14,354 research outputs found
The Herschel Virgo Cluster Survey. III. A constraint on dust grain lifetime in early-type galaxies
Passive early-type galaxies (ETGs) provide an ideal laboratory for studying the interplay between dust formation around evolved stars and its subsequent destruction in a hot gas. Using Spitzer-IRS and Herschel data we compare the dust production rate in the envelopes
of evolved AGB stars with a constraint on the total dust mass. Early-type galaxies which appear to be truly passively evolving are not detected by Herschel. We thus derive a distance independent upper limit to the dust grain survival time in the hostile environment of ETGs of <46 ± 25 Myr for amorphous silicate grains. This implies that ETGs which are detected at far-infrared wavelengths have
acquired a cool dusty medium via interaction. Given likely time-scales for ram-pressure stripping, this also implies that only galaxies with dust in a cool (atomic) medium can release dust into the intra-cluster medium
Dephasing-assisted Gain and Loss in Mesoscopic Quantum Systems
Motivated by recent experiments, we analyse the phonon-assisted steady-state
gain of a microwave field driving a double quantum-dot in a resonator. We apply
the results of our companion paper, which derives the complete set of
fourth-order Lindblad dissipators using Keldysh methods, to show that resonator
gain and loss are substantially affected by dephasing-assisted dissipative
processes in the quantum-dot system. These additional processes, which go
beyond recently proposed polaronic theories, are in good quantitative agreement
with experimental observationsComment: 5 pages, 3 Figures, published together with arXiv:1608.0416
Surface flux pinning in superconducting amorphous (Mo0.6Ru0.4)B18
Superconducting critical current density was measured as a function of a perpendicular applied magnetic field in glassy (Mo0.6Ru0.4)82B18. The pinning force density was observed to depend linearly on 1/w, where w is the sample width measured perpendicular to both the current and field. This dependence is attributed to pinning by the sample edges. The bulk pinning contribution can be separated from the edge pinning contribution by extrapolation of the Fp vs 1/w curve. The edge contribution of the flux pinning was nearly eliminated by electrolytically polishing the sample. The contribution of the flux pinning profile due to edge pinning is analyzed in terms of the dynamic pinning model modified for edge pinning
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Estimating the uncertainty of areal precipitation using data assimilation
We present a method to estimate spatially and temporally variable uncertainty of areal precipitation data. The aim of the method is to merge measurements from different sources, remote sensing and in situ, into a combined precipitation product and to provide an associated dynamic uncertainty estimate. This estimate should provide an accurate representation of uncertainty both in time and space, an adjustment to additional observations merged into the product through data assimilation, and flow dependency. Such a detailed uncertainty description is important for example to generate precipitation ensembles for probabilistic hydrological modelling or to specify accurate error covariances when using precipitation observations for data assimilation into numerical weather prediction models. The presented method uses the Local Ensemble Transform Kalman Filter and an ensemble nowcasting model. The model provides information about the precipitation displacement over time and is continuously updated by assimilation of observations. In this way, the precipitation product and its uncertainty estimate provided by the nowcasting ensemble evolve consistently in time and become flow-dependent. The method is evaluated in a proof of concept study focusing on weather radar data of four precipitation events. The study demonstrates that the dynamic areal uncertainty estimate outperforms a constant benchmark uncertainty value in all cases for one of the evaluated scores, and in half the number of cases for the other score. Thus, the flow dependency introduced by the coupling of data assimilation and nowcasting enables a more accurate spatial and temporal distribution of uncertainty. The mixed results achieved in the second score point out the importance of a good probabilistic nowcasting scheme for the performance of the method
Ifosfamide with regional hyperthermia in soft-tissue sarcomas
For high-risk soft tissue sarcomas (HR-STS) of adults, new treatment strategies are needed to improve outcome with regard to local control and overall survival. Therefore, systemic chemotherapy has been integrated either after (adjuvant) or before (neoadjuvant) optimal local treatment by surgery and radiotherapy in HR-STS. The combination with regional hyperthermia as a new treatment strategy seems to open a new therapeutic window. Copyright (C) 2003 S. Karger AG, Basel
Mid-infrared colour gradients and the colour-magnitude relation in Virgo early-type galaxies
We make use of Spitzer imaging between 4 and 16 micron and near-infrared data
at 2.2 micron to investigate the nature and distribution of the mid-infrared
emission in a sample of early-type galaxies in the Virgo cluster. These data
allow us to conclude, with some confidence, that the emission at 16 micron in
passive ETGs is stellar in origin, consistent with previous work concluding
that the excess mid-infrared emission comes from the dusty envelopes around
evolved AGB stars. There is little evidence for the mid-infrared emission of an
unresolved central component, as might arise in the presence of a dusty torus
associated with a low-luminosity AGN. We nonetheless find that the 16 micron
emission is more centrally peaked than the near-infrared emission, implying a
radial stellar population gradient. By comparing with independent evidence from
studies at optical wavelengths, we conclude that a metallicity that falls with
increasing radius is the principal driver of the observed gradient. We also
plot the mid-infrared colour-magnitude diagram and combine with similar work on
the Coma cluster to define the colour-magnitude relation for absolute K-band
magnitudes from -26 to -19. Because a correlation between mass and age would
produce a relation with a gradient in the opposite sense to that observed, we
conclude that the relation reflects the fact that passive ETGs of lower mass
also have a lower average metallicity. The colour-magnitude relation is thus
driven by metallicity effects. In contrast to what is found in Coma, we do not
find any objects with anomalously bright 16 micron emission relative to the
colour-magnitude relation. Although there is little overlap in the mass ranges
probed in the two clusters, this may suggest that observable ``rejuvenation''
episodes are limited to intermediate mass objects.Comment: 8 pages, 4 figure
Surface motion in the pulsating DA white dwarf G 29-38
We present time-resolved spectrophotometry of the pulsating DA white dwarf G
29-38. As in previous broad-band photometry, the light curve shows the presence
of a large number of periodicities. Many of these are combination frequencies,
i.e., periodicities occurring at frequencies that are sums or differences of
frequencies of stronger, real modes. We identify at least six real modes, and
at least five combination frequencies. We measure line-of-sight velocities for
our spectra and detect periodic variations at the frequencies of five of the
six real modes, with amplitudes of up to 5 km/s. We argue that these variations
reflect the horizontal surface motion associated with the g-mode pulsations. No
velocity signals are detected at any of the combination frequencies, confirming
that the flux variations at these frequencies do not reflect physical
pulsation, but rather mixing of frequencies due to a non-linear transformation
in the outer layers of the star. We discuss the amplitude ratios and phase
differences found for the velocity and light variations, as well as those found
for the real modes and their combination frequencies, both in a
model-independent way and in the context of models based on the
convective-driving mechanism. In a companion paper, we use the wavelength
dependence of the amplitudes of the modes to infer their spherical degree.Comment: 12 pages, 5 figures, mn.sty. Accepted for publication in MNRA
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