The effect of host glass on optical absorption and fluorescence of Nd3+ in xNa(2)O-(30-x)K2O-70B(2)O(3) glasses

The effect of host glass composition on the optical absorption and fluorescence spectra of Nd3+ has been studied in mixed alkali borate glasses of the type xNa(2)O-(30-x)K2O-69.5B(2)O(3)-0.5Nd(2)O(3) (X = 5,10,15,20 and 25). Various spectroscopic parameters such as Racah (E-1, E-2 and E-3), spin-orbit (xi(4f)) and configuration interaction (alpha, beta) parameters have been calculated. The Judd-Ofelt intensity parameters (Omega(lambda)) have been calculated and the radiative transition probabilities (A(rad)), radiative lifetimes (tau(r)), branching ratios (beta) and integrated absorption cross sections (Sigma) have been obtained for certain excited states of the Nd3+, ion and are discussed with respect to x. From the fluorescence spectra, the effective fluorescence line widths (Deltalambda(eff)) and stimulated emission cross sections (sigma(p)) have been obtained for the three transitions F-4(3/2) --> I-4(9/2), F-4(3/2) --> I-4(11/2) and F-4(3/2) --> I-4(13/2) of Nd3+. The stimulated emission cross section (sigma(p)) values are found to be in the range (2.0-4.8) x 10(-2)0 cm(2) and they are large enough to indicate that the mixed alkali borate glasses could be potential laser host materials.

The inactive X chromosome in the human female is enriched in 5-methylcytosine to an unusual degree and appears to contain more of this modified nucleotide than the remainder of the genome

By employing a procedure that combines ELISA and photoacoustic spectroscopy, we have examined the content of 5-methylcytosine (m(5)C) in DNA of individuals who differed from one another in the number of X chromosomes in their genomes. The results show that the human inactive X chromosome (Xi) contains very high amounts of this modified nucleotide. We estimate that in the 46,XX female there is more m(5)C in Xi (similar to3.6 x 10(7)) than in all the remaining chromosomes put together (similar to2.1 x 10(7)). Our results also suggest that nearly one-fifth of all cytosines in Xi are methylated and that, in addition to CpG methylation, there is extensive non-CpG methylation as well.

The nature of the prompt X-ray and radio emission from SN 2002ap

We report on the combined X-ray and radio observations of the type Ic SN 2002ap, using XMM-Newton TOO observation of M 74 and the Giant Metrewave Radio Telescope ( GMRT). We account for the presence of a nearby source in the pre-supernova Chandra field of view in our measurements of the X-ray flux (0.3-10 KeV) 5.2 days after the explosion. The X-ray spectrum is well fitted by a power law spectrum with photon index alpha = 2.6. Our results suggest that the prompt X-ray emission originates from inverse Compton scattering of photospheric thermal emission by energetic electrons. Radio observations with the GMRT at 610 MHz (8 days after the explosion) and 1420 MHz (70 days after the explosion) are combined with the high frequency VLA observations of SN 2002ap reported by Berger et al. ( 2002), and the early radiospheric properties of SN 2002ap are compared with similar data from two other supernovae. Finally, the GMRT radio map reveals four other X-ray sources in the field of view of M 74 with radio counterparts.

Role of rigidity and temperature in the kinetics of photodarkening in Ge(x)As((45-x))Se(55) thin films

We present insightful results on the kinetics of photodarkening (PD) in Ge(x)As(45-x)Se(55) glasses at the ambient and liquid helium temperatures when the network rigidity is increased by varying x from 0 to 16. We observe a many fold change in PD and its kinetics with decreasing network flexibility and temperature. Moreover, temporal evolution of PD shows a dramatic change with increasing x. (C)2011 Optical Society of America

From the Icosahedron to Natural Triangulations of CP(2) and S(2) x S(2)

We present two constructions in this paper: (a) a 10-vertex triangulation CP(10)(2) of the complex projective plane CP(2) as a subcomplex of the join of the standard sphere (S(4)(2)) and the standard real projective plane (RP(6)(2), the decahedron), its automorphism group is A(4); (b) a 12-vertex triangulation (S(2) x S(2))(12) of S(2) x S(2) with automorphism group 2S(5), the Schur double cover of the symmetric group S(5). It is obtained by generalized bistellar moves from a simplicial subdivision of the standard cell structure of S(2) x S(2). Both constructions have surprising and intimate relationships with the icosahedron. It is well known that CP(2) has S(2) x S(2) as a two-fold branched cover; we construct the triangulation CP(10)(2) of CP(2) by presenting a simplicial realization of this covering map S(2) x S(2) -> CP(2). The domain of this simplicial map is a simplicial subdivision of the standard cell structure of S(2) x S(2), different from the triangulation alluded to in (b). This gives a new proof that Kuhnel's CP(9)(2) triangulates CP(2). It is also shown that CP(10)(2) and (S(2) x S(2))(12) induce the standard piecewise linear structure on CP(2) and S(2) x S(2) respectively.

CO adsorption on ionic Pt, Pd and Cu sites in Ce(1-x)M(x)O(2-delta) (M = Pt(2+), Pd(2+), Cu(2+))

Noble metal ion substituted CeO(2) in the form of Ce(0.98)M(0.02)O(2-delta) solid solution (where M = Pt, Pd, Cu) are the new generation catalysts with applications in three-way exhaust catalysis. While adsorption of CO on noble metals ions is well-known, adsorption of CO on noble metal ions has not been studied because creating exclusive ionic sites has been difficult. Using first-principles density functional theory (DFT) we have shown that CO gets adsorbed on the noble metal Pt(2+), Pd(2+), Cu(2+) ionic sites in the respective compounds, and the net energy of the overall system decreases. Adsorption of CO on metal ions is also confirmed by Fourier transform infrared spectroscopy (FTIR).

A 100MHz to 1GHz, 0.35V to 1.5V Supply 256 x 64 SRAM Block Using Symmetrized 9T SRAM Cell with Controlled Read

In this paper, we present dynamic voltage and frequency Managed 256 x 64 SRAM block in 65 nm technology, for frequency ranging from 100 MHz to 1 GHz. The total energy is minimized for any operating frequency in the above range and leakage energy is minimized during standby mode. Since noise margin of SRAM cell deteriorates at low voltages, we propose static noise margin improvement circuitry, which symmetrizes the SRAM cell by controlling the body bias of pull down NMOS transistor. We used a 9T SRAM cell that isolates Read and hold noise margin and has less leakage. We have implemented an efficient technique of pushing address decoder into zigzag- super-cut-off in stand-by mode without affecting its performance in active mode of operation. The read bit line (RBL) voltage drop is controlled and pre-charge of bit lines is done only when needed for reducing power wastage.

Infrared studies of the phase transitions of alkylammonium halides, RNH3X, and bis-(alkylammonium) tetrahalogenometallates(II), (RNH3)2MX4, (R = alkyl, M = metal, X = Cl or Br)

Internal vibration modes of bis-(alkylammonium) tetrachlorometallates(II) and the corresponding alkylammonium chlorides have been studied through their phase transitions using infrared spectroscopy. The studies show that the vibrational states of alkylammonium ions change markedly through the phase transitions. Spectra of the analogous tetrabromometallates and alkylammonium bromides also confirm this behaviour. There is appreciable motion of the alkylammonium ions in the high-temperature phases; thus, CH3NH+3 ions are essentially undistorted in these phases. The low-temperature, ordered phases show evidence of stronger hydrogen bonding of the cations and for the presence of C—N torsional modes.

Effect of irradiation on the microstructure and mechanical behavior of nanocrystalline nickel

The effect of 4.0 MeV proton irradiation on the microstructure and mechanical properties of nanocrystalline (nc) nickel was investigated. The irradiation damage induced in the sample was of the order of 0.004 dpa. Transmission electron microscopy of irradiated samples indicated the presence of dislocation loops within the grains. An increase in hardness and strain-rate sensitivity (m) of nc-Ni with irradiation was noted. The rate-controlling deformation mechanism in irradiated nc-Ni was identified to be interaction of dislocations with irradiation-induced defects. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.