2,455 research outputs found
X-Ray Spectral Variability of PKS 2005-489 During the Spectacular November 1998 Flare
We report on monitoring of the BL Lac object PKS 2005-489 by the Rossi X-ray
Timing Explorer (RXTE) in October-December 1998. During these months, the
source underwent a spectacular flare; at its peak on November 10, its 2-10 keV
flux was , over 30 times
brighter than in quiescence. During the rising phase, the X-ray spectrum of PKS
2005-489 hardened considerably, reaching near maximum. During the declining phase, the X-ray spectrum
steepened rapidly, reaching , then became somewhat harder
towards the end of December (). While such behavior has been
seen before, the simplicity, magnitude and duration of this flare allowed us to
study it in great detail. We argue that this flare was caused by either the
injection of particles into the jet or {\it in situ} particle acceleration, and
that the spectral steepening which followed the flare maximum was the result of
synchrotron cooling. Contrary to other recently observed blazar flares (e.g.,
Mkn 501, 3C 279, PKS 2155-304), our results do not imply a major shift in the
location of the synchrotron peak during this flare.Comment: ApJ Letters in press, 6 pages, 2 figures Corrected reference
Sport Participation in Latin America
Abstract This study has three purposes. First, it compares the organization of sport in two rather different Latin American countries. Belize has primarily an English heritage, plays soccer as its major sport, and has been shown to be fairly representative of Caribbean plantation societies (Cross, 197
BL Lac X-ray Spectra: simpler than we thought
We report results from {\it XMM-Newton} observations of thirteen X-ray bright
BL Lacertae objects, selected from the {\it Einstein} Slew Survey sample. The
spectra are generally well fit by power-law models, with four objects having
hard () spectra that indicates
synchrotron peaks at keV. None of our spectra show line features,
indicating that soft X-ray absorption ``notches'' must be rare amongst BL Lacs,
rather than common or ubiquitous as had previously been asserted. We find
significant curvature in most of the spectra. This curvature is almost
certainly intrinsic, as it appears nearly constant from 0.5 to 6 keV, an
observation which is inconsistent with the small columns seen in these sources.Comment: 4 pages, 1 figure; to be published in proceedings of the Cozumel
meeting on "Multiwavelength Surveys for AGN", Cozumel 200
A perpetual switching system in pulmonary capillaries
Of the 300 billion capillaries in the human lung, a small fraction meet normal oxygen requirements at rest, with the remainder forming a large reserve. The maximum oxygen demands of the acute stress response require that the reserve capillaries are rapidly recruited. To remain primed for emergencies, the normal cardiac output must be parceled throughout the capillary bed to maintain low opening pressures. The flow-distributing system requires complex switching. Because the pulmonary microcirculation contains contractile machinery, one hypothesis posits an active switching system. The opposing hypothesis is based on passive switching that requires no regulation. Both hypotheses were tested ex vivo in canine lung lobes. The lobes were perfused first with autologous blood, and capillary switching patterns were recorded by videomicroscopy. Next, the vasculature of the lobes was saline flushed, fixed by glutaraldehyde perfusion, flushed again, and then reperfused with the original, unfixed blood. Flow patterns through the same capillaries were recorded again. The 16-min-long videos were divided into 4-s increments. Each capillary segment was recorded as being perfused if at least one red blood cell crossed the entire segment. Otherwise it was recorded as unperfused. These binary measurements were made manually for each segment during every 4 s throughout the 16-min recordings of the fresh and fixed capillaries (>60,000 measurements). Unexpectedly, the switching patterns did not change after fixation. We conclude that the pulmonary capillaries can remain primed for emergencies without requiring regulation: no detectors, no feedback loops, and no effectors-a rare system in biology. NEW & NOTEWORTHY The fluctuating flow patterns of red blood cells within the pulmonary capillary networks have been assumed to be actively controlled within the pulmonary microcirculation. Here we show that the capillary flow switching patterns in the same network are the same whether the lungs are fresh or fixed. This unexpected observation can be successfully explained by a new model of pulmonary capillary flow based on chaos theory and fractal mathematics
Addition Spectra of Quantum Dots in Strong Magnetic Fields
We consider the magnetic field dependence of the chemical potential for
parabolically confined quantum dots in a strong magnetic field. Approximate
expressions based on the notion that the size of a dot is determined by a
competition between confinement and interaction energies are shown to be
consistent with exact diagonalization studies for small quantum dots. Fine
structure is present in the magnetic field dependence which cannot be explained
without a full many-body description and is associated with ground-state level
crossings as a function of confinement strength or Zeeman interaction strength.
Some of this fine structure is associated with precursors of the bulk
incompressible states responsible for the fractional quantum Hall effect.Comment: 11 pages, 3 figures (available from [email protected]). Revtex
3.0. (IUCM93-010
Efficacy against nematode and cestode infections and safety of a novel topical fipronil, (S)-methoprene, eprinomectin and praziquantel combination product in domestic cats under field conditions in Europe
AbstractA novel topical combination product (BROADLINE®, Merial) composed of fipronil, (S)-methoprene, eprinomectin and praziquantel was evaluated for safety and efficacy against nematode and cestode infections in domestic cats. The study comprised a multi-centre, positive control, blinded, field study, using a randomized block design based on order of presentation for allocation. In total 196 client-owned cats, confirmed as positive for naturally acquired infections of nematodes and/or cestodes by pre-treatment faecal examination, were studied in seven countries in Europe. Pre-treatment faecal examination revealed the presence of Toxocara, hookworm, Capillaria and/or spirurid nematode infections in 129, 73, 33 or 1 cat(s), respectively; infections with taeniid and Dipylidium cestodes were demonstrated in 39 and 17 cats, respectively. Cats were allocated randomly to one of two treatments in a ratio of 2, topical fipronil (8.3%, w/v), (S)-methoprene (10%, w/v), eprinomectin (0.4%, w/v) and praziquantel (8.3%, w/v) (BROADLINE®, Merial; 130 cats); and 1, topical PROFENDER® Spot-On (Bayer; 66 cats) and treated once on Day 0. For evaluation of efficacy, two faecal samples were collected, one prior to treatment (Day −4±4 days) and one at the end of the study (Day 14±5 days). These were examined for fecal forms of nematode and cestode parasites. For evaluation of safety, cats were examined by a veterinarian before treatment and at the end of the study, and cat owners recorded the health status of their cats daily until the end of the study.For cats treated with Broadline®, the efficacy was >99.9%, 100%, and 99.6% for Toxocara, hookworms, and Capillaria, respectively; and the efficacy was >99.9%, >99.9%, and 98.5%, respectively, for the cats treated with Profender® (p<0.001 for all nematodes and both treatments). Efficacy was 100% for both cestodes for both treatments (p<0.001).No treatment related adverse experiences were observed throughout the study. For both treatments, every cat that completed the study was given a safety score of ‘excellent’ for both local and systemic evaluations. The topical combination product of fipronil, (S)-methoprene, eprinomectin and praziquantel was shown to have an excellent safety profile and demonstrated high levels of efficacy when administered once as topical solution to cats infected with nematodes and cestodes under field conditions
790-2 Baseline Electrocardiogram Predicts 30-day Mortality Among 32,812 Patients with Acute Myocardial Infarction Treated with Thrombolysis
To determine the initial electrocardiographic variables predictive of survival among patients with acute myocardial infarction, we analyzed the baseline 12-lead ECGs in 32,812 patients enrolled into the GUSTO trial. All patients had≥0.1mV of ST segment elevation in at least one lead and received thrombolytic therapy. Those with LBBB or ventricular rhythm were excluded from analysis. Clinical follow-up was > 99.5% complete. 2218 (6.8%) patients died within 30 days of the initial ECG. Death within 30 days was more common in patients with RBBB (17%), LAFB (14%), and LPFB (17%), than in those with a normal conduction pattern (6%). Patients with ECG evidence of previous MI in a location distinct from the acute MI had a higher risk of death (9.8% vs. 5.9%) than those without prior infarction (p<0.0001). The variable having the greatest univariate predictive power for 30-day survival was the sum of the absolute ST-segment deviation in each lead (x2=341), as shown in the following mortality curve.Other ST segment variables that predicted 30-day survival were the sum of ST-segment elevation in each lead (x2=287). the maximum ST elevation in anyone lead (X2=257), and the number of leads with ST elevation (x2=250). When multivariate modeling was performed the sum of the absolute ST deviations, number of leads with ST elevation, prior ECG MI, RBBB, and LAFB each added independent prognostic information.We conclude that an ECG at the time of presentation contains substantial prognostic information which can be used to help stratify risk among thrombelytic-treated patients with acute myocardial infarction
Lrg1 Regulates β (1, 3)-Glucan Masking in Candida albicans through the Cek1 MAP Kinase Pathway
Candida albicans is among the most prevalent opportunistic human fungal pathogens. The ability to mask the immunogenic polysaccharide β (1,3)-glucan from immune detection via a layer of mannosylated proteins is a key virulence factor of C. albicans. We previously reported that hyperactivation of the Cek1 mitogen-activated protein (MAP) kinase pathway promotes β (1,3)-glucan exposure. In this communication, we report a novel upstream regulator of Cek1 activation and characterize the impact of Cek1 activity on fungal virulence. Lrg1 encodes a GTPase-activating protein (GAP) that has been suggested to inhibit the GTPase Rho1. We found that disruption of LRG1 causes Cek1 hyperactivation and β (1,3)-glucan unmasking. However, when GTPase activation was measured for a panel of GTPases, the lrg1ΔΔ mutant exhibited increased activation of Cdc42 and Ras1 but not Rho1 or Rac1. Unmasking and Cek1 activation in the lrg1ΔΔ mutant can be blocked by inhibition of the Ste11 MAP kinase kinase kinase (MAPKKK), indicating that the lrg1ΔΔ mutant acts through the canonical Cek1 MAP kinase cascade. In order to determine how Cek1 hyperactivation specifically impacts virulence, a doxycycline-repressible hyperactive STE11ΔN467 allele was expressed in C. albicans. In the absence of doxycycline, this allele overexpressed STE11ΔN467, which induced production of proinflammatory tumor necrosis factor alpha (TNF-α) from murine macrophages. This in vitrophenotype correlates with decreased colonization and virulence in a mouse model of systemic infection. The mechanism by which Ste11ΔN467 causes unmasking was explored with RNA sequencing (RNA-Seq) analysis. Overexpression of Ste11ΔN467 caused upregulation of the Cph1 transcription factor and of a group of cell wall-modifying proteins which are predicted to impact cell wall architecture
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Real-Time Analysis of Individual Airborne Microparticles Using Laser Ablation Mass Spectroscopy and Genetically Trained Neural Networks
We are developing a method for analysis of airborne microparticles based on laser ablation of individual molecules in an ion trap mass spectrometer. Airborne particles enter the spectrometer through a differentially-pumped inlet, are detected by light scattered from two CW laser beams, and sampled by a pulsed excimer laser as they pass through the center of the ion trap electrodes. After the laser pulse, the stored ions are separated by conventional ion trap methods. The mass spectra are then analyzed using genetically-trained neural networks (NNs). A number of mass spectra are averaged to obtain training cases which contain a recognizable spectral signature. Averaged spectra for a bacteria and a non-bacteria are shown to the NNs, the response evaluated, and the weights of the connections between neurodes adjusted by a Genetic Algorithm (GA) such that the output from the NN ranges from 0 for non-bacteria to 1 for bacteria. This process is iterated until the population of the GA converges or satisfies predetermined stopping criteria. Using this type of bipolar training we have obtained generalizing NNs able to distinguish five new bacteria from five new non-bacteria, none of which were used in training the NN
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Analysis and control of distributed cooperative systems.
As part of DARPA Information Processing Technology Office (IPTO) Software for Distributed Robotics (SDR) Program, Sandia National Laboratories has developed analysis and control software for coordinating tens to thousands of autonomous cooperative robotic agents (primarily unmanned ground vehicles) performing military operations such as reconnaissance, surveillance and target acquisition; countermine and explosive ordnance disposal; force protection and physical security; and logistics support. Due to the nature of these applications, the control techniques must be distributed, and they must not rely on high bandwidth communication between agents. At the same time, a single soldier must easily direct these large-scale systems. Finally, the control techniques must be provably convergent so as not to cause undo harm to civilians. In this project, provably convergent, moderate communication bandwidth, distributed control algorithms have been developed that can be regulated by a single soldier. We have simulated in great detail the control of low numbers of vehicles (up to 20) navigating throughout a building, and we have simulated in lesser detail the control of larger numbers of vehicles (up to 1000) trying to locate several targets in a large outdoor facility. Finally, we have experimentally validated the resulting control algorithms on smaller numbers of autonomous vehicles
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