Two-dimensional flow of foam around a circular obstacle: local measurements of elasticity, plasticity and flow

We investigate the two-dimensional flow of a liquid foam around circular obstacles by measuring all the local fields necessary to describe this flow: velocity, pressure, bubble deformations and rearrangements. We show how our experimental setup, a quasi-2D "liquid pool" system, is adapted to the determination of these fields: the velocity and bubble deformations are easy to measure from 2D movies, and the pressure can be measured by exploiting a specific feature of this system, a 2D effective compressibility. To describe accurately bubble rearrangements, we propose a new, tensorial descriptor. All these quantities are evaluated via an averaging procedure that we justify showing that the fluctuations of the fields are essentially random. The flow is extensively studied in a reference experimental case; the velocity presents an overshoot in the wake of the obstacle, the pressure is maximum at the leading side and minimal at the trailing side. The study of the elastic deformations and of the velocity gradients shows that the transition between plug flow and yielded regions is smooth. Our tensorial description of T1s highlight their correlation both with the bubble deformations and the velocity gradients. A salient feature of the flow, notably on the velocity and T1 repartition, is a marked asymmetry upstream/downstream, signature of the elastic behaviour of the foam. We show that the results do not change qualitatively when various control parameters vary, identifying a robust quasistatic regime. These results are discussed in the frame of the actual foam rheology literature, and we argue that they constitute a severe test for existing rheological models, since they capture both the elastic, plastic and fluid behaviour of the foam.Comment: 41 pages, 25 figures, submitted to Journal of Fluid Mechanics (but not in JFM style), short version of the abstrac

Designing a Roadmap for Building Effective Positive Interventions

Liberty Community Connections (LCC), a disability services provider, has a goal to be the premier support coordination agency in Pennsylvania. This goal requires that LCC recruit and retain a talented, resilient, and engaged workforce. LCC has developed a robust training institute with four arms: recruitment, social work education, training, and engagement and development. LCC wishes to use positive psychology to seamlessly align these arms and to improve staff retention and resilience. Drawing from research in positive psychology, our cohort designed a process that will serve as a roadmap for building effective interventions to achieve LCC’s goals and to leverage their core values. To facilitate the execution of the roadmap, the supplemental toolkit offers steps from the appreciative inquiry process to explore positive psychology topics and positive interventions. Once a topic or goal is identified, a comprehensive checklist supports a review of the topic’s alignment with other LCC activities and the design of an implementation strategy. Other organizations can use the findings of this paper, the roadmap and the supplemental toolkit to improve the well-being and quality of life of their staff, consumers, and stakeholders

Relative effects of different non-vitamin K antagonist oral anticoagulants on global thrombotic status in atrial fibrillation

This is an Accepted Manuscript of an article published by Taylor & Francis GroupNon-vitamin K antagonist oral anticoagulants (NOACs) reduce the risk of thromboembolism in patients with atrial fibrillation (AF). There has been no head-to-head comparison of the effect of these agents on ex vivo thrombotic and thrombolytic status. Enhanced platelet reactivity and impaired endogenous thrombolysis are risk factors for recurrent thrombotic events. We aimed to assess the comparative effect of NOACs and warfarin using an ex vivo test of thrombosis and thrombolysis. Eighty patients with newly diagnosed non-valvular AF were tested before, and after being established on apixaban (n = 20), dabigatran (n = 20), rivaroxaban (n = 20), or warfarin (n = 20). Thrombotic status was assessed with the automated, point-of-care Global Thrombosis Test (GTT) that assesses both platelet reactivity and endogenous thrombolysis from native blood. The time taken to form an occlusive thrombus (occlusion time, OT) and the time required to restore flow through endogenous thrombolysis (lysis time, LT) were measured. All anticoagulants caused OT prolongation compared to baseline (apixaban 403 ± 102s vs. 496 ± 125s, p = 0.006; dabigatran 471 ± 106s vs. 656 ± 165s, p < 0.00001; rivaroxaban 381 ± 119s vs. 579 ± 158, p < 0.00001; warfarin 420 ± 145s vs. 604 ± 124s, p < 0.00001). Apixaban reduced LT from baseline (1895[1702-2167]s vs. 1435[347-1990]s; p = 0.006). A trend for LT reduction was seen with other NOACs (dabigatran 1594[1226-2069]s vs. 1539[561-2316]s, p = 0.499; rivaroxaban 2085[1366-2428]s vs. 1885[724-2420]s, p = 0.295) but not with warfarin (1490[1206-1960]s vs. 1776[1545-2334], p = 0.601). Our results suggest that NOACs and warfarin have a similar favorable effect on reducing platelet reactivity. All NOACs exhibited a trend toward enhancing endogenous thrombolytic status, although this was significant only for apixaban. This raises the possibility of using NOACs to enhance impaired endogenous fibrinolysis in patients at high-thrombotic risk.Peer reviewedFinal Accepted Versio

Tax farming redux: experimental evidence on performance pay for tax collectors

Performance pay for tax collectors has the potential to raise revenues, but might come at a cost if it increases the bargaining power of tax collectors vis-à-vis taxpayers. We report the first large-scale field experiment on these issues, where we experimentally allocated 482 property tax units in Punjab, Pakistan, into one of three performance pay schemes or a control. After two years, incentivized units had 9.4 log points higher revenue than controls, which translates to a 46% higher growth rate. The scheme that rewarded purely on revenue did best, increasing revenue by 12.9 log points (64% higher growth rate), with little penalty for customer satisfaction and assessment accuracy compared to the two other schemes that explicitly also rewarded these dimensions. The revenue gains accrue from a small number of properties becoming taxed at their true value, which is substantially more than they had been taxed at previously. The majority of properties in incentivized areas in fact pay no more taxes, but instead report higher bribes. The results are consistent with a collusive setting in which performance pay increases collectors’ bargaining power over taxpayers, who have to either pay higher bribes to avoid being reassessed or pay substantially higher taxes if collusion breaks down

Purple Urine Bag Syndrome: An Alarming Hue? A Brief Review of the Literature

Purple urine bag syndrome (PUBS) is a unique disease entity characterized by an alarming purple discoloration of the urine secondary to recurrent urinary tract infections with indigo- and indirubin-producing bacteria. It is usually associated with prolonged urinary catheterization and chronic debilitated states. We hereby present a concise review of this rare phenomenon with historic perspectives, epidemiology, emphasizing on current concepts of etiology, pathogenesis, relevant clinical associations, treatment modalities, prognosis, and future directions in PUBS. In addition, we highlight an interesting occurrence of this intriguing phenomenon in a 39-year-old gentleman at our institution

g(B*Bpi)-coupling in the static heavy quark limit

By means of QCD simulations on the lattice, we compute the coupling of the heavy-light mesons to a soft pion in the static heavy quark limit. The gauge field configurations used in this calculations include the effect of N_f=2 dynamical Wilson quarks, while for the static quark propagator we use its improved form (so called HYP). On the basis of our results we obtain that the coupling g=0.44 +/- 0.03 (+0.07/-0.00), where the second error is flat (not gaussian).Comment: 7 pages, 3 figs (published version