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Birdwings are butterflies in the swallowtail family, that belong to the genera Trogonoptera, Troides, and Ornithoptera. Most recent authorities recognise 36 species, however, this is debated, and some authorities include additional genera. Birdwings are named for their exceptional size, angular wings, and birdlike flight. They are found across tropical Asia, mainland and archipelagic Southeast Asia, and Australasia.
Included among the birdwings are some of the largest butterflies in the world: the largest, Queen Alexandra's birdwing; the second largest, the Goliath birdwing; the largest butterfly endemic to Australia, the Cairns birdwing; and the largest butterfly in India, the southern birdwing. Another well-known species is Rajah Brooke's birdwing, a particularly attractive species named after Sir James Brooke, the first White Rajah of 19th-century Sarawak.
Due to their size and brightly coloured males, they are popular among collectors of butterflies, but all birdwings are now listed by CITES, thereby limiting (and in the case of O. alexandrae completely banning) international trade.
Taxonomy
Genera and species
genus: Troides
subgenus: Ripponia
Troides hypolitus – Rippon's birdwing
subgenus: Troides
species group: Troides aeacus
Troides aeacus – golden birdwing
Troides dohertyi – Talaud black birdwing
Troides magellanus – Magellan birdwing
Troides minos – southern birdwing
Troides plateni – Dr. Platen's birdwing
Troides prattorum – Buru opalescent birdwing
Troides rhadamantus – golden birdwing
species group: Troides amphrysus
Troides amphrysus – Malay birdwing
Troides andromache – Borneo birdwing
Troides cuneifera
Troides miranda – Miranda birdwing
species group: Troides haliphron
Troides criton – Criton birdwing
Troides darsius – Sri Lankan birdwing
Troides haliphron – haliphron birdwing
Troides plato – silver birdwing
Troides riedeli – Riedel's birdwing
Troides staudingeri
Troides vandepolli – van de Poll's birdwing
species group: Troides helena
Troides helena – common birdwing
Troides oblongomaculatus – oblong-spotted birdwing
genus: Trogonoptera | Birdwing | Wikipedia | 499 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
Trogonoptera brookiana – Rajah Brooke's birdwing
Trogonoptera trojana – Palawan birdwing
genus: Ornithoptera
subgenus: Aetheoptera
Ornithoptera victoriae – Queen Victoria's birdwing
subgenus: Ornithoptera
Ornithoptera aesacus – Obi Island birdwing
Ornithoptera croesus – Wallace's golden birdwing
Ornithoptera euphorion – Cairns birdwing
Ornithoptera priamus – common green birdwing
Ornithoptera richmondia – Richmond birdwing
subgenus: Schoenbergia
Ornithoptera chimaera – chimaera birdwing
Ornithoptera goliath – Goliath birdwing
Ornithoptera meridionalis – southern tailed birdwing
Ornithoptera paradisea – paradise birdwing
Ornithoptera rothschildi – Rothschild's birdwing
Ornithoptera tithonus – Tithonus birdwing
subgenus: Straatmana
Ornithoptera alexandrae – Queen Alexandra's birdwing
Natural hybrids
Troides prattorum × Troides oblongomaculatus bouruensis — Troides mixtum
Ornithoptera rothschildi × Ornithoptera priamus poseidon — Ornithoptera akakeae
Ornithoptera victoriae × Ornithoptera priamus urvillianus — Ornithoptera allotei
Description
Ova
After mating, females immediately begin to seek appropriate host plants; climbing vines of the genera Aristolochia and Pararistolochia (both in the family Aristolochiaceae) are sought exclusively. The female lays her spherical eggs under the tips of the vine's leaves, one egg per leaf.
Larva | Birdwing | Wikipedia | 356 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
The caterpillars are voracious eaters but move very little; a small group will defoliate an entire vine. If starved due to overcrowding, the caterpillars may resort to cannibalism. Fleshy spine-like tubercles line the caterpillars' backs, and their bodies are dark red to brown and velvety black. Some species have tubercles of contrasting colours, often red, or pale "saddle" markings. Like other members of their family, birdwing caterpillars possess a retractable organ behind their heads called an osmeterium. Shaped like the forked tongue of a snake, the osmeterium excretes a fetid terpene-based compound and is deployed when the caterpillar is provoked. The caterpillars are also unappealing to most predators due to their toxicity: the vines which the caterpillars feed upon contain aristolochic acid, a poisonous compound known to be carcinogenic in rats. The feeding caterpillars incorporate and concentrate the aristolochic acid into their tissues, where the poison will persist through metamorphosis and into adulthood.
Pupa
Birdwing chrysalids are camouflaged to look like a dead leaf or twig. Before pupating, the caterpillars may wander considerable distances from their host plants. In O. alexandrae, it takes about four months to get from egg to adult. Barring predation, this species can also survive up to three months as an adult.
Imago
Birdwings inhabit rainforests and adults are usually glimpsed along the forest periphery. They feed upon—and are important long-range pollinators of—nectar-bearing flowers of the forest canopy, as well as terrestrial flowers, such as lantana. They are strong flyers and seek sunlit spots in which to bask.
Breeding behaviour varies little between species; the female's role is relatively passive, slowly fluttering from perch to perch while the male performs an elaborate, quivering yet stationary dance 20–50 cm above her. | Birdwing | Wikipedia | 430 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
Birdwings are typified by large size (up to a maximum body length of 7.6 cm or 3 inches and a wingspan of 28 cm or 11 inches in O. alexandrae), showy colouration (in contrasting shades of green, yellow, black, white, and sometimes blue or orange), and slender, lanceolate forewings. With few exceptions (i.e., the New Guinean O. meridionalis and O. paradisea), the hindwings lack tails. Sexual dimorphism is strong in Ornithoptera species only, where males are black combined with bright iridescent green, blue, orange, or yellow while the larger and less colourful females are overall black or dark brownish with white, pale brown, or yellow markings.
Males and females of most Troides birdwings are similar and have jet black to brown dorsal forewings, often with the veins bordered in grey to creamy white. At least one of these darkly-coloured species (T. rhadamantus) possesses thermoreceptors on the anal veins (A2 and A3) of the wings and on the antennal clubs. The antennal receptors of the clubs—which also possess hygroreceptors that measure atmospheric humidity—are known as sensilla basiconica. The thermoreceptors are sensitive to sudden increases in temperature; they are thought to help the butterfly thermoregulate and avoid overheating while basking.
The colours of most species are pigmentary (via papiliochrome); but two species, Troides magellanus and the much rarer T. prattorum, are noted for their use of limited-view iridescence: the yellow of the dorsal hindwings is modified by bright blue-green iridescence which is only seen when the butterfly is viewed at a narrow, oblique angle. This "grazing iridescence" is brought about through diffraction of light (after back-reflection) by the wings' extremely steeply-set, multilayered rib-like scales (rather than the ridge-lamellae of most other iridescent butterflies, such as Morpho species). Such limited-view iridescence was previously only known from one other species, the riodinid Ancyluris meliboeus. In A. meliboeus, however, the iridescence is produced by ridge-lamellar scales and features a wider range of colours. | Birdwing | Wikipedia | 507 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
The close evolutionary relationship between Troides and Ornithoptera butterflies is well demonstrated by the fact that commercial breeders have produced numerous hybrids between the two.
The final and smallest genus is Trogonoptera with just two species. They resemble each other, being overall black with iridescent green markings and a red head. Females are duller than males.
Distribution
Birdwings are generally found from Southeast Asia to northern Australasia. Trogonoptera brookiana inhabits the Thai-Malay Peninsula, Borneo, Natuna, Sumatra, and various surrounding islands. Trogonoptera trojana is endemic to Palawan in the Philippines. Troides species are distributed widely across the Indomalayan realm, but may be found as far east as New Guinea in the case of Troides oblongomaculatus. Some species may be found as far west as India, and are the westernmost distributed of all birdwings. All Ornithoptera species are found in the northern portion of the Australasian realm, east of Weber's line; the Moluccas, New Guinea, the Solomon Islands, and northeastern Australia. An outlier is Ornithoptera richmondia, which may be found in far northeastern New South Wales, Australia in the southernmost area of its range; the southernmost distribution of all birdwings.
Status and protection
With the exception of Queen Alexandra's birdwing (O. alexandrae), all birdwings are listed in Appendix II of CITES, and accordingly their trade is restricted in countries that have signed the CITES convention. Exceptions are made for captive-reared specimens, which mainly originate from ranches in Papua New Guinea and Indonesia. Most species of all three genera have now been reared in captivity, though with significant differences in the quantities reared of each species. O. alexandrae is listed on Appendix I and therefore cannot legally be traded internationally. At the 2006 meeting of the CITES Animals Committee some suggested O. alexandrae should be moved to Appendix II, as the conservation benefits of sustainable management perhaps are higher than those of the trade ban.
Three Troides and eight Ornithoptera species have been given assessments by the IUCN Red List, with classifications ranging from "least concern" to "endangered". | Birdwing | Wikipedia | 455 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
Richmond birdwings (O. richmondia) depend on the plant Aristolochia praevenosa which they need for their caterpillars. However, the very similar Aristolochia elegans (Dutchman's pipe) which can be found in many Australian backyards, kills the caterpillars.
Reproduction
Ornithoptera, or the genus of birdwing butterflies, usually reproduce sexually and are oviparous. In butterflies sex is determined by a WW/WZ system, with a heterogametic female, reverse of that found in mammals and many other insects, which have a heterogametic male. During copulation males will transfer an ejaculate containing both sperm and accessory substances that can make up to fifteen percent of a males body mass.
Mating systems
Mating systems, first explored in evolutionary terms by Darwin, includes all behaviours associated with sexual reproduction. Mating systems include all costs and benefits, pre- and postcopulatory competitions, displays and mate choice. Butterfly mating systems have great variation, including strict monandry, one male and one female, to polyandry, having many mates of the opposite sex. Typically Ornithoptera tend to be polygamous, mating with more than one individual.
Female choice
Female choice can have a serious impact on mate selection and successful reproduction. Several species of Ornithoptera have been known to create hybrids if they have no access to their own species. Troides oblongamaculatus females have been known to choose to mate with other species such as Ornithoptera priamus poseidon, which will attempt mating if their own species is not to be found near by. The females will typically resist mating attempts by covering their abdomen with their forewings or dropping to the ground, making mating near impossible. Although the females usually resist these mating attempts, they have been noted to be more susceptible if they have not had previous encounters with males of their own species.
Male courtship | Birdwing | Wikipedia | 403 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
Some male Ornithoptera species demonstrate courtship behaviour. Ornithoptera priamus posedion males will approach a female carefully, and examine the female for several minutes. After consideration, the male may choose to hover twenty to thirty centimeters above the female, displaying the bright yellow marking on its hindwings. Meanwhile, the forewings will move forward, exposing the abdomen and androconial hair tufts. Mating is only attempted when the female has ceased to flap her wings. After about thirty seconds of the display, the male will attempt copulation.
Cryptic choice: sperm competition and postcopulatory guarding
In many animals, females often mate with more than one male. Males who are able will adapt strategies such as postcopulatory guarding to ensure the paternity of the offspring. Following insemination, it is common for the male Ornithoptera to produce a mating plug, which will seal the ostium bursae and prevent remating by the female, as new sperm is unable to enter the opening. The plug does not impede oviposition and may stay in place for the duration of the female's life.
Sexual dimorphism
Sexual dimorphism is very prominent in Ornithoptera species, the males being black with brightly colored markings of blue, green, orange or yellow and the females are overall black or dark brown. The sexual dichromatism functions in mate recognition by the use of photoreceptors. Due to the protected nature of Ornithoptera it has been difficult to study the spectral sensitivities of the sexes although this difference in coloration alludes to the idea of sensory exploitation of the female's photoreceptors. The sensory bias of females to select for males with brighter wings has yet to be studied in Ornithoptera. | Birdwing | Wikipedia | 372 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
Gyanandromorphism is a very rare condition in which an organism simultaneously expresses both male and female phenotypes. It is only observed in species that express strong sexual dimorphism. Gynandromorphs are suspected to be due to genetic errors associated with cell division such as nondisjunction, as well as fertilization of binucleate ova and fertilisation of multiple sperm that may fuse and act as a second nucleus. Ornithoptera is known to commonly exhibit this phenomenon, but little to no research has been successful in determining why. Those who experience this phenomenon, usually females, show male-pigmented tissues on their wings. | Birdwing | Wikipedia | 141 | 2134303 | https://en.wikipedia.org/wiki/Birdwing | Biology and health sciences | Lepidoptera | Animals |
The lips are a horizontal pair of soft appendages attached to the jaws and are the most visible part of the mouth of many animals, including humans. Vertebrate lips are soft, movable and serve to facilitate the ingestion of food (e.g. suckling and gulping) and the articulation of sound and speech. Human lips are also a somatosensory organ, and can be an erogenous zone when used in kissing and other acts of intimacy.
Structure
The upper and lower lips are referred to as the labium superius oris and labium inferius oris, respectively. The juncture where the lips meet the surrounding skin of the mouth area is the vermilion border, and the typically reddish area within the borders is called the vermilion zone. The vermilion border of the upper lip is known as the Cupid's bow. The fleshy protuberance located in the center of the upper lip is a tubercle known by various terms including the procheilon (also spelled prochilon), the "tuberculum labii superioris", and the "labial tubercle". The vertical groove extending from the procheilon to the nasal septum is called the philtrum.
The skin of the lip, with three to five cellular layers, is very thin compared to typical face skin, which has up to 16 layers. With light skin color, the lip skin contains fewer melanocytes (cells which produce melanin pigment, which give skin its color). Because of this, the blood vessels appear through the skin of the lips, which leads to their notable red coloring. With darker skin color this effect is less prominent, as in this case the skin of the lips contains more melanin and thus is visually darker. The skin of the lip forms the border between the exterior skin of the face, and the interior mucous membrane of the inside of the mouth.
The lip skin is not hairy and does not have sweat glands. Therefore, it does not have the usual protection layer of sweat and body oils which keep the skin smooth, inhibit pathogens, and regulate warmth. For these reasons, the lips dry out faster and become chapped more easily. | Lip | Wikipedia | 461 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
The lower lip is formed from the mandibular prominence, a branch of the first pharyngeal arch. The lower lip covers the anterior body of the mandible. It is lowered by the depressor labii inferioris muscle and the orbicularis oris borders it inferiorly.
The upper lip covers the anterior surface of the body of the maxilla. Its upper half is of usual skin color and has a depression at its center, directly under the nasal septum, called the philtrum, which is Latin for "lower nose", while its lower half is a markedly different, red-colored skin tone more similar to the color of the inside of the mouth, and the term vermillion refers to the colored portion of either the upper or lower lip.
It is raised by the levator labii superioris and is connected to the lower lip by the thin lining of the lip itself.
Thinning of the vermilion of the upper lip and flattening of the philtrum are two of the facial characteristics of fetal alcohol syndrome, a lifelong disability caused by the mother's consumption of alcohol during pregnancy.
Microanatomy
The skin of the lips is stratified squamous epithelium. The mucous membrane is represented by a large area in the sensory cortex, and is therefore highly sensitive. The frenulum labii inferioris is the frenulum of the lower lip. The frenulum labii superioris is the frenulum of the upper lip.
Nerve supply
Trigeminal nerve
The infraorbital nerve is a branch of the maxillary branch. It supplies not only the upper lip but also much of the skin of the face between the upper lip and the lower eyelid, except for the bridge of the nose.
The mental nerve is a branch of the mandibular branch (via the inferior alveolar nerve). It supplies the skin and mucous membrane of the lower lip and labial gingiva (gum) anteriorly.
Blood supply
The facial artery is one of the six non-terminal branches of the external carotid artery.
This artery supplies both lips by its superior and inferior labial branches. Each of the two branches bifurcate and anastomose with their companion branch from the other terminal. | Lip | Wikipedia | 470 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
Muscles
The muscles acting on the lips are considered part of the muscles of facial expression. All muscles of facial expression are derived from the mesoderm of the second pharyngeal arch and are therefore supplied (motor supply) by the nerve of the second pharyngeal arch, the facial nerve (7th cranial nerve). The muscles of facial expression are all specialized members of the panniculus carnosus, which attach to the dermis and so wrinkle or dimple the overlying skin. Functionally, the muscles of facial expression are arranged in groups around the orbits, nose, and mouth.
The muscles acting on the lips:
Buccinator
Orbicularis oris (a complex of muscles, formerly thought to be a single sphincter or ring of muscle)
Anchor point for several muscles
Modiolus
Lip elevation
Levator labii superioris
levator labii superioris alaeque nasi
Levator anguli oris
Zygomaticus minor
Zygomaticus major
Lip depression
Risorius
Depressor anguli oris
Depressor labii inferioris
Mentalis
Functions
Food intake
Because they have their own muscles and bordering muscles, the lips are easily movable. Lips are used for eating functions, like holding food or to get it in the mouth. In addition, lips serve to close the mouth airtight shut, to hold food and drink inside, and to keep out unwanted objects. Through making a narrow funnel with the lips, the suction of the mouth is increased. This suction is essential for babies to breast feed. Lips can also be used to suck in other contexts, such as sucking on a straw to drink liquids.
Articulation
The lips serve for creating different sounds—mainly labial, bilabial, and labiodental consonant sounds as well as vowel rounding—and thus are an important part of the speech apparatus. The lips enable whistling and the performing of wind instruments such as the trumpet, clarinet, flute, and saxophone. People who have hearing loss may unconsciously or consciously lip read to understand speech without needing to perceive the actual sounds, and visual cues from the lips affect the perception of what sounds have been heard, for example the McGurk effect.
Tactile organ
The lip has many nerve endings and reacts as part of the tactile (touch) senses. Lips are very sensitive to touch, warmth, and cold. It is therefore an important aid for exploring unknown objects for babies and toddlers.
Erogenous zone | Lip | Wikipedia | 510 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
Because of their high number of nerve endings, the lips are an erogenous zone. The lips therefore play a crucial role in kissing and other acts of intimacy.
A woman's lips are also a visible expression of her fertility. In studies performed on the science of human attraction, psychologists have concluded that a woman's facial and sexual attractiveness is closely linked to the makeup of her hormones during puberty and development. Contrary to the effects of testosterone on a man's facial structure, the effects of a woman's oestrogen levels serve to maintain a relatively "childlike" and youthful facial structure during puberty and during final maturation. It has been shown that the more oestrogen a woman has, the larger her eyes and the fuller her lips, characteristics which are perceived as more feminine. Surveys performed by sexual psychologists have also found that universally, men find a woman's full lips to be more sexually attractive than lips that are less so. A woman's lips are therefore sexually attractive to males because they serve as a biological indicator of a woman's health and fertility. A woman's lipstick (or collagen lip enhancement) attempts to take advantage of this fact by creating the illusion that a woman has more oestrogen than she actually has and thus that she is more fertile and attractive.
Lip size is linked to sexual attraction in both men and women. Women are attracted to men with masculine lips that are more middle size and not too big or too small; they are to be rugged and sensual. In general, the researchers found that a small nose, big eyes and voluptuous lips are sexually attractive both in men and women. The lips may temporarily swell during sexual arousal due to engorgement with blood.
Facial expression
The lips contribute substantially to facial expressions. The lips visibly express emotions such as a smile or frown, iconically by the curve of the lips forming an up-open or down-open arc, respectively. Lips can also be made pouty when whining or perky to be provocative.
Open questions
The function of the abrupt change in skin structure between the lips and surrounding face (in particular, the function of the less keratinized vermillion and the white roll) is not completely understood. Possible reasons for the difference may include advantages to somatosensory function, better communication of facial expressions, and/or emphasis of the lips' slight sexual dimorphism as a secondary sex characteristic.
Clinical significance | Lip | Wikipedia | 503 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
As an organ of the body, the lip can be a focus of disease or show symptoms of a disease:
One of the most frequent changes of the lips is a blue coloring due to cyanosis; the blood contains less oxygen and thus has a dark red to blue color, which shows through the thin skin. Cyanosis is the reason why corpses sometimes have blue lips. In cold weather cyanosis can appear, so especially in the winter, blue lips may not be an uncommon sight.
Inflammation of the lips is termed cheilitis. This can be in several forms such as chapped lips (dry, peeling lips), angular cheilitis (inflammation of the corners of the mouth), herpes labialis (cold sore, a form of herpes simplex) and actinic cheilitis (chronically sun damaged lips).
Cleft lip is a type of birth defect that can be successfully treated with surgery.
Carcinoma (a malignant cancer that arises from epithelial cells) at the lips is caused predominantly by using tobacco and overexposure of sunlight. Alcohol appears to increase the carcinoma risk associated with tobacco use. It is most often a diffuse and often hyperkeratinised lesion, occasionally has the form of nodules and grows infiltratively, and can also be a combination of the two types. It more often occurs at the lower lip, where it is also much more malign. Lower lip carcinoma is exclusively planocellular carcinoma, whereas at the upper lip, it can also be basocellular carcinoma.
Society and culture
Lips are often viewed as a symbol of sensuality and sexuality. This has many origins; above all, the lips are a very sensitive erogenous and tactile organ. Furthermore, in many cultures of the world, a woman's mouth and lips are veiled because of their representative association with the vulva, and because of their role as a woman's secondary sexual organ.
As part of the mouth, the lips are also associated with the symbolism associated with the mouth as orifice by which food is taken in. The lips are also linked symbolically to neonatal psychology (see for example oral stage of the psychology according to Sigmund Freud).
Lip piercing or lip augmentation is sometimes carried out for cosmetic reasons. Products designed for use on the lips include lipstick, lip gloss and lip balm.
Other animals | Lip | Wikipedia | 502 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
In most vertebrates, the lips are relatively unimportant folds of tissue lying just outside the jaws. However, in mammals, they become much more prominent, being separated from the jaws by a deep cleft (a notable exception being the naked mole-rat, whose lips close behind the front teeth). They are also more mobile in mammals than in other groups since it is only in this group that they have any attached muscles. In some teleost fish, the lips may be modified to carry sensitive barbels. In birds and turtles, the lips are hard and keratinous, forming a solid beak. Clevosaurids like Clevosaurus are notable for the presence of bone "lips"; in these species the tooth-like jaw projections common to all sphenodontians form a beak-like edge around the jaws, protecting the teeth within. | Lip | Wikipedia | 180 | 2136925 | https://en.wikipedia.org/wiki/Lip | Biology and health sciences | Gastrointestinal tract | Biology |
In fluid dynamics, drag, sometimes referred to as fluid resistance, is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid. This can exist between two fluid layers, two solid surfaces, or between a fluid and a solid surface. Drag forces tend to decrease fluid velocity relative to the solid object in the fluid's path.
Unlike other resistive forces, drag force depends on velocity. Drag force is proportional to the relative velocity for low-speed flow and is proportional to the velocity squared for high-speed flow. This distinction between low and high-speed flow is measured by the Reynolds number.
Examples
Examples of drag include:
Net aerodynamic or hydrodynamic force: Drag acting opposite to the direction of movement of a solid object such as cars, aircraft, and boat hulls.
Viscous drag of fluid in a pipe: Drag force on the immobile pipe decreases fluid velocity relative to the pipe.
In the physics of sports, drag force is necessary to explain the motion of balls, javelins, arrows, and frisbees and the performance of runners and swimmers. For a top sprinter, overcoming drag can require 5% of their energy output.
Types
Types of drag are generally divided into the following categories:
form drag due to the size and shape of a body
skin friction drag or viscous drag due to the friction between the fluid and a surface which may be the outside of an object, or inside such as the bore of a pipe
The effect of streamlining on the relative proportions of skin friction and form drag is shown for two different body sections: An airfoil, which is a streamlined body, and a cylinder, which is a bluff body. Also shown is a flat plate illustrating the effect that orientation has on the relative proportions of skin friction, and pressure difference between front and back.
A body is known as bluff or blunt when the source of drag is dominated by pressure forces, and streamlined if the drag is dominated by viscous forces. For example, road vehicles are bluff bodies. For aircraft, pressure and friction drag are included in the definition of parasitic drag. Parasite drag is often expressed in terms of a hypothetical.
Parasitic drag
This is the area of a flat plate perpendicular to the flow. It is used when comparing the drag of different aircraft For example, the Douglas DC-3 has an equivalent parasite area of and the McDonnell Douglas DC-9, with 30 years of advancement in aircraft design, an area of although it carried five times as many passengers. | Drag (physics) | Wikipedia | 504 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
lift-induced drag appears with wings or a lifting body in aviation and with semi-planing or planing hulls for watercraft
wave drag (aerodynamics) is caused by the presence of shockwaves and first appears at subsonic aircraft speeds when local flow velocities become supersonic. The wave drag of the supersonic Concorde prototype aircraft was reduced at Mach 2 by 1.8% by applying the area rule which extended the rear fuselage on the production aircraft.
wave resistance (ship hydrodynamics) or wave drag occurs when a solid object is moving along a fluid boundary and making surface waves
boat-tail drag on an aircraft is caused by the angle with which the rear fuselage, or engine nacelle, narrows to the engine exhaust diameter.
Lift-induced drag and parasitic drag
Lift-induced drag
Lift-induced drag (also called induced drag) is drag which occurs as the result of the creation of lift on a three-dimensional lifting body, such as the wing or propeller of an airplane. Induced drag consists primarily of two components: drag due to the creation of trailing vortices (vortex drag); and the presence of additional viscous drag (lift-induced viscous drag) that is not present when lift is zero. The trailing vortices in the flow-field, present in the wake of a lifting body, derive from the turbulent mixing of air from above and below the body which flows in slightly different directions as a consequence of creation of lift.
With other parameters remaining the same, as the lift generated by a body increases, so does the lift-induced drag. This means that as the wing's angle of attack increases (up to a maximum called the stalling angle), the lift coefficient also increases, and so too does the lift-induced drag. At the onset of stall, lift is abruptly decreased, as is lift-induced drag, but viscous pressure drag, a component of parasite drag, increases due to the formation of turbulent unattached flow in the wake behind the body.
Parasitic drag
Parasitic drag, or profile drag, is drag caused by moving a solid object through a fluid. Parasitic drag is made up of multiple components including viscous pressure drag (form drag), and drag due to surface roughness (skin friction drag). Additionally, the presence of multiple bodies in relative proximity may incur so called interference drag, which is sometimes described as a component of parasitic drag. | Drag (physics) | Wikipedia | 494 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
In aviation, induced drag tends to be greater at lower speeds because a high angle of attack is required to maintain lift, creating more drag. However, as speed increases the angle of attack can be reduced and the induced drag decreases. Parasitic drag, however, increases because the fluid is flowing more quickly around protruding objects increasing friction or drag. At even higher speeds (transonic), wave drag enters the picture. Each of these forms of drag changes in proportion to the others based on speed. The combined overall drag curve therefore shows a minimum at some airspeed - an aircraft flying at this speed will be at or close to its optimal efficiency. Pilots will use this speed to maximize endurance (minimum fuel consumption), or maximize gliding range in the event of an engine failure.
The drag equation
Drag depends on the properties of the fluid and on the size, shape, and speed of the object. One way to express this is by means of the drag equation:
where
is the drag force,
is the density of the fluid,
is the speed of the object relative to the fluid,
is the cross sectional area, and
is the drag coefficient – a dimensionless number.
The drag coefficient depends on the shape of the object and on the Reynolds number
where
is some characteristic diameter or linear dimension. Actually, is the equivalent diameter of the object. For a sphere, is the D of the sphere itself.
For a rectangular shape cross-section in the motion direction, , where a and b are the rectangle edges.
is the kinematic viscosity of the fluid (equal to the dynamic viscosity divided by the density ).
At low , is asymptotically proportional to , which means that the drag is linearly proportional to the speed, i.e. the drag force on a small sphere moving through a viscous fluid is given by the Stokes Law:
At high , is more or less constant, but drag will vary as the square of the speed varies. The graph to the right shows how varies with for the case of a sphere. Since the power needed to overcome the drag force is the product of the force times speed, the power needed to overcome drag will vary as the square of the speed at low Reynolds numbers, and as the cube of the speed at high numbers. | Drag (physics) | Wikipedia | 460 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
It can be demonstrated that drag force can be expressed as a function of a dimensionless number, which is dimensionally identical to the Bejan number. Consequently, drag force and drag coefficient can be a function of Bejan number. In fact, from the expression of drag force it has been obtained:
and consequently allows expressing the drag coefficient as a function of Bejan number and the ratio between wet area and front area :
where is the Reynolds number related to fluid path length L.
At high velocity
As mentioned, the drag equation with a constant drag coefficient gives the force moving through fluid a relatively large velocity, i.e. high Reynolds number, Re > ~1000. This is also called quadratic drag.
The derivation of this equation is presented at .
The reference area A is often the orthographic projection of the object, or the frontal area, on a plane perpendicular to the direction of motion. For objects with a simple shape, such as a sphere, this is the cross sectional area. Sometimes a body is a composite of different parts, each with a different reference area (drag coefficient corresponding to each of those different areas must be determined).
In the case of a wing, the reference areas are the same, and the drag force is in the same ratio as the lift force. Therefore, the reference for a wing is often the lifting area, sometimes referred to as "wing area" rather than the frontal area.
For an object with a smooth surface, and non-fixed separation points (like a sphere or circular cylinder), the drag coefficient may vary with Reynolds number Re, up to extremely high values (Re of the order 107).
For an object with well-defined fixed separation points, like a circular disk with its plane normal to the flow direction, the drag coefficient is constant for Re > 3,500.
The further the drag coefficient Cd is, in general, a function of the orientation of the flow with respect to the object (apart from symmetrical objects like a sphere).
Power
Under the assumption that the fluid is not moving relative to the currently used reference system, the power required to overcome the aerodynamic drag is given by: | Drag (physics) | Wikipedia | 432 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
The power needed to push an object through a fluid increases as the cube of the velocity increases. For example, a car cruising on a highway at may require only to overcome aerodynamic drag, but that same car at requires . With a doubling of speeds, the drag/force quadruples per the formula. Exerting 4 times the force over a fixed distance produces 4 times as much work. At twice the speed, the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, 4 times the work done in half the time requires 8 times the power.
When the fluid is moving relative to the reference system, for example, a car driving into headwind, the power required to overcome the aerodynamic drag is given by the following formula:
Where is the wind speed and is the object speed (both relative to ground).
Velocity of a falling object
Velocity as a function of time for an object falling through a non-dense medium, and released at zero relative-velocity v = 0 at time t = 0, is roughly given by a function involving a hyperbolic tangent (tanh):
The hyperbolic tangent has a limit value of one, for large time t. In other words, velocity asymptotically approaches a maximum value called the terminal velocity vt:
For an object falling and released at relative-velocity v = vi at time t = 0, with vi < vt, is also defined in terms of the hyperbolic tangent function:
For vi > vt, the velocity function is defined in terms of the hyperbolic cotangent function:
The hyperbolic cotangent also has a limit value of one, for large time t. Velocity asymptotically tends to the terminal velocity vt, strictly from above vt.
For vi = vt, the velocity is constant:
These functions are defined by the solution of the following differential equation:
Or, more generically (where F(v) are the forces acting on the object beyond drag):
For a potato-shaped object of average diameter d and of density ρobj, terminal velocity is about
For objects of water-like density (raindrops, hail, live objects—mammals, birds, insects, etc.) falling in air near Earth's surface at sea level, the terminal velocity is roughly equal to with d in metre and vt in m/s. | Drag (physics) | Wikipedia | 484 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
For example, for a human body ( ≈0.6 m) ≈70 m/s, for a small animal like a cat ( ≈0.2 m) ≈40 m/s, for a small bird ( ≈0.05 m) ≈20 m/s, for an insect ( ≈0.01 m) ≈9 m/s, and so on. Terminal velocity for very small objects (pollen, etc.) at low Reynolds numbers is determined by Stokes law.
In short, terminal velocity is higher for larger creatures, and thus potentially more deadly. A creature such as a mouse falling at its terminal velocity is much more likely to survive impact with the ground than a human falling at its terminal velocity.
Low Reynolds numbers: Stokes' drag
The equation for viscous resistance or linear drag is appropriate for objects or particles moving through a fluid at relatively slow speeds (assuming there is no turbulence). Purely laminar flow only exists up to Re = 0.1 under this definition. In this case, the force of drag is approximately proportional to velocity. The equation for viscous resistance is:
where:
is a constant that depends on both the material properties of the object and fluid, as well as the geometry of the object; and
is the velocity of the object.
When an object falls from rest, its velocity will be
where:
is the density of the object,
is density of the fluid,
is the volume of the object,
is the acceleration due to gravity (i.e., 9.8 m/s), and
is mass of the object.
The velocity asymptotically approaches the terminal velocity . For a given , denser objects fall more quickly.
For the special case of small spherical objects moving slowly through a viscous fluid (and thus at small Reynolds number), George Gabriel Stokes derived an expression for the drag constant:
where is the Stokes radius of the particle, and is the fluid viscosity.
The resulting expression for the drag is known as Stokes' drag:
For example, consider a small sphere with radius = 0.5 micrometre (diameter = 1.0 μm) moving through water at a velocity of 10 μm/s. Using 10−3 Pa·s as the dynamic viscosity of water in SI units,
we find a drag force of 0.09 pN. This is about the drag force that a bacterium experiences as it swims through water. | Drag (physics) | Wikipedia | 493 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
The drag coefficient of a sphere can be determined for the general case of a laminar flow with Reynolds numbers less than using the following formula:
For Reynolds numbers less than 1, Stokes' law applies and the drag coefficient approaches !
Aerodynamics
In aerodynamics, aerodynamic drag, also known as air resistance, is the fluid drag force that acts on any moving solid body in the direction of the air's freestream flow.
From the body's perspective (near-field approach), the drag results from forces due to pressure distributions over the body surface, symbolized .
Forces due to skin friction, which is a result of viscosity, denoted .
Alternatively, calculated from the flow field perspective (far-field approach), the drag force results from three natural phenomena: shock waves, vortex sheet, and viscosity.
Overview of aerodynamics
When the airplane produces lift, another drag component results. Induced drag, symbolized , is due to a modification of the pressure distribution due to the trailing vortex system that accompanies the lift production. An alternative perspective on lift and drag is gained from considering the change of momentum of the airflow. The wing intercepts the airflow and forces the flow to move downward. This results in an equal and opposite force acting upward on the wing which is the lift force. The change of momentum of the airflow downward results in a reduction of the rearward momentum of the flow which is the result of a force acting forward on the airflow and applied by the wing to the air flow; an equal but opposite force acts on the wing rearward which is the induced drag. Another drag component, namely wave drag, , results from shock waves in transonic and supersonic flight speeds. The shock waves induce changes in the boundary layer and pressure distribution over the body surface.
Therefore, there are three ways of categorizing drag.
Pressure drag and friction drag
Profile drag and induced drag
Vortex drag, wave drag and wake drag
The pressure distribution acting on a body's surface exerts normal forces on the body. Those forces can be added together and the component of that force that acts downstream represents the drag force, . The nature of these normal forces combines shock wave effects, vortex system generation effects, and wake viscous mechanisms. | Drag (physics) | Wikipedia | 458 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
Viscosity of the fluid has a major effect on drag. In the absence of viscosity, the pressure forces acting to hinder the vehicle are canceled by a pressure force further aft that acts to push the vehicle forward; this is called pressure recovery and the result is that the drag is zero. That is to say, the work the body does on the airflow is reversible and is recovered as there are no frictional effects to convert the flow energy into heat. Pressure recovery acts even in the case of viscous flow. Viscosity, however results in pressure drag and it is the dominant component of drag in the case of vehicles with regions of separated flow, in which the pressure recovery is infective.
The friction drag force, which is a tangential force on the aircraft surface, depends substantially on boundary layer configuration and viscosity. The net friction drag, , is calculated as the downstream projection of the viscous forces evaluated over the body's surface. The sum of friction drag and pressure (form) drag is called viscous drag. This drag component is due to viscosity. | Drag (physics) | Wikipedia | 226 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
History
The idea that a moving body passing through air or another fluid encounters resistance had been known since the time of Aristotle. According to Mervyn O'Gorman, this was named "drag" by Archibald Reith Low. Louis Charles Breguet's paper of 1922 began efforts to reduce drag by streamlining. Breguet went on to put his ideas into practice by designing several record-breaking aircraft in the 1920s and 1930s. Ludwig Prandtl's boundary layer theory in the 1920s provided the impetus to minimise skin friction. A further major call for streamlining was made by Sir Melvill Jones who provided the theoretical concepts to demonstrate emphatically the importance of streamlining in aircraft design.
In 1929 his paper 'The Streamline Airplane' presented to the Royal Aeronautical Society was seminal. He proposed an ideal aircraft that would have minimal drag which led to the concepts of a 'clean' monoplane and retractable undercarriage. The aspect of Jones's paper that most shocked the designers of the time was his plot of the horse power required versus velocity, for an actual and an ideal plane. By looking at a data point for a given aircraft and extrapolating it horizontally to the ideal curve, the velocity gain for the same power can be seen. When Jones finished his presentation, a member of the audience described the results as being of the same level of importance as the Carnot cycle in thermodynamics.
Power curve in aviation
The interaction of parasitic and induced drag vs. airspeed can be plotted as a characteristic curve, illustrated here. In aviation, this is often referred to as the power curve, and is important to pilots because it shows that, below a certain airspeed, maintaining airspeed counterintuitively requires more thrust as speed decreases, rather than less. The consequences of being "behind the curve" in flight are important and are taught as part of pilot training. At the subsonic airspeeds where the "U" shape of this curve is significant, wave drag has not yet become a factor, and so it is not shown in the curve.
Wave drag in transonic and supersonic flow
Wave drag, sometimes referred to as compressibility drag, is drag that is created when a body moves in a compressible fluid and at the speed that is close to the speed of sound in that fluid. In aerodynamics, wave drag consists of multiple components depending on the speed regime of the flight. | Drag (physics) | Wikipedia | 493 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
In transonic flight, wave drag is the result of the formation of shockwaves in the fluid, formed when local areas of supersonic (Mach number greater than 1.0) flow are created. In practice, supersonic flow occurs on bodies traveling well below the speed of sound, as the local speed of air increases as it accelerates over the body to speeds above Mach 1.0. However, full supersonic flow over the vehicle will not develop until well past Mach 1.0. Aircraft flying at transonic speed often incur wave drag through the normal course of operation. In transonic flight, wave drag is commonly referred to as transonic compressibility drag. Transonic compressibility drag increases significantly as the speed of flight increases towards Mach 1.0, dominating other forms of drag at those speeds.
In supersonic flight (Mach numbers greater than 1.0), wave drag is the result of shockwaves present in the fluid and attached to the body, typically oblique shockwaves formed at the leading and trailing edges of the body. In highly supersonic flows, or in bodies with turning angles sufficiently large, unattached shockwaves, or bow waves will instead form. Additionally, local areas of transonic flow behind the initial shockwave may occur at lower supersonic speeds, and can lead to the development of additional, smaller shockwaves present on the surfaces of other lifting bodies, similar to those found in transonic flows. In supersonic flow regimes, wave drag is commonly separated into two components, supersonic lift-dependent wave drag and supersonic volume-dependent wave drag.
The closed form solution for the minimum wave drag of a body of revolution with a fixed length was found by Sears and Haack, and is known as the Sears-Haack Distribution. Similarly, for a fixed volume, the shape for minimum wave drag is the Von Karman Ogive.
The Busemann biplane theoretical concept is not subject to wave drag when operated at its design speed, but is incapable of generating lift in this condition.
d'Alembert's paradox | Drag (physics) | Wikipedia | 422 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
In 1752 d'Alembert proved that potential flow, the 18th century state-of-the-art inviscid flow theory amenable to mathematical solutions, resulted in the prediction of zero drag. This was in contradiction with experimental evidence, and became known as d'Alembert's paradox. In the 19th century the Navier–Stokes equations for the description of viscous flow were developed by Saint-Venant, Navier and Stokes. Stokes derived the drag around a sphere at very low Reynolds numbers, the result of which is called Stokes' law.
In the limit of high Reynolds numbers, the Navier–Stokes equations approach the inviscid Euler equations, of which the potential-flow solutions considered by d'Alembert are solutions. However, all experiments at high Reynolds numbers showed there is drag. Attempts to construct inviscid steady flow solutions to the Euler equations, other than the potential flow solutions, did not result in realistic results.
The notion of boundary layers—introduced by Prandtl in 1904, founded on both theory and experiments—explained the causes of drag at high Reynolds numbers. The boundary layer is the thin layer of fluid close to the object's boundary, where viscous effects remain important even when the viscosity is very small (or equivalently the Reynolds number is very large). | Drag (physics) | Wikipedia | 276 | 2137292 | https://en.wikipedia.org/wiki/Drag%20%28physics%29 | Physical sciences | Fluid mechanics | null |
A viral disease (or viral infection) occurs when an organism's body is invaded by pathogenic viruses, and infectious virus particles (virions) attach to and enter susceptible cells.
Examples are the common cold, gastroenteritis,corona,flu,pneumonia.
Structural characteristics
Basic structural characteristics, such as genome type, virion shape and replication site, generally share the same features among virus species within the same family.
Double-stranded DNA families: three are non-enveloped (Adenoviridae, Papillomaviridae and Polyomaviridae) and two are enveloped (Herpesviridae and Poxviridae). All of the non-enveloped families have icosahedral capsids.
Partly double-stranded DNA viruses: Hepadnaviridae. These viruses are enveloped.
One family of single-stranded DNA viruses infects humans: Parvoviridae. These viruses are non-enveloped.
Positive single-stranded RNA families: three non-enveloped (Astroviridae, Caliciviridae and Picornaviridae) and four enveloped (Coronaviridae, Flaviviridae, Retroviridae and Togaviridae). All the non-enveloped families have icosahedral nucleocapsids.
Negative single-stranded RNA families: Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, Paramyxoviridae and Rhabdoviridae. All are enveloped with helical nucleocapsids.
Double-stranded RNA genome: Reoviridae.
The Hepatitis D virus has not yet been assigned to a family, but is clearly distinct from the other families infecting humans.
Viruses known to infect humans that have not been associated with disease: the family Anelloviridae and the genus Dependovirus. Both of these taxa are non-enveloped single-stranded DNA viruses.
Pragmatic rules
Human-infecting virus families offer rules that may assist physicians and medical microbiologists/virologists. | Viral disease | Wikipedia | 415 | 15845253 | https://en.wikipedia.org/wiki/Viral%20disease | Biology and health sciences | Concepts | Health |
As a general rule, DNA viruses replicate within the cell nucleus while RNA viruses replicate within the cytoplasm. Exceptions are known to this rule: poxviruses replicate within the cytoplasm and orthomyxoviruses and hepatitis D virus (RNA viruses) replicate within the nucleus.
Segmented genomes: Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae (acronym BOAR). All are RNA viruses.
Viruses transmitted almost exclusively by arthropods: Bunyavirus, Flavivirus, and Togavirus. Some Reoviruses are transmitted from arthropod vectors. All are RNA viruses.
One family of enveloped viruses causes gastroenteritis (Coronaviridae). All other viruses associated with gastroenteritis are non-enveloped.
Baltimore group
This group of analysts defined multiple categories of virus. Groups:
I - dsDNA
II - ssDNA
III - dsRNA
IV - positive-sense ssRNA
V - negative-sense ssRNA
VI - ssRNA-RT
VII - dsDNA-RT
Clinical characteristics
The clinical characteristics of viruses may differ substantially among species within the same family: | Viral disease | Wikipedia | 240 | 15845253 | https://en.wikipedia.org/wiki/Viral%20disease | Biology and health sciences | Concepts | Health |
Messier 15 or M15 (also designated NGC 7078 and sometimes known as the Great Pegasus Cluster) is a globular cluster in the constellation Pegasus. It was discovered by Jean-Dominique Maraldi in 1746 and included in Charles Messier's catalogue of comet-like objects in 1764. At an estimated billion years old, it is one of the oldest known globular clusters.
Characteristics
M 15 is about 35,700 light-years from Earth, and 175 light-years in diameter. It has an absolute magnitude of −9.2, which translates to a total luminosity of 360,000 times that of the Sun. Messier 15 is one of the most densely packed globulars known in the Milky Way galaxy. Its core has undergone a contraction known as "core collapse" and it has a central density cusp with an enormous number of stars surrounding what may be a central black hole.
Home to over 100,000 stars, the cluster is notable for containing a large number of variable stars (112) and pulsars (8), including one double neutron star system, M15-C. It also contains Pease 1, the first planetary nebula discovered within a globular cluster in 1928. Just three others have been found in globular clusters since then.
Amateur astronomy
At magnitude 6.2, M15 approaches naked eye visibility under good conditions and can be observed with binoculars or a small telescope, appearing as a fuzzy star. Telescopes with a larger aperture (at least 6 in. (150 mm)) will start to reveal individual stars, the brightest of which are of magnitude +12.6. The cluster appears 18 arc minutes in size (three tenths of a degree across). M15 is around 4° WNW of the brightest star of Pegasus, Epsilon Pegasi.
X-ray sources
Earth-orbiting satellites Uhuru and Chandra X-ray Observatory have detected two bright X-ray sources in this cluster: Messier 15 X-1 (4U 2129+12) and Messier 15 X-2. The former appears to be the first astronomical X-ray source detected in Pegasus.
Gallery | Messier 15 | Wikipedia | 440 | 958996 | https://en.wikipedia.org/wiki/Messier%2015 | Physical sciences | Notable star clusters | Astronomy |
The Omega Nebula is an H II region in the constellation Sagittarius. It was discovered by Philippe Loys de Chéseaux in 1745. Charles Messier catalogued it in 1764. It is by some of the richest starfields of the Milky Way, figuring in the northern two-thirds of Sagittarius. This feature is also known as the Swan Nebula, Checkmark Nebula, Lobster Nebula, and the Horseshoe Nebula, and catalogued as Messier 17 or M17 or NGC 6618.
Characteristics
The Omega Nebula is between 5,000 and 6,000 light-years from Earth and it spans some 15 light-years in diameter. The cloud of interstellar matter of which this nebula is a part is roughly 40 light-years in diameter and has a mass of 30,000 solar masses. The total mass of the Omega Nebula is an estimated 800 solar masses.
It is considered one of the brightest and most massive star-forming regions of our galaxy. Its local geometry is similar to the Orion Nebula except that it is viewed edge-on rather than face-on.
The open cluster NGC 6618 lies embedded in the nebulosity and causes the gases of the nebula to shine due to radiation from these hot, young stars; however, the actual number of stars in the nebula is much higher – up to 800, 100 of spectral type earlier than B9, and 9 of spectral type O, plus over a thousand stars in formation on its outer regions. It is also one of the youngest clusters known, with an age of just 1 million years.
The luminous blue variable HD 168607, in the south-east part of the nebula, is generally assumed to be associated with it; its close neighbor, the blue hypergiant HD 168625, may be too.
The Swan portion of M17, the Omega Nebula in the Sagittarius nebulosity is said to resemble a barber's pole.
Early research
The first attempt to accurately draw the nebula (as part of a series of sketches of nebulae) was made by John Herschel in 1833, and published in 1836. He described the nebula as such:
A second, more detailed sketch was made during his visit to South Africa in 1837. The nebula was also studied by Johann von Lamont and separately by an undergraduate at Yale College, Mr Mason, starting from around 1836. When Herschel published his 1837 sketch in 1847, he wrote: | Omega Nebula | Wikipedia | 493 | 959018 | https://en.wikipedia.org/wiki/Omega%20Nebula | Physical sciences | Notable nebulae | Astronomy |
Sketches were also made by William Lassell in 1862 using his four-foot telescope at Malta, and by M. Trouvelot from Cambridge, Massachusetts, and Edward Singleton Holden in 1875 using the twenty-six inch Clark refractor at the United States Naval Observatory.
Observations by SOFIA
In January 2020, the Stratospheric Observatory for Infrared Astronomy (SOFIA) provided new insights into the Omega Nebula. SOFIA's composite image revealed that blue areas (20 microns) near the center indicate gas heated by massive stars, while green areas (37 microns) trace dust warmed by massive stars and newborn stars. Nine previously unseen protostars were discovered primarily in the southern regions. Red areas near the edges represent cold dust detected by the Herschel Space Telescope (70 microns), and the white star field was observed by the Spitzer Space Telescope (3.6 microns). These observations suggest that parts of the nebula formed separately, contributing to its distinctive swan-like shape.
Gallery | Omega Nebula | Wikipedia | 202 | 959018 | https://en.wikipedia.org/wiki/Omega%20Nebula | Physical sciences | Notable nebulae | Astronomy |
Hypovolemic shock is a form of shock caused by severe hypovolemia (insufficient blood volume or extracellular fluid in the body). It can be caused by severe dehydration or blood loss. Hypovolemic shock is a medical emergency; if left untreated, the insufficient blood flow can cause damage to organs, leading to multiple organ failure.
In treating hypovolemic shock, it is important to determine the cause of the underlying hypovolemia, which may be the result of bleeding or other fluid losses. To minimize ischemic damage to tissues, treatment involves quickly replacing lost blood or fluids, with consideration of both rate and the type of fluids used.
Tachycardia, a fast heart rate, is typically the first abnormal vital sign. When resulting from blood loss, trauma is the most common root cause, but severe blood loss can also happen in various body systems without clear traumatic injury. The body in hypovolemic shock prioritizes getting oxygen to the brain and heart, which reduces blood flow to nonvital organs and extremities, causing them to grow cold, look mottled, and exhibit delayed capillary refill. The lack of adequate oxygen delivery ultimately leads to a worsening increase in the acidity of the blood (acidosis). The "lethal triad" of ways trauma can lead to death is acidosis, hypothermia, and coagulopathy. It is possible for trauma to cause clotting problems even without resuscitation efforts.
Damage control resuscitation is based on three principles:
permissive hypotension: tries to balance temporary suboptimal perfusion to organs with conditions for halting blood loss by setting a goal of 90 mmHg systolic blood pressure
hemostatic resuscitation: restoring blood volume in ways (with whole blood or equivalent) that interfere minimally with the natural process of stopping bleeding.
damage control surgery.
Signs and symptoms
Symptoms of hypovolemic shock can be related to volume depletion, electrolyte imbalances, or acid–base disorders that accompany hypovolemic shock. | Hypovolemic shock | Wikipedia | 450 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Patients with volume depletion may complain of thirst, muscle cramps, and/or orthostatic hypotension. Severe hypovolemic shock can result in mesenteric and coronary ischemia that can cause abdominal or chest pain. Agitation, lethargy, or confusion may characterize brain mal-perfusion.
Dry mucous membranes, decreased skin turgor, low jugular venous distention, tachycardia, and hypotension can be seen along with decreased urinary output. Patients in shock can appear cold, clammy, and cyanotic.
Early signs and symptoms include tachycardia given rise to by catecholamine release; skin pallor due to vasoconstriction triggered by catecholamine release; hypotension followed by hypovolaemia and perhaps arising after myocardial insufficiency; and confusion, aggression, drowsiness and coma caused by cerebral hypoxia or acidosis. Tachypnoea owing to hypoxia and acidosis, general weakness caused by hypoxia and acidosis, thirst induced by hypovolaemia, and oliguria caused by reduced perfusion may also arise.
Abnormal growing central venous pressure indicates either hypotension or hypovolemia. Tachycardia accompanied by declined urine outflow implies either tension pneumothorax, cardiac tamponade or cardiac failure which is thought secondary to cardiac contusion or ischaemic heart disease. Echocardiography in such case may be helpful to distinguish cardiac failure from other diseases. Cardiac failure manifests a weak contractibility myocardium; treatment with an inotropic drug such as dobutamine may be appropriate.
Cause
The annual incidence of shock of any etiology is 0.3 to 0.7 per 1000, with hemorrhagic shock being most common in the intensive care unit. Hypovolemic shock is the most common type of shock in children, most commonly due to diarrheal illness in the developing world.
Hypovolemic shock occurs as a result of either blood loss or extracellular fluid loss.
Blood loss | Hypovolemic shock | Wikipedia | 464 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Hemorrhagic shock is hypovolemic shock from blood loss. Traumatic injury is by far the most common cause of hemorrhagic shock, particularly blunt and penetrating trauma, followed by upper and lower gastrointestinal sources, such as gastrointestinal (GI) bleed. Other causes of hemorrhagic shock include bleed from an ectopic pregnancy, bleeding from surgical intervention, vaginal bleeding, and splenic rupture.
Obstetrical, vascular, iatrogenic, and even urological sources have all been described. Bleeding may be either external or internal. A substantial amount of blood loss to the point of hemodynamic compromise may occur in the chest, abdomen, or the retroperitoneum. The thigh itself can hold up to 1 L to 2 L of blood.
Localizing and controlling the source of bleeding is of utmost importance to the treatment of hemorrhagic shock.
The sequence of the most-commonly-seen causes that lead to hemorrhagic type of hypovolemic shock is given in order of frequencies: blunt or penetrating trauma including multiple fractures absent from vessel impairment, upper gastrointestinal bleeding e.g., variceal hemorrhage, peptic ulcer., or lower GI bleeding e.g., diverticular, and arteriovenous malformation.
Except for the two most common causes, the less common causes are intra-operative and post-operative bleeding, abdominal aortic rupture or left ventricle aneurysm rupture, aortic–enteric fistula, hemorrhagic pancreatitis, iatrogenic e.g., inadvertent biopsy of arteriovenous malformation, severed artery., tumors or abscess erosion into major vessels, post-partum hemorrhage, uterine or vaginal hemorrhage owing to infection, tumors, lacerations, spontaneous peritoneal hemorrhage caused by bleeding diathesis, and ruptured hematoma.
Fluid loss
In spite of hemorrhage, the amount of circulating blood in the body may drop as well when one loses excessive body fluid owing to non-hemorrhagic reasons.
Hypovolemic shock as a result of extracellular fluid loss can be of the 4 etiologies.
Gastrointestinal | Hypovolemic shock | Wikipedia | 501 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Gastrointestinal (GI) losses can occur via many different etiologies. The gastrointestinal tract usually secretes between 3 and 6 liters of fluid per day. However, most of this fluid is reabsorbed as only 100 to 200 mL are lost in the stool. Volume depletion occurs when the fluid ordinarily secreted by the GI tract cannot be reabsorbed. This occurs when there is retractable vomiting, diarrhea, or external drainage via stoma or fistulas.
Kidneys
Renal losses of salt and fluid can lead to hypovolemic shock. The kidneys usually excrete sodium and water in a manner that matches sodium intake and water intake.
Diuretic therapy and osmotic diuresis from hyperglycemia can lead to excessive renal sodium and volume loss. In addition, there are several tubular and interstitial diseases beyond the scope of this article that cause severe salt-wasting nephropathy.
Skin
Fluid loss also can occur from the skin. In a hot and dry climate, skin fluid losses can be as high as 1 to 2 liters/hour. Patients with a skin barrier interrupted by burns or other skin lesions also can experience large fluid losses that lead to hypovolemic shock.
Third-spacing
Sequestration of fluid into a third space also can lead to volume loss and hypovolemic shock. Third-spacing of fluid can occur in intestinal obstruction, pancreatitis, obstruction of a major venous system, vascular endothelium or any other pathological condition that results in a massive inflammatory response.
Pathophysiology
Blood loss
Hemorrhagic shock is due to the depletion of intravascular volume through blood loss to the point of being unable to match the tissues' demand for oxygen. As a result, mitochondria are no longer able to sustain aerobic metabolism for the production of oxygen and switch to the less efficient anaerobic metabolism to meet the cellular demand for adenosine triphosphate. In the latter process, pyruvate is produced and converted to lactic acid to regenerate nicotinamide adenine dinucleotide (NAD+) to maintain some degree of cellular respiration in the absence of oxygen. | Hypovolemic shock | Wikipedia | 473 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
The body compensates for volume loss by increasing heart rate and contractility, followed by baroreceptor activation resulting in sympathetic nervous system activation and peripheral vasoconstriction. Typically, there is a slight increase in the diastolic blood pressure with narrowing of the pulse pressure. As diastolic ventricular filling continues to decline and cardiac output decreases, systolic blood pressure drops.
Due to sympathetic nervous system activation, blood is diverted away from noncritical organs and tissues to preserve blood supply to vital organs such as the heart and brain. While prolonging heart and brain function, this also leads to other tissues being further deprived of oxygen causing more lactic acid production and worsening acidosis. This worsening acidosis along with hypoxemia, if left uncorrected, eventually causes the loss of peripheral vasoconstriction, worsening hemodynamic compromise, and death.
The body's compensation varies by cardiopulmonary comorbidities, age, and vasoactive medications. Due to these factors, heart rate and blood pressure responses are extremely variable and, therefore, cannot be relied upon as the sole means of diagnosis.
A key factor in the pathophysiology of hemorrhagic shock is the development of trauma-induced coagulopathy. Coagulopathy develops as a combination of several processes. The simultaneous loss of coagulation factors via hemorrhage, hemodilution with resuscitation fluids, and coagulation cascade dysfunction secondary to acidosis and hypothermia have been traditionally thought to be the cause of coagulopathy in trauma. However, this traditional model of trauma-induced coagulopathy may be too limited. Further studies have shown that a degree of coagulopathy begins in 25% to 56% of patients before initiation of the resuscitation. This has led to the recognition of trauma-induced coagulopathy as the sum of two distinct processes: acute coagulopathy of trauma and resuscitation-induced coagulopathy. | Hypovolemic shock | Wikipedia | 431 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Trauma-induced coagulopathy is acutely worsened by the presence of acidosis and hypothermia. The activity of coagulation factors, fibrinogen depletion, and platelet quantity are all adversely affected by acidosis. Hypothermia (less than 34 C) compounds coagulopathy by impairing coagulation and is an independent risk factor for death in hemorrhagic shock.
Fluid loss
Hypovolemic shock results from depletion of intravascular volume, whether by extracellular fluid loss or blood loss. The body compensates with increased sympathetic tone resulting in increased heart rate, increased cardiac contractility, and peripheral vasoconstriction. The first changes in vital signs seen in hypovolemic shock include an increase in diastolic blood pressure with narrowed pulse pressure.
As volume status continues to decrease, systolic blood pressure drops. As a result, oxygen delivery to vital organs is unable to meet the oxygen needs of the cells. Cells switch from aerobic metabolism to anaerobic metabolism, resulting in lactic acidosis. As sympathetic drive increases, blood flow is diverted from other organs to preserve blood flow to the heart and brain. This propagates tissue ischemia and worsens lactic acidosis. If not corrected, there will be worsening hemodynamic compromise and, eventually, death.
Diagnosis
Shock index (SI) has been defined as ; SI≥0.6 is a clinical shock.
Such ratio value is clinically employed to determine the scope or emergence of shock. The SI correlates with the extent of hypovolemia and thus may facilitate the early identification of severely injured patients threatened by complications due to blood loss and therefore need urgent treatment, i.e. blood transfusion.
Data presented as n (%), mean ± standard deviation or median (interquartile range (IQR)). n = 21,853; P <0.001 for all parameters. ED Emergency department, GCS Glasgow coma scale, HR Heart rate, SBP Systolic blood pressure, SI = Shock index.
Bleeding | Hypovolemic shock | Wikipedia | 441 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Recognizing the degree of blood loss via vital sign and mental status abnormalities is important. The American College of Surgeons Advanced Trauma Life Support (ATLS) hemorrhagic shock classification links the amount of blood loss to expected physiologic responses in a healthy 70 kg patient. As total circulating blood volume accounts for approximately 7% of total body weight, this equals approximately five liters in the average 70 kg male patient.
Class 1: Volume loss up to 15% of total blood volume, approximately 750 mL. Heart rate is minimally elevated or normal. Typically, there is no change in blood pressure, pulse pressure, or respiratory rate.
Class 2: Volume loss from 15% to 30% of total blood volume, from 750 mL to 1500 mL. Heart rate and respiratory rate become elevated (100 BPM to 120 BPM, 20 RR to 24 RR). Pulse pressure begins to narrow, but systolic blood pressure may be unchanged to slightly decreased.
Class 3: Volume loss from 30% to 40% of total blood volume, from 1500 mL to 2000 mL. A significant drop in blood pressure and changes in mental status occur. Heart rate and respiratory rate are significantly elevated (more than 120 BPM). Urine output declines. Capillary refill is delayed.
Class 4: Volume loss over 40% of total blood volume. Hypotension with narrow pulse pressure (less than 25 mmHg). Tachycardia becomes more pronounced (more than 120 BPM), and mental status becomes increasingly altered. Urine output is minimal or absent. Capillary refill is delayed.
Again, the above is outlined for a healthy 70 kg individual. Clinical factors must be taken into account when assessing patients. For example, elderly patients taking beta blockers can alter the patient's physiologic response to decreased blood volume by inhibiting mechanism to increase heart rate. As another, patients with baseline hypertension may be functionally hypotensive with a systolic blood pressure of 110 mmHg.
Non-bleeding
Various laboratory values can be abnormal in hypovolemic shock. Patients can have increased BUN and serum creatinine as a result of pre-renal kidney failure. Hypernatremia or hyponatremia can result, as can hyperkalemia or hypokalemia. | Hypovolemic shock | Wikipedia | 476 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Lactic acidosis can result from increased anaerobic metabolism. However, the effect of acid–base balance can be variable as patients with large GI losses can become alkalotic.
In cases of hemorrhagic shock, hematocrit and hemoglobin can be severely decreased. However, with a reduction in plasma volume, hematocrit and hemoglobin can be increased due to hemoconcentration.
Low urinary sodium is commonly found in hypovolemic patients as the kidneys attempt to conserve sodium and water to expand the extracellular volume. However, sodium urine can be low in a euvolemic patient with heart failure, cirrhosis, or nephrotic syndrome. Fractional excretion of sodium under 1% is also suggestive of volume depletion. Elevated urine osmolality can also suggest hypovolemia. However, this number also can be elevated in the setting of impaired concentrating ability by the kidneys.
Central venous pressure (CVP) is often used to assess volume status. However, its usefulness in determining volume responsiveness has recently come into question. Ventilator settings, chest wall compliance, and right-sided heart failure can compromise CVPs accuracy as a measure of volume status. Measurements of pulse pressure variation via various commercial devices has also been postulated as a measure of volume responsiveness. However, pulse pressure variation as a measure of fluid responsiveness is only valid in patients without spontaneous breaths or arrhythmias. The accuracy of pulse pressure variation also can be compromised in right heart failure, decreased lung or chest wall compliance, and high respiratory rates.
Similar to examining pulse pressure variation, measuring respiratory variation in inferior vena cava diameter as a measure of volume responsiveness has only been validated in patients without spontaneous breaths or arrhythmias.
Measuring the effect of passive leg raises on cardiac contractility by echo appears to be the most accurate measurement of volume responsiveness, although it is also subject to limitations.
History and physical can often make the diagnosis of hypovolemic shock. For patients with hemorrhagic shock, a history of trauma or recent surgery is present. For hypovolemic shock due to fluid losses, history and physical should attempt to identify possible GI, renal, skin, or third-spacing as a cause of extracellular fluid loss. | Hypovolemic shock | Wikipedia | 491 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Although relatively nonsensitive and nonspecific, physical exam can be helpful in determining the presence of hypovolemic shock. Physical findings suggestive of volume depletion include dry mucous membranes, decreased skin turgor, and low jugular venous distention. Tachycardia and hypotension can be seen along with decreased urinary output.
Differential diagnosis
While hemorrhage is the most common cause of shock in the trauma patient, other causes of shock are to remain on the differential. Obstructive shock can occur in the setting of tension pneumothorax and cardiac tamponade. These etiologies should be uncovered in the primary survey. In the setting of head or neck trauma, an inadequate sympathetic response, or neurogenic shock, is a type of distributive shock that is caused by a decrease in peripheral vascular resistance. This is suggested by an inappropriately low heart rate in the setting of hypotension. Cardiac contusion and infarctions can result in cardiogenic shock. Finally, other causes should be considered that are not related to trauma or blood loss. In the undifferentiated patient with shock, septic shock and toxic causes are also on the differential.
Management
The first step in managing hemorrhagic shock is recognition. Ideally, This should occur before the development of hypotension. Close attention should be paid to physiological responses to low-blood volume. Tachycardia, tachypnea, and narrowing pulse pressure may be the initial signs. Cool extremities and delayed capillary refill are signs of peripheral vasoconstriction.
Bleeding
In the setting of trauma, an algorithmic approach via the primary and secondary surveys is suggested by ATLS. Physical exam and radiological evaluations can help localize sources of bleeding. A trauma ultrasound, or Focused Assessment with Sonography for Trauma (FAST), has been incorporated in many circumstances into the initial surveys. The specificity of a FAST scan has been reported above 99%, but a negative ultrasound does not rule out intra-abdominal pathology. | Hypovolemic shock | Wikipedia | 444 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
With a broader understanding of the pathophysiology of hemorrhagic shock, treatment in trauma has expanded from a simple massive transfusion method to a more comprehensive management strategy of "damage control resuscitation". The concept of damage control resuscitation focuses on permissive hypotension, hemostatic resuscitation, and hemorrhage control to adequately treat the "lethal triad" of coagulopathy, acidosis, and hypothermia that occurs in trauma.
Hypotensive resuscitation has been suggested for the hemorrhagic shock patient without head trauma. The aim is to achieve a systolic blood pressure of 90 mmHg in order to maintain tissue perfusion without inducing re-bleeding from recently clotted vessels. Permissive hypotension is a means of restricting fluid administration until hemorrhage is controlled while accepting a short period of suboptimal end-organ perfusion. Studies regarding permissive hypotension have yielded conflicting results and must take into account type of injury (penetrating versus blunt), the likelihood of intracranial injury, the severity of the injury, as well as proximity to a trauma center and definitive hemorrhage control.
The quantity, type of fluids to be used, and endpoints of resuscitation remain topics of much study and debate. For crystalloid resuscitation, normal saline and lactated ringers are the most commonly used fluids. Normal saline has the drawback of causing a non-anion gap hyperchloremic metabolic acidosis due to the high chloride content, while lactated ringers can cause a metabolic alkalosis as lactate metabolism regenerates into bicarbonate. | Hypovolemic shock | Wikipedia | 360 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Recent trends in damage control resuscitation focus on "hemostatic resuscitation" which pushes for early use of blood products rather than an abundance of crystalloids in order to minimize the metabolic derangement, resuscitation-induced coagulopathy, and the hemodilution that occurs with crystalloid resuscitation. The end goal of resuscitation and the ratios of blood products remain at the center of much study and debate. A recent study has shown no significant difference in mortality at 24 hours or 30 days between ratios of 1:1:1 and 1:1:2 of plasma to platelets to packed RBCs. However, patients that received the more balanced ratio of 1:1:1 were less likely to die as a result of exsanguination in 24 hours and were more likely to achieve hemostasis. Additionally, reduction in time to first plasma transfusion has shown a significant reduction in mortality in damage control resuscitation.
In addition to blood products, products that prevent the breakdown of fibrin in clots, or antifibrinolytics, have been studied for their utility in the treatment of hemorrhagic shock in the trauma patient. Several antifibrinolytics have been shown to be safe and effective in elective surgery. The CRASH-2 study was a randomized control trial of tranexamic acid versus placebo in trauma has been shown to decrease overall mortality when given in the first three hours of injury. Follow-up analysis shows additional benefit to tranexamic acid when given in the first three hours after surgery.
Damage control resuscitation is to occur in conjunction with prompt intervention to control the source of bleeding. Strategies may differ depending on proximity to definitive treatment.
For patients in hemorrhagic shock, early use of blood products over crystalloid resuscitation results in better outcomes. Balanced transfusion using 1:1:1 or 1:1:2 of plasma to platelets to packed red blood cells results in better hemostasis. Anti-fibrinolytic administration to patients with severe bleed within 3 hours of traumatic injury appears to decrease death from major bleed as shown in the CRASH-2 trial. Research on oxygen-carrying substitutes as an alternative to packed red blood cells is ongoing, although no blood substitutes have been approved for use in the United States.
Fluid loss | Hypovolemic shock | Wikipedia | 491 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
For patients in hypovolemic shock due to fluid losses, the exact fluid deficit cannot be determined. Therefore, it is prudent to start with 2 liters of isotonic crystalloid solution infused rapidly as an attempt to quickly restore tissue perfusion. Fluid repletion can be monitored by measuring blood pressure, urine output, mental status, and peripheral edema. Multiple modalities exist for measuring fluid responsiveness such as ultrasound, central venous pressure monitoring, and pulse pressure fluctuation as described above. Vasopressors may be used if blood pressure does not improve with fluids.
Crystalloid fluid resuscitation is preferred over colloid solutions for severe volume depletion not due to bleeding. The type of crystalloid used to resuscitate the patient can be individualized based on the patients' chemistries, estimated volume of resuscitation, acid/base status, and physician or institutional preferences.
Isotonic saline is hyperchloremic relative to blood plasma, and resuscitation with large amounts can lead to hyperchloremic metabolic acidosis. Several other isotonic fluids with lower chloride concentrations exist, such as lactated Ringer's solution or PlasmaLyte. These solutions are often referred to as buffered or balanced crystalloids. Some evidence suggests that patients who need large volume resuscitation may have a less renal injury with restrictive chloride strategies and use of balanced crystalloids. Crystalloid solutions are equally as effective and much less expensive than colloid. Commonly used colloid solutions include those containing albumin or hyperoncotic starch. Studies examining albumin solutions for resuscitation have not shown improved outcomes, while other studies have shown resuscitation with hyper-oncotic starch leads to increased mortality rate and renal failure. Patients in shock can appear cold, clammy, and cyanotic.
Hypothermia increases the mortality rate of patients with hypovolemic shock. It is advised to keep the patient warm for the sake of maintaining the temperatures of all kinds of fluids inside the patient.
Monitoring parameters
Oxygen saturation by pulse oximetry (SpO2).
Respiratory rate.
Pulse rate.
Arterial blood pressure.
Pulse pressure.
Central venous pressure.
Urine output.
Base deficit and/or lactic acid.
Temperature.
Mental state.
Changes in the electrocardiogram.
Prognosis | Hypovolemic shock | Wikipedia | 489 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
If the vital organs are deprived of perfusion for more than just a short time, the prognosis is generally not good. Shock is still a medical emergency characterized by a high mortality rate. Early identification of patients who are likely to succumb to their illness is of utmost importance.
Epidemiology
Blood loss
Trauma remains a leading cause of death worldwide with approximately half of these attributed to hemorrhage. In the United States in 2001, trauma was the third leading cause of death overall, and the leading cause of death in those aged 1 to 44 years. While trauma spans all demographics, it disproportionately affects the young with 40% of injuries occurring in ages 20 to 39 years by one country's account. Of this 40%, the greatest incidence was in the 20 to 24-year-old range.
The preponderance of hemorrhagic shock cases resulting from trauma is high. During one year, one trauma center reported 62.2% of massive transfusions occur in the setting of trauma. The remaining cases are divided among cardiovascular surgery, critical care, cardiology, obstetrics, and general surgery, with trauma utilizing over 75% of the blood products.
As patients age, physiological reserves decrease the likelihood of anticoagulant use increases and the number of comorbidities increases. Due to this, elderly patients are less likely to handle the physiological stresses of hemorrhagic shock and may decompensate more quickly.
Fluid loss
While the incidence of hypovolemic shock from extracellular fluid loss is difficult to quantify, it is known that hemorrhagic shock is most commonly due to trauma. In one study, 62.2% of massive transfusions at a level 1 trauma center were due to traumatic injury. In this study, 75% of the blood products used were related to traumatic injury. Elderly patients are more likely to experience hypovolemic shock due to fluid losses as they have less physiologic reserve.
Hypovolemia secondary to diarrhea and/or dehydration is thought to be predominant in low-income countries. | Hypovolemic shock | Wikipedia | 442 | 959491 | https://en.wikipedia.org/wiki/Hypovolemic%20shock | Biology and health sciences | Cardiovascular disease | Health |
Tennis elbow, also known as lateral epicondylitis is an enthesopathy (attachment point disease) of the origin of the extensor carpi radialis brevis on the lateral epicondyle. It causes pain and tenderness over the bony part of the lateral epicondyle. Symptoms range from mild tenderness to severe, persistent pain. The pain may also extend into the back of the forearm. It usually has a gradual onset, but it can seem sudden and be misinterpreted as an injury.
Tennis elbow is often idiopathic. Its cause and pathogenesis are unknown. It likely involves tendinosis, a degeneration of the local tendon.
It is thought this condition is caused by excessive use of the muscles of the back of the forearm, but this is not supported by evidence. It may be associated with work or sports, classically racquet sports (including paddle sports), but most people with the condition are not exposed to these activities. The diagnosis is based on the symptoms and examination. Medical imaging is not very useful.
Untreated enthesopathy usually resolves in 1–2 years. Treating the symptoms and pain involves medications such as NSAIDS or acetaminophen, a wrist brace, or a strap over the upper forearm. The role of corticosteroid injections as a form of treatment is still debated. Recent studies suggests that corticosteroid injections may delay symptom resolution.
Signs and symptoms
Patients typically feel pain or burning around the outer part of the elbow (lateral epicondyle of the humerus), which can move down the forearm and sometimes up to the upper arm. The pain is worsened by activities that involve wrist extension, such as gripping objects. Pain intensity varies from mild to severe and can be intermittent or constant, significantly impacting daily life. Patients also commonly report grip weakness and difficulty lifting.
Terminology
The term "tennis elbow" is widely used (although informal), but the condition affects non-tennis players. More recently, with the explosive growth of pickleball, the term "pickleball elbow" is frequently used. Historically, the medical term "lateral epicondylitis" was most commonly used for the condition, but "itis" implies inflammation and the condition is not inflammatory. It is also referred to as enthesopathy of the extensor carpi radialis origin. | Tennis elbow | Wikipedia | 491 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Since histological findings reveal noninflammatory tissue, the terms "lateral elbow tendinopathy" and "tendinosis" are suggested. In 2019, a group of international experts suggested that "lateral elbow tendinopathy" was the most appropriate terminology. But a disease of an attachment point (or enthesia) is most accurately referred to as an "enthesopathy."
Causes
The exact cause of lateral epicondylitis remains unclear. However, it is often linked to repetitive microtrauma resulting from excessive gripping, wrist extension, radial deviation, and/or forearm supination.
Traditionally, people have speculated that tennis elbow is a type of repetitive strain injury resulting from tendon overuse and failed healing of the tendon, but there is no evidence of injury or repair, and misinterpretation of painful activities as a source of damage is common.
Pathophysiology
The extensor carpi radialis brevis is the most commonly affected muscle in lateral epicondylitis (LE), along with other extensor carpal muscles. Due to its unique origin, the ECRB tendon is prone to abrasion during elbow movements, leading to repetitive microtrauma.
Lateral epicondylitis was initially considered an inflammatory process, however there is no evidence of inflammation or repair. Therefore, the disorder is more appropriately referred to as tendinosis or tendinopopathy. Tendinosis, a degenerative condition with fibroblasts, abnormal collagen, and increased blood vessels. Repetitive stress causes microtears, scar tissue formation, and biomechanical changes, worsening symptoms over time. | Tennis elbow | Wikipedia | 341 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Recently, successful results of a prospective therapeutic study of tennis elbow were published. It was observed that tennis elbow symptoms were most painful after awakening. It was hypothesized that a very common sleep position was interfering with healing and causing pain. The study evaluated if changing this position would avoid pressure on the lateral elbow while asleep. Patients who changed this sleep position reported successful resolution of symptoms, whereas those who were unable to change continued to have pain. The conclusion reached is that the pathophysiology of tennis elbow is due to an initial microscopic tear from a sprain/strain. This initial injury is aggravated at night by pressure on the sprain which delays healing. In other words, tennis elbow is neither a tendonitis nor a tendinosis, but more like a pressure sore. If the pressure is removed the initial injury goes on to heal. The importance of this finding is that other conditions characterized by nocturnal or early morning symptoms may also be worsened by a “pathological sleep position.” We know this applies to carpal and cubital tunnel syndrome, plantar fasciitis, shoulder/neck pain and Gerd.
Clinical evaluation
Physical examination
Diagnosis is based on symptoms and clinical signs that are discrete and characteristic. For example, the extension of the elbow and flexion of the wrist causes outer elbow pain. The physical examination usually reveals marked tenderness at the origin of the extensor carpi radialis brevis muscle from the lateral epicondyle (extensor carpi radialis brevis origin). Pain may worsen with resisted wrist extension, middle finger extension, and forearm supination with an extended elbow, although normal elbow movement is often maintained, even in severe cases.
Cozen's test
Cozen's test is a physical examination performed to evaluate for tennis elbow involving pain with resisted wrist extension. The test is said to be positive if a resisted wrist extension triggers pain to the lateral aspect of the elbow owing to stress placed upon the tendon of the extensor carpi radialis brevis muscle. The test is performed with extended elbow. NOTE: With elbow flexed the extensor carpi radialis longus is in a shortened position as its origin is the lateral supracondylar ridge of the humerus. To rule out the ECRB (extensor carpi radialis brevis), repeat the test with the elbow in full extension.
Medical imaging
Medical imaging is not necessary or helpful. | Tennis elbow | Wikipedia | 501 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Radiographs (X-rays) may demonstrate calcification where the extensor muscles attach to the lateral epicondyle. Medical ultrasonography and magnetic resonance imaging (MRI) can demonstrate the pathology, but are not helpful for diagnosis and do not influence treatment.
Longitudinal sonogram of the lateral elbow displays thickening and heterogeneity of the common extensor tendon that is consistent with tendinosis, as the ultrasound reveals calcifications, intrasubstance tears, and marked irregularity of the lateral epicondyle. Although the term “epicondylitis” is frequently used to describe this disorder, most histopathologic findings of studies have displayed no evidence of an acute, or a chronic inflammatory process. Histologic studies have demonstrated that this condition is the result of tendon degeneration, which replaces normal tissue with a disorganized arrangement of collagen. Colour Doppler ultrasound reveals structural tendon changes, with vascularity and hypo-echoic areas that correspond to the areas of pain in the extensor origin.
Table of Clinical classification of lateral epicondylitis phases.
Prevention
Activity modification is the best way to prevent the occurrence of lateral epicondylitis. Prevention can include avoiding extreme end range motions in extension and flexion, limit repetitive hand and wrist motions, and modification of heavy lifting with extended arms. Lifestyle factors such as smoking, alcohol drinking, and dietary habits are known to influence the prognosis of various medical conditions. Smokers showed a higher chance of developing lateral epicondylitis compared to non-smokers. Current research indicates that alcohol intake is not significantly associated with lateral epicondylitis.
Treatment
Non-Operative Treatment
Non operative treatment resolves 90% of symptomatic lateral epicondylitis. Nonoperative care usually includes activity modification, physical therapy, non-steroidal anti-inflammatory medications, bracing, extracorporeal shock-wave therapy, and acupuncture. Modifying activity and avoiding overuse are key to treatment. Lifting with the palm up and avoiding palm-down movements can shift strain from the lateral to the medial epicondyle, easing pain. Patients should also improve lifestyle habits and avoid triggering activities. Following the RICE method (rest, ice, compression, elevation) can help relieve pain initially.
Exercises
Stretching and isometric strengthening are the most common recommended exercises.
The muscle is stretched with the elbow straight and the wrist passively flexed. | Tennis elbow | Wikipedia | 504 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Isometric strengthening can be done by pushing the top of the hand up against the undersurface of a table and holding the wrist straight.
Orthotic devices
Orthosis is a device externally used on the limb to improve the function or reduce the pain. Orthotics may be useful in tennis elbow; however, long-term effects are unknown. There are two main types of orthoses prescribed for this problem: counterforce elbow orthoses and wrist extension orthoses. Counterforce orthosis has a circumferential structure surrounding the arm. This orthosis usually has a strap which applies a binding force over the origin of the wrist extensors. The applied force by orthosis reduces the elongation within the musculotendinous fibers. Wrist extensor orthosis maintains the wrist in the slight extension.
Speculative treatments
Other approaches that are not experimentally tested include eccentric exercise using a rubber bar, joint manipulation directed at the elbow and wrist, spinal manipulation directed at the cervical and thoracic spinal regions, low level laser therapy, and extracorporeal shockwave therapy.
Medication
Recent studies demonstrate that topical nonsteroidal anti-inflammatory medications are effective within four weeks for lateral epicondylitis. Evidence for oral NSAIDs is mixed. Research indicates that corticosteroid injections improved outcomes more effectively than NSAIDs within four weeks but offered no long-term benefits at 12 months.
Other studies suggest that, while helpful for short-term pain relief, corticosteroid injections are less effective than watchful waiting or physical therapy after one year. Repeated injections can also lead to tendon rupture and muscle atrophy. Thus, clinicians should be cautious with corticosteroid use for lateral epicondylitis due to limited long-term effectiveness and possible adverse effects.
Alternative Treatments
While many alternative treatments, such as shockwave, laser, low-frequency electrical nerve stimulation, ultrasound, and pulsed magnetic wave therapies, have been used, none have been proven effective. Current evidence is inconclusive on the effectiveness of acupuncture was effective for lateral epicondylitits. | Tennis elbow | Wikipedia | 445 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Platelet-Rich Plasma (PRP) Injections
Platelet-Rich Plasma (PRP) has emerged as a potential treatment for lateral epicondylitis. PRP is derived from the patient's own blood and contains concentrated platelets, which are rich in growth factors. These growth factors are believed to initiate and accelerate tissue repair and regeneration support healing of the tendons and connective tissue and promote the growth of new blood vessels, aiding the recovery process.
The PRP procedure for lateral epicondylitis involves extracting a small amount of the patient's blood, separating the plasma through centrifugation, and re-injecting it directly into the lateral epicondyle. While good outcomes have been reported with PRP for lateral epicondylitis, the overall literature is still unclear on its effectiveness. Additionally, variations in PRP preparation methods and injection techniques across different commercial systems add further complexity to assessing its effectiveness.
Overall, current research on PRP as a treatment for lateral epicondylitis is promising. However, more studies are needed to provide clear evidence of its effectiveness.
Surgery
Most patients with lateral epicondylitis (tennis elbow) improve with conservative treatments and do not need surgery. However, if symptoms persist despite prolonged conservative therapy, surgical options should be reconsidered. Several surgical procedures are available for lateral epicondylitis, most involving the removal of damaged tissue from the ECRB and scraping of the lateral epicondyle. This procedure can be done through open, percutaneous, or arthroscopic methods.
Percutaneous Surgery
Percutaneous surgical approach is mainly used for releasing the common extensor tendon origin at the lateral epicondyle. This technique has been demonstrated to be safe, reliable, and cost-effective Good midterm outcomes in pain relief have been widely reported with a percutaneous surgical approach. However there is some limited evidence reported that arthroscopic and open techniques achieved a better prognosis than the percutaneous surgical approach for the treatment of lateral epicondylitis. In recent years, a new technique termed as ultrasound-guided percutaneous tenotomy has been reported as a safe and effective for the treatment of lateral epicondylitis, with improvements in symptoms, function, and ultrasound imaging at 1-year follow-up. | Tennis elbow | Wikipedia | 472 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Arthroscopic Surgery
Arthroscopic surgery is a minimally invasive option for treating lateral epicondylitis. This technique fully visualizes the elbow joint, and leads to a quicker return to work. In the past, studies have shown good long term effects and fewer complications with arthroscopic surgery compared to open or percutaneous approaches. However, the literature is currently mixed with some recent reviews suggest no significant differences among open, arthroscopic, and percutaneous methods regarding recovery time, complication rates, or patient satisfaction. While others state that arthroscopic surgery may allow for a quicker return to work, suggesting a potential advantage in the early postoperative period. While results are generally positive, arthroscopic surgery carries risks of injury to the radial nerve and lateral ulnar collateral ligament.
Epidemiology
Tennis Elbow is a commonly seen condition and has been reported to affect 1% to 3% of adults each year. The incidence of lateral elbow tendinosis has declined, which could be due to shifts in diagnostic practices or an actual drop in cases. Understanding the typical disease progression can help patients and providers choose the best treatment approach.
Symptoms of lateral epicondylitis
Symptoms suggestive of lateral epicondylitis are present in about 1% of the adult population and are most common between ages 40 and 60. The prevalence varies somewhat between studies, likely as a result of varied diagnostic criteria and limited reliability between different observers. The data regarding symptoms of lateral epicondylitis in relation to occupations and sports are inconsistent and inconclusive. The shortcomings of the evidence that addresses the relationship between symptoms and occupation/sport include: variation in diagnostic criteria, limited reliability of diagnosis, confounding association of psychosocial factors, selection bias due to a high non-response rate, and the fact that exposures are usually by subjective patient reports and symptomatic patients might receive greater exposure.
History
German physician F. Runge is usually credited for the first description of the condition, calling it "writer's cramp" (Schreibekrampf) in 1873. Later, it was called as "washer women's elbow". British surgeon Henry Morris published an article in The Lancet describing "lawn tennis arm" in 1883. The popular term "tennis elbow" first appeared the same year in a paper by H. P. Major, described as "lawn-tennis elbow". | Tennis elbow | Wikipedia | 496 | 960460 | https://en.wikipedia.org/wiki/Tennis%20elbow | Biology and health sciences | Types | Health |
Messier 22 or M22, also known as NGC 6656 or the Great Sagittarius Cluster, is an elliptical globular cluster of stars in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars visible in the night sky. The brightest stars are 11th magnitude, with hundreds of stars bright enough to resolve with an 8" telescope. It is just south of the sun's position in mid-December, and northeast of Lambda Sagittarii (Kaus Borealis), the northernmost star of the "Teapot" asterism.
M22 was one of the first globulars to be discovered, in 1665 by Abraham Ihle and it was included in Charles Messier's catalog of comet-like objects in 1764. It was one of the first globular clusters to be carefully studied – first by Harlow Shapley in 1930. He placed within it roughly 70,000 stars and found it had a dense core. Then Halton Arp and William G. Melbourne continued studies in 1959. Due to the large color spread of its red giant branch (RGB) sequence, akin to that in Omega Centauri, it became the object of intense scrutiny starting in 1977 with James E. Hesser et al.
M22 is one of the nearer globular clusters to Earth – at about 10,600 light-years away. It spans 32′ on the sky which means its diameter (width across) is 99 ± 9 light-years, given its estimated distance. 32 variable stars have been recorded in M22. It is in front of part of the galactic bulge and is therefore useful for its microlensing effect on those background stars.
Despite its relative proximity to us, this metal-poor cluster's light is limited by dust extinction, giving it an apparent magnitude of 5.5; even so, it is the brightest globular cluster visible from mid-northern latitudes (such as Japan, Korea, Europe and most of North America). From those latitudes due to its declination of nearly 24° south of the (celestial) equator, its daily path is low in the southern sky. It thus appears less impressive to people in the temperate northern hemisphere than counterparts fairly near in angle (best viewed in the Summer night sky) such as M13 and M5. | Messier 22 | Wikipedia | 485 | 960596 | https://en.wikipedia.org/wiki/Messier%2022 | Physical sciences | Notable star clusters | Astronomy |
M22 is one of only four globulars of our galaxy known to contain a planetary nebula (an expanding, glowing gas swell from a massive star, often a red giant). It was an object first noted of interest using the IRAS satellite by Fred Gillett and his associates in 1986, as a pointlike light source and its nature was found in 1989 by Gillett et al. The planetary nebula's central star is a blue star. The nebula, designated GJJC1, is likely about only 6,000 years old.
Two black holes of between 10 and 20 solar masses () each were unearthed with the Very Large Array radio telescope in New Mexico and corroborated by the Chandra X-ray telescope in 2012. These imply that gravitational ejection of black holes from clusters is not as efficient as was previously thought, and leads to estimates of a total 5 to 100 black holes within M22. Interactions between stars and black holes could explain the unusually large core of the cluster.
Gallery | Messier 22 | Wikipedia | 206 | 960596 | https://en.wikipedia.org/wiki/Messier%2022 | Physical sciences | Notable star clusters | Astronomy |
Nitrous oxide, as medical gas supply, is an inhaled gas used as pain medication, and is typically administered with 50% oxygen mix. It is often used together with other medications for anesthesia. Common uses include during childbirth, following trauma, and as part of end-of-life care. Onset of effect is typically within half a minute, and the effect lasts for about a minute.
Nitrous oxide was discovered between 1772 and 1793 and used for anesthesia in 1844. It is on the World Health Organization's List of Essential Medicines. It often comes as a 50/50 mixture with oxygen. Devices with a demand valve are available for self-administration. The setup and maintenance is relatively expensive for developing countries.
There are few side effects, other than vomiting, with short-term use. With long-term use anemia or numbness may occur. It should always be given with at least 21% oxygen. It is not recommended in people with a bowel obstruction or pneumothorax. Use in the early part of pregnancy is not recommended. It is possible to continue breastfeeding following use.
History
Pure N2O was first used as a medical analgesic in December 1844, when Horace Wells made the first 12–15 dental operations with the gas in Hartford.
Its debut as a generally accepted method, however, came in 1863, when Gardner Quincy Colton introduced it more broadly at all the Colton Dental Association clinics, that he founded in New Haven and New York City.
The first devices used in dentistry to administer the gas consisted of a simple breathing bag made of rubber cloth.
Breathing the pure gas often caused hypoxia (oxygen insufficiency) and sometimes death by asphyxiation. Eventually practitioners became aware of the need to provide at least 21% oxygen content in the gas (the same percentage as in air). In 1911, the anaesthetist Arthur Ernest Guedel first described the use of self-administration of a nitrous oxide and oxygen mix. It was not until 1961 that the first paper was published by Michael Tunstall and others, describing the administration of a pre-mixed 50:50 nitrous oxide and oxygen mix, which led to the commercialisation of the product. | Nitrous oxide (medication) | Wikipedia | 458 | 960789 | https://en.wikipedia.org/wiki/Nitrous%20oxide%20%28medication%29 | Biology and health sciences | Anesthetics | Health |
In 1970, Peter Baskett recognised that pre-mixed nitrous oxide and oxygen mix could have an important part to play in the provision of pre-hospital pain relief management, provided by ambulance personnel. Baskett contacted the Chief Ambulance Officer for the Gloucestershire Ambulance Brigade, Alan Withnell, to suggest this idea. This gained traction when Baskett negotiated with the British Oxygen Company, the availability of pre-mixed nitrous oxide and oxygen mix apparatus for training. Regular training sessions began at Frenchay Hospital (Bristol) and a pilot study was run in Gloucestershire (in which ambulances were crewed by a driver and one of the new highly trained ambulance men), the results of this trial were published in 1970.
Today the nitrous oxide is administered in hospitals by a relative analgesia machine, which includes several improvements such as flowmeters and constant-flow regulators, an anaesthetic vaporiser, a medical ventilator, and a scavenger system, and delivers a precisely dosed and breath-actuated flow of nitrous oxide mixed with oxygen.
The machine used in dentistry is much simpler, and is meant to be used by the patient in a fully conscious state. The gas is delivered through a demand-valve inhaler over the nose, which will only release gas when the patient inhales through it.
Medical uses
Nitrous oxide (N2O) is itself active (does not require any changes in the body to become active), and so has an onset in roughly the lung–brain circulation time with peak action 30 seconds after the start of administration. It is removed from the body unchanged via the lungs, and does not accumulate under normal conditions, explaining the rapid offset of around 60 seconds. It is effective in managing pain during labor and delivery.
Nitrous oxide has been shown to be an effective and safe treatment for alcohol withdrawal.
Nitrous oxide is more soluble than oxygen and nitrogen, so will tend to diffuse into any air spaces within the body. This makes it dangerous to use in patients with pneumothorax or those who have recently been scuba diving, and there are cautions over its use with any bowel obstruction.
Its analgesic effect is strong (equivalent to 15 mg of subcutaneous route morphine) and characterised by rapid onset and offset, i.e. it is very fast-acting and wears off very quickly. | Nitrous oxide (medication) | Wikipedia | 488 | 960789 | https://en.wikipedia.org/wiki/Nitrous%20oxide%20%28medication%29 | Biology and health sciences | Anesthetics | Health |
When used in combination with other anesthetics gases, nitrous oxide causes a dose dependent increased respiratory rate and decreased tidal volumes, the net effect is a lower minute ventilation. Like volatile anesthetics, it increases cerebral blood flow and intracranial pressure. However, contrary to volatile anesthetics, it leads to an increase in cerebral metabolic rate of oxygen.
Contraindications
N2O should not be used in patients with bowel obstruction, pneumothorax, or middle ear or sinus disease, or who have had a recent intraocular injection of gas and should also not be used on any patient who has been scuba diving within the preceding 24 hours or in violently disturbed psychiatric patients.
There are also clinical cautions in place for the first two trimesters of pregnancy and in patients with decreased levels of consciousness.
Composition
The gas is a mixture of half nitrous oxide (N2O) and half oxygen (O2). The ability to combine N2O and oxygen at high pressure while remaining in the gaseous form is caused by the Poynting effect (after John Henry Poynting, an English physicist).
The Poynting effect involves the dissolution of gaseous O2 when bubbled through liquid N2O, with vaporisation of the liquid to form a gaseous O2/N2O mixture.
Inhalation of pure N2O over a continued period would deprive the patient of oxygen, but the 50% oxygen content prevents this from occurring. The two gases will separate at low temperatures (<4 °C), which would permit administration of hypoxic mixtures. Therefore, it is not given from a cold cylinder without being shaken (usually by cylinder inversion) to remix the gases.
Administration
The gas is self-administered through a demand valve, using a mouthpiece, bite block or face mask. Self-administration of Entonox is safe because if enough is inhaled to start to induce anaesthesia, the patient becomes unable to hold the valve, and so will drop it and soon exhale the residual gas. This means that unlike other anaesthetic gases, it does not require the presence of an anaesthetist for administration. The 50% oxygen in Entonox ensures the person will have sufficient oxygen in their alveoli and conducting airways for a short period of apnea to be safe.
Mechanism of action | Nitrous oxide (medication) | Wikipedia | 490 | 960789 | https://en.wikipedia.org/wiki/Nitrous%20oxide%20%28medication%29 | Biology and health sciences | Anesthetics | Health |
The pharmacological mechanism of action of in medicine is not fully known. However, it has been shown to directly modulate a broad range of ligand-gated ion channels, and this likely plays a major role in many of its effects. It moderately blocks NMDAR and β-subunit-containing nACh channels, weakly inhibits AMPA, kainate, GABA and 5-HT receptors, and slightly potentiates GABA and glycine receptors. It also has been shown to activate two-pore-domain channels. While affects quite a few ion channels, its anesthetic, hallucinogenic and euphoriant effects are likely caused predominantly, or fully, via inhibition of NMDA receptor-mediated currents. In addition to its effects on ion channels, may act to imitate nitric oxide (NO) in the central nervous system, and this may be related to its analgesic and anxiolytic properties. Nitrous oxide is 30 to 40 times more soluble than nitrogen.
Society and culture
Nitronox was a registered trademark of the BOC Group between 1966 and 1999, and was reregistered by Hs Tm Inc since 2005 It is also colloquially known as "gas and air" in the United Kingdom.
Research
Investigational trials show potential for antidepressant applications of N2O, especially for treatment-resistant forms of depression, and it is rapid-acting. In a phase 2 clinical trial, a treatment with 25% nitrous oxide had comparable efficacy to 50% nitrous oxide but was associated with significantly fewer adverse effects. | Nitrous oxide (medication) | Wikipedia | 326 | 960789 | https://en.wikipedia.org/wiki/Nitrous%20oxide%20%28medication%29 | Biology and health sciences | Anesthetics | Health |
Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".
Hot Jupiters are the easiest extrasolar planets to detect via the radial-velocity method, because the oscillations they induce in their parent stars' motion are relatively large and rapid compared to those of other known types of planets. One of the best-known hot Jupiters is . Discovered in 1995, it was the first extrasolar planet found orbiting a Sun-like star. has an orbital period of about four days.
General characteristics | Hot Jupiter | Wikipedia | 152 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Though there is diversity among hot Jupiters, they do share some common properties.
Their defining characteristics are their large masses and short orbital periods, spanning 0.36–11.8 Jupiter masses and 1.3–111 Earth days. The mass cannot be greater than approximately 13.6 Jupiter masses because then the pressure and temperature inside the planet would be high enough to cause deuterium fusion, and the planet would be a brown dwarf.
Most have nearly circular orbits (low eccentricities). It is thought that their orbits are circularized by perturbations from nearby stars or tidal forces. Whether they remain in these circular orbits for long periods of time or collide with their host stars depends on the coupling of their orbital and physical evolution, which are related through the dissipation of energy and tidal deformation.
Many have unusually low densities. The lowest one measured thus far is that of TrES-4b at 0.222 g/cm3. The large radii of hot Jupiters are not yet fully understood but it is thought that the expanded envelopes can be attributed to high stellar irradiation, high atmospheric opacities, possible internal energy sources, and orbits close enough to their stars for the outer layers of the planets to exceed their Roche limit and be pulled further outward.
Usually they are tidally locked, with one side always facing its host star.
They are likely to have extreme and exotic atmospheres due to their short periods, relatively long days, and tidal locking.
Atmospheric dynamics models predict strong vertical stratification with intense winds and super-rotating equatorial jets driven by radiative forcing and the transfer of heat and momentum. Recent models also predict a variety of storms (vortices) that can mix their atmospheres and transport hot and cold regions of gas.
The day-night temperature difference at the photosphere is predicted to be substantial, approximately for a model based on HD 209458 b.
They appear to be more common around F- and G-type stars and less so around K-type stars. Hot Jupiters around red dwarfs are very rare. Generalizations about the distribution of these planets must take into account the various observational biases, but in general their prevalence decreases exponentially as a function of the absolute stellar magnitude. | Hot Jupiter | Wikipedia | 461 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Formation and evolution
There are three schools of thought regarding the possible origin of hot Jupiters. One possibility is that they were formed in situ at the distances at which they are currently observed. Another possibility is that they were formed at a distance but later migrated inward. Such a shift in position might occur due to interactions with gas and dust during the solar nebula phase. It might also occur as a result of a close encounter with another large object destabilizing a Jupiter's orbit.
Migration
In the migration hypothesis, a hot Jupiter forms beyond the frost line, from rock, ice, and gases via the core accretion method of planetary formation. The planet then migrates inwards to the star where it eventually forms a stable orbit. The planet may have migrated inward smoothly via type II orbital migration. Or it may have migrated more suddenly due to gravitational scattering onto eccentric orbits during an encounter with another massive planet, followed by the circularization and shrinking of the orbits due to tidal interactions with the star. A hot Jupiter's orbit could also have been altered via the Kozai mechanism, causing an exchange of inclination for eccentricity resulting in a high eccentricity low perihelion orbit, in combination with tidal friction. This requires a massive body—another planet or a stellar companion—on a more distant and inclined orbit; approximately 50% of hot Jupiters have distant Jupiter-mass or larger companions, which can leave the hot Jupiter with an orbit inclined relative to the star's rotation.
The type II migration happens during the solar nebula phase, i.e. when gas is still present. Energetic stellar photons and strong stellar winds at this time remove most of the remaining nebula. Migration via the other mechanism can happen after the loss of the gas disk. | Hot Jupiter | Wikipedia | 354 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
In situ
Instead of being gas giants that migrated inward, in an alternate hypothesis the cores of the hot Jupiters began as more common super-Earths which accreted their gas envelopes at their current locations, becoming gas giants in situ. The super-Earths providing the cores in this hypothesis could have formed either in situ or at greater distances and have undergone migration before acquiring their gas envelopes. Since super-Earths are often found with companions, the hot Jupiters formed in situ could also be expected to have companions. The increase of the mass of the locally growing hot Jupiter has a number of possible effects on neighboring planets. If the hot Jupiter maintains an eccentricity greater than 0.01, sweeping secular resonances can increase the eccentricity of a companion planet, causing it to collide with the hot Jupiter. The core of the hot Jupiter in this case would be unusually large. If the hot Jupiter's eccentricity remains small the sweeping secular resonances could also tilt the orbit of the companion. Traditionally, the in situ mode of conglomeration has been disfavored because the assembly of massive cores, which is necessary for the formation of hot Jupiters, requires surface densities of solids ≈ 104 g/cm2, or larger. Recent surveys, however, have found that the inner regions of planetary systems are frequently occupied by super-Earth type planets. If these super-Earths formed at greater distances and migrated closer, the formation of in situ hot Jupiters is not entirely in situ.
Atmospheric loss
If the atmosphere of a hot Jupiter is stripped away via hydrodynamic escape, its core may become a chthonian planet. The amount of gas removed from the outermost layers depends on the planet's size, the gases forming the envelope, the orbital distance from the star, and the star's luminosity. In a typical system, a gas giant orbiting at 0.02 AU around its parent star loses 5–7% of its mass during its lifetime, but orbiting closer than 0.015 AU can mean evaporation of a substantially larger fraction of the planet's mass. No such objects have been found yet and they are still hypothetical. | Hot Jupiter | Wikipedia | 445 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Terrestrial planets in systems with hot Jupiters
Simulations have shown that the migration of a Jupiter-sized planet through the inner protoplanetary disk (the region between 5 and 0.1 AU from the star) is not as destructive as expected. More than 60% of the solid disk materials in that region are scattered outward, including planetesimals and protoplanets, allowing the planet-forming disk to reform in the gas giant's wake. In the simulation, planets up to two Earth masses were able to form in the habitable zone after the hot Jupiter passed through and its orbit stabilized at 0.1 AU. Due to the mixing of inner-planetary-system material with outer-planetary-system material from beyond the frost line, simulations indicated that the terrestrial planets that formed after a hot Jupiter's passage would be particularly water-rich. According to a 2011 study, hot Jupiters may become disrupted planets while migrating inwards; this could explain an abundance of "hot" Earth-sized to Neptune-sized planets within 0.2 AU of their host star.
One example of these sorts of systems is that of WASP-47. There are three inner planets and an outer gas giant in the habitable zone. The innermost planet, WASP-47e, is a large terrestrial planet of 6.83 Earth masses and 1.8 Earth radii; the hot Jupiter, b, is little heavier than Jupiter, but about 12.63 Earth radii; a final hot Neptune, c, is 15.2 Earth masses and 3.6 Earth radii. A similar orbital architecture is also exhibited by the Kepler-30 system. | Hot Jupiter | Wikipedia | 334 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Misaligned orbits
Several hot Jupiters, such as HD 80606 b, have orbits that are misaligned with their host stars, including several with retrograde orbits such as HAT-P-14b. This misalignment may be related to the heat of the photosphere the hot Jupiter is orbiting. There are several proposed hypotheses as to why this might occur. One such hypothesis involves tidal dissipation and suggests there is a single mechanism for producing hot Jupiters and this mechanism yields a range of obliquities. Cooler stars with higher tidal dissipation damps the obliquity (explaining why hot Jupiters orbiting cooler stars are well aligned) while hotter stars do not damp the obliquity (explaining the observed misalignment). Another hypothesis is that the host star sometimes changes rotation early in its evolution, rather than the orbit changing. Yet another hypothesis is that hot Jupiters tend to form in dense clusters, where perturbations are more common and gravitational capture of planets by neighboring stars is possible.
Ultra-hot Jupiters
Ultra-hot Jupiters are hot Jupiters with a dayside temperature greater than . In such dayside atmospheres, most molecules dissociate into their constituent atoms and circulate to the nightside where they recombine into molecules again.
One example is TOI-1431b, announced by the University of Southern Queensland in April 2021, which has an orbital period of just two and a half days. Its dayside temperature is , making it hotter than 40% of stars in our galaxy. The nightside temperature is .
Ultra-short period planets
Ultra-short period planets (USP) are a class of planets with orbital periods below one day and occur only around stars of less than about 1.25 solar masses.
Confirmed transiting hot Jupiters that have orbital periods of less than one day include WASP-18b, Banksia, Astrolábos and WASP-103b. | Hot Jupiter | Wikipedia | 406 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Puffy planets
Gas giants with a large radius and very low density are sometimes called "puffy planets" or "hot Saturns", due to their density being similar to Saturn's. Puffy planets orbit close to their stars so that the intense heat from the star combined with internal heating within the planet will help inflate the atmosphere. Six large-radius low-density planets have been detected by the transit method. In order of discovery they are: HAT-P-1b, CoRoT-1b, TrES-4b, WASP-12b, WASP-17b, and Kepler-7b. Some hot Jupiters detected by the radial-velocity method may be puffy planets. Most of these planets are around or below Jupiter mass as more massive planets have stronger gravity keeping them at roughly Jupiter's size. Indeed, hot Jupiters with masses below Jupiter, and temperatures above 1800 Kelvin, are so inflated and puffed out that they are all on unstable evolutionary paths which eventually lead to Roche-Lobe overflow and the evaporation and loss of the planet's atmosphere.
Even when taking surface heating from the star into account, many transiting hot Jupiters have a larger radius than expected. This could be caused by the interaction between atmospheric winds and the planet's magnetosphere creating an electric current through the planet that heats it up, causing it to expand. The hotter the planet, the greater the atmospheric ionization, and thus the greater the magnitude of the interaction and the larger the electric current, leading to more heating and expansion of the planet. This theory matches the observation that planetary temperature is correlated with inflated planetary radii.
Moons
Theoretical research suggests that hot Jupiters are unlikely to have moons, due to both a small Hill sphere and the tidal forces of the stars they orbit, which would destabilize any satellite's orbit, the latter process being stronger for larger moons. This means that for most hot Jupiters, stable satellites would be small asteroid-sized bodies. Furthermore, the physical evolution of hot Jupiters can determine the final fate of their moons: stall them in semi-asymptotic semimajor axes, or eject them from the system where they may undergo other unknown processes. In spite of this, observations of WASP-12b suggest that it is orbited by at least one large exomoon. | Hot Jupiter | Wikipedia | 480 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Hot Jupiters around red giants
It has been proposed that gas giants orbiting red giants at distances similar to that of Jupiter could be hot Jupiters due to the intense irradiation they would receive from their stars. It is very likely that in the Solar System Jupiter will become a hot Jupiter after the transformation of the Sun into a red giant. The recent discovery of particularly low-density gas giants orbiting red giant stars supports this hypothesis.
Hot Jupiters orbiting red giants would differ from those orbiting main-sequence stars in a number of ways, most notably the possibility of accreting material from the stellar winds of their stars and, assuming a fast rotation (not tidally locked to their stars), a much more evenly distributed heat with many narrow-banded jets. Their detection using the transit method would be much more difficult due to their tiny size compared to the stars they orbit, as well as the long time needed (months or even years) for one to transit their star as well as to be occulted by it.
Star–planet interactions
Theoretical research since 2000 suggested that "hot Jupiters" may cause increased flaring due to the interaction of the magnetic fields of the star and its orbiting exoplanet, or because of tidal forces between them. These effects are called "star–planet interactions" or SPIs. The HD 189733 system is the best-studied exoplanet system where this effect was thought to occur. | Hot Jupiter | Wikipedia | 288 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
In 2008, a team of astronomers first described how as the exoplanet orbiting HD 189733 A reaches a certain place in its orbit, it causes increased stellar flaring. In 2010, a different team found that every time they observe the exoplanet at a certain position in its orbit, they also detected X-ray flares. In 2019, astronomers analyzed data from Arecibo Observatory, MOST, and the Automated Photoelectric Telescope, in addition to historical observations of the star at radio, optical, ultraviolet, and X-ray wavelengths to examine these claims. They found that the previous claims were exaggerated and the host star failed to display many of the brightness and spectral characteristics associated with stellar flaring and solar active regions, including sunspots. Their statistical analysis also found that many stellar flares are seen regardless of the position of the exoplanet, therefore debunking the earlier claims. The magnetic fields of the host star and exoplanet do not interact, and this system is no longer believed to have a "star-planet interaction." Some researchers had also suggested that HD 189733 accretes, or pulls, material from its orbiting exoplanet at a rate similar to those found around young protostars in T Tauri star systems. Later analysis demonstrated that very little, if any, gas was accreted from the "hot Jupiter" companion. | Hot Jupiter | Wikipedia | 285 | 961349 | https://en.wikipedia.org/wiki/Hot%20Jupiter | Physical sciences | Planetary science | Astronomy |
Lip balm or lip salve is a wax-like substance applied to the lips to moisturize and relieve chapped or dry lips, angular cheilitis, stomatitis, or cold sores. Lip balm often contains beeswax or carnauba wax, camphor, cetyl alcohol, lanolin, paraffin, and petrolatum, among other ingredients. Some varieties contain dyes, flavor, fragrance, phenol, salicylic acid, and sunscreen.
Overview
The primary purpose of lip balm is to provide an occlusive layer on the lip surface to seal moisture in lips and protect them from external exposure. Dry air, cold temperatures, and wind all have a drying effect on skin by drawing moisture away from the body. Lips are particularly vulnerable because the skin is so thin, and thus they are often the first to present signs of dryness. Occlusive materials like waxes and petroleum jelly prevent moisture loss and maintain lip comfort while flavorings, colorants, sunscreens, and various medicaments can provide additional, specific benefits. Lip balms are produced from bee wax and natural candelilla and carnauba waxes.
Lip balm can be applied by a finger to the lips, or in a lipstick-style tube from which it can be applied directly.
In 2022, the global lip balm market was valued at US$732.76 mln. The market is predicted to grow at a rate of 9.28% within the next five years and is likely to reach US$1247.74 mln by 2027.
Production
Production for lip balms includes the following stages:
Raw materials are checked for its quality (cosmetic products must comply with strict safety standards)
The ingredients are dosed, melted, and mixed (this stage involves special equipment)
This mixture is treated in a vacuum to remove bubbles
The mixture is crystallized for about 48 hours
The mixture is then remelted
The mixture is cut into pieces which are shaped as required
The lip balm is packaged into a casing
History
Early lip balms
Since 40 BC, the Egyptians made treatment for lip care, which was made with a mixture of beeswax, olive oil, and animal fat. | Lip balm | Wikipedia | 460 | 961611 | https://en.wikipedia.org/wiki/Lip%20balm | Biology and health sciences | Hygiene products | Health |
United States
In the 1800s, Lydia Maria Child recommended earwax as a treatment for cracked lips in her highly-popular book, Child observed that, "Those who are troubled with cracked lips have found this earwax remedy successful when others have failed. It is one of those sorts of cures, which are very likely to be laughed at; but I know of its having produced very beneficial results." The invention of the lip balm was first formally invented in the 1880s by physician Charles Brown Fleet though its origins may be traced to earwax. Fleet later named his lip balm product "ChapStick".
In 1872, chemist Robert Chesebrough discovered and sampled a new petroleum jelly, initially describing it as a "natural, waxy ingredient, rich in minerals from deep within the earth" which could be used as a solution for skin repair. He then distributed his product under the name "Wonder Jelly" before shortly changing it to "Vaseline".
In the early 1880s, Charles Brown Fleet created ChapStick. However, due to the lack of sales, Fleet sold his formula and rights to ChapStick to John Morton in 1912 for $5, who saw the marketing potential in the brand. After making the purchase, Morton commissioned Frank Wright, Jr. to create a design for the logo of ChapStick for $15 in 1936. In 1972, ChapStick tubes concealing hidden microphones were used during the Watergate scandal.
In 1937, Alfred Woelbing created Carmex to treat cold sores in Milwaukee, though the occurrence of World War 2 would slow the production and sales due to the lack of lanolin. In 1980, Carmex underwent a product change by converting its packaging into squeezable tubes.
In 1973, Bonne Bell created the first flavored lip balm and marketed the company as Lip Smackers. The company would later collaborate on various different-flavored lip balms including Dr. Pepper in 1975, The Wrigley Company in 2004, and The Coca-Cola Company in 2006. Bonne Bell also collaborated with Disney to produce lip balms with various princess characters in 2010.
In 1991, Burt Shavitz and Roxanne Quimby created their first beeswax based lip balm solution through their company, Burt's Bees. In 2020, it was reported that Burt's Bees had used 50 percent of recycled material to package various products and that 100 percent of the products were recyclable. | Lip balm | Wikipedia | 506 | 961611 | https://en.wikipedia.org/wiki/Lip%20balm | Biology and health sciences | Hygiene products | Health |
In 2011, Evolution of Smooth (or commonly known as EOS) created a spherical-shaped lip balm as well as describing its 95% organic ingredients.
Cannabis infused lip balms
With the gradual legalization of cannabis in the United States, some companies have produced lip balms containing doses of THC or CBD oil. The lip balms were infused with a low dosage of THC in order to prevent the occurrence of any psychoactive or related effect.
Notable brands
Burt's Bees
Blistex
Carmex
ChapStick
Labello
Lip Smacker
Lypsyl
EOS
Vaseline
Aquaphor
Nivea
Dependency
Addictive ingredients
Some physicians have suggested that certain types of lip balm can be addictive or contain ingredients that actually cause drying, the accuracy of which has been debated by many professionals. Lip balm manufacturers sometimes state in their FAQs that there is nothing addictive in their products or that all ingredients are listed and approved by the FDA. Snopes found the claim that there are substances in Carmex that are irritants necessitating reapplication, such as ground glass, to be false. However, some experts such as dermatologist Dr. Cynthia Bailey state that some ingredients in lip balm directly causes sensitive lip skin which may lead to addiction. Dermatology professor Marcia Driscoll also adds onto this argument by stating that aroma ingredients found in flavored or scented lip balms have the potential to irritate skin.
Causes for Dependency
According to a report, professor Brad Rohu states that it is natural for the lips to feel dry. The exposure to environments with cold, dry, or windy weather can directly cause the chapping of the lips as well as behaviors such as lip licking or mouth breathing. These factors may directly contribute to an increased amount of lip balm usage. According to dermatologist Amy Derick, those who have expressed dependencies on lip balm have developed a desire of how the lips feel after application. She also mentions that the variety of lip balm flavor may also directly cause lip balm dependency as a person may want to lick their lips to taste the flavor, which may consequentially remove the lip balm coating from the lips. This may also leave saliva on the lips which can dry up and make the lips feel even more dry than they initially were. | Lip balm | Wikipedia | 480 | 961611 | https://en.wikipedia.org/wiki/Lip%20balm | Biology and health sciences | Hygiene products | Health |
Effects on lip barrier
The human lips have an inadequate capability of holding moisture as well as an imperfect lip barrier function. The Journal of the American Academy of Dermatology performed a study in order to determine whether consistent use of lip balm would enhance the overall quality of the lips. The study used 32 female participants within the ages of 20 to 40 years and the participants had mild to moderate dried lips without any history of health-related complications. The participants underwent a procedure in which no lip treatment was provided on the first 3 days, then 2 weeks of consistent lip balm usage, and then a period of no treatment for 3 days. The study determined the quality of the lips based on the physical details and appearance throughout the study. The study showed a direct improvement of the physical details of the lips except for lip cracking during the second week of treatment and after the period of no treatment. The study also showed that hydration of the lips lasted for approximately 8 hours after usage and the lip balm improved the lip barrier function despite discontinued usage. The study concluded that lip balms assist the hydration of the lips which consequentially improves the lip barrier function and the quality. This study was completely funded by Burt's Bees, a lip balm company.
Mineral oil
In 2015, German consumer watchdog Stiftung Warentest analyzed cosmetics containing mineral oils. After developing a new detection method they found high concentrations of Mineral Oil Aromatic Hydrocarbons (MOAH) and even polyaromatics in products containing mineral oils with Vaseline products containing the most MOAH of all tested cosmetics (up to 9%). The European Food Safety Authority sees MOAH and polyaromatics as possibly carcinogenic. Based on the results, Stiftung Warentest warns not to use Vaseline or any product that is based on mineral oils for lip care.
Lip balm market
United States
In 2019, a research report conducted by the Statista Research Department concluded that ChapStick was the leading lip balm brand in the United States with an approximate unit sale of 55.8 million. Carmex was the second leading brand with approximately 35.2 million units sold and Burt's Bees being the third leading brand with approximately 32.3 million units sold.
Trends
Beezin' | Lip balm | Wikipedia | 461 | 961611 | https://en.wikipedia.org/wiki/Lip%20balm | Biology and health sciences | Hygiene products | Health |
Beezin' is a trend dating back to 2013 in which a person applies Burt's Bees brand lip balm onto the eyelids. The practice is done in order to feel a sensation of being high or drunk, and even to increase the desired effects of alcohol and other substances. In 2022, Beezin' became a viral trend on the social media platform TikTok. Some ingredients, including peppermint oil, are known to be eye irritants which can cause an unintentional inflammatory response which may require treatment and may also cause dermatitis on the eyelids. | Lip balm | Wikipedia | 118 | 961611 | https://en.wikipedia.org/wiki/Lip%20balm | Biology and health sciences | Hygiene products | Health |
The Malayan tapir (Tapirus indicus), also called Asian tapir, Asiatic tapir, oriental tapir, Indian tapir, piebald tapir, or black-and-white tapir, is the only living tapir species outside of the Americas. It is native to Southeast Asia from the Malay Peninsula to Sumatra. It has been listed as Endangered on the IUCN Red List since 2008, as the population is estimated to comprise fewer than 2,500 mature individuals.
Taxonomy
The scientific name Tapirus indicus was proposed by Anselme Gaëtan Desmarest in 1819 who referred to a tapir described by Pierre-Médard Diard.
Tapirus indicus brevetianus was coined by a Dutch zoologist in 1926 who described a black Malayan tapir from Sumatra that had been sent to Rotterdam Zoo in the early 1920s.
Phylogenetic analyses of 13 Malayan tapirs showed that the species is monophyletic.
It was placed in the genus Acrocodia by Colin Groves and Peter Grubb in 2011. However, a comparison of mitochondrial DNA of 16 perissodactyl species revealed that the Malayan tapir forms a sister group together with the Tapirus species native to the Americas. It was the first Tapirus species that genetically diverged from the group, estimated about in the Late Oligocene.
Description
The Malayan tapir is easily identified by its markings, most notably the light-colored patch that extends from its shoulders to its hindquarters. Black hair covers its head, shoulders, and legs, while white hair covers its midsection, rear, and the tips of its ears; these white edges around the rims of the outer ear as is true of other tapirs. The disrupted coloration breaks up its outline, providing camouflage by making the animal difficult to recognize against the varied terrain and dense flora of its habitat; potential predators may mistake it for a large rock, rather than prey, when it is lying down to sleep. | Malayan tapir | Wikipedia | 404 | 961680 | https://en.wikipedia.org/wiki/Malayan%20tapir | Biology and health sciences | Perissodactyla | Animals |
The Malayan tapir is the largest of the four extant tapir species and grows to between in length, not counting a stubby tail of only in length, and stands tall. It typically weighs between , although some adults can weigh up to . The females are usually larger than the males. Like other tapir species, it has a small, stubby tail and a long, flexible proboscis. It has four toes on each front foot and three toes on each back foot. The Malayan tapir has rather poor eyesight, but excellent hearing and sense of smell.
The tapir's unique proboscis is supported by several evolutionary adaptations of its skull. It has a large sagittal crest, unusually positioned orbits, an unusually shaped cranium with elevated frontal bones, and a retracted nasal incision as well as retracted facial cartilage. This evolutionary process is believed to have caused the loss of some cartilages, facial muscles, and the bony wall of the tapir's nasal chamber.
Vision
Malayan tapirs have very poor eyesight, both on land and in water, instead relying heavily on their excellent senses of smell and hearing to navigate and forage. Their eyes are small and, like many herbivores, positioned on the sides of the face. They have brown irises, but the corneas are often covered in a blue haze; this corneal cloudiness is thought to be caused by repetitive exposure to light. This loss of transparency impacts the ability of the cornea to transmit and focus outside light as it enters the eye, impairing the animal's overall vision. As these tapirs are most active at night on top of having poor eyesight, this habit may make it harder for them to search for food and avoid predators.
Color variation
Two melanistic Malayan tapirs were observed in Jerangau Forest Reserve in Malaysia in 2000. A black Malayan tapir was also recorded in Tekai Tembeling Forest Reserve in Pahang state in 2016.
Distribution and habitat
The Malayan tapir lives throughout the tropical lowland rainforests of Southeast Asia, including Sumatra in Indonesia, Peninsular Malaysia, Myanmar, and Thailand. | Malayan tapir | Wikipedia | 442 | 961680 | https://en.wikipedia.org/wiki/Malayan%20tapir | Biology and health sciences | Perissodactyla | Animals |
Pleistocene fossils were found in Java and other locations accompanied by herbivores more typical of grasslands, indicating that it evolved in more open habitats and retreated to closed forests in later times. It was found in Borneo until at least 8,000 years ago during the early Holocene in the Niah Caves of Sarawak, and some 19th century writers mentioned it as a contemporary species in Borneo, likely based on native accounts. It has been proposed to reintroduce the tapir to the island as a conservation measure.
In the continent, the Malayan tapir was found in historical times as far north as China.
Behaviour and ecology
Malayan tapirs are primarily solitary, marking out large tracts of land as their territory, though these areas usually overlap with those of other individuals. Tapirs mark out their territories by spraying urine on plants, and they often follow distinct paths which they have bulldozed through the undergrowth.
Exclusively herbivorous, the animal forages for the tender shoots and leaves of more than 115 species of plants, of which around 30 are particularly preferred, moving slowly through the forest and pausing often to eat and note the scents left behind by other tapirs in the area. The tapir can run quickly when threatened or frightened, and if forced to fight can defend itself with its strong jaws and sharp teeth. Malayan tapirs communicate with high-pitched squeaks and whistles. They usually prefer to live near water and often bathe and swim, and they are also able to climb steep slopes. Tapirs are mainly active at night, though they are not exclusively nocturnal; because they tend to eat soon after sunset or before sunrise, and they will often nap in the middle of the night, they are considered to be crepuscular animals.
Life cycle | Malayan tapir | Wikipedia | 357 | 961680 | https://en.wikipedia.org/wiki/Malayan%20tapir | Biology and health sciences | Perissodactyla | Animals |
The gestation period of the Malayan tapir is about 390–395 days, after which a single calf is born that weighs around . Malayan tapirs are the largest of the four tapir species at birth and tend to grow more quickly than their relatives. Young tapirs of all species have brown hair with white stripes and spots, a pattern that enables them to hide effectively in the dappled light of the forest. This baby coat fades into adult coloration between four and seven months after birth. Weaning occurs between six and eight months of age, at which time the babies are nearly full-grown, and the animals reach sexual maturity around age three. Breeding typically occurs in April, May or June, and females generally produce one calf every two years. Malayan tapirs can live up to 30 years, both in the wild and in captivity.
Predators
Because of its size, the Malayan tapir has few natural predators, and even reports of killings by tigers (Panthera tigris) are scarce.
Malayan tapirs can defend themselves with their very powerful bite; in 1998, the bite of a captive female Malayan tapir severed off a zookeeper's left arm at the mid-bicep, likely because she stood between her and her offspring.
Threats
The main threats to the Malayan tapir are loss and destruction of habitat through deforestation. Large tracts of forests in Thailand and Malaysia have been converted for planting oil palms. Habitat fragmentation in peninsular Malaysia caused displacement of 142 Malayan tapirs between 2006 and 2010; some were rescued and relocated, while 15 of them were killed in vehicle collisions. | Malayan tapir | Wikipedia | 329 | 961680 | https://en.wikipedia.org/wiki/Malayan%20tapir | Biology and health sciences | Perissodactyla | Animals |
Choy sum (also spelled choi sum, choi sam in Cantonese; cai xin, caixin in Standard Mandarin) is a leafy vegetable commonly used in Chinese cuisine. It is a member of the genus Brassica of the mustard family, Brassicaceae (Brassica rapa var. parachinensis or Brassica chinensis var. parachinensis). Choy sum is a transliteration of the Cantonese name (), which can be literally translated as "heart of the vegetable". Choy sum is also called yu choy (you cai in Standard Mandarin; Chinese: 油菜). It is also known as Chinese flowering cabbage.
Description
Choy sum is a green leafy vegetable similar to gai lan, and can be characterized by the distinct yellow flowers which it bears. Each flower has four yellow, oval to round petals with six stamens on fleshy, erect stems which are in diameter and tall with light to dark green, and are oval (becomes acuminate shaped, or basal-shaped near the flowering stage) with slightly serrated margins leaves, which never forms compact heads like the cabbage. Fruits can develop out of cross-pollination or self-pollination, and are silique structured, that open at maturity through dehiscence or drying to bare open to brown or black seeds that are small and round in shape. A single pod can bear 4 to 46 seeds.
The height of the plant varies greatly, ranging from depending on the growing conditions and the variety. Flowering usually appears when there are about 7 to 8 leaves on the plant or about tall. The bulk of the root system is found within a depth of and is confined to a radius of .
The whole plant is overall an annual, herbaceous plant, rarely perennial, rarely growing into subshrubs. The whole plant consists of a simple or branched (when it is near the flowering stage), leafy structure. It grows best in soil with a minimum pH level of 5.6, maximum pH level of 7.5.
Use
Choy sum is highly valued as a vegetable in China and Japan. It is commonly consumed in soup, blanched, or stir-fried.
Gallery | Choy sum | Wikipedia | 444 | 961724 | https://en.wikipedia.org/wiki/Choy%20sum | Biology and health sciences | Leafy vegetables | Plants |
Seismic refraction is a geophysical principle governed by Snell's Law of refraction. The seismic refraction method utilizes the refraction of seismic waves by rock or soil layers to characterize the subsurface geologic conditions and geologic structure.
Seismic refraction is exploited in engineering geology, geotechnical engineering and exploration geophysics. Seismic refraction traverses (seismic lines) are performed using an array of seismographs or geophones and an energy source.
The methods depend on the fact that seismic waves have differing velocities in different types of soil or rock. The waves are refracted when they cross the boundary between different types (or conditions) of soil or rock. The methods enable the general soil types and the approximate depth to strata boundaries, or to bedrock, to be determined.
P-wave refraction
P-wave refraction evaluates the compression wave generated by the seismic source located at a known distance from the array. The wave is generated by vertically striking a striker plate with a sledgehammer, shooting a seismic shotgun into the ground, or detonating an explosive charge in the ground. Since the compression wave is the fastest of the seismic waves, it is sometimes referred to as the primary wave and is usually more-readily identifiable within the seismic recording as compared to the other seismic waves.
S-wave refraction
S-wave refraction evaluates the shear wave generated by the seismic source located at a known distance from the array. The wave is generated by horizontally striking an object on the ground surface to induce the shear wave. Since the shear wave is the second fastest wave, it is sometimes referred to as the secondary wave. When compared to the compression wave, the shear wave is approximately one-half (but may vary significantly from this estimate) the velocity depending on the medium.
Two horizontal layers
ic0 - critical angle
V0 - velocity of the first layer
V1 - velocity of the second layer
h0 - thickness of the first layer
T01 - intercept
Several horizontal layers
Inversion methods
The General Reciprocal method
The Plus minus method
Refraction inversion modeling (refraction tomography)
Monte Carlo simulation
Genetic algorithms
Applications
Seismic refraction has been successfully applied to tailings characterisation through P- and S-wave travel time tomographic inversions. | Seismic refraction | Wikipedia | 458 | 962035 | https://en.wikipedia.org/wiki/Seismic%20refraction | Physical sciences | Seismology | Earth science |
The Beehive Cluster (also known as Praesepe (Latin for "manger", "cot" or "crib"), M44, NGC 2632, or Cr 189), is an open cluster in the constellation Cancer. One of the nearest open clusters to Earth, it contains a larger population of stars than other nearby bright open clusters holding around 1,000 stars. Under dark skies, the Beehive Cluster looks like a small nebulous object to the naked eye, and has been known since ancient times. Classical astronomer Ptolemy described it as a "nebulous mass in the breast of Cancer". It was among the first objects that Galileo studied with his
telescope.
Age and proper motion coincide with those of the Hyades, suggesting they may share similar origins. Both clusters also contain red giants and white dwarfs, which represent later stages of stellar evolution, along with many main sequence stars.
Distance to M44 is often cited to be between 160 and 187 parsecs (520–610 light years), but the revised Hipparcos parallaxes (2009) for Praesepe members and the latest infrared color-magnitude diagram favors an analogous distance of 182 pc. There are better age estimates of around 600 million years (compared to about 625 million years for the Hyades). The diameter of the bright inner cluster core is about 7.0 parsecs (23 light years).
At 1.5° across, the cluster easily fits within the field of view of binoculars or low-powered small telescopes. Regulus, Castor, and Pollux are guide stars. | Beehive Cluster | Wikipedia | 330 | 962148 | https://en.wikipedia.org/wiki/Beehive%20Cluster | Physical sciences | Notable star clusters | Astronomy |
History
In 1609, Galileo first telescopically observed the Beehive and was able to resolve it into 40 stars. Charles Messier added it to his famous catalog in 1769 after precisely measuring its position in the sky. Along with the Orion Nebula and the Pleiades cluster, Messier's inclusion of the Beehive has been noted as curious, as most of Messier's objects were much fainter and more easily confused with comets. Another possibility is that Messier simply wanted to have a larger catalog than his scientific rival Lacaille, whose 1755 catalog contained 42 objects, and so he added some well-known bright objects to boost his list. Wilhelm Schur, as director of the Göttingen Observatory, drew a map of the cluster in 1894.Ancient Greeks and Romans saw this object as a manger from which two donkeys, the adjacent stars Asellus Borealis and Asellus Australis, are eating; these are the donkeys that Dionysos and Silenus rode into battle against the Titans.
Hipparchus (c.130 BC) refers to the cluster as Nephelion ("Little Cloud") in his star catalog. Claudius Ptolemy's Almagest includes the Beehive Cluster as one of seven "nebulae" (four of which are real), describing it as "The Nebulous Mass in the Breast (of Cancer)". Aratus (c.260–270 BC) calls the cluster Achlus or "Little Mist" in his poem Phainomena.
Johann Bayer showed the cluster as a nebulous star on his Uranometria atlas of 1603, and labeled it Epsilon. The letter is now applied specifically to the brightest star of the cluster Epsilon Cancri, of magnitude 6.29.
This perceived nebulous object is in the Ghost (Gui Xiu), the 23rd lunar mansion of ancient Chinese astrology. Ancient Chinese skywatchers saw this as a ghost or demon riding in a carriage and likened its appearance to a "cloud of pollen blown from willow catkins". It was also known by the somewhat less romantic name of Jishi qi (積屍氣, also transliterated Tseih She Ke), the "Exhalation of Piled-up Corpses". It is also known simply as Jishi (積屍), "cumulative corpses". | Beehive Cluster | Wikipedia | 484 | 962148 | https://en.wikipedia.org/wiki/Beehive%20Cluster | Physical sciences | Notable star clusters | Astronomy |
Morphology and composition
Like many star clusters of all kinds, Praesepe has experienced mass segregation. This means that bright massive stars are concentrated in the cluster's core, while dimmer and less massive stars populate its halo (sometimes called the corona). The cluster's core radius is estimated at 3.5 parsecs (11.4 light years); its half-mass radius is about 3.9 parsecs (12.7 light years); and its tidal radius is about 12 parsecs (39 light years). However, the tidal radius also includes many stars that are merely "passing through" and not bona fide cluster members.
Altogether, the cluster contains at least 1000 gravitationally bound stars, for a total mass of about 500–600 Solar masses. A recent survey counts 1010 high-probability members, of which 68% are M dwarfs, 30% are Sun-like stars of spectral classes F, G, and K, and about 2% are bright stars of spectral class A. Also present are five giant stars, four of which have spectral class K0 III and the fifth G0 III.
So far, eleven white dwarfs have been identified, representing the final evolutionary phase of the cluster's most massive stars, which originally belonged to spectral type B. Brown dwarfs, however, are rare in this cluster, probably because they have been lost by tidal stripping from the halo. A brown dwarf has been found in the eclipsing binary system AD 3116.
The cluster has a visual brightness of magnitude 3.7. Its brightest stars are blue-white and of magnitude 6 to 6.5. 42 Cancri is a confirmed member.
Planets
In September 2012, two planets which orbit separate stars were discovered in the Beehive Cluster. The finding was significant for being the first planets detected orbiting stars like Earth's Sun that were situated in stellar clusters. Planets had previously been detected in such clusters, but not orbiting stars like the Sun.
The planets have been designated Pr0201 b and Pr0211 b. The 'b' at the end of their names indicates that the bodies are planets. The discoveries are what have been termed hot Jupiters, massive gas giants that, unlike the planet Jupiter, orbit very close to their parent stars. | Beehive Cluster | Wikipedia | 467 | 962148 | https://en.wikipedia.org/wiki/Beehive%20Cluster | Physical sciences | Notable star clusters | Astronomy |
The announcement describing the planetary finds, written by Sam Quinn as the lead author, was published in the Astrophysical Journal Letters. Quinn's team worked with David Latham of the Harvard–Smithsonian Center for Astrophysics, utilizing the Smithsonian Astrophysical Observatory's Fred Lawrence Whipple Observatory.
In 2016 additional observations found a second planet in the Pr0211 system, Pr0211 c. This made Pr0211 the first multi-planet system to be discovered in an open cluster.
The Kepler space telescope, in its K2 mission, discovered planets around several more stars in the Beehive Cluster. The stars K2-95, K2-100, K2-101, K2-102, K2-103, and K2-104 host a single planet each, and K2-264 has a two-planet system. | Beehive Cluster | Wikipedia | 173 | 962148 | https://en.wikipedia.org/wiki/Beehive%20Cluster | Physical sciences | Notable star clusters | Astronomy |
In quantum physics, the Stern–Gerlach experiment demonstrated that the spatial orientation of angular momentum is quantized. Thus an atomic-scale system was shown to have intrinsically quantum properties. In the original experiment, silver atoms were sent through a spatially-varying magnetic field, which deflected them before they struck a detector screen, such as a glass slide. Particles with non-zero magnetic moment were deflected, owing to the magnetic field gradient, from a straight path. The screen revealed discrete points of accumulation, rather than a continuous distribution, owing to their quantized spin. Historically, this experiment was decisive in convincing physicists of the reality of angular-momentum quantization in all atomic-scale systems.
After its conception by Otto Stern in 1921, the experiment was first successfully conducted with Walther Gerlach in early 1922.
Description
The Stern–Gerlach experiment involves sending silver atoms through an inhomogeneous magnetic field and observing their deflection. Silver atoms were evaporated using an electric furnace in a vacuum. Using thin slits, the atoms were guided into a flat beam and the beam sent through an inhomogeneous magnetic field before colliding with a metallic plate. The laws of classical physics predict that the collection of condensed silver atoms on the plate should form a thin solid line in the same shape as the original beam. However, the inhomogeneous magnetic field caused the beam to split in two separate directions, creating two lines on the metallic plate.
The results show that particles possess an intrinsic angular momentum that is closely analogous to the angular momentum of a classically spinning object, but that takes only certain quantized values. Another important result is that only one component of a particle's spin can be measured at one time, meaning that the measurement of the spin along the z-axis destroys information about a particle's spin along the x and y axis.
The experiment is normally conducted using electrically neutral particles such as silver atoms. This avoids the large deflection in the path of a charged particle moving through a magnetic field and allows spin-dependent effects to dominate. | Stern–Gerlach experiment | Wikipedia | 427 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
If the particle is treated as a classical spinning magnetic dipole, it will precess in a magnetic field because of the torque that the magnetic field exerts on the dipole (see torque-induced precession). If it moves through a homogeneous magnetic field, the forces exerted on opposite ends of the dipole cancel each other out and the trajectory of the particle is unaffected. However, if the magnetic field is inhomogeneous then the force on one end of the dipole will be slightly greater than the opposing force on the other end, so that there is a net force which deflects the particle's trajectory. If the particles were classical spinning objects, one would expect the distribution of their spin angular momentum vectors to be random and continuous. Each particle would be deflected by an amount proportional to the dot product of its magnetic moment with the external field gradient, producing some density distribution on the detector screen. Instead, the particles passing through the Stern–Gerlach apparatus are deflected either up or down by a specific amount. This was a measurement of the quantum observable now known as spin angular momentum, which demonstrated possible outcomes of a measurement where the observable has a discrete set of values or point spectrum.
Although some discrete quantum phenomena, such as atomic spectra, were observed much earlier, the Stern–Gerlach experiment allowed scientists to directly observe separation between discrete quantum states for the first time.
Theoretically, quantum angular momentum of any kind has a discrete spectrum, which is sometimes briefly expressed as "angular momentum is quantized".
Experiment using particles with +1/2 or −1/2 spin
If the experiment is conducted using charged particles like electrons, there will be a Lorentz force that tends to bend the trajectory in a circle. This force can be cancelled by an electric field of appropriate magnitude oriented transverse to the charged particle's path.
Electrons are spin-1/2 particles. These have only two possible spin angular momentum values measured along any axis, or , a purely quantum mechanical phenomenon. Because its value is always the same, it is regarded as an intrinsic property of electrons, and is sometimes known as "intrinsic angular momentum" (to distinguish it from orbital angular momentum, which can vary and depends on the presence of other particles). If one measures the spin along a vertical axis, electrons are described as "spin up" or "spin down", based on the magnetic moment pointing up or down, respectively. | Stern–Gerlach experiment | Wikipedia | 501 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
To mathematically describe the experiment with spin particles, it is easiest to use Dirac's bra–ket notation. As the particles pass through the Stern–Gerlach device, they are deflected either up or down, and observed by the detector which resolves to either spin up or spin down. These are described by the angular momentum quantum number , which can take on one of the two possible allowed values, either or . The act of observing (measuring) the momentum along the axis corresponds to the -axis angular momentum operator, often denoted . In mathematical terms, the initial state of the particles is
where constants and are complex numbers. This initial state spin can point in any direction. The squares of the absolute values
and are respectively the probabilities for a system in the state to be found in and after the measurement along axis is made. The constants and must also be normalized in order that the probability of finding either one of the values be unity, that is we must ensure that . However, this information is not sufficient to determine the values of and , because they are complex numbers. Therefore, the measurement yields only the squared magnitudes of the constants, which are interpreted as probabilities.
Sequential experiments
If we link multiple Stern–Gerlach apparatuses (the rectangles containing S-G), we can clearly see that they do not act as simple selectors, i.e. filtering out particles with one of the states (pre-existing to the measurement) and blocking the others. Instead they alter the state by observing it (as in light polarization). In the figure below, x and z name the directions of the (inhomogenous) magnetic field, with the x-z-plane being orthogonal to the particle beam. In the three S-G systems shown below, the cross-hatched squares denote the blocking of a given output, i.e. each of the S-G systems with a blocker allows only particles with one of two states to enter the next S-G apparatus in the sequence.
Experiment 1
The top illustration shows that when a second, identical, S-G apparatus is placed at the exit of the first apparatus, only z+ is seen in the output of the second apparatus. This result is expected since all particles at this point are expected to have z+ spin, as only the z+ beam from the first apparatus entered the second apparatus. | Stern–Gerlach experiment | Wikipedia | 495 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
Experiment 2
The middle system shows what happens when a different S-G apparatus is placed at the exit of the z+ beam resulting of the first apparatus, the second apparatus measuring the deflection of the beams on the x axis instead of the z axis. The second apparatus produces x+ and x- outputs. Now classically we would expect to have one beam with the x characteristic oriented + and the z characteristic oriented +, and another with the x characteristic oriented - and the z characteristic oriented +.
Experiment 3
The bottom system contradicts that expectation. The output of the third apparatus which measures the deflection on the z axis again shows an output of z- as well as z+. Given that the input to the second S-G apparatus consisted only of z+, it can be inferred that a S-G apparatus must be altering the states of the particles that pass through it. This experiment can be interpreted to exhibit the uncertainty principle: since the angular momentum cannot be measured on two perpendicular directions at the same time, the measurement of the angular momentum on the x direction destroys the previous determination of the angular momentum in the z direction. That's why the third apparatus measures renewed z+ and z- beams like the x measurement really made a clean slate of the z+ output.
History | Stern–Gerlach experiment | Wikipedia | 264 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
The Stern–Gerlach experiment was conceived by Otto Stern in 1921 and performed by him and Walther Gerlach in Frankfurt in 1922.
At the time of the experiment, the most prevalent model for describing the atom was the Bohr-Sommerfeld model, which described electrons as going around the positively charged nucleus only in certain discrete atomic orbitals or energy levels. Since the electron was quantized to be only in certain positions in space, the separation into distinct orbits was referred to as space quantization. The Stern–Gerlach experiment was meant to test the Bohr–Sommerfeld hypothesis that the direction of the angular momentum of a silver atom is quantized.
The experiment was first performed with an electromagnet that allowed the non-uniform magnetic field to be turned on gradually from a null value. When the field was null, the silver atoms were deposited as a single band on the detecting glass slide. When the field was made stronger, the middle of the band began to widen and eventually to split into two, so that the glass-slide image looked like a lip-print, with an opening in the middle, and closure at either end. In the middle, where the magnetic field was strong enough to split the beam into two, statistically half of the silver atoms had been deflected by the non-uniformity of the field.
Note that the experiment was performed several years before George Uhlenbeck and Samuel Goudsmit formulated their hypothesis about the existence of electron spin in 1925. Even though the result of the Stern−Gerlach experiment has later turned out to be in agreement with the predictions of quantum mechanics for a spin-1/2 particle, the experimental result was also consistent with the Bohr–Sommerfeld theory.
In 1927, T.E. Phipps and J.B. Taylor reproduced the effect using hydrogen atoms in their ground state, thereby eliminating any doubts that may have been caused by the use of silver atoms. However, in 1926 the non-relativistic scalar Schrödinger equation had incorrectly predicted the magnetic moment of hydrogen to be zero in its ground state. To correct this problem Wolfgang Pauli considered a spin-1/2 version of the Schrödinger equation using the 3 Pauli matrices which now bear his name, which was later shown by Paul Dirac in 1928 to be a consequence of his relativistic Dirac equation. | Stern–Gerlach experiment | Wikipedia | 493 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
In the early 1930s Stern, together with Otto Robert Frisch and Immanuel Estermann improved the molecular beam apparatus sufficiently to measure the magnetic moment of the proton, a value nearly 2000 times smaller than the electron moment. In 1931, theoretical analysis by Gregory Breit and Isidor Isaac Rabi showed that this apparatus could be used to measure nuclear spin whenever the electronic configuration of the atom was known. The concept was applied by Rabi and Victor W. Cohen in 1934 to determine the spin of sodium atoms.
In 1938 Rabi and coworkers inserted an oscillating magnetic field element into their apparatus, inventing nuclear magnetic resonance spectroscopy. By tuning the frequency of the oscillator to the frequency of the nuclear precessions they could selectively tune into each quantum level of the material under study. Rabi was awarded the Nobel Prize in 1944 for this work.
Importance
The Stern–Gerlach experiment was the first direct evidence of angular-momentum quantization in quantum mechanics, and it strongly influenced later developments in modern physics: | Stern–Gerlach experiment | Wikipedia | 213 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
In the decade that followed, scientists showed using similar techniques, that the nuclei of some atoms also have quantized angular momentum. It is the interaction of this nuclear angular momentum with the spin of the electron that is responsible for the hyperfine structure of the spectroscopic lines.
Norman F. Ramsey later modified the Rabi apparatus to improve its sensitivity (using the separated oscillatory field method). In the early sixties, Ramsey, H. Mark Goldenberg, and Daniel Kleppner used a Stern–Gerlach system to produce a beam of polarized hydrogen as the source of energy for the hydrogen maser. This led to developing an extremely stable clock based on a hydrogen maser. From 1967 until 2019, the second was defined based on 9,192,631,770 Hz hyperfine transition of a cesium-133 atom; the atomic clock which is used to set this standard is an application of Ramsey's work.
The Stern–Gerlach experiment has become a prototype for quantum measurement, demonstrating the observation of a discrete value (eigenvalue) of a physical property, previously assumed to be continuous. Entering the Stern–Gerlach magnet, the direction of the silver atom's magnetic moment is indefinite, but when the atom is registered at the screen, it is observed to be at either one spot or the other, and this outcome cannot be predicted in advance. Because the experiment illustrates the character of quantum measurements, The Feynman Lectures on Physics use idealized Stern–Gerlach apparatuses to explain the basic mathematics of quantum theory. | Stern–Gerlach experiment | Wikipedia | 322 | 962171 | https://en.wikipedia.org/wiki/Stern%E2%80%93Gerlach%20experiment | Physical sciences | Quantum mechanics | Physics |
The viviparous lizard, or common lizard, (Zootoca vivipara, formerly Lacerta vivipara) is a Eurasian lizard. It lives farther north than any other species of non-marine reptile, and is named for the fact that it is viviparous, meaning it gives birth to live young (although they will sometimes lay eggs normally). Both "Zootoca" and "vivipara" mean "live birth", in (Latinized) Greek and Latin respectively. It was called Lacerta vivipara until the genus Lacerta was split into nine genera in 2007 by Arnold, Arribas & Carranza.
Male and female Zootoca vivipara are equally likely to contract blood parasites. Additionally, larger males have been shown to reproduce more times in a given reproductive season than smaller ones.
The lizard is also unique as it is exclusively carnivorous, eating only flies, spiders, and insects. Studies show that the more carnivorous an individual is (the more insects they eat), the less diverse the population of parasitic helminths that infest the lizards.
Zootoca vivipara lives in very cold climates, yet participates in normal thermoregulation instead of thermoconformity. They have the largest range of all terrestrial lizards which even include subarctic regions. It is able to survive these harsh climates as individuals will freeze in especially cold seasons and thaw two months later. They also live closer to geological phenomena that provide a warmer environment for them.
Description
Zootoca vivipara is a small lizard, with an average length between {150-200 mm} . They exhibit no particular colour, but can be brown, red, grey, green, or black. The species exhibits some sexual dimorphisms. Female Z. vivipara undergo colour polymorphism more commonly than males. A female lizard's display differs in ventral coloration, ranging from pale yellow to bright orange and a mixed coloration. There have been many hypotheses for the genetic cause of this polymorphic coloration. These hypothesis test for coloration due to thermoregulation, predator avoidance, and social cues, specifically sexual reproduction. Through an experiment conducted by Vercken et al., colour polymorphism in viviparous lizard is caused by social cues, rather than the other hypotheses. More specifically, the ventral coloration that is seen in female lizards is associated with patterns of sexual reproduction and sex allocation. | Viviparous lizard | Wikipedia | 505 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
The underside of the male is typically more colourful and bright, with yellow, orange, green, and blue, and the male typically has spots along its back. On the other hand, females typically have darker stripes down their backs and sides. Additionally, males have been found to have larger heads than their female counterparts, and this trait appears to be sexually selected for. Males with larger heads are more likely to be successful in mating and male-male interactions than smaller-headed Z. vivipara. Larger males also have been shown to reproduce more frequently during one mating season compared to smaller males. Characteristic behaviors of the species includes tongue flicking in the presence of a predator and female-female aggression that seems to be mediated by the colour of their side stripe.
Habitat and distribution
Habitat
Z. vivipara is terrestrial, so they spend most of their time on the ground, though they do occasionally visit sites of higher elevation. The lizard thermoregulates by basking in the sun for much of the time. In colder weather, they have been known to hibernate to maintain proper body temperatures. They hibernate between October and March. Their typical habitats include heathland, moorland, woodland and grassland.
The viviparous lizard is native to much of northern Eurasia. In Europe, it is mainly found north of the Alps and the Carpathians, including the British Isles but not Iceland, as well as in parts of northern Iberia and the Balkans; In Asia it is mostly found in Russia, excluding northern Siberia, and in northern Kazakhstan, Mongolia, China, and Japan. Z. vivipara has the largest distribution of any species of lizard in the world.
Home range
The size of the home range of the lizard ranges from 539 m2 to 1692 m2, with males generally having larger home ranges. The size of an individual lizard's home range is also dependent on population density and the presence of prey.
Ecology
Diet
Unlike many other lizards, Z. vivipara is exclusively carnivorous. Their diet consists of flies, spiders, and various other insects, including hemipterans (such as cicadas), moth larvae, and mealworms. The species is a predator, so it actively hunts down all of its prey. One study found that when controlled for body size, females consumed more food than males. Feeding rates also increased with increased sunshine. | Viviparous lizard | Wikipedia | 481 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
Predation
Birds are common predators of Z. vivipara. Male-biased predation of Z. vivipara by the great grey shrike (L. excubitor) has been studied, finding that adult males, over adult females and juveniles, were preferentially predated on. This bias may be due to increased activity of adult males during the reproductive season.
Predators of this species include birds of prey, crows, snakes, shrikes, hedgehogs, shrews, foxes, and domestic cats.
Diseases and parasites
Z. vivpara can be infested by helminths, a small parasitic worm. The species diversity of parasites is affected by the diet of the individual lizard and the number of parasites on a host is affected by the host's size. Results of a study shows that the more carnivorous an individual is, the less diverse its parasite population. Additionally, larger lizards had a greater number of parasites on them.
Z. vivipara is also infected by blood parasites. In a study investigating the prevalence of blood parasites in Z. vivipara and L. agilis, Z. vivipara was found to be parasitized with an incidence rate of 39.8%, while L. agilis was parasitized with an incidence rate of 22.3%. This same study shows that there was not a significant difference between the parasitization of male and female Z. vivipara.
Reproduction and life history
Viviparity and oviparity
The viviparous lizard is named as such because it is viviparous. This refers to its ability to give birth to live young, although the lizards are also able to lay eggs. The origin of this characteristic is under debate. Some scientists argue that viviparity evolved from oviparity, or the laying of eggs, only once. Proponents of this theory also argue that if this is the case, it is possible, though rare, for species to transition back to oviparity. Research from Yann Surget-Groba suggests that there have in fact been multiple events of the evolution of viviparity from oviparity across different clades of the viviparous lizard. They also argue that a reversion to oviparity is not as rare as once believed, but has occurred 2 to 3 times in the history of the species. | Viviparous lizard | Wikipedia | 492 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
The range of viviparous populations of Z. vivipara extends from France to Russia. Oviparous populations are only found in northern Spain and the southwest of France. Some research in the Italian alps has suggested that distinct populations of oviparous and viviparous Z. vivipara should be considered separate species. Cornetti et al. (2015) identified that viviparous and oviparous subpopulations in contact with each other in the Italian alps are reproductively isolated. Hybridization between viviparous and oviparous individuals of Z. vivipara leads to embryonic malformations in the laboratory. However, these crosses do produce a "hybridized" generation of offspring, with females retaining embryos for much longer in utero than oviparous females, with embryos surrounded by thin, translucent shells.
Fertilization
Z. vivipara juveniles reach sexual maturity during their second year of their life. A study that explored the presence of male sex cells in reproducing males found that for the two weeks following the end of hibernation, males are infertile, and therefore incapable of reproducing. The same study also found that larger males produce more sperm during the reproductive season and have fewer left over at the end of the reproductive season than their smaller counterparts. This suggests that the larger a male is, the more reproductive events they participate in.
Brood size
Research also suggests that in exclusively oviparous populations of Z. vivipara, altitude influences the number of clutches laid in a reproductive season as well as when reproduction begins. Generally, lizards living at higher altitudes have been found to begin reproduction later and lay fewer clutches (often 1) in a given reproductive season.
Life span
Z. vivipara typically lives for 5 to 6 years.
Mating
Mate searching behavior
Head size is a sexually dimorphic trait, with males having larger heads than females. The average head width and length of the males measured were found to be , respectively. The average head width and length of the females measured were found to be , respectively. During the first state of courtship in Z. vivipara, called "Capture", the male uses its mouth and jaw to capture the female and initiate copulation. The results of this study demonstrated that males with larger head sizes (both length and width) were more successful in mating than those with smaller heads, suggesting that head size undergoes sexual selection. | Viviparous lizard | Wikipedia | 501 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
Male-male interaction
Head size has also been shown to be a predictor of success in male-male interactions. The head is used as a weapon in male-male interactions, and a larger head is typically more effective, leading to greater success during male-male aggressive encounters. This aggression and interaction is centered around available mates, so males with smaller heads have significantly less access to females for reproduction.
Thermoregulation
This lizard has an exceptionally large range that includes subarctic geography. As a result, thermoregulation is necessary for the thermal homeostasis of the species. Typically, in temperature extremes, a species will adopt the behavioral strategy of thermoconformity, where they do not actively thermoregulate, but adapt to survive in the harsh temperature. This occurs because the cost of thermoregulating in such an extreme environment becomes too high and begins to outweigh the benefits. Despite this, Z. vivipara still employs the strategy of thermoregulation, like basking. Thermoregulation is important in Z. vivipara as it allows for proper locomotive performance, escape behavior, and other key behaviors for survival. The ability of Z. vivipara to thermoregulate in such harsh environments has been attributed to two primary reasons. The first is that Z. vivipara has remarkable behaviors to combat the cold, and there are geological phenomena in their distribution that maintains their habitats at a temperature that the species can survive in. One of the specific behaviors used to combat the extreme cold is a "supercooled" state. Z. vivipara remains in this state through the winter until temperatures dropped below . After that, individuals completely froze until they were thawed by warmer weather later in the year, often 2 months later. Despite very cold air in the subarctic habitats of these lizards, the soil-heating effects of unfrozen groundwater has been observed regulating the temperature of their soil habitats. They find warm microhabitats that do not drop below the freezing point of their body fluids. These lizards have exceptional hardiness to the cold, which allows them to hibernate in upper soil layers in temperatures as low as . This cold hardiness along with the favorable hydrogeological conditions of groundwater-warmed soil habitats allows for the wide distribution of lizards throughout the palearctic.
Colour polymorphism | Viviparous lizard | Wikipedia | 487 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
The colour polymorphism of female Z. vivipara has not been thoroughly studied in past years, regardless of the extensive research done on the species itself. Females exhibit three types of body colouration within a population: yellow, orange, and mixture of the two. These discrete traits are inherited maternally and exist throughout the individual's lifetime. The organism's colour morphs are determined by their genotype as well as their environment.
The frequency of multiple morphs occurring in a population varies with the level of population density and frequency-dependent environments. These factors cause the lizards to vary in terms of their fitness (clutch size, sex ratio, hatching success). In lower density populations, colour polymorphism is more prevalent. This is because viviparous lizards thrive in environments where intraspecific competition is low. Increased competition among individuals results in lower survival rates of lizards. Additionally, female lizards disperse through habitats based on the frequency of colour types that are already present in the population. Their reproductive abilities vary according to this frequency-dependent environment. The number of offspring that they produce correlates with the colour morph: yellow females produce the fewest offspring, while orange females produce more than yellow, but fewer than mixed females, which produce the most offspring. The amount of offspring produced varies in regards to colour frequencies in the population; for example, if yellow females have higher density within the population, the clutch size for orange lizards is usually lower. | Viviparous lizard | Wikipedia | 295 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
Orange females are more sensitive to intraspecific and colour-specific competition. They have smaller clutch sizes when the density of the population is high, or when the number of yellow females in the population is high. This could be due to their need to conserve energy for survival and reproductive events. Their colour morph remains in the population due to the trade-off between the size of offspring and the clutch size. Offspring born in smaller clutches are often larger and thus have a higher survival likelihood. Natural selection will favor individuals with larger size because of their advantage in physical competition with others. Yellow females have larger clutch sizes early in their life, but their hatch success decreases as the female ages. Their reproductive viability decreases, resulting in fewer offspring throughout their lifetime. Yellow morphs remain in the population due to their large clutch size, which causes an increased frequency of those females. Selection favors the yellow morph because of the ability to produce large clutch sizes, which increases the female's fitness. In mixed-coloured females, reproductive success is less sensitive to competition and frequency-dependent environments. Since these lizards show a mixture of yellow and orange colouration, they adopt benefits from both of the morphs. As a result, they can maintain high reproductive success and hatching success with large clutch sizes. Their colour morph remains in the population due to its high fitness, which selection will favor.
All three colours have evolutionary advantages in different ways. While yellow females have higher fitness due to their large clutch sizes, orange females enjoy high fitness due to their large body size and increased competitive advantages. Mixed females exhibit both of these advantages. | Viviparous lizard | Wikipedia | 326 | 962527 | https://en.wikipedia.org/wiki/Viviparous%20lizard | Biology and health sciences | Lizards and other Squamata | Animals |
A rogue planet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf.
Rogue planets may originate from planetary systems in which they are formed and later ejected, or they can also form on their own, outside a planetary system. The Milky Way alone may have billions to trillions of rogue planets, a range the upcoming Nancy Grace Roman Space Telescope is expected to refine.
Some planetary-mass objects may have formed in a similar way to stars, and the International Astronomical Union has proposed that such objects be called sub-brown dwarfs. A possible example is Cha 110913−773444, which may either have been ejected and become a rogue planet or formed on its own to become a sub-brown dwarf.
Terminology
The two first discovery papers use the names isolated planetary-mass objects (iPMO) and free-floating planets (FFP). Most astronomical papers use one of these terms. The term rogue planet is more often used for microlensing studies, which also often uses the term FFP. A press release intended for the public might use an alternative name. The discovery of at least 70 FFPs in 2021, for example, used the terms rogue planet, starless planet, wandering planet and free-floating planet in different press releases.
Discovery
Isolated planetary-mass objects (iPMO) were first discovered in 2000 by the UK team Lucas & Roche with UKIRT in the Orion Nebula. In the same year the Spanish team Zapatero Osorio et al. discovered iPMOs with Keck spectroscopy in the σ Orionis cluster. The spectroscopy of the objects in the Orion Nebula was published in 2001. Both European teams are now recognized for their quasi-simultaneous discoveries. In 1999 the Japanese team Oasa et al. discovered objects in Chamaeleon I that were spectroscopically confirmed years later in 2004 by the US team Luhman et al.
Observation
There are two techniques to discover free-floating planets: direct imaging and microlensing. | Rogue planet | Wikipedia | 430 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
Microlensing
Astrophysicist Takahiro Sumi of Osaka University in Japan and colleagues, who form the Microlensing Observations in Astrophysics and the Optical Gravitational Lensing Experiment collaborations, published their study of microlensing in 2011. They observed 50 million stars in the Milky Way by using the MOA-II telescope at New Zealand's Mount John Observatory and the University of Warsaw telescope at Chile's Las Campanas Observatory. They found 474 incidents of microlensing, ten of which were brief enough to be planets of around Jupiter's size with no associated star in the immediate vicinity. The researchers estimated from their observations that there are nearly two Jupiter-mass rogue planets for every star in the Milky Way. One study suggested a much larger number, up to 100,000 times more rogue planets than stars in the Milky Way, though this study encompassed hypothetical objects much smaller than Jupiter. A 2017 study by Przemek Mróz of Warsaw University Observatory and colleagues, with six times larger statistics than the 2011 study, indicates an upper limit on Jupiter-mass free-floating or wide-orbit planets of 0.25 planets per main-sequence star in the Milky Way.
In September 2020, astronomers using microlensing techniques reported the detection, for the first time, of an Earth-mass rogue planet (named OGLE-2016-BLG-1928) unbound to any star and free floating in the Milky Way galaxy.
Direct imaging | Rogue planet | Wikipedia | 296 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
Microlensing planets can only be studied by the microlensing event, which makes the characterization of the planet difficult. Astronomers therefore turn to isolated planetary-mass objects (iPMO) that were found via the direct imaging method. To determine a mass of a brown dwarf or iPMO one needs for example the luminosity and the age of an object. Determining the age of a low-mass object has proven to be difficult. It is no surprise that the vast majority of iPMOs are found inside young nearby star-forming regions of which astronomers know their age. These objects are younger than 200 Myrs, are massive (>5 ) and belong to the L- and T-dwarfs. There is however a small growing sample of cold and old Y-dwarfs that have estimated masses of 8-20 . Nearby rogue planet candidates of spectral type Y include WISE 0855−0714 at a distance of . If this sample of Y-dwarfs can be characterized with more accurate measurements or if a way to better characterize their ages can be found, the number of old and cold iPMOs will likely increase significantly.
The first iPMOs were discovered in the early 2000s via direct imaging inside young star-forming regions. These iPMOs found via direct imaging formed probably like stars (sometimes called sub-brown dwarf). There might be iPMOs that form like a planet, which are then ejected. These objects will however be kinematically different from their natal star-forming region, should not be surrounded by a circumstellar disk and have high metallicity. None of the iPMOs found inside young star-forming regions show a high velocity compared to their star-forming region. For old iPMOs the cold WISE J0830+2837 shows a Vtan of about 100 km/s, which is high, but still consistent with formation in our galaxy. For WISE 1534–1043 one alternative scenario explains this object as an ejected exoplanet due to its high Vtan of about 200 km/s, but its color suggests it is an old metal-poor brown dwarf. Most astronomers studying massive iPMOs believe that they represent the low-mass end of the star-formation process. | Rogue planet | Wikipedia | 447 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
Astronomers have used the Herschel Space Observatory and the Very Large Telescope to observe a very young free-floating planetary-mass object, OTS 44, and demonstrate that the processes characterizing the canonical star-like mode of formation apply to isolated objects down to a few Jupiter masses. Herschel far-infrared observations have shown that OTS 44 is surrounded by a disk of at least 10 Earth masses and thus could eventually form a mini planetary system. Spectroscopic observations of OTS 44 with the SINFONI spectrograph at the Very Large Telescope have revealed that the disk is actively accreting matter, similar to the disks of young stars.
Binaries
The first discovery of a resolved planetary-mass binary was 2MASS J1119–1137AB. There are however other binaries known, such as 2MASS J1553022+153236AB, WISE 1828+2650, WISE 0146+4234, WISE J0336−0143 (could also be a brown dwarf and a planetary-mass object (BD+PMO) binary), NIRISS-NGC1333-12 and several objects discovered by Zhang et al. | Rogue planet | Wikipedia | 240 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
In the Orion Nebula a population of 40 wide binaries and 2 triple systems were discovered. This was surprising for two reasons: The trend of binaries of brown dwarfs predicted a decrease of distance between low mass objects with decreasing mass. It was also predicted that the binary fraction decreases with mass. These binaries were named Jupiter-mass binary objects (JuMBOs). They make up at least 9% of the iPMOs and have a separation smaller than 340 AU. It is unclear how these JuMBOs formed, but an extensive study argued that they formed in situ, like stars. If they formed like stars, then there must be an unknown "extra ingredient" to allow them to form. If they formed like planets and were later ejected, then it has to be explained why these binaries did not break apart during the ejection process. Future measurements with JWST might resolve if these objects formed as ejected planets or as stars. A study by Kevin Luhman reanalysed the NIRCam data and found that most JuMBOs did not appear in his sample of substellar objects. Moreover the color were consistent with reddened background sources or low signal-to-noise sources. Only JuMBO 29 is identified as a good candidate in this work. JuMBO 29 also was observed with NIRSpec and one component was identified as a young M8 source. This spectral type is consistent with a low mass for the age of the Orion Nebula.
Total number of known iPMOs
There are likely hundreds of known candidate iPMOs, over a hundred objects with spectra and a small but growing number of candidates discovered via microlensing. Some large surveys include:
As of December 2021, the largest-ever group of rogue planets was discovered, numbering at least 70 and up to 170 depending on the assumed age. They are found in the OB association between Upper Scorpius and Ophiuchus with masses between 4 and 13 and age around 3 to 10 million years, and were most likely formed by either gravitational collapse of gas clouds, or formation in a protoplanetary disk followed by ejection due to dynamical instabilities. Follow-up observations with spectroscopy from the Subaru Telescope and Gran Telescopio Canarias showed that the contamination of this sample is quite low (≤6%). The 16 young objects had a mass between 3 and 14 , confirming that they are indeed planetary-mass objects. | Rogue planet | Wikipedia | 492 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
In October 2023 an even larger group of 540 planetary-mass object candidates was discovered in the Trapezium Cluster and inner Orion Nebula with JWST. The objects have a mass between 13 and 0.6 . A surprising number of these objects formed wide binaries, which was not predicted.
Formation
There are in general two scenarios that can lead to the formation of an isolated planetary-mass object (iPMO). It can form like a planet around a star and is then ejected, or it forms like a low-mass star or brown dwarf in isolation. This can influence its composition and motion.
Formation like a star
Objects with a mass of at least one Jupiter mass were thought to be able to form via collapse and fragmentation of molecular clouds from models in 2001. Pre-JWST observations have shown that objects below 3-5 are unlikely to form on their own. Observations in 2023 in the Trapezium Cluster with JWST have shown that objects as massive as 0.6 might form on their own, not requiring a steep cut-off mass. A particular type of globule, called globulettes, are thought to be birthplaces for brown dwarfs and planetary-mass objects. Globulettes are found in the Rosette Nebula and IC 1805. Sometimes young iPMOs are still surrounded by a disk that could form exomoons. Due to the tight orbit of this type of exomoon around their host planet, they have a high chance of 10-15% to be transiting. | Rogue planet | Wikipedia | 312 | 558397 | https://en.wikipedia.org/wiki/Rogue%20planet | Physical sciences | Planetary science | Astronomy |
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