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Dynamic crack involves instabilities promoted by either external perturbation or intrinsic front oscillation. In an effort to decipher fracture surface markings of brittle materials, crack roughness of Wallner lines promoted by shear waves and surface corrugations induced by spontaneous front oscillations was investigated with silicon single crystal. The statistical distribution of surface height variations and the corresponding roughness exponents were determined. The Wallner lines are found to be self-affine with a Gaussian distribution and a roughness exponent of 0.8, which are consistent with the surface flaws giving rise to shear waves. In contrast, the surface corrugations do not exhibit self-affinity, due to their scale invariant characteristic shape. Interestingly, specific instabilities, which appear at very high speed and exhibit similar physical properties as front waves, render the crack roughness self-affine with a Gaussian distribution and a roughness exponent of 0.5. The findings of the present work will help to understand the origin of fracture surface markings for brittle materials, especially for single crystalline ceramics. [ABSTRACT FROM AUTHOR]

In order to solve the problem of low molecular weight in the synthesis of poly(ethylene 2,5-furandicarboxylate) (PEF) copolyester with titanium-based catalysts, this paper introduce an appropriate amount of glycerol (GC) into PEF to branch the straight chain polyester though the transesterification-melt polycondensation method, which solve the problem of low resin viscosity and low molecular weight. The structures of the copolymers were characterized by 1H-NMR and 13C-NMR, and the results showed that the modified PEF copolyesters and poly(ethylene-co-glycerol 2,5-furandicarboxylate) (PEGFs) were successfully prepared. The intrinsic viscosity ([η]) of PEGFs copolyesters was characterized by Ubbelohde viscosity, and the results showed that the copolyester [η] was increased from 0.25 dL/g to 0.755 dL/g. The thermal properties of copolyester were characterized by differential scanning calorimetry and thermo gravimetry, and it was found that the glass transition temperature of PEGFs copolyester increased from 67.8 °C to 89.5 °C, and the maximum pyrolysis rate temperature increased from 386.6 °C to 402.8 °C. We characterized the UV resistance of PEGFs copolyester, and the results showed that PEGFs copolyester could be well degraded under ultraviolet light. [ABSTRACT FROM AUTHOR]

As a typical body-centered cubic material, Ta has both high strength and high temperature resistance and is, thus, widely applied in the field of high-energy physics. In this work, the spallation behavior and its underlying physical mechanism of nano-polycrystalline Ta was systematically studied by non-equilibrium molecular dynamics simulations, with special attention to the internal grain size effect vs external shock intensity. The results reveal that the grain size effects on void evolution, spallation strength, and corresponding mechanical and thermodynamic responses are different under different shock intensities. Under the piston velocity of 0.75 km/s, when the grain size decreases from 30 to 2 nm, the spallation mechanism switches from intergranular fracture (d ≥ 10 nm) to cavitation failure (d ≤ 5 nm), and the correlation between spallation strength and grain size also switches from an inverse Hall–Petch to a Hall–Petch relation at a critical grain size dc ∼ 10–20 nm. As the piston velocity increases to 1.5 or 1.8 km/s, a failure mode transition from classical spallation to micro-spallation is observed, leading to a significantly weakened grain size effect on the spallation strength. Through thermodynamic analysis, melting is detected in the tensile region, which is responsible for the micro-spallation. These results can help to understand the effects of internal grain size and external shock intensity on the spallation behavior of Ta and make a leap in the design of shock-resistant materials. [ABSTRACT FROM AUTHOR]

Engineering structures or materials are often subjected to multiple shock loadings. Mechanical response and its physical mechanism under such loadings are extremely complex and need to be studied in depth. To reveal double shock-induced deformation and microstructural evolution in the key structural material Ta, large-scale non-equilibrium molecular dynamics simulations of monocrystalline and polycrystalline Ta under double shock loading were performed. The results show that the activation and re-evolution of twins and dislocations introduced by the first shock dominate the plastic deformation during the second one. Some crystallographic orientation dependent mechanisms of plastic deformation under the second shock are revealed. Twin-dislocation conversion is dominant in the ⟨100⟩-orientated monocrystalline and polycrystalline Ta, while dislocation slipping is dominant in the ⟨110⟩- and ⟨111⟩-orientated Ta. The dependence of flow strength on the loading-paths of single and double shocks was also investigated. Shock-induced amorphization and recrystallization are observed in the single shock-loaded Ta models, leading to lower flow strengths than those of the double shock-loaded ones. These results help understand the complex relationship between the dynamic strength and intrinsic deformation mechanism of Ta under multiple shock loadings. [ABSTRACT FROM AUTHOR]

2,5-Furandicarboxylic acid (FDCA) is non-toxic, biodegradable, and structurally similar to aromatic di-acids derived from petroleum (petroleum-based aromatic di-acids). In this paper, the polyamide (POF) of FDCA and 4,4′-diaminodiphenyl ether was synthesized in presence of LiCl and N,N-dimethylformamide, and then the new POF membrane was prepared from POF polymer by non-solvent-induced phase separation (NIPS) method. The surface morphology, roughness, contact angle, and zeta potential of the POF membrane surface were well investigated. The results showed that the POF membrane was a hydrophilic, negatively charged, and hard brittle material with high tensile strength. The effects of different POF concentrations in membrane casting solution on the performance of POF membrane were studied through the characterization of flux and interception. When POF concentration was 20 wt%, the prepared membrane exhibited the best performance in long-term stability test, and the flux was 43.9 L m−2 h−1 bar−1, and the rejection rates of the POF membrane for Evans blue, Congo red, and naphthol green B were 95.6%, 93.7%, and 89%, respectively. [ABSTRACT FROM AUTHOR]

The stress overshoot (or elastic overshoot) and its mechanism during the high-strain rate deformation of metals are systematically and comprehensively investigated by crystal plasticity finite element simulation. The constitutive model by Austin and McDowell (Int J Plast 27(1):1–24, 2011) is adopted to simulate the crystal anisotropic properties and the deformation with a wide range of strain rates by introducing the individual slip system and a new mechanism of dislocation evolution. Based on the validated constitutive model, the effects of strain rate, temperature, and crystal orientation on the stress overshoot phenomenon are studied, and the corresponding physical mechanism is analyzed. The results show that both strain rate and temperature have significant influences on the stress overshoot and all crystal orientations show the stress overshoot. [ABSTRACT FROM AUTHOR]

Transient phase transitions in ⟨ 100 ⟩ -oriented monocrystal coppers under ultrafast lasers induced shock compression are investigated using molecular dynamics simulation. Due to propagations and attenuations of compressive stress waves induced by ultrafast laser pulses, monocrystal coppers show distinct processes of structural phase transitions, i.e., first, face-centered cubic (FCC) → body-centered cubic (BCC), then BCC → FCC, then FCC → hexagonal close-packed (HCP), and finally some of HCP → FCC. The known Bain's phase transition path of FCC → BCC in copper is discussed in detail and the mechanisms are disclosed by using the modified Born stability criteria and the local minimum energy criterion. By considering the initiation of stacking faults, the mechanism of phase transition of FCC → HCP is well explained. Through the analysis of phonon spectra, the results show that both BCC and HCP phases are unstable phases of monocrystal coppers. [ABSTRACT FROM AUTHOR]

The construction of smart grid is an important part of improving the utilization rate of electric energy. As an important way for the construction of smart grid, non-intrusive load decomposition methods have been extensively studied. In this type of method, limited by transmission cost and network bandwidth, low-frequency data has been widely used in practical applications. However, the accuracy of device identification in this case faces challenges. Due to the relatively single characteristics of low-frequency data, it is difficult to express the operating status of complex electrical appliances, resulting in low decomposition performance. In this paper, a non-intrusive load is proposed based on household electrical habits by studying the relationship between household electricity consumption habits and load status decomposition method. The Gaussian mixture model and time information are used to model the probability distribution of the electrical appliance state. This probability distribution is then used as the observation probability distribution of the factor hidden Markov model. In such a way, the BH-FHMM model is proposed. Finally, load decomposition is carried out through the load decomposition process of the FHMM model. In order to verify the performance of the proposed method, an experimental comparison is conducted based on the REDD data set. According to the results, a significant improvement in equipment recognition accuracy is obtained. [ABSTRACT FROM AUTHOR]

This paper aims to develop a chloride transport model of engineered cementitious composites (ECC) that can consider the influence of both exposure time and crack width. ECC specimens with crack widths of 0.1 mm, 0.2 mm and 0.3 mm were soaked into NaCl solution with periods of 30, 60, 90 and 120 days. The free chloride content profile was measured and used for the development of the transport model. Regression analysis was applied to build the time and crack width dependent models of apparent diffusion coefficient and surface chloride content. The results show that the crack width has significant influence on the free chloride concentration profile when it is above 0.2 mm and the time-dependent constant n decreases linearly with the crack width. The chloride transport model was obtained by subscribing the models of apparent diffusion coefficient and surface chloride content into the analytical solution of Fick's second law. The model was further validated with the experimental results, showing a deviation within 20%. The findings of the presented study can enhance the current understanding on the chloride transportation in ECC. [ABSTRACT FROM AUTHOR]

The construction of highly ordered hierarchical nanoarrays is crucial for obtaining effective transition metal carbon nanomaterial electrocatalysts for oxygen evolution reaction (OER) in water splitting. Herein, we adopted a Co metal zeolitic imidazolate framework (Co-ZIF) as a precursor by ion-exchange/etching reaction with Fe(NO3)3 to obtain hierarchical N-doped Co-Fe layered double hydroxide (CoFe-LDH) in situ generated in Co-ZIF nanoarrays based on a self-supported carbon cloth (CC) substrate noted as CoFe-LDH@Co-ZIF@CC. Benefiting from the synergistic effect of these species and their highly ordered self-supported nanoarray structure, the catalytic active sites were fully exposed and highly protected in alkaline electrolyte, which significantly promoted electron transport and improved electrochemical performance. The CoFe-LDH@Co-ZIF@CC exhibited the low overpotentials of about 225 and 319 mV at 10 and 100 mA cm−2 with a small Tafel slope of 81.8 mV dec−1 recorded in a 1.0 M KOH electrolyte. In addition, it also showed a long-term durability without obvious decay after 30 h. Therefore, its remarkable OER activity demonstrates this material's promising application in the green hydrogen energy industry. [ABSTRACT FROM AUTHOR]

Technology innovation has changed the patterns with its advanced features for travel and tourism industry during the outbreak of COVID-19 pandemic, which massively hit tourism and travel worldwide. The profound adverse effects of the coronavirus disease resulted in a steep decline in the demand for travel and tourism activities worldwide. This study focused on the literature based on travel and tourism in the wake global crisis due to infectious virus. The study aims to review the emerging literature critically to help researchers better understand the situation. It valorizes transformational affordance, tourism, and travel industries impacts posed by the virus COVID-19. The study proposed a research model on reviving the international tourism activities post COVID-19 pandemic to gain sustainable development and recovery. The scholars have debated seeking the best possible ways to predict a sustainable recovery of travel, tourism, and leisure sectors from the devastating consequences of coronavirus COVID-19. In the first phase, the study describes how the current pandemic can become transformational opportunities. It debates the situation and questions related to the emergence of the COVID-19 outbreak. The present research focuses on identifying fundamental values, organizations, and pre-assumptions related to travel and tourism revival and help academia and researchers to a breakthrough in initiating the frontiers based on research and practice. This study aims at exploring the role of technological innovation in the crisis management of COVID-19 tourism impacts, tourists' behavior, and experiences. The travel and tourism industry's main stakeholders include tourism demand and organizations that manage tourists' destinations and policymakers. They have already experienced the stages of responses, recovery, and resetting tourism recovery strategies. The study provides valuable insight into the coronavirus consequences on travel and tourism and practical implications for global tourism and academic research revitalization. [ABSTRACT FROM AUTHOR]

Many experiments have shown that plastic deformation of metals generates heat, leading to temperature rise of the material. However, little is known about the underlying factors that govern the heat generation, especially in polycrystalline metals involving high-rate plastic deformation. In this work, the work-to-heat conversion during high-rate plastic deformation of polycrystalline coppers with and without nanotwins is studied using molecular dynamics simulations. The results show that within a certain range of imposed deformation, smaller grain size results in higher plastic work-to-heat conversion, due to larger proportion of grain boundaries. For a given grain size of polycrystalline copper with twins, the portion of plastic work converted to heat increases as the twin-boundary spacing decreases within a certain deformation range. However, at large deformation the plastic work-to-heat conversion coefficient should be analyzed specifically for each individual sample due to the transformation of the deformation mechanism (i.e., the change of the energy storage). [ABSTRACT FROM AUTHOR]

Counterexample models to the Nelson-Seiberg theorem have been discovered, and their features have been studied in previous literature. All currently known counterexamples have generic superpotentials respecting the R-symmetry, and more R-charge 2 fields than R-charge 0 fields. But they give supersymmetric vacua with spontaneous R-symmetry breaking, thus violate both the Nelson-Seiberg theorem and its revisions. This work proves that the other type of counterexamples do not exist. When there is no R-symmetry, or there are no more R-charge 2 fields than R-charge 0 fields in models with R-symmetries, generic superpotentials always give supersymmetric vacua. There exists no specific arrangement of R-charges or non-R symmetry representations which makes a counterexample with a supersymmetry breaking vacuum. This nonexistence theorem contributes to a refined classification of R-symmetric Wess-Zumino models. [ABSTRACT FROM AUTHOR]

With the development of experimental techniques and characterization methods at the microscopic scale, a high concentration of hydrogen-induced vacancies and their clusters have been detected in a large variety of metals and alloys charged with hydrogen, which is supposed to play an important role in hydrogen-induced fracture process. In hydrogen environment, vacancies and their clusters can trap a certain number of H atoms to form vacancy-H complexes or clusters. To investigate the role of hydrogen-induced vacancies and their clusters in brittle-like failure in hydrogen environment, multi-scale modelling was performed in this work, with a particular attention on the interaction between dislocations and vacancy-H complexes. Firstly, the H-enhanced vacancy formation due to H-induced reduction in vacancy formation energy in Al was modelled by first principles calculations, and a hydrogen-influenced vacancy concentration model was proposed. Then, to capture the interaction between gliding edge dislocations and vacancy-H complexes and clusters, atomistic simulations were performed, and a mesoscale model quantitatively describing the pinning effect of vacancy-H complexes and clusters on the gliding edge dislocations was obtained. Finally, these quantitative models were introduced into a newly developed XFEM-based discrete dislocation plasticity scheme. With this scheme, mode-I crack propagation was simulated, where dislocation emission from crack-tip, dislocation evolution and cohesive crack propagation were considered, with a particular attention to the key role of the hydrogen-influenced dislocation evolution in the brittle-like failure of the H-charged metals. Based on these multi-scale simulations, a pinning effect of H-enhanced vacancies and vacancy-H complexes on edge dislocations was identified, which was proposed to be responsible for the brittle-like failure of Al in hydrogen environment. This pinning effect presents a good agreement with the hydrogen-restricted dislocation mobility observed in in situ fracture experiments. [ABSTRACT FROM AUTHOR]

Abdominal aortic aneurysm (AAA) is a vascular disease found to have progressive growth in the area of aorta. Rupturing of aorta causes excessive bleeding that leads to health‐related issues, which can be fatal sometimes. Therefore, it becomes important to make early diagnosis of AAA and its condition and start immediate treatment. Blood‐based biomarker helps to diagnose AAA and to monitor the condition after AAA surgery. N‐terminal pro‐B‐type natriuretic peptide (NT‐proBNP) is a hormone produced in the heart in small quantities and increased when the heart needs to work harder. NT‐proBNP was proved to be strongly linked with AAA incidence. Moreover, quantifying the level of NT‐proBNP helps to determine the risk factors on cardiovascular system after the surgery. This work is quantifying the NT‐proBNP on interdigitated electrode sensor by using NT‐proBNP binding aptamer. The detection limit of NT‐proBNP was calculated as 1 pg/mL on a linear regression curve [y = 0.2148x + 0.8849; R² = 0.9049]. The linear range with dose‐dependent analysis was from 0.01 until 100 ng/mL. Moreover, the control experiment with complementary aptamer sequence did not show the current signal, specifying the detection of NT‐proBNP. This research benefits to identify the heart condition of patient after the removal of AAA. [ABSTRACT FROM AUTHOR]

In view of the disadvantages of concentration polarization and trade-off effects in the application of membrane in desalination field, oxide-nano graphene oxide/polyamide (O-NGO/PA) loose intermediate layer and PA ultra-thin dense layer were introduced to fabricate PA/O-NGO/polyphenylene sulfide composite membrane with sandwich structure via multi-step interfacial polymerization (MS-IP) method. The selective permeation mechanism of ultrathin layer produced by different aqueous monomers (PIP and MPD) was studied, the effect of its physicochemical structure on the relief of concentration polarization phenomenon and the breakthrough of trade-off effect was analyzed. The ultra-thin and dense PA layer mainly played the role of interception and shortened the water molecular penetration path. In the retention test of metal salt solution, compared with the rough surface, it was found that the smooth surface was more conducive to the diffusion of intercepted metal ions into the feed solution, thus alleviating the concentration polarization phenomenon. [ABSTRACT FROM AUTHOR]

Shock compression behaviors of copper single crystals at room and elevated temperatures are investigated by molecular dynamics simulations. The results show that when increasing the initial temperature, the kinetic energy part of stress increases while the potential energy part of stress decreases; the shear strain and the density of defects decrease while the magnitude of temperature rise increases. To understand the effect of initial temperature on the shock response, the evolutions of dislocations under different initial temperatures are studied in detail. Finally, the effect of initial temperature on quasi-static compression behavior is also investigated and analyzed. [ABSTRACT FROM AUTHOR]

Single crystals subjected to shock compression exhibit responses with distinct two-wave structures for certain crystal orientations. However, little is known to date regarding how the shock response depends on crystal orientation, and especially why the two-wave structure depends on the crystal orientation. In this work, molecular dynamics simulations of shock compressions in copper single crystals are performed to investigate the orientation dependence of shock responses and the corresponding deformation mechanisms. Four copper single crystals with [001], [011], [012], and [123] crystal orientations along the depth direction are investigated. The [011], [012], and [123] crystal orientations of copper single crystals show distinct two-wave structures in their shock responses, while such a two-wave structure in the shock response is not seen for those orientations having a [001] crystal orientation. The potential causes are analyzed by considering the propagation velocities of both elastic and plastic waves. We develop a technique for identifying twin structures in face-centered cubic crystals and this technique can effectively identify the twin structure. The morphology of shock-induced defects (e.g., dislocations and twins) shows the significant dependence of crystal orientation and the mechanisms behind these are discussed in detail. Finally, the Johnson-Cook constitutive model describing dynamic deformations at high temperatures and high strain rates is used to analyze the relationships between the shock responses and microscopic defects. The predictions of the Johnson-Cook constitutive model are consistent with the results of the molecular dynamics simulations. [ABSTRACT FROM AUTHOR]

A series of dynamic shock compressions of metal films are simulated using molecular dynamics method. Characteristics of mechanical shock load are analyzed theoretically. Thermomechanical responses induced by mechanical shock, including pressure, temperature, volumetric strain, and shear strain, are presented graphically and analyzed from viewpoint of thermomechanical coupling. The results show that the temperature rise caused by volumetric strain (elastic) is reversible, while that caused by shear strain is irreversible. Under the same mechanical shock load, several metal films exhibit significant differences in thermomechanical responses and the potential reasons are analyzed from the differences of thermophysical parameters. [ABSTRACT FROM AUTHOR]

(CF3C6H4)2SnO, (CH3C6H4)2SnO and Ph2SnO were successfully synthesized for the transesterification of DMC with BPA. The products of mono-methylcarbonate-ended-BPA (MmC(1)) and two-methylcarbonate-ended-BPA (DmC(1)) were selectively synthesized over them. The catalysts were characterized by FT-IR, TG and XPS. When Ph2SnO was used as the catalyst at 170 °C, the BPA conversion reached to 28.60% and the transesterification selectivity reached to 98.35%. As for (CF3C6H4)2SnO, BPA conversion and transesterification selectivity declined to 12.48% and 64.74%, respectively. The BPA conversion increased to 42.83%, but the transesterification selectivity declined to 44.55% over (CF3C6H4)2SnO. Notability, the higher transesterification selectivity of Ph2SnO was due to its lowest electron binding energy of Sn4+. More importantly, the DMC adsorption, activation and decomposition process over (CF3C6H4)2SnO, (CH3C6H4)2SnO and Ph2SnO were characterized by TG–MS and in situ DRIFT techniques, which provided more information about the mechanism of transesterification and methylation. [ABSTRACT FROM AUTHOR]

The selective oxidation of cyclohexane (CHA) is still a significant challenge in the field of current catalysis chemistry and chemical industry. Here, nano-V2O5/Ti porous membrane electrodes with different morphologies, i.e., nanorods (NRs), nanosheets (NSs), and nanoparticles (NPs), were prepared by loading nano-V2O5 onto porous Ti membranes. Simultaneously, a nano-V2O5/Ti membrane electrode was employed to constitute an electrocatalytic membrane reactor (ECMR) for CHA oxidation. Results indicated that the electrochemical performance was significantly associated with the morphology of the nano-V2O5 catalysts on the membrane electrode. ECMR with V2O5 NSs/Ti electrode exhibited superior properties. Excellent electrochemical activity was obtained in the application of CHA oxidation with 28.4% conversion and 99.9% selectivity to cyclohexanone and cyclohexanol (KA oil), which is better than most noble-metal-based catalysts reported in the literature under aerobic reaction conditions. Further, a prominent catalytic activity (10.5% conversion and 99.5% selectivity to KA oil) was first achieved even under 0 °C. The preferable electrocatalytic performance of V2O5 NSs/Ti electrode for CHA oxidation was attributed to the large effective electrocatalytic surface area, high electron transfer rate, and high rate of hydroxyl radical (ṖOH) generation. Furthermore, the mechanism of CHA oxidation was explored. It was established that the valence change of V catalysts is an essential step during the selective oxidation of CHA by ECMR. Moreover, the V2O5 NSs/Ti electrode displayed excellent stability of oxidation during the selective oxidation of CHA. Therefore, our research opens up a new avenue toward the fundamental understanding and design of nanocatalysts in heterogeneous and electrochemical catalysis. [ABSTRACT FROM AUTHOR]

Polyphenylene sulfide (PPS) membranes were modified by chloromethylation and quaternary amination reaction to prepare a hydrophilic PPS microporous membrane. The structures of the modified PPS membranes were characterized by the use of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. The results showed that the modified membranes maintain the same microporous structures as the PPS membrane. The hydrophilicity of the modified membranes was significantly improved compared to that of the PPS membranes, and the water flux of N-methylimidazole modified membranes, triethylamine modified membranes, and both mixture modified membranes achieved 110.475, 168.94, 150.59 L·m−2·h−1, respectively. The quaternary amination of the PPS membranes made much less bovine serum albumin (BSA) pollution accumulation on the top surface of the modified membranes, and there was a significant improvement, to 94%, in the BSA rejection rate. Most importantly, the antibacterial activity of the modified membranes was effectively improved, and the bactericidal rate was elevated to above 80% in comparison with pure PPS membranes, which was attributed to the introduction of quaternary ammonium salts and imidazolium salts in out-surface of the membranes. [ABSTRACT FROM AUTHOR]

Biomass product 5-hydroxymethylfurfural (5-HMF) can be used to synthesize a broad range of value added compounds currently derived from petroleum. Thus, the effective conversion of glucose or cellulose (the major components of biomass) into fuels and chemical commodities has been capturing increasing attention. Previous studies have been extensively focused on a two-step process for producing 5-HMF from glucose or cellulose, i.e., the isomerization of glucose into fructose and then the dehydration of fructose. We herein discovered that heterogeneous sulfonated poly(phenylene sulfide) (SPPS) containing strong Brønsted acid sites is able to convert glucose and cellulose into 5-HMF with a high yield in ionic liquids (ILs). The optimal activity of glucose conversion to 5-HMF achieves a yield of 87.2% after 4 h reaction at 140 °C. For direct cellulose conversion, a 5-HMF yield of 68.2% can be achieved. The reaction mechanism over the SPPS catalyst in ILs was studied by DFT calculations, and the results indicated that the SO3H group of SPPS plays a crucial role in glucose conversion into 5-HMF, and it acts as a proton donor as a Brønsted acid and functions as a proton acceptor as the conjugate base. Furthermore, the anions and cations of ILs together with SO3H-SPPS helped in stabilizing the reaction intermediates and transition states, which also resulted in glucose facile conversion into 5-HMF. The new catalyst system highlights new opportunities offered by optimizing the production of 5-HMF directly from glucose and cellulose. [ABSTRACT FROM AUTHOR]

Organic solvent free 5-hydroxymethylfurfural (HMF) oxidation into 2,5-furandicarboxylic acid (FDCA) with hydrogen peroxide using quaternary ammonium octamolybdate and quaternary ammonium dectungstate was studied. Tetra-1-ethyl-3-methylimidazolium octamolybdate ([EMIM]4Mo8O26), tetra-hexadecyltrimethyl ammonium octamolybdate ([CTAB]4Mo8O26) and tetra-ethylpyridinium octamolybdate ([EPy]4Mo8O26) displayed high activity for the selective oxidation of HMF to FDCA, and the selectivity of FDCA could reach 100% with a 99.5% conversion of HMF in the presence of [EMIM]4Mo8O26. The byproduct formed in competition with FDCA was identified as the intermediate 5-hydroxymethyl-2-furan carboxylic acid (HMFCA) and 5-formyl-2-furan carboxylic acid (FFCA), and neither 2,5-diformyl furan (DFF) nor any other byproducts from the oxidative cleavage of the HMF furan ring were detected during the oxidation process, which indicated that the aldehyde group of HMF oxidizes first, followed by the oxidation of the hydroxymethyl group in this reaction system. Although the quaternary ammonium salts, such as [EMIM]Br, EPyBr and CTAB, prevented FDCA formation from the HMFCA advanced oxidation, they could eliminate the oxidative cleavage of the furan ring and improve the affinity of HMF and catalysts, to make the catalytic active centers readily accessible to HMF molecules. However, tetra-1-ethyl-3-methylimidazolium dectungstate ([EMIM]4W10O32), tetra-hexadecyltrimethyl ammonium dectungstate ([CTAB]4W10O32) and tetra-ethylpyridinium dectungstate ([EPy]4W10O32) were unfavorable for FDCA formation. The great difference in performance of quaternary ammonium octamolybdate and quaternary ammonium dectungstate in HMF oxidation with H2O2 was attributed to their different structure. [ABSTRACT FROM AUTHOR]

This paper studies the stress field and crack nucleation behavior in a disclinated nanowire with a continuum model. The surface stress effects of the nanowire is accounted for with the Gurtin-Murdoch model. The Green's functions for the stress fields of a single wedge disclination and a single edge dislocation in a cylindrical nanowire are solved respectively with the complex variable method. To make the superposition principle valid, the stress field induced by the residual surface tension is properly handled in the Green's functions. After that, the distributed dislocation method is applied to simulate the crack nucleation behavior. The influences of the surface stress effects on the stress fields of the wedge disclination and edge dislocation as well as on the Griffith crack nucleation behavior are systematically discussed. [ABSTRACT FROM AUTHOR]

Nucleus pulposus (NP) apoptosis and subsequent excessive degradation of the extracellular matrix (ECM) are key pathological characteristics of intervertebral disc degeneration (IDD). The present study aims to examine the signaling processes underlying the effects of taurine on IDD, with specific focus on endoplasmic reticulum (ER) stress-mediated apoptosis and ECM degradation, in NP cells. To clarify the role of taurine in IDD, NP cells were treated with various concentrations of taurine and IL-1β or thapsigargin (TG). Cell Counting Kit-8, western blotting, TUNEL, immunofluorescence assays and reverse transcription-quantitative PCR were applied to measure cell viability, the expression of ER stress-associated proteins (GRP78, CHOP and caspase-12), apoptosis and the levels of metabolic factors associated with ECM (MMP-1, 3, 9, ADAMTS-4, 5 and collagen II), respectively. Taurine was found to attenuate ER stress and prevent apoptosis in NP cells induced by IL-1β treatment. Additionally, taurine significantly decreased the expression of ER stress-activated glucose regulatory protein 78, C/EBP homologous protein and caspase-12. TUNEL results revealed that taurine decreased the number of apoptotic TG-treated NP cells. TG-treated NP cells also exhibited characteristics of increased ECM degradation, supported by observations of increased MMP-1, MMP-3, MMP-9 and A disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4 and ADAMTS-5 expression in addition to decreased collagen-II expression. However, taurine treatment significantly reversed all indicators of excessive ECM catabolism aforementioned. These data suggest that taurine can mediate protection against apoptosis and ECM degradation in NP cells by inhibiting ER stress, implicating therapeutic potential for the treatment of IDD. [ABSTRACT FROM AUTHOR]

Transesterification of dimethyl carbonate (DMC) with hydrogenated bisphenol A (HBPA) was studied over various organotin oxides under pressured condition without removal of by-producing methanol. BuSnO displayed higher activities in HBPA conversion and bis-methylcarbonate of hydrogenated bisphenol-A (BMHBPA) synthesis, and HBPA conversion and BMHBPA selectivity reached 97.4% and 84.0%. However, when PhSnO was used as catalyst, HBPA conversion and BMHBPA selectivity decreased to 81.5 and 37.7%. Catalyst steric hindrance significantly influenced HBPA conversion and BMHBPA formation, and π-d interaction between phenyl ring and Sn was unfavorable for the transesterification of HBPA with DMC. Moreover, the catalytic system was further optimized. [ABSTRACT FROM AUTHOR]

The thermal decomposition kinetics of the N,N′-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxan-2-yl) ethylenediamine (DPTDEDA) in air were studied by TGDTG techniques. The kinetic parameters of the decomposition process for the title compound in the two main thermal decomposition steps were calculated through the Friedman and Flynn-Wall-Ozawsa (FWO) methods and the thermal decomposition mechanism of DPTDEDA was also studied with the Coats-Redfern and Achar methods. The results show that the activation energies for the two main thermal decomposition steps are 128.03 and 92.59 kJ·mol−1 with the Friedman method, and 138.75 and 106.78 kJ·mol−1 with the FWO method, respectively. Although there are two main thermal decomposition steps for DPTDEDA in air, the thermal decomposition mechanism of DPTDEDA in the two steps are the same, i.e. f( α) = 3/2(1 − α)4/3[(1 − α)−1/3 − 1]−1. [ABSTRACT FROM AUTHOR]