Phonon-drag effect in FeGa3

The thermoelectric properties of single- and polycrystalline FeGa3 are systematically investigated over a wide temperature range. At low temperatures, below 20 K, previously not known pronounced peaks in the thermal conductivity (400-800 W K^-1m-1) with corresponding maxima in the thermopower (in the order of -16000 microV/K) were found in single crystalline samples. Measurements in single crystals along [100] and [001] directions indicate only a slight anisotropy in both the electrical and thermal transport. From susceptibility and heat capacity measurements, a structural or magnetic phase transition was excluded. Using density functional theory-based calculations, we have revisited the electronic structure of FeGa3 and compared the magnetic (including correlations) and non-magnetic electronic density of states. Thermopower at fixed carrier concentrations are calculated using semi-classical Boltzmann transport theory, and the calculated results match fairly with our experimental data and exclude the possibility of strong electronic correlations as an explanation for the low temperature enhancement. Eventually, after a careful review, we assign the peaks in the thermopower as a manifestation of the phonon-drag effect, which is supported by thermopower measurements in a magnetic field.Comment: Phys. Rev. B accepted (2014

Discovery of the high thermoelectric performance in low-cost Cu8SiSxSe6-x argyrodites

Cu-based argyrodites have gained much attention as a new class of thermoelectric materials for energy harvesting. However, the phase transition occurring in these materials and low energy conversion performance limited their broad application in thermoelectric converters. In this work, we disclose a newly discovered highly efficient Cu8SiSxSe6-x argyrodite with stabilized high-symmetry cubic phase at above 282 K opening the practical potential of this material for the mid-temperature region applications. The temperature range broadening of the high-symmetry phase existence was possible due to the successful substitution of Se with S in Cu8SiSxSe6-x, which enhances the configurational entropy. The developed argyrodites show excellent thermoelectric performance thanks to the increased density of states effective mass and ultralow lattice thermal conductivity. Further tuning of the carrier concentration through the Cu-deviation improves the thermoelectric performance significantly. The dimensionless thermoelectric figure of merit ZT and estimated energy conversion efficiency {\eta} for Cu7.95SiS3Se3 achieve outstanding values of the 1.45 and 13 %, respectively, offering this argyrodite as a low-cost and Te-free alternative for the thermoelectric energy conversion applications.Comment: 25 pages, 8 figure

Electronic and Thermoelectric Properties of RuIn_{3-x}A_{x} (A = Sn, Zn)

Recently, we reported [M. Wagner et al., J. Mater. Res. 26, 1886 (2011)] transport measurements on the semiconducting intermetallic system RuIn3 and its substitution derivatives RuIn_{3-x}A_{x} (A = Sn, Zn). Higher values of the thermoelectric figure of merit (zT = 0.45) compared to the parent compound were achieved by chemical substitution. Here, using density functional theory based calculations, we report on the microscopic picture behind the measured phenomenon. We show in detail that the electronic structure of the substitution variants of the intermetallic system RuIn_{3-x}A_{x} (A = Sn, Zn) changes in a rigid-band like fashion. This behavior makes possible the fine tuning of the substitution concentration to take advantage of the sharp peak-like features in the density of states of the semiconducting parent compound. Trends in the transport properties calculated using the semi-classical Boltzmann transport equations within the constant scattering time approximation are in good agreement with the former experimental results for RuIn_{3-x}Sn_{x}. Based on the calculated thermopower for the p-doped systems, we reinvestigated the Zn-substituted derivative and obtained ZnO-free RuIn_{3-x}Zn_{x}. The new experimental results are consistent with the calculated trend in thermopower and yield large zT value of 0.8.Comment: PRB Accepted, 11 pages, 10 figure

Proton energy loss in multilayer graphene and carbon nanotubes

Results of a study of electronic energy loss of low keV protons interacting with multilayer graphene targets are presented. Proton energy loss shows an unexpectedly high value as compared with measurements in amorphous carbon and carbon nanotubes. Furthermore, we observe a classical linear behavior of the energy loss with the ion velocity but with an apparent velocity threshold around 0.1 a.u., which is not observed in other carbon allotropes. This suggests low dimensionality effects which can be due to the extraordinary graphene properties.This work was mainly supported by the grants Fondecyt [grant number 1100759], CONICYT-MEC [grant number 80150073] and DGIIP-UTFSM [grant number 216.11.3]. MM and BF acknowledge the Basal Program for Centers of Excellence, Grant FB0807 CEDENNA, CONICYT. RGM and IA acknowledge financial support provided by the Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (Project No. FIS2014-58849-P), as well as by the Fundación Séneca (Project No. 19907/GERM/15)

Global patient outcomes after elective surgery: prospective cohort study in 27 low-, middle- and high-income countries.

BACKGROUND: As global initiatives increase patient access to surgical treatments, there remains a need to understand the adverse effects of surgery and define appropriate levels of perioperative care. METHODS: We designed a prospective international 7-day cohort study of outcomes following elective adult inpatient surgery in 27 countries. The primary outcome was in-hospital complications. Secondary outcomes were death following a complication (failure to rescue) and death in hospital. Process measures were admission to critical care immediately after surgery or to treat a complication and duration of hospital stay. A single definition of critical care was used for all countries. RESULTS: A total of 474 hospitals in 19 high-, 7 middle- and 1 low-income country were included in the primary analysis. Data included 44 814 patients with a median hospital stay of 4 (range 2-7) days. A total of 7508 patients (16.8%) developed one or more postoperative complication and 207 died (0.5%). The overall mortality among patients who developed complications was 2.8%. Mortality following complications ranged from 2.4% for pulmonary embolism to 43.9% for cardiac arrest. A total of 4360 (9.7%) patients were admitted to a critical care unit as routine immediately after surgery, of whom 2198 (50.4%) developed a complication, with 105 (2.4%) deaths. A total of 1233 patients (16.4%) were admitted to a critical care unit to treat complications, with 119 (9.7%) deaths. Despite lower baseline risk, outcomes were similar in low- and middle-income compared with high-income countries. CONCLUSIONS: Poor patient outcomes are common after inpatient surgery. Global initiatives to increase access to surgical treatments should also address the need for safe perioperative care. STUDY REGISTRATION: ISRCTN5181700

Chemical Bonding and Physical Properties of Yb5Bi3Yb_{5}Bi_{3}

The binary compound Yb 5 Bi 3 was synthesized by reaction of the elements in a sealed Ta container. Its crystal structure was determined from single-crystal X-ray diffraction data: β -Yb 5 Sb 3 -type, space group Pnma, Pearson code oP32, a = 12.6375(6), b = 9.7243(4), c = 8.4117(5)Å, V = 1033.72(9)Å 3 , Z = 4, R gt (F) = 0.028, wR ref (F 2 ) = 0.069, T = 290 K. Band structure calculations and analysis of the chemical bonding suggest mainly ionic interactions in the crystal structure and a possible presence of ytterbium in two valence states Yb 2+ and Yb 3+ . The magnetization measurements showed that at low temperatures Yb 5 Bi 3 contains ytterbium exclusively in the 4 f 14 configuration without fluctuations to the Yb 4 f 13 configuration up to 400 K. From the Yb-L III X-ray absorption spectroscopy data the effective valence of ytterbium was found to be 2.11 (89 % of Yb in 4 f 14 configuration)

Two new hybrid organic/inorganic copper(II)-oxovanadate(V) diphosphonates: [Cu2(phen)2(O3PCH2PO 3)(V2O5)(H2O)]·H 2O and [Cu2(phen)2(O3P(CH 2)3PO3)(V2O5)] ·C3H8. Synthesis, ...

Full title: Two new hybrid organic/inorganic copper(II)-oxovanadate(V) diphosphonates: [Cu2(phen)2(O3PCH2PO 3)(V2O5)(H2O)]·H 2O and [Cu2(phen)2(O3P(CH 2)3PO3)(V2O5)] ·C3H8. Synthesis, structure, and magnetic properties. Two new hybrid organic/inorganic copper oxovanadium diphosphonates [Cu 2(phen)2(O3PCH2PO 3)(V2O5)(H20)]· H 2O (1) and [(Cu2(phen)2(O3P(CH 2)3PO3)(V2O5)] ·C3H8 (2) have been obtained by hydrothermal synthesis. The compounds are monoclinic, and they crystallize in the space group P21/n with cell parameters of a = 11.788(2) Å, b = 17.887(3) Å, c = 14.158(2) Å, and β = 93.99(0)° and in the space group C2/c with cell parameters of a = 11.025(1) Å, b = 18.664(2) Å, c = 15.054(2) Å, and β = 90.06(0)°, respectively. Both compounds present two-dimensional frameworks built up from infinite chains of corner-sharing vanadium tetrahedra and diphosphonate groups connected by copper tetramers for (1) and copper dimers for (2). The remarkable feature of (2) is the encapsulation of pro