocks, augite is almost universally present. But the plutonic representatives of the same magma, granite and syenite contain biotite and hornblende far more commonly than augite | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Those rocks that contain the most silica, and on crystallizing yield free quartz, form a group generally designated the "felsic" rocks. Those again that contain least silica and most magnesia and iron, so that quartz is absent while olivine is usually abundant, form the "mafic" group. The "intermediate" rocks include those characterized by the general absence of both quartz and olivine. An important subdivision of these contains a very high percentage of alkalis, especially soda, and consequently has minerals such as nepheline and leucite not common in other rocks. It is often separated from the others as the "alkali" or "soda" rocks, and there is a corresponding series of mafic rocks. Lastly a small sub-group rich in olivine and without feldspar has been called the "ultramafic" rocks. They have very low percentages of silica but much iron and magnesia. Except these last, practically all rocks contain felspars or feldspathoid minerals. In the acid rocks the common feldspars are orthoclase, perthite, microcline, and oligoclase—all having much silica and alkalis. In the mafic rocks labradorite, anorthite and bytownite prevail, being rich in lime and poor in silica, potash and soda. Augite is the most common ferro-magnesian in mafic rocks, but biotite and hornblende are on the whole more frequent in felsic rocks. Rocks that contain leucite or nepheline, either partly or a wholly replacing felspar, are not included in this table. They are essentially of intermediate or of mafic character | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry We might in consequence regard them as varieties of syenite, diorite, gabbro, etc., in which feldspathoid minerals occur, and indeed there are many transitions between syenites of ordinary type and nepheline — or leucite — syenite, and between gabbro or dolerite and theralite or essexite. But, as many minerals develop in these "alkali" rocks that are uncommon elsewhere, it is convenient in a purely formal classification like that outlined here to treat the whole assemblage as a distinct series. This classification is based essentially on the mineralogical constitution of the igneous rocks. Any chemical distinctions between the different groups, though implied, are relegated to a subordinate position. It is admittedly artificial but it has grown up with the growth of the science and is still adopted as the basis on which more minute subdivisions are erected. The subdivisions are by no means of equal value. The syenites, for example, and the peridotites, are far less important than the granites, diorites and gabbros. Moreover, the effusive andesites do not always correspond to the plutonic diorites but partly also to the gabbros. As the different kinds of rock, regarded as aggregates of minerals, pass gradually into one another, transitional types are very common and are often so important as to receive special names | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry The quartz-syenites and nordmarkites may be interposed between granite and syenite, the tonalites and adamellites between granite and diorite, the monzoaites between syenite and diorite, norites and hyperites between diorite and gabbro, and so on. Trace metals readily form complexes with major ions in the ocean, including hydroxide, carbonate, and chloride and their chemical speciation changes depending on whether the environment is oxidized or reduced. Benjamin (2002) defines complexes of metals with more than one type of ligand, other than water, as mixed-ligand-complexes. In some cases, a ligand contains more than one "donor" atom, forming very strong complexes, also called chelates (the ligand is the chelator). One of the most common chelators is EDTA (ethylenediaminetetraacetic acid), which can replace six molecules of water and form strong bonds with metals that have a plus two charge. With stronger complexation, lower activity of the free metal ion is observed. One consequence of the lower reactivity of complexed metals compared to the same concentration of free metal is that the chelation tends to stabilize metals in the aqueous solution instead of in solids. Concentrations of the trace metals cadmium, copper, molybdenum, manganese, rhenium, uranium and vanadium in sediments record the redox history of the oceans. Within aquatic environments, cadmium(II) can either be in the form CdCl in oxic waters or CdS(s) in a reduced environment | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Thus higher concentrations of Cd in marine sediments may indicate low redox potential conditions in the past. For copper(II), a prevalent form is CuCl(aq) within oxic environments and CuS(s) and CuS within reduced environments. The reduced seawater environment leads to two possible oxidation states of copper, Cu(I) and Cu(II). Molybdenum is present as the Mo(VI) oxidation state as MoO in oxic environments. Mo(V) and Mo(IV) are present in reduced environments in the forms MoO and MoS. Rhenium is present as the Re(VII) oxidation state as ReO within oxic conditions, but is reduced to Re(IV) which may form ReO or ReS. Uranium is in oxidation state VI in UO(CO)(aq) and is found in the reduced form UO(s). Vanadium is in several forms in oxidation state V(V); HVO and HVO. Its reduced forms can include VO, VO(OH), and V(OH). These relative dominance of these species depends on pH. In the water column of the ocean or deep lakes, vertical profiles of dissolved trace metals are characterized as following "conservative–type", "nutrient–type", or "scavenged–type" distributions. Across these three distributions, trace metals have different residence times and are used to varying extents by planktonic microorganisms. Trace metals with conservative-type distributions have high concentrations relative to their biological use. One example of a trace metal with a conservative-type distribution is molybdenum. It has a residence time within the oceans of around 8 x 10 years and is generally present as the molybdate anion (MoO) | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Molybdenum interacts weakly with particles and displays an almost uniform vertical profile in the ocean. Relative to the abundance of molybdenum in the ocean, the amount required as a metal cofactor for enzymes in marine phytoplankton is negligible. Trace metals with nutrient-type distributions are strongly associated with the internal cycles of particulate organic matter, especially the assimilation by plankton. The lowest dissolved concentrations of these metals are at the surface of the ocean, where they are assimilated by plankton. As dissolution and decomposition occur at greater depths, concentrations of these trace metals increase. Residence times of these metals, such as zinc, are several thousand to one hundred thousand years. Finally, an example of a scavenged-type trace metal is aluminium, which has strong interactions with particles as well as a short residence time in the ocean. The residence times of scavenged-type trace metals are around 100 to 1000 years. The concentrations of these metals are highest around bottom sediments, hydrothermal vents, and rivers. For aluminium, atmospheric dust provides the greatest source of external inputs into the ocean. Iron and copper show hybrid distributions in the ocean. They are influenced by recycling and intense scavenging. Iron is a limiting nutrient in vast areas of the oceans, and is found in high abundance along with manganese near hydrothermal vents | https://en.wikipedia.org/wiki?curid=39562 |
Geochemistry Here, many iron precipitates are found, mostly in the forms of iron sulfides and oxidized iron oxyhydroxide compounds. Concentrations of iron near hydrothermal vents can be up to one million times the concentrations found in the open ocean. Using electrochemical techniques, it is possible to show that bioactive trace metals (zinc, cobalt, cadmium, iron and copper) are bound by organic ligands in surface seawater. These ligand complexes serve to lower the bioavailability of trace metals within the ocean. For example, copper, which may be toxic to open ocean phytoplankton and bacteria, can form organic complexes. The formation of these complexes reduces the concentrations of bioavailable inorganic complexes of copper that could be toxic to sea life at high concentrations. Unlike copper, zinc toxicity in marine phytoplankton is low and there is no advantage to increasing the organic binding of Zn. In high nutrient-low chlorophyll regions, iron is the limiting nutrient, with the dominant species being strong organic complexes of Fe(III). | https://en.wikipedia.org/wiki?curid=39562 |
Electroporation Electroporation, or electropermeabilization, is a microbiology technique in which an electrical field is applied to cells in order to increase the permeability of the cell membrane, allowing chemicals, drugs, or DNA to be introduced into the cell (also called electrotransfer). In microbiology, the process of electroporation is often used to transform bacteria, yeast, or plant protoplasts by introducing new coding DNA. If bacteria and plasmids are mixed together, the plasmids can be transferred into the bacteria after electroporation, though depending on what is being transferred cell-penetrating peptides or CellSqueeze could also be used. works by passing thousands of volts across a distance of one to two millimeters of suspended cells in an electroporation cuvette (1.0 – 1.5 kV, 250 – 750 V/cm). Afterwards, the cells have to be handled carefully until they have had a chance to divide, producing new cells that contain reproduced plasmids. This process is approximately ten times more effective than chemical transformation. is also highly efficient for the introduction of foreign genes into tissue culture cells, especially mammalian cells. For example, it is used in the process of producing knockout mice, as well as in tumor treatment, gene therapy, and cell-based therapy. The process of introducing foreign DNA into eukaryotic cells is known as transfection. is highly effective for transfecting cells in suspension using electroporation cuvettes | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation has proven efficient for use on tissues in vivo, for in utero applications as well as in ovo transfection. Adherent cells can also be transfected using electroporation, providing researchers with an alternative to trypsinizing their cells prior to transfection. One downside to electroporation, however, is that after the process the gene expression of over 7,000 genes can be affected. This can cause problems in studies where gene expression has to be controlled to ensure accurate and precise results. Although bulk electroporation has many benefits over physical delivery methods such as microinjections and gene guns, it still has limitations including low cell viability. Miniaturization of electroporation has been studied leading to microelectroporation and nanotransfection of tissue utilizing electroporation based techniques via nanochannels to minimally invasively deliver cargo to the cells. Cell fusion is of interest not only as an essential process in cell biology, but also as a useful method in biotechnology and medicine. Artificially induced fusion can be used to investigate and treat different diseases, like diabetes, regenerate axons of the central nerve system, and produce cells with desired properties, such as in cell vaccines for cancer immunotherapy | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation However, the first and most known application of cell fusion is production of monoclonal antibodies in hybridoma technology, where hybrid cell lines (hybridomas) are formed by fusing specific antibody-producing B lymphocytes with a myeloma (B lymphocyte cancer) cell line. is performed with electroporators, purpose-built appliances which create an electrostatic field in a cell solution. The cell suspension is pipetted into a glass or plastic cuvette which has two aluminium electrodes on its sides. For bacterial electroporation, typically a suspension of around 50 microliters is used. Prior to electroporation, this suspension of bacteria is mixed with the plasmid to be transformed. The mixture is pipetted into the cuvette, the voltage and capacitance are set, and the cuvette is inserted into the electroporator. The process requires direct contact between the electrodes and the suspension. Immediately after electroporation, one milliliter of liquid medium is added to the bacteria (in the cuvette or in an Eppendorf tube), and the tube is incubated at the bacteria's optimal temperature for an hour or more to allow recovery of the cells and expression of the plasmid, followed by bacterial culture on agar plates. The success of the electroporation depends greatly on the purity of the plasmid solution, especially on its salt content. Solutions with high salt concentrations might cause an electrical discharge (known as arcing), which often reduces the viability of the bacteria | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation For a further detailed investigation of the process, more attention should be paid to the output impedance of the porator device and the input impedance of the cells suspension (e.g. salt content). Since the cell membrane is not able to pass current (except in ion channels), it acts as an electrical capacitor. Subjecting membranes to a high-voltage electric field results in their temporary breakdown, resulting in pores that are large enough to allow macromolecules (such as DNA) to enter or leave the cell. Additionally, electroporation can be used to increase permeability of cells during in Utero injections and surgeries. Particularly, the electroporation allows for a more efficient transfection of DNA, RNA, shRNA, and all nucleic acids into the cells of mice and rats. The success of in vivo electroporation depends greatly on voltage, repetition, pulses, and duration. Developing central nervous systems are most effective for in vivo electroporation due to the visibility of ventricles for injections of nucleic acids, as well as the increased permeability of dividing cells. of injected in utero embryos is performed through the uterus wall, often with forceps-type electrodes to limit damage to the embryo. In vivo gene electrotransfer was first described in 1991 and today there are many preclinical studies of gene electrotransfer | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation The method is used to deliver large variety of therapeutic genes for potential treatment of several diseases, such as: disorders in immune system, tumors, metabolic disorders, monogenetic diseases, cardiovascular diseases, analgesia…. With regards to irreversible electroporation, the first successful treatment of malignant cutaneous tumors implanted in mice was completed in 2007 by a group of scientists who achieved complete tumor ablation in 12 out of 13 mice. They accomplished this by sending 80 pulses of 100 microseconds at 0.3 Hz with an electrical field magnitude of 2500 V/cm to treat the cutaneous tumors. Currently, a number of companies, including AngioDynamics, Inc. and VoltMed, Inc., are continuing to develop and deploy irreversible electroporation-based technologies within clinical environments. The first group to look at electroporation for medical applications was led by Lluis M Mir at the Institute Gustave Roussy. In this case, they looked at the use of reversible electroporation in conjunction with impermeable macromolecules. The first research looking at how nanosecond pulses might be used on human cells was conducted by researchers at Eastern Virginia Medical School and Old Dominion University, and published in 2003. The first medical application of electroporation was used for introducing poorly permeant anticancer drugs into tumor nodules. Soon also gene electrotransfer became of special interest because of its low cost, easiness of realization and safety | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation Namely, viral vectors can have serious limitations in terms of immunogenicity and pathogenicity when used for DNA transfer. A higher voltage of electroporation was found in pigs to irreversibly destroy target cells within a narrow range while leaving neighboring cells unaffected, and thus represents a promising new treatment for cancer, heart disease and other disease states that require removal of tissue. Irreversible electroporation (IRE) has since proven effective in treating human cancer, with surgeons at Johns Hopkins and other institutions now using the technology to treat pancreatic cancer previously thought to be unresectable. Also first phase I clinical trial of gene electrotransfer in patients with metastatic melanoma was reported. mediated delivery of a plasmid coding gene for interleukin-12 (pIL-12) was performed and safety, tolerability and therapeutic effect were monitored. Study concluded, that gene electrotransfer with pIL-12 is safe and well tolerated. In addition partial or complete response was observed also in distant non treated metastases, suggesting the systemic treatment effect. Based on these results they are already planning to move to Phase II clinical study. There are currently several ongoing clinical studies of gene electrotransfer, where safety, tolerability and effectiveness of immunization with DNA vaccine, which is administered by the electric pulses is monitored | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation Although the method is not systemic, but strictly local one, it is still the most efficient non-viral strategy for gene delivery. A recent technique called non-thermal irreversible electroporation (N-TIRE) has proven successful in treating many different types of tumors and other unwanted tissue. This procedure is done using small electrodes (about 1mm in diameter), placed either inside or surrounding the target tissue to apply short, repetitive bursts of electricity at a predetermined voltage and frequency. These bursts of electricity increase the resting transmembrane potential (TMP), so that nanopores form in the plasma membrane. When the electricity applied to the tissue is above the electric field threshold of the target tissue, the cells become permanently permeable from the formation of nanopores. As a result, the cells are unable to repair the damage and die due to a loss of homeostasis. N-TIRE is unique to other tumor ablation techniques in that it does not create thermal damage to the tissue around it. Contrastingly, reversible electroporation occurs when the electricity applied with the electrodes is below the electric field threshold of the target tissue. Because the electricity applied is below the cells' threshold, it allows the cells to repair their phospholipid bilayer and continue on with their normal cell functions | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation Reversible electroporation is typically done with treatments that involve getting a drug or gene (or other molecule that is not normally permeable to the cell membrane) into the cell. Not all tissue has the same electric field threshold; therefore careful calculations need to be made prior to a treatment to ensure safety and efficacy. One major advantage of using N-TIRE is that, when done correctly according to careful calculations, it only affects the target tissue. Proteins, the extracellular matrix, and critical structures such as blood vessels and nerves are all unaffected and left healthy by this treatment. This allows for a quicker recovery, and facilitates a more rapid replacement of dead tumor cells with healthy cells. Before doing the procedure, scientists must carefully calculate exactly what needs to be done, and treat each patient on an individual case-by-case basis. To do this, imaging technology such as CT scans and MRI's are commonly used to create a 3D image of the tumor. From this information, they can approximate the volume of the tumor and decide on the best course of action including the insertion site of electrodes, the angle they are inserted in, the voltage needed, and more, using software technology. Often, a CT machine will be used to help with the placement of electrodes during the procedure, particularly when the electrodes are being used to treat tumors in the brain. The entire procedure is very quick, typically taking about five minutes | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation The success rate of these procedures is high and is very promising for future treatment in humans. One disadvantage to using N-TIRE is that the electricity delivered from the electrodes can stimulate muscle cells to contract, which could have lethal consequences depending on the situation. Therefore, a paralytic agent must be used when performing the procedure. The paralytic agents that have been used in such research are successful; however, there is always some risk, albeit slight, when using anesthetics. A more recent technique has been developed called high-frequency irreversible electroporation (H-FIRE). This technique uses electrodes to apply bipolar bursts of electricity at a high frequency, as opposed to unipolar bursts of electricity at a low frequency. This type of procedure has the same tumor ablation success as N-TIRE. However, it has one distinct advantage, H-FIRE does not cause muscle contraction in the patient and therefore there is no need for a paralytic agent. Furthermore, H-FIRE has been demonstrated to produce more predicable ablations due to the lesser difference in the electrical properties of tissues at higher frequencies. can also be used to help deliver drugs or genes into the cell by applying short and intense electric pulses that transiently permeabilize cell membrane, thus allowing transport of molecules otherwise not transported through a cellular membrane | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation This procedure is referred to as electrochemotherapy when the molecules to be transported are chemotherapeutic agents or gene electrotransfer when the molecule to be transported is DNA. Scientists from Karolinska Institutet and the University of Oxford use electroporation of exosomes to deliver siRNAs, antisense oligonucleotides, chemotherapeutic agents and proteins specifically to neurons after inject them systemically (in blood). Because these exosomes are able to cross the blood brain barrier, this protocol could solve the problem of poor delivery of medications to the central nervous system, and potentially treat Alzheimer's disease, Parkinson's disease, and brain cancer, among other conditions. Bacterial transformation is generally the easiest way to make large amounts of a particular protein needed for biotechnology purposes or in medicine. Since gene electrotransfer is very simple, rapid and highly effective technique it first became very convenient replacement for other transformation procedures. allows cellular introduction of large highly charged molecules such as DNA which would never passively diffuse across the hydrophobic bilayer core. This phenomenon indicates that the mechanism is the creation of nm-scale water-filled holes in the membrane. Although electroporation and dielectric breakdown both result from application of an electric field, the mechanisms involved are fundamentally different. In dielectric breakdown the barrier material is ionized, creating a conductive pathway | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation The material alteration is thus chemical in nature. In contrast, during electroporation the lipid molecules are not chemically altered but simply shift position, opening up a pore which acts as the conductive pathway through the bilayer as it is filled with water. is a dynamic phenomenon that depends on the local transmembrane voltage at each point on the cell membrane. It is generally accepted that for a given pulse duration and shape, a specific transmembrane voltage threshold exists for the manifestation of the electroporation phenomenon (from 0.5 V to 1 V). This leads to the definition of an electric field magnitude threshold for electroporation (E). That is, only the cells within areas where E≧E are electroporated. If a second threshold (E) is reached or surpassed, electroporation will compromise the viability of the cells, "i.e.", irreversible electroporation (IRE). is a multi-step process with several distinct phases. First, a short electrical pulse must be applied. Typical parameters would be 300–400 mV for < 1 ms across the membrane (note- the voltages used in cell experiments are typically much larger because they are being applied across large distances to the bulk solution so the resulting field across the actual membrane is only a small fraction of the applied bias). Upon application of this potential the membrane charges like a capacitor through the migration of ions from the surrounding solution. Once the critical field is achieved there is a rapid localized rearrangement in lipid morphology | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation The resulting structure is believed to be a "pre-pore" since it is not electrically conductive but leads rapidly to the creation of a conductive pore. Evidence for the existence of such pre-pores comes mostly from the "flickering" of pores, which suggests a transition between conductive and insulating states. It has been suggested that these pre-pores are small (~3 Å) hydrophobic defects. If this theory is correct, then the transition to a conductive state could be explained by a rearrangement at the pore edge, in which the lipid heads fold over to create a hydrophilic interface. Finally, these conductive pores can either heal, resealing the bilayer or expand, eventually rupturing it. The resultant fate depends on whether the critical defect size was exceeded which in turn depends on the applied field, local mechanical stress and bilayer edge energy. Application of electric pulses of sufficient strength to the cell causes an increase in the trans-membrane potential difference, which provokes the membrane destabilization. Cell membrane permeability is increased and otherwise nonpermeant molecules enter the cell | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation Although the mechanisms of gene electrotransfer are not yet fully understood, it was shown that the introduction of DNA only occurs in the part of the membrane facing the cathode and that several steps are needed for successful transfection: electrophoretic migration of DNA towards the cell, DNA insertion into the membrane, translocation across the membrane, migration of DNA towards the nucleus, transfer of DNA across the nuclear envelope and finally gene expression. There are a number of factors that can influence the efficiency of gene electrotransfer, such as: temperature, parameters of electric pulses, DNA concentration, electroporation buffer used, cell size and the ability of cells to express transfected genes. In in vivo gene electrotransfer also DNA diffusion through extracellular matrix, properties of tissue and overall tissue conductivity are crucial. It was in the 1960s that there were publications reporting that by applying an external electric field, a large membrane potential at the two pole of a cell can be created. Then in 1970s, several groups, including Crowley, Zimmermann, Neumann reported that when this membrane potential reached a critical level, the membrane will breakdown. By the end of 1970s and the beginning of 1980s, people found that when applying the electric pulse short enough, the "pores" created on the cell membrane can be resealed, and the cell can recover and survive | https://en.wikipedia.org/wiki?curid=39619 |
Electroporation In the 1980s, many labs began to use this electroporation method to introduce various of materials/molecules into the cells, for example, drugs (Zimmermann), DNA/genes (Neumann). The electroporation techniques were also under active improvement. At that time, the electro-pore was mainly a theoretical concept. In order to experimentally prove the existence of the electro-pore, Chang and Reese conducted a rapid-freezing freeze-fracture electron microscopy technique to visualize the structure of membrane pores following electro-poration. Since then due to its ease of application and efficiency has become a routine method for introducing foreign genes into bacterial, yeast, plant, and animal cells "in vitro" and into different tissues, including muscle, tumors, liver, and skin "in vivo". | https://en.wikipedia.org/wiki?curid=39619 |
Caesium standard The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfine ground states of caesium-133 atoms are used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK. and promoted worldwide by Gernot M. R. Winkler of the USNO. Caesium atomic clocks are the most accurate time and frequency standards, and serve as the primary standard for the definition of the second in the International System of Units (SI) (the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth's magnetic field) has a frequency, , of exactly . That value was chosen so that the caesium second equalled, to the limit of human measuring ability in 1960 when it was adopted, the existing standard ephemeris second based on the Earth's orbit around the Sun. Because no other measurement involving time had been as precise, the effect of the change was less than the experimental uncertainty of all existing measurements. The official definition of the second was first given by the BIPM at the 13th General Conference on Weights and Measures in 1967 as: ""The second is the duration of periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom | https://en.wikipedia.org/wiki?curid=40858 |
Caesium standard "" At its 1997 meeting the BIPM added to the previous definition the following specification: ""This definition refers to a caesium atom at rest at a temperature of 0 K."" The BIPM restated this definition in its 26th conference (2018), ""The second is defined by taking the fixed numerical value of the caesium frequency ∆Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s."" The meaning of the preceding definition is as follows. The caesium atom has a ground state electron state with configuration [Xe] 6s and, consequently, atomic term symbol S. This means that there is one unpaired electron and the total electron spin of the atom is 1/2. Moreover, the nucleus of caesium-133 has a nuclear spin equal to 7/2. The simultaneous presence of electron spin and nuclear spin leads, by a mechanism called hyperfine interaction, to a (small) splitting of all energy levels into two sub-levels. One of the sub-levels corresponds to the electron and nuclear spin being parallel (i.e., pointing in the same direction), leading to a total spin "F" equal to ; the other sub-level corresponds to anti-parallel electron and nuclear spin (i.e., pointing in opposite directions), leading to a total spin . In the caesium atom it so happens that the sub-level lowest in energy is the one with , while the sub-level lies energetically slightly above | https://en.wikipedia.org/wiki?curid=40858 |
Caesium standard When the atom is irradiated with electromagnetic radiation having an energy corresponding to the energetic difference between the two sub-levels the radiation is absorbed and the atom is excited, going from the sub-level to the one. After a small fraction of a second the atom will re-emit the radiation and return to its ground state. From the definition of the second it follows that the radiation in question has a frequency of exactly , corresponding to a wavelength of about 3.26 cm and therefore belonging to the microwave range. | https://en.wikipedia.org/wiki?curid=40858 |
Cosmic noise and galactic radio noise is random noise that originates outside the Earth's atmosphere. It can be detected and heard in radio receivers. characteristics are similar to those of thermal noise. is experienced at frequencies above about 15 MHz when highly directional antennas are pointed toward the sun or to certain other regions of the sky such as the center of the Milky Way Galaxy. Celestial objects like quasars, super dense objects that lie far from Earth, emit electromagnetic waves in its full spectrum including radio waves. We can also hear the fall of a meteorite in a radio receiver; the falling object burns from friction with the Earth's atmosphere, ionizing surrounding gases and producing radio waves. Cosmic microwave background radiation (CMBR) from outer space, discovered by Arno Penzias and Robert Wilson, who later won the Nobel Prize for this discovery, is also a form of cosmic noise. CMBR is thought to be a relic of the Big Bang, and pervades the space almost homogeneously over the entire celestial sphere. The bandwidth of the CMBR is wide, though the peak is in the microwave range. | https://en.wikipedia.org/wiki?curid=40969 |
Field strength In physics, field strength means the "magnitude" of a vector-valued field (e.g., in volts per meter, V/m, for an electric field E). For example, an electromagnetic field results in both electric field strength and magnetic field strength. As an application, in radio frequency telecommunications, the signal strength excites a receiving antenna and thereby induces a voltage at a specific frequency and polarization in order to provide an input signal to a radio receiver. meters are used for such applications as cellular, broadcasting, wi-fi and a wide variety of other radio-related applications. | https://en.wikipedia.org/wiki?curid=41150 |
Harmonic A harmonic is any member of the harmonic series. The term is employed in various disciplines, including music, physics, acoustics, electronic power transmission, radio technology, and other fields. It is typically applied to repeating signals, such as sinusoidal waves. A harmonic of such a wave is a wave with a frequency that is a positive integer multiple of the frequency of the original wave, known as the fundamental frequency. The original wave is also called the 1st harmonic, the following harmonics are known as higher harmonics. As all harmonics are periodic at the fundamental frequency, the sum of harmonics is also periodic at that frequency. For example, if the fundamental frequency is 50 Hz, a common AC power supply frequency, the frequencies of the first three higher harmonics are 100 Hz (2nd harmonic), 150 Hz (3rd harmonic), 200 Hz (4th harmonic) and any addition of waves with these frequencies is periodic at 50 Hz. In music, harmonics are used on string instruments and wind instruments as a way of producing sound on the instrument, particularly to play higher notes and, with strings, obtain notes that have a unique sound quality or "tone colour". On strings, harmonics that are bowed have a "glassy", pure tone. On stringed instruments, harmonics are played by touching (but not fully pressing down the string) at an exact point on the string while sounding the string (plucking, bowing, etc.); this allows the harmonic to sound, a pitch which is always higher than the fundamental frequency of the string | https://en.wikipedia.org/wiki?curid=41232 |
Harmonic Harmonics may also be called "overtones", "partials" or "upper partials". The difference between "harmonic" and "overtone" is that the term "harmonic" includes all of the notes in a series, including the fundamental frequency (e.g., the open string of a guitar). The term "overtone" only includes the pitches above the fundamental. In some music contexts, the terms "harmonic", "overtone" and "partial" are used fairly interchangeably. Most acoustic instruments emit complex tones containing many individual partials (component simple tones or sinusoidal waves), but the untrained human ear typically does not perceive those partials as separate phenomena. Rather, a musical note is perceived as one sound, the quality or timbre of that sound being a result of the relative strengths of the individual partials. Many acoustic oscillators, such as the human voice or a bowed violin string, produce complex tones that are more or less periodic, and thus are composed of partials that are near matches to integer multiples of the fundamental frequency and therefore resemble the ideal harmonics and are called "harmonic partials" or simply "harmonics" for convenience (although it's not strictly accurate to call a partial a harmonic, the first being real and the second being ideal). Oscillators that produce harmonic partials behave somewhat like one-dimensional resonators, and are often long and thin, such as a guitar string or a column of air open at both ends (as with the modern orchestral transverse flute) | https://en.wikipedia.org/wiki?curid=41232 |
Harmonic Wind instruments whose air column is open at only one end, such as trumpets and clarinets, also produce partials resembling harmonics. However they only produce partials matching the odd harmonics, at least in theory. The reality of acoustic instruments is such that none of them behaves as perfectly as the somewhat simplified theoretical models would predict. Partials whose frequencies are not integer multiples of the fundamental are referred to as "inharmonic partials". Some acoustic instruments emit a mix of harmonic and inharmonic partials but still produce an effect on the ear of having a definite fundamental pitch, such as pianos, strings plucked pizzicato, vibraphones, marimbas, and certain pure-sounding bells or chimes. Antique singing bowls are known for producing multiple harmonic partials or multiphonics. An overtone is any partial higher than the lowest partial in a compound tone. The relative strengths and frequency relationships of the component partials determine the timbre of an instrument. The similarity between the terms overtone and partial sometimes leads to their being loosely used interchangeably in a musical context, but they are counted differently, leading to some possible confusion | https://en.wikipedia.org/wiki?curid=41232 |
Harmonic In the special case of instrumental timbres whose component partials closely match a harmonic series (such as with most strings and winds) rather than being inharmonic partials (such as with most pitched percussion instruments), it is also convenient to call the component partials "harmonics" but not strictly correct (because harmonics are numbered the same even when missing, while partials and overtones are only counted when present). This chart demonstrates how the three types of names (partial, overtone, and harmonic) are counted (assuming that the harmonics are present): In many musical instruments, it is possible to play the upper harmonics without the fundamental note being present. In a simple case (e.g., recorder) this has the effect of making the note go up in pitch by an octave, but in more complex cases many other pitch variations are obtained. In some cases it also changes the timbre of the note. This is part of the normal method of obtaining higher notes in wind instruments, where it is called "overblowing". The extended technique of playing multiphonics also produces harmonics. On string instruments it is possible to produce very pure sounding notes, called harmonics or "flageolets" by string players, which have an eerie quality, as well as being high in pitch. Harmonics may be used to check at a unison the tuning of strings that are not tuned to the unison | https://en.wikipedia.org/wiki?curid=41232 |
Harmonic For example, lightly fingering the node found halfway down the highest string of a cello produces the same pitch as lightly fingering the node of the way down the second highest string. For the human voice see Overtone singing, which uses harmonics. While it is true that electronically produced periodic tones (e.g. square waves or other non-sinusoidal waves) have "harmonics" that are whole number multiples of the fundamental frequency, practical instruments do not all have this characteristic. For example, higher "harmonics"' of piano notes are not true harmonics but are "overtones" and can be very sharp, i.e. a higher frequency than given by a pure harmonic series. This is especially true of instruments other than stringed or brass/woodwind ones, e.g., xylophone, drums, bells etc., where not all the overtones have a simple whole number ratio with the fundamental frequency. The fundamental frequency is the reciprocal of the period of the periodic phenomenon. The following table displays the stop points on a stringed instrument, such as the guitar (guitar harmonics), at which gentle touching of a string will force it into a harmonic mode when vibrated. String harmonics (flageolet tones) are described as having a "flutelike, silvery quality" that can be highly effective as a special color or tone color (timbre) when used and heard in orchestration. It is unusual to encounter natural harmonics higher than the fifth partial on any stringed instrument except the double bass, on account of its much longer strings | https://en.wikipedia.org/wiki?curid=41232 |
Harmonic Harmonics are widely used in plucked string instruments, such as acoustic guitar, electric guitar and electric bass. On an electric guitar played loudly through a guitar amplifier with distortion, harmonics are more sustained and can be used in guitar solos. In the heavy metal music lead guitar style known as shred guitar, harmonics, both natural and artificial, are widely used. Although harmonics are most often used on open strings (natural harmonics), occasionally a score will call for an artificial harmonic, produced by playing an overtone on an already stopped string. As a performance technique, it is accomplished by using two fingers on the fingerboard, the first to shorten the string to the desired fundamental, with the second touching the node corresponding to the appropriate harmonic. On fretted instruments, such as an electric guitar, the performer can look at the frets to determine where to stop the string and where to touch the node. On unfretted instruments, such as the violin and related instruments, playing artificial harmonics is an advanced technique, as it requires the performer to find two precise locations on the same string. Harmonics may be either used or considered as the basis of just intonation systems. Composer Arnold Dreyblatt is able to bring out different harmonics on the single string of his modified double bass by slightly altering his unique bowing technique halfway between hitting and bowing the strings. Composer Lawrence Ball uses harmonics to generate music electronically. | https://en.wikipedia.org/wiki?curid=41232 |
Phase distortion In signal processing, phase distortion or phase-frequency distortion is distortion, that is, change in the shape of the waveform, that occurs when (a) a filter's phase response is not linear over the frequency range of interest, that is, the phase shift introduced by a circuit or device is not directly proportional to frequency, or (b) the zero-frequency intercept of the phase-frequency characteristic is not 0 or an integral multiple of 2π radians. Grossly changed phase relationships, without changing amplitudes, can be audible but the degree of audibility of the type of phase shifts expected from typical sound systems remains debated. | https://en.wikipedia.org/wiki?curid=41510 |
Tropospheric wave In telecommunication, a tropospheric wave is a radio wave that is propagated by reflection from a place of abrupt change in the dielectric constant, or its gradient, in the troposphere. In some cases, a ground wave may be so altered that new components appear to arise from reflection in regions of rapidly changing dielectric constant. When these components are distinguishable from the other components, they are called ""tropospheric waves."" | https://en.wikipedia.org/wiki?curid=41823 |
Antonie van Leeuwenhoek Antonie Philips van Leeuwenhoek ( ; ; 24 October 1632 – 26 August 1723) was a Dutch businessman and scientist in the Golden Age of Dutch science and technology. A largely self-taught man in science, he is commonly known as "the Father of Microbiology", and one of the first microscopists and microbiologists. Van Leeuwenhoek is best known for his pioneering work in microscopy and for his contributions toward the establishment of microbiology as a scientific discipline. Raised in Delft, Dutch Republic, van Leeuwenhoek worked as a draper in his youth and founded his own shop in 1654. He became well recognized in municipal politics and developed an interest in lensmaking. In the 1670s, he started to explore microbial life with his microscope. This was one of the notable achievements of the Golden Age of Dutch exploration and discovery (c. 1590s–1720s). Using single-lensed microscopes of his own design, van Leeuwenhoek was the first to experiment with microbes, which he originally referred to as "dierkens", "diertgens" or "diertjes" (Dutch for "small animals" [translated into English as "animalcules", from Latin "animalculum" = "tiny animal"]). Through his experiments, he was the first to relatively determine their size. Most of the "animalcules" are now referred to as unicellular organisms, although he observed multicellular organisms in pond water | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek He was also the first to document microscopic observations of muscle fibers, bacteria, spermatozoa, red blood cells, crystals in gouty tophi, and blood flow in capillaries. Although van Leeuwenhoek did not write any books, his discoveries came to light through correspondence with the Royal Society, which published his letters. was born in Delft, Dutch Republic, on 24 October 1632. On 4 November, he was baptized as "Thonis". His father, Philips Antonisz van Leeuwenhoek, was a basket maker who died when Antonie was only five years old. His mother, Margaretha (Bel van den Berch), came from a well-to-do brewer's family. She remarried Jacob Jansz Molijn, a painter. Antonie had four older sisters: Margriet, Geertruyt, Neeltje, and Catharina. When he was around ten years old his step-father died. He attended school in Warmond for a short time before being sent to live in Benthuizen with his uncle, an attorney. At the age of 16 he became a bookkeeper's apprentice at a linen-draper's shop in Amsterdam, which was owned by the Scot William Davidson. Van Leeuwenhoek left there after six years. Van Leeuwenhoek married Barbara de Mey in July 1654, with whom he fathered one surviving daughter, Maria (four other children died in infancy). That same year he returned to Delft, where he would live and study for the rest of his life. He opened a draper's shop, which he ran throughout the 1650s. His wife died in 1666, and in 1671, van Leeuwenhoek remarried to Cornelia Swalmius with whom he had no children | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek His status in Delft had grown throughout the years. In 1660 he received a lucrative job as chamberlain for the assembly chamber of the Delft sheriffs in the city hall, a position which he would hold for almost 40 years. In 1669 he was appointed as a land surveyor by the court of Holland; at some time he combined it with another municipal job, being the official "wine-gauger" of Delft and in charge of the city wine imports and taxation. Van Leeuwenhoek was a contemporary of another famous Delft citizen, the painter Johannes Vermeer, who was baptized just four days earlier. It has been suggested that he is the man portrayed in two Vermeer paintings of the late 1660s, "The Astronomer" and "The Geographer", but others argue that there appears to be little physical similarity. Because they were both relatively important men in a city with only 24,000 inhabitants, it is likely that they were at least acquaintances; van Leeuwenhoek acted as the executor of Vermeer's will after the painter died in 1675. While running his draper shop, van Leeuwenhoek wanted to see the quality of the thread better than what was possible using the magnifying lenses of the time. He developed an interest in lensmaking, although few records exist of his early activity | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek Van Leeuwenhoek's interest in microscopes and a familiarity with glass processing led to one of the most significant, and simultaneously well-hidden, technical insights in the history of science: By placing the middle of a small rod of soda lime glass in a hot flame, van Leeuwenhoek could pull the hot section apart to create two long whiskers of glass. Then, by reinserting the end of one whisker into the flame, he could create a very small, high-quality glass sphere. These spheres became the lenses of his microscopes, with the smallest spheres providing the highest magnifications. After developing his method for creating powerful lenses and applying them to the study of the microscopic world, van Leeuwenhoek introduced his work to his friend, the prominent Dutch physician Reinier de Graaf. When the Royal Society in London published the groundbreaking work of an Italian lensmaker in their journal "Philosophical Transactions of the Royal Society", de Graaf wrote to the editor of the journal, Henry Oldenburg, with a ringing endorsement of van Leeuwenhoek's microscopes which, he claimed, "far surpass those which we have hitherto seen". In response, in 1673 the society published a letter from van Leeuwenhoek that included his microscopic observations on mold, bees, and lice. Van Leeuwenhoek's work fully captured the attention of the Royal Society, and he began corresponding regularly with the society regarding his observations | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek At first he had been reluctant to publicize his findings, regarding himself as a businessman with little scientific, artistic, or writing background, but de Graaf urged him to be more confident in his work. By the time van Leeuwenhoek died in 1723, he had written some 190 letters to the Royal Society, detailing his findings in a wide variety of fields, centered on his work in microscopy. He only wrote letters in his own colloquial Dutch; he never published a proper scientific paper in Latin. He strongly preferred to work alone, distrusting the sincerity of those who offered their assistance. The letters were translated into Latin or English by Henry Oldenburg, who had learned Dutch for this very purpose. He was also the first to use the word "animalcules" to translate the Dutch words that Leeuwenhoek used to describe microorganisms. Despite the initial success of van Leeuwenhoek's relationship with the Royal Society, soon relations became severely strained. His credibility was questioned when he sent the Royal Society a copy of his first observations of microscopic single-celled organisms dated 9 October 1676. Previously, the existence of single-celled organisms was entirely unknown. Thus, even with his established reputation with the Royal Society as a reliable observer, his observations of microscopic life were initially met with some skepticism | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek Eventually, in the face of van Leeuwenhoek's insistence, the Royal Society arranged for Alexander Petrie, minister to the English Reformed Church in Delft; Benedict Haan, at that time Lutheran minister at Delft; and Henrik Cordes, then Lutheran minister at the Hague, accompanied by Sir Robert Gordon and four others, to determine whether it was in fact van Leeuwenhoek's ability to observe and reason clearly, or perhaps, the Royal Society's theories of life that might require reform. Finally in 1677, van Leeuwenhoek's observations were fully acknowledged by the Royal Society. was elected to the Royal Society in February 1680 on the nomination of William Croone, a then-prominent physician. Van Leeuwenhoek was "taken aback" by the nomination, which he considered a high honor, although he did not attend the induction ceremony in London, nor did he ever attend a Royal Society meeting. By the end of the seventeenth century, van Leeuwenhoek had a virtual monopoly on microscopic study and discovery. His contemporary Robert Hooke, an early microscope pioneer, bemoaned that the field had come to rest entirely on one man's shoulders. He was visited over the years by many notable individuals, such as the Russian Tsar Peter the Great. To the disappointment of his guests, van Leeuwenhoek refused to reveal the cutting-edge microscopes he relied on for his discoveries, instead showing visitors a collection of average-quality lenses | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek An experienced businessman, van Leeuwenhoek believed that if his simple method for creating the critically important lens was revealed, the scientific community of his time would likely disregard or even forget his role in microscopy. He therefore allowed others to believe that he was laboriously spending most of his nights and free time grinding increasingly tiny lenses to use in microscopes, even though this belief conflicted both with his construction of hundreds of microscopes and his habit of building a new microscope whenever he chanced upon an interesting specimen that he wanted to preserve. He made about 200 microscopes of various magnifications. Van Leeuwenhoek was visited by Leibniz, William III of Orange and his wife, Mary II of England, and the burgemeester (mayor) Johan Huydecoper of Amsterdam, the latter being very interested in collecting and growing plants for the Hortus Botanicus Amsterdam, and all gazed at the "tiny creatures". In 1698, van Leeuwenhoek was invited to visit the Tsar Peter the Great on his boat. On this occasion van Leeuwenhoek presented the Tsar with an "eel-viewer", so Peter could study blood circulation whenever he wanted. made more than 500 optical lenses. He also created at least 25 single-lens microscopes, of differing types, of which only nine have survived. These microscopes were made of silver or copper frames, holding hand-made lenses. Those that have survived are capable of magnification up to 275 times | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek It is suspected that van Leeuwenhoek possessed some microscopes that could magnify up to 500 times. Although he has been widely regarded as a dilettante or amateur, his scientific research was of remarkably high quality. The single-lens microscopes of van Leeuwenhoek were relatively small devices, the largest being about 5 cm long. They are used by placing the lens very close in front of the eye, while looking in the direction of the sun. The other side of the microscope had a pin, where the sample was attached in order to stay close to the lens. There were also three screws to move the pin and the sample along three axes: one axis to change the focus, and the two other axes to navigate through the sample. Van Leeuwenhoek maintained throughout his life that there are aspects of microscope construction ""which I only keep for myself"", in particular his most critical secret of how he made the lenses. For many years no one was able to reconstruct van Leeuwenhoek's design techniques, but in 1957, C. L. Stong used thin glass thread fusing instead of polishing, and successfully created some working samples of a van Leeuwenhoek design microscope. Such a method was also discovered independently by A. Mosolov and A. Belkin at the Russian Novosibirsk State Medical Institute. Van Leeuwenhoek used samples and measurements to estimate numbers of microorganisms in units of water. He also made good use of the huge advantage provided by his method | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek He studied a broad range of microscopic phenomena, and shared the resulting observations freely with groups such as the British Royal Society. Such work firmly established his place in history as one of the first and most important explorers of the microscopic world. Van Leeuwenhoek was one of the first people to observe cells, much like Robert Hooke. Van Leeuwenhoek's main discoveries are: In 1687, van Leeuwenhoek reported his research on the coffee bean. He roasted the bean, cut it into slices and saw a spongy interior. The bean was pressed, and an oil appeared. He boiled the coffee with rain water twice and set it aside. Van Leeuwenhoek has been attributed as the first person to use a histological stain to color specimens observed under the microscope using saffron Like Robert Boyle and Nicolaas Hartsoeker, van Leeuwenhoek was interested in dried cochineal, trying to find out if the dye came from a berry or an insect. Van Leeuwenhoek's religion was "Dutch Reformed" Calvinist. He often referred with reverence to the wonders God designed in making creatures great and small, and believed that his discoveries were merely further proof of the wonder of creation. By the end of his life, van Leeuwenhoek had written approximately 560 letters to the Royal Society and other scientific institutions concerning his observations and discoveries. Even during the last weeks of his life, van Leeuwenhoek continued to send letters full of observations to London. The last few contained a precise description of his own illness | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek He suffered from a rare disease, an uncontrolled movement of the midriff, which now is named "van Leeuwenhoek's disease". He died at the age of 90, on 26 August 1723, and was buried four days later in the Oude Kerk in Delft. In 1981, the British microscopist Brian J. Ford found that van Leeuwenhoek's original specimens had survived in the collections of the Royal Society of London. They were found to be of high quality, and all were well preserved. Ford carried out observations with a range of single-lens microscopes, adding to our knowledge of van Leeuwenhoek's work. In Ford's opinion, Leeuwenhoek remained imperfectly understood, the popular view that his work was crude and undisciplined at odds with the evidence of conscientious and painstaking observation. He constructed rational and repeatable experimental procedures and was willing to oppose received opinion, such as spontaneous generation, and he changed his mind in the light of evidence." On his importance in the history of microbiology and science in general, the British biochemist Nick Lane wrote that he was "the first even to think of looking—certainly, the first with the power to see." His experiments were ingenious and he was "a scientist of the highest calibre", attacked by people who envied him or "scorned his unschooled origins", not helped by his secrecy about his methods. The Antoni van Leeuwenhoek Hospital in Amsterdam, named after van Leeuwenhoek, is specialized in oncology | https://en.wikipedia.org/wiki?curid=42001 |
Antonie van Leeuwenhoek In 2004, a public poll in the Netherlands to determine the greatest Dutchman ("De Grootste Nederlander") named van Leeuwenhoek the 4th-greatest Dutchman of all time. On 24 October 2016, Google commemorated the 384th anniversary of van Leeuwenhoek's birth with a Doodle that depicted his discovery of "little animals" or animalcules, now known as bacteria. The Leeuwenhoek Medal, Leeuwenhoek Lecture, Leeuwenhoek (crater), "Leeuwenhoeckia", "Levenhookia" (a genus in the family Stylidiaceae), and "Leeuwenhoekiella" (an aerobic bacterial genus) are named after him. | https://en.wikipedia.org/wiki?curid=42001 |
Trace radioisotope A trace radioisotope is a radioisotope that occurs naturally in trace amounts (i.e. extremely small). Generally speaking, trace radioisotopes have half-lives that are short in comparison with the age of the Earth, since primordial nuclides tend to occur in larger than trace amounts. Trace radioisotopes are therefore present only because they are continually produced on Earth by natural processes. Natural processes which produce trace radioisotopes include cosmic ray bombardment of stable nuclides, ordinary alpha and beta decay of the long-lived heavy nuclides, thorium-232, uranium-238, and uranium-235, spontaneous fission of uranium-238, and nuclear transmutation reactions induced by natural radioactivity, such as the production of plutonium-239 and uranium-236 from neutron capture by natural uranium. The elements that occur on Earth only in traces are listed below. Isotopes of other elements (not exhaustive): | https://en.wikipedia.org/wiki?curid=42021 |
Aristid Lindenmayer (17 November 1925 – 30 October 1989) was a Hungarian biologist. In 1968 he developed a type of formal languages that is today called L-systems or Lindenmayer Systems. Using those systems Lindenmayer modelled the behaviour of cells of plants. L-systems nowadays are also used to model whole plants. Lindenmayer worked with yeast and filamentous fungi and studied the growth patterns of various types of algae, such as the blue/green bacteria "Anabaena catenula". Originally the L-systems were devised to provide a formal description of the development of such simple multicellular organisms, and to illustrate the neighbourhood relationships between plant cells. Later on, this system was extended to describe higher plants and complex branching structures. Lindenmayer studied chemistry and biology at the University of Budapest from 1943 to 1948. He received his Ph.D. in plant physiology in 1956 at the University of Michigan. In 1968 he became professor in Philosophy of Life Sciences and Biology at the University of Utrecht, The Netherlands. From 1972 onward he headed the Theoretical Biology Group at Utrecht University. | https://en.wikipedia.org/wiki?curid=42231 |
Ionic crystal An ionic crystal is a crystal consisting of ions bound together by their electrostatic attraction. Examples of such crystals are the alkali halides, including potassium fluoride, potassium chloride, potassium bromide, potassium iodide, sodium fluoride, and other combinations of sodium, caesium, rubidium, or lithium ions with fluoride, bromide, chloride or iodide ions. NaCl has a 6:6 co-ordination. The properties of NaCl reflect the strong interactions that exist between the ions. It is a good conductor of electricity when molten, but very poor in the solid state. When fused the mobile ions carry charge through the liquid. They are characterized by strong absorption of infrared radiation and have planes along which they cleave easily. The exact arrangement of ions in an ionic lattice varies according to the size of the ions in the solid. | https://en.wikipedia.org/wiki?curid=42566 |
Biostasis or Cryptobiosis is the ability of an organism to tolerate environmental changes without having to actively adapt to them. is found in organisms that live in habitats that likely encounter unfavorable living conditions, such as drought, freezing temperatures, change in pH levels, pressure, or temperature. Insects undergo a type of dormancy to survive these conditions, called diapause. Diapause may be obligatory for these insects to survive. The insect may also be able to undergo change prior to the arrival of the initiating event. in this context is also synonymous for viable but nonculturable state. In the past when bacteria were no longer growing on culture media it was assumed that they were dead. Now we can understand that there are many instances where bacteria cells may go into biostasis or suspended animation, fail to grow on media, and on resuscitation are again culturable. VBNC state differs from 'starvation survival state' (where a cell just reduces metabolism significantly). Bacteria cells may enter the VBNC state as a result of some outside stressor such as "starvation, incubation outside the temperature range of growth, elevated osmotic concentrations (seawater), oxygen concentrations, or exposure to white light" (9). Any of these instances could very easily mean death for the bacteria if it was not able to enter this state of dormancy | https://en.wikipedia.org/wiki?curid=42940 |
Biostasis It has also been observed that in may instances where it was thought that bacteria had been destroyed (pasteurization of milk) and later caused spoilage or harmful effects to consumers because the bacteria had entered the VBNC state. Effects on cells entering the VBNC state include "dwarfing, changes in metabolic activity, reduced nutrient transport, respiration rates and macromolecular synthesis". (9) Yet biosynthesis continues, and shock proteins are made. Most importantly has been observed that ATP levels and generation remain high, completely contrary to dying cells which show rapid decreases in generation and retention. Changes to the cell walls of bacteria in the VBNC state have also been observed. In E.coli a large amount of cross-linking was observed in the peptidoglycan. The autolytic capability was also observed to be much higher in VBNC cells than those who were in the growth state. It is far easier to induce bacteria to the VBNC state and once bacteria cells have entered the VBNC state it is very hard to return them to a culturable state. "They examined nonculturability and resuscitation in Legionella Pneumophila and while entry into this state was easily induced by nutrient starvation, resuscitation could only be demonstrated following co-incubation of the VBNC cells with the amoeba, Acanthamoeba Castellani" (9) Fungistasis or mycostasis a naturally occurring VBNC (viable but nonculturable) state found in fungi in soil | https://en.wikipedia.org/wiki?curid=42940 |
Biostasis Watson and Ford defined fungistasis as "when viable fungal propagules, which are not subject to endogenous or constitutive dormancy do not germinate in soil at their favorable temperature or moisture conditions or growth of fungal hyphae is retarded or terminated by conditions of the soil environment other than temperature or moisture." (10). Essentially (and mostly observed naturally occurring in soil) several types of fungi have been found to enter the VBNC state resulting from outside stressors (temperature, available nutrients, oxygen availability etc.) or from no observable stressors at all. On March 1, 2018, the Defense Advanced Research Projects Agency (DARPA) announced their new program under the direction of Dr. Tristan McClure-Begley. The aim of the program is to develop new possibilities for extending the golden hour in patients who suffered a traumatic injury by slowing down the human body at the cellular level, addressing the need for additional time in continuously operating biological systems faced with catastrophic, life-threatening events. By leveraging molecular biology, the program aims to control the speed at which living systems operate and figure out a way to "slow life to save life." On March 20, 2018, the team held a Webinar which, along with a Broad Agency Announcement (BAA), solicited five-year research proposals from outside organizations. The full proposals were due on May 22, 2018. In their Webinar, DARPA outlined a number of possible research approaches for the project | https://en.wikipedia.org/wiki?curid=42940 |
Biostasis These approaches are based on research into diapause in tardigrades and wood frogs which suggests that selective stabilization of intracellular machinery occurs at the protein level. In molecular biology, molecular chaperones are proteins that assist in the folding, unfolding, assembly, or disassembly of other macromolecular structures. Under typical conditions, molecular chaperones facilitate changes in shape (conformational change) of macromolecules in response to changes in environmental factors like temperature, pH, and voltage. By reducing conformational flexibility, scientists can constrain the function of certain proteins. Recent research has shown that proteins are promiscuous, or able to do jobs in addition to the ones they evolved to carry out. Additionally, protein promiscuity plays a key role in the adaptation of species to new environments. It is possible that finding a way to control conformational change in promiscuous proteins could allow scientists to induce biostasis in living organisms. The crowdedness of cells is a critical aspect of biological systems. Intracellular crowding refers to the fact that protein function and interaction with water is constrained when the interior of the cell is overcrowded. Intracellular organelles are either membrane-bound vesicles or membrane-less compartments that compartmentalize the cell and enable spatiotemporal control of biological reactions | https://en.wikipedia.org/wiki?curid=42940 |
Biostasis By introducing these intracellular polymers to a biological system and manipulating the crowdedness of a cell, scientists may be able to slow down the rate of biological reactions in the system. Tardigrades are microscopic animals that are able to enter a state of diapause and survive a remarkable array of environmental stressors, including freezing and desiccation. Research has shown that intrinsically disordered proteins in these organisms may work to stabilize cell function and protect against these extreme environmental stressors. By using peptide engineering, it is possible that scientists may be able to introduce intrinsically disordered proteins to the biological systems of larger animal organisms. This could allow larger animals to enter a state of biostasis similar to that of tardigrades under extreme biological stress. | https://en.wikipedia.org/wiki?curid=42940 |
Nature (journal) Nature is a British multidisciplinary scientific journal, first published on 4 November 1869. It is one of the most recognizable scientific journals in the world, and was ranked the world's most cited scientific journal by the Science Edition of the 2018 "Journal Citation Reports" and is ascribed an impact factor of 43.070, making it one of the world's top academic journals. Research scientists are the primary audience for the journal, but summaries and accompanying articles are intended to make many of the most important papers understandable to scientists in other fields and the educated public. Towards the front of each issue are editorials, news and feature articles on issues of general interest to scientists, including current affairs, science funding, business, scientific ethics and research breakthroughs. There are also sections on books, arts, and short science fiction stories. The remainder of the journal consists mostly of research papers (articles or letters), which are often dense and highly technical. Because of strict limits on the length of papers, often the printed text is actually a summary of the work in question with many details relegated to accompanying "supplementary material" on the journal's website. There are many fields of research in which important new advances and original research are published as either articles or letters in "Nature." The papers that have been published in this journal are internationally acclaimed for maintaining high research standards | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) Fewer than 8% of submitted papers are accepted for publication. In 2007 "Nature" (together with "Science") received the Prince of Asturias Award for Communications and Humanity. The enormous progress in science and mathematics during the 19th century was recorded in journals written mostly in German or French, as well as in English. Britain underwent enormous technological and industrial changes and advances particularly in the latter half of the 19th century. In English the most respected scientific journals of this time were the refereed journals of the Royal Society, which had published many of the great works from Isaac Newton, Michael Faraday through to early works from Charles Darwin. In addition, during this period, the number of popular science periodicals doubled from the 1850s to the 1860s. According to the editors of these popular science magazines, the publications were designed to serve as "organs of science", in essence, a means of connecting the public to the scientific world. "Nature", first created in 1869, was not the first magazine of its kind in Britain. One journal to precede "Nature" was "Recreative Science: A Record and Remembrancer of Intellectual Observation", which, created in 1859, began as a natural history magazine and progressed to include more physical observational science and technical subjects and less natural history | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) The journal's name changed from its original title to "Intellectual Observer: A Review of Natural History, Microscopic Research, and Recreative Science" and then later to the "Student and Intellectual Observer of Science, Literature, and Art". While "Recreative Science" had attempted to include more physical sciences such as astronomy and archaeology, the "Intellectual Observer" broadened itself further to include literature and art as well. Similar to "Recreative Science" was the scientific journal "Popular Science Review", created in 1862, which covered different fields of science by creating subsections titled "Scientific Summary" or "Quarterly Retrospect", with book reviews and commentary on the latest scientific works and publications. Two other journals produced in England prior to the development of "Nature" were the "Quarterly Journal of Science" and "Scientific Opinion", established in 1864 and 1868, respectively. The journal most closely related to "Nature" in its editorship and format was "The Reader", created in 1863; the publication mixed science with literature and art in an attempt to reach an audience outside of the scientific community, similar to "Popular Science Review". These similar journals all ultimately failed. The "Popular Science Review" survived longest, lasting 20 years and ending its publication in 1881; "Recreative Science" ceased publication as the "Student and Intellectual Observer" in 1871 | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) The "Quarterly Journal", after undergoing a number of editorial changes, ceased publication in 1885. "The Reader" terminated in 1867, and finally, "Scientific Opinion" lasted a mere 2 years, until June 1870. Not long after the conclusion of "The Reader", a former editor, Norman Lockyer, decided to create a new scientific journal titled "Nature", taking its name from a line by William Wordsworth: "To the solid ground of nature trusts the Mind that builds for aye". First owned and published by Alexander Macmillan, "Nature" was similar to its predecessors in its attempt to "provide cultivated readers with an accessible forum for reading about advances in scientific knowledge." Janet Browne has proposed that "far more than any other science journal of the period, "Nature" was conceived, born, and raised to serve polemic purpose." Many of the early editions of "Nature" consisted of articles written by members of a group that called itself the X Club, a group of scientists known for having liberal, progressive, and somewhat controversial scientific beliefs relative to the time period. Initiated by Thomas Henry Huxley, the group consisted of such important scientists as Joseph Dalton Hooker, Herbert Spencer, and John Tyndall, along with another five scientists and mathematicians; these scientists were all avid supporters of Darwin's theory of evolution as common descent, a theory which, during the latter half of the 19th century, received a great deal of criticism among more conservative groups of scientists | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) Perhaps it was in part its scientific liberality that made "Nature" a longer-lasting success than its predecessors. John Maddox, editor of "Nature" from 1966 to 1973 as well as from 1980 to 1995, suggested at a celebratory dinner for the journal's centennial edition that perhaps it was the journalistic qualities of Nature that drew readers in; "journalism" Maddox states, "is a way of creating a sense of community among people who would otherwise be isolated from each other. This is what Lockyer's journal did from the start." In addition, Maddox mentions that the financial backing of the journal in its first years by the Macmillan family also allowed the journal to flourish and develop more freely than scientific journals before it. Norman Lockyer, the founder of "Nature", was a professor at Imperial College. He was succeeded as editor in 1919 by Sir Richard Gregory. Gregory helped to establish "Nature" in the international scientific community. His obituary by the Royal Society stated: "Gregory was always very interested in the international contacts of science, and in the columns of "Nature" he always gave generous space to accounts of the activities of the International Scientific Unions." During the years 1945 to 1973, editorship of "Nature" changed three times, first in 1945 to A. J. V. Gale and L. J. F. Brimble (who in 1958 became the sole editor), then to John Maddox in 1965, and finally to David Davies in 1973. In 1980, Maddox returned as editor and retained his position until 1995 | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) Philip Campbell became Editor-in-chief of all "Nature" publications until 2018. Magdalena Skipper has since become Editor-in-chief. In 1970, "Nature" first opened its Washington office; other branches opened in New York in 1985, Tokyo and Munich in 1987, Paris in 1989, San Francisco in 2001, Boston in 2004, and Hong Kong in 2005. In 1971, under John Maddox's editorship, the journal split into "Nature Physical Sciences" (published on Mondays), "Nature New Biology" (published on Wednesdays) and "Nature" (published on Fridays). In 1974, Maddox was no longer editor, and the journals were merged into "Nature". Starting in the 1980s, the journal underwent a great deal of expansion, launching over ten new journals. These new journals comprise Nature Research, which was created in 1999 under the name Nature Publishing Group and includes "Nature", Nature Research Journals, Stockton Press Specialist Journals and Macmillan Reference (renamed NPG Reference). In 1996, "Nature" created its own website and in 1999 Nature Publishing Group began its series of "Nature Reviews". Some articles and papers are available for free on the Nature website. Others require the purchase of premium access to the site. "Nature" claims an online readership of about 3 million unique readers per month. On 30 October 2008, "Nature" endorsed an American presidential candidate for the first time when it supported Barack Obama during his campaign in America's 2008 presidential election | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) In October 2012, an Arabic edition of the magazine was launched in partnership with King Abdulaziz City for Science and Technology. As of the time it was released, it had about 10,000 subscribers. On 2 December 2014, "Nature" announced that it would allow its subscribers and a group of selected media outlets to share links allowing free, "read-only" access to content from its journals. These articles are presented using the digital rights management system ReadCube (which is funded by the Macmillan subsidiary Digital Science), and does not allow readers to download, copy, print, or otherwise distribute the content. While it does, to an extent, provide free online access to articles, it is not a true open access scheme due to its restrictions on re-use and distribution. On 15 January 2015, details of a proposed merger with Springer Science+Business Media were announced. In May 2015 it came under the umbrella of Springer Nature, by the merger of Springer Science+Business Media and Holtzbrinck Publishing Group's Nature Publishing Group, Palgrave Macmillan, and Macmillan Education. Since 2011, the journal has published Nature's 10 "people who mattered" during the year, as part of their annual review. Being published in "Nature" is very prestigious. In particular, empirical papers are often highly cited, which can lead to promotions, grant funding, and attention from the mainstream media | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) Because of these positive feedback effects, competition among scientists to publish in high-level journals like "Nature" and its closest competitor, "Science", can be very fierce. "Nature"s impact factor, a measure of how many citations a journal generates in other works, was 38.138 in 2015 (as measured by Thomson ISI), among the highest of any science journal. As with most other professional scientific journals, papers undergo an initial screening by the editor, followed by peer review (in which other scientists, chosen by the editor for expertise with the subject matter but who have no connection to the research under review, will read and critique articles), before publication. In the case of "Nature", they are only sent for review if it is decided that they deal with a topical subject and are sufficiently ground-breaking in that particular field. As a consequence, the majority of submitted papers are rejected without review. According to "Nature"s original mission statement: This was revised in 2000 to: Many of the most significant scientific breakthroughs in modern history have been first published in "Nature". The following is a selection of scientific breakthroughs published in "Nature", all of which had far-reaching consequences, and the citation for the article in which they were published. In 2017, Nature published an editorial entitled "Removing Statues of Historical figures risks whitewashing history: Science must acknowledge mistakes as it marks its past" | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) The article commented on the placement and maintenance of statues honouring scientists with known unethical, abusive and torturous histories. Specifically, the editorial called on examples of J. Marion Sims, the 'Father of gynecology' who experimented on African American female slaves who were unable to give informed consent, and Thomas Parran Jr. who oversaw the Tuskegee syphilis experiment. The editorial as written made the case that removing such statues, and erasing names, runs the risk of "whitewashing history", and stated "Instead of removing painful reminders, perhaps these should be supplemented". The article caused a large outcry and was quickly modified by Nature. The article was largely seen as offensive, inappropriate, and by many, racist. Nature acknowledged that the article as originally written was "offensive and poorly worded" and published selected letters of response. The editorial came just weeks after hundreds of white supremacists marched in Charlottesville, Virginia in the Unite the Right rally to oppose the removal of a statue of Robert E. Lee, setting off violence in the streets and killing a young woman. When Nature posted a link to the editorial on Twitter, the thread quickly exploded with criticisms. In response, several scientists called for a boycott. On 18 September 2017, the editorial was updated and edited by Philip Campbell, the editor of the journal | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) When Paul Lauterbur and Peter Mansfield won a Nobel Prize in Physiology or Medicine for research initially rejected by "Nature" and published only after Lauterbur appealed against the rejection, "Nature" acknowledged more of its own missteps in rejecting papers in an editorial titled, "Coping with Peer Rejection": From 2000 to 2001, a series of five fraudulent papers by Jan Hendrik Schön was published in "Nature". The papers, about semiconductors, were revealed to contain falsified data and other scientific fraud. In 2003, "Nature" retracted the papers. The Schön scandal was not limited to "Nature"; other prominent journals, such as "Science" and "Physical Review", also retracted papers by Schön. In June 1988, after nearly a year of guided scrutiny from its editors, "Nature" published a controversial and seemingly anomalous paper detailing Jacques Benveniste and his team's work studying human basophil degranulation in the presence of extremely dilute antibody serum. The paper concluded that less than a single molecule of antibody could trigger an immune response in human basophils, defying the physical law of mass action. The paper excited substantial media attention in Paris, chiefly because their research sought funding from homeopathic medicine companies. Public inquiry prompted "Nature" to mandate an extensive and stringent experimental replication in Benveniste's lab, through which his team's results were refuted | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) Before publishing one of its most famous discoveries, Watson and Crick's 1953 on the structure of DNA, "Nature" did not send the paper out for peer review. John Maddox, "Nature"s editor, stated: "the Watson and Crick paper was not peer-reviewed by "Nature" ... the paper could not have been refereed: its correctness is self-evident. No referee working in the field ... could have kept his mouth shut once he saw the structure". An earlier error occurred when Enrico Fermi submitted his breakthrough paper on the weak interaction theory of beta decay. "Nature" rejected the paper because it was considered too remote from reality. Fermi's paper was published by "Zeitschrift für Physik" in 1934. The journal apologised for its initial coverage of the 2019–20 coronavirus pandemic in which it linked China and Wuhan with the outbreak, which may have led to racist attacks. In 1999 "Nature" began publishing science fiction short stories. The brief "vignettes" are printed in a series called "Futures". The stories appeared in 1999 and 2000, again in 2005 and 2006, and have appeared weekly since July 2007. Sister publication "Nature Physics" also printed stories in 2007 and 2008. In 2005, "Nature" was awarded the European Science Fiction Society's Best Publisher award for the "Futures" series. One hundred of the "Nature" stories between 1999 and 2006 were published as the collection "Futures from Nature" in 2008. Another collection, "Futures from Nature 2", was published in 2014 | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) The journal has a weekly circulation of around 53,000 and a pass-along rate of 8.0, resulting in a readership of over 400,000. "Nature" is edited and published in the United Kingdom by a division of the international scientific publishing company Springer Nature that publishes academic journals, magazines, online databases, and services in science and medicine. "Nature" has offices in London, New York City, San Francisco, Washington, D.C., Boston, Tokyo, Hong Kong, Paris, Munich, and Basingstoke. Nature Research also publishes other specialized journals including "Nature Neuroscience", "Nature Biotechnology," "Nature Methods", the "Nature Clinical Practice" series of journals, "Nature Structural & Molecular Biology", "Nature Chemistry", and the "Nature Reviews" series of journals. Since 2005, each issue of "Nature" has been accompanied by a "Nature Podcast" featuring highlights from the issue and interviews with the articles' authors and the journalists covering the research. It is presented by Kerri Smith, and features interviews with scientists on the latest research, as well as news reports from Nature's editors and journalists. The Nature Podcast was founded – and the first 100 episodes were produced and presented – by clinician and virologist Chris Smith of Cambridge and "The Naked Scientists" | https://en.wikipedia.org/wiki?curid=43427 |
Nature (journal) In 2007, Nature Publishing Group began publishing "Clinical Pharmacology & Therapeutics", the official journal of the American Society of Clinical Pharmacology & Therapeutics and "Molecular Therapy", the American Society of Gene Therapy's official journal, as well as the "International Society for Microbial Ecology (ISME) Journal". Nature Publishing Group launched "Nature Photonics" in 2007 and "Nature Geoscience" in 2008. "Nature Chemistry" published its first issue in April 2009. Nature Research actively supports the self-archiving process and in 2002 was one of the first publishers to allow authors to post their contributions on their personal websites, by requesting an exclusive licence to publish, rather than requiring authors to transfer copyright. In December 2007, Nature Publishing Group introduced the Creative Commons attribution-non-commercial-share alike unported licence for those articles in Nature journals that are publishing the primary sequence of an organism's genome for the first time. In 2008, a collection of articles from "Nature" was edited by John S. Partington under the title "H. G. Wells in Nature, 1893–1946: A Reception Reader" and published by Peter Lang. After a 2015 merger, Nature Publishing Group dissolved and was afterwards known as Nature Research. | https://en.wikipedia.org/wiki?curid=43427 |
Oceanography (compound of the Greek words ὠκεανός meaning "ocean" and γράφω meaning "write"), also known as oceanology, is the study of the physical and biological aspects of the ocean. It is an important Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries. These diverse topics reflect multiple disciplines that oceanographers blend to further knowledge of the world ocean and understanding of processes within: astronomy, biology, chemistry, climatology, geography, geology, hydrology, meteorology and physics. Paleoceanography studies the history of the oceans in the geologic past. An oceanographer is a person who studies many matters concerned with oceans including marine geology, physics, chemistry and biology . Humans first acquired knowledge of the waves and currents of the seas and oceans in pre-historic times. Observations on tides were recorded by Aristotle and Strabo. Early exploration of the oceans was primarily for cartography and mainly limited to its surfaces and of the animals that fishermen brought up in nets, though depth soundings by lead line were taken. Although Juan Ponce de León in 1513 first identified the Gulf Stream, and the current was well known to mariners, Benjamin Franklin made the first scientific study of it and gave it its name | https://en.wikipedia.org/wiki?curid=44044 |
Oceanography Franklin measured water temperatures during several Atlantic crossings and correctly explained the Gulf Stream's cause. Franklin and Timothy Folger printed the first map of the Gulf Stream in 1769–1770. Information on the currents of the Pacific Ocean was gathered by explorers of the late 18th century, including James Cook and Louis Antoine de Bougainville. James Rennell wrote the first scientific textbooks on oceanography, detailing the current flows of the Atlantic and Indian oceans. During a voyage around the Cape of Good Hope in 1777, he mapped ""the banks and currents at the Lagullas"". He was also the first to understand the nature of the intermittent current near the Isles of Scilly, (now known as Rennell's Current). Sir James Clark Ross took the first modern sounding in deep sea in 1840, and Charles Darwin published a paper on reefs and the formation of atolls as a result of the second voyage of HMS "Beagle" in 1831–1836. Robert FitzRoy published a four-volume report of "Beagle"s three voyages. In 1841–1842 Edward Forbes undertook dredging in the Aegean Sea that founded marine ecology. The first superintendent of the United States Naval Observatory (1842–1861), Matthew Fontaine Maury devoted his time to the study of marine meteorology, navigation, and charting prevailing winds and currents. His 1855 textbook "Physical Geography of the Sea" was one of the first comprehensive oceanography studies | https://en.wikipedia.org/wiki?curid=44044 |
Oceanography Many nations sent oceanographic observations to Maury at the Naval Observatory, where he and his colleagues evaluated the information and distributed the results worldwide. Despite all this, human knowledge of the oceans remained confined to the topmost few fathoms of the water and a small amount of the bottom, mainly in shallow areas. Almost nothing was known of the ocean depths. The British Royal Navy's efforts to chart all of the world's coastlines in the mid-19th century reinforced the vague idea that most of the ocean was very deep, although little more was known. As exploration ignited both popular and scientific interest in the polar regions and Africa, so too did the mysteries of the unexplored oceans. The seminal event in the founding of the modern science of oceanography was the 1872–1876 " Challenger" expedition. As the first true oceanographic cruise, this expedition laid the groundwork for an entire academic and research discipline. In response to a recommendation from the Royal Society, the British Government announced in 1871 an expedition to explore world's oceans and conduct appropriate scientific investigation. Charles Wyville Thompson and Sir John Murray launched the "Challenger" expedition. , leased from the Royal Navy, was modified for scientific work and equipped with separate laboratories for natural history and chemistry. Under the scientific supervision of Thomson, "Challenger" travelled nearly surveying and exploring | https://en.wikipedia.org/wiki?curid=44044 |
Oceanography On her journey circumnavigating the globe, 492 deep sea soundings, 133 bottom dredges, 151 open water trawls and 263 serial water temperature observations were taken. Around 4,700 new species of marine life were discovered. The result was the "Report Of The Scientific Results of the Exploring Voyage of H.M.S. Challenger during the years 1873–76". Murray, who supervised the publication, described the report as "the greatest advance in the knowledge of our planet since the celebrated discoveries of the fifteenth and sixteenth centuries". He went on to found the academic discipline of oceanography at the University of Edinburgh, which remained the centre for oceanographic research well into the 20th century. Murray was the first to study marine trenches and in particular the Mid-Atlantic Ridge, and map the sedimentary deposits in the oceans. He tried to map out the world's ocean currents based on salinity and temperature observations, and was the first to correctly understand the nature of coral reef development. In the late 19th century, other Western nations also sent out scientific expeditions (as did private individuals and institutions). The first purpose built oceanographic ship, "Albatros", was built in 1882. In 1893, Fridtjof Nansen allowed his ship, "Fram", to be frozen in the Arctic ice. This enabled him to obtain oceanographic, meteorological and astronomical data at a stationary spot over an extended period | https://en.wikipedia.org/wiki?curid=44044 |
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