326 research outputs found

    RJK Observations of the Optical Afterglow of GRB 991216

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    We present near-infrared and optical observations of the afterglow to the Gamma-Ray Burst (GRB) 991216 obtained with the F. L. Whipple Observatory 1.2-m telescope and the University of Hawaii 2.2-m telescope. The observations range from 15 hours to 3.8 days after the burst. The temporal behavior of the data is well described by a single power-law decay with index -1.36 +/-0.04, independent of wavelength. The optical spectral energy distribution, corrected for significant Galactic reddening of E(B-V)=0.626, is well fitted by a single power-law with index -0.58 +/- 0.08. Combining the IR/optical observations with a Chandra X-ray measurement gives a spectral index of -0.8 +/- 0.1 in the synchrotron cooling regime. A comparison between the spectral and temporal power-law indices suggest that a jet is a better match to the observations than a simple spherical shock.Comment: Accepted to the Astrophysical Journal, 12 pages, 4 postscript figure

    Rapid UBVRI Follow-up of the Highly Collimated Optical Afterglow of GRB010222

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    (Abridged) We present the earliest optical observations of the optical counterpart to the GRB 010222, obtained with the FLWO 1.2-m telescope in UBVRI passbands, starting 3.64 hours after the burst. We also present late R-band observations of the afterglow obtained with the 1.8-m VATT ~25 days after the burst. The temporal analysis of our data joined with published data indicates a steepening decay, independent of wavelength, asymptotically approaching t^{-0.80+/-0.05} at early times (t << 1 day) and t^{-1.30+/-0.05} at late times, with a sharp break at t_b=0.72+/-0.1 days. This is the second earliest observed break of any afterglow (after GRB 980519), which clearly indicates the importance of rapid multi-band follow-up for GRB afterglow research. The optical spectral energy distribution, corrected for small Galactic reddening, can be fit fairly well by a single power-law with a slope of -1.07+/-0.09. However, when we fit using our BVRI data only, we obtain a shallower slope of -0.88+/- 0.1, in excellent agreement with the slope derived from our low-resolution spectrum (-0.89 +/- 0.03). The spectral slope and light curve decay slopes we derive are not consistent with a jet model despite the presence of a temporal break. Significant host dust extinction with a star-burst reddening law would flatten the spectral index to match jet predictions and still be consistent with the observed spectral energy distribution. We derive an opening angle of 2.1 deg, smaller than any listed in the recent compilation of Frail et al. The total beamed energy corrected for the jet geometry is 4x10^50 erg, very close to the ``standard'' value of 5x10^50 erg found by Frail et al. for a number of other bursts with light-curve breaks.Comment: revised version (minor changes only) to be published in the ApJ Part 1, 12 pages, 4 figures; all data used for the fits and our CCD frames available at ftp://cfa-ftp.harvard.edu/pub/kstanek/GRB010222/ and through WWW at http://cfa-www.harvard.edu/cfa/oir/Research/GRB

    SN 2008in—Bridging the Gap between Normal and Faint Supernovae of Type IIP

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    We present optical photometric and low-resolution spectroscopic observations of the Type II plateau supernova (SN) 2008in, which occurred in the outskirts of the nearly face-on spiral galaxy M61. Photometric data in the X-ray, ultraviolet, and near-infrared bands have been used to characterize this event. The SN field was imaged with the ROTSE-IIIb optical telescope about seven days before the explosion. This allowed us to constrain the epoch of the shock breakout to JD = 2454825.6. The duration of the plateau phase, as derived from the photometric monitoring, was ~98 days. The spectra of SN 2008in show a striking resemblance to those of the archetypal low-luminosity IIP SNe 1997D and 1999br. A comparison of ejecta kinematics of SN 2008in with the hydrodynamical simulations of Type IIP SNe by Dessart et al. indicates that it is a less energetic event (~5 × 10^(50) erg). However, the light curve indicates that the production of radioactive ^(56)Ni is significantly higher than that in the low-luminosity SNe. Adopting an interstellar absorption along the SN direction of AV ~ 0.3 mag and a distance of 13.2 Mpc, we estimated a synthesized ^(56)Ni mass of ~0.015 M_☉. Employing semi-analytical formulae derived by Litvinova and Nadezhin, we derived a pre-SN radius of ~126 R_☉, an explosion energy of ~5.4 × 10^(50) erg, and a total ejected mass of ~16.7 M_☉. The latter indicates that the zero-age main-sequence mass of the progenitor did not exceed 20 M_☉. Considering the above properties of SN 2008in and its occurrence in a region of sub-solar metallicity ([O/H] ~ 8.44 dex), it is unlikely that fall-back of the ejecta onto a newly formed black hole occurred in SN 2008in. We therefore favor a low-energy explosion scenario of a relatively compact, moderate-mass progenitor star that generates a neutron star

    Prevalence and Impact of Concomitant Atrial Fibrillation in Patients Undergoing Percutaneous Coronary Intervention for Acute Myocardial Infarction

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    Background: Concomitant atrial fibrillation (AF) is associated with an adverse prognosis in patients with acute myocardial infarction (MI). However, it remains unclear whether this is due to a causal effect of AF or whether AF acts as a surrogate marker for comorbidities in this population. Furthermore, there are limited data on whether coronary artery disease distribution impacts the risk of developing AF. Methods: Consecutive patients admitted with acute MI and treated using percutaneous coronary intervention (PCI) at a single centre were retrospectively identified. Associations between AF and major adverse cardiac and cerebrovascular events (MACCEs) over a median of five years of follow-up were assessed using Cox regression, with adjustment for confounding factors performed using both multivariable modelling and a propensity-score-matched analysis. Results: AF was identified in N = 65/1000 (6.5%) of cases; these patients were significantly older (mean: 73 vs. 65 years, p &lt; 0.001), with lower creatinine clearance (p &lt; 0.001), and were more likely to have a history of cerebrovascular disease (p = 0.011) than those without AF. In addition, patients with AF had a greater propensity for left main stem (p = 0.001) or left circumflex artery (p = 0.004) involvement. Long-term MACCE rates were significantly higher in the AF group than in the non-AF group (50.8% vs. 34.2% at five years), yielding an unadjusted hazard ratio (HR) of 1.86 (95% CI: 1.32–2.64, p &lt; 0.001). However, after adjustment for confounding factors, AF was no longer independently associated with MACCEs, either on multivariable (adjusted HR: 1.25, 95% CI: 0.81–1.92, p = 0.319) or propensity-score-matched (HR: 1.04, 95% CI: 0.59–1.82, p = 0.886) analyses. Conclusions: AF is observed in 6.5% of patients admitted with acute MI, and those with AF are more likely to have significant diseases involving left main or circumflex arteries. Although unadjusted MACCE rates were significantly higher in patients with AF, this effect was not found to remain significant after adjustment for comorbidities. As such, this study provided no evidence to suggest that AF is independently associated with MACCEs

    Recruiting in surgical trial in the emergency setting: understanding clinician and patient perspectives: a mixed methods study

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    Background. Undertaking randomised controlled trials (RCT) in emergency surgical setting is associated with methodological and practical challenges. This study explored patients and clinicians’ perspectives associated with the conduct of a RCT comparing laparoscopic and open colorectal surgery in the acute setting.Method. All eligible patients screened/enrolled for the ‘Laparoscopic versus Open Colorectal Surgery in the Acute Setting multicentre, randomised controlled feasibility (LaCeS) trial’ in five NHS Trusts were invited to respond to a survey. Also, patients and healthcare professionals were invited to take part in semi-structured interviews. Survey and interviews explored acceptability of the feasibility trial. Interviews were audio-recorded, transcribed verbatim and analysed using thematic analysis. Survey data were analysed descriptively to assess patient views of the trial and intervention. Results. Out of 72 patients enrolled for the LaCeS RCT, survey data was collected from 28 patients (38.9%), and interviews were conducted with 16 patients and 14 healthcare professionals. Thirteen out of 28 patients (46%) had treatment preferences but these were not strong enough to deter participation. Twelve of the patients interviewed believed their surgeon preferred laparoscopic surgery, but this did not deter them from participating in the trial. Half of the surgeons interviewed expressed the view that laparoscopic surgery was of benefit in this setting, but recognised that the need for research evidence outweighed their personal treatment preferences. Eight of the 14 recruiters reported that the emergency setting affected recruitment, especially in centres with fewer recruiting surgeons. Interviewees reported that recruitment was helped significantly by using surgical trainees to consent patients. Conclusion. This study identified specific challenges for the LaCeS2 trial design to address, and adds to our understanding of recruiting to emergency surgical trials more broadly

    Translational treatment paradigm for managing non‐unions secondary to radiation injury utilizing adipose derived stem cells and angiogenic therapy

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    BackgroundBony non‐unions arising in the aftermath of collateral radiation injury are commonly managed with vascularized free tissue transfers. Unfortunately, these procedures are invasive and fraught with attendant morbidities. This study investigated a novel, alternative treatment paradigm utilizing adipose‐derived stem cells (ASCs) combined with angiogenic deferoxamine (DFO) in the rat mandible.MethodsRats were exposed to a bioequivalent dose of radiation and mandibular osteotomy. Those exhibiting non‐unions were subsequently treated with surgical debridement alone or debridement plus combination therapy. Radiographic and biomechanical outcomes were assessed after healing.ResultsSignificant increases in biomechanical strength and radiographic metrics were observed in response to combination therapy (p < .05). Importantly, combined therapy enabled a 65% reduction in persisting non‐unions when compared to debridement alone.ConclusionWe support the continued investigation of this promising combination therapy in its potential translation for the management of radiation‐induced bony pathology. © 2015 Wiley Periodicals, Inc. Head Neck 38: E837–E843, 2016Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137613/1/hed24110.pd

    Poor transferability of species distribution models for a pelagic predator, the grey petrel, Indicates contrasting habitat preferences across ocean basins

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    Species distribution models (SDMs) are increasingly applied in conservation management to predict suitable habitat for poorly known populations. High predictive performance of SDMs is evident in validations performed within the model calibration area (interpolation), but few studies have assessed SDM transferability to novel areas (extrapolation), particularly across large spatial scales or pelagic ecosystems. We performed rigorous SDM validation tests on distribution data from three populations of a long-ranging marine predator, the grey petrel Procellaria cinerea , to assess model transferability across the Southern Hemisphere (25-65°S). Oceanographic data were combined with tracks of grey petrels from two remote sub-Antarctic islands (Antipodes and Kerguelen) using boosted regression trees to generate three SDMs: one for each island population, and a combined model. The predictive performance of these models was assessed using withheld tracking data from within the model calibration areas (interpolation), and from a third population, Marion Island (extrapolation). Predictive performance was assessed using k-fold cross validation and point biserial correlation. The two population-specific SDMs included the same predictor variables and suggested birds responded to the same broad-scale oceanographic influences. However, all model validation tests, including of the combined model, determined strong interpolation but weak extrapolation capabilities. These results indicate that habitat use reflects both its availability and bird preferences, such that the realized distribution patterns differ for each population. The spatial predictions by the three SDMs were compared with tracking data and fishing effort to demonstrate the conservation pitfalls of extrapolating SDMs outside calibration regions. This exercise revealed that SDM predictions would have led to an underestimate of overlap with fishing effort and potentially misinformed bycatch mitigation efforts. Although SDMs can elucidate potential distribution patterns relative to large-scale climatic and oceanographic conditions, knowledge of local habitat availability and preferences is necessary to understand and successfully predict region-specific realized distribution patterns

    Theoretical Studies of Spectroscopy and Dynamics of Hydrated Electrons.

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    International consensus definition of low anterior resection syndrome

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    BACKGROUND: Low anterior resection syndrome is pragmatically defined as disordered bowel function after rectal resection leading to a detriment in quality of life. This broad characterization does not allow for precise estimates of prevalence. The low anterior resection syndrome score was designed as a simple tool for clinical evaluation of low anterior resection syndrome. Although the low anterior resection syndrome score has good clinical utility, it may not capture all important aspects that patients may experience. OBJECTIVE: The aim of this collaboration was to develop an international consensus definition of low anterior resection syndrome that encompasses all aspects of the condition and is informed by all stakeholders. DESIGN: This international patient-provider initiative used an online Delphi survey, regional patient consultation meetings, and an international consensus meeting. PARTICIPANTS: Three expert groups participated: patients, surgeons, and other health professionals from 5 regions (Australasia, Denmark, Spain, Great Britain and Ireland, and North America) and in 3 languages (English, Spanish, and Danish). MAIN OUTCOME MEASURE: The primary outcome measured was the priorities for the definition of low anterior resection syndrome. RESULTS: Three hundred twenty-five participants (156 patients) registered. The response rates for successive rounds of the Delphi survey were 86%, 96%, and 99%. Eighteen priorities emerged from the Delphi survey. Patient consultation and consensus meetings refined these priorities to 8 symptoms and 8 consequences that capture essential aspects of the syndrome. LIMITATIONS: Sampling bias may have been present, in particular, in the patient panel because social media was used extensively in recruitment. There was also dominance of the surgical panel at the final consensus meeting despite attempts to mitigate this. CONCLUSIONS: This is the first definition of low anterior resection syndrome developed with direct input from a large international patient panel. The involvement of patients in all phases has ensured that the definition presented encompasses the vital aspects of the patient experience of low anterior resection syndrome. The novel separation of symptoms and consequences may enable greater sensitivity to detect changes in low anterior resection syndrome over time and with intervention
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