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Stratification
Stratification may refer to: Mathematics * Stratification (mathematics), any consistent assignment of numbers to predicate symbols * Data stratification in statistics Earth sciences * Stable and unstable stratification * Stratification, or stratum, the layering of rocks * Stratification (archeology), the formation of layers (strata) in which objects are found * Stratification (water), the formation of water layers based on temperature (and salinity, in oceans) * Lake stratification, the formation of water layers based on temperature, with mixing in the spring and fall in seasonal climates. * Atmospheric stratification, the dividing of the Earth's atmosphere into strata * Inversion (meteorology) Social sciences * Social stratification, the dividing of a society into levels based on power or socioeconomic status Biology * Stratification (seeds), where seeds are treated to simulate winter conditions so that germination may occur * Stratification (clinical trials), partitioning of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Social Stratification
Social stratification refers to a society's categorization of its people into groups based on socioeconomic factors like wealth, income, race, education, ethnicity, gender, occupation, social status, or derived power (social and political). As such, stratification is the relative social position of persons within a social group, category, geographic region, or social unit. In modern Western societies, social stratification is typically defined in terms of three social classes: the upper class, the middle class, and the lower class; in turn, each class can be subdivided into the upper-stratum, the middle-stratum, and the lower stratum. Moreover, a social stratum can be formed upon the bases of kinship, clan, tribe, or caste, or all four. The categorization of people by social stratum occurs most clearly in complex state-based, polycentric, or feudal societies, the latter being based upon socio-economic relations among classes of nobility and classes of peasants. Whether socia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (water)
Stratification is the separation of water in layers. Two main types of stratification of water are uniform and layered stratification. Layered stratification occurs in all ocean basins. Stratified layers act as a barrier to the mixing of water, which impacts the exchange of heat, carbon, oxygen and other nutrients. Due to upwelling and downwelling, which are both wind-driven, mixing of different layers can occur through the rise of cold nutrient-rich and warm water, respectively. Generally, layers are based on water density: heavier, and hence denser, water is below the lighter water, representing a stable stratification. For example, the pycnocline is a layer in the ocean where the change in density is relatively large compared to that of other layers in the ocean. The thickness of the thermocline is not constant everywhere and depends on a variety of variables. Between 1960 and 2018, upper ocean stratification increased between 0.7-1.2% per decade. This means that the differenc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Stratification
Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers, the Epilimnion comprising the top warm layer, the thermocline (or Metalimnion): the middle layer, which may change depth throughout the day, and the colder Hypolimnion extending to the floor of the lake. Definition The thermal stratification of lakes refers to a change in the temperature at different depths in the lake, and is due to the density of water varying with temperature. Cold water is denser than warm water and the epilimnion generally consists of water that is not as dense as the water in the hypolimnion. However, the temperature of maximum density for freshwater is 4 °C. In Temperate climate, temperate regions where lake water warms up and cools through the seasons, a cyclical pattern of overturn occurs that is repeated from year to year as the cold dense water at the top of the lake sinks (see stab ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stable And Unstable Stratification
Stable stratification of fluids occurs when each layer is less dense than the one below it. Unstable stratification is when each layer is denser than the one below it. Buoyancy forces tend to preserve stable stratification; the higher layers float on the lower ones. In unstable stratification, on the other hand, buoyancy forces cause convection. The less-dense layers rise though the denser layers above, and the denser layers sink though the less-dense layers below. Stratifications can become more or less stable if layers change density. The processes involved are important in many science and engineering fields. Destablization and mixing Stable stratifications can become unstable if layers change density. This can happen due to outside influences (for instance, if water evaporates from a freshwater lens, making it saltier and denser, or if a pot or layered beverage is heated from below, making the bottom layer less dense). However, it can also happen due to internal diffusi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (seeds)
In horticulture, stratification is a process of treating seeds to simulate natural conditions that the seeds must experience before germination can occur. Many seed species have an embryonic dormancy phase, and generally will not sprout until this dormancy is broken. The term stratification can be traced back to at least 1664 in ''Sylva, or A Discourse of Forest-Trees and the Propagation of Timber'', where seeds were layered (stratified) between layers of moist soil and exposing these strata to winter conditions. Thus, stratification became the process by which seeds were artificially exposed to conditions to encourage subsequent germination. Cold stratification Cold stratification is the process of subjecting seeds to both cold and moist conditions. Seeds of many trees, shrubs and perennials require these conditions before germination will ensue. In the wild In the wild, seed dormancy is usually overcome by the seed spending time in the ground through a winter period and having ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (mathematics)
Stratification has several usages in mathematics. In mathematical logic In mathematical logic, stratification is any consistent assignment of numbers to Predicate (logic), predicate symbols guaranteeing that a unique formal Interpretation (logic), interpretation of a logical theory exists. Specifically, we say that a set of Clause (logic), clauses of the form Q_1 \wedge \dots \wedge Q_n \wedge \neg Q_ \wedge \dots \wedge \neg Q_ \rightarrow P is stratified if and only if there is a stratification assignment S that fulfills the following conditions: # If a predicate P is positively derived from a predicate Q (i.e., P is the head of a rule, and Q occurs positively in the body of the same rule), then the stratification number of P must be greater than or equal to the stratification number of Q, in short S(P) \geq S(Q). # If a predicate P is derived from a negated predicate Q (i.e., P is the head of a rule, and Q occurs negatively in the body of the same rule), then the stratification ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Population Stratification
Population structure (also called genetic structure and population stratification) is the presence of a systematic difference in allele frequencies between subpopulations. In a randomly mating (or ''panmictic'') population, allele frequencies are expected to be roughly similar between groups. However, mating tends to be non-random to some degree, causing structure to arise. For example, a barrier like a river can separate two groups of the same species and make it difficult for potential mates to cross; if a mutation occurs, over many generations it can spread and become common in one subpopulation while being completely absent in the other. Genetic variants do not necessarily cause observable changes in organisms, but can be correlated by coincidence because of population structure—a variant that is common in a population that has a high rate of disease may erroneously be thought to cause the disease. For this reason, population structure is a common confounding variable in medi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (linguistics)
In linguistics, stratification refers to the idea that language is organized in terms of hierarchically ordered strata (such as phonology, morphology, syntax, and semantics). This notion can be traced back to Saussure's dichotomy between signified and signifier and Hjelmslev's expression plane and content plane, but has been explicictly explored as a theoretical concept in stratificational linguistics and systemic functional linguistics. Gleason, H. 1964. The organization of language: a stratificational view. In Stuart, C. (ed.), ''Report of the Fifteenth Annual (First International) Round Table Meeting on Linguistics and Language Studies'' (Monograph Series on Languages and Linguistics, 17). Washington: Georgetown University Press, 75–95. In systemic functional linguistics In systemic functional linguistics, stratification is one of the global semiotic dimensions that define the organization of language in context, alongside instantiation and metafunction. Stratification or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (archeology)
Stratigraphy is a key concept to modern archaeological theory and practice. Modern excavation techniques are based on stratigraphic principles. The concept derives from the geological use of the idea that sedimentation takes place according to uniform principles. When archaeological finds are below the surface of the ground (as is most commonly the case), the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation. It is the archaeologist's role to attempt to discover what contexts exist and how they came to be created. Archaeological stratification or sequence is the dynamic superimposition of single units of stratigraphy, or contexts. Contexts are single events or actions that leave discrete, detectable traces in the archaeological sequence or stratigraphy. They can be deposits (such as the back-fill of a ditch), structures (such as walls), or "zero thickness surfaciq ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Destratification (other) , mixing water to eliminate stratified layers of temperature, plant, or animal life
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Destratification may refer to: * Thermal destratification, mixing air to reduce stratified layers of heat that become trapped near the ceiling in buildings * Lake stratification Lake stratification is the tendency of lakes to form separate and distinct thermal layers during warm weather. Typically stratified lakes show three distinct layers, the Epilimnion comprising the top warm layer, the thermocline (or Metalimnion) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratification (vegetation)
Stratification in the field of ecology refers to the vertical layering of a habitat; the arrangement of vegetation in layers. It classifies the layers (sing. ''stratum'', pl. ''strata'') of vegetation largely according to the different heights to which their plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ... grow. The individual layers are inhabited by different animal and plant community (ecology), communities (stratozones). Vertical structure in terrestrial plant habitats The following layers are generally distinguished: forest floor (root and moss layers), herbaceous plant, herb, shrub, understory and canopy (trees), canopy layers. These vegetation layers are primarily determined by the height of their individual plants, the different elements may however have a range of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atmospheric Stratification
The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for liquid water to exist on the Earth's surface, absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation). By mole fraction (i.e., by number of molecules), dry air contains 78.08% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1% at sea level, and 0.4% over the entire atmosphere. Air composition, temperature, and atmospheric pressure vary with altitude. Within the atmosphere, air suitable for use in photosynthesis by terrestrial plants and breathing of terrestrial animals is found only in E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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