Split (1)

train · 253k rows

page_content stringlengths 51 3.15k
Non-conservative force Informal definition Non-conservative_force > Informal definition Informally, a conservative force can be thought of as a force that conserves mechanical energy. Suppose a particle starts at point A, and there is a force F acting on it. Then the particle is moved around by other forces, and eventually ends up at A again. Though the particle may still be moving, at that instant when it passes point A again, it has traveled a closed path.
Symbol table Summary Symbol_tables In computer science, a symbol table is a data structure used by a language translator such as a compiler or interpreter, where each identifier (or symbol), constant, procedure and function in a program's source code is associated with information relating to its declaration or appearance in the source. In other words, the entries of a symbol table store the information related to the entry's corresponding symbol.
Elaboration likelihood model Relations to other theories Elaboration_likelihood_model > Relations to other theories If the number, strength, and immediacy of the people trying to influence a person are high, the person being persuaded is more likely to take the central processing route. Heuristic-systematic model - is very similar to the ELM because it is also a two-way model that explores how people gather and dissect persuasive messages. Extended transportation-imagery model
Intrinsic variable SX Arietis variables Eclipsing_Variable_star > Extrinsic variable stars > Rotating variable stars > Magnetic fields > SX Arietis variables Stars in this class exhibit brightness fluctuations of some 0.1 magnitude caused by changes in their magnetic fields due to high rotation speeds.
Mass digitization Databases Mass_digitization > Technical Infrastructures > Databases Other databases allow researchers from all over the world to upload or view data for scientific inquiry. In this case, raw data from scientific experiments - anonymized for participant privacy - is uploaded and stored on a mass scale. A prime example of such databases for research purposes include the Child Language Data Exchange System (CHILDES) Database.
CD8+ T-cell Development Cytotoxic_T-lymphocyte > Development If that rearrangement is successful, the cells then rearrange their alpha-chain TCR DNA to create a functional alpha-beta TCR complex. This highly-variable genetic rearrangement product in the TCR genes helps create millions of different T cells with different TCRs, helping the body's immune system respond to virtually any protein of an invader.
HCO2H Biosynthesis HCO2H > Production > Biosynthesis Formic acid is named after ants which have high concentrations of the compound in their venom. In ants, formic acid is derived from serine through a 5,10-methenyltetrahydrofolate intermediate. The conjugate base of formic acid, formate, also occurs widely in nature. An assay for formic acid in body fluids, designed for determination of formate after methanol poisoning, is based on the reaction of formate with bacterial formate dehydrogenase.
Commutator (electric) Summary Commutator_(electric) Commutators are used in direct current (DC) machines: dynamos (DC generators) and many DC motors as well as universal motors. In a motor the commutator applies electric current to the windings. By reversing the current direction in the rotating windings each half turn, a steady rotating force (torque) is produced.
Software metric Limitations Software_Metrics > Limitations As software development is a complex process, with high variance on both methodologies and objectives, it is difficult to define or measure software qualities and quantities and to determine a valid and concurrent measurement metric, especially when making such a prediction prior to the detail design. Another source of difficulty and debate is in determining which metrics matter, and what they mean. The practical utility of software measurements has therefore been limited to the following domains: Scheduling Software sizing Programming complexity Software development effort estimation Software qualityA specific measurement may target one or more of the above aspects, or the balance between them, for example as an indicator of team motivation or project performance. Additionally metrics vary between static and dynamic program code, as well as for object oriented software (systems).
Cap torque tester Summary Cap_torque_tester The cap torque tester is used in the packaging industry to measure the opening or closing torque of the screwing cap. It is a piece of specific quality control equipment that can be placed on the production line or in the laboratory.
Floral scent Regulation of emissions Floral_scent > Regulation of emissions Floral scent emissions of most flowering plants vary predictably throughout the day, following a circadian rhythm. This variation is controlled by light intensity. Maximal emissions coincide with peaks of the highest activity of visiting pollinators. For instance, snapdragon flowers, mostly pollinated by bees, have the highest emissions at noon, whereas nocturnally-visited tobacco plants have the highest emissions at night.Floral scent emissions also vary along with floral development, with the highest emissions at anthesis, i.e. when the flower is fecund (highly fertile), and reduced emissions after pollination, probably due to mechanisms linked with fecundation.
Statistical significance History Statistical_significance > History Statistical significance dates to the 18th century, in the work of John Arbuthnot and Pierre-Simon Laplace, who computed the p-value for the human sex ratio at birth, assuming a null hypothesis of equal probability of male and female births; see p-value § History for details.In 1925, Ronald Fisher advanced the idea of statistical hypothesis testing, which he called "tests of significance", in his publication Statistical Methods for Research Workers. Fisher suggested a probability of one in twenty (0.05) as a convenient cutoff level to reject the null hypothesis. In a 1933 paper, Jerzy Neyman and Egon Pearson called this cutoff the significance level, which they named α {\displaystyle \alpha } . They recommended that α {\displaystyle \alpha } be set ahead of time, prior to any data collection.Despite his initial suggestion of 0.05 as a significance level, Fisher did not intend this cutoff value to be fixed. In his 1956 publication Statistical Methods and Scientific Inference, he recommended that significance levels be set according to specific circumstances.
Findability Evaluation and measures Findability > Evaluation and measures Baseline findability is the existing findability before changes are made in order to improve it. This is measured by participants who represent the customer base of the website, who try to locate a sample set of items using the existing navigation of the website.In order to evaluate how easily information can be found by searching a site using a search engine or information retrieval system, retrievability measures were developed, and similarly, navigability measures now measure ease of information access through browsing a site (e.g. PageRank, MNav, InfoScent (see Information foraging), etc.). Findability also can be evaluated via the following techniques: Usability testing: Conducted to find out how and why users navigate through a website to accomplish tasks. Tree testing: An information architecture based technique, to determine if critical information can be found on the website. Closed card sorting: A usability technique based on information architecture, for evaluating the strength of categories. Click testing: Accounts for the implicit data collected through clicks on the user interface.
Structural formulae Unspecified Stereochemistry Molecular_structure_diagram > Structures in Structural Formulas > Unspecified Stereochemistry Wavy single bonds represent unknown or unspecified stereochemistry or a mixture of isomers. For example, the adjacent diagram shows the fructose molecule with a wavy bond to the HOCH2- group at the left. In this case the two possible ring structures are in chemical equilibrium with each other and also with the open-chain structure. The ring automatically opens and closes, sometimes closing with one stereochemistry and sometimes with the other.
DNA molecule Genetic recombination DNA_molecule > Genetic recombination The first step in recombination is a double-stranded break caused by either an endonuclease or damage to the DNA. A series of steps catalyzed in part by the recombinase then leads to joining of the two helices by at least one Holliday junction, in which a segment of a single strand in each helix is annealed to the complementary strand in the other helix. The Holliday junction is a tetrahedral junction structure that can be moved along the pair of chromosomes, swapping one strand for another.
Rado's theorem (Ramsey theory) Computability Rado's_theorem_(Ramsey_theory) > Computability However, the subset sum problem can be reduced to the problem of computing the required partition C1, C2, ..., Cn of columns: Given an input set S for the subset sum problem we can write the elements of S in a matrix of shape 1 × \|S\|. Then the elements of S corresponding to vectors in the partition C1 sum to zero. The subset sum problem is NP-complete. Hence, verifying that a system of linear equations is regular is also an NP-complete problem. == References ==
Psychoneuroimmunology The immune-brain loop Psychoneuroimmunology > The immune-brain loop The HPA axis responds to physical and mental challenge to maintain homeostasis in part by controlling the body's cortisol level. Dysregulation of the HPA axis is implicated in numerous stress-related diseases, with evidence from meta-analyses indicating that different types/duration of stressors and unique personal variables can shape the HPA response.
Pyroelectric detector Heat sensors Pyroelectricity > Applications > Heat sensors Very small changes in temperature can produce a pyroelectric potential. Passive infrared sensors are often designed around pyroelectric materials, as the heat of a human or animal from several feet away is enough to generate a voltage.
Satellite Radio System design Satellite_Radio > System design The satellites send the signals back down to radio receivers in cars and homes. This signal contains scrambled broadcasts, along with meta data about each specific broadcast. The signals are unscrambled by the radio receiver modules, which display the broadcast information. In urban areas, ground repeaters enable signals to be available even if the satellite signal is blocked. The technology allows for nationwide broadcasting, so that, for instance US listeners can hear the same stations anywhere in the country.
Symmetric federalism Summary Symmetric_federalism Symmetric federalism refers to a federal system of government in which each constituent state to the federation possess equal powers. In a symmetric federalism no distinction is made between constituent states. This is in contrast to asymmetric federalism, where a distinction is made between constituent states.
Data forensics Computer-related crimes Data_forensics > Overview > Computer-related crimes Copyright Infringement is using, reproducing, and distributing copyrighted information, including software piracy. Fabrication is accusing someone of using false data and information put in the system through an unauthorized source. Examples of interceptions are the Bank NSP case, Sony.Sambandh.com case, and business email compromise scams.
Dimension one Polynomials and transcendental functions Dimensional_Analysis > Properties > Polynomials and transcendental functions {\displaystyle {\tfrac {1}{2}}\cdot (\mathrm {-9.8~m/s^{2}} )\cdot t^{2}+(\mathrm {500~m/s} )\cdot t.} This is the height to which an object rises in time t if the acceleration of gravity is 9.8 metres per second per second and the initial upward speed is 500 metres per second. It is not necessary for t to be in seconds.
Phenylsulfinic acid Acidity Phenylsulfinic_acid > Acidity There is a large range of pKa values in the literature, with most authors giving a value of around 1.30. This inconsistency can be explained by differences in ionic strength between quoted values. By measuring the pKa at various ionic strengths and extrapolating to zero ionic strength, the pKa of phenylsulfinic acid was determined to be 2.76. This makes phenylsulfinic acid a stronger acid than its corresponding carboxylic acid, benzoic acid (pKa = 4.2), but weaker than its corresponding sulfonic acid, benzenesulfonic acid (pKa = −6.5).
Fundamental groups Intuition Fundamental_group > Intuition Start with a space (for example, a surface), and some point in it, and all the loops both starting and ending at this point—paths that start at this point, wander around and eventually return to the starting point. Two loops can be combined in an obvious way: travel along the first loop, then along the second. Two loops are considered equivalent if one can be deformed into the other without breaking. The set of all such loops with this method of combining and this equivalence between them is the fundamental group for that particular space.
Holographic principle Black hole entropy Holographic_entropy_bound > Black hole entropy But, to his surprise, a careful analysis convinced him that they do, and in just the right way to come to equilibrium with a gas at a finite temperature. Hawking's calculation fixed the constant of proportionality at 1/4; the entropy of a black hole is one quarter its horizon area in Planck units.The entropy is proportional to the logarithm of the number of microstates, the enumerated ways a system can be configured microscopically while leaving the macroscopic description unchanged. Black hole entropy is deeply puzzling – it says that the logarithm of the number of states of a black hole is proportional to the area of the horizon, not the volume in the interior.Later, Raphael Bousso came up with a covariant version of the bound based upon null sheets.
Industrial controllers History Industrial_Control_Systems > History For large control systems, the general commercial name distributed control system (DCS) was coined to refer to proprietary modular systems from many manufacturers which integrated high-speed networking and a full suite of displays and control racks. While the DCS was tailored to meet the needs of large continuous industrial processes, in industries where combinatorial and sequential logic was the primary requirement, the PLC evolved out of a need to replace racks of relays and timers used for event-driven control. The old controls were difficult to re-configure and debug, and PLC control enabled networking of signals to a central control area with electronic displays.
Manipulation check Overview Manipulation_check > Overview Manipulation checks are measured variables that show what the manipulated variables concurrently affect besides the dependent variable of interest. In experiments, an experimenter manipulates some aspect of a process or task and randomly assigns subjects to different levels of the manipulation ("experimental conditions"). The experimenter then observes whether variation in the manipulated variables cause differences in the dependent variable.
Synchronization Uses Synchronization > Uses Synchronizers, unlike arbiters, are prone to failure. (See metastability in electronics). Encryption systems usually require some synchronization mechanism to ensure that the receiving cipher is decoding the right bits at the right time.
Profinite integers Using Factorial number system Profinite_integers > Construction > Using Factorial number system {\displaystyle k!} . More specifically, there is a ring homomorphism Z ^ → Z / k ! Z {\displaystyle {\widehat {\mathbb {Z} }}\to \mathbb {Z} /k!\,\mathbb {Z} } sending The difference of a profinite integer from an integer is that the "finitely many nonzero digits" condition is dropped, allowing for its factorial number representation to have infinitely many nonzero digits.
CSF glucose Low CSF glucose levels CSF_glucose > Abnormalities in CSF glucose concentration > Low CSF glucose levels Hypoglycorrhachia (low CSF glucose levels) can be caused by CNS infections, inflammatory conditions, subarachnoid hemorrhage, hypoglycemia (low blood sugar), impaired glucose transport (e.g. GLUT1 deficiency syndrome), increased CNS glycolytic activity and metastatic carcinoma.CSF glucose levels can be useful in distinguishing among causes of meningitis as more than 50% of patients with bacterial meningitis have decreased CSF glucose levels while patients with viral meningitis usually have normal CSF glucose levels. Decrease in glucose levels during a CNS infection is caused due to glycolysis by both white cells and the pathogen, and impaired CSF glucose transport through the blood-brain barrier.
Explicit Data Graph Execution CPUs Explicit_Data_Graph_Execution > EDGE > CPUs An EDGE-based CPU would consist of one or more small block engines with their own local registers; realistic designs might have hundreds of these units. The units are interconnected to each other using dedicated inter-block communication links. Due to the information encoded into the block by the compiler, the scheduler can examine an entire block to see if its inputs are available and send it into an engine for execution – there is no need to examine the individual instructions within. With a small increase in complexity, the scheduler can examine multiple blocks to see if the outputs of one are fed in as the inputs of another, and place these blocks on units that reduce their inter-unit communications delays.
Thermodynamic operation Distinction between thermodynamic operation and thermodynamic process Thermodynamic_operation > Distinction between thermodynamic operation and thermodynamic process A typical thermodynamic operation is externally imposed change of position of a piston, so as to alter the volume of the system of interest. Another thermodynamic operation is a removal of an initially separating wall, a manipulation that unites two systems into one undivided system. A typical thermodynamic process consists of a redistribution that spreads a conserved quantity between a system and its surroundings across a previously impermeable but newly semi-permeable wall between them.More generally, a process can be considered as a transfer of some quantity that is defined by a change of an extensive state variable of the system, corresponding to a conserved quantity, so that a transfer balance equation can be written.
World Community Grid Help Cure Muscular Dystrophy – Phase 1 World_Community_Grid > Completed subprojects > Help Cure Muscular Dystrophy – Phase 1 Help Cure Muscular Dystrophy is run by Décrypthon, a collaboration between French Muscular Dystrophy Association, French National Center for Scientific Research and IBM. Phase 1 was launched on December 19, 2006, and completed on June 11, 2007. The project investigated protein–protein interactions for 40,000 proteins whose structures are known, with particular focus on those proteins that play a role in neuromuscular diseases. The database of information produced will help researchers design molecules to inhibit or enhance binding of particular macromolecules, hopefully leading to better treatments for muscular dystrophy and other neuromuscular diseases. This project was available only to agents running the Grid MP client, making it unavailable to users running BOINC.
Folding Boat Equipment Configuration and deployment Folding_Boat_Equipment > Configuration and deployment Class 9 Bridge, F.B.E., Mk. III.Bridges are constructed by joining rafts together. The connectors have limited articulation, which permits the FBE Mk II bridge to carry a load of class 5 while an FBE MK III bridge can carry a vehicle of load class 9 (approximately 10 tons). The trestles are set up at each end and fix the end of the bridge to the bank. Anchors are placed at different positions along the length to anchor the bridge from being swept away by a changed current.
Poly(phthalaldehyde) Summary Poly(phthalaldehyde) Poly(phthalaldehyde), abbreviated as PPA, is a metastable stimuli-responsive polymer first synthesized in 1967. It has garnered significant attention during the past couple of years due to its ease of synthesis and outstanding transient and mechanical properties. for this reason, It has been exploited for a variety of applications including sensing, drug delivery, and EUV lithography. As of 2023, it is considered the only aromatic aldehyde polymerized through a living chain growth polymerization.
Ovarian tissue Hormone secretion Ovary > Function > Hormone secretion At maturity, ovaries secrete estrogen, androgen, inhibin, and progestogen. In women before menopause, 50% of testosterone is produced by the ovaries and released directly into the blood stream. The other 50% of testosterone in the blood stream is made from conversion of the adrenal pre-androgens ( DHEA and androstenedione) to testosterone in other parts of the body. Estrogen is responsible for the appearance of secondary sex characteristics for females at puberty and for the maturation and maintenance of the reproductive organs in their mature functional state. Progesterone prepares the uterus for pregnancy, and the mammary glands for lactation. Progesterone functions with estrogen by promoting menstrual cycle changes in the endometrium.
Parasitic oscillation Conditions Parasitic_oscillation > Conditions Feedback control theory was developed to address the problem of parasitic oscillation in servo control systems – the systems oscillated rather than performing their intended function, for example velocity control in engines. The Barkhausen stability criterion gives the necessary condition for oscillation; the loop gain around the feedback loop, which is equal to the amplifier gain multiplied by the transfer function of the inadvertent feedback path, must be equal to one, and the phase shift around the loop must be zero or a multiple of 360° (2π radians). In practice, feedback may occur over a range of frequencies (for example the operating range of an amplifier); at various frequencies, the phase of the amplifier may be different.
Bayesian quadrature Software Bayesian_quadrature > Software ProbNum: Probabilistic numerical methods in Python, including a Bayesian quadrature implementation. Emukit: Emulation and decision making under uncertainty in Python. QMCPy: Bayesian quadrature with QMC point sets in Python. == References ==
Coil whine Capacitors Coil_whine > Electromagnetic noise and vibrations in passive components > Capacitors Capacitors are also subject to large electrostatic forces. When the capacitor voltage/current waveform is not constant and contains time harmonics, some harmonic electric forces appear and acoustic noise can be generated. Ferroelectric capacitors also exhibit a piezoelectric effect that can be source of audible noise. This phenomenon is known as the "singing capacitor" effect.
Higher-spin theory Summary Higher-spin_theory Higher-spin theory or higher-spin gravity is a common name for field theories that contain massless fields of spin greater than two. Usually, the spectrum of such theories contains the graviton as a massless spin-two field, which explains the second name. Massless fields are gauge fields and the theories should be (almost) completely fixed by these higher-spin symmetries.
Categorical quantization Mathematical setup Categorical_quantum_mechanics > Mathematical setup Mathematically, the basic setup is captured by a dagger symmetric monoidal category: composition of morphisms models sequential composition of processes, and the tensor product describes parallel composition of processes. The role of the dagger is to assign to each state a corresponding test. These can then be adorned with more structure to study various aspects. For instance: A dagger compact category allows one to distinguish between an "input" and "output" of a process.
Altered mental state Pharmacological Altered_mental_state > Induction methods > Pharmacological If one takes a large dose of opioids to compensate for the lack of natural endorphins, the result may be death.Cocaine alters one's state of consciousness. Cocaine affects the neurotransmitters that nerves use to communicate with each other. Cocaine inhibits the reuptake of norepinephrine, serotonin, dopamine, and other neurotransmitters in the synapse, resulting in an altered state of consciousness or a "high" (Aldridge, D., & Fachner, J. ö.
Method of Four Russians Summary Method_of_Four_Russians In computer science, the Method of Four Russians is a technique for speeding up algorithms involving Boolean matrices, or more generally algorithms involving matrices in which each cell may take on only a bounded number of possible values.
Position four-vector Four-vectors in a real-valued basis Four-vector > Four-vector algebra > Four-vectors in a real-valued basis In special relativity, the spacelike basis E1, E2, E3 and components A1, A2, A3 are often Cartesian basis and components: although, of course, any other basis and components may be used, such as spherical polar coordinates or cylindrical polar coordinates, or any other orthogonal coordinates, or even general curvilinear coordinates. Note the coordinate labels are always subscripted as labels and are not indices taking numerical values. In general relativity, local curvilinear coordinates in a local basis must be used.
MO diagram s-p mixing MO_diagram > s-p mixing For instance, in dioxygen the 3σg MO can be roughly considered to be formed from interaction of oxygen 2pz AOs only. It is found to be lower in energy than the 1πu MO, both experimentally and from more sophisticated computational models, so that the expected order of filling is the 3σg before the 1πu. Hence the approximation to ignore the effects of further interactions is valid.
Visceral layer Molecular regulation of somite differentiation Mesoderm > Molecular regulation of somite differentiation However, there are still some doubts in how the prospective mesodermal cells integrate the various signals they receive and how they regulate their morphogenic behaviours and cell-fate decisions. Human embryonic stem cells for example have the potential to produce all of the cells in the body and they are able to self-renew indefinitely so they can be used for a large-scale production of therapeutic cell lines. They are also able to remodel and contract collagen and were induced to express muscle actin. This shows that these cells are multipotent cells.
Surface and bulk erosion Erosion Kinetics Surface_and_bulk_erosion > Erosion Kinetics If the degradation process is faster than the diffusion process, surface erosion will occur since the material's surface will quickly degrade before water has time to diffuse and penetrate through the material. If the diffusion process is faster than the degradation process bulk erosion will occur because water penetrates through the material before significant erosion occurs on the surface. A kinetics of the erosion of a polymer can be modified by changing the diffusion process or the degradation process. For example, blending a polymer with another polymer that is very reactive to water will speed up the degradation process and cause surface erosion. On the other hand, decreasing the dimensions of a material will allow water to travel to the center of the material more quickly, which speeds up the diffusion process and causes bulk erosion.
Scientific theory Formation Scientific_theory > Formation The strength of the evidence is evaluated by the scientific community, and the most important experiments will have been replicated by multiple independent groups.Theories do not have to be perfectly accurate to be scientifically useful. For example, the predictions made by classical mechanics are known to be inaccurate in the relativistic realm, but they are almost exactly correct at the comparatively low velocities of common human experience. In chemistry, there are many acid-base theories providing highly divergent explanations of the underlying nature of acidic and basic compounds, but they are very useful for predicting their chemical behavior.
Choi–Jamiołkowski isomorphism Circuit complexity reduction Choi–Jamiołkowski_isomorphism > Quantum circuit complexity reduction > Circuit complexity reduction It's important to note that this discussion focuses on the primary components of the model and does not address fault tolerance, as it is beyond the scope of this model. We assume fault-tolerant qubits, gates, and measurements, which can be achieved with quantum error-correcting codes. Additionally, we highlight two intriguing issues that establish connections with standard frameworks and results.
Telecommunications circuit Applications Communication_circuit > Applications Originally, telecommunication circuits transmitted analog signals. Radio stations used them as studio transmitter links (STLs) or as remote pickup unit (RPU) for sound reproduction, sometimes as a backup to other means. Later lines were digital, used in pair-gain applications, such as carrier systems, or in enterprise data networks. A leased line, private circuit, or dedicated circuit, is a circuit that is dedicated to only one use and is typically not switched at a central office.
Timeline of virtualization development As an overview, there are three levels of virtualization Timeline_of_virtualization_development > Overview of Virtualization > As an overview, there are three levels of virtualization At the hardware level, the VMs can run multiple guest OSes. This is best used for testing and training that require networking interoperability between more than one OSes, since not only can the guest OSes be different from the host OS, there can be as many guest OS as VMs, as long as there is enough CPU, RAM and storage space. IBM introduced this around 1990 under the name logical partitioning (LPAR), at first only in the mainframe field. At the operating system level, it can only virtualize one OS: the guest OS is the host OS.
Geometrical optics Explanation Geometrical_optics > Explanation A light ray is a line or curve that is perpendicular to the light's wavefronts (and is therefore collinear with the wave vector). A slightly more rigorous definition of a light ray follows from Fermat's principle, which states that the path taken between two points by a ray of light is the path that can be traversed in the least time.Geometrical optics is often simplified by making the paraxial approximation, or "small angle approximation". The mathematical behavior then becomes linear, allowing optical components and systems to be described by simple matrices. This leads to the techniques of Gaussian optics and paraxial ray tracing, which are used to find basic properties of optical systems, such as approximate image and object positions and magnifications.
Gateaux derivative Linearity and continuity Gateaux_derivative > Linearity and continuity Linearity need not be assumed: if X {\displaystyle X} and Y {\displaystyle Y} are Fréchet spaces, then d F ( u ; ⋅ ) {\displaystyle dF(u;\cdot )} is automatically bounded and linear for all u {\displaystyle u} (Hamilton 1982). A stronger notion of continuous differentiability requires that be a continuous mapping from U {\displaystyle U} to the space of continuous linear functions from X {\displaystyle X} to Y . {\displaystyle Y.}
Cycles per byte Data at rest Encryption_software > Data at rest Data at rest refers to data that has been saved to persistent storage. Data at rest is generally encrypted by a symmetric key. Encryption may be applied at different layers in the storage stack. For example, encryption can be configured at the disk layer, on a subset of a disk called a partition, on a volume, which is a combination of disks or partitions, at the layer of a file system, or within user space applications such as database or other applications that run on the host operating system.
List of things named after Johannes Kepler Celestial mechanics List_of_things_named_after_Johannes_Kepler > Celestial mechanics Kepler's laws of planetary motion Kepler's equation Keplerian elements Kepler problem Kepler problem in general relativity
Gene-centric view of evolution Organisms as vehicles Gene-centred_view_of_evolution > Overview > Organisms as vehicles Genes are usually packed together inside a genome, which is itself contained inside an organism. Genes group together into genomes because "genetic replication makes use of energy and substrates that are supplied by the metabolic economy in much greater quantities than would be possible without a genetic division of labour." They build vehicles to promote their mutual interests of jumping into the next generation of vehicles. As Dawkins puts it, organisms are the "survival machines" of genes.The phenotypic effect of a particular gene is contingent on its environment, including the fellow genes constituting with it the total genome.
Metabolic equivalent of task Based on resting metabolic rate Metabolic_equivalent_of_task > Quantitative definitions > Based on resting metabolic rate Originally, 1 MET was considered as the resting metabolic rate (RMR) obtained during quiet sitting.Although the RMR of any person may deviate from the reference value, MET can be thought of as an index of the intensity of activities: for example, an activity with a MET value of 2, such as walking at a slow pace (e.g., 3 km/h) would require twice the energy that an average person consumes at rest (e.g., sitting quietly).
Blockchain technology History Blockchain > History Cryptographer David Chaum first proposed a blockchain-like protocol in his 1982 dissertation "Computer Systems Established, Maintained, and Trusted by Mutually Suspicious Groups." Further work on a cryptographically secured chain of blocks was described in 1991 by Stuart Haber and W. Scott Stornetta. They wanted to implement a system wherein document timestamps could not be tampered with. In 1992, Haber, Stornetta, and Dave Bayer incorporated Merkle trees into the design, which improved its efficiency by allowing several document certificates to be collected into one block.
List of mathematical series Sum of reciprocal of factorials List_of_mathematical_series > Numeric series > Sum of reciprocal of factorials + 1 6 ! + 1 9 ! + 1 12 !
P53 Stem cells P53 > Function > Stem cells p53 also activates miR-34a and miR-145, which then repress the hESCs pluripotency factors, further instigating differentiation.In adult stem cells, p53 regulation is important for maintenance of stemness in adult stem cell niches. Mechanical signals such as hypoxia affect levels of p53 in these niche cells through the hypoxia inducible factors, HIF-1α and HIF-2α. While HIF-1α stabilizes p53, HIF-2α suppresses it.
Photoemission electron microscopy Photoelectron imaging Photoemission_electron_microscopy > Background > Photoelectron imaging Photoelectron imaging includes any form of imaging in which the source of information is the distribution of points from which electrons are ejected from the specimen by the action of photons. The technique with the highest resolution photoelectron imaging is presently photoelectron emission microscopy using UV light.
Induced stem cells Cardiomyocytes Induced_stem_cells > Induced progenitor stem cells > Cardiomyocytes This chemical reprogramming approach, after further optimization, may offer an easy way to provide the cues that induce heart muscle to regenerate locally.In another study, ischemic cardiomyopathy in the murine infarction model was targeted by iPS cell transplantation. It synchronized failing ventricles, offering a regenerative strategy to achieve resynchronization and protection from decompensation by dint of improved left ventricular conduction and contractility, reduced scarring and reversal of structural remodelling. One protocol generated populations of up to 98% cardiomyocytes from hPSCs simply by modulating the canonical Wnt signaling pathway at defined time points in during differentiation, using readily accessible small molecule compounds.Discovery of the mechanisms controlling the formation of cardiomyocytes led to the development of the drug ITD-1, which effectively clears the cell surface from TGF-β receptor type II and selectively inhibits intracellular TGF-β signaling.
Otto cycle engine Processes Otto_cycle > Processes The system is defined to be the mass of air that's drawn from the atmosphere into the cylinder, compressed by the piston, heated by the spark ignition of the added fuel, allowed to expand as it pushes on the piston, and finally exhausted back into the atmosphere. The mass of air is followed as its volume, pressure and temperature change during the various thermodynamic steps. As the piston is capable of moving along the cylinder, the volume of the air changes with its position in the cylinder.
Types of artificial neural networks Deep stacking network Types_of_artificial_neural_networks > Feedforward > Deep stacking network The hidden layer h has logistic sigmoidal units, and the output layer has linear units. Connections between these layers are represented by weight matrix U; input-to-hidden-layer connections have weight matrix W. Target vectors t form the columns of matrix T, and the input data vectors x form the columns of matrix X. The matrix of hidden units is H = σ ( W T X ) {\displaystyle {\boldsymbol {H}}=\sigma ({\boldsymbol {W}}^{T}{\boldsymbol {X}})} . Modules are trained in order, so lower-layer weights W are known at each stage.
Cynthia Larive Research Cynthia_Larive > Research She developed NMR pulse sequences to study protein ligand interactions in complexes with multiple ligands. She also researches analytical methods for metabolomics and chemogenomics for the reaction of plants to pesticides and hypoxia using NMR and mass spectroscopy.NMR is often thought of as a low-sensitivity method, but Larive's laboratory has developed ways of increasing the sensitivity of their measurements to obtain precise chemical and structural information. The techniques she has developed are relevant to understanding carbohydrate structure and biosynthesis, designing new drugs and measuring the purity of pharmaceuticals. Her work in developing chemical profiles for substances also has relevance for the authentication of foodstuffs such as wine, olive oil, and pomegranate juice.
The Vectors of Mind Synopsis The_Vectors_of_Mind > Synopsis Examples are provided of such man-made constructs from physics. He responds to skepticism from the practitioners of "rigorous science" that human behavior can ever be brought into the fold of such science by pointing out that there is considerable individuality in physical events even though described by rigorous scientific laws, such as the fact that every explosion is unique. Human abilities are the cause of individual differences in the "completion of a task".
Shear joint Failure modes Bolted_joint > Failure modes Fatigue Failure When Axial or Transverse Loading overcomes the bolts preload or causes the bolt to slip transversely, movement in the bolt can cause small cracks to build up in the material eventually leading to Fatigue Failure of the bolt or male threaded component. According to Bill Eccles from boltscience, Brinelling Brinelling may occur with poor quality washers, leading to a loss of clamp load and subsequent fatigue failure of the joint. Other Failure modes Other modes of failure include corrosion, embedment, and exceeding the shear stress limit.Bolted joints may be used intentionally as sacrificial parts, which are intended to fail before other parts, as in a shear pin.
Log jam Summary Log_jam A log jam is a naturally occurring phenomenon characterized by a dense accumulation of tree trunks and pieces of large wood across a vast section of a river, stream, or lake. ("Large wood" is commonly defined to be pieces of wood more than 10 cm (4 in) in diameter and more than 1 m (3 ft 3 in) long.) Log jams in rivers and streams often span the entirety of the water's surface from bank to bank. Log jams form when trees floating in the water become entangled with other trees floating in the water or become snagged on rocks, large woody debris, or other objects anchored underwater.
Matrix factorization Eigendecomposition Matrix_factorization > Decompositions based on eigenvalues and related concepts > Eigendecomposition A sufficient (but not necessary) condition for this to happen is that all the eigenvalues are different (in this case geometric and algebraic multiplicity are equal to 1) Comment: One can always normalize the eigenvectors to have length one (see the definition of the eigenvalue equation) Comment: Every normal matrix A (that is, matrix for which A A ∗ = A ∗ A {\displaystyle AA^{}=A^{}A} , where A ∗ {\displaystyle A^{}} is a conjugate transpose) can be eigendecomposed. For a normal matrix A (and only for a normal matrix), the eigenvectors can also be made orthonormal ( V V ∗ = I {\displaystyle VV^{}=I} ) and the eigendecomposition reads as A = V D V ∗ {\displaystyle A=VDV^{*}} . In particular all unitary, Hermitian, or skew-Hermitian (in the real-valued case, all orthogonal, symmetric, or skew-symmetric, respectively) matrices are normal and therefore possess this property.
Rete algorithm Overview Rete_algorithm > Overview The path from the root node to a leaf node defines a complete rule left-hand-side. Each node has a memory of facts which satisfy that pattern. This structure is essentially a generalized trie.
Materials strength Design terms Material_strength > Design terms Such failures are called fatigue failure. The failure is by a fracture that appears to be brittle with little or no visible evidence of yielding. However, when the stress is kept below "fatigue stress" or "endurance limit stress", the part will endure indefinitely.
Factorial moment measure n th factorial moment measure Factorial_moment_measure > Definitions > n th factorial moment measure The n th factorial moment measure or n th order factorial moment measure is defined as: M ( n ) ( B 1 × ⋯ × B n ) = E , {\displaystyle M^{(n)}(B_{1}\times \cdots \times B_{n})=E,} where the E denotes the expectation (operator) of the point process N. In other words, the n-th factorial moment measure is the expectation of the n th factorial power of some point process. The n th factorial moment measure of a point process N is equivalently defined by: ∫ R n d f ( x 1 , … , x n ) M ( n ) ( d x 1 , … , d x n ) = E , {\displaystyle \int _{{\textbf {R}}^{nd}}f(x_{1},\ldots ,x_{n})M^{(n)}(dx_{1},\ldots ,dx_{n})=E\left,} where f {\displaystyle f} is any non-negative measurable function on R n d {\displaystyle {\textbf {R}}^{nd}} , and the above summation is performed over all n {\displaystyle n} tuples of distinct points, including permutations. Consequently, the factorial moment measure is defined such that there are no points repeating in the product set, as opposed to the moment measure.
PAC-1 Mechanism of action PAC-1 > Mechanism of action In cells, the executioner protein, caspase-3, is stored in its inactive form, procaspase-3. This way, the cell can quickly undergo apoptosis by activating the protein that is already there. This inactive form is called a zymogen. Procaspase-3 is known to be inhibited by low levels of zinc.
Cytosine methylation In atherosclerosis Cytosine_methylation > In mammals > In atherosclerosis The downregulation of MCT3 impairs lactate transport and significantly increases smooth muscle cell proliferation, which further contributes to the atherosclerotic lesion. An ex vivo experiment using the demethylating agent Decitabine (5-aza-2 -deoxycytidine) was shown to induce MCT3 expression in a dose dependent manner, as all hypermethylated sites in the exon 2 CpG island became demethylated after treatment. This may serve as a novel therapeutic agent to treat atherosclerosis, although no human studies have been conducted thus far.
Electronic Engineering Electronic Control systems Electronics_engineering > Education and training > Supporting knowledge areas > Electronic Control systems Tools and techniques for LTI control system analysis and design: root loci, Routh–Hurwitz stability criterion, Bode and Nyquist plots. Control system compensators: elements of lead and lag compensation, elements of proportional–integral–derivative (PID) control. Discretization of continuous-time systems using zero-order hold and ADCs for digital controller implementation.
Social simulation Current research Social_simulation > Current research This research will ultimately aid policy-makers at all political levels in improving the effectiveness and efficiency of network-based policy instruments at promoting the knowledge economy in Europe. "Agent-based Simulations of Market and Consumer Behavior" is another research group that is funded by the Unilever Corporate Research. The current research that is being conducted is investigating the usefulness of agent-based simulations for modeling consumer behavior and to show the potential value and insights it can add to long-established marketing methods.
Limestone block Formation Cretaceous_limestone > Formation Modern carbonate mud is composed mostly of aragonite needles around 5 μm (0.20 mils) in length. Needles of this shape and composition are produced by calcareous algae such as Penicillus, making this a plausible source of mud. Another possibility is direct precipitation from the water.
Data cleansing Data quality Data_cleansing > Data quality Consistency: The degree to which a set of measures are equivalent in across systems (see also Consistency). Inconsistency occurs when two data items in the data set contradict each other: e.g., a customer is recorded in two different systems as having two different current addresses, and only one of them can be correct. Fixing inconsistency is not always possible: it requires a variety of strategies - e.g., deciding which data were recorded more recently, which data source is likely to be most reliable (the latter knowledge may be specific to a given organization), or simply trying to find the truth by testing both data items (e.g., calling up the customer).
Bi-additive map Summary Bi-additive_map In algebra, an additive map, Z {\displaystyle Z} -linear map or additive function is a function f {\displaystyle f} that preserves the addition operation: for every pair of elements x {\displaystyle x} and y {\displaystyle y} in the domain of f . {\displaystyle f.} For example, any linear map is additive.
Fano's inequality Intuition Fano's_inequality > Intuition Fano's inequality can be interpreted as a way of dividing the uncertainty of a conditional distribution into two questions given an arbitrary predictor. The first question, corresponding to the term H b ( e ) {\displaystyle H_{b}(e)} , relates to the uncertainty of the predictor. If the prediction is correct, there is no more uncertainty remaining. If the prediction is incorrect, the uncertainty of any discrete distribution has an upper bound of the entropy of the uniform distribution over all choices besides the incorrect prediction.
Hydrogen isotope biogeochemistry Quantum properties Hydrogen_isotope_biogeochemistry > Physical chemistry > Quantum properties This fundamental difference in 1H and 2H manifests in many physical properties. Integer spin particles like deuterium follow Bose-Einstein statistics while fermions with half integer spins follow Fermi-Dirac statistics.
Astrochicken Description Astrochicken > Description The solar collector would feed an ion drive engine that would power the craft. Once Astrochicken entered a planet's vicinity, it would collect material from the moons and rings of the planet, taking in nutrients. It could land and take off using an auxiliary chemical rocket similar to that used by bombardier beetles. It would periodically transmit details of its journey when it could make radio contact with Earth.
Prophase Prophase I arrest Prophase > Prophase I arrest Female mammals and birds are born possessing all the oocytes needed for future ovulations, and these oocytes are arrested at the prophase I stage of meiosis. In humans, as an example, oocytes are formed between three and four months of gestation within the fetus and are therefor present at birth. During this prophase I arrested stage (dictyate), which may last for decades, four copies of the genome are present in the oocytes.
Deflagration Flame physics Deflagration > Flame physics The underlying flame physics can be understood with the help of an idealized model consisting of a uniform one-dimensional tube of unburnt and burned gaseous fuel, separated by a thin transitional region of width δ {\displaystyle \delta \;} in which the burning occurs. The burning region is commonly referred to as the flame or flame front. In equilibrium, thermal diffusion across the flame front is balanced by the heat supplied by burning.Two characteristic timescales are important here. The first is the thermal diffusion timescale τ d {\displaystyle \tau _{d}\;} , which is approximately equal to τ d ≃ δ 2 / κ {\displaystyle \tau _{d}\simeq \delta ^{2}/\kappa } ,where κ {\displaystyle \kappa \;} is the thermal diffusivity.
Curly arrow Acid-base reactions Curly_arrow > Breaking of bonds > Acid-base reactions A Lewis acid-base reaction occurs when a molecule with a lone electron pair, or a base, donates its electrons to an electron-pair acceptor, also known as an acid. This can be shown in a reaction with a curved arrow pointing from the nonbonding electron pair to the electron acceptor. In a reaction involving Brønsted-Lowry acids and bases, the arrows are used in the same manner, and they help to indicate the attacking proton. In a Brønsted-Lowry acid-base reaction the arrow will begin from the acid, the proton acceptor, to the base, the proton donor.
Gene co-expression network Co-expression measure Gene_co-expression_network > Constructing gene co-expression networks > Co-expression measure The expression values of a gene for different samples can be represented as a vector, thus calculating the co-expression measure between a pair of genes is the same as calculating the selected measure for two vectors of numbers. Pearson's correlation coefficient, Mutual Information, Spearman's rank correlation coefficient and Euclidean distance are the four mostly used co-expression measures for constructing gene co-expression networks. Euclidean distance measures the geometric distance between two vectors, and so considers both the direction and the magnitude of the vectors of gene expression values. Mutual information measures how much knowing the expression levels of one gene reduces the uncertainty about the expression levels of another.
Spartan (chemistry software) Tasks performed Spartan_(chemistry_software) > Tasks performed Often performed before calculating structure using a quantum chemical model. Conformer distribution – Obtains a selection of low-energy conformers. Commonly used to identify the shapes a specific molecule is likely to adopt and to determine a Boltzmann distribution for calculating average molecular properties.
Calcite Properties Calcite > Properties The diagnostic properties of calcite include a defining Mohs hardness of 3, a specific gravity of 2.71 and, in crystalline varieties, a vitreous luster. Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities.
Situated knowledge Science Human_knowledge > In various disciplines > Science The scientific approach is usually regarded as an exemplary process for how to gain knowledge about empirical facts. Scientific knowledge includes mundane knowledge about easily observable facts, for example, chemical knowledge that certain reactants become hot when mixed together. But it also encompasses knowledge of less tangible issues, like claims about the behavior of genes, neutrinos, and black holes.A key aspect of most forms of science is that they seek natural laws that explain empirical observations. Scientific knowledge is discovered and tested using the scientific method.
Circuit quantum electrodynamics Theory Circuit_quantum_electrodynamics > Theory The full quantum description of matter-light interaction is given by the Jaynes–Cummings model. The three terms of the Jaynes–Cummings model can be ascribed to a cavity term, which is mimicked by a harmonic oscillator, an atomic term and an interaction term. H JC = ℏ ω r ( a † a + 1 2 ) ⏟ cavity term + 1 2 ℏ ω a σ z ⏟ atomic term + ℏ g ( σ + a + a † σ − ) ⏟ interaction term {\displaystyle {\mathcal {H}}_{\text{JC}}=\underbrace {\hbar \omega _{r}\left(a^{\dagger }a+{\frac {1}{2}}\right)} _{\text{cavity term}}+\underbrace {{\frac {1}{2}}\hbar \omega _{a}\sigma _{z}} _{\text{atomic term}}+\underbrace {\hbar g\left(\sigma _{+}a+a^{\dagger }\sigma _{-}\right)} _{\text{interaction term}}} In this formulation ω r {\displaystyle \omega _{r}} is the resonance frequency of the cavity and a † {\displaystyle a^{\dagger }} and a {\displaystyle a} are photon creation and annihilation operators, respectively. The atomic term is given by the Hamiltonian of a spin-½ system with ω a {\displaystyle \omega _{a}} being the transition frequency and σ z {\displaystyle \sigma _{z}} the Pauli matrix.
31P NMR spectroscopy Historical note Phosphorus_NMR > Applications in chemistry > Historical note The convention surrounding 31P-NMR (and other nuclei) changed convention in 1975: "The dimensionless scale should be defined as positive in the high frequency (low field) direction." Therefore, note that manuscripts published before 1976 will generally have the opposite sign.
Debye function Derivative Debye_function > Mathematical properties > Derivative The derivative obeys the relation x D n ′ ( x ) = n ( B ( x ) − D n ( x ) ) , {\displaystyle xD_{n}^{\prime }(x)=n(B(x)-D_{n}(x)),} where B ( x ) = x / ( e x − 1 ) {\displaystyle B(x)=x/(e^{x}-1)} is the Bernoulli function.
Symmetry of diatomic molecules Spin and total angular momentum Symmetry_of_diatomic_molecules > Molecular term symbol, Λ-doubling > Spin and total angular momentum {\displaystyle A,B,C,...} in front) for a heteronuclear molecule and a 1 Σ g + {\displaystyle {}^{1}\Sigma _{g}^{+}} state (written as X 1 Σ g + {\displaystyle X{}^{1}\Sigma _{g}^{+}} ) for a homonuclear molecule. Spin–orbit coupling lifts the degeneracy of the electronic states. This is because the z-component of spin interacts with the z-component of the orbital angular momentum, generating a total electronic angular momentum along the molecule axis Jz.
Hamiltonian (quantum mechanics) One particle Hamiltonian_(quantum_theory) > Schrödinger Hamiltonian > One particle Combining these yields the form used in the Schrödinger equation: which allows to apply the Hamiltonian to systems described by a wave function Ψ ( r , t ) {\displaystyle \Psi (\mathbf {r} ,t)} . This is the approach commonly taken in introductory treatments of quantum mechanics, using the formalism of Schrödinger's wave mechanics. One can also make substitutions to certain variables to fit specific cases, such as some involving electromagnetic fields.
Chronic cerebrospinal venous insufficiency History Chronic_cerebrospinal_venous_insufficiency > History Venous pathology has been associated with MS for more than a century. Pathologist Georg Eduard Rindfleisch noted in 1863 that the inflammation-associated lesions were distributed around veins. Later, in 1935, Tracy Putnam was able to produce similar lesions in dogs blocking their veinsThe term "chronic cerebrospinal venous insufficiency" was coined in 2008 by Paolo Zamboni, who described it in patients with multiple sclerosis. According to Zamboni, CCSVI had a high sensitivity and specificity differentiating healthy individuals from those with multiple sclerosis. Zamboni's results were criticized because his study was not blinded and his results needed to be verified by further studies. Zamboni had become interested in CCSVI in 1999 when his wife was diagnosed with MS.
Randomized control trial Procedures Controlled_trial > Randomization > Procedures The treatment allocation is the desired proportion of patients in each treatment arm. An ideal randomization procedure would achieve the following goals: Maximize statistical power, especially in subgroup analyses. Generally, equal group sizes maximize statistical power, however, unequal groups sizes may be more powerful for some analyses (e.g., multiple comparisons of placebo versus several doses using Dunnett's procedure ), and are sometimes desired for non-analytic reasons (e.g., patients may be more motivated to enroll if there is a higher chance of getting the test treatment, or regulatory agencies may require a minimum number of patients exposed to treatment).
Philosophy of physics Philosophy of thermal and statistical physics Philosophy_of_physics > Philosophy of thermal and statistical physics The philosophy of thermal and statistical physics is that part of the philosophy of physics whose subject matter is an amalgam of classical thermodynamics, statistical mechanics, and related theories. Its central questions include: What is entropy, and what does the second law of thermodynamics say about it? What is the correct resolution of the Maxwell's demon paradox? Does either thermodynamics or statistical mechanics contain an element of time-irreversibility? If so, what does statistical mechanics tell us about the arrow of time? What is the nature of the probabilities that appear in statistical mechanics?
Glyph (data visualization) Summary Glyph_(data_visualization) In the context of data visualization, a glyph is any marker, such as an arrow or similar marking, used to specify part of a visualization. This is a representation to visualize data where the data set is presented as a collection of visual objects. These visual objects are collectively called a glyph. It helps visualizing data relation in data analysis, statistics, etc. by using any custom notation. In the context of data visualization, a glyph is the visual representation of a piece of data where the attributes of a graphical entity are dictated by one or more attributes of a data record.
Fermi surface of superconducting cuprates Yttrium–barium cuprate High_temperature_superconductors > Cuprates > Yttrium–barium cuprate The other superconducting cuprates have another structure: they have a tetragonal cell. Each perovskite cell contains a Y or Ba atom at the center: Ba in the bottom unit cell, Y in the middle one, and Ba in the top unit cell.
Flowers of sulfur Uses Flowers_of_sulfur > Uses These compounds can be produced artificially or naturally. Paper mills, craters, and volcanoes are examples of sulfur sources. FoS provides a source of elemental sulfur that can be used to test conformal coatings and have caused creep corrosion on printed circuit boards (PCBs).

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.