Encyclopedia of Chemistry

induced by gravitational pull; hydrotropism is a response to water gradients; and thigmotropism is a response to touch. troposph ...

ultrasound The use of sound with a frequency higher than 20,000 Hz. Used to obtain images for medical diagnostic purposes, espec ...

unsaturated fatty acids Fatty acids are the essential building blocks of all fats in our food supply and body, but not all of th ...

mark. He then became an associate in chemistry at Johns Hopkins University, where he championed the application of quantum mecha ...

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valence The maximum number of univalent atoms (originally hydrogen or chlorine atoms) that can com- bine with an atom of the ele ...

DIPOLE, DIPOLE-INDUCED DIPOLE, and LONDON FORCES (instantaneous induced dipole-induced dipole forces). The term is sometimes use ...

voltage-gated channel Ion channels are pores in cell membranes that allow the passage of ions in and out of cells. There are two ...

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Waksman, Selman Abraham(1888–1973) Ameri- canBiochemist Selman Abraham Waksman was born in Priluka, near Kiev, Russia, on July 2 ...

enzyme work but was not allowed to accept it, since he was living under the Hitler regime. He later discovered how the conversio ...

SION), and therefore increases its adhesion to a solid surface. Wheland intermediate SeeMEISENHEIMER ADDUCT; SIGMA(σ) ADDUCT. Wh ...

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XANES(X-ray absorption near-edge structure) See EXTENDEDX-RAY ABSORPTION FINE STRUCTURE. xenobiotic A xenobiotic (Greek xenos“fo ...

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yeast Mothers and brewers have been familiar with yeast for centuries. It is considered to be the oldest “plant” cultivated by h ...

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zeolite A group of hydrated aluminosilicate minerals that occur in nature or are manufactured. They are crystalline compounds co ...

zwitterionic compound A neutral compound hav- ing electrical charges of opposite sign, delocalized or not, on adjacent or nonadj ...

289 BIBLIOGRAPHY Aboul-Enein, Hassan Y., Raluca-Ioana Stefan, and George Baiulescu. Quality and Reliability in Analytical Chemis ...