3D Coronal Density Reconstruction and Retrieving the Magnetic Field Structure during Solar Minimum

Measurement of the coronal magnetic field is a crucial ingredient in understanding the nature of solar coronal phenomena at all scales. We employed STEREO/COR1 data obtained during a deep minimum of solar activity in February 2008 (Carrington rotation CR 2066) to retrieve and analyze the three-dimensional (3D) coronal electron density in the range of heights from 1.5 to 4 Rsun using a tomography method. With this, we qualitatively deduced structures of the coronal magnetic field. The 3D electron density analysis is complemented by the 3D STEREO/EUVI emissivity in the 195 A band obtained by tomography for the same CR. A global 3D MHD model of the solar corona was used to relate the reconstructed 3D density and emissivity to open/closed magnetic field structures. We show that the density maximum locations can serve as an indicator of current sheet position, while the locations of the density gradient maximum can be a reliable indicator of coronal hole boundaries. We find that the magnetic field configuration during CR 2066 has a tendency to become radially open at heliocentric distances greater than 2.5 Rsun. We also find that the potential field model with a fixed source surface (PFSS) is inconsistent with the boundaries between the regions with open and closed magnetic field structures. This indicates that the assumption of the potential nature of the coronal global magnetic field is not satisfied even during the deep solar minimum. Results of our 3D density reconstruction will help to constrain solar coronal field models and test the accuracy of the magnetic field approximations for coronal modeling.Comment: Published in "Solar Physics

A search for the decay B+→K+ννˉB^+ \to K^+ \nu \bar{\nu}

We search for the rare flavor-changing neutral-current decay $B^+ \to K^+ \nu \bar{\nu}$ in a data sample of 82 fb$^{-1}$ collected with the {\sl BABAR} detector at the PEP-II B-factory. Signal events are selected by examining the properties of the system recoiling against either a reconstructed hadronic or semileptonic charged-B decay. Using these two independent samples we obtain a combined limit of ${\mathcal B}(B^+ \to K^+ \nu \bar{\nu})<5.2 \times 10^{-5}$ at the 90% confidence level. In addition, by selecting for pions rather than kaons, we obtain a limit of ${\mathcal B}(B^+ \to \pi^+ \nu \bar{\nu})<1.0 \times 10^{-4}$ using only the hadronic B reconstruction method.Comment: 7 pages, 8 postscript figures, submitted to Phys. Rev. Let

High-reflectivity broadband distributed Bragg reflector lattice matched to ZnTe

We report on the realization of a high quality distributed Bragg reflector with both high and low refractive index layers lattice matched to ZnTe. Our structure is grown by molecular beam epitaxy and is based on binary compounds only. The high refractive index layer is made of ZnTe, while the low index material is made of a short period triple superlattice containing MgSe, MgTe, and ZnTe. The high refractive index step of Delta_n=0.5 in the structure results in a broad stopband and the reflectivity coefficient exceeding 99% for only 15 Bragg pairs.Comment: 4 pages, 3 figure

EuFe2_2As2_2 under high pressure: an antiferromagnetic bulk superconductor

We report the ac magnetic susceptibility $\chi_{ac}$ and resistivity $\rho$ measurements of EuFe$_2$As$_2$ under high pressure $P$. By observing nearly 100% superconducting shielding and zero resistivity at $P$ = 28 kbar, we establish that $P$-induced superconductivity occurs at $T_c \sim$~30 K in EuFe$_2$As$_2$. $\rho$ shows an anomalous nearly linear temperature dependence from room temperature down to $T_c$ at the same $P$. $\chi_{ac}$ indicates that an antiferromagnetic order of Eu$^{2+}$ moments with $T_N \sim$~20 K persists in the superconducting phase. The temperature dependence of the upper critical field is also determined.Comment: To appear in J. Phys. Soc. Jpn., Vol. 78 No.

Improved measurement of CP asymmetries in B-0 ->(c(c)over-bar)K0((*)) decays

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 227x10(6) Upsilon(4S)-> B (B) over bar decays collected by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The amplitude of the CPasymmetry, sin2 beta in the standard model, is derived from decay-time distributions from events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B-0 or (0) from its decay products. We measure sin2 beta=0.722 +/- 0.040(stat)+/- 0.023(syst) in agreement with the standard model expectation

Feasibility of using low pressure steam for sootblowing

Copyright Pulp & Paper Canada. Reprinted with permission from Annex Business Media.With correctly designed fully-expanded nozzles, the sootblower steam pressure in recov- ery boilers can be reduced from 300 psig (20 bars) to 150 psig (10 bars), without significantly reducing the deposit removal efficiency. Results of laboratory tests show that a 20% increase in sootblower steam flow can make a low pressure nozzle (150 psig) more effective than a 300 psig nozzle. Since low pressure steam can be extracted from downstream of the steam turbine, it is a less expensive source of steam for use in sootblowingThis work was part of the research program on “Increasing the Throughput and Reliability of Recovery Boilers and Lime Kilns” jointly supported by Alstom Power Inc., Andritz Corporation, Aracruz Celulose S.A., Babcock & Wilcox Company, Boise Paper Solutions, Bowater Canadian Forest Products Inc., Canfor Inc., Clyde-Bergemann Inc., Daishowa-Marubeni International Ltd., Domtar Inc., Georgia Pacific Corporation, International Paper Company, Irving Pulp & Paper Limited, Kvaerner Power OY, MeadWestvaco, Stora Enso Research AB, Tembec Inc., Votorantim Celulose e Papel, and Weyerhaeuser Company, and by the Natural Sciences and Engineering Research Council of Canad

Interaction between sootblower jet and superheater platens in recovery boilers

Copyright Pulp & Paper Canada. Reprinted with permission from Annex Business Media.The flow characteristics of a sootblower jet passing between superheater platens in a recovery boiler are examined experimentally using a laboratory apparatus and numerically using a computational fluid dynamics code with a modified turbulence model. Experimental and simulation results show that, depending on the jet position, the interaction between the jet and the platen surface greatly lowers the jet peak impact pressure. The interaction is pronounced as the jet axis is near the platen, but becomes negligible as the jet moves away from it.This work was part of the research program on “Increasing the Throughput and Reliability of Recovery Boilers and Lime Kilns” jointly supported by Alstom Power Inc., Andritz Corporation, Aracruz Celulose S.A., Babcock & Wilcox Company, Boise Paper Solutions, Bowater Canadian Forest Products Inc., Canfor Inc., Clyde-Bergemann Inc., Daishowa-Marubeni International Ltd., Domtar Inc., Georgia Pacific Corporation, International Paper Company, Irving Pulp & Paper Limited, Kvaerner Power OY, MeadWestvaco, Stora Enso Research AB, Tembec, Votorantim Celulose e Papel, and Weyerhaeuser Company, and by the Nat- ural Sciences and Engineering Research Council of Canada