Atomically straight steps on vicinal Si (111) surfaces prepared by step-parallel current in the kink-up direction

We demonstrate that annealing of a vicinal Si(111) surface at about 800 C with a direct current in the direction that ascends the kinks enhances the formation of atomically straight step edges over micrometer lengths, while annealing with a current in the opposite direction does not. Every straight step edge has the same atomic configuration U(2,0), which is useful as a template for the formation of a variety of nanostructures. A phenomenological model based on electromigration of charged mobile atoms explains the observed current-polarity dependent behavior.Comment: Accepted for publication in Appl. Phys. Lett. Numbers of pages and figures are 12 and 4, respectivel

Tidally Triggered Star Formation in Close Pairs of Galaxies: Major and Minor Interactions

We study star formation in a sample of 345 galaxies in 167 pairs and compact groups drawn from the original CfA2 Redshift Survey and from a follow-up search for companions. We construct our sample with attention to including pairs with luminosity contrast |\Delta m_R| >= 2. These 57 galaxies with |\Delta m_R| >= 2 provide a set of nearby representative cases of minor interactions, a central feature of the hierarchical galaxy formation model. Here we report the redshifts and positions of the 345 galaxies in our sample, and of 136 galaxies in apparent pairs that are superpositions. In the pairs sample as a whole, there are strong correlations between the equivalent width of the H\alpha emission line and the projected spatial and the line-of-sight velocity separation of the pair. For pairs of small luminosity contrast, |\Delta m_R| < 2, the member galaxies show a correlation between the equivalent width of H\alpha and the projected spatial separation of the pair. However, for pairs with large luminosity contrast, |\Delta m_R| >= 2, we detect no correlation between the equivalent width of H\alpha and the projected spatial separation. The relative luminosity of the companion galaxy is more important in a gravitational tidal interaction than the intrinsic luminosity of the galaxy. Central star formation across the entire pairs sample depends strongly on the luminosity ratio, |\Delta m_R|, a reasonable proxy for the mass ratio of the pair; pairs composed of similarly luminous galaxies produce the strongest bursts of star formation. Pairs with |\Delta m_R| >= 2 rarely have EW(H\alpha) >~ 70 Ang.Comment: Minor revisions following journal proof

Microstructural influences on stress migration in electroplated Cu metallization

科研費報告書収録論文(課題番号:13450281・基盤研究(B)(2) ・H13～H15/研究代表者:小池, 淳一/超高速LSI用Cu配線におけるボイド形成機構の研究

The 2000 outburst of the recurrent nova CI Aquilae: optical spectroscopy

We present low- and medium resolution spectra of the recurrent nova CI Aquilae taken at 14 epochs in May and June, 2000. The overall appearance is similar to other U Sco-type recurrent novae (U Sco, V394 CrA). Medium resolution (R=7000-10000) hydrogen and iron profiles suggest an early expansion velocity of 2000-2500 km/s. The H\alpha evolution is followed from Dt = -0.6 d to +53 d, starting from a nearly Gaussian shape to a double peaked profile through strong P-Cyg profiles. The interstellar component of the sodium D line and two diffuse interstellar bands put constraints on the interstellar reddening which is estimated to be E(B-V)=0.85\pm0.3. The available visual and CCD-V observations are used to determine t0,t2 and t3. The resulting parameters are: t0=2451669.5\pm0.1, t2=30\pm1 d, t3=36\pm1 d. The recent lightcurve is found to be generally similar to that observed in 1917 with departures as large as 1-2 mag in certain phases. This behaviour is also typical for the U Sco subclass.Comment: 8 pages, 7 figures, accepted for publication in A&

A Theoretical Light-Curve Model for the Recurrent Nova V394 Coronae Austrinae

A theoretical light curve for the 1987 outburst of V394 Coronae Austrinae (V394 CrA) is modeled to obtain various physical parameters of this recurrent nova. We then apply the same set of parametersto a quiescent phase and confirm that these parameters give a unified picture of the binary. The early visual light curve (1-10 days after the optical maximum) is well reproduced by a thermonuclear runaway model on a very massive WD close to the Chandrasekhar limit (1.37 +- 0.01 M_sun). The ensuing plateau phase (10-30 days) is also reproduced by the combination of a slightly irradiated MS and a fully irradiated flaring-up disk with a radius ~1.4 times the Roche lobe size. The best fit parameters are the WD mass 1.37 M_sun, the companion mass 1.5 M_sun (0.8-2.0 M_sun is acceptable), the inclination angle of the orbit i~65-68 degree, and the flaring-up rim ~0.30 times the disk radius. The envelope mass at the optical peak is estimated to be ~6 x 10^{-6} M_sun, which indicates an average mass accretion rate of 1.5 x 10^{-7} M_sun yr^{-1} during the quiescent phase between the 1949 and 1987 outbursts. In the quiescent phase, the observed light curve can be reproduced with a disk size of 0.7 times the Roche lobe size and a rather slim thickness of 0.05 times the accretion disk size at the rim. About 0.5 mag sinusoidal variation of the light curve requires the mass accretion rate higher than ~1.0 x 10^{-7} M_sun yr^{-1}, which is consistent with the above estimation from the 1987 outburst. These newly obtained quantities are exactly the same as those predicted in a new progenitor model of Type Ia supernovae.Comment: 9 pages including 4 figures, to appear in the Astrophysical Journal, Part

Spin dependent recombination based magnetic resonance spectroscopy of bismuth donor spins in silicon at low magnetic fields

Low-field (6-110 mT) magnetic resonance of bismuth (Bi) donors in silicon has been observed by monitoring the change in photoconductivity induced by spin dependent recombination. The spectra at various resonance frequencies show signal intensity distributions drastically different from that observed in conventional electron paramagnetic resonance, attributed to different recombination rates for the forty possible combinations of spin states of a pair of a Bi donor and a paramagnetic recombination center. An excellent tunability of Bi excitation energy for the future coupling with superconducting flux qubits at low fields has been demonstrated.Comment: 5 pages, 4 figure

Self-consistent picture of the mass ejection from a one second-long binary neutron star merger leaving a short-lived remnant in general-relativistic neutrino-radiation magnetohydrodynamic simulation

We perform a general-relativistic neutrino-radiation magnetohydrodynamicsimulation of a one second-long binary neutron star merger on Japanesesupercomputer Fugaku using about $72$ million CPU hours with $20,736$ CPUs. Weconsider an asymmetric binary neutron star merger with masses of $1.2$ and$1.5M_\odot$ and a `soft' equation of state SFHo. It results in a short-livedremnant with the lifetime of $\approx 0.017$\,s, and subsequent massive torusformation with the mass of $\approx 0.05M_\odot$ after the remnant collapses toa black hole. For the first time, we confirm that after the dynamical massejection, which drives the fast tail and mildly relativistic components, thepost-merger mass ejection from the massive torus takes place due to themagnetorotational instability-driven turbulent viscosity and the two ejectacomponents are seen in the distributions of the electron fraction and velocitywith distinct features.<br

Effective combination therapy using interferon-gamma and interleukin-2 for disseminated Mycobacterium avium complex infection in a pediatric patient with AIDS

© 2006 by [The University of Chicago Press ]ArticleCLINICAL INFECTIOUS DISEASES. 41(11): E104-E106 (2005)journal articl