3,426 research outputs found

    Kinetics of Surfactant Adsorption at Fluid/Fluid Interfaces: Non-ionic Surfactants

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    We present a model treating the kinetics of adsorption of soluble surface-active molecules at the interface between an aqueous solution and another fluid phase. The model accounts for both the diffusive transport inside the solution and the kinetics taking place at the interface using a free-energy formulation. In addition, it offers a general method of calculating dynamic surface tensions. Non-ionic surfactants are shown, in general, to undergo a diffusion-limited adsorption, in accord with experimental findings.Comment: 6 pages, 3 figures, see also cond-mat/960814

    Tests for, origins of, and corrections to non-Gaussian statistics. The dipole-flip model

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    The following article appeared in Schile, A. J., & Thompson, W. H. (2017). Tests for, origins of, and corrections to non-Gaussian statistics. The dipole-flip model. The Journal of Chemical Physics, 146(15), 154109. and may be found at https://aip.scitation.org/doi/abs/10.1063/1.4981009.Linear response approximations are central to our understanding and simulations of nonequilibrium statistical mechanics. Despite the success of these approaches in predicting nonequilibrium dynamics, open questions remain. Laird and Thompson [J. Chem. Phys. 126, 211104 (2007)] previously formalized, in the context of solvation dynamics, the connection between the static linear-response approximation and the assumption of Gaussian statistics. The Gaussian statistics perspective is useful in understanding why linear response approximations are still accurate for perturbations much larger than thermal energies. In this paper, we use this approach to address three outstanding issues in the context of the “dipole-flip” model, which is known to exhibit nonlinear response. First, we demonstrate how non-Gaussian statistics can be predicted from purely equilibrium molecular dynamics (MD) simulations (i.e., without resort to a full nonequilibrium MD as is the current practice). Second, we show that the Gaussian statistics approximation may also be used to identify the physical origins of nonlinear response residing in a small number of coordinates. Third, we explore an approach for correcting the Gaussian statistics approximation for nonlinear response effects using the same equilibrium simulation. The results are discussed in the context of several other examples of nonlinear responses throughout the literature

    Examining Turnover Intention: Preparedness, Retention, and Certification Type

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    A capstone submitted in partial fulfillment of the requirements for the degree of Doctor of Education in the Ernst and Sara Lane Volgenau College of Education at Morehead State University by Rachel H. Addison-Miller and Pamela O. Puryear on April 12, 2024

    Value Co-creation in Buy Online Pickup In-store (BOPIS)

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    The purpose of this study is to identify consumer attitudes toward buy online pickup in-store (BOPIS). This study examines how value perceptions change as consumers progress in the online ordering and physical pickup processes within the BOPIS channel. We use a multivariate regression and two separate multiple regression analyses to examine the differential effects of multiple constructs on BOPIS customer satisfaction. As consumers start the process by engaging with the retailer online, perceived usefulness and hedonic value online play a critical role in customer satisfaction. Consumer attitudes change as they pick up their order at the store where the degree of ease and hedonic pickup in collecting their products increases in importance in customer satisfaction. Furthermore, the study findings suggest a halo-effect for trust on BOPIS customer satisfaction. As BOPIS continues to expand into various industries, understanding the complexity of consumer value will be of importance to improve the omni-channel experience

    A Review of Leaf-mining Insects and Control Options for their Management, with Special Reference to Holocacista capensis (Lepidoptera: Heliozelidae) in Vineyards in South Africa

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    A leaf-mining pest occurring on commercial varieties of Vitis vinifera in South Africa was investigated due to the presence of cocoons on fruit. The leaf miner, Holocacista capensis, was reported on grapevines in 2012. Since its discovery on commercial grape varieties, control strategies have consisted solely of insecticide applications. Despite the fact that the leaf-mining habit is taxonomically diverse and considered ancient, little is generally known of leaf-mining larvae. A review was conducted in order to better understand the leaf-mining strategy and amalgamate the current knowledge of other leaf-mining insects.  The general evolutionary history within the full complement of taxa that display the leaf-mining habit is discussed. The review focuses on lepidopteran leaf-mining pests and discloses the known information associated with the first report and the impact of H. capensis in the Western Cape, South Africa. As no control methods have been identified for H. capensis in vineyards, various chemical, biological and cultural control strategies adopted for other leaf-mining pests were investigated. Control options, including theuse of entomopathogenic nematodes (EPNs), parasitoids, physical and cultural control measures, were considered and are discussed. Alternate control methods are pertinent for the grape-growing industry to avoid the development of the insecticide resistance that is common amongst leaf miners. This review aims to consolidate the available literature and therefore aid in the development of an integrated pest management strategy to effectively control H. capensis in infested vineyards in South Africa

    Variation in contents of crude protein and mineral elements in 32 cowpea (Vigna unguiculata (L.) Walp) accessions in Ghana

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    Thirty-two cowpea accessions were studied for variation in contents of protein and mineral nutrients (calcium, magnesium, potassium and sodium). Cowpea flour from 40 wholesome dried seeds of each accession was used for the analysis. The wet oxidation method was used to determine the content of mineral nutrients. Nitrogen content was determined by the Kjeldahl procedure. Protein content ranged from 16.35 to 27.27 per cent. Sodium content ranged from 90.53 to 91.30 ppm, and potassium content from 30.33 to 71.30 ppm. Similarly, values for magnesium and calcium ranged from 146.73 to 968.20 ppm and from 43.33 to 171.20 ppm, respectively. Percent crude protein correlated significantly positively with sodium and negatively with calcium. Magnesium was correlated significantly with potassium. Black seeds generally recorded the highest percent crude protein on the average, while cream seeds had the highest magnesium and calcium contents, respectively. Trente-deux accessions de dolique étaient étudiées pour la variation en teneurs de protéines et de nutriments minérales (le calcium). La farine de dolique de quarante graines saines séchés de chaque accession était utilisée pour l'analyse. La détermination de nutriments minérales était par la méthode d'oxydation humide. La teneur d'azote était déterminée par la procédure de Kjeldahl. Teneur de protéine variait entre 16.35 et 27.27 %. La teneur de sodium variait entre 90.53 et 91.30 ppm, la teneur de potassium variait entre 30.33 et 71.30 ppm. De la même façon les valeurs pour le magnésium et le calcium variaient respectivement entre 146.73 et 98.20 ppm et entre 43.33 et 171.20 ppm. Le pourcentage de protéine brute corrélait considérablement positivement avec sodium en négativement avec calcium. Le magnésium était corrélé considérablement avec le potassium. Les graines colorées noires enregistraient en général le plus élevé du pourcentage de protéine brute en moyenne, alors que les graines colorées crèmes avaient les teneurs de magnésium et de calcium les plus élevées respectivement. Ghana Journal of Agricultural Science Vol. 39 (1) 2006: pp. 83-8

    History of Childhood Physical Abuse and Current Risky Drinking: The Role of Coping Motives

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    A childhood history of physical abuse is associated with increased risky drinking in adolescence, and a two-fold risk of alcohol dependence. Research on substance use disorders (SUD) suggests that people who drink with the motivation to cope with their emotions face a greater risk of SUD. Given that childhood physical abuse is associated with emotional difficulties, the current study examined the interplay between childhood physical discipline (inclusive of abuse) and coping motives in predicting risky drinking. Specifically, we expected ratings of childhood physical discipline and current risky drinking to be associated positively and for that relation to be mediated (explained) to some extent by their motivation to drink for emotional coping

    Aid to conflict-affected countries : lessons for donors

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    The first section looks at the implications of conflict for aid effectiveness and selectivity. We argue that, while aid is generally effective in promoting growth and by implication reducing poverty, it is more effective in promoting growth in post-conflict countries. We then consider the implications of these findings for donor selectivity models and for assessment of donor performance in allocating development aid among recipient countries. We argue that, while further research on aid effectiveness in post-conflict scenarios is needed, existing selectivity models should be augmented with, inter alia, post-conflict variables, and donors should be evaluated on the basis, inter alia, of the share of their aid budgets allocated to countries experiencing post-conflict episodes. We also argue for aid delivered in the form of projects to countries with weak institutions in early post-conflict years. The second section focuses on policies for donors operating in conflict-affected countries. We set out five of the most important principles: (1) focus on broad-based recovery from war; (2) to achieve a broad-based recovery, get involved before the conflict ends; (3) focus on poverty, but avoid &lsquo;wish lists&rsquo;; (4) help to reduce insecurity so aid can contribute more effectively to growth and poverty reduction; and (5) in economic reform, focus on improving public expenditure management and revenue mobilisation. The third section concludes by emphasising the fact that there is no hard or fast dividing line between &lsquo;war&rsquo; and &lsquo;peace&rsquo; and that it may take many years for a society to become truly &lsquo;post&rsquo;-conflict&rsquo;. Donors, therefore, need to prepare for the long haul.<br /
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