Characterization Of Porous Media In Proton Exchange Membrane Fuel Cell Based on Percolation Studies

Water management in the porous media of proton exchange membrane (PEM) fuel cells, catalyst layer and porous transport layers (PTL) is confronted by two issues, flooding and dry out, both of which result in improper functioning of the fuel cell and lead to poor performance and degradation. The data that has been reported about water percolation and wettability within a fuel cell catalyst layer is limited to porosimetry. A new method and apparatus for measuring the percolation pressure in the catalyst layer has been developed. The experimental setup is similar to a Hele-Shaw experiment where samples are compressed and a fluid is injected into the sample. Pressure-Wetted Volume plots as well as Permeability plots for the catalyst layers were generated from the percolation testing. PTL samples were also characterizes using a Hele-Shaw method. Characterization for the PTLs was completed for the three states: new, conditioned and aged. This is represented in a Ce-t* plots, which show a large offset between new and aged samples.

Homelessness, Social Work, Social Policy and the Print Media in Australian Cities

Homelessness is a significant social problem worldwide. This paper describes an Australian study that examined print media representations of homelessness and social work, social policy and social work responses to homelessness in three Australian cities. The research included a content analysis of seven Australian newspapers and semi-structured interviews with 39 social workers employed in the field of homelessness in Adelaide, Melbourne and Sydney. The detailed results of these studies have been published separately elsewhere. This paper reports on how discourses in the print media, social policy and social work practice co-exist in constructing homelessness as a particular social problem, influencing social work responses to homelessness. The research found that individualism is central to many dominant discourses evident in the print media, social policy and social work practice, and that social work is practiced within unequal power relations embedded in organisational contexts.

[Mass culling in the context of animal disease outbreaks--veterinarians caught between ethical issues and control policies]

In recent years controversial discussions arose during major animal disease outbreaks in the EU about the ethical soundness of mass culling. In contrast to numerous publications about ethical issues and laboratory animals/animal experiments, literature concerning ethical deliberations in the case of mass culling as a means of outbreak control remain scarce. Veterinarians in charge of decision about and implementation of mass culling actions find themselves in an area of conflict in between the officially required animal disease control policy and a public that is increasingly critical. Those veterinarians are faced with the challenge to defend the relevant decisions against all stakeholders and also themselves. In this context an interdisciplinary workshop was initiated in Switzerland in October 2007 with ethicians and (official) veterinarians from Germany, Switzerland and Austria. With the aim to identify ethical components of animal disease control for official veterinarians, talks and moderated group discussions took place. This article summarizes selected discussion points and conclusions.

Design and Impact of Awareness Functions – A Study about Social Media in Virtual Teams

The usage of social media in leisure time settings has become a prominent research topic. However, less research has been done on the design of social media in collaboration settings. In this study, we investigate how social media can support asynchronous collaboration in virtual teams and specifically how they can increase activity awareness. On the basis of an open source social networking platform, we present two prototype designs: a standard platform with basic support for information processing, communication and process – as suggested by Zigurs and Buckland (1998) – and an advanced platform with additional support for activity awareness via specialfeed functions. We argue that the standard platform already conveys activity awareness to a certain extent, however, that this awareness can be increased even more by the feeds in the advanced platform. Both prototypes are tested in a field experiment and evaluated with respect to their impact on perceived activity awareness, coordination and satisfaction. We show that the advanced design increases coordination and satisfaction through increased perceived activity awareness.

Charm mass effects in bulk channel correlations

The bulk viscosity of thermalized QCD matter at temperatures above a few hundred MeV could be significantly influenced by charm quarks because their contribution arises four perturbative orders before purely gluonic effects. In an attempt to clarify the challenges of a lattice study, we determine the relevant imaginary-time correlator (of massive scalar densities) up to NLO in perturbation theory, and compare with existing data. We find discrepancies much larger than in the vector channel; this may hint, apart from the importance of taking a continuum limit, to larger non-perturbative effects in the scalar channel. We also recall how a transport peak related to the scalar density spectral function encodes non-perturbative information concerning the charm quark chemical equilibration rate close to equilibrium.