961 research outputs found
Compensation for time fluctuations of phase modulation in a liquid-crystal-on-silicon display by process synchronization in laser materials processing
Quantum state-resolved gas/surface reaction dynamics probed by reflection absorption infrared spectroscopy
International audienceWe report the design and characterization of a new molecular-beam/surface-science apparatus for quantum state-resolved studies of gas/surface reaction dynamics combining optical state-specific reactant preparation in a molecular beam by rapid adiabatic passage with detection of surface-bound reaction products by reflection absorption infrared spectroscopy (RAIRS). RAIRS is a non-invasive infrared spectroscopic detection technique that enables online monitoring of the buildup of reaction products on the target surface during reactant deposition by a molecular beam. The product uptake rate obtained by calibrated RAIRS detection yields the coverage dependent state-resolved reaction probability S(θ). Furthermore, the infrared absorption spectra of the adsorbed products obtained by the RAIRS technique provide structural information, which help to identify nascent reaction products, investigate reaction pathways, and determine branching ratios for different pathways of a chemisorption reaction. Measurements of the dissociative chemisorption of methane on Pt(111) with this new apparatus are presented to illustrate the utility of RAIRS detection for highly detailed studies of chemical reactions at the gas/surface interface
Radio Continuum Jet in NGC 7479
The barred galaxy NGC 7479 hosts a remarkable jet-like radio continuum
feature: bright, 12-kpc long in projection, and hosting an aligned magnetic
field. The degree of polarization is 6%-8% along the jet, and remarkably
constant, which is consistent with helical field models. The radio brightness
of the jet suggests strong interaction with the ISM and hence a location near
the disk plane. We observed NGC 7479 at four wavelengths with the VLA and
Effelsberg radio telescopes. The equipartition strength is 35-40 micro-G for
the total and >10 micro-G for the ordered magnetic field in the jet. The jet
acts as a bright, polarized background. Faraday rotation between 3.5 and 6 cm
and depolarization between 6 and 22 cm can be explained by magneto-ionic gas in
front of the jet, with thermal electron densities of ~0.06 cm**(-3) in the bar
and ~0.03 cm**(-3) outside the bar. The regular magnetic field along the bar
points toward the nucleus on both sides. The regular field in the disk reveals
multiple reversals, probably consisting of field loops stretched by a shearing
gas flow in the bar. The projection of the jet bending in the sky plane is in
the sense opposite to that of the underlying stellar and gaseous spiral
structure. The bending in 3-D is most easily explained as a precessing jet,
with an age less than 10**6 years. Our observations are consistent with very
recent triggering, possibly by a minor merger. NGC 7479 provides a unique
opportunity to study interaction-triggered 15-kpc scale radio jets within a
spiral galaxy.Comment: 18 pages, 21 figures, accepted for publication in the Astrophysical
Journa
An open-architecture metal powder bed fusion system for in-situ process measurements
We report the design of a metal powder bed fusion system for in-situ monitoring of the build process during additive manufacture. Its open-architecture design was originally determined to enable access for x-rays to the melt pool, but it also provides access to the build area for a range of other in-situ measurement techniques. The system is sufficiently automated to enable single tracks and high-density, multiple layer components to be built. It is easily transportable to enable measurements at different measurement facilities and its modular design enables straightforward modification for the specific measurements being made. We demonstrate that the system produces components with >99% density. Hence the build conditions are representative to observe process fundamentals and to develop process control strategies
Regulated expression of HCN channels and cAMP levels shape the properties of the h current in developing rat hippocampus.
The hyperpolarization-activated current (I(h)) contributes to intrinsic properties and network responses of neurons. Its biophysical properties depend on the expression profiles of the underlying hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels and the presence of cyclic AMP (cAMP) that potently and differentially modulates I(h) conducted by HCN1, HCN2 and/or HCN4. Here, we studied the properties of I(h) in hippocampal CA1 pyramidal cells, the developmental evolution of the HCN-subunit isoforms that contribute to this current, and their interplay with age-dependent free cAMP concentrations, using electrophysiological, molecular and biochemical methods. I(h) amplitude increased progressively during the first four postnatal weeks, consistent with the observed overall increased expression of HCN channels. Activation kinetics of the current accelerated during this period, consonant with the quantitative reduction of mRNA and protein expression of the slow-kinetics HCN4 isoform and increased levels of HCN1. The sensitivity of I(h) to cAMP, and the contribution of the slow component to the overall I(h), decreased with age. These are likely a result of the developmentally regulated transition of the complement of HCN channel isoforms from cAMP sensitive to relatively cAMP insensitive. Thus, although hippocampal cAMP concentrations increased over twofold during the developmental period studied, the coordinated changes in expression of three HCN channel isoforms resulted in reduced effects of this signalling molecule on neuronal h currents
CHANG-ES VI: Probing Supernova Energy Deposition in Spiral Galaxies Through Multi-Wavelength Relationships
How a galaxy regulates its SNe energy into different
interstellar/circumgalactic medium components strongly affects galaxy
evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz)
continuum observations, we perform statistical analysis comparing
multi-wavelength properties of the CHANG-ES galaxies. The high-quality JVLA
data and edge-on orientation enable us for the first time to include the halo
into the energy budget for a complete radio-flux-limited sample. We find tight
correlations of with the mid-IR-based SFR. The normalization of
our relation is 2-3 times of
those obtained for face-on galaxies, probably a result of enhanced IR
extinction at high inclination. We also find tight correlations between and the SNe energy injection rate , indicating
the energy loss via synchrotron radio continuum accounts for of
, comparable to the energy contained in CR electrons. The
integrated C-to-L-band spectral index is for non-AGN
galaxies, indicating a dominance by the diffuse synchrotron component. The
low-scatter /
relationships have super-linear logarithmic slopes at in L-band
(/) while consistent with linear in C-band
(/). The super-linearity could be naturally
reproduced with non-calorimeter models for galaxy disks. Using Chandra halo
X-ray measurements, we find sub-linear relations.
These results indicate that the observed radio halo of a starburst galaxy is
close to electron calorimeter, and a galaxy with higher SFR tends to distribute
an increased fraction of SNe energy into radio emission (than X-ray).Comment: 16 pages, 6 figures, 1 table, MNRAS in pres
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