937 research outputs found
The asteroseismological potential of the pulsating DB white dwarf stars CBS 114 and PG 1456+103
We have acquired 65 h of single-site time-resolved CCD photometry of the
pulsating DB white dwarf star CBS 114 and 62 h of two-site high-speed CCD
photometry of another DBV, PG 1456+103. The pulsation spectrum of PG 1456+103
is complicated and variable on time scales of about one week and could only
partly be deciphered with our measurements. The modes of CBS 114 are more
stable in time and we were able to arrive at a frequency solution somewhat
affected by aliasing, but still satisfactory, involving seven independent modes
and two combination frequencies. These frequencies also explain the discovery
data of the star, taken 13 years earlier. We find a mean period spacing of 37.1
+/- 0.7 s significant at the 98% level between the independent modes of CBS 114
and argue that they are due to nonradial g-mode pulsations of spherical degree
l=1. We performed a global search for asteroseismological models of CBS 114
using a genetic algorithm, and we examined the susceptibility of the results to
the uncertainties of the observational frequency determinations and mode
identifications (we could not provide m values). The families of possible
solutions are identified correctly even without knowledge of m. Our optimal
model suggests Teff = 21,000 K and M_* = 0.730 M_sun as well as log(M_He/M_*) =
-6.66, X_O = 0.61. This measurement of the central oxygen mass fraction implies
a rate for the ^12C(alpha,gamma)^16O nuclear reaction near S_300=180 keV b,
consistent with laboratory measurements.Comment: 10 pages, 10 embedded figures, 3 embedded tables. Accepted for
publication in MNRA
Spectroscopic characterization and detection of Ethyl Mercaptan in Orion
New laboratory data of ethyl mercaptan, CHCHSH, in the millimeter
and submillimeter-wave domains (up to 880 GHz) provided very precise values of
the spectroscopic constants that allowed the detection of
-CHCHSH towards Orion KL. 77 unblended or slightly blended
lines plus no missing transitions in the range 80-280 GHz support this
identification. A detection of methyl mercaptan, CHSH, in the spectral
survey of Orion KL is reported as well. Our column density results indicate
that methyl mercaptan is 5 times more abundant than ethyl mercaptan in
the hot core of Orion KL.Comment: Accepted for publication in ApJL (30 January 2014)/ submitted (8
January 2014
Open Systems Viewed Through Their Conservative Extensions
A typical linear open system is often defined as a component of a larger
conservative one. For instance, a dielectric medium, defined by its frequency
dependent electric permittivity and magnetic permeability is a part of a
conservative system which includes the matter with all its atomic complexity. A
finite slab of a lattice array of coupled oscillators modelling a solid is
another example. Assuming that such an open system is all one wants to observe,
we ask how big a part of the original conservative system (possibly very
complex) is relevant to the observations, or, in other words, how big a part of
it is coupled to the open system? We study here the structure of the system
coupling and its coupled and decoupled components, showing, in particular, that
it is only the system's unique minimal extension that is relevant to its
dynamics, and this extension often is tiny part of the original conservative
system. We also give a scenario explaining why certain degrees of freedom of a
solid do not contribute to its specific heat.Comment: 51 page
CDDO-Me Redirects Activation of Breast Tumor Associated Macrophages
Tumor-associated macrophages can account for up to 50% of the tumor mass in breast cancer patients and high TAM density is associated with poor clinical prognosis. Because TAMs enhance tumor growth, development, and metastatic potential, redirection of TAM activation may have significant therapeutic benefit. Our studies in primary human macrophages and murine breast TAMs suggest that the synthetic oleanane triterpenoid CDDO-methyl ester (CDDO-Me) reprograms the activation profile of TAMs from tumor-promoting to tumor-inhibiting. We show that CDDO-Me treatment inhibits expression of IL-10 and VEGF in stimulated human M2 macrophages and TAMs but increases expression of TNF-α and IL-6. Surface expression of CD206 and CD163, which are characteristic of M2 activation, is significantly attenuated by CDDO-Me. In contrast, CDDO-Me up-regulates surface expression of HLA-DR and CD80, which are markers of M1 activation, and importantly potentiates macrophage activation of autologous T cells but inhibits endothelial cell vascularization. These results show for the first time that CDDO-Me redirects activation of M2 macrophages and TAMs from immune-suppressive to immune-stimulatory, and implicate a role for CDDO-Me as an immunotherapeutic in the treatment of breast and potentially other types of cancer
ELVIS: Entertainment-led video summaries
© ACM, 2010. This is the author's version of the work. It is posted here by permission of ACM for your personal use. Not for redistribution. The definitive version was published in ACM Transactions on Multimedia Computing, Communications, and Applications, 6(3): Article no. 17 (2010) http://doi.acm.org/10.1145/1823746.1823751Video summaries present the user with a condensed and succinct representation of the content of a video stream. Usually this is achieved by attaching degrees of importance to low-level image, audio and text features. However, video content elicits strong and measurable physiological responses in the user, which are potentially rich indicators of what video content is memorable to or emotionally engaging for an individual user. This article proposes a technique that exploits such physiological responses to a given video stream by a given user to produce Entertainment-Led VIdeo Summaries (ELVIS). ELVIS is made up of five analysis phases which correspond to the analyses of five physiological response measures: electro-dermal response (EDR), heart rate (HR), blood volume pulse (BVP), respiration rate (RR), and respiration amplitude (RA). Through these analyses, the temporal locations of the most entertaining video subsegments, as they occur within the video stream as a whole, are automatically identified. The effectiveness of the ELVIS technique is verified through a statistical analysis of data collected during a set of user trials. Our results show that ELVIS is more consistent than RANDOM, EDR, HR, BVP, RR and RA selections in identifying the most entertaining video subsegments for content in the comedy, horror/comedy, and horror genres. Subjective user reports also reveal that ELVIS video summaries are comparatively easy to understand, enjoyable, and informative
Perceived Realism of Pedestrian Crowds Trajectories in VR
Crowd simulation algorithms play an essential role in populating Virtual Reality (VR) environments with multiple autonomous humanoid agents. The generation of plausible trajectories can be a significant computational cost for real-time graphics engines, especially in untethered and mobile devices such as portable VR devices. Previous research explores the plausibility and realism of crowd simulations on desktop computers but fails to account the impact it has on immersion. This study explores how the realism of crowd trajectories affects the perceived immersion in VR. We do so by running a psychophysical experiment in which participants rate the realism of real/synthetic trajectories data, showing similar level of perceived realism
Multi-line Herschel/HIFI observations of water reveal infall motions and chemical segregation around high-mass protostars
(Abridged) We use HIFI maps of the 987 GHz H2O 2(02)-1(11) emission to
measure the sizes and shapes of 19 high-mass protostellar envelopes. To
identify infall, we use HIFI spectra of the optically thin C18O 9-8 and H2O-18
1(11)-0(00) lines. The high-J C18O line traces the warm central material and
redshifted H2O-18 1(11)-0(00) absorption indicates material falling onto the
warm core. We probe small-scale chemical differentiation by comparing H2O 752
and 987 GHz spectra with those of H2O-18.
Our measured radii of the central part of the H2O 2(02)-1(11) emission are
30-40% larger than the predictions from spherical envelope models, and axis
ratios are <2, which we consider good agreement. For 11 of the 19 sources, we
find a significant redshift of the H2O-18 1(11)-0(00) line relative to C18O
9-8. The inferred infall velocities are 0.6-3.2 km/s, and estimated mass inflow
rates range from 7e-5 to 2e-2 M0/yr, with the highest mass inflow rates
occurring toward the sources with the highest masses, and possibly the youngest
ages. The other sources show either expanding motions or H2O-18 lines in
emission. The H2O-18 1(11)-0(00) line profiles are remarkably similar to the
"differences" between the H2O 2(02)-1(11) and 2(11)-2(02) profiles, suggesting
that the H2O-18 line and the H2O 2(02)-1(11) absorption originate just inside
the radius where water evaporates from grains, typically 1000-5000 au from the
center. In some sources, the H2O-18 line is detectable in the outflow, where no
C18O emission is seen.
Together, the H2O-18 absorption and C18O emission profiles show that the
water abundance around high-mass protostars has at least three levels: low in
the cool outer envelope, high within the 100 K radius, and very high in the
outflowing gas. Thus, despite the small regions, the combination of lines
presented here reveals systematic inflows and chemical information about the
outflows.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages body +
10 pages appendi
Massive Stars in the Quintuplet Cluster
We present near-infrared photometry and K-band spectra of newly-identified
massive stars in the Quintuplet Cluster, one of the three massive clusters
projected within 50 pc of the Galactic Center. We find that the cluster
contains a variety of massive stars, including more unambiguously identified
Wolf-Rayet stars than any cluster in the Galaxy, and over a dozen stars in
earlier stages of evolution, i.e., LBV, Ofpe/WN9, and OB supergiants. One newly
identified star is the second ``Luminous Blue Variable'' in the cluster, after
the ``Pistol Star.'' Given the evolutionary stages of the identified stars, the
cluster appears to be about 4 \pm 1 Myr old, assuming coeval formation. The
total mass in observed stars is \sim 10^3 \Msun, and the implied mass is
\sim 10^4 \Msun, assuming a lower mass cutoff of 1 \Msun and a Salpeter
initial mass function. The implied mass density in stars is at least a few
thousand \Msun pc^{-3}. The newly-identified stars increase the estimated
ionizing flux from this cluster by about an order of magnitude with respect to
earlier estimates, to 10^{50.9} photons/s, or roughly what is required to
ionize the nearby ``Sickle'' HII region (G0.18 - 0.04). The total luminosity
from the massive cluster stars is \Lsun, enough to account
for the heating of the nearby molecular cloud, M0.20 - 0.033. We propose a
picture which integrates most of the major features in this part of the sky,
excepting the non-thermal filaments. We compare the cluster to other young
massive clusters and globular clusters, finding that it is unique in stellar
content and age, except, perhaps, for the young cluster in the central parsec
of the Galaxy. In addition, we find that the cluster is comparable to small
``super star clusters.'
Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System
Crab crossing is essential for high-luminosity colliders. The High Luminosity
Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1)
with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation
of deflecting RF cavities that stands out for its compactness and broad
frequency separation between fundamental and first high-order modes. The
deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity
shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may
be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6
MV. This paper describes a new, highly optimized cavity, designated DQW
SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance
requirements for beam tests at SPS and operation in LHC. Two prototypes of this
DQW SPS-series were fabricated by US industry and cold tested after following
conventional SRF surface treatment. Both units outperformed the PoP cavity,
reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached
by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even
operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper
covers fabrication, surface preparation and cryogenic RF test results and
implications
Effective area calibration of the reflection grating spectrometers of XMM-Newton. II. X-ray spectroscopy of DA white dwarfs
White dwarf spectra have been widely used as a calibration source for X-ray
and EUV instruments. The in-flight effective area calibration of the reflection
grating spectrometers (RGS) of XMM-Newton depend upon the availability of
reliable calibration sources. We investigate how well these white dwarf spectra
can be used as standard candles at the lowest X-ray energies in order to gauge
the absolute effective area scale of X-ray instruments. We calculate a grid of
model atmospheres for Sirius B and HZ 43A, and adjust the parameters using
several constraints until the ratio of the spectra of both stars agrees with
the ratio as observed by the low energy transmission grating spectrometer
(LETGS) of Chandra. This ratio is independent of any errors in the effective
area of the LETGS. We find that we can constrain the absolute X-ray spectrum of
both stars with better than 5 % accuracy. The best-fit model for both stars is
close to a pure hydrogen atmosphere, and we put tight limits to the amount of
helium or the thickness of a hydrogen layer in both stars. Our upper limit to
the helium abundance in Sirius B is 4 times below the previous detection based
on EUVE data. We also find that our results are sensitive to the adopted
cut-off in the Lyman pseudo-continuum opacity in Sirius B. We get best
agreement with a long wavelength cut-off. White dwarf model atmospheres can be
used to derive the effective area of X-ray spectrometers in the lowest energy
band. An accuracy of 3-4 % in the absolute effective area can be achieved.Comment: 15 pages, 7 figures, accepted for publication in Astronomy &
Astrophysics, main journa
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