A correction for dead-time losses in γ-ray spectrometry for a mixture of short-lived radionuclides

A simple procedure for the correction of residual dead-time losses in γ-ray spectrometry of mixtures of short-lived radionuclides is given. It is based on the value of the total deadtime at the beginning of the measurement and three constants which are characteristics for a given matrix. The application to the instrumental neutron activation analysis of fluorine and sodium in bone is given as an exaple.     

Problems concerning representative sampling for possible contamination in a complex waste processing facility

A survey is given of the main activities of the Belgoprocess Company, with special emphasis on safety precautions. The routine sampling program for internal contamination consists of urinary and faecal sampling, among others. Faecal samples sometimes reveal low contamination levels. This contamination can be considered as low-level, frequent, and intermittent. No distinct correlation is found with another control technique.A survey is given about uncertainties that might hamper a representative sampling and/or a correct interpretation of the obtained data. Reference is made to the dosimetric models regarding complexity and uncertainties.     

Hysteresis effects in the plasma-electrode boundary sheath for frequencies of the order of the ion plasma frequency

The well-known boundary sheath theory applicable to low frequencies is extended for frequencies of the order of the ion plasma frequency. Phase shifts in the linear and nonlinear oscillations exist at different points of the sheath. A hysteresis effect is observed for the current-voltage characteristics and for the dependence of the sheath capacity on the voltage. An analytical approximation of the hysteresis curve is given. A comparison with experiments confirms the applicability of the theory. A simple analytical approximation formula for the sheath thickness as a function of the applied voltage is given.     

Observations relative to epithermal and fast neutrons in INAA

Various theoretical and practical aspects of epithermal neutron activation analysis (ENAA) and fast-neutron-induced reaction interferences in conventional instrumental thermal neutron activation analysis (TNAA) have been considered. A new generalized advantage factor which reflects a practical improvement of detection limits in ENAA is proposed. In the determination of practical advantage factors, consideration is also given to the different irradiation channels available for the experiment in a given reactor, or even in several accessible reactors. Fast neutron reaction interference factors are tabulated for both ENAA and TNAA and examples are given of specific interferences in TNAA for some biological and geological matrices.     

A Simple,Quick, and Precise Procedure for the Determination of Water in Organic Solvents

Abstract

A procedure for the UV/VIS-spectroscopic determination of water by the use of a solvatochromic pyridiniumphenolate betaine is given. The water content of organic solvents is calculated by a two parameter equation from λ_max of the dye. A typical, detection limit is of the order of 1 mg in 1 ml solvent for routine spectrometers. The parameters for the determination of water are given for a number of commonly used solvents.     

Precise timing in program-controlled data acquisition for 14 MeV neutron activation analysis

A solution for the automation of a fast pneumatic transport system and its application is given.     

One-phonon spectra in absorption and fluorescence spectra of molecular impurities: breakdown of mirror symmetry

Conditions for breakdown of the structural and intensity mirror symmetry relationship between the one-phonon spectra in the absorption and fluorescence spectra of molecular impurities are established. A criterion is given for determining when the contribution of quadratic coupling to the zero-phonon bandwidth, for a given linear electron— phonon coupling strength, is expected to be minimal.     

Determination of the position distribution of fatty acids in natural phosphatidylcholines

Summary It has been shown that the snake venom ofVipera lebetina obtusa/ul can be used as a source of phospholipase A.A method is given for the accelerated enzymatic hydrolysis of natural phosphatidylcholines in order to determine the position distribution of the fatty acids by bringing the pH of the medium to 10.15.A technique for calculating the composition of the diglycerides of the phosphatidylcholines is given.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 137–141, March, 1971.     

Coupling of equivalent particles in a field of given symmetry

A formula of Kotani for the coupling of equivalent particles in a field of a given symmetry is rederived using group algebraic methods.     

X-ray determination of crystallinity and orientation in poly(ethylene terephthalate)

The measurement of crystallinity and orientation in poly(ethylene terephthalate) is discussed. A simple procedure is given for the estimation of orientation from the (1 05) plane, and it is shown that methods which use the equatorial planes are subject to certain disadvantages. In addition a method is given for the measurement of x-ray crystallinity. The technique is applied to fibers and films of various treatments and a linear relation is found between density and x-ray crystallinity.     

Long-chain branching in low-density polyethylene

A method is given for the analysis of long-chain branching in polymers by using combined GPC and intrinsic viscosity measurements. A computer program was written to evaluate branching indices by a tabular, iterative method. The method was applied to the evaluation of long-chain branching in low-density polyethylene.     

Self-similar power transforms in extrapolation problems

A method is suggested allowing for the improvement of accuracy of self-similar factor and root approximants, constructed from asymptotic series. The method is based on performing a power transforms of the given asymptotic series, with the power of this transformation being a control function. The latter is defined by a fixed-point condition, which improves the convergence of the sequence of the resulting approximants. The method makes it possible to extrapolate the behaviour of a function, given as an expansion over a small variable, to the region of the large values of this variable. Several examples illustrate the effectiveness of the method     

Gradient elution under hydrostatic equilibrium in liquid chromatography. Part 1

The theory of gradient elution under hydrostatic equilibrium is developed for the case where only one reservoir and one mixing chamber are used and where both solvents have equal densities. Given the shapes of the two vessels, effluent concentration curve equations are deduced for different mixing chamber-reservoir combinations. On the other hand, given the equation for the effluent concentration curve, the reservoir cross-sectional area, as a function of height, can be deduced when the mixing chamber has a constant cross-section. The varying cross-section of the reservoir is accomplished by inserting thin discs of different areas on top of one another inside a regular vessel of constant cross-section. Except for complicated gradients, a given gradient can be accomplished using a reservoir with a cross-sectional area which varies linearly with height. In the case of complex gradients, a reservoir having two or more linear segments becomes necessary. A numerical method is given for the calculation of the continuously varying reservoir cross-section for the exact duplication of a given gradient.     

Bubble formation in vulcanized rubbers

A theoretical treatment is given for the formation of visible holes in an elastic solid. It differs from previous treatments of bubble formation in liquids by neglecting the problem of hole nucleation altogether. Instead, a small spherical hole is assumed to be present initially. The inflation of such a hole by a dissolved gas is then considered. A critical internal pressure is deduced, at which the hypothetical hole would become infinitely large. This pressure is given by 5G/2; where G is the shear modulus of the rubber. Some model experiments are described in which swollen rubber vulcanizates were rapidly heated to bring the dissolved liquid into a superheated conditions. The temperatures of rapid bubble formation were determined for a number of vulcanizates having different degrees of crosslinking and hence different values of shear modulus, and for different swelling liquids. The results are shown to be in reasonably good quantitative agreement with the theoretical predictions.