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Highlights: [•] This paper investigates the effect of stress singularities on the scaling of fracture of hybrid structures. [•] The scaling mechanism transits from energetic to statistical as the stress singularities get weaker. [•] The energetic-statistical scaling relation agrees well with the numerical simulations by a stochastic cohesive crack model. [Copyright &y& Elsevier]

Understanding the relationships between the molecular structure and electronic transport characteristics of single-molecule junctions is of fundamental and technological importance for future molecular electronics. Herein, we report a combined experimental and theoretical study on the single-molecule conductance of a series of oligo(phenylene ethynylene) (OPE) molecular wires, which consist of two phenyl-ethynyl-phenyl π units with different dihedral angles. The molecular conductance was studied by scanning tunneling microscopy (STM)-based break-junction techniques under different conditions, including variable temperature and bias potential, which suggested that a coherent tunneling mechanism takes place in the OPE molecular wires with a length of 2.5 nm. The conductance of OPE molecular junctions are strongly affected by the coupling strength between the two π systems, which can be tuned by controlling their conformation. A cos2 θ dependence was revealed between the molecular conductance and dihedral angles between the two conjugated units. Theoretical investigations on the basis of density functional theory and nonequilibrium Green's functions (NEGF) gave consistent results with the experimental observations and provided insights into the conformation-dominated molecular conductance. [ABSTRACT FROM AUTHOR]

Abstract: A cyclic cohesive zone model is proposed to simulate the mode-I crack growth in quasibrittle structures under compressive fatigue. The constitutive behavior of the cohesive elements is formulated for both tension and compression regimes. A strain-softening cohesive law is adopted for the tension regime whereas a plastic-type cohesive behavior is considered for the compression regime. It is shown that the proposed model is able to capture some essential fracture behaviors of quasibrittle structures under compressive fatigue, which include the onset of fatigue crack growth, the gradual decrease in crack growth rate, and the exhaustion of residual tensile stress over the cycles. Based on a fracture process zone (FPZ)-equivalence principle, it is further shown that the existing kinetics equation for tensile fatigue crack can be extended to the crack growth under cyclic compression. [Copyright &y& Elsevier]

Engineering structures such as aircraft, bridges, dams, nuclear containments and ships, as well as computer circuits, chips and MEMS, should be designed for failure probability < 10-10 per lifetime. The safety factors required to ensure it are still determined empirically, even though they represent much larger and much more uncertain corrections to deterministic calculations than do the typical errors of modern computer analysis of structures. The empirical approach is sufficient for perfectly brittle and perfectly ductile structures since the cumulative distribution function (cdf) of random strength is known, making it possible to extrapolate to the tail from the mean and variance. However, the empirical approach does not apply to structures consisting of quasibrittle materials, which are brittle materials with inhomogeneities that are not negligible compared to structure size. This paper presents a refined theory on the strength distribution of quasibrittle structures, which is based on the fracture mechanics of nanocracks propagating by activation energy controlled small jumps through the atomic lattice and an analytical model for the multi-scale transition of strength statistics. Based on the power law for creep crack growth rate and the cdf of material strength, the lifetime distribution of quasibrittle structures under constant load is derived. Both the strength and lifetime cdf's are shown to be size- and geometry-dependent. The theory predicts intricate size effects on both the mean structural strength and lifetime, the latter being much stronger. The theory is shown to match the experimentally observed systematic deviations of strength and lifetime histograms of industrial ceramics from the Weibull distribution. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents a new probability distribution function for the breakdown lifetime of high-k gate dielectrics under unipolar AC voltage stress. This function is derived from a finite weakest-link model, where the gate oxide layer is considered to consist of many potential breakdown cells. Each potential breakdown cell is modeled as a series coupling of several subcells, which is analogous to the fiber-bundle model for the strength statistics of structures. The present model indicates that the type of lifetime distribution varies with the gate area and the dependence of the mean lifetime on the gate area deviates from the classical Weibull scaling law. It is shown that the model agrees well with the observed lifetime histograms of HfO2 based gate dielectrics under unipolar AC voltage stress. [Copyright &y& Elsevier]

This paper presents a general size effect equation for the strength of hybrid structures, which are made of two dissimilar quasibrittle materials with a thin and weak bimaterial interface. Depending on the material mismatch and structure geometry, a singular stress field could occur at the bimaterial corner. For structures with strong stress singularities, an energetic size effect is derived based on the equivalent linear elastic fracture mechanics and asymptotic matching. For structures without stress singularities, a finite weakest link model is adopted to derive the size effect. A general scaling equation that bridges the limits of strong and zero stress singularities is formulated by combining the energetic scaling of fracture of the bimaterial corner and the finite weakest link model. [ABSTRACT FROM AUTHOR]

Compaction of hot mix asphalt (HMA) requires high temperatures in the range of 125 to 145 ° C to ensure the fluidity of asphalt binder and, therefore, the workability of asphalt mixtures. The high temperatures are associated with high energy consumption, and higher NOx emissions, and can also accelerate the aging of asphalt binders. In previous research, the authors have developed two approaches for improving the compactability of asphalt mixtures: (1) addition of Graphite Nanoplatelets (GNPs), and (2) optimizing aggregate packing. This research explores the effects of these two approaches, and the combination of them, on reducing compaction temperatures while the production temperature is kept at the traditional levels. A reduction in compaction temperatures is desired for prolonging the paving window, extending the hauling distance, reducing the energy consumption for reheating, and for reducing the number of repairs and their negative environmental and safety effects, by improving the durability of the mixtures. A Superpave asphalt mixture was chosen as the control mixture. Three modified mixtures were designed, respectively, by (1) adding 6% GNP by the weight of binder, (2) optimizing aggregate packing, and (3) combining the two previous approaches. Gyratory compaction tests were performed on the four mixtures at two compaction temperatures: 135 ° C (the compaction temperature of the control mixture) and 95 ° C. A method was proposed based on the gyratory compaction to estimate the compaction temperature of the mixtures. The results show that all the three methods increase the compactability of mixtures and thus significantly reduce the compaction temperatures. Method 3 (combining GNP modification and aggregate packing optimization) has the most significant effect, followed by method 1 (GNP modification), and method 2 (aggregate packing optimization). [ABSTRACT FROM AUTHOR]

Recent disagreements on the mathematical modeling of fracture and size effect in concrete and other quasi-brittle materials are obstacles to improvements in design practice, and especially in design codes for concrete structures. In an attempt to overcome this impediment to progress, this paper compares the Hu-Duan boundary effect model (BEM) expounded since 2000 to the size-shape effect law (SEL) proposed at Northwestern University in 1984 and extended to the geometry (or shape) effects in 1990. It is found that within a rather limited part of the range of sizes and shapes, the fracture energy values identified by BEM and SEL from the test data on maximum loads are nearly the same. But in other parts of the range the BEM is either inferior or inapplicable. The material tensile strength values identified by BEM have a much larger error than those obtained from the SEL after calibration by the cohesive crack model. From the theoretical viewpoint, several hypotheses of BEM are shown to be unrealistic. [ABSTRACT FROM AUTHOR]

Abstract: The statistics of structural lifetime under constant load are related to the statistics of structural strength. The safety factors applied to structural strength must ensure failure probability no larger than , which is beyond the means of direct verification by histogram testing. For perfectly brittle materials, extrapolation from the mean and variance to such a small tail probability is no problem because it is known that the Weibull distribution applies. Unfortunately, this is not possible for quasibrittle materials because the type of cumulative distribution function (cdf) has been shown to vary with structure size and shape. These are materials with inhomogeneities and fracture process zones (FPZ) that are not negligible compared to structural dimensions. A probabilistic theory of strength of quasibrittle structures failing at macro-crack initiation, which can be experimentally verified and calibrated indirectly, has recently been deduced from the rate of jumps of atomic lattice cracks governed by activation energy barriers. This paper extends this nano-mechanics based theory to the distribution of structural lifetime. Based on the cdf of strength and a power law for subcritical crack growth rate, the lifetime cdf of quasibrittle structures under constant loads is derived. The lifetime cdf is shown to depend strongly on the structure size as well as geometry. It is found that, for the creep rupture case, the mean structural lifetime exhibits a very strong size effect, much stronger than the size effect on the mean structure strength. The theory also implies temperature dependence of the lifetime cdf. For various quasibrittle materials, such as industrial ceramics and fiber composites, it is demonstrated that the proposed theory correctly predicts the experimentally observed deviations of lifetime histograms from the Weibull distribution. [Copyright &y& Elsevier]

Abstract: Ensuring a small enough failure probability is important for the design and selection of restorative dental ceramics. For this purpose, the two-parameter Weibull distribution, which is based on the weakest link model with infinitely many links, is usually adopted to model the strength distribution of dental ceramics. This distribution has been thoroughly validated for perfectly brittle materials. However, dental ceramics are generally quasibrittle because the inhomogeneity size is not negligible compared to the size of the ceramic part. For such materials, the experimental histograms of many quasibrittle materials have been shown to exhibit strong deviations from the two-parameter Weibull distribution. As a remedy, the three-parameter Weibull distribution, which has a nonzero threshold, has been proposed. However, the improvement of the fits of histograms of quasibrittle materials has been only partial. Instead of making the threshold non-zero, the correct remedy is to consider the weakest link model to have a finite number of links, each of them representing one finite-size representative volume element of material. This model has recently been justified on the basis of the probability of random jumps of atomic lattice cracks over the activation energy barriers on the free energy potential of the lattice. It is shown that, in similarity to other quasibrittle materials, this new model allows excellent fits of the experimental strength histograms of various types of dental ceramics. [Copyright &y& Elsevier]

Previous analysis of progressive collapse showed that gravity alone suffices to explain the overall collapse of the World Trade Center Towers. However, it remains to be determined whether the recent allegations of controlled demolition have any scientific merit. The present analysis proves that they do not. The video record available for the first few seconds of collapse is shown to agree with the motion history calculated from the differential equation of progressive collapse but, despite uncertain values of some parameters, it is totally out of range of the free fall hypothesis, on which these allegations rest. It is shown that the observed size range (0.01–0.1 mm) of the dust particles of pulverized concrete is consistent with the theory of comminution caused by impact, and that less than 10% of the total gravitational energy, converted to kinetic energy, sufficed to produce this dust (whereas, more than 150 t of TNT per tower would have to be installed, into many small holes drilled into concrete, to produce the same pulverization). The air ejected from the building by gravitational collapse must have attained, near the ground, the speed of almost 500 miles per hour (or 223 m/s, or 803 km/h) on average, and fluctuations must have reached the speed of sound. This explains the loud booms and wide spreading of pulverized concrete and other fragments, and shows that the lower margin of the dust cloud could not have coincided with the crushing front. The resisting upward forces due to pulverization and to ejection of air, dust, and solid fragments, neglected in previous studies, are indeed found to be negligible during the first few seconds of collapse but not insignificant near the end of crush-down. The calculated crush-down duration is found to match a logical interpretation of seismic record, while the free fall duration grossly disagrees with this record. [ABSTRACT FROM AUTHOR]

Two series of oligo(phenylene ethynylene)s (OPEs) with different dendrimer side groups have been designed and synthesized. The molecules contain thiol groups at both ends to enable interconnection between nanoscale gapped metallic electrodes. The different dendrimer groups act as “shells”, allowing tailoring to the nanoscopic environment surrounding the OPE “core”. Meanwhile, the dendrimer shells also act as spacers for the precise control of the packing density and intermolecular interaction between the OPE cores. [ABSTRACT FROM AUTHOR]

Abstract: The selective electroanalysis of dopamine (DA) using the self-assembled monolayers of an oligo(phenyleneethynylene)s (OPEs) type molecular wire have been studied for the first time. Cyclic voltammetry measurement showed the OPE modified electrodes preferentially inhibit the electrochemical reaction of ascorbic acid (AA). Using square-wave voltammetry technique, DA was quantitatively determined in the presence of high concentration AA. This work reveals that, besides molecular electronics, biosensor could be an attractive new field of application for the OPE type molecular wires. [Copyright &y& Elsevier]

Based on the potential flow theory of water waves, the interaction mechanism between the free-surface and internal waves generated by a moving point source in the lower layer of a two-layer fluid was studied. By virtue of the method of Green's function, the properties of the divergence field at the free surface were obtained, which plays an important role in the SAR (Synthetic Aperture Radar) image. It is shown that the coupling interaction between the surface-wave mode and internal-wave mode must be taken into account for the cases of large density difference between two layers, the source approaching to the pynocline and the total Froude number Fr close to the critical number Fr2. The theoretical analysis is qualitatively consistent with the experimental results presented by Ma Hui-yang. [ABSTRACT FROM AUTHOR]

Unraveling the origin of Helmholtz capacitance is of paramount importance for understanding the interfacial structure and electrostatic potential distribution of electric double layers (EDL). In this work, we combined the methods of ab initio molecular dynamics and classical molecular dynamics and modeled electrified Cu(100)/electrolyte and graphene/electrolyte interfaces for comparison. It was proposed that the Helmholtz capacitance is composed of three parts connected in series: the usual solvent capacitance, water chemisorption induced capacitance, and Pauling repulsion caused gap capacitance. We found the Helmholtz capacitance of graphene is significantly lower than that of Cu(100), which was attributed to two intrinsic factors. One is that graphene has a wider gap layer at interface, and the other is that graphene is less active for water chemisorption. Finally, based on our findings, we provide suggestions for how to increase the EDL capacitance of graphene-based materials in future work, and we also suggest that the new understanding of the potential distribution across the Helmholtz layer may help explain some experimental phenomena of electrocatalysis. [ABSTRACT FROM AUTHOR]

The article presents a study which explores the environmental eustress (EE) improves postinfarction cardiac repair via enhancing cardiac macrophage survival. It mentions that findings of the study demonstrate that EE optimizes postinfarction cardiac repair and highlights the significance of EE as a previously unidentified strategy for impeding adverse ventricular remodeling.

Gyratory compaction has widely been used to evaluate the compactability of hot asphalt mixtures. Existing efforts on modeling of gyratory compaction have largely been devoted to sophisticated high-fidelity numerical simulations. This paper presents a one-dimensional nonlocal model for gyratory compaction. The model is anchored by the principle of mass conversation, in which the local densification rate is formulated as a function of the nonlocal packing fraction. The nonlocal model involves a material characteristic length scale, which is independent of the specimen size. The nonlocality gives rise to strong effects of the specimen height on the overall compaction curve as well as on the profile of the local packing fraction. A set of gyratory compaction experiments is performed on specimens of different heights. It is shown that the model is able to capture the measured size effect on the compaction curves. A parametric study is carried out to investigate the effects of nonlocality and model parameters on the predictions of compaction curve and profile of packing fraction. [ABSTRACT FROM AUTHOR]

The collapse of the World Trade Center towers was initiated by the impact of the upper falling part onto the underlying intact story. At the moment of impact, the velocity of the upper part must have decreased. The fact that no velocity decrease can be discerned in the videos of the early motion of the tower top has been recently exploited to claim that the collapse explanation generally accepted within the structural mechanics community was invalid. This claim is here shown to be groundless. Calculations show that the velocity drop is far too small to be perceptible in amateur video records and is much smaller than the inevitable error of such video records. [ABSTRACT FROM AUTHOR]

• Reduced order reaction-diffusion model allows efficient chemo-mechanical analysis. • Chemo-mechanical model predicts three different regimes of stress-life curve. • The simulation yields the crack growth kinetics of HDPE members in bleach solution. High density polyethylene (HDPE) is increasingly used in infrastructure applications with a design service lifetime of several decades. In many cases, the HDPE member is exposed to a corrosive environment, such as in pipes carrying potable water, where the dissolved bleach selectively attacks the loosely packed amorphous phase of the polymer. The failure mechanism of HDPE transitions from a ductile to a brittle mode as the corrosion level increases. This leads to subcritical crack propagation, which deteriorates the load capacity of the structure. In this study, we develop a coupled chemo-mechanical model to simulate stress corrosion cracking (SCC) in HDPE members exposed to a bleach solution. The mechanical response of the polymer is described by a constitutive model that separately considers the individual deformation and damage behaviors of the amorphous and the crystalline phases. The model accounts for the intermolecular deformation and homogeneous void growth in the crystalline and amorphous phases, along with the resistance of the entangled network and craze damage in the amorphous phase. The embrittlement due to corrosion is captured by relating the constitutive parameters of amorphous phase to the molecular weight of the polymer. The diffusion and chemical reaction of bleach are described by a reduced order kinetics model that links the extent of polymer oxidation to the reduction of the molecular weight. The material constitutive model and diffusion–reaction model are combined in a single finite element (FE) code to investigate the SCC behavior of double edge notched HDPE specimens. The simulation yields the stress-life curves and fracture kinetics under different environments. The predicted stress-life curve qualitatively matches the measured stress-life data of polymer pipes. It is shown that the stress-life curve exhibits different regimes corresponding to distinct failure mechanisms, as indicated by the stress and strain distributions in the specimen. [ABSTRACT FROM AUTHOR]

Owing to the random nature of heterogeneity, damage and fracture behavior of quasi-brittle materials exhibits a considerable degree of uncertainty. Computational modeling of stochastic fracture in quasi-brittle materials has become an indispensable tool for analysis and design of engineering structures. To this end, we present in this paper a computational framework to capture probabilistic fracture in heterogeneous quasi-brittle solids by combining the random field theory and the phase-field cohesive zone model (PF-CZM). The spatial variation of the material strength and fracture energy is represented by a cross-correlated bivariate random field generated by the Karhunen–Loève expansion. The recently proposed PF-CZM is employed to simulate the stochastic crack nucleation and propagation in quasi-brittle solids. The objectivity of the Monte-Carlo simulation is achieved by imposing a specific condition on the phase-field length scale parameter and the correlation length of the random field. In particular, upon this condition the width of the fracture process zone (FPZ) is considerably smaller than the correlation length of the random field such that the material inside the FPZ does not exhibit significant spatial variations of mechanical properties. As the fracture energy is intrinsically incorporated in the PF-CZM, it is unnecessary in this case to explicitly consider the FPZ width. The resulting probabilistic PF-CZM together is applied to the Monte-Carlo simulations of fracture in concrete structures of different geometries. It is shown that the stochastic simulation results are insensitive to both the phase-field length scale parameter and the finite element mesh discretization as in the previous deterministic analyses. Enhanced with the specific condition on the involved characteristic lengths, the PF-CZM provides a viable tool for stochastic simulations of damage and fracture in quasi-brittle structures. [ABSTRACT FROM AUTHOR]

The adsorption and electrooxidation of CO molecules at well‐defined Pt(hkl) single‐crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top‐ and bridge‐site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top‐site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre‐oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti‐poisoning and highly effective catalysts. [ABSTRACT FROM AUTHOR]

The adsorption and electrooxidation of CO molecules at well‐defined Pt(hkl) single‐crystal electrode surfaces is a key step towards addressing catalyst poisoning mechanisms in fuel cells. Herein, we employed in situ electrochemical shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) coupled with theoretical calculation to investigate CO electrooxidation on Pt(hkl) surfaces in acidic solution. We obtained the Raman signal of top‐ and bridge‐site adsorbed CO* molecules on Pt(111) and Pt(100). In contrast, on Pt(110) surfaces only top‐site adsorbed CO* was detected during the entire electrooxidation process. Direct spectroscopic evidence for OH* and COOH* species forming on Pt(100) and Pt(111) surfaces was afforded and confirmed subsequently via isotope substitution experiments and DFT calculations. In summary, the formation and adsorption of OH* and COOH* species plays a vital role in expediting the electrooxidation process, which relates with the pre‐oxidation peak of CO electrooxidation. This work deepens knowledge of the CO electrooxidation process and provides new perspectives for the design of anti‐poisoning and highly effective catalysts. [ABSTRACT FROM AUTHOR]

This corrigendum corrects a typographical error in the paper entitled “Simplified energy-based analysis of collapse risk of reinforced concrete buildings” by B. Xue and J.-L. Le (Structural Safety 63 (2016) 47–58). [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) fiber‐reinforced SiC matrix (SiC/SiC) composites have emerged as a new material candidate for fuel claddings in light water reactors. Recent studies showed that the load capacity of SiC/SiC materials exhibits a considerable statistical variation. Therefore, reliability analysis plays a critical role in design of SiC/SiC composite claddings. This paper presents a probabilistic model for the lifetime distribution of SiC/SiC composites. The model is anchored by a multiaxial stress‐based failure criterion and subcritical damage accumulation mechanism. Based on the kinetics of subcritical damage growth, the lifetime distribution of a laboratory test specimen for any given loading history can be calculated. A finite weakest‐link model is used to extrapolate the lifetime distribution of test specimens to full‐length claddings. It is shown that the damage accumulation mechanism has a strong influence on the lifetime distribution of the cladding. This finding highlights the importance of understanding the static fatigue behavior of SiC/SiC composites. The present analysis also demonstrates an intricate length effect on the failure probability of the cladding, which is expected to play a crucial role in design extrapolation. [ABSTRACT FROM AUTHOR]

Dietary usage of microencapsulated oils has been proved to promote growth and gut health in land animals, however, these beneficial effects have not been intensively investigated in aquatic animals. The present study hypothesized that dietary microencapsulated oils could alleviate negative effects caused by high-fat diet (HFD) in fish, thus we fed juvenile Nile tilapia with HFD (15% fat) by using normal or microencapsulated oils as lipid sources for 8 weeks. To compare the effects between different microencapsulated oils with different fatty acid composition, two oil mixtures (PL: 60% palm oil +40% linseed oil; FL: 60% fish oil +40% linseed oil) were used. After feeding trial, the growth, body composition, fatty acid composition, resistance to pathogenic bacteria challenge, activities of immune enzymes, expressions of inflammation genes, intestinal structure and microbiota were measured, respectively. The results indicated that microencapsulated oils didn’t affect fish growth, body composition, and muscle fatty acid composition, but improved the intestinal activities of lysozyme (LZM) and resistance against Aeromonas hydrophila . Further tests showed that microencapsulated oils not only improved the structure of intestine, but also increased the number of beneficial bacteria ( Bacillus and Paenibacillus ) and decreased the number of harmful bacteria ( Pseudoalteromonas and Roseovarius ) in the intestine. Those beneficial effects are more significant between normal PL oil and microencapsulated PL oil, but no significant difference in FL oil groups. Taken together, these results suggested that microencapsulated oil might enhance immune activities in the Nile tilapia fed with HFD by improving intestinal structure and microflora. Moreover, the beneficial effects of the microencapsulated oil are correlated to the oil composition. To the best of our knowledge, this is the first study illustrating the beneficial effects of dietary microencapsulated oil in the fish fed with HFD. [ABSTRACT FROM AUTHOR]

In this article, the authors present their views in response to a comment on their article related to the claims against the scientific basis for gravity-driven progressive collapse occurred in the towers of the World Trade Center (WTC) in New York City. As per them, the claims include violation of momentum conservation principles and sustained column heating. They state that structural mechanics without standard simplifying hypothesis made structural analysis feasible.

An abstract of the article "Regulation of Neurogenic Airway Inflammation via the Dorsal Vagal Complex in a Guinea Pig Model of Gastroesophageal Reflux" is presented.

Understanding cohesive fracture interacting with a stationary capillary fluid is essential for fracture mechanics based analysis and design of many quasibrittle structures in contact with fluids. In this study, an equivalent linear elastic fracture mechanics (LEFM) model is used to determine the equilibrium state for a cohesive crack partially filled with a capillary fluid. The model is shown to deliver predictions similar to the cohesive zone model (CZM) at a much lower computational cost. The equivalent LEFM model is applied to determine the instantaneous failure pressure of high-density polyethylene (HDPE) pipes as well as the wetting zone size for modeling the stress corrosion cracking of HDPE pipes. [ABSTRACT FROM AUTHOR]

Perforated cold-formed steel (PCFS) beams are increasingly used in constructional industry and become popular due to their advantages and economic benefit. Apart from the light weight, the openings in PCFS beams can also be used for services such as pipe utilities to release more building space. However, beams with web perforations may collapse as the result of web-distortional buckling or flange/web distortional buckling due to the web weakness caused by perforations. In this paper a study on the flange/web distortional buckling of PCFS beams is presented. An analytical solution to determine the critical stress of flange/web distortional buckling of PCFS beams is derived by using energy method. To demonstrate the analytical solution, finite element analysis is also carried out. The finite element analysis results show that the analytical solution provided can give good and reliable prediction for the flange/web distortional buckling of PCFS beams. [ABSTRACT FROM AUTHOR]

Morphometrics are fundamental for the analysis of size and shape in fossils, particularly because soft parts or DNA are rarely preserved and hard parts such as shells are commonly the only source of information. Geometric morphometrics, that is, landmark analysis, is well established for the description of shape but it exhibits a couple of shortcomings resulting from subjective choices during landmarking (number and position of landmarks) and from difficulties in resolving shape at the level of micro‐sculpture.With the aid of high‐resolution 3D scanning technology and analyses of fractal dimensions, we test whether such shortcomings of linear and landmark morphometrics can be overcome. As a model group, we selected a clade of modern viviparid gastropods from Lake Lugu, with shells that show a high degree of sculptural variation. Linear and landmark analyses were applied to the same shells in order to establish the fractal dimensions. The genetic diversity of the gastropod clade was assessed.The genetic results suggest that the gastropod clade represents a single species. The results of all morphometric methods applied are in line with the genetic results, which is that no specific morphotype could be delimited. Apart from this overall agreement, landmark and fractal dimension analyses do not correspond to each other but represent data sets with different information. Generally, the fractal dimension values quantify the roughness of the shell surface, the resolution of the 3D scans determining the level. In our approach, we captured the micro‐sculpture but not the first‐order sculptural elements, which explains that fractal dimension and landmark data are not in phase.We can show that analyzing fractal dimensions of gastropod shells opens a window to more detailed information that can be considered in evolutionary and ecological contexts. We propose that using low‐resolution 3D scans may successfully substitute landmark analyses because it overcomes the subjective landmarking. Analyses of 3D scans with higher resolution than used in this study will provide surface roughness information at the mineralogical level. We suggest that fractal dimension analyses of a combination of differently resolved 3D models will significantly improve the quality of shell morphometrics. [ABSTRACT FROM AUTHOR]

This paper presents the work carried out on a collaborative tripartite project between the USA, Republic of Ireland and Northern Ireland to create and investigate the design, development and testing of a new class of intermeshed steel connections (ISCs) that do not rely on field welding and minimise bolting, thus targeting the facilitation of fast disassembly of steel structures and material reuse. This research took advantage of fully automated, precise, advanced manufacturing cutting technologies (e.g. laser, waterjet and high-definition plasma cutting) to achieve a connection method in steel that previously was only possible in materials such as timber, with the potential to revolutionise the steel construction industry. The paper outlines the ongoing research work by the collaborative team, focusing on the design, fabrication, finite-element analysis (FEA) and scaled experimental testing of side ISCs for the flanges of open sections, which included the use of state-of-the-art digital image correlation technology for non-contact measurements. A simplified connection design procedure is presented based on yielding of the side plates. This design procedure is refined based on the results of experimental testing and FEA of the local axial behaviour of the flange connection, addressing stress concentrations in the flange, fabrication tolerances and material overstrength. [ABSTRACT FROM AUTHOR]

Abstract: We designed two cruciform-structured oligo(phenylenethynylene) (OPE) molecular wires for probing the intra- and inter-molecular exciton migration pathways, and constructed highly ordered molecular assembly using Langmuir–Blodgett (LB) technique. Minor structural variation turns out to influence significantly exciton migration routes. Though the molecular structures are similar, these two molecules exhibit distinct exciton migration behaviors. Intermolecular exciton migration is observed in unmodified molecular wire OPE1; while only intramolecular exciton migration is allowed in the side-chain modified molecular wire OPE2. This work presents a facile strategy for controlling exciton migration in solid state, and provides useful insights for designing active components for opto-electronic devices. [Copyright &y& Elsevier]

Abstract: In this work, the effects of various dendrimer shells on the intermolecular interactions of oligo(phenyleneethynylene)s (OPE) molecular wires in thin films have been studied. Electronic and fluorescence spectra showed that the dendrimer shells can effectively inhibit the aggregation of the molecular wires in both solutions and thin films. Tapping mode atomic force microscopy (TM-AFM) revealed that with the increase of dendrimer size, the film morphologies changed from fibrous to dendritic, indicating a strong shell-dependent molecular packing. This work demonstrated that such ‘core–shell’ molecular design strategy can be used to precisely tailor the molecular environment surrounding the molecular wires. [Copyright &y& Elsevier]

Abstract: In this work, a series of dendrimer functionalized ‘core-shell’ like oligo(phenyleneethynylene)s (OPEs) molecular wires have been reported. This new type of molecular wires could be well dissolved in common organic solvents, and form self-assembled monolayers (SAMs) on gold surfaces. Electrochemical investigation shows that the density of the SAMs depends on the size of the dendrimer ‘shell’. UV–vis absorption spectra and fluorescence emission spectra indicate that little aggregations occur in the solutions. Complication due to π–π interactions between OPEs decreases with the increase of the size of the dendrimer ‘shell’. [Copyright &y& Elsevier]

• Advanced cutting techniques could help eliminate welding or bolting in steel connections. • Abaqus can accurately simulate the global and local behavior of the intermeshed connection. • The intermeshed connection transfers loads through interlocking pieces. • The modified design procedure assures a practical margin of overstrength in the connection. • In the redesigned specimens, most of the damage occurs in the connecting parts as planned. The aim of the present study is to develop insights into the structural performance of a recently developed 'intermeshed' steel connection, which transfers loads mainly through direct contact rather than by welds or bolts. This investigation was conducted through a step-by-step state assessment of the intermeshed connection subjected to multiple scenarios of gravity loading and by use of a nonlinear finite element platform. Implementation of the intermeshed connection would cause a discontinuity in the beam, so this paper addresses concerns regarding the load-transfer mechanisms and failure modes for these connections. The finite element simulations were performed in Abaqus, which is capable of handling material and geometrical nonlinearity, as well as the contact between individual surfaces. In order to verify the accuracy of these simulations, the numerical results were compared with experimental data from four physical tests. Finally, some important factors of influence such as connection segments sizes, lateral constraint, support conditions, and failure modes were also investigated through numerical analysis. The results of finite element analysis on different prototypes of steel intermeshed connection showed that the specimens with this connection provided sufficient ductility and resistance to meet design requirements. [ABSTRACT FROM AUTHOR]

In order to improve delivery network efficiency and to solve consumer satisfaction problems, parcel locker location optimisation scheme is proposed based on the delivery demand under the e-commerce environment. In this paper, a bilevel programming (BLP) model is established to identify the optimal location for parcel lockers by considering benefits of consumers and logistics planning departments. The upper-level model is to determine the optimal location by minimising the planners' cost, and the lower one gives an equilibrium demand distribution by minimising the consumers' pick-up cost. On the special form of constraints, a bilevel genetic algorithm is proposed based on GIS data and a genetic algorithm. Finally, a numerical example is employed to demonstrate the application of the method, which indicates that the model can solve the problem of parcel locker location. [ABSTRACT FROM AUTHOR]

Gastric cancer (GC) is one of the most malignant tumors with high incidence and mortality worldwide, and the multidrug resistance (MDR) often results in chemotherapy failure in GC. DJ-1 has been well indicated to be associated with drug resistance in multiple cancers. However, the role of DJ-1 in the MDR of gastric cancer cells and its possible mechanism remain to be elucidated. Therefore, the current study was investigated whether DJ-1 expression is differential in parental gastric cancer cell SGC7901 and vincristine (VCR)-induced gastric cancer MDR cell SGC7901/VCR, and whether DJ-1 plays a significant role in development of MDR in gastric cancer. The results showed that DJ-1 expression in SGC7901/VCR cells was significantly higher than its sensitive parental SGC7901 cells. Furthermore, DJ-1 overexpressed gastric cancer cell line SGC7901/LV-DJ-1 led to the increase of cell survival rate, the IC 50 of chemotherapeutic drugs and number of cell clones as well as decrease of cell cycle G0/G1 phase ratio compared with its parental cells under the treatment of VCR, adriamycin (ADR), 5-Fluorouracil (5-FU) and cisplatin (DDP). However, the DJ-1 knockdown stable cell line SGC7901/VCR/shDJ-1 reversed the above mentioned series of MDR. Moreover, it was found that upregulation of DJ-1 protein expression promoted the pumping rate of GC cells to ADR and reduced the apoptotic index of GC cells treated with chemotherapeutic drugs by upregulating P-gp and Bcl-2. Similarly, knocking down DJ-1, P-gp or Bcl-2 displayed a converse effect. In conclusion, the current study demonstrated that DJ-1 overexpression confers the MDR phenotype to SGC7901 cells and this process is related to DJ-1 promoting active efflux of drugs and enhancing the anti-apoptotic ability of MDR GC cells by upregulating P-gp and Bcl-2. • DJ-1 expression in SGC7901/VCR cells was significantly higher than SGC7901 cells. • SGC7901/VCR and SGC7901/LV-DJ-1 cells led to a series of MDR phenomenon. • DJ-1 overexpression promoted the adriamycin pumping rate of SGC7901 cells. • DJ-1 overexpression reduced the apoptotic index of SGC7901 cells. • DJ-1 overexpression upregulated P-gp and Bcl-2 expression of SGC7901 cells. [ABSTRACT FROM AUTHOR]

• Develop micro-kinetic models of electrocatalytic PCET reactions. • Propose theory for optimizing catalysts and reaction conditions for PCET. • Validate the theory by experiment on model catalysts for CO 2 reduction. Understanding the effects of pH and potential on proton-coupled electron transfer (PCET) steps and optimizing the reaction activity are of key importance for efficient applications of energy conversion processes. In this work, we develop a simple theory to optimize the electrocatalytic PCET reactions, in which electron and proton transfer take place in sequential steps, by combining an energy level diagram and micro-kinetic theories. Our theory suggests matching conditions on PCET energetics (redox potentials and p K a 's) and reaction environments (potential and pH) in order to achieve maximum kinetics. Consequently, a descriptor representing deviation from the ideal condition, i.e. |Δ U re |+ 2.30 k B T/ e |Δp K a |, is proposed to measure catalyst (in)activity. To test our theory, we further investigate CO 2 electroreduction on a model catalyst both computationally and experimentally, and show that the activity for CO 2 reduction on FePc (Iron Phthalocyanine) molecule is higher than H 2 evolution at near neutral condition. Our theory not only identifies the individual contribution of electron and proton transfer to overpotentials but also provides simple guidelines for optimizing the experimental conditions and searching for efficient catalysts. [ABSTRACT FROM AUTHOR]

Galactomannan-based biogums were derived from fenugreek, guar, tara, and carob and consisted of mannose and galactose with different ratios, as well as the implementation of high-value utilization was very significant for sustainable development. In this work, renewable and low-cost galactomannan-based biogums were designed and developed as functional coatings protected on the Zn metal anodes. The molecule structure of galactomannan-based biogums were explored on the effect of anticorrosion ability and uniform deposition behavior through the introduction of fenugreek gum, guar gum, tara gum, and carob gum with different ratios of mannose to galactose as 1.2:1, 2:1, 3:1, and 4:1. The existence of biogum protective layers can reduce the contact area between Zn anodes and aqueous electrolyte to enhance the anticorrosion ability of Zn anodes. Rich oxygen-containing groups in galactomannan-based biogums can coordinate with Zn2+ and Zn atoms to form ion conductivity gel layer and adsorb closely on the surface of Zn metal, which can induce uniform deposition of Zn2+ to avoid dendrite growth. Zn electrodes protected by biogums can cycle impressively for 1980 h with 2 mA cm−2 and 2 mAh cm−2. This work can provide a novel strategy to enhance Zn metal anodes' electrochemical performance, as well as implement the high-value application of biomass-based biogums as functional coatings. [Display omitted] [ABSTRACT FROM AUTHOR]

The strong effect of the electrolyte cation on the activity and selectivity of the CO 2 reduction reaction (CO 2 RR) can only be understood and controlled if the cation's effect on the interfacial potential distribution is known. Using CO (the key intermediate in the CO 2 RR) adsorbed on Pt as a probe molecule, and combining IR spectroscopy, capacitance measurements and ab initio molecular dynamics, we show that the cation size determines the location of the outer Helmholtz plane, whereby smaller cations increase not just the polarisation but, most importantly, the polarizability of adsorbed CO (CO ad) and the accumulation of electronic density on the oxygen atom of CO ad. This strongly affects its adsorption energy, the degree of hydrogen bonding of interfacial water to CO ad and the degree of polarisation of water molecules in the cation's solvation shell, all of which can deeply affect the subsequent steps of the CO 2 RR. Image 1 [ABSTRACT FROM AUTHOR]

• A morphology based constitutive model for ductile and brittle failures of HDPE is developed. • The model captures the transition from ductile to brittle failure as corrosion level increases. • The model is calibrated and validated by tensile tests on HDPE exposed to a chlorinated environment. High density polyethylene (HDPE) has been widely used in pipe systems for water delivery. Over the course of service, chlorine diffuses into HDPE and causes changes in the material morphology. This process has a significant influence on the deformation and failure mechanisms of HDPE. It has been demonstrated that the failure of HDPE exhibits a ductile-to-brittle transition as the corrosion level increases. Capturing this transition in the material failure mode is essential for predicting the long-term behavior of HDPE structures exposed to a chlorinated environment. In this study, a morphology based constitutive model of HDPE is developed. The model takes into account several essential deformation and failure mechanisms, which include viscoplastic deformation due to intermolecular resistance and homogeneous void growth in the crystalline and amorphous phases, as well as entangled network resistance and craze damage in the amorphous phase. The constitutive parameters are explicitly related to the molecular weight, which varies with the corrosion level. The proposed model is calibrated using uniaxial tensile tests on HDPE samples performed at different deformation rates, crystallinities, and corrosion levels. The model is then used to simulate the mechanical behavior of double-edge notched tension specimens exposed to different corrosion levels. It is shown that the model is capable of capturing the rate-dependent elasto-viscoplastic behavior of HDPE under the unexposed condition as well as the brittle failure behavior after exposure to a highly corrosive environment. [ABSTRACT FROM AUTHOR]

Resveratrol, a multi-functional phytoalexin, has been well indicated to exert cardioprotective effects by weakening ischemia/reperfusion (I/R) injury, and cell apoptosis is a vital way in I/R injury. SIRT1-p53 pathway has strong significance in regulating cell apoptosis. DJ-1 can directly bind to SIRT1 and stimulate the activity of SIRT1-p53. Therefore, the current study was determined whether Resveratrol attenuates hypoxia/reoxygenation (H/R)-induced cell apoptosis, and whether DJ-1-mediated SIRT1 activation involves in the cardioprotective effects of Resveratrol. The results showed that remarkable decrease in the number of apoptotic cells along with reduction of lactate dehydrogenase release and restoration of cell viability emerged when Resveratrol was applied in the H9c2 cells exposed to H/R. Moreover, Resveratrol increased DJ-1 expression and promoted the interaction of DJ-1 with SIRT1, which further contributed to subsequent restoration of SIRT1 activity and decrease of acetylation level of p53. However, above cardioprotective effects of Resveratrol were abrogated by DJ-1 siRNA and SIRT1 specific inhibitor Sirtinol. In conclusion, the current study demonstrated that Resveratrol suppressed H/R-induced cell apoptosis, which may be conducted by up-regulating DJ-1, and later activating SIRT1 activity and subsequently inhibiting p53 acetylation level in the H9c2 cells. • Resveratrol increased the DJ-1 expression and promoted the interaction of DJ-1 with SIRT1 in the H9c2 cells exposed to H/R. • Resveratrol restored SIRT1 activity in a way of DJ-1-dependence in the H9c2 cells exposed to H/R. • Resveratrol decreased H/R-induced p53 acetylation level by DJ-1-mediated SIRT1 activation in the H9c2 cells. • Resveratrol attenuated H/R-induced cell apoptosis by DJ-1-mediated SIRT1 activation in the H9c2 cells. [ABSTRACT FROM AUTHOR]

• The energetic and statistical size effects in quasibrittle structures are critically analyzed. • Size Effect Law (SEL) is in excellent agreement with a large bulk of experimental data. • SEL agrees asymptotically with Cohesive Fracture Mechanics. • The main errors, weaknesses and inconsistencies of the Boundary Effect Model (BEM) are identified. • The BEM features incorrect large and small-size asymptotic size effects. • The BEM conflicts with broad-range comprehensive test data and with the cohesive crack model. • The BEM predicts an incorrect aggregate-size dependence of strength. • The BEM features an illogical dependence on the ligament stress profile. • The BEM cannot to capture the statistical part of size effect at large sizes. • The BEM does not capture the difference between type I and II size effects. For several decades it has been clear that the size effect on structural strength, exhibiting a major non-statistical component, is a quintessential property of all quasibrittle materials. However, progress in design codes and practice for these materials has been retarded by protracted controversies about the proper mathematical form and justification of the size effect law (SEL). A fresh exception is the American Concrete Institute which, in 2019, becomes the first concrete code-making society to adopt the SEL based on quasibrittle fracture mechanics. This article begins by discussing several long-running controversies that have recently abated, and then focuses critically on the so-called Boundary Effect Model (BEM), promoted for concrete relentlessly for two decades, in ever-changing versions, by Xiaozhi Hu et al. The BEM is here compared to the quasibrittle SEL based on asymptotic matching. Its errors, weaknesses and inconsistencies are identified—including incorrect large- and small-size asymptotic size effects, conflicts with broad-range comprehensive test data and with the cohesive crack model, incorrect aggregate-size dependence of strength, illogical dependence on ligament stress profile, inability to capture the statistical part of size effect at large sizes, simplistic effect of boundary proximity, and lack of distinction between Type 1 and 2 size effects. In contrast to the SEL, the BEM is not applicable to mixed and shear fracture modes and to complex geometries of engineering structures, and is not transplantable from concrete to other quasibrittle materials. The purpose of this critique is to help crystallize a consensus about the proper size effect formulation, not only for concrete structures but also, and mainly, for other quasibrittle materials and structures, including airframes made of fiber composites, ceramic components and micrometer-scale devices, and for failure assessments of sea ice, rock, stiff soils, bone, and various bio- or bio-mimetic materials, for all of which the non-statistical size effect is yet to be widely accepted in practice. [ABSTRACT FROM AUTHOR]

Aims/Introduction A meta-analysis was carried out to evaluate the efficacy of yoga in adults with type 2 diabetes mellitus. Materials and Methods The PubMed, EMBASE and Cochrane databases were searched to obtain eligible randomized controlled trials. The primary outcome was fasting blood glucose, and the secondary outcomes included glycosylated hemoglobin A1c, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglyceride and postprandial blood glucose. Weighted mean differences and 95% confidence intervals ( CIs) were calculated. The I2 statistic represented heterogeneity. Results A total of 12 randomized controlled trials with a total of 864 patients met the inclusion criteria. The pooled weighted mean differences were −23.72 mg/dL (95% CI −37.78 to −9.65; P = 0.001; I2 = 82%) for fasting blood glucose and −0.47% (95% CI −0.87 to −0.07; P = 0.02; I2 = 82%) for hemoglobin A1c. The weighted mean differences were −17.38 mg/dL (95% CI −27.88 to −6.89; P = 0.001; I2 = 0%) for postprandial blood glucose, −18.50 mg/dL (95% CI −29.88 to −7.11; P = 0.001; I2 = 75%) for total cholesterol, 4.30 mg/dL (95% CI 3.25 to 5.36; P < 0.00001; I2 = 10%) for high-density lipoprotein cholesterol, −12.95 mg/dL (95% CI −18.84 to −7.06; P < 0.0001; I2 = 37%) for low-density lipoprotein cholesterol and −12.57 mg/dL (95% CI −29.91 to 4.76; P = 0.16; I2 = 48%) for triglycerides. Conclusions The available evidence suggests that yoga benefits adult patients with type 2 diabetes mellitus. However, considering the limited methodology and the potential heterogeneity, further studies are necessary to support our findings and investigate the long-term effects of yoga in type 2 diabetes mellitus patients. [ABSTRACT FROM AUTHOR]

As antidepressants commonly used in the clinic have proved to be problematic, it is urgent to gain an updated understanding of the pathogenesis of depression and find potential therapeutic targets. Since both functional brain imaging studies and autopsy reports indicated that there is indeed a loss of synapses in depressed patients, it is necessary to explore the mechanism of this process. We firstly investigated the effect of chronic social defeat stress (CSDS), a mouse model of depression, on behaviors, synapses, microglia, and microglial phagocytosis of synapses in mice. Then, as it is unclear whether microglial phagocytosis leads to synaptic loss, or synaptic loss induces the microglial clearance in CSDS mice, we used minocycline, a microglial activation inhibitor, to inhibit the microglial phagocytosis of synapses and study its effect on synapses and behaviors in CSDS mice. Our results showed that the expression levels of PSD-95 in the hippocampal dentate gyrus (DG) of CSDS mice were significantly reduced, while the microglia were significantly activated and the Iba1+CD68+ cell (phagocytic microglia) density was increased. We co-labeled the synaptic protein PSD-95 with the microglia marker Iba1 and found that the microglia in the hippocampal DG of CSDS mice contained significantly more PSD-95 engulfed puncta, which revealed that microglia in CSDS mice abnormally phagocytized synapses. Moreover, our results indicated that minocycline treatment dampened microglial activation, decreased the phagocytic microglia density, reduced abnormal microglial phagocytosis of synapses, reversed synaptic loss, and alleviated behavioral impairment in CSDS mice. Under depressive pathological conditions, the activated microglia may abnormally engulf neuronal synapses causing synaptic loss and behavioral impairments. Thus, microglial phagocytosis may be a novel therapeutic target for the treatment of depression. • The phagocytic microglia density was increased in hippocampal DG in CSDS mice. • The microglia in the hippocampal DG of CSDS mice abnormally phagocytized synapses. • Minocycline treatment reduced microglial phagocytosis of synapses in CSDS mice. • Microglial phagocytosis may be a novel target for the treatment of depression. [ABSTRACT FROM AUTHOR]