Combined X-ray diffraction and diffuse reflectance analysis of nanocrystalline mixed Sn(II) and Sn(IV) Oxide Powders

Nanocrystalline mixtures of Sn(II) and Sn(IV) oxide powders, potential gas sensor materials, are synthesized via a simple precipitation route using SnCl(2) as the precursor. Materials are characterized by powder X-ray diffraction, thermogravimetric analysis, UV-visible diffuse reflectance spectroscopy (DRS), and Fourier transform infrared spectroscopy. The ratio of Sn(II)/Sn(IV) in powders precipitated at room temperature, as well as the identity of the primary Sn(II) product (SnO or Sn(6)O(4)(OH)(4)), can be varied by adjusting aging time and washing procedures. The identity of the initial Sn(II) product influences the subsequent phase composition and degree of disorder in the tetragonal SnO(2) phase obtained following sintering in air. Analysis of the DRS absorption edge and long-wavelength (Urbach) absorption tail is used to determine the SnO(2) optical band gap and extent of disorder. SnO(2) obtained by heating the SnO/SnO(2) mixture at 600 or 800 degrees C has a smaller optical band gap and a broader Urbach tail than the analogous sample obtained from heating Sn(6)O(4)(OH)(4), indicating a more disordered material

Synthesis of Tin Oxide Nanocrystalline Phases Via Use of Tin (II) Halide Precursors

Nanocrystalline tin oxides are synthesized via precipitation from heated solutions as well as from a novel above-solution vapor deposition route that occurs at low temperatures and atmospheric pressure. Crystalline phases are characterized via powder X-ray diffraction. Samples precipitated from reactions of SnCl2 are found to exist primarily as mixtures of tetragonal SnO and tetragonal SnO2 or tetragonal SnO2 and tin(II) oxyhydroxide (Sn6O4- (OH)4), depending on reaction conditions. A mixed tin(II)/tin(IV) sample is shown to produce a rarely observed form of the intermediate oxide Sn3O4 upon annealing in air at 600 °C. SnBr2 exclusively forms tetragonal SnO2 via precipitation. Variation in the solvent composition with SnBr2 is shown to result in vapor deposition of SnO2 at temperatures below 160 °C. The average crystallite sizes of the vapor-deposited material are ≈ 3 nm and grow slowly upon heating. Partially hydrolyzed SnBr4 is proposed as the vapor deposition intermediate based on variations in precursor/solvent combinations along with FTIR and GC-MS analysis of the reaction solution removed prior to the onset of deposition

Rethinking the Detection Head Configuration for Traffic Object Detection

Multi-scale detection plays an important role in object detection models. However, researchers usually feel blank on how to reasonably configure detection heads combining multi-scale features at different input resolutions. We find that there are different matching relationships between the object distribution and the detection head at different input resolutions. Based on the instructive findings, we propose a lightweight traffic object detection network based on matching between detection head and object distribution, termed as MHD-Net. It consists of three main parts. The first is the detection head and object distribution matching strategy, which guides the rational configuration of detection head, so as to leverage multi-scale features to effectively detect objects at vastly different scales. The second is the cross-scale detection head configuration guideline, which instructs to replace multiple detection heads with only two detection heads possessing of rich feature representations to achieve an excellent balance between detection accuracy, model parameters, FLOPs and detection speed. The third is the receptive field enlargement method, which combines the dilated convolution module with shallow features of backbone to further improve the detection accuracy at the cost of increasing model parameters very slightly. The proposed model achieves more competitive performance than other models on BDD100K dataset and our proposed ETFOD-v2 dataset. The code will be available.Comment: 26 pages, 4 figures, 7 table

Gender Gaps in the Measurement of Public Opinion About Homosexuality in Cross-national Surveys: A Question-Wording Experiment

Measures of attitudes towards homosexuality in cross-national studies have received criticism for not being ‘gender-sensitive’. The current study used a split-ballot design allowing for separate analyses of the attitudes towards ‘gay men and lesbian women’, ‘gay men’, and ‘lesbian women’ in a pooled sample of 3,381 participants from Great Britain, Hungary, and Portugal. Analyses controlling for sociodemographics showed that differences in attitudes towards male and female targets were generally small and did not interact with the gender of the rater. In addition, results showed that men’s attitudes towards homosexuality were more strongly related to their gender ideology than women’s attitudes. Implications of these findings for cross-national studies measuring attitudes towards homosexuality are discussed

Transformation of microbially-induced protodolomite to dolomite proceeds under dry-heating conditions

The genesis of sedimentary dolomite remains an unresolved issue. Protodolomite has been considered as a metastable precursor for some sedimentary dolomites. Through laboratory experiments, much has been learnt about the transformation of protodolomite into dolomite under hydrothermal conditions mimicking those in open diagenetic systems. However, it is still unclear whether such mineral transformation could proceed in closed diagenetic systems, in which the supply of externally-derived fluids is often limited. Here through dry-heating experiments we demonstrated that low-temperature protodolomite converts into dolomite in the absence of external fluid. The starting materials for the recrystallization reactions included two types of protodolomite: biotic protodolomite and its abiotic counterpart. Biotic protodolomite was synthesized by means of a halophilic bacterium at 30 °C. Since the synthesis of abiotic protodolomite normally requires higher temperatures than biotic ones, the abiotic protodolomite samples used herein were prepared at 60 °C and 100 °C. These protodolomites were spherical in shape and composed of nano-globular subunits. Our protodolomite samples contained considerable structural water in the range of 1.4-7 wt%. The water content of protodolomites was linearly correlated with their synthesis temperature, that is, biotic protodolomite had a higher amount of water than its abiotic counterparts. The protodolomite samples were then dry-annealed at temperatures of 100 to 300 °C for two months. The results indicated that the rate of protodolomite-to-dolomite transformation was higher in the reactors using biotic protodolomite than those using abiotic protodolomites. This conversion was likely triggered by the dehydration of structural water within protodolomite. The resulting dolomite mostly retained spherical morphology, whereas its nanosized subunits tended to become rhombohedral. Calcite neoformation was also found to accompany the dolomite formation. Our findings suggest that structural water within protodolomite is an overlooked internal fluid and it might have an impact on the genesis of sedimentary dolomite during burial diagenesis

Structure and Magnetotransport Properties of Epitaxial Nanocomposite La0.67Ca0.33MnO3:SrTiO3 Thin Films Grown by a Chemical Solution Approach

Epitaxial La0.67Ca0.33MnO3:SrTiO3 (LCMO:STO) composite thin films have been grown on single crystal LaAlO3(001) substrates by a cost effective polymer-assisted deposition method. Both x-ray diffraction and high-resolution transmission electron microscopy confirm the growth of epitaxial films with an epitaxial relationship between the films and the substrates as (002)film||(002)sub and [202]film||[202]sub. The transport property measurement shows that the STO phase significantly increases the resistivity and enhances the magnetoresistance (MR) effect of LCMO and moves the metal-insulator transition to lower temperatures. For example, the MR values measured at magnetic fields of 0 and 3 T are −44.6% at 255 K for LCMO, −94.2% at 125 K for LCMO:3% STO, and −99.4% at 100 K for LCMO:5% STO, respectively