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Due to the ultrawide bandgap (4.9 eV), high carrier mobility (300 cm 2 V − 1 s − 1 ), and high thermal stability, β − Ga 2 O 3 can be a potential candidate for high-temperature thermoelectric materials. However, the intrinsically high thermal conductivity may hinder its application for thermoelectric conversion. In this work, porous β − Ga 2 O 3 was prepared by the solvothermal method together with spark plasma sintering technology. Positron lifetime measurement and N 2 adsorption confirm the introduction of pores by adding sucrose in the sample preparation. The sucrose-derived β − Ga 2 O 3 sintered at a relatively low temperature of 600 ° C remains highly porous, which results in an extremely low thermal conductivity of 0.45 W m − 1 K − 1 at room temperature, and it further decreases to 0.29 W m − 1 K − 1 at 600 ° C. This is the lowest thermal conductivity for β − Ga 2 O 3 reported so far. Our work provides an avenue to reduce the thermal conductivity for β − Ga 2 O 3 and is believed to be widely applicable to many other thermoelectric materials. [ABSTRACT FROM AUTHOR]

In this study, polycrystalline SnSe was synthesized via a rapid, cost-effective, and large-scale synthesis route. The obtained SnSe powders were pressed into pellets via spark plasma sintering (SPS) at different temperatures. Powder X-ray diffraction (XRD) and field-emission scanning electron microscopy (FESEM) were used to characterize the crystal structures and morphology of the SnSe samples. The XRD results indicate that the orientation factors increase monotonously with the increase of sintering temperature. The FESEM images show that sintering temperatures have no obvious influence on the particle size. Positron annihilation measurements indicate that vacancy defects exist in all the sintered SnSe samples, and they recover gradually with increasing sintering temperatures. These vacancy defects are responsible for the lower lattice thermal conductivity in samples sintered at lower temperatures. The electrical conductivity, power factor, thermal conductivity, and figure of merit ZT show nearly the same variation trend, which increases initially with the increasing sintering temperature up to 550 ° C then decreases with further increase of the sintering temperature, which is possibly due to slight oxidation of SnSe. A maximum ZT value of ∼ 0.47 at 430 ° C was achieved for the 550 ° C sintered sample, which is higher than those reported for undoped polycrystalline SnSe around this temperature. Thus, we provide a simple, energy-saving, and effective method to synthesize polycrystalline SnSe in large quantities, and SPS is an effective method to optimize thermoelectric performance. [ABSTRACT FROM AUTHOR]

1. The aim of this study was to explore the effects of acute heat stress on serum hormone levels and the expression of genes and proteins related to the unfolded protein response (UPR) pathway and apoptotic process in the liver of broilers. 2. A total of 144 Arbor Acres broilers (35-d-old) were randomly allocated to 4 different environmental-controlled chambers for acute heat exposure. The temperature of the 4 environmental chambers was adjusted to 26°C (control), 29°C, 32°C, and 35°C within 1 h, respectively. The blood and liver samples were collected after 6 h of constant heat exposure at set temperatures. 3. The results showed that 6 h of acute heat stress increased serum hormone levels and up-regulated the expression of heat shock protein. The endoplasmic reticulum (ER) stress markers, GRP78 and GRP94, in the liver of broilers were significantly upregulated at the mRNA and protein levels. The PERK, IRE1, and XBP1 genes, which are involved in the unfolded protein response signalling, were significantly up-regulated at the mRNA levels. However, other pro-apoptotic genes showed no significant changes in the liver of broiler chickens in all groups except for upregulation of the anti-apoptotic gene BCL-xl. 4. The results suggested that broilers have tolerance to acute heat stress to a certain extent. The UPR activation can alleviate ER stress and further prevent apoptosis in the liver of broilers under short-term exposure to high ambient temperatures. [ABSTRACT FROM AUTHOR]

Nominal stoichiometric NaxCo2O4 (x?=?1.0, 1.2, 1.4, 1.6, 1.8, and 2.0) polycrystals were synthesized by a solid-state reaction method. They were further pressed into pellets by the spark plasma sintering. The crystal structure and morphology of NaxCo2O4 samples were characterized by X-ray diffraction and scanning electron microscopy measurements. Good crystallinity and layered structures were observed for all the samples. Positron annihilation measurements were performed for NaxCo2O4 as a function of Na content. Two lifetime components are resolved. τ1 is attributed mainly to positron annihilation in the O-Co-O layers and shifts to Na layers only in the H3 phase. The second lifetime τ2 is due to positron annihilation in vacancy clusters which may exist in the Na layers or grain boundary region. The size of vacancy clusters grow larger but their concentration decreases with increasing Na content in the range of 1.0?1. The thermal conductivity κ, on the other hand, shows systematic decrease with increasing Na content. This suggests that the increasing spacing of O-Co-O layer could effectively reduce the thermal conductivity of NaxCo2O4. [ABSTRACT FROM AUTHOR]

Microstructure of unfilled and Ba-filled CoSb3 has been studied by positron lifetime measurements together with theoretical calculation. Positron trapping in intrinsic voids is observed in the CoSb3, which contributes a positron lifetime of 263 6 2 ps. After filling Ba atoms with content up to x=0.4, the positron lifetime shows continuous increase. By comparing the experimental results with calculation following the phase diagram of BaxCo4Sb12 with x in the range of 0-0.5, it is found that when the Ba content is lower than 0.16, the filling of Ba atoms is in a phase of solid solution. At x=0.2, γ phase is formed, which is mixed with solid solution. At x>0.25, transition from γ phase to a mixture of γ and α phases is confirmed. [ABSTRACT FROM AUTHOR]

The electronic structure of a quintuple layer (QL) of Bi2Te3 is calculated using the first-principles pseudopotential method. It is found that the band gap of an isolated QL is considerably larger than that of bulk Bi2Te3. The electronic transport of the QL is, then, evaluated using the semiclassical Boltzmann theory within the relaxation time approximation. By fitting the energy surface from first-principles calculations, a suitable Morse potential is constructed and used to predicate the lattice thermal conductivity via equilibrium molecular dynamics simulations. By optimizing the carrier concentration of the system, the ZT of Bi2Te3 QL can be enhanced to a relatively high value. Moreover, the ZT value exhibits strong temperature dependence and can reach as high as 2.0 at 800 K. This value can be further increased to 2.2 by the substitution of Bi atoms with Sb atoms, giving nominal formula of (Bi0.25Sb0.75)2Te3. The significantly enhanced ZT value makes QL a very appealing candidate for thermoelectric applications. [ABSTRACT FROM AUTHOR]

The electronic structures of half-Heusler compounds TiNiSn and TiCoSb are investigated by using the full-potential linearized augmented plane-wave method. When the spin-orbital coupling is included in the calculations, there is only a slight change in the energy band structures. The transport coefficients (Seebeck coefficient, electrical conductivity, and power factor) are then calculated within the Boltzmann theory, and further evaluated as a function of chemical potential assuming a rigid band picture. Our calculations offer a valuable insight on how to improve the thermoelectric performance of these two compounds. [ABSTRACT FROM AUTHOR]

Barium and indium double-filled skutterudites BaxInyCo4Sb12-z have been synthesized by a melting method using a series of starting materials with nominal compositions Ba0.3-mInmCo4Sb12 (0≤m≤0.3). Rietveld structure refinement shows that both barium and indium occupied the Sb-icosahedron voids in skutterudite structure. The thermal vibration parameter Uiso of indium is an order of magnitude bigger than that of barium. The electron probe microanalysis data prove that the filling fraction limit of indium is about 0.22. Hall effect was measured by the Van de Pauw method at room temperature. All BaxInyCo4Sb12-z compounds exhibit n-type conduction. The temperature dependences of electrical conductivity, Seebeck coefficient, and thermal conductivity have been measured on these compounds in the range of 300–850 K. Ba0.13In0.14Co4Sb11.75 with close filling fractions for barium and indium exhibits anomalously excellent thermoelectric properties, which may be due to the presence of the localized state in the gap occupied by one electron from indium impurity. The lattice thermal conductivity of BaxInyCo4Sb12-z is significantly low compared to single barium-filled skutterudite Ba0.27Co4Sb11.85 and reached a minimum for Ba0.13In0.14Co4Sb11.75. The dimensionless thermoelectric figure of merit ZT increased with increasing temperature in the range of 300–675 K and reached a maximum value of 1.19 for Ba0.13In0.14Co4Sb11.75 at 850 K. [ABSTRACT FROM AUTHOR]

Barium-filled skutterudites BaCoSb with an anomalously large filling fraction of up to y=0.44 have been synthesized. The lattice parameters increase linearly with Ba content. Magnetic susceptibility data show that BaCoSb is paramagnetic, which implies that some of the Co atoms in BaCoSb have acquired a magnetic moment. The presence of the two different valence states of Co (Co3+ and Co2+) leads to the anomalously large barium filling fraction even without extra charge compensation. All samples show n-type conduction. The electrical conductivity increases with increasing the Ba filling fraction. The lattice thermal conductivity of BaCoSb is significantly depressed as compared to unfilled CoSb. The dimensionless thermoelectric figure of merit, ZT, increases with increasing temperature reaching a maximum value of 1.1 for BaCoSb at 850 K. c 2001 American Institute of Physics. [DOI: 10.1063/1.1388162]. [ABSTRACT FROM AUTHOR]

High purity In2O3 nanopowders were subjected to different thermal treatments to investigate the role of defects on the lattice thermal conductivity. The powders were first treated by spark plasma sintering (SPS) at 700∘C and annealed in air between 700 and 1300∘C. X-ray diffraction measurements show that the samples are single phase, and the diffraction peaks become sharper with increasing of annealing temperature, indicating improvement in crystallinity and increase in grain size. The In2O3 nanopowders were also treated by SPS sintering at different temperatures without subsequent annealing. On the contrary, the average grain size of In2O3 treated by SPS has no obvious change with the increase in sintering temperatures. Positron annihilation measurements reveal large amounts of monovacancies and vacancy clusters in the In2O3 nanocrystals. The monovacancies gradually recover and the vacancy clusters transform into smaller vacancies with increasing annealing or sintering temperatures. The lattice thermal conductivity increases with the increase in annealing or sintering temperature, which shows close correlation with the recovery of vacancy defects after heat treatment. This gives us strong evidence that vacancy defects play an important role on the suppression of lattice thermal conductivity in nanostructured thermoelectric materials. [ABSTRACT FROM AUTHOR]

Abstract: Cyclin‐dependent kinase inhibitors (CKIs) are negative regulators of the cell cycle. They can bind to cyclin‐dependent kinase (CDK)‐cyclin complexes and inhibit CDK activities. We identified a single homologous gene of the CDK interacting protein/kinase inhibitory protein (Cip/Kip) family, BmCKI, in the silkworm, Bombyx mori. The gene transcribes two splice variants: a 654‐bp‐long BmCKI‐L (the longer splice variant) encoding a protein with 217 amino acids and a 579‐bp‐long BmCKI‐S (the shorter splice variant) encoding a protein with 192 amino acids. BmCKI‐L and BmCKI‐S contain the Cip/Kip family conserved cyclin‐binding domain and the CDK‐binding domain. They are localized in the nucleus and have an unconventional bipartite nuclear localization signal at amino acid residues 181–210. Overexpression of BmCKI‐L or BmCKI‐S affected cell cycle progression; the cell cycle was arrested in the first gap phase of cell cycle (G1). RNA interference of BmCKI‐L or BmCKI‐S led to cells accumulating in the second gap phase and the mitotic phase of cell cycle (G2/M). Both BmCKI‐L and BmCKI‐S are involved in cell cycle regulation and probably have similar effects. The transgenic silkworm with BmCKI‐L overexpression (BmCKI‐L‐OE), exhibited embryonic lethal, larva developmental retardation and lethal phenotypes. These results suggest that BmCKI‐L might regulate the growth and development of silkworm. These findings clarify the function of CKIs and increase our understanding of cell cycle regulation in the silkworm. [ABSTRACT FROM AUTHOR]