The loaded matrix:neurotrophin-enriched hydrogels for stem cell brain repair in Parkinson's disease

More than 200 years after Parkinson's disease was first described by the English surgeon whose name would eventually be given to the condition,available treatments remain purely symptomatic,leaving a critical unmet clinical need for a diseasemodifying therapy.

High Fe‑Loading Single‑Atom Catalyst Boosts ROS Production by Density Effect for Efficient Antibacterial Therapy

The current single-atom catalysts(SACs)for medicine still suffer from the limited active site density.Here,we develop a synthetic method capable of increasing both the metal loading and mass-specific activity of SACs by exchanging zinc with iron.The constructed iron SACs(h^(3)-FNC)with a high metal loading of 6.27 wt%and an optimized adjacent Fe distance of~4 A exhibit excellent oxidase-like catalytic performance without significant activity decay after being stored for six months and promising antibacterial effects.Attractively,a“density effect”has been found at a high-enough metal doping amount,at which individual active sites become close enough to interact with each other and alter the electronic structure,resulting in significantly boosted intrinsic activity of single-atomic iron sites in h^(3)-FNCs by 2.3 times compared to low-and medium-loading SACs.Consequently,the overall catalytic activity of h^(3)-FNC is highly improved,with mass activity and metal mass-specific activity that are,respectively,66 and 315 times higher than those of commercial Pt/C.In addition,h^(3)-FNCs demonstrate efficiently enhanced capability in catalyzing oxygen reduction into superoxide anion(O_(2)·^(−))and glutathione(GSH)depletion.Both in vitro and in vivo assays demonstrate the superior antibacterial efficacy of h^(3)-FNCs in promoting wound healing.This work presents an intriguing activity-enhancement effect in catalysts and exhibits impressive therapeutic efficacy in combating bacterial infections.

Efficacy of a New Geometric Stiffness Matrix for Buckling Load Analyses

This paper investigates the development and performance of a new higher-order geometric stiffness matrix that more closely approximates the theoretically derived stiffness coefficients.Factors that influence the accuracy of the solution are studied using two columns,two braced frames,and one unbraced frame.Discussion is provided when the new geometric stiffness matrix can be used to improve the buckling load analysis results and when it may provide only nominal additional benefit.

Multi-Scenario Probabilistic Load Flow Calculation Considering Wind Speed Correlation

As the proportion of newenergy increases,the traditional cumulant method(CM)produces significant errorswhen performing probabilistic load flow(PLF)calculations with large-scale wind power integrated.Considering the wind speed correlation,a multi-scenario PLF calculation method that combines random sampling and segmented discrete wind farm power was proposed.Firstly,based on constructing discrete scenes of wind farms,the Nataf transform is used to handle the correlation between wind speeds.Then,the random sampling method determines the output probability of discrete wind power scenarios when wind speed exhibits correlation.Finally,the PLF calculation results of each scenario areweighted and superimposed following the total probability formula to obtain the final power flow calculation result.Verified in the IEEE standard node system,the absolute percent error(APE)for the mean and standard deviation(SD)of the node voltages and branch active power are all within 1%,and the average root mean square(AMSR)values of the probability curves are all less than 1%.

A Damage Control Model for Reinforced Concrete Pier Columns Based on Pre-Damage Tests under Cyclic Reverse Loading

To mitigate the challenges in managing the damage level of reinforced concrete(RC)pier columns subjected to cyclic reverse loading,this study conducted a series of cyclic reverse tests on RC pier columns.By analyzing the outcomes of destructive testing on various specimens and fine-tuning the results with the aid of the IMK(Ibarra Medina Krawinkler)recovery model,the energy dissipation capacity coefficient of the pier columns were able to be determined.Furthermore,utilizing the calibrated damage model parameters,the damage index for each specimen were calculated.Based on the obtained damage levels,three distinct pre-damage conditions were designed for the pier columns:minor damage,moderate damage,and severe damage.The study then predicted the variations in hysteresis curves and damage indices under cyclic loading conditions.The experimental findings reveal that the displacement at the top of the pier columns can serve as a reliable indicator for controlling the damage level of pier columns post-loading.Moreover,the calibrated damage index model exhibits proficiency in accurately predicting the damage level of RC pier columns under cyclic loading.

Undrained bearing capacity of obliquely-eccentrically loaded shallow foundations overlying a heterogeneous and inherently anisotropic clay deposit

Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.

Bi-directional interaction of joint shear strength in non-seismically designed corner RC beam-column connections under seismic loading

Non-seismically designed(NSD)beam-column joints are susceptible to joint shear failure under seismic loads.Although significant research is available on the seismic behavior of such joints of planar frames,the information on the seismic behavior of joints of space frames(3D joints)is insufficient.The 3D joints are subjected to bi-directional excitation,which results in an interaction between the shear strength obtained for the joint in the two orthogonal directions separately.The bi-directional seismic behavior of corner reinforced concrete(RC)joints is the focus of this study.First,a detailed finite element(FE)model using the FE software Abaqus,is developed and validated using the test results from the literature.The validated modeling procedure is used to conduct a parametric study to investigate the influence of different parameters such as concrete strength,dimensions of main and transverse beams framing into the joint,presence or absence of a slab,axial load ratio and loading direction on the seismic behavior of joints.By subjecting the models to different combinations of loads on the beams along perpendicular directions,the interaction of the joint shear strength in two orthogonal directions is studied.The comparison of the interaction curves of the joints obtained from the numerical study with a quadratic(circular)interaction curve indicates that in a majority of cases,the quadratic interaction model can represent the strength interaction diagrams of RC beam to column connections with governing joint shear failure reasonably well.

Fracture behavior of sandstone with partial filling flaw under mixed-mode loading: Three-point bending tests and discrete element method

The fracture behavior of natural fracture in the geological reservoir subjected to filling property,affects the crack initiation and propagation under stress perturbation.Partial filling flaws were intermediate between open fractures and filled fractures,the fracture response may be worth exploring.In this work,the effect of the filling property of sandstone with partial filling flaws on the fracture behavior was systematically investigated based on three-point bending tests and the numerical approach of discrete element method(DEM).In the laboratory,semi-circular three-point bending tests were carried out with partial filling flaws of various filling strengths.Based on this,numerical simulations were used to further investigate the effect of the filling ratio and the inclination of the partial filling flaw on the mechanical and fracture responses,and the effect of the partial filling flaw under mixed-mode loading on the fracture mechanism was elucidated coupled with acoustic emission(AE)characteristics.The obtained results showed that the increase in filling strength and filling ratio of partial filling flaw led to an increase in peak strength,with a decreasing trend in peak strength with the inclination of partial filling flaw.In terms of crack propagation pattern,the increasing filling strength of the partial filling flaw induced the transformation of the fracture mechanism toward deflection,with a tortuosity path,while the filling ratio and inclination of partial filling flaw led to fracture mechanism change from deflection to penetration and attraction,accompanied with a larger AE event source in filler.Accordingly,the b-value based on the Gutenberg-Richter equation fluctuated between 5 and 4 at low filling ratio and inclination and remained around 5 at high filling ratio and inclination of partial filling flaw.Related results may provide an application prospective for reservoir stimulation using the natural fracture system.

Dynamic compressive characteristics of a green sandstone under coupled hydraulic-mechanical loading: Experiments and theoretical modeling

Deep rock is under a complex geological environment with high geo-stress, high pore pressure, and strong dynamic disturbance. Understanding the dynamic response of rocks under coupled hydraulic-mechanical loading is thus essential in evaluating the stability and safety of subterranean engineering structures. Nevertheless, the constraints in experimental techniques have led to limited prior investigations into the dynamic compression behavior of rocks subjected to simultaneous high in-situ stress and pore pressure conditions. This study utilizes a triaxial split Hopkinson pressure bar (SHPB) system in conjunction with a pore pressure loading cell to conduct dynamic experiments on rocks subjected to hydraulic-mechanical loading. A porous green sandstone (GS) was adopted as the testing rock material. The findings reveal that the dynamic behavior of rock specimens is significantly influenced by multiple factors, including the loading rate, confining stress, and pore pressure. Specifically, the dynamic compressive strength of GS exhibits an increase with higher loading rates and greater confining pressures, while it decreases with elevated pore pressure. Moreover, the classical Ashby-Sammis micromechanical model was augmented to account for dynamic loading and pore pressure considerations. By deducing the connection between crack length and damage evolution, the resulting law of crack expansion rate is related to the strain rate. In addition, the influence of hydraulic factors on the stress intensity factor at the crack tip is introduced. Thereby, a dynamic constitutive model for deep rocks under coupled hydraulic-mechanical loading was established and then validated against the experimental results. Subsequently, the characteristics of introduced parameter for quantifying the water-induced effects were carefully discussed.

Mechanical responses of anchoring structure under triaxial cyclic loading

Dynamic load on anchoring structures(AS)within deep roadways can result in cumulative damage and failure.This study develops an experimental device designed to test AS under triaxial loads.The device enables the investigation of the mechanical response,failure mode,instability assessment criteria,and anchorage effect of AS subjected to combined cyclic dynamic-static triaxial stress paths.The results show that the peak bearing strength is positively correlated with the anchoring matrix strength,anchorage length,and edgewise compressive strength.The bearing capacity decreases significantly when the anchorage direction is severely inclined.The free face failure modes are typically transverse cracking,concave fracturing,V-shaped slipping and detachment,and spallation detachment.Besides,when the anchoring matrix strength and the anchorage length decrease while the edgewise compressive strength,loading rate,and anchorage inclination angle increase,the failure intensity rises.Instability is determined by a negative tangent modulus of the displacement-strength curve or the continued deformation increase against the general downward trend.Under cyclic loads,the driving force that breaks the rock mass along the normal vector and the rigidity of the AS are the two factors that determine roadway stability.Finally,a control measure for surrounding rock stability is proposed to reduce the internal driving force via a pressure relief method and improve the rigidity of the AS by full-length anchorage and grouting modification.

Energy mechanism of bolt supporting effect to fissured rock under static and dynamic loads in deep coal mines

The stability control of fissured rock is difficult,especially under static and dynamic loads in deep coal mines.In this paper,the dynamic mechanical properties,strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests.It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance,and this effect increased quadratically with decrease in anchoring angles.Then,the energy dissipation mechanism of anchored rock was obtained by slipping model.Furthermore,bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics,which was the larger the anchoring angle,the smaller the energy absorption,and the less the contribution to supporting efficiency improvement.On this basis,the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established.Taking the coal-gangue separation system of Longgu coal mine as an example,the optimal anchoring angle can be determined as 57.5°–67.5°.Field monitoring showed fissured rock with the optimal anchoring angle,can not only effectively control the deformation,but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself.This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.

State-of-the-art on the anchorage performance of rock bolts subjected to shear load

Rock bolts are extensively utilized in underground engineering as a means of offering support and stability to rock masses in tunnels,mines,and other underground structures.In environments of high ground stress,faults or weak zones can frequently arise in rock formations,presenting a significant challenge for engineering and potentially leading to underground engineering collapse.Rock bolts serve as a crucial structural element for the transmission of tensile stress and are capable of withstanding shear loads to prevent sliding of weak zones within rock mass.Therefore,a complete understanding of the behavior of rock bolts subjected to shear loads is essential.This paper presents a state-of-the-art review of the research progress of rock bolts subjected to shear load in three categories:experiment,numerical simulation,and analytical model.The review focuses on the research studies and developments in this area since the 1970s,providing a comprehensive overview of numerous factors that influence the anchorage performance of rock bolts.These factors include the diameter and angle of the rock bolt installation,rock strength,grouting material,bolt material,borehole diameter,rock bolt preload,normal stress,joint surface roughness and joint expansion angle.The paper reviews the improvement of mechanical parameter setting in numerical simulation of rock bolt shear.Furthermore,it delves into the optimization of the analytical model concerning rock bolt shear theory,approached from the perspectives of both Elastic foundation beam theory coupled with Elastoplasticity theory and Structural mechanic methods.The significance of this review lies in its ability to provide insights into the mechanical behavior of rock bolts.The paper also highlights the limitations of current research and guidelines for further research of rock bolts.

Mechanical behavior and failure mechanisms of rock bolts subjected to static-dynamic loads

This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts.Employing a housemade load frame to simulate various failure scenarios,pretension-impact-pull tests on rock bolts were conducted to scrutinize their dynamic responses under varied static load conditions and their failure traits under combined loads.The experimental results denote that with increased impact energy,maximum and average impact loads on rock bolts escalate significantly under pretension,initiating plastic deformation beyond a certain threshold.Despite minor reductions in the yield load due to impactinduced damage,pretension aids in constraining post-impact deformation rate and fluctuation degree of rock bolts.Moreover,impact-induced plastic deformation causes internal microstructure dislocation,fortifying the stiffness of the rock bolt support system.The magnitude of this fortification is directly related to the plastic deformation induced by the impact.These findings provide crucial guidance for designing rock bolt support in coal mine roadway excavation,emphasizing the necessity to consider both static and dynamic loads for improved safety and efficiency.

A drug-loaded flexible substrate improves the performance of conformal cortical electrodes

Cortical electrodes are a powerful tool for the stimulation and/or recording of electrical activity in the nervous system.However,the inevitable wound caused by surgical implantation of electrodes presents bacterial infection and inflammatory reaction risks associated with foreign body exposure.Moreover,inflammation of the wound area can dramatically worsen in response to bacterial infection.These consequences can not only lead to the failure of cortical electrode implantation but also threaten the lives of patients.Herein,we prepared a hydrogel made of bacterial cellulose(BC),a flexible substrate for cortical electrodes,and further loaded antibiotic tetracycline(TC)and the anti-inflammatory drug dexamethasone(DEX)onto it.The encapsulated drugs can be released from the BC hydrogel and effectively inhibit the growth of Gram-negative and Gram-positive bacteria.Next,therapeutic cortical electrodes were developed by integrating the drug-loaded BC hydrogel and nine-channel serpentine arrays;these were used to record electrocorticography(ECoG)signals in a rat model.Due to the controlled release of TC and DEX from the BC hydrogel substrate,therapeutic cortical electrodes can alleviate or prevent symptoms associated with the bacterial infection and inflammation of brain tissue.This approach facilitates the development of drug delivery electrodes for resolving complications caused by implantable electrodes.

Reinforcing effects of polypropylene on energy absorption and fracturing of cement-based tailings backfill under impact loading

Polypropylene(PP)fiber-reinforced cement-based tailings backfill(FRCTB)is a green compound material with superior crack resistance and has good prospects for application in underground mining.However,FRCTB exhibits susceptibility to dynamic events,such as impact ground pressure and blast vibrations.This paper investigates the energy and crack distribution behavior of FRCTB under dynamic impact,considering the height/diameter(H/D)effect.Split Hopkinson pressure bar,industrial computed tomography scan,and scanning electron microscopy(SEM)experiments were carried out on six types of FRCTB.Laboratory outcomes confirmed fiber aggregation at the bottom of specimens.When H/D was less than 0.8,the proportion of PP fibers distributed along theθangle direction of80°-90°increased.For the total energy,all samples presented similar energy absorption,reflectance,and transmittance.However,a rise in H/D may cause a rise in the energy absorption rate of FRCTB during the peak phase.A positive correlation existed between the average strain rate and absorbed energy per unit volume.The increase in H/D resulted in a decreased crack volume fraction of FRCTB.When the H/D was greater than or equal to 0.7,the maximum crack volume fraction of FRCTB was observed close to the incidence plane.Radial cracks were present only in the FRCTB with an H/D ratio of 0.5.Samples with H/D ratios of 0.5 and 0.6 showed similar distributions of weakly and heavily damaged areas.PP fibers can limit the emergence and expansion of cracks by influencing their path.SEM observations revealed considerable differences in the bonding strengths between fibers and the FRCTB.Fibers that adhered particularly well to the substrate were attracted together with the hydration products adhering to surfaces.These results show that FRCTB is promising as a sustainable and green backfill for determining the design properties of mining with backfill.

Experimental study of the damage characteristics of rocks containing non-penetrating cracks under cyclic loading

The damage evolution process of non-penetrating cracks often causes some unexpected engineering disasters.Gypsum specimens containing non-penetrating crack(s)are used to study the damage evolution and characteristics under cyclic loading.The results show that under cyclic loading,the relationship between the number of non-penetrating crack(s)and the characteristic parameters(cyclic number,peak stress,peak strain,failure stress,and failure strain)of the pre-cracked specimens can be represented by a decreasing linear function.The damage evolution equation is fitted by calibrating the accumulative plastic strain for each cycle,and the damage constitutive equation is proposed by the concept of effective stress.Additionally,non-penetrating cracks are more likely to cause uneven stress distribution,damage accumulation,and local failure of specimen.The local failure can change the stress distribution and relieve the inhibition of non-penetrating crack extension and eventually cause a dramatic destruction of the specimen.Therefore,the evolution process caused by non-penetrating cracks can be regarded as one of the important reasons for inducing rockburst.These results are expected to improve the understanding of the process of spalling formation and rockburst and can be used to analyze the stability of rocks or rock structures.

Conservation genomic investigation of an endangered conifer,Thuja sutchuenensis,reveals low genetic diversity but also low genetic load

Endangered species generally have small populations with low genetic diversity and a high genetic load.Thuja sutchuenensis is an endangered conifer endemic to southwestern China.It was once considered extinct in the wild,but in 1999 was rediscovered.However,little is known about its genetic load.We collected 67 individuals from five wild,isolated T.sutchuenensis populations,and used 636,151 SNPs to analyze the level of genetic diversity and genetic load in T.sutchuenensis to delineate the conservation units of T.sutchuenensis,based on whole transcriptome sequencing data,as well as target capture sequencing data.We found that populations of T.sutchuenensis could be divided into three groups.These groups had low levels genetic diversity and were moderately genetically differentiated.Our findings also indicate that T.sutchuenensis suffered two severe bottlenecks around the Last Glaciation Period and Last Glacial Maximum.Among Thuja species,T.sutchuenensis presented the lowest genetic load and hence might have purged deleterious mutations efficiently through purifying selection.However,distribution of fitness effects analysis indicated a high extinction risk for T.sutchuenensis.Multiple lines of evidence identified three management units for T.sutchuenensis.Although T.sutchuenensis possesses a low genetic load,low genetic diversity,suboptimal fitness,and anthropogenic pressures all present an extinction risk for this rare conifer.This might also hold true for many endangered plant species in the mountains all over the world.

Transient response of doubly-curved bio-inspired composite shells resting on viscoelastic foundation subject to blast load using improved first-order shear theory and isogeometric approach

Investigating natural-inspired applications is a perennially appealing subject for scientists. The current increase in the speed of natural-origin structure growth may be linked to their superior mechanical properties and environmental resilience. Biological composite structures with helicoidal schemes and designs have remarkable capacities to absorb impact energy and withstand damage. However, there is a dearth of extensive study on the influence of fiber redirection and reorientation inside the matrix of a helicoid structure on its mechanical performance and reactivity. The present study aimed to explore the static and transient responses of a bio-inspired helicoid laminated composite(B-iHLC) shell under the influence of an explosive load using an isomorphic method. The structural integrity of the shell is maintained by a viscoelastic basis known as the Pasternak foundation, which encompasses two coefficients of stiffness and one coefficient of damping. The equilibrium equations governing shell dynamics are obtained by using Hamilton's principle and including the modified first-order shear theory,therefore obviating the need to employ a shear correction factor. The paper's model and approach are validated by doing numerical comparisons with respected publications. The findings of this study may be used in the construction of military and civilian infrastructure in situations when the structure is subjected to severe stresses that might potentially result in catastrophic collapse. The findings of this paper serve as the foundation for several other issues, including geometric optimization and the dynamic response of similar mechanical structures.

Damage evolution of rock-encased-backfill structure under stepwise cyclic triaxial loading

Rock-encased-backfill(RB)structures are common in underground mining,for example in the cut-andfill and stoping methods.To understand the effects of cyclic excavation and blasting activities on the damage of these RB structures,a series of triaxial stepwise-increasing-amplitude cyclic loading experiments was conducted with cylindrical RB specimens(rock on outside,backfill on inside)with different volume fractions of rock(VF=0.48,0.61,0.73,and 0.84),confining pressures(0,6,9,and 12 MPa),and cyclic loading rates(200,300,400,and 500 N/s).The damage evolution and meso-crack formation during the cyclic tests were analyzed with results from stress-strain hysteresis loops,acoustic emission events,and post-failure X-ray 3D fracture morphology.The results showed significant differences between cyclic and monotonic loadings of RB specimens,particularly with regard to the generation of shear microcracks,the development of stress memory and strain hardening,and the contact forces and associated friction that develops along the rock-backfill interface.One important finding is that as a function of the number of cycles,the elastic strain increases linearly and the dissipated energy increases exponentially.Also,compared with monotonic loading,the cyclic strain hardening characteristics are more sensitive to rising confining pressures during the initial compaction stage.Another finding is that compared with monotonic loading,more shear microcracks are generated during every reloading stage,but these microcracks tend to be dispersed and lessen the likelihood of large shear fracture formation.The transition from elastic to plastic behavior varies depending on the parameters of each test(confinement,volume fraction,and cyclic rate),and an interesting finding was that the transformation to plastic behavior is significantly lower under the conditions of 0.73 rock volume fraction,400 N/s cyclic loading rate,and 9 MPa confinement.All the findings have important practical implications on the ability of backfill to support underground excavations.

Liquefaction susceptibility and deformation characteristics of saturated coral sandy soils subjected to cyclic loadings-a critical review

Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.