783,615 research outputs found

    Electrolytic depletion interactions

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    We consider the interactions between two uncharged planar macroscopic surfaces immersed in an electrolyte solution which are induced by interfacial selectivity. These forces are taken into account by introducing a depletion free-energy density functional, in addition to the usual mean-field Poisson-Boltzmann functional. The minimization of the total free-energy functional yields the density profiles of the microions and the electrostatic potential. The disjoining pressure is obtained by differentiation of the total free energy with respect to the separation of the surfaces, holding the range and strength of the depletion forces constant. We find that the induced interaction between the two surfaces is always repulsive for sufficiently large separations, and becomes attractive at shorter separations. The nature of the induced interactions changes from attractive to repulsive at a distance corresponding to the range of the depletion forces.Comment: 17 pages, 4 Postscript figures, submitted to Physical Review

    Full Disclosure: Financial Statement Disclosures Under CERCLA

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    This paper presents a comprehensive mathematical framework for depletion rate analysis and ties it to the physics of depletion. Theory was compared with empirical data from 1036 fields and a number of regions. Strong agreement between theory and practice was found, indicating that the framework is plausible. Both single fields and entire regions exhibit similar depletion rate patterns, showing the generality of the approach. The maximum depletion rates for fields were found to be well described by a Weibull distribution. Depletion rates were also found to strongly correlate with decline rates. In particular, the depletion rate at peak was shown to be useful for predicting the future decline rate. Studies of regions indicate that a depletion rate of remaining recoverable resources in the range of 2–3% is consistent with historical experience. This agrees well with earlier “peak oil” forecasts and indicates that they rest on a solid scientific ground.

    Does a brief mindfulness intervention counteract the detrimental effects of ego-depletion in basketball free throw under pressure?

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    Research has shown that a brief mindfulness intervention may counteract the depleting effects of an emotion suppression task upon a subsequent psychological task that requires self-control. However, the effects of a brief mindfulness intervention on perceptual–motor tasks particularly in stressful situations have not yet been examined. The purpose of this study was to investigate whether a brief mindfulness intervention can counteract the detrimental effects of ego-depletion in basketball free throw performance under pressure. Seventy-two basketball players (mean age = 28.6 ± 4.0 yrs) were randomly assigned to one of the following 4 groups: depletion/mindfulness, no depletion/mindfulness, depletion/no mindfulness and control (no depletion/no mindfulness). The mindfulness intervention consisted of a 15-min breathe and body mindfulness audio exercise, while the control condition (no mindfulness) listened to an audio book. A modified Stroop color-word task was used to manipulate self–control and induce ego depletion. Participants performed 30 free throws before and after the experimental manipulations. Results showed that basketball players’ free throw performance decreased after ego-depletion, but when ego-depletion was followed by the mindfulness intervention, free throw performance was maintained at a level similar to the control group. Our results indicate that a brief mindfulness intervention mitigates the effects of ego depletion in a basketball free-throw task

    Book Review

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    Acute cholesterol depletion is generally associated with decreased or abolished T cell signalling but it can also cause T cell activation. This anomaly has been addressed in Jurkat T cells using progressive cholesterol depletion with methyl-beta-cyclodextrin (MBCD). At depletion levels higher than 50% there is substantial cell death, which explains reports of signalling inhibition. At 10–20% depletion levels, tyrosine phosphorylation is increased, ERK is activated and there is a small increase in cytoplasmic Ca2+. Peripheral actin polymerisation is also triggered by limited cholesterol depletion. Strikingly, the lipid raft marker GM1 aggregates upon cholesterol depletion and these aggregated domains concentrate the signalling proteins Lck and LAT, whereas the opposite is true for the non lipid raft marker the transferrin receptor. Using PP2, an inhibitor of Src family kinase activation, it is demonstrated that the lipid raft aggregation occurs independently of and thus upstream of the signalling response. Upon cholesterol depletion there is an increase in overall plasma membrane order, indicative of more ordered domains forming at the expense of disordered domains. That cholesterol depletion and not unspecific effects of MBCD was behind the reported results was confirmed by performing all experiments with MBCD–cholesterol, when no net cholesterol extraction took place. We conclude that non-lethal cholesterol depletion causes the aggregation of lipid rafts which then induces T cell signalling

    Depletion and social reproduction

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    Much work has been done on the unaccounted contribution of social reproductive work to national economies. What has been less studied is the consequence of this neglect for individuals, households and communities engaged in social reproduction. Where these consequences have been recognised, it has largely been in the context of economic crises. So, for example, Elson has pointed out in her analysis of gendered impact of crises, "If too much pressure is put upon the domestic sector to provide unpaid care work to make up for deficiencies elsewhere, the result may be a depletion of human capabilities, ...To maintain and enhance human capabilities, the domestic sector needs adequate inputs from all other sectors. It cannot be treated as a bottomless well, able to provide the care needed regardless of the resources it gets from the other sectors" (2000:28). In this paper we take this insight and develop it in the context of the everyday political economy. We argue that the inputs into social reproduction are less than the outputs generated by it. We term this difference depletion

    Tuning Nanocrystal Surface Depletion by Controlling Dopant Distribution as a Route Toward Enhanced Film Conductivity

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    Electron conduction through bare metal oxide nanocrystal (NC) films is hindered by surface depletion regions resulting from the presence of surface states. We control the radial dopant distribution in tin-doped indium oxide (ITO) NCs as a means to manipulate the NC depletion width. We find in films of ITO NCs of equal overall dopant concentration that those with dopant-enriched surfaces show decreased depletion width and increased conductivity. Variable temperature conductivity data shows electron localization length increases and associated depletion width decreases monotonically with increased density of dopants near the NC surface. We calculate band profiles for NCs of differing radial dopant distributions and, in agreement with variable temperature conductivity fits, find NCs with dopant-enriched surfaces have narrower depletion widths and longer localization lengths than those with dopant-enriched cores. Following amelioration of NC surface depletion by atomic layer deposition of alumina, all films of equal overall dopant concentration have similar conductivity. Variable temperature conductivity measurements on alumina-capped films indicate all films behave as granular metals. Herein, we conclude that dopant-enriched surfaces decrease the near-surface depletion region, which directly increases the electron localization length and conductivity of NC films

    Age-related mitochondrial DNA depletion and the impact on pancreatic beta cell function

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    Type 2 diabetes is characterised by an age-related decline in insulin secretion. We previously identified a 50% age-related decline in mitochondrial DNA (mtDNA) copy number in isolated human islets. The purpose of this study was to mimic this degree of mtDNA depletion in MIN6 cells to determine whether there is a direct impact on insulin secretion. Transcriptional silencing of mitochondrial transcription factor A, TFAM, decreased mtDNA levels by 40% in MIN6 cells. This level of mtDNA depletion significantly decreased mtDNA gene transcription and translation, resulting in reduced mitochondrial respiratory capacity and ATP production. Glucose-stimulated insulin secretion was impaired following partial mtDNA depletion, but was normalised following treatment with glibenclamide. This confirms that the deficit in the insulin secretory pathway precedes K+ channel closure, indicating that the impact of mtDNA depletion is at the level of mitochondrial respiration. In conclusion, partial mtDNA depletion to a degree comparable to that seen in aged human islets impaired mitochondrial function and directly decreased insulin secretion. Using our model of partial mtDNA depletion following targeted gene silencing of TFAM, we have managed to mimic the degree of mtDNA depletion observed in aged human islets, and have shown how this correlates with impaired insulin secretion. We therefore predict that the age-related mtDNA depletion in human islets is not simply a biomarker of the aging process, but will contribute to the age-related risk of type 2 diabetes