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The flow conditions of the grinding fluid during grinding are analyzed with regard to the problem of easy burns during surface profile grinding of difficult-to-machine materials, nickel-based high-temperature alloys. The CFD simulations were carried out to analyze the grinding fluid flow in the grinding zone during flat and circular profile grinding according to the gas–liquid two-phase flow VOF theory. Numerical simulations were performed using FLUENT software to analyze the pressure and volume fraction in the gas–liquid two-phase flow field under different parameters by changing the injection speed and injection position. The effects of different injection positions and injection speeds on the grinding fluid flow in the grinding zone were investigated. The study showed that the higher the injection speed of the grinding fluid, the higher the dynamic pressure of the grinding fluid on the workpiece surface and the higher the return flow rate on the grinding wheel surface; the lower the speed, the lower the dynamic pressure of the grinding fluid on the workpiece surface but the higher the return flow rate. At the same injection position, the volume fraction of grinding fluid flowing from the outlet first increases with increasing injection speed, and then tends to level off; at the same injection speed, the integral number of grinding fluid flowing from the outlet is greatest for the central injection. Thus, the optimal injection position and injection speed of grinding fluid are proposed. It provides an important reference for improving the quality of profile grinding and preventing the workpiece from being burned during grinding, and provides a basis for subsequent profile grinding tests on high-temperature alloys. [ABSTRACT FROM AUTHOR]

Structure has been considered to play an important role in photocatalytic performance of the semiconductors, but the intrinsic factors were rarely revealed. Herein, ZnO nanomaterials in the structures of thin film, nanowire array and nanosheet array were synthesized, and their structural characteristics, optical properties, photocurrent response and photocatalytic efficiency were compared with each other for illustrating the issue. The photoluminescence intensity decreased in the order of nanosheets, thin film and nanowires for improved lifetime of the photoexcited charges. The absorption of the nanosheets and nanowires improved obviously in the visible range with a redshift of the absorption edge than that of the thin film. The nanowires possessed the highest response current of 82.65 μA at a response time of 2.0 ms in a sensitivity of 87.93 at the light frequency of 1 Hz, and gained the largest catalytic efficiency of 2.45 μg/cm2 h for the methylene blue degradation in UV light. Nevertheless, the improvement of catalytic efficiency of the nanosheets (up to 42.4%) was much larger than that of nanowires (5.7%) and thin film (2.6%) for the Au coating. The analysis revealed that the photocatalytic efficiency of the ZnO nanomaterials was modulated by the structure as it contained different surface area, roughness, defect and doping states, vacancies, polar and non-polar crystalline faces, which would provide structural design of semiconductor nanomaterials for the photoelectric and photocatalytic applications. [ABSTRACT FROM AUTHOR]

1,2-Azoles are privileged structures in ligand/catalyst design and widely exist in many important natural products and drugs. In this report, two types of axially chiral 1,2-azoles (naphthyl-isothiazole S-oxides with a stereogenic sulfur center and atropoisomeric naphthyl pyrazoles) are synthesized via modified vinylidene ortho-quinone methide intermediates. Diverse products are acquired in satisfying yields and good to excellent enantioselectivities. The vinylidene ortho-quinone methide intermediates bearing two hetero atoms at 5-position have been demonstrated as a platform molecule for the atroposelective synthesis of axially chiral 1,2-azoles. This finding not only enrich our knowledge of vinylidene ortho-quinone methide chemistry but also provide the easy preparation method for diverse atropisomeric heterobiaryls that were inaccessible by existing methodologies. The obtained chiral naphthyl-isothiazole S-oxides and naphthyl-pyrazoles have demonstrated their potential application in further synthetic transformations and therapeutic agents. 1,2-Azoles are privileged structures in many natural products and drugs. The authors report an atroposelective synthesis of two types of axially chiral 1,2-azoles, through vinylidene ortho-quinone methide intermediates. [ABSTRACT FROM AUTHOR]

Extracellular vesicles are membrane-packed entities that are involved in various physiological and pathological processes. Recently, the role of exosomes and microvesicles in regenerative medicine has been elucidated. Indeed, therapeutic potential of stem cells may be partly due to exosomes or microvesicles. However, injection of these vesicles may lead to their rapid clearance from the injection site. To address this challenge, different delivery systems for these vesicles' sustained delivery have been developed. In this regard, chitosan based hydrogels have been successfully utilized as delivery platforms for exosomes and microvesicles. In the current review, the prospects, challenges, and applications of chitosan-based hydrogels as a delivery vehicle for exosomes and microvesicles will be discussed. [ABSTRACT FROM AUTHOR]

Tips of multi-walled carbon nanotube of dissimilar shapes with/without gold nanoparticles are irradiated under electron beam. The tips become meta-stable and cause reduction in lengths of tubes under a high intense uniform electron beam by their smaller radius of curvature when the diffusion and evaporation of carbon atoms are activated. Meanwhile, normal-tube-tips and volcano-tube-tips with/without gold nanoparticles present dissimilar changes in their diameters. The gold nanoparticles with size ≥ 3 nm not only slow down length reduction process in the normal-tube-tips and increase tips diameters but also increase their size on the normal-tube-tip by the interaction and growth, while gold nanoparticles with size ≤ 1.5 nm retard the length reduction process in volcano-tube-tips without any change in the tips diameters. Furthermore, they also activate formation of carbon shells over their surface and keep their positions fixed on the volcano-tube-tip. This abnormal interaction of gold nanoparticles with the unstable tips is elucidated in terms of irradiation-induced activation of the graphitic layers, diffusion of Au atoms and bonding between adjacent large (≥ 3 nm) Au NPs, and catalytic effects of small (≤ 1.5 nm) Au NPs. The method can be employed to modify nanotubes with almost atomic precision and to create a predefined pattern of metal nanoparticles on tube tips and surface. [ABSTRACT FROM AUTHOR]

Purpose: To determine the safe range of shortening the spinal column at middle thoracic spine and to observe the changes in blood-spinal cord barrier (BSCB), microglia/macrophage activation and inducible nitric oxide synthase (iNOS) activity after shortening-induced spinal cord injury.Methods: Dogs were allocated to four groups. Group A (control) underwent laminectomy of T7 without shortening the spinal column. Groups B, C and D had 1/3, 1/2, and 2/3 of T7 resected, respectively, followed by spinal shortening. Somatosensory evoked potential (SSEP) and hind-limb function were recorded periodically for 14 days after operation. Spinal cord blood flow (SCBF) and BSCB were detected at the acute phase of shortening. Microglia/macrophage reactions and iNOS activity were observed by immunohistochemistry.Results: Shortening of 1/3 of a vertebral height caused no significant changes in SSEP and hind-limb function after operation, whereas shortening of 1/2 of the height caused SSEP abnormality and paraparesis, and severe neurologic deficit of hind-limb was observed when the shortening reached 2/3 of the height. SCBF increased temporarily and showed a trend of recovery when the shortening was within 1/2 of a vertebral segment height. When it reached 1/2 or 2/3 of the height, SCBF at 6 h post-operation was 86.33% or 74.95% of the baseline, and an increasing BSCB permeability was observed. In the subsequent 7 days, obvious activation of macrophage and increased number of iNOS-positive cells were observed.Conclusion: It is safe to shorten the spinal cord within 1/3 of a vertebral height in middle thoracic spine under two-segment laminectomy in canine. The BSCB disruption, macrophage activation, and increased iNOS activity were observed in the acute phase of the injury. These slides can be retrieved under Electronic Supplementary Material. [ABSTRACT FROM AUTHOR]

The extraordinary optical transmission and Faraday effects of the bilayer heterostructure consisting of a metallic film perforated with subwavelength hole arrays and a uniform dielectric film magnetized perpendicular to its plane were systematically studied by three-dimensional finite-difference time-domain method. Results of the calculation found that for the magneto-plasmonic crystals under polarized incident light with transverse magnetic mode, the resonant transmittance reached 36.9%, the Faraday rotation acquired 1.216°, and the ellipticity got a positive value of 0.840. The value of Faraday rotation and ellipticity is respectively 15.2 and 93.3 times enhancement of the 0.08° and −0.009 of the bare BIG film at the wavelength. In the transverse electric mode, the Faraday effects of the systems also had a large enhancement in contrast to the bare magnetic film. The magneto-optical effects of the systems could be manipulated by polarization mode of incident light, geometry of perforated subwavelength hole arrays, and thickness of metallic and magnetic films. Evolution of the magneto-optical properties on the structural parameters was also analyzed. Possible mechanisms underlying the extraordinary phenomena were profoundly discussed. All these results indicated that the systems could find potential applications in magneto-optical devices such as data storages, sensors, and telecommunications. [ABSTRACT FROM AUTHOR]

ZnO/Si nanowire arrays with hierarchical architecture were synthesized by solution method with ZnO seed layer grown by atomic layer deposition and magnetron sputtering, respectively. The photocatalytic activity of the as-grown tree-like arrays was evaluated by the degradation of methylene blue under ultraviolet light at ambient temperature. The comparison of morphology, crystal structure, optical properties, and photocatalysis efficiency of the two samples in different seeding processes was conducted. It was found that the ZnO/Si nanowire arrays presented a larger surface area with better crystalline and more uniform ZnO branches on the whole sidewall of Si backbones for the seed layer by atomic layer deposition, which gained a strong light absorption as high as 98% in the ultraviolet and visible range. The samples were proven to have a potential use in photocatalyst, but suffered from photodissolution and memory effect. The mechanism of the photocatalysis was analyzed, and the stability and recycling ability were also evaluated and enhanced. [ABSTRACT FROM AUTHOR]

Boreal fires can cool the climate; however, this conclusion came from individual fires and may not represent the whole story. We hypothesize that the climatic impact of boreal fires depends on local landscape heterogeneity such as burn severity, prefire vegetation type, and soil properties. To test this hypothesis, spatially explicit emission of greenhouse gases (GHGs) and aerosols and their resulting radiative forcing are required as an important and necessary component towards a full assessment. In this study, we integrated remote sensing (Landsat and MODIS) and models (carbon consumption model, emission factors model, and radiative forcing model) to calculate the carbon consumption, GHGs and aerosol emissions, and their radiative forcing of 2001-2010 fires at 30 m resolution in the Yukon River Basin of Alaska. Total carbon consumption showed significant spatial variation, with a mean of 2,615 g C m and a standard deviation of 2,589 g C m. The carbon consumption led to different amounts of GHGs and aerosol emissions, ranging from 593.26 Tg (CO) to 0.16 Tg (NO). When converted to equivalent CO based on global warming potential metric, the maximum 20 years equivalent CO was black carbon (713.77 Tg), and the lowest 20 years equivalent CO was organic carbon (−583.13 Tg). The resulting radiative forcing also showed significant spatial variation: CO, CH, and NO can cause a 20-year mean radiative forcing of 7.41 W m with a standard deviation of 2.87 W m. This emission forcing heterogeneity indicates that different boreal fires have different climatic impacts. When considering the spatial variation of other forcings, such as surface shortwave forcing, we may conclude that some boreal fires, especially boreal deciduous fires, can warm the climate. [ABSTRACT FROM AUTHOR]

La-modified thin films of multiferroic 0.7(BiLa)FeO-0.3PbTiO (BFPT, x = 0, 0.01, 0.03, 0.05 and 0.1) solid solution were prepared by sol-gel method. Perovskite BFPT single-phase thin films were successfully synthesized at 600 °C by optimizing several preparation conditions. It was confirmed from X-ray diffraction that BFPT films tend to display sharper peaks with the La concentration, which could be attributed to the changes in grain size and the promotion of La doping in the crystallization. The dielectric constant ε also showed a significant increase as compared to those of the undoped BFPT thin films. Furthermore, substitution of small amount of La atoms in BFPT films was effective in reducing leakage current and improving the ferroelectric behavior at a low electric field, which may strongly associated with the grain size and the domain wall density. The P and E values of 5 mol% La-doped BFPT thin films at room temperature were approximately 23 µC/cm and 80 kV/cm, indicating the potential applications of BFPT thin films in non-volatile ferroelectric memory fields. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Spatially explicit precipitation data are required in the research of hydrology, agriculture, ecology, and environmental sciences. In this study, two established techniques of local ordinary linear regression (OLR) and geographically weighted regression (GWR) and two new local hybrid interpolation techniques of local regression-kriging (LRK) and geographically weighted regression kriging (GWRK) were compared to predict the spatial distribution of mean annual precipitation of China. Precipitation data from 684 meteorological stations were used in the analysis, and a stepwise regression analysis was used to select six covariates, including longitude, latitude, elevation, slope, surface roughness, and river density. The four spatial prediction methods (OLR, GWR, LRK, and GWRK) were implemented with local regression techniques with different number of neighbors (50, 100, 150, and 200). The prediction accuracy was assessed at validation sites with the root mean squared deviation, mean estimation error, and R-square values. The results showed that LRK outperforms OLR and GWRK outperforms GWR, indicating that adding the kriging of regression residuals can help improve the prediction performance. GWRK gives the best prediction but the accuracy of estimation varies with the number of neighborhood points used for modeling. Although LRK is outperformed by GWRK, LRK is still recommended as a powerful and practical interpolation method given its computation efficiency. However, if LRK and GWRK are used to extrapolate prediction values, post-processing in the areal interpolation will be needed. [ABSTRACT FROM AUTHOR]

Different compositionally graded PbSrTiO (x = 0.2, 0.3, 0.4, 0.5 and 0.6; PST) thin films were deposited on LaNiO(LNO)-buffered stainless steel (SS) substrates. Both LNO and PST thin films were prepared by the sol-gel method. X-ray diffraction and scanning electron microscopy analysis were used to investigate the crystallinity and surface morphology of PST thin films. It showed that the crack-free PST thin films presented pure perovskite phase. The dielectric permittivity was measured in the frequency range of 10-10Hz. The tunable value of compositionally graded PST films can be as high as about 30 % (measured at E = 300 kV/cm, 10Hz). The LNO-buffered layers can effectively reduce the dissipation constant of PST films on SS, which was about 3 % and in the same level with the PST films deposited on traditional Si substrates. The temperature and frequency stability of tunability has been improved. The value of (Δn/n) % (rate of tunability change) could be less than 5 % in the most range of temperature, which demonstrated that PST could be a promising candidate material for tunable devices applications. [ABSTRACT FROM AUTHOR]

A rational approach for creating branched ZnO/Si nanowire arrays with hierarchical structure was developed based on a combination of three simple and cost-effective synthesis pathways. The crucial procedure included growth of crystalline Si nanowire arrays as backbones by chemical etching of Si substrates, deposition of ZnO thin film as a seed layer by magnetron sputtering, and fabrication of ZnO nanowire arrays as branches by hydrothermal growth. The successful synthesis of ZnO/Si heterogeneous nanostructures was confirmed by morphologic, structural, and optical characterizations. The roles of key experimental parameters, such as the etchant solution, the substrate direction, and the seed layer on the hierarchical nanostructure formation, were systematically investigated. It was demonstrated that an etchant solution with an appropriate redox potential of the oxidant was crucial for a moderate etching speed to achieve a well-aligned Si nanowire array with solid and round surface. Meanwhile, the presence of gravity gradient was a key issue for the growth of branched ZnO nanowire arrays. The substrate should be placed vertically or facedown in contrast to the solution surface during the hydrothermal growth. Otherwise, only the condensation of the ZnO nanoparticles took place in a form of film on the substrate surface. The seed layer played another important role in the growth of ZnO nanowire arrays, as it provided nucleation sites and determined the growing direction and density of the nanowire arrays for reducing the thermodynamic barrier. The results of this study might provide insight on the synthesis of hierarchical three-dimensional nanostructure materials and offer an approach for the development of complex devices and advanced applications. [ABSTRACT FROM AUTHOR]

Extrapolating energy fluxes between the ground surface and the atmospheric boundary layer from point-based measurements to spatially explicit landscape estimation is critical to understand and quantify the energy balance components and exchanges in the hydrosphere, atmosphere, and biosphere. This information is difficult to quantify and are often lacking. Using a Landsat image (acquired on 5 August 2004), the flux measurements from three eddy covariance flux towers (a 1987 burn, a 1999 burn, and an unburned control site) and a customized satellite-based surface energy balance model of Mapping Evapotranspiration at High Resolution with Internalized Calibration (METRIC), we estimated net radiation, sensible heat flux ( H), latent heat flux (LE), and soil heat flux ( G) for the boreal Yukon River Basin of Interior Alaska. The model requires user selection of two extreme conditions present within the image area to calibrate and anchor the sensible flux output. One is the 'hot' condition which refers to a bare soil condition with specified residual evaporation rates. Another one is the 'cold' condition which refers to a fully transpiring vegetation such as full-cover agricultural crops. We selected one bare field as the 'hot' condition while we explored three different scenarios for the 'cold' pixel because of the absence of larger expanses of agricultural fields within the image area. For this application over boreal forest, selecting agricultural fields whose evapotranspiration was assumed to be 1.05 times the alfalfa-based reference evapotranspiration as the 'cold' pixel could result in large errors. Selecting an unburned flux tower site as the 'cold' pixel could achieve acceptable results, but uncertainties remain about the energy balance closure of the flux towers. We found that METRIC performs reasonably well in partitioning energy fluxes in a boreal landscape. [ABSTRACT FROM AUTHOR]

Fault diagnosis is becoming increasingly important in improving the reliability of power electronic devices. The research in this paper focuses on the issue of the faulty operation that can occur after partial IGBT open-circuit faults in three-phase PWM rectifier circuits. To promptly and effectively diagnose faults and to determine their locations, a fault diagnosis method based on transient characteristics and random forest classification is proposed. First, the characteristics of single and double IGBT open-circuit faults in three-phase PWM rectifier circuits are analyzed. It is discovered that these faults do not immediately manifest. Instead, they exhibit fault characteristics in the corresponding time sequence. Then the random forest classifier is trained using transient fault samples from the three-phase PWM rectifier circuit. Finally, generalized testing is performed on data that was not involved in the training process, with an accuracy rate of over 98%. The use of frequency distribution graphs for visual analysis of the diagnostic results solves the problem of diagnosing multiple IGBT open-circuit faults. [ABSTRACT FROM AUTHOR]