3,912 research outputs found
Energy and pressure densities of a hot quark-gluon plasma
We calculate the energy and hydrostatic pressure densities of a hot
quark-gluon plasma in thermal equilibrium through diagrammatic analyses of the
statistical average, , of the
energy-momentum-tensor operator . To leading order at high
temperature, the energy density of the long wave length modes is consistently
extracted by applying the hard-thermal-loop resummation scheme to the
operator-inserted no-leg thermal amplitudes .
We find that, for the long wave length gluons, the energy density, being
positive, is tremendously enhanced as compared to the noninteracting case,
while, for the quarks, no noticeable deviation from the noninteracting case is
found.Comment: 33 pages. Figures are not include
High-cadence measurements of electron pitch-angle distributions from Solar Orbiter SWA-EAS burst mode operations
Nonequilibrium Steady States of Matrix Product Form: A Solver's Guide
We consider the general problem of determining the steady state of stochastic
nonequilibrium systems such as those that have been used to model (among other
things) biological transport and traffic flow. We begin with a broad overview
of this class of driven diffusive systems - which includes exclusion processes
- focusing on interesting physical properties, such as shocks and phase
transitions. We then turn our attention specifically to those models for which
the exact distribution of microstates in the steady state can be expressed in a
matrix product form. In addition to a gentle introduction to this matrix
product approach, how it works and how it relates to similar constructions that
arise in other physical contexts, we present a unified, pedagogical account of
the various means by which the statistical mechanical calculations of
macroscopic physical quantities are actually performed. We also review a number
of more advanced topics, including nonequilibrium free energy functionals, the
classification of exclusion processes involving multiple particle species,
existence proofs of a matrix product state for a given model and more
complicated variants of the matrix product state that allow various types of
parallel dynamics to be handled. We conclude with a brief discussion of open
problems for future research.Comment: 127 pages, 31 figures, invited topical review for J. Phys. A (uses
IOP class file
Disentangling the Imaginary-Time Formalism at Finite Temperature
We rewrite the imaginary-time formalism of finite temperature field theory in
a form that all graphs used in calculating physical processes do not have any
loops. Any production of a particle from a heat bath which is itself not
thermalized or the decay and absorption of a similar particle in the bath is
expressed entirely in terms of the sum of particle interaction processes. These
are themselves very general in meaning. They can be straight forward
interactions or the more subtle and less well-known purely interference
processes that do not have a counter part in the vacuum.Comment: 14 pages revtex style, 20 embedded EPS figures, added discussion of
the connection with the real-time formalism + reference
PARP-1 regulates DNA repair factor availability.
PARP-1 holds major functions on chromatin, DNA damage repair and transcriptional regulation, both of which are relevant in the context of cancer. Here, unbiased transcriptional profiling revealed the downstream transcriptional profile of PARP-1 enzymatic activity. Further investigation of the PARP-1-regulated transcriptome and secondary strategies for assessing PARP-1 activity in patient tissues revealed that PARP-1 activity was unexpectedly enriched as a function of disease progression and was associated with poor outcome independent of DNA double-strand breaks, suggesting that enhanced PARP-1 activity may promote aggressive phenotypes. Mechanistic investigation revealed that active PARP-1 served to enhance E2F1 transcription factor activity, and specifically promoted E2F1-mediated induction of DNA repair factors involved in homologous recombination (HR). Conversely, PARP-1 inhibition reduced HR factor availability and thus acted to induce or enhance BRCA-ness . These observations bring new understanding of PARP-1 function in cancer and have significant ramifications on predicting PARP-1 inhibitor function in the clinical setting
Observations of chemical differentiation in clumpy molecular clouds
We have extensively mapped a sample of dense molecular clouds (L1512, TMC-1C,
L1262, Per 7, L1389, L1251E) in lines of HC3N, CH3OH, SO and C^{18}O. We
demonstrate that a high degree of chemical differentiation is present in all of
the observed clouds. We analyse the molecular maps for each cloud,
demonstrating a systematic chemical differentiation across the sample, which we
relate to the evolutionary state of the cloud. We relate our observations to
the cloud physical, kinematical and evolutionary properties, and also compare
them to the predictions of simple chemical models. The implications of this
work for understanding the origin of the clumpy structures and chemical
differentiation observed in dense clouds are discussed.Comment: 20 pages, 7 figures. Higher quality figures appear in the published
journal articl
Precision Measurement of The Most Distant Spectroscopically Confirmed Supernova Ia with the Hubble Space Telescope
We report the discovery of a redshift 1.71 supernova in the GOODS North
field. The Hubble Space Telescope (HST) ACS spectrum has almost negligible
contamination from the host or neighboring galaxies. Although the rest frame
sampled range is too blue to include any Si ii line, a principal component
analysis allows us to confirm it as a Type Ia supernova with 92% confidence. A
recent serendipitous archival HST WFC3 grism spectrum contributed a key element
of the confirmation by giving a host-galaxy redshift of 1.713 +/- 0.007. In
addition to being the most distant SN Ia with spectroscopic confirmation, this
is the most distant Ia with a precision color measurement. We present the ACS
WFC and NICMOS 2 photometry and ACS and WFC3 spectroscopy. Our derived
supernova distance is in agreement with the prediction of LambdaCDM.Comment: 13 pages, 6 figures, published in ApJ with updated analysi
Evaluation of a brief anti-stigma campaign in Cambridge: do short-term campaigns work?
<p>Abstract</p> <p>Background</p> <p>In view of the high costs of mass-media campaigns, it is important to understand whether it is possible for a media campaign to have significant population effects over a short period of time. This paper explores this question specifically in reference to stigma and discrimination against people with mental health problems using the <it>Time to Change </it>Cambridge anti-stigma campaign as an example.</p> <p>Methods</p> <p>410 face-to-face interviews were performed pre, during and post campaign activity to assess campaign awareness and mental health-related knowledge, attitudes and behaviours.</p> <p>Results</p> <p>Although campaign awareness was not sustained following campaign activity, significant and sustained shifts occurred for mental health-related knowledge items. Specifically, there was a 24% (p < 0.001) increase in persons agreeing with the statement: <it>If a friend had a mental health problem, I know what advice to give them to get professional help</it>, following the campaign. Additionally, for the statement: <it>Medication can be an effective treatment for people with mental health problems</it>, there was a 10% rise (p = 0.05) in the proportion of interviewees responding 'agree' or 'strongly agree' following the campaign. These changes, however, were not evident for attitudinal or behaviour related questions.</p> <p>Conclusions</p> <p>Although these results only reflect the impact of one small scale campaign, these preliminary findings suggest several considerations for mass-media campaign development and evaluation strategies such as: (1) Aiming to influence outcomes pertaining to knowledge in the short term; (2) Planning realistic and targeted outcomes over the short, medium and long term during sustained campaigns; and (3) Monitoring indirect campaign effects such as social discourse or other social networking/contact in the evaluation.</p
The angular-momentum flux in the solar wind observed during Solar Orbiter's first orbit
Aims: We present the first measurements of the angular-momentum flux in the solar wind recorded by the Solar Orbiter spacecraft.
Our aim is to validate these measurements to support future studies of the Sun’s angular-momentum loss.
Methods: We combined 60-min averages of the proton bulk moments and the magnetic field measured by the Solar Wind Analyser
(SWA) and the magnetometer (MAG) onboard Solar Orbiter. We calculated the angular-momentum flux per solid-angle element using
data from the first orbit of the mission’s cruise phase in 2020. We separated the contributions from protons and from magnetic stresses
to the total angular-momentum flux.
Results: The angular-momentum flux varies significantly over time. The particle contribution typically dominates over the magneticfield contribution during our measurement interval. The total angular-momentum flux shows the largest variation and is typically anticorrelated with the radial solar-wind speed. We identify a compression region, potentially associated with a co-rotating interaction
region or a coronal mass ejection, which leads to a significant localised increase in the angular-momentum flux, albeit without a
significant increase in the angular momentum per unit mass. We repeated our analysis using the density estimate from the Radio and
Plasma Waves (RPW) instrument. Using this independent method, we find a decrease in the peaks of positive angular-momentum
flux, but otherwise, our results remain consistent.
Conclusions: Our results largely agree with previous measurements of the solar wind’s angular-momentum flux in terms of amplitude,
variability, and dependence on radial solar-wind bulk speed. Our analysis highlights the potential for more detailed future studies of
the solar wind’s angular momentum and its other large-scale properties with data from Solar Orbiter. We emphasise the need for
studying the radial evolution and latitudinal dependence of the angular-momentum flux in combination with data from Parker Solar
Probe and other assets at heliocentric distances of 1 au and beyond
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