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Corneal epithelium: an exceedingly thin multicellular epithelial tissue layer (non-keratinized stratified squamous epithelium) of fast-growing and easily regenerated cells, kept moist with tears. Irregularity or edema of the corneal epithelium disrupts the smoothness of the air/tear-film interface, the most significant... | Cornea | Wikipedia | 483 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
The spacing of the neighboring collagen fibrils in the stroma must be < 200 nm for there to be transparency. (Goldman and Benedek)
Descemet's membrane (also posterior limiting membrane): a thin acellular layer that serves as the modified basement membrane of the corneal endothelium, from which the cells are derived. T... | Cornea | Wikipedia | 423 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
Nerve supply
The cornea is one of the most sensitive tissues of the body, as it is densely innervated with sensory nerve fibres via the ophthalmic division of the trigeminal nerve by way of 70–80 long ciliary nerves. Research suggests the density of pain receptors in the cornea is 300–600 times greater than skin and 20... | Cornea | Wikipedia | 483 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
Upon death or removal of an eye the cornea absorbs the aqueous humor, thickens, and becomes hazy. Transparency can be restored by putting it in a warm, well-ventilated chamber at 31 °C (88 °F, the normal temperature), allowing the fluid to leave the cornea and become transparent. The cornea takes in fluid from the aque... | Cornea | Wikipedia | 458 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
Various refractive eye surgery techniques change the shape of the cornea in order to reduce the need for corrective lenses or otherwise improve the refractive state of the eye. In many of the techniques used today, reshaping of the cornea is performed by photoablation using the excimer laser.
There are also synthetic ... | Cornea | Wikipedia | 371 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
Corneal retention and permeability in topical drug delivery to the eye
The majority of ocular therapeutic agents are administered to the eye via the topical route. Cornea is one of the main barriers for drug diffusion because of its highly impermeable nature. Its continuous irrigation with a tear fluid also results in ... | Cornea | Wikipedia | 377 | 311888 | https://en.wikipedia.org/wiki/Cornea | Biology and health sciences | Visual system | Biology | vital_articles |
Fourier optics is the study of classical optics using Fourier transforms (FTs), in which the waveform being considered is regarded as made up of a combination, or superposition, of plane waves. It has some parallels to the Huygens–Fresnel principle, in which the wavefront is regarded as being made up of a combination o... | Fourier optics | Wikipedia | 442 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Fourier optics forms much of the theory behind image processing techniques, as well as applications where information needs to be extracted from optical sources such as in quantum optics. To put it in a slightly complex way, similar to the concept of frequency and time used in traditional Fourier transform theory, Four... | Fourier optics | Wikipedia | 425 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
If light of a fixed frequency in time/wavelength/color (as from a single-mode laser) is assumed, then, based on the engineering time convention, which assumes an time dependence in wave solutions at the angular frequency with where is a time period of the waves, the time-harmonic form of the optical field is given ... | Fourier optics | Wikipedia | 409 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
It may now be argued that each quotient in the equation above must, of necessity, be constant. To justify this, let's say that the first quotient is not a constant, and is a function of x. Since none of the other terms in the equation has any dependence on the variable x, so the first term also must not have any x-depe... | Fourier optics | Wikipedia | 486 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The plane wave spectrum representation of a general electromagnetic field (e.g., a spherical wave) in the equation () is the basic foundation of Fourier optics (this point cannot be emphasized strongly enough), because at z = 0, the equation simply becomes a Fourier transform (FT) relationship between the field and its... | Fourier optics | Wikipedia | 144 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Connection between Fourier optics and imaging resolution
Let's consider an imaging system where the z-axis is the optical axis of the system and the object plane (to be imaged on the image plane of the system) is the plane at . On the object plane, the spatial part of a complex-valued Cartesian component of a wave is,... | Fourier optics | Wikipedia | 421 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
In connection with photolithography of electronic components, these (1) and (2) are the reasons why light of a higher frequency (smaller wavelength, thus larger magnitude of ) or a higher NA imaging system is required to image finer features of integrated circuits on a photoresist on a wafer. As a result, machines real... | Fourier optics | Wikipedia | 500 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Stated another way, the radiation pattern of any planar field distribution is the FT (Fourier Transform) of that source distribution (see Huygens–Fresnel principle, wherein the same equation is developed using a Green's function approach). Note that this is NOT a plane wave. The radial dependence is a spherical wave -... | Fourier optics | Wikipedia | 374 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
In this equation, it is assumed that the unit vector in the z-direction points into the half-space where the far field calculations will be made. These equivalent magnetic currents are obtained using equivalence principles which, in the case of an infinite planar interface, allow any electric currents J to be "imaged a... | Fourier optics | Wikipedia | 313 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Likely to electrical signals, bandwidth in optics is a measure of how finely detailed an image is; the finer the detail, the greater the bandwidth required to represent it. A DC (Direct Current) electrical signal is constant and has no oscillations; a plane wave propagating parallel to the optic () axis has constant va... | Fourier optics | Wikipedia | 344 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
In the case of differential equations, as in the case of matrix equations, whenever the right-hand side of an equation is zero (For example, a forcing function, forcing vector, or the source of a force is zero.), the equation may still admit a non-trivial solution, known in applied mathematics as an eigenfunction solut... | Fourier optics | Wikipedia | 457 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
In the matrix equation case in which A is a square matrix, eigenvalues may be found by setting the determinant of the matrix equal to zero, i.e. finding where the matrix has no inverse. (Such a square matrix is said to be singular.) Finite matrices have only a finite number of eigenvalues/eigenvectors, whereas linear ... | Fourier optics | Wikipedia | 508 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The notion of k-space is central to many disciplines in engineering and physics, especially in the study of periodic volumes, such as in crystallography and the band theory of semiconductor materials.
The two-dimensional Fourier transform
A spectrum analysis equation (calculating the spectrum of a function ):
A syn... | Fourier optics | Wikipedia | 415 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Optical systems typically fall into one of two different categories. The first is ordinary focused optical imaging systems (e.g., cameras), wherein the input plane is called the object plane and the output plane is called the image plane. An optical field in the image plane (the output plane of the imaging system) is d... | Fourier optics | Wikipedia | 419 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The alert reader will note that the integral above tacitly assumes that the impulse response is NOT a function of the position (x',y') of the impulse of light in the input plane (if this were not the case, this type of convolution would not be possible). This property is known as shift invariance (Scott [1998]). No opt... | Fourier optics | Wikipedia | 394 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
It is then presumed that the system under consideration is linear, that is to say that the output of the system due to two different inputs (possibly at two different times) is the sum of the individual outputs of the system to the two inputs, when introduced individually. Thus the optical system may contain no nonline... | Fourier optics | Wikipedia | 490 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
This equation takes on its real meaning when the Fourier transform, is associated with the coefficient of the plane wave whose transverse wavenumbers are . Thus, the input-plane plane wave spectrum is transformed into the output-plane plane wave spectrum through the multiplicative action of the system transfer functio... | Fourier optics | Wikipedia | 487 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
and the sum of the two path lengths is f (1 + θ2/2 + 1 − θ2/2) = 2f; i.e., it is a constant value, independent of tilt angle, θ, for paraxial plane waves. Each paraxial plane wave component of the field in the front focal plane appears as a point spread function spot in the back focal plane, with an intensity and phase... | Fourier optics | Wikipedia | 448 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The spatially modulated electric field, shown on the left-hand side of eqn. (), typically only occupies a finite (usually rectangular) aperture in the x,y plane. The rectangular aperture function acts like a 2D square-top filter, where the field is assumed to be zero outside this 2D rectangle. The spatial domain integr... | Fourier optics | Wikipedia | 445 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Even though the input transparency only occupies a finite portion of the x-y plane (Plane 1), the uniform plane waves comprising the plane wave spectrum occupy the entire x-y plane, which is why (for this purpose) only the longitudinal plane wave phase (in the z-direction, from Plane 1 to Plane 2) must be considered, a... | Fourier optics | Wikipedia | 431 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
On the other hand, sinc functions and Airy functions - which are not only the point spread functions of rectangular and circular apertures, respectively, but are also cardinal functions commonly used for functional decomposition in interpolation/sampling theory [Scott 1990] - do''' correspond to converging or diverging... | Fourier optics | Wikipedia | 326 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
In the figure above, illustrating the Fourier transforming property of lenses, the lens is in the near field of the object plane transparency, therefore the object plane field at the lens may be regarded as a superposition of plane waves, each one of which propagates at some angle with respect to the z-axis. In this re... | Fourier optics | Wikipedia | 352 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
A lens is basically a low-pass plane wave filter (see Low-pass filter). Consider a "small" light source located on-axis in the object plane of the lens. It is assumed that the source is small enough that, by the far-field criterion, the lens is in the far field of the "small" source. Then, the field radiated by the sma... | Fourier optics | Wikipedia | 437 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
While working in the frequency domain, with an assumed ejωt (engineering) time dependence, coherent (laser) light is implicitly assumed, which has a delta function dependence in the frequency domain. Light at different (delta function) frequencies will "spray" the plane wave spectrum out at different angles, and as a r... | Fourier optics | Wikipedia | 305 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The 4F correlator is based on the convolution theorem from Fourier transform theory, which states that convolution in the spatial (x,y) domain is equivalent to direct multiplication in the spatial frequency (kx, ky) domain (aka: spectral domain). Once again, a plane wave is assumed incident from the left and a transpar... | Fourier optics | Wikipedia | 492 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The 4F correlator is an excellent device for illustrating the "systems" aspects of optical instruments, alluded to in the section 5 above. The FT plane mask function, G(kx,ky) is the system transfer function of the correlator, which we'd in general denote as H(kx,ky), and it is the FT of the impulse response function o... | Fourier optics | Wikipedia | 433 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
The upper portion is first focused (i.e., Fourier transformed) by a lens L2 to a spot in the front focal plan of lens L3, forming a virtual point source generating a spherical wave. The wave is then collimated by lens L3 and produces a tilted plane wave with the form at the recording plane.
The lower portion is direc... | Fourier optics | Wikipedia | 313 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
Electrical fields can be represented mathematically in many different ways. In the Huygens–Fresnel or Stratton-Chu viewpoints, the electric field is represented as a superposition of point sources, each one of which gives rise to a Green's function field. The total field is then the weighted sum of all of the individua... | Fourier optics | Wikipedia | 433 | 312008 | https://en.wikipedia.org/wiki/Fourier%20optics | Physical sciences | Optics | Physics | vital_articles |
VMware LLC is an American cloud computing and virtualization technology company headquartered in Palo Alto, California. VMware was the first commercially successful company to virtualize the x86 architecture.
VMware's desktop software runs on Microsoft Windows, Linux, and macOS. VMware ESXi, its enterprise software hy... | VMware | Wikipedia | 430 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
On July 8, 2008, after disappointing financial performance, the board of directors fired VMware co-founder, president and CEO Diane Greene, who was replaced by Paul Maritz, a 14-year Microsoft veteran who was heading EMC's cloud computing business unit. Greene had been CEO since the company's founding, ten years earlie... | VMware | Wikipedia | 481 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
In September 2013, at VMworld San Francisco, VMware announced the general availability of vCloud Hybrid Service and expansion to Sterling, Virginia, Santa Clara, California, Dallas, Texas, and a service beta in the UK. It announced the acquisition of Desktone in October 2013.
Acquisition by Dell
In January 2016, in a... | VMware | Wikipedia | 498 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
On May 12, 2021, VMware announced that Raghu Raghuram would take over as CEO.
In May 2022, VMware announced that the company had partnered with Formula One motor racing team, McLaren Racing.
Log4Shell vulnerability
Beginning in January 2022, hackers infiltrated servers using the Log4Shell vulnerability at organizatio... | VMware | Wikipedia | 467 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
In February 2024 private equity firm KKR and Broadcom agreed for KKR to acquire Broadcom's End-User Computing (EUC) Division, formerly a division of VMware, for about $4 billion. This includes the VDI product Horizon and the device management suite Workspace ONE, formerly AirWatch.
On May 14, 2024, it was announced th... | VMware | Wikipedia | 462 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
VMware software provides a completely virtualized set of hardware to the guest operating system. VMware software virtualizes the hardware for a video adapter, a network adapter, and hard disk adapters. The host provides pass-through drivers for guest USB, serial, and parallel devices. In this way, VMware virtual machin... | VMware | Wikipedia | 421 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
Desktop software
VMware Workstation, introduced in 1999, was the first product launched by VMware. This software suite allows users to run multiple instances of x86 or x86-64-compatible operating systems on a single physical personal computer. Version 17.0 was released on November 17, 2022. Originally a commercial app... | VMware | Wikipedia | 480 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
VMware vSAN (previously called VMware Virtual SAN) is software-defined storage that is embedded in VMware's ESXi hypervisor. The vSphere and vSAN software runs on industry-standard x86 servers to form a hyper-converged infrastructure (or HCI). However, network operators need to have servers from HCL (Hardware Compatibi... | VMware | Wikipedia | 425 | 312018 | https://en.wikipedia.org/wiki/VMware | Technology | Virtualization | null | vital_articles |
Cowrie or cowry () is the common name for a group of small to large sea snails in the family Cypraeidae.
The term porcelain derives from the old Italian term for the cowrie shell () due to their similar appearance.
Cowrie shells have held cultural, economic, and ornamental significance in various cultures. The cowrie... | Cowrie | Wikipedia | 486 | 312029 | https://en.wikipedia.org/wiki/Cowrie | Biology and health sciences | Gastropods | Animals | vital_articles |
Nearly all cowries have a porcelain-like shine, with some exceptions such as Hawaii's granulated cowrie, Nucleolaria granulata. Many have colorful patterns. Lengths range from for some species up to for the Atlantic deer cowrie, Macrocypraea cervus.
Human use
Monetary use
Cowrie shells, especially Monetaria moneta... | Cowrie | Wikipedia | 505 | 312029 | https://en.wikipedia.org/wiki/Cowrie | Biology and health sciences | Gastropods | Animals | vital_articles |
In Brazil, as a result of the Atlantic slave trade from Africa, cowrie shells (called búzios) are also used to consult the Orixás divinities and hear their replies.
Cowrie shells were among the devices used for divination by the Kaniyar Panicker astrologers of Kerala, India.
In certain parts of Africa, cowries were p... | Cowrie | Wikipedia | 472 | 312029 | https://en.wikipedia.org/wiki/Cowrie | Biology and health sciences | Gastropods | Animals | vital_articles |
Other
Large cowrie shells such as that of a Cypraea tigris have been used in Europe in the recent past as a darning egg over which sock heels were stretched. The cowrie's smooth surface allows the needle to be positioned under the cloth more easily.
In the 1940s and 1950s, small cowry shells were used as a teaching a... | Cowrie | Wikipedia | 86 | 312029 | https://en.wikipedia.org/wiki/Cowrie | Biology and health sciences | Gastropods | Animals | vital_articles |
Bryophytes () are a group of land plants (embryophytes), sometimes treated as a taxonomic division, that contains three groups of non-vascular land plants: the liverworts, hornworts, and mosses. In the strict sense, the division Bryophyta consists of the mosses only. Bryophytes are characteristically limited in size an... | Bryophyte | Wikipedia | 480 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
Bryophytes are gametophyte dominant, meaning that the more prominent, longer-lived plant is the haploid gametophyte. The diploid sporophytes appear only occasionally and remain attached to and nutritionally dependent on the gametophyte. In bryophytes, the sporophytes are always unbranched and produce a single sporangiu... | Bryophyte | Wikipedia | 381 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
The sporophyte develops differently in the three groups. Both mosses and hornworts have a meristem zone where cell division occurs. In hornworts, the meristem starts at the base where the foot ends, and the division of cells pushes the sporophyte body upwards. In mosses, the meristem is located between the capsule and ... | Bryophyte | Wikipedia | 406 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
Monoicous plants are necessarily hermaphroditic, meaning that the same plant produces gametes of both sexes. The exact arrangement of the antheridia and archegonia in monoicous plants varies. They may be borne on different shoots (autoicous), on the same shoot but not together in a common structure (paroicous or paroec... | Bryophyte | Wikipedia | 445 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
The three bryophyte clades are the Marchantiophyta (liverworts), Bryophyta (mosses) and Anthocerotophyta (hornworts). However, it has been proposed that these clades are de-ranked to the classes Marchantiopsida, Bryopsida, and Anthocerotopsida, respectively. There is now strong evidence that the liverworts and mosses b... | Bryophyte | Wikipedia | 501 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
Evolution
There have probably been several different terrestrialization events, in which originally aquatic organisms colonized the land, just within the lineage of the Viridiplantae. Between 510 and 630 million years ago, however, land plants emerged within the green algae. Molecular phylogenetic studies conclude that... | Bryophyte | Wikipedia | 451 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
Uses
Environmental
Characteristics of bryophytes make them useful to the environment. Depending on the specific plant texture, bryophytes have been shown to help improve the water retention and air space within soil. Bryophytes are used in pollution studies to indicate soil pollution (such as the presence of heavy met... | Bryophyte | Wikipedia | 254 | 312249 | https://en.wikipedia.org/wiki/Bryophyte | Biology and health sciences | Bryophytes | null | vital_articles |
In physics, a partition function describes the statistical properties of a system in thermodynamic equilibrium. Partition functions are functions of the thermodynamic state variables, such as the temperature and volume. Most of the aggregate thermodynamic variables of the system, such as the total energy, free energy... | Partition function (statistical mechanics) | Wikipedia | 508 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
where
is the Planck constant;
is the thermodynamic beta, defined as ;
is the Hamiltonian of the system;
is the canonical position;
is the canonical momentum.
To make it into a dimensionless quantity, we must divide it by h, which is some quantity with units of action (usually taken to be the Planck constant)... | Partition function (statistical mechanics) | Wikipedia | 484 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
The above treatment applies to quantum statistical mechanics, where a physical system inside a finite-sized box will typically have a discrete set of energy eigenstates, which we can use as the states s above. In quantum mechanics, the partition function can be more formally written as a trace over the state space (whi... | Partition function (statistical mechanics) | Wikipedia | 511 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
Calculating the thermodynamic total energy
In order to demonstrate the usefulness of the partition function, let us calculate the thermodynamic value of the total energy. This is simply the expected value, or ensemble average for the energy, which is the sum of the microstate energies weighted by their probabilities:... | Partition function (statistical mechanics) | Wikipedia | 512 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
However, there is a well-known exception to this rule. If the sub-systems are actually identical particles, in the quantum mechanical sense that they are impossible to distinguish even in principle, the total partition function must be divided by a N! (N factorial):
This is to ensure that we do not "over-count" the nu... | Partition function (statistical mechanics) | Wikipedia | 343 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
This is the reason for calling Z the "partition function": it encodes how the probabilities are partitioned among the different microstates, based on their individual energies. Other partition functions for different ensembles divide up the probabilities based on other macrostate variables. As an example: the partition... | Partition function (statistical mechanics) | Wikipedia | 488 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
The grand partition function is sometimes written (equivalently) in terms of alternate variables as
where is known as the absolute activity (or fugacity) and is the canonical partition function. | Partition function (statistical mechanics) | Wikipedia | 37 | 312252 | https://en.wikipedia.org/wiki/Partition%20function%20%28statistical%20mechanics%29 | Physical sciences | Statistical mechanics | Physics | vital_articles |
Chinampa ( ) is a technique used in Mesoamerican agriculture which relies on small, rectangular areas of fertile arable land to grow crops on the shallow lake beds in the Valley of Mexico. The word chinampa has Nahuatl origins, chinampa meaning “in the fence of reeds”. They are built up on wetlands of a lake or freshwa... | Chinampa | Wikipedia | 306 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
When creating chinampas, in addition to building up masses of land, a drainage system was developed. This drainage system was multi-purposed. A ditch was created to allow for the flow of water and sediments (likely including night soil). Over time, the ditch would slowly accumulate piles of mud. This mud would then be ... | Chinampa | Wikipedia | 248 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
Evidence from Nahuatl wills from late seventeenth-century Pueblo Culhuacán suggests chinampas were measured in matl (one matl = 1.67 meters), often listed in groups of seven. One scholar has calculated the size of chinampas using Codex Vergara as a source, finding that they usually measured roughly . In Tenochtitlan, t... | Chinampa | Wikipedia | 318 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
The earliest fields that have been securely dated are from the Middle Postclassic period, 1150 – 1350 CE. Chinampas were used primarily in Lakes Xochimilco and Chalco near the springs that lined the south shore of those lakes. The Aztecs not only conducted military campaigns to obtain control over these regions but, ac... | Chinampa | Wikipedia | 509 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
The extent to which Tenochtitlan depended on chinampas for its fresh food supply has been the topic of a number of scholarly studies.
Among the crops grown on chinampas were maize, beans, squash, amaranth, tomatoes, chili peppers, and flowers. Maize was planted with digging stick huictli with a wooden blade on one en... | Chinampa | Wikipedia | 379 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
According to Antonio Vera, through the UH Hilo website, within the framework of chinampas, there was two versions; inland and irrigated chinampas. Inland’s are created on banks, irrigated is built on water. Through steps, the structure of chinampas is to locate shallow land by the bank and surround said area with stake... | Chinampa | Wikipedia | 428 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
Challenges
Although many locals and farmers are happy to return to their agricultural roots, they are faced with several challenges. During the Spanish conquest, many lakes were drained, limiting their agricultural capacity, such as the lake at Xochimilco. In addition, in 1985 an earthquake struck, further damaging se... | Chinampa | Wikipedia | 95 | 312259 | https://en.wikipedia.org/wiki/Chinampa | Technology | Buildings and infrastructure | null | vital_articles |
In complex analysis, Liouville's theorem, named after Joseph Liouville (although the theorem was first proven by Cauchy in 1844), states that every bounded entire function must be constant. That is, every holomorphic function for which there exists a positive number such that for all is constant. Equivalently, non-... | Liouville's theorem (complex analysis) | Wikipedia | 498 | 312293 | https://en.wikipedia.org/wiki/Liouville%27s%20theorem%20%28complex%20analysis%29 | Mathematics | Complex analysis | null | vital_articles |
Non-constant elliptic functions cannot be defined on the complex plane
The theorem can also be used to deduce that the domain of a non-constant elliptic function cannot be . Suppose it was. Then, if and are two periods of such that is not real, consider the parallelogram whose vertices are 0, , , and . Then the i... | Liouville's theorem (complex analysis) | Wikipedia | 450 | 312293 | https://en.wikipedia.org/wiki/Liouville%27s%20theorem%20%28complex%20analysis%29 | Mathematics | Complex analysis | null | vital_articles |
Similarly, if an entire function has a pole of order at —that is, it grows in magnitude comparably to in some neighborhood of
—then is a polynomial. This extended version of Liouville's theorem can be more precisely stated: if for sufficiently large, then is a polynomial of degree at most . This can be proved ... | Liouville's theorem (complex analysis) | Wikipedia | 127 | 312293 | https://en.wikipedia.org/wiki/Liouville%27s%20theorem%20%28complex%20analysis%29 | Mathematics | Complex analysis | null | vital_articles |
An avalanche photodiode (APD) is a highly sensitive type of photodiode, which in general are semiconductor diodes that convert light into electricity via interband excitation coupled with impact ionization. APDs use materials and a structure optimised for operating with high reverse bias, approaching the reverse breakd... | Avalanche photodiode | Wikipedia | 512 | 312299 | https://en.wikipedia.org/wiki/Avalanche%20photodiode | Technology | Components | null | vital_articles |
Geiger mode counting
If very high gain is needed (105 to 106), detectors related to APDs called SPADs (single-photon avalanche diodes) can be used and operated with a reverse voltage above a typical APD's breakdown voltage. In this case, the photodetector needs to have its signal current limited and quickly diminished... | Avalanche photodiode | Wikipedia | 467 | 312299 | https://en.wikipedia.org/wiki/Avalanche%20photodiode | Technology | Components | null | vital_articles |
Performance limits
APD applicability and usefulness depends on many parameters. Two of the larger factors are: quantum efficiency, which indicates how well incident optical photons are absorbed and then used to generate primary charge carriers; and total leakage current, which is the sum of the dark current, photocurre... | Avalanche photodiode | Wikipedia | 333 | 312299 | https://en.wikipedia.org/wiki/Avalanche%20photodiode | Technology | Components | null | vital_articles |
The noise term for an APD may also contain a Fano factor, which is a multiplicative correction applied to the Poisson noise associated with the conversion of the energy deposited by a charged particle to the electron-hole pairs, which is the signal before multiplication. The correction factor describes the decrease in ... | Avalanche photodiode | Wikipedia | 358 | 312299 | https://en.wikipedia.org/wiki/Avalanche%20photodiode | Technology | Components | null | vital_articles |
The Tarantula Nebula (also known as 30 Doradus) is a large H II region in the Large Magellanic Cloud (LMC), forming its south-east corner (from Earth's perspective).
Discovery
The Tarantula Nebula was observed by Nicolas-Louis de Lacaille during an expedition to the Cape of Good Hope between 1751 and 1753. He catalog... | Tarantula Nebula | Wikipedia | 463 | 312335 | https://en.wikipedia.org/wiki/Tarantula%20Nebula | Physical sciences | Notable nebulae | Astronomy | vital_articles |
30 Doradus has at its centre the star cluster NGC 2070 which includes the compact concentration of stars known as R136 that produces most of the energy that makes the nebula visible. The estimated mass of the cluster is 450,000 solar masses, suggesting it will likely become a globular cluster in the future. In additio... | Tarantula Nebula | Wikipedia | 243 | 312335 | https://en.wikipedia.org/wiki/Tarantula%20Nebula | Physical sciences | Notable nebulae | Astronomy | vital_articles |
In economics, unit of account is one of the functions of money. A unit of account is a standard numerical monetary unit of measurement of the market value of goods, services, and other transactions. Also known as a "measure" or "standard" of relative worth and deferred payment, a unit of account is a necessary prerequi... | Unit of account | Wikipedia | 494 | 312461 | https://en.wikipedia.org/wiki/Unit%20of%20account | Physical sciences | Measurement systems | Basics and measurement | vital_articles |
History
Historic examples of units of measure include the livre tournois, used in France from 1302 to 1794 whether or not livre coins were minted. In the 14th century Naples used the grossi gigliati, and Bohemia used the Prague groschen. (2021)
At any one time there might be two or three units of account in one region... | Unit of account | Wikipedia | 509 | 312461 | https://en.wikipedia.org/wiki/Unit%20of%20account | Physical sciences | Measurement systems | Basics and measurement | vital_articles |
Accounting
The unit of account in financial accounting refers to the words used to describe the specific assets and liabilities that are reported in financial statements rather than the units used to measure them. That is, unit of account refers to the object of recognition or display whereas unit of measure refers to ... | Unit of account | Wikipedia | 122 | 312461 | https://en.wikipedia.org/wiki/Unit%20of%20account | Physical sciences | Measurement systems | Basics and measurement | vital_articles |
Dots per inch (DPI, or dpi) is a measure of spatial printing, video or image scanner dot density, in particular the number of individual dots that can be placed in a line within the span of . Similarly, dots per centimetre (d/cm or dpcm) refers to the number of individual dots that can be placed within a line of .
DPI... | Dots per inch | Wikipedia | 461 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Higher-end inkjet printers can offer 5, 6 or 7 ink colours giving 32, 64 or 128 possible tones per dot location (and again, it can be that not all combinations will produce a unique result). Contrast this to a standard sRGB monitor where each pixel produces 256 intensities of light in each of three channels (RGB).
Whi... | Dots per inch | Wikipedia | 392 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
This dithered printing process could require a region of four to six dots (measured across each side) to accurately reproduce the color in a single pixel. An image that is 100 pixels wide may need to be 400 to 600 dots in width in the printed output; if a 100 × 100-pixel image is to be printed in a one-inch square, the... | Dots per inch | Wikipedia | 249 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
In printing, DPI (dots per inch) refers to the output resolution of a printer or imagesetter, and PPI (pixels per inch) refers to the input resolution of a photograph or image.
DPI refers to the physical dot density of an image when it is reproduced as a real physical entity, for example printed onto paper. A digitally... | Dots per inch | Wikipedia | 301 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
For vector images, since the file is resolution independent, there is no need to resample the image before resizing it as it prints equally well at all sizes. However, there is still a target printing size. Some image formats, such as Photoshop format, can contain both bitmap and vector data in the same file. Adjusting... | Dots per inch | Wikipedia | 238 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Computer monitor DPI standards
Since the 1980s, Macs have set the default display "DPI" to 72 PPI, while the Microsoft Windows operating system has used a default of 96 PPI. These default specifications arose out of the problems rendering standard fonts in the early display systems of the 1980s, including the IBM-base... | Dots per inch | Wikipedia | 465 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Microsoft tried to solve both problems with a hack that has had long-term consequences for the understanding of what DPI and PPI mean. Microsoft began writing its software to treat the screen as though it provided a PPI characteristic that is of what the screen actually displayed. Because most screens at the time prov... | Dots per inch | Wikipedia | 407 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Without using supplemental, software-provided zoom levels, the 1:1 relationship between display and print size was (deliberately) lost; the availability of different-sized, user-adjustable monitors and display adaptors with varying output resolutions exacerbated this, as it was not possible to rely on a properly-adjust... | Dots per inch | Wikipedia | 344 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Thus, for example, a 10-point font on a Macintosh (at 72 PPI) was represented with 10 pixels (i.e., 10 PPEm), whereas a 10-point font on a Windows platform (at 96 PPI) at the same zoom level is represented with 13 pixels (i.e., Microsoft rounded to 13 pixels, or 13 PPEm) – and, on a typical consumer grade monitor, wou... | Dots per inch | Wikipedia | 425 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
Displays with high pixel densities were not common up to the Windows XP era. High DPI displays became mainstream around the time Windows 8 was released. Display scaling by entering a custom DPI irrespective of the display resolution has been a feature of Microsoft Windows since Windows 95. Windows XP introduced the GDI... | Dots per inch | Wikipedia | 399 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
In Windows 8, only the DPI scaling percentage is shown in the DPI changing dialog and the display of the raw DPI value has been removed. In Windows 8.1, the global setting to disable DPI virtualization (only use XP-style scaling) is removed and a per-app setting added for the user to disable DPI virtualization from the... | Dots per inch | Wikipedia | 314 | 312833 | https://en.wikipedia.org/wiki/Dots%20per%20inch | Physical sciences | Visual | Basics and measurement | vital_articles |
In physics, action is a scalar quantity that describes how the balance of kinetic versus potential energy of a physical system changes with trajectory. Action is significant because it is an input to the principle of stationary action, an approach to classical mechanics that is simpler for multiple objects. Action and ... | Action (physics) | Wikipedia | 509 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
Planck's quantum of action
The Planck constant, written as or when including a factor of , is called the quantum of action. Like action, this constant has unit of energy times time. It figures in all significant quantum equations, like the uncertainty principle and the de Broglie wavelength. Whenever the value of t... | Action (physics) | Wikipedia | 467 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
where the endpoints of the evolution are fixed and defined as and . According to Hamilton's principle, the true evolution qtrue(t) is an evolution for which the action is stationary (a minimum, maximum, or a saddle point). This principle results in the equations of motion in Lagrangian mechanics.
Abbreviated action ... | Action (physics) | Wikipedia | 511 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
When relativistic effects are significant, the action of a point particle of mass m travelling a world line C parametrized by the proper time is
If instead, the particle is parametrized by the coordinate time t of the particle and the coordinate time ranges from t1 to t2, then the action becomes
where the Lagrangian... | Action (physics) | Wikipedia | 498 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
Hamilton's principal function is obtained from the action functional by fixing the initial time and the initial endpoint while allowing the upper time limit and the second endpoint to vary. The Hamilton's principal function satisfies the Hamilton–Jacobi equation, a formulation of classical mechanics. Due to a sim... | Action (physics) | Wikipedia | 463 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
The action principle can be generalized still further. For example, the action need not be an integral, because nonlocal actions are possible. The configuration space need not even be a functional space, given certain features such as noncommutative geometry. However, a physical basis for these mathematical extensio... | Action (physics) | Wikipedia | 66 | 312881 | https://en.wikipedia.org/wiki/Action%20%28physics%29 | Physical sciences | Classical mechanics | Physics | vital_articles |
A tenrec () is a mammal belonging to any species within the afrotherian family Tenrecidae, which is endemic to Madagascar. Tenrecs are a very diverse group; as a result of adaptive radiation and exhibit convergent evolution, some resemble hedgehogs, shrews, opossums, rats, and mice. They occupy aquatic, arboreal, terre... | Tenrec | Wikipedia | 428 | 312933 | https://en.wikipedia.org/wiki/Tenrec | Biology and health sciences | Other afrotheres | Animals | vital_articles |
Tenrecs are small mammals of variable body form. The smallest species are the size of shrews, with a body length of around , and weighing just , while the largest, the common or tailless tenrec, is in length, and can weigh over . Although they may resemble shrews, hedgehogs, or opossums, they are not closely related t... | Tenrec | Wikipedia | 507 | 312933 | https://en.wikipedia.org/wiki/Tenrec | Biology and health sciences | Other afrotheres | Animals | vital_articles |
Tenrecs have a gestation period of 50 to 64 days, and give birth to a number of relatively undeveloped young. While the otter shrews have just two young per litter, the tailless tenrec can have as many as 32, and females possess up to 29 teats, more than any other mammal. Some tenrec species are social, living in multi... | Tenrec | Wikipedia | 510 | 312933 | https://en.wikipedia.org/wiki/Tenrec | Biology and health sciences | Other afrotheres | Animals | vital_articles |
FAMILY TENRECIDAE
Subfamily Geogalinae
Genus Geogale
Large-eared tenrec (Geogale aurita)
Subfamily Oryzorictinae
Genus Microgale
Short-tailed shrew tenrec (Microgale brevicaudata)
Cowan's shrew tenrec (Microgale cowani)
Drouhard's shrew tenrec (Microgale drouhardi)
Dryad shrew tenrec (Microgale dryas)
Pale sh... | Tenrec | Wikipedia | 512 | 312933 | https://en.wikipedia.org/wiki/Tenrec | Biology and health sciences | Other afrotheres | Animals | vital_articles |
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