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Spark Gap
A spark gap consists of an arrangement of two conducting electrodes separated by a gap usually filled with a gas such as air, designed to allow an electric spark to pass between the conductors. When the potential difference between the conductors exceeds the breakdown voltage of the gas within the gap, a spark forms, ionizing the gas and drastically reducing its electrical resistance. An electric current then flows until the path of ionized gas is broken or the current reduces below a minimum value called the "holding current". This usually happens when the voltage drops, but in some cases occurs when the heated gas rises, stretching out and then breaking the filament of ionized gas. Usually, the action of ionizing the gas is violent and disruptive, often leading to sound (ranging from a snap for a spark plug to thunder for a lightning discharge), light and heat. Spark gaps were used historically in early electrical equipment, such as spark gap radio transmitters, electrostatic machines, and X-ray machines. Their most widespread use today is in spark plugs to ignite the fuel in internal combustion engines, but they are also used in lightning arresters and other devices to protect electrical equipment from high-voltage transients.
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  • 08 Oct 2022
Topic Review
Defining Equation
In physics, defining equations are equations that define new quantities in terms of base quantities. This article uses the current SI system of units, not natural or characteristic units.
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  • 08 Oct 2022
Topic Review
Alpha Crucis
Alpha Crucis (α Crucis, abbreviated Alpha Cru, α Cru) is a multiple star system 321 light-years from the Sun in the constellation of Crux and part of the asterism known as the Southern Cross. With a combined visual magnitude of 0.76, it is the brightest star in Crux and the 13th brightest star in the night sky. It is the southernmost first-magnitude star, 2.3 degrees more southerly than Alpha Centauri. To the naked eye Alpha Crucis appears as a single star, but it is actually a multiple star system. Two components are visually distinguishable: α1 Crucis and α2 Crucis; alternatively designated α Crucis A and α Crucis B. Both are B-type stars, and are many times more massive and luminous than the Sun. α1 Crucis is itself a spectroscopic binary with components designated α Crucis Aa (also named Acrux) and α Crucis Ab. Its two component stars orbit every 76 days at a separation of about 1 astronomical unit (au).
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  • 08 Oct 2022
Topic Review
Liquid Cooling and Ventilation Garment
A Liquid Cooling Garment (LCG) is a form-fitting garment that is used to remove body heat from the wearer in environments where evaporative cooling from sweating and open-air convection cooling does not work, or the wearer has a biological problem that hinders self-regulation of body temperature. A Liquid Cooling and Ventilation Garment (LCVG) has additional crush-resistant ventilation ducts, which draw moist air from the wearer's extremities, keeping the wearer dry. In a fully enclosing suit where exhaled breathing air can enter the suit, the exhaled air is moist and can lead to an uncomfortable feeling of dampness or wetness. While this technology is most commonly associated with space suits, it is also used in a wide range of Earth-bound applications where open-air cooling is difficult or impossible to achieve, such as fire fighting, working in a steel mill and increasingly by surgeons during long or strenuous procedures.
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  • 08 Oct 2022
Topic Review
Sodium Cyclamate
Sodium cyclamate (sweetener code 952) is an artificial sweetener. It is 30–50 times sweeter than sucrose (table sugar), making it the least potent of the commercially used artificial sweeteners. It is often used with other artificial sweeteners, especially saccharin; the mixture of 10 parts cyclamate to 1 part saccharin is common and masks the off-tastes of both sweeteners. It is less expensive than most sweeteners, including sucralose, and is stable under heating. Safety concerns led to it being banned in a few countries, though the European Union considers it safe.
  • 3.0K
  • 08 Oct 2022
Topic Review
Carboniferous Rainforest Collapse
The Carboniferous rainforest collapse (CRC) was a minor extinction event that occurred around 305 million years ago in the Carboniferous period. It altered the vast coal forests that covered the equatorial region of Euramerica (Europe and America). This event may have fragmented the forests into isolated 'islands', which in turn caused dwarfism and, shortly after, extinction of many plant and animal species. Following the event, coal-forming tropical forests continued in large areas of the Earth, but their extent and composition were changed. The event occurred at the end of the Moscovian and continued into the early Kasimovian stages of the Pennsylvanian (Upper Carboniferous).
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  • 08 Oct 2022
Topic Review
Electron (Rocket)
Electron is a two-stage orbital expendable launch vehicle (with an optional third stage) developed by the American aerospace company Rocket Lab to service the commercial small satellite launch segment. Its Rutherford engines, manufactured in California , are the first electric-pump-fed engine to power an orbital rocket. In December 2016, Electron completed flight qualification. The first rocket was launched on 25 May 2017, reaching space but not achieving orbit due to a glitch in communication equipment on the ground. During its second flight on 21 January 2018, Electron reached orbit and deployed three CubeSats. The first commercial launch of Electron, and the third launch overall, occurred on 11 November 2018.
  • 3.0K
  • 08 Oct 2022
Topic Review
Probation and Parole Officer
A probation and parole officer is an official appointed to investigate, report on, and supervise the conduct of convicted offenders on probation and/or those released from incarceration to community supervision such as parole. Most probation and parole officers are employed by the government of the jurisdiction in which they operate, although some are employed by private companies that provide contracted services to the government.
  • 1.2K
  • 08 Oct 2022
Topic Review
Necrotizing Gingivitis
Acute necrotizing ulcerative gingivitis (ANUG) is a common, non-contagious infection of the gums with sudden onset. The main features are painful, bleeding gums, and ulceration of inter-dental papillae (the sections of gum between adjacent teeth). This disease, along with necrotizing (ulcerative) periodontitis (NP or NUP) is classified as a necrotizing periodontal disease, one of the seven general types of gum disease caused by inflammation of the gums (periodontitis). The often severe gum pain that characterizes ANUG distinguishes it from the more common chronic periodontitis which is rarely painful. If ANUG is improperly treated or neglected, it may become chronic and/or recurrent. The causative organisms are mostly anaerobic bacteria, particularly Fusobacteriota and spirochete species. Predisposing factors include poor oral hygiene, smoking, poor nutrition, psychological stress, and a weakened immune system. When the attachments of the teeth to the bone are involved, the term NUP is used. Treatment of ANUG is by removal of dead gum tissue and antibiotics (usually metronidazole) in the acute phase, and improving oral hygiene to prevent recurrence. Although the condition has a rapid onset and is debilitating, it usually resolves quickly and does no serious harm. The informal name trench mouth arose during World War I as many soldiers developed the disease, probably because of the poor conditions and extreme psychological stress.
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  • 08 Oct 2022
Topic Review
Schwarz Triangle Function
In complex analysis, the Schwarz triangle function or Schwarz s-function is a function that conformally maps the upper half plane to a triangle in the upper half plane having lines or circular arcs for edges. Let πα, πβ, and πγ be the interior angles at the vertices of the triangle. If any of α, β, and γ are greater than zero, then the Schwarz triangle function can be given in terms of hypergeometric functions as: where a = (1−α−β−γ)/2, b = (1−α+β−γ)/2, c = 1−α, a′ = a − c + 1 = (1+α−β−γ)/2, b′ = b − c + 1 = (1+α+β−γ)/2, and c′ = 2 − c = 1 + α. This mapping has singular points at z = 0, 1, and ∞, corresponding to the vertices of the triangle with angles πα, πγ, and πβ respectively. At these singular points, This formula can be derived using the Schwarzian derivative. This function can be used to map the upper half-plane to a spherical triangle on the Riemann sphere if α + β + γ > 1, or a hyperbolic triangle on the Poincaré disk if α + β + γ < 1. When α + β + γ = 1, then the triangle is a Euclidean triangle with straight edges: a = 0, [math]\displaystyle{ _2 F_1 \left(a, b; c; z\right) = 1 }[/math], and the formula reduces to that given by the Schwarz–Christoffel transformation. In the special case of ideal triangles, where all the angles are zero, the triangle function yields the modular lambda function. This function was introduced by H. A. Schwarz as the inverse function of the conformal mapping uniformizing a Schwarz triangle. Applying successive hyperbolic reflections in its sides, such a triangle generates a tessellation of the upper half plane (or the unit disk after composition with the Cayley transform). The conformal mapping of the upper half plane onto the interior of the geodesic triangle generalizes the Schwarz–Christoffel transformation. By the Schwarz reflection principle, the discrete group generated by hyperbolic reflections in the sides of the triangle induces an action on the two dimensional space of solutions. On the orientation-preserving normal subgroup, this two dimensional representation corresponds to the monodromy of the ordinary differential equation and induces a group of Möbius transformations on quotients of solutions. Since the triangle function is the inverse function of such a quotient, it is therefore an automorphic function for this discrete group of Möbius transformations. This is a special case of a general method of Henri Poincaré that associates automorphic forms with ordinary differential equations with regular singular points.
  • 1.8K
  • 13 Oct 2022
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