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Moment of truth
The fastest man-made object that ever leave the Earth is the New Horizon spacecraft, launched in January 2006, and attained a speed of more than 36000 mph.

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sublimation Chem.
A direct change of the state of matter from solid to gas. Iodine shows such behavior which does not go through the process of melting as the temperature is increased. A solid substance that is formed by sublimation is called sublimate.

subsere Eco.
A secondary series of ecological communities beginning after succession has been interrupted by fire, glazing, agriculture or other destructive agent.

sun spot Astron.
A dark, cooler region (4000C) of the Sun's surface (photosphere). It is an area with high concentration of magnetic flux. Solar flares usually occur at the sun spots. The larger the spot, the more intense is the flare.

superbug Biol.
A common name for bacteria that can resist antibiotics such as penicillin. The microorganisms formed are due to inappropriate use of antibiotics for non-bacterial illness, or when prescriptions are not taken for the full cycle. The bacteria that survives subsequently pass on the resistant-traits to next generations. One of the most resistant bacteria is the methicillin-resistant staphylococcus aureus (MRSA) which can be found in hospitals. It can cause skin infections, bloodstream infections and even death. One effective, and extremely simply way of prevention is by hand washing with soaps.

superfluid Phys.
A fluid that is able to creep up at the walls of vessels and to overcome potential barriers.The term was first coined by the Soviet physicist P. Kapitsa in 1938. A superfluid can exhibit a range of unusual phenomena that defy logic. The most popular observation being able to creep up, against gravity, to the rim of a beaker and flows down the inner wall until the liquid level inside the beaker equals the level outside. The superfluid is said to have zero viscosity and infinite thermal conductivity. One example of superfluid is the helium II (He II), which is a fluid phase of helium cooled to 2.18 K or below at standard atmospheric pressure.

supermassive blackhole Astron.
A black hole with a mass much much greater than the most massive stars. It is thought that the central regions of almost every galaxy contain a supermassive black hole of a million solar masses (A solar mass is the mass of our Sun = 1.989 x 1030 kg) or more.

supernova Astron.
Massive outburst, signifying the death of a star. One of the most energetic events of the universe. At its peak, a supernova may become 15 000 000 times as luminous as the Sun. If it occurs in our galaxy, the Milky Way, a very dim star may suddenly (and temporarily) out-shine the rest of the stars. Basically, there are two types of supernovae. The type I is caused by the sudden onset of huge thermonuclear explosion. This usually occurs when the material from a companion star falls (accretion) at a slow rate onto the surface of a white dwarf. The gradual build up of materials causes the white dwarf to collapse and heat up as a whole until the entire star blows up. A faster rate may cause the infalling materials to explode all at once and hence a nova occurs instead.

In type II supernova, the core of an old star no longer be able to sustain a fusion reaction. Consequently, the core becomes colder and the star collapse under its own gravity. This results in super-dense core to a point the massive gravitational energy is released in the form of heat in a few seconds. The massive explosion pushes the stellar materials outward near to the speed of light.

superoxide dismutase Bio.
A dimeric enzyme (molecular weight of 32000) containing a copper ion and a zinc ion in each subunit. It prevents oxidative cellular damage by catalyzing the dismutation of super oxide radical anions to oxygen and hydrogen peroxide. The copper is believed to responsible for the enzymatic activity via the following possible chemical routes:

SOD's enzymatic process
crystal structure of SOD

where SOD is the abbreviation of the enzyme. Mutation of the enzyme may lead to the destruction of large motor neurons in the spinal cord and brain. Diagram above shows the crystal structures of bovine SOD.

superpartner Phys.
See supersymmetry.

supersymmetry Phys.
An unusual symmetry that interchanges bosons and fermions via some mathematical symmetry transformations that involve both space and time. In a supersymmetric world, every known particle is paired with a supersymmetric partner (superpartner) which interchanges by a supersymmetry transformation. The transformation turns a fermion into its boson partner and a boson into its fermion partner. It is called 'super' becuase it is an unusal symmetry that involves the interchanges of a pair of objects with different properties. However, such symmetry is shown to exist only if bosons and fermions are present in equal numbers. In addition, the paired particles must have the same mass and charges and interact in the same way. The exception is that their spins are different, which is what distingushes a boson from a fermion.

The existence of supersymmtry in nature is still not proven, although it must be incorporated into the string thoery in order for the theory to become more feasible to describe the particles in nature. However, if such symmetry should exist, the nature should contain at least twice the number of particles as described by the Standard Model.

There is a standard nomenclature to name these superpartners: A bosonic superpartner will be named by adding an 's' as the first letter to the name of the corresponding fermion; while a fermionic superpartner will be named by adding '-ino' to the end of the name of the corresponding boson. For instance, the superpartner of the electron (a fermion) is called selectron (a boson). The superpartner of gluon (a boson) is called gluino.

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