Patients with venous tromboembolism have higher prevalence of obstructive sleep apnea [abstract]

Background: Obstructive sleep apnea (OSA) has been linked to many cardiovascular diseases. Recent studies have linked OSA, endothelial dysfunction, and elevated CRP. The link between OSA and venous thromboembolic events (VTE) has not been well elucidated. Methods: We retrospectively collected data based on ICD-9 codes at the UMHC from August 1999 - April 2009. Patients were identified as VTE with ICD-9 codes 415.11, 415.12, 415.19, 453.4, 453.9, 453.41, 453.42, 671.33, 671.44 and as OSA with codes 327.2, 327.23, 780.5, 780.51, 780.53, 780.57, 786.03. Continuous data were expressed as means or medians and compared using the student t or the Mann-Whitney tests. Categorical variables were expressed as percentages and compared using the Chi-square or Fisher exact tests. Eighty-two random charts were reviewed for validation. Results: 1412 patients were identified with the diagnosis of VTE; 57.2% were females and the mean age was 54.2 ±17.4 years. Of 1412 patients, 301 were also diagnosed with OSA yielding a prevalence of 21.3%. There was no difference between the two groups (with or without OSA) in age or gender. The random sample analysis revealed that the prevalence of sleep apnea was 23%. Conclusion: In patients with VTE, the prevalence of OSA appears to be much higher than the general population. We found that prevalence was as high as 23%

X-ray Spectroscopy of QSOs with Broad Ultraviolet Absorption Lines

For the population of QSOs with broad ultraviolet absorption lines, we are just beginning to accumulate X-ray observations with enough counts for spectral analysis at CCD resolution. From a sample of eight QSOs [including four Broad Absorption Line (BAL) QSOs and three mini-BAL QSOs] with ASCA or Chandra spectra with more than 200 counts, general patterns are emerging. Their power-law X-ray continua are typical of normal QSOs with Gamma~2.0, and the signatures of a significant column density [N_H~(0.1-4)x10^{23} cm^{-2}] of intrinsic, absorbing gas are clear. Correcting the X-ray spectra for intrinsic absorption recovers a normal ultraviolet-to-X-ray flux ratio, indicating that the spectral energy distributions of this population are not inherently anomalous. In addition, a large fraction of our sample shows significant evidence for complexity in the absorption. The subset of BAL QSOs with broad MgII absorption apparently suffers from Compton-thick absorption completely obscuring the direct continuum in the 2-10 keV X-ray band, complicating any measurement of their intrinsic X-ray spectral shapes.Comment: 9 pages, 6 figures, uses AASTeX. Accepted to the Astrophysical Journa

Parametric Investigation of Combustion and Heat Transfer Characteristics of Oscillating Linear Engine Alternator

An Oscillating Linear Engine Alternator (OLEA) has the potential to overcome the thermal, mechanical, and combustion inadequacies encountered by the conventional slider-crank engines. The linear engines convert the reciprocating piston motion into electricity, thereby eliminating needless crankshaft linkages and rotational motion. As the dead center positions are not explicitly identified unlike crankshaft engines, the linear engine exhibits different stroke and compression ratio every cycle and should manage the unfavorable events like misfire, rapid load changes, and overfueling without the energy storage of a flywheel. Further, the apparatus control and management strategy is difficult for OLEA when compared to conventional engines and depends on the combustion event influencing the translator dynamics. In this research paper, the MATLAB/Simulink numerical model of a single cylinder, mechanical spring assisted, 2-stroke natural gas fueled, spark-ignited OLEA was investigated to enhance the perception of the coupled system. The effect of combustion and heat transfer characteristics on translator dynamics and performance of OLEA were analyzed by using Wiebe form factors, combustion duration, and heat transfer correlations. Variation in the Wiebe form factors revealed interesting insights into the translator dynamics and in-cylinder thermodynamics of a coupled system. High translator velocity, acceleration, and higher heat transfer rate were favored by low combustion duration

HLA-F*01:01 presents peptides with N-terminal flexibility and a preferred length of 16 residues.

HLA-F belongs to the non-classical HLA-Ib molecules with a marginal polymorphic nature and tissue-restricted distribution. HLA-F is a ligand of the NK cell receptor KIR3DS1, whose activation initiates an antiviral downstream immune response and lead to delayed disease progression of HIV-1. During the time course of HIV infection, the expression of HLA-F is upregulated while its interaction with KIR3DS1 is diminished. Understanding HLA-F peptide selection and presentation is essential to a comprehensive understanding of this dynamic immune response and the molecules function. In this study, we were able to recover stable pHLA-F*01:01 complexes and analyze the characteristics of peptides naturally presented by HLA-F. These HLA-F-restricted peptides exhibit a non-canonical length without a defined N-terminal anchor. The peptide characteristics lead to a unique presentation profile and influence the stability of the protein. Furthermore, we demonstrate that almost all source proteins of HLA-F-restricted peptides are described to interact with HIV proteins. Understanding the balance switch between HLA-Ia and HLA-F expression and peptide selection will support to understand the role of HLA-F in viral pathogenesis

The Giant X-Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown Dwarf, or a Planet?

We model the 1990 giant X-ray flare of the quiescent galaxy NGC 5905 as the tidal disruption of a star by a supermassive black hole. From the observed rapid decline of the luminosity, over a timescale of a few years, we argue that the flare was powered by the fallback of debris rather than subsequent accretion via a thin disk. The fallback model allows constraints to be set on the black hole mass and the mass of debris. The latter must be very much less than a solar mass to explain the very low luminosity of the flare. The observations can be explained either as the partial stripping of the outer layers of a low-mass main sequence star or as the disruption of a brown dwarf or a giant planet. We find that the X-ray emission in the flare must have originated within a small patch rather than over the entire torus of circularized material surrounding the black hole. We suggest that the patch corresponds to the ``bright spot'' where the stream of returning debris impacts the torus. Interestingly, although the peak luminosity of the flare was highly sub-Eddington, the peak flux from the bright spot was close to the Eddington limit. We speculate on the implications of this result for observations of other flare events.Comment: 25 pages, including 5 figure

Chandra Detects a Rapid Flare in the Gravitationally Lensed Mini-BALQSO RX J0911.4+0551

The mini Broad Absorption Line (BAL) quasar RX J0911.4+0551 was observed with the Advanced CCD Imaging Spectrometer (ACIS) of the Chandra X-ray Observatory for ~ 29 ks as part of a gravitational lens (GL) survey aimed at measuring time-delays. Timing analysis of the light-curve of the lensed image A2 shows a rapid flux variation with a duration of about 2000s. A Kolmogorov-Smirnov test shows that the probability that a constant-intensity source would produce the observed variability is less than ~ 0.2 percent. We discuss possible origins for the observed short-term X-ray variability. Our gravitational lens models for the RX J0911.4+0551 GL system predict a time-delay of less than a day between images A1 and A2. The rapid variability combined with the predicted short-time delay make RX J0911.4+0551 an ideal system to apply the GL method for estimating the Hubble constant. We describe the prospects of measuring H_0 within single X-ray observations of GL systems with relatively short time delays. Modeling of the spectrum of the mini-BAL quasar RX J0911.4+0551 suggests the presence of an intrinsic absorber. Partial covering models are slightly preferred over models that contain absorption due to intrinsic ionized or neutral gas.Comment: 17 pages, includes 5 figures, Accepted for publication in Ap

X-ray Observations of Gravitationally Lensed Quasars; Evidence for a Hidden Quasar Population

The large magnification factors of gravitationally lensed (GL) systems allow us to investigate the properties of quasars with X-ray luminosities that are substantially lower than those of unlensed ones and also provide an independent means of estimating the contribution of faint quasars to the hard X-ray component of the cosmic X-ray background. Our spectral analysis indicate a flattening of the spectral index in the hard band (4-20keV restframe) for 2 radio-loud quasars in the GL quasar sample for which the data have moderate signal-to-noise ratio. We have identified a large fraction of Broad Absorption Line (BAL) quasars amongst the GL quasar population. We find that approximately 35% of radio-quiet GL quasars contain BAL features which is significantly larger than the 10% fraction of BAL quasars presently found in optically selected flux limited quasar samples. We present a simple model that estimates the effects of attenuation and lens magnification on the luminosity function of quasars and that explains the observed fraction of GL BAL quasars. These observations suggest that a large fraction of BAL quasars are missed from flux limited optical surveys. Modeling of several X-ray observations of the GL BAL quasar PG1115+080 suggests that the observed large X-ray variability may be caused in part by a variable intrinsic absorber consistent with previously observed variability of the BAL troughs in the UV band. The observed large X-ray flux variations in PG1115+080 offer the prospect of considerably reducing errors in determining the time delay with future X-ray monitoring of this system and hence constraining the Hubble constant H$_{0}$.Comment: 19 pages, 10 figures, 9 Tables, accepted for publication in Ap

The Quasar Pair Q 1634+267 A, B and the Binary QSO vs. Dark Lens Hypotheses

Deep HST/NICMOS H (F160W) band observations of the z=1.96 quasar pair Q 1634+267A,B reveal no signs of a lens galaxy to a 1 sigma threshold of approximately 22.5 mag. The minimum luminosity for a normal lens galaxy would be a 6L_* galaxy at z > 0.5, which is 650 times greater than our detection threshold. Our observation constrains the infrared mass-to-light ratio of any putative, early-type, lens galaxy to (M/L)_H > 690h_65 (1200h_65) for Omega_0=0.1 (1.0) and H_0=65h_65 km/s/Mpc. We would expect to detect a galaxy somewhere in the field because of the very strong Mg II absorption lines at z=1.1262 in the Q 1634+267 A spectrum, but the HST H-band, I-band (F785LP) and V-band (F555W) images require that any associated galaxy be very under-luminous less than 0.1 L^*_H (1.0 L^*_I) if it lies within less than 40 h^{-1} (100 h^{-1}) kpc from Q 1634+267 A,B. While the large image separation (3.86 arcsec) and the lack of a lens galaxy strongly favor interpreting Q 1634+267A,B as a binary quasar system, the spectral similarity remains a puzzle. We estimate that at most 0.06% of randomly selected quasar pairs would have spectra as similar to each other as the spectra of Q 1634+267 A and B. Moreover, spectral similarities observed for the 14 quasar pairs are significantly greater than would be expected for an equivalent sample of randomly selected field quasars. Depending on how strictly we define similarity, we estimate that only 0.01--3% of randomly drawn samples of 14 quasar pairs would have as many similar pairs as the observational sample.Comment: 24 pages, including 4 figures, LaTex, ApJ accepted, comments from the editor included, minor editorial change