WorldWideScience

Sample records for main transport mechanism

  1. Filtration as the main transport mechanism of protein exchange between plasma and the peritoneal cavity in hepatic cirrhosis

    DEFF Research Database (Denmark)

    Henriksen, Jens Henrik Sahl; Lassen, N A; Parving, H H; Winkler, K

    1980-01-01

    to plasma protein flux averaged 0.4% of the intravascular protein mass per hour. The results point to filtration (convective flux) as the main transport mechanism responsible for protein passage into the peritoneal cavity as well as for the protein passage (lymphatic drainage) back into the plasma...

  2. Filtration as the main transport mechanism of protein exchange between plasma and the peritoneal cavity in hepatic cirrhosis

    DEFF Research Database (Denmark)

    Henriksen, J H; Lassen, N A; Parving, H H; Winkler, K

    1980-01-01

    plasma protein flux averaged 0.4% of the intravascular protein mass per hour. The results point to filtration (convective flux) as the main transport mechanism responsible for protein passage into the peritoneal cavity as well as for the protein passage (lymphatic drainage) back into the plasma. Pressure...

  3. Nature and main kinds of psychopathological mechanisms

    Directory of Open Access Journals (Sweden)

    Panagiotis Oulis

    2010-12-01

    Full Text Available The paper deals with two central issues in the philosophy of neuroscience and psychiatry, namely those of the nature and the major kinds and types of psychopathological mechanisms. Contrary to a widespread view, I argue that mechanisms are not kinds of systems but kinds of processes unfolding in systems or between systems. More precisely, I argue that psychopathological mechanisms are sets of actions and interactions between brain-systems or circuits as well as between the latter and other systems in one's body and external environment, both physical and social, involved in human psychopathology. According to the kinds of properties of the interacting systems or their component-parts, psychopathological mechanisms may be physical, chemical, biological, psychological, social, or, typically, mixed ones. Furthermore, I focus on two main kinds of psychopathological mechanisms involved in the causation of mental disorders, namely the pathogenetic and pathophysiological ones, stressing the importance of their careful distinction for the integrative understanding of otherwise disparate and apparently incommensurable psychiatric research findings. I illustrate my analysis with an example drawn from contemporary research on the mechanisms of acute psychosis. Finally, I stress the relevance of psychopathological mechanisms to a more scientifi cally-grounded classifi cation of mental disorders.

  4. Alveolobronchiolar transport mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Green, G.M.

    1973-01-01

    In this proposed transport mechanism, particles impinging on alveolar surface layer are drawn, probably by random surface tension forces, to macrophages. Then, laden macrophages are transported along with alveolar fluid either via airways or more probably via pores of Kohn from alveolus to alveolus and eventually into ciliated airways. Additionally, lymphatic fluid transported centripetally to centrilobular lymphatics or centrifugally to perilobular lymphatics (on opposite side of fibrous separation of lobules). ''Sumps'' at broncho-alveolar junctions are for movement of macrophages out of alveoli and interstitial locations and into broncho-alveolar junction. Blind-pocket lymphatics are short-cuts to ciliary stream rather than drainages. (These sumps are drainages during flooding but not normally). Tissue fluid passes into lymph system but cellular material does not. Energetic mechanism is respiratory action in which mid-lobular areas would receive maximum deformation, producing the bidirectional movement. This mechanism is the only accounting for bidirectional movement and parallels lymphatic transport in other body areas. Clearance kinetics of particles are 4-phase: (1) deposition in upper airways with 1 to 2 hr clearance, (2) deposition in respiratory bronchioles with moderately rapid clearance, (3) deposition in alveoli and 1 to 14 day clearance via lymphatic short-cut, and (4) long-term retention of particles trapped in septal or perivascular lymphatics or subpleurally. Extended peribronchiolar retention is only in disease states or with heavy particulate burdens. Compartment model documentation is still lacking. Evidence of lymphoid nodules along macrophage pathways suggests mechanism for local immunity.

  5. Main transport challenges in South Eastern Europe, after enlargement

    OpenAIRE

    Giannopoulos, G. A.

    2005-01-01

    This paper looks at the main challenges that are facing the Transport sector in the countries of S. E. Europe after enlargement. First, it looks at the challenge of setting a common Transport policy and points as priority areas the questions of: frontier crossings, road transport quotas, working hours (road transport), restructuring of railways, promotion of Rail Freight ‘Freeways’, new financing schemes through Public Private Partnerships, and other issues. Then it looks at the factors that ...

  6. Tape transport mechanism

    International Nuclear Information System (INIS)

    A device is provided for transporting, in a stepwise manner, tape between a feed reel and takeup reel. An indexer moves across the normal path of the tape displacing it while the tape on the takeup reel side of the indexer is braked. After displacement, the takeup reel takes up the displaced tape while the tape on the feed reel side of the indexer is braked, providing stepwise tape transport in precise intervals determined by the amount of displacement caused by the indexer

  7. Turbulent transport and lithium destruction in main sequence stars

    International Nuclear Information System (INIS)

    The depletion of lithium in giants seems to result from the destruction of lithium on the main sequence prior to the formation of the giants. Lithium is carried by turbulent diffusion towards the region where it is burned. The measurement of the abundance of lithium in giants gives then the possibility of determining the rate of transport. It explains the depletion of lithium on the main sequence, the depletion of lithium in the Sun, is compatible with the loss of angular momentum of the Sun and suggests an explanation of the (V sin i) distribution function for main sequence stars, and for giant stars. (orig./BJ)

  8. Truck and Transport Mechanic. Occupational Analyses Series.

    Science.gov (United States)

    McRory, Aline; Ally, Mohamed

    This analysis covers tasks performed by a truck and transport mechanic, an occupational title some provinces and territories of Canada have also identified as commercial transport vehicle mechanic; transport truck mechanic; truck and coach technician; and truck and transport service technician. A guide to analysis discusses development, structure,…

  9. Membranes, mechanics, and intracellular transport

    Science.gov (United States)

    Parthasarathy, Raghuveer

    2012-10-01

    Cellular membranes are remarkable materials -- self-assembled, flexible, two-dimensional fluids. Understanding how proteins manipulate membrane curvature is crucial to understanding the transport of cargo in cells, yet the mechanical activities of trafficking proteins remain poorly understood. Using an optical-trap based assay involving dynamic deformation of biomimetic membranes, we have examined the behavior of Sar1, a key component of the COPII family of transport proteins. We find that Sar1 from yeast (S. cerevisiae) lowers membrane rigidity by up to 100% as a function of its concentration, thereby lowering the energetic cost of membrane deformation. Human Sar1 proteins can also lower the mechanical rigidity of the membranes to which they bind. However, unlike the yeast proteins, the rigidity is not a monotonically decreasing function of concentration but rather shows increased rigidity and decreased mobility at high concentrations that implies interactions between proteins. In addition to describing this study of membrane mechanics, I'll also discuss some topics relevant to a range of biophysical investigations, such as the insights provided by imaging methods and open questions in the dynamics of multicellular systems.

  10. Summary on main policies, funding mechanisms, actors and trends

    DEFF Research Database (Denmark)

    Kressler, Florian; Weiss, Lucas; Åkerman, Jonas; Gudmundsson, Henrik; Guihéry, Laurent; Vesela, Jirina

    2014-01-01

    This document summarizes the output of WP 3 on policies, funding mechanisms, actors and trends relating the four thematic groups. Each thematic group examines one goal of the White Paper on Transport, published by the European Commission in 2011. The purpose of this document is to provide input for further work carried out in the project, especially the road-mapping exercises and the strategic outlook carried out in WP 6. The inputs for this document include information from a literature review ...

  11. MAIN DIRECTIONS OF EFFICIENCY IMPROVEMENT OF TRANSPORT INTERCHANGES FUNCTIONING

    Directory of Open Access Journals (Sweden)

    V. Naumov

    2015-07-01

    Full Text Available The article deals with the areas of study concerning transport interchanges. It has been determined that the most perspective directions for the future research is synchronization of the schedule that allous reducing the wating time, preventing the public transport congestion at bus stops and stations, and by doing this to ensure their sustainable development.

  12. Main academic institutions conducting research in the public transport area

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, B.E. [Lund Inst. of Tech. (Sweden). Dept. of Traffic Planning and Engineering

    1997-12-01

    The international exchange of knowledge is becoming increasingly important for all activities. Within Europe, the need for simple reviews of institutions within one and the same subject area has become more tangible since the European Union started its public transport research program. The survey has been carried out in two stages. First a questionnaire was sent to those institutions, public transport authorities, public transport associations and individuals within the subject area that were known to the Department. In this questionnaire we asked for the names and addresses of institutions at colleges and universities where significant research on public transport is carried out. In a second stage, a list was compiled of the 48 institutions that were named in the results of the first questionnaire. This list was sent to these institutions with the request for a brief presentation of their research within the public transport sector and information on any institution they felt were missing in the list. We found further interesting institutions on the Internet. The final list contains more than 60 institutions outside the Nordic area. Within the Nordic countries we have exclusively followed our own address list of institutions with long-term research work within the subject area

  13. Manganese Transport via the Transferrin Mechanism

    OpenAIRE

    Gunter, Thomas E.; Gerstner, Brent; Gunter, Karlene K.; Malecki, Jon; Gelein, Robert; Valentine, William M.; Aschner, Michael; Yule, David I.

    2012-01-01

    Excessive manganese (Mn) uptake by brain cells, particularly in regions like the basal ganglia, can lead to toxicity. Mn2+ is transported into cells via a number of mechanisms, while Mn3+ is believed to be transported similarly to iron (Fe) via the transferrin (Tf) mechanism. Cellular Mn uptake is therefore determined by the activity of the mechanisms transporting Mn into each type of cell and by the amounts of Mn2+, Mn3+ and their complexes to which these cells are exposed; this complicates ...

  14. Ethanol as a Future Fuel for Road Transportation : Main report

    OpenAIRE

    Larsen, Ulrik; Johansen, Troels; Schramm, Jesper

    2011-01-01

    IEA Implementing Agreement on Advanced Motor Fuels. This report is financed by the Danish Energy Authority (EFP 2006 — Ethanol som motorbrændstof) and made in cooperation with the International Energy Agency — Advanced Motor Fuels Agreement. The report is a contribution to Annex XXXV: “Ethanol as a Motor Fuel — Subtask 1: Ethanol as a Fuel in Road Vehicles.” The work has been carried out by The Technical University of Denmark, Department of Mechanical Engineering.

  15. Main Directions and Mechanisms of Industrial Policy of Russia

    Directory of Open Access Journals (Sweden)

    Irina M. Podmolodina

    2015-06-01

    Full Text Available Under difficult economic conditions for Russian business, characterized by difficulties of Russian companies’ access to foreign modern technologies and long-term financial resources, there is a need for elaborated industrial policy which facilitates the development of national industry and provision of economic security of the country. With current sanctions, the Russian enterprises faced the problems of impossibility of getting foreign equipment under the previously signed contracts, re-orientation of orders for the similar domestic production, and attraction of financial resources from internal sources. Solution to these problems lies in the plane of development of “new” industrial policy. The purpose of the article is to determine main directions and mechanisms for realization of measures of industrial policy which facilitates the development of domestic industrial production, implementation of achievements of scientific and technological progress into industrial processes, and import substitution of science intensive products. Realization of industrial policy of Russia supposes the formation of special conditions. These are favorable economic and socio-infrastructural conditions, attractive entrepreneurial regime, high level of training of personnel for various industries, and informational support of government structures. Activation of innovational activity requires mechanisms that ensure the improvement of conditions for fair competition and increase of motivation of companies for innovations; regulation of product markets (service markets and sectorial regulation for distribution of leading technologies; development of the system of technical regulation, which includes harmonization of legislative basis of Russia and the EU countries in this sphere; simplification of a procedure of entry of new products into the market; simplification and quickening of the procedures of certification, including as to the international quality standards; simplification of a mechanism of import of technologies; strengthening of requirements to efficiency of enterprises’ usage of natural resources, safety of products (services for ecology and health of population, decrease of energy and materials consumption; development of the system of appropriate bonuses and sanctions, harmonization of Russian standards with international ones, particularly, in the directions that are characterized by perspectives of expansion for export of innovational products.

  16. Introduction to fluid mechanics and transport phenomena

    CERN Document Server

    Hauke, G

    2008-01-01

    This book presents the foundations of fluid mechanics and transport phenomena in a concise way. It is suitable as an introduction to the subject as it contains many examples, proposed problems and a chapter for self-evaluation. The solutions to all problems are displayed in the corresponding appendix. The content is divided into four parts: fundamentals, conservation principles, dimensional analysis and transport phenomena at interfaces. The transport phenomena of momentum, heat and mass are presented from a rigorous fluid mechanics point of view, and they are explained using a unified, system

  17. Angular momentum transport efficiency in post-main sequence low-mass stars

    CERN Document Server

    Spada, F; Arlt, R; Deheuvels, S

    2016-01-01

    Context. Using asteroseismic techniques, it has recently become possible to probe the internal rotation profile of low-mass (~1.1-1.5 Msun) subgiant and red giant stars. Under the assumption of local angular momentum conservation, the core contraction and envelope expansion occurring at the end of the main sequence would result in a much larger internal differential rotation than observed. This suggests that angular momentum redistribution must be taking place in the interior of these stars. Aims. We investigate the physical nature of the angular momentum redistribution mechanisms operating in stellar interiors by constraining the efficiency of post-main sequence rotational coupling. Methods. We model the rotational evolution of a 1.25 Msun star using the Yale Rotational stellar Evolution Code. Our models take into account the magnetic wind braking occurring at the surface of the star and the angular momentum transport in the interior, with an efficiency dependent on the degree of internal differential rotati...

  18. Seesaw mechanism in turbulence and turbulent transport

    International Nuclear Information System (INIS)

    Full text: Theory of nonlocal transport has been developed, based upon the statistical theory of plasma turbulence. Essence is that fluctuations (with long radial correlation length) can be excited by nonlinear processes, although they are linearly stable. Experiments have reported the non-diffusive mechanisms in rapid response of transport between distant radii. Simulations have demonstrated that transport barrier can be established while increasing linear growth rate of local instabilities. These await application of theory of nonlocal transport. Example of such nonlinearly-driven, meso-scale fluctuations is the zonal flow (ZF). ZFs grow extracting energy from microscopic fluctuations so as to reduce the turbulence and turbulent transport. Because the radial correlation length of ZF is longer than those for microscopic fluctuations, which are inducing turbulent transport, ZF, which is driven fluctuations at one radius, can suppress fluctuations at distant radii. Thus, the fluctuations exchange energy over the distance that is much longer than autocorrelation length of microscopic fluctuations. This mechanism induces new nonlocal interactions in turbulent transport. That is, strong fluctuations at particular radius can suppress fluctuations at different radius, via induction of ZFs. Stronger fluctuations suppress weaker fluctuations. This is called the seesaw mechanism via ZFs. Owing to this mechanism, the turbulence transport is not determined by local parameters alone, but by parameters at far distance. The transient response is much faster than the process governed by diffusive processes. [This work is partly supported by the Grant-in-Aid for Specially-Promoted Research (16002005), the Grant-in-Aid for Scientific Research (19360418) and collaboration programme of NIFS.] (author)

  19. Main mechanical and thermal problems of the FTU tokamak machine

    International Nuclear Information System (INIS)

    The FTU tokamak in order to reach the expected performance will have to operate steadily at high magnetic fields. Its magnet and vacuum chamber will undergo very high stresses due to thermal and electromagnetic loads for a large number of shots. In order to assess the feasibility of these components, numerical codes tocompute current, magnetic field and temperature distributions and extensive three dimensional finite element stress analysis have been developed. The main results obtained are illustrated. (orig.)

  20. Invasive home mechanical ventilation, mainly focused on neuromuscular disorders

    Directory of Open Access Journals (Sweden)

    Börger, Sandra

    2010-01-01

    Full Text Available Introduction and background: Invasive home mechanical ventilation is used for patients with chronic respiratory insufficiency. This elaborate and technology-dependent ventilation is carried out via an artificial airway (tracheal cannula to the trachea. Exact numbers about the incidence of home mechanical ventilation are not available. Patients with neuromuscular diseases represent a large portion of it. Research questions: Specific research questions are formulated and answered concerning the dimensions of medicine/nursing, economics, social, ethical and legal aspects. Beyond the technical aspect of the invasive home, mechanical ventilation, medical questions also deal with the patient’s symptoms and clinical signs as well as the frequency of complications. Economic questions pertain to the composition of costs and the differences to other ways of homecare concerning costs and quality of care. Questions regarding social aspects consider the health-related quality of life of patients and caregivers. Additionally, the ethical aspects connected to the decision of home mechanical ventilation are viewed. Finally, legal aspects of financing invasive home mechanical ventilation are discussed. Methods: Based on a systematic literature search in 2008 in a total of 31 relevant databases current literature is viewed and selected by means of fixed criteria. Randomized controlled studies, systematic reviews and HTA reports (health technology assessment, clinical studies with patient numbers above ten, health-economic evaluations, primary studies with particular cost analyses and quality-of-life studies related to the research questions are included in the analysis. Results and discussion: Invasive mechanical ventilation may improve symptoms of hypoventilation, as the analysis of the literature shows. An increase in life expectancy is likely, but for ethical reasons it is not confirmed by premium-quality studies. Complications (e. g. pneumonia are rare. Mobile home ventilators are available for the implementation of the ventilation. Their technical performance however, differs regrettably. Studies comparing the economic aspects of ventilation in a hospital to outpatient ventilation, describe home ventilation as a more cost-effective alternative to in-patient care in an intensive care unit, however, more expensive in comparison to a noninvasive (via mask ventilation. Higher expenses arise due to the necessary equipment and the high expenditure of time for the partial 24-hour care of the affected patients through highly qualified personnel. However, none of the studies applies to the German provisionary conditions. The calculated costs strongly depend on national medical fees and wages of caregivers, which barely allows a transmission of the results. The results of quality-of-life studies are mostly qualitative. The patient’s quality of life using mechanical ventilation is predominantly considered well. Caregivers of ventilated patients report positive as well as negative ratings. Regarding the ethical questions, it was researched which aspects of ventilation implementation will have to be considered. From a legal point of view the financing of home ventilation, especially invasive mechanical ventilation, requiring specialised technical nursing is regulated in the code of social law (Sozialgesetzbuch V. The absorption of costs is distributed to different insurance carriers, who often, due to cost pressures within the health care system, insurance carriers, who consider others and not themselves as responsible. Therefore in practice, the necessity to enforce a claim of cost absorption often arises in order to exercise the basic right of free choice of location. Conclusion: Positive effects of the invasive mechanical ventilation (overall survival and symptomatic are highly probable based on the analysed literature, although with a low level of evidence. An establishment of a home ventilation registry and health care research to ascertain valid data to improve outpatient structures is necessary. Gathering specific G

  1. Peroxisomal ABC transporters: functions and mechanism.

    Science.gov (United States)

    Baker, Alison; Carrier, David J; Schaedler, Theresia; Waterham, Hans R; van Roermund, Carlo W; Theodoulou, Frederica L

    2015-10-01

    Peroxisomes are arguably the most biochemically versatile of all eukaryotic organelles. Their metabolic functions vary between different organisms, between different tissue types of the same organism and even between different developmental stages or in response to changed environmental conditions. New functions for peroxisomes are still being discovered and their importance is underscored by the severe phenotypes that can arise as a result of peroxisome dysfunction. The ?-oxidation pathway is central to peroxisomal metabolism, but the substrates processed are very diverse, reflecting the diversity of peroxisomes across species. Substrates for ?-oxidation enter peroxisomes via ATP-binding cassette (ABC) transporters of subfamily D; (ABCD) and are activated by specific acyl CoA synthetases for further metabolism. Humans have three peroxisomal ABCD family members, which are half transporters that homodimerize and have distinct but partially overlapping substrate specificity; Saccharomyces cerevisiae has two half transporters that heterodimerize and plants have a single peroxisomal ABC transporter that is a fused heterodimer and which appears to be the single entry point into peroxisomes for a very wide variety of ?-oxidation substrates. Our studies suggest that the Arabidopsis peroxisomal ABC transporter AtABCD1 accepts acyl CoA substrates, cleaves them before or during transport followed by reactivation by peroxisomal synthetases. We propose that this is a general mechanism to provide specificity to this class of transporters and by which amphipathic compounds are moved across peroxisome membranes. PMID:26517910

  2. Molecular mechanism of biological proton transport

    International Nuclear Information System (INIS)

    Proton transport across lipid membranes is a fundamental aspect of biological energy transduction (metabolism). This function is believed to be mediated by a Grotthuss mechanism involving proton hopping along hydrogen-bonded networks embedded in membrane-spanning proteins. Using molecular simulations, we have explored the structural, dynamic, and thermodynamic properties giving rise to long-range proton translocation in hydrogen-bonded networks involving water molecules, or 'water wires,' which are emerging as ubiquitous H+-transport devices in biological systems. (c) 1999 American Institute of Physics

  3. Dynamic analysis of the mechanical systems vibrating transversally in transportation

    Directory of Open Access Journals (Sweden)

    A. Buchacz

    2007-01-01

    Full Text Available Purpose: Purpose of this paper is analysis and modelling of mechanical systems in transportation. Thecontemporary technical problems are lashed with high work demands such as high speeds of mechanisms, usinglower density materials, high precision of work, etc. The main objective of this thesis was the dynamical analysiswith taking into consideration the interaction between main motion and local vibrations during the model isloaded by transverse forces.Design/methodology/approach: Equations of motion were derived by classical methods, the Lagrangeequations with generalized coordinates and generalized velocities assumed as orthogonal projections ofindividual coordinates and velocities of the beam and manipulators to axes of the global inertial frame.Findings: Presented mathematical model of the transversally vibrating systems in planar transportation can beput to use to derivation of the dynamical flexibility of these systems, moreover those equations are the startingpoint to the analysis of complex systems. In particular we can use those equations to derivation of the substitutedynamical flexibility of multibody systems.Research limitations/implications: There were considered mechanical systems vibrating transversally in termsof plane motion. Next problem of dynamical analysis is the analysis of systems in non-planar transportation andsystems loaded by longitudinal forces.Practical implications: Results of this thesis can be put to use into all machines and mechanisms running intransportation such as wind power plants, high speed turbines, rotors, manipulators and in aerodynamics issues,etc. Some results ought to be modified and adopted to appropriate models.Originality/value: High requirements applying to parameters of work of machines and mechanisms are causedthe new research and new ways of modelling and analyzing those systems. One of these ways are presented inthis thesis. There was defined the transportation effect for models vibrating transversally.

  4. Prenatal caffeine exposure induced a lower level of fetal blood leptin mainly via placental mechanism.

    Science.gov (United States)

    Wu, Yi-Meng; Luo, Han-Wen; Kou, Hao; Wen, Yin-Xian; Shen, Lang; Pei, Ling-Guo; Zhou, Jin; Zhang, Yuan-Zhen; Wang, Hui

    2015-11-15

    It's known that blood leptin level is reduced in intrauterine growth retardation (IUGR) fetus, and placental leptin is the major source of fetal blood leptin. This study aimed to investigate the decreased fetal blood leptin level by prenatal caffeine exposure (PCE) and its underlying placental mechanisms. Pregnant Wistar rats were intragastrically administered caffeine (30-120mg/kgday) from gestational day 9 to 20. The level of fetal serum leptin and the expression of placental leptin-related genes were analyzed. Furthermore, we investigated the molecular mechanism of the reduced placental leptin's expression by treatment with caffeine (0.8-20?M) in the BeWo cells. In vivo, PCE significantly decreased fetal serum leptin level in caffeine dose-dependent manner. Meanwhile, placental mRNA expression of adenosine A2a receptor (Adora2a), cAMP-response element binding protein (CREB), a short-type leptin receptor (Ob-Ra) and leptin was reduced in the PCE groups. In vitro, caffeine significantly decreased the mRNA expression of leptin, CREB and ADORA2A in concentration and time-dependent manners. The addition of ADORA2A agonist or adenylyl cyclase (AC) agonist reversed the inhibition of leptin expression induced by caffeine. PCE induced a lower level of fetal blood leptin, which the primary mechanism is that caffeine inhibited antagonized Adora2a and AC activities to decreased cAMP synthesis, thus inhibited the expression of the transcription factor CREB and target gene leptin in the placenta. Meantime, the reduced transportation of maternal leptin by placental Ob-Ra also contributed to the reduced fetal blood leptin. Together, PCE decreased fetal blood leptin mainly via reducing the expression and transportation of leptin in the placenta. PMID:26367767

  5. Rat hepatocytes transport water mainly via a non-channel-mediated pathway.

    Science.gov (United States)

    Yano, M; Marinelli, R A; Roberts, S K; Balan, V; Pham, L; Tarara, J E; de Groen, P C; LaRusso, N F

    1996-03-22

    During bile formation by the liver, large volumes of water are transported across two epithelial barriers consisting of hepatocytes and cholangiocytes (i.e. intrahepatic bile duct epithelial cells). We recently reported that a water channel, aquaporin-channel-forming integral protein of 28 kDa, is present in cholangiocytes and suggested that it plays a major role in water transport by these cells. Since the mechanisms of water transport across hepatocytes remain obscure, we performed physiological, molecular, and biochemical studies on hepatocytes to determine if they also contain water channels. Water permeability was studied by exposing isolated rat hepatocytes to buffers of different osmolarity and measuring cell volume by quantitative phase contrast, fluorescence and laser scanning confocal microscopy. Using this method, hepatocytes exposed to hypotonic buffers at 23 degrees C increased their cell volume in a time and osmolarity-dependent manner with an osmotic water permeability coefficient of 66.4 x 10(-4) cm/s. In studies done at 10 degrees C, the osmotic water permeability coefficient decreased by 55% (p < 0.001, at 23 degrees C; t test). The derived activation energy from these studies was 12.8 kcal/mol. After incubation of hepatocytes with amphotericin B at 10 degrees C, the osmotic water permeability coefficient increased by 198% (p < 0.001) and the activation energy value decreased to 3.6 kcal/mol, consistent with the insertion of artificial water channels into the hepatocyte plasma membrane. Reverse transcriptase polymerase chain reaction with hepatocyte RNA as template did not produce cDNAs for three of the known water channels. Both the cholesterol content and the cholesterol/phospholipid ratio of hepatocyte plasma membranes were significantly (p < 0.005) less than those of cholangiocytes; membrane fluidity of hepatocytes estimated by measuring steady-state anisotropy was higher than that of cholangiocytes. Our data suggests that the osmotic flow of water across hepatocyte membranes occurs mainly by diffusion via the lipid bilayer (not by permeation through water channels as in cholangiocytes). PMID:8636089

  6. Evaporation as the transport mechanism of metals in arid regions

    KAUST Repository

    Lima, Ana T.

    2014-09-01

    Soils of arid regions are exposed to drought and drastic temperature oscillations throughout the year. Transport mechanisms in these soils are therefore very different from the ones in temperate regions, where rain dictates the fate of most elements in soils. Due to the low rainfall and high evaporation rates in arid regions, groundwater quality is not threatened and all soil contamination issues tend to be overlooked. But if soil contamination happens, where do contaminants go? This study tests the hypothesis of upward metal movement in soils when evaporation is the main transport mechanism. Laboratory evaporation tests were carried out with heavy metal spiked Saudi soil, using circulation of air as the driving force (Fig. 1). Main results show that loamy soil retains heavy metals quite well while evaporation drives heavy metals to the surface of a sandy soil. Evaporation transports heavy metals upward in sandy soils of arid regions, making them accumulate at the soil surface. Sand being the dominating type of soil in arid regions, soils can then be a potential source of contaminated aerosols and atmospheric pollution - a transboundary problem. Some other repercussions for this problem are foreseen, such as the public ingestion or inhalation of dust. © 2014 Elsevier Ltd.

  7. As if Kyoto mattered: The clean development mechanism and transportation

    International Nuclear Information System (INIS)

    Transportation is a major source of greenhouse gas (GHG) emissions and the most rapidly growing anthropogenic source. In the future, the developing world will account for the largest share of transport GHG increases. Four basic components drive transportation energy consumption and GHG emissions: activities (A), mode share (S), fuel intensity (I) and fuel choice (F) (ASIF). Currently, the Kyoto Protocol's clean development mechanism (CDM) serves as the main international market-based tool designed to reduce GHG emissions from the developing world. Theoretically, the CDM has the dual purpose of helping developing countries achieve 'sustainable development' goals and industrialized countries meet their Kyoto emissions reduction commitments. This paper reviews overall CDM activities and transportation CDM activities to date and then presents findings from three case studies of transportation CDM possibilities examined with the ASIF framework in Santiago de Chile. The analysis suggests that bus technology switch (I) provides a fairly good project fit for the CDM, while options aimed at inducing mode share (S) to bicycle, or modifying travel demand via land use changes (ASI) face considerable challenges. The implications of the findings for the CDM and the 'post-Kyoto' world are discussed

  8. Detection of Explosives by Nqr Method: Main Aspects for Transport Security

    Science.gov (United States)

    Rudakov, Taras N.

    The main aspects specific to the Nuclear Quadrupole Resonance (NQR) application for the transport security are analyzed and discussed. The continuing efforts to improve the function of the NQR based Explosive Detection Systems (EDS) through a more sensitive detection are described. The methods of reducing false alarm events generated from the RF excitation and interference are presented and discussed. The operational features of the NQR scanners are also presented and discussed.

  9. Chemical and mechanical control of corrosion product transport

    Energy Technology Data Exchange (ETDEWEB)

    Hede Larsen, O.; Blum, R. [I/S Fynsvaerket, Faelleskemikerne, Odense (Denmark); Daucik, K. [I/S Skaerbaekvaerket, Faelleskemikerne, Fredericia (Denmark)

    1996-12-01

    The corrosion products formed in the condensate and feedwater system of once-through boilers are precipitated and deposited inside the evaporator tubes mainly in the burner zone at the highest heat flux. Depositions lead to increased oxidation rate and increased metal temperature of the evaporator tubes, hereby decreasing tube lifetime. This effect is more important in the new high efficiency USC boilers due to increased feedwater temperature and hence higher thermal load on the evaporator tubes. The only way to reduce the load on the evaporator tubes is to minimise corrosion product transport to the boiler. Two general methods for minimising corrosion product transport to the boiler have been evaluated through measurement campaigns for Fe in the water/steam cycle in supercritical boilers within the ELSAM area. One method is to reduce corrosion in the low temperature condensate system by changing conditioning mode from alkaline volatile treatment (AVT) to oxygenated treatment (OT). The other method is to filtrate part of the condensate with a mechanical filter at the deaerator. The results show, that both methods are effective at minimising Fe-transport to the boiler, but changing to OT has the highest effect and should always be used, whenever high purity condensate is maintained. Whether mechanical filtration also is required, depends on the boiler, specifically the load on the evaporator. A simplified calculation model for lifetime evaluation of evaporator tubes has been developed. This model has been used for evaluating the effect of corrosion product transport to the boiler on evaporator tube lifetime. Conventional supercritical boilers generally can achieve sufficient lifetime by AVT and even better by OT, whereas all measures to reduce Fe-content of feedwater, including OT and mechanical filtration, should be taken, to ensure sufficient lifetime for the new boilers with advanced steam data - 290 bar/580 deg. C and above. (au)

  10. Mechanism of ochratoxin A transport in kidney

    Energy Technology Data Exchange (ETDEWEB)

    Sokol, P.P.; Ripich, G.; Holohan, P.D.; Ross, C.R.

    1988-08-01

    The effect of the fungal metabolite (mycotoxin) Ochratoxin A (OTA) on the transport of p-amino(/sup 3/H)hippurate (PAH), a prototypic organic anion, was examined in renal brush border (BBMV) and basolateral membrane vesicles (BLMV). OTA was as effective an inhibitor of PAH uptake in both membranes as probenecid. The dose response curves for OTA in BBMV and BLMV gave IC50 values of 20 +/- 6 and 32 +/- 7 microM, respectively. The effect was specific since the transport of the organic cation N1-methylnicotinamide was not affected. The phenomenon of counterflow was studied to establish that OTA is translocated. OTA produced trans stimulation of PAH transport in both BBMV and BLMV, demonstrating that OTA is transported across both these membranes. The data suggest that OTA interacts with the PAH transport system in both BBMV and BLMV. We conclude that OTA transport in the kidney is mediated via the renal organic anion transport system.

  11. Challenges in materials and welding of main heat transport system piping of AHWR

    International Nuclear Information System (INIS)

    Advanced Heavy Water Reactor (AHWR) is a 920 MWth, 300 MW vertical pressure tube type reactor, with boiling light water as a coolant in a high-pressure main heat transport (MHT) system. In view of the proposed 100 year life of AHWR, materials and welding of piping of the MHT system are of concern because of lack of experience and material data for such long duration. First challenge was to select the materials, where the coolant is a two-phase steam water mixture and the chemistry of coolant is similar to that of typical boiling water reactor. Failure of austenitic stainless steel piping of boiling water reactors due to Intergranular Stress Corrosion Cracking (IGSCC) has been reported extensively in the literature. Austenitic stainless steel of SS 304L or 304LN grade has been chosen based on its satisfactory low temperature sensitization behaviour and superior low temperature embrittlement behaviour. The material specification was optimized to gain maximum advantage in respect of intergranular stress corrosion cracking. In order to demonstrate the absence of proneness of the chosen material to LTS, the material (base and weld including HAZ) was subjected to accelerated thermal ageing; 1300 and 8000 Hours at 450 deg C and 400 deg C simulating 100 years at 300 deg C. Thermally aged materials were tested for susceptibility to sensitization by carrying out the tests as per ASTM A262 and Electo-Potentiokinetic Reactivation (EPR) method. It was observed that degree of sensitization increases with ageing time. However, it was less than acceptable limit. Second challenge was minimization of residual stress during welding which was addressed by using narrow gap welding technique and the high deposition rate welding process. Pipe weld joints were produced and reduction in residual stress was quantified. Embrittlement of the weld joints has been addressed by carrying out fracture toughness tests on specimens and piping components. Effect of ageing was brought out by Charpy V-notch test on thermally aged specimens (aged for 5000 Hours). Third challenge was the welding of dissimilar metals viz. austenitic to ferritic. Fracture toughness tests on welds with Inconel 82 (filler for GTAW) as buttering and Inconel 182 (electrode for SMAW) as welding, indicate that the fracture resistance of the buttering region is lowest. Further studies with Inconel 52 and 309L are in progress. Fatigue is another major ageing degradation mechanism which leads to failure of the components and the same has been extensively studied. Fatigue crack initiation and its growth has been addressed by carrying out tests on specimens (Compact Tension and Three Point Bend) and piping components (Pipe including pipe welds and elbows). The paper presents the details of the above mentioned studies. (author)

  12. Role of different scattering mechanisms on the temperature dependence of transport in graphene

    Science.gov (United States)

    Sarkar, Suman; Amin, Kazi Rafsanjani; Modak, Ranjan; Singh, Amandeep; Mukerjee, Subroto; Bid, Aveek

    2015-01-01

    Detailed experimental and theoretical studies of the temperature dependence of the effect of different scattering mechanisms on electrical transport properties of graphene devices are presented. We find that for high mobility devices the transport properties are mainly governed by completely screened short range impurity scattering. On the other hand, for the low mobility devices transport properties are determined by both types of scattering potentials - long range due to ionized impurities and short range due to completely screened charged impurities. The results could be explained in the framework of Boltzmann transport equations involving the two independent scattering mechanisms. PMID:26608479

  13. Osmoregulation in zebrafish: ion transport mechanisms and functional regulation.

    Science.gov (United States)

    Guh, Ying-Jey; Lin, Chia-Hao; Hwang, Pung-Pung

    2015-01-01

    Fish, like mammals, have to maintain their body fluid ionic and osmotic homeostasis through sophisticated iono-/osmoregulation mechanisms, which are conducted mainly by ionocytes of the gill (the skin in embryonic stages), instead of the renal tubular cells in mammals. Given the advantages in terms of genetic database availability and manipulation, zebrafish is an emerging model for research into regulatory and integrative physiology. At least five types of ionocytes, HR, NaR, NCC, SLC26, and KS cells, have been identified to carry out Na(+) uptake/H(+) secretion/NH4 (+) excretion, Ca(2+) uptake, Na(+)/Cl(-) uptake, K(+) secretion, and Cl(-) uptake/HCO3 (-) secretion, respectively, through distinct sets of transporters. Several hormones, namely isotocin, prolactin, cortisol, stanniocalcin-1, calcitonin, endothelin-1, vitamin D, parathyorid hormone 1, catecholamines, and the renin-angiotensin-system, have been demonstrated to positively or negatively regulate ion transport through specific receptors at different ionocytes stages, at either the transcriptional/translational or posttranslational level. The knowledge obtained using zebrafish answered many long-term contentious or unknown issues in the field of fish iono-/osmoregulation. The homology of ion transport pathways and hormone systems also means that the zebrafish model informs studies on mammals or other animal species, thereby providing insights into related fields. PMID:26600749

  14. [Review on the main microorganisms and their metabolic mechanisms in enhanced biological phosphorus removal (EBPR) systems].

    Science.gov (United States)

    Sun, Xue; Zhu, Wei-Jing; Wang, Liang; Wu, Wei-Xiang

    2014-03-01

    Enhanced biological phosphorus removal (EBPR) process is applied widely for removing phosphorus from wastewater. Studies on functional microorganisms and their metabolic mechanisms are fundamental to effective regulation for stable operation and performance improvement of EBPR process. Two main types of microorganisms in EBPR systems, polyphosphate accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) were selected to summarize their metabolic mechanisms such as substrate uptake mechanisms, glycogen degradation pathways, extent of TCA cycle involvement and metabolic similarity between PAOs and GAOs. Application of molecular biology techniques in microbiology and metabolic mechanisms involved in the EBPR system was evaluated. Potential future research areas for the EBPR system and process optimization were also proposed. PMID:24984512

  15. Treatment of main heat transport system of Embalse Nuclear Power Plant with hydrazine at 150 deg C

    International Nuclear Information System (INIS)

    Ion exchange resins entrance to the main heat transport system of Embalse Nuclear Power Plant in April 1988 produced an increase of crud transport in the media, an increase of D2 evolution and mild steel corrosion rates. The removal of aggressive species from steady zones and a soft passivation of surfaces using hydrazine at moderate temperature, was recommended. The aim of this treatment was a partial dissolution of superficial defective oxides followed by the build up of a protective, homogeneous and adherent layer, to reduce generalized corrosion rate to historical values. The technique consisted of successive additions of the reagent solution to complete the prefixed amount, keeping a constant temperature of 150-152 deg C during 26 hours with continuous filtration through 1um mechanical filter, followed by a period at 180 deg C. Reagent addition was limited by ammonia concentration increase due to decomposition of hydrazine. Crud evolution was according to start up operation. Latter chemical control of the media consumes a 1000 litres resin bed. The results of this very soft treatment compatible with the start up operation of the plant, are very promising from the point of view that transported crud, deuterium concentration and corrosion rates decreased to the normal values before the mentioned event. (Author)

  16. Membrane transport mechanism 3D structure and beyond

    CERN Document Server

    Ziegler, Christine

    2014-01-01

    This book provides a molecular view of membrane transport by means of numerous biochemical and biophysical techniques. The rapidly growing number of atomic structures of transporters in different conformations and the constant progress in bioinformatics have recently added deeper insights.   The unifying mechanism of energized solute transport across membranes is assumed to consist of the conformational cycling of a carrier protein to provide access to substrate binding sites from either side of a cellular membrane. Due to the central role of active membrane transport there is considerable interest in deciphering the principles of one of the most fundamental processes in nature: the alternating access mechanism.   This book brings together particularly significant structure-function studies on a variety of carrier systems from different transporter families: Glutamate symporters, LeuT-like fold transporters, MFS transporters and SMR (RND) exporters, as well as ABC-type importers.   The selected examples im...

  17. Grain transport mechanics in shallow flow

    Science.gov (United States)

    A physical model based on continuum multiphase flow is described to represent saltating transport of grains in shallow overland flows. The two-phase continuum flow of water and sediment considers coupled St.Venant type equations. The interactive cumulative effect of grains is incorporated by a dispe...

  18. Grain transport mechanics in shallow overland flow

    Science.gov (United States)

    A physical model based on continuum multiphase flow is described to represent saltating transport of grains in shallow overland flow. The two phase continuum flow of water and sediment considers coupled St.Venant type equations. The interactive cumulative effect of grains is incorporated by a disper...

  19. Mesoscopic mechanism of adiabatic charge transport

    CERN Document Server

    Zhou, F; Altshuler, B L

    1998-01-01

    We consider adiabatic charge transport through mesoscopic metallic samples caused by a periodically changing external potential. We find that both the amplitude and the sign of the charge transferred through a sample per period are random sample specific quantities. The characteristic magnitude of the charge is determined by the quantum interference.

  20. IMPROVEMENT OF FREIGHT TRANSPORTATION PROCESS AND THEIR MANAGEMENT MECHANISM

    Directory of Open Access Journals (Sweden)

    L. V. Martsenyuk

    2014-03-01

    Full Text Available Purpose. For Ukraine as for a post-socialist state there is an objective need of reforming on railway transport. In order to meet the requirements of consumers both within the country and outside of it, it is necessary to solve transport problems in time and to introduce new technologies, without lagging behind the developed European states. The purpose of this article is identification of problems in the process of freight transportations and development of ways of their overcoming, formation of the principles of economic efficiency increase for the use of freight cars using the improvement of management mechanism of freight transportations in the conditions of reforming. Methodology. Methods of strategic planning, system approach for research on improvement of the management mechanism of freight transportations, as well as the organizational-administrative method for structure of management construction were used in this research. Findings. Authors have explored the problems arising in the process of transportation of goods and measures, which will increase the efficiency of goods transportation. Advanced mechanism of freight transportation management for its application in the conditions of the railway transport reforming was developed. It is based on management centralization. Originality. The major factors, which slow down process of cargo transportations, are investigated in the article. The principles of management mechanism improvement of freight transportations are stated. They are based on association of commercial and car-repair activity of depots. All this will allow reducing considerably a car turn by decrease in duration of idle times on railway transport, increasing the speed of freight delivery and cutting down a transport component in the price of delivered production. Practical value. The offered measures will improve the efficiency of rolling stock use and increase cargo volumes turnover, promote links of Ukraine with neighboring countries.

  1. A Study on the Main Steam Safety Valve Opening Mechanism by Flashing on NPPs

    International Nuclear Information System (INIS)

    A safety injection event happened by opening of the Main Steam Safety Valve at Kori unit 1 on April 16, 2005. The safety valves were opened at the lower system pressure than the valve opening set point due to rapid system pressure drop by opening of the Power Operated Relief Valve installed at the upstream of the Main Steam System. But the opening mechanism of safety valve at the lower set point pressure was not explained exactly. So, it needs to be understood about the safety valve opening mechanism to prevent a recurrence of this kind of event at a similar system of Nuclear Power Plant. This study is aimed to suggest the hydrodynamic mechanism for the safety valve opening at the lower set point pressure and the possibility of the recurrence at similar system conditions through document reviewing for the related previous studies and Kori unit 1 event

  2. Transport mechanisms in MoTe_{2-x} single crystals

    Science.gov (United States)

    Bonnet, A.; Conan, A.; Tregouet, Y.; Zoaeter, M.; Morsli, M.

    1991-05-01

    Transport coefficient measurements (electrical conductivity, thermoelectric power, Hall effect) have been performed on single crystals of MoTe{2-x} (x= 0.040 and 0.045). Experimental results are interpreted on the basis of a compensated p-type semiconductor model where donor and acceptor lacunar levels broaden in two energy bands. At low temperatures, the conduction mechanisms are mainly governed by a thermal hopping of carriers in these bands. At higher temperatures, the contribution of the extended states must be taken into account. MoTe{1,960} and MoTe{1,955} exhibit a quasi metallic behaviour which reflects the high delocalization of the electronic states in the broadened levels. Les mesures des coefficients de transport (conductivité électrique, pouvoir thermoélectrique, effet Hall ont été effectuées sur des monocristaux de dans une gamme étendue de température. Les résultats expérimentaux sont interprétés sur la base d'un modèle de semi-conducteur compensé de type p à niveaux élargis d'origine lacunaire. A basse température les mécanismes de conduction sont principalement gouvernés par des sauts activés thermiquement des porteurs dans le niveau accepteur élargi. A plus haute température, la contribution des états étendus doit être prise en compte. MoTe{1,960} et MoTe{1,955} présentent un comportement de type quasi métallique associé à la délocalisation élevée des états électroniques dans les niveaux élargis.

  3. Walking mechanism of the intracellular cargo transporter myosin V

    International Nuclear Information System (INIS)

    Motor proteins of the myosin, kinesin and dynein families transport vesicles and other cargo along tracks of actin filaments or microtubules through the cytoplasm of cells. The mechanism by which myosin V, a motor involved in several types of intracellular transport, moves processively along actin filaments, has recently been the subject of many single molecule biophysical studies. Details of the molecular mechanisms by which this molecular motor operates are starting to emerge

  4. Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds

    Directory of Open Access Journals (Sweden)

    Wycliffe K. Kipnusu

    2009-01-01

    Full Text Available Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4 μm thick Nandi flame [Spathodea campanulata P. Beauv.] seed cuticles. J-V characteristics showed ohmic conduction at low fields and space charge limited current at high fields. Charge mobility in ohmic region was 4.06×10−5  (m2V−1s−1. Temperature-dependent conductivity measurements have been carried out in the temperature range 320 K 450 K. Activation energy within a temperature of 320 K–440 K was about 0.86 eV. Variable range hopping (VRH is the main current transport mechanism at the range of 330–440 K. The VRH mechanism was analyzed based on Mott theory and the Mott parameters: density of localized states near the Fermi-level N(EF≈9.04×1019  (eV−1cm−3 and hopping distance R≈1.44×10−7 cm, while the hopping energy (W was in the range of 0.72 eV–0.98 eV.

  5. The proton-coupled amino acid transporter hPAT1 is the main transporter involved in vigabatrin uptake in intestinal Caco-2 cells

    DEFF Research Database (Denmark)

    Nøhr, Martha Kampp; Hansen, Steen Honore'; Brodin, Birger; Holm, René; Nielsen, Carsten Uhd

    2012-01-01

    Introduction: Many drug substances are substrates for membrane transporters, which influence their intestinal absorption. Vigabatrin is a drug substance used in the treatment of epilepsy, mainly for treatment of infantile spasms. Vigabatrin is a substrate for the human proton-coupled amino acid transporter hPAT1. The aim of the project was to identify if transporters are involved in cellular uptake of vigabatrin in Caco-2 cells. Methods: The uptake rate of vigabatrin was measured in Caco-2 cells...

  6. Remote controlled apparatus comprising a main motor unit and a slave unit for transporting contaminated substances

    International Nuclear Information System (INIS)

    This invention describes an apparatus for transporting objects over a previously determined path, in particular a transport apparatus that can be remotely controlled and powered from a distance that is suitable for use in contaminated areas. The aim of this invention is to suggest a transport appliance capable of treating or transporting contaminated substances and in which the parts of the apparatus, which are the most likely to require maintenance whilst in use, are not exposed to contamination

  7. Mechanical deformations in smectic-C main-chain liquid-crystalline elastomers

    OpenAIRE

    Sánchez-Ferrer, Antoni; Finkelmann, Heino

    2009-01-01

    A novel crosslinked smectic-C Main-Chain Liquid-Crystalline Elastomer (MCLCE) has been synthesized by polycondensation of vinyloxy-terminated mesogens, tetramethyldisiloxane and pentamethylpentaoxapentasilecane. The introduction of the functional vinyloxy group allows the synthesis of well-defined networks having low soluble content and good mechanical properties. Networks having a macroscopic uniformly ordered director and a conical distribution of the smectic layer normal with respect to th...

  8. Structural basis for the mechanism of ABC transporters.

    Science.gov (United States)

    Beis, Konstantinos

    2015-10-01

    The ATP-binding cassette (ABC) transporters are primary transporters that couple the energy stored in adenosine triphosphate (ATP) to the movement of molecules across the membrane. ABC transporters can be divided into exporters and importers; importers mediate the uptake of essential nutrients into cells and are found predominantly in prokaryotes whereas exporters transport molecules out of cells or into organelles and are found in all organisms. ABC exporters have been linked with multi-drug resistance in both bacterial and eukaryotic cells. ABC transporters are powered by the hydrolysis of ATP and transport their substrate via the alternating access mechanism, whereby the protein alternates between a conformation in which the substrate-binding site is accessible from the outside of the membrane, outward-facing and one in which it is inward-facing. In this mini-review, the structures of different ABC transporter types in different conformations are presented within the context of the alternating access mechanism and how they have shaped our current understanding of the mechanism of ABC transporters. PMID:26517899

  9. Structure and mechanism of ATP-binding cassette transporters

    Science.gov (United States)

    Locher, Kaspar P.

    2008-01-01

    ATP-binding cassette (ABC) transporters constitute a large superfamily of integral membrane proteins that includes both importers and exporters. In recent years, several structures of complete ABC transporters have been determined by X-ray crystallography. These structures suggest a mechanism by which binding and hydrolysis of ATP by the cytoplasmic, nucleotide-binding domains control the conformation of the transmembrane domains and therefore which side of the membrane the translocation pathway is exposed to. A basic, conserved two-state mechanism can explain active transport of both ABC importers and ABC exporters, but various questions remain unresolved. In this article, I will review some of the crystal structures and the mechanistic insight gained from them. Future challenges for a better understanding of the mechanism of ABC transporters will be outlined. PMID:18957379

  10. Quantum mechanisms of density wave transport

    International Nuclear Information System (INIS)

    We report on new developments in the quantum picture of correlated electron transport in charge and spin density waves. The model treats the condensate as a quantum fluid in which charge soliton domain wall pairs nucleate above a Coulomb blockade threshold field. We employ a time-correlated soliton tunneling model, analogous to the theory of time-correlated single electron tunneling, to interpret the voltage oscillations and nonlinear current-voltage characteristics above threshold. An inverse scaling relationship between threshold field and dielectric response, originally proposed by Grüner, emerges naturally from the model. Flat dielectric and other ac responses below threshold in NbSe3 and TaS3, as well as small density wave phase displacements, indicate that the measured threshold is often much smaller than the classical depinning field. In some materials, the existence of two distinct threshold fields suggests that both soliton nucleation and classical depinning may occur. In our model, the ratio of electrostatic charging to pinning energy helps determine whether soliton nucleation or classical depinning dominates.

  11. Mechanical energy transport. [during stellar turbulences

    Science.gov (United States)

    Stein, R. F.; Leibacher, J. W.

    1980-01-01

    The properties, generation, and dissipation mechanisms of acoustic, gravity and Alfven waves are described, whose restoring forces are pressure, buoyancy, and magnetic tension, respectively. For acoustic waves, generation by turbulent convective motions and by the Eddington Valve thermal overstability is discussed, considering the 'five-minute' oscillation; dissipation is possible either by radiation or shocks. Generation of gravity waves by penetrative convective motions and by shear arising from supergranule motions is reviewed, and dissipation due to wave breaking, interaction with the mean horizontal fluid flow, and very severe radiative damping is considered. Attention is given to Alfven wave generation by convective motions and thermal overstability, and to dissipation by mode coupling, wave decay, current dissipation, and particle collisions producing Joule or viscous heating.

  12. Transport mechanisms of contaminants released from fine sediment in rivers

    Science.gov (United States)

    Cheng, Pengda; Zhu, Hongwei; Zhong, Baochang; Wang, Daozeng

    2015-09-01

    Contaminants released from sediment into rivers are one of the main problems to study in environmental hydrodynamics. For contaminants released into the overlying water under different hydrodynamic conditions, the mechanical mechanisms involved can be roughly divided into convective diffusion, molecular diffusion, and adsorption/desorption. Because of the obvious environmental influence of fine sediment (D_{90}= 0.06 mm), non-cohesive fine sediment, and cohesive fine sediment are researched in this paper, and phosphorus is chosen for a typical adsorption of a contaminant. Through theoretical analysis of the contaminant release process, according to different hydraulic conditions, the contaminant release coupling mathematical model can be established by the N-S equation, the Darcy equation, the solute transport equation, and the adsorption/desorption equation. Then, the experiments are completed in an open water flume. The simulation results and experimental results show that convective diffusion dominates the contaminant release both in non-cohesive and cohesive fine sediment after their suspension, and that they contribute more than 90 % of the total release. Molecular diffusion and desorption have more of a contribution for contaminant release from unsuspended sediment. In unsuspension sediment, convective diffusion is about 10-50 times larger than molecular diffusion during the initial stages under high velocity; it is close to molecular diffusion in the later stages. Convective diffusion is about 6 times larger than molecular diffusion during the initial stages under low velocity, it is about a quarter of molecular diffusion in later stages, and has a similar level with desorption/adsorption. In unsuspended sediment, a seepage boundary layer exists below the water-sediment interface, and various release mechanisms in that layer mostly dominate the contaminant release process. In non-cohesive fine sediment, the depth of that layer increases linearly with shear stress. In cohesive fine sediment, the range seepage boundary is different from that in non-cohesive sediment, and that phenomenon is more obvious under a lower shear stress.

  13. The alternating access mechanism of transport as observed in the sodium-hydantoin transporter Mhp1

    International Nuclear Information System (INIS)

    Crystal structures of a membrane protein transporter in three different conformational states provide insights into the transport mechanism. Secondary active transporters move molecules across cell membranes by coupling this process to the energetically favourable downhill movement of ions or protons along an electrochemical gradient. They function by the alternating access model of transport in which, through conformational changes, the substrate binding site alternately faces either side of the membrane. Owing to the difficulties in obtaining the crystal structure of a single transporter in different conformational states, relatively little structural information is known to explain how this process occurs. Here, the structure of the sodium-benzylhydantoin transporter, Mhp1, from Microbacterium liquefaciens, has been determined in three conformational states; from this a mechanism is proposed for switching from the outward-facing open conformation through an occluded structure to the inward-facing open state

  14. Controllable Lubrication for Main Engine Bearings Using Mechanical and Piezoelectric Actuators

    DEFF Research Database (Denmark)

    Estupinan, Edgar; Santos, Ilmar

    2012-01-01

    Although mechatronic systems are nowadays implemented in a large number of systems in vehicles, active lubrication systems are still incipient in industrial applications. This study is an attempt to extend the active lubrication concept to combustion engines and gives a theoretical contribution to this field. One refers to active lubrication when conventional hydrodynamic lubrication is combined with dynamically modified hydrostatic lubrication. In this study, two different schemes for the oil injection system in actively lubricated main engine bearings are presented. The use of active lubrication in journal bearings helps to enhance the hydrodynamic fluid film by increasing the fluid film thickness and consequently reducing viscous friction losses and vibrations. In this study, the hydrostatic lubrication is modified by injecting oil at controllable pressures through orifices circumferentially located around the bearing surface. The main equations that govern the dynamics of the injection for a piezo-actuated oil injector and a mechanical-actuated oil injector are presented. It is shown how the dynamics of the oil injection system is coupled to the dynamics of the bearing fluid film through equations. The global system is numerically solved using as a case study a single-cylinder combustion engine, where the conventional lubrication of the main bearing is modified by applying radial oil injection using piezo-actuated injection. The performance of such a hybrid bearing is compared to an equivalent conventional lubricated bearing in terms of the maximum fluid film pressures, minimum fluid film thicknesses, and reduction of viscous friction losses.

  15. Increased coordination in public transport – which mechanisms are available?

    DEFF Research Database (Denmark)

    Sørensen, Claus Hedegaard; Longva, Frode

    2011-01-01

    After several years of New Public Management reforms within public transport, coordination seems to receive increased attention. With examples of actual as well as suggested changes taken from Denmark, Sweden and the UK the aim of the article is to analyse and classify the mechanisms utilized and suggested to increase coordination between core stakeholders within passenger railway services and bus services. Four distinctive mechanisms of coordination are suggested, namely organisational coordina...

  16. Increased coordination in public transport-which mechanisms are available?

    DEFF Research Database (Denmark)

    Sørensen, Claus Hedegaard; Longva, Frode

    2011-01-01

    After several years of New Public Management reforms within public transport, coordination seems to receive increased attention. With examples of actual as well as suggested changes taken from Denmark. Sweden and the UK the aim of the article is to analyse and classify the mechanisms utilized and suggested to increase coordination between core stakeholders within passenger railway services and bus services. Four distinctive mechanisms of coordination are suggested, namely organisational coordina...

  17. Catalyst transport in corn stover internodes: elucidating transport mechanisms using Direct Blue-I.

    Science.gov (United States)

    Viamajala, Sridhar; Selig, Michael J; Vinzant, Todd B; Tucker, Melvin P; Himmel, Michael E; McMillan, James D; Decker, Stephen R

    2006-01-01

    The transport of catalysts (chemicals and enzymes) within plant biomass is believed to be a major bottleneck during thermochemical pretreatment and enzymatic conversion of lignocellulose. Subjecting biomass to size reduction and mechanical homogenization can reduce catalyst transport limitations; however, such processing adds complexity and cost to the overall process. Using high-resolution light microscopy, we have monitored the transport of an aqueous solution of Direct Blue-I (DB-I) dye through intact corn internodes under a variety of impregnation conditions. DB-I is a hydrophilic anionic dye with affinity for cellulose. This model system has enabled us to visualize likely barriers and mechanisms of catalyst transport in corn stems. Microscopic images were compared with calculated degrees of saturation (i.e., volume fraction of internode void space occupied by dye solution) to correlate impregnation strategies with dye distribution and transport mechanisms. Results show the waxy rind exterior and air trapped within individual cells to be the major barriers to dye transport, whereas the vascular bundles, apoplastic continuum (i.e., the intercellular void space at cell junctions), and fissures formed during the drying process provided the most utilized pathways for transport. Although representing only 20-30% of the internode volume, complete saturation of the apoplast and vascular bundles by fluid allowed dye contact with a majority of the cells in the internode interior. PMID:16915666

  18. Issues in tokamak/stellarator transport and confinement enhancement mechanisms

    International Nuclear Information System (INIS)

    At present, the mechanism for anomalous energy transport in low-β toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E x B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs

  19. Perturbations to SOC models as a mechanism for transport control

    International Nuclear Information System (INIS)

    Recently the concept of Self-Organized Criticality (SOC) was advanced as a paradigm for turbulent transport in magnetically confined plasmas. The type of model has the advantage of predicting general features of the transport dynamics and profiles independent of the local instability driving the fluctuations. Such a model predicts profile resiliency, sub-marginal profiles maintaining active transport, intermittency in flux and transport events which have large correlation lengths while the underlying fluctuations have short correlation lengths. Given that many of these features have been observed in experiments, an investigation is made of the dynamics of a perturbed SOC system as a mechanism for the control of transport. One of the problems faced by magnetic confinement devices is the control of the heat and particle fluxes. If the fluxes are very open-quotes burstyclose quotes then even if the walls and divertor can safely absorb the average flux the instantaneous flux could damage or destroy these surfaces. Additionally, in enhanced confinement regimes (H-mode, VH-mode, Enhanced Reversed Shear modes and such) the limiting factor is often the buildup of a super-critical gradient which gives rise to a sudden large transport event. Computational experiments with a sandpile model of SOC dynamics suggests that some modification of the transport dynamics may be possible with periodic perturbations of the internal sources

  20. ELECTRO-THERMAL AND MECHANICAL VALIDATION EXPERIMENT ON THE LHC MAIN BUSBAR SPLICE CONSOLIDATION

    CERN Document Server

    Willering, GP; Bourcey, N; Bottura, L; Charrondiere, M; Cerqueira Bastos, M; Deferne, G; Dib, G; Giloux, Chr; Grand-Clement, L; Heck, S; Hudson, G; Kudryavtsev, D; Perret, P; Pozzobon, M; Prin, H; Scheuerlein, Chr; Rijllart, A; Triquet, S; Verweij, AP

    2012-01-01

    To eliminate the risk of thermal runaways in LHC interconnections a consolidation by placing shunts on the main bus bar interconnections is proposed by the Task Force Splices Consolidation. To validate the design two special SSS magnet spares are placed on a test bench in SM-18 to measure the interconnection in between with conditions as close as possible to the LHC conditions. Two dipole interconnections are instrumented and prepared with worst-case-conditions to study the thermo-electric stability limits. Two quadrupole interconnections are instrumented and prepared for studying the effect of current cycling on the mechanical stability of the consolidation design. All 4 shunted interconnections showed very stable behaviour, well beyond the LHC design current cycle.

  1. From PHENIX to SUPER PHENIX: mechanical structures assuring reactor vessel tightness at main sodium pump penetrations

    International Nuclear Information System (INIS)

    It is shown how the mechanical problems concerning the tightness of main sodium pump penetrations through the deck of a pool type reactor have been solved in joint SNECMA - HISPANO-SUIZA/CIRNA studies. Extensive general studies have been performed and a comprehensive dossier of different possible solutions compiled. Whereever appropriate, information has been extrapolated from PHENIX experience. In the solution finally adopted, an elastic torus shaped ring, which forms a ball-and-socket type joint is used. A thin shell structure connects the bottom to the reactor internals in such a way as to permit both vertical and rotational displacements. Studies and calculation have been completed with the realization of a 1/5 scale model of the upper torus ring. Displacement, and angular and axial stiffness measurements have confirmed the validity of the hypotheses. (Auth.)

  2. Charge carrier transport mechanisms in nanocrystalline indium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Forsh, E.A., E-mail: forsh_ea@nrcki.ru [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation); Faculty of Nano-, Bio-, Information and Cognitive Technologies, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Moscow Region (Russian Federation); Marikutsa, A.V. [Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Martyshov, M.N.; Forsh, P.A. [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Rumyantseva, M.N.; Gaskov, A.M. [Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow (Russian Federation); Kashkarov, P.K. [National Research Center “Kurchatov Institute”, 123182 Moscow (Russian Federation); Faculty of Nano-, Bio-, Information and Cognitive Technologies, Moscow Institute of Physics and Technology, 141700 Dolgoprudny, Moscow Region (Russian Federation); Faculty of Physics, Lomonosov Moscow State University, 119991 Moscow (Russian Federation)

    2014-05-02

    The charge transport properties of nanocrystalline indium oxide (In{sub 2}O{sub 3}) are studied. A number of nanostructured In{sub 2}O{sub 3} samples with various nanocrystal sizes are prepared by sol–gel method and characterized using various techniques. The mean nanocrystals size varies from 7–8 nm to 18–20 nm depending on the conditions of their preparation. Structural characterizations of the In{sub 2}O{sub 3} samples are performed by means of transmission electron microscopy and X-ray diffraction. The analysis of dc and ac conductivity in a wide temperature range (T = 50–300 K) shows that at high temperatures charge carrier transport takes place over conduction band and at low temperatures a variable range hopping transport mechanism can be observed. We find out that the temperature of transition from one mechanism to another depends on nanocrystal size: the transition temperature rises when nanocrystals are bigger in size. The average hopping distance between two sites and the activation energy are calculated basing on the analysis of dc conductivity at low temperature. Using random barrier model we show a uniform hopping mechanism taking place in our samples and conclude that nanocrystalline In{sub 2}O{sub 3} can be regarded as a disordered system. - Highlights: • In{sub 2}O{sub 3} samples with various nanocrystal sizes are prepared by sol–gel method. • The mean nanocrystal size varies from 7–8 nm to 18–20 nm. • At high temperatures charge carrier transport takes place over conduction band. • At low temperatures a variable range hopping transport mechanism can be observed. • We show a uniform hopping mechanism taking place in our samples.

  3. Modeling Transport and Flow Regulatory Mechanisms of the Kidney

    Science.gov (United States)

    Layton, Anita T.

    2013-01-01

    The kidney plays an indispensable role in the regulation of whole-organism water balance, electrolyte balance, and acid-base balance, and in the excretion of metabolic wastes and toxins. In this paper, we review representative mathematical models that have been developed to better understand kidney physiology and pathophysiology, including the regulation of glomerular filtration, the regulation of renal blood flow by means of the tubuloglomerular feedback mechanisms and of the myogenic mechanism, the urine concentrating mechanism, and regulation of renal oxygen transport. We discuss how such modeling efforts have significantly expanded our understanding of renal function in both health and disease. PMID:23914303

  4. [Vesicular intracellular transport in the digestive organs. Membrane vesicle--the universal mechanism of the functional transport].

    Science.gov (United States)

    Morozov, I A

    2014-01-01

    On the basis of long-term research of the morpho-functional characteristics of the cells of the stomach, small intestine and gallbladder the mechanism and function of membrane vesicles in the implementation of the main functions of these organs sets out in this article: the secretion of hydrochloric acid by parietal cells, the absorption of nutrients in the small intestine and the fluid at a concentration of bile epitheliocytes of gallbladder. Proofs of the intracellular formation of hydrochloric acid in tubulovesicles of the parietal cells and turnover of its secretory membranes in the process of secretory cycle, that has ensured the re-use and explained the extraordinary life of these unique cells are presented. The credible mechanism of HCl output oppression by H(+)-K(+)-ATPase activity blockers has set out on this basis. The article provides detailed endocytosis mechanism of the ions and nutrients absorption by enterocytes. The mechanism of participation of the apical contractile complex of brush border of epithelial cells in the initiation of endocytosis and cytoplasmic microtubules in transport of membrane vesicles in the cytoplasm was analyzed. Based on our research and numerous of the world scientific proceedings the conclusion was done about the existence of two energy dependent types of transport in the absorptive epithelium of the digestive--transmembrane (ionic and nutritive) homeostatic type which is realized by the ATP-system of the basal plasmalemma, and vesicular (endocytosis) type which is impltmented by apical contractile complex of brush border and cytoplasmic microtubules. Both types of transport are interrelated and are under constant cellular control. This observation is relevant to the majority of cells, including those involved in the secretion of various substances: hydrochloric acid by parietal cells, enzymes by main cells of the gastric glands and exocrinocytes of the pancreas, hormone by endocrine cells of the APUD system and, finally, mediators by nerve cells. To clarify the problem of cell transport two types: homeostatic and functional transport should be distinguished. The first type is carried out mainly in relation to ions on basolateral membrane with the help of its ATPase systems and provides intracellular homeostasis and nutritive co- transportation, the second (functional) type defines the basic specific function by means of membrane vesicles. PMID:25518468

  5. Mechanism of Transport through Wood Cell Wall Polymers

    Directory of Open Access Journals (Sweden)

    Joseph E Jakes

    2013-11-01

    Full Text Available The movement of chemicals through wood is necessaryfor decay and fastener corrosion to occur in forest products.However, the mechanism responsible for the onset of fastenercorrosion and decay in wood is not known. The onset occursbefore the formation of free water in wood cavities and aqueouschemical transport would be possible. Here, we propose that theonset mechanism is the hemicelluloses going through a moistureinducedglass transition. As nm-scale regions of mechanicallysoftened hemicelluloses in cell walls percolate, pathways forchemical transport are created. The ability of chemicals to movein cell walls enables fastener corrosion and decay to occur. Thismechanism suggests that wood treatments preventing the glasstransition of hemicelluloses will inhibit fastener corrosion andwood decay. The identification of this mechanism shouldaccelerate the development of wood treatments to improve forestproducts durability.

  6. Structure and mechanism of ATP-dependent phospholipid transporters

    DEFF Research Database (Denmark)

    Lopez Marques, Rosa Laura; Poulsen, Lisbeth Rosager

    2015-01-01

    Background ATP-binding cassette (ABC) transporters and P4-ATPases are two large and seemingly unrelated families of primary active pumps involved in moving phospholipids from one leaflet of a biological membrane to the other. Scope of review This review aims to identify common mechanistic features in the way phospholipid flipping is carried out by two evolutionarily unrelated families of transporters. Major conclusions Both protein families hydrolyze ATP, although they employ different mechanisms to use it, and have a comparable size with twelve transmembrane segments in the functional unit. Further, despite differences in overall architecture, both appear to operate by an alternating access mechanism and during transport they might allow access of phospholipids to the internal part of the transmembrane domain. The latter feature is obvious for ABC transporters, but phospholipids and other hydrophobic molecules have also been found embedded in P-type ATPase crystal structures. Taken together, in two diverse groups of pumps, nature appears to have evolved quite similar ways of flipping phospholipids. General significance Our understanding of the structural basis for phospholipid flipping is still limited but it seems plausible that a general mechanism for phospholipid flipping exists in nature. This article is part of a Special Issue entitled Structural biochemistry and biophysics of membrane proteins.

  7. Catalytic Mechanism of the Maltose Transporter Hydrolyzing ATP.

    Science.gov (United States)

    Huang, Wenting; Liao, Jie-Lou

    2016-01-12

    We use quantum mechanical and molecular mechanical (QM/MM) simulations to study ATP hydrolysis catalyzed by the maltose transporter. This protein is a prototypical member of a large family that consists of ATP-binding cassette (ABC) transporters. The ABC proteins catalyze ATP hydrolysis to perform a variety of biological functions. Despite extensive research efforts, the precise molecular mechanism of ATP hydrolysis catalyzed by the ABC enzymes remains elusive. In this work, the reaction pathway for ATP hydrolysis in the maltose transporter is evaluated using a QM/MM implementation of the nudged elastic band method without presuming reaction coordinates. The potential of mean force along the reaction pathway is obtained with an activation free energy of 19.2 kcal/mol in agreement with experiments. The results demonstrate that the reaction proceeds via a dissociative-like pathway with a trigonal bipyramidal transition state in which the cleavage of the ?-phosphate P-O bond occurs and the O-H bond of the lytic water molecule is not yet broken. Our calculations clearly show that the Walker B glutamate as well as the switch histidine stabilizes the transition state via electrostatic interactions rather than serving as a catalytic base. The results are consistent with biochemical and structural experiments, providing novel insight into the molecular mechanism of ATP hydrolysis in the ABC proteins. PMID:26666844

  8. General mechanism for helium blistering involving displaced atom transport

    International Nuclear Information System (INIS)

    A mechanism developed to account for formation of vertically elongated blisters in high displacement environments produced by 252Cf alpha particles and fission fragments has been extended to formation of done-shaped blisters in the low displacement environments produced by simple helium ion beams. In this mechanism, transport of displaced atoms to relieve compressive stresses in the helium-implanted layer allows interconnections of small, subsurface bubbles to form the blister cavity. The same transport may cause thickening of the blister caps at low implantation energies. The transition from dome-shaped to vertically elongated blistering occurs between the 300 and 3000 displacements per helium atom produced by simple helium ions and 252Cf radiations respectively

  9. Microscopic chaos, fractals and transport in nonequilibrium statistical mechanics

    CERN Document Server

    Klages, Rainer

    2007-01-01

    A valuable introduction for newcomers as well as an important reference and source of inspiration for established researchers, this book provides an up-to-date summary of central topics in the field of nonequilibrium statistical mechanics and dynamical systems theory. Understanding macroscopic properties of matter starting from microscopic chaos in the equations of motion of single atoms or molecules is a key problem in nonequilibrium statistical mechanics. Of particular interest both for theory and applications are transport processes such as diffusion, reaction, conduction and viscosity. Recent advances towards a deterministic theory of nonequilibrium statistical physics are summarized: Both Hamiltonian dynamical systems under nonequilibrium boundary conditions and non-Hamiltonian modelings of nonequilibrium steady states by using thermal reservoirs are considered. The surprising new results include transport coefficients that are fractal functions of control parameters, fundamental relations between transp...

  10. Estimation of the binding ability of main transport proteins of blood plasma with liver cirrhosis by the fluorescent probe method

    Science.gov (United States)

    Korolenko, E. A.; Korolik, E. V.; Korolik, A. K.; Kirkovskii, V. V.

    2007-07-01

    We present results from an investigation of the binding ability of the main transport proteins (albumin, lipoproteins, and ?-1-acid glycoprotein) of blood plasma from patients at different stages of liver cirrhosis by the fluorescent probe method. We used the hydrophobic fluorescent probes anionic 8-anilinonaphthalene-1-sulfonate, which interacts in blood plasma mainly with albumin; cationic Quinaldine red, which interacts with ?-1-acid glycoprotein; and neutral Nile red, which redistributes between lipoproteins and albumin in whole blood plasma. We show that the binding ability of albumin and ?-1-acid glycoprotein to negatively charged and positively charged hydrophobic metabolites, respectively, increases in the compensation stage of liver cirrhosis. As the pathology process deepens and transitions into the decompensation stage, the transport abilities of albumin and ?-1-acid glycoprotein decrease whereas the binding ability of lipoproteins remains high.

  11. Increased coordination in public transport-which mechanisms are available?

    DEFF Research Database (Denmark)

    Sørensen, Claus Hedegaard; Longva, Frode

    2011-01-01

    mechanism has its strengths and failures. The article also debates to what extent the mechanisms conflict with three core characteristics of New Public Management: Unbundling of the public sector into corporatized units; more contract-based competitive provision; and greater emphasis on output controls......After several years of New Public Management reforms within public transport, coordination seems to receive increased attention. With examples of actual as well as suggested changes taken from Denmark. Sweden and the UK the aim of the article is to analyse and classify the mechanisms utilized and...... suggested to increase coordination between core stakeholders within passenger railway services and bus services. Four distinctive mechanisms of coordination are suggested, namely organisational coordination, contractual coordination, partnership coordination and discursive coordination. Each coordination...

  12. Increased coordination in public transport – which mechanisms are available?

    DEFF Research Database (Denmark)

    Sørensen, Claus Hedegaard; Longva, Frode

    2011-01-01

    mechanism has its strengths and failures. The article also debates to what extent the mechanisms conflict with three core characteristics of New Public Management: Unbundling of the public sector into corporatized units; more contract-based competitive provision; and greater emphasis on output controls.......After several years of New Public Management reforms within public transport, coordination seems to receive increased attention. With examples of actual as well as suggested changes taken from Denmark, Sweden and the UK the aim of the article is to analyse and classify the mechanisms utilized and...... suggested to increase coordination between core stakeholders within passenger railway services and bus services. Four distinctive mechanisms of coordination are suggested, namely organisational coordination, contractual coordination, partnership coordination and discursive coordination. Each coordination...

  13. Co-current air-water flow in downward sloping pipes: Transport of capacity reducing gas pockets in wastewater mains:

    OpenAIRE

    Pothof, I.W.M.

    2011-01-01

    Air-water flow is an undesired condition in many systems for the transportation of water or wastewater. Air in storm water tunnels may get trapped and negatively affect the system. Air pockets in hydropower tunnels or sewers may cause blow-back events and inadmissible pressure spikes. Water pipes and wastewater pressure mains in particular are subject to air pocket formation in downward-sloping reaches, such as inverted siphons or terrain slopes. Air pocket accumulation causes energy losses a...

  14. Use of probabilistic design methods for NASA applications. [to be used in design phase of Space Transportation Main Engine

    Science.gov (United States)

    Safie, Fayssal M.

    1992-01-01

    This paper presents a reliability evaluation process designed to improve the reliability of advanced launch systems. The work performed includes the development of a reliability prediction methodology to be used in the design phase of the Space Transportation Main Engine (STME). This includes prediction techniques which use historical data bases as well as deterministic and probabilistic engineering models for predicting design reliability. In summary, this paper describes a probabilistic design approach for the next-generation liquid rocket engine, the STME.

  15. Calcium transport in strongly calcifying laying birds: mechanisms and regulation.

    Science.gov (United States)

    Bar, Arie

    2009-04-01

    Birds that lay long clutches (series of eggs laid sequentially before a "pause day"), among them the high-producing, strongly-calcifying Gallus gallus domesticus (domestic hen) and Coturnix coturnix japonica (Japanese quail), transfer about 10% of their total body calcium daily. They appear, therefore, to be the most efficient calcium-transporters among vertebrates. Such intensive transport imposes severe demands on ionic calcium (Ca2+) homeostasis, and activates at least two extremely effective mechanisms for Ca2+ transfer from food and bone to the eggshell. This review focuses on the development, action and regulation of the mechanisms associated with paracellular and transcellular Ca2+ transport in the intestine and the eggshell gland (ESG); it also considers some of the proteins (calbindin, Ca2+ATPase, Na+/Ca2+ exchange, epithelial calcium channels (TRPVs), osteopontin and carbonic anhydrase (CA) associated with this phenomenon. Calbindins are discussed in some detail, as they appear to be a major component of the transcellular transport system, and as only they have been studied extensively in birds. The review aims to gather old and new knowledge, which could form a conceptual basis, albeit not a completely accepted one, for our understanding of the mechanisms associated with this phenomenon. In the intestine, the transcellular pathway appears to compensate for low Ca2+ intake, but in birds fed adequate calcium the major drive for calcium absorption remains the electrochemical potential difference (ECPD) that facilitates paracellular transport. However, the mechanisms involved in Ca2+ transport into the ESG lumen are not yet established. In the ESG, the presence of Ca2+-ATPase and calbindin--two components of the transcellular transport pathway--and the apparently uphill transport of Ca2+ support the idea that Ca2+ is transported via the transcellular pathway. However, the positive (plasma with respect to mucosa) electrical potential difference (EPD) in the ESG, among other findings, indicates that there may be major alternative or complementary paracellular passive transport pathways. The available evidence hints that the flow from the gut to the ESG, which occurs during a relatively short period (11 to 14 h out the 24- to 25.5-h egg cycle), is primarily driven by carbonic anhydrase (CA) activity in the ESG, which results in high HCO3(-) content that, in turn, "sucks out" Ca2+ from the intestinal lumen via the blood and ESG cells, and deposits it in the shell crystals. The increased CA activity appears to be dependent on energy input, whereas it seems most likely that the Ca2+ movement is secondary, that it utilizes passive paracellular routes that fluctuate in accordance with the appearance of the energy-dependent CA activity, and that the level of Ca2+ movement mimics that of the CA activity. The on-off signals for the overall phenomenon have not yet been identified. They appear to be associated with the circadian cycle of gonadal hormones, coupled with the egg cycle: it is most likely that progesterone acts as the "off" signal, and that the "on" signal is provided by the combined effect of an as-yet undefined endocrine factor associated with ovulation and with the mechanical strain that results from "egg white" formation and "plumping". This strain may initially trigger the formation of the mammillae and the seeding of shell calcium crystals in the isthmus, and thereafter initiate the formation of the shell in the ESG. PMID:19118637

  16. Mechanisms of carrier transport induced by a microswimmer bath.

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, Andreas; Sokolov, Andrey; Aranson, Igor S.; Lowen, Hartmut

    2015-04-01

    Recently, it was found that a wedgelike microparticle (referred to as ”carrier”) which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used.

  17. Mechanisms of carrier transport induced by a microswimmer bath.

    Science.gov (United States)

    Kaiser, Andreas; Sokolov, Andrey; Aranson, Igor S; Löwen, Hartmut

    2015-04-01

    It was shown that a wedgelike microparticle (referred to as "carrier") exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of a V-shaped carrier. We show that the transport mechanism itself strongly depends on the degree of alignment embodied in the modeling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used. PMID:25347885

  18. IDDTL: A Novel Identified Internet Data Transport Layer Mechanism

    Directory of Open Access Journals (Sweden)

    Yangyang Gao

    2014-01-01

    Full Text Available This paper proposes an identified data transport layer (IDDTL mechanism, which is implemented based on our present concepts of connection identifier (CID and CID additional information (CID-info. Since the fast evolved Internet scale and largely emerging various applications, especially with the new Internet architectures developed such as information centric network (ICN, the traditional end-to-end transport model has been exposed many defects in sorts of aspects, such as network management, flexibility and security. The novelty of the mechanism consists of two points: 1 it always conceals part of the communication information during the specific data transport process; 2 it splits the whole end-to-end communication process into two segments and forms a three-party and two-segment communication process model. Performance analysis shows that the mechanism could easily mitigate the problems such as distributed denial of service (D/DOS attacks and greatly improve the network management, flexibility and mobility. Furthermore, our simulation and test results demonstrate that IDDTL can be implemented with unique identifiers within an acceptable extra time cost of about 3.6 useconds compared with the traditional end-to-end model.

  19. Modeling the coupled mechanics, transport, and growth processes in collagen tissues.

    Energy Technology Data Exchange (ETDEWEB)

    Holdych, David J.; Nguyen, Thao D.; Klein, Patrick A.; in' t Veld, Pieter J.; Stevens, Mark Jackson

    2006-11-01

    The purpose of this project is to develop tools to model and simulate the processes of self-assembly and growth in biological systems from the molecular to the continuum length scales. The model biological system chosen for the study is the tendon fiber which is composed mainly of Type I collagen fibrils. The macroscopic processes of self-assembly and growth at the fiber scale arise from microscopic processes at the fibrillar and molecular length scales. At these nano-scopic length scales, we employed molecular modeling and simulation method to characterize the mechanical behavior and stability of the collagen triple helix and the collagen fibril. To obtain the physical parameters governing mass transport in the tendon fiber we performed direct numerical simulations of fluid flow and solute transport through an idealized fibrillar microstructure. At the continuum scale, we developed a mixture theory approach for modeling the coupled processes of mechanical deformation, transport, and species inter-conversion involved in growth. In the mixture theory approach, the microstructure of the tissue is represented by the species concentration and transport and material parameters, obtained from fibril and molecular scale calculations, while the mechanical deformation, transport, and growth processes are governed by balance laws and constitutive relations developed within a thermodynamically consistent framework.

  20. Unraveling fatty acid transport and activation mechanisms in Yarrowia lipolytica.

    Science.gov (United States)

    Dulermo, Rémi; Gamboa-Meléndez, Heber; Ledesma-Amaro, Rodrigo; Thévenieau, France; Nicaud, Jean-Marc

    2015-09-01

    Fatty acid (FA) transport and activation have been extensively studied in the model yeast species Saccharomyces cerevisiae but have rarely been examined in oleaginous yeasts, such as Yarrowia lipolytica. Because the latter begins to be used in biodiesel production, understanding its FA transport and activation mechanisms is essential. We found that Y. lipolytica has FA transport and activation proteins similar to those of S. cerevisiae (Faa1p, Pxa1p, Pxa2p, Ant1p) but mechanism of FA peroxisomal transport and activation differs greatly with that of S. cerevisiae. While the ScPxa1p/ScPxa2p heterodimer is essential for growth on long-chain FAs, ?Ylpxa1 ?Ylpxa2 is not impaired for growth on FAs. Meanwhile, ScAnt1p and YlAnt1p are both essential for yeast growth on medium-chain FAs, suggesting they function similarly. Interestingly, we found that the ?Ylpxa1 ?Ylpxa2 ?Ylant1 mutant was unable to grow on short-, medium-, or long-chain FAs, suggesting that YlPxa1p, YlPxa2p, and YlAnt1p belong to two different FA degradation pathways. We also found that YlFaa1p is involved in FA storage in lipid bodies and that FA remobilization largely depended on YlFat1p, YlPxa1p and YlPxa2p. This study is the first to comprehensively examine FA intracellular transport and activation in oleaginous yeast. PMID:25887939

  1. Diffusion and the dislocation sweeping mechanism for hydrogen transport

    International Nuclear Information System (INIS)

    A mechanism for H diffusion in metals is proposed. The mechanism for hydrogen transport or sweeping by dislocations has a number of features which invite discussion. A feature which is of some importance is that the pressures calculated in voids due to the sweeping of hydrogen to the voids are not maximum values since ideal gas conditions were assumed. It also reflects a choice of reasonable rather than maximizing values of the parameters. The sweeping mechanism predicts that voids or inclusions can be pressurized by hydrogen, which in turn can account for the much-observed reductions in the ductility of ductile alloys. Similarly, the sweeping of hydrogen to grain boundaries can also result in insidious embrittlement through the loss of cohesion

  2. Molecular Mechanisms of Phosphorus Metabolism and Transport during Leaf Senescence

    Directory of Open Access Journals (Sweden)

    Kyla A. Stigter

    2015-12-01

    Full Text Available Leaf senescence, being the final developmental stage of the leaf, signifies the transition from a mature, photosynthetically active organ to the attenuation of said function and eventual death of the leaf. During senescence, essential nutrients sequestered in the leaf, such as phosphorus (P, are mobilized and transported to sink tissues, particularly expanding leaves and developing seeds. Phosphorus recycling is crucial, as it helps to ensure that previously acquired P is not lost to the environment, particularly under the naturally occurring condition where most unfertilized soils contain low levels of soluble orthophosphate (Pi, the only form of P that roots can directly assimilate from the soil. Piecing together the molecular mechanisms that underpin the highly variable efficiencies of P remobilization from senescing leaves by different plant species may be critical for devising effective strategies for improving overall crop P-use efficiency. Maximizing Pi remobilization from senescing leaves using selective breeding and/or biotechnological strategies will help to generate P-efficient crops that would minimize the use of unsustainable and polluting Pi-containing fertilizers in agriculture. This review focuses on the molecular mechanisms whereby P is remobilized from senescing leaves and transported to sink tissues, which encompasses the action of hormones, transcription factors, Pi-scavenging enzymes, and Pi transporters.

  3. Design and manufacture of JOYO MK-III heat transport system components. Main dump heat exchangers

    International Nuclear Information System (INIS)

    The MK-III project has three major purposes such: increasing high neutron flux, improvement of plant availability factor and upgrading in irradiation techniques. The reactor thermal power was increased from 100 MWt to 140 MWt along with the increase of fast neutron flux. The plant concept of the cooling system to increase the heat removal capability was decided in 1991. The main components in the cooling system such as intermediate heat exchangers (IHXs) and dump heat exchangers (DHXs) were designed and manufactured based on the plant concept of the cooling system. These component replacements were safely carried out from October 30, 2000 to September 21, 2001. System function tests of the cooling system, the performance tests, were carried out from June 2003 as the last phase of the MK-III modification work. During the performance tests, the reactor power was raised step by step, while confirming the nuclear and thermal characteristics of the MK-III core and the heat removal capability of IHXs and DHXs. After the performance tests, the MK-III license was granted by the government in November 2003. The new DHX for MK-III with 35 MWt heat exchange rate was installed in the same location where the old one was installed, so the MK-III DHX was installed in the same location where the old one was installed, so the MK-III DHX was designed with almost the same geometry as the old one. The design was carefully reviewed for thermal hydraulics, pressure loss, flow induced vibration etc. During the design of the MK-III DHX, the following problems were evaluated. (1) Securing the appropriate heat removal capability margin. (2) Measures to increase the installed load associated with increase of the heat transfer area. (3) Measures to increase the air side pressure loss (Design optimization of the main air blower). (4) Improvement of the maintenance performance based on the maintenance experience of the old DHX. After the design study and modification work of the MK-III DHX, the system faction and the performance tests were carried out. As a result of these tests, it was confirmed that the performance of the MK-III DHX satisfied the design. This report describes the specific characteristics in the design and manufacturing, the design data and principles of the design for the MK-III DHX. (author)

  4. Inner nuclear membrane protein transport is mediated by multiple mechanisms.

    Science.gov (United States)

    Zuleger, Nikolaj; Korfali, Nadia; Schirmer, Eric C

    2008-12-01

    Work in the nuclear transport field has led to an incredibly detailed description of protein translocation through the central channel of the nuclear pore complex, yet the mechanism by which nuclear envelope transmembrane proteins reach the inner nuclear membrane after synthesis in the endoplasmic reticulum is still hotly debated. Three different translocation models have gained experimental support: (i) simple lateral diffusion through the nuclear envelope membrane system; (ii) translocation by vesicle fusion events; and (iii) a variation on classical transport mediated by the nuclear pore complex. Although these models appear to be mutually exclusive, in the present paper we argue that they probably all function for different inner nuclear membrane proteins according to their unique characteristics. PMID:19021558

  5. [Mechanical stress of newborn infants caused by incubator transport].

    Science.gov (United States)

    Boenisch, H; Gaden, W; Mau, G; Gohrbandt, U; Teuteberg, H O; Braun, H; Beermann, H J

    1985-07-01

    Newborn babies transported in an incubator are obviously exposed to considerable mechanical vibrations. We measured these vibrations with the aim to improve these conditions. The vibrations measured on transportation by R.T.W. ambulance (Daimler-Benz 508 with an "anti-vibration platform") are almost tolerable; however on the K.T.W. ambulance (Volkswagen Type 2) the registered vertical accelerations were much greater and gave an unacceptable level of gravitational forces. Small constructive corrections to the stretcher and the connection between stretcher and incubator lead to a marked decrease in peak acceleration and the value of effective acceleration. We also found that it is of great importance to drive smoothly and that the vibrations are more pronounced with hasty driving. The influence of these vibrations as a possible co-factor in the pathogenesis of intracranial haemorrhage is discussed. PMID:4047059

  6. Mechanical Fatigue Testing of High Burnup Fuel for Transportation Applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jy-An John [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Wang, Hong [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-05-01

    This report describes testing designed to determine the ability of high burnup (HBU) (>45 GWd/MTU) spent fuel to maintain its integrity under normal conditions of transportation. An innovative system, Cyclic Integrated Reversible-bending Fatigue Tester (CIRFT), has been developed at Oak Ridge National Laboratory (ORNL) to test and evaluate the mechanical behavior of spent nuclear fuel (SNF) under conditions relevant to storage and transportation. The CIRFT system is composed of a U-frame equipped with load cells for imposing the pure bending loads on the SNF rod test specimen and measuring the in-situ curvature of the fuel rod during bending using a set up with three linear variable differential transformers (LVDTs).

  7. Mechanical transport in two-dimensional networks of fractures

    International Nuclear Information System (INIS)

    The objectives of this research are to evaluate directional mechanical transport parameters for anisotropic fracture systems, and to determine if fracture systems behave like equivalent porous media. The tracer experiments used to measure directional tortuosity, longitudinal geometric dispersivity, and hydraulic effective porosity are conducted with a uniform flow field and measurements are made from the fluid flowing within a test section where linear length of travel is constant. Since fluid flow and mechanical transport are coupled processes, the directional variations of specific discharge and hydraulic effective porosity are measured in regions with constant hydraulic gradients to evaluate porous medium equivalence for the two processes, respectively. If the fracture region behaves like an equivalent porous medium, the system has the following stable properties: (1) specific discharge is uniform in any direction and can be predicted from a permeability tensor; and (2) hydraulic effective porosity is directionally stable. Fracture systems with two parallel sets of continuous fractures satisfy criterion 1. However, in these systems hydraulic effective porosity is directionally dependent, and thus, criterion 2 is violated. Thus, for some fracture systems, fluid flow can be predicted using porous media assumptions, but it may not be possible to predict transport using porous media assumptions. Two discontinuous fracture systems were studied which satisfied both criteria. Hydraulic effective porosity for both systems has a value between rock effective porosity and total porosity. A length-density analysis (LDS) of Canadian fracture data shows that porous media equivalence for fluid flow and transport is likely when systems have narrow aperture distributions. 54 references, 90 figures, 7 tables

  8. Mechanical transport in two-dimensional networks of fractures

    Energy Technology Data Exchange (ETDEWEB)

    Endo, H.K.

    1984-04-01

    The objectives of this research are to evaluate directional mechanical transport parameters for anisotropic fracture systems, and to determine if fracture systems behave like equivalent porous media. The tracer experiments used to measure directional tortuosity, longitudinal geometric dispersivity, and hydraulic effective porosity are conducted with a uniform flow field and measurements are made from the fluid flowing within a test section where linear length of travel is constant. Since fluid flow and mechanical transport are coupled processes, the directional variations of specific discharge and hydraulic effective porosity are measured in regions with constant hydraulic gradients to evaluate porous medium equivalence for the two processes, respectively. If the fracture region behaves like an equivalent porous medium, the system has the following stable properties: (1) specific discharge is uniform in any direction and can be predicted from a permeability tensor; and (2) hydraulic effective porosity is directionally stable. Fracture systems with two parallel sets of continuous fractures satisfy criterion 1. However, in these systems hydraulic effective porosity is directionally dependent, and thus, criterion 2 is violated. Thus, for some fracture systems, fluid flow can be predicted using porous media assumptions, but it may not be possible to predict transport using porous media assumptions. Two discontinuous fracture systems were studied which satisfied both criteria. Hydraulic effective porosity for both systems has a value between rock effective porosity and total porosity. A length-density analysis (LDS) of Canadian fracture data shows that porous media equivalence for fluid flow and transport is likely when systems have narrow aperture distributions. 54 references, 90 figures, 7 tables.

  9. Design and manufacture of JOYO MK-III heat transport system. Main Intermediate heat exchanger

    International Nuclear Information System (INIS)

    The MK-III project to improve the irradiation capability of the experimental fast reactor JOYO have been in underway. The MK-III project has three major purposes such as increasing high neutron flux, improvement of plant availability factor and upgrading in irradiation techniques. The increase of fast neutron flux and the enlargement of that field increase the reactor thermal rate from 100 MWt to 140 MWt. The main components in the cooling system such as intermediate heat exchangers (IHXs) and dump heat exchangers (DHXs) were replaced in MK-III modification in order to increase heat removal capability. These components replacement has been safely carried out from October 30, 2000 to September 21, 2001. The new IHX that has 70 MWt rated heat exchange rate was installed to the location where old one was installed, so the mew IHX was designed with almost same geometry as old one. The design was carefully reviewed on structural integrity, shielding performance, thermal hydraulics, pressure loss, flow induced vibration and component design criterion and earthquake-proof class. A newly developed stainless steel named 316FR was adopted as a major structure material of the new IHX. The 316FR was developed for usage of sodium cooled fast reactor and has improved creep rupture and creep fatigue strength, In the design the following problems to be solved were cleared, These problems arise from defect of old IHX, increase of temperature difference between outlet and inlet and increase of sodium flow rate. (1) Reduction of ineffective flow to increase the heat transfer efficiency. (2) Suppression of CP (Corrosion Products) adhesion. (3) To prevent falling down of sodium free surface accompanied by increase of sodium flow. (4) Mitigation of thermal transient. This report describes the specific characteristic in the design and manufacturing, design data and principle of the design for the new IHX. The design was proved on above mentioned problem (3) by measurement of sodium free surface level up to the MK-II sodium flow rate during the comprehensive function test from February to March, 2003. The design adequacy for problem (1) and (4) will be confirmed in performance test. The CP adhesion will be investigated through long term operation. (author)

  10. Analysis of River – Sea Transport in the Direction of the Danube – Black Sea and the Danube Rhine River River Main

    Directory of Open Access Journals (Sweden)

    S. Šo?kic

    2014-12-01

    Full Text Available Development of the river sea transport is directly related to the characteristics of waterway network which enables navigation between river basins and seas. Inland waterways in Serbia belong to the Danube navigational system. There are two navigational directions: Danube East and Danube West. River-sea transport can be directly established in these directions between the Serbian international ports on the Danube (Apatin, Novi Sad, Belgrade, Pan?evo, Smederevo and Prahovo. Development of the Pan-European Corridor VII and the River Danube-Black Sea and Danube-Rhine-Main region would allow not only in Serbia but also in neighbouring states and all over Europe connection with the sea. In this paper the technical and exploitation characteristics of the river Danube will be analysed in terms of the navigation of various river and sea vessels with different exploitation characteristics.

  11. Transport of Sulfide-Reduced Graphene Oxide in Saturated Quartz Sand: Cation-Dependent Retention Mechanisms.

    Science.gov (United States)

    Xia, Tianjiao; Fortner, John D; Zhu, Dongqiang; Qi, Zhichong; Chen, Wei

    2015-10-01

    We describe how the reduction of graphene oxide (GO) via environmentally relevant pathways affects its transport behavior in porous media. A pair of sulfide-reduced GOs (RGOs), prepared by reducing 10 mg/L GO with 0.1 mM Na2S for 3 and 5 days, respectively, exhibited lower mobility than did parent GO in saturated quartz sand. Interestingly, decreased mobility cannot simply be attributed to the increased hydrophobicity and aggregation upon GO reduction because the retention mechanisms of RGOs were highly cation-dependent. In the presence of Na(+) (a representative monovalent cation), the main retention mechanism was deposition in the secondary energy minimum. However, in the presence of Ca(2+) (a model divalent cation), cation bridging between RGO and sand grains became the most predominant retention mechanism; this was because sulfide reduction markedly increased the amount of hydroxyl groups (a strong metal-complexing moiety) on GO. When Na(+) was the background cation, increasing pH (which increased the accumulation of large hydrated Na(+) ions on grain surface) and the presence of Suwannee River humic acid (SRHA) significantly enhanced the transport of RGO, mainly due to steric hindrance. However, pH and SRHA had little effect when Ca(2+) was the background cation because neither affected the extent of cation bridging that controlled particle retention. These findings highlight the significance of abiotic transformations on the fate and transport of GO in aqueous systems. PMID:26348539

  12. Driving mechanism of toroidal rotation and momentum transport in JT-60U

    International Nuclear Information System (INIS)

    The driving mechanism of toroidal rotation and the momentum transport are studied, utilizing nearperpendicular neutral beam injection (PERP-NBI), co tangential and counter tangential NBI in JT-60U. Main results are as follows: (i) fast ion losses due to the toroidal field ripple induce the toroidal rotation in the direction antiparallel to the plasma current, i.e. counter (CTR) direction in the peripheral region, (ii) the magnitude of CTR rotation increases with increasing the ripple loss power in the peripheral region. (iii) Diffusive and non-diffusive terms of momentum transport are evaluated from the transient analysis by using the momentum source modulation experiment. Fast ion losses which locally induce the edge CTR rotation have been used as a novel momentum source. (iv) Parameter dependence of these transport coefficients i.e. the toroidal momentum diffusivity ?? and the convection velocity Vconv, and the relation between heat and momentum diffusivities are investigated in L and H-mode plasmas systematically. The toroidal momentum diffusivity increases with increasing heating power, and decreases with increasing the plasma current in L-mode plasmas. The H-mode exhibits momentum diffusivity better than L-mode. Experiments indicate a positive correlation between the momentum and thermal transport at constant density. (v) We have also found that toroidal rotation velocity profiles in low .. plasmas can be almost explained by momentum transport considering diffusivity and convective velocity estimated from the transient momentum transport analysis. (author)

  13. Calcium transport mechanism in molting crayfish revealed by microanalysis

    International Nuclear Information System (INIS)

    Crayfish provide a good model in which to study the transport mechanism of Ca ions. During the molting stage, decalcified Ca ions are transferred into the blood and accumulate in the gastrolith epithelium, after which a gastrolith is formed on the surface of the epithelium. The gastrolith is dissolved in the stomach after molting, and the Ca is reabsorbed and redistributed throughout the newly formed exoskeleton. We studied the mechanism of Ca transport by cytochemical precipitation of Ca ions and by electron microanalysis, including X-ray microanalysis (EDX) and electron energy-loss spectroscopy (EELS), with a computer. In EDX analysis, the fine precipitates of K-antimonate in the gastrolith mitochondria clearly defined Ca with antimony; we also observed a large amount of Ca-oxalate in the mitochondria, and Ca-K X-ray pulses were clearly defined. Ca-K X-rays were also detected from fresh freeze-substituted mitochondria. Finally, we succeeded in taking a Ca-L EELS image from the mitochondria of fresh freeze-substituted thin sections. Only a very small amount of Ca was detected from the cell membrane and other organelles. Ca-adenosine triphosphatase (ATPase) and Mg-ATPase activity was also very clearly demonstrated in the mitochondria. These enzymes may play an important role in Ca metabolism

  14. Exciton delocalization and energy transport mechanisms in R-phycoerythrin.

    Science.gov (United States)

    Womick, Jordan M; Liu, Haoming; Moran, Andrew M

    2011-03-31

    Energy transport mechanisms in R-Phycoerythrin (RPE), a light harvesting protein located at the top of the phycobilisome antenna in red algae, are investigated using nonlinear optical spectroscopies and theoretical models. The RPE hexamer possesses a total of 30 bilin pigments, which can be subdivided into three classes based on their molecular structures and electronic resonance frequencies. Of particular interest to this study is the influence of exciton delocalization on the real-space paths traversed by photoexcitations as they concentrate on the lowest energy pigment sites. Transient grating measurements show that significant nuclear relaxation occurs at delay times less than 100 fs, whereas energy transport spans a wide range of time scales depending on the proximity of the initial and final states involved in the process. The fastest energy transport dynamics within the RPE complex are close to 1 ps; however, evidence for sub-100 fs exciton self-trapping is also obtained. In addition, photon echo experiments reveal vibronic interactions with overdamped and underdamped nuclear modes. To establish signatures of exciton delocalization, energy transport is simulated using both modified Redfield and Fo?rster theories, which respectively employ delocalized and localized basis states. We conclude that exciton delocalization occurs between six pairs of phycoerythrobilin pigments (i.e., dimers) within the protein hexamer. It is interesting that these dimers are bound in locations analogous to the well-studied phycocyanobilin dimers of cyanobacterial allophycocyanin and c-phycocyanin in which wave function delocalization is also known to take hold. Strong conclusions regarding the electronic structures of the remaining pigments cannot be drawn based on the present experiments and simulations due to overlapping resonances and broad spectroscopic line widths, which prevent the resolution of dynamics at particular pigment sites. PMID:21381708

  15. Mechanical Forces Impair Alveolar Ion Transport Processes – A Putative Mechanism Contributing to the Formation of Pulmonary Edema

    OpenAIRE

    Fronius, Martin

    2012-01-01

    The aim of this chapter is to highlight the importance of transepithelial ion transport processes for lung function in general and to focus on the impact of mechanical forces on pulmonary ion transport in particular. Linking mechanical forces with pulmonary ion transport derives from the fact that the lung is a dynamic organ as well as from several studies providing evidence that the amount of mechanical forces as used during artificial ventilation correlates with mortality rates in patients...

  16. New mechanism for the control of sodium transport in wheat

    International Nuclear Information System (INIS)

    Full text: Durum and other tetraploid wheats are typically very salt-sensitive compared to hexaploid bread wheats. This is primarily due to high rates of Na+ accumulation in the leaves in tetraploid wheat. Recently, we have discovered a durum landrace with low Na+ accumulation and enhanced K+/Na+ discrimination, much lower than current durum cultivars and similar to bread wheat. We have identified 3 different mechanisms for the control of Na+ transport to the leaves in this landrace, 1) control of Na+ uptake at the epidermis of the root, 2) control of Na+ loading into the xylem and 3) partitioning of Na+ into the leaf sheath. The low Na+ durum landrace had 3-4 fold lower Na+ uptake rates than durum cultivars. Using X ray microanalysis on snap-frozen root sections, we found Na+ to be high in the epidermis, a decreasing gradient through the cortex, low in the endodermis and again high in the stele (pencycle and xylem parenchyma), indicative of control points at the epidermis and in the stele. Partitioning of Na+ between shoot and root was at least 5 times lower in the durum landrace, suggestive of greater control of Na+ transport at the site of xylem loading. A third and novel control mechanism was found in the leaf sheath. Short and long term salinity treatments showed that Na+ was partitioned preferentially into the sheaths of the low Na+ durum landrace, keeping leaf blade Na+ levels very low and similar to that of bread wheat Na+ partitioned in the leaf sheath was stored primarily in the parenchyma cells and Cl- in the epidermal cells. Collectively, these data show that we have identified germplasm that has the potential to increase the salt tolerance of durum wheat. Additionally, as bread wheat does not contain the mechanism for partitioning Na+ into the sheath, this trait may be useful for further increasing the salt tolerance of this species

  17. Cellular Transport Mechanisms of Cytotoxic Metallodrugs: An Overview beyond Cisplatin

    Directory of Open Access Journals (Sweden)

    Sarah Spreckelmeyer

    2014-09-01

    Full Text Available The field of medicinal inorganic chemistry has grown consistently during the past 50 years; however, metal-containing coordination compounds represent only a minor proportion of drugs currently on the market, indicating that research in this area has not yet been thoroughly realized. Although platinum-based drugs as cancer chemotherapeutic agents have been widely studied, exact knowledge of the mechanisms governing their accumulation in cells is still lacking. However, evidence suggests active uptake and efflux mechanisms are involved; this may be involved also in other experimental metal coordination and organometallic compounds with promising antitumor activities in vitro and in vivo, such as ruthenium and gold compounds. Such knowledge would be necessary to elucidate the balance between activity and toxicity profiles of metal compounds. In this review, we present an overview of the information available on the cellular accumulation of Pt compounds from in vitro, in vivo and clinical studies, as well as a summary of reports on the possible accumulation mechanisms for different families of experimental anticancer metal complexes (e.g., Ru Au and Ir. Finally, we discuss the need for rationalization of the investigational approaches available to study metallodrug cellular transport.

  18. Correlation of microstructure and thermo-mechanical properties of a novel hydrogen transport membrane

    Science.gov (United States)

    Zhang, Yongjun

    A key part of the FutureGen concept is to support the production of hydrogen to fuel a "hydrogen economy," with the use of clean burning hydrogen in power-producing fuel cells, as well as for use as a transportation fuel. One of the key technical barriers to FutureGen deployment is reliable and efficient hydrogen separation technology. Most Hydrogen Transport Membrane (HTM) research currently focuses on separation technology and hydrogen flux characterization. No significant work has been performed on thermo-mechanical properties of HTMs. The objective of the thesis is to understand the structure-property correlation of HTM and to characterize (1) thermo mechanical properties under different reducing environments and thermal cycles (thermal shock), and (2) evaluate the stability of the novel HTM material. A novel HTM cermet bulk sample was characterized for its physical and mechanical properties at both room temperature and at elevated temperature up to 1000°C. Micro-structural properties and residual stresses were evaluated in order to understand the changing mechanism of the microstructure and its effects on the mechanical properties of materials. A correlation of the microstructural and thermo mechanical properties of the HTM system was established for both HTM and the substrate material. Mechanical properties of both selected structural ceramics and the novel HTM cermet bulk sample are affected mainly by porosity and microstructural features, such as grain size and pore size-distribution. The Young's Modulus (E-value) is positively correlated to the flexural strength for materials with similar crystallographic structure. However, for different crystallographic materials, physical properties are independent of mechanical properties. Microstructural properties, particularly, grain size and crystallographic structure, and thermodynamic properties are the main factors affecting the mechanical properties at both room and high temperatures. The HTM cermet behaves more like an elastic material at room temperature and as a ductile material at temperature above 850°C. The oxidation and the plasticity of Pd phase mainly affected the mechanical properties of HTM cermet at high temperature, also as a result of thermal cycling. Residual stress induced in the HTM by thermo cycles also plays a very critical role in defining the thermo-mechanical properties.

  19. Mechanical analysis of the main bus bars in the DFBA shuffling modules

    CERN Document Server

    Ramos, D

    2012-01-01

    The main bus bars (13 kA) inside the shuffling modules of the distribution feed boxes powering the LHC arcs (DFBA) are subjected to high Lorentz forces. The structural behaviour of the bus bars under such forces is here analysed. The results are discussed with respect to a risk of structural failure due to excessive deformation or degradation of the electrical insulation by repeated contact with other surfaces.

  20. Main mechanical and thermal problems in the vacuum vessel of the FTU Tokamak machine

    International Nuclear Information System (INIS)

    The FTU Tokamak, in order to reach the expected performance has to operate steadily at high magnetic fields. Its vacuum chamber would undergo very high stresses due to thermal and electromagnetic loads for a large number of shots. In order to assess the feasibility of this component, numerical codes to compute current, magnetic field and temperature distributions and extensive three dimensional finite element stress analysis have been developed. The main results obtained are illustrated

  1. Flexible Mechanical Conveyors for Regolith Extraction and Transport

    Science.gov (United States)

    Walton, Otis R.; Vollmer, Hubert J.

    2013-01-01

    A report describes flexible mechanical conveying systems for transporting fine cohesive regolith under microgravity and vacuum conditions. They are totally enclosed, virtually dust-free, and can include enough flexibility in the conveying path to enable an expanded range of extraction and transport scenarios, including nonlinear drill-holes and excavation of enlarged subsurface openings without large entry holes. The design of the conveyors is a modification of conventional screw conveyors such that the central screw-shaft and the outer housing or conveyingtube have a degree of bending flexibility, allowing the conveyors to become nonlinear conveying systems that can convey around gentle bends. The central flexible shaft is similar to those used in common tools like a weed whacker, consisting of multiple layers of tightly wound wires around a central wire core. Utilization of compliant components (screw blade or outer wall) increases the robustness of the conveying, allowing an occasional oversized particle to pass hough the conveyor without causing a jam or stoppage

  2. Mechanical reliability of geometrically imperfect tubular oxygen transport membranes

    DEFF Research Database (Denmark)

    Kwok, Kawai; Frandsen, Henrik Lund

    2014-01-01

    Mixed ionic and electronic conductors have potential applications as oxygen transport membranes. Realization of the technology is challenged by mechanical reliability of the components which are subjected to stresses arising from oxygen stoichiometry gradients and external overpressure during operation. This paper investigates numerically the failure risk of tubular oxygen transport membranes under industrial operating conditions using finite element modeling and Weibull strength analysis. The effects of component manufacturing defects on fracture probability are elucidated by explicit modeling of imperfections in the tubular membrane geometry. A supported membrane made of dense and porous Zr-doped-BSCF is studied as an illustrative example. It is shown that stresses induced by oxygen stoichiometry gradients relax over time due to creep and external pressure is the dominating source of stress in the long term. Therefore, creep has no adverse effect for geometrically perfect membranes. For geometrically imperfect membranes, curl and eccentricity are found to have insignificant influence on fracture risk while ovality is identified as the most critical geometric imperfection. Under the influence of external pressure, ovality may lead to dramatic stress increase and flattening of oval cross sections. Oval membranes can fail in the long term even though the instantaneous fracture risk is tolerable. Based on industrial relevant conditions, the requirements to the material creep rate and component quality (in terms of specification of tolerable deviation from perfect tubular shape) that allows fail-safe operation are deduced.

  3. Mechanisms of calcium transport in small intestine. Final report

    International Nuclear Information System (INIS)

    The vitamin D hormone, 1,25-dihydroxyvitamin D3, was demonstrated to be the prime hormonal agent regulating intestinal absorption of divalent cations. Production of the vitamin D hormone is, in turn, regulated by parathyroid hormone, low dietary calcium, low plasma phosphorus, and is suppressed by 1,25-dihydroxyvitamin D3, by high plasma phosphorus, high plasma calcium, and the absence of parathyroid hormone. A variety of analogs of the vitamin D hormone were prepared. In addition, the preparation of radiolabeled vitamin D hormone was accomplished using chemical synthesis, and this highly radioactive substance was found to localize in the nuclei of the intestinal villus cells that promote intestinal absorption of calcium. A receptor for the vitamin D hormone was also located, and the general mechanism of response to the vitamin D hormone included the binding to a receptor molecule, transfer to the nucleus, transcription of specific genes followed by translation to transport proteins. Methods were developed for the discovery of the appropriate gene products that play a role in calcium transport

  4. Approaching the Shockley-Queisser limit: General assessment of the main limiting mechanisms in photovoltaic cells

    International Nuclear Information System (INIS)

    In principle, the upper efficiency limit of any solar cell technology can be determined using the detailed-balance limit formalism. However, “real” solar cells show efficiencies which are always below this theoretical value due to several limiting mechanisms. We study the ability of a solar cell architecture to approach its own theoretical limit, using a novel index introduced in this work, and the amplitude with which the different limiting mechanisms affect the cell efficiency is scrutinized as a function of the electronic gap and the illumination level to which the cell is submitted. The implications for future generations of solar cells aiming at an improved conversion of the solar spectrum are also addressed

  5. Bioturbation as a mechanism for radionuclide transport in soil: relevance of earthworms

    Energy Technology Data Exchange (ETDEWEB)

    Mueller-Lemans, H. [Tergeso AG, Sargans (Switzerland); Dorp, F. van [NAGRA, Wettingen (Switzerland)

    1996-07-01

    In the context of safety analyses performed for radioactive waste repositories, one important group of scenarios assumes that radionuclides escaping from a repository will reach the biosphere via groundwater. Consequently, when calculating radionuclide migration in the biosphere, most of the models used to date concentrate on transport in the liquid phase. In the soil, however, transport in the solid phase can also be important, particularly when burrowing animals displace the soil together with sorbed and low-solubility radionuclides. Given the conditions prevailing in agricultural areas of central Europe, it is mainly earthworms which play a significant role in material displacement and these will be the subject of this report. A numerical example is used to present the equations which, for given distribution coefficients, can be applied to calculate the portions of the transfer coefficient which can be attributed to transport in the liquid and solid phases. The results demonstrate that material transport by soil fauna, and particularly by earthworms, is a relevant mechanism in many cases, especially for the upward transport of strongly sorbing radionuclides. It should therefore be considered in biosphere models. (Author).

  6. Tunnelling effect enhanced by lattice screening as main cold fusion mechanism: An brief theoretical overview

    International Nuclear Information System (INIS)

    In this paper are illustrated the main features of tunneling traveling between two deuterons within a lattice. Considering the screening effect due lattice electrons we compare the d-d fusion rate evaluated from different authors assuming different screening efficiency and different d-d potentials. Then, we propose a effective potential which describe very well the attractive contribute due to plasmon exchange between two deuterons and by means of it we will compute the d-d fusion rates for different energy values. Finally the good agreement between theoretical and experimental results proves the reality of cold fusion phenomena and the reliability of our model

  7. The present status of vacuum system of J-PARC main ring and 3-50 beam transport

    International Nuclear Information System (INIS)

    The vacuum system of J-PARC Main Ring synchrotron and 3-50 beam transport line were successfully developed in April 2008 and still progress synchronously with the accelerator study phases such as the injection, the acceleration, the fast extraction to the abort line, the slow extraction to the hadron laboratory, fast extraction to the neutrino line, and, also the remodeling of coil wiring of sextupole magnets in this summer. In the simple ducts of the arc section, a vacuum pressure is going down to about 2e-7 Pa so that the pumps are expected to be long life, otherwise, the vacuum chamber of in-vacuum magnets such as the injection or fast-extraction septum magnets with lamination cores keeps high pressure of over 1e-5 Pa by outgassing from huge surface area. The pumps at that chambers will die in a few years. (author)

  8. Correlation between magnetic field quality and mechanical components of the Large Hadron Collider main dipoles

    International Nuclear Information System (INIS)

    The 1234 superconducting dipoles of the Large Hadron Collider, working at a cryogenic temperature of 1.9 K, must guarantee a high quality magnetic field to steer the particles inside the beam pipe. Magnetic field measurements are a powerful way to detect assembly faults that could limit magnet performances. The aim of the thesis is the analysis of these measurements performed at room temperature during the production of the dipoles. In a large scale production the ideal situation is that all the magnets produced were identical. However all the components constituting a magnet are produced with certain tolerance and the assembly procedures are optimized during the production; due to these the reality drifts away from the ideal situation. We recollected geometrical data of the main components (superconducting cables, coil copper wedges and austenitic steel coil collars) and coupling them with adequate electro-magnetic models we reconstructed a multipolar field representation of the LHC dipoles defining their critical components and assembling procedures. This thesis is composed of 3 main parts: 1) influence of the geometry and of the assembling procedures of the dipoles on the quality of the magnetic field, 2) the use of measurement performed on the dipoles in the assembling step in order to solve production issues and to understand the behaviour of coils during the assembling step, and 3) a theoretical study of the uncertain harmonic components of the magnetic field in order to assess the dipole production

  9. Correlation between magnetic field quality and mechanical components of the Large Hadron Collider main dipoles

    Energy Technology Data Exchange (ETDEWEB)

    Bellesia, B

    2006-12-15

    The 1234 superconducting dipoles of the Large Hadron Collider, working at a cryogenic temperature of 1.9 K, must guarantee a high quality magnetic field to steer the particles inside the beam pipe. Magnetic field measurements are a powerful way to detect assembly faults that could limit magnet performances. The aim of the thesis is the analysis of these measurements performed at room temperature during the production of the dipoles. In a large scale production the ideal situation is that all the magnets produced were identical. However all the components constituting a magnet are produced with certain tolerance and the assembly procedures are optimized during the production; due to these the reality drifts away from the ideal situation. We recollected geometrical data of the main components (superconducting cables, coil copper wedges and austenitic steel coil collars) and coupling them with adequate electro-magnetic models we reconstructed a multipolar field representation of the LHC dipoles defining their critical components and assembling procedures. This thesis is composed of 3 main parts: 1) influence of the geometry and of the assembling procedures of the dipoles on the quality of the magnetic field, 2) the use of measurement performed on the dipoles in the assembling step in order to solve production issues and to understand the behaviour of coils during the assembling step, and 3) a theoretical study of the uncertain harmonic components of the magnetic field in order to assess the dipole production.

  10. Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes

    Science.gov (United States)

    McIntosh, Lucas D.

    Polymer electrolytes are mixtures of a polar polymer and salt, in which the polymer replaces small molecule solvents and provides a dielectric medium so that ions can dissociate and migrate under the influence of an external electric field. Beginning in the 1970s, research in polymer electrolytes has been primarily motivated by their promise to advance electrochemical energy storage and conversion devices, such as lithium ion batteries, flexible organic solar cells, and anhydrous fuel cells. In particular, polymer electrolyte membranes (PEMs) can improve both safety and energy density by eliminating small molecule, volatile solvents and enabling an all-solid-state design of electrochemical cells. The outstanding challenge in the field of polymer electrolytes is to maximize ionic conductivity while simultaneously addressing orthogonal mechanical properties, such as modulus, fracture toughness, or high temperature creep resistance. The crux of the challenge is that flexible, polar polymers best-suited for polymer electrolytes (e.g., poly(ethylene oxide)) offer little in the way of mechanical robustness. Similarly, polymers typically associated with superior mechanical performance (e.g., poly(methyl methacrylate)) slow ion transport due to their glassy polymer matrix. The design strategy is therefore to employ structured electrolytes that exhibit distinct conducting and mechanically robust phases on length scales of tens of nanometers. This thesis reports a remarkably simple, yet versatile synthetic strategy---termed polymerization-induced phase separation, or PIPS---to prepare PEMs exhibiting an unprecedented combination of both high conductivity and high modulus. This performance is enabled by co-continuous, isotropic networks of poly(ethylene oxide)/ionic liquid and highly crosslinked polystyrene. A suite of in situ, time-resolved experiments were performed to investigate the mechanism by which this network morphology forms, and it appears to be tied to the disordered structure observed in diblock polymer melts near the order-disorder transition. In the resulting solid PEMs, the conductivity and modulus are both high, exceeding the 1 mS/cm and approaching the 1 GPa metrics, respectively, often cited for lithium-metal batteries. In the final chapter, an alternative synthetic route to generate nanostructured PEMs is presented. This strategy relies on the formation of a thermodynamically stable network morphology exhibited by a triblock terpolymer prepared with crosslinking moieties along the backbone. Although the mechanical properties of the resulting PEM are excellent, the conductivity is found to be somewhat limited by network defects that result from the solvent-casting procedure.

  11. CLUB FORMATION MECHANISM FOR TRANSPORT-COMMUNITY CREDIT CARDS

    Science.gov (United States)

    Ding, Yue; Kobayashi, Kiyoshi; Nishida, Junji; Yoshida, Mamoru

    In this paper, the roles of transport-community cards jointly issued by a public transport firm and retails are investigated as a means to vitalize an obsolescence shopping center located in a middle of a city. When both the price of goods supplied by the retails and the transport fares affect the consumers' behavior, there exist pecuniary externality between the behaviors of the retails and transport firms. The introduction of a transport-community cards system enables to integrate a basket of goods and transport service into a single commodity; thus, the pecuniary externality can be internalized by price coordination. In addition, the paper clarifies theoretically that the transport firm initiatively decides the price of the transportation service and the retails transfer their incomes to the transport firm so that they are induced to jointly issue the transport-community cards.

  12. The role of lock-in mechanisms in transition processes: the case of energy for road transport

    OpenAIRE

    Klitkou, Antje; Bolwig, Simon; Hansen, Teis; Wessberg, Nina

    2015-01-01

    This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries, focussing on three technology platforms: advanced biofuels, e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies. The main lock-in mechanisms analysed are learning effects, economies of scale, economies of scope, network externalities, informational increasing ...

  13. Sensitivity of the Static Earthquake Triggering Mechanism to Elastic Heterogeneity and Main Event Slip

    CERN Document Server

    Maharramov, Musa

    2013-01-01

    This paper has evolved out of our previous work on static stress transfer, where we used the full-space elastostatic Green's tensor to compute the Coulomb stress transfer impact of the Landers earthquake on the Hector Mine event. In this work, we use the elastostatic Green's tensor for an arbitrary layered Earth model with free-surface boundary conditions to study the impact of elastic heterogeneity as well as source-fault slip and geometry on the stress transfer mechanism. Slip distribution and fault geometry of the source have a significant impact on the stress transfer, especially in case of spatially extended triggered events. Maximization of the Coulomb stress transfer function for known aftershocks provides a mechanism for inverting for the source event slip. Heterogeneity of the elastic earth parameters is shown to have a sizeable, but lower-magnitude, impact on the static stress transfer in 3D. The analysis is applied to Landers/Hector Mine and 100 small "aftershocks" of the Landers event. A computati...

  14. Organophosphate Resistance and its Main Mechanism in Populations of Codling Moth (Lepidoptera: Tortricidae) from Central Chile.

    Science.gov (United States)

    Reyes, Maritza; Barros-Parada, Wilson; Ramírez, Claudio C; Fuentes-Contreras, Eduardo

    2015-02-01

    The codling moth, Cydia pomonella (L.), is the key pest of apple production worldwide. Insecticide resistance has been reported in all producing countries, based on five different mechanisms. Codling moth in Chile has resistance to azinphos-methyl and tebufenozide in post-diapausing larvae. However, there are no studies about the susceptibility of these populations to insecticides from other chemical groups. Therefore, the efficacy of azinphos-methyl, chlorpyrifos-ethyl, esfenvalerate, methoxyfenozide, tebufenozide, and thiacloprid on neonate and post-diapausing larvae from six field populations was investigated, and identified resistance mechanisms in this species were evaluated. Neonate larvae were susceptible to all insecticides studied, but post-diapausing larvae from four populations were resistant to chlorpyrifos, one of them was also resistant to azinphos-methyl, and another one was resistant to tebufenozide. The acetylcholinesterase insensitivity mutation was not detected, and the sodium channel knockdown resistance mutation was present in a low frequency in one population. Detoxifying enzymatic activity of glutathione S-transferases, esterases, and cytochrome P-450 monooxygenases in adults differed among populations, but chlorpyrifos resistance was associated only with a decreased esterase activity as shown by a significant negative correlation between chlorpyrifos mortality and esterase activity. PMID:26470131

  15. Synthesis, characterization and charge transport mechanism of CdZnO nanorods

    International Nuclear Information System (INIS)

    ZnO and Cd-doped ZnO nanostructures were prepared by new facile method at 80 deg. C. XRD measurement indicated that both samples had typical hexagonal wurtzite structures. Transmission electron microscopy (TEM) measurement shows that rod-like crystals have been formed. EDX measurement confirms the incorporation of the cadmium ion into the crystalline lattice of ZnO and indicated that cadmium ions uniformly distributed on the surface of the rods. The doping with cadmium ions has a great influence on the optical properties of the ZnO. The electrical measurements of Cd-doped ZnO nanorod were measured. The current-voltage (I-V) characteristic curve revealed that the charge transport above 4 V is mainly non-linear due to grain boundary contribution. The complex impedance spectroscopy was confirmed that the grain boundary effect controls the charge transport mechanism through CdZnO ceramic material.

  16. [The main pathophysiological mechanisms of kidney injury in obstructive sleep apnea syndrome].

    Science.gov (United States)

    Zelveian, P A; Dgerian, L G

    2014-01-01

    Nowadays, obstructive sleep apnea syndrome (OSAS) has been established to promote both structural and functional changes in the kidneys. The basis for these changes is pathophysiological mechanisms, such as hyperproduction of free radicals and disruption of NO-mediated vasodilator responses, activation of the sympathetic autonomic nervous system and the renin-angiotensin-aldosterone system, endothelial dysfunction, development of renal venous hypertension, and stimulation of atrial natriuretic peptide production, which in turn results in increased intraglomerular pressure and glomerular hyperfiltration. In patients with OSAS, the kidneys may be damaged by OSAS-related abnormalities, such as hypertension, diabetes mellitus, metabolic syndrome, erythrocytosis, atherosclerosis, and cor pulmonale, which may also lead to kidney injury under isolated conditions and, when concurrent OSAS is present, may even aggravate the existing kidney injury. PMID:25095664

  17. Mechanism and regulation of phosphate transport in Streptococcus pyogenes

    International Nuclear Information System (INIS)

    In contrast to results reported with other bacteria, uptake of 32Pi in Streptococcus pyogenes was found to occur rapidly in starved cultures and to be strongly and immediately inhibited by addition of exogenous glycolytic energy sources (such as glucose) and nonglycolytic sources of ATP (such as arginine). Preincubation of starved cells with NaF, iodoacetate, or arsenate eliminated the inhibiting effect of glucose but not that of arginine. In accordance with the hypothesis that transport was attributable to P/sub i/-P/sub i/ exchange, uptake and efflux of 32P/sub i/ in the presence of trans unlabeled P/sub i/ exhibited similar characteristics and were largely eliminated by reduction of the trans P/sub i/ concentration. Neither process was inhibited appreciably by pretreatment of cells with ionophores or metabolic inhibitors, but both processes were abolished by exposure to p-chloromercuribenzoate. Inhibition by both exogenous energy sources resulted in a reduction in the maximal velocity of transport (V/sub max/). Whereas arginine also caused a shift in the apparent Michaelis-Menten constant (K/sub m/) to larger values, glucose did not alter the K/sub m/. On the basis of the results reported, it is proposed that the rate of P/sub i/ exchange is determined positively by the intracellular and extracellular concentrations of P/sub i/ and negatively by ATP or metabolites thereof. The mechanism of ATP action is unknown but could involve either covalent or noncovalent modification of the carrier protein

  18. From Phenix to Super Phenix: mechanical structures assuring reactor vessel tightness at main sodium pump penetrations

    International Nuclear Information System (INIS)

    Even though the components of SUPER PHENIX are larger than those of PHENIX, there is no corresponding increase in available vessel height. Furthermore the SUPER PHENIX vessel does not possess a roof. For these reasons, original and patented solutions, which, nevertheless, take advantage of the experimental results and operating experience acquired with PHENIX, were sought. The most important parameters are: weights and sizes of various components; stresses transmitted to the structures differential displacements between the top and bottom positions of components; inclinations due to deformation of the deck; preservation of containment at places where components penetrate the deck. In the solution finally adopted, an elastic torus shaped ring, which forms a ball-and-socket type joint is used. A thin shell structure connects the bottom to the reactor internals in such a way as to permit both vertical and rotational displacements. The upper joint consists of: a bolted double flange system; flanged component; a torus with a gear tooth shape profile made of elastic material; leaktight bellows attached to both flanges. Studies and calculations have been completed with the realization of a 1/5 scale model of the upper torus ring. Displacement, and angular and axial stiffness measurements have confirmed the validity of the hypotheses. Moreover, even though the lower part is an extrapolation of PHENIX, full scale experimental tests have been carried out in sodium, reproducing the real displacements and forces that will be experienced in the reactor. Finally, the pumps will be tested with water; the suspension will be studied (investigation of relevant mechanical parameters, measurement of leaktightness with respect to the outside)

  19. Ethanol as a fuel for road transportation. Main report; Contribution to IEA Implementing Agreement on Advanced Motor Fuels

    Energy Technology Data Exchange (ETDEWEB)

    Larsen, Ulrik; Johansen, T.; Schramm, J.

    2009-05-15

    Bioethanol as a motor fuel in the transportation sector, mainly for road transportation, has been subject to many studies and much discussion. Furthermore, the topic involves not only the application and engine technical aspects, but also the understanding of the entire life cycle of the fuel, well-to-wheels, including economical, environmental, and social aspects. It is not, however, the aim of this report to assess every single one of these aspects. The present report aims to address the technical potential and problems as well as the central issues related to the general application of bioethanol as an energy carrier in the near future. In discussions of the advantages and drawbacks of ethanol, the type of application is important. Generalization is not possible, because ethanol can be used in many forms. Furthermore, a wide range of ethanol/gasoline blends has not yet been investigated sufficiently. The most favorable type of application is determined by infrastructural factors, especially vehicle fleet configuration. From a technical point of view, optimal usage involves a high degree of water content in the ethanol, and this excludes low-percentage-ethanol fuels. The benefits seem strongly related to the amount of ethanol in a given blend, that is, the more the better. Both engine efficiencies and emissions improve with more ethanol in the fuel. Wet ethanol constitutes an even cleaner fuel in both the production and application phases. In summary, ethanol application has many possibilities, but with each type of application comes a set of challenges. Nevertheless, technical solutions for each challenge are available. (ln)

  20. Time-resolved Mechanism of Extracellular Gate Opening and Substrate Binding in a Glutamate Transporter*S?

    OpenAIRE

    Shrivastava, Indira H.; Jiang, Jie; Amara, Susan G.; Bahar, Ivet

    2008-01-01

    Glutamate transporters, also referred to as excitatory amino acid transporters (EAATs), are membrane proteins that regulate glutamatergic signal transmission by clearing excess glutamate after its release at synapses. A structure-based understanding of their molecular mechanisms of function has been elusive until the recent determination of the x-ray structure of an archaeal transporter, GltPh. GltPh exists as a trimer, with each subunit containing a core region that m...

  1. A comparison of mechanisms generating vertical transport in the Brazilian coastal upwelling regions

    Science.gov (United States)

    Mazzini, P. L. F.; Barth, J. A.

    2013-11-01

    Several mechanisms can drive vertical velocities in the coastal ocean, including wind-forcing and through gradients in the vorticity field generated by flow-topography interactions. A two-layer, steady, wind-driven, analytical model is applied to the major upwelling systems of Brazil: Cabo Frio (CF) and Cabo de Santa Marta (CSM) regions. Comparisons are made between the relative roles of wind and flow-topography interaction in inducing upwelling over these regions. Ekman pumping is the weakest mechanism over the shelf, but does influence the along-shelf temperature in the CF area. Away from coastline irregularities, wind-driven upwelling (Ekman transport) dominates over all mechanisms. However, in the vicinity of capes and coastal features, topographically driven upwelling plays a significant role, and its transports may vary from 43% to 94% of wind-driven upwelling. Upstream of capes, topographically driven vertical motions are downwelling favorable and act against the wind-driven coastal upwelling, while downstream of capes, they are upwelling favorable, where all mechanisms add up to create strong upwelling. Peaks in total upwelling in the CF region are about twice as large as those in the CSM area because the CF region has stronger winds and larger coastline perturbations than in the CSM region. Observed sea surface temperatures (SST) agree well with variability in the vertical transports where upwelling peaks are in phase with low temperature peaks along the coast. Results suggest that on larger scales, the SST variability along the coast is mainly controlled by wind-driven upwelling, while upwelling due to flow-topography interaction is responsible for the smaller scale SST variability.

  2. Qinshan CANDU 6 main heat transport system high accuracy performance tracking in support of regional overpower protection

    International Nuclear Information System (INIS)

    This paper deals with the Qinshan CANDU 6 main Heat Transport System (HTS) high accuracy performance tracking/adjustment up to about 7 years of operation in support of Regional Overpower Protection (ROP). Operational and aging related changes of the HTS throughout its lifetime may lead to restrictions in certain safety system settings and hence some restriction in performance under certain conditions. A step in confirming safe reactor operation is the tracking of relevant data and their corresponding interpretation by the use of appropriate thermalhydraulic analytic models. Analytic predictions, in association with an optimized parameter tracking and adjustment methodology, confirm continued safe reactor operation. This paper demonstrates that Qinshan CANDU Unit 1, as compared to other CANDU 6 nuclear reactors of earlier design, continues to exhibit significantly improved performance with much reduced plant aging effects. This paper further demonstrates the high accuracy of the advanced performance tracking and adjustment methodology and applies it to Qinshan CANDU Unit 1, ensuring and demonstrating the continued excellent performance of the reference analytic models. The analytic methodology as well as the advanced performance tracking and analysis methodology can also beneficially be applied to both new and refurbished CANDU type nuclear reactors. (author)

  3. Molecular Mechanisms of Urea Transport in Health and Disease

    OpenAIRE

    KLEIN, JANET D.; Blount, Mitsi A.; Sands, Jeff M.

    2012-01-01

    In the late 1980s, urea permeability measurements produced values that could not be explained by paracellular transport or lipid phase diffusion. The existence of urea transport proteins were thus proposed and less than a decade later, the first urea transporter was cloned. The SLC14A family of urea transporters has two major subgroups, designated SLC14A1 (or UT-B) and Slc14A2 (or UT-A). UT-B and UT-A gene products are glycoproteins located in various extra-renal tissues however, a majority o...

  4. Interannual forcing mechanisms of California Current transports II: Mesoscale eddies

    Science.gov (United States)

    Davis, Andrew; Di Lorenzo, Emanuele

    2015-02-01

    Mesoscale eddies exert dominant control of cross-shelf exchanges, yet the forcing dynamics underlying their interannual and decadal variability remain uncertain. Using an ensemble of high-resolution ocean model hindcasts of the central and eastern North Pacific from 1950 to 2010 we diagnose the forcing mechanisms of low-frequency eddy variability in the California Current System (CCS). We quantify eddy activity by developing eddy counts based on closed contours of the Okubo-Weiss parameter and find that the spatial and temporal features of model-derived counts largely reproduce the short AVISO observational record. Comparison of model ensemble members allows us to separate the intrinsic and deterministic fractions of eddy variability in the northern CCS (34.5-50°N) and in the southern CCS (28.5-34.5°N). In the North, a large fraction of low-frequency eddy variability (30% anticyclones, 20% cyclones) is deterministic and shared with satellite observations. We develop a diagnostic model based on indices of the large-scale barotropic and baroclinic states of the CCS which recovers this deterministic variance. This model also strongly correlates with local atmospheric forcing. In contrast to the North, Southern CCS eddy counts exhibit very little deterministic variance, and eddy formation closely resembles a red-noise process. This new understanding of the external forcings of eddy variability allows us to better estimate how climate variability and change impact mesoscale transports in the California Current. The skill of our diagnostic model and its close association with local wind stress curl indicate that local atmospheric forcing is the dominant driver of eddy activity on interannual and decadal time scales north of pt. conception (~33°N).

  5. Transport mechanisms in the outer region of RFX-mod

    International Nuclear Information System (INIS)

    Transport properties of the edge region of RFPs are characterized by complicated mechanisms further entangled by the complex magnetic topology. Recently on RFX-mod (Sonato 2003 Fusion Eng. Des. 66-68 161) the use of an efficient feedback system for MHD control allowed the achievement of an unprecedented plasma current for an RFP, of up to 1.6 MA, with an improvement in the confinement properties. This is accompanied by an amelioration of the magnetic boundary and the observation of different MHD regimes, moving from low current multiple helical regime, to high current quasi-single helical ones. At a low plasma current (Ip ? 300-400 kA) in multiple helicity discharge the plasma parameter profiles at the edge are strongly influenced by the presence of m = 0 islands which flatten the temperature profile and modify substantially both the electric drift flow and the E x B shear. The particle diffusion coefficient and the thermal conductivity ?e in this regime are 10-20 m2 s-1 and 100-200 m2 s-1, respectively. Both temperature and pressure characteristic scale lengths are found to scale favourably with the decrease in the secondary modes achieved through the increase in the plasma current. The same trend is observed for the thermal conductivity, and the recently discovered single helical axis states (Lorenzini et al 2008 Phys. Rev. Lett. 101 025005) exhibit an edge ?e reduced by a factor of up to 40%. Finally the perpendicular flow at the edge is found to scale with the density normalized to the Greenwald density with a saturation at values around n/nG ? 0.35.

  6. Transport mechanisms in the outer region of RFX-mod

    Science.gov (United States)

    Vianello, N.; Martines, E.; Agostini, M.; Alfier, A.; Canton, A.; Cavazzana, R.; DeMasi, G.; Fassina, A.; Lorenzini, R.; Scarin, P.; Serianni, G.; Spagnolo, S.; Spizzo, G.; Spolaore, M.; Zuin, M.; RFX-mod Team

    2009-04-01

    Transport properties of the edge region of RFPs are characterized by complicated mechanisms further entangled by the complex magnetic topology. Recently on RFX-mod (Sonato 2003 Fusion Eng. Des. 66-68 161) the use of an efficient feedback system for MHD control allowed the achievement of an unprecedented plasma current for an RFP, of up to 1.6 MA, with an improvement in the confinement properties. This is accompanied by an amelioration of the magnetic boundary and the observation of different MHD regimes, moving from low current multiple helical regime, to high current quasi-single helical ones. At a low plasma current (Ip ? 300-400 kA) in multiple helicity discharge the plasma parameter profiles at the edge are strongly influenced by the presence of m = 0 islands which flatten the temperature profile and modify substantially both the electric drift flow and the E × B shear. The particle diffusion coefficient and the thermal conductivity ?e in this regime are 10-20 m2 s-1 and 100-200 m2 s-1, respectively. Both temperature and pressure characteristic scale lengths are found to scale favourably with the decrease in the secondary modes achieved through the increase in the plasma current. The same trend is observed for the thermal conductivity, and the recently discovered single helical axis states (Lorenzini et al 2008 Phys. Rev. Lett. 101 025005) exhibit an edge ?e reduced by a factor of up to 40%. Finally the perpendicular flow at the edge is found to scale with the density normalized to the Greenwald density with a saturation at values around n/nG ? 0.35.

  7. Evaluation of hydrazine as an additive to provide reducing condition in the main heat transport system of AHWR

    International Nuclear Information System (INIS)

    Hydrogen is known to be injected in boiling water reactors to mitigate stress corrosion cracking (SCC) due to the oxidizing environment prevailing in the reactor coolant system. Further this technique has been modified by addition of noble metals such as Pt, Ir so that the required ECP can be achieved by injecting a lower concentration of hydrogen. All the boiling water reactors are pot type reactors. Unlike BWRs, the Advanced Heavy Water Reactor (AHWR) is a boiling tube type reactor. Here, boiling takes place in the tube and the coolant exits the core with 18 % steam. The steam containing water exits the core through tail pipes connected to each fuel channel. The material of construction of most of the AHWR main coolant system components is stainless steel. Hence, the possibility of stress corrosion cracking of stainless steel components can not be ruled out if oxidizing chemistry conditions prevail in the coolant. Addition of hydrogen and hydrogen with noble metal may not be effective in controlling the radiolytic generation of oxygen/hydrogen peroxide under the two phase conditions prevailing in the fuel channels (tubes) of the core. Hence, the feasibility of using hydrazine to provide reducing condition to the main heat transport system of AHWR was studied. Computation on the generation of oxidizing species (O2 and H2O2) and their distribution in steam and water phase were made. The difference in the distribution behavior of hydrogen and hydrazine under AHWR condition is explained in the paper. Analytical methods have been standardized to study the distribution of hydrazine, ammonia, oxygen and hydrogen peroxide and tested by carrying out radiolysis of water containing hydrazine etc. Experiments were also carried out in the High Temperature and High Pressure (HTHP) system at WSCD to study the thermal stability of hydrazine and to evaluate its effect on the redox potential and corrosion potential of stainless steel under the simulated AHWR temperature conditions. The effect of hydrazine concentration and temperature on the electrochemical corrosion potentials (ECP) and redox was monitored. Thermal stability of hydrazine was studied over a wide range of temperature. Redox potential changed from -0.4 V versus the standard hydrogen electrode (V(SHE)) to -0.67 V(SHE) on addition of 5 ppm of hydrazine at 240 deg C. The decomposition rate of hydrazine was observed to follow a first order decay at 240 deg C where as a mixed rate was observed at 200 deg C. (author)

  8. Mechanism of transport modulation by an extracellular loop in an archaeal excitatory amino acid transporter (EAAT) homolog.

    Science.gov (United States)

    Mulligan, Christopher; Mindell, Joseph A

    2013-12-01

    Secondary transporters in the excitatory amino acid transporter family terminate glutamatergic synaptic transmission by catalyzing Na(+)-dependent removal of glutamate from the synaptic cleft. Recent structural studies of the aspartate-specific archaeal homolog, Glt(Ph), suggest that transport is achieved by a rigid body, piston-like movement of the transport domain, which houses the substrate-binding site, between the extracellular and cytoplasmic sides of the membrane. This transport domain is connected to an immobile scaffold by three loops, one of which, the 3-4 loop (3L4), undergoes substrate-sensitive conformational change. Proteolytic cleavage of the 3L4 was found to abolish transport activity indicating an essential function for this loop in the transport mechanism. Here, we demonstrate that despite the presence of fully cleaved 3L4, Glt(Ph) is still able to sample conformations relevant for transport. Optimized reconstitution conditions reveal that fully cleaved Glt(Ph) retains some transport activity. Analysis of the kinetics and temperature dependence of transport accompanied by direct measurements of substrate binding reveal that this decreased transport activity is not due to alteration of the substrate binding characteristics but is caused by the significantly reduced turnover rate. By measuring solute counterflow activity and cross-link formation rates, we demonstrate that cleaving 3L4 severely and specifically compromises one or more steps contributing to the movement of the substrate-loaded transport domain between the outward- and inward-facing conformational states, sparing the equivalent step(s) during the movement of the empty transport domain. These results reveal a hitherto unknown role for the 3L4 in modulating an essential step in the transport process. PMID:24155238

  9. Mechanisms Underlying the Antinociceptive, Antiedematogenic, and Anti-Inflammatory Activity of the Main Flavonoid from Kalanchoe pinnata

    OpenAIRE

    Ferreira, Raquel Teixeira; Coutinho, Marcela Araújo Soares; Malvar, David do Carmo; Costa, Elson Alves; Florentino, Iziara Ferreira; Costa, Sônia Soares; Vanderlinde, Frederico Argollo

    2014-01-01

    Kalanchoe pinnata (KP) is popularly used for treating inflammatory diseases. This study investigated the antinociceptive, antiedematogenic, and anti-inflammatory potential of the subcutaneous administration of KP flower aqueous extract (KPFE), its ethyl acetate (EtOAcF) and butanol (BuOHF) fractions, and the main KP flavonoid [quercetin 3-O-?-L-arabinopyranosyl (1 ? 2) ?-L-rhamnopyranoside] (KPFV) in mice, as well as its possible mechanisms of action. KPFE (30–300?mg/kg) and KPFV (1–10?mg/kg)...

  10. Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

    Science.gov (United States)

    Appert-Rolland, C.; Ebbinghaus, M.; Santen, L.

    2015-09-01

    Cells are the elementary units of living organisms, which are able to carry out many vital functions. These functions rely on active processes on a microscopic scale. Therefore, they are strongly out-of-equilibrium systems, which are driven by continuous energy supply. The tasks that have to be performed in order to maintain the cell alive require transportation of various ingredients, some being small, others being large. Intracellular transport processes are able to induce concentration gradients and to carry objects to specific targets. These processes cannot be carried out only by diffusion, as cells may be crowded, and quite elongated on molecular scales. Therefore active transport has to be organized. The cytoskeleton, which is composed of three types of filaments (microtubules, actin and intermediate filaments), determines the shape of the cell, and plays a role in cell motion. It also serves as a road network for a special kind of vehicles, namely the cytoskeletal motors. These molecules can attach to a cytoskeletal filament, perform directed motion, possibly carrying along some cargo, and then detach. It is a central issue to understand how intracellular transport driven by molecular motors is regulated. The interest for this type of question was enhanced when it was discovered that intracellular transport breakdown is one of the signatures of some neuronal diseases like the Alzheimer. We give a survey of the current knowledge on microtubule based intracellular transport. Our review includes on the one hand an overview of biological facts, obtained from experiments, and on the other hand a presentation of some modeling attempts based on cellular automata. We present some background knowledge on the original and variants of the TASEP (Totally Asymmetric Simple Exclusion Process), before turning to more application oriented models. After addressing microtubule based transport in general, with a focus on in vitro experiments, and on cooperative effects in the transportation of large cargos by multiple motors, we concentrate on axonal transport, because of its relevance for neuronal diseases. Some important characteristics of axonal transport is that it takes place in a confined environment; besides several types of motors are involved, that move in opposite directions. It is a challenge to understand how this bidirectional transport is organized. We review several features that could contribute to the efficiency of bidirectional transport in the axon, including in particular the role of motor-motor interactions and of the dynamics of the underlying microtubule network. Finally, we also discuss some open questions that may be relevant for future research in this field.

  11. Main results on modeling of primary water stress corrosion cracking at control rod drive mechanism nozzles of pressurized water reactors

    International Nuclear Information System (INIS)

    One of the main failure mechanisms that cause risks to pressurized water reactors is the primary water stress corrosion cracking occurring at the control reactor displacement mechanism nozzles. It is caused by the joint effect of tensile stress, temperature, susceptible metallurgical microstructure and environmental conditions of the primary water. These cracks can cause accidents that reduce nuclear safety and reduce the reliability. The objective of this work is to propose the modeling of these cracks, for prediction of the initiation and propagation of them, and to validate it according with the experimental resulting and the literature in a nickel-based Alloy 600. The experimental data were obtained at CDTN-Brazilian Nuclear Technology Development Center, in a recent installed SSRT- slow strain rate testing equipment. It had been used tensile specimens not pre-cracked, made in Alloy 600 MA (mill annealed). In this paper was presented obtained models, experimental method used to its validation and conclusions. (author)

  12. Main results on modeling of primary water stress corrosion cracking at control rod drive mechanism nozzles of pressurized water reactors

    Energy Technology Data Exchange (ETDEWEB)

    Aly, Omar F.; Andrade, Arnaldo H.P. de; Mattar Neto, Miguel [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mails: ofaly@ipen.br; aandrade@ipen.br; mmattar@ipen.br; Schvartzman, Monica M.A.M. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)]. E-mail: monicas@cdtn.br

    2007-07-01

    One of the main failure mechanisms that cause risks to pressurized water reactors is the primary water stress corrosion cracking occurring at the control reactor displacement mechanism nozzles. It is caused by the joint effect of tensile stress, temperature, susceptible metallurgical microstructure and environmental conditions of the primary water. These cracks can cause accidents that reduce nuclear safety and reduce the reliability. The objective of this work is to propose the modeling of these cracks, for prediction of the initiation and propagation of them, and to validate it according with the experimental resulting and the literature in a nickel-based Alloy 600. The experimental data were obtained at CDTN-Brazilian Nuclear Technology Development Center, in a recent installed SSRT- slow strain rate testing equipment. It had been used tensile specimens not pre-cracked, made in Alloy 600 MA (mill annealed). In this paper was presented obtained models, experimental method used to its validation and conclusions. (author)

  13. Catch bond mechanism in Dynein motor driven collective transport

    CERN Document Server

    Nair, Anil; Mitra, Mithun K; Muhuri, Sudipto; Chaudhuri, Abhishek

    2016-01-01

    Recent experiments have demonstrated that dynein motor exhibits catch bonding behaviour, in which the unbinding rate of a single dynein decreases with increasing force, for a certain range of force. Motivated by these experiments, we propose a model for catch bonding in dynein using a threshold force bond deformation (TFBD) model wherein catch bonding sets in beyond a critical applied load force. We study the effect of catch bonding on unidirectional transport properties of cellular cargo carried by multiple dynein motors within the framework of this model. We find catch bonding can result in dramatic changes in the transport properties, which are in sharp contrast to kinesin driven unidirectional transport, where catch bonding is absent. We predict that, under certain conditions, the average velocity of the cellular cargo can actually increase as applied load is increased. We characterize the transport properties in terms of a velocity profile phase plot in the parameter space of the catch bond strength and ...

  14. Origin of traps and charge transport mechanism in hafnia

    OpenAIRE

    Islamov, D. R.; Gritsenko, V. A.; Cheng, C.H.; Chin, A.

    2014-01-01

    In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the charge transport in HfO$_2$. Basing on the model of phonon-assisted tunneling between traps, and assuming that the electron traps are oxygen vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics were achieved. The thermal trap energy of 1.25 eV in HfO$_2$ was determined based on the charge transport experiments.

  15. FEATURES FOR TRANSPORT AND AIR MECHANICAL SYSTEMS OF DANGEROUS GOODS

    Directory of Open Access Journals (Sweden)

    Eugen Dumitru BUSA

    2012-05-01

    Full Text Available Transport of dangerous goods are regulated activities, they take place under the direction and control of the authorities and specialized bodies in an institutional framework determined by national and international law. Of economic, transport infrastructure is the crucial element without which both production and trade would become meaningless, it is an essential element of a civilization, is also a necessary accessory of other economic activities.

  16. Cross-field transport in the SOL: Its relationship to main chamber and divertor neutral control in Alcator C-Mod

    International Nuclear Information System (INIS)

    The sources of neutrals at the outer midplane of the plasma are discussed. We find that both the flux of neutrals escaping the divertor through leaks and ion recycling at main chamber surfaces appear to contribute. The ion flux to the walls is larger than the flux entering the divertor and comparable to recycling at the divertor plate. The cause of these high wall ion fluxes is an enhancement of cross-field particle transport which gives rise to substantial convective heat transport at higher densities. We have further explored main chamber recycling and impurity transport utilizing a novel divertor 'bypass', which connects the outer divertor plenum to the main chamber. We find that leakage of neutrals (fuel and recycling impurities) from the divertor appears to be determined primarily by the conductance through the divertor structure, thus indicating that tight baffling would be desirable in a reactor for fuel and helium ash compression. (author)

  17. Proposal for the Award of a Contract for the Management and Operation of the Main Mechanical Workshop at CERN

    CERN Document Server

    2003-01-01

    This document concerns the award of a contract for the management and operation of the main mechanical workshop at CERN. Following a market survey carried out among 55 firms in thirteen Member States, a call for tenders (IT-3116/EST) was sent on 11 October 2002 to two firms and four consortia in seven Member States. By the closing date, CERN had received three tenders from three consortia in six Member States. The Finance Committee is invited to agree to the negotiation of a contract with the consortium CEGELEC (FR) - CEGELEC (NL) - CEGELEC (CH) - CLEMESSY (FR) - CLEMESSY (CH), the lowest bidder, for the management and operation of the main mechanical workshop, for an initial period of three years from 1 October 2003 and for a total amount not exceeding 9 680 000 Swiss francs, subject to revision for inflation from 1 October 2004. The contract will include options for two further one-year extensions beyond the initial three-year period. The consortium has indicated the following distribution by country of the...

  18. Intracellular transport driven by cytoskeletal motors: General mechanisms and defects

    CERN Document Server

    Appert-Rolland, Cecile; Santen, Ludger

    2015-01-01

    Cells are strongly out-of-equilibrium systems driven by continuous energy supply. They carry out many vital functions requiring active transport of various ingredients and organelles, some being small, others being large. The cytoskeleton, composed of three types of filaments, determines the shape of the cell and plays a role in cell motion. It also serves as a road network for the so-called cytoskeletal motors. These molecules can attach to a cytoskeletal filament, perform directed motion, possibly carrying along some cargo, and then detach. It is a central issue to understand how intracellular transport driven by molecular motors is regulated, in particular because its breakdown is one of the signatures of some neuronal diseases like the Alzheimer. We give a survey of the current knowledge on microtubule based intracellular transport. We first review some biological facts obtained from experiments, and present some modeling attempts based on cellular automata. We start with background knowledge on the origi...

  19. Identification of a Novel System for Boron Transport: Atr1 Is a Main Boron Exporter in Yeast? †

    OpenAIRE

    Kaya, Alaattin; Karakaya, Huseyin C.; Fomenko, Dmitri E; GLADYSHEV, Vadim N.; Koc, Ahmet

    2009-01-01

    Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent p...

  20. Origin of traps and charge transport mechanism in hafnia

    Energy Technology Data Exchange (ETDEWEB)

    Islamov, D. R., E-mail: damir@isp.nsc.ru; Gritsenko, V. A., E-mail: grits@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Cheng, C. H. [Department of Mechatronic Technology, National Taiwan Normal University, Taipei 106, Taiwan (China); Chin, A., E-mail: albert-achin@hotmail.com [National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2014-12-01

    In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the charge transport in HfO{sub 2}. Basing on the model of phonon-assisted tunneling between traps, and assuming that the electron traps are oxygen vacancies, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics was achieved. The thermal trap energy of 1.25?eV in HfO{sub 2} was determined based on the charge transport experiments.

  1. On-Chip Transportation and Measurement of Mechanical Characteristics of Oocytes in an Open Environment

    Directory of Open Access Journals (Sweden)

    Kou Nakahara

    2015-05-01

    Full Text Available We propose a system that transports oocytes and measures their mechanical characteristics in an open environment using a robot integrated microfluidic chip (chip. The cells are transported through a micropillar array in the chip, and their characteristics are measured by a mechanical probe and a force sensor. Because the chip has an open microchannel, important cells such as oocytes are easily introduced and collected without the risk for losing them. In addition, any bubbles trapped in the chip, which degrade the measurement precision, are easily removed. To transport the oocytes through the open microchannel, we adopt a transportation technique based on a vibration-induced flow. Under this flow, oocytes arrive at the measurement point, where their mechanical characteristics are determined. We demonstrate the introduction, transportation, measurement of mechanical characteristics, and collection of oocytes using this system.

  2. Electron transport mechanisms in thin boron-doped diamond films

    International Nuclear Information System (INIS)

    Electron transmission spectroscopy is used to examine the effect of transport distance, diamond nanostructure, and electron affinity on the cold emission characteristics of thin nanocrystalline diamond films. Energy distribution and intensity measurements are taken from films having different thicknesses (?0.15, 2, and 4 ?m) and surface properties (hydrogenated, cesiated), and two distinct transmission regimes are identified that exhibit fundamentally different characteristics. In measurements taken at sufficiently high beam energy Eo, electrons are transported through the conduction band of the diamond and emitted at a low-affinity surface, with transmission yields generally greater than 1. In this regime, the dependence on Eo results from the finite escape depth of the conduction-band electrons, which is determined to be ?1 ?m for these films based on a Monte Carlo analysis of the incident electron range. In measurements taken at lower values of Eo, electrons are generated outside of this escape range and are unable to reach the surface via conduction-band transport. In this regime, the transmission data are dominated by a much broader, low-intensity distribution, and the transmission yields are substantially lower than 1. The transmission is furthermore completely insensitive to changes in the surface properties of the diamond. Based on the nanostructure of the films, electrons are most likely transported along grain boundaries that propagate through the films

  3. Endoplasmic reticulum: Where nucleotide sugar transport meets cytokinin control mechanisms.

    Science.gov (United States)

    Niemann, Michael Ce; Werner, Tomáš

    2015-10-01

    The endoplasmic reticulum (ER) is a multifunctional eukaryotic organelle where the vast majority of secretory proteins are folded and assembled to achieve their correct tertiary structures. The lumen of the ER and Golgi apparatus also provides an environment for numerous glycosylation reactions essential for modifications of proteins and lipids, and for cell wall biosynthesis. These glycosylation reactions require a constant supply of cytosolically synthesized substrate precursors, nucleotide sugars, which are transported by a group of dedicated nucleotide sugar transporters (NST). Recently, we have reported on the identification of a novel ER-localized NST protein, ROCK1, which mediates the transport of UDP-linked acetylated hexosamines across the ER membrane in Arabidopsis. Interestingly, it has been demonstrated that the activity of ROCK1 is important for the regulation of cytokinin-degrading enzymes, cytokinin oxidases/dehydrogenases (CKX), in the ER and, thus, for cytokinin responses. In this addendum we will address the biochemical and cellular activity of the ROCK1 transporter and its phylogenetic relation to other NST proteins. PMID:26418963

  4. Price Analysis of Railway Freight Transport under Marketing Mechanism

    Science.gov (United States)

    Shi, Ying; Fang, Xiaoping; Chen, Zhiya

    Regarding the problems in the reform of the railway tariff system and the pricing of the transport, by means of assaying the influence of the price elasticity on the artifice used for price, this article proposed multiple regressive model which analyzed price elasticity quantitatively. This model conclude multi-factors which influences on the price elasticity, such as the averagely railway freight charge, the averagely freight haulage of proximate supersede transportation mode, the GDP per capita in the point of origin, and a series of dummy variable which can reflect the features of some productive and consume demesne. It can calculate the price elasticity of different classes in different domains, and predict the freight traffic volume on different rate levels. It can calculate confidence-level, and evaluate the relevance of each parameter to get rid of irrelevant or little relevant variables. It supplied a good theoretical basis for directing the pricing of transport enterprises in market economic conditions, which is suitable for railway freight, passenger traffic and other transportation manner as well. SPSS (Statistical Package for the Social Science) software was used to calculate and analysis the example. This article realized the calculation by HYFX system(Ministry of Railways fund).

  5. MANGANESE AS ESSENTIAL AND TOXIC ELEMENT FOR PLANTS: TRANSPORT, ACCUMULATION AND RESISTANCE MECHANISMS

    Scientific Electronic Library Online (English)

    R, Millaleo; M, Reyes- Diaz; A.G, Ivanov; M.L, Mora; M, Alberdi.

    Full Text Available Manganese is an essential element for plants, intervening in several metabolic processes, mainly in photosynthesis and as an enzyme antioxidant-cofactor. Nevertheless, an excess of this micronutrient is toxic for plants. Mn phytotoxicity is manifested in a reduction of biomass and photosynthesis, an [...] d biochemical disorders such as oxidative stress. Some studies on Mn toxicity and Mn translocation from soil to plant cells in Mn2+ form have demonstrated their importance under low pH and redox potential conditions in the soil. When Mn is inside the cells, mechanisms that can tolerate this toxicity are also observed, being important the compartmentalization of this metal in different organdíes of shoot and leaf plant cells. A key role of antioxidative systems in plants in relation to high Mn amounts has also been reported as a defense mechanism. The purpose of this review is to show the role of Mn as an essential micronutrient and as a toxic element to higher plants as well as to their transport and tolerance mechanisms. The forms and dynamics of this element in soils and the importance of the acidity for this dynamic and availability for plants are also given.

  6. MANGANESE AS ESSENTIAL AND TOXIC ELEMENT FOR PLANTS: TRANSPORT, ACCUMULATION AND RESISTANCE MECHANISMS

    Directory of Open Access Journals (Sweden)

    R Millaleo

    2010-01-01

    Full Text Available Manganese is an essential element for plants, intervening in several metabolic processes, mainly in photosynthesis and as an enzyme antioxidant-cofactor. Nevertheless, an excess of this micronutrient is toxic for plants. Mn phytotoxicity is manifested in a reduction of biomass and photosynthesis, and biochemical disorders such as oxidative stress. Some studies on Mn toxicity and Mn translocation from soil to plant cells in Mn2+ form have demonstrated their importance under low pH and redox potential conditions in the soil. When Mn is inside the cells, mechanisms that can tolerate this toxicity are also observed, being important the compartmentalization of this metal in different organdíes of shoot and leaf plant cells. A key role of antioxidative systems in plants in relation to high Mn amounts has also been reported as a defense mechanism. The purpose of this review is to show the role of Mn as an essential micronutrient and as a toxic element to higher plants as well as to their transport and tolerance mechanisms. The forms and dynamics of this element in soils and the importance of the acidity for this dynamic and availability for plants are also given.

  7. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    International Nuclear Information System (INIS)

    Lattice-matched Pt/Au-In0.17Al0.83N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier

  8. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Jian; Yan, Dawei, E-mail: daweiyan@jiangnan.edu.cn; Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng [Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122 (China)

    2015-04-21

    Lattice-matched Pt/Au-In{sub 0.17}Al{sub 0.83}N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  9. A multiclass vehicular dynamic traffic flow model for main roads and dedicated lanes/roads of multimodal transport network

    International Nuclear Information System (INIS)

    We present in this paper a model of vehicular traffic flow for a multimodal transportation road network. We introduce the notion of class of vehicles to refer to vehicles of different transport modes. Our model describes the traffic on highways (which may contain several lanes) and network transit for pubic transportation. The model is drafted with Eulerian and Lagrangian coordinates and uses a Logit model to describe the traffic assignment of our multiclass vehicular flow description on shared roads. The paper also discusses traffic streams on dedicated lanes for specific class of vehicles with event-based traffic laws. An Euler-Lagrangian-remap scheme is introduced to numerically approximate the model’s flow equations

  10. A multiclass vehicular dynamic traffic flow model for main roads and dedicated lanes/roads of multimodal transport network

    Energy Technology Data Exchange (ETDEWEB)

    Sossoe, K.S., E-mail: kwami.sossoe@irt-systemx.fr [TECHNOLOGICAL RESEARCH INSTITUTE SYSTEMX (France); Lebacque, J-P., E-mail: jean-patrick.lebacque@ifsttar.fr [UPE/IFSTTAR-COSYS-GRETTIA (France)

    2015-03-10

    We present in this paper a model of vehicular traffic flow for a multimodal transportation road network. We introduce the notion of class of vehicles to refer to vehicles of different transport modes. Our model describes the traffic on highways (which may contain several lanes) and network transit for pubic transportation. The model is drafted with Eulerian and Lagrangian coordinates and uses a Logit model to describe the traffic assignment of our multiclass vehicular flow description on shared roads. The paper also discusses traffic streams on dedicated lanes for specific class of vehicles with event-based traffic laws. An Euler-Lagrangian-remap scheme is introduced to numerically approximate the model’s flow equations.

  11. Mechanisms of acetylcholine synthesis: Coupling with choline transport

    International Nuclear Information System (INIS)

    Comparative studies were performed to assess the utilization of choline transported by synaptosomal sodium-dependent, high-affinity choline carriers for the synthesis of ACh; it was determined that a significantly higher percentage of tritium-choline transported into rat forebrain synaptosomes was acetylated immediately compared to that of guinea-pig. Studies were performed to determine whether inhibition of synaptosomal ChAT was produced by incubating guinea-pig brain synaptosomes with ChMAz, comparable to that observed with rat brain synaptosomes. Very little ChAT activity was measured in guinea-pig brain; that this difference could reflect differing subcellular localizations of ChAT and different relativities with respect to coupling with choline carriers is speculative and currtly being investigated

  12. Catch bond mechanism in Dynein motor driven collective transport

    OpenAIRE

    Nair, Anil; Chandel, Sameep; Mitra, Mithun K; Muhuri, Sudipto; Chaudhuri, Abhishek

    2016-01-01

    Recent experiments have demonstrated that dynein motor exhibits catch bonding behaviour, in which the unbinding rate of a single dynein decreases with increasing force, for a certain range of force. Motivated by these experiments, we propose a model for catch bonding in dynein using a threshold force bond deformation (TFBD) model wherein catch bonding sets in beyond a critical applied load force. We study the effect of catch bonding on unidirectional transport properties of cellular cargo car...

  13. Relative mechanical quantities in spaces with a transport along paths

    CERN Document Server

    Iliev, Bozhidar Z

    1994-01-01

    The concepts of relative velocity and acceleration, deviation velocity and acceleration and relative momentum of point particles in spaces (manifolds), the tangent bundle of which is equipped with a transport along paths, are introduced. If the tangent bundle is endowed also with a metric, it gives rise also to the notion of a relative energy. Certain ties between these quantities are considered. The cases of massless particles and of special relativity are presented in this context.

  14. Relative mechanical quantities in spaces with a transport along paths

    OpenAIRE

    Iliev, Bozhidar Z.

    2003-01-01

    The concepts of relative velocity and acceleration, deviation velocity and acceleration and relative momentum of point particles in spaces (manifolds), the tangent bundle of which is equipped with a transport along paths, are introduced. If the tangent bundle is endowed also with a metric, it gives rise also to the notion of a relative energy. Certain ties between these quantities are considered. The cases of massless particles and of special relativity are presented in this...

  15. Modeling Transport and Flow Regulatory Mechanisms of the Kidney

    OpenAIRE

    Layton, Anita T.

    2012-01-01

    The kidney plays an indispensable role in the regulation of whole-organism water balance, electrolyte balance, and acid-base balance, and in the excretion of metabolic wastes and toxins. In this paper, we review representative mathematical models that have been developed to better understand kidney physiology and pathophysiology, including the regulation of glomerular filtration, the regulation of renal blood flow by means of the tubuloglomerular feedback mechanisms and of the myogenic mechan...

  16. An ambiguous interface – on the transport mechanism of the ABC transport complex TAP

    OpenAIRE

    Großmann, Nina

    2012-01-01

    The adaptive immune system protects against daily infections and malignant transformation. In this, the translocation of antigenic peptides by the transporter associated with antigen processing (TAP) into the ER lumen is an essential step in the antigen presentation by MHC I molecules. The heterodimeric ATP-binding cassette transporter (ABC) TAP consist of the two halftransporters TAP1 and TAP2. Each monomer contains an N-terminal transmembrane domain (TMD) and a conserved C-terminal nucleoti...

  17. Mimicking cellular transport mechanism in stem cells through endosomal escape of new peptide-coated quantum dots

    OpenAIRE

    Narayanan, Karthikeyan; Yen, Swee Kuan; Dou, Qingqing; Padmanabhan, Parasuraman; Sudhaharan, Thankiah; Ahmed, Sohail; Ying, Jackie Y.; Selvan, Subramanian Tamil

    2013-01-01

    Protein transport is an important phenomenon in biological systems. Proteins are transported via several mechanisms to reach their destined compartment of cell for its complete function. One such mechanism is the microtubule mediated protein transport. Up to now, there are no reports on synthetic systems mimicking the biological protein transport mechanism. Here we report a highly efficient method of mimicking the microtubule mediated protein transport using newly designed biotinylated peptid...

  18. Envisaging palladium chemical transport mechanism from fuel kernel pellet to SiC cladding by bromination

    Energy Technology Data Exchange (ETDEWEB)

    Arias, F.J., E-mail: frarias@mit.edu [Nuclear Science and Engineering Department, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States)

    2012-07-15

    The SiC cladding corrosion in pellets by direct palladium chemical transport from fuel kernel through gap to SiC cladding by direct bromination is envisaged as feasible mechanism in corrosion of SiC pellets.

  19. LOS COMIENZOS DEL TRANSPORTE MECANIZADO TERRESTRE EN MAGALLANES (1900-1930) / THE BEGINNINGS OF MECHANIZED TERRESTRIAL TRANSPORT IN MAGELLAN (1900-1930)

    Scientific Electronic Library Online (English)

    Mateo, Martinic B.

    2009-07-01

    Full Text Available Se da cuenta de las formas y circunstancias que determinaron la evolución del sistema de transporte en Magallanes, desde los carruajes de tiro animal propios de la época de la colonización inicial, hasta los vehículos automotores, fenómeno entendido como la culminación del ciclo de modernización mec [...] ánica que caracterizó a la crianza ovejera extensiva, que fue la actividad vertebradora matriz de la economía magallánica. Abstract in english The forms and circumstances that determined the evolution of transport systems in Magellan are narrated, from the carriages pushed by animal’s characteristic of the initial settling epoch, up to the self-propelled vehicles, phenomenon understood as the culmination of the cycle of mechanical moderniz [...] ation that characterized the upbringing extensive sheep farming, main vertebrate activity of the magellanic economy.

  20. Computerized simulation of the mechanical behavior of wood-filled shock absorbers of radioactive materials transport casks

    International Nuclear Information System (INIS)

    In Germany the mechanical component inspection of transport containers for radioactive materials is performed by BAM (Bundesanstalt fuer Materialforschung und -pruefung) under consideration of national and international standards and guidelines. Experimental and calculative (analytical and numerical) techniques combined with material and/or component testing are the basis of assessment concepts according the state of the art. The authors describe the experiences of BAM concerning assessment and description of the mechanical behavior of shock absorbing components, including modeling strategies, material models, drop tests and experiment-calculation comparison. Energy absorbing components are used to reduce the impact forces at the container in case of a transport accident. In Germany wood filled thin-walled constructions are used. The deformation behavior of the wood is a main part of the calculative simulation procedures in comparison with experimental tests.

  1. Lamination in Atmospheric Ozone: A Diagnostic for Tracer Transport Mechanisms

    Science.gov (United States)

    Minschwaner, Kenneth; Manney, Gloria; Torres, Luis

    2015-03-01

    An understanding of ozone variability in the upper troposphere (from ~5 km altitude up to the tropopause level) is critical to assessing the radiative forcing of climate by ozone, and for evaluating the impact of transport on regional air quality. Part of this variability arises in fine-layered (~0.2 to ~2 km) structures seen in vertical profile measurements of ozone. These laminae are also generally limited on horizontal scales (10's to 100's of km), leading to spatial ozone variability observed on quasi-horizontal coordinate surfaces. Given the relatively long photochemical time constants for ozone in the upper troposphere, most of the observed variability arises from transport rather than photochemistry. There are a wide range of dynamical processes that can generate ozone laminae in the upper troposphere, such as gravity and Rossby waves, convective lofting and detrainment of either high or low ozone amounts from the boundary layer, and intrusions of air masses with high ozone concentrations from the stratosphere. Here, we examine the range of observed laminae characteristics and describe methods for tracing the origins of tropospheric ozone laminae.

  2. Angler awareness of aquatic nuisance species and potential transport mechanisms

    Science.gov (United States)

    Gates, K.K.; Guy, C.S.; Zale, A.V.; Horton, T.B.

    2009-01-01

    The role anglers play in transporting aquatic nuisance species (ANS) is important in managing infestations and preventing introductions. The objectives of this study were to: (1) quantify angler movement patterns in southwestern Montana, ANS awareness and equipment cleaning practices; and (2) quantify the amount of soil transported on boots and waders. Mean distance travelled by residents from their home to the survey site was 115 km (??17, 95% CI). Mean distance travelled by non-residents was 1738 km (??74). Fifty-one percent of residents and 49% of non-residents reported occasionally, rarely or never cleaning their boots and waders between uses. Mean weight of soil carried on one boot leg was 8.39 g (??1.50). Movement and equipment cleaning practices of anglers in southwestern Montana suggest that future control of ANS dispersal may require restricting the use of felt-soled wading boots, requiring river-specific wading equipment or providing cleaning stations and requiring their use. ?? 2009 Blackwell Publishing Ltd.

  3. Turbulence elasticity—A new mechanism for transport barrier dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Z. B., E-mail: guozhipku@gmail.com [WCI Center for Fusion Theory, NFRI, Daejeon 305-333 (Korea, Republic of); Diamond, P. H. [WCI Center for Fusion Theory, NFRI, Daejeon 305-333 (Korea, Republic of); CMTFO and CASS, University of California, San Diego, California 92093 (United States); Kosuga, Y. [IAS and RIAM, Kyushu University, Kasuga 816-8580 (Japan); Gürcan, Ö. D. [LPP, Ecole Polytechnique, CNRS, Palaiseau Cedex 91128 (France)

    2014-09-15

    We present a new, unified model of transport barrier formation in “elastic” drift wave-zonal flow (DW-ZF) turbulence. A new physical quantity—the delay time (i.e., the mixing time for the DW turbulence)—is demonstrated to parameterize each stage of the transport barrier formation. Quantitative predictions for the onset of limit-cycle-oscillation (LCO) among DW and ZF intensities (also denoted as I-mode) and I-mode to high-confinement mode (H-mode) transition are also given. The LCO occurs when the ZF shearing rate (|?v?{sub ZF}{sup ?}|) enters the regime ??{sub k}<|?V?{sub ZF}{sup ?}|?{sub cr}{sup ?1}, where the mean E?×?B shear flow driven by ion pressure “locks” the DW-ZF system to the H-mode by reducing the delay time below the threshold value.

  4. Mechanisms Underlying the Antinociceptive, Antiedematogenic, and Anti-Inflammatory Activity of the Main Flavonoid from Kalanchoe pinnata.

    Science.gov (United States)

    Ferreira, Raquel Teixeira; Coutinho, Marcela Araújo Soares; Malvar, David do Carmo; Costa, Elson Alves; Florentino, Iziara Ferreira; Costa, Sônia Soares; Vanderlinde, Frederico Argollo

    2014-01-01

    Kalanchoe pinnata (KP) is popularly used for treating inflammatory diseases. This study investigated the antinociceptive, antiedematogenic, and anti-inflammatory potential of the subcutaneous administration of KP flower aqueous extract (KPFE), its ethyl acetate (EtOAcF) and butanol (BuOHF) fractions, and the main KP flavonoid [quercetin 3-O-?-L-arabinopyranosyl (1 ? 2) ?-L-rhamnopyranoside] (KPFV) in mice, as well as its possible mechanisms of action. KPFE (30-300?mg/kg) and KPFV (1-10?mg/kg) inhibited the acetic acid-induced writhing (ID50 = 164.8 and 9.4?mg/kg, resp.). KPFE (300?mg/kg), EtOAcF (12?mg/kg), BuOHF (15?mg/kg), or KPFV (0.3-3.0?mg/kg) reduced leukocyte migration on carrageenan-induced pleurisy (ID50 = 2.0?mg/kg for KPFV). KPFE (3-30?mg/kg) and KPFV (0.3-3.0?mg/kg) reduced the croton oil-induced ear edema (ID50 = 4.3 and 0.76?mg/kg, resp.). KPFE and KPFV reduced the TNF-? concentration in the pleural exudates on carrageenan-induced pleurisy test. Moreover, KPFV inhibited COX-1 (IC50 = 22.1??g/mL) and COX-2 (IC50 > 50??g/mL). The selectivity index (COX-1IC50 /COX-2IC50 ) was <0.44. These results indicate that KPFE and KPFV produced antinociceptive, antiedematogenic, and anti-inflammatory activities through COX inhibition and TNF-? reduction, revealing that the main flavonoid in KP flowers and leaves plays an important role in the ethnomedicinal use of the plant. PMID:25580151

  5. Thermo-mechanical simulation of austenitic steel welding process with respect to main vessel roof slab shell joint

    International Nuclear Information System (INIS)

    Welding process involves high heat fluxes which give rise to high temperature gradient in vicinity of the weld region. Presence of various mechanical constraints to minimize the distortion results in high residual stresses in the weld region. Weld joint between main vessel and roof slab of Sodium cooled Fast Reactors (SFRs) results in distortion and residual stress; hence it is critical from functionality point of view. The welding of main vessel (13 m diameter) and roof slab of 25 mm thickness involves multi-pass weld. In the present work an attempt has been made to simulate the 3D multipass welding procedure using the element birth technique for the filler material addition. The accurate estimation of the residual stress distribution is required as one of the basic input for the study of crack propagation behavior in the critical weld zone. Also to minimize the global distortion of the shell prior information of the supports and clamping location is essential. The actual welding process involves an asymmetric k type of weld joint with 21 passes on alternating sides to neutralize the distortions produced by one pass by the other alternating pass on the opposite side. The whole vessel will be divided into four quarter circles and the welding will be started simultaneously from all the four points in counter-clockwise direction at same speed. In the view of very high computation time required for the actual simulation of this weld joint, a small mockup exercise has been done to investigate the local residual stress and the forces. (orig.)

  6. Structure and permeation mechanism of a mammalian urea transporter

    Energy Technology Data Exchange (ETDEWEB)

    Levin, Elena J.; Cao, Yu; Enkavi, Giray; Quick, Matthias; Pan, Yaping; Tajkhorshid, Emad; Zhou, Ming (UIUC); (Columbia)

    2012-09-17

    As an adaptation to infrequent access to water, terrestrial mammals produce urine that is hyperosmotic to plasma. To prevent osmotic diuresis by the large quantity of urea generated by protein catabolism, the kidney epithelia contain facilitative urea transporters (UTs) that allow rapid equilibration between the urinary space and the hyperosmotic interstitium. Here we report the first X-ray crystal structure of a mammalian UT, UT-B, at a resolution of 2.36 {angstrom}. UT-B is a homotrimer and each protomer contains a urea conduction pore with a narrow selectivity filter. Structural analyses and molecular dynamics simulations showed that the selectivity filter has two urea binding sites separated by an approximately 5.0 kcal/mol energy barrier. Functional studies showed that the rate of urea conduction in UT-B is increased by hypoosmotic stress, and that the site of osmoregulation coincides with the location of the energy barrier.

  7. Transport mechanisms in high Tc bismuth-based oxide superconductors

    International Nuclear Information System (INIS)

    We apply our transport theory (I) on high temperature oxide superconductor was presented. Our calculations on bismuth based high temperature oxide superconductors suggest that the polarons may exist. There exists, no bipolarons. The polarons are produced due to free or dangling bonds of oxygen. The Cooper pairs while remaining on a pseudo Fermi surface behave like weak fermions. When the Cooper pairs become free they behave as spinless bosons. The binding energies of Cooper pairs both in a weak fermions system and for spinless bosons are calculated. A kind of semimetallic transition is responsible for high temperature superconductivity and is temperature independent. There is no electron-polaron, coupling for high temperature superconductors. High temperature oxide superconductors before the onset of superconductivity are found to be Mott insulating materials. Our results are in conformity with theory (I). (author)

  8. Cellular Transport Mechanisms of Cytotoxic Metallodrugs: An Overview beyond Cisplatin

    OpenAIRE

    Sarah Spreckelmeyer; Chris Orvig; Angela Casini

    2014-01-01

    The field of medicinal inorganic chemistry has grown consistently during the past 50 years; however, metal-containing coordination compounds represent only a minor proportion of drugs currently on the market, indicating that research in this area has not yet been thoroughly realized. Although platinum-based drugs as cancer chemotherapeutic agents have been widely studied, exact knowledge of the mechanisms governing their accumulation in cells is still lacking. However, evidence suggests activ...

  9. Understanding the removal mechanisms of PPCPs and the influence of main technological parameters in anaerobic UASB and aerobic CAS reactors

    Energy Technology Data Exchange (ETDEWEB)

    Alvarino, T., E-mail: teresa.alvarino@usc.es; Suarez, S., E-mail: Sonia.suarez@usc.es; Lema, J.M., E-mail: juan.lema@usc.es; Omil, F., E-mail: francisco.omil@usc.es

    2014-08-15

    Highlights: • Removals of 16 PPCPs under aerobic and anaerobic conditions were quantified. • Operation conditions (HRT, v{sub up}, biomass activity and conformation) influenced removal. • Highest removals associated to aerobic biodegradation. • Sorption was only relevant for lipophilic compounds in the UASB reactor. - Abstract: The removal of 16 Pharmaceutical and Personal Care Products (PPCPs) were studied in a conventional activated sludge (CAS) unit and an upflow anaerobic sludge blanket (UASB) reactor. Special attention was paid to each biomass conformation and activity as well as to operational conditions. Biodegradation was the main PPCP removal mechanism, being higher removals achieved under aerobic conditions, except in the case of sulfamethoxazole and trimetrophim. Under anaerobic conditions, PPCP biodegradation was correlated with the methanogenic rate, while in the aerobic reactor a relationship with nitrification was found. Sorption onto sludge was influenced by biomass conformation, being only significant for musk fragrances in the UASB reactor, in which an increase of the upward velocity and hydraulic retention time improved this removal. Additionally, PPCP sorption increased with time in the UASB reactor, due to the granular biomass structure which suggests the existence of intra-molecular diffusion.

  10. Identification of a Novel System for Boron Transport: Atr1 Is a Main Boron Exporter in Yeast? †

    Science.gov (United States)

    Kaya, Alaattin; Karakaya, Huseyin C.; Fomenko, Dmitri E.; Gladyshev, Vadim N.; Koc, Ahmet

    2009-01-01

    Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1? mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1? cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1? cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance. PMID:19414602

  11. Identification of a novel system for boron transport: Atr1 is a main boron exporter in yeast.

    Science.gov (United States)

    Kaya, Alaattin; Karakaya, Huseyin C; Fomenko, Dmitri E; Gladyshev, Vadim N; Koc, Ahmet

    2009-07-01

    Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1Delta mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1Delta cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1Delta cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance. PMID:19414602

  12. Grotthuss mechanisms: from proton transport in proton wires to bioprotonic devices.

    Science.gov (United States)

    Miyake, Takeo; Rolandi, Marco

    2016-01-20

    In 1804, Theodore von Grotthuss proposed a mechanism for proton (H(+)) transport between water molecules that involves the exchange of a covalent bond between H and O with a hydrogen bond. This mechanism also supports the transport of OH(-) as a proton hole and is essential in explaining proton transport in intramembrane proton channels. Inspired by the Grotthuss mechanism and its similarity to electron and hole transport in semiconductors, we have developed semiconductor type devices that are able to control and monitor a current of H(+) as well as OH(-) in hydrated biopolymers. In this topical review, we revisit these devices that include protonic diodes, complementary, transistors, memories and transducers as well as a phenomenological description of their behavior that is analogous to electronic semiconductor devices. PMID:26657711

  13. Grotthuss mechanisms: from proton transport in proton wires to bioprotonic devices

    Science.gov (United States)

    Miyake, Takeo; Rolandi, Marco

    2016-01-01

    In 1804, Theodore von Grotthuss proposed a mechanism for proton (H+) transport between water molecules that involves the exchange of a covalent bond between H and O with a hydrogen bond. This mechanism also supports the transport of OH? as a proton hole and is essential in explaining proton transport in intramembrane proton channels. Inspired by the Grotthuss mechanism and its similarity to electron and hole transport in semiconductors, we have developed semiconductor type devices that are able to control and monitor a current of H+ as well as OH? in hydrated biopolymers. In this topical review, we revisit these devices that include protonic diodes, complementary, transistors, memories and transducers as well as a phenomenological description of their behavior that is analogous to electronic semiconductor devices.

  14. Cytoplasmic HIV-1 RNA is mainly transported by diffusion in the presence or absence of Gag protein

    DEFF Research Database (Denmark)

    Chen, Jianbo; Grunwald, David; Sardo, Luca; Galli, Andrea; Plisov, Sergey; Nikolaitchik, Olga A; Chen, De; Lockett, Stephen; Larson, Daniel R; Pathak, Vinay K; Hu, Wei-Shau

    2014-01-01

    Full-length HIV-1 RNA plays a central role in viral replication by serving as the mRNA for essential viral proteins and as the genome packaged into infectious virions. Proper RNA trafficking is required for the functions of RNA and its encoded proteins; however, the mechanism by which HIV-1 RNA i...

  15. Mechanism of unassisted ion transport across membrane bilayers

    Science.gov (United States)

    Wilson, M. A.; Pohorille, A.

    1996-01-01

    To establish how charged species move from water to the nonpolar membrane interior and to determine the energetic and structural effects accompanying this process, we performed molecular dynamics simulations of the transport of Na+ and Cl- across a lipid bilayer located between two water lamellae. The total length of molecular dynamics trajectories generated for each ion was 10 ns. Our simulations demonstrate that permeation of ions into the membrane is accompanied by the formation of deep, asymmetric thinning defects in the bilayer, whereby polar lipid head groups and water penetrate the nonpolar membrane interior. Once the ion crosses the midplane of the bilayer the deformation "switches sides"; the initial defect slowly relaxes, and a defect forms in the outgoing side of the bilayer. As a result, the ion remains well solvated during the process; the total number of oxygen atoms from water and lipid head groups in the first solvation shell remains constant. A similar membrane deformation is formed when the ion is instantaneously inserted into the interior of the bilayer. The formation of defects considerably lowers the free energy barrier to transfer of the ion across the bilayer and, consequently, increases the permeabilities of the membrane to ions, compared to the rigid, planar structure, by approximately 14 orders of magnitude. Our results have implications for drug delivery using liposomes and peptide insertion into membranes.

  16. Molecular parameters and transmembrane transport mechanism of imidazolium-functionalized binols.

    Science.gov (United States)

    Vidal, Marc; Schmitzer, Andreea

    2014-08-01

    We describe the molecular parameters governing the transmembrane activity of imidazolium-functionalized anion transporters and present a detailed mechanistic study. These ionophores adopt a mobile-carrier mechanism for short methyl and butyl chains, a combined mobile-carrier/transmembrane-pore mechanism for octyl and dodecyl chains, and form transmembrane aggregates for hexadecyl chains. PMID:25043746

  17. Critical review: Radionuclide transport, sediment transport, and water quality mathematical modeling; and radionuclide adsorption/desorption mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Onishi, Y.; Serne, R.J.; Arnold, E.M.; Cowan, C.E.; Thompson, F.L. [Pacific Northwest Lab., Richland, WA (United States)

    1981-01-01

    This report describes the results of a detailed literature review of radionuclide transport models applicable to rivers, estuaries, coastal waters, the Great Lakes, and impoundments. Some representatives sediment transport and water quality models were also reviewed to evaluate if they can be readily adapted to radionuclide transport modeling. The review showed that most available transport models were developed for dissolved radionuclide in rivers. These models include the mechanisms of advection, dispersion, and radionuclide decay. Since the models do not include sediment and radionuclide interactions, they are best suited for simulating short-term radionuclide migration where: (1) radionuclides have small distribution coefficients; (2) sediment concentrations in receiving water bodies are very low. Only 5 of the reviewed models include full sediment and radionuclide interactions: CHMSED developed by Fields; FETRA SERATRA, and TODAM developed by Onishi et al, and a model developed by Shull and Gloyna. The 5 models are applicable to cases where: (1) the distribution coefficient is large; (2) sediment concentrations are high; or (3) long-term migration and accumulation are under consideration. The report also discusses radionuclide absorption/desorption distribution ratios and addresses adsorption/desorption mechanisms and their controlling processes for 25 elements under surface water conditions. These elements are: Am, Sb, C, Ce, Cm, Co, Cr, Cs, Eu, I, Fe, Mn, Np, P, Pu, Pm, Ra, Ru, Sr, Tc, Th, {sup 3}H, U, Zn and Zr.

  18. The fluid mechanics of nutrient transport within biofilms

    Science.gov (United States)

    Brenner, Michael; Seminara, Agnese; Sinha, Naveen; Wilking, James; Angelini, Tommy; Kolter, Roberto; Weitz, David

    2011-11-01

    Bacterial biofilms are interface-associated colonies of bacteria embedded in an extracellular matrix that is composed primarily of polymers and proteins. During the growth of a biofilm, nutrient is taken up by the surface of the biofilm, and contained by cells in the bulk. A critical problem is that above a critical size there is necessarily a growth bottleneck, in which the biofilm cannot take up enough nutrients to feed all of the cells within it. We discuss, through theory and experiments, several strategies that are employed by biofilms of Bacillus subtilus to avoid this growth bottleneck. These include clever use and control of osmotic pressure (through the expression of polymeric extracellular matrix); the excretion of surfactants and the use of associated marangoni stresses; and the distribution of flagella (used as mixers) within the bulk of the biofilm. Some speculations about other potential mechanisms (for which there is no current experimental support) will also be presented.

  19. Dissolved load transport in the Ebro River Basin (Spain): Impact of main lithologies and role of tributaries

    Science.gov (United States)

    Petelet-Giraud, E.; Negrel, P. J.

    2012-12-01

    This study aims to evaluate, over more than 20 years, the export fluxes for dissolved loads at the Ebro River catchment scale. Data are compiled from the of the Confederacion Hidrografica del Ebro (CHE) databank. The spatial and temporal distribution of daily discharges, physico-chemical parameters and chemical data covering the last two decades (1981-2003) were investigated on five monitoring stations along the Ebro River (Mendavia, Castejon, Zaragoza, Sastago and Tortosa), as well as six stations at the outlet of the main tributaries (Arga, Aragon, Gallego, Jalon, Cinca and Segre). The dissolved load of the rivers at the Ebro Basin scale was characterized through the Electrical Conductivity (EC), total dissolved solids (TDS) and the major elements chemical data. The surface water can be classified into three main categories, a clear dominance of Ca-SO4 water type, a Ca-HCO3 type mainly encountered in the upper part of the basin and some data presenting a Na-Cl water type. The TDS values are highly variable, both in time and in space, in the range 390-1360 mg/L. The dissolved exportations to the Mediterranean Sea and the relative contribution of the different tributaries were calculated. The Ebro basin in its upper part (upstream Mendavia) contributes around 22.4% of the total exported flux near the outlet (Tortosa) over the studied period. The tributaries that mainly contribute to the total exported dissolved load are the Cinca and Segre (19% and 17% respectively). The Aragon, Gallego and Jalon contributions are very low, often less than 5% of the total exported flux. The specific TDS flux at the outlet of the Ebro is 70 +/- 23 t/km2/year and 108 +/- 24 t/km2/year upstream in Mendavia while the highest chemical erosion rate was calculated for the Arga with 251 +/- 55 t/km2/year. The dissolved export fluxes represent the major export from the Ebro basin, and the respective contribution of carbonate and evaporite (gypsum) with respect to the TDS was then calculated using the major element concentrations and discharge data. In the upper part of the Ebro Basin, carbonate weathering is dominant compared to gypsum weathering while downstream the dissolved exportations are dominated by gypsum weathering. For the tributaries, most of them are dominated by evaporite weathering. The exportation rates at the outlet of the watershed shows dissolved exportation derived from gypsum weathering, that are about 1.5 times that derived from carbonate weathering

  20. Main Achievements 2003-2004 - Experimental Nuclear Physics - Mechanisms of nuclear reactions - Thermal multifragmentation and liquid-fog transition

    International Nuclear Information System (INIS)

    The main decay mode of very excited nuclei is a copious emission of intermediate mass fragments (IMF), which are heavier than ?-particles but lighter than fission fragments. The FASA project is concentrated on the investigation of thermal multifragmentation induced in heavy targets by relativistic light ions. The 4?-setup is installed at the external beam of Nuclotron. It was proved that thermal multifragmentation should be considered as a spinodal decomposition, which is the liquid-fog phase transition. Measurements of critical temperature for the liquid-gas phase transition were refined. This temperature was found to be (17 ± 2) MeV, which is significantly larger than the temperature of the fragmenting system (5-6 MeV). This is a very important observation in favour of the mechanism of spinodal disintegration. The space characteristics for the target multifragmentation in p(8.1 GeV) + Au collisions were also determined experimentally. The inclusive experimental data on the fragment charge distribution, Y(Z), and kinetic energy spectra were analyzed within the framework of the statistical multifragmentation model. It is found from the shape of Y(Z) that the partition of hot nuclei is specified after expansion of the target spectator to a volume equal to Vt= (2.9 ± 0.2) V0, with V0 being the volume at normal density. However, the freeze-out volume is found from the energy spectra to be Vf = (11 ± 3) V0. The first volume, Vt, corresponds to the configuration of the system at the top of the energy barrier for fragmentation, when charge distribution is specified. The other volume, Vf, corresponds to the multi-scission point in terms of ordinary fission

  1. Identification of regulatory mechanisms of intestinal folate transport in condition of folate deficiency.

    Science.gov (United States)

    Thakur, Shilpa; Rahat, Beenish; Hamid, Abid; Najar, Rauf Ahmad; Kaur, Jyotdeep

    2015-10-01

    Folic acid is an essential micronutrient, deficiency of which can lead to disturbance in various metabolic processes of cell. Folate transport across intestine occurs via the involvement of specialized folate transporters viz. proton coupled folate transporter (PCFT) and reduced folate carrier (RFC), which express at the membrane surfaces. The current study was designed to identify the regulatory mechanisms underlying the effects of folate deficiency (FD) on folate transport in human intestinal cell line as well as in rats and to check the reversibility of such effects. Caco-2 cells were grown for five generations in control and FD medium. Following treatment, one subgroup of cells was shifted on folate sufficient medium and grown for three more generations. Similarly, rats were fed an FD diet for 3 and 5 months, and after 3 months of FD treatment, one group of rats were shifted on normal folate-containing diet. Increase in folate transport and expression of folate transporters were observed on FD treatment. However, when cells and rats were shifted to control conditions after treatment, transport and expression of these genes restored to the control level. FD was found to have no impact on promoter methylation of PCFT and RFC; however, messenger RNA stability of transporters was found to be decreased, suggesting some adaptive response. Overall, increased expression of transporters under FD conditions can be attributed to enhanced rate of transcription of folate transporters and also to the increased binding of specificity protein 1 transcription factor to the RFC promoter only. PMID:26168702

  2. Transport of Heat and Charge in Electromagnetic Metrology Based on Nonequilibrium Statistical Mechanics

    Directory of Open Access Journals (Sweden)

    James Baker-Jarvis

    2009-11-01

    Full Text Available Current research is probing transport on ever smaller scales. Modeling of the electromagnetic interaction with nanoparticles or small collections of dipoles and its associated energy transport and nonequilibrium characteristics requires a detailed understanding of transport properties. The goal of this paper is to use a nonequilibrium statistical-mechanical method to obtain exact time-correlation functions, fluctuation-dissipation theorems (FD, heat and charge transport, and associated transport expressions under electromagnetic driving. We extend the time-symmetric Robertson statistical-mechanical theory to study the exact time evolution of relevant variables and entropy rate in the electromagnetic interaction with materials. In this exact statistical-mechanical theory, a generalized canonical density is used to define an entropy in terms of a set of relevant variables and associated Lagrange multipliers. Then the entropy production rate are defined through the relevant variables. The influence of the nonrelevant variables enter the equations through the projection-like operator and thereby influences the entropy. We present applications to the response functions for the electrical and thermal conductivity, specific heat, generalized temperature, Boltzmann’s constant, and noise. The analysis can be performed either classically or quantum-mechanically, and there are only a few modifications in transferring between the approaches. As an application we study the energy, generalized temperature, and charge transport equations that are valid in nonequilibrium and relate it to heat flow and temperature relations in equilibrium states.

  3. Structure and Mechanism of the S Component of a Bacterial ECF Transporter

    Energy Technology Data Exchange (ETDEWEB)

    P Zhang; J Wang; Y Shi

    2011-12-31

    The energy-coupling factor (ECF) transporters, responsible for vitamin uptake in prokaryotes, are a unique family of membrane transporters. Each ECF transporter contains a membrane-embedded, substrate-binding protein (known as the S component), an energy-coupling module that comprises two ATP-binding proteins (known as the A and A' components) and a transmembrane protein (known as the T component). The structure and transport mechanism of the ECF family remain unknown. Here we report the crystal structure of RibU, the S component of the ECF-type riboflavin transporter from Staphylococcus aureus at 3.6-{angstrom} resolution. RibU contains six transmembrane segments, adopts a previously unreported transporter fold and contains a riboflavin molecule bound to the L1 loop and the periplasmic portion of transmembrane segments 4-6. Structural analysis reveals the essential ligand-binding residues, identifies the putative transport path and, with sequence alignment, uncovers conserved structural features and suggests potential mechanisms of action among the ECF transporters.

  4. Modeling of glycerol-3-phosphate transporter suggests a potential 'tilt' mechanism involved in its function.

    Science.gov (United States)

    Tsigelny, Igor F; Greenberg, Jerry; Kouznetsova, Valentina; Nigam, Sanjay K

    2008-10-01

    Many major facilitator superfamily (MFS) transporters have similar 12-transmembrane alpha-helical topologies with two six-helix halves connected by a long loop. In humans, these transporters participate in key physiological processes and are also, as in the case of members of the organic anion transporter (OAT) family, of pharmaceutical interest. Recently, crystal structures of two bacterial representatives of the MFS family--the glycerol-3-phosphate transporter (GlpT) and lac-permease (LacY)--have been solved and, because of assumptions regarding the high structural conservation of this family, there is hope that the results can be applied to mammalian transporters as well. Based on crystallography, it has been suggested that a major conformational "switching" mechanism accounts for ligand transport by MFS proteins. This conformational switch would then allow periodic changes in the overall transporter configuration, resulting in its cyclic opening to the periplasm or cytoplasm. Following this lead, we have modeled a possible "switch" mechanism in GlpT, using the concept of rotation of protein domains as in the DynDom program17 and membranephilic constraints predicted by the MAPAS program.(23) We found that the minima of energies of intersubunit interactions support two alternate positions consistent with their transport properties. Thus, for GlpT, a "tilt" of 9 degrees -10 degrees rotation had the most favorable energetics of electrostatic interaction between the two halves of the transporter; moreover, this confirmation was sufficient to suggest transport of the ligand across the membrane. We conducted steered molecular dynamics simulations of the GlpT-ligand system to explore how glycerol-3-phosphate would be handled by the "tilted" structure, and obtained results generally consistent with experimental mutagenesis data. While biochemical data remain most consistent with a single-site alternating access model, our results raise the possibility that, while the "rocker switch" may apply to certain MFS transporters, intermediate "tilted" states may exist under certain circumstances or as transitional structures. Although wet lab experimental confirmation is required, our results suggest that transport mechanisms in this transporter family should probably not be assumed to be conserved simply based on standard structural homology considerations. Furthermore, steered molecular dynamics elucidating energetic interactions of ligands with amino acid residues in an appropriately modeled transporter may have predictive value in understanding the impact of mutations and/or polymorphisms on transporter function. PMID:18942157

  5. Fluorescence measurement of chloride transport in monolayer cultured cells. Mechanisms of chloride transport in fibroblasts.

    OpenAIRE

    Chao, A. C.; Dix, J A; Sellers, M. C.; VERKMAN, A. S.

    1989-01-01

    The methodology has been developed to measure Cl activity and transport in cultured cells grown on a monolayer using the entrapped Cl-sensitive fluorophore 6-methoxy-N-[3-sulfopropyl] quinolinium (SPQ). The method was applied to a renal epithelial cell line, LLC-PKI, and a nonepithelial cell line, Swiss 3T3 fibroblasts. SPQ was nontoxic to cells when present for greater than h in the culture media. To load with SPQ (5 mM), cells were made transiently permeable by exposure to hypotonic buffer ...

  6. The Mechanical Design for the Darht-II Downstream Beam Transport Line

    CERN Document Server

    Westenskow, G A; Duffy, P T; Paul, A C

    2000-01-01

    This paper describes the mechanical design of the downstream beam transport line for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT II) Facility. The DARHT-II project is a collaboration between LANL, LBNL and LLNL. DARHT II is a 20-MeV, 2000-Amperes, 2-msec linear induction accelerator designed to generate short bursts of x-rays for the purpose of radiographing dense objects. The down-stream beam transport line is approximately 20-meter long region extending from the end of the accelerator to the bremsstrahlung target. Within this proposed transport line there are 15 conventional solenoid, quadrupole and dipole magnets; as well as several speciality magnets, which transport and focus the beam to the target and to the beam dumps. There are two high power beam dumps, which are designed to absorb 80-kJ per pulse during accelerator start-up and operation. Aspects of the mechanical design of these elements are presented.

  7. The Mechanical Design for the DARHT-II Downstream Beam Transport Line

    Science.gov (United States)

    Westenskow, Glen

    This paper describes the mechanical design of the downstream beam transport line for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT II) Facility. The DARHT-II project is a collaboration between LANL, LBNL and LLNL. DARHT II is a 20-MeV, 2000-Amperes, 2-msec linear induction accelerator designed to generate short bursts of x-rays for the purpose of radiographing dense objects. The down-stream beam transport line is approximately 20-meter long region extending from the end of the accelerator to the bremsstrahlung target. Within this proposed transport line there are 15 conventional solenoid, quadrupole and dipole magnets; as well as several speciality magnets, which transport and focus the beam to the target and to the beam dumps. There are two high power beam dumps, which are designed to absorb 80-kJ per pulse during accelerator start-up and operation. Aspects of the mechanical design of these elements are presented.

  8. Mechanism of methylmercury transport and transfer to the tissues of the rainbow trout (Salmo gairdneri)

    International Nuclear Information System (INIS)

    Hemoglobin (Hb) is the main methylmercury (Me Hg) transport protein in trout blood, binding 90 percent of whole blood MeHg as determined by gel filtration chromatography following an intragastric dose of Me 203HgCl. In vitro MeHg is taken up rapidly by red blood cells (RBC) with 84 percent of the Hg (5 ppM as MeHg) added to whole blood being accumulated by the RBCs in 3 minutes. The binding of MeHg within the RBC is freely reversible in vitro as demonstrated by the efflux of Hg from RBCs suspended in protein solutions. Trout hemolysate, containing 55 mg/ml HBB: removed 36 percent of the Hg from the RBCs in a 12 hour incubation period. The MeHg bond within the RBC is also reversible in vivo. Gel filtration chromatography of liver soluble proteins showed identical elution profiles for MeHg administered as the free salt or bound in RBCs. The number of reactive sulfhydryl (-SH) groups per molecule of Hb was found to be 4 by amperometric titration with MeHgCl. The reactive -SH concentration in the RBC was calculated to be at least 20 mM. A mechanism for the efflux of MeHg from the RBC is proposed involving the dissociation of MeHg from Hb initiated by -SH groups outside the RBC and migration of MeHg across the membrane as MeHgCl. (U.S.)

  9. A mechanism for the fast ionic transport in nanostructured oxide-ion solid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Bellino, M.G.; Lamas, D.G.; Walsoee de Reca, N.E. [CINSO (Centro de Investigaciones en Solidos), CITEFA-CONICET, J.B. de La Salle 4397 (B1603ALO) Villa Martelli, Pcia. de Buenos Aires (Argentina)

    2006-11-17

    Ionic transport in nanostructured solid electrolytes is investigated using an atomistic model that clarifies the enhanced conductivity of these materials. It is based on the fast diffusion of free oxygen vacancies through the grain boundaries. A transition observed in the ionic conductivity of the nanoceramics as a function of temperature, caused by a change in the transport mechanism, is also explained. (Abstract Copyright [2006], Wiley Periodicals, Inc.)

  10. D-cycloserine uses an active transport mechanism in the human intestinal cell line Caco 2.

    OpenAIRE

    Ranaldi, G; Islam, K.; Sambuy, Y

    1994-01-01

    In a previous study we have shown that cultured epithelial cell lines can be used to measure the transepithelial passage of antimicrobial agents across the intestine and to obtain information on the mechanisms of transport utilized and predict the bioavailability of the antimicrobial agents after oral administration. In particular, among the drugs investigated, D-cycloserine had been shown to be transported in a polarized manner only in the intestinal cells. In the present work, further chara...

  11. Buoyancy-driven flow in a peat moss layer as a mechanism for solute transport

    OpenAIRE

    Rappoldt, C.; Pieters, G.J.J.M.; Adema, E.B.; Baaijens, G.J.; Grootjans, A.P.; Duijn, C.J. van

    2003-01-01

    Transport of nutrients, CO2, methane, and oxygen plays an important ecological role at the surface of wetland ecosystems. A possibly important transport mechanism in a water-saturated peat moss layer (usually Sphagnum cuspidatum) is nocturnal buoyancy flow, the downward flow of relatively cold surface water, and the upward flow of warm water induced by nocturnal cooling. Mathematical stability analysis showed that buoyancy flow occurs in a cooling porous layer if the system¿s Rayleigh number ...

  12. Effect of Temperature on Thermal Transport and Mechanical Properties of Trans-polyisoprene

    Science.gov (United States)

    Baboo, Mahesh; Dixit, Manasvi; Sharma, Kananbala; Saxena, N. S.

    2010-06-01

    Thick and thin films of trans-polyisoprene (TPI) have been prepared using solution casting method by dissolving TPI in toluene. Thick films of TPI have been used to determine thermal transport properties at different temperatures through Thermal Constant Analyzer (TCA). The results show that thermal conductivity, thermal diffusivity and volumetric heat capacity increase with respect to temperature. Thin films of TPI on the other hand have been utilized for the measurement of mechanical properties such as Young's modulus, tensile strength and toughness. The effect of temperature on the mechanical properties of thin films of TPI has been investigated using Dynamic Mechanical analyzer (DMA) and it was found that the mechanical properties decrease with increasing temperature. Above said behavior of the thermal transport and mechanical properties as a function of temperatures is attributed to the increase in free volume of molecules in chains with temperature.

  13. Interim results of the F-5 irradiation experiment and proposed fission product transport mechanisms

    International Nuclear Information System (INIS)

    This paper presents: (1) results of a study of gamma-scan data for eight fuel rods removed at the end of the first phase of the GCFR F-5 (X317) irradiation experiment in EBR-II; (2) a comparison of cesium and iodine migration behavior in F-5 and previous GCFR irradiation experiments (GB-9, GB-10, and F-1); and (3) proposed cesium and iodine transport mechanisms, based primarily on observed fission product behavior in the irradiation experiments. Two modes of cesium transport, metal vapor transport and xenon precursor transport, are shown to be important. The formation of cesium uranate at the fuel-blanket interface and the effect of uranate formation on cesium transport to the fuel rod trap are discussed. It is shown how cesium isotope concentrations in the fuel rod trap differ for sealed and vented rods

  14. Psychostimulants affect dopamine transmission through both dopamine transporter-dependent and independent mechanisms.

    Science.gov (United States)

    dela Peña, Ike; Gevorkiana, Ruzanna; Shi, Wei-Xing

    2015-10-01

    The precise mechanisms by which cocaine and amphetamine-like psychostimulants exert their reinforcing effects are not yet fully defined. It is widely believed, however, that these drugs produce their effects by enhancing dopamine neurotransmission in the brain, especially in limbic areas such as the nucleus accumbens, by inducing dopamine transporter-mediated reverse transport and/or blocking dopamine reuptake though the dopamine transporter. Here, we present the evidence that aside from dopamine transporter, non-dopamine transporter-mediated mechanisms also participate in psychostimulant-induced dopamine release and contribute to the behavioral effects of these drugs, such as locomotor activation and reward. Accordingly, psychostimulants could increase norepinephrine release in the prefrontal cortex, the latter then alters the firing pattern of dopamine neurons resulting in changes in action potential-dependent dopamine release. These alterations would further affect the temporal pattern of dopamine release in the nucleus accumbens, thereby modifying information processing in that area. Hence, a synaptic input to a nucleus accumbens neuron may be enhanced or inhibited by dopamine depending on its temporal relationship to dopamine release. Specific temporal patterns of dopamine release may also be required for certain forms of synaptic plasticity in the nucleus accumbens. Together, these effects induced by psychostimulants, mediated through a non-dopamine transporter-mediated mechanism involving norepinephrine and the prefrontal cortex, may also contribute importantly to the reinforcing properties of these drugs. PMID:26209364

  15. The homodimeric ATP-binding cassette transporter LmrA mediates multidrug transport by an alternating two-site (two-cylinder engine) mechanism

    OpenAIRE

    Van Veen, Hendrik W.; Margolles, Abelardo; Müller, Michael; Higgins, Christopher F.; Wil N. Konings

    2000-01-01

    The bacterial LmrA protein and the mammalian multidrug resistance P-glycoprotein are closely related ATP-binding cassette (ABC) transporters that confer multidrug resistance on cells by mediating the extrusion of drugs at the expense of ATP hydrolysis. The mechanisms by which transport is mediated, and by which ATP hydrolysis is coupled to drug transport, are not known. Based on equilibrium binding experiments, photoaffinity labeling and drug transport assays, we conclude that homodimeric Lmr...

  16. Experimental Study on Influence of Mechanical Vibration during Transport of Transport/Storage Cask for Spent Nuclear Fuel on Containment Performance of Metal Gasket during Storage in Japan

    International Nuclear Information System (INIS)

    Transport casks of spent nuclear fuel will receive mechanical vibration during transport. It is known that the containment performance of metal gaskets is influenced by large external load or displacement. Quantitative influence of such vibration during transport on the containment performance of the metal gasket has not been known, but is crucial information particularly if the cask is stored as it is after the transport

  17. Towards a new generation of flow and transport models for the Aespoe Hard Rock Laboratory. Main results from the project Aespoe models 2005

    International Nuclear Information System (INIS)

    This report constitutes the outcome of a project called 'Aespoe models 2005'. The main objective of the project has been to provide a first step towards a new generation of numerical models of flow and transport, for the Aespoe HRL. In order to achieve this goal, work has been carried out along three parallel lines; discussion of basic concepts, compilation and analysis of data and model applications. A number of sub tasks are reported as appendices in the report. In fact, these appendices represent the main achievements of the project: an analysis of fracture properties, compilation of isotope and chemical data, dispersion and mixing in fractured rocks and model results. The conclusion of the project is that significant contributions to a new generation of Aespoe models have been obtained. It has further been demonstrated that working numerical simulations are up and running. Recommendations are provided for the continued work

  18. Complex Regulation of Plant Phosphate Transporters and the Gap between Molecular Mechanisms and Practical Application: What Is Missing?

    Science.gov (United States)

    Gu, Mian; Chen, Aiqun; Sun, Shubin; Xu, Guohua

    2016-03-01

    It has been almost 25 years since the first report of the gene encoding a high-affinity phosphate transporter (PT), PHO84, in yeast. Since then, an increasing number of yeast PHO84 homologs as well as other genes encoding proteins with phosphate (Pi) transport activities have been identified and functionally characterized in diverse plant species. Great progress has been made also in deciphering the molecular mechanism underlying the regulation of the abundance and/or activity of these genes and their products. The regulatory genes affect plant Pi homeostasis commonly through direct or indirect regulation of the abundance of PTs at different levels. However, little has been achieved in the use of PTs for developing genetically modified crops with high phosphorus use efficiency (PUE). This might be a consequence of overemphasizing Pi uptake from the rhizosphere and lack of knowledge about the roles of PTs in Pi transport and recycling within the plant that are required to optimize PUE. Here, we mainly focused on the genes encoding proteins with Pi transport activities and the emerging understanding of their regulation at the transcriptional, post-transcriptional, translational, and post-translational levels. In addition, we propose potential strategies for effective use of PTs in improving plant growth and development. PMID:26714050

  19. Tagged ozone mechanism for MOZART-4, CAM-chem and other chemical transport models

    OpenAIRE

    Emmons, L. K.; Hess, P. G.; J.-F. Lamarque; Pfister, G. G.

    2012-01-01

    A procedure for tagging ozone produced from NO sources through updates to an existing chemical mechanism is described, and results from its implementation in the Model for Ozone and Related chemical Tracers (MOZART-4), a global chemical transport model, are presented. Artificial tracers are added to the mechanism, thus, not affecting the standard chemistry. The results are linear in the troposphere, i.e., the sum of ozone from individual tagged sources equals the ...

  20. Gabapentin increases extracellular glutamatergic level in the locus coeruleus via astroglial glutamate transporter-dependent mechanisms

    OpenAIRE

    Suto, Takashi; Severino, Amie L.; Eisenach, James. C.; Hayashida, Ken-ichiro

    2014-01-01

    Gabapentin has shown to be effective in animals and humans with acute postoperative and chronic pain. Yet the mechanisms by which gabapentin reduces pain have not been fully addressed. The current study performed in vivo microdialysis in the locus coeruleus (LC) in normal and spinal nerve ligated (SNL) rats to examine the effect of gabapentin on extracellular glutamate concentration and its mechanisms of action with focus on presynaptic GABA-B receptors, astroglial glutamate transporter-1 (GL...

  1. Emergency Situation Prediction Mechanism: A Novel Approach for Intelligent Transportation System Using Vehicular Ad Hoc Networks

    OpenAIRE

    Ganeshkumar, P.; P. Gokulakrishnan

    2015-01-01

    In Indian four-lane express highway, millions of vehicles are travelling every day. Accidents are unfortunate and frequently occurring in these highways causing deaths, increase in death toll, and damage to infrastructure. A mechanism is required to avoid such road accidents at the maximum to reduce the death toll. An Emergency Situation Prediction Mechanism, a novel and proactive approach, is proposed in this paper for achieving the best of Intelligent Transportation System using Vehicular A...

  2. ABC transporters as a multidrug detoxification mechanism in Rhipicephalus (Boophilus) microplus.

    Science.gov (United States)

    Pohl, Paula C; Klafke, Guilherme M; Júnior, José Reck; Martins, João Ricardo; da Silva Vaz, Itabajara; Masuda, Aoi

    2012-12-01

    ATP-binding cassette (ABC) transporters are responsible for pumping drugs across membranes and are an important drug detoxification mechanism. Since ABC transporters act on a wide spectrum of chemical compounds, they have been associated with multidrug resistance phenotype in various parasites and cancer cells. Here, we document the presence of a Rhipicephalus (Boophilus) microplus tick population (Jaguar) resistant to four acaricide classes (organophosphates (OP), synthetic pyrethroids (SP), amitraz and macrocyclic lactones (ML)) and reveal that the cattle tick has a multidrug detoxification mechanism based on ABC transporter proteins. Acaricide toxicity was assessed using the larval packet test (LPT), and mortality data were subjected to probit analysis using a susceptible strain (POA) as reference. Larvae were pre-exposed to sub-lethal doses of the ABC-transporter inhibitors, cyclosporin A (CsA) and MK571, and subsequently treated with ivermectin, abamectin, moxidectin, chlorpyriphos, cypermethrin, or amitraz in LPT. Results show that lethal concentrations 50 % (LC(50)) of ivermectin, abamectin, moxidectin (MLs), and chlorpyriphos (OP) were significantly reduced in larvae exposed to CsA and MK571 inhibitors in the Jaguar resistant population, but LC(50) did not change in POA susceptible strain larvae. LC(50) of cypermetrin (SP) and amitraz remained unchanged in inhibitor-exposed larvae, compared to larvae from Jaguar and POA strains not exposed to inhibitor. These results suggest that ABC transporter proteins can protect ticks against a wide range of acaricides and have an important implication in drug resistance development as a multidrug detoxification mechanism. PMID:22926678

  3. Mechanical vibration: what is the importance of this physical quantity in the poultry transport?

    Directory of Open Access Journals (Sweden)

    Ana Carolina Donofre

    2014-01-01

    Full Text Available Mechanical vibrations are inherent to any system of transportation. In poultry production, the higher or lower intensity of this agent during the loading of eggs, chicks and chickens, can increase the production losses and decrease the efficiency of the system as a whole. However, despite its importance this factor is still unknown and little considered in the planning of the transport processes involved in the poultry industry. Therefore, the aim of raising the largest amount of data obtained so far to clarify the effects of mechanical vibrations already found in the transport of fertilized eggs, day-old chicks and broilers. A survey of international and national papers, from 1969 to 2014, which showed that the transport of fertilized eggs, the mechanical vibrations may be responsible for the incidence of cracks, in addition to promoting the agitation of internal constituents (yolk and albumen, which could potentially compromise the quality of birth and hatchlings. The transport of day-old chicks and broilers, the vibrations are related to situations of stress, discomfort and depreciation of the welfare of the birds, which still causes drops in the levels of glucose and corticosteroids and thus affect other parameters as the quality of the meat.

  4. Growth mechanism of ZnSe single crystal by chemical vapour transport method

    International Nuclear Information System (INIS)

    We attempted to grow ZnSe single crystals by the chemical vapour transport (CVT) method using the source material with different particle diameters. The purpose of this study is to examine the dependence the growth mechanism on the source particle diameter. We observed surface topographies of grown single crystals using the ultra-high vacuum atomic force microscopy (UHV-AFM) and investigated the growth mechanism. Dislocation densities were determined from etch pit density counts. It can be seen that the transport rate is decreasing with the increase in the source particle diameter. In the case of decreasing in the transport rate, transported atoms diffuse easily on the grown surface. Moreover, it turned out that the growth mechanism changed to the two-dimensional growth from the three-dimensional growth because the transport rate decreased. The average value of EPD of 3.0x103 cm-2 was obtained. We found that control of the source particle diameter is important for preparing high-quality ZnSe single crystals

  5. Electron transport mechanism of bathocuproine exciton blocking layer in organic photovoltaics.

    Science.gov (United States)

    Lee, Jeihyun; Park, Soohyung; Lee, Younjoo; Kim, Hyein; Shin, Dongguen; Jeong, Junkyeong; Jeong, Kwangho; Cho, Sang Wan; Lee, Hyunbok; Yi, Yeonjin

    2016-02-10

    Efficient exciton management is a key issue to improve the power conversion efficiency of organic photovoltaics (OPVs). It is well known that the insertion of an exciton blocking layer (ExBL) having a large band gap promotes the efficient dissociation of photogenerated excitons at the donor-acceptor interface. However, the large band gap induces an energy barrier which disrupts the charge transport. Therefore, building an adequate strategy based on the knowledge of the true charge transport mechanism is necessary. In this study, the true electron transport mechanism of a bathocuproine (BCP) ExBL in OPVs is comprehensively investigated by in situ ultraviolet photoemission spectroscopy, inverse photoemission spectroscopy, density functional theory calculation, and impedance spectroscopy. The chemical interaction between deposited Al and BCP induces new states within the band gap of BCP, so that electrons can transport through these new energy levels. Localized trap states are also formed upon the Al-BCP interaction. The activation energy of these traps is estimated with temperature-dependent conductance measurements to be 0.20 eV. The Al-BCP interaction induces both transport and trap levels in the energy gap of BCP and their interplay results in the electron transport observed. PMID:26821701

  6. Quantum Mechanical Study on Tunnelling and Ballistic Transport of Nanometer Si MOSFETs

    International Nuclear Information System (INIS)

    Using self-consistent calculations of million-atom Schrödinger-Poisson equations, we investigate the I–V characteristics of tunnelling and ballistic transport of nanometer metal oxide semiconductor held effect transistors (MOSFET) based on a full 3-D quantum mechanical simulation under nonequilibtium condition. Atomistic empirical pseudopotentials are used to describe the device Hamiltonian and the underlying bulk band structure. We find that the ballistic transport dominates the I–V characteristics, whereas the effects of tunnelling cannot be neglected with the maximal value up to 0.8 mA/?m when the channel length of MOSFET scales down to 25 nm. The effects of tunnelling transport lower the threshold voltage Vt. The ballistic current based on fully 3-D quantum mechanical simulation is relatively large and has small on-off ratio compared with results derived from the calculation methods of Luo et al

  7. Reform of refined oil product pricing mechanism and energy rebound effect for passenger transportation in China

    International Nuclear Information System (INIS)

    Improving energy efficiency is the primary method adopted by the Chinese government in an effort to achieve energy conservation target in the transport sector. However, the offsetting effect of energy rebound would greatly reduce its real energy-saving potentials. We set up a Linear Approximation of the Almost Ideal Demand System Model (LA-AIDS model) to estimate the rebound effect for passenger transportation in China. Real energy conservation effect of improving energy efficiency can also be obtained in the process. The result shows that the rebound effect is approximately 107.2%. This figure signifies the existence of ‘backfire effect’, indicating that efficiency improvement in practice does not always lead to energy-saving. We conclude that one important factor leading to the rebound effect, is the refined oil pricing mechanism. China's refined oil pricing mechanism has been subjected to criticism in recent years. The results of simulation analysis show that the rebound could be reduced to approximately 90.7% if the refined oil pricing mechanism is reformed. In this regard, we suggest further reforms in the current refined oil pricing mechanism. - Highlights: ? We set up the LA-AIDS model to estimate traffic service demand for urban residents. ? The size of the rebound effect for passenger transportation in China is evaluated. ? The rebound effect for passenger transportation in China is 107.2%. ? Reform of oil pricing could reduced the rebound to 90.7%. ? Reform of oil pricing might be an effective method for mitigating rebound effect

  8. Mechanical environmental transport of actinides and ¹³?Cs from an arid radioactive waste disposal site.

    Science.gov (United States)

    Snow, Mathew S; Clark, Sue B; Morrison, Samuel S; Watrous, Matthew G; Olson, John E; Snyder, Darin C

    2015-10-01

    Aeolian and pluvial processes represent important mechanisms for the movement of actinides and fission products at the Earth's surface. Soil samples taken in the early 1970's near a Department of Energy radioactive waste disposal site (the Subsurface Disposal Area, SDA, located in southeastern Idaho) provide a case study for studying the mechanisms and characteristics of environmental actinide and (137)Cs transport in an arid environment. Multi-component mixing models suggest actinide contamination within 2.5 km of the SDA can be described by mixing between 2 distinct SDA end members and regional nuclear weapons fallout. The absence of chemical fractionation between (241)Am and (239+240)Pu with depth for samples beyond the northeastern corner and lack of (241)Am in-growth over time (due to (241)Pu decay) suggest mechanical transport and mixing of discrete contaminated particles under arid conditions. Occasional samples northeast of the SDA (the direction of the prevailing winds) contain anomalously high concentrations of Pu with (240)Pu/(239)Pu isotopic ratios statistically identical to those in the northeastern corner. Taken together, these data suggest flooding resulted in mechanical transport of contaminated particles into the area between the SDA and a flood containment dike in the northeastern corner, following which subsequent contamination spreading in the northeastern direction resulted from wind transport of discrete particles. PMID:26107287

  9. Vibration-mediated Kondo transport in molecular junctions: conductance evolution during mechanical stretching

    OpenAIRE

    David Rakhmilevitch; Oren Tal

    2015-01-01

    The vibration-mediated Kondo effect attracted considerable theoretical interest during the last decade. However, due to lack of extensive experimental demonstrations, the fine details of the phenomenon were not addressed. Here, we analyze the evolution of vibration-mediated Kondo effect in molecular junctions during mechanical stretching. The described analysis reveals the different contributions of Kondo and inelastic transport.

  10. Vibration-mediated Kondo transport in molecular junctions: conductance evolution during mechanical stretching.

    Science.gov (United States)

    Rakhmilevitch, David; Tal, Oren

    2015-01-01

    The vibration-mediated Kondo effect attracted considerable theoretical interest during the last decade. However, due to lack of extensive experimental demonstrations, the fine details of the phenomenon were not addressed. Here, we analyze the evolution of vibration-mediated Kondo effect in molecular junctions during mechanical stretching. The described analysis reveals the different contributions of Kondo and inelastic transport. PMID:26734532

  11. Vibration-mediated Kondo transport in molecular junctions: conductance evolution during mechanical stretching

    Directory of Open Access Journals (Sweden)

    David Rakhmilevitch

    2015-12-01

    Full Text Available The vibration-mediated Kondo effect attracted considerable theoretical interest during the last decade. However, due to lack of extensive experimental demonstrations, the fine details of the phenomenon were not addressed. Here, we analyze the evolution of vibration-mediated Kondo effect in molecular junctions during mechanical stretching. The described analysis reveals the different contributions of Kondo and inelastic transport.

  12. Novel Transport Mechanism for Interacting Electrons in Disordered Systems: Variable-Range Resonant Tunneling

    OpenAIRE

    Baranovskii, S. D.; Shlimak, I. S.

    1998-01-01

    To interpret recent experimental observations of the phononless hopping conduction, we suggest a novel transport mechanism according to which the current-carrying single electrons move via quantum resonant tunneling between localized states brought into resonance by fast electron hops in their environment.

  13. A fully resolved active musculo-mechanical model for esophageal transport

    CERN Document Server

    Kou, Wenjun; Griffith, Boyce E; Pandolfino, John E; Kahrilas, Peter J; Patankar, Neelesh A

    2015-01-01

    Esophageal transport is a physiological process that mechanically transports an ingested food bolus from the pharynx to the stomach via the esophagus, a multi-layered muscular tube. This process involves interactions between the bolus, the esophagus, and the neurally coordinated activation of the esophageal muscles. In this work, we use an immersed boundary (IB) approach to simulate peristaltic transport in the esophagus. The bolus is treated as a viscous fluid that is actively transported by the muscular esophagus, which is modeled as an actively contracting, fiber-reinforced tube. A simplified version of our model is verified by comparison to an analytic solution to the tube dilation problem. Three different complex models of the multi-layered esophagus, which differ in their activation patterns and the layouts of the mucosal layers, are then extensively tested. To our knowledge, these simulations are the first of their kind to incorporate the bolus, the multi-layered esophagus tube, and muscle activation i...

  14. Rupture mechanics of metallic alloys for hydrogen transport; Mecanique de la rupture des alliages metalliques pour le transport de l'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Moro, I.; Briottet, L.; Lemoine, P. [CEA Grenoble (DRT/LITEN/DTH/LEV), 38 (France); Andrieu, E.; Blanc, C. [Centre Interuniversitaire de Recherche et d' Ingenierie des Materiaux (ENSIACET/CIRIMAT), 31 - Toulouse (France)

    2007-07-01

    With the aim to establish a cheap hydrogen distribution system, the transport by pipelines is a solution particularly interesting. Among the high limit of elasticity steels, the X80 has been chosen for hydrogen transport. Its chemical composition and microstructure are given. Important microstructural changes have been revealed in the sheet thickness: the microstructure is thinner and richer in perlite in surface than in bulk. In parallel to this microstructural evolution, a microhardness gradient has been observed: the material microhardness is stronger in surface than in bulk of the sheet. The use of this material for hydrogen transport requires to study its resistance to hydrogen embrittlement. The main aim of this work is to develop an easy rupture mechanics test allowing to qualify the studied material in a gaseous hydrogen environment, to determine the sensitivity of the studied material to the hydrogen embrittlement and to better understand the mechanisms of the hydrogen embrittlement for ferritic materials. Two experimental tests have been used for: the first one is a traction machine coupled to an autoclave; the second one allows to carry out disk rupture tests. The toughness of the material in a gaseous hydrogen environment has thus been determined. The resistance of the material to hydrogen embrittlement has been characterized and by simulation, it has been possible to identify the areas with a strong concentration in hydrogen. The second aim of this work is to study the influence of the steel microstructure on the hydrogen position in the material and on the resistance of the material to the hydrogen embrittlement. The preferential trapping sites on the material not mechanically loaded have at first been identified, as well as the hydrogen position on the different phases and at the ferrite/cementite interface. The interaction between the mechanical loads, the position and the trapping of the hydrogen have been studied then. At last, has been established a link between the preferential localization of hydrogen and the results of the rupture mechanics tests in a gaseous hydrogen environment. (O.M.)

  15. Receptor-mediated mechanism for the transport of prolactin from blood to cerebrospinal fluid

    International Nuclear Information System (INIS)

    Prolactin (PRL) interacts with areas of the central nervous system which reside behind the blood-brain barrier. While vascular PRL does not cross this barrier, it is readily accessible to the cerebrospinal fluid (CSF) from which it may gain access to the PRL-responsive areas of the brain. Studies were undertaken to characterize the mechanism responsible for the translocation of PRL from blood to CSF. Rats were given external jugular vein injections of [125-I]iodo-PRL in the presence or absence of an excess of unlabeled ovine PRL (oPRL), human GH, bovine GH, or porcine insulin. CSF and choroid plexus were removed 60 min later. CSF samples were electrophoresed on sodium dodecyl sulfate-polyacrylamide slab gels and resultant autoradiographs were analyzed with quantitative microdensitometry. The data revealed that unlabeled lactogenic hormones, viz. oPRL and human GH, caused a statistically significant inhibition of [125I]iodo-PRL transport from blood to CSF. In contrast, nonlactogenic hormones, viz bovine GH and insulin, had no effect on [125I]iodo-PRL transport into the CSF. An identical pattern of competition was observed in the binding of hormone to the choroid plexus. Furthermore, vascular injections of [125I]iodo-PRL administered with a range of concentrations of unlabeled oPRL revealed a dose-response inhibition in the transport of [125I]iodo-PRL from blood to CSF. The study demonstrates that PRL enters the CSF by a specific, PRL receptor-mediated transport mechanism. The data is consistent with the hypothesis that the transport mechanism resides at the choroid plexus. The existence of this transport mechanism reflects the importance of the cerebroventricular system in PRL-brain interactions

  16. Transport mechanisms for the uptake of organic compounds by rice (Oryza sativa) roots

    Energy Technology Data Exchange (ETDEWEB)

    Su Yuhong [Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China); Chemistry Department, Xinjiang University, Urumqi 830046 (China); Zhu Yongguan [Research Center for Eco-environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Beijing 100085 (China)]. E-mail: ygzhu@rcees.ac.cn

    2007-07-15

    Uptake of six organic compounds, dinitrobenzene (DNB), dinitrotoluene (DNT), lindan (LIN), 1,2,3-triclorobenzene (TCB), phenanthrene (PHN) and pyrene (PYR) by freshly excised rice roots and dead rice roots (heated for 40 min at 105 {sup o}C) were investigated. Results indicated that the uptake by the two types of roots did not increase proportionally with those in external solution. There appears to be some special chemical function of root cells other than simple absorption by the cells. The contribution of this special function can be roughly estimated by deducting the partition uptake into cells from the total uptake. Both time-dependent uptake data and concentration-dependent uptake curves demonstrate that, DNT and DNB transport is achieved presumably mainly via the symplastic pathway, while PHN and PYR transport mainly via the apoplastic pathway. For LIN and TCB, apoplastic transport pathway plays major roles in the first 2 h of uptake, then symplastic transport pathway dominates uptake. - Different organic compounds may be transported via different pathways in plant roots depending on log K {sub ow}.

  17. Transport mechanisms for the uptake of organic compounds by rice (Oryza sativa) roots

    International Nuclear Information System (INIS)

    Uptake of six organic compounds, dinitrobenzene (DNB), dinitrotoluene (DNT), lindan (LIN), 1,2,3-triclorobenzene (TCB), phenanthrene (PHN) and pyrene (PYR) by freshly excised rice roots and dead rice roots (heated for 40 min at 105 oC) were investigated. Results indicated that the uptake by the two types of roots did not increase proportionally with those in external solution. There appears to be some special chemical function of root cells other than simple absorption by the cells. The contribution of this special function can be roughly estimated by deducting the partition uptake into cells from the total uptake. Both time-dependent uptake data and concentration-dependent uptake curves demonstrate that, DNT and DNB transport is achieved presumably mainly via the symplastic pathway, while PHN and PYR transport mainly via the apoplastic pathway. For LIN and TCB, apoplastic transport pathway plays major roles in the first 2 h of uptake, then symplastic transport pathway dominates uptake. - Different organic compounds may be transported via different pathways in plant roots depending on log K ow

  18. Mechanisms of cellular uptake, intracellular transportation, and degradation of CIGB-300, a Tat-conjugated peptide, in tumor cell lines.

    Science.gov (United States)

    Benavent Acero, Fernando R; Perera Negrin, Yasser; Alonso, Daniel F; Perea, Silvio E; Gomez, Daniel E; Farina, Hernán G

    2014-06-01

    CIGB-300 is a cyclic synthetic peptide that induces apoptosis in malignant cells, elicits antitumor activity in cancer animal models, and shows tumor reduction signs when assayed in first-in-human phase I trial in patients with cervical tumors. CIGB-300 impairs phosphorylation by casein kinase 2 through targeting the substrate's phosphoacceptor domain. CIGB-300 was linked to the cell penetrating peptide Tat to facilitate the delivery into cells. Previously, we showed that CIGB-300 had a differential antiproliferative behavior in different tumor cell lines. In this work, we studied differential antiproliferative behavior in terms of cellular uptake, intracellular transportation, and degradation in tumor cell lines with dissimilar sensitivity to CIGB-300. The internalization of CIGB-300 was studied in different malignant cell lines. We found that the cell membrane heparan sulfate proteoglycans act as main receptors for extracellular CIGB-300 uptake. The most sensitive tumor cell lines showed higher intracellular incorporation of CIGB-300 in comparison to less sensitive cell lines. Furthermore, CIGB-300 uptake is time- and concentration-dependent in all studied cell lines. It was shown that CIGB-300 has the ability to penetrate cells mainly by direct membrane translocation. However, a minor proportion of the peptide uses an energy-dependent endocytic pathway mechanism to gain access into cells. CIGB-300 is internalized and transported into cells preferentially by caveolae-mediated endocytosis. Lysosomes are involved in CIGB-300 degradation; highly sensitive cell lines showed degradation at earlier times compared to low sensitive cells. Altogether, our data suggests a mechanism of internalization, vesicular transportation, and degradation for CIGB-300 in tumor cells. PMID:24773585

  19. OPTIMIZATION OF REGULATORY MECHANISMS AS A CONDITION OF COMPETITIVE TRANSPORT COMPLEX

    Directory of Open Access Journals (Sweden)

    S. Ilchenko

    2012-06-01

    Full Text Available At the present time for confident entrance to the European transport system with its standards, technical, organizational and ecological norms, the transport network of regions and the whole Ukraine requires constant qualitative updating. A number of important actions in this direction are already carried out, at the same time, to maintain an effective utilization of the international transport corridors in new conditions, it is important to reach the ultimate coordination of actions of all participants in this sphere.Complexity and immensity of the problems connected to the improvement of management of transport systems, leads to the necessity of an overall problem solution of the balanced transport development, transport systems and multi-modal transport development as a basic element of domestic potential growth of the state. Maintenance of these processes should be carried out through working out the programs of national transport system development and regional development programs in this direction. Therefore a research problem is to lay out the recommendations and methodical approaches to the problems of realization the above-stated programs and development strategy.In the presented article the basic problems of realization of the assigned tasks are designated, the principles underlying their performance are constructed, the legislative base which represents a legal mechanism of programs realization is defined, and recommendations which will give the chance to provide dynamic balanced development of a transport network of the country are presented. All these factors will help bring into the standards of living to the European ones and to create conditions for economic activity strengthening in all regions of the country that will contribute gradual easing of inter-regional disproportion, reduction of risks of formation of depressive territories and will protect society from considerable expenses on renewal of appropriate conditions of their ability to live.

  20. Use of molecular modelling to probe the mechanism of the nucleoside transporter NupG

    Science.gov (United States)

    Vaziri, Hamidreza; Baldwin, Stephen A.; Baldwin, Jocelyn M.; Adams, David G.; Young, James D.

    2013-01-01

    Nucleosides play key roles in biology as precursors for salvage pathways of nucleotide synthesis. Prokaryotes import nucleosides across the cytoplasmic membrane by proton- or sodium-driven transporters belonging to the Concentrative Nucleoside Transporter (CNT) family or the Nucleoside:H+ Symporter (NHS) family of the Major Facilitator Superfamily. The high resolution structure of a CNT from Vibrio cholerae has recently been determined, but no similar structural information is available for the NHS family. To gain a better understanding of the molecular mechanism of nucleoside transport, in the present study the structures of two conformations of the archetypical NHS transporter NupG from Escherichia coli were modelled on the inward- and outward-facing conformations of the lactose transporter LacY from E. coli, a member of the Oligosaccharide:H+ Symporter (OHS) family. Sequence alignment of these distantly related proteins (? 10% sequence identity), was facilitated by comparison of the patterns of residue conservation within the NHS and OHS families. Despite the low sequence similarity, the accessibilities of endogenous and introduced cysteine residues to thiol reagents were found to be consistent with the predictions of the models, supporting their validity. For example C358, located within the predicted nucleoside binding site, was shown to be responsible for the sensitivity of NupG to inhibition by p-chloromercuribenzene sulphonate. Functional analysis of mutants in residues predicted by the models to be involved in the translocation mechanism, including Q261, E264 and N228, supported the hypothesis that they play important roles, and suggested that the transport mechanisms of NupG and LacY, while different, share common features. PMID:23256604

  1. Species Transport Mechanisms Governing Crossover and Capacity Loss in Vanadium Redox Flow Batteries

    Science.gov (United States)

    Agar, Ertan

    Vanadium redox flow batteries (VRFBs) are an emerging energy storage technology that offers unique advantages for grid-scale energy storage due to their flexible design and decoupled power/energy feature. Despite their popularity, a series of technical challenges hinder their widespread implementation. Among these, capacity loss (i.e., loss of energy storage capability) due to the undesired species crossover across the membrane has been identified as the key issue limiting the longevity of these systems. This issue is primarily governed by the properties of the membrane and can be mitigated by using proper membrane architectures with desired features. Presently, identifying proper membrane architectures for VRFB systems is hampered by the lack of a fundamental understanding of the nature of species transport mechanisms and how they are related to the membrane properties and key operating conditions. This Ph.D. study seeks to address this critical challenge by exploring the fundamental mechanisms responsible for species transport within the membrane. The overall objective of this dissertation study is to establish a fundamental understanding of the multi-ionic transport in VRFB membranes by investigating the ionic transport mechanisms responsible for crossover, and utilize this understanding to reveal the role of membrane properties and operating conditions on the capacity loss. To achieve these goals, a combined experimental and computational study was designed. An experimentally validated, 2-D, transient VRFB model that can track the vanadium crossover and capture the related capacity loss was developed. In addition to the model, several electrochemical techniques were used to characterize different types of membrane and study the effects of various operating conditions on the species crossover. Using these computational and experimental tools, an in-depth understanding of the species transport mechanisms within the membrane and how they are related to membrane properties and operating conditions of VRFBs has been obtained. Finally, this understanding was utilized to identify effective mitigation strategies to minimize the capacity fade and improve the long-term performance of these systems.

  2. The Mechanical Design for the Darht-II Downstream Beam Transport Line

    OpenAIRE

    Westenskow, G. A.; Bertolini, L. R.; Duffy, P. T.; Paul, A.C.

    2000-01-01

    This paper describes the mechanical design of the downstream beam transport line for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT II) Facility. The DARHT-II project is a collaboration between LANL, LBNL and LLNL. DARHT II is a 20-MeV, 2000-Amperes, 2-msec linear induction accelerator designed to generate short bursts of x-rays for the purpose of radiographing dense objects. The down-stream beam transport line is approximately 20-meter long region extending from the e...

  3. The mechanism of the NH4 ion oscillatory transport across the excitable cell membrane

    Directory of Open Access Journals (Sweden)

    Radenovi? ?edomir N.

    2005-01-01

    Full Text Available This paper presents results on typical oscillations of the membrane potential induced by the excitation of the cell membrane by different concentrations of the NH4Cl solution. The existence of four classes of oscillations of the membrane potential and several different single and local impulses rhythmically occurring were determined. It is known that the oscillatory processes of the membrane potential are in direct dependence on oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane. A hypothesis on a possible mechanism of oscillatory transport processes of NH4 and Cl ions across the excitable cell membrane is also presented.

  4. Mechanism for Particle Transport and Size Sorting via Low-Frequency Vibrations

    Science.gov (United States)

    Sherrit, Stewart; Scott, James S.; Bar-Cohen, Yoseph; Badescu, Mircea; Bao, Xiaoqi

    2010-01-01

    There is a need for effective sample handling tools to deliver and sort particles for analytical instruments that are planned for use in future NASA missions. Specifically, a need exists for a compact mechanism that allows transporting and sieving particle sizes of powdered cuttings and soil grains that may be acquired by sampling tools such as a robotic scoop or drill. The required tool needs to be low mass and compact to operate from such platforms as a lander or rover. This technology also would be applicable to sample handling when transporting samples to analyzers and sorting particles by size.

  5. Mechanical and fracture behavior of nuclear fuel cladding in terms of transport and temporary dry storage; Comportamiento mecanio y en fractura de vainas de combustible nuclear en condiciones de transporte y almacenamiento temporal en seco

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz Hervias, J.; Martin Rengel, M. A.; Gomez, F. J.

    2012-11-01

    In this work, the most relevant results of a research project on the mechanical and fracture behavior of cladding in transport and dry storage conditions are summarized. the project is being carried out at Universidad Politecnica de Madrid in collaboration with ENUSA, ENRESA and CSN. Non-irradiated cladding is investigated. The main objective is to determine a failure criterion of cladding as a function of hydrogen content, temperature and strain rate. (Author)

  6. Alternating-access mechanism in conformationally asymmetric trimers of the betaine transporter BetP.

    Science.gov (United States)

    Perez, Camilo; Koshy, Caroline; Yildiz, Ozkan; Ziegler, Christine

    2012-10-01

    Betaine and Na(+) symport has been extensively studied in the osmotically regulated transporter BetP from Corynebacterium glutamicum, a member of the betaine/choline/carnitine transporter family, which shares the conserved LeuT-like fold of two inverted structural repeats. BetP adjusts its transport activity by sensing the cytoplasmic K(+) concentration as a measure for hyperosmotic stress via the osmosensing carboxy-terminal domain. BetP needs to be in a trimeric state for communication between individual protomers through several intratrimeric interaction sites. Recently, crystal structures of inward-facing BetP trimers have contributed to our understanding of activity regulation on a molecular level. Here we report new crystal structures, which reveal two conformationally asymmetric BetP trimers, capturing among them three distinct transport states. We observe a total of four new conformations at once: an outward-open apo and an outward-occluded apo state, and two closed transition states--one in complex with betaine and one substrate-free. On the basis of these new structures, we identified local and global conformational changes in BetP that underlie the molecular transport mechanism, which partially resemble structural changes observed in other sodium-coupled LeuT-like fold transporters, but show differences we attribute to the osmolytic nature of betaine, the exclusive substrate specificity and the regulatory properties of BetP. PMID:22940865

  7. A review of overseas financing mechanisms and incentives for commercial renewable energy projects. V. 1: Main report

    International Nuclear Information System (INIS)

    Overseas financing mechanisms and incentives for commercial renewable energy projects being undertaken worldwide are reviewed in this study funded by the United Kingdom Department of Trade and Industry. The study examines how commercial renewable energy projects have been financed in Europe and North America. Future trends are suggested. Financial, contractual or market incentives for each technology are examined for each country. Incentive programmes are evaluated and analysed in terms of cost to the government and consumer. The potential and issues involved for British companies aiming to export expertise or equipment for such projects is also evaluated briefly. (UK)

  8. Long-range transport of Asian pollution to North America: Mechanisms, chemistry and variability

    Science.gov (United States)

    Liang, Qing

    Long-range transport (LRT) of Asian pollutants affects the atmospheric composition over the North Pacific and has important implications in terms of air quality regulation in the United States. Through analysis of surface and aircraft observations with a global model of tropospheric chemistry, this dissertation investigates the mechanisms, chemistry, and variability of long-range transport of Asian pollution. This study has resulted in three papers, two of which have been published in the Journal of Geophysical Research - Atmospheres (Chapter 2 and 3), and one is in preparation for submission to the same journal (Chapter 4). Chapter 2 examines observations of carbon monoxide (CO, a tracer for anthropogenic emissions) in the North Pacific to understand the seasonality and transport of Asian pollution. The Asian influence on the North Pacific troposphere maximizes during spring and minimizes in summer, but LRT occurs throughout the year. We find that 80% of the export episodes over East Asia are mediated by mid-latitude cyclones and 3/4 of the events imported into the lower troposphere over the NE Pacific are by boundary layer transport. Chapter 3 focuses on the daily to interannual variability of transpacific transport. We relate the daily variability in Asian outflow to the passage of mid-latitude cyclones in East Asia, while transpacific transport is linked to the intensity of the Pacific High and the Aleutian low. On interannual timescales, we find that the variability in transpacific transport is favored by a strong Pacific High and a strong Aleutian Low. Chapter 4 focuses on observations of Asian pollution plumes in the free troposphere over North America during summer. The summertime Asian plumes are enhanced in many trace gases compared to background. When contrasted with previous springtime measurements, the summertime transport plumes show much higher levels of reactive nitrogen species and ozone as a result of active photochemistry.

  9. Mechanism of NaCl transport-stimulated prostaglandin formation in MDCK cells

    International Nuclear Information System (INIS)

    Recently the authors have found that stimulation of NaCl transport in high-resistance MDCK cells enhances their prostaglandin formation. In the present study, they investigated the mechanisms by which prostaglandin formation, measured by radioimmunoassay, could be linked to the ion transport in these cells. They found that stimulation of transport caused a transient stimulation of prostaglandin formation lasting 5-10 min. The rise in prostaglandin formation was paralleled by a rise of free intracellular [14C]-arachidonic acid. Analysis of membrane lipids revealed that the rise of free arachidonic acid was paralleled by a loss of arachidonic acid from polyphosphoinositides. They failed to obtain indications for the stimulation of calcium-dependent phospholipase A2. However, they did obtain evidence that the incorporation of arachidonic acid into phospholipids was diminished during stimulation of ion transport, indicating a decreased rate of reesterification. Despite the fact that there was no significant fall in total cellular ATP on stimulation of ion transport, they found a high and transient rise of lactate production of the cells on stimulation of the [45Ca]-ion transport indicating an alteration of the ADP/ATP ratio. The results suggest that an increase in the rate of sodium chloride transport by MDCK cells stimulates formation by an inhibition of reesterification of free arachidonic acid. Reesterification of arachidonic acid is most likely inhibited by a local and transient fall of ATP at the basal membrane side, which is caused by the enhanced ATP consumption of the sodium potassium adenosine triphosphatase (ATPase) during stimulation of ion transport

  10. Mechanical thermal and electric measurements on materials and components of the main coils of the Milan superconducting cyclotron

    International Nuclear Information System (INIS)

    The coils of the Milan Superconducting Cyclotron are the largest superconducting devices built up to now in Italy and constitute the first superconducting magnet for accelerator in Europe. Because of the large stored energy (more than 40 MJ), of the high stresses and of of the need of reliability, a lot of measurements were carried out as well on materials used for the coils, both on superconducting cable and structural materials, as on the main components of the coils and on two double pancakes prototypes (wound with full copper cable). In this paper the results on these measurements are reported and the results of tests on the prototypes are discussed. The aim is to provide an easy source of data for superconducting coils useful to verify calculations or to improve the performances

  11. Haemophilus parainfluenzae expresses diverse lipopolysaccharide O-antigens using ABC transporter and Wzy polymerase-dependent mechanisms.

    Science.gov (United States)

    Young, Rosanna E B; Twelkmeyer, Brigitte; Vitiazeva, Varvara; Power, Peter M; Schweda, Elke K H; Hood, Derek W

    2013-12-01

    Lipopolysaccharide O-antigens are the basis of serotyping schemes for Gram negative bacteria and help to determine the nature of host-bacterial interactions. Haemophilus parainfluenzae is a normal commensal of humans but is also an occasional pathogen. The prevalence, diversity and biosynthesis of O-antigens were investigated in this species for the first time. 18/18 commensal H. parainfluenzae isolates contain a O-antigen biosynthesis gene cluster flanked by glnA and pepB, the same position as the hmg locus for tetrasaccharide biosynthesis in Haemophilus influenzae. The O-antigen loci show diverse restriction digest patterns but fall into two main groups: (1) those encoding enzymes for the synthesis and transfer of FucNAc4N in addition to the Wzy-dependent mechanism of O-antigen synthesis and transport and (2) those encoding galactofuranose synthesis/transfer enzymes and an ABC transporter. The other glycosyltransferase genes differ between isolates. Three H. parainfluenzae isolates fell outside these groups and are predicted to synthesise O-antigens containing ribitol phosphate or deoxytalose. Isolates using the ABC transporter system encode a putative O-antigen ligase, required for the synthesis of O-antigen-containing LPS glycoforms, at a separate genomic location. The presence of an O-antigen contributes significantly to H. parainfluenzae resistance to the killing effect of human serum in vitro. The discovery of O-antigens in H. parainfluenzae is striking, as its close relative H. influenzae lacks this cell surface component. PMID:24035104

  12. Haemophilus parainfluenzae expresses diverse lipopolysaccharide O-antigens using ABC transporter and Wzy polymerase-dependent mechanisms

    Science.gov (United States)

    Young, Rosanna E.B.; Twelkmeyer, Brigitte; Vitiazeva, Varvara; Power, Peter M.; Schweda, Elke K.H.; Hood, Derek W.

    2013-01-01

    Lipopolysaccharide O-antigens are the basis of serotyping schemes for Gram negative bacteria and help to determine the nature of host–bacterial interactions. Haemophilus parainfluenzae is a normal commensal of humans but is also an occasional pathogen. The prevalence, diversity and biosynthesis of O-antigens were investigated in this species for the first time. 18/18 commensal H. parainfluenzae isolates contain a O-antigen biosynthesis gene cluster flanked by glnA and pepB, the same position as the hmg locus for tetrasaccharide biosynthesis in Haemophilus influenzae. The O-antigen loci show diverse restriction digest patterns but fall into two main groups: (1) those encoding enzymes for the synthesis and transfer of FucNAc4N in addition to the Wzy-dependent mechanism of O-antigen synthesis and transport and (2) those encoding galactofuranose synthesis/transfer enzymes and an ABC transporter. The other glycosyltransferase genes differ between isolates. Three H. parainfluenzae isolates fell outside these groups and are predicted to synthesise O-antigens containing ribitol phosphate or deoxytalose. Isolates using the ABC transporter system encode a putative O-antigen ligase, required for the synthesis of O-antigen-containing LPS glycoforms, at a separate genomic location. The presence of an O-antigen contributes significantly to H. parainfluenzae resistance to the killing effect of human serum in vitro. The discovery of O-antigens in H. parainfluenzae is striking, as its close relative H. influenzae lacks this cell surface component. PMID:24035104

  13. Mimicking cellular transport mechanism in stem cells through endosomal escape of new peptide-coated quantum dots

    Science.gov (United States)

    Narayanan, Karthikeyan; Yen, Swee Kuan; Dou, Qingqing; Padmanabhan, Parasuraman; Sudhaharan, Thankiah; Ahmed, Sohail; Ying, Jackie Y.; Selvan, Subramanian Tamil

    2013-07-01

    Protein transport is an important phenomenon in biological systems. Proteins are transported via several mechanisms to reach their destined compartment of cell for its complete function. One such mechanism is the microtubule mediated protein transport. Up to now, there are no reports on synthetic systems mimicking the biological protein transport mechanism. Here we report a highly efficient method of mimicking the microtubule mediated protein transport using newly designed biotinylated peptides encompassing a microtubule-associated sequence (MTAS) and a nuclear localization signaling (NLS) sequence, and their final conjugation with streptavidin-coated CdSe/ZnS quantum dots (QDs). Our results demonstrate that these novel bio-conjugated QDs enhance the endosomal escape and promote targeted delivery into the nucleus of human mesenchymal stem cells via microtubules. Mimicking the cellular transport mechanism in stem cells is highly desirable for diagnostics, targeting and therapeutic applications, opening up new avenues in the area of drug delivery.

  14. Recent Developments in Graphene-Based Membranes: Structure, Mass-Transport Mechanism and Potential Applications.

    Science.gov (United States)

    Sun, Pengzhan; Wang, Kunlin; Zhu, Hongwei

    2016-03-01

    Significant achievements have been made on the development of next-generation filtration and separation membranes using graphene materials, as graphene-based membranes can afford numerous novel mass-transport properties that are not possible in state-of-art commercial membranes, making them promising in areas such as membrane separation, water desalination, proton conductors, energy storage and conversion, etc. The latest developments on understanding mass transport through graphene-based membranes, including perfect graphene lattice, nanoporous graphene and graphene oxide membranes are reviewed here in relation to their potential applications. A summary and outlook is further provided on the opportunities and challenges in this arising field. The aspects discussed may enable researchers to better understand the mass-transport mechanism and to optimize the synthesis of graphene-based membranes toward large-scale production for a wide range of applications. PMID:26797529

  15. Transport equations, Level Set and Eulerian mechanics. Application to fluid-structure coupling

    International Nuclear Information System (INIS)

    My works were devoted to numerical analysis of non-linear elliptic-parabolic equations, to neutron transport equation and to the simulation of fabrics draping. More recently I developed an Eulerian method based on a level set formulation of the immersed boundary method to deal with fluid-structure coupling problems arising in bio-mechanics. Some of the more efficient algorithms to solve the neutron transport equation make use of the splitting of the transport operator taking into account its characteristics. In the present work we introduced a new algorithm based on this splitting and an adaptation of minimal residual methods to infinite dimensional case. We present the case where the velocity space is of dimension 1 (slab geometry) and 2 (plane geometry) because the splitting is simpler in the former

  16. Excess white noise to probe transport mechanisms in a membrane channel

    Science.gov (United States)

    Queralt-Martín, María; López, M. Lidón; Alcaraz, Antonio

    2015-06-01

    Current fluctuation analysis has been successfully used over the years to investigate the physical properties of different systems. Here, we perform single-channel time-resolved current experiments in a protein channel to evaluate the different transport mechanisms governing the channel function. Using different salts of monovalent and divalent cations in a wide range of concentrations and applied potentials, we analyze current fluctuations focusing on the voltage dependence of the additional white noise that appears in the low-frequency range of the spectra. We demonstrate that the channel displays two characteristic transport regimes: at low salt concentrations (10 mM to 1 M) ion permeation is controlled by the protein fixed charges that induce accumulation or exclusion of ions to preserve local electroneutrality. At high salt concentrations (>1 M ) adsorption processes associated to the binding of cations to the channel charges regulate the transport properties.

  17. Impact of mechanical- and maintenance-induced failures of main reactor coolant pump seals on plant safety

    International Nuclear Information System (INIS)

    This document presents an investigation of the safety impact resulting from mechanical- and maintenance-induced reactor coolant pump (RCP) seal failures in nuclear power plants. A data survey of the pump seal failures for existing nuclear power plants in the US from several available sources was performed. The annual frequency of pump seal failures in a nuclear power plant was estimated based on the concept of hazard rate and dependency evaluation. The conditional probability of various sizes of leak rates given seal failures was then evaluated. The safety impact of RCP seal failures, in terms of contribution to plant core-melt frequency, was also evaluated for three nuclear power plants. For leak rates below the normal makeup capacity and the impact of plant safety were discussed qualitatively, whereas for leak rates beyond the normal make up capacity, formal PRA methodologies were applied. 22 refs., 17 figs., 19 tabs

  18. Charge-transfer state excitation as the main mechanism of the photodarkening process in ytterbium-doped aluminosilicate fibres

    Energy Technology Data Exchange (ETDEWEB)

    Bobkov, K K; Rybaltovsky, A A; Vel' miskin, V V; Likhachev, M E; Bubnov, M M; Dianov, E M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Umnikov, A A; Gur' yanov, A N; Vechkanov, N N [G.G.Devyatykh Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation); Shestakova, I A [Open Joint-Stock Company M.F. Stel' makh Polyus Research Institute, Moscow (Russian Federation)

    2014-12-31

    We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb{sup 2+} ions in the glass network under IR laser pumping at a wavelength ? = 915 nm and under UV irradiation with an excimer laser (? = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb{sup 2+} ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicate glass, has been identified: photoinduced Yb{sup 3+} charge-transfer state excitation. (optical fibres)

  19. Investigation of Sediment Transport Mechanisms in the Durres Gulf – Albania Using Radiotracers [Case Study: Radiotracer Applications for Investigation of Bedload Transport of Sediments

    International Nuclear Information System (INIS)

    The radiotracer study had the following objectives: • to clarify the mechanism and to obtain quantitative results regarding the sediment transport in the gulf of Durres; • to find the sediment transport direction and quantity in the vicinity of the access channel of Durres port; • to determine the sediment quantity deposed every year in the channel

  20. Electrical transport mechanisms and structure of hydrogenated and non-hydrogenated nanocrystalline Ga1−xMnxAs films

    International Nuclear Information System (INIS)

    Highlights: • Ga1−xMnxAs films were produced by the RF magnetron sputtering technique. • The structures of the films were analyzed by Rietveld refinement. • Electrical conductivity was analyzed with basis on the structure and morphology. • Space charge limited current regime was identified in the films without manganese. • The electrical transport of the sample with manganese showed only “Ohmic regime”. - Abstract: The mechanisms of electrical conductivity in hydrogenated and non-hydrogenated nanocrystalline Ga1−xMnxAs (0.000 ⩽ x ⩽ 0.081) films were analyzed, first from a macroscopic perspective, followed by microscopic analysis to investigate the energy levels for trapping electric charges. The analysis of the current–voltage and resistivity–temperature characteristics allowed the development of a model based on the morphology and structure of the films. This model takes into account the main aspects of the transport above 300 K. Space charge limited current (SCLC) mechanism was observed in Mn-free films and is associated with deep trap states located at 0.10 and 0.22 eV below the conduction band. In samples containing Mn, the dark conductivity is highly dependent on the presence of hydrogen. This effect was related to the grain boundaries and interstitial regions of the films, in which the density of gap states is expected to be reduced by the presence of hydrogen

  1. Modeling of Colloid Transport Mechanisms Facilitating Migration of Radionuclides in Fractured Media

    International Nuclear Information System (INIS)

    Performance assessments of high-level radioactive waste disposal have emphasized the role of colloids in the migration of radionuclides in the geosphere. The transport of colloids often brings them in contact with fracture surfaces or porous rock matrix. Colloids that attach to these surfaces are treated as being immobile and are called filtered colloids. The filtered colloids could be released into the fracture again; that is, the attachment of colloids may be reversible. Also, the colloids in the fracture could diffuse into the porous matrix rock. A methodology is proposed to evaluate a predictive model to assess transport within the fractured rock as well as various phenomenological coefficients employed in the different mechanisms, such as filtration, remobilization, and matrix diffusion of colloids. The governing equations of colloids considering mechanisms of the colloidal transport in the fractured media, including filtration, remobilization, and matrix diffusion, have been modeled and solved analytically in previous studies. In the present study, transport equations of colloids and radionuclides that consider the combination of the aforementioned transport mechanisms have also been solved numerically and investigated. The total concentration of mobile radionuclides in the fracture becomes lower because the concentration of mobile colloids in the fracture decreases when the filtration coefficient for colloids increases. Additionally, the concentration of mobile radionuclides was increased at any given time step due to the higher sorption partition coefficient of radionuclides associated with colloids. The results also show that the concentration of radionuclides in the fracture zone decreases when the remobilization coefficient of colloids or the percentages of the matrix diffusion flux of colloids increase

  2. Mechanical evaluation of a natural UF6 transport container at high temperature

    International Nuclear Information System (INIS)

    International Atomic Energy Agency (IAEA) revised the transport regulation for natural uranium hexafluoride (UF6) transportation taking into account chemical and radiological hazards in 1996. A supplementary fire test requirement (800 deg. C for 30 minutes) was imposed on the natural UF6 transport container. In 1996, Central Research Institute of Electric Power Industry (CRIEPI) and Nuclear Protection and Safety Institute (IPSN) terminated experimental joint research works with the aim to determine the thermal-physical behavior of UF6 in a transport container under realistic fire conditions and to use the experimental data to validate a thermal-hydraulic numerical model. Now, they have started a new experimental joint research as to the rupture test of the 48Y-cylinder which will be terminated at the end of 1998. The purpose of this study is to evaluate numerically the mechanical integrity of this cylinder in the IAEA fire test conditions. Firstly, pre-thermal-hydraulic numerical analysis of the 48Y-cylinder under the IAEA fire test condition was performed. Nextly, the structural material model at high temperature for natural UF6 transport container was proposed based on the CRIEPI's material tests and applied to the ABAQUS computer code. According to the mechanical non-linear analysis results, it was found that it is necessary to evaluate the safety margin for the rupture of the 48Y-cylinder because considerable plastic and creep deformations are generated due to the temperature distribution of the cylinder and the inner pressure. This thermal-mechanical behavior of the container will be verified according to the rupture test results of the 48Y-cylinder until the end of 1998. (authors)

  3. Drug transport mechanism of P-glycoprotein monitored by single molecule fluorescence resonance energy transfer

    CERN Document Server

    Ernst, Stefan; Zarrabi, Nawid; Wilkens, Stephan; Boersch, Michael

    2011-01-01

    In this work we monitor the catalytic mechanism of P-glycoprotein (Pgp) using single-molecule fluorescence resonance energy transfer (FRET). Pgp, a member of the ATP binding cassette family of transport proteins, is found in the plasma membrane of animal cells where it is involved in the ATP hydrolysis driven export of hydrophobic molecules. When expressed in the plasma membrane of cancer cells, the transport activity of Pgp can lead to the failure of chemotherapy by excluding the mostly hydrophobic drugs from the interior of the cell. Despite ongoing effort, the catalytic mechanism by which Pgp couples MgATP binding and hydrolysis to translocation of drug molecules across the lipid bilayer is poorly understood. Using site directed mutagenesis, we have introduced cysteine residues for fluorescence labeling into different regions of the nucleotide binding domains (NBDs) of Pgp. Double-labeled single Pgp molecules showed fluctuating FRET efficiencies during drug stimulated ATP hydrolysis suggesting that the NBD...

  4. Experiment showing a mechanical manifestation of the helicity of transport current in superconducting wires

    International Nuclear Information System (INIS)

    The transport current density of the mixed state of type II wires will have the form J = z J/sub z/ + THETA J/sub THETA/ when the supercurrent exhibits a helical distribution due to the application of an external field H/sub z/. This is proved by the magnetic moment measurements of Walmsley and Timms, who observed the so-called paramagnetic component of moment M when J/sub THETA/ not equal to 0. A mechanical manifestation of the helical current was observed by combining a normal-zone propagation experiment with a capacitive technique for measuring mechanical torsion of the sample. Moreover, the torsion was observed even when H/sub z/ = 0, an effect that might be explained by the theory of Kondo and Kuroda on the helicity of transport currents in normal metals due to spiral dislocations

  5. The molecular mechanism of Zinc acquisition by the neisserial outer-membrane transporter ZnuD

    Science.gov (United States)

    Calmettes, Charles; Ing, Christopher; Buckwalter, Carolyn M.; El Bakkouri, Majida; Chieh-Lin Lai, Christine; Pogoutse, Anastassia; Gray-Owen, Scott D.; Pomès, Régis; Moraes, Trevor F.

    2015-08-01

    Invading bacteria from the Neisseriaceae, Acinetobacteriaceae, Bordetellaceae and Moraxellaceae families express the conserved outer-membrane zinc transporter zinc-uptake component D (ZnuD) to overcome nutritional restriction imposed by the host organism during infection. Here we demonstrate that ZnuD is required for efficient systemic infections by the causative agent of bacterial meningitis, Neisseria meningitidis, in a mouse model. We also combine X-ray crystallography and molecular dynamics simulations to gain insight into the mechanism of zinc recognition and transport across the bacterial outer-membrane by ZnuD. Because ZnuD is also considered a promising vaccine candidate against N. meningitidis, we use several ZnuD structural intermediates to map potential antigenic epitopes, and propose a mechanism by which ZnuD can maintain high sequence conservation yet avoid immune recognition by altering the conformation of surface-exposed loops.

  6. Fracture mechanics based design for radioactive material transport packagings -- Historical review

    International Nuclear Information System (INIS)

    The use of a fracture mechanics based design for the radioactive material transport (RAM) packagings has been the subject of extensive research for more than a decade. Sandia National Laboratories (SNL) has played an important role in the research and development of the application of this technology. Ductile iron has been internationally accepted as an exemplary material for the demonstration of a fracture mechanics based method of RAM packaging design and therefore is the subject of a large portion of the research discussed in this report. SNL's extensive research and development program, funded primarily by the U. S. Department of Energy's Office of Transportation, Energy Management and Analytical Services (EM-76) and in an auxiliary capacity, the office of Civilian Radioactive Waste Management, is summarized in this document along with a summary of the research conducted at other institutions throughout the world. In addition to the research and development work, code and standards development and regulatory positions are also discussed

  7. Advances in the numerical treatment of grain-boundary migration: Coupling with mass transport and mechanics

    CERN Document Server

    Mourad, H M; Mourad, Hashem M.; Garikipati, Krishna

    2004-01-01

    This work is based upon a coupled, atomically-based continuum formulation that was previously applied to problems involving strong coupling between mechanics and mass transport; e.g. diffusional creep and electromigration. Here we discuss an enhancement of this formulation to account for migrating grain boundaries. The treatment is based on the level set method and can easily be generalized to model other problems with migrating interfaces; e.g. void evolution and free-surface morphology evolution. The level-set formulation developed is remarkably simple and obviates the need for spatial stabilization. It also makes use of velocity extension, field re-initialization and least-squares smoothing techniques. The latter allow the local curvature of a grain boundary to be computed directly from the level-set field without resorting to higher-order interpolation. A notable feature is that the coupling between mass transport, mechanics and grain-boundary migration is fully accounted for. The complexities associated ...

  8. The application of fracture mechanics to the safety assessment of transport casks for radioactive materials

    International Nuclear Information System (INIS)

    BAM is the German responsible authority for the mechanical and thermal design safety assessment of packages for the transport of radioactive materials. The assessment has to cover the brittle fracture safety proof of package components made of potentially brittle materials. This paper gives a survey of the regulatory and technical requirements for such an assessment according to BAM's new ''Guidelines for the Application of Ductile Cast Iron for Transport and Storage Casks for Radioactive Materials''. Based on these guidelines higher stresses than before can become permissible, but it is necessary to put more effort into the safety assessment procedure. The fundamentals of such a proof with the help of the methods of fracture mechanics are presented. The recommended procedure takes into account the guidelines of the IAEA Advisory Material which are based on the prevention of crack initiation. Examples of BAM's research and safety assessment practices are given. Recommendations for further developments towards package designs with higher acceptable stress levels will be concluded

  9. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    International Nuclear Information System (INIS)

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure

  10. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    Energy Technology Data Exchange (ETDEWEB)

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Xu, Ke, E-mail: kxu2006@sinano.ac.cn; Wang, Jianfeng; Ren, Guoqiang [Suzhou Institute of Nano-Tech and Nano-Bionics, CAS, Suzhou 215123 (China); Suzhou Nanowin Science and Technology Co., Ltd., Suzhou 215123 (China)

    2014-01-07

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure.

  11. The role of lock-in mechanisms in transition processes: The case of energy for road transport

    DEFF Research Database (Denmark)

    Klitkou, Antje; Bolwig, Simon

    2015-01-01

    This paper revisits the theoretical concepts of lock-in mechanisms to analyse transition processes in energy production and road transportation in the Nordic countries, focussing on three technology platforms: advanced biofuels, e-mobility and hydrogen and fuel cell electrical vehicles. The paper is based on a comparative analysis of case studies. The main lock-in mechanisms analysed are learning effects, economies of scale, economies of scope, network externalities, informational increasing returns, technological interrelatedness, collective action, institutional learning effects and the differentiation of power. We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence, the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based, but may also include mature niches specialised in the exploitation of renewable sources. This implies a need to distinguish between lock-in mechanisms favouring the old fossil-based regime, well-established (mature) renewable energy niches, or new pathways.

  12. Analysis of Mechanical Energy Transport on Free-Falling Wedge during Water-Entry Phase

    OpenAIRE

    Yan-Ying Wang; Wen-Hua Wang; Yi Huang

    2012-01-01

    For better discussing and understanding the physical phenomena and body-fluid interaction of water-entry problem, here mechanical-energy transport (wedge, fluid, and each other) of water-entry model for free falling wedge is studied by numerical method based on free surface capturing method and Cartesian cut cell mesh. In this method, incompressible Euler equations for a variable density fluid are numerically calculated by the finite volume method. Then artificial compressibility method, dual...

  13. Ovariectomy Enhances Mechanical Load-Induced Solute Transport around Osteocytes in Rat Cancellous Bone

    OpenAIRE

    Ciani, Cesare; Sharma, Divya; Stephen B. Doty; Fritton, Susannah P.

    2013-01-01

    To test if osteoporosis alters mechanical load-induced interstitial fluid flow in bone, this study examined the combined effect of estrogen deficiency and external loading on solute transport around osteocytes. An in vivo tracer, FITC-labeled bovine serum albumin, was injected into anaesthetized ovariectomized and control female Sprague Dawley rats before the right tibia was subjected to a controlled, physiological, non-invasive sinusoidal load to mimic walking. Tracer movement through the la...

  14. Mechanically reinforced MgB2 wires and tapes with high transport currents

    OpenAIRE

    Nast, R.; Schlachter, S. I.; Zimmer, S.; H.; Reiner; Goldacker, W.

    2001-01-01

    Monofilamentary MgB2-wires with a 2- or 3-component sheath containing mechanical reinforcing stainless steel (SS) were prepared and characterized. In direct contact to the superconductor Nb, Ta or Fe was used. For a selection of samples with a Fe and Fe/SS sheath, we investigated the transport critical current behaviour in magnetic fields changing systematically the geometrical shape from a round wire to a flat tape. A strong increase of the current densities in flat tapes w...

  15. Zinc Transporters, Mechanisms of Action and Therapeutic Utility: Implications for Type 2 Diabetes Mellitus

    OpenAIRE

    Myers, Stephen A.; Alex Nield; Mark Myers

    2012-01-01

    Zinc is an essential trace element that plays a vital role in maintaining many biological processes and cellular homeostasis. Dysfunctional zinc signaling is associated with a number of chronic disease states including cancer, cardiovascular disease, Alzheimer’s disease, and diabetes. Cellular homeostasis requires mechanisms that tightly control the uptake, storage, and distribution of zinc. This is achieved through the coordinated actions of zinc transporters and metallothioneins. Evidence o...

  16. Investigations of particle transport mechanism during a blowdown test at the HDR

    International Nuclear Information System (INIS)

    Experiments have been performed in the HDR-Containment focussed on transport mechanism of solid particles after a loss of coolant accident. For this purpose at several locations marked particles of various size have been deposed before a LOCA-experiment and their distribution after the experiment investigated. The complex geometry of the HDR-Containment has many floors for deposition of solid particles, so no particles were drained to the containment sump. (orig.)

  17. Molecular mechanisms of cocaine reward: Combined dopamine and serotonin transporter knockouts eliminate cocaine place preference

    OpenAIRE

    Sora, Ichiro; Hall, F Scott; Andrews, Anne M; Itokawa, Masanari; Li, Xiao-Fei; Wei, Hong-Bing; Wichems, Christine; Lesch, Klaus-Peter; Murphy, Dennis L; Uhl, George R

    2001-01-01

    Cocaine blocks uptake by neuronal plasma membrane transporters for dopamine (DAT), serotonin (SERT), and norepinephrine (NET). Cocaine reward/reinforcement has been linked to actions at DAT or to blockade of SERT. However, knockouts of neither DAT, SERT, or NET reduce cocaine reward/reinforcement, leaving substantial uncertainty about cocaine's molecular mechanisms for reward. Conceivably, the molecular bases of cocaine reward might display sufficient redundancy th...

  18. A Novel Mechanism for Fire Detection in Subway Transportation Systems Based on Wireless Sensor Networks

    OpenAIRE

    Zhen-Jiang Zhang; Jun-Song Fu; Hua-Pei Chiang; Yueh-Min Huang

    2013-01-01

    Fire is a common and disastrous phenomenon in subway transportation systems because of closed environment and large passenger flow. Traditional methods detect and forecast fire incidents by fusing the data collected by wireless sensor networks and compare the fusion result with a threshold. However, this approach has a significant shortcoming. Fusion of data decreases the amount of useful information since the distribution of data is not considered. In this paper, a novel mechanism based on w...

  19. Mechanisms of vitamin K transport and metabolism in Swiss 3T3 mouse fibroblasts

    International Nuclear Information System (INIS)

    Transport of vitamin K into isolated fibroblasts was followed using 3H vitamin K1. The initial rate is saturable by 5 min. at 25?M vitamin K with a Km(app) of 10?M and V/sub max/ of 50 pmols/min/106 cells. Kinetics of uptake are biphasic with a second slower rate ensuing after 10 minutes. Insensitivity of the initial rate of uptake to FCCP or ouabain indicates an ATP-independent transport mechanism. Specificity of transport is shown by competition of uptake of 3H vitamin K by unlabelled vitamin and strong (>90%) inhibition of the initial rate by equimolar concentrations of the vitamin K analog, Chloro-K. In addition, following uptake, both vitamins K1 and K2 are metabolized to their respective epoxides. Vitamin K1 epoxide is also transported into fibroblasts and metabolized to the parent quinone in a Warfarin-sensitive reaction. Following alkaline hydrolysis of isolated intracellular protein, the vitamin K-dependent amino acid, gamma carboxyglutamic acid (gla) was detected. It is concluded that vitamin K is specifically transported into fibroblasts and metabolized via the classical pathway described in liver with the concomitant production of vitamin K-dependent proteins

  20. Analog performance of vertical nanowire TFETs as a function of temperature and transport mechanism

    Science.gov (United States)

    Martino, Marcio Dalla Valle; Neves, Felipe; Ghedini Der Agopian, Paula; Martino, João Antonio; Vandooren, Anne; Rooyackers, Rita; Simoen, Eddy; Thean, Aaron; Claeys, Cor

    2015-10-01

    The goal of this work is to study the analog performance of tunnel field effect transistors (TFETs) and its susceptibility to temperature variation and to different dominant transport mechanisms. The experimental input characteristic of nanowire TFETs with different source compositions (100% Si and Si1-xGex) has been presented, leading to the extraction of the Activation Energy for each bias condition. These first results have been connected to the prevailing transport mechanism for each configuration, namely band-to-band tunneling (BTBT) or trap assisted tunneling (TAT). Afterward, this work analyzes the analog behavior, with the intrinsic voltage gain calculated in terms of Early voltage, transistor efficiency, transconductance and output conductance. Comparing the results for devices with different source compositions, it is interesting to note how the analog trends vary depending on the source characteristics and the prevailing transport mechanisms. This behavior results in a different suitability analysis depending on the working temperature. In other words, devices with full-Silicon source and non-abrupt junction profile present the worst intrinsic voltage gain at room temperature, but the best results for high temperatures. This was possible since, among the 4 studied devices, this configuration was the only one with a positive intrinsic voltage gain dependence on the temperature variation.

  1. Buoyancy-driven flow in a peat moss layer as a mechanism for solute transport.

    Science.gov (United States)

    Rappoldt, Cornelis; Pieters, Gert-Jan J M; Adema, Erwin B; Baaijens, Gerrit J; Grootjans, Ab P; van Duijn, Cornelis J

    2003-12-01

    Transport of nutrients, CO2, methane, and oxygen plays an important ecological role at the surface of wetland ecosystems. A possibly important transport mechanism in a water-saturated peat moss layer (usually Sphagnum cuspidatum) is nocturnal buoyancy flow, the downward flow of relatively cold surface water, and the upward flow of warm water induced by nocturnal cooling. Mathematical stability analysis showed that buoyancy flow occurs in a cooling porous layer if the system's Rayleigh number (Ra) exceeds 25. For a temperature difference of 10 K between day and night, a typical Ra value for a peat moss layer is 80, which leads to quickly developing buoyancy cells. Numerical simulation demonstrated that fluid flow leads to a considerable mixing of water. Temperature measurements in a cylindrical peat sample of 50-cm height and 35-cm diameter were in agreement with the theoretical results. The nocturnal flow and the associated mixing of the water represent a mechanism for solute transport in water-saturated parts of peat land and in other types of terrestrializing vegetation. This mechanism may be particularly important in continental wetlands, where Ra values in summer are often much larger than the threshold for fluid flow. PMID:14657381

  2. Mechanical and transport characteristic exploration for coated conductors by hoop stress tests

    International Nuclear Information System (INIS)

    Mechanical and transport characteristics of coated conductors were explored by hoop stress tests at 4.2 K, 11 T. Deformation was investigated by strain gauges. Monolayer coils were simple, i.e. BJR-strain relations were observed. The first observation of radial deformation of a multilayer coil fabricated by YBCO coated conductor. The authors have explored mechanical and transport characteristics of coated conductors by hoop stress tests at 4.2 K, 11 T. Two monolayer coils, which were YBa2Cu3O7 (YBCO) and GdBa2Cu3O7 (GdBCO) coils, and a double-stacked single-pancake coil were tested. The mechanical and electrical behavior of monolayer coils were simple, thus they were well explained by simple forms. The stress and strain were easily evaluated by using BJR relation and strain gauge measurements. On the other hand, the behavior of the pancake coil was not simple. The analytically evaluated azimuthal strain was qualitatively consistent with measured strain. However, the measured radial strain was not explained by analytically because of non-monolithic deformation of the coil. The transport characteristic was influenced by the non-monolithic deformation.

  3. Delivery of marine larvae to shore requires multiple sequential transport mechanisms.

    Science.gov (United States)

    Pfaff, Maya C; Branch, George M; Fisher, Jennifer L; Hoffmann, Vera; Ellis, Allan G; Largier, John L

    2015-05-01

    Most sedentary marine animals disperse from their place of origin during their initial life stages as larvae. The delivery of planktonic larvae back to coastal adult habitats after weeks or months of offshore development is commonly thought to be stochastic, resulting in large recruitment fluctuations and making predictive understanding of population dynamics difficult. Time series of invertebrate settlement on intertidal shores have been used to infer how various oceanographic processes deliver planktonic larvae ashore. However, the possibility that successful settlement may involve a series of different transport mechanisms, which are sequentially utilized by late-stage larvae, has received little attention. To address this, we monitored both the delivery of mussel and barnacle larvae to inner-shelf moorings positioned 200-1400 m from the shore, and larval settlement in the intertidal adult habitat, at two contrasting sites: a headland forming an upwelling center and a downstream bay. Model selection was employed to determine the most likely scenario(s) of larval onshore transport from four a priori transport mechanisms individually and in combination: (1) upwelling or relaxation/downwelling, (2) tidal motions, (3) diurnal sea breezes, and (4) surface waves. Mussel larvae were delivered to the inner shelf during upwelling in the bay, but during downwelling at the headland, and were further transported to the shore by surface waves at both locales. In contrast, the delivery of barnacle larvae to the inner shelf occurred during relaxation/downwelling events at both sites, and intertidal settlement coincided with spring tides, suggesting a role for internal tides in their onshore transport. Thus, sequential mechanisms appear to be utilized by larvae to get to the shore, involving interactions of regional-scale upwelling/downwelling processes and local-scale tidal and surface-wave processes, which differ among taxa and among sites with different topography. A bottleneck for larval delivery across the surf zone may be a result of out-of-phase steps in sequential transport mechanisms leaving larvae lost "in transit." PMID:26236852

  4. Variability of the transport of anthropogenic CO2 at the Greenland–Portugal OVIDE section: controlling mechanisms

    Directory of Open Access Journals (Sweden)

    P. Zunino

    2013-10-01

    Full Text Available The interannual to decadal variability of the transport of anthropogenic carbon dioxide (Cant across the Subpolar North Atlantic (SPNA is investigated, using data of the OVIDE high resolution transoceanic section, from Greenland to Portugal, occupied six times from 1997 to 2010. The transport of Cant across this section, TCant hereafter, is northward, with a mean value of 254 ± 29 kmol s–1 over the 1997–2010 period. The TCant presents a high interannual variability, masking any trend different from 0 for this period. In order to understand the mechanisms controlling the variability of the TCant across the SPNA, we propose a new method that quantifies the transport of Cant caused by the diapycnal and isopycnal circulation. The diapycnal component yields a large northward transport of Cant (400 ± 29 kmol s–1 which is partially compensated by a southward transport of Cant caused by the isopycnal component (–171 ± 11 kmol s–1, mainly localized in the Irminger Sea. Most importantly, the diapycnal component is found to be the main driver of the variability of the TCant across the SPNA. Both the Meridional Overturning Circulation (MOC and the Cant increase in the water column have an important effect on the variability of the diapycnal component and of the TCant itself. Based on this analysis, we propose a simplified estimator for the variability of the TCant based on the intensity of the MOC and on the difference of Cant between the upper and lower limb of the MOC (?Cant. This estimator shows a good consistency with the diapycnal component of the TCant, and help to disentangle the effect of the variability of both the circulation and the Cant increase on the TCant variability. We find that ?Cant keeps increasing over the past decade, and it is very likely that the continuous Cant increase in the water masses will cause an increase in the TCant across the SPNA at long time scale. Nevertheless, at the time scale analyzed here (1997–2010, the MOC is controlling the TCant variability, blurring the expected TCant increase. Extrapolating the observed ?Cant increase rate and considering the predicted slow-down of 25% of the MOC, the TCant across the SPNA is expected to increase by 430 kmol s–1 during the 21st century. Consequently, an increase in the storage rate of Cant in the SPNA could be envisaged.

  5. Fibre bundle formulation of nonrelativistic quantum mechanics: I. Introduction. The evolution transport

    Energy Technology Data Exchange (ETDEWEB)

    Iliev, Bozhidar Z. [Department of Mathematical Modeling, Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Sofia (Bulgaria)]. E-mail: bozho@inrne.bas.bg

    2001-06-15

    We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one and is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it the Hilbert space of a quantum system (from conventional quantum mechanics) is replaced with an appropriate Hilbert bundle of states and a pure state of the system is described by a lifting of paths or sections along paths in this bundle. The evolution of a pure state is determined through the bundle (analogue of the) Schroedinger equation. Now the dynamical variables and density operators are described via liftings of paths or morphisms along paths in suitable bundles. The mentioned quantities are connected by a number of relations derived in this paper. The present, first, part of this investigation is devoted to the introduction of basic concepts on which the fibre bundle approach to quantum mechanics rests. We show that the evolution of pure quantum mechanical states can be described as a suitable linear transport along paths, called evolution transport, of the state liftings in the Hilbert bundle of states of a considered quantum system. (author)

  6. Vibrações mecânicas: um agente estressor no transporte de pintos / Mechanical vibrations: a stressor in the transport of chicken

    Scientific Electronic Library Online (English)

    Ana C., Donofre; Iran J. O. da, Silva; Aérica C., Nazareno.

    2014-04-01

    Full Text Available As vibrações mecânicas, presentes no transporte de cargas vivas, podem comprometer a estabilidade fisiológica e o futuro desempenho dos animais de produção. O objetivo desta pesquisa foi avaliar, por meio de simulações, o efeito de dois níveis de aceleração (9,64 e 15,19 m s-2) sobre o estresse e o [...] desempenho de pintos de corte de um dia. As vibrações foram simuladas utilizando-se um agitador mecânico e as intensidades de vibração estudadas por valores de aceleração geral. O período de simulação durou duas horas para cada tratamento e as aves tiveram seus parâmetros (diferença de peso; frequência respiratória e desempenho na primeira semana) comparados a grupos-controle (sem vibração). Realizou-se um delineamento inteiramente casualizado em que os resultados obtidos indicaram que esses níveis não influenciaram significativamente (p Abstract in english Mechanical vibrations present in transporting live loads can impair physiologic stability and the future performance of livestock. The aim of this study was to evaluate, using simulations, the effect of two levels of vibration (9.64 and 15.19 m s-2) in stress responses and performance of day-old chi [...] cken. The vibrations were simulated by means of a shaking machine and studied by general acceleration values. The simulation period lasted two hours for each treatment and the birds had their parameters (difference in weight, respiratory rate, and performance in the first week) compared to control groups (without vibration). The experiment was conducted in a randomized design and the results showed that these levels did not differ significantly (p

  7. Current transport mechanism and effect of hydrogen plasma treatment on Al-GaSb Schottky diode

    International Nuclear Information System (INIS)

    The aluminium Schottky contact to n-GaSb was fabricated using standard photolithography and lift-off techniques. The ohmic contact of low resistance was first formed by evaporating Ge-Au-Ni-Au (88% Au - 12% Ge by weight) on GaSb surface then followed by heat treatments. The I-V-T measurements were performed with a cryogenic system. The current transport mechanism of this non-ideal Al-GaSb Schottky diode was modelled for a wide temperature range. The conduction in both ? and L valleys was included in the calculation of the thermionic emission current component. The contribution of thermionic emission, recombination and other current transport mechanisms were evaluated. The I-V characteristic at 300 K had an ideality factor of about 2 since the recombination dominates the current transport. However, at higher temperatures the thermionic emission becomes important and the ideality factor decreases below 2. We also examined the electrical properties of this diode after exposure on hydrogen plasma

  8. Air pollutants and plant cuticles: mechanisms of gas and water transport, and effects on water permeability

    International Nuclear Information System (INIS)

    A short overview of studies carried out by K.J. Lendzian and his group on transport rates of pure pollutant gases across isolated cuticles will be given. They show that the boiling point of a gas is a good predictor of cuticular permeability. Apparently good prediction quality, however, contrasts with a considerable gap between uptake rates determined in stomata-free systems, and rates of dry deposition to whole leaves observed under conditions where stomata should be closed to the maximum extent. Apart from other possible reasons for this difference, examination of cuticular sorption and diffusion characteristics indicates two major problems that may account for inconsistencies to some extent: (1) transport rates of gases in cuticles may be concentration-dependent and (2) interactions in gas mixtures with respect to cuticular transport are possible. Potential mechanisms of transport across cuticles and ways of interaction between gases (including water vapour) will be discussed. There has long been the notion that air pollutants may affect the water barrier quality of plant cuticles. This hypothesis has been tested in a recent study of effects of a wide range of air pollutants and elevated UV-B radiation on adaxial in situ-cuticular water permeability of various broadleaf tree species. No effects were found unless the leaves showed visible signs of stress due to treatment or chamber effects. (orig.)

  9. The mechanical design for the second axis beam transport line for the DARHT facility

    International Nuclear Information System (INIS)

    This paper describes the mechanical design of the downstream beam transport line for the second axis of the Dual Axis Radiographic Hydrodynamic Test (DARHT II) facility. The DARHT II project is a collaboration between LANL, LBNL, and LLNL. DARHT II is a 20-MeV, 2000-Amperes, 2-ampersand micro;sec pulse length linear induction accelerator designed to generate short bursts of x-rays for the purpose of radiographing dense objects. The downstream beam transport line is an 18-meter long region extending from the end of the accelerator to the bremsstrahlung target. Within this proposed transport line there are 17 conventional solenoid, quadrupole and dipole magnets; as well as several specialty magnets, which transport and focus the beam to the target and beam dumps. There is a high power beam dump, which is designed to absorb the 80-kJ of beam energy during accelerator start-up and operation. The beamline vacuum chamber has an 8-cm diameter aperture and operates at an average pressure of 10-7 Torr

  10. How do we convert the transport sector to renewable energy and improve the sector's interplay with the energy system? Main findings and recommendations from Workshop on Transport - renewable energy in the transport sector and planning

    Energy Technology Data Exchange (ETDEWEB)

    Soenderberg Petersen, L.; Larsen, Hans (eds.)

    2009-07-15

    As part of the DTU Climate Change Technologies Programme, DTU arranged a series of workshops and conferences on climate change technology focusing on assessment of and adaptation to climate changes as well as on mitigation of greenhouse gasses (GHG). Each workshop targeted a specific technology problem area. The Workshop on Transport took place at DTU 17 - 18 March 2009. The workshop developed and discussed recommendations for future climate change technologies. This report presents summary and recommendations from the workshop. (au)

  11. Growth Dynamics and Gas Transport Mechanism of Nanobubbles in Graphene Liquid Cells

    CERN Document Server

    Shin, Dongha; Kim, Yong-Jin; Kim, Sang Jin; Kang, Jin Hyoun; Lee, Bora; Cho, Sung-Pyo; Hong, Byung Hee; Novoselov, Konstantin S

    2014-01-01

    Formation, evolution, and vanishing of bubbles are common phenomena in our nature, which can be easily observed in boiling or falling waters, carbonated drinks, gas-forming electrochemical reactions, etc. However, the morphology and the growth dynamics of the bubbles at nanoscale have not been fully investigated owing to the lack of proper imaging tools that can visualize nanoscale objects in liquid phase. Here we demonstrate, for the first time, that the nanobubbles in water encapsulated by graphene membrane can be visualized by in situ ultrahigh vacuum transmission electron microscopy (UHV-TEM), showing the critical radius of nanobubbles determining its unusual long-term stability as well as two distinct growth mechanisms of merging nanobubbles (Ostwald ripening and coalescing) depending on their relative sizes. Interestingly, the gas transport through ultrathin water membranes at nanobubble interface is free from dissolution, which is clearly different from conventional gas transport that includes condensa...

  12. Designing and testing regenerative pulp treatment strategies: modeling the transdentinal transport mechanisms

    Science.gov (United States)

    Passos, Agathoklis D.; Mouza, Aikaterini A.; Paras, Spiros V.; Gogos, Christos; Tziafas, Dimitrios

    2015-01-01

    The need for simulation models to thoroughly test the inflammatory effects of dental materials and dentinogenic effects of specific signaling molecules has been well recognized in current dental research. The development of a model that simulates the transdentinal flow and the mass transfer mechanisms is of prime importance in terms of achieving the objectives of developing more effective treatment modalities in restorative dentistry. The present protocol study is part of an ongoing investigation on the development of a methodology that can calculate the transport rate of selected molecules inside a typical dentinal tubule. The transport rate of biological molecules has been investigated using a validated CFD code. In that framework we propose a simple algorithm that, given the type of molecules of the therapeutic agent and the maximum acceptable time for the drug concentration to attain a required value at the pulpal side of the tubules, can estimate the initial concentration to be imposed. PMID:26441676

  13. spatial variability of solute transport mechanisms based on time domain reflectometry and generalized transfer function model

    International Nuclear Information System (INIS)

    the flexible generalized transfer function model (GTF ) and TDR based time normalized resident concentrations were combined in order to characterize solute transport mechanism both at local and field scale. a leaching experiment was carried out in a plot under greenhouse, where TDR probes were installed at the three different depths at 37 sites along a 40 m transect. the field plot was brought to steady-state water content; a pulse application of 3.87 mm of KCl solution was applied . measurements of water content (?) and impedance (Z) were simultaneously taken to follow the kcl solution propagation through the soil profile. time series of relative resident concentrations for each site where effectively interpreted in terms of GTF model. the field scale behavior was described by calculating a local average and an integral average, by averaging local scale parameters and local scale original measurements, respectively. the two different averaging schemes resulted in two significantly different field scale solute transport behaviors

  14. Transport mechanisms and rates for the long-lived Chernobyl deposits

    International Nuclear Information System (INIS)

    A programme of work has been carried out to determine the various transport rates and mechanisms of Chernobyl radionuclides moving from catchment areas to rivers, reservoirs, lakes and sediments. In so doing the potential for Cs to be retained by and remobilised from sediments was assessed, along with the amount of deposited radioactivity which was in soluble form and hence was available in drinking water. Only a limited Ru-103 data set was obtained before it had decayed away below detection limits. However, results from this period showed that Ru mirrored Cs in its behaviour as it was measurable in the sediments at the same time after the deposition and it was trapped in the bottom waters of the lake. A substantial Cs data set was obtained for two lakes, Windermere and Esthwaite Water and it could be interpreted, with the aid of mathematical models developed during this study, to indicate the major processes and pathways operating in the transport of Cs through lake catchments. During the initial period after the deposition a maximum of 27% of the Cs in the water column was found in the particulate form and rapidly (months) reduced to 10-15% of the total. Total water column concentrations had reduced to half their initial measured values within 15 days in Esthwaite Water and 70 days in Windermere. Cs-134 was observed in surface sediments within 7 days in Esthwaite Water (15.5 m deep) and 30 days in Windermere (65 m deep) which, from a knowledge of mixing regimes of the lakes can be interpreted in terms of similar settlement velocities of 1-2 m per day. A small proportion of Chernobyl material was rapidly moved into the sediment as shown by small concentrations of Cs-134 being found at a depth of 8 cm after one year. This indicates that a non-diffusional transport mechanism, such as bioturbation, may be important for the transport of particulate caesium in sediments. (author)

  15. Investigation of MCHM transport mechanisms and fate: implications for coal beneficiation.

    Science.gov (United States)

    He, Y Thomas; Noble, Aaron; Ziemkiewicz, Paul

    2015-05-01

    4-Methyl cyclohexane methanol (MCHM) is a flotation reagent often used in fine coal beneficiation and notably involved in the January 9, 2014 Elk River chemical spill in Charleston, WV. This study investigates the mechanisms controlling the transport and fate of MCHM in coal beneficiation plants and surrounding environments. Processes such as volatilization, sorption, and leaching were evaluated through laboratory batch and column experiments. The results indicate volatilization and sorption are important mechanisms which influence the removal of MCHM from water, with sorption being the most significant removal mechanism over short time scales (leaching experiments show both coal and tailings have high affinity for MCHM, and this reagent does not desorb readily. Overall, the results from these experiments indicate that MCHM is either volatilized or sorbed during coal beneficiation, and it is not likely to transport out of coal beneficiation plant. Thus, use of MCHM in coal beneficiation plant is not likely to pose threat to either surface or groundwater under normal operating conditions. PMID:25698101

  16. Fibre bundle formulation of nonrelativistic quantum mechanics; 1, Introduction The evolution transport

    CERN Document Server

    Iliev, Bozhidar Z

    1998-01-01

    We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one but it is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it a pure state of some quantum system is described by a state section (along paths) of a (Hilbert) fibre bundle. It's evolution is determined through the bundle (analogue of the) Schrödinger equation. Now the dynamical variables and the density operator are described via bundle morphisms (along paths). The mentioned quantities are connected by a number of relations derived in this work. The present first part of this investigation is devoted to the introduction of basic concepts on which the fibre bundle approach to quantum mechanics rests. We show that the evolution of pure quantum-mechanical states can be described as a suitable linear transport along paths, called evolution transport, of the state sections in the Hilbert f...

  17. MAINE AQUIFERS

    Science.gov (United States)

    AQFRS24 contains polygons of significant aquifers in Maine (glacial deposits that are a significant ground water resource) mapped at a scale 1:24,000. This statewide coverage was derived from aquifer boundaries delineated and digitized by the Maine Geological Survey from data com...

  18. Mechanical, electronic, and transport properties of functionalized graphene monolayers from ab initio studies

    International Nuclear Information System (INIS)

    We present exemplary results of extensive studies of mechanical, electronic and transport properties of covalent functionalization of graphene monolayers (GML). We report new results of ab initio studies for covalent functionalization of GML with ?NH2 groups up to 12.5 % concentration. Our studies are performed in the framework of the density functional theory (DFT) and non-equilibrium Green’s function (NEGF). We discuss the stability (adsorption energy), elastic moduli, electronic structure, band gaps, and effective electron masses as a function of the density of the adsorbed molecules. We also show the conductance and current – voltage I(V) characteristics for these systems

  19. Recent fracture mechanics results from NASA research related to the aging commercial transport fleet

    Science.gov (United States)

    Harris, Charles E.

    1991-01-01

    NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development to predict the fatigue crack growth in complex built-up shell structures. Innovative nondestructive examination technologies are also under development to provide large area inspection capability to detect corrosion, disbonds, and fatigue cracks. Recent fracture mechanics results applicable to predicting the growth of cracks initiating at the rivets of fuselage splice joints are reviewed.

  20. Fracture mechanics research at NASA related to the aging commercial transport fleet

    Science.gov (United States)

    Newman, James C., Jr.; Harris, Charles E.

    1992-01-01

    NASA is conducting the Airframe Structural Integrity Program in support of the aging commercial transport fleet. This interdisciplinary program is being worked in cooperation with the U.S. airframe manufacturers, airline operators, and the FAA. Advanced analysis methods are under development and an extensive testing program is under way to study fatigue crack growth and fracture in complex built-up shell structures. Innovative nondestructive examination technologies are also being developed to provide large area inspection capability to detect corrosion, disbonds, and cracks. Recent fracture mechanics results applicable to predicting the growth of cracks under monotonic and cyclic loading at rivets in fuselage lap-splice joints are reviewed.

  1. Dual mechanism for stimulation of glutamate transport by potassium ions in Streptococcus mutans.

    OpenAIRE

    Sato, Y.; Noji, S.; R Suzuki; Taniguchi, S

    1989-01-01

    An ATP-driven primary transport system operative for L-glutamate or L-aspartate in Streptococcus mutans is, through the entire pH range from 5.5 to 8.5, specifically stimulated by extracellular potassium ions. The stimulation by potassium ions observed in the low pH range between 5.5 and 7 has been interpreted to be due to potassium ion-dependent regulation of the intracellular pH (the first mechanism). In the high pH range from 7 to 8.5, on the other hand, the present study demonstrates that...

  2. Electron transport mechanism of thermally oxidized ZnO gas sensors

    International Nuclear Information System (INIS)

    ZnO gas sensor was fabricated by thermal oxidation of metallic Zn at different time periods. The sensors were characterized by I-V measurement with DC voltage, ranging from -2 to 2 volts, in both normal air and H2 gas with concentration from 40 to 160 ppm. The transport mechanism of the carriers was found to be due to thermionic process through both the grain boundaries and the metal-semiconductor junctions. Resistance of the ZnO sensing film is independent of applied voltage in the range 0.5 Va<2 V; however, it is dependent on gas concentration, which makes it useful for gas sensing application.

  3. Functional Anatomy and Biophysical Mechanisms of Fluid Transport in Vascular Plants : Implications for Structural Optimisation in Fossil and Extant Plants

    OpenAIRE

    Konrad, Wilfried.

    2007-01-01

    In plants, water and carbon dioxide molecules are transported either in liquid or gaseous state: From the roots to the leaves water flows as a liquid. Between leaves and atmosphere water and carbon dioxide are exchanged as gases. Accordingly, the driving forces and mechanisms of transport are also different. The driving force of the water transport between roots and leaves is transpiration which takes place in the gas-filled intercellulars of the leaves. Attached to this tissue is a netw...

  4. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    Directory of Open Access Journals (Sweden)

    Ince, C.

    2015-06-01

    Full Text Available The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs on water transport kinetics and mechanical properties of hydrated lime (CL90 and Portland cement (PC mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often are the main barriers to the use of hydrated lime in construction practice. The results show that transfer sorptivity and time to dewater freshly-mixed hydrated lime mortars can be modified when binder is partially replaced with SCMs. Compressive strength of CL90 mortars is increased systematically with the increased replacement levels of SCMs and the results are supported with the microstructural images. The ability to modify the water transport kinetics and mechanical properties allows compatibility between the mortar and the substrate unit in masonry construction.El objetivo de este artículo es investigar el papel de los materiales cementantes suplementarios (SCMs en la cinética de transporte del agua y en las propiedades mecánicas de los morteros de cal hidratada (CL90 y cemento Portland. Las propiedades de la cal hidratada son significativamente diferentes a las del cemento y por lo tanto el control de las propiedades de los morteros frescos y endurecidos es fundamental en la optimización mortero/substrato en albañilería. Los parámetros estudiados en este trabajo son a menudo las principales barreras para el uso de la cal hidratada en la práctica de la construcción. Los resultados indican que la absortividad y el tiempo necesario para deshidratar morteros de cal hidratada recién mezclados pueden ser controlados cuando el conglomerante es parcialmente remplazado por SCMs. La resistencia a compresión de los morteros CL90 aumenta sistemáticamente con el nivel de sustitución de SCM. Las imágenes microestructurales realizadas, confirman estos resultados. La posibilidad de manipular la cinética de transporte de agua y las propiedades mecánicas permite la compatibilidad entre el mortero y la unidad de sustrato en albañilería.

  5. Transport mechanisms of uranium released to the coolant from fuel defects

    International Nuclear Information System (INIS)

    Fuel performance at domestic CANDU-600s, Point Lepreau and Gentilly, has been very good, with only a small number of fuel defects releasing uranium to the coolant. The in-core monitoring on these early fuel defects using the delayed neutron system, provides some insight into uranium transport mechanisms and how they influence signal trends. Better understanding of these mechanisms, will assist the station operator in responding to trend changes and will ultimately provide guidance in assigning removal priorities should several fuel defects occur simultaneously. The average delayed neutron signal of all channels is the key parameter for monitoring fuel performance in-core, and should be regarded as an early warning indicator of fuel performance problems

  6. Photoluminescence and carrier transport mechanisms of silicon-rich silicon nitride light emitting device

    International Nuclear Information System (INIS)

    Highlights: • Amorphous silicon quantum dots (a-Si QDs) embedded in silicon nitride were fabricated using plasma-enhanced chemical vapor deposition (PECVD). • Two different excitation sources were used to investigate the PL mechanisms. • Light emitting diode (LED) with ITO/SiNx/p-Si/Al structure was fabricated and the carrier transport mechanisms were investigated. - Abstract: Silicon-rich silicon nitride (SRSN) films were prepared on p-type silicon substrates using plasma-enhanced chemical vapor deposition (PECVD). Small size (∼3 nm) amorphous silicon quantum dots (a-Si QDs) were obtained after 1100 °C annealing. Two different excitation sources, namely 325 nm and 532 nm lasers, were introduced to investigate the photoluminescence (PL) properties. The PL bands pumped by 325 nm laser at ∼2.90 eV and ∼1.80 eV were contributed to the radiative centers from N dangling bonds (DBs), while the dominant PL bands at 2.10 eV were ascribed to the instinct PL centers in the nitride matrix. However, PL emissions from band tail luminescence and quantum confined effect (QCE) in a-Si QDs were found under the excitation of 532 nm laser. Light emitting diode (LED) with ITO/SiNx/p-Si/Al structure was fabricated. Intensely red light emission was observed by naked eyes at room temperature under forward 20 V. Three different carrier transport mechanisms, namely Poole–Frenkel (P–F) tunneling, Fowler–Nordheim (F–N) tunneling and space charge limited current (SCLC), were found to fit different electric field regions. These results help to understand the PL mechanisms and to optimize the fabrication of a-Si QD LED

  7. Perturbation of the Electron Transport Mechanism by Proton Intercalation in Nanoporous TiO2 Films

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, A. F.; Zhu, K.; Erslev, P. T.; Kim, J. Y.; Neale, N. R.; Frank, A. J.

    2012-04-11

    This study addresses a long-standing controversy about the electron-transport mechanism in porous metal oxide semiconductor films that are commonly used in dye-sensitized solar cells and related systems. We investigated, by temperature-dependent time-of-flight measurements, the influence of proton intercalation on the electron-transport properties of nanoporous TiO{sub 2} films exposed to an ethanol electrolyte containing different percentages of water (0-10%). These measurements revealed that increasing the water content in the electrolyte led to increased proton intercalation into the TiO{sub 2} films, slower transport, and a dramatic change in the dependence of the thermal activation energy (E{sub a}) of the electron diffusion coefficient on the photogenerated electron density in the films. Random walk simulations based on a microscopic model incorporating exponential conduction band tail (CBT) trap states combined with a proton-induced shallow trap level with a long residence time accounted for the observed effects of proton intercalation on E{sub a}. Application of this model to the experimental results explains the conditions under which E{sub a} dependence on the photoelectron density is consistent with multiple trapping in exponential CBT states and under which it appears at variance with this model.

  8. Reaction mechanisms in the radiolysis of peptides, polypeptides, and proteins. I. Reactions of the peptide main-chain in model systems

    International Nuclear Information System (INIS)

    The object of this review is to bring together and to correlate our present knowledge of products and mechanisms in the radiolysis of peptides, polypeptides and proteins in both aqueous and solid-state systems. Results obtained with various experimental techniques such as product analysis, competition kinetics, ESR spectroscopy and pulse radiolysis are included. Here in part I the emphasis is on the various radiation-induced reactions of the peptide main-chain in model systems. In part II the emphasis is on the radiation chemistry of side-chain loci of the aliphatic, sulfur-containing, aromatic and other unsaturated amino acid residues in similar systems. And, in part III this information on model systems is used in interpreting the mechanisms of chemical change in the radiolysis of proteins in aqueous solution and in the solid state. 60 references

  9. The relative importance of decomposition and transport mechanisms in accounting for soil organic carbon profiles

    Directory of Open Access Journals (Sweden)

    B. Guenet

    2013-04-01

    Full Text Available Soil is the major terrestrial reservoir of carbon and a substantial part of this carbon is stored in deep layers, typically deeper than 50 cm below the surface. Several studies underlined the quantitative importance of this deep soil organic carbon (SOC pool and models are needed to better understand this stock and its evolution under climate and land-uses changes. In this study, we tested and compared three simple theoretical models of vertical transport for SOC against SOC profiles measurements from a long-term bare fallow experiment carried out by the Central-Chernozem State Natural Biosphere Reserve in the Kursk Region of Russia. The transport schemes tested are diffusion, advection and both diffusion and advection. They are coupled to three different formulations of soil carbon decomposition kinetics. The first formulation is a first order kinetics widely used in global SOC decomposition models; the second one, so-called "priming" model, links SOC decomposition rate to the amount of fresh organic matter, representing the substrate interactions. The last one is also a first order kinetics, but SOC is split into two pools. Field data are from a set of three bare fallow plots where soil received no input during the past 20, 26 and 58 yr, respectively. Parameters of the models were optimised using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter (i.e., the priming model. In comparison to the first-order kinetic model, the priming model reduces the overestimation in the deep layers. We also observed that the transport scheme that improved the fit with the data depended on the soil carbon mineralisation formulation chosen. When soil carbon decomposition was modelled to depend on the fresh organic matter amount, the transport mechanism which improved best the fit to the SOC profile data was the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the lesser the need for diffusion is, suggesting that stabilised carbon may not be transported within the profile by the same mechanisms than more labile carbon.

  10. JOYO MK-III heat transport system renovation operation. Primary heat transport mechanical system (IHXs (intermediate heat exchangers))

    International Nuclear Information System (INIS)

    The MK-III project to improve the irradiation capability of the experimental fast reactor JOYO have been carried out since 1987. The increase of fast neutron flux and the enlargement of irradiation field increase the reactor thermal power from 100 MWt to 140 MWt. To accommodate the increased thermal power, the IHXs and the IHX connecting piping were replaced. The IHXs were replaced with securing cooling system boundary in high dose rate surroundings and very limited operation space of the radiation controlled area in the containment vessel. Primary sodium contains radioactive 22Na, 24Na and radioactive CPs such as 60Co and 54Mn, and this sodium adhered to the inner surface of IHXs and pipe. Therefore, the renovation procedure and method were carefully examined based on the JOYO operation and maintenance experiences and research and development results on the sodium handling technique. The major results obtained in the primary heat transport mechanical system (IHXs) renovation operation were shown as follows; (1) The mock up tests to optimize the operating methods, to check the operability and for workers training were useful for reduction of radiation exposure by shortening the operation time in high dose rate surrounding. (2) The effectiveness of seal bag for prevention of impurity ingress to the sodium system and contamination during sodium boundary opening (cutting pipes, sodium removal and welding pipes) was confirmed. (3) The pipes were cut without foreign object such as cutting piece and tool ingress by careful examination of cutting procedure and methods such as bite, roller cutter. (4) The temporary closing equipment such as seal cap and seal plug were effectively worked to seal the cooling system boundary between cutting and welding pipes. (5) Sodium adhered on the inner surfaces of pipe was effectively and safely removed by a mechanical scraper or drill and a cloth moistened by a mixture of alcohol and water. (6) Control of low gas pressure difference between cover gas pressure and seal bag pressure and monitoring of pipe surface temperature is useful to avoid welding flaw during pipe welding in the seal bag. Replacement operations started October 30, 2000 and finished September 21, 2001 without major troubles. The above results obtained this operation will be applied not only the operation and maintenance activity of JOYO but also the renovation of FBR and design for future sodium cooled FBR. (author)

  11. Constraints on Transport and Emplacement Mechanisms of Labile Fractions in Lunar Cold Traps

    Science.gov (United States)

    Rickman, D.; Gertsch, L.

    2014-01-01

    Sustaining the scientific exploration of the Solar System will require a significant proportion of the necessary fuels and propellants, as well as other bulk commodities, to be produced from local raw materials [1]. The viability of mineral production depends on the ability to locate and characterize mineable deposits of the necessary feedstocks. This requires, among other things, a workable understanding of the mechanisms by which such deposits form, which is the subject of Economic Geology. Multiple deposition scenarios are possible for labile materials on the Moon. This paper suggests labile fractions moved diffusely through space; deposits may grow richer with depth until low porosity rock; lateral transport is likely to have occurred with the regolith, at least for short distances; crystalline ice may not exist; the constituent phases could be extremely complex. At present we can constrain the sources only mildly; once on the Moon, the transport mechanisms inherently mix and therefore obscure the origins. However, the importance of expanding our understanding of ore-forming processes on the Moon behooves us to make the attempt. Thus begins a time of new inquiry for Economic Geology.

  12. Fracture mechanics based design for radioactive material transport packagings -- Historical review

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J.A.; Salzbrenner, D.; Sorenson, K.; McConnell, P.

    1998-04-01

    The use of a fracture mechanics based design for the radioactive material transport (RAM) packagings has been the subject of extensive research for more than a decade. Sandia National Laboratories (SNL) has played an important role in the research and development of the application of this technology. Ductile iron has been internationally accepted as an exemplary material for the demonstration of a fracture mechanics based method of RAM packaging design and therefore is the subject of a large portion of the research discussed in this report. SNL`s extensive research and development program, funded primarily by the U. S. Department of Energy`s Office of Transportation, Energy Management and Analytical Services (EM-76) and in an auxiliary capacity, the office of Civilian Radioactive Waste Management, is summarized in this document along with a summary of the research conducted at other institutions throughout the world. In addition to the research and development work, code and standards development and regulatory positions are also discussed.

  13. Current transport mechanisms in plasma-enhanced atomic layer deposited AlN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Altuntas, Halit, E-mail: altunhalit@gmail.com, E-mail: biyikli@unam.bilkent.edu.tr [Faculty of Science, Department of Physics, Cankiri Karatekin University, Cankiri 18100 (Turkey); Ozgit-Akgun, Cagla; Donmez, Inci; Biyikli, Necmi, E-mail: altunhalit@gmail.com, E-mail: biyikli@unam.bilkent.edu.tr [National Nanotechnology Research Center (UNAM), Bilkent University, Bilkent, Ankara 06800 (Turkey); Institute of Materials Science and Nanotechnology, Bilkent University, Bilkent, Ankara 06800 (Turkey)

    2015-04-21

    Here, we report on the current transport mechanisms in AlN thin films deposited at a low temperature (i.e., 200?°C) on p-type Si substrates by plasma-enhanced atomic layer deposition. Structural characterization of the deposited AlN was carried out using grazing-incidence X-ray diffraction, revealing polycrystalline films with a wurtzite (hexagonal) structure. Al/AlN/ p-Si metal-insulator-semiconductor (MIS) capacitor structures were fabricated and investigated under negative bias by performing current-voltage measurements. As a function of the applied electric field, different types of current transport mechanisms were observed; i.e., ohmic conduction (15.2–21.5 MV/m), Schottky emission (23.6–39.5 MV/m), Frenkel-Poole emission (63.8–211.8 MV/m), trap-assisted tunneling (226–280 MV/m), and Fowler-Nordheim tunneling (290–447 MV/m). Electrical properties of the insulating AlN layer and the fabricated Al/AlN/p-Si MIS capacitor structure such as dielectric constant, flat-band voltage, effective charge density, and threshold voltage were also determined from the capacitance-voltage measurements.

  14. Carrier transport mechanism of Mo contact to amorphous hafnium indium zinc oxides

    International Nuclear Information System (INIS)

    We investigated the carrier transport mechanism of Mo contacts to amorphous hafnium indium zinc oxides (a-HIZO). As-deposited Mo exhibited nearly ohmic behavior, while the thermal annealing improved the ohmic contact significantly, i.e. the specific contact resistance was 1.9 x 10-1, 4.3 x 10-3, and 1.5 x 10-3 ? cm2 for the as-deposited, 200 and 400 C-annealed condition, respectively. The ohmic mechanism of as-deposited Mo contact might be attributed to the barrier inhomogeneity and/or to the trap-assisted tunneling. For the annealed contact, the carrier transport could be explained by thermionic field emission model, yielding a tunneling parameter of 57 meV and a Schottky barrier height of 0.82 eV, i.e. the ohmic behavior is due to the tunneling through thin barrier. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Carrier transport mechanism of Mo contact to amorphous hafnium indium zinc oxides

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seongjun; Gil, Youngun; Kim, Hyunsoo [School of Semiconductor and Chemical Engineering, Semiconductor Physics Research Center, Chonbuk National University, 561-756, Jeonju (Korea, Republic of); Kim, Kyoung-Kook [Department of Nano-Optical Engineering, Korea Polytechnic University, 429-793, Siheung (Korea, Republic of); Ahn, Kwang-Soon [School of Chemical Engineering, Yeungnam University, Gyeongsan, 712-749, Gyeongbuk (Korea, Republic of)

    2014-08-15

    We investigated the carrier transport mechanism of Mo contacts to amorphous hafnium indium zinc oxides (a-HIZO). As-deposited Mo exhibited nearly ohmic behavior, while the thermal annealing improved the ohmic contact significantly, i.e. the specific contact resistance was 1.9 x 10{sup -1}, 4.3 x 10{sup -3}, and 1.5 x 10{sup -3} ? cm{sup 2} for the as-deposited, 200 and 400 C-annealed condition, respectively. The ohmic mechanism of as-deposited Mo contact might be attributed to the barrier inhomogeneity and/or to the trap-assisted tunneling. For the annealed contact, the carrier transport could be explained by thermionic field emission model, yielding a tunneling parameter of 57 meV and a Schottky barrier height of 0.82 eV, i.e. the ohmic behavior is due to the tunneling through thin barrier. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes

    Science.gov (United States)

    Shi, Yanuo; Bork, Alexander Hansen; Schweiger, Sebastian; Rupp, Jennifer Lilia Marguerite

    2015-07-01

    Understanding `electro-chemo-mechanics’ in oxygen ion conducting membranes represents a foundational step towards new energy devices such as micro fuel cells and oxygen or fuel separation membranes. For ionic transport in macro crystalline electrolytes, doping is conventionally used to affect oxygen ionic association/migration energies. Recently, tuning ionic transport in films through lattice strain conveyed by substrates or heterostructures has generated much interest. However, reliable manipulation of strain states to twist the ionic conduction in real micro energy devices remains intractable. Here, we demonstrate that the oxygen ionic conductivity clearly correlates with the compressive strain energy acting on the near order of the electrolyte lattices by comparing thin-film ceria-based membrane devices against substrate-supported flat structures. It is possible to capitalize on this phenomenon with a smart choice of strain patterns achieved through microelectrode design. We highlight the importance of electro-chemo-mechanics in the electrolyte material for the next generation of solid-state energy conversion microdevices.

  17. Mechanisms of zinc uptake in gills of freshwater rainbow trout: interplay with calcium transport.

    Science.gov (United States)

    Hogstrand, C; Verbost, P M; Bonga, S E; Wood, C M

    1996-05-01

    The uptake mechanism of Zn2+ through the gill epithelium of freshwater rainbow trout was investigated both in intact animals and in isolated basolateral membranes. Involvement of the apical Ca2+ uptake sites in Zn2+ uptake was examined in vivo by pharmacological manipulation of the apical Ca2+ permeability. The apical entries of Ca2+ and Zn2+, but not Na2+ and Cl-, were inhibited by addition of La to the water. Addition of 1.0 microM La reduced the influxes of Ca2+ and Zn2+ to 22 +/- 3 and 53 +/- 7% (mean +/- SE) of the control value, respectively. Injection of CaCl2 also reduced the branchial influxes of Ca2+ and Zn2+. This treatment decreased the influx of Ca2- to 45 +/- 4% of the control level and the Zn2+ influx to 68 +/- 5%. These results strongly imply that Zn2+ passes across the apical membrane of the chloride cells of the gills via the same pathway as Ca2+. The presence of an active basolateral transporter for Zn2+ was investigated in vitro on isolated basolateral membranes. There was no ATP-dependent or Na2+(-)gradient driven transport of Zn2+ at physiological Zn2+ activities. The same system was used to study potential effects of Zn2+ on the basolateral Ca2+(-)adenosinetri-phosphatase. Zn2+ was found to be a potent blocker of this transporter, causing a mixed inhibitory effect on the ATP driven Ca2+ transport at a free Zn2+ activity of 100 pM. PMID:8928918

  18. Mechanical design engineering. NASA/university advanced design program: Lunar Bulk Material Transport Vehicle

    Science.gov (United States)

    Daugherty, Paul; Griner, Stewart; Hendrix, Alan; Makarov, Chris; Martiny, Stephen; Meyhoefer, Douglas Ralph; Platt, Cody Claxton; Sivak, John; Wheeler, Elizabeth Fitch

    1988-01-01

    The design of a Lunar Bulk Material Transport Vehicle (LBMTV) is discussed. Goals set in the project include a payload of 50 cubic feet of lunar soil with a lunar of approximately 800 moon-pounds, a speed of 15 mph, and the ability to handle a grade of 20 percent. Thermal control, an articulated steering mechanism, a dump mechanism, a self-righting mechanism, viable power sources, and a probable control panel are analyzed. The thermal control system involves the use of small strip heaters to heat the housing of electronic equipment in the absence of sufficient solar radiation and multi-layer insulation during periods of intense solar radiation. The entire system uses only 10 W and weighs about 60 pounds, or 10 moon-pounds. The steering mechanism is an articulated steering joint at the center of the vehicle. It utilizes two actuators and yields a turning radius of 10.3 feet. The dump mechanism rotates the bulk material container through an angle of 100 degree using one actuator. The self-righting mechanism consists of two four bar linkages, each of which is powered by the same size actuator as the other linkages. The LBMTV is powered by rechargeable batteries. A running time of at least two hours is attained under a worst case analysis. The weight of the batteries is 100 pounds. A control panel consisting of feedback and control instruments is described. The panel includes all critical information necessary to control the vehicle remotely. The LBMTV is capable of handling many types of cargo. It is able to interface with many types of removable bulk material containers. These containers are made to interface with the three-legged walker, SKITTER. The overall vehicle is about 15 feet in length and has a weight of about 1000 pounds, or 170 lunar pounds.

  19. Elastic tunneling charge transport mechanisms in silicon quantum dots /SiO{sub 2} thin films and superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Illera, S., E-mail: sillera@el.ub.edu; Prades, J. D.; Cirera, A. [MIND/IN2UB Departament d' Electrònica, Universitat de Barcelona, C/Martí i Franquès 1, E-08028 Barcelona (Spain)

    2015-05-07

    The role of different charge transport mechanisms in Si/SiO{sub 2} structures has been studied. A theoretical model based on the Transfer Hamiltonian Formalism has been developed to explain experimental current trends in terms of three different elastic tunneling processes: (1) trap assisted tunneling; (2) transport through an intermediate quantum dot; and (3) direct tunneling between leads. In general, at low fields carrier transport is dominated by the quantum dots whereas, for moderate and high fields, transport through deep traps inherent to the SiO{sub 2} is the most relevant process. Besides, current trends in Si/SiO{sub 2} superlattice structure have been properly reproduced.

  20. Elastic tunneling charge transport mechanisms in silicon quantum dots /SiO2 thin films and superlattices

    International Nuclear Information System (INIS)

    The role of different charge transport mechanisms in Si/SiO2 structures has been studied. A theoretical model based on the Transfer Hamiltonian Formalism has been developed to explain experimental current trends in terms of three different elastic tunneling processes: (1) trap assisted tunneling; (2) transport through an intermediate quantum dot; and (3) direct tunneling between leads. In general, at low fields carrier transport is dominated by the quantum dots whereas, for moderate and high fields, transport through deep traps inherent to the SiO2 is the most relevant process. Besides, current trends in Si/SiO2 superlattice structure have been properly reproduced

  1. Control of oxygen transport in the microcrustacean Daphnia: regulation of haemoglobin expression as central mechanism of adaptation to different oxygen and temperature conditions.

    Science.gov (United States)

    Paul, R J; Zeis, B; Lamkemeyer, T; Seidl, M; Pirow, R

    2004-11-01

    The pathway for oxygen, the control of oxygen transport and the role of haemoglobin expression for the physiological adaptation to different oxygen and temperature conditions were studied in the ecological model organism Daphnia magna. Ventilation of the inner walls of the carapace as the main gas exchange area as well as of the embryos in the brood pouch are controlled, oxygen-dependent processes. The P(O2)-dependent increase of heart rate as well as perfusion rate during short-term, progressive hypoxia improves the circulatory oxygen transport within the body. The regulation of haemoglobin (Hb) expression is the central mechanism for a medium-term adaptation to hypoxia. Genetic control elements and oxygen conditions near the two Hb synthesis sites (fat cells, epipodite epithelial cells) determine, which types of Hb subunits and, accordingly, hetero-multimeric Hb macromolecules are produced. One synthesis site may respond mainly to internal, the other one to external oxygen conditions. Depending on environmental condition, either higher quantities of macromolecules of unchanged functionality (P50) or increasing amounts of macromolecules with higher oxygen affinity are synthesized. The Hb subunit DmHbA is probably of considerable importance for this functional change. The physiological benefits of haemoglobin in Daphnia are discussed. Physiological adaptation of Daphnia to different temperatures is also related to the control of oxygen transport processes with the regulation of haemoglobin expression again as a central mechanism. PMID:15491405

  2. Oxygen transport and reaction mechanisms in rhenium gate contacts on hafnium oxide films on Si

    International Nuclear Information System (INIS)

    Oxygen transport and incorporation were investigated following postdeposition annealing of metal-oxide-semiconductor structures having ultrathin rhenium films as metal electrode and HfO2 films as dielectric on Si(001). Isotopic tracing, nuclear reaction analysis, narrow resonant nuclear reaction profiling, and x-ray photoelectron spectroscopy were used to pursue this investigation. For annealing temperatures below 400 deg. C, oxygen from the gas phase incorporates mainly in near-surface regions of the overlying Re cap. Significant oxygen incorporation into the HfO2 films is observed only after annealing at 500 deg. C. The present results are discussed considering that supplying oxygen to the metal/dielectric interface can cause device threshold voltage shifts

  3. Transportation

    International Nuclear Information System (INIS)

    Here is the decree of the thirtieth of July 1998 relative to road transportation, to trade and brokerage of wastes. It requires to firms which carry out a road transportation as well as to traders and to brokers of wastes to declare their operations to the prefect. The declaration has to be renewed every five years. (O.M.)

  4. Progress in Solving the Elusive Ag Transport Mechanism in TRISO Coated Particles: What is new?

    Energy Technology Data Exchange (ETDEWEB)

    Isabella Van Rooyen

    2014-10-01

    The TRISO particle for HTRs has been developed to an advanced state where the coating withstands internal gas pressures and retains fission products during irradiation and under postulated accidents. However, one exception is Ag that has been found to be released from high quality TRISO coated particles when irradiated and can also during high temperature accident heating tests. Although out- of- pile laboratory tests have never hither to been able to demonstrate a diffusion process of Ag in SiC, effective diffusion coefficients have been derived to successfully reproduce measured Ag-110m releases from irradiated HTR fuel elements, compacts and TRISO particles It was found that silver transport through SiC does not proceed via bulk volume diffusion. Presently grain boundary diffusion that may be irradiation enhanced either by neutron bombardment or by the presence of fission products such as Pd, are being investigated. Recent studies of irradiated AGR-1 TRISO fuel using scanning transmission electron microscopy (STEM), transmission kukuchi diffraction (TKD) patterns and high resolution transmission electron microscopy (HRTEM) have been used to further the understanding of Ag transport through TRISO particles. No silver was observed in SiC grains, but Ag was identified at triple-points and grain boundaries of the SiC layer in the TRISO particle. Cadmium was also found in some of the very same triple junctions, but this could be related to silver behavior as Ag-110m decays to Cd-110. Palladium was identified as the main constituent of micron-sized precipitates present at the SiC grain boundaries and in most SiC grain boundaries and the potential role of Pd in the transport of Ag will be discussed.

  5. Integrated Radiation Transport and Thermo-Mechanics Simulation of a PWR Assembly

    International Nuclear Information System (INIS)

    The Advanced Multi-Physics (AMP) Nuclear Fuel Performance code (AMPFuel) is focused on predicting the temperature and strain within a nuclear fuel assembly to evaluate the performance and safety of existing and advanced nuclear fuel bundles within existing and advanced nuclear reactors. AMPFuel was extended to include an integrated nuclear fuel assembly capability for (one-way) coupled radiation transport and nuclear fuel assembly thermo-mechanics. This capability is the initial step towards incorporating an improved predictive nuclear fuel assembly modeling capability to accurately account for source terms, such as the neutron flux distribution, coolant conditions, and assembly mechanical stresses, of traditional (single-pin) nuclear fuel performance simulation. AMPFuel was used to model an entire 17 x 17 Pressurized Water Reactor (PWR) fuel assembly with many of the features resolved in three dimensions (for thermo-mechanics and/or neutronics), including the fuel, gap, and cladding of each of the 264 fuel pins, the 25 guide tubes, top and bottom structural regions, and the upper and lower (neutron) reflector regions. The final full-assembly calculation was executed on Jaguar (Cray XT5) at the Oak Ridge Leadership Computing Facility using 40,000 cores in under 10 hours to model over 162 billion degrees of freedom for 10 loading steps.

  6. Transportation R and D included in thermal and mechanical sciences program

    Science.gov (United States)

    1995-06-01

    Argonne National Laboratory is a multiprogram research and development laboratory operated by The University of Chicago for the US Department of Energy. At Argonne, applied research in thermal and mechanical sciences is performed within the Thermal and Mechanical Sciences Section of the Energy Technology Division. Current program areas include compact evaporators and condensers for the process and transportation industries, ice slurries for district cooling, advanced fluids for improved heat transfer and reduced pressure drop, flow-induced vibration and flow distribution in shell-and-tube heat exchangers, and dynamics and control of maglev systems. In general, the objective of the research is to extend the technology base in each of these areas and to facilitate its application in solving problems of importance to US industries and utilities. This is accomplished by developing validated design correlations and predictive methods. The staff of the Thermal and Mechanical Sciences Section have extensive experimental and analytical experience in heat transfer, multiphase flow, structural dynamics and control, fluid-structure interaction, transient flow and mixing, thermally driven flows, and flow visualization using ultra-high-speed video. Large, general-purpose test facilities and smaller, single-purpose test apparatuses are available for experiments and component design evaluation. A world-class capability in the study of flow-induced vibrations exists within the section. Individual fact sheets, describing currently active research program areas and related facilities and listing, as a contact, the principal investigator, are included.

  7. Quantum mechanics of excitation transport in photosynthetic complexes: a key issues review

    Science.gov (United States)

    Levi, Federico; Mostarda, Stefano; Rao, Francesco; Mintert, Florian

    2015-07-01

    For a long time microscopic physical descriptions of biological processes have been based on quantum mechanical concepts and tools, and routinely employed by chemical physicists and quantum chemists. However, the last ten years have witnessed new developments on these studies from a different perspective, rooted in the framework of quantum information theory. The process that more, than others, has been subject of intense research is the transfer of excitation energy in photosynthetic light-harvesting complexes, a consequence of the unexpected experimental discovery of oscillating signals in such highly noisy systems. The fundamental interdisciplinary nature of this research makes it extremely fascinating, but can also constitute an obstacle to its advance. Here in this review our objective is to provide an essential summary of the progress made in the theoretical description of excitation energy dynamics in photosynthetic systems from a quantum mechanical perspective, with the goal of unifying the language employed by the different communities. This is initially realized through a stepwise presentation of the fundamental building blocks used to model excitation transfer, including protein dynamics and the theory of open quantum system. Afterwards, we shall review how these models have evolved as a consequence of experimental discoveries; this will lead us to present the numerical techniques that have been introduced to quantitatively describe photo-absorbed energy dynamics. Finally, we shall discuss which mechanisms have been proposed to explain the unusual coherent nature of excitation transport and what insights have been gathered so far on the potential functional role of such quantum features.

  8. Dissecting the Molecular Mechanism of Nucleotide-Dependent Activation of the KtrAB K+ Transporter

    Science.gov (United States)

    Szollosi, Andras; Vieira-Pires, Ricardo S.; Teixeira-Duarte, Celso M.; Rocha, Rita; Morais-Cabral, João H.

    2016-01-01

    KtrAB belongs to the Trk/Ktr/HKT superfamily of monovalent cation (K+ and Na+) transport proteins that closely resemble K+ channels. These proteins underlie a plethora of cellular functions that are crucial for environmental adaptation in plants, fungi, archaea, and bacteria. The activation mechanism of the Trk/Ktr/HKT proteins remains unknown. It has been shown that ATP stimulates the activity of KtrAB while ADP does not. Here, we present X-ray structural information on the KtrAB complex with bound ADP. A comparison with the KtrAB-ATP structure reveals conformational changes in the ring and in the membrane protein. In combination with a biochemical and functional analysis, we uncover how ligand-dependent changes in the KtrA ring are propagated to the KtrB membrane protein and conclude that, despite their structural similarity, the activation mechanism of KtrAB is markedly different from the activation mechanism of K+ channels. PMID:26771197

  9. Buffer transport mechanisms in intentionally carbon doped GaN heterojunction field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Uren, Michael J.; Cäsar, Markus; Kuball, Martin [Center for Device Thermography and Reliability, H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL (United Kingdom); Gajda, Mark A. [NXP Semiconductors, Bramhall Moor Lane, Hazel Grove, Stockport SK7 5BJ (United Kingdom)

    2014-06-30

    Temperature dependent pulsed and ramped substrate bias measurements are used to develop a detailed understanding of the vertical carrier transport in the buffer layers in a carbon doped GaN power heterojunction field effect transistor. Carbon doped GaN and multiple layers of AlGaN alloy are used in these devices to deliver an insulating and strain relieved buffer with high breakdown voltage capability. However, understanding of the detailed physical mechanism for its operation is still lacking. At the lowest electric fields (<10 MV/m), charge redistribution within the C doped layer is shown to occur by hole conduction in the valence band with activation energy 0.86?eV. At higher fields, leakage between the two-dimensional electron gas and the buffer dominates occurring by a Poole-Frenkel mechanism with activation energy ?0.65?eV, presumably along threading dislocations. At higher fields still, the strain relief buffer starts to conduct by a field dependent process. Balancing the onset of these leakage mechanisms is essential to allow the build-up of positive rather than negative space charge, and thus minimize bulk-related current-collapse in these devices.

  10. Dark current transport mechanisms in narrow-gap heterojunctions for IR arrays

    Science.gov (United States)

    Sizov, Fiodor F.; Gumenjuk-Sichevskaya, Joanna V.; Sidorov, Yuri G.; Vasilev, Vladimir; Golenkov, Alexandr G.; Zabudsky, Vyacheslav V.; Reva, Vladimir P.; Derkach, Yurii P.; Tetyorkin, Vladimir V.

    2001-11-01

    Dark carrier transport mechanisms in narrow-gap Hg1-xCdxTe multilayer structures and Pb1-zSnzTe/PbTe1-yS(Se)y heterojunctions at T~80 K for applications in IR arrays are analyzed and compared with homojunction mercury-cadmium telluride (MCT) photodiode characteristics in the temperature range T~70-150 K. In the analysis procedure two major current mechanisms were included into the current balance equations: trap-assisted tunneling (TAT) and Shockley-Reed-Hall (SRH) generation-recombination processes for a defect trap level. Other current mechanisms (e.g., band-to-band tunneling, bulk diffusion) were taken into account as additive contributions. For TAT the tunneling rate characteristics were calculated within the k-p-approximation. Using donor and acceptor concentrations, trap level energies and concentrations, and in-junction trap level lifetimes as fitting parameters, good agreement with experimental data for HgCdTe and PbSnTe heterojunction and homojunction diodes was obtained, which allows one to predict the diode parameters from the known material characteristics. Photodiode or array parameters itself, or with CCD readouts, or CCD readouts separately were tested to study the influence of readout cascade on the diodes' properties.

  11. Impact of strong magnetic fields on collision mechanism for transport of charged particles

    CERN Document Server

    Bostan, Mihai

    2012-01-01

    One of the main applications in plasma physics concerns the energy production through thermo-nuclear fusion. The controlled fusion is achieved by magnetic confinement i.e., the plasma is confined into a toroidal domain (tokamak) under the action of huge magnetic fields. Several models exist for describing the evolution of strongly magnetized plasmas, most of them by neglecting the collisions between particles. The subject matter of this paper is to investigate the effect of large magnetic fields with respect to a collision mechanism. We consider here linear collision Boltzmann operators and derive, by averaging with respect to the fast cyclotronic motion due to strong magnetic forces, their effective collision kernels.

  12. Diffusion and bulk flow in phloem loading: A theoretical analysis of the polymer trap mechanism for sugar transport in plants

    Science.gov (United States)

    Dölger, Julia; Rademaker, Hanna; Liesche, Johannes; Schulz, Alexander; Bohr, Tomas

    2014-10-01

    Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

  13. Diffusion and bulk flow in phloem loading : a theoretical analysis of the polymer trap mechanism for sugar transport in plants

    DEFF Research Database (Denmark)

    Dölger, Julia; Rademaker, Hanna

    2014-01-01

    Plants create sugar in the mesophyll cells of their leaves by photosynthesis. This sugar, mostly sucrose, has to be loaded via the bundle sheath into the phloem vascular system (the sieve elements), where it is distributed to growing parts of the plant. We analyze the feasibility of a particular loading mechanism, active symplasmic loading, also called the polymer trap mechanism, where sucrose is transformed into heavier sugars, such as raffinose and stachyose, in the intermediary-type companion cells bordering the sieve elements in the minor veins of the phloem. Keeping the heavier sugars from diffusing back requires that the plasmodesmata connecting the bundle sheath with the intermediary cell act as extremely precise filters, which are able to distinguish between molecules that differ by less than 20% in size. In our modeling, we take into account the coupled water and sugar movement across the relevant interfaces, without explicitly considering the chemical reactions transforming the sucrose into the heavier sugars. Based on the available data for plasmodesmata geometry, sugar concentrations, and flux rates, we conclude that this mechanism can in principle function, but that it requires pores of molecular sizes. Comparing with the somewhat uncertain experimental values for sugar export rates, we expect the pores to be only 5%-10% larger than the hydraulic radius of the sucrose molecules. We find that the water flow through the plasmodesmata, which has not been quantified before, contributes only 10%-20% to the sucrose flux into the intermediary cells, while the main part is transported by diffusion. On the other hand, the subsequent sugar translocation into the sieve elements would very likely be carried predominantly by bulk water flow through the plasmodesmata. Thus, in contrast to apoplasmic loaders, all the necessary water for phloem translocation would be supplied in this way with no need for additional water uptake across the plasma membranes of the phloem.

  14. Ion transport mechanisms linked to bicarbonate secretion in the esophageal submucosal glands.

    Science.gov (United States)

    Abdulnour-Nakhoul, Solange; Nakhoul, Hani N; Kalliny, Medhat I; Gyftopoulos, Alex; Rabon, Edd; Doetjes, Rienk; Brown, Karen; Nakhoul, Nazih L

    2011-07-01

    The esophageal submucosal glands (SMG) secrete HCO(3)(-) and mucus into the esophageal lumen, where they contribute to acid clearance and epithelial protection. This study characterized the ion transport mechanisms linked to HCO(3)(-) secretion in SMG. We localized ion transporters using immunofluorescence, and we examined their expression by RT-PCR and in situ hybridization. We measured HCO(3)(-) secretion by using pH stat and the isolated perfused esophagus. Using double labeling with Na(+)-K(+)-ATPase as a marker, we localized Na(+)-coupled bicarbonate transporter (NBCe1) and Cl(-)-HCO(3)(-) exchanger (SLC4A2/AE2) to the basolateral membrane of duct cells. Expression of cystic fibrosis transmembrane regulator channel (CFTR) was confirmed by immunofluorescence, RT-PCR, and in situ hybridization. We identified anion exchanger SLC26A6 at the ducts' luminal membrane and Na(+)-K(+)-2Cl(-) (NKCC1) at the basolateral membrane of mucous and duct cells. pH stat experiments showed that elevations in cAMP induced by forskolin or IBMX increased HCO(3)(-) secretion. Genistein, an activator of CFTR, which does not increase intracellular cAMP, also stimulated HCO(3)(-) secretion, whereas glibenclamide, a Cl(-) channel blocker, and bumetanide, a Na(+)-K(+)-2Cl(-) blocker, decreased it. CFTR(inh)-172, a specific CFTR channel blocker, inhibited basal HCO(3)(-) secretion as well as stimulation of HCO(3)(-) secretion by IBMX. This is the first report on the presence of CFTR channels in the esophagus. The role of CFTR in manifestations of esophageal disease in cystic fibrosis patients remains to be determined. PMID:21474426

  15. A mechanism of viral immune evasion revealed by cryo-EM analysis of the TAP transporter.

    Science.gov (United States)

    Oldham, Michael L; Hite, Richard K; Steffen, Alanna M; Damko, Ermelinda; Li, Zongli; Walz, Thomas; Chen, Jue

    2016-01-28

    Cellular immunity against viral infection and tumour cells depends on antigen presentation by major histocompatibility complex class I (MHC I) molecules. Intracellular antigenic peptides are transported into the endoplasmic reticulum by the transporter associated with antigen processing (TAP) and then loaded onto the nascent MHC I molecules, which are exported to the cell surface and present peptides to the immune system. Cytotoxic T lymphocytes recognize non-self peptides and program the infected or malignant cells for apoptosis. Defects in TAP account for immunodeficiency and tumour development. To escape immune surveillance, some viruses have evolved strategies either to downregulate TAP expression or directly inhibit TAP activity. So far, neither the architecture of TAP nor the mechanism of viral inhibition has been elucidated at the structural level. Here we describe the cryo-electron microscopy structure of human TAP in complex with its inhibitor ICP47, a small protein produced by the herpes simplex virus I. Here we show that the 12 transmembrane helices and 2 cytosolic nucleotide-binding domains of the transporter adopt an inward-facing conformation with the two nucleotide-binding domains separated. The viral inhibitor ICP47 forms a long helical hairpin, which plugs the translocation pathway of TAP from the cytoplasmic side. Association of ICP47 precludes substrate binding and prevents nucleotide-binding domain closure necessary for ATP hydrolysis. This work illustrates a striking example of immune evasion by persistent viruses. By blocking viral antigens from entering the endoplasmic reticulum, herpes simplex virus is hidden from cytotoxic T lymphocytes, which may contribute to establishing a lifelong infection in the host. PMID:26789246

  16. Understanding Kondo Peak Splitting and Novel Transport Mechanism in a Single-Electron Transistor

    CERN Document Server

    Hong, J; Hong, Jongbae; Woo, Wonmyung

    2007-01-01

    The peculiar behavior of Kondo peak splitting under a magnetic field and bias can be explained by calculating the nonequilibrium retarded Green's function via the nonperturbative dynamical theory (NDT). In the NDT, the application of a lead-dot-lead system reveals that new resonant tunneling levels are activated near the Fermi level and the conventional Kondo peak at the Fermi level diminishes when a bias is applied. Magnetic field causes asymmetry in the spectral density and transforms the new resonant peak into a major peak whose behavior explains all the features of the nonequilibrium Kondo phenomenon. Transport through the new resonant tunneling level is a novel mechanism of current occurring in a single-electron transistor.

  17. Electrical characteristics and carrier transport mechanism for Ti/ p-GaN Schottky diodes

    Science.gov (United States)

    Jang, Seon-Ho; Jang, Ja-Soon

    2013-03-01

    The temperature dependence of the electrical characteristics of non-alloyed Ti/ p-GaN Schottky diodes was examined using current-voltage-temperature, turn-on voltage-temperature, and series resistance-temperature measurements. The thermal coefficient ( K j ) and characteristic temperature ( T 0 ) at T ? 293 K were determined to be -4.1 mV/K and 65.06 K, respectively. The effective Schottky barrier height (SBH) was also determined to be 2.1 (±0.03) eV, which was in good agreement with the theoretical value. The possible carrier transport mechanisms at the interface are described in terms of the thermally decreased energy-band gap of p-GaN layers, thermally increased deep-level acceptor and increased further-activated-shallow-level acceptor. These were confirmed by the thermally increased ideality factor and high tunnelling parameter.

  18. Reaction mechanisms in transport theories: a test of the nuclear effective interaction

    CERN Document Server

    Colonna, M; Di Toro, M; Frecus, B; Zhang, Y X

    2012-01-01

    We review recent results concerning collective excitations in neutron-rich systems and reactions between charge asymmetric systems at Fermi energies. Solving numerically self-consistent transport equations for neutrons and protons with specific initial conditions, we explore the structure of the different dipole vibrations in the $^{132}Sn$ system and investigate their dependence on the symmetry energy. We evidence the existence of a distinctive collective mode, that can be associated with the Pygmy Dipole Resonance, with an energy well below the standard Giant Dipole Resonance and isoscalar-like character, i.e. very weakly dependent on the isovector part of the nuclear effective interaction. At variance, the corresponding strength is rather sensitive to the behavior of the symmetry energy below saturation, which rules the number of excess neutrons in the nuclear surface. In reactions between charge asymmetric systems at Fermi energies, we investigate the interplay between dissipation mechanisms and isospin e...

  19. Electron transport mechanism of thermally oxidized ZnO gas sensors

    Energy Technology Data Exchange (ETDEWEB)

    Al-Hardan, N.H., E-mail: naif.zd06@student.usm.m [School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang (Malaysia); Abdullah, M.J.; Abdul Aziz, A. [School of Physics, Universiti Sains Malaysia (USM), 11800 Minden, Pulau Pinang (Malaysia)

    2010-11-01

    ZnO gas sensor was fabricated by thermal oxidation of metallic Zn at different time periods. The sensors were characterized by I-V measurement with DC voltage, ranging from -2 to 2 volts, in both normal air and H{sub 2} gas with concentration from 40 to 160 ppm. The transport mechanism of the carriers was found to be due to thermionic process through both the grain boundaries and the metal-semiconductor junctions. Resistance of the ZnO sensing film is independent of applied voltage in the range 0.5 V

  20. Transport and Mechanical Characteristics of Corrosion-Inhibited High- Strength Self-Compacting Concrete

    Directory of Open Access Journals (Sweden)

    Marva Blankson

    2015-11-01

    Full Text Available This paper is on the study of traditional silica fume (SG self-compacting concrete (SCC samples that was made as control and then incorporated with carboxylic inhibitor (SM to study the transport, rheological and mechanical responses of the inhibited samples. Comparison with the respective SG control, showed that the carboxylic inhibitor resulted in the reduction of the homogeneity of the SM samples and there was the development of flaws that could have contributed to the reduction in strength of the SM samples. When the concentration of the inhibitor was increased from the basic content to 100% higher, there was a noticeable increase in the chloride migration resistance of the SM samples. The study also showed that the transit time of the ultrasonic pulse that was transmitted was slower in the carboxylic inhibited-samples.

  1. Solute transport in fractured media - The important mechanisms for performance assessment

    International Nuclear Information System (INIS)

    The most important mechanisms that control the release of contaminants from a repository for nuclear or chemical waste have been studied. For the time scale of interest for the disposal of nuclear or even chemical waste, diffusion into the rock matrix is an important factor which retards and dilutes the contaminants. It is found that the water flow-rate distribution and the flow-wetted surface are the entities that primarily determine the solute transport. If the diffusion in the rock matrix is negligible, the solute transport is determined by the water flow-rate and the flow porosity. This is shown by simulations using analytical solutions obtained for simple geometries, such as the flow in a fracture or a channel. Similar results are obtained for more complex systems, such as flow in a fracture with variable aperture and through a network of channels. It is also found that the use of a retardation factor relating the travel times of interacting and noninteracting solutes is inappropriate and may be misleading. 11 refs, 9 figs, 1 tab

  2. The extreme mobility of debris avalanches: A new model of transport mechanism

    Science.gov (United States)

    Perinotto, Hélène; Schneider, Jean-Luc; Bachèlery, Patrick; Le Bourdonnec, François-Xavier; Famin, Vincent; Michon, Laurent

    2015-12-01

    Large rockslide-debris avalanches, resulting from flank collapses that shape volcanoes and mountains on Earth and other object of the solar system, are rapid and dangerous gravity-driven granular flows that travel abnormal distances. During the last 50 years, numerous physical models have been put forward to explain their extreme mobility. The principal models are based on fluidization, lubrication, or dynamic disintegration. However, these processes remain poorly constrained. To identify precisely the transport mechanisms during debris avalanches, we examined morphometric (fractal dimension and circularity), grain size, and exoscopic characteristics of the various types of particles (clasts and matrix) from volcanic debris avalanche deposits of La Réunion Island (Indian Ocean). From these data we demonstrate for the first time that syn-transport dynamic disintegration continuously operates with the increasing runout distance from the source down to a grinding limit of 500 µm. Below this limit, the particle size reduction exclusively results from their attrition by frictional interactions. Consequently, the exceptional mobility of debris avalanches may be explained by the combined effect of elastic energy release during the dynamic disintegration of the larger clasts and frictional reduction within the matrix due to interactions between the finer particles.

  3. Mass transport mechanism of cu species at the metal/dielectric interfaces with a graphene barrier.

    Science.gov (United States)

    Zhao, Yuda; Liu, Zhaojun; Sun, Tieyu; Zhang, Ling; Jie, Wenjing; Wang, Xinsheng; Xie, Yizhu; Tsang, Yuen Hong; Long, Hui; Chai, Yang

    2014-12-23

    The interface between the metal and dielectric is an indispensable part in various electronic devices. The migration of metallic species into the dielectric can adversely affect the reliability of the insulating dielectric and can also form a functional solid-state electrolyte device. In this work, we insert graphene between Cu and SiO2 as a barrier layer and investigate the mass transport mechanism of Cu species through the graphene barrier using density functional theory calculations, second-ion mass spectroscopy (SIMS), capacitance-voltage measurement, and cyclic voltammetry. Our theoretical calculations suggest that the major migration path for Cu species to penetrate through the multiple-layered graphene is the overlapped defects larger than 0.25 nm2. The depth-profile SIMS characterizations indicate that the "critical" thickness of the graphene barrier for completely blocking the Cu migration is 5 times smaller than that of the conventional TaN barrier. Capacitance-voltage and cyclic voltammetry measurement reveal that the electrochemical reactions at the Cu/SiO2 interface become a rate-limiting factor during the bias-temperature stressing process with the use of a graphene barrier. These studies provide a distinct roadmap for designing controllable mass transport in solid-state electrolyte devices with the use of a graphene barrier. PMID:25423484

  4. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    Science.gov (United States)

    Imran, Z.; Rafiq, M. A.; Hasan, M. M.

    2014-06-01

    Electrical transport properties of electrospun cadmium titanate (CdTiO3) fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000 °C yielded the single phase perovskite fibers having diameter ˜600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K - 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC) with traps at higher voltages at all temperatures (200 K - 420 K). Trap density in our fibers system is Nt = 6.27 × 1017 /cm3. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH) from 200 K - 300 K. The localized density of states were found to be N(EF) = 5.51 × 1021 eV-1 cm-3 at 2 V. Other VRH parameters such as hopping distance (Rhop) and hopping energy (Whop) were also calculated. In the high temperature range of 320 K - 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO3 fibers efficient material for capacitive energy storage devices.

  5. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    International Nuclear Information System (INIS)

    Electrical transport properties of electrospun cadmium titanate (CdTiO3) fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000?°C yielded the single phase perovskite fibers having diameter ?600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K – 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC) with traps at higher voltages at all temperatures (200 K – 420 K). Trap density in our fibers system is Nt = 6.27 × 1017 /cm3. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH) from 200 K – 300 K. The localized density of states were found to be N(EF) = 5.51 × 1021 eV?1 cm?3 at 2 V. Other VRH parameters such as hopping distance (Rhop) and hopping energy (Whop) were also calculated. In the high temperature range of 320 K – 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO3 fibers efficient material for capacitive energy storage devices

  6. Effects of hydrophobic aggregation on the charge transport mechanism of quaternary ammonium ionic liquids

    Science.gov (United States)

    Griffin, Philip; Holt, Adam; Wang, Yangyang; Novikov, Vladimir; Sangoro, Joshua; Sokolov, Alexei

    2014-03-01

    Aprotic quaternary ammonium ionic liquids (ILs) are an important class of ILs due to their large electrochemical window and hydrophobicity. However, many of these ILs suffer from relatively low conductivity at room temperature which limits their use in electrochemical applications. In order to understand the nature of this low conductivity and its relation to the chemical structure of the alkyl ammonium cation, we have measured the charge transport properties and structural dynamics of the room temperature ionic liquid methyltrioctylammonium bistriflimide [m3oa][ntf2] over a broad temperature range using dielectric spectroscopy, dynamic light scattering, rheology, and pulsed field gradient nuclear magnetic resonance. We demonstrate that the low values of dc conductivity are due to the combined effects of significantly reduced ion mobility as well as reduced free ion concentration relative to other types of ILs. Secondly we find evidence for a mesoscopic scale structural relaxation process that we attribute to the reorientational motion of nanometer sized alkyl nanodomains. These two findings indicate that hydrophobic aggregation plays an important role in the charge transport mechanism of aprotic ammonium ionic liquids with long aliphatic side chains.

  7. Gamma ray attenuation studies of interception from Sitka spruce: some evidence for an additional transport mechanism

    International Nuclear Information System (INIS)

    Various forest canopy characteristics of stands of Sitka spruce (Picea sitchensis (Bong.) Carr.), including canopy density, the aerodynamic resistance to the transfer of water vapor, and the rates of change of drainage and evaporation of water with respect to canopy storage, were investigated using direct measurements of canopy mass and water storage. The measurements, made at sites located in Wales and Scotland, utilized the attenuation of a horizontal beam of gamma rays which was arranged to scan through the canopy at different levels. The aerodynamic resistance to the transport of water vapor from the canopy to a reference level 5 m above mean tree height was found to be consistent with the value of 3.5 s m?1, determined from earlier modeling studies (I. R. Calder, 1977). This value is, however, lower and shows less wind speed dependence than would be expected from conventional formulae which are based on eddy diffusion theory and tree height. The possibility of explaining these discrepancies in terms of an additional transport mechanism involving large-scale eddies is discussed

  8. Uptake and transport mechanisms of decabromodiphenyl ether (BDE-209) by rice (Oryza sativa).

    Science.gov (United States)

    Chow, Ka Lai; Man, Yu Bon; Tam, Nora Fung Yee; Liang, Yan; Wong, Ming Hung

    2015-01-01

    The extensive industrial use of brominated flame retardants has aroused rapidly growing public concerns about their ubiquity in the environment. The feasibility of uptake and translocation of decabromodiphenyl ether (BDE-209) by three rice cultivars, namely Fengmeizhan, Hefengzhan and Guangyinzhan, and the uptake mechanisms of BDE-209 into rice roots, were investigated by employing a partition-limited model. Uptake of BDE-209 by the rice cultivars (Fengmeizhan, Hefengzhan and Guangyinzhan) was examined by a 60-day cultivation in sterilized BDE-209 spiked sand, followed by Soxhlet extraction and gas chromatography-mass spectrometry (GC-MS) analysis. A partition-limited model was applied for estimating and describing the approach of the uptake of BDE-209 by rice in sand. The average quasi-equilibrium factor (?pt) of BDE-209 in root uptake in sand was 0.112×10(-3) for three rice cultivars in the present study (<1), implying a non-equilibrium movement of molecules and a dominated passive transport uptake. According to the results of sorption analysis of dead and fresh roots, apoplastic pathway likely dominated the transport of BDE-209 into roots cells. PMID:25460770

  9. Embedding a Multi-agents Collaboration Mechanism into the Hybrid Middleware of an Intelligent Transportation System

    Directory of Open Access Journals (Sweden)

    Huan-Chao Keh

    2011-01-01

    Full Text Available Even if wireless networks and mobile computing technologies have comprehensively developed in recent years. Letting people extract information anywhere at anytime is the goal of this development. But in the telematics domain, the drivers can obtain road information through radio or certain in-car equipment, there is still a wide gap with regard to the synchronization of this information with actual road conditions. In the absence of adequate information, drivers often react to conditions with behaviors that do not contribute to their own driving goals but rather cause more complicated traffic conditions. Therefore, this study employs a process known as multi-agent collaboration. Information exchanged between the features and established mutual communication and collaboration mechanisms is applied in Intelligent Transportation Systems (ITS. By allowing drivers to have distributed communication with other vehicles to share driving information, collect information and/or submit their own reasoned driving advice to other drivers, many traffic situations could effectively be improved and the efficiency of the computing processes could be improved through distributed communication. This study proposes an architecture design for middleware that includes vehicle information, navigation, announcements and communication which could prove to be a more convenient and efficient intelligent transportation system.

  10. Catecholamine transport in cultured bovine adrenal medullary cells: kinetics and mechanism

    International Nuclear Information System (INIS)

    In primary cultures of bovine adrenomedullary cells, catecholamine uptake was found to be a saturable process exhibiting Michaelis-Menten kinetics with an apparent K/sub m/ for 1-norepinephrine of 0.5 ?M. Radiolabeled catecholamines were employed to study the general characteristics and kinetic properties of catecholamine transport in cultured adrenomedullary cells. This process was found to be temperature, energy and Na+-dependent. In addition, uptake required the presence of extracellular Cl-, K+, and divalent cation such as Mn2+, Ca2+, or Mg2+. Agents that induce Ca2+-dependent, exocytotic secretion of catecholamines from these cells had significant inhibitory effects on catecholamine uptake. The secretagogues, nicotine, veratridine and elevated extracellular K+ concentrations, were all found to inhibit norepinephrine uptake. The inhibitory effects of the secretagogues could be fully demonstrated in the absence of catecholamine secretion. Investigation into the mechanism of catecholamine transport was pursued by measuring the effects of various catecholamine altering conditions or agents on the cellular membrane potential and/or the inwardly directed Na+ concentration gradient. Changes in the membrane potential were determined biochemically using tetraphenylphosphonium ion distribution, whereas changes in the Na+-gradient were assessed using 22Na+ distribution

  11. Mechanisms of molecular transport through the urea channel of Helicobacter pylori

    Science.gov (United States)

    McNulty, Reginald; Ulmschneider, Jakob P.; Luecke, Hartmut; Ulmschneider, Martin B.

    2013-12-01

    Helicobacter pylori survival in acidic environments relies on cytoplasmic hydrolysis of gastric urea into ammonia and carbon dioxide, which buffer the pathogen’s periplasm. Urea uptake is greatly enhanced and regulated by HpUreI, a proton-gated inner membrane channel protein essential for gastric survival of H. pylori. The crystal structure of HpUreI describes a static snapshot of the channel with two constriction sites near the center of the bilayer that are too narrow to allow passage of urea or even water. Here we describe the urea transport mechanism at atomic resolution, revealed by unrestrained microsecond equilibrium molecular dynamics simulations of the hexameric channel assembly. Two consecutive constrictions open to allow conduction of urea, which is guided through the channel by interplay between conserved residues that determine proton rejection and solute selectivity. Remarkably, HpUreI conducts water at rates equivalent to aquaporins, which might be essential for efficient transport of urea at small concentration gradients.

  12. Mechanism for transport of ivermectin to the stratum corneum in rats.

    Science.gov (United States)

    Miyajima, Atsushi; Kigure, Akira; Anata, Taichi; Hirota, Takashi

    2015-12-01

    Ivermectin (IVM) is used as an oral medication for scabies, a skin infection caused by a mite, sarcoptes scabiei, which parasitizes in the stratum corneum. After oral administration IVM is absorbed from the intestine, and finally distributed to the stratum corneum to eliminate the mites. However its transport mechanism remains unclear. A pharmacokinetic study was performed using hairless Wistar Yagi (HWY) rats, which have no or atrophied sebaceous glands, and Wistar rats as a reference. After oral administration of IVM to both groups, the area under the concentration-time curve of IVM in the dermis and epidermis (dermis-epidermis) of HWY rats were about 60% lower than that of Wistar rats, even though the plasma concentration profiles were comparable in both groups. In addition at 12 h after the administration, IVM concentration in the outer stratum corneum, the shallower layer of the dermis-epidermis, was higher compared to that in the deeper layer. In the dermis-epidermis of the skin from various locations, the concentrations of IVM and squalene, the latter of which is secreted to the skin surface via the sebaceous gland, were positively well correlated. Those results suggest that IVM is transported to the stratum corneum via the sebaceous glands. PMID:26613804

  13. Solute transport and storage mechanisms in wetlands of the Everglades, south Florida

    Science.gov (United States)

    Harvey, Judson W.; Saiers, James E.; Newlin, Jessica T.

    2005-05-01

    Solute transport and storage processes in wetlands play an important role in biogeochemical cycling and in wetland water quality functions. In the wetlands of the Everglades, there are few data or guidelines to characterize transport through the heterogeneous flow environment. Our goal was to conduct a tracer study to help quantify solute exchange between the relatively fast flowing water in the open part of the water column and much more slowly moving water in thick floating vegetation and in the pore water of the underlying peat. We performed a tracer experiment that consisted of a constant-rate injection of a sodium bromide (NaBr) solution for 22 hours into a 3 m wide, open-ended flume channel in Everglades National Park. Arrival of the bromide tracer was monitored at an array of surface water and subsurface samplers for 48 hours at a distance of 6.8 m downstream of the injection. A one-dimensional transport model was used in combination with an optimization code to identify the values of transport parameters that best explained the tracer observations. Parameters included dimensions and mass transfer coefficients describing exchange with both short (hours) and longer (tens of hours) storage zones as well as the average rates of advection and longitudinal dispersion in the open part of the water column (referred to as the ``main flow zone''). Comparison with a more detailed set of tracer measurements tested how well the model's storage zones approximated the average characteristics of tracer movement into and out of the layer of thick floating vegetation and the pore water in the underlying peat. The rate at which the relatively fast moving water in the open water column was exchanged with slowly moving water in the layer of floating vegetation and in sediment pore water amounted to 50 and 3% h-1, respectively. Storage processes decreased the depth-averaged velocity of surface water by 50% relative to the water velocity in the open part of the water column. As a result, flow measurements made with other methods that only work in the open part of the water column (e.g., acoustic Doppler) would have overestimated the true depth-averaged velocity by a factor of 2. We hypothesize that solute exchange and storage in zones of floating vegetation and peat pore water increase contact time of solutes with biogeochemically active surfaces in this heterogeneous wetland environment.

  14. Helium solubility in mica and mechanisms for deep transport of noble gases in subduction zones

    Science.gov (United States)

    Jackson, C.; Parman, S. W.; Kelley, S. P.; Cooper, R. F.

    2012-12-01

    We have experimentally determined helium solubility in mica to explore possible transport mechanisms of noble gases in subduction zones. Helium solubility in single crystals of muscovite and F-phlogopite investigated is relatively high, ~1 [He]/PHe (ppm/kbar). This solubility is approximately two orders of magnitude greater than values recently measured for olivine [1], and similar to values recently measured for amphibole with a low density of unoccupied ring sites [2]. Helium was dissolved into the micas by subjecting them to a high pressure noble gas atmosphere (1.26-1.48 He-Ne-Ar kbar) at moderate temperatures (450-700 C), allowing the micas to diffusively equilibrate with the imposed helium fugacity. Diffusion of Ne and Ar is too slow in both micas at the explored conditions to quantify their solubility. Experiments were conducted using a TZM gas pressure medium apparatus (Brown University). Analysis was completed by noble gas LA-MS (Open University, UK). Muscovite (dioctehedral) and F-phlogopite (trioctehedral) represent the two basic structural groups of micas, suggesting micas stabilized at higher pressures and temperatures, such as phengite, can provide a relatively deep transport mechanism for noble gases delivered to subduction zones. Thus, phengite may play a role in explaining atmospheric signatures in mantle derived noble gases [e.g.3,4]. 1. Heber, V. S., Brooker, R. A., Kelley, S. P. & Wood, B. J., GCA, 71, 1041-1061 2. Jackson C.R.M, Kelley S.P., Parman S.W., Cooper R.F., Goldschmidt 2012 Abstract 3. Holland, G. & Ballentine, C. J., Nature 441, 186-191 4. Mukhopadhyay, S.. Nature 486, 101-104

  15. Generation and transport mechanisms of chemical species by a post-discharge flow for inactivation of bacteria

    International Nuclear Information System (INIS)

    A post-discharge flow that is formed downstream of a microwave argon plasma in atmospheric air was investigated to clarify the generation and transport of chemical species, which are considered to result in the inactivation of bacteria. The flow, which is characterized by ultra-weak emission, can be visualized using an optical analysis system. This visualized jet-like flow forms downstream of the nozzle exit, and then, as the gas temperature is 877 K at the center of the nozzle exit, the main flow travels upstream around the quartz tube due to buoyancy, the reason being that the temperature decreases to room temperature at 30 mm downstream. It was clarified that excited argon atoms, molecular nitrogen (N2 second positive system) and OH radicals were generated in the post-discharge flow, subsequent to which NO2 and ions with a number density of 106 counts cm-3 were transported downstream below the main flow. These results imply that most of the heat and chemical species were transported by convective transport of the main flow, but that a small amount of chemically active species and ions might have been transported further downstream by diffusive transport, these species being considered to result in an inactivation effect on bacteria.

  16. Generation and transport mechanisms of chemical species by a post-discharge flow for inactivation of bacteria

    Energy Technology Data Exchange (ETDEWEB)

    Sato, Takehiko [Institute of Fluid Science, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Ochiai, Shiroh [Graduate School of Engineering, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Urayama, Takuya [Adtec Plasma Technology Co Ltd, 5-6-10 Hikino-chou, Fukuyama 721-0942 (Japan)], E-mail: sato@ifs.tohoku.ac.jp

    2009-11-15

    A post-discharge flow that is formed downstream of a microwave argon plasma in atmospheric air was investigated to clarify the generation and transport of chemical species, which are considered to result in the inactivation of bacteria. The flow, which is characterized by ultra-weak emission, can be visualized using an optical analysis system. This visualized jet-like flow forms downstream of the nozzle exit, and then, as the gas temperature is 877 K at the center of the nozzle exit, the main flow travels upstream around the quartz tube due to buoyancy, the reason being that the temperature decreases to room temperature at 30 mm downstream. It was clarified that excited argon atoms, molecular nitrogen (N{sub 2} second positive system) and OH radicals were generated in the post-discharge flow, subsequent to which NO{sub 2} and ions with a number density of 10{sup 6} counts cm{sup -3} were transported downstream below the main flow. These results imply that most of the heat and chemical species were transported by convective transport of the main flow, but that a small amount of chemically active species and ions might have been transported further downstream by diffusive transport, these species being considered to result in an inactivation effect on bacteria.

  17. Structural, mechanical and magnetic properties studies on high-energy Kr-ion irradiated Fe3O4 material (main corrosion layer of Fe-based alloys)

    Science.gov (United States)

    Sun, Jianrong; Wang, Zhiguang; Zhang, Hongpeng; Song, Peng; Chang, Hailong; Cui, Minghuan; Pang, Lilong; Zhu, Yabin; Li, Fashen

    2014-12-01

    The Fe-based (T91 and RAFM) alloys are considered as the promising candidate structural materials for DEMO and the first fusion power plant, and these two kinds of steels suffered more serious corrosion attack at 450 °C in liquid PbBi metal. So in order to further clarify the applicability of Fe-based structural materials in nuclear facilities, we should study not only the alloys itself but also its corrosion layers; and in order to simplify the discussion and clarify the irradiation effects of the different corrosion layer, we abstract the Fe3O4 (main corrosion layer of Fe-based alloys) to study the structural, micro-mechanical and magnetic properties under 2.03 GeV Kr-ion irradiation. The initial crystallographic structure of the Fe3O4 remains unaffected after irradiation at low damage levels, but as the Kr-ion fluence increases and the defects accumulate, the macroscopic magnetic properties (Ms, Hc, etc.) and micro-mechanical properties (nano-hardness and Young's modulus) are sensitive to high-energy Kr-ion irradiation and exhibit excruciating uniform changing regularities with varying fluences (firstly increases, then decreases). And these magnetism, hardening and softening phenomena can be interpreted very well by the effects related to the stress and defects (the production, accumulation and free) induced by high-energy ions irradiation.

  18. Transport in semiconductor nanowire superlattices described by coupled quantum mechanical and kinetic models.

    Science.gov (United States)

    Alvaro, M; Bonilla, L L; Carretero, M; Melnik, R V N; Prabhakar, S

    2013-08-21

    In this paper we develop a kinetic model for the analysis of semiconductor superlattices, accounting for quantum effects. The model consists of a Boltzmann-Poisson type system of equations with simplified Bhatnagar-Gross-Krook collisions, obtained from the general time-dependent Schrödinger-Poisson model using Wigner functions. This system for superlattice transport is supplemented by the quantum mechanical part of the model based on the Ben-Daniel-Duke form of the Schrödinger equation for a cylindrical superlattice of finite radius. The resulting energy spectrum is used to characterize the Fermi-Dirac distribution that appears in the Bhatnagar-Gross-Krook collision, thereby coupling the quantum mechanical and kinetic parts of the model. The kinetic model uses the dispersion relation obtained by the generalized Kronig-Penney method, and allows us to estimate radii of quantum wire superlattices that have the same miniband widths as in experiments. It also allows us to determine more accurately the time-dependent characteristics of superlattices, in particular their current density. Results, for several experimentally grown superlattices, are discussed in the context of self-sustained coherent oscillations of the current density which are important in an increasing range of current and potential applications. PMID:23877936

  19. ADSORPTION MECHANISMS AND TRANSPORT BEHAVIOR BETWEEN SELENATE AND SELENITE ON DIFFERENT SORBENTS

    Energy Technology Data Exchange (ETDEWEB)

    Snyder, Michelle MV; Um, Wooyong

    2014-04-30

    Adsorption of different oxidation species of selenium (Se), selenate (SeO42-) and selenite (SeO32-), with varying pHs (2 - 10) and ionic strengths (I = 0.01 M, 0.1 M and 1.0 M NaNO3) was measured on quartz, aluminum oxide, and synthetic iron oxide (ferrihydrite) using batch reactors to obtain a more detailed understanding of the adsorption mechanisms (e.g., inner- and outer-sphere complex). In addition to the batch experiments with single minerals contained in native Hanford Site sediment, additional batch adsorption studies were conducted with native Hanford Site sediment and groundwater as a function of 1) total Se concentration (from 0.01 to 10 mg L-1) and 2) soil to solution ratios (1:20 and 1:2 grams per mL). Results from these batch studies were compared to a set of saturated column experiments that were conducted with natural Hanford sediment and groundwater spiked with either selenite or selenate to observe the transport behavior of these species. Both batch and column results indicated that selenite adsorption was consistently higher than that of selenate in all experimental conditions used. These different adsorption mechanisms between selenite and selenate result in the varying mobility of Se in the subsurface environment and explain the dependence on the oxidation species.

  20. An alkaline phosphatase transport mechanism in the pathogenesis of Alzheimer's disease and neurodegeneration.

    Science.gov (United States)

    Pike, Adrianne F; Kramer, Nynke I; Blaauboer, Bas J; Seinen, Willem; Brands, Ruud

    2015-01-25

    Systemic inflammation is associated with loss of blood-brain barrier integrity and neuroinflammation that lead to the exacerbation of neurodegenerative diseases. It is also associated specifically with the characteristic amyloid-? and tau pathologies of Alzheimer's disease. We have previously proposed an immunosurveillance mechanism for epithelial barriers involving negative feedback-regulated alkaline phosphatase transcytosis as an acute phase anti-inflammatory response that hangs in the balance between the resolution and the progression of inflammation. We now extend this model to endothelial barriers, particularly the blood-brain barrier, and present a literature-supported mechanistic explanation for Alzheimer's disease pathology with this system at its foundation. In this mechanism, a switch in the role of alkaline phosphatase from its baseline duties to a stopgap anti-inflammatory function results in the loss of alkaline phosphatase from cell membranes into circulation, thereby decreasing blood-brain barrier integrity and functionality. This occurs with impairment of both amyloid-? efflux and tau dephosphorylating activity in the brain as alkaline phosphatase is replenished at the barrier by receptor-mediated transport. We suggest systemic alkaline phosphatase administration as a potential therapy for the resolution of inflammation and the prevention of Alzheimer's disease pathology as well as that of other inflammation-related neurodegenerative diseases. PMID:25500268

  1. Emergency Situation Prediction Mechanism: A Novel Approach for Intelligent Transportation System Using Vehicular Ad Hoc Networks

    Science.gov (United States)

    Gokulakrishnan, P.

    2015-01-01

    In Indian four-lane express highway, millions of vehicles are travelling every day. Accidents are unfortunate and frequently occurring in these highways causing deaths, increase in death toll, and damage to infrastructure. A mechanism is required to avoid such road accidents at the maximum to reduce the death toll. An Emergency Situation Prediction Mechanism, a novel and proactive approach, is proposed in this paper for achieving the best of Intelligent Transportation System using Vehicular Ad Hoc Network. ESPM intends to predict the possibility of occurrence of an accident in an Indian four-lane express highway. In ESPM, the emergency situation prediction is done by the Road Side Unit based on (i) the Status Report sent by the vehicles in the range of RSU and (ii) the road traffic flow analysis done by the RSU. Once the emergency situation or accident is predicted in advance, an Emergency Warning Message is constructed and disseminated to all vehicles in the area of RSU to alert and prevent the vehicles from accidents. ESPM performs well in emergency situation prediction in advance to the occurrence of an accident. ESPM predicts the emergency situation within 0.20 seconds which is comparatively less than the statistical value. The prediction accuracy of ESPM against vehicle density is found better in different traffic scenarios. PMID:26065014

  2. Emergency Situation Prediction Mechanism: A Novel Approach for Intelligent Transportation System Using Vehicular Ad Hoc Networks.

    Science.gov (United States)

    Ganeshkumar, P; Gokulakrishnan, P

    2015-01-01

    In Indian four-lane express highway, millions of vehicles are travelling every day. Accidents are unfortunate and frequently occurring in these highways causing deaths, increase in death toll, and damage to infrastructure. A mechanism is required to avoid such road accidents at the maximum to reduce the death toll. An Emergency Situation Prediction Mechanism, a novel and proactive approach, is proposed in this paper for achieving the best of Intelligent Transportation System using Vehicular Ad Hoc Network. ESPM intends to predict the possibility of occurrence of an accident in an Indian four-lane express highway. In ESPM, the emergency situation prediction is done by the Road Side Unit based on (i) the Status Report sent by the vehicles in the range of RSU and (ii) the road traffic flow analysis done by the RSU. Once the emergency situation or accident is predicted in advance, an Emergency Warning Message is constructed and disseminated to all vehicles in the area of RSU to alert and prevent the vehicles from accidents. ESPM performs well in emergency situation prediction in advance to the occurrence of an accident. ESPM predicts the emergency situation within 0.20 seconds which is comparatively less than the statistical value. The prediction accuracy of ESPM against vehicle density is found better in different traffic scenarios. PMID:26065014

  3. Tagged ozone mechanism for MOZART-4, CAM-chem and other chemical transport models

    Science.gov (United States)

    Emmons, L. K.; Hess, P. G.; Lamarque, J.-F.; Pfister, G. G.

    2012-12-01

    A procedure for tagging ozone produced from NO sources through updates to an existing chemical mechanism is described, and results from its implementation in the Model for Ozone and Related chemical Tracers (MOZART-4), a global chemical transport model, are presented. Artificial tracers are added to the mechanism, thus, not affecting the standard chemistry. The results are linear in the troposphere, i.e., the sum of ozone from individual tagged sources equals the ozone from all sources to within 3% in zonal mean monthly averages. In addition, the tagged ozone is shown to equal the standard ozone, when all tropospheric sources are tagged and stratospheric input is turned off. The stratospheric ozone contribution to the troposphere determined from the difference between total ozone and ozone from all tagged sources is significantly less than estimates using a traditional stratospheric ozone tracer (8 vs. 20 ppbv at the surface). The commonly used technique of perturbing NO emissions by 20% in a region to determine its ozone contribution is compared to the tagging technique, showing that the tagged ozone is 2-4 times the ozone contribution that was deduced from perturbing emissions. The ozone tagging described here is useful for identifying source contributions based on NO emissions in a given state of the atmosphere, such as for quantifying the ozone budget.

  4. Dual Mechanisms of Metabolite Acquisition by the Obligate Intracytosolic Pathogen Rickettsia prowazekii Reveal Novel Aspects of Triose Phosphate Transport

    OpenAIRE

    Frohlich, Kyla M.; Audia, Jonathon P.

    2013-01-01

    Rickettsia prowazekii is an obligate intracytosolic pathogen and the causative agent of epidemic typhus fever in humans. As an evolutionary model of intracellular pathogenesis, rickettsiae are notorious for their use of transport systems that parasitize eukaryotic host cell biochemical pathways. Rickettsial transport systems for substrates found only in eukaryotic cell cytoplasm are uncommon among free-living microorganisms and often possess distinctive mechanisms. We previously reported that...

  5. Main aspects in licensing of a type B(U) package design for the transport of 12.95 PBq of cobalt 60

    International Nuclear Information System (INIS)

    This paper points out the relevant technical issues related to the licensing process, of a type B(U) package design, with cylindrical form and 9.3 ton mass, approved by the Argentine Competent Authority for the transport of 12.95 PBq of cobalt 60 as special form radioactive material. It is briefly described the heat transfer analysis, the structural performance under impulsive loads and the shielding calculation under both normal and accidental conditions of transport, as well as the comparative analysis of the results obtained from design, pre-operational tests and independent evaluation performed by the Argentine Competent Authority to verify the compliance with the Regulations for the Safe Transport of Radioactive Material of the International Atomic Energy Agency. (author). 14 refs., 1 fig., tabs

  6. The allosteric regulatory mechanism of the Escherichia coli MetNI methionine ATP binding cassette (ABC) transporter.

    Science.gov (United States)

    Yang, Janet G; Rees, Douglas C

    2015-04-01

    The MetNI methionine importer of Escherichia coli, an ATP binding cassette (ABC) transporter, uses the energy of ATP binding and hydrolysis to catalyze the high affinity uptake of D- and L-methionine. Early in vivo studies showed that the uptake of external methionine is repressed by the level of the internal methionine pool, a phenomenon termed transinhibition. Our understanding of the MetNI mechanism has thus far been limited to a series of crystal structures in an inward-facing conformation. To understand the molecular mechanism of transinhibition, we studied the kinetics of ATP hydrolysis using detergent-solubilized MetNI. We find that transinhibition is due to noncompetitive inhibition by L-methionine, much like a negative feedback loop. Thermodynamic analyses revealed two allosteric methionine binding sites per transporter. This quantitative analysis of transinhibition, the first to our knowledge for a structurally defined transporter, builds upon the previously proposed structurally based model for regulation. This mechanism of regulation at the transporter activity level could be applicable to not only ABC transporters but other types of membrane transporters as well. PMID:25678706

  7. Dysregulation of glutamine transporter SNAT1 in Rett syndrome microglia: a mechanism for mitochondrial dysfunction and neurotoxicity.

    Science.gov (United States)

    Jin, Lee-Way; Horiuchi, Makoto; Wulff, Heike; Liu, Xiao-Bo; Cortopassi, Gino A; Erickson, Jeffrey D; Maezawa, Izumi

    2015-02-11

    Rett syndrome (RTT) is an autism spectrum disorder caused by loss-of-function mutations in the gene encoding MeCP2, an epigenetic modulator that binds the methyl CpG dinucleotide in target genes to regulate transcription. Previously, we and others reported a role of microglia in the pathophysiology of RTT. To understand the mechanism of microglia dysfunction in RTT, we identified a MeCP2 target gene, SLC38A1, which encodes a major glutamine transporter (SNAT1), and characterized its role in microglia. We found that MeCP2 acts as a microglia-specific transcriptional repressor of SNAT1. Because glutamine is mainly metabolized in the mitochondria, where it is used as an energy substrate and a precursor for glutamate production, we hypothesize that SNAT1 overexpression in MeCP2-deficient microglia would impair the glutamine homeostasis, resulting in mitochondrial dysfunction as well as microglial neurotoxicity because of glutamate overproduction. Supporting this hypothesis, we found that MeCP2 downregulation or SNAT1 overexpression in microglia resulted in (1) glutamine-dependent decrease in microglial viability, which was corroborated by reduced microglia counts in the brains of MECP2 knock-out mice; (2) proliferation of mitochondria and enhanced mitochondrial production of reactive oxygen species; (3) increased oxygen consumption but decreased ATP production (an energy-wasting state); and (4) overproduction of glutamate that caused NMDA receptor-dependent neurotoxicity. The abnormalities could be rectified by mitochondria-targeted expression of catalase and a mitochondria-targeted peptide antioxidant, Szeto-Schiller 31. Our results reveal a novel mechanism via which MeCP2 regulates bioenergetic pathways in microglia and suggest a therapeutic potential of mitochondria-targeted antioxidants for RTT. PMID:25673846

  8. “Green” fuel tax on private transportation services and subsidies to electric energy. A model-based assessment for the main European countries

    International Nuclear Information System (INIS)

    This paper evaluates the environmental and macroeconomic implications for France, Germany, Italy and Spain of taxing motor vehicle fuels for private transportation, a sector not subject to the Emissions Trading System, so as to reduce taxes on electricity consumption and increase subsidies to renewable sources of electricity generation. The assessment is based on a dynamic general equilibrium model calibrated for each of the four countries. The results suggest that the measures posited will reduce carbon dioxide emissions in the transportation sector and favor the development of electricity generation from renewable sources, thus limiting the growth of emissions from electricity generation. The measures do not jeopardize economic activity. The results are robust whether implementation is unilateral in one country or simultaneous throughout the EU. - Highlights: • The European Union's Agenda 2020 calls for member countries to reduce greenhouse gas emissions and increase renewable energy. • We evaluate implications in the EU of taxing fuels for private transportation, reducing taxes on electricity and increase subsidies to renewable sources of electricity. • The assessment is based on a dynamic general equilibrium model. • The measures reduce emissions, in particular in the transportation sector, favor electricity generation from renewable sources and do not jeopardize economic activity

  9. Heikkila's mechanism for impulsive plasma transport through the magnetopause: A reexamination

    International Nuclear Information System (INIS)

    It has been proposed by Heikkila (1982) that the impact upon a magnetically open magnetopause current sheet of a cloud of magnetosheath plasma having excess momentum will result in the transport of the cloud through the sheet, forming a plasma boundary layer located on both open and closed flux tubes in the interior. A reexamination of Heikkila's work shows, however, that the argument which was used to arrive at that conclusion is not correct. The error arises from the assumption that the induction electric field which is associated with the perturbation of the currect sheet will produce a flow which is just such as to cause the plasma to move with the sheet. This is not the case. The flow normal to the current sheet which is produced by the induction electric field alone will in general be less than the speed of the sheet itself, continuity being maintained by flows directed along the perturbed current layer. If it is assumed, with Heikkila, that the induction electric field component which is parallel to the magnetic field component which threads the open magnetopause is cancelled to zero by a curl-free charge-separation electric field, then the tangential electric field and normal flow are indeed increased, as argued by Heikkila, but only to the point where the flow just matches the speed of the boundary, and not to a speed which is in excess of the latter, as claimed. Heikkila's mechanism does not therefore lead to impulsive transport of magnetosheath plasma through the boundary onto open and closed magnetospheric flux tubes in the interior. Consequently, magnetosheath plasma can indeed flow through the open magnetopause to form a boundary layer inside the magnetosphere, but this layer will be confined to open flux tubes adjacent to the boundary as in reconnection models. Boundary layers are not formed on adjacent closed flux tubes by these means

  10. Charge carrier transport mechanisms in perovskite CdTiO{sub 3} fibers

    Energy Technology Data Exchange (ETDEWEB)

    Imran, Z.; Rafiq, M. A., E-mail: aftab@cantab.net; Hasan, M. M. [Micro and Nano Devices Group, Department of Metallurgy and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), P.O. Nilore, Islamabad, 45650 (Pakistan)

    2014-06-15

    Electrical transport properties of electrospun cadmium titanate (CdTiO{sub 3}) fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000?°C yielded the single phase perovskite fibers having diameter ?600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K – 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC) with traps at higher voltages at all temperatures (200 K – 420 K). Trap density in our fibers system is N{sub t} = 6.27 × 10{sup 17} /cm{sup 3}. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH) from 200 K – 300 K. The localized density of states were found to be N(E{sub F}) = 5.51 × 10{sup 21} eV{sup ?1} cm{sup ?3} at 2 V. Other VRH parameters such as hopping distance (R{sub hop}) and hopping energy (W{sub hop}) were also calculated. In the high temperature range of 320 K – 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO{sub 3} fibers efficient material for capacitive energy storage devices.

  11. Chalcopyrite solar cells: Formation of the buffer / absorber interface and related transport mechanisms

    International Nuclear Information System (INIS)

    Full text : It was investigated the chemistry and electronics as well as the related transport mechanisms of low-gap chalcopyrite Cu(In1-xGax)Se2- (CIGSe; Ga/(In+Ga) = 0.24) and wide-gap CuGaSe2- (CGSe; 0.94 ? Ga/Cu ? 1.39) based solar cells by addressing the following issues: (1) condition of the absorber surface, (2) condition of the buffer layer preparation, and (3) thermal annealing of the devices. The chemical structure is investigated by applying heavy-ion elastic recoil detection analysis (ERDA), non-destructive x-ray photoelectron spectroscopy (XPS) and x-ray emission spectroscopy (XES). The electronic structure is investigated by UV photoelectron spectroscopy (UPS) and Kelvin probe force microscopy (KPFM) in UHV (p ? 10-10 mbar). The device transport properties have been investigated by illumination- and temperature-dependent current-voltage [J(V,T)] measurements. As a result, for respective solar cells we find that independently from the absorber bulk composition the dominant recombination process takes place at the buffer/absorber interface. However, while in devices from near-stoichiometric absorbers a tunnelling enhanced interface recombination takes place competitively at CdS/CuGaSe2 - CdS/CuGa3Se5 interfaces, in solar cells from Ga-rich absorbers a dominant thermally activated Shockley-Read-Hall recombination via deep levels in the CuGa3Se5 layer occur at the buffer/absorber interface. Furthermore, it was found that the monotonic increase of the devices open circuit voltages is determined by the monotonic variation of the potential barrier of recombination

  12. Theoretical analysis of selectivity mechanisms in molecular transport through channels and nanopores

    International Nuclear Information System (INIS)

    Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed

  13. Paddle-wheel versus percolation mechanism for cation transport in some sulphate phases

    DEFF Research Database (Denmark)

    Andersen, N.H.; Bandaranyake, P.W.S.K.

    1992-01-01

    Lithium sulphate and a few other compounds have high temperature phases which are both solid electrolytes and plastic crystals (rotor phases). Three types of experiments are here considered in order to test the validity of a "paddle-wheel mechanism" that has been proposed for cation conductivity in these phases. A single-crystal neutron diffraction study has been performed for cubic lithium sulphate. The refinement of the data gives a very complex model for the location of the lithium ions. There is definitely a void at and near the octahedral (1/2, 1/2, 1/2) position. 90% of the lithium ions are located at the tetrahedral 8c-sites (1/4, 1/4, 1/4), although significantly distorted in the directions of the four neighbouring sulphate ions. The remaining 10% of the lithium ions are refined as an evenly distributed spherical shell which is surrounding the sulphate ions. The lithium ions are transported along a slightly curved pathway of continuous lithium occupation corresponding to a distance of about 3.7 angstrom. Thus, lithium transport occurs in one of the six directions [110], [110BAR], [101] etc. The electrical conductivity has been studied for solid solutions of lithium tungstate in cubic lithium sulphate. The conductivity is reduced in the one-phase region, while it is increased in a two phase (solid-melt) region. There are pronounced differences between the rotor phases and other phases concerning how partial cation substitution affects the electrical conductivity of solid solutions. Regarding self and interdiffusion, all studied mono- and divalent cations are very mobile in the rotor phases, which lack the pronounced correlation with ionic radii that is characteristic for diffusion in other classes of solid electrolytes. The quoted studies are to be considered as strong evidence against a percolation model proposed by Secco.

  14. Mechanism of Nitrate-N Transport in Surface Water and Groundwater in a Missourian Claypan Watershed

    Science.gov (United States)

    Liu, F.; Lerch, R. N.; Yang, J.; Baffaut, C.

    2014-12-01

    Nitrogen (N) fertilizer applications have resulted in widespread surface water and groundwater nitrate-N (NO3-N) contamination in the U.S. Corn Belt. However, the processes that control NO3-N concentrations in both surface water and groundwater were not well understood, particularly for claypan-dominated watersheds. The objective of this study was to understand the processes that control the transport of NO3-N in/from surface water and/to groundwater in Goodwater Creek Experimental Watershed (GCEW), a claypan-dominated watershed in north-central Missouri. The mean nitrate-N concentration in groundwater determined from more than 2000 samples collected during 1991 - 2004 was approximately three times that in stream water at GCEW. Despite the low hydraulic conductivity of the claypan soils, considerable NO3-N contamination of the glacial till aquifer occurred, with 38% of the wells exceeding 10 mg l-1. Groundwater recharge by preferential pathways through the claypan appeared to be the primary mechanism for NO3-N movement to the aquifer. In comparison, only 19-23% of sampled wells in non-claypan agricultural watersheds over the continental U.S. exceeded 10 mg l-1, suggesting that groundwater in GCEW appears to be more susceptible to NO3-N contamination than non-claypan watersheds. Using endmember mixing analysis based on conservative tracers, stream flow during the relatively low flow periods was primarily from surface runoff, shallow subsurface water and groundwater, with an average contribution of 25%, 44% and 31% from 2011 to 2014, respectively. Stable isotopic values of nitrate (d15N, d18O and D17O) also demonstrated that groundwater exerted a major control on nitrate concentrations in stream water. This information greatly improves our understanding of the processes that control NO3-N transport to the groundwater system of claypan-dominated watersheds.

  15. Charge carrier transport mechanisms in perovskite CdTiO3 fibers

    Directory of Open Access Journals (Sweden)

    Z. Imran

    2014-06-01

    Full Text Available Electrical transport properties of electrospun cadmium titanate (CdTiO3 fibers have been investigated using ac and dc measurements. Air annealing of as spun fibers at 1000 °C yielded the single phase perovskite fibers having diameter ∼600 nm - 800 nm. Both the ac and dc electrical measurements were carried out at temperatures from 200 K – 420 K. The complex impedance plane plots revealed a single semicircular arc which indicates the interfacial effect due to grain boundaries of fibers. The dielectric properties obey the Maxwell-Wagner theory of interfacial polarization. In dc transport study at low voltages, data show Ohmic like behavior followed by space charge limited current (SCLC with traps at higher voltages at all temperatures (200 K – 420 K. Trap density in our fibers system is Nt = 6.27 × 1017 /cm3. Conduction mechanism in the sample is governed by 3-D variable range hopping (VRH from 200 K – 300 K. The localized density of states were found to be N(EF = 5.51 × 1021 eV−1 cm−3 at 2 V. Other VRH parameters such as hopping distance (Rhop and hopping energy (Whop were also calculated. In the high temperature range of 320 K – 420 K, conductivity follows the Arrhenius law. The activation energy found at 2 V is 0.10 eV. Temperature dependent and higher values of dielectric constant make the perovskite CdTiO3 fibers efficient material for capacitive energy storage devices.

  16. Study on transportation and accumulation mechanisms of cesium in Camellia sinensis by SR-XRF imaging

    International Nuclear Information System (INIS)

    After the tragedy in Fukushima, soil and food pollution by radionuclides has become a serious problem. Cs can be uptaken by many plants due to its chemical similarities with K. So, removal of radioactive Cs from the soils can be carried out using the phytoremediation technology. However, the development of phytoremediation techniques require the knowledge on the interactions between the plants and soils. Although the competitive relation between K and Cs to enter the plant is known, few works were dedicated to the visual localization of Cs in the plant and its relation to potassium. In this study, we have used synchrotron radiation X-ray fluorescence (SR-XRF) imaging in order to reveal accumulation of Cs with a cellular spatial resolution. The Cs L? intensity measured in the XRF imaging were transformed into the Cs concentration based on the calibration curves prepared using in house standard samples of known Cs concentrations. It is remarkable that after exposure to 10 ppm Cs solution for 4 weeks Camellia sinensis accumulated Cs up to 300 ppm (expressed in dry weight) in the body. XRF imaging of the root show that Cs was located mainly at the epidermis. On the other hand, K was located mainly at endodermis and the cell wall. A correlation coefficient(R) between XRF intensity of K and that of Cs in the root was about R=0.5. This suggest that Cs is hardly absorbed from roots of Camellia sinensis compared with K, due to its large ionic radius. In the case of stem, distribution of Cs was similar to that of K. They were located at the exodermis, epidermis and the cell wall. Their correlation coefficient was about R=0.8. These results suggest that Cs was transported through the same pathway as that of K in the stem. (author)

  17. Mechanism of lipid mobilization by the small intestine after transport blockade

    International Nuclear Information System (INIS)

    The nonionic detergent, Pluronic L-81 (L-81) has been shown to block the transport of intestinal mucosal triacylglycerol (TG) in chylomicrons. This results in large lipid masses within the enterocyte that are greater in diameter than chylomicrons. On removal of L-81, mucosal TG is rapidly mobilized and appears in the lymph. We questioned whether the blocked TG requires partial or complete hydrolysis before its transport. Rats were infused intraduodenally with [3H]glyceryl, [14C]oleoyl trioleate (TO) and 0.5 mg L-81/h for 8 h, followed by 120 mumol/h linoleate for 18 h. Mesenteric lymph was collected and analyzed for TG content and radioactivity. An HPLC method was developed to separate TG on the basis of its acyl group species. The assumed acyl group composition was confirmed by gas liquid chromatography analysis. TG lymphatic output was low for the first 8 h but increased to 52 mumol/h at the 11th h of infusion (3 h after stopping L-81). 38% of the infused TO was retained in the mucosa after the 8-h infusion. 95% of mucosal TG was TO, 92% of the radioactivity was in TG, and 2.4% of the 14C disintegrations per minute was in fatty acid. HPLC analysis of lymph at 6, 10, 12, and 14.5 h of infusion showed a progressive rise in TG composed of one linoleate and two oleates, to 39%; and in TG composed of two linoleates and one oleate to 20% at 14.5 h of infusion. On a mass basis, however, 80% of the TG acyl groups were oleate. 3H/14C ratios in the various TG acyl group species reflected the decrease in oleate. We conclude that first, unlike liver, most mucosal TG is not hydrolyzed before transport. The mechanism of how the large lipid masses present in mucosal cells after L-81 infusion are converted to the much smaller chylomicrons is unknown. Second, the concomitant infusion of linoleate did not impair lymph TG delivery after L-81 blockade

  18. Fibre bundle formulation of nonrelativistic quantum mechanics; 4, Mixed states and evolution transport's curvature

    CERN Document Server

    Iliev, Bozhidar Z

    1999-01-01

    We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one but it is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it a pure state of some quantum system is described by a state section (along paths) of a (Hilbert) fibre bundle. It's evolution is determined through the bundle (analogue of the) Schrödinger equation. Now the dynamical variables and the density operator are described via bundle morphisms (along paths). The mentioned quantities are connected by a number of relations derived in this work. The present fourth part of this series is devoted mainly to the fibre bundle description of mixed quantum states. We show that to the conventional density operator there corresponds a unique density morphism (along paths) for which the corresponding equations of motion are derived. It is also investigated the bundle description of mixed quantu...

  19. Oxygen transport in perovskite-type solid oxide fuel cell materials: insights from quantum mechanics.

    Science.gov (United States)

    Muñoz-García, Ana B; Ritzmann, Andrew M; Pavone, Michele; Keith, John A; Carter, Emily A

    2014-11-18

    CONSPECTUS: Global advances in industrialization are precipitating increasingly rapid consumption of fossil fuel resources and heightened levels of atmospheric CO2. World sustainability requires viable sources of renewable energy and its efficient use. First-principles quantum mechanics (QM) studies can help guide developments in energy technologies by characterizing complex material properties and predicting reaction mechanisms at the atomic scale. QM can provide unbiased, qualitative guidelines for experimentally tailoring materials for energy applications. This Account primarily reviews our recent QM studies of electrode materials for solid oxide fuel cells (SOFCs), a promising technology for clean, efficient power generation. SOFCs presently must operate at very high temperatures to allow transport of oxygen ions and electrons through solid-state electrolytes and electrodes. High temperatures, however, engender slow startup times and accelerate material degradation. SOFC technologies need cathode and anode materials that function well at lower temperatures, which have been realized with mixed ion-electron conductor (MIEC) materials. Unfortunately, the complexity of MIECs has inhibited the rational tailoring of improved SOFC materials. Here, we gather theoretically obtained insights into oxygen ion conductivity in two classes of perovskite-type materials for SOFC applications: the conventional La1-xSrxMO3 family (M = Cr, Mn, Fe, Co) and the new, promising class of Sr2Fe2-xMoxO6 materials. Using density functional theory + U (DFT+U) with U-J values obtained from ab initio theory, we have characterized the accompanying electronic structures for the two processes that govern ionic diffusion in these materials: (i) oxygen vacancy formation and (ii) vacancy-mediated oxygen migration. We show how the corresponding macroscopic oxygen diffusion coefficient can be accurately obtained in terms of microscopic quantities calculated with first-principles QM. We find that the oxygen vacancy formation energy is a robust descriptor for evaluating oxide ion transport properties. We also find it has a direct relationship with (i) the transition metal-oxygen bond strength and (ii) the extent to which electrons left behind by the departing oxygen delocalize onto the oxygen sublattice. Design principles from our QM results may guide further development of perovskite-based MIEC materials for SOFC applications. PMID:24972154

  20. Main findings

    International Nuclear Information System (INIS)

    Licensing regimes vary from country to country. When the license regime involves several regulators and several licenses, this may lead to complex situations. Identifying a leading organisation in charge of overall coordination including preparation of the licensing decision is a useful practice. Also, if a stepwise licensing process is implemented, it is important to fix in legislation decisions and/or time points and to identify the relevant actors. There is considerable experience in civil and mining engineering that can be applied when constructing a deep geological disposal facility. Specific challenges are, however, the minimization of disturbances to the host rock and the understanding of its long-term behavior. Construction activities may affect the geo-hydraulic and geochemical properties of the various system components which are important safety features of the repository system. Clearly defined technical specifications and an effective quality management plan are important in ensuring successful repository implementation which is consistent with safety requirements. Monitoring plan should also be defined in advance. The regulatory organization should prepare itself to the licensing review before construction by allocating sufficient resources. It should increase its competence, e.g., by interacting early with the implementer and through its own R and D. This will allow the regulator to define appropriate technical conditions associated to the construction license and to elaborate a relevant inspection plan of the construction work. After construction, obtaining the operational license is the most important and crucial step. Main challenges include (a) establishing sufficient confidence so that the methods for closing the individual disposal units comply with the safety objectives and (b) addressing the issue of ageing of materials during a 50-100 years operational period. This latter challenge is amplified when reversibility/retrievability is required. Managing concomitant construction of new galleries with continuing operation and/or closure in the existing galleries remains as another challenge. There is a need, during the project, to address targets very different in nature and which may potentially compete with each other. Alternative solutions are typically compared and evaluated with a view to lower potential impacts and risks to workers, people and the environment in the short and the long term to as low as reasonably practicable. This is often called 'radiological optimisation'. In repository development, the set of target functions can be much broader, blurring the meaning of 'optimisation'. The visibility and importance to optimisation for licensing varies from country to country, and it may take different names

  1. Computational modelling of thermo-mechanical and transport properties of carbon nanotubes

    International Nuclear Information System (INIS)

    Over the recent years, numerical modelling and computer-based simulation of the properties of carbon nanotubes have become the focal points of research in computational nano-science and its associated fields of computational condensed matter physics and materials modelling. Modelling of the mechanical, thermal and transport properties of nanotubes via numerical simulations forms the central part of this research, concerned with the nano-scale mechanics and nano-scale thermodynamics of nanotubes, and nano-scale adsorption, storage and flow properties in nanotubes. A review of these properties, obtained via computational modelling studies, is presented here. We first introduce the physics of carbon nanotubes, and then present the computational simulation tools that are appropriate for conducting a modelling study at the nano-scales. These include the molecular dynamics (MD), the Monte Carlo (MC), and the ab initio MD simulation methods. A complete range of inter-atomic potentials, of two-body and many-body varieties, that underlie all the modelling studies considered in this review is also given. Mechanical models from continuum-based elasticity theory that have been extensively employed in computing the energetics of nanotubes, or interpret the results from atomistic modelling, are presented and discussed. These include models based on the continuum theory of curved plates, shells, vibrating rods and bending beams. The validity of these continuum-based models has also been examined and the conditions under which they are applicable to nanotube modelling have been listed. Pertinent concepts from continuum theories of stress analysis are included, and the relevant methods for conducting the computation of the stress tensor, elastic constants and elastic modulii at the atomic level are also given. We then survey a comprehensive range of modelling studies concerned with the adsorption and storage of gases, and flow of fluids, in carbon nanotubes of various types. This is then followed by an extensive survey of the numerical modelling investigations that have addressed the mechanical and thermal properties of these structures. The survey of modelling studies is supplemented by reviews of experimental investigations, where appropriate, to help clarify their results

  2. Multi-Path Transportation Futures Study. Vehicle Characterization and Scenario Analyses: Main Text and Appendices A, B, C, D, and F

    Energy Technology Data Exchange (ETDEWEB)

    Plotkin, Steve [Argonne National Lab. (ANL), Argonne, IL (United States); Singh, Margaret [Argonne National Lab. (ANL), Argonne, IL (United States); Patterson, Phil [U.S. Dept. of Energy, Washington, DC (United States); Ward, Jake [U.S. Dept. of Energy, Washington, DC (United States); Wood, Frances [OnLocation Inc., Vienna, VA (United States); Kydes, Niko [OnLocation Inc., Vienna, VA (United States); Holte, John [OnLocation Inc., Vienna, VA (United States); Moore, Jim [TA Engineering, Inc., Catonsville, MD (United States); Miller, Grant [TA Engineering, Inc., Catonsville, MD (United States); Das, Sujit [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Greene, David [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2009-07-22

    This report provides details for Phase 2 of the Multi-Path Transportation Futures Study, which compares alternative ways to make significant reductions in oil use and carbon emissions from U.S. light vehicles to 2050. Phase I, completed in 2009, examined the full range of pathways of interest to EERE, with multiple scenarios aimed at revealing the issues and impacts associated with a national effort to reduce U.S. dependence on oil use in transportation. Phase 2 expanded the scope of the analysis by examining the interactive effects of multiple pathways on each other and on oil and feedstock prices, focusing far more on costs; and substantially increasing the number of metrics used to compare pathways and scenarios.

  3. An evaluation of perfomance management in the Department of Public Works, Roads and Transport of the North West Privince / S. E Maine

    OpenAIRE

    Maine, S E

    2014-01-01

    Effective performance management is vital in all public and private sectors and contributes to service delivery of the organisations. Research on public-sector performance management, however, points out challenges in the implementation of the systems and questions the effectiveness of policy tools for enhancing the governmental accountability. The Department of Public Works, Roads and Transport is a large institution and its vision is to provide successful infrastructure projects...

  4. Electric vehicles and renewable energy in the transport sector - energy system consequences. Main focus: Battery electric vehicles and hydrogen based fuel cell vehicles

    DEFF Research Database (Denmark)

    Nielsen, L.H.; JØrgensen K., no-firstname

    2000-01-01

    The aim of the project is to analyse energy, environmental and economic aspects of integrating electric vehicles in the future Danish energy system. Consequences of large-scale utilisation of electric vehicles are analysed. The aim is furthermore toillustrate the potential synergistic interplay between the utilisation of electric vehicles and large-scale utilisation of fluctuating renewable energy resources, such as wind power. Economic aspects for electric vehicles interacting with a liberalisedelectricity market are analysed. The project focuses on battery electric vehicles and fuel cell vehicles based on hydrogen. Based on assumptions on the future technical development for battery electric vehicles, fuel cell vehicles on hydrogen, and forthe conventional internal combustion engine vehicles, scenarios are set up to reflect expected options for the long-term development of road transport vehicles. Focus is put on the Danish fleet of passenger cars and delivery vans. The scenario analysisincludes assumptions on market potential developments and market penetration for the alternative vehicles. Vehicle replacement rates in the Danish transport fleet and the size of fleet development are based on data from The Danish Road Directorate. Theelectricity supply system development assumed is based on the Danish energy plan, Energy 21, The Plan scenario. The time horizon of the analysis is year 2030. Results from the scenario analysis include the time scales involved for the potentialtransition towards electricity based vehicles, the fleet composition development, the associated developments in transport fuel consumption and fuel substitution, and the potential CO2-emission reduction achievable in the overall transport and powersupply system. Detailed model simulations, on an hourly basis, have furthermore been carried out for year 2005 that address potential electricity purchase options for electric vehicles in the context of a liberalised electricity market. The baselineelectricity market considered comprises a spot market and a balance market. The structure chosen for the baseline spot market is close to the structure of the Nord Pool electricity market, and the structure of the balance or regulatory market is close tothe Norwegian model.

  5. Reaction mechanisms in transport theories: a test of the nuclear effective interaction

    International Nuclear Information System (INIS)

    We review recent results concerning collective excitations in neutron-rich systems and reactions between charge asymmetric systems at Fermi energies. Solving numerically self-consistent transport equations for neutrons and protons with specific initial conditions, we explore the structure of the different dipole vibrations in the 132Sn system and investigate their dependence on the symmetry energy. We evidence the existence of a distinctive collective mode, that can be associated with the Pygmy Dipole Resonance, with an energy well below the standard Giant Dipole Resonance and isoscalar-like character, i.e. very weakly dependent on the isovector part of the nuclear effective interaction. At variance, the corresponding strength is rather sensitive to the behavior of the symmetry energy below saturation, which rules the number of excess neutrons in the nuclear surface. In reactions between charge asymmetric systems at Fermi energies, we investigate the interplay between dissipation mechanisms and isospin effects. Observables sensitive to the isospin dependent part of nuclear interaction are discussed, providing information on the symmetry energy density dependence below saturation.

  6. Carrier transport mechanisms of hybrid ZnO nanorod-polymer LEDs

    International Nuclear Information System (INIS)

    A hybrid polymer-nanorod (NR) light-emitting diode (LED), consisting of a hole-conducting polymer poly (9-vinyl carbazole) (PVK) and ZnO nanorod (NR) composite, with the device structure of glass/indium-tin-oxide (ITO)/PEDOT:PSS/(PVK + ZnO nanorods)/Al is fabricated through a simple spin coating technique. TEM images shows inhomogeneous deposition and the agglomeration of ZnO NRs, which is explained through their low probability of adsorption on PVK due to two-dimensional structural property. In the current-voltage characteristics, negative differential resistance (NDR) phenomenon is observed corresponding to device structure without ZnO NRs. The carrier transport behavior in the LED device is well described by both ohmic and space-charge-limited-current (SCLC) mechanisms. Broad blue electroluminescence (EL) consisting of two sub peaks, are centered at 441 nm and the other at 495 nm, is observed, which indicates that the ZnO nanorod play a role as a recombination center for excitons. The red shift in the position of the EL compared to that photoluminescence is well explained through band offsets at the heterojunction between the PVK and ZnO NRs.

  7. Red blood cell transport mechanisms in polyester thread-based blood typing devices.

    Science.gov (United States)

    Nilghaz, Azadeh; Ballerini, David R; Guan, Liyun; Li, Lizi; Shen, Wei

    2016-02-01

    A recently developed blood typing diagnostic based on a polyester thread substrate has shown great promise for use in medical emergencies and in impoverished regions. The device is easy to use and transport, while also being inexpensive, accurate, and rapid. This study used a fluorescent confocal microscope to delve deeper into how red blood cells were behaving within the polyester thread-based diagnostic at the cellular level, and how plasma separation could be made to visibly occur on the thread, making it possible to identify blood type in a single step. Red blood cells were stained and the plasma phase dyed with fluorescent compounds to enable them to be visualised under the confocal microscope at high magnification. The mechanisms uncovered were in surprising contrast with those found for a similar, paper-based method. Red blood cell aggregates did not flow over each other within the thread substrate as expected, but suffered from a restriction to their flow which resulted in the chromatographic separation of the RBCs from the liquid phase of the blood. It is hoped that these results will lead to the optimisation of the method to enable more accurate and sensitive detection, increasing the range of blood systems that can be detected. Graphical Abstract Agglutinated FITC stained A+ blood on anti-A antibody treated thread. Sheet like structures composed of agglutinated RBCs can be seen, wrapped around fibres and occupying the spaces between them. PMID:26163133

  8. Carrier transport mechanisms of hybrid ZnO nanorod-polymer LEDs

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Sungjae; Lee, Kyuseung; Son, Dongick [Korea Institute of Science and Technology, Wanju (Korea, Republic of); Oh, Youngjei; Choi, Wonkook [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Angadi, Basavaraj [Bangalore University, Bangalore (India)

    2014-07-15

    A hybrid polymer-nanorod (NR) light-emitting diode (LED), consisting of a hole-conducting polymer poly (9-vinyl carbazole) (PVK) and ZnO nanorod (NR) composite, with the device structure of glass/indium-tin-oxide (ITO)/PEDOT:PSS/(PVK + ZnO nanorods)/Al is fabricated through a simple spin coating technique. TEM images shows inhomogeneous deposition and the agglomeration of ZnO NRs, which is explained through their low probability of adsorption on PVK due to two-dimensional structural property. In the current-voltage characteristics, negative differential resistance (NDR) phenomenon is observed corresponding to device structure without ZnO NRs. The carrier transport behavior in the LED device is well described by both ohmic and space-charge-limited-current (SCLC) mechanisms. Broad blue electroluminescence (EL) consisting of two sub peaks, are centered at 441 nm and the other at 495 nm, is observed, which indicates that the ZnO nanorod play a role as a recombination center for excitons. The red shift in the position of the EL compared to that photoluminescence is well explained through band offsets at the heterojunction between the PVK and ZnO NRs.

  9. Threshold switching mechanism by high-field energy gain in the hopping transport of chalcogenide glasses

    Science.gov (United States)

    Ielmini, Daniele

    2008-07-01

    Chalcogenide glasses are widely used in phase-change nonvolatile memories and in optical recording media for their ability to rapidly change their structure to crystalline, thus obtaining different electrical resistance and optical reflectivity. Chalcogenide glasses universally display threshold switching, that is a sudden, reversible transition from a high-resistivity state to a low-resistivity state observed in the current-voltage (I-V) characteristic. Since threshold switching controls the operating voltage and speed of phase-change memories, the predictability of the switching voltage, current, and speed is of critical importance for selecting the proper chalcogenide material for memory applications. Although threshold switching has long been recognized to be an electronic process with an intimate relation to localized states, its detailed physical mechanism is still not clear. In this work, threshold switching is explained by the field-induced energy increase in electrons in their hopping transport, moderated by the energy relaxation due to phonon-electron interaction. The energy increase leads to an enhancement of conductivity and a collapse of the electric field within the amorphous chalcogenide layer, accounting for the observed negative differential resistance at switching. Threshold switching is found to obey to a constant electrical-power condition. The proposed model generally applies to low-mobility semiconductors featuring a deep Fermi level and hopping-type conduction, and can predict the thickness, temperature, and material dependence of threshold voltage and current.

  10. Electric vehicles and renewable energy in the transport sector - energy system consequences. Main focus: Battery electric vehicles and hydrogen based fuel cell vehicles

    International Nuclear Information System (INIS)

    The aim of the project is to analyse energy, environmental and economic aspects of integrating electric vehicles in the future Danish energy system. Consequences of large-scale utilisation of electric vehicles are analysed. The aim is furthermore to illustrate the potential synergistic interplay between the utilisation of electric vehicles and large-scale utilisation of fluctuating renewable energy resources, such as wind power. Economic aspects for electric vehicles interacting with a liberalised electricity market are analysed. The project focuses on battery electric vehicles and fuel cell vehicles based on hydrogen. Based on assumptions on the future technical development for battery electric vehicles, fuel cell vehicles on hydrogen, and for the conventional internal combustion engine vehicles, scenarios are set up to reflect expected options for the long-term development of road transport vehicles. Focus is put on the Danish fleet of passenger cars and delivery vans. The scenario analysis includes assumptions on market potential developments and market penetration for the alternative vehicles. Vehicle replacement rates in the Danish transport fleet and the size of fleet development are based on data from The Danish Road Directorate. The electricity supply system development assumed is based on the Danish energy plan, Energy 21, The Plan scenario. The time horizon of the analysis is year 2030. Results from the scenario analysis include the time scales involved for the potential transition towards electricity based vehicles, the fleet composition development, the associated developments in transport fuel consumption and fuel substitution, and the potential CO2-emission reduction achievable in the overall transport and power supply system. Detailed model simulations, on an hourly basis, have furthermore been carried out for year 2005 that address potential electricity purchase options for electric vehicles in the context of a liberalised electricity market. The baseline electricity market considered comprises a spot market and a balance market. The structure chosen for the baseline spot market is close to the structure of the Nord Pool electricity market, and the structure of the balance or regulatory market is close to the Norwegian model. (au)

  11. Investigating radionuclide bearing suspended sediment transport mechanisms in the Ribble estuary using airborne remote sensing

    International Nuclear Information System (INIS)

    BNFL Sellafield has been authorised to discharge radionuclides to the Irish Sea since 1952. In the aquatic environment the radionuclides are adsorbed by sediments and are thus redistributed by sediment transport mechanisms. This sediment is known to accumulate in the estuaries of the Irish Sea. BNFL Springfields is also licensed to discharge isotopically different radionuclides directly to the Ribble estuary. Thus there is a need to understand the sediment dynamics of the Ribble estuary in order to understand the fate of these radionuclides within the Ribble estuary. Estuaries are highly dynamic environments that are difficult to monitor using the conventional sampling techniques. However, remote sensing provides a potentially powerful tool for monitoring the hydrodynamics of the estuarine environment by providing data that are both spatially and temporally representative. This research develops a methodology for mapping suspended sediment concentration (SSC) in the Ribble estuary using airborne remote sensing. The first hypothesis, that there is a relationship between SSC and 137Cs concentration is proven in-situ (R2=0.94), thus remotely sensed SSC can act as a surrogate for 137Cs concentration. Initial in-situ characterisation of the suspended sediments was investigated to identify spatial and temporal variability in grain size distributions and reflectance characteristics for the Ribble estuary. Laboratory experiments were then performed to clearly define the SSC reflectance relationship, identify the optimum CASI wavelengths for quantifying SSC and to demonstrate the effects on reflectance of the environmental variables of salinity and clay content. Images were corrected for variation in solar elevation and angle to give a ground truth calibration for SSC, with an R2=0.76. The remaining scatter in this relationship was attributed to the differences in spatial and temporal representation between sampling techniques and remote sensing. The second hypothesis assumes that a series of images over a flood tide can be animated to provide information on the hydrodynamic regime, erosion, and deposition. Spatial and temporal data demonstrated the complex controls on sediment transport. The data also showed the importance of microphytobenthos in the stabilisation of intertidal sediments, highlighting their importance in defining sources and sinks of radionuclides in intertidal areas. Water volume data from the VERSE model were combined with SSC from the imagery to calculate the total sediment in suspension for each flight line. This provided the figures used to determine total erosion and deposition, which were then used to derive net suspended sediment and 137Cs influxes of 2.01x106 kg and 604MBq per flood tide. (author)

  12. Molecular mechanism of ?-tocopheryl-phosphate transport across the cell membrane

    International Nuclear Information System (INIS)

    ?-Tocopheryl-phosphate (?-TP) is synthesized and hydrolyzed in animal cells and tissues where it modulates several functions. ?-TP is more potent than ?-T in inhibiting cell proliferation, down-regulating CD36 transcription, inhibiting atherosclerotic plaque formation. Administration of ?-TP to cells or animals requires its transfer through membranes, via a transporter. We show here that ?-TP is passing the plasma membrane via a system that is inhibited by glibenclamide and probenecid, inhibitors of a number of transporters. Glibenclamide and probenecid prevent dose-dependently ?-TP inhibition of cell proliferation. The two inhibitors act on ATP binding cassette (ABC) and organic anion transporters (OAT). Since ABC transporters function to export solutes and ?-TP is transported into cells, it may be concluded that ?-TP transport may occur via an OAT family member. Due to the protection by glibenclamide and probenecid on the ?-TP induced cell growth inhibition it appears that ?-TP acts after its uptake inside cells

  13. Electrical transport and EPR investigations: A comparative study for d.c. conduction mechanism in monovalent and multivalent ions doped polyaniline

    Indian Academy of Sciences (India)

    Suresh Kumar Gupta; Vandna Luthra; Ramadhar Singh

    2012-10-01

    A detailed comparative study of electron paramagnetic resonance (EPR) in conjunction with d.c. electrical conductivity has been undertaken to know about the charge transport mechanism in polyaniline (PANI) doped with monovalent and multivalent protonic acids. This work is in continuation of our previous work for further understanding the conduction mechanism in conducting polymers. The results reveal that the polarons and bipolarons are the main charge carriers formed during doping process and these cause increase in electrical conductivity not only by increase in their concentration but also because of their enhanced mobility due to increased inter-chain transport in polyaniline at high doping levels. EPR line asymmetry having Dysonian line shape for highly doped samples shows a marked deviation of amplitudes / ratio from values close to one to much high values as usually observed in metals, thereby support the idea of high conductivity at higher doping levels. The nature of dopant ions and their doping levels control the charge carriers concentration as well as electrical conductivity of polyaniline. The electrical conductivity has also been studied as a function of temperature to know the thermally assisted transport process of these charge carriers at different doping levels which has been found to follow the Mott’s variable range hopping (VRH) conduction model for all the three dopants used. The charge carriers show a change over from 3D VRH to quasi 1D VRH hopping process for multivalent ions at higher doping levels whereas 1D VRH has been followed by monovalent ion for full doping range. These studies collectively give evidence of inter-chain percolation at higher doping levels causing increase in effective mobility of the charge carriers which mainly seems to govern the electrical conduction behaviour in this system.

  14. Evaluation of potential sources and transport mechanisms of fecal indicator bacteria to beach water, Murphy Park Beach, Door County, Wisconsin

    Science.gov (United States)

    Juckem, Paul F.; Corsi, Steven R.; McDermott, Colleen; Kleinheinz, Gregory; Fogarty, Lisa R.; Haack, Sheridan K.; Johnson, Heather E.

    2013-01-01

    Fecal Indicator Bacteria (FIB) concentrations in beach water have been used for many years as a criterion for closing beaches due to potential health concerns. Yet, current understanding of sources and transport mechanisms that drive FIB occurrence remains insufficient for accurate prediction of closures at many beaches. Murphy Park Beach, a relatively pristine beach on Green Bay in Door County, Wis., was selected for a study to evaluate FIB sources and transport mechanisms. Although the relatively pristine nature of the beach yielded no detection of pathogenic bacterial genes and relatively low FIB concentrations during the study period compared with other Great Lakes Beaches, its selection limited the number of confounding FIB sources and associated transport mechanisms. The primary sources of FIB appear to be internal to the beach rather than external sources such as rivers, storm sewer outfalls, and industrial discharges. Three potential FIB sources were identified: sand, swash-zone groundwater, and Cladophora mats. Modest correlations between FIB concentrations in these potential source reservoirs and FIB concentrations at the beach from the same day illustrate the importance of understanding transport mechanisms between FIB sources and the water column. One likely mechanism for transport and dispersion of FIB from sand and Cladophora sources appears to be agitation of Cladophora mats and erosion of beach sand due to storm activity, as inferred from storm indicators including turbidity, wave height, current speed, wind speed, sky visibility, 24-hour precipitation, and suspended particulate concentration. FIB concentrations in beach water had a statistically significant relation (p-value ‹0.05) with the magnitude of these storm indicators. In addition, transport of FIB in swash-zone groundwater into beach water appears to be driven by groundwater recharge associated with multiday precipitation and corresponding increased swash-zone groundwater discharge at the beach, as indicated by an increase in the specific conductance of beach water. Understanding the dynamics of FIB sources (sand, swash-zone groundwater, and Cladophora) and transport mechanisms (dispersion and erosion from storm energy, and swash-zone groundwater discharge) is important for improving predictions of potential health risks from FIB in beach water.

  15. Mechanical, sorption and transport experiments on a German high volatile bituminous coal

    Energy Technology Data Exchange (ETDEWEB)

    Gensterblum, Y.; Krooss, B.M. [RWTH Aachen Univ. (Germany). Inst. of Geology and Geochemistry of Petroleum and Coal; Massarotto, Paul [Queensland Univ., Brisbane, St Lucia, QLD (Australia). School of Engineering

    2013-08-01

    A high volatile bituminous coal (vitrinite reflectance: 0.93%, carbon content: 83%) from the Prosper-Haniel mine, North Rhine-Westphalia has been studied using a comprehensive set of measurements and experimental procedures at RWTH Aachen University and the University of Queensland. Using the True Triaxial Stress Coal Permeameter (TTSCP) (Massarotto 2003) of the University of Queensland, permeability and gas displacement tests were performed on an 80 mm cube of the Prosper-Haniel coal. Extensive data sets were recorded to assess the effects of stress changes on gas transport and the impact of nitrogen, methane and CO{sub 2} sorption on the mechanical properties. We investigate the permeability coefficients for helium, nitrogen, methane and carbon dioxide measured on this sample as a function of net stress. As expected, permeability values decrease with increasing stress. Methane and nitrogen have nearly identical permeability coefficients throughout the entire net stress range, while permeability coefficients measured with helium are higher and those measured with CO{sub 2} significantly lower. During the permeability measurements with CO{sub 2} an anisotropic swelling of the coal cube by about 0.19% to 0.23% was observed. The volumetric effect (swelling) is 100 times slower than gas displacement. Simultaneous mechanical tests indicated a softening of the coal block upon exposure to CO{sub 2}. Thus, a decrease of Young's modulus (YM) of the coal cube during the CO{sub 2} flow test was observed as compared to the methane and nitrogen tests. High-pressure sorption isotherms with CH{sub 4} and CO{sub 2} were determined on different grain-size fractions of the Prosper-Haniel coal at 318K and different moisture contents. Methane sorption capacity decreases by 29% with increasing moisture content. Also, a decrease of sorption rate was observed with increasing moisture content. While sorption rates are generally faster for CO{sub 2} than for CH{sub 4}, the sorption rates of CH{sub 4} and CO{sub 2} at a moisture content of 1.6 % were nearly identical. The results of this study are compared with those of similar experiments performed on a other sets of coals (Busch and Gensterblum, 2011). Finally several theoretical models to predict the reservoir permeability as a function of reservoir pressure has been tested. (orig.)

  16. Electric vehicles and renewable energy in the transport sector - energy system consequences. Main focus: Battery electric vehicles and hydrogen based fuel cell vehicles

    DEFF Research Database (Denmark)

    Nielsen, L.H.; Jørgensen K.

    2000-01-01

    vehicles. Focus is put on the Danish fleet of passenger cars and delivery vans. The scenario analysisincludes assumptions on market potential developments and market penetration for the alternative vehicles. Vehicle replacement rates in the Danish transport fleet and the size of fleet development are based...... between the utilisation of electric vehicles and large-scale utilisation of fluctuating renewable energy resources, such as wind power. Economic aspects for electric vehicles interacting with a liberalisedelectricity market are analysed. The project focuses on battery electric vehicles and fuel cell...... furthermore been carried out for year 2005 that address potential electricity purchase options for electric vehicles in the context of a liberalised electricity market. The baselineelectricity market considered comprises a spot market and a balance market. The structure chosen for the baseline spot market is...

  17. The role of biomembrane lipids in the molecular mechanism of ion transport radiation damage

    International Nuclear Information System (INIS)

    Increase in the rate of ATP synthesis (I.4-I.6 times), Ca2+-capacity (I.4-I.8 times), membrane potential (by 20-50 mv) and decrease in K--conductivity (2.5-3 times) in rat liver mitochondria was observed three hours after ?-irradiation at a dose of 1000r. The process of oxidative phosphorylation was normalized 24 hours later, whereas damages of Ca2+-accumulation and K+-conductivity remain. The molecular mechanism of reduction in K+-permeability of mitochondrial membranes has been studied. The endogenous regulators of ionic transport in the lipid phase of mitochondrial biomembranes were investigated before and after ?-irradiation. It was revealed that K+-conductivity of the artificial phospholipid membranes (APM) formed of the phospholipids from irradiated mitochondria was substantially lower than that in the control. Using thin-layer chromatography the minor phospholipid fraction which increases K+-conductivity of APM was isolated from the lipids of unirradiated mitochondria. In the lipid preparations of irradiated mitochondria the minor phospholipid fraction content is sharply lowered (or absent at all). Besides the content of lysoforms of phosphatidylcholine and phosphatidylethanolamine as well as that of fatty acids and cholesterol esters were reduced 24 hours after irradiation. Three compounds with different capability to increase the APM conductivity for monovalent ions were revealed in the composition of the minor fraction. One of these components was shown to be lysopolyglycerophosphatide (lysodiphosphatidylglycerol). The role of the enzyme systems involved in radiational changes of the membrane lipid components and the importance of these phenomena for cell radiosensitivity will be discussed

  18. Two-Dimensional Hopping Conductivity: Experimental Evidence for a Novel Electron Transport Mechanism

    International Nuclear Information System (INIS)

    Results are presented of measurements of two-dimensional (2D) variable-range-hopping (VRH) conductivity and magnetoresistance (MR) in a delta-doped GaAs/AlGaAs heterostructure. It is shown that at zero magnetic field and low temperatures (T xx(T) exhibits 'Coulomb-gap behavior': ρ(T) =: ρ0exp(T0/T)1/2 with the pre factor ρ0 = (h/e2) which is independent of temperature and electron density. This value of po exactly coincides with that observed by Mason et al. in a different material - Si-MOSFET. Universality of the hopping pre factor is considered as evidence that in some interval of electron densities close to the metal-insulator transition, the 2D VRH is assisted by the electron-electron interaction (EEI), rather than by conventional electron-phonon interaction. Experimental data show that (i) existence of a delta-doped layer in the proximate vicinity of the 2D conducting plane favors EEI-assisted VRH, and (ii) a strong magnetic field parallel to the 2D plane leads to the suppression of the EEI-assistance and the restoration of the conventional phonon-assisted hopping. To interpret these experimental observations, a novel electron transport mechanism is suggested, according to which the current-carrying single electron move via quantum resonant tunneling between localized states, brought into resonance by fast electron hops in their environment. The last hops can be assisted by phonons; however, the phonon frequency does not appear in the final expression for the current-carrying transition rate

  19. A simple modeling approach to elucidate the main transport processes and predict invasive spread: River-mediated invasion of Ageratina adenophora in China

    Science.gov (United States)

    Horvitz, Nir; Wang, Rui; Zhu, Min; Wan, Fang-Hao; Nathan, Ran

    2014-12-01

    A constantly increasing number of alien species invade novel environments and cause enormous damage to both biodiversity and economics worldwide. This global problem is calling for better understanding of the different mechanisms driving invasive spread, hence quantification of a range of dispersal vectors. Yet, methods for elucidating the mechanisms underlying large-scale invasive spread from empirical patterns have not yet been developed. Here we propose a new computationally efficient method to quantify the contribution of different dispersal vectors to the spread rate of invasive plants. Using data collected over 30 years regarding the invasive species Ageratina adenophora since its detection at the Sichuan province, we explored its spread by wind and animals, rivers, and roads into 153 subcounties in the Sichuan, Chongqingshi, and Hubei provinces of China. We found that rivers are the most plausible vector for the rapid invasion of this species in the study area. Model explorations revealed robustness to changes in key assumptions and configuration. Future predictions of this ongoing invasion process project that the species will quickly spread along the Yangtze River and colonize large areas within a few years. Further model developments would provide a much needed tool to mechanistically and realistically describe large-scale invasive spread, providing insights into the underlying mechanisms and an ability to predict future spatial invasive dynamics.

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

    International Nuclear Information System (INIS)

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

  1. Comparison of mechanical and manual ventilation during transport of patients to the intensive care unit after cardiac surgery

    Directory of Open Access Journals (Sweden)

    Atilla Canbulat

    2012-12-01

    Full Text Available Objectives: We compared effects of mechanical andmanual ventilation during transport to the intensive careunit(ICU in cardiac surgeries.Materials and methods: After ethical approval, 66 patients(ASAgrade II and III, 20-80years were assignedrandomly. Ventilation during transport to ICU was performedmanual (Group EV; n=36 or mechanical ventilation(Group MV; n=30. Measurements were recorded:operation room (A, during transport (T and in ICU (YB.Systolic, diastolic pressures (SAP, DAP, pulmonary arterialpressure (PAP, pulmonary capillary wedge pressure(PCWP, central venous pressure (CVP, heart rate (HR,cardiac output (CO, blood gases (pH, PCO2, PO2, BEand peripheral oxygen saturation (SpO2 were recorded.Stroke volume index (SVI, systemic and pulmonary vascularresistance indices (SVRI, PVRI and mean arterialpressures(MAP were calculated.Results: Patients were similar. Duration of transportwas shorter in Group MV (p< 0.01. The alterations inHR, MAP, DAP, CVP, PAP, PCWP, PVRI, SVRI, SVI, CO,SpO2 were similar, the increase in SAP during T periodwas higher in Group MV (p<0.05. Pulmonary arterial pHin Group MV was lower (p< 0.05. Arterial and pulmonaryarterial pO2, pCO2 decreased in Group MV, there was increasein Group EV during ICU (p< 0.001, p< 0.01, p<0.01, p< 0.05. During T period hypotension and tachycardiain Group EV, and hypertension in Group MV wereobserved.Conclusions: Mechanical ventilation had short transporttime, less alterations in hemodynamic and respiration valuesand less complication rates. We concluded that theuse of mechanical ventilation is a safer method for theintrahospital transport of critical patients. J Clin Exp Invest2012; 3(4: 521-528Key words: Cardiac surgery, patient transport, mechanicalventilator, manual ventilator, hemodynamia

  2. Structure and molecular mechanism of a nucleobase-cation-symport-1 family transporter

    DEFF Research Database (Denmark)

    Weyand, Simone; Shimamura, Tatsuro; Yajima, Shunsuke; Suzuki, Shun'ichi; Mirza, Osman Asghar; Krusong, Kuakarun; Carpenter, Elisabeth P; Rutherford, Nicholas G; Hadden, Jonathan M; O'Reilly, John; Ma, Pikyee; Saidijam, Massoud; Patching, Simon G; Hope, Ryan J; Norbertczak, Halina T; Roach, Peter C J; Iwata, So; Henderson, Peter J F; Cameron, Alexander D

    2008-01-01

    The nucleobase-cation-symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 trans...

  3. Transport mechanisms in low-resistance ohmic contacts to p-InP formed by rapid thermal annealing

    DEFF Research Database (Denmark)

    Clausen, Thomas; Leistiko, Otto

    1993-01-01

    Thermionic emission across a very small effective Schottky barrier (0-0.2 eV) are reported as being the dominant transport process mechanism in very low-resistance ohmic contacts for conventional AuZn(Ni) metallization systems top-InP formed by rapid thermal annealing. The barrier modulation process is related to interdiffusion and compound formation between the metal elements and the InP. The onset of low specific contact resistance is characterized by a change in the dominant transport mechani...

  4. Deposition patterns and transport mechanisms for the endocrine disruptor 4-nonylphenol across the Sierra Nevada Mountains, California.

    Science.gov (United States)

    Lyons, Rebecca; Van de Bittner, Kyle; Morgan-Jones, Sean

    2014-12-01

    Dust and particulate distribution patterns are shifting as global climate change brings about longer drought periods. Particulates act as vehicles for long range transport of organic pollutants, depositing at locations far from their source. Nonylphenol, a biodegradation product of nonylphenol polyethoxylate, is a known endocrine disruptor. Nonylphenol polyethoxylate enters the environment as an inert ingredient in pesticide sprays, potentially traveling great distances from its application site. This is of concern when a highly agricultural region, California's Central Valley, lies adjacent to sensitive areas like the Eastern Sierra Nevada Mountains. The distribution and transport mechanisms for 4-nonylphenol were investigated in Eastern Sierra Nevada canyons. Regions close to canyon headwalls showed trace amounts of 4-nonylphenol in surface water, snow, and atmospheric deposition. Exposed areas had yearly average concentrations as high as 9 ?g/L. Distribution patterns are consistent with particulate-bound transport. This suggests with increasing drought periods, higher levels of persistent organic pollutants are likely. PMID:25215456

  5. Mechanisms affecting the transport and retention of bacteria, bacteriophage and microspheres in laboratory-scale saturated fractures

    Science.gov (United States)

    Seggewiss, G.; Dickson, S. E.

    2013-12-01

    Groundwater is becoming an increasingly important water source due to the ever-increasing demands from agricultural, residential and industrial consumers. In search of more secure sources, wells are routinely finished over large vertical depths in bedrock aquifers, creating new hydraulic pathways and thus increasing the risk of cross contamination. Moreover, hydraulic pathways are also being altered and created by increasing water withdrawal rates from these wells. Currently, it is not well understood how biological contaminants are transported through, and retained in, fractured media thereby making risk assessment and land use decisions difficult. Colloid transport within fractured rock is a complex process with several mechanisms affecting transport and retention, including: advection, hydrodynamic dispersion, diffusion, size exclusion, adsorption, and decay. Several researchers have investigated the transport of bacteria, bacteriophage, and microspheres (both carboxylated and plain) to evaluate the effects of surface properties and size on transport and retention. These studies have suggested that transport is highly dependent on the physico-chemical properties of the particle, the fracture, and the carrying fluid. However, these studies contain little detail regarding the specific mechanisms responsible for transport beyond speculating about their existence. Further, little work has been done to compare the transport of these particulate materials through the same fracture, allowing for direct observations based on particulate size and surface properties. This research examines the similarities and differences in transport and retention between four different particles through two different laboratory-scale, saturated fractures. This work is designed to explore the effects of particle size, surface properties, ionic strength of the carrying solution, and aperture field characteristics on transport and retention in single, saturated fractures. The particulates chosen for this work include E.coli RS2-GFP, MS2, and carboxylated microspheres with diameters of 0.0425 ?m and 0.525 ?m. The results of this work will contribute to the understanding of risk posed by contaminants to bedrock aquifer sources. Dolomite rock samples were collected from the DoLime quarry in Guelph, Ontario. A single fracture was induced in the sample by applying a uniaxial force. Lengthwise edges were sealed to create no-flow boundaries, and flow cells were fitted on the up- and down-stream ends of the fracture. Aperture size and variability were characterized using hydraulic and solute tracer tests. Particulate tracer tests were conducted by injecting a pulse of particles (E.coli RS2-GFP, MS2, or microspheres) into the upstream flow cell, and measuring the subsequent effluent concentration profile. From these tests, the percent recovery and mean residence time of the particulate were analyzed. Generally, it was found that microspheres are a poor indication of biological particulate transport, likely due to differences in surface properties affecting the retention mechanisms. This talk will provide an analysis of the breakthrough curves, with specific details regarding the transport and retention mechanisms for the various types and sizes of particles employed in these experiments.

  6. The cytotoxicity of the ?1-adrenoceptor antagonist prazosin is linked to an endocytotic mechanism equivalent to transport-P.

    Science.gov (United States)

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

    2015-12-01

    Since the ?1-adrenergic antagonist prazosin (PRZ) was introduced into medicine as a treatment for hypertension and benign prostate hyperplasia, several studies have shown that PRZ induces apoptosis in various cell types and interferes with endocytotic trafficking. Because PRZ is also able to induce apoptosis in malignant cells, its cytotoxicity is a focus of interest in cancer research. Besides inducing apoptosis, PRZ was shown to serve as a substrate for an amine uptake mechanism originally discovered in neurones called transport-P. In line with our hypothesis that transport-P is an endocytotic mechanism also present in non-neuronal tissue and linked to the cytotoxicity of PRZ, we tested the uptake of QAPB, a fluorescent derivative of PRZ, in cancer cell lines in the presence of inhibitors of transport-P and endocytosis. Early endosomes and lysosomes were visualised by expression of RAB5-RFP and LAMP1-RFP, respectively; growth and viability of cells in the presence of PRZ and uptake inhibitors were also tested. Cancer cells showed co-localisation of QAPB with RAB5 and LAMP1 positive vesicles as well as tubulation of lysosomes. The uptake of QAPB was sensitive to transport-P inhibitors bafilomycin A1 (inhibits v-ATPase) and the antidepressant desipramine. Endocytosis inhibitors pitstop(®) 2 (general inhibitor of endocytosis), dynasore (dynamin inhibitor) and methyl-?-cyclodextrin (cholesterol chelator) inhibited the uptake of QAPB. Bafilomycin A1 and methyl-?-cyclodextrin but not desipramine were able to preserve growth and viability of cells in the presence of PRZ. In summary, we confirmed the hypothesis that the cellular uptake of QAPB/PRZ represents an endocytotic mechanism equivalent to transport-P. Endocytosis of QAPB/PRZ depends on a proton gradient, dynamin and cholesterol, and results in reorganisation of the LAMP1 positive endolysosomal system. Finally, the link seen between the cellular uptake of PRZ and cell death implies a still unknown pro-apoptotic membrane protein with affinity towards PRZ. PMID:26449523

  7. ABC transporters as multidrug resistance mechanisms and the development of chemosensitizers for their reversal

    Directory of Open Access Journals (Sweden)

    Choi Cheol-Hee

    2005-10-01

    Full Text Available Abstract One of the major problems related with anticancer chemotherapy is resistance against anticancer drugs. The ATP-binding cassette (ABC transporters are a family of transporter proteins that are responsible for drug resistance and a low bioavailability of drugs by pumping a variety of drugs out cells at the expense of ATP hydrolysis. One strategy for reversal of the resistance of tumor cells expressing ABC transporters is combined use of anticancer drugs with chemosensitizers. In this review, the physiological functions and structures of ABC transporters, and the development of chemosensitizers are described focusing on well-known proteins including P-glycoprotein, multidrug resistance associated protein, and breast cancer resistance protein.

  8. Mechanism of active transport: Free energy dissipation and free energy transduction

    OpenAIRE

    Tanford, C.

    1983-01-01

    The thermodynamic pathway for "chemiosmotic" free energy transduction in active transport is discussed with an ATP-driven Ca2+ pump as an illustrative example. Two innovations are made in the analysis. (i) Free energy dissipated as heat is rigorously excluded from overall free energy bookkeeping by focusing on the dynamic equilibrium state of the chemiosmotic process. (ii) Separate chemical potential terms for free energy donor and transported ions are used to keep track of the thermodynamic ...

  9. Introduction of Organic Anion Transporters (SLC22A) and a Regulatory Mechanism by Caveolins

    OpenAIRE

    Lee, Woon Kyu; Jung, Sun-Mi; Kwak, Jin-Oh; Cha, Seok Ho

    2006-01-01

    The kidney is an important organ for controlling the volume of body fluids, electrolytic balance and excretion/reabsorption of endogenous and exogenous compounds. Among these renal functions, excretion/reabsorption of endogenous and exogenous substance is very important for the maintenance of physiological homeostasis in the body. Recently discovered organic anion transporters (OAT or SLC22A) have important roles for renal functions. It is well known as drug transporter. Several isoforms belo...

  10. Evidence of transport, sedimentation and coagulation mechanisms in the relaxation of post-volcanic stratospheric aerosols

    OpenAIRE

    Fussen, D.; Vanhellemont, F.; Bingen, C.

    2001-01-01

    Spatio-temporal distributions of stratospheric aerosols, measured by the ORA instrument from August 1992 until May 1993, are presented in the latitude range (40° S–40° N). Particle total number density, mode radius and distribution width are derived and interpreted. The respective roles of advection, sedimentation and coagulation are discussed. We also identify clear transport/sedimentation patterns and we show the enhancement of coagulation in stagnation regions. Efficient transport o...

  11. Integrated evaluation of aerogenic pollution by air-transported heavy metals (Pb, Cd, Ni, Zn, Mn and Cu) in the analysis of the main deposit media.

    Science.gov (United States)

    Baltr?nait?, Edita; Baltr?nas, Pranas; Lietuvninkas, Arvydas; Serevi?ien?, Vaida; Zuokait?, Egl?

    2014-01-01

    The composition of the ambient air is constantly changing; therefore, the monitoring of ambient air quality to detect the changes caused by aerogenic pollutants makes the essential part of general environmental monitoring. To achieve more effective improvement of the ambient air quality, the Directive 2008/50/EC on 'Ambient Air Quality and Cleaner Air for Europe' was adopted by the European Parliament and the European Council. It informed the public and enterprises about a negative effect of pollution on humans, animals and plants, as well as about the need for monitoring aerogenic pollutants not only at the continuous monitoring stations but also by using indicator methods, i.e. by analysing natural deposit media. The problem of determining the relationship between the accumulation level of pollutants by a deposit medium and the level of air pollution and its risks is constantly growing in importance. The paper presents a comprehensive analysis of the response of the main four deposit media, i.e. snow cover, soil, pine bark and epigeic mosses, to the long-term pollution by aerogenic pollutants which can be observed in the area of oil refinery influence. Based on the quantitative expressions of the amounts of the accumulated pollutants in the deposit media, the territory of the oil refinery investigated in this paper has been referred to the areas of mild or moderate pollution. PMID:23933956

  12. Transport mechanisms for synoptic, seasonal and interannual SF6 variations and "age" of air in troposphere

    Directory of Open Access Journals (Sweden)

    K. Miyazaki

    2009-02-01

    Full Text Available We use an atmospheric general circulation model (AGCM driven chemistry-transport model (ACTM to simulate the evolution of sulfur hexafluoride (SF6 in the troposphere. The model results are compared with continuous measurements at 6 sites over 71° N–90° S. These comparisons demonstrate that the ACTM simulations lie within the measurement uncertainty over the analysis period (1999–2006 and capture salient features of synoptic, seasonal and interannual SF6 variability. To understand transport timescales of SF6 within the troposphere, transport times of air parcels from the surface to different regions of the troposphere ("age" are estimated from a simulation of an idealized tracer. The age estimation error and its sensitivity to the selection of reanalysis meteorology for ACTM nudging or the tracer transport by deep cumulus convection as represented in the model are discussed. Monthly-mean, 2-box model exchange times (?ex are calculated from both the observed and simulated SF6 time series at the 6 observing sites and show favorable agreement, suggesting that the ACTM adequately represents large-scale interhemispheric transport. The simulated SF6 variability is further investigated through decomposition of the mixing ratio time-tendency into advective, convective, and vertical diffusive components. The transport component analysis illustrates the role of each process in SF6 synoptic variability at the site level and provides insight into the seasonality of ?ex.

  13. Study of mechanical and thermal transport properties of Cis- and Trans-polyisoprene blends in low temperature range

    Science.gov (United States)

    Baboo, Mahesh; Sharma, Kananbala; Saxena, N. S.

    2014-10-01

    Measurements of mechanical and thermal transport properties have been carried out on the samples of polyisoprene (Cis and Trans) blends prepared by solution casting, in the temperature range from 173K to 273K using Dynamic Mechanical Analyzer and Transient Plane Source Technique, respectively. Results show that a sudden change is observed in the values of tan ?, storage modulus (G), thermal conductivity (?) and heat capacity per unit volume (?cp) at the glass transition temperature. Also the values of G, ? and ?cp have been observed higher for all the three blends as compared to their pure components. The variation of all these properties has been explained on the basis of crystallinity and crosslink density.

  14. Mechanisms controlling surface ozone over East Asia: a multiscale study coupling regional and global chemical transport models

    OpenAIRE

    Lin, M.; HOLLOWAY, T; Oki, T.; Streets, D. G.; Richter, A.

    2008-01-01

    Mechanisms controlling surface ozone (O3) over East Asia are examined using the regional Community Multiscale Air Quality (CMAQ) model at two horizontal scales: 81 km and 27 km. Through sensitivity studies and comparison with recently available satellite data and surface measurements in China and Japan, we find that the O3 budget over East Asia shows complex interactions among photochemical production, regional transport, meteorological conditions...

  15. Functional characterization of the vertebrate primary ureter: Structure and ion transport mechanisms of the pronephric duct in axolotl larvae (Amphibia)

    DEFF Research Database (Denmark)

    Haugan, Birgitte M; Halberg, Kenneth Agerlin; Jespersen, Åse; Prehn, Lea R; Møbjerg, Nadja

    2010-01-01

    layered epithelium consisting of one cell type comparable to the principal cell of the renal collecting duct system. The cells are characterized by a prominent basolateral labyrinth and a relatively smooth apical surface with one central cilium. Cellular impalements demonstrate the presence of apical Na...... collecting duct system, which provides a model of cell structure and basic mechanisms for ion transport. Such information may be important in understanding the evolution of vertebrate kidney systems and human diseases associated with congenital malformations....

  16. Adenoviral-Mediated Placental Gene Transfer of IGF-1 Corrects Placental Insufficiency via Enhanced Placental Glucose Transport Mechanisms

    OpenAIRE

    Jones, Helen N.; Crombleholme, Timothy; Habli, Mounira

    2013-01-01

    Previous work in our laboratory demonstrated that over-expression of human insulin-like growth factor -1 (hIGF-1) in the placenta corrects fetal weight deficits in mouse, rat, and rabbit models of intrauterine growth restriction without changes in placental weight. The underlying mechanisms of this effect have not been elucidated. To investigate the effect of intra-placental IGF-1 over-expression on placental function we examined glucose transporter expression and localization in both a mouse...

  17. Influence of supplementary cementitious materials on water transport kinetics and mechanical properties of hydrated lime and cement mortars

    OpenAIRE

    Ince, C.; Derogar, S.; Michelitsch, T. M.

    2015-01-01

    The purpose of this paper is an investigation of the possible role of supplementary cementitious materials (SCMs) on water transport kinetics and mechanical properties of hydrated lime (CL90) and Portland cement (PC) mortars. The properties of hydrated lime are significantly different from those of cement and therefore modifying fresh and hardened properties of these mortars are vital for mortar/substrate optimisation in masonry construction. The parameters investigated in this paper often ar...

  18. Metaiodobenzylguanidine [131I] scintigraphy detects impaired myocardial sympathetic neuronal transport function of canine mechanical-overload heart failure

    International Nuclear Information System (INIS)

    In heart failure secondary to chronic mechanical overload, cardiac sympathetic neurons demonstrate depressed catecholamine synthetic and transport function. To assess the potential of sympathetic neuronal imaging for detection of depressed transport function, serial scintigrams were acquired after the intravenous administration of metaiodobenzylguanidine [131I] to 13 normal dogs, 3 autotransplanted (denervated) dogs, 5 dogs with left ventricular failure, and 5 dogs with compensated left ventricular hypertrophy due to a surgical arteriovenous shunt. Nine dogs were killed at 14 hours postinjection for determination of metaiodobenzylguanidine [131I] and endogenous norepinephrine content in left atrium, left ventricle, liver, and spleen. By 4 hours postinjection, autotransplanted dogs had a 39% reduction in mean left ventricular tracer accumulation, reflecting an absent intraneuronal tracer pool. Failure dogs demonstrated an accelerated early mean left ventricular tracer efflux rate (26.0%/hour versus 13.7%/hour in normals), reflecting a disproportionately increased extraneuronal tracer pool. They also showed reduced late left ventricular and left atrial concentrations of tracer, consistent with a reduced intraneuronal tracer pool. By contrast, compensated hypertrophy dogs demonstrated a normal early mean left ventricular tracer efflux rate (16.4%/hour) and essentially normal late left ventricular and left atrial concentrations of tracer. Metaiodobenzylguanidine [131I] scintigraphic findings reflect the integrity of the cardiac sympathetic neuronal transport system in canine mechanical-overload heart failure. Metaiodobenzylguanidine [123I] scintigraphy should be explored as a means of early detection of mechanical-overload heart failure in patients

  19. The transport mechanism of the human sodium/myo-inositol transporter 2 (SMIT2/SGLT6), a member of the LeuT structural family.

    Science.gov (United States)

    Sasseville, Louis J; Longpré, Jean-Philippe; Wallendorff, Bernadette; Lapointe, Jean-Yves

    2014-09-01

    The sodium/myo-inositol transporter 2 (SMIT2) is a member of the SLC5A gene family, which is believed to share the five-transmembrane segment inverted repeat of the LeuT structural family. The two-electrode voltage-clamp (TEVC) technique was used to measure the steady-state and the pre-steady-state currents mediated by human SMIT2 after expression in Xenopus laevis oocytes. Phlorizin is first shown to be a poor inhibitor of pre-steady-state currents for depolarizing voltage pulse. From an up to threefold difference between the apparent ON and OFF transferred charges during a voltage pulse, we also show that a fraction of the transient current recorded for very negative potentials is not a true pre-steady-state current coming from the cotransporter conformational changes. We suggest that this transient current comes from a time-dependent leak current that can reach large amplitudes when external Na(+) concentration is reduced. A kinetic model was generated through a simulated annealing algorithm. This algorithm was used to identify the optimal connectivity among 19 different kinetic models and obtain the numerical values of the associated parameters. The proposed 5-state model includes cooperative binding of Na(+) ions, strong apparent asymmetry of the energy barriers, a rate-limiting step that is likely associated with the translocation of the empty transporter, and a turnover rate of 21 s(-1). The proposed model is a proof of concept for a novel approach to kinetic modeling of electrogenic transporters and allows insight into the transport mechanism of members of the LeuT structural family at the millisecond timescale. PMID:24944204

  20. Determinación de los principales parámetros de calidad que afectan la cosecha mecanizada de arroz / Determination of the main quality parameters that affect the mechanical harvest of rice

    Scientific Electronic Library Online (English)

    Alexander, Miranda Caballero; Ciro E, Iglesias Coronel; Erwin, Herrera González; Nathali, Abraham Ferro; Santiago, Castells Hernández.

    2010-12-01

    Full Text Available El presente trabajo tiene como objetivo analizar la calidad de la cosecha mecanizada de la semilla de arroz, realizada por las cosechadoras de arroz New Holland L521, en las condiciones de trabajo del Complejo Agroindustrial (CAI) Arrocero "Los Palacios". Fueron evaluados los parámetros tecnológicos [...] de la cosechadora en función de la calidad del producto cosechado, tales como: grano entero, pelado y/o quebrado, contenido de impurezas y pérdidas totales. Los resultados obtenidos para los parámetros estudiados indican que para las cosechadoras New Holland L 521 el comportamiento del grano pelado y/o quebrado en los cinco rendimientos agrícolas diferentes observados tomó valores de 5,2-6,4% y el contenido de impurezas estuvo entre 8,3-9,6%, encontrándose ambos parámetros por encima de los límites establecidos, influyendo principalmente en este aspecto la mala regulación de los órganos de trilla, la velocidad trabajo y la mala capacitación de los operadores. La aplicación de estos resultados le permite al CAI Arrocero "Los Palacios" disminuir las pérdidas durante la cosecha se redujeron las pérdidas de 206 kg/ha hasta 85 kg/ha, lo que representa un efecto económico de $ 316 202.04 pesos cubanos y a la vez permite dejar de invertir aproximadamente por la compra del arroz cáscara para ser procesado para la alimentación de nuestra población 184 793.4 USD. Abstract in english The present paper has as objective to analyze quality parameters that affect the mechanical harvest of the seed of rice, carried out by the New Holland L521 rice harvester machine, under the conditions of work of the Rice Enterprise "Los Palacios" the cropper's technological parameters were evaluate [...] d in function of the quality of the harvested product, such as: seed entirely, peeled broken and content of sludges and total losses. The results obtained for the studied parameters indicate that for the New Holland L521 rice harvester machine the behavior of the grain peeled y/o broken in the five observed different agricultural yields took values of 5,2-6,4% and the content of sludges was among 8,3-9,6%, being both parameters above the established limits, influencing mainly in this aspect the bad regulation of the organs of it thrashes, the speed work and the bad training of the operators. The application of these results allows him to the Rice Enterprise "Los Palacios to diminish the losses during the crop decreased the losses of 206 kg/ha up to 85 kg/ha, what represents an economic effect of $316 202.04 Cuban pesos and at the same time allows to stop to invest approximately for the purchase of the rice shell to be processed for our population's feeding 184 793.4 USD.

  1. Theoretical study and design of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane and intended for cooling of gas transported in a gas-main pipeline

    KAUST Repository

    Petrenko, V.O.

    2011-11-01

    This paper describes the construction and performance of a novel combined system intended for natural gas transportation and power production, and for cooling of gas transported in a gas-main pipeline. The proposed system includes a gas turbine compressor, a combined electrogenerating plant and an ejector refrigeration unit operating with a hydrocarbon refrigerant. The combined electrogenerating plant consists of a high-temperature steam-power cycle and a low-temperature hydrocarbon vapor power cycle, which together comprise a binary vapor system. The combined system is designed for the highest possible effectiveness of power generation and could find wide application in gas-transmission systems of gas-main pipelines. Application of the proposed system would enable year-round power generation and provide cooling of natural gas during periods of high ambient temperature operation. This paper presents the main results of a theoretical study and design performance specifications of a low-grade heat-driven pilot ejector refrigeration machine operating with butane and isobutane. © 2010 Elsevier Ltd and IIR. All rights reserved.

  2. Estimates of Cl atom concentrations and hydrocarbon kinetic reactivity in surface air at Appledore Island, Maine (USA), during International Consortium for Atmospheric Research on Transport and Transformation/Chemistry of Halogens at the Isles of Shoals

    Science.gov (United States)

    Pszenny, Alexander A. P.; Fischer, Emily V.; Russo, Rachel S.; Sive, Barkley C.; Varner, Ruth K.

    2007-05-01

    Average hydroxyl radical (OH) to chlorine atom (Cl·) ratios ranging from 45 to 119 were determined from variability-lifetime relationships for selected nonmethane hydrocarbons (NMHC) in surface air from six different transport sectors arriving at Appledore Island, Maine, during July 2004. Multiplying these ratios by an assumed average OH concentration of 2.5 × 106 cm-3 yielded estimates of Cl· concentrations of 2.2 to 5.6 × 104 cm-3. Summed reaction rates of methane and more than 30 abundant NMHCs with OH and Cl· suggest that Cl· reactions increased the kinetic reactivity of hydrocarbons by 16% to 30% over that due to OH alone in air associated with the various transport sectors. Isoprene and other abundant biogenic alkenes were the most important hydrocarbon contributors after methane to overall kinetic reactivity.

  3. Main regularities in variations of mechanical properties and microstructure of fuel element assembly can material (steel EhP-450) irradiated in BN-600 and BN-350 reactors

    International Nuclear Information System (INIS)

    The complex of mechanical properties of steel EhP-450 fuel assembly cans irradiated in fast reactors was under study. The steel is shown to possess a high resistance to swelling as well as acceptable values of mechanical properties under tension and impact bending. Based on the results obtained a conclusion is made that in a low-temperature zone of BN-600 reactor fuel assembly cans at 15% burnup the most essential change in mechanical properties should be expected in the vicinity of a lower reactor core boundary at damaging doses of 20-40 dpa

  4. Multi-scales modeling of reactive transport mechanisms. Impact on petrophysical properties during CO2 storage

    International Nuclear Information System (INIS)

    The geo-sequestration of carbon dioxide (CO2) is an attractive option to reduce the emission of greenhouse gases. Within carbonate reservoirs, acidification of brine in place can occur during CO2 injection. This acidification leads to mineral dissolution which can modify the transport properties of a solute in porous media. The aim of this study is to quantify the impact of reactive transport on a solute distribution and on the structural modification induced by the reaction from the pore to the reservoir scale. This study is focused on reactive transport problem in the case of single phase flow in the limit of long time. To do so, we used a multi-scale up-scaling method that takes into account (i) the local scale, where flow, reaction and transport are known; (ii) the pore scale, where the reactive transport is addressed by using averaged formulation of the local equations; (iii) the Darcy scale (also called core scale), where the structure of the rock is taken into account by using a three-dimensions network of pore-bodies connected by pore-throats; and (iv) the reservoir scale, where physical phenomenon, within each cell of the reservoir model, are taken into account by introducing macroscopic coefficients deduced from the study of these phenomenon at the Darcy scale, such as the permeability, the apparent reaction rate, the solute apparent velocity and dispersion. (author)

  5. Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone

    Energy Technology Data Exchange (ETDEWEB)

    Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA; Co-Principal Investigator: Jeff Terry, Illinois Institute of Technology, Chicago, IL

    2008-05-12

    There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of the most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H{sub 2}S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H{sub 2}S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H{sub 2}S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H{sub 2}S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The primary objective of this project was to understand the complex interactions among the contaminants (i.e., Cr, Tc, and U), H{sub 2}S, and various soil constituents. The reaction with iron sulfide is also the focus of the research, which could be formed from iron oxide reduction by hydrogen sulfide. Factors controlling the reductive immobilization of these contaminants were identified and quantified. The results and fundamental knowledge obtained from this project shall help better evaluate the potential of in situ gaseous treatment to immobilize toxic and radioactive metals examined.

  6. Differential localization of ion transporters suggests distinct cellular mechanisms for calcification and photosynthesis between two coral species.

    Science.gov (United States)

    Barott, Katie L; Perez, Sidney O; Linsmayer, Lauren B; Tresguerres, Martin

    2015-08-01

    Ion transport is fundamental for multiple physiological processes, including but not limited to pH regulation, calcification, and photosynthesis. Here, we investigated ion-transporting processes in tissues from the corals Acropora yongei and Stylophora pistillata, representatives of the complex and robust clades that diverged over 250 million years ago. Antibodies against complex IV revealed that mitochondria, an essential source of ATP for energetically costly ion transporters, were abundant throughout the tissues of A. yongei. Additionally, transmission electron microscopy revealed septate junctions in all cell layers of A. yongei, as previously reported for S. pistillata, as well as evidence for transcellular vesicular transport in calicoblastic cells. Antibodies against the alpha subunit of Na(+)/K(+)-ATPase (NKA) and plasma membrane Ca(2+)-ATPase (PMCA) immunolabeled cells in the calicoblastic epithelium of both species, suggesting conserved roles in calcification. However, NKA was abundant in the apical membrane of the oral epithelium in A. yongei but not S. pistillata, while PMCA was abundant in the gastroderm of S. pistillata but not A. yongei. These differences indicate that these two coral species utilize distinct pathways to deliver ions to the sites of calcification and photosynthesis. Finally, antibodies against mammalian sodium bicarbonate cotransporters (NBC; SLC4 family) resulted in strong immunostaining in the apical membrane of oral epithelial cells and in calicoblastic cells in A. yongei, a pattern identical to NKA. Characterization of ion transport mechanisms is an essential step toward understanding the cellular mechanisms of coral physiology and will help predict how different coral species respond to environmental stress. PMID:26062631

  7. High-speed transport and magneto-mechanical resonant sensing of superparamagnetic microbeads using magnetic domain walls

    Science.gov (United States)

    Rapoport, Elizabeth

    2013-03-01

    Surface-functionalized superparamagnetic (SPM) microbeads are of great interest in biomedical research and diagnostic device engineering for tagging, manipulating, and detecting chemical and biological species in a fluid environment. Recent work has shown that magnetic domain walls (DWs) can be used to shuttle individual SPM microbeads and magnetically tagged entities across the surface of a chip. This talk will describe the dynamics of SPM microbead transport by nanotrack-guided DWs, and show how these coupled dynamics can be exploited for on-chip digital biosensing applications. Using curvilinear magnetic nanotracks, we demonstrate rapid transport of SPM microbeads at speeds approaching 1000 μm/s, and present a mechanism for selective transport at a junction that allows for the design of complex bead routing networks. We further demonstrate that a SPM bead trapped by a DW exhibits a distinct magneto-mechanical resonance that depends on its hydrodynamic characteristics in the host fluid, and that this resonance can be used for robust size-based discrimination of commercial microbead populations. By embedding a spin-valve sensor within a DW transport conduit, we show that the resonance can be detected electrically and on-the-fly. Thus, we demonstrate a complete set of essential bead handling functions, including capture, transport, identification, and release, required for an integrated lab-on-a-chip platform. In collaboration with Daniel Montana, David Bono, and Geoffrey S.D. Beach, Massachusetts Institute of Technology. This work is supported by the MIT CMSE under NSF-DMR-0819762 and by the MIT Deshpande Center.

  8. Vibrational mechanics in an optical lattice: controlling transport via potential renormalization

    CERN Document Server

    Wickenbrock, A; Wahab, N A Abdul; Phoonthong, P; Cubero, D; Renzoni, F

    2011-01-01

    We demonstrate theoretically and experimentally the phenomenon of vibrational resonance in a periodic potential, using cold atoms in an optical lattice as a model system. A high-frequency (HF) drive, with frequency much larger than any characteristic frequency of the system, is applied by phase-modulating one of the lattice beams. We show that the HF drive leads to the renormalization of the potential. We used transport measurements as a probe of the potential renormalization. The very same experiments also demonstrate that transport can be controlled by the HF drive via potential renormalization.

  9. Pseudorabies Virus Fast Axonal Transport Occurs by a pUS9-Independent Mechanism.

    Science.gov (United States)

    Daniel, Gina R; Sollars, Patricia J; Pickard, Gary E; Smith, Gregory A

    2015-08-01

    Reactivation from latency results in transmission of neurotropic herpesviruses from the nervous system to body surfaces, referred to as anterograde axonal trafficking. The virus-encoded protein pUS9 promotes axonal dissemination by sorting virus particles into axons, but whether it is also an effector of fast axonal transport within axons is unknown. To determine the role of pUS9 in anterograde trafficking, we analyzed the axonal transport of pseudorabies virus in the presence and absence of pUS9. PMID:25995254

  10. Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality

    Energy Technology Data Exchange (ETDEWEB)

    Morrison, Glenn C.

    1999-12-01

    In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10{sup {minus}7}, 10{sup {minus}5}, and 10{sup {minus}5} respectively. To understand how internal surface area influences the equivalent reaction probability of whole carpet, a model of ozone diffusion into and reaction with internal carpet components was developed. This was then used to predict apparent reaction probabilities for carpet. He combines this with a modified model of turbulent mass transfer developed by Liu, et al. to predict deposition rates and indoor ozone concentrations. The model predicts that carpet should have an equivalent reaction probability of about 10{sup {minus}5}, matching laboratory measurements of the reaction probability. For both carpet and duct materials, surfaces become progressively quenched (aging), losing the ability to react or otherwise take up ozone. He evaluated the functional form of aging and find that the reaction probability follows a power function with respect to the cumulative uptake of ozone. To understand ozone aging of surfaces, he developed several mathematical descriptions of aging based on two different mechanisms. The observed functional form of aging is mimicked by a model which describes ozone diffusion with internal reaction in a solid. He shows that the fleecy nature of carpet materials in combination with the model of ozone diffusion below a fiber surface and internal reaction may explain the functional form and the magnitude of power function parameters observed due to ozone interactions with carpet. The ozone induced aldehyde emissions, measured from duct materials, were combined with an indoor air quality model to show that concentrations of aldehydes indoors may approach odorous levels. He shows that ducts are unlikely to be a significant sink for ozone due to the low reaction probability in combination with the short residence time of air in ducts.

  11. ACIDIFICATION TRENDS AND THE EVOLUTION OF NEUTRALIZATION MECHANISMS THROUGH TIME AT THE BEAR BROOK WATERSHED IN MAINE (BBWM), U.S.A.

    Science.gov (United States)

    The paired catchment study at the forested Bear Brook Watershed in Maine (BBWM) U.S.A. documents interactions among short- to long-term processes of acidification. In 1987-1989, runoff from the two catchments was nearly identical in quality and quantity. Ammonium sulfate has been...

  12. Mechanism of the Antimicrobial Action of Pyrithione: Effects on Membrane Transport, ATP Levels, and Protein Synthesis

    Science.gov (United States)

    Chandler, Carol J.; Segel, Irwin H.

    1978-01-01

    Pyrithione is a general inhibitor of membrane transport processes in fungi. A brief preincubation of Penicillium mycelia with pyrithione resulted in a marked decrease in the activities of a variety of independently regulated transport systems, including those for inorganic sulfate, inorganic phosphate, methylamine (actually, the NH4+ permease), choline-O-sulfate, glucose, l-methionine (a specific system), and several hydrophobic l-?-amino acids (the general amino acid permease). The degree of inhibition at any fixed pyrithione concentration and exposure time increased as the pH of the incubation medium was decreased. This result strongly suggests that the active species is the un-ionized molecule and that pyrithione acts by collapsing a transmembrane ?pH driving force. The degree of transport inhibition caused by a given concentration of pyrithione increased with increasing time of exposure to the inhibitor. However, exposure time and pyrithione concentration were not reciprocally related. At “low” pyrithione concentrations, transport inhibition plateaued at some finite value. This observation suggests that the fungi can detoxify low levels of the inhibitor. The concentration of pyrithione required for a given degree of growth inhibition increased as the experimental mycelial density increased. This phenomenon was consistent with the suggestion that the fungi are capable of inactivating pyrithione. PMID:28693

  13. Charge transport through DNA/DNA duplexes and DNA/RNA hybrids: complex mechanism study.

    Czech Academy of Sciences Publication Activity Database

    Kratochvílová, Irena; Vala, M.; Weiter, M.; Špérová, M.; Schneider, Bohdan; Páv, Ond?ej; Šebera, Jakub; Rosenberg, Ivan; Sychrovský, Vladimír

    2013-01-01

    Ro?. 20, ?. 1 (2013), s. 9-9. ISSN 1211-5894. [Discussions in Structural Molecular Biology. Annual Meeting of the Czech Society for Structural Biology /11./. 14.03.2013-16.03.2013, Nové Hrady] Institutional support: RVO:61388963 ; RVO:68378271 ; RVO:86652036 Keywords : charge transport * fluorescence spectroscopy * DFT Subject RIV: CF - Physical ; Theoretical Chemistry

  14. Asymmetric Transport Mechanisms of Hydronium and Hydroxide Ions in Amorphous Solid Water: Hydroxide Goes Brownian while Hydronium Hops.

    Science.gov (United States)

    Lee, Du Hyeong; Choi, Cheol Ho; Choi, Tae Hoon; Sung, Bong June; Kang, Heon

    2014-08-01

    The diffusion of hydronium (H3O(+)) and hydroxide (OH(-)) ions is one of the most intriguing topics in aqueous chemistry. It is considered that these ions in aqueous solutions move via sequential proton transfer events, known as the Grotthuss mechanisms. Here, we present an experimental study of the diffusion and H/D exchange of hydronium and hydroxide ions in amorphous solid water (ASW) at 140-180 K by using low-energy sputtering (LES) and temperature-programmed desorption (TPD) measurements. The study shows that the two species transport in ASW via fundamentally different molecular mechanisms. Whereas hydronium ions migrate via efficient proton transfer, hydroxide ions move via Brownian molecular diffusion without proton transfer. The molecular hydroxide diffusion in ASW is in stark contrast to the current view of the hydroxide diffusion mechanism in aqueous solution, which involves proton transfer. PMID:26277944

  15. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis1. In prokaryotes and photosynthetic eukaryotes, Zn2+-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn2+ and related elements2, 3. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2·Pi) of ZntA from Shigella sonnei, determined at 3.2 Å and 2.7 Å resolution, respectively. The structures reveal a similar fold to Cu+-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn2+ ions by the transporter. The E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including C392, C394 and D714. The pathway closes in the E2·Pi state, in which D714 interacts with the conserved residue K693, which possibly stimulates Zn2+ release as a built-in counter ion, as has been proposed for H+-ATPases. Indeed, transport studies in liposomes provide experimental support for ZntA activity without counter transport. These findings suggest a mechanistic link between PIB-type Zn2+-ATPases and PIII-type H+-ATPases and at the same time show structural features of the extracellular release pathway that resemble PII-type ATPases such as the sarcoplasmic/endoplasmic reticulum Ca2+-ATPase4, 5 (SERCA) and Na+, K+-ATPase6. These findings considerably increase our understanding of zinc transport in cells and represent new possibilities for biotechnology and biomedicine.

  16. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis. In prokaryotes and photosynthetic eukaryotes, Zn(2+)-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn(2+) and related elements. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2·Pi) of ZntA from Shigella sonnei, determined at 3.2 Å and 2.7 Å resolution, respectively. The structures reveal a similar fold to Cu(+)-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn(2+) ions by the transporter. The E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including C392, C394 and D714. The pathway closes in the E2·Pi state, in which D714 interacts with the conserved residue K693, which possibly stimulates Zn(2+) release as a built-in counter ion, as has been proposed for H(+)-ATPases. Indeed, transport studies in liposomes provide experimental support for ZntA activity without counter transport. These findings suggest a mechanistic link between PIB-type Zn(2+)-ATPases and PIII-type H(+)-ATPases and at the same time show structural features of the extracellular release pathway that resemble PII-type ATPases such as the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) and Na(+), K(+)-ATPase. These findings considerably increase our understanding of zinc transport in cells and represent new possibilities for biotechnology and biomedicine.

  17. Effect of PANI rate percentage on morphology, structure and charge transport mechanism in PANI–PVDF composites above percolation threshold

    International Nuclear Information System (INIS)

    Polyaniline–Poly(vinylidene) fluoride (PANI–PVDF) composites were prepared by adding PANI to the PVDF by different weight percentages p % (p = 0, 5, 10, 20, … until 100%). The dc and ac electrical conductivity were studied as a function of PANI percentage in the temperature range 303–453 K. The percolation threshold was found to be equal to 2.95%. When the amount of PANI varies from 5 to 30%, the charge transport mechanism was found to be governed by Mott's three-dimensional variable range hopping model and the dc conductivity decreases within this range. For p > 30%, the conductivity increases and the charge transport mechanism are better fitted by a fluctuation induced tunnelling model (FIT). By calculating the distance ‘s’ between two successive clusters (the distance between two active imines centres (=N+H–) of PANI) from the FIT model, we deduce that electron charge transfer is done by inter-chain hopping for the range [p = 40 to 60%] and by intra-chain hopping for p = 70 to 90%. Some insights about the contribution of the ionic charge transport for PANI concentrations in the interval 5% < p < 30% were obtained using impedance measurements at different frequencies. X-ray diffraction measurements, Fourier transform infrared spectroscopy and scanning electron microscopy were used to investigate the effect of PANI on the structure and morphology of composites. (paper)

  18. Aero-Mechanical Design Methodology for Subsonic Civil Transport High-Lift Systems

    Science.gov (United States)

    vanDam, C. P.; Shaw, S. G.; VanderKam, J. C.; Brodeur, R. R.; Rudolph, P. K. C.; Kinney, D.

    2000-01-01

    In today's highly competitive and economically driven commercial aviation market, the trend is to make aircraft systems simpler and to shorten their design cycle which reduces recurring, non-recurring and operating costs. One such system is the high-lift system. A methodology has been developed which merges aerodynamic data with kinematic analysis of the trailing-edge flap mechanism with minimum mechanism definition required. This methodology provides quick and accurate aerodynamic performance prediction for a given flap deployment mechanism early on in the high-lift system preliminary design stage. Sample analysis results for four different deployment mechanisms are presented as well as descriptions of the aerodynamic and mechanism data required for evaluation. Extensions to interactive design capabilities are also discussed.

  19. An Human Reliability Analysis to Identify Human Error Mechanisms for Reducing the Risks Associated with Human Errors in a Main Control Room of the SMART

    International Nuclear Information System (INIS)

    The research results are summarized as followed: (1) The task analysis performed on the EOGs of the SMART MMIS identified seven different human error mechanisms: Perception Error, Decision Error, Control-Identification Error, Control-Selection Error, Control-Execution Error, Communication Error, and Extraneous Error. The human error mechanisms includes 48 different human error types. 2) The design requirements were proposed to prevent 48 different possible human errors while running the HSI of SMART. 3) Sixteen different human errors were found for the SC designed by KAERI. Fifty six PSFs were also identified influencing the initiation of a human error mechanism. 4) Human factors design requirements were developed to hinder the human error mechanisms. CHED in KHU proposed a design alternative of the SC which took into account the human factors design requirements previously identified. 5) An human error quantification technique was applied to compare the CHED design with that the KAERI's in terms of the probabilities of the human errors caused by each design. The comparison showed that the CHD design was more effective than the KAERI's to reduce the human error probability from 0.0108 to 0.00004. It meant that 96.3% of the human error probability in the KAERI's was prevented by introducing the human factors design recommendations on the SC design

  20. A quantum mechanical flux correlation approach to steady-state transport rates in molecular junctions

    Energy Technology Data Exchange (ETDEWEB)

    Caspary Toroker, Maytal [Schulich Faculty of Chemistry, Lise Meitner Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel); Peskin, Uri, E-mail: uri@tx.technion.ac.il [Schulich Faculty of Chemistry, Lise Meitner Center for Computational Quantum Chemistry, Technion-Israel Institute of Technology, Haifa 32000 (Israel)

    2010-05-12

    A time-dependent approach for the calculation of steady-state currents through molecular junctions is presented. Using the close analogy between electronic currents and thermal reactive scattering rates, algorithms and methodologies originally developed for calculations of thermal reaction rates are utilized for electronic transport calculations. Resonant transport is considered in detail, in view of the dominant contribution of resonance states to the current in molecular junctions. The problem of long-time delays due to population of long-lived resonances is a challenge for most time-dependent calculation of steady-state currents, involving an infinite time-limit. A solution to this problem is presented by reformulating a flux-averaging method for the molecular junction scenario. The new formulation is implemented for commonly used simple tight binding models of molecular junctions, demonstrating its numerical advantages.

  1. A quantum mechanical flux correlation approach to steady-state transport rates in molecular junctions

    International Nuclear Information System (INIS)

    A time-dependent approach for the calculation of steady-state currents through molecular junctions is presented. Using the close analogy between electronic currents and thermal reactive scattering rates, algorithms and methodologies originally developed for calculations of thermal reaction rates are utilized for electronic transport calculations. Resonant transport is considered in detail, in view of the dominant contribution of resonance states to the current in molecular junctions. The problem of long-time delays due to population of long-lived resonances is a challenge for most time-dependent calculation of steady-state currents, involving an infinite time-limit. A solution to this problem is presented by reformulating a flux-averaging method for the molecular junction scenario. The new formulation is implemented for commonly used simple tight binding models of molecular junctions, demonstrating its numerical advantages.

  2. Investigation of silicate surface chemistry and reaction mechanisms associated with mass transport in geologic media

    International Nuclear Information System (INIS)

    The concentration and rate of transport of radionuclides through geologic media can be strongly influenced by the extent of sorption on aquifer surfaces. Over time intervals relevant to such transport processes, rock and mineral surfaces cannot be considered as inert, unreactive substrates but rather as groundwater/solidphase interfaces which are commonly in a state of natural or artificially induced disequilibrium. The goal of the present research is to define experimentally the type of water/rock interactions that will influence surface chemistry and hence sorption characteristics and capacities of natural aquifers. As wide a range of silicate minerals as possible was selected for study to represent rock-forming minerals in basalt, tuff, and granite. The minerals include K-feldspar, plagioclase feldspar, olivine, hornblende, biotite, and volcanic glass

  3. Receptor-mediated transcytosis: a mechanism for active extravascular transport of nanoparticles in solid tumors

    OpenAIRE

    Lu, Wei; Xiong, Chiyi; Zhang, Rui; Shi, Lifang; Huang, Miao; Zhang, Guodong; Song, Shaoli; Huang, Qian; Liu, Gang-Yu; Li, Chun

    2012-01-01

    Targeted nanoparticle-based delivery systems have been used extensively to develop effective cancer theranostics. However, how targeting ligands affect extravascular transport of nanoparticles in solid tumors remains unclear. Here, we show, using B16/F10 melanoma cells expressing melanocortin type-1 receptor (MC1R), that the nature of targeting ligands, i.e., whether they are agonists or antagonists, directs tumor uptake and intratumoral distribution after extravasation of nanoparticles from ...

  4. Transport Mechanism in Polyethylene Membrane during Vapor Permeation of Propan-1-ol and Toluene.

    Czech Academy of Sciences Publication Activity Database

    Fialová, Kate?ina; Petri?kovi?, Roman; Uchytil, Petr

    Sofia : University of Chemical Technology and Metallurgy, 2005 - (Mehmetli, E.; Kemperman, A.; Kozhukharov, V.), s. 45-50 ISBN 954-8954-55-9. [Application of Nanotechnologies for Separation and Recovery of Volatile Organic Compounds from Waste Air Streams. Istanbul (TR), 30.05.2005-01.06.2005] R&D Projects: GA AV ?R(CZ) IAA4072402 Institutional research plan: CEZ:AV0Z40720504 Keywords : vapor permeation * sorption * transport model Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  5. MAJOR TRANSPORT MECHANISMS OF PYRETHROIDS IN RESIDENTIAL SETTINGS AND EFFECTS OF MITIGATION MEASURES

    OpenAIRE

    Davidson, Paul C; Jones, Russell L.; Harbourt, Christopher M; Hendley, Paul; Goodwin, Gregory E; Sliz, Bradley A

    2013-01-01

    The major pathways for transport of pyrethroids were determined in runoff studies conducted at a full-scale test facility in central California, USA. The 6 replicate house lots were typical of front lawns and house fronts of California residential developments and consisted of stucco walls, garage doors, driveways, and residential lawn irrigation sprinkler systems. Each of the 6 lots also included a rainfall simulator to generate artificial rainfall events. Different pyrethroids were applied ...

  6. Uptake of waterborne tributyltin in the brain of fish: axonal transport as a proposed mechanism.

    Science.gov (United States)

    Rouleau, Claude; Xiong, Zheng-Hu; Pacepavicius, Grazina; Huang, Guo-Lan

    2003-08-01

    In previous studies, it was shown that waterborne Hg(II), Cd(II), and Mn(II) enter nerves innervating water-exposed sensory organs of fish and are transported to the brain by axonal transport. However, it is not known if organometals, such as tributyltin (TBT), can reach the brain of fish via the same route. In this work, we exposed rainbow trout (Oncorhynchus mykiss) to waterborne [113Sn]-TBT (4.2 kBq/L). Three fish were sampled after a 2-week exposure, and three others were sampled after a 2-week depuration period. Another group of four fish received an intravenous injection of [113Sn]-TBT and were sampled after 2 and 14 d. Distribution of the radiolabel was visualized and quantified by quantitative whole-body autoradiography. The brain accumulated a significant amount of 113Sn, with hot spots being found in parts receiving sensory nerves from water-exposed sensory organs, such as eminentia granulares (lateral lines organs). Labeling of the brain was also seen for i.v.-injected fish, indicating that the blood-brain barrier is not impervious to TBT or its metabolites. Nevertheless, the distribution of radioactivity in the brain was much more uniform, with no evident hot spot. Though the transfer [water --> gills --> blood stream --> blood-brain barrier --> brain] may account for a certain proportion of the radiolabel accumulation in fish brain, exposure to [113Sn]-TBT via water resulted in higher accumulation in some areas of the brain, of which the specific location strongly suggests that it was taken up in different water-exposed sensory nerve terminals and transported directly to the brain by axonal transport, as the parent compound or as a metabolite. The resulting local enhancement of the accumulation of butyltins might jeopardize the integrity of nervous system. Further work is needed to assess the toxicological significance of this process. PMID:12966973

  7. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg; Meloni, Gabriele; Autzen, Henriette Elisabeth; Andersson, Magnus; Klymchuk, Tetyana; Nielsen, Anna Marie; Rees, Douglas C; Nissen, Poul; Gourdon, Pontus

    2014-01-01

    Zinc is an essential micronutrient for all living organisms. It is required for signalling and proper functioning of a range of proteins involved in, for example, DNA binding and enzymatic catalysis1. In prokaryotes and photosynthetic eukaryotes, Zn2+-transporting P-type ATPases of class IB (ZntA) are crucial for cellular redistribution and detoxification of Zn2+ and related elements2, 3. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation...

  8. Sensitizing Curium Luminescence through an Antenna Protein to Investigate Biological Actinide Transport Mechanisms

    OpenAIRE

    Sturzbecher-Hoehne, Manuel; Goujon, Christophe; Deblonde, Gauthier J.-P.; Mason, Anne B; Abergel, Rebecca J.

    2013-01-01

    Worldwide stocks of actinides and lanthanide fission products produced through conventional nuclear spent fuel are increasing continuously, resulting in a growing risk of environmental and human exposure to these toxic radioactive metal ions. Understanding the bio-molecular pathways involved in mammalian uptake, transport and storage of these f-elements is crucial to the development of new decontamination strategies and could also be beneficial to the design of new containment and separation ...

  9. Towards the Restructuring and Co-ordination Mechanisms for the Architecture of Chinese Transport Logistics

    OpenAIRE

    Yang, Jiaqi

    2009-01-01

    With China’s emergence as a global manufacturing centre, reshaping the country’s logistics industry is assuming a global dimension too. The Chinese transport sector, despite its tremendous potential in facilitating the economic development of the country, is plagued with problems of insufficient infrastructure; overlapping regulatory authority; operational inefficiencies and a lack of logistics culture. The thesis shows that China urgently needs to restructure the architecture of its transpor...

  10. Controlling the transport of an ion: classical and quantum mechanical solutions

    International Nuclear Information System (INIS)

    The accurate transport of an ion over macroscopic distances represents a challenging control problem due to the different length and time scales that enter and the experimental limitations on the controls that need to be accounted for. Here, we investigate the performance of different control techniques for ion transport in state-of-the-art segmented miniaturized ion traps. We employ numerical optimization of classical trajectories and quantum wavepacket propagation as well as analytical solutions derived from invariant based inverse engineering and geometric optimal control. The applicability of each of the control methods depends on the length and time scales of the transport. Our comprehensive set of tools allows us make a number of observations. We find that accurate shuttling can be performed with operation times below the trap oscillation period. The maximum speed is limited by the maximum acceleration that can be exerted on the ion. When using controls obtained from classical dynamics for wavepacket propagation, wavepacket squeezing is the only quantum effect that comes into play for a large range of trapping parameters. We show that this can be corrected by a compensating force derived from invariant based inverse engineering, without a significant increase in the operation time. (paper)

  11. Observations of Intertidal Bars Welding to the Shoreline: Examining the Mechanisms of Onshore Sediment Transport and Beach Recovery

    Science.gov (United States)

    Cohn, N.; Anderson, D. L.; Susa, T.; Ruggiero, P.; Honegger, D.; Haller, M. C.

    2014-12-01

    Many coastlines throughout the world are in a net erosional state due to factors such as climate change and anthropogenic activities. While most coastal erosion occurs episodically during major storms, beaches recover during extended periods of low wave energy. Despite the importance of beach recovery on limiting coastal vulnerability, the mechanisms driving onshore sediment transport are much less well understood than those of storm-driven offshore transport. Intertidal bar (i.e., swash bar) welding to the shoreline is one proposed mechanism of sediment delivery from the nearshore to the backshore. However, studies of swash bars and their contribution to beach building have been scarce because of the sporadic nature of these events and difficulty measuring sediment fluxes in the intertidal zone. Several beaches in the US Pacific Northwest are prograding rapidly in part due to highly dissipative conditions and an abundant sediment supply. For example, at South Beach State Park (SBSP) in Newport, OR the shoreline accreted at an average of 6 m/yr from 1960 to 2002. To explore the role of intertidal bar welding on supplying sediment to this dynamic backshore, we recently completed a boutique field experiment at SBSP. Topographic and bathymetric surveys carried out over 9 months document the short term (welding on supplying sediment to the backshore as well as the environmental conditions and physical mechanisms that promote onshore delivery of sediment.

  12. The role of lock-in mechanisms in transition processes: The case of energy for road transport

    DEFF Research Database (Denmark)

    Klitkou, Antje; Bolwig, Simon; Hansen, Teis; Wessberg, Nina

    2015-01-01

    is based on a comparative analysis of case studies. The main lock-in mechanisms analysed are learning effects, economies of scale, economies of scope, network externalities, informational increasing returns, technological interrelatedness, collective action, institutional learning effects and the...... differentiation of power. We show that very different path dependencies have been reinforced by the lock-in mechanisms. Hence, the characteristics of existing regimes set the preconditions for the development of new transition pathways. The incumbent socio-technical regime is not just fossil-based, but may also...

  13. Implementing energy conservation strategies in energy materials transport: U. S. Department of Energy and other government agency policy-making mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Bertram, K. M.

    1978-11-01

    This report defines policy-making channels within Federal agencies for the strategy implementation efforts of a U.S. Department of Energy (DOE) project entitled ''Development and Implementation of Strategies to Conserve Energy in Energy Materials Transport and Through Modal Shifts.'' The report's research involved review and analysis of government-agency policy-making mechanisms. Research methods included interviews with 36 regulatory officials, and review of pertinent legislative, organizational and other technical materials. Emphasis was placed upon relevant Federal agencies and summary treatment given other federal, state, and local agencies. In addition to DOE, the ICC, DOT, DOI, EPA, and Council on Environmental Quality were found to be highly important to the implementation of strategies developed during this project. Brief case studies were also made of states and localities which have had significant effects upon energy materials transport systems. The main findings of the report are that two primary channels exist for effecting this project's policy-oriented strategies: inputs to legislation and inducement of regulatory involvements. In addition, interviews with Federal agency officials during the research produced two significant suggestions for implementing strategies--to hold internal DOE and inter-agency briefings.

  14. Environmental Impact of Flooding in the Main (Smallwood) Reservoir of the Churchill Falls Power Plant, Labrador, Canada. II. Chemical and Mechanical Analysis of Flooded Trees and Shoreline Changes.

    OpenAIRE

    Bruce A. Roberts; Denes Bajzak

    2011-01-01

    The Churchill Falls Hydro Project (called the “Upper Churchill Development”) in Labrador, Canada, was initiated in the late 1960s. At that time, in general, not much attention was paid to the impact of such devel-opment on the flooding of vegetation especially forest stands. Both forested and un-forested terrestrial vege-tation types were flooded (244 915 ha). Some islands were created and in addition portions of existing areas were flooded to form islands (74 075 ha) in the Main (Smallwood) ...

  15. FSV technology for passenger, materials and coarse debris transport in the main roadway network of the Haard satellite mine. Final report; Gleislostechnik fuer Personenbefoerderung, Material- und Grobbergetransport im Hauptstreckennetz des Anschlussbergwerkes Haard. Abschlussbericht

    Energy Technology Data Exchange (ETDEWEB)

    Einhaeuser, J.

    1992-09-01

    A free-steered transport system was developed which can be used for passenger, materials and, with restrictions, debris transport around the shaft (distance max. 4 km). The system includes all-wheel driven or center pivot steered passenger busses with max. 26 seats, a combination of trucks with trailers (20 t payload) and material transporters (5 and 8 t) as well as special vehicles for heavy loads of up to 14 t (shield supports) and loaders (4 and 6 t) for dinting, loading and transport work. The vehicles can be used in roadways with free cross sections of more than 3 m width and 2.4 m height and inclinations of up to 1 in 4. For inclinations of more than 1 in 10 the transport velocity is insufficient (with the exception of the loaders) because suitable Diesel engines are currently not available for the vehicles. The applicability of the vehicles is mainly determined by the condition of the lanes or roadways. Suitable lane construction methods were developed. An EDP assisted transport simulation model is available for the planning work. (orig.) [Deutsch] Es wurde ein gleisloses Transportsystem entwickelt, das fuer den schachtnahen Bereich (Umkreis max. 4 km) fuer die Personenbefoerderung, den Materialtransport und mit Einschraenkungen fuer den Bergetransport (Haufwerkstransport) einsetzbar ist. Das System besteht aus allrad- oder knickgelenkten Personenbussen bis maximal 26 Sitzplaetze, aus einer Kombination von Sattelschleppern mit Anhaengern (Nutzlast 20 t) und Materialtransportern (5 und 8 t) sowie Sonderfahrzeugen fuer Schwerlasten bis 14 t (Schildausbau und aus Fahrladern (4 und 6 t) fuer Senk-, Lade- und Transportarbeiten. Die Fahrzeuge sind einsetzbar in Strecken mit Lichtraumprofil ueber 3 m Breite und 2,4 m Hoehe, sowie Steigungen bis 15 Gon = 25%. Bei Neigungen ueber 6 Gon = 10% ist (bis auf die Fahrlader) die Transportgeschwindigkeit unzureichend, weil fuer die Fahrzeuge zur Zeit keine geeigneten Dieselmotoren gebaut werden. Die Betriebsbereitschaft der Fahrzeuge wird massgeblich durch den Zustand der Fahrbahnen bzw. der Strecken bestimmt. Geeignete Verfahren zum Fahrbahnbau wurden entwickelt. Fuer die Planung steht ein EDV-gestuetztes Transportmodel zur Verfuegung. (orig.)

  16. Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Sylow, Lykke

    2014-01-01

    Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca(2+) as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca(2+) release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca(2+) centric paradigm.

  17. Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release

    Directory of Open Access Journals (Sweden)

    Thomas E. Jensen

    2014-10-01

    Full Text Available Understanding how muscle contraction orchestrates insulin-independent muscle glucose transport may enable development of hyperglycemia-treating drugs. The prevailing concept implicates Ca2+ as a key feed forward regulator of glucose transport with secondary fine-tuning by metabolic feedback signals through proteins such as AMPK. Here, we demonstrate in incubated mouse muscle that Ca2+ release is neither sufficient nor strictly necessary to increase glucose transport. Rather, the glucose transport response is associated with metabolic feedback signals through AMPK, and mechanical stress-activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport during muscle contraction, and call for a major reconsideration of the established Ca2+ centric paradigm.

  18. Panorama 2013 - Air transport and the problem of CO2: ETS mechanisms and bio-jet fuels

    International Nuclear Information System (INIS)

    Air transport currently accounts for only 2% (∼600 Mt/year) of global CO2 emissions from human activity. Despite this 2% level, this industry is targeted by governments - especially European Union - and initiatives targeting zero growth in carbon from 2020 onwards, and a 50% reduction by 2050. Over and above aircraft technical innovations and the way in which air traffic is organised, the introduction of ETS (Emissions Trading System) mechanisms and the development of bio-jet fuels are the options most commonly cited in discussions on how to achieve that target. (author)

  19. Transport function and reaction mechanism of vacuolar H{sup +}- translocation inorganic pyrophosphatase. Annual technical progress report

    Energy Technology Data Exchange (ETDEWEB)

    1993-09-01

    These studies describe progress made in the definition of the transport capabilities and reaction mechanism of the V-PPase through biochemical analyses of native membrane vesicles isolated from etiolated hypocotyls of Vigna radiate and by reconstitution of the purified enzyme into artificial liposomes; delineation of the ligand requirements of the V-PPase; and the delineation of sequence motifs implicated in substrate-binding through the development of strategies for selective cleavage of the M{sub r} 66,000 polypeptide and the mapping of covalently modified peptide fragments.

  20. Mechanism of Insulin-resistant Glucose Transport Activity in the Enlarged Adipose Cell of the Aged, Obese Rat: RELATIVE DEPLETION OF INTRACELLULAR GLUCOSE TRANSPORT SYSTEMS

    OpenAIRE

    Hissin, Paul J.; Foley, James E; Wardzala, Lawrence J.; Karnieli, Eddy; Simpson, Ian A.; Salans, Lester B.; Cushman, Samuel W.

    1982-01-01

    The effects of increasing cell size on glucose transport activity and metabolism and on the concentrations of glucose transport systems in both the plasma and low density microsomal membranes in isolated adipose cells from the aging rat model of obesity have been examined. Glucose transport activity was assessed by measuring l-arabinose transport and the concentration of glucose transport systems estimated by measuring specific d-glucose-inhibitable cytochalasin B-binding. Basal glucose trans...

  1. Mechanisms of meridional transport processes in the tropical Atlantic; Mechanismen meridionaler Transportprozesse im tropischen Atlantik

    Energy Technology Data Exchange (ETDEWEB)

    Kroeger, J.

    2001-07-01

    Meridional transport processes of water masses and tracers in the subtropical and tropical Atlantic are investigated using a regional eddy resolving model of the wind driven and thermohaline circulation. Analytical emphasis is on float simulations in the model which, complementary to Eulerian means, represent the Lagrangian view and give further insight into the spreading and pathways of characteristic water masses in this area. In the tropics and subtropics shallow 3-dimensional circulation cells are superimposed on the northward warm water transfer within the deep reaching thermohaline overturning cell (MOC) as part of the global ''Conveyor Belt''. Under present-day climate conditions the model shows that the equatorial thermocline is exclusively ventilated by subsurface flow within the tropical-subtropical cell (STC) of the South Atlantic. Only with a prescribed ''Conveyor-off''-Mode the STC of the North Atlantic contributes to this ventilation process with equal amounts. Throughout the year the interhemispheric transport of surface and central water masses of South Atlantic origin into the Caribbean Sea is dominated by zonal detours to the east as a consequence of the interplay of several retroflection events occuring in the North Atlantic. The eulerian mean flow field in the deep layer postulates the interhemispheric mass transport into the South Atlantic to be confined entirely to the western boundary, whereas Lagrangian means indicate intermittent eastward excursions along the equator, related to seasonally alternating zonal currents due to long Rossby waves. It was suggested that the observed characteristic eastward maximum of tracer concentrations along the equator is a consequence of rectifying effects of single or interacting equatorial waves. The model does not validate this hypothesis. The response to transport anomalies of subpolar origin and long periodicity is subject to different time-scales in both hemispheres. The fast response is confined to the northern hemisphere and dominates the first two years because of the mediating waves which at first propagate only around the North Atlantic basin. After 8 to 10 years the changes in the overturning are not restricted to the North anymore but are apparent in both hemispheres. (orig.)

  2. Understanding of pairing mechanism and transport properties in double energy gap superconductors: MgB2

    International Nuclear Information System (INIS)

    It is intended to trace the evolution of an effective dynamic interaction embodying the screening of electrons by optical phonons and plasmons. A model dielectric function is set up for MgB2 with two energy gaps following realistic sum rules on electronic (ionic) polarizabilities. Developing this scheme within strong coupling theory, Tc is estimated as 40 K and energy gap ratio is larger than BCS value. The isotope exponent, pressure effect and magnetic penetration depth are also estimated. The transport properties as electrical resistivity, thermal conductivity, thermoelectric power and optical conductivity are discussed with both ?and ? carriers in MgB2. (author)

  3. The solar neutrino problem: limitations of energy transport by mechanical means

    International Nuclear Information System (INIS)

    The thermodynamic limitations of energy transfer by mechanical means in the solar core are examined in the context of the solar neutrino problem. Under the hypothesis that thermal energy is converted into mechanical energy in the nuclear-burning core of the sun, it is possible to find steady-state solar models with very low neutrino counting rates. However, the efficiencies required in the conversion of thermal into mechanical energy are very close to the maximum possible value given by Carnot's theorem. Moreover, these models are very helium-poor (Xi approximately < 0.84) since an adjustment of the initial composition is necessary to compensate for the overall decrease of the opacity. It is then quite unlikely that energy transfer by mechnaical means in the central regions of the sun can resolve the solar neutrino puzzle. (orig.)

  4. Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release

    DEFF Research Database (Denmark)

    Jensen, Thomas Elbenhardt; Sylow, Lykke; Rose, Adam John; Madsen, Agnete Louise Bjerregaard; Angin, Yeliz; Maarbjerg, Stine J; Richter, Erik

    2014-01-01

    -activated signals. Furthermore, artificial stimulation of AMPK combined with passive stretch of muscle is additive and sufficient to elicit the full contraction glucose transport response. These results suggest that ATP-turnover and mechanical stress feedback are sufficient to fully increase glucose transport...

  5. Analysis and further development of fracture mechanics failure concepts. Main topic: Application of the J integral concept and its extensions on component-relevant situations

    International Nuclear Information System (INIS)

    In many investigations with increasingly complex conditions of use, the concepts of elastic/plastic fracture mechanics and particularly the J integral concept for the quantitative evaluation of failure behaviour have proved successful. This was proved in this project by largely clearing up the effects of constraint in the environment of cracks and the use of the J integral concept with superimposed thermal and mechanical stresses which can occur in thermal shock transients important for safety analysis. In continuing the investigations of dynamic JR curves, it was confirmed that the tendency to form auxiliary cracks and therefore to raise the crack resistance curve increases with the stress parameters and also with the size of the sample. Here and in investigations on the effect of large crack widths on quickly loaded disks with side cracks caused some difficulties. The improvement of the J integral calculation aimed at by correction terms could not be satisfactorily achieved. One way out is the crack energy to describe great extensions of cracks. (orig.)

  6. Monitoring and modelling of thermo-hydro-mechanical processes - main results of a heater experiment at the Mont Terri underground rock laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Ingeborg, G.; Alheid, H.J. [BGR - Federal Institute for Geosciences and Natural Resources, Hannover (Germany); Jockwerz, N. [Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) - Final Repository Research Division, Braunschweig (Germany); Mayor, J.C. [ENRESA - Empresa Nacional des Residuos Radioactivos, Madrid (Spain); Garcia-Siner, J.L. [AITEMIN -Asociacion para la Investigacion y Desarrollo Industrial de los Recursos Naturales, Madrid, (Spain); Alonso, E. [CIMNE - Centre Internacional de Metodos Numerics en Ingenyeria, UPC, Barcelona (Spain); Weber, H.P. [NAGRA - National Cooperative for the Disposal of Radioactive Waste, Wettingen (Switzerland); Plotze, M. [ETHZ - Swiss Federal Institute of Technology Zurich, IGT, Zurich, (Switzerland); Klubertanz, G. [COLENCO Power Engineering Ltd., Baden (Switzerland)

    2005-07-01

    The long-term safety of permanent underground repositories relies on a combination of engineered and geological barriers, so that the interactions between the barriers in response to conditions expected in a high-level waste repository need to be identified and fully understood. Co-financed by the European Community, a heater experiment was realized on a pilot plant scale at the underground laboratory in Mont Terri, Switzerland. The experiment was accompanied by an extensive programme of continuous monitoring, experimental investigations on-site as well as in laboratories, and numerical modelling of the coupled thermo-hydro-mechanical processes. Heat-producing waste was simulated by a heater element of 10 cm diameter, held at a constant surface temperature of 100 C. The heater element (length 2 m) operated in a vertical borehole of 7 m depth at 4 to 6 m depth. It was embedded in a geotechnical barrier of pre-compacted bentonite blocks (outer diameter 30 cm) that were irrigated for 35 months before the heating phase (duration 18 months) began. The host rock is a highly consolidated stiff Jurassic clay stone (Opalinus Clay). After the heating phase, the vicinity of the heater element was explored by seismic, hydraulic, and geotechnical tests to investigate if the heating had induced changes in the Opalinus Clay. Additionally, rock mechanic specimens were tested in the laboratory. Finally, the experiment was dismantled to provide laboratory specimens of post - heating buffer and host rock material. The bentonite blocks were thoroughly wetted at the time of the dismantling. The volume increase amounted to 5 to 9% and was thus below the bentonite potential. Geo-electrical measurements showed no decrease of the water content in the vicinity of the heater during the heating phase. Decreasing energy input to the heater element over time suggests hence, that the bentonite dried leading to a decrease of its thermal conductivity. Gas release during the heating period occurred most pronouncedly in a borehole closest to the heater (0.5 m), where after an incubation period of about 6 months after the beginning of heating bell-shaped release curves of carbon dioxide and hydrogen sulphide developed over 10 months indicating that chemical reactions in the Opalinus Clay are restricted. Metal corrosion caused by Opalinus Clay (as it occurred in the rock mechanic laboratory) is probably restricted as well by the supply of a reactant such as oxygen. Gas release data also suggest that the gas permeability of the Opalinus Clay may be inhomogeneous. Bentonite and Opalinus Clay show only very weak modifications induced by the heater experiment. Numerical calculations were done with axisymmetric as well as with anisotropic models. The input data for the anisotropic properties of the Opalinus Clay were provided by the rock mechanic tests. Data of anisotropic creep properties were determined in the laboratory and integrated in a Burgers model (but have not yet been used in the Finite Element modeling). Mineralogical analysis shows that the mechanical properties of the Opalinus Clay depend on microstructure rather than mineralogy. The match between monitored and calculated time series of temperature and pore pressure is good. The pore pressure development shows the impact of transition processes in the Opalinus Clay caused b y watering of the bentonite, heating, and cooling. The hydraulic conductivity has considerable influence on the magnitude of the pore pressure values. The long-term steady stress field does not appear to be affected by the heating and cooling. The bentonite blocks insulate the heater element so that the host rock was only moderately heated (about 65 C at the interface buffer-rock). The temperature field extended to a maximum radial distance of about 5 m only. (authors)

  7. Monitoring and modelling of thermo-hydro-mechanical processes - main results of a heater experiment at the Mont Terri underground rock laboratory

    International Nuclear Information System (INIS)

    The long-term safety of permanent underground repositories relies on a combination of engineered and geological barriers, so that the interactions between the barriers in response to conditions expected in a high-level waste repository need to be identified and fully understood. Co-financed by the European Community, a heater experiment was realized on a pilot plant scale at the underground laboratory in Mont Terri, Switzerland. The experiment was accompanied by an extensive programme of continuous monitoring, experimental investigations on-site as well as in laboratories, and numerical modelling of the coupled thermo-hydro-mechanical processes. Heat-producing waste was simulated by a heater element of 10 cm diameter, held at a constant surface temperature of 100 C. The heater element (length 2 m) operated in a vertical borehole of 7 m depth at 4 to 6 m depth. It was embedded in a geotechnical barrier of pre-compacted bentonite blocks (outer diameter 30 cm) that were irrigated for 35 months before the heating phase (duration 18 months) began. The host rock is a highly consolidated stiff Jurassic clay stone (Opalinus Clay). After the heating phase, the vicinity of the heater element was explored by seismic, hydraulic, and geotechnical tests to investigate if the heating had induced changes in the Opalinus Clay. Additionally, rock mechanic specimens were tested in the laboratory. Finally, the experiment was dismantled to provide laboratory specimens of post - heating buffer and host rock material. The bentonite blocks were thoroughly wetted at the time of the dismantling. The volume increase amounted to 5 to 9% and was thus below the bentonite potential. Geo-electrical measurements showed no decrease of the water content in the vicinity of the heater during the heating phase. Decreasing energy input to the heater element over time suggests hence, that the bentonite dried leading to a decrease of its thermal conductivity. Gas release during the heating period occurred most pronouncedly in a borehole closest to the heater (0.5 m), where after an incubation period of about 6 months after the beginning of heating bell-shaped release curves of carbon dioxide and hydrogen sulphide developed over 10 months indicating that chemical reactions in the Opalinus Clay are restricted. Metal corrosion caused by Opalinus Clay (as it occurred in the rock mechanic laboratory) is probably restricted as well by the supply of a reactant such as oxygen. Gas release data also suggest that the gas permeability of the Opalinus Clay may be inhomogeneous. Bentonite and Opalinus Clay show only very weak modifications induced by the heater experiment. Numerical calculations were done with axisymmetric as well as with anisotropic models. The input data for the anisotropic properties of the Opalinus Clay were provided by the rock mechanic tests. Data of anisotropic creep properties were determined in the laboratory and integrated in a Burgers model (but have not yet been used in the Finite Element modeling). Mineralogical analysis shows that the mechanical properties of the Opalinus Clay depend on microstructure rather than mineralogy. The match between monitored and calculated time series of temperature and pore pressure is good. The pore pressure development shows the impact of transition processes in the Opalinus Clay caused b y watering of the bentonite, heating, and cooling. The hydraulic conductivity has considerable influence on the magnitude of the pore pressure values. The long-term steady stress field does not appear to be affected by the heating and cooling. The bentonite blocks insulate the heater element so that the host rock was only moderately heated (about 65 C at the interface buffer-rock). The temperature field extended to a maximum radial distance of about 5 m only. (authors)

  8. Protein Electronic Conductors: Hemin-Substrate Bonding Dictates Transport Mechanism and Efficiency across Myoglobin.

    Science.gov (United States)

    Raichlin, Sara; Pecht, Israel; Sheves, Mordechai; Cahen, David

    2015-10-12

    Electron transport (ETp) across met-myoglobin (m-Mb), as measured in a solid-state-like configuration between two electronic contacts, increases by up to 20 fold if Mb is covalently bound to one of the contacts, a Si electrode, in an oriented manner by its hemin (ferric) group, rather than in a non-oriented manner. Oriented binding of Mb is achieved by covalently binding hemin molecules to form a monolayer on the Si electrode, followed by reconstitution with apo-Mb. We found that the ETp temperature dependence (>120?K) of non-oriented m-Mb virtually disappears when bound in an oriented manner by the hemin group. Our results highlight that combining direct chemical coupling of the protein to one of the electrodes with uniform protein orientation strongly improves the efficiency of ET across the protein. We hypothesize that the behavior of reconstituted m-Mb is due to both strong protein-substrate electronic coupling (which is likely greater than in non-oriented m-Mb) and direct access to a highly efficient transport path provided by the hemin group in this configuration. PMID:26346916

  9. Mechanical CPR devices compared to manual CPR during out-of-hospital cardiac arrest and ambulance transport: a systematic review

    Directory of Open Access Journals (Sweden)

    Ong Marcus

    2012-06-01

    Full Text Available Abstract Aims The aim of this paper was to conduct a systematic review of the published literature to address the question: “In pre-hospital adult cardiac arrest (asystole, pulseless electrical activity, pulseless Ventricular Tachycardia and Ventricular Fibrillation, does the use of mechanical Cardio-Pulmonary Resuscitation (CPR devices compared to manual CPR during Out-of-Hospital Cardiac Arrest and ambulance transport, improve outcomes (e.g. Quality of CPR, Return Of Spontaneous Circulation, Survival”. Methods Databases including PubMed, Cochrane Library (including Cochrane database for systematic reviews and Cochrane Central Register of Controlled Trials, Embase, and AHA EndNote Master Library were systematically searched. Further references were gathered from cross-references from articles and reviews as well as forward search using SCOPUS and Google scholar. The inclusion criteria for this review included manikin and human studies of adult cardiac arrest and anti-arrhythmic agents, peer-review. Excluded were review articles, case series and case reports. Results Out of 88 articles identified, only 10 studies met the inclusion criteria for further review. Of these 10 articles, 1 was Level of Evidence (LOE 1, 4 LOE 2, 3 LOE 3, 0 LOE 4, 2 LOE 5. 4 studies evaluated the quality of CPR in terms of compression adequacy while the remaining six studies evaluated on clinical outcomes in terms of return of spontaneous circulation (ROSC, survival to hospital admission, survival to discharge and Cerebral Performance Categories (CPC. 7 studies were supporting the clinical question, 1 neutral and 2 opposing. Conclusion In this review, we found insufficient evidence to support or refute the use of mechanical CPR devices in settings of out-of-hospital cardiac arrest and during ambulance transport. While there is some low quality evidence suggesting that mechanical CPR can improve consistency and reduce interruptions in chest compressions, there is no evidence that mechanical CPR devices improve survival, to the contrary they may worsen neurological outcome.

  10. Noble gases as natural tracers of water circulation in the Paris Basin: 1. Measurements and discussion of their origin and mechanisms of vertical transport in the basin

    Science.gov (United States)

    Castro, Maria Clara; Jambon, Albert; de Marsily, Ghislain; Schlosser, Peter

    1998-10-01

    The concentrations and isotopic compositions of helium, neon, and argon were measured in 29 water samples collected from five superposed aquifers in the Paris Basin (Ypresian, Albian, Neocomian, Dogger, and Trias). In all these groundwater flow systems the data showed excesses of 3He, 4He, and 40Ar above the solubility equilibrium with the atmosphere (air saturated water (ASW)), as well as vertical concentration gradients of these isotopes throughout the basin. The water of the Dogger and the Trias formations also had a 21Ne excess above ASW values. The mean rate of radiogenic and nucleogenic isotope production in the entire sedimentary sequence of the basin cannot produce the measured quantities of 3He, 4He, 21Ne, and 40Ar, if reasonable water residence times are considered. The total calculated production is estimated to represent less than about 13% of the measured values for all isotopes. The greater part (>87%) of the radiogenic and nucleogenic noble gas isotopes is thus believed to originate from the bedrock, and the isotopes are transported vertically through the entire basin. Three mechanisms of transport are considered: advection, dispersion, and molecular diffusion. For the Trias the radiogenic/nucleogenic production ratios of 4He/40Ar and 21Ne/40Ar are close to the mean production rate in the crust (4 ± 3 and 0.96 × 10-7, respectively). For the overlying Dogger, however, these ratios are much higher (4He/40Ar: 10 to 70; 21Ne/40Ar: 8 × 10-7 to 23 × 10-7). We suggest that differences in the vertical diffusive flux of 4He, 21Ne, and 40Ar are the reason for the high isotope ratios observed in the Dogger. In the vertical direction, 4He is transported mostly by diffusion, whereas 40Ar is transported mostly by advection. Neon 21 represents an intermediate situation. The distribution of 3He, 4He,21Ne, and 40Ar throughout the basin can be explained by the existence of only two sources: an atmospheric component contributed by recharge water and a radiogenic/nucleogenic component originating mainly in the bedrock. This concept is supported by two-dimensional cross-section modeling of the water flow in the Paris Basin and the advective, dispersive, and diffusive transport of these noble gases in its multiaquifer system presented in part 2 of this study.

  11. [Transplacental transport mechanisms of drugs for transplacental treatment of fetal tachyarrhythmia of MDCKII/MDCKII-BCRP cell line].

    Science.gov (United States)

    Wang, Wei; Zhao, Jia-jia; Wang, Ting; Wang, Ling; Jiang, Xue-hua

    2015-03-01

    To study the transport mechanisms of drugs for transplacental treatment of fetal tachyarrhythmia, MDCKII-BCRP and MDCKII cell models was used. MDCKII-BCRP and MDCKII cell monolayer model was used to investigate the bi-direction transport of sotalol, propranolol, propafenone, procainamide and flecainide. Drug concentrations were measured by HPLC-UV or chemiluminescence. The apparent permeability coefficient (P(app)), efflux rate (R(E)) and net efflux rate (R(net)) were calculated. Drugs with R(net) greater than 1.5 were further investigated using cellular accumulation experiments with or without a BCRP inhibitor. The R(net) of sotalol, propranolol, propafenone and procainamide were less than 1.5, while R(net) of flecainide with concentrations of 20 and 5 ?mol x L(-1) were 1.6 and 1.9, respectively. The results showed that the transport of flecainide on MDCKII-BCRP cell monolayer could be mediated by BCRP; and the affinity increased when the concentration of flecainide decreased. Cellular accumulation experiments further suggested that accumulation of flecainide in MDCKII-BCRP cells was significantly lower than that in MDCKII cells in a concentration-dependent manner. BCRP inhibitor quercetin (50 ?mol x L(-1)) significantly increased the accumulation of flecainide in MDCKII-BCRP cells (P flecainide but not sotalol, propranolol, propafenone or procainamide can be a substrate of BCRP. Thus the effect of flecainide may be affected by the BCRP in the maternal placental trophoblast membrane layer when treating fetal tachyarrhythmia. PMID:26118109

  12. Theoretical preconditions and technical substantiation for mechanical compressed air drying method application on the railway transport

    Directory of Open Access Journals (Sweden)

    Tatiana RIPOL’-SARAGOSI

    2009-01-01

    Full Text Available The article is related to the compressed air purification for the rolling stock problems. The mechanical method is described as a potential way of the compressed air cooling and purificating. The temperature field at the heat conducting surface engineer function equation is given in the article as well.

  13. MANGANESE AS ESSENTIAL AND TOXIC ELEMENT FOR PLANTS: TRANSPORT, ACCUMULATION AND RESISTANCE MECHANISMS

    OpenAIRE

    R Millaleo; M Reyes- Diaz; A.G Ivanov; M.L Mora; Alberdi, M.

    2010-01-01

    Manganese is an essential element for plants, intervening in several metabolic processes, mainly in photosynthesis and as an enzyme antioxidant-cofactor. Nevertheless, an excess of this micronutrient is toxic for plants. Mn phytotoxicity is manifested in a reduction of biomass and photosynthesis, and biochemical disorders such as oxidative stress. Some studies on Mn toxicity and Mn translocation from soil to plant cells in Mn2+ form have demonstrated their importance under low pH and redox po...

  14. Seismic valve as the main mechanism for sedimentary fluid entrapment within extensional basin: example of the Lodève Permian Basin (Hérault, South of France).

    Science.gov (United States)

    Laurent, D.; Lopez, M.; Chauvet, A.; Imbert, P.; Sauvage, A. C.; Martine, B.; Thomas, M.

    2014-12-01

    During syn-sedimentary burial in basin, interstitial fluids initially trapped within the sedimentary pile are easily moving under overpressure gradient. Indeed, they have a significant role on deformation during basin evolution, particularly on fault reactivation. The Lodève Permian Basin (Hérault, France) is an exhumed half graben with exceptional outcrop conditions providing access to barite-sulfides mineralized systems and hydrocarbon trapped into rollover faults of the basin. Architectural studies shows a cyclic infilling of fault zone and associated S0-parallel veins according to three main fluid events during dextral/normal faulting. Contrasting fluid entrapment conditions are deduced from textural analysis, fluid inclusion microthermometry and sulfide isotope geothermometer: (i) the first stage is characterized by an implosion breccia cemented by silicifications and barite during abrupt pressure drop within fault zone; (ii) the second stage consists in succession of barite ribbons precipitated under overpressure fluctuations, derived from fault-valve action, with reactivation planes formed by sulphide-rich micro-shearing structures showing normal movement; and (iii) the third stage is associated to the formation of dextral strike-slip pull-apart infilling by large barite crystals and contemporary hydrocarbons under suprahydrostatic pressure values. Microthermometry, sulfide and strontium isotopic compositions of the barite-sulfides veins indicate that all stages were formed by mixing between deep basinal fluids at 230°C, derived from cinerite dewatering, and formation water from overlying sedimentary cover channelized trough fault planes. We conclude to a polyphase history of fluid trapping during Permian synrift formation of the basin: (i) a first event, associated with the dextral strike-slip motion on faults, leads to a first sealing of the fault zone; (ii) periodic reactivations of fault planes and bedding-controlled shearing form the main mineralized ore bodies by the single action of fluid overpressure fluctuations, undergoing changes in local stress distribution and (iii) a final tectonic activation of fault linked to last basinal fluid and hydrocarbon migration during which shear stress restoration on fault plane is faster than fluid pressure build-up.

  15. Mechanisms of hepatic transport of cyclosporin A: an explanation for its cholestatic action?

    Science.gov (United States)

    Fricker, G; Fahr, A

    1997-01-01

    The hepatic transport of the immunosuppressive Cyclosporin A (CyA) was studied using liposomal phospholipid membranes, freshly isolated rat hepatocytes and bile canalicular plasma membrane vesicles from rat liver. The Na(+)-dependent, saturable uptake of the bile acid 3H-taurocholate into isolated rat liver cells was apparently competitively inhibited by CyA. However, the uptake of CyA into the cells was neither saturable, nor temperature-dependent nor Na(+)-dependent, nor could it be inhibited by bile salts or CyA-derivatives, indicating passive diffusion. In steady state depolarization fluorescence studies, CyA caused a concentration-dependent decrease of anisotropy, indicating a membrane fluidizing effect. Ion flux experiments demonstrated that CyA dramatically increases the permeability of Na+ and Ca2+ across phospholipid membranes in a dose- and time-dependent manner, suggesting a iontophoretic activity that might have a direct impact on cellular ion homeostasis and regulation of bile acid uptake. Photoaffinity labeling with a [3H]-labeled photolabile CyA-derivative resulted in the predominant incorporation of radioactivity into a membrane polypeptide with an apparent molecular weight of 160,000 and a minor labeling of polypeptides with molecular weights of 85,000-90,000. In contrast, use of a photolabile bile acid resulted in the labeling of a membrane polypeptide with an apparent molecular weight of 110,000, representing the bile canalicular bile acid carrier. The photoaffinity labeling as well as CyA transport by canalicular membrane vesicles were inhibited by CyA and the p-glycoprotein substrates daunomycin and PSC-833, but not by taurocholate, indicating that CyA is excreted by p-glycoprotein. CyA uptake by bile canalicular membrane vesicles was ATP-dependent and could not be inhibited by taurocholate. CyA caused a decrease in the maximum amount of bile salt accumulated by the vesicles with time. However, initial rates of [3H]-taurocholate uptake within the first 2.5 min remained unchanged at increasing CyA concentrations. In summary, the data indicate that CyA does not directly interact with the hepatic bile acid transport systems. Its cholestatic action may rather be the result of alterations in membrane fluidity, intracellular effects and an interaction with p-glycoprotein. PMID:9626758

  16. Uranium series geochemistry in aquifers: quantification of transport mechanisms of uranium and daughter products: the chalk aquifer (Champagne, France)

    International Nuclear Information System (INIS)

    With the increase of contaminant flux of radionuclides in surface environment (soil, river, aquifer...), there is a need to understand and model the processes that control the distribution of uranium and its daughter products during transport within aquifers. We have used U-series disequilibria as an analogue for the transport of uranium and its daughter products in aquifer to understand such mechanisms. The measurements of uranium (234U et 238U), thorium (230Th et 232Th), 226Ra and 222Rn isotopes in the solid and liquid phases of the chalk aquifer in Champagne (East of France) allows us to understand the processes responsible for fractionation within the uranium decay chain. Fractionations are induced by physical and chemical properties of the elements (leaching, adsorption) but also by radioactive properties (recoil effect during α-decay). For the first time a comprehensive sampling of the solid phase has been performed, allowing quantifying mechanisms responsible for the long term evolution of the aquifer. A non steady state 1D model has been developed which takes into account leaching, adsorption processes as well as radioactive filiation and α-recoil effect. Retardation coefficients have been calculated for uranium, thorium and radium. The aquifer is characterised by a double porosity, and the contribution of fracture and matrix porosity on the water/rock interaction processes has been estimated. (author)

  17. Down-regulation of mechanisms involved in cell transport and maintenance of mucosal integrity in pigs infected with Lawsonia intracellularis.

    Science.gov (United States)

    Smith, Sionagh H; Wilson, Alison D; Van Ettinger, Imke; MacIntyre, Neil; Archibald, Alan L; Ait-Ali, Tahar

    2014-01-01

    Lawsonia intracellularis is an obligate intracellular bacterium, responsible for the disease complex known as proliferative enteropathy (PE). L. intracellularis is associated with intestinal crypt epithelial cell proliferation but the mechanisms responsible are yet to be defined. Microarray analysis was used to investigate the host-pathogen interaction in experimentally infected pigs to identify pathways that may be involved. Ileal samples originating from twenty-eight weaner pigs experimentally challenged with a pure culture of L. intracellularis (strain LR189/5/83) were subjected to microarray analysis. Microarray transcriptional signatures were validated using immunohistochemistry and quantitative real time PCR of selected genes at various time points post challenge. At peak of infection (14 days post challenge) 86% of altered transcripts were down regulated, particularly those involved in maintenance of mucosal integrity and regulation of cell transport. Among the up-regulated transcripts, CD163 and CDK1 were novel findings and considered to be important, due to their respective roles in innate immunity and cellular proliferation. Overall, targeted cellular mechanisms included those that are important in epithelial restitution, migration and protection; maintenance of stable inter-epithelial cell relationships; cell transport of nutrients and electrolytes; innate immunity; and cell cycle. PMID:24885874

  18. The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes.

    Science.gov (United States)

    Shi, Yanuo; Bork, Alexander Hansen; Schweiger, Sebastian; Rupp, Jennifer Lilia Marguerite

    2015-07-01

    Understanding 'electro-chemo-mechanics' in oxygen ion conducting membranes represents a foundational step towards new energy devices such as micro fuel cells and oxygen or fuel separation membranes. For ionic transport in macro crystalline electrolytes, doping is conventionally used to affect oxygen ionic association/migration energies. Recently, tuning ionic transport in films through lattice strain conveyed by substrates or heterostructures has generated much interest. However, reliable manipulation of strain states to twist the ionic conduction in real micro energy devices remains intractable. Here, we demonstrate that the oxygen ionic conductivity clearly correlates with the compressive strain energy acting on the near order of the electrolyte lattices by comparing thin-film ceria-based membrane devices against substrate-supported flat structures. It is possible to capitalize on this phenomenon with a smart choice of strain patterns achieved through microelectrode design. We highlight the importance of electro-chemo-mechanics in the electrolyte material for the next generation of solid-state energy conversion microdevices. PMID:26076303

  19. THE MAIN PROBLEMS IN THE PROCESS OF ESTABLISHMENT OF PUBLIC COUNCILS AT THE FEDERAL EXECUTIVE BODIES OF THE RUSSIAN FEDERATION AS A MECHANISM OF PUBLIC CONTROL

    Directory of Open Access Journals (Sweden)

    Liliya Anatol’evna Bespalaya

    2015-08-01

    Full Text Available The article is devoted to the analysis of the organization and activity of Public councils at Federal executive authorities as social institutes of the civil society and the structure of social control of the power institutes which is formed in our country.The main purpose of this article consisted in research of the principles of formation of these social institutes, their powers, positive and negative aspects of their activity and dynamics, beginning from the moment of attempts of their introduction within Administrative reform in the country and then in the following laws aimed at improving the institutions of social control over the authorities.In article it is noted that process of reforming of public councils is only at the initial stage. However these structures possess the considerable potential of growth of opportunities for implementation of effective control and monitoring of authorities. This situation is possible only in case of the solving problems and difficulties in the course of their institutionalization and at adjustment of mutual dialogue between the state and civil society.

  20. Mechanisms of energetic efficiency in the transportation sector: environmental impacts and reflections in final energy consumption: PNE 2030; Mecanismos de eficiencia energetica no setor de transportes: impactos ambientais e os reflexos no consumo final de energia: PNE 2030

    Energy Technology Data Exchange (ETDEWEB)

    Berni, Mauro Donizeti [Universidade Estadual de Campinas (NIPE/UNICAMP), SP (Brazil). Nucleo Interdisciplinar de Planejamento Energetico], email: mauro_berni@nipeunicamp.org.br; Dorileo, Ivo Leandro [Universidade Federal do Mato Grosso (NIEPE/UFMT), Cuiaba, MT (Brazil). Nucleo Interdisciplinar de Estudos em Planejamento Energetico; Perez, Andrea Juliana Ortiz [Universidade Estadual de Campinas (DE/FEM/UNICAMP), SP (Brazil). Dept. de Energia. Fac. de Engenharia Mecanica; Paccola, Jose Angelo; Silva Junior, Herculano Xavier da; Bernardes, Cyro Barbosa [MCPAR Engenharia, Campinas, SP (Brazil)

    2010-07-01

    This work presents an energy efficiency mechanisms analysis in the Brazilian transport sector. Significant energy savings can be made in this sector and rely on urgent widespread implementation of mechanisms. The experience of the developed countries serves as base for the critical evaluation of the Brazilian situation, considering the current technological period, the investments and initiatives to reduce CO{sub 2} emissions. (author)

  1. Fractional quantum mechanics on networks: Long-range dynamics and quantum transport

    Science.gov (United States)

    Riascos, A. P.; Mateos, José L.

    2015-11-01

    In this paper we study the quantum transport on networks with a temporal evolution governed by the fractional Schrödinger equation. We generalize the dynamics based on continuous-time quantum walks, with transitions to nearest neighbors on the network, to the fractional case that allows long-range displacements. By using the fractional Laplacian matrix of a network, we establish a formalism that combines a long-range dynamics with the quantum superposition of states; this general approach applies to any type of connected undirected networks, including regular, random, and complex networks, and can be implemented from the spectral properties of the Laplacian matrix. We study the fractional dynamics and its capacity to explore the network by means of the transition probability, the average probability of return, and global quantities that characterize the efficiency of this quantum process. As a particular case, we explore analytically these quantities for circulant networks such as rings, interacting cycles, and complete graphs.

  2. Atypical Dopamine Uptake Inhibitors that Provide Clues About Cocaine's Mechanism at the Dopamine Transporter

    Science.gov (United States)

    Hauck Newman, Amy; Katz, Jonathan L.

    The dopamine transporter (DAT) has been a primary target for cocaine abuse/addiction medication discovery. However predicted addiction liability and limited clinical evaluation has provided a formidable challenge for development of these agents for human use. The unique and atypical pharmacological profile of the benztropine (BZT) class of dopamine uptake inhibitors, in preclinical models of cocaine effects and abuse, has encouraged further development of these agents. Moreover, in vivo studies have challenged the original DAT hypothesis and demonstrated that DAT occupancy and subsequent increases in dopamine produced by BZT analogues are significantly delayed and long lasting, as compared to cocaine. These important and distinctive elements are critical to the lack of abuse liability among BZT analogues, and improve their potential for development as treatments for cocaine abuse and possibly other neuropsychiatric disorders.

  3. Structure and mechanism of Zn2+-transporting P-type ATPases

    DEFF Research Database (Denmark)

    Wang, Kaituo; Sitsel, Oleg; Meloni, Gabriele; Autzen, Henriette Elisabeth; Andersson, Magnus; Klymchuk, Tetyana; Nielsen, Anna Marie; Rees, Douglas C; Nissen, Poul; Gourdon, Pontus Emanuel

    2014-01-01

    A) are crucial for cellular redistribution and detoxification of Zn(2+) and related elements. Here we present crystal structures representing the phosphoenzyme ground state (E2P) and a dephosphorylation intermediate (E2·Pi) of ZntA from Shigella sonnei, determined at 3.2 Å and 2.7 Å resolution......, respectively. The structures reveal a similar fold to Cu(+)-ATPases, with an amphipathic helix at the membrane interface. A conserved electronegative funnel connects this region to the intramembranous high-affinity ion-binding site and may promote specific uptake of cellular Zn(2+) ions by the transporter. The...... E2P structure displays a wide extracellular release pathway reaching the invariant residues at the high-affinity site, including C392, C394 and D714. The pathway closes in the E2·Pi state, in which D714 interacts with the conserved residue K693, which possibly stimulates Zn(2+) release as a built...

  4. Numerical simulation of dynamic deformation of a spent nuclear fuel transport package in accidental mechanical impacts

    International Nuclear Information System (INIS)

    Numerical simulation results and their analysis are presented for dynamic deformations of the TUK-117 package, intended for the transport of spent nuclear fuel from nuclear power plants, subjected to accidental 9 m drops on to an unyielding surface at different angles. This paper focuses on the analysis of the deformation behaviour of container shock limiters. It is demonstrated that maximum loading affects the package during a side drop. For a side drop, the maximum strain levels are determined for the different construction elements, including the cask's body and the bolts securing the sealing lid. Dynamic simulation of the behaviour of the construction elements was carried out using the LS-DYNA code, version 970. (author)

  5. Transport mechanisms and rates for long lived Chernobyl deposits in mid-Wales

    International Nuclear Information System (INIS)

    The deposition and transport of 134Cs and 137Cs derived from Chernobyl within 3 upland catchments in mid-Wales (Upper Severn, Wye and Rheidol) has been examined between 1987-1989. An increase in the pre-existing inventory of 137Cs of 15% was observed. During the study period all fluvial outputs of 134Cs and 137Cs were in association with suspended and bedload sediments with no radiocaesium being detectable in solute form. The major source of 137Cs on suspended sediments was ''old'' 137Cs originating from fallout due to nuclear weapons testing. Mineral magnetic measurements combined with radiometric data suggest that the Chernobyl component in association with suspended sediments originates from top-soil sediment sources whilst the fine particulate material in association with bedload is supplied from subsurface and channel sources. Outputs of Chernobyl-labelled sediments from the catchments indicated by river and lake sampling were low. In 1988 ?0.08% of the soil inventory of Chernobyl derived radiocaesium was removed from the Wye and Severn catchments via fluvial transport, whilst between January and August 1989 ?0.04% was removed. Lake sediment inventories in Llyn Llygad Rheidol also suggest that rates of transfer across the upper Rheidol catchment are low. Sampling of the Hafren Forest indicates ?0.01 GBq of 137Cs and ?0.006 GBq of 134Cs deposited due to the Chernobyl accident is stored in the canopy of the forest. Losses to the forest floor from a Norway Spruce canopy were 13% and 15% of the activity contained in the overlying canopy in 1988 and 1989 and 16.5% and 9% in 1988 and 1989 under Sitka Spruce. (author)

  6. Comparative study of electron transport mechanisms in epitaxial and polycrystalline zinc nitride films

    Science.gov (United States)

    Cao, Xiang; Yamaguchi, Yuuki; Ninomiya, Yoshihiko; Yamada, Naoomi

    2016-01-01

    Zn3N2 has been reported to have high electron mobility even in polycrystalline films. The high mobility in polycrystalline films is a striking feature as compared with group-III nitrides. However, the origins of the high mobility have not been elucidated to date. In this paper, we discuss the reason for high mobility in Zn3N2. We grew epitaxial and polycrystalline films of Zn3N2. Electron effective mass (m*) was determined optically and found to decrease with a decrease in electron density. Using a nonparabolic conduction band model, the m* at the bottom of the conduction band was derived to be (0.08 ± 0.03)m0 (m0 denotes the free electron mass), which is comparable to that in InN. Optically determined intra-grain mobility (μopt) in the polycrystalline films was higher than 110 cm2 V-1 s-1, resulting from the small m*. The Hall mobility (μH) in the polycrystalline films was significantly smaller than μopt, indicating that electron transport is impeded by scattering at the grain boundaries. Nevertheless, μH higher than 70 cm2 V-1 s-1 was achievable owing to the beneficial effect of the high μopt. As for the epitaxial films, we revealed that electron transport is hardly affected by grain boundary scattering and is governed solely by ionized impurity scattering. The findings in this study suggest that Zn3N2 is a high-mobility semiconductor with small effective mass.

  7. Effect of chlordecone (Kepone) on calcium transport mechanisms in rat heart sarcoplasmic reticulum.

    Science.gov (United States)

    Kodavanti, P R; Cameron, J A; Yallapragada, P R; Desaiah, D

    1990-09-01

    Previous studies from our laboratory have indicated that chlordecone (Kepone CD), an organochlorine insecticide, inhibited cardiac sodium pump activity and catecholamine uptake suggesting that CD may interfere with cardiac function. Sarcoplasmic reticulum (SR) calcium pump has an important role in myocardial contraction and relaxation, besides Na+ transport. Since CD interferes with cardiac Na+ ion translocases, we have studied CD effects on cardiac SR calcium pump activity. Experiments were carried out both in vitro and in vivo. SR was isolated from heart ventricles of male Sprague-Dawley rats. Cardiac SR Ca2(+)-ATPase. 45Ca-uptake and cAMP as well as calmodulin (CaM) dependent protein phosphorylation were measured. Ca2(+)-ATPase was differentiated into low affinity and high affinity forms by measuring the activity using 50 and 0.7 microM free Ca2(+)-respectively. CD in vitro inhibited 45Ca-uptake by SR in a concentration dependent manner with an IC50 value of 7 microM and SR 45Ca-uptake was totally inhibited at 20-30 microM CD. In agreement with this, both high affinity and low affinity Ca2(+)-ATPases, which are involved in Ca2+ transport across membranes, were also inhibited by CD in a concentration dependent manner with IC50 values of 0.7 and 3.2 microM respectively. Both Ca2(+)-ATPase and 45Ca-uptake by cardiac SR were significantly lower in rats treated with CD (25, 50 or 75 mg/kg) when compared to control rats. cAMP as well as CaM significantly elevated the 32P-binding to SR proteins in vitro to about 70-80%. In the presence of CD, this 32P-binding was reduced, however, not concentration dependent.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:1701552

  8. Chaotic Advection at the Pore Scale: Mechanisms, Upscaling and Implications for Macroscopic Transport

    CERN Document Server

    Lester, D R; Metcalfe, Guy

    2016-01-01

    The macroscopic spreading and mixing of solute plumes in saturated porous media is ultimately controlled by processes operating at the pore scale. Whilst the conventional picture of pore-scale mechanical dispersion and molecular diffusion leading to persistent hydrodynamic dispersion is well accepted, this paradigm is inherently two-dimensional (2D) in nature and neglects important three-dimensional (3D) phenomena. We discuss how the kinematics of steady 3D flow at the porescale generate chaotic advection, involving exponential stretching and folding of fluid elements,the mechanisms by which it arises and implications of microscopic chaos for macroscopic dispersion and mixing. Prohibited in steady 2D flow due to topological constraints, these phenomena are ubiquitous due to the topological complexity inherent to all 3D porous media. Consequently 3D porous media flows generate profoundly different fluid deformation and mixing processes to those of 2D flow. The interplay of chaotic advection and broad transit t...

  9. Transport mechanism in ambipolar pentacene organic thin film transistors with lithium fluoride gate dielectric

    Science.gov (United States)

    Rahimi, R.; Korakakis, D.

    2011-07-01

    The electrical properties of organic thin film transistors (OTFTs) based on pentacene as the active layer and lithium fluoride (LiF) as the gate dielectric layer were investigated. Fabricated devices exhibited ambipolar behavior that can be controlled by the applied source, drain and gate biases. It was found that at low source-drain biases, multistep hopping is the dominant conduction mechanism, whereas in high voltage regimes, I-V data fits in the Fowler-Nordheim (FN) tunneling model. The relationship between the applied gate bias and the field enhancement factor, which is the ratio of the local surface electric field to the applied electric field, were determined from the slope of the FN plots. The dependency between the transition points in conduction mechanism upon gate bias has also been extracted from the FN plots. The transition points show more dependency on gate voltage for negative biases compared to the positive biases.

  10. Designing and testing regenerative pulp treatment strategies: modeling the transdentinal transport mechanisms

    OpenAIRE

    Passos, Agathoklis D.; Mouza, Aikaterini A.; Paras, Spiros V.; Gogos, Christos; Tziafas, Dimitrios

    2015-01-01

    The need for simulation models to thoroughly test the inflammatory effects of dental materials and dentinogenic effects of specific signaling molecules has been well recognized in current dental research. The development of a model that simulates the transdentinal flow and the mass transfer mechanisms is of prime importance in terms of achieving the objectives of developing more effective treatment modalities in restorative dentistry. The present protocol study is part of an ongoing investiga...

  11. Fibre bundle formulation of nonrelativistic quantum mechanics: I. Introduction. The evolution transport

    OpenAIRE

    Iliev, Bozhidar Z.

    1998-01-01

    We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one but it is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it a pure state of some quantum system is described by a state section (along paths) of a (Hilbert) fibre bundle. Its evolution is determined through the bundle (analogue of the) Schr\\"odinger...

  12. Fibre bundle formulation of nonrelativistic quantum mechanics. IV. Mixed states and evolution transport's curvature

    OpenAIRE

    Iliev, Bozhidar Z.

    1999-01-01

    We propose a new systematic fibre bundle formulation of nonrelativistic quantum mechanics. The new form of the theory is equivalent to the usual one but it is in harmony with the modern trends in theoretical physics and potentially admits new generalizations in different directions. In it a pure state of some quantum system is described by a state section (along paths) of a (Hilbert) fibre bundle. It's evolution is determined through the bundle (analogue of the) Schr\\"odinge...

  13. Mechanism of the Citrate Transporters in Carbohydrate and Citrate Cometabolism in Lactococcus and Leuconostoc Species

    OpenAIRE

    Bandell, M.; Lhotte, M. E.; Marty-Teysset, C; Veyrat, A.; Prévost, H.; Dartois, V.; Diviès, C; Konings, W. N.; Lolkema, J. S.

    1998-01-01

    Citrate metabolism in the lactic acid bacterium Leuconostoc mesenteroides generates an electrochemical proton gradient across the membrane by a secondary mechanism (C. Marty-Teysset, C. Posthuma, J. S. Lolkema, P. Schmitt, C. Divies, and W. N. Konings, J. Bacteriol. 178:2178–2185, 1996). Reports on the energetics of citrate metabolism in the related organism Lactococcus lactis are contradictory, and this study was performed to clarify this issue. Cloning of the membrane potential-generating c...

  14. Crustal melt granites and migmatites along the Himalaya: melt source, segregation, transport and granite emplacement mechanisms

    OpenAIRE

    Searle, MP; Cottle, JM; Streule, MJ; Waters, DJ

    2010-01-01

    India-Asia collision resulted in crustal thickening and shortening, metamorphism and partial melting along the 2200 km-long Himalayan range. In the core of the Greater Himalaya, widespread in situ partial melting in sillimanite+K-feldspar gneisses resulted in formation of migmatites and Ms+Bt+Grt+Tur±Crd±Sil leucogranites, mainly by muscovite dehydration melting. Melting occurred at shallow depths (4-6 kbar; 15-20 km depth) in the middle crust, but not in the lower crust. 87Sr/ 86Sr ratios of...

  15. Molecular mechanisms regulating oxygen transport and consumption in high altitude and hibernating mammals

    DEFF Research Database (Denmark)

    Revsbech, Inge Grønvall

    2016-01-01

    repeatedly found adaptive traits in animals living at high altitude and in hibernating mammals during hibernation compared with the active state. Factors that affect O2 affinity of Hb include temperature, H+/CO2 via the Bohr effect as well as Cl- and organic phosphates, in mammals mainly 2...... temperature to elevate blood O2 affinity. Additionally, our studies indicate a role for H2S during hibernation, possibly as part of the metabolic downregulation. Finally, results from this dessertaion support the growing theory that not necessarily only a few amino acids are paramount to protein function, but...

  16. Divergent mechanisms for the insulin resistant and hyperresponsive glucose transport in adipose cells from fasted and refed rats. Alterations in both glucose transporter number and intrinsic activity.

    OpenAIRE

    Kahn, B. B.; Simpson, I. A.; Cushman, S. W.

    1988-01-01

    The effects of fasting and refeeding on the glucose transport response to insulin in isolated rat adipose cells have been examined using 3-O-methylglucose transport in intact cells and cytochalasin B binding and Western blotting in subcellular membrane fractions. After a 72-h fast, basal glucose transport activity decreases slightly and insulin-stimulated activity decreases greater than 85%. Following 48 h of fasting, insulin-stimulated glucose transport activity is diminished from 3.9 +/- 0....

  17. Metabolismo do ferro: uma revisão sobre os principais mecanismos envolvidos em sua homeostase / Iron metabolism: an overview on the main mechanisms involved in its homeostasis

    Scientific Electronic Library Online (English)

    Helena Z. W., Grotto.

    2008-10-01

    Full Text Available Um perfeito sincronismo entre absorção, utilização e estoque de ferro é essencial para a manutenção do equilíbrio desse metal no organismo. Alterações nesses processos podem levar tanto à deficiência como ao seu acúmulo de ferro, duas situações com repercussões clínicas e laboratoriais importantes p [...] ara o paciente. Essa revisão aborda os diversos aspectos relacionados com a cinética do ferro, descrevendo as proteínas e mediadores nela envolvidos. Apresenta, ainda, como é feita a regulação intracelular e sistêmica do ferro que visa a manutenção de uma quantidade ótima de ferro para o metabolismo das células e, em especial, para uma perfeita hematopoiese.É discutido também o importante papel da hepcidina, como regulador da homeostase sistêmica. Será a apresenta da a relação entre a hepcidina e a resposta de fase aguda, e como as alterações na expressão da hepcidina podem contribuir com a fisiopatogênese da anemia de doença crônica. Abstract in english The perfect synchronism of intestinal absorption, use and storage of iron is critical for maintaining a balance in the organism. Disorders in these processes may lead either to iron deficiency or to iron overload, both of which have important clinical and laboratorial consequences for the patient. T [...] his review describes aspects related to iron metabolism and the participation of several proteins and mediators in these mechanisms. Moreover, intracellular and systemic regulation is responsible for providing the optimal iron concentration for cellular metabolism and, in particular, for adequate hematopoiesis. The relationship between hepcidin and acute phase response is presented and how changes in hepcidin expression may be related to the physiopathogenesis of anemia of chronic disease.

  18. Modeling Breadcrust Bombs to Better Understand Their Transportation Mechanisms and Thermal History

    Science.gov (United States)

    Benage, M. C.; Dufek, J.; Degruyter, W.

    2012-12-01

    The thermal history of pyroclastic density currents (PDCs) can influence their runout distance and dynamics and provides information about the concentration field and air entrainment in these flows. We have been investigating breadcrust bombs contained in PDCs as useful thermal proxies that can also be contrasted with ballistically ejected breadcrust bombs. Breadcrust bombs can have dense, non-vesicular rinds and/or surface cracks and are usually basaltic to andesitic in composition. Their textures may contain clues to the way they were transported, the thermal history they underwent, and their initial water concentration. To better interpret these textures, we model the morphology of the bomb as it is being transported. The juvenile clasts are modeled as Lagrangian particles in a coupled multiphase numerical model (Eulerian-Eulerian-Lagrangian [EEL]) that tracks the heat exchange between the current and the clasts. The volcanic clast morphology is modeled by coupling cooling, viscosity, and bubble growth models and the glass transition temperature. The cooling of the clast is calculated by convective and radiative heat transfer to the surrounding environment, as well as conductive cooling. The temperature profile of the clast is then used, along with composition of the clast, to calculate the distribution of viscosity. Viscosity can have a significant impact on restricting bubble growth within the clast. The Proussevitch et al., (1993) numerical bubble growth model is included to calculate post-eruption bubble evolution and the clast morphology, such as rind thickness and bubble size distributions. We examined the likely morphology of clasts that develop in PDCs and ballistic trajectories. We ran multiple models of ballistic and PDC eruptions with varying conditions such as initial current temperature, initial clast temperature, and initial water concentration. The results show that ballistic clasts rapidly cool and produce thicker rinds for higher temperature eruptions. There is less of a difference between the rind of a ballistic and PDC clast if the erupting gas temperature is low. However, the bubble sizes and rinds are also a function of the clast's initial water concentration. Therefore, the modeled volcanic clast's morphology is dependent not only on the cooling regime and rate but also the initial water content in the erupting magmatic clasts. We conclude that breadcrust bombs can provide information about the initial eruption temperature, water concentration, and that they are good proxies for the thermal history of a current, which is critical in determining current dynamics and deposit characteristics.

  19. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    International Nuclear Information System (INIS)

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions

  20. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    Science.gov (United States)

    Das, Kallol; Freund, Jonathan B.; Johnson, Harley T.

    2015-02-01

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.

  1. Mechanisms of material removal and mass transport in focused ion beam nanopore formation

    Energy Technology Data Exchange (ETDEWEB)

    Das, Kallol, E-mail: das7@illinois.edu; Johnson, Harley T., E-mail: htj@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, MC-244, Urbana, Illinois 61801 (United States); Freund, Jonathan B., E-mail: jbfreund@illinois.edu [Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, 1206 West Green Street, MC-244, Urbana, Illinois 61801 (United States); Department of Aerospace Engineering, University of Illinois at Urbana-Champaign, 306 Talbot Laboratory, MC-236, 104 South Wright Street Urbana, Illinois 61801 (United States)

    2015-02-28

    Despite the widespread use of focused ion beam (FIB) processing as a material removal method for applications ranging from electron microscope sample preparation to nanopore processing for DNA sequencing, the basic material removal mechanisms of FIB processing are not well understood. We present the first complete atomistic simulation of high-flux FIB using large-scale parallel molecular dynamics (MD) simulations of nanopore fabrication in freestanding thin films. We focus on the root mechanisms of material removal and rearrangement and describe the role of explosive boiling in forming nanopores. FIB nanopore fabrication is typically understood to occur via sputter erosion. This can be shown to be the case in low flux systems, where individual ion impacts are sufficiently separated in time that they may be considered as independent events. But our detailed MD simulations show that in high flux FIB processing, above a threshold level at which thermal effects become significant, the primary mechanism of material removal changes to a significantly accelerated, thermally dominated process. Under these conditions, the target is heated by the ion beam faster than heat is conducted away by the material, leading quickly to melting, and then continued heating to nearly the material critical temperature. This leads to explosive boiling of the target material with spontaneous bubble formation and coalescence. Mass is rapidly rearranged at the atomistic scale, and material removal occurs orders of magnitude faster than would occur by simple sputtering. While the phenomenology is demonstrated computationally in silicon, it can be expected to occur at lower beam fluxes in other cases where thermal conduction is suppressed due to material properties, geometry, or ambient thermal conditions.

  2. Junction formation and current transport mechanisms in hybrid n-Si/PEDOT:PSS solar cells

    Science.gov (United States)

    Jäckle, Sara; Mattiza, Matthias; Liebhaber, Martin; Brönstrup, Gerald; Rommel, Mathias; Lips, Klaus; Christiansen, Silke

    2015-08-01

    We investigated hybrid inorganic-organic solar cells combining monocrystalline n-type silicon (n-Si) and a highly conductive polymer poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS). The build-in potential, photo- and dark saturation current at this hybrid interface are monitored for varying n-Si doping concentrations. We corroborate that a high build-in potential forms at the hybrid junction leading to strong inversion of the n-Si surface. By extracting work function and valence band edge of the polymer from ultraviolet photoelectron spectroscopy, a band diagram of the hybrid n-Si/PEDOT:PSS heterojunction is presented. The current-voltage characteristics were analyzed using Schottky and abrupt pn-junction models. The magnitude as well as the dependence of dark saturation current on n-Si doping concentration proves that the transport is governed by diffusion of minority charge carriers in the n-Si and not by thermionic emission of majorities over a Schottky barrier. This leads to a comprehensive explanation of the high observed open-circuit voltages of up to 634?mV connected to high conversion efficiency of almost 14%, even for simple planar device structures without antireflection coating or optimized contacts. The presented work clearly shows that PEDOT:PSS forms a hybrid heterojunction with n-Si behaving similar to a conventional pn-junction and not, like commonly assumed, a Schottky junction.

  3. Surface Evolution of the Sun's Magnetic Field: A Historical Review of the Flux-Transport Mechanism

    Directory of Open Access Journals (Sweden)

    Sheeley Jr. Neil R.

    2005-10-01

    Full Text Available This paper reviews our attempts to understand the transport of magnetic flux on the Sun from the Babcock and Leighton models to the recent revisions that are being used to simulate the field over many sunspot cycles. In these models, the flux originates in sunspot groups and spreads outward on the surface via supergranular diffusion; the expanding patterns become sheared by differential rotation, and the remnants are carried poleward by meridional flow. The net result of all of the flux eruptions during a sunspot cycle is to replace the initial polar fields with new fields of opposite polarity. A central issue in this process is the role of meridional flow, whose relatively low speed is near the limit of detection with Doppler techniques. A compelling feature of Leighton’s original model was that it reversed the polar fields without the need for meridional flow. Now, we think that meridional flow is central to the reversal and to the dynamo itself.

  4. A possible mechanisms for quantum coherence assisted ion transport in ion channels

    Science.gov (United States)

    Vaziri, Alipasha

    2011-03-01

    Recently it was demonstrated that long-lived quantum coherence exists during excitation energy transport in photosynthesis. It is a valid question up to which length, time and mass scales quantum coherence may extend, how to one may detect this coherence and what if any role it plays for the dynamics of the system. Ion-channels are involved in many physiological processes. In the nervous system their coordinated opening and closing generates action potentials that form the basis for intra-neural communication which are essential for information representation and processing. We have recently suggested that the selectivity filter of ion channels may exhibit quantum coherence which might be relevant for the process of ion selectivity and conduction. I will discuss some of our current experimental efforts in this direction and show that quantum resonances could provide a viable approach to probe these quantum coherences. The emergence of resonances in the conduction of ion channels that are modulated periodically by time varying external fields can serve as signatures of quantum coherence in such a system.

  5. Main Achievements 2003-2004 - Interdisciplinary Research - Applications of nuclear methods to biomedical physics, environmental biology, environmental physics, and medical physics - Studies of the electron and energy transport in the process of photosynthesis

    International Nuclear Information System (INIS)

    In studies of the electron and energy transport in the process of photosynthesis it has been shown that allosteric interactions within the protein matrix of photosystem II (PSII) and charge stabilizing reactions at the donor and /or acceptor side of PSII mutually influence one another. The amount of H2O molecules in the cleavage site of the oxygen evolving complex depends on the temperature. It is estimated that there are about 12±2 water molecules at 20oC and 6±2 H2O at 9-11oC. The observed 18O isotope effect during the process of oxygen evolution has been enhanced by the clustering effect. With the use of Moessbauer spectroscopy fluorescence and absorption spectroscopy, and the fast polarographic method the molecular mechanism of variable fluorescence quenching in PSII caused by copper(II) ions and tocopherolquinone has been explained and the binding sites of these compounds indicated within photosystem II

  6. Mechanisms of turbulence transport in a turbine blade coolant passage with a rib turbulator

    Energy Technology Data Exchange (ETDEWEB)

    Panigrahi, P.K.; Acharya, S. [Louisiana State Univ., Baton Rouge, LA (United States). Dept. of Mechanical Engineering

    1999-01-01

    This paper provides detailed measurements of the flow in a ribbed coolant passage, and attempts to delineate the important mechanisms that contribute to the production of turbulent shear stress and the normal stresses. It is shown that the separated flow behind the rib is dictated by large-scale structures, and that the dynamics of the large-scale structures, associated with sweep, ejection, and inward and outward interactions, all play an important role in the production of the turbulent shear stress. Unlike the turbulent boundary layer, in a separated shear flow past the rib, the inward and outward interaction terms are both important, accounting for a negative stress production that is nearly half of the positive stress produced by the ejection and sweep mechanisms. It is further shown that the shear layer wake persists well past the re-attachment location of the shear layer, implying that the flow between ribbed passages never recovers to that of a turbulent boundary layer. Therefore, even past re-attachment, the use of statistical turbulence models that ignore coherent structure dynamics is inappropriate.

  7. Mechanized Verification of Security Properties of Transport Layer Security 1.2 Protocol with Crypto Verif in Computational Model

    Directory of Open Access Journals (Sweden)

    Bo Meng

    2014-01-01

    Full Text Available In modern society, many transactions have been processed through web-based applications. In order to protect those critical applications against attacks, Transport Layer Security (TLS protocol has been implemented and widely deployed. The related literatures show that security analysis of TLS 1.2 protocol where cipher suite is RSA encryption has not been implemented with mechanized tool in computational model. Hence in this study, Blanchet calculus is used to analyze TLS 1.2 protocol where cipher suite is RSA encryption with mechanized tool crypto verif in computational model. The term, process and correspondence are used to model authentication in TLS 1.2 protocol where cipher suite is RSA encryption. The result shows that TLS 1.2 protocol where Cipher suite is RSA encryption has the pre master key confidentiality and authentication from server to client. The first mechanized analysis on TLS 1.2 protocol where Cipher suite is RSA encryption is implemented in computational model with active adversary in this study.

  8. Virus in Groundwater: Characterization of transport mechanisms and impacts on an agricultural area in Uruguay

    Science.gov (United States)

    Gamazo, P. A.; Colina, R.; Victoria, M.; Alvareda, E.; Burutaran, L.; Ramos, J.; Lopez, F.; Soler, J.

    2014-12-01

    In many areas of Uruguay groundwater is the only source of water for human consumption and for industrial-agricultural economic activities. Traditionally considered as a safe source, due to the "natural filter" that occurs in porous media, groundwater is commonly used without any treatment. The Uruguayan law requires bacteriological analysis for most water uses, but virological analyses are not mentioned in the legislation. In the Salto district, where groundwater is used for human consumption and for agricultural activities, bacterial contamination has been detected in several wells but no viruses analysis have been performed. The Republic University (UDELAR), with the support of the National Agency for Research and Innovation (ANII), is studying the incidence of virus in groundwater on an intensive agriculture area of the Salto district. In this area water is pumped from the "Salto Aquifer", a free sedimentary aquifer. Below this sedimentary deposit is the "Arapey" basaltic formation, which is also exploited for water productions on its fractured zones. A screening campaign has been performed searching for bacterial and viral contamination. Total and fecal coliforms have been found on several wells and Rotavirus and Adenovirus have been detected. A subgroup of the screening wells has been selected for an annual survey. On this subgroup, besides bacteria and viruses analysis, a standard physical and chemical characterization was performed. Results show a significant seasonal variation on microbiological contamination. In addition to field studies, rotavirus circulation experiments on columns are being performed. The objective of this experiments is to determinate the parameters that control virus transport in porous media. The results of the study are expected to provide an insight into the impacts of groundwater on Salto's viral gastroenterocolitis outbreaks.

  9. Mechanism of Crystallization and Implications for Charge Transport in Poly(3-ethylhexylthiophene) Thin Films

    KAUST Repository

    Duong, Duc T.

    2014-04-09

    In this work, crystallization kinetics and aggregate growth of poly(3-ethylhexylthiophene) (P3EHT) thin films are studied as a function of film thickness. X-ray diffraction and optical absorption show that individual aggregates and crystallites grow anisotropically and mostly along only two packing directions: the alkyl stacking and the polymer chain backbone direction. Further, it is also determined that crystallization kinetics is limited by the reorganization of polymer chains and depends strongly on the film thickness and average molecular weight. Time-dependent, field-effect hole mobilities in thin films reveal a percolation threshold for both low and high molecular weight P3EHT. Structural analysis reveals that charge percolation requires bridged aggregates separated by a distance of ?2-3 nm, which is on the order of the polymer persistence length. These results thus highlight the importance of tie molecules and inter-aggregate distance in supporting charge percolation in semiconducting polymer thin films. The study as a whole also demonstrates that P3EHT is an ideal model system for polythiophenes and should prove to be useful for future investigations into crystallization kinetics. Recrystallization kinetics and its relationship to charge transport in poly(3-ethylhexylthiophene) (P3EHT) thin films are investigated using a combination of grazing incidence X-ray diffraction, optical absorption, and field-effect transistor measurements. These results show that thin film crystallization kinetics is limited by polymer chain reorganization and that charge percolation depends strongly on the edge-to-edge distance between aggregates. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Main: FEA5 [TP Atlas

    Lifescience Database Archive (English)

    Full Text Available FEA5 Structural biology on efflux transport machineries to understand multi-drug resistance Effl ... ness of a drug such as an antimicrobial or an anti-cancer ... drug, is the main cause of hospital-acquired infec ... ness of a drug such as an antimicrobial or an anti-cancer ... drug, is an emerging threat worldwide. One of the ...

  11. Technical-evaluation report on the proposed technical-specification changes for the inservice surveillance of safety-related hydraulic and mechanical snubbers at the Maine Yankee Nuclear Power Plant (Docket No. 50-309)

    International Nuclear Information System (INIS)

    This report documents the technical evaluation of the proposed Technical Specification changes to Limiting Conditions for Operation, Surveillance Requirements and Bases for safety-related hydraulic and mechanical snubbers at the Maine Yankee Nuclear Power Plant. The evaluation is to determine whether the proposed Technical Specifications are in conformance with the model Standard Technical Specification set forth by the NRC. A check list, Appendix A of this report, compares the licensee's submittal with the NRC requirements and includes Proposed Resolution of the Deviations

  12. Flow pathways and nutrient transport mechanisms drive hydrochemical sensitivity to climate change across catchments with different geology and topography

    Science.gov (United States)

    Crossman, J.; Futter, M. N.; Whitehead, P. G.; Stainsby, E.; Baulch, H. M.; Jin, L.; Oni, S. K.; Wilby, R. L.; Dillon, P. J.

    2014-12-01

    Hydrological processes determine the transport of nutrients and passage of diffuse pollution. Consequently, catchments are likely to exhibit individual hydrochemical responses (sensitivities) to climate change, which are expected to alter the timing and amount of runoff, and to impact in-stream water quality. In developing robust catchment management strategies and quantifying plausible future hydrochemical conditions it is therefore equally important to consider the potential for spatial variability in, and causal factors of, catchment sensitivity, as it is to explore future changes in climatic pressures. This study seeks to identify those factors which influence hydrochemical sensitivity to climate change. A perturbed physics ensemble (PPE), derived from a series of global climate model (GCM) variants with specific climate sensitivities was used to project future climate change and uncertainty. Using the INtegrated CAtchment model of Phosphorus dynamics (INCA-P), we quantified potential hydrochemical responses in four neighbouring catchments (with similar land use but varying topographic and geological characteristics) in southern Ontario, Canada. Responses were assessed by comparing a 30 year baseline (1968-1997) to two future periods: 2020-2049 and 2060-2089. Although projected climate change and uncertainties were similar across these catchments, hydrochemical responses (sensitivities) were highly varied. Sensitivity was governed by quaternary geology (influencing flow pathways) and nutrient transport mechanisms. Clay-rich catchments were most sensitive, with total phosphorus (TP) being rapidly transported to rivers via overland flow. In these catchments large annual reductions in TP loads were projected. Sensitivity in the other two catchments, dominated by sandy loams, was lower due to a larger proportion of soil matrix flow, longer soil water residence times and seasonal variability in soil-P saturation. Here smaller changes in TP loads, predominantly increases, were projected. These results suggest that the clay content of soils could be a good indicator of the sensitivity of catchments to climatic input, and reinforces calls for catchment-specific management plans.

  13. High CO2 emissions through porous media: Transport mechanisms and implications for flux measurement and fractionation

    Science.gov (United States)

    Evans, William C.; Sorey, M.L.; Kennedy, B.M.; Stonestrom, D.A.; Rogie, J.D.; Shuster, D.L.

    2001-01-01

    Diffuse emissions of CO2 are known to be large around some volcanoes and hydrothermal areas. Accumulation-chamber measurements of CO2 flux are increasingly used to estimate the total magmatic or metamorphic CO2 released from such areas. To assess the performance of accumulation chamber systems at fluxes one to three orders of magnitude higher than normally encountered in soil respiration studies, a test system was constructed in the laboratory where known fluxes could be maintained through dry sand. Steady-state gas concentration profiles and fractionation effects observed in the 30-cm sand column nearly match those predicted by the Stefan-Maxwell equations, indicating that the test system was functioning successfully as a uniform porous medium. Eight groups of investigators tested their accumulation chamber equipment, all configured with continuous infrared gas analyzers (IRGA), in this system. Over a flux range of ~ 200-12,000 g m-2 day-1, 90% of their 203 flux measurements were 0-25% lower than the imposed flux with a mean difference of - 12.5%. Although this difference would seem to be within the range of acceptability for many geologic investigations, some potential sources for larger errors were discovered. A steady-state pressure gradient of -20 Pa/m was measured in the sand column at a flux of 11,200 g m-2 day-1. The derived permeability (50 darcies) was used in the dusty-gas model (DGM) of transport to quantify various diffusive and viscous flux components. These calculations were used to demonstrate that accumulation chambers, in addition to reducing the underlying diffusive gradient, severely disrupt the steady-state pressure gradient. The resultant diversion of the net gas flow is probably responsible for the systematically low flux measurements. It was also shown that the fractionating effects of a viscous CO2 efflux against a diffusive influx of air will have a major impact on some important geochemical indicators, such as N2/Ar, ??15N-N2, and 4He/22Ne. Published by Elsevier Science B.V.

  14. Effect of chlordecone (kepone) on calcium transport mechanisms in rat heart sarcoplasmic reticulum

    International Nuclear Information System (INIS)

    Since chlordecone (Kepone, CD) interferes with cardiac Na+ ion translocases, we have studied CD effects on cardiac SR calcium pump activity. SR was isolated from heart ventricles of male Sprague-Dawley rats. Cardiac SR Ca2+-ATPase, 45Ca-uptake and cAMP as well as calmodulin (CaM) dependent protein phosphorylation were measured. Ca2+-ATPase was differentiated into low affinity and high affinity forms by measuring the activity using 50 and 0.7 ?M free Ca2+ respectively. CD in vitro inhibited 45Ca-uptake by SR in a concentration dependent manner with an IC50 value of 7 ?M and SR 45Ca-uptake was totally inhibited at 20-30 ?M CD. In agreement with this, both high affinity and low affinity Ca2+-ATPases, which are involved in Ca2+ transport across membranes, were also inhibited by CD in a concentration dependent manner with IC50 values of 0.7 and 3.2 ?M respectively. Both Ca2+-ATPase and 45Ca-uptake by cardiac SR were significantly lower in rats treated with CD (25, 50 or 75 mg/kg) when compared to control rats. cAMP as well as CaM significantly elevated the 32P-binding to SR proteins in vitro to about 70-80%. In the presence of CD, this 32P-binding was reduced, however, not concentration dependent. In agreement with in vitro studies, 32P-bound to proteins was significantly lowered in rats treated with CD. SDS-polyacrylamide gel electrophoresis of the cardiac SR revealed the presence of at least 30 comassie blue-stainable bands with mobilities corresponding to molecular weights ranging from 9 to 120 kDa using 15% acrylamide gels. Autoradiographs from samples incubated in the presence of cAMP or CaM indicated 32P-incorporation in 7 bands. Of these, bands corresponding to about 24 kDa and adjacent lower molecular weights decreased in their intensity by CD in vitro as well as in vivo. (LN)

  15. Effect of chlordecone (kepone) on calcium transport mechanisms in rat heart sarcoplasmic reticulum

    Energy Technology Data Exchange (ETDEWEB)

    Kodavanti, P.R.S.; Yallapragada, P.R.; Desaiah, D. (Department of Neurology, University of Mississippi Medical Center, Jackson (USA)); Cameron, J.A. (Department of Biology, Jackson State University, Jackson (USA))

    1990-01-01

    Since chlordecone (Kepone, CD) interferes with cardiac Na{sup +} ion translocases, we have studied CD effects on cardiac SR calcium pump activity. SR was isolated from heart ventricles of male Sprague-Dawley rats. Cardiac SR Ca{sup 2+}-ATPase, {sup 45}Ca-uptake and cAMP as well as calmodulin (CaM) dependent protein phosphorylation were measured. Ca{sup 2+}-ATPase was differentiated into low affinity and high affinity forms by measuring the activity using 50 and 0.7 {mu}M free Ca{sup 2+} respectively. CD in vitro inhibited {sup 45}Ca-uptake by SR in a concentration dependent manner with an IC50 value of 7 {mu}M and SR {sup 45}Ca-uptake was totally inhibited at 20-30 {mu}M CD. In agreement with this, both high affinity and low affinity Ca{sup 2+}-ATPases, which are involved in Ca{sup 2+} transport across membranes, were also inhibited by CD in a concentration dependent manner with IC50 values of 0.7 and 3.2 {mu}M respectively. Both Ca{sup 2+}-ATPase and {sup 45}Ca-uptake by cardiac SR were significantly lower in rats treated with CD (25, 50 or 75 mg/kg) when compared to control rats. cAMP as well as CaM significantly elevated the {sup 32}P-binding to SR proteins in vitro to about 70-80%. In the presence of CD, this {sup 32}P-binding was reduced, however, not concentration dependent. In agreement with in vitro studies, {sup 32}P-bound to proteins was significantly lowered in rats treated with CD. SDS-polyacrylamide gel electrophoresis of the cardiac SR revealed the presence of at least 30 comassie blue-stainable bands with mobilities corresponding to molecular weights ranging from 9 to 120 kDa using 15% acrylamide gels. Autoradiographs from samples incubated in the presence of cAMP or CaM indicated {sup 32}P-incorporation in 7 bands. Of these, bands corresponding to about 24 kDa and adjacent lower molecular weights decreased in their intensity by CD in vitro as well as in vivo. (LN).

  16. Investigation of transport mechanisms in Bi doped Ge2Sb2Te5 thin films for phase change memory application

    Science.gov (United States)

    Lazarenko, Petr I.; Sherchenkov, Alexey A.; Kozyukhin, Sergey S.; Shtern, Maxim Y.; Timoshenkov, Sergey P.; Gromov, Dmitry G.; Redichev, Evgeniy N.

    2014-12-01

    The influence of Bi doping on the charge carrier transport mechanism in GST225 thin films was investigated. The three regions with different current-voltage dependencies were established. The energy diagrams for Bi doped GST225 thin films for different regions were analyzed. Analysis of experimental data showed that space charge limited current is the most possible explanation for the nonlinear I-V dependence in the middle electrical field strength (103 mobility gap, Urbach energy, density distribution of localized states, and activation energy of conductivity. The most pronounced modification of current-voltage characteristic and parameters of the thin films was established for GST225 + 0,5 wt. % Bi. Thus, doping of Ge2Sb2Te5 by Bi expands the range of material properties, which is important for the optimization of PCM technology.

  17. Molière theory of multiple Coulomb scattering with ionization and the transport mechanism of the multiple scattering process.

    Science.gov (United States)

    Nakatsuka, Takao; Nishimura, Jun

    2008-08-01

    The Molière theory of multiple Coulomb scattering is improved to take account of ionization loss by applying a differential formulation of the theory. Distributions for the deflection angle theta over, as well as for any linear combination between theta over and the lateral displacement r over, under the ionization process are derived by a series expansion with the same universal functions f(n)(theta) of Molière, except that the values for both the expansion parameter B and the scale angle thetaM are corrected from those under the fixed-energy process. We find that Goudsmit-Saunderson angular distribution with ionization is also expressed by the same characteristic parameters B and thetaM derived above by the Molière theory. The transport mechanism of Molière process of multiple Coulomb scattering and the stochastic property of Molière series expansion are also investigated and discussed. PMID:18850815

  18. Macro-scale complexity of nano- to micro-scale architecture of olivine crystals through an iodine vapour transport mechanism

    Indian Academy of Sciences (India)

    Raymond L D Whitby; Takahiro Fukuda; Toru Maekawa

    2014-04-01

    The production of nano- to micro-scale olivine (magnesium and iron silicate) crystals has been achieved at relatively low temperatures through an iodine vapour transport of the metal onto amorphous silicon dioxide. The process occurs down a temperature gradient from 800 to 600°C yielding high quality crystals with long range crystallinity, highly complex interconnectivity and intricate macroscale architecture. Scanning electron microscopy (SEM) imaging of the substrate before and after the reaction reveals that the amorphous silicon oxide species is mobile, due to the lack of correlation between the silicon oxide layer and the final olivine particles, leading to a vapour–liquid–solid or vapour–solid growth mechanism. This technique demonstrates a facile, low temperature synthetic route towards olivine crystals with nano- to micro-scale dimensions.

  19. Mechanical and charge transport properties of alkanethiol self-assembled monolayers on Au (111) surface: The Role of Molecular Tilt

    Energy Technology Data Exchange (ETDEWEB)

    Mulleregan, Alice; Qi, Yabing; Ratera, Imma; Park, Jeong Y.; Ashby, Paul D.; Quek, Su Ying; Neaton, J. B.; Salmeron, Miquel

    2007-11-12

    The relationship between charge transport and mechanical properties of alkanethiol self-assembled monolayers (SAM) on Au(111) films has been investigated using an atomic force microscope with a conductive tip. Molecular tilts induced by the pressure applied by the tip cause stepwise increases in film conductivity. A decay constant {beta} = 0.57 {+-} 0.03 {angstrom}{sup -1} was found for the current passing through the film as a function of tip-substrate separation due to this molecular tilt. This is significantly smaller than the value of {approx} 1 {angstrom}{sup -1} found when the separation is changed by changing the length of the alkanethiol molecules. Calculations indicate that for isolated dithiol molecules S-bonded to hollow sites, the junction conductance does not vary significantly as a function of molecular tilt. The impact of S-Au bonding on SAM conductance is discussed.

  20. Exploring the pH-dependent substrate transport mechanism of FocA using molecular dynamics simulation.

    Science.gov (United States)

    Lv, Xiaoying; Liu, Huihui; Ke, Meng; Gong, Haipeng

    2013-12-17

    FocA belongs to the formate-nitrate transporter family and plays an essential role in the export and uptake of formate in organisms. According to the available crystal structures, the N-terminal residues of FocA are structurally featureless at physiological conditions but at reduced pH form helices to harbor the cytoplasmic entrance of the substrate permeation pathway, which apparently explains the cessation of electrical signal observed in electrophysiological experiments. In this work, we found by structural analysis and molecular dynamics simulations that those N-terminal helices cannot effectively preclude the substrate permeation. Equilibrium simulations and thermodynamic calculations suggest that FocA is permeable to both formate and formic acid, the latter of which is transparent to electrophysiological studies as an electrically neutral species. Hence, the cease of electrical current at acidic pH may be caused by the change of the transported substrate from formate to formic acid. In addition, the mechanism of formate export at physiological pH is discussed. PMID:24359743