Natural radioactivity in marble stones- Jordan

Natural radioactivity has been measured in marble stone samples collected from Dabaa'h, Ajloun and Azrak areas using a gamma spectroscopy technique. The measured ²²⁶Ra activities in the stones collected from Dabaa'h quarries varied from 264.9 Bq kg⁻¹ to 369.5 Bq kg⁻¹. In samples from Ajloun and Azrak the maximum values of ²²⁶Ra were 28.3 Bq kg⁻¹ and 23.41 Bq kg⁻¹, respectively. The measured values of ²³²Th were less than 17.89 Bq kg⁻¹. The average values of the radium equivalent activities as well as external and internal hazard indices were also calculated. It was observed that for marble stones from Dabaa'h area, estimated average value of the external hazard index is 0.873 and that of internal hazard index is 1.71.     

Rational approximation with sign-sensitive weight

For metrics of sign-sensitive weight, a generalization of the Jackson theorem and an analog of the Dolzhenko theorem on the estimate of the variation of a function in terms of its least rational deviations are obtained. In the same metric, two-sided estimates for rational deviations of the function signx are given.Translated fromMatematickeskie Zametki, Vol. 60, No. 5, pp. 715–725, November, 1996.     

Hyperfine structure and isotope shift of the neutron-rich barium isotopes139–146Ba and148Ba

The hyperfme structure and isotope shift in the 6s ² S _1/2?6p ²P_3/2 line of Ba II (455.4 nm) have been measured by collinear fast-beam laser spectroscopy for the neutron-rich isotopes^139–146Ba and¹⁴⁸Ba. Nuclear moments and mean square charge radii of these isotopes have been recalculated. The isotope shift of the isotope¹⁴⁸Ba (T_1/2=0.64 s) could be studied for the first time, yieldingδ〈r²〉^138,148=1.245(3) fm².     

Hydroxylation of benzene in the system vanadium(V)-hydrogen peroxide-acetic acid

Hydroxylation of benzene in acetic acid at 323 K was studied in the presence of a sodium orthovanadate catalyst. With hydrogen peroxide as aqueous solution, the yield of phenol was 12–14%. With hydrogen peroxide generated from dry sodium peroxide, the yield of phenol could be improved to 21–23%. The apparent decomposition rate constants of hydrogen peroxide in acetic acid are presented.     

Anion—surface interactions: Part I. Perchlorate decomposition and sulphate adsorption hysteresis studied by voltammetry

Cyclic voltammetry has been used to investigate the behaviour of sulphate and perchlorate anions adsorbed on Ir{111} and polycrystalline rhodium. In 0.1 M HClO₄, perchlorate anions decompose on polycrystalline rhodium to give a surface intermediate which inhibits hydrogen adsorption. This is in agreement with a previous study by Wieckowski and coworkers, who showed that the surface intermediate was, in fact, adsorbed chloride. The voltammetry of the same electrode in sulphate containing electrolytes depends critically on the concentration of sulphate and the potential sweep rate. We conclude that hydrogen adsorption can only occur after significant desorption of sulphate. Hysteresis in the adsorption and desorption of sulphate results in an asymmetric hydrogen adsorption region with respect to the potential axis. Ir{111} is shown also to cause decomposition of perchlorate anions, although, contrary to the case of rhodium, the process is very much a chemical one in which electric currents, arising from perchlorate decomposition, were not detected. In sulphuric acid, a strong interaction between anions and the Ir{111} surface is observed, which precludes oxide formation at potentials less than 1 V (Pd---H), behaviour characteristic of a Pt{111} surface in the same electrolyte.     

Effect of annealing on the electrical properties and refractive index of HgI2 single crystals

The effect of annealing on the electrical properties and the refractive index of red mercuric iodide (HgI₂) single crystals is investigated. The ac-impedance and phase angle were measured in the frequency range from 100 Hz to 10 kHz at different annealing temperatures. The ac-conductivity, dielectric constants, loss tangent and the refractive index as a function of frequency are determined. The results are discussed in terms of structural changes taking place as a result of the heat treatment of the HgI₂ single crystals.     

Design and fabrication of low-cost X-ray mirrors

Traditional X-ray mirrors made from Zerodur and silicon carbide are quite expensive because of the fabrication cost involved in achieving a very high surface finish of the order of 15 Å or better. The cost of X-ray mirrors can be greatly reduced by using replication methods for producing the grazing-incidence type mirrors. This paper presents the optical and optomechanical design for a Wolter type I mirror and its mount, and the fabrication method used to produce a low-cost replicated nickel mirror. The finite element analysis results for this mirror are also presented. The design and fabrication steps for the aluminium master mandrel used for replication are also discussed. A surface finish of better than 15 Å was achieved for a such an electroformed mirror with a wall thickness of only 1 mm.     

Kinetics and mechanism of copper(II) induced decomposition of 9-diazofluorene

The kinetics and products of the decompositon of 9-diazofluorene by copper(II) tetrafluoroborate in acetonitrile solvent have been investigated. The reaction is first order with respect to both 9-diazofluorene and copper(II) tetrafluoroborate. A reaction mechanism has also been proposed.     

Adoucissement des eaux calciques par échange d''ions transmembranaire à travers des membranes homogenes obtenues par greffage radiochimique

The potential application of DONNAN dialysis to water softening has been studied. The selective transportation of calcium and alkaline-earth ions through a cationic membrane appeared to be an interesting process, since materials with both optimal exchange capacity and transportation properties exist now.

Preliminary investigations allowed us to optimize some of these materials, as well as the conditions of their use. Thus we have found that for the membranes handled, the 3.10-2 M concentration of brine represented the best compromise between the extraction of calcium and the leakage of chlorine through the membrane (relating to the water to be softened).

We also observed that for a low and a medium flow, the extraction rate was high enough to allow the release of calcium at a rate comparable to the classical ion-exchange process using a resin bed.     

Reactions ofN-trimethylsilyl-imidazole and-2-methylimidazole with anhydrous CoCl2 and [Co(Ph3P)2Cl2]; synthesis and physicochemical studies on two-coordinate cobalt(II) complexes

Summary Reactions ofN-trimethylsilylimidazole andN-trimethyl-silyl-2-methylimidazole with CoCl₂ yield chloro(imidazolato)cobalt(II), (1), or chloro(2-methylimidazolato)-cobalt(II), (2). However, the corresponding reactions of [Co(Ph₃P)₂Cl₂] cause total removal of Ph₃P along with the substitution of both the chlorine atoms yielding bis(imidazolato)cobalt(II), (3), or bis(2-methylimidazolato)cobalt(II), (4), in the form of light blue microcrystalline solids. The complexes have been characterized by elemental analysis, molecular weight, and magnetic susceptibility measurements, and i.r., reflectance and electronic spectra. The results are consistent with formulations as rare examples of two-coordinate cobalt(II) derivatives.Author to whom all correspondence should be directed