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The giant reduction of the barrier properties due to self-healing microcapsules and the lack of real-time protection during the healing remained the main challenges in self-healing anticorrosion coatings. Herein, a facile strategy using Janus graphene oxide (GO) as a dense and flexible shell has been proposed to synergistically solve these challenges. Benzotriazole (BTA) was used to synthesize Janus GO at the oil–water interface, and Janus GO/BTA/poly(methyl methacrylate) microcapsules were prepared. Energy-dispersive X-ray spectroscopy, Fourier infrared spectroscopy, Raman spectroscopy, and ultraviolet spectrophotometer analysis confirmed the formation of a Janus GO structure with one surface hydrophilic and the other hydrophobic. The surface morphology of J-GO-capsules with a high GO coverage rate was observed by scanning electron microscopy. The high biobased content coating containing J-GO-capsules showed a low-frequency impedance value above 1010as assessed by electrochemical impedance spectroscopy after being immersed in 3.5 wt % NaCl solution for 60 days. In addition, the low-frequency impedance values of the coating were maintained after being scratched due to the self-healing properties of the J-GO-capsules as well as the real-time protective effect of the BTA. Biobased coatings with the best overall properties among all of the self-healing anticorrosion coatings were prepared.

The existing scales for measuring balanced time perspective (BTP) have limitations, such as poor‐fitting structures or a complex calculation method. Based on previous studies, we conceptualize BTP as an individual's overall positive outlook on the past and future and mindfully living in the present. The present study aimed to develop the Time Perspective Inventory (TPI) for Chinese adults, determine its psychometric properties, and examine a simple calculation method for generating a score to represent BTP. In study 1, a 7‐factor structure of TPI – Past Positive, Past Negative, Mindful Present, Present Hedonistic, Present Excessively Task‐oriented, Future Positive, and Future Negative – was established through exploratory (sample 1, N= 529) and confirmatory (sample 2, N= 577) factor analyses. Findings supported the internal consistency, test–retest reliability, and criterion‐related validity of the TPI. We proposed using the score difference between positive time perspectives and negative time perspectives to calculate the BTP. Findings showed that the correlations between BTP and subjective well‐being indicators and anxiety were higher than among individual dimensions of TPI. Study 2 (sample 3, N= 713) compared the effects of the TPI and the Chinese version of the Zimbardo Time Perspective Inventory (ZTPI‐C) on well‐being indicators and anxiety. Results indicated that the variance of life satisfaction, positive affect, negative affect, and anxiety explained by BTP measured with TPI was higher than deviation from BTP (DBTP) measured with ZTPI‐C. Together, the TPI yields reliable and valid BTP scores among Chinese adults.

Lesson study (LS), a teacher-oriented, student-focused professional development approach that originated in Asia, has spread globally. However, findings related to the effect of LS on teacher learning and growth have varied widely. This suggests a need to review current research on LS in the field of mathematics education. This paper focuses on mathematics teachers’ learning and professional growth through LS using Clarke and Hollingworth’s interconnected model of professional growth (IMPG) that contains three components: domains of change, mediating mechanisms, and change environment. With regard to domains of change, we found that although previous LS studies—often small scaled, qualitative studies—attended to all domains of change, they have more frequently reported changes in the personal (or collective) domain (e.g., teacher knowledge) but have relatively less frequently reported changes in other domains. In fact, there is a lack of research on systematic changes across domains in the IMPG. Regarding the mediating mechanisms, research has well explored both enactment (planning and teaching) and reflection (debriefing). For enactment, the planning process is less appreciated, and there is an inconsistent understanding of the role of the knowledgeable others. For reflection, there is a lack of focus on student thinking and constructive feedback during this process. Finally, research has suggested that LS has received support from the change environment but that tensions (e.g., time limits) have remained. These challenges call for systemic support and cross-cultural collaborations to develop sustainable and large-scale LS. We suggest future directions for continued research and practice.

Porous Ti–6Al–4V alloys have been widely applied in industry, serving as structural or functional materials. However, the conventional method of producing porous Ti–6Al–4V by metal injection molding (MIM) with a space holder has several drawbacks, such as long debinding time, sintering furnace contamination, uncontrolled porosity and pore size, poor mechanical properties and process instability. This study presents a novel method of fabricating porous Ti–6Al–4V by MIM without space holder that can overcome these challenges. The porosity, average pore size, tensile strength, and compressive strength were studied by scanning electron microscope characterization, optical micrograph analysis, and mechanical testing. Flexible changes in porosity (17 %–74 %), pore size (14 μm–84 μm), and tensile strength (15 MPa–457 MPa) could be achieved by adjusting the powder size and sintering temperature. A higher porosity can be achieved as compared to the previous studies. The relationships among particle size, sintering temperature, porosity, and tensile strength are investigated by multiple regression models, which facilitate the tailored design of porous Ti–6Al–4V alloys for industrial applications and enhance the combination of experimental and theoretical methods in the design of porous alloys using MIM.

Nanoparticle (NP) exsolution from perovskite-based oxides matrix upon reduction has emerged as an ideal platform for designing highly active catalysts for energy and environmental applications. However, the mechanism of how the material characteristics impacts the activity is still ambiguous. In this work, taking Pr0.4Sr0.6Co0.2Fe0.7Nb0.1O3thin film as the model system, we demonstrate the critical impact of the exsolution process on the local surface electronic structure. Combining advanced microscopic and spectroscopic techniques, particularly scanning tunneling microscopy/spectroscopy and synchrotron-based near ambient X-ray photoelectron spectroscopy, we find that the band gaps of both the oxide matrix and exsolved NP decrease during exsolution. Such changes are attributed to the defect state within the forbidden band introduced by oxygen vacancies and the charge transfer across the NP/matrix interface. Both the electronic activations of oxide matrix and the exsolved NP phase lead to good electrocatalytic activity toward the fuel oxidation reaction at elevated temperature.

Cloud detection plays a significant role in remote sensing (RS) image applications. Existing deep learning-based cloud detection methods rely on massive precise pixelwise annotations, which are time-consuming and expensive. To alleviate this problem, we propose a weakly supervised cloud detection framework that leverages physical rules to generate weak supervision for cloud detection in RS images. Specifically, a rule-based adaptive pseudo labeling (RAPL) algorithm is devised to adaptively annotate potential cloud pixels based on cloud spectral properties without manual intervention. Unlike existing physical annotations using fixed thresholds, RAPL employs the bidirectional threshold segmentation and adaptive gating mechanism to annotate cloud and boundary masks with more explicit semantic categories and spatial structures separately. Subsequently, these pseudo masks are treated as weak supervision to optimize the heuristic cloud detection network for pixelwise segmentation. Considering that clouds appear as complex geometric structures and nonuniform spectral reflectance, a deformable boundary refining module is designed to enhance the modeling ability of spatial transformation and activate sharp boundaries from translucent cloud regions. Moreover, a harmonic loss is employed to recognize clouds with nonuniform spectral reflectance and suppress the interference of bright backgrounds. Extensive experiments on the GF-1, L8 Biome, and weakly supervised cloud detection (WDCD) datasets demonstrate that the proposed method achieves state-of-the-art results. A public reference implementation of this work in PyTorch is available at https://github.com/NiAn-creator/HeuristicCloudDetection.

Contact electrification is a universal phenomenon that commonly occurs in almost every solid–solid contact pair. The tribo-charges deposited on two surfaces by contact electrification can significantly affect adhesion; however, contact electrification is often overlooked in the study of adhesive contact. Here, we develop an analytical model to investigate electroadhesion during the contact phase between two initially uncharged dielectric surfaces, namely, an elastic parabolic surface and a rigid flat. A system of nonlinear equations is derived to describe the relationship between the indentation, normal load, radius of contact area, and radius of the charged zone using the Barthel–Maugis–Dugdale model (Barthel, 1999, “Modelling the Adhesion of Spheres: When the Form of the Interaction Is Complex, Colloids. Surf., A., 149, pp. 99105.). The analytical results show good agreement with the numerical results of the full self-consistent contact model. When contact electrification leads to a higher tribo-charge density and a larger charged zone, it has a greater impact on the normal traction, interfacial gap, force-approach curves, jump-out, and dissipated energy. The analytical model developed in this study serves as the foundation for advances in rough surface electroadhesive contact and electroadhesion testing, and it sheds light on the usage of adhesive joints in ultra-high vacuum environments and outer space, where contact electrification has a significant impact.

To improve the flame retardancy of rigid polyurethane foam (RPUF), black liquor lignin-based rigid polyurethane foam (LRPUF) was prepared in this work through a one-step foaming method using lignin and inorganic salt in black liquor lignin as the structural modifier and the additive flame retardant, respectively. Effect of the addition of carbon dioxide treated black liquor lignin (CBL) on the structure and flame retardancy of LRPUF, as well as the flame flame-retardant mechanism of LRPUF, were investigated. The limiting oxygen index (LOI) test and cone calorimetric tests showed that compared to the RPUF, the LOI of LRPUF with 40 wt% CBL increased from 18.9 % to 21.3 %, and the peak heat release rate, total heat release, and total smoke production decreased by 19.5 %, 25.3 %, and 20.5 %, respectively, indicating that the addition of CBL improved the flame retardancy of LRPUF. The flame-retardant mechanism was investigated by analyzing the structure and components of the char residue. We found that a dense protective layer, consisted of char residue and a considerable amount of sodium sesquicarbonate on the surface of the char residue, was formed after combustion. This study provided a novel strategy for the resource utilization of black liquor lignin.

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/ZrO2molar ratio on the structure were investigated, and the results of characterization indicate that 1Ni1Cu/mWZr-13 has a high surface area (SBET= 86.96 m2·g–1). Using 1Ni1Cu/mWZr-13 calcined at 750 °C as a catalyst, the isobutane conversion and selectivity to n-butane were 80.74 and 62.66%, respectively, under optimal conditions. According to the characterization and catalytic activity results, the tungsten oxide of 1Ni1Cu/mWZr-13 calcined at 750 °C with a W surface density of 7.73 atom/nm2was mainly formed by WOxclusters, and WOxclusters with strong Brønsted acidity are catalytic active sites for skeletal rearrangement of hydroisomerization. The high activity of 1Ni1Cu/mWZr-13 calcined at 750 °C is attributed to the proper surface acidity sites (696.34 μmol·g–1) and Brønsted/Lewis ratio (0.35) of 1Ni1Cu/mWZr-13.

CsPbIxBry-based all-inorganic perovskite materials are a potential candidate for stable semitransparent and tandem structured photovoltaic devices. However, poor film (morphological and crystalline) quality and interfacial recombination lead consequently to a decline in the photoelectric conversion performance of the applied solar cells. In this work, we incorporated PbS quantum dots (QDs) at the interface of electron transporting layer (ETL) SnO2and perovskite to modulate the crystallization of CsPbIBr2and the interfacial charge dynamics in carbon-based solar cells. The as-casted PbS QDs behave as seeds for lattice-matching the epitaxial growth of pinhole-free CsPbIBr2films. The modified films with reduced defect density exhibit facilitated carrier transfer and suppressed charge recombination at the ETL/perovskite interface, contributing to an enhanced device efficiency from 7.00 to 9.09% and increased reproducibility and ambient stability. This strategic method of QD-assisted lattice-matched epitaxial growth is promising to prepare high-quality perovskite films for efficient perovskite solar cells.

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 the obtained catalyst (Pt/CTA) is 13.4 times and 4.3 times as high as that of the microcrystalline cellulose-supported Pt catalyst and Pt/TiO2under the parallel preparation condition, respectively. With facile shaping, the CTA microsphere-supported Pt catalyst and the CTA film-supported Pt catalyst could also exhibit similar HCHO decomposition performance to that of the powdery one. Structural analyses showed that Pt nanoparticles (∼2.3 nm) could densely disperse on the small-area surface of Pt/CTA and provide abundant active sites. Moreover, only the HCHO molecules could slightly adsorb onto CTA, while other HCHO decomposition-related species absolutely could not. This is beneficial to the coordination of various steps of HCHO decomposition and the transfer of reaction species to vicinal active sites of Pt/CTA. HCHO-diffuse reflectance infrared Fourier transformed spectroscopy studies demonstrated that no species were accumulated on the Pt/CTA catalyst. Both the good Pt dispersion and unique adsorption properties of CTA were responsible for the excellent low-temperature HCHO decomposition performance of Pt/CTA.

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-C3N4was 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–1g–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.

Abstract

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.

As a primary component of cell walls of plants, algae, bacteria, and other natural biomaterials, cellulose has attracted research attention and is the key to effective conversion of natural biomaterial into processable advanced functional materials. From the chemistry point of view, a typical crystalline cellulose is composed of linear chains of hundreds of β-1,4-linker glucose units. Therefore, inter and intra hydrogen bonding interactions play a decisive role of the structure–property relationship of cellulose based materials. Despite research progress from past decades, the fundamental mechanism of how cellulose structure transforms under pyrolysis conditions and the practical guideline of how cellulose properties are fined tuned accordingly are still incomplete. In this work, a series of reactive molecular dynamics calculations has been designed to reveal the structural evolution of crystalline cellulose under pyrolysis treatments. Through the detailed analysis of cellulose configuration change, hydrogen bonding network variation, reaction and redistribution of carbon, oxygen and hydrogen elements, and Young’s modulus, a molecule level insight of crystalline cellulose and its structural evolution under pyrolysis conditions has been constructed via reactive molecular dynamics simulations. We anticipate those theoretical results could effectively promote the design, the manufacture, and the optimization of cellulose based materials for relevant emerging applications.

To study bioactive compounds from the endophytic fungus Penicilliumsp. HJT-A-6 isolated from stem of Rhodiola tibetica, and evaluate its allelopathic activity.

Highly efficient catalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are key to the commercialization of rechargeable zinc–air batteries (ZABs). In this work, a catalyst with uniform nanospherical morphology was prepared from cobalt nitrate, acetylacetone, and hydrazine hydrate. The final catalyst possesses high ORR and OER performances, with a half-wave potential of 0.911 V [vs reversible hydrogen electrode (RHE)] for ORR and a low potential of 1.57 V (vs RHE) at 10 mA cm–2for OER in 0.1 M KOH solution. Specially, a ZAB based on the catalyst demonstrates an ultrahigh power density of 479.1 mW cm–2, as well as excellent stability, and potential in practical applications.

In this article, an electrochemical sensor based on a gold nanocage (AuNC)‐modified carbon ionic liquid electrode (CILE) was fabricated and applied to the sensitive rutin determination. The presence of AuNCs on the electrode surface greatly improved the electrochemical performance of the working electrode due to its specific microstructure and high metal conductivity. Electrochemical behavior of rutin on AuNCs/CILE was studied using cyclic voltammetry and differential pulse voltammetry with the related electrochemical parameters calculated. Under the optimal experimental conditions, the oxidation peak current of rutin and its concentration had good linear relationship in the range from 4.0 × 10−9to 7.0 × 10−4mol/L with a low detection limit of 1.33 × 10−9mol/L (3σ). This fabricated AuNCs/CILE was applied to direct detection of the rutin concentration in drug samples with satisfactory results, showing the real application of AuNCs in the field of chemically modified electrodes. Gold nanocages were modified on the surface of a carbon ionic liquid electrode. A pair of well‐defined redox peaks of rutin could be observed on voltammograms, indicating that the electrochemical reactions of rutin had taken place. Also, real samples were successfully detected using this proposed method.

External stimuli-controlled phase transitions are essential for fundamental physics and design of functional devices. Charge density wave (CDW) is a metastable collective electronic phase featured by the periodic lattice distortion. Much attention has been attracted to study the external control of CDW phases. Although much work has been done in the electric-field-induced CDW transition, the study of the role of Joule heating in the phase transition is insufficient. Here, using the Raman spectroscopy, the electric-field-driven phase transition is in situobserved in the ultrathin 1T-TaS2. By quantitative evaluation of the Joule heating effect in the electric-field-induced CDW transition, it is shown that Joule heating plays a secondary role in the nearly commensurate (NC) to incommensurate (IC) CDW transition, while it dominants the IC-NC CDW transition, providing a better understanding of the electric field-induced phase transition. More importantly, at room temperature, light illumination can modulate the CDW phase and thus tune the frequency of the ultrathin 1T-TaS2oscillators. This light tunability of the CDW phase transition is promising for multifunctional device applications.

Background: The development of nanomaterials modified electrode can provide more opportunities for the enhancement of the analytical performance in constructing electrochemical sensor and biosensor. LiFePO4 (LFP) is a promising candidate to develop new modified electrodes owing to its advantages such as cheap cost, environmental compatibility, high safety, non-toxicity, large theoretical capacity, long cycle life and abundant earth materials. Objective: The aim of this paper was to construct nanosized LFP modified electrodes, which could be applied as working electrode for rutin analysis and as an electrochemical biosensor for direct electrochemistry of Hemoglobin (Hb). Method: Nanosized LFP was characterized by scanning electron microscopy. The LFP modified electrodes with Carbon Ionic Liquid Electrode (CILE) as substrate electrode were fabricated by dropping method with chitosan (CTS) as film. Cyclic voltammetry and electrochemical impedance spectroscopy were carried out to examine the electrochemical performance of the modified electrodes. Differential pulse voltammetry was used to establish determination methods. Results: Two new LFP-based modified electrodes (CTS/LFP/CILE and CTS/Hb-LFP/CILE) were fabricated. The electrochemical behaviors of rutin on CTS/LFP/CILE were achieved with a pair of enhanced redox peaks. The linear range for rutin analysis was from 4.00-8 to 1.00-4 mol L-1 with a detection limit of 8.00-9 mol L-1. The direct electrochemistry of Hb in CTS/Hb-LFP/CILE was realized with a pair of obvious redox peaks. The electrocatalytic activity of CTS/Hb-LFP/CILE toward trichloroacetic acid and H2O2 reduction were investigated, and the detection limits of 0.068 mmol L-1 for TCA and 0.07 μmol L-1 for H2O2 were obtained. Conclusion: Two kinds of LFP modified electrodes were successfully constructed with improved electrochemical performances. Electrochemistry of rutin and Hb were realized on LFP based electrodes with enhanced responses, and the application of LFP nanoparticle in electrochemical sensor and biosensors was extended.

In this paper, a WS2nanosheet was modified on the surface of a carbon ionic liquid electrode (CILE), and horseradish peroxidase (HRP) was further fixed on the electrode with a Nafion film. Direct electrochemistry and bioelectrocatalysis of HRP incorporated on the modified electrode were investigated in detail. On Nafion/HRP/WS2/CILE, a pair of well‐defined quasi‐reversible redox peaks appeared on the cyclic voltammogram, indicating that the presence of the WS2nanosheet on the electrode surface could provide a specific interface with large surface area for HRP and its direct electron transfer rate was greatly enhanced. The formal potential (E0) obtained was –0.179 V, which was the typical feature of heme Fe(III)/Fe(II) in HRP. The electron transfer coefficient (α) and the heterogeneous electron transfer rate constant (ks) of HRP were calculated as 0.44 and 1.01 s–1, respectively. This HRP‐modified electrode showed excellent electrocatalytic activity for the reduction of trichloroacetic acid and NaNO2with a wide linear range and low detection limit. Real samples were detected by this proposed method, indicating the successful fabrication of a new third‐generation electrochemical enzyme sensor utilizing the WS2nanosheet. A WS2nanosheet was modified on the surface of a carbon ionic liquid electrode (CILE), and horseradish peroxidase (HRP) was further fixed on the electrode with a Nafion film. Direct electrochemistry and bioelectrocatalysis of HRP incorporated on the modified electrode were enhanced with a pair of well‐defined redox peaks. Also, real samples were successfully detected by the proposed method.

Herein the Block Mura is discussed. We analyze the formation mechanism of Block Mura in the ITO developing process with CFD simulation. A detailed study has carried out on the design of 2ndITO layer. Experimental results show that Block Mura can be quickly and effectively solved by using CFD simulation.

All dielectrics deform when subjected to an electric field. This behavior is attributed to the so-called Maxwell stress and the origins of this phenomenon can be traced to geometric deformation nonlinearities. In particular, the deformation is large when the dielectric is elastically soft (e.g. elastomer) and negligible for most “hard” materials. In this work, we develop a theoretical framework which shows that a striking analog of the electrostatic Maxwell stress also exists in the context of quantum mechanical-elasticity coupling. The newly derived quantum-elastic Maxwell stress is found to be significant for soft nanoscale structures (such as the DNA) and underscores a fresh perspective on the mechanics and physics of polarons. We discuss potential applications of the concept for soft nano-actuators and sensors and the relevance for the interpretation of opto-electronic properties. [ABSTRACT FROM AUTHOR]

ABSTRACTUreolytic biomineralization induced by urease-producing bacteria, particularly Proteus mirabilis, is responsible for the formation of urinary tract calculi and the encrustation of indwelling urinary catheters. Such microbial biofilms are challenging to eradicate and contribute to the persistence of catheter-associated urinary tract infections, but the mechanisms responsible for this recalcitrance remain obscure. In this study, we characterized the susceptibility of wild-type (ure+) and urease-negative (ure−) P. mirabilisbiofilms to killing by ciprofloxacin. Ure+ biofilms produced fine biomineral precipitates that were homogeneously distributed within the biofilm biomass in artificial urine, while ure− biofilms did not produce biomineral deposits under identical growth conditions. Following exposure to ciprofloxacin, ure+ biofilms showed greater survival (less killing) than ure− biofilms, indicating that biomineralization protected biofilm-resident cells against the antimicrobial. To evaluate the mechanism responsible for this recalcitrance, we observed and quantified the transport of Cy5-conjugated ciprofloxacin into the biofilm by video confocal microscopy. These observations revealed that the reduced susceptibility of ure+ biofilms resulted from hindered delivery of ciprofloxacin into biomineralized regions of the biofilm. Further, biomineralization enhanced retention of viable cells on the surface following antimicrobial exposure. These findings together show that ureolytic biomineralization induced by P. mirabilismetabolism strongly regulates antimicrobial susceptibility by reducing internal solute transport and increasing biofilm stability.

AbstractThis study qualitatively explored teachers’ responses to doubling errors (e.g., 3/4 × 2 = 6/8) that typically reflect students’ difficulties in understanding the “rule” for finding equivalent fractions (e.g., 3/4 × 2/2 = 6/8). Although all teachers claimed to teach for understanding in interviews, their responses varied in terms of effectiveness and types. One teacher grasped the doubling error to explain the reasons underlying the rule using symbolic representations only. The other two used concrete representations to explicate the reasons but tended to either prevent or ignore the doubling error. Although these teaching actions appeared different in form, all teachers essentially held the same perception-based perspectives; that is, they either assumed students could see what they saw or students could directly comprehend mathematical ideas through visualizing pictures only. Such perspectives overlook students’ available mathematical conceptions and might be at the root of the difficulties with those particular teaching strategies.

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.

A detailed study of Pt/alumina modified with cinchona alkaloids for the catalytic enantioselective hydrogenation of ethyl pyruvate to ethyl lactate and of butane-2,3-dione to 3-hydroxybutan-2-one is reported. Catalytic and 1H NMR spectroscopic studies have been carried out on both systems to investigate the influence of water on modifier conformation and enantioselectivity. Interestingly, the presence of small amounts of water has been shown to result in an increase the proportion of the open 3 conformer of cinchonidine when it is present in dilute solutions. Increased enantioselectivity, coupled with an increase in the proportion of the open 3 conformation of cinchonidine, is observed after pretreatment of the pyruvate ester with the modifier prior to admission to the reaction vessel. In contrast, no analogous effects are observed with butane-2,3-dione. It is proposed that the enhancements in enantioselectivity are a consequence of hydrolysis of ethyl pyruvate by a process that is catalysed by the basic cinchona modifier. The pyruvic acid formed during the hydrolysis interacts with the modifier and this leads to a further enhancement in the concentration of open 3 conformer present. The results contribute to an understanding of the widely variable enantioselectivities reported in the literature for this reaction.

In purely normal elastic rough surface contact problems, Persson's theory of contact shows that the evolution of the probability density function (PDF) of contact pressure with the magnification is governed by a diffusion equation. However, there is no partial differential equation describing the evolution of the PDF of the interfacial gap. In this study, we derive a convection–diffusion equation in terms of the PDF of the interfacial gap based on stochastic process theory, as well as the initial and boundary conditions. A finite difference method is developed to numerically solve the partial differential equation. The predicted PDF of the interfacial gap agrees well with that by Green's Function Molecular Dynamics (GFMD) and other variants of Persson's theory of contact at high load ranges. At low load ranges, the obvious deviation between the present work and GFMD is attributed to the overestimated mean interfacial gap and oversimplified magnification-dependent diffusion coefficient used in the present model. As one of its direct application, we show that the present work can effectively solve the adhesive contact problem under the DMT limit. The current study provides an alternative methodology for determining the PDF of the interfacial gap and a unified framework for solving the complementary problem of random contact pressure and random interfacial gap based on stochastic process theory. [Display omitted] [ABSTRACT FROM AUTHOR]

CO2electrochemical reduction in solid oxide electrolysis cells is an effective way to combine CO2conversion 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 situnear-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.

This study examined students' conceptions about the equal sign in light of historical findings with an international comparison group. Textbooks for preparation of students as mathematics teachers were examined. Participants were sixth-grade students from the USA (n= 105) and China (n= 145). About 98% of the Chinese children correctly answered all items by providing conceptually accurate explanations, but only 28% of the U.S. sample did. Textbooks for education majors who would teach in the USA rarely discussed the equal sign as equivalence while the Chinese texts introduced the “equal sign” in a context of relationships and discussed it as “balance,” “sameness,” or “equivalence.”

Surface tension, membrane stiffness and flexural rigidity all have been found to play significant roles in the determination of mechanical properties of nanosized materials and structures. In this work, Steigmann–Ogden theory of surface elasticity is applied for solving the contact properties between a rigid sphere and an elastic half-space. By integrating the surface Green's function of the corresponding nonclassical Boussinesq solution, the mixed boundary-value problem is transformed into a pair of singular integral equations, which are subsequently reduced to a nonlinear algebraic system of equations by Gauss–Chebyshev quadrature. Extensive numerical studies are performed to investigate the coupling effects of surface tension, membrane stiffness and flexural rigidity on contact radius, contact pressure, contact stiffness and displacement and stress distributions in the half-space. For microsized rigid spherical indenters, the inclusion of Steigmann–Ogden surface theory results in appreciably smaller contact radius, lower contact pressure, displacements and stresses, thus leading to higher contact stiffness. This observation suggests the increasing importance of the half-space boundary in load-carrying capability as the strength of surface material properties increases or the indenter size decreases. Moreover, least-squares based regression analysis proves that, in the presence of surface effects, the distribution of contact pressure obeys an elliptical curve less than a half. In addition, the sharp corners that are conventionally found in classical contact stress and subsidence displacement are replaced by smooth transitions across the circular contact perimeter. [ABSTRACT FROM AUTHOR]

Since the outbreak of coronavirus disease 2019 (COVID-19) in China, people have been exposed to a flood of media news related to the pandemic every day. Studies have shown that media news about public crisis events have a significant impact on individuals' depression. However, how and when the duration of attention to pandemic news predicts depression still remains an open question. This study established a moderated mediating model to investigate the relationship between the duration of attention to pandemic news and depression, the mediating effect of risk perception, and the moderating effect of future time perspective on the relationship. In early February 2020, 701 individuals from 29 provinces, autonomous regions, and municipalities across China were asked to self-report their duration of attention to pandemic news, level of depression, risk perception, and future time perspective during the COVID-19 outbreak. Results show that there is a significant positive correlation between the duration of attention to news on COVID-19 and depression; risk perception mediates the association between the duration of attention to pandemic news and depression; and future time perspective plays a moderating role between risk perception and depression. The findings of the present study provide theoretical implications and practically throw some light on alleviating the public's depression during pandemic periods. We highlight that the individual's hope for a better future, focusing on positive news, and time perspective balance during an epidemic disease are also beneficial to promoting positive emotion and reducing depression., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Wu, Li and Lyu.)