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Objective: To develop a model estimating the probability of an adult patient having severe functional limitations 2 months after being hospitalized with one of nine serious illnesses.Design: Prospective cohort study.Setting: Five teaching hospitals in the United States.Participants: 1746 patients (model development) who survived 2 months and completed an interview, selected from 4301 patients in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT); independent validation sample of 2478 patients.Measurements and Main Outcomes: Patient function 2 months after admission categorized as absence or presence of severe functional limitations (defined as Sickness Impact Profile scores > or = 30 or as activities of daily living scores > or = 4 [levels that require near-constant personal assistance]). A logistic regression model was constructed to predict severe functional limitation.Results: One third (n = 590) of patients who were interviewed at 2 months had severe functional limitations. Changes in functional status were common: Of those with no baseline dependencies (not dependent on personal assistance), 21% were severely limited at 2 months; of those with 4 or more baseline limitations, 30% had improved. The patient's ability to do activities of daily living was the most important predictor of functional status. Physiologic abnormalities, diagnosis, days in hospital, age, quality of life, and previous exercise capacity also contributed substantially. Model performance, assessed using receiver-operating characteristic curves, was 0.79 for the development sample and 0.75 for the validation sample. The model was well calibrated for the entire risk range.Conclusions: Functional outcome varied substantially after hospitalization for a serious illness. A small amount of readily available clinical information can estimate the probability of severe functional limitations. [ABSTRACT FROM AUTHOR]

Violent conduct by youths ranks among the types of inappropriate behavior generally originating in difficult family and social contexts. A proper understanding of the development of violent conduct must consider the situation taken as a whole. This article documents the results of a qualitative study which aimed to determine the psychosocial profiles and needs of youths with serious behavior problems and a family history of physical, psychological or sexual abuse. The results are based on the review of clinical files of 12 boys and 11 girls between the ages of 9 and 17, who were under child protection. The 23 files were analyzed to document the simultaneous evolution of behavior problems, abuse, family and school context, and the intervention of child protection services (reporting, evaluation, measures taken, foster care). The qualitative analysis followed the chronology and life history of each youth, resulting in the emergence of three generic profiles: the Undesirable, the Explosive, and the Delinquent. Each of the profiles is described and placed in perspective using the attachment, trauma and socialization theories respectively. The study concludes with proposals of distinct intervention models to be applied to these youths in the school environment. [ABSTRACT FROM AUTHOR]

The study evaluated the effect of a programme for elementary school students with behaviour problems integrated into the regular classroom. The programme combined in-class social skills training and specific educational activities with peers, namely cooperative learning and tutoring by a prosocial peer. The innovative aspect is that the social status and affiliations of children with behaviour problems are key components in the matching of children during peer support. The goal is to improve social behaviour and to change peer perception through interventional strategies, therefore improving social reputation. Pre-test/post-test control group design was used. Results from traditional analysis indicated no significant difference between treatment and control groups after the programme. A modest effect size showed a relative improvement for students with behavioural disorders who participated in social skills training. Results are discussed in terms of the role of friends in the intervention programme. [ABSTRACT FROM AUTHOR]

Background: Previous studies suggest that specialty care is more costly but may produce improved outcomes for patients with acute cardiac illnesses.Objective: To determine whether patients with congestive heart failure who are cared for by cardiologists experienced differences in costs, care patterns, and survival compared with patients of generalists.Design: Prospective cohort study.Setting: 5 U.S. teaching hospitals between 1989 and 1994.Patients: 1298 patients hospitalized with an exacerbation of congestive heart failure.Measurements: Hospital costs; average daily Therapeutic Intervention Scoring System (TISS) score; and survival censored at 30, 180, and 365 days and 31 December 1994.Results: Compared with patients of generalists, patients of cardiologists were younger (mean age, 63.3 and 71.4 years; P < 0.001) and had lower Acute Physiology Scores at the time of admission (35.1 and 36.7; P < 0.001) but were more likely to have a history of ventricular arrhythmias (21.0% and 10.2%; P < 0.001). At 6 months, 201 (27%) patients of cardiologists and 149 (27%) patients of generalists had died. After adjustment for sociodemographic characteristics and severity of illness, patients of cardiologists incurred costs that were 42.9% (95% CI, 27.8% to 59.8%) higher and average daily TISS scores that were 2.83 points (CI, 1.96 to 3.68 points) higher than those of patients of generalists. Patients of cardiologists were more likely to undergo right-heart catheterization (adjusted odds ratio, 2.9 [CI, 1.7 to 4.9]) or cardiac catheterization (adjusted odds ratio, 3.9 [CI, 2.4 to 6.2]) and had higher odds for transfer to an intensive care unit and electrocardiographic monitoring. Adjusted survival did not differ significantly between groups at 30 days; however, there was a trend toward improved survival among patients of cardiologists at 1 year (adjusted relative hazard, 0.82 [CI, 0.65 to 1.04]) and at maximum follow-up (adjusted relative hazard, 0.80 [CI, 0.66 to 0.96]).Conclusions: In this observational study of patients hospitalized with congestive heart failure, cardiologist care was associated with greater costs and resource use and no difference in survival at 30 days of follow-up. Whether the trend toward better survival at longer follow-up represents differences in care or unadjusted illness severity is uncertain. [ABSTRACT FROM AUTHOR]

Objective: To examine the association between the use of right heart catheterization (RHC) during the first 24 hours of care in the intensive care unit (ICU) and subsequent survival, length of stay, intensity of care, and cost of care.Design: Prospective cohort study.Setting: Five US teaching hospitals between 1989 and 1994.Subjects: A total of 5735 critically ill adult patients receiving care in an ICU for 1 of 9 prespecified disease categories.Main Outcome Measures: Survival time, cost of care, intensity of care, and length of stay in the ICU and hospital, determined from the clinical record and from the National Death Index. A propensity score for RHC was constructed using multivariable logistic regression. Case-matching and multivariable regression modeling techniques were used to estimate the association of RHC with specific outcomes after adjusting for treatment selection using the propensity score. Sensitivity analysis was used to estimate the potential effect of an unidentified or missing covariate on the results.Results: By case-matching analysis, patients with RHC had an increased 30-day mortality (odds ratio, 1.24; 95% confidence interval, 1.03-1.49). The mean cost (25th, 50th, 75th percentiles) per hospital stay was $49 300 ($17 000, $30 500, $56 600) with RHC and $35 700 ($11 300, $20 600, $39 200) without RHC. Mean length of stay in the ICU was 14.8 (5, 9, 17) days with RHC and 13.0 (4, 7, 14) days without RHC. These findings were all confirmed by multivariable modeling techniques. Subgroup analysis did not reveal any patient group or site for which RHC was associated with improved outcomes. Patients with higher baseline probability of surviving 2 months had the highest relative risk of death following RHC. Sensitivity analysis suggested that a missing covariate would have to increase the risk of death 6-fold and the risk of RHC 6-fold for a true beneficial effect of RHC to be misrepresented as harmful.Conclusion: In this observational study of critically ill patients, after adjustment for treatment selection bias, RHC was associated with increased mortality and increased utilization of resources. The cause of this apparent lack of benefit is unclear. The results of this analysis should be confirmed in other observational studies. These findings justify reconsideration of a randomized controlled trial of RHC and may guide patient selection for such a study. [ABSTRACT FROM AUTHOR]

Objective: To develop and validate a prognostic model that estimates survival over a 180-day period for seriously ill hospitalized adults (phase I of SUPPORT [Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments]) and to compare this model's predictions with those of an existing prognostic system and with physicians' independent estimates (SUPPORT phase II).Design: Prospective cohort study.Setting: 5 tertiary care academic centers in the United States.Participants: 4301 hospitalized adults were selected for phase I according to diagnosis and severity of illness; 4028 patients were evaluated from phase II.Measurements: A survival model was developed using the following predictor variables: diagnosis, age, number of days in the hospital before study entry, presence of cancer, neurologic function, and 11 physiologic measures recorded on day 3 after study entry. Physicians were interviewed on day 3. Patients were followed for survival for 180 days after study entry.Results: The area under the receiver-operating characteristics (ROC) curve for prediction of surviving 180 days was 0.79 in phase I, 0.78 in the phase II independent validation, and 0.78 when the acute physiology score from the APACHE (Acute Physiology, Age, Chronic Health Evaluation) III prognostic scoring system was substituted for the SUPPORT physiology score. For phase II patients, the SUPPORT model had equal discrimination and slightly improved calibration compared with physician's estimates. Combining the SUPPORT model with physician's estimates improved both predictive accuracy (ROC curve area = 0.82) and the ability to identify patients with high probabilities of survival or death.Conclusions: A limited amount of readily available clinical information can provide a foundation for long-term survival estimates that are as accurate as physicians' estimates. The best survival estimates combine an objective prognosis with a physician's clinical estimate. [ABSTRACT FROM AUTHOR]

BACKGROUND: Serious illness often causes economic hardship for patients' families. However, it is not known whether this hardship is associated with a preference for the goal of care to focus on maximizing comfort instead of maximizing life expectancy or whether economic hardship might give rise to disagreement between patients and surrogates over the goal of care. METHODS: We performed a cross-sectional study of 3158 seriously ill patients (median age, 63 years; 44% women) at 5 tertiary medical centers with 1 of 9 diagnoses associated with a high risk of mortality. Two months after their index hospitalization, patients and surrogates were surveyed about patients' preferences for the primary goal of care: either care focused on extending life or care focused on maximizing comfort. Patients and surrogates were also surveyed about the financial impact of the illness on the patient's family. RESULTS: A report of economic hardship on the family as a result of the illness was associated with a preference for comfort care over life-extending care (odds ratio, 1.26; 95% confidence interval, 1.07-1.48) in an age-stratified bivariate analysis. Similarly, in a multivariable analysis controlling for patient demographics, illness severity, functional dependency, depression, anxiety, and pain, economic hardship on the family remained associated with a preference for comfort care over life-extending care (odds ratio, 1.31; 95% confidence interval, 1.10-1.57). Economic hardship on the family did not affect either the frequency or direction of patient-surrogate disagreements about the goal of care. CONCLUSIONS: In patients with serious illness, economic hardship on the family is associated with preferences for comfort care over life-extending care. However, economic hardship on the family does not appear to be a factor in patient-surrogate disagreements about the goal of care. [ABSTRACT FROM AUTHOR]

Objective: To investigate the appropriateness of hospitalization as the time to elicit patients' medical care preferences, the authors evaluated the capability of seriously ill patients to participate in decision making early in hospitalization and their decision making capacity two weeks before hospital entry.Design: Cross-sectional study with retrospective evaluation of preadmission decision making capacity.Setting: Five acute care teaching hospitals.Patients: Four thousand three hundred one acutely ill hospitalized adults meeting predetermined severity of illness criteria in nine specific disease categories.Measurements: Surrogate decision makers' estimates of the prior mental capacities of patients unable to be interviewed early in hospitalization about care preferences due to intubation, coma, or cognitive impairment. Comparison of the demographics, degrees of sickness at admission, and outcomes of interviewable vs noninterviewable patients.Main Results: Forty percent of the patients were not interviewable concerning preferences. Of these, 83% could have participated in treatment decisions two weeks prior to hospitalization. The patients who were not interviewable were more acutely ill, had less chronic disease, and were more likely to die during hospitalization than the interviewable patients.Conclusions: Many acutely ill patients likely to die in the hospital lost their ability to make medical care decisions around the time of hospital admission. Preferences for care and advance directives should be discussed in the outpatient setting or very early in hospital admission. [ABSTRACT FROM AUTHOR]

Objective: To address a patient care problem suggested by a quality assurance study: Should physicians of patients with atrial fibrillation who have not had echocardiography performed be encouraged to obtain echocardiograms in order to discover heretofore undetected mitral stenosis, which could be treated with anticoagulation, in order to avert strokes?Design: Decision analysis using a Markov-chain technique and quality-adjusted life expectancy.Setting: Outpatient clinics.Patients: Patients aged 40-80 years with chronic atrial fibrillation.Interventions: The following strategies were studied: 1) obtain echocardiograms for all patients and anticoagulate those with mitral stenosis; 2) anticoagulate patients with classic auscultatory sounds of mitral stenosis and obtain echocardiograms for patients with other murmurs; if an echocardiogram reveals mitral stenosis, anticoagulate; 3) anticoagulate all patients with murmurs; 4) anticoagulate all patients; 5) observe all patients (natural history).Main Results: The base analysis, using data available in the literature and on site, indicated that though performing echocardiography on all patients with atrial fibrillation gave the best quality-adjusted life expectancy, the differences among the five strategies studied were small. In addition, sensitivity analysis revealed that the decision was sensitive to many of the variables used in the analysis, especially the efficacy and the risks of anticoagulation.Conclusion: A recommendation that cardiac ultrasonography be done for all patients with atrial fibrillation in order to detect clinically unrecognized mitral stenosis cannot be made. [ABSTRACT FROM AUTHOR]

Abstract: In the present study, the thermodynamic behaviour and transport properties of CO2 +N2O and CO2 +NO mixtures have been investigated using molecular simulation and equation of state modelling. Molecular simulations were based on Monte Carlo and Molecular Dynamics calculations using force fields calibrated from pure component properties and no adjustment of mixture properties was performed. Original force fields were proposed for N2O, NO and N2O2 molecules. Special attention must be paid when studying nitric oxide containing systems because this compound can exist as a mixture of monomers (NO) and dimers (N2O2) under certain pressure and temperature conditions. Liquid–vapour coexistence properties of the reacting NO–N2O2 system were thus first investigated using combined reaction ensemble and Gibbs ensemble Monte Carlo methods. Using the new force fields proposed, phase compositions, phase densities and phase viscosities were determined for CO2 +NOx mixtures. Due to the strong similarities between carbon dioxide and nitrous oxide (T c (CO2)=304.21K; T c (N2O)=309.57K; P c (CO2)=7.38MPa; P c (N2O)=7.24MPa), the obtained thermodynamic and transport properties for a CO2 +N2O mixture with 10mol% of N2O are similar to pure CO2 properties in the whole range of studied temperatures (273–293K), in agreement with available experimental data. Calculations of CO2 +NO equilibrium and transport properties were also performed at three different temperatures in the range of 253–273K. At these temperatures, only the monomer form of the nitric oxide (NO) has to be accounted for. The performed calculations are pure predictions since no experimental data are available in the open literature for this system. For a mixture containing 10mol% of NO, the simulation results show a decrease of the liquid densities and viscosities of 9% and 24% with respect to corresponding pure CO2 values, respectively. The new pseudo-experimental data generated in this work were finally used to calibrate binary interaction parameters required in standard cubic equations of states. Both Peng–Robinson and Soave–Redlich–Kwong equations of state have been considered and after the regression, they display a decent match with experimental and pseudo-experimental data of the vapour–liquid equilibrium for the two studied mixtures. [Copyright &y& Elsevier]

Purpose: Many patients with acute respiratory failure die despite prolonged and costly treatment. Our objective was to estimate the cost-effectiveness of providing rather than withholding mechanical ventilation and intensive care for patients with acute respiratory failure due to pneumonia or acute respiratory distress syndrome.Subjects and Methods: We studied 1,005 patients enrolled in a five-center study of seriously ill patients (the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments [SUPPORT]) with acute respiratory failure (pneumonia or acute respiratory distress syndrome and an Acute Physiology Score > or =10) who required ventilator support. We estimated life expectancy based on long-term follow-up of SUPPORT patients. Utilities were estimated using time-tradeoff questions. Costs (in 1998 dollars) were based on hospital fiscal data and Medicare data.Results: Of the 963 patients who received ventilator support, 48% survived for at least 6 months. At 6 months, survivors reported a median of 1 dependence in activities of daily living, and 72% rated their quality of life as good, very good, or excellent. Among the 42 patients in whom ventilator support was withheld, the median survival was 3 days. Among patients whose estimated probability of surviving at least 2 months from the time of ventilator support ("prognostic estimate") was 70% or more, the incremental cost per quality-adjusted life-year (QALY) saved by providing rather than withholding ventilator support and aggressive care was $29,000. For medium-risk patients (prognostic estimate 51% to 70%), the incremental cost-effectiveness was $44,000 per QALY, and for high-risk patients (prognostic estimate < or =50%), it was $110,000 per QALY. When assumptions were varied from 50% to 200% of baseline estimates, the results ranged from $19,000 to $48,000 for low-risk patients, from $29,000 to $76, 000 for medium-risk patients, and from $67,000 to $200,000 for high-risk patients.Conclusions: Ventilator support and intensive care for acute respiratory failure due to pneumonia or acute respiratory distress syndrome are relatively cost-effective for patients with >50% probability of surviving 2 months. However, for patients with an expected 2-month survival < or =50%, the cost per QALY is more than threefold greater at >$100,000. [ABSTRACT FROM AUTHOR]

Purpose: Both generalist and pulmonologist physicians care for patients with severe chronic obstructive pulmonary disease (COPD). We studied patients hospitalized with severe COPD to explore whether supervision of care by pulmonologists is associated with greater costs or better survival.Subjects and Methods: We studied 866 adults with severe COPD enrolled in the Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments (SUPPORT), a prospective study at five academic medical centers. Patients were admitted to the hospital or transferred to an intensive care setting for treatment of severe COPD, defined by hypoxia (PaO2 <60 mm Hg) and hypercapnia (PaCO2 >50 mm Hg) or hypercapnia alone if on supplemental oxygen. Resource intensity was measured using a modified version of the Therapeutic Intervention Scoring System and estimated hospital costs. To account for differences in the patient case mix, propensity scores were developed to represent each patient's probability of having a pulmonologist as attending physician and each patient's probability of being in an intensive care unit (ICU) at study admission.Results: Of the 866 patients studied, 512 had generalists and 354 pulmonologists as their attending physicians. The median patient age was 70 years; 52% were male; 14% died within 30 days. After adjusting for baseline differences in patient characteristics, there were no differences in resource intensity and hospital costs in those treated by pulmonologists or generalists. Adjusted average resource intensity scores for the entire hospitalization were 16.5 for pulmonologists and 17.0 for generalists (P = 0.34). Estimated hospital costs were the same ($6,400) for patients treated by pulmonologists and generalists (P = 0.99). Patients with pulmonologists as attending physicians did not experience better survival. Comparing patients of pulmonologists to patients of generalists, the adjusted hazard ratio for 30-day mortality was 1.6 (95% confidence interval: 0.98, 2.5); the hazard ratio for 180-day mortality was 1.2 (0.9, 1.7).Conclusions: Our findings suggest that for patients hospitalized with exacerbation of severe COPD, those with pulmonologist attending physicians do not have higher hospital resource use or better survival than those with generalist attending physicians. [ABSTRACT FROM AUTHOR]

Purpose: For patients hospitalized with serious illnesses, we identified factors associated with a stated preference to forgo cardiopulmonary resuscitation (CPR), examined physician-patient communication about these issues, and determined the relationship of patients' preferences to intensity of care and survival.Patients and Methods: The study was a cross-sectional evaluation of patient preferences. The setting was five geographically diverse academic acute-care medical centers participating in the SUPPORT (Study to Understand Prognoses and Preferences for Outcomes and Risks of Treatments) project. Study participants were hospitalized patients > or = 18 years of age with 1 of 9 serious illnesses who were interviewed between days 3 and 6 after qualifying for the study. Using standardized interviews, patients provided information on demographics, preferences for CPR and other treatments, quality of life, functional status, perceptions of prognosis, and whether the patient had discussed CPR preferences with his or her physician. Data abstracted from the medical record included physiologic measures, therapeutic intensity, whether CPR was provided, and whether there was a do-not-resuscitate order.Results: Of 1,995 eligible patients, 84% were interviewed (mean age 62 years, 58% men, inhospital mortality 7%, 6-month mortality 33%). Of the respondents, 28% did not want CPR. Factors associated independently with not wanting CPR included: hospital site; diagnosis; being older; being more functionally impaired; and patient perception of a worse prognosis. Only 29% of patients had discussed their preferences with their physician; 48% of those who did not want CPR reported such discussions. After adjusting for illness severity and factors associated with CPR preferences, patients not wanting CPR had lower intensity of care; similar inhospital mortality; and higher mortality at 2 and 6 months following study entry.Conclusions: The diagnosis, patients' perception of the prognosis, and hospital site were significantly associated with patients' resuscitation preferences after adjusting for patient demographics, severity of illness, and functional status. The rate of discussing CPR was low even for patients who did not want CPR. Patient preferences not to receive CPR were associated with a small decrease in intensity of care but no difference in hospital survival. [ABSTRACT FROM AUTHOR]

Molecular dynamics is often considered as a numerical experiment. The error bars on the results are therefore mandatory, but sometimes difficult to determine and computationally demanding. As a low-cost approach, we describe the application of the bootstrap (BS) method to the quantification of uncertainties pertaining to the time correlation functions. We chose the autocorrelation functions of velocity and interdiffusion current for a binary ionic mixture as a test bed, and we assessed the merit of the Darken approximation relating both of them. The intrinsic errors related to phase space sampling is investigated comparing the BS method with the reference method of replica. We also study how the BS method can assist in addressing the finite-size effects.

Transport properties of mixtures of elements in the dense plasma regime play an important role in natural astrophysical and experimental systems, e.g., inertial confinement fusion. We present a series of orbital-free molecular dynamics simulations on dense plasma mixtures with comparison to a global pseudo ion in jellium model. Hydrogen is mixed with elements of increasingly high atomic number (lithium, carbon, aluminum, copper, and silver) at a fixed temperature of 100 eV and constant pressure set by pure hydrogen at 2g/cm^{3}, namely, 370 Mbars. We compute ionic transport coefficients, such as self-diffusion, mutual diffusion, and viscosity for various concentrations. Small concentrations of the heavy atoms significantly change the density of the plasma and decrease the transport coefficients. The structure of the mixture evidences a strong Coulomb coupling between heavy ions and the appearance of a broad correlation peak at short distances between hydrogen atoms. The concept of an effective one component plasma is used to quantify the overcorrelation of the light element induced by the admixture of a heavy element.

We show that the Bayesian inference of recently measured x-ray diffraction spectra from laser-shocked aluminum [L. B. Fletcher et al., Nat. Photon. 9, 274 (2015)10.1038/nphoton.2015.41] with the one-component-plasma (OCP) model performs remarkably well at estimating the ionic density and temperature. This statistical approach requires many evaluations of the OCP static structure factor, which were done using a recently derived analytic fit. The atomic form factor is approximated by an exponential function in the diffraction window of the first peak. The electronic temperature is then estimated from a comparison of this approximated form factor with the electronic structure of an average atom model. Out-of-equilibrium states, with electrons hotter than ions, are diagnosed for the spectra obtained early after the pump, whereas at a late time delay the plasma is at thermal equilibrium. Apart from the present findings, this OCP-based modeling of warm dense matter has an important role to play in the interpretation of x-ray Thomson scattering measurements currently performed at large laser facilities.

We present a simple, fast, and promising method to compute the melting curves of materials with ab initio molecular dynamics. It is based on the two-phase thermodynamic model of Lin et al [J. Chem. Phys. 119, 11792 (2003)] and its improved version given by Desjarlais [Phys. Rev. E 88, 062145 (2013)]. In this model, the velocity autocorrelation function is utilized to calculate the contribution of the nuclei motion to the entropy of the solid and liquid phases. It is then possible to find the thermodynamic conditions of equal Gibbs free energy between these phases, defining the melting curve. The first benchmark on the face-centered cubic melting curve of aluminum from 0 to 300 GPa demonstrates how to obtain an accuracy of 5%-10%, comparable to the most sophisticated methods, for a much lower computational cost.

We compute the Hugoniot curves of both neat triaminotrinitrobenzene (TATB) and its detonation products mixture using atomistic simulation tools. To compute the Hugoniot states, we adapted our sampling constraints in average (SCA) method (Maillet et al. Appl. Math. Res. eXpress 2009, 2008, abn004) to Monte Carlo simulations. For neat TATB, we show that the potential proposed by Rai (Rai et al. J. Chem. Phys. 2008, 129, 194510) is not accurate enough to predict the Hugoniot curve and requires some optimization of its parameters. Concerning the detonation products, thermodynamic properties at chemical equilibrium are computed using a specific reaction ensemble Monte Carlo (RxMC) method (Bourasseau et al. Phys. Chem. Chem. Phys. 2011, 13, 7060), taking into account the presence of carbon clusters in the fluid mixture. We show that this explicit description of the solid phase immersed in the fluid phase modifies the chemical equilibrium.

An approach is proposed to obtain the equation of state of unreactive shocked liquid nitromethane. Unlike previous major works, this equation of state is not based on extended integration schemes [P.C. Lysne, D.R. Hardesty, Fundamental equation of state of liquid nitromethane to 100 kbar, J. Chem. Phys. 59 (1973) 6512]. It does not follow the way proposed by Winey et al. [J.M. Winey, G.E. Duvall, M.D. Knudson, Y.M. Gupta, Equation of state and temperature measurements for shocked nitromethane, J. Chem. Phys. 113 (2000) 7492] where the specific heat C(v), the isothermal bulk modulus B(T) and the coefficient of thermal pressure (deltaP/deltaT)(v) are modeled as functions of temperature and volume using experimental data. In this work, we compute the complete equation of state by microscopic calculations. Indeed, by means of Monte Carlo molecular simulations, we have proposed a new force field for nitromethane that lead to a good description of shock properties [N. Desbiens, E. Bourasseau, J.-B. Maillet, Potential optimization for the calculation of shocked liquid nitromethane properties, Mol. Sim. 33 (2007) 1061; A. Hervouët, N. Desbiens, E. Bourasseau, J.-B. Maillet, Microscopic approaches to liquid nitromethane detonation properties, J. Phys. Chem. B 112 (2008) 5070]. Particularly, it has been shown that shock temperatures and second shock temperatures are accurately reproduced which is significative of the quality of the potential. Here, thermodynamic derivative properties are computed: specific heats, Grüneisen parameter, sound velocity among others, along the Hugoniot curve. This work constitutes to our knowledge the first determination of the equation of state of an unreactive shocked explosive by molecular simulations.

The thermodynamic behavior of the carbon dioxide + nitrogen dioxide (CO2 + NO2) mixture was investigated using a Monte Carlo molecular simulation approach. This system is a particularly challenging one because nitrogen dioxide exists as a mixture of monomers (NO2) and dimers (N2O4) under certain pressure and temperature conditions. The chemical equilibrium between N2O4 and 2NO2 and the vapor-liquid equilibrium of CO2 + NO2/N2O4 mixtures were simulated using simultaneously the reaction ensemble and the Gibbs ensemble Monte Carlo (RxMC and GEMC) methods. Rigid all atoms molecular potentials bearing point charges were proposed to model both NO2 and N2O4 species. Liquid-vapor coexistence properties of the reacting NO2/N2O4 system were first investigated. The calculated vapor pressures and coexisting densities were compared to experimental values, leading to an average deviation of 10% for vapor pressures and 6% for liquid densities. The critical region was also addressed successfully using the subcritical Monte Carlo simulation results and some appropriate scaling laws. Predictions of CO2 + NO2/N2O4 phase diagrams at 300, 313, and 330 K were then proposed. Derivative properties calculations were also performed in the reaction ensemble at constant pressure and temperature for both NO2/N2O4 and CO2 + NO2/N2O4 systems. The calculated heat capacities show a maximum in the temperature range where N2O4 dissociation occurs, in agreement with available experimental data.

Background: Medical knowledge is essential for appropriate patient care; however, the accuracy of internal medicine (IM) residents' assessment of their medical knowledge is unknown., Methods: IM residents predicted their overall percentile performance 1 week (on average) before and after taking the in-training exam (ITE), an objective and well accepted method to assess medical knowledge to study resident assessment accuracy. Ordinary least squares regression was used to study the association between the absolute accuracy of their predictions of their percentile performance on the ITE examination and their actual percentile performance., Results: Ninety-three percent of our 28 residents participated. Residents were highly inaccurate in predicting their percentile performance. Only 31% had ITE scores that were within 10 points of their predictions. On average, most residents were pessimistic about their overall percentile performance with 18 (69%) underestimating their performance. Having just taken the examination and previous experience with the examination did not improve predictions of percentile performance., Conclusion: IM residents did not accurately predict their own level of medical knowledge. Taking the examination and experience with previous exams does not appear to improve the ability of these IM residents to predict their performance. Residents need to be taught to rely on the results of standardized examinations such as the ITE to best assess their overall medical knowledge. The factors important for accurate self-assessment of medical knowledge in individual clinical situations remain unexplored.

In this paper, thermodynamic and chemical properties of nitromethane are investigated using microscopic simulations. The Hugoniot curve of the inert explosive is computed using Monte Carlo simulations with a modified version of the adaptative Erpenbeck equation of state and a recently developed intermolecular potential. Molecular dynamic simulations of nitromethane decomposition have been performed using a reactive potential, allowing the calculation of kinetic rate constants and activation energies. Finally, the Crussard curve of detonation products as well as thermodynamic properties at the Chapman-Jouguet (CJ) point are computed using reactive ensemble Monte Carlo simulations. Results are in good agreement with both thermochemical calculations and experimental measurements.

In this work, we used simultaneously the reaction ensemble Monte Carlo (ReMC) method and the adaptive Erpenbeck equation of state (AE-EOS) method to directly calculate the thermodynamic and chemical equilibria of mixtures of detonation products on the Hugoniot curve. The ReMC method [W. R. Smith and B. Triska, J. Chem. Phys. 100, 3019 (1994)] allows us to reach the chemical equilibrium of a reacting mixture, and the AE-EOS method [J. J. Erpenbeck, Phys. Rev. A 46, 6406 (1992)] constrains the system to satisfy the Hugoniot relation. Once the Hugoniot curve of the detonation product mixture is established, the Chapman-Jouguet (CJ) state of the explosive can be determined. A NPT simulation at P(CJ) and T(CJ) is then performed in order to calculate direct thermodynamic properties and the following derivative properties of the system using a fluctuation method: calorific capacities, sound velocity, and Gruneisen coefficient. As the chemical composition fluctuates, and the number of particles is not necessarily constant in this ensemble, a fluctuation formula has been developed to take into account the fluctuations of mole number and composition. This type of calculation has been applied to several usual energetic materials: nitromethane, tetranitromethane, hexanitroethane, PETN, and RDX.

Introduction: A 45-year-old female presented with 8 hours of right lower extremity pain and dyspnea. She was tachycardic and her right lower extremity was dusky, cold, and pulseless., Discussion: Computerized tomography of the venous and arterial systems revealed massive pulmonary embolism and right lower extremity arterial and left lower extremity venous thromboses. Management included intra-arterial thrombolytics, right lower extremity arterial embolectomy, and anticoagulation. Echocardiogram revealed a patent foramen ovale (PFO) with a right-to-left shunt., Conclusion: We hypothesize that our patient developed deep venous thrombosis that led to major pulmonary embolization and increased right-sided pressures. In the setting of a patent foramen ovale, a later venous embolus transversed the PFO and lodged in the femoral artery. Our case illustrates the importance of a high index of suspicion for a paradoxical embolus in patients with arterial thrombosis.

We report a series of Grand Canonical Monte Carlo simulations of water adsorption in NaY and NaX faujasite, as well as in silicalite-1. Computed adsorption isotherms and heats of adsorption were in good agreement with the available experiments. The existence of cyclic water hexamers in NaX located in the 12-ring windows, recently disclosed by neutron diffraction experiments (Hunger et al., J. Phys. Chem. B, 2006, 110, 342-353) was reproduced in our simulations. Interestingly enough, such cyclic hexamer clusters were also observed in the case of NaY, in which no stabilizing cation is present in the 12-ring window. We also report cation redistribution upon water adsorption for sodium faujasite with varying cation contents (Si ratio Al ratio in the range 1.53-3). A simple and transferable forcefield was used, that enabled to reproduce the different aspects of water physisorption in stable zeolites. The high pressure water condensation in hydrophobic silicalite-1 was reproduced without any parameter readjustment. The method and forcefield used here should be useful for engineering oriented applications such as the prediction of multi-component mixture adsorptive separations in various stable zeolites. It allows to address the issue of the effect of the small amounts of water that are almost inevitably present in zeolite-based separation processes.

We report grand canonical Monte Carlo simulations of the gas and liquid phase adsorption of water in silicalite-1 zeolite. Simple but effective models and simulation methods, found useful for studying gas adsorption in nanoporous materials, have been extended to describe the intrusion/extrusion cycle of water in this hydrophobic solid. The picture of water confined to hydrophobic spaces of nanoscopic dimensions that emerges from this study is one of a strongly depleted and highly inhomogeneous fluid.

Morphine is a preferred narcotic since meperidine forms toxic metabolites. Determinants of meperidine use have been poorly described. The objective of this study is to explore factors associated with the ordering of meperidine versus morphine. Retrospective chart review of adult patients, randomly selected based on orders for morphine or meperidine. 1552 orders were written for 670 patients. Of these, 36% were for meperidine. In multivariable analysis, the ordering of meperidine was associated with the following variables in decreasing order of importance: physician specialty, total doses received, hospital location, patient race, age and insurance, and physician gender. More orders for meperidine were written for those receiving fewer doses. Though meperidine has little role in the routine management of hospital pain, we found it continues to be used frequently. Importantly, meperidine is ordered more frequently for patients who receive shorter courses of narcotics. Our study suggests that interventions targeted at more appropriate use of meperidine rather than complete elimination might be more acceptable to physicians while minimizing the risk of toxicity.

Part of the design of some randomized controlled trials has included asking patients to guess whether they are taking placebo or active drug. Some authors have stated that in randomized, double-blind placebo-controlled clinical trials patients in each group should guess that they are taking placebo half the time. However, this pattern should occur only under a limited set of circumstances. This paper explores the factors that affect the guess and the role of the guess in understanding both the establishment and the maintenance of the blind. It suggests that more than half of those in the treatment group should guess they are taking active drug if treatment or side-effects are powerful. Though the randomized controlled trial has become the paradigmatic tool to assess treatment efficacy, studies are still needed to validate key assumptions make by investigators and the effect of violation of these assumptions on study outcomes.