Biomedical subjects

C Zener

Publications and source records attributed to C Zener.

13 recordsLinked to original sources

PubMed1983

van't Hoff-van der Waals osmotic pressure and energy transformers.

We find the van't Hoff relations between osmotic pressure, freezing point depression, and boiling point elevation provide a clue on how, by using salt solutions, one may lower the cost of extracting power from low-grade heat sources. In particular, the ratio of 7 between the heat of evaporation and the heat of freezing of pure water suggests a chemical system that raises 7-fold the temperature difference between heat source and heat sink, while decreasing by the same factor the heat flux. Heat exchangers dominate the cost of heat engines operating upon low-grade heat. Their area for a fixed power output is inversely proportional to the available temperature differential. Herein lies the potential for a great cost reduction. We show that the simple van der Waals concept of a gas of hard elastic spheres suffices to understand the colligative properties of salt solutions, at least up to the concentration of the eutectic composition. This concept enables us to physically interpret the thermodynamic processes during the concentration of salt solutions by evaporation and during the mixing of ice and solid salt hydrates at their eutectic temperature. These are identical to the thermodynamic processes taking place during the isothermal compression and expansion of gases in pumps and in turbines.

Journal Article↗

PubMed1982

Periodic explosions by positive feedback in a rising foam column.

An aqueous foam rising adiabatically in a column suffers a drop in temperature. Under appropriate conditions, such a column periodically explodes. We here trace this explosion to the tight thermal coupling between the foam and its enclosing glass column. When the surface surfactant concentration is unbuffered by micelles, a positive feedback exists between the flow of heat from the walls into the foam and the thermal conductivity of the foam itself. In our highly expanded foam, heat is conducted through the foam cells' interior primarily by the heat-pipe effect. Such an effect is retarded by a dense layer of surfactant molecules. Heat absorption causes cell expansion, which, in a foam unbuffered by micelles, causes a reduction in surface concentration of surfactant molecules and, hence, in an increase in thermal conductivity. This interpretation of our observed periodic explosions is in agreement with all of our observations.

Journal Article↗

PubMed1970

Statistical theories of success.

The Pareto and the log-normal distributions are commonly used to describe the statistical distribution of success. A detailed comparison of these distributions is made with Lotka's extensive observations on success as measured by rate of publication. These distributions are found to adequately describe the observed distribution only for low and moderate success. Contrariwise, the flat factor analysis of performance recently developed by the author in these Proceedings (59, 1078 (1968)) is shown to give an excellent agreement over the whole range of success. Lotka's data allows a determination of the number of environmental factors.The Pareto distribution does give an excellent agreement with the tail of the success distribution where success is defined as income. An interpretation of this distribution is here presented based upon the expected behavior of entrepreneurs.

Journal Article↗

PubMed1969

Geometric programming, chemical equilibrium, and the anti-entropy function.

THE CULMINATION OF THIS PAPER IS THE FOLLOWING DUALITY PRINCIPLE OF THERMODYNAMICS: maximum S = minimum S(*). (1) The left side of relation (1) is the classical characterization of equilibrium. It says to maximize the entropy function S with respect to extensive variables which are subject to certain constraints. The right side of (1) is a new characterization of equilibrium and concerns minimization of an anti-entropy function S(*) with respect to intensive variables. Relation (1) is applied to the chemical equilibrium of a mixture of gases at constant temperature and volume. Then (1) specializes to minimum F = maximum F(*), (2) where F is the Helmholtz function for free energy and F(*) is an anti-Helmholtz function. The right-side of (2) is an unconstrained maximization problem and gives a simplified practical procedure for calculating equilibrium concentrations. We also give a direct proof of (2) by the duality theorem of geometric programming. The duality theorem of geometric programming states that minimum cost = maximum anti-cost. (30).

Journal Article↗

PubMed1968