Encyclopedia

Brain

The brain is the largest and most specialized portion of the encephalon. Vital organ of the central nervous system, the brain takes its place in the skull, above other nerve structures, also of the encephalon and always very important for life, such as the diencephalon, the brainstem and the cerebellum. The brain is composed of …

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Connective tissue

Connective tissues are defined as such because of their function to connect, functionally and structurally, other tissues within the body. They provide structural and metabolic support to other tissues, which is why the term “support tissue” has been proposed. They are also considered to be tissues with trophic function (in that through them nutrient exchanges …

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Water

Water is essential to life as we know it. Water is one of the more abundant molecules and the one most critical to life on Earth. Water comprises approximately 60-70% of the human body. Without it, life as we know it simply would not exist. The polarity of the water molecule and its resulting hydrogen …

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Neutron

The neutron is an uncharged, subatomic particle \((\sim 10^{-15}\;\textrm{m})\) consisting of an up quark and two down quarks, with a net electric charge equal to zero, located in the nucleus of an atom. As it consists of quarks, it belongs to the family of hadrons and in particular to the group of baryons. Having half-integer spin is …

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Froude number

The Froude number (Fr) is a dimensionless number that relates the force of inertia and the force of weight. It owes its name to the English hydrodynamic engineer and naval architect William Froude (1810 – 1879). Froude number has an important kinematic meaning because depending on the value that it assumes a current can be …

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Bone marrow

Bone marrow, in humans, is the principal hematopoietic organ; it is a soft, nutrient-rich, spongy tissue that occupies the canals of the long bones and the central fascia of the flat bones. Under normal conditions it performs a primary function in the production, maturation, and destruction of blood cells. The production of blood cells depends …

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Gas

Gas is aeriform whose temperature is higher than the critical temperature; as a result, gases cannot be liquefied without first being cooled, unlike vapors. Gas is a fluid that has no volume of its own (tends to occupy all the volume at its disposal) and that is easily compressible. A gas is one of the four …

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Threshold of hearing

The hearing threshold is the sound level below which a person’s ear is unable to detect any sound. For adults, 0 dB is the reference level. Sound level measurements in decibels are generally referenced to a standard threshold of hearing at 1000 Hz for the human ear which can be stated in terms of sound intensity: \[I_0=10^{-12}\;\dfrac{\textrm{W}}{\textrm{m}^2}=10^{-16}\;\dfrac{\textrm{W}}{\textrm{cm}^2}\] …

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Woodcut

Woodcut, a type of relief printing, is the oldest printmaking technique, and the only one traditionally used in the Far East, in which knives and other tools are used to carve a design into the surface of a wooden block. It was probably first developed as a means of printing patterns on cloth, and by the 5th …

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Electric current

Dynamic electricity, or electric current, is the uniform motion of electrons through an electrical conductor. Static electricity is an unmoving, accumulated charge formed by either an excess or deficiency of electrons in an object. Although it is electrons which are the mobile charge carriers that are responsible for electric current in conductors, it has long been the convention to …

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Physiology

Physiology (from the greek φύσις, physis, ‘nature’, and λόγος, logos, ‘speech’, then ‘study of natural phenomena’) is the branch of biology that studies the functioning of living organisms, analyzing the chemical and physical principles of the functioning of living beings, whether single or multi-cellular, animals or plants. A “physiological condition” is a state in which …

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Absolute

Absolute means not limited by exceptions or conditions. What does not depend on another for its existence, therefore opposed to “conditioned,” “dependent,” and does not exclude the relationship for which another would depend on it. The term is used in many different ways in mathematics, physics, philosophy, and everyday speech. Etymologically, the term absolute derives from …

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Allergy

Allergies, also known as allergic diseases, are a number of conditions caused by hypersensitivity of the immune system to typically harmless substances in the environment. Allergy is an excessive response by the immune system to contact with an external substance considered harmful (allergen). Examples are pollen or the hair of certain animals. Allergy indicates a …

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Predation

Predation is a type of interaction in which one organism uses another organism of a different species as a food source. This is referred to as prey in both the animal and plant kingdoms. Through predation, predators are able to play a key role in the food chain, keeping prey populations in check and aiding …

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Matter

The matter is any substance (composed of various types of particles) that has mass, inertia, and occupies physical space by having volume. This definition, adequate for macroscopic physics, the object of study of mechanics and thermodynamics, does not fit well with modern theories in the microscopic realm, proper to atomic and subatomic physics. In physics, …

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Solid-state chemistry

Solid-state chemistry, also sometimes referred as materials chemistry, is the study of the synthesis, structure, and properties of solid phase materials, particularly, but not necessarily exclusively of, non-molecular solids. Historically, the origin of solid state chemistry can be traced back to the use of experimental techniques for the characterization of minerals, and therefore to the …

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Solid

A solid is a state of matter in which atoms or molecules are tightly bound together by powerful forces thereby creating a rigid body (with a defined geometric shape and volume). In other words, a solid is a material object that is in a condensed state characterized by resistance to deformation and changes in volume. The branch …

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Comparative history

Comparative history presents itself as a discipline that, by analyzing similarities and differences between two or more historical phenomena, seeks to give, with respect to specific issues, general descriptions, explanations and interpretations of historical facts and processes. With the emergence of the comparative method, autonomous disciplines such as comparative anatomy, comparative law, comparative literature, and …

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Sociobiology

Sociobiology is a current in sociology that emerged in the first half of the 1970s as a direct result of the crisis of functionalism. Scientific field, associated primarily with the thought and work of E. O. Wilson, who succinctly defined it as “the systematic study of all social behavior.” That is, sociobiology strives to explain …

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Semiotics

Semiotics (from the Greek word σημεῖον semeion, meaning “sign”) is the discipline that studies signs and how they make sense (signification). A sign is generally something that refers to something else (for medieval philosophers aliquid stat pro aliquo), and semiotics is the discipline that studies the phenomena of signification. Signification means any relation that links …

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Social psychology

Social psychology is a branch of psychology that studies the interaction between the individual and social groups. The earliest study of social psychology can be considered The Psychology of Peoples (Völkerpsychologie) by Wilhelm Wundt, from 1900 and 1920. However, it established itself as a discipline in its own right in the U.S. from the early …

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Psychiatry

Psychiatry is the specialized branch of medicine concerned with the experimental study, prevention, treatment and rehabilitation of mental disorders. It can be defined as a “synthesis discipline,” in that the maintenance and pursuit of mental health, which is the fundamental purpose of psychiatry, is achieved by taking into consideration various fields: medical-pharmacological, neurological, psychological, sociological, …

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Drama

Drama (from the Greek δρᾶμα, “drama” = action, history) is literature intended for performance. The form is often combined with music and dance, as in opera and musical theatre, or on radio or television. In the broadest sense it is a narrative plot completed and intended for theatrical performance. It can be in written verbal …

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Statistics

Statistics is a discipline that has as its goal the quantitative and qualitative study of a particular collective phenomenon under conditions of uncertainty or non-determinism, that is, not complete knowledge of it or of a part of it. Based on the collection of a large number of data relating to the phenomena under consideration, and …

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Brazing

Brazing is a method of joining two pieces of metal (but also to ceramics) in which a non-ferrous alloy (the braze alloy) is introduced in a liquid state between the pieces of metal to joining allowed to solidify. It is an alternative to welding. Brazing differs from welding in that it does not involve melting …

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Heart

The heart is a muscular organ, which constitutes the motor center of the circulatory system and propeller of blood and lymph in several animal organisms, including humans, in which it is formed by a particular tissue, the myocardium, and is covered by a membrane, the pericardium. Most primitive worms do not possess a circulatory system: …

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Analogy

In philosophy, analogy denotes a relationship of similarity between two entities, called analogues, such that from the equality or similarity observed between some elements of these entities, the equality or similarity of all their other elements can also be deduced. More generally, in common usage, analogy is the relationship that the mind grasps between two …

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Hydrocarbon

Hydrocarbons are organic molecules consisting entirely of carbon and hydrogen, such as methane (CH4). The many covalent bonds between the atoms in hydrocarbons store a great amount of energy, which releases when these molecules burn (oxidize). Methane is the simplest hydrocarbon molecule, with a central carbon atom bonded to four different hydrogen atoms. The shape of its electron orbitals …

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Alice in Wonderland syndrome

Alice in Wonderland syndrome (AIWS), also known as Todd’s syndrome or Lilliputian hallucinations, is a neurological disorder that affects visual perception. Affected patients experience different types of dimensional and morphological distortions, including micropsia and macropsia. The disorder may be temporary when associated with migraine headaches, seizures, brain tumors, and psychoactive drug use. It may also …

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Reason

The reason is the capacity of consciously making sense of things, judgments, applying logic, and adapting or justifying practices, institutions, and beliefs based on new or existing information. It is closely associated with such characteristically human activities as philosophy, science, language, mathematics, and art, and is normally considered to be a distinguishing ability possessed by humans. The reasoning is a …

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Impedance

Impedance is the complex-valued generalization of resistance. It may refer to: Acoustic impedance: a constant related to the propagation of sound waves in an acoustic medium. Electrical impedance: the ratio of the voltage phasor to the electric current phasor, a measure of the opposition to time-varying electric current in an electric circuit. High impedance, when only …

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Wave impedance

The wave impedance of an electromagnetic wave is the ratio of the transverse components of the electric and magnetic fields (the transverse components being those at right angles to the direction of propagation). If the electric field strength is expressed in volts per meter and the magnetic field strength is expressed in ampere-turns per meter, the wave …

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Electrical impedance

Electrical impedance is a physical quantity that represents the opposition force of a circuit to the passage of alternating electric current, or, more generally, of a variable current. In other words, is the amount of opposition that an electrical element offers to current flow in a circuit when a voltage is applied at a specific frequency. …

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Acoustic impedance

Acoustic impedance and specific acoustic impedance are measures of the opposition that a system presents to the acoustic flow resulting from an acoustic pressure applied to the system. The SI unit of acoustic impedance is the pascal second per cubic metre (Pa·s/m3). There is a close analogy with electrical impedance, which measures the opposition that a system presents …

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Temperature

Temperature is a physical property of a material that gives a measure of the average kinetic energy of the molecular movement in an object or a system. Temperature can be defined as a condition of a body by virtue of which heat is transferred from one system to another. It is pertinent to mention here …

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Critical temperature

The critical temperature finds definitions in different areas; in the case of fluid transition is defined as the critical temperature, the temperature above which a substance can not exist in a liquid state (not even being subjected to compression). In the case of the superconducting transition, it is defined as the critical temperature, the temperature below which the material …

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Temperature gradient

The temperature gradient is a physical quantity that describes in which direction and at what rate the temperature changes the most rapidly around a particular location. It is normally negative in the lower atmosphere; that is, the temperature decreases with height under normal atmospheric conditions. In physics, the temperature gradient is a physical quantity used to describe the …

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Mass

The mass (or inertial mass, from Greek: μᾶζα, máza, barley cake, lump of dough) is a physical quantity that represents the amount of matter proper to material bodies that determines their dynamic behavior when subjected to the influence of external forces. In classical mechanics the term mass can refer to three different scalar physical quantities, distinct from each other: …

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Negative mass

In theoretical physics, negative mass is a hypothetical concept of matter whose mass has a negative sign relative to ordinary (positive) matter, e.g.: -2 kg. Such type of matter violates one or more conditions of energy and exhibits special properties, arising from the ambiguity of how attraction should refer to force or acceleration oriented opposite …

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Immunology

Immunology is a branch of biology that deals with the immune system, studying aspects of the host’s defenses against infection and the adverse consequences of immune responses. Thus, immunology deals with the physiological functions of the immune system (and its components) both during an illness and in a healthy condition, as well as malfunctions of …

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Glass

The glass is a non-equilibrium, non-crystalline condensed state of matter that exhibits a glass transition. The structure of glasses is similar to that of their parent supercooled liquids (SCL), and they spontaneously relax toward the SCL state. Their ultimate fate, in the limit of infinite time, is to crystallize. Glasses are also known as amorphous solids. The boundary between the …

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Atmosphere

The atmosphere (from ancient Greek ἀτμός, atmòs, “vapor” and σφαῖρα, sphàira, “sphere”) is a layer or a set of layers of gases (whose molecules are held in place by the force of gravity of the body itself) surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere …

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Positivism

Positivism is a philosophical and cultural movement, born in France in the first half of the nineteenth century by A. Comte. and inspired by some fundamental guiding ideas generally referred to the exaltation of scientific progress. This current of thought, driven by the industrial revolutions and literature related to it, spread in the second half …

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Motivation

Motivation is a process that initiates, guides, and maintains purposeful behavior. It is the stimulus, whether conscious or unconscious, for action aimed in the direction of achieving a desired goal (whether biological or social in nature). Motivation is everything that gives purpose to a behavior. In psychology we speak of primary motivations to indicate those …

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Thermodynamic system

A thermodynamic system is a defined quantity of matter, or a defined portion of space (geometrically delimited). This system is delimited by surfaces (or walls or boundaries), also known as control surfaces; everything that is external to the system, and is able to interact with it, is called an environment. The control surface of a thermodynamic system represents the …

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Biotechnology

Biotechnology (from the Greek βίος, bìos = “life”, τέχνη, téchne = “art”, in the sense of “expertise”, “knowing how to do”, “knowing how to operate”, and λόγος, lògos = “study”) is a new and sometimes controversial branch of biology concerning ’the use of living beings in order to obtain goods or useful services to satisfy the needs …

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Galileo Galilei

Galileo di Vincenzo Bonaiuti de’ Galilei (/ˌɡælɪˈleɪoʊ ˌɡælɪˈleɪiˌ/ , Italian: [ɡaliˈlɛːo ɡaliˈlɛi]; Pisa, February 15, 1564 – Arcetri, January 8, 1642) was an Italian physicist, astronomer, philosopher, mathematician, writer and academic, considered the father of modern science. Key figure in the scientific revolution, for having explicitly introduced the scientific method (also called “Galilean method” or …

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Light

The term light (from Latin lux) refers to the portion of the electromagnetic spectrum visible to the human eye, between 400 and 700 nanometers in wavelength, or between 790 and 434 THz in frequency. This interval coincides with the center of the spectral region of light emitted by the Sun that manages to reach the …

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Bioinformatics

Bioinformatics is an interdisciplinary research area concerned with developing new algorithms, methodologies, and software tools for the analysis of biological data. Bioinformatics combines computer science, statistics, mathematics and engineering to study and extract new knowledge from biological data. With the introduction of technology called high throughput, it has become a vital part of many areas …

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Mineralogy

Mineralogy is the science that studies the chemical composition, crystal structure, and physical characteristics (e.g., hardness, magnetism, and optical properties) of minerals, as well as their genesis, transformation, and use by humans. The classification and nomenclature of minerals is codified by the International Mineralogical Association (IMA), composed of various organizations representing mineralogists in different countries. …

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Sculpture

Sculpture is the art of giving shape to an object starting from a raw material or assembling different materials together. The term sculpture also refers to the final product, which is any three-dimensional object obtained as an expression of artistic inspiration. Like many other terms in the art world, the concept of sculpture has evolved …

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Graphene

Graphene is a material consisting of a monoatomic layer of carbon atoms (i.e., having a thickness equivalent to the size of a single atom). It has the theoretical strength of diamond and the flexibility of plastic. As suggested by the ending –ene of the name, the atoms are hybridized in the form sp2, and are …

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Love

The word love can mean a wide variety of different feelings and attitudes, ranging from a more general form of affection to a strong feeling that expresses itself in interpersonal attraction and attachment, a passionate dedication between people or, in its extended meaning, a deep inclination towards something. It can also be a human virtue …

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Polymer

Polymers (from the Greek poly and meros, “many parts”) are made up of macromolecules that form natural or synthetic substances generally of organic type. The macromolecules that make up polymers are of high size and weight, similar to each other (but not necessarily identical), in turn formed by a repetition of structural units (molecular groups …

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Fluoropolymer

Fluoropolymers are polymeric materials containing fluorine atoms bonded to carbon atoms in their structure. They have high resistance to chemical agents such as organic solvents, acids and inorganic bases. The different starting monomers contribute to the diversification of fluoropolymers and their respective properties. When all hydrogen atoms are substituted with fluorine we have perfluorinated polymers. …

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Heterocyclic compound

A heterocyclic compound is a cyclic molecule in which one or more of the ring atoms are heteroatoms, that is, atoms other than carbon. The most common heteroatoms are: nitrogen, oxygen, sulfur, boron, phosphorus. Each of them gives rise to large families of heterocyclic compounds. Pyridine and pyrimidine are heterocyclic analogs of benzene, glucose in …

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Amine polymer

Amine polymers are polymers that contain amino groups inserted in the main chain or substituting one or more hydrogen atoms of the same chain. Among the amino polymers of the first type we can mention polyethylenediamine and polymethylenamine, while among the polymers of the second type, that is among the polymers with amino groups as …

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Polyamide

Polyamides (PA) are macromolecules characterized by the CO-NH amide group, on which many properties of this type of compounds depend. Polyamides can be synthesized by condensation polymerization of a dicarboxylic acid and a diamine or by ring-opening polymerization of a lactam. The characteristics of the individual types of polyamide do not differ much: relatively low …

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Allyl

In chemistry, the allyl (or allyl group) is a functional group corresponding to a propylene deprived of a hydrogen atom, having formula: CH2=CH-CH2– This functional group causes a resonance phenomenon, which gives it greater stability. Compounds containing an allyl are called allyl compounds. Examples of compounds containing the allyl group are: allyl sulfide allyl isothiocyanate …

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Thermosetting polymer

Thermosetting polymers (or thermosetting resins) belong to the group of plastic materials; they are particular polymers that, after an initial softening phase due to heating, harden due to the effect of three-dimensional cross-linking; during the softening phase due to the combined effect of heat and pressure they are deformable and once hardened they are very …

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Thermoplastic

Thermoplastics (or thermoplastic polymers or thermoplastic resins) are those plastic materials that acquire malleability, that is, they soften under the action of heat. At this stage they can be molded or formed into finished objects and then by cooling they become rigid again. This process, theoretically, can be repeated several times according to the qualities …

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Acrylic polymers

Acrlic polymers are synthetic resins made from the polymerization of the esters of acrylic acid CH2=CHCOOH (2-propenoic acid), methacrylic acid CH2=C(CH3)COOH (2-methylpropenoic acid) or their esters. The most common acrylic polymers are polymethylacrylate and polyethylacrylate and are used to make paints, surface coatings, adhesives and in textiles. Acrylic acid or 2-propenoic acid is obtained from …

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Biopsychology [behavioral neuroscience]

Behavioral neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behavior in humans and other animals. While biological psychology is a broad field, many biological psychologists want to understand how the structure and function of the nervous system are related …

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Psychology

Psychology is the social science that studies mental states and its emotional, cognitive, social, and behavioral processes in their conscious and unconscious components, through the use of the scientific method and/or relying on a subjective intrapersonal perspective. It also deals with the study and treatment of psychic functions both in conditions of well-being and suffering or mental …

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Evolutionary psychology

Evolutionary psychology, and specifically, the evolutionary psychology of humans, has enjoyed a resurgence in recent decades. To be subject to evolution by natural selection, the behavior must have a significant genetic cause. In general, we expect all human cultures to express a behavior if it is caused genetically since the genetic differences among human groups are …

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Human geography

Anthropogenic geography, also called human geography or anthropogeography, is the science devoted to the analysis of the distribution, location and spatial organization of human events. This science is composed of a synchronic aspect, i.e., the analysis of human organizational designs present in the world at a given time, and a diachronic aspect, i.e., the analysis …

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Genetics

Genetics (from ancient Greek γενετικός, ghenetikós, “relating to birth,” from γένεσις ghénesis, “genesis, origin”) is the branch of biology that studies genes, heredity and genetic variability in living organisms. The field of study of genetics thus focuses on understanding the mechanisms underlying these phenomena, which have been known since antiquity, along with embryology, but were …

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Epistemology

Epistemology (from the ancient Greek ἐπιστήμη, epistème, “certain knowledge i.e. science” and λόγος, logos, “discourse”) is that branch of philosophy that deals with the conditions under which scientific knowledge can be had and the methods of attaining such knowledge. Epistemology can be considered a part of the philosophy of science, the discipline that in addition …

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Econometrics

In economics, econometrics is the use of mathematical and statistical methods to produce models to test the validity of assumptions about economic policy. Econometrics is now a branch of economic science; but to know it thoroughly, one must keep in mind that in its time it was also a movement advocating a new direction of …

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Demography

Demography (from Ancient Greek δῆμος (dêmos) ‘people, society’, and -γραφία (-graphía) ‘writing, drawing, description’) is the science concerned with the study of human populations, dealing with their amount, composition, development, and general characters, considered mainly from a quantitative point of view. Given its quantitative character, demography is based on multiple statistical indices. Modern demography was …

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Ethnology

Ethnology (from the Greek: ἔθνος, ethnos meaning ‘nation’) is a branch of anthropology concerned with studying and comparing populations currently existing in the world. Interdisciplinary science that studies every aspect of human societies, essentially those that have not expressed their own forms of written literature. Compared to cultural anthropology, ethnology has traditionally made greater use …

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Ethology

Ethology, or behavioral biology, is the branch of biology and zoology that studies animal behavior. The term “ethology” (from the greek ethos and logos, meaning “character or custom” and “study”) indicates in fact the modern scientific discipline that studies the behavioral expression of animals in their natural environment (including humans), following the same criteria with …

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Ecology

Ecology (from Greek: οἶκος, “house“, or “environment“; -λογία, “study of“) is a branch of biology that study the distribution and abundance of living organisms and how the distribution and abundance are affected by interactions between the organisms and their environment. The environment of an organism includes both physical properties, which can be described as the sum of local …

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Sociology

Sociology is the study of groups and group interactions, societies, and social interactions, from small and personal groups to very large groups. A group of people who live in a defined geographic area, who interact with one another, and who share a common culture is what sociologists call a society. Sociologists study all aspects and levels …

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History

History is the discipline that deals with the study of the past through the use of sources, that is, documents, testimonies and stories that can transmit knowledge. More precisely, history is the research on the facts of the past and the attempt of a continuous and systematic narration of the same facts, as they are …

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Biology

Biology (from the Ancient Greek words of βίος; romanized bíos meaning “life” and -λογία; romanized logía (-logy) meaning “branch of study” or “to speak”) is the study of life, that is, the physical and chemical processes of the phenomena that characterize living systems, including their biochemistry, molecular mechanisms, genetics, anatomy, physiology, as well as emerging processes …

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Infrared

In physics, infrared (IR) or infrared radiation (first discovered in 1800 by astronomer William Herschel) is the electromagnetic radiation with a frequency band of the electromagnetic spectrum lower than that of visible light but greater than that of radio waves, i.e. wavelength between 700 nm and 1 mm (infrared band). The range of Infrared region is 12800 ~ …

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International law

International law, that is, the order of the international community, reveals its structural characteristics through the principles relating to subjects, sources, ways of settling disputes, and means of ensuring compliance with the rules. International law relates to the policies and procedures that govern relationships among nations (Clarkson, Miller, & Cross, 2018). These are crucial for businesses …

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Law

In the legal lexicon, law is the set of legal norms present in a legal system and/or the legal rules governing a particular discipline, but also a synonym for power or faculty. By extension it also indicates the science that studies legal norms and legal sources; still other meanings may derive from detailed phraseologies. In …

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Radical

In chemistry, a radical (or free radical) is defined as a highly reactive molecular entity with a very short half-life, consisting of an atom or a molecule formed by several atoms, which has an unpaired electron: this electron makes the radical extremely reactive, able to bind to other radicals or to subtract an electron from …

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Philosophy

Philosophy can be defined as a form of knowledge that, despite the wide variety of its expressions, exhibits as almost constant characteristics two vocations: one towards universality and one towards the prescription of wisdom. The former manifests itself in two ways: philosophy is presented as the perfect form of knowledge, in any case as the …

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Disgust

Ekman (1992) defines the emotion of disgust as “experiencing a feeling that motivates, organizes, and guides the perception of thoughts and actions.” In the course of evolution, in fact, emotions have developed to provide new types of motivation and incentive for action to meet the demands of the external environment. In addition, the emotion (in …

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Honey bee

Honey bees are mostly grouped in a genus Apis. However within the family ‘Apinae’ are stingless bees, part of the Meliponini tribe. These bees are different from honey bees producing less abundant but more liquid-based honey. This type of honey, produced by stingless honey bees, is traditionally used more for medicinal purposes. Classification of honey …

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Geometry

Geometry began as a systematic study of physical space and the shapes that move in it. The space in which we move is for everyone one of the first experiences we have from the first months of life. Our senses determine the sensations that allow us to recognize the shapes of objects and their movements. …

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Mathematics

Mathematics (from the Greek μάθημα (máthema), which can be translated as “science”, “knowledge”, or “learning”; μαθηματικός (mathematikós) means “inclined to learn”) is the discipline that studies quantities, numbers, space, structures, and calculations. The term mathematics usually refers to the discipline (and its body of knowledge) that studies problems involving quantities, spatial extensions and figures, movements …

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Neurologist

The neurologist is the physician who specializes in the diagnosis, treatment, and management of diseases and injuries involving the nervous system. The neurologist has many skills: he/she is highly trained in the anatomy and physiology of the nervous system; he/she knows the diseases of the nervous system, the methods of investigation to diagnose them and …

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Electromyography

Electromyography (EMG), electroneurography (ENG) and single fiber electromyography (SFEMG) are neurophysiological methods that are used to study the peripheral nervous system (PNS) from a functional point of view. It represents a reliable method that can give information about the functionality of peripheral nerves and skeletal muscles. It is also a diagnostic tool that allows to …

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Drift

In metrology, drift can be defined as the variation caused in the output of an instrument, which is not caused by any change in the input. Drift in a measuring instrument is mainly caused by internal temperature variations and lack of component stability. It also represents a static characteristic of an instrument. A change in the zero output of …

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Accelerometer

An accelerometer is a measuring instrument able of detecting and/or measuring acceleration (or the gravitational force), calculating the force measured with respect to the mass of the object (force per unit of mass). Therefore the operating principle of an accelerometer is based on the detection of the inertia of a mass when it is subjected to an …

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Gravimeter

The gravimeter is a particular type of accelerometer specifically designed to measure the acceleration of gravity. According to the equivalence principle of general relativity, the effects of gravity and acceleration are the same; therefore, an accelerometer cannot distinguish between the two cases. As gravimeters, it is possible to use improved versions of accelerometers for static measurements, in …

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Error band

The error band is a worst-case error measurement. This is the best specification (with respect to linearity) for determining the suitability of the measuring device for an application. The range of maximum deviation of the transducer output from a reference curve due to the transducer is defined as error band; said deviation (which is generally expressed …

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Rapidity error

In metrology, the error of rapidity is that metrological quality of a measuring instrument that expresses the ability to follow the (dynamic) variations in the time of the measurand; it is essential because it allows evaluating the limits within which a measuring instrument can be suitable for measuring variable quantities over time (dynamic quantities). Another practical definition …

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Insertion error

In metrology, the insertion error is caused by the presence of the measuring instrument itself, inside the environment in which the measurement is carried out; in other words, the measuring instrument changes the measurement conditions and consequently also changes the final value of the measurand. Therefore it is said that a measuring instrument is the better, the …

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Dynamic error

A dynamic error is a difference between the true value of the quantity changing with time and the value indicated by the measurement system if no static error is assumed. This error may have an amplitude and usually a frequency related to the environmental influences and the parameters of the system itself. In metrology, dynamic errors are caused by …

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