Potential Mechanisms Underlying Response to Effects of the Fungicide Pyrimethanil from Gene Expression Profiling inSaccharomyces cerevisiae

OpenAIRE

Gil, Fátima N.; Becker, Jörg D.; Viegas, Cristina A.

2014-01-01

Pyrimethanil is a fungicide mostly applied in vineyards. When misused, residue levels detected in grape must or in the environment may be of concern. The present work aimed to analyze mechanisms underlying response to deleterious effects of pyrimethanil in the eukaryotic model Saccharomyces cerevisiae. Pyrimethanil concentration-dependent effects at phenotypic (inhibition of growth) and transcriptomic levels were examined. For transcriptional profiling, analysis focused on two sublethal expos...

Strain-rate effect on initial crush stress of irregular honeycomb under dynamic loading and its deformation mechanism

Science.gov (United States)

Wang, Peng; Zheng, Zhijun; Liao, Shenfei; Yu, Jilin

2018-02-01

The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored. The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.

On some mechanisms of the effect of thermal prehistory on the behavior of silicon parameters under irradiation

International Nuclear Information System (INIS)

Nejmash, V.B.; Sagan, T.R.; Tsmots', V.M.; Shakhovtsov, V.I.; Shindich, V.L.

1991-01-01

The effect of preliminary thermal treatment (TT) in 400-1200 degC temperature range on the behavior of Si monocrystal parameters under subsequent γ-, electron and neutron irradiation is investigated. Five mechanisms of Si thermal prehistory effect on its properties are proposed: 1) decomposition of solid solutions of impurities interacting with radiation defects (RD); 2) formation of electrically active thermal defects (TD) in concentrations wich are sufficient for a significant alteration of RD charged state; 3) origination of TD, which can efficiency as aresult of the redistribution of impurities under thermal treatment; 5) formation of clusters of electrically active TD, resulting in the disturbance of electric homogeneity of Si crystal

Underlying mechanisms of improving physical activity behavior after rehabilitation

NARCIS (Netherlands)

van der Ploeg, H.P.; Streppel, K.R.; van der Beek, A.J.; van der Woude, L.H.V.; van Harten, W.H.; van Mechelen, W.

2008-01-01

Background: Regular physical activity is beneficial for the health and functioning of people with a disability. Effective components of successful physical activity promotion interventions should be identified and disseminated. Purpose: To study the underlying mechanisms of the combined sport

Underlying Mechanisms of Improving Physical Activity Behavior after Rehabilitation

NARCIS (Netherlands)

van der Ploeg, Hidde P.; Streppel, Kitty R.M.; van der Beek, Allard J.; Woude, Luc H.V.; van Harten, Willem H.; Vollenbroek-Hutten, Miriam Marie Rosé; van Mechelen, Willem

2008-01-01

Background: Regular physical activity is beneficial for the health and functioning of people with a disability. Effective components of successful physical activity promotion interventions should be identified and disseminated. Purpose: To study the underlying mechanisms of the combined sport

Fracture mechanics of hydroxyapatite single crystals under geometric confinement.

Science.gov (United States)

Libonati, Flavia; Nair, Arun K; Vergani, Laura; Buehler, Markus J

2013-04-01

Geometric confinement to the nanoscale, a concept that refers to the characteristic dimensions of structural features of materials at this length scale, has been shown to control the mechanical behavior of many biological materials or their building blocks, and such effects have also been suggested to play a crucial role in enhancing the strength and toughness of bone. Here we study the effect of geometric confinement on the fracture mechanism of hydroxyapatite (HAP) crystals that form the mineralized phase in bone. We report a series of molecular simulations of HAP crystals with an edge crack on the (001) plane under tensile loading, and we systematically vary the sample height whilst keeping the sample and the crack length constant. We find that by decreasing the sample height the stress concentration at the tip of the crack disappears for samples with a height smaller than 4.15nm, below which the material shows a different failure mode characterized by a more ductile mechanism with much larger failure strains, and the strength approaching that of a flaw-less crystal. This study directly confirms an earlier suggestion of a flaw-tolerant state that appears under geometric confinement and may explain the mechanical stability of the reinforcing HAP platelets in bone. Copyright © 2012 Elsevier Ltd. All rights reserved.

A hypothesis regarding the molecular mechanism underlying dietary soy-induced effects on seizure propensity.

Directory of Open Access Journals (Sweden)

Cara Jean Westmark

2014-09-01

Full Text Available Numerous neurological disorders including fragile X syndrome, Down syndrome, autism and Alzheimer’s disease are comorbid with epilepsy. We have observed elevated seizure propensity in mouse models of these disorders dependent on diet. Specifically, soy-based diets exacerbate audiogenic-induced seizures in juvenile mice. We have also found potential associations between the consumption of soy-based infant formula and seizure incidence, epilepsy comorbidity and autism diagnostic scores in autistic children by retrospective analyses of medical record data. In total, these data suggest that consumption of high levels of soy protein during postnatal development may affect neuronal excitability. Herein, we present our theory regarding the molecular mechanism underlying soy-induced effects on seizure propensity. We hypothesize that soy phytoestrogens interfere with metabotropic glutamate receptor signaling through an estrogen receptor-dependent mechanism, which results in elevated production of key synaptic proteins and decreased seizure threshold.

Amount of fear extinction changes its underlying mechanisms.

Science.gov (United States)

An, Bobae; Kim, Jihye; Park, Kyungjoon; Lee, Sukwon; Song, Sukwoon; Choi, Sukwoo

2017-07-03

There has been a longstanding debate on whether original fear memory is inhibited or erased after extinction. One possibility that reconciles this uncertainty is that the inhibition and erasure mechanisms are engaged in different phases (early or late) of extinction. In this study, using single-session extinction training and its repetition (multiple-session extinction training), we investigated the inhibition and erasure mechanisms in the prefrontal cortex and amygdala of rats, where neural circuits underlying extinction reside. The inhibition mechanism was prevalent with single-session extinction training but faded when single-session extinction training was repeated. In contrast, the erasure mechanism became prevalent when single-session extinction training was repeated. Moreover, ablating the intercalated neurons of amygdala, which are responsible for maintaining extinction-induced inhibition, was no longer effective in multiple-session extinction training. We propose that the inhibition mechanism operates primarily in the early phase of extinction training, and the erasure mechanism takes over after that.

Effect of Ionizing Beta Radiation on the Mechanical Properties of Poly(ethylene under Thermal Stress

Directory of Open Access Journals (Sweden)

Bednarik Martin

2016-01-01

Full Text Available It was found in this study, that ionizing beta radiation has a positive effect on the mechanical properties of poly(ethylene. In recent years, there have been increasing requirements for quality and cost effectiveness of manufactured products in all areas of industrial production. These requirements are best met with the polymeric materials, which have many advantages in comparison to traditional materials. The main advantages of polymer materials are especially in their ease of processability, availability, and price of the raw materials. Radiation crosslinking is one of the ways to give the conventional plastics mechanical, thermal, and chemical properties of expensive and highly resistant construction polymers. Several types of ionizing radiation are used for crosslinking of polymers. Each of them has special characteristics. Electron beta and photon gamma radiation are used the most frequently. The great advantage is that the crosslinking occurs after the manufacturing process at normal temperature and pressure. The main purpose of this paper has been to determine the effect of ionizing beta radiation on the tensile modulus, strength and elongation of low and high density polyethylene (LDPE and HDPE. These properties were examined in dependence on the dosage of the ionizing beta radiation (non-irradiated samples and those irradiated by dosage 99 kGy were compared and on the test temperature. Radiation cross-linking of LDPE and HDPE results in increased tensile strength and modulus, and decreased of elongation. The measured results indicate that ionizing beta radiation treatment is effective tool for improvement of mechanical properties of LDPE and HDPE under thermal stress.

Experimental Investigation into Corrosion Effect on Mechanical Properties of High Strength Steel Bars under Dynamic Loadings

Directory of Open Access Journals (Sweden)

Hui Chen

2018-01-01

Full Text Available The tensile behaviors of corroded steel bars are important in the capacity evaluation of corroded reinforced concrete structures. The present paper studies the mechanical behavior of the corroded high strength reinforcing steel bars under static and dynamic loading. High strength reinforcing steel bars were corroded by using accelerated corrosion methods and the tensile tests were carried out under different strain rates. The results showed that the mechanical properties of corroded high strength steel bars were strain rate dependent, and the strain rate effect decreased with the increase of corrosion degree. The decreased nominal yield and ultimate strengths were mainly caused by the reduction of cross-sectional areas, and the decreased ultimate deformation and the shortened yield plateau resulted from the intensified stress concentration at the nonuniform reduction. Based on the test results, reduction factors were proposed to relate the tensile behaviors with the corrosion degree and strain rate for corroded bars. A modified Johnson-Cook strength model of corroded high strength steel bars under dynamic loading was proposed by taking into account the influence of corrosion degree. Comparison between the model and test results showed that proposed model properly describes the dynamic response of the corroded high strength rebars.

The effects of divided attention on encoding processes under incidental and intentional learning instructions: underlying mechanisms?

Science.gov (United States)

Naveh-Benjamin, Moshe; Guez, Jonathan; Hara, Yoko; Brubaker, Matthew S; Lowenschuss-Erlich, Iris

2014-01-01

Divided attention (DA) at encoding has been shown to significantly disrupt later memory for the studied information. However, what type of processing gets disrupted during DA remains unresolved. In this study, we assessed the degree to which strategic effortful processes are affected under DA by comparing the effects of DA at encoding under intentional and pure incidental learning instructions. In three experiments, participants studied list of words or word pairs under either full or divided attention. Results of three experiments, which used different methodologies, converged to show that the effects of DA at encoding reduce memory performance to the same degree under incidental and intentional learning. Secondary task performance indicated that encoding under intentional learning instructions was more effortful than under incidental learning instructions. In addition, the results indicated enhanced attention to the initial appearance of the words under both types of learning instructions. Results are interpreted to imply that other processes, rather than only strategic effortful ones, might be affected by DA at encoding.

Music and Memory in Alzheimer's Disease and The Potential Underlying Mechanisms.

Science.gov (United States)

Peck, Katlyn J; Girard, Todd A; Russo, Frank A; Fiocco, Alexandra J

2016-01-01

With population aging and a projected exponential expansion of persons diagnosed with Alzheimer's disease (AD), the development of treatment and prevention programs has become a fervent area of research and discovery. A growing body of evidence suggests that music exposure can enhance memory and emotional function in persons with AD. However, there is a paucity of research that aims to identify specific underlying neural mechanisms associated with music's beneficial effects in this particular population. As such, this paper reviews existing anecdotal and empirical evidence related to the enhancing effects of music exposure on cognitive function and further provides a discussion on the potential underlying mechanisms that may explain music's beneficial effect. Specifically, this paper will outline the potential role of the dopaminergic system, the autonomic nervous system, and the default network in explaining how music may enhance memory function in persons with AD.

The effect of grain and pore sizes on the mechanical behavior of thin Al films deposited under different conditions

International Nuclear Information System (INIS)

Ben-David, E.; Landa, M.; Janovská, M.; Seiner, H.; Gutman, O.; Tepper-Faran, T.; Shilo, D.

2015-01-01

This paper presents a comprehensive study of the relationships between deposition conditions, microstructure and mechanical behavior in thin aluminum films commonly used in micro and nano-devices. A particular focus is placed on the effect of porosity, which is present in all thin films deposited by evaporation or sputtering techniques. The influences of the deposition temperature on the grain size, pore size and crystallographic texture were characterized by X-ray diffraction and scanning electron microscopy. The mechanical behavior of the films was investigated using four different methods. Each method is suitable for characterizing different properties and for testing the material at different length scales. Nanoindentation was used to study hardness at the level of individual grains; resonant ultrasound spectroscopy was used to measure the elastic moduli and porosity; and bulge and tensile tests were used to study released films under biaxial and uniaxial tensions. Our results demonstrate that even low porosities may have tremendous effects on the mechanical properties and that different methods allow the capture of different aspects of these effects. Therefore, a combination of several methods is required to obtain a comprehensive understanding of the mechanical behavior of a film. It is also shown that porosity with different pore size leads to very different effects on the mechanical behavior

Reactive Molecular Dynamics Simulations to Understand Mechanical Response of Thaumasite under Temperature and Strain Rate Effects.

Science.gov (United States)

Hajilar, Shahin; Shafei, Behrouz; Cheng, Tao; Jaramillo-Botero, Andres

2017-06-22

Understanding the structural, thermal, and mechanical properties of thaumasite is of great interest to the cement industry, mainly because it is the phase responsible for the aging and deterioration of civil infrastructures made of cementitious materials attacked by external sources of sulfate. Despite the importance, effects of temperature and strain rate on the mechanical response of thaumasite had remained unexplored prior to the current study, in which the mechanical properties of thaumasite are fully characterized using the reactive molecular dynamics (RMD) method. With employing a first-principles based reactive force field, the RMD simulations enable the description of bond dissociation and formation under realistic conditions. From the stress-strain curves of thaumasite generated in the x, y, and z directions, the tensile strength, Young's modulus, and fracture strain are determined for the three orthogonal directions. During the course of each simulation, the chemical bonds undergoing tensile deformations are monitored to reveal the bonds responsible for the mechanical strength of thaumasite. The temperature increase is found to accelerate the bond breaking rate and consequently the degradation of mechanical properties of thaumasite, while the strain rate only leads to a slight enhancement of them for the ranges considered in this study.

Self-DNA inhibitory effects: Underlying mechanisms and ecological implications.

Science.gov (United States)

Cartenì, Fabrizio; Bonanomi, Giuliano; Giannino, Francesco; Incerti, Guido; Vincenot, Christian Ernest; Chiusano, Maria Luisa; Mazzoleni, Stefano

2016-01-01

DNA is usually known as the molecule that carries the instructions necessary for cell functioning and genetic inheritance. A recent discovery reported a new functional role for extracellular DNA. After fragmentation, either by natural or artificial decomposition, small DNA molecules (between ∼50 and ∼2000 bp) exert a species specific inhibitory effect on individuals of the same species. Evidence shows that such effect occurs for a wide range of organisms, suggesting a general biological process. In this paper we explore the possible molecular mechanisms behind those findings and discuss the ecological implications, specifically those related to plant species coexistence.

Mechanisms of action underlying the anti-inflammatory and immunomodulatory effects of propolis: a brief review

Directory of Open Access Journals (Sweden)

Marcio A. R. Araujo

2011-09-01

Full Text Available Many biological properties have been attributed to various types of propolis, including anti-inflammatory, antimicrobial, antioxidant, antitumor, wound healing, and immunomodulatory activities. This article reviewed studies published that investigated the anti-inflammatory activity of propolis of different origins and/or its isolated components, focusing on the mechanisms of action underlying this activity and also addressing some aspects of immunomodulatory effects. The search was performed of the following databases: PubMed, Science Direct, HighWire Press, Scielo, Google Academics, Research Gate and ISI Web of Knowledgement. The anti-inflammatory activity was associated with propolis or compounds such as polyphenols (flavonoids, phenolic acids and their esters, terpenoids, steroids and amino acids. CAPE is the most studied compounds. The main mechanisms underlying the anti-inflammatory activity of propolis included the inhibition of cyclooxygenase and consequent inhibition of prostaglandin biosynthesis, free radical scavenging, inhibition of nitric oxide synthesis, reduction in the concentration of inflammatory cytokines and immunosuppressive activity. Propolis was found to exert an anti-inflammatory activity in vivo and in vitro models of acute and chronic inflammation and others studies, indicating its promising potential as anti-inflammatory agent of natural origin and as a source of chemical compounds for the development of new drugs.

General equilibrium effects of a supply side GHG mitigation option under the Clean Development Mechanism.

Science.gov (United States)

Timilsina, Govinda R; Shrestha, Ram M

2006-09-01

The Clean Development Mechanism (CDM) under the Kyoto Protocol to the United Nations Framework Convention on Climate Change is considered a key instrument to encourage developing countries' participation in the mitigation of global climate change. Reduction of greenhouse gas (GHG) emissions through the energy supply and demand side activities are the main options to be implemented under the CDM. This paper analyses the general equilibrium effects of a supply side GHG mitigation option-the substitution of thermal power with hydropower--in Thailand under the CDM. A static multi-sector general equilibrium model has been developed for the purpose of this study. The key finding of the study is that the substitution of electricity generation from thermal power plants with that from hydropower plants would increase economic welfare in Thailand. The supply side option would, however, adversely affect the gross domestic product (GDP) and the trade balance. The percentage changes in economic welfare, GDP and trade balance increase with the level of substitution and the price of certified emission reduction (CER) units.

Heavy-ion radiobiology: new approaches to delineate mechanisms underlying enhanced biological effectiveness

Science.gov (United States)

Blakely, E. A.; Kronenberg, A.; Chatterjee, A. (Principal Investigator)

1998-01-01

Shortly after the discovery of polonium and radium by Marie Curie and her husband and colleague, Pierre Curie, it was learned that exposure to these alpha-particle emitters produced deleterious biological effects. The mechanisms underlying the increased biological effectiveness of densely ionizing radiations, including alpha particles, neutrons and highly energetic heavy charged particles, remain an active area of investigation. In this paper, we review recent advances in several areas of the radiobiology of these densely ionizing radiations, also known as heavy ions. Advances are described in the areas of DNA damage and repair, chromosome aberrations, mutagenesis, neoplastic transformation in vitro, genomic instability, normal tissue radiobiology and carcinogenesis in vivo. We focus on technical innovations, including novel applications of pulsed-field gel electrophoresis, fluorescence in situ hybridization (FISH), linkage analysis, and studies of gene expression and protein expression. We also highlight the use of new cellular and animal systems, including those with defined DNA repair deficiencies, as well as epithelial cell model systems to assess neoplastic transformation both in vitro and in vivo. The studies reviewed herein have had a substantial impact on our understanding of the genotoxic effects of heavy ions as well as their distinct effects on tissue homeostasis. The use of these radiations in cancer therapy is also discussed. The use of both heavy-ion and proton therapy is on the upswing in several centers around the world, due to their unique energy deposition characteristics that enhance the therapeutic effect and help reduce damage to normal tissue.

Numerical and experimental studies of mechanisms underlying the effect of pulsed broadband terahertz radiation on nerve cells

Energy Technology Data Exchange (ETDEWEB)

Duka, M V; Dvoretskaya, L N; Babelkin, N S; Khodzitskii, M K; Chivilikhin, S A; Smolyanskaya, O A [St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg (Russian Federation)

2014-08-31

We have studied the mechanisms underlying the effect of pulsed broadband terahertz radiation on the growth of neurites of sensory ganglia using a comparative analysis of measured reflection spectra of ganglion neurites (in the frequency range 0.1 – 2.0 THz) and spectra obtained by numerical simulation with CST Microwave Studio. The observed changes are shown to be mainly due to pulse energy absorption in the ganglion neurites. Of particular interest are the observed single resonance frequencies related to resonance size effects, which can be used to irradiate ganglia in order to activate their growth. (laser biophotonics)

Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

Energy Technology Data Exchange (ETDEWEB)

Utz, S.; Soppa, E.; Silcher, H.; Kohler, C. [Stuttgart Univ. (Germany). Materials Testing Inst.

2013-07-01

The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

Mechanism of crack initiation and crack growth under thermal and mechanical fatigue loading

International Nuclear Information System (INIS)

Utz, S.; Soppa, E.; Silcher, H.; Kohler, C.

2013-01-01

The present contribution is focused on the experimental investigations and numerical simulations of the deformation behaviour and crack development in the austenitic stainless steel X6CrNiNb18-10 under thermal and mechanical cyclic loading in HCF and LCF regimes. The main objective of this research is the understanding of the basic mechanisms of fatigue damage and the development of simulation methods, which can be applied further in safety evaluations of nuclear power plant components. In this context the modelling of crack initiation and crack growth inside the material structure induced by varying thermal or mechanical loads are of particular interest. The mechanisms of crack initiation depend among other things on the type of loading, microstructure, material properties and temperature. The Nb-stabilized austenitic stainless steel in the solution-annealed condition was chosen for the investigations. Experiments with two kinds of cyclic loading - pure thermal and pure mechanical - were carried out and simulated. The fatigue behaviour of the steel X6CrNiNb18-10 under thermal loading was studied within the framework of the joint research project [4]. Interrupted thermal cyclic tests in the temperature range of 150 C to 300 C combined with non-destructive residual stress measurements (XRD) and various microscopic investigations, e.g. in SEM (Scanning Electron Microscope), were used to study the effects of thermal cyclic loading on the material. This thermal cyclic loading leads to thermal induced stresses and strains. As a result intrusions and extrusions appear inside the grains (at the surface), at which microcracks arise and evolve to a dominant crack. Finally, these microcracks cause a continuous and significant decrease of residual stresses. The fatigue behaviour of the steel X6CrNiNb18-10 under mechanical loading at room temperature was studied within the framework of the research project [5], [8]. With a combination of interrupted LCF tests and EBSD

Peripheral afferent mechanisms underlying acupuncture inhibition of cocaine behavioral effects in rats.

Directory of Open Access Journals (Sweden)

Seol Ah Kim

Full Text Available Administration of cocaine increases locomotor activity by enhancing dopamine transmission. To explore the peripheral mechanisms underlying acupuncture treatment for drug addiction, we developed a novel mechanical acupuncture instrument (MAI for objective mechanical stimulation. The aim of this study was to evaluate whether acupuncture inhibition of cocaine-induced locomotor activity is mediated through specific peripheral nerves, the afferents from superficial or deep tissues, or specific groups of nerve fibers. Mechanical stimulation of acupuncture point HT7 with MAI suppressed cocaine-induced locomotor activity in a stimulus time-dependent manner, which was blocked by severing the ulnar nerve or by local anesthesia. Suppression of cocaine-induced locomotor activity was elicited after HT7 stimulation at frequencies of either 50 (for Meissner corpuscles or 200 (for Pacinian corpuscles Hz and was not affected by block of C/Aδ-fibers in the ulnar nerve with resiniferatoxin, nor generated by direct stimulation of C/Aδ-fiber afferents with capsaicin. These findings suggest that HT7 inhibition of cocaine-induced locomotor activity is mediated by A-fiber activation of ulnar nerve that originates in superficial and deep tissue.

Carbon Footprint Management of Road Freight Transport under the Carbon Emission Trading Mechanism

Directory of Open Access Journals (Sweden)

Jin Li

2015-01-01

Full Text Available Growing concern over environmental issues has considerably increased the number of regulations and legislation that aim to curb carbon emissions. Carbon emission trading mechanism, which is one of the most effective means, has been broadly adopted by several countries. This paper presents a road truck routing problem under the carbon emission trading mechanism. By introducing a calculation method of carbon emissions that considers the load and speed of the vehicle among other factors, a road truck routing optimizing model under the cap and trade mechanism based on the Travelling Salesman Problem (TSP is described. Compared with the classical TSP model that only considers the economic cost, this model suggests that the truck routing decision under the cap and trade mechanism is more effective in reducing carbon emissions. A modified tabu search algorithm is also proposed to obtain solutions within a reasonable amount of computation time. We theoretically and numerically examine the impacts of carbon trading, carbon cap, and carbon price on truck routing decision, carbon emissions, and total cost. From the results of numerical experiments, we derive interesting observations about how to control the total cost and reduce carbon emissions.

Temporomandibular disorders and painful comorbidities: clinical association and underlying mechanisms.

Science.gov (United States)

Costa, Yuri Martins; Conti, Paulo César Rodrigues; de Faria, Flavio Augusto Cardoso; Bonjardim, Leonardo Rigoldi

2017-03-01

The association between temporomandibular disorders (TMDs) and headaches, cervical spine dysfunction, and fibromyalgia is not artefactual. The aim of this review is to describe the comorbid relationship between TMD and these three major painful conditions and to discuss the clinical implications and the underlying pain mechanisms involved in these relationships. Common neuronal pathways and central sensitization processes are acknowledged as the main factors for the association between TMD and primary headaches, although the establishment of cause-effect mechanisms requires further clarification and characterization. The biomechanical aspects are not the main factors involved in the comorbid relationship between TMD and cervical spine dysfunction, which can be better explained by the neuronal convergence of the trigeminal and cervical spine sensory pathways as well as by central sensitization processes. The association between TMD and fibromyalgia also has supporting evidence in the literature, and the proposed main mechanism underlying this relationship is the impairment of the descending pain inhibitory system. In this particular scenario, a cause-effect relationship is more likely to occur in one direction, that is, fibromyalgia as a risk factor for TMD. Therefore, clinical awareness of the association between TMD and painful comorbidities and the support of multidisciplinary approaches are required to recognize these related conditions. Copyright © 2016 Elsevier Inc. All rights reserved.

Peeling mechanism of tomato under infrared heating

Science.gov (United States)

Critical behaviors of peeling tomatoes using infrared heat are thermally induced peel loosening and subsequent cracking. However, the mechanism of peel loosening and cracking due to infrared heating remains unclear. This study aimed at investigating the mechanism of peeling tomatoes under infrared h...

Effects of fatigue on microstructure and mechanical properties of bone organic matrix under compression

International Nuclear Information System (INIS)

Trębacz, Hanna; Zdunek, Artur; Cybulska, Justyna; Pieczywek, Piotr

2013-01-01

The aim of the study was to investigate whether a fatigue induced weakening of cortical bone was revealed in microstructure and mechanical competence of demineralized bone matrix. Two types of cortical bone samples (plexiform and Haversian) were use. Bone slabs from the midshaft of bovine femora were subjected to cyclical bending. Fatigued and adjacent control samples were cut into cubes and demineralized in ethylenediaminetetraacetic acid. Demineralized samples were either subjected to microscopic quantitative image analysis, or compressed to failure (in longitudinal or transverse direction) with a simultaneous analysis of acoustic emission (AE). In fatigued samples porosity of organic matrix and average area of pores have risen, along with a change in the pores shape. The effect of fatigue depended on the type of the bone, being more pronounced in the plexiform than in Haversian tissue. Demineralized bone matrix was anisotropic under compressive loads in both types of cortical structure. The main result of fatigue pretreatment on mechanical parameters was a significant decrease of ultimate strain in the transverse direction in plexiform samples. The decrease of strain in this group was accompanied by a considerable increase of the fraction of large pores and a significant change in AE energy.

Acoustic and mechanical response of reservoir rocks under variable saturation and effective pressure.

Science.gov (United States)

Ravazzoli, C L; Santos, J E; Carcione, J M

2003-04-01

We investigate the acoustic and mechanical properties of a reservoir sandstone saturated by two immiscible hydrocarbon fluids, under different saturations and pressure conditions. The modeling of static and dynamic deformation processes in porous rocks saturated by immiscible fluids depends on many parameters such as, for instance, porosity, permeability, pore fluid, fluid saturation, fluid pressures, capillary pressure, and effective stress. We use a formulation based on an extension of Biot's theory, which allows us to compute the coefficients of the stress-strain relations and the equations of motion in terms of the properties of the single phases at the in situ conditions. The dry-rock moduli are obtained from laboratory measurements for variable confining pressures. We obtain the bulk compressibilities, the effective pressure, and the ultrasonic phase velocities and quality factors for different saturations and pore-fluid pressures ranging from normal to abnormally high values. The objective is to relate the seismic and ultrasonic velocity and attenuation to the microstructural properties and pressure conditions of the reservoir. The problem has an application in the field of seismic exploration for predicting pore-fluid pressures and saturation regimes.

An investigation of the mechanism underlying teacher aggression : Testing I3 theory and the General Aggression Model

NARCIS (Netherlands)

Montuoro, Paul; Mainhard, Tim

2017-01-01

Background: Considerable research has investigated the deleterious effects of teachers responding aggressively to students who misbehave, but the mechanism underlying this dysfunctional behaviour remains unknown. Aims: This study investigated whether the mechanism underlying teacher aggression

The Effect of Small Additions of Carbon Nanotubes on the Mechanical Properties of Epoxy Polymers under Static and Dynamic Loads

Science.gov (United States)

Tarasov, A. E.; Badamshina, E. R.; Anokhin, D. V.; Razorenov, S. V.; Vakorina, G. S.

2018-01-01

The results of measurements of the mechanical characteristics of cured epoxy composites containing small and ultrasmall additions of single-walled carbon nanotubes in the concentration range from 0 to 0.133 wt % under static and dynamic loads are presented. Static measurements of strength characteristics have been carried out under standard test conditions. Measurements of the Hugoniot elastic limit and spall strength were performed under a shock wave loading of the samples at a deformation rate of (0.8-1.5) ß 105 s-1 before the fracture using explosive devices by recording and subsequent analyzing the evolution of the full wave profiles. It has been shown that agglomerates of nanotubes present in the structure of the composites after curing cause a significant scatter of the measured strength parameters, both in the static and in the dynamic test modes. However, the effects of carbon nanotube additions in the studied concentration interval on the physical and mechanical characteristics of the parameters were not revealed for both types of loading.

Change of plans: an evaluation of the effectiveness and underlying mechanisms of successful talent transfer.

Science.gov (United States)

Collins, Rosie; Collins, Dave; MacNamara, Aine; Jones, Martin Ian

2014-01-01

Talent transfer (TT) is a recently formalised process used to identify and develop talented athletes by selecting individuals who have already succeeded in one sport and transferring them to another. Despite the increasing popularity of TT amongst national organisations and sport governing body professionals, however, there is little empirical evidence as to its efficacy or how it may be most efficiently employed. Accordingly, this investigation was designed to gain a deeper understanding of the effectiveness and underlying mechanisms of TT, achieved through a two-part study. Stage 1 provided a quantitative analysis of the incidence and distribution or, in this respect, epidemiology of TT, finding the most popular transfer to be sprinting to bobsleigh, with an average transfer age of 19 years. Stage 2 scrutinised the TT process and explored the specific cases revealed in stage 1 by examining the perceptions of four sport science support specialists who had worked in TT settings, finding several emergent themes which, they felt, could explain the TT processes. The most prominent theme was the psychosocial mechanism of TT, an aspect currently missing from TT initiatives, suggesting that current TT systems are poorly structured and should redress their approach to develop a more integrated scheme that encompasses all potential mechanisms of transfer.

Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

Directory of Open Access Journals (Sweden)

Vanessa Cohignac

2014-07-01

Full Text Available The rapid development of nanotechnologies is raising safety concerns because of the potential effects of engineered nanomaterials on human health, particularly at the respiratory level. Since the last decades, many in vivo studies have been interested in the pulmonary effects of different classes of nanomaterials. It has been shown that some of them can induce toxic effects, essentially depending on their physico-chemical characteristics, but other studies did not identify such effects. Inflammation and oxidative stress are currently the two main mechanisms described to explain the observed toxicity. However, the exact underlying mechanism(s still remain(s unknown and autophagy could represent an interesting candidate. Autophagy is a physiological process in which cytoplasmic components are digested via a lysosomal pathway. It has been shown that autophagy is involved in the pathogenesis and the progression of human diseases, and is able to modulate the oxidative stress and pro-inflammatory responses. A growing amount of literature suggests that a link between nanomaterial toxicity and autophagy impairment could exist. In this review, we will first summarize what is known about the respiratory effects of nanomaterials and we will then discuss the possible involvement of autophagy in this toxicity. This review should help understand why autophagy impairment could be taken as a promising candidate to fully understand nanomaterials toxicity.

Deciphering the Cognitive and Neural Mechanisms Underlying ...

International Development Research Centre (IDRC) Digital Library (Canada)

Deciphering the Cognitive and Neural Mechanisms Underlying Auditory Learning. This project seeks to understand the brain mechanisms necessary for people to learn to perceive sounds. Neural circuits and learning. The research team will test people with and without musical training to evaluate their capacity to learn ...

Study on Mechanical Properties of Barite Concrete under Impact Load

Science.gov (United States)

Chen, Z. F.; Cheng, K.; Wu, D.; Gan, Y. C.; Tao, Q. W.

2018-03-01

In order to research the mechanical properties of Barite concrete under impact load, a group of concrete compression tests was carried out under the impact load by using the drop test machine. A high-speed camera was used to record the failure process of the specimen during the impact process. The test results show that:with the increase of drop height, the loading rate, the peak load, the strain under peak load, the strain rate and the dynamic increase factor (DIF) all increase gradually. The ultimate tensile strain is close to each other, and the time of impact force decreases significantly, showing significant strain rate effect.

Numerical simulation of effective mechanical properties of stochastic composites with consideration for structural evolution under intensive dynamic loading

Energy Technology Data Exchange (ETDEWEB)

Karakulov, Valerii V., E-mail: valery@ftf.tsu.ru [National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Smolin, Igor Yu., E-mail: smolin@ispms.ru, E-mail: skrp@ftf.tsu.ru; Skripnyak, Vladimir A., E-mail: smolin@ispms.ru, E-mail: skrp@ftf.tsu.ru [National Research Tomsk State University, Tomsk, 634050, Russia and Institute of Strength Physics and Materials Science SB RAS, Tomsk, 634055 (Russian Federation)

2014-11-14

Mechanical behavior of stochastic metal-ceramic composites with the aluminum matrix under high-rate deformation at shock-wave loading is numerically simulated with consideration for structural evolution. Effective values of mechanical parameters of metal-ceramic composites AlB{sub 4}C, AlSiC, and AlAl{sub 2}O{sub 3} are evaluated depending on different concentration of ceramic inclusions.

Gas Bubble Dynamics under Mechanical Vibrations

Science.gov (United States)

Mohagheghian, Shahrouz; Elbing, Brian

2017-11-01

The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to <5%. The bubble size is larger than resonance size and smaller than acoustic wavelength. The amplitude of acoustic pressure wave was estimated using the definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

Molecular mechanics of silk nanostructures under varied mechanical loading.

Science.gov (United States)

Bratzel, Graham; Buehler, Markus J

2012-06-01

Spider dragline silk is a self-assembling tunable protein composite fiber that rivals many engineering fibers in tensile strength, extensibility, and toughness, making it one of the most versatile biocompatible materials and most inviting for synthetic mimicry. While experimental studies have shown that the peptide sequence and molecular structure of silk have a direct influence on the stiffness, toughness, and failure strength of silk, few molecular-level analyses of the nanostructure of silk assemblies, in particular, under variations of genetic sequences have been reported. In this study, atomistic-level structures of wildtype as well as modified MaSp1 protein from the Nephila clavipes spider dragline silk sequences, obtained using an in silico approach based on replica exchange molecular dynamics and explicit water molecular dynamics, are subjected to simulated nanomechanical testing using different force-control loading conditions including stretch, pull-out, and peel. The authors have explored the effects of the poly-alanine length of the N. clavipes MaSp1 peptide sequence and identify differences in nanomechanical loading conditions on the behavior of a unit cell of 15 strands with 840-990 total residues used to represent a cross-linking β-sheet crystal node in the network within a fibril of the dragline silk thread. The specific loading condition used, representing concepts derived from the protein network connectivity at larger scales, have a significant effect on the mechanical behavior. Our analysis incorporates stretching, pull-out, and peel testing to connect biochemical features to mechanical behavior. The method used in this study could find broad applications in de novo design of silk-like tunable materials for an array of applications. Copyright © 2011 Wiley Periodicals, Inc.

Enhancement of radiation effect using beta-lapachone and underlying mechanism

International Nuclear Information System (INIS)

Ahn, Ki Jung; Lee, Hyung Sik; Bai, Se Kyung; Song, Chang Won

2013-01-01

Beta-lapachone (β-Lap; 3,4-dihydro-2, 2-dimethyl-2H-naphthol[1, 2-b]pyran-5,6-dione) is a novel anti-cancer drug under phase I/II clinical trials. (β-Lap has been demonstrated to cause apoptotic and necrotic death in a variety of human cancer cells in vitro and in vivo. The mechanisms underlying the (β-Lap toxicity against cancer cells has been controversial. The most recent view is that (β-Lap, which is a quinone compound, undergoes two-electron reduction to hydroquinone form utilizing NAD(P)H or NADH as electron source. This two-electron reduction of (β-Lap is mediated by NAD(P)H:quinone oxidoreductase (NQO1), which is known to mediate the reduction of many quinone compounds. The hydroquinone forms of (β-Lap then spontaneously oxidizes back to the original oxidized (β-Lap, creating futile cycling between the oxidized and reduced forms of (β-Lap. It is proposed that the futile recycling between oxidized and reduced forms of (β-Lap leads to two distinct cell death pathways. First one is that the two-electron reduced (β-Lap is converted first to one-electron reduced (β-Lap, i.e., semiquinone (β-Lap (SQ)- causing production of reactive oxygen species (ROS), which then causes apoptotic cell death. The second mechanism is that severe depletion of NAD(P)H and NADH as a result of futile cycling between the quinone and hydroquinone forms of β- p causes severe disturbance in cellular metabolism leading to apoptosis and necrosis. The relative importance of the aforementioned two mechanisms, i.e., generation of ROS or depletion of NAD(P)H/NADH, may vary depending on cell type and environment. Importantly, the NQO1 level in cancer cells has been found to be higher than that in normal cells indicating that β-Lap may be preferentially toxic to cancer cells relative to non-cancer cells. The cellular level of NQO1 has been found to be significantly increased by divergent physical and chemical stresses including ionizing radiation. Recent reports clearly demonstrated

Damage evolution of TBC system under in-phase thermo-mechanical tests

International Nuclear Information System (INIS)

Kitazawa, R.; Tanaka, M.; Kagawa, Y.; Liu, Y.F.

2010-01-01

In-phase thermo-mechanical tests (TMF) of EB-PVD Y 2 O 3 -ZrO 2 thermal barrier coating (TBC) system (8 wt% Y 2 O 3 -ZrO 2 /CoNiCrAlY/IN-738 substrate) were done under a through-the-thick-direction thermal gradient from TBC surface temperature at 1150 deg. C to substrate temperature at 1000 deg. C. Deformation and failure behaviors of the TBC system were observed at the macroscopic and microscopic scales and damage evolution of the system under in-phase thermo-mechanical test was discussed. Special attention was paid to TBC layer cracking, thermally grown oxide (TGO) layer formation and void formation in bond coat and substrate. Effect of TMF conditions on the damage evolution behaviors was also discussed.

PHYSIOLOGICAL QUALITY OF SOYBEAN SEEDS UNDER MECHANICAL INJURIES CAUSED BY COMBINES

OpenAIRE

FÁBIO PALCZEWSKI PACHECO; LÚCIA HELENA PEREIRA NÓBREGA; GISLAINE PICOLLO DE LIMA; MÁRCIA SANTORUM; WALTER BOLLER; LORIVAN FORMIGHIERI

2015-01-01

The mechanical harvesting causes injuries on seeds and may affect their quality. Different threshing mechanisms and their adjustments may also affect the intensity of impacts that machines cause on seeds. So, this study aimed at diagnosing and evaluating the effect of two combines: the first one with a threshing system of axial flow and the other one with a threshing system of tangential flow, under adjustments of concave opening (10 mm, 30 mm and 10 mm for a combine with axial ...

Mechanisms of action underlying the antiandrogenic effects of the fungicide prochloraz

DEFF Research Database (Denmark)

Laier, Peter; Metzdorff, Stine Broeng; Boberg, Julie

2006-01-01

The fungicide prochloraz has got multiple mechanisms of action that may influence the demasculinizing and reproductive toxic effects of the compound. In the present study, Wistar rats were dosed perinatally with prochloraz (50 and 150 mg/kg/day) from gestational day (GD) 7 to postnatal day (PND) ...... acts directly on the fetal testis to inhibit steroidogenesis and that this effect is exhibited at protein, and not at genomic, level. (c) 2005 Elsevier Inc. All rights reserved....

Effects of suture position on left ventricular fluid mechanics under mitral valve edge-to-edge repair.

Science.gov (United States)

Du, Dongxing; Jiang, Song; Wang, Ze; Hu, Yingying; He, Zhaoming

2014-01-01

Mitral valve (MV) edge-to-edge repair (ETER) is a surgical procedure for the correction of mitral valve regurgitation by suturing the free edge of the leaflets. The leaflets are often sutured at three different positions: central, lateral and commissural portions. To study the effects of position of suture on left ventricular (LV) fluid mechanics under mitral valve ETER, a parametric model of MV-LV system during diastole was developed. The distribution and development of vortex and atrio-ventricular pressure under different suture position were investigated. Results show that the MV sutured at central and lateral in ETER creates two vortex rings around two jets, compared with single vortex ring around one jet of the MV sutured at commissure. Smaller total orifices lead to a higher pressure difference across the atrio-ventricular leaflets in diastole. The central suture generates smaller wall shear stresses than the lateral suture, while the commissural suture generated the minimum wall shear stresses in ETER.

Coaching as a Developmental Intervention in Organisations: A Systematic Review of Its Effectiveness and the Mechanisms Underlying It.

Science.gov (United States)

Grover, Simmy; Furnham, Adrian

2016-01-01

The primary aim of this paper is to conduct a thorough and systematic review of the empirical and practitioner research on executive, leadership and business coaching to assess the current empirical evidence for the effectiveness of coaching and the mechanisms underlying it. Organisations are increasingly using business coaching as an intervention to improve the productivity and performance of their senior personnel. A consequence of this increased application is the demand for empirical data to understand the process by which it operates and its demonstrable efficacy in achieving pre-set goals. This paper is a systematic review of the academic and practitioner literature pertaining to the effectiveness of business and executive coaching as a developmental intervention for organisations. It focuses on published articles, conference papers and theses that cover business, leadership or executive coaching within organisations over the last 10 years. The main findings show that coaching is an effective tool that benefits organisations and a number of underlying facets contribute to this effectiveness. However, there is deficiency and scope for further investigation in key aspects of the academic research and we identify several areas that need further research and practitioner attention. ​.

Coaching as a Developmental Intervention in Organisations: A Systematic Review of Its Effectiveness and the Mechanisms Underlying It

Science.gov (United States)

Grover, Simmy; Furnham, Adrian

2016-01-01

Purpose The primary aim of this paper is to conduct a thorough and systematic review of the empirical and practitioner research on executive, leadership and business coaching to assess the current empirical evidence for the effectiveness of coaching and the mechanisms underlying it. Background Organisations are increasingly using business coaching as an intervention to improve the productivity and performance of their senior personnel. A consequence of this increased application is the demand for empirical data to understand the process by which it operates and its demonstrable efficacy in achieving pre-set goals. Method This paper is a systematic review of the academic and practitioner literature pertaining to the effectiveness of business and executive coaching as a developmental intervention for organisations. It focuses on published articles, conference papers and theses that cover business, leadership or executive coaching within organisations over the last 10 years. Conclusions The main findings show that coaching is an effective tool that benefits organisations and a number of underlying facets contribute to this effectiveness. However, there is deficiency and scope for further investigation in key aspects of the academic research and we identify several areas that need further research and practitioner attention. ​ PMID:27416061

Design options for cooperation mechanisms under the new European renewable energy directive

International Nuclear Information System (INIS)

Klessmann, Corinna; Lamers, Patrick; Ragwitz, Mario; Resch, Gustav

2010-01-01

In June 2009, a new EU directive on the promotion of renewable energy sources (RES) entered into effect. The directive 2009/28/EC, provides for three cooperation mechanisms that will allow member states to achieve their national RES target in cooperation with other member states: statistical transfer, joint projects, and joint support schemes. This article analyses the pros and cons of the three mechanisms and explores design options for their implementation through strategic and economic questions: How to counterbalance the major drawbacks of each mechanism? How to reflect a balance of costs and benefits between the involved member states? The analysis identifies a number of design options that respond to these questions, e.g. long term contracts to ensure sufficient flexibility for statistical transfers, a coordinated, standardised joint project approach to increase transparency in the European market, and a stepwise harmonisation of joint support schemes that is based on a cost-effective accounting approach. One conclusion is that the three cooperation mechanisms are closely interlinked. One can consider their relation to be a gradual transition from member state cooperation under fully closed national support systems in case of statistical transfers, to cooperation under fully open national support systems in a joint support scheme.

Damage evolution of TBC system under in-phase thermo-mechanical tests

Energy Technology Data Exchange (ETDEWEB)

Kitazawa, R.; Tanaka, M.; Kagawa, Y. [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan); Liu, Y.F., E-mail: yfliu@hyper.rcast.u-tokyo.ac.jp [Research Center for Advanced Science and Technology, University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8904 (Japan)

2010-10-15

In-phase thermo-mechanical tests (TMF) of EB-PVD Y{sub 2}O{sub 3}-ZrO{sub 2} thermal barrier coating (TBC) system (8 wt% Y{sub 2}O{sub 3}-ZrO{sub 2}/CoNiCrAlY/IN-738 substrate) were done under a through-the-thick-direction thermal gradient from TBC surface temperature at 1150 deg. C to substrate temperature at 1000 deg. C. Deformation and failure behaviors of the TBC system were observed at the macroscopic and microscopic scales and damage evolution of the system under in-phase thermo-mechanical test was discussed. Special attention was paid to TBC layer cracking, thermally grown oxide (TGO) layer formation and void formation in bond coat and substrate. Effect of TMF conditions on the damage evolution behaviors was also discussed.

Mechanisms Underlying the Antidepressant Response and Treatment Resistance

Directory of Open Access Journals (Sweden)

Marjorie Rose Levinstein

2014-06-01

Full Text Available Depression is a complex and heterogeneous disorder affecting millions of Americans. There are several different medications and other treatments that are available and effective for many patients with depression. However, a substantial percentage of patients fail to achieve remission with these currently available interventions, and relapse rates are high. Therefore, it is necessary to determine both the mechanisms underlying the antidepressant response and the differences between responders and non-responders to treatment. Delineation of these mechanisms largely relies on experiments that utilize animal models. Therefore, this review provides an overview of the various mouse models that are currently used to assess the antidepressant response, such as chronic mild stress, social defeat, and chronic corticosterone. We discuss how these mouse models can be used to advance our understanding of the differences between responders and non-responders to antidepressant treatment. We also provide an overview of experimental treatment modalities that are used for treatment-resistant depression, such as deep brain stimulation and ketamine administration. We will then review the various genetic polymorphisms and transgenic mice that display resistance to antidepressant treatment. Finally, we synthesize the published data to describe a potential neural circuit underlying the antidepressant response and treatment resistance.

Underlying mechanism in the water chemistry of nuclear systems

International Nuclear Information System (INIS)

Walton, G.N.

1978-01-01

The equilibrium between dissolved hydrogen and oxygen in the molecular decomposition of water, and the equilibrium between hydrogen ions and hydroxyl ions in the ionic dissociation of water, both constitute important underlying mechanisms in the corrosion behaviour of water. The two equilibria, and the rates of the reactions involved in water and steam, will be compared and contrasted as a function of temperature, pressure and radiation. The effects of the equilibria on the hydrolysis and solubility of ferrous and ferric ions, and the ions of other metals, will be discussed in relation to the control of conditions in the coolant circuits of nuclear reactors. A third mechanism to discussed is the electrochemical exchange reactions that can contribute to the contamination of circuits. (author)

Peripheral Receptor Mechanisms Underlying Orofacial Muscle Pain and Hyperalgesia

Science.gov (United States)

Saloman, Jami L.

gated ion channels form functional complexes in nociceptors. It is also important to further elucidate peripheral anti-nociceptive mechanisms to improve clinical utilization of currently available analgesics and uncover additional therapeutic targets. A side project examined the mechanisms underlying sex differences in the anti-hyperalgesic effects of delta opioid receptors (DORs). This study provides evidence of a sex difference in the potency at DORs that is mediated by differences in the expression of ATP-sensitive potassium channels. Collectively, understanding detailed molecular events that underlie the development of pathological pain conditions could benefit future pharmacotherapies.

Nonlinear Mechanics of MEMS Rectangular Microplates under Electrostatic Actuation

KAUST Repository

Saghir, Shahid

2016-12-01

The first objective of the dissertation is to develop a suitable reduced order model capable of investigating the nonlinear mechanical behavior of von-Karman plates under electrostatic actuation. The second objective is to investigate the nonlinear static and dynamic behavior of rectangular microplates under small and large actuating forces. In the first part, we present and compare various approaches to develop reduced order models for the nonlinear von-Karman rectangular microplates actuated by nonlinear electrostatic forces. The reduced-order models aim to investigate the static and dynamic behavior of the plate under small and large actuation forces. A fully clamped microplate is considered. Different types of basis functions are used in conjunction with the Galerkin method to discretize the governing equations. First we investigate the convergence with the number of modes retained in the model. Then for validation purpose, a comparison of the static results is made with the results calculated by a nonlinear finite element model. The linear eigenvalue problem for the plate under the electrostatic force is solved for a wide range of voltages up to pull-in. In the second part, we present an investigation of the static and dynamic behavior of a fully clamped microplate. We investigate the effect of different non-dimensional design parameters on the static response. The forced-vibration response of the plate is then investigated when the plate is excited by a harmonic AC load superimposed to a DC load. The dynamic behavior is examined near the primary and secondary (superharmonic and subharmonic) resonances. The microplate shows a strong hardening behavior due to the cubic nonlinearity of midplane stretching. However, the behavior switches to softening as the DC load is increased. Next, near-square plates are studied to understand the effect of geometric imperfections of microplates. In the final part of the dissertation, we investigate the mechanical behavior of

The impact of electricity market design upon investment under uncertainty: The effectiveness of capacity mechanisms

International Nuclear Information System (INIS)

Vries, Laurens de; Heijnen, Petra

2008-01-01

This paper presents an analysis of different market designs under uncertainty about the future growth rate of demand. Markets for electricity generation appear to be prone to an investment cycle due to their capital-intensiveness and the long lead time of new generation facilities. We tested the stability of different capacity mechanisms in the presence of uncertainty regarding the demand growth rate with a stochastic dynamic model. Investment decisions were assumed to maximize profit, based on an assumed growth rate of demand that was equal to the rolling average of the previous five years. All capacity mechanisms proved effective in reducing the tendency towards an investment cycle, but to different degrees. Interestingly, an oligopoly that is able to raise average prices by 10% would also be able to substantially reduce price volatility and decrease the risk of shortages by increasing the reserve margin. Benefits of such a strategy for the generating companies could be that it would deter new market entrants and stave off the political attention that shortages and price spikes would bring about. However, the benefits to consumers are compromised by the lack of economic efficiency and distributional effects of an oligopoly, while the stability of such an oligopolistic strategy can be questioned. The most attractive solution is a system of reliability contracts, which can be used to stabilize both investment and prices, while reducing market power and providing more efficient operational incentives to generating companies. (author)

Effect of the fungus Piriformospora indica on physiological characteristics and root morphology of wheat under combined drought and mechanical stresses.

Science.gov (United States)

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger

2017-09-01

This study was done to evaluate the effects of the root-colonizing endophytic fungus Piriformospora indica on wheat growth under combined drought and mechanical stresses. Inoculated (colonized) and non-inoculated (uncolonized) wheat (Triticum aestivum L. cv. Chamran) seedlings were planted in growth chambers filled with moist sand (at a matric suction of 20 hPa). Slight, moderate and severe mechanical stresses (i.e., penetration resistance, Q p , of 1.17, 4.17 and 5.96 MPa, respectively) were produced by a dead-load technique (i.e., placing a weight on the sand surface) in the root medium. Slight, moderate and severe drought stresses were induced using PEG 6000 solutions with osmotic potentials of 0, -0.3 and -0.5 MPa, respectively. After 30 days, plant physiological characteristics and root morphology were measured. An increase in Q p from 1.17 to 5.96 MPa led to greater leaf proline concentration and root diameter, and lower relative water content (RWC), leaf water potential (LWP), chlorophyll contents and root volume. Moreover, severe drought stress decreased root and shoot fresh weights, root volume, leaf area, RWC, LWP and chlorophyll content compared to control. Catalase (CAT) and ascorbate peroxidase (APX) activities under severe drought stress were about 1.5 and 2.9 times greater than control. Interaction of the stresses showed that mechanical stress primarily controls plant water status and physiological responses. However, endophyte presence mitigated the adverse effects of individual and combined stresses on plant growth. Colonized plants were better adapted and had greater root length and volume, RWC, LWP and chlorophyll contents under stressful conditions due to higher absorption sites for water and nutrients. Compared with uncolonized plants, colonized plants showed lower CAT activity implying that wheat inoculated with P. indica was more tolerant and experienced less oxidative damage induced by drought and/or mechanical stress. Copyright �

Mechanisms underlying UV-induced immune suppression

International Nuclear Information System (INIS)

Ullrich, Stephen E.

2005-01-01

Skin cancer is the most prevalent form of human neoplasia. Estimates suggest that in excess of one million new cases of skin cancer will be diagnosed this year alone in the United States (www.cancer.org/statistics). Fortunately, because of their highly visible location, skin cancers are more rapidly diagnosed and more easily treated than other types of cancer. Be that as it may, approximately 10,000 Americans a year die from skin cancer. The cost of treating non-melanoma skin cancer is estimated to be in excess of US$ 650 million a year [J.G. Chen, A.B. Fleischer, E.D. Smith, C. Kancler, N.D. Goldman, P.M. Williford, S.R. Feldman, Cost of non-melanoma skin cancer treatment in the United States, Dermatol. Surg. 27 (2001) 1035-1038], and when melanoma is included, the estimated cost of treating skin cancer in the United States is estimated to rise to US$ 2.9 billion annually (www.cancer.org/statistics). Because the morbidity and mortality associated with skin cancer is a major public health problem, it is important to understand the mechanisms underlying skin cancer development. The primary cause of skin cancer is the ultraviolet (UV) radiation found in sunlight. In addition to its carcinogenic potential, UV radiation is also immune suppressive. In fact, data from studies with both experimental animals and biopsy proven skin cancer patients suggest that there is an association between the immune suppressive effects of UV radiation and its carcinogenic potential. The focus of this manuscript will be to review the mechanisms underlying the induction of immune suppression following UV exposure. Particular attention will be directed to the role of soluble mediators in activating immune suppression

Cavitation behavior observed in three monoleaflet mechanical heart valves under accelerated testing conditions.

Science.gov (United States)

Lo, Chi-Wen; Liu, Jia-Shing; Li, Chi-Pei; Lu, Po-Chien; Hwang, Ned H

2008-01-01

Accelerated testing provides a substantial amount of data on mechanical heart valve durability in a short period of time, but such conditions may not accurately reflect in vivo performance. Cavitation, which occurs during mechanical heart valve closure when local flow field pressure decreases below vapor pressure, is thought to play a role in valve damage under accelerated conditions. The underlying flow dynamics and mechanisms behind cavitation bubble formation are poorly understood. Under physiologic conditions, random perivalvular cavitation is difficult to capture. We applied accelerated testing at a pulse rate of 600 bpm and transvalvular pressure of 120 mm Hg, with synchronized videographs and high-frequency pressure measurements, to study cavitation of the Medtronic Hall Standard (MHS), Medtronic Hall D-16 (MHD), and Omni Carbon (OC) valves. Results showed cavitation bubbles between 340 and 360 micros after leaflet/housing impact of the MHS, MHD, and OC valves, intensified by significant leaflet rebound. Squeeze flow, Venturi, and water hammer effects each contributed to cavitation, depending on valve design.

An Investigation of the Mechanism Underlying Teacher Aggression: Testing I[superscript 3] Theory and the General Aggression Model

Science.gov (United States)

Montuoro, Paul; Mainhard, Tim

2017-01-01

Background: Considerable research has investigated the deleterious effects of teachers responding aggressively to students who misbehave, but the mechanism underlying this dysfunctional behaviour remains unknown. Aims: This study investigated whether the mechanism underlying teacher aggression follows I[superscript 3] theory or General Aggression…

Deformation Mechanisms of Gum Metals Under Nanoindentation

Science.gov (United States)

Sankaran, Rohini Priya

Gum Metal is a set of multi-component beta-Ti alloys designed and developed by Toyota Central R&D Labs in 2003 to have a nearly zero shear modulus in the direction. After significant amounts of cold-work (>90%), these alloys were found to have yield strengths at a significant fraction of the predicted ideal strengths and exhibited very little work hardening. It has been speculated that this mechanical behavior may be realized through an ideal shear mechanism as opposed to conventional plastic deformation mechanisms, such as slip, and that such a mechanism may be realized through a defect structure termed "nanodisturbance". It is furthermore theorized that for near ideal strength to be attained, dislocations need to be pinned at sufficiently high stresses. It is the search for these defects and pinning points that motivates the present study. However, the mechanism of plastic deformation and the true origin of specific defect structures unique to gum metals is still controversial, mainly due to the complexity of the beta-Ti alloy system and the heavily distorted lattice exhibited in cold worked gum metals, rendering interpretation of images difficult. Accordingly, the first aim of this study is to clarify the starting as-received microstructures of gum metal alloys through conventional transmission electron microscopy (TEM) and aberration-corrected high resolution scanning transmission electron microscopy with high-angle annular dark field detector (HAADF-HRSTEM) imaging. To elucidate the effects of beta-stability and starting microstructure on the deformation behavior of gum metals and thus to provide adequate context for potentially novel deformation structures, we investigate three alloy conditions: gum metal that has undergone solution heat treatment (STGM), gum metal that has been heavily cold worked (CWGM), and a solution treated alloy of nominal gum metal composition, but leaner in beta-stabilizing content (ST Ref-1). In order to directly relate observed

Mechanisms underlying the effects of prenatal psychosocial stress on child outcomes: beyond the HPA axis

NARCIS (Netherlands)

Beijers, R.; Buitelaar, J.K.; Weerth, C. de

2014-01-01

Accumulating evidence from preclinical and clinical studies indicates that maternal psychosocial stress and anxiety during pregnancy adversely affect child outcomes. However, knowledge on the possible mechanisms underlying these relations is limited. In the present paper, we review the most often

Vibrational mechanics nonlinear dynamic effects, general approach, applications

CERN Document Server

Blekhman, Iliya I

2000-01-01

This important book deals with vibrational mechanics - the new, intensively developing section of nonlinear dynamics and the theory of nonlinear oscillations. It offers a general approach to the study of the effect of vibration on nonlinear mechanical systems.The book presents the mathematical apparatus of vibrational mechanics which is used to describe such nonlinear effects as the disappearance and appearance under vibration of stable positions of equilibrium and motions (i.e. attractors), the change of the rheological properties of the media, self-synchronization, self-balancing, the vibrat

Biochemical mechanisms of signaling: perspectives in plants under arsenic stress.

Science.gov (United States)

Islam, Ejazul; Khan, Muhammad Tahir; Irem, Samra

2015-04-01

Plants are the ultimate food source for humans, either directly or indirectly. Being sessile in nature, they are exposed to various biotic and abiotic stresses because of changing climate that adversely effects their growth and development. Contamination of heavy metals is one of the major abiotic stresses because of anthropogenic as well as natural factors which lead to increased toxicity and accumulation in plants. Arsenic is a naturally occurring metalloid toxin present in the earth crust. Due to its presence in terrestrial and aquatic environments, it effects the growth of plants. Plants can tolerate arsenic using several mechanisms like phytochelation, vacuole sequestration and activation of antioxidant defense systems. Several signaling mechanisms have evolved in plants that involve the use of proteins, calcium ions, hormones, reactive oxygen species and nitric oxide as signaling molecules to cope with arsenic toxicity. These mechanisms facilitate plants to survive under metal stress by activating their defense systems. The pathways by which these stress signals are perceived and responded is an unexplored area of research and there are lots of gaps still to be filled. A good understanding of these signaling pathways can help in raising the plants which can perform better in arsenic contaminated soil and water. In order to increase the survival of plants in contaminated areas there is a strong need to identify suitable gene targets that can be modified according to needs of the stakeholders using various biotechnological techniques. This review focuses on the signaling mechanisms of plants grown under arsenic stress and will give an insight of the different sensory systems in plants. Furthermore, it provides the knowledge about several pathways that can be exploited to develop plant cultivars which are resistant to arsenic stress or can reduce its uptake to minimize the risk of arsenic toxicity through food chain thus ensuring food security. Copyright © 2015

Identification and Sensitivity Analysis for Average Causal Mediation Effects with Time-Varying Treatments and Mediators: Investigating the Underlying Mechanisms of Kindergarten Retention Policy.

Science.gov (United States)

Park, Soojin; Steiner, Peter M; Kaplan, David

2018-06-01

Considering that causal mechanisms unfold over time, it is important to investigate the mechanisms over time, taking into account the time-varying features of treatments and mediators. However, identification of the average causal mediation effect in the presence of time-varying treatments and mediators is often complicated by time-varying confounding. This article aims to provide a novel approach to uncovering causal mechanisms in time-varying treatments and mediators in the presence of time-varying confounding. We provide different strategies for identification and sensitivity analysis under homogeneous and heterogeneous effects. Homogeneous effects are those in which each individual experiences the same effect, and heterogeneous effects are those in which the effects vary over individuals. Most importantly, we provide an alternative definition of average causal mediation effects that evaluates a partial mediation effect; the effect that is mediated by paths other than through an intermediate confounding variable. We argue that this alternative definition allows us to better assess at least a part of the mediated effect and provides meaningful and unique interpretations. A case study using ECLS-K data that evaluates kindergarten retention policy is offered to illustrate our proposed approach.

Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

Directory of Open Access Journals (Sweden)

Nan Zhao

2015-01-01

Full Text Available Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs. In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By modelling multiuser cooperative relay as a labour market, a contract model with moral hazard for relay incentive is proposed. To effectively incentivize the potential RNs to participate in cooperative relay, the optimization problems are formulated to maximize the source’s utility while meeting the feasible conditions under both symmetric and asymmetric information scenarios. Numerical simulation results demonstrate the effectiveness of the proposed contract design scheme for cooperative relay.

Advanced paternal age effects in neurodevelopmental disorders-review of potential underlying mechanisms.

Science.gov (United States)

Janecka, M; Mill, J; Basson, M A; Goriely, A; Spiers, H; Reichenberg, A; Schalkwyk, L; Fernandes, C

2017-01-31

Multiple epidemiological studies suggest a relationship between advanced paternal age (APA) at conception and adverse neurodevelopmental outcomes in offspring, particularly with regard to increased risk for autism and schizophrenia. Conclusive evidence about how age-related changes in paternal gametes, or age-independent behavioral traits affect neural development is still lacking. Recent evidence suggests that the origins of APA effects are likely to be multidimensional, involving both inherited predisposition and de novo events. Here we provide a review of the epidemiological and molecular findings to date. Focusing on the latter, we present the evidence for genetic and epigenetic mechanisms underpinning the association between late fatherhood and disorder in offspring. We also discuss the limitations of the APA literature. We propose that different hypotheses relating to the origins of the APA effects are not mutually exclusive. Instead, multiple mechanisms likely contribute, reflecting the etiological complexity of neurodevelopmental disorders.

Hepatoprotective effect of peony total glucosides and the underlying mechanisms in diabetic rats.

Science.gov (United States)

Xia, Ling-Ling; Zhu, Qi-Jin; Wu, Yong-Gui

2017-12-01

Total glucosides of peony (TGP), compounds extracted from the dried roots of Paeonia lactiflora Pall, have been reported to have anti-inflammatory and antioxidative activities. However, the protective effect of TGP on liver injury and the underlying mechanisms remains unknown in diabetic rats. Current study investigates prevention of liver injury by TGP in diabetic rats and its mechanism was related to the inhibition of endoplasmic reticulum stress (ERS). Fifty adult male rats were randomly divided into: Normal group, diabetic group, TGP (50, 100 and 200 mg/kg/day) treatment groups (n = 10 per group). At the end of the 8th week, the liver was removed for biochemical and histological examinations. Compared with the diabetic group, administration of TGP at doses of 50, 100 and 200 mg/kg significantly prevented the increase of hepatic fibrosis score (ED 50 139.4 mg/kg). Compared with diabetic group, TGP at doses of 50, 100 and 200 mg/kg showed an inhibition on the increased macrophage infiltration. MCP-1 and TNF-α mRNA and protein expression were significantly increased in diabetic group compared with normal group; TGP administration caused significant reduction of high levels of MCP-1 and TNF-α mRNA as well as protein levels. Also, TGP at all doses showed an inhibition on the increased GRP78 levels, p-Perk levels and p-Eif2α levels in liver from diabetic group. Our results indicate that TGP has potential as a treatment for diabetic liver injury attenuating liver lipid accumulation and inflammation as well as ERS induced by diabetic condition.

Effect of Positive End-Expiratory Pressure on Central Venous Pressure in Patients under Mechanical Ventilation.

Science.gov (United States)

Shojaee, Majid; Sabzghabaei, Anita; Alimohammadi, Hossein; Derakhshanfar, Hojjat; Amini, Afshin; Esmailzadeh, Bahareh

2017-01-01

Finding the probable governing pattern of PEEP and CVP changes is an area of interest for in-charge physicians and researchers. Therefore, the present study was designed with the aim of evaluating the relationship between the mentioned pressures. In this quasi-experimental study, patients under mechanical ventilation were evaluated with the aim of assessing the effect of PEEP change on CVP. Non-trauma patients, over 18 years of age, who were under mechanical ventilation and had stable hemodynamics, with inserted CV line were entered. After gathering demographic data, patients underwent 0, 5, and 10 cmH 2 O PEEPs and the respective CVPs of the mentioned points were recorded. The relationship of CVP and PEEP in different cut points were measured using SPSS 21.0 statistical software. 60 patients with the mean age of 73.95 ± 11.58 years were evaluated (68.3% male). The most frequent cause of ICU admission was sepsis with 45.0%. 5 cmH 2 O increase in PEEP led to 2.47 ± 1.53 mean difference in CVP level. If the PEEP baseline is 0 at the time of 5 cmH 2 O increase, it leads to a higher raise in CVP compared to when the baseline is 5 cmH 2 O (2.47 ± 1.53 vs. 1.57 ± 1.07; p = 0.039). The relationship between CVP and 5 cmH 2 O (p = 0.279), and 10 cmH 2 O (p = 0.292) PEEP changes were not dependent on the baseline level of CVP. The findings of this study revealed the direct relationship between PEEP and CVP. Approximately, a 5 cmH 2 O increase in PEEP will be associated with about 2.5 cmH 2 O raise in CVP. When applying a 5 cmH 2 O PEEP increase, if the baseline PEEP is 0, it leads to a significantly higher raise in CVP compared to when it is 5 cmH 2 O (2.5 vs. 1.6). It seems that sex, history of cardiac failure, baseline CVP level, and hypertension do not have a significant effect in this regard.

Effect of Positive End-Expiratory Pressure on Central Venous Pressure in Patients under Mechanical Ventilation

Directory of Open Access Journals (Sweden)

Majid Shojaee

2016-12-01

Full Text Available Introduction: Finding the probable governing pattern of PEEP and CVP changes is an area of interest for in-charge physicians and researchers. Therefore, the present study was designed with the aim of evaluating the relationship between the mentioned pressures. Methods: In this quasi-experimental study, patients under mechanical ventilation were evaluated with the aim of assessing the effect of PEEP change on CVP. Non-trauma patients, over 18 years of age, who were under mechanical ventilation and had stable hemodynamics, with inserted CV line were entered. After gathering demographic data, patients underwent 0, 5, and 10 cmH2O PEEPs and the respective CVPs of the mentioned points were recorded. The relationship of CVP and PEEP in different cut points were measured using SPSS 21.0 statistical software. Results: 60 patients with the mean age of 73.95 ± 11.58 years were evaluated (68.3% male. The most frequent cause of ICU admission was sepsis with 45.0%. 5 cmH2O increase in PEEP led to 2.47 ± 1.53 mean difference in CVP level. If the PEEP baseline is 0 at the time of 5 cmH2O increase, it leads to a higher raise in CVP compared to when the baseline is 5 cmH2O (2.47 ± 1.53 vs. 1.57 ± 1.07; p = 0.039. The relationship between CVP and 5 cmH2O (p = 0.279, and 10 cmH2O (p = 0.292 PEEP changes were not dependent on the baseline level of CVP. Conclusion: The findings of this study revealed the direct relationship between PEEP and CVP. Approximately, a 5 cmH2O increase in PEEP will be associated with about 2.5 cmH2O raise in CVP. When applying a 5 cmH2O PEEP increase, if the baseline PEEP is 0, it leads to a significantly higher raise in CVP compared to when it is 5 cmH2O (2.5 vs. 1.6. It seems that sex, history of cardiac failure, baseline CVP level, and hypertension do not have a significant effect in this regard.

The underlying toxicological mechanism of chemical mixtures: A case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum

International Nuclear Information System (INIS)

Tian, Dayong; Lin, Zhifen; Zhou, Xianghong; Yin, Daqiang

2013-01-01

Intracellular chemical reaction of chemical mixtures is one of the main reasons that cause synergistic or antagonistic effects. However, it still remains unclear what the influencing factors on the intracellular chemical reaction are, and how they influence on the toxicological mechanism of chemical mixtures. To reveal this underlying toxicological mechanism of chemical mixtures, a case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum was employed, and both their joint effects and mixture toxicity were observed. Then series of two-step linear regressions were performed to describe the relationships between joint effects, the expected additive toxicities and descriptors of individual chemicals (including concentrations, binding affinity to receptors, octanol/water partition coefficients). Based on the quantitative relationships, the underlying joint toxicological mechanisms were revealed. The result shows that, for mixtures with their joint effects resulting from intracellular chemical reaction, their underlying toxicological mechanism depends on not only their interaction with target proteins, but also their transmembrane actions and their concentrations. In addition, two generic points of toxicological mechanism were proposed including the influencing factors on intracellular chemical reaction and the difference of the toxicological mechanism between single reactive chemicals and their mixtures. This study provided an insight into the understanding of the underlying toxicological mechanism for chemical mixtures with intracellular chemical reaction. - Highlights: • Joint effects of nitriles and aldehydes at non-equitoxic ratios were determined. • A novel descriptor, ligand–receptor interaction energy (E binding ), was employed. • Quantitative relationships for mixtures were developed based on a novel descriptor. • The underlying toxic mechanism was revealed based on quantitative relationships. • Two generic

The underlying toxicological mechanism of chemical mixtures: A case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum

Energy Technology Data Exchange (ETDEWEB)

Tian, Dayong [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Department of Chemical and Environmental Engineering, Anyang Institute of Technology, Anyang 455000 (China); Lin, Zhifen, E-mail: lzhifen@tongji.edu.cn [State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China); Zhou, Xianghong [Department of Public Management, Tongji University, Shanghai 200092 (China); Yin, Daqiang [Key Laboratory of Yangtze River Water Environment, Ministry of Education, College of Environmental Science and Engineering, Tongji University, Shanghai 200092 (China)

2013-10-15

Intracellular chemical reaction of chemical mixtures is one of the main reasons that cause synergistic or antagonistic effects. However, it still remains unclear what the influencing factors on the intracellular chemical reaction are, and how they influence on the toxicological mechanism of chemical mixtures. To reveal this underlying toxicological mechanism of chemical mixtures, a case study on mixture toxicity of cyanogenic toxicants and aldehydes to Photobacterium phosphoreum was employed, and both their joint effects and mixture toxicity were observed. Then series of two-step linear regressions were performed to describe the relationships between joint effects, the expected additive toxicities and descriptors of individual chemicals (including concentrations, binding affinity to receptors, octanol/water partition coefficients). Based on the quantitative relationships, the underlying joint toxicological mechanisms were revealed. The result shows that, for mixtures with their joint effects resulting from intracellular chemical reaction, their underlying toxicological mechanism depends on not only their interaction with target proteins, but also their transmembrane actions and their concentrations. In addition, two generic points of toxicological mechanism were proposed including the influencing factors on intracellular chemical reaction and the difference of the toxicological mechanism between single reactive chemicals and their mixtures. This study provided an insight into the understanding of the underlying toxicological mechanism for chemical mixtures with intracellular chemical reaction. - Highlights: • Joint effects of nitriles and aldehydes at non-equitoxic ratios were determined. • A novel descriptor, ligand–receptor interaction energy (E{sub binding}), was employed. • Quantitative relationships for mixtures were developed based on a novel descriptor. • The underlying toxic mechanism was revealed based on quantitative relationships. • Two

Investigation on the interaction of catalase with sodium lauryl sulfonate and the underlying mechanisms.

Science.gov (United States)

Wang, Jing; Jia, Rui; Wang, Jiaxi; Sun, Zhiqiang; Wu, Zitao; Liu, Rutao; Zong, Wansong

2018-02-01

As a classic type of anionic surfactants, sodium lauryl sulfonate (SLS) might change the structure and function of antioxidant enzyme catalase (CAT) through their direct interactions. However, the underlying molecular mechanism is still unknown. This study investigated the direct interaction of SLS with CAT molecule and the underlying mechanisms using multi-spectroscopic methods, isothermal titration calorimetry, and molecular docking studies. No obvious effects were observed on CAT structure and activity under low SLS concentration exposure. The particle size of CAT molecule decreased and CAT activity was slightly inhibited under high SLS concentration exposure. SLS prefers to bind to the interface of CAT mainly via van der Waals' forces and hydrogen bonds. Subsequently, SLS interacts with the amino acid residues around the heme groups of CAT via hydrophobic interactions and might inhibit CAT activity. © 2017 Wiley Periodicals, Inc.

“Intensity-Response” Effects of Electroacupuncture on Gastric Motility and Its Underlying Peripheral Neural Mechanism

Directory of Open Access Journals (Sweden)

Yang-Shuai Su

2013-01-01

Full Text Available The aim of this study was to explore the “intensity-response” relationship between EAS and the effect of gastric motility of rats and its underlying peripheral neural mechanism by employing ASIC3 knockout (ASIC3−/−, TRPV1 knockout (TRPV1−/−, and C57BL/6 mice. For adult male Sprague-Dawley (n=18 rats, the intensities of EAS were 0.5, 1, 3, 5, 7, and 9 mA, respectively. For mice (n=8 in each group, only 1 mA was used, by which C fiber of the mice can be activated. Gastric antrum motility was measured by intrapyloric balloon. Gastric motility was facilitated by EAS at ST36 and inhibited by EAS at CV12. The half maximal facilitation intensity of EAS at ST36 was 2.1–2.3 mA, and the half maximal inhibitory intensity of EAS at CV12 was 2.8 mA. In comparison with C57BL/6 mice, the facilitatory effect of ST36 and inhibitive effect of CV12 in ASIC3−/− mice decreased, but the difference was not statistically significant (P>0.05. However, these effects in TRPV1−/− mice decreased significantly (P<0.001. The results indicated that there existed an “intensity-response” relationship between EAS and the effect of gastric motility. TRPV1 receptor was involved in the regulation of gastric motility of EAS.

Effects and mechanism on Kapton film under ozone exposure in a ground near space simulator

Science.gov (United States)

Wei, Qiang; Yang, Guimin; Liu, Gang; Jiang, Haifu; Zhang, Tingting

2018-05-01

The effect on aircraft materials in the near space environment is a key part of air-and-space integration research. Ozone and aerodynamic fluids are important organizational factors in the near space environment and both have significant influences on the performance of aircraft materials. In the present paper a simulated ozone environment was used to test polyimide material that was rotated at the approximate velocity of 150-250 m/s to form an aerodynamic fluid field. The goal was to evaluate the performance evolution of materials under a comprehensive environment of ozone molecular corrosion and aerodynamic fluids. The research results show that corrosion and sputtering by ozone molecules results in Kapton films exhibiting a rugged "carpet-like" morphology exhibits an increase in surface roughness. The morphology after ozone exposure led to higher surface roughness and an increase in surface optical diffuse reflection, which is expressed by the lower optical transmittance and the gradual transition from light orange to brown. The mass loss test, XPS, and FTIR analysis show that the molecular chains on the surface of the Kapton film are destroyed resulting in Csbnd C bond breaking to form small volatile molecules such as CO2 or CO, which are responsible for a linear increase in mass loss per unit area. The Csbnd N and Csbnd O structures exhibit weakening tendency under ozone exposure. The present paper explores the evaluation method for Kapton's adaptability under the ozone exposure test in the near space environment, and elucidates the corrosion mechanism and damage mode of the polyimide material under the combined action of ozone corrosion and the aerodynamic fluid. This work provides a methodology for studying materials in the near-space environment.

Curcumin-mediated regulation of intestinal barrier function: The mechanism underlying its beneficial effects.

Science.gov (United States)

Ghosh, Siddhartha S; He, Hongliang; Wang, Jing; Gehr, Todd W; Ghosh, Shobha

2018-01-02

Curcumin has anti-inflammatory, anti-oxidant and anti-proliferative properties established largely by in vitro studies. Accordingly, oral administration of curcumin beneficially modulates many diseases including diabetes, fatty-liver disease, atherosclerosis, arthritis, cancer and neurological disorders such as depression, Alzheimer's or Parkinson's disease. However, limited bioavailability and inability to detect curcumin in circulation or target tissues has hindered the validation of a causal role. We established curcumin-mediated decrease in the release of gut bacteria-derived lipopolysaccharide (LPS) into circulation by maintaining the integrity of the intestinal barrier function as the mechanism underlying the attenuation of metabolic diseases (diabetes, atherosclerosis, kidney disease) by curcumin supplementation precluding the need for curcumin absorption. In view of the causative role of circulating LPS and resulting chronic inflammation in the development of diseases listed above, this review summarizes the mechanism by which curcumin affects the several layers of the intestinal barrier and, despite negligible absorption, can beneficially modulate these diseases.

Local and systemic immune mechanisms underlying the anti-colitis effects of the dairy bacterium Lactobacillus delbrueckii.

Directory of Open Access Journals (Sweden)

Clarissa Santos Rocha

Full Text Available Several probiotic bacteria have been proposed for treatment or prevention of inflammatory bowel diseases (IBD, showing a protective effect in animal models of experimental colitis and for some of them also in human clinical trials. While most of these probiotic bacteria are isolated from the digestive tract, we recently reported that a Lactobacillus strain isolated from cheese, L. delbrueckii subsp. lactis CNRZ327 (Lb CNRZ327, also possesses anti-inflammatory effects in vitro and in vivo, demonstrating that common dairy bacteria may be useful in the treatment or prevention of IBD. Here, we studied the mechanisms underlying the protective effects of Lb CNRZ327 in vivo, in a mouse dextran sodium sulfate (DSS colitis model. During colitis, Lb CNRZ327 modulated the production of TGF-β, IL-6, and IL-12 in colonic tissue and of TGF-β and IL-6 in the spleen, and caused an expansion of CD4+Foxp3+ regulatory T cells in the cecal lymph nodes. Moreover, a strong tendency to CD4+Foxp3+ expansion was also observed in the spleen. The results of this study for the first time show that orally administered dairy lactobacilli can not only modulate mucosal but also systemic immune responses and constitute an effective treatment of IBD.

Local and systemic immune mechanisms underlying the anti-colitis effects of the dairy bacterium Lactobacillus delbrueckii.

Science.gov (United States)

Santos Rocha, Clarissa; Gomes-Santos, Ana Cristina; Garcias Moreira, Thais; de Azevedo, Marcela; Diniz Luerce, Tessalia; Mariadassou, Mahendra; Longaray Delamare, Ana Paula; Langella, Philippe; Maguin, Emmanuelle; Azevedo, Vasco; Caetano de Faria, Ana Maria; Miyoshi, Anderson; van de Guchte, Maarten

2014-01-01

Several probiotic bacteria have been proposed for treatment or prevention of inflammatory bowel diseases (IBD), showing a protective effect in animal models of experimental colitis and for some of them also in human clinical trials. While most of these probiotic bacteria are isolated from the digestive tract, we recently reported that a Lactobacillus strain isolated from cheese, L. delbrueckii subsp. lactis CNRZ327 (Lb CNRZ327), also possesses anti-inflammatory effects in vitro and in vivo, demonstrating that common dairy bacteria may be useful in the treatment or prevention of IBD. Here, we studied the mechanisms underlying the protective effects of Lb CNRZ327 in vivo, in a mouse dextran sodium sulfate (DSS) colitis model. During colitis, Lb CNRZ327 modulated the production of TGF-β, IL-6, and IL-12 in colonic tissue and of TGF-β and IL-6 in the spleen, and caused an expansion of CD4+Foxp3+ regulatory T cells in the cecal lymph nodes. Moreover, a strong tendency to CD4+Foxp3+ expansion was also observed in the spleen. The results of this study for the first time show that orally administered dairy lactobacilli can not only modulate mucosal but also systemic immune responses and constitute an effective treatment of IBD.

Push-and-stick mechanism for charged and excited small cluster emission under ion bombardment

International Nuclear Information System (INIS)

Bitensky, I.S.; Parilis, E.S.; Wojciechowski, I.A.

1992-01-01

The mechanism for the formation, excitation and ionization of small clusters emitted under ion bombardment is discussed. It is shown that the increased degree of ionization for the transition metal dimers, trimers and tetramers can be explained by the existence of an additional effective channel for their formation, namely the associative ionization process. A simple estimate shows that the sticking together of a fast cascade atom and the pushed out surface atom is 30-40 times more effective for dimer formation, than the recombination of two fast atoms. This push-and-stick mechanism of cluster formation could also be effective for the formation of trimers and tetramers. (orig.)

Mechanical failure of zigzag graphene nanoribbons under tensile strain induced by edge reconstruction

KAUST Repository

Cheng, Yingchun

2012-10-01

The structural and mechanical properties of graphene nanoribbons (GNRs) under uniaxial tensile strain are studied by density functional theory. The ideal strength of a zigzag GNR (120 GPa) is close to that of pristine graphene. However, for a GNR with both edges reconstructed to pentagon–heptagon pairs (from hexagon–hexagon pairs) it decreases to 94 GPa and the maximum tensile strain is reduced to 15%. Our results constitute a comprehensive picture of the edge structure effect on the mechanical properties of GNRs.

Mechanical failure of zigzag graphene nanoribbons under tensile strain induced by edge reconstruction

KAUST Repository

Cheng, Yingchun; Schwingenschlö gl, Udo; Zhu, Zhiyong

2012-01-01

The structural and mechanical properties of graphene nanoribbons (GNRs) under uniaxial tensile strain are studied by density functional theory. The ideal strength of a zigzag GNR (120 GPa) is close to that of pristine graphene. However, for a GNR with both edges reconstructed to pentagon–heptagon pairs (from hexagon–hexagon pairs) it decreases to 94 GPa and the maximum tensile strain is reduced to 15%. Our results constitute a comprehensive picture of the edge structure effect on the mechanical properties of GNRs.

Microcracking in composite laminates under thermal and mechanical loading. Thesis

Science.gov (United States)

Maddocks, Jason R.

1995-01-01

Composites used in space structures are exposed to both extremes in temperature and applied mechanical loads. Cracks in the matrix form, changing the laminate thermoelastic properties. The goal of the present investigation is to develop a predictive methodology to quantify microcracking in general composite laminates under both thermal and mechanical loading. This objective is successfully met through a combination of analytical modeling and experimental investigation. In the analysis, the stress and displacement distributions in the vicinity of a crack are determined using a shear lag model. These are incorporated into an energy based cracking criterion to determine the favorability of crack formation. A progressive damage algorithm allows the inclusion of material softening effects and temperature-dependent material properties. The analysis is implemented by a computer code which gives predicted crack density and degraded laminate properties as functions of any thermomechanical load history. Extensive experimentation provides verification of the analysis. AS4/3501-6 graphite/epoxy laminates are manufactured with three different layups to investigate ply thickness and orientation effects. Thermal specimens are cooled to progressively lower temperatures down to -184 C. After conditioning the specimens to each temperature, cracks are counted on their edges using optical microscopy and in their interiors by sanding to incremental depths. Tensile coupons are loaded monotonically to progressively higher loads until failure. Cracks are counted on the coupon edges after each loading. A data fit to all available results provides input parameters for the analysis and shows them to be material properties, independent of geometry and loading. Correlation between experiment and analysis is generally very good under both thermal and mechanical loading, showing the methodology to be a powerful, unified tool. Delayed crack initiation observed in a few cases is attributed to a

Cost Effectiveness of Genotype-Guided Warfarin Dosing in Patients with Mechanical Heart Valve Replacement Under the Fee-for-Service System.

Science.gov (United States)

Kim, Dong-Jin; Kim, Ho-Sook; Oh, Minkyung; Kim, Eun-Young; Shin, Jae-Gook

2017-10-01

Although studies assessing the cost effectiveness of genotype-guided warfarin dosing for the management of atrial fibrillation, deep vein thrombosis, and pulmonary embolism have been reported, no publications have addressed genotype-guided warfarin therapy in mechanical heart valve replacement (MHVR) patients or genotype-guided warfarin therapy under the fee-for-service (FFS) insurance system. The aim of this study was to evaluate the cost effectiveness of genotype-guided warfarin dosing in patients with MHVR under the FFS system from the Korea healthcare sector perspective. A decision-analytic Markov model was developed to evaluate the cost effectiveness of genotype-guided warfarin dosing compared with standard dosing. Estimates of clinical adverse event rates and health state utilities were derived from the published literature. The outcome measure was the incremental cost-effectiveness ratio (ICER) per quality-adjusted life-year (QALY). One-way and probabilistic sensitivity analyses were performed to explore the range of plausible results. In a base-case analysis, genotype-guided warfarin dosing was associated with marginally higher QALYs than standard warfarin dosing (6.088 vs. 6.083, respectively), at a slightly higher cost (US$6.8) (year 2016 values). The ICER was US$1356.2 per QALY gained. In probabilistic sensitivity analysis, there was an 82.7% probability that genotype-guided dosing was dominant compared with standard dosing, and a 99.8% probability that it was cost effective at a willingness-to-pay threshold of US$50,000 per QALY gained. Compared with only standard warfarin therapy, genotype-guided warfarin dosing was cost effective in MHVR patients under the FFS insurance system.

Biological mechanisms underlying the role of physical fitness in health and resilience

OpenAIRE

Silverman, Marni N.; Deuster, Patricia A.

2014-01-01

Physical fitness, achieved through regular exercise and/or spontaneous physical activity, confers resilience by inducing positive psychological and physiological benefits, blunting stress reactivity, protecting against potentially adverse behavioural and metabolic consequences of stressful events and preventing many chronic diseases. In this review, we discuss the biological mechanisms underlying the beneficial effects of physical fitness on mental and physical health. Physical fitness appear...

DNA under Force: Mechanics, Electrostatics, and Hydration

Directory of Open Access Journals (Sweden)

Jingqiang Li

2015-02-01

Full Text Available Quantifying the basic intra- and inter-molecular forces of DNA has helped us to better understand and further predict the behavior of DNA. Single molecule technique elucidates the mechanics of DNA under applied external forces, sometimes under extreme forces. On the other hand, ensemble studies of DNA molecular force allow us to extend our understanding of DNA molecules under other forces such as electrostatic and hydration forces. Using a variety of techniques, we can have a comprehensive understanding of DNA molecular forces, which is crucial in unraveling the complex DNA functions in living cells as well as in designing a system that utilizes the unique properties of DNA in nanotechnology.

Potential mechanisms underlying response to effects of the fungicide pyrimethanil from gene expression profiling in Saccharomyces cerevisiae.

Science.gov (United States)

Gil, Fátima N; Becker, Jörg D; Viegas, Cristina A

2014-06-11

Pyrimethanil is a fungicide mostly applied in vineyards. When misused, residue levels detected in grape must or in the environment may be of concern. The present work aimed to analyze mechanisms underlying response to deleterious effects of pyrimethanil in the eukaryotic model Saccharomyces cerevisiae. Pyrimethanil concentration-dependent effects at phenotypic (inhibition of growth) and transcriptomic levels were examined. For transcriptional profiling, analysis focused on two sublethal exposure conditions that inhibited yeast growth by 20% or 50% compared with control cells not exposed to the fungicide. Gene expression modifications increased with the magnitude of growth inhibition, in numbers and fold-change of differentially expressed genes and in diversity of over-represented functional categories. These included mostly biosynthesis of arginine and sulfur amino acids metabolism, as well as energy conservation, antioxidant response, and multidrug transport. Several pyrimethanil-responsive genes encoded proteins sharing significant homology with proteins from phytopathogenic fungi and ecologically relevant higher eukaryotes.

Underlying mechanisms and the evolving influence of diet

DEFF Research Database (Denmark)

Larsen, Lesli Hingstrup

2012-01-01

Obesity is determined by both genetic and environmental factors. Since 2007, 52 genes have been associated with obesity and obesity-related measurements in genome-wide association studies (GWAS), among these the fat and obesity-associated gene (FTO). Despite the success in identifying genes predi...... and the microbiome that can be modified by diet, and by genotype, adding to the complexity of determining the contributors to obesity....... has been shown to attenuate the effect of FTO on obesity. Several studies have examined gene-diet interactions in relation to obesity, but only a few suggestive interactions have been identified. This is most probably due to small effect sizes of the interactions and thereby a demand for large samples...... to increased risk of developing obesity. Recently, the intestinal microbiome, the collected genome of the bacteria, also has been associated with obesity and with specific dietary profiles. The underlying mechanisms determining the susceptibility to obesity do not only include the genome but also the epigenome...

Turing mechanism underlying a branching model for lung morphogenesis.

Science.gov (United States)

Xu, Hui; Sun, Mingzhu; Zhao, Xin

2017-01-01

The mammalian lung develops through branching morphogenesis. Two primary forms of branching, which occur in order, in the lung have been identified: tip bifurcation and side branching. However, the mechanisms of lung branching morphogenesis remain to be explored. In our previous study, a biological mechanism was presented for lung branching pattern formation through a branching model. Here, we provide a mathematical mechanism underlying the branching patterns. By decoupling the branching model, we demonstrated the existence of Turing instability. We performed Turing instability analysis to reveal the mathematical mechanism of the branching patterns. Our simulation results show that the Turing patterns underlying the branching patterns are spot patterns that exhibit high local morphogen concentration. The high local morphogen concentration induces the growth of branching. Furthermore, we found that the sparse spot patterns underlie the tip bifurcation patterns, while the dense spot patterns underlies the side branching patterns. The dispersion relation analysis shows that the Turing wavelength affects the branching structure. As the wavelength decreases, the spot patterns change from sparse to dense, the rate of tip bifurcation decreases and side branching eventually occurs instead. In the process of transformation, there may exists hybrid branching that mixes tip bifurcation and side branching. Since experimental studies have reported that branching mode switching from side branching to tip bifurcation in the lung is under genetic control, our simulation results suggest that genes control the switch of the branching mode by regulating the Turing wavelength. Our results provide a novel insight into and understanding of the formation of branching patterns in the lung and other biological systems.

Effect of chemical and mechanical weed control on cassava yield, soil quality and erosion under cassava cropping system

Science.gov (United States)

Islami, Titiek; Wisnubroto, Erwin; Utomo, Wani

2016-04-01

Three years field experiments were conducted to study the effect of chemical and mechanical weed control on soil quality and erosion under cassava cropping system. The experiment were conducted at University Brawijaya field experimental station, Jatikerto, Malang, Indonesia. The experiments were carried out from 2011 - 2014. The treatments consist of three cropping system (cassava mono culture; cassava + maize intercropping and cassava + peanut intercropping), and two weed control method (chemical and mechanical methods). The experimental result showed that the yield of cassava first year and second year did not influenced by weed control method and cropping system. However, the third year yield of cassava was influence by weed control method and cropping system. The cassava yield planted in cassava + maize intercropping system with chemical weed control methods was only 24 t/ha, which lower compared to other treatments, even with that of the same cropping system used mechanical weed control. The highest cassava yield in third year was obtained by cassava + peanuts cropping system with mechanical weed control method. After three years experiment, the soil of cassava monoculture system with chemical weed control method possessed the lowest soil organic matter, and soil aggregate stability. During three years of cropping soil erosion in chemical weed control method, especially on cassava monoculture, was higher compared to mechanical weed control method. The soil loss from chemical control method were 40 t/ha, 44 t/ha and 54 t/ha for the first, second and third year crop. The soil loss from mechanical weed control method for the same years was: 36 t/ha, 36 t/ha and 38 t/ha. Key words: herbicide, intercropping, soil organic matter, aggregate stability.

The toxic effects of chlorophenols and associated mechanisms in fish

International Nuclear Information System (INIS)

Ge, Tingting; Han, Jiangyuan; Qi, Yongmei; Gu, Xueyan; Ma, Lin; Zhang, Chen; Naeem, Sajid; Huang, Dejun

2017-01-01

Highlights: • We review the toxic effects of chlorophenols (CPs) and underlying mechanisms in fish. • CPs induce lethal effects, oxidative stress, endocrine disruption, reproductive toxicity and apoptosis in fish. • CPs exhibit toxicity through multiple signaling pathways in fish and different pathways co-exist under the same conditions. • Studies on DNA methylation provide new insights into our understanding of epigenetic mechanisms of CPs-induced toxicity. • Mechanisms studies on CPs toxicity performed under environmental concentrations need more attentions. - Abstract: Chlorophenols (CPs) are ubiquitous contaminants in the environment primarily released from agricultural and industrial wastewater. These compounds are not readily degraded naturally, and easily accumulate in organs, tissues and cells via food chains, further leading to acute and chronic toxic effects on aquatic organisms. Herein, we review the available literature regarding CP toxicity in fish, with special emphasis on the potential toxic mechanisms. CPs cause oxidative stress via generation of reactive oxygen species, induction of lipid peroxidation and/or oxidative DNA damage along with inhibition of antioxidant systems. CPs affect immune system by altering the number of mature B cells and macrophages, while suppressing phagocytosis and down-regulating the expression of immune factors. CPs also disrupt endocrine function by affecting hormone levels, or inducing abnormal gene expression and interference with hormone receptors. CPs at relatively higher concentrations induce apoptosis via mitochondria-mediated pathway, cell death receptor-mediated pathway, and/or DNA damage-mediated pathway. CPs at relatively lower concentrations promote cell proliferation, and foster cancers-prone environment by increasing the rate of point mutations and oxidative DNA lesions. These toxic effects in fish are induced directly by CPs per se or indirectly by their metabolic products. In addition, recent

The toxic effects of chlorophenols and associated mechanisms in fish

Energy Technology Data Exchange (ETDEWEB)

Ge, Tingting; Han, Jiangyuan; Qi, Yongmei; Gu, Xueyan; Ma, Lin; Zhang, Chen; Naeem, Sajid; Huang, Dejun, E-mail: huangdj@lzu.edu.cn

2017-03-15

Highlights: • We review the toxic effects of chlorophenols (CPs) and underlying mechanisms in fish. • CPs induce lethal effects, oxidative stress, endocrine disruption, reproductive toxicity and apoptosis in fish. • CPs exhibit toxicity through multiple signaling pathways in fish and different pathways co-exist under the same conditions. • Studies on DNA methylation provide new insights into our understanding of epigenetic mechanisms of CPs-induced toxicity. • Mechanisms studies on CPs toxicity performed under environmental concentrations need more attentions. - Abstract: Chlorophenols (CPs) are ubiquitous contaminants in the environment primarily released from agricultural and industrial wastewater. These compounds are not readily degraded naturally, and easily accumulate in organs, tissues and cells via food chains, further leading to acute and chronic toxic effects on aquatic organisms. Herein, we review the available literature regarding CP toxicity in fish, with special emphasis on the potential toxic mechanisms. CPs cause oxidative stress via generation of reactive oxygen species, induction of lipid peroxidation and/or oxidative DNA damage along with inhibition of antioxidant systems. CPs affect immune system by altering the number of mature B cells and macrophages, while suppressing phagocytosis and down-regulating the expression of immune factors. CPs also disrupt endocrine function by affecting hormone levels, or inducing abnormal gene expression and interference with hormone receptors. CPs at relatively higher concentrations induce apoptosis via mitochondria-mediated pathway, cell death receptor-mediated pathway, and/or DNA damage-mediated pathway. CPs at relatively lower concentrations promote cell proliferation, and foster cancers-prone environment by increasing the rate of point mutations and oxidative DNA lesions. These toxic effects in fish are induced directly by CPs per se or indirectly by their metabolic products. In addition, recent

Mechanisms underlying the antihypertensive properties of Urtica dioica.

Science.gov (United States)

Qayyum, Rahila; Qamar, Hafiz Misbah-Ud-Din; Khan, Shamim; Salma, Umme; Khan, Taous; Shah, Abdul Jabbar

2016-09-01

Urtica dioica has traditionally been used in the management of cardiovascular disorders especially hypertension. The aim of this study was to explore pharmacological base of its use in hypertension. Crude methanolic extract of U. dioica (Ud.Cr) and its fractions (Ud.EtAc, Ud.nHex, Ud.Chl and Ud.Aq) were tested in vivo on normotensive and hypertensive rats under anesthesia for blood pressure lowering effect. In-vitro experiments on rat and rabbit aortae were employed to probe the vasorelaxation mechanism(s). The responses were measured using pressure and force transducers connected to PowerLab Data Acquisition System. Ud.Cr and fractions were found more effective antihypertensive in hypertensive rats than normotensive with remarkable potency exhibited by the ethyl acetate fraction. The effect was same in the presence of atropine. In isolated rat aortic rings, Ud.Cr and all its fractions exhibited L-NAME sensitive endothelium-dependent vasodilator effect and also inhibit K(+) (80 mM)-induced pre-contractions. In isolated rabbit thoracic aortic rings Ud.Cr and its fractions induced relaxation with more potency against K(+) (80 mM) than phenylephrine (1 µM) like verapamil, showing Ud.EtAc fraction the most potent one. Pre-incubation of aortic rings with Ud.Cr and its fractions exhibited Ca(2+) channel blocking activity comparable with verapamil by shifting Ca(2+) concentration response curves to the right. Ud.Cr and its fractions also ablated the intracellular Ca(2+) release by suppressing PE peak formation in Ca(2+) free medium. When tested on basal tension, the crude extract and all fractions were devoid of any vasoconstrictor effect. These data indicate that crude methanolic extract and its fractions possess antihypertensive effect. Identification of NO-mediated vasorelaxation and calcium channel blocking effects explain the antihypertensive potential of U. dioica and provide a potential pharmacological base to its medicinal use in the management of hypertension.

Mechanisms for the antihyperglycemic effect of sitagliptin in patients with type 2 diabetes

DEFF Research Database (Denmark)

Muscelli, Elza; Casolaro, Arturo; Gastaldelli, Amalia

2012-01-01

Dipeptidyl peptidase IV (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes. The underlying mechanisms (incretin effect, β-cell function, endogenous glucose production) are not well known.......Dipeptidyl peptidase IV (DPP-4) inhibitors improve glycemic control in patients with type 2 diabetes. The underlying mechanisms (incretin effect, β-cell function, endogenous glucose production) are not well known....

Prediction study on mechanical and thermodynamic properties of orthorhombic Mg2SiO4 under high temperature

International Nuclear Information System (INIS)

Zhou, Jianting; Zhang, Hong; Chen, Yue; Shong, Jun; Chen, Zhuo; Yang, Juan; Zheng, Zhou; Wang, Feng

2014-01-01

In this work, based on density functional theory and quasi-harmonic Debye model, mechanical and thermodynamic properties of orthorhombic Mg 2 SiO 4 under high temperature are predicted. We found out that α-Mg 2 SiO 4 is mechanically stable under the condition from about 0 to 74 GPa. Results indicate that the main cause of mechanical instability is high pressure, and the effect caused by high temperature is small. C 11 , C 22 , C 33 , B and v p reduce with temperature just a little and increase with pressure obviously. Mg 2 SiO 4 has excellent resistance to strong compression; however the resistance to shear is unsatisfactory. The C v tends to the Petit and Dulong limit at high temperature under any pressure, and it is proportional to T 3 at extremely low temperature. Pressure has an opposite effect on C v than temperature. The suppressed effect on C v caused by pressure is not obvious under low and very high temperature. Mg 2 SiO 4 has three different thermal expansion coefficients (α) along a-, b- and c-axes, and α a <α c <α b . α increases rapidly at low temperature (about <300 K), and slows down at high temperature. High pressure would greatly suppress expansion caused by temperature. Nevertheless, increasing tendency of α b and α c is still obvious under high pressure, especially α b . All the properties are mainly due to Si–O covalent bonds and their directions

Muscle-related side-effects of statins: from mechanisms to evidence-based solutions.

Science.gov (United States)

Taylor, Beth A; Thompson, Paul D

2015-06-01

This article highlights the recent findings regarding statin-associated muscle side effects, including mechanisms and treatment as well as the need for more comprehensive clinical trials in statin myalgia. Statin myalgia is difficult to diagnose and treat, as major clinical trials have not routinely assessed muscle side-effects, there are few clinically relevant biomarkers and assessment tools for the symptoms, many apparent statin-related muscle symptoms may be nonspecific and related to other drugs or health conditions, and prevalence estimates vary widely. Data thus suggest that only 30-50% of patients with self-reported statin myalgia actually experience muscle pain on statins during blinded, placebo-controlled trials. In addition, evidence to date involving mechanisms underlying statin myalgia and its range of symptoms and presentations supports the hypothesis that there are multiple, interactive and potentially additive mechanisms underlying statin-associated muscle side-effects. There are likely multiple and interactive mechanisms underlying statin myalgia, and recent studies have produced equivocal data regarding prevalence of statin-associated muscle side-effects, contributing factors and effectiveness of common interventions. Therefore, more clinical trials on statin myalgia are critical to the field, as are systematic resources for quantifying, predicting and reporting statin-associated muscle side-effects.

Effects and underlying mechanisms of curcumin on the proliferation of vascular smooth muscle cells induced by Chol:MβCD

International Nuclear Information System (INIS)

Qin Li; Yang Yunbo; Tuo Qinhui; Zhu Bingyang; Chen Linxi; Zhang Liang; Liao Duanfang

2009-01-01

Proliferation of vascular smooth muscle cells (VSMCs) contributes to the development of various cardiovascular diseases. Curcumin, extracted from Curcumae longae, has been shown a variety of beneficial effects on human health, including anti-atherosclerosis by mechanisms poorly understood. In the present study, we attempted to investigate whether curcumin has any effect on VSMCs proliferation and the potential mechanisms involved. Our data showed curcumin concentration-dependently abrogated the proliferation of primary rat VSMCs induced by Chol:MβCD. To explore the underlying cellular and molecular mechanisms, we found that curcumin was capable of restoring caveolin-1 expression which was reduced by Chol:MβCD treatment. Moreover, curcumin abrogated the increment of phospho-ERK1/2 and nuclear accumulation of ERK1/2 in primary rat VSMCs induced by Chol:MβCD, which led to a suppression of AP-1 promoter activity stimulated by Chol:MβCD. In addition, curcumin was able to reverse cell cycle progression induced by Chol:MβCD, which was further supported by its down-regulation of cyclinD1 and E2F promoter activities in the presence of Chol:MβCD. Taking together, our data suggest curcumin inhibits Chol:MβCD-induced VSMCs proliferation via restoring caveolin-1 expression that leads to the suppression of over-activated ERK signaling and causes cell cycle arrest at G1/S phase. These novel findings support the beneficial potential of curcumin in cardiovascular disease.

Control of a perturbed under-actuated mechanical system

KAUST Repository

Zayane, Chadia; Laleg-Kirati, Taous-Meriem; Chemori, Ahmed

2015-01-01

In this work, the trajectory tracking problem for an under-actuated mechanical system in presence of unknown input disturbances is addressed. The studied inertia wheel inverted pendulum falls in the class of non minimum phase systems. The proposed

Renal Effects and Underlying Molecular Mechanisms of Long-Term Salt Content Diets in Spontaneously Hypertensive Rats

Science.gov (United States)

Berger, Rebeca Caldeira Machado; Vassallo, Paula Frizera; Crajoinas, Renato de Oliveira; Oliveira, Marilene Luzia; Martins, Flávia Letícia; Nogueira, Breno Valentim; Motta-Santos, Daisy; Araújo, Isabella Binotti; Forechi, Ludimila; Girardi, Adriana Castello Costa; Santos, Robson Augusto Souza; Mill, José Geraldo

2015-01-01

Several evidences have shown that salt excess is an important determinant of cardiovascular and renal derangement in hypertension. The present study aimed to investigate the renal effects of chronic high or low salt intake in the context of hypertension and to elucidate the molecular mechanisms underlying such effects. To this end, newly weaned male SHR were fed with diets only differing in NaCl content: normal salt (NS: 0.3%), low salt (LS: 0.03%), and high salt diet (HS: 3%) until 7 months of age. Analysis of renal function, morphology, and evaluation of the expression of the main molecular components involved in the renal handling of albumin, including podocyte slit-diaphragm proteins and proximal tubule endocytic receptors were performed. The relationship between diets and the balance of the renal angiotensin-converting enzyme (ACE) and ACE2 enzymes was also examined. HS produced glomerular hypertrophy and decreased ACE2 and nephrin expressions, loss of morphological integrity of the podocyte processes, and increased proteinuria, characterized by loss of albumin and high molecular weight proteins. Conversely, severe hypertension was attenuated and renal dysfunction was prevented by LS since proteinuria was much lower than in the NS SHRs. This was associated with a decrease in kidney ACE/ACE2 protein and activity ratio and increased cubilin renal expression. Taken together, these results suggest that LS attenuates hypertension progression in SHRs and preserves renal function. The mechanisms partially explaining these findings include modulation of the intrarenal ACE/ACE2 balance and the increased cubilin expression. Importantly, HS worsens hypertensive kidney injury and decreases the expression nephrin, a key component of the slit diaphragm. PMID:26495970

Renal Effects and Underlying Molecular Mechanisms of Long-Term Salt Content Diets in Spontaneously Hypertensive Rats.

Directory of Open Access Journals (Sweden)

Rebeca Caldeira Machado Berger

Full Text Available Several evidences have shown that salt excess is an important determinant of cardiovascular and renal derangement in hypertension. The present study aimed to investigate the renal effects of chronic high or low salt intake in the context of hypertension and to elucidate the molecular mechanisms underlying such effects. To this end, newly weaned male SHR were fed with diets only differing in NaCl content: normal salt (NS: 0.3%, low salt (LS: 0.03%, and high salt diet (HS: 3% until 7 months of age. Analysis of renal function, morphology, and evaluation of the expression of the main molecular components involved in the renal handling of albumin, including podocyte slit-diaphragm proteins and proximal tubule endocytic receptors were performed. The relationship between diets and the balance of the renal angiotensin-converting enzyme (ACE and ACE2 enzymes was also examined. HS produced glomerular hypertrophy and decreased ACE2 and nephrin expressions, loss of morphological integrity of the podocyte processes, and increased proteinuria, characterized by loss of albumin and high molecular weight proteins. Conversely, severe hypertension was attenuated and renal dysfunction was prevented by LS since proteinuria was much lower than in the NS SHRs. This was associated with a decrease in kidney ACE/ACE2 protein and activity ratio and increased cubilin renal expression. Taken together, these results suggest that LS attenuates hypertension progression in SHRs and preserves renal function. The mechanisms partially explaining these findings include modulation of the intrarenal ACE/ACE2 balance and the increased cubilin expression. Importantly, HS worsens hypertensive kidney injury and decreases the expression nephrin, a key component of the slit diaphragm.

Damage effects and mechanisms of proton irradiation on methyl silicone rubber

International Nuclear Information System (INIS)

Zhang, L.X.; He, Sh.Y.; Xu, Zh.; Wei, Q.

2004-01-01

A study was performed on the damage effects and mechanisms of proton irradiation with 150 keV energy to space-grade methyl silicone rubber. The changes in surface morphology, mechanical properties, infrared attenuated total reflection (ATR) spectrum, mass spectrum and pyrolysis gas chromatography-mass spectrum (PYGC-MS) indicated that, under lower fluence, the proton radiation would induce cross-linking effect, resulting in an increase in tensile strengths and hardness of the methyl silicon rubber. However, under higher proton fluence, the radiation-induced degradation, which decreased the tensile strengths and hardness, became a dominant effect. A macromolecular-network destruction model for the silicone rubber radiated with the protons was proposed

Exploration of mechanisms underlying the strain-rate-dependent mechanical property of single chondrocytes

Energy Technology Data Exchange (ETDEWEB)

Nguyen, Trung Dung; Gu, YuanTong, E-mail: yuantong.gu@qut.edu.au [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland (Australia)

2014-05-05

Based on the characterization by Atomic Force Microscopy, we report that the mechanical property of single chondrocytes has dependency on the strain-rates. By comparing the mechanical deformation responses and the Young's moduli of living and fixed chondrocytes at four different strain-rates, we explore the deformation mechanisms underlying this dependency property. We found that the strain-rate-dependent mechanical property of living cells is governed by both of the cellular cytoskeleton and the intracellular fluid when the fixed chondrocytes are mainly governed by their intracellular fluid, which is called the consolidation-dependent deformation behavior. Finally, we report that the porohyperelastic constitutive material model which can capture the consolidation-dependent behavior of both living and fixed chondrocytes is a potential candidature to study living cell biomechanics.

Effects of curcumin on growth of human cervical cancer xenograft in nude mice and underlying mechanism

Directory of Open Access Journals (Sweden)

Aixue LIU

Full Text Available Abstract The present study investigated the effects of curcumin (Cur on growth of human cervical cancer xenograft in nude mice and underlying mechanism. The nude mice modeled with human cervical cancer HeLa cell xenograft were treated with normal saline (control, 3 mg/kg Cisplatin, 50, 100 and 200 mg/kg Cur, respectively. The animal body weight and growth of tumor were measured. The expressions of Bax, Bcl-2, p53, p21, HIF-1α, VEGF and MIF protein in tumor tissue were determined. Results showed that, after treatment for 20 days, the tumor mass and tumor volume in 100 and 200 mg/kg Cur group were significantly lower than control group (P < 0.05. The expressions of Bax, p53 and p21 protein in tumor tissue in 200 mg/kg Cur group were significantly higher than control group (P < 0.05, and the expressions of Bcl-2, HIF-1α, VEGF and MIF protein in tumor tissue in 200 mg/kg Cur group were significantly lower than control group (P < 0.05. Cur can inhibit the growth of HeLa cell xenograft in nude mice. The possible mechanism may be related to its up-regulation of Bax, p53 and p21 protein expression in tumor tissue, and down-regulation of Bcl-2, HIF-1α, VEGF and MIF protein expression.

Effect mechanism of air deflectors on the cooling performance of dry cooling tower with vertical delta radiators under crosswind

International Nuclear Information System (INIS)

Zhao, Yuanbin; Long, Guoqing; Sun, Fengzhong; Li, Yan; Zhang, Cuijiao; Liu, Jiabin

2015-01-01

Highlights: • A 3D numerical model was set for NDDCTV to study the effect of air deflectors. • The air deflectors improve the tower performance by 1.375 °C at u c = 6 m/s for a case. • The air deflectors reduce the air inflow deviation angle θ d at most delta entries. • The reduced θ d can improve the cooling performance of former deteriorated columns. • Both the radial inflow air velocity and θ d impact the cooling performance of delta. - Abstract: To study the effect mechanism of air deflectors on dry cooling tower, a three dimensional numerical model was established, with full consideration of the delta structure. The accuracy and credibility of dry cooling tower numerical model were validated. By numerical model, the average air static pressure and the average radial inflow air velocity were computed and analyzed at delta air entry, sector air entry and exit faces. By the air inflow deviation angle θ d , the effect of air deflectors on the aerodynamic field around tower was analyzed. The water exit temperatures of θ −1 columns, θ +2 columns and cooling sectors were also presented to clarify the effect of air deflectors. It was found that the air deflectors improved the aerodynamic field around cooling columns. The reduced air inflow deviation degree at delta entry improved the cooling performance of deteriorated columns. Referring to the radial inflow air velocity u ra and the air inflow deviation degree at delta entry, the effect mechanism of air deflectors are clarified under crosswind

Neurobiological mechanisms underlying the blocking effect in aversive learning.

Science.gov (United States)

Eippert, Falk; Gamer, Matthias; Büchel, Christian

2012-09-19

Current theories of classical conditioning assume that learning depends on the predictive relationship between events, not just on their temporal contiguity. Here we employ the classic experiment substantiating this reasoning-the blocking paradigm-in combination with functional magnetic resonance imaging (fMRI) to investigate whether human amygdala responses in aversive learning conform to these assumptions. In accordance with blocking, we demonstrate that significantly stronger behavioral and amygdala responses are evoked by conditioned stimuli that are predictive of the unconditioned stimulus than by conditioned stimuli that have received the same pairing with the unconditioned stimulus, yet have no predictive value. When studying the development of this effect, we not only observed that it was related to the strength of previous conditioned responses, but also that predictive compared with nonpredictive conditioned stimuli received more overt attention, as measured by fMRI-concurrent eye tracking, and that this went along with enhanced amygdala responses. We furthermore observed that prefrontal regions play a role in the development of the blocking effect: ventromedial prefrontal cortex (subgenual anterior cingulate) only exhibited responses when conditioned stimuli had to be established as nonpredictive for an outcome, whereas dorsolateral prefrontal cortex also showed responses when conditioned stimuli had to be established as predictive. Most importantly, dorsolateral prefrontal cortex connectivity to amygdala flexibly switched between positive and negative coupling, depending on the requirements posed by predictive relationships. Together, our findings highlight the role of predictive value in explaining amygdala responses and identify mechanisms that shape these responses in human fear conditioning.

Neuro-cognitive mechanisms underlying the emotional modulation of word reading

Institute of Scientific and Technical Information of China (English)

无

2006-01-01

A novel neural model for emotional modulation of word reading is proposed. This model has four principal hypotheses: the dominant activation region hypothesis, the emotional modulation hypothesis, the attentional level hypothesis, and the interaction hypothesis. Four lines of research were reviewed to provide evidence for these hypotheses: (1) neuro-cognitive studies on the mechanisms of word reading (i.e., neural networks for reading); (2) studies on the influence of words' emotional valence on word reading; (3) studies of the effect of attention on word reading; and (4) studies on emotional modulation of word reading under different attentional levels.

Molecular mechanisms underlying mancozeb-induced inhibition of TNF-alpha production

International Nuclear Information System (INIS)

Corsini, Emanuela; Viviani, Barbara; Birindelli, Sarah; Gilardi, Federica; Torri, Anna; Codeca, Ilaria; Lucchi, Laura; Bartesaghi, Stefano; Galli, Corrado L.; Marinovich, Marina; Colosio, Claudio

2006-01-01

Mancozeb, a polymeric complex of manganese ethylenebisdithiocarbamate with zinc salt, is widely used in agriculture as fungicide. Literature data indicate that ethylenebisdithiocarbamates (EBDTCs) may have immunomodulatory effects in humans. We have recently found in agricultural workers occupationally exposed to the fungicide mancozeb a statistically significant decrease in lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF) production in leukocytes. TNF is an essential proinflammatory cytokine whose production is normally stimulated during an infection. The purpose of this work was to establish an in vitro model reflecting in vivo data and to characterize the molecular mechanism of action of mancozeb. The human promyelocytic cell line THP-1 was used as in vitro model to study the effects of mancozeb and its main metabolite ethylenthiourea (ETU) on LPS-induced TNF release. Mancozeb, but not ETU, at non-cytotoxic concentrations (1-100 μg/ml), induced a dose- and time-dependent inhibition of LPS-induced TNF release, reflecting in vivo data. The modulatory effect observed was not limited to mancozeb but also other EBDTCs, namely zineb and ziram, showed similar inhibitory effects. Mancozeb must be added before or simultaneously to LPS in order to observe the effect, indicating that it acts on early events triggered by LPS. It is known that nuclear factor-κB (NF-κB) tightly regulates TNF transcription. We could demonstrate that mancozeb, modulating LPS-induced reactive oxygen species generation, prevented IκB degradation and NF-κB nuclear translocation, which in turn resulted in decreased TNF production. To further understand the mechanism of the effect of mancozeb on TNF transcription, THP-1 cells were transfected with NF-κB promoter-luciferase construct, and the effect of mancozeb on luciferase activity was measured. Cells transfected with promoter constructs containing κB site showed decreased LPS-induced luciferase activity relative to control

Effects of triclosan on hormones and reproductive axis in female Yellow River carp (Cyprinus carpio): Potential mechanisms underlying estrogen effect.

Science.gov (United States)

Wang, Fan; Guo, Xiangmeng; Chen, Wanguang; Sun, Yaowen; Fan, Chaojie

2017-12-01

Triclosan (TCS), a member of the class of compounds called pharmaceutical and personal care products (PPCPs), is a broad antibacterial and antifungal agent found in a lot of consumer products. However, TCS hormone effect mechanism in teleost female fish is not clear. Female Yellow River carp (Cyprinus carpio) were exposed to 1/20, 1/10 and 1/5 LC 50 TCS (96h LC 50 of TCS to carp) under semi-static conditions for 42days. Vitellogenin (Vtg), 17β-estradiol (E 2 ), testosterone(T), estrogen receptor (Er), gonadotropin (GtH), and gonadotropin-releasing hormone (GnRH) levels were measured by enzyme-linked immunosorbent assay (ELISA). Meanwhile, we also examined the mRNA expressions of aromatase, GtHs-β, GnRH, and Er by quantitative real-time PCR (qRT-PCR). The results indicated that 1/5 LC 50 TCS induced Vtg in hepatopancreas of female carps by interference with the hypothalamic-pituitary-gonadal (HPG) axis at multiple potential loci through three mechanisms: (a) TCS exposure enhanced the mRNA expression of hypothalamus and gonadal aromatase which converts androgens into estrogens, subsequently increasing serum concentrations of E 2 to induce Vtg in hepatopancreas; (b) TCS treatment increased GnRH and GtH-β mRNA expression and secretion, causing the disturbance of reproductive endocrine and the increase of E 2 to induce Vtg in hepatopancreas; (c) TCS exposure enhanced synthesis and secretion of Er, then it bound to Er to active Vtg synthesis. These mechanisms showed that TCS may induce Vtg production in female Yellow River carp by Er-mediated and non-Er-mediated pathways. Copyright © 2017 Elsevier Inc. All rights reserved.

Different routes, same pathways: Molecular mechanisms under silver ion and nanoparticle exposures in the soil sentinel Eisenia fetida

International Nuclear Information System (INIS)

Novo, Marta; Lahive, Elma; Díez-Ortiz, María; Matzke, Marianne; Morgan, Andrew J.; Spurgeon, David J.; Svendsen, Claus; Kille, Peter

2015-01-01

Use of nanotechnology products is increasing; with silver (Ag) nanoparticles particularly widely used. A key uncertainty surrounding the risk assessment of AgNPs is whether their effects are driven through the same mechanism of action that underlies the toxic effects of Ag ions. We present the first full transcriptome study of the effects of Ag ions and NPs in an ecotoxicological model soil invertebrate, the earthworm Eisenia fetida. Gene expression analyses indicated similar mechanisms for both silver forms with toxicity being exerted through pathways related to ribosome function, sugar and protein metabolism, molecular stress, disruption of energy production and histones. The main difference seen between Ag ions and NPs was associated with potential toxicokinetic effects related to cellular internalisation and communication, with pathways related to endocytosis and cilia being significantly enriched. These results point to a common final toxicodynamic response, but initial internalisation driven by different exposure routes and toxicokinetic mechanisms. - Highlights: • Molecular effects underlying Ag ions and NPs exposure were studied in Eisenia fetida. • Full transcriptomic study of a genetically characterised lineage. • NPs and ions presented a similar toxicodynamic response. • Internalisation of the two Ag forms by different toxicokinetic mechanisms. - Transcriptomic analyses after exposure of earthworms to silver NPs or ions showed a final common toxicodynamic response, but internalisation by different toxicokinetic mechanisms

Cell-Nonautonomous Mechanisms Underlying Cellular and Organismal Aging.

Science.gov (United States)

Medkour, Younes; Svistkova, Veronika; Titorenko, Vladimir I

2016-01-01

Cell-autonomous mechanisms underlying cellular and organismal aging in evolutionarily distant eukaryotes have been established; these mechanisms regulate longevity-defining processes within a single eukaryotic cell. Recent findings have provided valuable insight into cell-nonautonomous mechanisms modulating cellular and organismal aging in eukaryotes across phyla; these mechanisms involve a transmission of various longevity factors between different cells, tissues, and organisms. Herein, we review such cell-nonautonomous mechanisms of aging in eukaryotes. We discuss the following: (1) how low molecular weight transmissible longevity factors modulate aging and define longevity of cells in yeast populations cultured in liquid media or on solid surfaces, (2) how communications between proteostasis stress networks operating in neurons and nonneuronal somatic tissues define longevity of the nematode Caenorhabditis elegans by modulating the rates of aging in different tissues, and (3) how different bacterial species colonizing the gut lumen of C. elegans define nematode longevity by modulating the rate of organismal aging. Copyright © 2016. Published by Elsevier Inc.

Crack assessment of pipe under combined thermal and mechanical load

International Nuclear Information System (INIS)

Song, Tae Kwang; Kim, Yun Jae

2009-01-01

In this paper, J-integral and transient C(t)-integral, which were key parameters in low temperature and high temperature fracture mechanics, under combined thermal and mechanical load were estimated via 3-dimensional finite element analyses. Various type of thermal and mechanical load, material hardening were considered to decrease conservatism in existing solutions. As a results, V-factor and redistribution time for combined thermal and mechanical load were proposed to calculate J-integral and C(t)-integral, respectively.

Effects and underlying mechanisms of irisin on the proliferation and apoptosis of pancreatic β cells.

Directory of Open Access Journals (Sweden)

Shiwei Liu

Full Text Available Pancreatic β cell dysfunction and reduction due to glucose toxicity play a crucial role in the development of type 2 diabetes mellitus (T2DM. Irisin, a novel exercise-induced myokine, reduces obesity, improves insulin resistance and lowers blood glucose by promoting the browning of white adipose tissue, thereby enhancing thermogenesis and increasing energy expenditure. Recent studies have reported that irisin promotes cell proliferation and protects cells from apoptosis. However, the effects of irisin on pancreatic β cells are unknown. Thus, the aim of this study was to investigate the effects and the potential underlying mechanisms of irisin on pancreatic β cell proliferation and apoptosis induced by high glucose. Both in vitro (INS-1 cells and in vivo (a T2DM rat model experiments were conducted. Irisin significantly increased the proliferation of INS-1 cells, with the most significant effect observed at 24 h with 100 ng/ml irisin. Irisin also promoted INS-1 cell proliferation via the ERK and p38 MAPK signaling pathways, protected the cells from high-glucose-induced apoptosis by regulating the expression of caspases, Bad, Bax, Bcl-2 and Bcl-xl, and improved pancreatic β cell function. Irisin significantly reduced the body weight and blood glucose values and increased the serum insulin levels of the diabetic rats. An oral glucose tolerance test (OGTT indicated that irisin also improved the glucose tolerance of T2DM rats. Together, these findings suggest that irisin may have applications in the prevention and treatment of T2DM because of its protective effect on the secretion of pancreatic β cells.

Effect of fiber distribution and realignment on the nonlinear and inhomogeneous mechanical properties of human supraspinatus tendon under longitudinal tensile loading.

Science.gov (United States)

Lake, Spencer P; Miller, Kristin S; Elliott, Dawn M; Soslowsky, Louis J

2009-12-01

Tendon exhibits nonlinear stress-strain behavior that may be partly due to movement of collagen fibers through the extracellular matrix. While a few techniques have been developed to evaluate the fiber architecture of other soft tissues, the organizational behavior of tendon under load has not been determined. The supraspinatus tendon (SST) of the rotator cuff is of particular interest for investigation due to its complex mechanical environment and corresponding inhomogeneity. In addition, SST injury occurs frequently with limited success in treatment strategies, illustrating the need for a better understanding of SST properties. Therefore, the objective of this study was to quantitatively evaluate the inhomogeneous tensile mechanical properties, fiber organization, and fiber realignment under load of human SST utilizing a novel polarized light technique. Fiber distributions were found to become more aligned under load, particularly during the low stiffness toe-region, suggesting that fiber realignment may be partly responsible for observed nonlinear behavior. Fiber alignment was found to correlate significantly with mechanical parameters, providing evidence for strong structure-function relationships in tendon. Human SST exhibits complex, inhomogeneous mechanical properties and fiber distributions, perhaps due to its complex loading environment. Surprisingly, histological grade of degeneration did not correlate with mechanical properties.

Poroelastic Mechanical Effects of Hemicelluloses on Cellulosic Hydrogels under Compression

Science.gov (United States)

Lopez-Sanchez, Patricia; Cersosimo, Julie; Wang, Dongjie; Flanagan, Bernadine; Stokes, Jason R.; Gidley, Michael J.

2015-01-01

Hemicelluloses exhibit a range of interactions with cellulose, the mechanical consequences of which in plant cell walls are incompletely understood. We report the mechanical properties of cell wall analogues based on cellulose hydrogels to elucidate the contribution of xyloglucan or arabinoxylan as examples of two hemicelluloses displaying different interactions with cellulose. We subjected the hydrogels to mechanical pressures to emulate the compressive stresses experienced by cell walls in planta. Our results revealed that the presence of either hemicellulose increased the resistance to compression at fast strain rates. However, at slow strain rates, only xyloglucan increased composite strength. This behaviour could be explained considering the microstructure and the flow of water through the composites confirming their poroelastic nature. In contrast, small deformation oscillatory rheology showed that only xyloglucan decreased the elastic moduli. These results provide evidence for contrasting roles of different hemicelluloses in plant cell wall mechanics and man-made cellulose-based composite materials. PMID:25794048

Reduction of irradiated tumor cells viability under effect of hyperglycemia

International Nuclear Information System (INIS)

Meshcherikova, V.V.; Voloshina, E.A.

1983-01-01

On Ehrlich carcinoma cells adapted to growth in vivo and in vitro, cellular mechanisms of short-term hyperglycemia effect have been studied. It has been found that SH by itself leads to the loss of viability of a part of cells of ELD solid tumors manifesting during the first 24 hours upon irradiation according to the interphase death type. Tumor cell radiation injuries arising under the effect of irradiation, usually non realized up to the first division, under SH conditions potentiate its injury effect. The phenomena observed explain partially selective injury of tumoral cells in the course of irradiation under SH conditions which testifies to the prospects of its use in clinics

Handedness is related to neural mechanisms underlying hemispheric lateralization of face processing

Science.gov (United States)

Frässle, Stefan; Krach, Sören; Paulus, Frieder Michel; Jansen, Andreas

2016-06-01

While the right-hemispheric lateralization of the face perception network is well established, recent evidence suggests that handedness affects the cerebral lateralization of face processing at the hierarchical level of the fusiform face area (FFA). However, the neural mechanisms underlying differential hemispheric lateralization of face perception in right- and left-handers are largely unknown. Using dynamic causal modeling (DCM) for fMRI, we aimed to unravel the putative processes that mediate handedness-related differences by investigating the effective connectivity in the bilateral core face perception network. Our results reveal an enhanced recruitment of the left FFA in left-handers compared to right-handers, as evidenced by more pronounced face-specific modulatory influences on both intra- and interhemispheric connections. As structural and physiological correlates of handedness-related differences in face processing, right- and left-handers varied with regard to their gray matter volume in the left fusiform gyrus and their pupil responses to face stimuli. Overall, these results describe how handedness is related to the lateralization of the core face perception network, and point to different neural mechanisms underlying face processing in right- and left-handers. In a wider context, this demonstrates the entanglement of structurally and functionally remote brain networks, suggesting a broader underlying process regulating brain lateralization.

Different mechanisms to explain the reversed effects of mental health on work characteristics

NARCIS (Netherlands)

Lange, A.H. de; Taris, T.W.; Kompier, M.A.J.; Houtman, I.L.D.; Bongers, P.M.

2005-01-01

Objectives: The number of longitudinal studies reporting evidence for reversed effects of strain on work is growing, but evidence regarding the mechanisms underlying such effects is scarce. In this study, earlier longitudinal findings were reviewed, and the following four mechanisms for reversed

Mechanisms of astrocytic K(+) clearance and swelling under high extracellular K(+) concentrations.

Science.gov (United States)

Murakami, Shingo; Kurachi, Yoshihisa

2016-03-01

In response to the elevation of extracellular K(+) concentration ([K(+)]out), astrocytes clear excessive K(+) to maintain conditions necessary for neural activity. K(+) clearance in astrocytes occurs via two processes: K(+) uptake and K(+) spatial buffering. High [K(+)]out also induces swelling in astrocytes, leading to edema and cell death in the brain. Despite the importance of astrocytic K(+) clearance and swelling, the underlying mechanisms remain unclear. Here, we report results from a simulation analysis of astrocytic K(+) clearance and swelling. Astrocyte models were constructed by incorporating various mechanisms such as intra/extracellular ion concentrations of Na(+), K(+), and Cl(-), cell volume, and models of Na,K-ATPase, Na-K-Cl cotransporter (NKCC), K-Cl cotransporter, inwardly-rectifying K(+) (KIR) channel, passive Cl(-) current, and aquaporin channel. The simulated response of astrocyte models under the uniform distribution of high [K(+)]out revealed significant contributions of NKCC and Na,K-ATPase to increases of intracellular K(+) and Cl(-) concentrations, and swelling. Moreover, we found that, under the non-uniform distribution of high [K(+)]out, KIR channels localized at synaptic clefts absorbed excess K(+) by depolarizing the equivalent potential of K(+) (E K) above membrane potential, while K(+) released through perivascular KIR channels was enhanced by hyperpolarizing E K and depolarizing membrane potential. Further analysis of simulated drug effects revealed that astrocyte swelling was modulated by blocking each of the ion channels and transporters. Our simulation analysis revealed controversial mechanisms of astrocytic K(+) clearance and swelling resulting from complex interactions among ion channels and transporters.

Inspection Mechanism and Experimental Study of Prestressed Reverse Tension Method under PC Beam Bridge Anchorage

Science.gov (United States)

Peng, Zhang

2018-03-01

the prestress under anchorage is directly related to the structural security and performance of PC beam bridge. The reverse tension method is a kind of inspection which confirms the prestress by exerting reversed tension load on the exposed prestressing tendon of beam bridge anchoring system. The thesis elaborately expounds the inspection mechanism and mechanical effect of reverse tension method, theoretically analyzes the influential elements of inspection like tool anchorage deformation, compression of conjuncture, device glide, friction of anchorage loop mouth and elastic compression of concrete, and then presents the following formula to calculate prestress under anchorage. On the basis of model experiment, the thesis systematically studies some key issues during the reverse tension process of PC beam bridge anchorage system like the formation of stress-elongation curve, influential factors, judgment method of prestress under anchorage, variation trend and compensation scale, verifies the accuracy of mechanism analysis and demonstrates: the prestress under anchorage is less than or equal to 75% of the ultimate strength of prestressing tendon, the error of inspect result is less than 1%, which can meet with the demands of construction. The research result has provided theoretical basis and technical foundation for the promotion and application of reverse tension in bridge construction.

Music listening after stroke: beneficial effects and potential neural mechanisms.

Science.gov (United States)

Särkämö, Teppo; Soto, David

2012-04-01

Music is an enjoyable leisure activity that also engages many emotional, cognitive, and motor processes in the brain. Here, we will first review previous literature on the emotional and cognitive effects of music listening in healthy persons and various clinical groups. Then we will present findings about the short- and long-term effects of music listening on the recovery of cognitive function in stroke patients and the underlying neural mechanisms of these music effects. First, our results indicate that listening to pleasant music can have a short-term facilitating effect on visual awareness in patients with visual neglect, which is associated with functional coupling between emotional and attentional brain regions. Second, daily music listening can improve auditory and verbal memory, focused attention, and mood as well as induce structural gray matter changes in the early poststroke stage. The psychological and neural mechanisms potentially underlying the rehabilitating effect of music after stroke are discussed. © 2012 New York Academy of Sciences.

Nonlinear Dynamic Analysis of Telescopic Mechanism for Truss Structure Bridge Inspection Vehicle Under Pedestrian Excitation

Directory of Open Access Journals (Sweden)

Wenwen Sui

Full Text Available Abstract Nonlinear dynamic analysis of an axially moving telescopic mechanism for truss structure bridge inspection vehicle under pedestrian excitation is carried out. A biomechanically inspired inverted-pendulum model is utilized to simplify the pedestrian. The nonlinear equations of motion for the beam-pedestrian system are derived using the Hamilton's principle. The equations are transformed into two ordinary differential equations by applying the Galerkin's method at the first two orders. The solutions to the equations are acquired by using the Newmark-β method associated with the Newton-Raphson method. The time-dependent feature of the eigenfunctions for the two beams are taken into consideration in the solutions. Accordingly, the equations of motion for a simplified system, in which the pedestrian is regarded as moving cart, are given. In the numerical examples, dynamic responses of the telescopic mechanism in eight conditions of different beam-telescoping and pedestrian-moving directions are simulated. Comparisons between the vibrations of the beams under pedestrian excitation and corresponding moving cart are carried out to investigate the influence of the pedestrian excitation on the telescopic mechanism. The results show that the displacement of the telescopic mechanism under pedestrian excitation is smaller than that under moving cart especially when the pedestrian approaches the beams end. Additionally, compared with moving cart, the pedestrian excitation can effectively strengthen the vibration when the beam extension is small or when the pedestrian is close to the beams end.

Klokwerk + study protocol: An observational study to the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects.

Science.gov (United States)

Loef, Bette; van Baarle, Debbie; van der Beek, Allard J; van Kerkhof, Linda W; van de Langenberg, Daniëlla; Proper, Karin I

2016-08-02

Night-shift work may cause severe disturbances in the worker's circadian rhythm, which has been associated with the onset of health problems and diseases. As a substantial part of the workforce is exposed to night-shift work, harmful aspects of night-shift work should not be overlooked. The aim of the Klokwerk + study is to study the effects of night-shift work on body weight and infection susceptibility and the mechanisms underlying these health effects. First, we will study the relation between night-shift work exposure and body weight and between night-shift work exposure and infection susceptibility. Second, we will examine the mechanisms linking night-shift work exposure to body weight and infection susceptibility, with a specific focus on sleep, physical activity, diet, light exposure, vitamin D level, and immunological factors. Lastly, we will focus on the identification of biomarkers for chronic circadian disturbance associated with night-shift work. The design of this study is a prospective observational cohort study consisting of 1,960 health care workers aged 18-65 years. The study population will consist of a group of night-shift workers and an equally sized group of non-night-shift workers. During the study, there will be two measurement periods. As one of the main outcomes of this study is infection susceptibility, the measurement periods will take place at approximately the first (September/October) (T0) and the last month (April/May) (T1, after 6 months) of the flu season. The measurements will consist of questionnaires, anthropometric measurements, a smartphone application to determine infection susceptibility, food diaries, actigraphy, light sensors, and blood sample analyses. The Klokwerk + study will contribute to the current need for high-quality data on the health effects of night-shift work and its underlying behavioral and physiological mechanisms. The findings can be the starting point for the development of interventions that

Klokwerk + study protocol: An observational study to the effects of night–shift work on body weight and infection susceptibility and the mechanisms underlying these health effects

Directory of Open Access Journals (Sweden)

Bette Loef

2016-08-01

Full Text Available Abstract Background Night–shift work may cause severe disturbances in the worker’s circadian rhythm, which has been associated with the onset of health problems and diseases. As a substantial part of the workforce is exposed to night–shift work, harmful aspects of night–shift work should not be overlooked. The aim of the Klokwerk + study is to study the effects of night–shift work on body weight and infection susceptibility and the mechanisms underlying these health effects. First, we will study the relation between night–shift work exposure and body weight and between night–shift work exposure and infection susceptibility. Second, we will examine the mechanisms linking night–shift work exposure to body weight and infection susceptibility, with a specific focus on sleep, physical activity, diet, light exposure, vitamin D level, and immunological factors. Lastly, we will focus on the identification of biomarkers for chronic circadian disturbance associated with night–shift work. Methods/design The design of this study is a prospective observational cohort study consisting of 1,960 health care workers aged 18–65 years. The study population will consist of a group of night–shift workers and an equally sized group of non–night–shift workers. During the study, there will be two measurement periods. As one of the main outcomes of this study is infection susceptibility, the measurement periods will take place at approximately the first (September/October (T0 and the last month (April/May (T1, after 6 months of the flu season. The measurements will consist of questionnaires, anthropometric measurements, a smartphone application to determine infection susceptibility, food diaries, actigraphy, light sensors, and blood sample analyses. Discussion The Klokwerk + study will contribute to the current need for high–quality data on the health effects of night–shift work and its underlying behavioral and physiological

Detecting method for crude oil price fluctuation mechanism under different periodic time series

International Nuclear Information System (INIS)

Gao, Xiangyun; Fang, Wei; An, Feng; Wang, Yue

2017-01-01

Highlights: • We proposed the concept of autoregressive modes to indicate the fluctuation patterns. • We constructed transmission networks for studying the fluctuation mechanism. • There are different fluctuation mechanism under different periodic time series. • Only a few types of autoregressive modes control the fluctuations in crude oil price. • There are cluster effects during the fluctuation mechanism of autoregressive modes. - Abstract: Current existing literatures can characterize the long-term fluctuation of crude oil price time series, however, it is difficult to detect the fluctuation mechanism specifically under short term. Because each fluctuation pattern for one short period contained in a long-term crude oil price time series have dynamic characteristics of diversity; in other words, there exhibit various fluctuation patterns in different short periods and transmit to each other, which reflects the reputedly complicate and chaotic oil market. Thus, we proposed an incorporated method to detect the fluctuation mechanism, which is the evolution of the different fluctuation patterns over time from the complex network perspective. We divided crude oil price time series into segments using sliding time windows, and defined autoregressive modes based on regression models to indicate the fluctuation patterns of each segment. Hence, the transmissions between different types of autoregressive modes over time form a transmission network that contains rich dynamic information. We then capture transmission characteristics of autoregressive modes under different periodic time series through the structure features of the transmission networks. The results indicate that there are various autoregressive modes with significantly different statistical characteristics under different periodic time series. However, only a few types of autoregressive modes and transmission patterns play a major role in the fluctuation mechanism of the crude oil price, and these

Effect of heat treatment upon the mechanical and poro-mechanical behaviour of cement-based materials: hydraulic properties and morphological changes

International Nuclear Information System (INIS)

Chen, Xiao-Ting

2009-01-01

This work investigates the effects of morphological changes of a cement-based material subjected to heat treatment (up to 400 C). For a model W/C=0.5 mortar, we have characterized experimentally hydraulic behaviour (gas permeability), mechanical behaviour (in uniaxial compression, hydrostatic compression with or without deviatoric stress) and poro-mechanical behaviour (incompressibility moduli Kb, Ks and Biot's coefficient b) after a heating/cooling cycle. We have also developed an original experiment aimed at quantifying the accessible pore space volume under hydrostatic compression. The creation of occluded porosity under high confinement is confirmed, which justifies the observed decrease of solid matrix rigidity Ks under high confinement. A gas retention phenomenon was identified under simultaneous thermal and hydrostatic loadings for mortar, and industrial concretes (provided by CERIB and ANDRA). A predictive thermo-elasto-plastic model with isotropic damage and a micro-mechanical approach, which represents micro-cracking, are coupled in order to analyze or predict the evolution of mechanical and poro-elastic properties after heat cycling. (author)

Believing versus interacting: Behavioural and neural mechanisms underlying interpersonal coordination

DEFF Research Database (Denmark)

Konvalinka, Ivana; Bauer, Markus; Kilner, James

When two people engage in a bidirectional interaction with each other, they use both bottom-up sensorimotor mechanisms such as monitoring and adapting to the behaviour of the other, as well as top-down cognitive processes, modulating their beliefs and allowing them to make decisions. Most research...... in joint action has investigated only one of these mechanisms at a time – low-level processes underlying joint coordination, or high-level cognitive mechanisms that give insight into how people think about another. In real interactions, interplay between these two mechanisms modulates how we interact...

Mechanical behavior of silicon carbide nanoparticles under uniaxial compression

Energy Technology Data Exchange (ETDEWEB)

He, Qiuxiang; Fei, Jing; Tang, Chao; Zhong, Jianxin; Meng, Lijun, E-mail: ljmeng@xtu.edu.cn [Xiangtan University, Hunan Key Laboratory for Micro-Nano Energy Materials and Devices, Faculty of School of Physics and Optoelectronics (China)

2016-03-15

The mechanical behavior of SiC nanoparticles under uniaxial compression was investigated using an atomic-level compression simulation technique. The results revealed that the mechanical deformation of SiC nanocrystals is highly dependent on compression orientation, particle size, and temperature. A structural transformation from the original zinc-blende to a rock-salt phase is identified for SiC nanoparticles compressed along the [001] direction at low temperature. However, the rock-salt phase is not observed for SiC nanoparticles compressed along the [110] and [111] directions irrespective of size and temperature. The high-pressure-generated rock-salt phase strongly affects the mechanical behavior of the nanoparticles, including their hardness and deformation process. The hardness of [001]-compressed nanoparticles decreases monotonically as their size increases, different from that of [110] and [111]-compressed nanoparticles, which reaches a maximal value at a critical size and then decreases. Additionally, a temperature-dependent mechanical response was observed for all simulated SiC nanoparticles regardless of compression orientation and size. Interestingly, the hardness of SiC nanocrystals with a diameter of 8 nm compressed in [001]-orientation undergoes a steep decrease at 0.1–200 K and then a gradual decline from 250 to 1500 K. This trend can be attributed to different deformation mechanisms related to phase transformation and dislocations. Our results will be useful for practical applications of SiC nanoparticles under high pressure.

Neural mechanisms underlying transcranial direct current stimulation in aphasia: A feasibility study.

Directory of Open Access Journals (Sweden)

Lena eUlm

2015-10-01

Full Text Available Little is known about the neural mechanisms by which transcranial direct current stimulation (tDCS impacts on language processing in post-stroke aphasia. This was addressed in a proof-of-principle study that explored the effects of tDCS application in aphasia during simultaneous functional magnetic resonance imaging (fMRI. We employed a single subject, cross-over, sham-tDCS controlled design and the stimulation was administered to an individualized perilesional stimulation site that was identified by a baseline fMRI scan and a picture naming task. Peak activity during the baseline scan was located in the spared left inferior frontal gyrus (IFG and this area was stimulated during a subsequent cross-over phase. tDCS was successfully administered to the target region and anodal- vs. sham-tDCS resulted in selectively increased activity at the stimulation site. Our results thus demonstrate that it is feasible to precisely target an individualized stimulation site in aphasia patients during simultaneous fMRI which allows assessing the neural mechanisms underlying tDCS application. The functional imaging results of this case report highlight one possible mechanism that may have contributed to beneficial behavioural stimulation effects in previous clinical tDCS trials in aphasia. In the future, this approach will allow identifying distinct patterns of stimulation effects on neural processing in larger cohorts of patients. This may ultimately yield information about the variability of tDCS-effects on brain functions in aphasia.

From Sound to Significance: Exploring the Mechanisms Underlying Emotional Reactions to Music.

Science.gov (United States)

Juslin, Patrik N; Barradas, Gonçalo; Eerola, Tuomas

2015-01-01

A common approach to studying emotional reactions to music is to attempt to obtain direct links between musical surface features such as tempo and a listener's responses. However, such an analysis ultimately fails to explain why emotions are aroused in the listener. In this article we explore an alternative approach, which aims to account for musical emotions in terms of a set of psychological mechanisms that are activated by different types of information in a musical event. This approach was tested in 4 experiments that manipulated 4 mechanisms (brain stem reflex, contagion, episodic memory, musical expectancy) by selecting existing musical pieces that featured information relevant for each mechanism. The excerpts were played to 60 listeners, who were asked to rate their felt emotions on 15 scales. Skin conductance levels and facial expressions were measured, and listeners reported subjective impressions of relevance to specific mechanisms. Results indicated that the target mechanism conditions evoked emotions largely as predicted by a multimechanism framework and that mostly similar effects occurred across the experiments that included different pieces of music. We conclude that a satisfactory account of musical emotions requires consideration of how musical features and responses are mediated by a range of underlying mechanisms.

Study on Collapse Mechanism of Steel Frame Structure under High Temperature and Blast Loading

Science.gov (United States)

Baoxin, Qi; Yan, Shi; Bi, Jialiang

2018-03-01

Numerical simulation analysis for collapsing process and mechanism of steel frame structures under the combined effects of fire and explosion is performed in this paper. First of all, a new steel constitutive model considering fire (high temperature softening effect) and blast (strain rate effect) is established. On the basis of the traditional Johnson-Cook model and the Perzyna model, the relationship between strain and scaled distance as well as the EOUROCODE3 standard heating curve taking into account the temperature effect parameters is introduced, and a modified Johnson-Cook constitutive model is established. Then, the influence of considering the scaled distance is introduced in order to more effectively describe the destruction and collapse phenomena of steel frame structures. Some conclusions are obtained based on the numerical analysis that the destruction will be serious and even progressively collapse with decreasing of the temperature of the steel column for the same scaled distance under the combined effects of fire and blast; the damage will be serious with decreasing of the scaled distance of the steel column under the same temperature under the combined effects of fire and blast; in the case of the combined effects of fire and blast happening in the side-spans, the partial progressive collapse occurs as the scaled distance is less than or equal to 1.28; six kinds of damages which are no damage, minor damage, moderate damage, severe damage, critical collapse, and progressive collapse.

Mechanisms underlying the anti-androgenic effects of diethylhexyl phthalate in fetal rat testis

DEFF Research Database (Denmark)

Boberg, Julie; Metzdorff, Stine Broeng; Vinggaard, Anne

2006-01-01

Diethylhexyl phthalate (DEHP) is widely used as a plasticizer in consumer products and is known to disturb the development of the male reproductive system in rats. The mechanisms by which DEHP exerts these effects are not yet fully elucidated, though some of the effects are related to reduced fetal...... in the downregulation of steroidogenic factors and testosterone levels and thereby underlie the disturbed development of the male reproductive system. (c) 2006 Elsevier Ireland Ltd. All rights reserved......., 30, 100 or 300 mg/kg bw/day of DEHP. In male fetuses examined at GD 21, testicular testosterone production ex vivo and testicular testosterone levels were reduced significantly at the highest dose. Histopathological effects on gonocytes were observed at 100 and 300 mg/kg bw/day, whereas Leydig cell...

First-principles predictions of structural, mechanical and electronic properties of βTiNb under high pressure

Science.gov (United States)

Wang, Z. P.; Fang, Q. H.; Li, J.; Liu, B.

2018-04-01

Structural, mechanical and electronic properties of βTiNb alloy under high pressure have been investigated based on the density functional theory (DFT). The dependences of dimensionless volume ratio, elastic constants, bulk modulus, Young's modulus, shear modulus, ductile/brittle, anisotropy and Poisson's ratio on applied pressure are all calculated successfully. The results reveal that βTiNb alloy is mechanically stable under pressure below 23.45 GPa, and the pressure-induced phase transformation could occur beyond this critical value. Meanwhile, the applied pressure can effectively promote the mechanical properties of βTiNb alloy, including the resistances to volume change, elastic deformation and shear deformation, as well as the material ductility and metallicity. Furthermore, the calculated electronic structures testify that βTiNb alloy performs the metallicity and the higher pressure reduces the structural stability of unit cell.

[Underlying Mechanisms of Methamphetamine-Induced Self-Injurious Behavior and Lethal Effects in Mice].

Science.gov (United States)

Mori, Tomohisa; Sawaguchi, Toshiko

2018-01-01

Relatively high doses of psychostimulants induce neurotoxicity on the dopaminergic system and self-injurious behavior (SIB) in rodents. However the underlying neuronal mechanisms of SIB remains unclear. Dopamine receptor antagonists, N-methyl-D-aspartic acid (NMDA) receptor antagonists, Nitric Oxide Synthase (NOS) inhibitors and free radical scavengers significantly attenuate methamphetamine-induced SIB. These findings indicate that activation of dopamine as well as NMDA receptors followed by radical formation and oxidative stress, especially when mediated by NOS activation, is associated with methamphetamine-induced SIB. On the other hand, an increase in the incidence of polydrug abuse is a major problem worldwide. Coadministered methamphetamine and morphine induced lethality in more than 80% in mice, accompanied by an increase in the number of poly (ADP-ribose) polymerase (PARP)-immunoreactive cells in the heart, kidney and liver. The lethal effect and the increase in the incidence of rupture or PARP-immunoreactive cells induced by the coadministration of methamphetamine and morphine were significantly attenuated by pretreatment with a phospholipase A2 inhibitor or a radical scavenger, or by cooling of body from 30 to 90 min after drug administration. These results suggest that free radicals play an important role in the increased lethality induced by the coadministration of methamphetamine and morphine. Therefore, free radical scavengers and cooling are beneficial for preventing death that is induced by the coadministration of methamphetamine and morphine. These findings may help us better understand for masochistic behavior, which is a clinical phenomenon on SIB, as well as polydrug-abuse-induced acute toxicity.

Reverse mechanical after effect during hydrogenation of zone refined iron

Energy Technology Data Exchange (ETDEWEB)

Spivak, L.V.; Skryabina, N.E.; Kurmaeva, L.D.; Smirnov, L.V. (Permskij Gosudarstvennyj Univ. (USSR); AN SSSR, Sverdlovsk. Inst. Fiziki Metallov)

1984-12-01

The relationship between the process of hydrogenation and the reverse mechanical after effect (RMA) microplastic deformation in the zone refined iron has been studied. Metallographic investigations and mechanical testing of the samples hydrogenated under torsional strain have been performed. It is shown that in the zone refined iron the formation of voids responsible for irreversible hydrogen embrittlement does not occur, but the hydrogen-initiated RMA strain is conserved, i. e. the RMA effects are independent of the presence of discontinuities.

Nonlinear Mechanics of MEMS Rectangular Microplates under Electrostatic Actuation

KAUST Repository

Saghir, Shahid

2016-01-01

The first objective of the dissertation is to develop a suitable reduced order model capable of investigating the nonlinear mechanical behavior of von-Karman plates under electrostatic actuation. The second objective is to investigate the nonlinear

Pyroelectric response mechanism of barium strontium titanate ceramics in dielectric bolometer mode: The underlying essence of the enhancing effect of direct current bias field

International Nuclear Information System (INIS)

Mao, Chaoliang; Cao, Sheng; Yan, Shiguang; Yao, Chunhua; Cao, Fei; Wang, Genshui; Dong, Xianlin; Hu, Xu; Yang, Chunli

2013-01-01

Pyroelectric response mechanism of Ba 0.70 Sr 0.30 TiO 3 ceramics under dielectric bolometer (DB) mode was investigated by dielectric and pyroelectric properties measurement. The variations of total, intrinsic, and induced pyroelectric coefficients (p tot , p int , p ind ) with temperatures and bias fields were analyzed. p int plays the dominant role to p tot through most of the temperature range and p ind will be slightly higher than p int above T 0 . The essence of the enhancing effect of DC bias field on pyroelectric coefficient can be attributed to the high value of p int . This mechanism is useful for the pyroelectric materials (DB mode) applications.

A numerical study of crack interactions under thermo-mechanical load using EFGM

International Nuclear Information System (INIS)

Pant, Mohit; Singh, I. V.; Mishra, B. K.

2011-01-01

In this work, element free Galerkin method (EFGM) has been used to obtain the solution of various edge crack problems under thermo-mechanical loads as it provides a versatile technique to model stationary as well as moving crack problems without re-meshing. Standard diffraction criterion has been modified with multiple crack weight technique to characterize the presence of various cracks in the domain of influence of a particular node. The effect of crack inclination has been studied for single as well as two edge cracks, whereas the cracks interaction has been studied for two edge cracks lying on same as well as opposite edges under plane stress conditions. The values of mode-I and mode-II stress intensity factors have been evaluated by the interaction integral approach

Tissue Acoustoelectric Effect Modeling From Solid Mechanics Theory.

Science.gov (United States)

Song, Xizi; Qin, Yexian; Xu, Yanbin; Ingram, Pier; Witte, Russell S; Dong, Feng

2017-10-01

The acoustoelectric (AE) effect is a basic physical phenomenon, which underlies the changes made in the conductivity of a medium by the application of focused ultrasound. Recently, based on the AE effect, several biomedical imaging techniques have been widely studied, such as ultrasound-modulated electrical impedance tomography and ultrasound current source density imaging. To further investigate the mechanism of the AE effect in tissue and to provide guidance for such techniques, we have modeled the tissue AE effect using the theory of solid mechanics. Both bulk compression and thermal expansion of tissue are considered and discussed. Computation simulation shows that the muscle AE effect result, conductivity change rate, is 3.26×10 -3 with 4.3-MPa peak pressure, satisfying the theoretical value. Bulk compression plays the main role for muscle AE effect, while thermal expansion makes almost no contribution to it. In addition, the AE signals of porcine muscle are measured at different focal positions. With the same magnitude order and the same change trend, the experiment result confirms that the simulation result is effective. Both simulation and experimental results validate that tissue AE effect modeling using solid mechanics theory is feasible, which is of significance for the further development of related biomedical imaging techniques.

A multi-scale approach of mechanical and transport properties of cementitious materials under rises of temperature

International Nuclear Information System (INIS)

Caratini, G.

2012-01-01

The modern industrial activities (storage of nuclear waste, geothermal wells, nuclear power plants,...) can submit cementitious materials to some extreme conditions, for example at temperatures above 200 C. This level of temperature will induce phenomena of dehydration in the cement paste, particularly impacting the CSH hydrates which led to the mechanical cohesion. The effects of these temperatures on the mechanical and transport properties have been the subject of this thesis.To understand these effects, we need to take into account the heterogeneous, porous, multi-scale aspects of these materials. To do this, micro-mechanics and homogenization tools based on the Eshelby problem's solution were used. Moreover, to support this multi-scale modeling, mechanical testing based on the theory of porous media were conducted. The measurements of modulus compressibility, permeability and porosity under confining pressure were used to investigate the mechanisms of degradation of these materials during thermal loads up to 400 C. (author)

Effects of Cooling Rates on Hydride Reorientation and Mechanical Properties of Zirconium Alloy Claddings under Interim Dry Storage Conditions

International Nuclear Information System (INIS)

Min, Su-Jeong; Kim, Myeong-Su; Won, Chu-chin; Kim, Kyu-Tae

2013-01-01

As-received Zr-Nb cladding tubes and 600 ppm hydrogen-charged tubes were employed to evaluate the effects of cladding cooling rates on the extent of hydride reorientation from circumferential hydrides to radial ones and mechanical property degradations with the use of cooling rates of 2, 4 and 15 °C/min from 400 °C to room temperature simulating cladding cooling under interim dry storage conditions. The as-received cladding tubes generated nearly the same ultimate tensile strengths and plastic elongations, regardless of the cooling rates, because of a negligible hydrogen content in the cladding. The 600 ppm-H cladding tubes indicate that the slower cooling rate generated the larger radial hydride fraction and the longer radial hydrides, which resulted in greater mechanical performance degradations. The cooling rate of 2 °C/min generates an ultimate tensile strength of 758 MPa and a plastic elongation of 1.0%, whereas the cooling rate of 15 °C/min generates an ultimate tensile strength of 825 MPa and a plastic elongation of 15.0%. These remarkable mechanical property degradations of the 600 ppm-H cladding tubes with the slowest cooling rate may be characterized by cleavage fracture surface appearance enhanced by longer radial hydrides and their higher fraction that have been precipitated through a relatively larger nucleation and growth rate.

Cross-border effects of capacity mechanisms in electricity markets

International Nuclear Information System (INIS)

Elberg, Christina

2014-01-01

To ensure security of supply in liberalized electricity markets, different types of capacity mechanisms are currently being debated or have recently been implemented in many European countries. The purpose of this study is to analyze the cross-border effects resulting from different choices on capacity mechanisms in neighboring countries. We consider a model with two connected countries that differ in the regulator's choice on capacity mechanism, namely strategic reserves or capacity payments. In both countries, competitive fi rms invest in generation capacity before selling electricity on the spot market. We characterize market equilibria and find the following main result: While consumers' costs may be the same under both capacity mechanisms in non-connected countries, we show that the different capacity mechanisms in interconnected countries induce redistribution effects. More precisely, we nd that consumers' costs are higher in countries in which reserve capacities are procured than in countries in which capacity payments are used to ensure the targeted reliable level of electricity.

Cross-border effects of capacity mechanisms in electricity markets

Energy Technology Data Exchange (ETDEWEB)

Elberg, Christina

2014-07-15

To ensure security of supply in liberalized electricity markets, different types of capacity mechanisms are currently being debated or have recently been implemented in many European countries. The purpose of this study is to analyze the cross-border effects resulting from different choices on capacity mechanisms in neighboring countries. We consider a model with two connected countries that differ in the regulator's choice on capacity mechanism, namely strategic reserves or capacity payments. In both countries, competitive fi rms invest in generation capacity before selling electricity on the spot market. We characterize market equilibria and find the following main result: While consumers' costs may be the same under both capacity mechanisms in non-connected countries, we show that the different capacity mechanisms in interconnected countries induce redistribution effects. More precisely, we nd that consumers' costs are higher in countries in which reserve capacities are procured than in countries in which capacity payments are used to ensure the targeted reliable level of electricity.

The Dynamic Evolution of Firms’ Pollution Control Strategy under Graded Reward-Penalty Mechanism

OpenAIRE

Li Ming Chen; Wen Ping Wang

2016-01-01

The externality of pollution problem makes firms lack enough incentive to reduce pollution emission. Therefore, it is necessary to design a reasonable environmental regulation mechanism so as to effectively urge firms to control pollution. In order to inspire firms to control pollution, we divide firms into different grades according to their pollution level and construct an evolutionary game model to analyze the interaction between government’s regulation and firms’ pollution control under g...

On the dynamic mechanical property and deformation mechanism of as-extruded Mg-Sn-Ca alloys under tension

International Nuclear Information System (INIS)

Huang, Qiuyan; Pan, Hucheng; Tang, Aitao; Ren, Yuping; Song, Bo; Qin, Gaowu; Zhang, Mingxing; Pan, Fusheng

2016-01-01

To further understand the deformation mechanism of magnesium alloys and expand their applications under dynamic conditions, the newly developed Mg-2Sn-1Ca alloy (TX21) is selected as the representative sample and tested under wide loading rate ranging from quasi-static to dynamic level (10"−"3–500/s). Both ultimate tensile strength and elongation of the as-extruded TX21 alloys increase with strain rate. Although twinning is accompanied due to the enhanced activity at higher strain rate, the preferential activation of dislocations is readily clarified and confirmed as the dominant deformation modes. Active interactions of pyramidal dislocations result in the higher strain hardening ability and could be correlated to the obviously positive strain-rate sensitivity for mechanical properties. Moreover, it is observed that the larger grain size and higher content of solute atoms dissolved in matrix would lead to the more active dislocations and twinning formations. The present results would provide insight into further understanding the deformation mechanism under dynamic rate loading and designing Mg alloy suitable for impact conditions.

On the dynamic mechanical property and deformation mechanism of as-extruded Mg-Sn-Ca alloys under tension

Energy Technology Data Exchange (ETDEWEB)

Huang, Qiuyan [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044 (China); Pan, Hucheng [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Tang, Aitao, E-mail: tat@cqu.edu.cn [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044 (China); Ren, Yuping [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Song, Bo [Faculty of Materials and Energy, Southwest University, Chongqing 400715 (China); Qin, Gaowu, E-mail: qingw@smm.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials (Ministry of Education), Northeastern University, Shenyang 110819 (China); Zhang, Mingxing [School of Mechanical and Mining Engineering, University of Queensland, St Lucia, QLD 4072 (Australia); Pan, Fusheng [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400044 (China)

2016-05-10

To further understand the deformation mechanism of magnesium alloys and expand their applications under dynamic conditions, the newly developed Mg-2Sn-1Ca alloy (TX21) is selected as the representative sample and tested under wide loading rate ranging from quasi-static to dynamic level (10{sup −3}–500/s). Both ultimate tensile strength and elongation of the as-extruded TX21 alloys increase with strain rate. Although twinning is accompanied due to the enhanced activity at higher strain rate, the preferential activation of dislocations is readily clarified and confirmed as the dominant deformation modes. Active interactions of pyramidal dislocations result in the higher strain hardening ability and could be correlated to the obviously positive strain-rate sensitivity for mechanical properties. Moreover, it is observed that the larger grain size and higher content of solute atoms dissolved in matrix would lead to the more active dislocations and twinning formations. The present results would provide insight into further understanding the deformation mechanism under dynamic rate loading and designing Mg alloy suitable for impact conditions.

Resveratrol increases nucleus pulposus matrix synthesis through activating the PI3K/Akt signaling pathway under mechanical compression in a disc organ culture.

Science.gov (United States)

Han, Xiaorui; Leng, Xiaoming; Zhao, Man; Wu, Mei; Chen, Amei; Hong, Guoju; Sun, Ping

2017-12-22

Disc nucleus pulposus (NP) matrix homeostasis is important for normal disc function. Mechanical overloading seriously decreases matrix synthesis and increases matrix degradation. The present study aims to investigate the effects of resveratrol on disc NP matrix homeostasis under a relatively high-magnitude mechanical compression and the potential mechanism underlying this process. Porcine discs were perfusion-cultured and subjected to a relatively high-magnitude mechanical compression (1.3 MPa at a frequency of 1.0 Hz for 2 h once per day) for 7 days in a mechanically active bioreactor. The non-compressed discs were used as controls. Resveratrol was added along with culture medium to observe the effects of resveratrol on NP matrix synthesis under mechanical load respectively. NP matrix synthesis was evaluated by histology, biochemical content (glycosaminoglycan (GAG) and hydroxyproline (HYP)), and expression of matrix macromolecules (aggrecan and collagen II). Results showed that this high-magnitude mechanical compression significantly decreased NP matrix content, indicated by the decreased staining intensity of Alcian Blue and biochemical content (GAG and HYP), and the down-regulated expression of NP matrix macromolecules (aggrecan and collagen II). Further analysis indicated that resveratrol partly stimulated NP matrix synthesis and increased activity of the PI3K/Akt pathway in a dose-dependent manner under mechanical compression. Together, resveratrol is beneficial for disc NP matrix synthesis under mechanical overloading, and the activation of the PI3K/Akt pathway may participate in this regulatory process. Resveratrol may be promising to regenerate mechanical overloading-induced disc degeneration. © 2017 The Author(s).

Size effects in the mechanical behavior of cellular materials

NARCIS (Netherlands)

Tekoglu, C; Onck, PR

Effective mechanical properties of cellular materials depend strongly on the specimen size to the cell size ratio. Experimental studies performed on aluminium foams show that under uniaxial compression, the stiffness of these materials falls below the corresponding bulk value, when the ratio of the

Animal behavior models of the mechanisms underlying antipsychotic atypicality.

NARCIS (Netherlands)

Geyer, M.A.; Ellenbroek, B.A.

2003-01-01

This review describes the animal behavior models that provide insight into the mechanisms underlying the critical differences between the actions of typical vs. atypical antipsychotic drugs. Although many of these models are capable of differentiating between antipsychotic and other psychotropic

Linear Analytical Solutions of Mechanical Sensitivity in Large Deflection of Unsymmetrically Layered Piezoelectric Plate under Pretension

Directory of Open Access Journals (Sweden)

Chun-Fu Chen

2014-03-01

Full Text Available Linear analytical study on the mechanical sensitivity in large deflection of unsymmetrically layered and laterally loaded piezoelectric plate under pretension is conducted. von Karman plate theory for large deflection is utilized but extended to the case of an unsymmetrically layered plate embedded with a piezoelectric layer. The governing equations thus obtained are simplified by omitting the arising nonlinear terms, yielding a Bessel or modified Bessel equation for the lateral slope. Depending on the relative magnitude of the piezoelectric effect, for both cases, analytical solutions of various geometrical responses are developed and formulated via Bessel and modified Bessel functions. The associated ultimate radial stresses are further derived following lamina constitutive law to evaluate the mechanical sensitivity of the considered plate. For a nearly monolithic plate under a very low applied voltage, the results are in good agreement with those for a single-layered case due to pure mechanical load available in literature, and thus the present approach is checked. For a two-layered unsymmetric plate made of typical silicon-based materials, a sound piezoelectric effect is illustrated particularly in a low pretension condition.

Molecular mechanisms underlying the emergence of bacterial pathogens: an ecological perspective.

Science.gov (United States)

Bartoli, Claudia; Roux, Fabrice; Lamichhane, Jay Ram

2016-02-01

The rapid emergence of new bacterial diseases negatively affects both human health and agricultural productivity. Although the molecular mechanisms underlying these disease emergences are shared between human- and plant-pathogenic bacteria, not much effort has been made to date to understand disease emergences caused by plant-pathogenic bacteria. In particular, there is a paucity of information in the literature on the role of environmental habitats in which plant-pathogenic bacteria evolve and on the stress factors to which these microbes are unceasingly exposed. In this microreview, we focus on three molecular mechanisms underlying pathogenicity in bacteria, namely mutations, genomic rearrangements and the acquisition of new DNA sequences through horizontal gene transfer (HGT). We briefly discuss the role of these mechanisms in bacterial disease emergence and elucidate how the environment can influence the occurrence and regulation of these molecular mechanisms by directly impacting disease emergence. The understanding of such molecular evolutionary mechanisms and their environmental drivers will represent an important step towards predicting bacterial disease emergence and developing sustainable management strategies for crops. © 2015 BSPP AND JOHN WILEY & SONS LTD.

Dynamic analysis of composite beam with piezoelectric layers under thermo-mechanical load

Science.gov (United States)

Toudehdehghan, A.; Rahman, M. M.; Nagi, Farrukh

2017-10-01

In this paper, the control of composite beam vibrations with sensor and actuator connected layers is considered with consideration of the effect of thermal environment. The coupling relation between electrical field and mechanical deformation with uncoupled thermal impact are used. The mathematical model of shear deformation (Timoshenko’s theory) has been applied and basic equations for piezoelectric sensors and actuators have been proposed. The equation of motion for the beam structure is obtained by the Hamilton principle and analyzed by finite element method. The control algorithm is based on proportional velocity control. Hence, the purpose of this article is to investigate the direct and inverse effects of piezoelectric on control of simply supported beam vibration under uniform temperature.

Concurrent material-fabrication optimization of metal-matrix laminates under thermo-mechanical loading

Science.gov (United States)

Saravanos, D. A.; Morel, M. R.; Chamis, C. C.

1991-01-01

A methodology is developed to tailor fabrication and material parameters of metal-matrix laminates for maximum loading capacity under thermomechanical loads. The stresses during the thermomechanical response are minimized subject to failure constrains and bounds on the laminate properties. The thermomechanical response of the laminate is simulated using nonlinear composite mechanics. Evaluations of the method on a graphite/copper symmetric cross-ply laminate were performed. The cross-ply laminate required different optimum fabrication procedures than a unidirectional composite. Also, the consideration of the thermomechanical cycle had a significant effect on the predicted optimal process.

Temperature-dependent dynamic mechanical properties of magnetorheological elastomers under magnetic field

Energy Technology Data Exchange (ETDEWEB)

Ju, Benxiang, E-mail: jubenxiang@qq.com [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Tang, Rui; Zhang, Dengyou; Yang, Bailian [National Instrument Functional Materials Engineering Technology Research Center, Chongqing 400707 (China); Yu, Miao; Liao, Changrong [College of Optoelectronic Engineering, Chongqing University, Chongqing 400044 (China)

2015-01-15

Both anisotropic and isotropic magnetorheological elastomer (MRE) samples were fabricated by using as-prepared polyurethane (PU) matrix and carbonyl iron particles. Temperature-dependent dynamic mechanical properties of MRE were investigated and analyzed. Due to the unique structural features of as-prepared matrix, temperature has a greater impact on the properties of as-prepared MRE, especially isotropic MRE. With increasing of temperature and magnetic field, MR effect of isotropic MRE can reach up to as high as 4176.5% at temperature of 80 °C, and the mechanism of the temperature-dependent in presence of magnetic field was discussed. These results indicated that MRE is a kind of temperature-dependent material, and can be cycled between MRE and MR plastomer (MRP) by varying temperature. - Highlights: • Both anisotropic and isotropic MRE were fabricated by using as-prepared matrix. • Temperature-dependent properties of MRE under magnetic field were investigated. • As-prepared MRE can transform MRE to MRP by adjusting temperature.

Effect of Particle Size on Mechanical Properties of Sawdust-High Density Polyethylene Composites under Various Strain Rates

Directory of Open Access Journals (Sweden)

Haliza Jaya

2016-06-01

Full Text Available There is a need to understand the effect of wood particle size, as it affects the characteristics of wood-based composites. This study considers the effect of wood particle size relative to the dynamic behavior of wood composites. The compression Split Hopkinson Pressure Bar (SHPB was introduced to execute dynamic compression testing at the strain rate of 650 s-1, 900 s-1, and 1100 s-1, whereas a conventional universal testing machine (UTM was used to perform static compression testing at the strain rate of 0.1 s-1, 0.01 s-1, and 0.001 s-1 for four different particle sizes (63 µm, 125 µm, 250 µm, and 500 µm. The results showed that mechanical properties of composites were positively affected by the particle sizes, where the smallest particle size gave the highest values compared to the others. Moreover, the particle size also affected the rate sensitivity and the thermal activation volume of sawdust/HDPE, where smaller particles resulted in lower rate sensitivity. For the post-damage analysis, the applied strain rates influenced deformation behavior differently for all particle sizes of the specimens. In a fractographic analysis under dynamic loading, the composites with large particles experienced severe catastrophic deformation and damages compared to the smaller particles.

Laboratory studies of the corrosion and mechanical properties of titanium grade-12 under WIPP repository conditions

International Nuclear Information System (INIS)

Sorensen, N.R.

1990-01-01

The author reviews laboratory work done at the Sandia Laboratories on the properties of titanium grade 12. The effect of gamma radiation on corrosion and mechanical properties has been investigated; no real effect has been detected on corrosion rate, Charpy impact energy, or tensile properties at 90 degrees and 10 4 rad/h. No structural changes are evident under examination by SEM or TEM. There is also no evidence of crevice corrosion after five years of exposure. The effect of radiation on hydrogen uptake was also investigated. Radiation appears to reduce the extent of uptake. The microstructure of titanium-12 changes with the addition of hydrogen to a structure with alternating layers of alpha and beta phase. A decrease in mechanical properties is associated with this change

Molecular Mechanisms Underlying Curcumin-Mediated Therapeutic Effects in Type 2 Diabetes and Cancer

Directory of Open Access Journals (Sweden)

Marzena Wojcik

2018-01-01

Full Text Available The growing prevalence of age-related diseases, especially type 2 diabetes mellitus (T2DM and cancer, has become global health and economic problems. Due to multifactorial nature of both diseases, their pathophysiology is not completely understood so far. Compelling evidence indicates that increased oxidative stress, resulting from an imbalance between production of reactive oxygen species (ROS and their clearance by antioxidant defense mechanisms, as well as the proinflammatory state contributes to the development and progression of the diseases. Curcumin (CUR; diferuloylmethane, a well-known polyphenol derived from the rhizomes of turmeric Curcuma longa, has attracted a great deal of attention as a natural compound with beneficial antidiabetic and anticancer properties, partly due to its antioxidative and anti-inflammatory actions. Although this polyphenolic compound is increasingly being recognized for its growing number of protective health effects, the precise molecular mechanisms through which it reduces diabetes- and cancer-related pathological events have not been fully unraveled. Hence, CUR is the subject of intensive research in the fields Diabetology and Oncology as a potential candidate in the treatment of both T2DM and cancer, particularly since current therapeutic options for their treatment are not satisfactory in clinics. In this review, we summarize the recent progress made on the molecular targets and pathways involved in antidiabetic and anticancer activities of CUR that are responsible for its beneficial health effects.

Effect of thermo-mechanical treatments on creep and fatigue properties of 9% Cr martensitic steels

International Nuclear Information System (INIS)

Hollner, S.; Fournier, B.; Le Pendu, J.; Caes, C.; Tournie, I.; Pineau, A.

2011-01-01

In the framework of the development of Generation IV nuclear reactors and fusion nuclear reactors, materials with high mechanical properties up to 550 C are required. In service the materials will be subjected to high-temperature creep and cyclic loadings. 9-12%Cr martensitic steels are candidate materials for these applications; however, they show a pronounced cyclic softening effect under cyclic loadings. This softening effect is linked to the coarsening of the martensitic microstructure. In order to refine its microstructure and its precipitation state, the commercial P91 steel has been submitted to a thermo-mechanical treatment including warm-rolling at 600 C and a tempering stage at 700 C. Microstructural observations confirm that this thermo-mechanical treatment led to a finer martensite with smaller MX-type precipitates. This evolution has an effect on the high-temperature mechanical properties: the optimized P91 steel is 100 Hv harder than the as-received P91, and its yield strength is 430 MPa higher at 20 C and 220 MPa higher at 550 C. Its lifetime under creep (at 650 C under 120 MPa) is at least 14 times longer; and the fatigue test at 650 C under 0.7% strain shows a slightly slower cyclic softening effect for the optimized P91. (authors)

Effects of surface atomistic modification on mechanical properties of gold nanowires

International Nuclear Information System (INIS)

Sun, Xiao-Yu; Xu, Yuanjie; Wang, Gang-Feng; Gu, Yuantong; Feng, Xi-Qiao

2015-01-01

Highlights: • Molecular dynamics simulations of surface modification effect of Au nanowires. • Surface modification can greatly affect the mechanical properties of nanowires. • Core–shell model is used to elucidate the effect of residual surface stress. - Abstract: Modulation of the physical and mechanical properties of nanowires is a challenging issue for their technological applications. In this paper, we investigate the effects of surface modification on the mechanical properties of gold nanowires by performing molecular dynamics simulations. It is found that by modifying a small density of silver atoms to the surface of a gold nanowire, the residual surface stress state can be altered, rendering a great improvement of its plastic yield strength. This finding is in good agreement with experimental measurements. The underlying physical mechanisms are analyzed by a core–shell nanowire model. The results are helpful for the design and optimization of advanced nanomaterial with superior mechanical properties

The Dynamic Evolution of Firms’ Pollution Control Strategy under Graded Reward-Penalty Mechanism

Directory of Open Access Journals (Sweden)

Li Ming Chen

2016-01-01

Full Text Available The externality of pollution problem makes firms lack enough incentive to reduce pollution emission. Therefore, it is necessary to design a reasonable environmental regulation mechanism so as to effectively urge firms to control pollution. In order to inspire firms to control pollution, we divide firms into different grades according to their pollution level and construct an evolutionary game model to analyze the interaction between government’s regulation and firms’ pollution control under graded reward-penalty mechanism. Then, we discuss stability of firms’ pollution control strategy and derive the condition of inspiring firms to control pollution. Our findings indicate that firms tend to control pollution after long-term repeated games if government’s excitation level and monitoring frequency meet some conditions. Otherwise, firms tend to discharge pollution that exceeds the stipulated standards. As a result, in order to effectively control pollution, a government should adjust its excitation level and monitoring frequency reasonably.

Microstructural development under interrupted hot deformation and the mechanical properties of a cast Mg–Gd–Y–Zr alloy

Energy Technology Data Exchange (ETDEWEB)

Xiao, Zhenyu [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Yang, Xuyue [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Institute for Materials Microstructure, Central South University, Changsha 410083 (China); Yang, Yi; Zhang, Zhirou; Zhang, Duxiu; Li, Yi [Educational Key Laboratory of Nonferrous Metal Materials Science and Engineering, School of Materials Science and Engineering, Central South University, Changsha 410083 (China); Sakai, Taku [UEC Tokyo (The University of Electro-Communications), Chofu, Tokyo 182-8585 (Japan)

2016-01-15

Microstructural development under interrupted hot deformation of a cast Mg–Gd–Y–Zr alloy was investigated by optical microscopy (OM) and electron backscattering diffraction (EBSD) technology and the resultant mechanical properties were detected through tensile tests at room temperature. Ultrafine grains (UFGs) were remarkably developed under the condition of interrupted hot forging, resulting in an improvement of ambient mechanical properties. The basal texture was weakened by an effective increase of the volume fraction of UFGs under interrupted hot forging. These resulted in an improvement of tensile ductility with little or no drop in strength, i.e. the volume fraction of UFGs was raised from 30% to 70%, leading to an increase of the ambient tensile elongation from 15% to 23%.

Neuroplasticity-related mechanisms underlying the antidepressant-like effects of traditional herbal medicines.

Science.gov (United States)

Hirshler, Yafit; Doron, Ravid

2017-10-01

Traditional herbal medicine can offer efficacious and safe alternative pharmacotherapies for depression. The ability of an herbal medicine to produce neuroadaptive processes, that enhance neuroplasticity and cellular resilience in response to chronic stress, may point to its antidepressant potential. We suggest that among many investigated herbal medicines, those that can enhance neuroplasticity may have stronger therapeutic potential. The current article presents a summary of traditional herbal medicines, which are thought to exert antidepressant-like effects in chronic stress models via neuroplasticity enhancement. Brain-derived neurotrophic factor (BDNF) is a biomarker for neuroplasticity-related mechanisms compromised in depression and recovered by conventional antidepressants, including synaptic plasticity, cell survival, neurogenesis and spine formation. We therefore presumed that if an herbal medicine up-regulates BDNF in the hippocampus and/or prefrontal cortex (PFC), its antidepressant-like effect is mediated, at least partially, via neuroplasticity-related mechanisms. Literature search was performed using the general terms depression, stress, neuroplasticity and herbal medicines. Screening of retrieved preclinical studies revealed 30 traditional herbal medicines: 8 single herbs, 15 bioactive constituents, and 7 herbal formulas. The antidepressant-like effects of these medicines were associated with reversal of chronic stress-induced impairment in neuroplasticity, most notably by BDNF up-regulation, activation of BDNF downstream signaling pathways and increase in neurogenesis in the hippocampus and/or PFC/frontal cortex. In light of the ability of these medicines to enhance neuroplasticity, we suggest that they may be suitable candidates for clinical investigation in depressed individuals. Once their efficacy, tolerability and safety will be substantiated, they may serve as natural alternatives to conventional antidepressants. Copyright © 2017 Elsevier B

Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity

Science.gov (United States)

2017-10-01

AWARD NUMBER: W81XWH-16-1-0652 TITLE: Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity PRINCIPAL INVESTIGATOR...5a. CONTRACT NUMBER W81XWH-16-1-0652 Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity 5b. GRANT NUMBER W81XWH...to stress fracture risk. In particular, in Study 1, we will perform advanced skeletal imaging along with gait-assessments in subjects with history of

Interaction effects between internal governance mechanisms on the components of initial returns during the IPO

Directory of Open Access Journals (Sweden)

Mediha Mezhoud

2012-12-01

Full Text Available Our work provides an analysis of the interaction effects between internal governance mechanisms on the components of initial returns during the listing period. The application of multivariate regressions on a sample of 110 IPO French companies during 2005-2010, has allowed us to conclude that the different interactions between these mechanisms significantly influence the level of under / overpricing. Indeed, the positive relationship between internal governance mechanisms and overpricing reflects a substitutability relationship. In contrast, the complementarity effect comes from the negative relationship characterizing the combination of governance mechanisms and the underpricing. Thus, the interactions effects between institutional ownership, board structure and under / overpricing are not conforming to the existence of a complementarity or substitutability relationship between these variables given the absence of a significant combination between these variables

Failure Mechanisms of Brittle Rocks under Uniaxial Compression

Science.gov (United States)

Liu, Taoying; Cao, Ping

2017-09-01

The behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

Enabling optimal energy options under the Clean Development Mechanism

International Nuclear Information System (INIS)

Gilau, Asmerom M.; Van Buskirk, Robert; Small, Mitchell J.

2007-01-01

This paper addresses the cost effectiveness of renewable energy technologies in achieving low abatement costs and promoting sustainable developments under the Clean Development Mechanism (CDM). According to the results of our optimal energy option's analysis, at project scale, compared with a diesel-only energy option, photovoltaic (PV)-diesel (PVDB), wind-diesel (WDB) and PV-wind-diesel (PVWDB) hybrids are very cost-effective energy options. Moreover, energy options with high levels of renewable energy, including 100% renewables, have the lowest net present cost and they are already cost effective without CDM. On the other hand, while the removal of about 87% carbon dioxide emissions could be achieved at negative cost, initial investment could increase by a factor of 40, which is one of the primary barriers hindering wider renewable energy applications in developing countries, among others. Thus, in order to increase developing countries' participation in the carbon market, CDM policy should shift from a purely market-oriented approach to investigating how to facilitate renewable energy projects through barrier removal. Thus, we recommend that further research should focus on how to efficiently remove renewable energy implementation barriers as a means to improve developing countries' participation in meaningful emission reduction while at the same time meeting the needs of sustainable economic development

Deciphering Molecular Mechanism Underlying Hypolipidemic Activity of Echinocystic Acid

Directory of Open Access Journals (Sweden)

Li Han

2014-01-01

Full Text Available Our previous study showed that a triterpene mixture, consisting of echinocystic acid (EA and oleanolic acid (OA at a ratio of 4 : 1, dose-dependently ameliorated the hyperlipidemia and atherosclerosis in rabbits fed with high fat/high cholesterol diets. This study was aimed at exploring the mechanisms underlying antihyperlipidemic effect of EA. Molecular docking simulation of EA was performed using Molegro Virtual Docker (version: 4.3.0 to investigate the potential targets related to lipid metabolism. Based on the molecular docking information, isotope labeling method or spectrophotometry was applied to examine the effect of EA on the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA reductase, acyl-CoA:cholesterol acyltransferase (ACAT, and diacylglycerol acyltransferase (DGAT in rat liver microsomes. Our results revealed a strong affinity of EA towards ACAT and DGAT in molecular docking analysis, while low binding affinity existed between EA and HMG-CoA reductase as well as between EA and cholesteryl ester transfer protein. Consistent with the results of molecular docking, in vitro enzyme activity assays showed that EA inhibited ACAT and DGAT, with IC50 values of 103 and 139 μM, respectively, and exhibited no significant effect on HMG-CoA reductase activity. The present findings suggest that EA may exert hypolipidemic effect by inhibiting the activity of ACAT and DGAT.

Mechanisms underlying rapid aldosterone effects in the kidney.

LENUS (Irish Health Repository)

Thomas, Warren

2012-02-01

The steroid hormone aldosterone is a key regulator of electrolyte transport in the kidney and contributes to both homeostatic whole-body electrolyte balance and the development of renal and cardiovascular pathologies. Aldosterone exerts its action principally through the mineralocorticoid receptor (MR), which acts as a ligand-dependent transcription factor in target tissues. Aldosterone also stimulates the activation of protein kinases and secondary messenger signaling cascades that act independently on specific molecular targets in the cell membrane and also modulate the transcriptional action of aldosterone through MR. This review describes current knowledge regarding the mechanisms and targets of rapid aldosterone action in the nephron and how aldosterone integrates these responses into the regulation of renal physiology.

Mechanisms underlying rapid aldosterone effects in the kidney.

LENUS (Irish Health Repository)

Thomas, Warren

2011-03-17

The steroid hormone aldosterone is a key regulator of electrolyte transport in the kidney and contributes to both homeostatic whole-body electrolyte balance and the development of renal and cardiovascular pathologies. Aldosterone exerts its action principally through the mineralocorticoid receptor (MR), which acts as a ligand-dependent transcription factor in target tissues. Aldosterone also stimulates the activation of protein kinases and secondary messenger signaling cascades that act independently on specific molecular targets in the cell membrane and also modulate the transcriptional action of aldosterone through MR. This review describes current knowledge regarding the mechanisms and targets of rapid aldosterone action in the nephron and how aldosterone integrates these responses into the regulation of renal physiology.

An investigation of the mechanical behavior of initially curved microplates under electrostatic actuation

KAUST Repository

Saghir, Shahid

2018-03-28

In this article, we investigate the mechanical behavior of initially curved microplates under electrostatic actuation. Microplates are essential components of many Micro-Electro-Mechanical System devices; however, they commonly undergo an initial curvature imperfection, due to the microfabrication process. Initial curvature imperfection significantly affects the mechanical behavior of microplates. In this work, we derive a dynamic analogue of the von Kármán governing equation for such plates. These equations are then used to develop a reduced order model based on the Galerkin procedure to simulate the static and dynamic behavior of the microplate. Two profiles of initial curvature commonly encountered in microfabricated structures are considered, where one assumes a variation in shape along one dimension of the plate only (cylindrical bending shape) while the other assumes a variation in shape along both dimensions of the plate. Their effects on both the static and dynamic responses of the microplates are examined and compared. We validate the reduced order model by comparing the calculated static behavior and the fundamental natural frequency with those computed by a finite element model over a range of the initial plate rise. The static behavior of the microplate is investigated when varying the DC voltage. Then, the dynamic behavior of the microplate is examined under the application of a harmonic AC voltage superimposed to a DC voltage.

Mechanisms underlying reduced fertility in anovular dairy cows.

Science.gov (United States)

Santos, J E P; Bisinotto, R S; Ribeiro, E S

2016-07-01

Resumption of ovulation after parturition is a coordinated process that involves recoupling of the GH/insulin-like growth factor 1 axis in the liver, increase in follicular development and steroidogenesis, and removal of negative feedback from estradiol in the hypothalamus. Infectious diseases and metabolic disorders associated with extensive negative energy balance during early lactation disrupt this pathway and delay first ovulation postpartum. Extended periods of anovulation postpartum exert long-lasting effects on fertility in dairy cows including the lack of spontaneous estrus, reduced pregnancy per artificial insemination (P/AI), and increased risk of pregnancy loss. Concentrations of progesterone in anovular cows subjected to synchronized programs for AI are insufficient to optimize follicular maturation, oocyte competence, and subsequent fertility to AI. Ovulation of first wave follicles, which develop under low concentrations of progesterone, reduces embryo quality in the first week after fertilization and P/AI in dairy cows. Although the specific mechanisms by which anovulation and low concentrations of progesterone impair oocyte quality have not been defined, studies with persistent follicles support the involvement of premature resumption of meiosis and degradation of maternal RNA. Suboptimal concentrations of progesterone before ovulation also increase the synthesis of PGF2α in response to oxytocin during the subsequent estrous cycle, which explains the greater incidence of short luteal phases after the first AI postpartum in anovular cows compared with estrous cyclic herd mates. It is suggested that increased spontaneous luteolysis early in the estrous cycle is one of the mechanisms that contributes to early embryonic losses in anovular cows. Anovulation also leads to major shifts in gene expression in elongated conceptuses during preimplantation stages of pregnancy. Transcripts involved with control of energy metabolism and DNA repair were

Antitumor effects and mechanisms of Ganoderma extracts and spores oil

OpenAIRE

Chen, Chun; Li, Peng; Li, Ye; Yao, Guan; Xu, Jian-Hua

2016-01-01

Ganoderma lucidum is a popular herbal medicine used in China to promote health. Modern studies have disclosed that the active ingredients of Ganoderma can exhibit several effects, including antitumor effects and immunomodulation. The present study evaluated the antitumor effects of self-prepared Ganoderma extracts and spores oil, and investigated the possible underlying mechanisms by observing the effects of the extracts and oil on topoisomerases and the cell cycle. The results showed that Ga...

Numerical and experimental characterization of ceramic pebble beds under cycling mechanical loading

Energy Technology Data Exchange (ETDEWEB)

Pupeschi, S., E-mail: pupeschi.simone@hotmail.it [Institute for Applied Materials, Karlsruhe Institute of Technology (KIT) (Germany); Knitter, R.; Kamlah, M. [Institute for Applied Materials, Karlsruhe Institute of Technology (KIT) (Germany); Gan, Y. [School of Civil Engineering, The University of Sydney, Sydney, NSW, 2006 (Australia)

2016-11-15

Highlights: • The effect of cyclic loading on the mechanical response of pebble beds was assessed. • Numerical simulations were performed with KIT-DEM code. • The numerical simulations were compared with the experimental outcomes. • A good qualitative agreement between experimental and simulation results was found. • The pebble size distribution affects the mechanical response of the assemblies. - Abstract: All solid breeder concepts considered to be tested in ITER (International Thermonuclear Experimental Reactor), make use of lithium-based ceramics in the form of pebble-packed beds as tritium breeder. A thorough understanding of the thermal and mechanical properties of the ceramic pebble beds under fusion relevant conditions is essential for the design of the breeder blanket modules of future fusion reactors. In this study, the effect of cyclic loading on the mechanical behaviour of pebble bed assemblies was investigated using a Discrete Element Method (DEM) code. The numerical simulations were compared with the experimental outcomes. The results of numerical simulations show that the pebble size distribution affects noticeably the stress-strain behaviour of the assemblies. A good qualitative agreement between experimental and simulation results was found in terms of difference between residual strains of consecutive cycles. An increase of the oedometric modulus with the compressive load was observed for all investigated compositions in both experimental and DEM simulations. The numerical results show an increase of the oedometric modulus (E) with progressive compaction of the assemblies due to the cycling loading, while no significant influence of the pebbles size distribution was observed.

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

Science.gov (United States)

2017-01-01

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment. PMID:28567415

Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

Directory of Open Access Journals (Sweden)

Nguyen Quoc Vuong Tran

2017-01-01

Full Text Available The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD and attention deficit hyperactivity disorder (ADHD, calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates, persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Effects of Tribulus terrestris saponins on exercise performance in overtraining rats and the underlying mechanisms.

Science.gov (United States)

Yin, Liang; Wang, Qian; Wang, Xiaohui; Song, Liang-Nian

2016-06-22

The objective of this study was to determine the effects of Tribulus terrestris L. (TT) saponins on exercise performance and the underlying mechanisms. A rat overtraining model was established and animals were treated with TT extracts (120 mg/kg body mass) 30 min before each training session. Serum levels of testosterone and corticosterone and levels of androgen receptor (AR) and insulin growth factor-1 receptor (IGF-1R) in the liver, gastrocnemius, and soleus were determined by ELISA and Western blot. Treatment of rats with TT saponins significantly improved the performance of the overtraining rats, reflected by the extension of time to exhaustion, with a concomitant increase in body mass, relative mass, and protein levels of gastrocnemius. Overtraining alone induced a significant decrease in the serum level of testosterone. In contrast, treatment with TT saponins dramatically increased the serum level of testosterone in overtraining rats to about 150% of control and 216% of overtraining groups, respectively. In addition, TT saponins resulted in a further significant increase in AR in gastrocnemius and significantly suppressed the overtraining-induced increase in IGF-1R in the liver. These results indicated that TT saponins increased performance, body mass, and gastrocnemius mass of rats undergoing overtraining, which might be attributed to the changes in androgen-AR axis and IGF-1R signaling.

Effects of competitive pressure on expert performance: underlying psychological, physiological, and kinematic mechanisms.

Science.gov (United States)

Cooke, Andrew; Kavussanu, Maria; McIntyre, David; Boardley, Ian D; Ring, Christopher

2011-08-01

Although it is well established that performance is influenced by competitive pressure, our understanding of the mechanisms which underlie the pressure-performance relationship is limited. The current experiment examined mediators of the relationship between competitive pressure and motor skill performance of experts. Psychological, physiological, and kinematic responses to three levels of competitive pressure were measured in 50 expert golfers, during a golf putting task. Elevated competitive pressure increased putting accuracy, anxiety, effort, and heart rate, but decreased grip force. Quadratic effects of pressure were noted for self-reported conscious processing and impact velocity. Mediation analyses revealed that effort and heart rate partially mediated improved performance. The findings indicate that competitive pressure elicits effects on expert performance through both psychological and physiological pathways. Copyright © 2011 Society for Psychophysiological Research.

Mechanical properties and fracture behaviour of defective phosphorene nanotubes under uniaxial tension

Science.gov (United States)

Liu, Ping; Pei, Qing-Xiang; Huang, Wei; Zhang, Yong-Wei

2017-12-01

The easy formation of vacancy defects and the asymmetry in the two sublayers of phosphorene nanotubes (PNTs) may result in brand new mechanical properties and failure behaviour. Herein, we investigate the mechanical properties and fracture behaviour of defective PNTs under uniaxial tension using molecular dynamics simulations. Our simulation results show that atomic vacancies cause local stress concentration and thus significantly reduce the fracture strength and fracture strain of PNTs. More specifically, a 1% defect concentration is able to reduce the fracture strength and fracture strain by as much as 50% and 66%, respectively. Interestingly, the reduction in the mechanical properties is found to depend on the defect location: a defect located in the outer sublayer has a stronger effect than one located in the inner layer, especially for PNTs with a small diameter. Temperature is also found to strongly influence the mechanical properties of both defect-free and defective PNTs. When the temperature is increased from 0 K to 400 K, the fracture strength and fracture strain of defective PNTs with a defect concentration of 1% are reduced further by 71% and 61%, respectively. These findings are of great importance for the structural design of PNTs as building blocks in nanodevices.

Elucidation of possible molecular mechanisms underlying the estrogen-induced disruption of cartilage development in zebrafish larvae.

Science.gov (United States)

He, Hanliang; Wang, Chunqing; Tang, Qifeng; Yang, Fan; Xu, Youjia

2018-06-01

Estrogen can affect the cartilage development of zebrafish; however, the mechanism underlying its effects is not completely understood. Four-day-old zebrafish larvae were treated with 0.8 μM estrogen, the 5 days post fertilization (dpf) zebrafish larvae did not demonstrate obvious abnormalities during development; however, the 6 dpf and 7 dpf larvae exhibited abnormal craniofacial bone development along with craniofacial bone degradation. RNA deep sequencing was performed to elucidate the mechanism involved. Gene Ontology functional and KEGG pathway enrichment analysis of differentially expressed genes (DEGs) showed that the extracellular matrix (ECM), extracellular region, ECM-interaction receptor, focal adhesion, cell cycle, apoptosis, and bone-related signaling pathways were disrupted. In these signaling pathways, the expressions of key genes, such as collagen encoded (col19a1a, col7a1, col7al, col18a1, and col9a3), MAPK signaling pathway (fgf19, fgf6a), TGF-beta signaling pathway (tgfbr1), and cell cycle (cdnk1a) genes were altered. The qRT-PCR results showed that after treatment with 0.8 μM 17-β estradiol (E2), col19a1a, col7a1, col7al, col18a1, col9a3, fgf6a, cdkn1a were downregulated, and fgf19, tgfr1 were upregulated, which were consistent with deep sequencing analysis. Therefore, the effect of estrogen on cartilage development might occur via multiple mechanisms. The study results demonstrate the mechanism underlying the effect of estrogen on cartilage development. Copyright © 2018 Elsevier B.V. All rights reserved.

Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

International Nuclear Information System (INIS)

Perkins, R. J.; Bell, R. E.; Bertelli, N.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; LeBlanc, B. P.; Kramer, G. J.; Maingi, R.; Phillips, C. K.; Podestà, M.; Roquemore, L.; Scotti, F.; Taylor, G.; Wilson, J. R.; Ahn, J-W.; Gray, T. K.; Green, D. L.; McLean, A.

2014-01-01

Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict

Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

Energy Technology Data Exchange (ETDEWEB)

Perkins, R. J.; Bell, R. E.; Bertelli, N.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; LeBlanc, B. P.; Kramer, G. J.; Maingi, R.; Phillips, C. K.; Podestà, M.; Roquemore, L.; Scotti, F.; Taylor, G.; Wilson, J. R. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States); Ahn, J-W.; Gray, T. K.; Green, D. L.; McLean, A. [Oak Ridge National Laboratory, Oak Ridge, TN (United States); and others

2014-02-12

Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict

Dynamic tensile behaviour and deformational mechanism of C5191 phosphor bronze under high strain rates deformation

Energy Technology Data Exchange (ETDEWEB)

Hu, Dao-chun [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Mechanical and Electrical Engineering, Taizhou Vocational & Technical College, Taizhou 318000 (China); Chen, Ming-he, E-mail: meemhchen@nuaa.edu.cn [College of Mechanical and Electrical Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Wang, Lei; Cheng, Hu [College of Mechanical Engineering, Taizhou University, Taizhou 318000 (China)

2016-01-01

High speed stamping process is used to high strength and high electrical conductivity phosphor bronze with extremely high strain rates more than 10{sup 3} s{sup −1}. This study on the dynamic tensile behaviour and deformational mechanism is to optimise the high speed stamping processes and improve geometrical precision in finished products. Thus, the tensile properties and deformation behaviour of C5191 phosphor bronze under quasi-static tensile condition at a strain rate of 0.001 s{sup −1} by electronic universal testing machine, and dynamic tensile condition at strain rate of 500, 1000 and 1500 s{sup −1} by split Hopkinson tensile bar (SHTB) apparatus were studied. The effects of strain rate and the deformation mechanism were investigated by means of SEM and TEM. The results showed that the yield strength and tensile strength of C5191 phosphor bronze under high strain rates deformation increased by 32.77% and 11.07% respectively compared with quasi-static condition, the strain hardening index increases from 0.075 to 0.251, and the strength of the material strain rates sensitivity index change from 0.005 to 0.022, which presented a clear sensitive to strain rates. Therefore, it is claimed that the dominant deformation mechanism was changed by the dislocation motion under different strain rates, and the ability of plastic deformation of C5191 phosphor bronze increased due to the number of movable dislocations increased significantly, started multi-line slip, and the soft effect of adiabatic temperature rise at the strain rate ranging from 500 to 1500 s{sup −1}.

Age-related mechanical strength evolution of trabecular bone under fatigue damage for both genders: Fracture risk evaluation.

Science.gov (United States)

Ben Kahla, Rabeb; Barkaoui, Abdelwahed; Merzouki, Tarek

2018-05-04

Bone tissue is a living composite material, providing mechanical and homeostatic functions, and able to constantly adapt its microstructure to changes in long term loading. This adaptation is conducted by a physiological process, known as "bone remodeling". This latter is manifested by interactions between osteoclasts and osteoblasts, and can be influenced by many local factors, via effects on bone cell differentiation and proliferation. In the current work, age and gender effects on damage rate evolution, throughout life, have been investigated using a mechanobiological finite element modeling. To achieve the aim, a mathematical model has been developed, coupling both cell activities and mechanical behavior of trabecular bone, under cyclic loadings. A series of computational simulations (ABAQUS/UMAT) has been performed on a 3D human proximal femur, allowing to investigate the effects of mechanical and biological parameters on mechanical strength of trabecular bone, in order to evaluate the fracture risk resulting from fatigue damage. The obtained results revealed that mechanical stimulus amplitude affects bone resorption and formation rates, and indicated that age and gender are major factors in bone response to the applied loadings. Copyright © 2018 Elsevier Ltd. All rights reserved.

Underlying Mechanisms of Tinnitus: Review and Clinical Implications

Science.gov (United States)

Henry, James A.; Roberts, Larry E.; Caspary, Donald M.; Theodoroff, Sarah M.; Salvi, Richard J.

2016-01-01

Background The study of tinnitus mechanisms has increased tenfold in the last decade. The common denominator for all of these studies is the goal of elucidating the underlying neural mechanisms of tinnitus with the ultimate purpose of finding a cure. While these basic science findings may not be immediately applicable to the clinician who works directly with patients to assist them in managing their reactions to tinnitus, a clear understanding of these findings is needed to develop the most effective procedures for alleviating tinnitus. Purpose The goal of this review is to provide audiologists and other health-care professionals with a basic understanding of the neurophysiological changes in the auditory system likely to be responsible for tinnitus. Results It is increasingly clear that tinnitus is a pathology involving neuroplastic changes in central auditory structures that take place when the brain is deprived of its normal input by pathology in the cochlea. Cochlear pathology is not always expressed in the audiogram but may be detected by more sensitive measures. Neural changes can occur at the level of synapses between inner hair cells and the auditory nerve and within multiple levels of the central auditory pathway. Long-term maintenance of tinnitus is likely a function of a complex network of structures involving central auditory and nonauditory systems. Conclusions Patients often have expectations that a treatment exists to cure their tinnitus. They should be made aware that research is increasing to discover such a cure and that their reactions to tinnitus can be mitigated through the use of evidence-based behavioral interventions. PMID:24622858

Depression and Chronic Liver Diseases: Are There Shared Underlying Mechanisms?

Directory of Open Access Journals (Sweden)

Xiaoqin Huang

2017-05-01

Full Text Available The occurrence of depression is higher in patients with chronic liver disease (CLD than that in the general population. The mechanism described in previous studies mainly focused on inflammation and stress, which not only exists in CLD, but also emerges in common chronic diseases, leaving the specific mechanism unknown. This review was to summarize the prevalence and risk factors of depression in CLD including chronic hepatitis B, chronic hepatitis, alcoholic liver disease, and non-alcoholic fatty liver disease, and to point out the possible underlying mechanism of this potential link. Clarifying the origins of this common comorbidity (depression and CLD may provide more information to understand both diseases.

Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

Directory of Open Access Journals (Sweden)

Shi-Jian Zhu

2014-01-01

Full Text Available Acoustic and vibration control for an underwater structure under mechanical excitation has been investigated by using negative feedback control algorithm. The underwater structure is modeled with cylindrical shells, conical shells, and circular bulkheads, of which the motion equations are built with the variational approach, respectively. Acoustic property is analyzed by the Helmholtz integration formulation with boundary element method. Based on negative feedback control algorithm, a control loop with a coupling use of piezoelectric sensor and actuator is built, and accordingly some numerical examples are carried out on active control of structural vibration and acoustic response. Effects of geometrical and material parameters on acoustic and vibration properties are investigated and discussed.

Mechanical Behavior of Red Sandstone under Incremental Uniaxial Cyclical Compressive and Tensile Loading

Directory of Open Access Journals (Sweden)

Baoyun Zhao

2017-01-01

Full Text Available Uniaxial experiments were carried out on red sandstone specimens to investigate their short-term and creep mechanical behavior under incremental cyclic compressive and tensile loading. First, based on the results of short-term uniaxial incremental cyclic compressive and tensile loading experiments, deformation characteristics and energy dissipation were analyzed. The results show that the stress-strain curve of red sandstone has an obvious memory effect in the compressive and tensile loading stages. The strains at peak stresses and residual strains increase with the cycle number. Energy dissipation, defined as the area of the hysteresis loop in the stress-strain curves, increases nearly in a power function with the cycle number. Creep test of the red sandstone was also conducted. Results show that the creep curve under each compressive or tensile stress level can be divided into decay and steady stages, which cannot be described by the conventional Burgers model. Therefore, an improved Burgers creep model of rock material is constructed through viscoplastic mechanics, which agrees very well with the experimental results and can describe the creep behavior of red sandstone better than the Burgers creep model.

The tunable mechanical property of water-filled carbon nanotubes under an electric field

Science.gov (United States)

Ye, Hongfei; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen; Zong, Zhi; Zheng, Yonggang

2014-03-01

The spring-induced compression of water-filled carbon nanotubes (CNTs) under an electric field is investigated by molecular dynamics simulations. Due to the incompressibility and polarity of water, the mechanical property of CNTs can be tuned through filling with water molecules and applying an electric field. To explore the variation of the mechanical property of water-filled CNTs, the effects of the CNT length, the filling density and the electric field intensity are examined. The simulation results indicate that the water filling and electric field can result in a slight change in the elastic property (the elastic modulus and Poisson's ratio) of water-filled CNTs. However, the yield stress and average post-buckling stress exhibit a significant response to the water density and electric field intensity. As compared to hollow CNTs, the increment in yield stress of the water-filled CNTs under an electric field of 2.0 V Å-1 is up to 35.29%, which is even higher than that resulting from metal filling. The findings from this study provide a valuable theoretical basis for designing and fabricating the controlling units at the nanoscale.

Thermo-Mechanical Properties of Semi-Degradable Poly(β-amino ester)-co-Methyl Methacrylate Networks under Simulated Physiological Conditions

Science.gov (United States)

Safranski, David L.; Crabtree, Jacob C.; Huq, Yameen R.; Gall, Ken

2011-01-01

Poly(β-amino ester) networks are being explored for biomedical applications, but they may lack the mechanical properties necessary for long term implantation. The objective of this study is to evaluate the effect of adding methyl methacrylate on networks' mechanical properties under simulated physiological conditions. The networks were synthesized in two parts: (1) a biodegradable crosslinker was formed from a diacrylate and amine, (2) and then varying concentrations of methyl methacrylate were added prior to photopolymerizing the network. Degradation rate, mechanical properties, and glass transition temperature were studied as a function of methyl methacrylate composition. The crosslinking density played a limited role on mechanical properties for these networks, but increasing methyl methacrylate concentration improved the toughness by several orders of magnitude. Under simulated physiological conditions, networks showed increasing toughness or sustained toughness as degradation occurred. This work establishes a method of creating degradable networks with tailorable toughness while undergoing partial degradation. PMID:21966028

The behavior of the planetary rings under the Kozai Mechanism

Science.gov (United States)

Sucerquia, M. A.; Ramírez, C. V.; Zuluaga, J. I.

2017-07-01

Rings are one of the main feature of almost all giant planets in the Solar System. Even though thousands of exoplanets have been discovered to date, no evidence of exoplanetary rings have been found despite the effort made in the development and enhancing of techniques and methods for direct or indirect detection. In the transit of a ringed planet, the dynamic of the ring itself could play a meaningful role due to the so called Kozai Mechanism (KM) acting on each particle of it. When some specific initial conditions of the ring are fulfilled (as a ring inclination greater than ˜ 39°), KM generates short periodic changes in the inclination and eccentricity of each particle, leading to a meaningful characteristic collective behavior of the ring: it changes its width, inclination and optical depth. These changes induce periodic variations on the eclipsed area of the parent star, generating slight changes in the observed transit signal. Under this mechanism, light curves depths and shapes oscillate according to the fluctuations of the ring. To show this effect we have performed numerical simulations of the dynamic of a system of particles to asses the ring inclination and width variations over time. We have calculated the expected variations in the transit depth and finally, we have estimated the effect on the light curve of a hypothetical ringed exoplanet affected by the KM. The detection of this effect could be used as an alternative method to detect/confirm exoplanetary rings, and also it could be considered as a way to explain anomalous light curves patterns of exoplanets, as the case of KIC 8462852 star.

Mechanical Behavior of Shale Rock under Uniaxial Cyclic Loading and Unloading Condition

Directory of Open Access Journals (Sweden)

Baoyun Zhao

2018-01-01

Full Text Available In order to investigate the mechanical behavior of shale rock under cyclic loading and unloading condition, two kinds of incremental cyclic loading tests were conducted. Based on the result of the short-term uniaxial incremental cyclic loading test, the permanent residual strain, modulus, and damage evolution were analyzed firstly. Results showed that the relationship between the residual strains and the cycle number can be expressed by an exponential function. The deformation modulus E50 and elastic modulus ES first increased and then decreased with the peak stress under the loading condition, and both of them increased approximately linearly with the peak stress under the unloading condition. On the basis of the energy dissipation, the damage variables showed an exponential increasing with the strain at peak stress. The creep behavior of the shale rock was also analyzed. Results showed that there are obvious instantaneous strain, decay creep, and steady creep under each stress level and the specimen appears the accelerated creep stage under the 4th stress of 51.16 MPa. Based on the characteristics of the Burgers creep model, a viscoelastic-plastic creep model was proposed through viscoplastic mechanics, which agrees very well with the experimental results and can better describe the creep behavior of shale rock better than the Burgers creep model. Results can provide some mechanics reference evidence for shale gas development.

The buzz on caffeine in invertebrates: effects on behavior and molecular mechanisms.

Science.gov (United States)

Mustard, Julie A

2014-04-01

A number of recent studies from as diverse fields as plant-pollinator interactions, analyses of caffeine as an environmental pollutant, and the ability of caffeine to provide protection against neurodegenerative diseases have generated interest in understanding the actions of caffeine in invertebrates. This review summarizes what is currently known about the effects of caffeine on behavior and its molecular mechanisms in invertebrates. Caffeine appears to have similar effects on locomotion and sleep in both invertebrates and mammals. Furthermore, as in mammals, caffeine appears to have complex effects on learning and memory. However, the underlying mechanisms for these effects may differ between invertebrates and vertebrates. While caffeine's ability to cause release of intracellular calcium stores via ryanodine receptors and its actions as a phosphodiesterase inhibitor have been clearly established in invertebrates, its ability to interact with invertebrate adenosine receptors remains an important open question. Initial studies in insects and mollusks suggest an interaction between caffeine and the dopamine signaling pathway; more work needs to be done to understand the mechanisms by which caffeine influences signaling via biogenic amines. As of yet, little is known about whether other actions of caffeine in vertebrates, such as its effects on GABAA and glycine receptors, are conserved. Furthermore, the pharmacokinetics of caffeine remains to be elucidated. Overall behavioral responses to caffeine appear to be conserved amongst organisms; however, we are just beginning to understand the mechanisms underlying its effects across animal phyla.

Consumption of polyphenol-rich Morus alba leaves extract attenuates early diabetic retinopathy: the underlying mechanism.

Science.gov (United States)

Mahmoud, Ayman M; Abd El-Twab, Sanaa M; Abdel-Reheim, Eman S

2017-06-01

Beneficial effects of white mulberry against diabetes mellitus have been reported. However, the molecular mechanisms of how white mulberry can attenuate diabetic retinopathy remain poorly understood. Here, the mechanism underlying the protective effect of Morus alba leaves ethanolic extract on oxidative stress, inflammation, apoptosis, and angiogenesis in diabetic retinopathy was investigated. Diabetes was induced by injection of streptozotocin. One week after, M. alba (100 mg/kg) was administrated to the rats daily for 16 weeks. Morus alba extract showed high content of polyphenolics and free radical scavenging activity. Oral M. alba administration significantly attenuated hyperglycemia and weight loss, and decreased sorbitol, fructose, protein kinase C, pro-inflammatory cytokines, and oxidative stress markers in retinas of the diabetic rats. Moreover, M. alba produced marked down-regulation of caspase-3 and Bax, with concomitant up-regulation of Bcl-2 in the diabetic retinas. M. alba also reduced the expression of VEGF in the retina. These results indicate that M. alba has protective effect on diabetic retinopathy with possible mechanisms of inhibiting hyperglycemia-induced oxidative stress, apoptosis, inflammation, polyol pathway activation, and VEGF expression in the retina.

A possible realization of Einstein's causal theory underlying quantum mechanics

International Nuclear Information System (INIS)

Yussouff, M.

1979-06-01

It is shown that a new microscopic mechanics formulated earlier can be looked upon as a possible causal theory underlying quantum mechanics, which removes Einstein's famous objections against quantum theory. This approach is free from objections raised against Bohm's hidden variable theory and leads to a clear physical picture in terms of familiar concepts, if self interactions are held responsible for deviations from classical behaviour. The new level of physics unfolded by this approach may reveal novel frontiers in high-energy physics. (author)

Statistical mechanics of fluids under internal constraints: Rigorous results for the one-dimensional hard rod fluid

International Nuclear Information System (INIS)

Corti, D.S.; Debenedetti, P.G.

1998-01-01

The rigorous statistical mechanics of metastability requires the imposition of internal constraints that prevent access to regions of phase space corresponding to inhomogeneous states. We derive exactly the Helmholtz energy and equation of state of the one-dimensional hard rod fluid under the influence of an internal constraint that places an upper bound on the distance between nearest-neighbor rods. This type of constraint is relevant to the suppression of boiling in a superheated liquid. We determine the effects of this constraint upon the thermophysical properties and internal structure of the hard rod fluid. By adding an infinitely weak and infinitely long-ranged attractive potential to the hard core, the fluid exhibits a first-order vapor-liquid transition. We determine exactly the equation of state of the one-dimensional superheated liquid and show that it exhibits metastable phase equilibrium. We also derive statistical mechanical relations for the equation of state of a fluid under the action of arbitrary constraints, and show the connection between the statistical mechanics of constrained and unconstrained ensembles. copyright 1998 The American Physical Society

Underlying mechanism of drug-drug interaction between pioglitazone and gemfibrozil: Gemfibrozil acyl-glucuronide is a mechanism-based inhibitor of CYP2C8.

Science.gov (United States)

Takagi, Motoi; Sakamoto, Masaya; Itoh, Tomoo; Fujiwara, Ryoichi

2015-08-01

While co-administered gemfibrozil can increase the area under the concentration/time curve (AUC) of pioglitazone more than 3-fold, the underlying mechanism of the drug-drug interaction between gemfibrozil and pioglitazone has not been fully understood. In the present study, gemfibrozil preincubation time-dependently inhibited the metabolism of pioglitazone in the cytochrome P450 (CYP)- and UDP-glucuronosyltransferase (UGT)-activated human liver microsomes. We estimated the kinact and K'app values, which are the maximum inactivation rate constant and the apparent dissociation constant, of gemfibrozil to be 0.071 min(-1) and 57.3 μM, respectively. In this study, the kobs, in vivo value was defined as a parameter that indicates the potency of the mechanism-based inhibitory effect at the blood drug concentration in vivo. The kobs, in vivo values of potent mechanism-based inhibitors, clarithromycin and erythromycin, were estimated to be 0.0096 min(-1) and 0.0051 min(-1), respectively. The kobs, in vivo value of gemfibrozil was 0.0060 min(-1), which was comparable to those of clarithromycin and erythromycin, suggesting that gemfibrozil could be a mechanism-based inhibitor as potent as clarithromycin and erythromycin in vivo. Copyright © 2015 The Japanese Society for the Study of Xenobiotics. Published by Elsevier Ltd. All rights reserved.

Cognitive mechanisms underlying disorganization of thought in a genetic syndrome (47,XXY)

NARCIS (Netherlands)

Van Rijn, Sophie; Aleman, Andre; De Sonneville, Leo; Swaab, Hanna

Because of the risk for development of psychopathology such as psychotic symptoms, it has been suggested that studying men with the XXY karyotype may help in the search for underlying cognitive, neural and genetic mechanisms. The aim of this study was to identify cognitive mechanisms that may

First-principles investigation of mechanical and electronic properties of tetragonal NbAl3 under tension

Science.gov (United States)

Jiao, Zhen; Liu, Qi-Jun; Liu, Fu-Sheng; Tang, Bin

2018-06-01

Using the density functional theory calculations, the mechanical and electronic properties of NbAl3 under different tensile loads were investigated. The calculated lattice parameters, elastic constants and mechanical properties (bulk modulus, shear modulus, Young's modulus, Poisson's ratio, Pugh's criterion and Cauchy's pressure) indicated that our results were in agreement with the published experimental and theoretical data at zero tension. With respect to NbAl3 under tension in this paper, the crystal structure was changed from tetragonal to orthorhombic under tension along the [100] and [101] directions. The NbAl3 crystal has been classified as brittle material under tension from 0 to 20 GPa. The obtained Young's modulus and Debye temperature monotonically decreased with increasing tension stress. Combining with mechanical and electronic properties in detail, the decreased mechanical properties were mainly due to the weakening of covalency.

Mechanisms Underlying Cytotoxicity Induced by Engineered Nanomaterials: A Review of In Vitro Studies

Science.gov (United States)

Nogueira, Daniele R.; Mitjans, Montserrat; Rolim, Clarice M. B.; Vinardell, M. Pilar

2014-01-01

Engineered nanomaterials are emerging functional materials with technologically interesting properties and a wide range of promising applications, such as drug delivery devices, medical imaging and diagnostics, and various other industrial products. However, concerns have been expressed about the risks of such materials and whether they can cause adverse effects. Studies of the potential hazards of nanomaterials have been widely performed using cell models and a range of in vitro approaches. In the present review, we provide a comprehensive and critical literature overview on current in vitro toxicity test methods that have been applied to determine the mechanisms underlying the cytotoxic effects induced by the nanostructures. The small size, surface charge, hydrophobicity and high adsorption capacity of nanomaterial allow for specific interactions within cell membrane and subcellular organelles, which in turn could lead to cytotoxicity through a range of different mechanisms. Finally, aggregating the given information on the relationships of nanomaterial cytotoxic responses with an understanding of its structure and physicochemical properties may promote the design of biologically safe nanostructures. PMID:28344232

Mechanisms underlying cellular responses of cells from haemopoietic tissue to low

Energy Technology Data Exchange (ETDEWEB)

Kadhim, Munira A

2012-08-22

The above studies will provide fundamental mechanistic information relating genetic predisposition to important low dose phenomena, and will aid in the development of Department of Energy policy, as well as radiation risk policy for the public and the workplace. We believe the proposed studies accurately reflect the goals of the DOE low dose program. To accurately define the risks associated with human exposure to relevant environmental doses of low LET ionizing radiation, it is necessary to completely understand the biological effects at very low doses (i.e. less than 0.1 Gy), including the lowest possible dose, that of a single electron track traversal. At such low doses, a range of studies have shown responses in biological systems which are not related to the direct interaction of radiation tracks with DNA. The role of these "non-targeted responses in critical tissues is poorly understood and little is known regarding the underlying mechanisms. Although critical for dosimetry and risk assessment, the role of individual genetic susceptibility in radiation risk is not satisfactorily defined at present. The aim of the proposed grant is to critically evaluate non-targeted effects of ionizing radiation with a focus on the induction of genomic instability (GI) in key stem cell populations from haemopoietic tissue. Using stem cells from two mouse strains (CBA/CaH and C57BL/6J) known to differ in their susceptibility to radiation effects, we plan to carefully dissect the role of genetic predisposition in these models on genomic instability. We will specifically focus on the effects of low doses of low LET radiation, down to the dose of 10mGy (0.01Gy) X-rays. Using conventional X-ray and we will be able to assess the role of genetic variation under various conditions at a range of doses down to the very low dose of 0.01Gy. Irradiations will be carried out using facilities in routine operation for such studies. Mechanistic studies of instability in different cell

Kinetic theory approach to modeling of cellular repair mechanisms under genome stress.

Directory of Open Access Journals (Sweden)

Jinpeng Qi

Full Text Available Under acute perturbations from outer environment, a normal cell can trigger cellular self-defense mechanism in response to genome stress. To investigate the kinetics of cellular self-repair process at single cell level further, a model of DNA damage generating and repair is proposed under acute Ion Radiation (IR by using mathematical framework of kinetic theory of active particles (KTAP. Firstly, we focus on illustrating the profile of Cellular Repair System (CRS instituted by two sub-populations, each of which is made up of the active particles with different discrete states. Then, we implement the mathematical framework of cellular self-repair mechanism, and illustrate the dynamic processes of Double Strand Breaks (DSBs and Repair Protein (RP generating, DSB-protein complexes (DSBCs synthesizing, and toxins accumulating. Finally, we roughly analyze the capability of cellular self-repair mechanism, cellular activity of transferring DNA damage, and genome stability, especially the different fates of a certain cell before and after the time thresholds of IR perturbations that a cell can tolerate maximally under different IR perturbation circumstances.

Kinetic theory approach to modeling of cellular repair mechanisms under genome stress.

Science.gov (United States)

Qi, Jinpeng; Ding, Yongsheng; Zhu, Ying; Wu, Yizhi

2011-01-01

Under acute perturbations from outer environment, a normal cell can trigger cellular self-defense mechanism in response to genome stress. To investigate the kinetics of cellular self-repair process at single cell level further, a model of DNA damage generating and repair is proposed under acute Ion Radiation (IR) by using mathematical framework of kinetic theory of active particles (KTAP). Firstly, we focus on illustrating the profile of Cellular Repair System (CRS) instituted by two sub-populations, each of which is made up of the active particles with different discrete states. Then, we implement the mathematical framework of cellular self-repair mechanism, and illustrate the dynamic processes of Double Strand Breaks (DSBs) and Repair Protein (RP) generating, DSB-protein complexes (DSBCs) synthesizing, and toxins accumulating. Finally, we roughly analyze the capability of cellular self-repair mechanism, cellular activity of transferring DNA damage, and genome stability, especially the different fates of a certain cell before and after the time thresholds of IR perturbations that a cell can tolerate maximally under different IR perturbation circumstances.

Control of a perturbed under-actuated mechanical system

KAUST Repository

Zayane, Chadia

2015-11-05

In this work, the trajectory tracking problem for an under-actuated mechanical system in presence of unknown input disturbances is addressed. The studied inertia wheel inverted pendulum falls in the class of non minimum phase systems. The proposed high order sliding mode control architecture including a controller and differentiator allows to track accurately the predefined trajectory and to stabilize the internal dynamics. The robustness of the proposed approach is illustrated through different perturbation and output noise configurations.

Mechanisms underlying astringency: introduction to an oral tribology approach

Science.gov (United States)

Upadhyay, Rutuja; Brossard, Natalia; Chen, Jianshe

2016-03-01

Astringency is one of the predominant factors in the sensory experience of many foods and beverages ranging from wine to nuts. The scientific community is discussing mechanisms that explain this complex phenomenon, since there are no conclusive results which correlate well with sensory astringency. Therefore, the mechanisms and perceptual characteristics of astringency warrant further discussion and investigation. This paper gives a brief introduction of the fundamentals of oral tribology forming a basis of the astringency mechanism. It discusses the current state of the literature on mechanisms underlying astringency describing the existing astringency models. The review discusses the crucial role of saliva and its physiology which contributes significantly in astringency perception in the mouth. It also provides an overview of research concerned with the physiological and psychophysical factors that mediate the perception of this sensation, establishing the ground for future research. Thus, the overall aim of the review is to establish the critical roles of oral friction (thin-film lubrication) in the sensation of astringency and possibly of some other specific sensory features.

Chemosensitizing effects of carbon-based nanomaterials in cancer cells: enhanced apoptosis and inhibition of proliferation as underlying mechanisms

International Nuclear Information System (INIS)

Erdmann, Kati; Ringel, Jessica; Rieger, Christiane; Huebner, Doreen; Wirth, Manfred P; Fuessel, Susanne; Hampel, Silke

2014-01-01

Recent studies have shown that carbon nanomaterials such as carbon nanofibres (CNFs) and multi-walled carbon nanotubes (CNTs) can exert antitumor activities themselves and sensitize cancer cells to conventional chemotherapeutics such as carboplatin and cisplatin. In the present study, the chemosensitizing effect of CNFs and CNTs on cancer cells of urological origin was investigated regarding the underlying mechanisms. Prostate cancer (DU-145, PC-3) and bladder cancer (EJ28) cells were treated with carbon nanomaterials (CNFs, CNTs) and chemotherapeutics (carboplatin, cisplatin) alone as well as in combination for 24 h. Forty-eight (EJ28) or 72 h (DU-145, PC-3) after the end of treatment the effects on cellular proliferation, clonogenic survival, cell death rate and cell cycle distribution were evaluated. Depending on the cell line, simultaneous administration of chemotherapeutics and carbon nanomaterials produced an additional inhibition of cellular proliferation and clonogenic survival of up to 77% and 98%, respectively, compared to the inhibitory effects of the chemotherapeutics alone. These strongly enhanced antiproliferative effects were accompanied by an elevated cell death rate, which was predominantly mediated via apoptosis and not by necrosis. The antitumor effects of combinations with CNTs were less pronounced than those with CNFs. The enhanced effects of the combinatory treatments on cellular function were mostly of additive to partly synergistic nature. Furthermore, cell cycle analysis demonstrated an arrest at the G2/M phase mediated by a monotreatment with chemotherapeutics. Following combinatory treatments, mostly less than or nearly additive increases of cell fractions in the G2/M phase could be observed. In conclusion, the pronounced chemosensitizing effects of CNFs and CNTs were mediated by an enhanced apoptosis and inhibition of proliferation. The combination of carbon-based nanomaterials and conventional chemotherapeutics represents a novel

Chemosensitizing effects of carbon-based nanomaterials in cancer cells: enhanced apoptosis and inhibition of proliferation as underlying mechanisms

Science.gov (United States)

Erdmann, Kati; Ringel, Jessica; Hampel, Silke; Rieger, Christiane; Huebner, Doreen; Wirth, Manfred P.; Fuessel, Susanne

2014-10-01

Recent studies have shown that carbon nanomaterials such as carbon nanofibres (CNFs) and multi-walled carbon nanotubes (CNTs) can exert antitumor activities themselves and sensitize cancer cells to conventional chemotherapeutics such as carboplatin and cisplatin. In the present study, the chemosensitizing effect of CNFs and CNTs on cancer cells of urological origin was investigated regarding the underlying mechanisms. Prostate cancer (DU-145, PC-3) and bladder cancer (EJ28) cells were treated with carbon nanomaterials (CNFs, CNTs) and chemotherapeutics (carboplatin, cisplatin) alone as well as in combination for 24 h. Forty-eight (EJ28) or 72 h (DU-145, PC-3) after the end of treatment the effects on cellular proliferation, clonogenic survival, cell death rate and cell cycle distribution were evaluated. Depending on the cell line, simultaneous administration of chemotherapeutics and carbon nanomaterials produced an additional inhibition of cellular proliferation and clonogenic survival of up to 77% and 98%, respectively, compared to the inhibitory effects of the chemotherapeutics alone. These strongly enhanced antiproliferative effects were accompanied by an elevated cell death rate, which was predominantly mediated via apoptosis and not by necrosis. The antitumor effects of combinations with CNTs were less pronounced than those with CNFs. The enhanced effects of the combinatory treatments on cellular function were mostly of additive to partly synergistic nature. Furthermore, cell cycle analysis demonstrated an arrest at the G2/M phase mediated by a monotreatment with chemotherapeutics. Following combinatory treatments, mostly less than or nearly additive increases of cell fractions in the G2/M phase could be observed. In conclusion, the pronounced chemosensitizing effects of CNFs and CNTs were mediated by an enhanced apoptosis and inhibition of proliferation. The combination of carbon-based nanomaterials and conventional chemotherapeutics represents a novel

Capacity of 50Ti-47Ni-3Cu composite to convert heat energy to mechanical work under cyclic measurement of temperature

International Nuclear Information System (INIS)

Belyaev, S.P.; Kuz'min, S.L.; Likhachev, V.A.

1984-01-01

The TiNiCu alloy with a shape memory which may be used as a working medium for the martensite engine converting heat energy to mechanical one is studied for its energy characteristics. Mechanical characteristics of the material are studied under torsion of cylindrical specimens of stressed thermocycling through temperature intervals of martensite transformations. It is established that the shape memory and transformation ductility effects determining serviceability and power of the martensite enginem vary gradually with the number of heat changes reaching saturation after 10-15 thermocycles, The heating-and-cooling stress dependence of deformations due to the shape memory and transformation ductility effects also varied with the number of heat changes, Cooling conditions under stress of 50 MPa and heating conditions under 200 MPa and above proved to be most optimal. Serviceability of the engine made of the TiNiCu alloy exceeds 10 MJ/m 3 and its power reaches 10 5 MW m -3 under operation frequency of 10 3 Hz

Mechanisms of action underlying the antiandrogenic effects of the fungicide prochloraz

International Nuclear Information System (INIS)

Laier, Peter; Metzdorff, Stine Broeng; Borch, Julie; Hagen, Marie Louise; Hass, Ulla; Christiansen, Sofie; Axelstad, Marta; Kledal, Thuri; Dalgaard, Majken; McKinnell, Chris; Brokken, Leon J.S.; Vinggaard, Anne Marie

2006-01-01

The fungicide prochloraz has got multiple mechanisms of action that may influence the demasculinizing and reproductive toxic effects of the compound. In the present study, Wistar rats were dosed perinatally with prochloraz (50 and 150 mg/kg/day) from gestational day (GD) 7 to postnatal day (PND) 16. Caesarian sections were performed on selected dams at GD 21, while others were allowed to give birth to pups that were followed until PND 16. Prochloraz caused mild dysgenesis of the male external genitalia as well as reduced anogenital distance and retention of nipples in male pups. An increased anogenital distance indicated virilization of female pups. Effects on steroidogenesis in male fetuses became evident as decreased testicular and plasma levels of testosterone and increased levels of progesterone. Ex vivo synthesis of both steroid hormones was qualitatively similarly affected by prochloraz. Immunohistochemistry of fetal testes showed increased expression of 17α-hydroxylase/17,20-lyase (P450c17) and a reduction in 17β-hydroxysteroid dehydrogenase (type 10) expression, whereas no changes in expression of genes involved in testicular steroidogenesis were observed. Increased expression of P450c17 mRNA was observed in fetal male adrenals, and the androgen-regulated genes ornithine decarboxylase, prostatic binding protein C3 as well as insulin-like growth factor I mRNA were reduced in ventral prostates PND 16. These results indicate that reduced activity of P450c17 may be a primary cause of the disrupted fetal steroidogenesis and that an altered androgen metabolism may play a role as well. In vitro studies on human adrenocortical carcinoma cells supported the findings in vivo as reduced testosterone and increased progesterone levels were observed. Overall, these results together indicate that prochloraz acts directly on the fetal testis to inhibit steroidogenesis and that this effect is exhibited at protein, and not at genomic, level

Effect of cyclic electron irradiation on mechanical properties of austenite steel

International Nuclear Information System (INIS)

Tsepelev, A.B.; Sadykhov, S.I.O.; Chernov, A.I.; Sevost'yanov, M.A.

2006-01-01

To check the supposition on the possibility of radiation-stimulated process enhancement under cyclic irradiation conditions an experimental investigation is carried out to elucidate the effect of the mode of irradiation (continuous or cyclic) on mechanical properties of chromium-manganese austenitic stainless steel type 10Kh12G20V. The effect of some radiation hardening is observed under cyclic irradiation, however, the data obtained cannot be considered as good evidence for the validity of proposed model of dynamic preference if the scatter in experimental data is taken into account [ru

On some mechanisms of the effect of thermal prehistory on the behavior of silicon parameters under irradiation. O nekotorykh mekhanizmakh vliyaniya teplovoj predystorii na povedenie parametrov kremniya pod oblucheniem

Energy Technology Data Exchange (ETDEWEB)

Nejmash, V B; Sagan, T R; Tsmots' , V M; Shakhovtsov, V I; Shindich, V L [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fiziki

1991-11-01

The effect of preliminary thermal treatment (TT) in 400-1200 degC temperature range on the behavior of Si monocrystal parameters under subsequent [gamma]-, electron and neutron irradiation is investigated. Five mechanisms of Si thermal prehistory effect on its properties are proposed: (1) decomposition of solid solutions of impurities interacting with radiation defects (RD); (2) formation of electrically active thermal defects (TD) in concentrations wich are sufficient for a significant alteration of RD charged state; (3) origination of TD, which can efficiency as aresult of the redistribution of impurities under thermal treatment; (5) formation of clusters of electrically active TD, resulting in the disturbance of electric homogeneity of Si crystal.

micro-mechanical experimental investigation and modelling of strain and damage of argillaceous rocks under combined hydric and mechanical loads

International Nuclear Information System (INIS)

Wang, L.

2012-01-01

The hydro-mechanical behavior of argillaceous rocks, which are possible host rocks for underground radioactive nuclear waste storage, is investigated by means of micro-mechanical experimental investigations and modellings. Strain fields at the micrometric scale of the composite structure of this rock, are measured by the combination of environmental scanning electron microscopy, in situ testing and digital image correlation technique. The evolution of argillaceous rocks under pure hydric loading is first investigated. The strain field is strongly heterogeneous and manifests anisotropy. The observed nonlinear deformation at high relative humidity (RH) is related not only to damage, but also to the nonlinear swelling of the clay mineral itself, controlled by different local mechanisms depending on RH. Irreversible deformations are observed during hydric cycles, as well as a network of microcracks located in the bulk of the clay matrix and/or at the inclusion-matrix interface. Second, the local deformation field of the material under combined hydric and mechanical loadings is quantified. Three types of deformation bands are evidenced under mechanical loading, either normal to stress direction (compaction), parallel (microcracking) or inclined (shear). Moreover, they are strongly controlled by the water content of the material: shear bands are in particular prone to appear at high RH states. In view of understanding the mechanical interactions a local scale, the material is modeled as a composite made of non-swelling elastic inclusions embedded in an elastic swelling clay matrix. The internal stress field induced by swelling strain incompatibilities between inclusions and matrix, as well as the overall deformation, is numerically computed at equilibrium but also during the transient stage associated with a moisture gradient. An analytical micro-mechanical model based on Eshelby's solution is proposed. In addition, 2D finite element computations are performed. Results

Progressive damage analysis of carbon/epoxy laminates under couple laser and mechanical loading

Directory of Open Access Journals (Sweden)

Wanlei Liu

Full Text Available A multiscale model based bridge theory is proposed for the progressive damage analysis of carbon/epoxy laminates under couple laser and mechanical loading. The ablation model is adopted to calculate ablation temperature changing and ablation surface degradation. The polynomial strengthening model of matrix is used to improve bridging model for reducing parameter input. Stiffness degradation methods of bridging model are also improved in order to analyze the stress redistribution more accurately when the damage occurs. Thermal-mechanical analyses of the composite plate are performed using the ABAQUS/Explicit program with the developed model implemented in the VUMAT. The simulation results show that this model can be used to proclaim the mesoscale damage mechanism of composite laminates under coupled loading. Keywords: Laser irradiation, Multiscale analysis, Bridge model, Thermal-mechanical

An NMDA Receptor-Dependent Mechanism Underlies Inhibitory Synapse Development

Directory of Open Access Journals (Sweden)

Xinglong Gu

2016-01-01

Full Text Available In the mammalian brain, GABAergic synaptic transmission provides inhibitory balance to glutamatergic excitatory drive and controls neuronal output. The molecular mechanisms underlying the development of GABAergic synapses remain largely unclear. Here, we report that NMDA-type ionotropic glutamate receptors (NMDARs in individual immature neurons are the upstream signaling molecules essential for GABAergic synapse development, which requires signaling via Calmodulin binding motif in the C0 domain of the NMDAR GluN1 subunit. Interestingly, in neurons lacking NMDARs, whereas GABAergic synaptic transmission is strongly reduced, the tonic inhibition mediated by extrasynaptic GABAA receptors is increased, suggesting a compensatory mechanism for the lack of synaptic inhibition. These results demonstrate a crucial role for NMDARs in specifying the development of inhibitory synapses, and suggest an important mechanism for controlling the establishment of the balance between synaptic excitation and inhibition in the developing brain.

The effect of education on the nursing care quality of patients who are under mechanical ventilation in ICU ward

Directory of Open Access Journals (Sweden)

Sahar Geravandi

2018-02-01

Full Text Available Nurses have the most important role among health care workers (HCWs in each hospital (Aiken et al., 2008 [1]. Nurses education can lead to the improvement of nursing care If is implemented and designed based on nurses’ needs and proper principles (Aiken et al., 2008 [1]. Nowadays, increased quality of the treatment and increase the chances of survival of patients with acute respiratory failure are very important (Teixeira et al., 2013 [2]. Nursing care plan in ICU patients is one of the important elements in nursing care, and one of the main strategies is promotion of education level. Nurses due to longtime relationship with nursing staff in 24 hours and use of multiple roles of education have excellent position in evaluating educational needs and performing clinical educator roles. The effect of education on the nursing care quality of patients who were under mechanical ventilation (UMV in intensive care unit (ICU ward of Razi hospital is evaluated during 2015. The present study is descriptive-analytical and semi experimental research. Research statistical population included 30 nurses. In this paper, the effects of communication with the patient, correct suctioning, compliance of aseptic techniques, the correct discharge of tube cuff, chest physiotherapy, the correct change positions, health food gavage, prevent of foot drop, oral hygiene, the eyes hygiene and protect the cornea have been studied. After completion of the questionnaires by patients, the obtained coded data were fed into EXCEL. Reliability was confirmed with coefficient Alfa 0.86 and the result of software and techniques were entered to SPSS for statistics and analysis. Keywords: Education, Nurse, Intensive care unit, Mechanical ventilation, Nursing care, Iran

Modulating conscious movement intention by noninvasive brain stimulation and the underlying neural mechanisms.

Science.gov (United States)

Douglas, Zachary H; Maniscalco, Brian; Hallett, Mark; Wassermann, Eric M; He, Biyu J

2015-05-06

Conscious intention is a fundamental aspect of the human experience. Despite long-standing interest in the basis and implications of intention, its underlying neurobiological mechanisms remain poorly understood. Using high-definition transcranial DC stimulation (tDCS), we observed that enhancing spontaneous neuronal excitability in both the angular gyrus and the primary motor cortex caused the reported time of conscious movement intention to be ∼60-70 ms earlier. Slow brain waves recorded ∼2-3 s before movement onset, as well as hundreds of milliseconds after movement onset, independently correlated with the modulation of conscious intention by brain stimulation. These brain activities together accounted for 81% of interindividual variability in the modulation of movement intention by brain stimulation. A computational model using coupled leaky integrator units with biophysically plausible assumptions about the effect of tDCS captured the effects of stimulation on both neural activity and behavior. These results reveal a temporally extended brain process underlying conscious movement intention that spans seconds around movement commencement. Copyright © 2015 Douglas et al.

"THE EVALUATION OF THE POSSIBLE EFFECT OF POSITIVE END EXPIRATORY PRESSURE (PEEP) ON PHARMACOKINETICS OF PHENYTOIN IN PATIENTS WITH ACUTE BRAIN INJURY UNDER MECHANICAL VENTILATION."

OpenAIRE

"Elham Hadidi; Mojtaba Mojtahedzadeh; Mohammad Reza Rouini; Behzad Eftekhar; Mohammad Abdollahi; Atabak Najafi; Mohammad R. Khajavi; Saeed Rezaee; Reza Ghaffari; Minoo Afshar"

2005-01-01

Positive ventilation has shown to have an influence on pharmacokinetic and disposition of some drugs.Beacause phenytoin with a narrow therapautic range, is the most commonly used drug for prophylaxis and treatment of early seizures after acute brain injuries, in the present study the effect of short term PEEP (5-10 cm H2O for at least 8 hours) on phenytoin serum concentration and pharmacokinetic parameters such as Vmax and clearance in brain injured patients under mechanical ventilation was e...

Mechanical properties of graphene nanoribbons under uniaxial tensile strain

Science.gov (United States)

Yoneyama, Kazufumi; Yamanaka, Ayaka; Okada, Susumu

2018-03-01

Based on the density functional theory with the generalized gradient approximation, we investigated the mechanical properties of graphene nanoribbons in terms of their edge shape under a uniaxial tensile strain. The nanoribbons with armchair and zigzag edges retain their structure under a large tensile strain, while the nanoribbons with chiral edges are fragile against the tensile strain compared with those with armchair and zigzag edges. The fracture started at the cove region, which corresponds to the border between the zigzag and armchair edges for the nanoribbons with chiral edges. For the nanoribbons with armchair edges, the fracture started at one of the cove regions at the edges. In contrast, the fracture started at the inner region of the nanoribbons with zigzag edges. The bond elongation under the tensile strain depends on the mutual arrangement of covalent bonds with respect to the strain direction.

Mechanical Design of AM Fabricated Prismatic Rods under Torsion

Directory of Open Access Journals (Sweden)

Manzhirov Alexander V.

2017-01-01

Full Text Available We study the stress-strain state of viscoelastic prismatic rods fabricated or repaired by additive manufacturing technologies under torsion. An adequate description of the processes involved is given by methods of a new scientific field, mechanics of growing solids. Three main stages of the deformation process (before the beginning of growth, in the course of growth, and after the termination of growth are studied. Two versions of statement of two problems are given: (i given the torque, find the stresses, displacements, and torsion; (ii given the torsion, find the stresses, displacements, and torque. Solution methods using techniques of complex analysis are presented. The results can be used in mechanical and instrument engineering.

[Underlying Mechanisms and Management of Refractory Gastroesophageal Reflux Disease].

Science.gov (United States)

Lee, Kwang Jae

2015-08-01

The prevalence of gastroesophageal reflux disease (GERD) in South Korea has increased over the past 10 years. Patients with erosive reflux disease (ERD) shows better response to proton pump inhibitors (PPIs) than those with non-erosive reflux disease (NERD). NERD is a heterogeneous condition, showing pathological gastroesophageal reflux or esophageal hypersensitivity to reflux contents. NERD patients with pathological gastroesophageal reflux or hypersensitivity to acid may respond to PPIs. However, many patients with esophageal hypersensitivity to nonacid or functional heartburn do not respond to PPIs. Therefore, careful history and investigations are required when managing patients with refractory GERD who show poor response to conventional dose PPIs. Combined pH-impedance studies and a PPI diagnostic trial are recommended to reveal underlying mechanisms of refractory symptoms. For those with ongoing reflux-related symptoms, split dose administration, change to long-acting PPIs or PPIs less influenced by CYP2C19 genotypes, increasing dose of PPIs, and the addition of alginate preparations, prokinetics, selective serotonin reuptake inhibitors, or tricyclic antidepressants can be considered. Pain modulators, selective serotonin reuptake inhibitors, or tricyclic antidepressants are more likely to be effective for those with reflux-unrelated symptoms. Surgery or endoscopic per oral fundoplication may be effective in selected patients.

Mechanical and tribological behaviour of molten salt processed self-lubricated aluminium composite under different treatments

Science.gov (United States)

Kannan, C.; Ramanujam, R.

2018-05-01

The aim of this research work is to evaluate the mechanical and tribological behaviour of Al 7075 based self-lubricated hybrid nanocomposite under different treated conditions viz. as-cast, T6 and deep cryo treated. In order to overcome the drawbacks associated with conventional stir casting, a combinational approach that consists of molten salt processing, ultrasonic assistance and optimized mechanical stirring is adopted in this study to fabricate the nanocomposite. The mechanical characterisation tests carried out on this nanocomposite reveals an improvement of about 39% in hardness and 22% in ultimate tensile strength possible under T6 condition. Under specific conditions, the wear rate can be reduced to the extent of about 63% through the usage of self-lubricated hybrid nanocomposite under T6 condition.

Mechanisms and pharmacogenetic signals underlying thiazide diuretics blood pressure response.

Science.gov (United States)

Shahin, Mohamed H; Johnson, Julie A

2016-04-01

Thiazide (TZD) diuretics are among the most commonly prescribed antihypertensives globally; however their chronic blood pressure (BP) lowering mechanism remains unclear. Herein we discuss the current evidence regarding specific mechanisms regulating the antihypertensive effects of TZDs, suggesting that TZDs act via multiple complex and interacting mechanisms, including natriuresis with short term use and direct vasodilatory effects chronically. Additionally, we review pharmacogenomics signals that have been associated with TZDs BP-response in several cohorts (i.e. NEDD4L, PRKCA, EDNRA-GNAS, and YEATS4) and discuss how these genes might be related to TZD BP-response mechanism. Understanding the association between these genes and TZD BP mechanism might facilitate the development of new drugs and therapeutic approaches based on a deeper understanding of the determinants of BP-response. Copyright © 2016. Published by Elsevier Ltd.

Experimental study on the thermo-mechanical behaviour of stiff clay under non-isotropic stress state

International Nuclear Information System (INIS)

Tang, Anh Minh; Cui, Yu-Jun; Li, Xiang-Ling

2012-01-01

Document available in extended abstract form only. Stiff clay is usually considered as possible host-rock for geological radioactive waste disposal due to its low permeability and its self-sealing capacity. Boom Clay, for instance, is one of the clays currently considered by the Belgian radioactive waste management agency Ondraf/Niras as a potential host for a geological repository. In order to analyse the performance of this material, it is important to understand its behaviour under the coupled thermo-hydro-mechanical solicitations. In laboratory, several studies have been performed to study the volume change of clay under coupled thermomechanical loading. The results show that heating under drained conditions can induce thermal dilation at low confining stress and thermal contraction at high confining stress. On the other hand, compression tests performed at constant temperature show that the compressibility parameters of soil can be modified by temperature change. These features are now well considered in constitutive laws based on the framework of elasto-plasticity. Under undrained conditions, heating can increase pore-water pressure and this behaviour can be simulated using the theoretical thermo-poro-elastic framework. The temperature effect on the soil behaviour under triaxial compression is also often considered. It is commonly accepted that heating decreases the shear strength of clay but this softening can be hidden by the thermal contraction that occurs during heating which can induce at the same time soil hardening. In spite of these existing works, laboratory tests considering the thermo-mechanical loading path that the soil can be subjected to are still rare. Actually, in the case of geological radioactive waste disposal, after the installation of waste canisters, the soil is expected to be heated under non-isotropic stress state. Most of the existing laboratory works show heating tests in odometer cell or triaxial cell under isotropic stress

The neuronal mechanisms underlying improvement of impulsivity in ADHD by theta/beta neurofeedback.

Science.gov (United States)

Bluschke, Annet; Broschwitz, Felicia; Kohl, Simon; Roessner, Veit; Beste, Christian

2016-08-12

Neurofeedback is increasingly recognized as an intervention to treat core symptoms of attention deficit hyperactivity disorder (ADHD). Despite the large number of studies having been carried out to evaluate its effectiveness, it is widely elusive what neuronal mechanisms related to the core symptoms of ADHD are modulated by neurofeedback. 19 children with ADHD undergoing 8 weeks of theta/beta neurofeedback and 17 waiting list controls performed a Go/Nogo task in a pre-post design. We used neurophysiological measures combining high-density EEG recording with source localization analyses using sLORETA. Compared to the waiting list ADHD control group, impulsive behaviour measured was reduced after neurofeedback treatment. The effects of neurofeedback were very specific for situations requiring inhibitory control over responses. The neurophysiological data shows that processes of perceptual gating, attentional selection and resource allocation processes were not affected by neurofeedback. Rather, neurofeedback effects seem to be based on the modulation of response inhibition processes in medial frontal cortices. The study shows that specific neuronal mechanisms underlying impulsivity are modulated by theta/beta neurofeedback in ADHD. The applied neurofeedback protocol could be particularly suitable to address inhibitory control. The study validates assumed functional neuroanatomical target regions of an established neurofeedback protocol on a neurophysiological level.

Two distinct neural mechanisms underlying indirect reciprocity.

Science.gov (United States)

Watanabe, Takamitsu; Takezawa, Masanori; Nakawake, Yo; Kunimatsu, Akira; Yamasue, Hidenori; Nakamura, Mitsuhiro; Miyashita, Yasushi; Masuda, Naoki

2014-03-18

Cooperation is a hallmark of human society. Humans often cooperate with strangers even if they will not meet each other again. This so-called indirect reciprocity enables large-scale cooperation among nonkin and can occur based on a reputation mechanism or as a succession of pay-it-forward behavior. Here, we provide the functional and anatomical neural evidence for two distinct mechanisms governing the two types of indirect reciprocity. Cooperation occurring as reputation-based reciprocity specifically recruited the precuneus, a region associated with self-centered cognition. During such cooperative behavior, the precuneus was functionally connected with the caudate, a region linking rewards to behavior. Furthermore, the precuneus of a cooperative subject had a strong resting-state functional connectivity (rsFC) with the caudate and a large gray matter volume. In contrast, pay-it-forward reciprocity recruited the anterior insula (AI), a brain region associated with affective empathy. The AI was functionally connected with the caudate during cooperation occurring as pay-it-forward reciprocity, and its gray matter volume and rsFC with the caudate predicted the tendency of such cooperation. The revealed difference is consistent with the existing results of evolutionary game theory: although reputation-based indirect reciprocity robustly evolves as a self-interested behavior in theory, pay-it-forward indirect reciprocity does not on its own. The present study provides neural mechanisms underlying indirect reciprocity and suggests that pay-it-forward reciprocity may not occur as myopic profit maximization but elicit emotional rewards.

Trained innate immunity as underlying mechanism for the long-term, nonspecific effects of vaccines

DEFF Research Database (Denmark)

Blok, Bastiaan A; Arts, Rob J W; van Crevel, Reinout

2015-01-01

An increasing body of evidence shows that the innate immune system has adaptive characteristics that involve a heterologous memory of past insults. Both experimental models and proof-of-principle clinical trials show that innate immune cells, such as monocytes, macrophages, and NK cells, can...... provide protection against certain infections in vaccination models independently of lymphocytes. This process is regulated through epigenetic reprogramming of innate immune cells and has been termed "trained immunity." It has been hypothesized that induction of trained immunity is responsible...... for the protective, nonspecific effects induced by vaccines, such as BCG, measles vaccination, and other whole-microorganism vaccines. In this review, we will present the mechanisms of trained immunity responsible for the long-lasting effects of vaccines on the innate immune system....

Alteration mechanisms of UOX spent fuel under water

International Nuclear Information System (INIS)

Muzeau, B.

2008-06-01

The mechanisms of spent fuel alteration in aqueous media need to be understood on the assumption of a direct disposal of the assemblies in a geological formation or for long duration storage in pool. This work is a contribution to the study of the effects of the alpha and/or beta/gamma radiolysis of water on the oxidation and the dissolution of the UO 2 matrix of UOX spent fuel. The effects of the alpha radiolysis, predominant in geological disposal conditions, were quantified by using samples of UO 2 doped with plutonium. The leaching experiments highlighted two types of control for the matrix alteration according to the alpha activity. The first is based on the radiolytic oxidation of the surface and leads to a continuous release of uranium in solution whereas the second is based on a control by the solubility of uranium. An activity threshold, between 18 MBq.g -1 and 33 MBq.g -1 , was defined in a carbonated water. The value of this threshold is dependent on the experimental conditions and the presence or not of electro-active species such as hydrogen in the system. The effects of the alpha/beta/gamma radiolysis in relation with the storage conditions were also quantified. The experimental data obtained on spent fuel indicate that the alteration rate of the matrix based on the behaviour of tracer elements (caesium and strontium) reached a maximum value of some mg.m -2 .d -1 , even under very oxidizing conditions. The solubility of uranium and the nature of the secondary phases depend however on the extent of the oxidizing conditions. (author)

Maize water status and physiological traits as affected by root endophytic fungus Piriformospora indica under combined drought and mechanical stresses.

Science.gov (United States)

Hosseini, Fatemeh; Mosaddeghi, Mohammad Reza; Dexter, Anthony Roger; Sepehri, Mozhgan

2018-05-01

Under combined drought and mechanical stresses, mechanical stress primarily controlled physiological responses of maize. Piriformospora indica mitigated the adverse effects of stresses, and inoculated maize experienced less oxidative damage and had better adaptation to stressful conditions. The objective of this study was to investigate the effect of maize root colonization by an endophytic fungus P. indica on plant water status, physiological traits and root morphology under combined drought and mechanical stresses. Seedlings of inoculated and non-inoculated maize (Zea mays L., cv. single cross 704) were cultivated in growth chambers filled with moistened siliceous sand at a matric suction of 20 hPa. Drought stress was induced using PEG 6000 solution with osmotic potentials of 0, - 0.3 and - 0.5 MPa. Mechanical stress (i.e., penetration resistances of 1.05, 4.23 and 6.34 MPa) was exerted by placing weights on the surface of the sand medium. After 30 days, leaf water potential (LWP) and relative water content (RWC), root and shoot fresh weights, root volume (RV) and diameter (RD), leaf proline content, leaf area (LA) and catalase (CAT) and ascorbate peroxidase (APX) activities were measured. The results show that exposure to individual drought and mechanical stresses led to higher RD and proline content and lower plant biomass, RV and LA. Moreover, increasing drought and mechanical stress severity increased APX activity by about 1.9- and 3.1-fold compared with the control. When plants were exposed to combined stresses, mechanical stress played the dominant role in controlling plant responses. P. indica-inoculated plants are better adapted to individual and combined stresses. The inoculated plants had greater RV, LA, RWC, LWP and proline content under stressful conditions. In comparison with non-inoculated plants, inoculated plants showed lower CAT and APX activities which means that they experienced less oxidative stress induced by stressful conditions.

Mechanisms underlying KCNQ1channel cell volume sensitivity

DEFF Research Database (Denmark)

Hammami, Sofia

Cells are constantly exposed to changes in cell volume during cell metabolism, nutrient uptake, cell proliferation, cell migration and salt and water transport. In order to cope with these perturbations, potassium channels in line with chloride channels have been shown to be likely contributors...... to the process of cell volume adjustments. A great diversity of potassium channels being members of either the 6TM, 4 TM or 2 TM K+ channel gene family have been shown to be strictly regulated by small, fast changes in cell volume. However, the precise mechanism underlying the K+ channel sensitivity to cell...... volume alterations is not yet fully understood. The KCNQ1 channel belonging to the voltage gated KCNQ family is considered a precise sensor of volume changes. The goal of this thesis was to elucidate the mechanism that induces cell volume sensitivity. Until now, a number of investigators have implicitly...

Crack formation and crack propagation under multiaxial mechanical and thermal stresses. Proceedings

International Nuclear Information System (INIS)

1993-01-01

The 25th meeting of the DV Fracture Group was held on 16/17 February 1993 at Karlsruhe Technical University. The main topic, ''Crack formation and crack propagation under multiaxial mechanical and thermal stresses'', was discussed by five invited papers (by K.J. Miller, D. Loehe, H.A. Richard, W. Brocks, A. Brueckner-Foit) and 23 short papers. The other 21 papers were devoted to various domains of fracture mechanics, with emphasis on elastoplastic fracture mechanics. (orig./MM) [de

A mechanical deformation model of metallic fuel pin under steady state conditions

International Nuclear Information System (INIS)

Lee, D. W.; Lee, B. W.; Kim, Y. I.; Han, D. H.

2004-01-01

As a mechanical deformation model of the MACSIS code predicts the cladding deformation due to the simple thin shell theory, it is impossible to predict the FCMI(Fuel-Cladding Mechanical Interaction). Therefore, a mechanical deformation model used the generalized plane strain is developed. The DEFORM is a mechanical deformation routine which is used to analyze the stresses and strains in the fuel and cladding of a metallic fuel pin of LMRs. The accuracy of the program is demonstrated by comparison of the DEFORM predictions with the result of another code calculations or experimental results in literature. The stress/strain distributions of elastic part under free thermal expansion condition are completely matched with the results of ANSYS code. The swelling and creep solutions are reasonably well agreed with the simulations of ALFUS and LIFE-M codes, respectively. The predicted cladding strains are under estimated than experimental data at the range of high burnup. Therefore, it is recommended that the fine tuning of the DEFORM based on various range of experimental data

Is there a common mechanism underlying genomic instability, bystander effects and other nontargeted effects of exposure to ionizing radiation?

Science.gov (United States)

Morgan, William F.

2003-01-01

A number of nontargeted and delayed effects associated with radiation exposure have now been described. These include radiation-induced genomic instability, death-inducing and bystander effects, clastogenic factors and transgenerational effects. It is unlikely that these nontargeted effects are directly induced by cellular irradiation. Instead, it is proposed that some as yet to be identified secreted factor can be produced by irradiated cells that can stimulate effects in nonirradiated cells (death-inducing and bystander effects, clastogenic factors) and perpetuate genomic instability in the clonally expanded progeny of an irradiated cell. The proposed factor must be soluble and capable of being transported between cells by cell-to-cell gap junction communication channels. Furthermore, it must have the potential to stimulate cellular cytokines and/or reactive oxygen species. While it is difficult to imagine a role for such a secreted factor in contributing to transgenerational effects, the other nontargeted effects of radiation may all share a common mechanism.

Research on the mechanical characteristic of the bentonite mixture material under the groundwater environment of Horonobe. 2

International Nuclear Information System (INIS)

Takaji, Kazuhiko; Shigeno, Yoshimasa; Simogouchi, Takafumi

2005-02-01

In the Horonobe underground research project, various in-situ experiments are conducted in order to confirm the applicability of the Engineered Barrier System (EBS) design techniques shown in H12 report, to understand the long-term effects of EBS, and to improve the reliability of the prediction method. Moreover, since it is assumed that the circumference of Horonobe underground research laboratory is the saline water environment, to understand the mechanical behavior of the bentonite mixture material under the saline water environment is important when influenced in design of in-situ experiments. In this study, unconfined compression tests, consolidated-undrained triaxial compression tests and long-term consolidation tests of the bentonite mixture material were performed using groundwater that is extracted near the Horonobe underground research laboratory, and simulation analyses of EBS over a period of time using the results of laboratory experiments etc. were carried out. Consequently, although compressive strength and the elastic modulus under the saline water environment declined compared with that the fresh water, neither shear deformation behavior under triaxial stress condition nor volume deformation behavior by consolidation test almost had a difference, and it was suggested that there were few possibilities that the saline water had serious influence mechanically also about long-term mechanical behavior. (author)

Stock price dynamics and option valuations under volatility feedback effect

Science.gov (United States)

Kanniainen, Juho; Piché, Robert

2013-02-01

According to the volatility feedback effect, an unexpected increase in squared volatility leads to an immediate decline in the price-dividend ratio. In this paper, we consider the properties of stock price dynamics and option valuations under the volatility feedback effect by modeling the joint dynamics of stock price, dividends, and volatility in continuous time. Most importantly, our model predicts the negative effect of an increase in squared return volatility on the value of deep-in-the-money call options and, furthermore, attempts to explain the volatility puzzle. We theoretically demonstrate a mechanism by which the market price of diffusion return risk, or an equity risk-premium, affects option prices and empirically illustrate how to identify that mechanism using forward-looking information on option contracts. Our theoretical and empirical results support the relevance of the volatility feedback effect. Overall, the results indicate that the prevailing practice of ignoring the time-varying dividend yield in option pricing can lead to oversimplification of the stock market dynamics.

Energy Evolution Mechanism and Confining Pressure Effect of Granite under Triaxial Loading-Unloading Cycles

Science.gov (United States)

Wang, Hao; Miao, Sheng-jun

2018-05-01

Rock mass undergoes some deformational failure under the action of external loads, a process known to be associated with energy dissipation and release. A triaxial loading-unloading cycle test was conducted on granite in order to investigate the energy evolution pattern of rock mass under the action of external loads. The study results demonstrated: (1) The stress peaks increased by 50% and 22% respectively and the pre-peak weakening became more apparent in the ascending process of the confining pressure from 10MPa to 30MPa; the area enclosed by the hysteresis loop corresponding to 30MPa diminished by nearly 60% than that corresponding to 10MPa, indicating a higher confining pressure prohibits rock mass from plastic deformation and shifts strain toward elastic deformation. (2) In the vicinity of the strength limit, the slope of dissipation energy increased to 1.6 from the original 0.7 and the dissipation energy grew at an accelerating rate, demonstrating stronger propagation and convergence of internal cracks. (3) At a pressure of 70% of the stress peak, the elastic energy of the granite accounted for 88% of its peak value, suggesting the rock mechanical energy from the outside mostly changes into the elastic energy inside the rock, with little energy loss.(4) Prior to test specimen failure, the axial bearing capacity dropped with a decreasing confining pressure in an essentially linear way, and the existence of confirming pressure played a role in stabilizing the axial bearing capacity.

Stress State Analysis and Failure Mechanisms of Masonry Columns Reinforced with FRP under Concentric Compressive Load

OpenAIRE

Jiří Witzany; Radek Zigler

2016-01-01

The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cra...

Mechanical behavior and coupling between mechanical and oxidation in alloy 718: effect of solide solution elements

International Nuclear Information System (INIS)

Max, Bertrand

2014-01-01

Alloy 718 is the superalloy the most widely used in industry due to its excellent mechanical properties, as well as oxidation and corrosion resistance in wide range of temperatures and solicitation modes. Nevertheless, it is a well-known fact that this alloy is sensitive to stress corrosion cracking and oxidation assisted cracking under loading in the range of temperatures met in service. Mechanisms explaining this phenomenon are not well understood: nevertheless, it is well established that a relation exists between a change in fracture mode and the apparition of plastic instabilities phenomenon. During this study, the instability phenomenon, Portevin-Le Chatelier effect, in alloy 718 was studied by tensile tests in wide ranges of temperatures and strain rates. Different domains of plastic instabilities have been evidenced. Their characteristics suggest the existence of interactions between dislocations and different types of solute elements: interstitials for lower temperatures and substitutionals for higher testing temperatures. Mechanical spectroscopy tests have been performed on alloy 718 and various alloys which composition is comparable to that of alloy 718. These tests prove the mobility of molybdenum atoms in the alloy in the studied temperature range. Specific tests have been performed to study interaction phenomenon between plasticity and oxidation. These results highlight the strong effect of plastic strain rate on both mechanical behavior and intergranular cracking in alloy 718. The subsequent discussion leads to propose hypothesis on coupling effects between deformation mechanisms and oxidation assisted embrittlement in the observed cracking processes. (author)

Study on cavitation effect of mechanical seals with laser-textured porous surface

Science.gov (United States)

Liu, T.; Chen, H. l.; Liu, Y. H.; Wang, Q.; Liu, Z. B.; Hou, D. H.

2012-11-01

Study on the mechanisms underlying generation of hydrodynamic pressure effect associated with laser-textured porous surface on mechanical seal, is the key to seal and lubricant properties. The theory model of mechanical seals with laser-textured porous surface (LES-MS) based on cavitation model was established. The LST-MS was calculated and analyzed by using Fluent software with full cavitation model and non-cavitation model and film thickness was predicted by the dynamic mesh technique. The results indicate that the effect of hydrodynamic pressure and cavitation are the important reasons to generate liquid film opening force on LST-MS; Cavitation effect can enhance hydrodynamic pressure effect of LST-MS; The thickness of liquid film could be well predicted with the method of dynamic mesh technique on Fluent and it becomes larger as the increasing of shaft speed and the decreasing of pressure.

Study on cavitation effect of mechanical seals with laser-textured porous surface

International Nuclear Information System (INIS)

Liu, T; Chen, H l; Liu, Y H; Wang, Q; Liu, Z B; Hou, D H

2012-01-01

Study on the mechanisms underlying generation of hydrodynamic pressure effect associated with laser-textured porous surface on mechanical seal, is the key to seal and lubricant properties. The theory model of mechanical seals with laser-textured porous surface (LES-MS) based on cavitation model was established. The LST-MS was calculated and analyzed by using Fluent software with full cavitation model and non-cavitation model and film thickness was predicted by the dynamic mesh technique. The results indicate that the effect of hydrodynamic pressure and cavitation are the important reasons to generate liquid film opening force on LST-MS; Cavitation effect can enhance hydrodynamic pressure effect of LST-MS; The thickness of liquid film could be well predicted with the method of dynamic mesh technique on Fluent and it becomes larger as the increasing of shaft speed and the decreasing of pressure.

Mechanical response of cross-ply Si3N4/BN fibrous monoliths under uniaxial and biaxial loading

International Nuclear Information System (INIS)

Singh, D.; Cruse, T. A.; Hermanson, D. J.; Goretta, K. C.; Zok, F. W.; McNulty, J. C.

2000-01-01

Mechanical properties of hot-pressed Si 3 N 4 /BN fibrous monoliths (FMs) were evaluated under ambient conditions in four-point and biaxial flexure modes. Effects of cell orientation, 0degree/90degree and ±45degree, on elastic modulus and fracture strength of the FMs were investigated. Fracture surfaces were examined by scanning electron microscopy

Mechanisms underlying the anti-inflammatory effects of Clinacanthus nutans Lindau extracts: inhibition of cytokine production and Toll-like receptor-4 activation

Directory of Open Access Journals (Sweden)

Chun Wai eMai

2016-02-01

Full Text Available Clinacanthus nutans has had a long history of use in folk medicine in Malaysia and Southeast Asia; mostly in the relief of inflammatory conditions. In this study, we investigated the effects of different extracts of C. nutans upon lipopolysaccharide (LPS induced inflammation in order to identify its mechanism of action. Extracts of leaves and stem bark of C. nutans were prepared using polar and non-polar solvents to produce four extracts, namely polar leaf extract (LP, non-polar leaf extract (LN, polar stem extract (SP and non-polar stem extracts (SN. The extracts were standardized by determining its total phenolic and total flavonoid contents. Its anti-inflammatory effects were assessed on LPS induced nitrite release in RAW264.7 macrophages and Toll-like receptor (TLR-4 activation in TLR-4 transfected human embryonic kidney cells (HEK-BlueTM-hTLR4 cells. The levels of inflammatory cytokines (TNF-α, IFN-γ, IL-1β, IL-6, IL-12p40 and IL-17 in treated RAW264.7 macrophages were quantified to verify its anti-inflammatory effects. Western blotting was used to investigate the effect of the most potent extract (LP on TLR-4 related inflammatory proteins (p65, p38, ERK, JNK, IRF3 in RAW264.7 macrophages. All four extracts produced a significant, concentration-dependent reduction in LPS-stimulated nitric oxide, LPS-induced TLR-4 activation in HEK-BlueTM-hTLR4 cells and LPS-stimulated cytokines production in RAW264.7 macrophages. The most potent extract, LP, also inhibited all LPS-induced TLR-4 inflammatory proteins. These results provide a basis for understanding the mechanisms underlying the previously demonstrated anti-inflammatory activity of C. nutans extracts.

Low-invasive reconstruction of spine discs under thermo-mechanical effect of fiber laser

Science.gov (United States)

Sobol, Emil; Baskov, Andrey; Borshchenko, Igor; Shekhter, Anatoly

2018-02-01

The paper considers physical processes and mechanisms of laser reparation of spine cartilage, presents results of investigations aimed to optimize laser settings and to develop feedback control system for laser reconstruction of spine discs. Possible mechanisms of laser-induced regeneration include: (1) Space and temporary modulated laser beam induces non-homogeneous and pulse repetitive thermal expansion and stress in the irradiated zone of cartilage. Mechanical effect due to controllable thermal expansion of the tissue and micro and nano gas bubbles formation in the course of the moderate (up to 50 °C) heating of the NP activate biological cells (chondrocytes) and promote cartilage regeneration. (2) Non-destructive laser radiation leads to the formation of nano and micro-pores in cartilage matrix in the in the immediate vicinity of chondrocytes. That promotes water permeability and increases the feeding of biological cells. Results provide the scientific and engineering basis for the novel low-invasive laser procedures to be used in neurosurgery and orthopedics for the treatment cartilages of spine. The technology and equipment for laser reconstruction of spine discs have been tested first on animals, and then in a clinical trial. Since 2001 the laser reconstruction of intervertebral discs have been performed (i) for more than 3,200 patients with chronic symptoms of low back or neck pain who failed to improve with non-operative care; and (ii) for 1100 patients underwent hernia removal surgery. Substantial relief of back pain was obtained in 92.5% of patients treated who returned to their daily activities. LRD allowed also to decrease secondary surgeries more than three times. Optical fiber technique based on light scattering measurements have been used to promote safety and efficacy of the laser procedures.

A novel role of dendritic gap junction and mechanisms underlying its interaction with thalamocortical conductance in fast spiking inhibitory neurons

Directory of Open Access Journals (Sweden)

Sun Qian-Quan

2009-10-01

Full Text Available Abstract Background Little is known about the roles of dendritic gap junctions (GJs of inhibitory interneurons in modulating temporal properties of sensory induced responses in sensory cortices. Electrophysiological dual patch-clamp recording and computational simulation methods were used in combination to examine a novel role of GJs in sensory mediated feed-forward inhibitory responses in barrel cortex layer IV and its underlying mechanisms. Results Under physiological conditions, excitatory post-junctional potentials (EPJPs interact with thalamocortical (TC inputs within an unprecedented few milliseconds (i.e. over 200 Hz to enhance the firing probability and synchrony of coupled fast-spiking (FS cells. Dendritic GJ coupling allows fourfold increase in synchrony and a significant enhancement in spike transmission efficacy in excitatory spiny stellate cells. The model revealed the following novel mechanisms: 1 rapid capacitive current (Icap underlies the activation of voltage-gated sodium channels; 2 there was less than 2 milliseconds in which the Icap underlying TC input and EPJP was coupled effectively; 3 cells with dendritic GJs had larger input conductance and smaller membrane response to weaker inputs; 4 synchrony in inhibitory networks by GJ coupling leads to reduced sporadic lateral inhibition and increased TC transmission efficacy. Conclusion Dendritic GJs of neocortical inhibitory networks can have very powerful effects in modulating the strength and the temporal properties of sensory induced feed-forward inhibitory and excitatory responses at a very high frequency band (>200 Hz. Rapid capacitive currents are identified as main mechanisms underlying interaction between two transient synaptic conductances.

Underlying mechanism of antimicrobial activity of chitosan microparticles and implications for the treatment of infectious diseases.

Directory of Open Access Journals (Sweden)

Soo Jin Jeon

Full Text Available The emergence of antibiotic resistant microorganisms is a great public health concern and has triggered an urgent need to develop alternative antibiotics. Chitosan microparticles (CM, derived from chitosan, have been shown to reduce E. coli O157:H7 shedding in a cattle model, indicating potential use as an alternative antimicrobial agent. However, the underlying mechanism of CM on reducing the shedding of this pathogen remains unclear. To understand the mode of action, we studied molecular mechanisms of antimicrobial activity of CM using in vitro and in vivo methods. We report that CM are an effective bactericidal agent with capability to disrupt cell membranes. Binding assays and genetic studies with an ompA mutant strain demonstrated that outer membrane protein OmpA of E. coli O157:H7 is critical for CM binding, and this binding activity is coupled with a bactericidal effect of CM. This activity was also demonstrated in an animal model using cows with uterine diseases. CM treatment effectively reduced shedding of intrauterine pathogenic E. coli (IUPEC in the uterus compared to antibiotic treatment. Since Shiga-toxins encoded in the genome of bacteriophage is often overexpressed during antibiotic treatment, antibiotic therapy is generally not recommended because of high risk of hemolytic uremic syndrome. However, CM treatment did not induce bacteriophage or Shiga-toxins in E. coli O157:H7; suggesting that CM can be a potential candidate to treat infections caused by this pathogen. This work establishes an underlying mechanism whereby CM exert antimicrobial activity in vitro and in vivo, providing significant insight for the treatment of diseases caused by a broad spectrum of pathogens including antibiotic resistant microorganisms.

Language Learning Enhanced by Massive Multiple Online Role-Playing Games (MMORPGs) and the Underlying Behavioral and Neural Mechanisms

OpenAIRE

Zhang, Yongjun; Song, Hongwen; Liu, Xiaoming; Tang, Dinghong; Chen, Yue-e; Zhang, Xiaochu

2017-01-01

Massive Multiple Online Role-Playing Games (MMORPGs) have increased in popularity among children, juveniles, and adults since MMORPGs’ appearance in this digital age. MMORPGs can be applied to enhancing language learning, which is drawing researchers’ attention from different fields and many studies have validated MMORPGs’ positive effect on language learning. However, there are few studies on the underlying behavioral or neural mechanism of such effect. This paper reviews the educational app...

The structural, mechanical, and electronic properties of LiAlB{sub 4} under pressure from first principles

Energy Technology Data Exchange (ETDEWEB)

Tayran, Ceren; Aydin, Sezgin [Department of Physics, Sciences Faculty, Gazi University, 06500, Ankara (Turkey)

2017-05-15

The structural, elastic, mechanical, and electronic properties of lithium aluminum tetraboride (LiAlB{sub 4}) under hydrostatic pressure have been investigated by using first-principles density functional theory calculations. The effects of pressure on the lattice parameters, volume, and bond lengths are studied. It is indicated from the calculated elastic constants that LiAlB{sub 4} compound is mechanically stable on 0-40 GPa pressure range. And, by means of these elastic constants set, some mechanical properties such as bulk, shear and Young's moduli, and then Poisson's ratio are determined as a function of pressure. Also, the ductile or brittle nature of LiAlB{sub 4} is examined. Additionally, using the first-principles data obtained from the geometry optimizations, the hardness of LiAlB{sub 4} is calculated, and its nature is investigated under pressure. Furthermore, in order to reveal the effects of pressure on the electronic and binding behavior of the compound, band structures, total and partial density of states, charge densities, Mulliken atomic charges, and bond overlap populations are searched as a function of pressure. To check the stability of the compound, phonon dispersion curves are calculated. And, the results are compared with the other convenient borides. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Numerical Analysis on Failure Modes and Mechanisms of Mine Pillars under Shear Loading

Directory of Open Access Journals (Sweden)

Tianhui Ma

2016-01-01

Full Text Available Severe damage occurs frequently in mine pillars subjected to shear stresses. The empirical design charts or formulas for mine pillars are not applicable to orebodies under shear. In this paper, the failure process of pillars under shear stresses was investigated by numerical simulations using the rock failure process analysis (RFPA 2D software. The numerical simulation results indicate that the strength of mine pillars and the corresponding failure mode vary with different width-to-height ratios and dip angles. With increasing dip angle, stress concentration first occurs at the intersection between the pillar and the roof, leading to formation of microcracks. Damage gradually develops from the surface to the core of the pillar. The damage process is tracked with acoustic emission monitoring. The study in this paper can provide an effective means for understanding the failure mechanism, planning, and design of mine pillars.

Plant-insect interactions under bacterial influence: ecological implications and underlying mechanisms.

Science.gov (United States)

Sugio, Akiko; Dubreuil, Géraldine; Giron, David; Simon, Jean-Christophe

2015-02-01

Plants and insects have been co-existing for more than 400 million years, leading to intimate and complex relationships. Throughout their own evolutionary history, plants and insects have also established intricate and very diverse relationships with microbial associates. Studies in recent years have revealed plant- or insect-associated microbes to be instrumental in plant-insect interactions, with important implications for plant defences and plant utilization by insects. Microbial communities associated with plants are rich in diversity, and their structure greatly differs between below- and above-ground levels. Microbial communities associated with insect herbivores generally present a lower diversity and can reside in different body parts of their hosts including bacteriocytes, haemolymph, gut, and salivary glands. Acquisition of microbial communities by vertical or horizontal transmission and possible genetic exchanges through lateral transfer could strongly impact on the host insect or plant fitness by conferring adaptations to new habitats. Recent developments in sequencing technologies and molecular tools have dramatically enhanced opportunities to characterize the microbial diversity associated with plants and insects and have unveiled some of the mechanisms by which symbionts modulate plant-insect interactions. Here, we focus on the diversity and ecological consequences of bacterial communities associated with plants and herbivorous insects. We also highlight the known mechanisms by which these microbes interfere with plant-insect interactions. Revealing such mechanisms in model systems under controlled environments but also in more natural ecological settings will help us to understand the evolution of complex multitrophic interactions in which plants, herbivorous insects, and micro-organisms are inserted. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions

Different neurophysiological mechanisms underlying word and rule extraction from speech.

Directory of Open Access Journals (Sweden)

Ruth De Diego Balaguer

Full Text Available The initial process of identifying words from spoken language and the detection of more subtle regularities underlying their structure are mandatory processes for language acquisition. Little is known about the cognitive mechanisms that allow us to extract these two types of information and their specific time-course of acquisition following initial contact with a new language. We report time-related electrophysiological changes that occurred while participants learned an artificial language. These changes strongly correlated with the discovery of the structural rules embedded in the words. These changes were clearly different from those related to word learning and occurred during the first minutes of exposition. There is a functional distinction in the nature of the electrophysiological signals during acquisition: an increase in negativity (N400 in the central electrodes is related to word-learning and development of a frontal positivity (P2 is related to rule-learning. In addition, the results of an online implicit and a post-learning test indicate that, once the rules of the language have been acquired, new words following the rule are processed as words of the language. By contrast, new words violating the rule induce syntax-related electrophysiological responses when inserted online in the stream (an early frontal negativity followed by a late posterior positivity and clear lexical effects when presented in isolation (N400 modulation. The present study provides direct evidence suggesting that the mechanisms to extract words and structural dependencies from continuous speech are functionally segregated. When these mechanisms are engaged, the electrophysiological marker associated with rule-learning appears very quickly, during the earliest phases of exposition to a new language.

Insights into the Mechanisms Underlying Boron Homeostasis in Plants

Directory of Open Access Journals (Sweden)

Akira Yoshinari

2017-11-01

Full Text Available Boron is an essential element for plants but is toxic in excess. Therefore, plants must adapt to both limiting and excess boron conditions for normal growth. Boron transport in plants is primarily based on three transport mechanisms across the plasma membrane: passive diffusion of boric acid, facilitated diffusion of boric acid via channels, and export of borate anion via transporters. Under boron -limiting conditions, boric acid channels and borate exporters function in the uptake and translocation of boron to support growth of various plant species. In Arabidopsis thaliana, NIP5;1 and BOR1 are located in the plasma membrane and polarized toward soil and stele, respectively, in various root cells, for efficient transport of boron from the soil to the stele. Importantly, sufficient levels of boron induce downregulation of NIP5;1 and BOR1 through mRNA degradation and proteolysis through endocytosis, respectively. In addition, borate exporters, such as Arabidopsis BOR4 and barley Bot1, function in boron exclusion from tissues and cells under conditions of excess boron. Thus, plants actively regulate intracellular localization and abundance of transport proteins to maintain boron homeostasis. In this review, the physiological roles and regulatory mechanisms of intracellular localization and abundance of boron transport proteins are discussed.

Mechanisms underlying mindfulness-based addiction treatment versus cognitive behavioral therapy and usual care for smoking cessation.

Science.gov (United States)

Spears, Claire Adams; Hedeker, Donald; Li, Liang; Wu, Cai; Anderson, Natalie K; Houchins, Sean C; Vinci, Christine; Hoover, Diana Stewart; Vidrine, Jennifer Irvin; Cinciripini, Paul M; Waters, Andrew J; Wetter, David W

2017-11-01

To examine cognitive and affective mechanisms underlying mindfulness-based addiction treatment (MBAT) versus cognitive-behavioral therapy (CBT) and usual care (UC) for smoking cessation. Participants in the parent study from which data were drawn (N = 412; 54.9% female; 48.2% African American, 41.5% non-Latino White, 5.4% Latino, 4.9% other; 57.6% annual income <$30,000) were randomized to MBAT (n = 154), CBT (n = 155), or UC (n = 103). From quit date through 26 weeks postquit, participants completed measures of emotions, craving, dependence, withdrawal, self-efficacy, and attentional bias. Biochemically confirmed 7-day smoking abstinence was assessed at 4 and 26 weeks postquit. Although the parent study did not find a significant treatment effect on abstinence, mixed-effects regression models were conducted to examine treatment effects on hypothesized mechanisms, and indirect effects of treatments on abstinence were tested. Participants receiving MBAT perceived greater volitional control over smoking and evidenced lower volatility of anger than participants in both other treatments. However, there were no other significant differences between MBAT and CBT. Compared with those receiving UC, MBAT participants reported lower anxiety, concentration difficulties, craving, and dependence, as well as higher self-efficacy for managing negative affect without smoking. Indirect effects of MBAT versus UC on abstinence occurred through each of these mechanisms. Whereas several differences emerged between MBAT and UC, MBAT and CBT had similar effects on several of the psychosocial mechanisms implicated in tobacco dependence. Results help to shed light on similarities and differences between mindfulness-based and other active smoking cessation treatments. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Effect of natural uranium on the UMR-106 osteoblastic cell line: impairment of the autophagic process as an underlying mechanism of uranium toxicity.

Science.gov (United States)

Pierrefite-Carle, Valérie; Santucci-Darmanin, Sabine; Breuil, Véronique; Gritsaenko, Tatiana; Vidaud, Claude; Creff, Gaelle; Solari, Pier Lorenzo; Pagnotta, Sophie; Al-Sahlanee, Rasha; Auwer, Christophe Den; Carle, Georges F

2017-04-01

Natural uranium (U), which is present in our environment, exerts a chemical toxicity, particularly in bone where it accumulates. Generally, U is found at oxidation state +VI in its oxocationic form [Formula: see text] in aqueous media. Although U(VI) has been reported to induce cell death in osteoblasts, the cells in charge of bone formation, the molecular mechanism for U(VI) effects in these cells remains poorly understood. The objective of our study was to explore U(VI) effect at doses ranging from 5 to 600 µM, on mineralization and autophagy induction in the UMR-106 model osteoblastic cell line and to determine U(VI) speciation after cellular uptake. Our results indicate that U(VI) affects mineralization function, even at subtoxic concentrations (metal exposure. We observed that U(VI) was able to rapidly activate autophagy but an inhibition of the autophagic flux was observed after 24 h. Thus, our results indicate that U(VI) perturbs osteoblastic functions by reducing mineralization capacity. Our study identifies for the first time U(VI) in the form of meta-autunite in mammalian cells. In addition, U(VI)-mediated inhibition of the autophagic flux may be one of the underlying mechanisms leading to the decreased mineralization and the toxicity observed in osteoblasts.

Frictional behaviour of polymer films under mechanical and electrostatic loads

International Nuclear Information System (INIS)

Ginés, R; Christen, R; Motavalli, M; Bergamini, A; Ermanni, P

2013-01-01

Different polymer foils, namely polyimide, FEP, PFA and PVDF were tested on a setup designed to measure the static coefficient of friction between them. The setup was designed according to the requirements of a damping device based on electrostatically tunable friction. The foils were tested under different mechanically applied forces and showed reproducible results for the static coefficient of friction. With the same setup the measurements were performed under an electric field as the source of the normal force. Up to a certain electric field the values were in good agreement. Beyond this field discrepancies were found. (paper)

Failure mechanism of monolayer graphene under hypervelocity impact of spherical projectile

Science.gov (United States)

Xia, Kang; Zhan, Haifei; Hu, De'An; Gu, Yuantong

2016-09-01

The excellent mechanical properties of graphene have enabled it as appealing candidate in the field of impact protection or protective shield. By considering a monolayer graphene membrane, in this work, we assessed its deformation mechanisms under hypervelocity impact (from 2 to 6 km/s), based on a serial of in silico studies. It is found that the cracks are formed preferentially in the zigzag directions which are consistent with that observed from tensile deformation. Specifically, the boundary condition is found to exert an obvious influence on the stress distribution and transmission during the impact process, which eventually influences the penetration energy and crack growth. For similar sample size, the circular shape graphene possesses the best impact resistance, followed by hexagonal graphene membrane. Moreover, it is found the failure shape of graphene membrane has a strong relationship with the initial kinetic energy of the projectile. The higher kinetic energy, the more number the cracks. This study provides a fundamental understanding of the deformation mechanisms of monolayer graphene under impact, which is crucial in order to facilitate their emerging future applications for impact protection, such as protective shield from orbital debris for spacecraft.

Behavior of duplex stainless steel casting defects under mechanical loadings

Energy Technology Data Exchange (ETDEWEB)

Jayet-Gendrot, S [Electricite de France, 77 - Moret-sur-Loing (France). Dept. of Materials Study; Gilles, P; Migne, C [Societe Franco-Americaine de Constructions Atomiques (FRAMATOME), 92 - Paris-La-Defense (France)

1997-04-01

Several components in the primary circuit of pressurized water reactors are made of cast duplex stainless steels. This material contains small casting defects, mainly shrinkage cavities, due to the manufacturing process. In safety analyses, the structural integrity of the components is studied. In order to assess the real severity of the casting defects under mechanical loadings, an experimental program was carried out. It consisted of testing, under both cyclic and monotonic solicitations, three-point bend specimens containing either a natural defect (in the form of a localized cluster of cavities) or a machined notch having the dimensions of the cluster`s envelope. The tests are analyzed in order to develop a method that takes into account the behavior of castings defects in a more realistic fashion than by an envelope crack. Various approaches are investigated, including the search of equivalent defects or of criteria based on continuum mechanics concepts, and compared with literature data. This study shows the conservatism of current safety analyses in modelling casting defects by envelope semi-elliptical cracks and contributes to the development of alternative approaches. (author) 18 refs.

Neural mechanisms underlying morphine withdrawal in addicted patients: a review

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Nima Babhadiashar

2015-06-01

Full Text Available Morphine is one of the most potent alkaloid in opium, which has substantial medical uses and needs and it is the first active principle purified from herbal source. Morphine has commonly been used for relief of moderate to severe pain as it acts directly on the central nervous system; nonetheless, its chronic abuse increases tolerance and physical dependence, which is commonly known as opiate addiction. Morphine withdrawal syndrome is physiological and behavioral symptoms that stem from prolonged exposure to morphine. A majority of brain regions are hypofunctional over prolonged abstinence and acute morphine withdrawal. Furthermore, several neural mechanisms are likely to contribute to morphine withdrawal. The present review summarizes the literature pertaining to neural mechanisms underlying morphine withdrawal. Despite the fact that morphine withdrawal is a complex process, it is suggested that neural mechanisms play key roles in morphine withdrawal.

A systems biology-based approach to uncovering the molecular mechanisms underlying the effects of dragon's blood tablet in colitis, involving the integration of chemical analysis, ADME prediction, and network pharmacology.

Directory of Open Access Journals (Sweden)

Haiyu Xu

Full Text Available Traditional Chinese medicine (TCM is one of the oldest East Asian medical systems. The present study adopted a systems biology-based approach to provide new insights relating to the active constituents and molecular mechanisms underlying the effects of dragon's blood (DB tablets for the treatment of colitis. This study integrated chemical analysis, prediction of absorption, distribution, metabolism, and excretion (ADME, and network pharmacology. Firstly, a rapid, reliable, and accurate ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry method was employed to identify 48 components of DB tablets. In silico prediction of the passive absorption of these compounds, based on Caco-2 cell permeability, and their P450 metabolism enabled the identification of 22 potentially absorbed components and 8 metabolites. Finally, networks were constructed to analyze interactions between these DB components/metabolites absorbed and their putative targets, and between the putative DB targets and known therapeutic targets for colitis. This study provided a great opportunity to deepen the understanding of the complex pharmacological mechanisms underlying the effects of DB in colitis treatment.

Effect of parenteral nutrition on the bone marrow recovery under exsperimental conditions of uneven irradiation

International Nuclear Information System (INIS)

Moroz, B.B.; Fedorovskij, L.L.; Deshevoj, Yu.B.

1986-01-01

Using white rats-males the effect of parenteral nutrition (PN) on blood formation (hemopoiesis) recovery under the conditions of total (control), subtotal (shielding of animal hind limb) with 7.5 Gy and X-ray partial irradiation of abdomen region with the 13.5 Gy has been studied. It has been found that bone marrow recovery increases either at subtotal or partial irradiation under the conditions of PN. Mechanisms of PN favourable effect are discussed. The advisability of using PN under uneven irradiations of organism is indicated

Computational study on the behaviors of granular materials under mechanical cycling

International Nuclear Information System (INIS)

Wang, Xiaoliang; Ye, Minyou; Chen, Hongli

2015-01-01

Considering that fusion pebble beds are probably subjected to the cyclic compression excitation in their future applications, we presented a computational study to report the effect of mechanical cycling on the behaviors of granular matter. The correctness of our numerical experiments was confirmed by a comparison with the effective medium theory. Under the cyclic loads, the fast granular compaction was observed to evolve in a stretched exponential law. Besides, the increasing stiffening in packing structure, especially the decreasing moduli pressure dependence due to granular consolidation, was also observed. For the force chains inside the pebble beds, both the internal force distribution and the spatial distribution of force chains would become increasingly uniform as the external force perturbation proceeded and therefore produced the stress relief on grains. In this case, the originally proposed 3-parameter Mueth function was found to fail to describe the internal force distribution. Thereby, its improved functional form with 4 parameters was proposed here and proved to better fit the data. These findings will provide more detailed information on the pebble beds for the relevant fusion design and analysis

Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

Energy Technology Data Exchange (ETDEWEB)

Leuning, N., E-mail: nora.leuning@iem.rwth-aachen.de [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Steentjes, S. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany); Schulte, M.; Bleck, W. [Steel Institute, RWTH Aachen University, D-52072 Aachen (Germany); Hameyer, K. [Institute of Electrical Machines, RWTH Aachen University, D-52062 Aachen (Germany)

2016-11-01

The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment. - Highlights: • A detailed look at magnetic anisotropy of FeSi NGO electrical steel. • Study of magnetic behavior under elastic as well as plastic tensile stresses. • Correlation of magnetic behavior with microscopic deformation mechanisms. • Discussion of detrimental and beneficial effects of external stresses. • Loss separation at different polarizations and frequencies under increasing stress.

Effect of elastic and plastic tensile mechanical loading on the magnetic properties of NGO electrical steel

International Nuclear Information System (INIS)

Leuning, N.; Steentjes, S.; Schulte, M.; Bleck, W.; Hameyer, K.

2016-01-01

The magnetic properties of non-grain-oriented (NGO) electrical steels are highly susceptible to mechanical stresses, i.e., residual, external or thermal ones. For rotating electrical machines, mechanical stresses are inevitable and originate from different sources, e.g., material processing, machine manufacturing and operating conditions. The efficiency and specific losses are largely altered by different mechanical stress states. In this paper the effect of tensile stresses and plastic deformations on the magnetic properties of a 2.9 wt% Si electrical steel are studied. Particular attention is paid to the effect of magnetic anisotropy, i.e., the influence of the direction of applied mechanical stress with respect to the rolling direction. Due to mechanical stress, the induced anisotropy has to be evaluated as it is related to the stress-dependent magnetostriction constant and the grain alignment. - Highlights: • A detailed look at magnetic anisotropy of FeSi NGO electrical steel. • Study of magnetic behavior under elastic as well as plastic tensile stresses. • Correlation of magnetic behavior with microscopic deformation mechanisms. • Discussion of detrimental and beneficial effects of external stresses. • Loss separation at different polarizations and frequencies under increasing stress.

Mechanisms underlying the anti-androgenic effects of diethylhexyl phthalate in fetal rat testis

International Nuclear Information System (INIS)

Borch, Julie; Metzdorff, Stine Broeng; Vinggaard, Anne Marie; Brokken, Leon; Dalgaard, Majken

2006-01-01

Diethylhexyl phthalate (DEHP) is widely used as a plasticizer in consumer products and is known to disturb the development of the male reproductive system in rats. The mechanisms by which DEHP exerts these effects are not yet fully elucidated, though some of the effects are related to reduced fetal testosterone production. The present study investigated the effects of four different doses of DEHP on fetal testicular histopathology, testosterone production and expression of proteins and genes involved in steroid synthesis in fetal testes. Pregnant Wistar rats were gavaged from GD 7 to 21 with vehicle, 10, 30, 100 or 300 mg/kg bw/day of DEHP. In male fetuses examined at GD 21, testicular testosterone production ex vivo and testicular testosterone levels were reduced significantly at the highest dose. Histopathological effects on gonocytes were observed at 100 and 300 mg/kg bw/day, whereas Leydig cell effects were mainly seen at 300 mg/kg bw/day. Quantitative RT-PCR revealed reduced testicular mRNA expression of the steroidogenesis related factors SR-B1, StAR, PBR and P450scc. Additionally, we observed reduced mRNA expression of the nuclear receptor SF-1, which regulates certain steps in steroid synthesis, and reduced expression of the cryptorchidism-associated Insl-3. Immunohistochemistry showed clear reductions of StAR, PBR, P450scc and PPARγ protein levels in fetal Leydig cells, indicating that DEHP affects regulation of certain steps in cholesterol transport and steroid synthesis. The suppression of testosterone levels observed in phthalate-exposed fetal rats was likely caused by the low expression of these receptors and enzymes involved in steroidogenesis. It is conceivable that the observed effects of DEHP on the expression of nuclear receptors SF-1 and PPARγ are involved in the downregulation of steroidogenic factors and testosterone levels and thereby underlie the disturbed development of the male reproductive system

An analytical model of the mechanical properties of bulk coal under confined stress

Science.gov (United States)

Wang, G.X.; Wang, Z.T.; Rudolph, V.; Massarotto, P.; Finley, R.J.

2007-01-01

This paper presents the development of an analytical model which can be used to relate the structural parameters of coal to its mechanical properties such as elastic modulus and Poisson's ratio under a confined stress condition. This model is developed primarily to support process modeling of coalbed methane (CBM) or CO2-enhanced CBM (ECBM) recovery from coal seam. It applied an innovative approach by which stresses acting on and strains occurring in coal are successively combined in rectangular coordinates, leading to the aggregated mechanical constants. These mechanical properties represent important information for improving CBM/ECBM simulations and incorporating within these considerations of directional permeability. The model, consisting of constitutive equations which implement a mechanically consistent stress-strains correlation, can be used as a generalized tool to study the mechanical and fluid behaviors of coal composites. An example using the model to predict the stress-strain correlation of coal under triaxial confined stress by accounting for the elastic and brittle (non-elastic) deformations is discussed. The result shows a good agreement between the prediction and the experimental measurement. ?? 2007 Elsevier Ltd. All rights reserved.

Fatigue response of a PZT multilayer actuator under high-field electric cycling with mechanical preload

Science.gov (United States)

Wang, Hong; Wereszczak, Andrew A.; Lin, Hua-Tay

2009-01-01

An electric fatigue test system was developed for evaluating the reliability of piezoelectric actuators with a mechanical loading capability. Fatigue responses of a lead zirconate titanate (PZT) multilayer actuator with a platethrough electrode configuration were studied under an electric field (1.7 times that of the coercive field of PZT material) and a concurrent mechanical preload (30.0 MPa). A total of 109 cycles was carried out. Variations in charge density and mechanical strain under the high electric field and constant mechanical loads were observed during the fatigue test. The dc and the first harmonic (at 10 Hz) dielectric and piezoelectric coefficients were subsequently characterized using fast Fourier transformation. Both the dielectric and the piezoelectric coefficients exhibited a monotonic decrease prior to 2.86×108 cycles under certain preloading conditions, and then fluctuated. Both the dielectric loss tangent and the piezoelectric loss tangent also fluctuated after a decrease. The results are interpreted and discussed with respect to domain wall activities, microdefects, and other anomalies.

Paramecium tetraurelia growth stimulation under low-level chronic irradiation: investigations on a possible mechanism

International Nuclear Information System (INIS)

Croute, F.; Soleilhavoup, J.P.; Vidal, S.; Dupouy, D.; Planel, H.

1982-01-01

Experiments were carried out to demonstrate the effects of low-level chronic irradiation on Paramecium tetraurelia proliferation. Biological effects were strongly dependent on the bacterial density of culture medium and more exactly on the catalase content of the medium. Significant growth stimulation was found under 60 Co chronic irradiation at a dose rate of 2 rad/year when paramecia were grown in a medium containing a high bacterial concentration (2.5 x 10 2 cells/m) or supplemented with catalase (300 U/ml). In a medium with a low bacterial density (1 x 10 6 cell/ml) or supplemented with a catalase activity inhibitor, growth simulation was preceded by a transitory inhibiting effect which could be correlated with extracellularly radioproduced H 2 O 2 . H 2 O 2 addition appeared to be able to simulate the biological effects of chronic irradiation. A possible mechanism is discussed.We proposed that the stimulating effects were the result of intracellular enzymatic scavenging of radioproduced H 2 O 2

Simulation of fatigue damage in ferroelectric polycrystals under mechanical/electrical loading

Science.gov (United States)

Kozinov, S.; Kuna, M.

2018-07-01

The reliability of smart-structures made of ferroelectric ceramics is essentially reduced by the formation of cracks under the action of external electrical and/or mechanical loading. In the current research a numerical model for low-cycle fatigue in ferroelectric mesostructures is proposed. In the finite element simulations a combination of two user element routines is utilized. The first one is used to model a micromechanical ferroelectric domain switching behavior inside the grains. The second one is used to simulate fatigue damage of grain boundaries by a cohesive zone model (EMCCZM) based on an electromechanical cyclic traction-separation law (TSL). For numerical simulations a scanning electron microscope image of the ceramic's grain structure was digitalized and meshed. The response of this mesostructure to cyclic electrical or mechanical loading is systematically analyzed. As a result of the simulations, the distribution of electric potential, field, displacement and polarization as well as mechanical stresses and deformations inside the grains are obtained. At the grain boundaries, the formation and evolution of damage are analyzed until final failure and induced degradation of electric permittivity. It is found that the proposed model correctly mimics polycrystalline behavior during poling processes and progressive damage under cyclic electromechanical loading. To the authors' knowledge, it is the first model and numerical analysis of ferroelectric polycrystals taking into account both domain reorientation and cohesive modeling of intergranular fracture. It can help to understand failure mechanisms taking place in ferroelectrics during fatigue processes.

The mechanical stability of retained austenite in low-alloyed TRIP steel under shear loading

Energy Technology Data Exchange (ETDEWEB)

Blondé, R., E-mail: r.j.p.blonde@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Jimenez-Melero, E., E-mail: enrique.jimenez-melero@manchester.ac.uk [Dalton Cumbrian Facility, The University of Manchester, Westlakes Science and Technology Park, Moor Row, Cumbria CA24 3HA (United Kingdom); Zhao, L., E-mail: lie.zhao@tudelft.nl [Materials Innovation Institute, Mekelweg 2, 2628 CD Delft (Netherlands); Department of Materials Science and Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Schell, N., E-mail: norbert.schell@hzg.de [Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Max Planck Strasse 1, 21502 Geesthacht (Germany); Brück, E., E-mail: e.h.bruck@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands); Zwaag, S. van der, E-mail: s.vanderzwaag@tudelft.nl [Novel Aerospace Materials Group, Faculty of Aerospace Engineering, Delft University of Technology, Kluyverweg 1, 2629 HS Delft (Netherlands); Dijk, N.H. van, E-mail: n.h.vandijk@tudelft.nl [Fundamental Aspects of Materials and Energy, Faculty of Applied Sciences, Delft University of Technology, Mekelweg 15, 2629 JB Delft (Netherlands)

2014-01-31

The microstructure evolution during shear loading of a low-alloyed TRIP steel with different amounts of the metastable austenite phase and its equivalent DP grade has been studied by in-situ high-energy X-ray diffraction. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing simultaneously the evolution of the austenite phase fraction and its carbon concentration, the load partitioning between the austenite and the ferritic matrix and the texture evolution of the constituent phases. Our results show that for shear deformation the TRIP effect extends over a significantly wider deformation range than for simple uniaxial loading. A clear increase in average carbon content during the mechanically-induced transformation indicates that austenite grains with a low carbon concentration are least stable during shear loading. The observed texture evolution indicates that under shear loading the orientation dependence of the austenite stability is relatively weak, while it has previously been found that under tensile load the {110}〈001〉 component transforms preferentially. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between the interstitial carbon concentration in the austenite, the grain orientation and the load partitioning.

A novel approach to mechanical foot stimulation during human locomotion under body weight support.

Science.gov (United States)

Gravano, S; Ivanenko, Y P; Maccioni, G; Macellari, V; Poppele, R E; Lacquaniti, F

2011-04-01

Input from the foot plays an essential part in perceiving support surfaces and determining kinematic events in human walking. To simulate adequate tactile pressure inputs under body weight support (BWS) conditions that represent an effective form of locomotion training, we here developed a new method of phasic mechanical foot stimulation using light-weight pneumatic insoles placed inside the shoes (under the heel and metatarsus). To test the system, we asked healthy participants to walk on a treadmill with different levels of BWS. The pressure under the stimulated areas of the feet and subjective sensations were higher at high levels of BWS and when applied to the ball and toes rather than heels. Foot stimulation did not disturb significantly the normal motor pattern, and in all participants we evoked a reliable step-synchronized triggering of stimuli for each leg separately. This approach has been performed in a general framework looking for "afferent templates" of human locomotion that could be used for functional sensory stimulation. The proposed technique can be used to imitate or partially restore surrogate contact forces under body weight support conditions. Copyright © 2010 Elsevier B.V. All rights reserved.

Effect of vacancy loops on swelling of metals under irradiation

International Nuclear Information System (INIS)

Golubov, S.I.

1981-01-01

Subsequent analysis of vacancy loops formation in metals under irradiation is carried out and effect of vacancy loops on vacancy porosity is studied. Expression for quasistationary function of vacancy loops distribution according to sizes taking into consideration two mechanisms of their initiation-cascade and fluctuational ones - is obtained. It is shown that rate of vacancy absorption and interstitials by vacancy loops in quasiequilibrium state is similar and depends only on summary length of loops, for its calculations the self-coordinated procedure is formulated. For the rate of metal swelling under irradiation obtained is the expression taking into consideration the presence of vacancy loops [ru

Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

Directory of Open Access Journals (Sweden)

Huamin Li

2015-01-01

Full Text Available To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

Reliability Issues and Solutions in Flexible Electronics Under Mechanical Fatigue

Science.gov (United States)

Yi, Seol-Min; Choi, In-Suk; Kim, Byoung-Joon; Joo, Young-Chang

2018-03-01

Flexible devices are of significant interest due to their potential expansion of the application of smart devices into various fields, such as energy harvesting, biological applications and consumer electronics. Due to the mechanically dynamic operations of flexible electronics, their mechanical reliability must be thoroughly investigated to understand their failure mechanisms and lifetimes. Reliability issue caused by bending fatigue, one of the typical operational limitations of flexible electronics, has been studied using various test methodologies; however, electromechanical evaluations which are essential to assess the reliability of electronic devices for flexible applications had not been investigated because the testing method was not established. By employing the in situ bending fatigue test, we has studied the failure mechanism for various conditions and parameters, such as bending strain, fatigue area, film thickness, and lateral dimensions. Moreover, various methods for improving the bending reliability have been developed based on the failure mechanism. Nanostructures such as holes, pores, wires and composites of nanoparticles and nanotubes have been suggested for better reliability. Flexible devices were also investigated to find the potential failures initiated by complex structures under bending fatigue strain. In this review, the recent advances in test methodology, mechanism studies, and practical applications are introduced. Additionally, perspectives including the future advance to stretchable electronics are discussed based on the current achievements in research.

High concentration of vitamin E decreases thermosensation and thermotaxis learning and the underlying mechanisms in the nematode Caenorhabditis elegans.

Science.gov (United States)

Li, Yiping; Li, Yinxia; Wu, Qiuli; Ye, Huayue; Sun, Lingmei; Ye, Boping; Wang, Dayong

2013-01-01

α-tocopherol is a powerful liposoluble antioxidant and the most abundant isoform of vitamin E in the body. Under normal physiological conditions, adverse effects of relatively high concentration of vitamin E on organisms and the underlying mechanisms are still largely unclear. In the present study, we used the nematode Caenorhabditis elegans as an in vivo assay system to investigate the possible adverse effects of high concentration of vitamin E on thermosensation and thermotaxis learning and the underlying mechanisms. Our data show that treatment with 100-200 µg/mL of vitamin E did not noticeably influence both thermosensation and thermotaxis learning; however, treatment with 400 µg/mL of vitamin E altered both thermosensation and thermotaxis learning. The observed decrease in thermotaxis learning in 400 µg/mL of vitamin E treated nematodes might be partially due to the moderate but significant deficits in thermosensation, but not due to deficits in locomotion behavior or perception to food and starvation. Treatment with 400 µg/mL of vitamin E did not noticeably influence the morphology of GABAergic neurons, but significantly decreased fluorescent intensities of the cell bodies in AFD sensory neurons and AIY interneurons, required for thermosensation and thermotaxis learning control. Treatment with 400 µg/mL of vitamin E affected presynaptic function of neurons, but had no remarkable effects on postsynaptic function. Moreover, promotion of synaptic transmission by activating PKC-1 effectively retrieved deficits in both thermosensation and thermotaxis learning induced by 400 µg/mL of vitamin E. Therefore, relatively high concentrations of vitamin E administration may cause adverse effects on thermosensation and thermotaxis learning by inducing damage on the development of specific neurons and presynaptic function under normal physiological conditions in C. elegans.

Thermal stability of nafion membranes under mechanical stress

Energy Technology Data Exchange (ETDEWEB)

Quintilii, M; Struis, R [Paul Scherrer Inst. (PSI), Villigen (Switzerland)

1997-06-01

The feasibility of adequately modified fluoro-ionomer membranes (NAFION{sup R}) is demonstrated for the selective separation of methanol synthesis products from the raw reactor gas at temperatures around 200{sup o}C. For an economically relevant application of this concept on a technical scale the Nafion membranes should be thin ({approx_equal}10 {mu}m) and thermally stable over a long period of time (1-2 years). In cooperation with industry (Methanol Casale SA, Lugano (CH)), we test the thermal stability of Nafion hollow fibers and supported Nafion thin sheet membranes at temperatures between 160 and 200{sup o}C under mechanical stress by applying a gas pressure difference over the membrane surface ({Delta}P{<=} 40 bar). Tests with the hollow fibers revealed that Nafion has visco-elastic properties. Tests with 50 {mu}m thin Nafion sheets supported by a porous metal carrier at 200{sup o}C and {Delta}P=39 bar showed no mechanical defects over a period of 92 days. (author) 5 figs., 4 refs.

PHYSIOLOGICAL QUALITY OF SOYBEAN SEEDS UNDER MECHANICAL INJURIES CAUSED BY COMBINES

Directory of Open Access Journals (Sweden)

FÁBIO PALCZEWSKI PACHECO

2015-01-01

Full Text Available The mechanical harvesting causes injuries on seeds and may affect their quality. Different threshing mechanisms and their adjustments may also affect the intensity of impacts that machines cause on seeds. So, this study aimed at diagnosing and evaluating the effect of two combines: the first one with a threshing system of axial flow and the other one with a threshing system of tangential flow, under adjustments of concave opening (10 mm, 30 mm and 10 mm for a combine with axial flow and 3.0 mm, 15 mm and 3.0 mm for a combine with tangential flow and three cylinder rotations on the quality of soybean seeds harvested at two moisture contents. Soybean seeds of cultivar 'ND 4910' were harvested at 16.6% moisture (mid - morning and 13.7% moisture in the afternoon. The seeds quality was evaluated by germination tests, germination speed index (GSI, germination rate, moisture content, percentage of purity and vigor by tetrazolium test. Despite the combine, the results showed that the mechanical injury has most reduced seeds quality, at 16.6% moisture content, concave opening of 30 mm (axial and 10 mm (tangential and cylinder rotation of 1100 rpm (axial and 1000 (tangential, both with the highest rotations used. The combine with tangential flow had the highest degree of seeds purity. When seeds moisture content at harvest was close to 13.7%, there was the highest seed injury, while, at 16.6%, there was the highest number of crushed soybeans, regardless the combine adjustment.

Dynamic Response and Failure Mechanism of Brittle Rocks Under Combined Compression-Shear Loading Experiments

Science.gov (United States)

Xu, Yuan; Dai, Feng

2018-03-01

A novel method is developed for characterizing the mechanical response and failure mechanism of brittle rocks under dynamic compression-shear loading: an inclined cylinder specimen using a modified split Hopkinson pressure bar (SHPB) system. With the specimen axis inclining to the loading direction of SHPB, a shear component can be introduced into the specimen. Both static and dynamic experiments are conducted on sandstone specimens. Given carefully pulse shaping, the dynamic equilibrium of the inclined specimens can be satisfied, and thus the quasi-static data reduction is employed. The normal and shear stress-strain relationships of specimens are subsequently established. The progressive failure process of the specimen illustrated via high-speed photographs manifests a mixed failure mode accommodating both the shear-dominated failure and the localized tensile damage. The elastic and shear moduli exhibit certain loading-path dependence under quasi-static loading but loading-path insensitivity under high loading rates. Loading rate dependence is evidently demonstrated through the failure characteristics involving fragmentation, compression and shear strength and failure surfaces based on Drucker-Prager criterion. Our proposed method is convenient and reliable to study the dynamic response and failure mechanism of rocks under combined compression-shear loading.

[The mechanisms underlying the therapeutic effects of reflexotherapy and drinking mineral waters in the patients presenting with metabolic syndrome].

Science.gov (United States)

Zhernov, V A; Frolkov, V K; Zubarkina, M M

Both acupuncture and drinking mineral water can influence the metabolism of carbohydrates and lipids as well as their hormonal regulation, but the possibility of the application of these therapeutic factors for the correction of insulin resistance has not been studied in the patients presenting with metabolic syndrome. The objective of the present study was to evaluate the effects produced by the intake of drinking mineral water and acupuncture on the various parameters characterizing the patients suffering from metabolic syndrome in combination with altered insulin resistance. Ninety patients with this condition included in the study underwent the analysis of their the blood pressure, body mass index, blood glucose and lipid levels, insulin and cortisol secretion. We undertook the analysis of the effects of the single and repeated intakes of Essentuki No 17 mineral water included in the combined treatment of the patients with metabolic syndrome and revealed many common responses of the organism to its therapeutic action. Specifically, the stress-type reactions suggested the initiation of the adaptive processes in the system of hormonal regulation of carbohydrate and lipid metabolism. Simultaneously, the manifestations of insulin resistance became less pronounced indicating that both acupuncture and drinking mineral water suppressed the action of the main pathogenic mechanisms underlying the development of metabolic syndrome. Moreover, it was shown that acupuncture had a stronger hypotensive effect in the combination with the decrease of the overproduction of cortisol whereas the intake of the mineral water had a greater metabolic potential and contributed to the intensification of the basal secretion of glucocorticoids. Both reflexotherapy and drinking mineral water have a well apparent effect on the pathogenetic reactions of the metabolic syndrome and therefore can be used in addition to the standard therapy to activate the non-specific, phylogenetically

Mechanisms underlying the associations of maternal age with adverse perinatal outcomes

DEFF Research Database (Denmark)

Lawlor, Debbie A; Mortensen, Laust; Andersen, Anne-Marie Nybo

2011-01-01

The mechanisms underlying the association between maternal age (both young and older maternal age) and adverse perinatal outcomes are unclear. Methods We examined the association of maternal age at first birth with preterm birth (<37 weeks gestation) and small for gestational age (SGA) in a cohor...

Investigation of sheet steel St 37.2 under mechanical impact

International Nuclear Information System (INIS)

Berg, H.P.; Brennecke, P.; Koester, R.; Friehmelt, V.

1990-01-01

Special waste originating, e.g. from chemical industry and radioactive wastes are emplaced in disposal mines. Slinger stowing is an approved technique to fill up residual voids in emplacement rooms. If it should be applied, possible mechanical loads on the integrity of sheet steel containers have to be considered. By theoretical calculations and by experiments under variation of different parameters using test specimen and backfill material from the Konrad mine using the container type V as an example it has been shown that sheet steel St 37.2 with a wall thickness of 3 mm will withstand mechanical impact imposed by backfill particles having a speed of 24 m/s. (orig.) [de

Physiological mechanisms of the effect of weightlessness on the body

Science.gov (United States)

Kasyan, I. I.; Kopanev, V. I.

1975-01-01

Experimental data show that physiological reactions observed under weightlessness conditions are caused by: (1) The direct effect of weightlessness, as a consequence of decrease (""disappearance'') of the weight of body tissues and organs; and (2) the mediated effect of weightlessness, as a result of changes in the functional state of the central nervous system and the cooperative work of the analyzers. The human body adopts to weightless conditions under the prolonged effects of it. In this case, four periods can be distinguished: The first period, a transitional process lasting from 1 to 24 hours; second period, initial adaptation to conditions of weightlessness and readjustment of all functional systems of the body; the third period, adaptation to the unusual mechanical conditions of the external environment, lasting from 3 to 8 days and more; and the fourth period, the stage of possible imbalance of the functions and the systems of some astronauts, as a result of the prolonged effect of weightlessness.

Mechanical effects in a rarified plasma

International Nuclear Information System (INIS)

Dubinov, A. E.; Sadovoy, S. A.

2007-01-01

A study is made of various mechanical effects that arise in a rarified plasma and set macroscopic solid bodies into motion: the magnetomechanical effect, the mechanical surface effect, the attraction of macrobodies, the levitation of a body in a plasma, and the orientation of a levitating body. Attention is focused on the design and construction of relevant experiments and experimental tests, as well as on the interpretation of the phenomena observed. Possible applications of the mechanical effects in physics and engineering are discussed

Organic nitrates: update on mechanisms underlying vasodilation, tolerance and endothelial dysfunction.

Science.gov (United States)

Münzel, Thomas; Steven, Sebastian; Daiber, Andreas

2014-12-01

Given acutely, organic nitrates, such as nitroglycerin (GTN), isosorbide mono- and dinitrates (ISMN, ISDN), and pentaerythrityl tetranitrate (PETN), have potent vasodilator and anti-ischemic effects in patients with acute coronary syndromes, acute and chronic congestive heart failure and arterial hypertension. During long-term treatment, however, side effects such as nitrate tolerance and endothelial dysfunction occur, and therapeutic efficacy of these drugs rapidly vanishes. Recent experimental and clinical studies have revealed that organic nitrates per se are not just nitric oxide (NO) donors, but rather a quite heterogeneous group of drugs considerably differing for mechanisms underlying vasodilation and the development of endothelial dysfunction and tolerance. Based on this, we propose that the term nitrate tolerance should be avoided and more specifically the terms of GTN, ISMN and ISDN tolerance should be used. The present review summarizes preclinical and clinical data concerning organic nitrates. Here we also emphasize the consequences of chronic nitrate therapy on the supersensitivity of the vasculature to vasoconstriction and on the increased autocrine expression of endothelin. We believe that these so far rather neglected and underestimated side effects of chronic therapy with at least GTN and ISMN are clinically important. Copyright © 2014 Elsevier Inc. All rights reserved.

The short-term stress response - Mother nature's mechanism for enhancing protection and performance under conditions of threat, challenge, and opportunity.

Science.gov (United States)

Dhabhar, Firdaus S

2018-03-26

Our group has proposed that in contrast to chronic stress that can have harmful effects, the short-term (fight-or-flight) stress response (lasting for minutes to hours) is nature's fundamental survival mechanism that enhances protection and performance under conditions involving threat/challenge/opportunity. Short-term stress enhances innate/primary, adaptive/secondary, vaccine-induced, and anti-tumor immune responses, and post-surgical recovery. Mechanisms and mediators include stress hormones, dendritic cell, neutrophil, macrophage, and lymphocyte trafficking/function and local/systemic chemokine and cytokine production. Short-term stress may also enhance mental/cognitive and physical performance through effects on brain, musculo-skeletal, and cardiovascular function, reappraisal of threat/anxiety, and training-induced stress-optimization. Therefore, short-term stress psychology/physiology could be harnessed to enhance immuno-protection, as well as mental and physical performance. This review aims to provide a conceptual framework and targets for further investigation of mechanisms and conditions under which the protective/adaptive aspects of short-term stress/exercise can be optimized/harnessed, and for developing pharmacological/biobehavioral interventions to enhance health/healing, and mental/cognitive/physical performance. Copyright © 2018 Elsevier Inc. All rights reserved.

Fracture mechanics analyses of ceramic/veneer interface under mixed-mode loading.

Science.gov (United States)

Wang, Gaoqi; Zhang, Song; Bian, Cuirong; Kong, Hui

2014-11-01

Few studies have focused on the interface fracture performance of zirconia/veneer bilayered structure, which plays an important role in dental all-ceramic restorations. The purpose of this study was to evaluate the fracture mechanics performance of zirconia/veneer interface in a wide range of mode-mixities (at phase angles ranging from 0° to 90°), and to examine the effect of mechanical properties of the materials and the interface on the fracture initiation and crack path of an interfacial crack. A modified sandwich test configuration with an oblique interfacial crack was proposed and calibrated to choose the appropriate geometry dimensions by means of finite element analysis. The specimens with different interface inclination angles were tested to failure under three-point bending configuration. Interface fracture parameters were obtained with finite element analyses. Based on the interfacial fracture mechanics, three fracture criteria for crack kinking were used to predict crack initiation and propagation. In addition, the effects of residual stresses due to coefficient of thermal expansion mismatch between zirconia and veneer on the crack behavior were evaluated. The crack initiation and propagation were well predicted by the three fracture criteria. For specimens at phase angle of 0, the cracks propagated in the interface; whereas for all the other specimens the cracks kinked into the veneer. Compressive residual stresses in the veneer can improve the toughness of the interface structure. The results suggest that, in zirconia/veneer bilayered structure the veneer is weaker than the interface, which can be used to explain the clinical phenomenon that veneer chipping rate is larger than interface delamination rate. Consequently, a veneer material with larger fracture toughness is needed to decrease the failure rate of all-ceramic restorations. And the coefficient of thermal expansion mismatch of the substrates can be larger to produce larger compressive

Neural mechanism of electroacupuncture's hypotensive effects

Science.gov (United States)

Li, Peng; Longhurst, John C.

2010-01-01

EA at P 5–6 and S 36–37 using low current and low frequency may be able to reduce elevated blood pressure in a subset of patients (~70%) with mild to moderate hypertension. The effect is slow in onset but is long-lasting. Experimental studies have shown that EA inhibition of cardiovascular sympathetic neurons that have been activated through visceral reflex stimulation is through activation of neurons in the arcuate nucleus of the hypothalamus, vlPAG in the midbrain and NRP in the medulla, which, in turn, inhibit the activity of premotor sympathetic neurons in the rVLM. The arcuate also provides direct projections to the rVLM that contain endorphins. Glutamate, acetylcholine, opioids, GABA, nociceptin, serotonin and endocannabinoids all appear to participate in the EA hypotensive response although their importance varies between nuclei. Thus, a number of mechanisms underlying the long-lasting effect of EA on cardiovascular function have been identified but clearly further investigation is warranted. PMID:20444652

The Effect of Bedding Structure on Mechanical Property of Coal

Directory of Open Access Journals (Sweden)

Zetian Zhang

2014-01-01

Full Text Available The mechanical property of coal, influencing mining activity considerably, is significantly determined by the natural fracture distributed within coal mass. In order to study the effecting mechanism of bedding structure on mechanical property of coal, a series of uniaxial compression tests and mesoscopic tests have been conducted. The experimental results show that the distribution characteristic of calcite particles, which significantly influences the growth of cracks and the macroscopic mechanical properties of coal, is obviously affected by the bedding structure. Specifically, the uniaxial compression strength of coal sample is mainly controlled by bedding structure, and the average peak stress of specimens with axes perpendicular to the bedding planes is 20.00 MPa, which is 2.88 times the average amount of parallel ones. The test results also show a close relationship between the bedding structure and the whole deformation process under uniaxial loading.

Mechanical properties of the human spinal cord under the compressive loading.

Science.gov (United States)

Karimi, Alireza; Shojaei, Ahmad; Tehrani, Pedram

2017-12-01

The spinal cord as the most complex and critical part of the human body is responsible for the transmission of both motor and sensory impulses between the body and the brain. Due to its pivotal role any types of physical injury in that disrupts its function following by shortfalls, including the minor motor and sensory malfunctions as well as complicate quadriplegia and lifelong ventilator dependency. In order to shed light on the injuries to the spinal cord, the application of the computational models to simulate the trauma impact loading to that are deemed required. Nonetheless, it has not been fulfilled since there is a paucity of knowledge about the mechanical properties of the spinal cord, especially the cervical one, under the compressive loading on the grounds of the difficulty in obtaining this tissue from the human body. This study was aimed at experimentally measuring the mechanical properties of the human cervical spinal cord of 24 isolated fresh samples under the unconfined compressive loading at a relatively low strain rate. The stress-strain data revealed the elastic modulus and maximum/failure stress of 40.12±6.90 and 62.26±5.02kPa, respectively. Owing to the nonlinear response of the spinal cord, the Yeoh, Ogden, and Mooney-Rivlin hyperelastic material models have also been employed. The results may have implications not only for understanding the linear elastic and nonlinear hyperelastic mechanical properties of the cervical spinal cord under the compressive loading, but also for providing a raw data for investigating the injury as a result of the trauma thru the numerical simulations. Copyright © 2017 Elsevier B.V. All rights reserved.

Reliability-based optimization of maintenance scheduling of mechanical components under fatigue

Science.gov (United States)

Beaurepaire, P.; Valdebenito, M.A.; Schuëller, G.I.; Jensen, H.A.

2012-01-01

This study presents the optimization of the maintenance scheduling of mechanical components under fatigue loading. The cracks of damaged structures may be detected during non-destructive inspection and subsequently repaired. Fatigue crack initiation and growth show inherent variability, and as well the outcome of inspection activities. The problem is addressed under the framework of reliability based optimization. The initiation and propagation of fatigue cracks are efficiently modeled using cohesive zone elements. The applicability of the method is demonstrated by a numerical example, which involves a plate with two holes subject to alternating stress. PMID:23564979

A role for PERK in the mechanism underlying fluoride-induced bone turnover

International Nuclear Information System (INIS)

Sun, Fei; Li, Xining; Yang, Chen; Lv, Peng; Li, Guangsheng; Xu, Hui

2014-01-01

While it has been well-documented that excessive fluoride exposure caused the skeletal disease and osteoblasts played a critical role in the advanced skeletal fluorosis, the underlying mechanism that mediated these effects remain poorly understood. The present study was undertaken to examine the effect of fluoride on bone of rats and MC3T3-E1 cells in vitro. Herein we found pathological features of high bone turnover in fluoride-treated rats, which was supported by an increase of osteogenic and osteoclastogenic genes expression in different stages of fluoride exposure. The skeletal toxicity of fluoride was accompanied by activation of endoplasmic reticulum (ER) stress and subsequent unfolded protein response (UPR). A novel finding of this study was that expression of PKR-like endoplasmic reticulum kinase (PERK) was the same trend with receptor activator for nuclear factor-κ B ligand (RANKL), and NF-E2 p45-related factor 2 (Nrf2) was the same trend with Runt-related transcription factor 2 (Runx2) in bones of rats exposed to varied fluoride condition. Based on these data, we hypothesized that up-regulation of PERK probably played a role in mediating bone turnover induced by fluoride. Action of fluoride on MC3T3-E1 cells differentiation was demonstrated through analysis of alkaline phosphatase (ALP) activity and mineralized nodules formation. Meantime, an increase of binding immunoglobulin protein (BiP) expression indicated the active ER stress in cells exposed to various dose of fluoride. Blocking PERK expression using siRNA showed the obvious decrease of osteogenic and osteoclastogenic factors expression in MC3T3-E1 cells exposed to certain dose of fluoride that could positively stimulate osteoblastic viability. In conclusion these findings underscore the importance of PERK in modulating fluoride induced bone formation and bone resorption. Understanding the link between PERK and bone turnover could probe into the mechanism underlying different bone lesion of

Effect of mechanization level on manpower needs in forestry

Directory of Open Access Journals (Sweden)

Błuszkowska Urszula

2014-12-01

Full Text Available High work consumption in forest operations is above all the result of the character and task realization mode in works undertaken in forestry. Development of mechanization in forest management activities allows to considerably decrease manpower needs. In the present study, there were analyzed the possibilities of reduction of work consumption by improving the mechanization level of forest works. The method was developed to consider the following assessments: 1 variant W1 - basic option comprising factual work consumption values in works carried out on the area administered by the Regional Directorate of State Forests (RDLP; 2 W2 - showing the effect of 25% upgrade of works to a higher level of mechanization; 3 W3 - showing the effect of 50% upgrade of works to a higher level of mechanization; 4 W4 - comprising analogous calculations to those in variant W1 , but work consumption upgrading was 75%. Simulation calculations revealed considerable differences in needs for labor of different categories of forest workers. On the other hand, with increasing mechanization level, there increase the demands concerning worker qualifications, e.g. a harvester operator must be trained for about 2 years, and the training has to include both simulator exercises (first using software and next - harvester simulator and field work under supervision to gain sufficient experience. The introduction of higher levels of mechanization into forest operations, and hence considerable reduction of jobs for unqualified workers who are replaced by qualified employees, can help decreasing work consumption in forest operations.

Behavior of duplex stainless steel casting defects under mechanical loadings

International Nuclear Information System (INIS)

Jayet-Gendrot, S.; Gilles, P.

2000-01-01

Several components in the primary circuit of pressurized water reactors are made of cast duplex stainless steels. This material contains small casting defects, mainly shrinkage cavities, due to the manufacturing process. In safety analyses, the structural integrity of the components is studied under the most severe assumptions: presence of a large defect, accidental loadings and end-of-life material properties accounting for its thermal aging embrittlement at the service temperature. The casting defects are idealized as semi-circular surface cracks or notches that have envelope dimensions. In order to assess the real severity of the casting defects under mechanical loadings, an experimental program was carried out. It consisted of testing, under both cyclic and monotonic solicitations, three-point bend specimens containing either a natural defect (in the form of a localized cluster of cavities) or a machined notch having the dimensions of the cluster's envelope. The results show that shrinkage cavities are far less harmful than envelope notches thanks to the metal bridges between cavities. Under fatigue loadings, the generalized initiation of a cluster of cavities (defined when the cluster becomes a crack of the same global size) is reached for a number of cycles that is much higher than the one leading to the initiation of a notch. In the case of monotonic loadings, specimens with casting defects offer a very high resistance to ductile tearing. The tests are analyzed in order to develop a method that takes into account the behavior of casting defects in a more realistic fashion than by an envelope crack. Various approaches are investigated, including the search of equivalent defects or of criteria based on continuum mechanics concepts, and compared with literature data. This study shows the conservatism of current safety analyses in modeling casting defects by envelope semi-elliptical cracks and contributes to the development of alternative approaches. (orig.)

Contact force and mechanical loss of multistage cable under tension and bending

Science.gov (United States)

Ru, Yanyun; Yong, Huadong; Zhou, Youhe

2016-10-01

A theoretical model for calculating the stress and strain states of cabling structures with different loadings has been developed in this paper. We solve the problem for the first- and second-stage cable with tensile or bending strain. The contact and friction forces between the strands are presented by two-dimensional contact model. Several theoretical models have been proposed to verify the results when the triplet subjected to the tensile strain, including contact force, contact stresses, and mechanical loss. It is found that loadings will affect the friction force and the mechanical loss of the triplet. The results show that the contact force and mechanical loss are dependent on the twist pitch. A shorter twist pitch can lead to higher contact force, while the trend of mechanical loss with twist pitch is complicated. The mechanical loss may be reduced by adjusting the twist pitch reasonably. The present model provides a simple analysis method to investigate the mechanical behaviors in multistage-structures under different loads.

Crack growth threshold under hold time conditions in DA Inconel 718 – A transition in the crack growth mechanism

Directory of Open Access Journals (Sweden)

E. Fessler

2016-01-01

Full Text Available Aeroengine manufacturers have to demonstrate that critical components such as turbine disks, made of DA Inconel 718, meet the certification requirements in term of fatigue crack growth. In order to be more representative of the in service loading conditions, crack growth under hold time conditions is studied. Modelling crack growth under these conditions is challenging due to the combined effect of fatigue, creep and environment. Under these conditions, established models are often conservative but the degree of conservatism can be reduced by introducing the crack growth threshold in models. Here, the emphasis is laid on the characterization of crack growth rates in the low ΔK regime under hold time conditions and in particular, on the involved crack growth mechanism. Crack growth tests were carried out at high temperature (550 °C to 650 °C under hold time conditions (up to 1200 s in the low ΔK regime using a K-decreasing procedure. Scanning electron microscopy was used to identify the fracture mode involved in the low ΔK regime. EBSD analyses and BSE imaging were also carried out along the crack path for a more accurate identification of the fracture mode. A transition from intergranular to transgranular fracture was evidenced in the low ΔK regime and slip bands have also been observed at the tip of an arrested crack at low ΔK. Transgranular fracture and slip bands are usually observed under pure fatigue loading conditions. At low ΔK, hold time cycles are believed to act as equivalent pure fatigue cycles. This change in the crack growth mechanism under hold time conditions at low ΔK is discussed regarding results related to intergranular crack tip oxidation and its effect on the crack growth behaviour of Inconel 718 alloy. A concept based on an “effective oxygen partial pressure” at the crack tip is proposed to explain the transition from transgranular to intergranular fracture in the low ΔK regime.

Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions

Science.gov (United States)

2013-01-01

REPORT Friction Stir Weld Failure Mechanisms in Aluminum-Armor Structures Under Ballistic Impact Loading Conditions 14. ABSTRACT 16. SECURITY...properties and of the attendant ballistic-impact failure mechanisms in prototypical friction stir welding (FSW) joints found in armor structures made of high...mechanisms, friction stir welding M. Grujicic, B. Pandurangan, A. Arakere, C-F. Yen, B. A. Cheeseman Clemson University Office of Sponsored Programs 300

Mechanisms underlying prorenin actions on hypothalamic neurons implicated in cardiometabolic control

Directory of Open Access Journals (Sweden)

Soledad Pitra

2016-10-01

Conclusions: We identified novel neuronal targets and cellular mechanisms underlying PR/PRR actions in critical hypothalamic neurons involved in cardiometabolic regulation. This fundamental mechanistic information regarding central PR/PRR actions is essential for the development of novel RAS-based therapeutic targets for the treatment of cardiometabolic disorders in obesity and hypertension.

Effect of water on the mechanical behaviour of shales

International Nuclear Information System (INIS)

Wakim, J.; Hadj-Hassen, F.; Tijani, M.; Noirel, J.F.

2005-01-01

This paper aims to presenting the results of a research conducted in order to study the effect of water on the mechanical behaviour of the Lorraine Basin Colliery shale. The work performed can be divided into four main parts. The first part is dedicated to classical tests and it includes geological and mineralogical analysis as well as mechanical laboratory tests. The second part is devoted to the phenomenon of shale swelling under water effect. New procedures and equipment of testing were set up in order to characterise this swelling behaviour and to determine its model parameters. The tests performed in this second part are allowed to develop a phenomenological model which describes the elasto-visco-plastic behaviour of shales before and after saturation. The last phase of the work is dedicated to implement the new model in the finite element code VIPLEF in order to apply in tunnel excavated in swelling anisotropic rocks. (authors)

Model test study of evaporation mechanism of sand under constant atmospheric condition

OpenAIRE

CUI, Yu Jun; DING, Wenqi; SONG, Weikang

2014-01-01

The evaporation mechanism of Fontainebleau sand using a large-scale model chamber is studied. First, the evaporation test on a layer of water above sand surface is performed under various atmospheric conditions, validating the performance of the chamber and the calculation method of actual evaporation rate by comparing the calculated and measured cumulative evaporations. Second,the evaporation test on sand without water layer is conducted under constant atmospheric condition. Both the evoluti...

Contraction and elongation: Mechanics underlying cell boundary deformations in epithelial tissue.

Science.gov (United States)

Hara, Yusuke

2017-06-01

The cell-cell boundaries of epithelial cells form cellular frameworks at the apical side of tissues. Deformations in these boundaries, for example, boundary contraction and elongation, and the associated forces form the mechanical basis of epithelial tissue morphogenesis. In this review, using data from recent Drosophila studies on cell boundary contraction and elongation, I provide an overview of the mechanism underlying the bi-directional deformations in the epithelial cell boundary, that are sustained by biased accumulations of junctional and apico-medial non-muscle myosin II. Moreover, how the junctional tensions exist on cell boundaries in different boundary dynamics and morphologies are discussed. Finally, some future perspectives on how recent knowledge about single cell boundary-level mechanics will contribute to our understanding of epithelial tissue morphogenesis are discussed. © 2017 Japanese Society of Developmental Biologists.

Mechanical behavior and stress effects in hard superconductors: a review

International Nuclear Information System (INIS)

Koch, C.C.; Easton, D.S.

1977-11-01

The mechanical properties of type II superconducting materials are reviewed as well as the effect of stress on the superconducting properties of these materials. The bcc alloys niobium-titanium and niobium-zirconium exhibit good strength and extensive ductility at room temperature. Mechanical tests on these alloys at 4.2 0 K revealed serrated stress-strain curves, nonlinear elastic effects and reduced ductility. The nonlinear behavior is probably due to twinning and detwinning or a reversible stress-induced martensitic transformation. The brittle A-15 compound superconductors, such as Nb 3 Sn and V 3 Ga, exhibit unusual elastic properties and structural instabilities at cryogenic temperatures. Multifilamentary composites consisting of superconducting filaments in a normal metal matrix are generally used for superconducting devices. The mechanical properties of alloy and compound composites, tapes, as well as composites of niobium carbonitride chemically vapor deposited on high strength carbon fibers are presented. Hysteretic stress-strain behavior in the metal matrix composites produces significant heat generation, an effect which may lead to degradation in the performance of high field magnets. Measurements of the critical current density, J/sub c/, under stress in a magnetic field are reported. Modest stress-reversible degradation in J/sub c/ was observed in niobium-titanium composites, while more serious degradation was found in Nb 3 Sn samples. The importance of mechanical behavior to device performance is discussed

Vasodilatory effects and underlying mechanisms of the ethyl acetate extracts from Gastrodia elata.

Science.gov (United States)

Dai, Rong; Wang, Ting; Si, Xiaoqin; Jia, Yuanyuan; Wang, Lili; Yuan, Yan; Lin, Qing; Yang, Cui

2017-05-01

The objective of this study was to assess the ethyl acetate extracts of Gastrodia elata Blume (GEB) on vascular tone and the mechanisms involved. GEB was extracted with 95% EtOH followed by a further extraction with ethyl acetate. The effects of GEB and its ingredients on the isometric tensions of the aortic rings from rats were measured. The ethyl acetate extract of GEB induced a vasodilatory effect on rat aorta, which was partially dependent on endothelium. Four chemical compounds isolated from GEB were identified as 3,4-dihydroxybenzaldehyde (DB), 4-hydroxybenzaldehyde (HB), 4-methoxybenzyl alcohol (MA), and 4,4'-dihydroxydiphenyl methane (DM), respectively. All of these compounds induced vasodilatations, which were dependent on the endothelium to different degrees. After pretreatment with N ω -nitro-l-arginine methyl ester, indomethacin, or methylene blue, the vasodilatations induced by DB, HB, and MA were significantly decreased. In addition, the contractions of the rat aortic rings due to Ca 2+ influx and intracellular Ca 2+ release were also inhibited by DM. Furthermore, the administration of DB significantly enhanced the productions of nitric oxide (NO) and the activities of the endothelial NO synthase in aorta and in endothelial cells. Thus, GEB may play an important role in the amelioration of hypertension by modulating vascular tones.

Protective effects of total glucosides of paeony and the underlying mechanisms in carbon tetrachloride-induced experimental liver injury

Science.gov (United States)

Qin, Ying; Tian, Ya-ping

2011-01-01

Introduction We explored the protective effects of total glucosides of paeony (TGP) and the underlying mechanisms in carbon tetrachloride (CCl4)-induced experimental liver injury in mice. Material and methods Chronic liver damage was induced by intraperitoneal injection of CCl4 (0.5 µl/g) three times per week for 8 weeks. Mice also received 25, 50 or 100 mg/kg TGP. Liver sections were stained with haematoxylin/eosin. Serum amino transferases, lipid peroxidation and tumour necrosis factor-α (TNF-α) levels were determined using commercial assays. Quantitative real-time polymerase chain reaction was used to determine the changes in hepatic TNF-α, COX-2, iNOS and HO-1 expression. Protein levels of nitric oxide synthase, cyclooxygenase-2, haem oxygenase-1 and cytochrome P450 2E1 were determined by western blotting. Results Histological results showed that TGP improved the CCl4-induced changes in liver structure and alleviated lobular necrosis. The increases in serum protein and hepatic mRNA expression of TNF-α induced by CCl4 treatment were suppressed by TGP. Total glucosides of paeony also attenuated the increase the expression in iNOS and CYP2E1 but augmented the increase in HO-1.The mRNA and protein expression levels of inducible HO-1 increased significantly after CCl4 treatment. Conclusions Total glucosides of paeony protects hepatocytes from oxidative damage induced by CCl4. Total glucosides of paeony may achieve these effects by enhancing HO-1 expression and inhibiting the expression of proinflammatory mediators. PMID:22291795

The Mediated MIMIC Model for Understanding the Underlying Mechanism of DIF

Science.gov (United States)

Cheng, Ying; Shao, Can; Lathrop, Quinn N.

2016-01-01

Due to its flexibility, the multiple-indicator, multiple-causes (MIMIC) model has become an increasingly popular method for the detection of differential item functioning (DIF). In this article, we propose the mediated MIMIC model method to uncover the underlying mechanism of DIF. This method extends the usual MIMIC model by including one variable…

Atrial Arrhythmias in Obstructive Sleep Apnea: Underlying Mechanisms and Implications in the Clinical Setting

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David Filgueiras-Rama

2013-01-01

Full Text Available Obstructive sleep apnea (OSA is a common disorder characterized by repetitive interruption of ventilation during sleep caused by recurrent upper airway collapse, which leads to intermittent hypoxia. The disorder is commonly undiagnosed despite its relationship with substantial cardiovascular morbidity and mortality. Moreover, the effects of the disorder appear to be particularly dangerous in young subjects. In the last decade, substantial clinical evidence has identified OSA as independent risk factor for both bradyarrhythmias and tachyarrhythmias. To date the mechanisms leading to such arrhythmias have not been completely understood. However, recent data from animal models and new molecular analyses have increased our knowledge of the field, which might lead to future improvement in current therapeutic strategies mainly based on continuous positive airway pressure. This paper aims at providing readers a brief and specific revision of current knowledge about the mechanisms underlying atrial arrhythmias in OSA and their clinical and therapeutic implications.

Language Learning Enhanced by Massive Multiple Online Role-Playing Games (MMORPGs) and the Underlying Behavioral and Neural Mechanisms

Science.gov (United States)

Zhang, Yongjun; Song, Hongwen; Liu, Xiaoming; Tang, Dinghong; Chen, Yue-e; Zhang, Xiaochu

2017-01-01

Massive Multiple Online Role-Playing Games (MMORPGs) have increased in popularity among children, juveniles, and adults since MMORPGs’ appearance in this digital age. MMORPGs can be applied to enhancing language learning, which is drawing researchers’ attention from different fields and many studies have validated MMORPGs’ positive effect on language learning. However, there are few studies on the underlying behavioral or neural mechanism of such effect. This paper reviews the educational application of the MMORPGs based on relevant macroscopic and microscopic studies, showing that gamers’ overall language proficiency or some specific language skills can be enhanced by real-time online interaction with peers and game narratives or instructions embedded in the MMORPGs. Mechanisms underlying the educational assistant role of MMORPGs in second language learning are discussed from both behavioral and neural perspectives. We suggest that attentional bias makes gamers/learners allocate more cognitive resources toward task-related stimuli in a controlled or an automatic way. Moreover, with a moderating role played by activation of reward circuit, playing the MMORPGs may strengthen or increase functional connectivity from seed regions such as left anterior insular/frontal operculum (AI/FO) and visual word form area to other language-related brain areas. PMID:28303097

Language Learning Enhanced by Massive Multiple Online Role-Playing Games (MMORPGs) and the Underlying Behavioral and Neural Mechanisms.

Science.gov (United States)

Zhang, Yongjun; Song, Hongwen; Liu, Xiaoming; Tang, Dinghong; Chen, Yue-E; Zhang, Xiaochu

2017-01-01

Massive Multiple Online Role-Playing Games (MMORPGs) have increased in popularity among children, juveniles, and adults since MMORPGs' appearance in this digital age. MMORPGs can be applied to enhancing language learning, which is drawing researchers' attention from different fields and many studies have validated MMORPGs' positive effect on language learning. However, there are few studies on the underlying behavioral or neural mechanism of such effect. This paper reviews the educational application of the MMORPGs based on relevant macroscopic and microscopic studies, showing that gamers' overall language proficiency or some specific language skills can be enhanced by real-time online interaction with peers and game narratives or instructions embedded in the MMORPGs. Mechanisms underlying the educational assistant role of MMORPGs in second language learning are discussed from both behavioral and neural perspectives. We suggest that attentional bias makes gamers/learners allocate more cognitive resources toward task-related stimuli in a controlled or an automatic way. Moreover, with a moderating role played by activation of reward circuit, playing the MMORPGs may strengthen or increase functional connectivity from seed regions such as left anterior insular/frontal operculum (AI/FO) and visual word form area to other language-related brain areas.

Mechanical Behaviour of Bolted Joints Under Impact Rates of Loading

Science.gov (United States)

2012-01-01

M. (1995). Bearing Strength of Autoclave and oven cured kevlar / epoxy laminates under static and dynamic loading. Compostes, 451-456. Kretsis, G...Joints in Glass Fibre/ Epoxy Laminates. Composites, Volume 16. No 2. Kolsky, H. (1949). An Investigation of the Mechanical Properties of Materials at...elongating the pulse width. The responses are read by the strain gages bonded on the incident and transmission bar with Vishay AE-10 epoxy . The gages

Effect of stacking sequence on mechanical properties neem wood veneer plastic composites

Science.gov (United States)

Nagamadhu, M.; Kumar, G. C. Mohan; Jeyaraj, P.

2018-04-01

This study investigates the effect of wood veneer stacking sequence on mechanical properties of neem wood polymer composite (WPC) experimentally. Wood laminated samples were fabricated by conventional hand layup technique in a mold and cured under pressure at room temperature and then post cured at elevated temperature. Initially, the tensile, flexural, and impact test were conducted to understand the effect of weight fraction of fiber on mechanical properties. The mechanical properties have increased with the weight fraction of fiber. Moreover the stacking sequence of neem wood plays an important role. As it has a significant impact on the mechanical properties. The results indicated that 0°/0° WPC shows highest mechanical properties as compared to other sequences (90°/90°, 0°/90°, 45°/90°, 45°/45°). The Fourier Transform Infrared Spectroscopy (FTIR) Analysis were carried out to identify chemical compounds both in raw neem wood and neem wood epoxy composite. The microstructure raw/neat neem wood and the interfacial bonding characteristics of neem wood composite investigated using Scanning electron microscopy images.

Neural mechanisms underlying cognitive control of men with lifelong antisocial behavior.

Science.gov (United States)

Schiffer, Boris; Pawliczek, Christina; Mu Ller, Bernhard; Forsting, Michael; Gizewski, Elke; Leygraf, Norbert; Hodgins, Sheilagh

2014-04-30

Results of meta-analyses suggested subtle deficits in cognitive control among antisocial individuals. Because almost all studies focused on children with conduct problems or adult psychopaths, however, little is known about cognitive control mechanisms among the majority of persistent violent offenders who present an antisocial personality disorder (ASPD). The present study aimed to determine whether offenders with ASPD, relative to non-offenders, display dysfunction in the neural mechanisms underlying cognitive control and to assess the extent to which these dysfunctions are associated with psychopathic traits and trait impulsivity. Participants comprised 21 violent offenders and 23 non-offenders who underwent event-related functional magnetic resonance imaging while performing a non-verbal Stroop task. The offenders, relative to the non-offenders, exhibited reduced response time interference and a different pattern of conflict- and error-related activity in brain areas involved in cognitive control, attention, language, and emotion processing, that is, the anterior cingulate, dorsolateral prefrontal, superior temporal and postcentral cortices, putamen, thalamus, and amygdala. Moreover, between-group differences in behavioural and neural responses revealed associations with core features of psychopathy and attentional impulsivity. Thus, the results of the present study confirmed the hypothesis that offenders with ASPD display alterations in the neural mechanisms underlying cognitive control and that those alterations relate, at least in part, to personality characteristics. Copyright © 2014. Published by Elsevier Ireland Ltd.

Mitochondrial ADP/ATP exchange inhibition: a novel off-target mechanism underlying ibipinabant-induced myotoxicity.

Science.gov (United States)

Schirris, Tom J J; Ritschel, Tina; Herma Renkema, G; Willems, Peter H G M; Smeitink, Jan A M; Russel, Frans G M

2015-09-29

Cannabinoid receptor 1 (CB1R) antagonists appear to be promising drugs for the treatment of obesity, however, serious side effects have hampered their clinical application. Rimonabant, the first in class CB1R antagonist, was withdrawn from the market because of psychiatric side effects. This has led to the search for more peripherally restricted CB1R antagonists, one of which is ibipinabant. However, this 3,4-diarylpyrazoline derivative showed muscle toxicity in a pre-clinical dog study with mitochondrial dysfunction. Here, we studied the molecular mechanism by which ibipinabant induces mitochondrial toxicity. We observed a strong cytotoxic potency of ibipinabant in C2C12 myoblasts. Functional characterization of mitochondria revealed increased cellular reactive oxygen species generation and a decreased ATP production capacity, without effects on the catalytic activities of mitochondrial enzyme complexes I-V or the complex specific-driven oxygen consumption. Using in silico off-target prediction modelling, combined with in vitro validation in isolated mitochondria and mitoplasts, we identified adenine nucleotide translocase (ANT)-dependent mitochondrial ADP/ATP exchange as a novel molecular mechanism underlying ibipinabant-induced toxicity. Minor structural modification of ibipinabant could abolish ANT inhibition leading to a decreased cytotoxic potency, as observed with the ibipinabant derivative CB23. Our results will be instrumental in the development of new types of safer CB1R antagonists.

The Cost Effectiveness of the U.S. Export Enhancement Program Bonus Allocation Mechanism

OpenAIRE

Humei Wang; Richard J. Sexton

2004-01-01

The U.S. Export Enhancement Program is evaluated from the perspective of the cost effectiveness of its bonus allocation mechanism. The current mechanism resembles a discriminatory-price, common-value auction. However, auction theory suggests that a discriminatory auction may not be optimal in this setting for several reasons. This article evaluates the current format relative to an alternative, uniform-price auction. Estimation results reveal evidence of strategic bidder behavior under the cu...

Modulatory mechanisms of cortisol effects on emotional learning and memory: novel perspectives.

Science.gov (United States)

van Ast, Vanessa A; Cornelisse, Sandra; Marin, Marie-France; Ackermann, Sandra; Garfinkel, Sarah N; Abercrombie, Heather C

2013-09-01

It has long been known that cortisol affects learning and memory processes. Despite a wealth of research dedicated to cortisol effects on learning and memory, the strength or even directionality of the effects often vary. A number of the factors that alter cortisol's effects on learning and memory are well-known. For instance, effects of cortisol can be modulated by emotional arousal and the memory phase under study. Despite great advances in understanding factors that explain variability in cortisol's effects, additional modulators of cortisol effects on memory exist that are less widely acknowledged in current basic experimental research. The goal of the current review is to disseminate knowledge regarding less well-known modulators of cortisol effects on learning and memory. Since several models for the etiology of anxiety, such as post-traumatic stress disorder (PTSD), incorporate stress and the concomitant release of cortisol as important vulnerability factors, enhanced understanding of mechanisms by which cortisol exerts beneficial as opposed to detrimental effects on memory is very important. Further elucidation of the factors that modulate (or alter) cortisol's effects on memory will allow reconciliation of seemingly inconsistent findings in the basic and clinical literatures. The present review is based on a symposium as part of the 42nd International Society of Psychoneuroendocrinology Conference, New York, USA, that highlighted some of those modulators and their underlying mechanisms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Unraveling the mechanisms underlying postural instability in Parkinson's disease using dynamic posturography

NARCIS (Netherlands)

Nonnekes, J.H.; Kam, D. de; Geurts, A.C.; Weerdesteijn, V.G.M.; Bloem, B.R.

2013-01-01

Postural instability, one of the cardinal symptoms of Parkinson's disease (PD), has devastating consequences for affected patients. Better strategies to prevent falls are needed, but this calls for an improved understanding of the complex mechanisms underlying postural instability. We must also

Feeding Problems and Their Underlying Mechanisms in the Esophageal Atresia–Tracheoesophageal Fistula Patient

Science.gov (United States)

Mahoney, Lisa; Rosen, Rachel

2017-01-01

Feeding difficulties such as dysphagia, coughing, choking, or vomiting during meals, slow eating, oral aversion, food refusal, and stressful mealtimes are common in children with repaired esophageal atresia (EA) and the reasons for this are often multifactorial. The aim of this review is to describe the possible underlying mechanisms contributing to feeding difficulties in patients with EA and approaches to management. Underlying mechanisms for these feeding difficulties include esophageal dysphagia, oropharyngeal dysphagia and aspiration, and aversions related to prolonged gastrostomy tube feeding. The initial diagnostic evaluation for feeding difficulties in a patient with EA may involve an esophagram, videofluoroscopic imaging or fiberoptic endoscopic evaluation during swallowing, upper endoscopy with biopsies, pH-impedance testing, and/or esophageal motility studies. The main goal of management is to reduce the factors contributing to feeding difficulties and may include reducing esophageal stasis, maximizing reflux therapies, treating underlying lung disease, dilating strictures, and altering feeding methods, routes, or schedules. PMID:28620597

[Study on mechanism of SOM stabilization of paddy soils under long-term fertilizations].

Science.gov (United States)

Luo, Lu; Zhou, Ping; Tong, Cheng-Li; Shi, Hui; Wu, Jin-Shui; Huang, Tie-Ping

2013-02-01

Fourier transform infrared spectroscopy (FTIR) was applied to study the structure of soil organic matter (SOM) of paddy soils under long-term different fertilization treatments. The aim was to clarify the different distribution of SOM between different fertilization methods and between topsoil and subsoil, and to explore the stability mechanism of SOM under different fertilization treatments. The results showed that the content of topsoil organic carbon (SOC) was the highest under organic-inorganic fertilizations, with the increment of SOC by 18.5%, 12.9% and 18.4% under high organic manure (HOM), low organic manure (LOM) and straw returning (STW) respectively compared with no fertilization treatment (CK). The long-term fertilizations also changed the chemical structure of SOM. As compared with CK, different fertilization treatments increased the functional group absorbing intensity of chemical resistance compounds (aliphatic, aromaticity), carbohydrate and organo-silicon compounds, which was the most distinctive under treatments of HOM, LOM and STW. For example, the absorbing intensity of alkyl was 0.30, 0.25 and 0.29 under HOM, LOM and STW, respectively. These values were increased by 87% , 56% and 81% as compared with that under CK treatment. The functional group absorbing intensity of SOM in the topsoil was stronger than that in the subsoil, with the most distinctive difference under HOM, LOM and STW treatments. The present research indicated that the enhanced chemical resistance of functional group of SOM may contribute to the high contents of SOC in the paddy soils under long-term organic-inorganic fertilizations, which also suggested a chemical stabilization mechanism of SOM in the paddy soils.

Antioxidant Property of Jobelyn as the Possible Mechanism Underlying

Directory of Open Access Journals (Sweden)

Solomon Umukoro

2013-01-01

Full Text Available   Introduction: Amnesia or loss of memory is the cardinal hallmark of Alzheimer’s disease (AD, a progressive neurodegenerative disorder associated with ageing process. Although, AD had been discovered over a century ago, drugs which could cure or halt the progression of the disease are yet to see the light of the day. However, there has been a growing interest in the use of phytomedicines with multipronged mechanisms of action that could target various aspects of the pathologies of AD. Jobelyn (JB is a potent antioxidant African polyherbal formulation with active components that have been acclaimed to show neuroprotection. T his investigation was carried out to evaluate whether JB has anti-amnesic and antioxidant activities.   Methods: The alteration of alternation behavior in the Y-maze paradigm was utilized as the test for memory function in mice. The effect of JB on a cetylcholinesterase (AChE activity, malondialdehyde (MDA level and the concentrations of glutathione (GSH in the frontal cortex and hippocampus were assessed in rats as means of providing insight into the mechanism underlying its anti-amnesic activity. The animals were given JB (1, 2.5 or 5mg/kg, i.p. daily for 7 days before the biochemical assays or test for memory functions were carried out.   Results: JB was found to produce a significant increase in the level of alternation behavior compared with the control, suggesting anti-amnesic activity. Also, JB reversed the memory impairment induced by scopolamine, which further indicates anti-amnesic property. Furthermore, JB demonstrated a significant inhibition of MDA formation in the frontal cortex and hippocampus of rats, indicating antioxidant property. In addition, it increased the defense armory of the brain tissues, as it significantly increased the concentrations of GSH in the frontal cortex and hippocampus of rats. However, JB did not demonstrate any inhibitory effect against AChE activity in the frontal cortex and

Mechanical properties of cellulose electro-active paper under different environmental conditions

International Nuclear Information System (INIS)

Kim, Heung Soo; Kim, Jaehwan; Jung, Woochul; Ampofo, Joshua; Craft, William; Sankar, Jagannathan

2008-01-01

The mechanical properties of cellulose-based electro-active paper (EAPap) are investigated under various environmental conditions. Cellulose EAPap has been discovered as a smart material that can be used as both sensor and actuator. Its advantages include low voltage operation, light weight, low power consumption, biodegradability and low cost. EAPap is made with cellulose paper coated with thin electrodes. EAPap shows a reversible and reproducible bending movement as well as longitudinal displacement under an electric field. However, EAPap is a complex anisotropic material which has not been fully characterized. This study investigates the mechanical properties of cellulose-based EAPap, including Young's modulus, yield strength, ultimate strength and creep, along with orientation directions, humidity and temperature levels. To test the materials in different humidity and temperature levels, a special material testing system was made that can control the testing environmental conditions. The initial Young's modulus of EAPap is in the range of 4–9 GPa, which was higher than that of other polymer materials. Also, the Young's modulus is orientation dependent, which may be associated with the piezoelectricity of EAPap materials. The elastic strength and stiffness gradually decreased when the humidity and temperature were increased. Creep and relaxation were observed under constant stress and strain, respectively. Through scanning electron microscopy, EAPap is shown to exhibit both layered and oriented cellulose macromolecular structures that impact both the elastic and plastic behavior

Effect of the weld joint configuration on stressed components, residual stresses and mechanical properties

Energy Technology Data Exchange (ETDEWEB)

Cevik, Bekir; Oezer, Alpay; Oezcatalbas, Yusuf [Gazi Univ., Ankara (Turkey)

2014-03-01

The effect of the weld joint configuration on components has been studied, which are under service loads, under repair or construction and the residual stresses as well as the mechanical properties of the joint have been determined. For this purpose, a horizontal positioned tensile testing device and a semi-automatic MIG welding machine have been used and then the weld joints of the plates were subjected to different elastic stresses. When the temperature of the joined elements decreased to room temperature, applied elastic stresses were released. By this means, the effects of the existing tensile stresses in the joined parts and the tensile stresses created by the welding processes were investigated. The tensile stresses occurring in the joined elements were determined by using the photo-elasticity analysis method and the hole-drilling method. Also, tensile-shear tests were applied in order to determine the effect of permanent tensile loads on the mechanical properties of the joint. Experimental results showed that the application of corner welded lap joints for components under tensile loading significantly decrease the shear strength and yielding capacities of the joint. (orig.)

Deterioration of mechanical properties of high strength structural steel S460N under transient state fire condition

International Nuclear Information System (INIS)

Qiang, Xuhong; Bijlaard, Frans S.K.; Kolstein, Henk

2012-01-01

Highlights: ► Mechanical properties of S460N under transient state fire condition are obtained. ► Elevated-temperature mechanical properties of steels are dependent on steel grades. ► No design standard is applicable to HSS S460N under transient state fire condition. ► Specific statements on various HSS in fire should be proposed in design standards. ► Research results offer accurate material property for structural design engineers. -- Abstract: 911 World Trade Centre Tragedy put fire safety of constructional steel structures into question. Since then, more and more research attention has been paid to the elevated-temperature mechanical properties of structural steels, which is a critical basis of evaluating the fire performance of steel structures. In the literature the available mechanical properties of structural steels under fire conditions were mainly obtained from steady state test method, as steady state test method is easier to perform than transient state test method and offers stress–strain curves directly. However, the transient state fire condition is considered to be more realistic to represent the real condition when constructions are exposed to fire. In order to reveal the deterioration of mechanical properties of the commonly used high strength structural steel S460N under transient state fire condition, tensile tests were conducted under various constant stress levels up to 800 MPa. The reduction factors of elastic modulus, yield and ultimate strengths of S460N under transient state fire condition were obtained and compared with current leading design standards and available literature. The application of such accurate elevated-temperature mechanical properties reduction factors of S460N can ensure a safe fire-resistance design and evaluation of steel structures with high strength steel S460N under transient state fire condition. This experimental study also supports other relative research on fire performance of steel structures with

How diagnostic tests help to disentangle the mechanisms underlying neuropathic pain symptoms in painful neuropathies.

Science.gov (United States)

Truini, Andrea; Cruccu, Giorgio

2016-02-01

Neuropathic pain, ie, pain arising directly from a lesion or disease affecting the somatosensory afferent pathway, manifests with various symptoms, the commonest being ongoing burning pain, electrical shock-like sensations, and dynamic mechanical allodynia. Reliable insights into the mechanisms underlying neuropathic pain symptoms come from diagnostic tests documenting and quantifying somatosensory afferent pathway damage in patients with painful neuropathies. Neurophysiological investigation and skin biopsy studies suggest that ongoing burning pain primarily reflects spontaneous activity in nociceptive-fiber pathways. Electrical shock-like sensations presumably arise from high-frequency ectopic bursts generated in demyelinated, nonnociceptive, Aβ fibers. Although the mechanisms underlying dynamic mechanical allodynia remain debatable, normally innocuous stimuli might cause pain by activating spared and sensitized nociceptive afferents. Extending the mechanistic approach to neuropathic pain symptoms might advance targeted therapy for the individual patient and improve testing for new drugs.

Mechanisms underlying the ameliorative property of lisinopril in progressive mesangioproliferative nephritis.

Science.gov (United States)

Shinosaki, Toshihiro; Miyai, Ikuko; Nomura, Yasuharu; Kobayashi, Tatsuo; Sunagawa, Norio; Kurihara, Hidetake

2002-08-01

The present study was performed to clarify the mechanism underlying the beneficial effects of lisinopril on chronic glomerulonephritis. Chronic glomerulonephritis was induced by a single injection of E30 monoclonal antibody (E30) recognizing Thy-1.1 antigen to unilaterally nephrectomized rats. E30 injection resulted in persistent massive proteinuria with a decrease in anionic charge sites on the glomerular basement membrane (GBM) at 8 weeks. Also, renal tissue from rats treated with E30 showed typical glomerulosclerosis and tubulointerstitial fibrosis. Lisinopril exerted a potent antiproteinuric effect and suppressed the progression of both glomerulosclerosis and tubulointerstitial fibrosis. Lisinopril recovered the reduced number of anionic charge sites on GBM, accounting for the positive action against massive proteinuria. Immunostaining for desmin revealed that lisinopril treatment prevented the injury of glomerular epithelial cells (GECs) occurring in the chronic nephritic stage. Also, the level of gene expression of transforming growth factor-beta (TGF-beta) and plasminogen activator inhibitor-1 (PAI-1) in the renal cortex were reduced, suggesting that lisinopril improved extracellular matrix (ECM) metabolism. These results indicated that proteinuria in Thy-1.1 antibody-induced chronic nephritis is associated with a decrease in anionic charge sites on GBM, and that the antiproteinuric effect of lisinopril is attributable to protection against GEC damage. Suppression of TGF-beta and PAI-1 expression contributed to the preventive effect of lisinopril on ECM deposition in renal tissue. Copyright 2002 S. Karger AG, Basel

Changes Of Hydration Level In Type I Collagen And Glycosaminoglycans Synthesized In The Rat’s Skin Under The Mechanical Stress

Directory of Open Access Journals (Sweden)

Alexandr M. Ponomarenko

2013-01-01

Full Text Available Changes of Hydratation Level Of Type I Collagen And Glycosaminoglycans That Are Synthesized In The Rat’s Skin Under The Mechanical Stress. The effect of the mechanical stress on the levels of hydratation of type I collagen and glycosaminoglycans that are synthesized in it, has been studied in vitro using the rats’ skin. The measured hydration of isotherms has shown that mechanical stress in the skin increases and decreases the amount of absorbed water in glycosaminoglycans and in collagen, respectively. Сalculated the average amounts of water molecules in collagen tripeptide and glycosaminoglycans disaccharide unit in the inside and outside layers of their hydrate shells

Molecular mechanism of catalase activity change under sodium dodecyl sulfate-induced oxidative stress in the mouse primary hepatocytes.

Science.gov (United States)

Wang, Jing; Wang, Jiaxi; Xu, Chi; Liu, Rutao; Chen, Yadong

2016-04-15

Sodium dodecyl sulfate (SDS) contributes to adverse effects of organisms probably because of its ability to induce oxidative stress via changing the activity of antioxidant enzyme catalase (CAT). But the underlying molecular mechanisms still remain unclear. This study characterized the harmful effects of SDS-induced oxidative stress on the mouse primary hepatocytes as well as the structure and function of CAT molecule and investigated the underlying molecular mechanism. After 12h SDS (0.1μM to 0.2mM) exposure, no significant change was observed in CAT activity of the hepatocytes. After 0.5 and 0.8mM SDS exposure, the state of oxidative stress stimulated CAT production in the hepatocytes. The inhibition of CAT activity induced by directly interacting with SDS was unable to catch the synthesis of CAT and therefore resulted in the increased activity and elevated ROS level. Further molecular experiments showed that SDS prefers to bind to the interface with no direct effect on the active site and the structure of heme groups of CAT molecule. When the sites in the interface is saturated, SDS interacts with VAL 73, HIS 74, ASN 147 and PHE 152, the key residues of the enzyme activity, and leads to the decrease of CAT activity. Copyright © 2015 Elsevier B.V. All rights reserved.

Mechanical deformation of atomic-scale metallic contacts: Structure and mechanisms

DEFF Research Database (Denmark)

Sørensen, Mads Reinholdt; Brandbyge, Mads; Jacobsen, Karsten Wedel

1998-01-01

We have simulated the mechanical deformation of atomic-scale metallic contacts under tensile strain using molecular dynamics and effective medium theory potentials. The evolution of the structure of the contacts and the underlying deformation mechanisms are described along with the calculated......, but vacancies can be permanently present. The transition states and energies for slip mechanisms have been determined using the nudged elastic band method, and we find a size-dependent crossover from a dislocation-mediated slip to a homogeneous slip when the contact diameter becomes less than a few nm. We show...

The Mechanisms of Traditional Chinese Medicine Underlying the Prevention and Treatment of Parkinson's Disease

Directory of Open Access Journals (Sweden)

Xiaoliang Li

2017-09-01

Full Text Available Parkinson's disease (PD, characterized with bradykinesia, static tremor, rigidity and disturbances in balance, is the second most common neurodegenerative disorder. Along with the largely aging population in the world, the incidence is increasing year by year, which imposes the negative impacts on patients, their families and the whole society. Traditional Chinese medicine (TCM has a positive prospect for the prevention and cure of PD due to its advantages of less side effects and multi-target effects. At present, the pathogenesis of PD is not yet fully discovered. This paper elaborates the mechanisms of TCM underlying the prevention and treatment of PD with regards to the inhibition of oxidative stress, the regulation of mitochondrial dysfunction, the reduction of toxic excitatory amino acids (EAA, the inhibition of neuroinflammation, the inhibition of neuronal apoptosis, and the inhibition of abnormal protein aggregation.

Mechanisms Underlying the Analgesic Effect of Moxibustion on Visceral Pain in Irritable Bowel Syndrome: A Review

Directory of Open Access Journals (Sweden)

Renjia Huang

2014-01-01

Full Text Available Irritable bowel syndrome (IBS is a functional bowel disorder that causes recurrent abdominal (visceral pain. Epidemiological data show that the incidence rate of IBS is as high as 25%. Most of the medications may lead to tolerance, addiction and toxic side effects. Moxibustion is an important component of traditional Chinese medicine and has been used to treat IBS-like abdominal pain for several thousand years in China. As a mild treatment, moxibustion has been widely applied in clinical treatment of visceral pain in IBS. In recent years, it has played an irreplaceable role in alternative medicine. Extensive clinical studies have demonstrated that moxibustion for treatment of visceral pain is simple, convenient, and inexpensive, and it is being accepted by an increasing number of patients. There have not been many studies investigating the analgesic mechanisms of moxibustion. Studies exploring the analgesic mechanisms have mainly focused on visceral hypersensitivity, brain-gut axis neuroendocrine system, and immune system. This paper reviews the latest developments in moxibustion use for treatment of visceral pain in IBS from these perspectives. It also evaluates potential problems in relevant studies on the mechanisms of moxibustion therapy to promote the application of moxibustion in the treatment of IBS.

An investigation of the mechanism underlying teacher aggression: Testing I3 theory and the General Aggression Model.

Science.gov (United States)

Montuoro, Paul; Mainhard, Tim

2017-12-01

Considerable research has investigated the deleterious effects of teachers responding aggressively to students who misbehave, but the mechanism underlying this dysfunctional behaviour remains unknown. This study investigated whether the mechanism underlying teacher aggression follows I 3 theory or General Aggression Model (GAM) metatheory of human aggression. I 3 theory explains exceptional, catastrophic events of human aggression, whereas the GAM explains common human aggression behaviours. A total of 249 Australian teachers participated in this study, including 142 primary school teachers (Mdn [age] = 35-39 years; Mdn [years teaching] = 10-14 years; 84% female) and 107 secondary school teachers (Mdn [age] = 45-49 years; Mdn [years teaching] = 15-19 years; 65% female). Participants completed four online self-report questionnaires, which assessed caregiving responsiveness, trait self-control, misbehaviour provocation, and teacher aggression. Analyses revealed that the GAM most accurately captures the mechanism underlying teacher aggression, with lower caregiving responsiveness appearing to indirectly lead to teacher aggression via higher misbehaviour provocation and lower trait self-control in serial, controlling for gender, age, years teaching, and current role (primary, secondary). This study indicates that teacher aggression proceeds from 'the person in the situation'. Specifically, lower caregiving responsiveness appears to negatively shape a teacher's affective, cognitive, and arousal states, which influence how they perceive and interpret student misbehaviour. These internal states, in turn, appear to negatively influence appraisal and decision processes, leading to immediate appraisal and impulsive actions. These results raise the possibility that teacher aggression is a form of countertransference. © 2017 The British Psychological Society.

Effect of acoustic softening on the thermal-mechanical process of ultrasonic welding.

Science.gov (United States)

Chen, Kunkun; Zhang, Yansong; Wang, Hongze

2017-03-01

Application of ultrasonic energy can reduce the static stress necessary for plastic deformation of metallic materials to reduce forming load and energy, namely acoustic softening effect (ASE). Ultrasonic welding (USW) is a rapid joining process utilizing ultrasonic energy to form a solid state joint between two or more pieces of metals. Quantitative characterization of ASE and its influence on specimen deformation and heat generation is essential to clarify the thermal-mechanical process of ultrasonic welding. In the present work, experiments were set up to found out mechanical behavior of copper and aluminum under combined effect of compression force and ultrasonic energy. Constitutive model was proposed and numerical implemented in finite element model of ultrasonic welding. Thermal-mechanical analysis was put forward to explore the effect of ultrasonic energy on the welding process quantitatively. Conclusions can be drawn that ASE increases structural deformation significantly, which is beneficial for joint formation. Meanwhile, heat generation from both frictional work and plastic deformation is slightly influenced by ASE. Based on the proposed model, relationship between ultrasonic energy and thermal-mechanical behavior of structure during ultrasonic welding was constructed. Copyright © 2016 Elsevier B.V. All rights reserved.

Effective mechanic training

International Nuclear Information System (INIS)

Burdge, R.E.

1979-01-01

The need for the training of mechanics is discussed, and the increased interest within the utility industry of placing a similar importance on this training as it has traditionally placed on operator training, is expressed. Effective approaches and techniques are described. Fundamental mechanical maintenance concepts and their practical application are discussed, including the use of supporting video programs. The importance of follow-up practical shop exercise which reinforces classroom instruction is stressed, drawing from practical utility experience. Utilizing success in training as a measure of eligibility for advancement is discussed as well as the interface between training and the company bargaining unit

Improvement of Learning and Memory Induced by Cordyceps Polypeptide Treatment and the Underlying Mechanism

Directory of Open Access Journals (Sweden)

Guangxin Yuan

2018-01-01

Full Text Available Our previous research revealed that Cordyceps militaris can improve the learning and memory, and although the main active ingredient should be its polypeptide complexes, the underlying mechanism of its activity remains poorly understood. In this study, we explored the mechanisms by which Cordyceps militaris improves learning and memory in a mouse model. Mice were given scopolamine hydrobromide intraperitoneally to establish a mouse model of learning and memory impairment. The effects of Cordyceps polypeptide in this model were tested using the Morris water maze test; serum superoxide dismutase activity; serum malondialdehyde levels; activities of acetyl cholinesterase, Na+-k+-ATPase, and nitric oxide synthase; and gamma aminobutyric acid and glutamate contents in brain tissue. Moreover, differentially expressed genes and the related cellular signaling pathways were screened using an mRNA expression profile chip. The results showed that the genes Pik3r5, Il-1β, and Slc18a2 were involved in the effects of Cordyceps polypeptide on the nervous system of these mice. Our findings suggest that Cordyceps polypeptide may improve learning and memory in the scopolamine-induced mouse model of learning and memory impairment by scavenging oxygen free radicals, preventing oxidative damage, and protecting the nervous system.

Neurocognitive mechanisms underlying social learning in infancy: infants' neural processing of the effects of others' actions.

Science.gov (United States)

Paulus, Markus; Hunnius, Sabine; Bekkering, Harold

2013-10-01

Social transmission of knowledge is one of the reasons for human evolutionary success, and it has been suggested that already human infants possess eminent social learning abilities. However, nothing is known about the neurocognitive mechanisms that subserve infants' acquisition of novel action knowledge through the observation of other people's actions and their consequences in the physical world. In an electroencephalogram study on social learning in infancy, we demonstrate that 9-month-old infants represent the environmental effects of others' actions in their own motor system, although they never achieved these effects themselves before. The results provide first insights into the neurocognitive basis of human infants' unique ability for social learning of novel action knowledge.

Microscale failure mechanisms leading to internal short circuit in Li-ion batteries under complex loading scenarios

NARCIS (Netherlands)

Sahraei, E.; Bosco, E.; Dixon, B.; Lai, B.

2016-01-01

One of the least understood mechanisms of Li-ion batteries is the development of internal short circuits under mechanical loads. In this study, a micro mechanical model is developed and subjected to various loading scenarios to understand the sequence of failure in the multi-layer, multi-material

Evolution of the bonding mechanism of ZnO under isotropic compression: A first-principles study

International Nuclear Information System (INIS)

Zhou, G.C.; Sun, L.Z.; Wang, J.B.; Zhong, X.L.; Zhou, Y.C.

2008-01-01

The electronic structure and the bonding mechanism of ZnO under isotropic pressure have been studied by using the full-potential linear augmented plane wave (FP-LAPW) method within the density-functional theory (DFT) based on LDA+U exchange correlation (EXC) potential. We used the theory of Atoms in Molecules (AIM) method to analyze the change of the charge transfer and the bonding strength under isotropic pressure. The results of the theoretical analysis show that charge transfer between Zn and O atomic basins nearly linearly increases with the increasing pressure. Charge density along the Zn-O bond increases under the high pressure. The bonding strength and the ionicity of Zn-O bond also increase with the increasing pressure. The linear evolution process of the bonding mechanism under isotropic pressure was shown clearly in the present paper

The effect of natural weathering on the mechanical, morphological and thermal properties of high impact polystyrene (HIPS)

International Nuclear Information System (INIS)

Sahin, Tuelin; Sinmazcelik, Tamer; Sahin, Senol

2007-01-01

The effect of natural weathering on the mechanical, morphological and thermal properties on the high impact polystyrene (HIPS) and cold drawn HIPS are investigated. After natural weathering period of 8760 h, under known meteorological parameters, the changes in mechanical properties are investigated by using tensile, instrumented impact and hardness tests. Thermo-mechanical properties are characterized by using thermomechanical analysis (TMA) and melt flow index (MFI). Fractured surfaces of the materials are investigated by scanning electron microscope (SEM). Natural weathering effects on fracture mechanisms are discussed by means of fractographical analysis. Remarkable morphological changes were observed especially at the surface of the material. This results in dramatic loss in mechanical properties

The pathologic mechanisms underlying lumbar distraction spinal cord injury in rabbits.

Science.gov (United States)

Wu, Di; Zheng, Chao; Wu, Ji; Xue, Jing; Huang, Rongrong; Wu, Di; Song, Yueming

2017-11-01

A reliable experimental rabbit model of distraction spinal cord injury (SCI) was established to successfully simulate gradable and replicable distraction SCI. However, further research is needed to elucidate the pathologic mechanisms underlying distraction SCI. The aim of this study was to investigate the pathologic mechanisms underlying lumbar distraction SCI in rabbits. This is an animal laboratory study. Using a self-designed spine distractor, the experimental animals were divided into a control group and 10%, 20%, and 30% distraction groups. Pathologic changes to the spinal cord microvessels in the early stage of distraction SCI were identified by perfusion of the spinal cord vasculature with ink, production of transparent specimens, observation by light microscopy, and observation of corrosion casts of the spinal cord microvascular architecture by scanning electron microscopy. Malondialdehyde (MDA) and superoxide dismutase (SOD) concentrations in the injured spinal cord tissue were measured after 8 hours. With an increasing degree and duration of distraction, the spinal cord microvessels were only partially filled and had the appearance of spasm until rupture and hemorrhage were observed. The MDA concentration increased and the SOD concentration decreased in the spinal cord tissue. Changes to the internal and external spinal cord vessels led to spinal cord ischemia, which is a primary pathologic mechanism of distraction SCI. Lipid peroxidation mediated by free radicals took part in secondary pathologic damage of distraction SCI. Copyright © 2017 Elsevier Inc. All rights reserved.

The comparison of two continuum damage mechanics-based material models for formability prediction of AA6082 under hot stamping conditions

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Shao, Z.; Li, N.; Lin, J.

2017-09-01

The hot stamping and cold die quenching process has experienced tremendous development in order to obtain shapes of structural components with great complexity in automotive applications. Prediction of the formability of a metal sheet is significant for practical applications of forming components in the automotive industry. Since microstructural evolution in an alloy at elevated temperature has a large effect on formability, continuum damage mechanics (CDM)-based material models can be used to characterise the behaviour of metals when a forming process is conducted at elevated temperatures. In this paper, two sets of unified multi-axial constitutive equations based on material’s stress states and strain states, respectively, were calibrated and used to effectively predict the thermo-mechanical response and forming limits of alloys under complex hot stamping conditions. In order to determine and calibrate the two material models, formability tests of AA6082 using a developed novel biaxial testing system were conducted at various temperatures and strain rates under hot stamping conditions. The determined unified constitutive equations from experimental data are presented in this paper. It is found that both of the stress-state based and strain-state based material models can predict the formability of AA6082 under hot stamping conditions.

Effects of oxidation in the mechanical behavior of zircaloy-4 tubes

International Nuclear Information System (INIS)

Santos, A.M.M. dos.

1981-07-01

The kinetics of oxidation of zircaloy-4 is isothermally studied utilizing discontinous gravimetric method under two different oxidizing conditions, using gaseous oxigen and steam. The total weight gain during oxidation occurs in two different way: formation of oxide and solid solution. A mechanical test for studying the effect of embrittlement due to the absorption of oxygen in small zircalloy tubes have been developed. (Author) [pt

The proximate memory mechanism underlying the survival-processing effect: richness of encoding or interactive imagery?

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Kroneisen, Meike; Erdfelder, Edgar; Buchner, Axel

2013-01-01

Nairne and collaborators showed that assessing the relevance of words in the context of an imagined survival scenario boosts memory for these words. Although this survival-processing advantage has attracted a considerable amount of research, little is known about the proximate memory mechanism mediating this effect. Recently, Kroneisen and Erdfelder (2011) argued that it is not survival processing itself that facilitates recall but rather the richness and distinctiveness of encoding that is triggered by the survival-processing task. Alternatively, however, it is also conceivable that survival processing fosters interactive imagery, a process known to improve associative learning. To test these explanations we compared relevance-rating and interactive imagery tasks for survival and control scenarios. Results show that the survival advantage replicates in the relevance-rating condition but vanishes in the interactive imagery condition. This refutes the interactive imagery explanation and corroborates the richness-of-encoding hypothesis of the survival-processing effect.

Monitoring the effect of mechanical stress on mesenchymal stem cell collagen production by multiphoton microscopy

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Chen, Wei-Liang; Chang, Chia-Cheng; Chiou, Ling-Ling; Li, Tsung-Hsien; Liu, Yuan; Lee, Hsuan-Shu; Dong, Chen-Yuan

2008-02-01

Tissue engineering is emerging as a promising method for repairing damaged tissues. Due to cartilage's common wear and injury, in vitro production of cartilage replacements have been an active area of research. Finding the optimal condition for the generation of the collagen matrix is crucial in reproducing cartilages that closely match those found in human. Using multiphoton autofluorescence and second-harmonic generation (SHG) microscopy we monitored the effect of mechanical stress on mesenchymal stem cell collagen production. Bone marrow mesenchymal stem cells in the form of pellets were cultured and periodically placed under different mechanical stress by centrifugation over a period of four weeks. The differently stressed samples were imaged several times during the four week period, and the collagen production under different mechanical stress is characterized.

Mechanisms for closing bores and releasably securing articles within the bores under longitudinal load

International Nuclear Information System (INIS)

Klahn, F.C.; Nolan, J.H.; Wills, C.

1979-01-01

This invention relates to mechanisms for closing bores of tubular passages and for releasably securing articles within the bores under longitudinal load. The system includes an axially movable latch, an actuator and locking devices. Embodiments of the invention can be used as closure mechanisms for tubular irradiation surveillance specimen assembly holders used in nuclear reactors. (UK)

Mechanisms for closing bores and releasably securing articles within the bores under longitudinal load

International Nuclear Information System (INIS)

Kalen, D.D.; Mitchem, J.W.

1979-01-01

This invention relates to mechanisms for closing bores of tubular passages and for releasably securing articles within the bores under longitudinal load. The system includes an axially movable actuator and a latch which engages the tubular opening. Embodiments of the invention can be used as closure mechanisms for tubular irradiation surveillance specimen assembly holders used in nuclear reactors. (UK)

Cyclic life of superalloy IN738LC under in-phase and out-of-phase thermo-mechanical fatigue loading

International Nuclear Information System (INIS)

Chen Hongjun; Wahi, R.P.; Wever, H.

1995-01-01

The cyclic life of IN738LC, a widely used nickel base superalloy for blades in stationary gas turbines, was investigated under thermo-mechanical fatigue loading using a temperature variation range of 1023 to 1223 K, with temperature variation rate in the range of 6 to 15 K/min. Simple thermo-mechanical cycles with linear sequences corresponding to in-phase (IP) and out-of-phase (OP) tests were performed. Both the IP and OP tests were carried out at different constant mechanical strain ranges varied between 0.8 to 2.0% and at a constant mechanical strain rate of 10 -5 s -1 . Thermo-mechanical fatigue lives under both test conditions were compared with each other and with those of isothermal LCF tests at a temperature of 1223 K. The results show that the life under thermo-mechanical fatigue is strongly dependent on the nature of the test, i.e. stress controlled or strain controlled. (orig.)

Phototransformation of membrane lipids and its role in biomembrane function change under the effect of UV-radiation

International Nuclear Information System (INIS)

Roshchupkin, D.I.; Anosov, A.K.; Murina, M.A.; Lordkipanidze, A.T.

1988-01-01

The papers devoted to the investigation of photochemical transformations of lipid under the effect of UV radiation of biological membranes are reviewed. The mechanism of peroxide photooxidation of mebrane lipid is considered. Data on the effect of antioxidants and the structure state of membranes on the process of peroxide photooxidation of lipid are presented. The problem on the role of this process under the effect of UV-radiation on blood and skin of mammals is discussed. 48 refs.; 4 refs

Nanomaterials modulate stem cell differentiation: biological interaction and underlying mechanisms.

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Wei, Min; Li, Song; Le, Weidong

2017-10-25

Stem cells are unspecialized cells that have the potential for self-renewal and differentiation into more specialized cell types. The chemical and physical properties of surrounding microenvironment contribute to the growth and differentiation of stem cells and consequently play crucial roles in the regulation of stem cells' fate. Nanomaterials hold great promise in biological and biomedical fields owing to their unique properties, such as controllable particle size, facile synthesis, large surface-to-volume ratio, tunable surface chemistry, and biocompatibility. Over the recent years, accumulating evidence has shown that nanomaterials can facilitate stem cell proliferation and differentiation, and great effort is undertaken to explore their possible modulating manners and mechanisms on stem cell differentiation. In present review, we summarize recent progress in the regulating potential of various nanomaterials on stem cell differentiation and discuss the possible cell uptake, biological interaction and underlying mechanisms.

Mechanisms Underlying HIV-Associated Noninfectious Lung Disease.

Science.gov (United States)

Presti, Rachel M; Flores, Sonia C; Palmer, Brent E; Atkinson, Jeffrey J; Lesko, Catherine R; Lau, Bryan; Fontenot, Andrew P; Roman, Jesse; McDyer, John F; Twigg, Homer L

2017-11-01

Pulmonary disease remains a primary source of morbidity and mortality in persons living with HIV (PLWH), although the advent of potent combination antiretroviral therapy has resulted in a shift from predominantly infectious to noninfectious pulmonary complications. PLWH are at high risk for COPD, pulmonary hypertension, and lung cancer even in the era of combination antiretroviral therapy. The underlying mechanisms of this are incompletely understood, but recent research in both human and animal models suggests that oxidative stress, expression of matrix metalloproteinases, and genetic instability may result in lung damage, which predisposes PLWH to these conditions. Some of the factors that drive these processes include tobacco and other substance use, direct HIV infection and expression of specific HIV proteins, inflammation, and shifts in the microbiome toward pathogenic and opportunistic organisms. Further studies are needed to understand the relative importance of these factors to the development of lung disease in PLWH. Copyright © 2017 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

Neural mechanisms underlying human consensus decision-making.

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Suzuki, Shinsuke; Adachi, Ryo; Dunne, Simon; Bossaerts, Peter; O'Doherty, John P

2015-04-22

Consensus building in a group is a hallmark of animal societies, yet little is known about its underlying computational and neural mechanisms. Here, we applied a computational framework to behavioral and fMRI data from human participants performing a consensus decision-making task with up to five other participants. We found that participants reached consensus decisions through integrating their own preferences with information about the majority group members' prior choices, as well as inferences about how much each option was stuck to by the other people. These distinct decision variables were separately encoded in distinct brain areas-the ventromedial prefrontal cortex, posterior superior temporal sulcus/temporoparietal junction, and intraparietal sulcus-and were integrated in the dorsal anterior cingulate cortex. Our findings provide support for a theoretical account in which collective decisions are made through integrating multiple types of inference about oneself, others, and environments, processed in distinct brain modules. Copyright © 2015 Elsevier Inc. All rights reserved.

Radiation Bystander Effects Mechanism

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Shokohzaman Soleymanifard

2009-06-01

Full Text Available Introduction: Radiation Induced Bystander Effect (RIBE which cause radiation effects in non-irradiated cells, has challenged the principle according to which radiation traversal through the nucleus of a cell is necessary for producing biological responses. What is the mechanism of this phenomenon? To have a better understanding of this rather ambiguous concept substantial number of original and reviewed article were carefully examined. Results: Irradiated cells release molecules which can propagate in cell environment and/or transmit through gap junction intercellular communication. These molecules can reach to non-irradiated cells and transmit bystander signals. In many investigations, it has been confirmed that these molecules are growth factors, cytokines, nitric oxide and free radicals like reactive oxygen species (ROS. Transmission of by stander signal to neighboring cells persuades them to produce secondary growth factors which in their turn cause further cell injuries. Some investigators suggest, organelles other than nucleus (mitochondria and cell membrane are the origin of these signals.  There is another opinion which suggests double strand breaks (DSB are not directly generated in bystander cells, rather they are due to smaller damage like single strand breaks which accumulate and end up to DSB. Although bystander mechanisms have not been exactly known, it can be confirmed that multiple mechanisms and various pathways are responsible for this effect. Cell type, radiation type, experimental conditions and end points identify the dominant mechanism. Conclusion: Molecules and pathways which are responsible for RIBE, also cause systemic responses to other non-irradiation stresses. So RIBE is a kind of systemic stress or innate immune responses, which are performed by cell microenvironment. Irradiated cells and their signals are components of microenvironment for creating bystander effects.

Exploring the molecular mechanisms underlying the potentiation of exogenous growth hormone on alcohol-induced fatty liver diseases in mice

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Tian Ya-ping

2010-11-01

Full Text Available Abstract Background Growth hormone (GH is an essential regulator of intrahepatic lipid metabolism by activating multiple complex hepatic signaling cascades. Here, we examined whether chronic exogenous GH administration (via gene therapy could ameliorate liver steatosis in animal models of alcoholic fatty liver disease (AFLD and explored the underlying molecular mechanisms. Methods Male C57BL/6J mice were fed either an alcohol or a control liquid diet with or without GH therapy for 6 weeks. Biochemical parameters, liver histology, oxidative stress markers, and serum high molecular weight (HMW adiponectin were measured. Quantitative real-time PCR and western blotting were also conducted to determine the underlying molecular mechanism. Results Serum HMW adiponectin levels were significantly higher in the GH1-treated control group than in the control group (3.98 ± 0.71 μg/mL vs. 3.07 ± 0.55 μg/mL; P P P P P Conclusions GH therapy had positive effects on AFLD and may offer a promising approach to prevent or treat AFLD. These beneficial effects of GH on AFLD were achieved through the activation of the hepatic adiponectin-SIRT1-AMPK and PPARα-AMPK signaling systems.

Multi-family group therapy for adolescent Internet addiction: exploring the underlying mechanisms.

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Liu, Qin-Xue; Fang, Xiao-Yi; Yan, Ni; Zhou, Zong-Kui; Yuan, Xiao-Jiao; Lan, Jing; Liu, Chao-Ying

2015-03-01

Internet addiction is one of the most common problems among adolescents and effective treatment is needed. This research aims to test the effectiveness and underlying mechanism of multi-family group therapy (MFGT) to reduce Internet addiction among adolescents. A total of 92 participants consisting of 46 adolescents with Internet addiction, aged 12-18years, and 46 their parents, aged 35-46years, were assigned to the experimental group (six-session MFGT intervention) or a waiting-list control. Structured questionnaires were administered at pre-intervention (T1), post-intervention (T2) and a three-month follow-up (T3). There was a significant difference in the decline both in the average score and proportion of adolescents with Internet addiction in MFGT group at post-intervention (MT1=3.40, MT2=2.46, pInternet use was partially explained by the satisfaction of their psychological needs and improved parent-adolescent communication and closeness. The six-session multi-family group therapy was effective in reducing Internet addiction behaviors among adolescents and could be implemented as part of routine primary care clinic services in similar populations. As family support system is critical in maintaining the intervention effect, fostering positive parent-adolescent interaction and addressing adolescents' psychological needs should be included in preventive programs for Internet addiction in the future. Copyright © 2014 Elsevier Ltd. All rights reserved.

Understanding and imitating unfamiliar actions: distinct underlying mechanisms.

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Joana C Carmo

Full Text Available The human "mirror neuron system" has been proposed to be the neural substrate that underlies understanding and, possibly, imitating actions. However, since the brain activity with mirror properties seems insufficient to provide a good description for imitation of actions outside one's own repertoire, the existence of supplementary processes has been proposed. Moreover, it is unclear whether action observation requires the same neural mechanisms as the explicit access to their meaning. The aim of this study was two-fold as we investigated whether action observation requires different processes depending on 1 whether the ultimate goal is to imitate or understand the presented actions and 2 whether the to-be-imitated actions are familiar or unfamiliar to the subject. Participants were presented with both meaningful familiar actions and meaningless unfamiliar actions that they had to either imitate or discriminate later. Event-related Potentials were used as differences in brain activity could have been masked by the use of other techniques with lower temporal resolution. In the imitation task, a sustained left frontal negativity was more pronounced for meaningless actions than for meaningful ones, starting from an early time-window. Conversely, observing unfamiliar versus familiar actions with the intention of discriminating them led to marked differences over right centro-posterior scalp regions, in both middle and latest time-windows. These findings suggest that action imitation and action understanding may be sustained by dissociable mechanisms: while imitation of unfamiliar actions activates left frontal processes, that are likely to be related to learning mechanisms, action understanding involves dedicated operations which probably require right posterior regions, consistent with their involvement in social interactions.

The mechanism underlying fast germination of tomato cultivar LA2711.

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Yang, Rongchao; Chu, Zhuannan; Zhang, Haijun; Li, Ying; Wang, Jinfang; Li, Dianbo; Weeda, Sarah; Ren, Shuxin; Ouyang, Bo; Guo, Yang-Dong

2015-09-01

Seed germination is important for early plant morphogenesis as well as abiotic stress tolerance, and is mainly controlled by the phytohormones abscisic acid (ABA) and gibberellic acid (GA). Our previous studies identified a salt-tolerant tomato cultivar, LA2711, which is also a fast-germinating genotype, compared to its salt-sensitive counterpart, ZS-5. In an effort to further clarify the mechanism underlying this phenomenon, we compared the dynamic levels of ABA and GA4, the transcript abundance of genes involved in their biosynthesis and catabolism as well as signal transduction between the two cultivars. In addition, we tested seed germination sensitivity to ABA and GAs. Our results revealed that insensitivity of seed germination to exogenous ABA and low ABA content in seeds are the physiological mechanisms conferring faster germination rates of LA2711 seeds. SlCYP707A2, which encodes an ABA catabolic enzyme, may play a decisive role in the fast germination rate of LA2711, as it showed a significantly higher level of expression in LA2711 than ZS-5 at most time points tested during germination. The current results will enable us to gain insight into the mechanism(s) regarding seed germination of tomato and the role of fast germination in stress tolerance. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Numerical analysis of the texture effect on the hydrodynamic performance of a mechanical seal

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Adjemout, M.; Brunetiere, N.; Bouyer, J.

2016-03-01

The purpose of this paper is to analyze the effect of the main geometrical characteristics of texture on the hydrodynamic lubrication of a mechanical seal. A parametric study was carried out in order to improve the performance of a mechanical seal. The numerical model used in this study solves the Reynolds equation coupled with a mass conservative model which takes into account the cavitation phenomenon. It is shown that among the six dimple shapes tested herein, namely cylinder, square, triangle, truncated cone, truncated pyramid, and spherical cap, the triangular dimples placed symmetrically with respect to their bases are more effective for enhancing the hydrodynamic performance of the mechanical seal. The effect of the area and depth ratios is studied and optimized as well. The optimized solution is able to minimize friction and leakage under a range of operating conditions.

Thermal creep effects on 20% cold worked AISI 316 mechanical properties

International Nuclear Information System (INIS)

Duncan, D.R.

1980-09-01

The effects of thermal creep on subsequent mechanical properties of 20% cold worked AISI 316 pressurized tubes were investigated. Specimens were subjected to temperatures of 811 to 977 0 K and stresses of 86 MPa to 276 MPa. This resulted in strains up to 1.3%. Subsequent mechanical property tests included load change stress rupture tests (original test pressure increased or decreased), uniaxial tensile tests, and temperature ramp burst tests. Load change stress rupture tests were consistent with predictions from isobaric tests, and thus, consistent with the linear life fraction rule. Tests with large stress increases and tests at 866 0 K displayed a tendency for earlier than predicted failure. Tensile and temperature ramp burst tests had only slight effects on material properties (property changes were attributed to thermal recovery). The test results showed that, under the conditions of investigation, dislocation structure recovery was the most significant effect of creep. 9 figures, 5 tables

EndoBarrier gastrointestinal liner. Delineation of underlying mechanisms and clinical effects.

Science.gov (United States)

Rohde, Ulrich

2016-11-01

Bariatric surgery (e.g. Roux-en-Y gastric bypass (RYGB)) has proven the most effective way of achieving sustainable weight losses and remission of type 2 diabetes (T2D). Studies indicate that the effectiveness of RYGB is mediated by an altered gastrointestinal tract anatomy, which in particular favours release of the gut incretin hormone glucagon-like peptide-1 (GLP-1). The EndoBarrier gastrointestinal liner or duodenal-jejunal bypass sleeve (DJBS) is an endoscopic deployable minimally invasive and fully reversible technique designed to mimic the bypass component of the RYGB. Not only GLP-1 is released when nutrients enter the gastrointestinal tract. Cholecystokinin (CCK), secreted from duodenal I cells, elicits gallbladder emptying. Traditionally, bile acids are thought of as essential elements for fat absorption. However, growing evidence suggests that bile acids have additional effects in metabolism. Thus, bile acids appear to increase GLP-1 secretion via activation of the TGR5 receptor on the intestinal L cell. Recently FXR receptors were postulated to contribute to GLP-1 secretion too. Furthermore, metformin has been shown to increase circulating GLP-1 levels but although the exact mechanism is not fully elucidated it may involve metformin-induced inhibition of bile acid reuptake from the small intestines. Small-sized studies reported varying degrees of weight loss and, in some, improvement of glucose metabolism. Therefore, the objectives of this thesis were to collect existing information on the DJBS in order to evaluate clinical efficacy and safety (study I and II). Furthermore, since the endocrine impact of the DJBS is not fully elucidated, and DJBS is expected to mimic RYGB, we investigated postprandial metabolic changes following 26 weeks of DJBS treatment in ten obese subjects with normal glucose tolerance (NGT) and nine matched patients with T2D (study III). Finally, we studied the single and combined effects of CCK induced gallbladder emptying and

Antiatherogenic effects of n-3 fatty acids - evidence and mechanisms

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Antonella Zampolli

2006-12-01

Full Text Available N-3 (omega-3 (polyunsaturated fatty acids are thought to display a variety of beneficial effects for human health. Clues to the occurrence of cardiovascular protective effects have been, however, the spur for the first biomedical interest in these compounds, and are the best documented. Historically, the epidemiologic association between dietary consumption of n-3 fatty acids and cardiovascular protection was first suggested by Bang and Dyerberg, who identified the high consumption of fish, and therefore, of fish oil-derived n-3 fatty acids, as the likely explanation for the strikingly low rate of coronary heart disease events reported in the Inuit population. Since their initial reports, research has proceeded in parallel to provide further evidence for their cardioprotection and to understand underlying mechanisms. Decreased atherogenesis is currently thought to be a part of the cardiovascular protection by n-3 fatty acids. This article summarizes the evidence for such a claim and the mechanisms putatively involved. (Heart International 2006; 3-4: 141-54

Effects of different mechanized soil fertilization methods on corn nutrient accumulation and yield

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Shi, Qingwen; Bai, Chunming; Wang, Huixin; Wu, Di; Song, Qiaobo; Dong, Zengqi; Gao, Depeng; Dong, Qiping; Cheng, Xin; Zhang, Yahao; Mu, Jiahui; Chen, Qinghong; Liao, Wenqing; Qu, Tianru; Zhang, Chunling; Zhang, Xinyu; Liu, Yifei; Han, Xiaori

2017-05-01

Aim: Experiments for mechanized corn soil fertilization were conducted in Faku demonstration zone. On this basis, we studied effects on corn nutrient accumulation and yield traits at brown soil regions due to different mechanized soil fertilization measures. We also evaluated and optimized the regulation effects of mechanized soil fertilization for the purpose of crop yield increase and production efficiency improvement. Method: Based on the survey of soil background value in the demonstration zone, we collected plant samples during different corn growth periods to determine and make statistical analysis. Conclusions: Decomposed cow dung, when under mechanical broadcasting, was able to remarkably increase nitrogen and potassium accumulation content of corns at their ripe stage. Crushed stalk returning combined with deep tillage would remarkably increase phosphorus accumulation content of corn plants. When compared with top application, crushed stalk returning combined with deep tillage would remarkably increase corn thousand kernel weight (TKW). Mechanized broadcasting of granular organic fertilizer and crushed stalk returning combined with deep tillage, when compared with surface application, were able to boost corn yield in the in the demonstration zone.

Asymmetric migration of human keratinocytes under mechanical stretch and cocultured fibroblasts in a wound repair model.

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Dongyuan Lü

Full Text Available Keratinocyte migration during re-epithelization is crucial in wound healing under biochemical and biomechanical microenvironment. However, little is known about the underlying mechanisms whereby mechanical tension and cocultured fibroblasts or keratinocytes modulate the migration of keratinocytes or fibroblasts. Here we applied a tensile device together with a modified transwell assay to determine the lateral and transmembrane migration dynamics of human HaCaT keratinocytes or HF fibroblasts. A novel pattern of asymmetric migration was observed for keratinocytes when they were cocultured with non-contact fibroblasts, i.e., the accumulative distance of HaCaT cells was significantly higher when moving away from HF cells or migrating from down to up cross the membrane than that when moving close to HF cells or when migrating from up to down, whereas HF migration was symmetric. This asymmetric migration was mainly regulated by EGF derived from fibroblasts, but not transforming growth factor α or β1 production. Mechanical stretch subjected to fibroblasts fostered keratinocyte asymmetric migration by increasing EGF secretion, while no role of mechanical stretch was found for EGF secretion by keratinocytes. These results provided a new insight into understanding the regulating mechanisms of two- or three-dimensional migration of keratinocytes or fibroblasts along or across dermis and epidermis under biomechanical microenvironment.

Differential effects of ethanol on feline rage and predatory attack behavior: an underlying neural mechanism.

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Schubert, K; Shaikh, M B; Han, Y; Poherecky, L; Siegel, A

1996-08-01

Previous studies have shown that, at certain dose levels, ethanol can exert a powerful, facilitatory effect on aggressive behavior in both animals and humans. In the cat, however, it was discovered that ethanol differentially alters two forms of aggression that are common to this species. Defensive rage behavior is significantly enhanced, whereas predatory attack behavior is suppressed by ethanol administration. One possible mechanism governing alcohol's potentiation of defensive rage behavior is that it acts on the descending pathway from the medial hypothalamus to the midbrain periaqueductal gray (PAG)-an essential pathway for the expression of defensive rage behavior that uses excitatory amino acids as a neurotransmitter. This hypothesis is supported by the finding that the excitatory effects of alcohol on defensive rage behavior are blocked by administration of the N-methyl-D-aspartate antagonist alpha-2-amino-7-phosphoheptanoic acid (AP-7) when microinjected into the periaqueductal gray, a primary neuronal target of descending fibers from the medial hypothalamus that mediate the expression of defensive rage behavior. Thus, the present study establishes for the first time a specific component of the neural circuit for defensive rage behavior over which the potentiating effects of ethanol are mediated.

Exact solution for stresses/displacements in a multilayered hollow cylinder under thermo-mechanical loading

International Nuclear Information System (INIS)

Yeo, W.H.; Purbolaksono, J.; Aliabadi, M.H.; Ramesh, S.; Liew, H.L.

2017-01-01

In this study, a new analytical solution by the recursive method for evaluating stresses/displacements in multilayered hollow cylinder under thermo-mechanical loading was developed. The results for temperature distribution, displacements and stresses obtained by using the proposed solution were shown to be in good agreement with the FEM results. The proposed analytical solution was also found to produce more accurate results than those by the analytical solution reported in literature. - Highlights: • A new analytical solution for evaluating stresses in multilayered hollow cylinder under thermo-mechanical loading. • A simple computational procedure using a recursive method. • A promising technique for evaluating the operating axial and hoop stresses in pressurized composite vessels.

Radiation-thermal degradation of PE and PVC: Mechanism of synergism and dose rate effects

Science.gov (United States)

Clough, Roger L.; Gillen, Kenneth T.

Polyethylene insulation and polyvinyl chloride jacketing materials that had been in use in a nuclear application were recently found to be substantially deteriorated. The damage had occurred under conditions where both the total estimated dose (about 2.5 Mrad) and the operating temperatures (about 43°C average) seemed relatively moderate. These results prompted us to initiate a program to study polyvinyl chloride and polyethylene degradation under conditions of combined γ-radiation and elevated temperature environments. A number of interesting aging effects were observed, including 1) a striking synergism between radiation and temperature and 2) strong dose-rate dependent effects which occur over a wide range of dose rates. The aging effects are explained in terms of a chain branching degradation mechanism involving thermally induced breakdown of peroxides which are formed in reactions initiated by the radiation. Evidence for this mechanism is derived from infrared spectra, from sequential radiation-elevated temperature experiments including experiments under inert atmosphere, from activation energy estimates and from a new technique involving treatment of intact samples with PH 3 for chemical reduction of peroxides. The results of our studies raise significant doubts about the utility of earlier compilations which purportedly serve as radiation life expectancy guides by indicating "tolerable radiation doses" for a variety of polymers.

LCT-coil design: Mechanical interaction between composite winding and steel casing under various test conditions

International Nuclear Information System (INIS)

Dolensky, B.; Messemer, G.; Zehlein, H.; Erb, J.

1981-01-01

Finite element computations for the structural design of the large superconducting toroidal field coil contributed by EURATOM to the Large Coil Test Facility (LCTF) at ORNL, USA were performed at KfK, using the ASKA code. The layout of the coil must consider different types of requirements: firstly, an optimal D-shaped contour minimizing circumferential stress gradients under normal operation in the toroidal arrangement must be defined. Secondly, the three-dimensional real design effects due to the actual support conditions, manufacturing tolerances etc. must be mastered for different basic operational and failure load cases. And, thirdly, the design must stand a single coil qualification test in the TOSKA-facility at KfK, Karlsruhe, FRG, before it is plugged into the LCTF. The emphasis of the paper is three-pronged according to these requirements: i) the 3D magnetic body forces as well as the underlying magnetic fields as computed by the HEDO-code are described. ii) The mechanical interaction between casing and winding as given elsewhere in terms of high stress regions, gaps, slide movements and contact forces for various load cases representing the LCTF test conditions is illustrated here by a juxtaposition of the operational deformations and stresses within the LCTF and the TOSKA. iii) Particular effects like the restraint imposed by a corset-type reinforcement of the coil in the TOSKA test facility to limit the breathing deformation are parametrically studied. Moreover, the possibilities to derive scaling laws which make essential results transferable to larger coils by extracting a 1D mechanical response from the 3D finite element model is also demonstrated. (orig./GG)

The effects and mechanism of action of methane on ileal motor function.

Science.gov (United States)

Park, Y M; Lee, Y J; Hussain, Z; Lee, Y H; Park, H

2017-09-01

Methane has been associated with constipation-predominant irritable bowel syndrome, slowing intestinal transit time by augmenting contractile activity. However, the precise mechanism underlying this effect remains unclear. Therefore, we investigated the mechanisms underlying the effect of methane on contractile activity, and whether such effects are mediated by nerve impulses or muscular contraction. We connected guinea pig ileal muscle strips to a force/tension transducer and measured amplitudes of contraction in response to electrical field stimulation (EFS; 1, 2, 8, 16 Hz) following methane infusion in the presence of tetradotoxin (TTX), atropine, guanethidine, or GR 113808. We then performed calcium imaging using Oregon Green 488 BAPTA-1 AM in order to visualize changes in calcium fluorescence in response to EFS following methane infusion in the presence of TTX, atropine, or a high K + solution. Methane significantly increased amplitudes of contraction (PMethane-induced increases in amplitude were inhibited when lower-frequency (1, 2 Hz) EFS was applied following atropine infusion (PMethane significantly increased calcium fluorescence, while this increase was attenuated following atropine infusion (Pmethane infusion. The actions of methane on the intestine are influenced by the cholinergic pathway of the enteric nervous system. Our findings support the classification of methane as a gasotransmitter. © 2017 John Wiley & Sons Ltd.

Cellular mechanisms underlying the inhibitory effect of flufenamic acid on chloride secretion in human intestinal epithelial cells

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Pawin Pongkorpsakol

2017-06-01

Full Text Available Intestinal Cl− secretion is involved in the pathogenesis of secretory diarrheas including cholera. We recently demonstrated that flufenamic acid (FFA suppressed Vibrio cholerae El Tor variant-induced intestinal fluid secretion via mechanisms involving AMPK activation and NF-κB-suppression. The present study aimed to investigate the effect of FFA on transepithelial Cl− secretion in human intestinal epithelial (T84 cells. FFA inhibited cAMP-dependent Cl− secretion in T84 cell monolayers with IC50 of ∼8 μM. Other fenamate drugs including tolfenamic acid, meclofenamic acid and mefenamic acid exhibited the same effect albeit with lower potency. FFA also inhibited activities of CFTR, a cAMP-activated apical Cl− channel, and KCNQ1/KCNE3, a cAMP-activated basolateral K+ channel. Mechanisms of CFTR inhibition by FFA did not involve activation of its negative regulators. Interestingly, FFA inhibited Ca2+-dependent Cl− secretion with IC50 of ∼10 μM. FFA inhibited activities of Ca2+-activated Cl− channels and KCa3.1, a Ca2+-activated basolateral K+ channels, but had no effect on activities of Na+–K+–Cl− cotransporters and Na+–K+ ATPases. These results indicate that FFA inhibits both cAMP and Ca2+-dependent Cl− secretion by suppressing activities of both apical Cl− channels and basolateral K+ channels. FFA and other fenamate drugs may be useful in the treatment of secretory diarrheas.

Effect of Thermal Environment on the Mechanical Behaviors of Building Marble

Directory of Open Access Journals (Sweden)

Haijian Su

2018-01-01

Full Text Available High temperature and thermal environment can influence the mechanical properties of building materials worked in the civil engineering, for example, concrete, building rock, and steel. This paper examines standard cylindrical building marble specimens (Φ50 × 100 mm that were treated with high temperatures in two different thermal environments: vacuum (VE and airiness (AE. Uniaxial compression tests were also carried out on those specimens after heat treatment to study the effect that the thermal environment has on mechanical behaviors. With an increase in temperature, the mechanical behavior of marble in this study indicates a critical temperature of 600°C. Both the peak stress and elasticity modulus were larger for the VE than they were for the AE. The thermal environment has an obvious influence on the mechanical properties, especially at temperatures of 450∼750°C. The failure mode of marble specimens under uniaxial compression is mainly affected by the thermal environment at 600°C.

Sertraline-induced reproductive toxicity in male rats: evaluation of possible underlying mechanisms

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Ozlem Atli

2017-01-01

Full Text Available This study was conducted to clarify the toxic effects of sertraline (SRT on the reproductive system of male rats and to elucidate the underlying mechanisms. Rats were treated orally with SRT at doses of 5, 10, and 20 mg kg−1 for 28 consecutive days. At the end of the treatment period, sperm concentration, sperm motility, and sperm morphology were investigated by computer-assisted sperm analysis system whereas sperm DNA damage was detected by comet assay. The oxidative status of the testes was investigated, and a histopathological examination was conducted. Serum testosterone, follicle-stimulating hormone (FSH, and luteinizing hormone (LH levels were measured to determine the effects of SRT on the spermatogenesis process. One-way ANOVA, post-hoc Dunnett′s T3 test for the sperm comet assay, and post-hoc Tukey′s test for the others were performed for statistical analysis. The results showed that SRT caused an increase in sperm DNA damage and induced histopathological lesions in all groups treated with SRT. There was abnormal sperm morphology and increased malondialdehyde (MDA in the 10 mg kg−1 treatment group. More dramatic changes were observed in the 20 mg kg−1 treatment group. Decreased sperm count was accompanied by a significant increase in abnormal sperm morphology, DNA damage, and degeneration in cellular-tubular structures. Serum LH and testosterone levels were elevated in the 20 mg kg−1 treatment group. Decreased glutathione (GSH and increased MDA were signs of enhanced oxidative stress (OS. In conclusion, SRT induced testicular toxicity in a dose-dependent manner and OS is suggested as a crucial mechanism.

Evanescent radiation, quantum mechanics and the Casimir effect

Science.gov (United States)

Schatten, Kenneth H.

1989-01-01

An attempt to bridge the gap between classical and quantum mechanics and to explain the Casimir effect is presented. The general nature of chaotic motion is discussed from two points of view: the first uses catastrophe theory and strange attractors to describe the deterministic view of this motion; the underlying framework for chaos in these classical dynamic systems is their extreme sensitivity to initial conditions. The second interpretation refers to randomness associated with probabilistic dynamics, as for Brownian motion. The present approach to understanding evanescent radiation and its relation to the Casimir effect corresponds to the first interpretation, whereas stochastic electrodynamics corresponds to the second viewpoint. The nonlinear behavior of the electromagnetic field is also studied. This well-understood behavior is utilized to examine the motions of two orbiting charges and shows a closeness between the classical behavior and the quantum uncertainty principle. The evanescent radiation is used to help explain the Casimir effect.

An integrative view of mechanisms underlying generalized spike-and-wave epileptic seizures and its implication on optimal therapeutic treatments.

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Boyuan Yan

Full Text Available Many types of epileptic seizures are characterized by generalized spike-and-wave discharges. In the past, notable effort has been devoted to understanding seizure dynamics and various hypotheses have been proposed to explain the underlying mechanisms. In this paper, by taking an integrative view of the underlying mechanisms, we demonstrate that epileptic seizures can be generated by many different combinations of synaptic strengths and intrinsic membrane properties. This integrative view has important medical implications: the specific state of a patient characterized by a set of biophysical characteristics ultimately determines the optimal therapeutic treatment. Through the same view, we further demonstrate the potentiation effect of rational polypharmacy in the treatment of epilepsy and provide a new angle to resolve the debate on polypharmacy. Our results underscore the need for personalized medicine and demonstrate that computer modeling and simulation may play an important role in assisting the clinicians in selecting the optimal treatment on an individual basis.

Mechanisms underlying apoptosis-inducing effects of Kaempferol in HT-29 human colon cancer cells.

Science.gov (United States)

Lee, Hyun Sook; Cho, Han Jin; Yu, Rina; Lee, Ki Won; Chun, Hyang Sook; Park, Jung Han Yoon

2014-02-17

We previously noted that kaempferol, a flavonol present in vegetables and fruits, reduced cell cycle progression of HT-29 cells. To examine whether kaempferol induces apoptosis of HT-29 cells and to explore the underlying molecular mechanisms, cells were treated with various concentrations (0-60 μmol/L) of kaempferol and analyzed by Hoechst staining, Annexin V staining, JC-1 labeling of the mitochondria, immunoprecipitation, in vitro kinase assays, Western blot analyses, and caspase-8 assays. Kaempferol increased chromatin condensation, DNA fragmentation and the number of early apoptotic cells in HT-29 cells in a dose-dependent manner. In addition, kaempferol increased the levels of cleaved caspase-9, caspase-3 and caspase-7 as well as those of cleaved poly (ADP-ribose) polymerase. Moreover, it increased mitochondrial membrane permeability and cytosolic cytochrome c concentrations. Further, kaempferol decreased the levels of Bcl-xL proteins, but increased those of Bik. It also induced a reduction in Akt activation and Akt activity and an increase in mitochondrial Bad. Additionally, kaempferol increased the levels of membrane-bound FAS ligand, decreased those of uncleaved caspase-8 and intact Bid and increased caspase-8 activity. These results indicate that kaempferol induces the apoptosis of HT-29 cells via events associated with the activation of cell surface death receptors and the mitochondrial pathway.

Stress State Analysis and Failure Mechanisms of Masonry Columns Reinforced with FRP under Concentric Compressive Load

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Jiří Witzany

2016-04-01

Full Text Available The strengthening and stabilization of damaged compressed masonry columns with composites based on fabrics of high-strength fibers and epoxy resin, or polymer-modified cement mixtures, belongs to novel, partially non-invasive and reversible progressive methods. The stabilizing and reinforcing effect of these fabrics significantly applies to masonry structures under concentric compressive loading whose failure mechanism is characterized by the appearance and development of vertical tensile cracks accompanied by an increase in horizontal masonry strain. During the appearance of micro and hairline cracks (10−3 to 10−1 mm, the effect of non-pre-stressed wrapping composite is very small. The favorable effect of passive wrapping is only intensively manifested after the appearance of cracks (10−1 mm and bigger at higher loading levels. In the case of “optimum” reinforcement of a masonry column, the experimental research showed an increase in vertical displacements δy (up to 247%, horizontal displacements δx (up to 742% and ultimate load-bearing capacity (up to 136% compared to the values reached in unreinforced masonry columns. In the case of masonry structures in which no intensive “bed joint filler–masonry unit” interaction occurs, e.g., in regular coursed masonry with little differences in the mechanical characteristics of masonry units and the binder, the reinforcing effect of the fabric applies only partially.

First-principles investigation of mechanical and electronic properties of LaAg5 Laves phase under pressure

Institute of Scientific and Technical Information of China (English)

高恩强; 黄福祥; 陈志谦; 王兰兰; 张照超

2016-01-01

The effects of applied pressure on the structural, mechanical, and electronic properties of LaAg5 compound were investi-gated employing the first-principles method based on the density functional theory. The mechanical results demonstrated that bulk modulus, shear modulus and Young’s modulus presented the linearly increasing dependences on the external pressure; theB/G and Poisson’s ratio indicated that LaAg5 compound was a ductile material with central forces in interatomic under pressure from 0 to 40 GPa; the universal anisotropic index was performed to investigate the elastic anisotropic of LaAg5. Additionally, the pressure de-pendence of the density of states and Mulliken charge were also discussed. The bonding characterization in LaAg5 was composed of metallic, covalent and ionic. The metallic component was derived from free-electron transferring from Ag-s and Ag-d to Ag-p, and from La-s to La-d. The ionic component was due to the charge movement from La to Ag. The covalent was owing to Ag-p-La-d bonding hybridization and Ag-s-Ag-p in the Ag atomic chains. The covalent and ionic bonds were stronger under pressure but there was no significant change in metallic nature.

Mechanisms Underlying the Antidepressant Response of Acupuncture via PKA/CREB Signaling Pathway.

Science.gov (United States)

Jiang, Huili; Zhang, Xuhui; Wang, Yu; Zhang, Huimin; Li, Jing; Yang, Xinjing; Zhao, Bingcong; Zhang, Chuntao; Yu, Miao; Xu, Mingmin; Yu, Qiuyun; Liang, Xingchen; Li, Xiang; Shi, Peng; Bao, Tuya

2017-01-01

Protein kinase A (PKA)/cAMP response element-binding (CREB) protein signaling pathway, contributing to impaired neurogenesis parallel to depressive-like behaviors, has been identified as the crucial factor involved in the antidepressant response of acupuncture. However, the molecular mechanisms associated with antidepressant response of acupuncture, neurogenesis, and depressive-like behaviors ameliorating remain unexplored. The objective was to identify the mechanisms underlying the antidepressant response of acupuncture through PKA signaling pathway in depression rats by employing the PKA signaling pathway inhibitor H89 in in vivo experiments. Our results indicated that the expression of hippocampal PKA- α and p-CREB was significantly downregulated by chronic unpredicted mild stress (CUMS) procedures. Importantly, acupuncture reversed the downregulation of PKA- α and p-CREB. The expression of PKA- α was upregulated by fluoxetine, but not p-CREB. No significant difference was found between Acu and FLX groups on the expression of PKA- α and p-CREB. Interestingly, H89 inhibited the effects of acupuncture or fluoxetine on upregulating the expression of p-CREB, but not PKA- α . There was no significant difference in expression of CREB among the groups. Conclusively, our findings further support the hypothesis that acupuncture could ameliorate depressive-like behaviors by regulating PKA/CREB signaling pathway, which might be mainly mediated by regulating the phosphorylation level of CREB.

New developments on the neurobiological and pharmaco-genetic mechanisms underlying internet and videogame addiction.

Science.gov (United States)

Weinstein, Aviv; Lejoyeux, Michel

2015-03-01

There is emerging evidence that the psychobiological mechanisms underlying behavioral addictions such as internet and videogame addiction resemble those of addiction for substances of abuse. Review of brain imaging, treatment and genetic studies on videogame and internet addiction. Literature search of published articles between 2009 and 2013 in Pubmed using "internet addiction" and "videogame addiction" as the search word. Twenty-nine studies have been selected and evaluated under the criteria of brain imaging, treatment, and genetics. Brain imaging studies of the resting state have shown that long-term internet game playing affected brain regions responsible for reward, impulse control and sensory-motor coordination. Brain activation studies have shown that videogame playing involved changes in reward and loss of control and that gaming pictures have activated regions similarly to those activated by cue-exposure to drugs. Structural studies have shown alterations in the volume of the ventral striatum possible as result of changes in reward. Furthermore, videogame playing was associated with dopamine release similar in magnitude to those of drugs of abuse and that there were faulty inhibitory control and reward mechanisms videogame addicted individuals. Finally, treatment studies using fMRI have shown reduction in craving for videogames and reduced associated brain activity. Videogame playing may be supported by similar neural mechanisms underlying drug abuse. Similar to drug and alcohol abuse, internet addiction results in sub-sensitivity of dopamine reward mechanisms. Given the fact that this research is in its early stage it is premature to conclude that internet addiction is equivalent to substance addictions. © American Academy of Addiction Psychiatry.

Ablation characteristics and reaction mechanism of insulation materials under slag deposition condition

Science.gov (United States)

Guan, Yiwen; Li, Jiang; Liu, Yang

2017-07-01

Current understanding of the physical and chemical processes involved in the ablation of insulation materials by highly aluminized solid propellants is limited. The study on the heat transfer and ablation principle of ethylene propylene diene monomer (EPDM) materials under slag deposition condition is essential for future design or modification of large solid rocket motors (SRMs) for launch application. In this paper, the alumina liquid flow pattern and the deposition principle in full-scale SRM engines are discussed. The interaction mechanism between the alumina droplets and the wall are analyzed. Then, an experimental method was developed to simulate the insulation material ablation under slag deposition condition. Experimental study was conducted based on a laboratory-scale device. Meanwhile, from the analysis of the cross-sectional morphology and chemical composition of the charring layer after ablation, the reaction mechanism of the charring layer under deposition condition was discussed, and the main reaction equation was derived. The numerical simulation and experimental results show the following. (i) The alumina droplet flow in the deposition section of the laboratory-scale device is similar to that of a full-scale SRM. (ii) The charring layer of the EPDM insulator displays a porous tight/loose structure under high-temperature slag deposition condition. (iii) A seven-step carbothermal reduction in the alumina is derived and established under high-pressure and high-temperature environment in the SRM combustion chamber. (iv) The analysis using thermodynamic software indicates that the reaction of the alumina and charring layer initially forms Al4C3 during the operation. Then, Al element and Al2OC compound are subsequently produced with the reduction in the release of gas CO as well with continuous environmental heating.

Peer influence: neural mechanisms underlying in-group conformity.

Science.gov (United States)

Stallen, Mirre; Smidts, Ale; Sanfey, Alan G

2013-01-01

People often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participants completed a perceptual decision-making task while undergoing fMRI, during which they were exposed to the judgments of both in-group and out-group members. Our data suggest that conformity to the in-group is mediated by both positive affect as well as the cognitive capacity of perspective taking. Examining the processes that drive in-group conformity by utilizing a basic decision-making paradigm combined with neuroimaging methods provides important insights into the potential mechanisms of conformity. These results may provide an integral step in developing more effective campaigns using group conformity as a tool for behavioral change.

Molecular Mechanisms Underlying the Epileptogenesis and Seizure Progression in Tuberous Sclerosis Complex 1 Deficient Mouse Models

Science.gov (United States)

2016-10-01

dysregulation in epileptogenesis in the developing brain? 2) What are the molecular mechanisms downstream of mTOR hyperactivation that trigger epileptogenesis...underlying epilepsy. Hopefully, a knowledge of these mechanisms will aid in a rational development of therapies. KEYWORDS Tuberous Sclerosis, Epilepsy

Underlying mechanisms of transient luminous events: a review

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V. V. Surkov

2012-08-01

Full Text Available Transient luminous events (TLEs occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloud-to-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency and ELF (extremely low frequency phenomena associated with sprites.

Distinct toxicological characteristics and mechanisms of Hg2+ and MeHg in Tetrahymena under low concentration exposure.

Science.gov (United States)

Liu, Cheng-Bin; Qu, Guang-Bo; Cao, Meng-Xi; Liang, Yong; Hu, Li-Gang; Shi, Jian-Bo; Cai, Yong; Jiang, Gui-Bin

2017-12-01

Inorganic divalent mercury complexes (Hg 2+ ) and monomethylmercury complexes (MeHg) are the main mercury species in aquatic systems and their toxicity to aquatic organisms is of great concern. Tetrahymena is a type of unicellular eukaryotic protozoa located at the bottom of food chain that plays a fundamental role in the biomagnification of mercury. In this work, the dynamic accumulation properties, toxicological characteristics and mechanisms of Hg 2+ and MeHg in five Tetrahymena species were evaluated in detail. The results showed that both Hg 2+ and MeHg were ingested and exhibited inhibitory effects on the proliferation or survival of Tetrahymena species. However, the ingestion rate of MeHg was significantly higher than that of Hg 2+ . The mechanisms responsible for the toxicity of MeHg and Hg 2+ were different, although both chemicals altered mitochondrial membrane potential (MMP). MeHg disrupted the integrity of membranes while Hg 2+ had detrimental effects on Tetrahymena as a result of the increased generation of reactive oxygen species (ROS). In addition, the five Tetrahymena species showed different capacities in accumulating Hg 2+ and MeHg, with T. corlissi exhibiting the highest accumulations. The study also found significant growth-promoting effect on T. corlissi under low concentration exposure (0.003 and 0.01μg Hg/mL (15 and 50nM)), suggesting different effect and mechanism that should be more closely examined when assessing the bioaccumulation and toxicity of mercury in aquatic ecosystems. Copyright © 2017 Elsevier B.V. All rights reserved.

Antihypertensive and Antihypertrophic Effects of Acupuncture at PC6 Acupoints in Spontaneously Hypertensive Rats and the Underlying Mechanisms

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Juan-Juan Xin

2017-01-01

Full Text Available The aim of this work is to investigate the effect of electroacupuncture (EA at PC6 on the hypertension and myocardial hypertrophy in spontaneously hypertensive rats (SHRs. Thirty SHRs were randomized into model, SHR + EA, and SHR + Sham EA group with WKY rats as normal control. EA was applied once a day in 8 consecutive weeks. The blood pressure (BP, cardiac function, and hypertrophy as well as the underlying mechanisms were investigated. After EA treatment, the enhanced BP in SHR + EA group was significantly lower compared to both the period before EA and model group. Echocardiographic, morphological studies showed that the enhanced left ventricular anterior and posterior wall end-diastolic (LVAWd and LVPWd thickness, diameters and cross-sectional area (CSA of cardiac myocyte, as well as the ratio of heart weight to body weight (HW/BW, were markedly diminished in SHR + EA group, while the reduced left ventricular ejection fraction, left ventricular short axis fraction shortening, and E/A ratio were significantly ameliorated. The levels of Angiotensin-converting enzyme (ACE and Angiotensin II Type 1 and 2 receptors (AT1R, AT2R in SHRs were also significantly attenuated by EA. The results suggest that EA at bilateral PC6 could arrest the hypertension development and ameliorate the cardiac hypertrophy and malfunction in SHRs, which might be mediated by the regulation of ACE, AT1R, and AT2R.

Mechanical stress analysis for a fuel rod under normal operating conditions

International Nuclear Information System (INIS)

Pino, Eddy S.; Giovedi, Claudia; Serra, Andre da Silva; Abe, Alfredo Y.

2013-01-01

Nuclear reactor fuel elements consist mainly in a system of a nuclear fuel encapsulated by a cladding material subject to high fluxes of energetic neutrons, high operating temperatures, pressure systems, thermal gradients, heat fluxes and with chemical compatibility with the reactor coolant. The design of a nuclear reactor requires, among a set of activities, the evaluation of the structural integrity of the fuel rod submitted to different loads acting on the fuel rod and the specific properties (dimensions and mechanical and thermal properties) of the cladding material and coolant, including thermal and pressure gradients produced inside the rod due to the fuel burnup. In this work were evaluated the structural mechanical stresses of a fuel rod using stainless steel as cladding material and UO 2 with a low degree of enrichment as fuel pellet on a PWR (pressurized water reactor) under normal operating conditions. In this sense, tangential, radial and axial stress on internal and external cladding surfaces considering the orientations of 0 deg, 90 deg and 180 deg were considered. The obtained values were compared with the limit values for stress to the studied material. From the obtained results, it was possible to conclude that, under the expected normal reactor operation conditions, the integrity of the fuel rod can be maintained. (author)

Uncovering the underlying physical mechanisms of biological systems via quantification of landscape and flux

International Nuclear Information System (INIS)

Xu Li; Chu Xiakun; Yan Zhiqiang; Zheng Xiliang; Zhang Kun; Zhang Feng; Yan Han; Wu Wei; Wang Jin

2016-01-01

In this review, we explore the physical mechanisms of biological processes such as protein folding and recognition, ligand binding, and systems biology, including cell cycle, stem cell, cancer, evolution, ecology, and neural networks. Our approach is based on the landscape and flux theory for nonequilibrium dynamical systems. This theory provides a unifying principle and foundation for investigating the underlying mechanisms and physical quantification of biological systems. (topical review)

The mechanisms underlying the hypolipidaemic effects of Grifola frondosa in the liver of rats

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Yinrun Ding

2016-08-01

Full Text Available The present study investigated the hypolipidaemic effects of Grifola frondosa and its regulation mechanism involved in lipid metabolism in liver of rats fed a high-cholesterol diet. The body weights and serum lipid levels of control rats, of hyperlipidaemic rats and of hyperlipidaemic rats treated with oral Grifola frondosa were determined. mRNA expression and concentration of key lipid metabolism enzymes were investigated. Serum cholesterol, triacylglycerol and low-density lipoprotein cholesterol levels were markedly decreased in hyperlipidaemic rats treated with Grifola frondosa compared with untreated hyperlipidaemic rats. mRNA expression of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR, acyl-coenzyme A: cholesterol acyltransferase (ACAT2, apolipoprotein B (ApoB, fatty acid synthase (FAS and acetyl-CoA carboxylase (ACC1 were significantly down-regulated, while expression of cholesterol 7-alpha-hydroxylase (CYP7A1 was significantly up-regulated in the livers of treated rats compared with untreated hyperlipidaemic rats. The concentrations of these enzymes also paralleled the observed changes in mRNA expression. Two-dimensional polyacrylamide gel electrophoresis (2-DE and Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS were used to identify twenty proteins differentially expressed in livers of rats treated with Grifola frondosa compared with untreated hyperlipidemic rats. Of these twenty proteins, seven proteins were down-regulated and thirteen proteins were up-regulated. These findings indicate that the hypolipidaemic effects of Grifola frondosa reflected its modulation of key enzymes involved in cholesterol and triacylglycerol biosynthesis, absorption and catabolic pathways. Grifola frondosa may exert anti-atherosclerotic effects by inhibiting LDL oxidation through down-regulation and up-regulating proteins expression in the liver of rats. Therefore, Grifola frondosa may produce both hypolipidaemic

Transformational Leadership and Organizational Citizenship Behavior: A Meta-Analytic Test of Underlying Mechanisms.

Science.gov (United States)

Nohe, Christoph; Hertel, Guido

2017-01-01

Based on social exchange theory, we examined and contrasted attitudinal mediators (affective organizational commitment, job satisfaction) and relational mediators (trust in leader, leader-member exchange; LMX) of the positive relationship between transformational leadership and organizational citizenship behavior (OCB). Hypotheses were tested using meta-analytic path models with correlations from published meta-analyses (761 samples with 227,419 individuals overall). When testing single-mediator models, results supported our expectations that each of the mediators explained the relationship between transformational leadership and OCB. When testing a multi-mediator model, LMX was the strongest mediator. When testing a model with a latent attitudinal mechanism and a latent relational mechanism, the relational mechanism was the stronger mediator of the relationship between transformational leadership and OCB. Our findings help to better understand the underlying mechanisms of the relationship between transformational leadership and OCB.

Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

DEFF Research Database (Denmark)

Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf

2010-01-01

This study investigated the mechanisms underlying epithelium-derived hyperpolarizing factor (EpDHF)-type relaxation in rat bronchioles. Immunohistochemistry was performed, and rat bronchioles and pulmonary arteries were mounted in microvascular myographs for functional studies. An opener of small...... (SK(Ca)) and intermediate (IK(Ca))-conductance calcium-activated potassium channels, NS309 (6,7-dichloro-1H-indole-2,3-dione 3-oxime) was used to induce EpDHF-type relaxation. IK(Ca) and SK(Ca)3 positive immunoreactions were observed mainly in the epithelium and endothelium of bronchioles and arteries......, respectively. In 5-hydroxytryptamine (1 microM)-contracted bronchioles (828 +/- 20 microm, n = 84) and U46619 (0.03 microM)-contracted arteries (720 +/- 24 microm, n = 68), NS309 (0.001-10 microM) induced concentration-dependent relaxations that were reduced by epithelium/endothelium removal and by blocking IK...

Microstructure, mechanical property and metal release of As-SLM CoCrW alloy under different solution treatment conditions.

Science.gov (United States)

Lu, Yanjin; Wu, Songquan; Gan, Yiliang; Zhang, Shuyuan; Guo, Sai; Lin, Junjie; Lin, Jinxin

2015-03-01

In the study, the microstructure, mechanical property and metal release behavior of selective laser melted CoCrW alloys under different solution treatment conditions were systemically investigated to assess their potential use in orthopedic implants. The effects of the solution treatment on the microstructure, mechanical properties and metal release were systematically studied by OM, SEM, XRD, tensile test, and ICP-AES, respectively. The XRD indicated that during the solution treatment the alloy underwent the transformation of γ-fcc to ε-hcp phase; the ε-hcp phase nearly dominated in the alloy when treated at 1200°C following the water quenching; the results from OM, SEM showed that the microstructural change was occurred under different solution treatments; solution at 1150°C with furnace cooling contributed to the formation of larger precipitates at the grain boundary regions, while the size and number of the precipitates was decreased as heated above 1100°C with the water quenching; moreover, the diamond-like structure was invisible at higher solution temperature over 1150°C following water quenching; compared with the furnace cooling, the alloy quenched by water showed excellent mechanical properties and low amount of metal release; as the alloy heated at 1200°C, the mechanical properties of the alloy reached their optimum combination at UTS=1113.6MPa, 0.2%YS=639.5MPa, and E%=20.1%, whilst showed the lower total quantity of metal release. It is suggested that a proper solution treatment is an efficient strategy for improving the mechanical properties and corrosion resistance of As-SLM CoCrW alloy that show acceptable tensile ductility. Copyright © 2015 Elsevier Ltd. All rights reserved.

Imitation in Newborn Infants: Exploring the Range of Gestures Imitated and the Underlying Mechanisms.

Science.gov (United States)

Meltzoff, Andrew N.; Moore, M. Keith

1989-01-01

Evaluated psychological mechanisms underlying imitation of facial actions in 40 newborn infants. Results showed imitation of head movement and a tongue-protrusion gesture. Subjects imitated from memory after displays had stopped. (RJC)

Deformation mechanisms in Ti/TiN multilayer under compressive loading

International Nuclear Information System (INIS)

Yang, Wei; Ayoub, Georges; Salehinia, Iman; Mansoor, Bilal; Zbib, Hussein

2017-01-01

The promising mechanical, physical and chemical properties of nano-scale metal/ceramic multilayers (MCMs) are of high interest for extreme environment applications. Understanding the plastic deformation mechanisms and the variables affecting those properties is therefore essential. The interface characteristics and the plastic deformation mechanisms under compressive loading in a Ti/TiN multilayer with a semi-coherent interface are numerically investigated. The interface structure of the Ti/TiN interface and the interface misfit dislocation were characterized using molecular dynamic simulations combined with atomically informed Frank-Bilby method. Three possible atomic stacking interface structures are identified according to the crystallographic analysis of the interface. Upon relaxation, large interface areas are occupied with the energetically stable configuration. Furthermore, the higher energy stacking are transformed into misfit dislocations or dislocation nodes. The molecular dynamic compressive stress strain response of the Ti/TiN multilayers exhibited three distinctive peaks. The first peak was generated by the dislocation dissociation of perfect dislocation into pairs of partials dislocation around extended nodes region at the interface. Upon further compression the second peak, identified as the first yielding, resulted from the activation of pyramidal slip planes in the Ti layer. Finally, a third peak identified as the second yielding, occurred when dislocation nucleated/transmitted in/into the TiN layer.

Mechanics of Failure Mechanisms in Structures

CERN Document Server

Carlson, R L; Craig, J I

2012-01-01

This book focuses on the mechanisms and underlying mechanics of failure in various classes of materials such as metallic, ceramic, polymeric, composite and bio-material.  Topics include tensile and compressive fracture, crack initiation and growth, fatigue and creep rupture in metallic materials, matrix cracking and delamination and environmental degradation in polymeric composites, failure of bio-materials such as prosthetic heart valves and prosthetic hip joints, failure of ceramics and ceramic matrix composites, failure of metallic matrix composites, static and dynamic buckling failure, dynamic excitations and creep buckling failure in structural systems. Chapters are devoted to failure mechanisms that are characteristic of each of the materials.  The work also provides the basic elements of fracture mechanics and studies in detail several niche topics such as the effects of toughness gradients, variable amplitude loading effects in fatigue, small fatigue cracks, and creep induced brittleness. Furthe...

Softening mechanisms of the AISI 410 martensitic stainless steel under hot torsion simulation

Energy Technology Data Exchange (ETDEWEB)

Oliveira, Thiago Santana de; Silva, Eden Santos; Rodrigues, Samuel Filgueiras; Nascimento, Carmem Celia Francisco; Leal, Valdemar Silva; Reis, Gedeon Silva, E-mail: samuel.filgueiras@ifma.edu.br [Instituto Federal do Maranhao (PPGEM/IFMA), Sao Luis, MA (Brazil)

2017-03-15

This study investigated the softening mechanisms of the AISI 410 martensitic stainless steel during torsion simulation under isothermal continuous in the temperature range of 900 to 1150 °C and strain rates of 0.1 to 5.0s{sup -1}. In the first part of the curves, before the peak, the results show that the critical (ε-c) and peak (ε-p) strains are elevated for higher strain rate and lower temperatures contributing for higher strain hardening rate (h). Moreover, this indicated that dynamic recrystallization (DRX) and dynamic recovery (DRV) are not effective in this region. After the peak, the reductions in stresses are associated to the different DRX/DRV competitions. For lower temperatures and higher strain rates there is a delay in the DRX while the DRV is acting predominantly (with low Avrami exponent (n) and high t{sub 0.5}). The steady state was reached after large strains showing DRX grains, formation of retained austenite and the presence of chromium carbide (Cr{sub 23}C{sub 6}) and ferrite δ at the martensitic grain boundaries. These contribute for impairing the toughness and ductility on the material. The constitutive equations at the peak strain indicated changes in the deformation mechanism, with variable strain rate sensitivity (m), which affected the final microstructure. (author)

Meta-analysis of the effects of cognitive-behavioral therapy on the core eating disorder maintaining mechanisms: implications for mechanisms of therapeutic change.

Science.gov (United States)

Linardon, Jake

2018-03-01

The original and enhanced cognitive model of eating disorders proposes that cognitive-behavioral therapy (CBT) "works" through modifying dietary restraint and dysfunctional attitudes towards shape and weight. However, evidence supporting the validity of this model is limited. This meta-analysis examined whether CBT can effectively modify these proposed maintaining mechanisms. Randomized controlled trials that compared CBT to control conditions or non-CBT interventions, and reported dietary restraint and shape and weight concern outcomes were searched. Twenty-nine trials were included. CBT was superior to control conditions in reducing shape (g=0.53) and weight (g=0.63) concerns, and dietary restraint (g=0.36). These effects occurred across all diagnoses and treatment formats. Improvements in shape and weight concerns and restraint were also greater in CBT than non-CBT interventions (g's=0.25, 0.24, 0.31, respectively) at post-treatment and follow-up. The magnitude of improvement in binge/purge symptoms was related to the magnitude of improvement in these maintaining mechanisms. Findings demonstrate that CBT has a specific effect in targeting the eating disorder maintaining mechanisms, and offers support to the underlying cognitive model. If changes in these variables during treatment are shown to be causal mechanisms, then these findings show that CBT, relative to non-CBT interventions, is better able to modify these mechanisms.

An agent-based simulation of power generation company behavior in electricity markets under different market-clearing mechanisms

International Nuclear Information System (INIS)

Aliabadi, Danial Esmaeili; Kaya, Murat; Şahin, Güvenç

2017-01-01

Deregulated electricity markets are expected to provide affordable electricity for consumers through promoting competition. Yet, the results do not always fulfill the expectations. The regulator's market-clearing mechanism is a strategic choice that may affect the level of competition in the market. We conceive of the market-clearing mechanism as composed of two components: pricing rules and rationing policies. We investigate the strategic behavior of power generation companies under different market-clearing mechanisms using an agent-based simulation model which integrates a game-theoretical understanding of the auction mechanism in the electricity market and generation companies' learning mechanism. Results of our simulation experiments are presented using various case studies representing different market settings. The market in simulations is observed to converge to a Nash equilibrium of the stage game or to a similar state under most parameter combinations. Compared to pay-as-bid pricing, bid prices are closer to marginal costs on average under uniform pricing while GenCos' total profit is also higher. The random rationing policy of the ISO turns out to be more successful in achieving lower bid prices and lower GenCo profits. In minimizing GenCos' total profit, a combination of pay-as-bid pricing rule and random rationing policy is observed to be the most promising. - Highlights: • An agent-based simulation of generation company behavior in electricity markets is developed. • Learning dynamics of companies is modeled with an extended Q-learning algorithm. • Different market clearing mechanisms of the regulator are compared. • Convergence to Nash equilibria is analyzed under different cases. • The level of competition in the market is studied.

Failure mechanisms of aluminium foams under compressive loads

Directory of Open Access Journals (Sweden)

Sáenz, E.

2000-08-01

Full Text Available The purpose of this paper is the investigation of the major failure mechanisms of aluminium foams, which were obtained by powder metallurgy route, under compressive loads. The study was focused on two commonly aluminium alloys AlMg1Si or A 6061 and AlSi12. Due to the fact that the failure mechanisms strongly depend on the density and the macrostructural properties of the material, the mechanical properties always have to be correlated to the structural properties. Therefore, macrostructural investigations were used as a basis to establish the correlation between structural and mechanical properties. This was done with a commercially available image analysis system. The average cell size, the cell size distribution and the cell density (number of cells/area were obtained. In order to evaluate the influence of foaming direction on the cell morphology, some cross sections parallel to the foaming direction were prepared. For the characterization of the mechanical compression properties the compressive or upper yield strength (UYS, the densification strain (eD, the energy absorption (Ea and the efficiency (Eff were obtained. Furthermore, the failure behavior of the samples was in-situ observed with a digital video camera and continuously recorded during the test.

El objetivo de este estudio es investigar los principales mecanismos de fallo de espumas de aluminio sometidas a cargas de compresión. Las espumas metálicas fueron obtenidas mediante el proceso pulvimetalúrgico, utilizándose como materia prima dos aleaciones comerciales AlMg1Si o A 6061 y AlSi12. Debido a que los mecanismos de fallo en este tipo de materiales depende fuertemente de la densidad y las características macroestructurales del material, en este estudio se busca correlacionar las propiedades mecánicas con estas características. La macroestructura se caracterizó mediante análisis de imagen. El tamaño de celda promedio, la distribución de tamaño y la densidad de

Mechanical wounding under field conditions: A potential tool to increase the allelopathic inhibitory effect of cover crops on weeds?

NARCIS (Netherlands)

Kruidhof, H.M.; Dam, van N.M.; Ritz, C.; Lotz, L.A.P.; Kropff, M.J.; Bastiaans, L.

2014-01-01

To increase the inhibitory effect of soil-incorporated cover crop residues on germination and early growth of weeds, the allelochemical content of the cover crop at the time of soil incorporation should be maximal. We investigated whether mechanical damaging in spring induced the production of

Research on energy conversion mechanism of a screw centrifugal pump under the water

International Nuclear Information System (INIS)

Quan, H; Li, R N; Han, W; Cheng, X R; Shen, Z J; Su, Q M

2013-01-01

In order to research screw centrifugal pump impeller power capability and energy conversion mechanism, we used Navier-Stokes equation and standard k-ε equation turbulence model on the basis of the Euler equations to carry out screw centrifugal pump internal flow numerical simulation. This was explored by simulating specific design conditions; the medium is water, variation of speed and pressure of flow filed under the action of the impeller, and the screw centrifugal impeller shroud line and wheel line segment take monitoring sites. The monitoring points are between dynamic head and static head change to analyze the energy conversion capability along the impeller corners of screw centrifugal pump. The results show that the energy of fluid of the screw centrifugal pump is provided by spiral segment, the spiral segment in front of the impeller has played a multi-level role, it has significant reference value to research the energy conversion mechanism of screw centrifugal pump under solid-liquid two phase

Classical treatments of quantum mechanical effects in collisions of weakly bound complexes

International Nuclear Information System (INIS)

Lopez, Jose G.; McCoy, Anne B.

2005-01-01

Classical and quantum simulations of Ne + Ar 2 collision dynamics are performed in order to investigate where quantum mechanical effects are most important and where classical simulations provide good descriptions of the dynamics. It is found that when Ar 2 is in a low-lying vibrational state, the differences between the results of quantum and quasiclassical simulations are profound. However, excellent agreement between the results of the quantum and classical simulations can be achieved when the initial conditions for the classical trajectories are sampled from the quantum phase space distribution given by the Wigner function. These effects are largest when collisions occur under constrained geometries or when Ar 2 is in its ground vibrational state. The results of this work suggest that sampling the initial conditions using the Wigner function provides a straightforward way to incorporate the most important quantum mechanical effects in simulations of collisions involving very cold weakly bound complexes

CISM course on mechanical behaviour of soils under environmentally induced cyclic loads

CERN Document Server

Wood, David; Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

2012-01-01

The book gives a comprehensive description of the mechanical response of soils (granular and cohesive materials) under cyclic loading. It provides the geotechnical engineer with the theoretical and analytical tools necessary for the evaluation of settlements developng with time under cyclic, einvironmentally idncued loads (such as wave motion, wind actions, water table level variation) and their consequences for the serviceability and durability of structures such as the shallow or deep foundations used in offshore engineering, caisson beakwaters, ballast and airport pavements and also to interpret monitoring data, obtained from both natural and artificial slopes and earth embankments, for the purposes of risk assessment and mitigation.

Alternative splicing and expression of the insulin-like growth factor (IGF-1) gene in osteoblasts under mechanical stretch

Institute of Scientific and Technical Information of China (English)

XIAN Chengyu; WANG Yuanliang; ZHANG Bingbing; TANG Liling; PAN Jun; LUO Yanfeng; JIANG Peng; LI Dajun

2006-01-01

Insulin-like growth factor 1 (IGF-1) promotes osteoblasts differentiation and bone formation,and its expression is induced by mechanical stretch,thus IGF-1 has been considered an effector molecule that links mechanical stimulation and local tissue responses. In this study, a mechanical stretching device was designed to apply physiological level static or cyclic stretching stimulation to osteoblasts.Different isoforms of IGF-1 mRNA were amplified by RT-PCR from the cells using respective primers and these amplified products were sequenced. An isoform of IGF-1 splicing product was found to be selectively produced by osteoblasts under stretching stimulation. This IGF-1 isoform had identical sequence with the mechano growth factor (MGF) which was originally identified in muscle cells. Regulations of the expression of the liver-type IGF (L.IGF-1) and MGF in osteoblasts under stretch stimulation were further studied using semi-quantitative RT-PCR.Stretch stimulation was found to promot the expression of IGF-1 (L.IGF-1 and MGF), and for both isoforms expression was more effectively stimulated by cyclic stretch than static stretch. MGF was detected only in osteoblasts subjected to mechanical stretch,suggesting MGF was a stretch sensitive growth factor.Expression of MGF peaked earlier than that of L.IGF-1, which was similar to their regulation in muscie and suggested similar roles of MGF and L.IGF-1in bone as in muscle cells. The functions of MGF and L.IGF-1 in osteoblasts shall be established by further experimental studies.

Mechanisms of microstructure formation under the influence of ultrasonic vibrations

Science.gov (United States)

Rakita, Milan

Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found that, under experimental conditions used in this work, cavitation-induced nucleation is the major contributor to the grain refinement. Ultrasonication at minimal supercoolings is expected to give maximal grain refinement. Dendrite fragmentation has not shown to be a significant contributor to the grain refinement. Dendrite fragmentation is maximal if done by bubbles that come in contact with the solidifying phase, or that are created there. Alloys/solutions with long solidification interval, or wide mushy zone, are expected to exhibit more dendrite fragmentation. Bubbles are recognized as a crucial feature in ultrasonication. Their size distribution in the liquid phase prior to ultrasonication dictates the cavitation threshold and intensity of cavitation. For the first time, radiation pressure has been recognized as potentially significant factor in grain refinement. In the experimental setup used in this study, acoustic pressure at the main (driving) frequency is not substantial to cause significant fragmentation, and only dendrites close to the sonotrode were fragmented. However, application of ultrasound with frequencies that are several times higher than the current industrial practice could substantially increase dendrite fragmentation. Appearance of fractional harmonics has also been recognized

MDMA-assisted psychotherapy for PTSD: Are memory reconsolidation and fear extinction underlying mechanisms?

Science.gov (United States)

Feduccia, Allison A; Mithoefer, Michael C

2018-06-08

MDMA-assisted psychotherapy for treatment of PTSD has recently progressed to Phase 3 clinical trials and received Breakthrough Therapy designation by the FDA. MDMA used as an adjunct during psychotherapy sessions has demonstrated effectiveness and acceptable safety in reducing PTSD symptoms in Phase 2 trials, with durable remission of PTSD diagnosis in 68% of participants. The underlying psychological and neurological mechanisms for the robust effects in mitigating PTSD are being investigated in animal models and in studies of healthy volunteers. This review explores the potential role of memory reconsolidation and fear extinction during MDMA-assisted psychotherapy. MDMA enhances release of monoamines (serotonin, norepinephrine, dopamine), hormones (oxytocin, cortisol), and other downstream signaling molecules (BDNF) to dynamically modulate emotional memory circuits. By reducing activation in brain regions implicated in the expression of fear- and anxiety-related behaviors, namely the amygdala and insula, and increasing connectivity between the amygdala and hippocampus, MDMA may allow for reprocessing of traumatic memories and emotional engagement with therapeutic processes. Based on the pharmacology of MDMA and the available translational literature of memory reconsolidation, fear learning, and PTSD, this review suggests a neurobiological rationale to explain, at least in part, the large effect sizes demonstrated for MDMA in treating PTSD. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Getting the phenotypes right: an essential ingredient for understanding aetiological mechanisms underlying persistent violence and developing effective treatments

Directory of Open Access Journals (Sweden)

Sheilagh Hodgins

2009-11-01

Full Text Available In order to reduce societal levels of violence, it is essential to advance understanding of the neurobiological mechanisms involved in initiating and maintaining individual patterns of physical aggression. New technologies such as Magnetic Resonance Imagining and analyses of DNA provide tools for identifying these mechanisms. The reliability and validity of the results of studies using these tools depend not only on aspects of the technology, but also on the methodological rigour with which the studies are conducted, particularly with respect to characterizing the phenotype. The present article discusses five challenges confronting scientists who aim to advance understanding of the neurobiological mechanisms associated with persistent violence. These challenges are: (1 to develop evidence-based hypotheses and to design studies that test alternate hypotheses; (2 to recruit samples that are homogeneous with respect to variables that may be linked to neurobiological mechanisms underpinning violent behaviour; (3 to use reliable and valid measures in order to fully characterize participants so that the external validity of the results is evident; (4 to restrict the range of age of participants so as not to confuse developmental change with group differences; and (5 to take account of sex. Our goal is to contribute to elevating methodological standards in this new field of research and to thereby improve the validity of results and move closer to finding effective ways to reduce violence

Mechanical measurement of hydrogen bonded host-guest systems under non-equilibrium, near-physiological conditions.

Science.gov (United States)

Naranjo, Teresa; Cerrón, Fernando; Nieto-Ortega, Belén; Latorre, Alfonso; Somoza, Álvaro; Ibarra, Borja; Pérez, Emilio M

2017-09-01

Decades after the birth of supramolecular chemistry, there are many techniques to measure noncovalent interactions, such as hydrogen bonding, under equilibrium conditions. As ensembles of molecules rapidly lose coherence, we cannot extrapolate bulk data to single-molecule events under non-equilibrium conditions, more relevant to the dynamics of biological systems. We present a new method that exploits the high force resolution of optical tweezers to measure at the single molecule level the mechanical strength of a hydrogen bonded host-guest pair out of equilibrium and under near-physiological conditions. We utilize a DNA reporter to unambiguously isolate single binding events. The Hamilton receptor-cyanuric acid host-guest system is used as a test bed. The force required to dissociate the host-guest system is ∼17 pN and increases with the pulling rate as expected for a system under non-equilibrium conditions. Blocking one of the hydrogen bonding sites results in a significant decrease of the force-to-break by 1-2 pN, pointing out the ability of the method to resolve subtle changes in the mechanical strength of the binding due to the individual H-bonding components. We believe the method will prove to be a versatile tool to address important questions in supramolecular chemistry.

Polarization effects in molecular mechanical force fields

Energy Technology Data Exchange (ETDEWEB)

Cieplak, Piotr [Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92120 (United States); Dupradeau, Francois-Yves [UMR CNRS 6219-Faculte de Pharmacie, Universite de Picardie Jules Verne, 1 rue des Louvels, F-80037 Amiens (France); Duan, Yong [Genome Center and Department of Applied Science, University of California, Davis, One Shields Avenue, Davis, CA 95616 (United States); Wang Junmei, E-mail: pcieplak@burnham.or [Department of Pharmacology, University of Texas Southwestern Medical Center, 6001 Forest Park Boulevard, ND9.136, Dallas, TX 75390-9050 (United States)

2009-08-19

The focus here is on incorporating electronic polarization into classical molecular mechanical force fields used for macromolecular simulations. First, we briefly examine currently used molecular mechanical force fields and the current status of intermolecular forces as viewed by quantum mechanical approaches. Next, we demonstrate how some components of quantum mechanical energy are effectively incorporated into classical molecular mechanical force fields. Finally, we assess the modeling methods of one such energy component-polarization energy-and present an overview of polarizable force fields and their current applications. Incorporating polarization effects into current force fields paves the way to developing potentially more accurate, though more complex, parameterizations that can be used for more realistic molecular simulations. (topical review)

The Effect of mechanical resistive loading on optimal respiratory signals and breathing patterns under added dead space and CO2 breathing

Directory of Open Access Journals (Sweden)

Lin Shyan-Lung

2016-01-01

Full Text Available Current study aims to investigate how the respiratory resistive loading affects the behaviour of the optimal chemical-mechanical respiratory control model, the respiratory signals and breathing pattern are optimized under external dead space loading and CO2 breathing. The respiratory control was modelled to include a neuro-muscular drive as the control output to derive the waveshapes of instantaneous airflow, lung volume profiles, and breathing pattern, including total/alveolar ventilation, breathing frequency, tidal volume, inspiratory/expiratory duration, duty cycle, and arterial CO2 pressure. The simulations were performed under various respiratory resistive loads, including no load, inspiratory resistive load, expiratory resistive load, and continuous resistive load. The dead space measurement was described with Gray’s derivation, and simulation results were studied and compared with experimental findings.

Mechanisms of the anomalous Pockels effect in bulk water

Science.gov (United States)

Yukita, Shunpei; Suzuki, Yuto; Shiokawa, Naoyuki; Kobayashi, Takayoshi; Tokunaga, Eiji

2018-04-01

The "anomalous" Pockels effect is a phenomenon that a light beam passing between two electrodes in an aqueous electrolyte solution is deflected by an AC voltage applied between the electrodes: the deflection angle is proportional to the voltage such that the incident beam alternately changes its direction. This phenomenon, the Pockels effect in bulk water, apparently contradicts what is believed in nonlinear optics, i.e., macroscopic inversion symmetry should be broken for the second-order nonlinear optical effect to occur such as the first-order electro-optic effect, i.e., the Pockels effect. To clarify the underlying mechanism, the dependence of the effect on the electrode material is investigated to find that the Pockels coefficient with Pt electrodes is two orders of magnitude smaller than with indium tin oxide (ITO) electrodes. It is experimentally confirmed that the Pockels effect of interfacial water in the electric double layer (EDL) on these electrodes shows an electrode dependence similar to the effect in bulk water while the effects depend on the frequency of the AC voltage such that the interfacial signal decreases with frequency but the bulk signal increases with frequency up to 221 Hz. These experimental results lead to a conclusion that the beam deflection is caused by the refractive index gradient in the bulk water region, which is formed transiently by the Pockels effect of interfacial water in the EDL when an AC electric field is applied. The refractive index gradient is caused by the diffuse layer spreading into the bulk region to work as a breaking factor of inversion symmetry of bulk water due to its charge-biased ionic distribution. This mechanism does not contradict the principle of nonlinear optics.

Determination of mechanical damage from wells under oil and gas flow condition; Determinacao de dano mecanico em pocos sob condicao de escoamento de oleo e gas

Energy Technology Data Exchange (ETDEWEB)

Marques, J. B.D. [PETROBRAS S.A., Rio de Janeiro, RJ (Brazil); Trevisan, O. V. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil)

2008-07-01

The well bore effect is one of the most difficult variables obtained from well test analysis under two-phase condition. The presence of the gas in a well inserted in reservoir, which operates under gas drive solution, hinders the development of the analytical model to determine the mechanical damage. It is one of the reasons of the using the single phase well test analysis methodologies become suitable to the multiphase cases. The determination of the well bore effect is justified; therefore it is possible to work over in the well in order to determinate the real potential productive. The main objective of this work is to reevaluate a method of determination of the mechanical damage gotten from a well test under two-phase condition. In this work a simplified model of reservoir simulation is constructed in a commercial simulator in order to validate the methodology. The refinement of the blocks near to the well adopted in the simulation is a good representation of the well mechanical damage which occurs in a homogeneous reservoir. The types of well test analysis used in this work are two: drawdown and buildup test. The results gotten for this methodology, as will be shown, are excellent quality and the model of simulation presented here can be used for other analytical methods studies in order to determinate the mechanical damage or other variable of the reservoir. (author)

Mathematical Modeling of Interacting Glucose-Sensing Mechanisms and Electrical Activity Underlying Glucagon-Like Peptide 1 Secretion.

Directory of Open Access Journals (Sweden)

Michela Riz

2015-12-01

Full Text Available Intestinal L-cells sense glucose and other nutrients, and in response release glucagon-like peptide 1 (GLP-1, peptide YY and other hormones with anti-diabetic and weight-reducing effects. The stimulus-secretion pathway in L-cells is still poorly understood, although it is known that GLP-1 secreting cells use sodium-glucose co-transporters (SGLT and ATP-sensitive K+-channels (K(ATP-channels to sense intestinal glucose levels. Electrical activity then transduces glucose sensing to Ca2+-stimulated exocytosis. This particular glucose-sensing arrangement with glucose triggering both a depolarizing SGLT current as well as leading to closure of the hyperpolarizing K(ATP current is of more general interest for our understanding of glucose-sensing cells. To dissect the interactions of these two glucose-sensing mechanisms, we build a mathematical model of electrical activity underlying GLP-1 secretion. Two sets of model parameters are presented: one set represents primary mouse colonic L-cells; the other set is based on data from the GLP-1 secreting GLUTag cell line. The model is then used to obtain insight into the differences in glucose-sensing between primary L-cells and GLUTag cells. Our results illuminate how the two glucose-sensing mechanisms interact, and suggest that the depolarizing effect of SGLT currents is modulated by K(ATP-channel activity. Based on our simulations, we propose that primary L-cells encode the glucose signal as changes in action potential amplitude, whereas GLUTag cells rely mainly on frequency modulation. The model should be useful for further basic, pharmacological and theoretical investigations of the cellular signals underlying endogenous GLP-1 and peptide YY release.

Effects of voids on thermal-mechanical reliability of lead-free solder joints