Kinetics of Ion-Pair Absorption

According to the 'pH-partition' theory, drugs in their ionized form cannot readily diffuse through biological membrane. However, it is well known that the permeation of many ionized drugs can be enhanced by the presence of anionic or cationic agents. One of the explanations for this observation is that the charged molecules of drug interact with the agents and form lipophillic ion-pair species, and as a result, the absorption of ionized molecules increases. In the present paper, the kinetic relationships of the formation of the ion-pair as a function of ion-pair agent and the type of the biological membrane have been discussed and analyzed. Criteria have been developed for the distinguishing the following two cases: 1) when the absorption is the rate limiting step in the process of permeation of the ion-pair, and 2) when the ion-pair crosses the membrane as though it were a fine sieve.     

Geothermal reservoir simulation

This paper is intended to be a state of the art review of geothermal reservoir simulation. Its recent application to the modelling of real geothermal reservoirs is described and put in the context of an emerging general approach to reservoir modelling. The use of computer simulation for geothermal well test analysis is described. One of the main recent uses of reservoir simulators has been for conducting numerical experiments aimed at improving the understanding of geothermal reservoir physics. Such studies on fractured reservoirs, the thermal structure of reservoirs and the effects of non-condensable gases and dissolved salts are outlined.     

WHIM, the Window Handler and Input Manager

This article describes WHIM, the Window Handler and Input Manager, a window management system being developed as part of the QuickSilver operating system project at IBM's Almaden Research Center. Another version of WHIM runs under AIX on the IBM PC RT. This article contrasts and compares the overlapped window scheme used in WHIM with the tiled window scheme used in other systems. The advantages of the window management scheme used in WHIM are detailed, and the effect of display interfaces on the window manager is described.