Background: Interstitial cells of Cajal (ICC) are required for normal intestinal motility. ICC are found throughout the human colon and are decreased in the sigmoid colon of patients with slow ...transit constipation. Aims: The aims of this study were to determine the normal distribution of ICC within the human colon and to determine if ICC are decreased throughout the colon in slow transit constipation. Patients: The caecum, ascending, transverse, and sigmoid colons from six patients with slow transit constipation and colonic tissue from patients with resected colon cancer were used for this study. Methods: ICC cells were identified with a polyclonal antibody to c-Kit, serial 0.5 μm sections were obtained by confocal microscopy, and three dimensional software was employed to reconstruct the entire thickness of the colonic muscularis propria and submucosa. Results: ICC were located within both the longitudinal and circular muscle layers. Two networks of ICC were identified, one in the myenteric plexus region and another, less defined network, in the submucosal border. Caecum, ascending colon, transverse colon, and sigmoid colon displayed similar ICC volumes. ICC volume was significantly lower in the slow transit constipation patients across all colonic regions. Conclusions: The data suggest that ICC distribution is relatively uniform throughout the human colon and that decreased ICC volume is pan-colonic in idiopathic slow transit constipation.
Owing to its kinetic nature and distinctive computational features, the lattice Boltzmann method for simulating rarefied gas flows has attracted significant research interest in recent years. In this ...article, a lattice Boltzmann (LB) model is presented to study microchannel flows in the transition flow regime, which have gained much attention because of fundamental scientific issues and technological applications in various micro-electro-mechanical system (MEMS) devices. In the model, a Bosanquet-type effective viscosity is used to account for the rarefaction effect on gas viscosity. To match the introduced effective viscosity and to gain an accurate simulation, a modified second-order slip boundary condition with a new set of slip coefficients is proposed. Numerical investigations demonstrate that the results, including the velocity profile, the non-linear pressure distribution along the channel, and the mass flow rate, are in good agreement with the solution of the linearized Boltzmann equation, the direct simulation Monte Carlo (DSMC) results, and the experimental results over a broad range of Knudsen numbers. It is shown that taking the rarefaction effect on gas viscosity into consideration and employing an appropriate slip boundary condition can lead to a significant improvement in the modeling of rarefied gas flows with moderate Knudsen numbers in the transition flow regime.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Post-crystallization annealing above the T
was applied to a lithium disilicate glass-ceramic with microstructure consisting of glassy matrix and rod-like lithium disilicate crystals, effect of the ...annealing on the mechanical behavior was investigated. Flexural strength and VIF toughness of the glass-ceramic unexpectedly decreased after the annealing. The mechanical behavior variation was understood based on residual micro-stress analysis. Coefficient of thermal expansion for the glassy matrix presented a tendency to increase after the annealing, which would enlarge the thermal expansion mismatch between the glassy matrix and the lithium disilicate crystals. As a result, the residual micro-stresses in the glass-ceramic abnormally increased with increasing the annealing time. The mechanical property degradation was attributed to the annealing-induced increase of the residual micro-stresses.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Warm and hot blanking processes were developed for solving problems in piercing and trimming of press-hardened parts, some fine blank parts with comprehensive mechanical properties could be produced ...by hot blanking. To establish the optimum blanking processes and evaluate the effect of blanking temperature on the sheared section surface and fracture direction. Along with the fracture mechanism and microstructure of the parts, a series of hot blanking experiments for B1500HS steels were carried out at different blanking temperatures (450–800°C) and an 8% die clearance. The experimental results show that with the blanking temperature, the smooth (burnish) zone width increases, and the fracture direction becomes nearly normal. The sheared section surface of the parts mainly demonstrates ductile fracture mainly, accompanied by local brittle fracture over the blanking temperature range of 450–600°C. A ductile fracture region contains a great amount of fine equiaxed dimples over the blanking temperature range of 650–800°C, their microstructure is of complete martensite.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•The microstructure of B-DLC film is studied by HRTEM in cross-sectional observation.•Many crystalline nanoparticles dispersed in the amorphous matrix film are observed.•Through composition and ...structure analysis, the nanoparticles are identified as B2O.•The work implies the doped B element exists as oxide state in the B-DLC film.
Boron doped diamond-like carbon (B-DLC) film was synthesized on silicon (100) wafer by biased target ion beam deposition. High-resolution transmission electron microscopy (HRTEM) is employed to investigate the microstructure of the B-DLC thin film in cross-sectional observation. Many crystalline nanoparticles randomly dispersed and embedded in the amorphous matrix film are observed. Through chemical compositional analysis of the B-DLC film, some amount of O element is confirmed to be contained. And also, some nanoparticles with near zone axes are indexed, which are accordance with B2O phase. Therefore, the contained O element causing the B element oxidized is proposed, resulting in the formation of the nanoparticles. Our work indicates that in the B-DLC film a significant amount of the doped B element exists as boron suboxide nanoparticles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ti-based bulk metallic glass composite alloys Ti56Zr6Cu19.8Pd8.4Sn1.8Nb8, Ti64Zr4Cu13.2Pd5.6Sn1.2Nb12 and Ti68Cu13.2Pd5.6Sn1.2Nb12 were designed to obtain the microstructure composing of β-Ti ...dendrites and glassy matrix. The compressive and three-point bending properties were investigated. It was found that the actual microstructure of the Nb-added alloys consisted of primarily precipitated β-Ti dendrites, network-like glassy matrix, and extra island-like Ti2Cu intermetallic phase with different volume fractions. Under compressive loading, all the Nb-added alloys presented higher yield strength combined with remarkably increased plasticity. Under bending condition, however, the alloys Ti56Zr6Cu19.8Pd8.4Sn1.8Nb8 and Ti64Zr4Cu13.2Pd5.6Sn1.2Nb12 with higher Ti2Cu volume fractions became completely brittle. The alloy Ti68Cu13.2Pd5.6Sn1.2Nb12 could keep its plastic deformability due to the decreased Ti2Cu volume fraction. Compressive deforming behavior of the Nb-added alloys was determined by the ductile β-Ti phase and glassy matrix, nevertheless, bending deforming behavior of the alloys was determined by the volume fraction and distribution of the brittle intermetallics.
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•Ti–Zr–Cu–Pd–Sn–Nb bulk metallic glass composites were prepared.•The composites consisted of dendritic β-Ti, glassy matrix and Ti2Cu phase.•All the composites presented excellent compressive plasticity.•Only the composite containing 8% Ti2Cu exhibited enhanced bending plasticity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We report the unique thermal and mechanical stability of a metastable B2 phase embedded in a metallic glass matrix at liquid-nitrogen temperature. The B2 phase is stabilized by the constraints of the ...hard amorphous matrix, which result from the increasing hydrostatic pressure during cryogenic cooling. The stability of the B2 phase contributes to the high strength and ductility of CuZr-based bulk metallic glass composites at cryogenic temperature. This discovery is expected to provide new strategies for designing strong and ductile materials containing a metastable phase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Extreme climate events are becoming more frequent, with poorly understood implications for carbon sequestration by terrestrial ecosystems. A better understanding will critically depend on accurate ...and precise quantification of ecosystems responses to these events. Taking the 2019 US Midwest floods as a case study, we investigate current capabilities for tracking regional flux anomalies with “top‐down” inversion analyses that assimilate atmospheric CO2 observations. For this analysis, we develop a regionally nested version of the NASA Carbon Monitoring System‐Flux system for North America (CMS‐Flux‐NA) that allows high resolution atmospheric transport (0.5° × 0.625°). Relative to a 2018 baseline, we find the 2019 US Midwest growing season net carbon uptake is reduced by 11–57 TgC (3%–16%, range across assimilated CO2 data sets). These estimates are found to be consistent with independent “bottom‐up” estimates of carbon uptake based on vegetation remote sensing (15–78 TgC). We then investigate current limitations in tracking regional carbon budgets using “top‐down” methods. In a set of observing system simulation experiments, we show that the ability of atmospheric CO2 inversions to capture regional carbon flux anomalies is still limited by observational coverage gaps for both in situ and satellite observations. Future space‐based missions that allow for daily observational coverage across North America would largely mitigate these observational gaps, allowing for improved top‐down estimates of ecosystem responses to extreme climate events.
Plain Language Summary
Extreme climate events, such as floods or heatwaves, can have major impacts on the carbon cycle. For example, widespread flooding in the US Midwest during 2019 delayed the planting of crops leading to reduced plant growth and carbon uptake relative to 2018. Here, we test how well this reduction in carbon uptake can be inferred from measurements of atmospheric CO2. We find that these data can identify reduced net carbon uptake to the US Midwest during the 2019 floods, but that sparse observational coverage limits our ability to quantify the anomaly in net carbon uptake. We show that expanded space‐based observations of CO2 would fill these gaps, allowing for improved estimates of interannual variations in the US CO2 budget.
Key Points
Bottom‐up and top‐down methods capture reduced 2019 US Midwest carbon uptake relative to 2018
Gaps in atmospheric CO2 observations drive uncertainties in top‐down estimates
Nested inversion better localizes US Midwest ΔNEE relative to coarse global model
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Semi-transparent perovskite solar cells attract significant attention in building-integrated photovoltaics, especially for solar window application. However, thinning the perovskite photoactive ...layer, setting up nanostructures in the perovskite layer, and improving the functional layer transparent can neither effectively balance the power conversion efficiency (PCE) and average visible transmittance (AVT), nor can it effectively resolve the issue of colorful transmitted light. Here, based on the light polarization-selective absorption characteristics of photonic crystals, a semi-transparent perovskite solar cell with the grating-based photonic crystals is presented. It can apply the original layer structure of high efficiency perovskite solar cells without any transparent replacement, including the retention of opaque electrodes. Through the developed multiphysics and multi-objective mathematical model, the semi-transparent FAPbI3 solar cells can be optimized with PCE of 10% and AVT of 60.3%. When PCE increases to 12%, 15%, and 17%, the corresponding AVTs are 52.6%, 41.1%, and 33.4%, respectively. The performance far exceeds the benchmark of PCE (10%) and AVT (25%) for solar window application. Also, the transmitted light remains white regardless of the values of AVT and PCE. Furthermore, the semi-transparent perovskite solar cells with the grating-based photonic crystals can exhibit stable high-performance when the dimension tolerance varies from 1% to 20%, which reduces the requirement of processing technology. In the end, a design and optimization guideline for the semi-transparent perovskite solar cells is proposed through the analyses on the effect of a broad incident angle. These findings provide effective design strategies for the semi-transparent perovskite solar cells in the context of building-integrated photovoltaics.
•A high-performance semi-transparent perovskite solar cell with a grating-based photonic crystal.•A multi-physics & multi-objective mathematical model for intelligent optimization.•A semi-transparent perovskite solar cell with PCE of 15%, AVT of 41.1%, and white transmitted light.•Stable high-performance with 1%–20% variation in dimensional tolerances.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The solar energy flux distribution on the outer wall of the inner absorber tube of a parabolic solar collector receiver is calculated successfully by adopting the Monte Carlo Ray-Trace Method (MCRT ...Method). It is revealed that the non-uniformity of the solar energy flux distribution is very large. Three-dimensional numerical simulation of coupled heat transfer characteristics in the receiver tube is calculated and analyzed by combining the MCRT Method and the FLUENT software, in which the heat transfer fluid and physical model are Syltherm 800 liquid oil and LS2 parabolic solar collector from the testing experiment of Dudley et al., respectively. Temperature-dependent properties of the oil and thermal radiation between the inner absorber tube and the outer glass cover tube are also taken into account. Comparing with test results from three typical testing conditions, the average difference is within 2%. And then the mechanism of the coupled heat transfer in the receiver tube is further studied.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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