80,969 research outputs found
Thermal and bias cycling stabilizes planar silicon devices
Terminal burn-in or baking step time in the processing of planar silicon devices is extended to reduce their inversion tendencies. The collector-base junction of the device is also cyclically biased during the burn-in
Aerodynamic characteristics of a spherically blunted 25 deg cone at a Mach number of 20
Aerodynamic characteristics and pressure distributions of spherically blunted 25 degree cone investigated in nitrogen at Mach 2
X-ray Emission from the Radio Jet in 3C 120
We report the discovery of X-ray emission from a radio knot at a projected
distance of 25" from the nucleus of the Seyfert galaxy, 3C 120. The data were
obtained with the ROSAT High Resolution Imager (HRI). Optical upper limits for
the knot preclude a simple power law extension of the radio spectrum and we
calculate some of the physical parameters for thermal bremsstrahlung and
synchrotron self-Compton models. We conclude that no simple model is consistent
with the data but if the knot contains small regions with flat spectra, these
could produce the observed X-rays (via synchrotron emission) without being
detected at other wavebands.Comment: 6 pages latex plus 3 ps/eps figures. Uses 10pt.sty and
emulateapj.sty. Accepted for publication in the ApJ (6 Jan 99
Fast wavelength-tunable ultra-violet laser source for confocal Fura-2AM imaging
We report a novel wavelength-flexible laser source for three-dimensional ultra-violet imaging. Based on supercontinuum generation in photonic crystal fiber, the resultant broadband laser source extended from A = 331 nm into the visible region of the spectrum. Using an electronically-controlled filter wheel and filter set with a response time of approximately 50 ins, rapid wavelength selection was performed. The described scheme is capable of exciting the current range of ultra-violet-excited fluorophores and the simple and rapid wavelength control also provides a new approach for fast ratiometric imaging of Fura-2AM, facilitating an easy method of performing quantitative intracellular calcium concentration measurements
On the absence of Shapiro-like steps in certain mesoscopic S-N-S junctions
In DC transport through mesoscopic S-N-S junctions, it is known that the
Josephson coupling decreases exponentially with increasing temperature, but the
phase dependence of the conductance persists to much higher temperatures and
decreases only as 1/T. It is pointed out here that, despite the fact that such
a phase-dependent conductance does bring about an AC current for a pure DC
voltage, it cannot, by itself, lead to the formation of Shapiro steps.Comment: 1 page, to be published in PRL (as Comment
On the Anomalous Temperature Distribution of the Intergalactic Medium in the NGC 3411 Group of Galaxies
We present XMM, Chandra and VLA observations of the USGC S152 group and its
central elliptical NGC 3411. Imaging of the group X-ray halo suggests it is
relaxed with little apparent structure. We investigate the temperature and
metal abundance structure of the group halo, and find that while the abundance
distribution is fairly typical, the temperature profile is highly unusual,
showing a hot inner core surrounded by a cool shell of gas with a radius of
\~20-40 kpc, at the center of the larger group halo. Spectral mapping confirms
an irregular ring of gas ~0.15 keV cooler than its surroundings. We estimate
the total mass, entropy and cooling time profiles within ~200 kpc, and find
that the cool shell contains ~9x10^9 Msun of gas. VLA observations at 1.4, 5
and 8 GHz reveal a relatively weak nuclear radio source, with a core radio
luminosity L_R=2.7x10^38 erg/s, and a diffuse component extended on scales of a
few arcseconds (or more). A lack of evidence for activity at optical or X-ray
wavelengths supports the conclusion that the central black hole is currently in
a quiescent state. We discuss possible mechanisms for the formation of
temperature features observed in the halo, including a previous period of AGN
activity, and settling of material stripped from the halo of one of the other
group member galaxies.Comment: 15 pages, 8 postscript figures, accepted for publication in ApJ
version with high resolution figures available at
http://hea-www.harvard.edu/~ejos/files/N3411_hires.pd
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