Inherent Stress Research Articles

Confirmation of the double-asperity model for the 2016 MW 6.6 Akto earthquake (NW China) by seismic and InSAR data

On November 25, 2016, an MW 6.6 earthquake struck Akto, a county in the Xinjiang Autonomous Region of China. This earthquake nucleated on the dextral steep-dip strike-slip segment of the Muji fault, in the western Tibetan Plateau. In this study we conducted a joint inversion using a higher number of data than in previous works (i.e., teleseismic P and SH waveform, near-field seismic waveform, and coseismic InSAR displacement data), in order to analyze the spatiotemporal rupture process of this seismic event. The results of the joint inversion showed that the event consisted in a primarily unilateral rupture toward east-southeast (along the Muji fault) and that 90% of the scalar seismic moment was released in the first 18 s. Moreover, we confirmed the occurrence of two major asperities: the first one located right next to the hypocenter, and the second one ~30–35 km east of the hypocenter. The first asperity was found at a deeper depth than the second asperity; additionally, it was larger and had a smaller slip. The results of the Coulomb stress change analysis suggested that the rupture of the first asperity triggered the rupture of the second one. The heterogeneity of the on-fault slip revealed the heterogeneity of the inherent strength and stress of the Muji fault; moreover, the clear slip deficit area, characterized by a high Coulomb stress, might indicate a high seismic risk.

Multifactorial and Species-Specific Feedback Regulation of the RNA Surveillance Pathway Nonsense-Mediated Decay in Plants

Nonsense-mediated decay (NMD) is an RNA surveillance mechanism that detects aberrant transcript features and triggers degradation of erroneous as well as physiological RNAs. Originally considered to be constitutive, NMD is now recognized to be tightly controlled in response to inherent signals and diverse stresses. To gain a better understanding of NMD regulation and its functional implications, we systematically examined feedback control of the central NMD components in two dicot and one monocot species. On the basis of the analysis of transcript features, turnover rates and steady-state levels, up-frameshift (UPF) 1, UPF3 and suppressor of morphological defects on genitalia (SMG) 7, but not UPF2, are under feedback control in both dicots. In the monocot investigated in this study, only SMG7 was slightly induced upon NMD inhibition. The detection of the endogenous NMD factor proteins in Arabidopsis thaliana substantiated a negative correlation between NMD activity and SMG7 amounts. Furthermore, evidence was provided that SMG7 is required for the dephosphorylation of UPF1. Our comprehensive and comparative study of NMD feedback control in plants reveals complex and species-specific attenuation of this RNA surveillance pathway, with critical implications for the numerous functions of NMD in physiology and stress responses.

Residual stresses prediction in machining: Hybrid FEM enhanced by assessment of plastic flow

Manufactured components are submitted to thermo-mechanical loads that can blemish their surface integrity and change the inherent residual stress distribution. The discontinuous machining process is relevant to the integrity conception because of their potential application at the end of the manufacturing chain. In order to consolidate a method to predict the residual stress state with a reduced CPU effort, this paper addresses the prediction of residual stress fields resulting from the milling process. The approach is using the hybrid FEM approach combined with the analysis of the plastic flow. The results obtained point out to the validity of the combination of the hybrid method and the visualization of the equivalent stress and equivalent strain rates. Moreover, a direct correspondence between the references and experimental dataset was observed, even when the input data for the model is associated with macro-loads obtained by piezoelectric platform measurements. The determination of the stress state as residual stress in mainly associated to the mesh convergence and the time to equilibrate the plastic flow. A conclusion is drawn regarding the viability of applying the same combination for other manufacturing processes.

Family workers, stress, and the limits of self-care

High levels of work-related stress have been frequently documented among front-line family service providers including social workers, home visitors, and agency staff members. Left unaddressed, such stress contributes to burn-out and job turnover, with negative effects on client families as well as agencies and the workers themselves. In response to this problem, some child and family service organizations have encouraged the use of self-care practices to counteract the inherent stresses of these jobs. The present study reports on descriptions of stress and self-care contained in written portfolios of 99 family workers enrolled in a strength-based training program, the Family Development Credential®.As found in other research, virtually all study participants reported an over-arching sense of stress and anxiety, with specific issues of workload, client problems, and work/family imbalance most frequently mentioned. To deal with their stress, workers described a variety of self-care practices: most common were mindfulness, exercise, social connections, changing self-expectations, and time management. Results show a significant curvilinear relationship between the number of stresses and the number of self-care practices mentioned, such that workers discussing both the lowest and the highest number of stresses discussed fewer self-care practices than workers naming a moderate number of stresses. Although a similar relationship between the level of stress and individuals' ability to take advantage of available resources has been demonstrated for low-income families, to our knowledge the present study is the first empirical demonstration of this principle for people who serve such families. These findings illustrate the limits of individual self-care for dealing with high levels of stress, and suggest the importance of strengthening worker support at the agency level, as well as tailoring stress management programs to the needs of individual workers.

BEEF SPECIES-RUMINANT NUTRITION CACTUS BEEF SYMPOSIUM: Energy and roughage levels in cattle receiving diets and impacts on health, performance, and immune responses1.

Transition of newly received feedlot cattle from a forage- to grain-based diet is challenging, and the appropriate roughage level in receiving diets is debatable. Nutritionists must consider the paradox of dietary transition and roughage level to mitigate ruminal acidosis, yet concomitantly low feed intake presents difficulty in achieving nutrient requirements when metabolic demand is increased due to inherent stress and disease challenge during the receiving period. Previous research suggests that performance is improved at the expense of increased morbidity for newly received cattle consuming diets with less roughage and greater starch concentration. The clinical signs of bovine respiratory disease (BRD) and acute acidosis are analogous; therefore, it is probable that acidotic cattle are incorrectly diagnosed with BRD in both research and production settings. Additional research efforts have attempted to elucidate alterations in microbial populations and digestion, physiological response to inflammatory challenge, and immunological response to infectious bovine rhinotracheitis virus challenge in cattle consuming diets of various roughage levels. Furthermore, our understanding of the rumen microbiome is improving rapidly with culture-independent assays, products such as direct-fed microbials are available, and increased availability and use of fibrous byproduct ingredients requires further attention. Beef cattle nutritionists and producers should consider that the health benefit of receiving diets containing greater levels of roughage and lower energy may not compensate for the reduction in performance compared with feeding receiving diets with lower roughage and greater energy.

Review of Wire Arc Additive Manufacturing for 3D Metal Printing

Wire arc additive manufacturing (WAAM) is a crucial technique in the fabrication of 3D metallic structures. It is increasingly being used worldwide to reduce costs and time. Generally, AM technology is used to overcome the limitations of traditional subtractive manufacturing (SM) for fabricating large-scale components with lower buy-to-fly ratios. There are three heat sources commonly used in WAAM: metal inert gas welding (MIG), tungsten inert gas welding (TIG), and plasma arc welding (PAW). MIG is easier and more convenient than TIG and PAW because it uses a continuous wire spool with the welding torch. Unlike MIG, tungsten inert gas welding (TIG) and plasma arc welding (PAW) need an external wire feed machine to supply the additive materials. WAAM is gaining popularity in the fabrication of 3D metal components, but the process is hard to control due to its inherent residual stress and distortion, which are generated by the high thermal input from its heat sources. Distortion and residual stress are always a challenge for WAAM because they can affect the component’s geometric accuracy and drastically degrade the mechanical properties of the components. In this paper, wire-based and wire arc technology processes for 3D metal printing, including their advantages and limitations are reviewed. The optimization parametric study and modification of WAAM to reduce both residual stress and distortion are tabulated, summarized, and discussed.

Intermediate structural state for maximizing the rejuvenation effect in metallic glass via thermo-cycling treatment

Annealing of metallic glasses (MGs) at temperature near glass transition temperature (Tg) triggers relaxation and often hampers their performances in service. Rejuvenation treatment of MGs by thermal cycling is recently intensively investigated. However, the mechanism responsible for the structural rejuvenation still remains elusive. In this work, we present a systematic study on the rejuvenation effect of a Zr46Cu38Al8Ag8 MG annealed at 0.9Tg for various durations, subjected to thermo-cycling treatment. It is found that well relaxed samples after long-term annealing are almost unaffected, while short-term annealed samples exhibit large rejuvenation effect by thermo-cycling treatment. Using synchrotron X-ray diffraction, we find that thermal cycling results in a disordering at the short-range scale, where the rejuvenation effect is large in a heterogeneous sample. More interestingly, the thermo-cycling treatment on intermediate structure with 20 h-annealed sample relatively exhibits a high degree rejuvenation effect, as compared to shorter- and longer-term annealed samples. This finding indicates that the activation barrier for rejuvenation strongly depends on the original structural states, e.g., free volume, inherent stress and structural heterogeneity.

Alterations in nucleus accumbens kappa opioid receptor‐mediated dopamine inhibition in response to stress and chronic alcohol exposure

Alcohol use disorders (AUDs) are a widely prevalent condition in the United States, made more pernicious by their high comorbidity with disorders of negative affect, such as major depression, anxiety disorders, and post‐traumatic stress disorder. Though underlying disorders of negative affect often predispose individuals to the development of AUDs, emerging evidence has demonstrated the inverse ‐ exposure to chronic alcohol itself may engender vulnerabilities to the development of mood disorders. For example, chronic access to ethanol in a two bottle choice paradigm resulted in the expression of anxiety‐ and depression‐like behavior that lasted long into abstinence in animals that were behaviorally indistinguishable from their control counterparts prior to ethanol exposure. In the present study, we further explored alterations in stress‐related neurobiological systems that may contribute to negative affect‐like behaviors observed during abstinence from chronic ethanol. To this end, we turned to the kappa opioid receptor (KOR) system. Specifically, we focused on the ability of the KOR agonist U50,488 to decrease dopamine release in the nucleus accumbens, a characteristic that is enhanced during early withdrawal following chronic exposure to ethanol, and is believed to contribute to protracted anhedonia during abstinence. We exposed mice to four weeks of chronic intermittent ethanol (CIE) vapor, and subsequently examined negative affect‐like behavior and alterations in KOR‐mediated dopamine release inhibition using fast scan cyclic voltammetry in ex vivo brain slices, both basally and in response to ethanol or stress exposure, following two weeks of abstinence. We found that CIE exposed mice display an increase latency to feed in the novelty‐suppressed feeding paradigm, indicating an increase in negative affect‐like behavior. However, in a separate group of animals, we did not observe increased KOR agonist‐mediated dopamine release inhibition following CIE. We hypothesized that the inherent stress of the novelty‐suppressed feeding paradigm ‐ that is, a fasting period prior to testing ‐ may have uncovered an underlying vulnerability to stressors in animals with a history of CIE. We therefore tested acute exposure to two stressors, a heterotypic fasting stress and a homotypic 2g/kg ethanol (i.p.) stress, in animals with and without a history of chronic ethanol exposure. We found that both stressors were able to acutely augment KOR agonist‐mediated dopamine inhibition in the nucleus accumbens of ethanol‐naïve animals. Interestingly, we found that animals with a history of CIE did not display augmented KOR functioning in response to acute ethanol injection after two weeks of ethanol abstinence. Together, these data indicate that chronic exposure to ethanol may alter stress responsivity, resulting in tolerance to the homotypic stressor ethanol, and increased vulnerability to heterotypic stressors, such as food deprivation, which may confer further susceptibility to stress‐induced ethanol seeking during abstinence.Support or Funding InformationU01 AA014091; T32 AA007565This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Temperature-Insensitive Structure Design of Micromachined Resonant Accelerometers.

Micromachined resonant accelerometers (MRAs), especially those devices fabricated by silicon on glass technology, suffer from temperature drift error caused by inherent thermal stress. This paper proposes two structure designs to attenuate the effect of thermal stress. The first MRA structure is realized by optimizing the locations of the bonding anchors and utilizing a special-shaped substrate to isolate the thermal stress generated during the die attach process. The second structure is designed using an isolation frame fixed by a single anchor to replace all dispersed anchors associated with the suspension beams and micro-levers. Simulated and experimental results show that both of the MRA structures can effectively reduce the thermal stress effect. The experimental results on one MRA prototype indicate that the differential temperature sensitivity reduces down to 1.9 μg/°C and its 15-day bias stability reaches 1.4 μg.

Micro-electro-mechanical-system based capacitive ultrasonic transducer as an efficient immersion sensor

In this paper we have analyzed the influence of the membrane inherent residual stress along with its Young’s modulus for evaluating the characteristics of a capacitive micromachined ultrasonic transducer (CMUT) for medical imaging and sensor applications. The membrane displacement profile, the frequency response characteristic and the coupling coefficient are evaluated and a close conformity with the PZFlex Finite Element method (FEM) simulations has been confirmed. The variation of the coupling coefficient with the different structural parameters indicates the use of thinner membranes with lower transduction gap as efficient transducers. Moreover, coupling factor increases as bias increases and an investigation of the collapse voltage is essential. Various coupling mediums are analyzed to find the transducer equivalent resistance and quality factor to predict its utility as a sensor for gaseous and liquid coupling mediums.

Mind-Body Wellness Project: An Exemplar Case

A growing body of literature concerning the inherent stresses of nursing and medical education report especially high stress levels, in some cases higher than those students in other health professions. Nursing students have attributed their stress to academic, financial, work-related, and interpersonal circumstances.

Dynamic Reliability Analysis of Rotary Steering Drilling System

Abstract. Vibration and high shock are major factors in the failure of downhole tools. It is important to study the causes of vibration and shock formation to prevent failure of the drillstring and bottom hole assembly (BHA). At present, it is generally recognized that the vibration of drillstring is the main reason for the failure, especially the lateral vibration. In this paper, the bottom tool of Rotary Steering Drilling System (RSS) calculation model was established based on the secondary development of ABAQUS software. Starting from the initial configuration of drilling tool, considering the contact impact of drilling tool and borehole wall, the dynamic excitation of guide mechanism and the drilling pressure, torque, rotational speed, gravity, buoyancy, drilling fluid damping. The dynamic characteristics of the inherent frequency and dynamic stress of the bottom hole assembly (BHA) were calculated and analyzed, and risk assessment method based on the quantitative vibration intensity was established. The reliability of typical drilling tool is evaluated, which provides a reference for the optimization design of BHA of Rotary Steering Drilling System.

R-loops: formation, function, and relevance to cell stress

Exposure of genomic, single-stranded DNA (ssDNA) during transcription and replication creates opportunities for the formation of inappropriate secondary structures. Cells manage this exposure by using topoisomerases and helicases to reduce the inherent topological stress that arises from unwinding the double helix and by coating ssDNA with protective protein complexes. Interestingly, specific DNA-RNA hybrids, known as R-loops, form during transcription and exist in homeostasis throughout the genomes of prokaryotes and eukaryotes. These hybrids nucleate from guanine rich clusters in the template strand and extend across GC rich spans of transcribed genes. In vivo regulatory functions have evolved from R-loops, including regulation of gene expression and telomere lengthening. However, they also exist as a form of stress, particularly when replication forks collide with the transcription machinery. New methodologies and models are being developed to delineate the biology of R-loops, including those related to cell stress-based diseases like cancer. As accumulation of R-loops is associated with disease, targeting molecular pathways that regulate their formation or removal could provide new avenues for therapeutic intervention. This review covers recent understandings of the molecular basis for R-loop formation, removal, and biological outcomes in the context of cellular stress.

Analysis of stress distribution in ceramic and titanium implants in alveolar sockets of the anterior region of the maxilla.

BackgroundIn the routine of dentistry, knowing the biomechanical properties of implant systems and their inherent stress distribution under force loading is an essential step to predict structural damage and biological responses. This study aimed to investigate stress distribution in zirconia and titanium implants and their biomechanical response in alveolar sockets of the anterior region of the maxilla through tridimensional finite element analysis.Material and MethodsFrom computed tomography scans of a reference patient, three models of the maxillary dental arch were designed with Rhinoceros 5.0 software (McNeel Europe™, Barcelona, Spain). In each model, a dental implant replaced the maxillary left central incisor. The implants consisted of M1) Zirconia Pure Ceramic Implant Monotype; M2) Zirconia Pure Ceramic ZLA; and M3) Titanium Bone Level - Roxolid SLA. Ceramic crowns were installed in all the implants. Implants and prostheses were loaded with 50N oblique and axial forces. Von-Mises and Mohr Coulomb criteria were used to assess stress distribution in the implant systems and perimplantar bone, respectively.ResultsTraction was detected in the cervical region of the palatal bone surface of all the models. Oppositely, compression was found in the cervical region of the vestibular bone surfaces.ConclusionsZirconia Pure Ceramic Implant Monotype had the best response under oblique force loading. Ceramic implants may be an alternative to replace titanium implants in fresh alveolar sockets in the anterior region of the maxilla. Key words:Finite elements, implants, stress, ceramic, titanium.

Sensitivity Analysis of a Wall Boundary Condition for the Turbulent Pipe Flow of Herschel–Bulkley Fluids

This article follows from a previous study by the authors on the computational fluid dynamics-based analysis of Herschel–Bulkley fluids in a pipe-bounded turbulent flow. The study aims to propose a numerical method that could support engineering processes involving the design and implementation of a waste water transport system, for concentrated domestic slurry. Concentrated domestic slurry results from the reduction in the amount of water used in domestic activities (and also the separation of black and grey water). This primarily saves water and also increases the concentration of nutrients and biomass in the slurry, facilitating efficient recovery. Experiments revealed that upon concentration, domestic slurry flows as a non-Newtonian fluid of the Herschel–Bulkley type. An analytical solution for the laminar transport of such a fluid is available in literature. However, a similar solution for the turbulent transport of a Herschel–Bulkley fluid is unavailable, which prompted the development of an appropriate wall function to aid the analysis of such flows. The wall function (called ψ 1 hereafter) was developed using Launder and Spalding’s standard wall function as a guide and was validated against a range of experimental test-cases, with positive results. ψ 1 is assessed for its sensitivity to rheological parameters, namely the yield stress, the fluid consistency index and the behaviour index and their impact on the accuracy with which ψ 1 can correctly quantify the pressure loss through a pipe. This is done while simulating the flow of concentrated domestic slurry using the Reynolds-Averaged Navier–Stokes (RANS) approach for turbulent flows. This serves to establish an operational envelope in terms of the rheological parameters and the average flow velocity within which ψ 1 is a must for accuracy. One observes that, regardless of the fluid behaviour index, ψ 1 is necessary to ensure accuracy with RANS models only in flow regimes where the wall shear stress is comparable to the yield stress within an order of magnitude. This is also the regime within which the concentrated slurry analysed as part of this research flows, making ψ 1 a requirement. In addition, when the wall shear stress exceeds the yield stress by more than one order (either due to an inherent lower yield stress or a high flow velocity), the regular Newtonian wall function proposed by Launder and Spalding is sufficient for an accurate estimate of the pressure loss, owing to the relative reduction in non-Newtonian viscosity as compared to the turbulent viscosity.

Methodology of studying the mechanical properties of composite materials (reinforced concrete)

The mechanical properties of a complex composite material formed by steel and hardened concrete, are studied. A technique of operative quality control of new credible concrete and reinforcement, both in laboratory and field conditions is developed for determination of the strength and strain characteristics of materials, as well as cohesion forces determining their joint operation under load. The design of the mobile unit is presented. The unit provides a possibility of changing the direction of loading and testing the reinforced element of the given shape both for tension and compression. Moreover, the nomenclature of testing equipment and the number of molds for manufacturing concrete samples substantially decrease. Using the values of forcing resulting in concrete cracking when the joint work of concrete and reinforcement is disrupted the values of the inherent stresses and strains attributed to the concrete shrinkage are determined. An analytical relationship between the forces and deformations of the reinforced concrete sample with central reinforcement is derived for axial tension and compression, with allowance for strains and stresses in the reinforcement and concrete resulted from concrete shrinkage. The results of experimental studies are presented, including tension diagrams and diagrams of developing axial deformations with an increase in the load under the central loading of the reinforced elements. A methodology of accounting for stresses and deformations resulted from concrete shrinkage is developed. The applicability of the derived analytical relationships between stresses and deformations on the material diagrams to calculations of the reinforced concrete structures in the framework of the deformation model is estimated.

Investigation of the performance of strain-engineered silicon nanowire field effect transistors (ɛ-Si-NWFET) on IOS substrates

In the current work, a design space for developing the performance enhanced strain-engineered Si nanowire field-effect-transistors has been provided. The fraction of insertion of the nanowire channel into the Insulator-on-Silicon substrate with judicious selection of high-k gate insulators is used as the key design parameter. The combined effect of fractional insertion and gate insulators results in inducing stress into the nanowire channel and, depending on their selection, it changes from tensile to compressive. Such induced-stress alters the existing inherent phononic-stress, leading to the modification of the carrier transport in the device channel. The carrier transport behavior in such partially embedded nanowire FETs has been modeled by incorporating the relevant stress-related effects into the indigenously developed self-consistent quantum-electrostatic framework. These equations are solved by employing the non-equilibrium Green's function formalism. The study shows the phonon scattering under tensile strain to occur at the expense of electron energy; however, the electrons can also gain energy during such scattering in compressive stress. Thus, the device current has been observed to increase with tensile stress and it achieves relatively smaller values when the inherent tensile phononic stress is balanced by the induced compressive stress. However, the current is finally observed to increase once the compressive stress overcomes the inherent tensile phononic stress. In general, the present devices exhibit promising Ion/Ioff ratio for all of the fractional insertions and gate dielectrics with a maximum Ioff of <10 nA/μm, threshold voltage of sub-0.3 V, gm of ∼104 µS/µm, sub-threshold swing of ∼100 mV/dec, and drain-induced-barrier-lowering of ∼100 mV/V.

Epitaxial thin film transfer for flexible devices from reusable substrates

A new epitaxial thin film transfer method is introduced which utilizes film/substrate systems with sufficiently strong interaction for heteroepitaxial alignment, but with weak adhesion interaction such that inherent stress caused by heteroepitaxy combined with thermomechanical stress causes the deposited structures to separate at the interface. The thin films retain their optical and structural properties following the transfer process to a secondary carrier, leaving the growth substrate for further reuse. We demonstrate the application of this technique by synthesizing a simple crystalline II–VI heterostructure device on sapphire and transferring it to a polysulfone flexible carrier. Devices produced by this method eliminate the need for selective chemical etch layers, ion-implantation or complex post-processing of the growth substrate, reducing processing steps and cost as well as providing the advantage of substrate flexibility compared to what is possible by conventional fabrication techniques.

Residual stress measurements of laser metal deposited Ti-6Al-4V parts using neutron diffraction

Strength of laser deposited parts is in strong dependence on microstructure, residual stresses, size and shape of defects. Knowledge of the residual stress field is crucial for a thorough understanding of the likely subsequent fatigue behaviour and fracture of the part during deposition. Neutron diffraction methods are well established for the study of residual stresses deep inside components. Neutron diffraction has the potential for measurement deep within metallic components. Distribution of residual stress in Ti-6Al-4V wall deposited on the stiff substrate was measured. Finite element simulation was carried out in order to obtain transient and residual inherent stress in the fabricated part. It was shown that peak tensile normal stress exceeds yield stress at the start and end of deposited wall near the substrate. Peak tensile longitudinal stress corresponds to the last deposited layer and lower than yield stress.

Comparative effects of seawater acidification on microalgae: Single and multispecies toxicity tests

In order to gain knowledge about the potential effects of acidification in aquatic ecosystems, global change research based on microalgae as sentinel species has been often developed. However, these studies are limited to single species tests and there is still a research gap about the behaviour of microalgal communities under this environmental stressor. Thus, the aim of this study was to assess the negative effects of CO2 under an ecologically realistic scenario. To achieve this objective, two types of toxicity tests were developed; i) single toxicity tests and ii) multispecies toxicity tests, in order to evaluate the effects on each species as well as the interspecific competition. For this purpose, three microalgae species (Tetraselmis chuii, Phaeodactylum tricornutum and Nannochloropsis gaditana) were exposed to two selected pH levels (7.4, 6.0) and a control (pH 8.0). The pH values were choosen for testing different scenarios of CO2 enrichment including the exchange atmosphere-ocean (pH 7.4) and natural or anthropogenic sources of CO2 (pH 6.0). The effects on growth, cell viability, oxidative stress, plus inherent cell properties (size, complexity and autofluorescence) were studied using flow cytometry (FCM). Results showed that T. chuii was the most resistant species to CO2 enrichment with less abrupt changes in terms of cell density, inherent cell properties, oxidative stress and cell viability. Although P. tricornutum was the dominant species in both single and multispecies tests, this species showed the highest decrease in cell density under pH 6.0. Effects of competence were recorded in the multispecies control (pH 8) but this competence was eclipsed by the effects of low pH. The knowledge of biological interactions made by different microalgae species is a useful tool to extrapolate research data from laboratory to the field.