WorldWideScience

Sample records for underlying generating mechanism

  1. Design mechanic generator under speed bumper to support electricity recourse for urban traffic light

    Science.gov (United States)

    Sabri, M.; Lauzuardy, Jason; Syam, Bustami

    2018-03-01

    The electrical energy needs for the traffic lights in some cities of developing countries cannot be achieved continuously due to limited capacity and interruption of electricity distribution, the main power plant. This issues can lead to congestion at the crossroads. To overcome the problem of street chaos due to power failure, we can cultivate to provide electrical energy from other sources such as using the bumper to generate kinetic energy, which can be converted into electrical energy. This study designed a generator mechanic that will be mounted on the bumper construction to generate electricity for the purposes of traffic lights at the crossroads. The Mechanical generator is composed of springs, levers, sprockets, chains, flywheel and customize power generator. Through the rotation of the flywheel, we can earned 9 Volt DC voltage and electrical current of 5.89 Ampere. This achievement can be used to charge the accumulator which can be used to power the traffic lights, and to charge the accumulator capacity of 6 Ah, the generator works in the charging time for 1.01 hours.

  2. Affirming independence: Exploring mechanisms underlying a values affirmation intervention for first-generation students.

    Science.gov (United States)

    Tibbetts, Yoi; Harackiewicz, Judith M; Canning, Elizabeth A; Boston, Jilana S; Priniski, Stacy J; Hyde, Janet S

    2016-05-01

    First-generation college students (students for whom neither parent has a 4-year college degree) earn lower grades and worry more about whether they belong in college, compared with continuing-generation students (who have at least 1 parent with a 4-year college degree). We conducted a longitudinal follow-up of participants from a study in which a values-affirmation intervention improved performance in a biology course for first-generation college students, and found that the treatment effect on grades persisted 3 years later. First-generation students in the treatment condition obtained a GPA that was, on average, .18 points higher than first-generation students in the control condition, 3 years after values affirmation was implemented (Study 1A). We explored mechanisms by testing whether the values-affirmation effects were predicated on first-generation students reflecting on interdependent values (thus affirming their values that are consistent with working-class culture) or independent values (thus affirming their values that are consistent with the culture of higher education). We found that when first-generation students wrote about their independence, they obtained higher grades (both in the semester in which values affirmation was implemented and in subsequent semesters) and felt less concerned about their background. In a separate laboratory experiment (Study 2) we manipulated the extent to which participants wrote about independence and found that encouraging first-generation students to write more about their independence improved their performance on a math test. These studies highlight the potential of having FG students focus on their own independence. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

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

    Directory of Open Access Journals (Sweden)

    Danylo Sirskyj

    2016-07-01

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

  4. An agent-based simulation of power generation company behavior in electricity markets under different market-clearing mechanisms

    International Nuclear Information System (INIS)

    Aliabadi, Danial Esmaeili; Kaya, Murat; Şahin, Güvenç

    2017-01-01

    Deregulated electricity markets are expected to provide affordable electricity for consumers through promoting competition. Yet, the results do not always fulfill the expectations. The regulator's market-clearing mechanism is a strategic choice that may affect the level of competition in the market. We conceive of the market-clearing mechanism as composed of two components: pricing rules and rationing policies. We investigate the strategic behavior of power generation companies under different market-clearing mechanisms using an agent-based simulation model which integrates a game-theoretical understanding of the auction mechanism in the electricity market and generation companies' learning mechanism. Results of our simulation experiments are presented using various case studies representing different market settings. The market in simulations is observed to converge to a Nash equilibrium of the stage game or to a similar state under most parameter combinations. Compared to pay-as-bid pricing, bid prices are closer to marginal costs on average under uniform pricing while GenCos' total profit is also higher. The random rationing policy of the ISO turns out to be more successful in achieving lower bid prices and lower GenCo profits. In minimizing GenCos' total profit, a combination of pay-as-bid pricing rule and random rationing policy is observed to be the most promising. - Highlights: • An agent-based simulation of generation company behavior in electricity markets is developed. • Learning dynamics of companies is modeled with an extended Q-learning algorithm. • Different market clearing mechanisms of the regulator are compared. • Convergence to Nash equilibria is analyzed under different cases. • The level of competition in the market is studied.

  5. Mechanisms for generating froissaron

    International Nuclear Information System (INIS)

    Glushko, N.I.; Kobylinski, N.A.; Martynov, E.S.; Shelest, V.P.

    1982-01-01

    From a common point of view, we consider the mechanisms for generating froissaron which arise due to the quasieikonal approximation, the U-matrix approach and the method of continued unitarity. A realistic model for the input pomeron is suggested and the data on high-energy pp-scattering are described. Likeness and difference of asymptotic and preasymptotic regimes for three variants of froissaron are discussed

  6. [Mechanisms of subspecies differentiation in a filial generation of rice indica-japonica hybridization under different ecological conditions].

    Science.gov (United States)

    Wang, He-Tong; Jin, Feng; Jiang, Yi-Jun; Lin, Qing-Shan; Xu, Hai; Chen, Wen-Fu; Xu, Zheng-Jin

    2013-11-01

    Indica-japonica hybridization is one of the most important breeding methods in China, whereas identifying subspecies differentiation mechanisms is the key in indica-japonica hybridization breeding. By using InDels (Insert/Deletion) and ILPs (Intron Length Polymorphism), an analysis was made on the F6 populations derived from the hybridization of indica-japonica (Qishanzhan/Akihikari) planted in Liaoning and Guangdong provinces and generated by bulk harvesting (BM), single-seed descent methods (SSD), and pedigree method (PM). No segregation distortion was observed for the BM and SSD populations. The frequency distribution of japonica kinship percentage (Dj) was concentrated in 40%-60%. The PM populations in the two provinces presented indica-deviated distribution (30%-55%), with significant difference between Guangdong (38%) and Liaoning (42%). In addition, there was a significant positive correlation between the Dj and the kinship of functional gene regions in the BM and SSD populations. However, part of the positive correlation was broken in the PM populations that showed a regular distribution in the genotype patterns of indica and japonica loci. The above results demonstrated that artificial selection could be the main factor affecting the population differentiation in indica-japonica hybridization, and, with the synergistic effect of natural selection, induced the phenomenon of segregation distortion. There existed a close relationship between the differentiation of subspecies and the important agronomic traits, which could be the main reason why indica-japonica hybridiation breeding could not achieve the expected effect of combining the two subspecies advantages.

  7. Mechanical generation of spin current

    Directory of Open Access Journals (Sweden)

    Mamoru eMatsuo

    2015-07-01

    Full Text Available We focus the recent results on spin-current generation from mechanical motion such as rigid rotation and elastic deformations. Spin transport theory in accelerating frames is constructed by using the low energy expansion of the generally covariant Dirac equation. Related issues on spin-manipulation by mechanical rotation are also discussed.

  8. Generating natural language under pragmatic constraints

    CERN Document Server

    Hovy, Eduard H

    2013-01-01

    Recognizing that the generation of natural language is a goal- driven process, where many of the goals are pragmatic (i.e., interpersonal and situational) in nature, this book provides an overview of the role of pragmatics in language generation. Each chapter states a problem that arises in generation, develops a pragmatics-based solution, and then describes how the solution is implemented in PAULINE, a language generator that can produce numerous versions of a single underlying message, depending on its setting.

  9. A generation mechanism for chorus emission

    Directory of Open Access Journals (Sweden)

    V. Y. Trakhtengerts

    1999-01-01

    Full Text Available A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.Key words. Magnetospheric physics (Energetic particles · trapped. Space plasma physics (wave-particle interactions; waves and instabilities

  10. A generation mechanism for chorus emission

    Directory of Open Access Journals (Sweden)

    V. Y. Trakhtengerts

    Full Text Available A chorus generation mechanism is discussed, which is based on interrelation of ELF/VLF noise-like and discrete emissions under the cyclotron wave-particle interactions. A natural ELF/VLF noise radiation is excited by the cyclotron instability mechanism in ducts with enhanced cold plasma density or at the plasmapause. This process is accompanied by a step-like deformation of the energetic electron distribution function in the velocity space, which is situated at the boundary between resonant and nonresonant particles. The step leads to the strong phase correlation of interacting particles and waves and to a new backward wave oscillator (BWO regime of wave generation, when an absolute cyclotron instability arises at the central cross section of the geomagnetic trap, in the form of a succession of discrete signals with growing frequency inside each element. The dynamical spectrum of a separate element is formed similar to triggered ELF/VLF emission, when the strong wavelet starts from the equatorial plane. The comparison is given of the model developed using some satellite and ground-based data. In particular, the appearance of separate groups of chorus signals with a duration 2-10 s can be connected with the preliminary stage of the step formation. BWO regime gives a succession period smaller than the bounce period of energetic electrons between the magnetic mirrors and can explain the observed intervals between chorus elements.

    Key words. Magnetospheric physics (Energetic particles · trapped. Space plasma physics (wave-particle interactions; waves and instabilities

  11. Teaching Practice generated stressors and coping mechanisms ...

    African Journals Online (AJOL)

    Teaching Practice generated stressors and coping mechanisms among student teachers in Zimbabwe. ... South African Journal of Education ... We sought to establish stressors and coping mechanisms for student teachers on Teaching Practice from a Christian-related university and a government-owned teachers' college ...

  12. Mathematical modelling of stress-deformation state of the steam generator collector (WWER-type) under pressure loading during fracture mechanics calculations

    International Nuclear Information System (INIS)

    Zaitsev, M.; Lyssakov, V.

    1993-01-01

    This paper describes a steam generator collector (WWER-type) designed as part of a Russian reactor power station. The collector is a thick cylindrical shell with a constant inner diameter of 850 mm and a height of 4,970 mm. The wall thickness varies from 78 to 163 mm. In the thicker section, a series of holes allows connection of steam generator heat exchanging tubes. Because of design considerations, the tubes are not symmetrically located about the circumference of the collector. This paper presents a model of the stress concentrations resulting from this design feature for a device operating at a nominal pressure of 16 MPa. 4 refs., 8 figs

  13. 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.

  14. 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.

  15. Interlinked bistable mechanisms generate robust mitotic transitions.

    Science.gov (United States)

    Hutter, Lukas H; Rata, Scott; Hochegger, Helfrid; Novák, Béla

    2017-10-18

    The transitions between phases of the cell cycle have evolved to be robust and switch-like, which ensures temporal separation of DNA replication, sister chromatid separation, and cell division. Mathematical models describing the biochemical interaction networks of cell cycle regulators attribute these properties to underlying bistable switches, which inherently generate robust, switch-like, and irreversible transitions between states. We have recently presented new mathematical models for two control systems that regulate crucial transitions in the cell cycle: mitotic entry and exit, 1 and the mitotic checkpoint. 2 Each of the two control systems is characterized by two interlinked bistable switches. In the case of mitotic checkpoint control, these switches are mutually activating, whereas in the case of the mitotic entry/exit network, the switches are mutually inhibiting. In this Perspective we describe the qualitative features of these regulatory motifs and show that having two interlinked bistable mechanisms further enhances robustness and irreversibility. We speculate that these network motifs also underlie other cell cycle transitions and cellular transitions between distinct biochemical states.

  16. Generation of Articulated Mechanisms by Optimization Techniques

    DEFF Research Database (Denmark)

    Kawamoto, Atsushi

    2004-01-01

    optimization [Paper 2] 3. Branch and bound global optimization [Paper 3] 4. Path-generation problems [Paper 4] In terms of the objective of the articulated mechanism design problems, the first to third papers deal with maximization of output displacement, while the fourth paper solves prescribed path...... generation problems. From a mathematical programming point of view, the methods proposed in the first and third papers are categorized as deterministic global optimization, while those of the second and fourth papers are categorized as gradient-based local optimization. With respect to design variables, only...... directly affects the result of the associated sensitivity analysis. Another critical issue for mechanism design is the concept of mechanical degrees of freedom and this should be also considered for obtaining a proper articulated mechanism. The thesis treats this inherently discrete criterion in some...

  17. Attentional mechanisms in the generation of sympathy

    OpenAIRE

    Stephan Dickert; Paul Slovic

    2009-01-01

    Empathic responses, such as sympathy towards others, are a key ingredient in the decision to provide help to those in need. The determinants of empathic responses are usually thought to be the vividness, similarity, and proximity of the victim. However, recent research highlights the role that attention plays in the generation of feelings. We expanded on this idea by investigating whether sympathy depends on cognitive mechanisms such as attention. In two studies we found that sympathy respons...

  18. 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 ...

  19. Peeling mechanism of tomato under infrared heating

    Science.gov (United States)

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

  20. Modeling and Generating Strategy Games Mechanics

    DEFF Research Database (Denmark)

    Mahlmann, Tobias

    of the game is, how players may manipulate the game world, etc. We present the Strategy Games Description Language (SGDL), a tree-based approach to model the game mechanics of strategy games. SGDL allows game designers to rapid prototype their game ideas with the help of our customisable game engine. We...... their games to individual players’ preferences by creating game content adaptively to how the player plays (and likes) a game. W we extend the notion of “procedural game content generation” by “game mechanics”. Game mechanics herein refer to the way that objects in a game may interact, what the goal...... present several example games to demonstrate the capabilities of the language and how to model common strategy game elements. Furthermore, we present methods to procedurally generate and evaluate game mechanics modelled in SGDL in terms of enjoyability. We argue that an evolutionary process can be used...

  1. Power Generation Using Mechanical Wave Energy Converter

    Directory of Open Access Journals (Sweden)

    Srinivasan Chandrasekaran

    2012-03-01

    Full Text Available Ocean wave energy plays a significant role in meeting the growing demand of electric power. Economic, environmental, and technical advantages of wave energy set it apart from other renewable energy resources. Present study describes a newly proposed Mechanical Wave Energy Converter (MEWC that is employed to harness heave motion of floating buoy to generate power. Focus is on the conceptual development of the device, illustrating details of component level analysis. Employed methodology has many advantages such as i simple and easy fabrication; ii easy to control the operations during rough weather; and iii low failure rate during normal sea conditions. Experimental investigations carried out on the scaled model of MWEC show better performance and its capability to generate power at higher efficiency in regular wave fields. Design Failure Mode and Effect Analysis (FMEA shows rare failure rates for all components except the floating buoy.

  2. Attentional mechanisms in the generation of sympathy

    Directory of Open Access Journals (Sweden)

    Stephan Dickert

    2009-06-01

    Full Text Available Empathic responses, such as sympathy towards others, are a key ingredient in the decision to provide help to those in need. The determinants of empathic responses are usually thought to be the vividness, similarity, and proximity of the victim. However, recent research highlights the role that attention plays in the generation of feelings. We expanded on this idea by investigating whether sympathy depends on cognitive mechanisms such as attention. In two studies we found that sympathy responses were lower and reaction times were longer when targets were presented with distractors. In addition, online sympathy judgments that allow attentional focusing on a target lead to greater affective responses than judgments made from memory. We conclude that attention is an ingredient in the generation of sympathy, and discuss implications for research on prosocial behaviour and the interaction between attention and emotions.

  3. Reaction Mechanism Generator: Automatic construction of chemical kinetic mechanisms

    Science.gov (United States)

    Gao, Connie W.; Allen, Joshua W.; Green, William H.; West, Richard H.

    2016-06-01

    Reaction Mechanism Generator (RMG) constructs kinetic models composed of elementary chemical reaction steps using a general understanding of how molecules react. Species thermochemistry is estimated through Benson group additivity and reaction rate coefficients are estimated using a database of known rate rules and reaction templates. At its core, RMG relies on two fundamental data structures: graphs and trees. Graphs are used to represent chemical structures, and trees are used to represent thermodynamic and kinetic data. Models are generated using a rate-based algorithm which excludes species from the model based on reaction fluxes. RMG can generate reaction mechanisms for species involving carbon, hydrogen, oxygen, sulfur, and nitrogen. It also has capabilities for estimating transport and solvation properties, and it automatically computes pressure-dependent rate coefficients and identifies chemically-activated reaction paths. RMG is an object-oriented program written in Python, which provides a stable, robust programming architecture for developing an extensible and modular code base with a large suite of unit tests. Computationally intensive functions are cythonized for speed improvements.

  4. Mechanical properties of cork under contact stresses

    International Nuclear Information System (INIS)

    Parralejo, A. D.; Guiberteau, F.; Fortes, M. A.; Rosa, M. E.

    2001-01-01

    In this work our interest is focussed on the mechanical behaviour of natural cork under contact stresses. Many of the applications of this curious material are related with its mechanical response under such a stress field, however this topic has not been still sufficiently considered in the scientific literature. For this purpose, we proposed the use of Hertzian indentation tests. By using this mythology we have investigated the cork structure influence on the corresponding mechanical properties. Our results reveal a clear mechanical anisotropy effect. Moreover, the elastic modulus corresponding to specific directions have been estimated. Several are the main advantages of this specific test mythology versus traditional uniaxial compression tests, specially simplicity and local character. (Author) 9 refs

  5. Neural mechanisms of sequence generation in songbirds

    Science.gov (United States)

    Langford, Bruce

    Animal models in research are useful for studying more complex behavior. For example, motor sequence generation of actions requiring good muscle coordination such as writing with a pen, playing an instrument, or speaking, may involve the interaction of many areas in the brain, each a complex system in itself; thus it can be difficult to determine causal relationships between neural behavior and the behavior being studied. Birdsong, however, provides an excellent model behavior for motor sequence learning, memory, and generation. The song consists of learned sequences of notes that are spectrographically stereotyped over multiple renditions of the song, similar to syllables in human speech. The main areas of the songbird brain involve in singing are known, however, the mechanisms by which these systems store and produce song are not well understood. We used a custom built, head-mounted, miniature motorized microdrive to chronically record the neural firing patterns of identified neurons in HVC, a pre-motor cortical nucleus which has been shown to be important in song timing. These were done in Bengalese finch which generate a song made up of stereotyped notes but variable note sequences. We observed song related bursting in neurons projecting to Area X, a homologue to basal ganglia, and tonic firing in HVC interneurons. Interneuron had firing rate patterns that were consistent over multiple renditions of the same note sequence. We also designed and built a light-weight, low-powered wireless programmable neural stimulator using Bluetooth Low Energy Protocol. It was able to generate perturbations in the song when current pulses were administered to RA, which projects to the brainstem nucleus responsible for syringeal muscle control.

  6. Electricity pricing model in thermal generating stations under deregulation

    International Nuclear Information System (INIS)

    Reji, P.; Ashok, S.; Moideenkutty, K.M.

    2007-01-01

    In regulated public utilities with competitive power markets, deregulation has replaced the monopoly. Under the deregulated power market, the electricity price primarily depends on market mechanism and power demand. In this market, generators generally follow marginal pricing. Each generator fixes the electricity price based on their pricing strategy and it leads to more price volatility. This paper proposed a model to determine the electricity price considering all operational constraints of the plant and economic variables that influenced the price, for a thermal generating station under deregulation. The purpose of the model was to assist existing stations, investors in the power sector, regulatory authorities, transmission utilities, and new power generators in decision-making. The model could accommodate price volatility in the market and was based on performance incentive/penalty considering plant load factor, availability of the plant and peak/ off peak demand. The model was applied as a case study to a typical thermal utility in India to determine the electricity price. It was concluded that the case study of a thermal generating station in a deregulated environment showed that the electricity price mainly depended on the gross calorific value (GCV) of fuel, mode of operation, price of the fuel, and operating charges. 11 refs., 2 tabs., 1 fig

  7. Surface Damage Mechanism of Monocrystalline Si Under Mechanical Loading

    Science.gov (United States)

    Zhao, Qingliang; Zhang, Quanli; To, Suet; Guo, Bing

    2017-03-01

    Single-point diamond scratching and nanoindentation on monocrystalline silicon wafer were performed to investigate the surface damage mechanism of Si under the contact loading. The results showed that three typical stages of material removal appeared during dynamic scratching, and a chemical reaction of Si with the diamond indenter and oxygen occurred under the high temperature. In addition, the Raman spectra of the various points in the scratching groove indicated that the Si-I to β-Sn structure (Si-II) and the following β-Sn structure (Si-II) to amorphous Si transformation appeared under the rapid loading/unloading condition of the diamond grit, and the volume change induced by the phase transformation resulted in a critical depth (ductile-brittle transition) of cut (˜60 nm ± 15 nm) much lower than the theoretical calculated results (˜387 nm). Moreover, it also led to abnormal load-displacement curves in the nanoindentation tests, resulting in the appearance of elbow and pop-out effects (˜270 nm at 20 s, 50 mN), which were highly dependent on the loading/unloading conditions. In summary, phase transformation of Si promoted surface deformation and fracture under both static and dynamic mechanical loading.

  8. 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.

  9. Molecular mechanism for generation of antibody memory.

    Science.gov (United States)

    Shivarov, Velizar; Shinkura, Reiko; Doi, Tomomitsu; Begum, Nasim A; Nagaoka, Hitoshi; Okazaki, Il-Mi; Ito, Satomi; Nonaka, Taichiro; Kinoshita, Kazuo; Honjo, Tasuku

    2009-03-12

    Activation-induced cytidine deaminase (AID) is the essential enzyme inducing the DNA cleavage required for both somatic hypermutation and class switch recombination (CSR) of the immunoglobulin gene. We originally proposed the RNA-editing model for the mechanism of DNA cleavage by AID. We obtained evidence that fulfils three requirements for CSR by this model, namely (i) AID shuttling between nucleus and cytoplasm, (ii) de novo protein synthesis for CSR, and (iii) AID-RNA complex formation. The alternative hypothesis, designated as the DNA-deamination model, assumes that the in vitro DNA deamination activity of AID is representative of its physiological function in vivo. Furthermore, the resulting dU was removed by uracil DNA glycosylase (UNG) to generate a basic site, followed by phosphodiester bond cleavage by AP endonuclease. We critically examined each of these provisional steps. We identified a cluster of mutants (H48A, L49A, R50A and N51A) that had particularly higher CSR activities than expected from their DNA deamination activities. The most striking was the N51A mutant that had no ability to deaminate DNA in vitro but retained approximately 50 per cent of the wild-type level of CSR activity. We also provide further evidence that UNG plays a non-canonical role in CSR, namely in the repair step of the DNA breaks. Taking these results together, we favour the RNA-editing model for the function of AID in CSR.

  10. Mechanisms of nanotoxicity: Generation of reactive oxygen species

    Directory of Open Access Journals (Sweden)

    Peter P. Fu

    2014-03-01

    Full Text Available Nanotechnology is a rapidly developing field in the 21st century, and the commercial use of nanomaterials for novel applications is increasing exponentially. To date, the scientific basis for the cytotoxicity and genotoxicity of most manufactured nanomaterials are not understood. The mechanisms underlying the toxicity of nanomaterials have recently been studied intensively. An important mechanism of nanotoxicity is the generation of reactive oxygen species (ROS. Overproduction of ROS can induce oxidative stress, resulting in cells failing to maintain normal physiological redox-regulated functions. This in turn leads to DNA damage, unregulated cell signaling, change in cell motility, cytotoxicity, apoptosis, and cancer initiation. There are critical determinants that can affect the generation of ROS. These critical determinants, discussed briefly here, include: size, shape, particle surface, surface positive charges, surface-containing groups, particle dissolution, metal ion release from nanometals and nanometal oxides, UV light activation, aggregation, mode of interaction with cells, inflammation, and pH of the medium.

  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 <5%. The bubble size is larger than resonance size and smaller than acoustic wavelength. The amplitude of acoustic pressure wave was estimated using the definition of Bjerknes force in combination with Rayleigh-Plesset equation. Physical behavior of the system was capture and classified. Bubble size, velocity as well as size and spatial distribution will be presented.

  12. Under used technetium-99m generators

    International Nuclear Information System (INIS)

    Mushtaq, A.

    2001-01-01

    Health care reform truly has become a global issue and it will undoubtedly have a dramatic impact on the future of nuclear medicine business in particular. A bigger concern within the nuclear medicine community is its competitiveness with other modalities and cost effectiveness.Technetium-99m and its generators are playing key role for the majority of diagnostic scans performed in the world today. Availability of ''9''9''mTc can be increased if it is separated from ''9''9Mo after much shorter growth times. After proper planning with the extra ''9''9''mTc, a significant number of scans can be performed or we would be able to order approximately 30% low activity ''9''9Tc generators to fulfill our requirements

  13. Ecton mechanism of ion flow generation in vacuum arc

    CERN Document Server

    Mesyats, G A

    2001-01-01

    The basic characteristics of cathode plasma generation in vacuum arc (ion erosion, ion average charge) were studied from the point of an ecton model of a cathode spot in vacuum arc. The estimates of ion parameters obtained for a single cell of a cathode spot show qualitative conformity with the experimental data. One introduces the following mechanism of cathode plasma generation in vacuum arc. In case of explosion-like destruction of a cathode segment under the effect of the Joule heating the cathode matter changes sequentially its state: condensed one, nonideal and ideal plasma ones. During this change one observes formation of plasma charge composition and ion acceleration under the effect of plasma pressure gradient

  14. A study on fixing force generation mechanism of ER gel

    International Nuclear Information System (INIS)

    Tanaka, H; Kakinuma, Y; Aoyama, T; Anzai, H

    2009-01-01

    Electro-rheological Gel (ERG) is a new functional elastomer which changes its surface frictional and adhesive property according to the intensity of applied electrical field. This unique property is called ERG effect. The upper sliding electrode placed on the surface of ERG is fixed by the adhesive effect of ERG under electrical field. Variable fixing forces due to adhesion are generated by this effect. However, relationship between physical factors and generated fixing force has not yet been clarified. In this study, physical mechanism of fixing phenomenon is elucidated experimentally from the view point of frictional force and adhesive force. From the results, empirical equation of generated fixing force is originally derived to establish the theory of ERG effect.

  15. A study on fixing force generation mechanism of ER gel

    Energy Technology Data Exchange (ETDEWEB)

    Tanaka, H; Kakinuma, Y; Aoyama, T [School of Integrated Design Engineering, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Anzai, H [Fujikura kasei Co., Ltd., 2-6-15 Shibakouen, Minato-ku, Tokyo (Japan)], E-mail: h-tanaka@ina.sd.keio.ac.jp

    2009-02-01

    Electro-rheological Gel (ERG) is a new functional elastomer which changes its surface frictional and adhesive property according to the intensity of applied electrical field. This unique property is called ERG effect. The upper sliding electrode placed on the surface of ERG is fixed by the adhesive effect of ERG under electrical field. Variable fixing forces due to adhesion are generated by this effect. However, relationship between physical factors and generated fixing force has not yet been clarified. In this study, physical mechanism of fixing phenomenon is elucidated experimentally from the view point of frictional force and adhesive force. From the results, empirical equation of generated fixing force is originally derived to establish the theory of ERG effect.

  16. Mechanically based generative laws of morphogenesis

    International Nuclear Information System (INIS)

    Beloussov, Lev V

    2008-01-01

    A deep (although at the first glance naïve) question which may be addressed to embryonic development is why during this process quite definite and accurately reproduced successions of precise and complicated shapes are taking place, or why, in several cases, the result of development is highly precise in spite of an extensive variability of intermediate stages. This problem can be attacked in two different ways. One of them, up to now just slightly employed, is to formulate robust macroscopic generative laws from which the observed successions of shapes could be derived. Another one, which dominates in modern embryology, regards the development as a succession of highly precise 'micropatterns', each of them arising due to the action of specific factors, having, as a rule, nothing in common with each other. We argue that the latter view contradicts a great bulk of firmly established data and gives no satisfactory answers to the main problems of development. Therefore we intend to follow the first way. By doing this, we regard developing embryos as self-organized systems transpierced by feedbacks among which we pay special attention to those linked with mechanical stresses (MS). We formulate a hypothesis of so-called MS hyper-restoration as a common basis for the developmentally important feedback loops. We present a number of examples confirming this hypothesis and use it for reconstructing prolonged chains of developmental events. Finally, we discuss the application of the same set of assumptions to the first steps of egg development and to the internal differentiation of embryonic cells

  17. Spray structure as generated under homogeneous flash boiling nucleation regime

    International Nuclear Information System (INIS)

    Levy, M.; Levy, Y.; Sher, E.

    2014-01-01

    We show the effect of the initial pressure and temperature on the spatial distribution of droplets size and their velocity profile inside a spray cloud that is generated by a flash boiling mechanism under homogeneous nucleation regime. We used TSI's Phase Doppler Particle Analyzer (PDPA) to characterize the spray. We conclude that the homogeneous nucleation process is strongly affected by the initial liquid temperature while the initial pressure has only a minor effect. The spray shape is not affected by temperature or pressure under homogeneous nucleation regime. We noted that the only visible effect is in the spray opacity. Finally, homogeneous nucleation may be easily achieved by using a simple atomizer construction, and thus is potentially suitable for fuel injection systems in combustors and engines. - Highlights: • We study the characteristics of a spray that is generated by a flash boiling process. • In this study, the flash boiling process occurs under homogeneous nucleation regime. • We used Phase Doppler Particle Analyzer (PDPA) to characterize the spray. • The SMD has been found to be strongly affected by the initial liquid temperature. • Homogeneous nucleation may be easily achieved by using a simple atomizer unit

  18. Analysis of Heat Generation Mechanism in Ultrasound Infrared Thermography

    International Nuclear Information System (INIS)

    Choi, Man Yong; Lee, Seung Seok; Park, Jeong Hak; Kang, Ki Soo; Kim, Won Tae

    2009-01-01

    Heat generation mechanism of ultrasound infrared thermography is still not well understood, yet and there are two reliable assumptions of heat generation, friction and thermo-mechanical effect. This paper investigates the principal cause of heat generation at fatigue crack with experimental and numerical approach. Our results show most of heat generation is contributed by friction between crack interface and thermo-mechanical effect is a negligible quantity

  19. Deformation Mechanisms of Gum Metals Under Nanoindentation

    Science.gov (United States)

    Sankaran, Rohini Priya

    defect structures to applied loading, we perform ex-situ nanoindentation. Nanoindentation is a convenient method as the plastic deformation is localized and probes a nominally defect free volume of the material. We subsequently characterize the defect structures in these alloys with both conventional TEM and advanced techniques such as HAADF HRSTEM and nanoprobe diffraction. These advanced techniques allow for a more thorough understanding of the observed deformation features. The main findings from this investigation are as follows. As expected we observe that a non-equilibrium phase, o, is present in the leaner beta-stabilized alloy, ST Ref-1. We do not find any direct evidence of secondary phases in STGM, and we find the beta phase in CWGM, along with lath microstructure with subgrain structure consisting of dislocation cell networks. Upon nanoindentation, we find twinning accompanied by beta nucleation on the twin boundary in ST Ref-1 samples. This result is consistent with previous findings and is reasonable considering the alloy is unstable with respect to beta transformation. We find deformation nanotwinning in cold worked gum metals under nanoindentation, which is initially surprising. We argue that when viewed as a nanocrystalline material, such a deformation mechanism is consistent with previous work, and furthermore, a deformation nanotwinned structure does not preclude an ideal shear mechanism from operating in the alloy. Lastly, we observe continuous lattice rotations in STGM under nanoindentation via nanoprobe diffraction. With this technique, for the first time we can demonstrate that the lattice rotations are truly continuous at the nanoscale. We can quantify this lattice rotation, and find that even though the rotation is large, it may be mediated by a reasonable geometrically necessary dislocation density, and note that similar rotations are typically observed in other materials under nanoindentation. HRSTEM and conventional TEM data confirm the

  20. Concentration processes under tubesheet sludge piles in nuclear steam generators

    International Nuclear Information System (INIS)

    Gonzalez, F.; Spekkens, P.

    1987-01-01

    The process by which bulk water solutes are concentrated under tubesheet sludge piles in nuclear steam generators was investigated in the laboratory under simulated CANDU operating conditions. Concentration rates were found to depend on the tube heat flux and pile depth, although beyond a critical depth the concentration efficiency decreased. This efficiency could be expressed by a concentration coefficient, and was found to depend also on the sludge pile porosity. Solute concentration profiles in the sludge pile suggested that the concentration mechanism in a high-porosity/permeability pile is characterized by boiling mainly near or at the tube surface, while in low-porosity piles, the change of phase may also become important in the body of the sludge pile. In all cases, the full depth of the pile was active to some extent in the concentration process. As long as the heat transfer under the pile was continued, the solute remained under the pile and slowly migrated toward the bottom. When the heat transfer was stopped, the solute diffused back into the bulk solution at a rate slower than that of the concentration process

  1. Mechanism of power generation - the MHD way

    International Nuclear Information System (INIS)

    Rangachari, S.; Ramash, V.R.; Subramanian, C.K.

    1975-01-01

    The basic physical principles of magnetohydrodynamics and the application of this principle for power generation (direct energy conversion) are explained. A magnetohydrodynamic generator (MHDG) is described both in the Faraday and Hall modes. The advantages of the Faraday mode and the Hall mode for different geometries of the generator are mentioned. The conductor used is a fluid - an ionised gas (plasma) or a liquid metal at high temperature. The difficulties in maintaining high temperature and high velocity for the gas and very low temperature at the same time side by side for superconducting magnets to produce a strong magnetic field, are pointed out. The most commonly used gas is purified air. The advantages of MHD generators and the present power crisis have compelled further research in this field in spite of the high costs involved. (A.K.)

  2. Numerical modeling of polar mesocyclones generation mechanisms

    Science.gov (United States)

    Sergeev, Dennis; Stepanenko, Victor

    2013-04-01

    Polar mesocyclones, commonly referred to as polar lows, remain of great interest due to their complicated dynamics. These mesoscale vortices are small short-living objects that are formed over the observation-sparse high-latitude oceans, and therefore, their evolution can hardly be observed and predicted numerically. The origin of polar mesoscale cyclones is still a matter of uncertainty, though the recent numerical investigations [3] have exposed a strong dependence of the polar mesocyclone development upon the magnitude of baroclinicity. Nevertheless, most of the previous studies focused on the individual polar low (the so-called case studies), with too many factors affecting it simultaneously. None of the earlier studies suggested a clear picture of polar mesocyclone generation within an idealized experiment, where it is possible to look deeper into each single physical process. The present paper concentrates on the initial triggering mechanism of the polar mesocyclone. As it is reported by many researchers, some mesocyclones are formed by the surface forcing, namely the uneven distribution of heat fluxes. That feature is common on the ice boundaries [2], where intense air stream flows from the cold ice surface to the warm sea surface. Hence, the resulting conditions are shallow baroclinicity and strong surface heat fluxes, which provide an arising polar mesocyclone with potential energy source converting it to the kinetic energy of the vortex. It is shown in this paper that different surface characteristics, including thermal parameters and, for example, the shape of an ice edge, determine an initial phase of a polar low life cycle. Moreover, it is shown what initial atmospheric state is most preferable for the formation of a new polar mesocyclone or in maintaining and reinforcing the existing one. The study is based on idealized high-resolution (~2 km) numerical experiment in which baroclinicity, stratification, initial wind profile and disturbance, surface

  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. 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.

  5. Payment mechanisms for micro-generation

    Energy Technology Data Exchange (ETDEWEB)

    Choudhury, W.; Andrews, S.

    2002-07-01

    The Department of Trade and Industry commissioned a study into payment options for the increasing number of micro-generators (in domestic dwellings and where the generating capacity is not more than 5kW i.e. essentially micro-CHP and photovoltaics) supplying power for the national distribution network. It is shown that small generators will impact on all aspects of industry and connection will need to be simplified. The network will call for a more actively managed regime. Metering will need to be more sophisticated and agreement reached on how costs should be allocated when demand is low and surplus electricity is exported to the system. Three options were considered to be viable.

  6. ON THE TOPOLOGY OF MECHANISMS DESIGNED FOR CURVES GENERATION

    Directory of Open Access Journals (Sweden)

    MEREUTA Elena

    2008-07-01

    Full Text Available The paper presents some mechanisms used for generating simple or complex curves. The mechanisms are shown in different positions and for some special curves the demonstrations are performed.

  7. Molecular mechanics of silk nanostructures under varied mechanical loading.

    Science.gov (United States)

    Bratzel, Graham; Buehler, Markus J

    2012-06-01

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

  8. Neural Mechanisms Underlying Risk and Ambiguity Attitudes.

    Science.gov (United States)

    Blankenstein, Neeltje E; Peper, Jiska S; Crone, Eveline A; van Duijvenvoorde, Anna C K

    2017-11-01

    Individual differences in attitudes to risk (a taste for risk, known probabilities) and ambiguity (a tolerance for uncertainty, unknown probabilities) differentially influence risky decision-making. However, it is not well understood whether risk and ambiguity are coded differently within individuals. Here, we tested whether individual differences in risk and ambiguity attitudes were reflected in distinct neural correlates during choice and outcome processing of risky and ambiguous gambles. To these ends, we developed a neuroimaging task in which participants ( n = 50) chose between a sure gain and a gamble, which was either risky or ambiguous, and presented decision outcomes (gains, no gains). From a separate task in which the amount, probability, and ambiguity level were varied, we estimated individuals' risk and ambiguity attitudes. Although there was pronounced neural overlap between risky and ambiguous gambling in a network typically related to decision-making under uncertainty, relatively more risk-seeking attitudes were associated with increased activation in valuation regions of the brain (medial and lateral OFC), whereas relatively more ambiguity-seeking attitudes were related to temporal cortex activation. In addition, although striatum activation was observed during reward processing irrespective of a prior risky or ambiguous gamble, reward processing after an ambiguous gamble resulted in enhanced dorsomedial PFC activation, possibly functioning as a general signal of uncertainty coding. These findings suggest that different neural mechanisms reflect individual differences in risk and ambiguity attitudes and that risk and ambiguity may impact overt risk-taking behavior in different ways.

  9. 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.

  10. Mechanical behavior of silicon carbide nanoparticles under uniaxial compression

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-15

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

  11. Electro-mechanical sine/cosine generator

    Science.gov (United States)

    Flagge, B. (Inventor)

    1972-01-01

    An electromechanical device for generating both sine and cosine functions is described. A motor rotates a cylinder about an axis parallel to and a slight distance from the central axis of the cylinder. Two noncontacting displacement sensing devices are placed ninety degrees apart, equal distances from the axis of rotation of the cylinder and short distances above the surface of cylinder. Each of these sensing devices produces an electrical signal proportional to the distance that it is away from the cylinder. Consequently, as the cylinder is rotated the outputs from the two sensing devices are the sine and cosine functions.

  12. The Generative Mechanisms of Open Government Data

    DEFF Research Database (Denmark)

    Jetzek, Thorhildur; Avital, Michel; Bjørn-Andersen, Niels

    2013-01-01

    The exponentially growing production of data enables global connectivity as well as increased openness and sharing, which turn into a powerful force that is changing the global economy and society. Governments around the world have become active participants in this evolution by opening up...... their data for access and re-use by public and private agents alike. The recent phenomenon of Open Government Data (OGD) has spread around the world, driven by the proposition that opening government data has the ability to generate both economic and social value. However, a review of the academic research...

  13. A simple method for generating exactly solvable quantum mechanical potentials

    CERN Document Server

    Williams, B W

    1993-01-01

    A simple transformation method permitting the generation of exactly solvable quantum mechanical potentials from special functions solving second-order differential equations is reviewed. This method is applied to Gegenbauer polynomials to generate an attractive radial potential. The relationship of this method to the determination of supersymmetric quantum mechanical superpotentials is discussed, and the superpotential for the radial potential is also derived. (author)

  14. Business environment change and decision making mechanism of nuclear generators

    International Nuclear Information System (INIS)

    Yamashita, Hiroko

    2010-01-01

    Change magnitude of business environment for Japanese nuclear generators is significant. It is rapidly growing in the last several years. There are possibilities that the change might impact to management model of nuclear generators. In the paper, the impact to management model, especially, decision making mechanism of the generators is discussed. (author)

  15. Mechanisms of nanotoxicity: generation of reactive oxygen species.

    Science.gov (United States)

    Fu, Peter P; Xia, Qingsu; Hwang, Huey-Min; Ray, Paresh C; Yu, Hongtao

    2014-03-01

    Nanotechnology is a rapidly developing field in the 21(st) century, and the commercial use of nanomaterials for novel applications is increasing exponentially. To date, the scientific basis for the cytotoxicity and genotoxicity of most manufactured nanomaterials are not understood. The mechanisms underlying the toxicity of nanomaterials have recently been studied intensively. An important mechanism of nanotoxicity is the generation of reactive oxygen species (ROS). Overproduction of ROS can induce oxidative stress, resulting in cells failing to maintain normal physiological redox-regulated functions. This in turn leads to DNA damage, unregulated cell signaling, change in cell motility, cytotoxicity, apoptosis, and cancer initiation. There are critical determinants that can affect the generation of ROS. These critical determinants, discussed briefly here, include: size, shape, particle surface, surface positive charges, surface-containing groups, particle dissolution, metal ion release from nanometals and nanometal oxides, UV light activation, aggregation, mode of interaction with cells, inflammation, and pH of the medium. Copyright © 2014. Published by Elsevier B.V.

  16. PLANAR MECHANISMS USED FOR GENERATING CURVE LINE TRANSLATION MOTION

    Directory of Open Access Journals (Sweden)

    Ovidiu ANTONESCU

    2015-05-01

    Full Text Available The curve line translation motion can be generated in the particular form of the circular translation, through mono-mobile mechanisms with articulated links of simple parallelogram type (with a fixed side or through transmission with toothed belt with a fixed wheel. Also, the circular translation can be generated through planar mechanisms with two cylindrical gears with a fixed central wheel. It is mentioned that the two cylindrical gearings of the Fergusson mechanisms are both exterior and interior.

  17. Current Control Method for Distributed Generation Power Generation Plants under Grid Fault Conditions

    DEFF Research Database (Denmark)

    Rodriguez, Pedro; Luna, Alvaro; Hermoso, Juan Ramon

    2011-01-01

    The operation of distributed power generation systems under grid fault conditions is a key issue for the massive integration of renewable energy systems. Several studies have been conducted to improve the response of such distributed generation systems under voltage dips. In spite of being less s...

  18. Magnetization reversal mechanisms under oblique magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Ntallis, N.; Efthimiadis, K.G., E-mail: kge@auth.gr

    2017-03-01

    In this work finite element micromagnetic simulations were performed in order to study the reversal mechanisms of spherical ferromagnetic particles with uniaxial magnetocrystalline anisotropy, when they are magnetized along an oblique direction with respect to the anisotropy axis. Magnetization loops are taken in different directions of external magnetic field, at different anisotropy constants and particle sizes. In the simulation results, the three reversal mechanisms (coherent, curling and domains) are observed and new phenomena arise due to the action of oblique magnetic fields. Moreover, the dependence of the critical fields with respect to the angle of the external field is presented. - Highlights: • Finite element micromagnetic simulation of the three different reversal mechanisms. • For the curling mechanism, the new phenomenon is the rotation of the vortex. • In the domain reversal mechanism, the formed domain wall is smaller than 180°. • In soft ferromagnetic particles a rearrangement of the magnetic domains is observed.

  19. Generating strain signals under consideration of road surface profiles

    Science.gov (United States)

    Putra, T. E.; Abdullah, S.; Schramm, D.; Nuawi, M. Z.; Bruckmann, T.

    2015-08-01

    The current study aimed to develop the mechanism for generating strain signal utilising computer-based simulation. The strain data, caused by the acceleration, were undertaken from a fatigue data acquisition involving car movements. Using a mathematical model, the measured strain signals yielded to acceleration data used to describe the bumpiness of road surfaces. The acceleration signals were considered as an external disturbance on generating strain signals. Based on this comparison, both the actual and simulated strain data have similar pattern. The results are expected to provide new knowledge to generate a strain signal via a simulation.

  20. Port-Hamiltonian approaches to motion generation for mechanical systems

    NARCIS (Netherlands)

    Sakai, Satoru; Stramigioli, Stefano

    This paper gives new motion generation methods for mechanical port-Hamiltonian systems. First, we propose a generation method based on an asymptotic stabilization method without damping assignment. This asymptotic stabilization method preserves the Hamiltonian structure in the closed-loop system

  1. Higgs bosons and other mechanisms of mass generation

    International Nuclear Information System (INIS)

    Konopleva, N. P.

    1997-01-01

    There are two problems under discuss here: 1) are Higgs bosons really necessary for the gauge field mass generation or not, and 2) why are Higgs bosons invisible in the elementary particles experiments? It is shown that in the frame of the classical Lagrangian gauge fields theory the transition from the usual variational problem to isoperimetric one permits us to conserve the local gauge invariance on the solutions of the massive gauge field theory equations. Hence in the massive gauge field theory we can have on the field equation solutions not only the conservation laws corresponding with the first Noether's theorem but Noether's identities corresponding with the second Noether's theorem also. Therefore the alternative renormalization procedure can exist which does not demand of Higgs bosons appearance in the massive gauge field theory for its renormalizability. The interpretation of Higgs mechanism as the phase transition mechanism is discussed. From this point of view the inexplicable absence of the individual Higgs bosons could be the result of the fact that the massive gauge field is the complex system of the massless gauge fields interacting with the condensate of Higgs bosons and quantum vortices in it. In this case the gauge field obtains the mass when the phase transition happens and after that the individual Higgs bosons can not be eliminated from the complex system

  2. Mechanisms of sharp wave initiation and ripple generation.

    Science.gov (United States)

    Schlingloff, Dániel; Káli, Szabolcs; Freund, Tamás F; Hájos, Norbert; Gulyás, Attila I

    2014-08-20

    Replay of neuronal activity during hippocampal sharp wave-ripples (SWRs) is essential in memory formation. To understand the mechanisms underlying the initiation of irregularly occurring SWRs and the generation of periodic ripples, we selectively manipulated different components of the CA3 network in mouse hippocampal slices. We recorded EPSCs and IPSCs to examine the buildup of neuronal activity preceding SWRs and analyzed the distribution of time intervals between subsequent SWR events. Our results suggest that SWRs are initiated through a combined refractory and stochastic mechanism. SWRs initiate when firing in a set of spontaneously active pyramidal cells triggers a gradual, exponential buildup of activity in the recurrent CA3 network. We showed that this tonic excitatory envelope drives reciprocally connected parvalbumin-positive basket cells, which start ripple-frequency spiking that is phase-locked through reciprocal inhibition. The synchronized GABA(A) receptor-mediated currents give rise to a major component of the ripple-frequency oscillation in the local field potential and organize the phase-locked spiking of pyramidal cells. Optogenetic stimulation of parvalbumin-positive cells evoked full SWRs and EPSC sequences in pyramidal cells. Even with excitation blocked, tonic driving of parvalbumin-positive cells evoked ripple oscillations. Conversely, optogenetic silencing of parvalbumin-positive cells interrupted the SWRs or inhibited their occurrence. Local drug applications and modeling experiments confirmed that the activity of parvalbumin-positive perisomatic inhibitory neurons is both necessary and sufficient for ripple-frequency current and rhythm generation. These interneurons are thus essential in organizing pyramidal cell activity not only during gamma oscillation, but, in a different configuration, during SWRs. Copyright © 2014 the authors 0270-6474/14/3411385-14$15.00/0.

  3. 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

  4. Steam generators under construction for the SNR-300 power plant

    Energy Technology Data Exchange (ETDEWEB)

    Essebaggers, J

    1975-07-01

    The prototype straight tube and the helical coil-steam generator has been designed and fabricated of which the straight tube steam generator has been successfully tested for over 3000 hours at prototypical conditions and is presently being dismantled for detailed examination of critical designed features. The prototype helical coil steam generator is presently under testing in the 50 MWt test facility at TNO-Hengelo with approximately 500 hours of operation at full load conditions. In an earlier presentation the design and fabrication of the prototype steam generators have been presented, while for this presentation the production units for SNR-300 will be discussed. Some preliminary information will be presented at this meeting of the dismantling operations of the prototype straight tube steam generator. (author)

  5. Steam generators under construction for the SNR-300 power plant

    International Nuclear Information System (INIS)

    Essebaggers, J.

    1975-01-01

    The prototype straight tube and the helical coil-steam generator has been designed and fabricated of which the straight tube steam generator has been successfully tested for over 3000 hours at prototypical conditions and is presently being dismantled for detailed examination of critical designed features. The prototype helical coil steam generator is presently under testing in the 50 MWt test facility at TNO-Hengelo with approximately 500 hours of operation at full load conditions. In an earlier presentation the design and fabrication of the prototype steam generators have been presented, while for this presentation the production units for SNR-300 will be discussed. Some preliminary information will be presented at this meeting of the dismantling operations of the prototype straight tube steam generator. (author)

  6. Optimal investment strategies in decentralized renewable power generation under uncertainty

    International Nuclear Information System (INIS)

    Fleten, S.-E.; Maribu, K.M.; Wangensteen, I.

    2007-01-01

    This paper presents a method for evaluating investments in decentralized renewable power generation under price un certainty. The analysis is applicable for a client with an electricity load and a renewable resource that can be utilized for power generation. The investor has a deferrable opportunity to invest in one local power generating unit, with the objective to maximize the profits from the opportunity. Renewable electricity generation can serve local load when generation and load coincide in time, and surplus power can be exported to the grid. The problem is to find the price intervals and the capacity of the generator at which to invest. Results from a case with wind power generation for an office building suggests it is optimal to wait for higher prices than the net present value break-even price under price uncertainty, and that capacity choice can depend on the current market price and the price volatility. With low price volatility there can be more than one investment price interval for different units with intermediate waiting regions between them. High price volatility increases the value of the investment opportunity, and therefore makes it more attractive to postpone investment until larger units are profitable. (author)

  7. Mechanism of neutron generation in Z-pinches

    International Nuclear Information System (INIS)

    Vikhrev, V.V.

    1986-01-01

    The review of experimental and theoretical investigations in a mechanism of neutron generation in Z-pinches is presented. Special attention is paid to the thermonuclear mechanism of neutron generation occuring due to the formation of high-temperature plasma regions in Z-pinch sausage-type instabilities. This mechanism is shown to be predominant in charges with the neutron yield more than 10 9 per a charge. Experimental data, which are considered to be contradicting to thermonuclear nature of neutron radiation, are explained

  8. New perspectives on mechanisms of sound generation in songbirds

    DEFF Research Database (Denmark)

    Goller, Franz; Larsen, Ole Næsbye

    2002-01-01

    -tone mechanism similar to human phonation with the labia forming a pneumatic valve. The classical avian model proposed that vibrations of the thin medial tympaniform membranes are the primary sound generating mechanism. As a direct test of these two hypotheses we ablated the medial tympaniform membranes in two......The physical mechanisms of sound generation in the vocal organ, the syrinx, of songbirds have been investigated mostly with indirect methods. Recent direct endoscopic observation identified vibrations of the labia as the principal sound source. This model suggests sound generation in a pulse...... atmosphere) as well as direct (labial vibration during tonal sound) measurements of syringeal vibrations support a vibration-based soundgenerating mechanism even for tonal sounds....

  9. 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

  10. V1 mechanisms underlying chromatic contrast detection

    Science.gov (United States)

    Hass, Charles A.

    2013-01-01

    To elucidate the cortical mechanisms of color vision, we recorded from individual primary visual cortex (V1) neurons in macaque monkeys performing a chromatic detection task. Roughly 30% of the neurons that we encountered were unresponsive at the monkeys' psychophysical detection threshold (PT). The other 70% were responsive at threshold but on average, were slightly less sensitive than the monkey. For these neurons, the relationship between neurometric threshold (NT) and PT was consistent across the four isoluminant color directions tested. A corollary of this result is that NTs were roughly four times lower for stimuli that modulated the long- and middle-wavelength sensitive cones out of phase. Nearly one-half of the neurons that responded to chromatic stimuli at the monkeys' detection threshold also responded to high-contrast luminance modulations, suggesting a role for neurons that are jointly tuned to color and luminance in chromatic detection. Analysis of neuronal contrast-response functions and signal-to-noise ratios yielded no evidence for a special set of “cardinal color directions,” for which V1 neurons are particularly sensitive. We conclude that at detection threshold—as shown previously with high-contrast stimuli—V1 neurons are tuned for a diverse set of color directions and do not segregate naturally into red–green and blue–yellow categories. PMID:23446689

  11. Analysis of mechanical behavior and hysteresis heat generating mechanism of PDM motor

    International Nuclear Information System (INIS)

    Shi, Changshuai; Zhu, Xiaohua; Tang, Liping; Deng, Juan

    2017-01-01

    Positive displacement motor (PDM), which is prone to high temperature fatigue failure, can be weakened in its application in deep and superdeep well. In order to study the forced state, deformation regularity and thermal hysteresis of PDM motor, the paper established the three-dimensional thermal-mechanical coupled Finite element model (FEM). Based on the theoretical research, experimental study and numerical simulation, the study found that the displacement of stator lining shows a sinusoidal variation under internal pressure, when adapting the general form of sine function to fitting inner contour line deformation function. Then the paper analyzed the hysteresis heat generating mechanism of the motor, learning that hysteresis thermogenous of stator lining occurs due to the viscoelastic of rubber material and cyclic loading of stator lining. A heartburn happens gradually in the center of the thickest part of the stator lining as temperature increases, which means work efficiency and service life of PDM will be decreased when used in deep or superdeep well. In this paper, we established a theory equation for the choice of interference fit and motor line type optimization design, showing hysteresis heat generating analyzing model and method are reasonable enough to significantly improve PDM’s structure and help better use PDM in deep and surdeep well

  12. Analysis of mechanical behavior and hysteresis heat generating mechanism of PDM motor

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Changshuai; Zhu, Xiaohua; Tang, Liping [Southwest Petroleum University, Chengdu (China); Deng, Juan [Avic Chengdu Engine (Group) Co.,Ltd, Chengdu (China)

    2017-03-15

    Positive displacement motor (PDM), which is prone to high temperature fatigue failure, can be weakened in its application in deep and superdeep well. In order to study the forced state, deformation regularity and thermal hysteresis of PDM motor, the paper established the three-dimensional thermal-mechanical coupled Finite element model (FEM). Based on the theoretical research, experimental study and numerical simulation, the study found that the displacement of stator lining shows a sinusoidal variation under internal pressure, when adapting the general form of sine function to fitting inner contour line deformation function. Then the paper analyzed the hysteresis heat generating mechanism of the motor, learning that hysteresis thermogenous of stator lining occurs due to the viscoelastic of rubber material and cyclic loading of stator lining. A heartburn happens gradually in the center of the thickest part of the stator lining as temperature increases, which means work efficiency and service life of PDM will be decreased when used in deep or superdeep well. In this paper, we established a theory equation for the choice of interference fit and motor line type optimization design, showing hysteresis heat generating analyzing model and method are reasonable enough to significantly improve PDM’s structure and help better use PDM in deep and surdeep well.

  13. 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).

  14. Generation mechanism and properties of plasma double layers

    International Nuclear Information System (INIS)

    Sanduloviciu, M.; Lozneanu, E.

    1985-01-01

    The generation mechanism of plasma double layers is studied surveying the results of some experiments. The main mechanism is the same in the cases of collisional and collisionless plasmas. Inelastic quantum collision processes taking place between plasma electrons, accelerated in a local field up to near the same oriented velocity and the neutral particles of the background gases create the necessary conditions for double layer formation. (D.Gy.)

  15. VOLCANIC TSUNAMI GENERATING SOURCE MECHANISMS IN THE EASTERN CARIBBEAN REGION

    Directory of Open Access Journals (Sweden)

    George Pararas-Carayannis

    2004-01-01

    Full Text Available Earthquakes, volcanic eruptions, volcanic island flank failures and underwater slides have generated numerous destructive tsunamis in the Caribbean region. Convergent, compressional and collisional tectonic activity caused primarily from the eastward movement of the Caribbean Plate in relation to the North American, Atlantic and South American Plates, is responsible for zones of subduction in the region, the formation of island arcs and the evolution of particular volcanic centers on the overlying plate. The inter-plate tectonic interaction and deformation along these marginal boundaries result in moderate seismic and volcanic events that can generate tsunamis by a number of different mechanisms. The active geo-dynamic processes have created the Lesser Antilles, an arc of small islands with volcanoes characterized by both effusive and explosive activity. Eruption mechanisms of these Caribbean volcanoes are complex and often anomalous. Collapses of lava domes often precede major eruptions, which may vary in intensity from Strombolian to Plinian. Locally catastrophic, short-period tsunami-like waves can be generated directly by lateral, direct or channelized volcanic blast episodes, or in combination with collateral air pressure perturbations, nuéss ardentes, pyroclastic flows, lahars, or cascading debris avalanches. Submarine volcanic caldera collapses can also generate locally destructive tsunami waves. Volcanoes in the Eastern Caribbean Region have unstable flanks. Destructive local tsunamis may be generated from aerial and submarine volcanic edifice mass edifice flank failures, which may be triggered by volcanic episodes, lava dome collapses, or simply by gravitational instabilities. The present report evaluates volcanic mechanisms, resulting flank failure processes and their potential for tsunami generation. More specifically, the report evaluates recent volcanic eruption mechanisms of the Soufriere Hills volcano on Montserrat, of Mt. Pel

  16. Generative models versus underlying symmetries to explain biological pattern.

    Science.gov (United States)

    Frank, S A

    2014-06-01

    Mathematical models play an increasingly important role in the interpretation of biological experiments. Studies often present a model that generates the observations, connecting hypothesized process to an observed pattern. Such generative models confirm the plausibility of an explanation and make testable hypotheses for further experiments. However, studies rarely consider the broad family of alternative models that match the same observed pattern. The symmetries that define the broad class of matching models are in fact the only aspects of information truly revealed by observed pattern. Commonly observed patterns derive from simple underlying symmetries. This article illustrates the problem by showing the symmetry associated with the observed rate of increase in fitness in a constant environment. That underlying symmetry reveals how each particular generative model defines a single example within the broad class of matching models. Further progress on the relation between pattern and process requires deeper consideration of the underlying symmetries. © 2014 The Author. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  17. 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.

  18. Linear modeling of possible mechanisms for parkinson tremor generation

    NARCIS (Netherlands)

    Lohnberg, P.

    1978-01-01

    The power of Parkinson tremor is expressed in terms of possibly changed frequency response functions between relevant variables in the neuromuscular system. The derivation starts out from a linear loopless equivalent model of mechanisms for general tremor generation. Hypothetical changes in this

  19. Effect of mechanical vibration generated in oscillating/vibratory ...

    African Journals Online (AJOL)

    Background: Whole body vibration (WBV) exercise has been used in health sciences. Authors have reported that changes on the concentration of plasma biomarkers could be associated with the WBV effects. The aim of this investigation is to assess the consequences of exposition of 25 Hz mechanical vibration generated ...

  20. Possible mechanism of solar noise storm generation in meter wavelength

    International Nuclear Information System (INIS)

    Genkin, L.G.; Erukhimov, L.M.; Levin, B.N.

    1989-01-01

    Fluctuation plasma mechanism of noise storm generation is proposed. The sporadic formation of density irregularities in plasma (Langmuir) turbulence region is shown to be the result of thermal stratification of plasma. The noise storm type 1 bursts in their typical parameters are like radio emission due to plasma turbulence conversion on this structures

  1. Mechanisms of elastic wave generation in solids by ion impact

    International Nuclear Information System (INIS)

    Deemer, B.; Murphy, J.; Claytor, T.

    1990-01-01

    This study is directed at understanding the mechanisms of acoustic signal generation by modulated beams of energetic ions as a function of ion energy. Interaction of ions with solids initiates a range of processes including sputtering, ion implantation, ionization, both internal and external, as well as thermal deposition in the solid. Accumulated internal stress also occurs by generation of dislocations resulting from, inelastic nuclear scattering of the incident ion beam. With respect to elastic wave generation, two potential mechanisms are thermoelastic induced stress and momentum transfer. The latter process includes contributions of momentum transfer from the incident beam and from ions ejected via sputtering. Other aspects of the generation process include the potential for shock wave generation since the mean particle velocity for a wide range of ion energies exceeds the velocity of sound in solids. This study seeks to distinguish the contribution of these mechanisms by studying the signature, angular distribution and energy dependence of the elastic wave response in the time domain and to use this information to understand technologically important processes such as implantation and sputtering

  2. Crack assessment of pipe under combined thermal and mechanical load

    International Nuclear Information System (INIS)

    Song, Tae Kwang; Kim, Yun Jae

    2009-01-01

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

  3. Power generation capacity planning under budget constraint in developing countries

    International Nuclear Information System (INIS)

    Afful-Dadzie, Anthony; Afful-Dadzie, Eric; Awudu, Iddrisu; Banuro, Joseph Kwaku

    2017-01-01

    Highlights: • A long term stochastic GEP model with budget constraint is developed. • Model suitable for analyzing GEP problems in developing countries. • Model determines optimal mix, size and timing of future generation capacity needs. • A real case study of the Ghana GEP problem was employed. • Insufficient budget leads to costly generation capacity expansion plans. - Abstract: This paper presents a novel multi-period stochastic optimization model for studying long-term power generation capacity planning in developing countries. A stylized model is developed to achieve three objectives: (1) to serve as a tool for determining optimal mix, size and timing of power generation types in the face of budget constraint, (2) to help decision makers appreciate the consequences of capacity expansion decisions on level of unserved electricity demand and its attendant impact on the national economy, and (3) to encourage the habit of periodic savings towards new generation capacity financing. The problem is modeled using a stochastic mixed-integer linear programming (MILP) technique under demand uncertainty. The effectiveness of the model, together with valuable insights derived from considering different levels of budget constraints are demonstrated using Ghana as a case study. The results indicate that at an annual savings equivalent to 0.75% of GDP, Ghana could finance the needed generation capacity to meet approximately 95% of its annual electricity demand between 2016 and 2035. Additionally, it is observed that as financial constraint becomes tighter, decisions on the mix of new generation capacities tend to be more costly compared to when sufficient funds are available.

  4. Mechanical design of a sodium heated steam generator

    International Nuclear Information System (INIS)

    Chetal, S.C.

    1975-01-01

    FBTR steam generator is a once through type unit consisting of four 12.5 MW thermal modules generating a total of 74 tons per hour of steam at 125 bar and 480 0 C. This paper outlines the mechanical design of such type of steam generator with emphasis on special design problems associated with this type of sodium to water steam heat exchanger, namely, thermal cycling of transition zone where nucleate boiling changes over to film boiling, application of pressure vessel design criteria for transient pressures, thermal stress evaluation resulting from differential expansion between shell and tube in this typical configuration, sodium headers support design, thermal sleeve, design, thermal shock analysis in thick tubes, thermal stress resulting from stratification and stability of expansion bends against vibration. Some of the possible design changes for the future large size steam generator are outlined. (author)

  5. New mechanism for generating density perturbations from inflation

    International Nuclear Information System (INIS)

    Dvali, Gia; Gruzinov, Andrei; Zaldarriaga, Matias

    2004-01-01

    We propose a new mechanism to generate density perturbations in inflationary models. Spatial fluctuations in the decay rate of the inflaton field to ordinary matter lead to fluctuations in the reheating temperature. We argue that in most realistic models of inflation the coupling of the inflaton to normal matter is determined by the vacuum expectation values of fields in the theory. If those fields are light during inflation (this is a generic situation in the minimal models of supersymmetric inflation) they will fluctuate leading to density perturbations through the proposed mechanism. We show that these fluctuations could easily dominate over the ones generated through the standard mechanism. The new scenario has several consequences for inflation model building and observations. The proposed mechanism allows us to generate the observed level of density perturbations with a much lower scale of inflation and thus generically predicts a smaller level of gravitational waves. The relation between the slope of the spectrum of the produced density perturbations and the potential of the inflaton field is different from the standard relations obtained in the context of slow roll inflation. Because the field responsible for the fluctuations is not the inflaton, it can have significantly larger self-couplings and thus density perturbations could be non-Gaussian. The non-Gaussianity can be large enough to be detectable by CMB and large scale structure observations

  6. Mechanics of torque generation in the bacterial flagellar motor.

    Science.gov (United States)

    Mandadapu, Kranthi K; Nirody, Jasmine A; Berry, Richard M; Oster, George

    2015-08-11

    The bacterial flagellar motor (BFM) is responsible for driving bacterial locomotion and chemotaxis, fundamental processes in pathogenesis and biofilm formation. In the BFM, torque is generated at the interface between transmembrane proteins (stators) and a rotor. It is well established that the passage of ions down a transmembrane gradient through the stator complex provides the energy for torque generation. However, the physics involved in this energy conversion remain poorly understood. Here we propose a mechanically specific model for torque generation in the BFM. In particular, we identify roles for two fundamental forces involved in torque generation: electrostatic and steric. We propose that electrostatic forces serve to position the stator, whereas steric forces comprise the actual "power stroke." Specifically, we propose that ion-induced conformational changes about a proline "hinge" residue in a stator α-helix are directly responsible for generating the power stroke. Our model predictions fit well with recent experiments on a single-stator motor. The proposed model provides a mechanical explanation for several fundamental properties of the flagellar motor, including torque-speed and speed-ion motive force relationships, backstepping, variation in step sizes, and the effects of key mutations in the stator.

  7. Equivalent Electrical Circuits of Thermoelectric Generators under Different Operating Conditions

    Directory of Open Access Journals (Sweden)

    Saima Siouane

    2017-03-01

    Full Text Available Energy harvesting has become a promising and alternative solution to conventional energy generation patterns to overcome the problem of supplying autonomous electrical systems. More particularly, thermal energy harvesting technologies have drawn a major interest in both research and industry. Thermoelectric Generators (TEGs can be used in two different operating conditions, under constant temperature gradient or constant heat flow. The commonly used TEG electrical model, based on a voltage source in series with an electrical resistance, shows its limitations especially under constant heat flow conditions. Here, the analytical electrical modeling, taking into consideration the internal and contact thermal resistances of a TEG under constant temperature gradient and constant heat flow conditions, is first given. To give further insight into the electrical behavior of a TEG module in different operating conditions, we propose a new and original way of emulating the above analytical expressions with usual electronics components (voltage source, resistors, diode, whose values are determined with the TEG’s parameters. Note that such a TEG emulation is particularly suited when designing the electronic circuitry commonly associated to the TEG, to realize both Maximum Power Point Tracking and output voltage regulation. First, the proposed equivalent electrical circuits are validated through simulation with a SPICE environment in static operating conditions using only one value of either temperature gradient or heat flow. Then, they are also analyzed in dynamic operating conditions where both temperature gradient and heat flow are considered as time-varying functions.

  8. Underlying mechanisms of improving physical activity behavior after rehabilitation

    NARCIS (Netherlands)

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

    2008-01-01

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

  9. 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

  10. Nonlinear Mechanics of MEMS Rectangular Microplates under Electrostatic Actuation

    KAUST Repository

    Saghir, Shahid

    2016-01-01

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

  11. Animal behavior models of the mechanisms underlying antipsychotic atypicality.

    NARCIS (Netherlands)

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

    2003-01-01

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

  12. Control of a perturbed under-actuated mechanical system

    KAUST Repository

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

    2015-01-01

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

  13. Grid-Connected Distributed Generation: Compensation Mechanism Basics

    Energy Technology Data Exchange (ETDEWEB)

    Aznar, Alexandra Y [National Renewable Energy Laboratory (NREL), Golden, CO (United States); ; ; ; Zinaman, Owen R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

    2017-10-02

    This short report defines compensation mechanisms for grid-connected, behind-the-meter distributed generation (DG) systems as instruments that comprise three core elements: (1) metering and billing arrangements, (2) sell rate design, and (3) retail rate design. This report describes metering and billing arrangements, with some limited discussion of sell rate design. We detail the three possible arrangements for metering and billing of DG: net energy metering (NEM); buy all, sell all; and net billing.

  14. Operating experience with the Harwell thermo-mechanical generators

    International Nuclear Information System (INIS)

    Cooke-Yarborough, E.H.

    1980-06-01

    The Stirling-cycle thermo-mechanical generator (TMG) provides small amounts of electrical power continuously over long periods, while requiring much less fuel than other power sources running from hydrocarbon fuel or radio-isotopes. Two of these 25-watt generators, fuelled by propane, have been used to power the UK National Buoy on two successive missions. A total of more than three years experience at sea has now been accumulated. In addition, a 60-watt version has provided the power for a major lighthouse for more than a year. An early development version of the Thermo-mechanical Generator, adapted to run from the heat of a radio-isotope source, was loaded with strontium 90 titanate in October 1974 and has run continuously in the laboratory ever since. The improvements and changes found necessary in the course of 90,000 generator-hours of running time are described, and the improvements in operational performance and reliability which have resulted are outlined. (author)

  15. Internal oxidation as a mechanism for steam generator tube degradation

    Energy Technology Data Exchange (ETDEWEB)

    Gendron, T.S. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada); Scott, P.M. [Framatome, Paris (France); Bruemmer, S.M. [Pacific Northwest National Laboratory, Richland, WA (United States); Thomas, L.E. [Washington State Univ., School of Mechanical and Materials Engineering, Pullman, WA (United States)

    1999-12-01

    Internal oxidation has been proposed as a plausible mechanism for intergranular stress-corrosion cracking (IGSCC) of alloy 600 steam generator tubing. This theory can reconcile the main thermodynamic and kinetic characteristics of the observed cracking in hydrogenated primary water. Although secondary-side IG attack or IGSCC is commonly attributed to the presence of strong, caustic or acidic solutions, more recent evidence suggests that this degradation takes place in a near neutral environment, possibly dry polluted steam. As a result, internal oxidation is also a feasible mechanism for secondary side degradation. The present paper reviews experimental work conducted in an attempt to determine the validity of this mechanism. The consequences for the expected behaviour of alloys 690 and 800 replacement materials are also described. (author)

  16. Internal oxidation as a mechanism for steam generator tube degradation

    Energy Technology Data Exchange (ETDEWEB)

    Gendron, T.S. [Atomic Energy of Canada Limited, Chalk River, Ontario (Canada); Scott, P.M. [Framatome, Paris (France); Bruemmer, S.M. [Pacific Northwest National Lab., Richland, Washington (United States); Thomas, L.E. [Washington State Univ., School of Mechanical and Materials Engineering, Pullman, WA (United States)

    1998-07-01

    Internal oxidation has been proposed as a plausible mechanism for intergranular stress corrosion cracking (IGSCC) of alloy 600 steam generator tubing. This theory can reconcile the main thermodynamic and kinetic characteristics of the observed cracking in hydrogenated primary water. Although secondary side IG attack or IGSCC is commonly attributed to the presence of strong caustic or acidic solutions, more recent evidence suggests that this degradation takes place in a near-neutral environment, possibly dry polluted steam. As a result, internal oxidation is also a feasible mechanism for secondary side degradation. The present paper reviews experimental work carried out in an attempt to determine the validity of this mechanism. The consequences for the expected behaviour of alloys 690 and 800 replacement materials are also described. (author)

  17. Internal oxidation as a mechanism for steam generator tube degradation

    International Nuclear Information System (INIS)

    Gendron, T.S.; Scott, P.M.; Bruemmer, S.M.; Thomas, L.E.

    1998-01-01

    Internal oxidation has been proposed as a plausible mechanism for intergranular stress corrosion cracking (IGSCC) of alloy 600 steam generator tubing. This theory can reconcile the main thermodynamic and kinetic characteristics of the observed cracking in hydrogenated primary water. Although secondary side IG attack or IGSCC is commonly attributed to the presence of strong caustic or acidic solutions, more recent evidence suggests that this degradation takes place in a near-neutral environment, possibly dry polluted steam. As a result, internal oxidation is also a feasible mechanism for secondary side degradation. The present paper reviews experimental work carried out in an attempt to determine the validity of this mechanism. The consequences for the expected behaviour of alloys 690 and 800 replacement materials are also described. (author)

  18. Believing versus interacting: Behavioural and neural mechanisms underlying interpersonal coordination

    DEFF Research Database (Denmark)

    Konvalinka, Ivana; Bauer, Markus; Kilner, James

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

  19. Lead telluride with increased mechanical stability for cylindrical thermoelectric generators

    International Nuclear Information System (INIS)

    Schmitz, Andreas

    2013-01-01

    The aim of this work is to improve the mechanical stability of lead telluride (PbTe), trying to vary its mechanical properties independently from its thermoelectric properties. Thus the influence of material preparation as well as different dopants on the mechanical and thermoelectric properties of lead telluride is being analysed. When using appropriately set process parameters, milling and sintering of lead telluride increases the material's hardness. With sintering temperatures exceeding 300 C stable material of high relative density can be achieved. Milling lead telluride generates lattice defects leading to a reduction of the material's charge carrier density. These defects can be reduced by increased sintering temperatures. Contamination of the powder due to the milling process leads to bloating during thermal cycling and thus reduced density of the sintered material. In addition to that, evaporation of tellurium at elevated temperatures causes instability of the material's thermoelectric properties. Based on the experimental results obtained in this work, the best thermoelectric and mechanical properties can be obtained by sintering coarse powders at around 400 C. Within this work a concept was developed to vary the mechanical properties of lead telluride via synthesis of PbTe with electrically nondoping elements, which thus may keep the thermoelectric properties unchanged. Therefore, the mechanical and thermoelectric properties of Pb 1-x Ca x Te were investigated. Doping pure PbTe with calcium causes a significant increase of the material's hardness while only slightly decreasing the charge carrier density and thus keeping the thermoelectric properties apart from a slight reduction of the electrical conductivity nearly unchanged. The abovementioned concept is proven using sodium doped lead telluride, as it is used for thermoelectric generators: The additional doping with calcium again increases the material's hardness while its thermoelectric properties

  20. The Mechanical Behaviors of Various Dental Implant Materials under Fatigue

    Directory of Open Access Journals (Sweden)

    Fatma Bayata

    2018-01-01

    Full Text Available The selection of materials has a considerable role on long-term stability of implants. The materials having high resistance to fatigue are required for dental implant applications since these implants are subjected to cyclic loads during chewing. This study evaluates the performance of different types of materials (AISI 316L stainless steel, alumina and its porous state, CoCr alloys, yttrium-stabilized zirconia (YSZ, zirconia-toughened alumina (ZTA, and cp Ti with the nanotubular TiO2 surface by finite element analysis (FEA under real cyclic biting loads and researches the optimum material for implant applications. For the analysis, the implant design generated by our group was utilized. The mechanical behavior and the life of the implant under biting loads were estimated based on the material and surface properties. According to the condition based on ISO 14801, the FEA results showed that the equivalent von Mises stress values were in the range of 226.95 MPa and 239.05 MPa. The penetration analysis was also performed, and the calculated penetration of the models onto the bone structure ranged between 0.0037389 mm and 0.013626 mm. L-605 CoCr alloy-assigned implant model showed the least penetration, while cp Ti with the nanotubular TiO2 surface led to the most one. However, the difference was about 0.01 mm, and it may not be evaluated as a distinct difference. As the final numerical evaluation item, the fatigue life was executed, and the results were achieved in the range of 4 × 105 and 1 × 109 cycles. These results indicated that different materials showed good performance for each evaluation component, but considering the overall mechanical performance and the treatment process (implant adsorption by means of surface properties, cp Ti with the nanotubular TiO2 surface material was evaluated as the suitable one, and it may also be implied that it displayed enough performance in the designed dental implant model.

  1. Reforming water to generate hydrogen using mechanical alloy

    International Nuclear Information System (INIS)

    Pena F, D. L.

    2016-01-01

    The objective of this research was to generate a hydrogen production system by means of mechanical milling, in which 0.1 g of magnesium were weighed using a volume of 300 μL for each water solvent (H_2O) and methanol (CH_3OH) in a container to start mechanical milling for 2, 4 and 6 h. Once the mechanical milling was finished, the hydrogen that was produced every two hours was measured to determine the appropriate milling time in the production, also in each period of time samples of the powders produced during the milling of Mg were taken, in this process we used characterization techniques such as: X-ray diffraction at an angle of 2θi 5 and 2θf 90 degrees and scanning electron microscopy, taking micrographs of 100, 500, 1000 and 5000 magnifications. According to the mechanical milling results hydrogen was obtained when using water, as well as with methanol. In the techniques of X-ray diffraction characterization different results were obtained before and after the milling, since by the diffractogram s is possible to observe how the magnesium to be put in the mechanical milling along with the water and methanol was diminishing to be transformed into hydroxide and magnesium oxide, as well as in the micrographs taken with scanning electron microscopy the change in the magnesium morphology to hydroxide and magnesium oxide is observed. (Author)

  2. Mechanism for the generation of cavitation maxima by pulsed ultrasound

    International Nuclear Information System (INIS)

    Flynn, H.G.; Church, C.C.

    1984-01-01

    A train of 1-MHz pulses can generate maxima of cavitation activity at pulse lengths of 6 and 60 ms and at pressure amplitudes, P/sub A/, between 5.4 and 9.4 bars (or intensities between 10 and 30 W/cm 2 ). Generation of maxima at P/sub A/ between these limits on pressure amplitude implies that the increase in cavitation activity originates from gas nuclei with radii lying in a critical size range centered at about 0.08 μm. The mechanism proposed for this phenomenon suggests that nuclei in this critical range are unstabilized nuclei generated in one pulse and surviving to the next with an appreciable fraction of the survivors lying in the critical range. Transient cavities that grow from such small nuclei are shown to behave as isolated mechanical systems that on reaching maximum size collapse as imploding spheres. The maximum pressures reached in such imploding cavities would then approximate those calculated for the spherical collapse of cavities. The occurrence of the observed maxima is ascribed to the spherical collapse of transient cavities. 17 references, 5 figures

  3. 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.

  4. A generating mechanism of spiral structure in barred galaxies

    International Nuclear Information System (INIS)

    Thielheim, K.O.; Wolff, H.

    1982-01-01

    The time-dependent response of non-interacting stars to growing oval distortions in disc galaxies is calculated by following their motion numerically and Fourier-analysing their positions. Long-lived spiral density waves are found for fast-growing perturbations as well as in cases in which the perturbation evolves only slowly, compared with a characteristic internal rotation period of the disc. This mechanism of driving a spiral structure in non-self-gravitating stellar discs provides an explanation for the long-lived global spiral patterns, observed in N-body experiments showing an evolving central bar, that is not based on the self-gravitation in the disc. In conjunction with the theory of Lynden-Bell according to which angular momentum transfer in the disc leads to a slow increase of the oval distortion, this effect provides a general mechanism for the generation of spiral structure in barred galaxies. In addition to stellar discs with velocity dispersion, cold discs, with the stars initially in circular motion, which bear great similarity to gaseous discs, are investigated. The linear epicyclic approximation is used to develop an analytical description of the generating mechanism. (author)

  5. The Value Generating Mechanisms of Open Government Data

    DEFF Research Database (Denmark)

    Jetzek, Thorhildur

    2013-01-01

    social progress, to an interconnected, networked world of shared resources and co-creation. One of the trends driving this change is open government data. This paper presents a framework of four value generating mechanisms from use of OGD. The framework makes it easier to compare and communicate......Recent trends towards openness and technical connectivity have offered the ability to drive massive social and economic change; however they demand a redefinition of relationships. We have observed a move from a polarized world where companies operate in economic markets while governments drive...

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

    Directory of Open Access Journals (Sweden)

    Xiaoqin Huang

    2017-05-01

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

  7. An Adaptive Test Sheet Generation Mechanism Using Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Huan-Yu Lin

    2012-01-01

    Full Text Available For test-sheet composition systems, it is important to adaptively compose test sheets with diverse conceptual scopes, discrimination and difficulty degrees to meet various assessment requirements during real learning situations. Computation time and item exposure rate also influence performance and item bank security. Therefore, this study proposes an Adaptive Test Sheet Generation (ATSG mechanism, where a Candidate Item Selection Strategy adaptively determines candidate test items and conceptual granularities according to desired conceptual scopes, and an Aggregate Objective Function applies Genetic Algorithm (GA to figure out the approximate solution of mixed integer programming problem for the test-sheet composition. Experimental results show that the ATSG mechanism can efficiently, precisely generate test sheets to meet the various assessment requirements than existing ones. Furthermore, according to experimental finding, Fractal Time Series approach can be applied to analyze the self-similarity characteristics of GA’s fitness scores for improving the quality of the test-sheet composition in the near future.

  8. Phantom auditory perception (tinnitus): mechanisms of generation and perception.

    Science.gov (United States)

    Jastreboff, P J

    1990-08-01

    Phantom auditory perception--tinnitus--is a symptom of many pathologies. Although there are a number of theories postulating certain mechanisms of its generation, none have been proven yet. This paper analyses the phenomenon of tinnitus from the point of view of general neurophysiology. Existing theories and their extrapolation are presented, together with some new potential mechanisms of tinnitus generation, encompassing the involvement of calcium and calcium channels in cochlear function, with implications for malfunction and aging of the auditory and vestibular systems. It is hypothesized that most tinnitus results from the perception of abnormal activity, defined as activity which cannot be induced by any combination of external sounds. Moreover, it is hypothesized that signal recognition and classification circuits, working on holographic or neuronal network-like representation, are involved in the perception of tinnitus and are subject to plastic modification. Furthermore, it is proposed that all levels of the nervous system, to varying degrees, are involved in tinnitus manifestation. These concepts are used to unravel the inexplicable, unique features of tinnitus and its masking. Some clinical implications of these theories are suggested.

  9. 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

  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. Potential aerosol generation mechanisms from damaged shipping packages

    International Nuclear Information System (INIS)

    Mishima, J.

    1976-07-01

    Estimates of the potential airborne release of radioactive materials in transportation accidents are necessary to compare the safety in various shipping methods. To make such estimates, information is required on various aspects of the accident situation (physical and chemical characteristics of the source materials, forces/conditions imposed upon the source material by the accident, etc.). Published data which may be useful in estimating the fractional airborne release of radionuclides are discussed. Special emphasis is given to experimental data generated under conditions similar to those found under accident conditions. Estimates of the fractional airborne release of a liquid and a powder for particular accident scenarios are discussed to illustrate the application of the data

  12. Generation Mechanism of Alternans in Luo-Rudy Model

    Science.gov (United States)

    Kitajima, Hiroyuki; Ioka, Eri; Yazawa, Toru

    Electrical alternans is the alternating amplitude from beat to beat in the action potential of the cardiac cell. It has been associated with ventricular arrhythmias in many clinical studies; however, its dynamical mechanisms remain unknown. The reason is that we do not have realistic network models of the heart system. Recently, Yazawa clarified the network structure of the heart and the central nerve system in the crustacean heart. In this study, we construct a simple model of the heart system based on Yazawa’s experimental data. Using this model, we clarify that two parameters (the conductance of sodium ions and free concentration of potassium ions in the extracellular compartment) play the key roles of generating alternans. In particular, we clarify that the inactivation gate of the time-independent potassium channel is the most important parameter. Moreover, interaction between the membrane potential and potassium ionic currents is significant for generating alternate rhythms. This result indicates that if the muscle cell has problems such as channelopathies, there is great risk of generating alternans.

  13. Safety significance of steam generator tube degradation mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Roussel, G; Mignot, P [AIB-Vincotte Nuclear - AVN, Brussels (Belgium)

    1991-07-01

    Steam generator (SG) tube bundle is a part of the Reactor Coolant Pressure Boundary (RCPB): this means that its integrity must be maintained. However, operating experience shows various types of tube degradation to occur in the SG tubing, which may lead to SG tube leaks or SG tube ruptures and create a loss of primary system coolant through the SG, therefore providing a direct path to the environment outside the primary containment structure. In this paper, the major types of known SG tube degradations are described and analyzed in order to assess their safety significance with regard to SG tube integrity. In conclusion: The operational reliability and the safety of the PWR steam generator s requires a sufficient knowledge of the degradation mechanisms to determine the amount of degradation that a tube can withstand and the time that it may remain in operation. They also require the availability of inspection techniques to accurately detect and characterize the various degradations. The status of understanding of the major types of degradation summarized in this paper shows and justifies why efforts are being performed to improve the management of the steam generator tube defects.

  14. Generation Mechanism of Work Hardened Surface Layer in Metal Cutting

    Science.gov (United States)

    Hikiji, Rikio; Kondo, Eiji; Kawagoishi, Norio; Arai, Minoru

    Finish machining used to be carried out in grinding, but it is being replaced by cutting with very small undeformed chip thickness. In ultra precision process, the effects of the cutting conditions and the complicated factors on the machined surface integrity are the serious problems. In this research, work hardened surface layer was dealt with as an evaluation of the machined surface integrity and the effect of the mechanical factors on work hardening was investigated experimentally in orthogonal cutting. As a result, it was found that work hardened surface layer was affected not only by the shear angle varied under the cutting conditions and the thrust force of cutting resistance, but also by the thrust force acting point, the coefficient of the thrust force and the compressive stress equivalent to the bulk hardness. Furthermore, these mechanical factors acting on the depth of the work hardened surface layer were investigated with the calculation model.

  15. Analysis of reverse flow in inverted U-tubes of steam generator under natural circulation condition

    International Nuclear Information System (INIS)

    Yang Ruichang; Liu Ruolei; Liu Jinggong; Qin Shiwei

    2008-01-01

    In this paper, we report on the analysis of reverse flow in inverted U-tubes of a steam generator under natural circulation condition. The mechanism of reverse flow in inverted U-tubes of the steam generator with natural circulation is graphically analyzed by using the full-range characteristic curve of parallel U-tubes. The mathematical model and numerical calculation method for analyzing the reverse flow in inverted U-tubes of the steam generator with natural circulation have been developed. The reverse flow in an inverted U-tube steam generator of a simulated pressurized water reactor with natural circulation in analyzed. Through the calculation, the mass flow rates of normal and reverse flows in individual U-tubes are obtained. The predicted sharp drop of the fluid temperature in the inlet plenum of the steam generator due to reverse flow agrees very well with the experimental data. This indicates that the developed mathematical model and solution method can be used to correctly predict the reverse flow in the inverted U-tubes of the steam generator with natural circulation. The obtained results also show that in the analysis of natural circulation flow in the primary circuit, the reverse flow in the inverted U-tubes of the steam generator must be taken into account. (author)

  16. Mechanisms of polymer degradation using an oxygen plasma generator

    Science.gov (United States)

    Colony, Joe A.; Sanford, Edward L.

    1987-01-01

    An RF oxygen plasma generator was used to produce polymer degradation which appears to be similar to that which has been observed in low Earth orbit. Mechanisms of this type of degradation were studied by collecting the reaction products in a cryogenic trap and identifying the molecular species using infrared, mass spectral, and X-ray diffraction techniques. No structurally dependent species were found from Kapton, Teflon, or Saran polymers. However, very reactive free radical entities are produced during the polymer degradation, as well as carbon dioxide and water. Reactions of the free radicals with the glass reaction vessel, with copper metal in the cold trap, and with a triphenyl phosphate scavenger in the cold trap, demonstrated the reactivity of the primary products.

  17. 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)

  18. 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)

  19. Neural Mechanisms Underlying Cross-Modal Phonetic Encoding.

    Science.gov (United States)

    Shahin, Antoine J; Backer, Kristina C; Rosenblum, Lawrence D; Kerlin, Jess R

    2018-02-14

    Audiovisual (AV) integration is essential for speech comprehension, especially in adverse listening situations. Divergent, but not mutually exclusive, theories have been proposed to explain the neural mechanisms underlying AV integration. One theory advocates that this process occurs via interactions between the auditory and visual cortices, as opposed to fusion of AV percepts in a multisensory integrator. Building upon this idea, we proposed that AV integration in spoken language reflects visually induced weighting of phonetic representations at the auditory cortex. EEG was recorded while male and female human subjects watched and listened to videos of a speaker uttering consonant vowel (CV) syllables /ba/ and /fa/, presented in Auditory-only, AV congruent or incongruent contexts. Subjects reported whether they heard /ba/ or /fa/. We hypothesized that vision alters phonetic encoding by dynamically weighting which phonetic representation in the auditory cortex is strengthened or weakened. That is, when subjects are presented with visual /fa/ and acoustic /ba/ and hear /fa/ ( illusion-fa ), the visual input strengthens the weighting of the phone /f/ representation. When subjects are presented with visual /ba/ and acoustic /fa/ and hear /ba/ ( illusion-ba ), the visual input weakens the weighting of the phone /f/ representation. Indeed, we found an enlarged N1 auditory evoked potential when subjects perceived illusion-ba , and a reduced N1 when they perceived illusion-fa , mirroring the N1 behavior for /ba/ and /fa/ in Auditory-only settings. These effects were especially pronounced in individuals with more robust illusory perception. These findings provide evidence that visual speech modifies phonetic encoding at the auditory cortex. SIGNIFICANCE STATEMENT The current study presents evidence that audiovisual integration in spoken language occurs when one modality (vision) acts on representations of a second modality (audition). Using the McGurk illusion, we show

  20. Steam Generator Analysis Tools and Modeling of Degradation Mechanisms

    International Nuclear Information System (INIS)

    Yetisir, M.; Pietralik, J.; Tapping, R.L.

    2004-01-01

    The degradation of steam generators (SGs) has a significant effect on nuclear heat transport system effectiveness and the lifetime and overall efficiency of a nuclear power plant. Hence, quantification of the effects of degradation mechanisms is an integral part of a SG degradation management strategy. Numerical analysis tools such as THIRST, a 3-dimensional (3D) thermal hydraulics code for recirculating SGs; SLUDGE, a 3D sludge prediction code; CHECWORKS a flow-accelerated corrosion prediction code for nuclear piping, PIPO-FE, a SG tube vibration code; and VIBIC and H3DMAP, 3D non-linear finite-element codes to predict SG tube fretting wear can be used to assess the impacts of various maintenance activities on SG thermal performance. These tools are also found to be invaluable at the design stage to influence the design by determining margins or by helping the designers minimize or avoid known degradation mechanisms. In this paper, the aforementioned numerical tools and their application to degradation mechanisms in CANDU recirculating SGs are described. In addition, the following degradation mechanisms are identified and their effect on SG thermal efficiency and lifetime are quantified: primary-side fouling, secondary-side fouling, fretting wear, and flow-accelerated corrosion (FAC). Primary-side tube inner diameter fouling has been a major contributor to SG thermal degradation. Using the results of thermalhydraulic analysis and field data, fouling margins are calculated. Individual effects of primary- and secondary-side fouling are separated through analyses, which allow station operators to decide what type of maintenance activity to perform and when to perform the maintenance activity. Prediction of the fretting-wear rate of tubes allows designers to decide on the number and locations of support plates and U-bend supports. The prediction of FAC rates for SG internals allows designers to select proper materials, and allows operators to adjust the SG maintenance

  1. 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.

  2. 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.

  3. Mechanized inspection of steam generator components during manufacture

    International Nuclear Information System (INIS)

    Otte, H.-J.; Leupoldt, K.; Meister, W.

    2009-01-01

    Steam Generator (SG) parts are intensively inspected by UT in the course of the manufacturing process. These inspections - mostly performed manually using different codes - are time consuming and call for a sophisticated documentation, figuring part of the life time documentation package. In order to reduce time and costs mechanized inspection equipment is introduced, combining short inspection times, avoiding influence of the human factor and providing proper electronic storage of all inspection results prepared for comparison with data generated during in-service inspection. Since 2001 Cegelec delivered various UT systems for gas turbine disks and rotor ends called SIRO-MAN. Within only a few years the majority of important providers of such components successfully switched from manual inspection to mechanized inspection following the requirements of manufacturers like ALSTOM, GE and Siemens. The SIRO-MAN is now adapted to the needs of mechanized inspection of SG components. The inspection is performed on the products during rotation around the vertical axis. The multi - probe assemblies are manoeuvred on the products by a manipulator system backed by a NC control unit. Acoustic coupling of UT probes to the product surface is performed with oil or water in a closed circuit. UT and - if requested ET - data along with position information of the probe assembly provided by the control unit are acquired, processed and evaluated by an UT / ET electronic system delivered by either Olympus or ZETEC. As performed already on rotor ends a sequence of inspections using different parameter settings can be programmed with simple means (Teach In) so that such inspection sequence can be executed without operating personnel. Probe assemblies allow for individual operation of probes out of the probe assembly according to the individual needs. Conventional UT and phased array applications or combination of both techniques can be provided. The UT / ET electronic equipment offers

  4. The electricity generation adequacy problem: Assessing dynamic effects of capacity remuneration mechanisms

    International Nuclear Information System (INIS)

    Hary, Nicolas; Rious, Vincent; Saguan, Marcelo

    2016-01-01

    Following liberalization reforms, the ability of power markets to provide satisfactory incentives for capacity investments has become a major concern. In particular, current energy markets can exhibit a phenomenon of investment cycles, which generate phases of under and over-capacity, and hence additional costs and risks for generation adequacy. To cope with these issues, new mechanisms, called capacity remuneration mechanisms (CRM), have been (or will be) implemented. This paper assesses the dynamic effects of two CRMs, the capacity market and the strategic reserve mechanism, and studies to what extent they can reduce the investment cycles. Generation costs and shortage costs of both mechanisms are also compared to conclude on their effectivity and economic efficiency. A simulation model, based on system dynamics, is developed to study the functioning of both CRMs and the related investment decisions. The results highlight the benefits of deploying CRMs to solve the adequacy issue: shortages are strongly reduced compared to an energy-only market. Besides, the capacity market appears to be more beneficial, since it experiences fewer shortages and generation costs are lower. These comparisons can be used by policy makers (in particular in Europe, where these two CRMs are mainly debated) to determine which CRM to adopt. - Highlights: •A study of the dynamic effects of CRMs on generation investments is provided. •Capacity market and strategic reserve mechanism are compared. •Both CRMs reduce the cyclical tendencies prone to appear in energy-only market. •The capacity market experiences fewer shortages and generation costs are lower.

  5. Turing mechanism underlying a branching model for lung morphogenesis.

    Science.gov (United States)

    Xu, Hui; Sun, Mingzhu; Zhao, Xin

    2017-01-01

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

  6. Mechanical Behaviour of Bolted Joints Under Impact Rates of Loading

    Science.gov (United States)

    2012-01-01

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

  7. 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.

  8. 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.

  9. 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.

  10. Fracture mechanics of hydroxyapatite single crystals under geometric confinement.

    Science.gov (United States)

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

    2013-04-01

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

  11. Doubly-Fed Induction Generator Control Under Voltage Sags

    DEFF Research Database (Denmark)

    Teodorescu, Remus; Blaabjerg, Frede; Lima, K.

    2008-01-01

    This paper proposes a new control technique to improve the fault-ride through capability of doubly fed induction generators (DFIG). In such generators the appearance of severe voltage sags at the coupling point make rise to high over currents at the rotor/stator windings, something that makes...

  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. 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.

  15. 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

  16. Cell-Nonautonomous Mechanisms Underlying Cellular and Organismal Aging.

    Science.gov (United States)

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

    2016-01-01

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

  17. Pressurizer and steam-generator behavior under PWR transient conditions

    International Nuclear Information System (INIS)

    Wahba, A.B.; Berta, V.T.; Pointner, W.

    1983-01-01

    Experiments have been conducted in the Loss-of-Fluid Test (LOFT) pressurized water reactor (PWR), at the Idaho National Engineering Laboratory, in which transient phenomena arising from accident events with and without reactor scram were studied. The main purpose of the LOFT facility is to provide data for the development of computer codes for PWR transient analyses. Significant thermal-hydraulic differences have been observed between the measured and calculated results for those transients in which the pressurizer and steam generator strongly influence the dominant transient phenomena. Pressurizer and steam generator phenomena that occurred during four specific PWR transients in the LOFT facility are discussed. Two transients were accompanied by pressurizer inflow and a reduction of the heat transfer in the steam generator to a very small value. The other two transients were accompanied by pressurizer outflow while the steam generator behavior was controlled

  18. Distributed Generation Investment by a Microgrid under Uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Marnay, Chris; Siddiqui, Afzal; Marnay, Chris

    2008-08-11

    This paper examines a California-based microgrid?s decision to invest in a distributed generation (DG) unit fuelled by natural gas. While the long-term natural gas generation cost is stochastic, we initially assume that the microgrid may purchase electricity at a fixed retail rate from its utility. Using the real options approach, we find a natural gas generation cost threshold that triggers DG investment. Furthermore, the consideration of operational flexibility by the microgrid increases DG investment, while the option to disconnect from the utility is not attractive. By allowing the electricity price to be stochastic, we next determine an investment threshold boundary and find that high electricity price volatility relative to that of natural gas generation cost delays investment while simultaneously increasing the value of the investment. We conclude by using this result to find the implicit option value of the DG unit when two sources of uncertainty exist.

  19. Distributed generation investment by a microgrid under uncertainty

    International Nuclear Information System (INIS)

    Siddiqui, Afzal S.; Marnay, Chris

    2008-01-01

    This paper examines a California-based microgrid's decision to invest in a distributed generation (DG) unit fuelled by natural gas. While the long-term natural gas generation cost is stochastic, we initially assume that the microgrid may purchase electricity at a fixed retail rate from its utility. Using the real options approach, we find a natural gas generation cost threshold that triggers DG investment. Furthermore, the consideration of operational flexibility by the microgrid increases DG investment, while the option to disconnect from the utility is not attractive. By allowing the electricity price to be stochastic, we next determine an investment threshold boundary and find that high electricity price volatility relative to that of natural gas generation cost delays investment while simultaneously increasing the value of the investment. We conclude by using this result to find the implicit option value of the DG unit when two sources of uncertainty exist. (author)

  20. Distributed generation investment by a microgrid under uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Afzal S. [Department of Statistical Science, University College London, Gower Street, London WC1E 6BT (United Kingdom); Marnay, Chris [Ernest Orlando Lawrence Berkeley National Laboratory, 1 Cyclotron Road, MS90R4000, Berkeley, CA 94720-8163 (United States)

    2008-12-15

    This paper examines a California-based microgrid's decision to invest in a distributed generation (DG) unit fuelled by natural gas. While the long-term natural gas generation cost is stochastic, we initially assume that the microgrid may purchase electricity at a fixed retail rate from its utility. Using the real options approach, we find a natural gas generation cost threshold that triggers DG investment. Furthermore, the consideration of operational flexibility by the microgrid increases DG investment, while the option to disconnect from the utility is not attractive. By allowing the electricity price to be stochastic, we next determine an investment threshold boundary and find that high electricity price volatility relative to that of natural gas generation cost delays investment while simultaneously increasing the value of the investment. We conclude by using this result to find the implicit option value of the DG unit when two sources of uncertainty exist. (author)

  1. The Value of Distributed Generation under Different Tariff Structures

    OpenAIRE

    Firestone, Ryan; Magnus Maribu, Karl; Marnay, Chris

    2006-01-01

    Distributed generation (DG) may play a key role in a modern energy system because it can improve energy efficiency. Reductions in the energy bill, and therefore DG attractiveness, depend on the electricity tariff structure; a system created before widespread adoption of distributed generation. Tariffs have been designed to recover costs equitably amongst customers with similar consumption patterns. Recently, electric utilities began to question the equity of this electricity pricing stru...

  2. Distributed Generation Dispatch Optimization under Various Electricity Tariffs

    OpenAIRE

    Firestone, Ryan; Marnay, Chris

    2007-01-01

    The on-site generation of electricity can offer building owners and occupiers financial benefits as well as social benefits such as reduced grid congestion, improved energy efficiency, and reduced greenhouse gas emissions. Combined heat and power (CHP), or cogeneration, systems make use of the waste heat from the generator for site heating needs. Real-time optimal dispatch of CHP systems is difficult to determine because of complicated electricity tariffs and uncertainty in CHP equipment...

  3. Dynamical mechanism of symmetry breaking and particle mass generation in gauge field theories

    International Nuclear Information System (INIS)

    Miranskij, V.A.; Fomin, P.I.

    1985-01-01

    The dynamics of the spotaneous symmetry breaking and the particle mass generation in gauge theories with no fundamental scalar fields is considered. The emphasis is on the consideration of the symmetry breaking mechanism connected with the dynamics of the supercritical Coulomb-like forces caused by the gauge boson exchange between fermions. This mechanism is applied to different gauge theories, in particular, to the description of the spontaneous chira symmetry breaking in quantum chromodynamics. The mass relations for pseudoscalar meson nonet are obtained and it is shown that this mechanism resuls in the dynamical realisation of the hypothesis of the partial conservation of the axial-vector currents. The qualitative description of scalar mesons is given. The nature of the ultraviolet divergencies in quantum electrodynamics (QED) is investigated from the viewpoint of the dynamics of the fermion mass generation. The mechanism of the appearance of the additional (in comparison with perturbation theory) ultraviolet divergencies in QED with large bare coupling constant is indicated. The physical phenomenon underlying this mechanism is identified as the field theory analogue of the quantum mechanical ''fall into the centre'' (collapse) phenomenon. The similr phenomenon is shown to take place in some two-dimensional quantum field models. The dynamics of the bifermion condensates formation in tumblin gauge theories is briefly discussed

  4. 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.

  5. Vascular mechanisms underlying the hypotensive effect of Rumex acetosa.

    Science.gov (United States)

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

    2018-12-01

    Rumex acetosa L. (Polygonaceae) is well known in traditional medicine for its therapeutic efficacy as an antihypertensive. The study investigates antihypertensive potential of crude methanol extract (Ra.Cr) and fractions of Rumex acetosa in normotensive and hypertensive rat models and probes the underlying vascular mechanisms. Ra.Cr and its fractions were tested in vivo on normotensive and hypertensive Sprague-Dawley rats under anaesthesia for blood pressure lowering effect. In vitro experiments on rat and Oryctolagus cuniculus rabbit aortae were employed to probe the underlying vasorelaxant mechanism. In normotensive rats under anaesthesia, Ra.Cr caused fall in MAP (40 mmHg) at 50 mg/kg with % fall of 27.88 ± 4.55. Among the fractions tested, aqueous fraction was more potent at the dose of 50 mg/kg with % fall of 45.63 ± 2.84. In hypertensive rats under similar conditions, extract and fractions showed antihypertensive effect at same doses while aqueous fraction being more potent, exhibited 68.53 ± 4.45% fall in MAP (70 mmHg). In isolated rat aortic rings precontracted with phenylephrine (PE), Ra.Cr and fractions induced endothelium-dependent vasorelaxation, which was partially blocked in presence of l-NAME, indomethacin and atropine. In isolated rabbit aortic rings pre-contracted with PE and K + -(80 mM), Ra.Cr induced vasorelaxation and shifted Ca 2+ concentration-response curves to the right and suppressed PE peak formation, similar to verapamil, in Ca 2+ -free medium. The data indicate that l-NAME and atropine-sensitive endothelial-derived NO and COX enzyme inhibitors and Ca 2+ entry blocking-mediated vasodilator effect of the extract explain its antihypertensive potential.

  6. Thermal mechanical analysis of applications with internal heat generation

    Science.gov (United States)

    Govindarajan, Srisharan Garg

    control blade, spatial variations in temperature within the control blade occur from the non-uniform heat generation within the BORAL as a result of the non-uniform thermal neutron flux along the longitudinal direction when the control blade is partially withdrawn. There is also variation in the heating profile through the thickness and about the circumferential width of the control blade. Mathematical curve-fits are generated for the non-uniform volumetric heat generation profile caused by the thermal neutron absorption and the functions are applied as heating conditions within a finite element model of the control blade built using the commercial finite element code Abaqus FEA. The finite element model is solved as a fully coupled thermal mechanical problem as in the case of the annular target. The resulting deflection is compared with the channel gap to determine if there is a significant risk of the control blade binding during reactor operation. Hence, this dissertation will consist of two sections. The first section will seek to present the thermal and structural safety analyses of the annular targets for the production of molybdenum-99. Since there hasn't been any detailed, documented, study on these annular targets in the past, the work complied in this dissertation will help to understand the thermal-mechanical behavior and failure margins of the target during in-vessel irradiation. As the work presented in this dissertation provides a general performance analysis envelope for the annular target, the tools developed in the process can also be used as useful references for future analyses that are specific to any reactor. The numerical analysis approach adopted and the analytical models developed, can also be applied to other applications, outside the Mo-99 project domain, where internal heat generation exists such as in electronic components and nuclear reactor control blades. The second section will focus on estimating the thermally induced deflection and hence

  7. Water plasma generation under atmospheric pressure for HFC destruction

    International Nuclear Information System (INIS)

    Watanabe, Takayuki; Tsuru, Taira

    2008-01-01

    The purpose of this paper is to investigate the decomposition process of hydrofluoroethylene (HFC-134a) by water plasmas. The water plasma was generated by DC arc discharge with a cathode of hafnium embedded into a copper rod and a nozzle-type copper anode. The advantage of the water plasma torch is the generation of 100%-water plasma by DC discharge. The distinctive steam generation leads to the portable light-weight plasma generation system that does not require the gas supply unit, as well as the high energy efficiency owing to the nonnecessity of the additional water-cooling. HFC-134a was injected into the water plasma jet to decompose it in the reaction tube. Neutralization vessel was combined to the reaction tube to absorb F 2 and HF generated from the HFC-134a decomposition. The decomposition was performed with changing the feed rate of HFC-134a up to 185 mmol/min. The decomposition efficiency of 99.9% can be obtained up to 0.43 mmol/kJ of the ratio of HFC-134a feed rate to the arc power, hence the maximum feed rate was estimated to be 160 g/h at 1 kW of the arc power

  8. 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.

  9. Mechanisms underlying astringency: introduction to an oral tribology approach

    Science.gov (United States)

    Upadhyay, Rutuja; Brossard, Natalia; Chen, Jianshe

    2016-03-01

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

  10. Failure Mechanisms of Brittle Rocks under Uniaxial Compression

    Science.gov (United States)

    Liu, Taoying; Cao, Ping

    2017-09-01

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

  11. Underlying mechanism in the water chemistry of nuclear systems

    International Nuclear Information System (INIS)

    Walton, G.N.

    1978-01-01

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

  12. 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.

  13. Mechanisms underlying KCNQ1channel cell volume sensitivity

    DEFF Research Database (Denmark)

    Hammami, Sofia

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

  14. 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.

  15. Entropy Generation in Natural Convection Under an Evanescent Magnetic Field

    International Nuclear Information System (INIS)

    Magherbi, Mourad; El Jery, Atef; Ben Brahim, Ammar

    2009-01-01

    We numerically study the effect of an externally-evanescent magnetic field on total entropy generation in conducting and non-reactive fluid enclosed in a square cavity. The horizontal walls of the enclosure are assumed to be insulated while the vertical walls are kept isothermal. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number equal to 10 5

  16. Generator scheduling under competitive environment using Memory Management Algorithm

    Directory of Open Access Journals (Sweden)

    A. Amudha

    2013-09-01

    Full Text Available This paper presents a new approach for Real-Time Application of Profit Based Unit Commitment using Memory Management Algorithm. The main objective of the restructured system is to maximize its own profit without the responsibility of satisfying the forecasted demand. The Profit Based Unit Commitment (PBUC is solved by Memory Management Algorithm (MMA in Real-Time Application. MMA approach is introduced in this paper considering power and reserve generation. The proposed method MMA uses Best Fit and Worst Fit allocation for generator scheduling in order to receive the maximum profit by considering the softer demand. Also, this method gives an idea regarding how much power and reserve should be sold in markets. The proposed approach has been tested on a power system with 2, 3, and 10 generating units. Simulation results of the proposed approach have been compared with the existing methods.

  17. 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.

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

    Science.gov (United States)

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

    2015-04-01

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

  19. Microfluidic droplet generator with controlled break-up mechanism

    KAUST Repository

    Gonzalez, David Conchouso

    2017-04-13

    Droplet generation devices and systems that parallelize droplet generation devices are provided. The droplet generation devices can include a symmetric block-and-break system and a tapered droplet generation zone. The symmetric block-and-break system can include a pair of break channels and a pair of bypass channels symmetrically arranged with respect to the dispersed-phase input channel and the output channel. The droplet generation devices can generate monodisperse droplets with a predefined volume over a range of flow rates, pressures, and fluid properties. The droplet generation devices are therefore capable of parallelization to achieve large-capacity droplet generation, e.g. greater than 1 L/hr, with small overall coefficients of variation.

  20. Behavior of duplex stainless steel casting defects under mechanical loadings

    International Nuclear Information System (INIS)

    Jayet-Gendrot, S.; Gilles, P.

    2000-01-01

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

  1. Biogas generation in anaerobic wastewater treatment under tetracycline antibiotic pressure

    Science.gov (United States)

    Lu, Meiqing; Niu, Xiaojun; Liu, Wei; Zhang, Jun; Wang, Jie; Yang, Jia; Wang, Wenqi; Yang, Zhiquan

    2016-01-01

    The effect of tetracycline (TC) antibiotic on biogas generation in anaerobic wastewater treatment was studied. A lab-scale Anaerobic Baffled Reactor (ABR) with three compartments was used. The reactor was operated with synthetic wastewater in the absence of TC and in the presence of 250 μg/L TC for 90 days, respectively. The removal rate of TC, volatile fatty acids (VFAs), biogas compositions (hydrogen (H2), methane (CH4), carbon dioxide (CO2)), and total biogas production in each compartment were monitored in the two operational conditions. Results showed that the removal rate of TC was 14.97–67.97% in the reactor. The presence of TC had a large negative effect on CH4 and CO2 generation, but appeared to have a positive effect on H2 production and VFAs accumulation. This response indicated that the methanogenesis process was sensitive to TC presence, but the acidogenesis process was insensitive. This suggested that the presence of TC had less influence on the degradation of organic matter but had a strong influence on biogas generation. Additionally, the decrease of CH4 and CO2 generation and the increase of H2 and VFAs accumulation suggest a promising strategy to help alleviate global warming and improve resource recovery in an environmentally friendly approach. PMID:27341657

  2. Generating unit maintenance scheduling under competitive market environments

    International Nuclear Information System (INIS)

    Jin Ho Kim; Jong Bae Park; Jong Keun Park; Yeung Han Chun

    2005-01-01

    A novel approach to a generating unit maintenance scheduling problem in competitive electricity markets is presented in this paper. The objective is to develop a game-theoretic framework for analyzing strategic behaviors of generating companies (Gencos) from the standpoint of the generating unit maintenance scheduling (GMS) game and for obtaining the equilibrium solution for the GMS game. The GMS problem is formulated as a dynamic non-cooperative game with complete information. The players correspond to profit maximizing individual Gencos, and the payoff of each player is defined as the profits from the energy market. The optimal schedule is defined by Nash equilibrium (equilibriums) of the game. Numerical results for two-Genco system are used to demonstrate that the proposed framework can be successfully applied to analyzing the strategic behaviors of each Genco and to obtaining the corresponding Nash equilibrium. The result indicates that generating unit maintenance schedule is one of the major strategic behaviors whereby Genco maximize their profits in a competitive market environment. (author)

  3. 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.

  4. Hadron collider tests of neutrino mass-generating mechanisms

    Science.gov (United States)

    Ruiz, Richard Efrain

    The Standard Model of particle physics (SM) is presently the best description of nature at small distances and high energies. However, with tiny but nonzero neutrino masses, a Higgs boson mass unstable under radiative corrections, and little guidance on understanding the hierarchy of fermion masses, the SM remains an unsatisfactory description of nature. Well-motivated scenarios that resolve these issues exist but also predict extended gauge (e.g., Left-Right Symmetric Models), scalar (e.g., Supersymmetry), and/or fermion sectors (e.g., Seesaw Models). Hence, discovering such new states would have far-reaching implications. After reviewing basic tenets of the SM and collider physics, several beyond the SM (BSM) scenarios that alleviate these shortcomings are investigated. Emphasis is placed on the production of a heavy Majorana neutrinos at hadron colliders in the context of low-energy, effective theories that simultaneously explain the origin of neutrino masses and their smallness compared to other elementary fermions, the so-called Seesaw Mechanisms. As probes of new physics, rare top quark decays to Higgs bosons in the context of the SM, the Types I and II Two Higgs Doublet Model (2HDM), and the semi-model independent framework of Effective Field Theory (EFT) have also been investigated. Observation prospects and discovery potentials of these models at current and future collider experiments are quantified.

  5. Genomic interrogation of mechanism(s) underlying cellular responses to toxicants

    International Nuclear Information System (INIS)

    Amin, Rupesh P.; Hamadeh, Hisham K.; Bushel, Pierre R.; Bennett, Lee; Afshari, Cynthia A.; Paules, Richard S.

    2002-01-01

    Assessment of the impact of xenobiotic exposure on human health and disease progression is complex. Knowledge of mode(s) of action, including mechanism(s) contributing to toxicity and disease progression, is valuable for evaluating compounds. Toxicogenomics, the subdiscipline which merges genomics with toxicology, holds the promise to contributing significantly toward the goal of elucidating mechanism(s) by studying genome-wide effects of xenobiotics. Global gene expression profiling, revolutionized by microarray technology and a crucial aspect of a toxicogenomic study, allows measuring transcriptional modulation of thousands of genes following exposure to a xenobiotic. We use our results from previous studies on compounds representing two different classes of xenobiotics (barbiturate and peroxisome proliferator) to discuss the application of computational approaches for analyzing microarray data to elucidate mechanism(s) underlying cellular responses to toxicants. In particular, our laboratory demonstrated that chemical-specific patterns of gene expression can be revealed using cDNA microarrays. Transcript profiling provides discrimination between classes of toxicants, as well as, genome-wide insight into mechanism(s) of toxicity and disease progression. Ultimately, the expectation is that novel approaches for predicting xenobiotic toxicity in humans will emerge from such information

  6. Insights into the Mechanisms Underlying Boron Homeostasis in Plants

    Directory of Open Access Journals (Sweden)

    Akira Yoshinari

    2017-11-01

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

  7. 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.

  8. Behavior of duplex stainless steel casting defects under mechanical loadings

    Energy Technology Data Exchange (ETDEWEB)

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

    1997-04-01

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

  9. Failure of fretted steam generator tubes under accident conditions

    International Nuclear Information System (INIS)

    Forrest, C.F.

    1996-10-01

    Tests were carried out with a bank of tubes in a water tunnel to determine the tolerance of flawed nuclear reactor steam generator tubes to accident conditions which would result in high cross-flow velocities. Fourteen specimen tubes were tested, each having one or two types of defect machined into the surface simulating fretting-wear type scars found in some operating steam generators. The tubes were tested at flow velocities sufficient to induce high fluid elastic-type vibrations. Seven of the tubes failed near the thinnest section of the defects during the one-hour tests, due to impacting and/or rubbing between the tube and the support. Strain gauges, displacement transducers, force gauges and an accelerometer were used on the target tube and/or the tube immediately downstream of it to measure their vibrational characteristics

  10. Beyond pure offsetting: Assessing options to generate Net-Mitigation-Effects in carbon market mechanisms

    International Nuclear Information System (INIS)

    Warnecke, Carsten; Wartmann, Sina; Höhne, Niklas; Blok, Kornelis

    2014-01-01

    The current project-based carbon market mechanisms such as the Clean Development Mechanism (CDM) and the Joint Implementation (JI) do not have a direct impact on global greenhouse gas emission levels, because they only replace or offset emissions. Nor do they contribute to host country's national greenhouse gas emission reduction targets. Contributions to net emission reductions in host countries is likely to become mandatory in new mechanisms under development such as in the framework for various approaches, a new market-based mechanism and even in a reformed JI. This research analysed the question if approaches for carbon market-based mechanisms exist that allow the generation of net emission reductions in host countries while keeping project initiation attractive. We present a criteria-based assessment method and apply it for four generic options in existing mechanisms and derive implications for future mechanism frameworks. We identified the application of “discounts” on the amount of avoided emissions for the issuance of carbon credits and “standardisation below business as usual” as most promising options over “limiting the crediting period” and “over-conservativeness”. We propose to apply these options differentiated over project types based on internal rate of return to ensure cost-efficiency and attractiveness. - Highlights: • Options for net emission reductions of market-based mechanisms are assessed. • Research combines past and current views for project and sector-based mechanisms. • Implementation ensures initiation of mitigation activities is not discouraged. • Important insights for methodological design of new market-based mechanisms. • Profitability-based approach for project-based mechanisms suggested

  11. Investment in Electricity Generation and Transmission: Decision Making Under Uncertainty

    DEFF Research Database (Denmark)

    Conejo, Antonio J.; Baringo, Luis; Kazempour, Jalal

    This book provides an in-depth analysis of investment problems pertaining to electric energy infrastructure, including both generation and transmission facilities. The analysis encompasses decision-making tools for expansion planning, reinforcement, and the selection and timing of investment...... undergraduate and graduate students in the fields of electric energy systems, operations research, management science, and economics. Practitioners in the electric energy sector will also benefit from the concepts and techniques presented here....

  12. Hardening and softening mechanisms of pearlitic steel wire under torsion

    International Nuclear Information System (INIS)

    Zhao, Tian-Zhang; Zhang, Shi-Hong; Zhang, Guang-Liang; Song, Hong-Wu; Cheng, Ming

    2014-01-01

    Highlights: • Mechanical behavior of pearlitic steel wire is studied using torsion. • Work hardening results from refinement lamellar pearlitic structure. • Softening results from recovery, shear bands and lamellar fragmentations. • A microstructure based analytical flow stress model is established. - Abstract: The mechanical behaviors and microstructure evolution of pearlitic steel wires under monotonic shear deformation have been investigated by a torsion test and a number of electron microscopy techniques including scanning electron microscopy (SEM) and transmission electron microscopy (TEM), with an aim to reveal the softening and hardening mechanisms of a randomly oriented pearlitic structure during a monotonic stain path. Significantly different from the remarkable strain hardening in cold wire drawing, the strain hardening rate during torsion drops to zero quickly after a short hardening stage. The microstructure observations indicate that the inter-lamellar spacing (ILS) decreases and the dislocations accumulate with strain, which leads to hardening of the material. Meanwhile, when the strain is larger than 0.154, the enhancement of dynamic recovery, shear bands (SBs) and cementite fragmentations results in the softening and balances the strain hardening. A microstructure based analytical flow stress model with considering the influence of ILS on the mean free path of dislocations and the softening caused by SBs and cementite fragmentations, has been established and the predicted flow shear curve meets well with the measured curve in the torsion test

  13. 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.

  14. 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.

  15. Coolant rate distribution in horizontal steam generator under natural circulation

    International Nuclear Information System (INIS)

    Blagovechtchenski, A.; Leontieva, V.; Mitrioukhin, A.

    1997-01-01

    In the presentation the major factors determining the conditions of NCC (Natural Coolant Circulation) in the primary circuit and in particular conditions of coolant rate distribution on the horizontal tubes of PGV-1000 in NPP with VVER-1000 under NCC are considered

  16. Coolant rate distribution in horizontal steam generator under natural circulation

    Energy Technology Data Exchange (ETDEWEB)

    Blagovechtchenski, A.; Leontieva, V.; Mitrioukhin, A. [St. Petersburg State Technical Univ. (Russian Federation)

    1997-12-31

    In the presentation the major factors determining the conditions of NCC (Natural Coolant Circulation) in the primary circuit and in particular conditions of coolant rate distribution on the horizontal tubes of PGV-1000 in NPP with VVER-1000 under NCC are considered. 5 refs.

  17. Coolant rate distribution in horizontal steam generator under natural circulation

    Energy Technology Data Exchange (ETDEWEB)

    Blagovechtchenski, A; Leontieva, V; Mitrioukhin, A [St. Petersburg State Technical Univ. (Russian Federation)

    1998-12-31

    In the presentation the major factors determining the conditions of NCC (Natural Coolant Circulation) in the primary circuit and in particular conditions of coolant rate distribution on the horizontal tubes of PGV-1000 in NPP with VVER-1000 under NCC are considered. 5 refs.

  18. Design Preliminaries for Direct Drive under Water Wind Turbine Generator

    DEFF Research Database (Denmark)

    Leban, Krisztina Monika; Ritchie, Ewen; Argeseanu, Alin

    2012-01-01

    This paper focuses on the preliminary design process of a 20 MW electric generator. The application calls for an offshore, vertical axis, direct drive wind turbine. Arguments for selecting the type of electric machine for the application are presented and discussed. Comparison criteria for deciding...... on a type of machine are listed. Additional constraints emerging from the direct drive, vertical axis concepts are considered. General rules and a preliminary algorithm are discussed for the machine selected to be most suitable for the imposed conditions....

  19. Investment and upgrade in distributed generation under uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Afzal S. [Department of Statistical Science, University College London, London WC1E 6BT (United Kingdom); Maribu, Karl [Centre d' Economie Industrielle, Ecole Nationale Superieure des Mines de Paris, Paris 75272 (France)

    2009-01-15

    The ongoing deregulation of electricity industries worldwide is providing incentives for microgrids to use small-scale distributed generation (DG) and combined heat and power (CHP) applications via heat exchangers (HXs) to meet local energy loads. Although the electric-only efficiency of DG is lower than that of central-station production, relatively high tariff rates and the potential for CHP applications increase the attraction of on-site generation. Nevertheless, a microgrid contemplating the installation of gas-fired DG has to be aware of the uncertainty in the natural gas price. Treatment of uncertainty via real options increases the value of the investment opportunity, which then delays the adoption decision as the opportunity cost of exercising the investment option increases as well. In this paper, we take the perspective of a microgrid that can proceed in a sequential manner with DG capacity and HX investment in order to reduce its exposure to risk from natural gas price volatility. In particular, with the availability of the HX, the microgrid faces a tradeoff between reducing its exposure to the natural gas price and maximising its cost savings. By varying the volatility parameter, we find that the microgrid prefers a direct investment strategy for low levels of volatility and a sequential one for higher levels of volatility. (author)

  20. Investment and upgrade in distributed generation under uncertainty

    International Nuclear Information System (INIS)

    Siddiqui, Afzal S.; Maribu, Karl

    2009-01-01

    The ongoing deregulation of electricity industries worldwide is providing incentives for microgrids to use small-scale distributed generation (DG) and combined heat and power (CHP) applications via heat exchangers (HXs) to meet local energy loads. Although the electric-only efficiency of DG is lower than that of central-station production, relatively high tariff rates and the potential for CHP applications increase the attraction of on-site generation. Nevertheless, a microgrid contemplating the installation of gas-fired DG has to be aware of the uncertainty in the natural gas price. Treatment of uncertainty via real options increases the value of the investment opportunity, which then delays the adoption decision as the opportunity cost of exercising the investment option increases as well. In this paper, we take the perspective of a microgrid that can proceed in a sequential manner with DG capacity and HX investment in order to reduce its exposure to risk from natural gas price volatility. In particular, with the availability of the HX, the microgrid faces a tradeoff between reducing its exposure to the natural gas price and maximising its cost savings. By varying the volatility parameter, we find that the microgrid prefers a direct investment strategy for low levels of volatility and a sequential one for higher levels of volatility. (author)

  1. Investment and Upgrade in Distributed Generation under Uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, Afzal; Maribu, Karl

    2008-08-18

    The ongoing deregulation of electricity industries worldwide is providing incentives for microgrids to use small-scale distributed generation (DG) and combined heat and power (CHP) applications via heat exchangers (HXs) to meet local energy loads. Although the electric-only efficiency of DG is lower than that of central-station production, relatively high tariff rates and the potential for CHP applications increase the attraction of on-site generation. Nevertheless, a microgrid contemplatingthe installation of gas-fired DG has to be aware of the uncertainty in the natural gas price. Treatment of uncertainty via real options increases the value of the investment opportunity, which then delays the adoption decision as the opportunity cost of exercising the investment option increases as well. In this paper, we take the perspective of a microgrid that can proceed in a sequential manner with DG capacity and HX investment in order to reduce its exposure to risk from natural gas price volatility. In particular, with the availability of the HX, the microgrid faces a tradeoff between reducing its exposure to the natural gas price and maximising its cost savings. By varying the volatility parameter, we find that the microgrid prefers a direct investment strategy for low levels of volatility and a sequential one for higher levels of volatility.

  2. Mechanisms underlying epithelium-dependent relaxation in rat bronchioles

    DEFF Research Database (Denmark)

    Kroigaard, Christel; Dalsgaard, Thomas; Simonsen, Ulf

    2010-01-01

    This study investigated the mechanisms underlying epithelium-derived hyperpolarizing factor (EpDHF)-type relaxation in rat bronchioles. Immunohistochemistry was performed, and rat bronchioles and pulmonary arteries were mounted in microvascular myographs for functional studies. An opener of small...... (SK(Ca)) and intermediate (IK(Ca))-conductance calcium-activated potassium channels, NS309 (6,7-dichloro-1H-indole-2,3-dione 3-oxime) was used to induce EpDHF-type relaxation. IK(Ca) and SK(Ca)3 positive immunoreactions were observed mainly in the epithelium and endothelium of bronchioles and arteries......, respectively. In 5-hydroxytryptamine (1 microM)-contracted bronchioles (828 +/- 20 microm, n = 84) and U46619 (0.03 microM)-contracted arteries (720 +/- 24 microm, n = 68), NS309 (0.001-10 microM) induced concentration-dependent relaxations that were reduced by epithelium/endothelium removal and by blocking IK...

  3. Neural mechanisms underlying human consensus decision-making.

    Science.gov (United States)

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

    2015-04-22

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

  4. Electricity generation sectors under purchase obligation: support arrangement analysis

    International Nuclear Information System (INIS)

    2013-04-01

    This report aims at assessing the operation of the support arrangement by which currently benefit some electricity production sectors in France (renewable energies, co-generation) with respect to the evolution of the energy mix within the frame of energy transition. Other support arrangements presently adopted in Europe are also addressed as lessons to be learned. Criteria are established for any support arrangement. The report presents the French and European context regarding such support arrangement with purchasing obligation, and addresses the future evolutions of the European Commission. It highlights challenges for the electric system and for the energy market (impact on investments, optimization of market operation), describes and assesses the French purchasing obligation arrangement, and describes and assesses other existing support arrangements

  5. 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.

  6. Possible Mechanisms Underlying the Therapeutic Effects of Transcranial Magnetic Stimulation

    Science.gov (United States)

    Chervyakov, Alexander V.; Chernyavsky, Andrey Yu.; Sinitsyn, Dmitry O.; Piradov, Michael A.

    2015-01-01

    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 and long-term depression. 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 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. PMID:26136672

  7. 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.

  8. 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

  9. 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.

  10. MECHANICAL BEHAVIOR OF PRESTRESSED VISCOELASTIC ADHESIVE AREAS UNDER COMBINING LOADINGS

    Directory of Open Access Journals (Sweden)

    Halil Murat Enginsoy

    2017-12-01

    Full Text Available In this article, mechanical behaviors of adhesive tape VHB 4950 elastomeric material, which is an element of acrylic polymer group and which is in viscoelastic behavior, under different pre-stress conditions and complex forces of different geometric parameters created by combining loadings have been experimentally and numerically investigated. In experimental studies, loading-unloading cyclic tests, one of the different standardized tests for the mechanical characterization of viscoelastic material, have been applied which give the most suitable convergent optimization parameters for the finite element model. Different material models were also investigated by using the data obtained from loading-unloading test results in all numerical models. According to the experimental results, the most suitable material parameters were determined with the Abaqus Parallel Rheological Framework Model (PRF for 4 Yeoh Networks with Bergstrom-Boyce Flow model created in the Mcalibration software for finite element analysis. Subsequently, using these material parameters, finite element analysis was performed as three dimension non-linear viscoelastic with a commercial finite element software Abaqus. The finite element analysis results showed good correlation to the Force (N-Displacement (mm experimental data for maximum load-carrying capacity of structural specimens.

  11. 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.

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

    Science.gov (United States)

    2017-01-01

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

  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. 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.

  15. 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.

  16. 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.

  17. 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

  18. Cleaner generation, free-riders, and environmental integrity: clean development mechanism and the power sector

    Energy Technology Data Exchange (ETDEWEB)

    Bernow, Stephen; Kartha, Sivan; Lazarus, Michael; Page, Tom [Tellus Institute and Stockholm Environmental Institute-Boston Center, Boston, MA (United States)

    2001-06-01

    This article provides a first-cut estimate of the potential impacts of the clean development mechanism (CDM) on electricity generation and carbon emissions in the power sector of non-Annex 1 countries. We construct four illustrative CDM regimes that represent a range of approaches under consideration within the climate community. We examine the impact of these CDM regimes on investments in new generation, under illustrative carbon trading prices of US$ 10 and 100/tC. In the cases that are most conductive to CDM activity, roughly 94% of new generation investments remains identical to the without-CDM situation, with only 6% shifting from higher to lower carbon intensity technologies. We estimate that the CDM would bolster renewable energy generation by as little as 15% at US$ 10/tC, or as much as 300% at US$ 100/tC. A striking finding comes from our examination of the potential magnitude of the 'free-rider' problem, i.e. crediting of activities that will occur even in the absence of the CDM. The CDM is intended to be globally carbon-neutral --- a project reduces emissions in the host country but generates credits that increase emissions in the investor country. However, to the extent that unwarranted credits are awarded to non-additional projects, the CDM would increase global carbon emissions above the without-CDM emissions level. Under two of the CDM regimes considered, cumulative free-riders credits total 250-600MtC through the end of the first budget period in 2012. This represents 10-23% of the likely OECD emissions reduction requirement during the first budget period. Since such a magnitude of free-rider credits from non-additional CDM projects could threaten the environmental integrity of the Kyoto protocol, it is imperative that policy makers devise CDM rules that encourage legitimate projects, while effectively screening out non-additional activities. (Author)

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

    Directory of Open Access Journals (Sweden)

    Jinpeng Qi

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

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

    Science.gov (United States)

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

    2011-01-01

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

  1. Next-Generation Dengue Vaccines: Novel Strategies Currently Under Development

    Directory of Open Access Journals (Sweden)

    Anna P. Durbin

    2011-09-01

    Full Text Available Dengue has become the most important arboviral infection worldwide with more than 30 million cases of dengue fever estimated to occur each year. The need for a dengue vaccine is great and several live attenuated dengue candidate vaccines are proceeding through clinical evaluation. The need to induce a balanced immune response against all four DENV serotypes with a single vaccine has been a challenge for dengue vaccine developers. A live attenuated DENV chimeric vaccine produced by Sanofi Pasteur has recently entered Phase III evaluation in numerous dengue-endemic regions of the world. Viral interference between serotypes contained in live vaccines has required up to three doses of the vaccine be given over a 12-month period of time. For this reason, novel DENV candidate vaccines are being developed with the goal of achieving a protective immune response with an immunization schedule that can be given over the course of a few months. These next-generation candidates include DNA vaccines, recombinant adenovirus vectored vaccines, alphavirus replicons, and sub-unit protein vaccines. Several of these novel candidates will be discussed.

  2. Next-generation dengue vaccines: novel strategies currently under development.

    Science.gov (United States)

    Durbin, Anna P; Whitehead, Stephen S

    2011-10-01

    Dengue has become the most important arboviral infection worldwide with more than 30 million cases of dengue fever estimated to occur each year. The need for a dengue vaccine is great and several live attenuated dengue candidate vaccines are proceeding through clinical evaluation. The need to induce a balanced immune response against all four DENV serotypes with a single vaccine has been a challenge for dengue vaccine developers. A live attenuated DENV chimeric vaccine produced by Sanofi Pasteur has recently entered Phase III evaluation in numerous dengue-endemic regions of the world. Viral interference between serotypes contained in live vaccines has required up to three doses of the vaccine be given over a 12-month period of time. For this reason, novel DENV candidate vaccines are being developed with the goal of achieving a protective immune response with an immunization schedule that can be given over the course of a few months. These next-generation candidates include DNA vaccines, recombinant adenovirus vectored vaccines, alphavirus replicons, and sub-unit protein vaccines. Several of these novel candidates will be discussed.

  3. Generation of Compliant Mechanisms using Hybrid Genetic Algorithm

    Science.gov (United States)

    Sharma, D.; Deb, K.

    2014-10-01

    Compliant mechanism is a single piece elastic structure which can deform to perform the assigned task. In this work, compliant mechanisms are evolved using a constraint based bi-objective optimization formulation which requires one user defined parameter ( η). This user defined parameter limits a gap between a desired path and an actual path traced by the compliant mechanism. The non-linear and discrete optimization problems are solved using the hybrid Genetic Algorithm (GA) wherein domain specific initialization, two-dimensional crossover operator and repairing techniques are adopted. A bit-wise local search method is used with elitist non-dominated sorting genetic algorithm to further refine the compliant mechanisms. Parallel computations are performed on the master-slave architecture to reduce the computation time. A parametric study is carried out for η value which suggests a range to evolve topologically different compliant mechanisms. The applied and boundary conditions to the compliant mechanisms are considered the variables that are evolved by the hybrid GA. The post-analysis of results unveils that the complaint mechanisms are always supported at unique location that can evolve the non-dominated solutions.

  4. 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

  5. Evaluation of Possible Proximate Mechanisms Underlying the Kinship Theory of Intragenomic Conflict in Social Insects.

    Science.gov (United States)

    Galbraith, David A; Yi, Soojin V; Grozinger, Christina M

    2016-12-01

    Kinship theory provides a universal framework in which to understand the evolution of altruism, but there are many molecular and genetic mechanisms that can generate altruistic behaviors. Interestingly, kinship theory specifically predicts intragenomic conflict between maternally-derived alleles (matrigenes) and paternally-derived alleles (patrigenes) over the generation of altruistic behavior in cases where the interests of the matrigenes and patrigenes are not aligned. Under these conditions, individual differences in selfish versus altruistic behavior are predicted to arise from differential expression of the matrigenes and patrigenes (parent-specific gene expression or PSGE) that regulate selfish versus altruistic behaviors. As one of the leading theories to describe PSGE and genomic imprinting, kinship theory has been used to generate predictions to describe the reproductive division of labor in social insect colonies, which represents an excellent model system to test the hypotheses of kinship theory and examine the underlying mechanisms driving it. Recent studies have confirmed the predicted differences in the influence of matrigenes and patrigenes on reproductive division of labor in social insects, and demonstrated that these differences are associated with differences in PSGE of key genes involved in regulating reproductive physiology, providing further support for kinship theory. However, the mechanisms mediating PSGE in social insects, and how PSGE leads to differences in selfish versus altruistic behavior, remain to be determined. Here, we review the available supporting evidence for three possible epigenetic mechanisms (DNA methylation, piRNAs, and histone modification) that may generate PSGE in social insects, and discuss how these may lead to variation in social behavior. © The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email

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

    Directory of Open Access Journals (Sweden)

    Antonio F. Hernández

    2016-03-01

    Full Text Available 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.

  7. An Automated Process for Generation of New Fuel Breakdown Mechanisms

    National Research Council Canada - National Science Library

    Violi, Angela

    2006-01-01

    .... It combines advanced computational techniques in a synergistic study of the critical processes in fuel decomposition at a level of detail that can help distinguish, correct, and quantify mechanisms for these processes...

  8. Mechanisms involved in stannane generation by aqueous tetrahydroborate(III)

    International Nuclear Information System (INIS)

    Pitzalis, Emanuela; Mascherpa, Marco Carlo; Onor, Massimo; D'Ulivo, Alessandro

    2009-01-01

    The role played by acidity (0.01-5 mol L -1 HNO 3 ) and L-cysteine (0.1-0.2 mol L -1 ) in the formation of stannane by reaction of Sn(IV) solution with aqueous tetrahydroborate(III) (0.05-0.2 mol L -1 ), has been investigated by continuous flow hydride generation coupled with atomic absorption spectrometry using a miniature argon-hydrogen diffusion flame as the atomizer. Different mixing sequences and reaction times of the reagents were useful in the identification of those processes which contribute to the generation of stannane in different reaction conditions, both in the absence and in the presence of L-cysteine. The lack of stannane generation at high acidities is due to the formation of Sn substrates and hydridoboron species which are unreactive. The capture of the stannane in solution, following its ionization to SnH 3 + from already formed stannane, does not play any role. While the presence of L-cysteine, does not affect the generation efficiency at lower acidities, it expands the optimum range of acidities for stannane generation to higher values. This effect can be addressed to both the buffering capacity of L-cysteine and to the formation of Sn-(L-cysteine) complexes, while the formation of (L-cysteine)-borane complexes do not play a significant role. Formation of Sn-(L-cysteine) complexes also appears to be useful for stabilization of tin solution at low acidities values.

  9. 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.

  10. 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.

  11. 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

  12. Rules and mechanisms governing octahedral tilts in perovskites under pressure

    Science.gov (United States)

    Xiang, H. J.; Guennou, Mael; Íñiguez, Jorge; Kreisel, Jens; Bellaiche, L.

    2017-08-01

    The rotation of octahedra (octahedral tilting) is common in A B O3 perovskites and relevant to many physical phenomena, ranging from electronic and magnetic properties, metal-insulator transitions to improper ferroelectricity. Hydrostatic pressure is an efficient way to tune and control octahedral tiltings. However, the pressure behavior of such tiltings can dramatically differ from one material to another, with the origins of such differences remaining controversial. In this paper, we discover several new mechanisms and formulate a set of simple rules that allow us to understand how pressure affects oxygen octahedral tiltings via the use and analysis of first-principles results for a variety of compounds. Besides the known A -O interactions, we reveal that the interactions between specific B ions and oxygen ions contribute to the tilting instability. We explain the previously reported trend that the derivative of the oxygen octahedral tilting with respect to pressure (dR /dP ) usually decreases with both the tolerance factor and the ionization state of the A ion by illustrating the key role of A -O interactions and their change under pressure. Furthermore, three new mechanisms/rules are discovered, namely that (i) the octahedral rotations in A B O3 perovskites with empty low-lying d states on the B site are greatly enhanced by pressure, in order to lower the electronic kinetic energy; (ii) dR /dP is enhanced when the system possesses weak tilt instabilities, and (iii) for the most common phase exhibited by perovskites—the orthorhombic Pbnm state—the in-phase and antiphase octahedral rotations are not automatically both suppressed or both enhanced by the application of pressure because of a trilinear coupling between these two rotation types and an antipolar mode involving the A ions. We further predict that the polarization associated with the so-called hybrid improper ferroelectricity could be manipulated by hydrostatic pressure by indirectly controlling the

  13. Neighbourhood generation mechanism applied in simulated annealing to job shop scheduling problems

    Science.gov (United States)

    Cruz-Chávez, Marco Antonio

    2015-11-01

    This paper presents a neighbourhood generation mechanism for the job shop scheduling problems (JSSPs). In order to obtain a feasible neighbour with the generation mechanism, it is only necessary to generate a permutation of an adjacent pair of operations in a scheduling of the JSSP. If there is no slack time between the adjacent pair of operations that is permuted, then it is proven, through theory and experimentation, that the new neighbour (schedule) generated is feasible. It is demonstrated that the neighbourhood generation mechanism is very efficient and effective in a simulated annealing.

  14. On the mechanical properties of tooth enamel under spherical indentation.

    Science.gov (United States)

    Chai, Herzl

    2014-11-01

    The mechanical properties of tooth enamel generally exhibit large variations, which reflect its structural and material complexity. Some key properties were evaluated under localized contact, simulating actual functioning conditions. Prominent cusps of extracted human molar teeth were polished down ~0.7 mm below the cusp tip and indented by tungsten carbide balls. The internal damage was assessed after unloading from longitudinal or transverse sections. The ultimate tensile stress (UTS) was determined using a novel bilayer specimen. The damage is characterized by penny-like radial cracks driven by hoop stresses and cylindrical cracks driven along protein-rich interrod materials by shear stresses. Shallow cone cracks typical of homogeneous materials which may cause rapid tooth wear under repeat contact are thus avoided. The mean stress vs. indentation strain curve is highly nonlinear, attributable to plastic shearing of protein between and within enamel rods. This curve is also affected by damage, especially radial cracks, the onset of which depends on ball radius. Several material properties were extracted from the tests, including shear strain at the onset of ring cracks γ(F) (=0.14), UTS (=119 MPa), toughness K(C) (=0.94 MPa m(1/2)), a crack propagation law and a constitutive response determined by trial and error with the aid of a finite-element analysis. These quantities, which are only slightly sensitive to anatomical location within the enamel region tested, facilitate a quantitative assessment of crown failure. Causes for variations in published UTS and K(C) values are discussed. Copyright © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  15. Failure mechanisms of aluminium foams under compressive loads

    Directory of Open Access Journals (Sweden)

    Sáenz, E.

    2000-08-01

    Full Text Available The purpose of this paper is the investigation of the major failure mechanisms of aluminium foams, which were obtained by powder metallurgy route, under compressive loads. The study was focused on two commonly aluminium alloys AlMg1Si or A 6061 and AlSi12. Due to the fact that the failure mechanisms strongly depend on the density and the macrostructural properties of the material, the mechanical properties always have to be correlated to the structural properties. Therefore, macrostructural investigations were used as a basis to establish the correlation between structural and mechanical properties. This was done with a commercially available image analysis system. The average cell size, the cell size distribution and the cell density (number of cells/area were obtained. In order to evaluate the influence of foaming direction on the cell morphology, some cross sections parallel to the foaming direction were prepared. For the characterization of the mechanical compression properties the compressive or upper yield strength (UYS, the densification strain (eD, the energy absorption (Ea and the efficiency (Eff were obtained. Furthermore, the failure behavior of the samples was in-situ observed with a digital video camera and continuously recorded during the test.

    El objetivo de este estudio es investigar los principales mecanismos de fallo de espumas de aluminio sometidas a cargas de compresión. Las espumas metálicas fueron obtenidas mediante el proceso pulvimetalúrgico, utilizándose como materia prima dos aleaciones comerciales AlMg1Si o A 6061 y AlSi12. Debido a que los mecanismos de fallo en este tipo de materiales depende fuertemente de la densidad y las características macroestructurales del material, en este estudio se busca correlacionar las propiedades mecánicas con estas características. La macroestructura se caracterizó mediante análisis de imagen. El tamaño de celda promedio, la distribución de tamaño y la densidad de

  16. Generation IV SFR Nuclear Reactors: Under Sodium Robotics for ASTRID

    International Nuclear Information System (INIS)

    Jouan-de-Kervenoael, T.; Rey, F.; Baque, F.

    2013-06-01

    For non-removable components of the future ASTRID prototype, repair operations will be performed in a gas environment. If the faulty area is located under the sodium free level, the gas-tight system will have to contain the inspection and repair tools and to protect them from the surrounding liquid sodium. Concerning repair tools, the unique laser tool has been selected for future SFRs: the repair scenario for in-sodium structures will first involve removing the sodium (after bulk draining), then machining and finally welding. Concerning conventional tools (brush or gas blower for sodium removal, milling machine for machining and TIG for welding for which its feasibility was demonstrated in the 1990's) are still considered as a back-up solution. The maintenance of future ASTRID nuclear reactor prototype (inspection, repair) will be performed during shut down periods with some robotic carriers which have to be introduced within the main vessel, in primary 200 deg. C sodium coolant with argon gas cover. Inspection campaigns will be 20 days long. These robots (or carriers) will allow bringing inspection and repairing tools up to concerned components and structures. The needed degrees of freedom associated to these operations will be assumed either directly by the carrier itself or by specifics lower end carrier device for accurate local positioning. Several carriers will be designed, well adapted to specific needs: type of maintenance operation and location of inspection and repair sites. Feedback experience was gained during Superphenix SFR operation with the MIR robot which allowed to successfully make the Non Destructive Examination of main vessel welding joints, the carrier being outside bulk sodium. Operating conditions for the ASTRID robots will be harder from those of the MIR robot: temperature ranging from 180 deg. C to 200 deg. C, radiation dose ranging from 105 to 106 Gy, but mainly direct immersion within liquid sodium coolant. At the design phase of

  17. Mechanisms involved in stannane generation by aqueous tetrahydroborate(III)

    Energy Technology Data Exchange (ETDEWEB)

    Pitzalis, Emanuela; Mascherpa, Marco Carlo; Onor, Massimo [C.N.R., Institute of Chemical and Physical Processes, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124, Pisa (Italy); D' Ulivo, Alessandro [C.N.R., Institute of Chemical and Physical Processes, Laboratory of Instrumental Analytical Chemistry, Via G. Moruzzi 1, 56124, Pisa (Italy)], E-mail: dulivo@ipcf.cnr.it

    2009-04-15

    The role played by acidity (0.01-5 mol L{sup -1} HNO{sub 3}) and L-cysteine (0.1-0.2 mol L{sup -1}) in the formation of stannane by reaction of Sn(IV) solution with aqueous tetrahydroborate(III) (0.05-0.2 mol L{sup -1}), has been investigated by continuous flow hydride generation coupled with atomic absorption spectrometry using a miniature argon-hydrogen diffusion flame as the atomizer. Different mixing sequences and reaction times of the reagents were useful in the identification of those processes which contribute to the generation of stannane in different reaction conditions, both in the absence and in the presence of L-cysteine. The lack of stannane generation at high acidities is due to the formation of Sn substrates and hydridoboron species which are unreactive. The capture of the stannane in solution, following its ionization to SnH{sub 3}{sup +} from already formed stannane, does not play any role. While the presence of L-cysteine, does not affect the generation efficiency at lower acidities, it expands the optimum range of acidities for stannane generation to higher values. This effect can be addressed to both the buffering capacity of L-cysteine and to the formation of Sn-(L-cysteine) complexes, while the formation of (L-cysteine)-borane complexes do not play a significant role. Formation of Sn-(L-cysteine) complexes also appears to be useful for stabilization of tin solution at low acidities values.

  18. Control of power converters in distributed generation applications under grid fault conditions

    DEFF Research Database (Denmark)

    Rodriguez, Pedro; Luna, Alvaro; Munoz-Aguilar, Raul

    2011-01-01

    The operation of distributed power generation systems under grid fault conditions is a key issue for the massive integration of renewable energy systems. Several studies have been conducted to improve the response of such distributed generation systems under voltage dips. In spite of being less s...

  19. 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.

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

    Science.gov (United States)

    Lee, Kwang Jae

    2015-08-01

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

  1. Enabling optimal energy options under the Clean Development Mechanism

    International Nuclear Information System (INIS)

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

    2007-01-01

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

  2. 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.

  3. Underlying mechanisms and the evolving influence of diet

    DEFF Research Database (Denmark)

    Larsen, Lesli Hingstrup

    2012-01-01

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

  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. 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.

  6. Radiation after-effects in daughter generations of barley grown under conditions of enhanced radioactive background

    International Nuclear Information System (INIS)

    Popova, O.N.; Shershunova, V.I.; Taskaev, A.I.

    1978-01-01

    Stimulation of growth and development was observed in the first daughter generation of barley plants grown under conditions simulating an enhanced radioactive background. The stimulatory effect was partially reproduced in the second generation, and signs of depression of initial growth of plants were found in the third generation. A great number of alterations and their regular occurrence allow to refer them to lingering modifications originating under the effect of a radiation factor on vegetating plants

  7. NREL Next Generation Drivetrain: Mechanical Design and Test Plan (Poster)

    Energy Technology Data Exchange (ETDEWEB)

    Keller, J.; Halse, C.

    2014-05-01

    The Department of Energy and industry partners are sponsoring a $3m project for design and testing of a 'Next Generation' wind turbine drivetrain at the National Renewable Energy Laboratory (NREL). This poster focuses on innovative aspects of the gearbox design, completed as part of an end-to-end systems engineering approach incorporating innovations that increase drivetrain reliability, efficiency, torque density and minimize capital cost.

  8. Mechanism of nitric acid generation on Ag-X Zeolite

    International Nuclear Information System (INIS)

    Kanazawa, T.; Kishimoto, T.; Haseba, S.; Mitoh, Y.; Itoh, S.; Nakai, I.

    1983-01-01

    When Ag-X Zeolite is used for the removal of iodine from the off gas streams of nuclear facilities, it is possible that nitric acid is formed on Ag-X Zeolite from co-existing nitrogen dioxide and water vapor. If nitric acid is formed on the surface of Ag-X zeolite, Ag-X zeolite is damaged and is not able to operate for a long time. When Ag-X zeolite is used in NO 2 -O 2 -H 2 O mixture, the nitric acid generation reaction is varied, depending upon the reaction temperature, and concentration of NO 2 and H 2 O. At a temperature of more than 40 deg. C, however, only the surface reaction will be progressed on the zeolite surface. The generation of nitric acid solution on the zeolite can be forecasted through the relationship between the concentration of nitric acid solution, equilibrium vapor pressure of H 2 O, and equilibrium vapor pressure of HNO 3 . Concerning the surface reaction caused on the zeolite, the adsorption water reacts on NO 2 , and the resulting HNO 3 is adsorbed firmly by the zeolite, which is thought to interfere with the surface reaction for generation of the HNO 3 . When the adsorption bed is long, the time required for adsorbed HNO 3 to saturate is increased in proportion to the bed length

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

    International Nuclear Information System (INIS)

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

    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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    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

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

    International Nuclear Information System (INIS)

    Vries, Laurens de; Heijnen, Petra

    2008-01-01

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

  12. Mechanical Design of a Second Generation LHC IR Quadrupole

    International Nuclear Information System (INIS)

    Caspi, S.; Bartlett, S.E.; Dietderich, D.R.; Ferracin, P.; Gourlay, S.A.; Hafalia, R.R.; Hannaford, C.R.; Lietzke, A.F.; McInturff, A.D.; Sabbi, G.; Scanlan, R.M.

    2003-01-01

    One of the proposed options to increase the LHC luminosity is the replacement of the existing inner triplets at the Interaction Regions with new low-beta larger aperture quadrupoles operating at the same gradient. Lawrence Berkeley National Laboratory (LBNL) is carrying out preliminary studies of a large-bore Nb 3 Sn quadrupole. The mechanical design presents a support structure based on the use of keys and bladders without self-supporting collars. This technology has been proven effective in several successful common coil Nb 3 Sn dipoles built at LBNL, and it is for the first time applied to a cos(2(var t heta)) design. In this paper we present a detailed analysis of the quadrupole mechanical behavior, demonstrating the possibility of delivering, through this method, well-controlled coil precompression during assembly, cool-down and excitation. The study has been performed with the finite element program ANSYS

  13. 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

  14. 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.

  15. A NEW CONGESTION MANAGEMENT MECHANISM FOR NEXT GENERATION ROUTERS

    Directory of Open Access Journals (Sweden)

    MOHAMMED M. KADHUM

    2008-12-01

    Full Text Available While computer networks go towards dealing with varied traffic types with different service requirements, there is a necessity for modern network control mechanisms that can control the network traffic to meet the users' service requirements. Optimizing the network utilization by improving the network performance can help to accommodate more users and thus increase operators’ profits. Controlling the congestion at the gateway leads to better performance of the network. Sending congestion signal sooner can be of great benefit to the TCP connection. In this paper, we propose Fast Congestion Notification (FCN mechanism which is a new method for managing the gateway queues and fast sending of congestion signal to the sender. We tested our mechanism on Explicit Congestion Notification (ECN packets which have higher priority; we achieved good results in terms of faster congestion signal propagation and better network utilization. Our analysis and simulations results show that the use of FCN over TCP connections sharing one bottleneck can improve the throughput, having less loss, less delay time, and better network utilization.

  16. Mechanisms of microstructure formation under the influence of ultrasonic vibrations

    Science.gov (United States)

    Rakita, Milan

    Positive effects of ultrasound on crystallization have been known for almost 90 years. Application of ultrasound has been very successful in many industries, most notably in chemistry, creating a new branch of science - sonochemistry. However, ultrasonication has not found wide commercial application in the solidification processing. The reason for that is the complexity of underlying phenomena and the lack of predicting models which correlate processing parameters with the properties of a product. The purpose of this study is to give some contribution toward better understanding of mechanisms that lead to changes in the solidifying microstructure. It has been found that, under experimental conditions used in this work, cavitation-induced nucleation is the major contributor to the grain refinement. Ultrasonication at minimal supercoolings is expected to give maximal grain refinement. Dendrite fragmentation has not shown to be a significant contributor to the grain refinement. Dendrite fragmentation is maximal if done by bubbles that come in contact with the solidifying phase, or that are created there. Alloys/solutions with long solidification interval, or wide mushy zone, are expected to exhibit more dendrite fragmentation. Bubbles are recognized as a crucial feature in ultrasonication. Their size distribution in the liquid phase prior to ultrasonication dictates the cavitation threshold and intensity of cavitation. For the first time, radiation pressure has been recognized as potentially significant factor in grain refinement. In the experimental setup used in this study, acoustic pressure at the main (driving) frequency is not substantial to cause significant fragmentation, and only dendrites close to the sonotrode were fragmented. However, application of ultrasound with frequencies that are several times higher than the current industrial practice could substantially increase dendrite fragmentation. Appearance of fractional harmonics has also been recognized

  17. Optimal trajectory generation for mechanical arms. M.S. Thesis

    Science.gov (United States)

    Iemenschot, J. A.

    1972-01-01

    A general method of generating optimal trajectories between an initial and a final position of an n degree of freedom manipulator arm with nonlinear equations of motion is proposed. The method is based on the assumption that the time history of each of the coordinates can be expanded in a series of simple time functions. By searching over the coefficients of the terms in the expansion, trajectories which minimize the value of a given cost function can be obtained. The method has been applied to a planar three degree of freedom arm.

  18. Polymer Composite Rebars under Moisture and Mechanical Loading

    Science.gov (United States)

    Adam, Mohamed Ibrahim

    structural GFRP composites will, through their design life, be exposed to a range of hygrothermal and other environmental conditions. This study aims to investigate the durability of glass fiber reinforced vinyl ester rebars exposed to moisture at different temperatures and under mechanical loading. Rebars of 10 mm, 13 mm, and 16 mm diameter were immersed in deionized water until saturation for 220 days at three different temperatures 30°C, 70°C, and 100°C. The rebars were examined as-received and following exposure to moisture by scanning electron microscopy and CT scan for possible microvoids and for modes of failures after being tested in both compression as well as non-tested specimens. Diffusion parameters were calculated and the accelerated hygrothermal effect on the compressive strength, modulus, and porosity was investigated. Significant decrease in compressive modulus and a much less degree of degradation in strength was observed. Three modes of failure were noted: splitting, fiber microbuckling, and fiber kinking. Presence of microvoids on both as-received and exposed to moisture specimens was evident. Despite this degradation due to hygrothermal exposure, GFRP rebars were able to maintain their strength. This can be regarded as an edge in their performance compared to steel. However this advantage may not hold with prolonged exposure. It was also noted that the specimens exposed to moisture and temperature exhibited an increase in microvoids of approximately 33% and new distribution of microvoids sizes was recorded. The degradation of the mechanical properties of the GFRP rebars was attributed to the hygrothermal effect that was facilitated by the presence of microvoids which allow moisture to diffuse. Presence and growth of Microvoids due to exposure to moisture and temperature was deemed the primary reason causing the degradation of GFRP rebars. Presence of microvoids needs to be addressed in order to enhance the durability and performance of GFRP rebar.

  19. Mechanisms underlying reduced fertility in anovular dairy cows.

    Science.gov (United States)

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

    2016-07-01

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

  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. 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

  2. Tsunamis: stochastic models of occurrence and generation mechanisms

    Science.gov (United States)

    Geist, Eric L.; Oglesby, David D.

    2014-01-01

    The devastating consequences of the 2004 Indian Ocean and 2011 Japan tsunamis have led to increased research into many different aspects of the tsunami phenomenon. In this entry, we review research related to the observed complexity and uncertainty associated with tsunami generation, propagation, and occurrence described and analyzed using a variety of stochastic methods. In each case, seismogenic tsunamis are primarily considered. Stochastic models are developed from the physical theories that govern tsunami evolution combined with empirical models fitted to seismic and tsunami observations, as well as tsunami catalogs. These stochastic methods are key to providing probabilistic forecasts and hazard assessments for tsunamis. The stochastic methods described here are similar to those described for earthquakes (Vere-Jones 2013) and volcanoes (Bebbington 2013) in this encyclopedia.

  3. Evaluation on mechanical and corrosion properties of steam generator tubing materials

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Sup; Lee, Byong Whi; Lee, Sang Kyu; Lee, Young Ho; Kim, Jun Whan; Lee, Ju Seok; Kwon, Hyuk Sang; Kim, Su Jung [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1998-06-15

    Steam generator is one of the major components of nuclear reactor pressure boundary. It's main function os transferring heat which generated in the reactor to turbine generator through steam generator tube. In these days, steam generator tubing materials of operating plant are used Inconel 600 alloys. But according to the operation time, there are many degradation phenomena which included mechanical damage due to flow induced vibration and corrosion damage due to PWSCC, IGA/SCC and pitting etc. Recently Inconel 690 alloys are selected as new and replacement steam generator tubes for domestic nuclear power plant. But there are few study about mechanical and corrosion properties of Inconel 600 and 690. The objectives of this study is to evaluate and compare mechanical and corrosion propertied of steam generator tube materials.

  4. Evaluation on mechanical and corrosion properties of steam generator tubing materials

    International Nuclear Information System (INIS)

    Kim, In Sup; Lee, Byong Whi; Lee, Sang Kyu; Lee, Young Ho; Kim, Jun Whan; Lee, Ju Seok; Kwon, Hyuk Sang; Kim, Su Jung

    1998-06-01

    Steam generator is one of the major components of nuclear reactor pressure boundary. It's main function os transferring heat which generated in the reactor to turbine generator through steam generator tube. In these days, steam generator tubing materials of operating plant are used Inconel 600 alloys. But according to the operation time, there are many degradation phenomena which included mechanical damage due to flow induced vibration and corrosion damage due to PWSCC, IGA/SCC and pitting etc. Recently Inconel 690 alloys are selected as new and replacement steam generator tubes for domestic nuclear power plant. But there are few study about mechanical and corrosion properties of Inconel 600 and 690. The objectives of this study is to evaluate and compare mechanical and corrosion propertied of steam generator tube materials

  5. On the generation mechanism of ULF seismogenic electromagnetic emissions

    Science.gov (United States)

    Molchanov, O. A.; Hayakawa, M.

    Microfracturing electrification is suggested as a possible mechanism for explaining ULF electromagnetic emissions observed before and after the earthquakes. This effect appears as fast fluctuation of microcracks and leads to the origination of wideband electromagnetic noise. This noise dissipates outside the source region and produces ULF emissions on the ground surface with an upper cutoff frequency ˜1 Hz due to the skin depth attenuation. Each microcurrent results from charge relaxation during microcrack opening and depends on the time of opening and conductivity of the rock medium. The normal size distribution of microcracks, their fast opening and healing (intermittence), and average size progression due to stress corrosion are assumed. Using this model, it is possible to compare these theoretical explanations with the observational results with reference to the intensity, frequency spectrum and temporal development of ULF magnetic field variations.

  6. [Neural mechanism underlying autistic savant and acquired savant syndrome].

    Science.gov (United States)

    Takahata, Keisuke; Kato, Motoichiro

    2008-07-01

    , especially that of the prefrontal cortex and the posterior regions of the brain. (3) Autistic models, including those based on weak central coherence theory (Frith, 1989), that focus on how savant skills emerge from an autistic brain. Based on recent neuroimaging studies of ASD, Just et al. (2004) suggested the underconnectivity theory, which emphasizes the disruption of long-range connectivity and the relative intact or even more enhanced local connectivity in the autistic brain. All the models listed above have certain advantages and shortcomings. At the end of this review, we propose another integrative model of savant syndrome. In this model, we predict an altered balance of local/global connectivity patterns that contribute to an altered functional segregation/integration ratio. In particular, we emphasize the crucial role played by the disruption of global connectivity in a parallel distributed cortical network, which might result in impairment in integrated cognitive processing, such as impairment in executive function and social cognition. On the other hand, the reduced inter-regional collaboration could lead to a disinhibitory enhancement of neural activity and connectivity in local cortical regions. In addition, enhanced connectivity in the local brain regions is partly due to the abnormal organization of the cortical network as a result of developmental and pathological states. This enhanced local connectivity results in the specialization and facilitation of low-level cognitive processing. The disruption of connectivity between the prefrontal cortex and other regions is considered to be a particularly important factor because the prefrontal region shows the most influential inhibitory control on other cortical areas. We propose that these neural mechanisms as the underlying causes for the emergence of savant ability in ASD and FTD patients.

  7. 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.

  8. A proposal for a dipole-generated BLUF domain mechanism

    Directory of Open Access Journals (Sweden)

    Tilo eMathes

    2015-11-01

    Full Text Available The resting and signaling structures of the blue-light sensing using flavin (BLUF photoreceptor domains are still controversially debated due to differences in the molecular models obtained by crystal and NMR structures. Photocycles for the given preferred structural framework have been established, but a unifying picture combining experiment and theory remains elusive. We summarize present work on the AppA BLUF domain from both experiment and theory. We focus on IR and UV/vis spectra, and to what extent theory was able to reproduce experimental data and predict the structural changes upon formation of the signaling state. We find that the experimental observables can be theoretically reproduced employing any structural model, as long as the orientation of the signaling essential Gln63 and its tautomer state are a choice of the modeler. We also observe that few approaches are comparative, e.g. by considering all structures in the same context. Based on recent experimental findings and a few basic calculations, we suggest the possibility for a BLUF activation mechanism that only relies on electron transfer and its effect on the local electrostatics, not requiring an associated proton transfer. In this regard, we investigate the impact of dispersion correction on the interaction energies arising from weakly bound amino acids.

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

    Science.gov (United States)

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

    2017-06-22

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

  10. 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

  11. 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.

  12. Mechanical response of collagen molecule under hydrostatic compression.

    Science.gov (United States)

    Saini, Karanvir; Kumar, Navin

    2015-04-01

    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. Copyright © 2015 Elsevier B.V. All rights

  13. Mechanical response of collagen molecule under hydrostatic compression

    Energy Technology Data Exchange (ETDEWEB)

    Saini, Karanvir, E-mail: karans@iitrpr.ac.in; Kumar, Navin

    2015-04-01

    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.

  14. Formation mechanisms of the powder porosity generated in the neighborhood of the shear plane

    International Nuclear Information System (INIS)

    Makino, K.; Kuramitsu, K.; Hoshikawa, H.; Mori, H.

    1988-01-01

    In recent years, the sophisticated technology on the process of powder feeding, packing, mixing, and compacting, by which homogeneous powder products can be manufactured in fine ceramics and electronics industries, is being established. And, in order to develop the technology, it is necessary to make clear the formation mechanism of powder porosity in the neighborhood of shear plane generated in the powder bed. However, this has not yet been sufficiently elucidated. In this paper, a single-plane shear tester which can simultaneously measure three quantities of stress, strain, and the powder porosity in the neighborhood of shear plane, was devised by using an X-ray radiograph system, and these three quantities were systematically measured under various shearing conditions. Next, a formation model of the powder porosity in the neighborhood of shear plane, composed of powder yield locus, critical state line, and Mohr stress semi, was experimentally checked by the three measured quantities mentioned above

  15. Placental vascular pathology and increased thrombin generation as mechanisms of disease in obstetrical syndromes

    Directory of Open Access Journals (Sweden)

    Salvatore Andrea Mastrolia

    2014-11-01

    Full Text Available Obstetrical complications including preeclampsia, fetal growth restriction, preterm labor, preterm prelabor rupture of membranes and fetal demise are all the clinical endpoint of several underlying mechanisms (i.e., infection, inflammation, thrombosis, endocrine disorder, immunologic rejection, genetic, and environmental, therefore, they may be regarded as syndromes. Placental vascular pathology and increased thrombin generation were reported in all of these obstetrical syndromes. Moreover, elevated concentrations of thrombin-anti thrombin III complexes and changes in the coagulation as well as anticoagulation factors can be detected in the maternal circulation prior to the clinical development of the disease in some of these syndromes. In this review, we will assess the changes in the hemostatic system during normal and complicated pregnancy in maternal blood, maternal–fetal interface and amniotic fluid, and describe the contribution of thrombosis and vascular pathology to the development of the great obstetrical syndromes.

  16. Poroelastic Mechanical Effects of Hemicelluloses on Cellulosic Hydrogels under Compression

    Science.gov (United States)

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

    2015-01-01

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

  17. An Analysis of the Dispute Settlement Mechanism under the

    African Journals Online (AJOL)

    user

    This article examines and evaluates the consumer redress mechanism, .... 23 The behaviour or conduct must be prohibited in terms of the Competition Act ...... appropriate orders and provide "sufficient" remedies to avoid the involvement of the.

  18. New Insights on Neurobiological Mechanisms underlying Alcohol Addiction

    Science.gov (United States)

    Cui, Changhai; Noronha, Antonio; Morikawa, Hitoshi; Alvarez, Veronica A.; Stuber, Garret D.; Szumlinski, Karen K.; Kash, Thomas L.; Roberto, Marisa; Wilcox, Mark V.

    2012-01-01

    Alcohol dependence/addiction is mediated by complex neural mechanisms that involve multiple brain circuits and neuroadaptive changes in a variety of neurotransmitter and neuropeptide systems. Although recent studies have provided substantial information on the neurobiological mechanisms that drive alcohol drinking behavior, significant challenges remain in understanding how alcohol-induced neuroadaptations occur and how different neurocircuits and pathways cross-talk. This review article highlights recent progress in understanding neural mechanisms of alcohol addiction from the perspectives of the development and maintenance of alcohol dependence. It provides insights on cross talks of different mechanisms and reviews the latest studies on metaplasticity, structural plasticity, interface of reward and stress pathways, and cross-talk of different neural signaling systems involved in binge-like drinking and alcohol dependence. PMID:23159531

  19. Fracture behavior and deformation mechanisms under fast neutron irradiation

    International Nuclear Information System (INIS)

    Boutard, J.L.; Dupouy, J.M.

    1980-09-01

    We have established the out-of-pile and in-pile deformation mechanism maps of a 316 stainless steel irradiated in a fast reactor. The knowledge of the dominating deformation mechanism either in post irradiation creep experiments or during the in-pile steady state operating conditions allows to rationalize the apparent discrepancy between the very low out-of-pile ductility and the rather high plastic diametral strains which are obtained in the fast reactor environment without fracture

  20. 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.

  1. 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.

  2. Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions

    Science.gov (United States)

    2013-08-26

    injection” protocol for myogenic cell transplantation throughout large volumes of muscles in a Duchenne muscular dystrophy patient: eighteen months follow-up...Oxygen Generating Biomaterials Preserve Skeletal Muscle Homeostasis under Hypoxic and Ischemic Conditions Catherine L. Ward, Benjamin T. Corona...investigation was to determine if sodium percarbonate (SPO), an oxygen generating biomaterial, is capable of maintaining resting skeletal muscle

  3. Global Mechanical Response and Its Relation to Deformation and Failure Modes at Various Length Scales Under Shock Impact in Alumina AD995 Armor Ceramic

    National Research Council Canada - National Science Library

    Dandekar, D. P; McCauley, J. W; Green, W. H; Bourne, N. K; Chen, M. W

    2008-01-01

    ... maps relating the experimentally measured global mechanical response of a material through matured shock wave diagnostics to the nature of concurrent deformation and damage generated at varying length scales under shock wave loading.

  4. Comparison of exciplex generation under optical and X-ray excitation

    Science.gov (United States)

    Kipriyanov, A. A.; Melnikov, A. R.; Stass, D. V.; Doktorov, A. B.

    2017-09-01

    Exciplex generation under optical and X-ray excitation in identical conditions is experimentally compared using a specially chosen model donor-acceptor system, anthracene (electron acceptor) and N,N-dimethylaniline (electron donor) in non-polar solution, and the results are analyzed and interpreted based on analytically calculated luminescence quantum yields. Calculations are performed on the basis of kinetic equations for multistage schemes of bulk exciplex production reaction under optical excitation and combination of bulk and geminate reactions of radical ion pairs under X-ray excitation. These results explain the earlier experimentally found difference in the ratio of the quantum yields of exciplexes and excited electron acceptors (exciplex generation efficiency) and the corresponding change in the exciplex generation efficiency under X-irradiation as compared to the reaction under optical excitation.

  5. Early stages of wind wave and drift current generation under non-stationary wind conditions.

    Science.gov (United States)

    Robles-Diaz, Lucia; Ocampo-Torres, Francisco J.; Branger, Hubert

    2016-04-01

    Generation and amplification mechanisms of ocean waves are well understood under constant wind speed or limited fetch conditions. Under these situations, the momentum and energy transfers from air to water are also quite well known. However during the wind field evolution over the ocean, we may observe sometime high wind acceleration/deceleration situations (e.g. Mexican Tehuano or Mediterranean Mistral wind systems). The evolution of wave systems under these conditions is not well understood. The purpose of these laboratory experiments is to better understand the early stages of water-waves and surface-drift currents under non-stationary wind conditions and to determine the balance between transfers creating waves and surface currents during non-equilibrium situations. The experiments were conducted in the Institut Pythéas wind-wave facility in Marseille-France. The wave tank is 40 m long, 2.7 m wide and 1 m deep. The air section is 50 m long, 3 m wide and 1.8 m height. We used 11 different resistive wave-gauges located along the tank. The momentum fluxes in the air column were estimated from single and X hot-film anemometer measurements. The sampling frequency for wind velocity and surface displacement measurements was 256 Hz. Water-current measurements were performed with a profiling velocimeter. This device measures the first 3.5 cm of the water column with a frequency rate of 100Hz. During the experiments, the wind intensity was abruptly modified with a constant acceleration and deceleration over time. We observed that wind drag coefficient values for accelerated wind periods are lower than the ones reported in previous studies for constant wind speed (Large and Pond 1981; Ocampo-Torres et al. 2010; Smith 1980; Yelland and Taylor 1996). This is probably because the turbulent boundary layer is not completely developed during the increasing-wind sequence. As it was reported in some theoretical studies (Miles 1957; Phillips 1957; Kahma and Donelan 1988), we

  6. Bandwidth increasing mechanism by introducing a curve fixture to the cantilever generator

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Weiqun, E-mail: weiqunliu@home.swjtu.edu.cn; Liu, Congzhi; Ren, Bingyu; Zhu, Qiao; Hu, Guangdi [School of Mechanical Engineering, Southwest Jiaotong University, 610031 Chengdu (China); Yang, Weiqing [School of Materials Science and Engineering, Southwest Jiaotong University, 610031 Chengdu (China)

    2016-07-25

    A nonlinear wideband generator architecture by clamping the cantilever beam generator with a curve fixture is proposed. Devices with different nonlinear stiffness can be obtained by properly choosing the fixture curve according to the design requirements. Three available generator types are presented and discussed for polynomial curves. Experimental investigations show that the proposed mechanism effectively extends the operation bandwidth with good power performance. Especially, the simplicity and easy feasibility allow the mechanism to be widely applied for vibration generators in different scales and environments.

  7. 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

  8. Mechanisms of generation of local ΔpH in mitochondria and bacteria.

    Science.gov (United States)

    Medvedev, E S; Stuchebrukhov, A A

    2014-05-01

    The concepts of global and local coupling between proton generators, the enzymes of the respiratory chain, and the consumer, the ATP synthase, coexist in the theory of oxidative phosphorylation. Global coupling is trivial proton transport via the aqueous medium, whereas local coupling implies that the protons pumped are consumed before they escape to the bulk phase. In this work, the conditions for the occurrence of local coupling are explored. It is supposed that the membrane retains protons near its surface and that the proton current generated by the proton pumps rapidly decreases with increasing proton motive force (pmf). It is shown that the competition between the processes of proton translocation across the membrane and their dissipation from the surface to the bulk can result in transient generation of a local ΔpH in reply to a sharp change in pmf; the appearance of local ΔpH, in turn, leads to rapid recovery of the pmf, and hence, it provides for stabilization of the potential at the membrane. Two mechanisms of such kind are discussed: 1) pH changes in the surface area due to proton pumping develop faster than those due to proton escape to the bulk; 2) the former does not take place, but the protons leaving the surface do not equilibrate with the bulk immediately; rather, they give rise to a non-equilibrium concentration near the surface and, as a result, to a back proton flow to the surface. The first mechanism is more efficient, but it does not occur in mitochondria and neutrophilic bacteria, whereas the second can produce ΔpH on the order of unity. In the absence of proton retardation at the surface, local ΔpH does not arise, whereas the formation of global ΔpH is possible only at buffer concentration of less than 10 mM. The role of the mechanisms proposed in transitions between States 3 and 4 of the respiratory chain is discussed. The main conclusion is that surface protons, under conditions where they play a role, support stabilization of the

  9. 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...

  10. 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

  11. A Facile Method and Novel Mechanism Using Microneedle-Structured PDMS for Triboelectric Generator Applications.

    Science.gov (United States)

    Trinh, Van-Long; Chung, Chen-Kuei

    2017-08-01

    The triboelectric generator (TEG) is a cost-effective, multi-fabricated, friendly mechanical-energy-harvesting device. The traditional TEG, generally formed by two triboelectric materials in multilayers or a simple pattern, generated triboelectricity as it worked in the cycling contact-separation operation. This paper demonstrates a novel, high-aspect-ratio, microneedle (MN)-structured polydimethylsiloxane (PDMS)-based triboelectric generator (MN-TEG) by means of a low-cost, simple fabrication using CO 2 laser ablation on the polymethyl methacrylate substrate and a molding process. The MN-TEG, consisting of an aluminum foil and a microneedle-structured PDMS (MN-PDMS) film, generates an output performance with an open-circuit voltage up to 102.8 V, and a short-circuit current of 43.1 µA, corresponding to the current density of 1.5 µA cm -2 . With introducing MN-PDMS into the MN-TEG, a great increase of randomly closed bending-friction-deformation (BFD) behavior of MNs leads to highly enhanced triboelectric performance of the MN-TEG. The BFD keeps increasingly on in-contact between MN with Al that results in enhancement of electrical capacitance of PDMS. The effect of aspect ratio and density of MN morphology on the output performance of MN-PDMS TEG is studied further. The MN-TEG can rapidly charge electric energy on a 0.1 µF capacitor up to 2.1 V in about 0.56 s. The MN-TEG source under tapping can light up 53 light-emitting diodes with different colors, connected in series. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. 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

  13. Mechanical behaviour of adhesive joint under tensile and shear loading

    NARCIS (Netherlands)

    Jiang, X.; Kolstein, M.H.; Bijlaard, F.S.K.

    2013-01-01

    Due to various advantages of Fibre-Reinforced Polymer (FRP) decks, the FRP to steel composite bridge system is being increasingly used in new bridge structures as well as rehabilitation projects for old bridges. This paper focuses on the mechanical behaviours and failure modes of the

  14. Wire bond degradation under thermo- and pure mechanical loading

    DEFF Research Database (Denmark)

    Pedersen, Kristian Bonderup; Nielsen, Dennis Achton; Czerny, Bernhard

    2017-01-01

    This paper presents a fundamental study on degradation of heavy Al bond wires typically used in high power modules. Customized samples are designed to only consist of Al bond wires on standard Si diodes. These samples are subjected to pure mechanical and passive thermal cycling to investigate...

  15. Transcriptome profiling reveals regulatory mechanisms underlying Corolla Senescence in Petunia

    Science.gov (United States)

    Genetic regulatory mechanisms that govern petal natural senescence in petunia is complicated and unclear. To identify key genes and pathways that regulate the process, we initiated a transcriptome analysis in petunia petals at four developmental time points, including petal opening without anthesis ...

  16. 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 ...

  17. Research on generation mechanism of single event transient current generated in the semiconductor using ion accelerator

    International Nuclear Information System (INIS)

    Hirao, Toshio

    2007-01-01

    Single-event upset (SEU) is triggered when an amount of electric charges induced by energetic ion incidence exceeds a value known as a critical charge in a very short time period. Therefore, accurate evaluation of electric charge and understanding of basic mechanism of SEU are necessary for the improvement of SEU torrance of electronic devices. In this paper, the collected charges for the single event transient current induced on semiconductor by heavy ion microbeams, and application to use microbeam for single event studies are presented. (author)

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

    Directory of Open Access Journals (Sweden)

    Seol Ah Kim

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

  19. Ab initio Algorithmic Causal Deconvolution of Intertwined Programs and Networks by Generative Mechanism

    KAUST Repository

    Zenil, Hector; Kiani, Narsis A.; Tegner, Jesper

    2018-01-01

    To extract and learn representations leading to generative mechanisms from data, especially without making arbitrary decisions and biased assumptions, is a central challenge in most areas of scientific research particularly in connection to current

  20. Variate generation for probabilistic fracture mechanics and fitness-for-service studies

    International Nuclear Information System (INIS)

    Walker, J.R.

    1987-01-01

    Atomic Energy of Canada Limited is conducting studies in Probabilistic Fracture Mechanics. These studies are being conducted as part of a fitness-for-service programme in support of CANDU reactors. The Monte Carlo analyses, which form part of the Probabilistic Fracture Mechanics studies, require that variates can be sampled from probability density functions. Accurate pseudo-random numbers are necessary for accurate variate generation. This report details the principles of variate generation, and describes the production and testing of pseudo-random numbers. A new algorithm has been produced for the correct performance of the lattice test for the independence of pseudo-random numbers. Two new pseudo-random number generators have been produced. These generators have excellent randomness properties and can be made fully machine-independent. Versions, in FORTRAN, for VAX and CDC computers are given. Accurate and efficient algorithms for the generation of variates from the specialized probability density functions of Probabilistic Fracture Mechanics are given. 38 refs

  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. Studies on Molecular Mechanisms Underlying Spinocerebellar Ataxia Type 3

    DEFF Research Database (Denmark)

    Kristensen, Line Vildbrad

    . 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...... in protein quality control. In SCA3 patients polyQ expanded ataxin-3 forms intranuclear inclusions in various brain areas, but why the polyQ expansion of ataxin-3 leads to neuronal dysfunction is still not well understood. This thesis describes molecular biological investigations of ataxin-3 biology, aimed...... at furthering our understanding of SCA3 disease mechanisms. In manuscript I, we investigated if post-translational modifications of ataxin-3 were changed by the polyQ expansion. The ubiquitin chain topology and ubiquitination pattern of ataxin-3 were unaltered by the polyQ expansion. In contrast...

  3. 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.

  4. 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.

  5. Pore closure in zeolitic imidazolate frameworks under mechanical pressure.

    Science.gov (United States)

    Henke, Sebastian; Wharmby, Michael T; Kieslich, Gregor; Hante, Inke; Schneemann, Andreas; Wu, Yue; Daisenberger, Dominik; Cheetham, Anthony K

    2018-02-14

    We investigate the pressure-dependent mechanical behaviour of the zeolitic imidazolate framework ZIF-4 (M(im) 2 ; M 2+ = Co 2+ or Zn 2+ , im - = imidazolate) with high pressure, synchrotron powder X-ray diffraction and mercury intrusion measurements. A displacive phase transition from a highly compressible open pore ( op ) phase with continuous porosity (space group Pbca , bulk modulus ∼1.4 GPa) to a closed pore ( cp ) phase with inaccessible porosity (space group P 2 1 / c , bulk modulus ∼3.3-4.9 GPa) is triggered by the application of mechanical pressure. Over the course of the transitions, both ZIF-4 materials contract by about 20% in volume. However, the threshold pressure, the reversibility and the immediate repeatability of the phase transition depend on the metal cation. ZIF-4(Zn) undergoes the op-cp phase transition at a hydrostatic mechanical pressure of only 28 MPa, while ZIF-4(Co) requires about 50 MPa to initiate the transition. Interestingly, ZIF-4(Co) fully returns to the op phase after decompression, whereas ZIF-4(Zn) remains in the cp phase after pressure release and requires subsequent heating to switch back to the op phase. These variations in high pressure behaviour can be rationalised on the basis of the different electron configurations of the respective M 2+ ions (3d 10 for Zn 2+ and 3d 7 for Co 2+ ). Our results present the first examples of op-cp phase transitions ( i.e. breathing transitions) of ZIFs driven by mechanical pressure and suggest potential applications of these functional materials as shock absorbers, nanodampers, or in mechanocalorics.

  6. Underlying mechanisms of transient luminous events: a review

    OpenAIRE

    V. V. Surkov; M. Hayakawa

    2012-01-01

    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...

  7. Mechanical Characterization of Femoral Cartilage Under Unicompartimental Osteoarthritis

    OpenAIRE

    Vidal-Lesso, A.; Ledesma-Orozco, E.; Daza-Benítez, L.; Lesso-Arroyo, R.

    2014-01-01

    The aim of this study was to determine the mechanical properties and thickness of articular cartilage in the unaffected femoral regions in cases of unicompartimental osteoarthritis on the knees. The specimens were tested using a 3mm plane-ended cylindrical indenter and a displacement of 0.5mm was applied at specific points in seven femoral knee cartilages with unicompartimental osteoarthritis. The thickness, stiffness, elastic modulus, shear modulus and bulk modulus were obtained. These prope...

  8. 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.

  9. Gas Supply, Pricing Mechanism and the Economics of Power Generation in China

    Directory of Open Access Journals (Sweden)

    Yuanxin Liu

    2018-04-01

    Full Text Available During the “13th Five-Year Plan” period, green energy is the top priority for China. China has realized that natural gas, as a low-carbon energy source, fits with the nation’s energy demand and will play a critical role in the energy transition, but the actual industry development is slower than expected. By analyzing the major gas corporations around the world, the paper finds that the key factors of the sector are supply and price of the energy resource. A comprehensive analysis on domestic and foreign imported gas reveals a trend of oversupply in China in the future. Given the critical import dependence, China has introduced a series of gas price reforms since 2013, which have led to negative impacts on important gas consumption sectors including power generation. With the levelized cost of electricity (LCOE model, we find that under the prevailing gas supply structure and price level, the economy of utility gas power generation will remain unprofitable, while combined cooling heating and power (CCHP is only commercially feasible in coastal developed regions. If continuing, such a trend will not only bring forth disastrous consequences to gas power industry, but also damage the upstream gas industry, more importantly, impede the energy transition. We conclude the paper with policy implications on pricing mechanism reform, developing domestic unconventional gas and the R&D of gas turbine.

  10. Expected utility violations evolve under status-based selection mechanisms.

    Science.gov (United States)

    Dickson, Eric S

    2008-10-07

    The expected utility theory of decision making under uncertainty, a cornerstone of modern economics, assumes that humans linearly weight "utilities" for different possible outcomes by the probabilities with which these outcomes occur. Despite the theory's intuitive appeal, both from normative and from evolutionary perspectives, many experiments demonstrate systematic, though poorly understood, patterns of deviation from EU predictions. This paper offers a novel theoretical account of such patterns of deviation by demonstrating that EU violations can emerge from evolutionary selection when individual "status" affects inclusive fitness. In humans, battles for resources and social standing involve high-stakes decision making, and assortative mating ensures that status matters for fitness outcomes. The paper therefore proposes grounding the study of decision making under uncertainty in an evolutionary game-theoretic framework.

  11. 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.

  12. Corrosion mechanisms of spent fuel under oxidizing conditions

    International Nuclear Information System (INIS)

    Finn, P.A.; Finch, R.; Buck, E.; Bates, J.

    1997-01-01

    The release of 99 Tc can be used as a reliable marker for the extent of spent oxide fuel reaction under unsaturated high-drip-rate conditions at 90 degrees C. Evidence from leachate data and from scanning and transmission electron microscopy (SEM and TEM) examination of reacted fuel samples is presented for radionuclide release, potential reaction pathways, and the formation of alteration products. In the ATM-103 fuel, 0.03 of the total inventory of 99 Tc is released in 3.7 years under unsaturated and oxidizing conditions. Two reaction pathways that have been identified from SEM are (1) through-grain dissolution with subsequent formation of uranyl alteration products, and (2) grain-boundary dissolution. The major alteration product identified by x-ray diffraction (XRD) and SEM, is Na-boltwoodite, Na[(UO 2 )(SiO 3 OH)]lg-bullet H 2 O, which is formed from sodium and silicon in the water leachant

  13. Engineering mechanical gradients in next generation biomaterials - Lessons learned from medical textile design.

    Science.gov (United States)

    Ng, Joanna L; Collins, Ciara E; Knothe Tate, Melissa L

    2017-07-01

    Nonwoven and textile membranes have been applied both externally and internally to prescribe boundary conditions for medical conditions as diverse as oedema and tissue defects. Incorporation of mechanical gradients in next generation medical membrane design offers great potential to enhance function in a dynamic, physiological context. Yet the gradient properties and resulting mechanical performance of current membranes are not well described. To bridge this knowledge gap, we tested and compared the mechanical properties of bounding membranes used in both external (compression sleeves for oedema, exercise bands) and internal (surgical membranes) physiological contexts. We showed that anisotropic compression garment textiles, isotropic exercise bands and surgical membranes exhibit similar ranges of resistance to tension under physiologic strains. However, their mechanical gradients and resulting stress-strain relationships show differences in work capacity and energy expenditure. Exercise bands' moduli of elasticity and respective thicknesses allow for controlled, incremental increases in loading to facilitate healing as injured tissues return to normal structure and function. In contrast, the gradients intrinsic to compression sleeve design exhibit gaps in the middle range (1-5N) of physiological strains and also inconsistencies along the length of the sleeve, resulting in less than optimal performance of these devices. These current shortcomings in compression textile and garment design may be addressed in the future through implementation of novel approaches. For example, patterns, fibre compositions, and fibre anisotropy can be incorporated into biomaterial design to achieve seamless mechanical gradients in structure and resulting dynamic function, which would be particularly useful in physiological contexts. These concepts can be applied further to biomaterial design to deliver pressure gradients during movement of oedematous limbs (compression garments) and

  14. Performance of multifilamentary Nb3Sn under mechanical load

    International Nuclear Information System (INIS)

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

    1976-11-01

    The critical current density of commercial multifilamentary Nb 3 Sn conductor has been measured during the application of uniaxial tension at 4.2 0 K and after bending at room temperature. Significant reductions in the critical current density J/sub c/ occurred 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

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

    Science.gov (United States)

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

    2016-01-01

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

  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. Generation and application of tri-dimensional animation in mechanical design

    International Nuclear Information System (INIS)

    Liu Li

    2003-01-01

    The mechanical design can be understood vividly and accurately and can be improved in time when there is any mistake if it is made in tri-dimensional animation. The author introduces the generation process and methods for animation in mechanical design with an example

  19. Generation mechanisms for magnetic-field-aligned electric fields in the magnetosphere

    International Nuclear Information System (INIS)

    Faelthammar, C.-G.

    1977-09-01

    Magnetic-field-aligned electric fields in the magnetosphere can be generated in several different ways, and in this review some possible mechanisms are presented. Observational data now available indicates that more than one of the mechanisms mentioned are operative in the magnetosphere but it is not yet possible to evaluate their relative importance. (author)

  20. 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.

  1. Mechanical Alterations Associated with Repeated Treadmill Sprinting under Heat Stress.

    Directory of Open Access Journals (Sweden)

    Olivier Girard

    Full Text Available Examine the mechanical alterations associated with repeated treadmill sprinting performed in HOT (38°C and CON (25°C conditions.Eleven recreationally active males performed a 30-min warm-up followed by three sets of five 5-s sprints with 25-s recovery and 3-min between sets in each environment. Constant-velocity running for 1-min at 10 and 20 km.h-1 was also performed prior to and following sprinting.Mean skin (37.2±0.7 vs. 32.7±0.8°C; P<0.001 and core (38.9±0.2 vs. 38.8±0.3°C; P<0.05 temperatures, together with thermal comfort (P<0.001 were higher following repeated sprinting in HOT vs. CON. Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P<0.001 and contact time (+3.2±2.4%; P<0.01 higher in HOT for the mean of sets 1-3 compared to CON. Running distance per sprint decreased from set 1 to 3 (-7.0±6.4%; P<0.001, with a tendency for shorter distance covered in HOT vs. CON (-2.7±3.4%; P = 0.06. Mean vertical (-2.6±5.5%; P<0.01, horizontal (-9.1±4.4%; P<0.001 and resultant ground reaction forces (-3.0±2.8%; P<0.01 along with vertical stiffness (-12.9±2.3%; P<0.001 and leg stiffness (-8.4±2.7%; P<0.01 decreased from set 1 to 3, independently of conditions. Propulsive power decreased from set 1 to 3 (-16.9±2.4%; P<0.001, with lower propulsive power values in set 2 (-6.6%; P<0.05 in HOT vs. CON. No changes in constant-velocity running patterns occurred between conditions, or from pre-to-post repeated-sprint exercise.Thermal strain alters step frequency and vertical stiffness during repeated sprinting; however without exacerbating mechanical alterations. The absence of changes in constant-velocity running patterns suggests a strong link between fatigue-induced velocity decrements during sprinting and mechanical alterations.

  2. Mechanical Alterations Associated with Repeated Treadmill Sprinting under Heat Stress

    Science.gov (United States)

    Brocherie, Franck; Morin, Jean-Benoit; Racinais, Sébastien; Millet, Grégoire P.; Périard, Julien D.

    2017-01-01

    Purpose Examine the mechanical alterations associated with repeated treadmill sprinting performed in HOT (38°C) and CON (25°C) conditions. Methods Eleven recreationally active males performed a 30-min warm-up followed by three sets of five 5-s sprints with 25-s recovery and 3-min between sets in each environment. Constant-velocity running for 1-min at 10 and 20 km.h-1 was also performed prior to and following sprinting. Results Mean skin (37.2±0.7 vs. 32.7±0.8°C; P<0.001) and core (38.9±0.2 vs. 38.8±0.3°C; P<0.05) temperatures, together with thermal comfort (P<0.001) were higher following repeated sprinting in HOT vs. CON. Step frequency and vertical stiffness were lower (-2.6±1.6% and -5.5±5.5%; both P<0.001) and contact time (+3.2±2.4%; P<0.01) higher in HOT for the mean of sets 1–3 compared to CON. Running distance per sprint decreased from set 1 to 3 (-7.0±6.4%; P<0.001), with a tendency for shorter distance covered in HOT vs. CON (-2.7±3.4%; P = 0.06). Mean vertical (-2.6±5.5%; P<0.01), horizontal (-9.1±4.4%; P<0.001) and resultant ground reaction forces (-3.0±2.8%; P<0.01) along with vertical stiffness (-12.9±2.3%; P<0.001) and leg stiffness (-8.4±2.7%; P<0.01) decreased from set 1 to 3, independently of conditions. Propulsive power decreased from set 1 to 3 (-16.9±2.4%; P<0.001), with lower propulsive power values in set 2 (-6.6%; P<0.05) in HOT vs. CON. No changes in constant-velocity running patterns occurred between conditions, or from pre-to-post repeated-sprint exercise. Conclusions Thermal strain alters step frequency and vertical stiffness during repeated sprinting; however without exacerbating mechanical alterations. The absence of changes in constant-velocity running patterns suggests a strong link between fatigue-induced velocity decrements during sprinting and mechanical alterations. PMID:28146582

  3. Functional methods underlying classical mechanics, relativity and quantum theory

    International Nuclear Information System (INIS)

    Kryukov, A

    2013-01-01

    The paper investigates the physical content of a recently proposed mathematical framework that unifies the standard formalisms of classical mechanics, relativity and quantum theory. In the framework states of a classical particle are identified with Dirac delta functions. The classical space is ''made'' of these functions and becomes a submanifold in a Hilbert space of states of the particle. The resulting embedding of the classical space into the space of states is highly non-trivial and accounts for numerous deep relations between classical and quantum physics and relativity. One of the most striking results is the proof that the normal probability distribution of position of a macroscopic particle (equivalently, position of the corresponding delta state within the classical space submanifold) yields the Born rule for transitions between arbitrary quantum states.

  4. 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.

  5. 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.

  6. Ecological mechanisms underlying arthropod species diversity in grasslands.

    Science.gov (United States)

    Joern, Anthony; Laws, Angela N

    2013-01-01

    Arthropods are an important component of grassland systems, contributing significantly to biodiversity and ecosystem structure and function. Climate, fire, and grazing by large herbivores are important drivers in grasslands worldwide. Arthropod responses to these drivers are highly variable and clear patterns are difficult to find, but responses are largely indirect with respect to changes in resources, species interactions, habitat structure, and habitat heterogeneity resulting from interactions among fire, grazing, and climate. Here, we review these ecological mechanisms influencing grassland arthropod diversity. We summarize hypotheses describing species diversity at local and regional scales and then discuss specific factors that may affect arthropod diversity in grassland systems. These factors include direct and indirect effects of grazing, fire, and climate, species interactions, above- and belowground interactions, and landscape-level effects.

  7. Uranium dioxide sintering Kinetics and mechanisms under controlled oxygen potentials

    International Nuclear Information System (INIS)

    Freitas, C.T. de.

    1980-06-01

    The initial, intermediate, and final sintering stages of uranium dioxide were investigated as a function of stoichiometry and temperature by following the kinetics of the sintering reaction. Stoichiometry was controlled by means of the oxygen potential of the sintering atmosphere, which was measured continuously by solid-state oxygen sensors. Included in the kinetic study were microspheres originated from UO 2 gels and UO 2 pellets produced by isostatic pressing ceramic grade powders. The microspheres sintering behavior was examined using hot-stage microscopy and a specially designed high-temperature, controlled atmosphere furnace. This same furnace was employed as part of an optical dilatometer, which was utilized in the UO 2 pellet sintering investigations. For controlling the deviations from stoichiometry during heat treatment, the oxygen partial pressure in the sintering atmosphere was varied by passing the gas through a Cu-Ti-Cu oxygen trap. The trap temperature determined the oxygen partial pressure of the outflowing mixture. Dry hydrogen was also used in some of the UO sub(2+x) sintering experiments. The determination of diametrial shrinkages and sintering indices was made utilizing high-speed microcinematography and ultra-microbalance techniques. It was observed that the oxygen potential has a substantial influence on the kinetics of the three sintering stages. The control of the sintering atmosphere oxygen partial pressure led to very fast densification of UO sub(2+x). Values in the interval 95.0 to 99.5% of theoretical density were reached in less than one minute. Uranium volume diffusion is the dominant mechanism in the initial and intermediate sintering stages. For the final stage, uranium grain boundary diffusion was found to be the main sintering mechanism. (Author) [pt

  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. Pathological mechanisms underlying single large‐scale mitochondrial DNA deletions

    Science.gov (United States)

    Rocha, Mariana C.; Rosa, Hannah S.; Grady, John P.; Blakely, Emma L.; He, Langping; Romain, Nadine; Haller, Ronald G.; Newman, Jane; McFarland, Robert; Ng, Yi Shiau; Gorman, Grainne S.; Schaefer, Andrew M.; Tuppen, Helen A.; Taylor, Robert W.

    2018-01-01

    Objective Single, large‐scale deletions in mitochondrial DNA (mtDNA) are a common cause of mitochondrial disease. This study aimed to investigate the relationship between the genetic defect and molecular phenotype to improve understanding of pathogenic mechanisms associated with single, large‐scale mtDNA deletions in skeletal muscle. Methods We investigated 23 muscle biopsies taken from adult patients (6 males/17 females with a mean age of 43 years) with characterized single, large‐scale mtDNA deletions. Mitochondrial respiratory chain deficiency in skeletal muscle biopsies was quantified by immunoreactivity levels for complex I and complex IV proteins. Single muscle fibers with varying degrees of deficiency were selected from 6 patient biopsies for determination of mtDNA deletion level and copy number by quantitative polymerase chain reaction. Results We have defined 3 “classes” of single, large‐scale deletion with distinct patterns of mitochondrial deficiency, determined by the size and location of the deletion. Single fiber analyses showed that fibers with greater respiratory chain deficiency harbored higher levels of mtDNA deletion with an increase in total mtDNA copy number. For the first time, we have demonstrated that threshold levels for complex I and complex IV deficiency differ based on deletion class. Interpretation Combining genetic and immunofluorescent assays, we conclude that thresholds for complex I and complex IV deficiency are modulated by the deletion of complex‐specific protein‐encoding genes. Furthermore, removal of mt‐tRNA genes impacts specific complexes only at high deletion levels, when complex‐specific protein‐encoding genes remain. These novel findings provide valuable insight into the pathogenic mechanisms associated with these mutations. Ann Neurol 2018;83:115–130 PMID:29283441

  10. Mechanism and kinetics of parathion degradation under ultrasonic irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Yao Juanjuan, E-mail: yao_juanjuan@yahoo.cn [State Key laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai, 200092 (China); Gao Naiyun; Li Cong; Li Lei; Xu Bin [State Key laboratory of Pollution Control and Resources Reuse, Tongji University, Shanghai, 200092 (China)

    2010-03-15

    The parathion degradation under ultrasonic irradiation in aqueous solution was investigated. The results indicate that at the conditions in question, degradation rate of parathion decreased with increasing initial concentration and decreasing power. The optimal frequency for parathion degradation was 600 kHz. The free radical reactions predominate in the sonochemical degradation of parathion and the reaction zones are predominately at the bubble interface and, to a much lesser extent, in bulk solution. The gas/liquid interfacial regions are the real effective reaction sites for sonochemical degradation of parathion. The reaction can be well described as a gas/liquid heterogeneous reaction which obeys a kinetic model based on Langmuir-Hinshelwood model. The main pathways of parathion degradation by ultrasonic irradiation were also proposed by qualitative and quantitative analysis of organic and inorganic byproducts. It is indicated that the N{sub 2} in air takes part in the parathion degradation through the formation of {center_dot}NO{sub 2} under ultrasonic irradiation. Parathion is decomposed into paraoxon and 4-nitrophenol in the first step via two different pathways, respectively, which is in agreement with the theoretical molecular orbital (MO) calculations.

  11. Mechanisms Underlying Mammalian Hybrid Sterility in Two Feline Interspecies Models.

    Science.gov (United States)

    Davis, Brian W; Seabury, Christopher M; Brashear, Wesley A; Li, Gang; Roelke-Parker, Melody; Murphy, William J

    2015-10-01

    The phenomenon of male sterility in interspecies hybrids has been observed for over a century, however, few genes influencing this recurrent phenotype have been identified. Genetic investigations have been primarily limited to a small number of model organisms, thus limiting our understanding of the underlying molecular basis of this well-documented "rule of speciation." We utilized two interspecies hybrid cat breeds in a genome-wide association study employing the Illumina 63 K single-nucleotide polymorphism array. Collectively, we identified eight autosomal genes/gene regions underlying associations with hybrid male sterility (HMS) involved in the function of the blood-testis barrier, gamete structural development, and transcriptional regulation. We also identified several candidate hybrid sterility regions on the X chromosome, with most residing in close proximity to complex duplicated regions. Differential gene expression analyses revealed significant chromosome-wide upregulation of X chromosome transcripts in testes of sterile hybrids, which were enriched for genes involved in chromatin regulation of gene expression. Our expression results parallel those reported in Mus hybrids, supporting the "Large X-Effect" in mammalian HMS and the potential epigenetic basis for this phenomenon. These results support the value of the interspecies feline model as a powerful tool for comparison to rodent models of HMS, demonstrating unique aspects and potential commonalities that underpin mammalian reproductive isolation. © The Author 2015. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  12. Acoustic emission generated by dislocation mechanisms during the deformation of metals

    Energy Technology Data Exchange (ETDEWEB)

    Heiple, C.R.

    1978-01-01

    Acoustic emission is a transient elastic wave generated by the rapid release of energy within a material. A wide variety of mechanisms have been proposed as possible sources of acoustic emission. Proposed mechanisms have included crack propagation, precipitate fracture, twin formation, martensite formation, dislocation motion and/or multiplication. This paper is concerned with acoustic emission generated by dislocation mechanisms operating during plastic deformation. Twinning and martensitic phase transformations are excluded even though dislocation motion is involved in the nucleation and growth of twins and the growth of martensite.

  13. Acoustic emission generated by dislocation mechanisms during the deformation of metals

    International Nuclear Information System (INIS)

    Heiple, C.R.

    1978-01-01

    Acoustic emission is a transient elastic wave generated by the rapid release of energy within a material. A wide variety of mechanisms have been proposed as possible sources of acoustic emission. Proposed mechanisms have included crack propagation, precipitate fracture, twin formation, martensite formation, dislocation motion and/or multiplication. This paper is concerned with acoustic emission generated by dislocation mechanisms operating during plastic deformation. Twinning and martensitic phase transformations are excluded even though dislocation motion is involved in the nucleation and growth of twins and the growth of martensite

  14. Effects of microbial processes on gas generation under expected WIPP repository conditions: Annual report through 1992

    International Nuclear Information System (INIS)

    Francis, A.J.; Gillow, J.B.

    1993-09-01

    Microbial processes involved in gas generation from degradation of the organic constituents of transuranic waste under conditions expected at the Waste Isolation Pilot Plant (WIPP) repository are being investigated at Brookhaven National Laboratory. These laboratory studies are part of the Sandia National Laboratories -- WIPP Gas Generation Program. Gas generation due to microbial degradation of representative cellulosic waste was investigated in short-term ( 6 months) experiments by incubating representative paper (filter paper, paper towels, and tissue) in WIPP brine under initially aerobic (air) and anaerobic (nitrogen) conditions. Samples from the WIPP surficial environment and underground workings harbor gas-producing halophilic microorganisms, the activities of which were studied in short-term experiments. The microorganisms metabolized a variety of organic compounds including cellulose under aerobic, anaerobic, and denitrifying conditions. In long-term experiments, the effects of added nutrients (trace amounts of ammonium nitrate, phosphate, and yeast extract), no nutrients, and nutrients plus excess nitrate on gas production from cellulose degradation

  15. Simulation of Mechanical Behavior and Damage of a Large Composite Wind Turbine Blade under Critical Loads

    Science.gov (United States)

    Tarfaoui, M.; Nachtane, M.; Khadimallah, H.; Saifaoui, D.

    2018-04-01

    Issues such as energy generation/transmission and greenhouse gas emissions are the two energy problems we face today. In this context, renewable energy sources are a necessary part of the solution essentially winds power, which is one of the most profitable sources of competition with new fossil energy facilities. This paper present the simulation of mechanical behavior and damage of a 48 m composite wind turbine blade under critical wind loads. The finite element analysis was performed by using ABAQUS code to predict the most critical damage behavior and to apprehend and obtain knowledge of the complex structural behavior of wind turbine blades. The approach developed based on the nonlinear FE analysis using mean values for the material properties and the failure criteria of Tsai-Hill to predict failure modes in large structures and to identify the sensitive zones.

  16. Protein metabolism in marine animals: the underlying mechanism of growth.

    Science.gov (United States)

    Fraser, Keiron P P; Rogers, Alex D

    2007-01-01

    Growth is a fundamental process within all marine organisms. In soft tissues, growth is primarily achieved by the synthesis and retention of proteins as protein growth. The protein pool (all the protein within the organism) is highly dynamic, with proteins constantly entering the pool via protein synthesis or being removed from the pool via protein degradation. Any net change in the size of the protein pool, positive or negative, is termed protein growth. The three inter-related processes of protein synthesis, degradation and growth are together termed protein metabolism. Measurement of protein metabolism is vital in helping us understand how biotic and abiotic factors affect growth and growth efficiency in marine animals. Recently, the developing fields of transcriptomics and proteomics have started to offer us a means of greatly increasing our knowledge of the underlying molecular control of protein metabolism. Transcriptomics may also allow us to detect subtle changes in gene expression associated with protein synthesis and degradation, which cannot be detected using classical methods. A large literature exists on protein metabolism in animals; however, this chapter concentrates on what we know of marine ectotherms; data from non-marine ectotherms and endotherms are only discussed when the data are of particular relevance. We first consider the techniques available to measure protein metabolism, their problems and what validation is required. Protein metabolism in marine organisms is highly sensitive to a wide variety of factors, including temperature, pollution, seasonality, nutrition, developmental stage, genetics, sexual maturation and moulting. We examine how these abiotic and biotic factors affect protein metabolism at the level of whole-animal (adult and larval), tissue and cellular protein metabolism. Available gene expression data, which help us understand the underlying control of protein metabolism, are also discussed. As protein metabolism appears to

  17. Deformation mechanisms in Ti/TiN multilayer under compressive loading

    International Nuclear Information System (INIS)

    Yang, Wei; Ayoub, Georges; Salehinia, Iman; Mansoor, Bilal; Zbib, Hussein

    2017-01-01

    The promising mechanical, physical and chemical properties of nano-scale metal/ceramic multilayers (MCMs) are of high interest for extreme environment applications. Understanding the plastic deformation mechanisms and the variables affecting those properties is therefore essential. The interface characteristics and the plastic deformation mechanisms under compressive loading in a Ti/TiN multilayer with a semi-coherent interface are numerically investigated. The interface structure of the Ti/TiN interface and the interface misfit dislocation were characterized using molecular dynamic simulations combined with atomically informed Frank-Bilby method. Three possible atomic stacking interface structures are identified according to the crystallographic analysis of the interface. Upon relaxation, large interface areas are occupied with the energetically stable configuration. Furthermore, the higher energy stacking are transformed into misfit dislocations or dislocation nodes. The molecular dynamic compressive stress strain response of the Ti/TiN multilayers exhibited three distinctive peaks. The first peak was generated by the dislocation dissociation of perfect dislocation into pairs of partials dislocation around extended nodes region at the interface. Upon further compression the second peak, identified as the first yielding, resulted from the activation of pyramidal slip planes in the Ti layer. Finally, a third peak identified as the second yielding, occurred when dislocation nucleated/transmitted in/into the TiN layer.

  18. Mechanisms underlying the organizer formation in Bufo arenarum embryos.

    Science.gov (United States)

    Manes, M E; Nieto, O L

    1989-06-01

    In the early gastrula of Bufo arenarum the prospective mesoderm was previously identified as a marginal belt of grey cells. To analyze their differentiation capacity explants of these cells were cultured within ectodermal vesicles, in isolation and in combination with vegetal components. When cultured in isolation, dorsal and ventral fragments from the deep marginal zone behaved differently. Whilst ventral explants produced blood cells, dorsal explants failed to differentiate, remaining as masses of yolk-laden cells. On the other hand, both cultures were drastically modified when associated with superficial cells from the blastoporal zone, which caused the following effects: a) Promotion of differentiation in dorsal marginal explants, able now to produce notochordal and somitic structures, in addition to mesenchymatic cells. b) Promotion of dorsalization in ventral marginal explants, which changed their expected destiny developing axial components, similar to those furnished by "activated" dorso marginal explants. On the contrary, combined cultures of animal and vegetal pieces were unable to generate mesodermal structures. These studies suggest that the axial mesoderm, identified as the "organizer", develops from a marginal substrate of genuine mesodermal cells through a dorsalizing inductive stimulus originated in superficial periblastoporal cells.

  19. 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.

  20. 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

  1. 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.

  2. Neural Mechanisms of Updating under Reducible and Irreducible Uncertainty.

    Science.gov (United States)

    Kobayashi, Kenji; Hsu, Ming

    2017-07-19

    Adaptive decision making depends on an agent's ability to use environmental signals to reduce uncertainty. However, because of multiple types of uncertainty, agents must take into account not only the extent to which signals violate prior expectations but also whether uncertainty can be reduced in the first place. Here we studied how human brains of both sexes respond to signals under conditions of reducible and irreducible uncertainty. We show behaviorally that subjects' value updating was sensitive to the reducibility of uncertainty, and could be quantitatively characterized by a Bayesian model where agents ignore expectancy violations that do not update beliefs or values. Using fMRI, we found that neural processes underlying belief and value updating were separable from responses to expectancy violation, and that reducibility of uncertainty in value modulated connections from belief-updating regions to value-updating regions. Together, these results provide insights into how agents use knowledge about uncertainty to make better decisions while ignoring mere expectancy violation. SIGNIFICANCE STATEMENT To make good decisions, a person must observe the environment carefully, and use these observations to reduce uncertainty about consequences of actions. Importantly, uncertainty should not be reduced purely based on how surprising the observations are, particularly because in some cases uncertainty is not reducible. Here we show that the human brain indeed reduces uncertainty adaptively by taking into account the nature of uncertainty and ignoring mere surprise. Behaviorally, we show that human subjects reduce uncertainty in a quasioptimal Bayesian manner. Using fMRI, we characterize brain regions that may be involved in uncertainty reduction, as well as the network they constitute, and dissociate them from brain regions that respond to mere surprise. Copyright © 2017 the authors 0270-6474/17/376972-11$15.00/0.

  3. Statistical model for the mechanical behavior of the tissue engineering non-woven fibrous matrices under large deformation.

    Science.gov (United States)

    Rizvi, Mohd Suhail; Pal, Anupam

    2014-09-01

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

  4. Calculation of a steam generating tube stressed state under temperature oscillations in burnout zone

    International Nuclear Information System (INIS)

    Vorob'ev, V.A.; Loshchinin, V.M.; Remizov, O.V.

    1982-01-01

    The technique for evaluating the steam generating tube stressed state under the wall temperature oscillations in the burnout zone is described. The technique is based on analytical solutions for transfer functions connecting the amplitude of surface temperature oscillation with the amplitude and frequency of heat transfer coefficient oscillation and amplitude of thermoelastic stress oscillation with that of temperature oscillation. The results of calculations according to considered technique are compared with that of the problem numerical solution. The conclusion is made that the technique under consideration may be applied for evaluation of steam generator evaporating tube lifetime [ru

  5. Biomechanical mechanisms underlying exosuit-induced improvements in walking economy after stroke.

    Science.gov (United States)

    Bae, Jaehyun; Awad, Louis N; Long, Andrew; O'Donnell, Kathleen; Hendron, Katy; Holt, Kenneth G; Ellis, Terry D; Walsh, Conor J

    2018-03-07

    Stroke-induced hemiparetic gait is characteristically asymmetric and metabolically expensive. Weakness and impaired control of the paretic ankle contribute to reduced forward propulsion and ground clearance - walking subtasks critical for safe and efficient locomotion. Targeted gait interventions that improve paretic ankle function after stroke are therefore warranted. We have developed textile-based, soft wearable robots that transmit mechanical power generated by off-board or body-worn actuators to the paretic ankle using Bowden cables (soft exosuits) and have demonstrated the exosuits can overcome deficits in paretic limb forward propulsion and ground clearance, ultimately reducing the metabolic cost of hemiparetic walking. This study elucidates the biomechanical mechanisms underlying exosuit-induced reductions in metabolic power. We evaluated the relationships between exosuit-induced changes in the body center of mass (COM) power generated by each limb, individual joint power and metabolic power. Compared with walking with an exosuit unpowered, exosuit assistance produced more symmetrical COM power generation during the critical period of the step-to-step transition (22.4±6.4% more symmetric). Changes in individual limb COM power were related to changes in paretic ( R 2 =0.83, P= 0.004) and non-paretic ( R 2 = 0.73, P= 0.014) ankle power. Interestingly, despite the exosuit providing direct assistance to only the paretic limb, changes in metabolic power were related to changes in non-paretic limb COM power ( R 2 =0.80, P= 0.007), not paretic limb COM power ( P> 0.05). These findings contribute to a fundamental understanding of how individuals post-stroke interact with an exosuit to reduce the metabolic cost of hemiparetic walking. © 2018. Published by The Company of Biologists Ltd.

  6. Thin circular cylinder under axisymmetrical thermal and mechanical loading

    International Nuclear Information System (INIS)

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

    1977-01-01

    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 ratchetting occurs is reduced when compared with the domain predicted by the Bree diagram. To investigate the effect of material hardening the authors verify Halphen's Theorem which states that a structure made of material with kinematic hardening behavior and constant properties with temperature will always shake down to a periodic behavior. (Auth.)

  7. 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.

  8. 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.

  9. Neurobiological mechanisms underlying the blocking effect in aversive learning.

    Science.gov (United States)

    Eippert, Falk; Gamer, Matthias; Büchel, Christian

    2012-09-19

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

  10. Coordination of frontline defense mechanisms under severe oxidative stress.

    Science.gov (United States)

    Kaur, Amardeep; Van, Phu T; Busch, Courtney R; Robinson, Courtney K; Pan, Min; Pang, Wyming Lee; Reiss, David J; DiRuggiero, Jocelyne; Baliga, Nitin S

    2010-07-01

    Complexity of cellular response to oxidative stress (OS) stems from its wide-ranging damage to nucleic acids, proteins, carbohydrates, and lipids. We have constructed a systems model of OS response (OSR) for Halobacterium salinarum NRC-1 in an attempt to understand the architecture of its regulatory network that coordinates this complex response. This has revealed a multi-tiered OS-management program to transcriptionally coordinate three peroxidase/catalase enzymes, two superoxide dismutases, production of rhodopsins, carotenoids and gas vesicles, metal trafficking, and various other aspects of metabolism. Through experimental validation of interactions within the OSR regulatory network, we show that despite their inability to directly sense reactive oxygen species, general transcription factors have an important function in coordinating this response. Remarkably, a significant fraction of this OSR was accurately recapitulated by a model that was earlier constructed from cellular responses to diverse environmental perturbations--this constitutes the general stress response component. Notwithstanding this observation, comparison of the two models has identified the coordination of frontline defense and repair systems by regulatory mechanisms that are triggered uniquely by severe OS and not by other environmental stressors, including sub-inhibitory levels of redox-active metals, extreme changes in oxygen tension, and a sub-lethal dose of gamma rays.

  11. 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.

  12. 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.

  13. 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.

  14. RISK FACTORS FOR PANCREATIC CANCER: UNDERLYING MECHANISMS AND POTENTIAL TARGETS

    Directory of Open Access Journals (Sweden)

    Thomas eKolodecik

    2014-01-01

    Full Text Available Purpose of the review:Pancreatic cancer is extremely aggressive, forming highly chemo-resistant tumors, and has one of the worst prognoses. The evolution of this cancer is multi-factorial. Repeated acute pancreatic injury and inflammation are important contributing factors in the development of pancreatic cancer. This article attempts to understand the common pathways linking pancreatitis to pancreatic cancer.Recent Findings:Intracellular activation of both pancreatic enzymes and the transcription factor NF-kB are important mechanisms that induce acute pancreatitis. Recurrent pancreatic injury due to genetic susceptibility, environmental factors such as smoking, alcohol intake, and conditions such as obesity lead to increases in oxidative stress, impaired autophagy and constitutive activation of inflammatory pathways. These processes can stimulate pancreatic stellate cells, thereby increasing fibrosis and encouraging chronic disease development. Activation of oncogneic Kras mutations through inflammation, coupled with altered levels of tumor suppressor proteins (p53 and p16 can ultimately lead to development of pancreatic cancer. Summary:Although our understanding of pancreatitis and pancreatic cancer has tremendously increased over many years, much remains to be elucidated in terms of common pathways linking these conditions.

  15. 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

  16. 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.

  17. Mechanical Model for Dynamic Behavior of Concrete Under Impact Loading

    Science.gov (United States)

    Sun, Yuanxiang

    Concrete is a geo-material which is used substantively in the civil building and military safeguard. One coupled model of damage and plasticity to describe the complex behavior of concrete subjected to impact loading is proposed in this research work. The concrete is assumed as homogeneous continuum with pre-existing micro-cracks and micro-voids. Damage to concrete is caused due to micro-crack nucleation, growth and coalescence, and defined as the probability of fracture at a given crack density. It induces a decrease of strength and stiffness of concrete. Compaction of concrete is physically a collapse of the material voids. It produces the plastic strain in the concrete and, at the same time, an increase of the bulk modulus. In terms of crack growth model, micro-cracks are activated, and begin to propagate gradually. When crack density reaches a critical value, concrete takes place the smashing destroy. The model parameters for mortar are determined using plate impact experiment with uni-axial strain state. Comparison with the test results shows that the proposed model can give consistent prediction of the impact behavior of concrete. The proposed model may be used to design and analysis of concrete structures under impact and shock loading. This work is supported by State Key Laboratory of Explosion science and Technology, Beijing Institute of Technology (YBKT14-02).

  18. 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.

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

    Science.gov (United States)

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

    2014-01-01

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

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

    Science.gov (United States)

    Timilsina, Govinda R; Shrestha, Ram M

    2006-09-01

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

  1. The Neural Mechanisms Underlying Internally and Externally Guided Task Selection

    Science.gov (United States)

    Orr, Joseph M.; Banich, Marie T.

    2013-01-01

    While some prior work suggests that medial prefrontal cortex (MFC) regions mediate freely chosen actions, other work suggests that the lateral frontal pole (LFP) is responsible for control of abstract, internal goals. The present study uses fMRI to determine whether the voluntary selection of a task in pursuit of an overall goal relies on MFC regions or the LFP. To do so, we used a modified voluntary task switching (VTS) paradigm, in which participants choose an individual task to perform on each trial (i.e., a subgoal), under instructions to perform the tasks equally often and in a random order (i.e. the overall goal). In conjunction, we examined patterns of activation in the face of irrelevant, but task-related external stimuli that might nonetheless influence task selection. While there was some evidence that the MFC was involved in voluntary task selection, we found that the LFP and anterior insula (AI) were crucial to task selection in the pursuit of an overall goal. In addition, activation of the LFP and AI increased in the face of environmental stimuli that might serve as an interfering or conflicting external bias on voluntary task choice. These findings suggest that the LFP supports task selection according to abstract, internal goals, and leaves open the possibility that MFC may guide action selection in situations lacking in such top-down biases. As such, the current study represents a critical step towards understanding the neural underpinnings of how tasks are selected voluntarily to enable an overarching goal. PMID:23994316

  2. Particle behavior and char burnout mechanisms under pressurized combustion conditions

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, C.M.; Spliethoff, H.; Hein, K.R.G.

    1999-07-01

    Combined cycle systems with coal-fired gas turbines promise highest cycle efficiencies for this fuel. Pressurized pulverized coal combustion, in particular, yields high cycle efficiencies due to the high flue gas temperatures possible. The main problem, however, is to ensure a flue gas clean enough to meet the high gas turbine standards with a dirty fuel like coal. On the one hand, a profound knowledge of the basic chemical and physical processes during fuel conversion under elevated pressures is required whereas on the other hand suitable hot gas cleaning systems need to be developed. The objective of this work was to provide experimental data to enable a detailed description of pressurized coal combustion processes. A series of experiments were performed with two German hvb coals, Ensdorf and Goettelborn, and one German brown coal, Garzweiler, using a semi-technical scale pressurized entrained flow reactor. The parameters varied in the experiments were pressure, gas temperature and bulk gas oxygen concentration. A two-color pyrometer was used for in-situ determination of particle surface temperatures and particle sizes. Flue gas composition was measured and solid residue samples taken and subsequently analyzed. The char burnout reaction rates were determinated varying the parameters pressure, gas temperature and initial oxygen concentration. Variation of residence time was achieved by taking the samples at different points along the reaction zone. The most influential parameters on char burnout reaction rates were found to be oxygen partial pressure and fuel volatile content. With increasing pressure the burn-out reactions are accelerated and are mostly controlled by product desorption and pore diffusion being the limiting processes. The char burnout process is enhanced by a higher fuel volatile content.

  3. 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.

  4. Efficient thermo-mechanical generation of electricity from the heat of radioisotopes

    International Nuclear Information System (INIS)

    Cooke-Yarborough, E.H.; Yeats, F.W.

    1975-01-01

    The thermomechanical generator uses a thermomechanical oscillator to convert heat efficiently into a mechanical oscillation which in turn excites a suitable transducer to generate alternating electricity. The thermomechanical oscillator used is based on the Stirling cycle, but avoids the need for rotary motion and for sliding pistons by having a mechanically-resonant, spring-suspended displacer, and by using an oscillating metal diaphragm to provide the mechanical output. The diaphragm drives an alternator consisting of a spring-suspended permanent magnet oscillating between fixed pole pieces which carry the electrical power output windings. Because a thermomechanical generator is much more efficient than a thermo-electric generator at comparable temperatures, it is particularly suitable for use with a radioisotope heat source. The amounts of radioisotope and of shielding required are both greatly reduced. A machine heated by radioisotopes and delivering 10.7W ac at 80Hz began operating in October, 1974. Operating experience with this machine is reported, and these results, together with those obtained with higher-powered machines heated by other means, are used to calculate characteristics and performance of thermo-mechanical radioisotope generators capable of using heat sources such as the waste-management 90 Sr radioisotope sources becoming available from the US nuclear waste management programme. A design to use one of these heat sources in a 52-W underwater generator is described

  5. Possibilities under the `Kreislaufwirtschaft- und Abfallgesetz` for the recycling or for energy generation from waste with a high calorific value having undergone mechanical-biological conditioning; Moeglichkeiten der energetischen und stofflichen Verwertung von heizwertreichen Reststoffen aus der mechanisch-biologischen Restabfallbehandlung im Rahmen des Kreislaufwirtschafts- und Abfallgesetzes

    Energy Technology Data Exchange (ETDEWEB)

    Franke, J.; Fricke, K. [Ingenieurgemeinschaft Witzenhausen Fricke und Turk GmbH, Witzenhausen (Germany)

    1998-12-31

    This (partial) project has the following aims: to describe comprehensively the possibilities for the recycling, or generation of energy from, waste with a high calorific value having undergone mechanical-biological conditioning; further, to formulate demands regarding the quality of the separated partial fractions. This basic study takes all relevant, commercial thermal processes into account (power plants, cement works, blast furnaces, etc.). Furthermore, the question is investigated of whether the thermal waste processing plants in the area of the Suedhessische Arbeitsgemeinschaft Abfall (SAGA) are suitable for waste utilization. An environmental compatibility statement is made, and the economic and legal boundary conditions are studied. (orig.) [Deutsch] Ziel des (Teil-)Forschungsvorhabens soll es sein, die Moeglichkeiten der energetischen und stofflichen Verwertung heizwertreicher Abfaelle aus der mechanisch-biologischen Restabfallbehandlung umfassend darzustellen und die Anforderungen an die Qualitaet der abgretrennten Teilfraktionen zu formulieren. Bei der Grundlagenermittlung sollen alle relevanten auf dem Markt angebotenen thermischen Verfahren (Kraftwerke, Zementwerke, Hochoefen usw.) mit einbezogen werden. Weiterhin sollen die im SAGA-Gebiet (Suedhessische Arbeitsgemeinschaft Abfall) vorhandenen thermsichen Anlagen auf ihre Eignung zur energetischen bzw. stofflichen Verwertung hin ueberprueft werden. Neben der Bewertung der Umweltvertraeglichkeit werden die oekonomischen und rechtlichen Rahmenbedingungen untersucht. (orig.)

  6. Mechanism underlying the development of unilateral spatial neglect

    International Nuclear Information System (INIS)

    Nishikiori, Etsuko

    1992-01-01

    To test the hypothesis that functional disturbance of the neural network involving the inferior parietal lobule (IPL), anterior cingulate gyrus (ACG), dorsolateral frontal lobe (DLF), and thalamus (TH) as components of the right hemisphere underlies the development of unilateral spatial neglect (USN), cerebral perfusion was measured by 123 I-IMP SPECT in 32 patients with cerebrovascular right brain damage, 20 of whom had USN and 12 of whom did not. In analyzing the SPECT data, RI uptake in the four component regions and cerebellum (serving as a control) were estimated by symmetrically placing 'regions of interest' from both hemispheres on SPECT slices, most suitable for each region. The 'regional to cerebellar ratio' (R/CE ratio) for each component region was calculated and the values were compared. In the USN group, R/CE ratio values for each component region in the right hemisphere were significantly lower than those in the left, whereas in the non-USN group there was no right-left difference. When R/CE ratio values for each component region in the right hemisphere were compared between the USN and non-USN group, those for the IPL, ACG and TH were significantly lower in the USN group; the value for the DLF was also lower in the USN group, although the difference was not significant. Significantly lower values of R/CE for each component region in the right hemisphere were noticed when the regions showed apparent involvement on X-ray CT/MRI. Furthermore, in seven of the USN patients where lesions revealed by CT/MRI did not involve network components, the R/CE ratio values for the components in the right hemisphere were lower than those in the left; the difference was significant for the IPL, ACG and TH, but not for the DLF. It is suggested that functional disturbance of the neural network involving the IPL, ACG, DLF and TH in the right hemisphere might underlie the development of USN. (author)

  7. Corticonic models of brain mechanisms underlying cognition and intelligence

    Science.gov (United States)

    Farhat, Nabil H.

    underlying intelligence and other higher level brain functions.

  8. RESEARCH OF HYDRODYNAMICS OF HEAT GENERATORS FOR MECHANICAL SYSTEMS AUTONOMOUS HEATING

    Directory of Open Access Journals (Sweden)

    E. M. Derbasova

    2014-01-01

    Full Text Available A design of mechanical heat source, allows direct conversion of mechanical energy of the wind flow into thermal energy due to friction forces in a highly viscous fluid. Obtained theoretical dependence for calculating the heat generated by converting mechanical energy into heat. For laminar flow of a highly viscous, fluid in the gap between the stationary and rotating disk heat source. Based on experimental studies to determine the average thickness of the boundary layer between the rotating and fixed disks. The dependences to identify key structural dimensions of mechanical heat sources for heating systems. 

  9. Electricity Generation Characteristics of Energy-Harvesting System with Piezoelectric Element Using Mechanical-Acoustic Coupling

    Directory of Open Access Journals (Sweden)

    Hirotarou Tsuchiya

    2016-01-01

    Full Text Available This paper describes the electricity generation characteristics of a new energy-harvesting system with piezoelectric elements. The proposed system is composed of a rigid cylinder and thin plates at both ends. The piezoelectric elements are installed at the centers of both plates, and one side of each plate is subjected to a harmonic point force. In this system, vibration energy is converted into electrical energy via electromechanical coupling between the plate vibration and piezoelectric effect. In addition, the plate vibration excited by the point force induces a self-sustained vibration at the other plate via mechanical-acoustic coupling between the plate vibrations and an internal sound field into the cylindrical enclosure. Therefore, the electricity generation characteristics should be considered as an electromechanical-acoustic coupling problem. The characteristics are estimated theoretically and experimentally from the electric power in the electricity generation, the mechanical power supplied to the plate, and the electricity generation efficiency that is derived from the ratio of both power. In particular, the electricity generation efficiency is one of the most appropriate factors to evaluate a performance of electricity generation systems. Thus, the effect of mechanical-acoustic coupling is principally evaluated by examining the electricity generation efficiency.

  10. Simulation of Entropy Generation under Stall Conditions in a Centrifugal Fan

    Directory of Open Access Journals (Sweden)

    Lei Zhang

    2014-06-01

    Full Text Available Rotating stalls are generally the first instability met in turbomachinery, before surges. This 3D phenomenon is characterized by one or more stalled flow cells which rotate at a fraction of the impeller speed. The goal of the present work is to shed some light on the entropy generation in a centrifugal fan under rotating stall conditions. A numerical simulation of entropy generation is carried out with the ANSYS Fluent software which solves the Navier-Stokes equations and user defined function (UDF. The entropy generation characteristics in the centrifugal fan for five typical conditions are presented and discussed, involving the design condition, conditions on occurrence and development of stall inception, the rotating stall conditions with two throttle coefficients. The results show that the entropy generation increases after the occurrence of stall inception. The high entropy generation areas move along the circumferential and axial directions, and finally merge into one stall cell. The entropy generation rate during circumferential propagation of the stall cell is also discussed, showing that the entropy generation history is similar to sine curves in impeller and volute, and the volute tongue has a great influence on entropy generation in the centrifugal fan.

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

    LENUS (Irish Health Repository)

    Lyons, Mathew

    2014-06-03

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

  12. Test of safety injection supply by diesel generator under reactor vessel closed condition

    International Nuclear Information System (INIS)

    Zhang Hao; Bi Fengchuan; Che Junxia; Zhang Jianwen; Yang Bo

    2014-01-01

    The paper studied that the test of diesel generator full load take-up under the condition of actual safety injection and reactor vessel closed in Ningde nuclear project unit l. It is proved that test result accorded with design criteria, meanwhile, the test was removed from the key path of project schedule, which cut a huge cost. (authors)

  13. High Order Sliding Mode Control of Doubly-fed Induction Generator under Unbalanced Grid Faults

    DEFF Research Database (Denmark)

    Zhu, Rongwu; Chen, Zhe; Wu, Xiaojie

    2013-01-01

    This paper deals with a doubly-fed induction generator-based (DFIG) wind turbine system under grid fault conditions such as: unbalanced grid voltage, three-phase grid fault, using a high order sliding mode control (SMC). A second order sliding mode controller, which is robust with respect...

  14. A study of different colour reconnection settings for Pythia8 generator using underlying event observables

    CERN Document Server

    The ATLAS collaboration

    2017-01-01

    A study of the performance of various colour reconnection models included in the Pythia8 Monte Carlo event generator is performed using leading charged-particle underlying event data in three centre-of-mass energies from Run 1 and Run 2, measured in ATLAS. Each model can be tuned to describe the data reasonably well.

  15. Transient thermal stresses in circular cylinder under intermittently sudden heat generation

    International Nuclear Information System (INIS)

    Sugano, Y.; Saito, K.; Takeuti, Y.

    1975-01-01

    The thermal stresses associated with the transient temperature distribution arising in a circular cylinder under intermittently changing sudden heat generation over a finite band and with heat loss to a surrounding medium on the remainder of the cylinder surface are exactly analysed. For the first time the temperature field in a circular cylinder under sudden heat generation over a finite band of the cylinder surface is determined by combined use of Fourier cosine, Laplace transforms in axial position and time, respectively. Secondly it is assumed that the temperature fields in a circular cylinder subjected to heat generation Qsub(i) (i=0, 1, 2, ...) independently over a finite band are given by T 0 (r,z,t), T 1 (r,z,t), T 2 (r,z,t),... respectively. Tsub(i)(r,z,t) indicates the temperature field before the i-th heat generation Qsub(i). The thermal stresses associated with the temperature field described above are analysed by using the Hoyle stress functions. Numerical calculations are carried out for the extensive case of the ratio of the heat-generating length to the diameter of cylinder. It is found that the time in which the maximum stresses occur on the cylinder surface does not depend on the heat-generating length-to-diameter ratio

  16. Comparison of control strategies for Doubly fed induction generator under recurring grid faults

    DEFF Research Database (Denmark)

    Chen, Wenjie; Blaabjerg, Frede; Zhu, Nan

    2014-01-01

    The new grid codes demand the wind turbine systems to ride through recurring grid faults. Many control strategies have been proposed for the Doubly Fed Induction Generator under single grid fault, but their performance under recurring grid faults have not been studied yet. In this paper, five...... different control strategies for DFIG to ride through single grid faults are presented, and their performance under recurring grid faults are analyzed. The controllable range, stator time constant and torque fluctuations of the DFIG with different control strategies are compared. The results are verified...

  17. Electricity generation: regulatory mechanisms to incentive renewable alternative energy sources in Brazil

    International Nuclear Information System (INIS)

    Cavaliero, Carla Kazue Nakao; Silva, E.P. da

    2005-01-01

    The dissemination of renewable alternative energy sources for electricity generation has always being done through regulatory mechanisms, created and managed by the government of each country. Since these sources are more costly to generate, they have received incentives in response to worldwide environmental concerns, above all with regard to the reduction of CO 2 emissions. In Brazil, the electricity generation from renewable alternative sources is experiencing a new phase of growth. Until a short time ago, environmental appeal was the strongest incentive to these sources in Brazil but it was insufficient to attain its objective. With the electricity crisis and the rationing imposed in 2001, another important factor gained awareness: the need to diversify energy sources. Within this context, this work has the objective of analyzing the regulatory mechanisms recently developed to stimulate electricity generation from renewable alternative energy sources in Brazil by following the experience of other countries such as the United States, United Kingdom and Germany

  18. Tuning of redox regulatory mechanisms, reactive oxygen species and redox homeostasis under salinity stress

    Directory of Open Access Journals (Sweden)

    Hossain eSazzad

    2016-05-01

    Full Text Available Soil salinity is a crucial environmental constraint which limits biomass production at many sites on a global scale. Saline growth conditions cause osmotic and ionic imbalances, oxidative stress and perturb metabolism, e.g. the photosynthetic electron flow. The plant ability to tolerate salinity is determined by multiple biochemical and physiological mechanisms protecting cell functions, in particular by regulating proper water relations and maintaining ion homeostasis. Redox homeostasis is a fundamental cell property. Its regulation includes control of reactive oxygen species (ROS generation, sensing deviation from and readjustment of the cellular redox state. All these redox related functions have been recognized as decisive factors in salinity acclimation and adaptation. This review focuses on the core response of plants to overcome the challenges of salinity stress through regulation of ROS generation and detoxification systems and to maintain redox homeostasis. Emphasis is given to the role of NADH oxidase (RBOH, alternative oxidase (AOX, the plastid terminal oxidase (PTOX and the malate valve with the malate dehydrogenase isoforms under salt stress. Overwhelming evidence assigns an essential auxiliary function of ROS and redox homeostasis to salinity acclimation of plants.

  19. Macroporous Double-Network Hydrogel for High-Efficiency Solar Steam Generation Under 1 sun Illumination.

    Science.gov (United States)

    Yin, Xiangyu; Zhang, Yue; Guo, Qiuquan; Cai, Xiaobing; Xiao, Junfeng; Ding, Zhifeng; Yang, Jun

    2018-04-04

    Solar steam generation is one of the most promising solar-energy-harvesting technologies to address the issue of water shortage. Despite intensive efforts to develop high-efficiency solar steam generation devices, challenges remain in terms of the relatively low solar thermal efficiency, complicated fabrications, high cost, and difficulty in scaling up. Herein, a double-network hydrogel with a porous structure (p-PEGDA-PANi) is demonstrated for the first time as a flexible, recyclable, and efficient photothermal platform for low-cost and scalable solar steam generation. As a novel photothermal platform, the p-PEGDA-PANi involves all necessary properties of efficient broadband solar absorption, exceptional hydrophilicity, low heat conductivity, and porous structure for high-efficiency solar steam generation. As a result, the hydrogel-based solar steam generator exhibits a maximum solar thermal efficiency of 91.5% with an evaporation rate of 1.40 kg m -2 h -1 under 1 sun illumination, which is comparable to state-of-the-art solar steam generation devices. Furthermore, the good durability and environmental stability of the p-PEGDA-PANi hydrogel enables a convenient recycling and reusing process toward real-life applications. The present research not only provides a novel photothermal platform for solar energy harvest but also opens a new avenue for the application of the hydrogel materials in solar steam generation.

  20. 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.

  1. Mechanisms underlying syntactic comprehension deficits in vascular aphasia: new evidence from self-paced listening.

    Science.gov (United States)

    Caplan, David; Michaud, Jennifer; Hufford, Rebecca

    2015-01-01

    Sixty-one people with aphasia (pwa) and 41 matched controls were tested for the ability to understand sentences that required the ability to process particular syntactic elements and assign particular syntactic structures. Participants paced themselves word-by-word through 20 examples of 11 spoken sentence types and indicated which of two pictures corresponded to the meaning of each sentence. Sentences were developed in pairs such that comprehension of the experimental version of a pair required an aspect of syntactic processing not required in the corresponding baseline sentence. The need for the syntactic operations required only in the experimental version was triggered at a "critical word" in the experimental sentence. Listening times for critical words in experimental sentences were compared to those for corresponding words in the corresponding baseline sentences. The results were consistent with several models of syntactic comprehension deficits in pwa: resource reduction, slowed lexical and/or syntactic processing, abnormal susceptibility to interference from thematic roles generated non-syntactically. They suggest that a previously unidentified disturbance limiting the duration of parsing and interpretation may lead to these deficits, and that this mechanism may lead to structure-specific deficits in pwa. The results thus point to more than one mechanism underlying syntactic comprehension disorders both across and within pwa.

  2. Grid Voltage Synchronization for Distributed Generation Systems under Grid Fault Conditions

    DEFF Research Database (Denmark)

    Luna, Alvaro; Rocabert, J.; Candela, I.

    2015-01-01

    on the installation of STATCOMs and DVRs, as well as on advanced control functionalities for the existing power converters of distributed generation plants, have contributed to enhance their response under faulty and distorted scenarios and, hence, to fulfill these requirements. In order to achieve satisfactory......The actual grid code requirements for the grid connection of distributed generation systems, mainly wind and PV systems, are becoming very demanding. The Transmission System Operators (TSOs) are especially concerned about the Low Voltage Ride Through requirements. Solutions based...

  3. Capacity expansion of stochastic power generation under two-stage electricity markets

    DEFF Research Database (Denmark)

    Pineda, Salvador; Morales González, Juan Miguel

    2016-01-01

    are first formulated from the standpoint of a social planner to characterize a perfectly competitive market. We investigate the effect of two paradigmatic market designs on generation expansion planning: a day-ahead market that is cleared following a conventional cost merit-order principle, and an ideal...... of stochastic power generating units. This framework includes the explicit representation of a day-ahead and a balancing market-clearing mechanisms to properly capture the impact of forecast errors of power production on the short-term operation of a power system. The proposed generation expansion problems...... market-clearing procedure that determines day-ahead dispatch decisions accounting for their impact on balancing operation costs. Furthermore, we reformulate the proposed models to determine the optimal expansion decisions that maximize the profit of a collusion of stochastic power producers in order...

  4. Frictional melt generated by the 2008 Mw 7.9 Wenchuan earthquake and its faulting mechanisms

    Science.gov (United States)

    Wang, H.; Li, H.; Si, J.; Sun, Z.; Zhang, L.; He, X.

    2017-12-01

    Fault-related pseudotachylytes are considered as fossil earthquakes, conveying significant information that provide improved insight into fault behaviors and their mechanical properties. The WFSD project was carried out right after the 2008 Wenchuan earthquake, detailed research was conducted in the drilling cores. 2 mm rigid black layer with fresh slickenlines was observed at 732.6 m in WFSD-1 cores drilled at the southern Yingxiu-Beichuan fault (YBF). Evidence of optical microscopy, FESEM and FIB-TEM show it's frictional melt (pseudotachylyte). In the northern part of YBF, 4 mm fresh melt was found at 1084 m with similar structures in WFSD-4S cores. The melts contain numerous microcracks. Considering that (1) the highly unstable property of the frictional melt (easily be altered or devitrified) under geological conditions; (2) the unfilled microcracks; (3) fresh slickenlines and (4) recent large earthquake in this area, we believe that 2-4 mm melt was produced by the 2008 Wenchuan earthquake. This is the first report of fresh pseudotachylyte with slickenlines in natural fault that generated by modern earthquake. Geochemical analyses show that fault rocks at 732.6 m are enriched in CaO, Fe2O3, FeO, H2O+ and LOI, whereas depleted in SiO2. XRF results show that Ca and Fe are enriched obviously in the 2.5 cm fine-grained fault rocks and Ba enriched in the slip surface. The melt has a higher magnetic susceptibility value, which may due to neoformed magnetite and metallic iron formed in fault frictional melt. Frictional melt visible in both southern and northern part of YBF reveals that frictional melt lubrication played a major role in the Wenchuan earthquake. Instead of vesicles and microlites, numerous randomly oriented microcracks in the melt, exhibiting a quenching texture. The quenching texture suggests the frictional melt was generated under rapid heat-dissipation condition, implying vigorous fluid circulation during the earthquake. We surmise that during

  5. Numerical modelling of crack initiation and propagation in concrete structure under hydro-mechanical loading

    International Nuclear Information System (INIS)

    Bian, H.B.; Jia, Y.; Shao, J.F.

    2012-01-01

    shrinkage in material as a result of variations of capillary pressure, surface tension or disjoining pressure. When the permeability of concrete is very low, the non uniform distribution of capillary pressure is generated and induces hydraulic gradient in the material. It is then necessary to take into account poro-mechanical coupling in partial conditions. The damage related to desiccation can be distinguished in two different processes. The first, called local effect, is related to micro-structural heterogeneity of cement-based materials. Local shear and tensile stresses can be generated at the grain scale, leading to nucleation and propagation of microcracks. In the second process, called structural effect, tensile strains or stress may be generated by non-uniform distribution of desiccation. Finally, with further coalescence of some of these defects results, the macroscopic cracks appear in the structure. After the initiation of these macro-cracks and fractures, they begin to propagate until the total failure of the structure. Thus, two failure phases could be distinguished: the inception and growth of micro-cracks and then the initiation and propagation of macroscopic discontinuous. For the first phase, the inception and growth of micro-cracks for the partially saturated porous media, a number of numerical modelling has been proposed. These works are mainly concerning the development the diffuse micro-cracks based on the continuum approaches. For avoiding pathological mesh dependence, these models generally require regularization, such as the famous non-local approach. From the computational standpoint, the numerical simulation of crack initiation and propagation in structures under mechanical loading, such as concrete beams, still represents a challenging work. More recently, in the framework of finite element methods, significant progress has been made, that is the use of extended finite element methods (XFEM) based on the partition of unity methods for the crack

  6. Variance Analysis of Wind and Natural Gas Generation under Different Market Structures: Some Observations

    Energy Technology Data Exchange (ETDEWEB)

    Bush, B.; Jenkin, T.; Lipowicz, D.; Arent, D. J.; Cooke, R.

    2012-01-01

    Does large scale penetration of renewable generation such as wind and solar power pose economic and operational burdens on the electricity system? A number of studies have pointed to the potential benefits of renewable generation as a hedge against the volatility and potential escalation of fossil fuel prices. Research also suggests that the lack of correlation of renewable energy costs with fossil fuel prices means that adding large amounts of wind or solar generation may also reduce the volatility of system-wide electricity costs. Such variance reduction of system costs may be of significant value to consumers due to risk aversion. The analysis in this report recognizes that the potential value of risk mitigation associated with wind generation and natural gas generation may depend on whether one considers the consumer's perspective or the investor's perspective and whether the market is regulated or deregulated. We analyze the risk and return trade-offs for wind and natural gas generation for deregulated markets based on hourly prices and load over a 10-year period using historical data in the PJM Interconnection (PJM) from 1999 to 2008. Similar analysis is then simulated and evaluated for regulated markets under certain assumptions.

  7. CURVES AND AESTHETIC SURFACES GENERATED BY THE R-R-RTR MECHANISM

    Directory of Open Access Journals (Sweden)

    Liliana LUCA

    2013-05-01

    Full Text Available Let’s consider a mechanism having two driving elements with revolving movements and a RTR dyad, with elements of null length and aesthetic tracks of a point are determined on a rod, for various linear movement laws of driving elements. The generated curves revolve around x and y axes and aesthetic surfaces result.

  8. Mechanism of the free charge carrier generation in the dielectric breakdown

    Science.gov (United States)

    Rahim, N. A. A.; Ranom, R.; Zainuddin, H.

    2017-12-01

    Many studies have been conducted to investigate the effect of environmental, mechanical and electrical stresses on insulator. However, studies on physical process of discharge phenomenon, leading to the breakdown of the insulator surface are lacking and difficult to comprehend. Therefore, this paper analysed charge carrier generation mechanism that can cause free charge carrier generation, leading toward surface discharge development. Besides, this paper developed a model of surface discharge based on the charge generation mechanism on the outdoor insulator. Nernst’s Planck theory was used in order to model the behaviour of the charge carriers while Poisson’s equation was used to determine the distribution of electric field on insulator surface. In the modelling of surface discharge on the outdoor insulator, electric field dependent molecular ionization was used as the charge generation mechanism. A mathematical model of the surface discharge was solved using method of line technique (MOL). The result from the mathematical model showed that the behaviour of net space charge density was correlated with the electric field distribution.

  9. Hierarchy of mechanisms involved in generating Na/K-ATPase polarity in MDCK epithelial cells

    NARCIS (Netherlands)

    Mays, R.W.; Siemers, K.A.; Fritz, B.A.; Lowe, A.W.; van Meer, G.; Nelson, W.J.

    1995-01-01

    We have studied mechanisms involved in generating a polarized distribution of Na/K-ATPase in the basal-lateral membrane of two clones of MDCK II cells. Both clones exhibit polarized distributions of marker proteins of the apical and basal-lateral membranes, including Na/K-ATPase, at steady state.

  10. Impact of Conflict Management Strategies on the Generation Mechanism of Miners' Unsafe Behavior Tendency

    Science.gov (United States)

    Li, Ji-Zu; Zhang, Ya-Ping; Liu, Xiao-Guang; Liu, Yao-Long; Wang, Tian-Ri

    2017-01-01

    In this paper, we examine the relationship between the generation mechanism of miners' unsafe behavior tendency and conflict management strategies, including cooperative conflict management strategy, competitive conflict management strategy and avoidant conflict management strategy. Miners from 3 collieries in Shanxi province completed a…

  11. Dynamic model of Stirling engine crank mechanism with connected electric generator

    Directory of Open Access Journals (Sweden)

    Vlach R.

    2009-06-01

    Full Text Available This paper treats of a numerical dynamic model of Stirling engine crank mechanism. The model is included in the complex model of combined heat and power unit. The unit is composed of the Stirling engine and of attached three-phase synchronous generator. This generator should start the Stirling engine in motor mode as well. It is necessary to combine the crank shaft dynamic model and the complete thermal model of Stirling engine for simulations and analyses of engine run. Our aim is to create a dynamics model which takes into account the parameters of crankshaft, piston rods, pistons, and attached generator. For unit working, the electro-mechanical behaviour of generator is also important. That is why we experimentally verified the parameters of generator. The measured characteristics are used in a complex model of heat and power unit. Moreover, it is also possible to determine the Stirling engine torque by the help of these electro-mechanical characteristics. These values can be used e. g. for determination of optimal engine working point or for unit control.

  12. Mechanisms behind the generation of protonated ions for polyaromatic hydrocarbons by atmospheric pressure photoionization.

    Science.gov (United States)

    Ahmed, Arif; Choi, Cheol Ho; Choi, Myoung Choul; Kim, Sunghwan

    2012-01-17

    In this study, the mechanism behind the generation of protonated polyaromatic hydrocarbon (PAH) ions without heteroatoms by atmospheric pressure photoionization (APPI) is investigated. Comparing data obtained by APPI of anthracene dissolved either in toluene or perdeuterated toluene suggests that toluene acts as a source of protons and that breakage of C-H bonds in the toluene molecule is important for the overall protonation reaction. Our data describing an Arrhenius-type temperature-dependent relationship between the signal intensities of molecular and protonated ions suggest a mechanistic relation between the generated molecular and protonated ions. The APPI protonation mechanism that best explains the observed phenomena is composed of two reactions: electron transfer followed by hydrogen transfer. This two-step mechanism for APPI was originally suggested by Syage (Syage, J. A. J. Am. Soc. Mass Spectrom. 2004, 15 , 1521-1533). Further quantum mechanical study shows that an energetically favorable ion-molecular complex can be generated as a result of electron transfer from toluene to PAH, which subsequently facilitates hydrogen transfer. This suggests that both electron transfer and hydrogen transfer can occur as a "concerted" reaction through the ion-molecular complex precursor state, which is consistent with experimental results. To our best knowledge, this is the first time that the dynamic nature of the APPI process is clearly revealed by combined experimental and quantum mechanical studies.

  13. Predictions of structural integrity of steam generator tubes under normal operating, accident, and severe accident conditions

    International Nuclear Information System (INIS)

    Majumdar, S.

    1996-09-01

    Available models for predicting failure of flawed and unflawed steam generator tubes under normal operating, accident, and severe accident conditions are reviewed. Tests conducted in the past, though limited, tended to show that the earlier flow-stress model for part-through-wall axial cracks overestimated the damaging influence of deep cracks. This observation is confirmed by further tests at high temperatures as well as by finite element analysis. A modified correlation for deep cracks can correct this shortcoming of the model. Recent tests have shown that lateral restraint can significantly increase the failure pressure of tubes with unsymmetrical circumferential cracks. This observation is confirmed by finite element analysis. The rate-independent flow stress models that are successful at low temperatures cannot predict the rate sensitive failure behavior of steam generator tubes at high temperatures. Therefore, a creep rupture model for predicting failure is developed and validated by tests under varying temperature and pressure loading expected during severe accidents

  14. Heat transfer characteristics of horizontal steam generators under natural circulation conditions

    International Nuclear Information System (INIS)

    Hyvaerinen, J.

    1996-01-01

    This paper deals with the heat transfer characteristics of horizontal steam generators, particularly under natural circulation (decay heat removal) conditions on the primary side. Special emphasis is on the inherent features of horizontal steam generator behaviour. A mathematical model of the horizontal steam generator primary side is developed and qualitative results are obtained analytically. A computer code, called HSG, is developed to solve the model numerically, and its predictions are compared with experimental data. The code is employed to obtain for VVER 440 steam generators quantitative results concerning the dependence of primary-to-secondary heat transfer efficiency on the primary side flow rate, temperature and secondary level. It turns out that the depletion of the secondary inventory leads to an inherent limitation of the decay energy removal in VVER steam generators. The limitation arises as a consequence of the steam generator tube bundle geometry. As an example, it is shown that the grace period associated with pressurizer safety valve opening during a station black-out is 2 1/2-3 hours instead of the 5-6 hours reported in several earlier studies. (However, the change in core heat-up timing is much less-about 1 h at most.) The heat transfer limitation explains the fact that, in the Greifswald VVER 440 station black-out accident in 1975, the steam generators never boiled dry. In addition, the stability of single-phase natural circulation is discussed and insights on the modelling of horizontal steam generators with general-purpose thermal-hydraulic system codes are also presented. (orig.)

  15. Contribution of anaerobic digesters to emissions mitigation and electricity generation under U.S. climate policy.

    Science.gov (United States)

    Zaks, David P M; Winchester, Niven; Kucharik, Christopher J; Barford, Carol C; Paltsev, Sergey; Reilly, John M

    2011-08-15

    Livestock husbandry in the U.S. significantly contributes to many environmental problems, including the release of methane, a potent greenhouse gas (GHG). Anaerobic digesters (ADs) break down organic wastes using bacteria that produce methane, which can be collected and combusted to generate electricity. ADs also reduce odors and pathogens that are common with manure storage and the digested manure can be used as a fertilizer. There are relatively few ADs in the U.S., mainly due to their high capital costs. We use the MIT Emissions Prediction and Policy Analysis (EPPA) model to test the effects of a representative U.S. climate stabilization policy on the adoption of ADs which sell electricity and generate methane mitigation credits. Under such policy, ADs become competitive at producing electricity in 2025, when they receive methane reduction credits and electricity from fossil fuels becomes more expensive. We find that ADs have the potential to generate 5.5% of U.S. electricity.

  16. Novel mechanism of network protection against the new generation of cyber attacks

    Science.gov (United States)

    Milovanov, Alexander; Bukshpun, Leonid; Pradhan, Ranjit

    2012-06-01

    A new intelligent mechanism is presented to protect networks against the new generation of cyber attacks. This mechanism integrates TCP/UDP/IP protocol stack protection and attacker/intruder deception to eliminate existing TCP/UDP/IP protocol stack vulnerabilities. It allows to detect currently undetectable, highly distributed, low-frequency attacks such as distributed denial-of-service (DDoS) attacks, coordinated attacks, botnet, and stealth network reconnaissance. The mechanism also allows insulating attacker/intruder from the network and redirecting the attack to a simulated network acting as a decoy. As a result, network security personnel gain sufficient time to defend the network and collect the attack information. The presented approach can be incorporated into wireless or wired networks that require protection against known and the new generation of cyber attacks.

  17. Development of microstructure to optimise mechanical performance of power generation equipment

    International Nuclear Information System (INIS)

    Marshall, P.

    1986-11-01

    The factors responsible for the development of microstructure in CEGB construction ceramics and steels is assessed as a function of composition, thermomechanical treatment, thermal ageing and environmental degradation. The relationships between microstructure and mechanical properties (tensile, toughness, creep and fatigue) of relevance to structures operating in power generation equipment is then developed in quantitative terms. The conclusions from the assessment are as follows: 1 The relationship between microstructure and mechanical properties of construction ceramics and steels used in the power generation industry has been assessed. 2 Factors which significantly influence microstructure and thus mechanical properties are chemical composition, thermomechanical treatment, ageing and environmental degradation. The influence of such microstructural changes in tensile, toughness, fatigue and creep properties of ceramics and steels is assessed. 3 The benefits arising from an understanding of materials behaviour are discussed in terms of improved materials and the assessment of plant performance. (author)

  18. Hydrogen generation, distribution and combustion under severe LWR accident conditions: a state-of-technology report

    International Nuclear Information System (INIS)

    Postma, A.K.; Hilliard, R.K.

    1983-03-01

    This report reviews the current state of technology regarding hydrogen safety issues in light water reactor plants. Topics considered in this report include hydrogen generation, distribution in containment, and combustion characteristics. A companion report addresses hydrogen control. The objectives of the study were to identify the key safety issues related to hydrogen produced under severe accident conditions, to describe the state of technology for each issue, and to point out ongoing programs aimed at resolving the open issues

  19. Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage

    International Nuclear Information System (INIS)

    Luo Yang; Wu Guang-Ning; Liu Ji-Wu; Peng Jia; Gao Guo-Qiang; Zhu Guang-Ya; Wang Peng; Cao Kai-Jiang

    2014-01-01

    Polyimide (PI) film is an important type of insulating material used in inverter-fed motors. Partial discharge (PD) under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage (BCSIV) is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage (PDIV). The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy (FTIR) and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy (SEM). The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond (C—O—C) and imide ring (C—N—C) on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant ε to increase and dielectric loss tan δ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI polymer bulk. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  20. New digital reference current generation for shunt active power filter under distorted voltage conditions

    Energy Technology Data Exchange (ETDEWEB)

    Abdusalam, Mohamed; Karimi, Shahram; Saadate, Shahrokh [Groupe de Recherche en Electrotechnique et Electronique de Nancy (GREEN), CNRS UMR 7037 (France); Poure, Philippe [Laboratoire d' Instrumentation Electronique de Nancy (LIEN), EA 3440, Universite Henri Poincare - Nancy Universite, B.P. 239, 54506 Vandoeuvre les Nancy Cedex (France)

    2009-05-15

    In this paper, a new reference current computation method suitable for shunt active power filter control under distorted voltage conditions is proposed. The active power filter control is based on the use of self-tuning filters (STF) for the reference current generation and on a modulated hysteresis current controller. This active filter is intended for harmonic compensation of a diode rectifier feeding a RL load under distorted voltage conditions. The study of the active filter control is divided in two parts. The first one deals with the harmonic isolator which generates the harmonic reference currents and is experimentally implemented in a DS1104 card of a DSPACE prototyping system. The second part focuses on the generation of the switching pattern of the inverter by using a modulated hysteresis current controller, implemented in an analogue card. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the {alpha}-{beta} axis without phase locked loop (PLL). The performances are good even under distorted voltage conditions. First, the effectiveness of the new proposed method is mathematically studied and verified by computer simulation. Then, experimental results are presented using a DSPACE system associated with the analogue current controller for a real shunt active power filter. (author)

  1. Dissection of the mechanism of manganese porphyrin-catalyzed chlorine dioxide generation.

    Science.gov (United States)

    Umile, Thomas P; Wang, Dong; Groves, John T

    2011-10-17

    Chlorine dioxide, an industrially important biocide and bleach, is produced rapidly and efficiently from chlorite ion in the presence of water-soluble, manganese porphyrins and porphyrazines at neutral pH under mild conditions. The electron-deficient manganese(III) tetra-(N,N-dimethyl)imidazolium porphyrin (MnTDMImP), tetra-(N,N-dimethyl)benzimidazolium (MnTDMBImP) porphyrin, and manganese(III) tetra-N-methyl-2,3-pyridinoporphyrazine (MnTM23PyPz) were found to be the most efficient catalysts for this process. The more typical manganese tetra-4-N-methylpyridiumporphyrin (Mn-4-TMPyP) was much less effective. Rates for the best catalysts were in the range of 0.24-32 TO/s with MnTM23PyPz being the fastest. The kinetics of reactions of the various ClO(x) species (e.g., chlorite ion, hypochlorous acid, and chlorine dioxide) with authentic oxomanganese(IV) and dioxomanganese(V)MnTDMImP intermediates were studied by stopped-flow spectroscopy. Rate-limiting oxidation of the manganese(III) catalyst by chlorite ion via oxygen atom transfer is proposed to afford a trans-dioxomanganese(V) intermediate. Both trans-dioxomanganese(V)TDMImP and oxoaqua-manganese(IV)TDMImP oxidize chlorite ion by 1-electron, generating the product chlorine dioxide with bimolecular rate constants of 6.30 × 10(3) M(-1) s(-1) and 3.13 × 10(3) M(-1) s(-1), respectively, at pH 6.8. Chlorine dioxide was able to oxidize manganese(III)TDMImP to oxomanganese(IV) at a similar rate, establishing a redox steady-state equilibrium under turnover conditions. Hypochlorous acid (HOCl) produced during turnover was found to rapidly and reversibly react with manganese(III)TDMImP to give dioxoMn(V)TDMImP and chloride ion. The measured equilibrium constant for this reaction (K(eq) = 2.2 at pH 5.1) afforded a value for the oxoMn(V)/Mn(III) redox couple under catalytic conditions (E' = 1.35 V vs NHE). In subsequent processes, chlorine dioxide reacts with both oxomanganese(V) and oxomanganese(IV)TDMImP to afford chlorate

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

    International Nuclear Information System (INIS)

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

    2013-01-01

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

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

    NARCIS (Netherlands)

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

    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

  4. Imitation in Newborn Infants: Exploring the Range of Gestures Imitated and the Underlying Mechanisms.

    Science.gov (United States)

    Meltzoff, Andrew N.; Moore, M. Keith

    1989-01-01

    Evaluated psychological mechanisms underlying imitation of facial actions in 40 newborn infants. Results showed imitation of head movement and a tongue-protrusion gesture. Subjects imitated from memory after displays had stopped. (RJC)

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  6. Elucidating the molecular mechanisms underlying cellular response to biophysical cues using synthetic biology approaches

    NARCIS (Netherlands)

    Denning, Denise; Roos, Wouter H

    2016-01-01

    The use of synthetic surfaces and materials to influence and study cell behavior has vastly progressed our understanding of the underlying molecular mechanisms involved in cellular response to physicochemical and biophysical cues. Reconstituting cytoskeletal proteins and interfacing them with a

  7. Development of a Zero-Dimensional Particle Generation Model in SFR-Containments under Accidental Conditions

    Energy Technology Data Exchange (ETDEWEB)

    García, M.; Herranz, L.E.

    2015-07-01

    During postulated Beyond Design Basis Accidents (BDBAs) in Sodium-cooled Fast Reactors (SFRs), contaminated-sodium at high temperature may leak into the containment and burns in the presence of oxygen. As a result, large quantities of sodium oxide aerosols are produced. In the frame of the EU-JASMIN project, a particle generation model to calculate the particle generation rate and their primary size during a generic sodium pool fire has been developed to be implemented in ASTEC-Na code. This paper presents the adaptation of the 3-D particle generation model to a 0-D model based on the generation of particles under average system conditions. Deviations between both approaches less than 20% have been found in all the simulated scenarios. From the 0-D model, simple correlations for the particle generation rate and the primary particle size as a function of Na-oxide vapour pressures, temperature and sodium pool characteristics have been derived for its straightforward implementation in the ASTEC-Na code. (Author)

  8. 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

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

    Science.gov (United States)

    2017-10-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  11. Generation mechanism of L-value dependence of oxygen flux enhancements during substorms

    Science.gov (United States)

    Nakayama, Y.; Ebihara, Y.; Tanaka, T.; Ohtani, S.; Gkioulidou, M.; Takahashi, K.; Kistler, L. M.; Kletzing, C.

    2015-12-01

    The Van Allen Probes Helium Oxygen Proton Electron (HOPE) instrument measures charged particles with an energy range from ~eV to ~ tens of keV. The observation shows that the energy flux of the particles increases inside the geosynchronous orbit during substorms. For some night-side events around the apogee, the energy flux of O+ ion enhances below ~10 keV at lower L shell, whereas the flux below ~8 keV sharply decreases at higher L shells. This structure of L-energy spectrogram of flux is observed only for the O+ ions. The purpose of this study is to investigate the generation mechanism of the structure by using numerical simulations. We utilized the global MHD simulation developed by Tanaka et al (2010, JGR) to simulate the electric and magnetic fields during substorms. We performed test particle simulation under the electric and magnetic fields by applying the same model introduced by Nakayama et al. (2015, JGR). In the test particle simulation each test particle carries the real number of particles in accordance with the Liouville theorem. Using the real number of particles, we reconstructed 6-dimensional phase space density and differential flux of O+ ions in the inner magnetosphere. We obtained the following results. (1) Just after the substorm onset, the dawn-to-dusk electric field is enhanced to ~ 20 mV/m in the night side tail region at L > 7. (2) The O+ ions are accelerated and transported to the inner region (L > ~5.5) by the large-amplitude electric field. (3) The reconstructed L-energy spectrogram shows a similar structure to the Van Allen Probes observation. (4) The difference in the flux enhancement between at lower L shell and higher L shells is due to two distinct acceleration processes: adiabatic and non-adiabatic. We will discuss the relationship between the particle acceleration and the structure of L-energy spectrogram of flux enhancement in detail.

  12. Generation of ROS mediated by mechanical waves (ultrasound) and its possible applications.

    Science.gov (United States)

    Duco, Walter; Grosso, Viviana; Zaccari, Daniel; Soltermann, Arnaldo T

    2016-10-15

    The thermal decomposition of 9,10 diphenylanthracene peroxide (DPAO 2 ) generates DPA and a mix of triplet and singlet molecular oxygen. For DPAO 2 the efficiency to produce singlet molecular oxygen is 0.35. On the other hand, it has shown that many thermal reactions can be carried out through the interaction of molecules with ultrasound. Ultrasound irradiation can create hydrodynamic stress (sonomechanical process), inertial cavitation (pyrolitic process) and long range effects mediated by radicals or ROS. Sonochemical reactions can be originated by pyrolytic like process, shock mechanical waves, thermal reactions and radical and ROS mediated reactions. Sonolysis of pure water can yield hydrogen or hydroxyl radicals and hydrogen peroxide (ROS). When DPAO 2 in 1,4 dioxane solution is treated with 20 or 24kHz and different power intensity the production of molecular singlet oxygen is observed. Specific scavengers like tetracyclone (TC) are used to demonstrate it. The efficiency now is 0.85 showing that the sonochemical process is much more efficient that the thermal one. Another endoperoxide, artemisinin was also studied. Unlike the concept of photosensitizer of photodynamic therapy, in spite of large amount of reported results in literature, the term sonosensitizer and the sonosensitization process are not well defined. We define sonosensitized reaction as one in which a chemical species decompose as consequence of cavitation phenomena producing ROS or other radicals and some other target species does undergo a chemical reaction. The concept could be reach rapidly other peroxides which are now under experimental studies. For artemisinin, an important antimalarian and anticancer drug, was established that ultrasound irradiation increases the effectiveness of the treatment but without any explanation. We show that artemisinin is an endoperoxide and behaves as a sonosensitizer in the sense of our definition. Copyright © 2016 Elsevier Inc. All rights reserved.

  13. 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

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

    International Nuclear Information System (INIS)

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

    1979-01-01

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

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

    International Nuclear Information System (INIS)

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

    1979-01-01

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

  16. Molecular Mechanisms Underlying the Epileptogenesis and Seizure Progression in Tuberous Sclerosis Complex 1 Deficient Mouse Models

    Science.gov (United States)

    2016-10-01

    dysregulation in epileptogenesis in the developing brain? 2) What are the molecular mechanisms downstream of mTOR hyperactivation that trigger epileptogenesis...underlying epilepsy. Hopefully, a knowledge of these mechanisms will aid in a rational development of therapies. KEYWORDS Tuberous Sclerosis, Epilepsy

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

    Science.gov (United States)

    2013-01-01

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

  18. Generation of net electric power with a tokamak reactor under foreseeable physical and engineering conditions

    International Nuclear Information System (INIS)

    Hiwatari, R.; Asaoka, Y.; Okano, K.; Yoshida, T.; Tomabechi, K.

    2004-01-01

    This study reveals for the first time the plasma performance required for a tokamak reactor to generate net electric power under foreseeable engineering conditions. It was found that the reference plasma performance of the ITER inductive operation mode with β N = 1.8, HH = 1.0, andf nGW 0.85 had sufficient potential to achieve the electric break-even condition (net electric power P e net = 0MW) under the following engineering conditions: machine major radius 6.5m ≤ R p ≤ 8.5m, the maximum magnetic field on TF coils B tmax = 16 T, thermal efficiency η e 30%, and NBI system efficiency η NBI = 50%. The key parameters used in demonstrating net electric power generation in tokamak reactors are β N and fη GW . ≥ 3.0 is required for P e net ∼ 600MW with fusion power P f ∼ 3000MW. On the other hand, fη GW ≥ 1.0 is inevitable to demonstrate net electric power generation, if high temperatures, such as average temperatures of T ave > 16 keV, cannot be selected for the reactor design. To apply these results to the design of a tokamak reactor for demonstrating net electric power generation, the plasma performance diagrams on the Q vs P f (energy multiplication factor vs fusion power) space for several major radii (i.e. 6.5, 7.5, and 8.5 m) were depicted. From these figures, we see that a design with a major radius R p ∼ 7.5m seems preferable for demonstrating net electric power generation when one aims at early realization of fusion energy. (author)

  19. Diversity Generator Mechanisms Are Essential Components of Biological Systems: The Two Queen Hypothesis

    Directory of Open Access Journals (Sweden)

    Eric Muraille

    2018-02-01

    Full Text Available Diversity is widely known to fuel adaptation and evolutionary processes and increase robustness at the population, species and ecosystem levels. The Neo-Darwinian paradigm proposes that the diversity of biological entities is the consequence of genetic changes arising spontaneously and randomly, without regard for their usefulness. However, a growing body of evidence demonstrates that the evolutionary process has shaped mechanisms, such as horizontal gene transfer mechanisms, meiosis and the adaptive immune system, which has resulted in the regulated generation of diversity among populations. Though their origins are unrelated, these diversity generator (DG mechanisms share common functional properties. They (i contribute to the great unpredictability of the composition and/or behavior of biological systems, (ii favor robustness and collectivism among populations and (iii operate mainly by manipulating the systems that control the interaction of living beings with their environment. The definition proposed here for DGs is based on these properties and can be used to identify them according to function. Interestingly, prokaryotic DGs appear to be mainly reactive, as they generate diversity in response to environmental stress. They are involved in the widely described Red Queen/arms race/Cairnsian dynamic. The emergence of multicellular organisms harboring K selection traits (longer reproductive life cycle and smaller population size has led to the acquisition of a new class of DGs that act anticipatively to stress pressures and generate a distinct dynamic called the “White Queen” here. The existence of DGs leads to the view of evolution as a more “intelligent” and Lamarckian-like process. Their repeated selection during evolution could be a neglected example of convergent evolution and suggests that some parts of the evolutionary process are tightly constrained by ecological factors, such as the population size, the generation time and

  20. Spatiotemporal impacts of LULC changes on hydrology from the perspective of runoff generation mechanism using SWAT model with evolving parameters

    Science.gov (United States)

    Li, Y.; Chang, J.; Luo, L.

    2017-12-01

    It is of great importance for water resources management to model the truly hydrological process under changing environment, especially under significant changes of underlying surfaces like the Wei River Bain (WRB) where the subsurface hydrology is highly influenced by human activities, and to systematically investigate the interactions among LULC change, streamflow variation and changes in runoff generation process. Therefore, we proposed the idea of evolving parameters in hydrological model (SWAT) to reflect the changes in physical environment with different LULC conditions. Then with these evolving parameters, the spatiotemporal impacts of LULC changes on streamflow were quantified, and qualitative analysis was conducted to further explore how LULC changes affect the streamflow from the perspective of runoff generation mechanism. Results indicate the following: 1) evolving parameter calibration is not only effective but necessary to ensure the validity of the model when dealing with significant changes in underlying surfaces due to human activities. 2) compared to the baseline period, the streamflow in wet seasons increased in the 1990s but decreased in the 2000s. While at yearly and dry seasonal scales, the streamflow decreased in both two decades; 3) the expansion of cropland is the major contributor to the reduction of surface water component, thus causing the decline in streamflow at yearly and dry seasonal scales. While compared to the 1990s, the expansions of woodland in the middle stream and grassland in the downstream are the main stressors that increased the soil water component, thus leading to the more decline of the streamflow in the 2000s.

  1. An integrative view of mechanisms underlying generalized spike-and-wave epileptic seizures and its implication on optimal therapeutic treatments.

    Directory of Open Access Journals (Sweden)

    Boyuan Yan

    Full Text Available Many types of epileptic seizures are characterized by generalized spike-and-wave discharges. In the past, notable effort has been devoted to understanding seizure dynamics and various hypotheses have been proposed to explain the underlying mechanisms. In this paper, by taking an integrative view of the underlying mechanisms, we demonstrate that epileptic seizures can be generated by many different combinations of synaptic strengths and intrinsic membrane properties. This integrative view has important medical implications: the specific state of a patient characterized by a set of biophysical characteristics ultimately determines the optimal therapeutic treatment. Through the same view, we further demonstrate the potentiation effect of rational polypharmacy in the treatment of epilepsy and provide a new angle to resolve the debate on polypharmacy. Our results underscore the need for personalized medicine and demonstrate that computer modeling and simulation may play an important role in assisting the clinicians in selecting the optimal treatment on an individual basis.

  2. Vulnerability of Hidropower Generation in Amazon's Tributaries Under Global Change Scenarios

    Science.gov (United States)

    Von Randow, R.; Siqueira, J. L., Jr.; Rodriguez, D. A.; Tomasella, J.; Floriano, L. E.

    2014-12-01

    The Brazilian energy sector is under continued expansion. The majority of energy power generation in the country is done through hydropower, which represents around 88% of the energy originated from renewable sources in the country. Still, only 10% of the high potential for production of the Amazon basin is currently availed, and this raises attention for the implantation of new hydropower plants in the region. When a hydropower plant is considered to be built, the natural characteristics of the region are taken into account, considering that the rainfall regime follows certain stationarity. However, under the possibility of global change, the expected capacity of the plants may be compromised. The objective of this study is to evaluate if the current hydropower plants of some Amazon River tributaries can maintain their functionality under global environmental change conditions. For that, based on the discharge data and hydropower information available by Brazilian National Agency of Water and Energy we will infer the energy potential of these hydropower dams for the historic period that will be compared with the energy potential for future discharge under global environmental change conditions. The future discharge will be generated by the Distributed Hydrological Model developed at the Brazilian National Institute for Space Research (MHD-INPE), driven by different climate change scenarios projected by regional and global atmospheric models, associated with land use scenarios projected by a dynamic land use model (LUCC-ME/INPE). MHD-INPE will be calibrated through observed discharges for 1970-1990 using current land use conditions, and will generate discharges for the period of 2000 to 2050. In addition, special attention will be given to the presence of secondary forest growth in the land use scenarios in order to identify the importance of considering this use in the modelling exercise, since that use is not usually considered in hydrological modelling studies.

  3. The investigation of the stochastization mechanisms of the beam generators using the method of functional map

    International Nuclear Information System (INIS)

    Bliokh, Yu.P.; Fajnberg, Ya.B.; Lyubarskij, M.G.; Podobinskij, V.O.

    1994-01-01

    Certain distributed dynamical systems describing the well-known beam generators of UHF oscillations are organized very simple: the nonlinear functional, which determines the current state of the system with respect to its behaviour in the past, is represented as a composition of the linear functional and the nonlinear finite-dimensional map. This property made it possible to find the mechanisms of auto modulation and stochastization of the signals from beam generators and to define corresponding range of parameters values. 12 refs., 6 figs

  4. Impedance analysis of a disk-type SOFC using doped lanthanum gallate under power generation

    Science.gov (United States)

    Kato, Tohru; Nozaki, Ken; Negishi, Akira; Kato, Ken; Monma, Akihiko; Kaga, Yasuo; Nagata, Susumu; Takano, Kiyonami; Inagaki, Toru; Yoshida, Hiroyuki; Hosoi, Kei; Hoshino, Koji; Akbay, Taner; Akikusa, Jun

    Impedance measurements were carried out under practical power generation conditions in a disk-type SOFC, which may be utilized as a small-scale power generator. The tested cell was composed of doped lanthanum gallate (La 0.8Sr 0.2Ga 0.8Mg 0.15Co 0.05O 3- δ) as the electrolyte, Sm 0.5Sr 0.5CoO 3 as the cathode electrode and Ni/Ce 0.8Sm 0.2O 2 cermet as the anode electrode. The cell impedance was measured between 10 mHz and 10 kHz by varying the fuel utilization and gas flow rate and plotted in complex impedance diagrams. The observed impedance shows a large semi-circular pattern on the low frequency side. The semi-circular impedance, having a noticeably low characteristic frequency between 0.13 and 0.4 Hz, comes from the change in gas composition, originally caused by the cell reaction. The change in impedance with the fuel utilization (load current) and the gas flow rate agreed qualitatively well with the theoretical predictions from a simulation. This impedance was dominant under high fuel-utilization power-generation conditions. The impedance, which described the activation polarizations in the electrode reactions, was comparatively small and scarcely changed with the change in fuel utilization (load current) and gas flow rate.

  5. Generation of electrical power under human skin by subdermal solar cell arrays for implantable bioelectronic devices.

    Science.gov (United States)

    Song, Kwangsun; Han, Jung Hyun; Yang, Hyung Chae; Nam, Kwang Il; Lee, Jongho

    2017-06-15

    Medical electronic implants can significantly improve people's health and quality of life. These implants are typically powered by batteries, which usually have a finite lifetime and therefore must be replaced periodically using surgical procedures. Recently, subdermal solar cells that can generate electricity by absorbing light transmitted through skin have been proposed as a sustainable electricity source to power medical electronic implants in bodies. However, the results to date have been obtained with animal models. To apply the technology to human beings, electrical performance should be characterized using human skin covering the subdermal solar cells. In this paper, we present electrical performance results (up to 9.05mW/cm 2 ) of the implantable solar cell array under 59 human skin samples isolated from 10 cadavers. The results indicate that the power densities depend on the thickness and tone of the human skin, e.g., higher power was generated under thinner and brighter skin. The generated power density is high enough to operate currently available medical electronic implants such as pacemakers that require tens of microwatt. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Temporal shifts in clinical presentation and underlying mechanisms of atherosclerotic disease.

    Science.gov (United States)

    Pasterkamp, Gerard; den Ruijter, Hester M; Libby, Peter

    2017-01-01

    The concept of the 'vulnerable plaque' originated from pathological observations in patients who died from acute coronary syndrome. This recognition spawned a generation of research that led to greater understanding of how complicated atherosclerotic plaques form and precipitate thrombotic events. In current practice, an increasing number of patients who survive their first event present with non-ST-segment elevation myocardial infarction (NSTEMI) rather than myocardial infarction (MI) with ST-segment elevation (STEMI). The culprit lesions that provide the pathological substrate for NSTEMI can vary considerably from the so-called 'vulnerable plaque'. The shift in clinical presentation of MI and stroke corresponds temporally to a progressive change in the characteristics of human plaques away from the supposed characteristics of vulnerability. These alterations in the structure and function of human atherosclerotic lesions might mirror the modifications that are produced in experimental plaques by lipid lowering, inspired by the vulnerable plaque construct. The shift in the clinical presentations of the acute coronary syndromes mandates a critical reassessment of the underlying mechanisms, proposed risk scores, the results and interpretation of preclinical experiments, as well as recognition of the limitations of the use of population data and samples collected before the application of current preventive interventions.

  7. Mechanical behavior of NiTi arc wires under pseudoelastic cycling and cathodically hydrogen charging

    Science.gov (United States)

    Sarraj, R.; Hassine, T.; Gamaoun, F.

    2018-01-01

    NiTi wires are mainly used to design orthodontic devices. However, they may be susceptible to a delayed fracture while they are submitted to cyclic loading with the presence of hydrogen in the oral cavity. Hydrogen may cause the embrittlement of the structure, leading to lower ductility and to a change in transformation behavior. The aim of the present study is to predict the NiTi behavior under cyclic loading with hydrogen charging. One the one hand, samples are submitted to superelastic cyclic loading, which results in investigating their performance degradations. On the other hand, after hydrogen charging, cyclic tensile aging tests are carried out on NiTi orthodontic wires at room temperature in the air. During cyclic loading, we notice that the critical stress for the martensite transformation evolves, the residual strain is accumulated in the structure and the hysteresis loop changes. Thus, via this work, we can assume that the embrittlement is due to the diffusion of hydrogen and the generation of dislocations after aging. The evolution of mechanical properties of specimens becomes more significant with hydrogen charging rather than without it.

  8. Combined toxicity and underlying mechanisms of a mixture of eight heavy metals.

    Science.gov (United States)

    Zhou, Qi; Gu, Yuanliang; Yue, Xia; Mao, Guochuan; Wang, Yafei; Su, Hong; Xu, Jin; Shi, Hongbo; Zou, Baobo; Zhao, Jinshun; Wang, Renyuan

    2017-02-01

    With the rapid development of modernization and industrialization in China, a large quantity of heavy metals, including zinc, copper, lead, cadmium and mercury, have been entering the atmosphere, soil and water, the latter being the primary route of pollution. In the present study, in vitro experiments were performed to examine the joint toxicity and the underlying mechanisms of the eight most common heavy metals contaminating offshore waters on the eastern coast of Ningbo region. Using a cell cycle assay, cell apoptosis and reactive oxygen species (ROS) detection methods, the present study demonstrated that the heavy metal mixture arrested JB6 cells at the S phase, induced the generation of ROS and cell apoptosis. A luciferase assay indicated that the levels of activator protein‑1 and nuclear factor‑κB transcription factors were upregulated. Upregulation of the protein levels of C‑jun and p65 were detected in the JB6 cells by western blot analysis; these two genes have important roles in cell carcinogenesis. These results provide a useful reference for further investigations on the combined toxicity of the exposure to multiple heavy metals.

  9. Common resting brain dynamics indicate a possible mechanism underlying zolpidem response in severe brain injury

    Science.gov (United States)

    Williams, Shawniqua T; Conte, Mary M; Goldfine, Andrew M; Noirhomme, Quentin; Gosseries, Olivia; Thonnard, Marie; Beattie, Bradley; Hersh, Jennifer; Katz, Douglas I; Victor, Jonathan D; Laureys, Steven; Schiff, Nicholas D

    2013-01-01

    Zolpidem produces paradoxical recovery of speech, cognitive and motor functions in select subjects with severe brain injury but underlying mechanisms remain unknown. In three diverse patients with known zolpidem responses we identify a distinctive pattern of EEG dynamics that suggests a mechanistic model. In the absence of zolpidem, all subjects show a strong low frequency oscillatory peak ∼6–10 Hz in the EEG power spectrum most prominent over frontocentral regions and with high coherence (∼0.7–0.8) within and between hemispheres. Zolpidem administration sharply reduces EEG power and coherence at these low frequencies. The ∼6–10 Hz activity is proposed to arise from intrinsic membrane properties of pyramidal neurons that are passively entrained across the cortex by locally-generated spontaneous activity. Activation by zolpidem is proposed to arise from a combination of initial direct drug effects on cortical, striatal, and thalamic populations and further activation of underactive brain regions induced by restoration of cognitively-mediated behaviors. DOI: http://dx.doi.org/10.7554/eLife.01157.001 PMID:24252875

  10. The e7 guide to implementing projects under the Clean Development Mechanism

    International Nuclear Information System (INIS)

    2003-09-01

    The e7 was formed in 1992 to play an active role in global electricity issues and to promote sustainable development. It consists of nine leading electricity companies: American Electric Power (United States), Electricite de France (France), ENEL (Italy), Hydro-Quebec (Canada), The Kansai Electric Power Company, Inc. (Japan), Ontario Power Generation, Inc. (Canada), RWE (Germany), ScottishPower (United Kingdom), and Tokyo Electric Power Company (Japan). This report provides a guide to help develop projects under the Clean Development Mechanism (CDM), which is an instrument that allows public or private entities to invest in greenhouse gas (GHG) mitigating activities in developing countries and earn credits in an emission trading system. The dual objectives of the CDM, one of three mechanisms set out in the Kyoto Protocol, are the reduction of global GHG emissions and a contribution to sustainable development in the host country. The guidelines and procedures detailed by the United Nations Framework Convention on Climate Change (UN FCCC) and the related Protocols and Accords, were followed in the preparation of this document. Recommendations based on e7 experience were also included. The criteria for success were stated, and additionality was discussed. Additionality refers to the reductions of emissions that are additional to any that would occur in the absence of the certified project activity. The baseline methodology was described. Project Design Document (PDD) is the format that must be used for presenting the information pertaining to a project and its evaluation. PDD contents include: general description of the project activity, baseline methodology, identification of crediting period, monitoring methodology and plan, calculation of GHG emissions by sources, environmental impacts, and stakeholder comments. Third party verification, and project risk and transaction costs were also addressed. refs., tabs., figs

  11. Frugivorous birds influence the spatial organization of tropical forests through the generation of seedling recruitment foci under zoochoric trees

    Science.gov (United States)

    Trolliet, Franck; Forget, Pierre-Michel; Doucet, Jean-Louis; Gillet, Jean-François; Hambuckers, Alain

    2017-11-01

    Animal-mediated seed dispersal is recognized to influence the spatial organization of plant communities but little is known about how frugivores cause such patterns. Here, we explored the role of hornbills and primates in generating recruitment foci under two zoochoric trees, namely Staudtia kamerunensis (Myristicaceae) and Dialium spp. (Fabaceae - Caesalpiniodea) in a forest-savanna mosaic landscape in D.R. Congo. We also examined the influence of the availability of fruits in the neighborhood and the amount of forest cover in the landscape on such clumping patterns. The density and species richness of hornbill-dispersed and the density of primate-dispersed seedlings were significantly higher under Staudtia kamerunensis trees than at control locations. However, we did not find such patterns under Dialium spp. trees compared to control locations except for the density of hornbill-dispersed seedlings which was lower at control locations. Also, we found that an increasing amount of forest cover in the landscape was associated with an increase in the density of hornbill-dispersed seedlings, although the tendency was weak (R2 = 0.065). We concluded that S. kamerunensis acts as a recruitment foci and plays a structuring role in Afrotropical forests. Hornbills were probably the main frugivore taxon responsible for the clumping under that tree and appear as a key ecological component in fragmented and disturbed landscapes where the diversity of large frugivores such as primates is reduced. Our findings improve our understanding of the causal mechanisms responsible for the spatial organization of tropical forests.

  12. Air-coupled acoustic radiation force for non-contact generation of broadband mechanical waves in soft media

    Energy Technology Data Exchange (ETDEWEB)

    Ambroziński, Łukasz [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); AGH University of Science and Technology, Krakow 30059 (Poland); Pelivanov, Ivan, E-mail: ivanp3@uw.edu [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Faculty of Physics, Moscow State University, Moscow 119991 (Russian Federation); Song, Shaozhen; Yoon, Soon Joon; Gao, Liang; O' Donnell, Matthew [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Li, David [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Chemical Engineering, University of Washington Seattle, Washington 98195 (United States); Shen, Tueng T.; Wang, Ruikang K. [Department of Bioengineering, University of Washington, Seattle, Washington 98195 (United States); Department of Ophthalmology, University of Washington, Seattle, Washington 98104 (United States)

    2016-07-25

    A non-contact method for efficient, non-invasive excitation of mechanical waves in soft media is proposed, in which we focus an ultrasound (US) signal through air onto the surface of a medium under study. The US wave reflected from the air/medium interface provides radiation force to the medium surface that launches a transient mechanical wave in the transverse (lateral) direction. The type of mechanical wave is determined by boundary conditions. To prove this concept, a home-made 1 MHz piezo-ceramic transducer with a matching layer to air sends a chirped US signal centered at 1 MHz to a 1.6 mm thick gelatin phantom mimicking soft biological tissue. A phase-sensitive (PhS)-optical coherence tomography system is used to track/image the mechanical wave. The reconstructed transient displacement of the mechanical wave in space and time demonstrates highly efficient generation, thus offering great promise for non-contact, non-invasive characterization of soft media, in general, and for elasticity measurements in delicate soft tissues and organs in bio-medicine, in particular.

  13. Investment in hydrogen tri-generation for wastewater treatment plants under uncertainties

    Science.gov (United States)

    Gharieh, Kaveh; Jafari, Mohsen A.; Guo, Qizhong

    2015-11-01

    In this article, we present a compound real option model for investment in hydrogen tri-generation and onsite hydrogen dispensing systems for a wastewater treatment plant under price and market uncertainties. The ultimate objective is to determine optimal timing and investment thresholds to exercise initial and subsequent options such that the total savings are maximized. Initial option includes investment in a 1.4 (MW) Molten Carbonate Fuel Cell (MCFC) fed by mixture of waste biogas from anaerobic digestion and natural gas, along with auxiliary equipment. Produced hydrogen in MCFC via internal reforming, is recovered from the exhaust gas stream using Pressure Swing Adsorption (PSA) purification technology. Therefore the expansion option includes investment in hydrogen compression, storage and dispensing (CSD) systems which creates additional revenue by selling hydrogen onsite in retail price. This work extends current state of investment modeling within the context of hydrogen tri-generation by considering: (i) Modular investment plan for hydrogen tri-generation and dispensing systems, (ii) Multiple sources of uncertainties along with more realistic probability distributions, (iii) Optimal operation of hydrogen tri-generation is considered, which results in realistic saving estimation.

  14. Modeling and solving a large-scale generation expansion planning problem under uncertainty

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Shan; Ryan, Sarah M. [Iowa State University, Department of Industrial and Manufacturing Systems Engineering, Ames (United States); Watson, Jean-Paul [Sandia National Laboratories, Discrete Math and Complex Systems Department, Albuquerque (United States); Woodruff, David L. [University of California Davis, Graduate School of Management, Davis (United States)

    2011-11-15

    We formulate a generation expansion planning problem to determine the type and quantity of power plants to be constructed over each year of an extended planning horizon, considering uncertainty regarding future demand and fuel prices. Our model is expressed as a two-stage stochastic mixed-integer program, which we use to compute solutions independently minimizing the expected cost and the Conditional Value-at-Risk; i.e., the risk of significantly larger-than-expected operational costs. We introduce stochastic process models to capture demand and fuel price uncertainty, which are in turn used to generate trees that accurately represent the uncertainty space. Using a realistic problem instance based on the Midwest US, we explore two fundamental, unexplored issues that arise when solving any stochastic generation expansion model. First, we introduce and discuss the use of an algorithm for computing confidence intervals on obtained solution costs, to account for the fact that a finite sample of scenarios was used to obtain a particular solution. Second, we analyze the nature of solutions obtained under different parameterizations of this method, to assess whether the recommended solutions themselves are invariant to changes in costs. The issues are critical for decision makers who seek truly robust recommendations for generation expansion planning. (orig.)

  15. Determination of tritium generation and release parameters at lithium CPS under neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ponkratov, Yuriy, E-mail: ponkratov@nnc.kz [Institute of Atomic Energy, National Nuclear Center of RK, Kurchatov (Kazakhstan); Baklanov, Viktor; Skakov, Mazhyn; Kulsartov, Timur; Tazhibayeva, Irina; Gordienko, Yuriy; Zaurbekova, Zhanna; Tulubayev, Yevgeniy [Institute of Atomic Energy, National Nuclear Center of RK, Kurchatov (Kazakhstan); Chikhray, Yevgeniy [Institute of Experimental and Theoretical Physics of Kazakh National University, Almaty (Kazakhstan); Lyublinski, Igor [JSC “Star”, Moscow (Russian Federation); NRNU “MEPhI”, Moscow (Russian Federation); Vertkov, Alexey [JSC “Star”, Moscow (Russian Federation)

    2016-11-01

    Highlights: • The main parameters of tritium generation and release from lithium capillary-porous system (CPS) under neutron irradiation at the IVG.1 M research reactor is described in paper. • In the experiments a very small tritium release was fixed likely due to its high solubility in liquid lithium. • If the lithium CPS will be used as a plasma facing material in temperature range up to 773 K under neutron irradiation only helium will release from lithium CPS into a vacuum chamber. - Abstract: This paper describes the main parameters of tritium generation and release from lithium capillary-porous system (CPS) under neutron irradiation at the IVG.1 M research reactor. The experiments were carried out using the method of mass-spectrometric registration of released gases and using a specially constructed ampoule device. Irradiation was carried out at different reactor thermal powers (1, 2 and 6 MW) and sample temperatures from 473 to 773 K. In the experiments a very small tritium release was detected likely due to its high solubility in liquid lithium. It can be caused by formation of lithium tritide during tritium diffusion to the lithium surface.

  16. Performance of droplet generator and droplet collector in liquid droplet radiator under microgravity

    Science.gov (United States)

    Totani, T.; Itami, M.; Nagata, H.; Kudo, I.; Iwasaki, A.; Hosokawa, S.

    2002-06-01

    The Liquid Droplet Radiator (LDR) has an advantage over comparable conventional radiators in terms of the rejected heat power-weight ratio. Therefore, the LDR has attracted attention as an advanced radiator for high-power space systems that will be prerequisite for large space structures. The performance of the LDR under microgravity condition has been studied from the viewpoint of operational space use of the LDR in the future. In this study, the performances of a droplet generator and a droplet collector in the LDR are investigated using drop shafts in Japan: MGLAB and JAMIC. As a result, it is considered that (1) the droplet generator can produce uniform droplet streams in the droplet diameter range from 200 to 280 [µm] and the spacing range from 400 to 950 [µm] under microgravity condition, (2) the droplet collector with the incidence angle of 35 degrees can prevent a uniform droplet stream, in which droplet diameter is 250 [µm] and the velocity is 16 [m/s], from splashing under microgravity condition, whereas splashes may occur at the surface of the droplet collector in the event that a nonuniform droplet stream collides against it.

  17. Generation and Evolution of Chaos in Double-Well Duffing Oscillator under Parametrical Excitation

    Directory of Open Access Journals (Sweden)

    Ying Zhang

    2016-01-01

    Full Text Available The generation and evolution of chaotic motion in double-well Duffing oscillator under harmonic parametrical excitation are investigated. Firstly, the complex dynamical behaviors are studied by applying multibifurcation diagram and Poincaré sections. Secondly, by means of Melnikov’s approach, the threshold value of parameter μ for generation of chaotic behavior in Smale horseshoe sense is calculated. By the numerical simulation, it is obvious that as μ exceeds this threshold value, the behavior of Duffing oscillator is still steady-state periodic but the transient motion is chaotic; until the top Lyapunov exponent turns to positive, the motion of system turns to permanent chaos. Therefore, in order to gain an insight into the evolution of chaotic behavior after μ passing the threshold value, the transient motion, basin of attraction, and basin boundary are also investigated.

  18. Microbial Gas Generation Under Expected Waste Isolation Pilot Plant Repository Conditions: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Gillow, J.B.; Francis, A.

    2011-07-01

    Gas generation from the microbial degradation of the organic constituents of transuranic (TRU) waste under conditions expected in the Waste Isolation Pilot Plant (WIPP) was investigated. The biodegradation of mixed cellulosic materials and electron-beam irradiated plastic and rubber materials (polyethylene, polyvinylchloride, hypalon, leaded hypalon, and neoprene) was examined. We evaluated the effects of environmental variables such as initial atmosphere (air or nitrogen), water content (humid ({approx}70% relative humidity, RH) and brine inundated), and nutrient amendments (nitogen phosphate, yeast extract, and excess nitrate) on microbial gas generation. Total gas production was determined by pressure measurement and carbon dioxide (CO{sub 2}) and methane (CH{sub 4}) were analyzed by gas chromatography; cellulose degradation products in solution were analyzed by high-performance liquid chromatography. Microbial populations in the samples were determined by direct microscopy and molecular analysis. The results of this work are summarized.

  19. Microbial Gas Generation Under Expected Waste Isolation Pilot Plant Repository Conditions: Final Report

    International Nuclear Information System (INIS)

    Gillow, J.B.; Francis, A.

    2011-01-01

    Gas generation from the microbial degradation of the organic constituents of transuranic (TRU) waste under conditions expected in the Waste Isolation Pilot Plant (WIPP) was investigated. The biodegradation of mixed cellulosic materials and electron-beam irradiated plastic and rubber materials (polyethylene, polyvinylchloride, hypalon, leaded hypalon, and neoprene) was examined. We evaluated the effects of environmental variables such as initial atmosphere (air or nitrogen), water content (humid (∼70% relative humidity, RH) and brine inundated), and nutrient amendments (nitogen phosphate, yeast extract, and excess nitrate) on microbial gas generation. Total gas production was determined by pressure measurement and carbon dioxide (CO 2 ) and methane (CH 4 ) were analyzed by gas chromatography; cellulose degradation products in solution were analyzed by high-performance liquid chromatography. Microbial populations in the samples were determined by direct microscopy and molecular analysis. The results of this work are summarized.

  20. Automatic generation control of TCPS based hydrothermal system under open market scenario: A fuzzy logic approach

    Energy Technology Data Exchange (ETDEWEB)

    Rao, C. Srinivasa [EEE Department, G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh (India); Nagaraju, S. Siva [EEE Department, J.N.T.U College of Engg., Kakinada, Andhra Pradesh (India); Raju, P. Sangameswara [EEE Department, S.V. University, Tirupati, Andhra Pradesh (India)

    2009-09-15

    This paper presents the analysis of automatic generation control of a two-area interconnected thyristor controlled phase shifter based hydrothermal system in the continuous mode using fuzzy logic controller under open market scenario. Open transmission access and the evolving of more socialized companies for generation, transmission and distribution affects the formulation of AGC problem. So the traditional AGC two-area system is modified to take into account the effect of bilateral contracts on the dynamics. It is possible to stabilize the system frequency and tie-power oscillations by controlling the phase angle of TCPS which is expected to provide a new ancillary service for the future power systems. A control strategy using TCPS is proposed to provide active control of system frequency. Further dynamic responses for small perturbation considering fuzzy logic controller and PI controller (dual mode controller) have been observed and the superior performance of fuzzy logic controller has been reported analytically and also through simulation. (author)

  1. Effects of the components in rice flour on thermal radical generation under microwave irradiation.

    Science.gov (United States)

    Lin, Lufen; Huang, Luelue; Fan, Daming; Hu, Bo; Gao, Yishu; Lian, Huizhang; Zhao, Jianxin; Zhang, Hao; Chen, Wei

    2016-12-01

    The relationships between radical generation under microwave irradiation and the components of various types of rice flour were investigated. Electron paramagnetic resonance (EPR) spectroscopy was used to characterize the radicals found in rice flour samples. The EPR spectra revealed that several types of radical (carbon-centered, tyrosyl and semiquinone) were localized in the starch and protein fractions of the rice flour. The signal intensity of the free radicals was observed to increase exponentially with increasing microwave power and residence time. The rice bran samples exhibited the greatest free radical signal intensity, followed by the brown rice samples and the white rice samples. This finding was consistent for both the native and the microwaved samples. The ratio of rice starch to rice protein also played an important role in the generation of radicals. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. The Generating Mechanism of the Perlocutionary Effects of Train Manner Posters

    OpenAIRE

    水田, 洋子

    2013-01-01

    Manner posters, which are used for the purpose of improving people’s manners in public spaces, attempt to be effective without being impositional. How do they meet the challenge? Manner posters can be considered to perform speech acts with written words and visual devices. The current work investigates the generating mechanism of their perlocutionary effects such as persuasion. It provides a case study of Japanese train manner posters by Tokyo Metro in 2008-2010. The analysis is conducted wit...

  3. The many-body content of quantum gauge theories and its connection to mass generation mechanisms

    International Nuclear Information System (INIS)

    Natoli, C.R.; Palumbo, F.

    1985-01-01

    The aim of the paper is to get more knowledge about many-body systems and their properties, about many-body content of quantum gauge theories and its connection with mass generation mechanisms. The way to achieve this is to perform the galilean limit of the relativistic theory by sending the speed of light c to infinity. This limiting process exposes the low energy behaviour of the relativistic theory

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

    Science.gov (United States)

    Kannan, C.; Ramanujam, R.

    2018-05-01

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

  5. CFD Analysis of Random Turbulent Flow Load in Steam Generator of APR1400 Under Normal Operation Condition

    International Nuclear Information System (INIS)

    Lim, Sang Gyu; You, Sung Chang; Kim, Han Gon

    2011-01-01

    Regulatory guide 1.20 revision 3 of the Nuclear Regulatory Committee (NRC) modifies guidance for vibration assessments of reactor internals and steam generator internals. The new guidance requires applicants to provide a preliminary analysis and evaluation of the design and performance of a facility, including the safety margins of during normal operation and transient conditions anticipated during the life of the facility. Especially, revision 3 require rigorous assessments of adverse flow effects in the steam dryer cased by flow-excited acoustic and structural resonances such as the abnormality from power-uprated BWR cases. For two nearly identical nuclear power plants, the steam system of one BWR plant experienced failure of steam dryers and the main steam system components when steam flow was increased by 16 percent for extended power uprate (EPU). The mechanisms of those failures have revealed that a small adverse flow changing from the prototype condition induced severe flow-excited acoustic and structural resonances, leading to structural failures. In accordance with the historical background, therefore, potential adverse flow effects should be evaluated rigorously for steam generator internals in both BWR and Pressurized Water Reactor (PWR). The Advanced Power Reactor 1400 (APR1400), an evolutionary light water reactor, increased the power by 7.7 percent from the design of the 'Valid Prototype', System80+. Thus, reliable evaluations of potential adverse flow effects on the steam generator of APR1400 are necessary according to the regulatory guide. This paper is part of the computational fluid dynamics (CFD) analysis results for evaluation of the adverse flow effect for the steam generator internals of APR1400, including a series of sensitivity analyses to enhance the reliability of CFD analysis and an estimation the effect of flow loads on the internals of the steam generator under normal operation conditions

  6. Native Cellulose Microfiber-Based Hybrid Piezoelectric Generator for Mechanical Energy Harvesting Utility.

    Science.gov (United States)

    Alam, Md Mehebub; Mandal, Dipankar

    2016-01-27

    A flexible hybrid piezoelectric generator (HPG) based on native cellulose microfiber (NCMF) and polydimethylsiloxane (PDMS) with multi wall carbon nanotubes (MWCNTs) as conducting filler is presented where the further chemical treatment of the cellulose and traditional electrical poling steps for piezoelectric voltage generation is avoided. It delivers a high electrical throughput that is an open circuit voltage of ∼30 V and power density ∼9.0 μW/cm(3) under repeated hand punching. We demonstrate to power up various portable electronic units by HPG. Because cellulose is a biocompatible material, suggesting that HPG may have greater potential in biomedical applications such as implantable power source in human body.

  7. Photocatalytic hydrogen generation from water under visible light using core/shell nano-catalysts.

    Science.gov (United States)

    Wang, X; Shih, K; Li, X Y

    2010-01-01

    A microemulsion technique was employed to synthesize nano-sized photocatalysts with a core (CdS)/shell (ZnS) structure. The primary particles of the photocatalysts were around 10 nm, and the mean size of the catalyst clusters in water was about 100 nm. The band gaps of the catalysts ranged from 2.25 to 2.46 eV. The experiments of photocatalytic H(2) generation showed that the catalysts (CdS)(x)/(ZnS)(1-x) with x ranging from 0.1 to 1 were able to produce hydrogen from water photolysis under visible light. The catalyst with x=0.9 had the highest rate of hydrogen production. The catalyst loading density also influenced the photo-hydrogen production rate, and the best catalyst concentration in water was 1 g L(-1). The stability of the nano-catalysts in terms of size, morphology and activity was satisfactory during an extended test period for a specific hydrogen production rate of 2.38 mmol g(-1) L(-1) h(-1) and a quantum yield of 16.1% under visible light (165 W Xe lamp, lambda>420 nm). The results demonstrate that the (CdS)/(ZnS) core/shell nano-particles are a novel photo-catalyst for renewable hydrogen generation from water under visible light. This is attributable to the large band-gap ZnS shell that separates the electron/hole pairs generated by the CdS core and hence reduces their recombinations.

  8. Role of dissolved oxygen on the degradation mechanism of Reactive Green 19 and electricity generation in photocatalytic fuel cell.

    Science.gov (United States)

    Lee, Sin-Li; Ho, Li-Ngee; Ong, Soon-An; Wong, Yee-Shian; Voon, Chun-Hong; Khalik, Wan Fadhilah; Yusoff, Nik Athirah; Nordin, Noradiba

    2018-03-01

    In this study, a membraneless photocatalytic fuel cell with zinc oxide loaded carbon photoanode and platinum loaded carbon cathode was constructed to investigate the impact of dissolved oxygen on the mechanism of dye degradation and electricity generation of photocatalytic fuel cell. The photocatalytic fuel cell with high and low aeration rate, no aeration and nitrogen purged were investigated, respectively. The degradation rate of diazo dye Reactive Green 19 and the electricity generation was enhanced in photocatalytic fuel cell with higher dissolved oxygen concentration. However, the photocatalytic fuel cell was still able to perform 37% of decolorization in a slow rate (k = 0.033 h -1 ) under extremely low dissolved oxygen concentration (approximately 0.2 mg L -1 ) when nitrogen gas was introduced into the fuel cell throughout the 8 h. However, the change of the UV-Vis spectrum indicates that the intermediates of the dye could not be mineralized under insufficient dissolved oxygen level. In the aspect of electricity generation, the maximum short circuit current (0.0041 mA cm -2 ) and power density (0.00028 mW cm -2 ) of the air purged photocatalytic fuel cell was obviously higher than that with nitrogen purging (0.0015 mA cm -2 and 0.00008 mW cm -2 ). Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Various bio-mechanical factors affecting heat generation during osteotomy preparation: A systematic review.

    Science.gov (United States)

    Chauhan, Chirag J; Shah, Darshana N; Sutaria, Foram B

    2018-01-01

    As implant site preparation and bone are critical precursors to primary healing, thermal and mechanical damage to the bone must be minimized during the preparation of the implant site. Moreover, excessively traumatic surgery can adversely affect the maturation of bone tissue at the bone/implant interface and consequently diminish the predictability of osseointegration. So, this study was carried out to evaluate the various biological and mechanical factors responsible for heat generation during osteotomy site preparation to reduce the same for successful osseointegration of dental implants. A broad search of the dental literature in PubMed added by manual search was performed for articles published between 1992 and December 2015. Various bio-mechanical factors related to dental implant osteotomy preparation such as dental implant drill designs/material/wear, drilling methods, type of irrigation, and bone quality were reviewed. Titles and abstracts were screened and articles which fulfilled the inclusion criteria were selected for a full-text reading. The initial database search yielded 123 titles, of which 59 titles were discarded after reading the titles and abstracts, 30 articles were again excluded based on inclusion and exclusion criteria, and finally 34 articles were selected for data extraction. Many biological and mechanical factors responsible for heat generation were found. Literatures of this review study have indicated that there are various bio-mechanical reasons, which affect the temperature rise during osteotomy and suggest that the amount of heat generation is a multifactorial in nature and it should be minimized for better primary healing of the implant site.

  10. Behavior of hybrid concentrated photovoltaic-thermoelectric generator under variable solar radiation

    DEFF Research Database (Denmark)

    Mahmoudi Nezhad, Sajjad; Rezaniakolaei, Alireza; Rosendahl, Lasse Aistrup

    2018-01-01

    diversely versus changing the solar radiation and module temperature. Moreover, the thermal response of the TEG stabilizes temperature fluctuation of the hybrid module when the solar radiation rapidly changes. In this work, impact of the thermal contact resistance on the temperature profile and system...... and solved by finite volume algorithm. In spite of temperatures profile in the hybrid CPV-TEG module, as results of variation of solar irradiation, power generation and efficiency of the CPV and TEG under the transient condition are presented. The results show that efficiency of the TEG and CPV varies...

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

    International Nuclear Information System (INIS)

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

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-05-10

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

  13. Temporal evolution of a granitic rock under thermal loads generated by fission products

    International Nuclear Information System (INIS)

    Ventura, M.A.; Ferreri, J.C.

    1985-01-01

    The thermal time history of a granitic mass under thermal loads, generated by the terminal subproducts arising from the Argentine nuclear programme is analyzed. This rock will be the final repository of those subproducts. The analysis is based on the consideration of a representative unit cell of the rock's centre using the Heating 5 programme. A preliminary analysis is made in order to obtain criteria with respect to the accuracy of the problem. Temporal evolution curves of the temperature on zones of interest of the unit cell considered are shown. Under the thermal loads considered, 500W by container, a maximum temperature of 55 deg C at the wall of the orifice subproducts' deposit is obtained. (Author) [es

  14. Ab initio Algorithmic Causal Deconvolution of Intertwined Programs and Networks by Generative Mechanism

    KAUST Repository

    Zenil, Hector

    2018-02-18

    To extract and learn representations leading to generative mechanisms from data, especially without making arbitrary decisions and biased assumptions, is a central challenge in most areas of scientific research particularly in connection to current major limitations of influential topics and methods of machine and deep learning as they have often lost sight of the model component. Complex data is usually produced by interacting sources with different mechanisms. Here we introduce a parameter-free model-based approach, based upon the seminal concept of Algorithmic Probability, that decomposes an observation and signal into its most likely algorithmic generative mechanisms. Our methods use a causal calculus to infer model representations. We demonstrate the method ability to distinguish interacting mechanisms and deconvolve them, regardless of whether the objects produce strings, space-time evolution diagrams, images or networks. We numerically test and evaluate our method and find that it can disentangle observations from discrete dynamic systems, random and complex networks. We think that these causal inference techniques can contribute as key pieces of information for estimations of probability distributions complementing other more statistical-oriented techniques that otherwise lack model inference capabilities.

  15. Sum frequency generation image reconstruction: Aliphatic membrane under spherical cap geometry

    Energy Technology Data Exchange (ETDEWEB)

    Volkov, Victor [Bereozovaya 2A, Konstantinovo, Moscow Region 140207 (Russian Federation)

    2014-10-07

    The article explores an opportunity to approach structural properties of phospholipid membranes using Sum Frequency Generation microscopy. To establish the principles of sum frequency generation image reconstruction in such systems, at first approach, we may adopt an idealistic spherical cap uniform assembly of hydrocarbon molecules. Quantum mechanical studies for decanoic acid (used here as a representative molecular system) provide necessary information on transition dipole moments and Raman tensors of the normal modes specific to methyl terminal – a typical moiety in aliphatic (and phospholipid) membranes. Relative degree of localization and frequencies of the normal modes of methyl terminals make nonlinearities of this moiety to be promising in structural analysis using Sum Frequency Generation imaging. Accordingly, the article describes derivations of relevant macroscopic nonlinearities and suggests a mapping procedure to translate amplitudes of the nonlinearities onto microscopy image plane according to geometry of spherical assembly, local molecular orientation, and optical geometry. Reconstructed images indicate a possibility to extract local curvature of bilayer envelopes of spherical character. This may have practical implications for structural extractions in membrane systems of practical relevance.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

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

  17. Effect of vortex generators on the closing transient flow of bileaflet mechanical heart valves

    Science.gov (United States)

    Murphy, David; Dasi, Lakshmi; Yoganathan, Ajit; Glezer, Ari

    2006-11-01

    The time-periodic closing of bileaflet mechanical heart valves is accompanied by a strong flow transient that is associated with the formation of a counter-rotating vortex pair near the b-datum line of leaflet edges. The strong transitory shear that is generated by these vortices may be damaging to blood elements and may result in platelet activation. In the present work, these flow transients are mitigated using miniature vortex generator arrays that are embedded on the surface of the leaflets. Two vortex generator designs were investigated: one design comprised staggered rectangular fins and the other one staggered hemispheres. The closing transients in the absence and presence of the passive vortex generators are characterized using phase locked PIV measurements. The study utilizes a 25 mm St. Jude Medical valve placed in the aortic position of the Georgia Tech left heart simulator. Measurements of the velocity field in the center plane of the leaflets demonstrate that the dynamics of the transient vortices that precede the formation of the leakage jets can be significantly altered and controlled by relatively simple passive modifications of existing valve designs. Human blood experiments validated the effectiveness of miniature vortex generators in reducing thrombus formation by over 42 percent.

  18. 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

  19. Composite Materials under Extreme Radiation and Temperature Environments of the Next Generation Nuclear Reactors

    International Nuclear Information System (INIS)

    Simos, N.

    2011-01-01

    In the nuclear energy renaissance, driven by fission reactor concepts utilizing very high temperatures and fast neutron spectra, materials with enhanced performance that exceeds are expected to play a central role. With the operating temperatures of the Generation III reactors bringing the classical reactor materials close to their performance limits there is an urgent need to develop and qualify new alloys and composites. Efforts have been focused on the intricate relations and the high demands placed on materials at the anticipated extreme states within the next generation fusion and fission reactors which combine high radiation fluxes, elevated temperatures and aggressive environments. While nuclear reactors have been in operation for several decades, the structural materials associated with the next generation options need to endure much higher temperatures (1200 C), higher neutron doses (tens of displacements per atom, dpa), and extremely corrosive environments, which are beyond the experience on materials accumulated to-date. The most important consideration is the performance and reliability of structural materials for both in-core and out-of-core functions. While there exists a great body of nuclear materials research and operating experience/performance from fission reactors where epithermal and thermal neutrons interact with materials and alter their physio-mechanical properties, a process that is well understood by now, there are no operating or even experimental facilities that will facilitate the extreme conditions of flux and temperature anticipated and thus provide insights into the behaviour of these well understood materials. Materials, however, still need to be developed and their interaction and damage potential or lifetime to be quantified for the next generation nuclear energy. Based on material development advances, composites, and in particular ceramic composites, seem to inherently possess properties suitable for key functions within the

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

    Directory of Open Access Journals (Sweden)

    Wanlei Liu

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

  1. Generation of blue chrysanthemums by anthocyanin B-ring hydroxylation and glucosylation and its coloration mechanism.

    Science.gov (United States)

    Noda, Naonobu; Yoshioka, Satoshi; Kishimoto, Sanae; Nakayama, Masayoshi; Douzono, Mitsuru; Tanaka, Yoshikazu; Aida, Ryutaro

    2017-07-01

    Various colored cultivars of ornamental flowers have been bred by hybridization and mutation breeding; however, the generation of blue flowers for major cut flower plants, such as roses, chrysanthemums, and carnations, has not been achieved by conventional breeding or genetic engineering. Most blue-hued flowers contain delphinidin-based anthocyanins; therefore, delphinidin-producing carnation, rose, and chrysanthemum flowers have been generated by overexpression of the gene encoding flavonoid 3',5'-hydroxylase (F3'5'H), the key enzyme for delphinidin biosynthesis. Even so, the flowers are purple/violet rather than blue. To generate true blue flowers, blue pigments, such as polyacylated anthocyanins and metal complexes, must be introduced by metabolic engineering; however, introducing and controlling multiple transgenes in plants are complicated processes. We succeeded in generating blue chrysanthemum flowers by introduction of butterfly pea UDP (uridine diphosphate)-glucose:anthocyanin 3',5'- O -glucosyltransferase gene, in addition to the expression of the Canterbury bells F3'5'H . Newly synthesized 3',5'-diglucosylated delphinidin-based anthocyanins exhibited a violet color under the weakly acidic pH conditions of flower petal juice and showed a blue color only through intermolecular association, termed "copigmentation," with flavone glucosides in planta. Thus, we achieved the development of blue color by a two-step modification of the anthocyanin structure. This simple method is a promising approach to generate blue flowers in various ornamental plants by metabolic engineering.

  2. PHYSIOLOGICAL QUALITY OF SOYBEAN SEEDS UNDER MECHANICAL INJURIES CAUSED BY COMBINES

    OpenAIRE

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

    2015-01-01

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

  3. Uncovering the underlying physical mechanisms of biological systems via quantification of landscape and flux

    International Nuclear Information System (INIS)

    Xu Li; Chu Xiakun; Yan Zhiqiang; Zheng Xiliang; Zhang Kun; Zhang Feng; Yan Han; Wu Wei; Wang Jin

    2016-01-01

    In this review, we explore the physical mechanisms of biological processes such as protein folding and recognition, ligand binding, and systems biology, including cell cycle, stem cell, cancer, evolution, ecology, and neural networks. Our approach is based on the landscape and flux theory for nonequilibrium dynamical systems. This theory provides a unifying principle and foundation for investigating the underlying mechanisms and physical quantification of biological systems. (topical review)

  4. Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

    International Nuclear Information System (INIS)

    Kenne, Godpromesse; Goma, Raphael; Nkwawo, Homere; Lamnabhi-Lagarrigue, Francoise; Arzande, Amir; Vannier, Jean Claude

    2010-01-01

    A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

  5. ASSESSMENT OF POTENTIAL TSUNAMI GENERATION IN CHINA'S BOHAI SEA FROM DIRECT GEOTECTONIC AND COLLATERAL SOURCE MECHANISMS

    Directory of Open Access Journals (Sweden)

    G. Pararas Carayannis

    2009-01-01

    Full Text Available The Bohai Sea borders northeastern China's most populous and highest economic valuecoastal areas where several megacities are located. Critical infrastructure facilities exist or areunder construction, including a nuclear power plant and super port facilities. Large reserves of oilhave been discovered and a number of offshore oil platforms have been built. The extent ofdevelopment along coastal areas requires a better assessment of potential tsunami risks. Althoughtsunamis do not pose as much of a threat as earthquakes in this region, locally destructive tsunamishave been generated in the past and future events could have significant impacts on coastalpopulations and China's economy, particularly because most of the development has taken place inlow-lying regions, including river deltas. The present study examines the geotectonics of the Bohaibasin region, the impact of past historical events, and the potential for local tsunami generationfrom a variety of direct and collateral source mechanisms triggered by intra plate earthquakes.More specifically, the present study examines: amajor active faults bounding the Bohai Basin; bthe resulting crustal deformation patterns of tectonic structures that have resulted in catastrophicearthquakes in recent years; c the basin-wide extension - with local inversion - extending into theBohai Sea that generated tsunamigenic earthquakes in 1888 and 1969; and d deformational futureseismic events with the potential to generate local tsunamis directly or by collateral mechanisms offolding, en-echelon bookshelf failures, or from destabilization/dissociation of structuralaccumulations of gas hydrate deposits within the basin's thick sedimentary stratigraphic layers.

  6. Fracture Mechanics Method for Word Embedding Generation of Neural Probabilistic Linguistic Model.

    Science.gov (United States)

    Bi, Size; Liang, Xiao; Huang, Ting-Lei

    2016-01-01

    Word embedding, a lexical vector representation generated via the neural linguistic model (NLM), is empirically demonstrated to be appropriate for improvement of the performance of traditional language model. However, the supreme dimensionality that is inherent in NLM contributes to the problems of hyperparameters and long-time training in modeling. Here, we propose a force-directed method to improve such problems for simplifying the generation of word embedding. In this framework, each word is assumed as a point in the real world; thus it can approximately simulate the physical movement following certain mechanics. To simulate the variation of meaning in phrases, we use the fracture mechanics to do the formation and breakdown of meaning combined by a 2-gram word group. With the experiments on the natural linguistic tasks of part-of-speech tagging, named entity recognition and semantic role labeling, the result demonstrated that the 2-dimensional word embedding can rival the word embeddings generated by classic NLMs, in terms of accuracy, recall, and text visualization.

  7. Fracture Mechanics Method for Word Embedding Generation of Neural Probabilistic Linguistic Model

    Directory of Open Access Journals (Sweden)

    Size Bi

    2016-01-01

    Full Text Available Word embedding, a lexical vector representation generated via the neural linguistic model (NLM, is empirically demonstrated to be appropriate for improvement of the performance of traditional language model. However, the supreme dimensionality that is inherent in NLM contributes to the problems of hyperparameters and long-time training in modeling. Here, we propose a force-directed method to improve such problems for simplifying the generation of word embedding. In this framework, each word is assumed as a point in the real world; thus it can approximately simulate the physical movement following certain mechanics. To simulate the variation of meaning in phrases, we use the fracture mechanics to do the formation and breakdown of meaning combined by a 2-gram word group. With the experiments on the natural linguistic tasks of part-of-speech tagging, named entity recognition and semantic role labeling, the result demonstrated that the 2-dimensional word embedding can rival the word embeddings generated by classic NLMs, in terms of accuracy, recall, and text visualization.

  8. Enhanced Efficiency of Thermoelectric Generator by Optimizing Mechanical and Electrical Structures

    Directory of Open Access Journals (Sweden)

    Jinlong Chen

    2017-09-01

    Full Text Available Much attention has been paid to the application of low temperature thermal resources, especially for power generation in recent years. Most of the current commercialized thermal (including geothermal power-generation technologies convert thermal energy to electric energy indirectly, that is, making mechanical work before producing electricity. Technology using a thermoelectric generator (TEG, however, can directly transform thermal energy into electricity through the Seebeck effect. TEG technology has many advantages such as compactness, quietness, and reliability because there are no moving parts. One of the biggest disadvantages of TEGs is the low efficiency from thermal to electric energy. For this reason, we redesigned and modified our previous 1 KW (at a temperature difference of around 120 °C TEG system. The output power of the system was improved significantly, about 34.6% greater; the instantaneous efficiency of the TEG system could reach about 6.5%. Laboratory experiments have been conducted to measure the output power at different conditions: different connection modes between TEG modules, different mechanical structures, and different temperature differences between hot and cold sides. The TEG apparatus has been tested and the data have been presented. This kind of TEG power system can be applied in many thermal and geothermal sites with low temperature resources, including oil fields where fossil and geothermal energies are coproduced.

  9. Real-time transient stabilization and voltage regulation of power generators with unknown mechanical power input

    Energy Technology Data Exchange (ETDEWEB)

    Kenne, Godpromesse, E-mail: gokenne@yahoo.co [Laboratoire d' Automatique et d' Informatique Appliquee (LAIA), Departement de Genie Electrique, Universite de Dschang, B.P. 134 Bandjoun (Cameroon); Goma, Raphael, E-mail: raphael.goma@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Nkwawo, Homere, E-mail: homere.nkwawo@iutv.univ-paris13.f [Departement GEII, Universite Paris XIII, 99 Avenue Jean Baptiste Clement, 93430 Villetaneuse (France); Lamnabhi-Lagarrigue, Francoise, E-mail: lamnabhi@lss.supelec.f [Laboratoire des Signaux et Systemes (L2S), CNRS-SUPELEC, Universite Paris XI, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Arzande, Amir, E-mail: Amir.arzande@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France); Vannier, Jean Claude, E-mail: Jean-claude.vannier@supelec.f [Departement Energie, Ecole Superieure d' Electricite-SUPELEC, 3 Rue Joliot Curie, 91192 Gif-sur-Yvette (France)

    2010-01-15

    A nonlinear adaptive excitation controller is proposed to enhance the transient stability and voltage regulation of synchronous generators with unknown power angle and mechanical power input. The proposed method is based on a standard third-order model of a synchronous generator which requires only information about the physical available measurements of relative angular speed, active electric power, infinite bus and generator terminal voltages. The operating conditions are computed online using the above physical available measurements, the terminal voltage reference value and the estimate of the mechanical power input. The proposed design is therefore capable of providing satisfactory voltage in the presence of unknown variations of the power system operating conditions. Using the concept of sliding mode equivalent control techniques, a robust decentralized adaptive controller which insures the exponential convergence of the outputs to the desired ones, is obtained. Real-time experimental results are reported, comparing the performance of the proposed adaptive nonlinear control scheme to one of the conventional AVR/PSS controller. The high simplicity of the overall adaptive control scheme and its robustness with respect to line impedance variation including critical unbalanced operating condition and temporary turbine fault, constitute the main positive features of the proposed approach.

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

    Science.gov (United States)

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

    2018-02-01

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

  11. Advanced modelling of doubly fed induction generator wind turbine under network disturbance

    DEFF Research Database (Denmark)

    Seman, S.; Iov, Florin; Niiranen, J.

    This paper presents a variable speed wind turbine simulator. The simulator is used for a 2 MW wind turbine transient behavior study during a short-term symmetrical network disturbance. The mechanical part of wind turbine model consists of the rotor aerodynamic model, the wind turbine control...... converter, the model of the main transformer and a simple model of the grid. The simulation results obtained by means of the detailed wind turbine model are compared with the results obtained from a simplified simulator with an analytical model and FEM model of DFIG. The comparison of the results shows...... and the drive train model. The Doubly Fed Induction Generator (DFIG) is represented by an analytical two-axis model with constant lumped parameters and by Finite Element Method (FEM) based model. The model of the DFIG is coupled with the model of the passive crowbar protected and DTC controlled frequency...

  12. Dye-sensitized solar cells for efficient power generation under ambient lighting

    Science.gov (United States)

    Freitag, Marina; Teuscher, Joël; Saygili, Yasemin; Zhang, Xiaoyu; Giordano, Fabrizio; Liska, Paul; Hua, Jianli; Zakeeruddin, Shaik M.; Moser, Jacques-E.; Grätzel, Michael; Hagfeldt, Anders

    2017-06-01

    Solar cells that operate efficiently under indoor lighting are of great practical interest as they can serve as electric power sources for portable electronics and devices for wireless sensor networks or the Internet of Things. Here, we demonstrate a dye-sensitized solar cell (DSC) that achieves very high power-conversion efficiencies (PCEs) under ambient light conditions. Our photosystem combines two judiciously designed sensitizers, coded D35 and XY1, with the copper complex Cu(II/I)(tmby) as a redox shuttle (tmby, 4,4‧,6,6‧-tetramethyl-2,2‧-bipyridine), and features a high open-circuit photovoltage of 1.1 V. The DSC achieves an external quantum efficiency for photocurrent generation that exceeds 90% across the whole visible domain from 400 to 650 nm, and achieves power outputs of 15.6 and 88.5 μW cm-2 at 200 and 1,000 lux, respectively, under illumination from a model Osram 930 warm-white fluorescent light tube. This translates into a PCE of 28.9%.

  13. Computational Models Describing Possible Mechanisms for Generation of Excessive Beta Oscillations in Parkinson's Disease.

    Directory of Open Access Journals (Sweden)

    Alex Pavlides

    2015-12-01

    Full Text Available In Parkinson's disease, an increase in beta oscillations within the basal ganglia nuclei has been shown to be associated with difficulty in movement initiation. An important role in the generation of these oscillations is thought to be played by the motor cortex and by a network composed of the subthalamic nucleus (STN and the external segment of globus pallidus (GPe. Several alternative models have been proposed to describe the mechanisms for generation of the Parkinsonian beta oscillations. However, a recent experimental study of Tachibana and colleagues yielded results which are challenging for all published computational models of beta generation. That study investigated how the presence of beta oscillations in a primate model of Parkinson's disease is affected by blocking different connections of the STN-GPe circuit. Due to a large number of experimental conditions, the study provides strong constraints that any mechanistic model of beta generation should satisfy. In this paper we present two models consistent with the data of Tachibana et al. The first model assumes that Parkinsonian beta oscillation are generated in the cortex and the STN-GPe circuits resonates at this frequency. The second model additionally assumes that the feedback from STN-GPe circuit to cortex is important for maintaining the oscillations in the network. Predictions are made about experimental evidence that is required to differentiate between the two models, both of which are able to reproduce firing rates, oscillation frequency and effects of lesions carried out by Tachibana and colleagues. Furthermore, an analysis of the models reveals how the amplitude and frequency of the generated oscillations depend on parameters.

  14. 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...

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

    International Nuclear Information System (INIS)

    1993-01-01

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

  16. Neural Mechanisms Underlying the Cost of Task Switching: An ERP Study

    Science.gov (United States)

    Li, Ling; Wang, Meng; Zhao, Qian-Jing; Fogelson, Noa

    2012-01-01

    Background When switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC). Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching. Methodology/Principal Findings An unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG) and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI) and cue-stimulus interval (CSI) were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs) and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP), and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA) for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC) and posterior parietal cortex (PPC). Conclusions/Significance The results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set. PMID:22860090

  17. Neural mechanisms underlying the cost of task switching: an ERP study.

    Directory of Open Access Journals (Sweden)

    Ling Li

    Full Text Available BACKGROUND: When switching from one task to a new one, reaction times are prolonged. This phenomenon is called switch cost (SC. Researchers have recently used several kinds of task-switching paradigms to uncover neural mechanisms underlying the SC. Task-set reconfiguration and passive dissipation of a previously relevant task-set have been reported to contribute to the cost of task switching. METHODOLOGY/PRINCIPAL FINDINGS: An unpredictable cued task-switching paradigm was used, during which subjects were instructed to switch between a color and an orientation discrimination task. Electroencephalography (EEG and behavioral measures were recorded in 14 subjects. Response-stimulus interval (RSI and cue-stimulus interval (CSI were manipulated with short and long intervals, respectively. Switch trials delayed reaction times (RTs and increased error rates compared with repeat trials. The SC of RTs was smaller in the long CSI condition. For cue-locked waveforms, switch trials generated a larger parietal positive event-related potential (ERP, and a larger slow parietal positivity compared with repeat trials in the short and long CSI condition. Neural SC of cue-related ERP positivity was smaller in the long RSI condition. For stimulus-locked waveforms, a larger switch-related central negative ERP component was observed, and the neural SC of the ERP negativity was smaller in the long CSI. Results of standardized low resolution electromagnetic tomography (sLORETA for both ERP positivity and negativity showed that switch trials evoked larger activation than repeat trials in dorsolateral prefrontal cortex (DLPFC and posterior parietal cortex (PPC. CONCLUSIONS/SIGNIFICANCE: The results provide evidence that both RSI and CSI modulate the neural activities in the process of task-switching, but that these have a differential role during task-set reconfiguration and passive dissipation of a previously relevant task-set.

  18. 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.

  19. Mechanical and microstructural stability of P92 steel under uniaxial tension at high temperature

    International Nuclear Information System (INIS)

    Giroux, P.F.; Dalle, F.; Sauzay, M.; Malaplate, J.; Fournier, B.; Gourgues-Lorenzon, A.F.

    2010-01-01

    9-12%Cr creep-resistant ferritic-martensitic steels are candidates for structural components of Generation IV nuclear power plants. However, they are sensitive to softening during low-cycle fatigue, creep and creep-fatigue tests, due to the destabilisation of the tempered martensite microstructure, possibly inducing a decrease in further creep resistance. To better identify the softening mechanisms in P92 steel during uniaxial deformation, tensile tests were carried out at 823 K, showing an extended and stable softening stage on true stress-strain curves after some work-hardening. Three phenomena were studied in order to understand this behaviour: mechanical instability (necking), damage and grain size evolution. Examination of fractured and non-fractured tensile specimens (light optical and electron microscopy, macrohardness) suggested that the physical mechanisms responsible for softening are mainly (sub)grain size evolution and diffuse necking. Models were proposed to predict grain growth and beginning of the mechanical instability during homogeneous deformation.

  20. Right-handed neutrinos at CERN LHC and the mechanism of neutrino mass generation

    International Nuclear Information System (INIS)

    Kersten, Joern; Smirnov, Alexei Yu.

    2007-01-01

    We consider the possibility to detect right-handed neutrinos, which are mostly singlets of the standard model gauge group, at future accelerators. Substantial mixing of these neutrinos with the active neutrinos requires a cancellation of different contributions to the light neutrino mass matrix at the level of 10 -8 . We discuss possible symmetries behind this cancellation and argue that for three right-handed neutrinos they always lead to conservation of total lepton number. Light neutrino masses can be generated by small perturbations violating these symmetries. In the most general case, LHC physics and the mechanism of neutrino mass generation are essentially decoupled; with additional assumptions, correlations can appear between collider observables and features of the neutrino mass matrix

  1. Enhanced Control for a Direct-driven Permanent Synchronous Generator Wind-power Generation System with Flywheel Energy Storage Unit Under Unbalanced Grid Fault

    DEFF Research Database (Denmark)

    Yao, Jun; Zhou, Te; Hu, Weihao

    2015-01-01

    This article presents an enhanced control strategy for a direct-driven permanent synchronous generator based wind-power generation system with a flywheel energy storage unit. The behaviors of the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit under......, the DC-link voltage oscillations can be effectively suppressed during the unbalanced grid fault by controlling the flywheel energy storage unit. Furthermore, a proportional–integral-resonant controller is designed for the flywheel motor to eliminate the oscillations in the DC-link voltage. Finally......, the proposed coordinated control strategy for the direct-driven permanent magnet synchronous generator system with a flywheel energy storage unit has been validated by the simulation results of a 1-MW direct-driven permanent magnet synchronous generator wind power generation system with a flywheel energy...

  2. Mechanisms Underlying Serotonergic Excitation of Callosal Projection Neurons in the Mouse Medial Prefrontal Cortex

    Directory of Open Access Journals (Sweden)

    Emily K. Stephens

    2018-01-01

    Full Text Available Serotonin (5-HT selectively excites subpopulations of pyramidal neurons in the neocortex via activation of 5-HT2A (2A receptors coupled to Gq subtype G-protein alpha subunits. Gq-mediated excitatory responses have been attributed primarily to suppression of potassium conductances, including those mediated by KV7 potassium channels (i.e., the M-current, or activation of non-specific cation conductances that underlie calcium-dependent afterdepolarizations (ADPs. However, 2A-dependent excitation of cortical neurons has not been extensively studied, and no consensus exists regarding the underlying ionic effector(s involved. In layer 5 of the mouse medial prefrontal cortex, we tested potential mechanisms of serotonergic excitation in commissural/callosal (COM projection neurons, a subpopulation of pyramidal neurons that exhibits 2A-dependent excitation in response to 5-HT. In baseline conditions, 5-HT enhanced the rate of action potential generation in COM neurons experiencing suprathreshold somatic current injection. This serotonergic excitation was occluded by activation of muscarinic acetylcholine (ACh receptors, confirming that 5-HT acts via the same Gq-signaling cascades engaged by ACh. Like ACh, 5-HT promoted the generation of calcium-dependent ADPs following spike trains. However, calcium was not necessary for serotonergic excitation, as responses to 5-HT were enhanced (by >100%, rather than reduced, by chelation of intracellular calcium with 10 mM BAPTA. This suggests intracellular calcium negatively regulates additional ionic conductances gated by 2A receptors. Removal of extracellular calcium had no effect when intracellular calcium signaling was intact, but suppressed 5-HT response amplitudes, by about 50%, when BAPTA was included in patch pipettes. This suggests that 2A excitation involves activation of a non-specific cation conductance that is both calcium-sensitive and calcium-permeable. M-current suppression was found to be a third

  3. Control mechanisms in the third-generation planning. Case study: Control to realize sustainable cities

    Science.gov (United States)

    Wicaksono, A. D.

    2017-06-01

    Since the last few years, Indonesia has experienced important events that bring significant changes to the social, political and economic life. The changes directly or indirectly impact the field of planning. With the challenging condition which grows fast and is more complex ahead, and the greater demands on the role of planning, it is required that planning should have higher quality. This paper seeks to answer some questions as follows: (i) How are changes in paradigm and also the development of planning model for the current transition era?, (ii) What is the best way to improve the quality of planning control on the last generation planning model to realize sustainable city?. Analysis steps that will be used to achieve the paper objectives are: (i) Review of planning and sustainable cities theory, (ii) Pattern recognition, (iii) Identifying control mechanisms and sustainable urban forms, (iv) conceptualization. Based on discussion about sustainable cities and control mechanism, some conclusions can be generated as follows: (i) The third generation planning model is based on the theory of expanded system, emphasizing on the constraint of capacity and the ability of planners within the context of larger environment, (ii) There are various theoretical studies that recommend prescriptive model or solution for sustainable urban form and structure. The concepts of Sustainable Cities can be grouped in Neotraditional Development, Urban Containment, Compact City and The Eco-City. The four models above have criteria, namely (i) high density; (ii) a high level of diversity; (iii) mixed land use; (iv) compactness; (5) sustainable transport; (6) passive solar design; (7) Greening Ecological Design. The three main activities in control mechanisms are: Monitoring and Recommendation; a comparative review of the facts (conditions that exist or are developing) with the purpose (expected conditions, set out in urban planning) and recommendations; Evaluation, a review on the

  4. Mechanisms of chemical vapor generation by aqueous tetrahydridoborate. Recent developments toward the definition of a more general reaction model

    Science.gov (United States)

    D'Ulivo, Alessandro

    2016-05-01

    A reaction model describing the reactivity of metal and semimetal species with aqueous tetrahydridoborate (THB) has been drawn taking into account the mechanism of chemical vapor generation (CVG) of hydrides, recent evidences on the mechanism of interference and formation of byproducts in arsane generation, and other evidences in the field of the synthesis of nanoparticles and catalytic hydrolysis of THB by metal nanoparticles. The new "non-analytical" reaction model is of more general validity than the previously described "analytical" reaction model for CVG. The non-analytical model is valid for reaction of a single analyte with THB and for conditions approaching those typically encountered in the synthesis of nanoparticles and macroprecipitates. It reduces to the previously proposed analytical model under conditions typically employed in CVG for trace analysis (analyte below the μM level, borane/analyte ≫ 103 mol/mol, no interference). The non-analytical reaction model is not able to explain all the interference effects observed in CVG, which can be achieved only by assuming the interaction among the species of reaction pathways of different analytical substrates. The reunification of CVG, the synthesis of nanoparticles by aqueous THB and the catalytic hydrolysis of THB inside a common frame contribute to rationalization of the complex reactivity of aqueous THB with metal and semimetal species.

  5. Population dynamics and current-generation mechanisms in cassette-electrode microbial fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Kazuya [ERATO/JST, Tokyo (Japan). Hashimoto Light Energy Conversion Project; Tokyo Univ. (Japan). Research Center for Advanced Science and Technology; Tokyo Univ. of Pharmacy and Life Sciences (Japan). School of Life Sciences; Miyahara, Morio [ERATO/JST, Tokyo (Japan). Hashimoto Light Energy Conversion Project; Shimoyama, Takefumi [Tokyo Univ. (Japan). Research Center for Advanced Science and Technology; Hashimoto, Kazuhito [ERATO/JST, Tokyo (Japan). Hashimoto Light Energy Conversion Project; Tokyo Univ. (Japan). Dept. of Applied Chemistry

    2011-12-15

    Cassette-electrode microbial fuel cells (CE-MFCs) have been demonstrated useful to treat biomass wastes and recover electric energy from them. In order to reveal electricity-generation mechanisms in CE-MFCs, the present study operated a bench-scale reactor (1 l in capacity; approximately 1,000 cm{sup 2} in anode and cathode areas) for treating a high-strength model organic wastewater (comprised of starch, peptone, and fish extract). Approximately 1 month was needed for the bench reactor to attain a stable performance, after which volumetric maximum power densities persisted between 120 and 150 mW/l throughout the experiment (for over 2 months). Temporal increases in the external resistance were found to induce subsequent increases in power outputs. After electric output became stable, electrolyte and anode were sampled from the reactor for evaluating their current-generation abilities; it was estimated that most of current (over 80%) was generated by microbes in the electrolyte. Cyclic voltammetry of an electrolyte supernatant detected several electron shuttles with different standard redox potentials at high concentrations (equivalent to or more than 100 {mu}M 5-hydroxy-1,4-naphthoquinone). Denaturing gradient gel electrophoresis and quantitative real-time PCR of 16S ribosomal RNA gene fragments showed that bacteria related to the genus Dysgonomonas occurred abundantly in association with the increases in power outputs. These results suggest that mediated electron transfer was the main mechanism for electricity generation in CE-MFC, where high-concentration electron shuttles and Dysgonomonas bacteria played important roles. (orig.)

  6. A study on the thermal and mechanical properties of inconel for steam generator U-tube

    International Nuclear Information System (INIS)

    Ryu, Woo Seong; Kang, Young Hwan; Park, Jong Man; Choo, Kee Nam; Kim, Sung Soo; Maeng, Wan Young; Park, Se Jin

    1993-12-01

    A series of laboratory tests was conducted to obtain the thermal and mechanical properties of Inconel 600 and 690 for the design document of steam generator U-tube. The following properties were measured as a function of temperature, and treated statistically to establish a database: 1) heat capacity, RT ∼ 500 deg C, 2) thermal expansion, RT ∼ 500 deg C, 3) thermal diffusivity, RT ∼ 500 deg C, 4) thermal conductivity, RT ∼ 500 deg C, 5) tensile property, RT ∼ 700 deg C 6) ductility, RT ∼ 700 deg C, 7) Elastic modulii and Poission's ratio, RT, 8) Microhardness, 9) Oxidation rate. (Author)

  7. Analytical and experimental studies of mechanical consequences of a steam generator tube rupture

    International Nuclear Information System (INIS)

    Duc, B.; Sudreau, F.; Rassineux, B.

    1995-01-01

    Concerning to steam generator tubes support mechanical loadings due to the impact f the ruptured one, Electricite de France, with the support of Commissariat a l'Energie. Atomique, has undertaken a large study in order to evaluate the consequences of such loadings. This paper first presents the results of the tests performed on AQUITAINE 2 facility (CEA Cadarache research center) for nominal, faulted and boiler effect conditions. Those results are then compared with numerical dynamic elastoplastic analyses performed with CASTEM 2000 code (CEA system). (author). 1 ref., 14 figs

  8. Study on tsunami damage mechanism in Fukushima Prefecture focusing on the generation of bores

    International Nuclear Information System (INIS)

    Okuma, Shohei; Sato, Shinji; Yamanaka, Yusuke; Sanuki, Hiroshi

    2015-01-01

    Destruction mechanisms of coastal structures due to the 2011 Tohoku Tsunami were investigated on the basis of field surveys in Fukushima Prefecture. Severe destruction appeared to be developed by the action of breaking bores. Laboratory experiments demonstrated that the angle of the tsunami front was an essential parameter for the generation of breaking bores. Larger wave force was observed as the angle of the tsunami front became steeper. Numerical simulation revealed that such a steep tsunami was developed in the central part of Fukushima Prefecture, where the reflection of the preceding tsunami by coastal cliff enhanced the steepness of the largest tsunami. (author)

  9. Application of probabilistic fracture mechanics to optimize the maintenance of PWR steam generator tubes

    International Nuclear Information System (INIS)

    Pitner, P.; Riffard, T.

    1993-09-01

    This paper describes the COMPROMIS code developed by Electricite de France (EDF) to optimize the tube bundle maintenance of steam generators (SG). The model, based on probabilistic fracture mechanics, makes it possible to quantify the influence of in-service inspections and maintenance work on the risk of an SG tube rupture, taking all significant parameters into account as random variables (initial defect size distribution, reliability of nondestructive detection and sizing, crack initiation and propagation, critical sizes, leak before risk of break, etc). (authors). 14 figs., 4 tabs., 12 refs

  10. Application of probabilistic fracture mechanics to estimate the risk of rupture of PWR steam generator tubes

    International Nuclear Information System (INIS)

    Pitner, P.; Riffard, T.; Granger, B.

    1992-01-01

    This paper describes the COMPROMIS code developed by Electricite de France (EDF) to optimize the tube bundle maintenance of steam generators. The model, based on probabilistic fracture mechanics, makes it possible to quantify the influence of in-service inspections and maintenance work on the risk of an SG tube rupture, taking all significant parameters into account as random variables (initial defect size distribution, reliability of non-destructive detection and sizing, crack initiation and propagation, critical sizes, leak before risk of break, etc.). (authors). 5 refs., 8 figs., 3 tabs

  11. Characteristics of semiconductor bridge (SCB) plasma generated in a micro-electro-mechanical system (MEMS)

    International Nuclear Information System (INIS)

    Kim, Jong-Uk; Park, Chong-Ook; Park, Myung-Il; Kim, Sun-Hwan; Lee, Jung-Bok

    2002-01-01

    Plasma ignition method has been applied in various fields particularly to the rocket propulsion, pyrotechnics, explosives, and to the automotive air-bag system. Ignition method for those applications should be safe and also operate reliably in hostile environments such as; electromagnetic noise, drift voltage, electrostatic background and so on. In the present Letter, a semiconductor bridge (SCB) plasma ignition device was fabricated and its plasma characteristics including the propagation speed of the plasma, plasma size, and plasma temperature were investigated with the aid of the visualization of micro scale plasma (i.e., ≤350 μm), which generated from a micro-electro-mechanical poly-silicon semiconductor bridge (SCB)

  12. Deteriorating mechanisms of electric generators; Mecanismos de deterioro de generadores electricos

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Tevillo, Arturo; Reyes Martinez, Oscar Alfonso; Robles Pimentel, Edgar Guillermo; Esparza Saucedo, Marcos; Lopez Azamar, Jose Ernesto; Medina Flores, Alfredo; Uribe Martinez, Manuel O [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1999-12-31

    It is of the greatest importance to know the deteriorating mechanisms that an electric generator undergoes, in order to take corrective measures to stop the process in order to avoid catastrophic damages that imply non scheduled interruptions for maintenance, or inclusively, to carry on the overhaul. In this paper are discussed the deteriorating mechanisms that have been found in the stator (winding and core) and the rotor of thermoelectric and hydroelectric power stations by the natural aging process and abnormal operation. [Espanol] Es de suma importancia conocer los mecanismos de deterioro que sufre un generador, para tomar medidas correctivas que detengan el proceso, con el fin de evitar danos catastroficos que impliquen salidas no programadas para dar mantenimiento, o incluso, para efectuar la rehabilitacion. En este articulo se discuten los mecanismos de deterioro que se han encontrado en el estator (devanado y nucleo) y el rotor de generadores termicos e hidroelectricos por el proceso natural de envejecimiento y por operacion anormal.

  13. Deteriorating mechanisms of electric generators; Mecanismos de deterioro de generadores electricos

    Energy Technology Data Exchange (ETDEWEB)

    Garcia Tevillo, Arturo; Reyes Martinez, Oscar Alfonso; Robles Pimentel, Edgar Guillermo; Esparza Saucedo, Marcos; Lopez Azamar, Jose Ernesto; Medina Flores, Alfredo; Uribe Martinez, Manuel O. [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)

    1998-12-31

    It is of the greatest importance to know the deteriorating mechanisms that an electric generator undergoes, in order to take corrective measures to stop the process in order to avoid catastrophic damages that imply non scheduled interruptions for maintenance, or inclusively, to carry on the overhaul. In this paper are discussed the deteriorating mechanisms that have been found in the stator (winding and core) and the rotor of thermoelectric and hydroelectric power stations by the natural aging process and abnormal operation. [Espanol] Es de suma importancia conocer los mecanismos de deterioro que sufre un generador, para tomar medidas correctivas que detengan el proceso, con el fin de evitar danos catastroficos que impliquen salidas no programadas para dar mantenimiento, o incluso, para efectuar la rehabilitacion. En este articulo se discuten los mecanismos de deterioro que se han encontrado en el estator (devanado y nucleo) y el rotor de generadores termicos e hidroelectricos por el proceso natural de envejecimiento y por operacion anormal.

  14. Failure mode, effect and criticality analysis (FMECA) on mechanical subsystems of diesel generator at NPP

    International Nuclear Information System (INIS)

    Kim, Tae Woon; Singh, Brijendra; Sung, Tae Yong; Park, Jin Hee; Lee, Yoon Hwan

    1996-06-01

    Largely, the RCM approach can be divided in three phases; (1) Functional failure analysis (FFA) on the selected system or subsystem, (2) Failure mode, effect and criticality analysis (FMECA) to identify the impact of failure to plant safety or economics, (3) Logical tree analysis (LTA) to select appropriate preventive maintenance and surveillance tasks. This report presents FMECA results for six mechanical subsystems of the diesel generators of nuclear power plants. The six mechanical subsystems are Starting air, Lub oil, Governor, Jacket water cooling, Fuel, and Engine subsystems. Generic and plant-specific failure and maintenance records are reviewed to identify critical components/failure modes. FMECA was performed for these critical component/failure modes. After reviewing current preventive maintenance activities of Wolsung unit 1, draft RCM recommendations are developed. 6 tabs., 16 refs. (Author)

  15. Failure mode, effect and criticality analysis (FMECA) on mechanical subsystems of diesel generator at NPP

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Woon; Singh, Brijendra; Sung, Tae Yong; Park, Jin Hee; Lee, Yoon Hwan [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1996-06-01

    Largely, the RCM approach can be divided in three phases; (1) Functional failure analysis (FFA) on the selected system or subsystem, (2) Failure mode, effect and criticality analysis (FMECA) to identify the impact of failure to plant safety or economics, (3) Logical tree analysis (LTA) to select appropriate preventive maintenance and surveillance tasks. This report presents FMECA results for six mechanical subsystems of the diesel generators of nuclear power plants. The six mechanical subsystems are Starting air, Lub oil, Governor, Jacket water cooling, Fuel, and Engine subsystems. Generic and plant-specific failure and maintenance records are reviewed to identify critical components/failure modes. FMECA was performed for these critical component/failure modes. After reviewing current preventive maintenance activities of Wolsung unit 1, draft RCM recommendations are developed. 6 tabs., 16 refs. (Author).

  16. Trajectory Generation and Stability Analysis for Reconfigurable Klann Mechanism Based Walking Robot

    Directory of Open Access Journals (Sweden)

    Jaichandar Kulandaidaasan Sheba

    2016-06-01

    Full Text Available Reconfigurable legged robots based on one degree of freedom are highly desired because they are effective on rough and irregular terrains and they provide mobility in such terrain with simple control schemes. It is necessary that reconfigurable legged robots should maintain stability during rest and motion, with a minimum number of legs while maintaining their full range of walking patterns resulting from different gait configuration. In this paper we present a method to generate input trajectory for reconfigurable quadruped robots based on Klann mechanism to properly synchronize movement. Six useful gait cycles based on this reconfigurable Klann mechanism for quadruped robots has been clearly shown here. The platform stability for these six useful gait cycles are validated through simulated results which clearly shows the capabilities of reconfigurable design.

  17. Enhancement of radiation effect using beta-lapachone and underlying mechanism

    International Nuclear Information System (INIS)

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

    2013-01-01

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

  18. Nanoscale copper in the soil–plant system – toxicity and underlying potential mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Anjum, Naser A., E-mail: anjum@ua.pt [CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, 3810-193 Aveiro (Portugal); Adam, Vojtech [Department of Chemistry and Biochemistry, Faculty of Agronomy, Mendel University in Brno, Zemedelska 1, CZ-613 00 Brno (Czech Republic); Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, CZ-616 00 Brno (Czech Republic); Kizek, Rene [Central European Institute of Technology, Brno University of Technology, Technicka 3058/10, CZ-616 00 Brno (Czech Republic); Duarte, Armando C.; Pereira, Eduarda [CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, 3810-193 Aveiro (Portugal); Iqbal, Muhammad [Department of Botany, Faculty of Science, Hamdard University, New Delhi 110062 (India); Lukatkin, Alexander S. [Department of Botany, Plant Physiology and Ecology, N.P. Ogarev Mordovia State University, Bolshevistskaja Str., 68. Saransk 430005 (Russian Federation); Ahmad, Iqbal, E-mail: ahmadr@ua.pt [CESAM-Centre for Environmental and Marine Studies & Department of Chemistry, University of Aveiro, 3810-193 Aveiro (Portugal); CESAM-Centre for Environmental and Marine Studies & Department of Biology, University of Aveiro, 3810-193 Aveiro (Portugal)

    2015-04-15

    Nanoscale copper particles (nano-Cu) are used in many antimicrobial formulations and products for their antimicrobial activity. They may enter deliberately and/or accidentally into terrestrial environments including soils. Being the major ‘eco-receptors’ of nanoscale particles in the terrestrial ecosystem, soil–microbiota and plants (the soil–plant system) have been used as a model to dissect the potential impact of these particles on the environmental and human health. In the soil–plant system, the plant can be an indirect non-target organism of the soil-associated nano-Cu that may in turn affect plant-based products and their consumers. By all accounts, information pertaining to nano-Cu toxicity and the underlying potential mechanisms in the soil–plant system remains scanty, deficient and little discussed. Therefore, based on some recent reports from (bio)chemical, molecular and genetic studies of nano-Cu versus soil–plant system, this article: (i) overviews the status, chemistry and toxicity of nano-Cu in soil and plants, (ii) discusses critically the poorly understood potential mechanisms of nano-Cu toxicity and tolerance both in soil–microbiota and plants, and (iii) proposes future research directions. It appears from studies hitherto made that the uncontrolled generation and inefficient metabolism of reactive oxygen species through different reactions are the major factors underpinning the overall nano-Cu consequences in both the systems. However, it is not clear whether the nano-Cu or the ion released from it is the cause of the toxicity. We advocate to intensify the multi-approach studies focused at a complete characterization of the nano-Cu, its toxicity (during life cycles of the least-explored soil–microbiota and plants), and behavior in an environmentally relevant terrestrial exposure setting. Such studies may help to obtain a deeper insight into nano-Cu actions and address adequately the nano-Cu-associated safety concerns in the

  19. Nanoscale copper in the soil–plant system – toxicity and underlying potential mechanisms

    International Nuclear Information System (INIS)

    Anjum, Naser A.; Adam, Vojtech; Kizek, Rene; Duarte, Armando C.; Pereira, Eduarda; Iqbal, Muhammad; Lukatkin, Alexander S.; Ahmad, Iqbal

    2015-01-01

    Nanoscale copper particles (nano-Cu) are used in many antimicrobial formulations and products for their antimicrobial activity. They may enter deliberately and/or accidentally into terrestrial environments including soils. Being the major ‘eco-receptors’ of nanoscale particles in the terrestrial ecosystem, soil–microbiota and plants (the soil–plant system) have been used as a model to dissect the potential impact of these particles on the environmental and human health. In the soil–plant system, the plant can be an indirect non-target organism of the soil-associated nano-Cu that may in turn affect plant-based products and their consumers. By all accounts, information pertaining to nano-Cu toxicity and the underlying potential mechanisms in the soil–plant system remains scanty, deficient and little discussed. Therefore, based on some recent reports from (bio)chemical, molecular and genetic studies of nano-Cu versus soil–plant system, this article: (i) overviews the status, chemistry and toxicity of nano-Cu in soil and plants, (ii) discusses critically the poorly understood potential mechanisms of nano-Cu toxicity and tolerance both in soil–microbiota and plants, and (iii) proposes future research directions. It appears from studies hitherto made that the uncontrolled generation and inefficient metabolism of reactive oxygen species through different reactions are the major factors underpinning the overall nano-Cu consequences in both the systems. However, it is not clear whether the nano-Cu or the ion released from it is the cause of the toxicity. We advocate to intensify the multi-approach studies focused at a complete characterization of the nano-Cu, its toxicity (during life cycles of the least-explored soil–microbiota and plants), and behavior in an environmentally relevant terrestrial exposure setting. Such studies may help to obtain a deeper insight into nano-Cu actions and address adequately the nano-Cu-associated safety concerns in the

  20. Flexible voltage support control for three-phase distributed generation inverters under grid fault

    DEFF Research Database (Denmark)

    Camacho, Antonio; Castilla, Miguel; Miret, Jaume

    2013-01-01

    Operators describe the behavior of the energy source, regulating voltage limits and reactive power injection to remain connected and support the grid under fault. On the basis that different kinds of voltage sags require different voltage support strategies, a flexible control scheme for three phase grid...... connected inverters is proposed. In three phase balanced voltage sags, the inverter should inject reactive power in order to raise the voltage in all phases. In one or two phase faults, the main concern of the distributed generation inverter is to equalize voltages by reducing the negative symmetric...... sequence and clear the phase jump. Due to system limitations, a balance between these two extreme policies is mandatory. Thus, over-voltage and undervoltage can be avoided, and the proposed control scheme prevents disconnection while achieving the desired voltage support service. The main contribution...

  1. Vector model for polarized second-harmonic generation microscopy under high numerical aperture

    International Nuclear Information System (INIS)

    Wang, Xiang-Hui; Chang, Sheng-Jiang; Lin, Lie; Wang, Lin-Rui; Huo, Bing-Zhong; Hao, Shu-Jian

    2010-01-01

    Based on the vector diffraction theory and the generalized Jones matrix formalism, a vector model for polarized second-harmonic generation (SHG) microscopy is developed, which includes the roles of the axial component P z , the weight factor and the cross-effect between the lateral components. The numerical results show that as the relative magnitude of P z increases, the polarization response of the second-harmonic signal will vary from linear polarization to elliptical polarization and the polarization orientation of the second-harmonic signal is different from that under the paraxial approximation. In addition, it is interesting that the polarization response of the detected second-harmonic signal can change with the value of the collimator lens NA. Therefore, it is more advantageous to adopt the vector model to investigate the property of polarized SHG microscopy for a variety of cases

  2. Generating Sub-nanometer Displacement Using Reduction Mechanism Consisting of Torsional Leaf Spring Hinges

    Directory of Open Access Journals (Sweden)

    Fukuda Makoto

    2014-02-01

    Full Text Available Recent demand on the measurement resolution of precise positioning comes up to tens of picometers. Some distinguished researches have been performed to measure the displacement in picometer order, however, few of them can verify the measurement performance as available tools in industry. This is not only because the picometer displacement is not yet required for industrial use, but also due to the lack of standard tools to verify such precise displacement. We proposed a displacement reduction mechanism for generating precise displacement using torsional leaf spring hinges (TLSHs that consist of four leaf springs arranged radially. It has been demonstrated that a prototype of the reduction mechanism was able to provide one-nanometer displacement with 1/1000 reduction rate by a piezoelectric actuator. In order to clarify the potential of the reduction mechanism, a displacement reduction table that can be mounted on AFM stage was newly developed using TLSHs. This paper describes the design of the reduction mechanism and the sub-nanometer displacement performance of the table obtained from its dynamic and static characteristics measured by displacement sensors and from the AFM images

  3. A Theoretical and Experimental Investigation of Mechanical Damage to Rodent Sperm Generated by Microscale Ice Formation.

    Science.gov (United States)

    Han, X; Critser, J K

      BACKGROUND: Rodent sperm cryopreservation is of critical importance for the maintenance of lines or strains of genetically engineered mice and rats. However, rodent sperm are extremely mechanically sensitive due to their unusual morphology, and are severely damaged using current methods of cryopreservation. Those methods result in poor post thaw motility (PTM) for mouse. To investigate the mechanism of mechanical damage introduced to rodent sperm during freezing, a micro-mechanical model was established to analyze the sperm radial and axial thermal stresses generated by microscale extracellular ice formation. PTM of mouse sperm cryopreserved in capillaries of different radii (100, 200, 344, 526, 775µm) was measured using a standard computer-assisted sperm analysis system. The model predicts that when one of the inner dimensions of the containers (the inner diameter of plastic straws or straw capillaries) is on the same order of magnitude of sperm length, axial stress is significantly increased. The experimental results showed that the value of PTM was decreased from 38 ± 8 % in the larger (775µm) capillaries to 0 ± 0 % in the smaller (100 µm) ones. Theoretical analysis based on the established model were experimentally validated and can be used to guide the design of novel devices to improve the efficiency of rodent sperm cryopreservation.

  4. Leak behavior of steam generator tube-to-tubesheet joints under creep condition: Experimental study

    International Nuclear Information System (INIS)

    Bahn, Chi Bum; Majumdar, Saurin; Kasza, Ken E.; Shack, William J.

    2013-01-01

    To address concerns regarding excessive leakage from throughwall cracks in steam generator tube-to-tubesheet joints under severe accident conditions, leak rate testing was conducted using tube-to-collar joint specimens. The tube interior and the interface between tube and collar (crevice) were pressurized independently using nitrogen gas. The leak rate through the crevice was almost zero when the specimens were pressurized at ∼500 °C; this low leak rate is attributed to thermal mismatch effects preventing much leakage. The near zero leak rate was maintained until the onset of large leakage at higher temperatures. The leak rate behavior after the onset of the large leakage was not much affected by the crevice length or heat-to-heat variation of Alloy 600 tubes. This suggests that once the crevice gap opens, the creep rate of the low alloy steel collar becomes dominant. Specimens with different tube diameters behaved essentially the same way. To simulate a flawed steam generator tube in the tubesheet, the crevice region was pressurized through a hole in the tube. This simulation resulted in essentially the same behavior as those specimens whose tubes and crevices were pressurized independently. Oxidation of low alloy steel collars in air tests can increase the flow resistance, and thus tests using nitrogen gas would provide more conservative leak rate data. Highlights: ► Leak rates were measured by using tube-to-collar joint specimens under creep condition. ► Leak rate through the joint interface was almost zero at ∼500 °C due to thermal mismatch. ► The near zero leak rate was maintained until the onset of large leakage at ∼680 °C. ► The leak behavior after the onset of the large leakage was not affected by hydraulic expansion length or tube heats.

  5. Learning Physics-based Models in Hydrology under the Framework of Generative Adversarial Networks

    Science.gov (United States)

    Karpatne, A.; Kumar, V.

    2017-12-01

    Generative adversarial networks (GANs), that have been highly successful in a number of applications involving large volumes of labeled and unlabeled data such as computer vision, offer huge potential for modeling the dynamics of physical processes that have been traditionally studied using simulations of physics-based models. While conventional physics-based models use labeled samples of input/output variables for model calibration (estimating the right parametric forms of relationships between variables) or data assimilation (identifying the most likely sequence of system states in dynamical systems), there is a greater opportunity to explore the full power of machine learning (ML) methods (e.g, GANs) for studying physical processes currently suffering from large knowledge gaps, e.g. ground-water flow. However, success in this endeavor requires a principled way of combining the strengths of ML methods with physics-based numerical models that are founded on a wealth of scientific knowledge. This is especially important in scientific domains like hydrology where the number of data samples is small (relative to Internet-scale applications such as image recognition where machine learning methods has found great success), and the physical relationships are complex (high-dimensional) and non-stationary. We will present a series of methods for guiding the learning of GANs using physics-based models, e.g., by using the outputs of physics-based models as input data to the generator-learner framework, and by using physics-based models as generators trained using validation data in the adversarial learning framework. These methods are being developed under the broad paradigm of theory-guided data science that we are developing to integrate scientific knowledge with data science methods for accelerating scientific discovery.

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

    Directory of Open Access Journals (Sweden)

    Dongyuan Lü

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

  7. 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.

  8. 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.

  9. 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

  10. Mechanisms underlying the associations of maternal age with adverse perinatal outcomes

    DEFF Research Database (Denmark)

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

    2011-01-01

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

  11. 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…

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

    OpenAIRE

    Silverman, Marni N.; Deuster, Patricia A.

    2014-01-01

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

  13. Radiatively Generating the Higgs Potential and Electroweak Scale via the Seesaw Mechanism.

    Science.gov (United States)

    Brivio, Ilaria; Trott, Michael

    2017-10-06

    The minimal seesaw scenario can radiatively generate the Higgs potential to induce electroweak symmetry breaking while supplying an origin of the Higgs vacuum expectation value from an underlying Majorana scale. If the Higgs potential and (derived) electroweak scale have this origin, the heavy SU(3)×SU(2)×U(1)_{Y} singlet states are expected to reside at m_{N}∼10-500  PeV for couplings |ω|∼10^{-4.5}-10^{-6} between the Majorana sector and the standard model. In this framework, the usual challenge of the electroweak scale hierarchy problem with a classically assumed potential is absent as the electroweak scale is not a fundamental scale. The new challenge is the need to generate or accommodate PeV Majorana mass scales while simultaneously suppressing tree-level contributions to the potential in ultraviolet models.

  14. Mechanical behavior of glass/epoxy composite laminate with varying amount of MWCNTs under different loadings

    Science.gov (United States)

    Singh, K. K.; Rawat, Prashant

    2018-05-01

    This paper investigates the mechanical response of three phased (glass/MWCNTs/epoxy) composite laminate under three different loadings. Flexural strength, short beam strength and low-velocity impact (LVI) testing are performed to find an optimum doping percentage value for maximum enhancement in mechanical properties. In this work, MWCNTs were used as secondary reinforcement for three-phased composite plate. MWCNT doping was done in a range of 0–4 wt% of the thermosetting matrix system. Symmetrical design eight layered glass/epoxy laminate with zero bending extension coupling laminate was fabricated using a hybrid method i.e. hand lay-up technique followed by vacuum bagging method. Ranging analysis of MWCNT mixing highlighted the enhancement in flexural, short beam strength and improvement in damage tolerance under LVI loading. While at higher doping wt%, agglomeration of MWCNTs are observed. Results of mechanical testing proposed an optimized doping value for maximum strength and damage resistance of the laminate.

  15. 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

  16. Antibacterial mechanisms of a novel type picosecond laser-generated silver-titanium nanoparticles and their toxicity to human cells.

    Science.gov (United States)

    Korshed, Peri; Li, Lin; Liu, Zhu; Mironov, Aleksandr; Wang, Tao

    2018-01-01

    In this study, we explored the antibacterial mechanisms for a novel type of Ag-TiO 2 compound nanoparticles (NPs) produced from an Ag-TiO 2 alloy using a picosecond laser and evaluated the toxicity of the Ag-TiO 2 NPs to a range of human cell types. Transmission electron microscopy was used to determine the morphology, shapes, and size distribution of the laser-generated Ag-TiO 2 NPs. UV-visible spectrometer was used to confirm the shift of light absorbance of the NPs toward visible light wavelength. Results showed that the laser-generated Ag-TiO 2 NPs had significant antibacterial activities against both Gram-negative and Gram-positive bacterial strains, including Escherichia coli, Pseudomonas aeruginosa , and the methicillin-resistant Staphylococcus aureus . Increased level of reactive oxygen species was produced by E. coli after exposure to the Ag-TiO 2 NPs, which was accompanied with lipid peroxidation, glutathione depletion, disintegration of cell membrane and protein leakage, leading to the cell death. Five types of human cells originated from lung (A549), liver (HePG2), kidney (HEK293), endothelium cells (human coronary artery endothelial cells [hCAECs]), and skin (human dermal fibroblast cells [HDFc]) were used to evaluate the cytotoxicity of the laser-generated Ag-TiO 2 NPs. A weak but statistically significant decrease in cell proliferation was observed for hCAECs, A549 and HDFc cells when co-cultured with 2.5 µg/mL or 20 µg/mL of the laser-generated Ag-TiO 2 NPs for 48 hours. However, this effect was no longer apparent when a higher concentration of NPs (20 µg/mL) was used after 72 hours of co-culture with human cells, suggesting a possible adaptive process in the cells had occurred. We conclude that picosecond laser-generated Ag-TiO 2 NPs have a broad spectrum of antibacterial effect, including against the drug-resistant strain, with multiple underlying molecular mechanisms and low human cell toxicity. The antimicrobial properties of the new type of

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

    Directory of Open Access Journals (Sweden)

    Baoyun Zhao

    2018-01-01

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

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

    Science.gov (United States)

    Mahoney, Lisa; Rosen, Rachel

    2017-01-01

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

  19. A review of porosity-generating mechanisms in crustal shear zones

    Science.gov (United States)

    Fusseis, F.; Regenauer-Lieb, K.; Revets, S.

    2009-04-01

    Knowledge of the spatiotemporal characteristics of permeability is critical for the understanding of fluid migration in rocks. In diagenetic and metamorphic rocks different porosity-generating mechanisms contribute to permeability and so influence fluid migration and fluid/rock interaction. However, little is known about their relative contributions to the porosity architecture of a rock in a tectono-metamorphic environment. This presentation reviews porosity-generating mechanisms that affect fluid migration in shear zones, the most important crustal fluid conduits, in the context of the tectonometamorphic evolution of rocks. Mechanisms that generate porosity can be classified in a) those that involve the direct action of a fluid, b) processes in which a fluid partakes or that are supported by a fluid or c) mechanism that do not involve a fluid. a) Hydraulic fracturing, where it happens through the formation of tensile fractures, occurs where pore fluid pressures equalize the combined lithostatic pressure and strength of the rock (Etheridge et al., 1984, Cox & Etheridge, 1989, Oliver, 1996). Here an internally released (devolatilisation reactions, e.g., Rumble, 1994, Hacker, 1997, Yardley, 1997 and references therein) or externally derived (infiltrating from metamorphic, magmatic or meteoric sources, Baumgartner et al., 1997, Jamtveit et al., 1997, Thompson, 1997, Gleeson et al., 2003) fluid directly causes the mechanical failure of a rock. Where a fluid is in chemical disequilibrium with a rock (undersaturated with regard to a chemical species) minerals will be dissolved, generating dissolution porosity. Rocks ‘leached' by the removal of chemical components by vast amounts of fluid are reported to lose up to 60% of their original volume (e.g., Kerrich et al., 1984, McCaig 1988). Dissolution porosity is probably an underrated porosity-generating mechanism. It can be expected along the entire metamorphic evolution, including diagenesis (Higgs et al., 2007) and

  20. State reference design and saturated control of doubly-fed induction generators under voltage dips

    Science.gov (United States)

    Tilli, Andrea; Conficoni, Christian; Hashemi, Ahmad

    2017-04-01

    In this paper, the stator/rotor currents control problem of doubly-fed induction generator under faulty line voltage is carried out. Common grid faults cause a steep decline in the line voltage profile, commonly denoted as voltage dip. This point is critical for such kind of machines, having their stator windings directly connected to the grid. In this respect, solid methodological nonlinear control theory arguments are exploited and applied to design a novel controller, whose main goal is to improve the system behaviour during voltage dips, endowing it with low voltage ride through capability, a fundamental feature required by modern Grid Codes. The proposed solution exploits both feedforward and feedback actions. The feedforward part relies on suitable reference trajectories for the system internal dynamics, which are designed to prevent large oscillations in the rotor currents and command voltages, excited by line perturbations. The feedback part uses state measurements and is designed according to Linear Matrix Inequalities (LMI) based saturated control techniques to further reduce oscillations, while explicitly accounting for the system constraints. Numerical simulations verify the benefits of the internal dynamics trajectory planning, and the saturated state feedback action, in crucially improving the Doubly-Fed Induction Machine response under severe grid faults.