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HandWiki is the world's largest wiki-style encyclopedia dedicated to science, technology and computing. It allows you to create and edit articles as long as you have external citations and login account. In addition, this is a content management environment that can be used for collaborative editing of original scholarly content, such as books, manuals, monographs and tutorials.

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Stellar Aberration (Derivation from Lorentz Transformation)
Stellar aberration is an astronomical phenomenon "which produces an apparent motion of celestial objects". It can be proven mathematically that stellar aberration is due to the change of the astronomer's inertial frame of reference. The formula is derived with the use of Lorentz transformation of the star's coordinates. As the astronomer John Herschel has already explained in 1844, the stellar aberration does not depend on the relative velocity of the star towards Earth. Otherwise eclipsing binary stars would appear to be separated, in stark contrast to observation: both stars are rotating with high speed —and ever changing and different velocity vectors— around each other, but they appear as one spot all the time.
  • 3.8K
  • 27 Oct 2022
Topic Review
Alcohol
In chemistry, alcohol is an organic compound that carries at least one hydroxyl functional group (−OH) bound to a saturated carbon atom. The term alcohol originally referred to the primary alcohol ethanol (ethyl alcohol), which is used as a drug and is the main alcohol present in alcoholic drinks. An important class of alcohols, of which methanol and ethanol are the simplest members, includes all compounds for which the general formula is CnH2n+1OH. Simple monoalcohols that are the subject of this article include primary (RCH2OH), secondary (R2CHOH) and tertiary (R3COH) alcohols. The suffix -ol appears in the IUPAC chemical name of all substances where the hydroxyl group is the functional group with the highest priority. When a higher priority group is present in the compound, the prefix hydroxy- is used in its IUPAC name. The suffix -ol in non-IUPAC names (such as paracetamol or cholesterol) also typically indicates that the substance is an alcohol. However, many substances that contain hydroxyl functional groups (particularly sugars, such as glucose and sucrose) have names which include neither the suffix -ol, nor the prefix hydroxy-.
  • 4.5K
  • 27 Oct 2022
Topic Review
Classroom Management
Classroom Management is a term teachers use to describe the process of ensuring that classroom lessons run smoothly without disruptive behavior from students compromising the delivery of instruction. The term also implies the prevention of disruptive behavior preemptively, as well as effectively responding to it after it happens. It is a difficult aspect of teaching for many teachers. Problems in this area causes some to leave teaching. In 1981, the US National Educational Association reported that 36% of teachers said they would probably not go into teaching if they had to decide again. A major reason was negative student attitudes and discipline. Classroom management is crucial in classrooms because it supports the proper execution of curriculum development, developing best teaching practices, and putting them into action. Classroom management can be explained as the actions and directions that teachers use to create a successful learning environment; indeed, having a positive impact on students achieving given learning requirements and goals (Soheili, Alizadeh, Murphy, Bajestani, Ferguson and Dreikurs). In an effort to ensure all students receive the best education it would seem beneficial for educator programs to spend more time and effort in ensuring educators and instructors are well versed in classroom management. Teachers do not focus on learning classroom management, because higher education programs do not put an emphasis on the teacher attaining classroom management; indeed, the focus is on creating a conducive learning atmosphere for the students (Eisenman, Edwards, and Cushman). These tools enable teachers to have the resources available to properly and successfully educate upcoming generations, and ensure future successes as a nation. According to Moskowitz & Hayman (1976), once a teacher loses control of their classroom, it becomes increasingly more difficult for them to regain that control. Also, research from Berliner (1988) and Brophy & Good (1986) shows that the time a teacher must take to correct misbehavior caused by poor classroom management skills results in a lower rate of academic engagement in the classroom. From the student's perspective, effective classroom management involves clear communication of behavioral and academic expectations as well as a cooperative learning environment.
  • 2.7K
  • 02 Nov 2022
Topic Review
Sinhapura
Sinhapura (Sanskrit, "Lion City"; IAST: Siṃhapura) was the capital of the legendary Indian king Sinhabahu. It has been mentioned in the Buddhist legends about Prince Vijaya. The name is also transliterated as Sihapura or Singhapura. The location of Sinhapura is disputed with some scholars claiming the city was located in eastern India and others claiming it was located in present-day Malaysia or Thailand. The city is linked to the origin of the Sinhalese people and Sinhalese Buddhist mythology.
  • 4.7K
  • 27 Oct 2022
Topic Review
Landscape Connectivity
Landscape connectivity in ecology is, broadly, "the degree to which the landscape facilitates or impedes movement among resource patches". Alternatively, connectivity may be a continuous property of the landscape and independent of patches and paths. Connectivity includes both structural connectivity (the physical arrangements of disturbance and/or patches) and functional connectivity (the movement of individuals across contours of disturbance and/or among patches). Functional connectivity includes actual connectivity (requires observations of individual movements) and potential connectivity in which movement paths are estimated using the life-history data. The degree to which a landscape is connected determines the amount of dispersal there is among patches, which influences gene flow, local adaptation, extinction risk, colonization probability, and the potential for organisms to move as they cope with climate change.
  • 1.9K
  • 27 Oct 2022
Topic Review
Dihedral (Aeronautics)
In aeronautics, dihedral is the angle between the left and right wings (or tail surfaces) of an aircraft. "Dihedral" is also used to describe the effect of sideslip on the rolling of the aircraft. Dihedral angle is the upward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. "Anhedral angle" is the name given to negative dihedral angle, that is, when there is a downward angle from horizontal of the wings or tailplane of a fixed-wing aircraft. Dihedral angle has a strong influence on dihedral effect, which is named after it. Dihedral effect is the amount of roll moment produced in proportion to the amount of sideslip. Dihedral effect is a critical factor in the stability of an aircraft about the roll axis (the spiral mode). It is also pertinent to the nature of an aircraft's Dutch roll oscillation and to maneuverability about the roll axis. Longitudinal dihedral is a comparatively obscure term related to the pitch axis of an airplane. It is the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal tail. Longitudinal dihedral can influence the nature of controllability about the pitch axis and the nature of an aircraft's phugoid-mode oscillation. When the term "dihedral" (of an aircraft) is used by itself it is usually intended to mean "dihedral angle". However, context may otherwise indicate that "dihedral effect" is the intended meaning.
  • 7.5K
  • 27 Oct 2022
Topic Review
Chirality
A chiral phenomenon is one that is not identical to its mirror image (see the article on mathematical chirality). The spin of a particle may be used to define a handedness, or helicity, for that particle, which, in the case of a massless particle, is the same as chirality. A symmetry transformation between the two is called parity transformation. Invariance under parity transformation by a Dirac fermion is called chiral symmetry.
  • 1.4K
  • 27 Oct 2022
Topic Review
Timeline of Rosetta Spacecraft
Rosetta is a space probe designed to rendezvous with the comet 67P/Churyumov–Gerasimenko, perform flybys of two asteroids (2867 Šteins and 21 Lutetia), and carry lander Philae until its landing on 67P. This page records a detailed timeline of this mission.
  • 1.1K
  • 27 Oct 2022
Topic Review
Isotopes of Osmium
Osmium (76Os) has seven naturally occurring isotopes, five of which are stable: 187Os, 188Os, 189Os, 190Os, and (most abundant) 192Os. The other natural isotopes, 184Os, and 186Os, have extremely long half-life (1.12×1013 years and 2×1015 years, respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.56×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio, as well as the 187Re/188Os ratio, have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However, the most notable application of Os in dating has been in conjunction with iridium, to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago. There are also 30 artificial radioisotopes, the longest-lived of which is 194Os with a half-life of six years; all others have half-lives under 94 days. There are also nine known nuclear isomers, the longest-lived of which is 191mOs with a half-life of 13.10 hours. All isotopes and nuclear isomers of osmium are either radioactive or observationally stable, meaning that they are predicted to be radioactive but no actual decay has been observed.
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  • 27 Oct 2022
Topic Review
Terma (Religion)
Terma (Tibetan: གཏེར་མ་, Wylie: gter ma; "hidden treasure") are various forms of hidden teachings that are key to Vajrayana or Tibetan Buddhist and Bon religious traditions. The belief is that these teachings were originally esoterically hidden by various adepts such as Padmasambhava and dakini such as Yeshe Tsogyal (consorts) during the 8th century, for future discovery at auspicious times by other adepts, who are known as tertöns. As such, terma represent a tradition of continuous revelation in Vajrayana or Tibetan Buddhism. Termas are a part of tantric literature.
  • 3.7K
  • 26 Oct 2022
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