22,971 research outputs found
Signatures of rotating binaries in micro-lensing experiments
Gravitational microlensing offers a powerful method with which to probe a
variety of binary-lens systems, as the binarity of the lens introduces
deviations from the typical (single-lens) Paczy\'nski behaviour in the event
light curves. Generally, a static binary lens is considered to fit the observed
light curve and, when the orbital motion is taken into account, an
oversimplified model is usually employed. In this paper, we treat the
binary-lens motion in a realistic way and focus on simulated events that are
fitted well by a Paczy\'nski curve. We show that an accurate timing analysis of
the residuals (calculated with respect to the best-fitting Paczy\'nski model)
is usually sufficient to infer the orbital period of the binary lens. It goes
without saying that the independently estimated period may be used to further
constrain the orbital parameters obtained by the best-fitting procedure, which
often gives degenerate solutions. We also present a preliminary analysis of the
event OGLE-2011-BLG-1127 / MOA-2011-BLG-322, which has been recognized to be
the result of a binary lens. The period analysis results in a periodicity of
\simeq 12 days, which confirms the oscillation of the observed data around the
best-fitting model. The estimated periodicity is probably associated with an
intrinsic variability of the source star, and therefore there is an opportunity
to use this technique to investigate either the intrinsic variability of the
source or the effects induced by the binary-lens orbital motion.Comment: In press on MNRAS, 2014. 8 pages, 4 figures. On-line material
available on the Journal web-pag
Temporal pattern of Klebsiella pneumoniae carbapenemase (KPC) on surface of an intensive care unit of a large hospital
Background: Carbapenem-resistant Enterobacteriaceae are an increasing cause of healthcare-associated infections worldwide. Patients with infections caused by Klebsiella pneumoniae resistant to carbapenems (KPC) have significant increases in both allcause mortality and 30-day mortality. The aims of this study was to investigate the prevalence of KPC on environmental samples collected during and after an outbreak caused by KPC in an intensive care unit (ICU) of a teaching hospital. Methods: Between 2010 and 2014 we conducted a total of 132 environmental monitoring campaigns from different critical surface of ICU ward in a Teaching Hospital Policlinico Umberto I. Samples were collected on surfaces in patient rooms and health care area. All samples were cultured and K. pneumoniae isolates were identified by standard microbiological techniques. The presumptive colonies were confirmed and tested for antibiotic resistance by an automated system. K. pneumoniae resitant to carbapenems were tested for carbapenemase production by modified Hodge test. Results: A total of 2526 environmental samples were collected from November 2010 to July 2014. Of those, 111 resulted positive for K. pneumoniae while KPC were 95 (85.6% of all K. pneumoniae, 3.8% of total samples). KPC was recovered in all patient rooms with similar proportion (5.1-5.6%) with the exception of patient 6 bed room where it was lower (2.4%). The pathogen was not recovered in rooms dedicated to healthcare personnel and doctors. Among surfaces, the highest proportion of KPC resulted on bedrail (6.8%), more than double than other surfaces. Washbasins had nearly half of samples KPC positive (1.2%). Conclusions: Despite previous studies suggested that environment plays a minor role in the transmission of carbapenem-resistant enterobacteriaceae, our data highlighted that surfaces represents a significant reservoir for KPC possibly supporting transiently contamination of hands of healthcare workers in our ICU. Our results confirm that KPC are more likely found on surfaces closer to the patient than on those situated further away
A catalogue sample of low mass galaxies observed in X-rays with central candidate black holes
We present a sample of -ray selected candidate black holes in 51 low mass
galaxies with {and mass up to M} obtained by
cross-correlating the NASA-SLOAN Atlas with the 3XMM catalogue. {We have also
searched in the available catalogues for radio counterparts of the black hole
candidates and find that 19 of the previously selected sources have also a
radio counterpart.} Our results show that about of the galaxies of our
sample host { an -ray source} (associated to a radio counterpart) spatially
coincident with the galaxy center, in agreement with { other recent works}. For
these {\it nuclear} sources, the -ray/radio fundamental plane relation
allows one to estimate the mass of the (central) candidate black holes which
results to be in the range M (with median
value of M and eight candidates having mass
below M). This result, while suggesting that -ray
emitting black holes in low-mass galaxies may have had a key role in the
evolution of such systems, makes even more urgent to explain how such massive
objects formed in galaxies. {Of course, dedicated follow-up observations both
in the -ray and radio bands, as well as in the optical, are necessary in
order to confirm our resultsComment: 15 Pages, 2 Figures, 3 Table
Astrometric microlensing
Astrometric microlensing will offer in the next future a new channel for
investigating the nature of both lenses and sources involved in a gravitational
microlensing event. The effect, corresponding to the shift of the position of
the multiple image centroid with respect to the source star location, is
expected to occurr on scales from micro-arcoseconds to milli-arcoseconds
depending on the characteristics of the lens-source system. Here, we consider
different classes of events (single/binary lens acting on a single/binary
source) also accounting for additional effects including the finite source
size, the blending and orbital motion. This is particularly important in the
era of Gaia observations which is making possible astrometric measurements with
unprecedent quality.Comment: On IJMP D, 15 pages, 6 Figure
Recommended from our members
Cardiac Memory-induced T-wave Inversions
Introduction: Cardiac memory refers to T-wave inversions that result when normal ventricular activation resumes following a period of abnormal ventricular activation.Case Report: We present a case of a 29-year-old man with a pacemaker who presented with new, deep symmetric T-wave inversions caused by cardiac memory.Discussion: Abnormal ventricular activation is most commonly induced by ventricular pacing but can also occur in the setting of transient left bundle branch blocks, ventricular tachycardia, and intermittent ventricular pre-excitation.Conclusion: Recognition of this phenomenon may help to reduce unnecessary admissions, cardiac testing, and cardiac catheterizations
A Professional Development Model to Promote Internet Integration in P-12 Teaching Practices
This mixed-methods study examined effects of a staff development model on instructional practices and dispositions of P-12 teachers. The model design was guided by participants’ varying developmental levels and their values and beliefs about teaching and learning. The study adds to our understanding of the need for teacher-centered professional development
Starspot induced effects in microlensing events with rotating source star
We consider the effects induced by the presence of hot and cold spots on the
source star in the light curves of simulated microlensing events due to either
single or binary lenses taking into account the rotation of the source star and
the orbital motion of the lens system. Our goal is to study the anomalies
induced by these effects on simulated microlensing light curves.Comment: 5 pages, 2 figures, accepted for publication in MNRA
The Effects of Group Member Experience and Task Complexity on Computer Mediated Collaborative Groups Facing Deception
Individuals often work together in environments where computers mediate their communication. One key area affected by computer mediated communication in group settings is the transmission of cues to deception. If cues to deception are filtered, such as they are with computer-mediated communication, deception detection accuracy can be hindered due to the lack of cues available, and group task performance can be lowered. Past deception research was not very applicable to many business settings since the tasks studied did not mimic the interactive, computer-mediated group settings where business decisions are often made. Past research also did not look at the influences of individuals’ familiarity with each other and their task complexity, which are key parts of group decision-making processes. We plan to conduct two experiments that simulate organizational collaborative group settings by having groups of subjects perform a computer-mediated collaborative task. Our experimental task will be a computerized strategy game where groups of subjects will methodically search a game board for a fixed number of targets, which they will attempt to destroy on their final turn. We will manipulate subjects’ task complexity and group members’ familiarity with each other in the experiments. We will then look at how their task performance and deception detection accuracy are influenced by these factors when they are facing a deceptive group member
Thermodynamics of the classical spin-ice model with nearest neighbour interactions using the Wang-Landau algorithm
In this article we study the classical nearest-neighbour spin-ice model
(nnSI) by means of Monte Carlo simulations, using the Wang-Landau algorithm.
The nnSI describes several of the salient features of the spin-ice materials.
Despite its simplicity it exhibits a remarkably rich behaviour. The model has
been studied using a variety of techniques, thus it serves as an ideal
benchmark to test the capabilities of the Wang Landau algorithm in magnetically
frustrated systems. We study in detail the residual entropy of the nnSI and, by
introducing an applied magnetic field in two different crystallographic
directions ([111] and [100],) we explore the physics of the kagome-ice phase,
the transition to full polarisation, and the three dimensional Kasteleyn
transition. In the latter case, we discuss how additional constraints can be
added to the Hamiltonian, by taking into account a selective choice of states
in the partition function and, then, show how this choice leads to the
realization of the ideal Kasteleyn transition in the system.Comment: 9 pages, 9 figure
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