The physics of accelerator driven sub-critical reactors

In recent years, there has been an increasing worldwide interest in accelerator driven systems (ADS) due to their perceived superior safety characteristics and their potential for burning actinides and long-lived fission products. Indian interest in ADS has an additional dimension, which is related to our planned large-scale thorium utilization for future nuclear energy generation. The physics of ADS is quite different from that of critical reactors. As such, physics studies on ADS reactors are necessary for gaining an understanding of these systems. Development of theoretical tools and experimental facilities for studying the physics of ADS reactors constitute important aspect of the ADS development program at BARC. This includes computer codes for burnup studies based on transport theory and Monte Carlo methods, codes for studying the kinetics of ADS and sub-critical facilities driven by 14 MeV neutron generators for ADS experiments and development of sub-criticality measurement methods. The paper discusses the physics issues specific to ADS reactors and presents the status of the reactor physics program and some of the ADS concepts under study.      

Binding of 5-(2'-carboxyphenyl)azoquinolin-8-ol to bovine serum albumin: a spectroscopic study

Dye-protein interactions are of immense importance in dye-ligand chromatography of protein purification. In this type of interactions, the structure of the dye molecules has a significant role. However, studies on the structure of these ligands are scanty. Therefore, we have spectroscopically investigated interactions of three 5-(aryl)azoquinolin-8-ol derivatives, which could be used as potent chelate forming agents, with bovine serum albumin (BSA). Among these, the carboxy derivative, 5-(2'-carboxyphenyl)azoquinolin-8-ol (CPAQ) has been selected for resonance Raman study. It has been shown that BSA has six independent binding sites for CPAQ at pH 7.2, the binding constant being 6.2 x 10(3) M(-1). Assignments of Raman modes of bound CPAQ are also presented. It has also been shown that bound CPAQ exists exclusively in hydrazone form. Results further demonstrate that the azo group nitrogen adjacent to the phenyl ring probably participated in the formation of a BSA-CPAQ complex.     

Large sea polarisation in quantum chromodynamics

The spin structure of sea quarks and gluons is obtained by using QCD evolution equations and the angular momentum sum rule. Several consequences of the predicted large polarisations are enumerated.     

A decomposition theorem for an analytic function

Let f(z), an analytic function with radius of convergence R (0 < R < ∞) be represented by the gap series ∑_{k = 0}^∞c_kz^λ_k. Set and define the growth constants ?, λ, T, t by

$\text{?}\text{λ}\text{=}\text{lim sup}\text{r→R}\text{inf}\text{{}\text{log}\text{[Rr /(R?r)]}{}^{\mathrm{?1}}\text{log}{}^{\mathrm{+}}\text{log}{}^{\mathrm{+}}\text{M(r)}}$

, and if 0 < ? < ∞,

$\text{T}\text{t}\text{=}\text{lim sup}\text{r→R}\text{inf}\text{{[Rr /(R?r)]}{}^{\mathrm{??}}\text{log}{}^{\mathrm{+}}\text{M(r)}}$

. Then, assuming 0 < t < T < ∞, we obtain a decomposition theorem for f(z).     

Open circuit thermally stimulated discharge current measurement on PMMA:PEMA:PVDF ternary blends

Ternary blends of Poly (methylmethacrylate), Poly (ethlymathacrylate) and poly (vinlylidenefluoride) were prepared using solution cast technique. The open circuit thermally stimulated discharge current (OC-TSDC) technique was used to study the hetero charges, homo-charges and interfacial charge formation in ternary system. The present investigation was carried out on bilaterally metallized electret. The thermograms were characterized with multiple peaks in the temperature ranges from 40, 60, 80 and 100oC and the current direction was, in general, found to correspond to homo- charge, i.e., the same as that during charging with a few exceptions. The resultant current polarity corresponds to the dominant charging process. To distinguish between homo-charge decay by ohmic conduction and space charge limited drift in an open circuit, homocharge magnitude is changed by varying the polarizing voltage. Decay of ohmic conduction is independent of the initial charge; however, space-charge-limited (SCL) drift dependence on the injection level. A high initial charge will enhance the drift because it increases the field that drives the charges to adhering back electrode. This proves unequivocally that the, ρ peak is caused by the motion of excess charges and not by dipole relaxations, hence, the useful for microelectronics and many special purpose insulation.     

Effect of Structure on Surfactant Properties

The surface tension and foaming properties of sodium oleate were altered by adding a large and electronegative moiety bromine, to its unsaturation. These properties were measured and compared to the original oleic soap. It was found that sodium oleate has a lower CMC than both of the brominated surfactants. The bromine moiety slows down the rate of adsorption with the doubly brominated surfactant being the slowest. Foamability of the brominated analogues were not affected, however its foam were found to be less stable. Bromination also caused the coalescence and bursting of large bubbles.