Stress Transmission Research Articles

Synergistic reinforcement mechanism of basalt fiber/cellulose nanocrystals/polypropylene composites

Abstract In this article, we prepared novel basalt fiber (BF)-reinforced polypropylene (PP) composites based on the synergistic reinforcement of cellulose nanocrystals (CNCs). First, we compared the enhancement effect of CNCs and silane coupling agent-modified BFs on PP, showing that the enhancement effect of the former was more significant. Subsequently, to further improve the mechanical properties of the composites, CNCs were introduced into the BF-reinforced PP composite system as the third phase, and the results suggested that their combination with BFs could synergistically strengthen the PP matrix composites. Simultaneously, the study also shows that when the mass percentage of CNCs and BFs are 1 and 30%, respectively, the composite achieves the highest mechanical strength, which is 64.31% higher than that of the PP matrix. The systematic characterization revealed the synergistic enhancement mechanism: on the one hand, CNCs not only promoted the improvement of PP crystallinity by heterogeneous nucleation but also formed a wedge-shaped structure between them and BFs through hydrogen bonding to prevent PP molecular movement; on the other hand, the BFs promote not only the extrusion crystallization of the resin matrix but also the network structure formed by the appropriate content of BFs can realize the rapid transmission of external stress.

Stress transmission along mid-crustal faults highlighted by the 2021 Mw 6.5 San Juan (Argentina) earthquake

Understanding the mechanisms of crustal deformation along convergent margins is critical to identifying seismogenic structures and assessing earthquake hazards for nearby urban centers. In the southern central Andes (28–33^{circ }S), differences in the style of middle to upper-crustal deformation and associated seismicity are highlighted by the January 19th, 2021 (Mw 6.5) San Juan earthquake. We integrate waveforms recorded at regional and teleseismic distances with co-seismic displacements calculated from local Global Navigation Satellite System time series, to re-estimate the source parameters of the 2021 San Juan earthquake, confirming a mid-crustal nucleation depth (21 ± 2 km) and right-lateral transpressional mechanism. Considered alongside decades of seismic observations and geological data, this event provides evidence for retroarc deformation partitioning among inherited basement faults and upper-crustal structures in response to oblique convergence of the Nazca and South American plates. As they may transfer shortening to active upper-crustal faults associated with historically devastating shallower earthquakes, a better understanding of seismogenic basement faults such as the mid-crustal structure activated during the 2021 San Juan earthquake earthquake could help future re-assessment of the seismic risk in western Argentina.

The Attenuation Ability of Saturated Joints Filled with Granular Materials under High-Amplitude Stress Wave Loading

Existing experimental evidence shows that the propagation of explosive waves in the free fields of soils is remarkably affected by the degree of saturation. In the surrounding rocks of underground protective structures, the underground water is normally unavoidable, which is supposed to reduce the isolation efficiency of a passive antiblast barrier. To investigate the effect of water saturation on the stress wave attenuation ability of infilled joints, impact tests were carried out on artificial joints filled with dry and saturated granular materials using a split Hopkinson pressure bar (SHPB). The test results revealed that under the same conditions, the stress and energy transmission coefficients of the waves crossing saturated sand-filled joints were about 3.16–4.13 times and 9.75–11.4 times those of joints filled with dry sand, respectively. The dynamic stress-strain relationship of the filling layer during the impact process and the crushing index of the infill were analyzed. The results showed that the compressibility and the granular crushing index of the dry sand were much greater than that of the saturated sand, and the dynamic stress-strain relationship of the dry sand exhibited three-stage nonlinear characteristics. The experimental results quantitatively uncovered the serious adverse effect of water on the wave absorption properties and markedly diminished the potential of the filled joints as a wave elimination barrier, which should be a matter of great concern in the design of underground protective structures.

Experimental study on laser peen texturing and tribological properties of E690 high-strength steel

To investigate how laser peen texturing (LPT) parameters affect the patterns formed on the surface of E690 high-strength steel, and how these patterns subsequently influence tribological properties, the LPT process, including multiple shocks, was simulated by ABAQUS and verified by experiments. The residual stress and microstructure on the surface of micro-dimples after LPT were measured and observed by X-ray stress analyzer and transmission electron microscope. The tribological properties of specimens with different LPT density and depth were tested by reciprocating friction experiments, and the worn surfaces were observed using a scanning electron microscope. The experimentally obtained plastic deformation depths of the micro-dimples were − 8.82 μm, −18.31 μm, −28.72 μm and − 36.34 μm when the shock number was varied from 1 to 4. The simulation and experiment results were within 3.3 %, verifying the accuracy and reliability of the simulation. When the shock number was ≥ 2, the residual stress values in all directions at the test points within the micro-dimples tended to be consistent, and the full width at half maximum (FWHM) values gradually increased with increasing shock number. The TEM images and electron diffraction pattern of the specimen after three shocks showed that nanocrystals are formed on the bottom surface of the micro-dimple. In the friction experiments, the average friction coefficient first decreased and then increased with increasing LPT density. The average friction coefficient was the lowest when the LPT density was 20 %, for a constant micro-dimple depth. When the LPT density was 20 %, increasing the micro-dimple depth had little effect on the average friction coefficient, but the stability time of the specimens increased substantially. The wear surface of the untextured specimen showed deep and wide wear marks, and serious abrasive wear and adhesive wear occurred.Suggested LPT parameters for optimum wear resistance are an LPT density of 20% and shock number of 3.

The contagious leader: a panel study on occupational stress transfer in a large Danish municipality

Occupational stress has immense economic and health-related consequences for individuals, organizations, and societies. In this context, the question of whether and how stress among managers transmits to their subordinates is highly interesting, yet not profoundly researched. This study aims to empirically investigate the effect of manager occupational stress on the development of subordinate stress and for how long such effects last in time. We exploit a unique panel dataset based on three different surveys among employees from a large Danish municipality, covering 5,688 employees and their 473 immediate managers between 2016 and 2020. We analyze this data using a fixed effects estimator with clustered robust standard errors, allowing us to significantly reduce potential endogeneity issues. The study shows that managers do in fact ‘transmit’ stress onto their employees, that the relationship is detectable a full year after the initial transmission of stress occurred, and that such an effect fades within additional two years. Our study serves to emphasize the great importance of the psychosocial wellbeing of managers as ‘nerve centers’ for entire job teams and urges organizations to treat stress among personnel on management levels with a high degree of concern.

Lateral stress and its transmission law caused by operation of a double-wing subsoiler in sandy loam soil

Sandy loam soils are widespread and important for agricultural soil use. The lateral stress caused by the loosening shovel of a subsoiler produces lateral disturbances in sandy loam soil, reducing compaction and improving soil structure. To explore the variation and transmission of lateral stress due to the operation of a double-wing subsoiler in sandy loam soil, a lattice of point-type soil sensors was arranged in a soil bin, and the lateral stress generated by subsoiling was measured in the shallow, medium, and deep soil layers. The experimental results show that when the lateral stress generated by the double-wing subsoiler is transferred to the lateral position of different distances.The lateral stress shows a sinusoidal fluctuation law with time, the sine wave frequency range is: shallow (0.366–0.549); middle (0.306–0.494); and deep (0.088–0.501). There were greater fluctuation amplitudes in the transfer process for the shallow and deep soil layers than for the middle layer. Shallow soil had the largest final stable lateral stress (0.1617 N), and middle soil the smallest (0.0733 N). Thus, lateral stress from deep loosening has the greatest effect on shallow soil and the least effect on middle soil. These results indicate that the fluctuating lateral stresses generated by double-wing-subsoiler operation drive a fluctuating soil disturbance that can improve soil structure, and that they are greater for shallow and deep soils than for middle soils.

DEM-based stress transmission in asphalt mixture skeleton filling system

• Stress transmission of skeleton filling system are obtained. • Skeleton aggregate is the main stress transmission medium. • Localization of contact force is affected by the modulus of asphalt mortar. Asphalt mixture is a skeleton filling system consisting of aggregate, asphalt, and mineral powder. High performance asphalt mixture design is directly affected by internal stress transmission of skeleton filling system. In this paper, the discrete element method based on digital image was employed to study the stress transmission. By analyzing the effect of skeleton structure on the contact force between aggregate and mortar, it is concluded that the skeleton aggregate in the asphalt mixture is the main stress transmission medium. The lower the degree of disruption, the higher the contact force of skeleton aggregate. At the same time, the variation coefficient of contact force of asphalt mortar with low filling coefficient is larger and the localization phenomenon is more serious. By analyzing the effect of mortar properties on the contact force between aggregate and mortar, it is concluded that the lower the modulus of asphalt mortar, the higher the degree of localization of contact force and the more likely to have local damage.

Maternal stress in the postpartum period is associated with altered human milk fatty acid composition

Maternal stress in the postpartum period affects not only the mother, but also her newborn child who is at increased risk for a wide range of disorders later in life. The mechanisms underlying transmission of maternal stress to the child remain elusive. Human milk (HM) is a potential candidate and is an important source of fatty acid (FA), which are crucial for child (neuro)development. This study aims to investigate whether maternal psychological and biological stress influences HM FA composition over the first month postpartum. The Amsterdam Mother's Milk study is a prospective cohort study. We included lactating women who delivered at term with a large range of stress levels: a high stress (HS) group, women whose child was hospitalized for a minimum of 2 days (n=23) and a control (CTL) group, women who gave birth to a healthy child (n=73). HM was collected three times a day at postpartum days 10, 17 and 24. Perceived psychological stress was measured using multiple validated questionnaires, while biological stress measures were based on cortisol in hair, saliva and HM. HM FAs were analyzed by gas-chromatography and compared between groups. Maternal perceived stress scores were significantly higher in the HS group (p<0.01), whereas cortisol measurements did not differ between groups. The absolute concentrations of total FA in HM (p=0.023), including the total amount of poly unsaturated fatty acids (PUFAs) (p=0.022) and omega-6 PUFAs (p=0.018), were lower in the HS group compared to the CTL group. Relative values of FAs did not differ between groups. Maternal stress in the first month postpartum was associated with overall lower levels of FA in HM. This possibly indicates a route of transmission of maternal stress signals to the infant. Future research should investigate if these stress-induced changes in HM FAs have consequences for child development.

Prenatal maternal stress and offspring aggressive behavior: Intergenerational and transgenerational inheritance.

Even though studies have shown that prenatal maternal stress is associated with increased reactivity of the HPA axis, the association between prenatal maternal stress and fetal glucocorticoid exposure is complex and most likely dependent on unidentified and poorly understood variables including nature and timing of prenatal insults. The precise mechanisms in which prenatal maternal stress influence neuroendocrine signaling between the maternal-placental-fetal interface are still unclear. The aim of this review article is to bring comprehensive basic concepts about prenatal maternal stress and mechanisms of transmission of maternal stress to the fetus. This review covers recent studies showing associations between maternal stress and alterations in offspring aggressive behavior, as well as the possible pathways for the “transmission” of maternal stress to the fetus: (1) maternal-fetal HPA axis dysregulation; (2) intrauterine environment disruption due to variations in uterine artery flow; (3) epigenetic modifications of genes implicated in aggressive behavior. Here, we present evidence for the phenomenon of intergenerational and transgenerational transmission, to better understands the mechanism(s) of transmission from parent to offspring. We discuss studies showing associations between maternal stress and alterations in offspring taking note of neuroendocrine, brain architecture and epigenetic changes that may suggest risk for aggressive behavior. We highlight animal and human studies that focus on intergenerational transmission following exposure to stress from a biological mechanistic point of view, and maternal stress-induced epigenetic modifications that have potential to impact on aggressive behavior in later generations.

Intergenerational Transmission of Stress: Multi-domain Stressors from Maternal Childhood and Pregnancy Predict Children’s Mental Health in a Racially and Socioeconomically Diverse, Multi-site Cohort

Intergenerational Transmission of Stress: Multi-domain Stressors from Maternal Childhood and Pregnancy Predict Children’s Mental Health in a Racially and Socioeconomically Diverse, Multi-site Cohort

Multi‐dimensional Self‐splitting Behaviors for Improving Wet Attachment on Nonuniform Bioinspired Pillar Surface

AbstractRobust and controllable wet attachment like tree frog toe pads attracts worldwide attention owing to potential applications in wet climbing robots, medical devices, and wearable sensors. Instead of conventional uniform pillars, nonuniform pillar arrays with features of inclination and gradients are discovered as typical structures on tree frog toe pads, whereas their effects on wet friction have been ignored. Micro‐nano in situ observation demonstrates that such a nonuniform pillar surface brings about unique multi‐dimensional self‐splitting behaviors in interfacial liquid films and contact stress distribution to enhance the wet attachment. The self‐splitting of the interfacial liquid film breaks the thick large area liquid film into an immense number of more uniform and robust tiny thin liquid bridges. Furthermore, the contact stress is redistributed by the inclined and gradient pillar array with contact stress self‐splitting, where the peak normal separating stress decreases ≈91% and lateral stress transmission increases ≈63%. Such contact stress self‐splitting further improves the liquid film self‐splitting by forming sturdy thin liquid films even under a larger load, which generates more robust capillarity with enhanced strong friction. Finally, theoretical models are built for the multi‐dimensional self‐splitting enhanced wet attachment, and applications in robotic and medical fields are performed to validate its feasibility.

Shear-driven reactions of organosulfur compounds on ferrous surfaces: A molecular dynamics study

Reactive molecular dynamics simulations were used to investigate reactions between di-tert-butyl disulfide and ferrous surfaces. Tribochemical reactions were characterized with and without a model base oil, n-dodecane, and on either Fe(100) or H-passivated Fe2O3 surfaces. Reaction yield increased with both temperature and pressure for all model systems. The presence of the base oil did not significantly affect the reaction yield or pathway, but the base oil impeded transmission of shear stress to the reactants. Replacing the ideal Fe(100) with H-passivated Fe2O3 surfaces enabled reaction pathways involving oxygen from the surface and decreased the reaction yield. The rate-limiting step of the reactions was analyzed in the context of the Bell model as a step towards better understanding tribochemical reactions.

Is zirconium or stainless steel the most suitable crown material for less dentin stress in endodontically treated teeth?

Stainless steel crowns (SSCs), which have been used frequently in the treatment of first permanent molars in children until now, has become less applicable due to its poor aesthetic appearance. Zirconia crowns (ZCs) have become more popular due to their aesthetic advantage. However, stress transmission of ZCs to dental tissues under occlusal forces in endodontically treated teeth has not been described. The aim of this study was to compare the stress distribution of different crown materials (ZCS, SSCs) and adhesive materials on dentin in endodontically treated permanent teeth and to specify the crown-adhesive model with lower stress. Finite element analysis (FEA) was used to apply a force of 300 N from the inner part of the buccal tubercles (vertical loading) and a lingo-buccal at an angle of 30 degrees (oblique loading) of the first permanent molars (FPM) with different crown (ZCS, SSCs) and adhesive (Glass ionomer cement, Resin modified glass ionomer cement, Resin cement) materials in twelve separate models. The von Mises values obtained from the models were compared and the optimal stress values were determined by FEA. The lowest stress values of dentin were found in zirconia crown model with glass ionomer cement (GIC) adhesive under vertical loading (26,793 Mpa). In the zircon crown and GIC adhesive model, less von Mises stress occurred on the dentin under all conditions. ZCs and GIC adhesive may be recommended for teeth with a high probability of dentin fracture.

Mechanical properties of shear-type hysteretic dampers supported by studs

The shear-type hysteretic damper of an energy-absorbing member reduces the damage to the main member, such as column or beam, by absorbing seismic energy as the shear deformation of steel. As a support element for connecting the damper to the structure, brace-type and stud-type systems are mainly used. In the stud support, the stress transmission mechanism to the damper is simple, and the degrees of freedom of the plane are higher than that of the other support types. For such a shear-type damper, an H-shaped cross-section with a panel made of a highly ductile material, such as a low-yield-point steel, is generally adopted. This study used a low-yield-point steel circular hollow-section damper, which was installed in the frame as a stud support form, and a case was used to receive the in-plane force. For the damper to function effectively in the frame, it was necessary to determine the elastoplastic mechanical properties of the damper and the dampers supported by the stud. The mechanical properties of the damper unit and damper system with the stud were examined by cyclic loading test. An H-shaped shear panel damper was used as the control group with almost the same full plastic shear strength, initial stiffness, and weight as the circular hollow-section damper and the cyclic loading test was conducted under the same conditions. The effectiveness of the low-yield-point steel circular hollow-section damper was examined as a shear-type hysteretic damper by comparing both. In addition, a nonlinear finite element analysis was performed to determine the influence of the initial stiffness on the damper supported by the stud.

Artificial gravity partially protects space-induced neurological deficits in Drosophila melanogaster.

Spaceflight poses risks to the central nervous system (CNS), and understanding neurological responses is important for future missions. We report CNS changes in Drosophila aboard the International Space Station in response to spaceflight microgravity (SFμg) and artificially simulated Earth gravity (SF1g) via inflight centrifugation as a countermeasure. While inflight behavioral analyses of SFμg exhibit increased activity, postflight analysis displays significant climbing defects, highlighting the sensitivity of behavior to altered gravity. Multi-omics analysis shows alterations in metabolic, oxidative stress and synaptic transmission pathways in both SFμg and SF1g; however, neurological changes immediately postflight, including neuronal loss, glial cell count alterations, oxidative damage, and apoptosis, are seen only in SFμg. Additionally, progressive neuronal loss and a glial phenotype in SF1g and SFμg brains, with pronounced phenotypes in SFμg, are seen upon acclimation to Earth conditions. Overall, our results indicate that artificial gravity partially protects the CNS from the adverse effects of spaceflight.

Thermal and mechanical properties of a high-density polyethylene (HDPE) composite reinforced with wood flour

To keep up with the rate of growth and global demand, it is necessary to manufacture products with high performance and improved durability. Wood-plastic composites (WPCs) are a rapidly growing class of construction materials formed by mixing wood fibers with a polymer matrix at a high temperature. However, significant technical issues remain, such as low thermal resistance, low water resistance, and limited interfacial contact or compatibility between wood fiber and the polymer matrix, which results in poor adhesion of the wood particles, etc. The structure and properties of the matrix/fiber interface can indeed have an impact on the final properties of the composites. To this end, good interfacial adhesion improves stress transmission from the matrix to the fiber, as well as composite performance. Therefore, chemical modification has been the most effective way to chemically bond the matrix to the filler. In this study, the modification is achieved by using maleic anhydride as a coupling agent which promotes the formation of chemical or material bonds between the wood flour (WF) and the polymer matrix. Three WF/high-density polyethylene (HDPE) composite blends with WF contents of 40%, 50%, and 60% were evaluated for density, flexural properties, hardness test, and thermal analysis. Physical tests showed that increasing the wood content of the composite from 40% to 60% increases the density and hardness of the WPC from 1,047 g/cm3 to 1,097 g/cm3 and from 64.5 to 67.7 respectively. On the other hand, increasing the wood flour content to 60% decreases the flexural strength from 37.524 MPa to 27.512 MPa, while the flexural modulus increases from 2176.125 MPa to 3568.284 MPa. In general, the results indicate that the developed WF/HDPE has suitable mechanical and thermal properties for outdoor applications.

Denudation of the Cordillera and intraplate belt in central Patagonia inferred by detrital multi-dating of foreland basin deposits

The evolution of central Patagonia is associated with episodic shortening and extension that have greatly affected the topography of the Cordillera and intraplate belt. The San Jorge Basin is a site of sediment accumulation in the foreland that is surrounded by igneous and broken foreland relief. The latter originated from episodic deformation and reactivation of inherited structures associated with a period of slab shallowing that allowed the far-field transmission of Andean stresses to the foreland. Thus, due to of its location, the San Jorge Basin provides an exceptional opportunity to study the denudation of both Cordilleran and intraplate topography during the Cenozoic, particularly during the late Eocene–early Miocene interval of mild deformation. In this study, we use a single-grain geochronological approach combining apatite fission tracks and UPb dating on apatite, along with maximum deposition ages obtained from UPb zircon dating for Neogene foreland basin deposits, to distinguish between two distinctive sediment source regions in central Patagonia during the Cenozoic, despite the persistent volcanic signal. A compilation of previously published cooling ages combined with our new data define: (i) a dominant local source from the northern broken foreland from the late Eocene until the early Miocene; and (ii) a widespread source in the Cordillera during the Miocene based on a very uniform thermochronological signal observed throughout the entire foreland. Therefore, this study provides new insights into the variation in sediment sourcing in the central Patagonian foreland. This variation is primarily controlled by the decrease of post-orogenic erosional processes during a period of relative tectonic quiescence following the highly active Early Cretaceous–middle Eocene time interval.

On the behavior of an innovative four-layer semi-supported steel plate shear wall

Observations of past earthquakes as well as numerical and experimental studies have confirmed the acceptable performance of Steel Plate Shear Walls (SPSW). Although the SPSW has a number of advantages, it has two major flaws: low elastic-buckling capacity of the infill plate and significant stresses generated by the infill plate on the boundary columns. There are some techniques to overcome these shortcomings. Among them, using the semi-supported SPSW is the most effective one. However, the weak point of this system is the reduction of stiffness and strength of the system in comparison with the conventional SPSW. To resolve this issue, an innovative four-layer semi-supported SPSW has been introduced recently. The system is composed up of the main frame, secondary columns, two corrugated infill plates, and two flat infill plates. Since there is no connection between the infill plates and the mainframe, there is no stress transmission from plates to columns. This fact, in turn, reduces the ductility demand. As a result of the combination of the corrugated and flat plates, the buckling capacity of the wall increases nearly up to the yielding point. This results in a more cost-effective system. The current study presents the results of a comprehensive numerical study to investigate the effect of plate thickness, wall length, and aspect ratio on the behavior of this system under the monotonic lateral load. To obtain the pushover curves, the finite element (FE) software package ABAQUS was utilized. The findings showed that, as the aspect ratio of the wall increases, the wall capacity increases and exceeds the capacity of the frame. Furthermore, the relevant equations for achieving the pushover curve were proposed without the need for FE simulation. Finally, the results showed a good match between the FE results and the intended relations.

Linear Correlation between Active and Resistive Stresses Provides Information on Force Generation and Stress Transmission in Adherent Cells.

Animal cells are active, contractile objects. While bioassays address the molecular characterization of cell contractility, the mechanical characterization of the active forces in cells remains challenging. Here by confronting theoretical analysis and experiments, we calculated both the resistive and the active components of the intracellular stresses that build up following cell adhesion. We obtained a linear relationship between the divergence of the passive stress and the traction forces, which we show is the consequence of the cell adhering and applying forces on the surface only through very localized adhesion points (whose size is inferior to our best resolution, of 400nm). This entails that there are no measurable forces outside of these active point sources, and also that the passive stresses and active stresses inside cells are proportional.

Changes and response mechanism of sugar and organic acids in fruits under water deficit stress.

The content and the ratio of soluble sugars and organic acids in fruits are significant indicators for fruit quality. They are affected by multiple environmental factors, in which water-deficient is the most concern. Previous studies found that the content of soluble sugars and organic acids in fruit displayed great differences under varied water stress. It is important to clarify the mechanism of such difference and to provide researchers with systematic knowledge about the response to drought stress and the mechanism of sugar and acid changes in fruits, so that they can better carry out the study of fruit quality under drought stress. Therefore, the researchers studied dozens of research articles about the content of soluble sugar and organic acid, the activity of related metabolic enzymes, and the expression of related metabolic genes in fruits under water stress, and the stress response of plants to water stress. We found that after plants perceived and transmitted the signal of water deficit, the expression of genes related to the metabolism of soluble sugars and organic acids changed. It was then affected the synthesis of metabolic enzymes and changed their metabolic rate, ultimately leading to changes in soluble sugar and organic acid content. Based on the literature review, we described the pathway diagrams of sugar metabolism, organic acid metabolism, mainly malic acid, tartaric acid, and citric acid metabolism, and of the response to drought stress. From many aspects including plants’ perception of water stress signal, signal conversion and transmission, induced gene expression, the changes in soluble sugar and the enzyme activities of organic acids, as well as the final sugar and acid content in fruits, this thesis summarized previous studies on the influence of water stress on soluble sugars and the metabolism of organic acids in fruits.