Discovery of an Exceptionally Strong ß-Decay Transition of

A significant fraction of stars between 7 and 11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on ^{20}Ne in the degenerate oxygen-neon stellar core. However, because of the unknown strength of the transition between the ground states of ^{20}Ne and ^{20}F, it has not previously been possible to fully constrain the rate. By measuring the transition, we establish that its strength is exceptionally large and that it enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupted by a thermonuclear explosion rather than collapsing to form a neutron star. Importantly, our measurement resolves the last remaining nuclear physics uncertainty in the final evolution of degenerate oxygen-neon stellar cores, allowing future studies to address the critical role of convection, which at present is poorly understood.

A community health worker program for the prevention of malaria in eastern Kenya.

OBJECTIVE: To assess whether the development and implementation of a community health worker (CHW) project in rural Kenya was associated with an increase in knowledge about malaria and the use of insecticide-treated nets (ITNs) in children under five years of age. METHODS: A baseline knowledge and behavior questionnaire, adopted from the Kenyan Demographic Health Survey, was conducted in August 2007 by Kenyan health officials in 75 villages. Two CHWs were chosen from each village and trained in appropriate use of ITNs. The CHWs provided educational sessions and ITNs to mothers in their respective villages. A follow-up survey was conducted in March 2008 of all families with children less than five years of age within randomly selected villages. The main questions addressed during the follow-up survey included knowledge about malaria and the practice of correctly using ITNs. FINDINGS: There were 267 surveys compiled for knowledge assessment before the intervention and 340 in the post-intervention analysis with an approximate 99% family participation rate. Of the families surveyed, 81% correctly knew the cause for malaria before the study and 93% after the CHW intervention (p < 0.01). Of those surveyed before the intervention, 70% owned and correctly used mosquito nets compared with 88% after the CHW intervention (p < 0.01). CONCLUSIONS: There was a significant increase in knowledge about malaria and use of ITNs after the implementation of the CHW program.

Distribution equilibrium of mercury (II) chloride between water and air applied to flue gas scrubbing.

In the literature, different values of the distribution coefficient KH for HgCl2 between water and air are present in a range that spans more than 3 orders of magnitude. In order to determine if a waste incineration scrubber solution could become saturated with regard to HgCl2, an accurate experimental determination of the distribution constant of HgCl2 at elevated temperatures is needed. In this work, the coefficient has been determined at four different temperatures between 10 and 50 degrees C. The Arrhenius expression obtained is 5.5 x 10(5) x exp[-(8060 +/- 2200)/T] with a corresponding enthalpy for the process HgCl2(aq)<==>HgCl2(g) of 67 +/- 20 kJ/mole. KH at 293 K was found to be approximately 5 x 10(-7) atm M-1, which is in almost perfect agreement with an earlier study. Applying the obtained KH values to waste incineration scrubber conditions shows that no major saturation effect will occur.

Modified on-line monitoring of total gaseous mercury in flue gases using Semtech Hg 2000 analyzer.

The Semtech Hg 2000 analyzer continuously monitors the Hg0 content in flue gas. An on-line measurement method of total gaseous mercury in flue gas developed in our laboratory is described, which uses the absorption cell of the Semtech Hg Analyzer connected to a converter that is located in a furnace heated up to 650 degrees C. The converter can be heated up to 800 degrees C by both the furnace and an extra heating of a Ni-Cr alloy heating wire. Both the absorption cell and the converter are made of quartz. All gaseous Hg2+ species in flue gas are thermally reduced to Hg0 by the converter and detected by the Semtech Hg 2000 analyzer. The thermal reduction efficiencies of different conversion materials, which were filled in the converter, such as quartz chips, granular MgO, Ni and CoO powder, were tested using different flue gas conditions. Studies have shown that HCI is the major factor to inhibit the thermal reduction of Hg2+ to Hg0, and in the converter and the absorption cell Hg0 will react readily with HCl to form HgCl2. Both MgO and Ni could be used in the converter to absorb HCl in the flue gas, but Ni has better absorption efficiency. By using an original Semtech and a modified one, both Hg0 and total gaseous Hg contents in flue gas could be monitored simultaneously and continuously.

Early initiation of peritoneal dialysis after surgical repair of congenital heart disease.

The mortality rate of infants who require renal replacement therapy after surgical repair of congenital heart disease has been reported to be 30%-79%. We report our experience with early initiation of continuous manual peritoneal dialysis (CPD) to treat fluid overload in 20 consecutive critically ill children who underwent CPD post cardiotomy. CPD catheters were inserted at the discretion of the cardiothoracic surgeon. CPD was started for evidence of total body fluid overload with inadequate urine output, and stopped when negative fluid balance was achieved and urine output improved. Median age was 10 days (range 3-186 days), mean time to start CPD post-operatively was 22 h (range 5-40 h), and mean duration of CPD was 50 h (range 13-92 h). CPD resulted in mean ultrafiltration of 93 ml/kg per day (range 43-233 ml/kg per day). Net negative fluid balance was 106 ml/kg per day (range 49-273 ml/kg per day). During CPD, the mean number of inotropes decreased from 2.2 to 1.6 (P<0.05) and urine output increased from 2.2 to 3.9 ml/kg per hour (P<0.01). No patient died during CPD or had CPD discontinued due to adverse hemodynamic effects. The overall mortality rate was 20%. We conclude that early initiation of CPD can safely and effectively promote fluid removal in infants after repair of congenital heart disease, with a lower mortality rate than has previously been reported.

Does ductal occlusion with the gianturco coil cause left pulmonary artery and/or descending aorta obstruction?

Thirty-two patients (median age 4.5 years) underwent transcatheter Gianturco coil occlusion of a patent ductus arteriosus. Transthoracic echocardiography was performed the day after coil placement and at intermediate follow-up (median 8.6 months). Echocardiographic results were compared with angiographic and hemodynamic data obtained during catheterization. Two-dimensional (2D) echocardiography performed the day after ductal occlusion displayed evidence of coil protrusion into the left pulmonary artery in 28 of 31 patients (90%) and into the descending aorta in 17 of 29 (59%). However, pulsed Doppler analysis demonstrated normal left pulmonary arterial flow velocities in 28 of 29 patients (97%) and normal descending aortic flow velocities in 26 of 27 (96%). Pulse Doppler results were corroborated by angiographic and hemodynamic catheterization data, which showed no evidence of adjacent vessel obstruction. Peak Doppler velocities among patients with and without 2D echocardiographic left pulmonary artery or descending aorta coil impingement did not differ significantly. The discrepancy between 2D and pulse Doppler findings did not change significantly at intermediate follow-up. Thus, transcatheter occlusion of the patent ductus arteriosus with properly implanted Gianturco coils does not cause significant obstruction to flow in the left pulmonary artery or descending aorta despite frequently misleading 2D echocardiographic images of coil impingement on these vessels.

Tracheal aspirate as a substrate for polymerase chain reaction detection of viral genome in childhood pneumonia and myocarditis.

BACKGROUND: Infectious respiratory disorders are important causes of childhood morbidity and mortality. Viral causes are common and may lead to rapid deterioration, requiring mechanical ventilation; myocardial dysfunction may accompany respiratory decompensation. The etiologic viral diagnosis may be difficult with classic methods. The purpose of this study was to evaluate polymerase chain reaction (PCR) as a diagnostic method for identification of causative agents. METHODS AND RESULTS: PCR was used to amplify sequences of viruses known to cause childhood viral pneumonia and myocarditis. Oligonucleotide primers were designed to amplify specific sequences of DNA virus (adenovirus, cytomegalovirus, herpes simplex virus, and Epstein-Barr virus) and RNA virus (enterovirus, respiratory syncytial virus, influenza A, and influenza B) genomes. Tracheal aspirate samples were obtained from 32 intubated patients and nucleic acid extracted before PCR. PCR results were compared with results of culture, serology, and antigen detection methods when available. In cases of myocarditis (n=7), endomyocardial biopsy samples were analyzed by PCR and compared with tracheal aspirate studies. PCR amplification of viral genome occurred in 18 of 32 samples (56%), with 3 samples PCR positive for 2 viral genomes. Amplified viral sequences included RSV (n=3), enterovirus (n=5), cytomegalovirus (n=4), adenovirus (n=3), herpes simplex virus (n=2), Epstein-Barr virus (n=1), influenza A (n=2), and influenza B (n=1). All 7 cases of myocarditis amplified the same viral genome from heart as found by tracheal aspirate. CONCLUSIONS: PCR is a rapid and sensitive diagnostic tool in cases of viral pneumonia with or without myocarditis, and tracheal aspirate appears to be excellent for analysis.

Peritoneal dialysis. An adjunct to pediatric postcardiotomy fluid management.

Patients requiring cardiopulmonary bypass for congenital heart surgery commonly exhibit impaired renal function and extravascular fluid retention. These conditions contribute to early postoperative fluid overload, which may result in significant morbidity and mortality. We examined the safety and efficacy of peritoneal dialysis in removing extravascular fluid from critically ill postcardiotomy patients. A retrospective case review from July of 1995 through April of 1996 was conducted. All patients undergoing peritoneal dialysis achieved a net negative fluid balance. Average urine output increased from 2.1 cc/kg/hr to 3.9 cc/kg/hr (P < 0.01) during the pre-peritoneal dialysis to post-peritoneal dialysis period, and the mean number of inotropic agents decreased from 2.2 to 1.7 (P < 0.05). Controlled comparison revealed that the peritoneal dialysis cohort more rapidly achieved a negative weight-adjusted fluid balance throughout the early postoperative course. The peritoneal dialysis group's illness severity decreased more rapidly within the 24-hour period after initiation of peritoneal dialysis than did that of the control cohort over the same period of time. No difference in postoperative morbidity or mortality existed between the study groups. Complications from the catheter placement were minimal, and no patient experienced peritonitis or metabolic or hemodynamic instability during peritoneal dialysis catheter placement, usage, or removal. Peritoneal dialysis is a safe and effective form of renal replacement therapy, even among critically ill pediatric postcardiotomy patients. Early postsurgical institution of peritoneal dialysis may hasten early postoperative recovery. We speculate that intraoperative catheter placement reduces the complication rate associated with this treatment modality.

Exploration of polygonal environments using range data.

Several robotic problems involve the systematic traversal of the environment, commonly referred to as exploration. We present a strategy for the exploration of unknown finite polygonal environments, using a point robot with 1) no positional uncertainty and 2) an ideal range sensor that measures range in N uniformly distributed directions. The range data vector, obtained from the range sensor, corresponds to a sampled version of a visibility polygon. Visibility polygon edges that do not correspond to environmental edges are called jump edges and the exploration strategy is based on the fact that jump edges indicate directions of possibly unexplored environmental regions. We describe conditions under which it is possible to identify jump edges in the range data. We also show how the exploration strategy can be used in a solution to the terrain acquisition problem and describe conditions under which a solution is guaranteed within a finite number of measurements.

Interstitial fluid oncotic pressures in rabbit subcutaneous tissue.

Interstitial fluid oncotic pressures in rabbit subcutaneous tissues were measured by chronically implanted membrane osmometers. Pairs of osmometers were used, one using a membrane permeable and one impermeable to plasma proteins. Measurements from the small-pore membranes averaged 10.2 mmHg while pressures measured from the large-pore membrane osmometers averaged -1.2 mmHg, indicating that the measured pressures were osmotic rather than hydrostatic in nature. These values are in agreement with previously published values from this laboratory on oncotic pressures of excised rabbit skin and with a computer-simulation study of capillary fluid balance. The oncotic pressures described in this study are of the s-me general magnitude as those of lymph from most organs in the body.