Sample records for underlying mechanism responsible

  1. Neurochemical mechanisms underlying responses to psychostimulants

    Energy Technology Data Exchange (ETDEWEB)

    Volkow, N.D.; Fowler, J.S.; Hitzemann, R.; Wang, G.J. [Brookhaven National Lab., Upton, NY (United States)]|[State Univ. of New York, Stony Brook, NY (United States)


    This study employed positron emission tomography (PET) to investigate biochemical and metabolic characteristics of the brain of individuals which could put them at risk for drug addiction. It takes advantage of the normal variability between individuals in response to psychoactive drugs to investigate relation between mental state, brain neurochemistry and metabolism and the behavioral response to drugs. We discuss its use to assess if there is an association between mental state and dompaminergic reactivity in response to the psychostimulant drug methylphenidate (MP). Changes in synaptic dopamine induced by MP were evaluated with PET and [11C]raclopride, a D{sub 2} receptor radioligand that is sensitive to endogenous dopamine. Methylpphenidate significantly decreased striatal [11C]raclopride binding. The study showed a correlation between the magnitude of the dopamine-induced changes by methylphenidate, and the mental state of the subjects. Subjects reporting high levels of anxiety and restlessness at baseline had larger changes in MP-induced dopamine changes than those that did not. Further investigations on the relation between an individual`s response to a drug and his/her mental state and personality as well as his neurochemical brain composition may enable to understand better differences in drug addiction vulnerability.

  2. Mechanisms Underlying the Antidepressant Response and Treatment Resistance

    Directory of Open Access Journals (Sweden)

    Marjorie Rose Levinstein


    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.

  3. Nonlinear mechanical response of supercooled melts under applied forces (United States)

    Cárdenas, Heliana; Frahsa, Fabian; Fritschi, Sebastian; Nicolas, Alexandre; Papenkort, Simon; Voigtmann, Thomas; Fuchs, Matthias


    We review recent progress on a microscopic theoretical approach to describe the nonlinear response of glass-forming colloidal dispersions under strong external forcing leading to homogeneous and inhomogeneous flow. Using mode-coupling theory (MCT), constitutive equations for the rheology of viscoelastic shear-thinning fluids are obtained. These are, in suitably simplified form, employed in continuum fluid dynamics, solved by a hybrid-Lattice Boltzmann (LB) algorithm that was developed to deal with long-lasting memory effects. The combined microscopic theoretical and mesoscopic numerical approach captures a number of phenomena far from equilibrium, including the yielding of metastable states, process-dependent mechanical properties, and inhomogeneous pressure-driven channel flow.

  4. Mechanisms and pharmacogenetic signals underlying thiazide diuretics blood pressure response. (United States)

    Shahin, Mohamed H; Johnson, Julie A


    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.

  5. Emotional responses to music: the need to consider underlying mechanisms. (United States)

    Juslin, Patrik N; Västfjäll, Daniel


    Research indicates that people value music primarily because of the emotions it evokes. Yet, the notion of musical emotions remains controversial, and researchers have so far been unable to offer a satisfactory account of such emotions. We argue that the study of musical emotions has suffered from a neglect of underlying mechanisms. Specifically, researchers have studied musical emotions without regard to how they were evoked, or have assumed that the emotions must be based on the "default" mechanism for emotion induction, a cognitive appraisal. Here, we present a novel theoretical framework featuring six additional mechanisms through which music listening may induce emotions: (1) brain stem reflexes, (2) evaluative conditioning, (3) emotional contagion, (4) visual imagery, (5) episodic memory, and (6) musical expectancy. We propose that these mechanisms differ regarding such characteristics as their information focus, ontogenetic development, key brain regions, cultural impact, induction speed, degree of volitional influence, modularity, and dependence on musical structure. By synthesizing theory and findings from different domains, we are able to provide the first set of hypotheses that can help researchers to distinguish among the mechanisms. We show that failure to control for the underlying mechanism may lead to inconsistent or non-interpretable findings. Thus, we argue that the new framework may guide future research and help to resolve previous disagreements in the field. We conclude that music evokes emotions through mechanisms that are not unique to music, and that the study of musical emotions could benefit the emotion field as a whole by providing novel paradigms for emotion induction.

  6. Passive and active response of bacteria under mechanical compression (United States)

    Garces, Renata; Miller, Samantha; Schmidt, Christoph F.; Byophysics Team; Institute of Medical Sciences Collaboration

    Bacteria display simple but fascinating cellular structures and geometries. Their shapes are the result of the interplay between osmotic pressure and cell wall construction. Typically, bacteria maintain a high difference of osmotic pressure (on the order of 1 atm) to the environment. This pressure difference (turgor pressure) is supported by the cell envelope, a composite of lipid membranes and a rigid cell wall. The response of the cell envelope to mechanical perturbations such as geometrical confinements is important for the cells survival. Another key property of bacteria is the ability to regulate turgor pressure after abrupt changes of external osmotic conditions. This response relies on the activity of mechanosensitive (MS) channels: membrane proteins that release solutes in response to excessive stress in the cell envelope. We here present experimental data on the mechanical response of the cell envelope and on turgor regulation of bacteria subjected to compressive forces. We indent living cells with micron-sized beads attached to the cantilever of an atomic force microscope (AFM). This approach ensures global deformation of the cell. We show that such mechanical loading is sufficient to gate mechanosensitive channels in isosmotic conditions.

  7. Mechanical response of human female breast skin under uniaxial stretching. (United States)

    Kumaraswamy, N; Khatam, Hamed; Reece, Gregory P; Fingeret, Michelle C; Markey, Mia K; Ravi-Chandar, Krishnaswamy


    Skin is a complex material covering the entire surface of the human body. Studying the mechanical properties of skin to calibrate a constitutive model is of great importance to many applications such as plastic or cosmetic surgery and treatment of skin-based diseases like decubitus ulcers. The main objective of the present study was to identify and calibrate an appropriate material constitutive model for skin and establish certain universal properties that are independent of patient-specific variability. We performed uniaxial tests performed on breast skin specimens freshly harvested during mastectomy. Two different constitutive models - one phenomenological and another microstructurally inspired - were used to interpret the mechanical responses observed in the experiments. Remarkably, we found that the model parameters that characterize dependence on previous maximum stretch (or preconditioning) exhibited specimen-independent universal behavior. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Phosphorene under strain:electronic, mechanical and piezoelectric responses (United States)

    Drissi, L. B.; Sadki, S.; Sadki, K.


    Structural, electronic, elastic and piezoelectric properties of pure phosphorene under in-plane strain are investigated using first-principles calculations based on density functional theory. The two critical yielding points are determined along armchair and zigzag directions. It is shown that the buckling, the band gap and the charge transfer can be controlled under strains. A semiconductor to metallic transition is observed in metastable region. Polar plots of Young's modulus, Poisson ratio, sound velocities and Debye temperature exhibit evident anisotropic feature of phosphorene and indicate auxetic behavior for some angles θ. Our calculations show also that phosphorene has both in-plane and out-of-plane piezoelectric responses comparable to known 2D materials. The findings of this work reveal the great potential of pure phosphorene in nanomechanical applications.

  9. Mechanical response of collagen molecule under hydrostatic compression

    International Nuclear Information System (INIS)

    Saini, Karanvir; Kumar, Navin


    Proteins like collagen are the basic building blocks of various body tissues (soft and hard). Collagen molecules find their presence in the skeletal system of the body where they bear mechanical loads from different directions, either individually or along with hydroxy-apatite crystals. Therefore, it is very important to understand the mechanical behavior of the collagen molecule which is subjected to multi-axial state of loading. The estimation of strains of collagen molecule along different directions resulting from the changes in hydrostatic pressure magnitude, can provide us new insights into its mechanical behavior. In the present work, full atomistic simulations have been used to study global (volumetric) as well as local (along different directions) mechanical properties of the hydrated collagen molecule which is subjected to different hydrostatic pressure magnitudes. To estimate the local mechanical properties, the strains of collagen molecule along its longitudinal and transverse directions have been acquired at different hydrostatic pressure magnitudes. In spite of non-homogeneous distribution of atoms within the collagen molecule, the calculated values of local mechanical properties have been found to carry the same order of magnitude along the longitudinal and transverse directions. It has been demonstrated that the values of global mechanical properties like compressibility, bulk modulus, etc. as well as local mechanical properties like linear compressibility, linear elastic modulus, etc. are functions of magnitudes of applied hydrostatic pressures. The mechanical characteristics of collagen molecule based on the atomistic model have also been compared with that of the continuum model in the present work. The comparison showed up orthotropic material behavior for the collagen molecule. The information on collagen molecule provided in the present study can be very helpful in designing the future bio-materials.

  10. Dynamic Response and Failure Mechanism of Brittle Rocks Under Combined Compression-Shear Loading Experiments (United States)

    Xu, Yuan; Dai, Feng


    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.

  11. Mechanisms underlying the nociceptive responses induced by platelet-activating factor (PAF) in the rat paw. (United States)

    Marotta, Denise M; Costa, Robson; Motta, Emerson M; Fernandes, Elizabeth S; Medeiros, Rodrigo; Quintão, Nara L M; Campos, Maria M; Calixto, João B


    Platelet-activating factor (PAF) is an inflammatory mediator widely known to exert relevant pathophysiological functions. However, the relevance of PAF in nociception has received much less attention. Herein, we have investigated the mechanisms underlying PAF-induced spontaneous nociception and mechanical hypersensitivity in the rat paw. PAF injection (1- 30 nmol/paw) resulted in a dose-related overt nociception, whilst only the dose of 10 nmol/ paw produced a significant and time-related mechanical hypersensitivity. Local coinjection of PAF antagonist WEB2086 significantly inhibited both spontaneous nociception and mechanical hypersensitivity. Moreover, the coinjection of the natural IL-1beta receptor antagonist (IRA) notably prevented both PAF-induced nociceptive responses, whilst these responses were not altered by anti-TNFalpha coinjection. Interestingly, pretreatment with the ultrapotent vaniloid agonist resiniferotoxin, coinjection of the TRPV1 receptor antagonist SB366791, or mast cell depletion with compound 48/80 markedly prevented PAF-induced spontaneous nociception. Conversely, PAF-elicited mechanical hypersensitivity was strikingly susceptible to distinct antineutrophil-related strategies, namely the antineutrophil antibody, the selectin blocker fucoidin, the chemokine CXCR2 receptor antagonist SB225002, and the C5a receptor antibody anti-CD88. Notably, the same antineutrophil migration strategies significantly prevented the increase of myeloperoxidase activity induced by PAF. The mechanical hypersensitivity caused by PAF was also prevented by the cyclooxygenase inhibitors indomethacin or celecoxib, and by the selective beta(1) adrenergic receptor antagonist atenolol. Collectively, the present results provide consistent evidence indicating that distinct mechanisms are involved in the spontaneous nociception and mechanical hypersensitivity caused by PAF. They also support the concept that selective PAF receptor antagonists might constitute interesting

  12. Adaptive response in animals exposed to non-ionizing radiofrequency fields: some underlying mechanisms. (United States)

    Cao, Yi; Tong, Jian


    During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of γ-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed.

  13. Adaptive Response in Animals Exposed to Non-Ionizing Radiofrequency Fields: Some Underlying Mechanisms

    Directory of Open Access Journals (Sweden)

    Yi Cao


    Full Text Available During the last few years, our research group has been investigating the phenomenon of adaptive response in animals exposed to non-ionizing radiofrequency fields. The results from several separate studies indicated a significant increase in survival, decreases in genetic damage as well as oxidative damage and, alterations in several cellular processes in mice pre-exposed to radiofrequency fields and subsequently subjected to sub-lethal or lethal doses of γ-radiation or injected with bleomycin, a radiomimetic chemical mutagen. These observations indicated the induction of adaptive response providing the animals the ability to resist subsequent damage. Similar studies conducted by independent researchers in mice and rats have supported our observation on increased survival. In this paper, we have presented a brief review of all of our own and other independent investigations on radiofrequency fields-induced adaptive response and some underlying mechanisms discussed.

  14. Basic psychological skills usage and competitive anxiety responses: perceived underlying mechanisms. (United States)

    Wadey, Ross; Hanton, Sheldon


    This study examined the relationship between basic psychological skills usage (i.e., goal-setting, imagery, self-talk, and relaxation) and the intensity and directional dimensions of competitive anxiety. Semistructured interviews were used on a sample of 15 elite athletes (M age = 24.3 years, SD = 4.2) from a variety of team and individual sports. Findings revealed that the participants maintained the intensity of their anxiety response prior to competition and could deploy goal-setting, imagery, or self-talk to enable facilitative interpretations of anxiety-related symptoms to performance. Higher levels of self-confidence and an optimistic outlook toward forthcoming competition were also expressed. The underlying mechanisms perceived to be responsible for these effects included effort and motivation, attentional focus, and perceived control over the anxiety response.

  15. Mechanisms Underlying the Antidepressant Response of Acupuncture via PKA/CREB Signaling Pathway. (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


    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.

  16. Mechanisms underlying cellular responses of cells from haemopoietic tissue to low dose/low LET radiation

    Energy Technology Data Exchange (ETDEWEB)

    Munira A Kadhim


    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 radiation-induced genomic instability and bystander responses in key stem cell populations from haemopoietic tissue. Using stem cells from two mouse strains (CBA/H and C57BL/6J) known to differ in their susceptibility to radiation effects, we plan to carefully dissect the role of genetic predisposition on two non-targeted radiation responses in these models; the bystander effect and genomic instability, which we believe are closely related. We will specifically focus on the effects of low doses of low LET radiation, down to doses approaching a single electron traversal. Using conventional X-ray and γ-ray sources, novel dish separation and targeted irradiation approaches, we will be able to assess the role of genetic variation under various bystander conditions at doses down to a few electron tracks. Irradiations will be carried out using facilities in routine operation for bystander targeted studies. Mechanistic studies of instability and the bystander response in different cell lineages will focus initially on the role of cytokines which have been shown to be involved in bystander signaling and the initiation of instability. These studies also aim

  17. Mechanisms underlying cellular responses of cells from haemopoietic tissue to low

    Energy Technology Data Exchange (ETDEWEB)

    Kadhim, Munira A


    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

  18. Modeling the Mechanical Response of In Vivo Human Skin Under a Rich Set of Deformations

    KAUST Repository

    Flynn, Cormac


    Determining the mechanical properties of an individual\\'s skin is important in the fields of pathology, biomedical device design, and plastic surgery. To address this need, we present a finite element model that simulates the skin of the anterior forearm and posterior upper arm under a rich set of three-dimensional deformations. We investigated the suitability of the Ogden and Tong and Fung strain energy functions along with a quasi-linear viscoelastic law. Using non-linear optimization techniques, we found material parameters and in vivo pre-stresses for different volunteers. The model simulated the experiments with errors-of-fit ranging from 13.7 to 21.5%. Pre-stresses ranging from 28 to 92 kPa were estimated. We show that using only in-plane experimental data in the parameter optimization results in a poor prediction of the out-of-plane response. The identifiability of the model parameters, which are evaluated using different determinability criteria, improves by increasing the number of deformation orientations in the experiments. © 2011 Biomedical Engineering Society.

  19. Mechanical response of FFTF reference and P1 cladding tubes under transient heating

    International Nuclear Information System (INIS)

    Youngahl, C.A.; Ariman, T.; Lepacek, B.E.


    Burst tests of Type 316 stainless steel cladding tube samples subjected to increasing temperature and relatively constant internal pressure were conducted to assist in the pretest analysis of the P1 experiment performed in the Sodium Loop Safety Facility. This paper reports and analyzes the burst test results and those of subsequent transient heating work. The use of a modified extensometer in obtaining mechanical response data for stainless steel in the high temperature range is illustrated, some of such data is provided, and the potential of further experiments and analysis is indicated. Tubing of the same design as Fast Flux Test Facility (FFTF) cladding (20% cold worked, 0.230 in. OD, 15 mil wall) was tested as-received and after annealing or electrolytic thinning. P1 tubing (38% cold worked, 0.230 in. OD, 10 mil wall) was tested before and after aging under conditions anticipated in the P1 reactor experiment. The P1 cladding was designed to simulate FFTF tubing that had experienced irradiation embrittlement and attack by cesium oxide and sodium impurities

  20. Perspectives on deciphering mechanisms underlying plant heat stress response and thermotolerance

    Directory of Open Access Journals (Sweden)

    Kamila Lucia Bokszczanin


    Full Text Available Global warming is a major threat for agriculture and food safety and in many cases the negative effects are already apparent. The current challenge of basic and applied plant science is to decipher the molecular mechanisms of heat stress response and thermotolerance in detail and use this information to identify genotypes that will withstand unfavorable environmental conditions. Nowadays X-omics approaches complement the findings of previous targeted studies and highlight the complexity of heat stress response mechanisms giving information for so far unrecognized genes, proteins and metabolites as potential key players of thermotolerance. Even more, roles of epigenetic mechanisms and the involvement of small RNAs in thermotolerance are currently emerging and thus open new directions of yet unexplored areas of plant heat stress response. In parallel it is emerging that although the whole plant is vulnerable to heat, specific organs are particularly sensitive to elevated temperatures. This has redirected research from the vegetative to generative tissues. The sexual reproduction phase is considered as the most sensitive to heat and specifically pollen exhibits the highest sensitivity and frequently an elevation of the temperature just a few degrees above the optimum during pollen development can have detrimental effects for crop production. Compared to our knowledge on heat stress response of vegetative tissues, the information on pollen is still scarce. Nowadays, several techniques for high-throughput X-omics approaches provide major tools to explore the principles of pollen heat stress response and thermotolerance mechanisms in specific genotypes. The collection of such information will provide an excellent support for improvement of breeding programs to facilitate the development of tolerant cultivars. The review aims at describing the current knowledge of thermotolerance mechanisms and the technical advances which will foster new insights into

  1. Differential sulphur assimilation mechanism regulates response of Arabidopsis thaliana natural variation towards arsenic stress under limiting sulphur condition. (United States)

    Khare, Ria; Kumar, Smita; Shukla, Tapsi; Ranjan, Avriti; Trivedi, Prabodh Kumar


    Arsenic (As) is a ubiquitous element, which imposes threat to crops productivity and human health through contaminated food chain. As a part of detoxification mechanism, As is chelated and sequestered into the vacuoles via sulphur containing compounds glutathione (GSH) and phytochelatins (PCs). Under limiting sulphur (LS) conditions, exposure of As leads to enhanced toxic effects in plants. Therefore, it is a prerequisite to understand molecular mechanisms involved in As stress response under sulphur deficiency conditions in plants. In recent years, natural variation has been utilized to explore the genetic determinants linked to plant development and stress response. In this study, natural variation in Arabidopsis has been utilized to understand the molecular mechanisms underlying LS and As(III) stress response. Analysis of different accession of Arabidopsis led to the identification of Koz2-2 and Ri-0 as the most tolerant and sensitive accessions, respectively, towards As(III) and LS+As(III) stress. Biochemical analysis and expression profiling of the genes responsible for sulphur transport and assimilation as well as metal detoxification and accumulation revealed significantly enhanced sulphur assimilation mechanism in Koz2-2 as compared to Ri-0. Analyses suggest that genetic variation regulates differential response of accessions towards As(III) under LS condition. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Mechanisms underlying psychosis and antipsychotic treatment response in schizophrenia: insights from PET and SPECT imaging


    Howes, OD; Egerton, A; Allan, V; McGuire, P; Stokes, P; Kapur, S


    Molecular imaging studies have generated important in vivo insights into the etiology of schizophrenia and treatment response. This article first reviews the PET and SPECT evidence implicating dopaminergic dysfunction, especially presynaptic dysregulation, as a mechanism for psychosis. Second, it summarises the neurochemical imaging studies of antipsychotic action, focussing on D2/3 receptors. These studies show that all currently licensed antipsychotic drugs block striatal D2/3 receptors in ...

  3. Failure analysis of porcupine quills under axial compression reveals their mechanical response during buckling. (United States)

    Torres, Fernando G; Troncoso, Omar P; Diaz, John; Arce, Diego


    Porcupine quills are natural structures formed by a thin walled conical shell and an inner foam core. Axial compression tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FT-IR) were all used to compare the characteristics and mechanical properties of porcupine quills with and without core. The failure mechanisms that occur during buckling were analyzed by scanning electron microscopy (SEM), and it was found that delamination buckling is mostly responsible for the decrease in the measured buckling stress of the quills with regard to predicted theoretical values. Our analysis also confirmed that the foam core works as an energy dissipater improving the mechanical response of an empty cylindrical shell, retarding the onset of buckling as well as producing a step wise decrease in force after buckling, instead of an instantaneous decrease in force typical for specimens without core. Cell collapse and cell densification in the inner foam core were identified as the key mechanisms that allow for energy absorption during buckling. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Mechanisms Underlying the Immune Response Generated by an Oral Vibrio cholerae Vaccine

    Directory of Open Access Journals (Sweden)

    Danylo Sirskyj


    Full Text Available Mechanistic details underlying the resulting protective immune response generated by mucosal vaccines remain largely unknown. We investigated the involvement of Toll-like receptor signaling in the induction of humoral immune responses following oral immunization with Dukoral, comparing wild type mice with TLR-2-, TLR-4-, MyD88- and Trif-deficient mice. Although all groups generated similar levels of IgG antibodies, the proliferation of CD4+ T-cells in response to V. cholerae was shown to be mediated via MyD88/TLR signaling, and independently of Trif signaling. The results demonstrate differential requirements for generation of immune responses. These results also suggest that TLR pathways may be modulators of the quality of immune response elicited by the Dukoral vaccine. Determining the critical signaling pathways involved in the induction of immune response to this vaccine would be beneficial, and could contribute to more precisely-designed versions of other oral vaccines in the future.

  5. Mechanical responses of a-axis GaN nanowires under axial loads (United States)

    Wang, R. J.; Wang, C. Y.; Feng, Y. T.; Tang, Chun


    Gallium nitride (GaN) nanowires (NWs) hold technological significance as functional components in emergent nano-piezotronics. However, the examination of their mechanical responses, especially the mechanistic understanding of behavior beyond elasticity (at failure) remains limited due to the constraints of in situ experimentation. We therefore performed simulations of the molecular dynamics (MD) of the mechanical behavior of [1\\bar{2}10]-oriented GaN NWs subjected to tension or compression loading until failure. The mechanical properties and critical deformation processes are characterized in relation to NW sizes and loading conditions. Detailed examinations revealed that the failure mechanisms are size-dependent and controlled by the dislocation mobility on shuffle-set pyramidal planes. The size dependence of the elastic behavior is also examined in terms of the surface structure determined modification of Young’s modulus. In addition, a comparison with c-axis NWs is made to show how size-effect trends vary with the growth orientation of NWs.

  6. Signaling Mechanisms Underlying Resistance Responses: What Have We Learned, and How Is It Being Applied? (United States)

    Kachroo, Aardra; Vincelli, Paul; Kachroo, Pradeep


    Plants have evolved highly specific mechanisms to resist pathogens including preformed barriers and the induction of elaborate signaling pathways. Induced signaling requires recognition of the pathogen either via conserved pathogen-derived factors or specific pathogen-encoded proteins called effectors. Recognition of these factors by host encoded receptor proteins can result in the elicitation of different tiers of resistance at the site of pathogen infection. In addition, plants induce a type of systemic immunity which is effective at the whole plant level and protects against a broad spectrum of pathogens. Advances in our understanding of pathogen-recognition mechanisms, identification of the underlying molecular components, and their significant conservation across diverse plant species has enabled the development of novel strategies to combat plant diseases. This review discusses key advances in plant defense signaling that have been adapted or have the potential to be adapted for plant protection against microbial diseases.

  7. Growth and stress response mechanisms underlying post-feeding regenerative organ growth in the Burmese python. (United States)

    Andrew, Audra L; Perry, Blair W; Card, Daren C; Schield, Drew R; Ruggiero, Robert P; McGaugh, Suzanne E; Choudhary, Amit; Secor, Stephen M; Castoe, Todd A


    Previous studies examining post-feeding organ regeneration in the Burmese python (Python molurus bivittatus) have identified thousands of genes that are significantly differentially regulated during this process. However, substantial gaps remain in our understanding of coherent mechanisms and specific growth pathways that underlie these rapid and extensive shifts in organ form and function. Here we addressed these gaps by comparing gene expression in the Burmese python heart, liver, kidney, and small intestine across pre- and post-feeding time points (fasted, one day post-feeding, and four days post-feeding), and by conducting detailed analyses of molecular pathways and predictions of upstream regulatory molecules across these organ systems. Identified enriched canonical pathways and upstream regulators indicate that while downstream transcriptional responses are fairly tissue specific, a suite of core pathways and upstream regulator molecules are shared among responsive tissues. Pathways such as mTOR signaling, PPAR/LXR/RXR signaling, and NRF2-mediated oxidative stress response are significantly differentially regulated in multiple tissues, indicative of cell growth and proliferation along with coordinated cell-protective stress responses. Upstream regulatory molecule analyses identify multiple growth factors, kinase receptors, and transmembrane receptors, both within individual organs and across separate tissues. Downstream transcription factors MYC and SREBF are induced in all tissues. These results suggest that largely divergent patterns of post-feeding gene regulation across tissues are mediated by a core set of higher-level signaling molecules. Consistent enrichment of the NRF2-mediated oxidative stress response indicates this pathway may be particularly important in mediating cellular stress during such extreme regenerative growth.

  8. Citric Acid Metabolism in Resistant Hypertension: Underlying Mechanisms and Metabolic Prediction of Treatment Response. (United States)

    Martin-Lorenzo, Marta; Martinez, Paula J; Baldan-Martin, Montserrat; Ruiz-Hurtado, Gema; Prado, Jose Carlos; Segura, Julian; de la Cuesta, Fernando; Barderas, Maria G; Vivanco, Fernando; Ruilope, Luis Miguel; Alvarez-Llamas, Gloria


    Resistant hypertension (RH) affects 9% to 12% of hypertensive adults. Prolonged exposure to suboptimal blood pressure control results in end-organ damage and cardiovascular risk. Spironolactone is the most effective drug for treatment, but not all patients respond and side effects are not negligible. Little is known on the mechanisms responsible for RH. We aimed to identify metabolic alterations in urine. In addition, a potential capacity of metabolites to predict response to spironolactone was investigated. Urine was collected from 29 patients with RH and from a group of 13 subjects with pseudo-RH. For patients, samples were collected before and after spironolactone administration and were classified in responders (n=19) and nonresponders (n=10). Nuclear magnetic resonance was applied to identify altered metabolites and pathways. Metabolites were confirmed by liquid chromatography-mass spectrometry. Citric acid cycle was the pathway most significantly altered ( P citric acid cycle and deregulation of reactive oxygen species homeostasis control continue its activation after hypertension was developed. A metabolic panel showing alteration before spironolactone treatment and predicting future response of patients is shown. These molecular indicators will contribute optimizing the rate of control of RH patients with spironolactone. © 2017 American Heart Association, Inc.

  9. Physiological and molecular responses to bariatric surgery: markers or mechanisms underlying T2DM resolution? (United States)

    Hutch, Chelsea R; Sandoval, Darleen A


    Bariatric surgery is currently the most effective treatment for obesity and associated comorbidities, including rapid resolution of type 2 diabetes mellitus (T2DM). Although the weight loss itself has substantial impact, bariatric surgery also has weight loss-independent effects on T2DM. Several variations of bariatric surgery exist, including the widely studied Roux-en-Y gastric bypass and vertical sleeve gastrectomy. The success of both of these bariatric surgeries was originally attributed to restrictive and malabsorptive modes of action; however, mounting evidence from both human and animal studies implicates mechanisms beyond surgery-induced mechanical changes to the gastrointestinal (GI) system. In fact, with bariatric surgery comes a spectrum of physiological responses, including postprandial enhancement of gut peptide and bile acids levels, restructuring of microbial composition, and changes in GI function and morphology. Although many of these processes are also essential for glucoregulation, the independent role of each in the success of surgery is still an open question. In this review, we explore whether these changes are necessary for the improvements in body mass and glucose homeostasis or whether they are simply markers of the physiological effect of surgery. © 2016 New York Academy of Sciences.

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


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


    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...

  11. Molecular mechanisms underlying antiproliferative and differentiating responses of hepatocarcinoma cells to subthermal electric stimulation.

    Directory of Open Access Journals (Sweden)

    María Luisa Hernández-Bule

    Full Text Available Capacitive Resistive Electric Transfer (CRET therapy applies currents of 0.4-0.6 MHz to treatment of inflammatory and musculoskeletal injuries. Previous studies have shown that intermittent exposure to CRET currents at subthermal doses exert cytotoxic or antiproliferative effects in human neuroblastoma or hepatocarcinoma cells, respectively. It has been proposed that such effects would be mediated by cell cycle arrest and by changes in the expression of cyclins and cyclin-dependent kinase inhibitors. The present work focuses on the study of the molecular mechanisms involved in CRET-induced cytostasis and investigates the possibility that the cellular response to the treatment extends to other phenomena, including induction of apoptosis and/or of changes in the differentiation stage of hepatocarcinoma cells. The obtained results show that the reported antiproliferative action of intermittent stimulation (5 m On/4 h Off with 0.57 MHz, sine wave signal at a current density of 50 µA/mm(2, could be mediated by significant increase of the apoptotic rate as well as significant changes in the expression of proteins p53 and Bcl-2. The results also revealed a significantly decreased expression of alpha-fetoprotein in the treated samples, which, together with an increased concentration of albumin released into the medium by the stimulated cells, can be interpreted as evidence of a transient cytodifferentiating response elicited by the current. The fact that this type of electrical stimulation is capable of promoting both, differentiation and cell cycle arrest in human cancer cells, is of potential interest for a possible extension of the applications of CRET therapy towards the field of oncology.

  12. Acoustic and mechanical response of reservoir rocks under variable saturation and effective pressure. (United States)

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


    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.

  13. Retinal ganglion cells: mechanisms underlying depolarization block and differential responses to high frequency electrical stimulation of ON and OFF cells (United States)

    Kameneva, T.; Maturana, M. I.; Hadjinicolaou, A. E.; Cloherty, S. L.; Ibbotson, M. R.; Grayden, D. B.; Burkitt, A. N.; Meffin, H.


    Objective. ON and OFF retinal ganglion cells (RGCs) are known to have non-monotonic responses to increasing amplitudes of high frequency (2 kHz) biphasic electrical stimulation. That is, an increase in stimulation amplitude causes an increase in the cell’s spike rate up to a peak value above which further increases in stimulation amplitude cause the cell to decrease its activity. The peak response for ON and OFF cells occurs at different stimulation amplitudes, which allows differential stimulation of these functional cell types. In this study, we investigate the mechanisms underlying the non-monotonic responses of ON and OFF brisk-transient RGCs and the mechanisms underlying their differential responses. Approach. Using in vitro patch-clamp recordings from rat RGCs, together with simulations of single and multiple compartment Hodgkin-Huxley models, we show that the non-monotonic response to increasing amplitudes of stimulation is due to depolarization block, a change in the membrane potential that prevents the cell from generating action potentials. Main results. We show that the onset for depolarization block depends on the amplitude and frequency of stimulation and reveal the biophysical mechanisms that lead to depolarization block during high frequency stimulation. Our results indicate that differences in transmembrane potassium conductance lead to shifts of the stimulus currents that generate peak spike rates, suggesting that the differential responses of ON and OFF cells may be due to differences in the expression of this current type. We also show that the length of the axon’s high sodium channel band (SOCB) affects non-monotonic responses and the stimulation amplitude that leads to the peak spike rate, suggesting that the length of the SOCB is shorter in ON cells. Significance. This may have important implications for stimulation strategies in visual prostheses.

  14. Mechanical responses, texture evolution, and yield loci of extruded AZ31 magnesium alloy under various loading conditions: Experiment and modeling (United States)

    Kabirian, Farhoud

    Mechanical responses and texture evolution of extruded AZ31 Mg are measured under uniaxial (tension-compression) and multiaxial (free-end torsion) loadings. Compression loading is carried out in three different directions at temperature and strain rate ranges of 77-423 K and 10-4 -3000 s -1, respectively. Texture evolution at different intermediate strains reveals that crystal reorientation is exhausted at smaller strains with increase in strain rate while increase in temperature retards twinning. In addition to the well-known tension-compression yield asymmetry, a strong anisotropy in strain hardening response is observed. Strain hardening during the compression experiment is intensified with decreasing and increasing temperature and strain rate, respectively. This complex behavior is explained through understanding the roles of deformation mechanisms using the Visco-Plastic Self Consistent (VPSC) model. In order to calibrate the VPSC model's constants as accurate as possible, a vast number of mechanical responses including stress-strain curves in tension, compression in three directions, and free-end torsion, texture evolution at different strains, lateral strains of compression samples, twin volume fraction, and axial strain during the torsion experiment. Modeling results show that depending on the number of measurements used for calibration, roles of different mechanisms in plastic deformation change significantly. In addition, a precise definition of yield is established for the extruded AZ31magnesium alloy after it is subjected to different loading conditions (uniaxial to multiaxial) at four different plastic strains. The yield response is measured in ?-? space. Several yield criteria are studied to predict yield response of extruded AZ31. This study proposes an asymmetrical fourth-order polynomial yield function. Material constants in this model can be directly calculated using mechanical measurements. Convexity of the proposed model is discussed, and

  15. Identifying serotonergic mechanisms underlying the corticolimbic response to threat in humans

    DEFF Research Database (Denmark)

    Fisher, Patrick M; Hariri, Ahmad R


    A corticolimbic circuit including the amygdala and medial prefrontal cortex (mPFC) plays an important role in regulating sensitivity to threat, which is heightened in mood and anxiety disorders. Serotonin is a potent neuromodulator of this circuit; however, specific serotonergic mechanisms....... Integrating these methodological approaches offers novel opportunities to identify mechanisms through which serotonin signalling contributes to differences in brain function and behaviour, which in turn can illuminate factors that confer risk for illness and inform the development of more effective treatment...

  16. Potential mechanisms underlying response to effects of the fungicide pyrimethanil from gene expression profiling in Saccharomyces cerevisiae. (United States)

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


    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.

  17. Electromagnetic dynamic response of HL-2M vacuum vessel under plasma disruption considering the electromagneto-mechanical coupling effect

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Hongwei; Yuan, Zhensheng; Li, Weixin; Pei, Cuixiang; Xie, Shejuan [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center for NDT and Structural Integrity Evaluation, Xi’an Jiaotong University, Xi’an 710049 (China); Chen, Zhenmao, E-mail: [State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center for NDT and Structural Integrity Evaluation, Xi’an Jiaotong University, Xi’an 710049 (China); Pan, Yudong; Cai, Lijun; Li, Jiaxian [Southwestern Institute of Physics, Chengdu 610041 (China)


    Highlights: • A 1/5 numerical model is established and validated for HL-2M vacuum vessel. • The Lagrangian approach used for treating the EM-mechanical coupling problem is introduced. • The EM field and structural dynamic response of HL-2M VV during plasma disruptions are simulated by using the Lagrangian strategy. • The dynamic responses of the VV of HL-2M are compared to clarify the effect of the EM-mechanical coupling under the MD and VED conditions. • The results present a basis for the safe operation of the HL-2M VV device. - Abstract: During plasma disruptions (PDs), transient eddy currents are induced in the HL-2M vacuum vessel (VV) which is a D-shaped, double thin-wall structure. Under the circumstance of high magnetic field, the resulting electromagnetic (EM) forces during PDs are large and the dynamic response of related structures may be violent. In this complicated EM circumstance, the EM-mechanical coupling effect may also have a great influence on the dynamic response of VV structure. In this paper, the EM field and structural dynamic response of HL-2M VV during PDs are simulated by adopting a numerical code of the Lagrangian approach. The Lagrangian approach is on the basis of the Maxwell equations in the Lagrangian description, which treats the coupling behavior of magnetic damping effect without explicitly using the velocity term. This approach can be easily applied to actual structures by updating FEM meshes and reforming coefficient matrices before calculating EM field at each time step. In this work, the disruption plasma currents of operating conditions are simulated by using the DINA code and then the dynamic responses of displacements and stresses of the VV of HL-2M are obtained for both cases with and without considering the coupling effect. The numerical results show that stresses under the disruptions (MD and VDE) are not significant and the coupling effect does not significantly affect the peak dynamic response for the HL-2M

  18. Possible mechanisms underlying abundance and diversity responses of nematode communities to plant diversity

    NARCIS (Netherlands)

    Cortois, R.; Veen, G.F.; Duyts, Henk; Abbas, Maike; Strecker, Tanja; Kostenko, Olga; Eisenhauer, Nico; Scheu, Stefan; Gleixner, Gerd; Deyn, De Gerlinde B.; Putten, van der Wim H.


    Plant diversity is known to influence the abundance and diversity of belowground biota; however, patterns are not well predictable and there is still much unknown about the driving mechanisms. We analyzed changes in soil nematode community composition as affected by long-term manipulations of

  19. Possible mechanisms underlying abundance and diversity responses of nematode communities to plant diversity

    NARCIS (Netherlands)

    Cortois, R.; Veen, G.F.; Duyts, H.; Abbas, M.; Strecker, T; Kostenko, O.; Eisenhauer, Nico; Scheu, S.; Gleixner, G.; De Deyn, G.B.; van der Putten, W.H.


    Plant diversity is known to influence the abundance and diversity of belowground biota; however, patterns are not well predictable and there is still much unknown about the driving mechanisms. We analyzed changes in soil nematode community composition as affected by long-term manipulations of plant

  20. The location- and depth-dependent mechanical response of the human cornea under shear loading. (United States)

    Sloan, Stephen R; Khalifa, Yousuf M; Buckley, Mark R


    To characterize the depth-dependent shear modulus of the central and peripheral human cornea along the superior-inferior and nasal-temporal directions with a high spatial resolution. Cylindrical explants from the central and peripheral corneas of 10 human donors were subjected to a 5% shear strain along the superior-inferior and nasal-temporal directions using a microscope-mounted mechanical testing device. Depth-dependent shear strain and shear modulus were computed through force measurements and displacement tracking. The shear modulus G of the human cornea varied continuously with depth, with a maximum occurring roughly 25% of the way from the anterior surface to the posterior surface. G also varied with direction in the superior region and (at some depths) was significantly higher for superior-inferior shear loading. In the anterior half of the cornea, the shear modulus along the nasal-temporal direction (GNT) did not vary with location; however, the superior region had significantly higher GNT in posterior cornea. In contrast, the shear modulus along the superior-inferior direction (GSI) was independent of location at all depths. This study demonstrates that the peak shear modulus of the human cornea occurs at a substantial distance within the corneal stroma. Depth-dependent differences between central and peripheral cornea possibly reflect the location-dependent mechanical environment of the cornea. Moreover, the cornea is not a transverse isotropic material, and must be characterized by more than a single shear modulus due to its dependence on loading direction. The material properties measured in this study are critical for developing accurate mechanical models to predict the vision-threatening morphological changes that can occur in the cornea. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

  1. Child abuse: underlying mechanisms


    Martínez, Gladys S.


    Exposure to traumatic stress during childhood, in the form of abuse or neglect, is related to an increased vulnerability resulting in the development of several pathologies, this relation has been confi rmed by epidemiological studies; however, the neural mechanisms underlying such abnormalities are still unknown. Most of the research done has focused on the effects in the infant, and only recently it has begun to focus on the neurobiological changes in the abusive parents. In this article, I...

  2. Central Mechanisms Underlying Variability in the Behavioral and Neuroendocrine Responses to Stress in Fish

    DEFF Research Database (Denmark)

    Moltesen, Maria Møller

    in the limbic system. In fish, the telencephalon contains regions that are functional homologues to the mammalian limbic system including amygdala and hippocampus. However, the involvement of this brain region in the regulation of the hypothalamicpituitary- interrenal (HPI) axis, the homologue of the mammalian...... glucocorticoid in fish, and if these effects were related to changes in neurochemistry and gene expression in the telencephalon of rainbow trout (Oncorhynchus mykiss). The results showed that chronic stress affected HPI axis reactivity and serotonergic neurochemistry in the telencephalon. Moreover, effects...... styles. It is concluded that both individuality in the behavioral stress response and effects of chronic stress are reflected in 5-HT-ergic turnover in the telencephalon. Moreover, different activation patterns in the telencephalon during hypoxia in fish with contrasting stress coping styles further...

  3. Computational Simulation of the Mechanical Response of Brain Tissue under Blast Loading (United States)

    Laksari, Kaveh; Assari, Soroush; Seibold, Benjamin; Sadeghipour, Keya; Darvish, Kurosh


    In the present study, numerical simulations of nonlinear wave propagation and shock formation in brain tissue have been presented and a new mechanism of injury for Blast-Induced Neurotrauma (BINT) is proposed. A quasilinear viscoelastic (QLV) constitutive material model was used that encompasses the nonlinearity as well as the rate dependence of the tissue relevant to BINT modeling. A one-dimensional model was implemented using the discontinuous Galerkin -finite element method and studied with displacement-input and pressure-input boundary conditions. The model was validated against LS-DYNA finite element code and theoretical results for speci c conditions that resulted in shock wave formation. It was shown that a continuous wave can become a shock wave as it propagates in the QLV brain tissue when the initial changes in acceleration are beyond a certain limit. The high spatial gradient of stress and strain at the shock front cause large relative motions at the cellular scale at high temporal rates even when the maximum stresses and strains are relatively low. This gradient-induced local deformation may occur away from the boundary and is proposed as a contributing factor to the diffuse nature of BINT. PMID:25205088

  4. Integrated physiological and proteomic analysis reveals underlying response and defense mechanisms of Brachypodium distachyon seedling leaves under osmotic stress, cadmium and their combined stresses. (United States)

    Cheng, Zhi-Wei; Chen, Zi-Yan; Yan, Xing; Bian, Yan-Wei; Deng, Xiong; Yan, Yue-Ming


    Drought stress, a major abiotic stress, commonly occurs in metal-contaminated environments and affects crop growth and yield. In this study, we performed the first integrated phenotypic, physiological, and proteomic analysis of Brachypodium distachyon L. seedling leaves under polyethylene glycol (PEG) mock osmotic stress, cadmium (Cd 2+ ), and their combined stresses. Combined osmotic and Cd 2+ stress had more significant effects than each individual stress on seedling growth, and the physiological traits and ultrastructures of leaves. Totally 117 differentially accumulated protein (DAP) spots detected by two-dimensional difference gel electrophoresis (2D-DIGE) were identified, and representing 89 unique proteins under individual and combined stresses. These DAPs were involved in photosynthesis/respiration (34%), energy and carbon metabolism (21%), stress/defense/detoxification (13%), protein folding and degradation (12%), and amino acid metabolism (7%). Principal component analysis (PCA) revealed that DAPs from the Cd 2+ and combined stresses grouped much closer than those from osmotic stress, indicating Cd 2+ and combined stresses resulted in more changes to the leaf proteome than osmotic stress alone. Protein-protein interaction analyses showed that a 14-3-3 centered sub-network could play important roles in responses to abiotic stresses. An overview pathway of proteome metabolic changes in Bd21 seedling leaves under combined stresses is proposed, representing a synergistic responsive network and underlying response and defense mechanisms. Drought stress is one of the major abiotic stresses, which commonly occurs in metal-contaminated environments, and affects crop growth and yield performance. We performed the first integrated phenotypic, physiological and proteomic analysis of Brachypodium distachyon L. seedling leaves under drought (PEG), cadmium (Cd 2+ ) and their combined stresses. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Modeling the cellular mechanisms and olfactory input underlying the triphasic response of moth pheromone-sensitive projection neurons.

    Directory of Open Access Journals (Sweden)

    Yuqiao Gu

    Full Text Available In the antennal lobe of the noctuid moth Agrotis ipsilon, most pheromone-sensitive projection neurons (PNs exhibit a triphasic firing pattern of excitation (E1-inhibition (I-excitation (E2 in response to a pulse of the sex pheromone. To understand the mechanisms underlying this stereotypical discharge, we developed a biophysical model of a PN receiving inputs from olfactory receptor neurons (ORNs via nicotinic cholinergic synapses. The ORN is modeled as an inhomogeneous Poisson process whose firing rate is a function of time and is fitted to extracellular data recorded in response to pheromone stimulations at various concentrations and durations. The PN model is based on the Hodgkin-Huxley formalism with realistic ionic currents whose parameters were derived from previous studies. Simulations revealed that the inhibitory phase I can be produced by a SK current (Ca2+-gated small conductance K+ current and that the excitatory phase E2 can result from the long-lasting response of the ORNs. Parameter analysis further revealed that the ending time of E1 depends on some parameters of SK, Ca2+, nACh and Na+ currents; I duration mainly depends on the time constant of intracellular Ca2+ dynamics, conductance of Ca2+ currents and some parameters of nACh currents; The mean firing frequency of E1 and E2 depends differentially on the interaction of various currents. Thus it is likely that the interplay between PN intrinsic currents and feedforward synaptic currents are sufficient to generate the triphasic firing patterns observed in the noctuid moth A. ipsilon.

  6. Neurophysiological mechanisms underlying sex- and maturation-related variation in pheromone responses in honey bees (Apis mellifera). (United States)

    Villar, Gabriel; Baker, Thomas C; Patch, Harland M; Grozinger, Christina M


    In the honey bee (Apis mellifera), social organization is primarily mediated by pheromones. Queen-produced 9-oxo-2-decenoic acid (9-ODA) functions as both a social and sex pheromone, eliciting attraction in both female workers and male drones, but also affecting other critical aspects of worker physiology and behavior. These effects are also maturation related, as younger workers and sexually mature drones are most receptive to 9-ODA. While changes in the peripheral nervous system drive sex-related differences in sensitivity to 9-ODA, the mechanisms driving maturation-related shifts in receptivity to 9-ODA remain unknown. Here, we investigate the hypothesis that changes at the peripheral nervous system may be mediating plastic responses to 9-ODA by characterizing expression levels of AmOR11 (the olfactory receptor tuned to 9-ODA) and electrophysiological responses to 9-ODA. We find that receptor expression correlates significantly with behavioral receptivity to 9-ODA, with nurses and sexually mature drones exhibiting higher levels of expression than foragers and immature drones, respectively. Electrophysiological responses to 9-ODA were not found to correlate with behavioral receptivity or receptor expression, however. Thus, while receptor expression at the periphery exhibits a level of plasticity that correlates with behavior, the mechanisms driving maturation-dependent responsiveness to 9-ODA appear to function primarily in the central nervous system.

  7. Numerical simulations of mechanical and ignition-deflagration responses for PBXs under low-to-medium-level velocity impact loading. (United States)

    Yang, Kun; Wu, Yanqing; Huang, Fenglei; Li, Ming


    An effective computational model is required to accurately predict the dynamic responses in accidental initiations of explosives. The present work uses a series of two-dimensional mechanical-chemical simulations performed via a hydrodynamic-code, DREXH-2D, to efficiently describe the mechanical and ignition-deflagration responses of cased cylindrical polymer-bonded explosives (PBXs) undergoing a low-to-medium-level impact (70-350m/s) in longitudinal direction. The ignition response was predicted based on an ignition criterion of effective plastic work. Slow burning and its growth to deflagration were described through a pressure-dependent reaction rate equation. The extreme value of effective plastic work was found to be useful to determine the ignition threshold velocity for PBXs. For low-level velocity impact, the incident stress wave reflection from lateral surfaces contributed to the formation of ignition regions. After the ignition, the deflagration was induced in the medium-level impact, and its violence was related to the shock strength. However, the low-strength stress wave only induced reaction at local regions, and sequent burning was no longer sensitive to the strength of incident wave. The predicted pressure and temperature results of PBXs were consistent with the medium-level impact tests performed by China Academy of Engineering Physics. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Numerical study on mechanical response of superelastic NiTi shape memory alloy under various loading conditions (United States)

    Xiao, Yao; Zeng, Pan; Lei, Liping


    In this paper, a micromechanical-based constitutive model is proposed for superelastic NiTi shape memory alloy and it is implemented into the finite element software. The thermodynamic driving forces of martensitic transformation and martensitic reorientation are derived from the reduced Clausius–Duhem inequality. In order to achieve numerical stability and to improve computational efficiency, additional constraints on the evolution of martensite volume fraction are introduced. The texture of NiTi tubes is taken into consideration. It is verified that the measured superelastic responses under various loading conditions are well approximated by the presented approach.

  9. Proteome and phosphoproteome characterization reveals new response and defense mechanisms of Brachypodium distachyon leaves under salt stress. (United States)

    Lv, Dong-Wen; Subburaj, Saminathan; Cao, Min; Yan, Xing; Li, Xiaohui; Appels, Rudi; Sun, Dong-Fa; Ma, Wujun; Yan, Yue-Ming


    Salinity is a major abiotic stress affecting plant growth and development. Understanding the molecular mechanisms of salt response and defense in plants will help in efforts to improve the salt tolerance of crops. Brachypodium distachyon is a new model plant for wheat, barley, and several potential biofuel grasses. In the current study, proteome and phosphoproteome changes induced by salt stress were the focus. The Bd21 leaves were initially treated with salt in concentrations ranging from 80 to 320 mm and then underwent a recovery process prior to proteome analysis. A total of 80 differentially expressed protein spots corresponding to 60 unique proteins were identified. The sample treated with a median salt level of 240 mm and the control were selected for phosphopeptide purification using TiO2 microcolumns and LC-MS/MS for phosphoproteome analysis to identify the phosphorylation sites and phosphoproteins. A total of 1509 phosphoproteins and 2839 phosphorylation sites were identified. Among them, 468 phosphoproteins containing 496 phosphorylation sites demonstrated significant changes at the phosphorylation level. Nine phosphorylation motifs were extracted from the 496 phosphorylation sites. Of the 60 unique differentially expressed proteins, 14 were also identified as phosphoproteins. Many proteins and phosphoproteins, as well as potential signal pathways associated with salt response and defense, were found, including three 14-3-3s (GF14A, GF14B, and 14-3-3A) for signal transduction and several ABA signal-associated proteins such as ABF2, TRAB1, and SAPK8. Finally, a schematic salt response and defense mechanism in B. distachyon was proposed.

  10. Nonlinear dynamic response of a simply supported rectangular functionally graded material plate under the time-dependent thermal mechanical loads

    Energy Technology Data Exchange (ETDEWEB)

    Hao, Y. X. [Beijing Information Science and Technology University, Beijing (China); Zhang, W. [Beijing University of Technology, Beijing (China); Yang, J. [RMIT University, Bundoora (Australia); Li, S. Y. [Ttianjin University of Technology and Education, Tianjin (China)


    An analysis on nonlinear dynamic characteristics of a simply supported functionally graded materials (FGMs) rectangular plate subjected to the transversal and in-plane excitations is presented in the time dependent thermal environment. Here we look the FGM Plates as isotropic materials which is assumed to be temperature dependent and graded in the thickness direction according to the power-law distribution in terms of volume fractions of the constituents. The geometrical nonlinearity using Von Karman's assumption is introduced. The formulation also includes in-plane and rotary inertia effects. In the framework of Reddy's third-order shear deformation plate theory, the governing equations of motion for the FGM plate are derived by the Hamilton's principle. Then the equations of motion with two degree- of-freedom under combined the time-dependent thermomechanical loads can be obtained by using Galerkin's method. Using numerical method, the control equations are analyzed to obtain the response curves. Under certain conditions the periodic and chaotic motions of the FGM plate are found. It is found that because of the existence of the temperature which relate to the time the motions of the FGM plate show the great difference. A period motion can be changed into the chaotic motions which are affected by the time dependent temperature.

  11. Underlying Mechanisms Affecting Institutionalisation of ...

    African Journals Online (AJOL)

    This paper discusses the underlying causal mechanisms that enabled or constrained institutionalisation of environmental education in 12 institutions in eight countries in southern Africa. The study was carried out in the context of the Southern Africa Development Community Regional Environmental Education Support ...

  12. Underlying Mechanisms Affecting Institutionalisation of ...

    African Journals Online (AJOL)

    doctoral study and draws on critical realism as the ontological lens. Data analysis was done by means of a retroductive mode of inference, as articulated by Danermark, Ekström, Jakosben and Karlsson (2002). The paper demonstrates that there are a number of underlying causal mechanisms, which may enable or.

  13. Molecular mechanisms underlying bacterial persisters

    DEFF Research Database (Denmark)

    Maisonneuve, Etienne; Gerdes, Kenn


    All bacteria form persisters, cells that are multidrug tolerant and therefore able to survive antibiotic treatment. Due to the low frequencies of persisters in growing bacterial cultures and the complex underlying molecular mechanisms, the phenomenon has been challenging to study. However, recent...

  14. Investigating the underlying mechanism of Saccharomyces cerevisiae in response to ethanol stress employing RNA-seq analysis. (United States)

    Li, Ruoyun; Xiong, Guotong; Yuan, Shukun; Wu, Zufang; Miao, Yingjie; Weng, Peifang


    Saccharomyces cerevisiae has been widely used for wine fermentation and bio-fuels production. A S. cerevisiae strain Sc131 isolated from tropical fruit shows good fermentation properties and ethanol tolerance, exhibiting significant potential in Chinese bayberry wine fermentation. In this study, RNA-sequence and RT-qPCR was used to investigate the transcriptome profile of Sc131 in response to ethanol stress. Scanning Electron Microscopy were carried out to observe surface morphology of yeast cells. Totally, 937 genes were identified differential expressed, including 587 up-regulated and 350 down-regulated genes, after 4-h ethanol stress (10% v/v). Transcriptomic analysis revealed that, most genes involved in regulating filamentous growth or pseudohyphal growth were significantly up-regulated in response to ethanol stress. The complex protein quality control machineries, Hsp90/Hsp70 and Hsp104/Hsp70/Hsp40 based chaperone system combining with ubiquitin-proteasome proteolytic pathway were both activated to recognize and degrade misfolding proteins. Genes related to biosynthesis and metabolism of two well-known stress-responsive substances trehalose and ergosterol were generally up-regulated, while genes associated with amino acids biosynthesis and metabolism processes were differentially expressed. Moreover, thiamine was also important in response to ethanol stress. This research may promote the potential applications of Sc131 in the fermentation of Chinese bayberry wine.

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

    Energy Technology Data Exchange (ETDEWEB)

    Mao, Chaoliang; Cao, Sheng; Yan, Shiguang; Yao, Chunhua; Cao, Fei; Wang, Genshui; Dong, Xianlin [Key Laboratory of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Changning, Shanghai 200050 (China); Hu, Xu; Yang, Chunli [Kunming Institute of Physics, Kunming 650223 (China)


    Pyroelectric response mechanism of Ba{sub 0.70}Sr{sub 0.30}TiO{sub 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{sub tot}, p{sub int}, p{sub ind}) with temperatures and bias fields were analyzed. p{sub int} plays the dominant role to p{sub tot} through most of the temperature range and p{sub ind} will be slightly higher than p{sub int} above T{sub 0}. The essence of the enhancing effect of DC bias field on pyroelectric coefficient can be attributed to the high value of p{sub int}. This mechanism is useful for the pyroelectric materials (DB mode) applications.

  16. Molecular Mechanisms Underlying Hepatocellular Carcinoma

    Directory of Open Access Journals (Sweden)

    Christian Trepo


    Full Text Available Hepatocarcinogenesis is a complex process that remains still partly understood. That might be explained by the multiplicity of etiologic factors, the genetic/epigenetic heterogeneity of tumors bulks and the ignorance of the liver cell types that give rise to tumorigenic cells that have stem cell-like properties. The DNA stress induced by hepatocyte turnover, inflammation and maybe early oncogenic pathway activation and sometimes viral factors, leads to DNA damage response which activates the key tumor suppressive checkpoints p53/p21Cip1 and p16INK4a/pRb responsible of cell cycle arrest and cellular senescence as reflected by the cirrhosis stage. Still obscure mechanisms, but maybe involving the Wnt signaling and Twist proteins, would allow pre-senescent hepatocytes to bypass senescence, acquire immortality by telomerase reactivation and get the last genetic/epigenetic hits necessary for cancerous transformation. Among some of the oncogenic pathways that might play key driving roles in hepatocarcinogenesis, c-myc and the Wnt/β-catenin signaling seem of particular interest. Finally, antiproliferative and apoptosis deficiencies involving TGF-β, Akt/PTEN, IGF2 pathways for instance are prerequisite for cancerous transformation. Of evidence, not only the transformed liver cell per se but the facilitating microenvironment is of fundamental importance for tumor bulk growth and metastasis.

  17. Response and Defense Mechanisms of Taxus chinensis Leaves Under UV-A Radiation are Revealed Using Comparative Proteomics and Metabolomics Analyses. (United States)

    Zheng, Wen; Komatsu, Setsuko; Zhu, Wei; Zhang, Lin; Li, Ximin; Cui, Lei; Tian, Jingkui


    Taxus chinensis var. mairei is a species endemic to south-eastern China and one of the natural sources for the anticancer medicine paclitaxel. To investigate the molecular response and defense mechanisms of T. chinensis leaves to enhanced ultraviolet-A (UV-A) radiation, gel-free/label-free and gel-based proteomics and gas chromatography-mass spectrometry (GC-MS) analyses were performed. The transmission electron microscopy results indicated damage to the chloroplast under UV-A radiation. Proteomics analyses in leaves and chloroplasts showed that photosynthesis-, glycolysis-, secondary metabolism-, stress-, and protein synthesis-, degradation- and activation-related systems were mainly changed under UV-A radiation. Forty-seven PSII proteins and six PSI proteins were identified as being changed in leaves and chloroplasts under UV-A treatment. This indicated that PSII was more sensitive to UV-A than PSI as the target of UV-A light. Enhanced glycolysis, with four glycolysis-related key enzymes increased, provided precursors for secondary metabolism. The 1-deoxy-d-xylulose-5-phosphate reductoisomerase and 4-hydroxy-3-methylbut-2-enyl diphosphate reductase were identified as being significantly increased during UV-A radiation, which resulted in paclitaxel enhancement. Additionally, mRNA expression levels of genes involved in the paclitaxel biosynthetic pathway indicated a down-regulation under UV-A irradiation and up-regulation in dark incubation. These results reveal that a short-term high dose of UV-A radiation could stimulate the plant stress defense system and paclitaxel production. © The Author 2016. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved. For permissions, please email:

  18. Mechanical Response of Thermoelectric Materials

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Case, Eldon D. [Michigan State Univ., East Lansing, MI (United States)


    A sufficient mechanical response of thermoelectric materials (TEMats) to structural loadings is a prerequisite to the exploitation of any candidate TEMat's thermoelectric efficiency. If a TEMat is mechanically damaged or cracks from service-induced stresses, then its thermal and electrical functions can be compromised or even cease. Semiconductor TEMats tend to be quite brittle and have a high coefficient of thermal expansion; therefore, they can be quite susceptible to mechanical failure when subjected to operational thermal gradients. Because of this, sufficient mechanical response (vis-a-vis, mechanical properties) of any candidate TEMat must be achieved and sustained in the context of the service-induced stress state to which it is subjected. This report provides an overview of the mechanical responses of state-of-the-art TEMats; discusses the relevant properties that are associated with those responses and their measurement; and describes important, nonequilibrium phenomena that further complicate their use in thermoelectric devices. For reference purposes, the report also includes several appendixes that list published data on elastic properties and strengths of a variety of TEMats.

  19. Brain mechanisms underlying human communication

    Directory of Open Access Journals (Sweden)

    Matthijs L Noordzij


    Full Text Available Human communication has been described as involving the coding-decoding of a conventional symbol system, which could be supported by parts of the human motor system (i.e. the “mirror neurons system”. However, this view does not explain how these conventions could develop in the first place. Here we target the neglected but crucial issue of how people organize their non-verbal behavior to communicate a given intention without pre-established conventions. We have measured behavioral and brain responses in pairs of subjects during communicative exchanges occurring in a real, interactive, on-line social context. In two fMRI studies, we found robust evidence that planning new communicative actions (by a sender and recognizing the communicative intention of the same actions (by a receiver relied on spatially overlapping portions of their brains (the right posterior superior temporal sulcus. The response of this region was lateralized to the right hemisphere, modulated by the ambiguity in meaning of the communicative acts, but not by their sensorimotor complexity. These results indicate that the sender of a communicative signal uses his own intention recognition system to make a prediction of the intention recognition performed by the receiver. This finding supports the notion that our communicative abilities are distinct from both sensorimotor processes and language abilities.

  20. Neurobiological mechanisms of placebo responses. (United States)

    Zubieta, Jon-Kar; Stohler, Christian S


    Expectations, positive or negative, are modulating factors influencing behavior. They are also thought to underlie placebo effects, potentially impacting perceptions and biological processes. We used sustained pain as a model to determine the neural mechanisms underlying placebo-induced analgesia and affective changes in healthy humans. Subjects were informed that they could receive either an active agent or an inactive compound, similar to routine clinical trials. Using PET and the mu-opioid selective radiotracer [(11)C]carfentanil we demonstrate placebo-induced activation of opioid neurotransmission in a number of brain regions. These include the rostral anterior cingulate, orbitofrontal and dorsolateral prefrontal cortex, anterior and posterior insula, nucleus accumbens, amygdala, thalamus, hypothalamus, and periaqueductal grey. Some of these regions overlap with those involved in pain and affective regulation but also motivated behavior. The activation of endogenous opioid neurotransmission was further associated with reductions in pain report and negative affective state. Additional studies with the radiotracer [(11)C]raclopride, studies labeling dopamine D2/3 receptors, also demonstrate the activation of nucleus accumbens dopamine during placebo administration under expectation of analgesia. Both dopamine and opioid neurotransmission were related to expectations of analgesia and deviations from those initial expectations. When the activity of the nucleus accumbens was probed with fMRI using a monetary reward expectation paradigm, its activation was correlated with both dopamine, opioid responses to placebo in this region and the formation of placebo analgesia. These data confirm that specific neural circuits and neurotransmitter systems respond to the expectation of benefit during placebo administration, inducing measurable physiological changes.

  1. Metacognitive mechanisms underlying lucid dreaming. (United States)

    Filevich, Elisa; Dresler, Martin; Brick, Timothy R; Kühn, Simone


    Lucid dreaming is a state of awareness that one is dreaming, without leaving the sleep state. Dream reports show that self-reflection and volitional control are more pronounced in lucid compared with nonlucid dreams. Mostly on these grounds, lucid dreaming has been associated with metacognition. However, the link to lucid dreaming at the neural level has not yet been explored. We sought for relationships between the neural correlates of lucid dreaming and thought monitoring. Human participants completed a questionnaire assessing lucid dreaming ability, and underwent structural and functional MRI. We split participants based on their reported dream lucidity. Participants in the high-lucidity group showed greater gray matter volume in the frontopolar cortex (BA9/10) compared with those in the low-lucidity group. Further, differences in brain structure were mirrored by differences in brain function. The BA9/10 regions identified through structural analyses showed increases in blood oxygen level-dependent signal during thought monitoring in both groups, and more strongly in the high-lucidity group. Our results reveal shared neural systems between lucid dreaming and metacognitive function, in particular in the domain of thought monitoring. This finding contributes to our understanding of the mechanisms enabling higher-order consciousness in dreams. Copyright © 2015 the authors 0270-6474/15/351082-07$15.00/0.

  2. The Global ECT-MRI Research Collaboration (GEMRIC: Establishing a multi-site investigation of the neural mechanisms underlying response to electroconvulsive therapy

    Directory of Open Access Journals (Sweden)

    Leif Oltedal


    Full Text Available Major depression, currently the world's primary cause of disability, leads to profound personal suffering and increased risk of suicide. Unfortunately, the success of antidepressant treatment varies amongst individuals and can take weeks to months in those who respond. Electroconvulsive therapy (ECT, generally prescribed for the most severely depressed and when standard treatments fail, produces a more rapid response and remains the most effective intervention for severe depression. Exploring the neurobiological effects of ECT is thus an ideal approach to better understand the mechanisms of successful therapeutic response. Though several recent neuroimaging studies show structural and functional changes associated with ECT, not all brain changes associate with clinical outcome. Larger studies that can address individual differences in clinical and treatment parameters may better target biological factors relating to or predictive of ECT-related therapeutic response. We have thus formed the Global ECT-MRI Research Collaboration (GEMRIC that aims to combine longitudinal neuroimaging as well as clinical, behavioral and other physiological data across multiple independent sites. Here, we summarize the ECT sample characteristics from currently participating sites, and the common data-repository and standardized image analysis pipeline developed for this initiative. This includes data harmonization across sites and MRI platforms, and a method for obtaining unbiased estimates of structural change based on longitudinal measurements with serial MRI scans. The optimized analysis pipeline, together with the large and heterogeneous combined GEMRIC dataset, will provide new opportunities to elucidate the mechanisms of ECT response and the factors mediating and predictive of clinical outcomes, which may ultimately lead to more effective personalized treatment approaches.

  3. Mechanical response of biopolymer double networks (United States)

    Carroll, Joshua; Das, Moumita

    We investigate a double network model of articular cartilage (AC) and characterize its equilibrium mechanical response. AC has very few cells and the extracellular matrix mainly determines its mechanical response. This matrix can be thought of as a double polymer network made of collagen and aggrecan. The collagen fibers are stiff and resist tension and compression forces, while aggrecans are flexible and control swelling and hydration. We construct a microscopic model made of two interconnected disordered polymer networks, with fiber elasticity chosen to qualitatively mimic the experimental system. We study the collective mechanical response of this double network as a function of the concentration and stiffness of the individual components as well as the strength of the connection between them using rigidity percolation theory. Our results may provide a better understanding of mechanisms underlying the mechanical resilience of AC, and more broadly may also lead to new perspectives on the mechanical response of multicomponent soft materials. This work was partially supported by a Cottrell College Science Award.

  4. 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 ...

  5. Mechanics of carbon nanotube scission under sonication. (United States)

    Stegen, J


    As-produced carbon nanotubes come in bundles that must be exfoliated for practical applications in nanocomposites. Sonication not only causes the exfoliation of nanotube bundles but also unwanted scission. An understanding of how precisely sonication induces the scission and exfoliation of nanotubes will help maximising the degree of exfoliation while minimising scission. We present a theoretical study of the mechanics of carbon nanotube scission under sonicaton, based on the accepted view that it is caused by strong gradients in the fluid velocity near a transiently collapsing bubble. We calculate the length-dependent scission rate by taking the actual movement of the nanotube during the collapse of a bubble into account, allowing for the prediction of the temporal evolution of the length distribution of the nanotubes. We show that the dependence of the scission rate on the sonication settings and the nanotube properties results in non-universal, experiment-dependent scission kinetics potentially explaining the variety in experimentally observed scission kinetics. The non-universality arises from the dependence of the maximum strain rate of the fluid experienced by a nanotube on its length. The maximum strain rate that a nanotube experiences increases with decreasing distance to the bubble. As short nanotubes are dragged along more easily by the fluid flow they experience a higher maximum strain rate than longer nanotubes. This dependence of the maximum strain rate on nanotube length affects the scaling of tensile strength with terminal length. We find that the terminal length scales with tensile strength to the power of 1/1.16 instead of with an exponent of 1/2 as found when nanotube motion is neglected. Finally, we show that the mechanism we propose responsible for scission can also explain the exfoliation of carbon nanotube bundles.

  6. Relation of mechanical dyssynchrony with underlying cardiac structure and performance in chronic systolic heart failure: implications on clinical response to cardiac resynchronization. (United States)

    Tang, Wai Hong Wilson; Mullens, Wilfried; Borowski, Allen G; Tong, Wilson; Shrestha, Kevin; Troughton, Richard W; Martin, Maureen G; Kassimatis, Kathleen; Agler, Debbie; Jasper, Sue; Grimm, Richard A; Starling, Randall C; Klein, Allan L


    The aim of this study is to describe the relationship between ventricular mechanical dyssynchrony (VMD) and echocardiographic indices of cardiac remodelling. We evaluated 219 ambulatory patients with chronic systolic heart failure [left ventricular ejection fraction (LVEF) Heart Association functional classes II-IV] who underwent echocardiographic evaluation. The presence of dyssynchrony was defined by Bader criteria (intra-VMD > 40 ms and/or inter-VMD > 38 ms). In our study cohort, 59% of patients had evidence of dyssynchrony (including 44% with intra-VMD and 38% with inter-VMD, and 20% with both). Inter-VMD correlated with QRS width (r = 0.48, P chronic systolic heart failure, evidence of mechanical dyssynchrony is prevalent but the underlying cardiac structure and performance may influence the degree of inter-VMD more so than intra-VMD. Our data suggest that the extent of inter-VMD is directly related to the degree of dilatation of the heart but inversely to diastolic dysfunction.

  7. Forests and global warming mitigation in Brazil: opportunities in the Brazilian forest sector for responses to global warming under the 'clean development mechanism''

    International Nuclear Information System (INIS)

    Fearnside, P.M.


    The Kyoto Protocol created global warming response opportunities through the clean development mechanism that allow countries like Brazil to receive investments from companies and governments wishing to offset their emissions of greenhouse gases. Brazil has a special place in strategies for combating global warming because its vast areas of tropical forest represent a potentially large source of emissions if deforested. A number of issues need to be settled to properly assign credit for carbon in the types of options presented by the Brazilian forest sector. These include definition of the units of carbon (permanent sequestration versus carbon-ton-years, the latter being most appropriate for forest options), the means of crediting forest reserve establishment, adoption of discounting or other time-preference weighting for carbon, definition of the accounting method (avoided emissions versus stock maintenance), and mechanism to allow program contributions to be counted, rather than restricting consideration to free-standing projects. Silvicultural plantations offer opportunities for carbon benefits, but have high social impacts in the Brazilian context. Plantations also inherently compete with deforestation reduction options for funds. Forest management has been proposed as a global warming response option, but the assignment of any value to time makes this unattractive in terms of carbon benefits. However, reduced-impact logging can substantially reduce emissions over those from traditional logging practices. Slowing deforestation is the major opportunity offered by Brazil. Slowing deforestation will require understanding its causes and creating functional models capable of generating land-use change scenarios with and without different policy changes and other activities. Brazil already has a number of programs designed to slow deforestation, but the continued rapid loss of forest highlights the vast gulf that exists between the magnitude of the problem and the

  8. Mechanical buckling of artery under pulsatile pressure. (United States)

    Liu, Qin; Han, Hai-Chao


    Tortuosity that often occurs in carotid and other arteries has been shown to be associated with high blood pressure, atherosclerosis, and other diseases. However the mechanisms of tortuosity development are not clear. Our previous studies have suggested that arteries buckling could be a possible mechanism for the initiation of tortuous shape but artery buckling under pulsatile flow condition has not been fully studied. The objectives of this study were to determine the artery critical buckling pressure under pulsatile pressure both experimentally and theoretically, and to elucidate the relationship of critical pressures under pulsatile flow, steady flow, and static pressure. We first tested the buckling pressures of porcine carotid arteries under these loading conditions, and then proposed a nonlinear elastic artery model to examine the buckling pressures under pulsatile pressure conditions. Experimental results showed that under pulsatile pressure arteries buckled when the peak pressures were approximately equal to the critical buckling pressures under static pressure. This was also confirmed by model simulations at low pulse frequencies. Our results provide an effective tool to predict artery buckling pressure under pulsatile pressure. Copyright © 2012 Elsevier Ltd. All rights reserved.

  9. Transient Mechanical Response of Lung Airway Tissue during Mechanical Ventilation

    Directory of Open Access Journals (Sweden)

    Israr Bin Muhammad Ibrahim


    Full Text Available Patients with acute lung injury, airway and other pulmonary diseases often require Mechanical Ventilation (MV. Knowledge of the stress/strain environment in lung airway tissues is very important in order to avoid lung injuries for patients undergoing MV. Airway tissue strains responsible for stressing the lung’s fiber network and rupturing the lung due to compliant airways are very difficult to measure experimentally. Multi-level modeling is adopted to investigate the transient mechanical response of the tissue under MV. First, airflow through a lung airway bifurcation (Generation 4–6 is modeled using Computational Fluid Dynamics (CFD to obtain air pressure during 2 seconds of MV breathing. Next, the transient air pressure was used in structural analysis to obtain mechanical strain experienced by the airway tissue wall. Structural analysis showed that airway tissue from Generation 5 in one bifurcation can stretch eight times that of airway tissue of the same generation number but with different bifurcation. The results suggest sensitivity of load to geometrical features. Furthermore, the results of strain levels obtained from the tissue analysis are very important because these strains at the cellular-level can create inflammatory responses, thus damaging the airway tissues.

  10. Amorphization of ice under mechanical stresses (United States)

    Bordonskii, G. S.; Krylov, S. D.


    The dielectric parameters of freshly produced freshwater ice in the microwave range are investigated. It is established that this kind of ice contains a noticeable amount of amorphous ice. Its production is associated with plastic deformation under mechanical stresses. An assessment of the dielectric-permeability change caused by amorphous ice in the state of a slowly flowing medium is given.

  11. Gas Bubble Dynamics under Mechanical Vibrations (United States)

    Mohagheghian, Shahrouz; Elbing, Brian


    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 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.

  12. Anti-inflammatory effect as a mechanism of effectiveness underlying the clinical benefits of pelotherapy in osteoarthritis patients: regulation of the altered inflammatory and stress feedback response (United States)

    Ortega, E.; Gálvez, I.; Hinchado, M. D.; Guerrero, J.; Martín-Cordero, L.; Torres-Piles, S.


    The purpose of the present investigation was to evaluate whether an anti-inflammatory effect together with an improvement of the regulation of the interaction between the inflammatory and stress responses underlies the clinical benefits of pelotherapy in osteoarthritis (OA) patients. This study evaluated the effects of a 10-day cycle of pelotherapy at the spa centre `El Raposo' (Spain) in a group of 21 OA patients diagnosed with primary knee OA. Clinical assessments included pain intensity using a visual analog scale; pain, stiffness and physical function using the Western Ontario and McMaster Universities Arthritis Index; and health-related quality of life using the EuroQol-5D questionnaire. Serum inflammatory cytokine levels (IL-1β, TNF-α, IL-8, IL-6, IL-10 and TGF-β) were evaluated using the Bio-Plex® Luminex® system. Circulating neuroendocrine-stress biomarkers, such as cortisol and extracellular 72 kDa heat shock protein (eHsp72), were measured by ELISA. After the cycle of mud therapy, OA patients improved the knee flexion angle and OA-related pain, stiffness and physical function, and they reported a better health-related quality of life. Serum concentrations of IL-1β, TNF-α, IL-8, IL-6 and TGF-β, as well as eHsp72, were markedly decreased. Besides, systemic levels of cortisol increased significantly. These results confirm that the clinical benefits of mud therapy may well be mediated, at least in part, by its systemic anti-inflammatory effects and neuroendocrine-immune regulation in OA patients. Thus, mud therapy could be an effective alternative treatment in the management of OA.

  13. Epigenetic mechanisms underlying nervous system diseases. (United States)

    Qureshi, Irfan A; Mehler, Mark F


    Epigenetic mechanisms act as control systems for modulating genomic structure and activity in response to evolving profiles of cell-extrinsic, cell-cell, and cell-intrinsic signals. These dynamic processes are responsible for mediating cell- and tissue-specific gene expression and function and gene-gene and gene-environmental interactions. The major epigenetic mechanisms include DNA methylation and hydroxymethylation; histone protein posttranslational modifications, nucleosome remodeling/repositioning, and higher-order chromatin reorganization; noncoding RNA regulation; and RNA editing. These mechanisms are intimately involved in executing fundamental genomic programs, including gene transcription, posttranscriptional RNA processing and transport, translation, X-chromosome inactivation, genomic imprinting, retrotransposon regulation, DNA replication, and DNA repair and the maintenance of genomic stability. For the nervous system, epigenetics offers a novel and robust framework for explaining how brain development and aging occur, neural cellular diversity is generated, synaptic and neural network connectivity and plasticity are mediated, and complex cognitive and behavioral phenotypes are inherited transgenerationally. Epigenetic factors and processes are, not surprisingly, implicated in nervous system disease pathophysiology through several emerging paradigms - mutations and genetic variation in genes encoding epigenetic factors; impairments in epigenetic factor expression, localization, and function; epigenetic mechanisms modulating disease-associated factors and pathways; and the presence of deregulated epigenetic profiles in central and peripheral tissues. Copyright © 2018 Elsevier B.V. All rights reserved.

  14. DNA under Force: Mechanics, Electrostatics, and Hydration

    Directory of Open Access Journals (Sweden)

    Jingqiang Li


    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.

  15. A finite element study on the mechanical response of the head-neck interface of hip implants under realistic forces and moments of daily activities: Part 1, level walking. (United States)

    Farhoudi, Hamidreza; Fallahnezhad, Khosro; Oskouei, Reza H; Taylor, Mark


    This paper investigates the mechanical response of a modular head-neck interface of hip joint implants under realistic loads of level walking. The realistic loads of the walking activity consist of three dimensional gait forces and the associated frictional moments. These forces and moments were extracted for a 32mm metal-on-metal bearing couple. A previously reported geometry of a modular CoCr/CoCr head-neck interface with a proximal contact was used for this investigation. An explicit finite element analysis was performed to investigate the interface mechanical responses. To study the level of contribution and also the effect of superposition of the load components, three different scenarios of loading were studied: gait forces only, frictional moments only, and combined gait forces and frictional moments. Stress field, micro-motions, shear stresses and fretting work at the contacting nodes of the interface were analysed. Gait forces only were found to significantly influence the mechanical environment of the head-neck interface by temporarily extending the contacting area (8.43% of initially non-contacting surface nodes temporarily came into contact), and therefore changing the stress field and resultant micro-motions during the gait cycle. The frictional moments only did not cause considerable changes in the mechanical response of the interface (only 0.27% of the non-contacting surface nodes temporarily came into contact). However, when superposed with the gait forces, the mechanical response of the interface, particularly micro-motions and fretting work, changed compared to the forces only case. The normal contact stresses and micro-motions obtained from this realistic load-controlled study were typically in the range of 0-275MPa and 0-38µm, respectively. These ranges were found comparable to previous experimental displacement-controlled pin/cylinder-on-disk fretting corrosion studies. Copyright © 2017 Elsevier Ltd. All rights reserved.

  16. Amount of fear extinction changes its underlying mechanisms. (United States)

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


    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.

  17. Brain Mechanisms of Extinction of the Classically Conditioned Eyeblink Response (United States)

    Thompson, Richard F.; Robleto, Karla; Poulos, Andrew M.


    It is well established that the cerebellum and its associated circuitry are essential for classical conditioning of the eyeblink response and other discrete motor responses (e.g., limb flexion, head turn, etc.) learned with an aversive unconditioned stimulus (US). However, brain mechanisms underlying extinction of these responses are still…

  18. Ultra-high performance fibre-reinforced concrete under impact: experimental analysis of the mechanical response in extreme conditions and modelling using the Pontiroli, Rouquand and Mazars model. (United States)

    Erzar, Benjamin; Pontiroli, Christophe; Buzaud, Eric


    To evaluate the vulnerability of ultra-high performance fibre-reinforced concrete (UHPFRC) infrastructure to rigid projectile penetration, over the last few years CEA-Gramat has led an experimental and numerical research programme in collaboration with French universities. During the penetration process, concrete is subjected to extreme conditions of pressure and strain rate. Plasticity mechanisms as well as dynamic tensile and/or shear damage are activated during the tunnelling phase and the cratering of the concrete target. Each mechanism has been investigated independently at the laboratory scale and the role of steel fibres especially has been analysed to understand their influence on the macroscopic behaviour. To extend the experimental results to the structural scale, penetration tests on UHPFRC slabs have been conducted by CEA-Gramat. The analysis of this dataset combined with material characterization experiments allows the role of steel fibres to be identified in the different plasticity and damage mechanisms occurring during penetration. In parallel, some improvements have been introduced into the concrete model developed by Pontiroli, Rouquand and Mazars (PRM model), especially to take into account the contribution made by the fibres in the tensile fracture process. After a primary phase of validation, the capabilities of the PRM model are illustrated by performing numerical simulations of projectile penetration into UHPFRC concrete structures.This article is part of the themed issue 'Experimental testing and modelling of brittle materials at high strain rates'. © 2016 The Author(s).

  19. Habitats under Mechanical and Herbicide Management Regimes

    Directory of Open Access Journals (Sweden)

    Wendy-Ann P. Isaac


    Full Text Available Commelina diffusa is a colonising species of banana orchard habitats in St. Vincent in the Windward Islands of the Caribbean. In the present study, the population dynamics of C. diffusa were investigated in response to mechanical weed management with either a rotary string trimmer or glufosinate in ruderal and banana habitats. The study focused on density and size distribution of the weed over time and their response to two weed management strategies. The population dynamics of C. diffusa differed between the two habitats. Seedling establishment appeared to be an important factor influencing the dynamics of C. diffusa in banana orchards as there was little recruitment of seeds with less flower production compared with ruderal habitats where plants produced more flowers. Plants of C. diffusa in the banana orchard habitat had a longer growth cycle. In the banana orchard habitat, the C. diffusa population was greater and the plants were shorter with mechanical management than in areas treated with glufosinate. The results suggest that it is possible to manipulate the dynamics of C. diffusa in banana orchards as there is less chance of seed recruitment. Further research is necessary to refine an IPM approach for the management of C. diffusa.

  20. Process assessment associated to microbial community response provides insight on possible mechanism of waste activated sludge digestion under typical chemical pretreatments

    DEFF Research Database (Denmark)

    Zhou, Aijuan; Zhang, Jiaguang; Varrone, Cristiano


    Current studies have employed various chemicals for disintegrating and hydrolyzing microbial cells in waste activated sludge (WAS). However, a comprehensive process assessment over the whole anaerobic digestion process has seldom been proposed. Besides, the characterization of microbial community...... responses to these chemicals is not well understood. In this study, the effects of five typical chemicals: solubilizer (β-cyclodextrin, CD), alkaline (NaOH), peroxide (peracetic-acid, PA), biological (rhamnolipid, RL) and chemical (sodium dodecylsulphate, SDS) surfactants on WAS digestion were examined...... was dominated by microorganisms that anaerobically hydrolyze organics to acids, while that in NaOH and SDS was mainly associated to biogas production. This study proved that the overall performance of WAS digestion was substantially depended on the initial chemical pretreatments, which in turn influenced...

  1. BIM-23A760 influences key functional endpoints in pituitary adenomas and normal pituitaries: molecular mechanisms underlying the differential response in adenomas. (United States)

    Ibáñez-Costa, Alejandro; López-Sánchez, Laura M; Gahete, Manuel D; Rivero-Cortés, Esther; Vázquez-Borrego, Mari C; Gálvez, María A; de la Riva, Andrés; Venegas-Moreno, Eva; Jiménez-Reina, Luis; Moreno-Carazo, Alberto; Tinahones, Francisco J; Maraver-Selfa, Silvia; Japón, Miguel A; García-Arnés, Juan A; Soto-Moreno, Alfonso; Webb, Susan M; Kineman, Rhonda D; Culler, Michael D; Castaño, Justo P; Luque, Raúl M


    Chimeric somatostatin/dopamine compounds such as BIM-23A760, an sst2/sst5/D 2 receptors-agonist, have emerged as promising new approaches to treat pituitary adenomas. However, information on direct in vitro effects of BIM-23A760 in normal and tumoral pituitaries remains incomplete. The objective of this study was to analyze BIM-23A760 effects on functional parameters (Ca 2+ signaling, hormone expression/secretion, cell viability and apoptosis) in pituitary adenomas (n = 74), and to compare with the responses of normal primate and human pituitaries (n = 3-5). Primate and human normal pituitaries exhibited similar sst2/sst5/D2 expression patterns, wherein BIM-23A760 inhibited the expression/secretion of several pituitary hormones (specially GH/PRL), which was accompanied by increased sst2/sst5/D2 expression in primates and decreased Ca 2+ concentration in human cells. In tumoral pituitaries, BIM-23A760 also inhibited Ca 2+ concentration, hormone secretion/expression and proliferation. However, BIM-23A760 elicited stimulatory effects in a subset of GHomas, ACTHomas and NFPAs in terms of Ca 2+ signaling and/or hormone secretion, which was associated with the relative somatostatin/dopamine-receptors levels, especially sst5 and sst5TMD4. The chimeric sst2/sst5/D 2 compound BIM-23A760 affects multiple, clinically relevant parameters on pituitary adenomas and may represent a valuable therapeutic tool. The relative ssts/D 2 expression profile, particularly sst5 and/or sst5TMD4 levels, might represent useful molecular markers to predict the ultimate response of pituitary adenomas to BIM-23A760.

  2. Environmental genotoxicity: Probing the underlying mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Shugart, L. [Oak Ridge National Lab., TN (United States); Theodorakis, C. [Tennessee Univ., Knoxville, TN (United States)


    Environmental pollution is a complex issue because of the diversity of anthropogenic agents, both chemical and physical, that have been detected and catalogued. The consequences to biota from exposure to genotoxic agents present an additional problem because of the potential for these agents to produce adverse change at the cellular and organismal levels. Past studies in genetic toxicology at the Oak Ridge National Laboratory have focused on structural damage to the DNA of environmental species that may occur after exposure to genotoxic agents and the use of this information to document exposure and to monitor remediation. In an effort to predict effects at the population, community and ecosystem levels, current studies in genetic ecotoxicology are attempting to characterize the biological mechanisms at the gene level that regulate and limit the response of an individual organism to genotoxic factors in their environment.

  3. Mechanism Underlying Time-dependent Cross-phenomenon between Concentration-response Curves and Concentration Addition Curves: A Case Study of Sulfonamides-Erythromycin mixtures on Escherichia coli (United States)

    Sun, Haoyu; Ge, Hongming; Zheng, Min; Lin, Zhifen; Liu, Ying


    Previous studies have identified a phenomenon in which the concentration-response curves (CRCs) for mixtures cross the curves for concentration addition model when predicting or judging joint toxic actions. However, mechanistic investigations of this phenomenon are extremely limited. In this study, a similar phenomenon was observed when we determined the joint toxic actions of sulfonamides (SAs) and erythromycin (ERY) on Escherichia coli (E. coli), which we named the “cross-phenomenon”, and it was characterized by antagonism in the low-concentration range, addition in the medium-concentration range, and synergism in the high-concentration range. The mechanistic investigation of the cross-phenomenon was as follows: SAs and ERY could form a double block to inhibit the bacterial growth by exhibiting a synergistic effect; however, the hormetic effect of SAs on E. coli led to antagonism in the low-concentration range, resulting from the stimulation of sdiA mRNA expression by SAs, which increased the expression of the efflux pump (AcrAB-TolC) to discharge ERY. Furthermore, this cross-phenomenon was observed to be a time-dependent process induced by the increase of both the concentration and extent of stimulation of sdiA mRNA with exposure time. This work explains the dose-dependent and time-dependent cross-phenomenon and provides evidence regarding the interaction between hormesis and cross-phenomenon.

  4. Evolved Mechanisms Versus Underlying Conditional Relations

    Directory of Open Access Journals (Sweden)

    Astorga Miguel López


    Full Text Available The social contracts theory claims that, in social exchange circumstances, human reasoning is not necessarily led by logic, but by certain evolved mental mechanisms that are useful for catching offenders. An emblematic experiment carried out with the intention to prove this thesis is the first experiment described by Fiddick, Cosmides, and Tooby in their paper of 2000. Lopez Astorga has questioned that experiment claiming that its results depend on an underlying conditional logical form not taken into account by Fiddick, Cosmides, and Tooby. In this paper, I propose an explanation alternative to that of Lopez Astorga, which does not depend on logical forms and is based on the mental models theory. Thus, I conclude that this other alternative explanation is one more proof that the experiment in question does not demonstrate the fundamental thesis of the social contracts theory.

  5. Mechanisms underlying UV-induced immune suppression

    Energy Technology Data Exchange (ETDEWEB)

    Ullrich, Stephen E. [Department of Immunology, University of Texas, MD Anderson Cancer Center, South Campus Research Building 1, 7455 Fannin St., P.O. Box 301402, Houston, TX 77030-1903 (United States)]. E-mail:


    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 ( 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 ( 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.

  6. Mechanisms underlying UV-induced immune suppression

    International Nuclear Information System (INIS)

    Ullrich, Stephen E.


    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 ( 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 ( 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

  7. Two distinct neural mechanisms underlying indirect reciprocity. (United States)

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


    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.

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

    International Nuclear Information System (INIS)

    Yussouff, M.


    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)

  9. Low Oxygen Response Mechanisms in Green Organisms

    Directory of Open Access Journals (Sweden)

    Pierdomenico Perata


    Full Text Available Low oxygen stress often occurs during the life of green organisms, mostly due to the environmental conditions affecting oxygen availability. Both plants and algae respond to low oxygen by resetting their metabolism. The shift from mitochondrial respiration to fermentation is the hallmark of anaerobic metabolism in most organisms. This involves a modified carbohydrate metabolism coupled with glycolysis and fermentation. For a coordinated response to low oxygen, plants exploit various molecular mechanisms to sense when oxygen is either absent or in limited amounts. In Arabidopsis thaliana, a direct oxygen sensing system has recently been discovered, where a conserved N-terminal motif on some ethylene responsive factors (ERFs, targets the fate of the protein under normoxia/hypoxia. In Oryza sativa, this same group of ERFs drives physiological and anatomical modifications that vary in relation to the genotype studied. The microalga Chlamydomonas reinhardtii responses to low oxygen seem to have evolved independently of higher plants, posing questions on how the fermentative metabolism is modulated. In this review, we summarize the most recent findings related to these topics, highlighting promising developments for the future.

  10. Dissociable cognitive mechanisms underlying human path integration. (United States)

    Wiener, Jan M; Berthoz, Alain; Wolbers, Thomas


    Path integration is a fundamental mechanism of spatial navigation. In non-human species, it is assumed to be an online process in which a homing vector is updated continuously during an outward journey. In contrast, human path integration has been conceptualized as a configural process in which travelers store working memory representations of path segments, with the computation of a homing vector only occurring when required. To resolve this apparent discrepancy, we tested whether humans can employ different path integration strategies in the same task. Using a triangle completion paradigm, participants were instructed either to continuously update the start position during locomotion (continuous strategy) or to remember the shape of the outbound path and to calculate home vectors on basis of this representation (configural strategy). While overall homing accuracy was superior in the configural condition, participants were quicker to respond during continuous updating, strongly suggesting that homing vectors were computed online. Corroborating these findings, we observed reliable differences in head orientation during the outbound path: when participants applied the continuous updating strategy, the head deviated significantly from straight ahead in direction of the start place, which can be interpreted as a continuous motor expression of the homing vector. Head orientation-a novel online measure for path integration-can thus inform about the underlying updating mechanism already during locomotion. In addition to demonstrating that humans can employ different cognitive strategies during path integration, our two-systems view helps to resolve recent controversies regarding the role of the medial temporal lobe in human path integration.

  11. Vascular Adventitia Calcification and Its Underlying Mechanism.

    Directory of Open Access Journals (Sweden)

    Na Li

    Full Text Available Previous research on vascular calcification has mainly focused on the vascular intima and media. However, we show here that vascular calcification may also occur in the adventitia. The purpose of this work is to help elucidate the pathogenic mechanisms underlying vascular calcification. The calcified lesions were examined by Von Kossa staining in ApoE-/- mice which were fed high fat diets (HFD for 48 weeks and human subjects aged 60 years and older that had died of coronary heart disease, heart failure or acute renal failure. Explant cultured fibroblasts and smooth muscle cells (SMCswere obtained from rat adventitia and media, respectively. After calcification induction, cells were collected for Alizarin Red S staining. Calcified lesions were observed in the aorta adventitia and coronary artery adventitia of ApoE-/-mice, as well as in the aorta adventitia of human subjects examined. Explant culture of fibroblasts, the primary cell type comprising the adventitia, was successfully induced for calcification after incubation with TGF-β1 (20 ng/ml + mineralization media for 4 days, and the phenotype conversion vascular adventitia fibroblasts into myofibroblasts was identified. Culture of SMCs, which comprise only a small percentage of all cells in the adventitia, in calcifying medium for 14 days resulted in significant calcification.Vascular calcification can occur in the adventitia. Adventitia calcification may arise from the fibroblasts which were transformed into myofibroblasts or smooth muscle cells.

  12. Proteoglycans remodeling in cancer: Underlying molecular mechanisms. (United States)

    Theocharis, Achilleas D; Karamanos, Nikos K


    Extracellular matrix is a highly dynamic macromolecular network. Proteoglycans are major components of extracellular matrix playing key roles in its structural organization and cell signaling contributing to the control of numerous normal and pathological processes. As multifunctional molecules, proteoglycans participate in various cell functions during morphogenesis, wound healing, inflammation and tumorigenesis. Their interactions with matrix effectors, cell surface receptors and enzymes enable them with unique properties. In malignancy, extensive remodeling of tumor stroma is associated with marked alterations in proteoglycans' expression and structural variability. Proteoglycans exert diverse functions in tumor stroma in a cell-specific and context-specific manner and they mainly contribute to the formation of a permissive provisional matrix for tumor growth affecting tissue organization, cell-cell and cell-matrix interactions and tumor cell signaling. Proteoglycans also modulate cancer cell phenotype and properties, the development of drug resistance and tumor stroma angiogenesis. This review summarizes the proteoglycans remodeling and their novel biological roles in malignancies with particular emphasis to the underlying molecular mechanisms. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Mechanical behaviour of nuclear fuel under irradiation

    International Nuclear Information System (INIS)

    Guerin, Y.


    The main mechanical properties (fracture, thermal and irradiation creep) of oxide and carbide fuels are summarised and discussed. Some examples are given of the influence of these mechanical properties on the in-pile behaviour of fuel pins [fr

  14. The Mechanical Response of Multifunctional Battery Systems (United States)

    Tsutsui, Waterloo

    The current state of the art in the field of the mechanical behavior of electric vehicle (EV) battery cells is limited to quasi-static analysis. The lack of published data in the dynamic mechanical behavior of EV battery cells blinds engineers and scientists with the uncertainty of what to expect when EVs experience such unexpected events as intrusions to their battery systems. To this end, the recent occurrences of several EVs catching fire after hitting road debris even make this topic timelier. In order to ensure the safety of EV battery, it is critical to develop quantitative understanding of battery cell mechanical behavior under dynamic compressive loadings. Specifically, the research focuses on the dynamic mechanical loading effect on the standard "18650" cylindrical lithium-ion battery cells. In the study, the force-displacement and voltage-displacement behavior of the battery cells were analyzed experimentally at two strain rates, two state-of-charges, and two unit-cell configurations. The results revealed the strain rate sensitivity of their mechanical responses with the solid sacrificial elements. When the hollow sacrificial cells are used, on the other hand, effect was negligible up to the point of densification strength. Also, the high state-of-charge appeared to increase the stiffness of the battery cells. The research also revealed the effectiveness of the sacrificial elements on the mechanical behavior of a unit cell that consists of one battery cell and six sacrificial elements. The use of the sacrificial elements resulted in the delayed initiation of electric short circuit. Based on the analysis of battery behavior at the cell level, granular battery assembly, a battery pack, was designed and fabricated. The behavior of the granular battery assembly was analyzed both quasistatically and dynamically. Building on the results of the research, various research plans were proposed. Through conducting the research, we sought to answer the following

  15. Physiological mechanisms underlying animal social behaviour. (United States)

    Seebacher, Frank; Krause, Jens


    Many species of animal live in groups, and the group represents the organizational level within which ecological and evolutionary processes occur. Understanding these processes, therefore, relies on knowledge of the mechanisms that permit or constrain group formation. We suggest that physiological capacities and differences in physiology between individuals modify fission-fusion dynamics. Differences between individuals in locomotor capacity and metabolism may lead to fission of groups and sorting of individuals into groups with similar physiological phenotypes. Environmental impacts such as hypoxia can influence maximum group sizes and structure in fish schools by altering access to oxygenated water. The nutritional environment determines group cohesion, and the increase in information collected by the group means that individuals should rely more on social information and form more cohesive groups in uncertain environments. Changing environmental contexts require rapid responses by individuals to maintain group coordination, which are mediated by neuroendocrine signalling systems such as nonapeptides and steroid hormones. Brain processing capacity may constrain social complexity by limiting information processing. Failure to evaluate socially relevant information correctly limits social interactions, which is seen, for example, in autism. Hence, functioning of a group relies to a large extent on the perception and appropriate processing of signals from conspecifics. Many if not all physiological systems are mechanistically linked, and therefore have synergistic effects on social behaviour. A challenge for the future lies in understanding these interactive effects, which will improve understanding of group dynamics, particularly in changing environments.This article is part of the themed issue 'Physiological determinants of social behaviour in animals'. © 2017 The Author(s).

  16. 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: [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland (Australia)


    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.

  17. Mechanisms underlying the endothelium-dependent vasodilatory ...

    African Journals Online (AJOL)

    Relaxations to EGE were significantly reduced by Nω-nitro-L-arginine (L-NA, a competitive inhibitor of NO synthase), slightly but not significantly by charybdotoxin plus apamin (two potent inhibitors of EDHF-mediated responses) and abolished by the combination of L-NA and charybdotoxin plus apamin. Relaxations to EGE ...

  18. An investigation into the mechanism underlying enhanced ...

    African Journals Online (AJOL)

    The solubilisation of primary sewage sludge under sulphate reducing conditions was conducted in controlled flask studies and previously reported findings of enhanced hydrolysis were confirmed. The maximum percentage solubilisation obtained in this study over a 10-day period was 31% and 64% for the methanogenic ...

  19. Supersymmetric quantum mechanics under point singularities

    International Nuclear Information System (INIS)

    Uchino, Takashi; Tsutsui, Izumi


    We provide a systematic study on the possibility of supersymmetry (SUSY) for one-dimensional quantum mechanical systems consisting of a pair of lines R or intervals [-l, l] each having a point singularity. We consider the most general singularities and walls (boundaries) at x = ±l admitted quantum mechanically, using a U(2) family of parameters to specify one singularity and similarly a U(1) family of parameters to specify one wall. With these parameter freedoms, we find that for a certain subfamily the line systems acquire an N = 1 SUSY which can be enhanced to N = 4 if the parameters are further tuned, and that these SUSY are generically broken except for a special case. The interval systems, on the other hand, can accommodate N = 2 or N = 4 SUSY, broken or unbroken, and exhibit a rich variety of (degenerate) spectra. Our SUSY systems include the familiar SUSY systems with the Dirac δ(x)-potential, and hence are extensions of the known SUSY quantum mechanics to those with general point singularities and walls. The self-adjointness of the supercharge in relation to the self-adjointness of the Hamiltonian is also discussed

  20. Decisional responsibility for mechanical ventilation and weaning

    DEFF Research Database (Denmark)

    Rose, Louise; Blackwood, Bronagh; Egerod, Ingrid


    Optimal management of mechanical ventilation and weaning requires dynamic and collaborative decision making to minimize complications and avoid delays in the transition to extubation. In the absence of collaboration, ventilation decision making may be fragmented, inconsistent, and delayed. Our...... objective was to describe the professional group with responsibility for key ventilation and weaning decisions and to examine organizational characteristics associated with nurse involvement....

  1. Factors responsible for accidents in instructional mechanic ...

    African Journals Online (AJOL)

    The Study investigated the factors responsible for accidents in instructional mechanic workshops in Rivers State. Four technical colleges were selected for the study. Properly validated questionnaire were developed and used for the study. In addition, two research questions were posed for the study. Data gathered were ...

  2. Swash Zone Response under Various Wave Regimes

    DEFF Research Database (Denmark)

    Vicinanza, Diego; Baldock, Tom; Contestabile, Pasquale


    The modelling of swash zone (SZ) sediment transport and the resulting morphodynamics have been areas of active research over the last decade. However, many details are still to be understood, whose knowledge will be greatly advanced by the collection of high-quality data under the controlled large......-scale laboratory conditions. The research describes tests carried out in the large wave flume of the Maritime Engineering Laboratory at Catalonia University of Technology, to investigate the SZ under the storm conditions. Its main aim was to compare beach-profile responses for monochromatic waves, monochromatic...... waves plus free long waves, bi-chromatic waves and random waves. Both erosive and accretive conditions were considered. Results discussed here were derived from the analysis of only a part of the whole data set....

  3. Polymers under mechanical stress- an NMR investigation

    Energy Technology Data Exchange (ETDEWEB)

    Boehme, Ute; Scheler, Ulrich [Leibniz Institute of Polymer Research Dresden (Germany); Xu, Bo; Leisen, Johannes; Beckham, Haskell W. [Georgia Institute of Technology, Atlanta, Georgia (United States)


    Low-field NMR using permanent magnets in Halbach arrangements permit NMR investigation without the limits present in high-field NMR. The lower field in conjunction with confined stray field permit the application of NMR, in particular relaxation NMR in a stretching apparatus and a rheometer. Crystalline and amorphous fraction of semi-crystalline polymers are distinguished by their transverse relaxation times. Upon mechanical load the relaxation times of the amorphous fraction changes as seen in in-situ measurements on polypropylene rods. During the formation of a neck the crystalline fraction becomes more prominent.

  4. Mechanisms Underlying Sex Differences in Cannabis Use. (United States)

    Calakos, Katina C; Bhatt, Shivani; Foster, Dawn W; Cosgrove, Kelly P


    Cannabis is the most commonly used illicit substance worldwide. In recent decades, highly concentrated products have flooded the market, and prevalence rates have increased. Gender differences exist in cannabis use, as men have higher prevalence of both cannabis use and cannabis use disorder (CUD), while women progress more rapidly from first use to CUD. This paper reviews findings from preclinical and human studies examining the sex-specific neurobiological underpinnings of cannabis use and CUD, and associations with psychiatric symptoms. Sex differences exist in the endocannabinoid system, in cannabis exposure effects on brain structure and function, and in the co-occurrence of cannabis use with symptoms of anxiety, depression and schizophrenia. In female cannabis users, anxiety symptoms correlate with larger amygdala volume and social anxiety disorder symptoms correlate with CUD symptoms. Female cannabis users are reported to be especially vulnerable to earlier onset of schizophrenia, and mixed trends emerge in the correlation of depressive symptoms with cannabis exposure in females and males. As prevalence of cannabis use may continue to increase given the shifting policy landscape regarding marijuana laws, understanding the neurobiological mechanisms of cannabis exposure in females and males is key. Examining these mechanisms may help inform future research on sex-specific pharmacological and behavioral interventions for women and men with high-risk cannabis use, comorbid psychiatric disease, and CUD.

  5. Mechanisms underlying HIV-1 Vpu-mediated viral egress

    Directory of Open Access Journals (Sweden)

    Nicolas eRoy


    Full Text Available Viruses such as lentiviruses that are responsible for long lasting infections, have to evade several level of cellular immune mechanisms to persist and efficiently disseminate in the host. Over the past decades, many evidences have emerged regarding the major role of accessory proteins of primate lentiviruses (Human (HIV and simian immunodeficiency viruses (SIV in viral evasion from the host immune defense. This short review will provide an overview of the mechanism whereby the accessory protein Vpu contributes to this escape. Vpu is a multifunctional protein that was shown to contribute to viral egress by down-regulating several mediators of the immune system such as CD4, CD1d, NTB-A and the restriction factor BST2. The mechanisms underlying its activity are not fully characterized but rely on its ability to interfere with the host machinery regulating proteins turnover and vesicular trafficking. This review will focus on our current understanding of the mechanisms whereby Vpu down-regulates CD4 and BST2 expression level to favour viral egress.

  6. Physical and chemical mechanisms underlying hematoma evolution

    International Nuclear Information System (INIS)

    Cho, K.J.; Fanders, B.L.; Smid, A.R.; McLaughlin, P.


    Angiostat, a new collagen embolic material supplied at a concentration of 35 mg/ml (Target Therapeutics, Los Angeles) was used for flow-directed hepatic artery embolization in a series of rabbits to examine its acute effects on hepatic microcirculation. Arteriograms were obtained both before and after embolization. The aorta and portal vein were perfused with two different colors of Microfil after the animals were killed,. Cleared liver specimens were examined under a dissection microscope. Extent of dearterialization, status of portal sinusoidal perfusion, and collateral formation after embolization with Angiostat were evaluated. Results will be compared with results achieved using other liquid and particulate embolic agents

  7. Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants. (United States)

    Zhang, Zhaoliang; Liao, Hong; Lucas, William J


    As an essential plant macronutrient, the low availability of phosphorus (P) in most soils imposes serious limitation on crop production. Plants have evolved complex responsive and adaptive mechanisms for acquisition, remobilization and recycling of phosphate (Pi) to maintain P homeostasis. Spatio-temporal molecular, physiological, and biochemical Pi deficiency responses developed by plants are the consequence of local and systemic sensing and signaling pathways. Pi deficiency is sensed locally by the root system where hormones serve as important signaling components in terms of developmental reprogramming, leading to changes in root system architecture. Root-to-shoot and shoot-to-root signals, delivered through the xylem and phloem, respectively, involving Pi itself, hormones, miRNAs, mRNAs, and sucrose, serve to coordinate Pi deficiency responses at the whole-plant level. A combination of chromatin remodeling, transcriptional and posttranslational events contribute to globally regulating a wide range of Pi deficiency responses. In this review, recent advances are evaluated in terms of progress toward developing a comprehensive understanding of the molecular events underlying control over P homeostasis. Application of this knowledge, in terms of developing crop plants having enhanced attributes for P use efficiency, is discussed from the perspective of agricultural sustainability in the face of diminishing global P supplies. © 2014 Institute of Botany, Chinese Academy of Sciences.

  8. The Cytoskeleton and Force Response Mechanisms (United States)

    Allen, Philip Goodwin


    The long term aim of this project was to define the mechanisms by which cells sense and respond to the physical forces experienced at 1g and missing in microgravity. Identification and characterization of the elements of the cells force response mechanism could provide pathways and molecules to serve as targets for pharmacological intervention to mitigate the pathologic effects of microgravity. Mechanical forces experienced by the organism can be transmitted to cells through molecules that allow cells to bind to the extracellular matrix and through other types of molecules which bind cells to each other. These molecules are coupled in large complexes of proteins to structural elements such as the actin cytoskeleton that give the cell the ability to sense, resist and respond to force. Application of small forces to tissue culture cells causes local elevation of intracellular calcium through stretch activated ion channels, increased tyrosine phosphorylation and a restructuring of the actin cytoskeleton. Using collagen coated iron oxide beads and strong magnets, we can apply different levels of force to cells in culture. We have found that force application causes the cells to polymerize actin at the site of mechanical deformation and unexpectedly, to depolymerize actin across the rest of the cell. Observations of GFP- actin expressing cells demonstrate that actin accumulates at the site of deformation within the first five minutes of force application and is maintained for many tens of minutes after force is removed. Consistent with the reinforcement of the cytoskeletal structures underlying the integrin-bead interaction, force also alters the motion of bound magnetic beads. This effect is seen following the removal of the magnetic field, and is only partially ablated by actin disruption with cytochalsin B. While actin is polymerizing locally at the site of force application, force also stimulates a global reduction in actin filament content within the cells. We have

  9. Mechanisms underlying selecting objects for action

    Directory of Open Access Journals (Sweden)

    Melanie eWulff


    Full Text Available We assessed the factors which affect the selection of objects for action, focusing on the role of action knowledge and its modulation by distracters. 14 neuropsychological patients and 10 healthy aged-matched controls selected pairs of objects commonly used together among distracters in two contexts: with real objects and with pictures of the same objects presented sequentially on a computer screen. Across both tasks, semantically related distracters led to slower responses and more errors than unrelated distracters and the object actively used for action was selected prior to the object that would be passively held during the action. We identified a sub-group of patients (N=6 whose accuracy was 2SD below the controls performances in the real object task. Interestingly, these impaired patients were more affected by the presence of unrelated distracters during both tasks than intact patients and healthy controls. Note the impaired had lesions to left parietal, right anterior temporal and bilateral pre-motor regions. We conclude that: (1 motor procedures guide object selection for action, (2 semantic knowledge affects action-based selection, (3 impaired action decision is associated with the inability to ignore distracting information and (4 lesions to either the dorsal or ventral visual stream can lead to deficits in making action decisions. Overall, the data indicate that impairments in everyday tasks can be evaluated using a simulated computer task. The implications for rehabilitation are discussed.

  10. The Stress Response of Escherichia coli under Microgravity. (United States)

    Lynch, S.; Matin, A.

    At the onset of adverse environmental conditions, bacteria induce a controlled stress response to enable survival. Escherichia coli induces stress-specific reactions in response to a variety of environmental strains. A family of proteins termed sigma (s) factors is pivotal to the regulation of stress responses in bacteria. In particular Sigma S (ss) regulates several stress responses in E. coli and serves as an important global stress regulatory protein. Under optimal growth conditions, levels of ss are maintained at low cellular concentrations primarily via a proteolytic regulatory mechanism. At the onset of stress, ss levels increase due to increased stability of the molecule, facilitating transcriptional initiation and up regulation of specific stress related proteins. Concentrations of ss can therefore be indicative of cellular stress levels. Recent work by Kendrick et al demonstrated that Salmonella species grown under conditions of simulated microgravity display increased virulence - a stress-related phenotype. Using E. coli as a model system we aim to investigate the stress response elicited by the organism under conditions of simulated microgravity (SMG). SMG is generated in specially constructed rotary cell culture systems termed HARVs (High Aspect Ratio Vessels- Synthecon Inc.). By rotating at constant velocity around a vertical axis an environment is produced in which the gravitational vectors are randomized over the surface of the cell, resulting in an overall-time-averaged gravitational vector of 10-2 x g (4). E. coli cultures grown in HARVs under conditions of normal gravity (NG) and SMG repeatedly display slower growth kinetics under SMG. Western analysis of cells at exponential and stationary phase of growth from both cultures reveal similar levels of ss exist in exponential phase under both SMG and NG conditions. However, during stationary phase, levels of ss are at least 2-fold higher under conditions of SMG as compared to NG. Translational fusion

  11. Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

    Directory of Open Access Journals (Sweden)

    Vanessa Cohignac


    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.

  12. Mechanical properties and failure mechanisms of graphene under a central load. (United States)

    Wang, Shuaiwei; Yang, Baocheng; Zhang, Shouren; Yuan, Jinyun; Si, Yubing; Chen, Houyang


    By employing molecular dynamics simulations, the evolution of deformation of a monolayer graphene sheet under a central transverse loading are investigated. Dependence of mechanical responses on the symmetry (shape) of the loading domain, on the size of the graphene sheet, and on temperature, is determined. It is found that the symmetry of the loading domain plays a central role in fracture strength and strain. By increasing the size of the graphene sheet or increasing temperature, the tensile strength and fracture strain decrease. The results have demonstrated that the breaking force and breaking displacement are sensitive to both temperature and the symmetry of the loading domain. In addition, we find that the intrinsic strength of graphene under a central load is much smaller than that of graphene under a uniaxial load. By examining the deformation processes, two failure mechanisms are identified namely, brittle bond breaking and plastic relaxation. In the second mechanism, the Stone-Wales transformation occurs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. The prestress-dependent mechanical response of magnetorheological elastomers

    International Nuclear Information System (INIS)

    Feng, Jiabin; Xuan, Shouhu; Liu, Taixiang; Ge, Lin; Zhou, Hong; Gong, Xinglong; Yan, Lixun


    Magnetorheological elastomers (MREs) are intelligent materials consisting of a rubber matrix filled with magnetizable particles. In many engineering applications, MREs are usually pre-confined and work with constraint-induced prestress. The prestress can significantly change the mechanical properties of MREs. In this work, the influence of prestress on the mechanical response of MREs is studieds both experimentally and theoretically. The storage modulus as well as the magneto-induced modulus change non-linearly with increasing prestress and three regions can be found in the non-linear change. In the non-full contact region, the MREs present poor mechanical properties at small prestress due to the unevenness of the sample surface. In the full contact region, the MREs are under suitable prestress, thus they present good mechanical properties. In the overload region, the pre-configured microstructure of the MREs is destroyed under the large prestress. Moreover, an analytical model is proposed to study the prestress-dependent mechanical properties of MREs. It is revealed that the prestress can change the inter-particle distance, thus further affecting the mechanical response of MREs. (paper)

  14. Nonlinear Mechanics of MEMS Rectangular Microplates under Electrostatic Actuation

    KAUST Repository

    Saghir, Shahid


    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

  15. Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf


    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...

  16. 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


    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

  17. Mechanisms underlying temperature extremes in Iberia: a Lagrangian perspective

    Directory of Open Access Journals (Sweden)

    João A. Santos


    Full Text Available The mechanisms underlying the occurrence of temperature extremes in Iberia are analysed considering a Lagrangian perspective of the atmospheric flow, using 6-hourly ERA-Interim reanalysis data for the years 1979–2012. Daily 2-m minimum temperatures below the 1st percentile and 2-m maximum temperatures above the 99th percentile at each grid point over Iberia are selected separately for winter and summer. Four categories of extremes are analysed using 10-d backward trajectories initialized at the extreme temperature grid points close to the surface: winter cold (WCE and warm extremes (WWE, and summer cold (SCE and warm extremes (SWE. Air masses leading to temperature extremes are first transported from the North Atlantic towards Europe for all categories. While there is a clear relation to large-scale circulation patterns in winter, the Iberian thermal low is important in summer. Along the trajectories, air mass characteristics are significantly modified through adiabatic warming (air parcel descent, upper-air radiative cooling and near-surface warming (surface heat fluxes and radiation. High residence times over continental areas, such as over northern-central Europe for WCE and, to a lesser extent, over Iberia for SWE, significantly enhance these air mass modifications. Near-surface diabatic warming is particularly striking for SWE. WCE and SWE are responsible for the most extreme conditions in a given year. For WWE and SCE, strong temperature advection associated with important meridional air mass transports are the main driving mechanisms, accompanied by comparatively minor changes in the air mass properties. These results permit a better understanding of mechanisms leading to temperature extremes in Iberia.

  18. 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.

  19. Stress analysis in a functionally graded disc under mechanical loads ...

    Indian Academy of Sciences (India)

    Stress analysis in a functionally graded disc under mechanical loads and a steady state temperature distribution. HASAN ÇALLIO ˘GLU. Department of Mechanical Engineering, Pamukkale University, 20070,. Denizli, Turkey e-mail: MS received 25 November 2009; revised 12 August 2010; accepted.

  20. 42 CFR 408.86 - Responsibilities under group billing arrangement. (United States)


    ... Payment § 408.86 Responsibilities under group billing arrangement. (a) Enrollee responsibilities. (1) The enrollee is still responsible for premium payments; the group payer simply acts as his agent. If the agent... 42 Public Health 2 2010-10-01 2010-10-01 false Responsibilities under group billing arrangement...

  1. Banking efficiency under corporate social responsibilities

    DEFF Research Database (Denmark)

    Ohene-Asare, Kwaku; Asmild, Mette


    This paper expands the banking efficiency literature by developing a banking intermediation model that captures both profit-maximizing and Corporate Social Responsibilities (CSR) of banks. Using a data set of 21 banks for each year 2006-2008, we evaluate the relative efficiency of Ghanaian banks...... that are socially responsible may have economic advantages....

  2. Host response mechanisms in periodontal diseases

    Directory of Open Access Journals (Sweden)

    Nora SILVA


    a stage that presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors.

  3. Host response mechanisms in periodontal diseases (United States)

    SILVA, Nora; ABUSLEME, Loreto; BRAVO, Denisse; DUTZAN, Nicolás; GARCIA-SESNICH, Jocelyn; VERNAL, Rolando; HERNÁNDEZ, Marcela; GAMONAL, Jorge


    presents a significantly host immune and inflammatory response to the microbial challenge that determine of susceptibility to develop the destructive/progressive periodontitis under the influence of multiple behavioral, environmental and genetic factors. PMID:26221929

  4. The mechanisms for social and environmentally responsible agricultural land use


    Ye. Mishenin; I. Yarova


    This paper deals with arguments that the most effective mechanism for greening use of land resources is to increase the level of social and environmental responsibility. The mechanisms for social and environmentally responsible agricultural land use are formed.

  5. Thermodynamical aspects of modeling the mechanical response of granular materials

    International Nuclear Information System (INIS)

    Elata, D.


    In many applications in rock physics, the material is treated as a continuum. By supplementing the related conservation laws with constitutive equations such as stress-strain relations, a well-posed problem can be formulated and solved. The stress-strain relations may be based on a combination of experimental data and a phenomenological or micromechanical model. If the model is physically sound and its parameters have a physical meaning, it can serve to predict the stress response of the material to unmeasured deformations, predict the stress response of other materials, and perhaps predict other categories of the mechanical response such as failure, permeability, and conductivity. However, it is essential that the model be consistent with all conservation laws and consistent with the second law of thermodynamics. Specifically, some models of the mechanical response of granular materials proposed in literature, are based on intergranular contact force-displacement laws that violate the second law of thermodynamics by permitting energy generation at no cost. This diminishes the usefulness of these models as it invalidates their predictive capabilities. [This work was performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.

  6. Underlying Mechanisms of Tinnitus: Review and Clinical Implications (United States)

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


    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

  7. Neural Mechanisms Underlying Hyperphagia in Prader-Willi Syndrome (United States)

    Holsen, Laura M.; Zarcone, Jennifer R.; Brooks, William M.; Butler, Merlin G.; Thompson, Travis I.; Ahluwalia, Jasjit S.; Nollen, Nicole L.; Savage, Cary R.


    Objective Prader-Willi syndrome (PWS) is a genetic disorder associated with developmental delay, obesity, and obsessive behavior related to food consumption. The most striking symptom of PWS is hyperphagia; as such, PWS may provide important insights into factors leading to overeating and obesity in the general population. We used functional magnetic resonance imaging to study the neural mechanisms underlying responses to visual food stimuli, before and after eating, in individuals with PWS and a healthy weight control (HWC) group. Research Methods and Procedures Participants were scanned once before (pre-meal) and once after (post-meal) eating a standardized meal. Pictures of food, animals, and blurred control images were presented in a block design format during acquisition of functional magnetic resonance imaging data. Results Statistical contrasts in the HWC group showed greater activation to food pictures in the pre-meal condition compared with the post-meal condition in the amygdala, orbitofrontal cortex, medial prefrontal cortex (medial PFC), and frontal operculum. In comparison, the PWS group exhibited greater activation to food pictures in the post-meal condition compared with the pre-meal condition in the orbitofrontal cortex, medial PFC, insula, hippocampus, and parahippocampal gyrus. Between-group contrasts in the pre- and post-meal conditions confirmed group differences, with the PWS group showing greater activation than the HWC group after the meal in food motivation networks. Discussion Results point to distinct neural mechanisms associated with hyperphagia in PWS. After eating a meal, the PWS group showed hyperfunction in limbic and para-limbic regions that drive eating behavior (e.g., the amygdala) and in regions that suppress food intake (e.g., the medial PFC). PMID:16861608

  8. Neural mechanisms underlying hyperphagia in Prader-Willi syndrome. (United States)

    Holsen, Laura M; Zarcone, Jennifer R; Brooks, William M; Butler, Merlin G; Thompson, Travis I; Ahluwalia, Jasjit S; Nollen, Nicole L; Savage, Cary R


    Prader-Willi syndrome (PWS) is a genetic disorder associated with developmental delay, obesity, and obsessive behavior related to food consumption. The most striking symptom of PWS is hyperphagia; as such, PWS may provide important insights into factors leading to overeating and obesity in the general population. We used functional magnetic resonance imaging to study the neural mechanisms underlying responses to visual food stimuli, before and after eating, in individuals with PWS and a healthy weight control (HWC) group. Participants were scanned once before (pre-meal) and once after (post-meal) eating a standardized meal. Pictures of food, animals, and blurred control images were presented in a block design format during acquisition of functional magnetic resonance imaging data. Statistical contrasts in the HWC group showed greater activation to food pictures in the pre-meal condition compared with the post-meal condition in the amygdala, orbitofrontal cortex, medial prefrontal cortex (medial PFC), and frontal operculum. In comparison, the PWS group exhibited greater activation to food pictures in the post-meal condition compared with the pre-meal condition in the orbitofrontal cortex, medial PFC, insula, hippocampus, and parahippocampal gyrus. Between-group contrasts in the pre- and post-meal conditions confirmed group differences, with the PWS group showing greater activation than the HWC group after the meal in food motivation networks. Results point to distinct neural mechanisms associated with hyperphagia in PWS. After eating a meal, the PWS group showed hyperfunction in limbic and paralimbic regions that drive eating behavior (e.g., the amygdala) and in regions that suppress food intake (e.g., the medial PFC).

  9. Mechanics of responsive polymers via conformationally switchable molecules (United States)

    Brighenti, Roberto; Artoni, Federico; Vernerey, Franck; Torelli, Martina; Pedrini, Alessandro; Domenichelli, Ilaria; Dalcanale, Enrico


    Active materials are those capable of giving some physical reaction under external stimuli coming from the environment such as temperature, pH, light, mechanical stress, etc. Reactive polymeric materials can be obtained through the introduction of switchable molecules in their network, i.e. molecules having two distinct stable conformations: if properly linked to the hosting polymer chains, the switching from one state to the other can promote a mechanical reaction of the material, detectable at the macroscale, and thus enables us to tune the response according to a desired functionality. In the present paper, the main aspects of the mechanical behavior of polymeric materials with embedded switchable molecules-properly linked to the polymer's chains-are presented and discussed. Starting from the micro mechanisms occurring in such active material, a continuum model is developed, providing a straightforward implementation in computational approaches. Finally, some experimental outcomes related to a switchable molecules (known as quinoxaline cavitands) added to an elastomeric PDMS under chemical stimuli, are presented and quantitatively discussed through the use of the developed mechanical framework.

  10. Mechanisms underlying the antihypertensive properties of Urtica dioica. (United States)

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


    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.

  11. Corporate Social Responsibility Under Authoritarian Capitalism

    DEFF Research Database (Denmark)

    Hofman, Peter S.; Moon, Jeremy; Wu, Bin


    This article introduces the concept of corporate social responsibility (CSR) in the seemingly oxymoronic context of Chinese “authoritarian capitalism.” Following an introduction to the emergence of authoritarian capitalism, the article considers the emergence of CSR in China using Matten and Moon’s...

  12. Banking efficiency under corporate social responsibilities

    DEFF Research Database (Denmark)

    Ohene-Asare, Kwaku; Asmild, Mette


    This paper expands the banking efficiency literature by developing a banking intermediation model that captures both profit-maximizing and Corporate Social Responsibilities (CSR) of banks. Using a data set of 21 banks for each year 2006-2008, we evaluate the relative efficiency of Ghanaian banks...

  13. Mechanical Property Analysis of Circular Polymer Membrane under Uniform Pressure


    Jianbing, Sang; Xiang, Li; Sufang, Xing; Wenjia, Wang


    Mechanical property analysis of circular hyperelastic polymer membrane under uniform pressure has been researched in this work. The polymer membrane material is assumed to be homogeneous and isotropic and incompressibility of materials has been considered. Based on the modified stain energy function from Gao and nonmomental theory of axial symmetry thin shell, finite deformation analysis of polymer membrane under uniform pressure has been proposed in current configuration and governing equati...

  14. Parametric study of control mechanism of cortical bone remodeling under mechanical stimulus (United States)

    Wang, Yanan; Qin, Qing-Hua


    The control mechanism of mechanical bone remodeling at cellular level was investigated by means of an extensive parametric study on a theoretical model described in this paper. From a perspective of control mechanism, it was found that there are several control mechanisms working simultaneously in bone remodeling which is a complex process. Typically, an extensive parametric study was carried out for investigating model parameter space related to cell differentiation and apoptosis which can describe the fundamental cell lineage behaviors. After analyzing all the combinations of 728 permutations in six model parameters, we have identified a small number of parameter combinations that can lead to physiologically realistic responses which are similar to theoretically idealized physiological responses. The results presented in the work enhanced our understanding on mechanical bone remodeling and the identified control mechanisms can help researchers to develop combined pharmacological-mechanical therapies to treat bone loss diseases such as osteoporosis.

  15. Shared Responsibility under Article 80 CISG

    DEFF Research Database (Denmark)

    Neumann, Thomas


    Article 80 exempts from liability in the situation where the promisor's failure to perform has been caused by the promisee. The Article has been insufficiently dealt with in the literature and has been overlooked in case law. The paper demonstrates that article 80 has an independent scope compared...... of shared responsibility in which both the promisor and the promisee seem to have caused the promisor's failure to perform. Article 80 applies to three different case types. Firstly, cases of sole causation by the promisee. Secondly, cases of joint causation by both parties where the consequences of each...... contribution can be delimited. Thirdly, cases of joint causation where the consequences of each party's contribution cannot be delimited (shared responsibility). The third case type is investigated further and it is established that an apportionment based on a comparative evaluation of the parties is called...

  16. Study on Mechanical Properties of Barite Concrete under Impact Load (United States)

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


    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.

  17. Damage mechanisms in PBT-GF30 under thermo-mechanical cyclic loading

    International Nuclear Information System (INIS)

    Schaaf, A.; De Monte, M.; Hoffmann, C.; Vormwald, M.; Quaresimin, M.


    The scope of this paper is the investigation of damage mechanisms at microscopic scale on a short glass fiber reinforced polybutylene terephthalate (PBT-GF30) under thermo-mechanical cyclic loading. In addition the principal mechanisms are verified through micro mechanical FE models. In order to investigate the fatigue behavior of the material both isothermal strain controlled fatigue (ISCF) tests at three different temperatures and thermo-mechanical fatigue (TMF) tests were conducted on plain and notched specimens, manufactured by injection molding. The goal of the work is to determine the damage mechanisms occurring under TMF conditions and to compare them with the mechanisms occurring under ISCF. For this reason fracture surfaces of TMF and ISCF samples loaded at different temperature levels were analyzed using scanning electron microscopy. Furthermore, specimens that failed under TMF were examined on microsections revealing insight into both crack initiation and crack propagation. The findings of this investigation give valuable information about the main damage mechanisms of PBT-GF30 under TMF loading and serve as basis for the development of a TMF life estimation methodology

  18. Bucket Foundation Response Under Various Displacement Rates

    DEFF Research Database (Denmark)

    Vaitkunaite, Evelina; Nielsen, Benjaminn Nordahl; Ibsen, Lars Bo


    The present testing program aims at showing the pore pressure response around a bucket foundation skirt as well as the load and displacement change due to ten different displacement rates. Research findings are useful for a numerical model calibration focusing on the design of the upwind foundation...... in a multi-bucket foundation system. The foundation model is at a scale of approximately 1:20 prototype foundation size. The tests are performed in a pressure tank with the foundation model installed in dense sand. Based on the data, the conclusion is that the bucket foundation design in a storm case should...

  19. Neural Circuitry and Plasticity Mechanisms Underlying Delay Eyeblink Conditioning (United States)

    Freeman, John H.; Steinmetz, Adam B.


    Pavlovian eyeblink conditioning has been used extensively as a model system for examining the neural mechanisms underlying associative learning. Delay eyeblink conditioning depends on the intermediate cerebellum ipsilateral to the conditioned eye. Evidence favors a two-site plasticity model within the cerebellum with long-term depression of…

  20. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics. (United States)

    Prescott, Aaron M; McCollough, Forest W; Eldreth, Bryan L; Binder, Brad M; Abel, Steven M


    Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. The dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i) whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii) what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB). In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB). Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations, and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms underlying ethylene

  1. Analysis of Network Topologies Underlying Ethylene Growth Response Kinetics

    Directory of Open Access Journals (Sweden)

    Aaron M. Prescott


    Full Text Available Most models for ethylene signaling involve a linear pathway. However, measurements of seedling growth kinetics when ethylene is applied and removed have resulted in more complex network models that include coherent feedforward, negative feedback, and positive feedback motifs. However, the dynamical responses of the proposed networks have not been explored in a quantitative manner. Here, we explore (i whether any of the proposed models are capable of producing growth-response behaviors consistent with experimental observations and (ii what mechanistic roles various parts of the network topologies play in ethylene signaling. To address this, we used computational methods to explore two general network topologies: The first contains a coherent feedforward loop that inhibits growth and a negative feedback from growth onto itself (CFF/NFB. In the second, ethylene promotes the cleavage of EIN2, with the product of the cleavage inhibiting growth and promoting the production of EIN2 through a positive feedback loop (PFB. Since few network parameters for ethylene signaling are known in detail, we used an evolutionary algorithm to explore sets of parameters that produce behaviors similar to experimental growth response kinetics of both wildtype and mutant seedlings. We generated a library of parameter sets by independently running the evolutionary algorithm many times. Both network topologies produce behavior consistent with experimental observations and analysis of the parameter sets allows us to identify important network interactions and parameter constraints. We additionally screened these parameter sets for growth recovery in the presence of sub-saturating ethylene doses, which is an experimentally-observed property that emerges in some of the evolved parameter sets. Finally, we probed simplified networks maintaining key features of the CFF/NFB and PFB topologies. From this, we verified observations drawn from the larger networks about mechanisms

  2. Intercomparison of chemical mechanisms for air quality policy formulation and assessment under North American conditions. (United States)

    Derwent, Richard


    The intercomparison of seven chemical mechanisms for their suitability for air quality policy formulation and assessment is described. Box modeling techniques were employed using 44 sets of background environmental conditions covering North America to constrain the chemical development of the longer lived species. The selected mechanisms were modified to enable an unbiased assessment of the adequacy of the parameterizations of photochemical ozone production from volatile organic compound (VOC) oxidation in the presence of NO x . Photochemical ozone production rates responded differently to 30% NO x and VOC reductions with the different mechanisms, despite the striking similarities between the base-case ozone production rates. The 30% reductions in NO x and VOCs also produced changes in OH. The responses in OH to 30% reductions in NO x and VOCs appeared to be more sensitive to mechanism choice, compared with the responses in the photochemical ozone production rates. Although 30% NO x reductions generally led to decreases in OH, 30% reductions in VOCs led to increases in OH, irrespective of mechanism choice and background environmental conditions. The different mechanisms therefore gave different OH responses to NO x and VOC reductions and so would give different responses in terms of changes in the fate and behavior of air toxics, acidification and eutrophication, and fine particle formation compared with others, in response to ozone control strategies. Policymakers need to understand that there are likely to be inherent differences in the responses to ozone control strategies between different mechanisms, depending on background environmental conditions and the extents of NO x and VOC reductions under consideration. The purpose of this paper is to compare predicted ozone responses to NO x and VOC reductions with seven chemical mechanisms under North American conditions. The good agreement found between the tested mechanisms should provide some support for their


    Directory of Open Access Journals (Sweden)

    Iván Darío Ocampo


    Full Text Available The immune system maintains the integrity of the organisms through a complex network of molecules, cells, and tissues that recognize internal or external antigenic substances to neutralized and eliminate them. The mechanisms of immune response have evolved in a modular fashion, where members of a given module interact strongly among them, but weakly with members of other modules, providing robustness and evolvability to the immune system. Ancestral modules are the raw material for the generation of new modules through evolution. Thus, the study of immune systems in basal metazoans such as cnidarians seeks to determine the basic tool kit from which the metazoans started to construct their immune systems. In addition, understanding the immune mechanisms in cnidarians contributes to decipher the etiopathology of coral diseases of infectious nature that are affecting coral reefs worldwide. RESUMEN El sistema inmune mantiene la integridad de los organismos vivos por medio de una red compleja de moléculas, células y tejidos que reconocen sustancias antigénicas internas o externas para neutralizarlas y eliminarlas. Los mecanismos de respuesta inmune han evolucionado de una manera modular, en donde miembros de un módulo dado interactúan fuertemente entre sí, pero débilmente con componentes de otros módulos, otorgando así robustez y potencial evolutivo al sistema inmune. Módulos ancestrales representan el material básico para la generación de nuevos módulos durante el proceso evolutivo. Así, el estudio de sistemas inmunes en metazoarios basales como los cnidarios busca determinar cuales son los módulos ancestrales a partir de los cuales se constituyen los sistemas inmunes de animales derivados. Adicionalmente, el entendimiento de los mecanismos de respuesta inmune en cnidarios eventualmente contribuirá a descifrar la etiopatología de las enfermedades de corales de carácter infeccioso que está afectando los corales en el mundo.

  4. Potential Mechanisms Underlying Centralized Pain and Emerging Therapeutic Interventions

    Directory of Open Access Journals (Sweden)

    Olivia C. Eller-Smith


    Full Text Available Centralized pain syndromes are associated with changes within the central nervous system that amplify peripheral input and/or generate the perception of pain in the absence of a noxious stimulus. Examples of idiopathic functional disorders that are often categorized as centralized pain syndromes include fibromyalgia, chronic pelvic pain syndromes, migraine, and temporomandibular disorder. Patients often suffer from widespread pain, associated with more than one specific syndrome, and report fatigue, mood and sleep disturbances, and poor quality of life. The high degree of symptom comorbidity and a lack of definitive underlying etiology make these syndromes notoriously difficult to treat. The main purpose of this review article is to discuss potential mechanisms of centrally-driven pain amplification and how they may contribute to increased comorbidity, poorer pain outcomes, and decreased quality of life in patients diagnosed with centralized pain syndromes, as well as discuss emerging non-pharmacological therapies that improve symptomology associated with these syndromes. Abnormal regulation and output of the hypothalamic-pituitary-adrenal (HPA axis is commonly associated with centralized pain disorders. The HPA axis is the primary stress response system and its activation results in downstream production of cortisol and a dampening of the immune response. Patients with centralized pain syndromes often present with hyper- or hypocortisolism and evidence of altered downstream signaling from the HPA axis including increased Mast cell (MC infiltration and activation, which can lead to sensitization of nearby nociceptive afferents. Increased peripheral input via nociceptor activation can lead to “hyperalgesic priming” and/or “wind-up” and eventually to central sensitization through long term potentiation in the central nervous system. Other evidence of central modifications has been observed through brain imaging studies of functional

  5. Earthquake responses of a beam supported by a mechanical snubber

    International Nuclear Information System (INIS)

    Ohmata, Kenichiro; Ishizu, Seiji.


    The mechanical snubber is an earthquakeproof device for piping systems under particular circumstances such as high temperature and radioactivity. It has nonlinearities in both load and frequency response. In this report, the resisting force characteristics of the snubber and earthquake responses of piping (a simply supported beam) which is supported by the snubber are simulated using Continuous System Simulation Language (CSSL). Digital simulations are carried out for various kinds of physical properties of the snubber. The restraint effect and the maximum resisting force of the snubber during earthquakes are discussed and compared with the case of an oil damper. The earthquake waves used here are E1 Centro N-S and Akita Harbour N-S (Nihonkai-Chubu earthquake). (author)

  6. Permeability and mechanical properties of cracked glass under pressure

    International Nuclear Information System (INIS)

    Ougier-Simonin, A.


    Crack initiation and growth in brittle solids under tension have been extensively studied by various experimental, theoretical and numerical approaches. If has been established that dynamic brittle fracture is related to fundamental physical parameters and processes, such as crack speed, crack branching, surface roughening, and dynamic instabilities. On the other hand, less studies have been done in the area of compressive fracture despite its vital importance in geology, material science and engineering applications (such as the improvement and the insurance of the nuclear wastes storage). The present work aims to investigate thermo-mechanical cracking effects on elastic wave velocities, mechanical strength and permeability und r pressure to evaluate damage evolution, brittle failure and transport properties on a synthetic glass (SON 68), and to highlight the very different behavior of the glass amorphous structure compared to any rock structure. The original glass, produced in ideal conditions of slow cooling that prevent from any crack formation, exhibits a linear and reversible mechanical behavior and isotropic elastic velocities, as expected. It also presents a high strength as it fails at about 700 MPa of deviatoric stress for a confining pressure of 15 MPa. We choose to apply to some original glass samples a reproducible method (thermal treatment with a thermal shock of T=100,200 and 300 C) which creates cracks with a homogeneous distribution. The impact of the thermal treatment is clearly visible through the elastic wave velocity measurements as we observe crack closure under hydrostatic conditions (at about 30 MPa). For T ≥ 200 C, the glass mechanical behavior becomes non linear and records an irreversible damage. The total damage observed with the acoustic emissions in these samples underlines the combination of the thermal and the mechanical cracks which drive to the sample failure. The results obtained with pore fluid pressure show a very small

  7. Response mechanisms of attached premixed flames subjected to harmonic forcing (United States)


    The persistent thrust for a cleaner, greener environment has prompted air pollution regulations to be enforced with increased stringency by environmental protection bodies all over the world. This has prompted gas turbine manufacturers to move from nonpremixed combustion to lean, premixed combustion. These lean premixed combustors operate quite fuel-lean compared to the stochiometric, in order to minimize CO and NOx productions, and are very susceptible to oscillations in any of the upstream flow variables. These oscillations cause the heat release rate of the flame to oscillate, which can engage one or more acoustic modes of the combustor or gas turbine components, and under certain conditions, lead to limit cycle oscillations. This phenomenon, called thermoacoustic instabilities, is characterized by very high pressure oscillations and increased heat fluxes at system walls, and can cause significant problems in the routine operability of these combustors, not to mention the occasional hardware damages that could occur, all of which cumulatively cost several millions of dollars. In a bid towards understanding this flow-flame interaction, this research works studies the heat release response of premixed flames to oscillations in reactant equivalence ratio, reactant velocity and pressure, under conditions where the flame preheat zone is convectively compact to these disturbances, using the G-equation. The heat release response is quantified by means of the flame transfer function and together with combustor acoustics, forms a critical component of the analytical models that can predict combustor dynamics. To this end, low excitation amplitude (linear) and high excitation amplitude (nonlinear) responses of the flame are studied in this work. The linear heat release response of lean, premixed flames are seen to be dominated by responses to velocity and equivalence ratio fluctuations at low frequencies, and to pressure fluctuations at high frequencies which are in the

  8. 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


    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)

  9. Reliability Issues and Solutions in Flexible Electronics Under Mechanical Fatigue (United States)

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


    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.

  10. Decentralized control mechanism underlying interlimb coordination of millipedes. (United States)

    Kano, Takeshi; Sakai, Kazuhiko; Yasui, Kotaro; Owaki, Dai; Ishiguro, Akio


    Legged animals exhibit adaptive and resilient locomotion through interlimb coordination. The long-term goal of this study is to clarify the relationship between the number of legs and the inherent decentralized control mechanism for interlimb coordination. As a preliminary step, the study focuses on millipedes as they represent the species with the greatest number of legs among various animal species. A decentralized control mechanism involving local force feedback was proposed based on the qualitative findings of behavioural experiments in which responses to the removal of part of the terrain and leg amputation were observed. The proposed mechanism was implemented in a developed millipede-like robot to demonstrate that the robot can adapt to the removal of the part of the terrain and leg amputation in a manner similar to that in behavioural experiments.

  11. Control of a perturbed under-actuated mechanical system

    KAUST Repository

    Zayane, Chadia


    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.

  12. Neural mechanisms underlying morphine withdrawal in addicted patients: a review

    Directory of Open Access Journals (Sweden)

    Nima Babhadiashar


    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.

  13. An NMDA Receptor-Dependent Mechanism Underlies Inhibitory Synapse Development

    Directory of Open Access Journals (Sweden)

    Xinglong Gu


    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.

  14. Worms under stress: C. elegans stress response and its relevance to complex human disease and aging

    NARCIS (Netherlands)

    Rodriguez Sanchez, M.; Snoek, L.B.; Bono, de M.; Kammenga, J.E.


    Many organisms have stress response pathways, components of which share homology with players in complex human disease pathways. Research on stress response in the nematode worm Caenorhabditis elegans has provided detailed insights into the genetic and molecular mechanisms underlying complex human

  15. Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation. (United States)

    Weng, Z Y; Liu, Z Q; Ritchie, R O; Jiao, D; Li, D S; Wu, H L; Deng, L H; Zhang, Z F


    The giant panda׳s teeth possess remarkable load-bearing capacity and damage resistance for masticating bamboos. In this study, the hierarchical structure and mechanical behavior of the giant panda׳s tooth enamel were investigated under indentation. The effects of loading orientation and location on mechanical properties of the enamel were clarified and the evolution of damage in the enamel under increasing load evaluated. The nature of the damage, both at and beneath the indentation surfaces, and the underlying toughening mechanisms were explored. Indentation cracks invariably were seen to propagate along the internal interfaces, specifically the sheaths between enamel rods, and multiple extrinsic toughening mechanisms, e.g., crack deflection/twisting and uncracked-ligament bridging, were active to shield the tips of cracks from the applied stress. The giant panda׳s tooth enamel is analogous to human enamel in its mechanical properties, yet it has superior hardness and Young׳s modulus but inferior toughness as compared to the bamboo that pandas primarily feed on, highlighting the critical roles of the integration of underlying tissues in the entire tooth and the highly hydrated state of bamboo foods. Our objective is that this study can aid the understanding of the structure-mechanical property relations in the tooth enamel of mammals and further provide some insight on the food habits of the giant pandas. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. HAWT dynamic stall response asymmetries under yawed flow conditions

    Energy Technology Data Exchange (ETDEWEB)

    Schreck, S.; Robinson, M.; Hand, M.; Simms, D.


    Horizontal axis wind turbines can experience significant time varying aerodynamic loads, potentially causing adverse effects on structures, mechanical components, and power production. As designers attempt lighter and more flexible wind energy machines, greater accuracy and robustness will become even more critical in future aerodynamics models. Aerodynamics modeling advances, in turn, will rely on more thorough comprehension of the three-dimensional, unsteady, vortical flows that dominate wind turbine blade aerodynamics under high load conditions. To experimentally characterize these flows, turbine blade surface pressures were acquired at multiple span locations via the NREL Phase IV Unsteady Aerodynamics Experiment. Surface pressures and associated normal force histories were used to characterize dynamic stall vortex kinematics and normal force amplification. Dynamic stall vortices and normal force amplification were confirmed to occur in response to angle of attack excursions above the static stall threshold. Stall vortices occupied approximately one-half of the blade span and persisted for nearly one-fourth of the blade rotation cycle. Stall vortex convection varied along the blade, resulting in dramatic deformation of the vortex. Presence and deformation of the dynamic stall vortex produced corresponding amplification of normal forces. Analyses revealed consistent alterations to vortex kinematics in response to changes in reduced frequency, span location, and yaw error. Finally, vortex structures and kinematics not previously documented for wind turbine blades were isolated.

  17. Mechanical properties of graphene nanoribbons under uniaxial tensile strain (United States)

    Yoneyama, Kazufumi; Yamanaka, Ayaka; Okada, Susumu


    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.

  18. Peripheral Receptor Mechanisms Underlying Orofacial Muscle Pain and Hyperalgesia (United States)

    Saloman, Jami L.

    Musculoskeletal pain conditions, particularly those associated with temporomandibular joint and muscle disorders (TMD) are severely debilitating and affect approximately 12% of the population. Identifying peripheral nociceptive mechanisms underlying mechanical hyperalgesia, a prominent feature of persistent muscle pain, could contribute to the development of new treatment strategies for the management of TMD and other muscle pain conditions. This study provides evidence of functional interactions between ligand-gated channels, P2X3 and TRPV1/TRPA1, in trigeminal sensory neurons, and proposes that these interactions underlie the development of mechanical hyperalgesia. In the masseter muscle, direct P2X3 activation, via the selective agonist αβmeATP, induced a dose- and time-dependent hyperalgesia. Importantly, the αβmeATP-induced hyperalgesia was prevented by pretreatment of the muscle with a TRPV1 antagonist, AMG9810, or the TRPA1 antagonist, AP18. P2X3 was co-expressed with both TRPV1 and TRPA1 in masseter muscle afferents confirming the possibility for intracellular interactions. Moreover, in a subpopulation of P2X3 /TRPV1 positive neurons, capsaicin-induced Ca2+ transients were significantly potentiated following P2X3 activation. Inhibition of Ca2+-dependent kinases, PKC and CaMKII, prevented P2X3-mechanical hyperalgesia whereas blockade of Ca2+-independent PKA did not. Finally, activation of P2X3 induced phosphorylation of serine, but not threonine, residues in TRPV1 in trigeminal sensory neurons. Significant phosphorylation was observed at 15 minutes, the time point at which behavioral hyperalgesia was prominent. Similar data were obtained regarding another nonselective cation channel, the NMDA receptor (NMDAR). Our data propose P2X3 and NMDARs interact with TRPV1 in a facilitatory manner, which could contribute to the peripheral sensitization underlying masseter hyperalgesia. This study offers novel mechanisms by which individual pro-nociceptive ligand

  19. Mechanical properties of a collagen fibril under simulated degradation. (United States)

    Malaspina, David C; Szleifer, Igal; Dhaher, Yasin


    Collagen fibrils are a very important component in most of the connective tissue in humans. An important process associated with several physiological and pathological states is the degradation of collagen. Collagen degradation is usually mediated by enzymatic and non-enzymatic processes. In this work we use molecular dynamics simulations to study the influence of simulated degradation on the mechanical properties of the collagen fibril. We applied tensile stress to the collagen fiber at different stages of degradation. We compared the difference in the fibril mechanical priorities due the removal of enzymatic crosslink, surface degradation and volumetric degradation. As anticipated, our results indicated that, regardless of the degradation scenario, fibril mechanical properties is reduced. The type of degradation mechanism (crosslink, surface or volumetric) expressed differential effect on the change in the fibril stiffness. Our simulation results showed dramatic change in the fibril stiffness with a small amount of degradation. This suggests that the hierarchical structure of the fibril is a key component for the toughness and is very sensitive to changes in the organization of the fibril. The overall results are intended to provide a theoretical framework for the understanding the mechanical behavior of collagen fibrils under degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Temporomandibular disorders and painful comorbidities: clinical association and underlying mechanisms. (United States)

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


    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.

  1. Airway Humidification Reduces the Inflammatory Response During Mechanical Ventilation. (United States)

    Jiang, Min; Song, Jun-Jie; Guo, Xiao-Li; Tang, Yong-Lin; Li, Hai-Bo


    Currently, no clinical or animal studies have been performed to establish the relationship between airway humidification and mechanical ventilation-induced lung inflammatory responses. Therefore, an animal model was established to better define this relationship. Rabbits (n = 40) were randomly divided into 6 groups: control animals, sacrificed immediately after anesthesia (n = 2); dry gas group animals, subjected to mechanical ventilation for 8 h without humidification (n = 6); and experimental animals, subjected to mechanical ventilation for 8 h under humidification at 30, 35, 40, and 45°C, respectively (n = 8). Inflammatory cytokines in the bronchi alveolar lavage fluid (BALF) were measured. The integrity of the airway cilia and the tracheal epithelium was examined by scanning and transmission electron microscopy, respectively. Peripheral blood white blood cell counts and the wet to dry ratio and lung pathology were determined. Dry gas group animals showed increased tumor necrosis factor alpha levels in BALF compared with control animals (P humidification temperature was increased to 40°C. Scanning and transmission electron microscopy analysis revealed that cilia integrity was maintained in the 40°C groups. Peripheral white blood cell counts were not different among those groups. Compared with control animals, the wet to dry ratio was significantly elevated in the dry gas group (P humidification at 40°C resulted in reduced pathologic injury compared with the other groups based on the histologic score. Pathology and reduced inflammation observed in animals treated at 40°C was similar to that observed in the control animals, suggesting that appropriate humidification reduced inflammatory responses elicited as a consequence of mechanical ventilation, in addition to reducing damage to the cilia and reducing water loss in the airway. Copyright © 2015 by Daedalus Enterprises.

  2. Behavioral Effects of Upper Respiratory Tract Illnesses: A Consideration of Possible Underlying Cognitive Mechanisms

    Directory of Open Access Journals (Sweden)

    Andrew P. Smith


    Full Text Available Previous research has shown that both experimentally induced upper respiratory tract illnesses (URTIs and naturally occurring URTIs influence mood and performance. The present study investigated possible cognitive mechanisms underlying the URTI-performance changes. Those who developed a cold (N = 47 had significantly faster, but less accurate, performance than those who remained healthy (N = 54. Illness had no effect on manipulations designed to influence encoding, response organisation (stimulus-response compatilibility or response preparation. Similarly, there was no evidence that different components of working memory were impaired. Overall, the present research confirms that URTIs can have an effect on performance efficiency. Further research is required to identify the physiological and behavioral mechanisms underlying these effects.

  3. Provincial responsibility for carbon emissions in China under different principles

    International Nuclear Information System (INIS)

    Zhang, Youguo


    By applying a multi-regional input–output model, the study compares the provincial responsibility for carbon emissions and provincial carbon multipliers in China under seven responsibility-allocating principles, including three basic principles, the production, income and consumption principles, and four shared responsibility principles, the income-weighted, consumption weighted, comprehensive, and weighted comprehensive principles. Empirical results indicate that carbon multipliers of provinces under these principles are significantly different from one another. The carbon multipliers of provinces with higher ratios of carbon intensive sectors in their outputs are also larger. At the same time, the carbon multipliers of the same sector in the provinces are significantly different from one another. Changing the principle causes significant changes in the responsibility for carbon emissions of some provinces, but only slight changes in the responsibilities of some other provinces. However, the responsibilities of provinces with large economic sizes (output) are always the largest, whereas provinces with the smallest economic sizes are always the smallest regardless of the principles. Further, this study proposes a series of regional policies for carbon mitigation according to provincial carbon multipliers and responsibility allocation features under the different principles. - Highlights: • We link regional environmental responsibility to seven benefit principles. • We analyze provincial responsibility for carbon emissions in China. • We also report provincial carbon multipliers under different principles. • We compare the seven principles from the regional perspective. • Policy implications of the study are discussed.

  4. Fluoride inhibits the response of bone cells to mechanical loading

    NARCIS (Netherlands)

    Willems, H.M.E.; van den Heuvel, E.G.H.M.; Castelein, S.; Buisman, J.K.; Bronckers, A.L.J.J.; Bakker, A.D.; Klein-Nulend, J.


    The response of bone cells to mechanical loading is mediated by the cytoskeleton. Since the bone anabolic agent fluoride disrupts the cytoskeleton, we investigated whether fluoride affects the response of bone cells to mechanical loading, and whether this is cytoskeleton mediated. The

  5. Mechanisms of the training response in patients with peripheral ...

    African Journals Online (AJOL)

    Mechanisms of the training response in patients with peripheral arterial disease – a review. ... South African Journal of Sports Medicine ... The review summarises the mechanism of the training response in patients with PAD, focusing on improvements in bloodflow as well as biochemical, muscle recruitment and ...

  6. Failure Mechanisms of Brittle Rocks under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Liu Taoying


    Full Text Available 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.

  7. The mechanism underlying fast germination of tomato cultivar LA2711. (United States)

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


    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.

  8. Mechanical Design of AM Fabricated Prismatic Rods under Torsion

    Directory of Open Access Journals (Sweden)

    Manzhirov Alexander V.


    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.

  9. Nanomaterials modulate stem cell differentiation: biological interaction and underlying mechanisms. (United States)

    Wei, Min; Li, Song; Le, Weidong


    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.

  10. Cognitive and Ocular Factors Jointly Determine Pupil Responses under Equiluminance.

    Directory of Open Access Journals (Sweden)

    Tomas Knapen

    Full Text Available Changes in pupil diameter can reflect high-level cognitive signals that depend on central neuromodulatory mechanisms. However, brain mechanisms that adjust pupil size are also exquisitely sensitive to changes in luminance and other events that would be considered a nuisance in cognitive experiments recording pupil size. We implemented a simple auditory experiment involving no changes in visual stimulation. Using finite impulse-response fitting we found pupil responses triggered by different types of events. Among these are pupil responses to auditory events and associated surprise: cognitive effects. However, these cognitive responses were overshadowed by pupil responses associated with blinks and eye movements, both inevitable nuisance factors that lead to changes in effective luminance. Of note, these latter pupil responses were not recording artifacts caused by blinks and eye movements, but endogenous pupil responses that occurred in the wake of these events. Furthermore, we identified slow (tonic changes in pupil size that differentially influenced faster (phasic pupil responses. Fitting all pupil responses using gamma functions, we provide accurate characterisations of cognitive and non-cognitive response shapes, and quantify each response's dependence on tonic pupil size. These results allow us to create a set of recommendations for pupil size analysis in cognitive neuroscience, which we have implemented in freely available software.

  11. A linear chromatic mechanism drives the pupillary response. (United States)

    Tsujimura, S; Wolffsohn, J S; Gilmartin, B


    Previous studies have shown that a chromatic mechanism can drive pupil responses. The aim of this research was to clarify whether a linear or nonlinear chromatic mechanism drives pupillary responses by using test stimuli of various colours that are defined in cone contrast space. The pupil and accommodation responses evoked by these test stimuli were continuously and simultaneously objectively measured by photorefraction. The results with isochromatic and isoluminant stimuli showed that the accommodative level remained approximately constant (linear chromatic mechanism, whereby a signal from the long wavelength cone is subtracted from that of the middle wavelength cone and vice versa, drives pupillary responses.

  12. Mechanisms of the training response in patients with peripheral ...

    African Journals Online (AJOL)

    following exercise training.18 Despite the clear evidence of patients clinically benefiting from exercise training, the mechanism(s) of the training response remains unclear. Several mechanisms have been proposed and researched and these will be discussed in this paper. Improvements in blood flow – increased collateral.

  13. Self-burial mechanics of hygroscopically responsive awns. (United States)

    Jung, Wonjong; Kim, Wonjung; Kim, Ho-Young


    We present the results of a combined experimental and theoretical investigation of the mechanics of self-burial of some plant seeds whose morphologies respond to environmental changes in humidity. The seeds of Erodium and Pelargonium have hygroscopically responsive awns that play a critical role in their self-burial into soil. The awn, coiled in a dry state, uncoils to stretch linearly under highly humid condition because of a tilted arrangement of cellulose microfibrils in one of the layers of the awn's bilayered structure. By measuring the mechanical characteristics of the awns of Pelargonium carnosum, we find that the extensional force of the awn can be aptly modeled by the theory of elasticity for a coiled spring. We further show that although the resistance to the seed-head penetrating relatively coarse soils without spinning is large enough to block the digging seed, the rotation of the seed greatly reduces the soil's resistance down to a level the awn can easily overcome. Our mechanical analysis reveals that the self-burial of the seed is a sophisticated outcome of the helically coiled configuration of the awn. © The Author 2014. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email:

  14. Age differences in the underlying mechanisms of stereotype threat effects. (United States)

    Popham, Lauren E; Hess, Thomas M


    The goals of the present study were to (a) examine whether age differences exist in the mechanisms underlying stereotype threat effects on cognitive performance and (b) examine whether emotion regulation abilities may buffer against threat effects on performance. Older and younger adults were exposed to positive or negative age-relevant stereotypes, allowing us to examine the impact of threat on regulatory focus and working memory. Self-reported emotion regulation measures were completed prior to the session. Older adults' performance under threat suggested a prevention-focused approach to the task, indexed by increased accuracy and reduced speed. The same pattern was observed in younger adults, but the effects were not as strong. Age differences emerged when examining the availability of working memory resources under threat, with young adults showing decrements, whereas older adults did not. Emotion regulation abilities moderated threat effects in young adults but not in older adults. The results provide support for the notion that stereotype threat may lead to underperformance through somewhat different pathways in older and younger adults. Future research should further examine whether the underlying reason for this age difference is rooted in age-related improvements in emotion regulation. © The Author 2013. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved. For permissions, please e-mail:

  15. Investigations on response time of magnetorheological elastomer under compression mode (United States)

    Zhu, Mi; Yu, Miao; Qi, Song; Fu, Jie


    For efficient fast control of vibration system with magnetorheological elastomer (MRE)-based smart device, the response time of MRE material is the key parameter which directly affects the control performance of the vibration system. For a step coil current excitation, this paper proposed a Maxwell behavior model with time constant λ to describe the normal force response of MRE, and the response time of MRE was extracted through the separation of coil response time. Besides, the transient responses of MRE under compression mode were experimentally investigated, and the effects of (i) applied current, (ii) particle distribution and (iii) compressive strain on the response time of MRE were addressed. The results revealed that the three factors can affect the response characteristic of MRE quite significantly. Besides the intrinsic importance for contributing to the response evaluation and effective design of MRE device, this study may conduce to the optimal design of controller for MRE control system.

  16. Electrochemical mechanism of tin membrane electrodeposition under ultrasonic waves. (United States)

    Nan, Tianxiang; Yang, Jianguang; Chen, Bing


    Tin was electrodeposited from chloride solutions using a membrane cell under ultrasonic waves. Cyclic voltammetry (CV), linear sweep voltammetry (LSV), chronoamperometry (CHR), and chronopotentiometry were applied to investigate the electrochemical mechanism of tin electrodeposition under ultrasonic field. Chronoamperometry curves showed that the initial process of tin electrodeposition followed the diffusion controlled three-dimensional nucleation and grain growth mechanism. The analysis of the cyclic voltammetry and linear sweep voltammetry diagrams showed that the application of ultrasound can change the tin membrane electro-deposition reaction from diffusion to electrochemical control, and the optimum parameters for tin electrodeposition were H + concentration 3.5 mol·L -1 , temperature 35 °C and ultrasonic power 100 W. The coupling ultrasonic field played a role in refining the grain in this process. The growth of tin crystals showed no orientation preferential, and the tin deposition showed a tendency to form a regular network structure after ultrasonic coupling. While in the absence of ultrasonic coupling, the growth of tin crystals has a high preferential orientation, and the tin deposition showed a tendency to form tin whiskers. Ultrasonic coupling was more favorable for obtaining a more compact and smoother cathode tin layer. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. [Mechanisms underlying glucocorticoid resistance in chronic rhinosinusitis with nasal polyps]. (United States)

    Zhang, Y Y; Lou, H F; Wang, C S; Zhang, L


    Chronic rhinosinusitis with nasal polyps (CRSwNP) is a chronic inflammatory disease that occurs in the nasal and sinus mucosa, which is a common disease in otorhinolaryngology. At present, CRSwNP can be effectively treated by glucocorticoids (GC). GC binds to GC receptors in the nasal mucosa, affects the expression of inflammatory genes, inhibits the activation and action of eosinophils, T cell-associated inflammatory responses in nasal polyps, as well as tissue remodeling. However, there are some patients fall reponse to GC, so called GC resistance. The study suggests that the possible mechanism of CRSwNP GC resistance is mainly related to GC receptor abnormal, the role of cytokines and transcription factors, such as Th cells and IL-8. In addition, MAPK-related kinases and histone deacetylase in the GC signaling pathway also play important roles in the GC resistance process. This paper reviews the mechanism of GC treatment of CRSwNP, the mechanism of GC resistance and alternative treatment of GC.

  18. High-strain-rate tensile mechanical response of a polyurethane elastomeric material

    NARCIS (Netherlands)

    Fan, J.T.; Weerheijm, J.; Sluys, L.J.


    The dynamic tensile mechanical response of a soft polymer material (Clear Flex 75) is investigated using a split Hopkinson tension bar (SHTB). Stress-strain relations are derived to reveal the mechanical properties at moderate and high strain rates. These relations appear to be rate dependent. Under

  19. Effects of manual hyperinflation in preterm newborns under mechanical ventilation. (United States)

    Viana, Camila Chaves; Nicolau, Carla Marques; Juliani, Regina Celia Turola Passos; Carvalho, Werther Brunow de; Krebs, Vera Lucia Jornada


    To assess the effects of manual hyperinflation, performed with a manual resuscitator with and without the positive end-expiratory pressure valve, on the respiratory function of preterm newborns under mechanical ventilation. Cross-sectional study of hemodynamically stable preterm newborns with gestational age of less than 32 weeks, under mechanical ventilation and dependent on it at 28 days of life. Manual hyperinflation was applied randomly, alternating the use or not of the positive end-expiratory pressure valve, followed by tracheal aspiration for ending the maneuver. For nominal data, the two-tailed Wilcoxon test was applied at the 5% significance level and 80% power. Twenty-eight preterm newborns, with an average birth weight of 1,005.71 ± 372.16g, an average gestational age of 28.90 ± 1.79 weeks, an average corrected age of 33.26 ± 1.78 weeks, and an average mechanical ventilation time of 29.5 (15 - 53) days, were studied. Increases in inspiratory and expiratory volumes occurred between time-points A5 (before the maneuver) and C1 (immediately after tracheal aspiration) in both the maneuver with the valve (p = 0.001 and p = 0.009) and without the valve (p = 0.026 and p = 0.001), respectively. There was also an increase in expiratory resistance between time-points A5 and C1 (p = 0.044). Lung volumes increased when performing the maneuver with and without the valve, with a significant difference in the first minute after aspiration. There was a significant difference in expiratory resistance between the time-points A5 (before the maneuver) and C1 (immediately after tracheal aspiration) in the first minute after aspiration within each maneuver.

  20. The neural sociometer: brain mechanisms underlying state self-esteem. (United States)

    Eisenberger, Naomi I; Inagaki, Tristen K; Muscatell, Keely A; Byrne Haltom, Kate E; Leary, Mark R


    On the basis of the importance of social connection for survival, humans may have evolved a "sociometer"-a mechanism that translates perceptions of rejection or acceptance into state self-esteem. Here, we explored the neural underpinnings of the sociometer by examining whether neural regions responsive to rejection or acceptance were associated with state self-esteem. Participants underwent fMRI while viewing feedback words ("interesting," "boring") ostensibly chosen by another individual (confederate) to describe the participant's previously recorded interview. Participants rated their state self-esteem in response to each feedback word. Results demonstrated that greater activity in rejection-related neural regions (dorsal ACC, anterior insula) and mentalizing regions was associated with lower-state self-esteem. Additionally, participants whose self-esteem decreased from prescan to postscan versus those whose self-esteem did not showed greater medial prefrontal cortical activity, previously associated with self-referential processing, in response to negative feedback. Together, the results inform our understanding of the origin and nature of our feelings about ourselves.

  1. Dynamic response characteristics analysis of the doubly-fed wind power system under grid voltage drop (United States)

    Chen, Y.; Wang, J.; Wang, H. H.; Yang, L.; Chen, W.; Xu, Y. T.


    Double-fed induction generator (DFIG) is sensitive to the disturbances of grid, so the security and stability of the grid and the DFIG itself are under threat with the rapid increase of DFIG. Therefore, it is important to study dynamic response of the DFIG when voltage drop failure is happened in power system. In this paper, firstly, mathematical models and the control strategy about mechanical and electrical response processes is respectively introduced. Then through the analysis of response process, it is concluded that the dynamic response characteristics are related to voltage drop level, operating status of DFIG and control strategy adapted to rotor side. Last, the correctness of conclusion is validated by the simulation about mechanical and electrical response processes in different voltage levels drop and different DFIG output levels under DIgSILENT/PowerFactory software platform.

  2. On the Mechanical Response of Chopped Glass/Urethane Resin Composite: Data and Model

    Energy Technology Data Exchange (ETDEWEB)

    Elahi, M.; Weitsman, Y.J.


    This report presents data on the creep response of a polymeric composite that is a candidate material for automotive applications. The above data were used to establish the basis for the mechanical characterization of the material's response over a wide range of stresses and temperatures, as well as under cyclic loading and due to exposure to distilled water. A constitutive model based upon fundamental principles of irreversible thermodynamics and continuum mechanics was employed to encompass the above mentioned database and to predict the response under more complex inputs. These latter tests verified the validity of the model.

  3. The dance of the perivascular and endothelial cells: mechanisms of brain response to immune signaling. (United States)

    Saper, Clifford B


    The mechanisms underlying the brain response to systemic inflammation remain unclear. In this issue of Neuron, Serrats and colleagues demonstrate that two cell types that produce prostaglandins that act on the brain, perivascular and endothelial cells, have an unexpectedly complex interaction in regulating the timing and types of brain responses that occur.

  4. Mechanical response of proton beam irradiated nitinol

    Energy Technology Data Exchange (ETDEWEB)

    Afzal, Naveed [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan); Ghauri, I.M., E-mail: [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan); Mubarik, F.E.; Amin, F. [Centre for Advanced Studies in Physics, GC University, Lahore (Pakistan)


    The present investigation deals with the study of mechanical behavior of proton beam irradiated nitinol at room temperature. The specimens in austenitic phase were irradiated over periods of 15, 30, 45 and 60 min at room temperature using 2 MeV proton beam obtained from Pelletron accelerator. The stress-strain curves of both unirradiated and irradiated specimens were obtained using a universal testing machine at room temperature. The results of the experiment show that an intermediate rhombohedral (R) phase has been introduced between austenite and martensite phase, which resulted in the suppression of direct transformation from austenite to martensite (A-M). Stresses required to start R-phase ({sigma}{sub RS}) and martensitic phase ({sigma}{sub MS}) were observed to decrease with increase in exposure time. The hardness tests of samples before and after irradiation were also carried out using Vickers hardness tester. The comparison reveals that the hardness is higher in irradiated specimens than that of the unirradiated one. The increase in hardness is quite sharp in specimens irradiated for 15 min, which then increases linearly as the exposure time is increased up to 60 min. The generation of R-phase, variations in the transformation stresses {sigma}{sub RS} and {sigma}{sub MS} and increase in hardness of irradiated nitinol may be attributed to lattice disorder and associated changes in crystal structure induced by proton beam irradiation.

  5. Neuronal mechanisms underlying differences in spatial resolution between darks and lights in human vision. (United States)

    Pons, Carmen; Mazade, Reece; Jin, Jianzhong; Dul, Mitchell W; Zaidi, Qasim; Alonso, Jose-Manuel


    Artists and astronomers noticed centuries ago that humans perceive dark features in an image differently from light ones; however, the neuronal mechanisms underlying these dark/light asymmetries remained unknown. Based on computational modeling of neuronal responses, we have previously proposed that such perceptual dark/light asymmetries originate from a luminance/response saturation within the ON retinal pathway. Consistent with this prediction, here we show that stimulus conditions that increase ON luminance/response saturation (e.g., dark backgrounds) or its effect on light stimuli (e.g., optical blur) impair the perceptual discrimination and salience of light targets more than dark targets in human vision. We also show that, in cat visual cortex, the magnitude of the ON luminance/response saturation remains relatively constant under a wide range of luminance conditions that are common indoors, and only shifts away from the lowest luminance contrasts under low mesopic light. Finally, we show that the ON luminance/response saturation affects visual salience mostly when the high spatial frequencies of the image are reduced by poor illumination or optical blur. Because both low luminance and optical blur are risk factors in myopia, our results suggest a possible neuronal mechanism linking myopia progression with the function of the ON visual pathway.

  6. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren


    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.

  7. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren


    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.

  8. The mechanisms underlying fructose-induced hypertension: a review (United States)

    Klein, Alice Victoria; Kiat, Hosen


    We are currently in the midst of an epidemic of metabolic disorders, which may, in part, be explained by excess fructose intake. This theory is supported by epidemiological observations as well as experimental studies in animals and humans. Rising consumption of fructose has been matched with growing rates of hypertension, leading to concern from public health experts. At this stage, the mechanisms underlying fructose-induced hypertension have not been fully characterized and the bulk of our knowledge is derived from animal models. Animal studies have shown that high-fructose diets up-regulate sodium and chloride transporters, resulting in a state of salt overload that increases blood pressure. Excess fructose has also been found to activate vasoconstrictors, inactivate vasodilators, and over-stimulate the sympathetic nervous system. Further work is required to determine the relevance of these findings to humans and to establish the level at which dietary fructose increases the risk of developing hypertension PMID:25715094

  9. Degradation Mechanisms of Transparent Polyurethane Interlayer under UV Irradiation

    Directory of Open Access Journals (Sweden)

    OU Yingchun


    Full Text Available According to the ageing problem of laminated transparency, the trasparent polyurethane film used as interlayer had been irradiated by fluorescent ultraviolet lamp for 0 h, 200 h, 300 h, and 500 h respectively. With the aid of ultraviolet/visible spectrophotometer, FTIR and SEM etc., the color, structure and morphology of the materials were studied. SEM shows that when the irradiation time is increased to 500 h, the film surface cracks. The UV degradation mechanisms are that -CH2- of the position connecting the O and N from hard segment and the soft segment are easy to oxidize and produce hydrogen peroxide under UV and oxygen, which is furtherly oxidized to CO, and some part of the C-O and C-N bonds is cracked through β scission, and then the materials are fractured.

  10. Simulated airplane headache: a proxy towards identification of underlying mechanisms. (United States)

    Bui, Sebastian Bao Dinh; Petersen, Torben; Poulsen, Jeppe Nørgaard; Gazerani, Parisa


    Airplane Headache (AH) occurs during flights and often appears as an intense, short lasting headache during take-off or landing. Reports are limited on pathological mechanisms underlying the occurrence of this headache. Proper diagnosis and treatments would benefit from identification of potential pathways involved in AH pathogenesis. This study aimed at providing a simulated airplane headache condition as a proxy towards identification of its underlying mechanisms. Fourteen participants including 7 volunteers suffering from AH and 7 healthy matched controls were recruited after meeting the diagnostic and safety criteria based on an approved study protocol. Simulation of AH was achieved by entering a pressure chamber with similar characteristics of an airplane flight. Selected potential biomarkers including salivary prostaglandin E 2 (PGE 2 ), cortisol, facial thermo-images, blood pressure, pulse, and saturation pulse oxygen (SPO) were defined and values were collected before, during and after flight simulation in the pressure chamber. Salivary samples were analyzed with ELISA techniques, while data analysis and statistical tests were handled with SPSS version 22.0. All participants in the AH-group experienced a headache attack similar to AH experience during flight. The non-AH-group did not experience any headaches. Our data showed that the values for PGE 2 , cortisol and SPO were significantly different in the AH-group in comparison with the non-AH-group during the flight simulation in the pressure chamber. The pressure chamber proved useful not only to provoke AH-like attack but also to study potential biomarkers for AH in this study. PGE 2 , and cortisol levels together with SPO presented dysregulation during the simulated AH-attack in affected individuals compared with healthy controls. Based on these findings we propose to use pressure chamber as a model to induce AH, and thus assess new potential biomarkers for AH in future studies.


    Directory of Open Access Journals (Sweden)

    Alexander eChervyakov


    Full Text Available Transcranial magnetic stimulation (TMS is an effective method used to diagnose and treat many neurological disorders. Although repetitive TMS (rTMS has been used to treat a variety of serious pathological conditions including stroke, depression, Parkinson's disease, epilepsy, pain, and migraines, the pathophysiological mechanisms underlying the effects of long-term TMS remain unclear. In the present review, the effects of rTMS on neurotransmitters and synaptic plasticity are described, including the classic interpretations of TMS effects on synaptic plasticity via long-term potentiation (LTP and long-term depression (LTD. We also discuss the effects of rTMS on the genetic apparatus of neurons, glial cells and the prevention of neuronal death. The neurotrophic effects of rTMS on dendritic growth and sprouting and neurotrophic factors are described, including change in brain-derived neurotrophic factor (BDNF concentration under the influence of rTMS. Also, non-classical effects of TMS related to biophysical effects of magnetic fields are described, including the quantum effects, the magnetic spin effects, genetic magnetoreception, the macromolecular effects of TMS, and the electromagnetic theory of consciousness. Finally, we discuss possible interpretations of TMS effects according to dynamical systems theory. Evidence suggests that a rTMS-induced magnetic field should be considered a separate physical factor that can be impactful at the subatomic level and that rTMS is capable of significantly altering the reactivity of molecules (radicals. It is thought that these factors underlie the therapeutic benefits of therapy with TMS. Future research on these mechanisms will be instrumental to the development of more powerful and reliable TMS treatment protocols.

  12. Fracture mechanics in new designed power module under thermo-mechanical loads

    Directory of Open Access Journals (Sweden)

    Durand Camille


    Full Text Available Thermo-mechanically induced failure is a major reliability issue in the microelectronic industry. On this account, a new type of Assembly Interconnected Technology used to connect MOSFETs in power modules has been developed. The reliability is increased by using a copper clip soldered on the top side of the chip, avoiding the use of aluminium wire bonds, often responsible for the failure of the device. Thus the new designed MOSFET package does not follow the same failure mechanisms as standard modules. Thermal and power cycling tests were performed on these new packages and resulting failures were analyzed. Thermo-mechanical simulations including cracks in the aluminium metallization and intermetallics (IMC were performed using Finite Element Analysis in order to better understand crack propagation and module behaviour.

  13. Mechanisms underlying the social enhancement of vocal learning in songbirds. (United States)

    Chen, Yining; Matheson, Laura E; Sakata, Jon T


    Social processes profoundly influence speech and language acquisition. Despite the importance of social influences, little is known about how social interactions modulate vocal learning. Like humans, songbirds learn their vocalizations during development, and they provide an excellent opportunity to reveal mechanisms of social influences on vocal learning. Using yoked experimental designs, we demonstrate that social interactions with adult tutors for as little as 1 d significantly enhanced vocal learning. Social influences on attention to song seemed central to the social enhancement of learning because socially tutored birds were more attentive to the tutor's songs than passively tutored birds, and because variation in attentiveness and in the social modulation of attention significantly predicted variation in vocal learning. Attention to song was influenced by both the nature and amount of tutor song: Pupils paid more attention to songs that tutors directed at them and to tutors that produced fewer songs. Tutors altered their song structure when directing songs at pupils in a manner that resembled how humans alter their vocalizations when speaking to infants, that was distinct from how tutors changed their songs when singing to females, and that could influence attention and learning. Furthermore, social interactions that rapidly enhanced learning increased the activity of noradrenergic and dopaminergic midbrain neurons. These data highlight striking parallels between humans and songbirds in the social modulation of vocal learning and suggest that social influences on attention and midbrain circuitry could represent shared mechanisms underlying the social modulation of vocal learning.

  14. Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

    Directory of Open Access Journals (Sweden)

    Nguyen Quoc Vuong Tran


    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.

  15. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

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


    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.

  16. Using Drosophila to discover mechanisms underlying type 2 diabetes

    Directory of Open Access Journals (Sweden)

    Ronald W. Alfa


    Full Text Available Mechanisms of glucose homeostasis are remarkably well conserved between the fruit fly Drosophila melanogaster and mammals. From the initial characterization of insulin signaling in the fly came the identification of downstream metabolic pathways for nutrient storage and utilization. Defects in these pathways lead to phenotypes that are analogous to diabetic states in mammals. These discoveries have stimulated interest in leveraging the fly to better understand the genetics of type 2 diabetes mellitus in humans. Type 2 diabetes results from insulin insufficiency in the context of ongoing insulin resistance. Although genetic susceptibility is thought to govern the propensity of individuals to develop type 2 diabetes mellitus under appropriate environmental conditions, many of the human genes associated with the disease in genome-wide association studies have not been functionally studied. Recent advances in the phenotyping of metabolic defects have positioned Drosophila as an excellent model for the functional characterization of large numbers of genes associated with type 2 diabetes mellitus. Here, we examine results from studies modeling metabolic disease in the fruit fly and compare findings to proposed mechanisms for diabetic phenotypes in mammals. We provide a systematic framework for assessing the contribution of gene candidates to insulin-secretion or insulin-resistance pathways relevant to diabetes pathogenesis.

  17. Understanding and imitating unfamiliar actions: distinct underlying mechanisms.

    Directory of Open Access Journals (Sweden)

    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.

  18. Mechanical Responses and Physical Factors of the Fingertip Pulp

    Directory of Open Access Journals (Sweden)

    N. Sakai


    Full Text Available The images of the mechanical responses were analysed when the fingertip was pressed against a plateau plate, and the influence of the contact angle on the loading pressure and the mechanical responses was investigated. As a result, as the contact angle was smaller, the change ratios due to the loading pressure were significantly larger in the contact length, the contact width and the distortion of lateral-view area. These parameters were thought to be useful in clinical medicine as indices for the degrees of mechanical responses of the fingertip. The length of the central axis and the maximum width of the fingertip were inappropriate as the parameters to represent the mechanical responses of the fingertip. The maximum width of the fingertip scarcely changed. This does not reflect the compressibility of the fingertip, and the fingertip as a whole extended along the central axis and in the vertical direction, and the change was not reflected in the maximum width.

  19. Collecting response times using Amazon Mechanical Turk and Adobe Flash. (United States)

    Simcox, Travis; Fiez, Julie A


    Crowdsourcing systems like Amazon's Mechanical Turk (AMT) allow data to be collected from a large sample of people in a short amount of time. This use has garnered considerable interest from behavioral scientists. So far, most experiments conducted on AMT have focused on survey-type instruments because of difficulties inherent in running many experimental paradigms over the Internet. This study investigated the viability of presenting stimuli and collecting response times using Adobe Flash to run ActionScript 3 code in conjunction with AMT. First, the timing properties of Adobe Flash were investigated using a phototransistor and two desktop computers running under several conditions mimicking those that may be present in research using AMT. This experiment revealed some strengths and weaknesses of the timing capabilities of this method. Next, a flanker task and a lexical decision task implemented in Adobe Flash were administered to participants recruited with AMT. The expected effects in these tasks were replicated. Power analyses were conducted to describe the number of participants needed to replicate these effects. A questionnaire was used to investigate previously undescribed computer use habits of 100 participants on AMT. We conclude that a Flash program in conjunction with AMT can be successfully used for running many experimental paradigms that rely on response times, although experimenters must understand the limitations of the method.

  20. Microcracking in composite laminates under thermal and mechanical loading. Thesis (United States)

    Maddocks, Jason R.


    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

  1. Structural and Mechanical Properties of Intermediate Filaments under Extreme Conditions and Disease (United States)

    Qin, Zhao

    Intermediate filaments are one of the three major components of the cytoskeleton in eukaryotic cells. It was discovered during the recent decades that intermediate filament proteins play key roles to reinforce cells subjected to large-deformation as well as participate in signal transduction. However, it is still poorly understood how the nanoscopic structure, as well as the biochemical properties of these protein molecules contribute to their biomechanical functions. In this research we investigate the material function of intermediate filaments under various extreme mechanical conditions as well as disease states. We use a full atomistic model and study its response to mechanical stresses. Learning from the mechanical response obtained from atomistic simulations, we build mesoscopic models following the finer-trains-coarser principles. By using this multiple-scale model, we present a detailed analysis of the mechanical properties and associated deformation mechanisms of intermediate filament network. We reveal the mechanism of a transition from alpha-helices to beta-sheets with subsequent intermolecular sliding under mechanical force, which has been inferred previously from experimental results. This nanoscale mechanism results in a characteristic nonlinear force-extension curve, which leads to a delocalization of mechanical energy and prevents catastrophic fracture. This explains how intermediate filament can withstand extreme mechanical deformation of > 1 00% strain despite the presence of structural defects. We combine computational and experimental techniques to investigate the molecular mechanism of Hutchinson-Gilford progeria syndrome, a premature aging disease. We find that the mutated lamin tail .domain is more compact and stable than the normal one. This altered structure and stability may enhance the association of intermediate filaments with the nuclear membrane, providing a molecular mechanism of the disease. We study the nuclear membrane association

  2. Molecular mechanisms underlying the development of hepatocellular carcinoma. (United States)

    Bergsland, E K


    Hepatocellular carcinoma (HCC) is a disease that is extremely difficult to manage and is markedly increasing in incidence. Malignant transformation generally occurs in the setting of liver dysfunction related to a number of different diseases, including viral hepatitis, alcoholic liver disease, and aflatoxin exposure. Short of surgical or ablative approaches, no standard therapy exists for HCC and the prognosis is poor. Perhaps our best hope is that further elucidation of the specific molecular features underlying the disease will translate into innovative, and potentially disease-specific strategies to manage this difficult cancer. Exposure to aflatoxin is associated with a specific mutation in the tumor-suppressor gene p53. The exact molecular events underlying hepatocarcinogenesis in the setting of viral infection have yet to be elucidated, although there is evidence to suggest that virus-encoded proteins contribute to malignant transformation. Both hepatitis B X antigen and hepatitis C core protein appear to interact with a variety of cellular proteins leading to alterations in signal transduction and transcriptional activity. These events presumably cooperate to facilitate malignant progression by promoting extended hepatocyte survival, evasion of the immune response, and acquisition of mutations through genomic instability. Copyright 2001 by W.B. Saunders Company.

  3. Mechanical Modeling of a WIPP Drum Under Pressure

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Jeffrey A. [Sandia National Laboratories, Albuquerque, NM (United States)


    Mechanical modeling was undertaken to support the Waste Isolation Pilot Plant (WIPP) technical assessment team (TAT) investigating the February 14th 2014 event where there was a radiological release at the WIPP. The initial goal of the modeling was to examine if a mechanical model could inform the team about the event. The intention was to have a model that could test scenarios with respect to the rate of pressurization. It was expected that the deformation and failure (inability of the drum to contain any pressure) would vary according to the pressurization rate. As the work progressed there was also interest in using the mechanical analysis of the drum to investigate what would happen if a drum pressurized when it was located under a standard waste package. Specifically, would the deformation be detectable from camera views within the room. A finite element model of a WIPP 55-gallon drum was developed that used all hex elements. Analyses were conducted using the explicit transient dynamics module of Sierra/SM to explore potential pressurization scenarios of the drum. Theses analysis show similar deformation patterns to documented pressurization tests of drums in the literature. The calculated failure pressures from previous tests documented in the literature vary from as little as 16 psi to 320 psi. In addition, previous testing documented in the literature shows drums bulging but not failing at pressures ranging from 69 to 138 psi. The analyses performed for this study found the drums failing at pressures ranging from 35 psi to 75 psi. When the drums are pressurized quickly (in 0.01 seconds) there is significant deformation to the lid. At lower pressurization rates the deformation of the lid is considerably less, yet the lids will still open from the pressure. The analyses demonstrate the influence of pressurization rate on deformation and opening pressure of the drums. Analyses conducted with a substantial mass on top of the closed drum demonstrate that the

  4. 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


    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.

  5. Response of a Light Aircraft Under Gust Loads

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    P. Chudý


    Full Text Available This project presents work performed by the Institute of Aerospace Engineering, Brno University of Technology. The primary purpose of this work was to estimate the aeroelastic response of a light aircraft under gust loads. In the past, the gust response has been investigated using the Pratt - Walker formula. This formula is derived from the response of a rigid airplane to a discrete gust. However, the Pratt-Walker formula does not capture either the stochastic nature of continuous turbulence or the effects of structural flexibility. The analysis described here was performed using the advanced FEM software package MSC Nastran.

  6. Mechanisms establishing TLR4-responsive activation states of inflammatory response genes.

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    Laure Escoubet-Lozach


    Full Text Available Precise control of the innate immune response is required for resistance to microbial infections and maintenance of normal tissue homeostasis. Because this response involves coordinate regulation of hundreds of genes, it provides a powerful biological system to elucidate the molecular strategies that underlie signal- and time-dependent transitions of gene expression. Comprehensive genome-wide analysis of the epigenetic and transcription status of the TLR4-induced transcriptional program in macrophages suggests that Toll-like receptor 4 (TLR4-dependent activation of nearly all immediate/early- (I/E and late-response genes results from a sequential process in which signal-independent factors initially establish basal levels of gene expression that are then amplified by signal-dependent transcription factors. Promoters of I/E genes are distinguished from those of late genes by encoding a distinct set of signal-dependent transcription factor elements, including TATA boxes, which lead to preferential binding of TBP and basal enrichment for RNA polymerase II immediately downstream of transcriptional start sites. Global nuclear run-on (GRO sequencing and total RNA sequencing further indicates that TLR4 signaling markedly increases the overall rates of both transcriptional initiation and the efficiency of transcriptional elongation of nearly all I/E genes, while RNA splicing is largely unaffected. Collectively, these findings reveal broadly utilized mechanisms underlying temporally distinct patterns of TLR4-dependent gene activation required for homeostasis and effective immune responses.

  7. 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.

  8. Video analysis of concussion injury mechanism in under-18 rugby (United States)

    Hendricks, Sharief; O'Connor, Sam; Lambert, Michael; Brown, James C; Burger, Nicholas; Mc Fie, Sarah; Readhead, Clint; Viljoen, Wayne


    Background Understanding the mechanism of injury is necessary for the development of effective injury prevention strategies. Video analysis of injuries provides valuable information on the playing situation and athlete-movement patterns, which can be used to formulate these strategies. Therefore, we conducted a video analysis of the mechanism of concussion injury in junior-level rugby union and compared it with a representative and matched non-injury sample. Methods Injury reports for 18 concussion events were collected from the 2011 to 2013 under-18 Craven Week tournaments. Also, video footage was recorded for all 3 years. On the basis of the injury events, a representative ‘control’ sample of matched non-injury events in the same players was identified. The video footage, which had been recorded at each tournament, was then retrospectively analysed and coded. 10 injury events (5 tackle, 4 ruck, 1 aerial collision) and 83 non-injury events were analysed. Results All concussions were a result of contact with an opponent and 60% of players were unaware of the impending contact. For the measurement of head position on contact, 43% had a ‘down’ position, 29% the ‘up and forward’ and 29% the ‘away’ position (n=7). The speed of the injured tackler was observed as ‘slow’ in 60% of injurious tackles (n=5). In 3 of the 4 rucks in which injury occurred (75%), the concussed player was acting defensively either in the capacity of ‘support’ (n=2) or as the ‘jackal’ (n=1). Conclusions Training interventions aimed at improving peripheral vision, strengthening of the cervical muscles, targeted conditioning programmes to reduce the effects of fatigue, and emphasising safe and effective playing techniques have the potential to reduce the risk of sustaining a concussion injury. PMID:27900149

  9. Video analysis of concussion injury mechanism in under-18 rugby. (United States)

    Hendricks, Sharief; O'Connor, Sam; Lambert, Michael; Brown, James C; Burger, Nicholas; Mc Fie, Sarah; Readhead, Clint; Viljoen, Wayne


    Understanding the mechanism of injury is necessary for the development of effective injury prevention strategies. Video analysis of injuries provides valuable information on the playing situation and athlete-movement patterns, which can be used to formulate these strategies. Therefore, we conducted a video analysis of the mechanism of concussion injury in junior-level rugby union and compared it with a representative and matched non-injury sample. Injury reports for 18 concussion events were collected from the 2011 to 2013 under-18 Craven Week tournaments. Also, video footage was recorded for all 3 years. On the basis of the injury events, a representative 'control' sample of matched non-injury events in the same players was identified. The video footage, which had been recorded at each tournament, was then retrospectively analysed and coded. 10 injury events (5 tackle, 4 ruck, 1 aerial collision) and 83 non-injury events were analysed. All concussions were a result of contact with an opponent and 60% of players were unaware of the impending contact. For the measurement of head position on contact , 43% had a 'down' position, 29% the 'up and forward' and 29% the 'away' position (n=7). The speed of the injured tackler was observed as 'slow' in 60% of injurious tackles (n=5). In 3 of the 4 rucks in which injury occurred (75%), the concussed player was acting defensively either in the capacity of 'support' (n=2) or as the 'jackal' (n=1). Training interventions aimed at improving peripheral vision, strengthening of the cervical muscles, targeted conditioning programmes to reduce the effects of fatigue, and emphasising safe and effective playing techniques have the potential to reduce the risk of sustaining a concussion injury.

  10. Mechanisms underlying recovery of zooplankton in Lake Orta after liming

    Directory of Open Access Journals (Sweden)

    Roberta Piscia


    Full Text Available The goal of this study was to improve the understanding of the large-scale mechanisms underlying the recovery of the zooplankton of Lake Orta from historical contamination, following reduced input of ammonia and metals and the subsequent 1989/90 liming intervention. The industrial pollution had been severe and long-lasting (1929-1990. Zooplankton biodiversity has improved, but most of the new taxa appearing in our counts are rotifers, while many calanoids and the large cladoceran predators (Bythotrephes and Leptodora that are common in the nearby Lake Maggiore, were still absent from Lake Orta 17 years after liming. To aid understanding of the large-scale mechanisms controlling changes in annual richness, we assessed the annual persistence (P of Crustacea and Rotifera taxa as an estimator of whether propagules that survived introduction, as result of the natural recolonization process, also thrived. We found that the rate of introduction of zooplankton colonists and their persistence in the water column of Lake Orta changed from 1971 to 2007. New rotifer taxa appeared in the lake after the mid-1980s, when discharge of toxic substances decreased, but their annual persistence was low (P<0.5 until the turn of the century. The numerical values of rotifer and crustacean persistence in Lake Orta were unexpectedly high in 2001 and 2007 (0.55 and 0.72 for rotifers, 0.85 and 0.86 for crustacean, respectively, much higher than in limed lakes in Sudbury, Canada, and in adjacent Lake Maggiore. We hypothesize this could be related to the lack of Cladoceran predators and zooplanktivorous fish in the pelagic waters of Lake Orta.

  11. Mechanisms underlying stage-1 TRPL channel translocation in Drosophila photoreceptors.

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    Minh-Ha Lieu

    Full Text Available TRP channels function as key mediators of sensory transduction and other cellular signaling pathways. In Drosophila, TRP and TRPL are the light-activated channels in photoreceptors. While TRP is statically localized in the signaling compartment of the cell (the rhabdomere, TRPL localization is regulated by light. TRPL channels translocate out of the rhabdomere in two distinct stages, returning to the rhabdomere with dark-incubation. Translocation of TRPL channels regulates their availability, and thereby the gain of the signal. Little, however, is known about the mechanisms underlying this trafficking of TRPL channels.We first examine the involvement of de novo protein synthesis in TRPL translocation. We feed flies cycloheximide, verify inhibition of protein synthesis, and test for TRPL translocation in photoreceptors. We find that protein synthesis is not involved in either stage of TRPL translocation out of the rhabdomere, but that re-localization to the rhabdomere from stage-1, but not stage-2, depends on protein synthesis. We also characterize an ex vivo eye preparation that is amenable to biochemical and genetic manipulation. We use this preparation to examine mechanisms of stage-1 TRPL translocation. We find that stage-1 translocation is: induced with ATP depletion, unaltered with perturbation of the actin cytoskeleton or inhibition of endocytosis, and slowed with increased membrane sterol content.Our results indicate that translocation of TRPL out of the rhabdomere is likely due to protein transport, and not degradation/re-synthesis. Re-localization from each stage to the rhabdomere likely involves different strategies. Since TRPL channels can translocate to stage-1 in the absence of ATP, with no major requirement of the cytoskeleton, we suggest that stage-1 translocation involves simple diffusion through the apical membrane, which may be regulated by release of a light-dependent anchor in the rhabdomere.

  12. The behavior of the planetary rings under the Kozai Mechanism (United States)

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


    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.

  13. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields


    Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin


    This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particul...

  14. Morphological responses of plant roots to mechanical stress. (United States)

    Potocka, Izabela; Szymanowska-Pulka, Joanna


    Roots are continuously exposed to mechanical pressure and this often results in their morphological modification. Most obvious are changes in the overall form of the root system as well as in the shapes of particular roots. These changes are often accompanied by modifications of the cell pattern and cell morphology. This review focuses on the morphological responses of roots to mechanical stress. Results of early and recent experiments in which roots have been exposed to mechanical pressure are assembled, analysed and discussed. Research applying different experimental sets, obstacles, media of various compactness and structure are reviewed. An effect of the combination of mechanical stresses with other abiotic stresses on roots, and results of estimating the force exerted by the roots are briefly discussed. Possible consequences of the cell pattern rearrangements are considered. Several modifications in root morphology are commonly reported: (1) decreased root size, (2) radial swelling accompanied by increased radial dimension of the cortex cell layers and (3) enhanced cap cell sloughing. Nevertheless, because of differences between species and individual plants, a universal scenario for root morphological changes resulting from externally applied pressures is not possible. Thus, knowledge of the root response to mechanical impedance remains incomplete. Studies on the mechanical properties of the root as well as on possible modifications in cell wall structure and composition as the elements responsible for the mechanical properties of the plant tissue are required to understand the response of root tissue as a biomaterial.

  15. From Sound to Significance: Exploring the Mechanisms Underlying Emotional Reactions to Music. (United States)

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


    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.

  16. Asymmetric flexural behavior from bamboo's functionally graded hierarchical structure: underlying mechanisms. (United States)

    Habibi, Meisam K; Samaei, Arash T; Gheshlaghi, Behnam; Lu, Jian; Lu, Yang


    As one of the most renewable resources on Earth, bamboo has recently attracted increasing interest for its promising applications in sustainable structural purposes. Its superior mechanical properties arising from the unique functionally-graded (FG) hierarchical structure also make bamboo an excellent candidate for bio-mimicking purposes in advanced material design. However, despite its well-documented, impressive mechanical characteristics, the intriguing asymmetry in flexural behavior of bamboo, alongside its underlying mechanisms, has not yet been fully understood. Here, we used multi-scale mechanical characterizations assisted with advanced environmental scanning electron microscopy (ESEM) to investigate the asymmetric flexural responses of natural bamboo (Phyllostachys edulis) strips under different loading configurations, during "elastic bending" and "fracture failure" stages, with their respective deformation mechanisms at microstructural level. Results showed that the gradient distribution of the vascular bundles along the thickness direction is mainly responsible for the exhibited asymmetry, whereas the hierarchical fiber/parenchyma cellular structure plays a critical role in alternating the dominant factors for determining the distinctly different failure mechanisms. A numerical model has been likewise adopted to validate the effective flexural moduli of bamboo strips as a function of their FG parameters, while additional experiments on uniaxial loading of bamboo specimens were performed to assess the tension-compression asymmetry, for further understanding of the microstructure evolution of bamboo's outer and innermost layers under different bending states. This work could provide insights to help the processing of novel bamboo-based composites and enable the bio-inspired design of advanced structural materials with desired flexural behavior. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  17. Raynaud's Phenomenon: A Brief Review of the Underlying Mechanisms. (United States)

    Fardoun, Manal M; Nassif, Joseph; Issa, Khodr; Baydoun, Elias; Eid, Ali H


    Raynaud's phenomenon (RP) is characterized by exaggerated cold-induced vasoconstriction. This augmented vasoconstriction occurs by virtue of a reflex response to cooling via the sympathetic nervous system as well as by local activation of α 2C adrenoceptors (α 2C -AR). In a cold-initiated, mitochondrion-mediated mechanism involving reactive oxygen species and the Rho/ROCK pathway, cytoskeletal rearrangement in vascular smooth muscle cells orchestrates the translocation of α 2C -AR to the cell membrane, where this receptor readily interacts with its ligand. Different parameters are involved in this spatial and functional rescue of α 2C -AR. Of notable relevance is the female hormone, 17β-estradiol, or estrogen. This is consistent with the high prevalence of RP in premenopausal women compared to age-matched males. In addition to dissecting the role of these various players, the contribution of pollution as well as genetic background to the onset and prevalence of RP are also discussed. Different therapeutic approaches employed as treatment modalities for this disease are also highlighted and analyzed. The lack of an appropriate animal model for RP mandates that more efforts be undertaken in order to better understand and eventually treat this disease. Although several lines of treatment are utilized, it is important to note that precaution is often effective in reducing severity or frequency of RP attacks.

  18. Neural mechanisms underlying social conformity in an ultimatum game

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    Zhenyu eWei


    Full Text Available When individuals’ actions are incongruent with those of the group they belong to, they may change their initial behavior in order to conform to the group norm. This phenomenon is known as social conformity. In the present study, we used event-related functional magnetic resonance imaging (fMRI to investigate brain activity in response to group opinion during an ultimatum game. Results showed that participants changed their choices when these choices conflicted with the normative opinion of the group they were members of, especially in conditions of unfair treatment. The fMRI data revealed that a conflict with group norms activated the brain regions involved in norm violations and behavioral adjustment. Furthermore, in the reject-unfair condition, we observed that a conflict with group norms activated the medial frontal gyrus. These findings contribute to recent research examining neural mechanisms involved in detecting violations of social norms, and provide information regarding the neural representation of conformity behavior in an economic game.

  19. Raynaud's Phenomenon: a Brief Review of the Underlying Mechanisms

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    Manal Fardoun


    Full Text Available Raynaud's phenomenon (RP is characterized by exaggerated cold-induced vasoconstriction. This augmented vasoconstriction occurs by virtue of a reflex response to cooling via the sympathetic nervous system as well as by local activation of α2C adrenoceptors (α2C-AR. In a cold-initiated, mitochondrion-mediated mechanism involving reactive oxygen species and the Rho/ROCK pathway, cytoskeletal rearrangement in vascular smooth muscle cells (VSMCs orchestrates the translocation of α2C-AR to the cell membrane, where this receptor readily interacts with its ligand. Different parameters are involved in this spatial and functional rescue of α2C-AR. Of notable relevance is the female hormone, 17β-estradiol, or estrogen. This is consistent with the high prevalence of RP in pre-menopausal women compared to age-matched males. In addition to dissecting the role of these various players, the contribution of pollution as well as genetic background to the onset and prevalence of RP are also discussed. Different therapeutic approaches employed as treatment modalities for this disease are also highlighted and analyzed. The lack of an appropriate animal model for RP mandates that more efforts be undertaken in order to better understand and eventually treat this disease. Although several lines of treatment are utilized, it is important to note that precaution is often effective in reducing severity or frequency of RP attacks.

  20. Separable mechanisms underlying global feature-based attention. (United States)

    Bondarenko, Rowena; Boehler, Carsten N; Stoppel, Christian M; Heinze, Hans-Jochen; Schoenfeld, Mircea A; Hopf, Jens-Max


    Feature-based attention is known to operate in a spatially global manner, in that the selection of attended features is not bound to the spatial focus of attention. Here we used electromagnetic recordings in human observers to characterize the spatiotemporal signature of such global selection of an orientation feature. Observers performed a simple orientation-discrimination task while ignoring task-irrelevant orientation probes outside the focus of attention. We observed that global feature-based selection, indexed by the brain response to unattended orientation probes, is composed of separable functional components. One such component reflects global selection based on the similarity of the probe with task-relevant orientation values ("template matching"), which is followed by a component reflecting selection based on the similarity of the probe with the orientation value under discrimination in the focus of attention ("discrimination matching"). Importantly, template matching occurs at ∼150 ms after stimulus onset, ∼80 ms before the onset of discrimination matching. Moreover, source activity underlying template matching and discrimination matching was found to originate from ventral extrastriate cortex, with the former being generated in more anterolateral and the latter in more posteromedial parts, suggesting template matching to occur in visual cortex higher up in the visual processing hierarchy than discrimination matching. We take these observations to indicate that the population-level signature of global feature-based selection reflects a sequence of hierarchically ordered operations in extrastriate visual cortex, in which the selection based on task relevance has temporal priority over the selection based on the sensory similarity between input representations.

  1. Mechanisms Underlying HIV-Associated Noninfectious Lung Disease. (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


    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.

  2. [Neurophysiologic mechanisms of arterial hypertension under experimental chronic emotional stress]. (United States)

    Baumann, H; Martin, G; Urmantscheeva, T G; Degen, G; Wolter, F; Chasabova, W A; Gurk, C; Hinays, I; Läuter, J


    Neurophysiological studies were conducted with subhuman primates (macaca mulatta) in order to obtain an estimate of central nervous effects of socio-emotional stress. This was combined with continuously aggravated conditioning procedures in view of the possible significance of chronic environmental stress escalation for etiology and pathogenesis of an arterial hypertension model. Our conclusions are based on evoked potentials (EP) as integrative characteristics of cerebral information processing. The EPs were recorded by means of electrodes chronically implanted in brain structures of emotional and cardio-vascular relevance. Multivariate mathematico-statistical analyses of average EPs (AEP) provide an objective measure of stress sensibility of the individual, particularly of the effects of acute and chronic environmental stress factors upon the functional organization of the CNS. By means of a quantitative approach to AEP we were able to demonstrate a disjunction between distinct limbic and hypothalamic structures starting under stress conditions of subchronic character. We assume that the constancy of functionally antagonistic hyperactive excitation foci at diencephalic and supradiencephalic levels and their specific interaction with the equally stress related neocortical functional insufficiency constitutes a decisive pathogenetic central mechanism of neurotic behaviour. Long-term changes of amplification of external and internal afferences could be demonstrated on the basis of hypo- and hyperreactive neuroelectric functional patterns. These processes cause cerebro-visceral regulatory diseases as, e. g., a primary arterial hypertension by restriction of neocortical control and the corresponding efferent reactions for re-establishment of the dynamic homeostasis.

  3. Deciphering Molecular Mechanism Underlying Hypolipidemic Activity of Echinocystic Acid

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    Li Han


    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.

  4. Fatigue life prediction of mechanical structures under stochastic loading

    Directory of Open Access Journals (Sweden)

    Leitner Bohuš


    Full Text Available Problems of fatigue life prediction of materials and structures are discussed in the paper. Service loading is assumed as a continuous loading process with possible discontinuous events, which are caused by various operating conditions. The damage in a material is due to a cumulative degradation process. The damaging process is then represented either by rain-flow matrices or by a fatigue damage function which is derived using some hypothesis of a fatigue failure criterion. Presented theoretical procedure enables a very effective estimation of a service life and/or reliable evaluation of residual life of any structures under various types of loading and environmental conditions. This approach creates a good basis for powerful expert systems in structural and mechanical engineering. The aim of the paper is to present briefly some results of analysis of load-bearing steel structure loads of special railway crane PKP 25/20i which was utilized in some specific ad relatively hard operating conditions. Virtual models of the structure were being used in an analysis of acting working dynamics loads influence to be able to forecast fatigue life of load-bearing of the crane jib.

  5. Neural mechanisms underlying the induction and relief of perceptual curiosity

    Directory of Open Access Journals (Sweden)

    Marieke eJepma


    Full Text Available Curiosity is one of the most basic biological drives in both animals and humans, and has been identified as a key motive for learning and discovery. Despite the importance of curiosity and related behaviors, the topic has been largely neglected in human neuroscience; hence little is known about the neurobiological mechanisms underlying curiosity. We used functional magnetic resonance imaging (fMRI to investigate what happens in our brain during the induction and subsequent relief of perceptual curiosity. Our core findings were that (i the induction of perceptual curiosity, through the presentation of ambiguous visual input, activated the anterior insula and anterior cingulate cortex, brain regions sensitive to conflict and arousal; (ii the relief of perceptual curiosity, through visual disambiguation, activated regions of the striatum that have been related to reward processing; and (iii the relief of perceptual curiosity was associated with hippocampal activation and enhanced incidental memory. These findings provide the first demonstration of the neural basis of human perceptual curiosity. Our results provide neurobiological support for a classic psychological theory of curiosity, which holds that curiosity is an aversive condition of increased arousal whose termination is rewarding and facilitates memory.

  6. Spread of Epidemic on Complex Networks Under Voluntary Vaccination Mechanism (United States)

    Xue, Shengjun; Ruan, Feng; Yin, Chuanyang; Zhang, Haifeng; Wang, Binghong

    Under the assumption that the decision of vaccination is a voluntary behavior, in this paper, we use two forms of risk functions to characterize how susceptible individuals estimate the perceived risk of infection. One is uniform case, where each susceptible individual estimates the perceived risk of infection only based on the density of infection at each time step, so the risk function is only a function of the density of infection; another is preferential case, where each susceptible individual estimates the perceived risk of infection not only based on the density of infection but only related to its own activities/immediate neighbors (in network terminology, the activity or the number of immediate neighbors is the degree of node), so the risk function is a function of the density of infection and the degree of individuals. By investigating two different ways of estimating the risk of infection for susceptible individuals on complex network, we find that, for the preferential case, the spread of epidemic can be effectively controlled; yet, for the uniform case, voluntary vaccination mechanism is almost invalid in controlling the spread of epidemic on networks. Furthermore, given the temporality of some vaccines, the waves of epidemic for two cases are also different. Therefore, our work insight that the way of estimating the perceived risk of infection determines the decision on vaccination options, and then determines the success or failure of control strategy.

  7. Mechanisms underlying the antihypertensive effects of garlic bioactives. (United States)

    Shouk, Reem; Abdou, Aya; Shetty, Kalidas; Sarkar, Dipayan; Eid, Ali H


    Cardiovascular disease remains the leading cause of death worldwide with hypertension being a major contributing factor to cardiovascular disease-associated mortality. On a population level, non-pharmacological approaches, such as alternative/complementary medicine, including phytochemicals, have the potential to ameliorate cardiovascular risk factors, including high blood pressure. Several epidemiological studies suggest an antihypertensive effect of garlic (Allium sativum) and of many its bioactive components. The aim of this review is to present an in-depth discussion regarding the molecular, biochemical and cellular rationale underlying the antihypertensive properties of garlic and its bioactive constituents with a primary focus on S-allyl cysteine and allicin. Key studies, largely from PubMed, were selected and screened to develop a comprehensive understanding of the specific role of garlic and its bioactive constituents in the management of hypertension. We also reviewed recent advances focusing on the role of garlic bioactives, S-allyl cysteine and allicin, in modulating various parameters implicated in the pathogenesis of hypertension. These parameters include oxidative stress, nitric oxide bioavailability, hydrogen sulfide production, angiotensin converting enzyme activity, expression of nuclear factor-κB and the proliferation of vascular smooth muscle cells. This review suggests that garlic and garlic derived bioactives have significant medicinal properties with the potential for ameliorating hypertension and associated morbidity; however, further clinical and epidemiological studies are required to determine completely the specific physiological and biochemical mechanisms involved in disease prevention and management. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Response of Magnetic Force Microscopy Probes under AC Magnetic Field (United States)

    Sungthong, A.; Ruksasakchai, P.; Saengkaew, K.; Cheowanish, I.; Damrongsak, B.


    In this paper, magnetic force microscopy (MFM) probes with different coating materials were characterized under AC magnetic field. A perpendicular magnetic write head similar to those used in hard disk drives was employed as the AC magnetic field generator. In order to measure a response of MFM probes to AC magnetic field, a MFM probe under test was scanned, at a scan height of 10 nm, across the surface of the magnetic write head. During MFM imaging, the write head was biased by a sufficient magnitude of AC current, approximately 30 mA. A spectral analysis for a frequency sweep from 1 kHz to 100 MHz was extracted from post-processing MFM images. As expected, a MFM probe coated with hard magnetic alloys, i.e. FePt, has the lowest response to AC magnetic fields. MFM probes coated with soft magnetic alloys, i.e. NiFe and NiCoCr, have a relatively high and flat response across the frequency range. Ni coated MFM probe has the highest response to AC magnetic fields. In addition, CoCr and NiCo coated MFM probes show lower response than NiFe and NiCoCr probes at low frequencies; however, theirs response to AC magnetic field increase for the AC magnetic field with a frequency above 50 kHz. This can be implied that those MFM probes are a good candidate for being used to study the high-frequency performance of perpendicular magnetic write heads. Noting that response of all MFM probes significantly decreased when driven frequencies above 1 MHz due to the limitation of the hardware, i.e. response of quadrant photodiode and op-amp in a pre-amplifier.

  9. 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.


    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

  10. 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.


    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

  11. Molecular and Microbial Mechanisms Increasing Soil C Storage Under Future Rates of Anthropogenic N Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Zak, Donald R.


    A growing body of evidence reveals that anthropogenic N deposition can reduce the microbial decay of plant detritus and increase soil C storage across a wide range of terrestrial ecosystems. This aspect of global change has the potential to constrain the accumulation of anthropogenic CO2 in the Earth’s atmosphere, and hence slow the pace of climate warming. The molecular and microbial mechanisms underlying this biogeochemical response are not understood, and they are not a component of any coupled climate-biogeochemical model estimating ecosystem C storage, and hence, the future climate of an N-enriched Earth. Here, we report the use of genomic-enabled approaches to identify the molecular underpinnings of the microbial mechanisms leading to greater soil C storage in response to anthropogenic N deposition, thereby enabling us to better anticipate changes in soil C storage.

  12. Periodic forces trigger a complex mechanical response in ubiquitin. (United States)

    Szymczak, Piotr; Janovjak, Harald


    Mechanical forces govern physiological processes in all living organisms. Many cellular forces, for example, those generated in cyclic conformational changes of biological machines, have repetitive components. In apparent contrast, little is known about how dynamic protein structures respond to periodic mechanical information. Ubiquitin is a small protein found in all eukaryotes. We developed molecular dynamics simulations to unfold single and multimeric ubiquitins with periodic forces. By using a coarse-grained representation, we were able to model forces with periods about 2 orders of magnitude longer than the protein's relaxation time. We found that even a moderate periodic force weakened the protein and shifted its unfolding pathways in a frequency- and amplitude-dependent manner. A complex dynamic response with secondary structure refolding and an increasing importance of local interactions was revealed. Importantly, repetitive forces with broadly distributed frequencies elicited very similar molecular responses compared to fixed-frequency forces. When testing the influence of pulling geometry on ubiquitin's mechanical stability, it was found that the linkage involved in the mechanical degradation of cellular proteins renders the protein remarkably insensitive to periodic forces. We also devised a complementary kinetic energy landscape model that traces these observations and explains periodic-force, single-molecule measurements. In turn, this analytical model is capable of predicting dynamic protein responses. These results provide new insights into ubiquitin mechanics and a potential mechanical role during protein degradation, as well as first frameworks for dynamic protein stability and the modeling of repetitive mechanical processes.

  13. Antioxidant Property of Jobelyn as the Possible Mechanism Underlying

    Directory of Open Access Journals (Sweden)

    Solomon Umukoro


    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

  14. Bronchopulmonary dysplasia: understanding of the underlying pathological mechanisms

    Directory of Open Access Journals (Sweden)

    Daniela Fanni


    better understanding of the underlying pathological mechanisms of BPD might provide insight into development of new therapeutic and preventive strategies.  Proceedings of the International Course on Perinatal Pathology (part of the 10th International Workshop on Neonatology · October 22nd-25th, 2014 · Cagliari (Italy · October 25th, 2014 · The role of the clinical pathological dialogue in problem solving Guest Editors: Gavino Faa, Vassilios Fanos, Peter Van Eyken

  15. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields (United States)

    Piao, Shang Hao; Kwon, Seung Hyuk; Choi, Hyoung Jin


    This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER) behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications. PMID:28787852

  16. Stimuli-Responsive Polymer-Clay Nanocomposites under Electric Fields

    Directory of Open Access Journals (Sweden)

    Shang Hao Piao


    Full Text Available This short Feature Article reviews electric stimuli-responsive polymer/clay nanocomposites with respect to their fabrication, physical characteristics and electrorheological (ER behaviors under applied electric fields when dispersed in oil. Their structural characteristics, morphological features and thermal degradation behavior were examined by X-ray diffraction pattern, scanning electron microscopy and transmission electron microscopy, and thermogravimetric analysis, respectively. Particular focus is given to the electro-responsive ER characteristics of the polymer/clay nanocomposites in terms of the yield stress and viscoelastic properties along with their applications.

  17. Response of mechanical properties of glasses to their chemical, thermal and mechanical histories

    DEFF Research Database (Denmark)

    Yue, Yuanzheng

    Mechanical properties are a key factor to be considered when designing new glass compositions, optimizing glass processing parameters and defining the glass application fields. However, mechanical properties of glasses are complex values since they are influenced by many factors such as structure......, surface, thermal history or excess entropy of the final glass state. Here I review recent progresses in understanding of the responses of mechanical properties of oxide glasses to the compositional variation, thermal history and mechanical deformation. The tensile strength, elastic modulus and hardness...... and micro-cracks occurring during indentation of a glass is discussed briefly. Finally I describe the future perspectives and challenges in understanding responses of mechanical properties of oxide glasses to compositional variation, thermal history and mechanical deformation....

  18. Alteration mechanisms of UOX spent fuel under water

    International Nuclear Information System (INIS)

    Muzeau, B.


    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)

  19. Unraveling the Molecular Mechanisms Underlying the Nasopharyngeal Bacterial Community Structure

    Directory of Open Access Journals (Sweden)

    Wouter A. A. de Steenhuijsen Piters


    Full Text Available The upper respiratory tract is colonized by a diverse array of commensal bacteria that harbor potential pathogens, such as Streptococcus pneumoniae. As long as the local microbial ecosystem—also called “microbiome”—is in balance, these potentially pathogenic bacterial residents cause no harm to the host. However, similar to macrobiological ecosystems, when the bacterial community structure gets perturbed, potential pathogens can overtake the niche and cause mild to severe infections. Recent studies using next-generation sequencing show that S. pneumoniae, as well as other potential pathogens, might be kept at bay by certain commensal bacteria, including Corynebacterium and Dolosigranulum spp. Bomar and colleagues are the first to explore a specific biological mechanism contributing to the antagonistic interaction between Corynebacterium accolens and S. pneumoniae in vitro [L. Bomar, S. D. Brugger, B. H. Yost, S. S. Davies, K. P. Lemon, mBio 7(1:e01725-15, 2016, doi:10.1128/mBio.01725-15]. The authors comprehensively show that C. accolens is capable of hydrolyzing host triacylglycerols into free fatty acids, which display antipneumococcal properties, suggesting that these bacteria might contribute to the containment of pneumococcus. This work exemplifies how molecular epidemiological findings can lay the foundation for mechanistic studies to elucidate the host-microbe and microbial interspecies interactions underlying the bacterial community structure. Next, translation of these results to an in vivo setting seems necessary to unveil the magnitude and importance of the observed effect in its natural, polymicrobial setting.

  20. Cognitive mechanisms underlying instructed choice exploration of small city maps

    Directory of Open Access Journals (Sweden)

    Sofia eSakellaridi


    Full Text Available We investigated the cognitive mechanisms underlying the exploration and decision-making in realistic and novel environments. Twelve human subjects were shown small circular U.S. city maps with two locations highlighted on the circumference, as possible choices for a post office (targets. At the beginning of a trial, subjects fixated a spot at the center of the map and ultimately chose one of the two locations. A space syntax analysis of the map paths (from the center to each target revealed that the chosen location was associated with the less convoluted path, as if subjects navigated mentally the paths in an ant’s way, i.e. by staying within street boundaries, and ultimately choosing the target that could be reached from the center in the shortest way, and the fewest turns and intersections. The subjects’ strategy for map exploration and decision making was investigated by monitoring eye position during the task. This revealed a restricted exploration of the map delimited by the location of the two alternative options and the center of the map. Specifically, subjects explored the areas around the two target options by repeatedly looking at them before deciding which one to choose, presumably implementing an evaluation and decision-making process. The ultimate selection of a specific target was significantly associated with the time spent exploring the area around that target. Finally, an analysis of the sequence of eye fixations revealed that subjects tended to look systematically towards the target ultimately chosen even from the beginning of the trial. This finding indicates an early cognitive selection bias for the ensuing decision process.

  1. Piezoelectric Response of Ferroelectric Ceramics Under Mechanical Stress (United States)


    Chair William F. Bailey, Ph.D. Member Maj Darrell S. Crowe , Ph.D. Member Lt Col Richard E. Huffman Jr., Ph.D. Member Jason R. Foley, Ph.D. Member ADEDEJI...Robert B. Greendyke, for his whole-hearted dedication and guidance as my advisor, teacher and mentor, Dr William F. Bailey, Dr Darrell S. Crowe and Dr...assembled with Pb-free and Tin–Lead solders. Device and Materials Reliability, IEEE Transactions on, 8(1):182–192, 2008. [47] John D. Prymak and Jim

  2. Plant-insect interactions under bacterial influence: ecological implications and underlying mechanisms. (United States)

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


    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

  3. Photodegradation kinetics, products and mechanism of timolol under simulated sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yong, E-mail: [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Liang, Qi; Zhou, Danna [College of Material Science and Chemical Engineering, China University of Geosciences, Wuhan 430074 (China); Wang, Zongping, E-mail: [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Tao, Tao [School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074 (China); Zuo, Yuegang [Department of Chemistry and Biochemistry, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02747 (United States)


    Highlights: ► The indirect degradation of timolol is first investigated in fulvic acid solution. ► {sup 3}FA{sup *} and {sup 1}O{sub 2} accounted for the degradation of timolol in the aerated FA solutions. ► The presence of halides inhibited the degradation in the order of Cl{sup −} < Br{sup −} < I{sup −}. ► The role of I{sup −} in the degradation was first found to be concentration-dependent. ► The photoproducts of timolol were identified by LC-DAD/ESI-MS/MS analysis. -- Abstract: The photodegradation of β-blocker timolol in fulvic acid (FA) solution was investigated under simulated sunlight. The triplet excited state of FA ({sup 3}FA{sup *}) and singlet oxygen ({sup 1}O{sub 2}) were the main reactive species responsible for the degradation of timolol in the aerated FA solutions. Both dissolved oxygen and iodide ions (I{sup −}) are the efficient quenchers of {sup 3}FA{sup *}. The photodegradation was drastically accelerated after removing the dissolved oxygen. The presence of I{sup −} inhibited the photosensitized degradation of timolol in the deoxygenated FA solutions, whereas the role of I{sup −} in the reaction was concentration-dependent in the aerated solutions. The other halide ions such as chloride (Cl{sup −}) and bromide (Br{sup −}) exhibited less effect on the photodegradation of timolol in both aerated and deoxygenated solutions. By LC-DAD/ESI-MS/MS analysis, the photoproducts of timolol in both aerated and deoxygenated FA solutions were identified. Electron transfer interaction occurred between {sup 3}FA{sup *} and amine moiety of timolol, leading to the cleavage of C–O bond in the side chain and oxidation of the hexatomic ring. These findings suggest the photosensitized degradation was a significant pathway for the elimination of timolol in natural waters.

  4. Nociceptive responses to thermal and mechanical stimulations in awake pigs

    DEFF Research Database (Denmark)

    di Giminiani, Pierpaolo; Petersen, Lars Jelstrup; Herskin, Mette S.


    body sizes (30 and 60 kg) were exposed to thermal (CO(2) laser) and mechanical (pressure application measurement device) stimulations to the flank and the hind legs in a balanced order. The median response latency and the type of behavioural response were recorded. RESULTS: Small pigs exhibited...... animal studies in a large species require further examination. This manuscript describes the initial development of a porcine model of cutaneous nociception and focuses on interactions between the sensory modality, body size and the anatomical location of the stimulation site. METHODS: Pigs of different...... significantly lower pain thresholds (shorter latency to response) than large pigs to thermal and mechanical stimulations. Stimulations at the two anatomical locations elicited very distinct sets of behavioural responses, with different levels of sensitivity between the flank and the hind legs. Furthermore...

  5. Effects of delaying transplanting on agronomic traits and grain yield of rice under mechanical transplantation pattern.

    Directory of Open Access Journals (Sweden)

    Qihua Liu

    Full Text Available A delay in the mechanical transplantation (MT of rice seedlings frequently occurs in Huanghuai wheat-rice rotation cropping districts of China, due to the late harvest of wheat, the poor weather conditions and the insufficiency of transplanters, missing the optimum transplanting time and causing seedlings to age. To identify how delaying transplanting rice affects the agronomic characteristics including the growth duration, photosynthetic productivity and dry matter remobilization efficiency and the grain yield under mechanical transplanting pattern, an experiment with a split-plot design was conducted over two consecutive years. The main plot includes two types of cultivation: mechanical transplanting and artificial transplanting (AT. The subplot comprises four japonica rice cultivars. The results indicate that the rice jointing, booting, heading and maturity stages were postponed under MT when using AT as a control. The tiller occurrence number, dry matter weight per tiller, accumulative dry matter for the population, leaf area index, crop growth rate, photosynthetic potential, and dry matter remobilization efficiency of the leaf under MT significantly decreased compared to those under AT. In contrast, the reduction rate of the leaf area during the heading-maturity stage was markedly enhanced under MT. The numbers of effective panicles and filled grains per panicle and the grain yield significantly decreased under MT. A significant correlation was observed between the dry matter production, remobilization and distribution characteristics and the grain yield. We infer that, as with rice from old seedlings, the decrease in the tiller occurrence, the photosynthetic productivity and the assimilate remobilization efficiency may be important agronomic traits that are responsible for the reduced grain yield under MT.

  6. Molecular analysis of Hsp70 mechanisms in plants and their function in response to stress. (United States)

    Usman, Magaji G; Rafii, Mohd Y; Martini, Mohammad Y; Yusuff, Oladosu A; Ismail, Mohd R; Miah, Gous


    Studying the strategies of improving abiotic stress tolerance is quite imperative and research under this field will increase our understanding of response mechanisms to abiotic stress such as heat. The Hsp70 is an essential regulator of protein having the tendency to maintain internal cell stability like proper folding protein and breakdown of unfolded proteins. Hsp70 holds together protein substrates to help in movement, regulation, and prevent aggregation under physical and or chemical pressure. However, this review reports the molecular mechanism of heat shock protein 70 kDa (Hsp70) action and its structural and functional analysis, research progress on the interaction of Hsp70 with other proteins and their interaction mechanisms as well as the involvement of Hsp70 in abiotic stress responses as an adaptive defense mechanism.

  7. Molecular Mechanics: The Method and Its Underlying Philosophy. (United States)

    Boyd, Donald B.; Lipkowitz, Kenny B.


    Molecular mechanics is a nonquantum mechanical method for solving problems concerning molecular geometries and energy. Methodology based on: the principle of combining potential energy functions of all structural features of a particular molecule into a total force field; derivation of basic equations; and use of available computer programs is…

  8. A noise level prediction method based on electro-mechanical frequency response function for capacitors. (United States)

    Zhu, Lingyu; Ji, Shengchang; Shen, Qi; Liu, Yuan; Li, Jinyu; Liu, Hao


    The capacitors in high-voltage direct-current (HVDC) converter stations radiate a lot of audible noise which can reach higher than 100 dB. The existing noise level prediction methods are not satisfying enough. In this paper, a new noise level prediction method is proposed based on a frequency response function considering both electrical and mechanical characteristics of capacitors. The electro-mechanical frequency response function (EMFRF) is defined as the frequency domain quotient of the vibration response and the squared capacitor voltage, and it is obtained from impulse current experiment. Under given excitations, the vibration response of the capacitor tank is the product of EMFRF and the square of the given capacitor voltage in frequency domain, and the radiated audible noise is calculated by structure acoustic coupling formulas. The noise level under the same excitations is also measured in laboratory, and the results are compared with the prediction. The comparison proves that the noise prediction method is effective.

  9. [Study on main pharmacodynamics and underlying mechanisms of 999 Ganmaoling]. (United States)

    Xu, Qi-Hua; He, Rong; Peng, Bo; Ye, Zu-Guang; Li, Jian-Rong; Zhang, Yue-Fei; Dai, Zhi


    To observe synergistic effects of 999 Ganmaoling (GML) and its Chinese/Western materia medica (CMM and WMM) on pharmacodynamic action and to study underlying mechanisms, their anti-inflammatory, antipyretic effects were compared by assaying the increased capillary permeability induced by glacial acetic acid in mice, ear swelling induced by Xylene in mice, non-specific pleurisy induced by carrageenan in rats, and yeast induced fever in rats. Crystal violet (CV) and microbial activity (XTT) assay were used to evaluate the inhibition of GML and its CMM and WMM on KPN biofilm formation, and scanning electron microscopy (SEM) was applied for observing KPN biofilm morphology changes. The results showed that compared with control group, GML could reduce exudation amount of Evans-Blue and the degree of Ear swelling significantly, and CMM and WMM have no significant effects. The concentration of TNF-α and IL-1β of rat pleural effusion in GML, CMM and WMM group decreased significantly. The concentration of TNF-α, IL-1β and IL-8 in GML group, TNF-α, IL-8 in WMM group and IL-8 in CMM in rats serum decreased significantly. The body temperature in rats decreased significantly in GML and WMM group after 4-8 h of administration. CMM group showed no significant difference in rat body temperature compare with control. Compared with control group, GML (55-13.75 g•L⁻¹) could inhibit KPN biofilm formation and reduce number of viable cells in the KPN biofilm. CMM (45-22.5 g•L⁻¹) and WMM (10 g•L⁻¹) could also inhibit KPN biofilm formation and reduce number of viable cells (P<0.01). Result of SEM also showed that GML (55 g•L⁻¹) and its CMM (45 g•L⁻¹) and WMM (10 g•L⁻¹) could interfere the bacterial arrangement of KPN biofilm and extracellular matrix. GML and its CMM & WMM could inhibit the formation of KPN biofilm, CMM & WMM in GML showed synergism and complementation in inhibit KPN biofilm. Results showed that GML had obvious anti-inflammatory and

  10. Music and literature: are there shared empathy and predictive mechanisms underlying their affective impact?

    Directory of Open Access Journals (Sweden)

    Diana eOmigie


    Full Text Available It has been suggested that music and language had a shared evolutionary precursor before becoming mainly responsible for the communication of emotive and referential meaning respectively. However, emphasis on potential differences between music and language may discourage a consideration of the commonalities that music and literature share. Indeed, one possibility is that common mechanisms underlie their affective impact, and the current paper carefully reviews relevant neuroscientific findings to examine such a prospect. First and foremost, it will be demonstrated that considerable evidence of a common role of empathy and predictive processes now exists for the two domains. However, it will also be noted that an important open question remains: namely, whether the mechanisms underlying the subjective experience of uncertainty differ between the two with respect to recruitment of phylogenetically ancient emotion areas. It will be concluded that a comparative approach may not only help to reveal general mechanisms underlying our responses to music and literature, but may also help us better understand any idiosyncrasies in their capacity for affective impact.

  11. Mechanisms of initial heart rate response to postural change

    NARCIS (Netherlands)

    Borst, C.; Wieling, W.; van Brederode, J. F.; Hond, A.; de Rijk, L. G.; Dunning, A. J.


    We explored in 43 healthy subjects the afferent mechanisms of the initial heart rate response to standing by comparing free standing, 70 degrees head-up tilt, handgrip, and contraction of abdominal and leg muscles. The results indicate the following. 1) Standing evokes an immediate, large, bimodal

  12. Neural Mechanisms Underlying Action Observation in Adults with Down Syndrome (United States)

    Virji-Babul, Naznin; Moiseev, Alexander; Cheung, Teresa; Weeks, Daniel J.; Cheyne, Douglas; Ribary, Urs


    Results of a magnetoencephalography (MEG) brain imaging study conducted to examine the cortical responses during action execution and action observation in 10 healthy adults and 8 age-matched adults with Down syndrome are reported. During execution, the motor responses were strongly lateralized on the ipsilateral rather than the contralateral side…

  13. Mechanical behavior of irradiated fuel-pin cladding evaluated under transient heating and pressure conditions

    International Nuclear Information System (INIS)

    Hamilton, M.L.; Johnson, G.D.; Hunter, C.W.; Duncan, D.R.


    Fast breeder fuel-pin cladding has been tested under experimental conditions simulating the temperature and pressure history characteristic of anticipated transient events. Irradiation induces severe reductions in both strength and ductility. Ductility losses are independent of the rate of temperature increase and saturate by a fluence of approx. 2 x 10 22 n/cm 2 (E > 0.1 MeV). Losses in strength are dependent on the rate of temperature increase but saturate at a fluence of approx.5 x 10 22 n/cm 2 . Evidence is presented to show that fission products are probably responsible for the degradation in mechanical properties

  14. Radiation pneumonitis and fibrosis: mechanisms underlying its pathogenesis and implications for future research. (United States)

    Tsoutsou, Pelagia G; Koukourakis, Michael I


    Radiation pneumonitis and subsequent radiation pulmonary fibrosis are the two main dose-limiting factors when irradiating the thorax that can have severe implications for patients' quality of life. In this article, the current concepts about the pathogenetic mechanisms underlying radiation pneumonitis and fibrosis are presented. The clinical course of fibrosis, a postulated acute inflammatory stage, and a late fibrotic and irreversible stage are discussed. The interplay of cells and the wide variety of molecules orchestrating the immunologic response to radiation, their interactions with specific receptors, and the cascade of events they trigger are elucidated. Finally, the implications of this knowledge with respect to the therapeutic interventions are critically presented.

  15. Acoustic and Vibration Control for an Underwater Structure under Mechanical Excitation

    Directory of Open Access Journals (Sweden)

    Shi-Jian Zhu


    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.

  16. Response to various periods of mechanical stimuli in Physarum plasmodium (United States)

    Umedachi, Takuya; Ito, Kentaro; Kobayashi, Ryo; Ishiguro, Akio; Nakagaki, Toshiyuki


    Response to mechanical stimuli is a fundamental and critical ability for living cells to survive in hazardous conditions or to form adaptive and functional structures against force(s) from the environment. Although this ability has been extensively studied by molecular biology strategies, it is also important to investigate the ability from the viewpoint of biological rhythm phenomena so as to reveal the mechanisms that underlie these phenomena. Here, we use the plasmodium of the true slime mold Physarum polycephalum as the experimental system for investigating this ability. The plasmodium was repetitively stretched for various periods during which its locomotion speed was observed. Since the plasmodium has inherent oscillation cycles of protoplasmic streaming and thickness variation, how the plasmodium responds to various periods of external stretching stimuli can shed light on the other biological rhythm phenomena. The experimental results show that the plasmodium exhibits response to periodic mechanical stimulation and changes its locomotion speed depending on the period of the stretching stimuli.

  17. Response mechanisms of thermionic detectors with enhanced nitrogen selectivity. (United States)

    Carlsson, H; Robertsson, G; Colmsjö, A


    The response mechanisms of a thermionic detector with enhanced nitrogen selectivity operating in an inert gas environment were investigated. According to accepted theory, the analyte has to contain electronegative functional groups in order for negative ions to be formed by the extraction of electrons from the thermionic source. This leads to a selective detector response for compounds containing nitro groups or multiple halogens. However, in the tests described here, polycyclic aromatic nitrogen hydrocarbons (PANHs), acridines, and carbazoles were used as reference substances. These compounds contain no electronegative functional groups. None of the investigated acridines exhibited any response from the detector, but carbazoles generated a strong structure-related detector response. By examining partial charges for all hydrogens of all individual carbazoles and acridine, it was demonstrated that the acidic hydrogen atom attached to the nitrogen heteroatom of the carbazoles has a strong influence on the detector response. Ionization of carbazoles may occur by dissociation of the nitrogen-hydrogen bond during contact with the thermionic surface. Support for this theory was provided by the linear relationship between the relative detector response and the deprotonization energy of the carbazoles (coefficients of determination of 0.90 and 0.98 for linear and quadratic models, respectively, were obtained). Further, there appeared to be no linear relationship between the detector response and electron affinity of the carbazoles, (R2 value, 0.32). Thus, the mechanism involved in ionization of the carbazoles is probably not direct electron transfer from the thermionic surface to the carbazoles. Principal component analysis (PCA) showed that the thermal conductivity of chemically inert detector gases also has an influence on the detector response. The investigated gases were helium, neon, nitrogen, carbon dioxide, and argon. It was found that thermal conductivity can be

  18. Electro-chemo-mechanical response of a free-standing polypyrrole strip

    International Nuclear Information System (INIS)

    Vazquez, G; Otero, T F; Cascales, J J L


    Further development of mechanical devices based on conducting polymers; require a precise understanding of their mechanical response, i.e. their control, under a controlled external current. In this work, we show some results for the relation between the electrical current consumed in the electrochemical process and the mechanical work developed by a freestanding polypyrrole strip, when it is subjected to a stretching force (stress). Under these conditions, from the results obtained in this work, we observe how it results almost impossible to predict a straight relationship between mechanical work and current consumed in the electrochemical process. In addition, we will quantify the variation of the mechanical properties of the free standing polypyrrole strip associated with the oxidation state of the polymer by measuring its Young's modulus.

  19. Mechanical Characterization of Anion Exchange Membranes Under Controlled Environmental Conditions (United States)


    supporting textiles and test the mechanical properties. Even though their films were only 10 microns, the SER fixture was used by applying double stick tape...aramid and stainless steel. The authors conclude that supporting textile has a large impact on mechanical properties due to the difference in...Elongation) are depicted. 2.2 Conductivity Ionic conductivity was measured by electrochemical impedance spectroscopy using a four- electrode in-plane

  20. Features wear nodes mechanization wing aircraft operating under dynamic loads

    Directory of Open Access Journals (Sweden)

    А.М. Хімко


    Full Text Available  The conducted researches of titanic alloy ВТ-22 at dynamic loading with cycled sliding and dynamic loading in conditions of rolling with slipping. It is established that roller jamming in the carriage increases wear of rod of mechanization of a wing to twenty times. The optimum covering for strengthening wearied sites and restoration of working surfaces of wing’s mechanization rod is defined.

  1. Brain activation for response inhibition under gaming cue distraction in internet gaming disorder

    Directory of Open Access Journals (Sweden)

    Gin-Chung Liu


    Full Text Available We evaluated neural substrates related to the loss of control in college students with internet gaming disorder (IGD. We hypothesized that deficit in response inhibition under gaming cue distraction was the possible mechanism for the loss of control internet use. Eleven cases of IGD and 11 controls performed Go/NoGo tasks with/without gaming distraction in the functional magnetic resonance imaging scanner. When the gaming picture was shown as background while individuals were performing Go/NoGo tasks, the IGD group committed more commission errors. The control group increased their brain activations more over the right dorsolateral prefrontal cortex (DLPFC and superior parietal lobe under gaming cue distraction in comparison with the IGD group. Furthermore, brain activation of the right DLPFC and superior parietal lobe were negatively associated with performance of response inhibition among the IGD group. The results suggest that the function of response inhibition was impaired under gaming distraction among the IGD group, and individuals with IGD could not activate right DLPFC and superior parietal lobe to keep cognitive control and attention allocation for response inhibition under gaming cue distraction. This mechanism should be addressed in any intervention for IGD.

  2. Synthetic oligorotaxanes exert high forces when folding under mechanical load (United States)

    Sluysmans, Damien; Hubert, Sandrine; Bruns, Carson J.; Zhu, Zhixue; Stoddart, J. Fraser; Duwez, Anne-Sophie


    Folding is a ubiquitous process that nature uses to control the conformations of its molecular machines, allowing them to perform chemical and mechanical tasks. Over the years, chemists have synthesized foldamers that adopt well-defined and stable folded architectures, mimicking the control expressed by natural systems1,2. Mechanically interlocked molecules, such as rotaxanes and catenanes, are prototypical molecular machines that enable the controlled movement and positioning of their component parts3-5. Recently, combining the exquisite complexity of these two classes of molecules, donor-acceptor oligorotaxane foldamers have been synthesized, in which interactions between the mechanically interlocked component parts dictate the single-molecule assembly into a folded secondary structure6-8. Here we report on the mechanochemical properties of these molecules. We use atomic force microscopy-based single-molecule force spectroscopy to mechanically unfold oligorotaxanes, made of oligomeric dumbbells incorporating 1,5-dioxynaphthalene units encircled by cyclobis(paraquat-p-phenylene) rings. Real-time capture of fluctuations between unfolded and folded states reveals that the molecules exert forces of up to 50 pN against a mechanical load of up to 150 pN, and displays transition times of less than 10 μs. While the folding is at least as fast as that observed in proteins, it is remarkably more robust, thanks to the mechanically interlocked structure. Our results show that synthetic oligorotaxanes have the potential to exceed the performance of natural folding proteins.

  3. Seasonal Climate Extremes : Mechanism, Predictability and Responses to Global Warming (United States)

    Shongwe, M. E.


    Climate extremes are rarely occurring natural phenomena in the climate system. They often pose one of the greatest environmental threats to human and natural systems. Statistical methods are commonly used to investigate characteristics of climate extremes. The fitted statistical properties are often interpolated or extrapolated to give an indication of the likelihood of a certain event within a given period or interval. Under changing climatic conditions, the statistical properties of climate extremes are also changing. It is an important scientific goal to predict how the properties of extreme events change. To achieve this goal, observational and model studies aimed at revealing important features are a necessary prerequisite. Notable progress has been made in understanding mechanisms that influence climate variability and extremes in many parts of the globe including Europe. However, some of the recently observed unprecedented extremes cannot be fully explained from the already identified forcing factors. A better understanding of why these extreme events occur and their sensitivity to certain reinforcing and/or competing factors is useful. Understanding their basic form as well as their temporal variability is also vital and can contribute to global scientific efforts directed at advancing climate prediction capabilities, particularly making skilful forecasts and realistic projections of extremes. In this thesis temperature and precipitation extremes in Europe and Africa, respectively, are investigated. Emphasis is placed on the mechanisms underlying the occurrence of the extremes, their predictability and their likely response to global warming. The focus is on some selected seasons when extremes typically occur. An atmospheric energy budget analysis for the record-breaking European Autumn 2006 event has been carried out with the goal to identify the sources of energy for the extreme event. Net radiational heating is compared to surface turbulent fluxes of

  4. Response to recurrent selection under small effective population size

    Directory of Open Access Journals (Sweden)

    Souza Jr. Cláudio Lopes de


    Full Text Available A formula was derived for the prediction of the response to recurrent selection when the effective population size (Ne is small. Usually, responses to selection have been estimated by Rs = icsigma²A/sigmaPh, where i, c, sigma²A, and sigmaPh stand for standardized selection differential, parental control, additive variance, and phenotypic standard deviation, respectively. This expression, however, was derived under the assumption of infinite population size. By introducing the effects of finite population size, the expression derived was Rs = [ic(sigma²A + deltaFD1/sigmaPh] - DFID, where deltaF, ID and D1 are the changes in the inbreeding coefficient, the inbreeding depression, and the covariance of additive and homozygous dominance effects, respectively. Thus, the predicted responses to selection based on these expressions will be smaller than those based on the standard procedures for traits with a high level of dominance such as yield. Responses to five cycles of half-sib selection were predicted for maize by both expressions, considering that 100 progenies were evaluated and 10 S1 progenies were recombined, which corresponds to Ne = 10 for each cycle. The accumulated response to selection estimated with the new expression was about 47 and 28% smaller than that based on the standard expression for yield and plant height, respectively. Thus, the expression usually used overestimates the responses to selection, which is in agreement with reported results, because it does not take into account the effective population size that is generally small in recurrent selection programs

  5. Hydrodynamic response of viscous fluids under seismic excitation

    International Nuclear Information System (INIS)

    Ma, D.C.


    Hydrodynamic response of liquid-tank systems, such as reactor vessels, spent-fuel pools and liquid storage tanks have been studied extensively in the last decade (Chang et al. 1988; Ma et al. 1991). However, most of the studies are conducted with the assumption of an inviscid fluid. In recent years, the hydrodynamic response of viscous fluids has received increasing attention in high level waste storage tanks containing viscous waste material. This paper presents a numerical study on the hydrodynamic response of viscous fluids in a large 2-D fluid-tank system under seismic excitation. Hydrodynamic responses (i.e. sloshing wave height, fluid pressures, shear stress, etc.) are calculated for a fluid with various viscosities. Four fluid viscosities are considered. They are 1 cp, 120 cp, 1,000 cp and 12,000 cp (1 cp = 1.45 x 10 -7 lb-sec/in 2 ). Note that the liquid sodium of the Liquid-Metal Reactor (LMR) reactor has a viscosity of 1.38 x 10 -5 lb-sec/in 2 (about 95 cp) at an operational temperature of 900 degree F. Section 2 describes the pertinent features of the mathematical model. In Section 3, the fundamental sloshing phenomena of viscous fluid are examined. Sloshing wave height and shear stress for fluid with different viscosities are compared. The conclusions are given in Section 4

  6. Mechanism and kinetics of mineral weathering under acid conditions

    NARCIS (Netherlands)

    Anbeek, C.


    This study deals with the relationships between crystal structure, grain diameter, surface morphology and dissolution kinetics for feldspar and quartz under acid conditions.

    Intensively ground samples from large, naturally weathered mineral fragments are frequently used in

  7. The tank's dynamic response under nuclear explosion blast wave

    International Nuclear Information System (INIS)

    Xu Mei; Wang Lianghou; Li Xiaotian; Yu Suyuan; Zhang Zhengming; Wan Li


    To weapons and equipment, blast wave is the primary destructive factor. In this paper, taken the real model-59 tank as an example, we try to transform the damage estimation problem into computing a fluid structure interaction problem with finite element method. The response of tank under nuclear explosion blast wave is computed with the general-coupling algorithm. Also, the dynamical interaction of blast wave and tank is reflected in real time. The deformation of each part of the tank is worked out and the result corresponds to the real-measured data. (authors)

  8. Wind turbine aerodynamic response under atmospheric icing conditions

    DEFF Research Database (Denmark)

    Etemaddar, M.; Hansen, Martin Otto Laver; Moan, T.


    -four hours of icing, with time varying wind speed and atmospheric icing conditions, was simulated on a rotor. Computational fluid dynamics code, FLUENT, was used to estimate the aerodynamic coefficients of the blade after icing. The results were also validated against wind tunnel measurements performed at LM...... Wind Power using a NACA64618 airfoil. The effects of changes in geometry and surface roughness are considered in the simulation. A blade element momentum code WT-Perf is then used to quantify the degradation in performance curves. The dynamic responses of the wind turbine under normal and iced...

  9. Performance of multifilamentary Nb3Sn under mechanical load

    International Nuclear Information System (INIS)

    Easton, D.S.; Schwall, R.E.


    The critical current of a commercial multifilamentary Nb 3 Sn conductor has been measured under the application of uniaxial tension at 4.2 K and following bending at room temperature. Significant reductions in J/subc/ are observed under uniaxial loading. Results are presented for a monolithic conductor manufactured by the bronze diffusion technique and for cable conductors formed by the tin-dip technique

  10. Exertional rhabdomyolysis: physiological response or manifestation of an underlying myopathy? (United States)

    Scalco, Renata S; Snoeck, Marc; Quinlivan, Ros; Treves, Susan; Laforét, Pascal; Jungbluth, Heinz; Voermans, Nicol C


    Exertional rhabdomyolysis is characterised by muscle breakdown associated with strenuous exercise or normal exercise under extreme circumstances. Key features are severe muscle pain and sudden transient elevation of serum creatine kinase (CK) levels with or without associated myoglobinuria. Mild cases may remain unnoticed or undiagnosed. Exertional rhabdomyolysis is well described among athletes and military personnel, but may occur in anybody exposed to unaccustomed exercise. In contrast, exertional rhabdomyolysis may be the first manifestation of a genetic muscle disease that lowers the exercise threshold for developing muscle breakdown. Repeated episodes of exertional rhabdomyolysis should raise the suspicion of such an underlying disorder, in particular in individuals in whom the severity of the rhabdomyolysis episodes exceeds the expected response to the exercise performed. The present review aims to provide a practical guideline for the acute management and postepisode counselling of patients with exertional rhabdomyolysis, with a particular emphasis on when to suspect an underlying genetic disorder. The pathophysiology and its clinical features are reviewed, emphasising four main stepwise approaches: (1) the clinical significance of an acute episode, (2) risks of renal impairment, (3) clinical indicators of an underlying genetic disorders and (4) when and how to recommence sport activity following an acute episode of rhabdomyolysis. Genetic backgrounds that appear to be associated with both enhanced athletic performance and increased rhabdomyolysis risk are briefly reviewed. PMID:27900193

  11. Advanced waterflooding in chalk reservoirs: Understanding of underlying mechanisms

    DEFF Research Database (Denmark)

    Zahid, Adeel; Sandersen, Sara Bülow; Stenby, Erling Halfdan


    Over the last decade, a number of studies have shown SO42−, Ca2+ and Mg2+ to be potential determining ions, which may be added to the injected brine for improving oil recovery during waterflooding in chalk reservoirs. However the understanding of the mechanism leading to an increase in oil recove...... of a microemulsion phase could be the possible reasons for the observed increase in oil recovery with sulfate ions at high temperature in chalk reservoirs besides the mechanism of the rock wettability alteration, which has been reported in most previous studies.......Over the last decade, a number of studies have shown SO42−, Ca2+ and Mg2+ to be potential determining ions, which may be added to the injected brine for improving oil recovery during waterflooding in chalk reservoirs. However the understanding of the mechanism leading to an increase in oil recovery...

  12. Epigenetic mechanisms underlying the pathogenesis of neurogenetic diseases. (United States)

    Qureshi, Irfan A; Mehler, Mark F


    There have been considerable advances in uncovering the complex genetic mechanisms that underlie nervous system disease pathogenesis, particularly with the advent of exome and whole genome sequencing techniques. The emerging field of epigenetics is also providing further insights into these mechanisms. Here, we discuss our understanding of the interplay that exists between genetic and epigenetic mechanisms in these disorders, highlighting the nascent field of epigenetic epidemiology-which focuses on analyzing relationships between the epigenome and environmental exposures, development and aging, other health-related phenotypes, and disease states-and next-generation research tools (i.e., those leveraging synthetic and chemical biology and optogenetics) for examining precisely how epigenetic modifications at specific genomic sites affect disease processes.

  13. Dynamic Response of Linear Mechanical Systems Modeling, Analysis and Simulation

    CERN Document Server

    Angeles, Jorge


    Dynamic Response of Linear Mechanical Systems: Modeling, Analysis and Simulation can be utilized for a variety of courses, including junior and senior-level vibration and linear mechanical analysis courses. The author connects, by means of a rigorous, yet intuitive approach, the theory of vibration with the more general theory of systems. The book features: A seven-step modeling technique that helps structure the rather unstructured process of mechanical-system modeling A system-theoretic approach to deriving the time response of the linear mathematical models of mechanical systems The modal analysis and the time response of two-degree-of-freedom systems—the first step on the long way to the more elaborate study of multi-degree-of-freedom systems—using the Mohr circle Simple, yet powerful simulation algorithms that exploit the linearity of the system for both single- and multi-degree-of-freedom systems Examples and exercises that rely on modern computational toolboxes for both numerical and symbolic compu...

  14. Evaluating the Mechanism of Oil Price Shocks and Fiscal Policy Responses in the Malaysian Economy

    International Nuclear Information System (INIS)

    Bekhet, Hussain A; Yusoff, Nora Yusma Mohamed


    The paper aims to explore the symmetric impact of oil price shock on economy, to understand its mechanism channel and how fiscal policy response towards it. The Generalized Impulse Response Function and Variance Decomposition under the VAR methodology were employed. The empirical findings suggest that symmetric oil price shock has a positive and direct impact on oil revenue and government expenditure. However, the real GDP is vulnerable in a short-term but not in the long term period. These results would confirm that fiscal policy is the main mechanism channel that mitigates the adverse effects oil price shocks to the economy.

  15. Molecular mechanisms of radioadaptive responses in human lymphoblastoid cells

    International Nuclear Information System (INIS)

    Kakimoto, Ayana; Taki, Keiko; Nakajima, Tetsuo


    Radioadaptive response is a biodefensive response observed in a variety of mammalian cells and animals where exposure to low dose radiation induces resistance against the subsequent high dose radiation. Elucidation of its mechanisms is important for risk estimation of low dose radiation because the radioadaptive response implies that low dose radiation affects cells/individuals in a different manner from high dose radiation. In the present study, we explored the molecular mechanisms of the radioadaptive response in human lymphoblastoid cells AHH-1 in terms of mutation at the hypoxanthine phosphoribosyltransferase (HPRT) gene locus. First we observed that preexposure to the priming dose in the range from 0.02 Gy to 0.2 Gy significantly reduced mutation frequency at HPRT gene locus after irradiation with 3 Gy of X rays. As no significant adaptive response was observed with the priming dose of 0.005 Gy, it was indicated that the lower limit of the priming dose to induce radioadaptive response may be between 0.005 Gy and 0.02 Gy. Second, we examined the effect of 3-amino-benzamide (3AB), an inhibitor of poly(ADP-ribose)polymerase1, which has been reported to inhibit the radioadaptive response in terms of chromosome aberration. However we could observe significant radioadaptive responses in terms of mutation even in the presence of 3AB. These findings suggested that molecular mechanisms of the radioadaptive response in terms of mutation may be different from that for radioadaptive responses in terms of chromosomal aberration, although we could not exclude a possibility that the differential effects of 3AB was due to cell type difference. Finally, by performing a comprehensive analysis of alterations in gene expression using high coverage expression profiling (HiCEP), we could identify 17 genes whose expressions were significantly altered 6 h after irradiation with 0.02 Gy. We also found 17 and 20 genes, the expressions of which were different with or without priming

  16. A review of mechanisms underlying anticarcinogenicity by brassica vegetables

    NARCIS (Netherlands)

    Verhoeven, D.T.H.; Verhagen, H.; Goldbohm, R.A.; Brandt, P.A. van den; Poppel, G. van


    The mechanisms by which brassica vegetables might decrease the risk of cancer are reviewed in this paper. Brassicas, including all types of cabbages, broccoli, cauliflower and Brussels sprouts, may be protective against cancer due to their relatively high glucosinolate content. Glucosinolates are

  17. Peer influence: neural mechanisms underlying in-group conformity

    NARCIS (Netherlands)

    Stallen, M.; Smidts, A.; Sanfey, A.G.


    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

  18. Peer influence: Neural mechanisms underlying in-group conformity

    NARCIS (Netherlands)

    M. Stallen (Mirre); A. Smidts (Ale); A.G. Sanfey (Alan)


    textabstractPeople 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).

  19. Survival under stress: molecular mechanisms of metabolic rate ...

    African Journals Online (AJOL)

    Studies in my laboratory are analysing the molecular mechanisms and regulatory events that underlie transitions to and from hypometabolic states In systems including anoxia-tolerant turtles and molluscs, estivating snails and toads, hibernating small mammals, and freeze tolerant frogs and insects. Our newest research ...

  20. Time History Forced Response in Nonlinear Mechanical Systems

    Directory of Open Access Journals (Sweden)

    Magnevall M.


    Full Text Available A formulation of a digital filter method for computing the forced response of a linear MDOF mechanical system is proposed. It is shown how aliasing error effects can be avoided at the expense of a bias error. The bias error is however completely known and it is system independent, as it only depends on the sampling frequency used. The mechanical system is described by its modal parameters, poles and residues. The method is extended to include non-linear elements. A toolbox in MATLAB has been created where nonlinear elements with and without memory can be treated, as well as system described by coupled non-linear equations.

  1. Underlying mechanisms of transient luminous events: a review

    Directory of Open Access Journals (Sweden)

    V. V. Surkov


    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.

  2. Mechanical properties of the human spinal cord under the compressive loading. (United States)

    Karimi, Alireza; Shojaei, Ahmad; Tehrani, Pedram


    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.

  3. Observed magnified runoff response to rainfall intensification under global warming

    International Nuclear Information System (INIS)

    Huang, Jr-Chuan; Lee, Tsung-Yu; Lee, Jun-Yi


    Runoff response to rainfall intensification under global warming is crucial, but is poorly discussed due to the limited data length and human alteration. Historical rainfall and runoff records in pristine catchments in Taiwan were investigated through trend analysis and cross temperature difference analysis. Trend analysis showed that both rainfall and runoff in the 99.9-percentile have been significantly increasing in terms of frequency and intensity over the past four decades. Cross temperature difference analysis quantified that the rainfall and runoff extremes (including the 99.0–99.9-percentiles) may increase by 69.5% and 99.8%, respectively, under a future scenario of 1  ° C increase in temperature. This increase in intensity resembles the increase in intensity observed between 1971–1990 and 1991–2010. The amplified runoff response can be related to the limited catchment storage capacity being preoccupied by rainfall extremes. The quantified temperature effect on rainfall and runoff intensification can be a strong basis for designing scenarios, confirming and fusing GCMs’ results. In addition, the runoff amplification should be a warning for other regions with significant rainfall intensification. Appropriate strategies are indispensable and urgently needed to maintain and protect the development of societies. (paper)

  4. Dynamic response of multiple nanobeam system under a moving nanoparticle

    Directory of Open Access Journals (Sweden)

    Shahrokh Hosseini Hashemi


    Full Text Available In this article, nonlocal continuum based model of multiple nanobeam system (MNBS under a moving nanoparticle is investigated using Eringen’s nonlocal theory. Beam layers are assumed to be coupled by winkler elastic medium and the nonlocal Euler-Bernoulli beam theory is used to model each layer of beam. The Hamilton’s principle, Eigen function technique and the Laplace transform method are employed to solve the governing equations. Analytical solutions of the transverse displacements for MNBs with simply supported boundary condition are presented for double layered and three layered MNBSs. For higher number of layers, the governing set of equations is solved numerically and the results are presented. This study shows that small-scale parameter has a significant effect on dynamic response of MNBS under a moving nanoparticle. Sensitivity of dynamical deflection to variation of nonlocal parameter, stiffness of Winkler elastic medium and number of nanobeams are presented in nondimensional form for each layer. Keywords: Dynamic response, Analytical solution, Moving particle, Nanobeam, Multi-layered nanobeam

  5. Mechanisms underlying social inequality in post-menopausal breast cancer. (United States)

    Hvidtfeldt, Ulla Arthur


    This thesis is based on studies conducted in the period 2010-2014 at Department of Public Health, University of Copenhagen and at Department of Epidemiology and Population Health, Albert Einstein College of Medicine, New York. The results are presented in three scientific papers and a synopsis. The main objective of the thesis was to determine mechanisms underlying social inequality (defined by educational level) in postmenopausal breast cancer (BC) by addressing mediating effects through hormone therapy (HT) use, BMI, lifestyle and reproductive factors. The results of previous studies suggest that the higher risk of postmenopausal BC among women of high socioeconomic position (SEP) may be explained by reproductive factors and health behaviors. Women of higher SEP generally have fewer children and give birth at older ages than women of low SEP, and these factors have been found to affect the risk of BC - probably through altered hormone levels. Adverse effects on BC risk have also been documented for modifiable health behaviors that may affect hormone levels, such as alcohol consumption, high BMI, physical inactivity, and HT use. Alcohol consumption and HT use are likewise more common among women of higher SEP. The analyses were based on the Social Inequality in Cancer (SIC) cohort and a subsample of the Women's Health Initiative Observational Study (WHI-OS). The SIC cohort was derived by pooling 6 individual studies from the Copenhagen area including 33,562 women (1,733 BC cases) aged 50-70 years at baseline. The subsample of WHI-OS consisted of two case-cohort studies with measurements of endogenous estradiol (N = 1,601) and insulin (N = 791). Assessment of mediation often relies on comparing multiplicative models with and without the potential mediator. Such approaches provide potentially biased results, because they do not account for mediator-outcome confounding, exposure-dependent mediator-outcome confounding, exposure-mediator interaction and interactions

  6. Mechanisms Underlying the Risk to Develop Drug Addiction, Insights From Studies in Drosophila melanogaster

    Directory of Open Access Journals (Sweden)

    Julia Ryvkin


    Full Text Available The ability to adapt to environmental changes is an essential feature of biological systems, achieved in animals by a coordinated crosstalk between neuronal and hormonal programs that allow rapid and integrated organismal responses. Reward systems play a key role in mediating this adaptation by reinforcing behaviors that enhance immediate survival, such as eating or drinking, or those that ensure long-term survival, such as sexual behavior or caring for offspring. Drugs of abuse co-opt neuronal and molecular pathways that mediate natural rewards, which under certain circumstances can lead to addiction. Many factors can contribute to the transition from drug use to drug addiction, highlighting the need to discover mechanisms underlying the progression from initial drug use to drug addiction. Since similar responses to natural and drug rewards are present in very different animals, it is likely that the central systems that process reward stimuli originated early in evolution, and that common ancient biological principles and genes are involved in these processes. Thus, the neurobiology of natural and drug rewards can be studied using simpler model organisms that have their systems stripped of some of the immense complexity that exists in mammalian brains. In this paper we review studies in Drosophila melanogaster that model different aspects of natural and drug rewards, with an emphasis on how motivational states shape the value of the rewarding experience, as an entry point to understanding the mechanisms that contribute to the vulnerability of drug addiction.

  7. Stress analysis in a functionally graded disc under mechanical loads ...

    Indian Academy of Sciences (India)

    Some relative results for the stress and displacement components along the radius are presented due to internal pressure, external pressure, centrifugal force and steady state temperature. From the results, it is found that the grading indexes play an important role in determining the thermomechanical responses of FG disc ...

  8. Peer influence: Neural mechanisms underlying in-group conformity

    Directory of Open Access Journals (Sweden)

    Mirre eStallen


    Full Text Available 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.

  9. Peer influence: neural mechanisms underlying in-group conformity. (United States)

    Stallen, Mirre; Smidts, Ale; Sanfey, Alan G


    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.

  10. Molecular Mechanism Underlying Lymphatic Metastasis in Pancreatic Cancer

    Directory of Open Access Journals (Sweden)

    Zhiwen Xiao


    Full Text Available As the most challenging human malignancies, pancreatic cancer is characterized by its insidious symptoms, low rate of surgical resection, high risk of local invasion, metastasis and recurrence, and overall dismal prognosis. Lymphatic metastasis, above all, is recognized as an early adverse event in progression of pancreatic cancer and has been described to be an independent poor prognostic factor. It should be noted that the occurrence of lymphatic metastasis is not a casual or stochastic but an ineluctable and designed event. Increasing evidences suggest that metastasis-initiating cells (MICs and the microenvironments may act as a double-reed style in this crime. However, the exact mechanisms on how they function synergistically for this dismal clinical course remain largely elusive. Therefore, a better understanding of its molecular and cellular mechanisms involved in pancreatic lymphatic metastasis is urgently required. In this review, we will summarize the latest advances on lymphatic metastasis in pancreatic cancer.

  11. Mental imagery in music performance: underlying mechanisms and potential benefits. (United States)

    Keller, Peter E


    This paper examines the role of mental imagery in music performance. Self-reports by musicians, and various other sources of anecdotal evidence, suggest that covert auditory, motor, and/or visual imagery facilitate multiple aspects of music performance. The cognitive and motor mechanisms that underlie such imagery include working memory, action simulation, and internal models. Together these mechanisms support the generation of anticipatory images that enable thorough action planning and movement execution that is characterized by efficiency, temporal precision, and biomechanical economy. In ensemble performance, anticipatory imagery may facilitate interpersonal coordination by enhancing online predictions about others' action timing. Overlap in brain regions subserving auditory imagery and temporal prediction is consistent with this view. It is concluded that individual differences in anticipatory imagery may be a source of variation in expressive performance excellence and the quality of ensemble cohesion. Engaging in effortful musical imagery is therefore justified when artistic perfection is the goal. © 2012 New York Academy of Sciences.

  12. Neural mechanisms underlying context-dependent shifts in risk preferences

    NARCIS (Netherlands)

    Losecaat Vermeer, A.B.; Boksem, M.A.S.; Sanfey, A.G.


    Studies of risky decision-making have demonstrated that humans typically prefer risky options after incurring a financial loss, while generally preferring safer options after a monetary gain. Here, we examined the neural processes underlying these inconsistent risk preferences by investigating the

  13. Phenomena of synchronized response in biosystems and the possible mechanism. (United States)

    Xu, Jingjing; Yang, Fan; Han, Danhong; Xu, Shengyong


    Phenomena of synchronized response is common among organs, tissues and cells in biosystems. We have analyzed and discussed three examples of synchronization in biosystems, including the direction-changing movement of paramecia, the prey behavior of flytraps, and the simultaneous discharge of electric eels. These phenomena and discussions support an electrical communication mechanism that in biosystems, the electrical signals are mainly soliton-like electromagnetic pulses, which are generated by the transient transmembrane ionic current through the ion channels and propagate along the dielectric membrane-based softmaterial waveguide network to complete synchronized responses. This transmission model implies that a uniform electrical communication mechanism might have been naturally developed in biosystem. Copyright © 2018 Elsevier Inc. All rights reserved.

  14. Effect of support conditions on structural response under dynamic loading

    International Nuclear Information System (INIS)

    Akram, T.; Memon, S.A.


    In design practice, dynamic structural analysis is carried out with base of structure considered as fixed; this means that foundation is placed on rock like soil material. While conducting this type of analyses the role of foundation and soil behaviour is totally neglected. The actions in members and loads transferred at foundation level obtained in this manner do not depict the true structural behaviour. FEM (Finite Element Methods) analysis where both superstructure and foundation soil are coupled together is quite complicated and expensive for design environments. A simplified model is required to depict dynamic response of structures with foundations based on flexible soils. The primary purpose of this research is to compare the superstructure dynamic responses of structural systems with fixed base to that of simple soil model base. The selected simple soil model is to be suitable for use in a design environment to give more realistic results. For this purpose building models are idealized with various heights and structural systems in both 2D (Two Dimensional) and 3D (Three Dimensional) space. These models are then provided with visco-elastic supports representing three soil bearing capacities and the analysis results are compared to that of fixed supports models. The results indicate that fixed support system underestimates natural time period of the structures. Dynamic behavior and force response of visco-elastic support is different from fixed support model. Fixed support models result in over designed base columns and under designed beams. (author)

  15. Dynamical anisotropic response of black phosphorus under magnetic field (United States)

    Liu, Xuefeng; Lu, Wei; Zhou, Xiaoying; Zhou, Yang; Zhang, Chenglong; Lai, Jiawei; Ge, Shaofeng; Sekhar, M. Chandra; Jia, Shuang; Chang, Kai; Sun, Dong


    Black phosphorus (BP) has emerged as a promising material candidate for next generation electronic and optoelectronic devices due to its high mobility, tunable band gap and highly anisotropic properties. In this work, polarization resolved ultrafast mid-infrared transient reflection spectroscopy measurements are performed to study the dynamical anisotropic optical properties of BP under magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is found to be insensitive to the applied magnetic field due to the broadening of the Landau levels and large effective mass of carriers. While the anisotropic optical response of BP decreases with increasing magnetic field, its enhancement due to the excitation of hot carriers is similar to that without magnetic field. These experimental results can be well interpreted by the magneto-optical conductivity of the Landau levels of BP thin film, based on an effective k · p Hamiltonian and linear response theory. These findings suggest attractive possibilities of multi-dimensional control of anisotropic response (AR) of BP with light, electric and magnetic field, which further introduces BP to the fantastic magnetic field sensitive applications.

  16. The Survival Advantage: Underlying Mechanisms and Extant Limitations

    Directory of Open Access Journals (Sweden)

    Stephanie A. Kazanas


    Full Text Available Recently, researchers have begun to investigate the function of memory in our evolutionary history. According to Nairne and colleagues (e.g., Nairne, Pandeirada, and Thompson, 2008; Nairne, Thompson, and Pandeirada, 2007, the best mnemonic strategy for learning lists of unrelated words may be one that addresses the same problems that our Pleistocene ancestors faced: fitness-relevant problems including securing food and water, as well as protecting themselves from predators. Survival processing has been shown to promote better recall and recognition memory than many well-known mnemonic strategies (e.g., pleasantness ratings, imagery, generation, etc.. However, the survival advantage does not extend to all types of stimuli and tasks. The current review presents research that has replicated Nairne et al.'s (2007 original findings, in addition to the research designs that fail to replicate the survival advantage. In other words, there are specific manipulations in which survival processing does not appear to benefit memory any more than other strategies. Potential mechanisms for the survival advantage are described, with an emphasis on those that are the most plausible. These proximate mechanisms outline the memory processes that may contribute to the advantage, although the ultimate mechanism may be the congruity between the survival scenario and Pleistocene problem-solving.

  17. The Venturia Apple Pathosystem: Pathogenicity Mechanisms and Plant Defense Responses

    Directory of Open Access Journals (Sweden)

    Gopaljee Jha


    Full Text Available Venturia inaequalis is the causal agent of apple scab, a devastating disease of apple. We outline several unique features of this pathogen which are useful for molecular genetics studies intended to understand plant-pathogen interactions. The pathogenicity mechanisms of the pathogen and overview of apple defense responses, monogenic and polygenic resistance, and their utilization in scab resistance breeding programs are also reviewed.

  18. Perceived decisional responsibility for mechanical ventilation and weaning

    DEFF Research Database (Denmark)

    Haugdahl, Hege S; Storli, Sissel; Rose, Louise


    AIM: To explore variability in perceptions of nurse managers and physician directors regarding roles, responsibilities and clinical-decision making related to mechanical ventilator weaning in Norwegian intensive care units (ICUs). BACKGROUND: Effective teamwork is crucial for providing optimal...... to extubate (p importance of 'knowing the patient' for weaning success, and agreed that the assessment of work of breathing, well-being, and clinical deterioration were important for determining weaning tolerance. CONCLUSIONS: Nurse managers perceived...

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

    KAUST Repository

    Saghir, Shahid


    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.

  20. 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


    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.

  1. Cellular and deafness mechanisms underlying connexin mutation induced hearing loss – A common hereditary deafness

    Directory of Open Access Journals (Sweden)

    Jeffrey C Wingard


    Full Text Available Hearing loss due to mutations in the connexin gene family which encodes gap junctional proteins is a common form of hereditary deafness. In particular, connexin 26 (Cx26, GJB2 mutations are responsible for ~50% of nonsyndromic hearing loss, which is the highest incidence of genetic disease. In the clinic, Cx26 mutations cause various auditory phenotypes ranging from profound congenital deafness at birth to mild, progressive hearing loss in late childhood. Recent experiments demonstrate that congenital deafness mainly results from cochlear developmental disorders rather than hair cell degeneration and endocochlear potential (EP reduction, while late-onset hearing loss results from reduction of active cochlear amplification, even though cochlear hair cells have no connexin expression. Moreover, new experiments further demonstrate that the hypothesized K+-recycling disruption is not a principal deafness mechanism for connexin deficiency induced hearing loss. Additionally, there is no clear relationship between specific changes in connexin (channel functions and the phenotypes of mutation-induced hearing loss. Cx30, Cx29, Cx31, and Cx43 mutations can also cause hearing loss with distinct pathological changes in the cochlea. These new studies provide invaluable information about deafness mechanisms underlying connexin mutation induced hearing loss and also provide important information for developing new protective and therapeutic strategies for this common deafness. However, the detailed cellular mechanisms underlying these pathological changes and pathogeneses of specific-mutation induced hearing loss remain unclear. Finally, little information is available for humans. Further studies to address these deficiencies are urgently required.

  2. New developments on the neurobiological and pharmaco-genetic mechanisms underlying internet and videogame addiction. (United States)

    Weinstein, Aviv; Lejoyeux, Michel


    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.

  3. Mechanisms underlying KCNQ1channel cell volume sensitivity

    DEFF Research Database (Denmark)

    Hammami, Sofia

    in which ATP released from the cells in response to volume changes activates signaling pathways that subsequently lead to ion channel stimulation. Whether volume sensitivity of KCNQ1 is modulated by ATP release was investigated in Manuscript II. ATP release from KCNQ1 injected oocytes was monitored...... by a Luciferin/Luciferase assay during cell volume changes and the effect of exogenously added ATP and apyrase on the cell volume induced KCNQ1 current was studied. Based on our data to date, we postulate that KCNQ1 does not seem to be responsive to ATP during cell volume changes, which indicates another...... the level of KCNQ1 surface expression by using an enzyme-linked immunoassay (Manuscript III). To do this, a HA-tagged version of the KCNQ1 channel was expressed with and without KCNE1 in Xenopus oocytes. The results show that the KCNQ1 surface expression was significantly lower when KCNE1 is coexpressed...

  4. Neural mechanisms underlying social conformity in an ultimatum game


    Wei, Zhenyu; Zhao, Zhiying; Zheng, Yong


    When individuals’ actions are incongruent with those of the group they belong to, they may change their initial behavior in order to conform to the group norm. This phenomenon is known as “social conformity.” In the present study, we used event-related functional magnetic resonance imaging (fMRI) to investigate brain activity in response to group opinion during an ultimatum game. Results showed that participants changed their choices when these choices conflicted with the normative opinion of...

  5. Mechanisms Underlying the Nonconsumptive Effects of Parasitoid Wasps on Aphids. (United States)

    Ingerslew, K S; Finke, D L


    Natural enemies need not consume herbivores to suppress herbivore populations. Behavioral interactions can adversely impact herbivore fitness from reduced time feeding, investment in defense, or injury from failed attacks. The importance of such "nonconsumptive effects" for herbivore suppression may vary across species based on the specificity and intensity of the herbivore defensive response. In a series of manipulative studies, we quantified the nature and consequences of nonconsumptive interactions between two parasitoid wasps, Aphidius ervi Haliday and Aphidius colemani Viereck, on two aphid species, pea aphids (Acyrthosiphon pisum (Harris)) and green peach aphids (Myzus persicae (Sulzer)). Both wasps successfully parasitize green peach aphids, but only A. ervi parasitizes pea aphids. We observed A. ervi antennating and stinging pea aphids and documented a decrease in pea aphid longevity in response to stinging even when the aphid survived the interaction and no mummy formed. The primary defensive tactic of pea aphids in response to either wasp species was dropping from the host plant. Both wasp species antennated and stung green peach aphids, but they elicited unique defensive behaviors. Green peach aphids kicked or emitted cornicle secretions in response to A. colemani but spent more time off the plant in the presence of A. ervi. Green peach aphid longevity and fecundity were not affected by wasp stings when the aphid survived and no mummy formed. Our study demonstrates the complexity of behavioral interactions between parasitoids and their potential hosts and contributes to a mechanistic understanding of variation in the nonconsumptive suppression of herbivore populations. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email:

  6. Early Transient Incapacitation: A Review with Consideration of Underlying Mechanisms (United States)


    depression within hours to a few dkys. In subhuman primates trained to perform various physical and visual tasks, several CNS-associated responses have...incapacitation (ETI) is defined as a decrement in performance of a trained task, occurring transiently and withih, minutes of exposure to supralethal...most usual time for ETI. Such experiments should be repeated. Bruner et al. 7 studied the effect of 1000 rads of cobalt-60 exposure on the baroreflex

  7. Excessive Response-Repetition Costs under Task Switching: How Response Inhibition Amplifies Response Conflict (United States)

    Grzyb, Kai Robin; Hubner, Ronald


    The size of response-repetition (RR) costs, which are usually observed on task-switch trials, strongly varies between conditions with univalent and bivalent stimuli. To test whether top-down or bottom-up processes can account for this effect, we assessed in Experiment 1 baselines for univalent and bivalent stimulus conditions (i.e., for stimuli…

  8. Electronic, mechanical and dielectric properties of silicane under tensile strain

    Energy Technology Data Exchange (ETDEWEB)

    Jamdagni, Pooja, E-mail:; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Physics Department, Panjab University, Chandigarh, India, 160014 (India); Thakur, Anil [Physics Department, Govt. Collage Solan, Himachal Pradesh, India,173212 (India)


    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  9. Electronic, mechanical and dielectric properties of silicane under tensile strain

    International Nuclear Information System (INIS)

    Jamdagni, Pooja; Sharma, Munish; Ahluwalia, P. K.; Kumar, Ashok; Thakur, Anil


    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices

  10. Studies on Molecular Mechanisms Underlying Spinocerebellar Ataxia Type 3

    DEFF Research Database (Denmark)

    Kristensen, Line Vildbrad

    The polyglutamine (polyQ) disorders comprise nine diseases characterized by an expanded polyQ tract within the respective proteins. These disorders are rare but include the well-known Huntington’s disease, and several spinocerebellar ataxias (SCAs). The diseases usually strike midlife and progress....... Even though a range of mechanisms contributing to polyQ diseases have been uncovered, there is still no treatment available. One of the more common polyQ diseases is SCA3, which is caused by a polyQ expansion in the ataxin-3 protein that normally functions as a deubiquitinating enzyme involved...

  11. Mechanisms regulating osteoblast response to surface microtopography and vitamin D (United States)

    Bell, Bryan Frederick, Jr.

    A comprehensive understanding of the interactions between orthopaedic and dental implant surfaces with the surrounding host tissue is essential in the design of advanced biomaterials that better promote bone growth and osseointegration of implants. Dental implants with roughened surfaces and high surface energy are well known to promote osteoblast differentiation in vitro and promote increased bone-to-implant contact in vivo. In addition, increased surface roughness increases osteoblasts response to the vitamin D metabolite 1alpha,25(OH)2D3. However, the exact mechanisms mediating cell response to surface properties and 1alpha,25(OH)2D3 are still being elucidated. The central aim of the thesis is to investigate whether integrin signaling in response to rough surface microtopography enhances osteoblast differentiation and responsiveness to 1alpha,25(OH)2D3. The hypothesis is that the integrin alpha5beta1 plays a role in osteoblast response to surface microtopography and that 1alpha,25(OH) 2D3 acts through VDR-independent pathways involving caveolae to synergistically enhance osteoblast response to surface roughness and 1alpha,25(OH) 2D3. To test this hypothesis the objectives of the studies performed in this thesis were: (1) to determine if alpha5beta 1 signaling is required for osteoblast response to surface microstructure; (2) to determine if increased responsiveness to 1alpha,25(OH)2D 3 requires the vitamin D receptor, (3) to determine if rough titanium surfaces functionalized with the peptides targeting integrins (RGD) and transmembrane proteoglycans (KRSR) will enhance both osteoblast proliferation and differentiation, and (4) to determine whether caveolae, which are associated with integrin and 1alpha,25(OH)2D3 signaling, are required for enhance osteogenic response to surface microstructure and 1alpha,25(OH)2D 3. The results demonstrate that integrins, VDR, and caveolae play important roles in mediating osteoblast response to surface properties and 1alpha,25

  12. Ethanol Neurotoxicity in the Developing Cerebellum: Underlying Mechanisms and Implications

    Directory of Open Access Journals (Sweden)

    Ambrish Kumar


    Full Text Available Ethanol is the main constituent of alcoholic beverages that exerts toxicity to neuronal development. Ethanol affects synaptogenesis and prevents proper brain development. In humans, synaptogenesis takes place during the third trimester of pregnancy, and in rodents this period corresponds to the initial few weeks of postnatal development. In this period neuronal maturation and differentiation begin and neuronal cells start migrating to their ultimate destinations. Although the neuronal development of all areas of the brain is affected, the cerebellum and cerebellar neurons are more susceptible to the damaging effects of ethanol. Ethanol’s harmful effects include neuronal cell death, impaired differentiation, reduction of neuronal numbers, and weakening of neuronal plasticity. Neuronal development requires many hormones and growth factors such as retinoic acid, nerve growth factors, and cytokines. These factors regulate development and differentiation of neurons by acting through various receptors and their signaling pathways. Ethanol exposure during development impairs neuronal signaling mechanisms mediated by the N-methyl-d-aspartate (NMDA receptors, the retinoic acid receptors, and by growth factors such as brain-derived neurotrophic factor (BDNF, insulin-like growth factor 1 (IGF-I, and basic fibroblast growth factor (bFGF. In combination, these ethanol effects disrupt cellular homeostasis, reduce the survival and migration of neurons, and lead to various developmental defects in the brain. Here we review the signaling mechanisms that are required for proper neuronal development, and how these processes are impaired by ethanol resulting in harmful consequences to brain development.

  13. Brainstem mechanisms underlying the cough reflex and its regulation. (United States)

    Mutolo, Donatella


    Cough is a very important airway protective reflex. Cough-related inputs are conveyed to the caudal nucleus tractus solitarii (cNTS) that projects to the brainstem respiratory network. The latter is reconfigured to generate the cough motor pattern. A high degree of modulation is exerted on second-order neurons and the brainstem respiratory network by sensory inputs and higher brain areas. Two medullary structures proved to have key functions in cough production and to be strategic sites of action for centrally active drugs: the cNTS and the caudal ventral respiratory group (cVRG). Drugs microinjected into these medullary structures caused downregulation or upregulation of the cough reflex. The results suggest that inhibition and disinhibition are prominent regulatory mechanisms of this reflex and that both the cNTS and the cVRG are essential in the generation of the entire cough motor pattern. Studies on the basic neural mechanisms subserving the cough reflex may provide hints for novel therapeutic approaches. Different proposals for further investigations are advanced. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Correlating HIV tropism with immunological response under combination antiretroviral therapy. (United States)

    Bader, J; Schöni-Affolter, F; Böni, J; Gorgievski-Hrisoho, M; Martinetti, G; Battegay, M; Klimkait, T


    A significant percentage of patients infected with HIV-1 experience only suboptimal CD4 cell recovery while treated with combination therapy (cART). It is still unclear whether viral properties such as cell tropism play a major role in this incomplete immune response. This study therefore intended to follow the tropism evolution of the HIV-1 envelope during periods of suppressive cART. Viruses from two distinct patient groups, one with good and another one with poor CD4 recovery after 5 years of suppressive cART, were genotypically analysed for viral tropism at baseline and at the end of the study period. Patients with CCR5-tropic CC-motif chemokine receptor 5 viruses at baseline tended to maintain this tropism to the study end. Patients who had a CXCR4-tropic CXC-motif chemokine receptor 4 virus at baseline were overrepresented in the poor CD4 recovery group. Overall, however, the majority of patients presented with CCR5-tropic viruses at follow-up. Our data lend support to the hypothesis that tropism determination can be used as a parameter for disease progression even if analysed long before the establishment of a poorer immune response. Moreover, the lasting predominating CCR5-tropism during periods of full viral control suggests the involvement of cellular mechanisms that preferentially reduce CXCR4-tropic viruses during cART. © 2016 British HIV Association.

  15. Kidney branching morphogenesis under the control of a ligand-receptor-based Turing mechanism (United States)

    Menshykau, Denis; Iber, Dagmar


    The main signalling proteins that control early kidney branching have been defined. Yet the underlying mechanism is still elusive. We have previously shown that a Schnakenberg-type Turing mechanism can recapitulate the branching and protein expression patterns in wild-type and mutant lungs, but it is unclear whether this mechanism would extend to other branched organs that are regulated by other proteins. Here, we show that the glial cell line-derived neurotrophic factor-RET regulatory interaction gives rise to a Schnakenberg-type Turing model that reproduces the observed budding of the ureteric bud from the Wolffian duct, its invasion into the mesenchyme and the observed branching pattern. The model also recapitulates all relevant protein expression patterns in wild-type and mutant mice. The lung and kidney models are both based on a particular receptor-ligand interaction and require (1) cooperative binding of ligand and receptor, (2) a lower diffusion coefficient for the receptor than for the ligand and (3) an increase in the receptor concentration in response to receptor-ligand binding (by enhanced transcription, more recycling or similar). These conditions are met also by other receptor-ligand systems. We propose that ligand-receptor-based Turing patterns represent a general mechanism to control branching morphogenesis and other developmental processes.

  16. Response of cylindrical steel shell under seismic loading

    International Nuclear Information System (INIS)

    Tariq, M.; Amin, K.M.


    The seismic response of a cylindrical shell is simulated using the finite element method, and by spectral analysis. For this purpose the fundamental frequency of the cylinder is first calculated and compared with a published result. The mode shapes are also calculated which are later used for spectral analysis. The boundary nodes of the shell are displaced periodically according to a predetermined function of time by employing the acceleration time history of the El Centro earthquake to simulate the seismic loading. However, to conduct spectral analysis, the displacements are first transformed from the time domain to frequency domain using the Fast Fourier transformation. This spectral data is then used to obtain the actual displacement in the first mode under the given seismic loading. The techniques employed here can be used for cylindrical shell structures like rotor of a gas centrifuge, besides other structures that are subjected to seismic loading, besides in other time dependent loading conditions, for example rocket motor vibrations. (author)

  17. Internal insulation failure mechanisms of HV equipment under service conditions

    Energy Technology Data Exchange (ETDEWEB)

    Lokhanin, A.K.; Morozova, T.I. [All-Russian Electrochemical Inst. (Russian Federation); Shneider, G.Y. [Electrozavod Holding Company (Russian Federation); Sokolov, V.V. [Scientific and Engineering Centre, ZTZ Service Research Inst. (Russian Federation); Chornogotsky, V.M. [Ukrainian Transformer Research Inst. (Ukraine)


    Failure mechanisms in oil-barrier transformer insulation and oil-paper condenser type insulation of transformers and HV bushing were discussed with reference to typical defects and failure modes of oil-barrier insulation of transformers, shunt reactor, condenser type bushing and instrument current transformers. It was noted that insulation problems predominantly involve the impairment of insulation, and that the relative rate of major failures in shunt reactors is about 1 per cent. It was suggested that bushings can cause about 45 per cent of major transformer failures, with aged mode failure occurring most frequently. The failure rate of 220-500 kV CTs accounts for more than 60 per cent of total instrument transformer failures. Two failure modes were observed: ionisation-mode and aging-mode failures. The reduction of switching surge breakdown voltage due to deposit of insoluble aging products was discussed. A long-term dielectric strength test revealed the following 2 mechanisms of insulation breakdown: accidental breakdown during the first period of aging and wearing mode breakdown due to degradation of materials at the last stage of the calculated terms of aging. Issues concerning the mechanism of the incipient irreversible failure in oil-barrier insulation were discussed, as well as issues concerning creeping discharge and large failures during normal operating conditions. It was suggested that the occurrence of surface discharge is associated with increased voltage due to oil breakdown progressing into insulation destruction and surface discharge as a self-firing phenomenon. Failure modes induced by peculiar oil and staining of internal porcelain were reviewed. It was noted that the discharges across the inner part of the transformer and porcelain were the out-come of a typical aging-mode phenomenon in the bushing. In addition, failure modes induced by staining the outer surface of bottom porcelain were discussed, as well as failure of oil-filled paper

  18. Cellular and molecular mechanisms for the bone response to mechanical loading (United States)

    Bloomfield, S. A.


    To define the cellular and molecular mechanisms for the osteogenic response of bone to increased loading, several key steps must be defined: sensing of the mechanical signal by cells in bone, transduction of the mechanical signal to a biochemical one, and transmission of that biochemical signal to effector cells. Osteocytes are likely to serve as sensors of loading, probably via interstitial fluid flow produced during loading. Evidence is presented for the role of integrins, the cell's actin cytoskeleton, G proteins, and various intracellular signaling pathways in transducing that mechanical signal to a biochemical one. Nitric oxide, prostaglandins, and insulin-like growth factors all play important roles in these pathways. There is growing evidence for modulation of these mechanotransduction steps by endocrine factors, particularly parathyroid hormone and estrogen. The efficiency of this process is also impaired in the aged animal, yet what remains undefined is at what step mechanotransduction is affected.

  19. Mechanisms Underlying Profibrotic Epithelial Phenotype and Epithelial-Mesenchymal Crosstalk

    DEFF Research Database (Denmark)

    Bialik, Janne Folke

    , their roles in epithelial reprogramming are unclear. The aim of this thesis was to elucidate (i) the mechanism of TGFβ-induced TAZ expression in kidney fibrosis, (ii) the roles of MRTF and TAZ in PEP, (iii) how MRTF and TAZ regulate the oxidative state of the epithelium, and (iv) if the ensuing ROS production...... and TAZ prevented this, linking the cytoskeleton to the oxidative state of the cell. In Paper II TGFβ-induced increase in TAZ expression was investigated. Using pharmacological inhibition we show that non-canonical signaling via p38 and its downstream target MK2 mediates this upregulation. Furthermore......, MRTF regulates TAZ expression in a translocation-independent manner. Pharmacological inhibition of Nox4, a known activator of p38, resulted in decreased TAZ, suggesting a feedback loop in which Nox4 regulates TAZ and MRTF, which in turn regulates Nox4. In Paper III we investigated cytokine expression...

  20. Neural mechanisms underlying neurooptometric rehabilitation following traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Hudac CM


    Full Text Available Caitlin M Hudac1, Srinivas Kota1, James L Nedrow2, Dennis L Molfese1,31Department of Psychology, University of Nebraska-Lincoln, 2Oculi Vision Rehabilitation, 3Center for Brain, Biology, and Behavior, University of Nebraska-Lincoln, Lincoln, NEAbstract: Mild to severe traumatic brain injuries have lasting effects on everyday functioning. Issues relating to sensory problems are often overlooked or not addressed until well after the onset of the injury. In particular, vision problems related to ambient vision and the magnocellular pathway often result in posttrauma vision syndrome or visual midline shift syndrome. Symptoms from these syndromes are not restricted to the visual domain. Patients commonly experience proprioceptive, kinesthetic, vestibular, cognitive, and language problems. Neurooptometric rehabilitation often entails the use of corrective lenses, prisms, and binasal occlusion to accommodate the unstable magnocellular system. However, little is known regarding the neural mechanisms engaged during neurooptometric rehabilitation, nor how these mechanisms impact other domains. Event-related potentials from noninvasive electrophysiological recordings can be used to assess rehabilitation progress in patients. In this case report, high-density visual event-related potentials were recorded from one patient with posttrauma vision syndrome and secondary visual midline shift syndrome during a pattern reversal task, both with and without prisms. Results indicate that two factors occurring during the end portion of the P148 component (168–256 milliseconds poststimulus onset map onto two separate neural systems that were engaged with and without neurooptometric rehabilitation. Without prisms, neural sources within somatosensory, language, and executive brain regions engage inefficient magnocellular system processing. However, when corrective prisms were worn, primary visual areas were appropriately engaged. The impact of using early

  1. Mechanical characterization of stomach tissue under uniaxial tensile action. (United States)

    Jia, Z G; Li, W; Zhou, Z R


    In this article, the tensile properties of gastric wall were investigated by using biomechanical test and theoretical analysis. The samples of porcine stomach strips from smaller and greater curvature of the stomach were cut in longitudinal and circumferential direction, respectively. The loading-unloading, stress relaxation, strain creep, tensile fracture tests were performed at mucosa-submucosa, serosa-muscle and intact layer, respectively. Results showed that the biomechanical properties of the porcine stomach depended on the layers, orientations and locations of the gastric wall and presented typical viscoelastic, nonlinear and anisotropic mechanical properties. During loading-unloading test, the stress of serosa-muscle layer in the longitudinal direction was 15-20% more than that in the circumferential direction at 12% stretch ratio, while it could reach about 40% for the intact layer and 50% for the mucosa-submucosa layer. The results of stress relaxation and strain creep showed that the variation degree was obviously faster in the circumferential direction than that in the longitudinal direction, and the ultimate residual values were also different for the different layers, orientations and locations. In the process of fracture test, the serosa-muscle layer fractured firstly followed by the mucosa-submucosa layer when the intact layer was tested, the longitudinal strips firstly began to fracture and the required stress value was about twice as much as that in the circumferential strips. The anisotropy and heterogeneity of mechanical characterization of the porcine stomach were related to its complicated geometry, structure and functions. The results would help us to understand the biomechanics of soft organ tissue. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Mechanisms underlying probucol-induced hERG-channel deficiency

    Directory of Open Access Journals (Sweden)

    Shi YQ


    Full Text Available Yuan-Qi Shi,1,* Cai-Chuan Yan,1,* Xiao Zhang,1 Meng Yan,1 Li-Rong Liu,1 Huai-Ze Geng,1 Lin Lv,1 Bao-Xin Li1,21Department of Pharmacology, Harbin Medical University, 2State-Province Key Laboratory of Biopharmaceutical Engineering, Harbin, Heilongjiang, People’s Republic of China*These authors contributed equally to this workAbstract: The hERG gene encodes the pore-forming α-subunit of the rapidly activating delayed rectifier potassium channel (IKr, which is important for cardiac repolarization. Reduction of IhERG due to genetic mutations or drug interferences causes long QT syndrome, leading to life-threatening cardiac arrhythmias (torsades de pointes or sudden death. Probucol is a cholesterol-lowering drug that could reduce hERG current by decreasing plasma membrane hERG protein expression and eventually cause long QT syndrome. Here, we investigated the mechanisms of probucol effects on IhERG and hERG-channel expression. Our data demonstrated that probucol reduces SGK1 expression, known as SGK isoform, in a concentration-dependent manner, resulting in downregulation of phosphorylated E3 ubiquitin ligase Nedd4-2 expression, but not the total level of Nedd4-2. As a result, the hERG protein reduces, due to the enhanced ubiquitination level. On the contrary, carbachol could enhance the phosphorylation level of Nedd4-2 as an alternative to SGK1, and thus rescue the ubiquitin-mediated degradation of hERG channels caused by probucol. These discoveries provide a novel mechanism of probucol-induced hERG-channel deficiency, and imply that carbachol or its analog may serve as potential therapeutic compounds for the handling of probucol cardiotoxicity.Keywords: long QT, hERG potassium channels, probucol, SGK1, Nedd4-2

  3. Cytomegalovirus: pathophysiological mechanisms of the cytomegalovirus-induced cellular responses

    International Nuclear Information System (INIS)

    Nokta, M.A.


    Cytomegalovirus (CMV) infection of fibroblasts of human origin is associated with a cascade of morphologic cellular responses which in other systems have been associated with regulation of intracellular free (IF) [Ca ++ ]. In the present study, the relationship of specific ion fluxes (Ca ++ , Na + ) to the development of cytomegalovirus (CMV)-induced morphologic cellular responses was investigated. An influx of Ca ++ was observed by the first hour after CMV infection (PI), and total calcium sequestered by infected cells was enhanced by 5 hr Pl. A gradual rise in intracellular free (IF) [Ca ++ ] was observed that continued through 48 hour postinfection (hr Pl). The IF [Ca ++ ] response to CMV infection was shown to be multiplicity dependent, require viable virus, and occur under conditions consistent with the expression of immediate early CMV genes. Development and progression of cytomegaly was found to be independent of CMV DNA synthesis and appeared to be dependent on the IF [Ca ++ ] response. Ca ++ influx blockers (e.g. verapamil) and cyclic nucleotide modulators (e.g. papaverine) inhibited both Ca ++ responses and cytomegaly. Quabain-sensitive 86 Rb uptake and sequestering of Ca ++ increased in parallel with development of cytomegaly. There may be a relationship between Ca ++ influx, IF [Ca ++ ], activation of the Na + /H + exchanger, induction of Na + , Cl - , HCO 3 cotransport, Na + entry, Na + /K + ATPase activity and development of CMV-induced morphologic cellular responses including cytomegaly

  4. STEP Accelerometer Response under Non-Equilibrium Conditions (United States)

    Wang, S.; Ambekar, P.; Bayart, C.; Torii, R.; Worden, P.; Debra, D.

    The STEP Satellite Test of the Equivalence Principle accelerometer performance is derived under the assumption that the test mass is properly constrained and positioned 5DOF in the housing cavity test mass is in the operational sweet-spot It is extremely useful to check system response when the mass is outside the sweet-spot Using a 1m long fiber suspended test mass we have made past studies on magnetic suspension forces Fy and Fz and have explored the housing cavity in 3DOF x y and z translation limited by uncertainty in test mass tilt angle qy and qz To address this limitation we have recently constructed a 2-axis cryogenic tilt platform The laboratory version of position readout electronics allow us to measure the test mass position at 4K to a precision of 1 nm and tilt angle to less than 1 arc sec in 100 seconds We will present recent experimental data showing the dynamic response of the capacitance measurement subsystem as a function of test mass position

  5. Improving yield by exploiting mechanisms underlying natural variation of photosynthesis. (United States)

    Lawson, Tracy; Kramer, David M; Raines, Christine A


    Increasing photosynthesis in C3 species has been identified as an approach to increase the yield of crop plants. Most of our knowledge of photosynthetic performance has come from studies in which plants were grown in controlled growth conditions but plants in natural environments have to cope with unpredictable and rapidly changing conditions. Plants adapt to the light environment in which they grow and this is demonstrated by the differences in anatomy and morphology of leaves in sun and shade leaves. Superimposed on this are the dynamic responses of plants to rapid changes in the light environment that occur throughout the day. Application of next generation sequencing (NGS), QTL analysis and innovative phenomic screening can provide information to underpin approaches for breeding of higher yielding crop plants. Copyright © 2012. Published by Elsevier Ltd.

  6. Diverging responses of tropical Andean biomes under future climate conditions. (United States)

    Tovar, Carolina; Arnillas, Carlos Alberto; Cuesta, Francisco; Buytaert, Wouter


    Observations and projections for mountain regions show a strong tendency towards upslope displacement of their biomes under future climate conditions. Because of their climatic and topographic heterogeneity, a more complex response is expected for biodiversity hotspots such as tropical mountain regions. This study analyzes potential changes in the distribution of biomes in the Tropical Andes and identifies target areas for conservation. Biome distribution models were developed using logistic regressions. These models were then coupled to an ensemble of 8 global climate models to project future distribution of the Andean biomes and their uncertainties. We analysed projected changes in extent and elevational range and identified regions most prone to change. Our results show a heterogeneous response to climate change. Although the wetter biomes exhibit an upslope displacement of both the upper and the lower boundaries as expected, most dry biomes tend to show downslope expansion. Despite important losses being projected for several biomes, projections suggest that between 74.8% and 83.1% of the current total Tropical Andes will remain stable, depending on the emission scenario and time horizon. Between 3.3% and 7.6% of the study area is projected to change, mostly towards an increase in vertical structure. For the remaining area (13.1%-17.4%), there is no agreement between model projections. These results challenge the common believe that climate change will lead to an upslope displacement of biome boundaries in mountain regions. Instead, our models project diverging responses, including downslope expansion and large areas projected to remain stable. Lastly, a significant part of the area expected to change is already affected by land use changes, which has important implications for management. This, and the inclusion of a comprehensive uncertainty analysis, will help to inform conservation strategies in the Tropical Andes, and to guide similar assessments for other

  7. Algorithmic mechanisms for reliable crowdsourcing computation under collusion. (United States)

    Fernández Anta, Antonio; Georgiou, Chryssis; Mosteiro, Miguel A; Pareja, Daniel


    We consider a computing system where a master processor assigns a task for execution to worker processors that may collude. We model the workers' decision of whether to comply (compute the task) or not (return a bogus result to save the computation cost) as a game among workers. That is, we assume that workers are rational in a game-theoretic sense. We identify analytically the parameter conditions for a unique Nash Equilibrium where the master obtains the correct result. We also evaluate experimentally mixed equilibria aiming to attain better reliability-profit trade-offs. For a wide range of parameter values that may be used in practice, our simulations show that, in fact, both master and workers are better off using a pure equilibrium where no worker cheats, even under collusion, and even for colluding behaviors that involve deviating from the game.

  8. Mechanisms of microstructural changes of fuel under irradiation

    International Nuclear Information System (INIS)

    Garcia, P.; Carlot, G.; Dorado, B.; Maillard, S.; Sabathier, C.; Martin, G.; Oh, J.Y.; Welland, M.J.


    Nuclear fuels are subjected to high levels of radiation damage mainly due to the slowing of fission fragments, which results in substantial modifications of the initial fuel microstructure. Microstructure changes alter practically all engineering fuel properties such as atomic transport or thermomechanical properties so understanding these changes is essential to predicting the performance of fuel elements. Also, with increasing burn-up, the fuel drifts away from its initial composition as the fission process produces new chemical elements. Because nuclear fuels operate at high temperature and usually under high-temperature gradients, damage annealing, foreign atom or defect clustering and migration occur on multiple time and length scales, which make long-term predictions difficult. The end result is a fuel microstructure which may show extensive differences on the scale of a single fuel pellet. The main challenge we are faced with is, therefore, to identify the phenomena occurring on the atom scale that are liable to have macroscopic effects that will determine the microstructure changes and ultimately the life-span of a fuel element. One step towards meeting this challenge is to develop and apply experimental or modelling methods capable of connecting events that occur over very short length and timescales to changes in the fuel microstructure over engineering length and timescales. In the first part of this chapter, we provide an overview of some of the more important microstructure modifications observed in nuclear fuels. The emphasis is placed on oxide fuels because of the extensive amount of data available in relation to these materials under neutron or ion irradiation. When possible and relevant, the specifics of other types of fuels such as metallic or carbide fuels are alluded to. Throughout this chapter but more specifically in the latter part, we attempt to give examples of how modelling and experimentation at various scales can provide us with

  9. Neural mechanisms underlying melodic perception and memory for pitch. (United States)

    Zatorre, R J; Evans, A C; Meyer, E


    The neural correlates of music perception were studied by measuring cerebral blood flow (CBF) changes with positron emission tomography (PET). Twelve volunteers were scanned using the bolus water method under four separate conditions: (1) listening to a sequence of noise bursts, (2) listening to unfamiliar tonal melodies, (3) comparing the pitch of the first two notes of the same set of melodies, and (4) comparing the pitch of the first and last notes of the melodies. The latter two conditions were designed to investigate short-term pitch retention under low or high memory load, respectively. Subtraction of the obtained PET images, superimposed on matched MRI scans, provides anatomical localization of CBF changes associated with specific cognitive functions. Listening to melodies, relative to acoustically matched noise sequences, resulted in CBF increases in the right superior temporal and right occipital cortices. Pitch judgments of the first two notes of each melody, relative to passive listening to the same stimuli, resulted in right frontal-lobe activation. Analysis of the high memory load condition relative to passive listening revealed the participation of a number of cortical and subcortical regions, notably in the right frontal and right temporal lobes, as well as in parietal and insular cortex. Both pitch judgment conditions also revealed CBF decreases within the left primary auditory cortex. We conclude that specialized neural systems in the right superior temporal cortex participate in perceptual analysis of melodies; pitch comparisons are effected via a neural network that includes right prefrontal cortex, but active retention of pitch involves the interaction of right temporal and frontal cortices.

  10. Comparative analysis reveals the underlying mechanism of vertebrate seasonal reproduction. (United States)

    Ikegami, Keisuke; Yoshimura, Takashi


    Animals utilize photoperiodic changes as a calendar to regulate seasonal reproduction. Birds have highly sophisticated photoperiodic mechanisms and functional genomics analysis in quail uncovered the signal transduction pathway regulating avian seasonal reproduction. Birds detect light with deep brain photoreceptors. Long day (LD) stimulus induces secretion of thyroid-stimulating hormone (TSH) from the pars tuberalis (PT) of the pituitary gland. PT-derived TSH locally activates thyroid hormone (TH) in the hypothalamus, which induces gonadotropin-releasing hormone (GnRH) and hence gonadotropin secretion. However, during winter, low temperatures increase serum TH for adaptive thermogenesis, which accelerates germ cell apoptosis by activating the genes involved in metamorphosis. Therefore, TH has a dual role in the regulation of seasonal reproduction. Studies using TSH receptor knockout mice confirmed the involvement of PT-derived TSH in mammalian seasonal reproduction. In addition, studies in mice revealed that the tissue-specific glycosylation of TSH diversifies its function in the circulation to avoid crosstalk. In contrast to birds and mammals, one of the molecular machineries necessary for the seasonal reproduction of fish are localized in the saccus vasculosus from the photoreceptor to the neuroendocrine output. Thus, comparative analysis is a powerful tool to uncover the universality and diversity of fundamental properties in various organisms. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Mechanisms underlying the formation of induced pluripotent stem cells (United States)

    González, Federico; Huangfu, Danwei


    Human pluripotent stem cells (hPSCs) offer unique opportunities for studying human biology, modeling diseases and for therapeutic applications. The simplest approach so far to generate human PSCs lines is through reprogramming of somatic cells from an individual by defined factors, referred to simply as reprogramming. Reprogramming circumvents the ethical issues associated with human embryonic stem cells (hESCs) and nuclear transfer hESCs (nt-hESCs), and the resulting induced pluripotent stem cells (hiPSCs) retain the same basic genetic makeup as the somatic cell used for reprogramming. Since the first report of iPSCs by Takahashi and Yamanaka, the molecular mechanisms of reprogramming have been extensively investigated. A better mechanistic understanding of reprogramming is fundamental not only to iPSC biology and improving the quality of iPSCs for therapeutic use, but also to our understanding of the molecular basis of cell identity, pluripotency and plasticity. Here we summarize the genetic, epigenetic and cellular events during reprogramming, and the roles of various factors identified thus far in the reprogramming process. PMID:26383234

  12. Adhesive wear mechanism under combined electric diamond grinding

    Directory of Open Access Journals (Sweden)

    Popov Vyacheslav


    Full Text Available The article provides a scientific substantiation of loading of metal-bond diamond grinding wheels and describes the mechanism of contact interaction (interlocking of wheels with tool steel as well as its general properties having an influence on combined electric diamond grinding efficiency. The study concluded that a loaded layer can be formed in a few stages different by nature. It is known, that one of the causes of grinding degradation is a continuous loading of active grits (abrasive grinding tool by workpiece chips. It all affects the diamond grinding wheels efficiency and grinding ability with a result in increase of tool pressure, contact temperature and wheels specific removal rate. Science has partially identified some various methods to minimize grinding wheel loading, however, as to loading of metal-bond diamond grinding wheels the search is still in progress. Therefore, research people have to state, that in spite of the fact that the wheels made of cubic boron nitride are of little use as applied to ceramic, ultrahard, hard-alloyed hard-to-machine and nano-materials of the time, but manufactures have to apply cubic boron nitride wheels wherein diamond ones preferable.

  13. Linking Pesticide Exposure with Pediatric Leukemia: Potential Underlying Mechanisms. (United States)

    Hernández, Antonio F; Menéndez, Pablo


    Leukemia is the most common cancer in children, representing 30% of all childhood cancers. The disease arises from recurrent genetic insults that block differentiation of hematopoietic stem and/or progenitor cells (HSPCs) and drives uncontrolled proliferation and survival of the differentiation-blocked clone. Pediatric leukemia is phenotypically and genetically heterogeneous with an obscure etiology. The interaction between genetic factors and environmental agents represents a potential etiological driver. Although information is limited, the principal toxic mechanisms of potential leukemogenic agents (e.g., etoposide, benzene metabolites, bioflavonoids and some pesticides) include topoisomerase II inhibition and/or excessive generation of free radicals, which may induce DNA single- and double-strand breaks (DNA-DSBs) in early HSPCs. Chromosomal rearrangements (duplications, deletions and translocations) may occur if these lesions are not properly repaired. The initiating hit usually occurs in utero and commonly leads to the expression of oncogenic fusion proteins. Subsequent cooperating hits define the disease latency and occur after birth and may be of a genetic, epigenetic or immune nature (i.e., delayed infection-mediated immune deregulation). Here, we review the available experimental and epidemiological evidence linking pesticide exposure to infant and childhood leukemia and provide a mechanistic basis to support the association, focusing on early initiating molecular events.

  14. Assessing mechanical vulnerability in water distribution networks under multiple failures (United States)

    Berardi, Luigi; Ugarelli, Rita; Røstum, Jon; Giustolisi, Orazio


    Understanding mechanical vulnerability of water distribution networks (WDN) is of direct relevance for water utilities since it entails two different purposes. On the one hand, it might support the identification of severe failure scenarios due to external causes (e.g., natural or intentional events) which result into the most critical consequences on WDN supply capacity. On the other hand, it aims at figure out the WDN portions which are more prone to be affected by asset disruptions. The complexity of such analysis stems from the number of possible scenarios with single and multiple simultaneous shutdowns of asset elements leading to modifications of network topology and insufficient water supply to customers. In this work, the search for the most disruptive combinations of multiple asset failure events is formulated and solved as a multiobjective optimization problem. The higher vulnerability failure scenarios are detected as those causing the lower supplied demand due to the lower number of simultaneous failures. The automatic detection of WDN topology, subsequent to the detachments of failed elements, is combined with pressure-driven analysis. The methodology is demonstrated on a real water distribution network. Results show that, besides the failures causing the detachment of reservoirs, tanks, or pumps, there are other different topological modifications which may cause severe WDN service disruptions. Such information is of direct relevance to support planning asset enhancement works and improve the preparedness to extreme events.

  15. Obstructive sleep apnea and dyslipidemia: evidence and underlying mechanism. (United States)

    Adedayo, Ajibola Monsur; Olafiranye, Oladipupo; Smith, David; Hill, Alethea; Zizi, Ferdinand; Brown, Clinton; Jean-Louis, Girardin


    Over the past half century, evidence has been accumulating on the emergence of obstructive sleep apnea (OSA), the most prevalent sleep-disordered breathing, as a major risk factor for cardiovascular disease. A significant body of research has been focused on elucidating the complex interplay between OSA and cardiovascular risk factors, including dyslipidemia, obesity, hypertension, and diabetes mellitus that portend increased morbidity and mortality in susceptible individuals. Although a clear causal relationship of OSA and dyslipidemia is yet to be demonstrated, there is increasing evidence that chronic intermittent hypoxia, a major component of OSA, is independently associated and possibly the root cause of the dyslipidemia via the generation of stearoyl-coenzyme A desaturase-1 and reactive oxygen species, peroxidation of lipids, and sympathetic system dysfunction. The aim of this review is to highlight the relationship between OSA and dyslipidemia in the development of atherosclerosis and present the pathophysiologic mechanisms linking its association to clinical disease. Issues relating to epidemiology, confounding factors, significant gaps in research and future directions are also discussed.

  16. The Electrical Response to Injury: Molecular Mechanisms and Wound Healing (United States)

    Reid, Brian; Zhao, Min


    Significance: Natural, endogenous electric fields (EFs) and currents arise spontaneously after wounding of many tissues, especially epithelia, and are necessary for normal healing. This wound electrical activity is a long-lasting and regulated response. Enhancing or inhibiting this electrical activity increases or decreases wound healing, respectively. Cells that are responsible for wound closure such as corneal epithelial cells or skin keratinocytes migrate directionally in EFs of physiological magnitude. However, the mechanisms of how the wound electrical response is initiated and regulated remain unclear. Recent Advances: Wound EFs and currents appear to arise by ion channel up-regulation and redistribution, which are perhaps triggered by an intracellular calcium wave or cell depolarization. We discuss the possibility of stimulation of wound healing via pharmacological enhancement of the wound electric signal by stimulation of ion pumping. Critical Issues: Chronic wounds are a major problem in the elderly and diabetic patient. Any strategy to stimulate wound healing in these patients is desirable. Applying electrical stimulation directly is problematic, but pharmacological enhancement of the wound signal may be a promising strategy. Future Directions: Understanding the molecular regulation of wound electric signals may reveal some fundamental mechanisms in wound healing. Manipulating fluxes of ions and electric currents at wounds might offer new approaches to achieve better wound healing and to heal chronic wounds. PMID:24761358

  17. Neural mechanism underlying autobiographical memory modulated by remoteness and emotion (United States)

    Ge, Ruiyang; Fu, Yan; Wang, DaHua; Yao, Li; Long, Zhiying


    Autobiographical memory is the ability to recollect past events from one's own life. Both emotional tone and memory remoteness can influence autobiographical memory retrieval along the time axis of one's life. Although numerous studies have been performed to investigate brain regions involved in retrieving processes of autobiographical memory, the effect of emotional tone and memory age on autobiographical memory retrieval remains to be clarified. Moreover, whether the involvement of hippocampus in consolidation of autobiographical events is time dependent or independent has been controversial. In this study, we investigated the effect of memory remoteness (factor1: recent and remote) and emotional valence (factor2: positive and negative) on neural correlates underlying autobiographical memory by using functional magnetic resonance imaging (fMRI) technique. Although all four conditions activated some common regions known as "core" regions in autobiographical memory retrieval, there are some other regions showing significantly different activation for recent versus remote and positive versus negative memories. In particular, we found that bilateral hippocampal regions were activated in the four conditions regardless of memory remoteness and emotional valence. Thus, our study confirmed some findings of previous studies and provided further evidence to support the multi-trace theory which believes that the role of hippocampus involved in autobiographical memory retrieval is time-independent and permanent in memory consolidation.

  18. Molecular Mechanisms Underlying Origin and Diversification of the Angiosperm Flower (United States)

    Theissen, Guenter; Melzer, Rainer


    Background Understanding the mode and mechanisms of the evolution of the angiosperm flower is a long-standing and central problem of evolutionary biology and botany. It has essentially remained unsolved, however. In contrast, considerable progress has recently been made in our understanding of the genetic basis of flower development in some extant model species. The knowledge that accumulated this way has been pulled together in two major hypotheses, termed the ‘ABC model’ and the ‘floral quartet model’. These models explain how the identity of the different types of floral organs is specified during flower development by homeotic selector genes encoding transcription factors. Scope We intend to explain how the ‘ABC model’ and the ‘floral quartet model’ are now guiding investigations that help to understand the origin and diversification of the angiosperm flower. Conclusions Investigation of orthologues of class B and class C floral homeotic genes in gymnosperms suggest that bisexuality was one of the first innovations during the origin of the flower. The transition from dimer to tetramer formation of floral homeotic proteins after establishment of class E proteins may have increased cooperativity of DNA binding of the transcription factors controlling reproductive growth. That way, we hypothesize, better ‘developmental switches’ originated that facilitated the early evolution of the flower. Expression studies of ABC genes in basally diverging angiosperm lineages, monocots and basal eudicots suggest that the ‘classical’ ABC system known from core eudicots originated from a more fuzzy system with fading borders of gene expression and gradual transitions in organ identity, by sharpening of ABC gene expression domains and organ borders. Shifting boundaries of ABC gene expression may have contributed to the diversification of the angiosperm flower many times independently, as may have changes in interactions between ABC genes and their target

  19. Enhancement of sleep slow waves: underlying mechanisms and practical consequences.

    Directory of Open Access Journals (Sweden)

    Michele eBellesi


    Full Text Available Even modest sleep restriction, especially the loss of sleep slow wave activity, is invariably associated with slower EEG activity during wake, the occurrence of local sleep in an otherwise awake brain, and impaired performance due to cognitive and memory deficits. Recent studies not only confirm the beneficial role of sleep in memory consolidation, but also point to a specific role for sleep slow waves. Thus, the implementation of methods to enhance sleep slow waves without unwanted arousals or lightening of sleep could have significant practical implications. Here we first review the evidence that it is possible to enhance sleep slow waves in humans using transcranial direct-current stimulation and transcranial magnetic stimulation. Since these methods are currently impractical and their safety is questionable, especially for chronic long-term exposure, we then discuss novel data suggesting that it is possible to enhance slow waves using sensory stimuli. We consider the physiology of the K-complex, a peripheral evoked slow wave, and show that, among different sensory modalities, acoustic stimulation is the most effective in increasing the magnitude of slow waves, likely through the activation of non-lemniscal ascending pathways to the thalamo-cortical system. In addition, we discuss how intensity and frequency of the acoustic stimuli, as well as exact timing and pattern of stimulation, affect sleep enhancement. Finally, we discuss automated algorithms that read the EEG and, in real-time, adjust the stimulation parameters in a closed-loop manner to obtain an increase in sleep slow waves and avoid undesirable arousals. In conclusion, while discussing the mechanisms that underlie the generation of sleep slow waves, we review the converging evidence showing that acoustic stimulation is safe and represents an ideal tool for slow wave sleep enhancement.

  20. Thin circular cylinder under axisymmetrical thermal and mechanical loading

    International Nuclear Information System (INIS)

    Arnaudeau, F.; Zarka, J.; Gerij, J.


    To assess structural integrity of components subjected to cyclic thermal loadings one must look at thermal ratchetting as a possible failure mode. Considering a thin circular cylinder subjected to constant internal pressure and cyclically varying thermal gradient through the thickness Bree, J. Strain Analysis 2 (1967) No.3, obtained a diagram that serves as a foundation for many design rules (e.g.: ASME code). The upper part of the french LMFBR main vessel is subjected to an axisymmetrical axial thermal loading and an axial load (own weight). Operation of the reactor leads to cyclic variations of the axial thermal loading. The question that arises is whether or not the Bree diagram is realistic for such loading conditions. A special purpose computer code (Ratch) was developed to analyse a thin circular cylinder subjected to axisymmetrical mechanical and thermal loadings. The Mendelson's approach of this problem is followed. Classical Kirchoff-Love hypothesis of thin shells is used and a state of plane stress is assumed. Space integrations are performed by Gaussian quadrature in the axial direction and by Simpson's one third rule throughout the thickness. Thermoelastic-plastic constitutive equations are solved with an implicit scheme (Nguyen). Thermovisco-plastic constitutive equations are solved with an explicit time integration scheme (Treanor's algorithm especially fitted). A Bree type diagram is obtained for an axial step of temperature which varies cyclically and a sustained constant axial load. The material behavior is assumed perfectly plastic and creep effect is not considered. Results show that the domain where no ratchetting occurs is reduced when compared with the domain predicted by the Bree diagram

  1. Compression under a mechanical counter pressure space suit glove (United States)

    Waldie, James M A.; Tanaka, Kunihiko; Tourbier, Dietmar; Webb, Paul; Jarvis, Christine W.; Hargens, Alan R.


    Background: Current gas-pressurized space suits are bulky stiff shells severely limiting astronaut function and capability. A mechanical counter pressure (MCP) space suit in the form of a tight elastic garment could dramatically improve extravehicular activity (EVA) dexterity, but also be advantageous in safety, cost, mass and volume. The purpose of this study was to verify that a prototype MCP glove exerts the design compression of 200 mmHg, a pressure similar to the current NASA EVA suit. Methods: Seven male subjects donned a pressure measurement array and MCP glove on the right hand, which was placed into a partial vacuum chamber. Average compression was recorded on the palm, the bottom of the middle finger, the top of the middle finger and the dorsum of the hand at pressures of 760 (ambient), 660 and 580 mmHg. The vacuum chamber was used to simulate the pressure difference between the low breathing pressure of the current NASA space suits (approximately 200 mmHg) and an unprotected hand in space. Results: At ambient conditions, the MCP glove compressed the dorsum of the hand at 203.5 +/- 22.7 mmHg, the bottom of the middle finger at 179.4 +/- 16.0 mmHg, and the top of the middle finger at 183.8 +/- 22.6 mmHg. The palm compression was significantly lower (59.6 +/- 18.8 mmHg, pglove compression with the chamber pressure reductions. Conclusions: The MCP glove compressed the dorsum of the hand and middle finger at the design pressure.

  2. Neural mechanisms underlying cognitive inflexibility in Parkinson's disease. (United States)

    Lange, Florian; Seer, Caroline; Loens, Sebastian; Wegner, Florian; Schrader, Christoph; Dressler, Dirk; Dengler, Reinhard; Kopp, Bruno


    Cognitive inflexibility is a hallmark of executive dysfunction in Parkinson's disease (PD). This deficit consistently manifests itself in a PD-related increase in the number of perseverative errors committed on the Wisconsin Card Sorting Test (WCST). However, the neural processes underlying perseverative WCST performance in PD are still largely unknown. The present study is the first to investigate the event-related potential (ERP) correlates of cognitive inflexibility on the WCST in PD patients. Thirty-two PD patients and 35 matched control participants completed a computerized version of the WCST while the electroencephalogram (EEG) was recorded. Behavioral results revealed the expected increase in perseverative errors in patients with PD. ERP analysis focused on two established indicators of executive processes: the fronto-central P3a as an index of attentional orienting and the sustained parietal positivity (SPP) as an index of set-shifting processes. In comparison to controls, P3a amplitudes were significantly attenuated in PD patients. Regression analysis further revealed that P3a and SPP amplitudes interactively contributed to the prediction of perseverative errors in PD patients: The number of perseverative errors was only increased when both ERP amplitudes were attenuated. Notably, the two ERP markers of executive processes accounted for more than 40% of the variance in perseverative errors in PD patients. We conclude that cognitive inflexibility in PD occurs when the neural bases of multiple executive processes are affected by the pathophysiology of PD. The combined measurement of P3a and SPP might yield an electrophysiological marker of cognitive inflexibility in PD. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. Design principles and developmental mechanisms underlying retinal mosaics. (United States)

    Reese, Benjamin E; Keeley, Patrick W


    Most structures within the central nervous system (CNS) are composed of different types of neuron that vary in both number and morphology, but relatively little is known about the interplay between these two features, i.e. about the population dynamics of a given cell type. How such arrays of neurons are distributed within a structure, and how they differentiate their dendrites relative to each other, are issues that have recently drawn attention in the invertebrate nervous system, where the genetic and molecular underpinnings of these organizing principles are being revealed in exquisite detail. The retina is one of the few locations where these principles have been extensively studied in the vertebrate CNS, indeed, where the design principles of 'mosaic regularity' and 'uniformity of coverage' were first explicitly defined, quantified, and related to each other. Recent studies have revealed a number of genes that influence the formation of these histotypical features in the retina, including homologues of those invertebrate genes, although close inspection reveals that they do not always mediate comparable developmental processes nor elucidate fundamental design principles. The present review considers just how pervasive these features of 'mosaic regularity' and 'uniform dendritic coverage' are within the mammalian retina, discussing the means by which such features can be assessed in the mature and developing nervous system and examining the limitations associated with those assessments. We then address the extent to which these two design principles co-exist within different populations of neurons, and how they are achieved during development. Finally, we consider the neural phenotypes obtained in mutant nervous systems, to address whether a prospective gene of interest underlies those very design principles. © 2014 The Authors. Biological Reviews © 2014 Cambridge Philosophical Society.

  4. Mechanism of attenuation of leptin signaling under chronic ligand stimulation

    Directory of Open Access Journals (Sweden)

    Bamberg-Lemper Simone


    Full Text Available Abstract Background Leptin is an adipocyte-derived hormone that acts via its hypothalamic receptor (LEPRb to regulate energy balance. A downstream effect essential for the weight-regulatory action of leptin is the phosphorylation and activation of the latent transcription factor STAT3 by LEPRb-associated Janus kinases (JAKs. Obesity is typically associated with chronically elevated leptin levels and a decreased ability of LEPRb to activate intracellular signal transduction pathways (leptin resistance. Here we have studied the roles of the intracellular tyrosine residues in the negative feedback regulation of LEPRb-signaling under chronic leptin stimulation. Results Mutational analysis showed that the presence of either Tyr985 and Tyr1077 in the intracellular domain of LEPRb was sufficient for the attenuation of STAT3 phosphorylation, whereas mutation of both tyrosines rendered LEPRb resistant to feedback regulation. Overexpression and RNA interference-mediated downregulation of suppressor of cytokine signaling 3 (SOCS3 revealed that both Tyr985 and Tyr1077 were capable of supporting the negative modulatory effect of SOCS3 in reporter gene assays. In contrast, the inhibitory effect of SOCS1 was enhanced by the presence of Tyr985 but not Tyr1077. Finally, the reduction of the STAT-phosphorylating activity of the LEPRb complex after 2 h of leptin stimulation was not accompanied by the dephosphorylation or degradation of LEPRb or the receptor-associated JAK molecule, but depended on Tyr985 and/or Tyr1077. Conclusions Both Tyr985 and Tyr1077 contribute to the negative regulation of LEPRb signaling. The inhibitory effects of SOCS1 and SOCS3 differ in the dependence on the tyrosine residues in the intracellular domain of LEPRb.

  5. Mechanism of cellular response to nanoscale aggregates of small molecules (United States)

    Kuang, Yi

    This dissertation research focused on the illustration of the molecular mechanism of cellular response to nanoscale aggregates formed by small molecules. There are five chapters in this dissertation. Chapter 1 summarizes the current research on the evaluation of cell response (i.e., biocompatibility/cytotoxicity) to small molecular hydrogelators. Chapter 2 describes an interesting phenomenon that supramolecular hydrogelators consisting of N-terminated dipeptides, which exhibit selective inhibitory effects against cancer cells. This study calls for the development of a new approach for identification of protein targets of the hydrogelators. Chapter 3 describes the evaluation of interactions between cytosol proteins of a mammalian cell line and morphologically different nanoscale molecular aggregates formed by small peptidic molecules. Chapter 4 describes the research on the mechanism of a type of molecular aggregates, which cluster short microtubules to prevent the growth of microtubule. This unprecedented mechanism of "self-assembly to interfere with self-organization " contributes to inhibiting growth of cancer cells in several mammalian cell based assays and a xenograft tumor mice model. At the end, Chapter 5 reports a novel supramolecular hydrogelator, which consists of fluorene and the pentapeptide epitope (TIGYG) of potassium ion (K+) channels, to self-assemble in water to form the tunable, hierarchical nanostructures dictated by the concentration of K+. In conclusion, this dissertation research demonstrates a new approach for investigating cellular target and molecular mechanism of self-assembled aggregates formed by small peptide derivatives based hydrogelators, which will make contribution to the development of supramolecular hydrogelators as biomaterials. Moreover, the differential cytotoxicity of molecular aggregates illustrated in this research promises a new direction for developing anti-cancer drug based on interactions between molecular aggregates and

  6. Escape response of planktonic protists to fluid mechanical signals

    DEFF Research Database (Denmark)

    Jakobsen, Hans Henrik


    The escape response to fluid mechanical signals was examined in 6 protists, 4 ciliates and 2 dinoflagellates. When exposed to a siphon flow. 3 species of ciliates, Balanion comatum, Strobilidium sp., and Mesodinium pulex, responded with escape jumps. The threshold deformation rates required...... to elicit an escape ranged between 1.8 and 3 s(-1). Escape speeds varied between 100 to 150 body length s(-1). Jump directions were non- random in all jumping species and had a negative geotactic component. In a grazing experiment with copepods, the predation mortality of a jumping ciliate was about 15...

  7. Evaluation of the sheet mechanical response to laser welding processes

    International Nuclear Information System (INIS)

    Carmignani, B.; Daneri, A.; Toselli, G.; Bellei, M.


    The simulation of the mechanical response of steel sheets, due to the heating during welding processes by a laser source beam, obtained by Abaqus standard code, is discussed. Different hypotheses for the material behaviour at temperatures greater than the fusion one have been tested and compared; in particular, some tests have been made taking the annealing effect into account by means of an user routine UMAT developed ad hoc. This work was presented at the 8th international Abaqus Users' conference at Paris, 31 May - 2 June 1995

  8. Mechanisms responsible for decreased glomerular filtration in hibernation and hypothermia (United States)

    Tempel, G. E.; Musacchia, X. J.; Jones, S. B.


    Measurements of blood pressure, heart rate, red blood cell and plasma volumes, and relative distribution of cardiac output were made on hibernating and hypothermic adult male and female golden hamsters weighing 120-140 g to study the mechanisms underlying the elimination or marked depression of renal function in hibernation and hypothermia. The results suggest that the elimination or marked depression in renal function reported in hibernation and hypothermia may partly be explained by alterations in cardiovascular system function. Renal perfusion pressure which decreases nearly 60% in both hibernation and hypothermia and a decrease in plasma volume of roughly 35% in the hypothermic animal might both be expected to markedly alter glomerular function.

  9. Thermal equilibrium responses in Guzerat cattle raised under tropical conditions. (United States)

    Camerro, Leandro Zuccherato; Maia, Alex Sandro Campos; Neto, Marcos Chiquitelli; Costa, Cintia Carol de Melo; Castro, Patric André


    The literature is very sparse regarding research on the thermal equilibrium in Guzerat cattle (Bos indicus) under field conditions. Some factors can modify the physiological response of Guzerat cattle, such as the reactivity of these animals to handling. Thus, the development of a methodology to condition and select Guzerat cattle to acclimate them to the routine collection of data without altering their physiological response was the objective of the preliminary experiment. Furthermore, the animals selected were used in the main experiment to determine their thermal equilibrium according to the thermal environment. For this proposal, the metabolic heat production and heat exchange between the animal and the environment were measured simultaneously in the field with an indirect calorimetry system coupled to a facial mask. The results of the preliminary experiment showed that the respiratory rate could demonstrate that conditioning efficiently reduced the reactivity of the animals to experimental handling. Furthermore, the respiratory rate can be used to select animals with less reactivity. The results of the main experiment demonstrate that the skin, hair-coat surface and expired air temperature depend on the air temperature, whereas the rectal temperature depends on the time of day; consequently, the sensible heat flow was substantially reduced from 70 to 20Wm(-2) when the air temperature increased from 24 to 34°C. However, the respiratory latent heat flow increased from 10 to 15Wm(-2) with the same temperature increase. Furthermore, the metabolic heat production remained stable, independent of the variation of the air temperature; however, it was higher in males than in females (by approximately 25%). This fact can be explained by the variation of the ventilation rate, which had a mean value of 1.6 and 2.2Ls(-1) for females and males, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Dynamical mechanisms for sensitive response of aperiodic firing cells to external stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Xie Yong E-mail:; Xu Jianxue; Hu Sanjue; Kang Yanmei; Yang Hongjun; Duan Yubin


    An interesting phenomenon that aperiodic firing neurons have a higher sensitivity to drugs than periodic firing neurons have been reported for the chronically compressed dorsal root ganglion neurons in rats. In this study, the dynamical mechanisms for such a phenomenon are uncovered from the viewpoint of dynamical systems theory. We use the Rose-Hindmarsh neuron model to illustrate our opinions. Periodic orbit theory is introduced to characterize the dynamical behavior of aperiodic firing neurons. It is considered that bifurcations, crises and sensitive dependence of chaotic motions on control parameters can be the underlying mechanisms. And then, a similar analysis is applied to the modified Chay model describing the firing behavior of pancreatic beta cells. The same dynamical mechanisms can be obtained underlying that aperiodic firing cells are more sensitive to external stimulation than periodic firing ones. As a result, we conjecture that sensitive response of aperiodic firing cells to external stimulation is a universal property of excitable cells.

  11. Revealing the Neural Mechanisms Underlying the Beneficial Effects of Tai Chi: A Neuroimaging Perspective. (United States)

    Yu, Angus P; Tam, Bjorn T; Lai, Christopher W; Yu, Doris S; Woo, Jean; Chung, Ka-Fai; Hui, Stanley S; Liu, Justina Y; Wei, Gao X; Siu, Parco M


    Tai Chi Chuan (TCC), a traditional Chinese martial art, is well-documented to result in beneficial consequences in physical and mental health. TCC is regarded as a mind-body exercise that is comprised of physical exercise and meditation. Favorable effects of TCC on body balance, gait, bone mineral density, metabolic parameters, anxiety, depression, cognitive function, and sleep have been previously reported. However, the underlying mechanisms explaining the effects of TCC remain largely unclear. Recently, advances in neuroimaging technology have offered new investigative opportunities to reveal the effects of TCC on anatomical morphologies and neurological activities in different regions of the brain. These neuroimaging findings have provided new clues for revealing the mechanisms behind the observed effects of TCC. In this review paper, we discussed the possible effects of TCC-induced modulation of brain morphology, functional homogeneity and connectivity, regional activity and macro-scale network activity on health. Moreover, we identified possible links between the alterations in brain and beneficial effects of TCC, such as improved motor functions, pain perception, metabolic profile, cognitive functions, mental health and sleep quality. This paper aimed to stimulate further mechanistic neuroimaging studies in TCC and its effects on brain morphology, functional homogeneity and connectivity, regional activity and macro-scale network activity, which ultimately lead to a better understanding of the mechanisms responsible for the beneficial effects of TCC on human health.

  12. 3D deformation field in growing plant roots reveals both mechanical and biological responses to axial mechanical forces. (United States)

    Bizet, François; Bengough, A Glyn; Hummel, Irène; Bogeat-Triboulot, Marie-Béatrice; Dupuy, Lionel X


    Strong regions and physical barriers in soils may slow root elongation, leading to reduced water and nutrient uptake and decreased yield. In this study, the biomechanical responses of roots to axial mechanical forces were assessed by combining 3D live imaging, kinematics and a novel mechanical sensor. This system quantified Young's elastic modulus of intact poplar roots (32MPa), a rapid 3D. Measured critical elongation force was accurately predicted from an Euler buckling model, indicating that no biologically mediated accommodation to mechanical forces influenced bending during this short period of time. Force applied by growing roots increased more than 15-fold when buckling was prevented by lateral bracing of the root. The junction between the growing and the mature zones was identified as a zone of mechanical weakness that seemed critical to the bending process. This work identified key limiting factors for root growth and buckling under mechanical constraints. The findings are relevant to crop and soil sciences, and advance our understanding of root growth in heterogeneous structured soils. © The Author 2016. Published by Oxford University Press on behalf of the Society for Experimental Biology.

  13. Natural variation in germination responses of Arabidopsis to seasonal cues and their associated physiological mechanisms (United States)

    Barua, Deepak; Butler, Colleen; Tisdale, Tracy E.; Donohue, Kathleen


    Background and Aims Despite the intense interest in phenological adaptation to environmental change, the fundamental character of natural variation in germination is almost entirely unknown. Specifically, it is not known whether different genotypes within a species are germination specialists to particular conditions, nor is it known what physiological mechanisms of germination regulation vary in natural populations and how they are associated with responses to particular environmental factors. Methods We used a set of recombinant inbred genotypes of Arabidopsis thaliana, in which linkage disequilibrium has been disrupted over seven generations, to test for genetic variation and covariation in germination responses to distinct environmental factors. We then examined physiological mechanisms associated with those responses, including seed-coat permeability and sensitivity to the phytohormones gibberellic acid (GA) and abscisic acid (ABA). Key Results Genetic variation for germination was environment-dependent, but no evidence for specialization of germination to different conditions was found. Hormonal sensitivities also exhibited significant genetic variation, but seed-coat properties did not. GA sensitivity was associated with germination responses to multiple environmental factors, but seed-coat permeability and ABA sensitivity were associated with specific germination responses, suggesting that an evolutionary change in GA sensitivity could affect germination in multiple environments, but that of ABA sensitivity may affect germination under more restricted conditions. Conclusions The physiological mechanisms of germination responses to specific environmental factors therefore can influence the ability to adapt to diverse seasonal environments encountered during colonization of new habitats or with future predicted climate change. PMID:22012958

  14. The effects of stoichiometry on the mechanical properties of icosahedral boron carbide under loading. (United States)

    Taylor, DeCarlos E; McCauley, James W; Wright, T W


    The effects of stoichiometry on the atomic structure and the related mechanical properties of boron carbide (B(4)C) have been studied using density functional theory and quantum molecular dynamics simulations. Computational cells of boron carbide containing up to 960 atoms and spanning compositions ranging from 6.7% to 26.7% carbon were used to determine the effects of stoichiometry on the atomic structure, elastic properties, and stress-strain response as a function of hydrostatic, uniaxial, and shear loading paths. It was found that different stoichiometries, as well as variable atomic arrangements within a fixed stoichiometry, can have a significant impact on the yield stress of boron carbide when compressed uniaxially (by as much as 70% in some cases); the significantly reduced strength of boron carbide under shear loading is also demonstrated.

  15. Computer-aided study of the mechanical behavior of the jaw bone fragments under uniaxial compression (United States)

    Kolmakova, Tatyana V.


    The article presents the calculated results of the mechanical behavior of simulative bone mesovolumes under uniaxial compression with their architectonics corresponding to the human jaw bone fragments. The results of the calculation show that changes in the structure and mineral content of the bone fragments can lead to the change of their prevailing deformation response. New effective parameters were introduced to reflect the character of the distribution of stresses and strains in the bone mesovolumes. Implants are to be created and selected to correspond to the offered parameters and longitudinal modulus of elasticity of bone mesovolumes in order to maintain the stress and strain state existing in bone macrovolume during the implantation and in order to avoid bone restructuring through its borderline resorption.

  16. Mechanical vibrations of tubes bundles under transversal flow; Vibration des faisceaux de tubes sous ecoulement trasversal

    Energy Technology Data Exchange (ETDEWEB)

    Hadj-Sadok, C. [ENSTA - Laboratoire de Mecanique Groupe Structure et Proprietes des Materiaux, 91 Palaiseau (France)


    Flow-induced vibrations have been a major cause of tube failure in heat exchangers. Among the various fluid excitation mechanisms, fluid-elastic coupling can cause dynamic instability and induce rapid deterioration of tubes. We present in this paper a methodology to determine fluid-elastic forces in tube bundles vibrating freely under-induced excitation. Computations of the response of loosely supported tube to fluid-elastic forces and turbulence are performed. The fluid-elastic forces were modelled as reduced velocity dependent fluid-stiffness and fluid-damping coefficients. A corrective methodology is proposed to account for the frequency dependence associated with fluid-stiffness and fluid-damping coefficients. (author). 40 refs.

  17. Acclimation of green algae to sulfur deficiency: underlying mechanisms and application for hydrogen production. (United States)

    Antal, Taras K; Krendeleva, Tatyana E; Rubin, Andrew B


    Hydrogen is definitely one of the most acceptable fuels in the future. Some photosynthetic microorganisms, such as green algae and cyanobacteria, can produce hydrogen gas from water by using solar energy. In green algae, hydrogen evolution is coupled to the photosynthetic electron transport in thylakoid membranes via reaction catalyzed by the specific enzyme, (FeFe)-hydrogenase. However, this enzyme is highly sensitive to oxygen and can be quickly inhibited when water splitting is active. A problem of incompatibility between the water splitting and hydrogenase reaction can be overcome by depletion of algal cells of sulfur which is essential element for life. In this review the mechanisms underlying sustained hydrogen photoproduction in sulfur deprived C. reinhardtii and the recent achievements in studying of this process are discussed. The attention is focused on the biophysical and physiological aspects of photosynthetic response to sulfur deficiency in green algae.

  18. Modeling of the response under radiation of electronic dosemeters

    International Nuclear Information System (INIS)

    Menard, S.


    The simulation with with calculation codes the interactions and the transport of primary and secondary radiations in the detectors allows to reduce the number of developed prototypes and the number of experiments under radiation. The simulation makes possible the determination of the response of the instrument for exposure configurations more extended that these ones of references radiations produced in laboratories. The M.C.N.P.X. allows to transport, over the photons, electrons and neutrons, the charged particles heavier than the electrons and to simulate the radiation - matter interactions for a certain number of particles. The present paper aims to present the interest of the use of the M.C.N.P.X. code in the study, research and evaluation phases of the instrumentation necessary to the dosimetry monitoring. To do that the presentation gives the results of the modeling of a prototype of a equivalent tissue proportional counter (C.P.E.T.) and of the C.R.A.M.A.L. ( radiation protection apparatus marketed by the Eurisys Mesures society). (N.C.)

  19. Conservation of the piezoelectric response of PVDF films under irradiation (United States)

    Melilli, G.; Lairez, D.; Gorse, D.; Garcia-Caurel, E.; Peinado, A.; Cavani, O.; Boizot, B.; Clochard, M.-C.


    As opposed to piezo-ceramics (i.e PZT), flexibility and robustness characterize piezoelectric polymers. The main advantage of a piezoelectric polymer, such as Poly (vinylidene fluoride) (PVDF), is an electric power generation under large reversible elastic deformation. Starting from polarized PVDF, we have shown that, despite the fact that irradiation is known to structurally modify the PVDF by introducing defects (radicals, chain scission and crosslinks), the electro-active properties were not affected. At doses lower than 100 kGy, a comparison between swift heavy-ion (SHI) and e-beam irradiations is presented. A homemade device was realized to measure the output voltage as a function of the bending deformation for irradiated and non-irradiated PVDF film. DSC and FT-IR techniques give new insights on which crystalline part or structural change contributes to the conservation of the output voltage. Results suggest that despite the material after irradiation is composed of smaller crystallites, the β-phase content remains stable around 36%, which explains the remarkable preservation of the piezoelectric response in irradiated polarized PVDF films.

  20. 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


    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


    Directory of Open Access Journals (Sweden)



    Full Text Available The objective of this study was to characterize the physiological acclimation responses of young plants of the dwarf coconut cultivar ̳Jiqui Green‘ associated with tolerance to conditions of multiple abiotic stresses (drought and soil salinity, acting either independently or in combination. The study was conducted under controlled conditions and evaluated the following parameters: leaf gas exchange, quantum yield of chlorophyll a fluorescence, and relative contents of total chlorophyll (SPAD index. The experiment was conducted under a randomized block experimental design, in a split plot arrangement. In the plots, plants were exposed to different levels of water stress, by imposing potential crop evapotranspiration replacement levels equivalent to 100%, 80%, 60%, 40%, and 20%, whereas in subplots, plants were exposed to different levels of soil salinity (1.72, 6.25, 25.80, and 40.70 dS m - 1 . Physiological mechanisms were effectively limited when water deficit and salinity acted separately and/or together. Compared with soil salinity, water stress was more effective in reducing the measured physiological parameters. The magnitudes of the responses of plants to water supply and salinity depended on the intensity of stress and evaluation period. The physiological acclimation responses of plants were mainly related to stomatal regulation. The coconut tree has a number of physiological adjustment mechanisms that give the species partial tolerance to drought stress and/or salt, thereby enabling it to revegetate salinated areas, provided that its water requirements are at least partially met.

  2. Mechanical characterisation of porcine rectus sheath under uniaxial and biaxial tension.

    LENUS (Irish Health Repository)

    Lyons, Mathew


    Incisional hernia development is a significant complication after laparoscopic abdominal surgery. Intra-abdominal pressure (IAP) is known to initiate the extrusion of intestines through the abdominal wall, but there is limited data on the mechanics of IAP generation and the structural properties of rectus sheath. This paper presents an explanation of the mechanics of IAP development, a study of the uniaxial and biaxial tensile properties of porcine rectus sheath, and a simple computational investigation of the tissue. Analysis using Laplace׳s law showed a circumferential stress in the abdominal wall of approx. 1.1MPa due to an IAP of 11kPa, commonly seen during coughing. Uniaxial and biaxial tensile tests were conducted on samples of porcine rectus sheath to characterise the stress-stretch responses of the tissue. Under uniaxial tension, fibre direction samples failed on average at a stress of 4.5MPa at a stretch of 1.07 while cross-fibre samples failed at a stress of 1.6MPa under a stretch of 1.29. Under equi-biaxial tension, failure occurred at 1.6MPa with the fibre direction stretching to only 1.02 while the cross-fibre direction stretched to 1.13. Uniaxial and biaxial stress-stretch plots are presented allowing detailed modelling of the tissue either in silico or in a surrogate material. An FeBio computational model of the tissue is presented using a combination of an Ogden and an exponential power law model to represent the matrix and fibres respectively. The structural properties of porcine rectus sheath have been characterised and add to the small set of human data in the literature with which it may be possible to develop methods to reduce the incidence of incisional hernia development.

  3. Distinct mechanisms underlying tolerance to intermittent and constant hypoxia in Drosophila melanogaster.

    Directory of Open Access Journals (Sweden)

    Priti Azad

    Full Text Available BACKGROUND: Constant hypoxia (CH and intermittent hypoxia (IH occur during several pathological conditions such as asthma and obstructive sleep apnea. Our research is focused on understanding the molecular mechanisms that lead to injury or adaptation to hypoxic stress using Drosophila as a model system. Our current genome-wide study is designed to investigate gene expression changes and identify protective mechanism(s in D. melanogaster after exposure to severe (1% O(2 intermittent or constant hypoxia. METHODOLOGY/PRINCIPAL FINDINGS: Our microarray analysis has identified multiple gene families that are up- or down-regulated in response to acute CH or IH. We observed distinct responses to IH and CH in gene expression that varied in the number of genes and type of gene families. We then studied the role of candidate genes (up-or down-regulated in hypoxia tolerance (adult survival for longer periods (CH-7 days, IH-10 days under severe CH or IH. Heat shock proteins up-regulation (specifically Hsp23 and Hsp70 led to a significant increase in adult survival (as compared to controls of P-element lines during CH. In contrast, during IH treatment the up-regulation of Mdr49 and l(208717 genes (P-element lines provided survival advantage over controls. This suggests that the increased transcript levels following treatment with either paradigm play an important role in tolerance to severe hypoxia. Furthermore, by over-expressing Hsp70 in specific tissues, we found that up-regulation of Hsp70 in heart and brain play critical role in tolerance to CH in flies. CONCLUSIONS/SIGNIFICANCE: We observed that the gene expression response to IH or CH is specific and paradigm-dependent. We have identified several genes Hsp23, Hsp70, CG1600, l(208717 and Mdr49 that play an important role in hypoxia tolerance whether it is in CH or IH. These data provide further clues about the mechanisms by which IH or CH lead to cell injury and morbidity or adaptation and survival.

  4. Metabolomic Analysis of Alfalfa (Medicago sativa L.) Root-Symbiotic Rhizobia Responses under Alkali Stress


    Song, Tingting; Xu, Huihui; Sun, Na; Jiang, Liu; Tian, Pu; Yong, Yueyuan; Yang, Weiwei; Cai, Hua; Cui, Guowen


    Alkaline salts (e.g., NaHCO3 and Na2CO3) causes more severe morphological and physiological damage to plants than neutral salts (e.g., NaCl and Na2SO4) due to differences in pH. The mechanism by which plants respond to alkali stress is not fully understood, especially in plants having symbotic relationships such as alfalfa (Medicago sativa L.). Therefore, a study was designed to evaluate the metabolic response of the root-nodule symbiosis in alfalfa under alkali stress using comparative metab...

  5. Transcriptomic responses to darkness stress point to common coral bleaching mechanisms (United States)

    Desalvo, M. K.; Estrada, A.; Sunagawa, S.; Medina, Mónica


    Coral bleaching occurs in response to numerous abiotic stressors, the ecologically most relevant of which is hyperthermic stress due to increasing seawater temperatures. Bleaching events can span large geographic areas and are currently a salient threat to coral reefs worldwide. Much effort has been focused on understanding the molecular and cellular events underlying bleaching, and these studies have mainly utilized heat and light stress regimes. In an effort to determine whether different stressors share common bleaching mechanisms, we used complementary DNA (cDNA) microarrays for the corals Acropora palmata and Montastraea faveolata (containing >10,000 features) to measure differential gene expression during darkness stress. Our results reveal a striking transcriptomic response to darkness in A. palmata involving chaperone and antioxidant up-regulation, growth arrest, and metabolic modifications. As these responses were previously measured during thermal stress, our results suggest that different stressors may share common bleaching mechanisms. Furthermore, our results point to hypoxia and endoplasmic reticulum stress as critical cellular events involved in molecular bleaching mechanisms. On the other hand, we identified a meager transcriptomic response to darkness in M. faveolata where gene expression differences between host colonies and sampling locations were greater than differences between control and stressed fragments. This and previous coral microarray studies reveal the immense range of transcriptomic responses that are possible when studying two coral species that differ greatly in their ecophysiology, thus pointing to the importance of comparative approaches in forecasting how corals will respond to future environmental change.

  6. 40 CFR 85.1907 - Responsibility under other legal provisions preserved. (United States)


    ... 40 Protection of Environment 18 2010-07-01 2010-07-01 false Responsibility under other legal... Requirements § 85.1907 Responsibility under other legal provisions preserved. The filing of any report under the provisions of this subpart shall not affect a manufacturer's responsibility to file reports or...

  7. 40 CFR 90.806 - Responsibility under other legal provisions preserved. (United States)


    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Responsibility under other legal... § 90.806 Responsibility under other legal provisions preserved. The filing of any report under the provisions of this subpart does not affect a manufacturer's responsibility to file reports or applications...

  8. Using stable isotopes and functional wood anatomy to identify underlying mechanisms of drought tolerance in different provenances of lodgepole pine (United States)

    Isaac-Renton, Miriam; Montwé, David; Hamann, Andreas; Spiecker, Heinrich; Cherubini, Paolo; Treydte, Kerstin


    Choosing drought-tolerant seed sources for reforestation may help adapt forests to climate change. By combining dendroecological growth analysis with a long-term provenance trial, we assessed growth and drought tolerance of different populations of a wide-ranging conifer, lodgepole pine (Pinus contorta). This experimental design simulated a climate warming scenario through southward seed transfer, and an exceptional drought also occurred in 2002. We felled over 500 trees, representing 23 seed sources, which were grown for 32 years at three warm, dry sites in southern British Columbia, Canada. Northern populations showed poor growth and drought tolerance. These seed sources therefore appear to be especially at risk under climate change. Before recommending assisted migration of southern seeds towards the north, however, it is important to understand the physiological mechanisms underlying these responses. We combine functional wood anatomy with a dual-isotope approach to evaluate these mechanisms to drought response.

  9. The time course of pupil dilation evoked by visual sexual stimuli: Exploring the underlying ANS mechanisms. (United States)

    Finke, Johannes B; Deuter, Christian E; Hengesch, Xenia; Schächinger, Hartmut


    The early processing of visual sexual stimuli shows signs of automaticity. Moreover, there is evidence for sex-specific patterns in cognitive and physiological responding to erotica. However, little is known about the time course of rapid pupillary responses to sexual stimuli and their correspondence with other measures of autonomic activity in women and men. To study pupil dilation as an implicit measure of sexual arousal at various stages of picture processing, we presented 35 heterosexual participants with pictures showing either erotic couples or single (male/female) erotic nudes, contrasted with people involved in everyday situations. Brightness-adjusted grayscale pictures were shown for a duration of 2,500 ms within the central visual field, alternating with perceptually matched patches. Left pupil diameter was recorded at 500 Hz using a video-based eye tracker. Skin conductance and heart rate were coregistered and correlated with latent components of pupil dilation (dissociated by temporal PCA). Whereas stimulus-evoked changes in pupil size indicated virtually no initial constriction, a rapid effect of appetence emerged (dilation to erotica within 500 ms). Responses at early stages of processing were remarkably consistent across both sexes. In contrast, later phases of pupil dilation, subjective ratings, and skin conductance responses showed a sex-specific pattern. Moreover, evidence for an association of early-onset pupil dilation and heart rate acceleration was found, suggestive of parasympathetic inhibition, whereas the late component was mainly related to sympathetically mediated skin conductance. Taken together, our results indicate that different temporal components of pupil responses to erotic stimuli may reflect divergent underlying neural mechanisms. © 2017 Society for Psychophysiological Research.

  10. Mechanical response of spiral interconnect arrays for highly stretchable electronics

    KAUST Repository

    Qaiser, Nadeem


    A spiral interconnect array is a commonly used architecture for stretchable electronics, which accommodates large deformations during stretching. Here, we show the effect of different geometrical morphologies on the deformation behavior of the spiral island network. We use numerical modeling to calculate the stresses and strains in the spiral interconnects under the prescribed displacement of 1000 μm. Our result shows that spiral arm elongation depends on the angular position of that particular spiral in the array. We also introduce the concept of a unit-cell, which fairly replicates the deformation mechanism for full complex hexagon, diamond, and square shaped arrays. The spiral interconnects which are axially connected between displaced and fixed islands attain higher stretchability and thus experience the maximum deformations. We perform tensile testing of 3D printed replica and find that experimental observations corroborate with theoretical study.

  11. Physiological responses and differential gene expression in Prunus rootstocks under iron deficiency conditions. (United States)

    Gonzalo, María José; Moreno, María Ángeles; Gogorcena, Yolanda


    Two Prunus rootstocks, the Myrobalan plum P 2175 and the interspecific peach-almond hybrid, Felinem, were studied to characterize their biochemical and molecular responses induced under iron-Deficient conditions. Plants of both genotypes were submitted to different treatments using a hydroponic system that permitted removal of Fe from the nutrient solution. Control plants were grown in 90 μM Fe (III)-EDTA, Deficient plants were grown in an iron free solution, and plants submitted to an Inductor treatment were resupplied with 180 μM Fe (III)-EDTA over 1 and 2 days after a period of 4 or 15 days of growth on an iron-free solution. Felinem increased the activity of the iron chelate reductase (FC-R) in the Inductor treatment after 4 days of iron deprivation. In contrast, P 2175 did not show any response after at least 15 days without iron. The induction of the FC-R activity in this genotype was coincident in time with the medium acidification. These results suggest two different mechanisms of iron chlorosis tolerance in both Strategy I genotypes. Felinem would use the iron reduction as the main mechanism to capture the iron from the soil, and in P 2175, the mechanism of response would be slower and start with the acidification of the medium synchronized with the gradual loss of chlorophyll in leaves. To better understand the control of these responses at the molecular level, the differential expression of PFRO2, PIRT1 and PAHA2 genes involved in the reductase activity, the iron transport in roots, and the proton release, respectively, were analyzed. The expression of these genes, estimated by quantitative real-time PCR, was different between genotypes and among treatments. The results were in agreement with the physiological responses observed. Copyright © 2011 Elsevier GmbH. All rights reserved.

  12. Effects and mechanism on Kapton film under ozone exposure in a ground near space simulator (United States)

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


    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.

  13. Mechanisms Underlying Cytotoxicity Induced by Engineered Nanomaterials: A Review of In Vitro Studies (United States)

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


    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

  14. Collecting psycholinguistic response time data using Amazon mechanical Turk.

    Directory of Open Access Journals (Sweden)

    Kelly Enochson

    Full Text Available Researchers in linguistics and related fields have recently begun exploiting online crowd-sourcing tools, like Amazon Mechanical Turk (AMT, to gather behavioral data. While this method has been successfully validated for various offline measures--grammaticality judgment or other forced-choice tasks--its use for mainstream psycholinguistic research remains limited. This is because psycholinguistic effects are often dependent on relatively small differences in response times, and there remains some doubt as to whether precise timing measurements can be gathered over the web. Here we show that three classic psycholinguistic effects can in fact be replicated using AMT in combination with open-source software for gathering response times client-side. Specifically, we find reliable effects of subject definiteness, filler-gap dependency processing, and agreement attraction in self-paced reading tasks using approximately the same numbers of participants and/or trials as similar laboratory studies. Our results suggest that psycholinguists can and should be taking advantage of AMT and similar online crowd-sourcing marketplaces as a fast, low-resource alternative to traditional laboratory research.

  15. Collecting psycholinguistic response time data using Amazon mechanical Turk. (United States)

    Enochson, Kelly; Culbertson, Jennifer


    Researchers in linguistics and related fields have recently begun exploiting online crowd-sourcing tools, like Amazon Mechanical Turk (AMT), to gather behavioral data. While this method has been successfully validated for various offline measures--grammaticality judgment or other forced-choice tasks--its use for mainstream psycholinguistic research remains limited. This is because psycholinguistic effects are often dependent on relatively small differences in response times, and there remains some doubt as to whether precise timing measurements can be gathered over the web. Here we show that three classic psycholinguistic effects can in fact be replicated using AMT in combination with open-source software for gathering response times client-side. Specifically, we find reliable effects of subject definiteness, filler-gap dependency processing, and agreement attraction in self-paced reading tasks using approximately the same numbers of participants and/or trials as similar laboratory studies. Our results suggest that psycholinguists can and should be taking advantage of AMT and similar online crowd-sourcing marketplaces as a fast, low-resource alternative to traditional laboratory research.

  16. The mechanisms of low nitrogen induced weakened photosynthesis in summer maize (Zea mays L.) under field conditions. (United States)

    Wei, Shanshan; Wang, Xiangyu; Shi, Deyang; Li, Yanhong; Zhang, Jiwang; Liu, Peng; Zhao, Bin; Dong, Shuting


    Soil nitrogen (N) shortage is a problem which affects many developing nations. Crops grown with low soil N levels show a marked decrease in the rate of photosynthesis and this deficiency reduces crop yield significantly. Therefore, developing a better understanding of the mechanisms by which low N levels cause decreased photosynthesis is crucial for maize agriculture. To better understand this process, we assessed the responses of photosynthesis traits and enzymatic activities in the summer maize cultivar Denghai 618 under field conditions with and without the use of N fertilisers. We measured photosynthesis parameters, and compared proteome compositions to identify the mechanisms of physiological and biochemical adaptations to N deficiency in maize. We observed that parameters that indicated the rate of photosynthesis decreased significantly under N deficiency, and this response was associated with leaf senescence. Moreover, we identified 37 proteins involved in leaf photosynthesis, and found that N deficiency significantly affected light-dependent and light-independent reactions in maize leaf photosynthesis. Although further analysis is required to fully elucidate the roles of these proteins in the response to N deficiency, our study identified candidate proteins which may be involved in the regulatory mechanisms involved in reduced photosynthesis under low N conditions in maize. Copyright © 2016 Elsevier Masson SAS. All rights reserved.

  17. 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


    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.

  18. Dissecting the signaling mechanisms underlying recognition and preference of food odors. (United States)

    Harris, Gareth; Shen, Yu; Ha, Heonick; Donato, Alessandra; Wallis, Samuel; Zhang, Xiaodong; Zhang, Yun


    Food is critical for survival. Many animals, including the nematode Caenorhabditis elegans, use sensorimotor systems to detect and locate preferred food sources. However, the signaling mechanisms underlying food-choice behaviors are poorly understood. Here, we characterize the molecular signaling that regulates recognition and preference between different food odors in C. elegans. We show that the major olfactory sensory neurons, AWB and AWC, play essential roles in this behavior. A canonical Gα-protein, together with guanylate cyclases and cGMP-gated channels, is needed for the recognition of food odors. The food-odor-evoked signal is transmitted via glutamatergic neurotransmission from AWC and through AMPA and kainate-like glutamate receptor subunits. In contrast, peptidergic signaling is required to generate preference between different food odors while being dispensable for the recognition of the odors. We show that this regulation is achieved by the neuropeptide NLP-9 produced in AWB, which acts with its putative receptor NPR-18, and by the neuropeptide NLP-1 produced in AWC. In addition, another set of sensory neurons inhibits food-odor preference. These mechanistic logics, together with a previously mapped neural circuit underlying food-odor preference, provide a functional network linking sensory response, transduction, and downstream receptors to process complex olfactory information and generate the appropriate behavioral decision essential for survival. Copyright © 2014 the authors 0270-6474/14/339389-15$15.00/0.

  19. Mechanisms underlying the acute toxicity of fullerene to Daphnia magna: Energy acquisition restriction and oxidative stress. (United States)

    Lv, Xiaohui; Huang, Boming; Zhu, Xiaoshan; Jiang, Yuelu; Chen, Baiyang; Tao, Yi; Zhou, Jin; Cai, Zhonghua


    The toxicity of fullerene (C 60 ) to Daphnia magna has been a subject with increasing concerns. Nevertheless, the underlying mechanisms are still poorly understood. In the present study, we evaluated various aspects of the toxicological impacts of C 60 on daphnia. After a 72-h exposure, the 50% effective concentration of C 60 was 14.9 mg/L for immobilization, and 16.3 mg/L for mortality. Daphnia exhibited a quick uptake of C 60 with a body burden value of 413 μg/g in wet weight in the 1 mg/L C 60 treatment group. Transmission electron microscopy observations revealed that C 60 had mainly accumulated in the guts of organisms. The feeding rate, gut ultra-structural alterations, and digestive enzyme activities of daphnia in response to C 60 treatment were evaluated. The results revealed a significant reduction in the digestion and filtration rates, as well as gut impairment and inhibition of digestive enzymes (cellulose, amylase, trypsin, and β-galactosidase) activity of C 60 exposed daphnia. In addition, the changes in superoxide dismutase (SOD) and malondialdehyde (MDA) levels in daphnia under C 60 exposures were also discovered. These results, for the first time, provide systematic evidence that C 60 caused a restriction in energy acquisition and increased oxidative damage in daphnia, which might be related to the bioaccumulation of C 60 and finally led to the immobility and mortality. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Improvement of Soybean Products Through the Response Mechanism Analysis Using Proteomic Technique. (United States)

    Wang, Xin; Komatsu, Setsuko

    Soybean is rich in protein/vegetable oil and contains several phytochemicals such as isoflavones and phenolic compounds. Because of the predominated nutritional values, soybean is considered as traditional health benefit food. Soybean is a widely cultivated crop; however, its growth and yield are markedly affected by adverse environmental conditions. Proteomic techniques make it feasible to map protein profiles both during soybean growth and under unfavorable conditions. The stress-responsive mechanisms during soybean growth have been uncovered with the help of proteomic studies. In this review, the history of soybean as food and the morphology/physiology of soybean are described. The utilization of proteomics during soybean germination and development is summarized. In addition, the stress-responsive mechanisms explored using proteomic techniques are reviewed in soybean. © 2017 Elsevier Inc. All rights reserved.

  1. Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid

    Directory of Open Access Journals (Sweden)

    Sergio eGiannattasio


    Full Text Available Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.

  2. Molecular mechanisms of Saccharomyces cerevisiae stress adaptation and programmed cell death in response to acetic acid. (United States)

    Giannattasio, Sergio; Guaragnella, Nicoletta; Zdralević, Maša; Marra, Ersilia


    Beyond its classical biotechnological applications such as food and beverage production or as a cell factory, the yeast Saccharomyces cerevisiae is a valuable model organism to study fundamental mechanisms of cell response to stressful environmental changes. Acetic acid is a physiological product of yeast fermentation and it is a well-known food preservative due to its antimicrobial action. Acetic acid has recently been shown to cause yeast cell death and aging. Here we shall focus on the molecular mechanisms of S. cerevisiae stress adaptation and programmed cell death in response to acetic acid. We shall elaborate on the intracellular signaling pathways involved in the cross-talk of pro-survival and pro-death pathways underlying the importance of understanding fundamental aspects of yeast cell homeostasis to improve the performance of a given yeast strain in biotechnological applications.

  3. Interactivity effects in social media marketing on brand engagement: an investigation of underlying mechanisms

    NARCIS (Netherlands)

    Antheunis, M.L.; van Noort, G.; Eisend, M.; Langner, T.


    Although, SNS advertising spending increases, research on SNS campaigning is still underexposed. First, this study aims to investigate the effect of SNS campaign interactivity on the receivers brand engagement, taking four underlying mechanisms into account (brand identification, campaign

  4. 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.


    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)

  5. Responses of Phospholipase D and Antioxidant System to Mechanical Wounding in Postharvest Banana Fruits

    Directory of Open Access Journals (Sweden)

    Li Li


    Full Text Available Banana fruits are susceptible to mechanical damage. The present study was to investigate the responses of phospholipase D (PLD and antioxidant system to mechanical wounding in postharvest banana fruits. During 16 d storage at 25°C and 90% relative humidity, PLD activity in wounded fruits was significantly higher than that in control (without artificial wounding fruits. The higher value of PLD mRNA was found in wounded fruits than in control. PLD mRNA expression reached the highest peak on day 4 in both groups, but it was 2.67 times in wounded fruits compared to control at that time, indicating that PLD gene expression was activated in response to wounding stress. In response to wounding stress, the higher lipoxygenase (LOX activity was observed and malondialdehyde (MDA production was accelerated. The activities of antioxidant enzymes such as superoxide dismutase (SOD, catalase (CAT, peroxidase (POD, and ascorbate peroxidase (APX in wounded fruits were significantly higher than those in control. The concentrations of reactive oxygen species (ROS such as superoxide anion (O2•- and hydrogen peroxide (H2O2 in fruits increased under mechanical wounding. The above results provided a basis for further investigating the mechanism of postharvest banana fruits adapting to environmental stress.

  6. Statistical model for the mechanical behavior of the tissue engineering non-woven fibrous matrices under large deformation. (United States)

    Rizvi, Mohd Suhail; Pal, Anupam


    The fibrous matrices are widely used as scaffolds for the regeneration of load-bearing tissues due to their structural and mechanical similarities with the fibrous components of the extracellular matrix. These scaffolds not only provide the appropriate microenvironment for the residing cells but also act as medium for the transmission of the mechanical stimuli, essential for the tissue regeneration, from macroscopic scale of the scaffolds to the microscopic scale of cells. The requirement of the mechanical loading for the tissue regeneration requires the fibrous scaffolds to be able to sustain the complex three-dimensional mechanical loading conditions. In order to gain insight into the mechanical behavior of the fibrous matrices under large amount of elongation as well as shear, a statistical model has been formulated to study the macroscopic mechanical behavior of the electrospun fibrous matrix and the transmission of the mechanical stimuli from scaffolds to the cells via the constituting fibers. The study establishes the load-deformation relationships for the fibrous matrices for different structural parameters. It also quantifies the changes in the fiber arrangement and tension generated in the fibers with the deformation of the matrix. The model reveals that the tension generated in the fibers on matrix deformation is not homogeneous and hence the cells located in different regions of the fibrous scaffold might experience different mechanical stimuli. The mechanical response of fibrous matrices was also found to be dependent on the aspect ratio of the matrix. Therefore, the model establishes a structure-mechanics interdependence of the fibrous matrices under large deformation, which can be utilized in identifying the appropriate structure and external mechanical loading conditions for the regeneration of load-bearing tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Stress Response Modulation Underlying the Psychobiology of Resilience. (United States)

    Averill, Lynnette A; Averill, Christopher L; Kelmendi, Benjamin; Abdallah, Chadi G; Southwick, Steven M


    This review focuses on the relationship between resilience and the ability to effectively modulate the stress response. Neurobiological and behavioral responses to stress are highly variable. Exposure to a similar stressor can lead to heterogeneous outcomes-manifesting psychopathology in one individual, but having minimal effect, or even enhancing resilience, in another. We highlight aspects of stress response modulation related to early life development and epigenetics, selected neurobiological and neurochemical systems, and a number of emotional, cognitive, psychosocial, and behavioral factors important in resilience. We also briefly discuss interventions with potential to build and promote resilience. Throughout this review, we include evidence from recent preclinical and clinical studies relevant to the psychobiology of resilient stress response modulation. Effective modulation of the stress response is an essential component of resilience and is dependent on a complex interplay of neurobiological and behavioral factors.

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

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


    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.

  9. Toxicological responses in alfalfa ( Medicago sativa ) under joint ...

    African Journals Online (AJOL)

    Joint effects of Cd2+ and napropamide in seeds, roots or leaves of alfalfa were investigated under different treatments. It was shown that single stress of Cd2+ or napropamide decreased chlorophyll content after 30 days of treatment in different concentrations. The decrease in chlorophyll content became insignificant under ...

  10. Transcriptional Regulation of Aluminum-Tolerance Genes in Higher Plants: Clarifying the Underlying Molecular Mechanisms

    Directory of Open Access Journals (Sweden)

    Abhijit A. Daspute


    Full Text Available Aluminum (Al rhizotoxicity is one of the major environmental stresses that decrease global food production. Clarifying the molecular mechanisms underlying Al tolerance may contribute to the breeding of Al-tolerant crops. Recent studies identified various Al-tolerance genes. The expression of these genes is inducible by Al. Studies of the major Arabidopsis thaliana Al-tolerance gene, ARABIDOPSIS THALIANA ALUMINUM-ACTIVATED MALATE TRANSPORTER 1 (AtALMT1, which encodes an Al-activated malate transporter, revealed that the Al-inducible expression is regulated by a SENSITIVE TO PROTON RHIXOTOXICITY 1 (STOP1 zinc-finger transcription factor. This system, which involves STOP1 and organic acid transporters, is conserved in diverse plant species. The expression of AtALMT1 is also upregulated by several phytohormones and hydrogen peroxide, suggesting there is crosstalk among the signals involved in the transcriptional regulation of AtALMT1. Additionally, phytohormones and reactive oxygen species (ROS activate various transcriptional responses, including the expression of genes related to increased Al tolerance or the suppression of root growth under Al stress conditions. For example, Al suppressed root growth due to abnormal accumulation of auxin and cytokinin. It activates transcription of TRYPTOPHAN AMINOTRANSFERASE OF ARABIDOPSIS 1 and other phytohormone responsive genes in distal transition zone, which causes suppression of root elongation. On the other hand, overexpression of Al inducible genes for ROS-detoxifying enzymes such as GLUTATHIONE–S-TRANSFERASE, PEROXIDASE, SUPEROXIDE DISMUTASE enhances Al resistance in several plant species. We herein summarize the complex transcriptional regulation of an Al-inducible genes affected by STOP1, phytohormones, and ROS.

  11. 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.


    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


    Directory of Open Access Journals (Sweden)

    M. V. Osikov


    Full Text Available Disorders of immune state in desynchronosis may be associated with reduced concentrations of melatonin in blood, thus being a prerequisite for pharmacological correction of appropriate homeostatic changes. The purpose of this work was to explore some mechanisms of exogenous melatonin actions upon parameters of innate and adaptive immunity in experimental model of desynchronosis under the conditions of LED illumination. The study was performed with 196 adult guinea pigs. Light desynchronosis was produced by day-and-night illumination of the animals having been continued for 30 days. Melatonin was administered applied per os daily at the total dose of 30 mg/kg. A solution of melatonin in isotonic NaCl solution was prepared from the Melaxen drug (INN: melatonin, “Unipharm Inc.,” USA ex tempore. To study innate immunity of blood cells, we determined leukocyte numbers, WBC differential counts, and functional activity of phagocytes, as spontaneous and induced NBT test, as well as engulfment of polystyrene latex particles. Th1-specific immune response was studied according to degree of delayed type hypersensitivity reaction; Th2-dependent response was assessed as the numbers of antibody-forming cells in the spleen of the animals after immunization with allogeneic erythrocytes. Serum concentrations of interleukin 4 (IL-4, interferon-gamma (IFNγ, melatonin, and cortisol were measured by enzyme immunoassay, using the “Immulayt 2000” (USA with guinea pigspecific test systems. It was found that experimental desynchronosis was associated with leukocytosis, lymphoand monocytopenia, activation of oxygen-dependent metabolism of blood phagocytes, suppression of Th1-and Th2-dependent immune response. Desynchronosis was also accompanied by decreased concentrations of serum melatonin, IFNγ and IL-4, along with increased cortisol concentrations. Reduced IFNγ and IL-4 amounts was associated with decreased melatonin concentrations

  13. Microbial Mechanisms Underlying Acidity-induced Reduction in Soil Respiration Under Nitrogen Fertilization (United States)

    Niu, S.; Li, Y.


    Terrestrial ecosystems are receiving increasing amounts of reactive nitrogen (N) due to anthropogenic activities, which largely changes soil respiration and its feedback to climate change. N enrichment can not only increase N availability but also induce soil acidification, both may affect soil microbial activity and root growth with a consequent impact on soil respiration. However, it remains unclear whether elevated N availability or soil acidity has greater impact on soil respiration (Rs). We conducted a manipulative experiment to simulate N enrichment (10 g m-2 yr-1 NH4NO3) and soil acidity (0.552 mol H+ m-2 yr-1 sulfuric acid) and studied their effects on Rs and its components in a temperate forest. Our results showed that soil pH was reduced by 0.2 under N addition or acid addition treatment. Acid addition significantly decreased autotrophic respiration (Ra) and heterotrophic respiration (Rh) by 21.5% and 22.7% in 2014, 34.8% and 21.9% in 2015, respectively, resulting in a reduction of Rs by 22.2% in 2014 and 26.1% in 2015. Nitrogen enrichment reduced Ra, Rh, Rs by 21.9%, 16.2%, 18.6% in 2014 and 22.1%, 5.9%, 11.7% in 2015, respectively. The reductions of Rs and its components were attributable to decrease of fine root biomass, microbial biomass, and cellulose degrading enzymes. N addition did not change microbial community but acid addition increased both fungal and arbuscular mycorrhiza fungi PLFAs, and N plus acid addition significantly enhanced fungal to bacterial ratio. All the hydrolase enzymes were reduced more by soil acidity (43-50%) than nitrogen addition (30-39%). Structural equation model showed that soil acidity played more important role than N availability in reducing soil respiration mainly by changing microbial extracellular enzymes. We therefore suggest that N deposition induced indirect effect of soil acidification on microbial properties is critical and should be taken into account to better understand and predict ecosystem C cycling in

  14. Elucidating the sponge stress response; lipids and fatty acids can facilitate survival under future climate scenarios. (United States)

    Bennett, Holly; Bell, James J; Davy, Simon K; Webster, Nicole S; Francis, David S


    Ocean warming (OW) and ocean acidification (OA) are threatening coral reef ecosystems, with a bleak future forecast for reef-building corals, which are already experiencing global declines in abundance. In contrast, many coral reef sponge species are able to tolerate climate change conditions projected for 2100. To increase our understanding of the mechanisms underpinning this tolerance, we explored the lipid and fatty acid (FA) composition of four sponge species with differing sensitivities to climate change, experimentally exposed to OW and OA levels predicted for 2100, under two CO 2 Representative Concentration Pathways (RCPs). Sponges with greater concentrations of storage lipid, phospholipids, sterols and elevated concentrations of n-3 and n-6 long-chain polyunsaturated FA (LC PUFA), were more resistant to OW. Such biochemical constituents likely contribute to the ability of these sponges to maintain membrane function and cell homeostasis in the face of environmental change. Our results suggest that n-3 and n-6 LC PUFA are important components of the sponge stress response potentially via chain elongation and the eicosanoid stress-signalling pathways. The capacity for sponges to compositionally alter their membrane lipids in response to stress was also explored using a number of specific homeoviscous adaptation (HVA) indicators. This revealed a potential mechanism via which additional CO 2 could facilitate the resistance of phototrophic sponges to thermal stress through an increased synthesis of membrane-stabilising sterols. Finally, OW induced an increase in FA unsaturation in phototrophic sponges but a decrease in heterotrophic species, providing support for a difference in the thermal response pathway between the sponge host and the associated photosymbionts. Here we have shown that sponge lipids and FA are likely to be an important component of the sponge stress response and may play a role in facilitating sponge survival under future climate conditions

  15. Study Under AC Stimulation on Excitement Properties of Weighted Small-World Biological Neural Networks with Side-Restrain Mechanism

    International Nuclear Information System (INIS)

    Yuan Wujie; Luo Xiaoshu; Jiang Pinqun


    In this paper, we propose a new model of weighted small-world biological neural networks based on biophysical Hodgkin-Huxley neurons with side-restrain mechanism. Then we study excitement properties of the model under alternating current (AC) stimulation. The study shows that the excitement properties in the networks are preferably consistent with the behavior properties of a brain nervous system under different AC stimuli, such as refractory period and the brain neural excitement response induced by different intensities of noise and coupling. The results of the study have reference worthiness for the brain nerve electrophysiology and epistemological science.

  16. Plasticity of the MAPK signaling network in response to mechanical stress

    NARCIS (Netherlands)

    Pereira, Andrea M; Tudor, Cicerone; Pouille, Philippe-Alexandre; Shekhar, Shashank; Kanger, Johannes S; Subramaniam, Vinod; Martín-Blanco, Enrique


    Cells display versatile responses to mechanical inputs and recent studies have identified the mitogen-activated protein kinase (MAPK) cascades mediating the biological effects observed upon mechanical stimulation. Although, MAPK pathways can act insulated from each other, several mechanisms

  17. The oxidative response and viable reaction mechanism of the textile dyes by fenton reagent

    International Nuclear Information System (INIS)

    Masooda, Q.; Hijira, T.; Sitara, M.; Sehar, M.; Sundus, A.; Mohsin, A.


    The mechanism of the degradation of the Reactive Red 239 and Reactive Blue 19 by Fenton reagent was studied by advanced oxidation process in aqueous medium. The spectroscopic technique was adopted for the measurements of dye concentration. Moreover they were determined at 540 nm and 590 nm, respectively. Kinetics of the reaction was studied under the effect of concentration of reactive dyes, concentration of oxidant were followed under pseudo first order condition and found to influence the catalytic mechanism. The pH of the medium, vibrant response of several cations and anions and influence of ionic strength on the reaction kinetics were also monitored. Physical evidences for the degradation and mineralization of the dyes were evaluated by Lime water test, Ring Test and TLC test also confirmed the degradation of dye. Inhibitory effects of dyes were observed by CO3-, HCO3-, HPO42-, Cl-, I- Al3+ and Na+. Thermodynamic activation parameters in the oxidation reaction were studied and mode of mechanism was suggested on the basic of these parameters. This study explored the safe and eco friendly degradation of the textile dyes under Pseudo first order rate constant. It was observed that Fenton assisted degradation of the dyes under controlled conditions was found to be favorable for the treatment of textile wastewater. Moreover compared to other chemical methods it is effective and harmless to the environment. (author)

  18. 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

  19. Physiological and agronomical responses of Syrah grapevine under protected cultivation

    Directory of Open Access Journals (Sweden)

    Claudia Rita de Souza


    Full Text Available The performance of Syrah grapevine under protected cultivation with different plastic films was evaluated during 2012 and 2013 seasons in South of Minas Gerais State. Agronomical and physiological measurements were done on eight years old grapevines, grafted onto ‘1103 Paulsen’ rootstock cultivated under uncovered conditions, covered with transparent and with diffuse plastic films. Both plastic covers induced the highest shoot growth rate and specific leaf area. The diffuse plastic induced greater differences on leaf area, pruning weight and leaf chlorophyll content as compared to uncovered vines. Grapevines under diffuse plastic also had the lowest rates of photosynthesis, stomatal conductance and transpiration. Leaf starch, glucose and fructose contents were not affected by treatment, but leaf sucrose was reduced by transparent plastic. The leaf and stem water potential were higher under diffuse plastic. In 2013, grapevines under diffuse plastic showed the highest yields mainly due to decreased rot incidence and increased cluster weight. Furthermore, berries under diffuse plastic showed the highest anthocyanins concentration. The use of diffuse plastic induces more agronomical benefits to produce Syrah grape under protected cultivation.


    Directory of Open Access Journals (Sweden)

    Iosif TEMPEA


    Full Text Available The paper presents a synthesis of the Double SCARA Robot modelling, leading to an optimal solution, from workspace point of view, as well as precision and stability of the endeffector in performing the planned trajectory. For the design of the final mechanism CATIA software has been used, as well as NASTRAN/PATRAN software, for the mechanism analysis under mechanical and thermal loads.

  1. The effects of different size gold nanoparticles on mechanical properties of vascular smooth muscle cells under mechanical stretching (United States)

    Kieu, Tri Minh

    Nanotechnology is an emerging and promising frontier for medicine and biomedical research due to its potential for applications such as drug delivery, imaging enhancement, and cancer treatment. While these materials may possess significant possibilities, the effects of these particles in the body and how the particles affect the cells is not fully understood. In this study, vascular smooth muscle cells (VSMCs) will be exposed to 5 and 20 nm diameter citrate AuNPs under mechanical conditions. The cytotoxicity properties of these particles will be investigated using LDH and MTT assays. Atomic force microscopy will be used to study how the size of the nanoparticles affect the mechanical properties of the VSMCs. Immunofluorescence staining for alpha actin will also be performed to enhance understanding of the phenotypic shift. The LDH and MTT cytotoxicity assay results demonstrated that neither 5 nor 20 nm diameter nanoparticles are cytotoxic to the cells. However, the mechanical properties and cell morphology of the VSMCs was altered. Under static conditions, both AuNP treatments decreased the mechanical properties of the cells. The size of the nanoparticles had a softening effect on elastic modulus of the cell and sign of a synthetic phenotype was observed. The VSMCs subjected to mechanical stretching exhibited higher elastic modulus compared to the static experimental groups. Again, both AuNPs treatments decreased the mechanical properties of the cells and signs of more synthetic phenotype was seen. However, the size of the nanoparticles did not have any influence on cell's elastic modulus unlike the static treated cells. The mechanical testing condition provided a better look at how these particles would affect the cells in vivo. While the nanoparticles are not cytotoxic to the VSMCs, they are altering the mechanical properties and phenotype of the cell.

  2. Human operant learning under concurrent reinforcement of response variability

    NARCIS (Netherlands)

    Maes, J.H.R.; Goot, M.H. van der


    This study asked whether the concurrent reinforcement of behavioral variability facilitates learning to emit a difficult target response. Sixty students repeatedly pressed sequences of keys, with an originally infrequently occurring target sequence consistently being followed by positive feedback.

  3. Peak earthquake response of structures under multi-component excitations (United States)

    Song, Jianwei; Liang, Zach; Chu, Yi-Lun; Lee, George C.


    Accurate estimation of the peak seismic responses of structures is important in earthquake resistant design. The internal force distributions and the seismic responses of structures are quite complex, since ground motions are multi-directional. One key issue is the uncertainty of the incident angle between the directions of ground motion and the reference axes of the structure. Different assumed seismic incidences can result in different peak values within the scope of design spectrum analysis for a given structure and earthquake ground motion record combination. Using time history analysis to determine the maximum structural responses excited by a given earthquake record requires repetitive calculations to determine the critical incident angle. This paper presents a transformation approach for relatively accurate and rapid determination of the maximum peak responses of a linear structure subjected to three-dimensional excitations within all possible seismic incident angles. The responses can be deformations, internal forces, strains and so on. An irregular building structure model is established using SAP2000 program. Several typical earthquake records and an artificial white noise are applied to the structure model to illustrate the variation of the maximum structural responses for different incident angles. Numerical results show that for many structural parameters, the variation can be greater than 100%. This method can be directly applied to time history analysis of structures using existing computer software to determine the peak responses without carrying out the analyses for all possible incident angles. It can also be used to verify and/or modify aseismic designs by using response spectrum analysis.

  4. Boron deficiency in woody plants: various responses and tolerance mechanisms

    Directory of Open Access Journals (Sweden)

    Nannan eWang


    Full Text Available Boron (B is an essential microelement for higher plants, and its deficiency is widespread around the world and constrains the productivity of both agriculture and forestry. In the last decades, accumulating studies on model or herbaceous plants have contributed greatly to our understanding of the complex network of B-deficiency responses and mechanisms for tolerance. In woody plants, however, only a few studies have been conducted and they are not well synthesised. Trees have a larger body size, longer lifespan and more B reserves than do herbaceous plants, indicating that woody species might undergo long-term or mild B deficiency more commonly and that a more complicated B reserves must accordingly be developed to cope with B deficiency. In addition, the highly heterozygous genetic background of tree species suggests that they may have a more complicated mechanism of response and tolerance to B deficiency than do model plants.B-deficient trees usually exhibit two key visible symptoms: depression of growing points (root tip, bud, flower, and young leaf and deformity of organs (root, shoot, leaf, and fruit. These symptoms may be ascribed to B functioning in the cell wall and membrane, and B deficiency results in damage to vascular tissues and the suppression of both B and water transport. B deficiency also affects metabolic processes, such as increased lignin and phenol, and decreased leaf photosynthesis. These negative effects will influence the quality and quantity of wood, fruit and other agricultural products.B efficiency probably originates from a combined effect of three processes: B uptake, B translocation and retranslocation, and B utilization. Root morphology and mycorrhiza can affect the B uptake efficiency of trees. During B translocation from the root to shoot, differences in B concentration between root cell saps and xylem exudates, as well as water use efficiency, may play key roles in tolerance to B deficiency. In addition, B

  5. Response of bread wheat genotypes to drought simulation under a ...

    African Journals Online (AJOL)

    ASALS) of Kenya, which consist of 83% of total land area, can provide alternative agricultural land for expansion. To reduce cost of dryland research, simulated drought under a rain shelter offers a good alternative for screening because marginal ...

  6. Exertional rhabdomyolysis: physiological response or manifestation of an underlying myopathy?

    NARCIS (Netherlands)

    Scalco, R.S.; Snoeck, M.; Quinlivan, R.; Treves, S.; Laforet, P.; Jungbluth, H.; Voermans, N.C.


    Exertional rhabdomyolysis is characterised by muscle breakdown associated with strenuous exercise or normal exercise under extreme circumstances. Key features are severe muscle pain and sudden transient elevation of serum creatine kinase (CK) levels with or without associated myoglobinuria. Mild

  7. Neuronal response impedance mechanism implementing cooperative networks with low firing rates and μs precision. (United States)

    Vardi, Roni; Goldental, Amir; Marmari, Hagar; Brama, Haya; Stern, Edward A; Sardi, Shira; Sabo, Pinhas; Kanter, Ido


    Realizations of low firing rates in neural networks usually require globally balanced distributions among excitatory and inhibitory links, while feasibility of temporal coding is limited by neuronal millisecond precision. We show that cooperation, governing global network features, emerges through nodal properties, as opposed to link distributions. Using in vitro and in vivo experiments we demonstrate microsecond precision of neuronal response timings under low stimulation frequencies, whereas moderate frequencies result in a chaotic neuronal phase characterized by degraded precision. Above a critical stimulation frequency, which varies among neurons, response failures were found to emerge stochastically such that the neuron functions as a low pass filter, saturating the average inter-spike-interval. This intrinsic neuronal response impedance mechanism leads to cooperation on a network level, such that firing rates are suppressed toward the lowest neuronal critical frequency simultaneously with neuronal microsecond precision. Our findings open up opportunities of controlling global features of network dynamics through few nodes with extreme properties.

  8. Analysis of thermomechanical response of polycrystalline HMX under impact loading through mesoscale simulations

    Directory of Open Access Journals (Sweden)

    D. B. Hardin


    Full Text Available We investigate the response of polycrystalline HMX (Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine under impact loading through a 3-dimensional mesoscale model that explicitly accounts for anisotropic elasticity, crystalline plasticity, and heat conduction. This model is used to quantify the variability in temperature and stress fields due to random distributions of the orientations of crystalline grains in HMX under the loading scenarios considered. The simulations carried out concern the response of fully dense HMX polycrystalline ensembles under impact loading at imposed boundary velocities from 50 to 400 m/s. The polycrystalline ensemble studied consists of a geometrically arranged distribution of bi-modally sized and shaped grains. To quantify the effect of crystalline slip, two models with different numbers of available slip systems are used, reflecting differing characterizations of the slip systems of the HMX molecular crystal in the literature. The effects of microstructure and anisotropy on the distribution of heating and stress evolution are investigated. The results obtained indicate that crystalline response anisotropy at the microstructure level plays an important role in influencing both the overall response and the localization of stress and temperature. The overall longitudinal stress is up to 16% higher and the average temperature rise is only half in the material with fewer potential slip systems compared to those in the material with more available slip systems. Local stresses can be as high as twice the average stresses. The results show that crystalline anisotropy induces significant heterogeneities in both mechanical and thermal fields that previously have been neglected in the analyses of the behavior of HMX-based energetic materials.

  9. Effect of surface loading on the hydro-mechanical response of a tunnel in saturated ground

    Directory of Open Access Journals (Sweden)

    Simon Heru Prassetyo


    Full Text Available The design of underground spaces in urban areas must account not only for the current overburden load but also for future surface loads, such as from construction of high-rise buildings above underground structures. In saturated ground, the surface load will generate an additional mechanical response through stress changes and ground displacement, as well as a hydraulic response through pore pressure changes. These hydro-mechanical (H-M changes can severely influence tunnel stability. This paper examines the effect of surface loading on the H-M response of a typical horseshoe-shaped tunnel in saturated ground. Two tunnel models were created in the computer code Fast Lagrangian Analysis of Continua (FLAC. One model represented weak and low permeability ground (stiff clay, and the other represented strong and high permeability ground (weathered granite. Each of the models was run under two liner permeabilities: permeable and impermeable. Two main cases were compared. In Case 1, the surface load was applied 10 years after tunnel construction. In Case 2, the surface load was applied after the steady state pore pressure condition was achieved. The simulation results show that tunnels with impermeable liners experienced the most severe influence from the surface loading, with high pore pressures, large inward displacement around the tunnels, and high bending moments in the liner. In addition, the severity of the response increased toward steady state. This induced H-M response was worse for tunnels in clay than for those in granite. Furthermore, the long-term liner stabilities in Case 1 and Case 2 were similar, indicating that the influence of the length of time between when the tunnel was completed and when the surface load was applied was negligible. These findings suggest that under surface loading, in addition to the ground strength, tunnel stability in saturated ground is largely influenced by liner permeability and the long-term H-M response of

  10. Comparison of mechanical and thermodynamic properties of fcc and bcc titanium under high pressure (United States)

    Zhang, Yongmei; Zhao, Yuhong; Hou, Hua; Wen, Zhiqin; Duan, Meiling


    The mechanical and thermodynamic properties of fcc and bcc Ti have been discussed based on the first-principles calculation combined with the quasi-harmonic Debye model. We find that the bulk modulus B, shear modulus G, Young’s modulus E of fcc Ti are larger, while Poisson’s ratio σ is smaller than that of bcc Ti under the same pressure, which indicates the better mechanical performance of fcc Ti compared with bcc Ti. The values of B/G and σ indicate that mechanically stable fcc structure is much less ductile than the bcc structure, while mechanically metastable fcc structure has better ductility than stable bcc structure under high pressure. The normalized volume, isothermal bulk modulus, heat capacity, volume thermal expansion coefficient and Debye temperature under pressure and temperature for fcc and bcc Ti are predicted.

  11. Heavy Metal Stress and Some Mechanisms of Plant Defense Response

    Directory of Open Access Journals (Sweden)

    Abolghassem Emamverdian


    Full Text Available Unprecedented bioaccumulation and biomagnification of heavy metals (HMs in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS. This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs or metallothioneins (MTs metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants.

  12. Heavy Metal Stress and Some Mechanisms of Plant Defense Response (United States)

    Emamverdian, Abolghassem; Ding, Yulong; Mokhberdoran, Farzad; Xie, Yinfeng


    Unprecedented bioaccumulation and biomagnification of heavy metals (HMs) in the environment have become a dilemma for all living organisms including plants. HMs at toxic levels have the capability to interact with several vital cellular biomolecules such as nuclear proteins and DNA, leading to excessive augmentation of reactive oxygen species (ROS). This would inflict serious morphological, metabolic, and physiological anomalies in plants ranging from chlorosis of shoot to lipid peroxidation and protein degradation. In response, plants are equipped with a repertoire of mechanisms to counteract heavy metal (HM) toxicity. The key elements of these are chelating metals by forming phytochelatins (PCs) or metallothioneins (MTs) metal complex at the intra- and intercellular level, which is followed by the removal of HM ions from sensitive sites or vacuolar sequestration of ligand-metal complex. Nonenzymatically synthesized compounds such as proline (Pro) are able to strengthen metal-detoxification capacity of intracellular antioxidant enzymes. Another important additive component of plant defense system is symbiotic association with arbuscular mycorrhizal (AM) fungi. AM can effectively immobilize HMs and reduce their uptake by host plants via binding metal ions to hyphal cell wall and excreting several extracellular biomolecules. Additionally, AM fungi can enhance activities of antioxidant defense machinery of plants. PMID:25688377

  13. Fast-Response electric drives of Mechanical Engineering objects (United States)

    Doykina, L. A.; Bukhanov, S. S.; Gryzlov, A. A.


    The article gives a solution to the problem of increasing the speed in the electrical drives of machine-building enterprises due to the application of a structure with ISC control. In this case, it is possible to get rid of the speed sensors. It is noted that in this case no circulating pulsations are applied to the input of the control system, caused by a non-identical interface between the sensor and the shaft of the operating mechanism. For detailed modeling, a mathematical model of an electric drive with distributed parameters was proposed. The calculation of such system was carried out by the finite element method. Taking into account the distributed characteristic of the system parameters allowed one to take into account the discrete nature of the electric machine’s work. The simulation results showed that the response time in the control circuit is estimated at a time constant of 0.0015, which is about twice as fast as in traditional vector control schemes.

  14. 40 CFR 92.407 - Responsibility under other legal provisions preserved. (United States)


    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Responsibility under other legal... Emission-Related Defect Reporting Requirements, Voluntary Emission Recall Program § 92.407 Responsibility under other legal provisions preserved. The filing of any report under the provisions of this subpart...

  15. 40 CFR 94.407 - Responsibility under other legal provisions preserved. (United States)


    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Responsibility under other legal...-related Defect Reporting Requirements, Voluntary Emission Recall Program § 94.407 Responsibility under other legal provisions preserved. The filing of any report under the provisions of this subpart shall...

  16. 40 CFR 91.906 - Responsibility under other legal provisions preserved. (United States)


    ... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Responsibility under other legal... Defect Reporting Requirements, Voluntary Emission Recall Program § 91.906 Responsibility under other legal provisions preserved. The filing of any report under the provisions of this subpart will not...

  17. 34 CFR 76.789 - What are an SEA's responsibilities under this subpart? (United States)


    ... 34 Education 1 2010-07-01 2010-07-01 false What are an SEA's responsibilities under this subpart... for Notice and Information § 76.789 What are an SEA's responsibilities under this subpart? (a... the SEA's allocation under the applicable covered program for the academic year in which the charter...

  18. 30 CFR 285.102 - What are MMS's responsibilities under this part? (United States)


    ... 30 Mineral Resources 2 2010-07-01 2010-07-01 false What are MMS's responsibilities under this part... Provisions § 285.102 What are MMS's responsibilities under this part? (a) The MMS will ensure that any..., monitoring, and enforcement of activities authorized by a lease or grant under this part. (b) The MMS will...

  19. Association between neuroticism and amygdala responsivity emerges under stressful conditions

    NARCIS (Netherlands)

    Everaerd, Daphne; Klumpers, Floris; van Wingen, Guido; Tendolkar, Indira; Fernández, Guillén


    Increased amygdala reactivity in response to salient stimuli is seen in patients with affective disorders, in healthy subjects at risk for these disorders, and in stressed individuals, making it a prime target for mechanistic studies into the pathophysiology of affective disorders. However, whereas

  20. Deformation and damage modes of deep argillaceous rocks under hydro-mechanical stresses

    International Nuclear Information System (INIS)

    Vales, F.


    An experimental identification of the hydro-mechanical behaviour of an argillite rock is proposed within a multi-scale approach. In particular, interest is focused on the spatial and temporal localization of strain and damage in a specimen during hydro-mechanical loading. Firstly, we describe the techniques used to follow the rock evolutions under loading, and in particular Digital Images Correlation (DIC), Acoustic Emission, microscopy and mercury intrusion porosimetry. Measurement errors and device limitations are discussed. The studied material is the Callovo-Oxfordian indurated argillaceous rock (or argillite) of the Bure site where ANDRA has built an underground research laboratory to study the radioactive waste storage. Petrophysical characterizations and microstructural observations by optical and scanning electron microscopy provide an identification of the constitutive phase and a characterization of their spatial distribution and typical sizes. Argillite can be described as a composite structure with a continuous clay matrix and embedded mineral particles, essentially quartz and carbonates. The typical size of these particles ranges from a few micrometers to a few hundreds micrometers, with an average close to 50 μ.m. The general experimental procedure combines two steps: in a fist time, imposed suctions bring samples to a given degree of water saturation, and, in a second time, uniaxial mechanical compression tests are performed. To understand the evolutions of the material under hydric and mechanical loading, samples are instrumented with standard measurement techniques, but also with Digital Image Correlation, at both the global scale of the sample and the local scale of the composite microstructure, and with Acoustic Emissions recording. Moisture transfers are imposed by controlled suctions on the range of 150 to 2.8 MPa, corresponding to the relative humidity range of 32 to 98%RH. During pure hydric solicitation, the changes in physical parameters

  1. Response of sunflower hybrids to management practices under ...

    African Journals Online (AJOL)



    Apr 4, 2011 ... practices under irrigated arid-environment. H. Ali, M. Riaz, A. Zahoor and S. ... photo-synthetically active radiation (PAR), yield components and oil contents to planting geometries and nitrogen rates. Experiment 1 ... be fairly stable (Monteith, 1977; Gallagher and Biscoe,. 1978; Kiniry et al., 1989; Hall et al., ...

  2. Nonlinear Dynamics Response of a Planar Mechanism with Two Driving Links and Prismatic Pair Clearance

    Directory of Open Access Journals (Sweden)

    Lijuan Wu


    Full Text Available The influence of the joint clearance on the dynamic response of a planar mechanism with two driving links and prismatic pair clearance is investigated under variable input speeds of the system. The simulation model was built with a nonlinear impact model. The normal contact force is characterized by Hertz contact theory and an energy dissipation term. A tangential friction force is involved in the simulation model based on Coulomb’s friction law. The simulation results indicate that the largest Lyapunov exponents are dependent on the clearance size and the input speed.

  3. Dynamic response of the target container under pulsed heating

    Energy Technology Data Exchange (ETDEWEB)

    Liping Ni [Paul Scherrer Inst. (PSI), Villigen (Switzerland)


    The structural mechanics of a liquid target container for pulsed spallation sources have been simulated using both a commercial code and a PSI-developed program. Results from the transient thermal-structural analysis showed that, due to inertia effects, the dynamic stress in the target container is contributed mainly from direct heating in the initial time stage, and later from the pressure wave in the target liquid once it reaches the wall. (author) figs., tab., refs.

  4. Mechanical behaviour and microstructural evolution of alloy 800H under biaxial cyclic loading

    International Nuclear Information System (INIS)

    Dolabella Portella, P.; Feng Jiao; Oesterle, W.; Ziebs, J.


    The mechanical behaviour of alloy 800H under biaxial cyclic loading was investigated at room temperature and at 800 C. The low-cycle fatigue experiments were carried out using tubular specimens under axial and torsional loading with constant total equivalent strain amplitude following either proportional or nonproportional loading paths. The cyclic hardening observed under nonproportional loading was clearly higher than that under proportional loading. The extra hardening due to the nonproportional loading path was more pronounced at room temperature. The evolution of the dislocation structure was characterized by transmission electron microscopy of specimens after interrupted fatigue tests. The changes in the dislocation structure and the precipitation phenomena are in accordance with the observed mechanical behaviour of the specimens. Twinning was observed in very few grains of some specimens and does not influence the extra hardening under nonproportional loading, martensite was not detected in any specimen. (orig.)

  5. Conceptual approaches to the formation the mechanism of enterprises social responsibility stimulation


    Ohorodnikova, Natalia


    The article defines the economic content of the enterprise social responsibility incentive mechanism, the concept of its perfection. There are formulated the purpose and objectives of the proposed mechanisms, sounded principles of its formation. As tools of the enterprise social responsibility incentive mechanism, it is advised to use: methods of corporate social responsibility stimulating, a model of corporate strategy in the context of implementing the practice of social responsibility in t...

  6. Cardiovascular responses to strength training under occlusive training


    Sergio Benito Hernández; Iván Chulvi Medrano


    Occlusive strength training is shown like an alternative to intensive training. Present study shown cardiovascular responses to this training. 10 subjects were subjected to two occlusion training protocols, differentiated by the weight lifted (30 % of maximum weight lifted, post30, and 70 % of maximum weight lifted, post70). The values of arterial systolic tension (TAS), diastolic (TAD) and heart rate (FC) were recorded. The results showing a significant decline in TAS and TAD after post30 of...

  7. Cognitive aspects underlying pain and neuro-physiological responses


    Helen Bedinoto Durgante


    La Psicología de la Salud ha investigado intensamente los posibles factores cognitivos implicados en, o responsables de, bienestar físico, emocional y comportamental de los individuos. Los estudios sobre el dolor se abordaron como un factor importante de preocupación en este ámbito, debido a que la construcción depende de diferencias individuales y susceptibles de poseer interpretaciones de los sujetos. Investigaciones han identificado que diferentes mecanismos cognitivos juegan un papel...

  8. Surviving a Dry Future: Abscisic Acid (ABA-Mediated Plant Mechanisms for Conserving Water under Low Humidity

    Directory of Open Access Journals (Sweden)

    Frances C. Sussmilch


    Full Text Available Angiosperms are able to respond rapidly to the first sign of dry conditions, a decrease in air humidity, more accurately described as an increase in the vapor pressure deficit between the leaf and the atmosphere (VPD, by abscisic acid (ABA-mediated stomatal closure. The genes underlying this response offer valuable candidates for targeted selection of crop varieties with improved drought tolerance, a critical goal for current plant breeding programs, to maximize crop production in drier and increasingly marginalized environments, and meet the demands of a growing population in the face of a changing climate. Here, we review current understanding of the genetic mechanisms underpinning ABA-mediated stomatal closure, a key means for conserving water under dry conditions, examine how these mechanisms evolved, and discuss what remains to be investigated.

  9. Provider Behavior Under Global Budgeting and Policy Responses

    Directory of Open Access Journals (Sweden)

    Chao-Kai Chang MD, PhD


    Full Text Available Third-party payer systems are consistently associated with health care cost escalation. Taiwan’s single-payer, universal coverage National Health Insurance (NHI adopted global budgeting (GB to achieve cost control. This study captures ophthalmologists’ response to GB, specifically service volume changes and service substitution between low-revenue and high-revenue services following GB implementation, the subsequent Bureau of NHI policy response, and the policy impact. De-identified eye clinic claims data for the years 2000, 2005, and 2007 were analyzed to study the changes in Simple Claim Form (SCF claims versus Special Case Claims (SCCs. The 3 study years represent the pre-GB period, post-GB but prior to region-wise service cap implementation period, and the post-service cap period, respectively. Repeated measures multilevel regression analysis was used to study the changes adjusting for clinic characteristics and competition within each health care market. SCF service volume (low-revenue, fixed-price patient visits remained constant throughout the study period, but SCCs (covering services involving variable provider effort and resource use with flexibility for discretionary billing increased in 2005 with no further change in 2007. The latter is attributable to a 30% cap negotiated by the NHI Bureau with the ophthalmology association and enforced by the association. This study demonstrates that GB deployed with ongoing monitoring and timely policy responses that are designed in collaboration with professional stakeholders can contain costs in a health insurance–financed health care system.

  10. Tuning of redox regulatory mechanisms, reactive oxygen species and redox homeostasis under salinity stress

    Directory of Open Access Journals (Sweden)

    Hossain eSazzad


    Full Text Available Soil salinity is a crucial environmental constraint which limits biomass production at many sites on a global scale. Saline growth conditions cause osmotic and ionic imbalances, oxidative stress and perturb metabolism, e.g. the photosynthetic electron flow. The plant ability to tolerate salinity is determined by multiple biochemical and physiological mechanisms protecting cell functions, in particular by regulating proper water relations and maintaining ion homeostasis. Redox homeostasis is a fundamental cell property. Its regulation includes control of reactive oxygen species (ROS generation, sensing deviation from and readjustment of the cellular redox state. All these redox related functions have been recognized as decisive factors in salinity acclimation and adaptation. This review focuses on the core response of plants to overcome the challenges of salinity stress through regulation of ROS generation and detoxification systems and to maintain redox homeostasis. Emphasis is given to the role of NADH oxidase (RBOH, alternative oxidase (AOX, the plastid terminal oxidase (PTOX and the malate valve with the malate dehydrogenase isoforms under salt stress. Overwhelming evidence assigns an essential auxiliary function of ROS and redox homeostasis to salinity acclimation of plants.

  11. Studies of Neuronal Gene Regulation Controlling the Molecular Mechanisms Underlying Neural Plasticity. (United States)

    Fukuchi, Mamoru


    The regulation of the development and function of the nervous system is not preprogramed but responds to environmental stimuli to change neural development and function flexibly. This neural plasticity is a characteristic property of the nervous system. For example, strong synaptic activation evoked by environmental stimuli leads to changes in synaptic functions (known as synaptic plasticity). Long-lasting synaptic plasticity is one of the molecular mechanisms underlying long-term learning and memory. Since discovering the role of the transcription factor cAMP-response element-binding protein in learning and memory, it has been widely accepted that gene regulation in neurons contributes to long-lasting changes in neural functions. However, it remains unclear how synaptic activation is converted into gene regulation that results in long-lasting neural functions like long-term memory. We continue to address this question. This review introduces our recent findings on the gene regulation of brain-derived neurotrophic factor and discusses how regulation of the gene participates in long-lasting changes in neural functions.

  12. [Spectrometric characteristics and underlying mechanisms of protective effects of selenium on Spirulina platensis against oxidative stress]. (United States)

    Wu, Hua-lian; Chen, Tian-feng; Yin, Xi; Zheng, Wen-jie


    To investigate the possibility and the underlying mechanisms of sodium selenite as antagonist for oxidative stress, the authors examined the effects of pretreatment with selenium on the growth, morphology, spectrometric characteristics and content of reactive oxygen species (ROS) in Spirulina platensis (S. platensis) exposed to H2O2 stress for 24 h in the present study. The results showed that H2O2 induced obvious inhibition of growth and serious morphological damage. The intensity of absorbance peak at 440 nm increased, whereas the peaks at 620 and 680 nm decreased after exposed to H2O2. The emission and excitation spectrum of S. platensis decreased dramatically after H2O2 treatment, and the emission peak from phycocyanin exhibited blue-shift from 660 to 650 nm. The results of FTIR analysis showed that the positions of transmission peaks had no shift, but the relative intensity of characteristic bands from protein and polypeptides including amide I and amide II decreased. Furthermore, the intracellular ROS generation in S. platensis increased significantly in response to H2O2 treatment. In contrast, pretreatments of the cells with selenium for 24 h significantly prevented the H2O2-induced oxidative damages in a dose-dependent manner. Taken together, our results indicate that pretreatments with selenium could prevent ROS overproduction in S. platensis and improve its antioxidant ability. Moreover, selenium could also reduce the effects of free radicals on energy harvest and energy transfer in S. platensis that play vital roles in its photosynthesis.

  13. Molecular mechanisms of the yeast adaptive response and tolerance to stresses encountered during ethanol fermentation. (United States)

    Auesukaree, Choowong


    During ethanol fermentation, yeast cells encounter various stresses including sugar substrates-induced high osmolarity, increased ethanol concentration, oxygen metabolism-derived reactive oxygen species (ROS), and elevated temperature. To cope with these fermentation-associated stresses, appropriate adaptive responses are required to prevent stress-induced cellular dysfunctions and to acquire stress tolerances. This review will focus on the cellular effects of these stresses, molecular basis of the adaptive response to each stress, and the cellular mechanisms contributing to stress tolerance. Since a single stress can cause diverse effects, including specific and non-specific effects, both specific and general stress responses are needed for achieving comprehensive protection. For instance, the high-osmolarity glycerol (HOG) pathway and the Yap1/Skn7-mediated pathways are specifically involved in responses to osmotic and oxidative stresses, respectively. On the other hand, due to the common effect of these stresses on disturbing protein structures, the upregulation of heat shock proteins (HSPs) and trehalose is induced upon exposures to all of these stresses. A better understanding of molecular mechanisms underlying yeast tolerance to these fermentation-associated stresses is essential for improvement of yeast stress tolerance by genetic engineering approaches. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

  14. Common and Distinct Neural Mechanisms of Attentional Switching and Response Conflict (United States)

    Kim, Chobok; Johnson, Nathan F.; Gold, Brian T.


    The human capacities for overcoming prepotent actions and flexibly switching between tasks represent cornerstones of cognitive control. Functional neuroimaging has implicated a diverse set of brain regions contributing to each of these cognitive control processes. However, the extent to which attentional switching and response conflict draw on shared or distinct neural mechanisms remains unclear. The current study examined the neural correlates of response conflict and attentional switching using event-related functional magnetic resonance imaging (fMRI) and a fully randomized 2×2 design. We manipulated an arrow-word version of the Stroop task to measure conflict and switching in the context of a single task decision, in response to a common set of stimuli. Under these common conditions, both behavioral and imaging data showed significant main effects of conflict and switching but no interaction. However, conjunction analyses identified frontal regions involved in both switching and response conflict, including the dorsal anterior cingulate cortex (dACC) and left inferior frontal junction. In addition, connectivity analyses demonstrated task-dependent functional connectivity patterns between dACC and inferior temporal cortex for attentional switching and between dACC and posterior parietal cortex for response conflict. These results suggest that the brain makes use of shared frontal regions, but can dynamically modulate the connectivity patterns of some of those regions, to deal with attentional switching and response conflict. PMID:22750124

  15. Mechanisms Underlying Serotonergic Excitation of Callosal Projection Neurons in the Mouse Medial Prefrontal Cortex

    Directory of Open Access Journals (Sweden)

    Emily K. Stephens


    Full Text Available Serotonin (5-HT selectively excites subpopulations of pyramidal neurons in the neocortex via activation of 5-HT2A (2A receptors coupled to Gq subtype G-protein alpha subunits. Gq-mediated excitatory responses have been attributed primarily to suppression of potassium conductances, including those mediated by KV7 potassium channels (i.e., the M-current, or activation of non-specific cation conductances that underlie calcium-dependent afterdepolarizations (ADPs. However, 2A-dependent excitation of cortical neurons has not been extensively studied, and no consensus exists regarding the underlying ionic effector(s involved. In layer 5 of the mouse medial prefrontal cortex, we tested potential mechanisms of serotonergic excitation in commissural/callosal (COM projection neurons, a subpopulation of pyramidal neurons that exhibits 2A-dependent excitation in response to 5-HT. In baseline conditions, 5-HT enhanced the rate of action potential generation in COM neurons experiencing suprathreshold somatic current injection. This serotonergic excitation was occluded by activation of muscarinic acetylcholine (ACh receptors, confirming that 5-HT acts via the same Gq-signaling cascades engaged by ACh. Like ACh, 5-HT promoted the generation of calcium-dependent ADPs following spike trains. However, calcium was not necessary for serotonergic excitation, as responses to 5-HT were enhanced (by >100%, rather than reduced, by chelation of intracellular calcium with 10 mM BAPTA. This suggests intracellular calcium negatively regulates additional ionic conductances gated by 2A receptors. Removal of extracellular calcium had no effect when intracellular calcium signaling was intact, but suppressed 5-HT response amplitudes, by about 50%, when BAPTA was included in patch pipettes. This suggests that 2A excitation involves activation of a non-specific cation conductance that is both calcium-sensitive and calcium-permeable. M-current suppression was found to be a third

  16. Human mesostriatal response tracks motivational tendencies under naturalistic goal conflict. (United States)

    Gonen, Tal; Soreq, Eyal; Eldar, Eran; Ben-Simon, Eti; Raz, Gal; Hendler, Talma


    Goal conflict situations, involving the simultaneous presence of reward and punishment, occur commonly in real life, and reflect well-known individual differences in the behavioral tendency to approach or avoid. However, despite accumulating neural depiction of motivational processing, the investigation of naturalistic approach behavior and its interplay with individual tendencies is remarkably lacking. We developed a novel ecological interactive scenario which triggers motivational behavior under high or low goal conflict conditions. Fifty-five healthy subjects played the game during a functional magnetic resonance imaging scan. A machine-learning approach was applied to classify approach/avoidance behaviors during the game. To achieve an independent measure of individual tendencies, an integrative profile was composed from three established theoretical models. Results demonstrated that approach under high relative to low conflict involved increased activity in the ventral tegmental area (VTA), peri-aquaductal gray, ventral striatum (VS) and precuneus. Notably, only VS and VTA activations during high conflict discriminated between approach/avoidance personality profiles, suggesting that the relationship between individual personality and naturalistic motivational tendencies is uniquely associated with the mesostriatal pathway. VTA-VS further demonstrated stronger coupling during high vs low conflict. These findings are the first to unravel the multilevel relationship among personality profile, approach tendencies in naturalistic set-up and their underlying neural manifestation, thus enabling new avenues for investigating approach-related psychopathologies. © The Author (2016). Published by Oxford University Press. For Permissions, please email:

  17. Mechanisms underlying the augmentation of phenylbiguanide and capsaicin induced cardiorespiratory reflexes by Mesobuthus tamulus venom. (United States)

    Dutta, Abhaya; Akella, Aparna; Deshpande, Shripad B


    Phenylbiguanide (PBG) and capsaicin evoke cardiorespiratory reflexes utilizing two separate pathways. It is known that Indian Red Scorpion (Mesobuthus tumulus; MBT) venom augments PBG (5-HT(3)) responses but, the effect of MBT venom on capsaicin (TRPV1)-induced response is not known. Therefore, the present study was undertaken to ascertain whether MBT venom also augments the capsaicin-induced reflex responses involving mechanisms similar to PBG. Experiments were performed on anaesthetized adult rats. Blood pressure, respiratory excursions and ECG were recorded. At the end of each experiment pulmonary water content was determined. PBG (10 μg/kg) produced hypotension, bradycardia and apnoea-bradypnoea. Capsaicin (10 μg/kg) also produced hypotension, bradycardia and apnoea-bradypnoea. MBT venom (100 μg/kg) augmented PBG as well as capsaicin-induced responses and produced pulmonary oedema (increased pulmonary water content). Prostaglandin synthase inhibitor (indomethacin; 10 mg/kg) blocked the venom-induced augmentation of PBG and capsaicin reflexes. Kinin synthase inhibitor (aprotinin; 6000 KIU) and guanylate cyclase (GC) inhibitor (methylene blue; 5 mg/kg) blocked the venom-induced augmentation of PBG response but not the capsaicin response. However, pulmonary oedema was blocked by these antagonists. Phosphodiesterase V inhibitor (sildenafil; 100 μg/kg) augmented the PBG response but not the capsaicin response, though pulmonary oedema was seen in both the groups. The present results indicate that MBT venom also augments the capsaicin-induced responses. The augmentation of capsaicin response involves PGs and pulmonary oedema-independent mechanisms whereas, the augmentation of PBG response involves kinin mediated GC-cGMP pathway and pulmonary oedema-dependent mechanisms. Copyright © 2012 Elsevier Ltd. All rights reserved.

  18. Unraveling the Mechanism Underlying the Glycosylation and Methylation of Anthocyanins in Peach1[C][W (United States)

    Cheng, Jun; Wei, Guochao; Zhou, Hui; Gu, Chao; Vimolmangkang, Sornkanok; Liao, Liao; Han, Yuepeng


    Modification of anthocyanin plays an important role in increasing its stability in plants. Here, six anthocyanins were identified in peach (Prunus persica), and their structural diversity is attributed to glycosylation and methylation. Interestingly, peach is quite similar to the wild species Prunus ferganensis but differs from both Prunus davidiana and Prunus kansueasis in terms of anthocyanin composition in flowers. This indicates that peach is probably domesticated from P. ferganensis. Subsequently, genes responsible for both methylation and glycosylation of anthocyanins were identified, and their spatiotemporal expression results in different patterns of anthocyanin accumulation in flowers, leaves, and fruits. Two tandem-duplicated genes encoding flavonoid 3-O-glycosyltransferase (F3GT) in peach, PpUGT78A1 and PpUGT78A2, showed different activity toward anthocyanin, providing an example of divergent evolution of F3GT genes in plants. Two genes encoding anthocyanin O-methyltransferase (AOMT), PpAOMT1 and PpAOMT2, are expressed in leaves and flowers, but only PpAOMT2 is responsible for the O-methylation of anthocyanins at the 3′ position in peach. In addition, our study reveals a novel branch of UGT78 genes in plants that lack the highly conserved intron 2 of the UGT gene family, with a great variation of the amino acid residue at position 22 of the plant secondary product glycosyltransferase box. Our results not only provide insights into the mechanisms underlying anthocyanin glycosylation and methylation in peach but will also aid in future attempts to manipulate flavonoid biosynthesis in peach as well as in other plants. PMID:25106821

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

    NARCIS (Netherlands)

    Montuoro, Paul; Mainhard, Tim


    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

  20. Ferric ion mediated photodecomposition of aqueous perfluorooctane sulfonate (PFOS) under UV irradiation and its mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Ling; Zhang, Pengyi, E-mail:; Shao, Tian; Zhao, Shiliang


    Graphical abstract: - Highlights: • Photodecomposition of PFOS under UV increased 50 times by ferric ions. • Addition of ferric ion results in reduction of PFOS signal in UPLC–MS/MS. • Excitation of PFOS–Fe{sup 3+} complex by UV leads to PFOS decomposition. • The main intermediates, i.e. perfluorocarboxylic acids were further decomposed. - Abstract: Perfluorooctane sulfonate (PFOS) recently has received much attention due to its global distribution, environmental persistence and bioaccumulation. The methods for PFOS decomposition are very limited due to its inertness. In this report we first found the photodecomposition of PFOS under UV was greatly accelerated by addition of ferric ions. In the presence of ferric ion (100 μM), PFOS (20 μM) decreased to below the detection limit within 48 h, with the rate constant of 1.67 d{sup −1}, which was 50 times higher than that by direct photolysis (0.033 d{sup −1}). Besides fluoride and sulfate ions, C2–C8 perfluorocarboxylic acids (PFCAs) were identified as the main intermediates. It was found that addition of PFOS into the FeCl{sub 3} aqueous solution led to reduction of UV absorption, and the presence of ferric ion reduced the response of PFOS as analyzed by UPLC–MS/MS, which indicated that PFOS formed a complex with ferric ion. The ESR detection indicated that the electronic state of Fe{sup 3+}–PFOS complex changed during reaction. And the role of oxygen and hydroxyl radical on the defluorination of PFOS was investigated. Accordingly the mechanism for PFOS photodecomposition in the presence of ferric ion was proposed.

  1. Tensile mechanical behavior of hollow and filled carbon nanotubes under tension or combined tension-torsion (United States)

    Jeong, Byeong-Woo; Lim, Jang-Keun; Sinnott, Susan B.


    The tensile mechanical behavior of hollow and filled single-walled carbon nanotubes under tension or combined tension-torsion is examined using classical molecular dynamics simulations. These simulations indicate that the tensile strength under combined tension-torsion can be increased by filling the carbon nanotubes, and the amount of this increase depends on the kind of filling material. They also predict that the tensile strength under combined tension-torsion decreases linearly under applied torsion. The tensile strength can be modified by adjusting the system temperature and through chemical functionalization to the carbon nanotube walls.

  2. Long-term clinical response to cardiac resynchronisation therapy under a multidisciplinary model. (United States)

    O'Donnell, D; Lin, T; Swale, M; Rae, P; Flannery, D; Srivastava, P M


    Cardiac resynchronisation therapy (CRT) is established in the management of cardiac failure in patients with systolic dysfunction. Clinical response to CRT is not uniform, and response has been difficult to predict. Patient management within a high volume, multidisciplinary service focused on optimal delivery of CRT would improve response rates. Four hundred and thirty-five consecutive patients who underwent CRT under a multidisciplinary heart failure service were enrolled prospectively over a 5-year period. Medically optimised, symptomatic patients with an ejection fraction (EF) mechanical activation, and electrically to a site with maximal intrinsic intracardiac electrogram separation. Routine device and clinical follow up, as well as CRT optimisations, were performed at baseline and at 3-monthly intervals. Responders were defined as having an absolute reduction in left ventricular end-diastolic diameter >10% and an improvement in EF >5%. With a mean follow up of 53 ± 11 months, response rate to CRT was 81%. Mean EF improved from 26 ± 10% to 37 ± 11%, and mean left ventricular end-diastolic diameter reduced from 68.6 ± 9.2 mm to 57.8 ± 9.3 mm. Predictors of response were sinus rhythm, high dyssynchrony index and intrinsic electrical dyssynchrony >80 ms. Successful LV lead implantation at initial procedure was achieved in 99.1%, and at latest follow up 94.6% of initial LV leads were still active. CRT undertaken with a unit focus on optimal LV lead positioning and device optimisation, along with a multidisciplinary follow-up model, results in an excellent response rate to CRT. © 2013 The Authors; Internal Medicine Journal © 2013 Royal Australasian College of Physicians.

  3. Delegation of Authority Under the Community Environmental Response Facilitation Act (CERFA) - Decision Memorandum (United States)

    This memorandum concerns how the Office of Enforcement (OE) proposed that two new authorities under the Community Environmental Response Facilitation Act (CERFA) be delegated to the Regional Administrators.

  4. Autotoxicity mechanism of Oryza sativa: transcriptome response in rice roots exposed to ferulic acid (United States)


    Background Autotoxicity plays an important role in regulating crop yield and quality. To help characterize the autotoxicity mechanism of rice, we performed a large-scale, transcriptomic analysis of the rice root response to ferulic acid, an autotoxin from rice straw. Results Root growth rate was decreased and reactive oxygen species, calcium content and lipoxygenase activity were increased with increasing ferulic acid concentration in roots. Transcriptome analysis revealed more transcripts responsive to short ferulic-acid exposure (1- and 3-h treatments, 1,204 genes) than long exposure (24 h, 176 genes). Induced genes were involved in cell wall formation, chemical detoxification, secondary metabolism, signal transduction, and abiotic stress response. Genes associated with signaling and biosynthesis for ethylene and jasmonic acid were upregulated with ferulic acid. Ferulic acid upregulated ATP-binding cassette and amino acid/auxin permease transporters as well as genes encoding signaling components such as leucine-rich repeat VIII and receptor-like cytoplasmic kinases VII protein kinases, APETALA2/ethylene response factor, WRKY, MYB and Zinc-finger protein expressed in inflorescence meristem transcription factors. Conclusions The results of a transcriptome analysis suggest the molecular mechanisms of plants in response to FA, including toxicity, detoxicification and signaling machinery. FA may have a significant effect on inhibiting rice root elongation through modulating ET and JA hormone homeostasis. FA-induced gene expression of AAAP transporters may contribute to detoxicification of the autotoxin. Moreover, the WRKY and Myb TFs and LRR-VIII and SD-2b kinases might regulate downstream genes under FA stress but not general allelochemical stress. This comprehensive description of gene expression information could greatly facilitate our understanding of the mechanisms of autotoxicity in plants. PMID:23705659

  5. Immunotoxicity in green mussels under perfluoroalkyl substance (PFAS) exposure: Reversible response and response model development. (United States)

    Liu, Changhui; Gin, Karina Yew-Hoong


    The immunotoxicity of 4 commonly detected perfluoroalkyl substances (PFASs), namely, perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and perfluorodecanoic acid (PFDA) was investigated by measuring biomarkers of the immune profile of green mussels, Perna viridis. The biomarkers included neutral red retention, phagocytosis, and spontaneous cytotoxicity, all of which were tested on mussel hemocytes. Hemocytes are an important component of the invertebrate immune system. We found that exposure to PFASs could lead to reduced hemocyte cell viability and suppress immune function by up to 50% of normal performance within the experimental exposure range. The results indicate that PFASs have an immunotoxic potential and thus could pose severe health risks to aquatic organisms. The reported immunotoxicity is likely to result from the compounds' direct and indirect interactions with the hemocyte membrane, and therefore likely to affect the functionality of these cells. The immunotoxic response was found to be related to the organism's burden of PFASs, and was reversible when the compounds were removed from the test organisms. Based on this relationship, models using an organism's PFAS concentration and bioaccumulation factor (BAF) as the independent variables were established to quantify PFAS-induced immunotoxicity. The models help us to gain a better understanding of the toxic mechanism of PFASs, and provide a tool to evaluate adverse effects for the whole group of compounds with one mathematical equation. Environ Toxicol Chem 2018;37:1138-1145. © 2018 SETAC. © 2018 SETAC.

  6. Exploring the Response of Plants Grown under Uranium Stress

    Energy Technology Data Exchange (ETDEWEB)

    Doustaly, Fany; Berthet, Serge; Bourguignon, Jacques [CEA, iRTSV, Laboratoire de Physiologie Cellulaire Vegetale, UMR 5168 CEA-CNRS-INRA-Univ. Grenoble Alpes (France); Combes, Florence; Vandenbrouck, Yves [CEA, iRTSV, Laboratoire de Biologie a Grande Echelle, EDyP, CEA-Grenoble (France); Carriere, Marie [CEA, INAC, LAN, UMR E3 CEA-Universite Joseph Fourier, Grenoble (France); Vavasseur, Alain [CEA, IBEB, LBDP, Saint Paul lez Durance, CEA Cadarache (France)


    Uranium is a natural element which is mainly redistributed in the environment due to human activity, including accidents and spillages. Plants may be useful in cleaning up after incidents, although little is yet known about the relationship between uranium speciation and plant response. We analyzed the impact of different uranium (U) treatments on three plant species namely sunflower, oilseed rape and wheat. Using inductively coupled plasma mass spectrometry elemental analysis, together with a panel of imaging techniques including scanning electron microscopy coupled with energy dispersive spectroscopy, transmission electron microscopy and particle-induced X-ray emission spectroscopy, we have recently shown how chemical speciation greatly influences the accumulation and distribution of U in plants. Uranyl (UO{sub 2}{sup 2+} free ion) is the predominant mobile form in soil surface at low pH in absence of ligands. With the aim to characterize the early plant response to U exposure, complete Arabidopsis transcriptome microarray experiments were conducted on plants exposed to 50 μM uranyl nitrate for 2, 6 and 30 h and highlighted a set of 111 genes with modified expression at these three time points. Quantitative real-time RT-PCR experiments confirmed and completed CATMA micro-arrays results allowing the characterization of biological processes perturbed by U. Functional categorization of deregulated genes emphasizes oxidative stress, cell wall biosynthesis and hormone biosynthesis and signaling. We showed that U stress is perceived by plant cells like a phosphate starvation stress since several phosphate deprivation marker genes were deregulated by U and also highlighted perturbation of iron homeostasis by U. Hypotheses are presented to explain how U perturbs the iron uptake and signaling response. These results give preliminary insights into the pathways affected by uranyl uptake, which will be of interest for engineering plants to help clean areas contaminated with

  7. The Headache Under-Response to Treatment (HURT) Questionnaire

    DEFF Research Database (Denmark)

    Westergaard, Maria Ls; Steiner, Timothy J; Macgregor, E Anne


    The HURT Questionnaire consists of eight questions which the patient answers as a measure of effectiveness of intervention against headache. This first assessment of clinical utility was conducted in headache specialist centres in three countries in order to demonstrate that HURT was responsive...... that the best possible outcome had been achieved in each patient. Questionnaires were also answered by 42 patients at initial and final visits to a centre in Italy. Internal consistency reliability was very good (α = 0.85) while test-retest reliability was fair to low (κ = 0.38-0.62 and r(s) = 0...

  8. How diagnostic tests help to disentangle the mechanisms underlying neuropathic pain symptoms in painful neuropathies. (United States)

    Truini, Andrea; Cruccu, Giorgio


    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.

  9. Visualization of hot spot formation in energetic materials under periodic mechanical excitation using phosphor thermography (United States)

    Casey, Alex; Fenoglio, Gabriel; Detrinidad, Humberto


    Under mechanical excitation, energy is known to localize within an energetic material resulting in `hot spot' formation. While many formation mechanisms have been proposed, additional insight to heat generation mechanisms, the effect of binder/crystal interfaces, and predication capabilities can be gained by quantifying the initiation and growth of the hot spots. Phosphor thermography is a well established temperature sensing technique wherein an object's temperature is obtained by collecting the temperature dependent luminescence of an optically excited phosphor. Herein, the phosphor thermography technique has been applied to Dow Corning Sylgard® 184/octahydro 1,3,5,7 tetranitro 1,3,5,7 tetrazocine (HMX) composite materials under mechanical excitation in order to visualize the evolution of the temperature field, and thus hot spot formation, within the binder. Funded by AFOSR. Supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

  10. The Response of Simple Polymer Structures Under Dynamic Loading (United States)

    Proud, William; Ellison, Kay; Yapp, Su; Cole, Cloe; Galimberti, Stefano; Institute of Shock Physics Team


    The dynamic response of polymeric materials has been widely studied with the effects of degree of crystallinity, strain rate, temperature and sample size being commonly reported. This study uses a simple PMMA structure, a right cylindrical sample, with structural features such as holes. The features are added an varied in a systematic fashion. Samples were dynamically loaded using a Split Hopkinson Pressure Bar up to failure. The resulting stress-strain curves are presented showing the change in sample response. The strain to failure is shown to increase initially with the presence of holes, while failure stress is relatively unaffected. The fracture patterns seen in the failed samples change, with tensile cracks, Hertzian cones, shear effects being dominant for different holes sizes and geometries. The sample were prepared by laser cutting and checked for residual stress before experiment. The data is used to validate predictive model predictions where material, structure and damage are included.. The Institute of Shock Physics acknowledges the support of Imperial College London and the Atomic Weapons Establishment.

  11. Response of unirradiated and irradiated PWR fuel rods tested under power-cooling-mismatch conditions

    International Nuclear Information System (INIS)

    MacDonald, P.E.; Quapp, W.J.; Martinson, Z.R.; McCardell, R.K.; Mehner, A.S.


    This report summarizes the results from the single-rod power-cooling-mismatch (PCM) and irradiation effects (IE) tests conducted to date in the Power Burst Facility (PBF) at the U.S. DOE Idaho National Engineering Laboratory. This work was performed for the U.S. NRC under contact to the Department of Energy. These tests are part of the NRC Fuel Behavior Program, which is designed to provide data for the development and verification of analytical fuel behavior models that are used to predict fuel response to abnormal or postulated accident conditions in commercial LWRs. The mechanical, chemical and thermal response of both previously unirradiated and previously irradiated LWR-type fuel rods tested under power-cooling-mismatch condition is discussed. A brief description of the test designs is presented. The results of the PCM thermal-hydraulic studies are summarized. Primary emphasis is placed on the behavior of the fuel and cladding during and after stable film boiling. (orig.) [de

  12. Hydrogel efficiency and physiological responses of seedless citrus cultivars seedlings under water deficit

    Directory of Open Access Journals (Sweden)

    Ester Alice Ferreira


    Full Text Available Water is a limiting factor in citrus development which makes hydric replacement a common practice in plantations where its distribution is scarce. The hydroretentor gel has been one of the available technologies for water supply to plants and may also be an alternative that contributes to the rational use of water for planting citrus seedlings. This study evaluated the efficiency of hydrogel as an alternative to minimize the effects of water deficit in seedlings of seedless cultivars of tangerines ('Ortanique', 'Okitsu' and 'Clemenules' and oranges ('Navelina', 'Navelate' and 'Lanelate', all grafted on Poncirus trifoliata. The experiment was carried out in a greenhouse, in a randomized blocks design, where plants with hydrogel were compared to plants under conventional irrigation and also to plants under water deficit, in a triple factorial arrangement. The rates of carbon liquid assimilation, stomatal conductance and transpiration and the ratio between internal and external CO2 concentrations were evaluated. It was verified that the effect of the hydrogel for maintaining the hydric status of citrus seedlings is variable and dependent on physiological mechanisms of response to water deficit. There was no response of 'Ortanique' and 'Navelate'seedlings to the hydrogel application. The hydrogel promoted the recovering and maintenance of the hydric status of 'Okitsu', 'Clemenules', 'Navelina' and 'Lanelate' seedlings, however, these cultivars were sensitive to changes in the water status, with considerable reduction of gas exchange.

  13. Mechanical critical phenomena and the elastic response of fiber networks (United States)

    Mackintosh, Fred

    The mechanics of cells and tissues are largely governed by scaffolds of filamentous proteins that make up the cytoskeleton, as well as extracellular matrices. Evidence is emerging that such networks can exhibit rich mechanical phase behavior. A classic example of a mechanical phase transition was identified by Maxwell for macroscopic engineering structures: networks of struts or springs exhibit a continuous, second-order phase transition at the isostatic point, where the number of constraints imposed by connectivity just equals the number of mechanical degrees of freedom. We present recent theoretical predictions and experimental evidence for mechanical phase transitions in in both synthetic and biopolymer networks. We show, in particular, excellent quantitative agreement between the mechanics of collagen matrices and the predictions of a strain-controlled phase transition in sub-isostatic networks.

  14. A Cross-Cultural Approach to Psychological Mechanisms Underlying Emotional Reactions to Music


    Barradas, Gonçalo


    Music plays a crucial role in everyday life by enabling listeners to seek individual emotional experiences. To explain why such emotions occur, we must understand the underlying process that mediates between surface-level features of the music and aroused emotions. This thesis aimed to investigate how musical emotions are mediated by psychological mechanisms from a cross-cultural perspective. Study I manipulated four mechanisms by selecting ecologically valid pieces of music that featured inf...

  15. The Mechanical Response of Advanced Claddings during Proposed Reactivity Initiated Accident Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Cinbiz, Mahmut N [ORNL; Brown, Nicholas R [ORNL; Terrani, Kurt A [ORNL; Lowden, Rick R [ORNL; ERDMAN III, DONALD L [ORNL


    This study investigates the failure mechanisms of advanced nuclear fuel cladding of FeCrAl at high-strain rates, similar to design basis reactivity initiated accidents (RIA). During RIA, the nuclear fuel cladding was subjected to the plane-strain to equibiaxial tension strain states. To achieve those accident conditions, the samples were deformed by the expansion of high strength Inconel alloy tube under pre-specified pressure pulses as occurring RIA. The mechanical response of the advanced claddings was compared to that of hydrided zirconium-based nuclear fuel cladding alloy. The hoop strain evolution during pressure pulses were collected in situ; the permanent diametral strains of both accident tolerant fuel (ATF) claddings and the current nuclear fuel alloys were determined after rupture.

  16. Elucidation of the molecular mechanisms underlying adverse reactions associated with a kinase inhibitor using systems toxicology. (United States)

    Amemiya, Takahiro; Honma, Masashi; Kariya, Yoshiaki; Ghosh, Samik; Kitano, Hiroaki; Kurachi, Yoshihisa; Fujita, Ken-Ichi; Sasaki, Yasutsuna; Homma, Yukio; Abernethy, Darrel R; Kume, Haruki; Suzuki, Hiroshi


    Targeted kinase inhibitors are an important class of agents in anticancer therapeutics, but their limited tolerability hampers their clinical performance. Identification of the molecular mechanisms underlying the development of adverse reactions will be helpful in establishing a rational method for the management of clinically adverse reactions. Here, we selected sunitinib as a model and demonstrated that the molecular mechanisms underlying the adverse reactions associated with kinase inhibitors can efficiently be identified using a systems toxicological approach. First, toxicological target candidates were short-listed by comparing the human kinase occupancy profiles of sunitinib and sorafenib, and the molecular mechanisms underlying adverse reactions were predicted by sequential simulations using publicly available mathematical models. Next, to evaluate the probability of these predictions, a clinical observation study was conducted in six patients treated with sunitinib. Finally, mouse experiments were performed for detailed confirmation of the hypothesized molecular mechanisms and to evaluate the efficacy of a proposed countermeasure against adverse reactions to sunitinib. In silico simulations indicated the possibility that sunitinib-mediated off-target inhibition of phosphorylase kinase leads to the generation of oxidative stress in various tissues. Clinical observations of patients and mouse experiments confirmed the validity of this prediction. The simulation further suggested that concomitant use of an antioxidant may prevent sunitinib-mediated adverse reactions, which was confirmed in mouse experiments. A systems toxicological approach successfully predicted the molecular mechanisms underlying clinically adverse reactions associated with sunitinib and was used to plan a rational method for the management of these adverse reactions.

  17. Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity (United States)


    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...Email addresses:;; ; E-Mail: 5f. WORK UNIT NUMBER 7

  18. Molecular signal networks and regulating mechanisms of the unfolded protein response. (United States)

    Gong, Jing; Wang, Xing-Zhi; Wang, Tao; Chen, Jiao-Jiao; Xie, Xiao-Yuan; Hu, Hui; Yu, Fang; Liu, Hui-Lin; Jiang, Xing-Yan; Fan, Han-Dong

    Within the cell, several mechanisms exist to maintain homeostasis of the endoplasmic reticulum (ER). One of the primary mechanisms is the unfolded protein response (UPR). In this review, we primarily focus on the latest signal webs and regulation mechanisms of the UPR. The relationships among ER stress, apoptosis, and cancer are also discussed. Under the normal state, binding immunoglobulin protein (BiP) interacts with the three sensors (protein kinase RNA-like ER kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1α (IRE1α)). Under ER stress, misfolded proteins interact with BiP, resulting in the release of BiP from the sensors. Subsequently, the three sensors dimerize and autophosphorylate to promote the signal cascades of ER stress. ER stress includes a series of positive and negative feedback signals, such as those regulating the stabilization of the sensors/BiP complex, activating and inactivating the sensors by autophosphorylation and dephosphorylation, activating specific transcription factors to enable selective transcription, and augmenting the ability to refold and export. Apart from the three basic pathways, vascular endothelial growth factor (VEGF)-VEGF receptor (VEGFR)-phospholipase C-γ (PLCγ)-mammalian target of rapamycin complex 1 (mTORC1) pathway, induced only in solid tumors, can also activate ATF6 and PERK signal cascades, and IRE1α also can be activated by activated RAC-alpha serine/threonine-protein kinase (AKT). A moderate UPR functions as a pro-survival signal to return the cell to its state of homeostasis. However, persistent ER stress will induce cells to undergo apoptosis in response to increasing reactive oxygen species (ROS), Ca 2+ in the cytoplasmic matrix, and other apoptosis signal cascades, such as c-Jun N-terminal kinase (JNK), signal transducer and activator of transcription 3 (STAT3), and P38, when cellular damage exceeds the capacity of this adaptive response.

  19. Transplant ethics under scrutiny – responsibilities of all medical professionals (United States)

    Trey, Torsten; Caplan, Arthur L.; Lavee, Jacob


    In this text, we present and elaborate ethical challenges in transplant medicine related to organ procurement and organ distribution, together with measures to solve such challenges. Based on internationally acknowledged ethical standards, we looked at cases of organ procurement and distribution practices that deviated from such ethical standards. One form of organ procurement is known as commercial organ trafficking, while in China the organ procurement is mostly based on executing prisoners, including killing of detained Falun Gong practitioners for their organs. Efforts from within the medical community as well as from governments have contributed to provide solutions to uphold ethical standards in medicine. The medical profession has the responsibility to actively promote ethical guidelines in medicine to prevent a decay of ethical standards and to ensure best medical practices. PMID:23444249

  20. Human thermal physiological and psychological responses under different heating environments. (United States)

    Wang, Zhaojun; Ning, Haoran; Ji, Yuchen; Hou, Juan; He, Yanan


    Anecdotal evidence suggests that many residents of severely cold areas of China who use floor heating (FH) systems feel warmer but drier compared to those using radiant heating (RH) systems. However, this phenomenon has not been verified experimentally. In order to validate the empirical hypothesis, and research the differences of human physiological and psychological responses in these two asymmetrical heating environments, an experiment was designed to mimic FH and RH systems. The subjects participating in the experiment were volunteer college-students. During the experiment, the indoor air temperature, air speed, relative humidity, globe temperature, and inner surface temperatures were measured, and subjects' heart rate, blood pressure and skin temperatures were recorded. The subjects were required to fill in questionnaires about their thermal responses during testing. The results showed that the subjects' skin temperatures, heart rate and blood pressure were significantly affected by the type of heating environment. Ankle temperature had greatest impact on overall thermal comfort relative to other body parts, and a slightly cool FH condition was the most pleasurable environment for sedentary subjects. The overall thermal sensation, comfort and acceptability of FH were higher than that of RH. However, the subjects of FH felt drier than that of RH, although the relative humidity in FH environments was higher than that of the RH environment. In future environmental design, the thermal comfort of the ankles should be scrutinized, and a FH cool condition is recommended as the most comfortable thermal environment for office workers. Consequently, large amounts of heating energy could be saved in this area in the winter. The results of this study may lead to more efficient energy use for office or home heating systems. Copyright © 2015 Elsevier Ltd. All rights reserved.

  1. Comparative proteomics of peanut gynophore development under dark and mechanical stimulation. (United States)

    Sun, Yong; Wang, Qingguo; Li, Zhen; Hou, Lei; Dai, Shaojun; Liu, Wei


    Peanut (Arachis hypogaea. L) is an important leguminous crop and source of proteins and lipids. It has attracted widespread attention of researchers due to its unique growth habit of geocarpy, which is regulated by geotropism, negative phototropism, and haptotropism. However, the protein expression pattern and molecular regulatory mechanism underlying the physiological processes of peanut remain unknown. In this study, the peanut gynophores under five treatment conditions were used for proteomic analysis, including aerial growth of the gynophores, the gynophores penetrated into the soil, as well as aerial growth of the gynophores under mechanical stimulation, dark, and mechanical stimulation combined with dark. The analysis of protein abundances in peanut gynophores under these conditions were conducted using comparative proteomic approaches. A total of 27 differentially expressed proteins were identified and further classified into nine biological functional groups of stress and defense, carbohydrate and energy metabolism, metabolism, photosynthesis, cell structure, signaling, transcription, protein folding and degradation, and function unknown. By searching gene functions against peanut database, 10 genes with similar annotations were selected as corresponding changed proteins, and their variation trends in gynophores under such growth conditions were further verified using quantitative real-time PCR. Overall, the investigation will benefit to enrich our understanding of the internal mechanisms of peanut gynophore development and lay a foundation for breeding and improving crop varieties and qualities.

  2. Postsynaptic mechanisms underlying the excitatory action of histamine on medial vestibular nucleus neurons in rats (United States)

    Zhang, Xiao-Yang; Yu, Lei; Zhuang, Qian-Xing; Peng, Shi-Yu; Zhu, Jing-Ning; Wang, Jian-Jun


    Background and Purpose Anti-histaminergic drugs have been widely used in the clinical treatment of vestibular disorders and most studies concentrate on their presynaptic actions. The present study investigated the postsynaptic effect of histamine on medial vestibular nucleus (MVN) neurons and the underlying mechanisms. Experimental Approach Histamine-induced postsynaptic actions on MVN neurons and the corresponding receptor and ionic mechanisms were detected by whole-cell patch-clamp recordings on rat brain slices. The distribution of postsynaptic histamine H1, H2 and H4 receptors was mapped by double and single immunostaining. Furthermore, the expression of mRNAs for H1, H2 and H4 receptors and for subtypes of Na+–Ca2+ exchangers (NCXs) and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels was assessed by quantitative real-time RT-PCR. Key Results A marked postsynaptic excitatory effect, co-mediated by histamine H1 and H2 receptors, was involved in the histamine-induced depolarization of MVN neurons. Postsynaptic H1 and H2 rather than H4 receptors were co-localized in the same MVN neurons. NCXs contributed to the inward current mediated by H1 receptors, whereas HCN channels were responsible for excitation induced by activation of H2 receptors. Moreover, NCX1 and NCX3 rather than NCX2, and HCN1 rather than HCN2-4 mRNAs, were abundantly expressed in MVN. Conclusion and Implications NCXs coupled to H1 receptors and HCN channels linked to H2 receptors co-mediate the strong postsynaptic excitatory action of histamine on MVN neurons. These results highlight an active role of postsynaptic mechanisms in the modulation by central histaminergic systems of vestibular functions and suggest potential targets for clinical treatment of vestibular disorders. Linked Articles This article is part of a themed issue on Histamine Pharmacology Update. To view the other articles in this issue visit PMID:23713466

  3. Luminescence response of synthetic opal under femtosecond laser pumping

    International Nuclear Information System (INIS)

    Vasnetsov, M.V.; Bazhenov, V.Yu.; Dmitruk, I.N.; Kudryavtseva, A.D.; Tcherniega, N.V.


    Synthetic opal is an artificial photonic metamaterial composed from spherical globules of amorphous silica (SiO 2 ) about 300 nm in diameter. We report, for the first time to our knowledge, the origin of a narrow luminescence spectral peak (4 nm HWHM) and optical second and third harmonic generation in synthetic opal samples under femtosecond laser excitation (800 nm) at liquid-nitrogen temperature. Stimulated-emission effects are discussed related to the possibility of nanocavity lasing at the condition of the first Mie resonance in a dielectric sphere. - Highlights: • Second harmonic generation in a synthetic opal (amorphous material composed from spherical SiO 2 globules) was observed. • Narrow luminescence peak which we assign to a Mie resonance in a globule was detected at liquid-nitrogen temperature

  4. Nonlinear ecosystem services response to groundwater availability under climate extremes (United States)

    Qiu, J.; Zipper, S. C.; Motew, M.; Booth, E.; Kucharik, C. J.; Steven, L. I.


    Depletion of groundwater has been accelerating at regional to global scales. Besides serving domestic, industrial and agricultural needs, in situ groundwater is also a key control on biological, physical and chemical processes across the critical zone, all of which underpin supply of ecosystem services essential for humanity. While there is a rich history of research on groundwater effects on subsurface and surface processes, understanding interactions, nonlinearity and feedbacks between groundwater and ecosystem services remain limited, and almost absent in the ecosystem service literature. Moreover, how climate extremes may alter groundwater effects on services is underexplored. In this research, we used a process-based ecosystem model (Agro-IBIS) to quantify groundwater effects on eight ecosystem services related to food, water and biogeochemical processes in an urbanizing agricultural watershed in the Midwest, USA. We asked: (1) Which ecosystem services are more susceptible to shallow groundwater influences? (2) Do effects of groundwater on ecosystem services vary under contrasting climate conditions (i.e., dry, wet and average)? (3) Where on the landscape are groundwater effects on ecosystem services most pronounced? (4) How do groundwater effects depend on water table depth? Overall, groundwater significantly impacted all services studied, with the largest effects on food production, water quality and quantity, and flood regulation services. Climate also mediated groundwater effects with the strongest effects occurring under dry climatic conditions. There was substantial spatial heterogeneity in groundwater effects across the landscape that is driven in part by spatial variations in water table depth. Most ecosystem services responded nonlinearly to groundwater availability, with most apparent groundwater effects occurring when the water table is shallower than a critical depth of 2.5-m. Our findings provide compelling evidence that groundwater plays a vital

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


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


    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...

  6. Mechanical behavior of confined self-compacting reinforced concrete circular columns under concentric axial loading


    Khairallah, Fouad


    While there is abundant research information on ordinary confined concrete, there are little data on the behavior of Self-Compacting Concrete (SCC) under such condition. Due to higher shrinkage and lower coarse aggregate content of SCC compared to that of Normal Concrete (NC), its composite performance under confined conditions needs more investigation. This paper has been devoted to investigate and compare the mechanical behavior of confined concrete circular columns cast with SCC and NC und...

  7. Temperature extremes in Europe: mechanisms and responses to climatic change

    International Nuclear Information System (INIS)

    Cattiaux, Julien


    Europe witnessed a spate of record-breaking warm seasons during the 2000's. As illustrated by the devastating heat-wave of the summer 2003, these episodes induced strong societal and environmental impacts. Such occurrence of exceptional events over a relatively short time period raised up many questionings in the present context of climate change. In particular, can recent temperature extremes be considered as 'previews' of future climate conditions? Do they result from an increasing temperature variability? These questions constitute the main motivations of this thesis. Thus, our work aims to contribute to the understanding of physical mechanisms responsible for seasonal temperature extremes in Europe, in order to anticipate their future statistical characteristics. Involved processes are assessed by both statistical data-analysis of observations and climate projections and regional modeling experiments. First we show that while the inter-annual European temperature variability appears driven by disturbances in the North-Atlantic dynamics, the recent warming is likely to be dissociated with potential circulation changes. This inconsistency climaxes during the exceptionally mild autumn of 2006, whose temperature anomaly is only half explained by the atmospheric flow. Recent warm surface conditions in the North-Atlantic ocean seem to substantially contribute to the European warming in autumn-winter, through the establishment of advective and radiative processes. In spring-summer, since both advection by the westerlies and Atlantic warming are reduced, more local processes appear predominant (e.g. soil moisture, clouds, aerosols). Then the issue of future evolution of the relationship between North-Atlantic dynamics and European temperatures is addressed, based on climate projections of the International Panel on Climate Change. Multi-model analysis, using both flow-analogues and weather regimes methods, show that the inconsistency noticed over recent decades is

  8. Woody-plant ecosystems under climate change and air pollution-response consistencies across zonobiomes? (United States)

    Matyssek, R; Kozovits, A R; Wieser, G; King, J; Rennenberg, H


    Forests store the largest terrestrial pools of carbon (C), helping to stabilize the global climate system, yet are threatened by climate change (CC) and associated air pollution (AP, highlighting ozone (O3) and nitrogen oxides (NOx)). We adopt the perspective that CC-AP drivers and physiological impacts are universal, resulting in consistent stress responses of forest ecosystems across zonobiomes. Evidence supporting this viewpoint is presented from the literature on ecosystem gross/net primary productivity and water cycling. Responses to CC-AP are compared across evergreen/deciduous foliage types, discussing implications of nutrition and resource turnover at tree and ecosystem scales. The availability of data is extremely uneven across zonobiomes, yet unifying patterns of ecosystem response are discernable. Ecosystem warming results in trade-offs between respiration and biomass production, affecting high elevation forests more than in the lowland tropics and low-elevation temperate zone. Resilience to drought is modulated by tree size and species richness. Elevated O3 tends to counteract stimulation by elevated carbon dioxide (CO2). Biotic stress and genomic structure ultimately determine ecosystem responsiveness. Aggrading early- rather than mature late-successional communities respond to CO2 enhancement, whereas O3 affects North American and Eurasian tree species consistently under free-air fumigation. Insect herbivory is exacerbated by CC-AP in biome-specific ways. Rhizosphere responses reflect similar stand-level nutritional dynamics across zonobiomes, but are modulated by differences in tree-soil nutrient cycling between deciduous and evergreen systems, and natural versus anthropogenic nitrogen (N) oversupply. The hypothesis of consistency of forest responses to interacting CC-AP is supported by currently available data, establishing the precedent for a global network of long-term coordinated research sites across zonobiomes to simultaneously advance both

  9. Jatropha curcasand Ricinus communisdisplay contrasting photosynthetic mechanisms in response to environmental conditions

    Directory of Open Access Journals (Sweden)

    Milton Costa Lima Neto


    Full Text Available Higher plants display different adaptive strategies in photosynthesis to cope with abiotic stress. In this study, photosynthetic mechanisms and water relationships displayed byJatropha curcasL. (physic nuts andRicinus communisL. (castor bean, in response to variations in environmental conditions, were assessed.R. communis showed higher CO2 assimilation, stomatal and mesophyll conductance thanJ. curcas as light intensity and intercellular CO2 pressure increased. On the other hand,R. communis was less effective in stomatal control in response to adverse environmental factors such as high temperature, water deficit and vapor pressure deficit, indicating lower water use efficiency. Conversely,J. curcas exhibited higher photosynthetic efficiency (gas exchange and photochemistry and water use efficiency under these adverse environmental conditions.R. communisdisplayed higher potential photosynthesis, but exhibited a lowerin vivo Rubisco carboxylation rate (Vcmax and maximum electron transport rate (Jmax. During the course of a typical day, in a semiarid environment, with high irradiation, high temperature and high vapor pressure deficit, but exposed to well-watered conditions, the two studied species presented similar photosynthesis. Losing potential photosynthesis, but maintaining favorable water status and increasing non-photochemical quenching to avoid photoinhibition, are important acclimation mechanisms developed byJ. curcas to cope with dry and hot conditions. We suggest thatJ. curcas is more tolerant to hot and dry environments thanR. communis but the latter species displays higher photosynthetic efficiency under well-watered and non-stressful conditions.

  10. Molecular mechanisms of glucose uptake in skeletal muscle at rest and in response to exercise

    Directory of Open Access Journals (Sweden)

    Rodrigo Martins Pereira


    Full Text Available Abstract Glucose uptake is an important phenomenon for cell homeostasis and for organism health. Under resting conditions, skeletal muscle is dependent on insulin to promote glucose uptake.Insulin, after binding to its membrane receptor, triggers a cascade of intracellular reactions culminating in activation of the glucose transporter 4, GLUT4, among other outcomes.This transporter migrates to the plasma membrane and assists in glucose internalization.However, under special conditions such as physical exercise, alterations in the levels of intracellular molecules such as ATP and calcium actto regulate GLUT4 translocation and glucose uptake in skeletal muscle, regardless of insulinlevels.Regular physical exercise, due to stimulating pathways related to glucose uptake, is an important non-pharmacological intervention for improving glycemic control in obese and diabetic patients. In this mini-review the main mechanisms involved in glucose uptake in skeletal muscle in response to muscle contraction will be investigated.

  11. Interface traps contribution on transport mechanisms under illumination in metal-oxide-semiconductor structures based on silicon nanocrystals (United States)

    Chatbouri, S.; Troudi, M.; Kalboussi, A.; Souifi, A.


    The transport phenomena in metal-oxide-semiconductor (MOS) structures having silicon nanocrystals (Si-NCs) inside the dielectric layer have been investigated, in dark condition and under visible illumination. At first, using deep-level transient spectroscopy (DLTS), we find the presence of series electron traps having very close energy levels (comprised between 0.28 and 0.45 eV) for ours devices (with/without Si-NCs). And a single peak appears at low temperature only for MOS with Si-NCs related to Si-NCs DLTS response. In dark condition, the conduction mechanism is dominated by the thermionic fast emission/capture of charge carriers from the highly doped polysilicon layer to Si-substrate through interface trap states for MOS without Si-NCs. The tunneling of charge carriers from highly poly-Si to Si substrate trough the trapping/detrapping mechanism in the Si-NCs, at low temperature, contributed to the conduction mechanism for MOS with Si-NCs. The light effect on transport mechanisms has been investigated using current-voltage ( I- V), and high frequency capacitance-voltage ( C- V) methods. We have been marked the photoactive trap effect in inversion zone at room temperature in I- V characteristics, which confirm the contribution of photo-generated charge on the transport mechanisms from highly poly-Si to Si substrate trough the photo-trapping/detrapping mechanism in the Si-NCs and interfaces traps levels. These results have been confirmed by an increasing about 10 pF in capacity's values for the C- V characteristics of MOS with Si-NCs, in the inversion region for inverse high voltage applied under photoexcitation at low temperature. These results are helpful to understand the principle of charge transport in dark condition and under illumination, of MOS structures having Si-NCs in the SiO x = 1.5 oxide matrix.

  12. Dynamic compressive mechanical response of a soft polymer material

    NARCIS (Netherlands)

    Fan, J.T.; Weerheijm, J.; Sluys, L.J.


    The dynamic mechanical behaviour of a soft polymer material (Clear Flex 75) was studied using a split Hopkinson pressure bar (SHPB) apparatus. Mechanical properties have been determined at moderate to high strain rates. Real time deformation and fracture were recorded using a high-speed camera.

  13. Unraveling the mechano-responsive mechanisms at Focal Adherens Junctions

    NARCIS (Netherlands)

    Oldenburg, Joppe


    Formation and maintenance of cell-cell junctions is paramount for proper epithelial and endothelial barrier formation. Cell-cell adhesions are regulated by chemical and mechanical cues from the environment. Mechanical regulation of both epithelial and endothelial barrier occurs predominantly through

  14. Ultrastructural changes of cell walls under intense mechanical treatment of selective plant raw material

    International Nuclear Information System (INIS)

    Bychkov, Aleksey L.; Ryabchikova, E.I.; Korolev, K.G.; Lomovsky, O.I.


    Structural changes of cell walls under intense mechanical treatment of corn straw and oil-palm fibers were studied by electron and light microscopy. Differences in the character of destruction of plant biomass were revealed, and the dependence of destruction mechanisms on the structure of cell walls and lignin content was demonstrated. We suggest that the high reactivity of the particles of corn straw (about 18% of lignin) after intense mechanical treatment is related to disordering of cell walls and an increase of the surface area, while in the case of oil palm (10% of lignin) the major contribution into an increase in the reactivity is made by an increase of surface area. -- Highlights: ► Structure of cell walls determines the processes of plant materials' destruction. ► Ultrastructure of highly lignified materials strongly disordering by mechanical action. ► Ultrastructure of low-lignified materials is not disordering by mechanical action.

  15. Proteomic Characterization of Armillaria mellea Reveals Oxidative Stress Response Mechanisms and Altered Secondary Metabolism Profiles

    Directory of Open Access Journals (Sweden)

    Cassandra Collins


    Full Text Available Armillaria mellea is a major plant pathogen. Yet, the strategies the organism uses to infect susceptible species, degrade lignocellulose and other plant material and protect itself against plant defences and its own glycodegradative arsenal are largely unknown. Here, we use a combination of gel and MS-based proteomics to profile A. mellea under conditions of oxidative stress and changes in growth matrix. 2-DE and LC-MS/MS were used to investigate the response of A. mellea to H2O2 and menadione/FeCl3 exposure, respectively. Several proteins were detected with altered abundance in response to H2O2, but not menadione/FeCl3 (i.e., valosin-containing protein, indicating distinct responses to these different forms of oxidative stress. One protein, cobalamin-independent methionine synthase, demonstrated a common response in both conditions, which may be a marker for a more general stress response mechanism. Further changes to the A. mellea proteome were investigated using MS-based proteomics, which identified changes to putative secondary metabolism (SM enzymes upon growth in agar compared to liquid cultures. Metabolomic analyses revealed distinct profiles, highlighting the effect of growth matrix on SM production. This establishes robust methods by which to utilize comparative proteomics to characterize this important phytopathogen.

  16. Proteomic Characterization of Armillaria mellea Reveals Oxidative Stress Response Mechanisms and Altered Secondary Metabolism Profiles. (United States)

    Collins, Cassandra; Hurley, Rachel; Almutlaqah, Nada; O'Keeffe, Grainne; Keane, Thomas M; Fitzpatrick, David A; Owens, Rebecca A


    Armillaria mellea is a major plant pathogen. Yet, the strategies the organism uses to infect susceptible species, degrade lignocellulose and other plant material and protect itself against plant defences and its own glycodegradative arsenal are largely unknown. Here, we use a combination of gel and MS-based proteomics to profile A. mellea under conditions of oxidative stress and changes in growth matrix. 2-DE and LC-MS/MS were used to investigate the response of A. mellea to H₂O₂ and menadione/FeCl₃ exposure, respectively. Several proteins were detected with altered abundance in response to H₂O₂, but not menadione/FeCl₃ (i.e., valosin-containing protein), indicating distinct responses to these different forms of oxidative stress. One protein, cobalamin-independent methionine synthase, demonstrated a common response in both conditions, which may be a marker for a more general stress response mechanism. Further changes to the A. mellea proteome were investigated using MS-based proteomics, which identified changes to putative secondary metabolism (SM) enzymes upon growth in agar compared to liquid cultures. Metabolomic analyses revealed distinct profiles, highlighting the effect of growth matrix on SM production. This establishes robust methods by which to utilize comparative proteomics to characterize this important phytopathogen.

  17. Dendritic compartmentalization of chloride cotransporters underlies directional responses of starburst amacrine cells in retina. (United States)

    Gavrikov, Konstantin E; Nilson, James E; Dmitriev, Andrey V; Zucker, Charles L; Mangel, Stuart C


    The mechanisms in the retina that generate light responses selective for the direction of image motion remain unresolved. Recent evidence indicates that directionally selective light responses occur first in the retina in the dendrites of an interneuron, i.e., the starburst amacrine cell, and that these responses are highly sensitive to the activity of Na-K-2Cl (NKCC) and K-Cl (KCC), two types of chloride cotransporter that determine whether the neurotransmitter GABA depolarizes or hyperpolarizes neurons, respectively. We show here that selective blockade of the NKCC2 and KCC2 cotransporters located on starburst dendrites consistently hyperpolarized and depolarized the starburst cells, respectively, and greatly reduced or eliminated their directionally selective light responses. By mapping NKCC2 and KCC2 antibody staining on these dendrites, we further show that NKCC2 and KCC2 are preferentially located in the proximal and distal dendritic compartments, respectively. Finally, measurements of the GABA reversal potential in different starburst dendritic compartments indicate that the GABA reversal potential at the distal dendrite is more hyperpolarized than at the proximal dendrite due to KCC2 activity. These results thus demonstrate that the differential distribution of NKCC2 on the proximal dendrites and KCC2 on the distal dendrites of starburst cells results in a GABA-evoked depolarization and hyperpolarization at the NKCC2 and KCC2 compartments, respectively, and underlies the directionally selective light responses of the dendrites. The functional compartmentalization of interneuron dendrites may be an important means by which the nervous system encodes complex information at the subcellular level.

  18. Dynamical Response of Networks Under External Perturbations: Exact Results (United States)

    Chinellato, David D.; Epstein, Irving R.; Braha, Dan; Bar-Yam, Yaneer; de Aguiar, Marcus A. M.


    We give exact statistical distributions for the dynamic response of influence networks subjected to external perturbations. We consider networks whose nodes have two internal states labeled 0 and 1. We let nodes be frozen in state 0, in state 1, and the remaining nodes change by adopting the state of a connected node with a fixed probability per time step. The frozen nodes can be interpreted as external perturbations to the subnetwork of free nodes. Analytically extending and to be smaller than 1 enables modeling the case of weak coupling. We solve the dynamical equations exactly for fully connected networks, obtaining the equilibrium distribution, transition probabilities between any two states and the characteristic time to equilibration. Our exact results are excellent approximations for other topologies, including random, regular lattice, scale-free and small world networks, when the numbers of fixed nodes are adjusted to take account of the effect of topology on coupling to the environment. This model can describe a variety of complex systems, from magnetic spins to social networks to population genetics, and was recently applied as a framework for early warning signals for real-world self-organized economic market crises.

  19. Cognitive aspects underlying pain and neuro-physiological responses

    Directory of Open Access Journals (Sweden)

    Helen Bedinoto Durgante


    Full Text Available La Psicología de la Salud ha investigado intensamente los posibles factores cognitivos implicados en, o responsables de, bienestar físico, emocional y comportamental de los individuos. Los estudios sobre el dolor se abordaron como un factor importante de preocupación en este ámbito, debido a que la construcción depende de diferencias individuales y susceptibles de poseer interpretaciones de los sujetos. Investigaciones han identificado que diferentes mecanismos cognitivos juegan un papel en los relatos de señales de dolor de los individuos a. El impacto de la cognición en la percepción del dolor de individuos puede incluso provocar respuestas neurológicas, que en algu - nos casos podrían evitarse mediante el uso de ciertas estrategias cognitivas. Este artículo describe los principales aspectos y procesos cognitivos del dolor y las res - puestas neurofisiológicas.

  20. Cardiovascular responses to strength training under occlusive training

    Directory of Open Access Journals (Sweden)

    Sergio Benito Hernández


    Full Text Available Occlusive strength training is shown like an alternative to intensive training. Present study shown cardiovascular responses to this training. 10 subjects were subjected to two occlusion training protocols, differentiated by the weight lifted (30 % of maximum weight lifted, post30, and 70 % of maximum weight lifted, post70. The values of arterial systolic tension (TAS, diastolic (TAD and heart rate (FC were recorded. The results showing a significant decline in TAS and TAD after post30 of 7 and 13 mm Hg respectively from basis values (p0.005. Heart rate (FC values do not change from the basal value by any protocol (p>0.05. Trivial effect size (ES<0.25 were observed for all groups. In conclusion, results from present study shown a significant reduction in TAS and TAD in occlusive training protocols, resulting in more pronounced when is applied the greatest intensity of training. Further studies are needed to examine the behaviour of cardiovascular parameters after occlusive strength training.

  1. Conventional estimating method of earthquake response of mechanical appendage system

    International Nuclear Information System (INIS)

    Aoki, Shigeru; Suzuki, Kohei


    Generally, for the estimation of the earthquake response of appendage structure system installed in main structure system, the method of floor response analysis using the response spectra at the point of installing the appendage system has been used. On the other hand, the research on the estimation of the earthquake response of appendage system by the statistical procedure based on probability process theory has been reported. The development of a practical method for simply estimating the response is an important subject in aseismatic engineering. In this study, the method of estimating the earthquake response of appendage system in the general case that the natural frequencies of both structure systems were different was investigated. First, it was shown that floor response amplification factor was able to be estimated simply by giving the ratio of the natural frequencies of both structure systems, and its statistical property was clarified. Next, it was elucidated that the procedure of expressing acceleration, velocity and displacement responses with tri-axial response spectra simultaneously was able to be applied to the expression of FRAF. The applicability of this procedure to nonlinear system was examined. (Kako, I.)

  2. Transcriptome analysis reveals regulatory networks underlying differential susceptibility to Botrytis cinerea in response to nitrogen availability in Solanum lycopersicum.

    Directory of Open Access Journals (Sweden)

    Andrea eVega


    Full Text Available Nitrogen (N is one of the main limiting nutrients for plant growth and crop yield. It is well documented that changes in nitrate availability, the main N source found in agricultural soils, influences a myriad of developmental programs and processes including the plant defense response. Indeed, many agronomical reports indicate that the plant N nutritional status influences their ability to respond effectively when challenged by different pathogens. However, the molecular mechanisms involved in N-modulation of plant susceptibility to pathogens are poorly characterized. In this work, we show that Solanum lycopersicum defense response to the necrotrophic fungus Botrytis cinerea is affected by plant N availability, with higher susceptibility in nitrate-limiting conditions. Global gene expression responses of tomato against B. cinerea under contrasting nitrate conditions reveals that plant primary metabolism is affected by the fungal infection regardless of N regimes. This result suggests that differential susceptibility to pathogen attack under contrasting N conditions is not only explained by a metabolic alteration. We used a systems biology approach to identify the transcriptional regulatory network implicated in plant response to the fungus infection under contrasting nitrate conditions. Interestingly, hub genes in this network are known key transcription factors involved in ethylene and jasmonic acid signaling. This result positions these hormones as key integrators of nitrate and defense against B. cinerea in tomato plants. Our results provide insights into potential crosstalk mechanisms between necrotrophic defense response and N status in plants.

  3. An investigation of the mechanism underlying teacher aggression: Testing I3 theory and the General Aggression Model. (United States)

    Montuoro, Paul; Mainhard, Tim


    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.

  4. Dynamic mechanical response of brain tissue in indentation in vivo, in situ and in vitro. (United States)

    Prevost, Thibault P; Jin, Guang; de Moya, Marc A; Alam, Hasan B; Suresh, Subra; Socrate, Simona


    Characterizing the dynamic mechanical properties of brain tissue is deemed important for developing a comprehensive knowledge of the mechanisms underlying brain injury. The results gathered to date on the tissue properties have been mostly obtained in vitro. Learning how these results might differ quantitatively from those encountered in vivo is a critical step towards the development of biofidelic brain models. The present study provides novel and unique experimental results on, and insights into, brain biorheology in vivo, in situ and in vitro, at large deformations, in the quasi-static and dynamic regimes. The nonlinear dynamic response of the cerebral cortex was measured in indentation on the exposed frontal and parietal lobes of anesthetized porcine subjects. Load-unload cycles were applied to the tissue surface at sinusoidal frequencies of 10, 1, 0.1 and 0.01 Hz. Ramp-relaxation tests were also conducted to assess the tissue viscoelastic behavior at longer times. After euthanasia, the indentation test sequences were repeated in situ on the exposed cortex maintained in its native configuration within the cranium. Mixed gray and white matter samples were subsequently excised from the superior cortex to be subjected to identical indentation test segments in vitro within 6-7 h post mortem. The main response features (e.g. nonlinearities, rate dependencies, hysteresis and conditioning) were measured and contrasted in vivo, in situ and in vitro. The indentation response was found to be significantly stiffer in situ than in vivo. The consistent, quantitative set of mechanical measurements thereby collected provides a preliminary experimental database, which may be used to support the development of constitutive models for the study of mechanically mediated pathways leading to traumatic brain injury. Copyright © 2011 Acta Materialia Inc. All rights reserved.

  5. Common mechanism in endothelin-3 and PAF receptor function for anti-inflammatory responses. (United States)

    Sato, Akira; Ebina, Keiichi


    Platelet-activating factor (PAF) is a potent lipid mediator that is implicated in numerous inflammatory diseases. Under inflammatory conditions, PAF is biosynthesized through the remodelling pathway and elicits many inflammatory responses through binding to its specific PAF receptor. Endogenous bioactive endothelins (ETs: ET-1, -2, and -3) are also considered potent inflammatory mediators that play a critical role in many inflammatory diseases. In this perspective, we provide a brief overview of possible common mechanisms in ETs and PAF receptor function for inflammatory responses. Accumulating evidence strongly suggests that ET-3, but not ET-1 and ET-2, can attenuate PAF-induced inflammation through direct binding of the Tyr-Lys-Asp (YKD) region in the peptide to PAF and its metabolite/precursor lyso-PAF, followed by inhibition of binding between PAF and its receptor. Additionally, YKD sequence-containing peptides may be useful as a novel type of anti-inflammatory drugs targeting this mechanism. These findings should lead to new treatment strategies for numerous inflammatory diseases by targeting the common mechanism in ET and PAF receptor function. © 2013 Elsevier B.V. All rights reserved.

  6. Thermal response of nanocomposite materials under pulsed laser excitation

    International Nuclear Information System (INIS)

    Rashidi-Huyeh, Majid; Palpant, Bruno


    The optical properties of nanocomposite materials made of matrix-embedded noble metal nanoparticles strongly depend on thermal effects from different origins. We propose a classical model describing the energy exchanges within the nanoparticles and between the latter and the surrounding dielectric host subsequent to a light pulse absorption. This model, which accounts for the thermal interactions between neighboring particles, allows us to calculate numerically the temperature dynamics of the electrons, metal lattice and matrix as functions of particle size, and metal concentration of the medium, whatever be the pulsed excitation temporal regime. It is illustrated in the case of Au:SiO 2 materials under femtosecond and nanosecond pulse excitation. It is shown that, in the femtosecond regime, the heat transfer to the matrix cannot be neglected beyond a few picosecond delay from which particle size and metal concentration play a significant role in the electron relaxation. In the nanosecond regime, these morphologic parameters influence crucially the material thermal behavior with the possibility of generating a thermal lens effect. The implications in the analysis of experimental results regarding both the electron relaxation dynamics and the nonlinear optical properties are also discussed. Finally, a method to adapt the model to the case of thin nanocomposite film is proposed

  7. Analyses of transient plant response under emergency situations

    Energy Technology Data Exchange (ETDEWEB)

    Koyama, Kazuya [Advanced Reactor Technology, Co. Ltd., Engineering Department, Tokyo (Japan); Shimakawa, Yoshio; Hishida, Masahiko [Mitsubishi Heavy Industry, Ltd., Reactor Core Engineering and Safety Engineering Department, Tokyo (Japan)


    In order to support development of the dynamic reliability analysis program DYANA, analyses were made on the event sequences anticipated under emergency situations using the plant dynamics simulation computer code Super-COPD. The analytical models were developed for Super-COPD such as the guard vessel, the maintenance cooling system, the sodium overflow and makeup system, etc. in order to apply the code to the simulation of the emergency situations. The input data were prepared for the analyses. About 70 sequences were analyzed, which are categorized into the following events: (1) PLOHS (Protected Loss of Heat Sink), (2) LORL (Loss of Reactor Level)-J: failure of sodium makeup by the primary sodium overflow and makeup system, (3) LORL-G : failure of primary coolant pump trip, (4) LORL-I: failure of the argon cover gas isolation, and (5) heat removal only using the ventilation system of the primary cooling system rooms. The results were integrated into an input file for preparing the functions for the neural network simulation. (author)

  8. 29 CFR 17.4 - What are the Secretary's general responsibilities under the Order? (United States)


    ... 29 Labor 1 2010-07-01 2010-07-01 true What are the Secretary's general responsibilities under the Order? 17.4 Section 17.4 Labor Office of the Secretary of Labor INTERGOVERNMENTAL REVIEW OF DEPARTMENT OF LABOR PROGRAMS AND ACTIVITIES § 17.4 What are the Secretary's general responsibilities under the...

  9. 20 CFR 667.705 - Who is responsible for funds provided under title I of WIA? (United States)


    ... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Who is responsible for funds provided under title I of WIA? 667.705 Section 667.705 Employees' Benefits EMPLOYMENT AND TRAINING ADMINISTRATION... WIA? (a) The recipient is responsible for all funds under its grant(s). (b) The political jurisdiction...

  10. Response of structural elements under non-uniformly distributed dynamic loads

    NARCIS (Netherlands)

    Westerhof, T.A.T.; Huebner, M.; Ferretti, D.L.; Doormaal, J.C.A.M. van; Gebbeken, N.


    Determination of the structural response of a structural element under blast loading is of interest to vulnerability / lethality (V/L) studies of military operations in urban terrain. These studies require a quick and easy to use method to simulate the structural response of e.g. a wall under

  11. Organic Matter Responses to Radiation under Lunar Conditions. (United States)

    Matthewman, Richard; Crawford, Ian A; Jones, Adrian P; Joy, Katherine H; Sephton, Mark A


    Large bodies, such as the Moon, that have remained relatively unaltered for long periods of time have the potential to preserve a record of organic chemical processes from early in the history of the Solar System. A record of volatiles and impactors may be preserved in buried lunar regolith layers that have been capped by protective lava flows. Of particular interest is the possible preservation of prebiotic organic materials delivered by ejected fragments of other bodies, including those originating from the surface of early Earth. Lava flow layers would shield the underlying regolith and any carbon-bearing materials within them from most of the effects of space weathering, but the encapsulated organic materials would still be subject to irradiation before they were buried by regolith formation and capped with lava. We have performed a study to simulate the effects of solar radiation on a variety of organic materials mixed with lunar and meteorite analog substrates. A fluence of ∼3 × 10 13 protons cm -2 at 4-13 MeV, intended to be representative of solar energetic particles, has little detectable effect on low-molecular-weight (≤C 30 ) hydrocarbon structures that can be used to indicate biological activity (biomarkers) or the high-molecular-weight hydrocarbon polymer poly(styrene-co-divinylbenzene), and has little apparent effect on a selection of amino acids (≤C 9 ). Inevitably, more lengthy durations of exposure to solar energetic particles may have more deleterious effects, and rapid burial and encapsulation will always be more favorable to organic preservation. Our data indicate that biomarker compounds that may be used to infer biological activity on their parent planet can be relatively resistant to the effects of radiation and may have a high preservation potential in paleoregolith layers on the Moon. Key Words: Radiation-Moon-Regolith-Amino acids-Biomarkers. Astrobiology 16, 900-912.

  12. Organic Matter Responses to Radiation under Lunar Conditions (United States)

    Matthewman, Richard; Crawford, Ian A.; Jones, Adrian P.; Joy, Katherine H.; Sephton, Mark A.


    Large bodies, such as the Moon, that have remained relatively unaltered for long periods of time have the potential to preserve a record of organic chemical processes from early in the history of the Solar System. A record of volatiles and impactors may be preserved in buried lunar regolith layers that have been capped by protective lava flows. Of particular interest is the possible preservation of prebiotic organic materials delivered by ejected fragments of other bodies, including those originating from the surface of early Earth. Lava flow layers would shield the underlying regolith and any carbon-bearing materials within them from most of the effects of space weathering, but the encapsulated organic materials would still be subject to irradiation before they were buried by regolith formation and capped with lava. We have performed a study to simulate the effects of solar radiation on a variety of organic materials mixed with lunar and meteorite analog substrates. A fluence of ˜3 × 1013 protons cm-2 at 4-13 MeV, intended to be representative of solar energetic particles, has little detectable effect on low-molecular-weight (≤C30) hydrocarbon structures that can be used to indicate biological activity (biomarkers) or the high-molecular-weight hydrocarbon polymer poly(styrene-co-divinylbenzene), and has little apparent effect on a selection of amino acids (≤C9). Inevitably, more lengthy durations of exposure to solar energetic particles may have more deleterious effects, and rapid burial and encapsulation will always be more favorable to organic preservation. Our data indicate that biomarker compounds that may be used to infer biological activity on their parent planet can be relatively resistant to the effects of radiation and may have a high preservation potential in paleoregolith layers o