Diffusion in gold and Au-Ag alloys

The self-diffusion coefficients of gold in pure gold and alloys of gold and silver have been measured over a range of temperatures. Chemical interdiffusion coefficients have been measured on pure metal and incremental couples, but are of lower accuracy because of the development of porosity. The results are compared with earlier work and internally on the basis of Darken’s equations.     

Potassium channels: a computer prediction of structure and selectivity

Model structures for the pore of the potassium channels Shakerand ROMK1 are predicted. The models arise from computer simulationsand suggest reasons for the striking selectivity of these channelsfor K+ and the blocking of ROMK1 by internal Mg²⁺. The modelledstructure of the Shaker pore is supported by mutagenesis data.The mutagenesis experiments indicate the side chains responsiblefor binding to blocking agents [tetraethylammonium (TEA) andcharybdotoxin (CTX)] and the model has these side chains suitablyoriented for binding. An aromatic K+ binding site part way downthe pore is also predicted by the Shaker pore model.     

Rotating Heat Exchangers and the Optimization of a Heat Pump

Flow and heat transfer conditions are investigated on rotating flat plates and on blades of tangential blowers. The solution of the three dimensional boundary layer equations for rotating flat plates show that 3-D effects are of influence only in the neighborhood of the axis of rotation. The conditions outside this region can be treated as flow in a 2-D system. The measurements indicate that turbulent flow exists already at Re-values much smaller than Reclit for stationary flat plates. As a result of this, high heat transfer rates can be achieved at lower average velocities. All data taken on rotating flat plates and on the blades of a tangential blower can be correlated by a single dimensionless relationship. The results obtained by theory and measurements are used to derive design curves for the construction of a heat pump. A device built in accordance to these curves performed as predicted. Discussed are also rotating furnaces, radiators and condensers for vapor driven engines.     

Interaction Between a Linearly Polarized Electromagnetic Plane and a Double Spherical Shell

An exact solution inside, outside, and within two arbitrary concentric spherical shells is presented for an impinging monochromatic linearly polarized electromagnetic wave. Specifically, the solution was found for a double-shell spherical acrylic plastic enclosure irradiated with 2450-MHz microwaves. The enclosure is used as an environmentally controlled exposure chamber for experimental animals during microwave irradiation. The analysis shows that an air foamed material, such as styrofoam, would be a better material than either Plexiglas or Teflon, provided it is sufficiently durable.     

Compound types and properties of Utah and Athabasca tar sand bitumens

Properties and compound types were examined in detail for tar-sand bitumens representative of four major deposits in Utah and Alberta. Methods for bitumen extraction, separation, and compound type (functional group) analysis are presented. Results of the analyses are compared with each other and with results in the literature for tar-sand bitumens and petroleum. Comparison of the results of Utah bitumens with the Athabasca bitumen provides a basis for evaluation of the Utah bitumens because considerable information about the processing characteristics of the Athabasca bitumen has been reported. Simulated distillation and Chromatographic separation data indicate that, in general, the tarsand bitumens most closely resemble Wilmington petroleum with respect to hydrocarbon/non-hydrocarbon distribution, especially in the non-distilling portion (the distillable portions, mainly hydrocarbons, are similar for all samples). Tar-sand bitumens were also shown to differ significantly from one another, principally in the amounts and kinds of heteroatomic compound types present. This information is important because of the effects that composition has on recovery and refining processes. Analyses of the chemical functionalities also provide a basis for developing correlations between bitumen composition and the recovery and processing characteristics of the bitumen.     

Some aspects of the role of coal thermoplasticity and coke structure in coal gasification. 2. The effects of pressure and heating rate on dilatometric parameters and optical anisotropy development

An examination of the influence of pressure and heating rate on the thermoplastic properties of a weakly coking coal and of coal with various pitch-like additives was carried out using a high pressure dilatometer. Pressure up to 4 MPa markedly increased the swelling properties and increased the plastic range by decreasing the softening temperature, but the effects of pressure were strongly influenced by rate of heating with high heating rates enhancing the effects. Additions of tar or pitch also enhanced swelling at low pressure. The solid carbonization residues from the dilatometer were examined by polarized light microscopy to determine the content and composition of optically anisotropic species. The anisotropic content was increased by increases in pressure and heating rate and pitch additives enhanced the anisotropic content, especially at low pressure, without affecting the composition of the anisotropy. No direct correlations exist between the dilatometric parameters and the optical anisotropy but their dependence on the conditions emphasizes that when considering high pressure gasification of coal, it is necessary to obtain data under appropriate conditions.     

Longitudinal mixing in the dispersed phase in pulsed perforated-plate columns

A method is presented to identify flow model parameters from radioactive signals with a high noise content. The method is based on the two detection points method with a highly accurate identification of the parameters by optimization in the frequency domain. The study of dispersed phase of a pulsed column with perforated plate using this method has shown evidence that there are operating conditions for which the piston-diffusion flow does not describe well the behavior of the dispersed phase.     

Adsorption of dissolved organics from industrial effluents on to activated carbon

Industrial effluents usually include multicomponent organic solutes. The optimum pH for adsorption of a specific industrial effluent on activated carbon should be determined experimentally because, in general, more than one mechanism is involved. A series of experiments was conducted to establish the influence of the initial hydrogen ion concentration on carbon adsorption of organic solutes. For these studies, powdered activated carbon was used, and the water systems studied included both single component pure organic compounds as well as multicomponent organic wastes. Results indicate that the pH effect upon the effectiveness of carbon adsorption mainly depends upon the nature of the adsorbed substance. In general, the degree of ionisation is the controlling factor for adsorption of ionic organic solutes on activated carbon. Adsorption reaches a maximum at the point of least ionisation of the adsorbate. As the organic compounds become more complex (i.e. longer hydrocarbon chains, higher molecular weights, increased branching), the electrical adsorption forces between activated carbon and ionic organic solutes will govern. Anionic surfactants meet with decreased electronegative repulsive forces at low pH levels, which increase the effectiveness of carbon adsorption. However, the adsorption of a cationic surfactant is increased by an increase in the electronegative carbon surface at high pH levels. When ionic organic solutes become much more complex, like a polymer, the effects of both ionisation and electrical adsorption forces become less important. Instead, the adsorption rate will be controlled by the extent of hydrolysis caused by the pH adjustment. For non-ionic organic solutes, chemical reaction(s) between the adsorbate and the added chemical (acid or base) for pH adjustment is an important controlling factor. Again, hydrolysis is responsible for the breakdown of larger size molecules to smaller sizes. Then an increase in adsorption rate with decreasing molecular weight of adsorbate is expected.     

Property stabilization in filled,drawn polyethylene

Mechanical properties of high density polyethylene (HDPE) extended to draw ratios in the 20–40 range have been determined and compared with corresponding properties of the polymers containing particulates including rutile, carbon black, iron oxide, and mica. Shrinkage of drawn structures was studied to temperatures near the fusion of the polymer host. The degree of interaction at polymer/additive interfaces was varied by surface coating certain of the solids with standard coupling agents. Solids were found to increase tensile moduli and to decrease shrinkage, particularly at higher exposure temperatures. The magnitude of changes due to the presence of solids was shown to depend on the apparent interaction at contacts between host and additive. In a dispersion–force matrix, like HDPE, benefits were optimized when the particulates were amphoteric or neutral, rather than having pronounced acid or base interaction potentials.