922 research outputs found
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
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
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
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
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ALUMINUM HYDRIDE, A1H3, AS A HYDROGEN STORAGE COMPOUND.
Aluminum hydride is a covalent, binary hydride that has been known for more than 60 years and is an attractive medium for on-board automotive hydrogen storage, since it contains 10.1% by wt. hydrogen with a density of 1.48 g/ml. There are at least 7 non-solvated AlH{sub 3} phases, namely {alpha}, {alpha}{prime}, {beta}, {gamma}, {var_epsilon} and {zeta}. The properties of {alpha}-AlH{sub 3}, obtained from the Dow Chemical Co. in 1980, have been previously reported. Here we present a description of the thermodynamic and kinetic properties of freshly prepared {alpha}, {beta} and {gamma} phases of AlH{sub 3}. In all cases the decomposition kinetics are appreciable below 100 C and all will meet the DOE 2010 gravimetric and volumetric vehicular system targets (6 wt% H{sub 2} and 0.045 kg/L). However, further research will be required to develop an efficient and economical process to regenerate AlH{sub 3} from the spent Al powder
The pleasures and perils of inheritance
Facing death, reflecting on one’s legacies (material and ethical, personal and political) and the legal and interpersonal attempts to resolve or prevent inheritance conflicts, all bring to the fore constructions of memory and identity, intergenerational relations, and the complexities of doing and undoing family and kinship. Consequently, drawing attention to inheritance, keeping sight of it, and bringing it into play is a useful piece of the puzzle of ageing across a range of disciplines and this article provides an overview of some of the key themes in this emerging field
An examination of health care utilization during the COVID-19 pandemic among women with early-stage hormone receptor-positive breast cancer
Background: Women undergoing treatment for breast cancer require frequent clinic visits for maintenance of therapy. With COVID-19 causing health care disruptions, it is important to learn about how this population’s access to health care has changed. This study compares self-reported health care utilization and changes in factors related to health care access among women treated at a cancer center in the mid-South US before and during the pandemic. Methods: Participants (N = 306) part of a longitudinal study to improve adjuvant endocrine therapy (AET) adherence completed pre-intervention baseline surveys about their health care utilization prior to AET initiation. Questions about the impact of COVID-19 were added after the pandemic started assessing financial loss and factors related to care. Participants were categorized into three time periods based on the survey completion date: (1) pre-COVID (December 2018 to March 2020), (2) early COVID (April 2020 – December 2020), and later COVID (January 2021 to June 2021). Negative binomial regression analyses used to compare health care utilization at different phases of the pandemic controlling for patient characteristics. Results: Adjusted analyses indicated office visits declined from pre-COVID, with an adjusted average of 17.7 visits, to 12.1 visits during the early COVID period (p = 0.01) and 9.9 visits during the later COVID period (p < 0.01). Hospitalizations declined from an adjusted average 0.45 admissions during early COVID to 0.21 during later COVID, after vaccines became available (p = 0.05). Among COVID period participants, the proportion reporting changes/gaps in health insurance coverage increased from 9.5% participants during early-COVID to 14.8% in the later-COVID period (p = 0.05). The proportion reporting financial loss due to the pandemic was similar during both COVID periods (34.3% early- and 37.7% later-COVID, p = 0.72). The proportion of participants reporting delaying care or refilling prescriptions decreased from 15.2% in early-COVID to 4.9% in the later-COVID period (p = 0.04). Conclusion: COVID-19 caused disruptions to routine health care for women with breast cancer. Patients reported having fewer office visits at the start of the pandemic that continued to decrease even after vaccines were available. Fewer patients reported delaying in-person care as the pandemic progressed.National Cancer Institute ; Division of Cancer Prevention, National Cancer Institute ; Center for Strategic Scientific Initiatives, National Cancer Institute ; Division of Cancer Epidemiology and Genetics, National Cancer Institut
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