Shear-stress controlled dynamics of nematic complex fluids

Based on a mesoscopic theory we investigate the non-equilibrium dynamics of a sheared nematic liquid, with the control parameter being the shear stress $\sigma_{\mathrm{xy}}$ (rather than the usual shear rate, $\dot\gamma$). To this end we supplement the equations of motion for the orientational order parameters by an equation for $\dot\gamma$, which then becomes time-dependent. Shearing the system from an isotropic state, the stress- controlled flow properties turn out to be essentially identical to those at fixed $\dot\gamma$. Pronounced differences when the equilibrium state is nematic. Here, shearing at controlled $\dot\gamma$ yields several non-equilibrium transitions between different dynamic states, including chaotic regimes. The corresponding stress-controlled system has only one transition from a regular periodic into a stationary (shear-aligned) state. The position of this transition in the $\sigma_{\mathrm{xy}}$-$\dot\gamma$ plane turns out to be tunable by the delay time entering our control scheme for $\sigma_{\mathrm{xy}}$. Moreover, a sudden change of the control method can {\it stabilize} the chaotic states appearing at fixed $\dot\gamma$.Comment: 10 pages, 11 figure

Intestinal epithelial responses to Salmonella enterica serovar Enteritidis: Effects on intestinal permeability and ion transport

Salmonella infection of chickens that leads to potential human foodborne salmonellosis continues to be a major concern. Chickens serve as carriers but, in contrast to humans, rarely show any clinical signs including diarrhea. The present investigations aimed to elucidate whether the absence of diarrhea during acute Salmonella enterica serovar Enteritidis (Salmonella Enteritidis) infection may be linked to specific changes in the electrophysiological properties of the chicken gut. Immediately after slaughter, intestinal pieces of the mid-jejunum and cecum of either commercial broiler or specific pathogen-free (SPF) chickens were mounted in Ussing chambers in 2 separate experimental series. Living Salmonella Enteritidis (3 × 109) or Salmonella Enteritidis endotoxin (20 mg/L), or both, were added to the mucosal side for 1 h. In both experimental series, the Salmonella infection decreased the trans-epithelial ion conductance Gt (P < 0.05). In the jejunum of SPF chickens, there was also a marked decrease in net charge transfer across the epithelium, evidenced by decreased short-circuit current (Isc, P < 0.05). Interestingly, the mucosal application of Salmonella endotoxin to the epithelial preparations from jejunum and cecum of SPF chicken had an effect similar to living bacteria. However, the endotoxin had no additional effect on the intestinal function in the presence of bacteria. The decreasing effect of Salmonella and or its endotoxin on Gt could be partly reversed by serosal addition of histamine. To our knowledge, this is the first study to address the functional response of native intestinal epithelium of chicken to an in vitro Salmonella infection. For the first time, it can be reported that intestinal ion permeability of chicken decreases acutely by the presence of Salmonella. This type of response could counteract ion and fluid secretion and may thus, at least in part, explain why chickens do not develop overt diarrhea after Salmonella infection

Gaussian quantum fluctuations in interacting many particle systems

We consider a many particle quantum system, in which each particle interacts only with its nearest neighbours. Provided that the energy per particle has an upper bound, we show, that the energy distribution of almost every product state becomes a Gaussian normal distribution in the limit of infinite number of particles. We indicate some possible applications.Comment: 10 pages, formulation made mathematically more precise, two examples added, accepted for publication in Letters in Mathematical Physic

What Helps Law Professors Develop as Teachers? -- An Empirical Study

The overall goal of this article is to provide concrete suggestions for how law schools can improve teaching and enrich law student learning. In doing so, it reviews and analyzes the data collected from two national surveys about the kinds of faculty development activities that are most effective in improving law professors’ teaching. One survey was designed to quantify how many law teachers engaged in twenty-two types of teaching development activities over the previous five years and to assess the effectiveness of each of those activities. The other survey focused on the effectiveness of a national conference on teaching and learning in law school. This article builds upon Improving Teaching and Learning in Law School: Faculty Development Research, Principles, and Programs, 12 WIDENER L. REV. 443 (2006), which presented the principles fundamental to effective faculty development programs. This article shows how these principles apply by providing data about the effectiveness of a wide range of teaching development activities

What Has Financed Government Debt?

Dynamic rational expectations models imply that the real value of debt in the hands of the public must be equal to the expected present-value of surpluses. We impose this equilibrium condition on an identified VAR and characterize the way in which the present-value support of debt varies across various types of fiscal policy shocks and between fiscal and non-fiscal shocks. The role of expected primary surpluses in supporting innovations to debt depends on the nature of the shock. For some fiscal policy shocks, debt is supported almost entirely by changes in the present-value of surpluses, however, in the case of other fiscal policy shocks, surpluses fail to adjust and instead leave a large role for expected changes in discount rates. Horizons over which debt innovations are financed are long – on the order of fifty years – while present-values calculated up to any finite horizon up to then fluctuate wildly, particularly following government spending and transfer shocks.