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Bra–ket notation-Vector spaces-In quantum mechanics, it is common practice to write down kets which have infinite norm, i.e. non-normalizable wavefunctions. Examples include states whose wavefunctions are Dirac delta functions or infinite plane waves. These do not, technically, belong to the Hilbert space itself. Howev... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Vector spaces-Banach spaces are a different generalization of Hilbert spaces. In a Banach space B, the vectors may be notated by kets and the continuous linear functionals by bras. Over any vector space without topology, we may also notate the vectors by kets and the linear functionals by bras. In thes... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-The mathematical structure of quantum mechanics is based in large part on linear algebra: Wave functions and other quantum states can be represented as vectors in a complex Hilbert space. (The exact structure of this Hilbert space depends on the situation.) In bra–ket notatio... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-Measurements are associated with linear operators (called observables) on the Hilbert space of quantum states.
Dynamics are also described by linear operators on the Hilbert space. For example, in the Schrödinger picture, there is a linear time evolution operator U with the p... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-Wave function normalization is scaling a wave function so that its norm is 1.Since virtually every calculation in quantum mechanics involves vectors and linear operators, it can involve, and often does involve, bra–ket notation. A few examples follow: Spinless position–space ... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-Starting from any ket |Ψ⟩ in this Hilbert space, one may define a complex scalar function of r, known as a wavefunction, On the left-hand side, Ψ(r) is a function mapping any point in space to a complex number; on the right-hand side, is a ket consisting of a superposition of... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-It is then customary to define linear operators acting on wavefunctions in terms of linear operators acting on kets, by For instance, the momentum operator p^ has the following coordinate representation, One occasionally even encounters a expressions such as ∇|Ψ⟩ , though t... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Usage in quantum mechanics-Changing basis for a spin-1/2 particle A stationary spin-1⁄2 particle has a two-dimensional Hilbert space. One orthonormal basis is: where |↑z⟩ is the state with a definite value of the spin operator Sz equal to +1⁄2 and |↓z⟩ is the state with a definite value of the spin ope... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Pitfalls and ambiguous uses-There are some conventions and uses of notation that may be confusing or ambiguous for the non-initiated or early student. | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Pitfalls and ambiguous uses-Separation of inner product and vectors A cause for confusion is that the notation does not separate the inner-product operation from the notation for a (bra) vector. If a (dual space) bra-vector is constructed as a linear combination of other bra-vectors (for instance when ... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Pitfalls and ambiguous uses-Reuse of symbols It is common to use the same symbol for labels and constants. For example, α^|α⟩=α|α⟩ , where the symbol α is used simultaneously as the name of the operator α^ , its eigenvector |α⟩ and the associated eigenvalue α . Sometimes the hat is also dropped fo... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Pitfalls and ambiguous uses-Operations inside bras and kets This is done for a fast notation of scaling vectors. For instance, if the vector |α⟩ is scaled by 1/2 , it may be denoted |α/2⟩ . This can be ambiguous since α is simply a label for a state, and not a mathematical object on which operation... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-Linear operators acting on kets A linear operator is a map that inputs a ket and outputs a ket. (In order to be called "linear", it is required to have certain properties.) In other words, if A^ is a linear operator and |ψ⟩ is a ket-vector, then A^|ψ⟩ is another ket-vector.
In an N... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-Linear operators acting on bras Operators can also be viewed as acting on bras from the right hand side. Specifically, if A is a linear operator and ⟨φ| is a bra, then ⟨φ|A is another bra defined by the rule (in other words, a function composition). This expression is commonly written ... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-If the same state vector appears on both bra and ket side, then this expression gives the expectation value, or mean or average value, of the observable represented by operator A for the physical system in the state |ψ⟩. | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-Outer products A convenient way to define linear operators on a Hilbert space H is given by the outer product: if ⟨ϕ| is a bra and |ψ⟩ is a ket, the outer product denotes the rank-one operator with the rule For a finite-dimensional vector space, the outer product can be understood as ... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-One of the uses of the outer product is to construct projection operators. Given a ket |ψ⟩ of norm 1, the orthogonal projection onto the subspace spanned by |ψ⟩ is This is an idempotent in the algebra of observables that acts on the Hilbert space. | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-Hermitian conjugate operator Just as kets and bras can be transformed into each other (making |ψ⟩ into ⟨ψ|), the element from the dual space corresponding to A|ψ⟩ is ⟨ψ|A†, where A† denotes the Hermitian conjugate (or adjoint) of the operator A. In other words, If A is expressed as an ... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Linear operators-Self-adjoint operators, where A = A†, play an important role in quantum mechanics; for example, an observable is always described by a self-adjoint operator. If A is a self-adjoint operator, then ⟨ψ|A|ψ⟩ is always a real number (not complex). This implies that expectation values of obs... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Properties-Bra–ket notation was designed to facilitate the formal manipulation of linear-algebraic expressions. Some of the properties that allow this manipulation are listed herein. In what follows, c1 and c2 denote arbitrary complex numbers, c* denotes the complex conjugate of c, A and B denote arbit... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Properties-Linearity Since bras are linear functionals, By the definition of addition and scalar multiplication of linear functionals in the dual space, Associativity Given any expression involving complex numbers, bras, kets, inner products, outer products, and/or linear operators (but not addition),... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Properties-Hermitian conjugation Bra–ket notation makes it particularly easy to compute the Hermitian conjugate (also called dagger, and denoted †) of expressions. The formal rules are: The Hermitian conjugate of a bra is the corresponding ket, and vice versa.
The Hermitian conjugate of a complex numbe... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Properties-The Hermitian conjugate of the Hermitian conjugate of anything (linear operators, bras, kets, numbers) is itself—i.e., Given any combination of complex numbers, bras, kets, inner products, outer products, and/or linear operators, written in bra–ket notation, its Hermitian conjugate can be c... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Composite bras and kets-Two Hilbert spaces V and W may form a third space V ⊗ W by a tensor product. In quantum mechanics, this is used for describing composite systems. If a system is composed of two subsystems described in V and W respectively, then the Hilbert space of the entire system is the tenso... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Composite bras and kets-See quantum entanglement and the EPR paradox for applications of this product. | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-The unit operator-Consider a complete orthonormal system (basis), for a Hilbert space H, with respect to the norm from an inner product ⟨·,·⟩.
From basic functional analysis, it is known that any ket |ψ⟩ can also be written as with ⟨·|·⟩ the inner product on the Hilbert space.
From the commutativity o... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-The unit operator-In quantum mechanics, it often occurs that little or no information about the inner product ⟨ψ|φ⟩ of two arbitrary (state) kets is present, while it is still possible to say something about the expansion coefficients ⟨ψ|ei⟩ = ⟨ei|ψ⟩* and ⟨ei|φ⟩ of those vectors with respect to a speci... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-The unit operator-For more information, see Resolution of the identity, where Since ⟨x′|x⟩ = δ(x − x′), plane waves follow, In his book (1958), Ch. III.20, Dirac defines the standard ket which, up to a normalization, is the translationally invariant momentum eigenstate lim {\textstyle |\varpi \rangl... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Notation used by mathematicians-The object physicists are considering when using bra–ket notation is a Hilbert space (a complete inner product space). | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Notation used by mathematicians-Let (H,⟨⋅,⋅⟩) be a Hilbert space and h ∈ H a vector in H. What physicists would denote by |h⟩ is the vector itself. That is, Let H* be the dual space of H. This is the space of linear functionals on H. The embedding Φ:H↪H∗ is defined by Φ(h)=φh , where for every h ∈ H... | milkshake721/2.1M-wiki-STEM |
Bra–ket notation-Notation used by mathematicians-Moreover, mathematicians usually write the dual entity not at the first place, as the physicists do, but at the second one, and they usually use not an asterisk but an overline (which the physicists reserve for averages and the Dirac spinor adjoint) to denote complex con... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-G beta-gamma complex-The G beta-gamma complex (Gβγ) is a tightly bound dimeric protein complex, composed of one Gβ and one Gγ subunit, and is a component of heterotrimeric G proteins. Heterotrimeric G proteins, also called guanosine nucleotide-binding proteins, consist of three subunits, called alp... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-History-The individual subunits of the G protein complex were first identified in 1980 when the regulatory component of adenylate cyclase was successfully purified, yielding three polypeptides of different molecular weights. Initially, it was thought that Gα, the largest subunit, was the major effe... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Structure-The Gβγ subunit is a dimer composed of two polypeptides, however it acts functionally as a monomer, as the individual subunits do not separate, and have not been found to function independently. | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Structure-The Gβ subunit is a member of the β-propeller family of proteins, which typically possess 4-8 antiparallel β-sheets arranged in the shape of a propeller. Gβ contains a 7 bladed β-propeller, each blade arranged around a central axis and composed of 4 antiparallel β-sheets. The amino acid s... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Structure-Of additional structural interest is the discovery of a so-called “hotspot” present on the surface of the Gβγ dimer; a specific site of the protein that binds to diverse range of peptides and is thought to be a contributing factor in the ability of Gβγ to interact with a wide variety of e... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Structure-Synthesis and Modification Synthesis of the subunits occurs in the cytosol. Folding of the β-subunit is thought to be aided by the chaperone CCT (chaperonin containing tailless-complex polypeptide 1), which also prevents aggregation of folded subunits. A second chaperone, PhLP (phosducin-... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Function-The Gβγ complex is an essential element in the GPCR signaling cascade. It has two main states for which it performs different functions. When Gβγ is interacting with Gα it functions as a negative regulator. In the heterotrimer form, the Gβγ dimer increases the affinity of Gα for GDP, which... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Function-Once separated, both Gα and Gβγ are free to participate in their own distinct signaling pathways. Gβγ does not go through any conformational changes when it dissociates from Gα and it acts as a signaling molecule as a dimer. The Gβγ dimer has been found to interact with many different effe... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Medical implications-Drug design The Gβγ subunit plays a variety of roles in cell signalling processes and as such researchers are now examining its potential as a therapeutic drug target for the treatment of many medical conditions. However, it is recognized that there are a number of consideratio... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Medical implications-Gβγ expression is universal throughout almost all the cells of the body so any agent acting to inhibit this subunit could elicit numerous side effects.
Small molecule inhibitors that target the coupling of Gβγ to specific effectors and do not interfere with normal G protein cyc... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Medical implications-Heart failure Heart failure can be characterized by a loss of β adrenergic receptor (βAR) signalling in heart cells. When the βAR is stimulated by catecholamines such as adrenaline and noradrenaline, there is normally an increase in the contractility of the heart. However, in h... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Medical implications-Inflammation When particular GPCRs are activated by their specific chemokines Gβγ directly activates PI3Kγ which is involved in the recruitment of neutrophils that contribute to inflammation. It has been discovered that the inhibition of PI3Kγ significantly reduces inflammation... | milkshake721/2.1M-wiki-STEM |
G beta-gamma complex-Medical implications-Leukemia The Gβγ subunit has been shown to activate a Rho guanine nucleotide exchange factor (RhoGef) gene PLEKHG2 which is upregulated in a number of leukemia cell lines and mouse models of leukemia. Lymphocyte chemotaxis as a result of Rac and CDC42 activation as well as acti... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Cinoxacin-Cinoxacin is a quinolone antibiotic that has been discontinued in the U.K. as well the United States, both as a branded drug or a generic. The marketing authorization of cinoxacin has been suspended throughout the EU.Cinoxacin was an older synthetic antimicrobial related to the quinolone class of an... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-History-Cinoxacin is one of the original quinolone drugs, which were introduced in the 1970s. Commonly referred to as the first generation quinolones. This first generation also included other quinolone drugs such as pipemidic acid, and oxolinic acid, but this first generation proved to be only marginal impro... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-History-Oclassen Pharmaceuticals (Oclassen Dermatologics) commenced sales of Cinobac in the United States and Canada back in September 1992, under an agreement with Eli Lilly which granted Oclassen exclusive United States and Canadian distribution rights. Oclassen promoted Cinobac primarily to urologists for ... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Mode of action-Cinoxacin mode of action involves the inhibiting of DNA gyrase, a type II topoisomerase, and topoisomerase iv, which is an enzyme necessary to separate replicated DNA, thereby inhibiting cell division. | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Contraindications-Within the most recent package insert (c. 1999) Cinobac is listed as being contraindicated in patients with a history of hypersensitivity to cinoxacin or other quinolones. | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Adverse reactions-The safety profile of cinoxacin appears to be rather unremarkable. Adverse drug reactions appear to be limited to the gastrointestinal system and the central nervous system. Hypersensitivity resulting in an anaphylactic reactions (as seen with all drugs found within this class) has also been... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Overdose-Symptoms following an overdose of cinoxacin may include anorexia, nausea, vomiting, epigastric distress, and diarrhea. The severity of the epigastric distress and the diarrhea are dose related. Patients who have ingested an overdose of cinoxacin should be kept well hydrated to prevent crystalluria. F... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Pharmacokinetics-Biotransformation is mainly hepatic, with approximately 30-40% metabolized to inactive metabolites. Protein Binding ranges from 60 to 80%. Cinoxacin is rapidly absorbed after oral administration. The presence of food delays absorption but does not affect total absorption. The mean serum half-... | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Dosing-The usual adult dosage for the treatment of urinary tract infections is 1 gram daily, administered orally in two or four divided doses (500 mg b.i.d. or 250 mg q.i.d. respectively) for seven to 14 days.
Impaired renal function When renal function is impaired, a reduced dosage must be employed. | milkshake721/2.1M-wiki-STEM |
Cinoxacin-Susceptible bacteria-Gram-negative aerobes: Enterobacter species Escherichia coli Klebsiella species Proteus mirabilis Proteus vulgarisEnterococcus species, Pseudomonas species, and Staphylococcus species are resistant. | milkshake721/2.1M-wiki-STEM |
Chiating Series-Chiating Series-The Chiating Series is a Mesozoic geologic formation in China. Fossil ornithopod tracks have been reported from the formation. | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Pioneer anomaly-The Pioneer anomaly, or Pioneer effect, was the observed deviation from predicted accelerations of the Pioneer 10 and Pioneer 11 spacecraft after they passed about 20 astronomical units (3×109 km; 2×109 mi) on their trajectories out of the Solar System. The apparent anomaly was a matter ... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Pioneer anomaly-Both Pioneer spacecraft are escaping the Solar System but are slowing under the influence of the Sun's gravity. Upon very close examination of navigational data, the spacecraft were found to be slowing slightly more than expected. The effect is an extremely small acceleration towards the... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Pioneer anomaly-Various explanations, both of spacecraft behavior and of gravitation itself, were proposed to explain the anomaly. Over the period from 1998 to 2012, one particular explanation became accepted. The spacecraft, which are surrounded by an ultra-high vacuum and are each powered by a radiois... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Pioneer anomaly-By 2012, several papers by different groups, all reanalyzing the thermal radiation pressure forces inherent in the spacecraft, showed that a careful accounting of this explains the entire anomaly; thus the cause is mundane and does not point to any new phenomenon or need to update the la... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Description-Pioneer 10 and 11 were sent on missions to Jupiter and Jupiter/Saturn respectively. Both spacecraft were spin-stabilised in order to keep their high-gain antennas pointed towards Earth using gyroscopic forces. Although the spacecraft included thrusters, after the planetary encounters they we... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Description-Because the spacecraft were flying with almost no additional stabilization thrusts during their "cruise", it is possible to characterize the density of the solar medium by its effect on the spacecraft's motion. In the outer Solar System this effect would be easily calculable, based on ground... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Description-As the anomaly was growing, it appeared that the spacecraft were moving more slowly than expected. Measurements of the spacecraft's speed using the Doppler effect demonstrated the same thing: the observed redshift was less than expected, which meant that the Pioneers had slowed down more tha... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Description-When all known forces acting on the spacecraft were taken into consideration, a very small but unexplained force remained. It appeared to cause an approximately constant sunward acceleration of (8.74±1.33)×10−10 m/s2 for both spacecraft. If the positions of the spacecraft were predicted one ... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Explanation: thermal recoil force-Starting in 1998, there were suggestions that the thermal recoil force was underestimated, and perhaps could account for the entire anomaly. However, accurately accounting for thermal forces was hard, because it needed telemetry records of the spacecraft temperatures an... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Explanation: thermal recoil force-One by one these objections were addressed. Many of the old telemetry records were found, and converted to modern formats. This gave power consumption figures and some temperatures for parts of the spacecraft. Several groups built detailed thermal models, which could be... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Indications from other missions-The Pioneers were uniquely suited to discover the effect because they have been flying for long periods of time without additional course corrections. Most deep-space probes launched after the Pioneers either stopped at one of the planets, or used thrusting throughout the... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Indications from other missions-The Voyagers flew a mission profile similar to the Pioneers, but were not spin stabilized. Instead, they required frequent firings of their thrusters for attitude control to stay aligned with Earth. Spacecraft like the Voyagers acquire small and unpredictable changes in s... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Potential issues with the thermal solution-There are two features of the anomaly, as originally reported, that are not addressed by the thermal solution: periodic variations in the anomaly, and the onset of the anomaly near the orbit of Saturn. | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Potential issues with the thermal solution-First, the anomaly has an apparent annual periodicity and an apparent Earth sidereal daily periodicity with amplitudes that are formally greater than the error budget. However, the same paper also states this problem is most likely not related to the anomaly: "... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Before the thermal recoil explanation became accepted, other proposed explanations fell into two classes—"mundane causes" or "new physics". Mundane causes include conventional effects that were overlooked or mis-modeled in the initial analysis, such as measurement error,... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-If the Pioneer anomaly had been a gravitational effect due to some long-range modifications of the known laws of gravity, it did not affect the orbital motions of the major natural bodies in the same way (in particular those moving in the regions in which the Pioneer ano... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Deceleration model It has been viewed as possible that a real deceleration is not accounted for in the current model for several reasons. | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Gravity It is possible that deceleration is caused by gravitational forces from unidentified sources such as the Kuiper belt or dark matter. However, this acceleration does not show up in the orbits of the outer planets, so any generic gravitational answer would need to ... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Drag The cause could be drag from the interplanetary medium, including dust, solar wind and cosmic rays. However, the measured densities are too small to cause the effect.
Gas leaks Gas leaks, including helium from the spacecraft's radioisotope thermoelectric generators ... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Observational or recording errors The possibility of observational errors, which include measurement and computational errors, has been advanced as a reason for interpreting the data as an anomaly. Hence, this would result in approximation and statistical errors. However... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-New physics Because the "Pioneer anomaly" does not show up as an effect on the planets, Anderson et al. speculated that this would be interesting if this was new physics. Later, with the Doppler shifted signal confirmed, the team again speculated that one explanation may... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Clock acceleration Clock acceleration was an alternate explanation to anomalous acceleration of the spacecraft towards the Sun. This theory took notice of an expanding universe, which was thought to create an increasing background 'gravitational potential'. The increased... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Definition of gravity modified The Modified Newtonian dynamics or MOND hypothesis proposed that the force of gravity deviates from the traditional Newtonian value to a very different force law at very low accelerations on the order of 10−10 m/s2. Given the low accelerati... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Definition of inertia modified MOND can also be interpreted as a modification of inertia, perhaps due to an interaction with vacuum energy, and such a trajectory-dependent theory could account for the different accelerations apparently acting on the orbiting planets and ... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Parametric time Another theoretical explanation was based on a possible non-equivalence of the atomic time and the astronomical time, which could give the same observational fingerprint as the anomaly. | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Previously proposed explanations-Celestial ephemerides in an expanding universe Another proposed explanation of Pioneer anomaly is that the background spacetime is described by a cosmological Friedmann–Lemaître–Robertson–Walker metric that is not Minkowski flat. In this model of spacetime manifold, ligh... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Further research avenues-It is possible, but not proven, that this anomaly is linked to the flyby anomaly, which has been observed in other spacecraft. Although the circumstances are very different (planet flyby vs. deep space cruise), the overall effect is similar—a small but unexplained velocity chang... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Further research avenues-The Pioneer spacecraft are no longer providing new data (the last contact was on 23 January 2003) and other deep-space missions that might be studied (Galileo and Cassini) were deliberately disposed of in the atmospheres of Jupiter and Saturn respectively at the ends of their mi... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Further research avenues-The New Horizons spacecraft to Pluto is spin-stabilised for long intervals, and there were proposals to use it to investigate the anomaly. It was known that New Horizons would have the same problem that precluded good data from the cruise portion of Cassini mission—its RTG is mo... | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Further research avenues-A dedicated mission has also been proposed. Such a mission would probably need to surpass 200 AU from the Sun in a hyperbolic escape orbit.
Observations of asteroids around 20 AU may provide insights if the anomaly's cause is gravitational. | milkshake721/2.1M-wiki-STEM |
Pioneer anomaly-Meetings and conferences about the anomaly-A meeting was held at the University of Bremen in 2004 to discuss the Pioneer anomaly.The Pioneer Explorer Collaboration was formed to study the Pioneer Anomaly and has hosted three meetings (2005, 2007, and 2008) at International Space Science Institute in Ber... | milkshake721/2.1M-wiki-STEM |
Session Announcement Protocol-Session Announcement Protocol-The Session Announcement Protocol (SAP) is an experimental protocol for advertising multicast session information. SAP typically uses Session Description Protocol (SDP) as the format for Real-time Transport Protocol (RTP) session descriptions. Announcement dat... | milkshake721/2.1M-wiki-STEM |
Session Announcement Protocol-Announcement interval-The announcement interval is cooperatively modulated such that all SAP announcements in the multicast delivery scope, by default, consume 4000 bits per second. Regardless, the maximum announce interval is 300 seconds (5 minutes). Announcements automatically expire aft... | milkshake721/2.1M-wiki-STEM |
Session Announcement Protocol-Authentication, encryption and compression-SAP features separate methods for authenticating and encrypting announcements. Use of encryption is not recommended. Authentication prevents unauthorized modification and other DoS attacks. Authentication is optional. Two authentication schemes ar... | milkshake721/2.1M-wiki-STEM |
Session Announcement Protocol-Applications and implementations-VLC media player monitors SAP announcements and presents the user a list of available streams.SAP is one of the optional discovery and connection management techniques described in the AES67 audio-over-Ethernet interoperability standard. | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Protective distribution system-A protective distribution system (PDS), also called protected distribution system, is a US government term for wireline or fiber-optics telecommunication system that includes terminals and adequate acoustical, electrical, electromagnetic, and physical safegu... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Description-The purpose of a PDS is to deter, detect and/or make difficult physical access to the communication lines carrying national security information.
A specification called the National Security Telecommunications and Information Systems Security Instruction (NSTISSI) 7003 was iss... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Hardened distribution PDSs provide significant physical protection and can be implemented in three forms: hardened carrier PDSs, alarmed carrier PDSs and continuously viewed carrier PDSs. | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Hardened carrier In a hardened carrier PDS, the data cables are installed in a carrier constructed of electrical metallic tubing (EMT), ferrous conduit or pipe, or rigid sheet steel ducting. All of the connections in a Hardened Carrier System are permanently sealed c... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-With a hardened carrier system, detection is accomplished via human inspections that are required to be performed periodically. Therefore, hardened carriers are installed below ceilings or above flooring so they can be visually inspected to ensure that no intrusions ... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Alarmed carrier As an alternative to conducting human visual inspections, an alarmed carrier PDS may be constructed to automate the inspection process through electronic monitoring with an alarm system. In an Alarmed Carrier PDS, the carrier system is “alarmed” with ... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Alarmed carrier PDS offers several advantages over hardened carrier PDS: Provides continuous monitoring 24/7/365 Eliminates the requirement for periodic visual inspections Allows the carrier to be hidden above the ceiling or below the floor, since periodic visual ins... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Depending on the government organization, utilizing an alarmed carrier PDS in conjunction with interlocking armored cable may, in some cases, allow for the elimination of the carrier systems altogether. In these instances, the cables being protected can be installed ... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-Continuously viewed carrier A Continuously Viewed Carrier PDS is one that is under continuous observation, 24 hours per day (including when operational). Such circuits may be grouped together, but should be separated from all non-continuously viewed circuits ensuring... | milkshake721/2.1M-wiki-STEM |
Protective distribution system-Hardened distribution-UAA is an Uncontrolled Access Area (UAA). Like definitions include Controlled Access Area (CAA) and Restricted Access Area (RAA). A Secure Room (SR) offers the highest degree of protection.
Therefore, from the least protected (least secure) to the most protected is a... | milkshake721/2.1M-wiki-STEM |
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