Determination of boron in nickel-base alloys by the dianthrimide method

The dianthrimide method for the determination of boron in iron and low-alloy steels may be applied to nickel-base materials. The sample is dissolved, without any loss of boron, by hydrochloric and sulphuric acids and the resulting boric acid determined spectrophotometrically with dianthrimide. Background corrections are necessary to compensate for the absorbance from ions such as nickel and iron.     

6- and 7-aryl-1,2,4-triazolo[4,3-b]-1,2,4-triazines. Synthesis and characterization

Synthetic methods for the preparation of 6-aryl-1,2,4-triazolo[4,3-b]-1,2,4-triazines ( 1 ) and the 7-aryl isomers ( 2 ) are described. Compounds 1 were prepared from aryl glyoxaldoximes 76 via 6-aryl-1,2,4-triazin-3(2H)ones ( 75 ). A simple procedure for the preparation of the 7-aryl isomers was effected using arylglyoxals 11 and the triazoles ( 4, 12a and 12b ). However, complete regioselectivity was not realized in all cases, especially when the triazoles were substituted at the C-5 position. A regiospecific synthesis of the 7-aryl isomers 2 was developed via the 3-methylthio-5-aryl-1,2,4-triazines ( 61 ). The structure of the parent 6-phenyl derivative 5 was confirmed by x-ray crystallography.     

Pressure induced phase transition behaviour in f-electron based dialuminides

The rare-earth and actinide based compounds are endowed with several exotic physical and chemical properties due to the presence of f-electrons. These properties exhibit interesting changes under the action of various thermodynamic fields and hence continues to be a subject of extensive research. For instance, under pressure, the nature of f-electrons can be changed from localized to itinerant, leading to a variety of changes in their structural, physical and chemical properties. The present review on the high pressure phase transition behaviour of dialuminides of rare earths and actinides is an outcome of research in our laboratory during the last five years using a unique combination of a Guinier diffractometer and a diamond anvil cell built in-house. To bring out the correlations between the compressibility and structural behaviour with the electronic structure, we have also carried out electronic structure calculation. Further, the usefulness of Villars’ three parameter structure maps in predicting pressure induced structural transitions has been explored and this has been illustrated with the available phase transition data.     

Truncation rules for modelling discontinuities with Galerkin method in electromagnetic theory

It is well known that apparently similar discretization schemes of Maxwell's equations in Fourier series may provide very different convergence performances because of truncation. We argue that this work performed in grating theory can be applied to other electromagnetic theories relying on expansions over series different from Fourier series. This generalization is supported by an intuitive argument and by a simple numerical example with Hermite–Gauss functions.     

Small-angle Coulomb collision model for particle-in-cell simulations

We construct and investigate a set of stochastic differential equations that incorporate the physics of velocity-dependent small-angle Coulomb collisions among the plasma particles in a particle-in-cell simulation. Each particle is scattered stochastically from all the other particles in a simulation cell modeled as one or more Maxwellians. Total energy and momentum are conserved by linear transformation of the velocity increments. In two test simulations the proposed “particle-moment” collision algorithm performs well with time steps as large as 10% of the relaxation time – far larger than a particle-pairing collision algorithm, in which pairs of particles are scattered from one another, requires to achieve the same accuracy.     

Experimental results on neutrino-electron scattering

A determination of sin² θ _w based on measurements of elastic scattering of muon-neutrinos and muon-anti-neutrinos on atomic electrons is described. These purely leptonic processes were studied using the CHARM calorimeter exposed to neutrino and antineutrino wide-band beams at the CERN super proton synchrotron. A total of 83±16 neutrino-electron and 112±21 antineutrino-electron events have been detected. From the measurement of the ratio of muon-neutrino and muon-antineutrino cross-sections a value of sin² θ _w =0.211±0.037 was obtained.     

Box-modeling of bone and tooth phosphate oxygen isotope compositions as a function of environmental and physiological parameters*

A time-dependent box model is developed to calculate oxygen isotope compositions of bone phosphate as a function of environmental and physiological parameters. Input and output oxygen fluxes related to body water and bone reservoirs are scaled to the body mass. The oxygen fluxes are evaluated by stoichiometric scaling to the calcium accretion and resorption rates, assuming a pure hydroxylapatite composition for the bone and tooth mineral. The model shows how the diet composition, body mass, ambient relative humidity and temperature may control the oxygen isotope composition of bone phosphate. The model also computes how bones and teeth record short-term variations in relative humidity, air temperature and δ¹⁸O of drinking water, depending on body mass. The documented diversity of oxygen isotope fractionation equations for vertebrates is accounted for by our model when for each specimen the physiological and diet parameters are adjusted in the living range of environmental conditions.     

Expressions for the Activity Coefficients and Osmotic Coefficients of Solutions of Electrolytes and Nonelectrolytes Based on the Hydration Model of Zavitsas

In two papers Zavitsas described a model for the thermodynamic properties of aqueous solutions of a single electrolyte or nonelectrolyte (Zavitsas, J Phys Chem B 105:7805–7817, 2001; J Solution Chem 39:301–317, 2010) in which he assumed that part of the water is so strongly bound to the solute that it can be considered as part of it, and thus only the remaining unbound water is considered to be the solvent. He showed that when the usual water mole fraction was replaced by the resulting mole fraction of unbound water, obtained by optimizing an effective hydration number, basically linear relations were obtained to fairly high molalities for the freezing temperature lowering, boiling temperature elevation, and the water activity/vapor pressure of water. However, Zavitsas only considered the properties of the solvent, not the solute. In this paper we derive the corresponding expressions for the activity coefficient of the solute for the usual molality scale based on 1 kg of water, for the modified molality scale based on 1 kg of unbound water, for the mole fraction scale based on the total number of moles of water, and for the modified mole fraction scale based on the number of moles of unbound water. These equations show that if the hydration number is larger than the stoichiometric ionization number of the electrolyte, then all four types of mean activity coefficients are predicted to always be >1 (nearly all hydration numbers reported by Zavitsas for electrolyte solutions are greater than the corresponding ionization numbers), which directly conflicts with extensive experimental and theoretical evidence that the mean activity coefficients of electrolytes in aqueous solutions always initially decrease below unity. In contrast, for nonelectrolyte solutions, the hydration model of Zavitsas gives more realistic values of the activity coefficients.