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Bo Thidé
Bo Yngve Thidé (born 8 January 1948) is a Swedish physicist and professor emeritus at Uppsala University. He has studied radio waves and other electromagnetic radiation in space, particularly their interaction with matter and fields. Thidé was born in Gothenburg, Sweden. He received his B.Sc. in 1972, his M.Sc. in 1973, and defended his Ph.D. thesis on semiclassical quantum theory at Uppsala University in 1979. His Ph.D. was obtained under the supervision of professor Per Olof Fröman at the Department of Theoretical Physics, Uppsala University. He has worked at the Swedish Institute of Space Physics in Uppsala since 1980, where he has been a professor since 2000. In 1981, Bo Thidé discovered electromagnetic emissions stimulated by powerful radio waves in the ionosphere during experiments in August 1981 at the EISCAT facility in Tromsø, Norway. For the first time it was shown that the plasma turbulence excited by powerful radio waves in the ionosphere radiates secondary elec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gothenburg
Gothenburg (; abbreviated Gbg; sv, Göteborg ) is the second-largest city in Sweden, fifth-largest in the Nordic countries, and capital of the Västra Götaland County. It is situated by the Kattegat, on the west coast of Sweden, and has a population of approximately 590,000 in the city proper and about 1.1 million inhabitants in the metropolitan area. Gothenburg was founded as a heavily fortified, primarily Dutch, trading colony, by royal charter in 1621 by King Gustavus Adolphus. In addition to the generous privileges (e.g. tax relaxation) given to his Dutch allies from the ongoing Thirty Years' War, the king also attracted significant numbers of his German and Scottish allies to populate his only town on the western coast. At a key strategic location at the mouth of the Göta älv, where Scandinavia's largest drainage basin enters the sea, the Port of Gothenburg is now the largest port in the Nordic countries. Gothenburg is home to many students, as the city includes ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polarization (waves)
Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the wave. A simple example of a polarized transverse wave is vibrations traveling along a taut string ''(see image)''; for example, in a musical instrument like a guitar string. Depending on how the string is plucked, the vibrations can be in a vertical direction, horizontal direction, or at any angle perpendicular to the string. In contrast, in longitudinal waves, such as sound waves in a liquid or gas, the displacement of the particles in the oscillation is always in the direction of propagation, so these waves do not exhibit polarization. Transverse waves that exhibit polarization include electromagnetic waves such as light and radio waves, gravitational waves, and transverse sound waves (shear waves) in solids. An electromagnetic wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Angular Momentum Multiplexing
Orbital angular momentum (OAM) multiplexing is a physical layer method for multiplexing signals carried on electromagnetic waves using the orbital angular momentum of the electromagnetic waves to distinguish between the different orthogonal signals. Orbital angular momentum is one of two forms of angular momentum of light. OAM is distinct from, and should not be confused with, light spin angular momentum. The spin angular momentum of light offers only two orthogonal quantum states corresponding to the two states of circular polarization, and can be demonstrated to be equivalent to a combination of polarization multiplexing and phase shifting. OAM on the other hand relies on an extended beam of light, and the higher quantum degrees of freedom which come with the extension. OAM multiplexing can thus access a potentially unbounded set of states, and as such offer a much larger number of channels, subject only to the constraint of real-world optics. The constraint been clarified in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borlänge Tidning
''Borlänge Tidning'' (''BT'') is a daily newspaper based in Dalarna, Sweden. History and profile ''BT'' was founded by Axel Lidman in 1885. The paper is sold and delivered to readers in Borlänge, Hedemora and Säter. It is a local edition of ''Dalarnas Tidningar'', Sweden's second largest provincial newspaper. ''BT'' has never had a specific political affiliation, but since becoming a part of ''Dalarnas Tidningar'', it shares editorial pages with liberal ''Falu-Kuriren''. All papers are part of Dalarnas Tidningar AB which is a subsidiary of MittMedia AB. In 2005 ''BT'' had a circulation of 15,600 copies. See also *List of Swedish newspapers The number of newspapers in Sweden was 235 in 1919. It decreased to 125 papers in the mid-1960s. In 2009 the number of the newspapers in the country was 90. This is a list of Swedish-language newspapers with their respective cities of publicatio ... References External links * 1885 establishments in Sweden Dalarna County M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nature Physics
''Nature Physics'' is a monthly peer-reviewed scientific journal published by Nature Portfolio. It was first published in October 2005 (volume 1, issue 1). The chief editor is Andrea Taroni, who is a full-time professional editor employed by this journal. Scope ''Nature Physics'' publishes both pure and applied research from all areas of physics. Subject areas covered by the journal include quantum mechanics, condensed-matter physics, optics, thermodynamics, particle physics, and biophysics. Abstracting and indexing The journal is indexed in the following databases: *Chemical Abstracts Service – CASSI *Science Citation Index * Science Citation Index Expanded *Current Contents – Physical, Chemical & Earth Sciences According to the ''Journal Citation Reports'', the journal has a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Optical Vortex
An optical vortex (also known as a photonic quantum vortex, screw dislocation or phase singularity) is a zero of an optical field; a point of zero Intensity (physics), intensity. The term is also used to describe a beam of light that has such a zero in it. The study of these phenomena is known as singular optics. Explanation In an optical vortex, light is twisted like a corkscrew around its axis of travel. Because of the twisting, the light waves at the axis itself cancel each other out. When projected onto a flat surface, an optical vortex looks like a ring of light, with a dark hole in the center. The vortex is given a number, called the topological charge, according to how many twists the light does in one wavelength. The number is always an integer, and can be positive or negative, depending on the direction of the twist. The higher the number of the twist, the faster the light is spinning around the axis. This spinning carries Orbital angular momentum of light, orbital angula ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Orbital Angular Momentum Of Light
The orbital angular momentum of light (OAM) is the component of angular momentum of a light beam that is dependent on the field spatial distribution, and not on the polarization. It can be further split into an internal and an external OAM. The internal OAM is an origin-independent angular momentum of a light beam that can be associated with a helical or twisted wavefront. The external OAM is the origin-dependent angular momentum that can be obtained as cross product of the light beam position (center of the beam) and its total linear momentum. Introduction A beam of light carries a linear momentum \mathbf, and hence it can be also attributed an external angular momentum \mathbf_e=\mathbf\times\mathbf. This external angular momentum depends on the choice of the origin of the coordinate system. If one chooses the origin at the beam axis and the beam is cylindrically symmetric (at least in its momentum distribution), the external angular momentum will vanish. The external angul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
General Relativity
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the ' is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations. Newton's law of universal gravitation, which describes classical gravity, can be seen as a prediction of general relativity for the almost flat spacetime geometry around stationary mass distributions. Some predictions of general relativity, however, are beyond Newton's law of universal gravitat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aftonbladet
''Aftonbladet'' (, lit. "The evening paper") is a Swedish daily newspaper published in Stockholm, Sweden. It is one of the largest daily newspapers in the Nordic countries. History and profile The newspaper was founded by Lars Johan Hierta in December 1830 under the name of ''Aftonbladet i Stockholm'' during the modernization of Sweden. Often critical and oppositional, the paper was repeatedly banned from publishing. However, Hierta circumvented the bans by constantly reviving the paper under slightly modified names, as, legally speaking, a new publication. Thus, on 16 February 1835, he issued the first edition of New Aftonbladet, which would – after yet another ban – be followed by Newer Aftonbladet, in turn followed by Fourth Aftonbladet, Fifth Aftonbladet, and so on. In 1852 the paper began to use its current name, ''Aftonbladet'', after a total of 25 name changes. It currently describes itself as an "independent social-democratic newspaper." The owners of ''A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Big Bang
The Big Bang event is a physical theory that describes how the universe expanded from an initial state of high density and temperature. Various cosmological models of the Big Bang explain the evolution of the observable universe from the earliest known periods through its subsequent large-scale form. These models offer a comprehensive explanation for a broad range of observed phenomena, including the abundance of light elements, the cosmic microwave background (CMB) radiation, and large-scale structure. The overall uniformity of the Universe, known as the flatness problem, is explained through cosmic inflation: a sudden and very rapid expansion of space during the earliest moments. However, physics currently lacks a widely accepted theory of quantum gravity that can successfully model the earliest conditions of the Big Bang. Crucially, these models are compatible with the Hubble–Lemaître law—the observation that the farther away a galaxy is, the faster it is mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Low-Frequency Array (LOFAR)
The Low-Frequency Array, or LOFAR, is a large radio telescope, with an antenna network located mainly in the Netherlands, and spreading across 7 other European countries as of 2019. Originally designed and built by ASTRON, the Netherlands Institute for Radio Astronomy, it was first opened by queen Beatrix of The Netherlands in 2010, and has since been operated on behalf of the International LOFAR Telescope (ILT) partnership by ASTRON. LOFAR consists of a vast array of omnidirectional radio antennas using a modern concept, in which the signals from the separate antennas are not connected directly electrically to act as a single large antenna, as they are in most array antennas. Instead, the LOFAR dipole antennas (of two types) are distributed in stations, within which the antenna signals can be partly combined in analogue electronics, then digitised, then combined again across the full station. This step-wise approach provides great flexibility in setting and rapidly changing the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
