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Based on an accurate numerical solution of the kinetic equation using well-resolved spatial and velocity grids, the separation of rarefied gas flow in a microchannel with double rectangular bends is investigated over a wide range of Knudsen and Reynolds numbers. Rarefaction effects are found to play different roles in flow separation (vortex formation) at the concave and convex corners. Flow separations near the concave and convex corners are only observed for a Knudsen number up to
, respectively. With further increase of the Knudsen number, flow separation disappears. Due to the velocity slip at the solid walls, the concave (convex) vortex is suppressed (enhanced), which leads to the late (early) onset of separation of rarefied gas flows with respect to the Reynolds number. The critical Reynolds numbers for the emergence of concave and convex vortices are found to be as low as
, respectively. The slip velocity near the concave (convex) corner is found to increase (decrease) when the Knudsen number increases. An adverse pressure gradient appears near the concave corner for all the examined Knudsen numbers, while for the convex corner it only occurs when the Knudsen number is less than
. Due to the secondary flow and adverse pressure gradient near the rectangular bends, the mass flow rate ratio between the bent and straight channels of the same length is a non-monotonic function of the Knudsen number. Our results clarify the diversified and often contradictory observations reported in the literature about flow rate enhancement and vortex formation in bent microchannels.
To explore the changes in quality of life from the acute hospitalization period to 6 months after discharge in patients with first-ever ischemic stroke and to identify the association between resilience and the course of quality of life.
A prospective longitudinal cohort study.
This study was conducted in Shanghai, China.
Two hundred and seventeen stroke patients were recruited for an initial questionnaire survey from two tertiary hospitals from February 2017 to January 2018.
Quality of life was measured using the Stroke Scale Quality of Life. Resilience was assessed using the Connor–Davidson Resilience Scale. Other validated measurement instruments included the modified Rankin Scale and Hospital Anxiety and Depression Scale. A multilevel model was used for the analysis of repeated measurements and to determine the association between resilience and quality of life.
Quality of life scores significantly improved over the 6 months after discharge (B = 7.31, p < .0001). The multilevel model indicated that resilience was positively correlated with the course of quality of life (B = .133, p < .0001), independent of stroke severity (B = −.051, p = .0006), neurological function (B = −.577, p < .0001), hospitalization days (B = .023, p = .0099), anxiety (B = −.100, p =< .0001), depression (B = −.149, p < .0001), time (B = .360, p < .0001), and the interactions of time with hospitalization days (B = −.008, p = .0002), neurological function (B = .021, p < .0024), depression (B = −.014, p = .0273), and time (B = −.031, p < .0001).
Resilience played an important role in predicting the self-reported course of quality of life in stroke patients. Our findings emphasized the reasonableness and importance of developing suitable resilience-targeted clinical strategies for improving prognosis in stroke patients.
The mammary gland, a unique exocrine organ, is responsible for milk synthesis in mammals. Neonatal growth and health are predominantly determined by quality and quantity of milk production. Amino acids are crucial maternal nutrients that are the building blocks for milk protein and are potential energy sources for neonates. Recent advances made regarding the mammary gland further demonstrate that some functional amino acids also regulate milk protein and fat synthesis through distinct intracellular and extracellular pathways. In the present study, we discuss recent advances in the role of amino acids (especially branched-chain amino acids, methionine, arginine and lysine) in the regulation of milk synthesis. The present review also addresses the crucial questions of how amino acids are transported, sensed and transduced in the mammary gland.
To assess helical tomotherapy (TOMO) current clinical application and practice in mainland China.
Materials and methods:
Data were collected for all TOMO units clinically operational in mainland China by 30 April 2016, including (a) the distribution of installation and staffing levels; (b) types of cancers treated; (c) utilisation efficiency; (d) quality assurance; (e) maintenance; (f) optional features; and (g) satisfaction levels. The data were collected as a census and analysed qualitatively and quantitatively.
As of 30 April 2016, 23 TOMO units were used clinically by 22 hospitals in mainland China. In the same period, 22,558 cancer patients were treated. For TOMO units with more than a year of clinical utilisation, a median of 378 cases were treated annually per machine. The median daily operation was 10·5 hours, and treatment headcount was 38·3 patients. The median service outage rate was 2·6%, and the most common cause was malfunction of the multi-leaf collimator. In terms of overall satisfaction levels, 3 hospitals were very satisfied, 16 were satisfied and 3 considered their satisfaction level as average.
The overall operation of TOMO is good, but there are some problems due to running at full capacity, lack of clinical efficacy research and insufficient quality assurance regulations.
The objective of this study was to investigate the effects of dietary pyrroloquinoline quinone disodium (PQQ·Na2) supplementation on the reproductive performance and intestinal barrier functions of gestating and lactating female Sprague–Dawley (SD) rats and their offspring. Dietary supplementation with PQQ·Na2 increased the number of implanted embryos per litter during gestation and lactation at GD 20 and increased the number of viable fetuses per litter, and the weight of uterine horns with fetuses increased at 1 d of newborn. The mRNA expression levels of catalase (CAT), glutathione peroxidase (GPx2), superoxide dismutase (SOD1), solute carrier family 2 member 1 (Slc2a1) and solute carrier family 2 member 3 (Slc2a3) in the placenta were increased with dietary PQQ·Na2 supplementation. Dietary supplementation with PQQ·Na2 in gestating and lactating rats increased the CAT, SOD and GPx activities of the jejunal mucosa of weaned rats on PD 21. Dietary supplementation with PQQ·Na2 in female rats affected the expression of tight junction proteins (claudin, zonula occludens-1 (ZO-1) and occludin) in the jejunal mucosa of their offspring by increasing the expression of ZO-1 mRNA in the expression of ZO-1 and claudin mRNA in the jejunal mucosa of weaned rats on PD 21. In conclusion, dietary supplementation with PQQ·Na2 in gestating and lactating female rats had positive effects on their reproductive performance and on the intestinal barrier of weaned rats.
The kernel extreme learning machine (KELM) is more robust and has a faster learning speed when compared with the traditional neural networks, and thus it is increasingly gaining attention in hyperspectral image (HSI) classification. Although the Gaussian radial basis function kernel widely used in KELM has achieved promising classification performance in supervised HSI classification, it does not consider the underlying data structure of HSIs. In this paper, we propose a novel spectral-spatial KELM method (termed as MF-KELM) by incorporating the mean filtering kernel into the KELM model, which can properly compute the mean value of the spatial neighboring pixels in the kernel space. Considering that in the situation of limited training samples the classification result is very noisy, the spatial bilateral filtering information on spectral band-subsets is introduced to improve the accuracy. Experiment results show that our method outperforms other kernel functions based on KELM in terms of classification accuracy and visual comparison.
The Mn-steel matrix composite locally reinforced with in situ TiC–TiB2 ceramic particulate was successfully fabricated using a thermal explosion-casting route in a Cu–Ti–B4C system with various B4C particle sizes. With the increase of B4C particle size, the ignition temperature increased, the combustion temperature decreased, and the size of the TiC and TiB2 ceramic particulates became smaller. The hardness, friction coefficient, and wear resistance of the composite were higher than those of the Mn-steel matrix. With the increase of B4C particle size, the size of the TiC and TiB2 ceramic particulates fabricated in the local reinforcing region decreased, the interface bonding between reinforcing region and matrix became poor, and the number of pores in the local reinforcing region increased. Moreover, the composite with ∼3.5 μm B4C showed the best antiwear property. At a low load of 20 N, the dominant wear mechanisms of the Mn-steel matrix composite were microcutting and abrasive wear. While, at a high load of 80 N, the dominant wear mechanisms were microcutting and adhesion wear associated with the formation of delamination layer.
Retention of a nanostructure in thermoelectric materials through rapid sintering (e.g., field-assisted sintering) is generally associated with leaving certain amounts of porosity due to short sintering times. In this study, the influence of porosity on the thermoelectric transport properties in Bi2Te3-based alloys was studied by changing the sintering pressure during spark plasma sintering. N-type Bi2Te3 and p-type (Bi0.2Sb0.8)2Te3 were sintered at 673 K using pressures from 50 to 300 MPa to obtain different levels of porosity. Electrical resistivity, thermal conductivity, Seebeck coefficient, carrier concentrations, and Hall mobility were measured and characterized. The results show that increasing sintering pressure is effective in reducing porosity, which lowers electrical resistivity and increases the carrier concentrations. The transport properties were fitted to general effective medium equations and demonstrate that in p-type (Bi0.2Sb0.8)2Te3 sintered at high pressures, decreases in electrical resistivity and lattice thermal conductivity exceeded the Seebeck coefficient reduction, improving the thermoelectric figure of merit.
SrAl2O4:Eu2+,Dy3+ polynary complex nanobelts with long-persisting phosphorescence were synthesized via a facile but efficient combustion method followed by a postannealing reaction at temperature above 900 °C. All the samples emit greenish-yellow light from the d-f transition of Eu2+, and moreover, their wavelength redshifts with increasing calcination temperature since the increase in crystal size and crystalline quality causes a large average optical path and high crystal symmetry, respectively. The decay constant of the sample calcined at low temperature is smaller than that of the one annealed at high temperature owing to the presence of higher densities and depths of electron traps donated by host defects, and the initial brightness of the sample calcined at low temperature is relatively low owing to the small volume fraction from relatively low crystallinity.
Iodine-doped CdS (I-CdS) with controllable morphologies, pure hexagonal phase, and enhanced photocatalytic activity was synthesized via a mild hydrothermal process with polyvinylpyrrolidone-iodine (PVP-I) acting as the template-directing reagent and iodine source. The morphologies of the as-prepared samples could be adjusted from irregular cone-shaped particles to uneven microspheres, further to smooth microspheres, while the crystal phases were also transformed from mixed cubic and hexagonal phases to pure hexagonal phase upon increasing the molar ratio of PVP-I to Cd2+ from 0 to 2. The iodine doping could result in red shift of the absorption edges and band gap narrowing of the I-CdS samples. Importantly, a critical point of 0.5 of molar ratio of PVP-I to Cd2+ for iodine doping was found to be necessary for obtaining a pure hexagonal phase that facilitates the improving of photocatalytic activity on the degradation of Rhodamine B in aqueous solution under visible light irradiation.
N-type Bi2Te3 alloys with different microstructural length scales were prepared by mechanical milling and spark plasma sintering (SPS). The electrical resistivity, thermal conductivity, Seebeck coefficient, carrier concentration, and Hall mobility along and perpendicular to the loading direction were determined and characterized. The SPS sintered bulk disks using nanostructured powder contain high nanoporosity and weak (00l) texture along the loading axis, in contrast to those obtained with coarse powder. The influence of nanoporosity and texture on the thermoelectric and transport properties in the n-type Bi2Te3 alloys is discussed in light of the microstructural characteristics at different length scales.
Indentation techniques have been carried out to study the mechanical behavior of amorphous Al85Ni10La5 alloy powders produced by inert gas atomization. The present work reveals that this amorphous alloy undergoes a three-stage crystallization process in the temperature range of 250°C ~ 390°C, with a glass transition temperature of approximately 259°C. In this study, the influence of devitrification on mechanical response was investigated via indentation of the Al85Ni10La5 alloy powders annealed at various temperatures, for instance, at temperatures well below or close to glass transition (235°C, 245°C, 250°C), and well above glass transition (283°C). Moreover, the microstructure evolution and the formation of nanoscale crystallites were studied using TEM and XRD. The influence of devitrification on the indentation response was characterized, paying particular attention to shear band formation and variations in hardness. The hardening behavior was analyzed on the basis of a rule-of-mixtures approach by treating the partially crystallized alloy as a nanocomposite.
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