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Index (S)

SA - SC

SD - SF

SG - SJ

SK - SN

SO - SR

SS - ST

SU - SV

SW - SZ

Moment of truth
The word 'nanotechnology' is first coined by University of Tokyo researcher Norio Taniguchi back in 1974.


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stainless steel Eng.
A form of corrosion resistance steel containing at least 10% chromium and often some other elements, especially nickel and molybdenum. The material does not rust or stain and is highly resistant to chemical attack by organic acids, weak mineral acids and atmospheric oxidation. It does not easily tarnish and has found in a wide variety of uses in industry and domestic applications such as cooking utensils, case watches, water heaters etc.

standard atmosphere Phys.
See atmospheric pressure

Standard Model Phys.
In particle physics, the Standard Model describes the fundamental constituents of matter consist of quarks and leptons, both of which grouped into three families or generations. The three families of quarks consist of up and down; charm and strange; bottom and top. The three families of leptons consist of the electron and electron neutrino; muon and muon neutrino; tau and tau neutrino.

These fundamental particles interact with gauge bosons that mediate three of the four basic forces of nature: strong, weak and electromagnetic. The gravitational force is not included in the Standard Model because it is extremely weak between particles.

standard solution Chem.
A solution of known concentration for use in volumetric analysis. Often quoted in unit M or mol/dm3. For instance, a standard solution of 1M HCl (hydrochloric acid) can be used to titrate against a sodium hydroxide solution of unknown concentration.

statcoulomb Metro.
Unit of electrical charge quantity in the cgs system. Abbreviated as statC. The equivalent International System units (SI units) for electrical charge is coulomb (C), of which 1 statC = 3.3356 x 10-10 C. Two charged objects that are placed 1 cm apart and exert an electrical repulsive force of 1 dyne are said to carry like electrical charges of 1 statC.

state symbol Chem.
A symbol that provides information about the state of a chemical in a reaction. Usually there are a total of four different state symbols in a normal chemical reaction. They are s for solid, g for gas, l for liquid and aq for aqueous solution.

stem cell Biol.
An unprogrammed, biological cell that has the ability to divide, differentiate and transform into various other kind of cell tissues such as heart, kidney, blood vessel, bones, etc. It is used in the body to identify damaged tissue and produce or repair it. Stem cells can be found in human embryos, fetal, umbilical cord or even an adult tissue. However, the first two sources of stem cells have the greatest ability to change into a wider variety of cells than the adult tissues.

stere Metro.
A unit volume equal to 1 m3. It is no longer used for scientific purposes.

strangeness Phys.
Abbreviated as S, it is a quantum number that relates to particles contain the strange as one of the constituent. A particle that contains one strange quark will have a strangeness of -1, and if a particle contains one antistrange quark will have a strangeness of +1.

For example, the kaon-meson, K+, is made of one up quark and one antistrange quark has S = +1, while the Lambda-baryon, L0, with one up quark, one down quark and one strange quark has S = -1. The Xi-baryon, X-, has S = -2 because it has one down quark and two strange quarks. All leptons and bosons have S = 0.

stress Eng., Phys.
A measure of the internal forces acting in a body between its constituent particles that resist deformation as a result of externally applied forces. Mathematically, it is defined as the force per unit area:

stress definition

It is in the standard unit of Nm-2 or Pa (Pascal). A force is applied to a plane can be resolved into normal stress (force acting perpendicular to the plane) and shear stress (force acting parrallel to the plane).

stress protein Biochem.
See heat shock protein.

string theory Phys.
A theory that describes the 'elementary particles' are manifestations of indivisible, 1-dimensional strings of 10-35 m in length (Planck length). These fundamental strings can be regarded as vibrating, one-dimensional loops or segments of energy. Different particles such as electrons, quarks are differentiated by the different resonant modes of string oscillations. The way that the string oscillates dictates a particle's properties such as its mass, charge and spin.

In this theory, all fundamental interactions are described in terms of the string tension. However, this only occurs in an imaginary, supersymmetric 10-dimensional world. To describe these interaction in our usual 4-dimensional world (3 spatial and 1 time), all other extra dimensions are 'compactified' and supersymmetry must be broken. However, this leads to at least 10500 mathematical solutions (or landscape) and there is no way to tell which one is the true solution and why. There is as yet any experimental evidence to show string theory can provide true description of our nature. Nevertheless, it is the only best working theory of quantum gravity that may unite the extremely weak gravity with the other three forces as described in the Standard Model.

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