The effect of single electrolytes on the vapor-liquid equilibrium of mixed solvents

A group-contribution model for the prediction of salt-effects on the vapor-liquid equilibria of multicomponent electrolytic solutions containing a single electrolyte is presented. Coulombic interactions are represented through a Pitzer term. Solvation effects and short-range interactions are represented through a UNIQUAC-type expression. An ion-size, a solvation and three ion-solvent interaction parameters per salt-solvent binary are required for multicomponent predictions. All parameters are obtained only through the correlation of binary salt-solvent osmotic coefficient and vapor-pressure depression data at 25°C, in most cases, and binary solvent VLE data. The salt-solvent binary data were correlated with an average percent error in CD of 2.5 and an average percent error in P of 0.35 mm Hg up to a molality of 6 for 1-1 and 2-1 salts. The model is also useful in the prediction of aqueous binary salt data up to a molality of 6 and 200°C and nonaqueous binary salt data up to a molality of 6 and 60°C. Methods are also presented for the estimation of the ion-solvent interaction parameters needed for multicomponent prediction when the constituent binary data are not available. 25 data sets of isothermal and isobaric salt-alcohol-water and salt-alcohol mixtures were predicted using the binary interaction parameters and gave an average absolute error in the vapor phase composition of 0.019. The model predicts correctly the salting-in of the appropriate component. Vapor-pressure depression data of Nal, KCH3COO, NaSCN, and NH4SCN in methanol at temperatures of 25 and 40°C were measured in the molality range of 0.1-5.0 m using a static method, where the vapor pressure of the electrolytic solution is compared to that of the pure solvent. Osmotic coefficients were calculated from the vapor pressure data. This data was used to obtain additional binary interaction parameters which could not be determined from the existing literature data

Osmotic and mean activity coefficients of LiBr and LiC in methanol at 25, 35, and 45 degrees C

Vapor pressure depression data of LiBr and LiCl in methanol at temperatures of 25,35, and 45°C were measured in the molality range 0.1-4.4m using a static method, where the difference in vapor pressure of the electrolytic solution is compared to that of pure methanol. Osmotic coefficients were calculated from the vapor pressure data. This data was then correlated with both the one parameter Bromley equation and the three parameter Pitzer equation. For all systems at all temperatures, the data were better correlated by the Pitzer equation than with the Bromley equation. Mean activity coefficients of the two salts at the three temperatures were calculated based on the parameters obtained by regression of the experimental osmotic coefficient data. They were also calculated using a graphical procedure. However, it was shown that if data are not available at low concentrations with which to extrapolate the data to infinite dilution, the mean activity coefficients determined graphically can be in error by 20%. Although the Pitzer equation fit the experimental osmotic coefficient data better than the Bromley equation, it appears that the constants of both equations that reflect an aqueous media must be modified to reflect the properties of the nonaqueous methanol. The temperature dependency of B in the Bromley equation was investigated using a two parameter equation for both the LiBr and LiCl systems. Since the fit is good, the equation can be used to estimate the value of B in the range of 25-45 °C. The temperature dependency of the parameters in the Pitzer equation was also studied. However, no relation ship between the parameters and temperature could be found. Since the temperature dependency of the parameter B in the Bromley equation can easily be expressed with a two parameter equation, it appears that this equation is more useful in the correlation of salt-solvent data over many temperatures than is Pitzer\u27s equation

Identifying the missing piece of suicide prevention : Formative risk assessment

Suicide is the third leading cause of death among adolescents and young adults (Centers for Disease Control [CDC], 2011). However, no evidence-based suicide prevention programs currently exist that utilize formative assessment measures to screen for individuals deemed at-risk (National Registry of Evidence-based Programs and Practices [NREPP], n.d.). Given that timely intervention may prevent premature death, there is a dire need to create a direct, formative measure to account for the time-sensitive nature of the data. Glover and Albers (2007) suggest that universal screening measures should be feasible, contextually appropriate, and technically adequate. Borrowing from the literature base of school-based behavior assessment, a widely used, formative measure known as Direct Behavior Rating (DBR; Chafouleas, Riley-Tillman, & McDougal, 2002) was adapted to create a formative suicide risk assessment measure, known as the Direct Behavior Risk Rating (DBRR). The DBRR is a no-cost, 5-item measure that is designed to identify students at-risk for engaging in suicidal activity. The present study tested the hypotheses that DBRRs demonstrate concurrent validity with regard to the Beck Scale for Suicidal Ideation (BSI; Hypothesis 1), demonstrate overall classification accuracy with regard to BSI risk status (Hypothesis 2), and identify cut scores associated with optimal conditional probability statistics (Hypothesis 3). Compared to single DBRR items, the DBRR-Multiple Item Scale (DBRR-MIS) demonstrated a moderate to strong correlation with the BSI and appropriate discriminatory power when modeled against the BSI as the criterion, respectively. Adequate cut scores were identified for the DBRR-MIS for potential differentiation of risk status. However, as the purpose of a screening measurement tool is to achieve an optimal percentage of correct decisions (i.e., true positives & true negatives), results of receiver operating characteristic (ROC) curve analyses indicated that the DBRR-MIS displays a disproportionate balance among probability statistics (i.e., positive predictive power & negative predictive power), resulting in over-identification of those at risk. Given that limited resources often thwart screening implementation in educational settings, further research is needed to improve the technical adequacy of the DBRR. Initial findings indicate that, upon continued examination, the DBRR-MIS may be an innovative method of assessing suicide risk among the student population.Ph.D

Adolescent Sexual Assault and Suicidal Behaviors : Investigating a National Sample

This study was designed to shed light on two public health concerns: sexual assault and suicidal behaviors among the adolescent population. Sexual assault history, sex differences, and the combination of both sexual assault history and sex were examined when considering suicidal behaviors among high-school adolescents. This study utilized responses from the most recent national survey, 2007 Youth Risk Behavior Surveillance System. Adolescents reporting a history of sexual assault were approximately six times (OR=6.384) more likely to have attempted suicide in the past year when compared to adolescents reporting no history of sexual assault. When examining each sex separately, the relationship was stronger for males: Males reporting a history of sexual assault were nearly ten times (OR=9.757) as likely to have attempted suicide at least once in the past year when compared to males reporting no such history. Females reporting a history of sexual assault were nearly five times (OR=4.712) more likely to have attempted suicide in the previous twelve months when compared to females reporting no such history. When examining suicidal behaviors among adolescents reporting a sexual assault history, the rates between male and female adolescents were indistinguishable. That is, on average, 26% of males and females with a sexual assault history attempted suicide within the past 12 months. In order to investigate the impact on suicide attempts requiring medical attention, the final, iterative logistic regression models included age, sexual assault history, and sex x sexual assault history as an interaction term. A statistically significant sex x sexual assault history emerged, Wald chi-square (1, 40)=11.00, p=.002 when examining responses from adolescents reporting suicidal behavior within the past 12 months. That is, males reporting a sexual assault history reported suicide attempts requiring medical attention more frequently than male suicide attempters without sexual assault histories, as well as both groups of female suicide attempters - both with and without sexual assault histories. Implications for the existing literature base and potential school-based suicide prevention and intervention programs are discussed.  M.A

Pilot-scale crossflow-microfiltration and pasteurization to remove spores of Bacillus anthracis (Sterne) from milk

High-temperature, short-time pasteurization of milk is ineffective against spore-forming bacteria such as Bacillus anthracis (BA), but is lethal to its vegetative cells. Crossflow microfiltration (MF) using ceramic membranes with a pore size of 1.4 μm has been shown to reject most microorganisms from skim milk; and, in combination with pasteurization, has been shown to extend its shelf life. The objectives of this study were to evaluate MF for its efficiency in removing spores of the attenuated Sterne strain of BA from milk; to evaluate the combined efficiency of MF using a 0.8-μm ceramic membrane, followed by pasteurization (72°C, 18.6 s); and to monitor any residual BA in the permeates when stored at temperatures of 4, 10, and 25°C for up to 28 d. In each trial, 95 L of raw skim milk was inoculated with about 6.5 log10 BA spores/mL of milk. It was then microfiltered in total recycle mode at 50°C using ceramic membranes with pore sizes of either 0.8 μm or 1.4 μm, at crossflow velocity of 6.2 m/s and transmembrane pressure of 127.6 kPa, conditions selected to exploit the selectivity of the membrane. Microfiltration using the 0.8-μm membrane removed 5.91 ± 0.05 log10 BA spores/mL of milk and the 1.4- μm membrane removed 4.50 ± 0.35 log10 BA spores/ mL of milk. The 0.8-μm membrane showed efficient removal of the native microflora and both membranes showed near complete transmission of the casein proteins. Spore germination was evident in the permeates obtained at 10, 30, and 120 min of MF time (0.8-μm membrane) but when stored at 4 or 10°C, spore levels were decreased to below detection levels (≤0.3 log10 spores/mL) by d 7 or 3 of storage, respectively. Permeates stored at 25°C showed coagulation and were not evaluated further. Pasteurization of the permeate samples immediately after MF resulted in additional spore germination that was related to the length of MF time. Pasteurized permeates obtained at 10 min of MF and stored at 4 or 10°C showed no growth of BA by d 7 and 3, respectively. Pasteurization of permeates obtained at 30 and 120 min of MF resulted in spore germination of up to 2.42 log10 BA spores/mL. Spore levels decreased over the length of the storage period at 4 or 10°C for the samples obtained at 30 min of MF but not for the samples obtained at 120 min of MF. This study confirms that MF using a 0.8-μm membrane before high-temperature, short-time pasteurization may improve the safety and quality of the fluid milk supply; however, the duration of MF should be limited to prevent spore germination following pasteurization