Radiation Equivalence and Natural Similitude in Handling Radioactive Wastes

The possibility of long-term safe disposal of radioactive wastes based on their radiation and radiation-migration balance with the initial fuel component and taking account of the thermal, radiation, and elastic loads due to waste dispoasl on the natural medium is examined. The specific radiation and radiation-migration equivalence is established on the basis of the radiotoxicity of uranium and the components of the decay of uranium and individual radionuclides as well as the sum of the latter.     

Rheological behaviour of concentrated yeast suspension

The effect of yeast cell volumetric concentration on the rheological properties of the suspensions was measured in a pipe-flow viscometer at 30°C: at low microbial concentrations the suspensions were Newtonian; however, non-Newtonian behaviour, which could be described by the power-law equation, was observed with suspensions at high microbial volumetric concentrations. At conditions of constant microbial morphology and growth rate, the results also indicated that a relationship could be developed between the power-law constants and the microbial volumetric concentration.     

Theory of MSW transducers

This is a review of two electrical equivalent circuits for multi-element magnetostatic wave transducers. The two circuit models are identified as a transmission line and a two terminal model. Both models have been extended to all three principal MSW modes of propagation to the point where computer programs have been written to plot phase and amplitude response as measured by commercial network analyzers. A review is provided of the basic assumptions, similarities and differences, advantages and disadvantages, and limitations of the two models. The useful range of them covers many cases of practical interest in the one to twelve Ghz frequency range.     

Generalized concentration dependence of makromolecule selfdiffusion coefficients in polyethyleneoxide solutions

Summary The polyethyleneoxide (PEO) macroraolecule translational mobility in dioxane and benzene solutions was studied by pulsed field gradient nmr. The generalized dependence describing the macromolecule translational mobility in solutions — invariant with respect to the polymer molecular mass, solvent,as well as to temperature — was obtained.     

Flow of polymeric melts in short tubes

In an attempt to further understand the flow of polymeric melts through gates in injection molding, the present investigation deals with measurement of pressure drops during isothermal extrusion of fiber-filled and unfilled polystyrene, polypropylene, and polycarbonate melts in short tubes with sudden contraction at high shear rates typical of injection molding. Flow curves for these materials have been determined over a wide range of shear rates at various temperatures by using a capillary rheometer and extruder. Measurements indicate that rheological properties of fiber-filled melts after injection molding differ from those of fresh samples. Moreover, it has been found that decreasing the tube length increases the slope of the curve for pressure drop vs. Volumetric flow rate. Extra pressure losses due to end effects have been determined which show that at high shear rates these losses can reach levels as high as 100 bar, with the effect being higher for the fiber-filled melts. By using a viscoelastic consitutive equation, the extra pressure losses have been separated into entrance and exit losses. Model parameters required for this calculation have been determined from viscosity-shear rate curves for the melts. For various polymers, master curves useful for industrial applications have been constructed for the extra pressure losses.     

On Pontryagin’s example with many evadors

The problem of pursuit of a single evador or several evadors by a group of pursuers with equal capabilities of all players is considered in Pontryagin’s example under the condition that the characterstic equation has at least one positive root. Some sufficient conditions of the solvability of the pursuit problems are obtained.     

Induced chemiluminescence of oxidized fatty acids and oils

The injection of a strong organic base into milligram quantities of fats and oils dissolved in methylene chloride results in a burst of chemiluminescence whose peak intensity is a function of the previous thermal oxidation history and of the degree of unsaturation of the starting material. The flash of this induced chemiluminescence can be 10⁸ times higher than the steady-state “spontaneous” chemiluminescence. The kinetics of the induced chemiluminescence are first order in concentration and second order in time. The emission spectrum is broad and extends into the near infrared. A model based on dioxetane chemiluminescence is proposed to explain the observed kinetics.     

Dynamics of hydrated iron(II) cations in nafion polymer membranes

Mössbauer studies of Fe²⁺ in water-soaked nafion polymer membranes in the temperature range between 90 K and 250 K have been performed. Above a critical temperature (～ 180 K) the spectra exhibit both elastic narrow absorption lines and quasielastic broad lines. These spectra are typical of bounded diffusion phenomena observed by Mössbauer spectroscopy in macromolecular systems like haemoglobin, myoglobin and ferritin. Similar spectral shapes have been observed by quasielastic neutron scattering from water in nafion membranes. Within 50 K above the critical temperature the total Mössbauer absorption area decreases by an order of magnitude whereas the narrow absorption line decreases by two orders of magnitude. The results are interpreted in terms of bounded diffusive motion of the iron. Using a model based on overdamped harmonically bound Brownian motion, the essential parameters of the iron motion can be derived as a function of temperature. The iron motion most probably reflects the motion of a large Fe²⁺ complex, e.g. Fe(H₂O)²⁺₆, which is attached to the polymer side chains via the sulphonic group.