329 research outputs found

    A QM/MM approach for the study of monolayer-protected gold clusters

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    We report the development and implementation of hybrid methods that combine quantum mechanics (QM) with molecular mechanics (MM) to theoretically characterize thiolated gold clusters. We use, as training systems, structures such as Au25(SCH2-R)18 and Au38(SCH2-R)24, which can be readily compared with recent crystallographic data. We envision that such an approach will lead to an accurate description of key structural and electronic signatures at a fraction of the cost of a full quantum chemical treatment. As an example, we demonstrate that calculations of the 1H and 13C NMR shielding constants with our proposed QM/MM model maintain the qualitative features of a full DFT calculation, with an order-of-magnitude increase in computational efficiency.Comment: Journal of Materials Science, 201

    Lawson Criterion for Ignition Exceeded in an Inertial Fusion Experiment

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    For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin burn propagation into surrounding cold fuel, enabling the possibility of high energy gain. While scientific breakeven (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion

    An Analytic Study of the Professional Development Research in Early Childhood Education

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    The goal of this study was to examine empirical research on the design, delivery, and measurement of the effects of professional development (PD) for early childhood educators in order to provide insight into what the field has accomplished as well as suggest directions for future PD programs and research. Through the use of rigorous inclusion criteria outlined by S. M. Wilson, R. E. Floden, and J. Ferrini-Mundy (2001), 73 studies were included and analyzed. On average, 25% (M = 12.68, SD = 9.99) of references in each study were specifically about PD. The majority of studies (n = 39) targeted some form of language and literacy instruction, whereas only 5 studies targeted math and 1 study targeted science. A total of 35 different delivery mechanisms were used to provide PD, with 40 studies including some form of coaching and 45 including training workshops. The studies used a wide range of methods to measure PD-related outcomes: 51% (n = 37) of studies examined changes in teacher practice, 18% (n = 13) measured changes in teachers’ knowledge, 40% (n = 29) measured changes in children’s learning, and 11% (n = 8) measured changes in children’s behavior. Practice or Policy: Based on the results of this study, there are 4 major ways in which PD for early childhood educators can be developed. Researchers and providers of PD should (a) continue to draw from multiple resources to inform PD implementation designs, (b) include more diversity in the content of instruction targeted by PD, (c) experiment with innovative formats for delivering PD, and (d) create better means of evaluating PD

    Electronic Structure and Bonding of Icosahedral Core-Shell Gold-Silver Nanoalloy Clusters Au_(144-x)Ag_x(SR)_60

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    Atomically precise thiolate-stabilized gold nanoclusters are currently of interest for many cross-disciplinary applications in chemistry, physics and molecular biology. Very recently, synthesis and electronic properties of "nanoalloy" clusters Au_(144-x)Ag_x(SR)_60 were reported. Here, density functional theory is used for electronic structure and bonding in Au_(144-x)Ag_x(SR)_60 based on a structural model of the icosahedral Au_144(SR)_60 that features a 114-atom metal core with 60 symmetry-equivalent surface sites, and a protecting layer of 30 RSAuSR units. In the optimal configuration the 60 surface sites of the core are occupied by silver in Au_84Ag_60(SR)_60. Silver enhances the electron shell structure around the Fermi level in the metal core, which predicts a structured absorption spectrum around the onset (about 0.8 eV) of electronic metal-to-metal transitions. The calculations also imply element-dependent absorption edges for Au(5d) \rightarrow Au(6sp) and Ag(4d) \rightarrow Ag(5sp) interband transitions in the "plasmonic" region, with their relative intensities controlled by the Ag/Au mixing ratio.Comment: 4 figure

    Validation of the questionnaire on beliefs about medication with type 2 diabetic patients

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    O presente trabalho teve como objectivo validar o QuestionĂĄrio Crenças sobre a Medicação, que avalia Crenças Gerais e Crenças EspecĂ­ficas, estudando suas propriedades psicomĂ©tricas em uma amostra de 387 pacientes diabĂ©ticos tipo 2. O estudo de validade para as Crenças Gerais revelou uma solução de um factor, com um alfa de 0,76, e para as Crenças EspecĂ­ficas, dois factores – Necessidades e PreocupaçÔes –, com um alfa de 0,77 e 0,69 respectivamente. Quanto Ă  validade de constructo, verificou-se uma relação entre as Crenças Gerais e a subescala Necessidades das Crenças EspecĂ­ficas com AdesĂŁo Ă  Medicação, avaliada pela Escala de Avaliação de AderĂȘncia MĂ©dica. O instrumento apresenta boas qualidades psicomĂ©tricas para ser utilizado em pacientes diabĂ©ticos tipo 2.The present paper focused on the validation of the Questionnaire on Beliefs about Medication, which assesses both General Beliefs and Specific Beliefs. The psychometric properties of the instrument were analyzed on a sample of 387 type 2 diabetic patients. The validity study for General Beliefs found a unifactorial solution, with an alpha of .76, and for Specific Beliefs, a two-factor solution – Necessities and Concern –, with an alpha of .77 and .69, respectively. In terms of construct validity, a relationship between General Beliefs, subscale Necessities from Specific Beliefs, and adherence to medication, as evaluated by Medical Adherence Rating Scale, was found. The instrument presents good psychometric qualities to be used in type 2 diabetic patients.Fundação para a CiĂȘncia e Tecnologia (FCT

    Achievement of target gain larger than unity in an inertial fusion experiment.

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    On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result

    What works for whom in the management of diabetes in people living with dementia: a realist review

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    Background Dementia and diabetes mellitus are common long-term conditions and co-exist in a large number of older people. People living with dementia (PLWD) may be less able to manage their diabetes, putting them at increased risk of complications such as hypoglycaemia. The aim of this review was to identify key mechanisms within different interventions that are likely to improve diabetes outcomes in PLWD. Methods This is a realist review involving scoping of the literature and stakeholder interviews to develop theoretical explanations of how interventions might work, systematic searches of the evidence to test and develop the theories and their validation with a purposive sample of stakeholders. Twenty-six stakeholders — user/patient representatives, dementia care providers, clinicians specialising in diabetes or dementia and researchers — took part in interviews, and 24 participated in a consensus conference. Results We included 89 papers. Ten focused on PLWD and diabetes, and the remainder related to people with either dementia, diabetes or other long-term conditions. We identified six context-mechanism-outcome configurations which provide an explanatory account of how interventions might work to improve the management of diabetes in PLWD. This includes embedding positive attitudes towards PLWD, person-centred approaches to care planning, developing skills to provide tailored and flexible care, regular contact, family engagement and usability of assistive devices. An overarching contingency emerged concerning the synergy between an intervention strategy, the dementia trajectory and social and environmental factors, especially family involvement. Conclusions Evidence highlighted the need for personalised care, continuity and family-centred approaches, although there was limited evidence that this happens routinely. This review suggests there is a need for a flexible service model that prioritises quality of life, independence and patient and carer priorities. Future research on the management of diabetes in older people with complex health needs, including those with dementia, needs to look at how organisational structures and workforce development can be better aligned to their needs. Trial registration PROSPERO, CRD42015020625. Registered on 18 May 2015
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