655 research outputs found
Systematic calculation of molecular vibrational spectra through a complete Morse expansion
We propose an accurate and efficient method to compute vibrational spectra of
molecules, based on exact diagonalization of an algebraically calculated matrix
based on powers of Morse coordinate. The present work focuses on the 1D
potential of diatomic molecules: as typical examples, we apply this method to
the standard Lennard-Jones oscillator, and to the ab initio potential of the H2
molecule. Global cm-1 accuracy is exhibited through the H2 spectrum, obtained
through the diagonalization of a 30 x 30 matrix. This theory is at the root of
a new method to obtain globally accurate vibrational spectral data in the
context of the multi-dimensional potential of polyatomic molecules, at an
affordable computational cost.Comment: 30 pages including 6 figure
Supersymmetry and the relationship between a class of singular potentials in arbitrary dimensions
The eigenvalues of the potentials
and
, and of the special cases of these potentials such as the Kratzer and
Goldman-Krivchenkov potentials, are obtained in N-dimensional space. The
explicit dependence of these potentials in higher-dimensional space is
discussed, which have not been previously covered.Comment: 13 pages article in LaTEX (uses standard article.sty). Please check
"http://www1.gantep.edu.tr/~ozer" for other studies of Nuclear Physics Group
at University of Gaziante
Markets for Nutrition: What Role for Business?
Policymakers are increasingly seeking to use food systems to help reduce rates of chronic undernutrition and to use markets to deliver nutrient?rich foods to vulnerable populations. This article examines how this might be achieved, drawing lessons from three intervention types: ready?to?use therapeutic foods (RUTFs), mandatory fortification and voluntarily fortified products. We find that a common set of constraints tends to inhibit markets from delivering nutrition and makes it difficult to reach populations at the âbottom of the pyramidâ. Overcoming these constraints requires a shift from working at the level of individual businesses to that of market and food systems. It also suggests a need for renewed focus on the effectiveness of products in reaching key groups, on the informal markets that serve the poor and on the inherent complexity of market systems. These findings suggest that food and nutrition policies and partnerships should be based on principles of experimentation and adaptive learning
Cytogerontology since 1881: A reappraisal of August Weismann and a review of modern progress
Cytogerontology, the science of cellular ageing, originated in 1881 with the prediction by August Weismann that the somatic cells of higher animals have limited division potential. Weismann's prediction was derived by considering the role of natural selection in regulating the duration of an organism's life. For various reasons, Weismann's ideas on ageing fell into neglect following his death in 1914, and cytogerontology has only reappeared as a major research area following the demonstration by Hayflick and Moorhead in the early 1960s that diploid human fibroblasts are restricted to a finite number of divisions in vitro.
In this review we give a detailed account of Weismann's theory, and we reveal that his ideas were both more extensive in their scope and more pertinent to current research than is generally recognised. We also appraise the progress which has been made over the past hundred years in investigating the causes of ageing, with particular emphasis being given to (i) the evolution of ageing, and (ii) ageing at the cellular level. We critically assess the current state of knowledge in these areas and recommend a series of points as primary targets for future research
Towards an effective potential for the monomer, dimer, hexamer, solid and liquid forms of hydrogen fluoride
We present an attempt to build up a new two-body effective potential for
hydrogen fluoride, fitted to theoretical and experimental data relevant not
only to the gas and liquid phases, but also to the crystal. The model is simple
enough to be used in Molecular Dynamics and Monte Carlo simulations. The
potential consists of: a) an intra-molecular contribution, allowing for
variations of the molecular length, plus b) an inter-molecular part, with three
charged sites on each monomer and a Buckingham "exp-6" interaction between
fluorines. The model is able to reproduce a significant number of observables
on the monomer, dimer, hexamer, solid and liquid forms of HF. The shortcomings
of the model are pointed out and possible improvements are finally discussed.Comment: LaTeX, 24 pages, 2 figures. For related papers see also
http://www.chim.unifi.it:8080/~valle
Access and utilisation of maternity care for disabled women who experience domestic abuse:a systematic review
BACKGROUND: Although disabled women are significantly more likely to experience domestic abuse during pregnancy than non-disabled women, very little is known about how maternity care access and utilisation is affected by the co-existence of disability and domestic abuse. This systematic review of the literature explored how domestic abuse impacts upon disabled womenâs access to maternity services. METHODS: Eleven articles were identified through a search of six electronic databases and data were analysed to identify: the factors that facilitate or compromise access to care; the consequences of inadequate care for pregnant womenâs health and wellbeing; and the effectiveness of existing strategies for improvement. RESULTS: Findings indicate that a mental health diagnosis, poor relationships with health professionals and environmental barriers can compromise womenâs utilisation of maternity services. Domestic abuse can both compromise, and catalyse, access to services and social support is a positive factor when accessing care. Delayed and inadequate care has adverse effects on womenâs physical and psychological health, however further research is required to fully explore the nature and extent of these consequences. Only one study identified strategies currently being used to improve access to services for disabled women experiencing abuse. CONCLUSIONS: Based upon the barriers and facilitators identified within the review, we suggest that future strategies for improvement should focus on: understanding womenâs reasons for accessing care; fostering positive relationships; being women-centred; promoting environmental accessibility; and improving the strength of the evidence base
Molecular determinants for subcellular trafficking of the malarial sheddase PfSUB2.
The malaria merozoite invades erythrocytes in the vertebrate host. Iterative rounds of asexual intraerythrocytic replication result in disease. Proteases play pivotal roles in erythrocyte invasion, but little is understood about their mode of action. The Plasmodium falciparum malaria merozoite surface sheddase, PfSUB2, is one such poorly characterized example. We have examined the molecular determinants that underlie the mechanisms by which PfSUB2 is trafficked initially to invasion-associated apical organelles (micronemes) and then across the surface of the free merozoite. We show that authentic promoter activity is important for correct localization of PfSUB2, likely requiring canonical features within the intergenic region 5' of the pfsub2 locus. We further demonstrate that trafficking of PfSUB2 beyond an early compartment in the secretory pathway requires autocatalytic protease activity. Finally, we show that the PfSUB2 transmembrane domain is required for microneme targeting, while the cytoplasmic domain is essential for surface translocation of the protease to the parasite posterior following discharge from micronemes. The interplay of pre- and post-translational regulatory elements that coordinate subcellular trafficking of PfSUB2 provides the parasite with exquisite control over enzyme-substrate interactions
How environmental managers perceive and approach the issue of invasive species: the case of Japanese knotweed s.l. (RhĂŽne River, France)
We would like to thank Springer for publishing our article. The final publication is available at http://link.springer.com/article/10.1007%2Fs10530-015-0969-1International audienceStudying the perceptions of stakeholders or interested parties is a good way to better understand behaviours and decisions. This is especially true for the management of invasive species such as Japanese knotweed s.l. This plant has spread widely in the RhĂŽne basin, where signiïŹcant ïŹnancial resources have been devoted to its management. However, no control technique is recognized as being particularly effective. Many uncertainties remain and many documents have been produced by environmental managers to disseminate current knowledge about the plant and its management. This article aims at characterizing the perceptions that environmental managers have of Japanese knotweed s.l. A discourse analysis was conducted on the printed documentation produced about Japanese knotweed s.l. by environmental managers working along the RhĂŽne River (France). The corpus was both qualitatively and quantitatively analysed. The results indicated a diversity of perceptions depending on the type of environmental managers involved, as well as the geographicalareas and scales on which they acted. Whereas some focused on general knowledge relating to the origins and strategies of colonization, others emphasized the diversity and efïŹcacy of the prospective eradication techniques. There is a real interest in implementing targeted actions to meet local issues. To do so, however, these issues must be better deïŹned. This is a challenging task, as it must involve all types of stakeholders
Cognitive and environmental predictors of early literacy skills
Not all young children benefit from book exposure in preschool age. It is claimed that the ability to hold information in mind (short-term memory), to ignore distraction (inhibition), and to focus attention and stay focused (sustained attention) may have a moderating effect on childrenâs reactions to the home literacy environment. In a group of 228 junior kindergarten children with a native Dutch background, with a mean age of 54.29Â months (SDÂ =Â 2.12Â months), we explored therefore the relationship between book exposure, cognitive control and early literacy skills. Parents filled in a HLE questionnaire (book sharing frequency and an author recognition checklist as indicator of parental leisure reading habits), and children completed several tests in individual sessions with the researcher (a book-cover recognition test, PPVT, letter knowledge test, the subtests categories and patterns of the SON, and cognitive control measures namely digit span of the KABC, a peg tapping task and sustained attention of the ANT). Main findings were: (1) Childrenâs storybook knowledge mediated the relationship between home literacy environment and literacy skills. (2) Both vocabulary and letter knowledge were predicted by book exposure. (3) Short-term memory predicted vocabulary over and above book exposure. (4) None of the cognitive control mechanisms moderated the beneficial effects of book exposure
Zimbabwean diabetics' beliefs about health and illness: an interview study
<p>Abstract</p> <p>Background</p> <p>Diabetes mellitus (DM) is increasing globally, with the greatest increase in Africa and Asia. In Zimbabwe a threefold increase was shown in the 1990s. Health-related behaviour is important in maintaining health and is determined by individual beliefs about health and illness but has seen little study. The purpose of the study was to explore beliefs about health and illness that might affect self-care practice and health care seeking behaviour in persons diagnosed with DM, living in Zimbabwe.</p> <p>Methods</p> <p>Exploratory study. Consecutive sample from a diabetes clinic at a central hospital. Semi-structured interviews were held with 21 persons aged 19-65 years. Data were analysed using qualitative content analysis.</p> <p>Results</p> <p>Health was described as freedom from disease and well-being, and individual factors such as compliance with advice received and drugs were considered important to promote health. A mixture of causes of DM, predominantly individual factors such as heredity, overweight and wrong diet in combination with supernatural factors such as fate, punishment from God and witchcraft were mentioned. Most respondents did not recognize the symptoms of DM when falling ill but related the problems to other diseases, e.g. HIV, malaria etc. Limited knowledge about DM and the body was indicated. Poor economy was mentioned as harmful to health and a consequence of DM because the need to buy expensive drugs, food and attend check-ups. Self-care was used to a limited extent but if used, a combination of individual measures, household remedies or herbs and religious acts such as prayers and holy water were frequently used, and in some cases health care professionals were consulted.</p> <p>Conclusions</p> <p>Limited knowledge about DM, based on beliefs about health and illness including biomedical and traditional explanations related to the influence of supernatural forces, e.g. fate, God etc., were found, which affected patients' self-care and care-seeking behaviour. Strained economy was stated to be a factor of the utmost importance affecting the management of DM and thus health. To develop cost-effective and optimal diabetes care in a country with limited resources, not only educational efforts based on individual beliefs are needed but also considering systemic and structural conditions in order to promote health and to prevent costly consequences of DM.</p
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