1,053 research outputs found
Real-time broadening of non-equilibrium density profiles and the role of the specific initial-state realization
The real-time broadening of density profiles starting from non-equilibrium
states is at the center of transport in condensed-matter systems and dynamics
in ultracold atomic gases. Initial profiles close to equilibrium are expected
to evolve according to linear response, e.g., as given by the current
correlator evaluated exactly at equilibrium. Significantly off equilibrium,
linear response is expected to break down and even a description in terms of
canonical ensembles is questionable. We unveil that single pure states with
density profiles of maximum amplitude yield a broadening in perfect agreement
with linear response, if the structure of these states involves randomness in
terms of decoherent off-diagonal density-matrix elements. While these states
allow for spin diffusion in the XXZ spin-1/2 chain at large exchange
anisotropies, coherences yield entirely different behavior.Comment: 7 pages, 7 figures, accepted for publication in Phys. Rev.
FUSE Spectra of the Black Hole Binary LMC X-3
Far-ultraviolet spectra of LMC X-3 were taken covering photometric phases
0.47 to 0.74 in the 1.7-day orbital period of the black-hole binary (phase zero
being superior conjunction of the X-ray source). The continuum is faint and
flat, but appears to vary significantly during the observations. Concurrent
RXTE/ASM observations show the system was in its most luminous X-ray state
during the FUSE observations. The FUV spectrum contains strong terrestrial
airglow emission lines, while the only stellar lines clearly present are
emissions from the O VI resonance doublet. Their flux does not change
significantly during the FUSE observations. These lines are modelled as two
asymmetrical profiles, including the local ISM absorptions due to C II and
possibly O VI. Velocity variations of O VI emission are consistent with the
orbital velocity of the black hole and provide a new constraint on its mass.Comment: 12 pages including 1 table, 4 diagrams To appear in A
Discovery of 16.6 and 25.5 s Pulsations from the Small Magellanic Cloud
We report the serendipitous detection of two previously unreported pulsars
from the direction of the Small Magellanic Cloud, with periods of 16.6 and 25.5
seconds. The detections are based on archival PCA data from the Rossi X-ray
Timing Explorer (RXTE). The observation leading to these detections occurred in
September 2000 extending over 2.1 days with an exposure of 121 ks. A possible
identification of the 16.6 s pulsar with an X-ray source RX J0051.8-7310 seen
by both ROSAT and ASCA imaging X-ray satellites is presented.Comment: 9 pages with 3 figures. Submitted to ApJ Letter
Orbital Period Determinations for Four SMC Be/X-ray Binaries
We present an optical and X-ray study of four Be/X-ray binaries located in
the Small Magellanic Cloud (SMC). OGLE I-band data of up to 11 years of
semi-continuous monitoring has been analysed for SMC X-2, SXP172 and SXP202B,
providing both a measurement of the orbital period (Porb = 18.62, 68.90, and
229.9 days for the pulsars respectively) and a detailed optical orbital profile
for each pulsar. For SXP172 this has allowed a direct comparison of the optical
and X-ray emission seen through regular RXTE monitoring, revealing that the
X-ray outbursts precede the optical by around 7 days. Recent X-ray studies by
XMM-Newton have identified a new source in the vicinity of SXP15.3 raising
doubt on the identification of the optical counterpart to this X-ray pulsar.
Here we present a discussion of the observations that led to the proposal of
the original counterpart and a detailed optical analysis of the counterpart to
the new X-ray source, identifying a 21.7 d periodicity in the OGLE I-band data.
The optical characteristics of this star are consistent with that of a SMC
Be/X-ray binary. However, this star was rejected as the counterpart to SXP15.3
in previous studies due to the lack of H{\alpha} emission.Comment: Accepted for publication in MNRAS, 11 pages, 17 figure
Magellanic Cloud X-ray Sources: III. Completion of a ROSAT Survey
This paper concludes a series of three papers presenting ROSAT
High-Resolution Imager (HRI) observations of unidentified Einstein and
serendipitous ROSAT X-ray sources in the direction of the Magellanic Clouds.
Accurate positions and fluxes have been measured for these sources. Optical
photometry and spectroscopy were obtained to search for identifications in
order to determine the physical nature of these sources. The present paper
includes new data for 24 objects; identifications are given or confirmed for 30
sources. For six sources optical finding charts showing the X-ray positions are
provided. The results from this program are summarized, showing the populations
of luminous X-ray sources in the Magellanic Clouds are quite different from
those in the Galaxy.Comment: 28 pages, 2 figures; to appear in Astronomical Journa
Aspergillus nidulans ArfB Plays a Role in Endocytosis and Polarized Growth
Filamentous fungi undergo polarized growth throughout most of their life cycles. The Spitzenkörper is an apical organelle composed primarily of vesicles that is unique to filamentous fungi and is likely to act as a vesicle supply center for tip growth. Vesicle assembly and trafficking are therefore important for hyphal growth. ADP ribosylation factors (Arfs), a group of small GTPase proteins, play an important role in nucleating vesicle assembly. Little is known about the role of Arfs in filamentous hyphal growth. We found that Aspergillus nidulans is predicted to encode six Arf family proteins. Analysis of protein sequence alignments suggests that A. nidulans ArfB shares similarity with ARF6 of Homo sapiens and Arf3p of Saccharomyces cerevisiae. An arfB null allele (arfB disrupted by a transposon [arfB::Tn]) was characterized by extended isotropic growth of germinating conidia followed by cell lysis or multiple, random germ tube emergence, consistent with a failure to establish polarity. The mutant germ tubes and hyphae that do form initially meander abnormally off of the axis of polarity and frequently exhibit dichotomous branching at cell apices, consistent with a defect in polarity maintenance. FM4-64 staining of the arfB::Tn strain revealed that another phenotypic characteristic seen for arfB::Tn is a reduction and delay in endocytosis. ArfB is myristoylated at its N terminus. Green fluorescent protein-tagged ArfB (ArfB::GFP) localizes to the plasma membrane and endomembranes and mutation (ArfB(G2A)::GFP) of the N-terminal myristoylation motif disperses the protein to the cytoplasm rather than to the membranes. These results demonstrate that ArfB functions in endocytosis to play important roles in polarity establishment during isotropic growth and polarity maintenance during hyphal extension
An Investigation of Be/X-ray Pulsars with OGLE-III Data
We have studied five seasons of OGLE-III data for eight SMC Be/X-ray pulsars
for which no other survey data were available. We have determined orbital
periods for four of these binary systems, one of which also shows nonradial
pulsations. Optical identification of SMC X-2 is reconsidered, but no periods
were found for either of the two possible candidates
FUV Spectroscopy of the Supersoft X-ray Binary RX J0513.9-6951
We have obtained spectroscopy with the Far Ultraviolet Spectroscopic Explorer
(FUSE) of the supersoft X-ray binary RX J0513.9-6951 over a complete binary
orbital cycle. The spectra show a hot continuum with extremely broad O VI
emission and weak Lyman absorptions. He II emission is weak and narrow, while N
III and C III emissions are undetected, although lines from these ions are
prominent at optical wavelengths. The broad O VI emission and Lyman absorption
show radial velocity curves that are approximately antiphased and have
semiamplitudes of ~117 +- 40 and 54 +- 10 km/s, respectively. Narrow emissions
from He II and O VI show small velocity variations with phasing different from
the broad O VI, but consistent with the optical line peaks. We also measure
considerable changes in the FUV continuum and O VI emission line flux. We
discuss the possible causes of the measured variations and a tentative binary
interpretation.Comment: 21 pages, including 2 tables, 6 figures. To appear in A
The use of commitment techniques to support weight loss maintenance in obese adolescents
Objectives:
Obesity is a rising problem in adolescents related to unhealthy behaviours. Commitment devises are one type of behavioural intervention that may help people change their behaviours. The current pilot trial tests whether commitment devices delivered via text message help adolescents maintain their recent weight loss.
Methods:
During a 12-week pilot trial adolescents who attended a weight loss camp were randomly assigned to either received text messages that contained only information, i.e., advice, about weight loss management (n=13) or asked for them to commit to following the same advise (n=14).
Results:
The BMI of the adolescents in the commitment group did not change. In contrast, the BMI of adolescents in the information group increased. A linear regression revealed that group was a significant predictor of BMI change. A logistic regression revealed that adolescents in the information group were nearly eight times more likely to regain weight than those in the commitment group.
Conclusions:
This is the first study with adolescents to show weight maintenance using a commitment device. The results suggest that commitment devices can help adolescents maintain their recent weight loss
FUSE Observations of RX J0513.9-6951
FUSE observations were obtained in July 2003 during 1.2 cycles of the
0.76-day binary orbit of RX J0513.9-6951. Radial velocity measurements of the
broad O VI emission profile show a semiamplitude of K~26 km/sec, which is much
smaller than the value of 117 km/sec measured from 2001 FUSE data. Narrow O VI
emissions show no measurable velocity variation. The mean velocity of the broad
O VI emission is red-shifted by ~500 km/sec with respect to both the systemic
and narrow emission-line velocities. Spectral difference plots show
phase-related changes in the broad emission profile. Other phase-related
changes such as line and continuum variations are also smaller than in the 2001
spectra. We describe a moving broad absorption feature near 1020A as possible O
VI outflow associated with a precessing jet. We discuss the implications for
the stellar masses if the 2003 broad O VI velocities outline the compact star's
orbital motion.Comment: 16 pages, including 7 figures. To appear in A
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