A thermoluminescence study of defect centres in MgO

Thermoluminescence glow curves are a fairly good representation of the different defect centres in MgO produced by γ or reactor irradiation. The glow peaks at 370, 440, 485 and 545 K have been found to be due to hole trapped centres. The 370 K peak has been found to be due to holes released from V_M centres (hole trapped at action vacancy associated with a neighbouring impurity ion). The 665 K peak in γ-irradiated MgO is due to charge transfer between the adsobred oxygen ions and surface defect centres. The F-type centres produced on reactor irradiation (neutron and γ) and on quenching from high temperatures before γ-irradiation are also found to give thermoluminescence peaks at temperatures higher than 560 K. It has also been found that reactor irradiation partially annihilates the trapping centres which are responsible for lower temperature glow peaks.     

Angular forces in the lattice dynamics of b.c.c. metals

The lattice dynamics of the b.c.c. lattice has been investigated using the central and the angular forces which are in general rotationally invariant. It has been observed that the four force constants are related to three elastic constants only. Dispersion curves for sodium were calculated and were found to be in excellent agreement with experiment.     

Theory of mass-yield distributions in “quasi-fission” reactions

A two-step process of “fission after a few nucleon transfer” is studied for the mass-yield distributions in the reaction of 605 MeV⁸⁴Kr ions with²³⁸U. The general agreement between the theory and experiment is qualitatively good. Based on the phenomenological considerations, sequential fission is also included partially. The transfer process is also shown to be given by the charge dispersion calculations.     

Studies in sesquiterpenes—LI : β-Himachalene epoxide—stereochemistry and solvolysis

Stereochemistry of β-himachalene oxide has been established by its correlation with himachalol. Products of solvolysis of this oxide are dependent on conditions and reagents used. Homoallylic participation becomes the dominant mode with perchloric acid in aqueous dioxane.     

α-Chlor-nitrone II: Eine Methode zur Darstellung von γ-Lactonen aus Olefinen. Über synthetische Methoden, 6. (vorläufige) Mitteilung

The addition products obtained by the Ag⁺-induced reaction of α-chloro-aldonitrones with olefins (see preceding communication) can be utilized efficiently for making γ-lactones (see scheme 1).     

A two (multicomponent) unit parallel system with standby and common cause failure

This paper investigates the mathematical model of a system composed of two non-identical active parallel units and one cold standby. A unit has N components, each having a constant failure and repair rate. These vary from component to component. Several reliability characteristics of interest to system designers as well as operations managers have been computed. Results obtained earlier are verified as particular cases.     

Processability characteristics of chlorinated poly(vinyl chloride)

Chlorinated poly(vinyl chloride) (CPVC) is known to have a higher softening temperature than conventional poly(vinyl chloride) (PVC). Its processability characteristics are, however, different; it has been reported that CPVC is more difficult to process. However, only limited information on the processability characteristics is available. This paper describes some studies of the flow behavior of CPVC melts in a capillary rheometer. The true melt viscosity and activation energy were determined between 190° and 210°C for a number of samples, and they appear to be related to the cohesive energy density of the samples. It was observed that melt fracture, i.e., gross distortion of the extrudate, occurs even at low shear rates in samples having a high chlorine content. This has been attributed to the relatively high pressures that have to be used, the pronounced non-Newtonian nature of the melt, and melt elasticity. It is postulated that melt elasticity could result from crosslinking at the site of the double bond which is known to be formed by dehydrochlorination.     

The conjugacy problem for centre-by-metabelian groups

Archiv der Mathematik -     

Synthesis of some new mesoionic heterocycles

The synthesis of various substituted 1-hydroxy-2-chloroacetyl-6-thia-10b-aza-2a-azoniaaceanthrylene hydroxide inner salt, 1-hydroxy-6-thia-10b-aza-2a-azoniaaceanthrylene hydroxide inner salt, 1-hydroxy-2-piperidinoacetyl-6-thia-10b-aza-2a-azoniaaceanthrylene hydroxide inner salt is described. The ir is also included.