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chemotherapeutic regiment such as the combination of chemotherapy and radiotherapy (chemoradiation) where despite allowing a more effective treatment or reducing the risk of the cancer returning (adjuvant chemotherapy). It has extensive associations with fertility damage than receiving either treatment individually. Sometimes these patients experience symptoms resembling menopause (in females) or andropause (in men), which can indicate reproductive damage. In females this can be premature menopause of menopause in premenopausal women; this state can be permanent or reversible, dependent on many factors. A study indicated that fewer oocytes are recovered from cancer patients wanting to perform embryo preservation when compared with an age-matched control group, but the mean number of zygotes generated appears to be similar. The same study found that, of 65 patients referred to the program, 28% declined to undergo embryo, oocyte, or tissue cryopreservation. 9% were found not to be eligible for medical reasons. Of the remaining 41 patients, 85% chose to cryopreserve embryos, 10% chose to cryopreserve oocytes, and 5% chose to undergo ovarian tissue freezing. No serious clinical sequelae resulted from participation. Prior to females undergoing these treatments, a testing for the level of anti-Müllerian hormone (AMH) is useful in predicting the long-term post-chemotherapy loss of ovarian function, in turn predicting the need for fertility preservation strategies in the future. === Ageing === Increasing age in females is directly associated with decreasing reproductive potential. This can be the result of many factors such as the amount of eggs available and their overall reproductive quality. Fertility preservation, such as ovarian tissue or oocyte cryopreservation, may also be used to prevent infertility, as well as birth defects, associated with advanced maternal age. Males also have decreasing fertility as they age, however this is associated with a problem in sperm quality as opposed to the overall sperm count. These
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changes can be attributed to the reduction in testosterone males experience when ageing. === PCOS === Polycystic Ovarian Syndrome is the most prevalent endocrine disorder females experience during prime reproductive age. PCOS has a direct relationship with many health risks such as the development of Type 2 Diabetes, increasing insulin levels, obesity and increased waist size. females with PCOS usually experience anovulation (where they will not regularly release an egg). The link between infertility and PCOS is well documented and so females may therefore seek fertility treatment like ovulation induction. === POI === Primary Ovarian Insufficiency is defined as when ovarian function is stopped prematurely (before the age of 40). This is also known premature ovarian failure or premature menopause. Ovarian deficiency causes a reduction in serum oestrogen levels which can lead to infertility, giving a reason for females to seek fertility treatment. POI can result in a long term risk of serious physical symptoms including bone fragility and heart problems. It has also been linked to psychological distress specifically in regards to fertility loss and the long term consequences of that. == Methods == The main methods of fertility preservation are ovarian protection by GnRH agonists, cryopreservation of ovarian tissue, eggs or sperm, or of embryos after in vitro fertilization. The patient may also choose to use egg or sperm from a donor by third party reproduction rather than having biological children. === Semen cryopreservation === Men hoping to preserve their fertility before undergoing treatment for cancer or another fertility-threatening disease can cryopreserve, or freeze, their sperm, which can be obtained through masturbation in post-pubescent boys and men. This is the most established fertility preservation method for males. For pre-pubescent boys, sperm can be obtained through testicular aspiration or electrostimulation and then stored for future use. Researchers are also
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looking at methods for cryopreserving testicular tissue samples so that they can be re-implanted into the body after treatment. === Cryopreservation of ovarian tissue or oocytes === ==== Oocyte cryopreservation ==== Oocyte cryopreservation involves the extraction and freezing of a female's eggs, to preserve their viability for future use. This is often for medical reasons such as females undergoing cancer treatment. It is also increasingly being used for elective fertility preservation in females who are not ready to become pregnant but who are conscious of their age-related decline in fertility. This process is different to embryo cryopreservation, where mature eggs are fertilised in vitro (outside the body) with sperm from a donor or partner, and the embryo is frozen. The religious and ethical concerns and legislative restrictions surrounding embryo cryopreservation has prompted significant technical advances in oocyte cryopreservation techniques. Oocyte cryopreservation is now considered a well-established technique for fertility preservation in women. ==== Embryo cryopreservation ==== Some female patients choose to have mature eggs extracted and fertilized outside of the body with sperm from a partner or donor. The resulting embryo is then frozen until the female's is in remission from disease. When the female's is ready to initiate pregnancy, the embryo is thawed and implanted into the uterus for maturation and birth. While this option is the most common fertility preservation method in females, it is not available to pre-pubescent girls, who do not have mature eggs that can be fertilized. females who do not have a partner will need to use donor sperm. Additionally, because this procedure requires a two-week period of hormonal stimulation to encourage egg maturation, it is not optimal for female patients who are diagnosed with hormone-sensitive cancers (such as breast cancer, ovarian cancer, etc.) or those who cannot delay cancer treatment. Alternative methods of
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hormonal stimulation using letrozole or tamoxifen may be used for females with hormone-sensitive cancers. ==== Ovarian tissue cryopreservation ==== Cryopreservation of human ovarian tissue has been successfully carried out around the world to preserve fertility in female cancer patients and in other pathologies where the patient is at increased risk of primary ovarian insufficiency. Most notably, this technique can provide an option for fertility preservation in prepubertal girls. Part of the ovary is removed, frozen and stored until after treatment. The tissue is then thawed and re-implanted. According to a meta-analysis performed in 2017, the success rate of reestablishment of ovarian activity was 63.9%, restoring normal fertility and endocrine function. Over 130 live births have been reported as of June 2017. Strips of cortical ovarian tissue can also be cryopreserved, but it must be re-implanted into the body to allow the encapsulated immature follicles to complete their maturation. Furthermore, ovarian tissue is fragile under hard freezing conditions and putting it back into the body carries the risk of re-introducing cancerous cells. In vitro maturation has been achieved experimentally, but the technique is not yet clinically available. With this technique, cryopreserved ovarian tissue could possibly be used to make oocytes that can directly undergo in vitro fertilization. === Third-party reproduction === Many patients diagnosed with a malignancy or another disease requiring treatment that may impair their fertility consider alternatives to bearing biological children, such as assisted reproductive technology (ART) using in vitro fertilization (IVF) with donor eggs or donor sperm. The resulting embryo can be implanted into the female's's uterus after her endometrium (the lining of the uterus) is stimulated with hormones to prepare for the development of the embryo. === Others === In females requiring local pelvic radiation therapy may benefit from surgical transposition of the ovaries to a site
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remote from maximal radiation exposure. The use of GnRH agonists for ovarian protection during chemotherapy is suggested to benefit the ability to ovulate, but benefits in terms of e.g. pregnancy rate are lacking. Table 1: Main Options of Fertility Preservation == Adverse effects == Compared with the general population, people with cancer have a higher risk of arterial thrombotic events such as stroke, myocardial infarction and peripheral arterial embolism. This risk has a potential to be further increased in females undergoing controlled ovarian hyperstimulation for fertility preservation, but is usually only associated with cases of ovarian hyperstimulation syndrome (OHSS). On the other hand, venous thromboembolism rarely occurs unless a pregnancy is achieved, and is therefore usually not particularly relevant in the stage of oocyte retrieval. Therefore, the recommended controlled ovarian hyperstimulation protocol for in females with cancer is an antagonist protocol using a GnRH agonist for final maturation induction, in order to decrease the risk of OHSS. When used in conjunction with oocyte or embryo cryopreservation, using GnRH agonist rather than hCG for final maturation induction has no evidence of a difference in live birth rate (in contrast to fresh cycles where usage of GnRH agonist has a lower live birth rate). Anticoagulant prophylaxis is recommended to be administered only to selected subgroups of females such as those with other risk factors of hypercoagulability or those who do develop early OHSS. == Fertility preservation in transgender men == Transgender men should be given the opportunity to have counselling on preserving their fertility before undergoing any type of medical transition, otherwise they may be unable to have biological children in the future. This is important as individuals may start their transition at a young age where they have no interest in future children, however half of adult trans men do wish
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to have children. Suppressing puberty in paediatric patients does pause the development of fertility, however this is reversible. Some fertility options in adults trans men present problems as they may require stopping hormone treatment for around 3 months to carry out the procedure, as well as multiple transvaginal ultrasounds (a probe entering and scanning the inside of the vagina) - both of which may be distressing for a transgender individual. Various methods of fertility preservation are detailed in the table above. == References == == Further reading == == External links == Fertility Preservation, ReproTech website Semen Storage through Cryopreservation Embryo Storage through Cryopreservation Oocyte Cryostorage Ovarian Tissue Cryostorage Services http://oncofertility.northwestern.edu http://savemyfertility.org/ FertiPROTEKT, network for fertility protection of German-speaking countries
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The Arrhenius Plaque (Swedish: Arrhenius-plaketten) is awarded annually by the Swedish Chemical Society in memory of Svante Arrhenius, a Swedish physicist, chemist, and long-time member of the society, "to a person or persons who have distinguished themselves through outstanding research in the field of chemistry or who have performed valuable work for the good of the Swedish Chemical Society". Past recipients include Ragnar Ryhage (1962), Jerker Porath and Per Flodin (1963), Carl-Ivar Brändén (1976), Svante Wold (1984), Gunnar von Heijne (1997), Per Claesson (2008), Jonas Bergquist (2009), Lisbeth Olsson (2018) and Berit Olofsson (2021) == References ==
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"page_id": 78251560,
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In classical mechanics, Newton's theorem of revolving orbits identifies the type of central force needed to multiply the angular speed of a particle by a factor k without affecting its radial motion (Figures 1 and 2). Newton applied his theorem to understanding the overall rotation of orbits (apsidal precession, Figure 3) that is observed for the Moon and planets. The term "radial motion" signifies the motion towards or away from the center of force, whereas the angular motion is perpendicular to the radial motion. Isaac Newton derived this theorem in Propositions 43–45 of Book I of his Philosophiæ Naturalis Principia Mathematica, first published in 1687. In Proposition 43, he showed that the added force must be a central force, one whose magnitude depends only upon the distance r between the particle and a point fixed in space (the center). In Proposition 44, he derived a formula for the force, showing that it was an inverse-cube force, one that varies as the inverse cube of r. In Proposition 45 Newton extended his theorem to arbitrary central forces by assuming that the particle moved in nearly circular orbit. This theorem remained largely unknown and undeveloped for over three centuries, as noted by astrophysicist Subrahmanyan Chandrasekhar in his 1995 commentary on Newton's Principia. Since 1997, the theorem has been studied by Donald Lynden-Bell and collaborators. Its first exact extension came in 2000 with the work of Mahomed and Vawda. == Historical context == The motion of astronomical bodies has been studied systematically for thousands of years. The stars were observed to rotate uniformly, always maintaining the same relative positions to one another. However, other bodies were observed to wander against the background of the fixed stars; most such bodies were called planets after the Greek word "πλανήτοι" (planētoi) for "wanderers". Although they generally
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move in the same direction along a path across the sky (the ecliptic), individual planets sometimes reverse their direction briefly, exhibiting retrograde motion. To describe this forward-and-backward motion, Apollonius of Perga (c. 262 – c. 190 BC) developed the concept of deferents and epicycles, according to which the planets are carried on rotating circles that are themselves carried on other rotating circles, and so on. Any orbit can be described with a sufficient number of judiciously chosen epicycles, since this approach corresponds to a modern Fourier transform. Roughly 350 years later, Claudius Ptolemaeus published his Almagest, in which he developed this system to match the best astronomical observations of his era. To explain the epicycles, Ptolemy adopted the geocentric cosmology of Aristotle, according to which planets were confined to concentric rotating spheres. This model of the universe was authoritative for nearly 1500 years. The modern understanding of planetary motion arose from the combined efforts of astronomer Tycho Brahe and physicist Johannes Kepler in the 16th century. Tycho is credited with extremely accurate measurements of planetary motions, from which Kepler was able to derive his laws of planetary motion. According to these laws, planets move on ellipses (not epicycles) about the Sun (not the Earth). Kepler's second and third laws make specific quantitative predictions: planets sweep out equal areas in equal time, and the square of their orbital periods equals a fixed constant times the cube of their semi-major axis. Subsequent observations of the planetary orbits showed that the long axis of the ellipse (the so-called line of apsides) rotates gradually with time; this rotation is known as apsidal precession. The apses of an orbit are the points at which the orbiting body is closest or furthest away from the attracting center; for planets orbiting the Sun, the apses correspond to
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the perihelion (closest) and aphelion (furthest). With the publication of his Principia roughly eighty years later (1687), Isaac Newton provided a physical theory that accounted for all three of Kepler's laws, a theory based on Newton's laws of motion and his law of universal gravitation. In particular, Newton proposed that the gravitational force between any two bodies was a central force F(r) that varied as the inverse square of the distance r between them. Arguing from his laws of motion, Newton showed that the orbit of any particle acted upon by one such force is always a conic section, specifically an ellipse if it does not go to infinity. However, this conclusion holds only when two bodies are present (the two-body problem); the motion of three bodies or more acting under their mutual gravitation (the n-body problem) remained unsolved for centuries after Newton, although solutions to a few special cases were discovered. Newton proposed that the orbits of planets about the Sun are largely elliptical because the Sun's gravitation is dominant; to first approximation, the presence of the other planets can be ignored. By analogy, the elliptical orbit of the Moon about the Earth was dominated by the Earth's gravity; to first approximation, the Sun's gravity and those of other bodies of the Solar System can be neglected. However, Newton stated that the gradual apsidal precession of the planetary and lunar orbits was due to the effects of these neglected interactions; in particular, he stated that the precession of the Moon's orbit was due to the perturbing effects of gravitational interactions with the Sun. Newton's theorem of revolving orbits was his first attempt to understand apsidal precession quantitatively. According to this theorem, the addition of a particular type of central force—the inverse-cube force—can produce a rotating orbit; the angular speed
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is multiplied by a factor k, whereas the radial motion is left unchanged. However, this theorem is restricted to a specific type of force that may not be relevant; several perturbing inverse-square interactions (such as those of other planets) seem unlikely to sum exactly to an inverse-cube force. To make his theorem applicable to other types of forces, Newton found the best approximation of an arbitrary central force F(r) to an inverse-cube potential in the limit of nearly circular orbits, that is, elliptical orbits of low eccentricity, as is indeed true for most orbits in the Solar System. To find this approximation, Newton developed an infinite series that can be viewed as the forerunner of the Taylor expansion. This approximation allowed Newton to estimate the rate of precession for arbitrary central forces. Newton applied this approximation to test models of the force causing the apsidal precession of the Moon's orbit. However, the problem of the Moon's motion is dauntingly complex, and Newton never published an accurate gravitational model of the Moon's apsidal precession. After a more accurate model by Clairaut in 1747, analytical models of the Moon's motion were developed in the late 19th century by Hill, Brown, and Delaunay. However, Newton's theorem is more general than merely explaining apsidal precession. It describes the effects of adding an inverse-cube force to any central force F(r), not only to inverse-square forces such as Newton's law of universal gravitation and Coulomb's law. Newton's theorem simplifies orbital problems in classical mechanics by eliminating inverse-cube forces from consideration. The radial and angular motions, r(t) and θ1(t), can be calculated without the inverse-cube force; afterwards, its effect can be calculated by multiplying the angular speed of the particle ω 2 = d θ 2 d t = k d θ 1 d t = k
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ω 1 . {\displaystyle \omega _{2}={\frac {d\theta _{2}}{dt}}=k{\frac {d\theta _{1}}{dt}}=k\omega _{1}.} == Mathematical statement == Consider a particle moving under an arbitrary central force F1(r) whose magnitude depends only on the distance r between the particle and a fixed center. Since the motion of a particle under a central force always lies in a plane, the position of the particle can be described by polar coordinates (r, θ1), the radius and angle of the particle relative to the center of force (Figure 1). Both of these coordinates, r(t) and θ1(t), change with time t as the particle moves. Imagine a second particle with the same mass m and with the same radial motion r(t), but one whose angular speed is k times faster than that of the first particle. In other words, the azimuthal angles of the two particles are related by the equation θ2(t) = k θ1(t). Newton showed that the motion of the second particle can be produced by adding an inverse-cube central force to whatever force F1(r) acts on the first particle F 2 ( r ) − F 1 ( r ) = L 1 2 m r 3 ( 1 − k 2 ) {\displaystyle F_{2}(r)-F_{1}(r)={\frac {L_{1}^{2}}{mr^{3}}}\left(1-k^{2}\right)} where L1 is the magnitude of the first particle's angular momentum, which is a constant of motion (conserved) for central forces. If k2 is greater than one, F2 − F1 is a negative number; thus, the added inverse-cube force is attractive, as observed in the green planet of Figures 1–4 and 9. By contrast, if k2 is less than one, F2−F1 is a positive number; the added inverse-cube force is repulsive, as observed in the green planet of Figures 5 and 10, and in the red planet of Figures 4 and 5. === Alteration of the particle path
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=== The addition of such an inverse-cube force also changes the path followed by the particle. The path of the particle ignores the time dependencies of the radial and angular motions, such as r(t) and θ1(t); rather, it relates the radius and angle variables to one another. For this purpose, the angle variable is unrestricted and can increase indefinitely as the particle revolves around the central point multiple times. For example, if the particle revolves twice about the central point and returns to its starting position, its final angle is not the same as its initial angle; rather, it has increased by 2×360° = 720°. Formally, the angle variable is defined as the integral of the angular speed θ 1 ≡ ∫ ω 1 ( t ) d t . {\displaystyle \theta _{1}\equiv \int \omega _{1}(t)\,dt.} A similar definition holds for θ2, the angle of the second particle. If the path of the first particle is described in the form r = g(θ1), the path of the second particle is given by the function r = g(θ2/k), since θ2 = k θ1. For example, let the path of the first particle be an ellipse 1 r = A + B cos θ 1 {\displaystyle {\frac {1}{r}}=A+B\cos \theta _{1}} where A and B are constants; then, the path of the second particle is given by 1 r = A + B cos ( θ 2 k ) . {\displaystyle {\frac {1}{r}}=A+B\cos \left({\frac {\theta _{2}}{k}}\right).} == Orbital precession == If k is close, but not equal, to one, the second orbit resembles the first, but revolves gradually about the center of force; this is known as orbital precession (Figure 3). If k is greater than one, the orbit precesses in the same direction as the orbit (Figure 3); if k
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is less than one, the orbit precesses in the opposite direction. Although the orbit in Figure 3 may seem to rotate uniformly, i.e., at a constant angular speed, this is true only for circular orbits. If the orbit rotates at an angular speed Ω, the angular speed of the second particle is faster or slower than that of the first particle by Ω; in other words, the angular speeds would satisfy the equation ω2 = ω1 + Ω. However, Newton's theorem of revolving orbits states that the angular speeds are related by multiplication: ω2 = kω1, where k is a constant. Combining these two equations shows that the angular speed of the precession equals Ω = (k − 1)ω1. Hence, Ω is constant only if ω1 is constant. According to the conservation of angular momentum, ω1 changes with the radius r ω 1 = L 1 m r 2 ; {\displaystyle \omega _{1}={\frac {L_{1}}{mr^{2}}};} where m and L1 are the first particle's mass and angular momentum, respectively, both of which are constant. Hence, ω1 is constant only if the radius r is constant, i.e., when the orbit is a circle. However, in that case, the orbit does not change as it precesses. == Illustrative example: Cotes's spirals == The simplest illustration of Newton's theorem occurs when there is no initial force, i.e., F1(r) = 0. In this case, the first particle is stationary or travels in a straight line. If it travels in a straight line that does not pass through the origin (yellow line in Figure 6) the equation for such a line may be written in the polar coordinates (r, θ1) as 1 r = 1 b cos ( θ 1 − θ 0 ) {\displaystyle {\frac {1}{r}}={\frac {1}{b}}\cos \ (\theta _{1}-\theta _{0})} where θ0 is the
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angle at which the distance is minimized (Figure 6). The distance r begins at infinity (when θ1 – θ0 = −90°), and decreases gradually until θ1 – θ0 = 0°, when the distance reaches a minimum, then gradually increases again to infinity at θ1 – θ0 = 90°. The minimum distance b is the impact parameter, which is defined as the length of the perpendicular from the fixed center to the line of motion. The same radial motion is possible when an inverse-cube central force is added. An inverse-cube central force F2(r) has the form F 2 ( r ) = μ r 3 {\displaystyle F_{2}(r)={\frac {\mu }{r^{3}}}} where the numerator μ may be positive (repulsive) or negative (attractive). If such an inverse-cube force is introduced, Newton's theorem says that the corresponding solutions have a shape called Cotes's spirals. These are curves defined by the equation 1 r = 1 b cos ( θ 2 − θ 0 k ) {\displaystyle {\frac {1}{r}}={\frac {1}{b}}\cos \ \left({\frac {\theta _{2}-\theta _{0}}{k}}\right)} where the constant k equals k 2 = 1 − m μ L 1 2 {\displaystyle k^{2}=1-{\frac {m\mu }{L_{1}^{2}}}} When the right-hand side of the equation is a positive real number, the solution corresponds to an epispiral. When the argument θ1 – θ0 equals ±90°×k, the cosine goes to zero and the radius goes to infinity. Thus, when k is less than one, the range of allowed angles becomes small and the force is repulsive (red curve on right in Figure 7). On the other hand, when k is greater than one, the range of allowed angles increases, corresponding to an attractive force (green, cyan and blue curves on left in Figure 7); the orbit of the particle can even wrap around the center several times. The possible values of
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the parameter k may range from zero to infinity, which corresponds to values of μ ranging from negative infinity up to the positive upper limit, L12/m. Thus, for all attractive inverse-cube forces (negative μ) there is a corresponding epispiral orbit, as for some repulsive ones (μ < L12/m), as illustrated in Figure 7. Stronger repulsive forces correspond to a faster linear motion. One of the other solution types is given in terms of the hyperbolic cosine: 1 r = 1 b cosh ( θ 0 − θ 2 λ ) {\displaystyle {\frac {1}{r}}={\frac {1}{b}}\cosh \ \left({\frac {\theta _{0}-\theta _{2}}{\lambda }}\right)} where the constant λ satisfies λ 2 = m μ L 1 2 − 1 {\displaystyle \lambda ^{2}={\frac {m\mu }{L_{1}^{2}}}-1} This form of Cotes's spirals corresponds to one of the two Poinsot's spirals (Figure 8). The possible values of λ range from zero to infinity, which corresponds to values of μ greater than the positive number L12/m. Thus, Poinsot spiral motion only occurs for repulsive inverse-cube central forces, and applies in the case that L is not too large for the given μ. Taking the limit of k or λ going to zero yields the third form of a Cotes's spiral, the so-called reciprocal spiral or hyperbolic spiral, as a solution 1 r = A θ 2 + ε {\displaystyle {\frac {1}{r}}=A\theta _{2}+\varepsilon } where A and ε are arbitrary constants. Such curves result when the strength μ of the repulsive force exactly balances the angular momentum-mass term μ = L 1 2 m {\displaystyle \mu ={\frac {L_{1}^{2}}{m}}} == Closed orbits and inverse-cube central forces == Two types of central forces—those that increase linearly with distance, F = Cr, such as Hooke's law, and inverse-square forces, F = C/r2, such as Newton's law of universal gravitation and Coulomb's law—have
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a very unusual property. A particle moving under either type of force always returns to its starting place with its initial velocity, provided that it lacks sufficient energy to move out to infinity. In other words, the path of a bound particle is always closed and its motion repeats indefinitely, no matter what its initial position or velocity. As shown by Bertrand's theorem, this property is not true for other types of forces; in general, a particle will not return to its starting point with the same velocity. However, Newton's theorem shows that an inverse-cubic force may be applied to a particle moving under a linear or inverse-square force such that its orbit remains closed, provided that k equals a rational number. (A number is called "rational" if it can be written as a fraction m/n, where m and n are integers.) In such cases, the addition of the inverse-cubic force causes the particle to complete m rotations about the center of force in the same time that the original particle completes n rotations. This method for producing closed orbits does not violate Bertrand's theorem, because the added inverse-cubic force depends on the initial velocity of the particle. Harmonic and subharmonic orbits are special types of such closed orbits. A closed trajectory is called a harmonic orbit if k is an integer, i.e., if n = 1 in the formula k = m/n. For example, if k = 3 (green planet in Figures 1 and 4, green orbit in Figure 9), the resulting orbit is the third harmonic of the original orbit. Conversely, the closed trajectory is called a subharmonic orbit if k is the inverse of an integer, i.e., if m = 1 in the formula k = m/n. For example, if k = 1/3 (green planet in Figure
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5, green orbit in Figure 10), the resulting orbit is called the third subharmonic of the original orbit. Although such orbits are unlikely to occur in nature, they are helpful for illustrating Newton's theorem. == Limit of nearly circular orbits == In Proposition 45 of his Principia, Newton applies his theorem of revolving orbits to develop a method for finding the force laws that govern the motions of planets. Johannes Kepler had noted that the orbits of most planets and the Moon seemed to be ellipses, and the long axis of those ellipses can determined accurately from astronomical measurements. The long axis is defined as the line connecting the positions of minimum and maximum distances to the central point, i.e., the line connecting the two apses. For illustration, the long axis of the planet Mercury is defined as the line through its successive positions of perihelion and aphelion. Over time, the long axis of most orbiting bodies rotates gradually, generally no more than a few degrees per complete revolution, because of gravitational perturbations from other bodies, oblateness in the attracting body, general relativistic effects, and other effects. Newton's method uses this apsidal precession as a sensitive probe of the type of force being applied to the planets. Newton's theorem describes only the effects of adding an inverse-cube central force. However, Newton extends his theorem to an arbitrary central force F(r) by restricting his attention to orbits that are nearly circular, such as ellipses with low orbital eccentricity (ε ≤ 0.1), which is true of seven of the eight planetary orbits in the solar system. Newton also applied his theorem to the planet Mercury, which has an eccentricity ε of roughly 0.21, and suggested that it may pertain to Halley's comet, whose orbit has an eccentricity of roughly 0.97. A qualitative
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justification for this extrapolation of his method has been suggested by Valluri, Wilson and Harper. According to their argument, Newton considered the apsidal precession angle α (the angle between the vectors of successive minimum and maximum distance from the center) to be a smooth, continuous function of the orbital eccentricity ε. For the inverse-square force, α equals 180°; the vectors to the positions of minimum and maximum distances lie on the same line. If α is initially not 180° at low ε (quasi-circular orbits) then, in general, α will equal 180° only for isolated values of ε; a randomly chosen value of ε would be very unlikely to give α = 180°. Therefore, the observed slow rotation of the apsides of planetary orbits suggest that the force of gravity is an inverse-square law. === Quantitative formula === To simplify the equations, Newton writes F(r) in terms of a new function C(r) F ( r ) = C ( r ) R r 3 {\displaystyle F(r)={\frac {C(r)}{Rr^{3}}}} where R is the average radius of the nearly circular orbit. Newton expands C(r) in a series—now known as a Taylor expansion—in powers of the distance r, one of the first appearances of such a series. By equating the resulting inverse-cube force term with the inverse-cube force for revolving orbits, Newton derives an equivalent angular scaling factor k for nearly circular orbits： 1 k 2 = ( R C ) d C d r | r = R {\displaystyle {\frac {1}{k^{2}}}=\left({\frac {R}{C}}\right)\left.{\frac {dC}{dr}}\right|_{r=R}} In other words, the application of an arbitrary central force F(r) to a nearly circular elliptical orbit can accelerate the angular motion by the factor k without affecting the radial motion significantly. If an elliptical orbit is stationary, the particle rotates about the center of force by 180° as it moves
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from one end of the long axis to the other (the two apses). Thus, the corresponding apsidal angle α for a general central force equals k×180°, using the general law θ2 = k θ1. === Examples === Newton illustrates his formula with three examples. In the first two, the central force is a power law, F(r) = rn−3, so C(r) is proportional to rn. The formula above indicates that the angular motion is multiplied by a factor k = 1/√n, so that the apsidal angle α equals 180°/√n. This angular scaling can be seen in the apsidal precession, i.e., in the gradual rotation of the long axis of the ellipse (Figure 3). As noted above, the orbit as a whole rotates with a mean angular speed Ω=(k−1)ω, where ω equals the mean angular speed of the particle about the stationary ellipse. If the particle requires a time T to move from one apse to the other, this implies that, in the same time, the long axis will rotate by an angle β = ΩT = (k − 1)ωT = (k − 1)×180°. For an inverse-square law such as Newton's law of universal gravitation, where n equals 1, there is no angular scaling (k = 1), the apsidal angle α is 180°, and the elliptical orbit is stationary (Ω = β = 0). As a final illustration, Newton considers a sum of two power laws C ( r ) ∝ a r m + b r n {\displaystyle C(r)\propto ar^{m}+br^{n}} which multiplies the angular speed by a factor k = a + b a m + b n {\displaystyle k={\sqrt {\frac {a+b}{am+bn}}}} Newton applies both of these formulae (the power law and sum of two power laws) to examine the apsidal precession of the Moon's orbit. == Precession of the Moon's
|
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"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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|
orbit == The motion of the Moon can be measured accurately, and is noticeably more complex than that of the planets. The ancient Greek astronomers, Hipparchus and Ptolemy, had noted several periodic variations in the Moon's orbit, such as small oscillations in its orbital eccentricity and the inclination of its orbit to the plane of the ecliptic. These oscillations generally occur on a once-monthly or twice-monthly time-scale. The line of its apses precesses gradually with a period of roughly 8.85 years, while its line of nodes turns a full circle in roughly double that time, 18.6 years. This accounts for the roughly 18-year periodicity of eclipses, the so-called Saros cycle. However, both lines experience small fluctuations in their motion, again on the monthly time-scale. In 1673, Jeremiah Horrocks published a reasonably accurate model of the Moon's motion in which the Moon was assumed to follow a precessing elliptical orbit. A sufficiently accurate and simple method for predicting the Moon's motion would have solved the navigational problem of determining a ship's longitude; in Newton's time, the goal was to predict the Moon's position to 2' (two arc-minutes), which would correspond to a 1° error in terrestrial longitude. Horrocks' model predicted the lunar position with errors no more than 10 arc-minutes; for comparison, the diameter of the Moon is roughly 30 arc-minutes. Newton used his theorem of revolving orbits in two ways to account for the apsidal precession of the Moon. First, he showed that the Moon's observed apsidal precession could be accounted for by changing the force law of gravity from an inverse-square law to a power law in which the exponent was 2 + 4/243 (roughly 2.0165) F ( r ) = − G M m r 2 + 4 / 243 {\displaystyle F(r)=-{\frac {GMm}{r^{2+4/243}}}} In 1894, Asaph Hall adopted
|
{
"page_id": 12191272,
"source": null,
"title": "Newton's theorem of revolving orbits"
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this approach of modifying the exponent in the inverse-square law slightly to explain an anomalous orbital precession of the planet Mercury, which had been observed in 1859 by Urbain Le Verrier. Ironically, Hall's theory was ruled out by careful astronomical observations of the Moon. The currently accepted explanation for this precession involves the theory of general relativity, which (to first approximation) adds an inverse-quartic force, i.e., one that varies as the inverse fourth power of distance. As a second approach to explaining the Moon's precession, Newton suggested that the perturbing influence of the Sun on the Moon's motion might be approximately equivalent to an additional linear force F ( r ) = A r 2 + B r {\displaystyle F(r)={\frac {A}{r^{2}}}+Br} The first term corresponds to the gravitational attraction between the Moon and the Earth, where r is the Moon's distance from the Earth. The second term, so Newton reasoned, might represent the average perturbing force of the Sun's gravity of the Earth-Moon system. Such a force law could also result if the Earth were surrounded by a spherical dust cloud of uniform density. Using the formula for k for nearly circular orbits, and estimates of A and B, Newton showed that this force law could not account for the Moon's precession, since the predicted apsidal angle α was (≈ 180.76°) rather than the observed α (≈ 181.525°). For every revolution, the long axis would rotate 1.5°, roughly half of the observed 3.0° == Generalization == Isaac Newton first published his theorem in 1687, as Propositions 43–45 of Book I of his Philosophiæ Naturalis Principia Mathematica. However, as astrophysicist Subrahmanyan Chandrasekhar noted in his 1995 commentary on Newton's Principia, the theorem remained largely unknown and undeveloped for over three centuries. The first generalization of Newton's theorem was discovered by Mahomed
|
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"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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|
and Vawda in 2000. As Newton did, they assumed that the angular motion of the second particle was k times faster than that of the first particle, θ2 = k θ1. In contrast to Newton, however, Mahomed and Vawda did not require that the radial motion of the two particles be the same, r1 = r2. Rather, they required that the inverse radii be related by a linear equation 1 r 2 ( t ) = a r 1 ( t ) + b {\displaystyle {\frac {1}{r_{2}(t)}}={\frac {a}{r_{1}(t)}}+b} This transformation of the variables changes the path of the particle. If the path of the first particle is written r1 = g(θ1), the second particle's path can be written as a r 2 1 − b r 2 = g ( θ 2 k ) {\displaystyle {\frac {ar_{2}}{1-br_{2}}}=g\left({\frac {\theta _{2}}{k}}\right)} If the motion of the first particle is produced by a central force F1(r), Mahomed and Vawda showed that the motion of the second particle can be produced by the following force F 2 ( r 2 ) = a 3 ( 1 − b r 2 ) 2 F 1 ( a r 2 1 − b r 2 ) + L 2 m r 3 ( 1 − k 2 ) − b L 2 m r 2 {\displaystyle F_{2}(r_{2})={\frac {a^{3}}{\left(1-br_{2}\right)^{2}}}F_{1}\left({\frac {ar_{2}}{1-br_{2}}}\right)+{\frac {L^{2}}{mr^{3}}}\left(1-k^{2}\right)-{\frac {bL^{2}}{mr^{2}}}} According to this equation, the second force F2(r) is obtained by scaling the first force and changing its argument, as well as by adding inverse-square and inverse-cube central forces. For comparison, Newton's theorem of revolving orbits corresponds to the case a = 1 and b = 0, so that r1 = r2. In this case, the original force is not scaled, and its argument is unchanged; the inverse-cube force is added, but the inverse-square term
|
{
"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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is not. Also, the path of the second particle is r2 = g(θ2/k), consistent with the formula given above. == Derivations == === Newton's derivation === Newton's derivation is found in Section IX of his Principia, specifically Propositions 43–45. His derivations of these Propositions are based largely on geometry. Proposition 43; Problem 30 It is required to make a body move in a curve that revolves about the center of force in the same manner as another body in the same curve at rest. Newton's derivation of Proposition 43 depends on his Proposition 2, derived earlier in the Principia. Proposition 2 provides a geometrical test for whether the net force acting on a point mass (a particle) is a central force. Newton showed that a force is central if and only if the particle sweeps out equal areas in equal times as measured from the center. Newton's derivation begins with a particle moving under an arbitrary central force F1(r); the motion of this particle under this force is described by its radius r(t) from the center as a function of time, and also its angle θ1(t). In an infinitesimal time dt, the particle sweeps out an approximate right triangle whose area is d A 1 = 1 2 r 2 d θ 1 {\displaystyle dA_{1}={\frac {1}{2}}r^{2}d\theta _{1}} Since the force acting on the particle is assumed to be a central force, the particle sweeps out equal angles in equal times, by Newton's Proposition 2. Expressed another way, the rate of sweeping out area is constant d A 1 d t = 1 2 r 2 d θ 1 d t = c o n s t a n t {\displaystyle {\frac {dA_{1}}{dt}}={\frac {1}{2}}r^{2}{\frac {d\theta _{1}}{dt}}=\mathrm {constant} } This constant areal velocity can be calculated as follows. At the apapsis and
|
{
"page_id": 12191272,
"source": null,
"title": "Newton's theorem of revolving orbits"
}
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periapsis, the positions of closest and furthest distance from the attracting center, the velocity and radius vectors are perpendicular; therefore, the angular momentum L1 per mass m of the particle (written as h1) can be related to the rate of sweeping out areas h 1 = L 1 m = r v 1 = r 2 d θ 1 d t = 2 d A 1 d t {\displaystyle h_{1}={\frac {L_{1}}{m}}=rv_{1}=r^{2}{\frac {d\theta _{1}}{dt}}=2{\frac {dA_{1}}{dt}}} Now consider a second particle whose orbit is identical in its radius, but whose angular variation is multiplied by a constant factor k θ 2 ( t ) = k θ 1 ( t ) {\displaystyle \theta _{2}(t)=k\theta _{1}(t)\,\!} The areal velocity of the second particle equals that of the first particle multiplied by the same factor k h 2 = 2 d A 2 d t = r 2 d θ 2 d t = k r 2 d θ 1 d t = 2 k d A 1 d t = k h 1 {\displaystyle h_{2}=2{\frac {dA_{2}}{dt}}=r^{2}{\frac {d\theta _{2}}{dt}}=kr^{2}{\frac {d\theta _{1}}{dt}}=2k{\frac {dA_{1}}{dt}}=kh_{1}} Since k is a constant, the second particle also sweeps out equal areas in equal times. Therefore, by Proposition 2, the second particle is also acted upon by a central force F2(r). This is the conclusion of Proposition 43. Proposition 44 The difference of the forces, by which two bodies may be made to move equally, one in a fixed, the other in the same orbit revolving, varies inversely as the cube of their common altitudes. To find the magnitude of F2(r) from the original central force F1(r), Newton calculated their difference F2(r) − F1(r) using geometry and the definition of centripetal acceleration. In Proposition 44 of his Principia, he showed that the difference is proportional to the inverse cube of the
|
{
"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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radius, specifically by the formula given above, which Newtons writes in terms of the two constant areal velocities, h1 and h2 F 2 ( r ) − F 1 ( r ) = m h 1 2 − h 2 2 r 3 {\displaystyle F_{2}(r)-F_{1}(r)=m{\frac {h_{1}^{2}-h_{2}^{2}}{r^{3}}}} Proposition 45; Problem 31 To find the motion of the apsides in orbits approaching very near to circles. In this Proposition, Newton derives the consequences of his theorem of revolving orbits in the limit of nearly circular orbits. This approximation is generally valid for planetary orbits and the orbit of the Moon about the Earth. This approximation also allows Newton to consider a great variety of central force laws, not merely inverse-square and inverse-cube force laws. === Modern derivation === Modern derivations of Newton's theorem have been published by Whittaker (1937) and Chandrasekhar (1995). By assumption, the second angular speed is k times faster than the first ω 2 = d θ 2 d t = k d θ 1 d t = k ω 1 {\displaystyle \omega _{2}={\frac {d\theta _{2}}{dt}}=k{\frac {d\theta _{1}}{dt}}=k\omega _{1}} Since the two radii have the same behavior with time, r(t), the conserved angular momenta are related by the same factor k L 2 = m r 2 ω 2 = m r 2 k ω 1 = k L 1 {\displaystyle L_{2}=mr^{2}\omega _{2}=mr^{2}k\omega _{1}=kL_{1}\,\!} The equation of motion for a radius r of a particle of mass m moving in a central potential V(r) is given by Lagrange's equations m d 2 r d t 2 − m r ω 2 = m d 2 r d t 2 − L 2 m r 3 = F ( r ) {\displaystyle m{\frac {d^{2}r}{dt^{2}}}-mr\omega ^{2}=m{\frac {d^{2}r}{dt^{2}}}-{\frac {L^{2}}{mr^{3}}}=F(r)} Applying the general formula to the two orbits yields the equation m d
|
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"page_id": 12191272,
"source": null,
"title": "Newton's theorem of revolving orbits"
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2 r d t 2 = F 1 ( r ) + L 1 2 m r 3 = F 2 ( r ) + L 2 2 m r 3 = F 2 ( r ) + k 2 L 1 2 m r 3 {\displaystyle m{\frac {d^{2}r}{dt^{2}}}=F_{1}(r)+{\frac {L_{1}^{2}}{mr^{3}}}=F_{2}(r)+{\frac {L_{2}^{2}}{mr^{3}}}=F_{2}(r)+{\frac {k^{2}L_{1}^{2}}{mr^{3}}}} which can be re-arranged to the form F 2 ( r ) = F 1 ( r ) + L 1 2 m r 3 ( 1 − k 2 ) {\displaystyle F_{2}(r)=F_{1}(r)+{\frac {L_{1}^{2}}{mr^{3}}}\left(1-k^{2}\right)} This equation relating the two radial forces can be understood qualitatively as follows. The difference in angular speeds (or equivalently, in angular momenta) causes a difference in the centripetal force requirement; to offset this, the radial force must be altered with an inverse-cube force. Newton's theorem can be expressed equivalently in terms of potential energy, which is defined for central forces F ( r ) = − d V d r {\displaystyle F(r)=-{\frac {dV}{dr}}} The radial force equation can be written in terms of the two potential energies − d V 2 d r = − d V 1 d r + L 1 2 m r 3 ( 1 − k 2 ) {\displaystyle -{\frac {dV_{2}}{dr}}=-{\frac {dV_{1}}{dr}}+{\frac {L_{1}^{2}}{mr^{3}}}\left(1-k^{2}\right)} Integrating with respect to the distance r, Newtons's theorem states that a k-fold change in angular speed results from adding an inverse-square potential energy to any given potential energy V1(r) V 2 ( r ) = V 1 ( r ) + L 1 2 2 m r 2 ( 1 − k 2 ) {\displaystyle V_{2}(r)=V_{1}(r)+{\frac {L_{1}^{2}}{2mr^{2}}}\left(1-k^{2}\right)} == See also == Kepler problem Laplace–Runge–Lenz vector Two-body problem in general relativity Newton's theorem about ovals == References == == Bibliography == Newton I (1999) [1726]. The Principia: Mathematical Principles of Natural Philosophy. Translated by I.
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{
"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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Bernard Cohen; Anne Whitman; Julia Budenz (3rd ed.). Berkeley, CA: University of California Press. pp. 147–148, 246–264, 534–545. ISBN 978-0-520-08816-0. Chandrasekhar S (1995), Newton's Principia for the Common Reader, Oxford University Press, pp. 183–200, ISBN 978-0-19-852675-9 Pars, L.A. (1965). A Treatise on Analytical Dynamics. John Wiley and Sons. p. 56. ISBN 978-0-918024-07-7. LCCN 64024556. Whittaker ET (1937). A Treatise on the Analytical Dynamics of Particles and Rigid Bodies, with an Introduction to the Problem of Three Bodies (4th ed.). New York: Dover Publications. p. 83. ISBN 978-0-521-35883-5. {{cite book}}: ISBN / Date incompatibility (help) Routh EJ (1960). A Treatise on Dynamics of a Particle (reprint of 1898 ed.). New York: Dover Publications. pp. 230–233 (sections §356–359). ISBN 978-0-548-96521-4. {{cite book}}: ISBN / Date incompatibility (help) Rouse Ball WW (1893). An Essay on Newton's "Principia". Macmillan and Co. (reprint, Merchant Books). pp. 84–85. ISBN 978-1-60386-012-3. {{cite book}}: ISBN / Date incompatibility (help) Heilbron, J. (2005), The Oxford Guide to the History of Physics and Astronomy, Oxford University Press, USA, Bibcode:2005oghp.book.....H, ISBN 978-0-19-517198-3 Fitzpartrick, Richard (2012), An Introduction to Celestial Mechanics, Cambridge University Press, ISBN 978-1-107-02381-9 Lambourne, Robert (2010), Relativity, Gravitation and Cosmology, Cambridge University Press, ISBN 978-0-521-13138-4 Grossman, Nathaniel (1996), The Sheer Joy of Celestial Mechanics, Springer Science & Business Media, ISBN 978-0-8176-3832-0 Shikin, Eugene (1995), Handbook and Atlas of Curves, CRC Press, ISBN 978-0-8493-8963-4 Lawrence, J. Dennis (1972), A Catalog of Special Plane Curves, New York: Dover, ISBN 0486602885 Weisstein, Eric (2002), CRC Concise Encyclopedia of Mathematics, Second Edition, CRC Press, ISBN 978-1-4200-3522-3 == Further reading == Bertrand J (1873). "Théorème relatif au mouvement d'un point attiré vers un centre fixe". Comptes rendus hebdomadaires des séances de l'Académie des Sciences. xxvii/10: 849–853. (séance du lundi 20 Octobre 1873) Cohen IB (1999). "A Guide to Newton's Principia". The Principia: Mathematical Principles
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{
"page_id": 12191272,
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"title": "Newton's theorem of revolving orbits"
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of Natural Philosophy. Berkeley, CA: University of California Press. pp. 147–148, 246–252. ISBN 978-0-520-08816-0. Cook A (1988). The Motion of the Moon. Bristol: Adam Hilger. ISBN 0-85274-348-3. D’Eliseo, MM (2007). "The first-order orbital equation". American Journal of Physics. 75 (4): 352–355. Bibcode:2007AmJPh..75..352D. doi:10.1119/1.2432126. Guicciardini, Niccolò (1999). Reading the Principia: The Debate on Newton's Mathematical Methods for Natural Philosophy from 1687 to 1736. Cambridge University Press. ISBN 978-0-521-54403-0. Newton I (1966). Principia Vol. I The Motion of Bodies (based on Newton's 2nd edition (1713); translated by Andrew Motte (1729) and revised by Florian Cajori (1934) ed.). Berkeley, CA: University of California Press. pp. 135–147 (Section IX of Book I). ISBN 978-0-520-00928-8. Alternative translation of earlier (2nd) edition of Newton's Principia. Smith GE (1999). "Newton and the Problem of the Moon's Motion". The Principia: Mathematical Principles of Natural Philosophy. Berkeley, CA: University of California Press. pp. 252–257. ISBN 978-0-520-08816-0. Smith GE (1999). "Motion of the Lunar Apsis". The Principia: Mathematical Principles of Natural Philosophy. Berkeley, CA: University of California Press. pp. 257–264. ISBN 978-0-520-08816-0. Spivak, Michael (1994). "Planetary Motion". Calculus (3rd ed.). Publish or Perish. ISBN 0-914098-89-6. == External links == Three-body problem discussed by Alain Chenciner at Scholarpedia
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{
"page_id": 12191272,
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Hox genes play a massive role in some amphibians and reptiles in their ability to regenerate lost limbs, especially HoxA and HoxD genes. If the processes involved in forming new tissue can be reverse-engineered into humans, it may be possible to heal injuries of the spinal cord or brain, repair damaged organs and reduce scarring and fibrosis after surgery. Despite the large conservation of the Hox genes through evolution, mammals and humans specifically cannot regenerate any of their limbs. This raises a question as to why humans which also possess an analog to these genes cannot regrow and regenerate limbs. Beside the lack of specific growth factor, studies have shown that something as small as base pair differences between amphibian and human Hox analogs play a crucial role in human inability to reproduce limbs. Undifferentiated stem cells and the ability to have polarity in tissues is vital to this process. == Overview == Some amphibians and reptiles have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and upper and lower jaws. The Japanese fire belly newt can regenerate its eye lens 18 times over a period of 16 years and retain its structural and functional properties. The cells at the site of the injury have the ability to undifferentiate, reproduce rapidly, and differentiate again to create a new limb or organ. Hox genes are a group of related genes that control the body plan of an embryo along the head-tail axis. They are responsible for body segment differentiation and express the arrangement of numerous body components during initial embryonic development. Primarily, these sets of genes are utilized during the development of body plans by coding for the transcription factors that trigger production of body segment specific structures. Additionally in most animals, these genes are laid out along the
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{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
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chromosome similar to the order in which they are expressed along the anterior–posterior axis. Variants of the Hox genes are found almost in every phylum with the exception of the sponge which use a different type of developmental genes. The homology of these genes is of important interest to scientists as they may hold more answers to the evolution of many species. In fact, these genes demonstrate such a high degree of homology that a human Hox gene variant – HOXB4 – could mimic the function of its homolog in the fruit fly (Drosophila). Studies suggest that the regulation and other target genes in different species are actually what causes such a great difference in phenotypic difference between species. Hox genes contain a DNA sequence known as the homeobox that are involved in the regulation of patterns of anatomical development. They contain a specific DNA sequence with the aim of providing instructions for making a string of 60 protein building blocks - amino acids- which are referred to as the homeodomain. Most homeodomain-containing proteins function as transcription factors and fundamentally bind and regulate the activity of different genes. The homeodomain is the segment of the protein that binds to precise regulatory regions of the target genes. Genes within the homeobox family are implicated in a wide variety of significant activities during growth. These activities include directing the development of limbs and organs along the anterior-posterior axis and regulating the process by which cells mature to carry out specific functions, a process known as cellular differentiation. Certain homeobox genes can act tumor suppressors, which means they help prevent cells from growing and dividing too rapidly or in an uncontrolled way. Due to the fact that homeobox genes have so many important functions, mutations in these genes are accountable for a wide
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{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
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array of developmental disorders. Changes in certain homeobox genes often result in eye disorders, cause abnormal head, face, and tooth development. Additionally, increased or decreased activity of certain homeobox genes has been associated with several forms of cancer later in life. == Limb development == Essentially, Hox genes contribute to the specification of three main components of limb development, including the stylopod, zeugopod and autopod. Certain mutations in Hox genes can potentially lead to the proximal and/or distal losses along with different abnormalities. Three different models have been created for outlining the patterning of these regions. The Zone of polarizing activity (ZPA) in the limb bud has pattern-organizing activity through the utilization of a morphogen gradient of a protein called Sonic hedgehog (Shh). Sonic hedgehog is turned on in the posterior region via the early expression of HoxD genes, along with the expression of Hoxb8. Shh is maintained in the posterior through a feedback loop between the ZPA and the AER. Shh cleaves the Ci/Gli3 transcriptional repressor complex to convert the transcription factor Gli3 to an activator, which activates the transcription of HoxD genes along the anterior/posterior axis. It is evident that different Hox genes are critical for proper limb development in different amphibians. Researchers conducted a study targeting the Hox-9 to Hox-13 genes in different species of frogs and other amphibians. Similar to an ancient tetrapod group with assorted limb types, it is important to note that amphibians are required for the understanding of the origin and diversification of limbs in different land vertebrates. A PCR (Polymerase Chain Reaction) study was conducted in two species of each amphibian order to identify Hox-9 to Hox-13. Fifteen distinct posterior Hox genes and one retro-pseudogene were identified, and the former confirm the existence of four Hox clusters in each amphibian order. Certain
|
{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
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|
genes expected to occur in all tetrapods, based on the posterior Hox complement of mammals, fishes and coelacanth, were not recovered. HoxD-12 is absent in frogs and possibly other amphibians. By definition, the autopodium is distal segment of a limb, comprising the hand or foot. Considering Hox-12’s function in autopodium development, the loss of this gene may be related to the absence of the fifth finger in frogs and salamanders. == Hox clusters == As previously mentioned, Hox genes encode transcription factors that regulate embryonic and post-embryonic developmental processes. The expression of Hox genes is regulated in part by the tight, spatial arrangement of conserved coding and non-coding DNA regions. The potential for evolutionary alterations in Hox cluster composition is viewed to be small among vertebrates. On the other hand, recent studies of a small number of non-mammalian taxa propose greater dissimilarity than initially considered. Next, generation sequencing of considerable genomic fragments greater than 100 kilobases from the eastern newt (Notophthalmus viridescens) was analyzed. Subsequently, it was found that the composition of Hox cluster genes were conserved relative to orthologous regions from other vertebrates. Furthermore, it was found that the length of introns and intergenic regions varied. In particular, the distance between HoxD13 and HoxD11 is longer in newt than orthologous regions from vertebrate species with expanded Hox clusters and is predicted to exceed the length of the entire HoxD clusters (HoxD13–HoxD4) of humans, mice, and frogs. Many recurring DNA sequences were recognized for newt Hox clusters, counting an enrichment of DNA transposon-like sequences similar to non-coding genomic fragments. Researchers found the results to suggest that Hox cluster expansion and transposon accumulation are common features of non-mammalian tetrapod vertebrates. After the loss of a limb, cells draw together to form a clump known as a blastema. This superficially appears undifferentiated,
|
{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
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|
but cells that originated in the skin later develop into new skin, muscle cells into new muscle and cartilage cells into new cartilage. It is only the cells from just beneath the surface of the skin that are pluripotent and able to develop into any type of cell. Salamander Hox genomic regions show elements of conservation and variety in comparison to other vertebrate species. Whereas the structure and organization of Hox coding genes is conserved, newt Hox clusters show variation in the lengths of introns and intergenic regions, and the HoxD13–11 region exceeds the lengths of orthologous segments even among vertebrate species with expanded Hox clusters. Researchers have suggested that the HoxD13–11 expansion predated a basal salamander genome size amplification that occurred approximately 191 million years ago, because it preserved in all three extant amphibian groups. Supplementary verification supports the proposal that Hox clusters are acquiescent to structural evolution and variation is present in the lengths of introns and intergenic regions, relatively high numbers of repetitive sequences, and non-random accumulations of DNA transposons in newts and lizards. Researchers found that the non-random accretion of DNA-like transposons could possibly change developmental encoding by generating sequence motifs for transcriptional control. In conclusion, the available data from several non-mammalian tetrapods suggest that Hox structural flexibility is the rule, not the exception. It is thought that this elasticity may allow for developmental variation across non-mammalian taxa. This is of course true for both embryogenesis and during the redeployment of Hox genes during post-embryonic developmental processes, such as metamorphosis and regeneration. == Gradient fields == Another phenomena that exists in animal models is the presence of gradient fields in early development. More specifically, this has been shown in the aquatic amphibian: the newt. These "gradient fields" as they are known in developmental biology, have the
|
{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
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|
ability to form the appropriate tissues that they are designed to form when cells from other parts of the embryo are introduced or transplanted into specific fields. The first reporting of this was in 1934. Originally, the specific mechanism behind this rather bizarre phenomenon was not known, however Hox genes have been shown to be prevalent behind this process. More specifically, a concept now known as polarity has been implemented as one - but not the only one - of the mechanisms that are driving this development. Studies done by Oliver and colleagues in 1988 showed that different concentrations of XIHbox 1 antigen was present along the anterior-posterior mesoderm of various developing animal models. One conclusion that this varied concentration of protein expression is actually causing differentiation amongst various tissues and could be one of the culprits behind these so-called "gradient fields". While the protein products of Hox genes are strongly involved in these fields and differentiation in amphibians and reptiles, there are other causality factors involved. For example, retinoic acid and other growth factors have been shown to play a role in these gradient fields. == References ==
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{
"page_id": 46335535,
"source": null,
"title": "Hox genes in amphibians and reptiles"
}
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AICD (activation-induced cell death) is programmed cell death caused by the interaction of Fas receptors (Fas, CD95) and Fas ligands (FasL, CD95 ligand). AICD is a negative regulator of activated T lymphocytes that results from repeated stimulation of their T-cell receptors (TCR) and helps to maintain peripheral immune tolerance. Alteration of the process may lead to autoimmune diseases. In fact AICD in T cells might be one of the mechanisms of resistance to cancer immunotherapy. The AICD effector cell is one that expresses FasL, and apoptosis is induced in the cell expressing the Fas receptor. Both activated T cells and B cells express Fas and undergo clonal deletion by the AICD mechanism. Activated T cells that express both Fas and FasL may be killed by themselves or by each other. == Signaling == The binding of Fas ligand to Fas receptor triggers trimerization of Fas, whose cytoplasmic domain is then able to bind the death domain of the adaptor protein FADD (Fas-associated protein with death domain). Procaspase 8 binds to FADD's death effector domain (DED) and proteolytically self-activates as caspase 8. Fas, FADD, and procaspase 8 together form a death-inducing signaling complex (DISC). Activated caspase 8 is released into the cytosol, where it activates the caspase cascade that initiates apoptosis. == Regulation of Fas-FasL and AICD == FasL is primarily regulated at the transcriptional level. (The other option is regulation of the signal emanating from the death receptor itself, controlling sensitivity to the induction of apoptosis.) NFAT activated by TCR stimulation activates FasL transcription, possibly indirectly by upregulating early growth response proteins. T cell activation-induced transcription of FasL is further regulated by c-Myc–MAX heterodimers, and can be blocked by c-Myc downregulation. Interferon regulatory factors IRF1 and IRF2 also upregulate FasL transcription by directly binding to the FasL promoter. Not much
|
{
"page_id": 40568371,
"source": null,
"title": "Activation-induced cell death"
}
|
is known about the regulation of Fas and other death receptors. However, overexpression of the protein CFLAR (caspase and FADD-like apoptosis regulator) inhibits Fas-mediated apoptosis. == See also == Immune system Autoimmunity == References ==
|
{
"page_id": 40568371,
"source": null,
"title": "Activation-induced cell death"
}
|
In biochemical protein targeting, a peroxisomal targeting signal (PTS) is a region of the peroxisomal protein that receptors recognize and bind to. It is responsible for specifying that proteins containing this motif are localised to the peroxisome. == Overview == All peroxisomal proteins are synthesized in the cytoplasm and must be directed to the peroxisome. The first step in this process is the binding of the protein to a receptor. The receptor then directs the complex to the peroxisome. Receptors recognize and bind to a region of the peroxisomal protein called a peroxisomal targeting signal, or PTS. Peroxisomes consist of a matrix surrounded by a specific membrane. Most peroxisomal matrix proteins contain a short sequence, usually three amino acids at the extreme carboxy tail of the protein, that serves as the PTS. The prototypic sequence (many variations exist) is serine-lysine-leucine (-SKL in the one-letter amino acid code). This motif, and its variations, is known as the PTS1, and the receptor is termed the PTS1 receptor. It was found that the PTS1 receptor is encoded by the PEX5 gene. PEX5 imports folded proteins into the peroxisome, shuttling between the peroxisome and cytosol. PEX5 interacts with a large number of other proteins, including Pex8p, 10p, 12p, 13p, 14p. A few peroxisomal matrix proteins have a different, and less conserved sequence, at their amino termini. This PTS2 signal is recognized by the PTS2 receptor, encoded by the PEX7 gene. "PEX" refers to a group of genes that were identified as being important for peroxisomal synthesis. The numerical attributions, such as PEX5, generally refer to the order in which they were first discovered. A distinct motif is used for proteins destined for the peroxisomal membrane called the "mPTS" motif, which is more poorly defined and may consist of discontinuous subdomains. One of these usually
|
{
"page_id": 3081780,
"source": null,
"title": "Peroxisomal targeting signal"
}
|
is a cluster of basic amino acids (arginines and lysines) within a loop of protein (i.e., between membrane spans) that will face the matrix. The mPTS receptor is the product of PEX19. == References == == External links == Eukaryotic Linear Motif resource motif class TRG_PTS1
|
{
"page_id": 3081780,
"source": null,
"title": "Peroxisomal targeting signal"
}
|
Valentin Fyodorovich Turchin (Russian: Валенти́н Фёдорович Турчи́н, 14 February 1931 – 7 April 2010) was a Soviet and American physicist, cybernetician, and computer scientist. He developed the Refal programming language, the theory of metasystem transitions and the notion of supercompilation. He was a pioneer in artificial intelligence and a proponent of the global brain hypothesis. == Biography == Turchin was born in 1931 in Podolsk, Soviet Union. In 1952, he graduated from Moscow University with a degree in Theoretical Physics and got his Ph.D. in 1957. After working on neutron and solid-state physics at the Institute for Physics of Energy in Obninsk, in 1964 he accepted a position at the Keldysh Institute of Applied Mathematics in Moscow. There he worked on statistical regularization methods and authored REFAL, one of the first AI languages and the AI language of choice in the Soviet Union. In the 1960s, Turchin became politically active. In the Fall of 1968, he wrote the pamphlet The Inertia of Fear, which was quite widely circulated in samizdat, the writing began to be circulated under the title The Inertia of Fear: Socialism and Totalitarianism in Moscow in 1976. Following its publication in the underground press, he lost his research laboratory. In 1970 he authored "The Phenomenon of Science", a grand cybernetic meta-theory of universal evolution, which broadened and deepened the earlier book. By 1973, Turchin had founded the Moscow chapter of Amnesty International with Andrey Tverdokhlebov and was working closely with the well-known physicist and Soviet dissident Andrei Sakharov. In 1974 he lost his position at the Institute and was persecuted by the KGB. Facing almost certain imprisonment, he and his family were forced to emigrate from the Soviet Union in 1977. He went to New York, where he joined the faculty of the City College of New
|
{
"page_id": 2360885,
"source": null,
"title": "Valentin Turchin"
}
|
York in 1979. In 1990, together with Cliff Joslyn and Francis Heylighen, he founded the Principia Cybernetica Project, a worldwide organization devoted to the collaborative development of an evolutionary-cybernetic philosophy. In 1998, he co-founded the software start-up SuperCompilers, LLC. He retired from his post as Professor of Computer Science at City College in 1999. A resident of Oakland, New Jersey, he died there on 7 April 2010. He has two sons named Peter Turchin (a specialist in population dynamics and the mathematical modeling of historical dynamics) and Dimitri Turchin. == Work == The philosophical core of Turchin's scientific work is the concept of the metasystem transition, which denotes the evolutionary process through which higher levels of control emerge in system structure and function. Turchin uses this concept to provide a global theory of evolution and a coherent social systems theory, to develop a complete cybernetics philosophical and ethical system, and to build a constructivist foundation for mathematics. Using the REFAL language he has implemented Supercompiler, a unified method for program transformation and optimization based on a metasystem transition. == Major publications == Valentin F. Turchin (1977). The Phenomenon of Science. New York: Columbia University Press. ISBN 978-0-231-03983-3. Sakharov, Andrei; Turchin, Valentin; Medvedev, Roy (6 June 1970). "The need for democratization". The Saturday Review: 26–27. Sakharov, Andrei; Turchin, Valentin; Medvedev, Roy (Summer 1970). "An open letter". Survey: 160–170. Valentin F. Turchin (May 1978). "Why you should boycott the Russians". Nature. 273 (5660): 256–257. Bibcode:1978Natur.273..256T. doi:10.1038/273256a0. S2CID 4222713. Valentin F. Turchin (September 1978). "Boycotting the Soviet Union". Bulletin of the Atomic Scientists. 34 (7): 7–11. Bibcode:1978BuAtS..34g...7T. doi:10.1080/00963402.1978.11458530. Турчин, Валентин (1978). Инерция страха: социализм и тоталитаризм [The inertia of fear: socialism and totalitarianism] (in Russian) (2 ed.). New York: Khronika. Turchin, Valentin; Handle, Philip (January 1980). "Boycott Helsinki meeting". Physics Today. 33 (1):
|
{
"page_id": 2360885,
"source": null,
"title": "Valentin Turchin"
}
|
11. Bibcode:1980PhT....33a..11T. doi:10.1063/1.2913894. Turchin, Valentin (4 January 1980). "From Helsinki to Hamburg". Science. 207 (4426): 8. Bibcode:1980Sci...207....8T. doi:10.1126/science.6444253. JSTOR 1683174. Valentin F. Turchin (1981). The Inertia of Fear and the Scientific Worldview. New York: Columbia University Press. ISBN 978-0-231-04622-0. Turchin, Valentin (July 1985). "Orlov in exile". Physics Today. 38 (7): 9. Bibcode:1985PhT....38g...9T. doi:10.1063/1.2814623. Valentin F. Turchin (July 1986). "The concept of a supercompiler". ACM Transactions on Programming Languages and Systems. 8 (3): 292–325. doi:10.1145/5956.5957. S2CID 8403840. Valentin F. Turchin (March 1987). "A constructive interpretation of the full set theory". Journal of Symbolic Logic. 52 (1): 172–201. doi:10.2307/2273872. JSTOR 2273872. S2CID 2205937. Valentin F. Turchin (1993). "On cybernetic epistemology". Systems Research. 10 (1): 1–28. doi:10.1002/sres.3850100102. S2CID 60953576. Turchin, Valentin F. (1993). "The Cybernetic Ontology of Action" (PDF). Kybernetes. 22 (2): 10–30. CiteSeerX 10.1.1.359.6176. doi:10.1108/eb005960. Turchin, Valentin F. (1995). "A dialogue on metasystem transition" (PDF). World Futures. 45 (1): 5–57. CiteSeerX 10.1.1.214.9001. doi:10.1080/02604027.1995.9972553. Refal-5: Programming Guide and Reference Manual, New England Publishing Co. Holyoke MA, 1989 Principia Cybernetica Web (as editor, together with F. Heylighen and C. Joslyn) (1993–2005) Most cited publications according to Google Scholar == References == == External links == Valentin Turchin, eulogy by Edward Kline, President of The Andrei Sakharov Foundation Turchin's home page on Principia Cybernetica web Profile of Valentin Turchin by Ben Goertzel Russian edition. The Phenomenon of Science The Phenomenon of Science. A cybernetic approach to human evolution. ETS Publishing House. Moscow - 2000, 398 pp, ISBN 5-93386-019-0 refal.ru - REFAL and Supercompilation community
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{
"page_id": 2360885,
"source": null,
"title": "Valentin Turchin"
}
|
BioModels is a free and open-source repository for storing, exchanging and retrieving quantitative models of biological interest created in 2006. All the models in the curated section of BioModels Database have been described in peer-reviewed scientific literature. The models stored in BioModels' curated branch are compliant with MIRIAM, the standard of model curation and annotation. The models have been simulated by curators to check that when run in simulations, they provide the same results as described in the publication. Model components are annotated, so the users can conveniently identify each model element and retrieve further information from other resources. Modellers can submit the models in SBML and CellML. Models can subsequently be downloaded in SBML, VCML Archived 2006-12-09 at the Wayback Machine, XPP, SciLab, Octave, BioPAX and RDF/XML. The reaction networks of models are presented in some graphic formats, such as PNG, SVG and graphic Java applet, in which some networks were presented by following Systems Biology Graphical Notation. And a human readable summary of each model is available in PDF. == Content == BioModels is composed of several branches. The curated branch hosts models that are well curated and annotated. The non-curated-branch provides models that are still not curated, are non-curatable (spatial models, steady-state models etc.), or too huge to be curated. Non-curated models can be later moved into the curated branch. The repository also hosts models which were automatically generated from pathways databases. All the models are freely available under the Creative Commons CC0 Public Domain Dedication, and can be easily accessed via the website or Web Services. One can also download archives of all the models from the EBI FTP server. BioModels announced its 31st release on June 26, 2017. It now publicly provides 144,710 models. This corresponds to 1,640 models published in the literature and 143,070
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{
"page_id": 6948407,
"source": null,
"title": "BioModels"
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models automatically generated from pathway resources. Deposition of models in BioModels is advocated by many scientific journals, included Molecular Systems Biology, all the journals of the Public Library of Science, all the journals of BioMed Central and all the journals published by the Royal Society of Chemistry. == Development == BioModels is developed by the BioModels.net Team at the EMBL-EBI, UK, the Le Novère lab at the Babraham Institute, UK, and the SBML Team in Caltech, USA. == Funding == BioModels Development has benefited from the funds of the European Molecular Biology Laboratory, the Biotechnology and Biological Sciences Research Council, the Innovative Medicines Initiative, the Seventh Framework Programme (FP7), the National Institute of General Medical Sciences, the DARPA, and the National Center for Research Resources. == References == == External links == Official website of BioModels Caltech Mirror site
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{
"page_id": 6948407,
"source": null,
"title": "BioModels"
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A BioBlitz, also written without capitals as bioblitz, is an intense period of biological surveying in an attempt to record all the living species within a designated area. Groups of scientists, naturalists, and volunteers conduct an intensive field study over a continuous time period (e.g., usually 24 hours). There is a public component to many BioBlitzes, with the goal of getting the public interested in biodiversity. To encourage more public participation, these BioBlitzes are often held in urban parks or nature reserves close to cities. Research into the best practices for a successful BioBlitz has found that collaboration with local natural history museums can improve public participation. As well, BioBlitzes have been shown to be a successful tool in teaching post-secondary students about biodiversity. == Features == A BioBlitz has different opportunities and benefits than a traditional, scientific field study. Some of these potential benefits include: Enjoyment – Instead of a highly structured and measured field survey, this sort of event has the atmosphere of a festival. The short time frame makes the search more exciting. Local – The concept of biodiversity tends to be associated with coral reefs or tropical rainforests. A BioBlitz offers the chance for people to visit a nearby setting and see that local parks have biodiversity and are important to conserve. Science – These one-day events gather basic taxonomic information on some groups of species. Meet the Scientists – A BioBlitz encourages people to meet working scientists and ask them questions. Identifying rare and unique species/groups – When volunteers and scientists work together, they are able to identify uncommon or special habitats for protection and management and, in some cases, rare species may be uncovered. Documenting species occurrence – BioBlitzes do not provide a complete species inventory for a site, but they provide a species
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{
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list which makes a basis for a more complete inventory and will often show what area or what taxon would benefit from a further study. Increases interest in science – BioBlitzes helps to build interest from the general public in science and environmental studies by enabling direct communication and inclusive activities. == History == The term "BioBlitz" was first coined by U.S. National Park Service naturalist Susan Rudy while assisting with the first BioBlitz. The first BioBlitz was held at Kenilworth Aquatic Gardens, Washington, D.C. in 1996. Approximately 1000 species were identified at this first event. This first accounting of biodiversity was organized by Sam Droege (USGS) and Dan Roddy (NPS) with the assistance of other government scientists. The public and especially the news media were invited. Since the success of the first bioblitz, many organizations around the world have repeated this concept. Since then, most BioBlitz contain a public component so that adults, kids, teens and anyone interested can join experts and scientists in the field. Participating in these hands-on field studies is a fun and exciting way for people to learn about biodiversity and better understand how to protect it. In 1998, Harvard biologist E.O. Wilson and Massachusetts wildlife expert Peter Alden developed a program to catalog the organisms around Walden Pond. This led to a statewide program known as Biodiversity Days. This concept is very similar to a BioBlitz and occasionally the two terms are used interchangeably. A variation on the BioBlitz, the Blogger Blitz began in 2007. Rather than gather volunteers and scientists at one location, participant blogs pledged to conduct individual surveys of biodiversity. These results were then compiled and mapped. The purpose of this blitz is not to survey down to species level across all taxonomic groups, but rather to raise awareness about biodiversity
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{
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and provide a general snapshot of diversity. From 2007 through 2016 National Geographic Society and the US National Park Service partnered to put on a Bioblitz in a different National Park each year culminating in a Bioblitz across the National Park Service in 2016 as part of the National Park Service Centennial Celebration. The iNaturalist platform was used as the recording tool for the 2014, 2015, and 2016 Centennial Bioblitzes in this series. Highlights of the 2016 nationwide BioBlitz include: The National Parks BioBlitz—Washington, D.C. was the cornerstone of the national event. Nearly 300 scientists and experts led more than 2,600 students and thousands of members of the general public in all 13 of the National Capital Region's parks. As of the closing ceremony on May 21, nearly 900 species were recorded from this area alone. The Biodiversity Festival at Constitution Gardens on the National Mall served as a window to events across the country, with regular live feeds featuring species discoveries on jumbo screens located on the National Mall. E. O. Wilson, "father of biodiversity", was a significant part of the pre-BioBlitz events, including the Special Speaker Series at the American Association for the Advancement of Science and the 2016 National Parks BioBlitz Scientist Dinner at National Geographic Headquarters on Thursday, May 19. The BioBlitz Dance was a common activity throughout the festival weekend. Participants danced with John Griffith, founder of the dance, on the main stage several times at Constitution Gardens, and on the jumbotron from other park units across the nation. National parks and participating partners shared their BioBlitz activities via social media, using the hashtags #BioBlitz2016 and #FindYourPark. During the weekend's event, #BioBlitz2016 ranked in the top 10 on Twitter! At Cabrillo National Monument, Green Abalone (Haliotis fulgens) was documented. For the past thirty years, abalone
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{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
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have faced substantial conservation concerns due to overharvesting and disease. Their presence in the Cabrillo Rocky Intertidal Zone can be described as ephemeral at best. Knife River National Park conducted an ArcheoBlitz. A centuries-old bison tooth was found at Big Hidatsa Village, which was occupied from about 1740 to 1850. DNA extracted from this tooth can provide data on bison populations before their near-extinction at the end of the 19th century, a useful comparison for managers of modern herds. At Great Smoky Mountain National Park, experts teamed up with about 100 5th graders. Together they set out to explore pollinators and succeeded in discovering nearly 200 species. While it is too early to tell if they found any new species, they have added significant information to the park's database. Craters of the Moon National Monument and Preserve conducted a lichen survey and added several new species to their park list. One of those identified is Xanthoria elegans. This species of lichen survived an 18-month exposure to solar UV radiation, cosmic rays, vacuum and varying temperatures in an experiment performed by the ESA outside of the ISS. Channel Islands National Park broadcast a dive with oceanographer and National Geographic Explorer, Dr. Sylvia Earle, with support from the National Park Trust. The feed was featured online and on the jumbotrons on the National Mall and enabled the public to follow the exploration of one of the richest marine ecosystems in the world, the giant kelp forest. The National Parks BioBlitz used the iNaturalist app to deliver real-time information on species finds. Verified data will be included in National Park Service databases and international databases tracking biodiversity on the planet. This application can be used by parks and citizen scientists well into the future. Beginning with the 2010 NPS/NGS BioBlitz at Biscayne National
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{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
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Park, NPS initiated a corps of Biodiversity Youth Ambassadors. Each year through 2016, a student ambassador is selected by the host park to participate in the BioBlitz and assist in raising biodiversity awareness to their peers and in their home communities. In addition to the new NCR Biodiversity Youth Ambassador, Ms. Katherine Hagan, Ms. Mikaila Ulmer, 11, was selected to be the National Park Service Biodiversity Youth Ambassador representing the President's Pollinator Conservation Initiative for the National Park Service. == BioBlitzes by country == === Australia === The Woodland Watch Project (part of the World Wide Fund for Nature) (WWF) has organised BioBlitz's in the wheatbelt area of Western Australia in 2002, 2003, 2004, 2006, 2008, 2009 and 2010. Two 'SpiderBlitz's' (variants of the BioBlitz concept) were organised in 2007 and 2008 in the wheatbelt by WWF to focus attention on threatened trapdoor spiders, and their unique habitats. Wheatbelt Natural Resource Management Wheatbelt NRM ran a BioBlitz around the wheatbelt town of Korrelocking in 2012. The Discovery Circle program (UniSA) ran two BioBlitzes at a park in Salisbury and wetlands at Marion, South Australia. The Atlas of Life in the Coastal Wilderness www.alcw.org.au has run three successful bioblitzes – in Bermagui 2012, Pambula 2014 and Mimosa Rocks National Park 2014. The Atlas of Life works in association with the Atlas of Living Australia (the national biodiversity database) takayna BioBlitz The Bob Brown Foundation runs an annual takayna BioBlitz in Tasmania, Australia. The takayna BioBlitz is a festival of science in nature, held in one of the world's last truly wild places. This event brings together scientists, experts, naturalists and members of the public for a weekend of environmental scientific discovery. See: bobbrown.org.au Tarkine BioBlitz, 19–22 November 2015, was the first BioBlitz in Tasmania. More than 100 people surveyed moorland, rainforest,
|
{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
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|
rivers and coastline in the remote Tarkine region in support of the Bob Brown Foundation's campaign for a Tarkine National Park to protect the natural values of the region. Melbourne City Council conducted a BioBlitz in 2014 and 2016, engaging citizens in nature conservation in cities [2]. === Canada === Active Bioblitz The Robert Bateman Get to Know BioBlitz started in 2010 to celebrate the international year of biodiversity. In a partnership with Parks Canada there were many sites all across Canada which celebrated bioblitzes on the international day of biodiversity (May 22). British Columbia There has been an annual BioBlitz in Whistler, BC since 2007. The 2013 BioBlitz reported 497 species. Metro Vancouver has hosted their annual BioBlitz at Burnaby Lake Regional Park since 2010. This bioblitz has much public participation with many activities including pond-dipping, nature walks and meeting live animals up close. The species count currently stands at 488, including a Western Screech Owl, Red-legged Frog, Brassy Minnows and Common Fern which, despite its name, had never been found in the area before. Ontario: The Royal Ontario Museum and several other organizations have sponsored BioBlitz in the Toronto area since 2012, with the 2015 event scheduled for the Don River watershed. The 2014 Humber BioBlitz had over 500 participants and counted 1,560 species, including 2 spiders that were new to Canada. The Rouge National Urban Park hosted a Bioblitz event on June 24 and 25 of 2017. The previous Bioblitz at the park was held in 2013 where over 1700 species of flora and fauna were identified. New Brunswick: The New Brunswick Museum has held an annual bioblitz since 2009 in Protected Natural Areas (PNA) around the province. Scientists spend two weeks each year in the field, alternating June in one year with August in the next
|
{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
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|
to catch seasonally available biodiversity. The bioblitz was held in Jacquet River Gorge PNA 2009–2010, Caldonia Gorge PNA in 2011–2012, Grand Lake PNA in 2013–2014, Nepisiguit PNA in 2015–2016, and Spednic Lake PNA in 2017–2018. More information is here. The 2013-2014 bioblitzes were the subject of a documentary Inactive and historic BioBlitz The Canadian Biodiversity Institute held numerous BioBlitzes between 1997 and 2001. Victoria's Beacon Hill has had two BioBlitzes, in April 2007 and October 2007. They successfully gave thanks for the biodiversity of the region. Beacon Hill has since been a site for Arborblitzs, which focus on identifying all the trees within the park. Saint Mary's University (Halifax) held BioBlitz in Nova Scotia between 2008 and 2010 with the report on the 2010 BioBlitz available here. The Warren Lake BioBlitz was scheduled for 11–13 August 2011. Warren Lake is on the east side of Cape Breton Highlands National Park. There is a hiking trail which circumnavigates the lake and it will be considered the border of the BioBlitz, i.e., there will be quite an extensive aquatic focus. Stanley Park in Vancouver held BioBlitz between 2011 and 2013. Harrison Hot Springs had a BioBlitz in July 2011 to highlight the biodiversity of species in the Fraser Valley. === Hong Kong === In Traditional Chinese this has been referred to as: 生態速查 (Ecological quick check). First HK's BioBlitz was organized by Tai Tam Tuk Foundation from 24 to 25 Oct, 2015. 50 experts leading 300 secondary students recorded more than 680 species in 30 hours, covering marine, terrestrial and intertidal habitats, in Tai Tam site of special scientific interest (SSSI). This event comes as part of the ‘Biodiversity Festival 2015’, an Agriculture, Fisheries and Conservation Department (AFCD) lead project that encompasses many events, exhibitions and seminars, and is a major section
|
{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
}
|
of Hong Kong's Biodiversity Strategy and Action Plan (BSAP). Highlights included 2 species of moth that are extremely rare and native to Hong Kong, the first official record of coral in Tai Tam Bay and the first official record of juvenile horseshoe crabs on Hong Kong island. Data are made available through an online platform iSpot. BioBlitz@CityU is a competition in the small wooded park on university campus organized by City University of Hong Kong on 4 March 2016. On 21–22 Oct, 2017, Lung Fu Shan Environmental Education Centre organized their first BioBlitz. This center was jointly established by the Environmental Protection Department of HK Government and The University of Hong Kong in 2008. 100 participants and volunteers found 151 species in Lung Fu Shan with the guidance of 11 experts within 24 hours. In 2018 this was expanded to separate bioblitz surveys into four animal groups: Birds; Butterflies, (other) Insects, and Amphibians and Reptiles. And in 2019 another bioblitz is planned. Tai Tam Tuk Foundation organized their second BioBlitz on 3–4 Nov, 2017. They translated the iNaturalist app and slideshow into Chinese with the help of Hong Kong Explorers Initiative and the technical support of Scott Loarie and Alex Shepard from iNaturalist.org for better data collection among local participants. Also, they organized the pilot self-guided activity "DIY BioBlitz" with the help of Environmental Life Science Society, HKU and the teacher training in this event. Data are made available: https://www.inaturalist.org/projects/hk-bioblitz-2017 This event is subvented by Agriculture, Fisheries and Conservation Department of HK Government. In January 2019 the Hong Kong BioBlitz @ Hong Kong Park was carried out in Kong Kong Park. Utilizing iNaturalist and experts from the Natural History Museum, London, and Tai Tam Tuk Eco Education Centre. With popularity of City Nature Challenge in Hong Kong since its first
|
{
"page_id": 1574457,
"source": null,
"title": "BioBlitz"
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participation in 2018, bioblitzes have increasingly been combined with this and other iNaturalist based challenges such as the Hong Kong Inter-School City Nature Challenge. === Hungary === BioBlitz Events in Hungary are organized by the Hungarian Biodiversity Research Society http://www.biodiverzitasnap.hu/ since 2006, starting with the eco-village Gyürüfű and its surroundings in Baranya County. Since then the Society organizes BioBlitz Events (called also Biodiversity Days) every year, sometimes even several events a year, during which 60-80 experts and researchers contribute to a profound momentary inventory of a chosen area in Hungary, and from time to time in cross-border areas in joint-projects with neighbour countries. The Hungarian Biodiversity Research Society invites local inhabitants and the interested public to join their events, and focusses in its outreach to young local and regional pupils and their teachers just like students from Hungary and abroad. The BioBlitz Events are taking place in partnership with the local National Park Directories, Municipalities and Civil Organisations. A rather fresh approach is the involvement of high school students during their obligatory community/voluntary work into research and field work in the topics of biodiversity and nature protection based upon long term co-operation contracts with schools and educational centres. The main goals pursued by the Hungarian Biodiversity Research Society are to promote the correct understanding of biodiversity in its true context, based upon data collection, monitoring, research and expertise, passing on knowledge from generation to generation and outreach to the broader public. It also aims to strengthen national and international networks. The results of the BioBlitz Events are published in print and on-line media and serve mainly as fundamentals for maintenance-instructions for protected areas and for appropriate natural-resource management, but also for educational purposes. === India === On May 20, 2025, the first BioBlitz event took place in Odisha at Nandankanan
|
{
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"title": "BioBlitz"
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Wildlife Sanctuary, Bhubaneswar. More than 400 species of various taxa have been documented during the 24 hours of rigorous survey. A total of 50 participants of 30 institutions/organizations have participated in the event. === Ireland === An Ireland's BioBlitz Event has been held annually since 2010 – established by the National Biodiversity Data Centre http://www.biodiversityireland.ie/ to celebrate International Year of Biodiversity. A unique feature of this event is that it has a number of parks through the island competing against each other to see which site records the most species over a 24hr period. The event is usually held on the third weekend in May each year. In 2010, the first year it was held, Connemara National Park won the competition having recording 542 species. In 2011, Killareny National Park won the event having recorded an astonishing tally of 1088 species. Crawfordsburn Country Park won in 2012 having recorded 984 species. All of the data are made available through an online mapping system, Biodiversity Maps http://maps.biodiversityireland.ie/# and hard copy species lists are produced http://bioblitz.biodiversityireland.ie/bioblitz-species-lists-now-available/ The event is co-ordinated by the National Biodiversity Data Centre who maintain a special website http://bioblitz.biodiversityireland.ie/ each year so that progress with the event can be tracked on-line. To cater for the success of BioBlitz in Ireland, support is provided for a special 'Local BioBlitz Challenge' for local sites. Also, on 14–15 June 2013 Limerick City hosts the first Urban BioBlitz in Ireland. On May 1, 2014, the first Intervarsity BioBlitz was held with support from the National Biodiversity Data Centre. University College Cork, National University of Ireland Galway, Trinity, Dublin City University and Dundalk IT all competed to count Biodiversity on campus, with NUIG being the inaugural winner. === Israel === On April 24, 2014, the first BioBlitz in Israel took place in Yeruham lake
|
{
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park. The event was supported by Ben Gurion University of the Negev. 531 different species were found. A second Bioblitz is scheduled to take place on March 26, 2015. === Malaysia === Since 2011 the Malaysian Nature Society has held an annual birdwatching bioblitz named "MY Garden Birdwatch". === México === Since 2019 the Rancho Komchén de los Pájaros has held an annual bioblitz. Check out the iNaturalist results === New Zealand === Landcare Research, in conjunction with colleagues in other institutes and agencies, held BioBlitzes in Auckland in 2004, 2005, 2006, and 2008; and in Christchurch in 2005. A BioBlitz was planned for early April 2009 in Christchurch. Other New Zealand BioBlitzes have been held in Hamilton and in Wellington. The first marine BioBlitz occurred on the Wellington South Coast over a month, since a marine BioBlitz is trickier weatherwise than a terrestrial one. In March 2012 Forest and Bird organised a BioBlitz on the Denniston Plateau on the West Coast of the South Island. It is the site of the proposed Escarpment Mine Project. See a List of BioBlitzes in New Zealand. === Pakistan === The first BioBlitz in Pakistan was organized at Hazarganji Chiltan National Park on April 15, 2023, by The First Steps School. === Poland === The first BioBlitz in Poland was organized in Sopot in May 2008 by the Polish Scientific Committee on Oceanic Research of the Polish Academy of Sciences. === Portugal === Faro was the first city in Portugal to have a BioBlitz, in October 2009. === Singapore === The Singapore National Parks (NParks) Community in Nature (CIN) program have been running BioBlitz in various parks and gardens across Singapore to coincide with the International Day for Biological Diversity. === Slovenia === Slovene's first BioBlitz took place on May 19/20, 2017, in
|
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"title": "BioBlitz"
}
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Draga (in central Slovenia). The event was conducted during the project "Invazivke nikoli ne počivajo: Ozaveščanje o in preprečevanje negativnega vpliva invazivnih vrst na evropsko ogrožene vrste" and supported by the Slovene Ministry of the Environment and Spatial Planning. The event was held in cooperation with Societas herpetologica slovenica, the Botanical Society of Slovenia, the Centre for Cartography of Fauna and Flora, and the Slovene Dragonfly Society. During the event, 124 experts participated and 1,588 different species were found. BioBlitz Slovenia 2018 was held in Rače (in northeastern Slovenia) on June 15/16. Altogether, 71 experts from 21 different organisations participated, and at the end of the 24-hour event 934 species or higher taxon were identified. BioBlitz Slovenia 2018 was organised by four NGOs: Societas herpetologica slovenica, the Slovene Dragonfly Society, the Botanical Society of Slovenia, and the Centre for Cartography of Fauna and Flora. A third BioBlitz Slovenia took place on May 17/18, 2019, in the Lož Karst Field. As a part of the project "Še smo tu – domorodne vrste še nismo izrinjene", it was supported by the Slovene Ministry of the Environment and Spatial Planning. Eighty experts participated and 899 different species were found. BioBlitz Slovenia 2019 was organised by three NGOs: Societas herpetologica slovenica, the Slovene Dragonfly Society, and the Centre for Cartography of Fauna and Flora. The results of the events are published in print and on-line media and journals, also together with the list of species. BioBlitz Slovenia became a traditional annual event and has its own webpage. === Spain === In Formentera (Balearic Islands), during the Posidonia Festival 2008, there was a bioblitz. Barcelona (Catalonia) hosts a BioBlitz yearly since 2010, organized by Barcelona City Council, University of Barcelona and Natural History Museum of Barcelona, in collaboration with several naturalist and scientific societies. First
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BioBlitzBcn was held in June 2010 at Laberint d'Horta and Parc de la Ciutadella. Second in October 2011 at Jardí Botànic de Barcelona. Third in May 2012 at Jardí Botànic Històric. The university of Almeria organizes the AmBioBlitz in April yearly since 2018, with the collaboration of CECOUAL (Centre of Scientific Collections of the University of Almería) and Observation.org The Pablo de Olavide University, from Seville, will host in April 2021 its first BioBlitz in collaboration with Observation.org and Biological Station of Doñana-CSIC === Sweden === Sweden's first BioBlitz was organized in Röttle (Gränna) on the 4th and 5 August 2012. On the 7th and 8 September 2012 a BioBlitz was organized in Fliseryd near the river Emån. A total of 345 species were reported in this former industrial site on islands in the river. Sweden's fourth BioBlitz will be organized in Högsby on June 5 and 6 2014. === Taiwan === Taipei 228 Peace Park 2008 BioBlitz on December 20, sponsored by Taiwan Forestry Bureau and National Taiwan Museum, found more than 180 plants, 11 birds and 1 mammal. === Trinidad & Tobago === Tucker Valley Bioblitz 2012 was the first bioblitz in Trinidad and possibly the Caribbean. It was organised by Mike G. Rutherford, curator of the University of the West Indies Zoology Museum (UWIZM) with help from the Trinidad and Tobago Field Naturalists' Club (TTFNC) and was sponsored by First Citizens Bank. The 24-hour event found 654 species – 211 plants and 443 animals. Arima Valley Bioblitz 2013 was based at the Asa Wright Nature Centre. The event found 139 vertebrates, 247 invertebrates, 30 fungi, 7 diatoms and 317 plants making a total of 740 species. Nariva Swamp Bioblitz 2014 was based at the Forestry Division Field Station near Bush Bush Forest Reserve, the teams found 742
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species. Charlotteville Bioblitz 2015 was the first event to take place in Tobago. Based at the Environmental Research Institute Charlotteville (ERIC) there was a large marine component and all together 1,044 species were recorded. Port of Spain Bioblitz 2016 took the event to the nation's capital and included a Nature Fair with over 20 local NGOs, government organisations and charity groups putting on a biodiversity and environmental display. 762 species were found in and around the city. Icacos Bioblitz 2017 was the final event organised by Rutherford and took the bioblitz to the far south-west of Trinidad and recorded 769 species. Toco Bioblitz 2018 was organised by a committee made up of TTFNC members and staff from the University of the West Indies Department of Life Sciences from the St. Augustine campus. The north-east corner of Trinidad yielded 906 species records. === Türkiye === The first BioBlitz event in Kocaeli Province was held in Ormanya on September 17, 2021, with the support of Kocaeli Metropolitan Municipality. 113 different species were found at the event. === United Kingdom === Natural History Consortium host the National BioBlitz Network hosting free resources for running a BioBlitz event and the national BioBlitz Calendar. (www.bnhc.org.uk) Examples of regions and organisations which have held BioBlitz events include: First UK Marine BioBlitz undertaken by the Marine Biological Association and the Natural History Museum together with other partners. Wembury, South Devon 2009 Bristol – Organised by Bristol Natural History Consortium Northumberland – Organised by Northumberland Biodiversity Network New Forest National Park – Organised by New Forest National Park Authority Swansea – Organised by Swansea City Council Cairngorms – Organised by Cairngorms Biodiversity Dundee – Organised by Dundee City Council Leicester – Organised by Leicester City and County Council Isle of Wight – Organised by Isle of Wight Council
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London – Organised by OPAL Derby – Organised by Derby City Council Brighton – Organised by Sussex Wildlife Trust Bath – Organised by Bristol Natural History Consortium Mothecombe, Devon, – Marine and coastal BioBlitz – Organised by OPAL and the Marine Biological Association Jersey – Organised by the Durrell Wildlife Conservation Trust Fife – Organised by Fife Coast and Countryside Trust and "Celebrating Fife 2010" Cambridge – Organised by Cambridge University Lincolnshire – Organised by Lincolnshire Wildlife Trust Nottingham – Organised by Nottinghamshire Biodiversity Action Group Flintshire – Organised by Flintshire County Council North Ayrshire – Organised by North Ayrshire Council Lancashire – Organised by Lancashire Wildlife Trust Kent – Organised by Kent Wildlife Trust Corfe Mullen – Organised by Corfe Mullen Nature Watch Cornwall – Organised by ERCCIS North Devon – Organised by Coastwise North Devon. Sandford – Organised by Ambios Mount Edgcumb – Marine and coastal bioblitz organised by the Marine Biological Association === United States === Alaska: The Chugach National Forest and Alaska Department of Fish & Game-Diversity Program organized the first BioBlitz in Southcentral Alaska on July 23 and 24, 2011, to coincide with the International Year of Forests. Arizona: More than 5,500 people, including 2,000 students and 150 scientists, attended the 2011 Saguaro BioBlitz, (October 21–22) and discovered 859 species during the 24 hour inventory period. Included in that total were more than 400 species, mostly invertebrate animals and non-vascular plants, which were previously unknown in the park. The accompanying Biodiversity Festival had an integrated art program that included pieces featuring local species, created by local students, seniors, and artists. California: The Santa Monica Mountains NPS/National Geographic Society BioBlitz (May 30–31, 2008) was accomplished through collaboration with the Santa Monica Mountains Conservancy, California State Parks, and Los Angeles Recreation and Parks Department. Six thousand participants
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discovered more than 1,700 species during the 24 hour inventory period. California: The San Diego Zoo Institute for Conservation Research hosted a BioBlitz in the San Dieguito River Park on the North Shore of Lake Hodges in Escondido April 25–26. California: The San Diego Natural History Museum began hosting a yearly BioBlitz starting in 2008. The 2008 BioBlitz was held in Balboa Park and in 2009 the event was held at Mission Trails Regional Park on May 1–2. California: The Santa Barbara Botanic Garden organized a BioBlitz of its natural spaces in May 2007. California: Golden Gate National Recreation Area: On March 28–29, 2014, participants in the BioBlitz at Golden Gate Park sites, including Pt. Reyes National Seashore, Muir Woods National Monument, the Presidio of San Francisco, Mori Point, and Rancho Corral de Tierra observed and recorded biodiversity in habitats ranging from the redwood canopy to windswept beaches. Highlights included the first ever canopy survey of redwoods at Muir Woods, the first-ever, park sighting of a climbing salamander in Muir Woods; sightings of great horned, spotted, barred and saw-whet owls; and a mountain lion at Corral de Tierra. Colorado: The National Wildlife Federation has been providing a toolset based on the eNature.com species data in the Denver/Boulder metropolitan area since 2004. Results are online. Colorado: On August 24–25, 2012, more than 150 scientists joined forces with 5,000 people of all ages and backgrounds to seek out the living creatures in Rocky Mountain National Park. Inventories took place in various ecological life zones, including ponderosa pine forests, the subalpine region, the tundra, and mountain meadows. Among the overall total of 490 species discovered, 138 were previously unknown to be in the park. A companion festival at the Estes Park Fairgrounds advanced and celebrated public awareness of biodiversity. Connecticut: The Center for
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Conservation and Biodiversity and Connecticut State Museum of Natural History have held nine BioBlitz events since 1999. The current record for a single Connecticut BioBlitz was set June 3–4, 2016 in a 5-mile radius around the Two Rivers Magnet School in East Hartford, where 2,765 species were recorded in the 24-hour period. Many of the organisms sighted in the 2016 BioBlitz were documented in an online iNaturalist project. The previous record was set in 2001 at Tarrywile Park in Danbury, where 2,519 species were recorded in the 24-hour period. District of Columbia: A BioBlitz at the Kenilworth Park and Aquatic Gardens in Washington, D.C. in 1996 found approximately 1000 species. Washington, D.C. 2007: The National Geographic Society held a BioBlitz in Rock Creek Park on May 18–19. The event was later on a segment of the TV series Wild Chronicles which airs on PBS. Participants included J. Michael Fay, Sylvia Earle, and Boyd Matson. The first National Park Service/National Geographic Society BioBlitz took place on May 18–19, 2007. A wide breadth of taxonomic groups was examined, including amphibians and reptiles, invertebrates, birds, fish, fungi, mammals, plants, insects, and more. The total number of species found was 661 over a 24-hour period. Florida: In Manatee County, the local government's Department of Natural Resources (formerly Conservation Lands Management) has sponsored annual BioBlitz events, every spring since 2007. The surveys rotate between the county's different parks and preserves. This event, however, involves only a 12-hour survey instead of the standard 24-hour. Florida: On April 30-May 1, 2010, 2,500 citizen scientists worked with their professional counterparts to explore life in one of the nation's largest marine national parks, Biscayne National Park. More than 800 species were found, including a number of species rare to the park, such as the mangrove cuckoo, and silver hairstreak
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butterfly. Also, 11 species of lichen and 22 species of ants were found that had not previously been documented in the park. Hawaii: At Punahou School, a biannual BioBlitz is organized by the students. The event examines certain parts of the campus, and has been held there since the summer of 2008. The BioBlitz there happens once in winter, and once in summer. Hawai'i: at Hawai'i Volcanoes National Park in 2015, working under the theme of I ka nānā no a ’ike ("By observing, one Learns"), traditional Hawaiian cultural practitioners, "alakai’i," were integrated into the survey teams, providing a holistic approach to the research and exploration activities. More than 170 leading scientists and alakai’i, teamed with thousands of public participants of all ages to explore one of the most fascinating biological landscapes in the world. Together they documented species that thrive in ecosystems from sea level to the summit of Kīlauea Volcano. Exciting finds included 22 new species added to the park's species list, and sightings of 73 threatened species, including the nēnē and Kamehameha butterfly. The number of fungi species on the park's list more than doubled, with 17 new fungi documented at the close of the event. Illinois: The Field Museum of Natural History and other organizations held a BioBlitz in Chicago in 2002. There are several bioblitzes in parts of the forest preserves of Cook and Lake County. Indiana: Indiana Dunes National Park – On May 16-16, 2009, more than 150 scientists, assisted by 2,000 grade school students and other members of the public, explored the sand dunes, lake shore, forests, wetlands, prairie, and streams of the recreation area. The excitement persevered through driving rain and high winds and resulted in the discovery of more than 1,200 species. Louisiana: The NPS/National Geographic Society BioBlitz at Jean Lafitte
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National Historical Park and Preserve (May 17–18, 2013), brought together leading scientists and naturalists from around the country and local citizens of all ages. Inventories included herpetofaunal counts, aquatic and terrestrial invertebrate inventories, avifauna observations, and native and non-native plant surveys. Participants also used technology, such as tree cameras and smartphones, to record and understand the diverse ecosystems of this unique national park. At the time of the event's closing ceremony, 458 species had been identified, including a rare Louisiana milk snake, 288 plants, and 122 invertebrate species. Maine: The Maine Entomological Society and other organizations have been holding Entomological BioBlitzes at Acadia National Park every summer since 2003. Results of the 2003-2011 blitzes were summarized by Chandler et al., 2012, showing that 1,605 species representing 348 families of insects were taken and identified over the 8-year period. Many were new to the Park fauna, and a significant number were also new to the known state fauna. Maryland/DC/Virginia, 2006: The Nature Conservancy sponsored a Potomac Gorge BioBlitz where more than 130 field biologists and experienced naturalists volunteered their expertise in an effort to see how many species they could find. During a 30-hour survey period from Saturday, June 24, through Sunday, June 25 their surveys revealed more than 1,000 species. Maryland: Jug Bay BioBlitz was sponsored by the Maryland-National Capital Park and Planning Commission's (M-NCPPC) Patuxent River Park staff and rangers, May 30–31, 2009. Massachusetts 2006 collaboration between the Boston Museum of Science and the Cape Cod Museum of Natural History. The first bioblitz in a series sponsored by the E.O. Wilson Biodiversity Foundation. The first bioblitz to utilize CyberTracker and NatureMapping technologies for data collection. On June 25–26, 2010, a BioBlitz was held in Falmouth, Massachusetts, using town conservation land and adjacent land owned by the 300 Committee (T3C),
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Falmouth's land trust. Surveys for 15 taxa were planned. About 120 volunteers participated. Preliminary estimate of 930 species found but this number is likely to increase as data are finalized. Full results to be published later in 2010 on the T3C website. On September 29, 2010, the TDWG Techno/BioBlitz was held alongside the Annual Biodiversity Information Standards Conference in Woods Hole. On July 8, 2019, the Great Walden BioBlitz was held at Walden Pond, Massachusetts, surveying a five-mile radius around Walden Woods. Organized by Peter Alden in honor of E.O. Wilson's 90th birthday and the 30th Massachusetts bioblitz, public participants were encouraged to explore Walden Woods and Minute Man NHP using the iNaturalist phone app to help document species. Minnesota: A group of organizations including the Bell Museum of Natural History has sponsored BioBlitzes in natural areas in or near the Twin Cities yearly in June since 2004. Missouri: Sponsored by the Academy of Science of St. Louis, partners from the public, academic and corporate sectors collaborate on the Academy of Science-St. Louis BioBlitz at urban parks, such as Forest Park in St Louis . Held at least once a year since 2006, the academy's BioBlitz has hosted future BioBlitz leaders from throughout the country and is a signature event of one of the oldest Academies of Science in the USA. www.academyofsciencestl.org New Hampshire: Odiorne Point State Park: The Seacoast Science Center has been hosting an annual BioBlitz! in September since 2003. The park's diversity of coastal habitats provides BioBlitzers the opportunity to find marine, freshwater and terrestrial species. The Center compiles and maintains each year's data. Squam Lakes. 2008. The Squam Lakes Natural Science Center in collaboration with Squam Lakes Association and Squam Lakes Conservation Society in cooperation with the Holderness Conservation Commission, the US Forest Service Hubbard Brook
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Experimental Forest, UNH Cooperative Extension, Plymouth State University, NH Fish and Game Department, and Ecosystem Management Consultants. New Jersey State Highlands, NJ Gateway National Recreation Area, Sandy Hook Unit, 2011. On Sept. 16–17, science students, along with park staff and over 150 volunteers, located nearly 450 species, mostly birds, terrestrial plants and invertebrates. Gateway National Recreation Area, Sandy Hook Unit, 2015. On September 18–19, the American Littoral Society, in partnership with the National Park Service, hosted the second Sandy Hook BioBlitz. Over 150 scientists, naturalists, and volunteers raced against the clock to identify as many species as possible. This BioBlitz found 75 birds, 12 fungi/lichen, 21 fish, 2 reptiles/amphibians, 44 marine invertebrates, 2 insects, 13 mammals, 15 aquatic plants, and 87 terrestrial plants. New York State New York City Central Park, 2003. This BioBlitz found more than 800 species, including 393 species of plants, 78 of moths, 14 fungi, 10 spiders, 9 dragonflies, 2 tardigrades, 102 other invertebrates, 7 mammals, 3 turtles, 46 birds and 2 frog species. s. Central Park, 2006. In collaboration with the E.O. Wilson Biodiversity Foundation, the Explorers Club, the American Museum of Natural History and the Boston Museum of Science. This is the first bioblitz in history to incorporate the collection and analysis of microorganisms. Central Park, 2013. On August 27–28, 2013 a BioBlitz at Central Park was held in partnership with Macaulay Honors College of CUNY. With help from the Central Park Conservancy over 350 Macaulay students worked with nearly 30 scientists and cataloged more than 460 species. New York Botanical Garden in the Bronx, 2014, September 6 and 7, in partnership with Macaulay Honors College of CUNY. The Saw Mill River watershed in Westchester County, September 2009. Groundwork Hudson Valley, leading the Saw Mill River Coalition, conducted a Saw Mill River BioBlitz on
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September 25–26 with more than 50 scientists from a wide variety of fields. A concurrent conference on the health of the river was held at Pace University in Pleasantville that was open to the public and had activities geared for children. Funded by a grant from Westchester Community Foundation with additional support from US EPA and NYS/DEC Hudson River Estuary Program. Major co-sponsors joining the effort were Westchester County Parks, Recreation and Conservation; Teatown Lake Reservation; Pace University's Department of Biology and Health Sciences; Pace University's Academy for Applied Environmental Studies; Sigma Xi: The Scientific Research Society; Greenburgh Nature Center; and the Saw Mill River Audubon. North Carolina: The North Carolina Botanical Garden in collaboration with the Morehead Planetarium sponsor an annual bioblitz in September on garden-owned property. Ohio: The Geauga Park District has hosted an annual BioBlitz at different park district properties since 2003. Oklahoma: The Oklahoma Biological Survey hosted an annual BioBlitz at different locations around Oklahoma starting in 2001. Their 2010 BioBlitz will be held on October 8–9 at Kaw Lake in north-central Oklahoma with a base camp at Camp McFadden. Pennsylvania: Phipps Conservatory hosted a Bioblitz on June 10, 2018, in Pittsburgh. Rhode Island: Rhode Island Natural History Survey has conducted a BioBlitz at a different site in the state every year since 2000, including a "backyard bioblitz" held in 2020, during COVID. Rhode Island BioBlitz may be the longest running annual BioBlitz in the world. In the 23 events through 2022, the average participation is 163 and the average species count is 1022; the record participation of 302 people and the record species count of 1,308 species were both in the Jamestown Rhode Island BioBlitz of 2012. Vermont: The Vermont Institute of Natural Science held a BioBlitz in 2004 at Hartford. Washington: BioBlitzes conducted using
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NatureTracker software on PDAs for conservation planning./ Wisconsin: The Milwaukee Public Museum (MPM) hosts an annual BioBlitz program that began in 2015. MPM events have occurred at Schlitz Audubon Nature Center in Milwaukee (2015), Grant Park in South Milwaukee (2016), Fox River Park in Waukesha (2017), Lake Farm County Park/Capitol Springs Recreation Area in Madison (2018), Riveredge Nature Center in Saukville (2019), and Whitnall Park in Franklin (2020). The non-profit Biodiversity Project held three Great Lakes BioBlitzes with support from the Wisconsin Coastal Management Program and NOAA in 2004. The sites were Riverside Park in Milwaukee; Baird Creek Parkway in Green Bay; and Wisconsin Point in Superior. == See also == Australian Bird Count (ABC) Bush Blitz an Australian Government variant of the concept co funded by BHP Billiton and with the participation of Earthwatch Australia Breeding Bird Survey Christmas Bird Count (CBC) (in the Western Hemisphere) City Nature Challenge Seabird Colony Register (SCR) The EBCC Atlas of European Breeding Birds Tucson Bird Count (TBC) (in Arizona, US) == References == == External links == BioBlitzes at National Geographic National BioBlitz Network (United Kingdom)
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The global brain is a neuroscience-inspired and futurological vision of the planetary information and communications technology network that interconnects all humans and their technological artifacts. As this network stores ever more information, takes over ever more functions of coordination and communication from traditional organizations, and becomes increasingly intelligent, it increasingly plays the role of a brain for the planet Earth. In the philosophy of mind, global brain finds an analog in Averroes's theory of the unity of the intellect. == Basic ideas == Proponents of the global brain hypothesis claim that the Internet increasingly ties its users together into a single information processing system that functions as part of the collective nervous system of the planet. The intelligence of this network is collective or distributed: it is not centralized or localized in any particular individual, organization or computer system. Therefore, no one can command or control it. Rather, it self-organizes or emerges from the dynamic networks of interactions between its components. This is a property typical of complex adaptive systems. The World Wide Web in particular resembles the organization of a brain with its web pages (playing a role similar to neurons) connected by hyperlinks (playing a role similar to synapses), together forming an associative network along which information propagates. This analogy becomes stronger with the rise of social media, such as Facebook, where links between personal pages represent relationships in a social network along which information propagates from person to person. Such propagation is similar to the spreading activation that neural networks in the brain use to process information in a parallel, distributed manner. == History == Although some of the underlying ideas were already expressed by Nikola Tesla in the late 19th century and were written about by many others before him, the term "global brain" was coined
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in 1982 by Peter Russell in his book The Global Brain. How the Internet might be developed to achieve this was set out in 1986. The first peer-reviewed article on the subject was published by Gottfried Mayer-Kress in 1995, while the first algorithms that could turn the world-wide web into a collectively intelligent network were proposed by Francis Heylighen and Johan Bollen in 1996. Reviewing the strands of intellectual history that contributed to the global brain hypothesis, Francis Heylighen distinguishes four perspectives: organicism, encyclopedism, emergentism and evolutionary cybernetics. He asserts that these developed in relative independence but now are converging in his own scientific re-formulation. === Organicism === In the 19th century, the sociologist Herbert Spencer saw society as a social organism and reflected about its need for a nervous system. Entomologist William Wheeler developed the concept of the ant colony as a spatially extended organism, and in the 1930s he coined the term superorganism to describe such an entity. This concept was later adopted by thinkers such as Joël de Rosnay in the book Le Cerveau Planétaire (1986) and Gregory Stock in the book Metaman (1993) to describe planetary society as a superorganism. The mental aspects of such an organic system at the planetary level were perhaps first broadly elaborated by palaeontologist and Jesuit priest Pierre Teilhard de Chardin. In 1945, he described a coming "planetisation" of humanity, which he saw as the next phase of accelerating human "socialisation". Teilhard described both socialization and planetization as irreversible, irresistible processes of macrobiological development culminating in the emergence of a noosphere, or global mind (see Emergentism below). The more recent living systems theory describes both organisms and social systems in terms of the "critical subsystems" ("organs") they need to contain in order to survive, such as an internal transport system, a
|
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"page_id": 13305402,
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resource reserve, and a decision-making system. This theory has inspired several thinkers, including Peter Russell and Francis Heylighen to define the global brain as the network of information processing subsystems for the planetary social system. === Encyclopedism === In the perspective of encyclopedism, the emphasis is on developing a universal knowledge network. The first systematic attempt to create such an integrated system of the world's knowledge was the 18th century Encyclopédie of Denis Diderot and Jean le Rond d'Alembert. However, by the end of the 19th century, the amount of knowledge had become too large to be published in a single synthetic volume. To tackle this problem, Paul Otlet founded the science of documentation, now called information science. In the 1930s he envisaged a World Wide Web-like system of associations between documents and telecommunication links that would make all the world's knowledge available immediately to anybody. H. G. Wells proposed a similar vision of a collaboratively developed world encyclopedia that would be constantly updated by a global university-like institution. He called this a World Brain, as it would function as a continuously updated memory for the planet, although the image of humanity acting informally as a more organic global brain is a recurring motif in many of his other works. Tim Berners-Lee, the inventor of the World Wide Web, too, was inspired by the free-associative possibilities of the brain for his invention. The brain can link different kinds of information without any apparent link otherwise; Berners-Lee thought that computers could become much more powerful if they could imitate this functioning, i.e. make links between any arbitrary piece of information. The most powerful implementation of encyclopedism to date is Wikipedia, which integrates the associative powers of the world-wide-web with the collective intelligence of its millions of contributors, approaching the ideal of
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"page_id": 13305402,
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a global memory. The Semantic web, also first proposed by Berners-Lee, is a system of protocols to make the pieces of knowledge and their links readable by machines, so that they could be used to make automatic inferences, thus providing this brain-like network with some capacity for autonomous "thinking" or reflection. === Emergentism === This approach focuses on the emergent aspects of the evolution and development of complexity, including the spiritual, psychological, and moral-ethical aspects of the global brain, and is at present the most speculative approach. The global brain is here seen as a natural and emergent process of planetary evolutionary development. Here again Pierre Teilhard de Chardin attempted a synthesis of science, social values, and religion in his The Phenomenon of Man, which argues that the telos (drive, purpose) of universal evolutionary process is the development of greater levels of both complexity and consciousness. Teilhard proposed that if life persists then planetization, as a biological process producing a global brain, would necessarily also produce a global mind, a new level of planetary consciousness and a technologically supported network of thoughts which he called the noosphere. Teilhard's proposed technological layer for the noosphere can be interpreted as an early anticipation of the Internet and the Web. === Evolutionary cybernetics === Systems theorists and cyberneticians commonly describe the emergence of a higher order system in evolutionary development as a "metasystem transition" (a concept introduced by Valentin Turchin) or a "major evolutionary transition". Such a metasystem consists of a group of subsystems that work together in a coordinated, goal-directed manner. It is as such much more powerful and intelligent than its constituent systems. Francis Heylighen has argued that the global brain is an emerging metasystem with respect to the level of individual human intelligence, and investigated the specific evolutionary mechanisms that
|
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promote this transition. In this scenario, the Internet fulfils the role of the network of "nerves" that interconnect the subsystems and thus coordinates their activity. The cybernetic approach makes it possible to develop mathematical models and simulations of the processes of self-organization through which such coordination and collective intelligence emerges. == Recent developments == In 1994 Kevin Kelly, in his popular book Out of Control, posited the emergence of a "hive mind" from a discussion of cybernetics and evolutionary biology. In 1996, Francis Heylighen and Ben Goertzel founded the Global Brain group, a discussion forum grouping most of the researchers that had been working on the subject of the global brain to further investigate this phenomenon. The group organized the first international conference on the topic in 2001 at the Vrije Universiteit Brussel. After a period of relative neglect, the Global Brain idea has recently seen a resurgence in interest, in part due to talks given on the topic by Tim O'Reilly, the Internet forecaster who popularized the term Web 2.0, and Yuri Milner, the social media investor. In January 2012, the Global Brain Institute (GBI) was founded at the Vrije Universiteit Brussel to develop a mathematical theory of the "brainlike" propagation of information across the Internet. In the same year, Thomas W. Malone and collaborators from the MIT Center for Collective Intelligence have started to explore how the global brain could be "programmed" to work more effectively, using mechanisms of collective intelligence. The complexity scientist Dirk Helbing and his NervousNet group have recently started developing a "Planetary Nervous System", which includes a "Global Participatory Platform", as part of the large-scale FuturICT project, thus preparing some of the groundwork for a Global Brain. In July 2017, Elon Musk founded the company Neuralink, which aims to create a brain-computer interface (BCI)
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"page_id": 13305402,
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"title": "Global brain"
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with significantly greater information bandwidth than traditional human interface devices. Musk predicts that artificial intelligence systems will rapidly outpace human abilities in most domains and views them as an existential threat. He believes an advanced BCI would enable human cognition to remain relevant for longer. The firm raised $27m from 12 Investors in 2017. == Criticisms == A common criticism of the idea that humanity would become directed by a global brain is that this would reduce individual diversity and freedom, and lead to mass surveillance. This criticism is inspired by totalitarian forms of government, as exemplified by George Orwell's character of "Big Brother". It is also inspired by the analogy between collective intelligence or swarm intelligence and insect societies, such as beehives and ant colonies, in which individuals are essentially interchangeable. In a more extreme view, the global brain has been compared with the Borg, a race of collectively thinking cyborgs conceived by the Star Trek science fiction franchise. Global brain theorists reply that the emergence of distributed intelligence would lead to the exact opposite of this vision. James Surowiecki in his book The Wisdom of Crowds argued that the reason is that effective collective intelligence requires diversity of opinion, decentralization and individual independence. == See also == Collective consciousness – Shared beliefs and ideas in society Collective intelligence – Group intelligence that emerges from collective efforts Complex adaptive system – System whose behavior is not automatically predictable from its parts Gaia hypothesis – Scientific hypothesis about Earth Government by algorithm – Alternative form of government or social ordering Knowledge ecosystem – Approach to knowledge management Management cybernetics – Application of cybernetics to management and organizations Noeme – a combination of a distinct physical brain function and that of an outsourced virtual one Noosphere – Philosophical concept of biosphere
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successor via humankind's rational activities, described by Vladimir Vernadsky and Pierre Teilhard de Chardin Singleton (global governance) – Concept in futurology Smart city – City using integrated information and communication technology Social organism – Model of social interactions Superorganism – Group of synergistic organisms Technological singularity – Hypothetical point in time when technological growth becomes uncontrollable and irreversible Ubiquitous computing – Concept in software engineering and computer science World Brain – 1938 collection of essays by H. G. Wells == References == == Further reading == === Wide audience === Berners-Lee, Tim (1999). Weaving the Web: The Original Design and Ultimate Destiny of the World Wide Web by its inventor. Harper. ISBN 978-0-06-251586-5. Bloom, Howard (2000). Global Brain: The Evolution of Mass Mind from the Big Bang to the 21st Century. Russell, Peter (1982). The Awakening Earth: The Global Brain. London: Routledge & Kegan Paul. (emphasis on philosophy and consciousness) It from bit and fit from bit. On the origin and impact of information in the average evolution. Includes how life forms originate and from there evolve to become more and more complex, like organisations and multinational corporations and a "global brain" (Yves Decadt, 2000). Book published in Dutch with English paper summary in The Information Philosopher, http://www.informationphilosopher.com/solutions/scientists/decadt/ Stock, Gregory (1993). Metaman: The Merging of Humans and Machines into a Global Superorganism. de Rosnay, Joel (1999). The Symbiotic Man: A new understanding of the organization of life and a vision of the future (PDF). McGraw-Hill Companies. (new sciences and technologies). Nambisan, S.; Sawhney, M. (2007). The Global Brain. (emphasis on global innovation management) === Advanced literature === Goertzel, B. (2001). Plenum (ed.). Creating Internet Intelligence: Wild Computing, Distributed Digital Consciousness, and the Emerging Global Brain. Teilhard de Chardin, Pierre (1964). The Future of Man. (The classic on physical and psychological/mental
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{
"page_id": 13305402,
"source": null,
"title": "Global brain"
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development of global brain and global mind). Heylighen, Francis (2007). "Accelerating socio-technological evolution: from ephemeralization and stigmergy to the Global Brain" (PDF). In Modelski, George; Devezas, Tessaleno; Thompson, William (eds.). Globalization as evolutionary process: Modeling global change. Rethinking Globalizations. London: Routledge. pp. 284–335. ISBN 978-0-415-77361-4. ISBN 978-1-135-97764-1. For more references, check the GBI bibliography: == External links == The Global Brain FAQ on the Principia Cybernetica Web The Global Brain Institute at the Vrije Universiteit Brussel
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{
"page_id": 13305402,
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Qui-Lim Choo is a Singapore-born scientist, who along with Michael Houghton, George Kuo and Daniel W. Bradley, co-discovered and cloned Hepatitis C in 1989. He also co-discovered the Hepatitis D genome in 1986. The discovery of Hepatitis C led to the rapid development of diagnostic reagents to detect Hepatitis C virus in blood supplies which has reduced the risk of acquiring hepatitis C through blood transfusion from one in three to about one in two million. It is estimated that antibody testing has prevented at least 40,000 new infections per year in the US alone and many more worldwide. == Early life and education == Choo received his undergraduate training at Queen Elizabeth College in 1973 and completed his PhD in biochemistry at King's College London in 1980. He trained under William J. Rutter at the University of California, San Francisco before joining Chiron Corporation. == Awards and recognition == He was awarded the Karl Landsteiner Memorial Award (1992) and Dale A. Smith Memorial Award (2005) of the American Association of Blood Banks, and the William Beaumont Prize of the American Gastroenterological Association in 1994. == References ==
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"page_id": 41616956,
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"title": "Qui-Lim Choo"
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An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there by human activity, directly or indirectly, and either deliberately or accidentally. Non-native species can have various effects on the local ecosystem. Introduced species that become established and spread beyond the place of introduction are considered naturalized. The process of human-caused introduction is distinguished from biological colonization, in which species spread to new areas through "natural" (non-human) means such as storms and rafting. The Latin expression neobiota captures the characteristic that these species are new biota to their environment in terms of established biological network (e.g. food web) relationships. Neobiota can further be divided into neozoa (also: neozoons, sing. neozoon, i.e. animals) and neophyta (plants). The impact of introduced species is highly variable. Some have a substantial negative effect on a local ecosystem (in which case they are also classified more specifically as an invasive species), while other introduced species may have little or no negative impact (no invasiveness), and integrate well into the ecosystem they have been introduced to. Some species have been introduced intentionally to combat pests. They are called biocontrols and may be regarded as beneficial as an alternative to pesticides in agriculture for example. In some instances the potential for being beneficial or detrimental in the long run remains unknown. The effects of introduced species on natural environments have gained much scrutiny from scientists, governments, farmers and others. == Terminology == The formal definition of an introduced species from the United States Environmental Protection Agency is "A species that has been intentionally or inadvertently brought into a region or area. Also called an exotic or non-native species". In the broadest and most widely used sense,
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an introduced species is synonymous with "non-native" and therefore applies as well to most garden and farm organisms; these adequately fit the basic definition given above. However, some sources add to that basic definition "and are now reproducing in the wild", which means that species growing in a garden, farm, or house may not meet the criteria unless they escape and persist. === Subset descriptions === There are many terms associated with introduced species that represent subsets of introduced species, and the terminology associated with introduced species is now in flux for various reasons. Examples of these terms are "invasive", "acclimatized", "adventive", "naturalized", and "immigrant" species. The term "invasive" is used to describe introduced species that cause ecological, economic, or other damage to the area in which they were introduced. Acclimatized species are introduced species that have changed physically and/or behaviorally in order to adjust to their new environment. Acclimatized species are not necessarily optimally adjusted to their new environment and may just be physically/behaviorally sufficient for the new environment. Adventive species are often considered synonymous with "introduced species", but this term is sometimes applied exclusively to introduced species that are not permanently established. Naturalized species are often introduced species that do not need human help to reproduce and maintain their population in an area outside their native range (no longer adventive), but that also applies to populations migrating and establishing in a novel environment (e.g.: in Europe, house sparrows are well established since early Iron Age though they originated from Asia). Immigrant species are species that travel, sometimes by themselves, but often with human help, between two habitats. Invasiveness is not a requirement. === Invasive species === Introduction of a species outside its native range is all that is required to be qualified as an "introduced species". Such species
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"page_id": 394815,
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might be termed naturalized, "established", or "wild non-native species". If they further spread beyond the place of introduction and cause damage to nearby species, they are called "invasive species". The transition from introduction, to establishment and to invasion has been described in the context of plants. Introduced species are essentially "non-native" species. Invasive species are those introduced species that spread widely or quickly and cause harm, be that to the environment, human health, other valued resources, or the economy. There have been calls from scientists to consider a species "invasive" only in terms of their spread and reproduction rather than the harm they may cause. According to a practical definition, an invasive species is one that has been introduced and become a pest in its new location, spreading (invading) by natural means. The term is used to imply both a sense of urgency and actual or potential harm. For example, U.S. Executive Order 13112 (1999) defines "invasive species" as "an alien species whose introduction does or is likely to cause economic or environmental harm or harm to human health". The biological definition of invasive species, on the other hand, makes no reference to the harm they may cause, only to the fact that they spread beyond the area of original introduction. Some argue that "invasive" is a loaded word and harm is difficult to define. From a regulatory perspective, it is neither desirable nor practical to list as undesirable or outright ban all non-native species (although the State of Hawaii has adopted an approach that comes close to this). Regulations require a definitional distinction between non-natives that are deemed especially onerous and all others. Introduced "pest" species, that are officially listed as invasive, best fit the definition of an invasive species. Early detection and rapid response is the most effective
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strategy for regulating a pest species and reducing economic and environmental impacts of an introduction. Management of invasion pathways are on the forefront of eliminating unwanted invasive species this would include preliminary steps; educating the public, cooperation from industries and government resources. In Great Britain, the Wildlife and Countryside Act 1981 prevents the introduction of any animal not naturally occurring in the wild or any of a list of both animals or plants introduced previously and proved to be invasive. == Nature of introductions == By definition, a species is considered "introduced" when its transport into an area outside of its native range is human mediated. Introductions by humans can be described as either intentional or accidental. Intentional introductions have been motivated by individuals or groups who either (1) believe that the newly introduced species will be in some way beneficial to humans in its new location or, (2) species are introduced intentionally but with no regard to the potential impact. Unintentional or accidental introductions are most often a byproduct of human movements and are thus unbound to human motivations. Subsequent range expansion of introduced species may or may not involve human activity. === Intentional introductions === Species that humans intentionally transport to new regions can subsequently become successfully established in two ways. In the first case, organisms are purposely released for establishment in the wild. It is sometimes difficult to predict whether a species will become established upon release, and if not initially successful, humans have made repeated introductions to improve the probability that the species will survive and eventually reproduce in the wild. In these cases, it is clear that the introduction is directly facilitated by human desires. In the second case, species intentionally transported into a new region may escape from captive or cultivated populations and subsequently
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establish independent breeding populations. Escaped organisms are included in this category because their initial transport to a new region is human motivated. The widespread phenomena of intentional introduction has also been described as biological globalization. Positive Introductions Although most introduced species have negative impacts on the ecosystems they enter into, there are still some species that have affected the ecosystem in a positive way. For example, in New Hampshire invasive plants can provide some benefits to some species. Invasive species such as autumn olive, oriental bittersweet, and honeysuckle produce fruit that is used by a handful of fruit-eating bird species. The invasive plants can also be a source of pollen and nectar for many insects, such as bees. These invasive plants were able to help their ecosystem thriving, and increase the native animal's chances of survival. Several introduced exotic trees served as nest sites for resident waterbird species in Udaipur city, India. ==== Motivations for intentional introductions ==== ===== Economic ===== Perhaps the most common motivation for introducing a species into a new place is that of economic gain. Non-native species can become such a common part of an environment, culture, and even diet that little thought is given to their geographic origin. For example, soybeans, kiwi fruit, wheat, honey bees, and all livestock except the American bison and the turkey are non-native species to North America. Collectively, non-native crops and livestock account for 98% of US food. These and other benefits from non-natives are so vast that, according to the Congressional Research Service, they probably exceed the costs. Other examples of species introduced for the purposes of benefiting agriculture, aquaculture or other economic activities are widespread. Eurasian carp was first introduced to the United States as a potential food source. The apple snail was released in Southeast Asia with
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the intent that it be used as a protein source, and subsequently to places like Hawaii to establish a food industry. In Alaska, foxes were introduced to many islands to create new populations for the fur trade. About twenty species of African and European dung beetles have established themselves in Australia after deliberate introduction by the Australian Dung Beetle Project in an effort to reduce the impact of livestock manure. The timber industry promoted the introduction of Monterey pine (Pinus radiata) from California to Australia and New Zealand as a commercial timber crop. These examples represent only a small subsample of species that have been moved by humans for economic interests. The rise in the use of genetically modified organisms has added another potential economic advantage to introducing new/modified species into different environments. Companies such as Monsanto that earn much of their profit through the selling of genetically modified seeds has added to the controversy surrounding introduced species. The effect of genetically modified organisms varies from organism to organism and is still being researched today, however, the rise of genetically modified organisms has added complexity to the conversations surrounding introduced species. ===== Human enjoyment ===== Introductions have also been important in supporting recreation activities or otherwise increasing human enjoyment. Numerous fish and game animals have been introduced for the purposes of sport fishing and hunting. The introduced amphibian (Ambystoma tigrinum) that threatens the endemic California salamander (A. californiense) was introduced to California as a source of bait for fishermen. Pet animals have also been frequently transported into new areas by humans, and their escapes have resulted in several introductions, such as feral cats, parrots, and pond slider. Lophura nycthemera (silver pheasant), a native of East Asia, has been introduced into parts of Europe for ornamental reasons. Many plants have been
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introduced with the intent of aesthetically improving public recreation areas or private properties. The introduced Norway maple for example occupies a prominent status in many of Canada's parks. The transport of ornamental plants for landscaping use has and continues to be a source of many introductions. Some of these species have escaped horticultural control and become invasive. Notable examples include water hyacinth, salt cedar, and purple loosestrife. In other cases, species have been translocated for reasons of "cultural nostalgia", which refers to instances in which humans who have migrated to new regions have intentionally brought with them familiar organisms. Famous examples include the introduction of common starlings to North America by the American Eugene Schieffelin, a lover of the works of Shakespeare and the chairman of the American Acclimatization Society, who, it is rumoured, wanted to introduce all of the birds mentioned in Shakespeare's plays into the United States. He deliberately released eighty starlings into Central Park in New York City in 1890, and another forty in 1891. Yet another prominent example of an introduced species that became invasive is the European rabbit in Australia. Thomas Austin, a British landowner, had rabbits released on his estate in Victoria because he missed hunting them. A more recent example is the introduction of the common wall lizard (Podarcis muralis) to North America by a Cincinnati boy, George Rau, around 1950 after a family vacation to Italy. ===== Addressing environmental problems ===== Intentional introductions have also been undertaken with the aim of ameliorating environmental problems. A number of fast spreading plants such as kudzu have been introduced as a means of erosion control. Other species have been introduced as biological control agents to control invasive species. This involves the purposeful introduction of a natural enemy of the target species with the intention of
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reducing its numbers or controlling its spread. A special case of introduction is the reintroduction of a species that has become locally endangered or extinct, done in the interests of conservation. Examples of successful reintroductions include wolves to Yellowstone National Park in the U.S., and the red kite to parts of England and Scotland. Introductions or translocations of species have also been proposed in the interest of genetic conservation, which advocates the introduction of new individuals into genetically depauperate populations of endangered or threatened species. === Unintentional introductions === Unintentional introductions occur when species are transported by human vectors. Increasing rates of human travel are providing accelerating opportunities for species to be accidentally transported into areas in which they are not considered native. For example, three species of rat (the black, Norway and Polynesian) have spread to most of the world as hitchhikers on ships, and arachnids such as scorpions and exotic spiders are sometimes transported to areas far beyond their native range by riding in shipments of tropical fruit. This was seen during the introduction of Steatoda nobilis (Noble false widow) worldwide through banana shipments. Further there are numerous examples of marine organisms being transported in ballast water, among them the invasive comb jelly Mnemiopsis leidyi, the dangerous bacterium Vibrio cholerae, or the fouling zebra mussel. The Mediterranean and Black Seas, with their high volume shipping from exotic sources, are most impacted by this problem. Busy harbors are all potential hotspots as well: over 200 species have been introduced to the San Francisco Bay in this manner making it the most heavily invaded estuary in the world. There is also the accidental release of the Africanized honey bees (AHB), known colloquially as "killer bees") or Africanized bee to Brazil in 1957 and the Asian carp to the United States.
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The insect commonly known as the brown marmorated stink bug (Halyomorpha halys) was introduced accidentally in Pennsylvania. Another form of unintentional introductions is when an intentionally introduced plant carries a parasite or herbivore with it. Some become invasive, for example, the oleander aphid, accidentally introduced with the ornamental plant, oleander. Yet another unintentional pathway of introduction is during the delivery of humanitarian aid in the aftermath of natural disasters. This occurred during relief efforts for Hurricane Maria in Dominica, it was found that the common green iguana, the Cuban tree frog, and potentially the Venezuela snouted tree frog were introduced with the former two becoming established. Most accidentally or intentionally introduced species do not become invasive as the ones mentioned above. For instance, Some 179 coccinellid species have been introduced to the U.S. and Canada; about 27 of these non-native species have become established, and only a handful can be considered invasive, including the intentionally introduced Harmonia axyridis, multicolored Asian lady beetle. However the small percentage of introduced species that become invasive can produce profound ecological changes. In North America, Harmonia axyridis has become the most abundant lady beetle and probably accounts for more observations than all the native lady beetles put together. == Introduced plants == Many non-native plants have been introduced into new territories, initially as either ornamental plants or for erosion control, stock feed, or forestry. Whether an exotic will become an invasive species is seldom understood in the beginning. A very troublesome marine species in southern Europe is the seaweed Caulerpa taxifolia. Caulerpa was first observed in the Mediterranean Sea in 1984, off the coast of Monaco. By 1997, it had covered some 50 km2. It has a strong potential to overgrow natural biotopes, and represents a major risk for sublittoral ecosystems. The origin of the
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alga in the Mediterranean was thought to be either as a migration through the Suez Canal from the Red Sea, or as an accidental introduction from an aquarium. This species has become invasive in Australia, where it threatens native rare plants and causes erosion and soil slumping around river banks. It has also become invasive in France where it has been listed as an invasive plant species of concern in the Mediterranean region, where it can form monocultures that threaten critical conservation habitats. == Introduced animals == Most introduced species do not become invasive. Examples of introduced animals that have become invasive include the gypsy moth in eastern North America, the zebra mussel and alewife in the Great Lakes, the Canada goose and gray squirrel in Europe, the beaver in Tierra del Fuego, the muskrat in Europe and Asia, the cane toad and red fox in Australia, nutria in North America, Eurasia, and Africa, and the common brushtail possum in New Zealand. In Taiwan, the success of introduced bird species was related to their native range size and body size; larger species with larger native range sizes were found to have larger introduced range sizes. One notoriously devastating introduced species is the small Indian mongoose (Urva auropunctata). Originating in a region encompassing Iran and India, it was introduced to the West Indies and Hawaii in the late 1800s for pest control. Since then, it has thrived on prey unequipped to deal with its speed, nearly leading to the local extinction of a variety of species. In some cases, introduced animals may unintentionally promote the cause of rewilding. For example, escaped horses and donkeys that have gone feral in the Americas may play ecological roles similar to those of the equids that became extinct there at the end of the Pleistocene.
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The exotic pet trade has also been a large source of introduced species. The species favored as pets have more general habitat requirements and larger distributions. Therefore, as these pets escape or are released, unintentionally or intentionally, they are more likely to survive and establish non-native populations in the wild. Among the popular exotic pets that have become alien or invasive species are parrots, frogs, terrapins, and iguanas. === Most commonly introduced species === Some species, such as the Western honey bee, brown rat, house sparrow, ring-necked pheasant, and European starling, have been introduced very widely. In addition there are some agricultural and pet species that frequently become feral; these include rabbits, dogs, ducks, snakes, goats, fish, pigs, and cats. Many water fleas such as Daphnia, Bosmina and Bythotrephes have introduced around the world, causing dramatic changes in native freshwater ecosystems. == Genetics == When a new species is introduced, the species could potentially breed with members of native species, producing hybrids. The effect of the creating of hybrids can range from having little effect, a negative effect, to having devastating effects on native species. Potential negative effects include hybrids that are less fit for their environment resulting in a population decrease. This was seen in the Atlantic Salmon population when high levels of escape from Atlantic Salmon farms into the wild populations resulted in hybrids that had reduced survival. Potential positive effects include adding to the genetic diversity of the population which can increase the adaptation ability of the population and increase the number of healthy individuals within a population. This was seen in the introduction of guppies in Trinidad to encourage population growth and introduce new alleles into the population. The results of this introduction included increased levels of heterozygosity and a larger population size. Wide-spread introductions of
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non-native iguanas are causing devastating effects on native Iguana populations in the Caribbean Lesser Antilles, as hybrids appear to have higher fitness than native iguanas, leading to competitive outcompetition and replacement. Numerous populations have already become extinct and hybridization continues to reduce the number of native iguanas on multiple islands. In plants, introduced species have been observed to undergo rapid evolutionary change to adapt to their new environments, with changes in plant height, size, leaf shape, dispersal ability, reproductive output, vegetative reproduction ability, level of dependence on the mycorrhizal network, and level of phenotype plasticity appearing on timescales of decades to centuries. == On a planetary body == It has been hypothesized that invasive species of microbial life could contaminate a planetary body after the former is introduced by a space probe or spacecraft, either deliberately or unintentionally. It has also been hypothesized that the origin of life on earth is due to introductions of life from other planets billions of years ago, possibly by a sentient race. Projects have been proposed to introduce life to other lifeless but habitable planets in other star systems some time in the future. In preparation for this, projects have been proposed to see if anything is still alive from any of the feces left behind during the six Moon landings from 1969 to 1972. == See also == Archaeophyte Biological dispersal Biological hazard Colonisation (biology) Directed panspermia Genetic pollution Hemerochory Nativar Naturalisation (biology) == References == == Further reading == Chris D. Thomas (2017). Inheritors of the Earth: How Nature Is Thriving in an Age of Extinction. PublicAffairs. ISBN 978-1610397278. == External links == National Estuarine and Marine Exotic Species Information System (NEMESIS) Archived 2019-08-27 at the Wayback Machine The Naked Scientists Invasive Species Articles Ecologists challenge the categories that identify some species
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as natives and others as invaders.
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In condensed matter physics, the density of states (DOS) of a system describes the number of allowed modes or states per unit energy range. The density of states is defined as D ( E ) = N ( E ) / V {\displaystyle D(E)=N(E)/V} , where N ( E ) δ E {\displaystyle N(E)\delta E} is the number of states in the system of volume V {\displaystyle V} whose energies lie in the range from E {\displaystyle E} to E + δ E {\displaystyle E+\delta E} . It is mathematically represented as a distribution by a probability density function, and it is generally an average over the space and time domains of the various states occupied by the system. The density of states is directly related to the dispersion relations of the properties of the system. High DOS at a specific energy level means that many states are available for occupation. Generally, the density of states of matter is continuous. In isolated systems however, such as atoms or molecules in the gas phase, the density distribution is discrete, like a spectral density. Local variations, most often due to distortions of the original system, are often referred to as local densities of states (LDOSs). == Introduction == In quantum mechanical systems, waves, or wave-like particles, can occupy modes or states with wavelengths and propagation directions dictated by the system. For example, in some systems, the interatomic spacing and the atomic charge of a material might allow only electrons of certain wavelengths to exist. In other systems, the crystalline structure of a material might allow waves to propagate in one direction, while suppressing wave propagation in another direction. Often, only specific states are permitted. Thus, it can happen that many states are available for occupation at a specific energy level, while no
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
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|
states are available at other energy levels. Looking at the density of states of electrons at the band edge between the valence and conduction bands in a semiconductor, for an electron in the conduction band, an increase of the electron energy makes more states available for occupation. Alternatively, the density of states is discontinuous for an interval of energy, which means that no states are available for electrons to occupy within the band gap of the material. This condition also means that an electron at the conduction band edge must lose at least the band gap energy of the material in order to transition to another state in the valence band. This determines if the material is an insulator or a metal in the dimension of the propagation. The result of the number of states in a band is also useful for predicting the conduction properties. For example, in a one dimensional crystalline structure an odd number of electrons per atom results in a half-filled top band; there are free electrons at the Fermi level resulting in a metal. On the other hand, an even number of electrons exactly fills a whole number of bands, leaving the rest empty. If then the Fermi level lies in an occupied band gap between the highest occupied state and the lowest empty state, the material will be an insulator or semiconductor. Depending on the quantum mechanical system, the density of states can be calculated for electrons, photons, or phonons, and can be given as a function of either energy or the wave vector k. To convert between the DOS as a function of the energy and the DOS as a function of the wave vector, the system-specific energy dispersion relation between E and k must be known. In general, the topological properties of
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
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the system such as the band structure, have a major impact on the properties of the density of states. The most well-known systems, like neutron matter in neutron stars and free electron gases in metals (examples of degenerate matter and a Fermi gas), have a 3-dimensional Euclidean topology. Less familiar systems, like two-dimensional electron gases (2DEG) in graphite layers and the quantum Hall effect system in MOSFET type devices, have a 2-dimensional Euclidean topology. Even less familiar are carbon nanotubes, the quantum wire and Luttinger liquid with their 1-dimensional topologies. Systems with 1D and 2D topologies are likely to become more common, assuming developments in nanotechnology and materials science proceed. == Definition == The density of states related to volume V and N countable energy levels is defined as: D ( E ) = 1 V ∑ i = 1 N δ ( E − E ( k i ) ) . {\displaystyle D(E)={\frac {1}{V}}\,\sum _{i=1}^{N}\delta (E-E({\mathbf {k} }_{i})).} Because the smallest allowed change of momentum k {\displaystyle k} for a particle in a box of dimension d {\displaystyle d} and length L {\displaystyle L} is ( Δ k ) d = ( 2 π / L ) d {\displaystyle (\Delta k)^{d}=({2\pi }/{L})^{d}} , the volume-related density of states for continuous energy levels is obtained in the limit L → ∞ {\displaystyle L\to \infty } as D ( E ) := ∫ R d d d k ( 2 π ) d ⋅ δ ( E − E ( k ) ) , {\displaystyle D(E):=\int _{\mathbb {R} ^{d}}{\frac {\mathrm {d} ^{d}k}{(2\pi )^{d}}}\cdot \delta (E-E(\mathbf {k} )),} Here, d {\displaystyle d} is the spatial dimension of the considered system and k {\displaystyle \mathbf {k} } the wave vector. For isotropic one-dimensional systems with parabolic energy dispersion, the density of states is
|
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"page_id": 525887,
"source": null,
"title": "Density of states"
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D 1 D ( E ) = 1 2 π ℏ ( 2 m E ) 1 / 2 {\textstyle D_{1D}(E)={\tfrac {1}{2\pi \hbar }}({\tfrac {2m}{E}})^{1/2}} . In two dimensions the density of states is a constant D 2 D = m 2 π ℏ 2 {\displaystyle D_{2D}={\tfrac {m}{2\pi \hbar ^{2}}}} , while in three dimensions it becomes D 3 D ( E ) = m 2 π 2 ℏ 3 ( 2 m E ) 1 / 2 {\displaystyle D_{3D}(E)={\tfrac {m}{2\pi ^{2}\hbar ^{3}}}(2mE)^{1/2}} . Equivalently, the density of states can also be understood as the derivative of the microcanonical partition function Z m ( E ) {\displaystyle Z_{m}(E)} (that is, the total number of states with energy less than E {\displaystyle E} ) with respect to the energy: D ( E ) = 1 V ⋅ d Z m ( E ) d E . {\displaystyle D(E)={\frac {1}{V}}\cdot {\frac {\mathrm {d} Z_{m}(E)}{\mathrm {d} E}}.} The number of states with energy E ′ {\displaystyle E'} (degree of degeneracy) is given by: g ( E ′ ) = lim Δ E → 0 ∫ E ′ E ′ + Δ E D ( E ) d E = lim Δ E → 0 D ( E ′ ) Δ E , {\displaystyle g\left(E'\right)=\lim _{\Delta E\to 0}\int _{E'}^{E'+\Delta E}D(E)\,\mathrm {d} E=\lim _{\Delta E\to 0}D\left(E'\right)\Delta E,} where the last equality only applies when the mean value theorem for integrals is valid. == Symmetry == There is a large variety of systems and types of states for which DOS calculations can be done. Some condensed matter systems possess a structural symmetry on the microscopic scale which can be exploited to simplify calculation of their densities of states. In spherically symmetric systems, the integrals of functions are one-dimensional because all variables in the calculation depend only
|
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"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
on the radial parameter of the dispersion relation. Fluids, glasses and amorphous solids are examples of a symmetric system whose dispersion relations have a rotational symmetry. Measurements on powders or polycrystalline samples require evaluation and calculation functions and integrals over the whole domain, most often a Brillouin zone, of the dispersion relations of the system of interest. Sometimes the symmetry of the system is high, which causes the shape of the functions describing the dispersion relations of the system to appear many times over the whole domain of the dispersion relation. In such cases the effort to calculate the DOS can be reduced by a great amount when the calculation is limited to a reduced zone or fundamental domain. The Brillouin zone of the face-centered cubic lattice (FCC) in the figure on the right has the 48-fold symmetry of the point group Oh with full octahedral symmetry. This configuration means that the integration over the whole domain of the Brillouin zone can be reduced to a 48-th part of the whole Brillouin zone. As a crystal structure periodic table shows, there are many elements with a FCC crystal structure, like diamond, silicon and platinum and their Brillouin zones and dispersion relations have this 48-fold symmetry. Two other familiar crystal structures are the body-centered cubic lattice (BCC) and hexagonal closed packed structures (HCP) with cubic and hexagonal lattices, respectively. The BCC structure has the 24-fold pyritohedral symmetry of the point group Th. The HCP structure has the 12-fold prismatic dihedral symmetry of the point group D3h. A complete list of symmetry properties of a point group can be found in point group character tables. In general it is easier to calculate a DOS when the symmetry of the system is higher and the number of topological dimensions of the dispersion relation
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
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is lower. The DOS of dispersion relations with rotational symmetry can often be calculated analytically. This result is fortunate, since many materials of practical interest, such as steel and silicon, have high symmetry. In anisotropic condensed matter systems such as a single crystal of a compound, the density of states could be different in one crystallographic direction than in another. These causes the anisotropic density of states to be more difficult to visualize, and might require methods such as calculating the DOS for particular points or directions only, or calculating the projected density of states (PDOS) to a particular crystal orientation. == k-space topologies == The density of states is dependent upon the dimensional limits of the object itself. In a system described by three orthogonal parameters (3 Dimension), the units of DOS is [Energy]−1[Volume]−1, in a two dimensional system, the units of DOS is [Energy]−1[Area]−1, in a one dimensional system, the units of DOS is [Energy]−1[Length]−1. The referenced volume is the volume of k-space; the space enclosed by the constant energy surface of the system derived through a dispersion relation that relates E to k. An example of a 3-dimensional k-space is given in Fig. 1. It can be seen that the dimensionality of the system confines the momentum of particles inside the system. === Density of wave vector states (sphere) === The calculation for DOS starts by counting the N allowed states at a certain k that are contained within [k, k + dk] inside the volume of the system. This procedure is done by differentiating the whole k-space volume Ω n , k {\displaystyle \Omega _{n,k}} in n-dimensions at an arbitrary k, with respect to k. The volume, area or length in 3, 2 or 1-dimensional spherical k-spaces are expressed by Ω n ( k ) =
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
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c n k n {\displaystyle \Omega _{n}(k)=c_{n}k^{n}} for a n-dimensional k-space with the topologically determined constants c 1 = 2 , c 2 = π , c 3 = 4 π 3 {\displaystyle c_{1}=2,\ c_{2}=\pi ,\ c_{3}={\frac {4\pi }{3}}} for linear, disk and spherical symmetrical shaped functions in 1, 2 and 3-dimensional Euclidean k-spaces respectively. According to this scheme, the density of wave vector states N is, through differentiating Ω n , k {\displaystyle \Omega _{n,k}} with respect to k, expressed by N n ( k ) = d Ω n ( k ) d k = n c n k n − 1 {\displaystyle N_{n}(k)={\frac {\mathrm {d} \Omega _{n}(k)}{\mathrm {d} k}}=n\;c_{n}\;k^{n-1}} The 1, 2 and 3-dimensional density of wave vector states for a line, disk, or sphere are explicitly written as N 1 ( k ) = 2 N 2 ( k ) = 2 π k N 3 ( k ) = 4 π k 2 {\displaystyle {\begin{aligned}N_{1}(k)&=2\\N_{2}(k)&=2\pi k\\N_{3}(k)&=4\pi k^{2}\end{aligned}}} One state is large enough to contain particles having wavelength λ. The wavelength is related to k through the relationship. k = 2 π λ {\displaystyle k={\frac {2\pi }{\lambda }}} In a quantum system the length of λ will depend on a characteristic spacing of the system L that is confining the particles. Finally the density of states N is multiplied by a factor s / V k {\displaystyle s/V_{k}} , where s is a constant degeneracy factor that accounts for internal degrees of freedom due to such physical phenomena as spin or polarization. If no such phenomenon is present then s = 1 {\displaystyle s=1} . Vk is the volume in k-space whose wavevectors are smaller than the smallest possible wavevectors decided by the characteristic spacing of the system. === Density of energy states === To finish
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
the calculation for DOS find the number of states per unit sample volume at an energy E {\displaystyle E} inside an interval [ E , E + d E ] {\displaystyle [E,E+\mathrm {d} E]} . The general form of DOS of a system is given as D n ( E ) = d Ω n ( E ) d E {\displaystyle D_{n}\left(E\right)={\frac {\mathrm {d} \Omega _{n}(E)}{\mathrm {d} E}}} The scheme sketched so far only applies to monotonically rising and spherically symmetric dispersion relations. In general the dispersion relation E ( k ) {\displaystyle E(k)} is not spherically symmetric and in many cases it isn't continuously rising either. To express D as a function of E the inverse of the dispersion relation E ( k ) {\displaystyle E(k)} has to be substituted into the expression of Ω n ( k ) {\displaystyle \Omega _{n}(k)} as a function of k to get the expression of Ω n ( E ) {\displaystyle \Omega _{n}(E)} as a function of the energy. If the dispersion relation is not spherically symmetric or continuously rising and can't be inverted easily then in most cases the DOS has to be calculated numerically. More detailed derivations are available. == Dispersion relations == The dispersion relation for electrons in a solid is given by the electronic band structure. The kinetic energy of a particle depends on the magnitude and direction of the wave vector k, the properties of the particle and the environment in which the particle is moving. For example, the kinetic energy of an electron in a Fermi gas is given by E = E 0 + ( ℏ k ) 2 2 m , {\displaystyle E=E_{0}+{\frac {\left(\hbar k\right)^{2}}{2m}}\ ,} where m is the electron mass. The dispersion relation is a spherically symmetric parabola and it is continuously
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
rising so the DOS can be calculated easily. For longitudinal phonons in a string of atoms the dispersion relation of the kinetic energy in a 1-dimensional k-space, as shown in Figure 2, is given by E = 2 ℏ ω 0 | sin ( k a 2 ) | {\displaystyle E=2\hbar \omega _{0}\left|\sin \left({\frac {ka}{2}}\right)\right|} where ω 0 = k F / m {\textstyle \omega _{0}={\sqrt {k_{\text{F}}/m}}} is the oscillator frequency, m {\displaystyle m} the mass of the atoms, k F {\displaystyle k_{\text{F}}} the inter-atomic force constant and a {\displaystyle a} inter-atomic spacing. For small values of k ≪ π / a {\displaystyle k\ll \pi /a} the dispersion relation is linear: E = ℏ ω 0 k a {\displaystyle E=\hbar \omega _{0}ka} When k ≈ π / a {\displaystyle k\approx \pi /a} the energy is E = 2 ℏ ω 0 | cos ( π − k a 2 ) | {\displaystyle E=2\hbar \omega _{0}\left|\cos \left({\frac {\pi -ka}{2}}\right)\right|} With the transformation q = k − π / a {\displaystyle q=k-\pi /a} and small q {\displaystyle q} this relation can be transformed to E ≈ 2 ℏ ω 0 [ 1 − ( q a 2 ) 2 ] {\displaystyle E\approx 2\hbar \omega _{0}\left[1-\left({\frac {qa}{2}}\right)^{2}\right]} === Isotropic dispersion relations === The two examples mentioned here can be expressed like E = E 0 + c k k p {\displaystyle E=E_{0}+c_{k}k^{p}} This expression is a kind of dispersion relation because it interrelates two wave properties and it is isotropic because only the length and not the direction of the wave vector appears in the expression. The magnitude of the wave vector is related to the energy as: k = ( E − E 0 c k ) 1 / p , {\displaystyle k=\left({\frac {E-E_{0}}{c_{k}}}\right)^{{1}/{p}},} Accordingly, the volume of n-dimensional k-space
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
containing wave vectors smaller than k is: Ω n ( k ) = c n k n {\displaystyle \Omega _{n}(k)=c_{n}k^{n}} Substitution of the isotropic energy relation gives the volume of occupied states Ω n ( E ) = c n c k n p ( E − E 0 ) n / p , {\displaystyle \Omega _{n}(E)={\frac {c_{n}}{{c_{k}}^{\frac {n}{p}}}}\left(E-E_{0}\right)^{{n}/{p}},} Differentiating this volume with respect to the energy gives an expression for the DOS of the isotropic dispersion relation D n ( E ) = d d E Ω n ( E ) = n c n p c k n p ( E − E 0 ) n p − 1 {\displaystyle D_{n}\left(E\right)={\frac {\mathrm {d} }{\mathrm {d} E}}\Omega _{n}(E)={\frac {nc_{n}}{p{c_{k}}^{\frac {n}{p}}}}\left(E-E_{0}\right)^{{\frac {n}{p}}-1}} === Parabolic dispersion === In the case of a parabolic dispersion relation (p = 2), such as applies to free electrons in a Fermi gas, the resulting density of states, D n ( E ) {\displaystyle D_{n}\left(E\right)} , for electrons in a n-dimensional systems is D 1 ( E ) = 1 c k ( E − E 0 ) D 2 ( E ) = π c k D 3 ( E ) = 2 π E − E 0 c k 3 . {\displaystyle {\begin{aligned}D_{1}\left(E\right)&={\frac {1}{\sqrt {c_{k}\left(E-E_{0}\right)}}}\\[1ex]D_{2}\left(E\right)&={\frac {\pi }{c_{k}}}\\[1ex]D_{3}\left(E\right)&=2\pi {\sqrt {\frac {E-E_{0}}{c_{k}^{3}}}}\,.\end{aligned}}} for E > E 0 {\displaystyle E>E_{0}} , with D ( E ) = 0 {\displaystyle D(E)=0} for E < E 0 {\displaystyle E<E_{0}} . In 1-dimensional systems the DOS diverges at the bottom of the band as E {\displaystyle E} drops to E 0 {\displaystyle E_{0}} . In 2-dimensional systems the DOS turns out to be independent of E {\displaystyle E} . Finally for 3-dimensional systems the DOS rises as the square root of the energy. Including the prefactor s / V k
|
{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
{\displaystyle s/V_{k}} , the expression for the 3D DOS is N ( E ) = V 2 π 2 ( 2 m ℏ 2 ) 3 2 E − E 0 , {\displaystyle N(E)={\frac {V}{2\pi ^{2}}}\left({\frac {2m}{\hbar ^{2}}}\right)^{\frac {3}{2}}{\sqrt {E-E_{0}}},} where V {\displaystyle V} is the total volume, and N ( E − E 0 ) {\displaystyle N(E-E_{0})} includes the 2-fold spin degeneracy. === Linear dispersion === In the case of a linear relation (p = 1), such as applies to photons, acoustic phonons, or to some special kinds of electronic bands in a solid, the DOS in 1, 2 and 3 dimensional systems is related to the energy as: D 1 ( E ) = 2 c k D 2 ( E ) = 2 π E − E 0 c k 2 D 3 ( E ) = 4 π ( E − E 0 ) 2 c k 3 {\displaystyle {\begin{aligned}D_{1}\left(E\right)&={\frac {2}{c_{k}}}\\[1ex]D_{2}\left(E\right)&=2\pi {\frac {E-E_{0}}{c_{k}^{2}}}\\[1ex]D_{3}\left(E\right)&=4\pi {\frac {\left(E-E_{0}\right)^{2}}{c_{k}^{3}}}\end{aligned}}} == Distribution functions == The density of states plays an important role in the kinetic theory of solids. The product of the density of states and the probability distribution function is the number of occupied states per unit volume at a given energy for a system in thermal equilibrium. This value is widely used to investigate various physical properties of matter. The following are examples, using two common distribution functions, of how applying a distribution function to the density of states can give rise to physical properties. Fermi–Dirac statistics: The Fermi–Dirac probability distribution function, Fig. 4, is used to find the probability that a fermion occupies a specific quantum state in a system at thermal equilibrium. Fermions are particles which obey the Pauli exclusion principle (e.g. electrons, protons, neutrons). The distribution function can be written as f F D ( E
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{
"page_id": 525887,
"source": null,
"title": "Density of states"
}
|
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