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Metallic nanolaminated materials possess excellent mechanical properties due to their unique modulation structures and interfacial properties. However, how microdefects affect their mechanical properties is still uncertain. To evaluate the influences of void location (in the crystalline layer and the Ti/Ni interface), void diameter (d) and thickness of the intermediate layer (h) on overall tensile behaviors, various types of defective Ti/Ni nanolaminates with pre-existing void are established by the molecular dynamics method in this work. The results indicate that the strength and plastic deformation mechanisms are strongly dependent on those determinants. Yield stresses of Ti/Ni nanolaminates decrease distinctly with increasing void diameter, while peak stresses with a void in the crystalline layer decrease with increasing d/h. Different void locations lead eventually to disparate initial plastic deformation carriers around the void, and various evolutions in the microstructure of the defective Ti/Ni nanolaminates. The Ti/Ni interface plays a significant role in the tensile process. The semi-coherent interface impedes new grains and lattice dislocations from passing across the interface, while the incoherent interface facilitates dislocations generating and sliding along the interface, and absorbs the dislocations moving to the interface. The results also indicate that the strain rate significantly affects the evolution of the microstructure and the tensile properties of defective Ti/Ni nanolaminates.

The present work investigated the effects of thermal cycles in air on the tensile properties of a two-dimensional carbon fibre reinforced silicon carbide composite (2D C/SiC) prepared by chemical vapour infiltration at different heating rates. The composite was exposed to different cycles of thermal shock between 20 °C and 1300 °C in air. The damage mechanisms were investigated by AE online monitoring and fractured morphology offline analysis. The tensile strength of 2D-C/SiC decreases with increasing thermal cycles. However, the modulus only decrease within 40 cycles. Due to oxidation, with the decrease in heating rate, the residual properties of the material decrease more obviously. Meanwhile, the results of AE online monitoring and fracture analysis show that the matrix damage is more serious at higher heating rate and that more delamination occours in tensile fractures. The above results indicate that for the thermal shock of 2D C/SiC composites in air, oxidative damage plays a key role in the residual properties.

Background N6-methyladenosine (m6A) related long noncoding RNAs (lncRNAs) may have prognostic value in bladder cancer for their key role in tumorigenesis and innate immunity. Methods Bladder cancer transcriptome data and the corresponding clinical data were acquired from the Cancer Genome Atlas (TCGA) database. The m6A-immune-related lncRNAs were identified using univariate Cox regression analysis and Pearson correlation analysis. A risk model was established using least absolute shrinkage and selection operator (LASSO) Cox regression analyses, and analyzed using nomogram, time-dependent receiver operating characteristics (ROC) and Kaplan–Meier survival analysis. The differences in infiltration scores, clinical features, and sensitivity to Talazoparib of various immune cells between low- and high-risk groups were investigated. Results Totally 618 m6A-immune-related lncRNAs and 490 immune-related lncRNAs were identified from TCGA, and 47 lncRNAs of their intersection demonstrated prognostic values. A risk model with 11 lncRNAs was established by Lasso Cox regression, and can predict the prognosis of bladder cancer patients as demonstrated by time-dependent ROC and Kaplan–Meier analysis. Significant correlations were determined between risk score and tumor malignancy or immune cell infiltration. Meanwhile, significant differences were observed in tumor mutation burden and stemness-score between the low-risk group and high-risk group. Moreover, high-risk group patients were more responsive to Talazoparib. Conclusions An m6A-immune-related lncRNA risk model was established in this study, which can be applied to predict prognosis, immune landscape and chemotherapeutic response in bladder cancer.

Background: Increasing numbers of confirmed cases and deaths due to 2019-coronavirus infected disease (COVID-19) have occurred in Wuhan, China since December 20

In this study, AZ31 magnesium alloy plates with fine grained microstructure were processed by cold dynamic extrusion followed by low temperature annealing. The corresponding microstructure evolution and mechanical properties were systematically investigated, with a great emphasis on the effect of high {10−12} extension twin density. Profuse {10–12} extension twin and nanograined structure was generated in various regions after 20% cold dynamic extrusion. Thus, pre-twinning greatly improved the strength and ductility in magnesium alloy. In addition, the introduction of high twin density can be an effective way to improve mechanical properties of magnesium alloy via twin-dislocation interaction during plastic deformation. With mechanical behavior properly described, high twin density increases the uniformity of localized dislocation plasticity, thereby improving the strain hardening property. Also, we conclude that high strain rate in cold dynamic extrusion can be considered as an effective method for preparation of pre-twinning magnesium alloy, which exhibits good mechanical properties.

The mechanical behaviour and microstructure evolution of twinning-induced plasticity (TWIP) steel subjected to tensile tests at high strain rate and low temperature were investigated. Under extreme conditions (3 × 103 s−1 and liquid nitrogen temperature), the TWIP steel exhibits high strain hardening capability and high strength, which are intimately related to deformation twinning. Here we investigate the plasticity and failure processes of a TWIP steel under extreme conditions, such as shock and/or cryogenic loading, and identify that deformation twinning no longer serves the fine plasticity. Obvious ductility loss has been found in TWIP steel even with strong strain hardening capability, which always leads to large uniform tensile ductility against local necking. In this study, the microstructure observations suggest that both of the second twin systems and nanotwin structures are highly active under extreme conditions. Twin-twin and dislocation-twin interactions accelerate the crack nucleation at and propagation along the twin boundaries. The conversion from twinning-induced plasticity to twinning-assisted cracking is controlled by twin structure and its spatio-temporal evolution, which are most susceptible to strain rate and temperature. These results provide an underlying micromechanism that controls the plasticity and failure in TWIP materials under extreme conditions and contributes to the understanding of twin structure-related processes to a broad community.

Hopkinson bar has already worked to measure mechanical properties of materials under high strain rates, but it fails to conduct intermediate strain rates loading with considerable deformation. Thereby, a methodology is proposed for achieving enough large strains under intermediate strain rates. The experimental system based on it is then constructed: a striker bar with same length as incident bar is selected to generate continuous stress wave loading, and a long polymethylmethacrylate bar is preferred as the transmitted bar to guide and record transmitted signals. Thus, loading stress wave is achievable with a nearly constant amplitude and an infinite loading duration. The involved data interpretations are deduced, and verified both theoretically and experimentally. Its measurement capacity is confirmed by loading a thermoplastic polyurethane, and maximum strains up to 12% and 65% under strain rates of 40/s and 270/s, respectively. Finally, the involved influences and factor sensitivities are analyzed for enough experimental accuracy and extensive measurements.

This paper is focused on the determination of dynamic elastic modulus of polymer materials under high strain rate loading using the split Hopkinson pressure bar (SHPB) technique. Experiments conducted on the epoxy specimen by the traditional SHPB and the proposed vertical SHPB equipment demonstrates that the vertical SHPB can give more accurate measurements. The related factors, namely, the effect of stress inequilibrium in specimen, indentation in bars due to specimen and the tilt between specimen and bars, are extensively studied. It is concluded through theoretical analysis and numerical calculations that the influence of stress inequilibrium becomes negligible after two characteristic times. The numerical study on the indentation effect shows that the bar to specimen specific elastic modulus ratio and specific diameter ratio are critical to the level of influence on indentation. However, polymers with low elastic modulus values can still be accurately measured regardless of the indentation displayed. The numerical investigation on tilt effect indicates that the imperfect contact condition severely affects the accuracy of measured elastic modulus. This issue can be rectified by the newly proposed vertical SHPB. It can improve the contact conditions between bars and specimen significantly and offer acceptable accurate measurements for the dynamic elastic modulus of polymeric materials.

Summary The safety and efficacy of anti-diabetic drugs are critical for maximizing the benefical impacts of well-controlled blood glucose on the prognosis of individuals with COVID-19 and pre-existing type 2 diabetes (T2D). Metformin is the most commonly prescribed first-line medication for T2D, but its impact on the outcomes of individuals with COVID-19 and T2D remains to be clarified. Our current retrospective study in a cohort of 1,213 hospitalized individuals with COVID-19 and pre-existing T2D indicated that metformin use was significantly associated with a higher incidence of acidosis, particularly in cases with severe COVID-19, but not with 28-day COVID-19-related mortality. Furthermore, metformin use was significantly associated with reduced heart failure and inflammation. Our findings provide clinical evidence in support of continuing metformin treatment in individuals with COVID-19 and pre-existing T2D, but acidosis and kidney function should be carefully monitored in individuals with severe COVID-19., Graphical Abstract, Highlight ● A retrospective study of 1,213 patients on metformin with COVID-19 was performed ● Metformin was associated with increased incidence of acidosis in such patients ● Metformin was not associated with increased 28-day all-cause mortality in the patients ● Metformin was significantly associated with reduced heart failure and inflammation, In a cohort of 1,213 hospitalized patients with COVID-19 and pre-existing type 2 diabetes, Cheng et al. show that metformin use is significantly associated with higher incidence of acidosis, particularly in cases with severe COVID-19, but not with 28-day all-cause mortality. They also found that metformin use is significantly associated with reduced heart failure and inflammation.

Membrane association of estrogen receptors (ER) depends on cysteine palmitoylation and two leucines in the ligand binding domain (LBD), conserved in most steroid receptors. The role of this region, corresponding to helix 8 of the glucocorticoid receptor (GR) LBD, on membrane association of GR was studied in 4B cells, expressing endogenous GR, and Cos-7 cells transfected EGFP-GR constructs. 4B cells preloaded with radiolabeled palmitic acid showed no radioactivity incorporation into immunoprecipitated GR. Moreover, mutation C683A (corresponding to ER palmitoylation site) did not affect corticosterone-induced membrane association of GR. Mutations L687-690A, L682A, E680G and K685G, prevented membrane and also nuclear localization through reduced ligand binding. L687-690A mutation decreased association of GR with heat shock protein 90 and transcriptional activity, without overt effects on receptor protein stability. The data demonstrate that palmitoylation does not mediate membrane association of GR, but that the region 680-690 (helix 8), is critical for ligand binding and receptor function.

Vibration tests were carried out on three types of stiffened aluminum plates with fully clamped boundaries under random base excitation. During the test, the response of the specimens was monitored using strain gauges. Based on the strain history, the accumulation of fatigue damage of the stiffened plates was estimated by means of the rainflow cycle counting technique and the Miner linear damage accumulation model in the time domain. Utilizing the change of natural frequencies, a nonlinear model was fitted for predicting the fatigue damage of plate and then the foregone failure criterion of 5% reduction in natural frequency is improved. The influence of section and spacing of the stiffeners on the vibration fatigue behavior of the aluminum plate was investigated. The results show that the fatigue life of aluminum plate increases with adding either T or L section riveted stiffeners. With the same cross-sectional area of stiffener, the T section stiffened plate shows longer fatigue life than L section stiffened plate. Meanwhile, the vibration fatigue life also shows great sensitivity to the spacing between the stiffeners.

In this work, molecular dynamics simulation and linear elastic fracture mechanics were employed to analyze the crack-tip behavior of a Mode I crack in nanocrystalline titanium. The effects of crystalline orientation, twin boundary and stacking fault on crack propagation were taken into account. Simulation results demonstrate that the crack-tip behavior and thus the crack propagation mode strongly depend on crystalline orientations and plane defects. Cracks lying on the hexagonal close-packed basal plane, the prismatic plane, or along a stacking fault plane defect propagate in a brittle manner, without involving proper dislocation emissions and twin nucleations in the crack-tip vicinity. In contrast, cracks show a ductile propagation behavior when aligned along the pyramidal plane, the { 10 1 ¯ 2 } plane, or the { 10 1 ¯ 2 } 〈 1 ¯ 011 〉 twin boundary. For these cases, local crack-tip plasticity and crack-tip reconstructions are found to play significant roles. The impact of strain rate on the crack-tip behavior of a basal crack was also investigated in detail. Five strain rates varied between 109 s − 1 and 1010 s − 1 were considered. With increased strain rates, a brittle-to-ductile transition was clearly observed for crack propagation. The desired transition can be attributed to the high stress and energy concentrations near the crack-tip under elevated strain rates, leading to the successive emission and propagation of partial dislocations. To verify and validate the simulation results, a theoretical analysis on the competition between brittle and ductile crack propagations was also implemented. The theoretical predictions based on the linear elastic fracture mechanics were found to reasonably agree with the simulation results. The observations and conclusions deduced from the combined modeling and theoretical study are helpful to the better understanding of fracture mechanics in nanocrystalline titanium.

Ballistic impact tests on composite laminated plates were carried out with a preloading device to investigate the impact responses at nominal velocities of 50 m/s and 70 m/s. Not only the center locations but also the near-edge regions of the laminated plates were impacted. Furthermore, finite element models were developed using three-dimensional solid elements and cohesive elements, and a user subroutine VUMAT of Ladeveze failure criterion was used in support of simulations in ABAQUS Explicit, providing detailed insights into the characteristics of delamination and target response. Results showed that there was a significant promotion of delamination resistance in the center location when applying appropriate preloads, but some weakening parts were also generated over large areas at the same time. A competition mechanism between the increased bending stiffness induced enhancement effect and the interlaminar stresses induced weakening effect was proposed to explain the influence of the biaxial in-plane tensile preloads on the delamination resistance of laminated plate. The work in this study may provide guidance for the impact resistance design of composite aircraft wing skin.

The corrosion inhibitive efficiency of diverse 1,2,3-triazolyl benzyl glucoside-, galactoside- and mannoside-serine/threonine conjugates readily synthesized via Cu I -catalyzed azide–alkyne cycloaddition reaction (Cue-AAC) for mild steel in HCl was examined via electrochemical impedance spectroscopy. The results indicate that these compounds are potent corrosion inhibitors even in highly concentrated HCl solutions. The potential mechanism of three inhibitors was characterized in detail via polarization and isotherm calculations. This study implies that benzyl glycoside-amino acid hybrids effectively constructed via the Cue-AAC between the highly biocompatible sugars and amino acids may represent a new class of promising and potentially green corrosion inhibitors.

Triazolyl glycolipid derivatives constructed via CuI-catalyzed azide-alkyne 1,3-dipolar cycloaddition reaction (Cue-AAC) represent a new range of carbohydrate-based scaffolds for use in many fields of the chemical research. Here the surface adsorptive ability of series of our previously prepared C1- or C6-triazole linked gluco- and galactolipid derivatives for mild steel in 1 M HCl was studied via electrochemical impedance spectroscopy (EIS). Results indicated that these monosaccharide–fatty acid conjugates are weak inhibitors against HCl corrosion for mild steel. Moreover, some newly synthesized triazolyl disaccharide (maltose)–fatty alcohol conjugates failed to display enhanced activity, meaning that the structural enlargement of the sugar moiety does not favor the iron surface adsorption. However, a bis-triazolyl glycolipid derivative, which was realized by introducing a benzenesulfonamide group via Cue-AAC to the C6-position of a C1-triazolyl glucolipid analog, eventually showed significantly improved adsorptive potency compared to that of its former counterparts. The corrosion inhibitive modality of this compound for mild steel in HCl was subsequently studied via potentiodynamic polarization and thermodynamic calculations.

Triazolyl bis-amino acid derivatives readily synthesized via click chemistry were identified as novel potent corrosion inhibitors for mild steel in HCl. The inhibitive characteristic of compound 4 was studied in detail via gravimetric measurement, electrochemical impedance spectroscopy, potentiodynamic polarization and scanning electron microscopy. In addition, a quantum chemical study suggests that the triazole ring involved in these inhibitors is structurally essential for the protection of metal surface.

Quasi-static and dynamic compression tests on ultra-fine grained (UFG) copper (Cu 99.9) were performed at temperatures ranging from 77 to 573 K and strain rates ranging from 10−3 to 5 × 103 1/s using an electronic universal testing machine and the split Hopkinson pressure bar system, respectively. We focused on the strain rate sensitivity and its dependence on experimental temperatures. The results show that UFG-Cu has enhanced strain rate sensitivity that is apparently temperature dependent. The activation volume of UFG-Cu is estimated to be on the order of ∼10b3 at current experimental temperature and strain rate range. The plastic deformation mechanism is suggested to be dislocation–grain boundary interactions.

Commercial cathode material (LiCoO2) was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The performance including cycling stability, diffusion coefficient under different voltage, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor (Sr0.5La0.05Li0.35 Ti0.5Ta0.5O3) and as a protecting shell to prevent LiCoO2 particles from being attacked by the acidic electrolyte.

The reaction of N 2 with lithium at electrode in lithium ion batteries was reported in this paper. At room temperature, N 2 can react with lithium, mainly at anode, to form Li 3 N in an electrochemical system very easily during charge–discharge cycles. Li 3 N has been characterized by XPS. Experimental results also revealed that the higher of the current density and higher of the temperature resulted in quicker of the nitrogen-fixation reaction. Moreover, the reaction of nitrogen with Li was faster at the TiO 2 -coated cathode than at the uncoated cathode. The reaction can be brought about almost completely in the lithium ion batteries at room temperature. This could be a new method for preparation of Li 3 N at room temperature.

In this paper, the deformation distribution of billets after multi-passes by using equal channel angular pressing (ECAP) routes is investigated by 3D finite element models. The simulation results show that the deformation distribution is more homogenous after two passes by using pressing route C. But if the deformation character of different routes was considered, it may be deduced that route BC is the most effective for deformation homogeneity after multi-pressing as long as the total pressing passes are times of four. The above deduction is ultimately proved by the simulation results of four passes of ECAP process. It means that this route is the most favorable for achieving ultra-fine grained material with more homogenous microstructure.