High-Temperature Transport Properties of the Zintl Phases Yb_(11)GaSb_9 and Yb_(11)InSb_9

Two rare-earth Zintl phases, Yb_(11)GaSb_9 and Yb_(11)InSb_9, were synthesized in high-temperature self-fluxes of molten Ga and In, respectively. Structures were characterized by both single-crystal X-ray diffraction and powder X-ray diffraction and are consistent with the published orthorhombic structure, with the space group Iba2. High-temperature differential scanning calorimetry (DSC) and thermal gravimetry (TG) measurements reveal thermal stability to 1300 K. Seebeck coefficient and resistivity measurements to 1000 K are consistent with the hypothesis that Yb_(11)GaSb_9 and Yb_(11)InSb_9 are small band gap semiconductors or semimetals. Low doping levels lead to bipolar conduction at high temperature, preventing a detailed analysis of the transport properties. Thermal diffusivity measurements yield particularly low lattice thermal conductivity values, less than 0.6 W/m K for both compounds. The low lattice thermal conductivity suggests that Yb_(11)MSb_9 (M = Ga, In) has the potential for high thermoelectric efficiency at high temperature if charge-carrier doping can be controlled

Two-dimensional flow of foam around an obstacle: force measurements

A Stokes experiment for foams is proposed. It consists in a two-dimensional flow of a foam, confined between a water subphase and a top plate, around a fixed circular obstacle. We present systematic measurements of the drag exerted by the flowing foam on the obstacle, \emph{versus} various separately controlled parameters: flow rate, bubble volume, bulk viscosity, obstacle size, shape and boundary conditions. We separate the drag into two contributions, an elastic one (yield drag) at vanishing flow rate, and a fluid one (viscous coefficient) increasing with flow rate. We quantify the influence of each control parameter on the drag. The results exhibit in particular a power-law dependence of the drag as a function of the bulk viscosity and the flow rate with two different exponents. Moreover, we show that the drag decreases with bubble size, and increases proportionally to the obstacle size. We quantify the effect of shape through a dimensioned drag coefficient, and we show that the effect of boundary conditions is small.Comment: 26 pages, 13 figures, resubmitted version to Phys. Rev.

Parameter identifiability in a class of random graph mixture models

We prove identifiability of parameters for a broad class of random graph mixture models. These models are characterized by a partition of the set of graph nodes into latent (unobservable) groups. The connectivities between nodes are independent random variables when conditioned on the groups of the nodes being connected. In the binary random graph case, in which edges are either present or absent, these models are known as stochastic blockmodels and have been widely used in the social sciences and, more recently, in biology. Their generalizations to weighted random graphs, either in parametric or non-parametric form, are also of interest in many areas. Despite a broad range of applications, the parameter identifiability issue for such models is involved, and previously has only been touched upon in the literature. We give here a thorough investigation of this problem. Our work also has consequences for parameter estimation. In particular, the estimation procedure proposed by Frank and Harary for binary affiliation models is revisited in this article

Development and Preliminary Evaluation of a Telephone-based Mindfulness Training Intervention for Survivors of Critical Illness

Rationale: Persistent symptoms of psychological distress represent an unmet need among intensive care unit (ICU) survivors. Objectives: We aimed to develop and pilot test a simple telephone-based mindfulness training intervention to address this population’s unique needs. Methods: Open trial involving survivors of medical and surgical critical illness and their informal caregivers, using a pretest–posttest design. Measurements and Main Results: We developed a six-session, telephone-delivered, ICU survivor–specific mindfulness intervention based on past focus groups, the medical literature, and the precedent of the most effective components of existing mindfulness programs. A total of 11 survivors of mechanical ventilation were enrolled, together with 2 informal caregivers for exploratory purposes. Three patients dropped out before intervention initiation because of progressive illness or severe social stressors. Of the 10 remaining participants, 8 (80%) completed the program within 7 weeks. Among these eight patients and caregivers who completed all study procedures, six (75%) experienced improvement in symptoms of psychological distress (anxiety, depression, or post-traumatic stress disorder). Changes in distress symptoms were correlated with improvement in mindfulness qualities, adaptive coping, and emotion regulation. Participants reported high satisfaction with the program in postintervention interviews. Conclusions: A new ICU survivor–specific mindfulness training intervention delivered by telephone was acceptable and feasible. Changes in symptoms of distress were correlated with changes in skills that were targeted by the mindfulness program. Controlled trials are needed to further evaluate this promising intervention