Fast Transition between High-soft and Low-soft States in GRS 1915+105: Evidence for a Critically Viscous Accretion Flow

We present the results of a detailed analysis of RXTE observations of class $\omega$ which show an unusual state transition between high-soft and low-soft states in the microquasar GRS 1915+105. Out of about 600 pointed RXTE observations, the source was found to exhibit such state transition only on 16 occasions. An examination of the RXTE/ASM data in conjunction with the pointed observations reveals that these events appeared as a series of quasi-regular dips in two stretches of long duration (about 20 days during each occasions) when hard X-ray and radio flux were very low. The X-ray light curve and color-color diagram of the source during these observations are found to be different from any reported so far. The duration of these dips is found to be of the order of a few tens of seconds with a repetition time of a few hundred seconds. The transition between these dips and non-dips which differ in intensity by a factor of ~ 3.5, is observed to be very fast (~ a few seconds). It is observed that the low-frequency narrow QPOs are absent in the power density spectrum (PDS) of the dip and non-dip regions of class $\omega$ and the PDS is a power law in 0.1 - 10 Hz frequency range. There is a remarkable similarity in the spectral and timing properties of the source during the dip and non-dip regions in these set of observations. These properties of the source are distinctly different from those seen in the observations of other classes. This indicates that the basic accretion disk structure during both dip and non-dip regions of class $\omega$ is similar, but differ only in intensity. To explain these observations, we invoke a model in which the viscosity is very close to critical viscosity and the shock wave is weak or absent.Comment: Replaced with correct figures, Jour. of Astrophysics and Astronomy (accepted

Mode of interaction of calcium oxalate crystal with human phosphate cytidylyltransferase 1: a novel inhibitor purified from human renal stone matrix

Nephrolithiasis is a common clinical disorder, and calcium oxalate (CaOx) is the principal crystalline component in approximately 75% of all renal stones. It is widely believed that proteins act as inhibitors of crystal growth and aggregation. Acidic amino acids present in these proteins play a significant role in the inhibition process. In this study, interaction of cal-cium oxalate with human phosphate cytidylyltrans-ferase 1(CCT), a novel calcium oxalate crystal growth inhibitor purified from human renal stone matrix has been elucidated in silico and involvement of acidic amino acids in the same. As only sequence of CCT is available, henceforth its 3-D structure was modeled via Homology modeling using Prime module of Schrodinger package. Molecular dynamic simulation of modeled protein with solvation was done by mac-romodel (Schrodinger). The quality of modeled pro-tein was validated by JCSG protein structure valida-tion (PROCHECK & ERRAT) server. To analyze the interaction of modeled protein CCT with calcium oxalate along with role played by acidic amino acids, ‘Docking simulation’ was done using MOE–Dock. Interaction between calcium oxalate and CCT was also studied by substituting acidic amino acid in the active sites of the protein with neutral and positively charged amino acids. The in silico analysis showed the bond formation between the acidic amino acids and calcium atom, which was further substantiated when substitution of these acidic amino acids with alanine, glycine, lysine, arginine and histidine com-pletely diminished the interaction with calcium ox-alate

Synthesis, Spectral and Antimicrobial Studies of Lanthanide (III) Chloride Complexes with the Schiff’s Base Derived from 2-Benzimidazolyl Mercaptoaceto Hydrazide and 2-Acetyl Pyridine

AbstractFew lanthanide (III) chloride complexes with Schiff’s base obtained by the condensation of 2-benzimidazolyl mercaptoaceto hydrazide and 2-acetyl pyridine have been prepared and characterized on the basis of elemental analysis, molar conductance, magnetic, electronic, infrared and 1H NMR spectral studies, IR and 1H NMR spectra indicates coordination through azomethine nitrogen, pyridine ring nitrogen and the carbonyl oxygen of the hydrazone moiety. A coordination number eight is suggested for these complexes.  The ligand and complexes were screened for their antimicrobial activity.Keywords: Schiffs base; Lanthanide (III) chloride complexes; Antimicrobial activit

Synthesis, Spectral and Antimicrobial Studies of Lanthanide (III) Nitrate Complexes with Terdentate ONO Donor Hydrazones

Few lanthanide (III) nitrate complexes with hydrazones obtained by the condensation of 3-[m/p (hydrazino carbonyl)] phenyl sydnone and hydroxy aryl aldehyde or ketones have been synthesized and characterized by elemental analysis, molar conductance measurements, magnetic moments, Infrared, electronic and 1HNMR spectral studies. The spectral studies show that the hydrazones reacts in enol form and as dibasic terdentate ONO donor nature. From the results the coordination number eight for lanthanide ion in the complexes is proposed. The thermal behaviour, stability ranges, percentage of weight loss, percentage of residue obtained after decomposition of Ln (III) nitrate complexes has been studied. Further more the antimicrobial activity of the ligand and its complexes as inhibiting agents has been screened in vitro against two kinds of pathogenic bacteria Salmonella paratyphi, Bacillus cirroflagellosus and pathogenic fungi Aspergillus niger, Candida albicans

New, efficient and robust, fiber-based quantum key distribution schemes

We present a new fiber based quantum key distribution (QKD) scheme which can be regarded as a modification of an idea proposed by Inoue, Waks and Yamamoto (IWY) [1]. The scheme described here uses a single phase modulator and two differential delay elements in series at the transmitter that form an interferometer when combined with a third differential delay element at the receiver. The protocol is characterized by a high efficiency, reduced exposure to an attack by an eavesdropper, and higher sensitivity to such an attack when compared to other QKD schemes. For example, the efficiency with which transmitted data contribute to the private key is 3/4 compared with 1/4 for BB84 [2]. Moreover, an eavesdropper can aquire a maximum of 1/3 of the key which leads to an error probability in the private key of 1/3. This can be compared to 1/2 and 1/4 for these same parameters in both BB84 and IWY. The combination of these considerations should lead to increased range and key distribution rate over present fiber-based QKD schemes.Comment: 4 pages, 5 figures, 1 equatio

Diffuse neutron reflectivity and AFM study of interface morphology of an electro-deposited Ni/Cu film

We present a detailed study of the interface morphology of an electro-deposited (ED) Ni/Cu bilayer film by using off-specular (diffuse) neutron reflectivity technique and Atomic Force Microscopy (AFM). The Ni/Cu bilayer has been electro-deposited on seed layers of Ti/Cu. These two seed layers were deposited by magnetron sputtering. The depth profile of density in the sample has been obtained from specular neutron reflectivity data. AFM image of the air-film interface shows that the surface is covered by globular islands of different sizes. The AFM height distribution of the surface clearly shows two peaks [Fig. 3] and the relief structure (islands) on the surface in the film can be treated as a quasi-two-level random rough surface structure. We have demonstrated that the detailed morphology of air-film interfaces, the quasi-two level surface structure as well as morphology of the buried interfaces can be obtained from off-specular neutron reflectivity data. We have shown from AFM and off-specular neutron reflectivity data that the morphologies of electro-deposited surface is distinctly different from that of sputter-deposited interface in this sample. To the best of our knowledge this is the first attempt to microscopically quantify the differences in morphologies of metallic interfaces deposited by two different techniques viz. electro-deposition and sputtering

Study of star formation in RCW 106 using far infrared observations

High resolution far-infrared observations of a large area of the star forming complex RCW 106 obtained using the TIFR 1-metre balloon-borne telescope are presented. Intensity maps have been obtained simultaneously in two bands centred around 150 & 210 micron. Intensity maps have also been obtained at the 4 IRAS bands using HIRES processed IRAS data. From the 150 & 210 micron maps, reliable maps of dust temperature and optical depth have been generated. The star formation in this complex has occured in five linear subclumps. Using the map at 210 micron, which has a spatial resolution superior to that of the IRAS at 100 micron, 23 sources have been identified. The SED and luminosity of these sources have been determined using the associations wit hthe IRAS maps. Luminosity distribution of these sources has been obtained. Assuming these embedded sources to be ZAMS stars and using the mass-luminosity relation, the power law slope of the Initial Mass Function is found to be -1.73+-0.5. This index for this very young complex is about the same as that for more evolved complexes and clusters. Radiation transfer calculations in spherical geometry have been undertaken to fit the SEDs of 13 sources with fluxes in both the TIFR and IRAS bands. From this, the r^-2 density distribution in the envelopes is ruled out. Finally, a correlation is seen between the luminosity of embedded sources and the computed dust masses of the envelopes.Comment: Accepted for publication in MNRAS (21 pages, 8 figures & 3 tables

Heavy quarkonium: progress, puzzles, and opportunities

A golden age for heavy quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the $B$-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations. The plethora of newly-found quarkonium-like states unleashed a flood of theoretical investigations into new forms of matter such as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b}, and b\bar{c} bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark-gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K. Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D. Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A. Petrov, P. Robbe, A. Vair

Measurement of the Bs0→J/ψKS0B_s^0\to J/\psi K_S^0 branching fraction

The $B_s^0\to J/\psi K_S^0$ branching fraction is measured in a data sample corresponding to 0.41$fb^{-1}$ of integrated luminosity collected with the LHCb detector at the LHC. This channel is sensitive to the penguin contributions affecting the sin2$\beta$ measurement from $B^0\to J/\psi K_S^0$ The time-integrated branching fraction is measured to be $BF(B_s^0\to J/\psi K_S^0)=(1.83\pm0.28)\times10^{-5}$. This is the most precise measurement to date