Flame Evolution During Type Ia Supernovae and the Deflagration Phase in the Gravitationally Confined Detonation Scenario

We develop an improved method for tracking the nuclear flame during the deflagration phase of a Type Ia supernova, and apply it to study the variation in outcomes expected from the gravitationally confined detonation (GCD) paradigm. A simplified 3-stage burning model and a non-static ash state are integrated with an artificially thickened advection-diffusion-reaction (ADR) flame front in order to provide an accurate but highly efficient representation of the energy release and electron capture in and after the unresolvable flame. We demonstrate that both our ADR and energy release methods do not generate significant acoustic noise, as has been a problem with previous ADR-based schemes. We proceed to model aspects of the deflagration, particularly the role of buoyancy of the hot ash, and find that our methods are reasonably well-behaved with respect to numerical resolution. We show that if a detonation occurs in material swept up by the material ejected by the first rising bubble but gravitationally confined to the white dwarf (WD) surface (the GCD paradigm), the density structure of the WD at detonation is systematically correlated with the distance of the deflagration ignition point from the center of the star. Coupled to a suitably stochastic ignition process, this correlation may provide a plausible explanation for the variety of nickel masses seen in Type Ia Supernovae.Comment: 14 pages, 10 figures, accepted to the Astrophysical Journa

Calibrating the Mixing Length Parameter for a Red Giant Envelope

Two-dimensional hydrodynamical simulations were made to calibrate the mixing length parameter for modeling red giant's convective envelope. As was briefly reported in Asida & Tuchman (97), a comparison of simulations starting with models integrated with different values of the mixing length parameter, has been made. In this paper more results are presented, including tests of the spatial resolution and Large Eddy Simulation terms used by the numerical code. The consistent value of the mixing length parameter was found to be 1.4, for a red giant of mass 1.2 solar-mass, core mass of 0.96 solar-mass, luminosity of 200 solar-luminosities, and metallicity Z=0.001.Comment: 18 pages, 1 table, 13 figures. Accepted for publication in Ap.

Finite-temperature reaction-rate formula: Finite volume system, detailed balance, T→0T \to 0 limit, and cutting rules

A complete derivation, from first principles, of the reaction-rate formula for a generic process taking place in a heat bath of finite volume is given. It is shown that the formula involves no finite-volume correction. Through perturbative diagrammatic analysis of the resultant formula, the detailed-balance formula is derived. The zero-temperature limit of the formula is discussed. Thermal cutting rules, which are introduced in previous work, are compared with those introduced by other authors.Comment: 35pages (text) plus 4pages (figures

Ease of insertion of the laryngeal mask airway in pediatric surgical patients: Predictors of failure and outcome

Background: Laryngeal mask airway (LMA) is an useful alternative to endotracheal tube for airway management. The risk of life-threatening adverse respiratory events during its use is rare, but we need to know about the risk-adjusted prediction of its insertion failure requiring rescue tracheal intubation and its impact on patient outcome. Materials and Methods: Five hundred patients; 6 months to 12-year-old, American Society of Anesthesiologists I and II scheduled to undergo elective surgical procedures that require general anesthesia were included in this study. LMA was inserted after induction of anesthesia. The insertion conditions, intra, and postoperative events were recorded. Our primary outcome variable was trial success from the first time. Results: We recorded 426 cases (85.2%) of first trial success with clear airway compared to 46 case (9.2%) of second trial success (P ≤ 0.001). Predictors of failure of first attempt of LMA insertion include abnormal airway anatomy (91%), body weight <16 kg and age below 5 years (44%), the use of LMA size of 1 and 1.5 (3.8%), the intraoperative lateral position (3.8%). Conclusion: The data obtained from this study support the use of the LMA as a reliable pediatric supraglottic airway device, demonstrating relatively low failure rates. Predictors of LMA failure in the pediatric surgical population should be independently considered. Trial Registration: The study is registered in the Australian and New Zealand clinical trial registry with the allocated trial number: ACTRN12614000994684. Web address of trial: http://www.ANZCTR.org.au/A CTRN12614000994684.aspx

Impact of PCO2 gap protocol application on early postoperative mortality and organ failure in high risk surgical patients undergoing major abdominal surgeries

Background: high risk surgical patients undergoing major abdominal surgeries still have higher rate of mortality and organ failure rates in the early postoperative period. Objective: We aimed to assess PCO2 gap&nbsp; protocol application in the intraoperative and early post-operative (first 12 hours) on&nbsp; postoperative mortality and organ failure in high risk surgical patients undergoing major abdominal surgeries compared to a classical goal directed therapy protocol (GDT) targeting mean arterial blood pressure (MAP), mixed venous oxygen saturation (SvO2), central venous pressure (CVP), Haematocrite value (Hct) and urine output (UOP). Patients and Methods: Guided by Shoemacker et al score 80 high risk surgical patients undergoing major abdominal surgeries were divided into two groups group A PCO2 gap algorithm was applied intraoperative and 12 h postoperative end point PCO2 gap 2-6mm Hg ,group B goal directed therapy protocol targeting MAP &gt; 65mmHg, CVP between 8-12cmH2O , Haematocrite value more than 30, Svo2 &gt;75% and urine output more than &gt;0.5 ml/kg/hr an applied intraoperative and 12 postoperative end point . Postoperative organs dysfuctions were assessed using the Sequential Organ Failure Assessment (SOFA) score recorded daily ICU discharge then every three days till discharge home.&nbsp