367 research outputs found
Nano-micro-porous skutterudites with 100% enhancement in ZT for high performance thermoelectricity
No full textAbstractIncreasing energy demands require new materials, e.g., thermoelectrics, for efficient energy conversion of fossil fuels. However, their low figure of merit (ZT) limits widespread applications. Nanostructuring has been an effective way of lowering the thermal conductivity. However, grain growth at elevated temperature is still a big concern, for otherwise expected to be long-lasting thermoelectric generators. Here, we report a porous architecture containing nano- to micrometer size irregularly shaped and randomly oriented pores, scattering a wide spectrum of phonons without employing the conventional rattling phenomenon. Lattice thermal conductivity reaches the phonon glass limit. This design yields &$2gt;100% enhancement in ZT, as compared to the pristine sample. An unprecedented and very promising ZT of 1.6 is obtained for Co23.4Sb69.1Si1.5Te6.0 alloy, by far the highest ZT ever reported for un-filled skutterudites, with further benefits, i.e. rare-earth-free and improved oxidation resistance enabling simple processing
Layered cobalt oxide epitaxial films exhibiting thermoelectric ZT = 0.11 at room temperature
No full textAmong many thermoelectric materials, oxide-based materials draw significant interest due to their environmental compatibility. In particular, layered cobaltite, Na0.75CoO2, shows a large thermoelectric power factor parallel to the layers. However, the thermal conductivity (k) is rather high (5-7 W m(-1) K-1), and therefore, its thermoelectric figure of merit ZT is small (similar to 0.03) at room temperature. Here we show that substituting the Na+ ion with the Ba2+ ion in NaxCoO2 drastically reduces the kappa while keeping the large power factor, resulting in a large enhancement in ZT. We fabricated epitaxial films of Na0.75CoO2 by the reactive solid-phase epitaxy method and performed ion-exchange treatment from Na+ to Ba2+ to synthesize Ba0.27CoO2 films. The room temperature electrical conductivity (s), thermopower (S), and power factor of the c-axis oriented Ba0.27CoO2 films along the in-plane direction were 2310 S cm(-1), +72 mV K-1, and 1.2 mW m(-1) K-2, respectively, while the k along the in-plane, which was clarified by measuring the k of the c-axis inclined (55 degrees) film, was 3.3 W m(-1) K-1. This yields a ZT (= S-2 sigma T/kappa) value along the in-plane as high as 0.11 at room temperature, which is the highest among those reported for oxide thermoelectric materials except oxychalcogenide (BiO)(CuSe)
Efficacy of novel SPAK inhibitor ZT-1a derivatives (1c, 1d, 1g & 1h) on improving post-stroke neurological outcome and brain lesion in mice
No full textThis is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordData availability:
Data will be made available on request.SPAK inhibitor ZT-1a was previously shown to be neuroprotective in murine ischemic stroke models. In this study, we further examined the efficacy of four ZT-1a derivatives (ZT-1c, -1d, -1g and -1h) on reducing stroke-induced sensorimotor function impairment and brain lesions. Vehicle control (Veh) or ZT-1 derivatives were administered via osmotic pump to adult C57BL/6J mice during 3–21 h post-stroke. Neurological behavior of these mice was assessed at days 1, 3, 5, and 7 post-stroke and MRI T2WI and DTI analysis was subsequently conducted in ex vivo brains. Veh-treated stroke mice displayed sensorimotor function deficits compared to Sham mice. In contrast, mice receiving ZT-1a derivatives displayed significantly lower neurological deficits at days 3–7 post-stroke (p -1c > -1g > -1h. The Veh-treated stroke mice displayed white matter tissue injury, reflected by reduced fractional anisotropy (FA) or axial diffusivity (AD) values in external capsule, internal capsule and hippocampus. In contrast, only ZT-1a-as well as ZT-1c-treated stroke mice exhibited significantly higher FA and AD values. These findings demonstrate that post-stroke administration of SPAK inhibitor ZT-1a and its derivatives (ZT-1c and ZT-1d) is effective in protecting gray and white matter tissues in ischemic brains, showing a potential for ischemic stroke therapy development.Veteran AffairsNational Institutes of Health (NIH)Royal Societ
Men’s education and intimate partner violence—Beyond the victim-oriented perspective: Evidence from demographic and health surveys in Central Africa
No full textBACKGROUND Intimate partner violence (IPV) has increasingly received attention in the last three decades. However, IPV-related studies in both high- and low- and middle-income countries adopted a victim-oriented perspective in which men are perpetrators and women, the victims. Using socio-cultural and resource theories as guiding frameworks, this paper assessed the associations between men s education and IPV in Central Africa, using nationally representative data of married and cohabiting women of reproductive ages. METHODS Data included in the analyses come from Demographic and Health Surveys (DHSs) in the Democratic Republic of the Congo (DRC), Cameroon, Gabon, and Chad. Analyzed sub-samples consisted of 3421, 5023, 3930, and 3221 married/cohabiting women of reproductive ages in Chad, DRC, Cameroon, and Gabon, respectively. RESULTS Findings indicated significant variations of IPV prevalence within and across countries. Previous research demonstrated that men s education is a protective factor in health-related studies. The present study, however, provide no clear evidence on the linkages between men s education and IPV. In contrast, the paper substantiated that highly educated women were at higher risks of IPV when spouses/partners were less educated. CONCLUSION These findings have policy and programmatic implications because they might impede progress towards SDG goals on the elimination of all forms of violence against girls and women in Central Africa, which recorded the worst development indicators in sub-Saharan Africa. On a methodological note, studies are increasingly using pooled data to increase statistical power. Those studies can be very limited to devise effective IPV-interventions since they mask geographical variations within and across countries. More effective IPV-interventions should be culturally rooted and accounting for geographical variations because some areas are more affected than others
Pion properties as a goldstone boson in the dual Ginzburg-Landau theory
No full textBy solving the Schwinger-Dyson equation for quark self-energy and Bethe-Salpeter equation for pseudo-scalar vertex, we investigate the static pion properties in the dual Ginzburg-Landau theory that includes a description of confinement. Pion mass formula and the Gell-Mann-Oakes-Renner relation are shown. The pion mass, resulting from the current quark mass, and pion decay constant are calculated. Our results show that the dynamical effect of light quarks is unimportant for the mass of pion.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000086601000020&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Physics, MultidisciplinarySCI(E)中国科学引文数据库(CSCD)0ARTICLE2291-2963
Gaseous nitrogen losses from soils under zero-till as compared with conventional-till management systems
No full textThe gaseous losses of N from conventional-till (CT) and zero-till (ZT) crop fields were 3 to 7 and 12 to 16 kg N ha−1 y−1, respectively. In contrast, losses from CT and ZT fallow were severalfold higher, namely, 12 to 14 and 34 kg N ha−1, respectively. The more dense surface soil and consistently higher moisture content (lower air-filled porosity) were identified as major factors affecting increased denitrification under ZT. The potential denitrification rates were markedly higher under ZT, and the population of denitrifiers was up to six times higher than in CT soil samples. The contribution of lower soil horizons towards gaseous N losses was found to be low on both CT and ZT fields, and this finding was confirmed from a survey carried out on three other widely differing soils. Volumetric soil moisture and air temperature were the only two of several factors that accounted for a significant portion of the variations in gaseous N fluxes under field conditions. The average mole fraction of N2O ranged from almost 100% to as low as 28% of the total gaseous products and showed a negative relationship with soil moisture
SnSe2 결함 도입으로 인한 SnSe의 고온 열전성능 증대 메커니즘
No full textSnSe is a promising thermoelectric material due to its low toxicity, low thermal conductivity, and multiple valence band structures, which are ideal for high electronic transport properties. The multiple valence band structure has attracted many attempts to engineer the carrier concentration of the SnSe via doping, to place its fermi level at a position where the maximum number of valence bands can participate in the electronic transport. Up until now, ~5 × 1019 cm-3 was the highest carrier concentration achieved in SnSe via doping. Recently, introducing SnSe2 into SnSe was found to effectively increase the carrier concentration as high as ~6.5 × 1019 cm-3 (at 300 K) due to the generated Sn vacancies. This high carrier concentration at 300 K, combined with the reduction in lattice thermal conductivity due to SnSe2 micro-domains formed within the SnSe lattice, improved the thermoelectric performance (zT) of SnSe – xSnSe2 as high as ~2.2 at 773 K. Here, we analyzed the changes in the electronic band parameters of SnSe as a function of temperature with varying SnSe2 content using the Single Parabolic Band (SPB) model. According to the SPB model, the calculated density-of-states effective mass and the fermi level are changed with temperature in such a way that the Hall carrier concentration (nH) of the SnSe – xSnSe2 samples at 773 K coincides with the optimum nH where the theoretically maximum zT is predicted. To optimize the nH at high temperatures for the highest zT, it is essential to tune the 300 K nH and the rate of nH change with increasing temperature via doping.Aerospace Structures & Computational Mechanic
Multi-Sommerfeld enhancement in dark sector
No full textAbstractWe study the multi-Sommerfeld enhancement in the case where V(r) is composed of different kinds of potentials. We show that there are special properties of the multi-Sommerfeld enhancement. The physical content of the multi-Sommerfeld mechanism is carefully demonstrated. The multi-Sommerfeld enhancement might play a role in dark matter annihilation
- …
