173 research outputs found
Optimizing antibiotic therapy-the Aberdeen experience
ObjectiveTo study the quality and continuity of treatment in the Acute Medicines Assessment Unit (AMAU) with regard to empirical prescription of antibiotics, mode of administration, adherence to ward antibiotic policy, as well as collection, awareness and utilization of microbiological investigations.MethodsA prospective study over a 3-month period at the AMAU, Aberdeen Royal Infirmary (ARI), a teaching hospital in north-eastern Scotland, was performed. The study included all patients started on empirical antibiotics on admission to the AMAU and followed up until their discharge.ResultsOf 1303 patients admitted, 221 (17%) were started on empirical antibiotics. This was in accordance with hospital antibiotic policy in 52% of cases. Appropriate specimens were taken from 77% of patients. Culture results showed that 29% (n = 65) of the patients had clinically significant growth of organisms. Of the 65 patients with clinically significant culture results, 49% (n = 32) were on an inappropriate empirical regimen. In 55%, the medication was not changed to a more appropriate antibiotic. In 72% of the patients with a negative culture, the culture report had no obvious effect on the duration or type of antibiotic being administered. Intravenous antibiotics were used in 60% of patients.ConclusionThis study demonstrates a significant overuse of antibiotics, especially intravenous forms, despite a paucity of positive sepsis parameters and chest X-ray findings in these patients The duration of treatment could be shortened and an early switch policy introduced if culture results and sepsis profiles were taken into consideration, as there was a large number of unproven infections. Suggestions are made about how these improvements in prescribing could be made within the current administrative set-up of AMAUs
The peritoneal tumour microenvironment of high-grade serous ovarian cancer
High-grade serous ovarian cancer (HGSC) disseminates early and extensively throughout the peritoneal space, causing multiple lesions that are a major clinical problem. The aim of this study was to investigate the cellular composition of peritoneal tumour deposits in patient biopsies and their evolution in mouse models using immunohistochemistry, intravital microscopy, confocal microscopy, and 3D modelling. Tumour deposits from the omentum of HGSC patients contained a prominent leukocyte infiltrate of CD3(+) T cells and CD68(+) macrophages, with occasional neutrophils. Alpha-smooth muscle actin(+) (α-SMA(+) ) pericytes and/or fibroblasts surrounded these well-vascularized tumour deposits. Using the murine bowel mesentery as an accessible mouse peritoneal tissue that could be easily imaged, and two different transplantable models, we found multiple microscopic tumour deposits after i.p. injection of malignant cells. Attachment to the peritoneal surface was rapid (6-48 h) with an extensive CD45(+) leukocyte infiltrate visible by 48 h. This infiltrate persisted until end point and in the syngeneic murine ID8 model, it primarily consisted of CD3(+) T lymphocytes and CD68(+) macrophages with α-SMA(+) cells also involved from the earliest stages. A majority of tumour deposits developed above existing mesenteric blood vessels, but in avascular spaces new blood vessels tracked towards the tumour deposits by 2-3 weeks in the IGROV-1 xenografts and 6 weeks in the ID8 syngeneic model; a vigorous convoluted blood supply was established by end point. Inhibition of tumour cell cytokine production by stable expression of shRNA to CXCR4 in IGROV-1 cells did not influence the attachment of cells to the mesentery but delayed neovascularization and reduced tumour deposit size. We conclude that the multiple peritoneal tumour deposits found in HGSC patients can be modelled in the mouse. The techniques described here may be useful for assessing treatments that target the disseminated stage of this disease
Detection of Extrasolar Planets by Gravitational Microlensing
Gravitational microlensing provides a unique window on the properties and
prevalence of extrasolar planetary systems because of its ability to find
low-mass planets at separations of a few AU. The early evidence from
microlensing indicates that the most common type of exoplanet yet detected are
the so-called "super-Earth" planets of ~10 Earth-masses at a separation of a
few AU from their host stars. The detection of two such planets indicates that
roughly one third of stars have such planets in the separation range 1.5-4 AU,
which is about an order of magnitude larger than the prevalence of gas-giant
planets at these separations. We review the basic physics of the microlensing
method, and show why this method allows the detection of Earth-mass planets at
separations of 2-3 AU with ground-based observations. We explore the conditions
that allow the detection of the planetary host stars and allow measurement of
planetary orbital parameters. Finally, we show that a low-cost, space-based
microlensing survey can provide a comprehensive statistical census of
extrasolar planetary systems with sensitivity down to 0.1 Earth-masses at
separations ranging from 0.5 AU to infinity.Comment: 43 pages. Very similar to chapter 3 of Exoplanets: Detection,
Formation, Properties, Habitability, John Mason, ed. Springer (April 3, 2008
QCD Corrections to QED Vacuum Polarization
We compute QCD corrections to QED calculations for vacuum polarization in
background magnetic fields. Formally, the diagram for virtual loops
is identical to the one for virtual loops. However due to
confinement, or to the growth of as decreases, a direct
calculation of the diagram is not allowed. At large we consider the
virtual diagram, in the intermediate region we discuss the role of
the contribution of quark condensates \left and at the
low-energy limit we consider the , as well as charged pion
loops. Although these effects seem to be out of the measurement accuracy of
photon-photon laboratory experiments they may be relevant for -ray
burst propagation. In particular, for emissions from the center of the galaxy
(8.5 kpc), we show that the mixing between the neutral pseudo-scalar pion
and photons renders a deviation from the power-law spectrum in the
range. As for scalar quark condensates \left and
virtual loops are relevant only for very high radiation density
and very strong magnetic fields of order .Comment: 15 pages, 4 figures; Final versio
Microlensing as a probe of the Galactic structure; 20 years of microlensing optical depth studies
Microlensing is now a very popular observational astronomical technique. The
investigations accessible through this effect range from the dark matter
problem to the search for extra-solar planets. In this review, the techniques
to search for microlensing effects and to determine optical depths through the
monitoring of large samples of stars will be described. The consequences of the
published results on the knowledge of the Milky-Way structure and its dark
matter component will be discussed. The difficulties and limitations of the
ongoing programs and the perspectives of the microlensing optical depth
technique as a probe of the Galaxy structure will also be detailed.Comment: Accepted for publication in General Relativity and Gravitation.
General Relativity and Gravitation in press (2010) 0
Physical Processes in Star Formation
© 2020 Springer-Verlag. The final publication is available at Springer via https://doi.org/10.1007/s11214-020-00693-8.Star formation is a complex multi-scale phenomenon that is of significant importance for astrophysics in general. Stars and star formation are key pillars in observational astronomy from local star forming regions in the Milky Way up to high-redshift galaxies. From a theoretical perspective, star formation and feedback processes (radiation, winds, and supernovae) play a pivotal role in advancing our understanding of the physical processes at work, both individually and of their interactions. In this review we will give an overview of the main processes that are important for the understanding of star formation. We start with an observationally motivated view on star formation from a global perspective and outline the general paradigm of the life-cycle of molecular clouds, in which star formation is the key process to close the cycle. After that we focus on the thermal and chemical aspects in star forming regions, discuss turbulence and magnetic fields as well as gravitational forces. Finally, we review the most important stellar feedback mechanisms.Peer reviewedFinal Accepted Versio
Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO-Virgo Run O3b
We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC-2020 March 27 17:00 UTC). We conduct two independent searches: A generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate. © 2022. The Author(s). Published by the American Astronomical Society
Narrowband Searches for Continuous and Long-duration Transient Gravitational Waves from Known Pulsars in the LIGO-Virgo Third Observing Run
Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow both the frequency and the time derivative of the frequency of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search, we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets. © 2022. The Author(s). Published by the American Astronomical Society
Spitzer Parallax Of Ogle-2015-blg-0966: A Cold Neptune In The Galactic Disk
We report the detection of a cold Neptune mplanet = 21 ± 2 M? orbiting a 0.38 M? M dwarf lying 2.5–3.3 kpc toward the Galactic center as part of a campaign combining ground-based and Spitzer observations to measure the Galactic distribution of planets. This is the first time that the complex real-time protocols described by Yee et al., which aim to maximize planet sensitivity while maintaining sample integrity, have been carried out in practice. Multiple survey and follow up teams successfully combined their efforts within the framework of these protocols to detect this planet. This is the second planet in the Spitzer Galactic distribution sample. Both are in the near to mid-disk and are clearly not in the Galactic bulge
The Spitzer Microlensing Program As A Probe For Globular Cluster Planets: Analysis Of Ogle-2015-BLG-0448
The microlensing event OGLE-2015-BLG-0448 was observed by Spitzer and lay within the tidal radius of the globular cluster NGC 6558. The event had moderate magnification and was intensively observed, hence it had the potential to probe the distribution of planets in globular clusters. We measure the proper motion of NGC 6558 () as well as the source and show that the lens is not a cluster member. Even though this particular event does not probe the distribution of planets in globular clusters, other potential cluster lens events can be verified using our methodology. Additionally, we find that microlens parallax measured using Optical Gravitational Lens Experiment (OGLE) photometry is consistent with the value found based on the light curve displacement between the Earth and Spitzer
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