25,221 research outputs found
Out of equilibrium quantum field dynamics of an initial thermal state after a change in the external field
The effects of the initial temperature in the out of equilibrium quantum
field dynamics in the presence of an homogeneous external field are
investigated. We consider an initial thermal state of temperature T for a
constant external field J. A subsequent sign flip of the external field, J to
-J, gives rise to an out of equilibrium nonperturbative quantum field dynamics.
The dynamics is studied here for the symmetry broken lambda(Phi^2)^2 scalar N
component field theory in the large N limit. We find a dynamical effective
potential for the expectation value that helps to understand the dynamics. The
dynamics presents two regimes defined by the presence or absence of a temporal
trapping close to the metastable equilibrium position of the potential. The two
regimes are separated by a critical value of the external field that depends on
the initial temperature. The temporal trapping is shorter for larger initial
temperatures or larger external fields. Parametric resonances and spinodal
instabilities amplify the quantum fluctuations in the field components
transverse to the external field. When there is a temporal trapping this is the
main mechanism that allows the system to escape from the metastable state for
large N. Subsequently backreaction stops the growth of the quantum fluctuations
and the system enters a quasiperiodic regime.Comment: LaTeX, 19 pages, 12 .eps figures, improved version to appear in Phys
Rev
Electro-osmosis on anisotropic super-hydrophobic surfaces
We give a general theoretical description of electro-osmotic flow at striped
super-hydrophobic surfaces in a thin double layer limit, and derive a relation
between the electro-osmotic mobility and hydrodynamic slip-length tensors. Our
analysis demonstrates that electro-osmotic flow shows a very rich behavior
controlled by slip length and charge at the gas sectors. In case of uncharged
liquid-gas interface, the flow is the same or inhibited relative to flow in
homogeneous channel with zero interfacial slip. By contrast, it can be
amplified by several orders of magnitude provided slip regions are uniformly
charged. When gas and solid regions are oppositely charged, we predict a flow
reversal, which suggests a possibility of huge electro-osmotic slip even for
electro-neutral surfaces. On the basis of these observations we suggest
strategies for practical microfluidic mixing devices. These results provide a
framework for the rational design of super-hydrophobic surfaces.Comment: 4 pages, 4 figures; submitted to PRL Revised version: several
references added, typos corrected. Supplementary file was restructured, the
second part of the original EPAPS was removed and is supposed to be published
as a separate pape
Age work in organizations: maintaining and disrupting institutionalized understandings of higher age
Age diversity research calls for new approaches in explaining the persistence of age inequalities, which integrate different levels of analysis and display greater context sensitivity. Concurrently, neoinstitutionalist research interested in social inequalities calls for merging institutional theory with critical perspectives and to account for issues of power. In this study, we address the calls of both research streams through developing the concept of âage workâ: the institutional work actors undertake on age as a social institution. Applying our novel concept to a multi-actor study of four German organizations known for their age management, we come across a counterintuitive insight regarding actorsâ age work: maintaining stereotypical age images can serve to counter age inequalities, whereas deconstructing age images can reinforce age inequalities. The multi-actor perspective of our study allows us to categorize different forms of power-laden and interest-driven age work and to portray the reproduction of age inequalities as a result of actorsâ age work, embedded in different contexts and complex power relations. Comparing employeesâ forms of age work across sectors and organizations, we detail how notions of masculinity as well as income and job security shaped the categorized forms of age work
Reporting on sustainability and HRM: a comparative study of sustainability reporting practices by the worldâs largest companies
As a response to the growing public awareness on the importance of organisational contributions to sustainable development, there is an increased incentive for corporations to report on their sustainability activities. In parallel with this has been the development of âSustainable HRMâ which embraces a growing body of practitioner and academic literature connecting the notions of corporate sustainability to HRM. The aim of this article is to analyse corporate sustainability reporting amongst the worldâs largest companies and to assess the HRM aspects of sustainability within these reports in comparison to environmental aspects of sustainable management and whether organisational attributes â principally country-of-origin â influences the reporting of such practices. A focus in this article is the extent to which the reporting of various aspects of sustainability may reflect dominant models of corporate governance in the country in which a company is headquartered. The findings suggest, first and against expectations, that the overall disclosure on HRM-related performance is not lower than that on environmental performance. Second, companies report more on their internal workforce compared to their external workforce. Finally, international differences, in particular those between companies headquartered in liberal market economies and coordinated market economies, are not as apparent as expected
Plasmodium falciparum glutamate dehydrogenase a is dispensable and not a drug target during erythrocytic development
<p>Background: Plasmodium falciparum contains three genes encoding potential glutamate dehydrogenases. The protein encoded by gdha has previously been biochemically and structurally characterized. It was suggested that it is important for the supply of reducing equivalents during intra-erythrocytic development of Plasmodium and, therefore, a suitable drug target.</p>
<p>Methods: The gene encoding the NADP(H)-dependent GDHa has been disrupted by reverse genetics in P. falciparum and the effect on the antioxidant and metabolic capacities of the resulting mutant parasites was investigated.</p>
<p>Results: No growth defect under low and elevated oxygen tension, no up-or down-regulation of a number of antioxidant and NADP(H)-generating proteins or mRNAs and no increased levels of GSH were detected in the D10(Delta gdha) parasite lines. Further, the fate of the carbon skeleton of [(13)C] labelled glutamine was assessed by metabolomic studies, revealing no differences in the labelling of a-ketoglutarate and other TCA pathway intermediates between wild type and mutant parasites.</p>
<p>Conclusions: First, the data support the conclusion that D10(Delta gdha) parasites are not experiencing enhanced oxidative stress and that GDHa function may not be the provision of NADP(H) for reductive reactions. Second, the results imply that the cytosolic, NADP(H)-dependent GDHa protein is not involved in the oxidative deamination of glutamate but that the protein may play a role in ammonia assimilation as has been described for other NADP(H)dependent GDH from plants and fungi. The lack of an obvious phenotype in the absence of GDHa may point to a regulatory role of the protein providing glutamate (as nitrogen storage molecule) in situations where the parasites experience a limiting supply of carbon sources and, therefore, under in vitro conditions the enzyme is unlikely to be of significant importance. The data imply that the protein is not a suitable target for future drug development against intra-erythrocytic parasite development.</p>
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