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Greyout (medical)
A greyout is a transient loss of vision characterized by a perceived dimming of light and color, sometimes accompanied by a loss of peripheral vision. It is a precursor to fainting or a blackout and is caused by hypoxia (low brain oxygen level), often due to a loss of blood pressure. Greyouts have a variety of possible causes: * Shock, such as hypovolemia, even in mild form such as when drawing blood. * Standing up suddenly (see orthostatic hypotension), especially if sick, hungover, or experiencing low blood pressure. * Fatigue * Hyperventilation, paradoxically: self-induced hypocapnia, such as in the fainting game or in shallow water blackout. * Overexertion * Panic attack Recovery is usually rapid. A greyout can be readily reversed by lying down as the cardiovascular system does not need to work against gravity for blood to reach the brain. A greyout may be experienced by aircraft pilots pulling high positive g-forces as when pulling up into a loop or a tight turn, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grey Out Illustration
Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be composed of black and white. It is the color of a cloud-covered sky, of wood ash, ash and of lead. The first recorded use of ''grey'' as a color name in the English language was in 700 Common Era, CE.Maerz and Paul ''A Dictionary of Color'' New York:1930 McGraw-Hill Page 196 ''Grey'' is the dominant spelling in English language in Europe, European and Commonwealth English, while ''gray'' has been the preferred spelling in American English; both spellings are valid in both varieties of English. In Europe and North America, surveys show that grey is the color most commonly associated with Neutrality (philosophy), neutrality, conformity, boredom, uncertainty, old age, apathy, indifference, and modesty. Only one percent of respondents chose it a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-force
The gravitational force equivalent, or, more commonly, g-force, is a measurement of the type of force per unit mass – typically acceleration – that causes a perception of weight, with a g-force of 1 g (not gram in mass measurement) equal to the conventional value of gravitational acceleration on Earth, ''g'', of about . Since g-forces indirectly produce weight, any g-force can be described as a "weight per unit mass" (see the synonym specific weight). When the g-force is produced by the surface of one object being pushed by the surface of another object, the reaction force to this push produces an equal and opposite weight for every unit of each object's mass. The types of forces involved are transmitted through objects by interior mechanical stresses. Gravitational acceleration (except certain electromagnetic force influences) is the cause of an object's acceleration in relation to free fall. The g-force experienced by an object is due to the vector sum of all ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Visual System
The visual system comprises the sensory organ (the eye) and parts of the central nervous system (the retina containing photoreceptor cells, the optic nerve, the optic tract and the visual cortex) which gives organisms the sense of sight (the ability to perception, detect and process visible light) as well as enabling the formation of several non-image photo response functions. It detects and interprets information from the optical spectrum perceptible to that species to "build a representation" of the surrounding environment. The visual system carries out a number of complex tasks, including the reception of light and the formation of monocular neural representations, colour vision, the neural mechanisms underlying stereopsis and assessment of distances to and between objects, the identification of a particular object of interest, motion perception, the analysis and integration of visual information, pattern recognition, accurate motor coordination under visual guidance, and mor ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Presyncope
Lightheadedness is a common and typically unpleasant sensation of dizziness or a feeling that one may faint. The sensation of lightheadedness can be short-lived, prolonged, or, rarely, recurring. In addition to dizziness, the individual may feel as though their head is weightless. The individual may also feel as though the room is "spinning" or moving (vertigo). Most causes of lightheadedness are not serious and either cure themselves quickly, or are easily treated. Keeping a sense of balance requires the brain to process a variety of information received from the eyes, the nervous system, and the inner ears. If the brain is unable to process these signals, such as when the messages are contradictory, or if the sensory systems are improperly functioning, an individual may experience lightheadedness or dizziness. Lightheadedness is very similar to pre-syncope. Pre-syncope is the immediate stage before syncope (fainting), particularly in cases of temporary visual field loss (i.e. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphene
A phosphene is the phenomenon of seeing light without light entering the eye. The word ''phosphene'' comes from the Greek words ''phos'' (light) and ''phainein'' (to show). Phosphenes that are induced by movement or sound may be associated with optic neuritis. Phosphenes can be induced by mechanical, electrical, or magnetic stimulation of the retina or visual cortex, or by random firing of cells in the visual system. Phosphenes have also been reported by meditators (called '' nimitta''), people who endure long periods without visual stimulation (the prisoner's cinema), or those who ingest psychedelic drugs. Causes Mechanical stimulation The most common phosphenes are pressure phosphenes, caused by rubbing or applying pressure on or near the closed eyes. They have been known since antiquity, and described by the Greeks. The pressure mechanically stimulates the cells of the retina. Experiences include a darkening of the visual field that moves against the rubbing, a diffus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eigengrau
Eigengrau (German for "intrinsic gray"; ), also called Eigenlicht (Dutch and German for "intrinsic light"), dark light, or brain gray, is the uniform dark gray background color that many people report seeing in the absence of light. The term ''Eigenlicht'' dates back to the nineteenth century, but has rarely been used in recent scientific publications. Common scientific terms for the phenomenon include "visual noise" or "background adaptation". These terms arise due to the perception of an ever-changing field of tiny black and white dots seen in the phenomenon. Eigengrau is perceived as lighter than a black object in normal lighting conditions, because contrast is more important to the visual system than absolute brightness. For example, the night sky looks darker than Eigengrau because of the contrast provided by the stars. Cause Researchers noticed early on that the shape of intensity-sensitivity curves could be explained by assuming that an intrinsic source of noise in the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Zero G Roll
Roller coaster elements are the individual parts of roller coaster design and operation, such as a track, hill, loop, or turn. Variations in normal track movement that add thrill or excitement to the ride are often called "thrill elements". Common elements Banked turn A banked turn is when the track twists from the horizontal plane into the vertical plane, tipping the train to the side in the direction of the turn. Banking is used to minimize the lateral G-forces on the riders to make the turn more comfortable. When a banked turn continues to create an upward or downward spiral of approximately 360 degrees or more, it becomes a helix. Brake run A brake run on a roller coaster is any section of track meant to slow or stop a roller coaster train. Brake runs may be located anywhere or hidden along the circuit of a coaster and may be designed to bring the train to a complete halt or to simply adjust the train's speed. The vast majority of roller coasters do not have any form of bra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Helix
A helix () is a shape like a corkscrew or spiral staircase. It is a type of smooth space curve with tangent lines at a constant angle to a fixed axis. Helices are important in biology, as the DNA molecule is formed as two intertwined helices, and many proteins have helical substructures, known as alpha helices. The word ''helix'' comes from the Greek word ''ἕλιξ'', "twisted, curved". A "filled-in" helix – for example, a "spiral" (helical) ramp – is a surface called ''helicoid''. Properties and types The ''pitch'' of a helix is the height of one complete helix turn, measured parallel to the axis of the helix. A double helix consists of two (typically congruent) helices with the same axis, differing by a translation along the axis. A circular helix (i.e. one with constant radius) has constant band curvature and constant torsion. A ''conic helix'', also known as a ''conic spiral'', may be defined as a spiral on a conic surface, with the distance to the apex an expo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertical Loop
The generic roller coaster vertical loop, where a section of track causes the riders to complete a 360 degree turn, is the most basic of roller coaster inversions. At the top of the loop, riders are completely inverted. History The vertical loop is not a recent roller coaster innovation. Its origins can be traced back to the 1850s when '' centrifugal railways'' were built in France and Great Britain. The rides relied on centrifugal forces to hold the car in the loop. One early looping coaster was shut down after an accident. Later attempts to build a looping roller coaster were carried out during the late 19th century with the ''Flip Flap Railway'' at Sea Lion Park. The ride was designed with a completely circular loop (rather than the teardrop shape used by many modern looping roller coasters), and caused neck injuries due to the intense G-forces pulled with the tight radius of the loop. The next attempt at building a looping roller coaster was in 1901 when Edwin Prescott bu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Roller Coaster
A roller coaster, or rollercoaster, is a type of amusement ride that employs a form of elevated railroad track designed with tight turns, steep slopes, and sometimes inversions. Passengers ride along the track in open cars, and the rides are often found in amusement parks and theme parks around the world. LaMarcus Adna Thompson obtained one of the first known patents for a roller coaster design in 1885, related to the Switchback Railway that opened a year earlier at Coney Island. The track in a coaster design does not necessarily have to be a complete circuit, as shuttle roller coasters demonstrate. Most roller coasters have multiple cars in which passengers sit and are restrained. Two or more cars hooked together are called a train. Some roller coasters, notably Wild Mouse roller coasters, run with single cars. History The Russian mountain and the Aerial Promenades The oldest roller coasters are believed to have originated from the so-called "Russian Mountains", speciall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-LOC
g-force induced loss of consciousness (abbreviated as G-LOC, pronounced "JEE-lock") is a term generally used in aerospace physiology to describe a loss of consciousness occurring from excessive and sustained g-forces draining blood away from the brain causing cerebral hypoxia. The condition is most likely to affect pilots of high performance fighter and aerobatic aircraft or astronauts but is possible on some extreme amusement park rides. G-LOC incidents have caused fatal accidents in high performance aircraft capable of sustaining high ''g'' for extended periods. High-g training for pilots of high performance aircraft or spacecraft often includes ground training for G-LOC in special centrifuges, with some profiles exposing pilots to 9 ''g''s for a sustained period. Effects of ''g''-forces Under increasing positive ''g''-force, blood in the body will tend to move from the head toward the feet. For higher intensity or longer duration, this can manifest progressively as: * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
G-suit
A g-suit, or anti-''g'' suit, is a flight suit worn by aviators and astronauts who are subject to high levels of acceleration force ( g). It is designed to prevent a black-out and g-LOC (g-induced loss of consciousness) caused by the blood pooling in the lower part of the body when under acceleration, thus depriving the brain of blood. Black-out and g-LOC have caused a number of fatal aircraft accidents. Operation If blood is allowed to pool in the lower areas of the body, the brain will be deprived of blood. This lack of blood flow to the brain first causes a greyout (a dimming of the vision also called brownout), followed by tunnel vision and ultimately complete loss of vision 'blackout' followed by g-induced Loss Of Consciousness or 'g-LOC'. The danger of g-LOC to aircraft pilots is magnified because on relaxation of g-force there is a period of disorientation before full sensation is re-gained. A g-suit does not so much increase the g-threshold, but makes it possible to su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
