Fibroblast growth factorFibroblast growth factors (FGF) are a family of cell signalling proteins produced by macrophages; they are involved in a wide variety of processes, most notably as crucial elements for normal development in animal cells. Any irregularities in their function lead to a range of developmental defects. These growth factors typically act as systemic or locally circulating molecules of extracellular origin that activate cell surface receptors. A defining property of FGFs is that they bind to heparin and to heparan sulfate.
Reynolds numberIn fluid mechanics, the Reynolds number (Re) is a dimensionless quantity that helps predict fluid flow patterns in different situations by measuring the ratio between inertial and viscous forces. At low Reynolds numbers, flows tend to be dominated by laminar (sheet-like) flow, while at high Reynolds numbers, flows tend to be turbulent. The turbulence results from differences in the fluid's speed and direction, which may sometimes intersect or even move counter to the overall direction of the flow (eddy currents).
Glossary of biologyThis glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology, Glossary of environmental science and Glossary of scientific naming, or any of the organism-specific glossaries in .
GlycosaminoglycanGlycosaminoglycans (GAGs) or mucopolysaccharides are long, linear polysaccharides consisting of repeating disaccharide units (i.e. two-sugar units). The repeating two-sugar unit consists of a uronic sugar and an amino sugar, except in the case of the sulfated glycosaminoglycan keratan, where, in place of the uronic sugar there is a galactose unit. GAGs are found in vertebrates, invertebrates and bacteria. Because GAGs are highly polar molecules and attract water; the body uses them as lubricants or shock absorbers.
Null-subject languageIn linguistic typology, a null-subject language is a language whose grammar permits an independent clause to lack an explicit subject; such a clause is then said to have a null subject. In the principles and parameters framework, the null subject is controlled by the pro-drop parameter, which is either on or off for a particular language. Typically, null-subject languages express person, number, and/or gender agreement with the referent on the verb, rendering a subject noun phrase redundant.
Agreement (linguistics)In linguistics, agreement or concord (abbreviated ) occurs when a word changes form depending on the other words to which it relates. It is an instance of inflection, and usually involves making the value of some (such as gender or person) "agree" between varied words or parts of the sentence. For example, in Standard English, one may say I am or he is, but not "I is" or "he am". This is because English grammar requires that the verb and its subject agree in person.
