Indentation studies of alkali halides at elevated temperatures

The hardness of NaCl and KCl crystals has been estimated from the lengths of dislocation rosette formed around indentation at various temperatures up to 400°C. The hardness decreases with increasing temperature. This is due to the softening of the crystals at elevated temperatures which results in the easy movement of dislocations. The results are discussed using a few available relations which connect hardness to temperature. Arms of indentation dislocation rosette are well defined up to 300°C but around 400°C the rosette pattern is spread over a circular region. A possible mechanism is discussed.     

One- and two-sample match statistics

A mathc statistic considered by Khidr (1981) is interpreted in terms of crossings of the empirical and true distribution functions and a simpler alternate derivation of its distribution provided. This approach can also be used to obtain the distribution of a two-sample match statistic, considered earlier by Takács (1971).     

Chemical ordering in As-Se glasses: X-ray absorption edge and XPES studies

X-ray absorption edge and X-ray photoelectron spectroscopic studies of As-Se glasses seem to support a chemical ordering model. Communication No. 94 from Solid State and Structural Chemistry Unit.     

Cyclohexanol dehydrogenation over Cu/SiO2 and CuO/SiO2: A comparison

Various CuO/SiO₂ catalysts were prepared and characterized by XRD, surface area and metal area measurements. While dehydrogenation activity for cyclohexanol was observed at 473–573 K on reduced catalysts, it was observed only at 573 K on the unreduced catalyst.IICT Communication No: 3261     

Internal Bremsstrahlung from14C and36Cl

The Internal Bremsstrahlung (IB) spectra emitted in the beta decays of¹⁴C and³⁶Cl are measured with a HPGe detector and a multichannel analyser along with a standard geometrical set up. The experimental results are compared with the corresponding theoretical distributions due to Knipp and Uhlenbeck and Bloch (KUB), Lewis and Ford, Nilsson and also due to Chang and Falkoff. The total IB yields of intensity and of energy from each of the isotopes in the investigated energy regions are also determined and compared with the corresponding theoretical values. The present results of IB from¹⁴C are found to be in excess over all the corresponding theoretical distributions throughout the investigated photon energy region from 60 keV to 130 keV. It may also be pointed out that the IB from this isotope has not been studied earlier and as such the results in this case are considered new and important. In the case of³⁶Cl the experimental results are found to be above KUB theory but corresponding closely to the theory of Chang and Falkoff, except below 150 keV where there is experimental excess over theory.     

The Resonant Characteristics of Concentric Circular-Elliptical Ring Microstrip Antennas

In this paper, the resonant wavenumbers of concentric circular- elliptical ring microstrip antennas are partially calculated with the shape perturbation method, which is connected with the concentric ring microstrip antenna and based on the perturbation.     

Formation of H and D atoms in pyrolysis of 1,3-butadiene and 1,3 butadiene-1,1,4,4,-d4 behind shock waves

Highly dilute mixtures of 1,3-butadiene and 1,3-butadiene-1,1,4,4-d₄ were pyrolyzed behind reflected and incident shock waves, respectively. Concentrations of H and D atoms were measured by resonance absorption spectroscopy. In the early stages of the reaction, nearly equal amounts of H and D were formed from CD₂CHCHCD₂, indicating that loss of H from C₂ followed by loss of D from C₁ is a more important reaction than breaking of the central C? C bond. Overall, rate constants for atom-forming reactions are much slower than rate constants for disappearance of butadiene in earlier experiments, suggesting that most of the butadiene disappears by processes that do not involve H or D atoms or by radicals that produce them rapidly.