Lifetime measurements in Sb121

Employing delayed coincidence techniques lifetime measurements have been carried out in the decay of Te¹²¹ to decide between two alternative level schemes for Sb¹²¹. Our results support the scheme proposed by Gupta which consists of excited levels in Sb¹²¹ at 70 and 576 KeV.     

Collision dynamics of non-integrable systems: Validity of classical scaling

The classical collision dynamics of a model atom—molecule non-integrable collision system is studied, and the energy transfer (ET) moment is examined as a function of the initial semiclassical level of the molecule. A recently derived classical scaling theory is shown to be valid in the case when the molecular motion remains regular throughout the collision, and the ET variation is then characterized by a polynomial dependence on the initial (semiclassical) quantum numbers. When chaotic motions participate, the ET no longer follows the scaling law. The utility of the scaling theory in providing the proper interpolation form for extending classical trajectory data in non-integrable collision systems is discussed.     

Systematics of magnetic dipole transitions

An empirical approach to distinguish betweenl-allowed andl-forbidden magnetic dipole transitions is made. The reduced lifetimes of these transitions are calculated and their variation with neutron number is studied. It is observed that their general tendency is to remain constant whilel-forbidden andl-allowed odd-proton magnetic dipole transitions are distinguishable from their reduced lifetimes, it is not so in the case of odd-neutron transitions. A slight increase in reduced lifetime with neutron number is observed for fixed proton number.     

A Y-fed directional coupler modulator with a highly linear transfer curve

We demonstrated a linearized Y-fed directional coupler modulator in Z-cut LiNbO/sub 3/. The proof-of-concept device employed two electrode sections of opposite polarity whose lengths were chosen based on the results of our previous theoretical modeling. A highly linear modulation characteristic and improved tolerance to fabrication errors were achieved with a simple design, in excellent agreement with the theory. The linearity exceeded 90% over a wavelength range of 45 nm, centered around 1530 nm, with a maximum linearity of 97% at 1510 nm and a maximum modulation depth of 98%. By comparison, the linearity of conventional modulators is typically around 70%. Thus the device was proven to have a high linearity with a wide usable spectral range and relaxed fabrication tolerances.     

GC–MS method for the determination of paraben preservatives in the human breast cancerous tissue

The general presumption that the preservative laden personal care products may be one of the causative agents for breast cancer, has remained a matter of controversy during this decade. Extensive studies have not been carried out to either prove or disprove the role of preservatives in breast cancer incidences. In this study we have developed a new method for the identification and quantification of the preservatives such as methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP) and butyl paraben (BuP) in breast tissue using Gas Chromatography and Mass Spectrometry (GC–MS). Tissue was extracted by using acetone:n-hexane mixture (1:1 v/v) and derivatized with N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA). The extent of reaction time and the amount of MSTFA to attain greater derivatization were optimized. The developed method yielded good recovery (mean ± SD) of 99.8 ± 5.1, 96 ± 4.4, 107 ± 17 and 113 ± 13% with relative standard deviations (RSDs) of 5.1, 4.6, 15.6 and 13%, and the limits of detection (LOD) of 2.02, 1.05, 1.71 and 3.75 ng g^{− 1} for MeP, EtP, PrP and BuP, respectively. The method was successfully validated for the determination of parabens including butyl paraben (log K_ow = 3.57) in cancerous breast tissues; this could be a promising one for screening of breast tissues and also the environment for paraben residues. As far as our knowledge goes this is the first GC–MS method for the determination of parabens in human tissue.     

Construction of Approximate Saddle-Point Strategies for Differential Games in a Hilbert Space

Two-person zero-sum infinite-dimensional differential games with strategies and payoff as in Berkovitz (SIAM J. Control Optim. 23: 173–196, 1985) are studied. Using Yosida type approximations of the infinitesimal generator (of the unbounded dynamics) by bounded linear operators, we prove convergence theorems for the approximate value functions. This is used to construct approximate saddle-point strategies in feedback form. A.J. Shaiju: NBHM Postdoctoral Fellow and the financial support from NBHM is gratefully acknowledged.     

Rings, chains and cages in metal phosphate chemistry: The interdependence and possible interconversion between various structural forms

Our endeavour to build soluble model compounds of basic building blocks in zeolite structures have resulted in a plethora of main group and transition metal phosphate complexes. Many of these complexes show highly intriguing and novel structural features. Careful examination of the core structures allowed us to rationalize the interdependence between the different structural types and visualize their plausible pathway of formation. Due to the high reactivity and short life span of the intermediates it has not been possible to characterize many intermediates. However, the common structural features present in the isolated products drive us to arrive at a plausible mechanism. Further investigation and isolation of other structural types will definitely provide more credential to these hypotheses and help us to solve the zeolite jigsaw.