Radiometric Measurements of Rain Attenuation at 22.2 and 31.4 GHz Over Calcutta

Measurements of rain attenuation over Calcutta have been made using radiometers operating at frequencies of 22.235 and 31.4 GHz. The results have been correlated with observations of rainfall rates made with a fast-response rain gauge. The distributions of peak rain rates over Calcutta for two different years and the cumulative occurrences of rainfall rates and attenuations at the two frequencies are presented.     

Negative differential mobility in PbTe and PbSnTe at high electric fields

Monte Carlo calculations of hot-electron drift velocity in PbTe and Pb_0.8Sn_0.2Te at 77 K are reported. The relevant scattering mechanisms together with band-structure nonparabolicity and anisotropy are included in the calculations. A negative differential mobility (NDM) does not appear when the electrons are assumed to remain confined within the L valleys of the conduction band. On the contrary, allowing for electron transfer into the W valleys and taking suitable values of the parameters related to these valleys, an NDM appears and the threshold field for the same agrees well with the experimental data. Alloy scattering in PbSnTe is found to reduce the NDM.     

A nonlinear extension of the RPA and its application to the even nickel isotopes

A nonlinear extension of the RPA is proposed and applied to calculate anharmonic effects in the even nickel isotopes. It is shown, by comparison with an exact diagonalization, to be highly accurate.     

Studies on synergic extraction of uranium/VI/ by combination of 8-hydroxyquinoline and neutral donors

Extraction of U/VI/ by mixtures of 8-hydroxy quinoline /Oxine/ and neutral donors was studied from 0.1M NaCl at a pH 4.5. The presence of a neutral donor enhanced the extraction of U/VI/ and the species responsible for synergism was established to be 11 adduct UO₂Ox₂S. From the data, the equilibrium constants for the adduct formation reaction were calculated and was found to be the lowest with TBP and the highest with TOPO.     

Crystal structure of aluminium containing superconducting oxides: single crystal study of GdBa2Cu3−x AL x O6.88 (x=0.28) and ErBa2Cu3−y Al y O6.6 (y=0.14)

Following the discovery of the high temperature super-conductivity in YBa₂Cu₃O_7– (T _c 93 K) [1] it has been found that Y atoms can be substituted entirely by almost all of the rare-earth elements, except for Ce, Pr, and Tb, without changing the superconducting properties appreciably [2, 3]. The magnetic moments carried by the rare-earth atoms have apparently no influence on the superconducting properties. In Nd-, Sm-, Gd-, Dy- and Er-based compounds the rare earth moments order at low temperatures (0.025–2.2 K) [4–8] and the ordered antiferromagnetic state coexists with the superconducting state. We have investigated the antiferromagnetic ordering of these compounds by neutron diffraction both on powder and single crystal samples obtained from several laboratories [8–10]. Magnetic structures of all these compounds consist of antiferromagnetic (001) planes stacked ferro- or antiferromagnetically. There have been some controversies as to the stacking of antiferromagnetic (001) planes in GdBa₂Cu₃O_7–.     

Conductometric study on the quantitative precipitation of samarium (III) as normal tungstate

Summary Conductometric titrations of samarium nitrate with sodium tungstate were carried out with 30% ethanol concentration at 25° ± 0.5° C. The breaks were sharp in both the direct and reverse titrations. The present method is an easy titrimetric procedure for the micro-determination of samarium as well as tungstate ions.

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Zusammenfassung Konduktometrische Titrationen von Samariumnitrat mit Natriumwolframat wurden in 30% iger äthanolischer Lösung bei 25°±0,5° C durchgeführt. Bei direkten sowie auch bei umgekehrten Titrationen wurden scharfe Endpunkte erhalten. Das beschriebene Verfahren wird als einfache Methode zur Samarium- oder Wolframbestimmung empfohlen.

     

Absorption spectroscopic study of EDA complexes of

[70]Fullerene has been shown to form 1:1 molecular complexes with toluene, p-xylene, m-xylene, 1,2,4,5-tetramethyl benzene (durene) and pentamethyl benzene (PMB) in CCl4 medium by absorption spectroscopic method. Isosbestic points have been detected in case of complexes with PMB and durene. Charge transfer absorption band could not be detected but the intensity of the broad absorption band of C70 in CCl4 decreases systematically with increase in the concentration of the added methylbenzenes. From this trend the formation constants (Kc) of the complexes have been determined at three different wavelengths. The constancy of Kc with respect to change in the wavelength of measurement supports the view that complex of a single stoichiometry (1:1) is formed in each case.     

Crystal engineering with aroyl hydrazones of diacetyl monooxime – Molecular and supramolecular structures of two Ni(II) and two Zn(II) complexes

Four new Schiff bases of aroyl hydrazides with diacetyl monooxime have been prepared, and Ni(II) and Zn(II) complexes of these ligands have been synthesized. Two Ni(II) and two Zn(II) complexes have been characterized by X-ray crystallography. The aroyl hydrazone ligands were designed in such a way that there is a systematic variation in the H-bond forming abilities of their aroyl moiety, e.g. both H-bond acceptor and donor (salicyloyl), only H-bond donor (anthraniloyl), only H-bond acceptor (isonicotinoyl). It is shown in this work that such a variation in the H-bond donor acceptor properties of the ligands leads to considerable diversity in their supramolecular architecture.     

Scalp hair as a monitor of population exposure to environmental pollutants

Concentrations of As, Cd, Hg, Pb, Sb and Zn have been measured in hair from population groups with varied types of environmental exposure. Rural and urban controls have exhibited low levels of most toxic elements, whereas people residing near urban lead refineries, rural gold refinery and other industries have shown high elemental concentrations in their hair. A combination of instrumental as well as radiochemical neutron and photon activation analysis methods have been used to determine the concentrations of the above elements. The precision and accuracy of these methods have been evaluated.