Natural Sciences


Buoyancy or upthrust is an upward force exerted by a fluid that opposes the weight of an immersed object; it is what makes an object float, sink, or remain neutrally buoyant in the water (or other fluids). The symbol for the magnitude of buoyancy is \(B\) or \(F_B\). As a vector, it must be stated with both magnitude […]

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The taiga (from Russian тайга, tajgà, a term of probable Altaic origin) or boreal forest is one of the main terrestrial biomes, formed by coniferous forests that totally cover the sub-arctic boreal regions of Eurasia and America, constituting one third of the world’s forest mass. From the ecological point of view, it can be defined as a

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Applied physics

The research area of applied physics brings together many expertise, groups, and application areas. Experimental activity focuses primarily on research and development of advanced methods and technologies, targeting both new experimental approaches to fundamental investigation and applications. The activity of the area can be divided into four main parts: It usually differs from engineering in

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Lyoluminescence refers to the emission of light while dissolving a solid into a liquid solvent. It is a form of chemiluminescence. The most common lyoluminescent effect is seen when solid samples which have been heavily irradiated by ionizing radiation are dissolved in water. The total amount of light emitted by the material increases proportionally with the total radiation dose received by the

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The eumetazoa (Eumetazoa, Butschli, 1910) (from the Greek εὖ [eu], good/true + μετά [half], above + ζῷον [zóon], animal), also known as Diploblasts, Epitheliozoa, or Histozoa, represent a subkingdom to which the vast majority of animal organisms belong. In them, the remarkable histological differentiation into true tissues has always suggested a phylogenetic position above the

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Phototropism (from Greek phós, light, and trépestai, to move) is a phenomenon related to the orientation of biological organisms, or part of them, with respect to a light source. It can be positive or negative depending on the direction of the response: positive if in the direction of the light source, negative if in the opposite

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Lamarckism [19th century; named after the biologist J.-B. Lamarck] address developed in biology since 1880 (also called neolamarckism), including a very heterogeneous group of theories of evolution that converged in supporting the heritability of acquired characters, the non-random or accidental origin of evolutionary variations or their strict dependence on environmental conditions. Rather than through a

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Bioluminescence is a type of reaction that involves the emission of electromagnetic radiation in the visible and near infrared, by certain living organisms. Bioluminescence is to be considered a particular case of another phenomenon, luminescence. The latter is characterized by the emission of radiation without the emission of heat. For luminescence to occur, there must be

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Electric displacement field

In physics, electric induction, also called electric displacement field, is a vector field used in electromagnetism to describe the electric polarization of a dielectric material following the application of an electric field. It is a generalization of the electric field used in Maxwell’s equations to describe the effect of polarization charges on the spatial and temporal configuration

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Chemiluminescence, is the emission of electromagnetic radiation, particularly in the visible and near infrared, that can accompany a chemical reaction. Particular type of luminescence that accompanies some chemical reactions, such as the slow oxidation of phosphorus and many organic substances in decomposition. When the phenomenon occurs in living organisms, it is more properly called bioluminescence.

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Gamma ray

In nuclear physics gamma rays, often indicated with the corresponding lower case Greek letter γ, are the electromagnetic radiations produced by radioactive decay of atomic nuclei. They are very high frequency radiations and they are among the most dangerous for man, as all ionizing radiations. The danger derives from the fact that they are high energy

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Candoluminescence is the (archaic) term used to describe the light given off by certain materials which have been heated to incandescence and emit light at shorter wavelengths than would be expected for a typical blackbody radiator. The phenomenon is noted in certain transition metal and rare earth metal oxide materials (ceramics) such as zinc oxide and cerium oxide or thorium dioxide, where some of the light from incandescence causes fluorescence of the material.

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Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state; this transformation occurs with heat acquisition and is, therefore, an endothermic process. Usually, in normal environmental conditions, to pass from solid to gaseous state it is necessary to go through the liquid state. Under certain pressure conditions, as the

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Airglow or nocturnal luminescence is a weak light emission from the Earth’s atmosphere; as a result, the night sky is never completely dark. It was first noticed in 1868 by Anders Jonas Ångström and it is caused by a set of processes in the upper layers of the atmosphere, such as the recombination of ions that

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In physics, refraction (from medieval Latin refractio-onis, from refractus, refracted) is the change in direction of a wave passing from one medium to another or from a gradual change in the medium with a different refractive index (\(n\)). In optics, the refractive index or index of refraction of a material is a dimensionless number that describes how fast light

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Acoustic refraction

The speed of propagation of sound waves can change either due to changes in temperature or due to changes in the molecular weight of the gas in which propagation occurs. The first effect is the one that occurs in practice: going to higher altitudes of the atmosphere the temperature decreases, then decreases the speed of

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By nature (word borrowed from the old French nature and is derived from the Latin word natura, or “essential qualities, innate disposition”, and in ancient times, literally meant “birth”) is meant the universe considered in the totality of the phenomena and forces manifested in it, from those of the physical world to those of life in general. The total system of living beings,

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A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different (but equally specific) wavelength. The amount and wavelength of the emitted energy depend on

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Weak interaction

The weak interaction, which is also often called the weak force or weak nuclear force, is responsible for some nuclear phenomena such as beta decay of the atomic nuclei associated with radioactivity and acts between leptons and quarks (semileptonic interactions), between only leptons (leptonic interactions) and between only quarks (non-leptonic interactions) through the exchange of massive vector bosons called

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Thermogenesis is a particular metabolic process that consists in the production of heat by the body, especially in adipose and muscle tissue. Metabolism, and therefore also the extent of thermogenesis, depends among other things on genetic factors and can therefore vary from individual to individual. These factors also influence the amount of so-called brown adipose tissue

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Electrochemiluminescence or electrogenerated chemiluminescence (ECL) is a kind of luminescence produced during electrochemical reactions in solutions. In electrochemiluminescence, electrochemically generated intermediates undergo a high degree of exergonic reaction to produce an electronically excited state and then emits light when relaxed to a lower energy level. This wavelength of emitted photons corresponds to the energy gap between these two states. ECL

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Luminous intensity

Luminous intensity is a physical quantity whose unit of measurement in the International System is the candela. The luminous intensity (I_{textrm{V}}) of a point source in a given direction in the unit solid angle is the luminous flux. It belongs, among other groupings of physical quantities, to the group of photometric quantities. In other words, the

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Protostome [protostomia]

Protostomia (/ˌproʊtəˈstoʊmi.ə/) is the clade of animals once thought to be characterized by the formation of the organism’s mouth before its anus during embryonic development. This nature has since been discovered to be extremely variable among Protostomia’s members, although the reverse is typically true of its sister clade, Deuterostomia.[1][2] Some examples of protostomes are nematodes,

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Biological tissue

A biological tissue is an ensemble of similar cells and their extracellular matrix, characterized by similar structure and functions. Tissues represent the next level of organization after cellular organization; in practice, they are formed by cells of the same type that associate together to perform a common function. Each tissue therefore possesses one or more of its

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