Theory of electron-phonon interaction in a nonequilibrium open electronic system

We study the effects of time-independent nonequilibrium drive on an open 2D electron gas system coupled to 2D longitudinal acoustic phonons using the Keldysh path integral method. The layer electron-phonon system is defined at the two-dimensional interface between a pair of three-dimensional Fermi liquid leads, which act both as a particle pump and an infinite bath. The nonequilibrium steady state is achieved in the layer by assuming the leads to be thermally equilibrated at two different chemical potentials. This subjects the layer to an out-of-plane voltage $V$ and drives a steady-state charge current perpendicular to the system. We compute the effects of small voltages (V\ll\w_D) on the in-plane electron-phonon scattering rate and the electron effective mass at zero temperature. We also find that the obtained onequilibrium modification to the acoustic phonon velocity and the Thomas-Fermi screening length reveal the possibility of tuning these quantities with the external voltage.Comment: 14 pages, 4 figure

Exploring knowledge exchange: a useful framework for practice and policy

Knowledge translation is underpinned by a dynamic and social knowledge exchange process but there are few descriptions of how this unfolds in practice settings. This has hampered attempts to produce realistic and useful models to help policymakers and researchers understand how knowledge exchange works. This paper reports the results of research which investigated the nature of knowledge exchange. We aimed to understand whether dynamic and fluid definitions of knowledge exchange are valid and to produce a realistic, descriptive framework of knowledge exchange. Our research was informed by a realist approach. We embedded a knowledge broker within three service delivery teams across a large mental health organisation, each of whom was grappling with specific challenges. The knowledge broker participated in the team's problem-solving process and collected observational fieldnotes. We also interviewed the team members. Observational and interview data were analysed quantitatively and qualitatively in order to determine and describe the nature of the knowledge exchange process in more detail. This enabled us to refine our conceptual framework of knowledge exchange. We found that knowledge exchange can be understood as a dynamic and fluid process which incorporates distinct forms of knowledge from multiple sources. Quantitative analysis illustrated that five broadly-defined components of knowledge exchange (problem, context, knowledge, activities, use) can all be in play at any one time and do not occur in a set order. Qualitative analysis revealed a number of distinct themes which better described the nature of knowledge exchange. By shedding light on the nature of knowledge exchange, our findings problematise some of the linear, technicist approaches to knowledge translation. The revised model of knowledge exchange which we propose here could therefore help to reorient thinking about knowledge exchange and act as a starting point for further exploration and evaluation of the knowledge exchange process

Integrating fish resources to agro-ecosystem analyses

In October 2005, a consortium of partners led by the International Water Management Institute (IWMI) proposed a project aimed at integrating fish resources management in agricultural management in the Tonle Sap area. This 2-years project assistance was accepted for funding by the Challenge Program on Water and Food and started in January 2008. The overall goal of this project is to improve allocation and use of water in combined farming and fishing systems in order to enhance food security of rural communities and water productivity. The general objectives of the Fisheries component are: 1) to contribute to the review of existing fisheries and aquaculture information, assessment and data collection systems and existing databases from a fisheries perspective 2) to determine key questions that could be asked at the commune level that would enable the identification of fisheries issues for different agroecosystem zones. These would include both threats and potential threats to fisheries based on key ecological variables and opportunities that fisheries and aquaculture could represent in local livelihoods.Research, Lake fisheries, Agropisciculture, Ecosystems, Analysis, Cambodia, Tonle Sap L.,

Nonequilibrium quantum criticality in open electronic systems

A theory is presented of quantum criticality in open (coupled to reservoirs) itinerant electron magnets, with nonequilibrium drive provided by current flow across the system. Both departures from equilibrium at conventional (equilibrium) quantum critical points and the physics of phase transitions induced by the nonequilibrium drive are treated. Nonequilibrium-induced phase transitions are found to have the same leading critical behavior as conventional thermal phase transitions.Comment: 5 pages, 1 figur

Topological superconductivity and Majorana fermions in hybrid structures involving cuprate high-T_c superconductors

The possibility of inducing topological superconductivity with cuprate high-temperature superconductors (HTSC) is studied for various heterostructures. We first consider a ballistic planar junction between a HTSC and a metallic ferromagnet. We assume that inversion symmetry breaking at the tunnel barrier gives rise to Rashba spin-orbit coupling in the barrier and allows equal-spin triplet superconductivity to exist in the ferromagnet. Bogoliubov-de Gennes equations are obtained by explicitly modeling the barrier, and taking account of the transport anisotropy in the HTSC. By making use of the self-consistent boundary conditions and solutions for the barrier and HTSC regions, an effective equation of motion for the ferromagnet is obtained where Andreev scattering at the barrier is incorporated as a boundary condition for the ferromagnetic region. For a ferromagnet layer deposited on a (100) facet of the HTSC, triplet p-wave superconductivity is induced. For the layer deposited on a (110) facet, the induced gap does not have the p-wave orbital character, but has an even orbital symmetry and an odd dependence on energy. For the layer on the (001) facet, an exotic f-wave superconductivity is induced. We also consider the induced triplet gap in a one-dimensional half-metallic nanowire deposited on a (001) facet of a HTSC. We find that for a wire axis along the a-axis, a robust triplet p-wave gap is induced. For a wire oriented 45 degrees away from the a-axis the induced triplet p-wave gap vanishes. For the appropriately oriented wire, the induced p-wave gap should give rise to Majorana fermions at the ends of the half-metallic wire. Based on our result, topological superconductivity in a semi-conductor nanowire may also be possible given that it is oriented along the a-axis of the HTSC.Comment: 14 pages, 4 figure

Prevalence of mental morbidity and its associated factors in two communities of Benin metropolis, Nigeria

Background: Mental morbidity is a public health problem that can lead to a great burden of disability in the community. Early detection and treatment of these morbidities could prevent deterioration. The aim of the survey was to determine and compare the prevalence of mental morbidity and its associated factors in two communities in Benin metropolis in Nigeria.Materials and Methods: The study was carried out among 400 residents of two urban communities of Benin metropolis, Benin City, Nigeria, between November 2012 and April 2013. The design of the study was descriptive, cross-sectional. The 28-item version of the General Health Questionnaire (GHQ-28) and a questionnaire for socio-demographic variables were used to collect information from participants who were selected using multistage sampling technique. Data collected were analyzed using SPSS version 16. Statistical test of association used were Chi square, Fisher's exact test and Multivariate logistic regression. P value of < 0.05 was taken as statistically signicant.Results: The overall prevalence of mental morbidity in both communities was 24.0%. However, prevalence of mental morbidity in BDPA and Uwelu communities, were 19.5% and 28.5% respectively. Education, income, type of accommodation, and number of co-habitants were variables found to be signicantly associated with mental morbidity. The two communities were found to differ signicantly on all indices of socio-economic status, and these indices signicantly differentiated between cases (GHQ-positives) in the surveyed communities. None of the socio-demographic variables independently predicted mental morbidity.Conclusion: The need for renewed effort at improving community mental health services and the standard of living of the populace by government and policy makers is emphasized.Keywords: Prevalence, Mental morbidity, Communities, Benin city, Nigeri

Regeneration of injured skin and peripheral nerves requires control of wound contraction, not scar formation

We review the mounting evidence that regeneration is induced in wounds in skin and peripheral nerves by a simple modification of the wound healing process. Here, the process of induced regeneration is compared to the other two well-known processes by which wounds close, i.e., contraction and scar formation. Direct evidence supports the hypothesis that the mechanical force of contraction (planar in skin wounds, circumferential in nerve wounds) is the driver guiding the orientation of assemblies of myofibroblasts (MFB) and collagen fibers during scar formation in untreated wounds. We conclude that scar formation depends critically on wound contraction and is, therefore, a healing process secondary to contraction. Wound contraction and regeneration did not coincide during healing in a number of experimental models of spontaneous (untreated) regeneration described in the literature. Furthermore, in other studies in which an efficient contraction-blocker, a collagen scaffold named dermis regeneration template (DRT), and variants of it, were grafted on skin wounds or peripheral nerve wounds, regeneration was systematically observed in the absence of contraction. We conclude that contraction and regeneration are mutually antagonistic processes. A dramatic change in the phenotype of MFB was observed when the contraction-blocking scaffold DRT was used to treat wounds in skin and peripheral nerves. The phenotype change was directly observed as drastic reduction in MFB density, dispersion of MFB assemblies and loss of alignment of the long MFB axes. These observations were explained by the evidence of a surface-biological interaction of MFB with the scaffold, specifically involving binding of MFB integrins α[subscript 1]β[subscript 1] and α[subscript 2]β[subscript 1] to ligands GFOGER and GLOGER naturally present on the surface of the collagen scaffold. In summary, we show that regeneration of wounded skin and peripheral nerves in the adult mammal can be induced simply by appropriate control of wound contraction, rather than of scar formation.National Institutes of Health (U.S.) (Grant RO1 NS051320)National Institutes of Health (U.S.) (Grant 5‐P41‐EB015871‐28)Horizon 2020 Framework Programme (European Commission) (Grant DLV‐658850)Singapore-MIT Alliance for Research and Technology (SMART) (Grant 5‐P41‐EB015871‐28)Hamamatsu Corporatio

Expression of protease-activated receptors in arthritic synovial tissues

Clinical and experimental evidence suggests that synovial thrombin formation in arthritic joints is prominent and deleterious, leading to exacerbation of rheumatoid arthritis (RA). In this context, cellular effects of thrombin mediated by the protease-activated receptors (PARs) in arthritic joints may be of paramount significance. Four PARs have now been identified. PAR1, PAR3, and PAR4 can all be activated by thrombin whereas PAR2 is activated by trypsin and few other proteases.We first explored PARs expression in RA synovial tissues. Synovial membranes from 11 RA patients were analyzed for PARs expression by RT-PCR and by immunohistology. PAR4 was found in all the biopsies, whereas the expression of PAR1, PAR 2 and PAR3 was more restricted (8/11, 5/11 and 3/11 respectively). In the arthritic synovial membrane of murine antigen-induced arthritis (AIA) we found coexpression of the four different PARs. Next, we explored the functional importance of PAR1 during AIA in vivo using PAR-1 deficient mice. The phenotype of PAR1-deficient mice (n = 22), based on the analysis of arthritis severity (as measured by 99 m tecnetium uptake, histological scoring and intra-articular fibrin measurements) was similar to that of wild-type mice (n = 24). In addition, the in vivo production of antibodies against mBSA was also similar. By contrast, the mBSA-induced in vitro lymph node cell proliferation was significantly decreased in PAR1-deficient mice as compared with controls. Accordingly, mBSA-induced production of interferon-γ by lymph node cells in culture was significantly decreased in PAR1-deficient mice as compared with controls, whereas opposite results were observed for production of IL-10