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Polymer bounded explosives (PBXs) consist of energetic crystals coated with a polymer binder. These materials exhibit a highly heterogeneous microstructure. The initiation of the detonation phenomenon in PBXs is believed to be generated at the microstructure scale through hotspots. Hence, many of the explosives properties (initiation, desensitization, etc.) are understood as a direct consequence of their microstructure. Mesoscale modeling directly addresses the physics of hotspot formation. Unfortunately, high computational cost prevents their use on laboratory-sized and large scale experiments. In practice, continuum-scale models remain mandatory. We describe a new reactive burn model, named WGT, aiming to represent, at the continuum scale, some of the complexity of the PBX's microstructure. The initiation regime is driven by the shock temperature and results from surrogate modeling of the kinetics of a heterogeneous nucleation and growth model. The other regimes follow the formulation of the WHS2D2 reactive burn model and are driven by the local temperature. This model was calibrated on experimental results for PBX 9502 available in the literature, such as detonation velocity–curvature laws, Pop-plot data, or embedded electromagnetic particle velocity gauges. The model was also tested against desensitization and propagation data. [ABSTRACT FROM AUTHOR]

We propose to assess the performance of density functional theory calculations to predict the properties of CO2, H2O, and N2 fluids under high pressure (up to 40?GPa), which are representatives of not only detonation products but also giant planet interiors. Twenty-two generalized-gradient approximation functionals, presently in the ABINIT code, have been compared to molecular data and experimental equations of state of supercritical fluids. We found that the Perdew, Burke, and Ernzerhof (PBE) functional with Grimme's dispersion correction (D3) gives the best results. The residual error of PBE-D3 on pressure is estimated around 15%. [ABSTRACT FROM AUTHOR]

The KLRR perturbation theory has been initially proposed by Kang et al. in order to compute the equation of state (EOS) of a fluid of soft spheres represented by an EXP-6 potential. Victorov and Gubin have recently improved this method and they showed that, compared to other theories (namely HMSA/C and MCRSR), this improved KLRR theory turns out to be more accurate. In the first part of this paper, the comparison is extended to a larger range of temperature and stiffness of potential. Then, in order to use such a perturbation theory in a thermochemical code, the treatment of mixtures has to be handled since the KLRR method is expressed for a pure fluid. Usually, the Van-der-Waals one fluid mixing rule (VdW-1f) is employed. It consists in averaging the mixture by an effective fluid. We also intend here to re-evaluate this well-known and largely used model.

We present the calibration of the CARTE thermochemical code that allows to compute the properties of a wide variety of CHON explosives. We have developed an optimization procedure to obtain an accurate multicomponents EOS (fluid phase and condensed phase of carbon). We show here that the results of CARTE code are in good agreement with the specific data of molecular systems and we extensively compare our calculations with measured detonation properties for several explosives.

Background: Patient age may influence decisions to withhold life-sustaining treatments, independent of patients' preferences for or ability to benefit from such treatments. Controversy exists about the appropriateness of using age as a criterion for making treatment decisions.Objective: To determine the effect of age on decisions to withhold life-sustaining therapies.Design: Prospective cohort study.Setting: Five medical centers participating in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT).Patients: 9105 hospitalized adults who had one of nine illnesses associated with an average 6-month mortality rate of 50%.Measurements: Outcomes were the presence and timing of decisions to withhold ventilator support, surgery, and dialysis. Adjustment was made for sociodemographic characteristics, prognoses, baseline function, patients' preferences for life-extending care, and physicians' understanding of patients' preferences for life-extending care.Results: The median patient age was 63 years; 44% of patients were women, and 53% survived to 180 days. In adjusted analyses, older age was associated with higher rates of withholding each of the three life-sustaining treatments studied. For ventilator support, the rate of decisions to withhold therapy increased 15% with each decade of age (hazard ratio, 1.15 [95% CI, 1.12 to 1.19]); for surgery, the increase per decade was 19% (hazard ratio, 1.19 [CI, 1.12 to 1.27]); and for dialysis, the increase per decade was 12% (hazard ratio, 1.12 [CI, 1.06 to 1.19]). Physicians underestimated older patients' preferences for life-extending care; adjustment for this underestimation resulted in an attenuation of the association between age and decisions to withhold treatments.Conclusion: Even after adjustment for differences in patients' prognoses and preferences, older age was associated with higher rates of decisions to withhold ventilator support, surgery, and dialysis. [ABSTRACT FROM AUTHOR]

Objective: To examine the impact of illness on the families of seriously ill adults and to determine the correlates of adverse economic impact.Design: Data were collected during the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatment (SUPPORT), a prospective cohort study of outcomes, preferences, and decision making in seriously ill hospitalized adults and their families.Setting: Five tertiary care hospitals in the United States.Participants: The 2661 seriously ill patients in nine diagnostic categories who survived their index hospitalization and were discharged home were eligible for this analysis. Surrogate and/or patient interviews about the impact of illness on the family were obtained for 2129 (80%) of these patients (mean age, 62 years; 43% women; 6-month survival, 75%).Outcome Measures: Surrogates and patients were surveyed to determine the frequency of adverse caregiving and economic burdens. Multivariable analyses were performed to determine correlates of loss of family savings.Results: One third (34%) of patients required considerable caregiving assistance from a family member. In 20% of cases, a family member had to quit work or make another major life change to provide care for the patient. Loss of most or all of the family savings was reported by 31% of families, whereas 29% reported loss of the major source of income. Patient factors independently associated with loss of the family's savings on multivariable analysis included poor functional status (odds ratio [OR], 1.40; 95% confidence interval [CI], 1.10 to 1.78 for patients needing assistance with three or more activities of daily living), lower family income (OR, 1.74; 95% CI, 1.37 to 2.21 for those with annual incomes below $25,000), and young age (OR, 2.85; 95% CI, 2.13 to 3.82 for those younger than 45 years compared with those 65 years or older).Conclusions: Many families of seriously ill patients experience severe caregiving and financial burdens. Families of younger, poorer, and more functionally dependent patients are most likely to report loss of most or all of the family's savings. [ABSTRACT FROM AUTHOR]

Background: Renal failure requiring dialysis in the setting of hospitalization for serious illness is a poor prognostic sign, and dialysis and aggressive care are sometimes withheld.Objective: To evaluate the clinical outcomes and cost-effectiveness of initiating dialysis and continuing aggressive care for seriously ill hospitalized patients.Design: Prospective cohort study and cost-effectiveness analysis.Setting: Five geographically diverse teaching hospitals.Patients: 490 patients (median age, 61 years; 58% women) enrolled in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT) in whom dialysis was initiated.Measurements: Survival, functional status, quality of life, and health care costs. Life expectancy was estimated by extrapolating survival data (up to 4.4 years of follow-up) using a declining exponential function. Utilities (quality-of-life weights) were estimated by using time-tradeoff questions. Costs were based on data from SUPPORT and published Medicare data.Results: Median duration of survival was 32 days, and only 27% of patients were alive after 5 months. Survivors reported a median of one dependency in activities of daily living, and 62% rated their quality of life as "good" or better. Overall, the estimated cost per quality-adjusted life-year saved by initiating dialysis and continuing aggressive care rather than withholding dialysis and allowing death to occur was $128,200. For the 103 patients in the worst prognostic category, the estimated cost per quality-adjusted life-year was $274,100; for the 94 patients in the best prognostic category, the cost per quality-adjusted life-year was $61,900.Conclusions: For the few patients who survived, clinical outcomes were fairly good. With the exception of patients with the best prognoses, however, the cost-effectiveness of initiating dialysis and continuing aggressive care far exceeded $50,000 per quality-adjusted life-year, a commonly cited threshold for cost-effective care. [ABSTRACT FROM AUTHOR]

Background: Physicians are frequently unaware of patient preferences for end-of-life care. Identifying and exploring barriers to patient-physician communication about end-of-life issues may help guide physicians and their patients toward more effective discussions.Objective: To examine correlates and associated outcomes of patient communication and patient preferences for communication with physicians about cardiopulmonary resuscitation and prolonged mechanical ventilation.Design: Prospective cohort study.Setting: Five tertiary care hospitals.Patients: 1832 (85%) of 2162 eligible patients completed interviews.Measurements: Surveys of patient characteristics and preferences for end-of-life care; perceptions of prognosis, decision making, and quality of life; and patient preferences for communication with physicians about end-of-life decisions.Results: Fewer than one fourth (23%) of seriously ill patients had discussed preferences for cardiopulmonary resuscitation with their physicians. Of patients who had not discussed their preferences for resuscitation, 58% were not interested in doing so. Of patients who had not discussed and did not want to discuss their preferences, 25% did not want resuscitation. In multivariable analyses, patient factors independently associated with not wanting to discuss preferences for cardiopulmonary resuscitation included being of an ethnicity other than black (adjusted odds ratio [OR], 1.48 [95% CI, 1.10 to 1.99), not having an advance directive (OR, 1.35 [CI, 1.04 to 1.76]), estimating an excellent prognosis (OR, 1.72 [CI, 1.32 to 2.59]), reporting fair to excellent quality of life (OR, 1.36 [CI, 1.05 to 1.76]), and not desiring active involvement in medical decisions (OR, 1.33 [CI, 1.07 to 1.65]). Factors independently associated with wanting to discuss preferences for resuscitation but not doing so included being black (OR, 1.53 [CI, 1.11 to 2.11]) and being younger (OR, 1.14 per 10-year interval younger [CI, 1.04 to 1.25]).Conclusions: Among seriously ill hospitalized adults, communication about preferences for cardiopulmonary resuscitation is uncommon. A majority of patients who have not discussed preferences for end-of-life care do not want to do so. For patients who do not want to discuss their preferences, as well as patients with an unmet need for such discussions, failure to discuss preferences for cardiopulmonary resuscitation and mechanical ventilation may result in unwanted interventions. [ABSTRACT FROM AUTHOR]

Background: Alleviating the problems faced by dying persons and their families has drawn substantial public attention, but little is known about the experience of dying.Objective: To characterize the experience of dying from the perspective of surrogate decision makers, usually close family members (89%).Design: Prospective cohort study.Setting: Five teaching hospitals.Patients: Persons who had one of nine serious medical conditions or were 80 years of age or older who died and for whom a surrogate decision maker completed an interview about the death.Measurements: Medical records were reviewed and surrogate decision makers were interviewed.Results: 4124 of 9105 seriously ill patients died (46%); 408 of 1176 elderly patients died (35%). The patients' family members were interviewed after 3357 persons (73%) had died. Of 1541 patients who survived the enrollment hospitalization, 46% died during a later hospitalization. In the last 3 days of life, 55% of patients were conscious. Among these patients, pain, dyspnea, and fatigue were prevalent. Four in 10 patients had severe pain most of the time. Severe fatigue affected almost 8 in 10 patients. More than 1 in 4 patients had moderate dysphoria. Sixty-three percent of patients had difficulty tolerating physical or emotional symptoms. Overall, 11% of patients had a final resuscitation attempt. A ventilator was used in one fourth of patients, and a feeding tube was used in four tenths of patients. Most patients (59%) were reported to prefer a treatment plan that focused on comfort, but care was reported to be contrary to the preferred approach in 10% of cases.Conclusions: Most elderly and seriously ill patients died in acute care hospitals. Pain and other symptoms were commonplace and troubling to patients. Family members believed that patients preferred comfort, but life-sustaining treatments were often used. These findings indicate important opportunities to improve the care of dying patients. [ABSTRACT FROM AUTHOR]