WorldWideScience

Sample records for underlying mechanisms linking

  1. Linking Pesticide Exposure with Pediatric Leukemia: Potential Underlying Mechanisms.

    Science.gov (United States)

    Hernández, Antonio F; Menéndez, Pablo

    2016-03-29

    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.

  2. A Behavioral Genetic Model of the Mechanisms Underlying the Link Between Obesity and Symptoms of ADHD.

    Science.gov (United States)

    Patte, Karen A; Davis, Caroline A; Levitan, Robert D; Kaplan, Allan S; Carter-Major, Jacqueline; Kennedy, James L

    2016-01-21

    The ADHD-obesity link has been suggested to result from a shared underlying basis of suboptimal dopamine (DA); however, this theory conflicts evidence that an amplified DA signal increases the risk for overeating and weight gain. A model was tested in which ADHD symptoms, predicted by hypodopaminergic functioning in the prefrontal cortex, in combination with an enhanced appetitive drive, predict hedonic eating and, in turn, higher body mass index (BMI). DRD2 and DRD4 markers were genotyped. The model was tested using structural equation modeling in a nonclinical sample (N = 421 adults). The model was a good fit to the data. Controlling for education, all parameter estimates were significant, except for the DRD4-ADHD symptom pathway. The significant indirect effect indicates that overeating mediated the ADHD symptoms-BMI association. Results support the hypothesis that overeating and elevated DA in the ventral striatum-representative of a greater reward response-contribute to the ADHD symptom-obesity relationship. © The Author(s) 2016.

  3. Neuron-specific chromatin remodeling: a missing link in epigenetic mechanisms underlying synaptic plasticity, memory, and intellectual disability disorders.

    Science.gov (United States)

    Vogel-Ciernia, Annie; Wood, Marcelo A

    2014-05-01

    Long-term memory formation requires the coordinated regulation of gene expression. Until recently nucleosome remodeling, one of the major epigenetic mechanisms for controlling gene expression, had been largely unexplored in the field of neuroscience. Nucleosome remodeling is carried out by chromatin remodeling complexes (CRCs) that interact with DNA and histones to physically alter chromatin structure and ultimately regulate gene expression. Human exome sequencing and gene wide association studies have linked mutations in CRC subunits to intellectual disability disorders, autism spectrum disorder and schizophrenia. However, how mutations in CRC subunits were related to human cognitive disorders was unknown. There appears to be both developmental and adult specific roles for the neuron specific CRC nBAF (neuronal Brg1/hBrm Associated Factor). nBAF regulates gene expression required for dendritic arborization during development, and in the adult, contributes to long-term potentiation, a form of synaptic plasticity, and long-term memory. We propose that the nBAF complex is a novel epigenetic mechanism for regulating transcription required for long-lasting forms of synaptic plasticity and memory processes and that impaired nBAF function may result in human cognitive disorders. Copyright © 2013 Elsevier Ltd. All rights reserved.

  4. Child abuse: underlying mechanisms

    OpenAIRE

    Martínez, Gladys S.

    2009-01-01

    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...

  5. Linking properties to microstructure through multiresolution mechanics

    Science.gov (United States)

    McVeigh, Cahal James

    The macroscale mechanical and physical properties of materials are inherently linked to the underlying microstructure. Traditional continuum mechanics theories have focused on approximating the heterogeneous microstructure as a continuum, which is conducive to a partial differential equation mathematical description. Although this makes large scale simulation of material much more efficient than modeling the detailed microstructure, the relationship between microstructure and macroscale properties becomes unclear. In order to perform computational materials design, material models must clearly relate the key underlying microstructural parameters (cause) to macroscale properties (effect). In this thesis, microstructure evolution and instability events are related to macroscale mechanical properties through a new multiresolution continuum analysis approach. The multiresolution nature of this theory allows prediction of the evolving magnitude and scale of deformation as a direct function of the changing microstructure. This is achieved via a two-pronged approach: (a) Constitutive models which track evolving microstructure are developed and calibrated to direct numerical simulations (DNS) of the microstructure. (b) The conventional homogenized continuum equations of motion are extended via a virtual power approach to include extra coupled microscale stresses and stress couples which are active at each characteristic length scale within the microstructure. The multiresolution approach is applied to model the fracture toughness of a cemented carbide, failure of a steel alloy under quasi-static loading conditions and the initiation and velocity of adiabatic shear bands under high speed dynamic loading. In each case the multiresolution analysis predicts the important scale effects which control the macroscale material response. The strain fields predicted in the multiresolution continuum analyses compare well to those observed in direct numerical simulations of the

  6. Identifying links between origami and compliant mechanisms

    Directory of Open Access Journals (Sweden)

    H. C. Greenberg

    2011-12-01

    Full Text Available Origami is the art of folding paper. In the context of engineering, orimimetics is the application of folding to solve problems. Kinetic origami behavior can be modeled with the pseudo-rigid-body model since the origami are compliant mechanisms. These compliant mechanisms, when having a flat initial state and motion emerging out of the fabrication plane, are classified as lamina emergent mechanisms (LEMs. To demonstrate the feasibility of identifying links between origami and compliant mechanism analysis and design methods, four flat folding paper mechanisms are presented with their corresponding kinematic and graph models. Principles from graph theory are used to abstract the mechanisms to show them as coupled, or inter-connected, mechanisms. It is anticipated that this work lays a foundation for exploring methods for LEM synthesis based on the analogy between flat-folding origami models and linkage assembly.

  7. 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 ...

  8. 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.

  9. Molecular mechanisms underlying bacterial persisters

    DEFF Research Database (Denmark)

    Maisonneuve, Etienne; Gerdes, Kenn

    2014-01-01

    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...

  10. Linking Quantum Mechanics to Freshman Physics

    Science.gov (United States)

    Vandegrift, Guy

    1998-10-01

    First-year quantum mechanics can be linked to introductory physics. One example is the Mossbauer effect, which is explained using a simple solution to Schrodinger's equation involving the Dirac delta function. Generalization to N coupled harmonic oscillators shows that the equality of the forces exerted by winner and loser in the game of "tug-of-war" is only an approximation because Newton's third law of motion is not valid (unless phonon momentum is considered). Another example is a treatment of the Gaussian wavepacket which involves less algebra than found in standard textbooks, yet shows that the peak moves according to the familiar equation of motion x = vt + (1/2)at^2 when the applied force is uniform. Finally, a rendition of "Turkey in the Straw" on the viola illustrates Heisenberg's uncertainty principle, which can be written in the less mysterious form, f=(N+-.1)/T , where N cycles are counted in T seconds. Students experience this uncertainty as they try to measure the frequency of a stretched slinky.

  11. Metacognitive mechanisms underlying lucid dreaming.

    Science.gov (United States)

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

    2015-01-21

    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.

  12. Linking plants, fungi and soil mechanics

    Science.gov (United States)

    Yildiz, Anil; Graf, Frank

    2017-04-01

    Plants provide important functions in respect soil strength and are increasingly considered for slope stabilisation within eco-engineering methods, particularly to prevent superficial soil failure. The protective functions include hydrological regulation through interception and evapo-transpiration as well as mechanical stabilisation through root reinforcement and, to a certain extent, chemical stabilisation through sticky metabolites. The ever-growing application of plants in slope stabilisation demanded more precise information of the vegetation effects and, concomitant, led the models for quantifying the reinforcement shoot up like mushrooms. However, so far, the framework and interrelationships for both the role of plants and the quantification concepts have not been thoroughly analysed and comprehensively considered, respectively, often resulting in unsatisfactory results. Although it seems obvious and is implicitly presupposed that the plant specific functions related to slope stability require growth and development, this is anything but given, particularly under the often hostile conditions dominating on bare and steep slopes. There, the superficial soil layer is often characterised by a lack of fines and missing medium-sized and fine pores due to an unstable soil matrix, predominantly formed by coarse grains. Low water retention capacity and substantial leaching of nutrients are the adverse consequences. Given this general set-up, sustainable plant growth and, particularly, root development is virtually unachievable. At exactly this point mycorrhizal fungi, the symbiotic partners of almost all plants used in eco-engineering, come into play. Though, they are probably well-known within the eco-engineering community, mycorrhizal fungi lead a humble existence. This is in spite of the fact that they supply their hosts with water and nutrients, improving the plant's ability to master otherwise unbridgeable environmental conditions. However, in order to support

  13. Linking metabolomics data to underlying metabolic regulation

    Directory of Open Access Journals (Sweden)

    Thomas eNägele

    2014-11-01

    Full Text Available The comprehensive experimental analysis of a metabolic constitution plays a central role in approaches of organismal systems biology.Quantifying the impact of a changing environment on the homeostasis of cellular metabolism has been the focus of numerous studies applying various metabolomics techniques. It has been proven that approaches which integrate different analytical techniques, e.g. LC-MS, GC-MS, CE-MS and H-NMR, can provide a comprehensive picture of a certain metabolic homeostasis. Identification of metabolic compounds and quantification of metabolite levels represent the groundwork for the analysis of regulatory strategies in cellular metabolism. This significantly promotes our current understanding of the molecular organization and regulation of cells, tissues and whole organisms.Nevertheless, it is demanding to elicit the pertinent information which is contained in metabolomics data sets.Based on the central dogma of molecular biology, metabolite levels and their fluctuations are the result of a directed flux of information from gene activation over transcription to translation and posttranslational modification.Hence, metabolomics data represent the summed output of a metabolic system comprising various levels of molecular organization.As a consequence, the inverse assignment of metabolomics data to underlying regulatory processes should yield information which-if deciphered correctly-provides comprehensive insight into a metabolic system.Yet, the deduction of regulatory principles is complex not only due to the high number of metabolic compounds, but also because of a high level of cellular compartmentalization and differentiation.Motivated by the question how metabolomics approaches can provide a representative view on regulatory biochemical processes, this article intends to present and discuss current metabolomics applications, strategies of data analysis and their limitations with respect to the interpretability in context of

  14. Linking scales in sea ice mechanics

    Science.gov (United States)

    Weiss, Jérôme; Dansereau, Véronique

    2017-02-01

    Mechanics plays a key role in the evolution of the sea ice cover through its control on drift, on momentum and thermal energy exchanges between the polar oceans and the atmosphere along cracks and faults, and on ice thickness distribution through opening and ridging processes. At the local scale, a significant variability of the mechanical strength is associated with the microstructural heterogeneity of saline ice, however characterized by a small correlation length, below the ice thickness scale. Conversely, the sea ice mechanical fields (velocity, strain and stress) are characterized by long-ranged (more than 1000 km) and long-lasting (approx. few months) correlations. The associated space and time scaling laws are the signature of the brittle character of sea ice mechanics, with deformation resulting from a multi-scale accumulation of episodic fracturing and faulting events. To translate the short-range-correlated disorder on strength into long-range-correlated mechanical fields, several key ingredients are identified: long-ranged elastic interactions, slow driving conditions, a slow viscous-like relaxation of elastic stresses and a restoring/healing mechanism. These ingredients constrained the development of a new continuum mechanics modelling framework for the sea ice cover, called Maxwell-elasto-brittle. Idealized simulations without advection demonstrate that this rheological framework reproduces the main characteristics of sea ice mechanics, including anisotropy, spatial localization and intermittency, as well as the associated scaling laws. This article is part of the themed issue 'Microdynamics of ice'.

  15. Linking metacommunity paradigms to spatial coexistence mechanisms.

    Science.gov (United States)

    Shoemaker, Lauren G; Melbourne, Brett A

    2016-09-01

    Four metacommunity paradigms-usually called neutral, species sorting, mass effects, and patch dynamics, respectively-are widely used for empirical and theoretical studies of spatial community dynamics. The paradigm framework highlights key ecological mechanisms operating in metacommunities, such as dispersal limitation, competition-colonization tradeoffs, or species equivalencies. However, differences in coexistence mechanisms between the paradigms and in situations with combined influences of multiple paradigms are not well understood. Here, we create a common model for competitive metacommunities, with unique parameterizations for each metacommunity paradigm and for scenarios with multiple paradigms operating simultaneously. We derive analytical expressions for the strength of Chesson's spatial coexistence mechanisms and quantify these for each paradigm via simulation. For our model, fitness-density covariance, a concentration effect measuring the importance of intraspecific aggregation of individuals, is the dominant coexistence mechanism in all three niche-based metacommunity paradigms. Increased dispersal between patches erodes intraspecific aggregation, leading to lower coexistence strength in the mass effects paradigm compared to species sorting. Our analysis demonstrates the potential importance of aggregation of individuals (fitness-density covariance) over co-variation in abiotic environments and competition between species (the storage effect), as fitness-density covariance can be stronger than the storage effect and is the sole stabilizing mechanism in the patch dynamics paradigm. As expected, stable coexistence does not occur in the neutral paradigm, which requires species to be equal and emphasizes the role of stochasticity. We show that stochasticity also plays an important role in niche-structured metacommunities by altering coexistence strength. We conclude that Chesson's spatial coexistence mechanisms provide a flexible framework for comparing

  16. Mechanism linking diabetes mellitus and obesity.

    Science.gov (United States)

    Al-Goblan, Abdullah S; Al-Alfi, Mohammed A; Khan, Muhammad Z

    2014-01-01

    Body mass index has a strong relationship to diabetes and insulin resistance. In obese individuals, the amount of nonesterified fatty acids, glycerol, hormones, cytokines, proinflammatory markers, and other substances that are involved in the development of insulin resistance, is increased. The pathogenesis in the development of diabetes is based on the fact that the β-islet cells of the pancreas are impaired, causing a lack of control of blood glucose. The development of diabetes becomes more inevitable if the failure of β-islet cells of the pancreas is accompanied by insulin resistance. Weight gain and body mass are central to the formation and rising incidence of type 1 and type 2 diabetes. This literature review will demonstrate the facts that link obesity with insulin resistance and pancreatic β-cell dysfunction. In conclusion, new approaches in managing and preventing diabetes in obese individuals must be studied and investigated based on the facts.

  17. Epidemiological bases and molecular mechanisms linking obesity, diabetes, and cancer.

    Science.gov (United States)

    Gutiérrez-Salmerón, María; Chocarro-Calvo, Ana; García-Martínez, José Manuel; de la Vieja, Antonio; García-Jiménez, Custodia

    2017-02-01

    The association between diabetes and cancer was hypothesized almost one century ago. Today, a vast number of epidemiological studies support that obese and diabetic populations are more likely to experience tissue-specific cancers, but the underlying molecular mechanisms remain unknown. Obesity, diabetes, and cancer share many hormonal, immune, and metabolic changes that may account for the relationship between diabetes and cancer. In addition, antidiabetic treatments may have an impact on the occurrence and course of some cancers. Moreover, some anticancer treatments may induce diabetes. These observations aroused a great controversy because of the ethical implications and the associated commercial interests. We report an epidemiological update from a mechanistic perspective that suggests the existence of many common and differential individual mechanisms linking obesity and type 1 and 2 diabetes mellitus to certain cancers. The challenge today is to identify the molecular links responsible for this association. Classification of cancers by their molecular signatures may facilitate future mechanistic and epidemiological studies. Copyright © 2016 SEEN. Publicado por Elsevier España, S.L.U. All rights reserved.

  18. Metacognitive mechanisms underlying lucid dreaming

    OpenAIRE

    Filevich, E.; Dresler, M.; Brick, T.R.; Kuhn, S.

    2015-01-01

    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 participant...

  19. Mechanism linking diabetes mellitus and obesity

    Directory of Open Access Journals (Sweden)

    Al-Goblan AS

    2014-12-01

    Full Text Available Abdullah S Al-Goblan,1 Mohammed A Al-Alfi,1 Muhammad Z Khan2 1Diabetes Center, King Fahad Specialist Hospital, Buraidah, Qassim, Kingdom of Saudi Arabia; 2Sulaiman AlRajhi Colleges, Al Bukairiyah, Kingdom of Saudi Arabia Abstract: Body mass index has a strong relationship to diabetes and insulin resistance. In obese individuals, the amount of nonesterified fatty acids, glycerol, hormones, cytokines, proinflammatory markers, and other substances that are involved in the development of insulin resistance, is increased. The pathogenesis in the development of diabetes is based on the fact that the β-islet cells of the pancreas are impaired, causing a lack of control of blood glucose. The development of diabetes becomes more inevitable if the failure of β-islet cells of the pancreas is accompanied by insulin resistance. Weight gain and body mass are central to the formation and rising incidence of type 1 and type 2 diabetes. This literature review will demonstrate the facts that link obesity with insulin resistance and pancreatic β-cell dysfunction. In conclusion, new approaches in managing and preventing diabetes in obese individuals must be studied and investigated based on the facts. Keywords: diabetes mellitus, obesity, insulin resistance

  20. Mechanisms linking excess adiposity and carcinogenesis promotion

    Directory of Open Access Journals (Sweden)

    Ana I. Pérez-Hernández

    2014-05-01

    Full Text Available Obesity constitutes one of the most important metabolic diseases being associated to insulin resistance development and increased cardiovascular risk. Association between obesity and cancer has also been well-established for several tumor types, such as breast cancer in postmenopausal women, colorectal and prostate cancer. Cancer is the first death cause in developed countries and the second one in developing countries, with high incidence rates around the world. Furthermore, it has been estimated that 15-20% of all cancer deaths may be attributable to obesity. Tumor growth is regulated by interactions between tumor cells and their tissue microenvironment. In this sense, obesity may lead to cancer development through dysfunctional adipose tissue and altered signaling pathways. In this review, three main pathways relating obesity and cancer development are examined: i inflammatory changes leading to macrophage polarization and altered adipokine profile; ii insulin resistance development; and iii adipose tissue hypoxia. Since obesity and cancer present a high prevalence, the association between these conditions is of great public health significance and studies showing mechanisms by which obesity lead to cancer development and progression are needed to improve prevention and management of these diseases.

  1. Two distinct neural mechanisms underlying indirect reciprocity.

    Science.gov (United States)

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

    2014-03-18

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

  2. Molecular Mechanisms Underlying Hepatocellular Carcinoma

    Directory of Open Access Journals (Sweden)

    Christian Trepo

    2009-11-01

    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.

  3. Mechanical behavior of highly cross-linked polymer networks and its links to microscopic structure.

    Science.gov (United States)

    Mukherji, Debashish; Abrams, Cameron F

    2009-06-01

    Highly cross-linked polymer (HCP) networks are becoming increasingly important as high-performance adhesives and multifunctional composite materials. Because of their cross-linked molecular architectures, HCPs can be strong but brittle. One key goal in improving the performance of an HCP is to increase toughness without sacrificing strength. Using large scale molecular-dynamics simulation, we compare and characterize the mechanical behavior of two model HCPs under tensile deformation. In the first case, bond angles among any three connected monomers are unconstrained and in the second case we impose harmonic tetrahedral bond angle constraints. We perform a detailed microstructural analysis that establishes a unique correlation between macroscopic mechanical behavior and the microscopic structure of an HCP. While, in the unconstrained system, strain-hardening behavior is observed that is attributed to the formation of microvoids, the void growth is completely arrested in the constrained system and no strain hardening is observed. Moreover, after the initial strain-hardening phase, the unconstrained system displays the same stress-strain behavior as that of a constrained network. Strain hardening makes the unconstrained system ductile while it retains the same tensile strength as the constrained system. We suggest that bond angle flexibility of cross-linkers might be a possible means to control ductility in an HCP network at a constant cross-linker density. We have also studied the effect of temperature, strain rate, and intermonomer nonbonded interaction strength on the stress-strain behavior. Interestingly at a strong intermonomer nonbonded interaction strength, no strain hardening is observed even in the unconstrained system and fracture sets in at around 1% strain, similar to what is observed in an experimental system such as epoxy and vinyl-ester based thermosets. This indicates that strong nonbonded interactions play a key role in making an HCP strong but

  4. Physical and mechanical properties of gamma radiation cross-linked polyethylene

    International Nuclear Information System (INIS)

    Gonzalez, Maria E.; Romero, G.; Smolko, Eduardo E.

    1999-01-01

    Granulated LDPE 2003 polyethylene was extruded and irradiated under nitrogen with 150, 200 and 300 kGy gamma rays doses to produce cross-linking. The study of the physical and mechanical properties shows that the product has a high degree of molecular cross-linking, can be heated up to 200 C for 2 hours without deformation and that the mechanical properties improve. Preliminary aging tests indicate that after heating at 60 C for 4 weeks no physical or mechanical deterioration can be observed. (author)

  5. 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 ...

  6. The Mechanisms Linking Health Literacy to Behavior and Health Status

    Science.gov (United States)

    Osborn, Chandra Y.; Paasche-Orlow, Michael K.; Bailey, Stacy Cooper; Wolf, Michael S.

    2011-01-01

    Objective To examine the mechanisms linking health literacy to physical activity and self-reported health. Methods From 2005–2007, patients (N=330) with hypertension were recruited from safety net clinics. Path analytic models tested the pathways linking health literacy to physical activity and self-reported health. Results There were significant paths from health literacy to knowledge (r=0.22, Pphysical activity (r=0.17, Pphysical activity to health status (r=0.17, Pliteracy sensitive and aim to enhance patient health knowledge and self-efficacy to promote self-care behavior and desirable health outcomes. PMID:20950164

  7. Links between fluid mechanics and quantum mechanics: a model for information in economics?

    Science.gov (United States)

    Haven, Emmanuel

    2016-05-28

    This paper tallies the links between fluid mechanics and quantum mechanics, and attempts to show whether those links can aid in beginning to build a formal template which is usable in economics models where time is (a)symmetric and memory is absent or present. An objective of this paper is to contemplate whether those formalisms can allow us to model information in economics in a novel way. © 2016 The Author(s).

  8. Mechanical buckling of artery under pulsatile pressure.

    Science.gov (United States)

    Liu, Qin; Han, Hai-Chao

    2012-04-30

    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. Amorphization of ice under mechanical stresses

    Science.gov (United States)

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

    2017-11-01

    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.

  10. Fundamental link between system theory and statistical mechanics

    International Nuclear Information System (INIS)

    Atmanspacher, H.; Scheingraber, H.

    1987-01-01

    A fundamental link between system theory and statistical mechanics has been found to be established by the Kolmogorov entropy. By this quantity the temporal evolution of dynamical systems can be classified into regular, chaotic, and stochastic processes. Since K represents a measure for the internal information creation rate of dynamical systems, it provides an approach to irreversibility. The formal relationship to statistical mechanics is derived by means of an operator formalism originally introduced by Prigogine. For a Liouville operator L and an information operator M tilde acting on a distribution in phase space, it is shown that i[L, M tilde] = KI (I = identity operator). As a first consequence of this equivalence, a relation is obtained between the chaotic correlation time of a system and Prigogine's concept of a finite duration of presence. Finally, the existence of chaos in quantum systems is discussed with respect to the existence of a quantum mechanical time operator

  11. Gas Bubble Dynamics under Mechanical Vibrations

    Science.gov (United States)

    Mohagheghian, Shahrouz; Elbing, Brian

    2017-11-01

    The scientific community has a limited understanding of the bubble dynamics under mechanical oscillations due to over simplification of Navier-Stockes equation by neglecting the shear stress tensor and not accounting for body forces when calculating the acoustic radiation force. The current work experimental investigates bubble dynamics under mechanical vibration and resulting acoustic field by measuring the bubble size and velocity using high-speed imaging. The experimental setup consists of a custom-designed shaker table, cast acrylic bubble column, compressed air injection manifold and an optical imaging system. The mechanical vibrations resulted in accelerations between 0.25 to 10 times gravitational acceleration corresponding to frequency and amplitude range of 8 - 22Hz and 1 - 10mm respectively. Throughout testing the void fraction was limited to 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. Neural Mechanisms of the Rejection-Aggression Link.

    Science.gov (United States)

    Chester, David S; Lynam, Donald R; Milich, Richard; DeWall, C Nathan

    2018-03-28

    Social rejection is a painful event that often increases aggression. However, the neural mechanisms of this rejection-aggression link remain unclear. A potential clue may be that rejected people often recruit the ventrolateral prefrontal cortex's (VLPFC) self-regulatory processes to manage the pain of rejection. Using functional MRI, we replicated previous links between rejection and activity in the brain's mentalizing network, social pain network, and VLPFC. VLPFC recruitment during rejection was associated with greater activity in the brain's reward network (i.e., the ventral striatum) when individuals were given an opportunity to retaliate. This retaliation-related striatal response was associated with greater levels of retaliatory aggression. Dispositionally aggressive individuals exhibited less functional connectivity between the ventral striatum and the right VLPFC during aggression. This connectivity exerted a suppressing effect on dispositionally aggressive individuals' greater aggressive responses to rejection. These results help explain how the pain of rejection and reward of revenge motivate rejected people to behave aggressively.

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

    Directory of Open Access Journals (Sweden)

    Jingqiang Li

    2015-02-01

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

  14. Theoretical and experimental analysis of inverter fed induction motor system under DC link capacitor failure

    Directory of Open Access Journals (Sweden)

    Hadeed A. Sher

    2017-04-01

    Full Text Available In this paper theoretical and experimental analysis of an AC–DC–AC inverter under DC link capacitor failure is presented. The failure study conducted for this paper is the open circuit of the DC link capacitor. The presented analysis incorporates the results for both single and three phase AC input. It has been observed that the higher ripple frequency provides better ride through capability for this fault. Furthermore, the effects of this fault on electrical characteristics of AC–DC–AC inverter and mechanical properties of the induction motor are also presented. Moreover, the effect of pulsating torque as a result of an open circuited DC link capacitor is also taken into consideration. Theoretical analysis is supported by computer aided simulation as well as with a real time experimental prototype.

  15. Enhancement of FSO communications links under complex environment

    Science.gov (United States)

    Alnajjar, Satea H.; Noori, Ammar A.; Moosa, Arwa A.

    2017-06-01

    Free space optical communication is a line-of-sight (LOS) technology that uses lasers to provide optical bandwidth connections. Potential disturbance arising from the weather condition is one of the most effective factors that influence the bi-directional free space optics (FSO) performance. The complex weather condition in the Middle East region and Arabian Gulf has been dominated by dust storms activities. Dust storms directly affect the characteristics of FSO and consequently lead to an increase in the bit error rate (BER) and deterioration Q-factor to bad levels due to the high attenuation factor. In this research, the authors compare the differences between two bi-directional FSOs. One is the traditional link, and the other has been developed to enhance the system performance under the dust storms condition. The proposed design consists of dual FSO channels, and each one includes erbium-doped fiber amplifier (EDFA) optical amplifiers. This design has demonstrated the proficiency in addressing the attenuation that occurs due to weather stickers. The results prove there is an improvement in performance by measuring the Q-factor. In addition, BER can be significantly improved, and further communicating distance can be achieved by utilizing 1550 nm with multiple channels and EDFA.

  16. Inflammatory Mechanisms Linking Periodontal Diseases to Cardiovascular Diseases

    Science.gov (United States)

    Schenkein, Harvey A.; Loos, Bruno G.

    2015-01-01

    Aims In this paper, inflammatory mechanisms that link periodontal diseases to cardiovascular diseases (CVD) are reviewed. Materials and Methods and Results This paper is a literature review. Studies in the literature implicate a number of possible mechanisms that could be responsible for increased inflammatory responses in atheromatous lesions due to periodontal infections. These include increased systemic levels of inflammatory mediators stimulated by bacteria and their products at sites distant from the oral cavity, elevated thrombotic and hemostatic markers that promote a prothrombotic state and inflammation, cross-reactive systemic antibodies that promote inflammation and interact with the atheroma, promotion of dyslipidemia with consequent increases in proinflammatory lipid classes and subclasses, and common genetic susceptibility factors present in both disease leading to increased inflammatory responses. Conclusions Such mechanisms may be thought to act in concert to increase systemic inflammation in periodontal disease and to promote or exacerbate atherogenesis. However, proof that the increase in systemic inflammation attributable to periodontitis impacts inflammatory responses during atheroma development, thrombotic events, or myocardial infarction or stroke is lacking. PMID:23627334

  17. Linking HRM and Knowledge Transfer via Individual-level Mechanisms

    DEFF Research Database (Denmark)

    Minbaeva, Dana; Mäkelä, Kristiina; Rabbiosi, Larissa

    2012-01-01

    In response to recent calls for more research on micro-foundations, we seek to link human resource management (HRM) and knowledge transfer through individual-level mechanisms, arguing that individual-level conditions of action influence the extent to which employees engage in knowledge exchange. We...... examine four such conditions empirically using data from 811 employees in three Danish multinational corporations (MNCs). Our findings suggest that individual-level perceptions of organizational commitment to knowledge sharing, and extrinsic motivation, directly influence the extent to which employees...... engage in firm-internal knowledge exchange. We also find that intrinsic motivation and engagement in social interaction significantly mediate the relationship between perceived organizational commitment and knowledge exchange. Given that HRM can influence such conditions through an overall signaling...

  18. Enhancing network performance under single link failure with AS-disjoint BGP extension

    DEFF Research Database (Denmark)

    Manolova, Anna Vasileva; Romeral, S.; Ruepp, Sarah Renée

    2009-01-01

    In this paper we propose an enhancement of the BGP protocol for obtaining AS-disjoint paths in GMPLS multi-domain networks. We evaluate the benefits of having AS-disjoint paths under single inter-domain link failure for two main applications: routing of future connection requests during routing...... protocol re-convergence and applying multi-domain restoration as survivability mechanism in case of a single link failure. The proposed BGP modification is a simple and effective solution for disjoint path selection in connection-oriented multi-domain networks. Our results show that applying the proper...... failure notification method combined with our proposal reduces the blocking of new connection requests under protocol re-convergence. Furthermore. we show that our proposal is a valuable complementary process for increasing the network resilience....

  19. Pathogenic mechanisms linking periodontal diseases with adverse pregnancy outcomes.

    Science.gov (United States)

    Cetin, I; Pileri, P; Villa, A; Calabrese, S; Ottolenghi, L; Abati, S

    2012-06-01

    In the last 2 decades, a large proportion of studies have focused on the relationship between maternal periodontal disease and poor obstetric outcomes. The aim of the present review is to summarize the current knowledge about human studies on the pathogenetic mechanisms linking periodontal diseases with adverse pregnancy outcomes. A search of the medical literature was conducted using NIH (National Institute of Health) Pubmed through April 2011. Articles were identified with the Medical Subject Heading (MeSH) and free text terms "small for gestational age (SGA)," "preeclampsia," "preterm labor," and "periodontal disease." Experimental human studies have shown that periodontal pathogens may disseminate toward placental and fetal tissues accompanied by an increase in inflammatory mediators in the placenta. As such, new inflammatory reactions within the placental tissues of the pregnant woman may occur, the physiological levels of prostaglandin E(2) (PGE(2)) and tumor necrosis factor-α (TNF-α) in the amniotic fluid may increase and eventually lead to premature delivery. Although many data from clinical trials suggest that periodontal disease may increase the adverse pregnancy outcome, the exact pathogenetic mechanism involved remains controversial. The findings explain the potential link between periodontal infections and adverse pregnancy outcomes. First, periodontal bacteria can directly cause infections both of the uteroplacenta and the fetus; second, systemic inflammatory changes induced by periodontal diseases can activate responses at the maternal-fetal interface. Of note, associative studies have produced different results in different population groups and no conclusive evidence has still been produced for the potential role of preventive periodontal care to reduce the risk factors of preterm birth.

  20. Mechanisms linking energy balance and reproduction: impact of prenatal environment.

    Science.gov (United States)

    Rhinehart, Erin M

    2016-01-01

    The burgeoning field of metabolic reproduction regulation has been gaining momentum due to highly frequent discoveries of new neuroendocrine factors regulating both energy balance and reproduction. Universally throughout the animal kingdom, energy deficits inhibit the reproductive axis, which demonstrates that reproduction is acutely sensitive to fuel availability. Entrainment of reproductive efforts with energy availability is especially critical for females because they expend large amounts of energy on gestation and lactation. Research has identified an assortment of both central and peripheral factors involved in the metabolic regulation of reproduction. From an evolutionary perspective, these mechanisms likely evolved to optimize reproductive fitness in an environment with an unpredictable food supply and regular bouts of famine. To be effective, however, the mechanisms responsible for the metabolic regulation of reproduction must also retain developmental plasticity to allow organisms to adapt their reproductive strategies to their particular niche. In particular, the prenatal environment has emerged as a critical developmental window for programming the mechanisms responsible for the metabolic control of reproduction. This review will discuss the current knowledge about hormonal and molecular mechanisms that entrain reproduction with prevailing energy availability. In addition, it will provide an evolutionary, human life-history framework to assist in the interpretation of findings on gestational programming of the female reproductive function, with a focus on pubertal timing as an example. Future research should aim to shed light on mechanisms underlying the prenatal modulation of the adaptation to an environment with unstable resources in a way that optimizes reproductive fitness.

  1. Evolved Mechanisms Versus Underlying Conditional Relations

    Directory of Open Access Journals (Sweden)

    Astorga Miguel López

    2015-03-01

    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.

  2. 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: sullrich@mdanderson.org

    2005-04-01

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

  3. Mechanisms underlying UV-induced immune suppression

    International Nuclear Information System (INIS)

    Ullrich, Stephen E.

    2005-01-01

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

  4. Physiological mechanisms underlying animal social behaviour.

    Science.gov (United States)

    Seebacher, Frank; Krause, Jens

    2017-08-19

    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).

  5. Analysis of Network Vulnerability Under Joint Node and Link Attacks

    Science.gov (United States)

    Li, Yongcheng; Liu, Shumei; Yu, Yao; Cao, Ting

    2018-03-01

    The security problem of computer network system is becoming more and more serious. The fundamental reason is that there are security vulnerabilities in the network system. Therefore, it’s very important to identify and reduce or eliminate these vulnerabilities before they are attacked. In this paper, we are interested in joint node and link attacks and propose a vulnerability evaluation method based on the overall connectivity of the network to defense this attack. Especially, we analyze the attack cost problem from the attackers’ perspective. The purpose is to find the set of least costs for joint links and nodes, and their deletion will lead to serious network connection damage. The simulation results show that the vulnerable elements obtained from the proposed method are more suitable for the attacking idea of the malicious persons in joint node and link attack. It is easy to find that the proposed method has more realistic protection significance.

  6. Developmental phonagnosia: Linking neural mechanisms with the behavioural phenotype.

    Science.gov (United States)

    Roswandowitz, Claudia; Schelinski, Stefanie; von Kriegstein, Katharina

    2017-07-15

    Human voice recognition is critical for many aspects of social communication. Recently, a rare disorder, developmental phonagnosia, which describes the inability to recognise a speaker's voice, has been discovered. The underlying neural mechanisms are unknown. Here, we used two functional magnetic resonance imaging experiments to investigate brain function in two behaviourally well characterised phonagnosia cases, both 32 years old: AS has apperceptive and SP associative phonagnosia. We found distinct malfunctioned brain mechanisms in AS and SP matching their behavioural profiles. In apperceptive phonagnosia, right-hemispheric auditory voice-sensitive regions (i.e., Heschl's gyrus, planum temporale, superior temporal gyrus) showed lower responses than in matched controls (n AS =16) for vocal versus non-vocal sounds and for speaker versus speech recognition. In associative phonagnosia, the connectivity between voice-sensitive (i.e. right posterior middle/inferior temporal gyrus) and supramodal (i.e. amygdala) regions was reduced in comparison to matched controls (n SP =16) during speaker versus speech recognition. Additionally, both cases recruited distinct potential compensatory mechanisms. Our results support a central assumption of current two-system models of voice-identity processing: They provide the first evidence that dysfunction of voice-sensitive regions and impaired connectivity between voice-sensitive and supramodal person recognition regions can selectively contribute to deficits in person recognition by voice. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. A Systems Biology Approach Reveals Converging Molecular Mechanisms that Link Different POPs to Common Metabolic Diseases.

    Science.gov (United States)

    Ruiz, Patricia; Perlina, Ally; Mumtaz, Moiz; Fowler, Bruce A

    2016-07-01

    A number of epidemiological studies have identified statistical associations between persistent organic pollutants (POPs) and metabolic diseases, but testable hypotheses regarding underlying molecular mechanisms to explain these linkages have not been published. We assessed the underlying mechanisms of POPs that have been associated with metabolic diseases; three well-known POPs [2,3,7,8-tetrachlorodibenzodioxin (TCDD), 2,2´,4,4´,5,5´-hexachlorobiphenyl (PCB 153), and 4,4´-dichlorodiphenyldichloroethylene (p,p´-DDE)] were studied. We used advanced database search tools to delineate testable hypotheses and to guide laboratory-based research studies into underlying mechanisms by which this POP mixture could produce or exacerbate metabolic diseases. For our searches, we used proprietary systems biology software (MetaCore™/MetaDrug™) to conduct advanced search queries for the underlying interactions database, followed by directional network construction to identify common mechanisms for these POPs within two or fewer interaction steps downstream of their primary targets. These common downstream pathways belong to various cytokine and chemokine families with experimentally well-documented causal associations with type 2 diabetes. Our systems biology approach allowed identification of converging pathways leading to activation of common downstream targets. To our knowledge, this is the first study to propose an integrated global set of step-by-step molecular mechanisms for a combination of three common POPs using a systems biology approach, which may link POP exposure to diseases. Experimental evaluation of the proposed pathways may lead to development of predictive biomarkers of the effects of POPs, which could translate into disease prevention and effective clinical treatment strategies. Ruiz P, Perlina A, Mumtaz M, Fowler BA. 2016. A systems biology approach reveals converging molecular mechanisms that link different POPs to common metabolic diseases. Environ

  8. Dissociable cognitive mechanisms underlying human path integration.

    Science.gov (United States)

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

    2011-01-01

    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.

  9. Mechanics of carbon nanotube scission under sonication.

    Science.gov (United States)

    Stegen, J

    2014-06-28

    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.

  10. 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.

  11. Proteoglycans remodeling in cancer: Underlying molecular mechanisms.

    Science.gov (United States)

    Theocharis, Achilleas D; Karamanos, Nikos K

    2017-11-08

    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.

  12. Neurocomputational mechanisms of prosocial learning and links to empathy.

    Science.gov (United States)

    Lockwood, Patricia L; Apps, Matthew A J; Valton, Vincent; Viding, Essi; Roiser, Jonathan P

    2016-08-30

    Reinforcement learning theory powerfully characterizes how we learn to benefit ourselves. In this theory, prediction errors-the difference between a predicted and actual outcome of a choice-drive learning. However, we do not operate in a social vacuum. To behave prosocially we must learn the consequences of our actions for other people. Empathy, the ability to vicariously experience and understand the affect of others, is hypothesized to be a critical facilitator of prosocial behaviors, but the link between empathy and prosocial behavior is still unclear. During functional magnetic resonance imaging (fMRI) participants chose between different stimuli that were probabilistically associated with rewards for themselves (self), another person (prosocial), or no one (control). Using computational modeling, we show that people can learn to obtain rewards for others but do so more slowly than when learning to obtain rewards for themselves. fMRI revealed that activity in a posterior portion of the subgenual anterior cingulate cortex/basal forebrain (sgACC) drives learning only when we are acting in a prosocial context and signals a prosocial prediction error conforming to classical principles of reinforcement learning theory. However, there is also substantial variability in the neural and behavioral efficiency of prosocial learning, which is predicted by trait empathy. More empathic people learn more quickly when benefitting others, and their sgACC response is the most selective for prosocial learning. We thus reveal a computational mechanism driving prosocial learning in humans. This framework could provide insights into atypical prosocial behavior in those with disorders of social cognition.

  13. Thermogelling and Chemoselectively Cross-Linked Hydrogels with Controlled Mechanical Properties and Degradation Behavior.

    Science.gov (United States)

    Boere, Kristel W M; van den Dikkenberg, Joep; Gao, Yuan; Visser, Jetze; Hennink, Wim E; Vermonden, Tina

    2015-09-14

    Chemoselectively cross-linked hydrogels have recently gained increasing attention for the development of novel, injectable biomaterials given their limited side reactions. In this study, we compared the properties of hydrogels obtained by native chemical ligation (NCL) and its recently described variation termed oxo-ester-mediated native chemical ligation (OMNCL) in combination with temperature-induced physical gelation. Triblock copolymers consisting of cysteine functionalities, thermoresponsive N-isopropylacrylamide (NIPAAm) units and degradable moieties were mixed with functionalized poly(ethylene glycol) (PEG) cross-linkers. Thioester or N-hydroxysuccinimide (NHS) functionalities attached to PEG reacted with cysteine residues of the triblock copolymers via either an NCL or OMNCL pathway. The combined physical and chemical cross-linking resulted in rapid network formation and mechanically strong hydrogels. Stiffness of the hydrogels was highest for thermogels that were covalently linked via OMNCL. Specifically, the storage modulus after 4 h reached a value of 26 kPa, which was over a 100 times higher than hydrogels formed by solely thermal physical interactions. Endothelial cells showed high cell viability of 98 ± 2% in the presence of OMNCL cross-linked hydrogels after 16 h of incubation, in contrast to a low cell viability (13 ± 7%) for hydrogels obtained by NCL cross-linking. Lysozyme was loaded in the gels and after 2 days more than 90% was released, indicating that the cross-linking reaction was indeed chemoselective as the protein was not covalently grafted to the hydrogel network. Moreover, the degradation rates of these hydrogels under physiological conditions could be tailored from 12 days up to 6 months by incorporation of a monomer containing a hydrolyzable lactone ring in the thermosensitive triblock copolymer. These results demonstrate a high tunability of mechanical properties and degradation rates of these in situ forming hydrogels that could be

  14. Mechanical behaviour of nuclear fuel under irradiation

    International Nuclear Information System (INIS)

    Guerin, Y.

    1985-01-01

    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

  15. Nonlinear Dynamics Response of a Planar Mechanism with Two Driving Links and Prismatic Pair Clearance

    Directory of Open Access Journals (Sweden)

    Lijuan Wu

    2017-01-01

    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.

  16. Towards aging mechanisms of cross-linked polyethylene (XLPE) cable insulation materials in nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shuaishuai; Fifield, Leonard S.; Bowler, Nicola

    2016-12-19

    Cross-linked polyethylene (XLPE) cable insulation material undergoes simultaneous, accelerated thermal and gamma-radiation aging to simulate the long-term aging environment within nuclear power plants (NPPs). A variety of materials characterization tests, including scanning electron microscopy, thermo-gravimetric analysis, differential scanning calorimetry, oxidation induction time, gel-fraction and dielectric properties measurement, are conducted on pristine and differently aged XLPE samples. A preliminary model of one possible aging mechanism of XLPE cable insulation material under gamma radiation at elevated temperature of 115 °C is suggested.

  17. Epidemiological, neurobiological, and genetic clues to the mechanisms linking cannabis use to risk for nonaffective psychosis.

    Science.gov (United States)

    van Winkel, Ruud; Kuepper, Rebecca

    2014-01-01

    Epidemiological studies have shown that the association between cannabis and psychosis is robust and consistent across different samples, with compelling evidence for a dose-response relationship. Because longitudinal work indicates that cannabis use precedes psychotic symptoms, it seems reasonable to assume a causal relationship. However, more work is needed to address the possibility of gene-environment correlation (for example, genetic risk for psychosis causing onset of cannabis use). Moreover, knowledge about underlying biological mechanisms linking cannabis use and psychosis is still relatively limited. In order to understand how cannabis use may lead to an increased risk for psychosis, in the present article we (a) review the epidemiological, neurobiological, and genetic evidence linking cannabinoids and psychosis, (b) assess the quality of the evidence, and finally (c) try to integrate the most robust findings into a neurodevelopmental model of cannabis-induced psychosis and identify the gaps in knowledge that are in need of further investigation.

  18. Thermal adaptation in Drosophila serrata under conditions linked to ...

    Indian Academy of Sciences (India)

    Unknown

    temperature-specific directional selection for increased viability and productivity under both temperature regimes, and reduced development time ... tested in the fluctuating environment, productivity of the 7–18°C lines selected with a cold shock was relatively lower than that of lines ..... overcome this problem. Despite this ...

  19. Dually cross-linked single network poly(acrylic acid) hydrogels with superior mechanical properties and water absorbency.

    Science.gov (United States)

    Zhong, Ming; Liu, Yi-Tao; Liu, Xiao-Ying; Shi, Fu-Kuan; Zhang, Li-Qin; Zhu, Mei-Fang; Xie, Xu-Ming

    2016-06-28

    Poly(acrylic acid) (PAA) hydrogels with superior mechanical properties, based on a single network structure with dual cross-linking, are prepared by one-pot free radical polymerization. The network structure of the PAA hydrogels is composed of dual cross-linking: a dynamic and reversible ionic cross-linking among the PAA chains enabled by Fe(3+) ions, and a sparse covalent cross-linking enabled by a covalent cross-linker (Bis). Under deformation, the covalently cross-linked PAA chains remain intact to maintain their original configuration, while the Fe(3+)-enabled ionic cross-linking among the PAA chains is broken to dissipate energy and then recombined. It is found that the mechanical properties of the PAA hydrogels are significantly influenced by the contents of covalent cross-linkers, Fe(3+) ions and water, which can be adjusted within a substantial range and thus broaden the applications of the hydrogels. Meanwhile, the PAA hydrogels have excellent recoverability based on the dynamic and reversible ionic cross-linking enabled by Fe(3+) ions. Moreover, the swelling capacity of the PAA hydrogels is as high as 1800 times in deionized water due to the synergistic effects of ionic and covalent cross-linkings. The combination of balanced mechanical properties, efficient recoverability, high swelling capacity and facile preparation provides a new method to obtain high-performance hydrogels.

  20. Autophagy as a Possible Underlying Mechanism of Nanomaterial Toxicity

    Directory of Open Access Journals (Sweden)

    Vanessa Cohignac

    2014-07-01

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

  1. Mechanically Strong, Polymer Cross-linked Aerogels (X-Aerogels)

    Science.gov (United States)

    Leventis, Nicholas

    2006-01-01

    Aerogels comprise a class of low-density, high porous solid objects consisting of dimensionally quasi-stable self-supported three-dimensional assemblies of nanoparticles. Aerogels are pursued because of properties above and beyond those of the individual nanoparticles, including low thermal conductivity, low dielectric constant and high acoustic impedance. Possible applications include thermal and vibration insulation, dielectrics for fast electronics, and hosting of functional guests for a wide variety of optical, chemical and electronic applications. Aerogels, however, are extremely fragile materials, hence they have found only limited application in some very specialized environments, for example as Cerenkov radiation detectors in certain types of nuclear reactors, aboard spacecraft as collectors of hypervelocity particles (refer to NASA's Stardust program) and as thermal insulators on planetary vehicles on Mars (refer to Sojourner Rover in 1997 and Spirit and Opportunity in 2004). Along these lines, the X-Aerogel is a new NASA-developed strong lightweight material that has resolved the fragility problem of traditional (native) aerogels. X-Aerogels are made by applying a conformal polymer coating on the surfaces of the skeletal nanoparticles of native aerogels (see Scanning Electron Micrographs). Since the relative amounts of the polymeric crosslinker and the backbone are comparable, X-Aerogels can be viewed either as aerogels modified by the templated accumulation of polymer on the skeletal nanoparticles, or as nanoporous polymers made by remplated casting of polymer on a nanostructured framework. The most striking feature of X-Aerogels is that for a nominal 3-fold increase in density (still a ultralighweight material), the mechanical strength can be up to 300 times higher than the strength of the underlying native aerogel. Thus, X-Aerogels combine a multiple of the specific compressive strength of steel, with the the thermal conductivity of styrofoam. X

  2. Mechanisms linking socioeconomic disadvantage and BMI in smokers.

    Science.gov (United States)

    Kendzor, Darla E; Businelle, Michael S; Cofta-Woerpel, Ludmila M; Reitzel, Lorraine R; Castro, Yessenia; Vidrine, Jennifer I; Mazas, Carlos A; Cinciripini, Paul M; Wetter, David W

    2013-09-01

    To evaluate a conceptual model of the psychosocial pathways linking socioeconomic status and body mass index (BMI) among smokers. A latent variable modeling approach was used to evaluate the interrelationships among socioeconomic status, perceived neighborhood disadvantage, social support, negative affect, and BMI among smokers recruited from the Houston metropolitan area (N = 424). A total of 42.4% of participants were obese, with the highest prevalence of obesity among Latinos followed by African Americans. Across all racial/ethnic groups, perceived neighborhood disadvantage, social support, and negative affect functioned as pathways linking socioeconomic status and BMI. Findings indicate the need for interventions that target obesity among socioeconomically disadvantaged smokers and provide potential intervention targets for the prevention and treatment of obesity.

  3. 49 CFR 238.207 - Link between coupling mechanism and car body.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 4 2010-10-01 2010-10-01 false Link between coupling mechanism and car body. 238.207 Section 238.207 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL... Requirements for Tier I Passenger Equipment § 238.207 Link between coupling mechanism and car body. All...

  4. Periodontitis and cardiovascular diseases: The link and relevant mechanisms

    Directory of Open Access Journals (Sweden)

    Yuichi Izumi

    2009-09-01

    Full Text Available This paper reviews the association between periodontitis and CVD. In addition, the potential mechanisms of any association between periodontitis and CVD as well as the effects of periodontal treatment on CVD are herein discussed. Among the studies carried out by this group and others on coronary artery diseases, peripheral arterial diseases, abdominal aortic aneurysm, and Buerger's disease, periodontopathic bacteria were frequently detected in the diseased blood vessels, thus suggesting an association between periodontitis and CVD. The potential mechanisms of the association between periodontitis and CVD are not fully elucidated. However, inflammation and some autoimmune mechanisms, including molecular mimicry between the periodontopathic bacteria and host molecules, are suggested. The effects of periodontal treatment on CVD might thus vary among the different treatment modalities, and full-mouth mechanical debridement might induce strong transient systemic inflammatory responses in comparison to the quadrant-wise mechanical debridement.

  5. Defense mechanisms and morality: a link between isolation and moralization.

    Science.gov (United States)

    Björklund, F

    2000-03-01

    The relationship between morality and perceptual defense mechanisms was studied. Three new scales were constructed to measure different aspects of morality: moralism (the tendency to evaluate everything in terms of right and wrong), conscience (strength of feelings of right and wrong) and reparation (inclination to repair the damage one has caused). Perceptual defense mechanisms were measured with Kragh's Defense Mechanism Test (DMT). Three hypotheses about relationships between morality and defense mechanisms, derived from psychoanalytical literature, were tested on 54 male University students. Results show positive correlations between the defense mechanism isolation of affect and moralism, and between identification with the aggressor and reparation. Total amount of perceptual defense correlated positively with moralism. It is argued that the psychological study of morality should take unconscious processes into consideration.

  6. Epigenetic mechanisms underlying nervous system diseases.

    Science.gov (United States)

    Qureshi, Irfan A; Mehler, Mark F

    2018-01-01

    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.

  7. Mechanisms Linking Red Blood Cell Disorders and Cardiovascular Diseases

    OpenAIRE

    Mozos, Ioana

    2015-01-01

    The present paper aims to review the main pathophysiological links between red blood cell disorders and cardiovascular diseases, provides a brief description of the latest studies in this area, and considers implications for clinical practice and therapy. Anemia is associated with a special risk in proatherosclerotic conditions and heart disease and became a new therapeutic target. Guidelines must be updated for the management of patients with red blood cell disorders and cardiovascular dise...

  8. Disruptions in Emotion Regulation as a Mechanism Linking Community Violence Exposure to Adolescent Internalizing Problems

    Science.gov (United States)

    Heleniak, Charlotte; King, Kevin M.; Monahan, Kathryn C.; McLaughlin, Katie A.

    2017-01-01

    Although community violence is an established risk factor for youth aggression, less research has examined its relation with internalizing psychopathology. This study examined associations of community violence exposure with internalizing symptoms, and state and trait emotion dysregulation as mechanisms underlying these associations, in 287 adolescents aged 16–17 (45.6% male; 40.8% White). Community violence exposure was associated with internalizing symptoms, negative affect during peer evaluation, trait emotional reactivity, and infrequent problem solving. Multiple emotion dysregulation indices were also associated with internalizing symptoms. In simultaneous multiple mediator models, indirect effects of community violence on internalizing problems were significantly explained by state and trait emotion dysregulation. Findings implicate emotion dysregulation as one mechanism linking community violence exposure to adolescent internalizing symptoms. PMID:28646545

  9. 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 ...

  10. Supersymmetric quantum mechanics under point singularities

    International Nuclear Information System (INIS)

    Uchino, Takashi; Tsutsui, Izumi

    2003-01-01

    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

  11. Integrating Mechanisms for Insulin Resistance: Common Threads and Missing Links

    Science.gov (United States)

    Samuel, Varman T.; Shulman, Gerald I.

    2012-01-01

    Insulin resistance is a complex metabolic disorder that defies a single etiological pathway. Accumulation of ectopic lipid metabolites, activation of the unfolded protein response (UPR) pathway and innate immune pathways have all been implicated in the pathogenesis of insulin resistance. However, these pathways are also closely linked to changes in fatty acid uptake, lipogenesis, and energy expenditure that can impact ectopic lipid deposition. Ultimately, accumulation of specific lipid metabolites (diacylglycerols and/or ceramides) in liver and skeletal muscle, may be a common pathway leading to impaired insulin signaling and insulin resistance. PMID:22385956

  12. 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)

    2010-07-01

    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.

  13. Mechanisms Underlying Sex Differences in Cannabis Use.

    Science.gov (United States)

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

    2017-12-01

    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.

  14. Habitats under Mechanical and Herbicide Management Regimes

    Directory of Open Access Journals (Sweden)

    Wendy-Ann P. Isaac

    2012-01-01

    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.

  15. Physical and chemical mechanisms underlying hematoma evolution

    International Nuclear Information System (INIS)

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

    1986-01-01

    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

  16. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks.

    Science.gov (United States)

    Jin, Zhigang; Wang, Ning; Su, Yishan; Yang, Qiuling

    2018-02-07

    Underwater acoustic sensor networks (UASNs) have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider's sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider's trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15-33% compared with cooperative opportunistic routing (OVAR), the hop-by-hop vector-based forwarding (HH-VBF) and the vector based forward (VBF) methods, and reduce communication energy consumption by 20-58% for a typical network's setting.

  17. A Glider-Assisted Link Disruption Restoration Mechanism in Underwater Acoustic Sensor Networks

    Directory of Open Access Journals (Sweden)

    Zhigang Jin

    2018-02-01

    Full Text Available Underwater acoustic sensor networks (UASNs have become a hot research topic. In UASNs, nodes can be affected by ocean currents and external forces, which could result in sudden link disruption. Therefore, designing a flexible and efficient link disruption restoration mechanism to ensure the network connectivity is a challenge. In the paper, we propose a glider-assisted restoration mechanism which includes link disruption recognition and related link restoring mechanism. In the link disruption recognition mechanism, the cluster heads collect the link disruption information and then schedule gliders acting as relay nodes to restore the disrupted link. Considering the glider’s sawtooth motion, we design a relay location optimization algorithm with a consideration of both the glider’s trajectory and acoustic channel attenuation model. The utility function is established by minimizing the channel attenuation and the optimal location of glider is solved by a multiplier method. The glider-assisted restoration mechanism can greatly improve the packet delivery rate and reduce the communication energy consumption and it is more general for the restoration of different link disruption scenarios. The simulation results show that glider-assisted restoration mechanism can improve the delivery rate of data packets by 15–33% compared with cooperative opportunistic routing (OVAR, the hop-by-hop vector-based forwarding (HH-VBF and the vector based forward (VBF methods, and reduce communication energy consumption by 20–58% for a typical network’s setting.

  18. 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)

    1993-12-31

    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.

  19. Integrative modelling reveals mechanisms linking productivity and plant species richness

    NARCIS (Netherlands)

    Grace, James B.; Anderson, T. Michael; Seabloom, Eric W.; Borer, Elizabeth T.; Adler, Peter B.; Harpole, W. Stanley; Hautier, Yann; Hillebrand, Helmut; Lind, Eric M.; Pärtel, Meelis; Bakker, Jonathan D.; Buckley, Yvonne M.; Crawley, Michael J.; Damschen, Ellen I.; Davies, Kendi F.; Fay, Philip A.; Firn, Jennifer; Gruner, Daniel S.; Hector, Andy; Knops, Johannes M. H.; MacDougall, Andrew S.; Melbourne, Brett A.; Morgan, John W.; Orrock, John L.; Prober, Suzanne M.; Smith, Melinda D.

    2016-01-01

    How ecosystem productivity and species richness are interrelated is one of the most debated subjects in the history of ecology. Decades of intensive study have yet to discern the actual mechanisms behind observed global patterns. Here, by integrating the predictions from multiple theories into a

  20. Study in Mice Links Key Signaling Molecule to Underlying Cause of Osteogenesis Imperfecta

    Science.gov (United States)

    ... on Research Study in Mice Links Key Signaling Molecule to Underlying Cause of Osteogenesis Imperfecta By Kirstie ... a connection between excessive activity of a signaling molecule and osteogenesis imperfecta (OI), a genetic disease characterized ...

  1. Trained Innate Immunity as a Novel Mechanism Linking Infection and the Development of Atherosclerosis.

    Science.gov (United States)

    Leentjens, Jenneke; Bekkering, Siroon; Joosten, Leo A B; Netea, Mihai G; Burgner, David P; Riksen, Niels P

    2018-03-02

    There is strong epidemiological evidence for an association between acute and chronic infections and the occurrence of atherosclerotic cardiovascular disease. The underlying pathophysiological mechanisms remain unclear. Monocyte-derived macrophages are the most abundant immune cells in atherosclerotic plaques. It has recently been established that monocytes/macrophages can develop a long-lasting proinflammatory phenotype after brief stimulation with micro-organisms or microbial products, which has been termed trained immunity. The aim of this study is to assess whether trained immunity mediates the link between infections and atherosclerotic cardiovascular disease. Brief exposure of monocytes to various micro-organisms results in the development of macrophages with a persistent proinflammatory phenotype: this represents a de facto nonspecific innate immune memory, which has been termed trained immunity. This is mediated by epigenetic reprogramming at the level of histone methylation and a profound rewiring of intracellular metabolism. Although this mechanism offers powerful protection against reinfection, trained macrophages display an atherogenic phenotype in terms of cytokine production and foam cell formation. Trained monocytes are present up to 3 months after experimental infection in humans. Moreover, a trained immunity phenotype is present in patients with established atherosclerosis. We propose that trained immunity provides the missing mechanistic link that explains the association between infections and atherosclerosis. Therefore, pharmacological modulation of trained immunity has the potential to prevent infection-related atherosclerotic cardiovascular disease in the future. © 2018 American Heart Association, Inc.

  2. Obesity and inflammation: the linking mechanism and the complications.

    Science.gov (United States)

    Ellulu, Mohammed S; Patimah, Ismail; Khaza'ai, Huzwah; Rahmat, Asmah; Abed, Yehia

    2017-06-01

    Obesity is the accumulation of abnormal or excessive fat that may interfere with the maintenance of an optimal state of health. The excess of macronutrients in the adipose tissues stimulates them to release inflammatory mediators such as tumor necrosis factor α and interleukin 6, and reduces production of adiponectin, predisposing to a pro-inflammatory state and oxidative stress. The increased level of interleukin 6 stimulates the liver to synthesize and secrete C-reactive protein. As a risk factor, inflammation is an imbedded mechanism of developed cardiovascular diseases including coagulation, atherosclerosis, metabolic syndrome, insulin resistance, and diabetes mellitus. It is also associated with development of non-cardiovascular diseases such as psoriasis, depression, cancer, and renal diseases. On the other hand, a reduced level of adiponectin, a significant predictor of cardiovascular mortality, is associated with impaired fasting glucose, leading to type-2 diabetes development, metabolic abnormalities, coronary artery calcification, and stroke. Finally, managing obesity can help reduce the risks of cardiovascular diseases and poor outcome via inhibiting inflammatory mechanisms.

  3. Mechanistic Links Underlying the Impact of C-Reactive Protein on Muscle Mass in Elderly.

    Science.gov (United States)

    Wåhlin-Larsson, Britta; Wilkinson, Daniel J; Strandberg, Emelie; Hosford-Donovan, Adrian; Atherton, Philip J; Kadi, Fawzi

    2017-01-01

    Mechanisms underlying the relationship between systemic inflammation and age-related decline in muscle mass are poorly defined. The purpose of this work was to investigate the relationship between the systemic inflammatory marker CRP and muscle mass in elderly and to identify mechanisms by which CRP mediates its effects on skeletal muscle, in-vitro. Muscle mass and serum CRP level were determined in a cohort of 118 older women (67±1.7 years). Human muscle cells were differentiated into myotubes and were exposed to CRP. The size of myotubes was determined after immunofluorescent staining using troponin. Muscle protein synthesis was assessed using stable isotope tracers and key signalling pathways controlling protein synthesis were determined using western-blotting. We observed an inverse relationship between circulating CRP level and muscle mass (β= -0.646 (95% CI: -0.888, -0.405) pmuscle protein fractional synthetic rate of human myotubes exposed to CRP for 24 h. We also identified a CRP-mediated increased phosphorylation (pprotein synthesis. This work established for the first time mechanistic links by which chronic elevation of CRP can contribute to age-related decline in muscle function. © 2017 The Author(s). Published by S. Karger AG, Basel.

  4. Epigenetic mechanisms linking early nutrition to long term health.

    Science.gov (United States)

    Lillycrop, Karen A; Burdge, Graham C

    2012-10-01

    Traditionally it has been widely accepted that our genes together with adult lifestyle factors determine our risk of developing non-communicable diseases such as type 2 diabetes mellitus, cardiovascular disease and obesity in later life. However, there is now substantial evidence that the pre and early postnatal environment plays a key role in determining our susceptible to such diseases in later life. Moreover the mechanism by which the environment can alter long term disease risk may involve epigenetic processes. Epigenetic processes play a central role in regulating tissue specific gene expression and hence alterations in these processes can induce long-term changes in gene expression and metabolism which persist throughout the lifecourse. This review will focus on how nutritional cues in early life can alter the epigenome, producing different phenotypes and altered disease susceptibilities. Copyright © 2012 Elsevier Ltd. All rights reserved.

  5. Durability and mechanical properties of silane cross-linked wood thermoplastic composites

    Science.gov (United States)

    Magnus Bengtsson; Nicole M. Stark; Kristiina Oksman

    2007-01-01

    In this study, silane cross-linked wood–polyethylene composite profiles were manufactured by reactive extrusion. These composites were evaluated regarding their durability and mechanical properties in comparison with two non-cross-linked wood– polyethylene composites. An addition of only 2% w/w of silane solution during manufacturing was enough to achieve almost 60%...

  6. Mechanisms linking employee affective delivery and customer behavioral intentions.

    Science.gov (United States)

    Tsai, Wei-Chi; Huang, Yin-Mei

    2002-10-01

    Past empirical evidence has indicated that employee affective delivery can influence customer reactions (e.g., customer satisfaction, service quality evaluation). This study extends previous research by empirically examining mediating processes underlying the relationship between employee affective delivery and customer behavioral intentions. Data were collected from 352 employee-customer pairs in 169 retail shoe stores in Taiwan. Results showed that the influence of employee affective delivery on customers' willingness to return to the store and pass positive comments to friends was indirect through the mediating processes of customer in-store positive moods and perceived friendliness. The study also indicated that employee affective delivery influences customers' time spent in store, which, in turn, influences customer behavioral intentions.

  7. Cardiovascular reactivity as a mechanism linking child trauma to adolescent psychopathology

    NARCIS (Netherlands)

    Heleniak, Charlotte; McLaughlin, Katie A.; Ormel, Johan; Riese, Harriette

    2016-01-01

    Alterations in physiological reactivity to stress are argued to be central mechanisms linking adverse childhood environmental experiences to internalizing and externalizing psychopathology. Childhood trauma exposure may influence physiological reactivity to stress in distinct ways from other forms

  8. A Link between Quantum Logic and Categorical Quantum Mechanics

    Science.gov (United States)

    Harding, John

    2009-03-01

    Abramsky and Coecke (Proceedings of the 19th Annual IEEE Symposium on Logic in Computer Science, pp. 415-425, IEEE Comput. Soc., New York, 2004) have recently introduced an approach to finite dimensional quantum mechanics based on strongly compact closed categories with biproducts. In this note it is shown that the projections of any object A in such a category form an orthoalgebra Proj A. Sufficient conditions are given to ensure this orthoalgebra is an orthomodular poset. A notion of a preparation for such an object is given by Abramsky and Coecke, and it is shown that each preparation induces a finitely additive map from Proj A to the unit interval of the semiring of scalars for this category. The tensor product for the category is shown to induce an orthoalgebra bimorphism Proj A× Proj B→ Proj ( A ⊗ B) that shares some of the properties required of a tensor product of orthoalgebras. These results are established in a setting more general than that of strongly compact closed categories. Many are valid in dagger biproduct categories, others require also a symmetric monoidal tensor compatible with the dagger and biproducts. Examples are considered for several familiar strongly compact closed categories.

  9. The molecular mechanism linking muscle fat accumulation to insulin resistance.

    Science.gov (United States)

    Hulver, Matthew W; Dohm, G Lynis

    2004-05-01

    Skeletal muscle insulin resistance is a co-morbidity of obesity and a risk factor for the development of type 2 diabetes mellitus. Insulin resistance is associated with the accumulation of intramyocellular lipids. Intramyocellular triacylglycerols do not appear to be the cause of insulin resistance but are more likely to be a marker of other lipid intermediates such as fatty acyl-CoA, ceramides or diacylglycerols. Fatty acyl-CoA, ceramides and diacylglycerols are known to directly alter various aspects of the insulin signalling cascade. Insulin signalling is inhibited by the phosphorylation of serine and threonine residues at the levels of the insulin receptor and insulin receptor substrate 1. Protein kinase C is responsible for the phosphorylation of the serine and threonine residues. Fatty acyl-CoA and diacylglycerols are known to activate protein kinase C. The cause of the intramyocellular accumulation of fatty acyl-CoA and diacylglycerols is unclear at this time. Reduced fatty acid oxidation does not appear to be responsible, as fatty acyl-CoA accumulates in skeletal muscle with a normal fatty acid oxidative capacity. Other potential mechanisms include oversupply of lipids to muscle and/or up regulated fatty acid transport.

  10. Evidence of Mitochondrial Dysfunction in Autism: Biochemical Links, Genetic-Based Associations, and Non-Energy-Related Mechanisms

    Directory of Open Access Journals (Sweden)

    Keren K. Griffiths

    2017-01-01

    Full Text Available Autism spectrum disorder (ASD, the fastest growing developmental disability in the United States, represents a group of neurodevelopmental disorders characterized by impaired social interaction and communication as well as restricted and repetitive behavior. The underlying cause of autism is unknown and therapy is currently limited to targeting behavioral abnormalities. Emerging studies suggest a link between mitochondrial dysfunction and ASD. Here, we review the evidence demonstrating this potential connection. We focus specifically on biochemical links, genetic-based associations, non-energy related mechanisms, and novel therapeutic strategies.

  11. Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf

    2010-01-01

    This study investigated the mechanisms underlying epithelium-derived hyperpolarizing factor (EpDHF)-type relaxation in rat bronchioles. Immunohistochemistry was performed, and rat bronchioles and pulmonary arteries were mounted in microvascular myographs for functional studies. An opener of small...

  12. Underlying Mechanisms of Improving Physical Activity Behavior after Rehabilitation

    NARCIS (Netherlands)

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

    2008-01-01

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

  13. A Neurobehavioral Mechanism Linking Behaviorally Inhibited Temperament and Later Adolescent Social Anxiety.

    Science.gov (United States)

    Buzzell, George A; Troller-Renfree, Sonya V; Barker, Tyson V; Bowman, Lindsay C; Chronis-Tuscano, Andrea; Henderson, Heather A; Kagan, Jerome; Pine, Daniel S; Fox, Nathan A

    2017-12-01

    Behavioral inhibition (BI) is a temperament identified in early childhood that is a risk factor for later social anxiety. However, mechanisms underlying the development of social anxiety remain unclear. To better understand the emergence of social anxiety, longitudinal studies investigating changes at behavioral neural levels are needed. BI was assessed in the laboratory at 2 and 3 years of age (N = 268). Children returned at 12 years, and an electroencephalogram was recorded while children performed a flanker task under 2 conditions: once while believing they were being observed by peers and once while not being observed. This methodology isolated changes in error monitoring (error-related negativity) and behavior (post-error reaction time slowing) as a function of social context. At 12 years, current social anxiety symptoms and lifetime diagnoses of social anxiety were obtained. Childhood BI prospectively predicted social-specific error-related negativity increases and social anxiety symptoms in adolescence; these symptoms directly related to clinical diagnoses. Serial mediation analysis showed that social error-related negativity changes explained relations between BI and social anxiety symptoms (n = 107) and diagnosis (n = 92), but only insofar as social context also led to increased post-error reaction time slowing (a measure of error preoccupation); this model was not significantly related to generalized anxiety. Results extend prior work on socially induced changes in error monitoring and error preoccupation. These measures could index a neurobehavioral mechanism linking BI to adolescent social anxiety symptoms and diagnosis. This mechanism could relate more strongly to social than to generalized anxiety in the peri-adolescent period. Copyright © 2017 American Academy of Child and Adolescent Psychiatry. All rights reserved.

  14. Somatic mosaicism underlies X-linked acrogigantism syndrome in sporadic male subjects

    NARCIS (Netherlands)

    A.F. Daly (Adrian); B. Yuan (Bo); Fina, F. (Frederic); J.-H. Caberg (Jean-Hubert); G. Trivellin (Giampaolo); L. Rostomyan (Liliya); W.W. de Herder (Wouter); L.A. Naves (Lucianna); D. Metzger (Daniel); T. Cuny (Thomas); Rabl, W. (Wolfgang); N.S. Shah (Nalini Samir); M-L. Jaffrain-Rea (Marie-Lise); Chiara Zatelli, M. (Maria); F.R. Faucz (Fabio R.); E. Castermans (Emilie); Nanni-Metellus, I. (Isabelle); Lodish, M. (Maya); A. Muhammad (Ammar); Palmeira, L. (Leonor); Potorac, I. (Iulia); G. Mantovani (Giovanna); S.J.C.M.M. Neggers (Bas); Klein, M. (Marc); A. Barlier (Anne); P. Liu (Pengfei); Ouafik, L. (L'houcine); V. Bours (Vincent); Lupski, J.R. (James R.); C.A. Stratakis (Constantine); A. Beckers (Albert)

    2016-01-01

    textabstractSomatic mosaicism has been implicated as a causative mechanism in a number of genetic and genomic disorders. X-linked acrogigantism (XLAG)syndrome is a recently characterized genomic form of pediatric gigantism due to aggressive pituitary tumors that is caused by submicroscopic

  15. 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: hcallioglu@pau.edu.tr. MS received 25 November 2009; revised 12 August 2010; accepted.

  16. Mechanistic Links Underlying the Impact of C-Reactive Protein on Muscle Mass in Elderly

    Directory of Open Access Journals (Sweden)

    Britta Wåhlin-Larsson

    2017-11-01

    Full Text Available Background/Aims: Mechanisms underlying the relationship between systemic inflammation and age-related decline in muscle mass are poorly defined. The purpose of this work was to investigate the relationship between the systemic inflammatory marker CRP and muscle mass in elderly and to identify mechanisms by which CRP mediates its effects on skeletal muscle, in-vitro. Methods: Muscle mass and serum CRP level were determined in a cohort of 118 older women (67±1.7 years. Human muscle cells were differentiated into myotubes and were exposed to CRP. The size of myotubes was determined after immunofluorescent staining using troponin. Muscle protein synthesis was assessed using stable isotope tracers and key signalling pathways controlling protein synthesis were determined using western-blotting. Results: We observed an inverse relationship between circulating CRP level and muscle mass (β= -0.646 (95% CI: -0.888, -0.405 p<0.05 and demonstrated a reduction (p < 0.05 in the size of human myotubes exposed to CRP for 72 h. We next showed that this morphological change was accompanied by a CRP-mediated reduction (p < 0.05 in muscle protein fractional synthetic rate of human myotubes exposed to CRP for 24 h. We also identified a CRP-mediated increased phosphorylation (p<0.05 of regulators of cellular energy stress including AMPK and downstream targets, raptor and ACC-β, together with decreased phosphorylation of Akt and rpS6, which are important factors controlling protein synthesis. Conclusion: This work established for the first time mechanistic links by which chronic elevation of CRP can contribute to age-related decline in muscle function.

  17. Linking project-based mechanisms with domestic greenhouse gas emissions trading schemes

    International Nuclear Information System (INIS)

    Bygrave, S.; Bosi, M.

    2004-01-01

    Although there are a number of possible links between emission trading and project-based mechanisms, the focus of this paper is on linking domestic GHG emission trading schemes with: (1) domestic; and, (2) international (JI and CDM) GHG reduction project activities. The objective is to examine some of the challenges in linking DETs and project-based mechanisms, as well as some possible solutions to address these challenges. The link between JI / CDM and intergovernmental international emissions trading (i.e. Article 17 of the Kyoto Protocol) is defined by the Kyoto Protocol, and therefore is not covered in this paper. The paper is written in the context of: (a) countries adhering to the Kyoto Protocol and elaborating their strategies to meet their GHG emission commitments, including through the use of the emissions trading and project-based mechanisms. For example, the European Union (EU) will be commencing a GHG Emissions Trading Scheme in January 2005, and recently, the Council of ministers and the European Parliament agreed on a text for an EU Linking Directive allowing the use of JI and CDM emission units in the EU Emission Trading Scheme (EU-ETS); and (b) all countries (and/or regions within countries) with GHG emission obligations that may choose to use domestic emissions trading and project-based mechanisms to meet their GHG commitments. The paper includes the following elements: (1) an overview of the different flexibility mechanisms (i.e. GHG emissions trading and PBMs), including a brief description and comparisons between the mechanisms (Section 3); (2) an exploration of the issues that emerge when project-based mechanisms link with domestic emissions trading schemes, as well as possible solutions to address some of the challenges raised (Section 4); (3) a case study examining the EU-ETS and the EU Linking Directive on project-based mechanisms, in particular on how the EU is addressing in a practical context relevant linking issues (Section 5); (4) a

  18. Time with friends and physical activity as mechanisms linking obesity and television viewing among youth

    OpenAIRE

    Vandewater, Elizabeth A; Park, Seoung Eun; H?bert, Emily T; Cummings, Hope M

    2015-01-01

    Background Though bivariate relationships between childhood obesity, physical activity, friendships and television viewing are well documented, empirical assessment of the extent to which links between obesity and television may be mediated by these factors is scarce. This study examines the possibility that time with friends and physical activity are potential mechanisms linking overweight/obesity to television viewing in youth. Methods Data were drawn from children ages 10-18 years old (M =...

  19. Analytical expression for an optimised link bar mechanism for a beta-type Stirling engine

    DEFF Research Database (Denmark)

    Carlsen, Henrik; Bovin, Jonas Kabell

    2007-01-01

    The design of a mechanism for kinematic beta-type Stirling engines, where the displacer piston and the working piston share the same cylinder, is complicated. A well-known solution is the rhombic drive, but this solution depends on oil lubrication because of the gear wheels connecting the two...... counter rotating crank shafts. In a hermetically sealed Stirling engine it is an advantage to avoid oil in the crank case, making the application of the rhombic drive difficult. In this paper, another crank mechanism is presented, which has been developed for a 9 kW single cylinder engine. The new crank...... mechanism is a further development of the mechanism in a previous 9 kW engine. The crank mechanism for the beta-type Stirling engine is based on two four-link straight line mechanisms pointing up and down, respectively. The mechanism pointing upwards is connected to the working piston, while the mechanism...

  20. Mechanisms linking electrical alternans and clinical ventricular arrhythmia in human heart failure.

    Science.gov (United States)

    Bayer, J D; Lalani, G G; Vigmond, E J; Narayan, S M; Trayanova, N A

    2016-09-01

    Mechanisms of ventricular tachycardia (VT) and ventricular fibrillation (VF) in patients with heart failure (HF) are undefined. The purpose of this study was to elucidate VT/VF mechanisms in HF by using a computational-clinical approach. In 53 patients with HF and 18 control patients, we established the relationship between low-amplitude action potential voltage alternans (APV-ALT) during ventricular pacing at near-resting heart rates and VT/VF on long-term follow-up. Mechanisms underlying the transition of APV-ALT to VT/VF, which cannot be ascertained in patients, were dissected with multiscale human ventricular models based on human electrophysiological and magnetic resonance imaging data (control and HF). For patients with APV-ALT k-score >1.7, complex action potential duration (APD) oscillations (≥2.3% of mean APD), rather than APD alternans, most accurately predicted VT/VF during long-term follow-up (+82%; -90% predictive values). In the failing human ventricular models, abnormal sarcoplasmic reticulum (SR) calcium handling caused APV-ALT (>1 mV) during pacing with a cycle length of 550 ms, which transitioned into large magnitude (>100 ms) discordant repolarization time alternans (RT-ALT) at faster rates. This initiated VT/VF (cycle length heart rates in patients with HF are linked to arrhythmogenic discordant RT-ALT. This may enable novel physiologically tailored, bioengineered indices to improve VT/VF risk stratification, where SR calcium handling and spatial apicobasal repolarization are potential therapeutic targets. Copyright © 2016 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.

  1. Amount of fear extinction changes its underlying mechanisms.

    Science.gov (United States)

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

    2017-07-03

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

  2. Computational exploration of polymer nanocomposite mechanical property modification via cross-linking topology

    Science.gov (United States)

    Lacevic, Naida; Gee, Richard H.; Saab, Andrew; Maxwell, Robert

    2008-09-01

    Molecular dynamics simulations have been performed in order to study the effects of nanoscale filler cross-linking topologies and loading levels on the mechanical properties of a model elastomeric nanocomposite. The model system considered here is constructed from octafunctional polyhedral oligomeric silsesquioxane (POSS) dispersed in a poly(dimethylsiloxane) (PDMS) matrix. Shear moduli, G, have been computed for pure and for filled and unfilled PDMS as a function of cross-linking density, POSS fill loading level, and polymer network topology. The results reported here show that G increases as the cross-linking (covalent bonds formed between the POSS and the PDMS network) density increases. Further, G is found to have a strong dependence on cross-linking topology. The increase in shear modulus, G, for POSS filled PDMS is significantly higher than that for unfilled PDMS cross-linked with standard molecular species, suggesting an enhanced reinforcement mechanism for POSS. In contrast, in blended systems (POSS/PDMS mixture with no cross-linking) G was not observed to significantly increase with POSS loading. Finally, we find intriguing differences in the structural arrangement of bond strains between the cross-linked and the blended systems. In the unfilled PDMS the distribution of highly strained bonds appears to be random, while in the POSS filled system, the strained bonds form a netlike distribution that spans the network. Such a distribution may form a structural network "holding" the composite together and resulting in increases in G compared to an unfilled, cross-linked system. These results are of importance for engineering of new POSS-based multifunctional materials with tailor-made mechanical properties.

  3. In-situcross-linked PVDF membranes with enhanced mechanical durability for vacuum membrane distillation

    KAUST Repository

    Zuo, Jian

    2016-05-12

    A novel and effective one-step method has been demonstrated to fabricate cross-linked polyvinylidene fluoride (PVDF) membranes with better mechanical properties and flux for seawater desalination via vacuum membrane distillation (VMD). This method involves the addition of two functional nonsolvent additives; namely, water and ethylenediamine (EDA), into the polymer casting solution. The former acts as a pore forming agent, while the latter performs as a cross-linking inducer. The incorporation of water tends to increase membrane flux via increasing porosity and pore size but sacrifices membrane mechanical properties. Conversely, the presence of EDA enhances membrane mechanical properties through in-situ cross-linking reaction. Therefore, by synergistically combining the effects of both functional additives, the resultant PVDF membranes have shown good MD performance and mechanical properties simultaneously. The parameters that affect the cross-link reaction and membrane mechanical properties such as reaction duration and EDA concentration have been systematically studied. The membranes cast from an optimal reaction condition comprising 0.8 wt % EDA and 3-hour reaction not only shows a 40% enhancement in membrane Young\\'s Modulus compared to the one without EDA but also achieves a good VMD flux of 43.6 L/m2-h at 60°C. This study may open up a totally new approach to design next-generation high performance MD membranes. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4013–4022, 2016

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

    OpenAIRE

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

    2017-01-01

    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...

  5. Emotional responses to music: the need to consider underlying mechanisms.

    Science.gov (United States)

    Juslin, Patrik N; Västfjäll, Daniel

    2008-10-01

    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. ATRX ADD Domain Links an Atypical Histone Methylation Recognition Mechanism to Human Mental-Retardation Syndrome

    Energy Technology Data Exchange (ETDEWEB)

    S Iwase; B Xiang; S Ghosh; T Ren; P Lewis; J Cochrane; C Allis; D Picketts; D Patel; et al.

    2011-12-31

    ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket, which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.

  7. ATRX ADD domain links an atypical histone methylation recognition mechanism to human mental-retardation syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Iwase, Shigeki; Xiang, Bin; Ghosh, Sharmistha; Ren, Ting; Lewis, Peter W.; Cochrane, Jesse C.; Allis, C. David; Picketts, David J.; Patel, Dinshaw J.; Li, Haitao; Shi, Yang (Harvard-Med); (Ottawa Hosp.); (MSKCC); (Rockefeller); (CH-Boston); (Tsinghua); (Mass. Gen. Hosp.)

    2011-07-19

    ATR-X (alpha-thalassemia/mental retardation, X-linked) syndrome is a human congenital disorder that causes severe intellectual disabilities. Mutations in the ATRX gene, which encodes an ATP-dependent chromatin-remodeler, are responsible for the syndrome. Approximately 50% of the missense mutations in affected persons are clustered in a cysteine-rich domain termed ADD (ATRX-DNMT3-DNMT3L, ADD{sub ATRX}), whose function has remained elusive. Here we identify ADD{sub ATRX} as a previously unknown histone H3-binding module, whose binding is promoted by lysine 9 trimethylation (H3K9me3) but inhibited by lysine 4 trimethylation (H3K4me3). The cocrystal structure of ADD{sub ATRX} bound to H3{sub 1-15}K9me3 peptide reveals an atypical composite H3K9me3-binding pocket, which is distinct from the conventional trimethyllysine-binding aromatic cage. Notably, H3K9me3-pocket mutants and ATR-X syndrome mutants are defective in both H3K9me3 binding and localization at pericentromeric heterochromatin; thus, we have discovered a unique histone-recognition mechanism underlying the ATR-X etiology.

  8. Air rudder mechanism dynamics considering two elements:Joint clearance and link flexibility

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yuntao; Quan, Qiquan; Li, He; Tang, Dewei; Li, Zhonghong; Fan, Wenyang; Deng, Zongquan [Harbin Institute of Technology, Harbin (China)

    2017-07-15

    Both the impact phenomenon in the clearance revolute joint and the link deformation will influence the dynamics of the air rudder transmission mechanism, which could reduce the flight quality of an aircraft. Given the effect of the two elements, a feasible simulation method with two improvements of previous methods is proposed to analyze the dynamic characteristics of the mechanism. In previous studies, the parameters of the contact force model in multi-body dynamics software were generally determined by experience, which may cause uncertainty in the calculation precision of the contact force. Furthermore, it is difficult to solve for the elastic link deformation in the practical mechanism using the available analytical methods due to the complicated section of the link. In this paper, a Continuous contact force (CCF) model was proposed and embedded in the ADAMS by developing a routine of the CCF model. Then, the flexible model was obtained by ANSYS to obtain the elastic link deformation. The experimental results indicate that the proposed simulation method can be effectively applied to predict the dynamic behavior of the mechanism.

  9. Capacity of cognitive radio under imperfect secondary and cross link channel state information

    KAUST Repository

    Sboui, Lokman

    2011-09-01

    In this paper, we study the ergodic capacity of secondary user channel in a spectrum sharing scenario in which the secondary transmitter is instantaneously aware of estimated versions of the cross link (between the secondary transmitter and the primary receiver) and the secondary link Channel State Information (CSI). The secondary link optimal power profile along with the ergodic capacity are derived for a class of fading channels, under an average power constraint and an instantaneous interference outage constraint. We also show that our framework is rather general as it encompasses several previously studied spectrum sharing settings as special cases. In order to gain some insights on the capacity behavior, numerical results are shown for independent Rayleigh fading channels where it is found for instance, that at low SNR regime, only the secondary channel estimation matters and that the cross link CSI has no effect on the ergodic capacity; whereas at high SNR regime, the capacity is rather driven by the cross link CSI. © 2011 IEEE.

  10. Study on Mechanical Properties of Barite Concrete under Impact Load

    Science.gov (United States)

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

    2018-03-01

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

  11. 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.

    2014-01-01

    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

  12. Neural Circuitry and Plasticity Mechanisms Underlying Delay Eyeblink Conditioning

    Science.gov (United States)

    Freeman, John H.; Steinmetz, Adam B.

    2011-01-01

    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…

  13. Lathyrism-induced alterations in collagen cross-links influence the mechanical properties of bone material without affecting the mineral

    Science.gov (United States)

    Paschalis, E.P.; Tatakis, D.N.; Robins, S.; Fratzl, P.; Manjubala, I.; Zoehrer, R.; Gamsjaeger, S.; Buchinger, B.; Roschger, A.; Phipps, R.; Boskey, A.L.; Dall'Ara, E.; Varga, P.; Zysset, P.; Klaushofer, K.; Roschger, P.

    2011-01-01

    In the present study a rat animal model of lathyrism was employed to decipher whether anatomically confined alterations in collagen cross-links are sufficient to influence the mechanical properties of whole bone. Animal experiments were performed under an ethics committee approved protocol. Sixty-four female (47 day old) rats of equivalent weights were divided into four groups (16 per group): Controls were fed a semi-synthetic diet containing 0.6% calcium and 0.6% phosphorus for 2 or 4 weeks and β-APN treated animals were fed additionally with β-aminopropionitrile (0.1% dry weight). At the end of this period the rats in the four groups were sacrificed, and L2–L6 vertebra were collected. Collagen cross-links were determined by both biochemical and spectroscopic (Fourier transform infrared imaging (FTIRI)) analyses. Mineral content and distribution (BMDD) were determined by quantitative backscattered electron imaging (qBEI), and mineral maturity/crystallinity by FTIRI techniques. Micro-CT was used to describe the architectural properties. Mechanical performance of whole bone as well as of bone matrix material was tested by vertebral compression tests and by nano-indentation, respectively. The data of the present study indicate that β-APN treatment changed whole vertebra properties compared to non-treated rats, including collagen cross-links pattern, trabecular bone volume to tissue ratio and trabecular thickness, which were all decreased (p < 0.05). Further, compression tests revealed a significant negative impact of β-APN treatment on maximal force to failure and energy to failure, while stiffness was not influenced. Bone mineral density distribution (BMDD) was not altered either. At the material level, β-APN treated rats exhibited increased Pyd/Divalent cross-link ratios in areas confined to a newly formed bone. Moreover, nano-indentation experiments showed that the E-modulus and hardness were reduced only in newly formed bone areas under the influence

  14. Can interactive educational technologies support the link between ultrasound theory and practice via feedback mechanisms?

    Science.gov (United States)

    Dickson, Diane

    2015-05-01

    Linking theory to practice is an area of concern for ultrasound students, clinical mentors and academic staff. The link between theory and practice requires a robust clinical mentorship scheme in addition to careful curricula design considerations to improve student outcomes. The introduction of interactive technology in education provides ripe opportunity to improve feedback to students to support the link between theory and practice. A series of three interactive learning and teaching activities were designed and delivered to a PostGraduate Ultrasound cohort, after which, evaluation was performed to answer the research question: Which interactive technologies support the link between theory and practice through improved feedback mechanisms? An action research methodology was adopted involving an enquiry based literature review, planning, design and action process. Data were collected following action of three interactive teaching and learning sessions within the Medical Ultrasound cohort of 2013/2014 at Glasgow Caledonian University via a paper based questionnaire. A 100% response rate was achieved (n = 14). All three interactive learning and teaching sessions were considered with 100% highest point agreement to support the link between ultrasound theory and practice via feedback. Students found all three designed and facilitated sessions valuable and relevant to their learning, which in turn provided positive experiences which were perceived to support the link between theory and practice through feedback. These activities can be considered valuable in Postgraduate Ultrasound education.

  15. A Mobility-Aware Link Enhancement Mechanism for Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Huang Chenn-Jung

    2008-01-01

    Full Text Available Abstract With the growth up of internet in mobile commerce, researchers have reproduced various mobile applications that vary from entertainment and commercial services to diagnostic and safety tools. Mobility management has widely been recognized as one of the most challenging problems for seamless access to wireless networks. In this paper, a novel link enhancement mechanism is proposed to deal with mobility management problem in vehicular ad hoc networks. Two machine learning techniques, namely, particle swarm optimization and fuzzy logic systems, are incorporated into the proposed schemes to enhance the accuracy of prediction of link break and congestion occurrence. The experimental results verify the effectiveness and feasibility of the proposed schemes.

  16. A Mobility-Aware Link Enhancement Mechanism for Vehicular Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Kai-Wen Hu

    2008-04-01

    Full Text Available With the growth up of internet in mobile commerce, researchers have reproduced various mobile applications that vary from entertainment and commercial services to diagnostic and safety tools. Mobility management has widely been recognized as one of the most challenging problems for seamless access to wireless networks. In this paper, a novel link enhancement mechanism is proposed to deal with mobility management problem in vehicular ad hoc networks. Two machine learning techniques, namely, particle swarm optimization and fuzzy logic systems, are incorporated into the proposed schemes to enhance the accuracy of prediction of link break and congestion occurrence. The experimental results verify the effectiveness and feasibility of the proposed schemes.

  17. Continuum mechanical model for cross-linked actin networks with contractile bundles

    Science.gov (United States)

    Ferreira, J. P. S.; Parente, M. P. L.; Natal Jorge, R. M.

    2018-01-01

    In the context of a mechanical approach to cell biology, there is a close relationship between cellular function and mechanical properties. In recent years, an increasing amount of attention has been given to the coupling between biochemical and mechanical signals by means of constitutive models. In particular, on the active contractility of the actin cytoskeleton. Given the importance of the actin contraction on the physiological functions, this study propose a constitutive model to describe how the filamentous network controls its mechanics actively. Embedded in a soft isotropic ground substance, the network behaves as a viscous mechanical continuum, comprised of isotropically distributed cross-linked actin filaments and actomyosin bundles. Trough virtual rheometry experiments, the present model relates the dynamics of the myosin motors with the network stiffness, which is to a large extent governed by the time-scale of the applied deformations/forces.

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

    International Nuclear Information System (INIS)

    Yussouff, M.

    1979-06-01

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

  19. Permeability and mechanical properties of cracked glass under pressure

    International Nuclear Information System (INIS)

    Ougier-Simonin, A.

    2010-01-01

    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

  20. Psychoses and creativity: is the missing link a biological mechanism related to phospholipids turnover?

    Science.gov (United States)

    Folley, Bradley S; Doop, Mikisha L; Park, Sohee

    2003-12-01

    Recent evidence suggests that genetic and biochemical factors associated with psychoses may also provide an increased propensity to think creatively. The evolutionary theories linking brain growth and diet to the appearance of creative endeavors have been made recently, but they lack a direct link to research on the biological correlates of divergent and creative thought. Expanding upon Horrobin's theory that changes in brain size and in neural microconnectivity came about as a result of changes in dietary fat and phospholipid incorporation of highly unsaturated fatty acids, we propose a theory relating phospholipase A2 (PLA2) activity to the neuromodulatory effects of the noradrenergic system. This theory offers probable links between attention, divergent thinking, and arousal through a mechanism that emphasizes optimal individual functioning of the PLA2 and NE systems as they interact with structural and biochemical states of the brain. We hope that this theory will stimulate new research in the neural basis of creativity and its connection to psychoses.

  1. Frictional behaviour of polymer films under mechanical and electrostatic loads

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  2. Reliability Issues and Solutions in Flexible Electronics Under Mechanical Fatigue

    Science.gov (United States)

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

    2018-03-01

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

  3. On the capacity of FSO links under lognormal and Rician-lognormal turbulences

    KAUST Repository

    Ansari, Imran Shafique

    2014-09-01

    A unified capacity analysis under weak and composite turbulences of a free-space optical (FSO) link that accounts for pointing errors and both types of detection techniques (i.e. intensity modulation/direct detection as well as heterodyne detection) is addressed in this work. More specifically, a unified exact closed-form expression for the moments of the end-to-end signal-to-noise ratio (SNR) of a single link FSO transmission system is presented in terms of well-known elementary functions. Capitalizing on these new moments expressions, unified approximate and simple closed- form results are offered for the ergodic capacity at high SNR regime as well as at low SNR regime. All the presented results are verified via computer- based Monte-Carlo simulations.

  4. Control of a perturbed under-actuated mechanical system

    KAUST Repository

    Zayane, Chadia

    2015-11-05

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

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

    Directory of Open Access Journals (Sweden)

    Nima Babhadiashar

    2015-06-01

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

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

    Directory of Open Access Journals (Sweden)

    Xinglong Gu

    2016-01-01

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

  7. Mechanical properties and collagen cross-linking of the patellar tendon in old and young men

    DEFF Research Database (Denmark)

    Couppé, C; Hansen, P; Kongsgaard, M

    2009-01-01

    were higher in OM than in YM (73 +/- 13 vs. 11 +/- 2 mmol/mol; P appreciably influence the dimensions or mechanical properties of the human patellar tendon in vivo. Collagen concentration was reduced, whereas both enzymatic......Age-related loss in muscle mass and strength impairs daily life function in the elderly. However, it remains unknown whether tendon properties also deteriorate with age. Cross-linking of collagen molecules provides structural integrity to the tendon fibrils and has been shown to change with age...... in animals but has never been examined in humans in vivo. In this study, we examined the mechanical properties and pyridinoline and pentosidine cross-link and collagen concentrations of the patellar tendon in vivo in old (OM) and young men (YM). Seven OM (67 +/- 3 years, 86 +/- 10 kg) and 10 YM (27 +/- 2...

  8. Potential mechanisms linking probiotics to diabetes: a narrative review of the literature

    OpenAIRE

    Miraghajani, Maryam; Dehsoukhteh, Somayeh Shahraki; Rafie, Nahid; Hamedani, Sahar Golpour; Sabihi, Sima; Ghiasvand, Reza

    2017-01-01

    ABSTRACT CONTEXT AND OBJECTIVE: Some studies have suggested a wide range of possible mechanisms through which probiotics may play a role in diabetes prevention and treatment. However, the underlying mechanisms are not fully understood. We conducted this study to review the potential mechanisms suggested for the effect of probiotics in diabetes. DESIGN AND SETTING: Narrative review conducted at the Food Security Research Center of Isfahan. METHODS: A search in the electronic databases ME...

  9. Effects of alginate hydrogel cross-linking density on mechanical and biological behaviors for tissue engineering.

    Science.gov (United States)

    Jang, Jinah; Seol, Young-Joon; Kim, Hyeon Ji; Kundu, Joydip; Kim, Sung Won; Cho, Dong-Woo

    2014-09-01

    An effective cross-linking of alginate gel was made through reaction with calcium carbonate (CaCO3). We used human chondrocytes as a model cell to study the effects of cross-linking density. Three different pore size ranges of cross-linked alginate hydrogels were fabricated. The morphological, mechanical, and rheological properties of various alginate hydrogels were characterized and responses of biosynthesis of cells encapsulated in each gel to the variation in cross-linking density were investigated. Desired outer shape of structure was maintained when the alginate solution was cross-linked with the applied method. The properties of alginate hydrogel could be tailored through applying various concentrations of CaCO3. The rate of synthesized GAGs and collagens was significantly higher in human chondrocytes encapsulated in the smaller pore structure than that in the larger pore structure. The expression of chondrogenic markers, including collagen type II and aggrecan, was enhanced in the smaller pore structure. It was found that proper structural morphology is a critical factor to enhance the performance and tissue regeneration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Modification mechanism of sesbania gum, and preparation, property, adsorption of dialdehyde cross-linked sesbania gum.

    Science.gov (United States)

    Tang, Hongbo; Gao, Shiqi; Li, Yanping; Dong, Siqing

    2016-09-20

    This paper studied the modification mechanism of Sesbania gum (SG) by means of the variations in the numbers of surface hydroxyl groups on the granules, Schiff's agent coloration of aldehyde groups, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), energy dispersive spectrum (EDS), etc., and also examined the preparation, property and adsorption of dialdehyde cross-linked sesbania gum (DCLSG). The results showed that the surface hydroxyl numbers of cross-linked sesbania gum (CLSG) decreased with increasing the cross-linking degree. The distribution of the aldehyde groups on the DCLSG particles was nonuniform because most of aldehyde groups mainly located on the edge of particles. The cross-linking occurred only on the surface of SG particles. The oxidization occurred not only on the surface of SG particles, but also in the interior of particles. The cross-linking or oxidization changed the thermal properties, and reduced the swelling power, viscosity, alkali and acid resistance of SG. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. 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...

  12. Giant panda׳s tooth enamel: Structure, mechanical behavior and toughening mechanisms under indentation.

    Science.gov (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

    2016-12-01

    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.

  13. Mechanical properties of graphene nanoribbons under uniaxial tensile strain

    Science.gov (United States)

    Yoneyama, Kazufumi; Yamanaka, Ayaka; Okada, Susumu

    2018-03-01

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

  14. Peripheral Receptor Mechanisms Underlying Orofacial Muscle Pain and Hyperalgesia

    Science.gov (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

  15. Mechanical properties of a collagen fibril under simulated degradation.

    Science.gov (United States)

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

    2017-11-01

    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.

  16. Identifying mechanisms that underlie links between COMT genotype and aggression in male adolescents with ADHD.

    Science.gov (United States)

    van Goozen, Stephanie H M; Langley, Kate; Northover, Clare; Hubble, Kelly; Rubia, Katya; Schepman, Karen; O'Donovan, Michael C; Thapar, Anita

    2016-04-01

    There is a known strong genetic contribution to aggression in those with ADHD. In a previous investigation of a large population cohort, impaired 'emotional/social cognitive' processing, assessed by questionnaire, was observed to mediate the link between COMT Val158Met and aggression in individuals with ADHD. We set out to replicate and extend this finding in a clinical sample, using task-based and physiological assessments of emotional and cognitive processing. Our aim was to test the hypothesis that directly assessed emotional processing mediates the link between COMT Val158Met and aggression in young people with ADHD. Males aged 10-17 years with ADHD were recruited from UK community clinics (n = 194). Research diagnostic interviews (parent and child) were used to assess psychopathology and generate DSM-IV Conduct Disorder symptom scores. Participants completed tasks assessing executive function (response inhibition and set shifting), empathy for fear, sadness and happiness, and fear conditioning [measured using skin conductance responses (SCR) to aversive stimuli]. COMT Val allele carriers showed poorer response inhibition (F = 5.27, p = .02) and set shifting abilities (F = 6.45, p = .01), reduced fear empathy (F = 4.33, p = .04) and reduced autonomic responsiveness (lower SCRs) to the conditioned aversive stimulus (F = 11.74, p = .001). COMT Val158Met did not predict impairments in recognising others' emotions or affective empathy for happiness or sadness. Mediation analysis revealed that impaired fear-related mechanisms indirectly mediated the link between COMT Val158Met and aggression. Our findings suggest fear mechanisms as possible targets for psychological interventions to disrupt links between genetic risk and aggressive outcomes in ADHD. Our findings also reveal the potential of hypothesis-driven approaches for identifying neuropsychological mechanisms that mediate genetic risk effects on behaviour and psychopathology. © 2015 The Authors. Journal of

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

    Science.gov (United States)

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

    2017-03-01

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

  18. In Situ Dual Cross-Linking of Neat Biogel with Controlled Mechanical and Delivery Properties.

    Science.gov (United States)

    Kelmansky, Regina; Shagan, Alona; Rozenblit, Boris; Omar, Rawan; Lufton, Maayan; Mizrahi, Boaz

    2017-10-02

    Injectable biomaterials play a critical role in many biomedical applications. These materials, however, often have limitations in mechanical and drug-eluting properties attributed to their high water content and the weak secondary forces holding them together. Here we describe a new injectable material based on two complementary water-free, prepolymers modified with succinimidyl carbonate (SC) or with NH 2 end groups that form a stiff matrix upon mixing. Cross-linking involves an immediate reaction between PEG 4 -SC and PEG 4 -NH 2 that forms carbamate bonds and a delayed reaction of PEG 4 -SC with hydroxyl functional groups that forms carbonate bonds. The mechanical properties, swelling, and erosion kinetics of this biomaterial can be fine-tuned by varying the ratio between the two prepolymers. Bovine serum albumin and poorly water-soluble free base doxorubicin were readily loaded into this system, resulting in a high drug loading content attributed to the absence of water in the formulation. Controlled release over a period of 1 to 30 days was observed, depending on mixture composition and drug properties. The injectable nature of the formulation, its tailored mechanical properties, the fact that it can be cross-linked by two separate mechanisms, and its ability to incorporate and release hydrophilic and hydrophobic drugs make it very attractive as a drug delivery system.

  19. Epigenetic Regulation of Placental "NR3C1": Mechanism Underlying Prenatal Programming of Infant Neurobehavior by Maternal Smoking?

    Science.gov (United States)

    Stroud, Laura R.; Papandonatos, George D.; Salisbury, Amy L.; Phipps, Maureen G.; Huestis, Marilyn A.; Niaura, Raymond; Padbury, James F.; Marsit, Carmen J.; Lester, Barry M.

    2016-01-01

    Epigenetic regulation of the placental glucocorticoid receptor gene ("NR3C1") was investigated as a mechanism underlying links between maternal smoking during pregnancy (MSDP) and infant neurobehavior in 45 mother-infant pairs (49% MSDP-exposed; 52% minorities; ages 18-35). The Neonatal Intensive Care Unit (NICU) Network Neurobehavioral…

  20. Failure Mechanisms of Brittle Rocks under Uniaxial Compression

    Directory of Open Access Journals (Sweden)

    Liu Taoying

    2017-09-01

    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.

  1. The mechanism underlying fast germination of tomato cultivar LA2711.

    Science.gov (United States)

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

    2015-09-01

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

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

    Directory of Open Access Journals (Sweden)

    Nicolas eRoy

    2014-05-01

    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.

  3. Mechanical Design of AM Fabricated Prismatic Rods under Torsion

    Directory of Open Access Journals (Sweden)

    Manzhirov Alexander V.

    2017-01-01

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

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

    Science.gov (United States)

    Wei, Min; Li, Song; Le, Weidong

    2017-10-25

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

  5. Investigating the work-family conflict and health link: Repetitive thought as a mechanism.

    Science.gov (United States)

    Davis, Kelly D; Gere, Judith; Sliwinski, Martin J

    2017-10-01

    Research is needed to investigate mechanisms linking work-family conflict to poor health in working adults. We took a novel approach to build on extant studies by testing a potential mechanism in these associations - repetitive thought. Data came from a sample of 203 partnered working adults. There were significant direct effects of work-family conflict with lower life satisfaction, positive affect, and perceived health as well as greater fatigue. As for total effects, work-family conflict was significantly associated with all health outcomes - life satisfaction, positive affect, negative affect, fatigue, perceived health, and chronic health conditions - in the expected directions through repetitive thought. This study provides support that repetitive thought is one potential mechanism of how work-family conflict can take a toll on psychological and physical health. Findings are discussed in relation to improving workplace policies to improve the health of working adults managing work-family conflict. Copyright © 2016 John Wiley & Sons, Ltd.

  6. Age differences in the underlying mechanisms of stereotype threat effects.

    Science.gov (United States)

    Popham, Lauren E; Hess, Thomas M

    2015-03-01

    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: journals.permissions@oup.com.

  7. Mechanisms linking socioeconomic status to smoking cessation: a structural equation modeling approach.

    Science.gov (United States)

    Businelle, Michael S; Kendzor, Darla E; Reitzel, Lorraine R; Costello, Tracy J; Cofta-Woerpel, Ludmila; Li, Yisheng; Mazas, Carlos A; Vidrine, Jennifer Irvin; Cinciripini, Paul M; Greisinger, Anthony J; Wetter, David W

    2010-05-01

    Although there has been a socioeconomic gradient in smoking prevalence, cessation, and disease burden for decades, these disparities have become even more pronounced over time. The aim of the current study was to develop and test a conceptual model of the mechanisms linking socioeconomic status (SES) to smoking cessation. The conceptual model was evaluated using a latent variable modeling approach in a sample of 424 smokers seeking treatment (34% African American; 33% Latino; 33% White). Hypothesized mechanisms included social support, neighborhood disadvantage, negative affect/stress, agency, and craving. The primary outcome was Week 4 smoking status. As was hypothesized, SES had significant direct and indirect effects on cessation. Specifically, neighborhood disadvantage, social support, negative affect/stress, and agency mediated the relation between SES and smoking cessation. A multiple group analysis indicated that the model was a good fit across racial/ethnic groups. The present study yielded one of the more comprehensive models illuminating the specific mechanisms that link SES and smoking cessation. Policy, community, and individual-level interventions that target low SES smokers and address the specific pathways identified in the current model could potentially attenuate the impact of SES on cessation. (c) 2010 APA, all rights reserved.

  8. Electrochemical mechanism of tin membrane electrodeposition under ultrasonic waves.

    Science.gov (United States)

    Nan, Tianxiang; Yang, Jianguang; Chen, Bing

    2018-04-01

    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.

  9. Mechanisms Underlying the Antidepressant Response and Treatment Resistance

    Directory of Open Access Journals (Sweden)

    Marjorie Rose Levinstein

    2014-06-01

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

  10. Effects of manual hyperinflation in preterm newborns under mechanical ventilation.

    Science.gov (United States)

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

    2016-09-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-05

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

  12. Obstructive sleep apnea and dyslipidemia: evidence and underlying mechanism.

    Science.gov (United States)

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

    2014-03-01

    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.

  13. Probabilistic Model for Free-Space Optical Links Under Continental Fog Conditions

    Directory of Open Access Journals (Sweden)

    Marzuki

    2010-09-01

    Full Text Available The error characteristics of a free-space optical (FSO channel are significantly different from the fiber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly influence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classified into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs such as Kumaraswamy, Johnson SB and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best fit for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson SB distribution best fits the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efficient FSO system.

  14. Analysis of Three-Phase Rectifier Systems with Controlled DC-Link Current Under Unbalanced Grids

    DEFF Research Database (Denmark)

    Kumar, Dinesh; Davari, Pooya; Zare, Firuz

    2017-01-01

    Voltage unbalance is the most common disturbance in distribution networks, which give undesirable effects on many grid connected power electronics systems including Adjustable Speed Drive (ASD). Severe voltage unbalance can force three-phase rectifiers into almost single-phase operation, which...... degrades the grid power quality and also imposes a significant negative impact on the ASD system. This major power quality issue affecting the conventional rectifiers can be attenuated by controlling the DC-link current based on an Electronic Inductor (EI) technique. The purpose of this digest...... is to analyze and compare the performance of an EI with a conventional three-phase rectifier under unbalanced grid conditions. Experimental and simulation results validate the proposed mathematical modelling. Further analysis and benchmarking will be provided in the final paper....

  15. Mechanically robust, readily repairable polymers via tailored noncovalent cross-linking

    Science.gov (United States)

    Yanagisawa, Yu; Nan, Yiling; Okuro, Kou; Aida, Takuzo

    2018-01-01

    Expanding the range of healable materials is an important challenge for sustainable societies. Noncrystalline, high-molecular-weight polymers generally form mechanically robust materials, which, however, are difficult to repair once they are fractured. This is because their polymer chains are heavily entangled and diffuse too sluggishly to unite fractured surfaces within reasonable time scales. Here we report that low-molecular-weight polymers, when cross-linked by dense hydrogen bonds, yield mechanically robust yet readily repairable materials, despite their extremely slow diffusion dynamics. A key was to use thiourea, which anomalously forms a zigzag hydrogen-bonded array that does not induce unfavorable crystallization. Another key was to incorporate a structural element for activating the exchange of hydrogen-bonded pairs, which enables the fractured portions to rejoin readily upon compression.

  16. Chemo-mechanical microscale characterization of materials heterogeneity in oil/gas shales: linking organics and inorganics

    Science.gov (United States)

    Ferralis, N.; Abedi, S.; Grossman, J. C.; Ulm, F.

    2013-12-01

    From a materials perspective, the unconventional peculiarity of oil/gas shales resides in the intrinsic multi-scale heterogeneity in their chemical composition, organic maturity, mineralogy and microtexture. In contrast to common assumptions of maturity being driven only by the reservoir conditions (temperature and pressure), the presence of organic matter with different maturity within a few microns apart calls into question the role played by the organic and mineral heterogeneity into the chemo-mechanical properties of the material. Understanding how the upscaling of chemical diversity affects the fracturability and in general the mechanical strength of oil/gas shales is crucial. Compared to conventional oil and gas reservoirs, as well as coal, such heterogeneity requires novel and additional characterization tools from nano- to macro-scales to allow for a complete understanding of the role played by such heterogeneity in the chemo- mechanical properties of gas shales. Here we present a novel suite of chemical and mineralogical characterization tools that allow the in situ, non-destructive imaging of organic maturity and mineralogy from the microscale to the millimeter scale. This method is based on a combination of Raman, fluorescence and UV-Visible absorption spectroscopy. The upscaling is designed to provide a maturity population distribution from the nanoscale to the conventionally used macro-scale averaged parameters (such as vitrinite reflectance). Furthermore, in combination with registered micro/nano-mechanical indentation data a direct correlation of fracture mechanics and chemistry is made, allowing for the determination of high yield strain regions, relations between organic and inorganic anisotropy and interface mechanics. The underlying scientific insight at the nano and micro-scale of the potential origin of fractures in oil/gas shales, will potentially provide a connection bottom-up link to continuum fracture mechanics.

  17. Neural mechanisms linking social status and inflammatory responses to social stress.

    Science.gov (United States)

    Muscatell, Keely A; Dedovic, Katarina; Slavich, George M; Jarcho, Michael R; Breen, Elizabeth C; Bower, Julienne E; Irwin, Michael R; Eisenberger, Naomi I

    2016-06-01

    Social stratification has important implications for health and well-being, with individuals lower in standing in a hierarchy experiencing worse outcomes than those higher up the social ladder. Separate lines of past research suggest that alterations in inflammatory processes and neural responses to threat may link lower social status with poorer outcomes. This study was designed to bridge these literatures to investigate the neurocognitive mechanisms linking subjective social status and inflammation. Thirty-one participants reported their subjective social status, and underwent a functional magnetic resonance imaging scan while they were socially evaluated. Participants also provided blood samples before and after the stressor, which were analysed for changes in inflammation. Results showed that lower subjective social status was associated with greater increases in inflammation. Neuroimaging data revealed lower subjective social status was associated with greater neural activity in the dorsomedial prefrontal cortex (DMPFC) in response to negative feedback. Finally, results indicated that activation in the DMPFC in response to negative feedback mediated the relation between social status and increases in inflammatory activity. This study provides the first evidence of a neurocognitive pathway linking subjective social status and inflammation, thus furthering our understanding of how social hierarchies shape neural and physiological responses to social interactions. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

  18. Neural mechanisms linking social status and inflammatory responses to social stress

    Science.gov (United States)

    Dedovic, Katarina; Slavich, George M.; Jarcho, Michael R.; Breen, Elizabeth C.; Bower, Julienne E.; Irwin, Michael R.; Eisenberger, Naomi I.

    2016-01-01

    Social stratification has important implications for health and well-being, with individuals lower in standing in a hierarchy experiencing worse outcomes than those higher up the social ladder. Separate lines of past research suggest that alterations in inflammatory processes and neural responses to threat may link lower social status with poorer outcomes. This study was designed to bridge these literatures to investigate the neurocognitive mechanisms linking subjective social status and inflammation. Thirty-one participants reported their subjective social status, and underwent a functional magnetic resonance imaging scan while they were socially evaluated. Participants also provided blood samples before and after the stressor, which were analysed for changes in inflammation. Results showed that lower subjective social status was associated with greater increases in inflammation. Neuroimaging data revealed lower subjective social status was associated with greater neural activity in the dorsomedial prefrontal cortex (DMPFC) in response to negative feedback. Finally, results indicated that activation in the DMPFC in response to negative feedback mediated the relation between social status and increases in inflammatory activity. This study provides the first evidence of a neurocognitive pathway linking subjective social status and inflammation, thus furthering our understanding of how social hierarchies shape neural and physiological responses to social interactions. PMID:26979965

  19. Cardiovascular reactivity as a mechanism linking child trauma to adolescent psychopathology

    Science.gov (United States)

    Heleniak, Charlotte; McLaughlin, Katie A.; Ormel, Johan; Riese, Harriette

    2016-01-01

    Alterations in physiological reactivity to stress are argued to be central mechanisms linking adverse childhood environmental experiences to internalizing and externalizing psychopathology. Childhood trauma exposure may influence physiological reactivity to stress in distinct ways from other forms of childhood adversity. This study applied a novel theoretical model to investigate the impact of childhood trauma on cardiovascular stress reactivity – the biopsychosocial model of challenge and threat. This model suggests that inefficient cardiovascular responses to stress – a threat as opposed to challenge profile – are characterized by blunted cardiac output (CO) reactivity and increased vascular resistance. We examined whether childhood trauma exposure predicted an indicator of the threat profile of cardiovascular reactivity and whether such a pattern was associated with adolescent psychopathology in a population-representative sample of 488 adolescents (M = 16.17 years old, 49.2% boys) in the TRacking Adolescents’ Individual Lives Survey (TRAILS). Exposure to trauma was associated with both internalizing and externalizing symptoms and a pattern of cardiovascular reactivity consistent with the threat profile, including blunted CO reactivity during a social stress task. Blunted CO reactivity, in turn, was positively associated with externalizing, but not internalizing symptoms and mediated the link between trauma and externalizing psychopathology. None of these associations varied by gender. The biopsychosocial model of challenge and threat provides a novel theoretical framework for understanding disruptions in physiological reactivity to stress following childhood trauma exposure, revealing a potential pathway linking such exposure with externalizing problems in adolescents. PMID:27568327

  20. Structural Analysis and Mechanical Characterization of Hyaluronic Acid-Based Doubly Cross-Linked Networks.

    Science.gov (United States)

    Jha, Amit K; Hule, Rohan A; Jiao, Tong; Teller, Sean S; Clifton, Rodney J; Duncan, Randall L; Pochan, Darrin J; Jia, Xinqiao

    2009-01-01

    We have created a new class of hyaluronic acid (HA)-based hydrogel materials with HA hydrogel particles (HGPs) embedded in and covalently cross-linked to a secondary network. HA HGPs with an average diameter of ∼900 nm and narrow particle size distribution were synthesized using a refined reverse micelle polymerization technique. The average mesh size of the HGPs was estimated to be approximately 5.5 to 7.0 nm by a protein uptake experiment. Sodium periodate oxidation not only introduced aldehyde groups to the particles but also reduced the average particle size. The aldehyde groups generated were used as reactive handles for subsequent cross-linking with an HA derivative containing hydrazide groups. The resulting macroscopic gels contain two distinct hierarchical networks (doubly cross-linked networks, DXNs): one within individual particles and another among different particles. Bulk gels (BGs) formed by direct mixing of HA derivatives with mutually reactive groups were included for comparison. The hydrogel microstructures were collectively characterized by microscopy and neutron scattering techniques. Their viscoelasticity was quantified at low frequencies (0.1-10 Hz) using a controlled stress rheometer and at high frequencies (up to 200 Hz) with a home-built torsional wave apparatus. Both BGs and DXNs are stable elastic gels that become stiffer at higher frequencies. The HA-based DXN offers unique structural hierarchy and mechanical properties that are suitable for soft tissue regeneration.

  1. SCTP-aware Link Layer Retransmission Mechanism for Smart-grid Communication Network

    Directory of Open Access Journals (Sweden)

    S. Zafar

    2016-08-01

    Full Text Available The smart grid delivers electricity from suppliers to consumers and uses bidirectional communication to exchange real-time information between supply system and smart meters at the user end. With a combined communication infrastructure, smart grid manages the operation of all associated components to provide reliable and supportable electricity supply. The Neighborhood Area Network (NAN of smart grid supports bi-directional data transfer between smart meters (installed at customer premises and control center of the utility company through an aggregator. This communication suffers low throughput and excessive delays due to the Head of Line (HOL blocking when the Transmission Control Protocol (TCP is implemented for reliability. In this paper we propose SCTP-aware Link Layer Retransmission mechanism (SCTP-LLR which augments the Stream Control Transmission Protocol (SCTP with Link Layer Retransmissions at the aggregator. SCTP-LLR uses the multi-streaming feature offered by SCTP and implements link layer retransmissions at the aggregator to mitigate the effect of HOL blocking. We carried out simulations using Network Simulator and compared the performance of SCTP-LLR against TCP and SCTP. Our results show that SCTP-LLR outperforms both TCP and SCTP in terms of throughput and packet delays and is a promising protocol to be implemented in smart grid NAN for reliable and efficient communication.

  2. Mechanical properties of the equine superficial digital flexor tendon relate to specific collagen cross-link levels.

    Science.gov (United States)

    Thorpe, C T; Stark, R J F; Goodship, A E; Birch, H L

    2010-11-01

    Damage to the flexor tendons, particularly the superficial digital flexor tendon (SDFT), is one of the most common musculoskeletal injuries sustained by horses competing in all disciplines. Our previous work has shown that SDFTs from different individuals show a wide variation in mechanical strengths; this is important clinically as it may relate to predisposition to injury. The high mechanical strength of tendon relies on the correct orientation of collagen molecules within fibrils and stabilisation by the formation of chemical cross-links between collagen molecules. It is not known whether the variation in SDFT mechanical properties between individuals relates to differences in collagen cross-link levels. Enzyme-derived, intermolecular cross-linking of tendon collagen correlates with mechanical properties of the SDFT. SDFTs were collected from 38 horses and mechanically tested to failure. Structural and material properties were calculated from the load/deformation plot and cross-sectional area for each tendon. Following mechanical testing, pyrrolic cross-link levels were measured using a spectrophotometric assay for Ehrlich's reactivity and pyridinoline levels were quantified by HPLC. Cross-link levels were correlated with mechanical properties and statistical significance tested using a Pearson's correlation test. Pyrrole cross-link levels showed a significant positive correlation with ultimate stress (P = 0.004), yield stress (P = 0.003) and elastic modulus (P = 0.018) of the tendons, despite being a minor cross-link in these tendons. There was no significant correlation of mechanical properties with either hydroxylysyl- or lysyl-pyridinoline levels. Given the low absolute levels of pyrrole, we suggest that the correlation with high mechanical strength is through an indirect mechanism. Understanding the nature of the relationships between pyrrole cross-links, other matrix characteristics and tendon material properties may allow development of strategies to

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

    Science.gov (United States)

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

    2015-01-01

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

  4. The mechanisms underlying fructose-induced hypertension: a review

    Science.gov (United States)

    Klein, Alice Victoria; Kiat, Hosen

    2015-01-01

    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

  5. Degradation Mechanisms of Transparent Polyurethane Interlayer under UV Irradiation

    Directory of Open Access Journals (Sweden)

    OU Yingchun

    2017-01-01

    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.

  6. Nonlinear mechanical response of supercooled melts under applied forces

    Science.gov (United States)

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

    2017-08-01

    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.

  7. Bioinspired composites from cross-linked galactoglucomannan and microfibrillated cellulose: Thermal, mechanical and oxygen barrier properties.

    Science.gov (United States)

    Oinonen, Petri; Krawczyk, Holger; Ek, Monica; Henriksson, Gunnar; Moriana, Rosana

    2016-01-20

    In this study, new wood-inspired films were developed from microfibrillated cellulose and galactoglucomannan-lignin networks isolated from chemothermomechanical pulping side streams and cross-linked using laccase enzymes. To the best of our knowledge, this is the first time that cross-linked galactoglucomannan-lignin networks have been used for the potential development of composite films inspired by woody-cell wall formation. Their capability as polymeric matrices was assessed based on thermal, structural, mechanical and oxygen permeability analyses. The addition of different amounts of microfibrillated cellulose as a reinforcing agent and glycerol as a plasticizer on the film performances was evaluated. In general, an increase in microfibrillated cellulose resulted in a film with better thermal, mechanical and oxygen barrier performance. However, the presence of glycerol decreased the thermal stability, stiffness and oxygen barrier properties of the films but improved their elongation. Therefore, depending on the application, the film properties can be tailored by adjusting the amounts of reinforcing agent and plasticizer in the film formulation. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Time with friends and physical activity as mechanisms linking obesity and television viewing among youth

    Science.gov (United States)

    2015-01-01

    Background Though bivariate relationships between childhood obesity, physical activity, friendships and television viewing are well documented, empirical assessment of the extent to which links between obesity and television may be mediated by these factors is scarce. This study examines the possibility that time with friends and physical activity are potential mechanisms linking overweight/obesity to television viewing in youth. Methods Data were drawn from children ages 10-18 years old (M = 13.81, SD = 2.55) participating in the 2002 wave of Child Development Supplement (CDS) to the Panel Study of Income Dynamics (PSID) (n = 1,545). Data were collected both directly and via self-report from children and their parents. Path analysis was employed to examine a model whereby the relationships between youth overweight/obesity and television viewing were mediated by time spent with friends and moderate-to-vigorous physical activity (MVPA). Results Overweight/obesity was directly related to less time spent with friends, but not to MVPA. Time spent with friends was directly and positively related to MVPA, and directly and negatively related to time spent watching television without friends. In turn, MVPA was directly and negatively related to watching television without friends. There were significant indirect effects of both overweight/obesity and time with friends on television viewing through MVPA, and of overweight/obesity on MVPA through time with friends. Net of any indirect effects, the direct effect of overweight/obesity on television viewing remained. The final model fit the data extremely well (χ2 = 5.77, df = 5, pobesity and television viewing in youth. These findings highlight the importance of moving from examinations of bivariate relationships between weight status and television viewing to more nuanced explanatory models which attempt to identify and unpack the possible mechanisms linking them. PMID:26221737

  9. Time with friends and physical activity as mechanisms linking obesity and television viewing among youth.

    Science.gov (United States)

    Vandewater, Elizabeth A; Park, Seoung Eun; Hébert, Emily T; Cummings, Hope M

    2015-07-27

    Though bivariate relationships between childhood obesity, physical activity, friendships and television viewing are well documented, empirical assessment of the extent to which links between obesity and television may be mediated by these factors is scarce. This study examines the possibility that time with friends and physical activity are potential mechanisms linking overweight/obesity to television viewing in youth. Data were drawn from children ages 10-18 years old (M = 13.81, SD = 2.55) participating in the 2002 wave of Child Development Supplement (CDS) to the Panel Study of Income Dynamics (PSID) (n = 1,545). Data were collected both directly and via self-report from children and their parents. Path analysis was employed to examine a model whereby the relationships between youth overweight/obesity and television viewing were mediated by time spent with friends and moderate-to-vigorous physical activity (MVPA). Overweight/obesity was directly related to less time spent with friends, but not to MVPA. Time spent with friends was directly and positively related to MVPA, and directly and negatively related to time spent watching television without friends. In turn, MVPA was directly and negatively related to watching television without friends. There were significant indirect effects of both overweight/obesity and time with friends on television viewing through MVPA, and of overweight/obesity on MVPA through time with friends. Net of any indirect effects, the direct effect of overweight/obesity on television viewing remained. The final model fit the data extremely well (χ2 = 5.77, df = 5, pobesity and television viewing in youth. These findings highlight the importance of moving from examinations of bivariate relationships between weight status and television viewing to more nuanced explanatory models which attempt to identify and unpack the possible mechanisms linking them.

  10. Simulated airplane headache: a proxy towards identification of underlying mechanisms.

    Science.gov (United States)

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

    2017-12-01

    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.

  11. POSSIBLE MECHANISMS UNDERLYING THE THERAPEUTIC EFFECTS OF TRANSCRANIAL MAGNETIC STIMULATION

    Directory of Open Access Journals (Sweden)

    Alexander eChervyakov

    2015-06-01

    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. Nonlinear Mechanics of MEMS Rectangular Microplates under Electrostatic Actuation

    KAUST Repository

    Saghir, Shahid

    2016-12-01

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

  13. Mechanisms underlying the social enhancement of vocal learning in songbirds.

    Science.gov (United States)

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

    2016-06-14

    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

    2017-01-01

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

  15. Thermal stability of nafion membranes under mechanical stress

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-06-01

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

  16. Using Drosophila to discover mechanisms underlying type 2 diabetes

    Directory of Open Access Journals (Sweden)

    Ronald W. Alfa

    2016-04-01

    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. Mechanisms underlying temperature extremes in Iberia: a Lagrangian perspective

    Directory of Open Access Journals (Sweden)

    João A. Santos

    2015-04-01

    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. 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.

  20. Cross-linking between thymine and indolyl radical: possible mechanisms for cross-linking of DNA and tryptophan-containing peptides.

    Science.gov (United States)

    Mitrasinovic, Petar M

    2005-01-01

    As experimentally observed in gamma-irradiated aqueous solutions of tryptophan-containing peptides in the presence of DNA, a fast electron (or hydrogen atom) transfer from the DNA restores an intact tryptophan residue at the expense of the DNA integrity. Alternatively, addition of the deprotonated electron-deficient indolyl radical to the DNA, followed by subsequent rearrangement, may lead toward DNA/tryptophan-containing peptide cross-linking. Herein, possible reaction mechanisms for thymine-indolyl radical cross-linking are proposed. The consistent use of the contact spin density distribution is the key virtue of this work. The Becke 3, Lee, Yang, and Parr (B3LYP) density functional theory (DFT) method is employed to investigate the feasibility of the proposed cross-linking mechanisms. A possible complete reaction mechanism consists of a combination of the C(5)-hydroxylated thymine and indolyl radicals forming the initial cross-linked product, a hydrogen transfer within the initial cross-linked product by use of a bridging water molecule, and a dehydration step. The overall thermodynamics of the free energy profiles at 0 and 298 K are similar and display differences of magnitude for the hydrogen-transfer reaction. Temperature may be a key factor influencing the overall mechanism. The skeletal structures and contact spin densities on the heavy atoms of the tryptophan side chain and indolyl radicals are essentially equal. Hence, it is believed that a direct combination of the C(5)-hydroxylated thymine and tryptophan radicals should form the initial cross-linked product, as far as addition of the tryptophan radical to the DNA is concerned.

  1. Mechanical properties and failure mechanisms of graphene under a central load.

    Science.gov (United States)

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

    2014-09-15

    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.

  2. Antenna Scan Mechanism for an Inter Satellite Link of a Constellation Program

    Science.gov (United States)

    Köker, Ingo; Härtel, Frank

    2015-09-01

    For a constellation program, RF Inter Satellite Links between single satellites can support ranging and communication for uploading mission data or telecommands. These data shall be uploaded from one single ground station to the next reachable satellite and transmitted by the Inter Satellite Link to further dedicated satellites. For this function each satellite has to be equipped with 2 Antenna Scan Mechanisms (ASM) for data transfer in the K-Band.The main challenges for the mechanisms are the high speed position change requirement, low mass requirement and the design to cost approach. Furthermore a small envelope to accommodate the 2- axes antenna scan mechanism was provided. The maximum position change of +/- 180° needs to be reached within 3 seconds. All requirements shall be achieved by relying on the heritage design of our downlink antenna pointing mechanism product.The ASM design approach was based on our 2-axes steerable downlink antenna; however during the definition phase it turned out that some major changes have to be implemented due to mission requirements (high operation speed and long lifetime). Following the design to cost approach most components could be procured from industrial standard but had to be qualified in terms of functionality, performance and life. The following industrial components have been selected: - Bearings procured from an industrial supplier and modified (cage) by a supporting supplier - The selected actuator is a standard stepper motor equipped with redundant windings - The slip ring design was used from a previous project in order to keep the heritage - Suitable rotary joints for the RF link were provided by a small and flexible company However at the very beginning of the project some difficulties with the bearings selection and procurementhave been identified. Since the most suitable standard catalog bearings were not available in time, we were forced to use alternatives. In parallel due to envelope constrains the re

  3. Microcracking in composite laminates under thermal and mechanical loading. Thesis

    Science.gov (United States)

    Maddocks, Jason R.

    1995-01-01

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

  4. Does the concept of "sensitization" provide a plausible mechanism for the putative link between the environment and schizophrenia?

    Science.gov (United States)

    Collip, Dina; Myin-Germeys, Inez; Van Os, Jim

    2008-03-01

    Previous evidence reviewed in Schizophrenia Bulletin suggests the importance of a range of different environmental factors in the development of psychotic illness. It is unlikely, however, that the diversity of environmental influences associated with schizophrenia can be linked to as many different underlying mechanisms. There is evidence that environmental exposures may induce, in interaction with (epi)genetic factors, psychological or physiological alterations that can be traced to a final common pathway of cognitive biases and/or altered dopamine neurotransmission, broadly referred to as "sensitization," facilitating the onset and persistence of psychotic symptoms. At the population level, the behavioral phenotype for sensitization may be examined by quantifying, in populations exposed to environmental risk factors associated with stress or dopamine-agonist drugs, (1) the increased rate of persistence (indicating lasting sensitization) of normally transient developmental expressions of subclinical psychotic experiences and (2) the subsequent increased rate of transition to clinical psychotic disorder.

  5. Extracurricular Activity Participation in High School: Mechanisms Linking Participation to Math Achievement and 4-Year College Attendance

    Science.gov (United States)

    Morris, David S.

    2016-01-01

    Extracurricular activity participation (EAP) has been positively linked with increased academic achievement and college attendance. However, the mechanisms linking EAP to educational outcomes are poorly understood. Using the Education Longitudinal Study of 2002 (ELS), this study contributes to our understanding of the relationship between EAP and…

  6. Mechanical Modeling of a WIPP Drum Under Pressure

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-25

    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

  7. Video analysis of concussion injury mechanism in under-18 rugby

    Science.gov (United States)

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

    2016-01-01

    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

  8. Video analysis of concussion injury mechanism in under-18 rugby.

    Science.gov (United States)

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

    2016-01-01

    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.

  9. Underlying Mechanisms of Tinnitus: Review and Clinical Implications

    Science.gov (United States)

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

    2016-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Roberta Piscia

    2016-04-01

    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.

    Directory of Open Access Journals (Sweden)

    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

    Science.gov (United States)

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

    2017-07-01

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

  13. Neural Mechanisms Underlying Hyperphagia in Prader-Willi Syndrome

    Science.gov (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.

    2006-01-01

    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

  14. Neural mechanisms underlying hyperphagia in Prader-Willi syndrome.

    Science.gov (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

    2006-06-01

    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).

  15. Biochemical mechanisms of pallidal deep brain stimulation in X-linked dystonia parkinsonism.

    Science.gov (United States)

    Tronnier, V M; Domingo, A; Moll, C K; Rasche, D; Mohr, C; Rosales, R; Capetian, P; Jamora, R D; Lee, L V; Münchau, A; Diesta, C C; Tadic, V; Klein, C; Brüggemann, N; Moser, A

    2015-08-01

    Invasive techniques such as in-vivo microdialysis provide the opportunity to directly assess neurotransmitter levels in subcortical brain areas. Five male Filipino patients (mean age 42.4, range 34-52 years) with severe X-linked dystonia-parkinsonism underwent bilateral implantation of deep brain leads into the internal part of the globus pallidus (GPi). Intraoperative microdialysis and measurement of gamma aminobutyric acid and glutamate was performed in the GPi in three patients and globus pallidus externus (GPe) in two patients at baseline for 25/30 min and during 25/30 min of high-frequency GPi stimulation. While the gamma-aminobutyric acid concentration increased in the GPi during high frequency stimulation (231 ± 102% in comparison to baseline values), a decrease was observed in the GPe (22 ± 10%). Extracellular glutamate levels largely remained unchanged. Pallidal microdialysis is a promising intraoperative monitoring tool to better understand pathophysiological implications in movement disorders and therapeutic mechanisms of high frequency stimulation. The increased inhibitory tone of GPi neurons and the subsequent thalamic inhibition could be one of the key mechanisms of GPi deep brain stimulation in dystonia. Such a mechanism may explain how competing (dystonic) movements can be suppressed in GPi/thalamic circuits in favour of desired motor programs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Integrin-linked kinase regulates cellular mechanics facilitating the motility in 3D extracellular matrices.

    Science.gov (United States)

    Kunschmann, Tom; Puder, Stefanie; Fischer, Tony; Perez, Jeremy; Wilharm, Nils; Mierke, Claudia Tanja

    2017-03-01

    The motility of cells plays an important role for many processes such as wound healing and malignant progression of cancer. The efficiency of cell motility is affected by the microenvironment. The connection between the cell and its microenvironment is facilitated by cell-matrix adhesion receptors and upon their activation focal adhesion proteins such as integrin-linked kinase (ILK) are recruited to sites of focal adhesion formation. In particular, ILK connects cell-matrix receptors to the actomyosin cytoskeleton. However, ILK's role in cell mechanics regulating cellular motility in 3D collagen matrices is still not well understood. We suggest that ILK facilitates 3D motility by regulating cellular mechanical properties such as stiffness and force transmission. Thus, ILK wild-type and knock-out cells are analyzed for their ability to migrate on 2D substrates serving as control and in dense 3D extracellular matrices. Indeed, ILK wild-type cells migrated faster on 2D substrates and migrated more numerous and deeper in 3D matrices. Hence, we analyzed cellular deformability, Young's modulus (stiffness) and adhesion forces. We found that ILK wild-type cells are less deformable (stiffer) and produce higher cell-matrix adhesion forces compared to ILK knock-out cells. Finally, ILK is essential for providing cellular mechanical stiffness regulating 3D motility. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. Radiation-induced genomic instability: Are epigenetic mechanisms the missing link?

    Energy Technology Data Exchange (ETDEWEB)

    Aypar, Umut; Morgan, William F.; Baulch, Janet E.

    2011-02-01

    Purpose: This review examines the evidence for the hypothesis that epigenetics are involved in the initiation and perpetuation of radiation-induced genomic instability (RIGI). Conclusion: In addition to the extensively studied targeted effects of radiation, it is now apparent that non-targeted delayed effects such as RIGI are also important post-irradiation outcomes. In RIGI, unirradiated progeny cells display phenotypic changes at delayed times after radiation of the parental cell. RIGI is thought to be important in the process of carcinogenesis, however, the mechanism by which this occurs remains to be elucidated. In the genomically unstable clones developed by Morgan and colleagues, radiation-induced mutations, double-strand breaks, or changes in mRNA levels alone could not account for the initiation or perpetuation of RIGI. Since changes in the DNA sequence could not fully explain the mechanism of RIGI, inherited epigenetic changes may be involved. Epigenetics are known to play an important role in many cellular processes and epigenetic aberrations can lead to carcinogenesis. Recent studies in the field of radiation biology suggest that the changes in methylation patterns may be involved in RIGI. Together these clues have led us to hypothesize that epigenetics may be the missing link in understanding the mechanism behind RIGI.

  18. Forever Young: Mechanisms of Natural Anoxia Tolerance and Potential Links to Longevity

    Directory of Open Access Journals (Sweden)

    Anastasia Krivoruchko

    2010-01-01

    Full Text Available While mammals cannot survive oxygen deprivation for more than a few minutes without sustaining severe organ damage, some animals have mastered anaerobic life. Freshwater turtles belonging to the Trachemys and Chrysemys genera are the champion facultative anaerobes of the vertebrate world, often surviving without oxygen for many weeks at a time. The physiological and biochemical mechanisms that underlie anoxia tolerance in turtles include profound metabolic rate depression, post-translational modification of proteins, strong antioxidant defenses, activation of specific stress-responsive transcription factors, and enhanced expression of cyto-protective proteins. Turtles are also known for their incredible longevity and display characteristics of “negligible senescence.” We propose that the robust stress-tolerance mechanisms that permit long term anaerobiosis by turtles may also support the longevity of these animals. Many of the mechanisms involved in natural anoxia tolerance, such as hypometabolism or the induction of various protective proteins/pathways, have been shown to play important roles in mammalian oxygen-related diseases and improved understanding of how cells survive without oxygen could aid in the understanding and treatment of various pathological conditions that involve hypoxia or oxidative stress. In the present review we discuss the recent advances made in understanding the molecular nature of anoxia tolerance in turtles and the potential links between this tolerance and longevity.

  19. Insights into the swelling process and drug release mechanisms from cross-linked pectin/high amylose starch matrices

    Directory of Open Access Journals (Sweden)

    Fernanda M. Carbinatto

    2014-02-01

    Full Text Available Cross-linked pectin/high amylose mixtures were evaluated as a new excipient for matrix tablets formulations, since the mixing of polymers and cross-linking reaction represent rational tools to reach materials with modulated and specific properties that meet specific therapeutic needs. Objective: In this work the influence of polymer ratio and cross-linking process on the swelling and the mechanism driving the drug release from swellable matrix tablets prepared with this excipient was investigated. Methods: Cross-linked samples were characterized by their micromeritic properties (size and shape, density, angle of repose and flow rate and liquid uptake ability. Matrix tablets were evaluated according their physical properties and the drug release rates and mechanisms were also investigated. Results: Cross-linked samples demonstrated size homogeneity and irregular shape, with liquid uptake ability insensible to pH. Cross-linking process of samples allowed the control of drug release rates and the drug release mechanism was influenced by both polymer ratio and cross-linking process. The drug release of samples with minor proportion of pectin was driven by an anomalous transport and the increase of the pectin proportion contributed to the erosion of the matrix. Conclusion: The cross-linked mixtures of high amylose and pectin showed a suitable excipient for slowing the drug release rates.

  20. Link between type 2 diabetes and Alzheimer's disease: from epidemiology to mechanism and treatment.

    Science.gov (United States)

    Li, Xiaohua; Song, Dalin; Leng, Sean X

    2015-01-01

    The aim of this paper is to provide a comprehensive review of the epidemiological evidence linking type 2 diabetes mellitus and its related conditions, including obesity, hyperinsulinemia, and metabolic syndrome, to Alzheimer's disease (AD). Several mechanisms could help to explain this proposed link; however, our focus is on insulin resistance and deficiency. Studies have shown that insulin resistance and deficiency can interact with amyloid-β protein and tau protein phosphorylation, each leading to the onset and development of AD. Based on those epidemiological data and basic research, it was recently proposed that AD can be considered as "type 3 diabetes". Special attention has been paid to determining whether antidiabetic agents might be effective in treating AD. There has been much research both experimental and clinical on this topic. We mainly discuss the clinical trials on insulin, metformin, thiazolidinediones, glucagon-like peptide-1 receptor agonists, and dipeptidyl peptidase-4 inhibitors in the treatment of AD. Although the results of these trials seem to be contradictory, this approach is also full of promise. It is worth mentioning that the therapeutic effects of these drugs are influenced by the apolipoprotein E (APOE)-ε4 genotype. Patients without the APOE-ε4 allele showed better treatment effects than those with this allele.

  1. Double strand break repair: two mechanisms in competition but tightly linked to cell cycle

    International Nuclear Information System (INIS)

    Delacote, F.

    2002-11-01

    DNA double strand breaks (DSB) are highly toxic damage although they can be induced to create genetic diversity. Two distinct pathways can repair DSB: Homologous Recombination (HR) and Non Homologous End Joining (NHEJ). If un- or mis-repaired, this damage can lead to cancer. Thus, it is essential to investigate how these two pathways are regulated for DSB repair. NHEJ inhibition leads to HR DSB repair stimulation. However, this channeling to HR is tightly linked to cell cycle since NHEJ and HR are active in G1/early S and late S/G2, respectively. Our results suggest that G1-unrepaired DSB go through S phase to be repaired by HR in G2. Those results allow a better understanding of DSB repair mechanisms regulation. (author)

  2. Mechanisms Underlying HIV-Associated Noninfectious Lung Disease.

    Science.gov (United States)

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

    2017-11-01

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

  3. [Neurophysiologic mechanisms of arterial hypertension under experimental chronic emotional stress].

    Science.gov (United States)

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

    1976-01-01

    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.

  4. Deciphering Molecular Mechanism Underlying Hypolipidemic Activity of Echinocystic Acid

    Directory of Open Access Journals (Sweden)

    Li Han

    2014-01-01

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

  5. Molecular mechanisms underlying phosphate sensing, signaling, and adaptation in plants.

    Science.gov (United States)

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

    2014-03-01

    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.

  6. Fatigue life prediction of mechanical structures under stochastic loading

    Directory of Open Access Journals (Sweden)

    Leitner Bohuš

    2018-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Marieke eJepma

    2012-02-01

    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.

  8. Spread of Epidemic on Complex Networks Under Voluntary Vaccination Mechanism

    Science.gov (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.

  9. Mechanisms underlying the antihypertensive effects of garlic bioactives.

    Science.gov (United States)

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

    2014-02-01

    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.

  10. NON-PRICE PROMOTION IMPACTS ON COTTON AND SOYBEANS EXPORTS UNDER EXCHANGE RATE LINKED SUBSIDIES

    OpenAIRE

    Paudel, Laxmi; Adhikari, Murali; Houston, Jack E.; Kinnucan, Henry W.

    2003-01-01

    Issue of exchange rate-linked subsidies for non-price export promotion has recently emerged as an area of interest among marketing researchers because of fluctuating strength of US dollars and position of US agricultural goods in export markets. One solution to mitigate these impacts was to link the federal export promotion subsidies with the changing value of US dollars. In the study, an equilibrium displacement framework was developed to analyze the effectiveness of exchange rate-linked sub...

  11. Potential mechanisms linking probiotics to diabetes: a narrative review of the literature

    Directory of Open Access Journals (Sweden)

    Maryam Miraghajani

    Full Text Available ABSTRACT CONTEXT AND OBJECTIVE: Some studies have suggested a wide range of possible mechanisms through which probiotics may play a role in diabetes prevention and treatment. However, the underlying mechanisms are not fully understood. We conducted this study to review the potential mechanisms suggested for the effect of probiotics in diabetes. DESIGN AND SETTING: Narrative review conducted at the Food Security Research Center of Isfahan. METHODS: A search in the electronic databases MEDLINE (PubMed, Cochrane Library, Web of Science and Google scholar was performed up to October 2016. RESULTS: The initial search yielded 1214 reports. After removing duplicates, 704 titles and abstracts were screened. Finally, out of 83 full-text articles that were reviewed for eligibility, 30 articles were included in the final analysis. The anti-diabetic mechanisms for probiotics reported encompass intraluminal and direct effects on the intestinal mucosa and microbiota (n = 13, anti-inflammatory and immunomodulatory effects (n = 10, antioxidative effects (n = 5, effects on endoplasmic reticulum (ER stress and expression of genes involved in glucose homeostasis and insulin resistance (n = 6, with some studies pointing to more than one mechanism. CONCLUSION: The results may throw some light on the capacity of probiotics as a novel approach towards controlling diabetes. However, further human studies are warranted to elucidate and confirm the potential role of probiotics in diabetes prevention and treatment. Also, it needs to be ascertained whether the effectiveness of probiotics in diabetes prevention and treatment is dependent on the strain of the microorganisms.

  12. Neuronal mechanisms underlying differences in spatial resolution between darks and lights in human vision.

    Science.gov (United States)

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

    2017-12-01

    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.

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

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

  15. Mechanisms underlying the antihypertensive properties of Urtica dioica.

    Science.gov (United States)

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

    2016-09-01

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

  16. Antioxidant Property of Jobelyn as the Possible Mechanism Underlying

    Directory of Open Access Journals (Sweden)

    Solomon Umukoro

    2013-01-01

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

  17. Bronchopulmonary dysplasia: understanding of the underlying pathological mechanisms

    Directory of Open Access Journals (Sweden)

    Daniela Fanni

    2014-06-01

    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

  18. Psychosocial Mechanisms Linking the Social Environment to Mental Health in African Americans.

    Science.gov (United States)

    Mama, Scherezade K; Li, Yisheng; Basen-Engquist, Karen; Lee, Rebecca E; Thompson, Deborah; Wetter, David W; Nguyen, Nga T; Reitzel, Lorraine R; McNeill, Lorna H

    2016-01-01

    Resource-poor social environments predict poor health, but the mechanisms and processes linking the social environment to psychological health and well-being remain unclear. This study explored psychosocial mediators of the association between the social environment and mental health in African American adults. African American men and women (n = 1467) completed questionnaires on the social environment, psychosocial factors (stress, depressive symptoms, and racial discrimination), and mental health. Multiple-mediator models were used to assess direct and indirect effects of the social environment on mental health. Low social status in the community (p social support (p social environment and mental health in multiple-mediator models. Low social status and social support were associated with greater perceived stress, depressive symptoms, and perceived racial discrimination, which were associated with poor mental health. Results suggest the relationship between the social environment and mental health is mediated by psychosocial factors and revealed potential mechanisms through which social status and social support influence the mental health of African American men and women. Findings from this study provide insight into the differential effects of stress, depression and discrimination on mental health. Ecological approaches that aim to improve the social environment and psychosocial mediators may enhance health-related quality of life and reduce health disparities in African Americans.

  19. Psychosocial Mechanisms Linking the Social Environment to Mental Health in African Americans.

    Directory of Open Access Journals (Sweden)

    Scherezade K Mama

    Full Text Available Resource-poor social environments predict poor health, but the mechanisms and processes linking the social environment to psychological health and well-being remain unclear. This study explored psychosocial mediators of the association between the social environment and mental health in African American adults. African American men and women (n = 1467 completed questionnaires on the social environment, psychosocial factors (stress, depressive symptoms, and racial discrimination, and mental health. Multiple-mediator models were used to assess direct and indirect effects of the social environment on mental health. Low social status in the community (p < .001 and U.S. (p < .001 and low social support (p < .001 were associated with poor mental health. Psychosocial factors significantly jointly mediated the relationship between the social environment and mental health in multiple-mediator models. Low social status and social support were associated with greater perceived stress, depressive symptoms, and perceived racial discrimination, which were associated with poor mental health. Results suggest the relationship between the social environment and mental health is mediated by psychosocial factors and revealed potential mechanisms through which social status and social support influence the mental health of African American men and women. Findings from this study provide insight into the differential effects of stress, depression and discrimination on mental health. Ecological approaches that aim to improve the social environment and psychosocial mediators may enhance health-related quality of life and reduce health disparities in African Americans.

  20. Alteration mechanisms of UOX spent fuel under water

    International Nuclear Information System (INIS)

    Muzeau, B.

    2008-06-01

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

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

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    Wouter A. A. de Steenhuijsen Piters

    2016-03-01

    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.

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

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    Sofia eSakellaridi

    2015-03-01

    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.

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

    Science.gov (United States)

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

    2015-02-01

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

  4. Dynamics and Fate of Beneficial Mutations Under Lineage Contamination by Linked Deleterious Mutations

    Science.gov (United States)

    Pénisson, Sophie; Singh, Tanya; Sniegowski, Paul

    2017-01-01

    Beneficial mutations drive adaptive evolution, yet their selective advantage does not ensure their fixation. Haldane’s application of single-type branching process theory showed that genetic drift alone could cause the extinction of newly arising beneficial mutations with high probability. With linkage, deleterious mutations will affect the dynamics of beneficial mutations and might further increase their extinction probability. Here, we model the lineage dynamics of a newly arising beneficial mutation as a multitype branching process. Our approach accounts for the combined effects of drift and the stochastic accumulation of linked deleterious mutations, which we call lineage contamination. We first study the lineage-contamination phenomenon in isolation, deriving dynamics and survival probabilities (the complement of extinction probabilities) of beneficial lineages. We find that survival probability is zero when U≳sb, where U is deleterious mutation rate and sb is the selective advantage of the beneficial mutation in question, and is otherwise depressed below classical predictions by a factor bounded from below by ∼1−U/sb. We then put the lineage contamination phenomenon into the context of an evolving population by incorporating the effects of background selection. We find that, under the combined effects of lineage contamination and background selection, ensemble survival probability is never zero but is depressed below classical predictions by a factor bounded from below by e−εU/s¯b, where s¯b is mean selective advantage of beneficial mutations, and ε=1−e−1≈0.63. This factor, and other bounds derived from it, are independent of the fitness effects of deleterious mutations. At high enough mutation rates, lineage contamination can depress fixation probabilities to values that approach zero. This fact suggests that high mutation rates can, perhaps paradoxically, (1) alleviate competition among beneficial mutations, or (2) potentially even shut

  5. Link between type 2 diabetes and Alzheimer’s disease: from epidemiology to mechanism and treatment

    Directory of Open Access Journals (Sweden)

    Li XH

    2015-03-01

    Full Text Available Xiaohua Li,1 Dalin Song,2 Sean X Leng31Dalian Medical University, Dalian, 2Department of Geriatrics, Qingdao Municipal Hospital, Qingdao, People’s Republic of China; 3Division of Geriatric Medicine and Gerontology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USAAbstract: The aim of this paper is to provide a comprehensive review of the epidemiological evidence linking type 2 diabetes mellitus and its related conditions, including obesity, hyperinsulinemia, and metabolic syndrome, to Alzheimer’s disease (AD. Several mechanisms could help to explain this proposed link; however, our focus is on insulin resistance and deficiency. Studies have shown that insulin resistance and deficiency can interact with amyloid-ß protein and tau protein phosphorylation, each leading to the onset and development of AD. Based on those epidemiological data and basic research, it was recently proposed that AD can be considered as “type 3 diabetes”. Special attention has been paid to determining whether antidiabetic agents might be effective in treating AD. There has been much research both experimental and clinical on this topic. We mainly discuss the clinical trials on insulin, metformin, thiazolidinediones, glucagon-like peptide-1 receptor agonists, and dipeptidyl peptidase-4 inhibitors in the treatment of AD. Although the results of these trials seem to be contradictory, this approach is also full of promise. It is worth mentioning that the therapeutic effects of these drugs are influenced by the apolipoprotein E (APOE-ε4 genotype. Patients without the APOE-ε4 allele showed better treatment effects than those with this allele.Keywords: type 2 diabetes mellitus, Alzheimer’s disease, insulinA Letter to Editor has been received and published for this article

  6. Efficient network disintegration under incomplete information: the comic effect of link prediction

    Science.gov (United States)

    Tan, Suo-Yi; Wu, Jun; Lü, Linyuan; Li, Meng-Jun; Lu, Xin

    2016-03-01

    The study of network disintegration has attracted much attention due to its wide applications, including suppressing the epidemic spreading, destabilizing terrorist network, preventing financial contagion, controlling the rumor diffusion and perturbing cancer networks. The crux of this matter is to find the critical nodes whose removal will lead to network collapse. This paper studies the disintegration of networks with incomplete link information. An effective method is proposed to find the critical nodes by the assistance of link prediction techniques. Extensive experiments in both synthetic and real networks suggest that, by using link prediction method to recover partial missing links in advance, the method can largely improve the network disintegration performance. Besides, to our surprise, we find that when the size of missing information is relatively small, our method even outperforms than the results based on complete information. We refer to this phenomenon as the “comic effect” of link prediction, which means that the network is reshaped through the addition of some links that identified by link prediction algorithms, and the reshaped network is like an exaggerated but characteristic comic of the original one, where the important parts are emphasized.

  7. Molecular Mechanics: The Method and Its Underlying Philosophy.

    Science.gov (United States)

    Boyd, Donald B.; Lipkowitz, Kenny B.

    1982-01-01

    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. Potential Mechanisms Underlying Centralized Pain and Emerging Therapeutic Interventions

    Directory of Open Access Journals (Sweden)

    Olivia C. Eller-Smith

    2018-02-01

    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

  9. [Study on main pharmacodynamics and underlying mechanisms of 999 Ganmaoling].

    Science.gov (United States)

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

    2016-04-01

    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. Mechanisms and pharmacogenetic signals underlying thiazide diuretics blood pressure response.

    Science.gov (United States)

    Shahin, Mohamed H; Johnson, Julie A

    2016-04-01

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

  11. Affect the Cross Linking Degree and Polymer Composition on the Mechanical Properties of Poly (vinyl alcohol/ Pullu-lan Films

    Directory of Open Access Journals (Sweden)

    Shemaa Abdul Satar Soud

    2018-04-01

    Full Text Available In this study Cross-linked PVA/Pullulan film was prepared. Cross-linking reaction done by addi-tion of gluteraldehyde at different reaction time (10,30and 60 min. Chemical interaction, me-chanical, thermal properties, water solubility and film morphology was studied for cross-linked PVA/Pullulan, PVA and Pullulan only. Thus FTIR investigated formation of hydrogen bonding between pullulan and PVA with (GA. Tensile strength, tensile modulus and elongation (% at break for PVA/Pullulan film was improved with addition of (GA as the reaction time proceed equivalent with increasing PVA content

  12. Mechanical response of collagen molecule under hydrostatic compression

    International Nuclear Information System (INIS)

    Saini, Karanvir; Kumar, Navin

    2015-01-01

    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.

  13. Revealing the Neural Mechanisms Underlying the Beneficial Effects of Tai Chi: A Neuroimaging Perspective.

    Science.gov (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

    2018-01-01

    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.

  14. Interactive evolution concept for analyzing a rock salt cavern under cyclic thermo-mechanical loading

    Science.gov (United States)

    König, Diethard; Mahmoudi, Elham; Khaledi, Kavan; von Blumenthal, Achim; Schanz, Tom

    2016-04-01

    The excess electricity produced by renewable energy sources available during off-peak periods of consumption can be used e.g. to produce and compress hydrogen or to compress air. Afterwards the pressurized gas is stored in the rock salt cavities. During this process, thermo-mechanical cyclic loading is applied to the rock salt surrounding the cavern. Compared to the operation of conventional storage caverns in rock salt the frequencies of filling and discharging cycles and therefore the thermo-mechanical loading cycles are much higher, e.g. daily or weekly compared to seasonally or yearly. The stress strain behavior of rock salt as well as the deformation behavior and the stability of caverns in rock salt under such loading conditions are unknown. To overcome this, existing experimental studies have to be supplemented by exploring the behavior of rock salt under combined thermo-mechanical cyclic loading. Existing constitutive relations have to be extended to cover degradation of rock salt under thermo-mechanical cyclic loading. At least the complex system of a cavern in rock salt under these loading conditions has to be analyzed by numerical modeling taking into account the uncertainties due to limited access in large depth to investigate material composition and properties. An interactive evolution concept is presented to link the different components of such a study - experimental modeling, constitutive modeling and numerical modeling. A triaxial experimental setup is designed to characterize the cyclic thermo-mechanical behavior of rock salt. The imposed boundary conditions in the experimental setup are assumed to be similar to the stress state obtained from a full-scale numerical simulation. The computational model relies primarily on the governing constitutive model for predicting the behavior of rock salt cavity. Hence, a sophisticated elasto-viscoplastic creep constitutive model is developed to take into account the dilatancy and damage progress, as well as

  15. Is mitochondrial dysfunction a driving mechanism linking COPD to nonsmall cell lung carcinoma?

    Directory of Open Access Journals (Sweden)

    Francois Ng Kee Kwong

    2017-10-01

    Full Text Available Chronic obstructive pulmonary disease (COPD patients are at increased risk of developing nonsmall cell lung carcinoma, irrespective of their smoking history. Although the mechanisms behind this observation are not clear, established drivers of carcinogenesis in COPD include oxidative stress and sustained chronic inflammation. Mitochondria are critical in these two processes and recent evidence links increased oxidative stress in COPD patients to mitochondrial damage. We therefore postulate that mitochondrial damage in COPD patients leads to increased oxidative stress and chronic inflammation, thereby increasing the risk of carcinogenesis. The functional state of the mitochondrion is dependent on the balance between its biogenesis and degradation (mitophagy. Dysfunctional mitochondria are a source of oxidative stress and inflammasome activation. In COPD, there is impaired translocation of the ubiquitin-related degradation molecule Parkin following activation of the Pink1 mitophagy pathway, resulting in excessive dysfunctional mitochondria. We hypothesise that deranged pathways in mitochondrial biogenesis and mitophagy in COPD can account for the increased risk in carcinogenesis. To test this hypothesis, animal models exposed to cigarette smoke and developing emphysema and lung cancer should be developed. In the future, the use of mitochondria-based antioxidants should be studied as an adjunct with the aim of reducing the risk of COPD-associated cancer.

  16. Supramolecular Cross-Links in Poly(alkyl methacrylate) Copolymers and Their Impact on the Mechanical and Reversible Adhesive Properties.

    Science.gov (United States)

    Heinzmann, Christian; Salz, Ulrich; Moszner, Norbert; Fiore, Gina L; Weder, Christoph

    2015-06-24

    Hydrogen-bonded, side-chain-functionalized supramolecular poly(alkyl methacrylate)s were investigated as light- and temperature-responsive reversible adhesives that are useful for bonding and debonding on demand applications. Here, 2-hydroxyethyl methacrylate (HEMA) was functionalized with 2-ureido-4[1H]pyrimidinone (UPy) via a hexamethylenediisocyanate (HMDI) linker, to create a monomer (UPy-HMDI-HEMA) that serves to form supramolecular cross-links by way of forming quadruple hydrogen bonded dimers. UPy-HMDI-HEMA was copolymerized with either hexyl methacrylate or butyl methacrylate to create copolymers comprising 2.5, 5, or 10 mol % of the cross-linker. The mechanical properties of all (co)polymers were investigated with stress-strain experiments and dynamic mechanical analysis. Furthermore, the adhesive properties were studied at temperatures between 20 and 60 °C by testing single lap joints formed with stainless steel substrates. It was found that increasing the concentration of the UPy-HMDI-HEMA cross-linker leads to improved mechanical and adhesive properties at elevated temperatures. Concurrently, the reversibility of the bond formation remained unaffected, where rebonded samples displayed the same adhesive strength as regularly bonded samples. Debonding on demand abilities were also tested exemplarily for one copolymer, which for light-induced debonding experiments was blended with a UV-absorber that served as light-heat converter. Single lap joints were subjected to a constant force and heated or irradiated with UV light until debonding occurred. The necessary debonding temperature was comparable for direct heating and UV irradiation and varied between 28 and 82 °C, depending on the applied force. The latter also influenced the debonding time, which under the chosen conditions ranged from 30 s to 12 min.

  17. Mechanical Characterization of Anion Exchange Membranes Under Controlled Environmental Conditions

    Science.gov (United States)

    2015-05-11

    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

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

    Directory of Open Access Journals (Sweden)

    А.М. Хімко

    2009-03-01

    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.

  19. Synthetic oligorotaxanes exert high forces when folding under mechanical load

    Science.gov (United States)

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

    2018-01-01

    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.

  20. Cyanobacterial crusts linked to soil productivity under different grazing management practices in Northern Australia

    Science.gov (United States)

    Alchin, Bruce; Williams, Wendy

    2015-04-01

    In arid and semi-arid Australia, the central role of healthy soil ecosystems in broad-acre grazing lands may be attributed to the widespread presence of cyanobacterial crusts. In terms of soil nutrient cycling and stability their role is particularly crucial in a climate dominated by annual dry seasons and variable wet seasons. In this study, we aimed to measure the contribution of cyanobacteria to soil nutrient cycling under contrasting levels of disturbance associated with grazing management. Field sampling was carried out on six paired sites (twelve properties) located across an east-west 3,000 km transect that covered different rangeland types on grazing properties in northern Australia (Queensland, Northern Territory and Western Australia). At each location paired sites were established and two different management systems were assessed, cell-paddock rotations (25-400 ha) and continuous grazing (200-2,000 ha). Cyanobacterial soil crusts were recorded from all of the twelve sites and cyanobacteria with the capacity to fix nitrogen were found at ten of the twelve sites. The overall diversity of cyanobacteria varied from three to ten species under any type of grazing system. As field work was conducted in the dry season, it is likely that the diversity may be greater in the wet season than the initial data may indicate. The average cyanobacterial soil crust cover across soil surfaces, between grass tussocks, during the dry season was estimated to be 50.9% and, 42.6% in the early wet season. This reflected longer established crust cover (dry season) versus newly established crusts. There was a high level of variability in the biomass of cyanobacteria however; the grazing system did not have any marked effect on the biomass for any one rangeland type. The grazing system differences did not appear to significantly influence the diversity at any location except on a floodplain in the Pilbara (WA). Biological nitrogen fixation by cyanobacteria was recorded at all

  1. Spatial distribution of water supply reliability and critical links of water supply to crucial water consumers under an earthquake

    International Nuclear Information System (INIS)

    Wang Yu; Au, S.-K.

    2009-01-01

    This paper describes a process to characterize spatial distribution of water supply reliability among various consumers in a water system and proposes methods to identify critical links of water supply to crucial water consumers under an earthquake. Probabilistic performance of water supply is reflected by the probability of satisfying consumers' water demand, Damage Consequence Index (DCI) and Upgrade Benefit Index (UBI). The process is illustrated using a hypothetical water supply system, where direct Monte Carlo simulation is used for estimating the performance indices. The reliability of water supply to consumers varies spatially, depending on their respective locations in the system and system configuration. The UBI is adopted as a primary index in the identification of critical links for crucial water consumers. A pipe with a relatively large damage probability is likely to have a relatively large UBI, and hence, to be a critical link. The concept of efficient frontier is employed to identify critical links of water supply to crucial water consumers. It is found that a group of links that have the largest UBI individually do not necessarily have the largest group UBI, or be the group of critical links

  2. Restorability on 3-connected WDM Networks Under Single and Dual Physical Link Failures

    DEFF Research Database (Denmark)

    Gutierrez Lopez, Jose Manuel; Jensen, Michael; Riaz, Tahir

    2013-01-01

    This work studies the influence the network interconnection has over restoration techniques. The way physical links are distributed to interconnect network nodes has a great impact on parameters such as path distances when failures occur and restoration is applied. The work focuses on single and ...... to network planning, the trade-off network length vs. performance of the different topological options is studied. The results show how 3-connected graphs could provide a reasonable trade-off between costs, link failure rates, and restored path parameters....

  3. Mechanism and kinetics of mineral weathering under acid conditions

    NARCIS (Netherlands)

    Anbeek, C.

    1994-01-01

    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

  4. Performance of multifilamentary Nb3Sn under mechanical load

    International Nuclear Information System (INIS)

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

    1976-01-01

    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

  5. Decentralized control mechanism underlying interlimb coordination of millipedes.

    Science.gov (United States)

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

    2017-04-04

    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.

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    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...

  7. Epigenetic mechanisms underlying the pathogenesis of neurogenetic diseases.

    Science.gov (United States)

    Qureshi, Irfan A; Mehler, Mark F

    2014-10-01

    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.

  8. Regulation of an Induction Motor under Broad Changes in DC-Link Voltage

    Czech Academy of Sciences Publication Activity Database

    Kokeš, Petr; Semerád, Radko

    2006-01-01

    Roč. 51, č. 4 (2006), s. 363-394 ISSN 0001-7043 Institutional research plan: CEZ:AV0Z20570509 Keywords : induction motor (IM) * DC-link voltage drop * stator flux vector control (SFVC) Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

  9. 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

    1997-01-01

    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

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

    NARCIS (Netherlands)

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

    2013-01-01

    People often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participants completed

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

    NARCIS (Netherlands)

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

    2013-01-01

    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).

  12. 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 ...

  13. 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...

  14. Evolution of antibiotic resistance is linked to any genetic mechanism affecting bacterial duration of carriage.

    Science.gov (United States)

    Lehtinen, Sonja; Blanquart, François; Croucher, Nicholas J; Turner, Paul; Lipsitch, Marc; Fraser, Christophe

    2017-01-31

    Understanding how changes in antibiotic consumption affect the prevalence of antibiotic resistance in bacterial pathogens is important for public health. In a number of bacterial species, including Streptococcus pneumoniae, the prevalence of resistance has remained relatively stable despite prolonged selection pressure from antibiotics. The evolutionary processes allowing the robust coexistence of antibiotic sensitive and resistant strains are not fully understood. While allelic diversity can be maintained at a locus by direct balancing selection, there is no evidence for such selection acting in the case of resistance. In this work, we propose a mechanism for maintaining coexistence at the resistance locus: linkage to a second locus that is under balancing selection and that modulates the fitness effect of resistance. We show that duration of carriage plays such a role, with long duration of carriage increasing the fitness advantage gained from resistance. We therefore predict that resistance will be more common in strains with a long duration of carriage and that mechanisms maintaining diversity in duration of carriage will also maintain diversity in antibiotic resistance. We test these predictions in S. pneumoniae and find that the duration of carriage of a serotype is indeed positively correlated with the prevalence of resistance in that serotype. These findings suggest heterogeneity in duration of carriage is a partial explanation for the coexistence of sensitive and resistant strains and that factors determining bacterial duration of carriage will also affect the prevalence of resistance.

  15. The missing link between sleep disorders and age-related dementia: recent evidence and plausible mechanisms.

    Science.gov (United States)

    Zhang, Feng; Zhong, Rujia; Li, Song; Chang, Raymond Chuen-Chung; Le, Weidong

    2017-05-01

    Sleep disorders are among the most common clinical problems and possess a significant concern for the geriatric population. More importantly, while around 40% of elderly adults have sleep-related complaints, sleep disorders are more frequently associated with co-morbidities including age-related neurodegenerative diseases and mild cognitive impairment. Recently, increasing evidence has indicated that disturbed sleep may not only serve as the consequence of brain atrophy, but also contribute to the pathogenesis of dementia and, therefore, significantly increase dementia risk. Since the current therapeutic interventions lack efficacies to prevent, delay or reverse the pathological progress of dementia, a better understanding of underlying mechanisms by which sleep disorders interact with the pathogenesis of dementia will provide possible targets for the prevention and treatment of dementia. In this review, we briefly describe the physiological roles of sleep in learning/memory, and specifically update the recent research evidence demonstrating the association between sleep disorders and dementia. Plausible mechanisms are further discussed. Moreover, we also evaluate the possibility of sleep therapy as a potential intervention for dementia.

  16. Underlying mechanisms of transient luminous events: a review

    Directory of Open Access Journals (Sweden)

    V. V. Surkov

    2012-08-01

    Full Text Available Transient luminous events (TLEs occasionally observed above a strong thunderstorm system have been the subject of a great deal of research during recent years. The main goal of this review is to introduce readers to recent theories of electrodynamics processes associated with TLEs. We examine the simplest versions of these theories in order to make their physics as transparent as possible. The study is begun with the conventional mechanism for air breakdown at stratospheric and mesospheric altitudes. An electron impact ionization and dissociative attachment to neutrals are discussed. A streamer size and mobility of electrons as a function of altitude in the atmosphere are estimated on the basis of similarity law. An alternative mechanism of air breakdown, runaway electron mechanism, is discussed. In this section we focus on a runaway breakdown field, characteristic length to increase avalanche of runaway electrons and on the role played by fast seed electrons in generation of the runaway breakdown. An effect of thunderclouds charge distribution on initiation of blue jets and gigantic jets is examined. A model in which the blue jet is treated as upward-propagating positive leader with a streamer zone/corona on the top is discussed. Sprite models based on streamer-like mechanism of air breakdown in the presence of atmospheric conductivity are reviewed. To analyze conditions for sprite generation, thunderstorm electric field arising just after positive cloud-to-ground stroke is compared with the thresholds for propagation of positively/negatively charged streamers and with runway breakdown. Our own estimate of tendril's length at the bottom of sprite is obtained to demonstrate that the runaway breakdown can trigger the streamer formation. In conclusion we discuss physical mechanisms of VLF (very low frequency and ELF (extremely low frequency phenomena associated with sprites.

  17. Mechanisms That Link Parenting Practices to Adolescents' Risky Sexual Behavior: A Test of Six Competing Theories.

    Science.gov (United States)

    Simons, Leslie Gordon; Sutton, Tara E; Simons, Ronald L; Gibbons, Frederick X; Murry, Velma McBride

    2016-02-01

    Risky sexual behavior, particularly among adolescents, continues to be a major source of concern. In order to develop effective education and prevention programs, there is a need for research that identifies the antecedents of such behavior. This study investigated the mediators that link parenting experiences during early adolescence to subsequent risky sexual behaviors among a diverse sample of African American youth (N = 629, 55 % female). While there is ample evidence that parenting practices (e.g., supportive parenting, harsh parenting, parental management) are antecedent to risky sexual behavior, few studies have examined whether one approach to parenting is more strongly related to risky sex than others. Using a developmental approach, the current study focused on factors associated with six theories of risky sexual behavior. While past research has provided support for all of the theories, few studies have assessed the relative contribution of each while controlling for the processes proposed by the others. The current study addresses these gaps in the literature and reports results separately by gender. Longitudinal analyses using structural equation modeling revealed that the mediating mechanisms associated with social learning and attachment theories were significantly related to the risky sexual behavior of males and females. Additionally, there was support for social control and self-control theories only for females and for life history theory only for males. We did not find support for problem behavior theory, a perspective that dominates the risky sex literature, after controlling for the factors associated with the other theories. Finally, supportive parenting emerged as the parenting behavior most influential with regard to adolescents' risky sexual behavior. These results provide insight regarding efficacious approaches to education and preventative programs designed to reduce risky sexual behaviors among adolescents.

  18. Mechanisms underlying social inequality in post-menopausal breast cancer.

    Science.gov (United States)

    Hvidtfeldt, Ulla Arthur

    2014-10-01

    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

  19. From Theory-Inspired to Theory-Based Interventions: A Protocol for Developing and Testing a Methodology for Linking Behaviour Change Techniques to Theoretical Mechanisms of Action.

    Science.gov (United States)

    Michie, Susan; Carey, Rachel N; Johnston, Marie; Rothman, Alexander J; de Bruin, Marijn; Kelly, Michael P; Connell, Lauren E

    2016-07-11

    Understanding links between behaviour change techniques (BCTs) and mechanisms of action (the processes through which they affect behaviour) helps inform the systematic development of behaviour change interventions. This research aims to develop and test a methodology for linking BCTs to their mechanisms of action. Study 1 (published explicit links): Hypothesised links between 93 BCTs (from the 93-item BCT taxonomy, BCTTv1) and mechanisms of action will be identified from published interventions and their frequency, explicitness and precision documented. Study 2 (expert-agreed explicit links): Behaviour change experts will identify links between 61 BCTs and 26 mechanisms of action in a formal consensus study. Study 3 (integrated matrix of explicit links): Agreement between studies 1 and 2 will be evaluated and a new group of experts will discuss discrepancies. An integrated matrix of BCT-mechanism of action links, annotated to indicate strength of evidence, will be generated. Study 4 (published implicit links): To determine whether groups of co-occurring BCTs can be linked to theories, we will identify groups of BCTs that are used together from the study 1 literature. A consensus exercise will be used to rate strength of links between groups of BCT and theories. A formal methodology for linking BCTs to their hypothesised mechanisms of action can contribute to the development and evaluation of behaviour change interventions. This research is a step towards developing a behaviour change 'ontology', specifying relations between BCTs, mechanisms of action, modes of delivery, populations, settings and types of behaviour.

  20. Compulsive Eating: The Emotional Link of Its Use as a Coping Mechanism for Resident Freshman Female College Students.

    Science.gov (United States)

    Beylerian, Nvair Kadian

    An 18-year old's freshman year in college is not only a test of his or her intellect, but also a test in social skills, adaptability to new living situations, and other conditions. This study examined the link of emotions to compulsive eating and its use as a coping mechanism for female college students. It explores the stresses of the transition…

  1. Mechanical response of human female breast skin under uniaxial stretching.

    Science.gov (United States)

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

    2017-10-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Mirre eStallen

    2013-03-01

    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.

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

    Science.gov (United States)

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

    2013-01-01

    People often conform to the behavior of others with whom they identify. However, it is unclear what fundamental mechanisms underlie this type of conformity. Here, we investigate the processes mediating in-group conformity by using functional magnetic resonance imaging (fMRI). Participants completed a perceptual decision-making task while undergoing fMRI, during which they were exposed to the judgments of both in-group and out-group members. Our data suggest that conformity to the in-group is mediated by both positive affect as well as the cognitive capacity of perspective taking. Examining the processes that drive in-group conformity by utilizing a basic decision-making paradigm combined with neuroimaging methods provides important insights into the potential mechanisms of conformity. These results may provide an integral step in developing more effective campaigns using group conformity as a tool for behavioral change.

  4. Molecular Mechanism Underlying Lymphatic Metastasis in Pancreatic Cancer

    Directory of Open Access Journals (Sweden)

    Zhiwen Xiao

    2014-01-01

    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.

  5. Mental imagery in music performance: underlying mechanisms and potential benefits.

    Science.gov (United States)

    Keller, Peter E

    2012-04-01

    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.

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

    NARCIS (Netherlands)

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

    2014-01-01

    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

  7. [Mechanisms underlying glucocorticoid resistance in chronic rhinosinusitis with nasal polyps].

    Science.gov (United States)

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

    2018-02-07

    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.

  8. The Survival Advantage: Underlying Mechanisms and Extant Limitations

    Directory of Open Access Journals (Sweden)

    Stephanie A. Kazanas

    2015-04-01

    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.

  9. Passive and active response of bacteria under mechanical compression

    Science.gov (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.

  10. Tendances Carbone no. 72 'EU ETS links to Australia: Lifted up from Down Under'

    International Nuclear Information System (INIS)

    Sartor, Oliver; Stephan, Nicolas

    2012-01-01

    Among the publications of CDC Climat Research, 'Tendances Carbone' bulletin specifically studies the developments of the European market for CO 2 allowances. This issue addresses the following points: On August 28 2012, the European Commission and the Australian Department for Climate Change announced that they will link their carbon markets. This link will take place in two stages: Australia will retain a fixed emission price of AU$ 23/tCO 2 ( euros 17.00) until 2015. Then, from July 1 2015 onwards, when the Australian Emission Trading Scheme (AETS) is introduced, EUAs will be eligible for Australian firms' domestic compliance, up to a usage limit of 50%. From 2018, the EU ETS facilities will become able to surrender Australian emissions allowances (AEUs) for their compliance purposes

  11. Bottom-up linking of carbon markets under far-sighted cap coordination and reversibility

    Science.gov (United States)

    Heitzig, Jobst; Kornek, Ulrike

    2018-02-01

    The Paris Agreement relies on nationally determined contributions to reach its targets and asks countries to increase ambitions over time, leaving open the details of this process. Although overcoming countries' myopic `free-riding' incentives requires cooperation, the global public good character of mitigation makes forming coalitions difficult. To cooperate, countries may link their carbon markets1, but is this option beneficial2? Some countries might not participate, not agree to lower caps, or not comply to agreements. While non-compliance might be deterred3, countries can hope that if they don't participate, others might still form a coalition. When considering only one coalition whose members can leave freely, the literature following the publication of refs 4,5 finds meagre prospects for effective collaboration6. Countries also face incentives to increase emissions when linking their markets without a cap agreement7,8. Here, we analyse the dynamics of market linkage using a game-theoretic model of far-sighted coalition formation. In contrast to non-dynamic models and dynamic models without far-sightedness9,10, in our model an efficient global coalition always forms eventually if players are sufficiently far-sighted or caps are coordinated immediately when markets are linked.

  12. Phosphorene under strain:electronic, mechanical and piezoelectric responses

    Science.gov (United States)

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

    2018-01-01

    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.

  13. Dissecting the signaling mechanisms underlying recognition and preference of food odors.

    Science.gov (United States)

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

    2014-07-09

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Jamdagni, Pooja, E-mail: j.poojaa1228@gmail.com; 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)

    2015-05-15

    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.

  15. 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

    2015-01-01

    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

  16. 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...

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

    Directory of Open Access Journals (Sweden)

    Ambrish Kumar

    2013-06-01

    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.

  18. Brainstem mechanisms underlying the cough reflex and its regulation.

    Science.gov (United States)

    Mutolo, Donatella

    2017-09-01

    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.

  19. On the Quantum Mechanical Wave Function as a Link Between Cognition and the Physical World A Role for Psychology

    CERN Document Server

    Snyder, D

    2002-01-01

    A straightforward explanation of fundamental tenets of quantum mechanics concerning the wave function results in the thesis that the quantum mechanical wave function is a link between human cognition and the physical world. The reticence on the part of physicists to adopt this thesis is discussed. A comparison is made to the behaviorists' consideration of mind, and the historical roots of how the problem concerning the quantum mechanical wave function arose are discussed. The basis for an empirical demonstration that the wave function is a link between human cognition and the physical world is provided through developing an experiment using methodology from psychology and physics. Based on research in psychology and physics that relied on this methodology, it is likely that Einstein, Podolsky, and Rosen's theoretical result that mutually exclusive wave functions can simultaneously apply to the same concrete physical circumstances can be implemented on an empirical level.

  20. Education and Liberalism: Pursuing the Link

    Science.gov (United States)

    Surridge, Paula

    2016-01-01

    This paper uses data from the 1970 Birth Cohort Study in the UK to explore the well-established link between "liberal" social values and education. Whilst the link itself is well-established, the underlying mechanism is not; the paper explores empirically mechanisms that have been proposed for this link. In particular it considers the…

  1. 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)

    2005-09-01

    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

  2. Parametric study of control mechanism of cortical bone remodeling under mechanical stimulus

    Science.gov (United States)

    Wang, Yanan; Qin, Qing-Hua

    2010-03-01

    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.

  3. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren

    2012-02-01

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

  4. Mechanisms underlying rapid aldosterone effects in the kidney.

    LENUS (Irish Health Repository)

    Thomas, Warren

    2011-03-17

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

  5. Molecular mechanisms underlying the development of hepatocellular carcinoma.

    Science.gov (United States)

    Bergsland, E K

    2001-10-01

    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.

  6. Neural mechanisms underlying neurooptometric rehabilitation following traumatic brain injury

    Directory of Open Access Journals (Sweden)

    Hudac CM

    2012-01-01

    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

  7. Mechanical characterization of stomach tissue under uniaxial tensile action.

    Science.gov (United States)

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

    2015-02-26

    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.

  8. Mechanisms underlying probucol-induced hERG-channel deficiency

    Directory of Open Access Journals (Sweden)

    Shi YQ

    2015-07-01

    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

  9. Glutaraldehyde Cross-Linking of TendonMechanical Effects at the Level of the Tendon Fascicle and Fibril

    DEFF Research Database (Denmark)

    Hansen, P.; Svensson, R.B.; Aagaard, P.

    2009-01-01

    were examined by atomic force microscopy. Peak forces increased from 1379 to 2622 pN while an extended Hertz fit of force-indentation data showed a 24 fold increase in Young's modulus on indentation. The effect of glutaraldehyde cross-linking on the tensile properties of a single collagen fibril...... was investigated by a novel methodology based on atomic force spectroscopy. The Young's modulus of a secluded fibril increased from 407 MPa to 1.1 GPa with glutaraldehyde treatment. Collectively, the findings indicate that cross-linking at the level of the collagen fibril is of key importance for the mechanical...

  10. Algorithmic mechanisms for reliable crowdsourcing computation under collusion.

    Science.gov (United States)

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

    2015-01-01

    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.

  11. 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.

    2015-01-01

    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

  12. Separable mechanisms underlying global feature-based attention.

    Science.gov (United States)

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

    2012-10-31

    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.

  13. Neural mechanisms underlying melodic perception and memory for pitch.

    Science.gov (United States)

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

    1994-04-01

    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.

  14. Epigenetic Mechanisms Underlying the Link between Non-Alcoholic Fatty Liver Diseases and Nutrition

    Directory of Open Access Journals (Sweden)

    Joo Ho Lee

    2014-08-01

    Full Text Available Non-alcoholic fatty liver disease (NAFLD is defined as a pathologic accumulation of fat in the form of triglycerides (TG in the liver (steatosis that is not caused by alcohol. A subgroup of NAFLD patients shows liver cell injury and inflammation coupled with the excessive fat accumulation (steatohepatitis, which is referred to as non-alcoholic steatohepatitis (NASH. Patients with NASH may develop cirrhosis and hepatocellular carcinoma (HCC. NAFLD shares the key features of metabolic syndrome including obesity, hyperlipidemia, hypertension, and insulin resistance. The pathogenesis of NAFLD is multi-factorial, however the oxidative stress seems to plays a major role in the development and progression of the disease. The emerging field of epigenetics provides a new perspective on the pathogenesis of NAFLD. Epigenetics is an inheritable but reversible phenomenon that affects gene expression without altering the DNA sequence and refers to DNA methylation, histone modifications and microRNAs. Epigenetic manipulation through metabolic pathways such as one-carbon metabolism has been proposed as a promising approach to retard the progression of NAFLD. Investigating the epigenetic modifiers in NAFLD may also lead to the development of preventive or therapeutic strategies for NASH-associated complications.

  15. Molecular Mechanisms Underlying the Link between Nuclear Receptor Function and Cholesterol Gallstone Formation

    Directory of Open Access Journals (Sweden)

    Mary Carmen Vázquez

    2012-01-01

    Full Text Available Cholesterol gallstone disease is highly prevalent in western countries, particularly in women and some specific ethnic groups. The formation of water-insoluble cholesterol crystals is due to a misbalance between the three major lipids present in the bile: cholesterol, bile salts, and phospholipids. Many proteins implicated in biliary lipid secretion in the liver are regulated by several transcription factors, including nuclear receptors LXR and FXR. Human and murine genetic, physiological, pathophysiological, and pharmacological evidence is consistent with the relevance of these nuclear receptors in gallstone formation. In addition, there is emerging data that also suggests a role for estrogen receptor ESR1 in abnormal cholesterol metabolism leading to gallstone disease. A better comprehension of the role of nuclear receptor function in gallstone formation may help to design new and more effective therapeutic strategies for this highly prevalent disease condition.

  16. Differential sulphur assimilation mechanism regulates response of Arabidopsis thaliana natural variation towards arsenic stress under limiting sulphur condition.

    Science.gov (United States)

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

    2017-09-05

    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.

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

    Directory of Open Access Journals (Sweden)

    Bednarik Martin

    2016-01-01

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

  18. Comparative analysis reveals the underlying mechanism of vertebrate seasonal reproduction.

    Science.gov (United States)

    Ikegami, Keisuke; Yoshimura, Takashi

    2016-02-01

    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.

  19. Mechanisms underlying the formation of induced pluripotent stem cells

    Science.gov (United States)

    González, Federico; Huangfu, Danwei

    2015-01-01

    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

  20. The neural sociometer: brain mechanisms underlying state self-esteem.

    Science.gov (United States)

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

    2011-11-01

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

    Science.gov (United States)

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

    2016-01-01

    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.

  2. Neural mechanisms underlying social conformity in an ultimatum game

    Directory of Open Access Journals (Sweden)

    Zhenyu eWei

    2013-12-01

    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.

  3. Adhesive wear mechanism under combined electric diamond grinding

    Directory of Open Access Journals (Sweden)

    Popov Vyacheslav

    2017-01-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Manal Fardoun

    2016-11-01

    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.

  5. Assessing mechanical vulnerability in water distribution networks under multiple failures

    Science.gov (United States)

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

    2014-03-01

    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.

  6. Postsynaptic mechanisms underlying the excitatory action of histamine on medial vestibular nucleus neurons in rats

    Science.gov (United States)

    Zhang, Xiao-Yang; Yu, Lei; Zhuang, Qian-Xing; Peng, Shi-Yu; Zhu, Jing-Ning; Wang, Jian-Jun

    2013-01-01

    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 http://dx.doi.org/10.1111/bph.2013.170.issue-1 PMID:23713466

  7. Neural mechanism underlying autobiographical memory modulated by remoteness and emotion

    Science.gov (United States)

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

    2012-03-01

    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.

  8. Molecular Mechanisms Underlying Origin and Diversification of the Angiosperm Flower

    Science.gov (United States)

    Theissen, Guenter; Melzer, Rainer

    2007-01-01

    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

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

    Directory of Open Access Journals (Sweden)

    Michele eBellesi

    2014-10-01

    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.

  10. Thin circular cylinder under axisymmetrical thermal and mechanical loading

    International Nuclear Information System (INIS)

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

    1977-01-01

    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

  11. Compression under a mechanical counter pressure space suit glove

    Science.gov (United States)

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

    2002-01-01

    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.

  12. On the Performance Analysis of Free-Space Optical Links under Generalized Turbulence and Misalignment Models

    KAUST Repository

    AlQuwaiee, Hessa

    2016-11-01

    One of the potential solutions to the radio frequency (RF) spectrum scarcity problem is optical wireless communications (OWC), which utilizes the unlicensed optical spectrum. Long-range outdoor OWC are usually referred to in the literature as free-space optical (FSO) communications. Unlike RF systems, FSO is immune to interference and multi-path fading. Also, the deployment of FSO systems is flexible and much faster than optical fibers. These attractive features make FSO applicable for broadband wireless transmission such as optical fiber backup, metropolitan area network, and last mile access. Although FSO communication is a promising technology, it is negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. These two critical issues have prompted intensive research in the last decade. To quantify the effect of these two factors on FSO system performance, we need effective mathematical models. In this work, we propose and study a generalized pointing error model based on the Beckmann distribution. Then, we aim to generalize the FSO channel model to span all turbulence conditions from weak to strong while taking pointing errors into consideration. Since scintillation in FSO is analogous to the fading phenomena in RF, diversity has been proposed too to overcome the effect of irradiance fluctuations. Thus, several combining techniques of not necessarily independent dual-branch free-space optical links were investigated over both weak and strong turbulence channels in the presence of pointing errors. On another front, improving the performance, enhancing the capacity and reducing the delay of the communication link has been the motivation of any newly developed schemes, especially for backhauling. Recently, there has been a growing interest in practical systems to integrate RF and FSO technologies to solve the last mile bottleneck. As such, we also study in this thesis asymmetric an RF-FSO dual-hop relay

  13. Neural mechanisms underlying cognitive inflexibility in Parkinson's disease.

    Science.gov (United States)

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

    2016-12-01

    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.

  14. Design principles and developmental mechanisms underlying retinal mosaics.

    Science.gov (United States)

    Reese, Benjamin E; Keeley, Patrick W

    2015-08-01

    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.

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

    Directory of Open Access Journals (Sweden)

    Bamberg-Lemper Simone

    2010-01-01

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yong, E-mail: ychen@hust.edu.cn [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: zongpingw@hust.edu.cn [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)

    2013-05-15

    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.

  17. Neurite, a finite difference large scale parallel program for the simulation of electrical signal propagation in neurites under mechanical loading.

    Directory of Open Access Journals (Sweden)

    Julián A García-Grajales

    Full Text Available With the growing body of research on traumatic brain injury and spinal cord injury, computational neuroscience has recently focused its modeling efforts on neuronal functional deficits following mechanical loading. However, in most of these efforts, cell damage is generally only characterized by purely mechanistic criteria, functions of quantities such as stress, strain or their corresponding rates. The modeling of functional deficits in neurites as a consequence of macroscopic mechanical insults has been rarely explored. In particular, a quantitative mechanically based model of electrophysiological impairment in neuronal cells, Neurite, has only very recently been proposed. In this paper, we present the implementation details of this model: a finite difference parallel program for simulating electrical signal propagation along neurites under mechanical loading. Following the application of a macroscopic strain at a given strain rate produced by a mechanical insult, Neurite is able to simulate the resulting neuronal electrical signal propagation, and thus the corresponding functional deficits. The simulation of the coupled mechanical and electrophysiological behaviors requires computational expensive calculations that increase in complexity as the network of the simulated cells grows. The solvers implemented in Neurite--explicit and implicit--were therefore parallelized using graphics processing units in order to reduce the burden of the simulation costs of large scale scenarios. Cable Theory and Hodgkin-Huxley models were implemented to account for the electrophysiological passive and active regions of a neurite, respectively, whereas a coupled mechanical model accounting for the neurite mechanical behavior within its surrounding medium was adopted as a link between electrophysiology and mechanics. This paper provides the details of the parallel implementation of Neurite, along with three different application examples: a long myelinated axon

  18. Adaptive simultaneous motion and vibration control for a multi flexible-link mechanism with uncertain general harmonic disturbance

    Science.gov (United States)

    Wang, Ji; Pi, Yangjun; Hu, Yumei; Zhu, Zhencai; Zeng, Lingbin

    2017-11-01

    In this paper, a new motion and vibration synthesized control system-a linear quadratic regulator/strain rate feedback controller (LQR/SRF) with adaptive disturbance attenuation is presented for a multi flexible-link mechanism subjected to uncertain harmonic disturbances with arbitrary frequencies and unknown magnitudes. In the proposed controller, nodal strain rates are introduced into the model of the multi flexible-link mechanism, based upon which a synthesized LQR controller where both rigid-body motion and elastic deformation are considered is designed. The uncertain harmonic disturbances would be canceled in the feedback loop by its approximated value which is computed online via an adaptive update law. Asymptotic stability of the closed-loop system is proved by the Lyapunov analysis. The effectiveness of the proposed controller is shown via simulation.

  19. Temporal links to performing under pressure in international soccer penalty shootouts

    NARCIS (Netherlands)

    Jordet, Geir; Hartman, Esther; Sigmundstad, Einar

    2009-01-01

    Objectives: This study examined the temporal characteristics of performing under pressure in a high-stakes real-world sport situation. Design: Behavior observation analyses were conducted of televised soccer games. Methods: Videos were obtained from all penalty shootouts ever held in three major

  20. Measurement of fog and haze extinction characteristics and availability evaluation of free space optical link under the sea surface environment.

    Science.gov (United States)

    Wu, Xiaojun; Wang, Hongxing; Song, Bo

    2015-02-10

    Fog and haze can lead to changes in extinction characteristics. Therefore, the performance of the free space optical link is highly influenced by severe weather conditions. Considering the influential behavior of weather conditions, a state-of-the-art solution for the observation of fog and haze over the sea surface is presented in this paper. A Mie scattering laser radar, with a wavelength of 532 nm, is used to observe the weather conditions of the sea surface environment. The horizontal extinction coefficients and visibilities are obtained from the observation data, and the results are presented in the paper. The changes in the characteristics of extinction coefficients and visibilities are analyzed based on both the short-term (6 days) severe weather data and long-term (6 months) data. Finally, the availability performance of the free space optical communication link is evaluated under the sea surface environment.

  1. Vehicle lateral motion regulation under unreliable communication links based on robust H∞ output-feedback control schema

    Science.gov (United States)

    Li, Cong; Jing, Hui; Wang, Rongrong; Chen, Nan

    2018-05-01

    This paper presents a robust control schema for vehicle lateral motion regulation under unreliable communication links via controller area network (CAN). The communication links between the system plant and the controller are assumed to be imperfect and therefore the data packet dropouts occur frequently. The paper takes the form of parallel distributed compensation and treats the dropouts as random binary numbers that form Bernoulli distribution. Both of the tire cornering stiffness uncertainty and external disturbances are considered to enhance the robustness of the controller. In addition, a robust H∞ static output-feedback control approach is proposed to realize the lateral motion control with relative low cost sensors. The stochastic stability of the closed-loop system and conservation of the guaranteed H∞ performance are investigated. Simulation results based on CarSim platform using a high-fidelity and full-car model verify the effectiveness of the proposed control approach.

  2. Thermogelling and chemoselectively cross-linked hydrogels with controlled mechanical properties and degradation behavior

    NARCIS (Netherlands)

    Boere, Kristel W M; Van Den Dikkenberg, Joep; Gao, Yuan; Visser, Jetze; Hennink, Wim E.; Vermonden, Tina

    2015-01-01

    Chemoselectively cross-linked hydrogels have recently gained increasing attention for the development of novel, injectable biomaterials given their limited side reactions. In this study, we compared the properties of hydrogels obtained by native chemical ligation (NCL) and its recently described

  3. Children's Attentional Biases and "5-HTTLPR" Genotype: Potential Mechanisms Linking Mother and Child Depression

    Science.gov (United States)

    Gibb, Brandon E.; Benas, Jessica S.; Grassia, Marie; McGeary, John

    2009-01-01

    In this study, we examined the roles of specific cognitive (attentional bias) and genetic ("5-HTTLPR") risk factors in the intergenerational transmission of depression. Focusing first on the link between maternal history of major depressive disorder (MDD) and children's attentional biases, we found that children of mothers with a history…

  4. Compassionate love as a mechanism linking sacred qualities of marriage to older couples' marital satisfaction.

    Science.gov (United States)

    Sabey, Allen K; Rauer, Amy J; Jensen, Jakob F

    2014-10-01

    Previous work has underscored the robust links between sanctification of marriage and marital outcomes, and recent developments in the literature suggest that compassionate love, which is important for intimate relationships, may act as a mediator of that relationship. Accordingly, the current study used actor-partner interdependence models to examine the relationship between a spiritual cognition (i.e., perceived sacred qualities of marriage) and marital satisfaction, and to determine whether that relationship is mediated by compassionate love, in a sample of older married couples (N = 64). Results revealed that wives' greater sacred qualities of marriage were significantly and positively linked to marital satisfaction on the part of both spouses, and that these links were partially mediated by couples' reports of compassionate love. These findings highlight the importance of moving beyond simply establishing the existence of the link between global markers of involvement of religion and marriage to understanding how specific spiritual cognitions may foster better relationship quality, especially among older couples. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  5. The Link between the Appendix and Ulcerative Colitis: Clinical Relevance and Potential Immunological Mechanisms

    NARCIS (Netherlands)

    Sahami, S.; Kooij, I. A.; Meijer, S. L.; van den Brink, G. R.; Buskens, C. J.; te Velde, A. A.

    2016-01-01

    The human appendix has long been considered as a vestigial organ, an organ that has lost its function during evolution. In recent years, however, reports have emerged that link the appendix to numerous immunological functions in humans. Evidence has been presented for an important role of the

  6. Inflammatory mechanisms linking periodontal diseases to cardiovascular diseases (also published in Journal of Periodontology 2013 Apr 84 (4 Suppl): S51-69)

    NARCIS (Netherlands)

    Schenkein, H.A.; Loos, B.G.

    2013-01-01

    Aims In this article, inflammatory mechanisms that link periodontal diseases to cardiovascular diseases are reviewed. Methods This article is a literature review. Results Studies in the literature implicate a number of possible mechanisms that could be responsible for increased inflammatory

  7. Neurocognitive Mechanisms Underlying Value-Based Decision-Making: From Core Values to Economic Value

    Directory of Open Access Journals (Sweden)

    Tobias eBrosch

    2013-07-01

    Full Text Available Value plays a central role in practically every aspect of human life that requires a decision: whether we choose between different consumer goods, whether we decide which person we marry or which political candidate gets our vote, we choose the option that has more value to us. Over the last decade, neuroeconomic research has mapped the neural substrates of economic value, revealing that activation in brain regions such as ventromedial prefrontal cortex (VMPFC, ventral striatum or posterior cingulate cortex reflects how much an individual values an option and which of several options he/she will choose. However, while great progress has been made exploring the mechanisms underlying concrete decisions, neuroeconomic research has been less concerned with the questions of why people value what they value, and why different people value different things. Social psychologists and sociologists have long been interested in core values, motivational constructs that are intrinsically linked to the self-schema and are used to guide actions and decisions across different situations and different time points. Core value may thus be an important determinant of individual differences in economic value computation and decision-making. Based on a review of recent neuroimaging studies investigating the neural representation of core values and their interactions with neural systems representing economic value, we outline a common framework that integrates the core value concept and neuroeconomic research on value-based decision-making.

  8. Neurocognitive mechanisms underlying value-based decision-making: from core values to economic value

    Science.gov (United States)

    Brosch, Tobias; Sander, David

    2013-01-01

    Value plays a central role in practically every aspect of human life that requires a decision: whether we choose between different consumer goods, whether we decide which person we marry or which political candidate gets our vote, we choose the option that has more value to us. Over the last decade, neuroeconomic research has mapped the neural substrates of economic value, revealing that activation in brain regions such as ventromedial prefrontal cortex (VMPFC), ventral striatum or posterior cingulate cortex reflects how much an individual values an option and which of several options he/she will choose. However, while great progress has been made exploring the mechanisms underlying concrete decisions, neuroeconomic research has been less concerned with the questions of why people value what they value, and why different people value different things. Social psychologists and sociologists have long been interested in core values, motivational constructs that are intrinsically linked to the self-schema and are used to guide actions and decisions across different situations and different time points. Core value may thus be an important determinant of individual differences in economic value computation and decision-making. Based on a review of recent neuroimaging studies investigating the neural representation of core values and their interactions with neural systems representing economic value, we outline a common framework that integrates the core value concept and neuroeconomic research on value-based decision-making. PMID:23898252

  9. Exome sequencing and network analysis identifies shared mechanisms underlying spinocerebellar ataxia.

    Science.gov (United States)

    Nibbeling, Esther A R; Duarri, Anna; Verschuuren-Bemelmans, Corien C; Fokkens, Michiel R; Karjalainen, Juha M; Smeets, Cleo J L M; de Boer-Bergsma, Jelkje J; van der Vries, Gerben; Dooijes, Dennis; Bampi, Giovana B; van Diemen, Cleo; Brunt, Ewout; Ippel, Elly; Kremer, Berry; Vlak, Monique; Adir, Noam; Wijmenga, Cisca; van de Warrenburg, Bart P C; Franke, Lude; Sinke, Richard J; Verbeek, Dineke S

    2017-11-01

    The autosomal dominant cerebellar ataxias, referred to as spinocerebellar ataxias in genetic nomenclature, are a rare group of progressive neurodegenerative disorders characterized by loss of balance and coordination. Despite the identification of numerous disease genes, a substantial number of cases still remain without a genetic diagnosis. Here, we report five novel spinocerebellar ataxia genes, FAT2, PLD3, KIF26B, EP300, and FAT1, identified through a combination of exome sequencing in genetically undiagnosed families and targeted resequencing of exome candidates in a cohort of singletons. We validated almost all genes genetically, assessed damaging effects of the gene variants in cell models and further consolidated a role for several of these genes in the aetiology of spinocerebellar ataxia through network analysis. Our work links spinocerebellar ataxia to alterations in synaptic transmission and transcription regulation, and identifies these as the main shared mechanisms underlying the genetically diverse spinocerebellar ataxia types. © The Author (2017). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  10. Improving arithmetic performance with number sense training: an investigation of underlying mechanism.

    Science.gov (United States)

    Park, Joonkoo; Brannon, Elizabeth M

    2014-10-01

    A nonverbal primitive number sense allows approximate estimation and mental manipulations on numerical quantities without the use of numerical symbols. In a recent randomized controlled intervention study in adults, we demonstrated that repeated training on a non-symbolic approximate arithmetic task resulted in improved exact symbolic arithmetic performance, suggesting a causal relationship between the primitive number sense and arithmetic competence. Here, we investigate the potential mechanisms underlying this causal relationship. We constructed multiple training conditions designed to isolate distinct cognitive components of the approximate arithmetic task. We then assessed the effectiveness of these training conditions in improving exact symbolic arithmetic in adults. We found that training on approximate arithmetic, but not on numerical comparison, numerical matching, or visuo-spatial short-term memory, improves symbolic arithmetic performance. In addition, a second experiment revealed that our approximate arithmetic task does not require verbal encoding of number, ruling out an alternative explanation that participants use exact symbolic strategies during approximate arithmetic training. Based on these results, we propose that nonverbal numerical quantity manipulation is one key factor that drives the link between the primitive number sense and symbolic arithmetic competence. Future work should investigate whether training young children on approximate arithmetic tasks even before they solidify their symbolic number understanding is fruitful for improving readiness for math education. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. Exploring the link between cognitive abilities and speech recognition in the elderly under different listening conditions

    DEFF Research Database (Denmark)

    Nuesse, Theresa; Steenken, Rike; Neher, Tobias

    2018-01-01

    , and it has been suggested that differences in cognitive abilities may also be important. The objective of this study was to investigate associations between performance in cognitive tasks and speech recognition under different listening conditions in older adults with either age appropriate hearing...... or hearing-impairment. To that end, speech recognition threshold (SRT) measurements were performed under several masking conditions that varied along the perceptual dimensions of dip listening, spatial separation, and informational masking. In addition, a neuropsychological test battery was administered....... In repeated linear regression analyses, composite scores of cognitive test outcomes (evaluated using PCA) were included to predict SRTs. These associations were different for the two groups. When hearing thresholds were controlled for, composed cognitive factors were significantly associated with the SRTs...

  12. Dynamic behavior of dual cross-linked nanoparticle networks under oscillatory shear

    International Nuclear Information System (INIS)

    Iyer, Balaji V S; Yashin, Victor V; Balazs, Anna C

    2014-01-01

    Via computer simulations, we investigate the linear and nonlinear viscoelastic response of polymer grafted nanoparticle networks subject to oscillatory shear at different amplitudes and frequencies. The individual nanoparticles are composed of a rigid spherical core and a corona of grafted polymers that encompass reactive end groups. With the overlap of the coronas on adjacent particles, the reactive end groups form permanent or labile bonds, and thus form a ‘dual cross-linked’ network. The existing labile bonds between particles can break and reform depending on the bond rupture rate, extent of deformation and the frequency of oscillation. We study how the viscoelastic behavior of the material depends on the energy of the labile bonds and identify the network characteristics that give rise to the observed viscoelastic response. We observe that with an increase in labile bond energy, the storage modulus increases while the loss modulus shows a more complex response depending on the labile bond energy. Specifically, in the case of the samples with the weaker labile bonds, the loss modulus increases monotonically, while for the samples with the stronger labile bonds, the loss modulus exhibits a minimum with an increase in frequency. We show that an increase in the storage modulus corresponds to an enhancement in the average number of bonds in the samples and the characteristics of the loss modulus depend on both the bond kinetics and the mobility of the particles in the network. Furthermore, we determine that the effective contribution of the bonds to the storage modulus decreases with increase in strain amplitude. In particular, while bond formation at small amplitude drives an increase in storage modulus, at large amplitudes it promotes clustering and formation of voids leading to strain softening. Our simulations provide a mesoscopic picture of how the nature of labile bonds affects the performance of cross-linked polymer-grafted nanoparticle networks. (paper)

  13. Role of the placenta in fetal programming: underlying mechanisms and potential interventional approaches.

    Science.gov (United States)

    Jansson, Thomas; Powell, Theresa L

    2007-07-01

    Adverse influences during fetal life alter the structure and function of distinct cells, organ systems or homoeostatic pathways, thereby 'programming' the individual for an increased risk of developing cardiovascular disease and diabetes in adult life. Fetal programming can be caused by a number of different perturbations in the maternal compartment, such as altered maternal nutrition and reduced utero-placental blood flow; however, the underlying mechanisms remain to be fully established. Perturbations in the maternal environment must be transmitted across the placenta in order to affect the fetus. Here, we review recent insights into how the placenta responds to changes in the maternal environment and discuss possible mechanisms by which the placenta mediates fetal programming. In IUGR (intrauterine growth restriction) pregnancies, the increased placental vascular resistance subjects the fetal heart to increased work load, representing a possible direct link between altered placental structure and fetal programming of cardiovascular disease. A decreased activity of placental 11beta-HSD-2 (type 2 isoform of 11beta-hydroxysteroid dehydrogenase) activity can increase fetal exposure to maternal cortisol, which programmes the fetus for later hypertension and metabolic disease. The placenta appears to function as a nutrient sensor regulating nutrient transport according to the ability of the maternal supply line to deliver nutrients. By directly regulating fetal nutrient supply and fetal growth, the placenta plays a central role in fetal programming. Furthermore, perturbations in the maternal compartment may affect the methylation status of placental genes and increase placental oxidative/nitrative stress, resulting in changes in placental function. Intervention strategies targeting the placenta in order to prevent or alleviate altered fetal growth and/or fetal programming include altering placental growth and nutrient transport by maternally administered IGFs (insulin

  14. Identifying mechanisms that underlie links between COMT genotype and aggression in male adolescents with ADHD

    OpenAIRE

    van Goozen, Stephanie H.M.; Langley, Kate; Northover, Clare; Hubble, Kelly; Rubia, Katya; Schepman, Karen; O'Donovan, Michael C.; Thapar, Anita

    2015-01-01

    © 2015 Association for Child and Adolescent Mental Health. Background: There is a known strong genetic contribution to aggression in those with ADHD. In a previous investigation of a large population cohort, impaired 'emotional/social cognitive' processing, assessed by questionnaire, was observed to mediate the link between COMT Val158Met and aggression in individuals with ADHD. We set out to replicate and extend this finding in a clinical sample, using task-based and physiological assessment...

  15. Link between type 2 diabetes and Alzheimer’s disease: from epidemiology to mechanism and treatment

    OpenAIRE

    Li XH; Song DL; Leng SX

    2015-01-01

    Xiaohua Li,1 Dalin Song,2 Sean X Leng31Dalian Medical University, Dalian, 2Department of Geriatrics, Qingdao Municipal Hospital, Qingdao, People’s Republic of China; 3Division of Geriatric Medicine and Gerontology, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USAAbstract: The aim of this paper is to provide a comprehensive review of the epidemiological evidence linking type 2 diabetes mellitus and its related conditions, including obesity, hype...

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

    Directory of Open Access Journals (Sweden)

    Durand Camille

    2014-06-01

    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.

  17. Linking sea level rise and socioeconomic indicators under the Shared Socioeconomic Pathways

    Science.gov (United States)

    Nauels, Alexander; Rogelj, Joeri; Schleussner, Carl-Friedrich; Meinshausen, Malte; Mengel, Matthias

    2017-11-01

    In order to assess future sea level rise and its societal impacts, we need to study climate change pathways combined with different scenarios of socioeconomic development. Here, we present sea level rise (SLR) projections for the Shared Socioeconomic Pathway (SSP) storylines and different year-2100 radiative forcing targets (FTs). Future SLR is estimated with a comprehensive SLR emulator that accounts for Antarctic rapid discharge from hydrofracturing and ice cliff instability. Across all baseline scenario realizations (no dedicated climate mitigation), we find 2100 median SLR relative to 1986-2005 of 89 cm (likely range: 57-130 cm) for SSP1, 105 cm (73-150 cm) for SSP2, 105 cm (75-147 cm) for SSP3, 93 cm (63-133 cm) for SSP4, and 132 cm (95-189 cm) for SSP5. The 2100 sea level responses for combined SSP-FT scenarios are dominated by the mitigation targets and yield median estimates of 52 cm (34-75 cm) for FT 2.6 Wm-2, 62 cm (40-96 cm) for FT 3.4 Wm-2, 75 cm (47-113 cm) for FT 4.5 Wm-2, and 91 cm (61-132 cm) for FT 6.0 Wm-2. Average 2081-2100 annual SLR rates are 5 mm yr-1 and 19 mm yr-1 for FT 2.6 Wm-2 and the baseline scenarios, respectively. Our model setup allows linking scenario-specific emission and socioeconomic indicators to projected SLR. We find that 2100 median SSP SLR projections could be limited to around 50 cm if 2050 cumulative CO2 emissions since pre-industrial stay below 850 GtC, with a global coal phase-out nearly completed by that time. For SSP mitigation scenarios, a 2050 carbon price of 100 US2005 tCO2 -1 would correspond to a median 2100 SLR of around 65 cm. Our results confirm that rapid and early emission reductions are essential for limiting 2100 SLR.

  18. On the capacity of multiple cognitive links through common relay under spectrum-sharing constraints

    KAUST Repository

    Yang, Yuli

    2011-06-01

    In this paper, we consider an underlay cognitive relaying network consisting of multiple secondary users and introduce a cooperative transmission protocol using a common relay to help with the communications between all secondary source-destination pairs for higher throughput and lower realization complexity. A whole relay-assisted transmission procedure is composed of multiple access phase and broadcast phase, where the relay is equipped with multiple antennas, and the secondary sources and destinations are single-antenna nodes. Considering the spectrum-sharing constraints on the secondary sources and the relay, we analyze the capacity behaviors of the underlay cognitive relaying network under study. The corresponding numerical results provide a convenient tool for the presented network design and substantiate a distinguishing feature of introduced design in that multiple secondary users\\' communications do not rely on multiple relays, hence allowing for a more efficient use of the radio resources. © 2011 IEEE.

  19. Exploring the genetics underlying autoimmune diseases with network analysis and link prediction

    KAUST Repository

    Alanis Lobato, Gregorio

    2014-02-01

    Ever since the first Genome Wide Association Study (GWAS) was carried out we have seen an important number of discoveries of biological and clinical relevance. However, there are some scientists that consider that these research outcomes and their utility are far from what was expected from this experimental design. We instead believe that the thousands of genetic variants associated with complex disorders by means of GWASs are an extremely valuable source of information that needs to be mined in a different way. Based on this philosophy, we followed a holistic perspective to analyze GWAS data and explored the structural properties of the network representation of one of these datasets with the aim to advance our understanding of the genetic intricacies underlying autoimmune human diseases. The simplicity, computational efficiency and precision of the tools proposed in this paper represent a new means to address GWAS data and contribute to the better exploitation of these rich sources of information. © 2014 IEEE.

  20. An NFC on Two-Coil WPT Link for Implantable Biomedical Sensors under Ultra-Weak Coupling

    Directory of Open Access Journals (Sweden)

    Chen Gong

    2017-06-01

    Full Text Available The inductive link is widely used in implantable biomedical sensor systems to achieve near-field communication (NFC and wireless power transfer (WPT. However, it is tough to achieve reliable NFC on an inductive WPT link when the coupling coefficient is ultra-low (0.01 typically, since the NFC signal (especially for the uplink from the in-body part to the out-body part could be too weak to be detected. Traditional load shift keying (LSK requires strong coupling to pass the load modulation information to the power source. Instead of using LSK, we propose a dual-carrier NFC scheme for the weak-coupled inductive link; using binary phase shift keying (BPSK modulation, its downlink data are modulated on the power carrier (2 MHz, while its uplink data are modulated on another carrier (125 kHz. The two carriers are transferred through the same coil pair. To overcome the strong interference of the power carrier, dedicated circuits are introduced. In addition, to minimize the power transfer efficiency decrease caused by adding NFC, we optimize the inductive link circuit parameters and approach the receiver sensitivity limit. In the prototype experiments, even though the coupling coefficient is as low as 0.008, the in-body transmitter costs only 0.61 mW power carrying 10 kbps of data, and achieves a 1 × 10 - 7 bit error rate under the strong interference of WPT. This dual-carrier NFC scheme could be useful for small-sized implantable biomedical sensor applications.

  1. Cross-linking mechanisms of arginine and lysine with α,β-dicarbonyl compounds in aqueous solution.

    Science.gov (United States)

    Nasiri, Rasoul; Field, Martin J; Zahedi, Mansour; Moosavi-Movahedi, Ali Akbar

    2011-11-24

    Cross-linking in proteins by α,β-dicarbonyl compounds is one of the most damaging consequences of reactive carbonyl species in vivo and in foodstuffs. In this article we investigate computationally the cross-linking of glyoxal and methylglyoxal with lysine and arginine residues using density functional theory and the wB97XD dispersion-corrected functional. Five pathways, A-E, have been characterized. In pathways A and B, the reaction proceeds via formation of the Schiff base, aldimine, followed by addition of arginine. In contrast, in pathways C-E, direct addition of arginine to the dicarbonyl compounds occurs first, leading to a dihydroxyimidazolidine intermediate, which then reacts with lysine after dehydration and proton transfer reactions. The results reveal that pathways A, C, and E are competitive whereas reactions via pathways B and D are much less favorable. Inclusion of up to five explicit water molecules in the proton transfer and dehydration steps is found to lower the energy barriers in the feasible pathways by about 5-20 kcal/mol. Comparison of the mechanisms of methylglyoxal-derived imidazolium cross-linking (MODIC) and glyoxal-derived imidazolium cross-linking (GODIC) shows that the activation barriers are lower for GODIC than MODIC, in agreement with experimental observations.

  2. Processes and conditions underlying the link between shyness and school adjustment among Turkish children.

    Science.gov (United States)

    Bayram Özdemir, Sevgi; Cheah, Charissa S L; Coplan, Robert J

    2017-06-01

    This study examined the underlying processes and conditions that contribute to the school adjustment of shy children in Turkey, where children's interpersonal relationships in social settings and academic achievement are highly emphasized. First, we examined the unique mediating roles of children's feelings of social anxiety, depressive symptoms, and loneliness in the associations between shyness and indices of school outcomes (academic achievement and school liking/avoidance). Second, we explored the moderating role of children's peer acceptance in these associations. Fourth- and fifth-grade children (N = 599; M age  = 10.11 years, SD = 0.65; 48% girls) provided information on shyness, social anxiety, depressive symptoms, loneliness, and school liking/avoidance. Head teachers in each classroom reported on students' academic performance. The peer nomination method was used to assess children's peer relationships. Results revealed that when children displayed shy behaviours, they reported more depressive symptoms that were, in turn, associated with poorer academic performance, less school liking, and higher school avoidance. Moreover, shyness negatively predicted school liking at low levels of peer acceptance, suggesting that difficulties in peer relationships increased shy children's risk of school dissatisfaction. Overall, our findings support the importance of the interpersonal relationship context for children's adjustment within the Turkish cultural context. Statement of contribution What is already known on this subject? Shy children have difficulties initiating and maintaining social interactions, which put them at risk for a wide range of socio-emotional difficulties. Shy children have poor academic performance and experience school adjustment difficulties in North America. What does this study add? Shyness is an important risk factor for poorer academic performance and adjustment among children in Turkey. The association between shyness and

  3. Microstructural evolutions of zirconium alloys under irradiation. Link with the irradiation growth phenomenon

    International Nuclear Information System (INIS)

    Simonot, C.

    1995-01-01

    This study deals with the irradiation-induced growth and microstructural evolutions of Zircaloy-4 type materials (ZrSn 1.2-1.7 Fe 0.18-0.24 Cr 0.07-0.13 O 0.09-0.15 ), used as cladding and guide-tubes in PWR's fuel assemblies. The main objective was to obtain a better understanding of the growth acceleration which may occur at high doses for the recrystallized metallurgical state. The elongation values of stress-free tubes irradiated at 400 deg in experimental reactors give clear indication of accelerated growth after a critical dose. Microstructural investigations reveal some large basal plane dislocation loops with vacancy character, which is an unexpected defect configuration for an hexagonal material with a c/a ratio less than the ideal value. In addition, a significant redistribution of iron and chromium solute elements comes from the dissolution of the initial Zr(Fe,Cr) 2 phases. In a guide-tube irradiated to high dose at 320 deg in a power reactor, a large density of these c-component loops was also observed in coincidence with a large iron re-solution due to the progressive partial amorphization of Laves phases. By contrast, as long as a negligible amount of iron is available in the matrix (start of progressive amorphization at 350 deg or complete amorphization without any chemical change at 280 deg, only prism plane loops with interstitial and vacancy character are observed and the steady-state growth rate is low. A mechanism taking into account the Diffusional Anisotropy Difference of the radiation induced point defects seems to be the most suitable to explain the correlations between microstructural evolutions and growth rates. However it does not allow to predict the dose necessary for the formation of the basal plane loops responsible for the growth acceleration. Several factors (dose, temperature, metallurgical state) are required and the iron re-solution is likely to play a major role to stabilize such defects, by a decrease in stacking fault energy

  4. Postmenopausal osteoporosis in rheumatoid arthritis: The estrogen deficiency-immune mechanisms link.

    Science.gov (United States)

    Sapir-Koren, Rony; Livshits, Gregory

    2017-10-01

    Rheumatoid arthritis (RA) is characterized, among other factors, by systemic bone loss, reaching ~50% prevalence of osteoporosis in postmenopausal women. This is roughly a doubled prevalence in comparison with age-matched non-RA women. Postmenopausal RA women are more likely to be sero-positive for the anti-citrullinated peptide antibody (ACPA). Our extensive review of recent scientific literature enabled us to propose several mechanisms as responsible for the accelerated bone loss in ACPA(+) RA postmenopausal women. Menopause-associated estrogen deficiency plays a major role in these pathological mechanisms, as follows. Copyright © 2017 Elsevier Inc. All rights reserved.

  5. 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.

    2011-01-01

    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

  6. Essential Features of Serious Games Design in Higher Education: Linking Learning Attributes to Game Mechanics

    Science.gov (United States)

    Lameras, Petros; Arnab, Sylvester; Dunwell, Ian; Stewart, Craig; Clarke, Samantha; Petridis, Panagiotis

    2017-01-01

    This paper consolidates evidence and material from a range of specialist and disciplinary fields to provide an evidence-based review and synthesis on the design and use of serious games in higher education. Search terms identified 165 papers reporting conceptual and empirical evidence on how learning attributes and game mechanics may be planned,…

  7. 3D mechanical stratigraphy of a deformed multi-layer: Linking sedimentary architecture and strain partitioning

    Science.gov (United States)

    Cawood, Adam J.; Bond, Clare E.

    2018-01-01

    Stratigraphic influence on structural style and strain distribution in deformed sedimentary sequences is well established, in models of 2D mechanical stratigraphy. In this study we attempt to refine existing models of stratigraphic-structure interaction by examining outcrop scale 3D variations in sedimentary architecture and the effects on subsequent deformation. At Monkstone Point, Pembrokeshire, SW Wales, digital mapping and virtual scanline data from a high resolution virtual outcrop have been combined with field observations, sedimentary logs and thin section analysis. Results show that significant variation in strain partitioning is controlled by changes, at a scale of tens of metres, in sedimentary architecture within Upper Carboniferous fluvio-deltaic deposits. Coupled vs uncoupled deformation of the sequence is defined by the composition and lateral continuity of mechanical units and unit interfaces. Where the sedimentary sequence is characterized by gradational changes in composition and grain size, we find that deformation structures are best characterized by patterns of distributed strain. In contrast, distinct compositional changes vertically and in laterally equivalent deposits results in highly partitioned deformation and strain. The mechanical stratigraphy of the study area is inherently 3D in nature, due to lateral and vertical compositional variability. Consideration should be given to 3D variations in mechanical stratigraphy, such as those outlined here, when predicting subsurface deformation in multi-layers.

  8. The Weakest Link : Spatial Variability in the Piping Failure Mechanism of Dikes

    NARCIS (Netherlands)

    Kanning, W.

    2012-01-01

    Piping is an important failure mechanism of flood defense structures. A dike fails due to piping when a head difference causes first the uplift of an inland blanket layer, and subsequently soil erosion due to a ground water flow. Spatial variability of subsoil parameters causes the probability of

  9. From Fragmented Knowledge to a Knowledge Structure: Linking the Domains of Mechanics and Electromagnetism.

    Science.gov (United States)

    Bagno, Esther; Eylon, Bat-Sheva; Ganiel, Uri

    2000-01-01

    Describes the MAOF physics education program which is designed to relate large parts of mechanics and electromagnetism to each other via the key concepts of field and potential, while at the same time treat students' conceptual difficulties. Finds that students who studied with the MAOF program significantly improved their physics knowledge…

  10. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling

    NARCIS (Netherlands)

    Pera, H.; Kleijn, J.M.; Leermakers, F.A.M.

    2014-01-01

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus k c and k ¯ and

  11. Linking susceptibility genes and pathogenesis mechanisms using mouse models of systemic lupus erythematosus

    Directory of Open Access Journals (Sweden)

    Steve P. Crampton

    2014-09-01

    Full Text Available Systemic lupus erythematosus (SLE represents a challenging autoimmune disease from a clinical perspective because of its varied forms of presentation. Although broad-spectrum steroids remain the standard treatment for SLE, they have many side effects and only provide temporary relief from the symptoms of the disease. Thus, gaining a deeper understanding of the genetic traits and biological pathways that confer susceptibility to SLE will help in the design of more targeted and effective therapeutics. Both human genome-wide association studies (GWAS and investigations using a variety of mouse models of SLE have been valuable for the identification of the genes and pathways involved in pathogenesis. In this Review, we link human susceptibility genes for SLE with biological pathways characterized in mouse models of lupus, and discuss how the mechanistic insights gained could advance drug discovery for the disease.

  12. Linking susceptibility genes and pathogenesis mechanisms using mouse models of systemic lupus erythematosus

    Science.gov (United States)

    Crampton, Steve P.; Morawski, Peter A.; Bolland, Silvia

    2014-01-01

    Systemic lupus erythematosus (SLE) represents a challenging autoimmune disease from a clinical perspective because of its varied forms of presentation. Although broad-spectrum steroids remain the standard treatment for SLE, they have many side effects and only provide temporary relief from the symptoms of the disease. Thus, gaining a deeper understanding of the genetic traits and biological pathways that confer susceptibility to SLE will help in the design of more targeted and effective therapeutics. Both human genome-wide association studies (GWAS) and investigations using a variety of mouse models of SLE have been valuable for the identification of the genes and pathways involved in pathogenesis. In this Review, we link human susceptibility genes for SLE with biological pathways characterized in mouse models of lupus, and discuss how the mechanistic insights gained could advance drug discovery for the disease. PMID:25147296

  13. Diversification and germ-line determination revisited: Linking developmental mechanism with species richness

    Directory of Open Access Journals (Sweden)

    Brian I Crother

    2016-03-01

    Full Text Available Abstract.– Background: Explanations for asymmetric patterns of diversification continue to challenge paleontologists and neontologists with competing hypotheses within genetic-development and ecological frameworks. In 1988, a hypothesis was proposed that tied a primordial germ cell (PGC determination mechanism to clade (phyla diversification. Two general mechanisms for PGC determination are recognized: one is termed induced because induction signals are required for the production of primordial germ cells. The other mechanism is cell-autonomous, i.e. determinative, because the cells that develop in response to specific cytoplasmic determinants in the oocyte are pre-destined to become PGCs. We revisited the hypothesis and analyzed phyla diversity with germ cell determination mechanisms and examined sister clade asymmetry.Results: After 25 years of additional data accumulation, the hypothesis that high levels of species diversification are associated with the induced mode is falsified, with the determinative mode revealed as associated with higher rates of diversification. The greater species numbers are significantly associated (ANOVA p>0.003 with the determinative mode. Analysis with appropriate sister clades is unanimous in showing the clade with the determinative mode has a significantly greater number of species relative to its induced sister clade .Conclusions: The primordial germ cell determination mechanism hypothesis explains asymmetrical species diversity and morphological disparity at the phylum level. We argue that the determinative mode of primordial germ cell determination is a constraint release that has enhanced evolvability and increased rates of speciation and morphological disparity among clades. Knowledge of the mechanism for extant theropods allows speculation that its sister clade, the Sauropodomorpha would have exhibited the induced mode.Results: After 25 years of additional data accumulation, the hypothesis that high

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

    International Nuclear Information System (INIS)

    Wang, L.

    2012-01-01

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

  15. Microbial Mechanisms Underlying Acidity-induced Reduction in Soil Respiration Under Nitrogen Fertilization

    Science.gov (United States)

    Niu, S.; Li, Y.

    2016-12-01

    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

  16. 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

  17. STATIC AND DYNAMIC ANALYSIS UNDER MECHANICAL AND THERMAL LOADS OF THE DOUBLE SCARA ROBOT

    Directory of Open Access Journals (Sweden)

    Iosif TEMPEA

    2016-05-01

    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.

  18. The effects of different size gold nanoparticles on mechanical properties of vascular smooth muscle cells under mechanical stretching

    Science.gov (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.

  19. REVIEWMolecular mechanisms underlying physiological and receptor pleiotropic effects mediated by GLP-1R activation

    Science.gov (United States)

    Pabreja, K; Mohd, M A; Koole, C; Wootten, D; Furness, S G B

    2014-01-01

    The incidence of type 2 diabetes in developed countries is increasing yearly with a significant negative impact on patient quality of life and an enormous burden on the healthcare system. Current biguanide and thiazolidinedione treatments for type 2 diabetes have a number of clinical limitations, the most serious long-term limitation being the eventual need for insulin replacement therapy (Table 1). Since 2007, drugs targeting the glucagon-like peptide-1 (GLP-1) receptor have been marketed for the treatment of type 2 diabetes. These drugs have enjoyed a great deal of success even though our underlying understanding of the mechanisms for their pleiotropic effects remain poorly characterized even while major pharmaceutical companies actively pursue small molecule alternatives. Coupling of the GLP-1 receptor to more than one signalling pathway (pleiotropic signalling) can result in ligand-dependent signalling bias and for a peptide receptor such as the GLP-1 receptor this can be exaggerated with the use of small molecule agonists. Better consideration of receptor signalling pleiotropy will be necessary for future drug development. This is particularly important given the recent failure of taspoglutide, the report of increased risk of pancreatitis associated with GLP-1 mimetics and the observed clinical differences between liraglutide, exenatide and the newly developed long-acting exenatide long acting release, albiglutide and dulaglutide. Linked ArticlesThis article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-5 PMID:23889512

  20. A dual analysis for recycled particulate composites: linking micro- and macro-mechanics

    International Nuclear Information System (INIS)

    Avila, Antonio F.; Rodrigues, Paulo C.M.; Santos, Dagoberto B.; Faria, Ana C.A.

    2003-01-01

    The large amount of disposable bottles produced nowadays makes imperative the search for alternative procedures for recycling them since they are not biodegradable. This paper takes into consideration the thermomechanical recycling of post-consumed plastic bottles, especially the ones made of polyethylene terephthalate (PET) and high-density polyethylene (HDPE), and their use as composite materials for engineering applications. As changes on the composite's microstructure can have an influence on macroscopic behavior, a new type of analysis is needed. To be able to evaluate the composite performance, a dual analysis procedure was developed. It consists of a micro-mechanical analysis where the microstructure is observed by optical microscopy, and variations in morphology are related to composite overall mechanical behavior. The macro-mechanical analysis is performed by ASTM D 3039/3039 M tensile tests. By doing this, the composite effective moduli can be determined. The new composite seems to be encouraging, i.e., an HDPE/PET composite with 40:60 ratio, in weight, experiments a stiffness recovery from the third to the fourth recycle. Moreover, the dual analysis was able to capture this variation

  1. The link between bond forfeiture and pretrial release mechanism: The case of Dallas County, Texas.

    Science.gov (United States)

    Clipper, Stephen J; Morris, Robert G; Russell-Kaplan, Amanda

    2017-01-01

    The goal of this study was to evaluate the efficacy of four pretrial jail release mechanisms (i.e., bond types) commonly used during the pretrial phase of the criminal justice process in terms of their ability to discriminate between defendants failing to appear in court (i.e., bond forfeiture). These include attorney bonds, cash bonds, commercial bail bonds, and release via a pretrial services agency. A multi-treatment propensity score matching protocol was employed to assess between-release-mechanism differences in the conditional probability of failure to appear/bond forfeiture. Data were culled from archival state justice records comprising all defendants booked into the Dallas County, Texas jail during 2008 (n = 29,416). The results suggest that defendants released via commercial bail bonds were less likely to experience failure to appear leading to the bond forfeiture process compared to equivalent defendants released via cash, attorney, and pretrial services bonds. This finding held across different offense categories. The study frames these differences within a discussion encompassing procedural variation within and between each release mechanism, thereby setting the stage for further research and dialog regarding potential justice reform.

  2. The link between bond forfeiture and pretrial release mechanism: The case of Dallas County, Texas.

    Directory of Open Access Journals (Sweden)

    Stephen J Clipper

    Full Text Available The goal of this study was to evaluate the efficacy of four pretrial jail release mechanisms (i.e., bond types commonly used during the pretrial phase of the criminal justice process in terms of their ability to discriminate between defendants failing to appear in court (i.e., bond forfeiture. These include attorney bonds, cash bonds, commercial bail bonds, and release via a pretrial services agency.A multi-treatment propensity score matching protocol was employed to assess between-release-mechanism differences in the conditional probability of failure to appear/bond forfeiture. Data were culled from archival state justice records comprising all defendants booked into the Dallas County, Texas jail during 2008 (n = 29,416.The results suggest that defendants released via commercial bail bonds were less likely to experience failure to appear leading to the bond forfeiture process compared to equivalent defendants released via cash, attorney, and pretrial services bonds. This finding held across different offense categories. The study frames these differences within a discussion encompassing procedural variation within and between each release mechanism, thereby setting the stage for further research and dialog regarding potential justice reform.

  3. Links between Gestures and Multisensory Processing: Individual Differences Suggest a Compensation Mechanism

    Directory of Open Access Journals (Sweden)

    Simon B. Schmalenbach

    2017-10-01

    Full Text Available Speech-associated gestures represent an important communication modality. However, individual differences in the production and perception of gestures are not well understood so far. We hypothesized that the perception of multisensory action consequences might play a crucial role. Verbal communication involves continuous calibration of audio–visual information produced by the speakers. The effective production and perception of gestures supporting this process could depend on the given capacities to perceive multisensory information accurately. We explored the association between the production and perception of gestures and the monitoring of multisensory action consequences in a sample of 31 participants. We applied a recently introduced gesture scale to assess self-reported gesture production and perception in everyday life situations. In the perceptual experiment, we presented unimodal (visual and bimodal (visual and auditory sensory outcomes with various delays after a self-initiated (active or externally generated (passive button press. Participants had to report whether they detected a delay between the button press and the visual stimulus. We derived psychometric functions for each condition and determined points of subjective equality, reflecting detection thresholds for delays. Results support a robust link between gesture scores and detection thresholds. Individuals with higher detection thresholds (lower performance reported more frequent gesture production and perception and furthermore profited more from multisensory information in the experimental task. We propose that our findings indicate a compensational function of multisensory processing as a basis for individual differences in both action outcome monitoring and gesture production and perception in everyday life situations.

  4. The Link between the Appendix and Ulcerative Colitis: Clinical Relevance and Potential Immunological Mechanisms.

    Science.gov (United States)

    Sahami, S; Kooij, I A; Meijer, S L; Van den Brink, G R; Buskens, C J; Te Velde, A A

    2016-02-01

    The human appendix has long been considered as a vestigial organ, an organ that has lost its function during evolution. In recent years, however, reports have emerged that link the appendix to numerous immunological functions in humans. Evidence has been presented for an important role of the appendix in maintaining intestinal health. This theory suggests that the appendix may be a reservoir or 'safe house' from which the commensal gut flora can rapidly be reestablished if it is eradicated from the colon. However, the appendix may also have a role in the development of inflammatory bowel disease (IBD). Several large epidemiological cohort studies have demonstrated the preventive effect of appendectomy on the development of ulcerative colitis, a finding that has been confirmed in murine colitis models. In addition, current studies are examining the possible therapeutic effect of an appendectomy to modulate disease course in patients with ulcerative colitis. This literature review assesses the current knowledge about the clinical and immunological aspects of the vermiform appendix in IBD and suggests that the idea of the appendix as a vestigial remnant should be discarded.

  5. Biobased chitosan/polybenzoxazine cross-linked films: preparation in aqueous media and synergistic improvements in thermal and mechanical properties.

    Science.gov (United States)

    Alhwaige, Almahdi A; Agag, Tarek; Ishida, Hatsuo; Qutubuddin, Syed

    2013-06-10

    A novel class of polymer blends has been prepared from main-chain-type benzoxazine polymer (MCBP) and chitosan (CTS), a modified biomacromolecule. A water-soluble, main-chain-type benzoxazine polymer, MCBP(BA-tepa), was synthesized from the reaction of bisphenol A (BA), tetraethylenepentamine (TEPA) and formalin. The structure of the MCBP(BA-tepa) was confirmed by proton nuclear magnetic resonance spectroscopy ((1)H NMR) and Fourier transform infrared spectroscopy (FT-IR). The polymer blends were prepared by mixing MCBP(BA-tepa) and CTS in aqueous acetic acid solution (1%). The CTS/MCBP(BA-tepa) films are cross-linked by thermal treatment via the ring-opening polymerization of benzoxazine structures in the main chain to produce an AB-cross-linked network. Differential scanning calorimetry (DSC) and FT-IR were used to study the effects of CTS on the polymerization behavior of benzoxazine. Hydrogen bonding between polybenzoxazine and CTS structures was also observed. The mechanical and thermal properties of cross-linked CTS/MCBP(BA-tepa) films were evaluated, and the results showed unusual levels of synergism. In particular, the tensile strength and thermal stability were significantly enhanced in a nonlinear fashion.

  6. Psychological mechanism linking abusive supervision and compulsory citizenship behavior: a moderated mediation study.

    Science.gov (United States)

    Zhao, Hongdan; Peng, Zhenglong; Han, Yong; Sheard, Geoff; Hudson, Alan

    2013-01-01

    This study seeks to examine the effect of abusive supervision on the "dark side" of organizational citizenship behavior (OCB) and, specifically, compulsory citizenship behavior (CCB). The study focuses on the mediating role of psychological safety underpinning the relationship between abusive supervision and CCB, and the moderating role of Chinese traditionality in influencing the mediation. The authors tested the model with data of 434 dyads (employee-coworker pairs) in a large Chinese service company. Results indicated that psychological safety fully mediated the relationship between abusive supervision and CCB. The authors also found that Chinese traditionality moderated the strength of the mediated relationship between abusive supervision and CCB via psychological safety, such that the mediated relationship is weaker under high Chinese traditionality than under low Chinese traditionality. The article also discusses the implications, limitations, and future research directions.

  7. Linking nanoscale mechanical behavior to bulk physical properties and phenomena of energetic materials

    Science.gov (United States)

    Taw, Matthew R.

    The hardness and reduced modulus of aspirin, RDX, HMX, TATB, FOX-7, ADAAF, and TNT/CL-20 were experimentally measured with nanoindentation. These values are reported for the first time using as-received micron sized crystals of energetic materials with no additional mechanical processing. The results for TATB, ADAAF, and TNT/CL-20 are the first of their kind, while comparisons to previous nanoindentation studies on large, carefully grown single crystals of the other energetic materials show that mechanical properties of the larger crystals are comparable to crystals in the condition they are practically used. Measurements on aspirin demonstrate the variation that can occur between nanoindentation indents based on the orientation of a Berkovich tip relative to the surface of the sample. The Hertzian elastic contact model was used to analyze the materials initial yield, or pop-in, behavior. The length, energy, indentation load, and shear stress at initial yielding were used to characterize each material. For the energetic materials the length and energy of the yield excursions were compared to the drop weight sensitivity. This comparison revealed a general trend that more impact sensitive materials have longer, more severe pop-in excursions. Hot spot initiation mechanisms involving crystal defects such as void collapses and dislocation pile-up followed by avalanche are supported by these trends. While this only takes one aspect of impact sensitivity into consideration, if this trend is observed in a larger range of energetics these methods could possibly be used to great advantage in the early stages of new explosives synthesis to obtain an estimation of drop weight sensitivity.

  8. Links between dissipation and Rényi divergences in PT -symmetric quantum mechanics

    Science.gov (United States)

    Wei, Bo-Bo

    2018-01-01

    Thermodynamics and information theory have been intimately related since the times of Maxwell and Boltzmann. Recently it was shown that the dissipated work in an arbitrary nonequilibrium process is related to the Rényi divergences between two states along the forward and reversed dynamics. Here we show that the relation between dissipated work and Renyi divergences generalizes to PT -symmetric quantum mechanics with unbroken PT symmetry. In the regime of broken PT symmetry, the relation between dissipated work and Renyi divergences does not hold as the norm is not preserved during the dynamics. This finding is illustrated for an experimentally relevant system of two-coupled cavities.

  9. Comparison of mechanical and thermodynamic properties of fcc and bcc titanium under high pressure

    Science.gov (United States)

    Zhang, Yongmei; Zhao, Yuhong; Hou, Hua; Wen, Zhiqin; Duan, Meiling

    2018-02-01

    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.

  10. Linking the mechanics and energetics of hopping with elastic ankle exoskeletons.

    Science.gov (United States)

    Farris, Dominic James; Sawicki, Gregory S

    2012-12-15

    The springlike mechanics of the human leg during bouncing gaits has inspired the design of passive assistive devices that use springs to aid locomotion. The purpose of this study was to test whether a passive spring-loaded ankle exoskeleton could reduce the mechanical and energetic demands of bilateral hopping on the musculoskeletal system. Joint level kinematics and kinetics were collected with electromyographic and metabolic energy consumption data for seven participants hopping at four frequencies (2.2, 2.5, 2.8, and 3.2 Hz). Hopping was performed without an exoskeleton; with an springless exoskeleton; and with a spring-loaded exoskeleton. Spring-loaded ankle exoskeletons reduced plantar flexor muscle activity and the biological contribution to ankle joint moment (15-25%) and average positive power (20-40%). They also facilitated reductions in metabolic power (15-20%) across frequencies from 2.2 to 2.8 Hz compared with hopping with a springless exoskeleton. Reductions in metabolic power compared with hopping with no exoskeleton were restricted to hopping at 2.5 Hz only (12%). These results highlighted the importance of reducing the rate of muscular force production and work to achieve metabolic reductions. They also highlighted the importance of assisting muscles acting at the knee joint. Exoskeleton designs may need to be tuned to optimize exoskeleton mass, spring stiffness, and spring slack length to achieve greater metabolic reductions.

  11. Intermediate strain rate behaviour of cancellous bone: Links between microstructural and mechanical properties

    Directory of Open Access Journals (Sweden)

    Prot Marianne

    2015-01-01

    Full Text Available Relationships between the micro-architecture description of cancellous bone, obtained from medical imaging, and its mechanical properties can be used to assess the compression fracture risk at high and low strain rate. This study extends the rupture prediction to the intermediate strain rate regime. The micro-architecture description was obtained with a CT-scan, for which geometry, topology, connectivity and anisotropy parameters were computed and compared to mechanical identified parameters in order to confirm their usefulness. Three strain rates were investigated: 1/s, 10/s and 100/s using two different devices: a Wedge-Bar apparatus and a conventional split Hopkinson pressure bar implemented with a Cone-in-Tube striker and a tandem momentum trap. This setup provides a constant strain rate loading with routine specimen recovery allowing the fracture zone to be investigated. This study reveals that a transition in the response behaviour occurred in the intermediate regime and confirms the significant porous organization influence through the regimes.

  12. Moist Orographic Convection: Physical Mechanisms and Links to Surface-Exchange Processes

    Directory of Open Access Journals (Sweden)

    Daniel J. Kirshbaum

    2018-02-01

    Full Text Available This paper reviews the current understanding of moist orographic convection and its regulation by surface-exchange processes. Such convection tends to develop when and where moist instability coincides with sufficient terrain-induced ascent to locally overcome convective inhibition. The terrain-induced ascent can be owing to mechanical (airflow over or around an obstacle and/or thermal (differential heating over sloping terrain forcing. For the former, the location of convective initiation depends on the dynamical flow regime. In “unblocked” flows that ascend the barrier, the convection tends to initiate over the windward slopes, while in “blocked” flows that detour around the barrier, the convection tends to initiate upstream and/or downstream of the high terrain where impinging flows split and rejoin, respectively. Processes that destabilize the upstream flow for mechanically forced moist convection include large-scale moistening and ascent, positive surface sensible and latent heat fluxes, and differential advection in baroclinic zones. For thermally forced flows, convective initiation is driven by thermally direct circulations with sharp updrafts over or downwind of the mountain crest (daytime or foot (nighttime. Along with the larger-scale background flow, local evapotranspiration and transport of moisture, as well as thermodynamic heterogeneities over the complex terrain, regulate moist instability in such events. Longstanding limitations in the quantitative understanding of related processes, including both convective preconditioning and initiation, must be overcome to improve the prediction of this convection, and its collective effects, in weather and climate models.

  13. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling.

    Science.gov (United States)

    Pera, H; Kleijn, J M; Leermakers, F A M

    2014-02-14

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus kc and k̄ and the preferred monolayer curvature J(0)(m), and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of kc and the area compression modulus kA are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k̄ and J(0)(m) can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k̄ and J(0)(m) change sign with relevant parameter changes. Although typically k̄ 0, especially at low ionic strengths. We anticipate that these changes lead to unstable membranes as these become vulnerable to pore formation or disintegration into lipid disks.

  14. Mechanisms of migration development at the community level: Migrant networks and types of links

    Directory of Open Access Journals (Sweden)

    Mónica Serban

    2014-11-01

    Full Text Available The paper approaches the problem of the development mechanism of international migration at community level.Some empirical observations cumulated during several researches,at origin and destination area, regarding Romanian migration to Spain constitute the starting points. Appealing to the distinction introduced by Mark Granovetter in 1976 between weak and strongties, we find that, if initially migration develops almost exclusively based on social relations that could be assimilated to strong ties,there is a moment in the process of development when the departures on the base of weak ties, with important consequences on the migrant’s situation at destination, increase.The paper tries to clarify, preponderantly invoking theoretical arguments,in what measure the departures based on weak ties between migrant and non migrant are normal in the process of international migration development at community level. The study concludes that, because of cumulative effects, migration evolution to a phase when the departure is possible based on weak ties is explainable.Two mechanisms mainly contribute to this result: enhancement of incentives to migrate (because of quantitative and qualitative information increase; visibility of migration effects in the origin area;changes of relative deprivation at community level and migration costs and risk lowering, with the consequence of reduction of effective support that a non-migrant needs from one migrant in order to migrate.

  15. Linking lipid architecture to bilayer structure and mechanics using self-consistent field modelling

    International Nuclear Information System (INIS)

    Pera, H.; Kleijn, J. M.; Leermakers, F. A. M.

    2014-01-01

    To understand how lipid architecture determines the lipid bilayer structure and its mechanics, we implement a molecularly detailed model that uses the self-consistent field theory. This numerical model accurately predicts parameters such as Helfrichs mean and Gaussian bending modulus k c and k ¯ and the preferred monolayer curvature J 0 m , and also delivers structural membrane properties like the core thickness, and head group position and orientation. We studied how these mechanical parameters vary with system variations, such as lipid tail length, membrane composition, and those parameters that control the lipid tail and head group solvent quality. For the membrane composition, negatively charged phosphatidylglycerol (PG) or zwitterionic, phosphatidylcholine (PC), and -ethanolamine (PE) lipids were used. In line with experimental findings, we find that the values of k c and the area compression modulus k A are always positive. They respond similarly to parameters that affect the core thickness, but differently to parameters that affect the head group properties. We found that the trends for k ¯ and J 0 m can be rationalised by the concept of Israelachivili's surfactant packing parameter, and that both k ¯ and J 0 m change sign with relevant parameter changes. Although typically k ¯ 0 m ≫0, especially at low ionic strengths. We anticipate that these changes lead to unstable membranes as these become vulnerable to pore formation or disintegration into lipid disks

  16. Nonlinear optical collagen cross-linking and mechanical stiffening: a possible photodynamic therapeutic approach to treating corneal ectasia

    Science.gov (United States)

    Chai, Dongyul; Juhasz, Tibor; Brown, Donald J.; Jester, James V.

    2013-03-01

    In this study we test the hypothesis that nonlinear optical (NLO) multiphoton photoactivation of riboflavin using a focused femtosecond (FS) laser light can be used to induce cross-linking (CXL) and mechanically stiffen collagen as a potential clinical therapy for the treatment of keratoconus and corneal ectasia. Riboflavin-soaked, compressed collagen hydrogels are cross-linked using a FS laser tuned to 760 nm and set to either 100 mW (NLO CXL I) or 150 mW (NLO CXL II) of laser power. FS pulses are focused into the hydrogel using a 0.75 NA objective lens, and the hydrogel is three-dimensionally scanned. Measurement of hydrogel stiffness by indentation testing show that the calculated elastic modulus (E) values are significantly increased over twofold following NLO CXL I and II compared with baseline values (P0.05). This data suggests that NLO CXL has a comparable effect to conventional UVA CXL in mechanically stiffening collagen and may provide a safe and effective approach to localize CXL at different regions and depths within the cornea.

  17. 5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds.

    Science.gov (United States)

    Isbell, Elif; Stevens, Courtney; Hampton Wray, Amanda; Bell, Theodore; Neville, Helen J

    2016-12-01

    While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR) genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES) backgrounds. Event-related potentials (ERPs) were recorded during a dichotic listening task from 121 children (76 females, aged 40-67 months), who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  18. A polypeptide-DNA hybrid with selective linking capability applied to single molecule nano-mechanical measurements using optical tweezers.

    Directory of Open Access Journals (Sweden)

    Fatemeh Moayed

    Full Text Available Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN and the peptide StrepTag II (ST. We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST. In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV linkage. It can be used in conjunction with Neutravidin (NTV-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications.

  19. 5-HTTLPR polymorphism is linked to neural mechanisms of selective attention in preschoolers from lower socioeconomic status backgrounds

    Directory of Open Access Journals (Sweden)

    Elif Isbell

    2016-12-01

    Full Text Available While a growing body of research has identified experiential factors associated with differences in selective attention, relatively little is known about the contribution of genetic factors to the skill of sustained selective attention, especially in early childhood. Here, we assessed the association between the serotonin transporter linked polymorphic region (5-HTTLPR genotypes and the neural mechanisms of selective attention in young children from lower socioeconomic status (SES backgrounds. Event-related potentials (ERPs were recorded during a dichotic listening task from 121 children (76 females, aged 40–67 months, who were also genotyped for the short and long allele of 5-HTTLPR. The effect of selective attention was measured as the difference in ERP mean amplitudes elicited by identical probe stimuli embedded in stories when they were attended versus unattended. Compared to children homozygous for the long allele, children who carried at least one copy of the short allele showed larger effects of selective attention on neural processing. These findings link the short allele of the 5-HTTLPR to enhanced neural mechanisms of selective attention and lay the groundwork for future studies of gene-by-environment interactions in the context of key cognitive skills.

  20. Trypanozoon: infectivity to humans is linked to reduced transmissibility in tsetse. II. Genetic mechanisms.

    Science.gov (United States)

    Milligan, P J; Maudlin, I; Welburn, S C

    1995-11-01

    Trypanozoon infections are less likely to mature in female tsetse than in males. Analysis of maturation data from 37 Trypanozoon isolates in Glossina m. morsitans showed that while the proportion of mature infections (salivary gland infections as a proportion of established midgut infections) varied from isolate to isolate, the proportion of mature infections in female flies was consistently smaller than the proportion in male flies. The log of the probability of maturation in females is, on average, twice the log of the probability in males (estimate of the ratio of the logged proportions is 2.09, 95% confidence interval (CI) 1.8 to 2.5). Human serum-resistant isolates were less likely to mature than human serum-sensitive isolates (ratio of logged proportions maturing was 1.5, 95% CI 1.3 to 1.8, in both male and female tsetse). Data for four other trypanosome stocks show that the probability of maturation decreases as the maturation time (the delay between the infected bloodmeal and maturation) increases. The decrease is approximately exponential with twice the half-life in male flies compared to that in female flies (estimate of the ratio of the exponential parameters is 1.97, 95% CI 0.7 to 3.3). A model is proposed to explain these observations which assumes that product(s) from an X-linked gene(s) kills or otherwise prevents migrating parasites from establishing a mature infection. Longer maturation times are associated with a heavy penalty in terms of transmissibility as measured by the vectorial capacity.

  1. Swelling and mechanical properties of hydrogels composed of binary blends of inter-linked pH-responsive microgel particles.

    Science.gov (United States)

    Milani, Amir H; Bramhill, Jane; Freemont, Anthony J; Saunders, Brian R

    2015-04-07

    We show that a new type of hydrogel can be prepared by covalently inter-linking binary blends of microgel (MG) particles and that the swelling ratio and modulus of the gels can be predicted from their composition. In previous work we established that physical gels of glycidyl methacrylate (GMA) functionalised poly(methyl methacrylate-co-methacrylic acid-co-ethyleneglycol dimethacrylate) microgel particles (GMA-MG) could be covalently inter-linked to give hydrogels, termed doubly crosslinked microgels, DX MGs. We build on this concept here by investigating the properties of DX MGs containing binary blends of GMA-MG particles and glycidyl oligo(ether ester) acrylate-functionalised microgel particles (GOE-MG). These new hydrogels were assembled by inter-linking nanoscale MG building blocks in the absence of small molecule monomers or crosslinkers. The volume fraction of GMA-MG particles used to prepare the GOE-GMA DX MGs was systematically varied. Rheology data showed that inclusion of GMA-MG and GOE-MG within the GOE-GMA DX MGs increased the modulus and yield strain, respectively, compared to the values measured for the respective physical gels. The data for the covalent GOE-GMA DX MG gels showed that the ductility increased with increasing GOE-MG content. GOE provided covalent inter-linking of the MG particles and also acted as a lubricant between particles due to its low Tg. By demonstrating compositionally determined swelling and mechanical properties for DX MG gels prepared using binary blends of MG particles, this study introduces a new, widely applicable, hydrogel construction assembly concept that is not available for conventional hydrogels.

  2. The ability to generate senescent progeny as a mechanism underlying breast cancer cell heterogeneity.

    Directory of Open Access Journals (Sweden)

    Mine Mumcuoglu

    Full Text Available BACKGROUND: Breast cancer is a remarkably heterogeneous disease. Luminal, basal-like, "normal-like", and ERBB2+ subgroups were identified and were shown to have different prognoses. The mechanisms underlying this heterogeneity are poorly understood. In our study, we explored the role of cellular differentiation and senescence as a potential cause of heterogeneity. METHODOLOGY/PRINCIPAL FINDINGS: A panel of breast cancer cell lines, isogenic clones, and breast tumors were used. Based on their ability to generate senescent progeny under low-density clonogenic conditions, we classified breast cancer cell lines as senescent cell progenitor (SCP and immortal cell progenitor (ICP subtypes. All SCP cell lines expressed estrogen receptor (ER. Loss of ER expression combined with the accumulation of p21(Cip1 correlated with senescence in these cell lines. p21(Cip1 knockdown, estrogen-mediated ER activation or ectopic ER overexpression protected cells against senescence. In contrast, tamoxifen triggered a robust senescence response. As ER expression has been linked to luminal differentiation, we compared the differentiation status of SCP and ICP cell lines using stem/progenitor, luminal, and myoepithelial markers. The SCP cells produced CD24+ or ER+ luminal-like and ASMA+ myoepithelial-like progeny, in addition to CD44+ stem/progenitor-like cells. In contrast, ICP cell lines acted as differentiation-defective stem/progenitor cells. Some ICP cell lines generated only CD44+/CD24-/ER-/ASMA- progenitor/stem-like cells, and others also produced CD24+/ER- luminal-like, but not ASMA+ myoepithelial-like cells. Furthermore, gene expression profiles clustered SCP cell lines with luminal A and "normal-like" tumors, and ICP cell lines with luminal B and basal-like tumors. The ICP cells displayed higher tumorigenicity in immunodeficient mice. CONCLUSIONS/SIGNIFICANCE: Luminal A and "normal-like" breast cancer cell lines were able to generate luminal-like and

  3. Linking governance mechanisms to health outcomes: a review of the literature in low- and middle-income countries.

    Science.gov (United States)

    Ciccone, Dana Karen; Vian, Taryn; Maurer, Lydia; Bradley, Elizabeth H

    2014-09-01

    We conducted a synthesis of peer-reviewed literature to shed light on links between governance mechanisms and health outcomes in low- and middle-income countries. Our review yielded 30 studies, highlighting four key governance mechanisms by which governance may influence health outcomes in these settings: Health system decentralization that enables responsiveness to local needs and values; health policymaking that aligns and empowers diverse stakeholders; enhanced community engagement; and strengthened social capital. Most, but not all, studies found a positive association between governance and health. Additionally, the nature of the association between governance mechanisms and health differed across studies. In some studies (N = 9), the governance effect was direct and positive, while in others (N = 5), the effect was indirect or modified by contextual factors. In still other studies (N = 4), governance was found to have a moderating effect, indicating that governance mechanisms influenced other system processes or structures that improved health. The remaining studies reported mixed findings about the association between governance and health (N = 6), no association between governance and health (N = 4), or had inconclusive results (N = 2). Further exploration is needed to fully understand the relationship between governance and health and to inform the design and delivery of evidence-based, effective governance interventions around the world. Copyright © 2014 Elsevier Ltd. All rights reserved.

  4. Toward molecular mechanism of xenon anesthesia: a link to studies of xenon complexes with small aromatic molecules.

    Science.gov (United States)

    Andrijchenko, Natalya N; Ermilov, Alexander Yu; Khriachtchev, Leonid; Räsänen, Markku; Nemukhin, Alexander V

    2015-03-19

    The present study illustrates the steps toward understanding molecular mechanism of xenon anesthesia by focusing on a link to the structures and spectra of intermolecular complexes of xenon with small aromatic molecules. A primary cause of xenon anesthesia is attributed to inhibition of N-methyl-D-aspartate (NMDA) receptors by an unknown mechanism. Following the results of quantum mechanics/molecular mechanics (QM/MM) and molecular dynamics (MD) calculations we report plausible xenon action sites in the ligand binding domain of the NMDA receptor, which are due to interaction of xenon atoms with aromatic amino-acid residues. We rely in these calculations on computational protocols adjusted in combined experimental and theoretical studies of intermolecular complexes of xenon with phenol. Successful reproduction of vibrational shifts in molecular species upon complexation with xenon measured in low-temperature matrices allowed us to select a proper functional form in density functional theory (DFT) approach for use in QM subsystems, as well as to calibrate force field parameters for MD simulations. The results of molecular modeling show that xenon atoms can compete with agonists for a place in the corresponding protein cavity, thus indicating their active role in anesthetic action.

  5. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi (New York Univ., NY (United States). Dept. of Chemistry); France, L.L.; Sutherland, J.D. (Brookhaven National Lab., Upton, NY (United States))

    1992-01-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo(a)pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo(a)pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  6. Photoinduced electron transfer and fluorescence mechanisms in covalently linked polynuclear aromatic-nucleotide complexes

    Energy Technology Data Exchange (ETDEWEB)

    Geacintov, N.E.; Mao, Bing; Zhao, Rushen; Chen, Junxin; Liu, Tong Ming; Ya, Nai-Qi [New York Univ., NY (United States). Dept. of Chemistry; France, L.L.; Sutherland, J.D. [Brookhaven National Lab., Upton, NY (United States)

    1992-04-01

    The fluorescence of polycyclic aromatic hydrocarbon-nucleic acid complexes is quenched by photoinduced electron transfer mechanisms in aqueous solutions at ambient temperatures. These effects are illustrated with the biologically important compound benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE), a mutagenic and carcinogenic metabolite of the environmental pollutant benzo[a]pyrene, which forms covalent mutagenic lesions with 2{prime}-deoxyguanosine (dG) residues in DNA. The dependence of the fluroescence yeild and fluorescence decay times of the covalent model adduct (+)-trans-BPDE-N{sup 2}-dG as a function of temperature and methanol/water composition are described. Because of the sensitivity of the fluorescence of the pyrenyl residue to the polarity of the microenvironment, the magnitude of the fluorescence yield can be used to distinguish between highly hydrophobic (e.g. intercalation) and other more solvent-exposed BPDE-nucleic acid binding sites.

  7. Spared behavioral repetition effects in Alzheimer's disease linked to an altered neural mechanism at posterior cortex.

    Science.gov (United States)

    Broster, Lucas S; Li, Juan; Wagner, Benjamin; Smith, Charles D; Jicha, Gregory A; Schmitt, Frederick A; Munro, Nancy; Haney, Ryan H; Jiang, Yang

    2018-02-20

    Individuals with dementia of the Alzheimer type (AD) classically show disproportionate impairment in measures of working memory, but repetition learning effects are relatively preserved. As AD affects brain regions implicated in both working memory and repetition effects, the neural basis of this discrepancy is poorly understood. We hypothesized that the posterior repetition effect could account for this discrepancy due to the milder effects of AD at visual cortex. Participants with early AD, amnestic mild cognitive impairment (MCI), and healthy controls performed a working memory task with superimposed repetition effects while electroencephalography was collected to identify possible neural mechanisms of preserved repetition effects. Participants with AD showed preserved behavioral repetition effects and a change in the posterior repetition effect. Visual cortex may play a role in maintained repetition effects in persons with early AD.

  8. Affective mechanisms linking dysfunctional behavior to performance in work teams: a moderated mediation study.

    Science.gov (United States)

    Cole, Michael S; Walter, Frank; Bruch, Heike

    2008-09-01

    The present study examines the association between dysfunctional team behavior and team performance. Data included measures of teams' dysfunctional behavior and negative affective tone as well as supervisors' ratings of teams' (nonverbal) negative emotional expressivity and performance. Utilizing a field sample of 61 work teams, the authors tested the proposed relationships with robust data analytic techniques. Results were consistent with the hypothesized conceptual scheme, in that negative team affective tone mediated the relationship between dysfunctional team behavior and performance when teams' nonverbal negative expressivity was high but not when nonverbal expressivity was low. On the basis of the findings, the authors conclude that the connection between dysfunctional behavior and performance in team situations is more complex than was previously believed--thereby yielding a pattern of moderated mediation. In sum, the findings demonstrated that team members' collective emotions and emotional processing represent key mechanisms in determining how dysfunctional team behavior is associated with team performance.

  9. Epigenetics as a mechanism linking developmental exposures to long-term toxicity

    DEFF Research Database (Denmark)

    Barouki, R; Melén, E; Herceg, Z

    2018-01-01

    methylation, histone modifications and the expression of certain RNAs have been suggested as possible mediators of long-term health effects of environmental stressors. This report captures discussions and conclusions debated during the last Prenatal Programming and Toxicity meeting held in Japan. Its first......A variety of experimental and epidemiological studies lend support to the Developmental Origin of Health and Disease (DOHaD) concept. Yet, the actual mechanisms accounting for mid- and long-term effects of early-life exposures remain unclear. Epigenetic alterations such as changes in DNA...... and function, the specificity of the epigenetic changes and the biological plausibility of the linkage between those changes and health outcomes. The second aim is to discuss long-term effects of a number of stressors such as smoking, air pollution and endocrine disruptors in order to identify the arguments...

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

    Energy Technology Data Exchange (ETDEWEB)

    Kadhim, Munira A

    2012-08-22

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

  11. Effects of cross-linking on mechanical, biological properties and biodegradation behavior of Nile tilapia skin collagen sponge as a biomedical material.

    Science.gov (United States)

    Sun, Leilei; Li, Bafang; Yao, Di; Song, Wenkui; Hou, Hu

    2018-04-01

    The objective of this study was to explore the effects of dehydrothermal treatment (DHT) and glutaraldehyde (GTA) cross-linking on mechanical, biological properties and biodegradation behavior of Nile tilapia skin collagen sponge fabricated by freeze-drying technology. It was found that the GTA cross-linked collagen sponge exhibited a higher degree of cross-linking in comparison with DHT. The extent of increased tensile strength as well as hygroscopicity indicated that GTA cross-linking was superior to DHT in mechanical properties and liquid absorption, which was attributed to different cross-linking mechanisms. Hygroscopicity assay indicated that cross-linking could improve stability of collagen in solutions. No obvious changes in porosity and blood coagulation time were observed whether cross-linking or not. Results from collagenase biodegradation assay in vitro illustrated that GTA-treated collagen sponge was more resistant to collagenase biodegradation, while DHT exhibited negligible resistance. In addition, photochemical stability of collagen sponge was studied by Fourier transforms infrared spectroscopy (FTIR), which indicated that both cross-linking treatments could not change the backbone structure of collagen. Furthermore, the microstructure of collagen sponge was stable after cross-linking. The highly porous and interconnected structure of collagen sponge was helpful to the absorption of wound exudates, supplement of oxygen and cell proliferation, accompanied with good blood compatibility, which indicated that our fabricated collagen sponge could be applied in biomedical materials field as wound dressings. Copyright © 2018. Published by Elsevier Ltd.

  12. 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.

    1999-01-01

    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.)

  13. Investigations into the Mechanisms of Cell Death: The Common Link between Anticancer Nanotherapeutics and Nanotoxicology

    Science.gov (United States)

    Minocha, Shalini

    Nanotoxicology and anticancer nanotherapeutics are essentially two sides of the same coin. The nanotoxicology discipline deals with the nanoparticle (NP)-induced toxicity and mechanisms of cell death in healthy cells, whereas anticancer agents delivered via nano-based approaches aim to induce cell death in abnormally proliferating cancer cells. The objectives of the studies presented herein were two-fold; to (a) systematically study the physico-chemical properties and cell death mechanisms of model NPs and (b) utilize the knowledge gained from cell death-nanotoxicity studies in developing a potentially novel anticancer nanotherapeutic agent. For the first objective, the effect of a distinguishing characteristic, i.e., surface carbon coating on the matched pairs of carbon-coated and non-coated copper and nickel NPs (Cu, C-Cu, Ni and C-Ni) on the physico-chemical properties and toxicity in A549 alveolar epithelial cells were evaluated. The effect of carbon coating on particle size, zeta potential, oxidation state, cellular uptake, release of soluble metal and concentration dependent toxicity of Cu and Ni NPs was systematically evaluated. A significant effect of carbon coating was observed on the physico-chemical properties, interaction with cellular membranes, and overall toxicity of the NPs. C-Cu NPs, compared to Cu NPs, showed four-fold lower release of soluble copper, ten-fold higher cellular uptake and protection against surface oxidation. In toxicity assays, C-Cu NPs induced higher mitochondrial damage than Cu NPs whereas Cu NPs were associated with a significant damage to plasma membrane integrity. Nickel and carbon coated nickel NPs were less toxic compared to Cu and C-Cu NPs. Thus, by studying the effect of carbon coating, correlations between physico-chemical properties and toxicity of NPs were established. The second objective was focused on utilizing nano-based approaches for the intracellular delivery of an anticancer agent, Cytochrome c (Cyt c), to

  14. The grand unified link between the Peccei-Quinn mechanism and the generation puzzle

    International Nuclear Information System (INIS)

    Davidson, A.; Wali, K.C.

    1982-03-01

    The essential ingredients of the Peccei-Quinn mechanism are shown to be dictated by a proper choice of a grand unification scheme. The presence of U(1)sub(PQ) gives rise to the possibility that the same physics which resolves the strong CP-violation problem may decode the generation puzzle with no extra cost. Multigenerational signatures of the invisible axion scenario, such as the canonical fermion mass matrix, are discussed. The uniqueness and the special values of the quantized PQ-assignments, namely 1,-3,5-7,... for successive generations, acquire an automatic explanation once the idea of ''horizontal compositeness'' is invoked. A characteristic feature then is that the muon appears to have a less complicated structure than the electron. Furthermore, U(1)sub(PQ) chooses SO(10) to be its only tenable gauge symmetry partner, and at the same time crucially restricts the associated Higgs system. All this finally results in a consistent fermion mass hierarchy with log m, to the crudest estimation, varying linearly with respect to the generation index. (author)

  15. Behavioral differences in aggressive children linked with neural mechanisms of emotion regulation.

    Science.gov (United States)

    Lewis, Marc D; Granic, Isabela; Lamm, Connie

    2006-12-01

    Children with aggressive behavior problems may have difficulties regulating negative emotions, resulting in harmful patterns of interpersonal behavior at home and in the schoolyard. Ventral and dorsal regions of the prefrontal cortex (PFC) have been associated with response inhibition and self-control-key components of emotion regulation. Our research program aims to explore differences among aggressive and normal children in the activation of these cortical regions during emotional episodes, to the extent possible using electrophysiological techniques, to identify diagnostic subtypes, gain insights into their interpersonal difficulties, and help develop effective treatment strategies. This report reviews several recent studies investigating individual and developmental differences in cortical mechanisms of emotion regulation, corresponding with different patterns of interpersonal behavior. Our methods include event-related potentials (ERPs) and cortical source modeling, using dense-array electroencephalography (EEG) technology, as well as videotaped observations of parent-child interactions, with both normal and aggressive children. By relating patterns of brain activation to observed behavioral differences, we find (i) a steady decrease in cortical activation subserving self-regulation across childhood and adolescence, (ii) different cortical activation patterns as well as behavioral constellations distinguishing subtypes of aggressive children, and (iii) robust correlations between the activation of cortical mediators of emotion regulation and flexibility in parent-child emotional communication in children referred for aggressive behavior problems. These findings point toward models of developmental psychopathology based on the interplay among biological, psychological, and social factors.

  16. The evolutionary ecology of complex lifecycle parasites: linking phenomena with mechanisms.

    Science.gov (United States)

    Auld, S K J R; Tinsley, M C

    2015-02-01

    Many parasitic infections, including those of humans, are caused by complex lifecycle parasites (CLPs): parasites that sequentially infect different hosts over the course of their lifecycle. CLPs come from a wide range of taxonomic groups-from single-celled bacteria to multicellular flatworms-yet share many common features in their life histories. Theory tells us when CLPs should be favoured by selection, but more empirical studies are required in order to quantify the costs and benefits of having a complex lifecycle, especially in parasites that facultatively vary their lifecycle complexity. In this article, we identify ecological conditions that favour CLPs over their simple lifecycle counterparts and highlight how a complex lifecycle can alter transmission rate and trade-offs between growth and reproduction. We show that CLPs participate in dynamic host-parasite coevolution, as more mobile hosts can fuel CLP adaptation to less mobile hosts. Then, we argue that a more general understanding of the evolutionary ecology of CLPs is essential for the development of effective frameworks to manage the many diseases they cause. More research is needed identifying the genetics of infection mechanisms used by CLPs, particularly into the role of gene duplication and neofunctionalisation in lifecycle evolution. We propose that testing for signatures of selection in infection genes will reveal much about how and when complex lifecycles evolved, and will help quantify complex patterns of coevolution between CLPs and their various hosts. Finally, we emphasise four key areas where new research approaches will provide fertile opportunities to advance this field.

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

    NARCIS (Netherlands)

    Montuoro, Paul; Mainhard, Tim

    2017-01-01

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

  18. Tensile mechanical behavior of hollow and filled carbon nanotubes under tension or combined tension-torsion

    Science.gov (United States)

    Jeong, Byeong-Woo; Lim, Jang-Keun; Sinnott, Susan B.

    2007-01-01

    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.

  19. Inhibition of O-linked N-acetylglucosamine transferase activity in PC12 cells - A molecular mechanism of organophosphate flame retardants developmental neurotoxicity.

    Science.gov (United States)

    Gu, Yuxin; Yang, Yu; Wan, Bin; Li, Minjie; Guo, Liang-Hong

    2018-03-17

    Organophosphate flame retardants (OPFRs), as alternatives of brominated flame retardants, can cause neurodevelopmental effects similar to organophosphate pesticides. However, the molecular mechanisms underlying the toxicity remain elusive. O-linked N-acetylglucosamine (O-GlcNAc) transferase (OGT) regulates numerous neural processes through the O-GlcNAcylation modification of nuclear and cytoplasmic proteins. In this study, we aimed to investigate the molecular mechanisms accounting for the developmental neurotoxicity of OPFRs by identifying potential targets of OPFRs and the attendant effects. Twelve OPFRs were evaluated for inhibition of OGT activity using an electrochemical biosensor. Their potency differed with substituent groups. The alkyl group substituted OPFRs had no inhibitory effect. Instead, the six OPFRs substituted with aromatic or chlorinated alkyl groups inhibited OGT activity significantly, with tri-m-cresyl phosphate (TCrP) being the strongest. The six OPFRs (0-100 μM exposure) also inhibited OGT activity in PC12 cells and decreased protein O-GlcNAcylation level. Inhibition of OGT by OPFRs might be involved in the subsequent toxic effects, including intracellular reactive oxygen species (ROS), calcium level, as well as cell proliferation and autophagy. Molecular docking of the OGT/OPFR complexes provided rationales for the difference in their structure-dependent inhibition potency. Our findings may provide a new biological target of OPFRs in their neurotoxicological actions, which might be a major molecular mechanism of OPFRs developmental neurotoxicity. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Linking rapid magma reservoir assembly and eruption trigger mechanisms at evolved Yellowstone-type supervolcanoes

    Science.gov (United States)

    Wotzlaw, J.F.; Bindeman, I.N.; Watts, Kathryn E.; Schmitt, A.K.; Caricchi, L.; Schaltegger, U.

    2014-01-01

    reservoir configurations inferred from seismic data at active supervolcanoes. The connection of magma batches vertically distributed over several kilometers in the upper crust would cause a substantial increase of buoyancy overpressure, providing an eruption trigger mechanism that is the direct consequence of the reservoir assembly process.

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

    Science.gov (United States)

    Truini, Andrea; Cruccu, Giorgio

    2016-02-01

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

  2. Visualization of hot spot formation in energetic materials under periodic mechanical excitation using phosphor thermography

    Science.gov (United States)

    Casey, Alex; Fenoglio, Gabriel; Detrinidad, Humberto

    2017-06-01

    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.

  3. A Cross-Cultural Approach to Psychological Mechanisms Underlying Emotional Reactions to Music

    OpenAIRE

    Barradas, Gonçalo

    2017-01-01

    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...

  4. Elucidation of the molecular mechanisms underlying adverse reactions associated with a kinase inhibitor using systems toxicology.

    Science.gov (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

    2015-01-01

    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.

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

    Science.gov (United States)

    2017-10-01

    AWARD NUMBER: W81XWH-16-1-0652 TITLE: Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity PRINCIPAL INVESTIGATOR...5a. CONTRACT NUMBER W81XWH-16-1-0652 Mechanisms Underlying Stress Fracture and the Influence of Sex and Race/Ethnicity 5b. GRANT NUMBER W81XWH...Email addresses: mbouxsei@bidmc.harvard.edu; scaksa@mgh.harvard.edu; serudolph@mgh.harvard.edu ; kpopp@mgh.harvard.edu E-Mail: 5f. WORK UNIT NUMBER 7

  6. Aging Mechanisms and Nondestructive Aging Indicator of Filled Cross-linked Polyethylene (XLPE) Exposed to Simultaneous Thermal and Gamma Radiation

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Shuaishuai; Fifield, Leonard S.; Bowler, Nicola

    2018-04-11

    Aging mechanisms and a nondestructive aging indicator of filled cross-linked polyethylene (XLPE) cable insulation material used in nuclear power plants (NPPs) are studied. Using various material characterization techniques, likely candidates and functions for the main additives in a commercial filled-XLPE insulation material have been identified. These include decabromodiphenyl ether and Sb2O3 as flame retardants, ZnS as white pigment and polymerized 1,2-dihydro-2,2,4-trimethylquinoline as antioxidant. Gas chromatography-mass spectrometry, differential scanning calorimetry, oxidation induction time and measurements of dielectric loss tangent are utilized to monitor property changes as a function of thermal and radiation exposure of the cable material. Small-molecular-weight hydrocarbons are evolve with gamma radiation aging at 90 °C. The level of antioxidant decreases with aging by volatilization and chemical reaction with free radicals. Thermal aging at 90 °C for 25 days or less causes no observable change to the cross-linked polymer structure. Gamma radiation causes damage to crystalline polymer regions and introduces defects. Dielectric loss tangent is shown to be an effective and reliable nondestructive indicator of the aging severity of the filled-XLPE insulation material.

  7. Comparative proteomics of peanut gynophore development under dark and mechanical stimulation.

    Science.gov (United States)

    Sun, Yong; Wang, Qingguo; Li, Zhen; Hou, Lei; Dai, Shaojun; Liu, Wei

    2013-12-06

    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.

  8. Effect of modified starch and nanoclay particles on biodegradability and mechanical properties of cross-linked poly lactic acid.

    Science.gov (United States)

    Shayan, M; Azizi, H; Ghasemi, I; Karrabi, M

    2015-06-25

    Mechanical properties and biodegradation of cross-linked poly(lactic acid) (PLA)/maleated thermoplastic starch (MTPS)/montmorillonite (MMT) nanocomposite were studied. Crosslinking was carried out by adding di-cumyl peroxide (DCP) in the presence of triallyl isocyanurate (TAIC) as coagent. At first, MTPS was prepared by grafting maleic anhydride (MA) to thermoplastic starch in internal mixer. Experimental design was performed by using Box-Behnken method at three variables: MTPS, nanoclay and TAIC at three levels. Results showed that increasing TAIC amount substantially increased the gel fraction, enhanced tensile strength, and caused a decrease in elongation at break. Biodegradation was prevented by increasing TAIC amount in nanocomposite. Increasing MTPS amount caused a slight increase in gel fraction and decreased the tensile strength of nanocomposite. Also, MTPS could increase the elongation at break of nanocomposite and improve the biodegradation. Nanoclay had no effect on the gel fraction, but it improved tensile strength. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

    OpenAIRE

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

    2014-01-01

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

  10. Mechanical behavior of confined self-compacting reinforced concrete circular columns under concentric axial loading

    OpenAIRE

    Khairallah, Fouad

    2013-01-01

    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...

  11. Environmental context affects microbial ecophysiological mechanisms underpinning soil carbon storage under different land use

    Science.gov (United States)

    Malik, A. A.; Puissant, J.; Buckeridge, K. M.; Goodall, T.; Jehmlich, N.; Chowdhury, S.; Gleixner, G.; Griffiths, R.

    2017-12-01

    Soil microorganisms act as gatekeepers for soil-atmosphere carbon exchange by balancing the accumulation and release of organic matter in soil. Increasing evidence now exists to suggest that microbial biomass contributes significantly to soil organic carbon formation. However, we do not fully understand the microbial mechanisms of organic matter processing and this hinders the development of effective land management strategies to enhance soil carbon storage. Here we empirically link key microbial ecophysiological traits to soil carbon storage in temperate grassland habitats ranging in land use from pristine species-rich grasslands to intensive croplands in 56 different soils across Britain. Physiological mechanisms of soil microorganisms were assessed using stable carbon isotope tracing and soil proteomics. Through spatial patterns and path analysis of structural equation modeling we discern two distinct pH-related mechanisms of soil carbon storage and highlight that the response of these mechanistic indicators is shaped by the environmental context. Land use intensification in low pH soils that increases soil pH above a threshold value ( 6.2) leads to loss of carbon due to increased microbial degradation as a result of lower acid retardation of organic matter decomposition. On the contrary, the loss of carbon through intensification in high pH (> 6.2) soils was linked to decreased microbial biomass and reduced carbon use efficiency that was linked to tradeoffs with stress alleviation and resource acquisition. We conclude that land use intensification-induced changes in soil pH can be used as a proxy to determine the effect of land management strategies on microbial soil carbon cycling processes and emphasize that more extensive land management practices at higher soil pH have greater potential for soil carbon storage through increased microbial metabolic efficiency, whereas in acidic soils abiotic factors exert a greater influence on the fate of soil carbon.

  12. Study of a Car Body Tilting System Using a Variable Link Mechanism: Fundamental Characteristics of Pendulum Motion and Strategy for Perfect Tilting

    Science.gov (United States)

    Yoshida, Hidehisa; Nagai, Masao

    This paper analyzes the fundamental dynamic characteristics of a tilting railway vehicle using a variable link mechanism for compensating both the lateral acceleration experienced by passengers and the wheel load imbalance between the inner and outer rails. The geometric relations between the center of rotation, the center of gravity, and the positions of all four links of the tilting system are analyzed. Then, equations of the pendulum motions of the railway vehicle body with a four-link mechanism are derived. A theoretically discussion is given on the geometrical shapes employed in the link mechanism that can simultaneously provide zero lateral acceleration and zero wheel load fluctuation. Then, the perfect tilting condition, which is the control target of the feedforward tilting control, is derived from the linear equation of tilting motion.

  13. 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.

    2012-01-01

    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.

  14. Robustness analysis of a constraint-based metabolic model links cell growth and proteomics of Thermoanaerobacter tengcongensis under temperature perturbation.

    Science.gov (United States)

    Tong, Wei; Chen, Zhen; Cao, Zhe; Wang, Quanhui; Zhang, Jiyuan; Bai, Xue; Wang, Rong; Liu, Siqi

    2013-04-05

    The integration of omic data with metabolic networks has been demonstrated to be an effective approach to elucidate the underlying metabolic mechanisms in life. Because the metabolic pathways of Thermoanaerobacter tengcongensis (T. tengcongensis) are incomplete, we used a 1-(13)C-glucose culture to monitor intracellular isotope-labeled metabolites by GC/MS and identified the gap gene in glucose catabolism, Re-citrate synthase. Based on genome annotation and biochemical information, we reconstructed the metabolic network of glucose metabolism and amino acid synthesis in T. tengcongensis, including 253 reactions, 227 metabolites, and 236 genes. Furthermore, we performed constraint based modeling (CBM)-derived robustness analysis on the model to study the dynamic changes of the metabolic network. By perturbing the culture temperature from 75 to 55 °C, we collected the bacterial growth rates and differential proteomes. Assuming that protein abundance changes represent metabolic flux variations, we proposed that the robustness analysis of the CBM model could decipher the effect of proteome change on the bacterial growth under perturbation. For approximately 73% of the reactions, the predicted cell growth changes due to such reaction flux variations matched the observed cell growth data. Our study, therefore, indicates that differential proteome data can be integrated with metabolic network modeling and that robustness analysis is a strong method for representing the dynamic change in cell phenotypes under perturbation.

  15. Structural and Mechanical Properties of Intermediate Filaments under Extreme Conditions and Disease

    Science.gov (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

  16. On the performance of telemedicine system using 17-GHz orthogonally polarized microwave links under the influence of heavy rainfall.

    Science.gov (United States)

    Fong, Bernard; Fong, A C M; Hong, G Y

    2005-09-01

    This paper describes the design of a telemedicine system based on next-generation wireless local area networks (WLANs) operating at 17 GHz. Seventeen gigahertz is proposed for next-generation WLAN services offering numerous advantages over traditional IEEE 802.11 networks that operate in the range of 2.4-5 GHz. Orthogonal polarization is often used to increase spectrum efficiency by utilizing signal paths of horizontal and vertical polarization. Radio waves exceeding 10 GHz are particularly vulnerable to signal degradation under the influence of rain which causes an effective reduction in isolation between polarized signal paths. This paper investigates the influence of heavy rain in a tropical region on wide-band microwave signals at 17 GHz using two links provided by a fixed broad-band wireless access system for two-way data exchange between paramedics attending an accident scene and the hospital via microwave equipment installed in the ambulance. We also study the effects of cross polarization and phase rotation due to persistent heavy rainfall in tropical regions.

  17. 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.

  18. Mechanisms underlying prorenin actions on hypothalamic neurons implicated in cardiometabolic control

    Directory of Open Access Journals (Sweden)

    Soledad Pitra

    2016-10-01

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

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

    NARCIS (Netherlands)

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

    2013-01-01

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

  20. The Mediated MIMIC Model for Understanding the Underlying Mechanism of DIF

    Science.gov (United States)

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

    2016-01-01

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

  1. Deformation Microstructures and Creep Mechanisms in Advanced ZR-Based Cladding Under Biazal Loading

    Energy Technology Data Exchange (ETDEWEB)

    K. Linga (KL) Murty

    2008-08-11

    Investigate creep behavior of Zr-based cladding tubes with attention to basic creep mechanisms and transitions in them at low stresses and/or temperatures and study the dislocation microstructures of deformed samples for correlation with the underlying micromechanism of creep

  2. Cementogenesis is inhibited under a mechanical static compressive force via Piezo1.

    Science.gov (United States)

    Zhang, Ying-Ying; Huang, Yi-Ping; Zhao, Hua-Xiang; Zhang, Ting; Chen, Feng; Liu, Yan

    2017-07-01

    To investigate whether Piezo1, a mechanotransduction gene mediates the cementogenic activity of cementoblasts under a static mechanical compressive force. Murine cementoblasts (OCCM-30) were exposed to a 2.0 g/cm 2 static compressive force for 3, 6, 12, and 24 hours. Then the expression profile of Piezo1 and the cementogenic activity markers osteoprotegerin (Opg), osteopontin (Opn), osteocalcin (Oc), and protein tyrosine phosphataselike member A (Ptpla) were analyzed. Opg, Opn, Oc, and Ptpla expression was further measured after using siRNA to knock down Piezo1. Real-time PCR, Western blot, and cell proliferation assays were performed according to standard procedures. After mechanical stimulation, cell morphology and proliferation did not change significantly. The expression of Piezo1, Opg, Opn, Oc, and Ptpla was significantly decreased, with a high positive correlation between Opg and Piezo1 expression. After Piezo1 knockdown, the expression of Opg, Opn, Oc, and Ptpla was further decreased under mechanical stimulation. Cementogenic activity was inhibited in OCCM-30 cells under static mechanical force, a process that was partially mediated by the decrease of Piezo1. This study provides a new viewpoint of the pathogenesis mechanism of orthodontically induced root resorption and repair.

  3. Mechanisms underlying skeletal muscle insulin resistance induced by fatty acids: importance of the mitochondrial function

    Directory of Open Access Journals (Sweden)

    Martins Amanda R

    2012-02-01

    Full Text Available Abstract Insulin resistance condition is associated to the development of several syndromes, such as obesity, type 2 diabetes mellitus and metabolic syndrome. Although the factors linking insulin resistance to these syndromes are not precisely defined yet, evidence suggests that the elevated plasma free fatty acid (FFA level plays an important role in the development of skeletal muscle insulin resistance. Accordantly, in vivo and in vitro exposure of skeletal muscle and myocytes to physiological concentrations of saturated fatty acids is associated with insulin resistance condition. Several mechanisms have been postulated to account for fatty acids-induced muscle insulin resistance, including Randle cycle, oxidative stress, inflammation and mitochondrial dysfunction. Here we reviewed experimental evidence supporting the involvement of each of these propositions in the development of skeletal muscle insulin resistance induced by saturated fatty acids and propose an integrative model placing mitochondrial dysfunction as an important and common factor to the other mechanisms.

  4. Dissecting the molecular mechanism underlying the intimate relationship between cellulose microfibrils and cortical microtubules

    Directory of Open Access Journals (Sweden)

    Lei eLei

    2014-03-01

    Full Text Available A central question in plant cell development is how the cell wall determines directional cell expansion and therefore the final shape of the cell. As the major load-bearing component of the cell wall, cellulose microfibrils are laid down transversely to the axis of elongation, thus forming a spring-like structure that reinforces the cell laterally and while favoring longitudinal expansion in most growing cells. Mounting evidence suggests that cortical microtubules organize the deposition of cellulose microfibrils, but the precise molecular mechanisms linking microtubules to cellulose organization have remained unclear until the recent discovery of CSI1, a linker protein between the cortical microtubules and the cellulose biosynthesizing machinery. In this review, we will focus on the intimate relationship between cellulose microfibrils and cortical microtubules, in particular, we will discuss microtubule arrangement and cell wall architecture, the linkage between cellulose synthase complexes and microtubules, and the feedback mechanisms between cell wall and microtubules.

  5. Self-disgust as a potential mechanism underlying the association between PTSD and suicide risk.

    Science.gov (United States)

    Brake, C Alex; Rojas, Sasha M; Badour, Christal L; Dutton, Courtney E; Feldner, Matthew T

    2017-04-01

    Suicide risk is highly prevalent among individuals with posttraumatic stress disorder (PTSD). Self-disgust, defined as disgust directed internally and comprised of disgust with oneself (disgusting self) and with one's behaviors (disgusting ways), may impact this increased risk. The present study examined self-disgust as a putative mechanism linking PTSD symptoms with suicide risk. A sample of 347 trauma-exposed undergraduates completed measures of PTSD symptoms, suicide risk, self-disgust, and depressive symptoms. Controlling for depressive symptoms, a process model indicated PTSD symptoms were positively linked to suicide risk via increased disgusting self but not disgusting ways. Process models examining individual PTSD symptom clusters revealed positive, indirect links between all PTSD symptom clusters except alterations in arousal and reactivity and suicide risk via disgusting self. These findings expand on growing literature documenting the importance of self-disgust in trauma-related pathology by identifying connections with suicide risk. Future directions and clinical considerations are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Linking valve closure behavior and sodium transport mechanism in freshwater clam Corbicula fluminea in response to copper

    Energy Technology Data Exchange (ETDEWEB)

    Liao, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)]. E-mail: cmliao@ntu.edu.tw; Lin, C.-M. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Jou, L.-J. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China); Department of Biomechatronic Engineering, National Ilan University, Ilan, Taiwan 260 (China); Chiang, K.-C. [Department of Bioenvironmental Systems Engineering, National Taiwan University, 1, Sec. 4, Roosevelt Road, Taipei, Taiwan 10617 (China)

    2007-06-15

    The purpose of this study is to develop a mechanistic model to describe a conceptually new 'flux-biological response' approach based on biotic ligand model (BLM) and Michaelis-Menten (M-M) kinetics to allow the linkage between valve closure behavior and sodium (Na) transport mechanism in freshwater clam Corbicula fluminea in response to waterborne copper (Cu). We test the proposed model against published data regarding Na uptake kinetics in rainbow trout and Na uptake profile in C. fluminea, confirming that the predictive model is robust. Here, we show that the predicted M-M maximum Cu internalization flux in C. fluminea is 0.369 {mu}mol g{sup -1} h{sup -1} with a half-saturation affinity constant of 7.87 x 10{sup -3} {mu}M. Dynamics of Na uptake and valve closure daily rhythm driven by external Cu can also be predicted simultaneously. We suggest that this 'Na transport-valve closure behavior' approach might provide the basis of a future design of biomonitoring tool. - A new flux-biological response model can link valve closure and sodium transport mechanisms in freshwater clam in response to copper.

  7. Ultra-high mechanical properties of porous composites based on regenerated cellulose and cross-linked poly(ethylene glycol).

    Science.gov (United States)

    Teng, Jian; Yang, Biao; Zhang, Liang-Qing; Lin, Sheng-Qiang; Xu, Ling; Zhong, Gan-Ji; Tang, Jian-Hua; Li, Zhong-Ming

    2018-01-01

    The ultra-high mechanical, biocompatible and biodegradable porous regenerated cellulose/poly(ethylene glycol) (RC/PEG) composites with double network structure were fabricated via an simple method to dissolve cellulose followed by UV irradiation. The porous structure of RC/PEG was sensitively altered by PEG contents, which led to the porous structure morphology transition from 3D fibrillar network to close-grained sheet-like-network with the loading of cross-linked PEG. The porous RC/PEG showed excellent mechanical properties, i.e., the compressive strength can reach 33 times higher than that of neat RC (0.07MPa) at the compressive strain of 30%. Porous RC/PEG also displayed outstanding properties with openly porous structure and structural stabilization. Besides, porous RC/PEG exhibited good water absorbency, which the water absorbency ratio at equilibrium state was 83% higher than that of porous RC. This work provides an environmentally friendly and simple pathway to prepare non-toxic and biocompatible porous regenerated cellulose-based composites with high strength, structural stabilization and good water absorbency, which could be useful for packaging, biomedical applications, sewage purification, etc. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Large Deflections Mechanical Analysis of a Suspended Single-Wall Carbon Nanotube under Thermoelectrical Loading

    Directory of Open Access Journals (Sweden)

    Assaf Ya'akobovitz

    2011-01-01

    Full Text Available Following the recent progress in integrating single-wall carbon nanotubes (SWCNTs into silicon-based micro-electromechanical systems (MEMS, new modeling tools are needed to predict their behavior under different loads, including thermal, electrical and mechanical. In the present study, the mechanical behavior of SWCNTs under thermoelectrical loading is analyzed using a large deflection geometrically nonlinear string model. The effect of the resistive heating was found to have a substantial influence on the SWCNTs behavior, including significant enhancement of the strain (up to the millistrains range and buckling due to the thermal expansion. The effect of local buckling sites was also studied and was found to enhance the local strain. The theoretical and numerical results obtained in the present study demonstrate the importance of resistive heating in the analysis of SWCNTs and provide an additional insight into the unique mechanics of suspended SWCNTs.

  9. Intercomparison of chemical mechanisms for air quality policy formulation and assessment under North American conditions.

    Science.gov (United States)

    Derwent, Richard

    2017-07-01

    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

  10. The cytotoxicity of the α1-adrenoceptor antagonist prazosin is linked to an endocytotic mechanism equivalent to transport-P

    International Nuclear Information System (INIS)

    Fuchs, Robert; Stracke, Anika; Ebner, Nadine; Zeller, Christian Wolfgang; Raninger, Anna Maria; Schittmayer, Matthias; Kueznik, Tatjana; Absenger-Novak, Markus; Birner-Gruenberger, Ruth

    2015-01-01

    Since the α1-adrenergic antagonist prazosin (PRZ) was introduced into medicine as a treatment for hypertension and benign prostate hyperplasia, several studies have shown that PRZ induces apoptosis in various cell types and interferes with endocytotic trafficking. Because PRZ is also able to induce apoptosis in malignant cells, its cytotoxicity is a focus of interest in cancer research. Besides inducing apoptosis, PRZ was shown to serve as a substrate for an amine uptake mechanism originally discovered in neurones called transport-P. In line with our hypothesis that transport-P is an endocytotic mechanism also present in non-neuronal tissue and linked to the cytotoxicity of PRZ, we tested the uptake of QAPB, a fluorescent derivative of PRZ, in cancer cell lines in the presence of inhibitors of transport-P and endocytosis. Early endosomes and lysosomes were visualised by expression of RAB5-RFP and LAMP1-RFP, respectively; growth and viability of cells in the presence of PRZ and uptake inhibitors were also tested. Cancer cells showed co-localisation of QAPB with RAB5 and LAMP1 positive vesicles as well as tubulation of lysosomes. The uptake of QAPB was sensitive to transport-P inhibitors bafilomycin A1 (inhibits v-ATPase) and the antidepressant desipramine. Endocytosis inhibitors pitstop ® 2 (general inhibitor of endocytosis), dynasore (dynamin inhibitor) and methyl-β-cyclodextrin (cholesterol chelator) inhibited the uptake of QAPB. Bafilomycin A1 and methyl-β-cyclodextrin but not desipramine were able to preserve growth and viability of cells in the presence of PRZ. In summary, we confirmed the hypothesis that the cellular uptake of QAPB/PRZ represents an endocytotic mechanism equivalent to transport-P. Endocytosis of QAPB/PRZ depends on a proton gradient, dynamin and cholesterol, and results in reorganisation of the LAMP1 positive endolysosomal system. Finally, the link seen between the cellular uptake of PRZ and cell death implies a still unknown pro

  11. [Pathophysiology of neuropathic pain: molecular mechanisms underlying central sensitization in the dorsal horn in neuropathic pain].

    Science.gov (United States)

    Yamanaka, Hiroki; Noguchi, Koichi

    2012-11-01

    Neuropathic pain syndromes are clinically characterized by spontaneous pain and evoked pain (hyperalgesia and allodynia). The optimal treatment approach for neuropathic pain is still under development because of the complex pathological mechanisms underlying this type of pain. The spinal cord is an important gateway thorough which peripheral pain signals are transmitted to the brain, and sensitization of the spinal neurons is one of the important mechanisms underlying neuropathic pain. Central sensitization represents enhancement of the function of neuronal circuits in nociceptive pathways and is a manifestation of the remarkable plasticity of the somatosensory nervous system after nerve injury. This review highlights the pathological features of central sensitization, which develops because of (1) injury-induced abnormal inputs from primary afferents, (2) increase in the excitability of dorsal horn neurons, and (3) activated glial cell-derived signals.

  12. Capturing the Energy Absorbing Mechanisms of Composite Structures under Crash Loading

    Science.gov (United States)

    Wade, Bonnie

    As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crashworthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crashworthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of

  13. Review of the damage mechanism in wind turbine gearbox bearings under rolling contact fatigue

    Science.gov (United States)

    Su, Yun-Shuai; Yu, Shu-Rong; Li, Shu-Xin; He, Yan-Ni

    2017-12-01

    Wind turbine gearbox bearings fail with the service life is much shorter than the designed life. Gearbox bearings are subjected to rolling contact fatigue (RCF) and they are observed to fail due to axial cracking, surface flaking, and the formation of white etching areas (WEAs). The current study reviewed these three typical failure modes. The underlying dominant mechanisms were discussed with emphasis on the formation mechanism of WEAs. Although numerous studies have been carried out, the formation of WEAs remains unclear. The prevailing mechanism of the rubbing of crack faces that generates WEAs was questioned by the authors. WEAs were compared with adiabatic shear bands (ASBs) generated in the high strain rate deformation in terms of microstructural compositions, grain refinement, and formation mechanism. Results indicate that a number of similarities exist between them. However, substantial evidence is required to verify whether or not WEAs and ASBs are the same matters.

  14. Transformational Leadership and Organizational Citizenship Behavior: A Meta-Analytic Test of Underlying Mechanisms.

    Science.gov (United States)

    Nohe, Christoph; Hertel, Guido

    2017-01-01

    Based on social exchange theory, we examined and contrasted attitudinal mediators (affective organizational commitment, job satisfaction) and relational mediators (trust in leader, leader-member exchange; LMX) of the positive relationship between transformational leadership and organizational citizenship behavior (OCB). Hypotheses were tested using meta-analytic path models with correlations from published meta-analyses (761 samples with 227,419 individuals overall). When testing single-mediator models, results supported our expectations that each of the mediators explained the relationship between transformational leadership and OCB. When testing a multi-mediator model, LMX was the strongest mediator. When testing a model with a latent attitudinal mechanism and a latent relational mechanism, the relational mechanism was the stronger mediator of the relationship between transformational leadership and OCB. Our findings help to better understand the underlying mechanisms of the relationship between transformational leadership and OCB.

  15. PRICING ELECTRIC POWER UNDER A HYBRID WHOLESALE MECHANISM: EVALUATING THE TURKISH ELECTRICITY MARKET

    Directory of Open Access Journals (Sweden)

    Hatice Karahan

    2013-01-01

    Full Text Available During the restructuring process, Turkish electricity sector has gone through significant changes both in wholesale and retail markets. In this framework, the Market Financial Settlement Mechanism established for handling market imbalances has become a spot market in time. So, it can be claimed that the wholesale electricity market in Turkey is a hybrid mechanism composed of bilateral contracts and the balancing market. On the other hand, the main target of liberalization program is providing consumers with affordable electric power. Hence, this study attempts to explore the link between retail tariffs for ineligible consumers and prices in the two wholesale mechanisms, in the period after the launch of the day-ahead market. Findings suggest that regulated wholesale prices are more effective in the determination of end-user prices, whereas unregulated ones might have a price reduction effect in case the free market dominates. However, the volatility in spot market prices implies that the sector would better continue with the hybrid mechanism for quite some time.

  16. Muscle co-contraction modulates damping and joint stability in a three-link bio mechanical limb

    Directory of Open Access Journals (Sweden)

    Stewart eHeitmann

    2012-01-01

    Full Text Available Computational models of neuromotor control require forward models of limb movement that can replicate the natural relationships between muscle activation and joint dynamics without the burdens of excessive anatomical detail. We present a model of a three-link biomechanical limb that emphasizes the dynamics of limb movement within a simplified two-dimensional framework. Muscle co-contraction effects were incorporated into the model by flanking each joint with a pair of antagonist muscles that may be activated independently. Muscle co-contraction is known to alter the damping and stiffness of limb joints without altering net joint torque. Idealized muscle actuators were implemented using the Voigt muscle model which incorporates the parallel elasticity of muscle and tendon but omits series elasticity. The natural force-length-velocity relationships of contractile muscle tissue were incorporated into the actuators using ideal mathematical forms. Numerical stability analysis confirmed that co-contraction of these simplified actuators increased damping in the biomechanical limb consistent with observations of human motor control. Dynamic changes in joint stiffness were excluded by the omission of series elasticity. The analysis also revealed the unexpected finding that distinct stable (bistable equilibrium positions can co-exist under identical levels of muscle co-contraction. We map the conditions under which bistability arises and prove analytically that monostability (equifinality is guaranteed when the antagonist muscles are identical. Lastly we verify these analytic findings in the full biomechanical limb model.

  17. 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.

  18. Cost-utility analysis of antiviral use under pandemic influenza using a novel approach - linking pharmacology, epidemiology and heath economics.

    Science.gov (United States)

    Wu, D B C; Chaiyakunapruk, N; Pratoomsoot, C; Lee, K K C; Chong, H Y; Nelson, R E; Smith, P F; Kirkpatrick, C M; Kamal, M A; Nieforth, K; Dall, G; Toovey, S; Kong, D C M; Kamauu, A; Rayner, C R

    2018-03-01

    Simulation models are used widely in pharmacology, epidemiology and health economics (HEs). However, there have been no attempts to incorporate models from these disciplines into a single integrated model. Accordingly, we explored this linkage to evaluate the epidemiological and economic impact of oseltamivir dose optimisation in supporting pandemic influenza planning in the USA. An HE decision analytic model was linked to a pharmacokinetic/pharmacodynamics (PK/PD) - dynamic transmission model simulating the impact of pandemic influenza with low virulence and low transmissibility and, high virulence and high transmissibility. The cost-utility analysis was from the payer and societal perspectives, comparing oseltamivir 75 and 150 mg twice daily (BID) to no treatment over a 1-year time horizon. Model parameters were derived from published studies. Outcomes were measured as cost per quality-adjusted life year (QALY) gained. Sensitivity analyses were performed to examine the integrated model's robustness. Under both pandemic scenarios, compared to no treatment, the use of oseltamivir 75 or 150 mg BID led to a significant reduction of influenza episodes and influenza-related deaths, translating to substantial savings of QALYs. Overall drug costs were offset by the reduction of both direct and indirect costs, making these two interventions cost-saving from both perspectives. The results were sensitive to the proportion of inpatient presentation at the emergency visit and patients' quality of life. Integrating PK/PD-EPI/HE models is achievable. Whilst further refinement of this novel linkage model to more closely mimic the reality is needed, the current study has generated useful insights to support influenza pandemic planning.

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

    Science.gov (United States)

    Xu, Yuan; Dai, Feng

    2018-03-01

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

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

    Science.gov (United States)

    Peng, Zhang

    2018-03-01

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

  1. Mechanical and electronic properties of monolayer and bilayer phosphorene under uniaxial and isotropic strains.

    Science.gov (United States)

    Hu, Ting; Han, Yang; Dong, Jinming

    2014-11-14

    The mechanical and electronic properties of both the monolayer and bilayer phosphorenes under either isotropic or uniaxial strain have been systematically investigated using first-principles calculations. It is interesting to find that: 1) Under a large enough isotropic tensile strain, the monolayer phosphorene would lose its pucker structure and transform into a flat hexagonal plane, while two inner sublayers of the bilayer phosphorene could be bonded due to its interlayer distance contraction. 2) Under the uniaxial tensile strain along a zigzag direction, the pucker distance of each layer in the bilayer phosphorene can exhibit a specific negative Poisson's ratio. 3) The electronic properties of both the monolayer and bilayer phosphorenes are sensitive to the magnitude and direction of the applied strains. Their band gaps decrease more rapidly under isotropic compressive strain than under uniaxial strain. Also, their direct-indirect band gap transitions happen at the larger isotropic tensile strains compared with that under uniaxial strain. 4) Under the isotropic compressive strain, the bilayer phosphorene exhibits a transition from a direct-gap semiconductor to a metal. In contrast, the monolayer phosphorene initially has the direct-indirect transition and then transitions to a metal. However, under isotropic tensile strain, both the bilayer and monolayer phosphorene show the direct-indirect transition and, finally, the transition to a metal. Our numerical results may open new potential applications of phosphorene in nanoelectronics and nanomechanical devices by external isotropic strain or uniaxial strain along different directions.

  2. Asymmetric flexural behavior from bamboo's functionally graded hierarchical structure: underlying mechanisms.

    Science.gov (United States)

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

    2015-04-01

    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.

  3. Developmental pathways linking childhood temperament with antisocial behavior and substance use in adolescence: Explanatory mechanisms in the peer environment.

    Science.gov (United States)

    Buil, J Marieke; van Lier, Pol A C; Brendgen, Mara R; Koot, Hans M; Vitaro, Frank

    2017-06-01

    This study investigated 3 developmental pathways involving the peer environment that may explain how certain temperamental dispositions in childhood may become manifested in later antisocial behavior and substance use. A total of 411 (52% boys) Canadian children were followed annually from ages 6 to 15 years. The study tested whether the temperamental traits approach, negative reactivity and attention (assessed at ages 6-7 years), were associated with overt antisocial behavior, covert antisocial behavior and illicit substance use (assessed at ages 14-15 years), via poor social preference among peers, inflated social self-perception and antisocial behavior of peer-group affiliates (assessed throughout ages 8-13 years). Results indicated that negative reactivity was indirectly associated with overt antisocial behavior and substance use via poor social preference. Specifically, negative reactivity in earlier childhood predicted poor social preference in later childhood and early adolescence. This poor social standing among peers, in turn, predicted more engagement in overt antisocial behavior but less substance use in later adolescence. Over and above the influence of social preference, negative reactivity predicted engagement in all 3 outcomes via children's antisocial behavior in childhood and early adolescence. Inflated social self-perception and antisocial behavior of peer-group affiliates did not mediate the link between temperament and the outcomes under scrutiny. No sex differences in developmental pathways from temperament to the outcomes were found. To further our understanding of the developmental link between childhood temperament and later antisocial behavior and substance use, we need to recognize the role of peer environmental factors, specifically poor preference among peers. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  4. Oxidative Stress and Mitochondrial Activation as the Main Mechanisms Underlying Graphene Toxicity against Human Cancer Cells

    Directory of Open Access Journals (Sweden)

    Anna Jarosz

    2016-01-01

    Full Text Available Due to the development of nanotechnology graphene and graphene-based nanomaterials have attracted the most attention owing to their unique physical, chemical, and mechanical properties. Graphene can be applied in many fields among which biomedical applications especially diagnostics, cancer therapy, and drug delivery have been arousing a lot of interest. Therefore it is essential to understand better the graphene-cell interactions, especially toxicity and underlying mechanisms for proper use and development. This review presents the recent knowledge concerning graphene cytotoxicity and influence on different cancer cell lines.

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

    KAUST Repository

    Cheng, Yingchun

    2012-10-01

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

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

    Science.gov (United States)

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

    2012-05-01

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

  7. CISM course on mechanical behaviour of soils under environmentally induced cyclic loads

    CERN Document Server

    Wood, David; Mechanical Behaviour of Soils Under Environmentally Induced Cyclic Loads

    2012-01-01

    The book gives a comprehensive description of the mechanical response of soils (granular and cohesive materials) under cyclic loading. It provides the geotechnical engineer with the theoretical and analytical tools necessary for the evaluation of settlements developng with time under cyclic, einvironmentally idncued loads (such as wave motion, wind actions, water table level variation) and their consequences for the serviceability and durability of structures such as the shallow or deep foundations used in offshore engineering, caisson beakwaters, ballast and airport pavements and also to interpret monitoring data, obtained from both natural and artificial slopes and earth embankments, for the purposes of risk assessment and mitigation.

  8. The influence of simulated aging on the mechanical properties of orthodontic elastomeric chains without an intermodular link.

    Science.gov (United States)

    Dittmer, Marc Philipp; Demling, Anton Phillip; Borchers, Lothar; Stiesch, Meike; Kohorst, Philipp; Schwestka-Polly, Rainer

    2012-08-01

    Orthodontic elastomeric chains are a main component in orthodontic therapy with fixed vestibular or lingual appliances. The objective of this study was to investigate the influence of artificial aging on the mechanical properties of orthodontic elastomeric chains (power chains, PCs) without an intermodular link using a test setup according to DIN EN ISO 21606:2007. In this study, 11 types of PCs supplied by seven manufacturers were investigated. Four groups with 10 specimens each were randomly generated for each type. Samples were separately mounted in a universal testing machine and extended by 300% (four times their initial length) at a crosshead rate of 100 mm/min and were held at this position for five seconds. The chain length was then reduced to three times the initial length (extension by 200%) and kept for 30 s. Then, within the control group (t = 0) and the force Fmin was recorded before extension until failure was performed and force (Fmax) and length (Lmax) at failure were determined. After prestretching, specimens of the three other groups were stored in water at 37°C with its three times initial length for one day (t = 1), 14 days (t = 2), and 28 days (t = 3), respectively. The specimens were then placed in the universal testing machine and the residual force (Fmin) measured, so as to subsequently extend them until failure at Fmax and Lmax. Data were statistically analyzed by one-way analysis of variance; the level of significance was set at p = 0.05. Statistical analysis revealed significant differences in Fmax, Fmin, and Lmax in each group (t = 0 to t = 3) between the various manufacturers (p < 0.001). Moreover, artificial aging significantly influenced Fmax, Fmin, and Lmax (p < 0.001). The orthodontist should consider both the mechanical properties of PCs and the duration of these appliances' application when treating patients. Artificial aging had a significant influence on the parameters we determined (p <0.001).

  9. Scientific conception on mechanisms of calcium homeostasis disorders under low dose effect of ionizing radiation

    International Nuclear Information System (INIS)

    Abylaev, Zh.A.; Dospolova, Zh.G.

    1997-01-01

    Scientific conception of probable consequences of calcium homeostasis disorders in personals, exposed to low dose effect of ionizing radiation has been developed. Principle positions of the conception is that pathologic processes development have different ways of conducting. During predominance of low doses of external gamma-radiation there is leading pathologic mechanism (mechanism 1) of disorder neuroendocrine regulation of both the calcium and the phosphor. In this case sicks have disorders of both the vegetative tonus and the endocrine status. Under internal irradiation (mechanism 2) there is disfunction of organs and systems (bore changes and disorders of hormone status). These changes are considered as consequence of negative action on organism of incorporated long-living radionuclides. Radio-toxic factors action (mechanism 3) provokes the excess of hormones, which acting on bone tissue and could be cause of steroid osteoporosis. Influence of chronic stress factor (mechanism 4) enlarges and burden action on organism of low radiation doses. It is emphasized, that decisive role in development of pathologic processes has mechanism of disturbance of neuroendocrine regulation of calcium exchange

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

    Science.gov (United States)

    Ru, Yanyun; Yong, Huadong; Zhou, Youhe

    2016-10-01

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

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

    Science.gov (United States)

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

    2016-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Andrew P. Smith

    2012-03-01

    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.

  14. Study of high density polyethylene under UV irradiation or mechanical stress by fluorescence spectroscopy

    International Nuclear Information System (INIS)

    Douminge, L.

    2010-05-01

    Due to their diversity and their wide range of applications, polymers have emerged in our environment. For technical applications, these materials can be exposed to aggressive environment leading to an alteration of their properties. The effects of this degradation are linked to the concept of life duration, corresponding to the time required for a property to reach a threshold below which the material becomes unusable. Monitoring the ageing of polymer materials constitute a major challenge. Fluorescence spectroscopy is a technique able to provide accurate information concerning this issue. In this study, emphasis was placed on the use of fluorescence spectroscopy to study the phenomena involved in either the UV radiation or mechanical stresses of a polymer. In the case of high density polyethylene, the lack of intrinsic fluorescent signal leads to the use of a dye. This dye gives a fluorescent response depending on its microenvironment. All modifications in the macromolecular chain generate a shift of the fluorescent peak. This work can be dissociated in two major parts, on one hand the influence of UV aging on the fluorescent response and in another hand the influence of mechanical stresses. In the first part, complementary analyses like FTIR or DSC are used to correlate fluorescent results with known photo degradation mechanisms. The results show the great sensibility of the technique to the microstructural rearrangement in the polymer. In the second part, the dependence between the stress and the fluorescence emission gives opportunity to evaluate internal stresses in the material during cyclic solicitations. (author)

  15. Comparative investigation of thermal and mechanical properties of cross-linked epoxy polymers with different curing agents by molecular dynamics simulation.

    Science.gov (United States)

    Jeyranpour, F; Alahyarizadeh, Gh; Arab, B

    2015-11-01

    Molecular dynamics (MD) simulations were carried out to predict the thermal and mechanical properties of the cross-linked epoxy system composed of DGEBA resin and the curing agent TETA. To investigate the effects of curing agents, a comprehensive and comparative study was also performed on the thermal and mechanical properties of DGEBA/TETA and DGEBA/DETDA epoxy systems such as density, glass transition temperature (Tg), coefficient of thermal expansion (CTE) and elastic properties of different cross-linking densities and different temperatures. The results indicated that the glass transition temperature of DGEBA/TETA system calculated through density-temperature data, ∼ 385-395 °K, for the epoxy system with the cross-linking density of 62.5% has a better agreement with the experimental value (Tg, ∼ 400 °K) in comparison to the value calculated through the variation of cell volume in terms of temperature, 430-440 °K. They also indicated that CTE related parameters and elastic properties including Young, Bulk, and shear's moduli, and Poisson's ratio have a relative agreement with the experimental results. Comparison between the thermal and mechanical properties of epoxy systems of DGEBA/TETA and DGEBA/DETDA showed that the DGEBA/DETDA has a higher Tg in all cross linking densities than that of DGEBA/TETA, while higher mechanical properties was observed in the case of DGEBA/TETA in almost all cross linking densities. Copyright © 2015 Elsevier Inc. All rights reserved.

  16. Physiological mechanisms contributing to increased water-use efficiency in winter wheat under organic fertilization.

    Science.gov (United States)

    Wang, Linlin; Wang, Shiwen; Chen, Wei; Li, Hongbing; Deng, Xiping

    2017-01-01

    Improving the efficiency of resource utilization has received increasing research attention in recent years. In this study, we explored the potential physiological mechanisms underlying improved grain yield and water-use efficiency of winter wheat (Triticum aestivum L.) following organic fertilizer application. Two wheat cultivars, ChangHan58 (CH58) and XiNong9871 (XN9871), were grown under the same nitrogen (N) fertilizer rate (urea-N, CK; and manure plus urea-N, M) and under two watering regimes (WW, well-watered; and WS, water stress) imposed after anthesis. The M fertilizer treatment had a higher Pn and lower gs and Tr than CK under both water conditions, in particular, it significantly increased WRC and Ψw, and decreased EWLR and MDA under WS. Also, the M treatment increased post-anthesis N uptake by 81.4 and 16.4% under WS and WW, thus increasing post-anthesis photosynthetic capacity and delaying leaf senescence. Consequently, the M treatment increased post-anthesis DM accumulation under WS and WW by 51.5 and 29.6%, WUEB by 44.5 and 50.9%, grain number per plant by 11.5 and 12.2% and 1000-grain weight by 7.3 and 3.6%, respectively, compared with CK. The grain yield under M treatment increased by 23 and 15%, and water use efficiency (WUEg) by 25 and 23%, respectively. The increased WUE under organic fertilizer treatment was due to elevated photosynthesis and decreased Tr and gs. Our results suggest that the organic fertilizer treatment enabled plants to use water more efficiently under drought stress.

  17. Characterization of Mechanical Properties of MgB$_2$ Conductor for the Superconducting Link Project at CERN

    CERN Document Server

    Sugano, M; Bartova, B; Bjoerstad, R; Scheuerlein, C; Grasso, G

    2015-01-01

    In the framework of high luminosity upgrade of Large Hadron Collider at CERN, superconducting links are being developed. MgB2 wire is a candidate conductor for use in high-current cables. Mechanical properties of this material are of key importance for the definition of the cable design and operating conditions. In this study, we evaluated the Young's modulus of MgB2 filaments extracted from ex situ processed composite wires. The wires were produced in unit lengths of about 1 km and used in high-current cables. Single fiber tensile test was carried out on filaments composed of MgB2, Nb barrier, and Nb-Ni reaction layer. From the unloading modulus of filament specimens measured with different gauge lengths, the Young's modulus of composite filaments extracted from two different strands was determined to be 114 and 122 GPa at room temperature, respectively. By using the rule-of-mixture, the Young's modulus of MgB2 was estimated to be lower than that reported for highly dense MgB2 bulks. The reason for such diff...

  18. Beneficial biofilms in marine aquaculture? Linking points of biofilm formation mechanisms in Pseudomonas aeruginosa and Pseudoalteromonas species

    Directory of Open Access Journals (Sweden)

    Wiebke Wesseling

    2015-07-01

    Full Text Available For marine aquaculture it is suggested that a specific substrate coated with a beneficial biofilm could prevent fish egg clutches from pathogenic infestations and improve the water quality and health of adult fish while, at the same time, minimising the need for the application of antibiotics. In marine biotopes, the habitat of Pseudoalteromonas species (a strain with suggested beneficial properties, biofilms are mostly discussed in the context of fouling processes. Hence research focuses on unravelling the mechanisms of biofilm formation aiming to prevent formation or to destroy existing biofilms. Initially in this review, particular components of biofilm formation in Pseudomonas aeruginosa, a gram-negative model organism that is responsible for nosocomial infections and considered as a food spoiling agent, are described (extracellular appendages, role of matrix components, cell-cell signalling to get an advanced understanding of biofilm formation. The aim of this treatise is to seek linking points for biofilm formation of P. aeruginosa and Pseudoalteromonas sp., respectively. Furthermore, approaches are discussed for how biofilm formation can be realized to improve fish (larvae rearing by species of the genus Pseudoalteromonas.

  19. Electron and excitation energy transfers in covalently linked donor-acceptor dyads: mechanisms and dynamics revealed using quantum chemistry.

    Science.gov (United States)

    Cupellini, Lorenzo; Giannini, Samuele; Mennucci, Benedetta

    2017-12-20

    Photoinduced electron transfer (ET), hole transfer (HT), charge recombination (CR) and energy transfer (EET) are fundamental mechanisms, which occur in both natural and artificial light harvesting systems. Here, we present a computational strategy which determines ET, HT, CR and EET rates in a consistent way and merges them in a kinetic model to reproduce the net excited state dynamics. The effects of the solvent are included in all steps of the calculations making the present strategy a useful tool for a rational design of charge and energy transfer processes in complex systems. An application to covalently linked zinc and free-base porphyrin-naphthalenediimide dyads is presented. For each of the two systems, ultrafast optical spectroscopy experiments have shown a specific photophysics with different processes taking place simultaneously. The model reveals that such a diversity is mainly due to the different relative stability of the charge-separated state, while the electronic couplings for charge and energy transfer processes are quite similar in the two dyads.

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  1. Adverse Effects from Clenbuterol and Ractopamine on Nematode Caenorhabditis elegans and the Underlying Mechanism

    OpenAIRE

    Zhuang, Ziheng; Zhao, Yunli; Wu, Qiuli; Li, Min; Liu, Haicui; Sun, Lingmei; Gao, Wei; Wang, Dayong

    2014-01-01

    In the present study, we used Caenorhabditis elegans assay system to investigate in vivo toxicity from clentuberol and ractopamine and the possible underlying mechanism. Both acute and prolonged exposures to clentuberol or ractopamine decreased brood size and locomotion behavior, and induced intestinal autofluorescence and reactive oxygen species (ROS) production. Although acute exposure to the examined concentrations of clentuberol or ractopamine did not induce lethality, prolonged exposure ...

  2. Optimal Contract Design for Cooperative Relay Incentive Mechanism under Moral Hazard

    OpenAIRE

    Zhao, Nan; Wu, Minghu; Xiong, Wei; Liu, Cong

    2015-01-01

    Cooperative relay can effectively improve spectrum efficiency by exploiting the spatial diversity in the wireless networks. However, wireless nodes may acquire different network information with various users’ location and mobility, channels’ conditions, and other factors, which results in asymmetric information between the source and the relay nodes (RNs). In this paper, the relay incentive mechanism between relay nodes and the source is investigated under the asymmetric information. By mode...

  3. Mechanisms underlying reductant-induced reactive oxygen species formation by anticancer copper(II) compounds

    OpenAIRE

    Kowol, Christian R.; Heffeter, Petra; Miklos, Walter; Gille, Lars; Trondl, Robert; Cappellacci, Loredana; Berger, Walter; Keppler, Bernhard K.

    2011-01-01

    Intracellular generation of reactive oxygen species (ROS) via thiol-mediated reduction of copper(II) to copper(I) has been assumed as the major mechanism underlying the anticancer activity of copper(II) complexes. The aim of this study was to compare the anticancer potential of copper(II) complexes of Triapine (3-amino-pyridine-2-carboxaldehyde thiosemicarbazone; currently in phase II clinical trials) and its terminally dimethylated derivative with that of 2-formylpyridine thiosemicarbazone a...

  4. A fracture mechanics study of tungsten failure under high heat flux loads

    International Nuclear Information System (INIS)

    Li, Muyuan

    2015-01-01

    The performance of fusion devices is highly dependent on plasma-facing components. Tungsten is the most promising candidate material for armors in plasma-facing components in ITER and DEMO. However, the brittleness of tungsten below the ductile-to-brittle transition temperature is very critical to the reliability of plasma-facing components. In this work, thermo-mechanical and fracture behaviors of tungsten are predicted numerically under fusion relevant thermal loadings.

  5. The effects and underlying mechanisms of mirror therapy – literature review

    OpenAIRE

    Urška Puh; Sonja Hlebš

    2013-01-01

    Background: Mirror therapy is a relatively new therapeutic modality, where movement of the unaffected limb is used to facilitate performance of the affected limb. Literature review of clinical studies regarding the effectiveness of mirror therapy in different groups of patients was performed. The review focussed on randomised controlled trials and studies, which explore the underlying mechanisms of mirror therapy. Conclusions: The majority of randomised controlled ...

  6. The chemical and mechanical behaviors of polymer / reactive metal systems under high strain rates

    Science.gov (United States)

    Shen, Yubin

    As one category of energetic materials, impact-initiated reactive materials are able to release a high amount of stored chemical energy under high strain rate impact loading, and are used extensively in civil and military applications. In general, polymers are introduced as binder materials to trap the reactive metal powders inside, and also act as an oxidizing agent for the metal ingredient. Since critical attention has been paid on the metal / metal reaction, only a few types of polymer / reactive metal interactions have been studied in the literature. With the higher requirement of materials resistant to different thermal and mechanical environments, the understanding and characterization of polymer / reactive metal interactions are in great demand. In this study, PTFE (Polytetrafluoroethylene) 7A / Ti (Titanium) composites were studied under high strain rates by utilizing the Taylor impact and SHPB tests. Taylor impact tests with different impact velocities, sample dimensions and sample configurations were conducted on the composite, equipped with a high-speed camera for tracking transient images during the sudden process. SHPB and Instron tests were carried out to obtain the stress vs. strain curves of the composite under a wide range of strain rates, the result of which were also utilized for fitting the constitutive relations of the composite based on the modified Johnson-Cook strength model. Thermal analyses by DTA tests under different flow rates accompanied with XRD identification were conducted to study the reaction mechanism between PTFE 7A and Ti when only heat was provided. Numerical simulations on Taylor impact tests and microstructural deformations were also performed to validate the constitutive model built for the composite system, and to investigate the possible reaction mechanism between two components. The results obtained from the high strain rate tests, thermal analyses and numerical simulations were combined to provide a systematic study on

  7. Modulating Conscious Movement Intention by Noninvasive Brain Stimulation and the Underlying Neural Mechanisms

    OpenAIRE

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

    2015-01-01

    Conscious intention is a fundamental aspect of the human experience. Despite long-standing interest in the basis and implications of intention, its underlying neurobiological mechanisms remain poorly understood. Using high-definition transcranial DC stimulation (tDCS), we observed that enhancing spontaneous neuronal excitability in both the angular gyrus and the primary motor cortex caused the reported time of conscious movement intention to be ∼60–70 ms earlier. Slow brain waves recorded ∼2–...

  8. Diffuse and Focal Brain Injury in a Large Animal Model of PTE: Mechanisms Underlying Epileptogenesis

    Science.gov (United States)

    2017-10-01

    Conclusions: A) Contusion injury validation and neuropathology B) Grid electrode development and testing C) Wireless Large Animal Custom Enclosure...In addition, we will test the NF-L and GFAP immunoassay to begin quantification of this biomarkers, as well as collecting serum from the animals pre...AWARD NUMBER: W81XWH-16-1-0675 TITLE: Diffuse and Focal Brain Injury in a Large Animal Model of PTE: Mechanisms Underlying Epileptogenesis

  9. Activation and Inhibition of Sodium-Hydrogen Exchanger Is a Mechanism That Links the Pathophysiology and Treatment of Diabetes Mellitus With That of Heart Failure.

    Science.gov (United States)

    Packer, Milton

    2017-10-17

    The mechanisms underlying the progression of diabetes mellitus and heart failure are closely intertwined, such that worsening of one condition is frequently accompanied by worsening of the other; the degree of clinical acceleration is marked when the 2 coexist. Activation of the sodium-hydrogen exchanger in the heart and vasculature (NHE1 isoform) and the kidneys (NHE3 isoform) may serve as a common mechanism that links both disorders and may underlie their interplay. Insulin insensitivity and adipokine abnormalities (the hallmarks of type 2 diabetes mellitus) are characteristic features of heart failure; conversely, neurohormonal systems activated in heart failure (norepinephrine, angiotensin II, aldosterone, and neprilysin) impair insulin sensitivity and contribute to microvascular disease in diabetes mellitus. Each of these neurohormonal derangements may act through increased activity of both NHE1 and NHE3. Drugs used to treat diabetes mellitus may favorably affect the pathophysiological mechanisms of heart failure by inhibiting either or both NHE isoforms, and drugs used to treat heart failure may have beneficial effects on glucose tolerance and the complications of diabetes mellitus by interfering with the actions of NHE1 and NHE3. The efficacy of NHE inhibitors on the risk of cardiovascular events may be enhanced when heart failure and glucose intolerance coexist and may be attenuated when drugs with NHE inhibitory actions are given concomitantly. Therefore, the sodium-hydrogen exchanger may play a central role in the interplay of diabetes mellitus and heart failure, contribute to the physiological and clinical progression of both diseases, and explain certain drug-drug and drug-disease interactions that have been reported in large-scale randomized clinical trials. © 2017 American Heart Association, Inc.

  10. Different intra- and interspecific facilitation mechanisms between two Mediterranean trees under a climate change scenario.

    Science.gov (United States)

    Gimeno, Teresa E; Escudero, Adrián; Valladares, Fernando

    2015-01-01

    In harsh environments facilitation alleviates biotic and abiotic constraints on tree recruitment. Under ongoing drier climate change, we expect facilitation to increase as a driver of coexistence. However, this might not hold under extreme abiotic stress and when the outcome depends on the interaction with other drivers such as altered herbivore pressure due to land use change. We performed a field water-manipulation experiment to quantify the importance of facilitation in two coexisting Mediterranean trees (dominant Juniperus thurifera and coexisting Quercus ilex subsp. ballota) under a climate change scenario. Shifts in canopy dominance favouring Q. ilex could be based on the extension of heterospecific facilitation to the detriment of conspecific alleviation. We found that saplings of both species transplanted under the canopy of nurse trees had greater survival probability, growth and photochemical efficiency. Intra- and interspecific facilitation mechanisms differed: alleviation of abiotic stress benefited both species during summer and J. thurifera during winter, whereas browsing protection was relevant only for Q. ilex. Facilitation was greater under the dry treatment only for Q. ilex, which partially agreed with the predictions of the stress gradient hypothesis. We conclude that present rainfall availability limits neither J. thurifera nor Q. ilex establishment. Nevertheless, under current global change scenarios, imposing increasing abiotic stress together with altered herbivore browsing, nurse trees could differentially facilitate the establishment of Q. ilex due to species-specific traits, i.e. palatability; drought, heat and cold tolerance, underlying species differences in the facilitation mechanisms and eventually triggering a change from pure juniper woodlands to mixed formations.

  11. FInal Report: First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality

    Energy Technology Data Exchange (ETDEWEB)

    Aberg, Daniel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sadigh, Babak [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zhou, Fei [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2015-01-01

    This final report presents work carried out on the project “First Principles Modeling of Mechanisms Underlying Scintillator Non-Proportionality” at Lawrence Livermore National Laboratory during 2013-2015. The scope of the work was to further the physical understanding of the microscopic mechanisms behind scintillator nonproportionality that effectively limits the achievable detector resolution. Thereby, crucial quantitative data for these processes as input to large-scale simulation codes has been provided. In particular, this project was divided into three tasks: (i) Quantum mechanical rates of non-radiative quenching, (ii) The thermodynamics of point defects and dopants, and (iii) Formation and migration of self-trapped polarons. The progress and results of each of these subtasks are detailed.

  12. Potential neural mechanisms underlying the effectiveness of early intervention for children with autism spectrum disorder

    Science.gov (United States)

    Sullivan, Katherine; Stone, Wendy L.; Dawson, Geraldine

    2014-01-01

    Although evidence supports the efficacy of early intervention for improving outcomes for children with autism spectrum disorder (ASD), the mechanisms underlying their effectiveness remain poorly understood. This paper reviews the research literature on the neural bases of the early core deficits in ASD and proposes three key features of early intervention related to the neural mechanisms that may contribute to its effectiveness in improving deficit areas. These features include (1) the early onset of intensive intervention which capitalizes on the experience-expectant plasticity of the immature brain, (2) the use of treatment strategies that address core deficits in social motivation through an emphasis on positive social engagement and arousal modulation, and (3) promotion of complex neural networks and connectivity through thematic, multi-sensory and multi-domain teaching approaches. Understanding the mechanisms of effective early intervention will enable us to identify common or foundational active ingredients for promoting optimal outcomes in children with ASD. PMID:25108609

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

    Science.gov (United States)

    Hara, Yusuke

    2017-06-01

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

  14. Compressive damage mechanism of GFRP composites under off-axis loading: Experimental and numerical investigations

    DEFF Research Database (Denmark)

    Zhou, H.W.; Li, H.Y.; Gui, L.L.

    2013-01-01

    Experimental and computational studies of the microscale mechanisms of damage formation and evolution in unidirectional glass fiber reinforced polymer composites (GFRP) under axial and off-axis compressive loading are carried out. A series of compressive testing of the composites with different...... the angle between the fiber direction and the loading vector goes from 0° to 45° (by 2.3–2.6 times), and then slightly increases (when the angle approaches 80–90°). At the low angles between the fiber and the loading vector, fiber buckling and kinking are the main mechanisms of fiber failure....... With increasing the angle between the fiber and applied loading, failure of glass fibers is mainly controlled by shear cracking. For the computational analysis of the damage mechanisms, 3D multifiber unit cell models of GFRP composites and X-FEM approach to the fracture modeling were used. The computational...

  15. [Progress of researches on mechanism of acupuncture therapy underlying improvement of acute cerebral hemorrhage].

    Science.gov (United States)

    Wang, Fan; Wang, Hai-qiao; Dong, Gui-rong

    2011-04-01

    In the present paper, the authors review the progress of researches on the mechanism of acupuncture therapy underlying improvement of acute cerebral hemorrhage from experimental studies and research methods. The effects of acupuncture intervention mainly involve (1) lessening inflammatory reactions, (2) reducing impairment of free radicals and excitatory amino acids on cerebral neurons, (3) balancing release of vascular bioactive substances to increase regional cerebral blood flow, and (4) promoting repair and regeneration of the neural tissue, etc. In regard to the research methods, many new biological techniques such as biological molecular approaches, neuro-cellular chemical methods, reverse transcription-polymerase chain reaction (RT-PCR) or quantitative real time-PCR, situ hybridization, western blotting, electron microscope, etc., have been extensively applied to researches on the underlying mechanism of acupuncture therapy for cerebral infarction. In addition, the authors also pointed out that in spite of achieving some bigger progresses in experimental studies, most of the results basically reflect static, isolated and regional changes rather than dynamic and whole body changes. For this reason, more vivo research techniques and noninvasive research methods are highly recommended to be used in the future research on the underlying mechanisms of acupuncture therapy for acute cerebral ischemia.

  16. Psychogenic non-epileptic seizures: so-called psychiatric comorbidity and underlying defense mechanisms.

    Science.gov (United States)

    Beghi, Massimiliano; Negrini, Paola Beffa; Perin, Cecilia; Peroni, Federica; Magaudda, Adriana; Cerri, Cesare; Cornaggia, Cesare Maria

    2015-01-01

    In Diagnostic and Statistical Manual of Mental Disorders, fifth edition, psychogenic non-epileptic seizures (PNES) do not have a unique classification as they can be found within different categories: conversion, dissociative, and somatization disorders. The ICD-10, instead, considers PNES within dissociative disorders, merging the dissociative disorders and conversion disorders, although the underlying defense mechanisms are different. The literature data show that PNES are associated with cluster B (mainly borderline) personality disorders and/or to people with depressive or anxiety disorders. Defense mechanisms in patients with PNES with a prevalence of anxious/depressive symptoms are of "neurotic" type; their goal is to lead to a "split", either vertical (dissociation) or horizontal (repression). The majority of patients with this type of PNES have alexithymia traits, meaning that they had difficulties in feeling or perceiving emotions. In subjects where PNES are associated with a borderline personality, in which the symbolic function is lost, the defense mechanisms are of a more archaic nature (denial). PNES with different underlying defense mechanisms have different prognoses (despite similar severity of PNES) and need usually a different treatment (pharmacological or psychological). Thus, it appears superfluous to talk about psychiatric comorbidity, since PNES are a different symptomatic expression of specific psychiatric disorders.

  17. Transcranial alternating current stimulation: A review of the underlying mechanisms and modulation of cognitive processes

    Directory of Open Access Journals (Sweden)

    Christoph S Herrmann

    2013-06-01

    Full Text Available Brain oscillations of different frequencies have been associated with a variety of cognitive functions. Convincing evidence supporting those associations has been provided by studies using intracranial stimulation, pharmacological interventions and lesion studies. The emergence of novel non-invasive brain stimulation techniques like repetitive transcranial magnetic stimulation (rTMS and transcranial alternating current stimulation (tACS now allows to modulate brain oscillations directly. Particularly, tACS offers the unique opportunity to causally link brain oscillations of a specific frequency range to cognitive processes, because it uses sinusoidal currents that are bound to one frequency only. Using tACS allows to modulate brain oscillations and in turn to influence cognitive processes, thereby demonstrating the causal link between the two. Here, we review findings about the physiological mechanism of tACS and studies that have used tACS to modulate basic motor and sensory processes as well as higher cognitive processes like memory, ambiguous perception, and decision making.

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

    Science.gov (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

    2009-04-01

    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

  19. Transcriptional and epigenetic mechanisms underlying enhanced in vitro adipocyte differentiation by the brominated flame retardant BDE-47

    DEFF Research Database (Denmark)

    Kamstra, Jorke H; Hruba, Eva; Blumberg, Bruce

    2014-01-01

    . The mechanisms by which EDCs direct preadipocytes to form adipocytes are poorly understood. Here, we examined transcriptional and epigenetic mechanisms underlying the induction of in vitro adipocyte differentiation by BDE-47. Quantitative high content microscopy revealed concentration-dependent enhanced...

  20. Epigenetic mechanisms underlying lifespan and age-related effects of dietary restriction and the ketogenic diet.

    Science.gov (United States)

    Moreno, Cesar L; Mobbs, Charles V

    2017-11-05

    Aging constitutes the central risk factor for major diseases including many forms of cancer, neurodegeneration, and cardiovascular diseases. The aging process is characterized by both global and tissue-specific changes in gene expression across taxonomically diverse species. While aging has historically been thought to entail cell-autonomous, even stochastic changes, recent evidence suggests that modulation of this process can be hierarchal, wherein manipulations of nutrient-sensing neurons (e.g., in the hypothalamus) produce peripheral effects that may modulate the aging process itself. The most robust intervention extending lifespan, plausibly impinging on the aging process, involves different modalities of dietary restriction (DR). Lifespan extension by DR is associated with broad protection against diseases (natural and engineered). Here we review potential epigenetic processes that may link lifespan to age-related diseases, particularly in the context of DR and (other) ketogenic diets, focusing on brain and hypothalamic mechanisms. Copyright © 2016. Published by Elsevier B.V.

  1. Fracture mechanics study on stress corrosion cracking behavior under corrosive environment

    International Nuclear Information System (INIS)

    Fujii, Tomoyuki; Tohgo, Keiichiro; Shimamura, Yoshinobu; Ishizuka, Naohiro; Takanashi, Masahiro; Itabashi, Yu; Nakayama, Gen; Sakakibara, Yohei; Hirano, Takashi

    2013-01-01

    This paper deals with applicability of non-linear fracture mechanics to crack growth by stress corrosion cracking (SCC) under large-scale yielding and in a plastically deformed area. Crack growth test by compact tension specimen is carried out to evaluate crack growth rate under small-scale and large-scale yielding conditions. To evaluate the crack growth behavior from a crack initiated in a plastically deformed area, crack growth test is also carried out for a very short pre-crack in a plastically deformed four-point bending specimen. Conventional stress intensity factor (K) and equivalent stress intensity factor (K J ) defined by J integral are used as fracture mechanics parameters which characterize the crack growth rate. On da/dt-K diagram, a data band shows wide scatter, especially the crack growth rate in a plastically deformed area is higher than that under small-scale yielding condition. On the other hand, da/dt-K J diagram exhibits narrower scatter on a data band than da/dt-K diagram. The equivalent stress intensity factor is appropriate for characterization of crack growth rate by SCC under small-scale yielding through large scale yielding conditions and in a plastically deformed area. (author)

  2. Mechanical behavior of confined self-compacting reinforced concrete circular columns under concentric axial loading

    Directory of Open Access Journals (Sweden)

    Fouad Khairallah

    2013-12-01

    Full Text Available 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 under concentric axial loading. The parameters affecting are including concrete compressive strength and confinement configuration. Twenty column specimens were casted and confined using four confinement techniques, CFRP wrap, FRP tube, GFRP wrap, and spiral steel hoops. The performance of the tested column specimens is evaluated based on mode of failure, load–displacement curve, stress–strain characteristics, ultimate strength, ductility, and degree of confinement.

  3. First-principles calculations of mechanical and electronic properties of silicene under strain

    Directory of Open Access Journals (Sweden)

    Rui Qin

    2012-06-01

    Full Text Available We perform first-principles calculations of mechanical and electronic properties of silicene under strains. The in-plane stiffness of silicene is much smaller than that of graphene. The yielding strain of silicene under uniform expansion in the ideal conditions is about 20%. The homogeneous strain can introduce a semimetal-metal transition. The semimetal state of silicene, in which the Dirac cone locates at the Fermi level, can only persist up to tensile strain of 7% with nearly invariant Fermi velocity. For larger strains, silicene changes into a conventional metal. The work function is found to change significantly under biaxial strain. Our calculations show that strain tuning is important for applications of silicene in nanoelectronics.

  4. Skin transcriptome reveals the intrinsic molecular mechanisms underlying hair follicle cycling in Cashmere goats under natural and shortened photoperiod conditions.

    Science.gov (United States)

    Yang, Min; Song, Shen; Dong, Kunzhe; Chen, XiaoFei; Liu, Xuexue; Rouzi, Marhaba; Zhao, Qianjun; He, Xiaohong; Pu, Yabin; Guan, Weijun; Ma, Yuehui; Jiang, Lin

    2017-10-18

    The growth of cashmere exhibits a seasonal pattern arising from photoperiod change. However, the underlying molecular mechanism remains unclear. We profiled the skin transcriptome of six goats at seven time points during hair follicle cycling via RNA-seq. The six goats comprised three goats exposed to a natural photoperiod and three exposed to a shortened photoperiod. During hair cycle transition, 1713 genes showed differential expression, and 332 genes showed a pattern of periodic expression. Moreover, a short photoperiod induced the hair follicle to enter anagen early, and 246 genes overlapped with the periodic genes. Among these key genes, cold-shock domain containing C2 (CSDC2) was highly expressed in the epidermis and dermis of Cashmere goat skin, although its function in hair-follicle development remains unknown. CSDC2 silencing in mouse fibroblasts resulted in the decreased mRNA expression of two key hair-follicle factors, leading to reduced cell numbers and a lower cell density. Cashmere growth or molting might be controlled by a set of periodic regulatory genes. The appropriate management of short light exposure can induce hair follicles to enter full anagen early through the activation of these regulators. The CSDC2 gene is a potentially important transcription factor in the hair growth cycle.

  5. Modeling and numerical analysis of granite rock specimen under mechanical loading and fire

    Directory of Open Access Journals (Sweden)

    Luc Leroy Ngueyep. Mambou

    2015-02-01

    Full Text Available The effect of ISO 834 fire on the mechanical properties of granite rock specimen submitted to uniaxial loading is numerically investigated. Based on Newton's second law, the rate-equation model of granite rock specimen under mechanical load and fire is established. The effect of heat treatment on the mechanical performance of granite is analyzed at the center and the ends of specimen. At the free end of granite rock specimen, it is shown that from 20 °C to 500 °C, the internal stress and internal strain are weak; whereas above 500 °C, they start to increase rapidly, announcing the imminent collapse. At the center of specimen, the analysis of the internal stress and internal strain reveals that the fire reduces the mechanical performance of granite significantly. Moreover, it is found that after 3 min of exposure to fire, the mechanical energy necessary to fragment the granite can be reduced up to 80%.

  6. New developments on the neurobiological and pharmaco-genetic mechanisms underlying internet and videogame addiction.

    Science.gov (United States)

    Weinstein, Aviv; Lejoyeux, Michel

    2015-03-01

    There is emerging evidence that the psychobiological mechanisms underlying behavioral addictions such as internet and videogame addiction resemble those of addiction for substances of abuse. Review of brain imaging, treatment and genetic studies on videogame and internet addiction. Literature search of published articles between 2009 and 2013 in Pubmed using "internet addiction" and "videogame addiction" as the search word. Twenty-nine studies have been selected and evaluated under the criteria of brain imaging, treatment, and genetics. Brain imaging studies of the resting state have shown that long-term internet game playing affected brain regions responsible for reward, impulse control and sensory-motor coordination. Brain activation studies have shown that videogame playing involved changes in reward and loss of control and that gaming pictures have activated regions similarly to those activated by cue-exposure to drugs. Structural studies have shown alterations in the volume of the ventral striatum possible as result of changes in reward. Furthermore, videogame playing was associated with dopamine release similar in magnitude to those of drugs of abuse and that there were faulty inhibitory control and reward mechanisms videogame addicted individuals. Finally, treatment studies using fMRI have shown reduction in craving for videogames and reduced associated brain activity. Videogame playing may be supported by similar neural mechanisms underlying drug abuse. Similar to drug and alcohol abuse, internet addiction results in sub-sensitivity of dopamine reward mechanisms. Given the fact that this research is in its early stage it is premature to conclude that internet addiction is equivalent to substance addictions. © American Academy of Addiction Psychiatry.

  7. Bacteriophage Resistance Mechanisms in the Fish Pathogen Flavobacterium psychrophilum: Linking Genomic Mutations to Changes in Bacterial Virulence Factors

    DEFF Research Database (Denmark)

    Castillo, Daniel; Christiansen, Rói Hammershaimb; Dalsgaard, Inger

    2015-01-01

    requires overcoming the selection for phage resistance in the bacterial populations. Here, we analyzed resistance mechanisms in F. psychrophilum after phage exposure using whole-genome sequencing of the ancestral phage-sensitive strain 950106-1/1 and six phage-resistant isolates. The phage-resistant...... resistance and the genetic modifications were supported by direct measurements of bacteriophage adsorption rates, biofilm formation, and secretion of extracellular enzymes, which were all impaired in the resistant strains, probably due to superficial structural changes. The clustered regularly interspaced...... were associated with a number of derived effects on the physiological properties of the pathogen, including reduced virulence under in vitro conditions. Consequently, phage-driven physiological changes associated with resistance may have implications for the impact of the pathogen in aquaculture...

  8. Microscale experimental investigation of deformation and damage of argillaceous rocks under cyclic hydric and mechanical loads

    International Nuclear Information System (INIS)

    Wang, Linlin; Yang, Diansen; Heripre, Eva; Chanchole, Serge; Bornert, Michel; Pouya, Ahmad; Halphen, Bernard

    2012-01-01

    Document available in abstract form only. Argillaceous rocks are possible host rocks for underground nuclear waste repositories. They exhibit complex coupled thermo-hydro-chemo-mechanical behavior, the description of which would strongly benefit from an improved experimental insight on their deformation and damage mechanisms at microscale. We present some recent observations of the evolution of these rocks at the scale of their composite microstructure, essentially made of a clay matrix with embedded carbonates and quartz particles with sizes ranging from a few to several tens of micrometers, when they are subjected to cyclic variations of relative humidity and mechanical loading. They are based on the combination of high definition and high resolution imaging in an environmental scanning electron microscope (ESEM), in situ hydro-mechanical loading of the samples, and digital image correlation techniques. Samples, several millimeters in diameter, are held at a constant temperature of 2 deg. Celsius while the vapor pressure in the ESEM chamber is varied from a few to several hundreds of Pascals, generating a relative humidity ranging from about 10% up to 90%. Results show a strongly heterogeneous deformation field at microscale, which is the result of complex hydro-mechanical interactions. In particular, it can be shown that local swelling incompatibilities can generate irreversible deformations in the clay matrix, even if the overall hydric deformations seem reversible. In addition, local damage can be generated, in the form of a network of microcracks, located in the bulk of the clay matrix and/or at the interface between clay and other mineral particles. The morphology of this network, described in terms of crack length, orientation and preferred location, has been observed to be dependent on the speed of the variation of the relative humidity, and is different in a saturation or desaturation process. Besides studying the deformation and damage under hydric

  9. Mind your errors: evidence for a neural mechanism linking growth mind-set to adaptive posterror adjustments.

    Science.gov (United States)

    Moser, Jason S; Schroder, Hans S; Heeter, Carrie; Moran, Tim P; Lee, Yu-Hao

    2011-12-01

    How well people bounce back from mistakes depends on their beliefs about learning and intelligence. For individuals with a growth mind-set, who believe intelligence develops through effort, mistakes are seen as opportunities to learn and improve. For individuals with a fixed mind-set, who believe intelligence is a stable characteristic, mistakes indicate lack of ability. We examined performance-monitoring event-related potentials (ERPs) to probe the neural mechanisms underlying these different reactions to mistakes. Findings revealed that a growth mind-set was associated with enhancement of the error positivity component (Pe), which reflects awareness of and allocation of attention to mistakes. More growth-minded individuals also showed superior accuracy after mistakes compared with individuals endorsing a more fixed mind-set. It is critical to note that Pe amplitude mediated the relationship between mind-set and posterror accuracy. These results suggest that neural mechanisms indexing on-line awareness of and attention to mistakes are intimately involved in growth-minded individuals' ability to rebound from mistakes.

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

    Science.gov (United States)

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

    2017-12-01

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

  11. Neural mechanisms underlying subsequent memory for personal beliefs:An fMRI study.

    Science.gov (United States)

    Wing, Erik A; Iyengar, Vijeth; Hess, Thomas M; LaBar, Kevin S; Huettel, Scott A; Cabeza, Roberto

    2018-04-01

    Many fMRI studies have examined the neural mechanisms supporting emotional memory for stimuli that generate emotion rather automatically (e.g., a picture of a dangerous animal or of appetizing food). However, far fewer studies have examined how memory is influenced by emotion related to social and political issues (e.g., a proposal for large changes in taxation policy), which clearly vary across individuals. In order to investigate the neural substrates of affective and mnemonic processes associated with personal opinions, we employed an fMRI task wherein participants rated the intensity of agreement/disagreement to sociopolitical belief statements paired with neural face pictures. Following the rating phase, participants performed an associative recognition test in which they distinguished identical versus recombined face-statement pairs. The study yielded three main findings: behaviorally, the intensity of agreement ratings was linked to greater subjective emotional arousal as well as enhanced high-confidence subsequent memory. Neurally, statements that elicited strong (vs. weak) agreement or disagreement were associated with greater activation of the amygdala. Finally, a subsequent memory analysis showed that the behavioral memory advantage for statements generating stronger ratings was dependent on the medial prefrontal cortex (mPFC). Together, these results both underscore consistencies in neural systems supporting emotional arousal and suggest a modulation of arousal-related encoding mechanisms when emotion is contingent on referencing personal beliefs.

  12. Potential mechanisms underlying anxiety and depression in Parkinson's disease: consequences of L-DOPA treatment

    Science.gov (United States)

    Eskow Jaunarajs, Karen L.; Angoa-Perez, Mariana; Kuhn, Donald M.; Bishop, Christopher

    2010-01-01

    Though the most recognizable symptoms of Parkinson's disease (PD) are motor-related, many patients also suffer from debilitating affective symptoms that deleteriously influence quality of life. Dopamine (DA) loss is likely involved in the onset of depression and anxiety in PD. However, these symptoms are not reliably improved by DA replacement therapy with L-3,4-dihydroxyphenylalanine (L-DOPA). In fact, preclinical and clinical evidence suggests that L-DOPA treatment may worsen affect. Though the neurobiological mechanisms remain unclear, recent research contends that L-DOPA further perturbs the function of the norepinephrine and serotonin systems, already affected by PD pathology, which have been intimately linked to the development and expression of anxiety and depression. As such, this review provides an overview of the clinical characteristics of affective disorders in PD, examines the utility of animal models for the study of anxiety and depression in PD, and finally, discusses potential mechanisms by which DA loss and subsequent L-DOPA therapy influence monoamine function and concomitant affective symptoms. PMID:20615430

  13. Diminished alternative reinforcement as a mechanism linking conduct problems and substance use in adolescence: a longitudinal examination.

    Science.gov (United States)

    Khoddam, Rubin; Cho, Junhan; Jackson, Nicholas J; Leventhal, Adam M

    2018-01-14

    To determine whether diminished alternative reinforcement (i.e. engagement and enjoyment from substance-free activities) mediated the longitudinal association of conduct problems with substance use in early-mid-adolescence. Structural equation modeling tested whether the association between wave 1 (baseline) conduct problems and wave 3 (24-month follow-up) substance use outcomes was mediated by diminished alternative reinforcement at wave 2 (12-month follow-up). Additional analyses tested whether sex and socio-economic status moderated this association. Ten high schools in Los Angeles, CA, USA, 2013-15. Students (n = 3396, 53.5% female, mean [standard deviation (SD)] age at wave 1 baseline = 14.1 (0.42) years). Self-reported conduct problems (11-item questionnaire), alternative reinforcement (44-item questionnaire) and use of alcohol, marijuana and combustible cigarettes during the past 6 months (yes/no) and the past 30 days (nine-level ordinal response based on days used in past 30 days). Significant associations of wave 1 conduct problems with wave 3 marijuana use during the past 6 months (β = 0.25) and past 30 days (β = 0.26) were mediated by wave 2 diminished alternative reinforcement (β indirect effect : 6 months = 0.013, 30 days = 0.017, Ps conduct problems with alcohol or combustible cigarette use were not mediated by alternative reinforcement. All associations did not differ by sex and socio-economic status. Diminished alternative reinforcement may be a modifiable mechanism linking early adolescent conduct problems and subsequent marijuana use that could be targeted in prevention programs to offset the adverse health and social sequelae associated with comorbid conduct problems and marijuana use in early-mid adolescence. © 2018 Society for the Study of Addiction.