Structure and Thermodynamics of the Mixed Alkali Alanates

The thermodynamics and structural properties of the hexahydride alanates (M2M'AlH6) with the elpasolite structure have been investigated. A series of mixed alkali alanates (Na2LiAlH6, K2LiAlH6 and K2NaAlH6) were synthesized and found to reversibly absorb and desorb hydrogen without the need for a catalyst. Pressure-composition isotherms were measured to investigate the thermodynamics of the absorption and desorption reactions with hydrogen. Isotherms for catalyzed (4 mol% TiCl3) and uncatalyzed Na2LiAlH6 exhibited an increase in kinetics, but no change in the bulk thermodynamics with the addition of a dopant. A structural analysis using synchrotron x-ray diffraction showed that these compounds favor the Fm-3m space group with the smaller ion (M') occupying an octahedral site. These results demonstrate that appropriate cation substitutions can be used to stabilize or destabilize the material and may provide an avenue to improving the unfavorable thermodynamics of a number of materials with promising gravimetric hydrogen densities.Comment: 6 pages, 7 figures,3 tables, submitted to PR

Use of medication by young people with attention-deficit/hyperactivity disorder

The document attached has been archived with permission from the editor of the Medical Journal of Australia (26 April 2007). An external link to the publisher’s copy is includedObjectivesTo examine the prevalence of psychotropic medication use by children with attention-deficit/hyperactivity disorder (ADHD) and children without ADHD. To identify factors associated with stimulant use by children in the community.DesignA representative, multistage probability sample of Australian households was conducted in 1998. Parents completed questionnaires assessing children's mental health problems and health-related quality of life. They also completed a structured interview to identify children's psychiatric disorders and their use of medications during the previous six months.ParticipantsParent or main caregiver of 3597 children aged 6-17 years.Main outcome measuresRates of use of stimulants (dexamphetamine and methylphenidate), antidepressants and clonidine by children.ResultsOverall, 1.8% of children (95% CI, 1.5%-2.3%) were receiving stimulant medication. Of those with ADHD, 12.6% (95% CI, 9.8%-16.1%) were being treated with stimulants, 2.3% (95% CI, 1.3%-4.3%) with antidepressants, and 1.9% (95% CI, 1.0%-3.7%) with clonidine. Among children without ADHD, 0.5% (95% CI, 0.3%-0.8%) were receiving stimulant medication. This represented 22.9% (95% CI, 14.6%-34.0%) of all the children who were receiving stimulants. Variables significantly associated with stimulant use were being male, having ADHD, attending a paediatrician, and having higher scores on the Aggressive Behaviour and Attention Problems scales on the Child Behaviour Checklist.ConclusionsAbout 13% of Australian children with ADHD, and a substantial number of children without ADHD, are taking stimulants. The question of whether Australian children are being undertreated or overtreated with stimulant medication depends on the criteria used to assess the appropriateness of stimulant use. Additional information is needed to clarify when stimulants should be used to treat ADHD.Michael G. Sawyer, Joseph M. Rey, Brian W. Graetz, Jennifer J. Clark and Peter A. Baghurs

Evaluating Modeling and Validation Strategies for Tooth Loss

Prediction models learn patterns from available data (training) and are then validated on new data (testing). Prediction modeling is increasingly common in dental research. We aimed to evaluate how different model development and validation steps affect the predictive performance of tooth loss prediction models of patients with periodontitis. Two independent cohorts (627 patients, 11,651 teeth) were followed over a mean ± SD 18.2 ± 5.6 y (Kiel cohort) and 6.6 ± 2.9 y (Greifswald cohort). Tooth loss and 10 patient- and tooth-level predictors were recorded. The impact of different model development and validation steps was evaluated: 1) model complexity (logistic regression, recursive partitioning, random forest, extreme gradient boosting), 2) sample size (full data set or 10%, 25%, or 75% of cases dropped at random), 3) prediction periods (maximum 10, 15, or 20 y or uncensored), and 4) validation schemes (internal or external by centers/time). Tooth loss was generally a rare event (880 teeth were lost). All models showed limited sensitivity but high specificity. Patients' age and tooth loss at baseline as well as probing pocket depths showed high variable importance. More complex models (random forest, extreme gradient boosting) had no consistent advantages over simpler ones (logistic regression, recursive partitioning). Internal validation (in sample) overestimated the predictive power (area under the curve up to 0.90), while external validation (out of sample) found lower areas under the curve (range 0.62 to 0.82). Reducing the sample size decreased the predictive power, particularly for more complex models. Censoring the prediction period had only limited impact. When the model was trained in one period and tested in another, model outcomes were similar to the base case, indicating temporal validation as a valid option. No model showed higher accuracy than the no-information rate. In conclusion, none of the developed models would be useful in a clinical setting, despite high accuracy. During modeling, rigorous development and external validation should be applied and reported accordingly

Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison

Knowledge of the relative stabilities of alane (AlH3) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for thirty-eight alane complexes with NH3-nRn (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH2-nRn (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine-alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine, and obtaining upper limits of delta G for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. Based on this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system.Comment: Accepted by the Journal of Physical Chemistry

Three Years In--Changing Plan Features in the U.S. Health Insurance Marketplace

Background: A central objective of recent U.S. healthcare policy reform, most notably the Affordable Care Act\u27s (ACA) Health Insurance Marketplace, has been to increase access to stable, affordable health insurance. However, changing market dynamics (rising premiums, changes in issuer participation and plan availability) raise significant concerns about the marketplaces\u27 ability to provide a stable source of healthcare for Americans that rely on them. By looking at the effect of instability on changes in the consumer choice set, we can analyze potential incentives to switch plans among price-sensitive enrollees, which can then be used to inform policy going forward. Methods: Data on health plan features for non-tobacco users in 2512 counties in 34 states participating in federally-facilitated exchanges from 2014 to 2016 was obtained from the Centers for Medicaid & Medicare Services. We examined how changes in individual plan features, including premiums, deductibles, issuers, and plan types, impact consumers who had purchased the lowest-cost silver or bronze plan in their county the previous year. We calculated the cost of staying in the same plan versus switching to another plan the following year, and analyzed how costs vary across geographic regions. Results: In most counties in 2015 and 2016 (53.7 and 68.2%, respectively), the lowest-cost silver plan from the previous year was still available, but was no longer the cheapest plan. In these counties, consumers who switched to the new lowest-cost plan would pay less in monthly premiums on average, by $51.48 and$55.01, respectively, compared to staying in the same plan. Despite potential premium savings from switching, however, the majority would still pay higher average premiums compared to the previous year, and most would face higher deductibles and an increased probability of having to change provider networks. Conclusion: While the ACA has shown promise in expanding healthcare access, continued changes in the availability and affordability of health plans are likely to result in churning and switching among enrollees, which may have negative ramifications for their health going forward. Future healthcare policy reform should aim to stabilize marketplace dynamics in order to encourage greater care continuity and limit churning

Three years in – changing plan features in the U.S. health insurance marketplace

Abstract Background A central objective of recent U.S. healthcare policy reform, most notably the Affordable Care Act’s (ACA) Health Insurance Marketplace, has been to increase access to stable, affordable health insurance. However, changing market dynamics (rising premiums, changes in issuer participation and plan availability) raise significant concerns about the marketplaces’ ability to provide a stable source of healthcare for Americans that rely on them. By looking at the effect of instability on changes in the consumer choice set, we can analyze potential incentives to switch plans among price-sensitive enrollees, which can then be used to inform policy going forward. Methods Data on health plan features for non-tobacco users in 2512 counties in 34 states participating in federally-facilitated exchanges from 2014 to 2016 was obtained from the Centers for Medicaid & Medicare Services. We examined how changes in individual plan features, including premiums, deductibles, issuers, and plan types, impact consumers who had purchased the lowest-cost silver or bronze plan in their county the previous year. We calculated the cost of staying in the same plan versus switching to another plan the following year, and analyzed how costs vary across geographic regions. Results In most counties in 2015 and 2016 (53.7 and 68.2%, respectively), the lowest-cost silver plan from the previous year was still available, but was no longer the cheapest plan. In these counties, consumers who switched to the new lowest-cost plan would pay less in monthly premiums on average, by $51.48 and$55.01, respectively, compared to staying in the same plan. Despite potential premium savings from switching, however, the majority would still pay higher average premiums compared to the previous year, and most would face higher deductibles and an increased probability of having to change provider networks. Conclusion While the ACA has shown promise in expanding healthcare access, continued changes in the availability and affordability of health plans are likely to result in churning and switching among enrollees, which may have negative ramifications for their health going forward. Future healthcare policy reform should aim to stabilize marketplace dynamics in order to encourage greater care continuity and limit churning.https://deepblue.lib.umich.edu/bitstream/2027.42/144501/1/12913_2018_Article_3198.pd

White Lines and 3d-Occupancy for the 3d Transition-Metal Oxides

Electron energy-loss spectrometry was employed to measure the white lines at the L23 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L3/L2) was found to increase between d^0 and d^5 and decrease between d^5 and d^10, consistent with previous results for the transition metals and their oxides. The intensities of the white lines, normalized to the post-edge background, are linear for the 3d transition-metal oxides and lithium transition-metal oxides. An empirical correlation between normalized white-line intensity and 3d occupancy is established. It provides a method for measuring changes in the 3d-state occupancy. As an example, this empirical relationship is used to measure changes in the transition-metal valences of Li_{1-x}Ni_{0.8}Co_{0.2}O_2 in the range of 0 < x < 0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.Comment: 6 pages, 7 figure

Evaluation of a Tennessee statewide initiative to reduce early elective deliveries using quasi-experimental methods

Abstract Background Concerted quality improvement (QI) efforts have been taken to discourage the practice of early elective deliveries (EEDs), but few studies have robustly examined the impact of directed QI interventions in reducing EED practices. Using quasi-experimental methods, we sought to evaluate the impact of a statewide QI intervention to reduce the practice of EEDs. Methods Retrospective cohort study of vital records data (2007 to 2013) for all singleton births occurring ≥36 weeks in 66 Tennessee hospitals grouped into three QI cohorts. We used interrupted-time series to estimate the effect of the QI intervention on the likelihood of an EED birth statewide, and by hospital cohort. We compared the distribution of hospital EED percentages pre- and post-intervention. Lastly, we used multivariable logistic regression to estimate the effect of QI interventions on maternal and infant outcomes. Results Implementation of the QI intervention was associated with significant declines in likelihood of EEDs immediately following the intervention (odds ratio, OR = 0.72; p < 0.001), but these results varied by hospital cohort. Hospital risk-adjusted EED percentages ranged from 1.6–13.6% in the pre-intervention period, which significantly declined to 2.2–9.6% in the post-intervention period (p < 0.001). The QI intervention was also associated with significant reductions in operative vaginal delivery and perineal laceration, and immediate infant ventilation, but increased NICU admissions. Conclusions A statewide QI intervention to reduce EEDs was associated with modest but significant declines in EEDs beyond concurrent and national trends, and showed mixed results in related infant and maternal outcomes.https://deepblue.lib.umich.edu/bitstream/2027.42/148522/1/12913_2019_Article_4033.pd