We describe how the contribution of crystallographic texture to the anisotropy of the resistivity of polycrystalline samples can be estimated by averaging over crystallographic orientations through a ...geometric mean approach. The calculation takes into account the orientation distribution refined from neutron diffraction data and literature values for the single crystal resistivity tensor. The example discussed here is a melt-cast processed Bi2Sr2CaCu2O8+δ (Bi-2212) polycrystalline tube in which the main texture component is a fiber texture with relatively low texture strength. Experimentally-measured resistivities along the longitudinal, radial, and tangential directions of the Bi-2212 tube were compared to calculated values and found to be of the same order of magnitude. Calculations for this example and additional simulations for various texture strengths and single crystal resistivity anisotropies confirm that in the case of highly anisotropic phases such as Bi-2212, even low texture strengths have a significant effect on the anisotropy of the resistivity in polycrystalline samples.
We describe how the contribution of crystallographic texture to the anisotropy of the resistivity of polycrystalline samples can be estimated by averaging over crystallographic orientations through a ...geometric mean approach. The calculation takes into account the orientation distribution refined from neutron diffraction data and literature values for the single crystal resistivity tensor. The example discussed here is a melt-cast processed Bi₂Sr₂CaCu₂O
(Bi-2212) polycrystalline tube in which the main texture component is a fiber texture with relatively low texture strength. Experimentally-measured resistivities along the longitudinal, radial, and tangential directions of the Bi-2212 tube were compared to calculated values and found to be of the same order of magnitude. Calculations for this example and additional simulations for various texture strengths and single crystal resistivity anisotropies confirm that in the case of highly anisotropic phases such as Bi-2212, even low texture strengths have a significant effect on the anisotropy of the resistivity in polycrystalline samples.
Multilayered YBa2Cu3O7−δ (YBCO) thick films were coated on silver substrates by electrophoretic deposition (EPD) followed by heat treatment. A butanol-based YBCO suspension is used instead of the ...common acetone–iodine combination. Tests with several dispersing agents reveal that a branched polyethyleneimine (PEI) dispersant develops large positive surface charge on suspended YBCO particles. As a demonstration of the performance of this new suspension formulation, a 12-layer 100µm-thick YBCO coating was deposited on an Ag tube. The superconducting transition is sharp with onset critical temperature at 92K. The sample can shield a magnetic field of ~1.3mT at 77K, i.e., the best value so far for an YBCO coating on a metallic substrate.
•YBa2Cu3O7−δ thick films were prepared by electrophoretic deposition and sintering.•Butanol-based suspension was formulated instead of the usual acetone-based suspension.•Branched polyethyleneimine is a better dispersant than fish oil, Emphos or iodine.•A 100µm-thick YBa2Cu3O7−δ coating on Ag tube is able to shield 1.3mT at 77K.
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There has been lots of controversies about vaterite structure in the past decades. Extra peaks occurring out of the hexagonal structure and best described by Kamhi 1 still resist any ...indexing. Lower space group symmetries, superspace groups, microtwinning, and first-principle calculations 2, all failed in taking account of these minor peaks, surprisingly always present in all synthetic and biogenic vaterite formations. Recently, secondary interspersed domains observed in high-resolution TEM images indicated their incoherence and rather incompatible character with the vaterite matrix 3. One of the major difficulty in resolving the vaterite structure lies in the absence of single crystals. Powder diffraction patterns are always composed of hexagonal and extra, but small, peaks, and temptation to index the pattern as a single phase is large, particularly since x-ray fluorescence invariably probes for CaCO3. We used Hyriopsis cumingii freshwater mussel pearls to help proving that vaterite is definitely crystallizing within the original hexagonal space group. Some of these pearls suffer defective growth toward vaterite. In such cases the hexagonal peaks clearly exhibit a strong texture while the extra peaks look more random. This is an invaluable evidence of the existence of clearly separated phases, though the minor phase (or phases) still resist indexing. The hexagonal structure refinement, thanks to the strong vaterite texture, is obtained with larger resolution than before.
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Bi2Sr2CaCu2O8+δ HTSC superconductor is characterized by a very strong normal-state resistivity anisotropy, with ρc/ρab typically above 10E4. The aim of this study is to use Quantitative ...Texture Analysis from x-ray diffraction measurements to estimate the orientation effect on the anisotropic macroscopic resistivity in melt-cast bulk Bi2Sr2CaCu2O8+δ superconductors. Our approach uses the geometric mean 1 of the single crystal resistivity tensor weighted by the Orientation Distribution Function (ODF) to quantitatively estimate the macroscopic resistivity tensor of the samples. The ODF is obtained from x-ray Combined Analysis 2, using the E-WIMV algorithm of the MAUD software. The GMA applies to the rank-two resistivity tensor of the orthorhombic space group considered tetragonal due to the small difference of a- and b-axes of the phase, with only two independent tensor components. We relate a relatively good agreement between measured and calculated macroscopic anisotropic resistivity ratios. Even with ρc/ρab between 10E4 and 10E5 for Bi2212 at room temperature in single crystals 3, we experiment macroscopic ratio in our bulk samples of around only 2. This small ratio is explained by the weak planar- or fiber-like (Figure) texture achieved in the melt-cast samples, characterized by maxima of orientation distributions not larger than 10 mrd. Calculated resistivities, based on homogeneous crystallites, perfect grain boundaries and no secondary phases, are 10 times larger than the observed ones. This suggests that the observed minor phases positively affect conductive pathways between grains. Calculated and measured anisotropic resistive ratios are coherent with one another, and Combined Analysis gives good predictions of these former.
The high economic impact and zoonotic potential of avian influenza call for detailed investigations of dispersal dynamics of epidemics. We integrated phylogeographic and epidemiologic analyses to ...investigate the dynamics of a low pathogenicity avian influenza (H3N1) epidemic that occurred in Belgium during 2019. Virus genomes from 104 clinical samples originating from 85% of affected farms were sequenced. A spatially explicit phylogeographic analysis confirmed a dominating northeast to southwest dispersal direction and a long-distance dispersal event linked to direct live animal transportation between farms. Spatiotemporal clustering, transport, and social contacts strongly correlated with the phylogeographic pattern of the epidemic. We detected only a limited association between wind direction and direction of viral lineage dispersal. Our results highlight the multifactorial nature of avian influenza epidemics and illustrate the use of genomic analyses of virus dispersal to complement epidemiologic and environmental data, improve knowledge of avian influenza epidemiologic dynamics, and enhance control strategies.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, ODKLJ, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
7.
A world apart Hardy, Olivier J.; Dubourg, Dominique; Bourguignon, Mélanie ...
Demographic research,
07/2021, Letnik:
45
Journal Article
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In Western countries, COVID-19 has been particularly deadly for care home residents. To understand the role of age and sex structures, health frailty, and contamination dynamics in COVID-19 mortality ...in populations living inside and outside care homes. We compared COVID-19 death data recorded in March-June 2020 in Wallonia (southern Belgium) for populations living inside and outside care homes, using annual death data (all-cause mortality in 2017) to assess the health condition of each population. Sixty-four percent of COVID-19 deaths were residents in care homes, where the outbreak started after that in the external population, but at a faster pace. The death rate varied between 0per thousand and 340per thousand (mean 43per thousand) per care home, increasing with the number of both residents and staff. All-cause and COVID-19 mortality rates increased exponentially with age but were much higher in care homes. The ratio of male (M) to female (F) death rates was 1.6 for all-cause mortality and 2.0 for COVID-19 mortality (both confirmed and suspected). The COVID-19 mortality reached 24% (M) and 18% (F) of the all-cause mortality rate in care homes, compared to 5% (M) and 4% (F) outside care homes. The COVID-19 mortality rate was 130x higher inside than outside care homes, due to the near multiplicative effects of differences in the residents' age and sex structure (11x), health frailty (3.8x), and infection risk (probably 3.5x).
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