改性石墨烯对硅橡胶复合材料的增强及性能的影响

利用化学还原性石墨烯(rGO)和3-氨基丙基三乙氧基硅烷改性石墨烯(FG)增强硅橡胶(VMQ)基体,比较了2种石墨烯对硅橡胶复合材料表面硬度、力学性能、压缩形变及压缩回复性能的影响。结果表明,与硅橡胶基体有较好相容性和相互作用的FG使基体强度提高了约6倍,rGO使基体强度提高了约2倍。FG的加入有助于增强复合材料抵抗外部压力的能力,VMQ/FG复合材料的压缩强度(1.40 MPa)分别是纯样品(0.79 MPa)和VMQ/rGO复合材料(1.16 MPa)的177%和120%,VMQ/FG复合材料的拉伸强度和断裂伸长率均高于VMQ/rGO复合材料。VMQ/FG压缩形变与压缩回复性能较好,压缩后可快速恢复(小于0.5 h),永久压缩形变仅为1.5%。

Protective effect of oxysophoridine on cerebral ischemia/reperfusion injury in mice

Oxysophoridine, a new alkaloid extracted from Sophora alopecuroides L., has been shown to have a protective effect against ischemic brain damage. In this study, a focal cerebral ischemia/reperfusion injury model was established using middle cerebral artery occlusion in mice. Both 62.5, 125, and 250 mg/kg oxysophoridine, via intraperitoneal injection, and 6 mg/kg nimodipine, via intragastric administration, were administered daily for 7 days before modeling. After 24 hours of reperfusion, mice were tested for neurological deficit, cerebral infarct size was assessed and brain tissue was collected. Results showed that oxysophoridine at 125, 250 mg/kg and 6 mg/kg nimodipine could reduce neurological deficit scores, cerebral infarct size and brain water content in mice. These results provided evidence that oxysophoridine plays a protective role in cerebral ischemia/reperfusion injury. In addition, oxysophoridine at 62.5, 125, and 250 mg/kg and 6 mg/kg nimodipine increased adenosine-triphosphate content, and decreased malondialdehyde and nitric oxide content. These compounds enhanced the activities of glutathione-peroxidase, superoxide dismutase, catalase, and lactate dehydrogenase, and decreased the activity of nitric oxide synthase Protein and mRNA expression levels of N-methyI-D-aspartate receptor subunit NR1 were markedly inhibited in the presence of 250 mg/kg oxysophoridine and 6 mg/kg nimodipine. Our experimental findings indicated that oxysophoridine has a neuroprotective effect against cerebral ischemia/reperfusion injury in mice, and that the effect may be due to its ability to inhibit oxidative stress and expression of the N-methyI-D-aspartate receptor subunit NR1.

Isothermal kinetic analysis on reduction of solid/liquid wustite by hydrogen

Isothermal thermogravimetric analysis was used to study the reduction process of solid/liquid wustite by hydrogen.Results show that wustite in both states can be reduced entirely at all temperatures.The thermal and kinetic conditions for the hydrogen reduction of molten phases are better than those when the reactants and products are in the solid state,with a higher reaction rate.The hydrogen reduction of different wustite phases fits the Mampel Power model(power exponent n=1/2)well,and this model is independent of the phase state.The average apparent activation energies of the reduction process calculated by the iso-conversional method are 5.85 kJ·mol^(−1) and 104.74 kJ·mol^(−1),when both reactants and products are in the solid state and the molten state,respectively.These values generally agree with those calculated by the model fitting method.

腹腔加压气溶胶化疗治疗结直肠癌腹膜转移研究进展

腹膜转移是结直肠癌的常见转移方式,即使进行积极治疗,结直肠癌腹膜转移患者的预后仍较差。近年来,腹腔加压气溶胶化疗(pressurized intraperitoneal aerosol chemotherapy,PIPAC)作为一种新的腹腔内化疗方式受到了广泛关注,全球多个国家的研究者开展了大量与PIPAC相关的前瞻性研究和临床试验,对于腹膜癌患者来说,PIPAC已成为一种安全有效的且有前景的治疗方式,多个医疗中心已经将其用于治疗腹膜癌患者。随着PIPAC相关的临床证据越来越多,其在临床中的应用越发受到重视。本文就PIPAC治疗结直肠癌腹膜转移的理论基础、发展历程、操作流程、适应证、禁忌证、药物方案和临床应用的最新进展进行综述,以期为临床实践和研究提供参考。

Dual-ionic imidazolium salts to promote synthesis of cyclic carbonates at atmospheric pressure

Novel dual-ionic imidazolium salts are shown to display excellent catalytic activity for cycloaddition of carbon dioxide and epoxides under room temperature and atmospheric pressure(0.1 MPa)without any solvent and co-catalyst leading to 96.1%product yield.It can be reused five times to keep the product yield over 90%.These intriguing results are attributed to a new reaction mechanism,which is supported by theoretical calculations along with the measurements of ^(13)C NMR spectrum and Fourier transform infrared spectroscopy(FT-IR).The excellent catalytic activity can be traced to a CO_(2)-philic group along with an electrophilic hydrogen atom.Our work shows that incorporation of CO_(2)-philic group is an feasible pathway to develop the new efficient ionic liquids.

Research on pile performance and state-of-the-art practice in cold regions

A pile foundation is commonly adopted in geotechnical engineering to support structures, and its application has been extended to cold-regions engineering. In past decades, a host of scholars investigated pile behaviors and proposed design guidelines for seasonally frozen ground or permafrost. This paper reviews the research with respect to pile performance and engineering practice in cold regions, organized as follows:(1) creep tests and bearing capacity,(2) frost-jacking hazards,(3) laterally loaded piles,(4) dynamic responses,(5) refreezing due to concrete-hydration heat, and(6) improved countermeasures and design methods. We first summarize previous research and recent progress; then, predict the development trend of pile foundations in cold regions and recommend further research.

Self-induced Secretion Expression of Trehalose Synthase in Bacillus subtilis WB800n

Bacillus subtilis is a non-pathogenic Gram-positive bacterium that has been widely used to produce industrially and pharmaceutically relevant proteins. Trehalose, a non reducing disaccharide used as protective agent and additive in foodstuffs and pharmaceutical products, can be prepared by trehalose synthase(TreS). The present work aims to construct a robust recombinant B. subtilis to achieve the secretory expression of TreS. In this study, the treS gene from Pseudomonas putida ATCC47054 was amplified by PCR and further cloned and expressed in B. subtilis WB800 N using pHT01 as expression vector. For avoiding the use of inducer, promoter P_(srfA) was used to replace the promoter P_(grac) in pHT01 and verify the activity of recombinant trehalose synthase. The TreS activity assay was employed to evaluate the performance of recombinant B. subtilis W800 N under different phosphate concentrations, carbon sources, carbon source concentrations, nitrogen sources and pH. The results showed that the P_(srfA) promoter had a good regulation effect under pH 8.0 condition, and the enzyme activity reached 6 000 U/L. Using the PhoD as the secretory signal peptide, TreS was effectively secreted, and the extracellular enzyme activity reached 2 100 U/L, accounting for 35% of the total enzyme activity. By optimizing the medium and fermentation conditions, the extracellular enzyme activity reached 6 900 U/L in 5 L of fermentor, and the proportion reached 48%. The pHT01-P_(srfA)-PhoD-treS secretory recombinant B. subtilis constructed in this study has great potential in trehalose synthase production.

Stress distribution in roadbeds of slab tracks with longitudinal discontinuities

Stress concentration occurs in the foundations of railway tracks where discontinuous components are located.The exacerbated stress under the expansion joints in slab tracks may trigger foundation failures such as mud pumping.Although the higher stress due to the discontinuities of track structures has been discussed in past studies,few focused on the stress response of roadbeds in slab tracks and quantitatively characterized the stress pattern.In this paper,we performed a dynamic finite element analysis of a track-formation system,incorporating expansion joints as primary longitudinal discontinuities.The configurations of CRTS Ⅲ slab tracks and the contact conditions between concrete layers were considered.Numerical results show that longitudinal influencing length of induced stress on roadbed under wheel load relates to the contact conditions between concrete layers,increasing nonlinearly at a larger coefficient of friction.Given a measured coefficient of friction of 0.7,the calculated longitudinal influencing length(9.0 m) matches with field data.The longitudinal influencing length is not affected with the increasing velocity.As stress concentration arises with expansion joints,the worstcase scenario emerges when double-axle loads are exerted immediately above the expansion joints between concrete bases.A stress concentration factor Cvon the roadbed is proposed;it increases with the increasing velocity,changing from 1.33 to 1.52 at velocities between 5 and 400 km/h.The stress distribution on roadbeds transforms from a trapezoid pattern at continuous sections to a triangle pattern at points with longitudinal discontinuities.An explicit expression is finally proposed for the stress pattern on roadbed under expansion joints.Although structural discontinuities induce stress raiser,the extent of concentration is mitigated with increasing depth at different velocity levels.

Simplified analytical solution for stress concentration ratio of piled embankments incorporating pile–soil interaction

Piled embankments have been extensively used for high-speed rail over soft soils because of their effectiveness in minimizing differential settlement and shortening the construction period.Stress concentration ratio,defined as the ratio of vertical stress carried by pile heads(or pile caps if applicable)to that by adjacent soils,is a fundamental parameter in the design of piled embankments.In view of the complicated load transfer mechanism in the framework of embankment system,this paper presents a simplified analytical solution for the stress concentration ratio of rigid pile-supported embankments.In the derivation,the effects of cushion stiffness,pile–soil interaction,and pile penetration behavior are considered and examined.A modified linearly elastic-perfectly plastic model was used to analyze the mechanical response of a rigid pile–soil system.The analytical model was verified against field data and the results of numerical simulations from the literature.According to the proposed method,the skin friction distribution,pile–soil relative displacement,location of neural point,and differential settlement between the pile head(or cap)and adjacent soils can be determined.This work serves as a fast algorithm for initial and reasonable approximation of stress concentration ratio on the design aspects of piled embankments.

Optimization of inter-helix spacing for helical piles in sand

The optimization of the inter-helix spacing is a key issue of the axial bearing capacity of helical piles.In this paper,based on the cavity expansion,an analytical approach considering the small-strain stiffness,strength,compressibility and stress level of sand around the helical pile was proposed to analyze the influence zone of the helices to determine the optimal inter-helix spacing in sand.The calculation results of the proposed method were verified using the centrifuge test data and finite element analysis for helical pile in Congleton HST95 sand.They were also compared with those using the Meyerhof pile foundation theory.The results show that the optimal inter-helix spacing based on Meyerhof pile foundation theory differs significantly from the measurement.The range of the influence zone for the helices in sand calculated by the cavity expansion theory matches with the data from literature.The calculation results with the proposed method are consistent with the range of the optimal spacing ratio inferred in the centrifuge tests.The results based on the two-dimensional(2D)finite element model(FEM)are also basically consistent with the calculated analytical solution.

Hydrochar Pelletization towards Solid Biofuel from Biowaste Hydrothermal Carbonization

Hydrothermal carbonization is highly applicable to high moisture biomass upgrading due to the fact that moist-ure involved can be directly used as reaction media under the subcritical-water region.With this,value-added utilization of hydrochar as solid fuel with high carbon and energy density is one of the important pathways for biomass conversion.In this review,the dewatering properties of hydrochar after the hydrothermal carbonization of biowaste,coalification degree with elemental composition and evolution,pelletization of hydrochar to enhance the mechanical properties and density,coupled with the combustion properties of hydrochar biofuel were discussed with various biomass and carbonization parameters.Potential applications for the co-combustion with coal,cleaner properties and energy balance for biowaste hydrothermal carbonization were presented as well as the challenges.

Effects of Biowaste-Derived Hydrochar on Anaerobic Digestion:Insights into Hydrochar Characteristics

Hydrochar prepared with four typical biowastes,pine wood,food waste,digested sewage sludge,and Chlorella were applied for the promotion of anaerobic digestion.The gas production and substrate composition were analyzed associated with the hydrochar characteristics.The results suggested that Chlorella hydrochar(C-C)showed the highest cumulative yield of methane(approximately 345 mL)with high total organic carbon(TOC)removal efficiency and low volatile fatty acids(VAFs)concentration.Especially,food waste hydrochar(F-C)showed a poor effect on anaerobic digestion and aroused 1.4–1.6 g/L accumulation of VAFs,in which the toxic components may account for the low efficiency.The C-C and sludge hydrochar(S-C)may develop direct interspecific electron transport(DIET)to facilitate the generation of methane by both surface groups and conductivity of the body structure,unlike pinewood hydrochar(P-C),which mainly depended on the aromatic matrix structure of hydrochar body.This work suggested that C-C can be the best candidate for the facilitation of anaerobic digestion,and N-containing biowaste like algae and lignocellulose like pine wood may establish different DIET pathways based on the physicochemical characteristics of hydrochar.

System reliability evaluation of long railway subgrade slopes considering discrete instability

This paper develops a dual-indicator discrete method(DDM)for evaluating the system reliability performance of long soil subgrade slopes.First,they are segmented into many slope sections using the random finite element method,to ensure each section statistically contains one potential local instability.Then,the k-out-of-n system model is used to describe the relationship between the total number of sections n,the acceptable number of failure sections m,the reliability of sections R_(sec),and the system reliability R_(sys).Finally,m and R_(sys)are jointly used to assess the system reliability performance.For cases lacking spatial data of soil properties,a simplified DDM is provided in which long subgrade slopes are segmented by the empirical value of section length and R_(sec)is substituted by that of crosssections taken from them.The results show that(1)DDM can provide the probability that the actual number of local instabilities does not exceed a desired threshold.(2)R_(sys)decreases with increasing n or decreasing R_(sec);that is,it is likely to encounter more local instabilities for longer or weaker subgrade slopes.n is negatively related to the horizontal scale of fluctuation of soil properties and positively related to the total length of subgrade slopes L.(3)When L is sufficiently large,there is a considerable opportunity to meet local instabilities even if R_(sec)is large enough.

Experimental study of the effects of non-uniformly distributed fine soil on mechanical properties of Shenyang–Dandong Railway coarse-grained soil

The stress produced by repeated train loads decreases with increasing railway subgrade bed depth, and slightly weathered coarse particles of subgrade bed fillings can be broken at different levels under continuous load. Thus, the mass of fine soil, with a diameter of not more than 0.075 mm, is different at different depths. Fine soil is also sensitive to frost heave and thaw settlement. In order to study the effects of non-uniformly distributed fine soil on the mechanical properties of coarse-grained soil of the Shenyang-Dandong Railway, triaxial tests were conducted with three types of specimens, un- dergoing six freeze-thaw cycle numbers （0, 1, 3, 7, 9, 12） and three confining pressures （100, 200, 300 kPa）. The freezing temperature is -5 ~C and the thawing temperature is ＋15 ~C. The stress-strain behavior, static strength, resilient modulus, cohesive force and the angle of internal friction were measured for different tested specimens. As a result, the law of static strength and resilient modulus of different specimens following the increase of freeze-thaw cycles under three confining pressures is obtained. The changing law of cohesive force and friction angle of three specimens following the increase of freeze-thaw cycles is also calculated, and the different results of different specimens are also compared.

Progress in Enzymatic Production of Trehalose

Trehalose is a non-reducing disaccharide, and widespread in nature. It is a typical stress metabolite that can protect macromolecules such as proteins in organisms under extreme conditions. Therefore, trehalose has been widely used in food, medicine and cosmetics. Trehalose is extracted from yeast or synthesized by chemical method. Due to the high cost of traditional methods, trehalose is mainly produced by enzymatic methods. There are mainly three pathways: TPS/TPP, TreY/TreZ and TreS. These enzymatic systems are expressed mainly through heterologous expression.

A combined experimental and DEM investigation of grain interlocking in sheared granular assemblies

Compacted granular material,integral to geotechnical engineering,undergoes translation,rotation,and interlocking when subject to shear displacements or external loads.The present study focuses on the interlocking of heterogeneous granular materials,a complex behavior influenced by gradation,compaction,and varying particle geometry,and has consequently received limited attention in existing research.To address this research gap,we conducted an analysis on the effect of grain interlocking on the shear resistance of granular assemblies,using a combination of laboratory testing and the discrete element method(DEM).Initially,large-scale direct shear tests were conducted on gravel−sand mixes with varying degrees of compaction and normal pressure.One of the mixes also underwent subsequent shear reversal to explore the differences in grain interlocking between the two shearing processes on the shear plane.After analyzing the laboratory results,a mesoscopic scale investigation was performed by replicating the test using discrete element simulations.To facilitate this,granular particle geometries were measured using 3D laser scanning based on the physical lab tests.Subsequently,based on these scans,discrete element R-block and ball models were utilized to construct both the coarse and fine particles within the mix.Surface vibro-compaction was employed to regulate the degree of compaction.The results indicate that an increase in vertical pressure,coupled with a zero dilatancy angle,results in a rising stress ratio,indicative of grain interlocking.This interlocking exhibits a positive correlation with both the coarse content and the degree of compaction,and varies depending on the shear displacement.As interlocking progresses,the shear band,induced by particle movement,expands and is associated with reduced particle rotation near the shear band.The study further reveals a consistent positive correlation between interlocking and the principal orientation angle of strong normal contact forces,as well as a correlation between interlocking and mobilized contacts.

From spatio-temporal landslide susceptibility to landslide risk forecast

The literature on landslide susceptibility is rich with examples that span a wide range of topics.However,the component that pertains to the extension of the susceptibility framework toward space–time modeling is largely unexplored.This statement holds true,particularly in the context of landslide risk,where few scientific contributions investigate risk dynamics in space and time.This manuscript proposes a modeling protocol where a dynamic landslide susceptibility is obtained via a binomial Generalized Additive Model whose inventories span nine years(from 2013 to 2021).For the analyses,the data cube is organized with a mapping unit consisting of 26,333 slope units repeated over an annual temporal unit,resulting in a total of 236,997 units.This phase already includes several interesting modeling experiments that have rarely appeared in the landslide literature(e.g.,variable interaction plots).However,the main innovative effort is in the subsequent phase of the protocol we propose,as we used climate projections of the main trigger(rainfall)to obtain future estimates of yearly susceptibility patterns.These estimates are then combined with projections of urban settlements and associated populations to create a dynamic risk model,assuming vulnerability=1.Overall,this manuscript presents a unique example of such a modeling routine and offers a potential standard for administrations to make informed decisions regarding future urban development.

Sunlight photocatalytic degradation of ofloxacin using UiO-66/wood composite photocatalysts

This study synthesized UiO-66(Zr)in situ on wood via a one-step solvothermal method.UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin(OFX)photodegradation under simulate sunlight was also explored.UiO-66/wood exhibited a better catalytic performance,and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood,respectively.The effects of solution initial concentration,pH of the system and dosage of the photocatalyst were explored.Additionally,the active species trapping experiments and UV-vis diffused reflectance spectra measurements were conducted to investigated the photocatalytic mechanism of the UiO-66/wood composite,superoxide radical(O_(2)^(·-))and hydroxyl radical(^(·)OH)were the main reactive species.In addition,the possible degradation pathways of OFX were analyzed by LC-MS.Meanwhile,the UiO-66/wood showed outstanding stability and reusability after 4 cycles experiments.The removal performance of UiO-66/wood towards real samples showed it has potential in actual application.

A self-powered ultraviolet photodetector with van der Waals Schottky junction based on TiO_(2) nanorod arrays/Au-modulated V2CTx MXene

A self-powered ultraviolet photodetector(UV PD)with van der Waals(vdW)Schottky junction based on TiO_(2) nanorod arrays/Au-modulated V2 CTx MXene is reported.The Schottky junction enables the device to operate in self-powered mode.The dangling bond-free surface of V2 CTx MXene reduces the charge recombination at the junction interface.Meanwhile,V2 CTx MXene,with the work function(WF)increasing to 5.35 eV,forms a hole transport layer by contacting with Au electrode,which facilitates the carrier extraction.The electron lifetime in the device has prolonged to 8.95μs.As a result,the responsivity and detectivity of the PD have achieved 28 mA/W and 1.2×10^(11) cm Hz1/2/W(340 nm,65 mW/cm2,0 V),respectively.In addition,the presence of the Au electrode prevents the vanadium from coming into contact with oxygen and oxidizing,preserving the properties of the V2 CTx films.After 180 days of exposure to the atmosphere,the device performance remained at a particularly high level,indicating enhanced durability.This work points out an effective approach to modulate the properties of V2 CTx to obtain the high performance and stability of the UV PD.

Backward bifurcation,basic reinfection number and robustness of an SEIRE epidemic model with reinfection

Recent evidences show that individuals who recovered from COVID-19 can be reinfected.However,this phenomenon has rarely been studied using mathematical models.In this paper,we propose an SEIRE epidemic model to describe the spread of the epidemic with reinfection.We obtain the important thresholds R_(0)(the basic reproduction number)and R_(c)(a threshold less than one).Our investigations show that when R_(0)>1,the system has an endemic equilibrium,which is globally asymptotically stable.When R_(c)<R_(0)<1,the epidemic system exhibits bistable dynamics.That is,the system has backward bifurcation and the disease cannot be eradicated.In order to eradicate the disease,we must ensure that the basic reproduction number R_(0) is less than R_(c).The basic reinfection number is obtained to measure the reinfection force,which turns out to be a new tipping point for disease dynamics.We also give definition of robustness,a new concept to measure the dificulty of completely eliminating the disease for a bistable epidemic system.Numerical simulations are carried out to verify the conclusions.