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Clive Bell 《Papers in Regional Science》2022,101(2):373-397
The effects of a rural roads programme depend on labour mobility, how the programme is financed, and agglomeration economies. If financed by a rural poll tax and cross-price effects and agglomeration economies are sufficiently small, the wage will rise, with some return migration. Taxes on trade act as countervailing distortions, yielding urban households some relief. Rural-urban commuting promotes the exploitation of agglomeration economies; taxes on international trade are then inferior to a poll tax. The change in the value, at producer prices, of the rural sector's net supply vector can be a poor measure of the programme's social profitability. 相似文献
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《Ceramics International》2022,48(3):3362-3367
The influence of high-energy ball milling on structural, microstructural, and optical properties of TiO2 by modifying the nanoparticle size was studied. Five samples were extracted at different milling times (0, 2, 4, 8, and 13 h). The average particle sizes estimated by dynamic light scattering (DLS) were 205, 155.8, 116.8, 82.9, and 82.7 nm at 0, 2, 4, 8, and 13 h, respectively. X-ray diffraction analysis confirmed progressive broadening of the peaks as the milling time elapsed. Besides, a correlation was found between d spacing and the average crystal size. The UV–Vis diffuse reflectance spectra of TiO2 revealed a decrease in reflectance due to particle size reduction. Similarly, an alteration of the bandgap transition energy was presented, whose values gradually decreased from 2.966 eV to 2.861 eV for the sample without and with the maximum duration milling performed (13 h), respectively. Likewise, the SEM analysis showed a distribution in nanoparticle size that became more homogeneous and smaller average grain size as the milling duration was longer. 相似文献
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利用水力空化过程产生局部的高温、高压、高射流以及强大的剪切力等极端化学物理条件改质处理沙特重质原油,试验结果表明:沙特重质原油经过水力空化改质后粘度由13.61降低至7.22mm2/s,残碳由7.16%降低至6.48%,实沸点蒸馏后减压渣油降低1个百分点。进一步采用APPI FT-IR MS、XRD、FT-IR、SEM和粒度分布等技术研究了水力空化改质对沙重原油分子组成,沥青质团聚体微晶结构、沥青质胶束粒径分布、沥青质官能团、沥青质形貌等方面的影响,从分子角度阐述空化改质重油的机理。研究结果表明:水力空化改质后沙重原油分子量分布、芳烃类化合物缔合作用变小;沥青质对低DBE化合物吸附性能降低;沥青质团聚体微晶结构更加松散;沥青质胶束粒度分布降低;沥青质分子相互团聚作用力减弱。进一步考察了水力空化改质前后减压渣油延迟焦化性能,改质处理后焦炭产率降低1.85个百分点,液体收率和气体产率分别增加1.52和0.33个百分点,水力空化改质对沥青质性质、结构特点的改善能够有效的提高其加工性能。 相似文献
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《Geotextiles and Geomembranes》2022,50(4):779-793
As a new type of material for civil engineering projects, the rubber and sand mixture is widely used in roadbed fillers, offering environmental benefits over traditional tyre disposal methods. This study uses a large-scale direct shear apparatus to examine the interface shear properties of the geogrid-reinforced rubber and sand mixture, considering different particle size ratios (r), rubber contents, and normal stresses. Based on indoor tests, direct shear models of the mixture with different values of r are established in PFC3D, revealing the meso-mechanical mechanism of the mixture in the direct shear process. The results show that when r is greater than 1, incorporating a certain amount of rubber particles can increase the shear strength of the mixture. The r values of 15.78, 7.63, and 3.98 correspond to an optimal rubber content of 30%, 10%, and 20%, respectively. When r is less than 1, mixing rubber particles can only reduce the shear strength of the mixture. When the rubber content is low, the smaller the value of r, the greater is the thickness of the shear band. Furthermore, the normal and tangential contact forces are greater. The fabric anisotropy evolution law of the mixture is consistent with the change in the contact force distribution. 相似文献
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Abhishek Nigam Sheetal Saini Ambak Kumar Rai S.J. Pawar 《Ceramics International》2021,47(14):19515-19525
In this study, MgO nanoparticles were successfully fabricated and incubated inside ZnO NPs to form MgO/ZnO nanocomposite for biomedical applications. The x-ray diffraction analysis of MgO, ZnO, and MgO/ZnO has shown the single-phase x-ray diffraction patterns through X'pert High score. The crystallite sizes were calculated as 18 nm, 42 nm, and 53 nm, respectively. The average particle size of MgO, ZnO, and MgO/ZnO nanopowders depicted from secondary electron images of field emission electron microscopy were 56 nm, 400 nm, and 450 nm, respectively. The presence of MgO NPs inside ZnO NPs was confirmed by transmission electron microscopy. The elemental dispersive spectroscopy of MgO, given the peaks of oxygen and magnesium, also showed only zinc and oxygen peaks in ZnO, which confirms no other impurities in MgO and ZnO powders. The elemental analysis of MgO/ZnO nanocomposite showed the peaks of Zinc and Oxygen, along with a tiny peak of Mg. The photoluminescence and UV–vis spectroscopy revealed the absorbance fluorescence limit of the nanomaterials. Fourier transform infrared spectroscopy confirmed the several groups present in the nanocomposite. The biocompatibility of MgO, ZnO, and MgO/ZnO was observed with human peripheral blood mononuclear cells. The cytotoxicity studies were also performed against human cancer (liver and breast) cell lines. The MgO, ZnO, and MgO/ZnO exhibited the antimicrobial properties against Escherichia coli and Staphylococcus aureus. 相似文献
10.
Corey R. Nelson Tyler Mrozowich Sean M. Park Simmone Dsouza Amy Henrickson Justin R. J. Vigar Hans-Joachim Wieden Raymond J. Owens Borries Demeler Trushar R. Patel 《International journal of molecular sciences》2021,22(1)
Rift Valley fever virus (RVFV) is a mosquito-transmitted virus from the Bunyaviridae family that causes high rates of mortality and morbidity in humans and ruminant animals. Previous studies indicated that DEAD-box helicase 17 (DDX17) restricts RVFV replication by recognizing two primary non-coding RNAs in the S-segment of the genome: the intergenic region (IGR) and 5′ non-coding region (NCR). However, we lack molecular insights into the direct binding of DDX17 with RVFV non-coding RNAs and information on the unwinding of both non-coding RNAs by DDX17. Therefore, we performed an extensive biophysical analysis of the DDX17 helicase domain (DDX17135–555) and RVFV non-coding RNAs, IGR and 5’ NCR. The homogeneity studies using analytical ultracentrifugation indicated that DDX17135–555, IGR, and 5’ NCR are pure. Next, we performed small-angle X-ray scattering (SAXS) experiments, which suggested that DDX17 and both RNAs are homogenous as well. SAXS analysis also demonstrated that DDX17 is globular to an extent, whereas the RNAs adopt an extended conformation in solution. Subsequently, microscale thermophoresis (MST) experiments were performed to investigate the direct binding of DDX17 to the non-coding RNAs. The MST experiments demonstrated that DDX17 binds with the IGR and 5’ NCR with a dissociation constant of 5.77 ± 0.15 µM and 9.85 ± 0.11 µM, respectively. As DDX17135–555 is an RNA helicase, we next determined if it could unwind IGR and NCR. We developed a helicase assay using MST and fluorescently-labeled oligos, which suggested DDX17135–555 can unwind both RNAs. Overall, our study provides direct evidence of DDX17135–555 interacting with and unwinding RVFV non-coding regions. 相似文献