Thermoelectric devices convert heat flow to charge flow, providing electricity. Materials for highly efficient devices must satisfy conflicting requirements of high electrical conductivity and low thermal conductivity. Thermal conductivity in caged compounds is known to be suppressed by a large vibration of guest atoms, so-called rattling, which effectively scatters phonons. Here, the crystal structure and phonon dynamics of tetrahedrites (Cu,Zn) (Sb,As) S are studied. The results reveal that the Cu atoms in a planar coordination are rattling. In contrast to caged compounds, chemical pressure enlarges the amplitude of the rattling vibration in the tetrahedrites so that the rattling atom is squeezed out of the planar coordination. Furthermore, the rattling vibration shakes neighbors through lone pairs of the metalloids, Sb and As, which is responsible for the low thermal conductivity of tetrahedrites. These findings provide a new strategy for the development of highly efficient thermoelectric materials with planar coordination.
Lifshitz transition, a change in Fermi surface topology, is likely to greatly influence exotic correlated phenomena in solids, such as high-temperature superconductivity and complex magnetism.However, since the observation of Fermi surfaces is generally difficult in the strongly correlated systems, a direct link between the Lifshitz transition and quantum phenomena has been elusive so far. Here, we report a marked impact of the pressure-induced Lifshitz transition on thermoelectric performance for SnSe, a promising thermoelectric material without strong electron correlation. By applying pressure up to 1.6 GPa, we have observed a large enhancement of thermoelectric power factor by more than 100% over a wide temperature range (10-300 K). Furthermore, the high carrier mobility enables the detection of quantum oscillations of resistivity, revealing the emergence of new Fermi pockets at ∼0.86 GPa. The observed thermoelectric properties linked to the multi-valley band structure are quantitatively reproduced by first-principles calculations, providing novel insight into designing the SnSe-related materials for potential valleytronic as well as thermoelectric applications.
The present study was carried out to examine the effects of valproic acid (VPA), a histone deacetylase inhibitor, on in vitro development of miniature pig somatic cell nuclear transfer (SCNT) embryos and on expression of a mouse Oct-3/4 promoter-driven enhanced green fluorescent protein (EGFP) gene (EGFP expression only detected in Oct-3/4-expressing cells) introduced into donor cells for SCNT during their development. The addition of 4 mM VPA to embryo culture medium for 48 h after activation significantly (p < 0.01) increased the blastocyst formation rate of SCNT embryos compared with the control, whereas VPA did not affect their cleavage rate. The rate of SCNT embryos expressing EGFP at 5 days of culture was not affected by the presence or absence of VPA treatment. At 7 days of culture, however, the addition of 4 mM VPA to embryo culture medium for 48 h after activation significantly (p < 0.05) increased the rate of SCNT embryos expressing EGFP compared with the control. The results indicate that VPA enhances the ability of miniature pig SCNT embryos to develop into blastocysts and maintains the ability of them to express Oct-3/4 gene.
The crystal structure of vivianite, Foa(PO4)9.8H20, and symplesite, F%(AsO4). 8H20, has been determined using Weissenberg and oscillation photographs (Me Ka, ~-0.710 A.). The unit cells have dimensions: Vivianite a= 10.08, b = 13.43, c= 4.70 A., fl= 104 ° 30', Symplesito a= 10.25, b = 13.48, c-4.71 A., fl= 103 ° 50', with two molecules in each cell. The space group is C~h-C2/m. The structure is built up of single and double octahedral groups of oxygen and H~O around Fe. The double group, Fe~O~(H90)o is linked to two neighbouring similar groups and four other single groups, FeO~(H~O)4, by P (or As) which is in the middle of a tetrahedron of oxygen, forming a complex band extended parallel to (010). Parallel bands are held to each other by H~O molecules which, lying on both sides of the band, are again grouped together tetrahedrally. The electrostatic balance of the component atoms and atom groups are almost ideally maintained.
Escherichia coli and Candida brassicae were cultivated in a fed-batch culture with a DO-stat under the condition that none of the components in the basal medium limited the growth of the microorganism. High densities of biomasses (125 g/7 for E. coli and 138 g// for C. brassicae) were obtained. The final biomasses obtained in the cultivations of E. coli and C brassicae corresponded to 57%and 51 %, respectively, of the limits that the organisms can be cultivated in view of viscosity of the broth. Metabolic products in the supernatant of the broth at the end of the cultivation and concentration of carbon dioxide in exit gas from the fermentor were measured, and the relations between cell concentration and growth yield with respect to carbon source were shown. It was considered that the decreases in growth yield and specific growth rate in the case of E. coli were due to the metabolites, including CO2, which increased to inhibitory concentrations. On the other hand, the possibility of obtaining a higher density of biomass was shown in the case of C. brassicae if a fermentor with higher oxygen transfer rate were used. Merits of using pure oxygen gas for production of biomass were exemplified.
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