4,371 research outputs found
The Meter Greeters
The United States and Canada became meter greeters away back in the 1800\u27s. The U.S. Congress passed an act in 1866 legalizing the metric system for weights and measures use, and metric units were on the law books of the Dominion of Canada in 1875
The materials processing research base of the Materials Processing Center
The goals and activities of the center are discussed. The center activities encompass all engineering materials including metals, ceramics, polymers, electronic materials, composites, superconductors, and thin films. Processes include crystallization, solidification, nucleation, and polymer synthesis
Scattering a pulse from a chaotic cavity: Transitioning from algebraic to exponential decay
The ensemble averaged power scattered in and out of lossless chaotic cavities
decays as a power law in time for large times. In the case of a pulse with a
finite duration, the power scattered from a single realization of a cavity
closely tracks the power law ensemble decay initially, but eventually
transitions to an exponential decay. In this paper, we explore the nature of
this transition in the case of coupling to a single port. We find that for a
given pulse shape, the properties of the transition are universal if time is
properly normalized. We define the crossover time to be the time at which the
deviations from the mean of the reflected power in individual realizations
become comparable to the mean reflected power. We demonstrate numerically that,
for randomly chosen cavity realizations and given pulse shapes, the probability
distribution function of reflected power depends only on time, normalized to
this crossover time.Comment: 23 pages, 5 figure
Ram-pressure stripped molecular gas in the Virgo spiral galaxy NGC 4522
IRAM 30m 12CO(1-0) and 12CO(2-1) HERA observations are presented for the
ram-pressure stripped Virgo spiral galaxy NGC 4522. The CO emission is detected
in the galactic disk and the extraplanar gas. The extraplanar CO emission
follows the morphology of the atomic gas closely but is less extended. The CO
maxima do not appear to correspond to regions where there is peak massive star
formation as probed by Halpha emission. The presence of molecular gas is a
necessary but not sufficient condition for star formation. Compared to the disk
gas, the molecular fraction of the extraplanar gas is 30% lower and the star
formation efficiency of the extraplanar gas is about 3 times lower. The
comparison with an existing dynamical model extended by a recipe for
distinguishing between atomic and molecular gas shows that a significant part
of the gas is stripped in the form of overdense arm-like structures. It is
argued that the molecular fraction depends on the square root of the total
large-scale density. Based on the combination of the CO/Halpha and an
analytical model, the total gas density is estimated to be about 4 times lower
than that of the galactic disk. Molecules and stars form within this dense gas
according to the same laws as in the galactic disk, i.e. they mainly depend on
the total large-scale gas density. Star formation proceeds where the local
large-scale gas density is highest. Given the complex 3D morphology this does
not correspond to the peaks in the surface density. In the absence of a
confining gravitational potential, the stripped gas arms will most probably
disperse; i.e. the density of the gas will decrease and star formation will
cease.Comment: 11 pages, 15 figures, A&A accepted for publicatio
Rescue of the Epstein–Barr Virus BZLF1 Mutant, Z(S186A), Early Gene Activation Defect by the BRLF1 Gene Product
Expression of the Epstein-Barr virus (EBV) immediate-early protein, BZLF1 (Z), is sufficient to disrupt viral latency. Z transcriptionally activates the EBV early genes by binding to upstream Z-responsive elements (ZREs). Recently, a serine-to-alanine mutation of Z residue 186 (within the basic DNA binding domain) was shown to inhibit the ability of Z to induce lytic infection in latently infected cells, although the Z(S186A) mutant could still bind several known ZREs and activated an early EBV promoter (BMRF1) in transient reporter gene assays (Francis, A. L., Gradoville, L., and Miller, G. (1997). J. Virol. 71, 3054-3061). We now show that a specific deficiency in the ability to bind to ZRE elements in the immediate-early BRLF1 promoter may account for the inability of Z(S186A) to activate BRLF1 expression. Furthermore, we demonstrate that the ability of Z(S186A) to induce early BMRF1 and BHRF1 gene expression is rescued by cotransfection with a BRLF1 expression vector. However, the Z(S186A)/BRLF1 (R) combination cannot induce full lytic replication, suggesting that Z(S186A) may also be deficient in a replication-specific function. These results suggest that in the context of the intact viral genome, both Z and R expression are required for activation of early gene transcription in latently infected cells
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