Two million volt terminal tandem accelerator

Design and construction details of a horizontal 2 MV Tandem Van de Graaff accelerator built at Bhabha Atomic Research Centre are given. A terminal voltage of 2.15 MV has been achieved. Energy analysed Corona stabilized beams of protons and oxygen ions have been obtained. Experiments have been carried out to test the performance of the accelerator.     

Resonant response of orthotropic cylindrical shells

The resonant response of simply supported, thin and thick, orthotropic cylindrical shells is determined by using modal analysis, for three levels of hysteretic damping. This response is significantly changed if the larger of the elastic constants associated with normal stresses refers to the meridional, instead of the circumferential, direction. These changes may be related to changes in the relevant natural frequency. The causes of the latter are studied by considering the modal amplitudes and the contributions to the strain energy function associated with the various stress resultants.     

B-factory signals for a warped extra dimension

We study predictions for B physics in a class of warped extra dimension models recently introduced, where few ( approximately 3) TeV Kaluza-Klein masses are consistent with electroweak data due to custodial symmetry. As in the standard model (SM), flavor violations arise due to the heavy top quark leading to striking signals: (i) New physics contributions to DeltaF=2 transitions are comparable to the SM, so the success of the SM unitarity triangle fit is a "coincidence." Thus, clean extractions of unitarity angles are likely to be affected, in addition to O(1) deviation from the SM prediction in B(s) mixing. (ii) O(1) deviation from various SM predictions for B-->X(s)l(+)l(-). (iii) Large mixing-induced CP asymmetry in radiative B decays. Also, the neutron electric dipole moment is roughly 20 times larger than the current bound so that this framework has a "CP problem."     

Biophysical aspects of cyclodextrin interaction with paraoxon

Cyclodextrins are torus‐shaped polymers of glucose that can bind organophosphorous compounds such as nerve agents and pesticides. We demonstrate here that cyclodextrin can bind up to two paraoxon molecules with a K_av of 6775 M^‐1. Molecular modeling shows that the paraoxon appears to bind in polar opposite orientation and have an average binding energy of ?89 Kcals/mol. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.     

Laser synthesis of aluminium nanoparticles in biocompatible polymer solutions

Pulsed laser ablation of Aluminium (Al) in pure water rapidly forms a thin alumina (Al₂O₃) layer which drastically modifies surface plasmon resonance (SPR) absorption characteristics in deep-UV region. Initially, pure aluminium nanoparticles (NPs) are generated in water without any stabilizers or surfactants at low laser fluence which gradually transform to stable Al-Al₂O₃ core-shell nanostructure with increasing either residency time or fluence. The role of laser wavelength and fluence on the SPR properties and oxidation characteristics of Al NPs has been investigated in detail. We also present a one-step in situ synthesis of oxide-free stable Al NPs in biocompatible polymer solutions using laser ablation in liquid method. We have used nonionic polymers (PVP, PVA and PEG) and anionic surfactant (SDS) stabilizer to suppress the Al₂O₃ formation and studied the effect of polymer functional group, polymeric chain length, polymer concentration and anionic surfactant on the incipient embryonic aluminium particles and their sizes. The different functional groups of polymers resulted in different oxidation states of Al. PVP and PVA polymers resulted in pure Al NPs; however, PEG and SDS resulted in alumina-modified Al NPs. The Al nanoparticles capped with PVP, PVA, and PEG show a good correlation between nanoparticle stability and monomeric length of the polymer chain.     

Laser-induced synthesis of silver nanoparticles and their conjugation with protein

Partially oxidized spherical silver nanoparticles (AgNPs) of different size are prepared by pulsed laser ablation in water and directly conjugated to protein S-ovalbumin for the first time and characterized by various optical techniques. UV–Visible spectrum of AgNPs showed localized surface plasmon resonance (LSPR) peak at 396 nm which red shift after protein addition. Further the increased concentration of AgNPs resulted a decrease in intensity and broadening of S-ovalbumin peak (278 nm), which can be related to the formation of protein NPs complex caused by the partial adsorption of S-ovalbumin on the surface of AgNPs. The red shift in LSPR peak of AgNPs after mixing with S-ovalbumin and decrease in protein-characteristic peak with increased silver loading confirmed the formation of protein–AgNPs bioconjugates. The effect of laser fluence on the size of AgNPs and nanoparticle–protein conjugation in the size range 5–38 nm is systematically studied. Raman spectra reveal broken disulphide bonds in the conjugated protein and formation of Ag–S bonds on the nanoparticle surface. Fluorescence spectroscopy showed quenching in fluorescence emission intensity of tryptophan residue of S-ovalbumin due to energy transfer from tryptophan moieties of albumin to AgNPs. Besides this, small blue shift in emission peak is also noticed in presence of AgNPs, which might be due to complex formation between protein and nanoparticles. The binding constant (K) and the number of binding sites (n) between AgNPs and S-ovalbumin have been found to be 0.006 M^?1 and 7.11, respectively.