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

Knowledge of the relative stabilities of alane (AlH(3)) 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 38 alane complexes with NH(3-n)R(n) (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH(2-n)R(n) (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 ΔG° 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. On the basis of 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

Do hydrotherapy exercise programmes improve exercise tolerance and quality of life in patients with chronic heart failure? A systematic review

The purpose of this study was to evaluate whether hydrotherapy programmes improve exercise tolerance and quality of life in patients with chronic heart failure. Data sources utilised were EBSCO, Scopus, Medline, PubMed, OVID, Proquest, PEDro and Cochrane Systematic Reviews databases. A systematic review of randomised controlled trials or quasi randomised controlled trials investigated hydrotherapy compared with a suitable control. Methodological quality was assessed using a modified version of the Downs and Black critical appraisal tool. Findings demonstrated that hydrotherapy was well tolerated with few adverse events reported. Two studies demonstrated hydrotherapy intervention groups significantly improved 6MWT from baseline (p≤0.05), while two studies found significantly greater improvements when compared to non-exercising (p=0.01) and land based exercising (p=0.001) controls. Four studies found significant gains (p≤0.05) in VO2 peak from baseline following hydrotherapy interventions. Two studies reported significant (p=0.01) intragroup improvements in total score of the Minnesota Living with Heart Failure Questionnaire in hydrotherapy intervention groups when compared with baseline and a non-exercising control respectively. In conclusion, hydrotherapy exercise programmes were well tolerated and appear to improve exercise capacity and quality of life in people with chronic heart failure but firm conclusions could not be drawn due to the poor to moderate quality of the evidence

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

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

Utilization of health care services by migrants in Europe-a systematic literature review.

Introduction: Our study reviewed the empirical evidence on the utilization of health care services by migrants in Europe, and on differences in health service utilization between migrants and non-migrants across European countries. Sources of data: A systematic literature review was performed, searching the databases Medline, Cinahl and Embase and covering the period from January 2009 to April 2016. The final number of articles included was 39. Areas of agreement: Utilization of accident and emergency services and hospitalizations were higher among migrants compared with non-migrants in most countries for which evidence was available. In contrast, screening and outpatient visits for specialized care were generally used less often by migrants. Areas of controversy: Utilization of general practitioner services among migrants compared with non-migrants presents a diverging picture. Growing points: Compared with previous systematic reviews, the results indicate a clearer picture of the differences in health service utilization between migrants and non-migrants in Europe. Areas timely for developing research: A comprehensive comparison across European countries is impossible because the number of studies is still limited. Further research should also help to identify barriers regarding the utilization of health care services by migrants

Mutual benefits? : Investigating a service teaching learning partnership

ABSTRACT: The study investigated a service learning partnership between mid-career teachers at a primary school in Atteridgeville and newly-qualified, mostly secondary, teachers from Nottingham University. The aim was to identify benefits and challenges with a view to optimising future partnerships. Data was gathered through participant observation and interviews, analysed by thematic content analysis and interpreted from a critical/postcolonial perspective. The research found a range of benefits accrued to the various stakeholders, including enhanced literacy teaching and learning, opportunities for shared teaching practice, and the lasting legacy of a functional library. While crosscultural contact was identified as a benefit, it also created some tensions related to equitable power-sharing. Therefore, recommendations for future partnerships include clear and consistent communication between partners regarding expectations, goals, and accountability, closer collaboration between partners, and proactive conflict resolution mechanisms. Finally, the research highlights the viable, yet scarcely tapped, potential of such partnerships to address both pre-service and in-service training needs in teacher education in South Africa

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

Convergence of the Generalized Volume Averaging Method on a Convection-Diffusion Problem: A Spectral Perspective

A mixed formulation is proposed and analyzed mathematically for coupled convection-diffusion in heterogeneous medias. Transfer in solid parts driven by pure diffusion is coupled with convection-diffusion transfer in fluid parts. This study is carried out for translation-invariant geometries (general infinite cylinders) and unidirectional flows. This formulation brings to the fore a new convection-diffusion operator, the properties of which are mathematically studied: its symmetry is first shown using a suitable scalar product. It is proved to be self-adjoint with compact resolvent on a simple Hilbert space. Its spectrum is characterized as being composed of a double set of eigenvalues: one converging towards −∞ and the other towards +∞, thus resulting in a nonsectorial operator. The decomposition of the convection-diffusion problem into a generalized eigenvalue problem permits the reduction of the original three-dimensional problem into a two-dimensional one. Despite the operator being nonsectorial, a complete solution on the infinite cylinder, associated to a step change of the wall temperature at the origin, is exhibited with the help of the operator’s two sets of eigenvalues/eigenfunctions. On the computational point of view, a mixed variational formulation is naturally associated to the eigenvalue problem. Numerical illustrations are provided for axisymmetrical situations, the convergence of which is found to be consistent with the numerical discretization

Retrospective analysis and clinical evaluation of mandible reconstruction with free fibula flap

The objective of this investigation was to evaluate the indications for and the functional and cosmetic results of mandible reconstruction using free vascularized fibular flaps. It was also designed to assess the patients' quality of life, daily activities, and self-esteem, with special emphasis on patient satisfaction. We conducted a retrospective chart review of all patients who underwent osseus or osteocutaneous free flap reconstruction of the mandible over a 10-year period (1992-2002). Those in whom a vascularized fibular flap was used were included in the study and invited for a follow-up comprehensive physical examination and x-ray evaluation. A questionnaire was also administered to evaluate patient satisfaction. Twenty-six patients were included in the study. Fourteen patients died after an average of 2years and 9months postoperatively due to their prognosis despite surgical intervention and adjuvant therapy. Of the remaining 12 patients, 6 appeared for the follow-up evaluation, 2 were unavailable for follow-up, and 4 denied participating. Of these 6 patients, all experienced a decrease in pain and were satisfied with their results. At the time of the latest follow-up, they experienced some difficulties swallowing, and in 3 patients, their articulation was impaired. All 6 patients would undergo the procedure again. Reconstruction of the mandible using a vascularized fibular graft produces satisfactory functional and cosmetic results. In benign lesions, the procedure is highly indicated. However, in the case of malignancy, most patients do not survive their primary tumor. Given the patients limited life expectancy, the improvement in their quality of life as a result of the improved appearance and function of the reconstructed mandible needs to be weighed against the potential morbidity of the operative intervention on an individual basi