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Photocross-linked alginate hydrogels, due to their biodegradability, biocompatibility, strong control for gelling kinetics in space and time, and admirable adaptability for in situ polymerization with a minimally invasive approach in surgical procedures, have created great expectations in bone regeneration. However, hydrogels with suitable degradation kinetics that can match the tissue regeneration process have not been designed, which limits their further application in bone tissue engineering. Herein, we finely developed an oxidation strategy for alginate to obtain hydrogels with more suitable degradation rates and comprehensively explored their physical and biological performances in vitro and in vivo to further advance the clinical application for the hydrogels in bone repair. The physical properties of the gels can be tuned via tailoring the degree of alginate oxidation. In particular, in vivo degradation studies showed that the degradation rates of the gels were significantly increased by oxidizing alginate. The activity, proliferation, initial adhesion, and osteogenic differentiation of rat and rabbit bone marrow stromal cells (BMSCs) cultured with/in the hydrogels were explored, and the results demonstrated that the gels possessed excellent biocompatibility and that the encapsulated BMSCs were capable of osteogenic differentiation. Furthermore, in vivo implantation of rabbit BMSC-loaded gels into tibial plateau defects of rabbits demonstrated the feasibility of hydrogels with appropriate degradation rates for bone repair. This study indicated that hydrogels with increasingly controllable and matchable degradation kinetics and satisfactory bioproperties demonstrate great clinical potential in bone tissue engineering and regenerative medicine and could also provide references for drug/growth-factor delivery therapeutic strategies for diseases requiring specific drug/growth-factor durations of action.

Fermented noni (Morinda citrifolia L.) fruit juice activated Nrf2/ARE pathway and regulated gut flora to ameliorate oxidative stress and insulin resistance.

A series of mesoporous Ni–Cu/WO3/ZrO2 (1Ni1Cu/mWZr) was successfully prepared with F127 as a template and used as catalysts for isobutane hydroisomerization to n-butane. The effects of the F127/ZrO...

CsPbIxBry-based all-inorganic perovskite materials are a potential candidate for stable semitransparent and tandem structured photovoltaic devices. However, poor film (morphological and crystalline...

This paper examines the interface elasticity between an elastic half-space and a spherical nanoinhomogeneity subjected to a unidirectional far-field tension that is parallel to the half-space plane boundary. The spherical interface is modeled by the full version of Steigmann–Ogden interface theory. Due to their marginal significance, the effects of half-space plane boundary are neglected. The problem is solved by decomposing the unidirectional load into an all-around and an equal-but-opposite traction field. Benefitting from the property of axial symmetry, the former subproblem is solved by the sole use of Boussinesq displacement potentials. The latter condition is addressed by six harmonic functions extracting from Boussinesq, Papkovich–Neuber and Dougall displacement potentials. The relations between cylindrical and spherical harmonic functions are employed to clear the tractions along the half-space plane boundary and to satisfy the nonclassical traction equilibrium conditions across the matrix/nanoinhomogeneity interface. Truncating the resultant infinite series and equating the coefficients preceding Legendre polynomials, associated Legendre functions as well as their derivatives lead to a system of algebraic equations with respect to the dimensionless unknown parameters in displacement potentials. Extensive parametric studies are further performed in order to analyze the importance of interface tension, interface Lame constants, interface flexural rigidities, shear moduli ratio and nanoinhomogeneity radius-to-depth ratio on stress distributions and stress concentrations. Comparisons against both the classical and the Gurtin–Murdoch solutions help to clarify the separate effects of individual interface material properties. Stresses inside a soft nanoinhomogeneity is most affected by the additional incorporation of interface flexural rigidities. In addition, the deviatoric component of the interface curvature change tensor is found to be more important than the mean part for the proposed nanoinhomogeneity problem.

Background Candida auris is a globally emerging multidrug-resistant fungal pathogen. It causes healthcare-associated infections (HAIs) and can be transmitted through contaminated surfaces and equipment. Pre-wetted disinfectant towelettes are increasingly used for infection control. Our objective was to test the efficacies of EPA registered disinfectant towelette products, with or without fungicidal claims, against C. auris, on hard, non-porous surfaces below, at, and beyond label contact times. or longer contact times. We hypothesized that towelette disinfection efficacy against C. auris would be significantly influenced by chemistry and contact time. Methods We tested one hydrogen peroxide (HP), three quaternary ammonium (QAC), and one quaternary ammonium plus alcohol (QAC-alcohol)-based disinfectant towelette products, with or without EPA registered fungicidal claims, against C. auris Satoh et Makimura (ATCC MYA-5001). All products were tested at 30 s, one-, two-, three- and 10-min contact time to compare their overall efficacies on a defined surface area following modifications to standard EPA protocol MB-33-00. Results HP-based disinfectant towelettes were more efficacious against C. auris than the QAC-alcohol-based disinfectant towelettes irrespective of tested contact times. Thirty s contact time was significantly less effective in reducing C. auris from the Formica surface compared to one-, two-, three-, and 10-min contact times. However, there were no statistically significant differences in the level of disinfection among one-min and longer contact times regardless of product chemistry. None of the products achieved a standard six-log10 reduction at any tested contact times. Conclusion Overall, the HP-based disinfectant towelette was significantly more fungicidal than the QAC-alcohol-based disinfectant towelette. For all product types, 30 s contact time did not achieve the same level of disinfection as one-min or longer contact times. Overall, disinfectant towelette efficacy is dependent upon product formulation and contact time.

Background The use of disinfectants, such as disinfectant towelettes, play an important role pathogen transmission that can lead to healthcare-associated infections (HAIs). However, the efficacy of disinfectant towelette products when tested under realistic use conditions is understudied. A test model was designed to replicate realistic wiping conditions. The objective of this study was to determine the impact of varied contact time on disinfectant towelette efficacy under these conditions. Methods Five product types were tested against Staphylococcus aureus (ATCC 6538) and Pseudomonas aeruginosa (ATCC 15442) at five contact times (30 s, one min, two min, three min, and 10 min) on hard, non-porous laminate templates to determine the impact of contact time on disinfectant towelette efficacy when tested under realistic use. Results Product type had a significant impact on the efficacy of disinfectant towelettes when tested under conditions reflective of realistic use. The effect of contact time was limited and no differences in efficacy were seen at a contact time of one min compared with the other contact times tested. Only one disinfectant towelette product achieved a 5-log reduction under the tested conditions. Conclusion Efficacy of disinfectant towelettes was primarily impacted by product type when applied in a model designed to replicate realistic use in which only a limited effect of contact time was observed. There is a need for further investigation into which factors have the greatest impact on disinfectant towelette efficacy when applied in clinical settings.

Metal injection molding (MIM) is one of the latest technologies for fabricating titanium-based products. However, there have been few systematic studies on the definition and generation mechanism of surface porosity of injection molded Ti-6Al-4V and its relationship with powder, process and mechanical properties so far. In this paper, MIM was selected to prepare Ti-6Al-4V alloy, and the effects of sintering and subsequent hot isostatic pressing (HIP) process on the microstructure and mechanical properties were investigated. The results indicate that Ti-6Al-4V alloy formed a dense layer after sintering because of the temperature gradient from surface to core. The thickness of dense layer, grain size, grain morphology, and grain orientation are the key factors that determining the mechanical properties of Ti-6Al-4V alloy. Under the condition of sintering at 1000℃ with HIP process, Ti-6Al-4V alloy formed a thick dense layer of 290 µm, equiaxed grains with the small average grain size of 16 µm, and a high proportion of high-angle grain boundaries of 88.9%. Due to the optimized microstructure, Ti-6Al-4V alloy exhibited excellent mechanical properties, with the tensile strength of 1067 MPa, yield strength of 997 MPa, and elongation of 17.5%. This approach can serve as a guideline for other MIM materials.

CO2 electrochemical reduction in solid oxide electrolysis cells is an effective way to combine CO2 conversion and renewable electricity storage. A Au layer is often used as a current collector, whereas Au nanoparticles are rarely used as a cathode because it is difficult to keep nanosized Au at high temperatures. Here we dispersed a Au layer into Au nanoparticles (down to 2 nm) at 800 °C by applying high voltages. A 75-fold decrease in the polarization resistance was observed, accompanied by a 38-fold improvement in the cell current density. Combining electronic microscopy, in situ near-ambient pressure X-ray photoelectron spectroscopy, and theoretical calculations, we found that the interface between the Au layer and the electrolyte (yttria-stabilized zirconia (YSZ)) was reconstructed into nano-Au/Zr-suboxide interfaces, which are active sites that show a much lower reaction activation energy than that of the Au/YSZ interface. The formation of Zr-suboxides promotes Au dispersion and Au nanoparticle stabilization due to the strong interaction between Au and Zr-suboxides.

Metal injection molding (MIM) is an advanced manufacturing technology that enables the mass production of high-performance and complex materials, such as the Ti-6Al-4V alloy. The determination of the size change and deformation of the Ti-6Al-4V alloy after the sintering process is challenging and critical for quality control. The numerical simulation could be a fast and cost-effective way to predict size change and deformation, given the large degrees of freedom for the sintering process. Herein, a finite element method based on the thermal-elastic-viscoplastic macroscopic model is developed to predict the shrinkage, deformation, relative density, and crack of injection-molded Ti-6Al-4V after sintering, using the Simufact software. Excellent agreements between experimental measurements and numerical simulations of the size and deformation are demonstrated (within a 3% error), confirming the accuracy of the numerical model. This approach can serve as a guideline for the mold design and sintering optimization of the MIM process.

This study aims to improve the thermal stability and mechanical properties of carboxymethyl bacterial cellulose (CMBC) composite films. Experiments were conducted by preparing bacterial cellulose (BC) into CMBC, then parametrically mixing sodium alginate/starch/xanthan gum/gelatin and glycerin/sorbitol/PEG 400/PEG 6000 with CMBC to form the film. Scanning electron microscopy, X-ray diffractometry, infrared spectroscopy, mechanical tests, and thermogravimetric analysis showed that the composite films had better mechanical properties and thermal stability with the addition of 1.5% CMBC (% v/v), 1% sodium alginate, and 0.4% glycerin. Tensile strength was 38.13 MPa, the elongation at break was 13.4%, the kinematic viscosity of the film solution was 257.3 mm2/s, the opacity was 4.76 A/mm, the water vapor permeability was 11.85%, and the pyrolysis residue was 45%. The potential causes for the differences in the performance of the composite films were discussed and compared, leading to the conclusion that CMBC/Sodium alginate (SA)/glycerin (GL) had the best thermal stability and mechanical properties.

Oxidative stress interferes with blood glucose homeostasis, leading to insulin resistance (IR) and hyperglycemia, which eventually induce type 2 diabetes (T2DM). Fermented noni (

N-doped carbon nanowires encapsulated with cobalt nanoparticles are designed and fabricated through solvothermal and pyrolysis procedures by using cobalt chloride and nitrilotriacetic acid as the precursors. The catalyst (C-NTACo-500) demonstrated great potential as highly active bifunctional catalyst for oxygen reduction and oxygen evolution reactions (ORR and OER), with a half wave potential (E1/2) of 0.84 V (vs. RHE) for ORR, and a small overpotential of 0.28 V for OER. Notably, it could provide zinc air batteries (ZAB) a maximum power density of 203.4 mW cm−2, and a high specific capacity of 822.4 mAh gZn−1, as well as excellent charge–discharge stability.

A new isoflavone (Z)-5,7,4′-trihydroxy-3′-[3-hydroxy-3-methyl-1-butenyl] isoflavone (1) together with seven known isoflavones (2–8) were isolated from the fruits of the Ficus auriculata. Their stru...

A novel fast multipole boundary element method (FM-BEM) is proposed to analyze 2-D potential problems by using linear and three-node quadratic elements. In FM-BEM, fast multipole expansions are used for the integrals on elements which are far away from the source point, whereas direct evaluations are used for the integrals on elements which are close to the source point. The use of higher-order elements results in more complex forms of the integrands, which increases the burden in direct evaluations, especially for singular and nearly singular integrals. Herein, the complex notation is introduced to simplify the computational formulations in boundary integral equations for 2-D potential problems. The singular and nearly singular integrals on linear elements are calculated by the analytic formulas, and those on three-node quadratic elements are evaluated by a robust semi-analytical algorithm. Numerical examples show that the proposed FM-BEM possesses higher accuracy than the conventional FM-BEM. Besides, the present method can analyze thin structures and evaluate accurately the physical quantities at interior points much closer to the boundary.

Ambient-pressure X-ray photoelectron spectroscopy (APXPS) is commonly used to identify active phases of Pt-based catalysts. Unavoidable beam-induced chemistry under in situ conditions with high-flux X-rays is important yet has often been disregarded. To evaluate beam effects on Pt oxidation, we revisited surface species on Pt(111) and Pt(110) in O

Optimization of automated floor disinfection practices using different application methods and product types is important to ensure that pathogens such as Staphylococcus aureus do not transfer from contaminated floors to other high contact areas resulting in healthcare-associated infections (HAIs). We hypothesized that there would be significant differences among the disinfectants and a cleaner under different application methods. Also, performance of application methods would be dependent upon type of product used.We tested and compared efficacies of 5 EPA registered disinfectants and one cleaner using an automated Taski 455B floor cleaner against S aureus ATCC 6538 on 2 meters of contaminated vinyl flooring using 3 application methods.Hydrogen peroxide and quaternary ammonium compounds were more efficacious against S aureus than the neutral cleaner. There were no significant differences among the sampling areas tested and application methods regardless of product type. Mean logAll disinfectants had more bactericidal efficacy than the cleaner for all sampling zones on the tested floor. Overall, performance of the floor machine is dependent upon the type of product used.

Smart structure vibration reduction based on adaptive active vibration control has become a hot research spot in recent years. A filtered-U least mean square algorithm based on an infinite impulse response filter structure is used to solve the interference of controller output to reference signal. The filtered-U least mean square algorithm is very suitable for the nonlinear vibration control of the flexible structure. This study focuses on the analysis and implementation of an adaptive active vibration control system for smart structure with a surface-bonded piezoelectric actuator. The piezoelectric actuator contained in the secondary path has nonlinear hysteresis property. The nonlinear hysteresis property will cause a nonlinear relationship between the structural vibration response and the control voltage, which deteriorates the robustness and control effect of the adaptive control. This study designs an improved version of the filtered-U least mean square algorithm with online hysteresis identification and compensation (filtered-U least mean square–online hysteresis identification and compensation) based on a discrete Prandtl–Ishlinskii model. The Prandtl–Ishlinskii model parameters of the nonlinear hysteresis property are identified online based on the least mean square algorithm. Based on the identified Prandtl–Ishlinskii model parameters, an inverse hysteresis compensator is established for feedforward compensation in the secondary path. Simulation results show that the proposed method can dynamically compensate the hysteresis nonlinearity of the secondary path, linearizing the nonlinear hysteresis. The vibration reduction effect of the proposed method is obviously better than that of other competing methods. A piezoelectric smart cantilever plate with PZT (or lead zirconate titanate, Pb (Zr, Ti)) actuators and sensors is designed to demonstrate the validity and efficiency of the proposed method by experiments. Experiment results demonstrate that the adverse effect of nonlinear hysteresis is eliminated well after feedforward hysteresis compensation is introduced; the unexpected frequency vibration caused by the hysteresis property is suppressed. The proposed methodology possesses an important advantage in application of the adaptive active vibration control of the piezoelectric smart structure.

Cellulose triacetate (CTA) was first applied as the catalytic support to load Pt nanoparticles for low-temperature formaldehyde (HCHO) decomposition. The room-temperature HCHO decomposition rate of...

Modulating and optimizing the diverse parameters of photocatalysts synergistically as well as exerting these advantages fully in photocatalytic reactions are crucial for the sufficient utilization of solar energy but still face various challenges. Herein, a novel and facile urea- and KOH-assisted thermal polymerization (UKATP) strategy is first developed for the preparation of defect-modified thin-layered and porous g-C3N4 (DTLP-CN), wherein the thickness of g-C3N4 was dramatically decreased, and cyano groups, nitrogen vacancies, and mesopores were simultaneously introduced into g-C3N4. Importantly, the roles of thickness, pores, and defects can be targetedly modulated and optimized by changing the mass ratio of urea, KOH, and melamine. This can remarkably increase the specific area, improve the light-harvesting capability, and enhance separation efficiency of photoexcited charge carriers, strengthening the mass transfer in g-C3N4. Consequently, the photocatalytic hydrogen evolution efficiency of the DTLP-CN (1.557 mmol h-1 g-1, λ > 420 nm) was significantly improved more than 48.5 times with the highest average apparent quantum yield (AQY) of 18.5% and reached as high as 0.82% at 500 nm. This work provides an effective strategy for synergistically regulating the properties of g-C3N4, and opens a new horizon to design g-C3N4-based catalysts for highly efficient solar-energy conversion.

Background Pre-wetted disinfectant wipes are increasingly being used in healthcare facilities to help address the risk of healthcare associated infections (HAIs). However, HAIs are still a major problem in the US with Clostridioides difficile being the most common cause, leading to approximately 12,800 deaths annually in the US. An underexplored risk when using disinfectant wipes is that they may cross-contaminate uncontaminated surfaces during the wiping process. The objective of this study was to determine the cross-contamination risk that pre-wetted disinfectant towelettes may pose when challenged with C. difficile spores. We hypothesized that although the tested disinfectant wipes had no sporicidal claims, they will reduce spore loads. We also hypothesized that hydrogen peroxide disinfectant towelettes would present a lower cross-contamination risk than quaternary ammonium products. Methods We evaluated the risk of cross-contamination when disinfectant wipes are challenged with C. difficile ATCC 43598 spores on Formica surfaces. A disinfectant wipe was used to wipe a Formica sheet inoculated with C. difficile. After the wiping process, we determined log10 CFU on previously uncontaminated pre-determined distances from the inoculation point and on the used wipes. Results We found that the disinfectant wipes transferred C. difficile spores from inoculated surfaces to previously uncontaminated surfaces. We also found that wipes physically removed C. difficile spores and that hydrogen peroxide disinfectants were more sporicidal than the quaternary ammonium disinfectants. Conclusion Regardless of the product type, all disinfectant wipes had some sporicidal effect but transferred C. difficile spores from contaminated to otherwise previously uncontaminated surfaces. Disinfectant wipes retain C. difficile spores during and after the wiping process.

In the present work, regenerated cellulose films with different pore sizes were prepared using cellulose, which can control the synthesis reaction of nano-ZnO and thus regulate its morphology. The results show that with 0, 4, and 8 g of cellulose applied, average pore sizes of samples increased from 7.0 nm to 14.4 and 20.1 nm, respectively. When no cellulose was used, only large Zn5(OH)8Cl2·H2O (ZHC) flakes were prepared. Long ZnO nano-sheets and ZHC flakes with a mass fraction of 0.51 and 0.33, respectively, were prepared by adding 4 g cellulose; and ZnO nano-sheets with a mass fraction of 0.73, with 0.04 ZHC, were synthesised while using 8 g cellulose. The results reveal that the addition of cellulose can improve the average pore diameter of films and enhance the reaction rate of ZnO, resulting in the formation of ZnO nano-sheets/regenerated cellulose films.

Well-shaped sulfated titania nanofibers were prepared by impregnation of hydrogen titanate with (NH4)2S2O8 and calcination. Various characterization results showed that sulfated titania nanofibers consisted of smooth-surface and long-size fibers with the diameter of dozens of nanometers. Moreover, acid characteristics of sulfated titania nanofibers exhibited the high acid content, multi-strength acid sites and large Bronsted/Lewis acid ratio. In low-viscosity esterification, sulfated titania nanofibers had 1.2 ~ 2.1 times the reaction rate of other sulfated titania and other typical solid acids. Simultaneously, sulfated titania nanofibers possessed the higher DS value of product than those by other solid acids in highly viscous cellulose acetylation (2.41 versus 2.06 ~ 2.21). Besides these, sulfated titania nanofibers could show the excellent recycling performance in viscous acid-catalytic reactions.

Previous studies have revealed a positive relationship between social class and subjective well-being, but it is still unclear why social class is associated with subjective well-being. In the current study, 4168 Chinese adults aged 17 to 67 years completed measures of social class, present fatalistic time perspective and subjective well-being. Then a mediation analysis was conducted to examine whether present fatalistic time perspective would mediate the association between social class and subjective well-being. Results indicated social class was positively associated with subjective well-being; subjective social class (SSC) had a stronger association with subjective well-being than did objective social class (OSC). Social class was negatively related to present fatalistic time perspective; however, OSC was more predictive of present fatalistic time perspective than was SSC. Moreover, the relationship between social class and subjective well-being was mediated by present fatalistic time perspective, whether SSC or OSC. These results add to our understanding of the theoretical concept of social class and shed new light on a mechanism involved in the social class/well-being association. The implications of this study and future directions are also discussed.

Grain boundary (GB) motions, such as migration, sliding and rotation, have been shown to play a vital role in the mechanical performance of polycrystalline metals. Despite extensive efforts have been made on the pure polycrystalline metals, few attentions have been paid to those in alloys. In this work, taking conventional nanoscale Cu–Al binary alloy system as an example, we intend to shed some light on understanding its GB motions under shear loading by means of molecular dynamics (MD) simulations. It is found that either shear-coupled GB migration or sliding motion can be observed, depending on GB tilt angles, temperatures and Al solute concentrations. By systematical MD simulations, the Al concentration required for transition between shear-coupled migration and sliding is found to decrease with increasing tilt angles (θ ≤ 50°) at fixed temperature, whereas it switches to the opposite trend for larger tilt angles. Furthermore, the GBs migrate much slower comparing with those in pure Cu, which shows the drag effects of the Al solutes in the alloy form. Moreover, the critical stress during shear loading shows a linear dependence on 2/3 power of the temperature.

Developing highly efficient and cost-effective oxygen evolution reaction (OER) electrocatalysts is critical for many energy devices. While regulating the proton-coupled electron transfer (PCET) process via introducing additive into the system has been reported effective in promoting OER activity, controlling the PCET process by tuning the intrinsic material properties remains a challenging task. In this work, we take double perovskite oxide PrBa0.5Sr0.5Co1.5Fe0.5O5+δ (PBSCF) as a model system to demonstrate enhancing OER activity through the promotion of PCET by tuning the crystal orientation and correlated proton diffusion. OER kinetics on PBSCF thin films with (100), (110), and (111) orientation, deposited on single crystal LaAlO3 substrates, were investigated using electrochemical measurements, density functional theory (DFT) calculations, and synchrotron-based near ambient X-ray photoelectron spectroscopy. The results clearly show that the OER activity and the ease of deprotonation depend on orientation and follow the order of (100) > (110) > (111). Correlated with OER activity, proton diffusion is found to be the fastest in the (100) film, followed by (110) and (111) films. Our results point out a way of boosting PCET and OER activity, which can also be successfully applied to a wide range of crucial applications in green energy and environment., Proton-coupled electron transfer (PCET) has been observed in chemical, energy, and biological transformation processes. Here we demonstrate that the rate of PCET and oxygen evolution reaction can be dramatically enhanced by tuning crystal orientation and the correlated proton diffusion.

Background Disinfectant products are used frequently on environmental surfaces (e.g. medical equipment, countertops, patient beds) and patient care equipment within healthcare facilities. The purpose of this study was to assess the risk of cross-contamination of Staphylococcus aureus and Pseudomonas aeruginosa during and after disinfection of predetermined surface areas with ready-to-use (RTU) pre-wetted disinfectant towelettes. Methods This study tested six disinfectant towelette products against S. aureus ATCC CRM-6538 and P. aeruginosa strain ATCC-15442 on Formica surfaces. Each disinfectant was evaluated on a hard nonporous surface and efficacy was measured every 0.5 m2 using a modified version of EPA MLB SOP-MB-33 to study the risk of cross-contamination. Results We found that all of the wipes used in this study transferred S. aureus and P. aeruginosa from an inoculated surface to previously uncontaminated surfaces. Disinfectant towelettes with certain chemistries also retained a high level of viable bacteria after disinfection of the surface area. The cross-contamination risk also varied by product chemistry and bacterial strain. Conclusion Disinfectant wipes can cross-contaminate hard nonporous surfaces and retain viable bacterial cells post-disinfection, especially over larger surface areas. This highlights a need to further investigate the risk disinfectant wipes pose during and post-disinfection and guidance on maximum surface areas treated with a single towelette.

In this article, a semianalytical method of solution is developed for the nanocontact problem of elastic half-space indented by a rigid cylindrical roller. The mechanical formulation is based on the complete version of Steigmann–Ogden surface elasticity theory. Surface tension, surface tensile stiffness and surface flexural rigidity of the half-space boundary are all taken into consideration. Fourier integral transform method converts the governing equations and displacement boundary conditions of the nanocontact problem into a singular integral equation. Gauss–Chebyshev quadrature and an iterative algorithm numerically solve this integral equation and the force equilibrium condition. The developed semianalytical solution is general in the sense that it can reduce to a few simplified theories. These include classical solution, considering only a single surface material parameter, and Gurtin–Murdoch surface elasticity theory, for which analytical kernel functions of the singular integral equation are presented. Dimension analysis demonstrates that the effects of Steigmann–Ogden surface elasticity on the two-dimensional Hertzian nanocontact properties are up to three dimensionless ratios among surface material parameters, shear modulus and the size of nanocontact. Moreover, least-squares regression analysis suggests that, in the presence of surface effects, an elliptic arc less than a half can represent the nanocontact pressure. When compared with their classical counterparts, lower maximum contact pressure and nonzero minimum pressure are found. Parametric experiments further show that surface tension and surface flexural rigidity significantly affect contact length, contact pressure, contact stiffness as well as displacements and stresses near the half-space boundary. In contrast, the effects of surface membrane stiffness are of secondary importance. In general, smaller indenters and larger surface constants lead to higher load-carrying capabilities of half-space and thus better mechanical responses.

Herein, we report that merging palladium catalysis with hydrogen atom transfer (HAT) photocatalysis enabled direct arylations and alkenylations of aldehyde C–H bonds, facilitating visible light-cat...

Background: Graphene quantum dots (GQD) is a new member of carbon nanomaterial that has attracted increasing attention owing to its better chemical inertness, low cytotoxicity, large specific surface area, cheap cost, suitable conductivity and excellent biocompatibility. Methods: Electrochemical behaviors of this modified electrode were studied by cyclic voltammetry and electrochemical impedance spectroscopy. Electrochemical investigations of Nafion/Hb/GQD/ CILE were carried out with electrochemical parameters calculated. Results: In the phosphate buffer solution with a pH value of 5.0, good linear relationships between the catalytic reduction current and the concentration of substrate were got for TCA (6.0~100.0 mmol·L-1), NaNO2 (2.0~12.0 mmol·L-1) and H2O2 (6.0~30.0 mmol·L-1). The proposed method was applied to NaNO2 concentration detection in soak water from picked vegetables with satisfactory results. Conclusion: This Nafion/Hb/GQD/CILE had a good bioelectrocatalytic activity to different substrates such as trichloroacetic acid, NaNO2 and H2O2 reduction with the advantages including wide detection range, low detection limit and good stability. Therefore, the application of GQD in electrochemical sensor was extended in this paper.

Instructional principles gleaned from cognitive science play a critical role in improving classroom teaching. This study examines how three cognitive instructional principles including worked examp...

The catalyst Au/cellulose@TiO₂ with a hierarchical structure was one-pot synthesized by conventional deposition-precipitation urea method. Nanosized TiO₂ particles, instead of self-agglomeration, homogeneously dispersed on the microsized microcrystalline cellulose. Simultaneously, gold particles with particle size of about 3.4 nm were mainly well-deposited on TiO₂ particles. It was found that the surface charges of TiO₂, cellulose and gold species played a key role in assisting in selfassembling them into the hierarchical structure. p-nitrophenol hydrogenation results displayed that the catalytic activity of Au/cellulose@TiO₂ was 1.8 times and 10.9 times higher than that of Au/TiO₂ and Au/cellulose, respectively. The improvement in catalytic performance of Au/cellulose@TiO₂ was closely related to its hierarchical structure that influenced mass transfer of reactants and recycle of catalysts.