Language Ideologies: Practice and Theory.

Language Ideologies: Practice and Theory. Bambi B. Schieffelin. Kathryn A. Woolard. and Paul V. Kroskrity. eds. New York: Oxford University Press, 1998. 338 pp.     

Anti-Racism Education: Theory and Practice.

Anti-Racism Education: Theory and Practice. George J. Sefa Dei. Halifax, Canada: Fernwood Publishing, 1996. 160 pp.     

Art and Agency: An Anthropological Theory.

Art and Agency: An Anthropological Theory. Alfred Gell. New York: Oxford University Press, 1998. 271 pp.     

Theory of muscle contraction: I. Isometric contraction

For each molecule of ATP hydrolyzed by the ATPase at the subfragment 1 of the heavy meromyosin, one H⁺ is produced and remains associated with the myosin heads until a contact with the G-actins of the I-filaments is established. This contact is brought about by the calcium ions released in the sarcomeres by the sarcoplasmic reticulum at the arrival of nerve impulses. A rapid flux of protons along the I-filaments towards the Z-membrane down the concentration gradient leads to the buildup of a diffusion potential which in turn causes a charge-compensating movement of the diffused cationic layer around the I-filaments in the opposite direction. The latter movement exerts a viscous drag on the actins and tends to move the I-filaments deeper into the inter-A-filament spaces towards the M-line. A consistent and straightforward theory of muscular contraction is developed on these lines. The value of the isometric tension in striated muscle fiber of frog at slack length calculated on the basis of this theory agrees well with the measured value.     

Nonsteady-State Three Compartment Tracer Kinetics: I. Theory

A set of differential equations is derived which describes the four unidirectional fluxes of a substance across the boundaries of the central compartment of a serially arranged three compartment system, and the amount of this substance present in the central compartment. An analytic solution is obtained which yields all of these quantities as functions of time. The analysis is associated with a defined set of repetitive experiments from which the necessary data are obtained and during which the two outer compartments must be subject to experimental control. The solution is applicable to both the initial steady state and a transient, time-dependent state created by making a step change in the initial conditions. It describes the fluxes and compartment size without assuming that constant kinetic coefficients relate the fluxes to compartmental quantities but is limited by the requirement that the response of the system be repeatable in time.