377 research outputs found
Violating the Shannon capacity of metric graphs with entanglement
The Shannon capacity of a graph G is the maximum asymptotic rate at which
messages can be sent with zero probability of error through a noisy channel
with confusability graph G. This extensively studied graph parameter disregards
the fact that on atomic scales, Nature behaves in line with quantum mechanics.
Entanglement, arguably the most counterintuitive feature of the theory, turns
out to be a useful resource for communication across noisy channels. Recently,
Leung, Mancinska, Matthews, Ozols and Roy [Comm. Math. Phys. 311, 2012]
presented two examples of graphs whose Shannon capacity is strictly less than
the capacity attainable if the sender and receiver have entangled quantum
systems. Here we give new, possibly infinite, families of graphs for which the
entangled capacity exceeds the Shannon capacity.Comment: 15 pages, 2 figure
Absolute continuity of the spectrum in a twisted Dirichlet-Neumann waveguide
International audienceQuantum waveguide with the shape of planar infinite straight strip and combined Dirichlet and Neumann boundary conditions on the opposite half-lines of the boundary is considered. The absence of the point as well as of the singular continuous spectrum is proved
Scattering through a straight quantum waveguide with combined boundary conditions
Scattering through a straight two-dimensional quantum waveguide Rx(0,d) with
Dirichlet boundary conditions on (-\infty,0)x{y=0} \cup (0,\infty)x{y=d} and
Neumann boundary condition on (-infty,0)x{y=d} \cup (0,\infty)x{y=0} is
considered using stationary scattering theory. The existence of a matching
conditions solution at x=0 is proved. The use of stationary scattering theory
is justified showing its relation to the wave packets motion. As an
illustration, the matching conditions are also solved numerically and the
transition probabilities are shown.Comment: 26 pages, 3 figure
Spectral flow and level spacing of edge states for quantum Hall hamiltonians
We consider a non relativistic particle on the surface of a semi-infinite
cylinder of circumference submitted to a perpendicular magnetic field of
strength and to the potential of impurities of maximal amplitude . This
model is of importance in the context of the integer quantum Hall effect. In
the regime of strong magnetic field or weak disorder it is known that
there are chiral edge states, which are localised within a few magnetic lengths
close to, and extended along the boundary of the cylinder, and whose energy
levels lie in the gaps of the bulk system. These energy levels have a spectral
flow, uniform in , as a function of a magnetic flux which threads the
cylinder along its axis. Through a detailed study of this spectral flow we
prove that the spacing between two consecutive levels of edge states is bounded
below by with , independent of , and of the
configuration of impurities. This implies that the level repulsion of the
chiral edge states is much stronger than that of extended states in the usual
Anderson model and their statistics cannot obey one of the Gaussian ensembles.
Our analysis uses the notion of relative index between two projections and
indicates that the level repulsion is connected to topological aspects of
quantum Hall systems.Comment: 22 pages, no figure
Endotoxemia related to cardiopulmonary bypass is associated with increased risk of infection after cardiac surgery: a prospective observational study
Abstract
Introduction
Previous studies have documented a high frequency of endotoxemia associated with cardiopulmonary bypass (CPB). Endotoxemia may be responsible for some of the complications associated with cardiac surgery. The purpose of the study was to examine the prevalence of endotoxemia during cardiopulmonary bypass supported aortocoronary bypass grafting surgery (ACB) using a new assay, the Endotoxin Activity Assay (EAA), and explore the association between endotoxemia and post-operative infection.
Methods
The study was a single center prospective observational study measuring EAA during the perioperative period for elective ACB. Blood samples were drawn at induction of anesthesia (T1), immediately prior to release of the aortic cross-clamp (T2), and on the first post-operative morning (T3). The primary outcome was the prevalence of endotoxemia. Secondary outcomes assessed included infection rates, intensive care unit (ICU) and hospital length of stay. An EAA of < 0.40 units was interpreted as "low", 0.41 to 0.59 units as "intermediate", and â„0.60 units as "high".
Results
A total of 57 patients were enrolled and 54 patients were analyzable. The mean EAA at T1 was 0.38 +/- 0.14, at T2 0.39 +/- 0.18, and at T3 0.33 +/- 0.18. At T2 only 13.5% (7/52) of patients had an EAA in the high range. There was a positive correlation between EAA and duration of surgery (P = 0.02). In patients with EAA â„0.40 at T2, 26.1% (6/23) of patients developed post-operative infections compared to 3.5% (1/29) of those that had a normal EAA (P = 0.0354). Maximum EAA over the first 24 hours was also strongly correlated with risk of post-operative infection (P = 0.0276).
Conclusions
High levels of endotoxin occur less frequently during ACB than previously documented. However, endotoxemia is associated with a significantly increased risk of the development of post-operative infection. Measuring endotoxin levels during ACB may provide a mechanism to identify and target a high risk patient population
'Nature or nurture': survival rate oviposition interval, and possible gonotrophic discordance among South East Asian anophelines
Background: Mosquito survival, oviposition interval and gonotrophic concordance are important determinants of vectorial capacity. These may vary between species or within a single species depending on the environment. They may be estimated by examination of the ovaries of host-seeking mosquitoes.
Methods: Landing collections, Furvela tent-trap and CDC light-trap collections were undertaken sequentially in four locations in Cambodia between February 2012 and December 2013 and samples from the collected mosquitoes were dissected to determine parity, sac stage (indicative of time spent prior to returning to feed) and egg stage.
Results: A total of 27,876 Anopheles from 15 species or species groups were collected in the four locations and 2883 specimens were dissected. Both the density and predominant species collected varied according to location and trapping method. Five species were dissected in sufficient numbers to allow comparisons between locations. Estimated oviposition interval differed markedly between species but less within species among different locations. Anopheles aconitus had the shortest cycle, which was 3.17 days (95 % CI 3â3.64), and Anopheles barbirostris had the longest cycle, which took four days (95 % CI 3.29â4). Anopheles minimus had a higher sac rate in weeks leading up to a full moon but there was apparently little effect of moon phase on Anopheles dirus. Despite the fact that many of the species occurred at very low densities, there was no evidence of gonotrophic dissociation in any of them, even during sustained hot, dry periods. The principal Cambodian malaria vector, An. dirus, was only common in one location where it was collected in miniature light-traps inside houses. It did not appear to have an exceptional survival rate (as judged by the low average parous rate) or oviposition cycle.
Conclusions: Differences in the oviposition interval were more pronounced among species within locations than within species among ecologically diverse locations. A nationwide survey using CDC light-traps for the collection of An. dirus inside houses may help in determining patterns of malaria transmission in Cambodia
Exponential splitting of bound states in a waveguide with a pair of distant windows
We consider Laplacian in a straight planar strip with Dirichlet boundary
which has two Neumann ``windows'' of the same length the centers of which are
apart, and study the asymptotic behaviour of the discrete spectrum as
. It is shown that there are pairs of eigenvalues around each
isolated eigenvalue of a single-window strip and their distances vanish
exponentially in the limit . We derive an asymptotic expansion also
in the case where a single window gives rise to a threshold resonance which the
presence of the other window turns into a single isolated eigenvalue
Impact of infection status and cyclosporine on voriconazole pharmacokinetics in an experimental model of cerebral scedosporiosis
Cerebral Scedosporium infections usually occur in lung transplant recipients as well as in immunocompetent patients in the context of near-drowning. Voriconazole is the first-line treatment. The diffusion of voriconazole through the blood-brain barriers in the context of cerebral infection and cyclosporine administration is crucial and remains a matter of debate. To address this issue, the pharmacokinetics of voriconazole were assessed in the plasma, cerebrospinal fluid (CSF), and brain, in an experimental model of cerebral scedosporiosis in rats receiving or not cyclosporine. A single dose of voriconazole (30 mg/kg, i.v.) was administrated to six groups of rats randomized according to the infection status and the cyclosporine dosing regimen (no cyclosporine, a single dose or three doses 15 mg/kg each). Voriconazole concentrations in plasma, CSF, and brain samples were quantified using UPLC-MS/MS and HPLC-UV methods and documented up to 48 hours after administration. Pharmacokinetic parameters were estimated using a non-compartmental approach. Voriconazole pharmacokinetic profiles were similar for plasma, CSF, and the brain in all groups studied. Voriconazole Cmax and AUC0=>48h were significantly higher in the plasma than in the CSF (CSF/plasma ratio, median [range] = 0.5 [0.39-0.55] for AUC0=>48h and 0.47 [0.35 and 0.75] for Cmax). Cyclosporine administration was significantly associated with an increase in voriconazole exposure in the plasma, CSF, and brain. In the plasma but not in the brain, an interaction between the infection and cyclosporine administration reduced the positive impact of cyclosporine on voriconazole exposure. Together these results emphasize the impact of cyclosporine on the brain voriconazole exposure
On the regularity of the Hausdorff distance between spectra of perturbed magnetic Hamiltonians
We study the regularity properties of the Hausdorff distance between spectra
of continuous Harper-like operators. As a special case we obtain H\"{o}lder
continuity of this Hausdorff distance with respect to the intensity of the
magnetic field for a large class of magnetic elliptic (pseudo)differential
operators with long range magnetic fields.Comment: to appear in the Proceedings of the 'Spectral Days' conference,
Santiago de Chile 201
Implementing an Advanced Laparoscopic Procedure by Monitoring with a Visiting Surgeon
Study Objective: To investigate the feasibility of safely implementing a total laparoscopic hysterectomy (LH) in established gynecologists' practices with on-site coaching and monitoring of the learning curve by an experienced visiting surgeon. Design: Multicenter prospective feasibility and implementation study (Canadian Task Force classification II-2). Setting: Eleven general gynecologists in 8 hospitals (1 university hospital and 7 regional hospitals) participated. Patients: Laparoscopic hysterectomy was performed in 83 patients during the learning curve, and in 83 patients after the learning curve. Interventions: During the learning curve, an experienced visiting laparoscopist was available for coaching during each LH. A competence score was marked on an Objective Structured Assessment of Technical Skills (OSATS) form. Complications were recorded intraoperatively and postoperatively for 6 weeks after surgery in all patients. Measurements and Main Results: Nine of 11 gynecologists reached the competence score of at least 28 points during the study, from January 2005 to January 2007. A major complication occurred in 3 of 83 LH procedures (4%) performed during the learning curve, and in 5 of 83 LH procedures (6%) performed after the learning curve (p = .72). Conclusion: The concept of a visiting surgeon for on-site coaching and monitoring of established gynecologists during the learning curve of an advanced laparoscopic procedure using Objectively Structured Assessment of Technical Skills is feasible. According to the observed complication rate during and after the learning curve, on-site coaching is a useful tool when implementing a new laparoscopic technique in established gynecologists' practices. Journal of Minimally Invasive Gynecology (2010) 17, 771-778 (C) 2010 AAGL. All rights reserved
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