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Aperture Desk Job-Development-Aperture Desk Job was developed by Valve on the Source 2 engine as a tech demo for the Steam Deck. It was released for free on March 1, 2022. | milkshake721/2.1M-wiki-STEM |
Aperture Desk Job-Reception-Rock Paper Shotgun praised the humor of the game. | milkshake721/2.1M-wiki-STEM |
Birding (magazine)-Birding (magazine)-Birding is the bimonthly magazine of the American Birding Association. Birding publishes articles on field identification, bird conservation, notable sightings, and other subjects of interest to the birding community. Each issue also includes critical reviews of new equipment and b... | milkshake721/2.1M-wiki-STEM |
ScicomP-ScicomP-The IBM HPC Systems Scientific Computing User Group (ScicomP) is an international organization open to all scientific and technical users of IBM systems. At yearly meetings application scientists and staff from HPC centers present talks about, and discuss, ways to develop efficient and scalable scientif... | milkshake721/2.1M-wiki-STEM |
ScicomP-History-ScicomP was formed in October 1999 when 285 researchers and engineers met at IBM's Advanced Computing Technology Center (ACTC) at IBM Research in Yorktown Heights, NY. | milkshake721/2.1M-wiki-STEM |
ScicomP-History-The meeting was a user-oriented and planned 3-day workshop to share information on scientific computing techniques for the users of IBM SP supercomputers. The meeting was created on the recommendations of the attendees of the IBM SP Scientific Applications Development and Optimization Workshop held in M... | milkshake721/2.1M-wiki-STEM |
ScicomP-History-ScicomP has held annual and semi-annual meetings that bring together scientific domain experts, computational scientists, systems engineers, and IBM technical specialists to share experiences using IBM High Performance Computing Systems. The domain encompasses all IBM HPC Systems, including Power, Blue ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Busy beaver-In theoretical computer science, the busy beaver game aims at finding a terminating program of a given size that produces the most output possible. Since an endlessly looping program producing infinite output is easily conceived, such programs are excluded from the game. | milkshake721/2.1M-wiki-STEM |
Busy beaver-Busy beaver-More precisely, the busy beaver game consists of designing a halting Turing machine with alphabet {0,1} which writes the most 1s on the tape, using only a given set of states. The rules for the 2-state game are as follows: the machine must have at most two states in addition to the halting state... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Busy beaver-An nth busy beaver, BB-n or simply "busy beaver" is a Turing machine that wins the n-state busy beaver game. That is, it attains the largest number of 1s among all other possible n-state competing Turing machines. The BB-2 Turing machine, for instance, achieves four 1s in six steps.
Determining ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-The n-state busy beaver game (or BB-n game), introduced in Tibor Radó's 1962 paper, involves a class of Turing machines, each member of which is required to meet the following design specifications: The machine has n "operational" states plus a Halt state, where n is a positive integer, and one of ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-The tape alphabet is {0, 1}, with 0 serving as the blank symbol. | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-The machine's transition function takes two inputs:the current non-Halt state, the symbol in the current tape cell, and produces three outputs: a symbol to write over the symbol in the current tape cell (it may be the same symbol as the symbol overwritten), a direction to move (left or right; that ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-The transition function may be seen as a finite table of 5-tuples, each of the form (current state, current symbol, symbol to write, direction of shift, next state)."Running" the machine consists of starting in the starting state, with the current tape cell being any cell of a blank (all-0) tape, ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-The n-state busy beaver (BB-n) game is a contest to find such an n-state Turing machine having the largest possible score — the largest number of 1s on its tape after halting. A machine that attains the largest possible score among all n-state Turing machines is called an n-state busy beaver, and a... | milkshake721/2.1M-wiki-STEM |
Busy beaver-The game-Radó required that each machine entered in the contest be accompanied by a statement of the exact number of steps it takes to reach the Halt state, thus allowing the score of each entry to be verified (in principle) by running the machine for the stated number of steps. (If entries were to consist ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-The busy beaver function Σ The busy beaver function quantifies the maximum score attainable by a busy beaver on a given measure. This is a noncomputable function. Also, a busy beaver function can be shown to grow faster asymptotically than any computable function.The busy beaver function, ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-It is clear that Σ is a well-defined function: for every n, there are at most finitely many n-state Turing machines as above, up to isomorphism, hence at most finitely many possible running times. | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-This infinite sequence Σ is the busy beaver function, and any n-state 2-symbol Turing machine M for which σ(M) = Σ(n) (i.e., which attains the maximum score) is called a busy beaver. Note that for each n, there exist at least four n-state busy beavers (because, given any n-state busy beave... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Non-computability Radó's 1962 paper proved that if f:N→N is any computable function, then Σ(n) > f(n) for all sufficiently large n, and hence that Σ is not a computable function. | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Moreover, this implies that it is undecidable by a general algorithm whether an arbitrary Turing machine is a busy beaver. (Such an algorithm cannot exist, because its existence would allow Σ to be computed, which is a proven impossibility. In particular, such an algorithm could be used to... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-In 2016, Adam Yedidia and Scott Aaronson obtained the first (explicit) upper bound on the minimum n for which Σ(n) is unprovable in ZFC. To do so they constructed a 7910-state Turing machine whose behavior cannot be proven based on the usual axioms of set theory (Zermelo–Fraenkel set theor... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Complexity and unprovability of Σ A variant of Kolmogorov complexity is defined as follows [cf. Boolos, Burgess & Jeffrey, 2007]: The complexity of a number n is the smallest number of states needed for a BB-class Turing machine that halts with a single block of n consecutive 1s on an init... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Radó showed that S is noncomputable for the same reason that Σ is noncomputable — it grows faster than any computable function. He proved this simply by noting that for each n, S(n) ≥ Σ(n). Each shift may write a 0 or a 1 on the tape, while Σ counts a subset of the shifts that wrote a 1, n... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-The following connection between Σ and S was used by Lin & Radó [Computer Studies of Turing Machine Problems, 1965] to prove that Σ(3) = 6: For a given n, if S(n) is known then all n-state Turing machines can (in principle) be run for up to S(n) steps, at which point any machine that hasn'... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Inequalities relating Σ and S include the following (from [Ben-Amram, et al., 1996]), which are valid for all n ≥ 1: S(n)≥Σ(n)S(n)≤(2n−1)Σ(3n+3)S(n)<Σ(3n+6); and an asymptotically improved bound (from [Ben-Amram, Petersen, 2002]): there exists a constant c, such that for all n ≥ 2, log 2n... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-S(n) tends to be close to the square of Σ(n) , and in fact many machines give S(n) less than Σ2(n) Known values for Σ and S As of 2016 the function values for Σ(n) and S(n) are only known exactly for n < 5.The current (as of 2023) 5-state busy beaver champion produces 4098 1s, using 471... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Milton Green, in his 1964 paper "A Lower Bound on Rado's Sigma Function for Binary Turing Machines", constructed a set of Turing machines demonstrating that for k≥2, where ↑ is Knuth up-arrow notation and A is Ackermann's function.
Thus 10 ↑↑↑ ↑↑ 333=333...3 (with 333 = 7625597484987 term... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-In 1964 Milton Green developed a lower bound for the Busy Beaver function that was published in the proceedings of the 1964 IEEE symposium on switching circuit theory and logical design. Heiner Marxen and Jürgen Buntrock described it as "a non-trivial (not primitive recursive) lower bound"... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-It can be derived from current lower bounds that: 31 for k≥2, In contrast, the best current (as of 2023) lower bound on Σ(6) is 10↑↑15, which is greater than the lower bound given by Green's formula, 33 = 27 (which is tiny in comparison). In fact, it is much greater than the lower bound: ... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Proof for uncomputability of S(n) and Σ(n) Suppose that S(n) is a computable function and let EvalS denote a TM, evaluating S(n). Given a tape with n 1s it will produce S(n) 1s on the tape and then halt. Let Clean denote a Turing machine cleaning the sequence of 1s initially written on the... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Let BadS denote the composition Create_n0 | Double | EvalS | Clean. Notice that this machine has N states. Starting with an initially blank tape it first creates a sequence of n0 1s and then doubles it, producing a sequence of N 1s. Then BadS will produce S(N) 1s on tape, and at last it wi... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-The uncomputability of Σ(n) may be proved in a similar way. In the above proof, one must exchange the machine EvalS with EvalΣ and Clean with Increment — a simple TM, searching for a first 0 on the tape and replacing it with 1. | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-The uncomputability of S(n) can also be established by reference to the blank tape halting problem. The blank tape halting problem is the problem of deciding for any Turing machine whether or not it will halt when started on an empty tape. The blank tape halting problem is equivalent to th... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Generalizations For any model of computation there exist simple analogs of the busy beaver. For example, the generalization to Turing machines with n states and m symbols defines the following generalized busy beaver functions: Σ(n, m): the largest number of non-zeros printable by an n-sta... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-It is possible to further generalize the busy beaver function by extending to more than one dimension.
Likewise we could define an analog to the Σ function for register machines as the largest number which can be present in any register on halting, for a given number of instructions. | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Exact values and lower bounds The following table lists the exact values and some known lower bounds for S(n, m) and Σ(n, m) for the generalized busy beaver problems. Note: entries listed as "?" are bounded from below by the maximum of all entries to left and above. These machines either h... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Related functions-Nondeterministic Turing machines The problem can be extended to Nondeterministic Turing machines by looking for the system with the most states across all branches or the branch with the longest number of steps. The question of whether a given NDTM will halt is still computationally irredu... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Applications-In addition to posing a rather challenging mathematical game, the busy beaver functions offer an entirely new approach to solving pure mathematics problems. Many open problems in mathematics could in theory, but not in practice, be solved in a systematic way given the value of S(n) for a suffic... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Applications-Thus specific values (or upper bounds) for S(n) could be used to systematically solve many open problems in mathematics (in theory). However, current results on the busy beaver problem suggest that this will not be practical for two reasons: It is extremely hard to prove values for the busy bea... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Applications-But even if one did find a better way to calculate S(n), the values of the busy beaver function (and max shift function) get very large, very fast. S(6) > 1036534 already requires special pattern-based acceleration to be able to simulate to completion. Likewise, we know that S(10) > Σ(10) > 3 ↑... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Applications-Notable instances A 748-state binary Turing machine has been constructed that halts iff ZFC is inconsistent. A 744-state Turing machine has been constructed that halts iff the Riemann hypothesis is false. A 43-state Turing machine has been constructed that halts iff Goldbach's conjecture is fal... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Examples-These are tables of rules for the Turing machines that generate Σ(1) and S(1), Σ(2) and S(2), Σ(3) (but not S(3)), Σ(4) and S(4), and the best known lower bound for Σ(5) and S(5), and Σ(6) and S(6). For other visualizations, In the tables, columns represent the current state and rows represent the... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Examples-Each machine begins in state A with an infinite tape that contains all 0s. Thus, the initial symbol read from the tape is a 0.
Result key: (starts at the position overlined, halts at the position underlined) Result: 0 0 1 0 0 (1 step, one "1" total) Result: 0 0 1 1 1 1 0 0 (6 steps, four "1"s total... | milkshake721/2.1M-wiki-STEM |
Busy beaver-Visualizations-In the following table, the rules for each busy beaver (maximizing Σ) are represented visually, with orange squares corresponding to a "1" on the tape, and white corresponding to "0". The position of the head is indicated by the black ovoid, with the orientation of the head representing the s... | milkshake721/2.1M-wiki-STEM |
Hydrodissection-Hydrodissection-Hydrodissection is the use of a directed jet of water to surgically separate tissues. It is generally used to develop tissue planes or divide soft tissues with less trauma than dissection using a cutting instrument. By using an appropriate pressure it will tend to follow the path of leas... | milkshake721/2.1M-wiki-STEM |
Hydrodissection-Applications-In cataract surgery it is used to release the lens from its capsule by projecting a continuous flow of water from a cannula under the flap of the anterior capsule, which lifts the capsule membrane from the lens. By directing the flow the surgeon lifts the membrane around the sides and back ... | milkshake721/2.1M-wiki-STEM |
Quicknet-Quicknet-Quicknet is an Ajax framework (using XMLHttpRequest in JavaScript) designed to develop web applications or websites that use passwords to identify correct users. Using this framework, no cleartext password would be sent over the network or stored in the server. Quicknet supports multi-language, JavaSc... | milkshake721/2.1M-wiki-STEM |
Quicknet-System requirements-Server-side Quicknet should run on any server with Apache 2.2+, MySQL 5.1+ and PHP 5+ .
Client-side Quicknet should be compatible with Internet Explorer 7+, Firefox 3+, Opera 9+, Safari 3+ and Google Chrome 1+ . | milkshake721/2.1M-wiki-STEM |
Quicknet-Session and Password Management-Quicknet is an AJAX framework that aims to protect users’ passwords with specially designed algorithm. This is achieved by using the same Cryptographic hash function in JavaScript code on the client-side, as well as PHP code on the server-side, to generate and compare hash resul... | milkshake721/2.1M-wiki-STEM |
Quicknet-Secure Data Transmission-Currently, Quicknet is possibly the only PHP AJAX framework that provides secure data transmission without SSL. | milkshake721/2.1M-wiki-STEM |
Quicknet-Multi-language-Currently, Quicknet is possibly the only PHP AJAX framework with built-in support for multi-language. Developers could easily add new language to build their own systems. | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering-Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass ... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-When countersteering to turn right, the following is performed: A torque on the handlebars to the left is applied.
The front wheel will then rotate about the steering axis to the left and the tire will generate forces in the contact patch to the left.
The machine as a whole steers to the le... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-The bike begins a turn to the right.While this appears to be a complex sequence of motions, it is performed by every child who rides a bicycle. The entire sequence goes largely unnoticed by most riders, which is why some assert that they do not do it.It is also important to distinguish the ... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-The initial steer torque and angle are both opposite the desired turn direction.
The sustained steer angle is in the same direction as the turn.
The sustained steer torque required to maintain that steer angle is either with or opposite the turn direction depending on forward speed, bike ge... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-Need to lean to turn A bike can negotiate a curve only when the combined center of mass of bike and rider leans toward the inside of the turn at an angle appropriate for the velocity and the radius of the turn: arctan (v2gr) where v is the forward speed, r is the radius of the turn and ... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-Stable lean As the desired angle is approached, the front wheel must usually be steered into the turn to maintain that angle or the bike will continue to lean with gravity, increasing in rate, until the side contacts the ground. This process often requires little or no physical effort, beca... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-The actual torque the rider must apply to the handlebars to maintain a steady-state turn is a complex function of bike geometry, mass distribution, rider position, tire properties, turn radius, and forward speed. At low speeds, the steering torque necessary from the rider is usually negativ... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-At low speeds At low speeds countersteering is equally necessary, but the countersteering is then so subtle that it is hidden by the continuous corrections that are made in balancing the bike, often falling below a just noticeable difference or threshold of perception of the rider. Counters... | milkshake721/2.1M-wiki-STEM |
Countersteering-How it works-Gyroscopic effects One effect of turning the front wheel is a roll moment caused by gyroscopic precession. The magnitude of this moment is proportional to the moment of inertia of the front wheel, its spin rate (forward motion), the rate that the rider turns the front wheel by applying a to... | milkshake721/2.1M-wiki-STEM |
Countersteering-Motorcycles-Deliberately countersteering is essential for safe motorcycle riding, and as a result is generally a part of safe riding courses run by organisations like the Motorcycle Safety Foundation, the Canada Safety Council, or Australian Q-Ride providers. Deliberately countersteering a motorcycle is... | milkshake721/2.1M-wiki-STEM |
Countersteering-Motorcycles-To encourage an understanding of the phenomena around countersteering, the phrase positive steering is sometimes used. Other phrases are "PRESS – To turn, the motorcycle must lean", "To lean the motorcycle, press on the handgrip in the direction of the turn" or "Press left – lean left – go l... | milkshake721/2.1M-wiki-STEM |
Countersteering-Motorcycles-Safety According to the Hurt Report, most motorcycle riders in the United States would over-brake and skid the rear wheel and under-brake the front when trying hard to avoid a collision. The ability to countersteer and swerve was essentially absent with many motorcycle operators. The often s... | milkshake721/2.1M-wiki-STEM |
Countersteering-Multi-track vehicles-Three wheeled motorcycles without the ability to lean have no need to be countersteered, and an initial steer torque in one direction does not automatically result in a turn in the other direction. This includes sidecar rigs where the car is rigidly mounted on the bike. The three wh... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-With a sufficiently light bike (especially a bicycle), the rider can initiate a lean and turn without using the handlebars by shifting body weight, called counter lean by some authors.
Documented physical experimentation shows that on heavy bikes (many motorcycles) shi... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-The combined center of mass of the bike and rider is only lowered and not moved out, but if the front of the bike is free to swivel about its steering axis, the lean to the right will cause it to steer to the right by some combination of gyroscopic precession, ground r... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-This countersteering to the right causes the ground contact to move to the right of the center of mass, as the bike moves forward, thus generating a leftward lean. Finally the front end steers to the left and the bike enters the left turn.The amount of leftward steerin... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-To straighten back out of the turn, the rider simply reverses the procedure for entering it: cause the bike to lean farther to the left; this causes it to steer farther to the left, which moves the wheel contact patches farther to the left, eventually reducing the left... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-A National Highway Traffic Safety Administration study showed that rider lean has a larger influence on a lighter motorcycle than a heavier one, which helps explain why no-hands steering is less effective on heavy motorcycles. Leaning the torso with respect to the bike... | milkshake721/2.1M-wiki-STEM |
Countersteering-Countersteering by weight shifting-Complex maneuvers are not possible using weight shifting alone because even for a light machine there is insufficient control authority.
Although on a sufficiently light bike (especially a bicycle), the rider can initiate a lean and turn by shifting body weight, there ... | milkshake721/2.1M-wiki-STEM |
Countersteering-Other uses-The term countersteering is also used by some authors to refer to the need on bikes to steer in the opposite direction of the turn (negative steering angle) to maintain control in response to significant rear wheel slippage. Motorcycle speedway racing takes place on an oval track with a loose... | milkshake721/2.1M-wiki-STEM |
Countersteering-Other uses-The term is also used in the discussion of the automobile driving technique called drifting. | milkshake721/2.1M-wiki-STEM |
Countersteering-The Wright Brothers-Wilbur Wright explained countersteering this way: I have asked dozens of bicycle riders how they turn to the left. I have never found a single person who stated all the facts correctly when first asked. They almost invariably said that to turn to the left, they turned the handlebar t... | milkshake721/2.1M-wiki-STEM |
M squared-M squared-In laser science, the parameter M2, also known as the beam propagation ratio or beam quality factor is a measure of laser beam quality. It represents the degree of variation of a beam from an ideal Gaussian beam. It is calculated from the ratio of the beam parameter product (BPP) of the beam to that... | milkshake721/2.1M-wiki-STEM |
M squared-M squared-The M2 value for a laser beam is widely used in the laser industry as a specification, and its method of measurement is regulated as an ISO Standard. | milkshake721/2.1M-wiki-STEM |
M squared-Measurement-There are several ways to define the width of a beam. When measuring the beam parameter product and M2, one uses the D4σ or "second moment" width of the beam to determine both the radius of the beam's waist and the divergence in the far field.M2 can be measured by placing an array detector or scan... | milkshake721/2.1M-wiki-STEM |
M squared-Measurement-Measure the D4σ widths at 5 axial positions at least one Rayleigh length away from the waist. | milkshake721/2.1M-wiki-STEM |
M squared-Measurement-Fit the 10 measured data points to W2(z)=W02+M4(λπW0)2(z−z0)2 ,Here W(z) is half of the D4 σ(z) beam width and z0 is the location of the beam waist with width W0 . Fitting the 10 data points yields M2, z0 , and W0 . Siegman showed that all beam profiles — Gaussian, flat top, TEMxy, or any s... | milkshake721/2.1M-wiki-STEM |
M squared-Utility-M2 is useful because it reflects how well a collimated laser beam can be focused to a small spot, or how well a divergent laser source can be collimated. It is a better guide to beam quality than Gaussian appearance because there are many cases in which a beam can look Gaussian, yet have an M2 value f... | milkshake721/2.1M-wiki-STEM |
M squared-Multi-mode beam propagation-Real laser beams are often non-Gaussian, being multi-mode or mixed-mode. Multi-mode beam propagation is often modeled by considering a so-called "embedded" Gaussian, whose beam waist is M times smaller than that of the multimode beam. The diameter of the multimode beam is then M ti... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Circumventricular organs-Circumventricular organs (CVOs) (circum-: around ; ventricular: of ventricle) are structures in the brain characterized by their extensive and highly permeable capillaries, unlike those in the rest of the brain where there exists a blood–brain barrier (BBB) at the capil... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Circumventricular organs-Although the choroid plexus also has permeable capillaries, it does not contain neural tissue; rather, its primary role is to produce cerebrospinal fluid (CSF), and therefore is typically not classified as a CVO. | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Area postrema Anatomy The area postrema is located in the caudal medulla oblongata near the junction of the brainstem and the spinal cord. In humans and in most other mammals that have been studied, it consists of swellings on either wall of the fourth ventricle. In rodents and l... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Function Relatively little is known about the function of the area postrema in humans. However, there is strong evidence that the area postrema acts as the chemoreceptor trigger zone for vomiting, which is triggered by the presence of noxious stimulation from the blood. There is ... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Vascular organ of the lamina terminalis Anatomy Classified as a sensory circumventricular organ (along with the SFO and AP), the vascular organ of lamina terminalis (VOLT) is situated in the anterior wall of the third ventricle. Characteristically of the CVOs, it lacks the tight ... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Function As previously mentioned, the vascular organ of lamina terminalis features neurons responsible for the homeostatic conservation of osmolarity. In addition, the fenestrated vasculature of the VOLT allows the astrocytes and neurons of the VOLT to perceive a wide variety of ... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Subfornical organ (SFO) Anatomy The subfornical organ is a sensory CVO situated on the underside of the fornix and lacking a BBB, the absence of which characterizes the circumventricular organs. Protruding into the third ventricle of the brain, the highly vascularized SFO can be ... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Sensory organs-Function The subfornical organ is active in many bodily processes including, but not limited to, osmoregulation, cardiovascular regulation, and energy homeostasis. In a study by Ferguson, both hyper- and hypotonic stimuli facilitated an osmotic response. This observation demonstr... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Subcommissural organ Anatomy The subcommissural organ (SCO) is a small secretory organ located on the ventral surface of the posterior commissure near the anterior entrance of the cerebral aqueduct. It differs from other CVOs in that it does not have highly permeable capillarie... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Function One function of the SCO is the secretion of the glycoprotein SCO-spondin, which is released into the third ventricle where it aggregates to create Reissner's fiber. Reissner's fiber is a long fibrous projection that travels caudally through the Sylvian aqueduct and ter... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Pituitary neural lobe The pituitary gland is subdivided into lobes – the anterior pituitary, the intermediate pituitary, and the posterior pituitary (also known as the adenohypophysis and neurohypophysis (or neural lobe), respectively). Each one functions as a separate endocrin... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-The intermediate lobe (also called pars intermedia) synthesizes and secretes a hormone stimulating melanocytes under neural control by the hypothalamus. It is not commonly included among circumventricular organs.The pituitary gland is located in the sella turcica of the sphenoi... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Median eminence The median eminence (ME) is located in the inferior portion of the hypothalamus and is ventral to the third ventricle. While some publications do not list the ME as a CVO, when it is considered to be a circumventricular organ, it is classified as a secretory org... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Pineal gland Anatomy Gross anatomy The morphology of the pineal gland varies greatly among mammals. The most commonly used classification for this gland takes into account its location relative to the diencephalon and the third ventricle of the brain, as well as its size and sh... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-The pineal gland starts to develop during the second month of gestation. In the average adult, the dimensions are as follow: 5-9mm in length, 1-5mm in width and 3-5mm in thickness. Its average weight is 100–180 mg.
The pineal gland consists of a central core made up of small lo... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Vascularization and innervation The level of vascularization in the pineal gland is high. It receives a large supply of blood from branches of the posterior choroidal arteries that derive from cerebral arteries in the posterior mesencephalon.The pineal gland is innervated by fi... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Function The pineal gland is considered a secretory organ and its activity shows circadian oscillations. Its main function – secretion of the hormone melatonin – rests when there is no input from the primary circadian pacemaker in the suprachiasmatic nuclei. Melatonin productio... | milkshake721/2.1M-wiki-STEM |
Circumventricular organs-Secretory organs-Other pineal substances Other peptides aside from melatonin have been detected in the pineal. They are most likely associated with a type of innervation deemed "pineal peptidergic innervation." These include vasopressin, oxytocin, VIP, NPY, peptide histidine isoleucine, calcito... | milkshake721/2.1M-wiki-STEM |
Impact crater lake-Impact crater lake-An impact crater lake is a lake inside a depression caused by the impact of a meteor. It is also known as an annular lake in cases where the water body is shaped like a ring, as many impact crater lakes are. | milkshake721/2.1M-wiki-STEM |
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