Coherent description of electrical and thermal impurity-and-phonon limited transport in simple metals

The electrical resistivity, thermoelectric power and electronic thermal conductivity of simple (isotropic) metals are studied in a uniform way. Starting from results of a variational solution of the Boltzmann equation, a generalized Matthiessen rule is used in order to superpose the inelastic (or not) electron-phonon and elastic electron-impurity scattering cross sections ("matrix elements"). The temperature dependence relative to these processes is given through simple functions and physical parameters over the usually investigated range of temperature for each transport coefficient. The coherence of such results is emphasized.Comment: 22 pages, 5 figures; to appear in International Journal of Modern Physics

Behavior of the thermopower in amorphous materials at the metal-insulator transition

Published versio

Analysis of Experimental Conditions for Simultaneous Measurements of Transport and Magnetotransport Coefficients of High Temperature Superconductors

Experimental conditions for simultaneous measurements of transport coefficients of high temperature superconductors in zero and non-zero magnetic fields are analysed. Test measurements of the thermal conductivity, the thermoelectric power and the Nernst - Ettingshausen effect of a textured Bi2212 sample are reported in an external magnetic field of 2T. Errors related to parameters of the thermocouple used and to the spurious heat flows are discussed for a new experimental set-up built based on a closed cycle helium refrigerator. Possible optimising of experimental conditions is suggested.Comment: 9 pages + 4 figures. accepted for publication in Cryogenic

General Formula for the Thermoelectric Transport Phenomena based on the Fermi Liquid Theory: Thermopower, Nernst Coefficient, and Thermal Conductivity

On the basis of the linear response transport theory, the general expressions for the thermoelectric transport coefficients, such as thermoelectric power (S), Nernst coefficient (\nu), and thermal conductivity (\kappa), are derived by using the Fermi liquid theory. The obtained expression is exact as for the most singular term in terms of 1/\gamma_k^* (\gamma_k^* being the quasiparticle damping rate). We utilize the Ward identities for the heat current which is derived by the local energy conservation law. Based on the derived expressions, we can calculate various thermoelectric transport coefficients within the framework of the Baym-Kadanoff type conserving approximation. Thus, the present expressions are very useful for studying the strongly correlated electrons such as high-Tc superconductors, organic metals, and heavy Fermion systems, where the current vertex corrections are expected to play important roles. By using the derived expression, we calculate the thermal conductivity \kappa in a free-dispersion model up to the second-order with respect to U. We find that it is slightly enhanced due to the vertex correction for the heat current, although the vertex correction for electron current makes the conductivity (\sigma) of this system diverge, reflecting the absence of the Umklapp process.Comment: 22 pages, 11 figures; accepted for publication in PR

Crystal-field effects on the thermal conductivity of localized spin metallic compounds

The influence of the crystal-electric-field (CEF) splitting on the thermal conductivity is calculated on the basis of a two-level system model applicable to intermetallic magnetic compounds. The localized spin scattering contribution kappa(s), in a manner similar to the total electronic thermal conductivity kappa(e), shows a larger increase at low and intermediate temperatures as compared to the case iii which-no crystal-electric-field splitting is taken into account. The influence of some theoretical parameters is also discussed. It is shown that the CEF effect enhances the effect of the magnetic scattering potential, and impurity contributions screen such an enhancement at temperatures below the Debye temperature. Other scattering contributions, e.g., electron-phonon and electron impurities, are also taken into account in our calculation. The theory is in quantitative agreement with data on RA1(2) systems taken as test cases, and leads to values of the level splitting in the 50 K range

Thermoelectric power of granular ceramic oxide superconductors

We discuss the Seebeck effect or thermoelectric power of granular ceramic oxide superconductors in an effective medium approximation. We compare experimental results to the theory. We find no evidence for attributing the behavior above the critical temperature to any phonon drag. The bump above Tc is simply due to electron-phonon (inelastic) scattering. The sign of the coefficient does not indicate the type of carrier. We show the necessity of theoretical work for compensated semi-metals as well. © 1988

Evaluation of selected dietary behaviours of students according to gender and nutritional knowledge

Introduction. Nutrition is a factor influencing physical and mental fitness. In this study we examine the lifestyle of university students and its impact on nutritional errors. Objective. To evaluate the dietary behaviours of students taking into account gender and nutritional knowledge. Material and methods. Using a QEB questionnaire, we were able to evaluate dietary behaviours and nutritional knowledge of respondents. Our analysis was conducted on data obtained from 456 students. Results. We found that nutritional knowledge for women was 34.7% satisfactory and 34.7% good. In contrast, nutritional knowledge for men varied, amounting to 40.2% satisfactory and 25.1% good. The number of meals and their regular consumption did not depend on gender or the nutritional knowledge of students, however, significant differences were recorded for the types of snacks they eat. A greater number of women than men snacked on sweets and biscuits, nuts and seeds, while in the case of salty snacks an opposite trend was observed. A higher level of nutritional knowledge correlated with the number of students snacking on fruit and vegetables instead of salty snacks. Moreover, it was observed that healthpromoting behaviours such as not adding sugar to beverages and not adding salt to dishes were more common with women and individuals with a higher level of nutritional knowledge. Conclusions. Women more frequently snack on sweets, biscuits, nuts and seeds. More men snack on salty snacks, add sugar to beverages and add salt to dishes. Individuals with insufficient nutritional knowledge more frequently snack on salty snacks rather than fruit. Students with insufficient nutritional knowledge more often commit nutritional errors.Wprowadzenie. Prawidłowe żywienie jest głównym czynnikiem wpływającym na zachowanie zdrowia oraz sprawności fizycznej i umysłowej. Czynnik ten nabiera szczególnego znaczenia w przypadku młodzieży akademickiej, z powodu wielu błędów żywieniowych, wynikających ze zmiany stylu życia studiującej młodzieży. Cel. Ocena wybranych zachowań żywieniowych studentów w zależności od ich płci i wiedzy żywieniowej. Materiał i metody. Badania przeprowadzono wśród 456 studentów, wykorzystując kwestionariusz QEB, który umożliwiał ocenę zachowań żywieniowych i wiedzy żywieniowej respondentów. Wyniki. Wykazano, iż po 34,7% kobiet charakteryzowało się dostateczną i dobrą wiedzą żywieniową. Odsetki dla mężczyzn były różne, wynosząc odpowiednio 40,2% i 25,1%. Liczba posiłków i regularność ich spożywania nie zależały od płci i wiedzy żywieniowej studentów. Odnotowano istotne różnice w rodzaju pojadanej żywności. Więcej kobiet niż mężczyzn pojadało cukierki i ciastka, orzechy i nasiona, a w przypadku słonych przekąsek zaobserwowano sytuację odwrotną. Wraz ze wzrostem poziomu wiedzy żywieniowej zwiększała się liczba studentów pojadających owoce i warzywa, zaś malała w odniesieniu do słonych przekąsek. Zaobserwowano ponadto, że zachowania prozdrowotne związane ze słodzeniem napojów i dosalaniem potraw dotyczyły przede wszystkim kobiet i osób o większej wiedzy żywieniowej. Wnioski. Kobiety częściej pojadają cukierki, ciastka, orzechy i nasiona. Więcej mężczyzn pojada słone przekąski, słodzi napoje i dosala potrawy. Osoby o niedostatecznej wiedzy żywieniowej rzadziej pojadają owoce, a częściej słone przekąski. Studenci popełniają błędy żywieniowe, których podłożem może być niewystarczająca wiedza żywieniowa

Thermoelectric power of granular ceramic oxide superconductors

We discuss the Seebeck effect or thermoelectric power of granular ceramic oxide superconductors in an effective medium approximation. We compare experimental results to the theory. We find no evidence for attributing the behavior above the critical temperature to any phonon drag. The bump above Tc is simply due to electron-phonon (inelastic) scattering. The sign of the coefficient does not indicate the type of carrier. We show the necessity of theoretical work for compensated semi-metals as well. © 1988

Influence of microstructure on the thermal conductivity of magnetoresistive La0.7Ca0.3MnO3/Mn3O4 manganite/insulating oxide polycrystalline bulk composites

We report the temperature dependence of the thermal conductivity kappa(T) of bulk polycrystalline composite samples containing a magnetoresistive manganite (La0.7Ca0.3MnO3) and an electrically insulating phase (Mn3O4). The sample porosity is shown to be a significant parameter affecting the experimental data: after porosity correction the curves display the characteristics of an ideal composite. A fit of the kappa(T) curves at low temperature using the Debye model enables the mean free path of phonons scattered on "boundaries" to be determined. The values are on the order of the grain size but are influenced by the grain arrangement and the presence of twins