High temperature thermoelectric efficiency in Ba8Ga16Ge30

The high thermoelectric figure of merit (zT) of Ba8Ga16Ge30 makes it one of the best n-type materials for thermoelectric power generation. Here, we describe the synthesis and characterization of a Czochralski pulled single crystal of Ba8Ga16Ge30 and polycrystalline disks. Measurements of the electrical conductivity, Hall effect, specific heat, coefficient of thermal expansion, thermal conductivity, and Seebeck coefficient were performed up to 1173 K and compared with literature results. Dilatometry measurements give a coefficient of thermal expansion of 16×10^−6 K^−1 up to 1175 K. The trend in electronic properties with composition is typical of a heavily doped semiconductor. The maximum in the thermoelectric figure of merit is found at 1050 K with a value of 0.8. The correction of zT due to thermal expansion is not significant compared to the measurement uncertainties involved. Comparing the thermoelectric efficiency of segmented materials, the effect of compatibility makes Ba8Ga16Ge30 more efficient than the higher zT n-type materials SiGe or skutterudite CoSb3

Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSb2−x_{2-x}Tex_x

Substitution of Sb in FeSb$_2$ by less than 0.5% of Te induces a transition from a correlated semiconductor to an unconventional metal with large effective charge carrier mass $m^*$. Spanning the entire range of the semiconductor-metal crossover, we observed an almost constant enhancement of the measured thermopower compared to that estimated by the classical theory of electron diffusion. Using the latter for a quantitative description one has to employ an enhancement factor of 10-30. Our observations point to the importance of electron-electron correlations in the thermal transport of FeSb$_2$, and suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett. (2011

Bayesian model search and multilevel inference for SNP association studies

Technological advances in genotyping have given rise to hypothesis-based association studies of increasing scope. As a result, the scientific hypotheses addressed by these studies have become more complex and more difficult to address using existing analytic methodologies. Obstacles to analysis include inference in the face of multiple comparisons, complications arising from correlations among the SNPs (single nucleotide polymorphisms), choice of their genetic parametrization and missing data. In this paper we present an efficient Bayesian model search strategy that searches over the space of genetic markers and their genetic parametrization. The resulting method for Multilevel Inference of SNP Associations, MISA, allows computation of multilevel posterior probabilities and Bayes factors at the global, gene and SNP level, with the prior distribution on SNP inclusion in the model providing an intrinsic multiplicity correction. We use simulated data sets to characterize MISA's statistical power, and show that MISA has higher power to detect association than standard procedures. Using data from the North Carolina Ovarian Cancer Study (NCOCS), MISA identifies variants that were not identified by standard methods and have been externally ``validated'' in independent studies. We examine sensitivity of the NCOCS results to prior choice and method for imputing missing data. MISA is available in an R package on CRAN.Comment: Published in at http://dx.doi.org/10.1214/09-AOAS322 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

The use of ultrasonography in the perioperative management of penetrating chest trauma with indwelling blade

We report on the anaesthetic and postoperative analgesic management of a patient presenting with a single penetrating thoracic injury, with radiological confirmation of a foreign object still present in the thorax. The patient underwent an emergency right posterolateral thoracotomy. We discuss the use of ultrasound for the insertion of a paravertebral catheter for perioperative analgesic management, and its efficacy in the emergency setting. Furthermore, we discuss the use of perioperative focus assessed transthoracic echocardiography, which had a positive impact on our management, although the case highlights the need for further large multi-centre trials.Keywords: focus assessed transthoracic echocardiography (FATE), paraverterbral block, penetrating thoracic injury, thoracotomy, ultrasound-guided regional anaesthesi