Electroweak tests with τ leptons at LEP

We report on two sensitive tests of lepton universality carried out by the 4 LEP experiments at the Z⁰ pole. From measurements of the τ polarization in e⁺ e^?→τ ⁺ τ ^?, the ratios of the vector and axial vector coupling constants of the electron and the tau lepton to the weak neutral current are obtained to beg _{v e} /g _{a e} =0.066±0.015 andg _{V τ} /g _{A τ} =0.070±0.009 respectively. From measurement of the τ lifetime and the τ leptonic branching ratios, the ratio of the coupling constants describing weak leptonic decays of the τ and the μ is measured to beG _τ /G _μ =0.996±0.008.     

Electrospray tandem mass spectrometric analysis of zeaxanthin and its oxidation products

Carotenoids have been implicated in protection of the eye from light-mediated photo-toxicity caused by free radicals. Under conditions of normal oxidative stress the carotenoids serve as protective antioxidants; however, when the oxidative stress exceeds the antioxidant capacity, carotenoids can be oxidized into numerous cleavage products. The determination and identification of oxidized carotenoids in biological samples remains a major challenge due to the small sample size and low stability of these compounds. We investigated the reaction of various zeaxanthin cleavage products with O-ethyl hydroxylamine to evaluate their levels in a biological sample. For this, a sensitive and specific electrospray tandem mass spectrometry (ESI-MS/MS) was developed, avoiding the classical lower sensitive and specific HPLC-UV and fluorescence absorption methods. Protonated molecules [M + H](+) of carotenoids upon collision-induced dissociation produced a number of structurally characteristic product ions. A series of complicated clusters of product ions differing in 14 (CH(2))and 26 (C(2)H(2))Da was characteristic of the polyene chain of intact carotenoids. All carotenoid ethyl oximes of zeaxanthin cleavage products were characterized by the losses of 60 and 61 Da in their MS/MS spectra. Through the application of the LC/MS/MS method, we identified two oxime derivatives of 3-hydroxy-beta-ionone and 3-hydroxy-14'-apocarotenal with protonated molecules at m/z 252 and m/z 370 respectively, in a human eye sample.     

On a new partitioning of the Hamiltonian in many-body calculation of pair-correlation energies in closed-shell systems

We introduce here a new partitioning of the Hamiltonian in calculating pair-correlation energies using many-body perturbation theory, by which we are able to eliminate the off-diagonal particle–hole (p–h) ladders exactly to all orders in the perturbation expansion. In this formulation, the particle states turn out to be different for each distinct pair of hole states in the correlation energy calculation. We have also included the contributions of the diagonal particle–particle (p–p) and hole–hole ladders exactly to all orders. The effect of the off-diagonal p–p ladders has been estimated for each pair by computing the third-, foruth- and fifth-order energies. For highly symmetric systems the present partitioning yields in general symmetry-broken orbitals. Here one may use an average kind of partitioning for all the partners of the degenerate sets, which restores the symmetry and at the same time ensures cancellation of the p–h ladders exactly at the lowest order and approximately at the higher orders. Results are presented for a selection of 6π-electron conjugated systems. The correlation energy for each pair is in excellent agreement with that obtained from a partial CI calculation involving all double excitations from this pair. The advantages of implementing the present scheme in larger systems has been discussed.     

Removal of actinides and fission products activity from intermediate alkaline waste using inorganic exchangers

Hydrated iron oxide or amorphous-Fe₂O₃·3.5 H₂O (HFeO), hydrated titanium oxide (HTiO) and hydrated thorium oxide (HThO) were synthesized and their applicability for the decontamination of intermediate level liquid wastes (ILLW) was tested. The sorption of a few actinides like plutonium and americium on HFeO, ¹³⁷Cs and ¹⁰⁶Ru on HTiO and ⁹⁰Sr on HThO was investigated as a function of pH, time and loading capacity of the hydrous oxide with metal ions. The influence of the total dissolved salt content was also monitored. Some of these parameters influenced the sorption behavior significantly. The radiation stability of these inorganic sorbents were studied by irradiating them up to 48 Mrad. Adsorbed actinides and fission products were successfully eluted from HFeO and from the mix-bed of HTiO and HThO by 0.5M nitric acid.The authors wish to thank Shri R. D. Changarani, Chief Superintendent NRG Facilities and Shri P. K. Dey, Head FRD for their valuable advice and constant support.     

Micropolar flow past a stretching sheet

Summary This paper studies the flow of an incompressible, constant density micropolar fluid past a stretching sheet. The governing boundary layer equations of the flow are solved numerically using a globally convergent homotopy method in conjunction with a least change secant update quasi-Newton algorithm. The flow pattern depends on three non-dimensional parameters. Some interesting results are illustrated graphically and discussed.

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Résumé Nous étudions l'écoulement d'un fluid micropolaire et incompressible, de densité constante, le long d'une surface qui l'étend. Les équations de la couche limite qui régissent l'écoulement sont résolues numériquement. On utilise un algorithme quasi-Newtonien de type least change secant update avec une méthode homotopique /`a convergence globale. Certains résultats intéressants sont discutés et illustrés graphiquement.

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This work performed at Sandia National Laboratories supported by the U. S. Department of Energy under contract number DE-AC04-76DP00789.     

Studies on the colloidal properties of papain with titanium dioxide sol

Summary The coagulation concentration for a titania sol decreases if the concentration of a mixture of electrolytes and papain decreases. If the concentration of papain is increased then lesser amount of electrolytes is needed to coagulate the sol. If glycine is added as an additional substance then the value decreases more rapidly. There is no significant change in the p_H and the electrical conductance of the sol by the addition of papain or electrolytes. There is a little change, when glycine is added as an additional substance. These observations are explained due to the formation of negative papain ions in a low p_H region. The possibility of the adsorption or the release of the counter ions is ruled out.The authors wish to thank Dr.R. C. Mehrotra, Professor and the Head of the Chemistry Department for providing all the facilities for this work. We are also thankful to the Ministry of Education, Government of India, for the award of a research scholarship to one of us (V.K.S.).     

Methods for the preparation of mercury and osmium samples suitable for ion microprobe measurements

Using radiotracer solutions of Hg (²⁰³Hg) and Os (¹⁸⁵Os), techniques have been developed for sampling these elements presumably suitable for ion probe measurements. Mercury has been electrodeposited on the cross-sectional area (5 mm²) of an electrochemically pure Cu wire giving a recovery 25 to 30% at the tip. Similar efficiency is found for Hg distillate solutions. Osmium has been collected in a Ni–NiS bead after loading its thiourea complex solution on filter paper. The recovery in the bead is 80–90%. These methods should be of help for isotopic study of these elements by ion microprobe. The suitability of these samples for measurements remains unconfirmed.     

Spectrophotometric studies on the zirconium complex of 2-(3,6-disulfo-8-hydroxynaphthylazo)-1,8-dihydroxynaphtualene-3, 6-disulfonic acid

Summary A chromotropic azo dye, DSNADNS, prepared from chromotropic acid and 1-amino-8-naphthol-3,6-disulfonic acid has been found to produce quantitative precipitation of zirconium in acid medium. The blue-violet complex formed is insoluble in all organic solvents commonly used for solvent extraction work, but is soluble in a number of liquid organic bases and solutions of ammonium salts in water showing pink to violet colouration. Spectrophotometric studies as to the nature of the complex in pyridine, triethanolamine ammonium acetate, oxalate and carbonate solutions and the analytical possibility of these solutions have been made. The complex appears to decompose in pyridine, ammonium acetate and ammonium oxalate solutions, but it is fairly stable in ammonium carbonate and triethanolamine solutions. The absorbance peaks of the dye in these solutions occur at 500 and 520 nm respectively, while the complex in triethanolamine and ammonium carbonate both shows absorbance maxima at 540 nm. The solution of the complex in these two solvents obeys Beer's law within a concentration range 4 to 25 mg of zirconium per litre. The molar absorbance coefficients of the complex in triethanolamine and ammonium carbonate are respectively 686 and 823, which indicate poor sensitivity. The solution of the complex in the former solvent is more stable than that in the latter and an analytical procedure for the spectrophotometric determination of zirconium, with little interference from foreign ions, may be developed with ease in the triethanolamine solution.

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Zusammenfassung Ein Azofarbstoff der Chromotropsäure, DSNADNS, der aus Chromotropsäure und 1-Amino-8-naphthol-3,6-disulfonsäure dargestellt werden kann, ergibt mit Zirkonium in saurer Lösung eine quantitative Fällung. Der blauviolett gefärbte Komplex ist in allen üblichen organischen Lösungsmitteln unlöslich, löst sich jedoch in einigen flüssigen organischen Basen sowie wäßrigen Lösungen von Ammoniumsalzen mit rosa bis violetter Färbung. Die Lösungen des Komplexes in Pyridin, Triäthanolamin sowie in Ammoniumacetat, -oxalat und -carbonatlösungen und ihre analytische Verwendbarkeit werden spektrophotometrisch untersucht. In Pyridin sowie in Ammoniumacetat und -oxalatlösungen scheint sich der Komplex zu zersetzen, während er in Triäthanolamin und Ammoniumcarbonatlösungen ziemlich beständig ist. Das Absorptionsmaximum des Farbstoffs in diesen beiden Lösungsmitteln liegt bei 500 bzw. 520 nm, der Komplex weist in beiden Fällen ein Maximum bei 540 nm auf. Das Beersche Gesetz wird in beiden Lösungsmitteln von 4–25 mg Zr/l erfüllt. Der molare Absorptionskoeffizient beträgt 686 bzw. 823. Die Lösung des Komplexes in Triäthanolamin ist stabiler als in Ammoniumcarbonatlösung. Eine spektrophotometrische Bestimmung von Zirkonium, die nur wenig von Fremdionen gestört wird, könnte daher gut in Triäthanolaminlösung durchgeführt werden.

     

EFFECTS OF QUENCHING AGENTS ON THE PHOTODYNAMICALLY-INDUCED CHEMOTACTIC RESPONSE OF THE COLORLESS FLAGELLATE Polytomella magna

Abstract In the presence of the photosensitizer riboflavin at high fluence rates a photoproduct, most probably H₂O₂, is formed which causes negative phototaxis in the colorless flagellate Polytomella magna . The aim of this study was to find out whether H₂O₂ is produced in a type I or II reaction. As has been shown, ¹O₂ quenchers either do not influence the photodynamic action of riboflavin (furfuryl ethanol, DPBF, l -histidine, crocetin) or show slight quenching effects only at very high concentrations ≧ 10⁻² M (DABCO, DMF, imidazole). D₂O is toxic to P. magna even in 1:1 and 1:2 mixtures with H₂O. On the other hand, the quenching effect of 1,4-benzoquinone, highly indicative for the type I pathway, is more than two orders of magnitude stronger than the one of the above mentioned ¹O₂ quenchers. The results suggest that H₂O₂ is produced in a type I reaction. Superoxide does not seem to be involved since superoxide dismutase does not diminish the photodynamic effect of riboflavin.