31P-NMR, 77Se-NMR and mass spectral studies on some tricoordinate P(III)-N and tetracoordinate P(V)-N systems

A series of aminophosphines were prepared by controlled condensation reaction between PCl3 or PhPCl2 and amines, and they were converted into the corresponding chalcogenides. 31P-NMR and mass spectral data were collected for characterization of these asymmetrically substituted phosphines, and in addition, 77Se- NMR data were collected for the phosphine selenides prepared. The spectral data revealed the importance of the dipolar structure for the heavier chalcogen atoms and the π-bond structure for the lighter ones. This study has also brought out the first examples of chiral tris(amino)phosphines and the corresponding selenides.KEY WORDS: Aminophosphines, Dichlorophenylphosphine, Chiral tris(amino)phosphines, Aminophosphine chalcogenides, 77Se-NMRBull. Chem. Soc. Ethiop. 2006, 20(2), 207-218

X-ray variability of GRS 1915+105 during the low-hard state observed with the Indian X-ray astronomy experiment (IXAE)

The galactic superluminal transient X-ray source GRS 1915+105 was observed with the pointed proportional counters (PPCs) onboard the Indian satellite IRS-P3 during 1996 July 23-27. We report here details of the behavior of this source during the relatively quiet and low luminosity state. Large intensity variations by a factor of 2 to 3, generally seen in black-hole candidates, are observed at a time scale of 100 ms to few seconds. No significant variation is detected over larger time scale of minute or more. The intensity variations are described as sum of shots in the light curve, and the number distribution of the shots are found to be exponential function of the fluence and duration of the shots. The cross correlation spectrum between 6-18 keV and 2-6 keV X-rays is found to have asymmetry signifying a delay of the hard X-rays by about 0.2 to 0.4 sec. This supports the idea of hard X-rays being generated by Compton up-scattering from high energy clouds near the source of soft X-rays. Very strong and narrow quasi periodic oscillations in the frequency range 0.62 to 0.82 Hz are observed. We discuss about a model which explains a gradual change in the QPO frequencies with corresponding changes in the mass accretion rate of the disk.Comment: 14 pages including 6 figures. To appear in Astronomy and Astrophysics Supplement Serie

An FPGA Based Testbench for Reliability and Endurance Characterization of Nonvolatile Memory

Coordinated Science Laboratory was formerly known as Control Systems LaboratoryJet Propulsion Laboratory / JPL 122991Ope

Raphides in urginea indica kunth. Liliacea

Micromorphological traits play a significant role both in systematic and functional aspects of plant survival in response to environmental stimuli. Plant structural trait such as raphides play a vital role in protecting plants from herbivore attack, cause discomfort by physical and chemical irritation by dermal contact to soft tissue thus acts as defensive mechanism. These morphological characteristics may have evolved as response to other environmental stimuli. The presence of raphides (Calcium oxalate crystals) in the anther endothecium represents a rare character, reported in the present study which is of systematic significance. In the present study raphides are present in vegetative and reproductive parts of Urginea indica. The mild inflammation and irritation caused when the bulb is rubbed on the skin reveals that it takes part both in mechanical and chemical irritation when they come in contact with tender tissue and protect themselves against herbivore attack. Results indicate that raphide bundle size varies considerably within species. These suggest that, Raphides have some potential to be a useful taxonomic tool. Polarized microscope shows variation in the colouration of raphides

X-ray and ion emission studies from subnanosecond laser-irradiated SiO2 aerogel foam targets

In this experiment, a comparative study of ion and X-ray emission from both a SiO2 aerogel foam and a quartz target is performed. The experiment is performed using Nd:glass laser system operated at laser energy up to 15 J with a pulse duration of 500 ps with focusable intensity of 1013–1014 W/cm2 on target. X-ray fluxes in different spectral ranges (soft and hard) are measured by using X-ray diodes covered with Al filters of thickness 5 µm (0.9–1.56 keV) and 20 µm (3.4–16 keV). A 2.5 times enhancement in soft X-ray flux (0.9–1.56 keV) and a decrease of 1.8 times in hard X rays (3.4–16 keV) for 50 mg/cc SiO2 aerogel foam is observed compared with the solid quartz. A decrease in the flux of the K-shell line emission spectrum of soft X rays is noticed in the case of the foam targets. The high-resolution K-shell spectra (He-like) of Si ions in both the cases are analyzed for the determination of plasma parameters by comparing with FLYCHK simulations. The estimated plasma temperature and density are T c = 180 eV, n e = 7 × 1020 cm−3 and T c = 190 eV, n e = 4 × 1020 cm−3 for quartz and SiO2 aerogel foam, respectively. To measure the evolution of the plasma moving away from the targets, four identical ion collectors are placed at different angles (22.5, 30, 45, and 67.5°) from target normal. The angular distribution of the thermal ions are scaled as cosnθ with respect to target normal, where n = 3.8 and 4.8 for the foam and quartz, respectively. The experimental plasma volume measured from the ion collectors and shadowgraphy images are verified by a two-dimensional Eulerian radiative–hydrodynamic simulation (POLLUX code

Synthesis, Crystal Structure, Antioxidant, Antimicrobial, and Mutagenic Activities and DNA Interaction Studies of Ni(II) Schiff Base 4-Methoxy-3-Benzyloxybenzaldehyde Thiosemicarbazide Complexes

Three new Ni(II) square planar complexes of 4-methoxy-3-benzyloxybenzaldehyde thiosemicarbazide(4m3BTSC) having polypyridyl bases of general formulation [ML2] (1) and [MLB] (2, 3), where L = 4m3BTSC and B is N,N-donor heterocyclic bases, namely, 1,10-phenanthroline (phen, 2), 2,2′-bipyridine (bpy, 3), are synthesized and characterized. The free radical scavenging assay results showed that complex 1 possesses significant activity when compared to complexes 2 and 3. The biological studies showed that the ligand and its complexes exhibited significant and different biological activities and also the prepared compounds are nonmutagenic. They may be potential commercial antioxidants because of their nonmutagenic and nontoxic nature. The DNA interaction of the new complexes is evaluated by absorption, emission, and melting temperature methods, and the results suggested that the binding affinity of the complexes increases with the presence of planar ligand in the molecule. The nickel (II) complexes with planar phenanthroline bases show moderate DNA binding and cleavage ability

Reversible Pressure-Induced Amorphization in Solid C70 : Raman and Photoluminescence Study

We have studied single crystals of $C_{70}$ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broad band similar to that of the amorphous carbon without any trace of the Raman lines of $C_{70}$. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting $C_{70}$ crystal. These results indicate that the $C_{70}$ molecules are stable upto 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid $C_{60}$. A qualitative explaination is suggested in terms of inter- versus intra-molecular interactions.Comment: To appear in Phys. Rev. Lett., 12 pages, RevTeX (preprint format), 3 figures available upon reques

Non-Fermi liquid behavior and scaling of low frequency suppression in optical conductivity spectra of CaRuO3_3

Optical conductivity spectra $\sigma_1(\omega)$ of paramagnetic CaRuO$_3$ are investigated at various temperatures. At T=10 K, it shows a non-Fermi liquid behavior of $\sigma_1(\omega)\sim 1/{\omega}^{\frac 12}$, similar to the case of a ferromagnet SrRuO$_3$. As the temperature ($T$) is increased, on the other hand, $\sigma_1(\omega)$ in the low frequency region is progressively suppressed, deviating from the 1/{\omega}^{\frac 12%}-dependence. Interestingly, the suppression of $\sigma_1(\omega)$ is found to scale with $\omega /T$ at all temperatures. The origin of the $$ scaling behavior coupled with the non-Fermi liquid behavior is discussed.Comment: 4 pages, 3 figure