Detection of a Cool, Accretion-Shock-Generated X-Ray Plasma in EX Lupi During the 2008 Optical Eruption

EX Lupi is the prototype for a class of young, pre-main-sequence stars which are observed to undergo irregular, presumably accretion-generated, optical outbursts that result in a several magnitude rise of the optical flux. EX Lupi was observed to optically erupt in 2008 January, triggering Chandra ACIS Target of Opportunity observations shortly thereafter. We find very strong evidence that most of the X-ray emission in the first few months after the optical outburst is generated by accretion of circumstellar material onto the stellar photosphere. Specifically, we find a strong correlation between the decreasing optical and X-ray fluxes following the peak of the outburst in the optical, which suggests that these observed declines in both the optical and X-ray fluxes are the result of declining accretion rate. In addition, in our models of the X-ray spectrum, we find strong evidence for an approx 0.4 keV plasma component, as expected for accretion shocks on low-mass, pre-main-sequence stars. From 2008 March through October, this cool plasma component appeared to fade as EX Lupi returned to its quiescent level in the optical, consistent with a decrease in the overall emission measure of accretion-shock-generated plasma. The overall small increase of the X-ray flux during the optical outburst of EX Lupi is similar to what was observed in previous X-ray observations of the 2005 optical outburst of the EX Lupi-type star V1118 Ori but contrasts with the large increase of the X-ray flux from the erupting young star V1647 Ori during its 2003 and 2008 optical outbursts

The effect of various resuscitative regimens on hemorrhagic shock in puppies

Since shock secondary to hemorrhage is not infrequently encountered in the pediatric patient, a puppy model was devised to help measure and monitor cardiovascular and metabolic changes that occur before and after resuscitation from hypovolemic shock (mean arterial pressure of 50 mm Hg for 1 hr). Three resuscitation protocols were compared: whole blood (replacement: shed) 1:1, 5% albumin in Ringer's lactate 1:1, and Ringer's lactate 3:1. All dogs survived the experiment and responded similarly during the shock period. Thermal dilution cardiac output rose in all groups after resuscitation; however, in the Ringer's lactate and 5% albumin groups, cardiac output was statistically greater than that observed in the blood group. In all groups, pH and blood pressure approached but did not return completely to baseline levels after resuscitation. In addition, early resuscitation demonstrated a further decrease in pH ("hidden acidosis") before it began to return toward normal as resuscitation progressed. This study suggests that the infusion of large volumes of Ringer's lactate or 5% albumin in Ringer's lactate are equally efficacious in the treatment of hemorrhage. However, 5% albumin seems to be preferable because it allows infusion of a smaller quantity of electrolyte solution with equivalent physiologic benefits.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/22801/1/0000358.pd

Assessment of thermodilution cardiac output in small subjects

Thermodilution cardiac output determinations were compared with dye-dilution measurements in normovolemic and hypovolemic puppies. Good correlation was achieved with small volumes of cold and warm saline. Injectate volumes and significant caval displacement of the injectate port did not significantly affect thermodilution output measurements. This study demonstrates that thermodilution is a reliable and practical method of cardiac output determination in small subjects and suggests that this technique may be useful in the clinical mangement of neonates and small infants.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21674/1/0000062.pd

X-raying the Beating Heart of a Newborn Star: Rotational Modulation of High-energy Radiation from V1647 Ori

We report a periodicity of ~1 day in the highly elevated X-ray emission from the protostar V1647 Ori during its two recent multiple-year outbursts of mass accretion. This periodicity is indicative of protostellar rotation at near-breakup speed. Modeling of the phased X-ray light curve indicates the high-temperature (~50 MK), X-ray-emitting plasma, which is most likely heated by accretion-induced magnetic reconnection, resides in dense (>~5e10 cm-3), pancake-shaped magnetic footprints where the accretion stream feeds the newborn star. The sustained X-ray periodicity of V1647 Ori demonstrates that such protostellar magnetospheric accretion configurations can be stable over timescales of years.Comment: 26 pages, 10 figure

Clinical Prediction Model Suitable for Assessing Hospital Quality for Patients Undergoing Carotid Endarterectomy

Background: Assessing hospital quality in the performance of carotid endarterectomy (CEA) requires appropriate risk adjustment across hospitals with varying case mixes. The aim of this study was to develop and validate a prediction model to assess the risk of in‐hospital stroke or death after CEA that could aid in the assessment of hospital quality. Methods and Results: Patients from National Cardiovascular Data Registry (NCDR)'s Carotid Artery Revascularization and Endarterectomy (CARE) Registry undergoing CEA without acute evolving stroke from 2005 to 2013 were included. In‐hospital stroke or death was modeled using hierarchical logistic regression with 20 candidate variables and accounting for hospital‐level clustering. Internal validation was achieved with bootstrapping; model discrimination and calibration were assessed. A total of 213 (1.7%) primary end point events occurred during 12 889 procedures. Independent predictors of stroke or death included age, prior peripheral artery disease, diabetes mellitus, prior coronary artery disease, having a symptomatic carotid lesion, having a contralateral carotid occlusion, or having New York Heart Association Class III or IV heart failure. The model was well calibrated and demonstrated moderate discriminative ability (c‐statistic 0.65). The NCDR CEA score was then developed to support simple, prospective risk quantification in the clinical setting. Conclusions: The NCDR CEA score, comprising 7 clinical variables, predicts in‐hospital stroke or death after CEA. This model can be used to estimate hospital risk‐adjusted outcomes for CEA and to assist with the assessment of hospital quality

Embedding clinical interventions into observational studies

Novel approaches to observational studies and clinical trials could improve the cost-effectiveness and speed of translation of research. Hybrid designs that combine elements of clinical trials with observational registries or cohort studies should be considered as part of a long-term strategy to transform clinical trials and epidemiology, adapting to the opportunities of big data and the challenges of constrained budgets. Important considerations include study aims, timing, breadth and depth of the existing infrastructure that can be leveraged, participant burden, likely participation rate and available sample size in the cohort, required sample size for the trial, and investigator expertise. Community engagement and stakeholder (including study participants) support are essential for these efforts to succeed

The effect of pyloromyotomy on serum and luminal gastrin in infants with hypertrophic pyloric stenosis

Previous studies of the pathogenesis of congenital hypertrophic pyloric stenosis (CHPS) have implicated immunoreactive gastrin, although no consistent relationship has been demonstrated. In this study we have examined the effect which pyloromyotomy has on serum and luminal gastrin concentration after a mechanical and protein stimulus. Seventeen infants were examined preoperatively, and 1 week after pyloromyotomy. On each occasion, samples of serum and gastric contents were collected from fasting infants. Sixty cubic centimeters of water was placed into the stomach and further samples collected 20 min later. The water was then aspirated and replaced by 60 cc of 10% peptone broth and a third set of samples collected after 20 min. All samples from each patient were analyzed for immunoreactive gastrin in the same assay. Pyloromyotomy did not alter fasting serum gastrin (119.3 pg +/- 11.9 preop vs 164.7 +/- 29.9 postop) nor did it alter the gastrin response to water. Pyloromyotomy decreased the incremental serum gastrin response to peptone broth (66.6 +/- 16.9 preop vs 18.9 +/- 11.7 postop). Luminal gastrin concentration was not significantly affected by pyloromyotomy. When the pre- and postoperative serum gastrin increments for water and peptone were plotted against the fasting gastrin levels, an inverse relationship was apparent which was statistically significant by regression analysis. Seen in this way, intragastric water and peptone have a dual effect on serum gastrin; a rise if the fasting serum gastrin concentration is low; a fall or lesser rise if the fasting serum gastrin concentration is high. The data suggest that the direction and magnitude of serum gastrin response to intragastric water or peptone is set by the fasting level, and is independent of pyloromyotomy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23236/1/0000169.pd