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Possible definitions for pacemake

pacemaker
Source of rhythmic electrical impulses that trigger heart contractions. In the heart's electrical system, impulses generated at a natural pacemaker are conducted to the atria and ventricles. Heart surgery or certain diseases can interrupt conduction (heart block), requiring use of a temporary or permanent artificial pacemaker. A small electrode attached to an electric generator outside the body is threaded through a vein into the heart. The generator, inserted beneath the skin, produces regular pulses of electric charge to maintain the heartbeat. Permanent pacemakers can also be implanted on the heart's surface.


lacemaking
Methods of producing lace. The popularity of handmade laces led to the invention of lacemaking machines in the 19th cent. (see J. Heathcoat). Early models required intricate engineering mechanisms. Later improvements included Nottingham-lace machines, primarily for coarse lace, and Barmens machines. Schiffli lace, a type of embroidery, is made by modern machines, evolved from a hand version, using needles with points at each end. Many types of machine-made laces are made, frequently with geometrically shaped nets forming their backgrounds. The high strength and comparatively low cost of man-made fiber yarns has made sheer laces widely available


racemate
Mixture of equal quantities of two enantiomers, substances whose molecular structures are mirror images of one another (see isomer). The two enantiomers rotate polarized light through opposite angles, canceling each other out so that the racemic mixture has no optical activity. Racemization is the conversion of an optically active form of a compound into a racemic mixture; reversing this process is called resolution.

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