WorldWideScience
1

Space Transportation Main Engine  

Science.gov (United States)

The topics are presented in viewgraph form and include the following: Space Transportation Main Engine (STME) definition, design philosophy, robust design, maximum design condition, casting vs. machined and welded forgings, operability considerations, high reliability design philosophy, engine reliability enhancement, low cost design philosophy, engine systems requirements, STME schematic, fuel turbopump, liquid oxygen turbopump, main injector, and gas generator. The major engine components of the STME and the Space Shuttle Main Engine are compared.

Monk, Jan C.

1992-07-01

2

The Cassini Main Engine Assembly Cover Mechanism  

Science.gov (United States)

This paper describes a micrometeroid protection system for the main engines of the Cassini spacecraft. The engine Cover Assembly is a deployable/restowable half sphere of multilayer insulation mounted to an articulatable frame over 2 meters (7 feet) in diameter. The Cover folds into a compact wedge only 25 cm (10 inches) at its maximum thickness. The micrometeroid environment and typical protection methods are described as well as the design details and development problems of the Cover Mechanism Assembly.

Sevilla, Donald R.

1997-01-01

3

Maine`s electric revenue adjustment mechanism: Why it fizzled  

Energy Technology Data Exchange (ETDEWEB)

Though entered into with broad support and good intentions, the Maine experiment in decoupling revenues from sales came undone in the face of poor regional economic conditions and mild weather. Any new approach to decoupling should be designed to endure these unexpected outcomes.

Hudson, L.; Seguino, S.; Townsend, R.E.

1995-10-01

4

MEGARA main optics opto-mechanics  

Science.gov (United States)

MEGARA is the future integral-field and multi-object spectrograph for the GTC 10.4m telescope located in the Observatorio del Roque de los Muchachos in La Palma. INAOE is a member of the MEGARA Consortium and it is in charge of the Optics Manufacturing work package. In addition to the manufacturing of 73 elements, the work package includes the opto-mechanics i.e. the opto-mechanical design, manufacture, tests and integration of the complete assembly of the main optics composed by the collimator and camera subsystems. MEGARA passed the Optics Detailed Design Review in May 2013 and will have the Detailed Design Review of the complete instrument early 2014. Here we describe the detailed design of the collimator and camera barrels. We also present the finite elements models developed to simulate the behavior of the barrel, sub-cells and other mechanical elements. These models verify that the expected stress fields and the gravitational displacements on the lenses are compatible with the optical quality tolerances. The design is finished and ready for fabrication.

Castillo-Domínguez, E.; Avilés, J. L.; Carrasco, E.; Maldonado, M.; Gil de Paz, Armando; Gallego, J.; Cedazo, R.; Iglesias, J.

2014-08-01

5

Truck and Transport Mechanic. Occupational Analyses Series.  

Science.gov (United States)

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,…

McRory, Aline; Ally, Mohamed

6

Mechanical Smoke Exhaust in Underground Transport Passage of Hydropower Station  

Directory of Open Access Journals (Sweden)

Full Text Available In this paper, the fire scenario occuring in the main transformer hall of an underground hydropower station is taken as an example of the mechanical smoke exhaust effect in the transport passage when the smoke spilled from the fired main transformer hall is analyzed by means of theoretical analysis, experiment and FDS simulation. Firstly, the mathematic correlations regarding the mechanical exhaust rate are derived through theoretical analysis. Secondly, a series of experiments are conducted to investigate the smoke spreading in the transport passage under different mechanical exhaust rates, and the same smoke spreading processes are simulated using FDS. By comparing the results of theoretical analysis, experiments and FDS simulations, it is showed that the mechanical exhaust rate prescribed in the regulation of China is adequate for the transport passage of main transformer under a main transformer hall fire.

Jiang Hu

2012-09-01

7

Radioactive materials' transportation main routes in Brazil. Radiation protection aspects about radioactive materials transportation  

International Nuclear Information System (INIS)

The heavy transportation in Brazil is generally done by highways. The radioactive material transportation follow this same rule. Whenever a radioactive material is carried by the road, by the sea or by the air, in some cases, a kind of combination of those transportation ways, the transport manager has to create a Transportation Plan and submit it to CNEN. Only after CNEN's approval, the transportation can be done. The plan must have the main action on Radiation Protection, giving responsibilities and showing all the directing that will be take. Although, the Brazilian's highways are not in good conditions, one could say that some of them are not good enough for any kind of transportation. But we are facing radioactive material use increase but the hospitals and industries, that the reason it's much more common that kind of transportation nowadays. So, because of that, a special attention by the governments must be provide to those activities. This paper goal is to show the real conditions of some important highways in Brazil in a radioactive protection's perspective and give some suggestions to adjust some of those roads to this new reality. (author)

8

Summary on main policies, funding mechanisms, actors and trends  

DEFF Research Database (Denmark)

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 and direct consultation with stakeholders.

Kressler, Florian; Weiss, Lucas

2014-01-01

9

Investigation into mechanical properties of bone and its main constituents  

Science.gov (United States)

Bone is a hierarchically structured natural composite material, consisting of organic phase (type-I collagen), inorganic phase (hydroxyapatite), and water. Studies of the two main bone constituents, utilizing controlled demineralization and deproteinization, can shed light on mineral-collagen interaction which makes bone such a unique biological material. This knowledge is necessary for computational analysis of bone structure to identify preferential sites in the collagen matrix and mineral network that degrade more easily. The main goal of this work is to develop a comprehensive picture of mechanical properties of bone and its main constituents. Following the Introduction, Chapter 2 presents an investigation of microstructure and compressive mechanical properties of bovine femur cortical bone carried out on completely demineralized, completely deproteinized, and untreated bone samples in three anatomical directions. Anisotropic nature of bone was clearly identified in all cases. Extra levels of porosity along with microstructural differences for the three directions were found to be the main sources of the anisotropy. In Chapter 3, a new theoretical model of cortical and trabecular bone as composite materials with hierarchical structure spanning from nanometer (collagen-mineral) level to millimeter (bone) level was developed. Compression testing was performed on untreated, demineralized, and deproteinized cortical and trabecular bovine femur bone samples to verify the model. The experimental data were compared with theoretical predictions; excellent agreement was found between the theory and experiments for all bone phases. Optical microscopy, scanning electron microscopy, and micro-computed tomography techniques were applied to characterize the structure of the samples at multiple length scales and provide further inputs for the modeling. Chapter 4 presents a comparative study of mechanical properties, microstructure, and porosity of mature and young bovine femur cortical bone. It was found that the amount of porosity decreases, while the microhardness increases with maturation. Osteoporotic degradation of trabecular bone elasticity, described in Chapter 5, was modeled using a cellular mechanics approach. Evolution equations for elastic modulus of bone in terms of those of mineral and protein trabeculae and in terms of demineralized and deproteinized bones were formulated and verified by the analysis of compressive properties of bovine femur trabecular bone.

Evdokimenko, Ekaterina

10

Main academic institutions conducting research in the public transport area  

Energy Technology Data Exchange (ETDEWEB)

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

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

1997-12-01

11

The cost of performance - A comparison of the space transportation main engine and the Space Shuttle main engine  

Science.gov (United States)

This paper compares the cost of the Space Shuttle Main Engine (SSME) and the Space Transportation Main Engine (STME) proposed by the Advanced Launch System Program. A brief description of the SSME and STME engines is presented, followed by a comparison of these engines that illustrates the impact of focusing on acceptable performance at minimum cost (as for the STME) or on maximum performance (as for the SSME). Several examples of cost reduction methods are presented.

Barisa, B. B.; Flinchbaugh, G. D.; Zachary, A. T.

1989-01-01

12

Mechanical forces and lymphatic transport.  

Science.gov (United States)

This review examines the current understanding of how the lymphatic vessel network can optimize lymph flow in response to various mechanical forces. Lymphatics are organized as a vascular tree, with blind-ended initial lymphatics, precollectors, prenodal collecting lymphatics, lymph nodes, postnodal collecting lymphatics and the larger trunks (thoracic duct and right lymph duct) that connect to the subclavian veins. The formation of lymph from interstitial fluid depends heavily on oscillating pressure gradients to drive fluid into initial lymphatics. Collecting lymphatics are segmented vessels with unidirectional valves, with each segment, called a lymphangion, possessing an intrinsic pumping mechanism. The lymphangions propel lymph forward against a hydrostatic pressure gradient. Fluid is returned to the central circulation both at lymph nodes and via the larger lymphatic trunks. Several recent developments are discussed, including evidence for the active role of endothelial cells in lymph formation; recent developments on how inflow pressure, outflow pressure, and shear stress affect the pump function of the lymphangion; lymphatic valve gating mechanisms; collecting lymphatic permeability; and current interpretations of the molecular mechanisms within lymphatic endothelial cells and smooth muscle. An improved understanding of the physiological mechanisms by which lymphatic vessels sense mechanical stimuli, integrate the information, and generate the appropriate response is key for determining the pathogenesis of lymphatic insufficiency and developing treatments for lymphedema. PMID:25107458

Breslin, Jerome W

2014-11-01

13

Qinshan CANDU 6 main heat transport system high operational performance  

International Nuclear Information System (INIS)

This paper deals with the Qinshan CANDU 6 Critical Channel Power (CCP) performance up to about 6 years of operation. Operational and aging related changes of the primary Heat Transport System (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. Based on these analytic models up to 10 years of reactor operation are predicted and presented. These predictions, in association with an optimized parameter tracking and adjustment methodology, confirm continued safe reactor operation. This paper demonstrates that Qinshan CANDU Units 1 and 2, as compared to other CANDU 6 nuclear reactors of earlier design, exhibit significantly improved performance with much reduced plant aging effects. This high performance may, in part, be attributed to design improvements as well as improved operating practices. These performance improvements can also be expected for both new and refurbished CANDU 6 type nuclear reactors. (author)

14

Qinshan CANDU 6 main heat transport system high operational performance  

Energy Technology Data Exchange (ETDEWEB)

This paper deals with the Qinshan CANDU 6 Critical Channel Power (CCP) performance up to about 6 years of operation. Operational and aging related changes of the primary Heat Transport System (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. Based on these analytic models up to 10 years of reactor operation are predicted and presented. These predictions, in association with an optimized parameter tracking and adjustment methodology, confirm continued safe reactor operation. This paper demonstrates that Qinshan CANDU Units 1 and 2, as compared to other CANDU 6 nuclear reactors of earlier design, exhibit significantly improved performance with much reduced plant aging effects. This high performance may, in part, be attributed to design improvements as well as improved operating practices. These performance improvements can also be expected for both new and refurbished CANDU 6 type nuclear reactors. (author)

Hartmann, W.J. [Atomic Energy of Canada Limited, Mississauga, Ontario (Canada); Zeng, C.; Feng, J. [Third Qinshan Nuclear Power Company Limited, Haiyan, Zhejiang Province (China)

2010-07-01

15

Energy transport, overshoot, and mixing in the atmospheres of M-type main- and pre-main-sequence objects  

CERN Document Server

We constructed hydrodynamical model atmospheres for mid M-type main-, as well as pre-main-sequence (PMS) objects. Despite the complex chemistry encountered in these cool atmospheres a reasonably accurate representation of the radiative transfer is possible, even in the context of time-dependent and three-dimensional models. The models provide detailed information about the morphology of M-type granulation and statistical properties of the convective surface flows. In particular, we determined the efficiency of the convective energy transport, and the efficiency of mixing by convective overshoot. The convective transport efficiency was expressed in terms of an equivalent mixing-length parameter alpha in the formulation of mixing-length theory (MLT) given by Mihalas (1978). Alpha amounts to values around 2 for matching the entropy of the deep, adiabatically stratified regions of the convective envelope, and lies between 2.5 and 3.0 for matching the thermal structure of the deep photosphere. For current spectral...

Ludwig, H G; Hauschildt, P H

2006-01-01

16

Transport mechanisms at the magnetopause  

Science.gov (United States)

Convection and diffusion are discussed as possible mechanisms of mass, momentum, and energy transfer across the magnetopause. For the case of a vanishing magnetic field component normal to the boundary, convective flow does not appear possible unless substantial electric fields occur parallel to the magnetic field. The case of a nonvanishing magnetic field constant includes exactly field-aligned flows as well as magnetic field reconnection. It is shown that the efficiency of the diffusive and the convective transfer should have a strong dependence on the angle between the magnetospheric and the magnetosheath magnetic fields.

Sonnerup, B. U. O.

1980-01-01

17

Invasive home mechanical ventilation, mainly focused on neuromuscular disorders  

OpenAIRE

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 th...

Bo?rger, Sandra; Becker, Kurt; Karg, Ortrud; Geiseler, Jens; Zimolong, Andreas

2010-01-01

18

Transportation and distribution of 14C-photosynthate produced in main stems of wheat  

International Nuclear Information System (INIS)

At tillering stage, the connection of main stem and tiller was close, 14C-photosynthate produced in main stems was used for the growth of leaves of main stem, tillers and roots. In Xuzhou 26 6.15% and 5.92% 14C-photosynthate were transported from main stem to tiller I and II respectively, Which were significantly higher than those in 9559 (4.38% and 3.84%). However with the growth of plant, the main stem and tiller was more and more independent, The proportion of 14C- photosynthate which were transported between main stem and tillers decreased, and the difference of 14C-photosynthate transportation among three varieties was smaller. At jointing stage, 14C-photosynthate produced in main stem was mostly used by stem and sheath of itself. At heading stage, 14C-photosynthate produced in main stem was mostly used by spike and stem of itself. At maturity, 14C-photosynthate produced at heading stage in the labelled leaf blade was mostly transported to grain, glumes, stem and leaf sheath, and the distribution to grain was the highest among all organs (32.76% -41.81%). (authors)

19

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

20

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.)

21

Invasive home mechanical ventilation, mainly focused on neuromuscular disorders  

Directory of Open Access Journals (Sweden)

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

Börger, Sandra

2010-01-01

22

Dynamic analysis of the mechanical systems vibrating transversally in transportation  

Directory of Open Access Journals (Sweden)

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.

A. Buchacz

2007-01-01

23

Mechanical systems vibrating longitudinally with the transportation effect  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: High work speeds of mechanisms, using materials with high flexibility, high precision of work, etc. are the cause of searching of the new ways of modelling. One of these ways is presented in this thesis. The main purpose of this thesis is the dynamical analysis with taking into consideration the interaction between main motion and local vibrations during the model is loaded by longitudinal forces.Design/methodology/approach: Derived equations of motion were made by classical methods, with generalized coordinates and generalized velocities assumed as orthogonal projections of individual coordinates and velocities of the rod and manipulators to axes of the global inertial frame.Findings: Mathematical model of the longitudinally vibrating systems in terms of plane motion can be put to use to derivation of the dynamical flexibility of these systems, and also those equations are the starting point to the analysis of complex systems, especially we can use those equations to derivation of the substitute dynamical flexibility of n-linked systems in transportation.Research limitations/implications: In the thesis were considered mechanical systems vibrating longitudinally in terms of rotation. Next problem of dynamical analysis is the analysis of systems in non-planar transportation and systems loaded by transversal forces.Practical implications: Results of this thesis can be put to use into machines and mechanisms in transportation such as: wind power plant, high speed turbines, rotors, manipulators and in aerodynamics issues, etc.Originality/value: Up to now there were analyzed beams and rods in a separate way, first main motion of the system and after that the local vibrations. The new approach of modelling were presented by authors of this thesis, a new modelling took into consideration the interaction between those two displacement. There was defined the transportation effect for models vibrating longitudinally in this thesis.

S. ?ó?kiewski

2007-03-01

24

Application of main crane lock mechanism in the turbine building of nuclear power plant  

International Nuclear Information System (INIS)

In order to avoid potential impact on safety of nuclear island side, anti-tornado lock mechanism are designed on the girder of turbine building main crane. Based on the experience of Haiyang NPP Phase I, this paper illustrates the installation plan for main crane lock mechanism of turbine building, calculation course, main characteristics and safety consideration, etc. (authors)

25

Low cycle fatigue and ratcheting behaviour of Advanced Heavy Water Reactor Main Heat Transport piping material  

International Nuclear Information System (INIS)

The integrity assessment of the primary piping components needs to be demonstrated under cyclic loadings, during the normal operation and the design basis accidents such as earthquake event. In order to understand material's cyclic plasticity and failure behaviour, systematic experimental investigations on specimens have been carried on SS 304LN stainless steel material. The material specifications of this steel are same as proposed for Indian Advance Heavy Water Reactor (AHWR) Main Heat Transport (MHT) piping. The tensile and axial fatigue tests were conducted to establish the material's mechanical properties, low cycle fatigue and cyclic plasticity behaviour. Further to understand fatigue-ratcheting behaviour, a series of uniaxial ratcheting tests were carried. Finite element analyses of all LCF tests with different strain amplitude have been carried out using different cyclic plasticity models such as multiaxial kinematic hardening and Chaboche3-decomposed model. Both these models, failed to simulate the stable stress-strain hysteresis behavior for LCF tests. Modifications have been proposed in the Chaboche model and modified model is able to simulate the cyclic plasticity response that is LCF and ratcheting behaviour for all the loading ranges considered. The test results, their analyses, interpretations and the finite element simulations have been presented in this paper. (author)

26

Evaporation as the transport mechanism of metals in arid regions.  

Science.gov (United States)

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. PMID:24997976

Lima, Ana T; Safar, Zeinab; Loch, J P Gustav

2014-09-01

27

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

28

Molecular Mechanism of Ochratoxin A Transport in the Kidney  

Directory of Open Access Journals (Sweden)

Full Text Available The mycotoxin, ochratoxin A (OTA, is thought to be responsible for Balkan endemic nephropathy. OTA accumulates in several tissues, especially in the kidneys and liver. The excretion of OTA into urine is thought to be mainly by tubular secretion, presumably via the organic anion transport system. Recently, several families of multispecific organic anion transporters have been identified: organic anion transporters (OATs, organic anion-transporting polypeptides (OATPs, oligopeptide transporters (PEPTs, and ATP-binding cassette (ABC transporters, such as MRP2 and BCRP. These renal transporters mediate the transmembrane transport of OTA and play a pivotal role in the development of OTA-induced nephrotoxicity.

Naohiko Anzai

2010-06-01

29

Mechanisms of calcium transport across the placenta: Review  

Directory of Open Access Journals (Sweden)

Full Text Available Studies of calcium transfer across the placenta have been reviewed because of the physiological and nutritional importance of this mineral during pregnancy, especially in order to better understand its contribution to development of the fetal skeleton. The placental transfer of maternal calcium to the fetus represents a vital mechanism for fetal development and breast-milk production, yet little meaningful information is currently available regarding the biochemical mechanisms involved in this process. Once again, the use of different animal models as rodents, rabbit, sheep and bovine have demonstrate different mechanisms of calcium transport across the placenta and contribute to better understand its effects in both fetus and mother during the gestation. In relation to the transfer of calcium from the mother to fetus data suggest it occur via an active mechanism; thus calcium concentration is higher in fetus than in maternal blood. Despite conflicting reports, several investigators agreed that calcium concentration in the fetal blood is mainly regulated by fetal parathyroid hormone and plasma concentration of vitamin D3, a metabolite that plays a key role in calcium transport through the syncytial cells.

Catarina Tivane

2013-01-01

30

Mechanisms of the meridional heat transport in the Southern Ocean  

Science.gov (United States)

The Southern Ocean (SO) transports heat towards Antarctica and plays an important role in determining the heat budget of the Antarctic climate system. A global ocean data synthesis product at eddy-permitting resolution from the Estimating the Circulation and Climate of the Ocean, Phase II (ECCO2) project is used to estimate the meridional heat transport (MHT) in the SO and to analyze its mechanisms. Despite the intense eddy activity, we demonstrate that most of the poleward MHT in the SO is due to the time-mean fields of the meridional velocity, V, and potential temperature, ?. This is because the mean circulation in the SO is not strictly zonal. The Antarctic Circumpolar Current carries warm waters from the region south of the Agulhas Retroflection to the lower latitudes of the Drake Passage and the Malvinas Current carries cold waters northward along the Argentinian shelf. Correlations between the time-varying fields of V and ? (defined as transient processes) significantly contribute to the horizontal-gyre heat transport, but not the overturning heat transport. In the highly energetic regions of the Agulhas Retroflection and the Brazil-Malvinas Confluence the contribution of the horizontal transient processes to the total MHT exceeds the contribution of the mean horizontal flow. We show that the southward total MHT is mainly maintained by the meridional excursion of the mean geostrophic horizontal shear flow (i.e., deviation from the zonal average) associated with the Antarctic Circumpolar Current that balances the equatorward MHT due to the Ekman transport and provides a net poleward MHT in the SO. The Indian sector of the SO serves as the main pathway for the poleward MHT.

Volkov, Denis L.; Fu, Lee-Lueng; Lee, Tong

2010-08-01

31

[Intestinal and renal transport mechanisms of phosphate].  

Science.gov (United States)

Since phosphorus plays a critical role in diverse biological processes, regulation of the phosphorus balance and homeostasis are critical to the well-being of the organism. Recent findings point to the presence of a phosphate-sensing mechanism in the various organs and the presence of novel intestinal effectors that alter the renal phosphate excretion after the ingestion of a phosphate-containing meal. Recent studies have provided strong evidence that the sodium-phosphate cotransporter NaPi-IIb is responsible for sodium-dependent phosphate absorption by the small intestine, and this protein might link changes in dietary phosphate to altered renal phosphate excretion in order to maintain the phosphate balance. It has been established that different regions of the small intestine respond differently to acute or chronic changes in dietary phosphate load and that phosphatonins inhibit both renal and intestinal phosphate transport. PMID:22538947

Senatore, Massimo; Mollica, Agata; Papalia, Teresa; Bonofiglio, Renzo

2012-01-01

32

Administrative mechanics of research fuel transportation  

International Nuclear Information System (INIS)

This presentation contains the discussion on the multitude of administrative mechanics that have to be meshed for the successful completion of a shipment of spent fuel, HEU or LEU in the research reactors fuel cycle. The costs associated with transportation may be the equivalent of 'a black hole', so an overview of cost factors is given. At the end one could find that this black hole factor in the budget is actually a bargain. The first step is the quotation phase. The cost variables in the quotation contain the cost of packaging i.e. containers; the complete routing of the packages and the materials. Factors that are of outmost importance are the routing restrictions and regulations, physical security regulations. All of this effort is just to provide a valid quotation not to accomplish the goal of completing a shipment. Public relations cannot be omitted either

33

Chemical and mechanical control of corrosion product transport  

Energy Technology Data Exchange (ETDEWEB)

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)

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

1996-12-01

34

Longitudinal vibrations of mechanical systems with the transportation effect  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: this thesis purpose is a new way of modelling systems working with high speeds of mechanisms. Systems are analyzed with taking into consideration the rotational movement and with criterions of using materials with high flexibility and high precision of work. The dynamical analysis was done with giving into consideration the interaction between working motion and local vibrations. During the motion a model is loaded by longitudinal forces.Design/methodology/approach: equations of motion were derived by the Lagrange method, with generalized coordinates and generalized velocities assumed as orthogonal projections of individual quantities of the rod and manipulators to axes of the global reference frame.Findings: the model of longitudinally vibrating systems in plane motion was derived, after that the model can be transformed to the dynamical flexibility of these systems. Derived equations are the beginning of analysis of complex systems, especially can be used in deducing of the substitute dynamical flexibility of multilinked systems in motion.Research limitations/implications: mechanical systems vibrating longitudinally in terms of rotation were considered in this thesis. Successive problem of the dynamical analysis is the analysis of systems in spatial transportation and systems loaded by transversal forces.Practical implications: effects of presented calculations can be applied into machines and mechanisms in transportation such as: high speed turbines, wind power plant, water-power plants, manipulators, aerodynamics issues, and in different rotors etc.Originality/value: the contemporary analysis of beams and rods were made in a separate way, first working motion of the main system and next the local vibrations. A new way of modelling took into consideration the interaction between those two displacement. There was defined the transportation effect for models vibrating longitudinally in this paper.

A. Buchacz

2009-01-01

35

Mechanism of ochratoxin A transport in kidney  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1988-08-01

36

Lithium abundance in cluster giants - Constraints on meridional circulation transport on the main sequence  

International Nuclear Information System (INIS)

The observed Li abundances in giants are used here to constrain meridional circulation transport on the main sequence. It is shown how meridional circulation, operating over the main-sequence lifetime, can lead to Li depletion in the upper radiative envelope and eventually to extreme Li underabundance in first-ascent giants, following convective dilution on the lower giant branch. In the mass range 1.2-2.0 solar, stars with equatorial rotational velocities greater than 30-35 km/s on the ZAMS should destroy most of their Li. These result are compared to recent Li abundance determination in three moderately old clusters, NGC 7789, NGC 752, and M67. Reasonably good agreement is found with data on M67 and NGC 752, but surprising disagreement with data on NGC 7789 is found. Possible explanations are considered. 60 refs

37

Molecular mechanism of the Escherichia coli maltose transporter  

OpenAIRE

ATP-binding cassette (ABC) transporters are ubiquitous membrane proteins that import and export a large variety of materials across the lipid bilayer. A key question that drives ABC transporter research is how ATP hydrolysis is coupled to substrate translocation. This review uses the maltose transporter of Escherichia coli as a model system to understand the molecular mechanism of ABC importers. X-ray crystallography was used to capture the structures of the maltose transporter in multiple co...

Chen, Jue

2013-01-01

38

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)

39

Transport and retention of dormant copepods in the Gulf of Maine  

Science.gov (United States)

Variability in the availability of dormant copepods to seed productive shelf areas has been hypothesized to influence the abundance of the dominant copepod species Calanus finmarchicus in several regions of the North Atlantic. One source of this variability is advection of dormant copepods in deep water. Using Lagrangian particle simulations, we examined the influence of environmental forcing and copepod behavior on transport and retention of dormant C. finmarchicus in the deep Gulf of Maine, in the northwestern Atlantic. Retention in the Gulf of Maine was relatively high, >40% over 6 months, under all conditions simulated. Transport within the Gulf of Maine was high, resulting in shifts of eastern copepods into the western Gulf and of upstream copepods, from slope and Scotian Shelf waters, into the eastern Gulf. Copepod behavior during dormancy was a major source of uncertainty, but it is probably not a major source of interannual variability in retention. Retention increased with the initial depth of dormant copepods, and vertical positioning behavior had a strong influence on retention for simulations started at depths greater than 150 m, because copepods that can stay below basin sill depths are retained. Mean cross-shore winds reduced retention slightly (<2% absolute difference), and mean alongshore winds increased retention by 4-8%. Wind-driven interannual variability in retention was low. Variability in Scotian Shelf inflow had a greater influence on retention than did variability in winds, and inflow-driven changes in retention may contribute to interannual variability in copepod abundance associated with changes in deep-water temperature. However, estimates of advective loss are relatively low compared to measured reductions in dormant copepod abundance, and mortality is probably a major factor in this reduction.

Johnson, Catherine; Pringle, James; Chen, Changsheng

2006-11-01

40

Rupture mechanics of metallic alloys for hydrogen transport  

International Nuclear Information System (INIS)

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.)

41

Investigation of nutrient transport mechanisms in the lacunae-canaliculi system  

International Nuclear Information System (INIS)

The aim of this study is to investigate nutrient transport mechanisms in the lacunae-canaliculi system. The latter has been identified as the main pathway for the supply of osteocytes, bone cells that play a crucial role in triggering bone remodeling-related cell activities, with vital nutrients. Recent findings suggest that their transport through the lacuna-canaliculi system is mainly driven by spatial concentration gradients and by mechanical stimuli exerted on the surrounding bone matrix, leading to changes in pore pressure and consequently to advective solute transport. Thus, the underlying mathematical framework is based on classical diffusion and Navier-Stokes equations. The set of governing equations is solved numerically, by means of the Finite Element method. Numerical studies are carried out to elucidate the influence of different loading and boundary conditions on the resulting nutrient transport. The results are finally compared to corresponding findings reported in the open bone biology literature.

42

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 sensithod. 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)

43

Structural insights into ABC transporter mechanism  

Energy Technology Data Exchange (ETDEWEB)

ATP-binding cassette (ABC) transporters utilize the energy from ATP hydrolysis to transport substances across the membrane. In recent years, crystal structures of several ABC transporters have become available. These structures show that both importers and exporters oscillate between two conformations: an inward-facing conformation with the substrate translocation pathway open to the cytoplasm and an outward-facing conformation with the translocation pathway facing the opposite side of the membrane. In this review, conformational differences found in the structures of homologous ABC transporters are analyzed to understand how alternating-access is achieved. It appears that rigid-body rotations of the transmembrane subunits, coinciding with the opening and closing of the nucleotide-binding subunits, couples ATP hydrolysis to substrate translocation.

Oldham, Michael L.; Davidson, Amy L.; Chen, Jue (Purdue)

2010-07-27

44

IMPROVEMENT OF FREIGHT TRANSPORTATION PROCESS AND THEIR MANAGEMENT MECHANISM  

Directory of Open Access Journals (Sweden)

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.

L. V. Martsenyuk

2014-03-01

45

Financial resources management during major overhaul of main facilities of railway transport in the process of its reforming  

Directory of Open Access Journals (Sweden)

Full Text Available In the article some directions of financing the programs of updating and modernizing the main facilities of the railways of Ukraine in the conditions of reforming the railway transport are considered.

O.M. Shalenyi

2012-12-01

46

Coal ash transportation as paste-like, highly loaded pulps in Brazil: characterization and main features  

Energy Technology Data Exchange (ETDEWEB)

The transportation of mineral coal ash in trucks with open top load compartments is inefficient, harmful to the environment, and costly. One solution to this problem is to utilize highly concentrated aqueous suspensions (paste) transportation systems, through steel pipes assisted by hydraulic pumping. In this study, coal ash (both fly ash and bottom ash), produced at a typical coal power plant (South Brazil), was utilized at different formulations, with mixtures of fly ash, bottom ash, and water (65%-70% solids content). These ash-bearing pulps were characterized in terms of their chemical and mineralogical composition, suspension pH that varied with the presence of Ca-bearing minerals, particle size distribution, and rheological behavior. Ash samples were distributed in fine, mean, and coarse sizes, facilitating the particles packing, diminishing voids, and contributing to the formation of paste with good consistency. The ash suspensions (32% water content) did not show compression strength and were plastically deformed after 48 hours of water addition. This behavior indicates that there were no chemical reactions, or pozzolanic activity, and that the particle interactions were mainly due to electrostatic forces and dispersions forces.

Braganca, S.R.; Goncalves, M.R.F.; Bergmann, C.P.; Rubio, J. [Universidade Federal do Rio Grande do Sul, Porto Alegre (Brazil)

2009-07-01

47

Jaumann transport in relativistic continuum mechanics  

International Nuclear Information System (INIS)

The Jaumann derivative of a tensor field in relativity is defined by a formal generalization of a stress rate in viscoelasticity. A tensor field is said to be Jaumann transported if its Jaumann derivative vanishes. It is found that the gravitational potentials are Jaumann transported identically. The concept of a ''complete rotation tensor'' has been introduced to study the Jaumann derivative with respect to a null vector field. This provides a characterization of the integrability of a hypersurface orthogonal congruence. A perfect fluid collapsing by neutrino emission and undergoing Jaumann transport with respect to the neutrino flow is found to be compatible with that of a catastrophic collapse. The circumstances leading to the existence of ''ghost neutrinos'' are cited. The degeneracy of the Kerr-Newmann black hole into the Reissner-Nordstrom black hole is expressed in terms of the Jaumann propagation. (author)

48

Directional auxin transport mechanisms in early diverging land plants  

OpenAIRE

The emergence and radiation of multicellular land plants was driven by crucial innovations to their body plans [1]. The directional transport of the phytohormone auxin represents a key, plant-specific mechanism for polarization and patterning in complex seed plants [2, 3, 4 and 5]. Here, we show that already in the early diverging land plant lineage, as exemplified by the moss Physcomitrella patens, auxin transport by PIN transporters is operational and diversified into ER-localized and plasm...

Viaene, Tom; Landberg, Katarina; Thelander, Mattias; Medvecka, Eva; Pederson, Eric; Feraru, Elena; Cooper, Endymion D.; Karimi, Mansour; Delwiche, Charles F.; Ljung, Karin; Geisler, Markus; Sundberg, Eva

2015-01-01

49

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...

50

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...

51

Charge transport mechanism in thin cuticles holding nandi flame seeds.  

Science.gov (United States)

Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4 mum 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 x 10(-5) (m(2)V(-1)s(-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(E(F)) approximately 9.04 x 10(19) (eV(-1)cm(-3)) and hopping distance R approximately 1.44 x 10(-7) cm, while the hopping energy (W) was in the range of 0.72 eV-0.98 eV. PMID:20130799

Kipnusu, Wycliffe K; Katana, Gabriel; Migwi, Charles M; Rathore, I V S; Sangoro, Joshua R

2009-01-01

52

Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds  

Directory of Open Access Journals (Sweden)

Full Text Available Metal-sample-metal sandwich configuration has been used to investigate DC conductivity in 4??m 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.

Wycliffe K. Kipnusu

2009-01-01

53

Transport Mechanisms in Polarized Semiconductor Photocathodes  

Energy Technology Data Exchange (ETDEWEB)

We investigated the effect of an accelerating field on the spin polarization of photogenerated electrons in a 100nm thick GaAs based photocathode active region. By decreasing the transport time of the electrons and the number of scattering events that cause depolarization, we expected to increase the polarization as was indicated by Monte Carlo simulations of the scattering and transport time statistics of the electrons. A tungsten (W) grid was deposited on the cathode surface to provide a uniform voltage distribution across the cathode surface. The metal grid formed a Schottky contact with the semiconductor surface. The bias voltage was primarily dropped at the metal semiconductor interface region, which is the cathode active region. For positive surface bias, the accelerating voltage not only increased the polarization, but it also enhanced the quantum efficiency of the photocathode. Preliminary results verify the bias effect on both quantum efficiency and polarization by a factor of 1.8 and 1% respectively.

Ioakeimidi, K.; Brachmann, A.; Clendenin, J.E.; Garwin, E.L.; Kirby, R.E.; Maruyama, T.; Prescott, C.Y.; /SLAC; Prepost, R.; /Wisconsin U., Madison

2006-12-18

54

Quantum mechanisms of density wave transport  

OpenAIRE

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 invers...

Miller, John H.; Wijesinghe, Asanga I.

2012-01-01

55

Optimal design of a main driving mechanism for servo punch press based on performance atlases  

Science.gov (United States)

The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed, high accuracy, high flexibility, high productivity, low noise, cleaning and energy saving. To effectively improve the performance and lower the cost, it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices. A new patented main driving mechanism and a new optimal design method are proposed. In the optimal design, the performance indices, i.e., the local motion/force transmission indices ITI, OTI, good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined. The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis. Thereafter, the performance atlases, which can present all possible design solutions, are depicted. As a result, the feasible solution of the mechanism with good motion/force transmission performance is obtained. And the solution can be flexibly adjusted by designer according to the practical design requirements. The proposed mechanism is original, and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.

Zhou, Yanhua; Xie, Fugui; Liu, Xinjun

2013-09-01

56

Molecular mechanism of the Escherichia coli maltose transporter.  

Science.gov (United States)

ATP-binding cassette (ABC) transporters are ubiquitous membrane proteins that import and export a large variety of materials across the lipid bilayer. A key question that drives ABC transporter research is how ATP hydrolysis is coupled to substrate translocation. This review uses the maltose transporter of Escherichia coli as a model system to understand the molecular mechanism of ABC importers. X-ray crystallography was used to capture the structures of the maltose transporter in multiple conformations. These structures, interpreted in the light of functional data, are discussed to address the following questions: first, what is the nature of conformational changes in a transport cycle? Second, how does substrate activate ATPase activity? Third, how does ATP hydrolysis enable substrate transport? PMID:23628288

Chen, Jue

2013-08-01

57

Transport mechanism in granular Ni deposited on carbon nanotubes fibers  

Science.gov (United States)

We investigate the transport properties of granular nickel electrodeposited on carbon nanotube fibers by measuring the electrical resistance and the current voltage characteristics as a function of the temperature. The bare fiber is governed by a three-dimensional variable range hopping transport mechanism, however, a semiconducting to metallic transition is observed after the Ni deposition as a consequence of the evolution from weak to strong coupling between the deposited nickel grains. The experimental results indicate that the charge transport in the Ni-coated fiber develops from hopping governed by the Coulomb blockade in the case of small grains dimensions to a metallic electron phonon interaction mechanism for large grains dimensions. Tunneling enhanced by thermal fluctuation is responsible for the transport in the intermediate conductivity range. The role of the fiber and the effects due to the magnetic nature of the nickel grains are also discussed.

Salvato, M.; Lucci, M.; Ottaviani, I.; Cirillo, M.; Tamburri, E.; Orlanducci, S.; Terranova, M. L.; Notarianni, M.; Young, C. C.; Behabtu, N.; Pasquali, M.

2012-09-01

58

The molecular mechanism of targeted vesicle transport in cytokinesis.  

Science.gov (United States)

Recent studies have demonstrated that vesicle transport to cleavage furrow is indispensable for cytokinesis. Some animal and plant cells form distinct structures during cell division known as central spindle and phragmoplast, respectively. Several essential factors involved in the vesicle transport have been isolated so far. SNARE proteins and molecular motors play a central role in this process. For future research of cytokinesis, it is important to investigate these factors as well as cytoskeletal components of the contractile ring in detail. This review focuses on the molecular mechanism of targeted vesicle transport in cytokinesis. PMID:11942610

Edamatsu, M

2001-12-01

59

Transport mechanisms acting in toroidal devices: A theoretician's view  

International Nuclear Information System (INIS)

Understanding the basic mechanisms of transport in toroidal confinement devices remains one of the more challenging scientific issues in magnetic confinement. At the same time, it is a critical issue for the magnetic fusion program. Recent progress in understanding fluctuations and transport has been fostered by the development and use of new diagnostics, bringing new perspectives on these studies. This has stimulated new theoretical developments. In this paper, a view of the most recent issues and progress in this area is given. The role of long wavelengths in core transport and the relation between shear flows and turbulence at the plasma edge are the primary topics considered in this paper

60

Transport mechanisms acting in toroidal devices: A theoretician's view  

International Nuclear Information System (INIS)

Understanding the basic mechanisms of transport in toroidal confinement devices remains one of the more challenging scientific issues in magnetic confinement. At the same time, it is a critical issue for the magnetic fusion program. Recent progress in understanding fluctuations and transport has been fostered by the development and use of new diagnostics, bringing new perspectives on these studies. This has stimulated new theoretical developments. A view of the most recent issues and progress in this area is given. The role of long wavelengths in core transport and the relation between shear flows and turbulence at the plasma edge are the primary topics considered

61

Mechanical Behaviour of the Short Models of LHC Main Dipole Magnets  

CERN Document Server

A series of single and twin aperture 1 metre magnet models has been built and tested in the framework of the R&D program of main superconducting dipole magnets for the Large Hadron Collider project. The se models, designed for a nominal field of 8.3 T at 1.8 K, have been constructed to test the performance of SC coils and to optimise various design options for the full length 15 metre long dipoles. T he models have been extensively equipped with a specially developed mechanical instrumentation, enabling both the control of main assembly parameters - like coil azimuthal and axial pre-load, stress i n the outer shrinking cylinder - and also the monitoring of magnet behaviour during cooling and energising, under the action of electromagnetic forces. The instrumentation used, mainly based on strain gauge transducers, is described and the results of mechanical measurements obtained during power tests of the models are discussed and compared with the design predictions based on Finite Element calc ulations.

Andreyev, N I; Casarejos, E; Kurtyka, T; Rathjen, C; Perini, D; Siegel, N; Tommasini, D; Vanenkov, I

1998-01-01

62

Overview of main-mechanical-components and critical manufacturing aspects of the Wendelstein 7-X cryostat  

International Nuclear Information System (INIS)

Wendelstein 7-X (W7-X) will be the world's largest superconducting helical advanced stellarator. This stellarator concept is deemed to be a desirable alternative for a future power plant like DEMO. The main advance of the static plasma is caused by the three dimensional shape of some of the main mechanical component inside the cryostat. The geometry of the plasma vessel is formed around the three dimensional shape of the plasma. The coils and their support structure are enclosed within the outer vessel. The space between the outer, the plasma vessel and the ports is called cryostat because the vacuum inside provides thermal insulation of the magnet system which is cooled down to 4 K. Due to the different thermal movements of both vessels and the support structure have to be supported separately. 10 cryo legs will bear the coil support structure. The plasma vessel supporting system is divided into two separate systems, allowing horizontal and vertical adjustments. This paper aims to give an overview of the main mechanical components of the cryostat. The authors delineate some disparate and special problems during the manufacturing of the components at the companies in Europe. It describes the current manufacturing and assembly.

63

Function and mechanism of cyclic electron transport  

Energy Technology Data Exchange (ETDEWEB)

In isolated intact chloroplasts from spinach, maximal rates of photosynthetic O/sub 2/ evolution (in saturating HCO/sub 3//sup -/) are associated with a critical transthylakoid pH gradient of about 3.9 units. O/sub 2/ evolution is inhibited by higher ..delta..pH values that arise when catalase is omitted from the medium; NH/sub 4/Cl and actimycin, but not the energy transfer inhibitor quercetin, decrease ..delta..pH and relieve this inhibition. The same low amount NH/sub 4/Cl added to control chloroplasts (..delta..pH=3.9) has little effect on ..delta..pH or the O/sub 2/ evolution rate. This resistance to uncoupling is due to an increase in the pumping of protons by cyclic electron flow. It suggests operation of feedback control in maintaining an optimal ATP/NADPH ratio. A general mechanism is proposed that allows the chloroplast to divert electrons from ferredoxin:NADP/sup +/ reductase into the cyclic pathway to provide a ..delta..pH appropriate to the ATP/NADPH ratio needed in the stroma. The stromal NADPH/NADP/sup +/ ratio is probably sensed indirectly by membrane components with redox mid point potentials around - 50 mV, such that reduction of these components causes partial loss of linear electron flow and commencement of cyclic turnover.

Hind, G; Crowther, D; Shahak, Y; Slovacek, R E

64

Catalyst Transport in Corn Stover Internodes: Elucidating Transport Mechanisms Using Direct Blue-I  

Energy Technology Data Exchange (ETDEWEB)

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 over-all 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.

Viamajala, S.; Selig, M. J.; Vinzant, T. B.; Tucker, M. P.; Himmel, M. E.; McMillan, J. D.; Decker, S. R.

2006-04-01

65

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

Science.gov (United States)

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

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

2006-01-01

66

Issues in tokamak/stellarator transport and confinement enhancement mechanisms  

International Nuclear Information System (INIS)

At present, the mechanism for anomalous energy transport in low-? 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

67

Mechanism of destruction of transport barriers in geophysical jets with Rossby waves  

CERN Document Server

The mechanism of destruction of a central transport barrier in a dynamical model of a geophysical zonal jet current in the ocean or the atmosphere with two propagating Rossby waves is studied. We develop a method for computing a central invariant curve which is an indicator of existence of the barrier. Breakdown of this curve under a variation of the Rossby wave amplitudes and onset of chaotic cross-jet transport happen due to specific resonances producing stochastic layers in the central jet. The main result is that there are resonances breaking the transport barrier at unexpectedly small values of the amplitudes that may have serious impact on mixing and transport in the ocean and the atmosphere. The effect can be found in laboratory experiments with azimuthal jets and Rossby waves in rotating tanks under specific values of the wave numbers that are predicted in the theory.

Uleysky, M Yu; Prants, S V; 10.1103/PhysRevE.81.017202

2012-01-01

68

Controllable Lubrication for Main Engine Bearings Using Mechanical and Piezoelectric Actuators  

DEFF Research Database (Denmark)

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.

Estupinan, Edgar; Santos, Ilmar

2012-01-01

69

Early metabolic effects and mechanism of ammonium transport in yeast  

International Nuclear Information System (INIS)

Studies were performed to define the effects and mechanism of NH+4 transport in yeast. The following results were obtained. Glucose was a better facilitator than ethanol-H2O2 for ammonium transport; low concentrations of uncouplers or respiratory inhibitors could inhibit the transport with ethanol as the substrate. With glucose, respiratory inhibitors showed only small inhibitory effects, and only high concentrations of azide or trifluoromethoxy carbonylcyanide phenylhydrazone could inhibit ammonium transport. Ammonium in the free state could be concentrated approximately 200-fold by the cells. Also, the addition of ammonium produced stimulation of both respiration and fermentation; an increased rate of H+ extrusion and an alkalinization of the interior of the cell; a decrease of the membrane potential, as monitored by fluorescent cyanine; an immediate decrease of the levels of ATP and an increase of ADP, which may account for the stimulation of both fermentation and respiration; and an increase of the levels of inorganic phosphate. Ammonium was found to inhibit 86Rb+ transport much less than K+. Also, while K+ produced a competitive type of inhibition, that produced by NH4+ was of the noncompetitive type. From the distribution ratio of ammonium and the pH gradient, an electrochemical potential gradient of around -180 mV was calculated. The results indicate that ammonium is transported in yeast by a mechanism similar to that of monovalent alkalinnism similar to that of monovalent alkaline cations, driven by a membrane potential. The immediate metabolic effects of this cation seem to be due to an increased [H+]ATPase, to which its transport is coupled. However, the carriers seem to be different. The transport system studied in this work was that of low affinity

70

Mechanical and fracture behavior of nuclear fuel cladding in terms of transport and temporary dry storage  

International Nuclear Information System (INIS)

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)

71

Analysis of radiation doses from operation of postulated commercial spent fuel transportation systems: Main report  

Energy Technology Data Exchange (ETDEWEB)

This report contains a system study of estimated radiation doses to the public and workers resulting from the transport of spent fuel from commercial nuclear power reactors to a geologic repository. The report contains a detailed breakdown of activities and a description of time/distance/dose-rate estimates for each activity within the system. Collective doses are estimated for each of the major activities at the reactor site, in transit, and at the repository receiving facility. Annual individual doses to the maximally exposed individuals or groups of individuals are also estimated. A total of 17 alternatives and subalternatives to the postulated reference transportation system are identified, conceptualized, and their dose-reduction potentials and costs estimated. Resulting ratios of ..delta..cost/..delta..collective system dose for each alternative relative to the postulated reference transportation system are given. Most of the alternatives evaluated are estimated to provide both cost and dose reductions. Major reductions in transportation system dose and cost are estimated to result from using higher-capacity rail and truck casks, and particularly when replacing legalweight truck casks with ''advanced design'' overweight truck casks. The greatest annual dose reduction to the highest exposed individual workers (i.e., at the repository) is estimated to be achieved by using remote handling equipment for the cask handling operations at the repository. Additional shielding is also effective in reducing doses to both radiation workers at the reactor and repository and to transport workers. 69 refs., 36 figs., 156 tabs.

Schneider, K.J.; Hostick, C.J.; Ross, W.A.; Peterson, R.W.; Smith, R.I.; Stiles, D.L.; Daling, P.M.; Weakley, S.A.; Grinde, R.B.; Young, J.R.

1987-11-01

72

Structure and mechanism of ATP-dependent phospholipid transporters  

DEFF Research Database (Denmark)

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.

Lopez Marques, Rosa Laura; Poulsen, Lisbeth Rosager

2015-01-01

73

Directed transport as a mechanism for protein folding in vivo  

CERN Document Server

We propose a model for protein folding in vivo based on a Brownian-ratchet mechanism in the multidimensional energy landscape space. The device is able to produce directed transport taking advantage of the assumed intrinsic asymmetric properties of the proteins and employing the consumption of energy provided by an external source. Through such a directed transport phenomenon, the polypeptide finds the native state starting from any initial state in the energy landscape with great efficacy and robustness, even in the presence of different type of obstacles. This model solves Levinthal's paradox without requiring biased transition probabilities but at the expense of opening the system to an external field.

Gonzalez-Candela, Ernesto

2009-01-01

74

Mechanism of regulation of glucose transport in Rhizobium leguminosarum.  

OpenAIRE

Multiple glucose transport systems were distinguished in Rhizobium leguminosarum. We found nonlinear Lineweaver-Burk plots for the uptake of glucose, 2-deoxy-D-glucose, and alpha-methyl-D-glucoside, and this implied the existence of at least two uptake mechanisms. Different patterns of inhibition of 2-deoxy-D-glucose uptake and alpha-methyl-D-glucoside uptake at 0.1 mM by various carbohydrates revealed differences in the stereospecificities of the transport systems. Osmotic shock treatment ab...

Vries, G. E.; Brussel, A. A.; Quispel, A.

1982-01-01

75

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

2006-11-01

76

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

CERN Document Server

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.

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

77

Control mechanisms for intelligent transportation systems (ITS) cooperative safety applications  

OpenAIRE

In the last decades, Intelligent Transportation Systems (ITS) have been considered as one of the most emerging research area due to their promising role in promoting traffic efficiency and enhancing road safety. ITS cooperative safety applications, being the most vital and critical, have gained a lot of attention. The effectiveness of these applications depends widely on the efficient exchange of two main types of information. The periodic awareness corresponding to the one-hop location infor...

Hrizi, Fatma

2012-01-01

78

A lidar-derived evaluation of watershed-scale large woody debris sources and recruitment mechanisms: coastal Maine, USA  

Science.gov (United States)

In-channel large woody debris (LWD) promotes quality aquatic habitat through sediment sorting, pool scouring, and in-stream nutrient retention and transport. LWD recruitment can occur by numerous ecological and geomorphic mechanisms including channel migration, mass wasting, and natural tree fall, yet LWD sourcing on the watershed scale remains poorly constrained. We develop a rapid and spatially extensive method for using high-resolution light detection and ranging (lidar) elevation data to (1) constrain tree height throughout a watershed, (2) determine the likelihood for streams to recruit channel-spanning trees at reach scales, (3) establish whether adjacent tree fall, mass wasting, or channel migration may be the dominant mechanism for delivery of LWD, and (4) understand the past and future role of LWD at a watershed scale. We utilize this method on the 78 km long Narraguagus River in coastal Maine, and find that potential channel-spanning LWD composes approximately 6% of valley area over the course of the river and is concentrated in spatially discrete reaches along the stream, with 5 km of the river valley accounting for 50% of total potential channel-spanning LWD found in the system. We also determine 83% of all potential channel-spanning LWD is located on valley sides, as opposed to 17% on lower-lying hillslope and terrace surfaces. Approximately 3% of channel-spanning vegetation along the river is located within one channel width of the stream. By examining topographic and morphologic variables (valley width, channel sinuosity, valley-side slope) over the length of the stream, we evaluate the dominant recruitment processes along the river and often find a spatial disconnect between the location of potential LWD and recruitment mechanisms, which likely explains the low levels of LWD found in the system. This rapid method for identification of potential LWD sources is extendable to other basins and may prove valuable in locating future restoration projects aimed at increasing aquatic habitat through wood additions.

Kasprak, A.; Magilligan, F. J.; Nislow, K.; Snyder, N. P.

2010-12-01

79

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

Science.gov (United States)

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.

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

2007-07-01

80

Transport mechanisms and enhanced confinement studies in RFX  

International Nuclear Information System (INIS)

The results of an extensive study on transport mechanisms and on improved confinement scenarios in RFX are reported. The scaling of the thermal conductivity in the core with the Lundquist number indicates that the magnetic field in this region is not fully stochastic, as proved by the existence of thermal barriers observed in Single Helicity configurations. The electrostatic transport at the edge has been proved to depend on the highly sheared ExB flow which has been interpreted by fluid and Monte Carlo models. Regimes of improved confinement have been obtained in the core by Poloidal Current Drive techniques and the electrostatic transport has been reduced at the edge by biasing experiments. A radiation mantle by impurity seeding has been found to successfully reduce the local plasma wall interaction without significantly deteriorating the plasma performance. (author)

81

Transport mechanisms and enhanced confinement studies in RFX  

International Nuclear Information System (INIS)

The results of an extensive study on transport mechanisms and on improved confinement scenarios in RFX are reported. The scaling of the thermal conductivity in the core with the Lundquist number indicates that the magnetic field in this region is not fully stochastic, as proved by the existence of thermal barriers observed in single helicity configurations. The electrostatic transport at the edge has been proved to depend on the highly sheared ExB flow, which has been interpreted using fluid and Monte Carlo models. Regimes of improved confinement have been obtained in the core by poloidal current drive techniques, and the electrostatic transport has been reduced at the edge by biasing experiments. A radiation mantle caused by impurity seeding has been found to successfully reduce the local plasma-wall interaction without causing a significant deterioration in the plasma performance. (author)

82

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

OpenAIRE

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...

Pothof, I. W. M.

2011-01-01

83

Critical Analysis of Fission Product Transport in the HTGRs: Main Research Areas  

Energy Technology Data Exchange (ETDEWEB)

Transport and plateout of radionuclides within the primary circuit of High Temperature Gas-cooled Reactor (HTGR) is essential during a blowdown transient. this paper analysis the existing database and illustrates the prediction capability presently existing. Beyond any doubt, the database should be extended particularly concerning fission product-dust interaction and phenomena such as liftoff which contribution is essential for in-confinement source term. Evidences point out the need to improve current analytical tools. (Author) 5 refs.

Garcia, M.; Fontanet, J.; Herranz, L. E.

2009-07-01

84

Critical Analysis of Fission Product Transport in the HTGRs: Main Research Areas  

International Nuclear Information System (INIS)

Transport and plateout of radionuclides within the primary circuit of High Temperature Gas-cooled Reactor (HTGR) is essential during a blowdown transient. this paper analysis the existing database and illustrates the prediction capability presently existing. Beyond any doubt, the database should be extended particularly concerning fission product-dust interaction and phenomena such as liftoff which contribution is essential for in-confinement source term. Evidences point out the need to improve current analytical tools. (Author) 5 refs.

85

Increased coordination in public transport – which mechanisms are available?  

DEFF Research Database (Denmark)

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 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.

SØrensen, Claus Hedegaard; Longva, Frode

2011-01-01

86

Mechanism of copper transport from plasma to hepatocytes  

International Nuclear Information System (INIS)

The effects of plasma components on the kinetics of copper transport by rat hepatocytes were examined in an attempt to determine how copper is mobilized from plasma for uptake by the liver. Specific protein-facilitated transport was indicated by saturation kinetics, competition by related substrates, and similar kinetic parameters for uptake and efflux. For copper uptake, K/sub m/ = 11 +/- 0.6 ?M and V/sub max/ = 2.7 +/- 0.6 nmol Cu/(min x mg protein). Zinc is a competitive inhibitor of copper uptake, and copper competes for zinc uptake. Copper efflux from preloaded cells is biphasic. The kinetic parameters for the initial rapid phase are similar to the parameters for uptake. Copper transport by hepatocytes is strictly passive. A variety of metabolic inhibitors have no effect on uptake and initial rates are solely dependent on extracellular-intracellular concentration gradients. Albumin markedly inhibits copper intake by a substrate removal mechanism, and histidine facilitates albumin-inhibited copper uptake. The active species that delivers copper to hepatocytes under conditions of excess albumin and excess histidine is the His2Cu complex. Experiments with [3H]His264Cu showed that the transported species is free ionic copper. The kinetic parameters of copper transport by hepatocytes isolated from the brindled mouse model of Menkes' disease are normal. However, these cells show a decreased capacity to accumulate copper on prolonged incubation. An intracellular metabolic defect seems to be involved

87

Atom transport mechanisms in irradiation-driven phase transformation  

International Nuclear Information System (INIS)

The steady state of a phase mixture under irradiation is controlled by the irradiation-induced atom transport. Quantitative understanding of phase stability under irradiation, therefore, requires measurements of all relevant components of the atom transport as well as of the quantities characterizing the mixture of phases. The paper presents two cases (1) and (2) for which this requirement is fulfilled. In each of the cases new aspects of the irradiation induced transport mechanisms become obvious. (1) From studies of the temperature dependent influence of irradiations by 300 keV Cu+ ions and 150 keV protons on the phase decompositions of Cu-Ni-Fe alloys containing 8 at. % Fe detailed conclusions on the spatially inhomogeneous and time dependent counteraction of recoil dissolution and irradiation-enhanced interdiffusion are derived. By means of small angle neutron scattering measurements in electron irradiated Cu-Ni-Fe alloys containing 4 at. % Fe a drastic influence of the atom transport due to interstitialcy migration on the phase decomposition is detected. It indicates a substantial modification of the thermodynamic driving force. (2) Studies of Cu+ ion irradiation-induced ? precipitation in undersaturated samples of Cu-1.4 at. % Be and Be monolayer broadening within a Cu single crystal prove the existence of a fast Be interstitial transport and show that the ? precipitates are not dissolved by recoil disordering via replacement collisions bdisordering via replacement collisions but by recoil displacements. (author) 18 refs., 12 figs

88

IDDTL: A Novel Identified Internet Data Transport Layer Mechanism  

Directory of Open Access Journals (Sweden)

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.

Yangyang Gao

2014-01-01

89

DEVELOPMENT OF SCIENTIFIC SCHOOL OF TRANSPORT MECHANICS: ARTISTIC LEGACY OF YE. P. BLOKHIN  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose. Development of domestic and global transport science occurred due to the contributions of many scientists and practicing engineers. The purpose of our study is the analysis of scientific documentary legacy of YE. P. Blokhin, Doctor of Technical Sciences, Professor of Dnipropetrovsk National University of Railway Transport named after Academician V. Lazaryan and identifying his place and role in the development of modern railway transport. Methodology. Application of problem-chronological, comparative, descriptive historical methods of research, systematization and analysis of scientific papers allowed the authors to submit the actual history of the railway transport development (1950-2013 through the prism of YE. P. Blokhin scientific activity. We identified 6 main periods of his scientific activity. Findings. It was found out that the overall intellectual plant of the scientist includes 555 scientific papers (written personally and co-authored in domestic and foreign publications on key issues of mechanics and operation of railway rolling stock. Artistic legacy of YE. P. Blokhin includes monographs, articles, reports, patents, author certificate, etc. It was found that the epistolary legacy of scientist, archive materials, his personal diaries, reference list of works of his students and followers are almost unexplored. Originality. Authors of the work for the first time in the history of science and technology of Ukraine conducted a complex study of the scientific legacy of YE. P. Blokhin in the context of railway transport. It is proved that the ideas, research, scientific works, implemented projects, numerous students and followers of YE. P. Blokhin are important factors, confirming a significant contribution of the scientist to the global engineering and transport science. Practical value. The work can be used to create historiographical papers and textbooks, to study the issues of formation and development of the scientific school for transport mechanics and university science ofUkraine in the railway branch, in the course of lectures on the subjects «History of railway transport development» and «Introduction to the profession»

S. V. Myamlin

2014-01-01

90

CO{sub 2} mitigation through biofuels in the transport sector - Status and perspectives. Main report  

Energy Technology Data Exchange (ETDEWEB)

Many studies have been conducted world-wide to examine the environmental impact of biofuels for transportation and estimate their cost and quantity potential. These studies have at times shown considerable differences in the findings and conclusions. In order to obtain an overview which identifies the strengths and weaknesses of the available studies and to determine further research needs, IFEU Institute Heidelberg conducted the present study. It was commissioned by the Research Association for Combustion Engines FVV - with member companies such as BMW, DaimlerChrysler, and Volkswagen - and the Union for the Promotion of Oil and Protein Plants gathering organizations such as the German Farmer's Association, the German Cooperative Association, and the Association of the Chambers of Agriculture Plant Breeding Companies. This study analyses and compares all international, publicly accessible publications about all biofuels for transportation currently used (e.g. biodiesel and bioethanol as well as those potential future biofuels like BTL). More than 800 studies were taken into account. From these, 63 studies satisfied the criteria for detailed analyses, leading to the valuation of 109 balances of energy and greenhouse gases of various biofuels, which were compared either to conventional fuels or other biofuels. In most cases the complete life-cycles of the fuels, from production to consumption, were considered. (orig.)

Quirin, M.; Gaertner, S.O.; Pehnt, M.; Reinhardt, G.A.

2004-08-01

91

Cross-field plasma transport and main-chamber recycling in diverted plasmas on Alcator C-Mod  

International Nuclear Information System (INIS)

Cross-field particle transport increases sharply with distance into the SOL and plays a dominant role in the 'main-chamber recycling' regime in Alcator C-Mod, a regime in which most of the plasma particle efflux recycles on the main-chamber walls rather than flows into the divertor volume. This observation has potentially important implications for a reactor: contrary to the ideal picture of divertor operation, a tightly baffled divertor may not offer control of the neutral density in the main-chamber such that charge exchange heat losses and sputtering of the main-chamber walls can be reduced. The conditions that give rise to the main-chamber recycling regime can be understood by considering the plasma-neutral particle balance: when the flux surface averaged neutral density exceeds a critical value, flows to the divertor can no longer compete with the ionization source and particle fluxes must increase with distance into the SOL. This critical neutral density condition can be recast into a critical cross-field plasma flux condition: particle fluxes must increase with distance into the SOL when the plasma flux crossing a given flux surface exceeds a critical value. Thus, the existence of the main-chamber recycling regime is intrinsically tied to the level of anomalous cross-field particle transport. Direct measurement of the effective cross-field particle diffusivities Deff in a number of ohmic L mode discharges indicates that Deff near the separicates that Deff near the separatrix strongly increases as plasma collisionality increases. Convected heat fluxes correspondingly increase, implying that there exists a critical plasma density (or perhaps collisionality) beyond which no steady state plasma can be maintained, even in the absence of radiation. (author)

92

Analysis of the main optical mechanisms responsible for fragmentation of gold nanoparticles by femtosecond laser radiation  

International Nuclear Information System (INIS)

Studies of fragmentation process of gold nanoparticles (Nps) in deionized water after generation by femtosecond laser ablation were performed. To analyze the fragmentation process, direct IR ultrafast pulses or super-continuum (SC) radiation focused in the colloidal solution were used in separate steps. IR pulses and SC generated externally in a sapphire crystal or directly inside the water were applied under low fluence regime. In the latter cases, to evaluate the effect on fragmentation of the different spectral bands present in the SC, we have determined different efficiency regions characterized by means of the product between the spectral response and the optical extinction spectrum corresponding to the initial Nps solution. From the analysis of this product function, we can conclude that the main fragmentation mechanism is due to linear absorption in the visible region. Likewise, the SC generated in water resulted more efficient than the SC obtained externally by a sapphire crystal. This fact may be attributed to the blue broadening of the water SC spectrum (as compared with the sapphire SC) due to the large intensity used for its generation. Transmission electron microscopy and small angle x-ray scattering measurements support the results found from optical extinction spectroscopy.

93

Physiological mechanism for enhancement of paracellular drug transport.  

Science.gov (United States)

We examined the action mechanisms of enhancers that improve paracellular drug transport. For sodium caprate (C10), the increase in the intracellular calcium level was considered to induce the contraction of calmodulin-dependent actin filaments, followed by dilation of the paracellular pathway. Although decanoylcarnitine (DC) also increased the intracellular calcium level, the action was independent of calmodulin and thus, the action mechanism of acylcarnitines was considered to differ from that of C10. Other acylcarnitines, lauroylcarnitine (LC) and palmitoylcarnitine (PC) and organic acids, tartaric acid (TA) and citric acid (CA) decreased the intracellular ATP level and the intracellular pH. From these results, it was considered that one of the action mechanism of acylcarnitines and organic acids is that the intracellular acidosis increases the calcium level through the decrease in ATP levels, followed by opening the tight junction. Membrane dysfunction which was expected from the above mechanism was assessed by the transport function of electrolytes. Membrane conductance, which was increased by C10, LC and PC, returned to the control value during a 3- to 6-h recovery period. On the other hand, Cl(-) ion secretion, which was obtained from short-circuit current (I(sc)), was decreased by these enhancers, but was normalized by C10 but not by LC and PC. Accordingly, C10 can be considered a safer enhancer than acylcarnitines. PMID:10518645

Hayashi, M; Sakai, T; Hasegawa, Y; Nishikawahara, T; Tomioka, H; Iida, A; Shimizu, N; Tomita, M; Awazu, S

1999-11-01

94

Effect of partial mixing of matter on the hydrodynamic angular momentum transport processes in massive main-sequence stars  

Science.gov (United States)

We consider the evolution of a rotating star with a mass of 16 M ? and an angular momentum of 3.25 × 1052 g cm2 s-1, along with the hydrodynamic transport of angular momentum and chemical elements in its interiors. When the partial mixing of matter of the turbulent radiative envelope and the convective core is taken into account, the efficiency of the angular momentum transport by meridional circulation in the stellar interiors and the duration of the hydrogen burning phase increase. Depending on the Schmidt number in the turbulent radiative stellar envelope, the ratio of the equatorial rotational velocity to the circular one increases with time in the process of stellar evolution and can become typical of early-type Be stars during an additional evolution time of the star on the main sequence. Partial mixing of matter is a necessary condition under which the hydrodynamic transport processes can increase the angular momentum of the outer stellar layer to an extent that the equatorial rotational velocity begins to increase during the second half of the evolutionary phase of the star on the main sequence, as shown by observations of the brightest stars in open star clusters with ages of 10-25 Myr. When the turbulent Schmidt number is 0.4, the equatorial rotational velocity of the star increases during the second half of the hydrogen burning phase in the convective core from 330 to 450 km s-1.

Staritsin, E. I.

2009-06-01

95

PKL small break tests and energy transport mechanisms  

International Nuclear Information System (INIS)

For a small break LOCA the energy removed from the primary system by the break flow is only small and an additional heat sink - the secondary side - may be needed. In a KWU-PWR the secondary side is cooled down automatically at a rate of 100 K/h. Heat rejection from the core to the steam generator secondary side by single phase natural circulation, two phase natural circulation and reflux condensation is a very important feature for a small break LOCA. The different energy transport modes have been verified by tests at KWU in the PKL test facility. The program is supported by the German Minister of Research and Technology. In steady-state tests without break and ECC injection the energy transport mechanisms with full and reduced primary water inventory have been investigated. The results proved that the decay heat can readily be removed via the steam generator secondary side by single phase and two phase natural circulation, and even better by heat transfer in the reflux condenser mode. In transient tests (starting at a pressure of 30 bar) the integral response of the system to a secondary cooldown of 100 K/h and the influence of break and ECC injection on the occurrence and transition of the different energy transport mechanisms have been studied. The transient tests proved that the primary system follows closely the secondary cooldown. They supplement and confirm the results of the steady-state tests

96

Mechanism of electrochemical charge transport in individual transition metal complexes.  

Science.gov (United States)

We used electrochemical scanning tunneling microscopy (STM) and spectroscopy (STS) to elucidate the mechanism of electron transport through individual pyridyl-based Os complexes. Our tunneling data obtained by two-dimensional electrochemical STS and STM imaging lead us to the conclusion that electron transport occurs by thermally activated hopping. The conductance enhancement around the redox potential of the complex, which is reminiscent of switching and transistor characterics in electronics, is reflected both in the STM imaging contrast and directly in the tunneling current. The latter shows a biphasic distance dependence, in line with a two-step electron hopping process. Under conditions where the substrate/molecule electron transfer (ET) step is dominant in determining the overall tunneling current, we determined the conductance of an individual Os complex to be 9 nS (Vbias = 0.1 V). We use theoretical approaches to connect the single-molecule conductance with electrochemical kinetics data obtained from monolayer experiments. While the latter leave some controversy regarding the degree of electronic coupling, our results suggest that electron transport occurs in the adiabatic limit of strong electronic coupling. Remarkably, and in contrast to established ET theory, the redox-mediated tunneling current remains strongly distance dependent due to the electronic coupling, even in the adiabatic limit. We exploit this feature and apply it to electrochemical single-molecule conductance data. In this way, we attempt to paint a unified picture of electrochemical charge transport at the single-molecule and monolayer levels. PMID:17177467

Albrecht, Tim; Guckian, Adrian; Kuznetsov, Alexander M; Vos, Johannes G; Ulstrup, Jens

2006-12-27

97

Fracture mechanics approach to spent nuclear fuel transportation cask design  

International Nuclear Information System (INIS)

The Transportation Technology Center at Sandia National Laboratories (SNL/TTC) is assessing the potential of using materials other than stainless steel in the manufacture of nuclear transport cask bodies for service in the United States. The program addresses issues which are a concern from a US licensing and design standpoint; specifically, failure modes at low temperatures with impact loading, fracture mechanics properties, and validation of analytic codes which model cask response due to impact loading. Specific materials which will be addressed in the course of this program are: (i) Ductile Cast Iron (DCI); (ii) Low Alloy Ferritic Steel (FS); (iii) Depleted Uranium (DU). Current efforts are focusing on DCI, primarily because this material is of immediate interest to the cask industry and there is an ample supply of material available for testing. FS will be addressed in the near future and DU will be addressed subsequent to FS

98

Nonlinear charge transport mechanism in periodic and disordered DNA  

CERN Document Server

We study a model for polaron-like charge transport mechanism along DNA molecules with emphasis on the impact of parametrical and structural disorder. Our model Hamiltonian takes into account the coupling of the charge carrier to two different kind of modes representing fluctuating twist motions of the base pairs and H-bond distortions within the double helix structure of $\\lambda-$DNA. Localized stationary states are constructed with the help of a nonlinear map approach for a periodic double helix and in the presence of intrinsic static parametrical and/or structural disorder reflecting the impact of ambient solvent coordinates. It is demonstrated that charge transport is mediated by moving polarons respectively breather compounds carrying not only the charge but causing also local temporal deformations of the helix structure through the traveling torsion and bond breather components illustrating the interplay of structure and function in biomolecules.

Hennig, D; Agarwal, J P

2003-01-01

99

Acid-base transport in pancreatic cancer: molecular mechanisms and clinical potential.  

Science.gov (United States)

Solid tumors are characterized by a microenvironment that is highly acidic, while intracellular pH (pHi) is normal or even elevated. This is the result of elevated metabolic rates in the highly proliferative cancer cells, in conjunction with often greatly increased rates of net cellular acid extrusion. Studies in various cancers have suggested that while the acid extrusion mechanisms employed are generally the same as those in healthy cells, the specific transporters upregulated vary with the cancer type. The main such transporters include Na(+)/H(+) exchangers, various HCO3(-) transporters, H(+) pumps, and lactate-H(+) cotransporters. The mechanisms leading to their dysregulation in cancer are incompletely understood but include changes in transporter expression levels, trafficking and membrane localization, and posttranslational modifications. In turn, accumulating evidence has revealed that in addition to supporting their elevated metabolic rate, their increased acid efflux capacity endows the cancer cells with increased capacity for invasiveness, proliferation, and chemotherapy resistance. The pancreatic duct exhibits an enormous capacity for acid-base transport, rendering pHi dysregulation a potentially very important topic in pancreatic ductal adenocarcinoma (PDAC). PDAC - accounting for about 90% of all pancreatic cancers - has one of the highest cancer mortality rates known, and new diagnostic and treatment options are highly needed. However, very little is known about whether pH regulation is altered in PDAC and, if so, the possible role of this in cancer development. Here, we review current models for pancreatic acid-base transport and pH homeostasis and summarize current views on acid-base dysregulation in cancer, focusing where possible on the few studies to date in PDAC. Finally, we present new data-mining analyses of acid-base transporter expression changes in PDAC and discuss essential directions for future work. PMID:25372771

Kong, Su Chii; Gianuzzo, Andrea; Novak, Ivana; Pedersen, Stine Falsig

2014-12-01

100

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

101

Analysis of mechanical systems with transversal vibrations in transportation  

Directory of Open Access Journals (Sweden)

Full Text Available Purpose: of this article are modelling and dynamic analysis of mechanical systems during the rotationalmovement. Nowadays technical problems are tied with high speeds of mechanisms, high precision of work,using lower density materials, and many other high demands for elements of work. Objective of this paper wasthe analysis with giving into consideration the interaction between working motion and local vibrations. Themodel is loaded by transverse forces and transformed to the global reference frame.Design/methodology/approach: derived equations of motion were made by the Lagrange equations methodwith generalized coordinates and generalized velocities assumed as orthogonal projections of individualcoordinates and velocities of each beam to axes of the global reference frame.Findings: systems of equations of motion of transversally vibrating systems in two-dimensional motion willbe put to use to derivation of the dynamical flexibility of these systems and complex systems. Those equationsare the beginning of the analysis of complex systems. They can also be used to derivation of the substitutedynamical flexibility of n-linked systems.Research limitations/implications: mechanical systems vibrating transversally in terms of two-dimensionalmotion were considered in the thesis. The consecutive problem of dynamical analysis is modelling of systemsin spatial motion and also the analysis of systems loaded by longitudinal forces.Practical implications: mathematical effects of this article can be put to use into many mechanisms andmachines running in rotational transportation. For example applications are: high speed turbines, wind powerplants, rotors, manipulators and in aerodynamics issues, etc. Of course results should be adopted and modifiedto appropriate system.Originality/value: High demands for parameters of work of mechanisms and machines are the postulation fornew research and new ways of modelling and analyzing those type systems. The example way of solution suchsystems is presented in this thesis. The transportation effect for models vibrating transversally was defined.

A. Buchacz

2008-12-01

102

NPC Mimics: Probing the Mechanism of Nucleocytoplasmic Transport  

Science.gov (United States)

In vitro mimics of cellular machines have been recently engineered and utilized to investigate processes within cells. These devices can provide novel insights into biological mechanisms and have the potential to improve biotechnological processes such as separation. In particular, several devices have been designed to mimic translocation through nuclear pore complexes (NPCs). We describe here the fabrication of a biomimetic NPC using nanoporous filters lined with FG-repeats of proteins that create a selectivity barrier. We show the utility of this nanoselective filter as a testbed for the investigation of nucleocytoplasmic transport and demonstrate that this device closely reproduces key features of trafficking through the NPC. PMID:24857739

Jovanovic-Talisman, Tijana; Chait, Brian T.; Rout, Michael P.

2014-01-01

103

Mechanical forces impair alveolar ion transport processes : A putative mechanism contributing to the formation of pulmonary edema  

OpenAIRE

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...

Fronius, Martin

2012-01-01

104

Developing Hypothetical Inhibition Mechanism of Novel Urea Transporter B Inhibitor  

Science.gov (United States)

Urea transporter B (UT-B) is a membrane channel protein that specifically transports urea. UT-B null mouse exhibited urea selective urine concentrating ability deficiency, which suggests the potential clinical applications of the UT-B inhibitors as novel diuretics. Primary high-throughput virtual screening (HTVS) of 50000 small-molecular drug-like compounds identified 2319 hit compounds. These 2319 compounds were screened by high-throughput screening using an erythrocyte osmotic lysis assay. Based on the pharmacological data, putative UT-B binding sites were identified by structure-based drug design and validated by ligand-based and QSAR model. Additionally, UT-B structural and functional characteristics under inhibitors treated and untreated conditions were simulated by molecular dynamics (MD). As the result, we identified four classes of compounds with UT-B inhibitory activity and predicted a human UT-B model, based on which computative binding sites were identified and validated. A novel potential mechanism of UT-B inhibitory activity was discovered by comparing UT-B from different species. Results suggest residue PHE198 in rat and mouse UT-B might block the inhibitor migration pathway. Inhibitory mechanisms of UT-B inhibitors and the functions of key residues in UT-B were proposed. The binding site analysis provides a structural basis for lead identification and optimization of UT-B inhibitors.

Li, Min; Tou, Weng Ieong; Zhou, Hong; Li, Fei; Ren, Huiwen; Chen, Calvin Yu-Chian; Yang, Baoxue

2014-07-01

105

Storm-induced sand transport and bedform genesis at beach and shoreface environments of the Maine Coast  

Energy Technology Data Exchange (ETDEWEB)

Hurricane Bob passed over a taught-wire mooring array of current meters in Saco Bay, Maine on 19 August 1991. Current speeds and directions from Bob are compared to more common extratropical northeaster storms that dominate the extreme wind and wave conditions in the Gulf of Maine. Currents, sampled and averaged to produce 30 minute vectors and burst-mode 1 second vectors, yield combined wave, tide, and wind-driven flows up to 40 cm/s, sufficient to induce sand transport. Comparison of the author's data with wind and wave measurements at the nearby Portland Large Navigation Buoy suggest sand transport events occur many times a year. During storms, 10 cm/s tidal currents may enhance or impede wind-driven offshore-directed bottom flow (coastal downwelling). Preliminary results suggest that a rapidly moving northeaster with a peak wind velocity of 7.7 m/s (15 knots) during a rising tide will lead to net seaward transport of sand during the ebb portion of the tidal cycle. Hurricane Bob data show 35 cm/s downwelling during the approach of the hurricane and 30 cm/s onshore-directed coastal upwelling following landfall. Upwelling lasted twice as long (24 hours) as downwelling and is believed to have been the cause of observed beach accretion. Repeated sidescan sonar surveys of Saco Bay and Cape Small's Kennebec River paleodelta indicate the persistence of large shore-normal ribbons of ripple bedforms (rippled scour depressions) across the nearshore during a period when storms reworked the seabed and could have reshaped the bedform field. Calculations of the threshold of motion and wave orbitals under storm conditions explain the origin of large ripples in coarse sand and gravel as well as plane beds in medium sand. The spatial pattern of each bed type on the shoreface in the 10--40 meter depth range may be due to downwelling, although further study is needed.

Dickson, S.M.; Kelley, J.T. (Maine Geological Survey, Augusta, ME (United States)); Belknap, D.F. (Univ. of Maine, Orono, ME (United States). Dept. of Geological Sciences)

1993-03-01

106

Transport mechanism and regulatory properties of the human amino acid transporter ASCT2 (SLC1A5).  

Science.gov (United States)

The kinetic mechanism of the transport catalyzed by the human glutamine/neutral amino acid transporter hASCT2 over-expressed in P. pastoris was determined in proteoliposomes by pseudo-bi-substrate kinetic analysis of the Na(+)-glutamineex/glutaminein transport reaction. A random simultaneous mechanism resulted from the experimental analysis. Purified functional hASCT2 was chemically cross-linked to a stable dimeric form. The oligomeric structure correlated well with the kinetic mechanism of transport. Half-saturation constants (Km) of the transporter for the other substrates Ala, Ser, Asn and Thr were measured both on the external and internal side. External Km were much lower than the internal ones confirming the asymmetry of the transporter. The electric nature of the transport reaction was determined imposing a negative inside membrane potential generated by K(+) gradients in the presence of valinomycin. The transport reaction resulted to be electrogenic and the electrogenicity originated from external Na(+). Internal Na(+) exerted a stimulatory effect on the transport activity which could be explained by a regulatory, not a counter-transport, effect. Native and deglycosylated hASCT2 extracted from HeLa showed the same transport features demonstrating that the glycosyl moiety has no role in transport function. Both in vitro and in vivo interactions of hASCT2 with the scaffold protein PDZK1 were revealed. PMID:25052780

Scalise, Mariafrancesca; Pochini, Lorena; Panni, Simona; Pingitore, Piero; Hedfalk, Kristina; Indiveri, Cesare

2014-11-01

107

Mass transport mechanisms during excimer laser nitriding of aluminum  

International Nuclear Information System (INIS)

Surface layers of aluminum nitride were formed by irradiating pure aluminum substrates in nitrogen atmosphere with a pulsed excimer laser. The beam was focused on the sample placed inside a chamber filled with nitrogen gas. The irradiation was carried out at various laser fluences, nitrogen gas pressures, and numbers of pulses in order to investigate the influence of each parameter on the nitrogen incorporation and the mass transport mechanisms. X-ray diffraction showed the formation of polycrystalline AlN phase with the wurtzite structure, and the analysis of the nitrogen depth profiles by means of resonant nuclear reaction Analysis revealed a monotonic increase of the nitrogen concentration with the ambient gas pressure and the number of laser shots. It has been found that the laser fluence directly determines the temperature of the substrate and strongly changes the transport mechanism. The thermal simulations and the experimental evidence show that for fluences higher than 3 J/cm2 the temperature of the substrate exceeds 2900 K. This value is higher than the dissociation temperature (?2400 K) and close to the melting point (?3070 K) of AlN, which can therefore dissociate or melt. The atomic nitrogen can rapidly diffuse to greater depths in the liquid Al matrix or it can degas (outgas) through the surface of the sample, leading to the formation of rather homogeneous concentration profiles. For fluences lower than 3 J/cm2 the temperature of 3 J/cm2 the temperature of the substrate is not sufficient to destroy the nitride phase and the AlN grains can move inside the molten Al. In this case, the material transport can be attributed to Brownian motion and thermophoretic drift, which in turn are correlated with the chemical and thermal gradient, respectively

108

Exciton delocalization and energy transport mechanisms in R-phycoerythrin.  

Science.gov (United States)

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

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

2011-03-31

109

Transport mechanism of 11C-labeled L- and D-methionine in human-derived tumor cells  

International Nuclear Information System (INIS)

Introduction: S-methyl-11C-labeled L- and D-methionine (11C-L- and D-MET) are useful as radiotracers for tumor imaging. However, it is not known whether the transport mechanism of 11C-D-MET is the same as that for 11C-L-MET, which is transported by the amino acid transport system L. In this study, we investigated the transport mechanism of 11C-L- and D-MET by analyzing the expression of transport system genes in human-derived tumor cells. Methods: The expression of transport system genes in human-derived tumor cells was quantitatively analyzed. The mechanism of MET transport in these cells was investigated by incubating the cells with [S-methyl-3H]-L-MET (3H-L-MET) or [S-methyl-3H]-D-MET (3H-D-MET) and the effect of 2-amino-2- norbornane-carboxylic acid, a system L transport inhibitor, or ?-(methylamino)isobutyric acid, a system A transport inhibitor, on their transport was measured. The transport and metabolic stability of [S-methyl-14C]-L-MET (14C-L-MET) and 3H-D-MET was also analyzed using bearing mice with H441 or PC14 tumor cells. Results: 3H-D-MET was mainly transported by both systems L and alanine–serine–cysteine (ASC), while system L was involved in 3H-L-MET transport. There was a high correlation between both 3H-L-MET and 3H-D-MET uptake and the expression of amino acid transport e expression of amino acid transport system genes. In the in vivo study, H441-cell accumulation of 3H-D-MET was higher than that of 14C-L-MET. Hepatic and renal accumulation of 3H-D-MET was lower than that of 14C-L-MET. Conclusion: The transport mechanism of 3H-D-MET was different from that of 3H-L-MET. Since 3H-D-MET has high metabolic stability, its accumulation reflects the transporter function of system L and ASC.

110

Cellular Transport Mechanisms of Cytotoxic Metallodrugs: An Overview beyond Cisplatin  

Directory of Open Access Journals (Sweden)

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.

Sarah Spreckelmeyer

2014-09-01

111

Cultural Diffusion Was the Main Driving Mechanism of the Neolithic Transition in Southern Africa  

OpenAIRE

It is well known that the Neolithic transition spread across Europe at a speed of about 1 km/yr. This result has been previously interpreted as a range expansion of the Neolithic driven mainly by demic diffusion (whereas cultural diffusion played a secondary role). However, a long-standing problem is whether this value (1 km/yr) and its interpretation (mainly demic diffusion) are characteristic only of Europe or universal (i.e. intrinsic features of Neolithic transitions all over the world). ...

Jerardino, Antonieta; Fort, Joaquim; Isern, Neus; Rondelli, Bernardo

2014-01-01

112

Mechanism of transport and distribution of organic solvents in blood  

Science.gov (United States)

Little is known about the mechanism of transport and distribution of volatile organic compounds in blood. Studies were conducted on five typical organic solvents to investigate how these compounds are transported and distributed in blood. Groups of four to five rats were exposed for 2 hr to 500 ppm of n-hexane, toluene, chloroform, methyl isobutyl ketone (MIBK), or diethyl ether vapor; 94, 66, 90, 51, or 49%, respectively, of these solvents in the blood were found in the red blood cells (RBCs). Very similar results were obtained in vitro when aqueous solutions of these solvents were added to rat blood. In vitro studies were also conducted on human blood with these solvents; 66, 43, 65, 49, or 46%, respectively, of the added solvent was taken up by the RBCs. These results indicate that RBCs from humans and rats exhibited substantial differences in affinity for the three more hydrophobic solvents studied. When solutions of these solvents were added to human plasma and RBC samples, large fractions (51-96%) of the solvents were recovered from ammonium sulfate-precipitated plasma proteins and hemoglobin. Smaller fractions were recovered from plasma water and red cell water. Less than 10% of each of the added solvents in RBC samples was found in the red cell membrane ghosts. These results indicate that RBCs play an important role in the uptake and transport of these solvents. Proteins, chiefly hemoglobin, are the major carriers of these compounds in blood. It can be inferred from the results of the present study that volatile lipophilic organic solvents are probably taken up by the hydrophobic sites of blood proteins.

Lam, C. W.; Galen, T. J.; Boyd, J. F.; Pierson, D. L.

1990-01-01

113

The Bear Brook Watershed in Maine (BBWM) at 25: manipulation, monitoring, mechanism, and modeling.  

Czech Academy of Sciences Publication Activity Database

Northport : University of Maine , 2012 - (Fernandez, I.; Norton, S.; Wilson, T.). s. 177-177 ISBN 978-0-87723-108-0. [BIOGEOMON : international symposium on ecosystem behavior /7./. 15.07.2012-20.07.2012, Northport] Institutional support: RVO:67985831 Keywords : geochemistry * monitoring * modeling Subject RIV: DD - Geochemistry

Norton, S. A.; Fernandez, I. J.; Navrátil, Tomáš; Simon, K. S.; Jain, S.

114

Mechanical reliability of geometrically imperfect tubular oxygen transport membranes  

DEFF Research Database (Denmark)

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.

Kwok, Kawai; Frandsen, Henrik Lund

2014-01-01

115

Hyporheic flow and transport processes: Mechanisms, models, and biogeochemical implications  

Science.gov (United States)

Fifty years of hyporheic zone research have shown the important role played by the hyporheic zone as an interface between groundwater and surface waters. However, it is only in the last two decades that what began as an empirical science has become a mechanistic science devoted to modeling studies of the complex fluid dynamical and biogeochemical mechanisms occurring in the hyporheic zone. These efforts have led to the picture of surface-subsurface water interactions as regulators of the form and function of fluvial ecosystems. Rather than being isolated systems, surface water bodies continuously interact with the subsurface. Exploration of hyporheic zone processes has led to a new appreciation of their wide reaching consequences for water quality and stream ecology. Modern research aims toward a unified approach, in which processes occurring in the hyporheic zone are key elements for the appreciation, management, and restoration of the whole river environment. In this unifying context, this review summarizes results from modeling studies and field observations about flow and transport processes in the hyporheic zone and describes the theories proposed in hydrology and fluid dynamics developed to quantitatively model and predict the hyporheic transport of water, heat, and dissolved and suspended compounds from sediment grain scale up to the watershed scale. The implications of these processes for stream biogeochemistry and ecology are also discussed.

Boano, F.; Harvey, J. W.; Marion, A.; Packman, A. I.; Revelli, R.; Ridolfi, L.; Wörman, A.

2014-12-01

116

Flexible Mechanical Conveyors for Regolith Extraction and Transport  

Science.gov (United States)

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

Walton, Otis R.; Vollmer, Hubert J.

2013-01-01

117

Comparative study of chemo-electro-mechanical transport models for an electrically stimulated hydrogel  

Science.gov (United States)

The main objective of this work is to introduce a new expression for the hydrogel’s hydration for use within the Poisson Nernst-Planck chemo electro mechanical (PNP CEM) transport models. This new contribution to the models support large deformation by considering the higher order terms in the Green-Lagrangian strain tensor. A detailed discussion of the CEM transport models using Poisson Nernst-Planck (PNP) and Poisson logarithmic Nernst-Planck (PLNP) equations for chemically and electrically stimulated hydrogels will be presented. The assumptions made to simplify both CEM transport models for electric field application in the order of 0.833 kV m-1 and a highly diluted electrolyte solution (97% is water) will be explained. This PNP CEM model has been verified accurately against experimental and numerical results. In addition, different definitions for normalizing the parameters are used to derive the dimensionless forms of both the PNP and PLNP CEM. Four models, PNP CEM, PLNP CEM, dimensionless PNP CEM and dimensionless PNLP CEM transport models were employed on an axially symmetric cylindrical hydrogel problem with an aspect ratio (diameter to thickness) of 175:3. The displacement and osmotic pressure obtained for the four models are compared against the variation of the number of elements for finite element analysis, simulation duration and solution rate when using the direct numerical solver.

Elshaer, S. E.; Moussa, W. A.

2014-07-01

118

Transport and killing mechanism of a novel camptothecin-deoxycholic acid derivate on hepatocellular carcinoma cells.  

Science.gov (United States)

Abstract Camptothecin-20(s)-O-glycine ester-[N-(3'?, 12'?-dihydroxy-24'-carbonyl-5'?-cholan)] (A2), 10-(3'?,12'?-dihydroxy-5'?-cholan-24'-carboxyl)-(20?s)-camptothecin (C2), and 10-O-(3-O-(3'?, 12'?-dihydroxy-24'-carbonyl-5'?-cholan)-propyl)-(20S)-camptothecin (D2) are novel camptothecin-deoxycholic acid analogues. MTT assays were performed to assess the anticancer activity of these compounds against hepatocellular carcinoma SMMC-7721, breast carcinoma MCF-7, and colorectal carcinoma HCT-116 cells. A2 had a high killing ability on SMMC-7721 cells selectively, but C2 and D2 did not exhibit selectivity with regard to SMMC-7721 killing. Uptake assays were performed in an effort to elucidate the transport mechanisms of A2 into SMMC-7721 cells. A2 increased the mRNA expression of OATP1B3 (an organic anion-transporting polypeptide) and uptake of A2 was inhibited by rifampin (inhibitor of OATP1B3), which indicated that the transporter-mediated transport of A2 was mediated by OATP1B3. In addition, according to the western blot and apoptosis assays, we found that A2 killed SMMC-7721 cells by inducing cell apoptosis mainly via an AIF (apoptosis-inducing factor) pathway and a caspase-dependent mitochondria apoptosis pathway. PMID:24725118

Li, Qingyong; Liu, Tianyu; Li, Yunchao; Luo, Shuyue; Zhu, Qiaochu; Zhang, Li; Zhao, Tengfei

2014-07-01

119

Structure and mechanism of a bacterial sodium-dependent dicarboxylate transporter.  

Science.gov (United States)

In human cells, cytosolic citrate is a chief precursor for the synthesis of fatty acids, triacylglycerols, cholesterol and low-density lipoprotein. Cytosolic citrate further regulates the energy balance of the cell by activating the fatty-acid-synthesis pathway while downregulating both the glycolysis and fatty-acid ?-oxidation pathways. The rate of fatty-acid synthesis in liver and adipose cells, the two main tissue types for such synthesis, correlates directly with the concentration of citrate in the cytosol, with the cytosolic citrate concentration partially depending on direct import across the plasma membrane through the Na(+)-dependent citrate transporter (NaCT). Mutations of the homologous fly gene (Indy; I'm not dead yet) result in reduced fat storage through calorie restriction. More recently, Nact (also known as Slc13a5)-knockout mice have been found to have increased hepatic mitochondrial biogenesis, higher lipid oxidation and energy expenditure, and reduced lipogenesis, which taken together protect the mice from obesity and insulin resistance. To understand the transport mechanism of NaCT and INDY proteins, here we report the 3.2 Å crystal structure of a bacterial INDY homologue. One citrate molecule and one sodium ion are bound per protein, and their binding sites are defined by conserved amino acid motifs, forming the structural basis for understanding the specificity of the transporter. Comparison of the structures of the two symmetrical halves of the transporter suggests conformational changes that propel substrate translocation. PMID:23086149

Mancusso, Romina; Gregorio, G Glenn; Liu, Qun; Wang, Da-Neng

2012-11-22

120

High-Performance Concurrency Control Mechanisms for Main-Memory Databases  

CERN Document Server

A database system optimized for in-memory storage can support much higher transaction rates than current systems. However, standard concurrency control methods used today do not scale to the high transaction rates achievable by such systems. In this paper we introduce two efficient concurrency control methods specifically designed for main-memory databases. Both use multiversioning to isolate read-only transactions from updates but differ in how atomicity is ensured: one is optimistic and one is pessimistic. To avoid expensive context switching, transactions never block during normal processing but they may have to wait before commit to ensure correct serialization ordering. We also implemented a main-memory optimized version of single-version locking. Experimental results show that while single-version locking works well when transactions are short and contention is low performance degrades under more demanding conditions. The multiversion schemes have higher overhead but are much less sensitive to hotspots ...

Larson, Per-Åke; Diaconu, Cristian; Freedman, Craig; Patel, Jignesh M; Zwilling, Mike

2012-01-01

121

Main mechanical and thermal loads and stresses of the FTU machine  

International Nuclear Information System (INIS)

The FTU tokamak will have to operate steadily at high magnetic fields in order to reach the expected performance. Its magnet and vacuum chamber, due to thermal and electromagnetic loads, will undergo very high stresses for a large number of shots. In order to assess the feasibility of the components, 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. (orig.)

122

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

123

The influence of mechanical properties of workpiece material on the main cutting force in face milling  

OpenAIRE

The paper presents the research into cutting forces in face milling of three different materials: steel ? 4732 (EN42CrMo4), nodular cast iron NL500 (EN-GJS-500-7) and silumine AlSi10Mg (EN AC-AlSi10Mg). Obtained results show that hardness and tensile strength values of workpiece material have a significant influence on the main cutting force, and thereby on the cutting energy in machining.

Sekulic?, M.; Jurkovic?, Z.; Hadz?istevic?, M.; Gostimirovic?, M.

2010-01-01

124

Decoupling Mechanical and Ion Transport Properties in Polymer Electrolyte Membranes  

Science.gov (United States)

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.

McIntosh, Lucas D.

125

CLUB FORMATION MECHANISM FOR TRANSPORT-COMMUNITY CREDIT CARDS  

Science.gov (United States)

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.

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

126

Alternating access mechanism in the POT family of oligopeptide transporters  

OpenAIRE

Short chain peptides are actively transported across membranes as an efficient route for dietary protein absorption and for maintaining cellular homeostasis. In mammals, peptide transport occurs via PepT1 and PepT2, which belong to the proton-dependent oligopeptide transporter, or POT family. The recent crystal structure of a bacterial POT transporter confirmed that they belong to the major facilitator superfamily of secondary active transporters. Despite the functional characterization of PO...

Solcan, N.; Kwok, J.; Fowler, Pw; Cameron, Ad; Drew, D.; Iwata, S.; Newstead, S.

2012-01-01

127

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

Science.gov (United States)

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.

Vossier, Alexis; Gualdi, Federico; Dollet, Alain; Ares, Richard; Aimez, Vincent

2015-01-01

128

Determining mechanical properties and main characteristic values of Poplar plywood by medium-sized test pieces.  

OpenAIRE

Wood-based panels represent an important category of composites consisting of natural raw materials and one or more synthetic products. They are available in a wide range of types and thus can satisfy the most frequent needs and functions of the building trades. In light of renewed interest in the structural uses of these materials, an adequate mechanical characterization is necessary to designers who require reliable information for structural analysis. In this context, an extensive research...

Zanuttini, Roberto

1998-01-01

129

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

Energy Technology Data Exchange (ETDEWEB)

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.

Bellesia, B

2006-12-15

130

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

131

A basic study with feasibility of applying clean development mechanism to the transport projects  

Energy Technology Data Exchange (ETDEWEB)

In the transport sector, there are few Clean Development Mechanism (CDM) and Joint Implementation (JI) projects. Since new transport infrastructure projects are more suited to Official Development Assistance (ODA) than CDM, this study will examine the feasibility of applying CDM to the transport sector from viewpoints of validation of processes and funding. A number of greenhouse gas emission reduction projects, as well as traffic management projects within existing transport infrastructures, can be implemented as CDM projects. New transport infrastructure projects can be validated by transport demand forecasting and traffic simulation methods, though application of Life Cycle Assessment (LCA) and Intelligent Transport Systems (ITS) technologies.

Kato, H.; Hayashi, Y. [Graduate School of Environmental Studies, Nagoya University Furo-cho, Chikusa-ku, Nagoya (Japan); Tanaka, K. [NS Solutions, Shinkawa 2-20-15, Chuo-ku, Tokyo (Japan)

2003-07-01

132

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 covalens unknown but could involve either covalent or noncovalent modification of the carrier protein

133

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

2009-05-15

134

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

CERN Document Server

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...

Maharramov, Musa

2013-01-01

135

Assembly and mechanism of a group II ECF transporter  

OpenAIRE

Energy-coupling factor (ECF) transporters are a recently discovered family of primary active transporters for micronutrients and vitamins, such as biotin, thiamine, and riboflavin. Found exclusively in archaea and bacteria, including the human pathogens Listeria, Streptococcus, and Staphylococcus, ECF transporters may be the only means of vitamin acquisition in these organisms. The subunit composition of ECF transporters is similar to that of ATP binding cassette (ABC) importers, whereby both...

Karpowich, Nathan K.; Wang, Da-neng

2013-01-01

136

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

OpenAIRE

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?...

Ferreira, Raquel Teixeira; Coutinho, Marcela Arau?jo Soares; Malvar, David Do Carmo; Costa, Elson Alves; Florentino, Iziara Ferreira; Costa, So?nia Soares; Vanderlinde, Frederico Argollo

2014-01-01

137

Mechanical transport and porous media equivalence in anisotropic fracture networks  

International Nuclear Information System (INIS)

The objective of this work is to investigate the directional characteristics of hydraulic effective porosity in an effort to understand porous medium equivalence for continuous and discontinuous fracture systems. Continuous systems contain infinitely long fractures. Discontinuous systems consist of fractures with finite lengths. The distribution of apertures (heterogeneity) has a major influence on the degree of porous medium equivalence for distributed continuous and discontinuous systems. When the aperture distribution is narrow, the hydraulic effective porosity is slightly less than the total porosity for continuous systems, and greater than the rock effective porosity for discontinuous systems. However, when heterogeneity is significant, the hydraulic effective porosity is directionally dependent and greater than total porosity for both systems. Non-porous medium behavior ws found to differ for distributed continuous systems and for continuous systems with parallel sets. For the latter systems, hydraulic effective porosity abruptly decreases below total porosity in those particular directions where the hydraulic gradient and the orientation of a fracture set are orthogonal. The results for the continuous systems with parallel sets also demonstrate that a system that behaves like a continuum for fluid flux may not behave like a continuum for mechanical transport. 3 references, 13 figures

138

Accident investigation practices in Europe--main responses from a recent study of accidents in industry and transport  

International Nuclear Information System (INIS)

Europe has during recent years been shocked by disasters from natural events and technical breakdowns. The consequences have been comprehensive, measured by lost lives, injuries, and material and environmental damage. ESReDA wanted in 2000 - by setting up a special expert group on accident investigation - to clarify the state of art of accident investigation practices and to map the use of thoroughly accident investigation in order to learn lessons from past disasters and prevent new ones. The scope was to cover three sectors in the society: transport, production processes and storage of hazardous materials, and energy production. The main method used was a questionnaire, which was sent in 2001 to about 150 organisations. About 50 replies were analysed. The replies showed great variations but also similarities, among others in definition of accident and incident, the objectives of the investigation team, criteria used to start an investigation, the status of the investigation organisation, the flow of information, the composition of the investigation team, and the use of internal or international procedures or rules. Several methods (in total 14 different methods were mentioned) were used for carrying out accident /incident investigations. Most of the respondents were willing to co-operate in one or another way with ESReDA. Although there are important biases in the material, the results from questionnaire are important inputs to the future work of ESReDA Expert group to the future work of ESReDA Expert group in this field. 3 safety approaches have been identified

139

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

Energy Technology Data Exchange (ETDEWEB)

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)

Hartmann, W.J. [Atomic Energy of Canada Limited, Mississauga, Ontario (Canada); Zeng, C.; Feng, J.; Mou, X. [Third Qinshan Nuclear Power Company Limited, Haiyan, Zhejiang Province (China)

2011-07-01

140

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)

141

Managing the manganese: molecular mechanisms of manganese transport and homeostasis.  

Science.gov (United States)

Manganese (Mn) is an essential metal nutrient for plants. Recently, some of the genes responsible for transition metal transport in plants have been identified; however, only relatively recently have Mn2+ transport pathways begun to be identified at the molecular level. These include transporters responsible for Mn accumulation into the cell and release from various organelles, and for active sequestration into endomembrane compartments, particularly the vacuole and the endoplasmic reticulum. Several transporter gene families have been implicated in Mn2+ transport, including cation/H+ antiporters, natural resistance-associated macrophage protein (Nramp) transporters, zinc-regulated transporter/iron-regulated transporter (ZRT/IRT1)-related protein (ZIP) transporters, the cation diffusion facilitator (CDF) transporter family, and P-type ATPases. The identification of mutants with altered Mn phenotypes can allow the identification of novel components in Mn homeostasis. In addition, the characterization of Mn hyperaccumulator plants can increase our understanding of how plants can adapt to excess Mn, and ultimately allow the identification of genes that confer this stress tolerance. The identification of genes responsible for Mn2+ transport has substantially improved our understanding of plant Mn homeostasis. PMID:16101910

Pittman, Jon K

2005-09-01

142

Main trends in heavy ion reaction mechanisms when the energy increases  

International Nuclear Information System (INIS)

The influence of collision terms on the dynamical processes leads to very important changes in the aspects of heavy ion reactions when the energy per nucleon increases from a few MeV/n up to some 45 MeV/n. For peripheral collisions the deep inelastic reactions are replaced by a slightly inelastic fast perturbation. Quasi-elastic phenomena are still observed with a few nucleon transfer reaction towards unbound states. For central collisions, fusion processes still persist but the transfer of linear momentum is limited due to a direct emission of fast light particles. Therefore, very high energy deposits are produced and very hot nuclei are formed which decay by statistical deexcitation. Residual nuclei and fission fragments are the final products up to a certain excitation energy. But limits are reached, at an excitation energy of the order of 4-5 MeV per nucleon -which is slightly higher for light systemps than for heavy ones- where the fusion process is not followed subsequently by the usual decay. Possibly a multifragmentation mechanism is the new way by which a very excited piece of nuclear matter disrupts very rapidly. Finally, in addition to peripheral and central collisions, it seems that collisions at intermediate impact parameters are responsible for the creation of a hot transient species made of the projectile plus a piece of the target, which, because of its high temperature, very promptly explodes into several light fragments and alpha-particles

143

Enrichment behavior and transport mechanism of soil-bound PAHs during rainfall-runoff events  

International Nuclear Information System (INIS)

Polycyclic Aromatic Hydrocarbons (PAHs) transported by surface runoff result in nonpoint source pollution and jeopardize aquatic ecosystems. The transport mechanism of PAHs during rainfall-runoff events has been rarely studied regarding pervious areas. An experimental system was setup to simulate the runoff pollution process on PAHs-contaminated soil. The enrichment behavior of soil-bound PAHs was investigated. The results show that soil organic matters (SOM), rather than clay particles, seem to be the main carrier of PAHs. The enrichment is highly conditioned on runoff and erosion processes, and its magnitude varies among PAH compounds. It is not feasible to build a simple and universal relationship between enrichment ratio and sediment discharge following the traditional enrichment theory. To estimate the flux of PAHs from pervious areas, soil erosion process has to be clearly understood, and both organic carbon content and composition of SOM should be factored into the calculation. - Highlights: ? Significant enrichment of particle-bound PAHs during rainfall-runoff events. ? Organic matters as the direct carrier of PAHs in runoff from contaminated soil. ? The traditional enrichment theory is not fully valid for PAHs. - The traditional enrichment theory is not fully valid for PAHs, and soil organic matters have a significant impact on the transport of PAHs during rainfall-runoff events.

144

Impact of Watershed Development on Sediment Transport and Seasonal Flooding in the Main Stream of the Mekong River  

Science.gov (United States)

The Mekong River watershed is undergoing rapid economic progress and population growth, raising conflicts between watershed development and environmental conservation. A typical conflict is between the benefits of dam construction versus the benefits of watershed ecological services. In developed countries, this conflict is changing to a coordinated search for outcomes that are mutually acceptable to all stakeholders. In the Mekong River, however, government policy gives priority to watershed development for ensuring steady energy supplies. Since the 1990s, a series of dams called “the Mekong Cascade” have been under construction. Dam construction has multiple economic values as electric power supply, irrigation water, flood control, etc. On the other hand, the artificial flow discharge controls of dam moderate seasonal hydrologic patterns of the Asian monsoon region. Dam operations can change the sediment transport regime and river structure. Furthermore, their impacts on watershed ecosystems and traditional economic activities of fisheries and agriculture in downstream areas may be severe. We focus on dam impacts on spatio-temporal patterns of sediment transport and seasonal flood in riparian areas downstream from Mekong River dams. Our study river section is located on 100 km down stream from the Golden Triangle region of Myanmar, Laos, and Thailand. We selected a 10-km section in this main channel to simulate seasonal flooding. We modeled the river hydrology in the years 1991 and 2002, before and after the Manwan dam construction (1986-1993). For this simulation, we adapted three models (distributed runoff model, 1-D hydrological model, and 2-D flood simulation with sediment movement algorithm.) Input data on river structure, water velocity, and flow volume were acquired from field survey data in November 2007 and 2008. In the step of parameter decision, we adopted the shuffled complex evolution method. To validate hydrologic parameters, we used annual water level data observed in Chiang Sean and Luang Prabang. To calculate sediment flux volume, we employed a Load-Quantity equation using total suspended solids data from monthly water sampling and flow discharge volumes over 13 months. To evaluate the impact of dam construction and watershed development, we inputted the same year of precipitation data using two watershed conditions with different parameters. Our results from the 1-D model displayed a seasonal delay of water flooding time after summer rainy season and an increase in sediment transport volume from September to October. In the flood simulation by the 2-D model, most of the annual sediment transport was concentrated from July to October. The spatial pattern of sediment dynamics was dependent largely on river structure including river meander shape, river bottom elevation, and geometry of the riparian zone. Our study approaches and simulation results show promise for beginning a quantitative assessment approach to cross-boundary environmental issues in the Mekong River watershed.

Kameyama, S.; Nohara, S.; Sato, T.; Fujii, Y.; Kudo, K.

2009-12-01

145

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 e 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)

146

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

Science.gov (United States)

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

Mulligan, Christopher; Mindell, Joseph A

2013-12-01

147

Agmatine transport in brain mitochondria: a different mechanism from that in liver mitochondria  

OpenAIRE

The diamine agmatine (AGM), exhibiting two positive charges at physiological pH, is transported into rat brain mitochondria (RBM) by an electrophoretic mechanism, requiring high membrane potential values and exhibiting a marked non-ohmic force-flux relationship. The mechanism of this transport apparently resembles that observed in rat liver mitochondria (RLM), but there are several characteristics that strongly suggest the presence of a different transporter of agmatine in RBM. In this type o...

Cravanzola, Carlo; Colombatto, Sebastiano; Grillo, Maria Angelica

2010-01-01

148

Agmatine is transported in liver mitochondria by a specific electrophoretic mechanism  

OpenAIRE

Abstract Agmatine, a divalent diamine having two positive charges at physiological pH, is transported into the matrix of liver mitochondria by an energy-dependent mechanism whose driving force is the electrical membrane potential ({Delta}{Psi}). Although this process shows strict electrophoretic behavior, qualitatively similar to that of polyamines, agmatine is most probably transported by a specific uniporter. Common transport with polyamines, by means of their transporter, must b...

Salvi, Mauro; Battaglia, Valentina; Mancon, Mario; Colombatto, Sebastiano; Cravanzola, Carlo; Calheiros, Rita; Marques, Maria Mp; Grillo, Maria A.; Toninello, Antonio

2006-01-01

149

Agmatine is transported into liver mitochondria by a specific electrophoretic mechanism  

OpenAIRE

Agmatine, a divalent diamine with two positive charges at physiological pH, is transported into the matrix of liver mitochondria by an energy-dependent mechanism the driving force of which is DeltaPsi (electrical membrane potential). Although this process showed strict electrophoretic behaviour, qualitatively similar to that of polyamines, agmatine is most probably transported by a specific uniporter. Shared transport with polyamines by means of their transporter is excluded, as divalent putr...

Cravanzola, Carlo; Colombatto, Sebastiano

2006-01-01

150

The Rocking Bundle: A Mechanism for Ion-Coupled Solute Flux by Symmetrical Transporters  

Science.gov (United States)

Crystal structures of the bacterial amino acid transporter LeuT have provided the basis for understanding the conformational changes associated with substrate translocation by a multitude of transport proteins with the same fold. Biochemical and modeling studies led to a "rocking bundle" mechanism for LeuT that was validated by subsequent transporter structures. These advances suggest how coupled solute transport might be defined by the internal symmetry of proteins containing inverted structural repeats.

Lucy R. Forrest (Max Planck Institute for Biophysics)

2009-12-01

151

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)

152

Alternating access mechanism in the POT family of oligopeptide transporters.  

Science.gov (United States)

Short chain peptides are actively transported across membranes as an efficient route for dietary protein absorption and for maintaining cellular homeostasis. In mammals, peptide transport occurs via PepT1 and PepT2, which belong to the proton-dependent oligopeptide transporter, or POT family. The recent crystal structure of a bacterial POT transporter confirmed that they belong to the major facilitator superfamily of secondary active transporters. Despite the functional characterization of POT family members in bacteria, fungi and mammals, a detailed model for peptide recognition and transport remains unavailable. In this study, we report the 3.3-Å resolution crystal structure and functional characterization of a POT family transporter from the bacterium Streptococcus thermophilus. Crystallized in an inward open conformation the structure identifies a hinge-like movement within the C-terminal half of the transporter that facilitates opening of an intracellular gate controlling access to a central peptide-binding site. Our associated functional data support a model for peptide transport that highlights the importance of salt bridge interactions in orchestrating alternating access within the POT family. PMID:22659829

Solcan, Nicolae; Kwok, Jane; Fowler, Philip W; Cameron, Alexander D; Drew, David; Iwata, So; Newstead, Simon

2012-08-15

153

Center for low-gravity fluid mechanics and transport phenomena  

Science.gov (United States)

Research projects in several areas are discussed. Mass transport in vapor phase systems, droplet collisions and coalescence in microgravity, and rapid solidification of undercooled melts are discussed.

Kassoy, D. R.; Sani, R. L.

1991-01-01

154

Mechanisms underlying methamphetamine-induced dopamine transporter complex formation.  

Science.gov (United States)

Repeated, high-dose methamphetamine (METH) administrations cause persistent dopaminergic deficits in rodents, nonhuman primates, and humans. In rats, this treatment also causes the formation of high-molecular mass (greater than approximately 120 kDa) dopamine transporter (DAT)-associated complexes, the loss of DAT monomer immunoreactivity, and a decrease in DAT function, as assessed in striatal synaptosomes prepared 24 h after METH treatment. The present study extends these findings by demonstrating the regional selectivity of DAT complex formation and monomer loss because these changes in DAT immunoreactivity were not observed in the nucleus accumbens. Furthermore, DAT complex formation was not a consequence limited to METH treatment because it was also caused by intrastriatal administration of 6-hydroxydopamine. Pretreatment with the D2 receptor antagonist, eticlopride [S-(-)-3-chloro-5-ethyl-N-[(1-ethyl-2-pyrrolidinyl)methyl]-6-hydroxy-2-methoxybenzamide hydrochloride], but not the D1 receptor antagonist, SCH23390 [R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride], attenuated METH-induced DAT complex formation. Eticlopride pretreatment also attenuated METH-induced DAT monomer loss and decreases in DAT function; however, the attenuation was much less pronounced than the effect on DAT complex formation. Finally, results also revealed a negative correlation between METH-induced DAT complex formation and DAT activity. Taken together, these data further elucidate the underlying mechanisms and the functional consequences of repeated administrations of METH on the DAT protein. Furthermore, these data suggest a multifaceted role for D2 receptors in mediating METH-induced alterations of the DAT and its function. PMID:19141713

Hadlock, Gregory C; Baucum, Anthony J; King, Jill L; Horner, Kristen A; Cook, Glen A; Gibb, James W; Wilkins, Diana G; Hanson, Glen R; Fleckenstein, Annette E

2009-04-01

155

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 hydrognce 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)

156

Primary heat transport pump mechanical seal replacement strategy for Pickering B  

International Nuclear Information System (INIS)

Pickering Nuclear Generating Station is a CANDU PHWR eight unit station located on Lake Ontario. The station is divided into Pickering A (Units 1 to 4) and Pickering B (Units 5 to 8). Pickering B is the focus of this paper. Each unit is rated at 540 MWe. The Primary Heat Transport (PHT) system, which is used to cool the fuel, is divided into four quadrants. Each quadrant has four vertical Byron Jackson PHT main circulation pumps. Three pumps in each quadrant are required for normal operation, leaving one pump in each quadrant as a spare. Each Pickering PHT pump has a Byron Jackson Type SU two stage mechanical seal. The typical pressure breakdown across the seal is 8.7-4.5-1.0 MPa. Certain features of seal operation and the PHT system which influence seal replacement are discussed below. (author)

157

The permeability and transport mechanism of graphene quantum dots (GQDs) across the biological barrier  

Science.gov (United States)

As an emerging nanomaterial, graphene quantum dots (GQDs) have shown enormous potential in theranostic applications. However, many aspects of the biological properties of GQDs require further clarification. In the present work, we prepared two sizes of GQDs and for the first time investigated their membrane permeabilities, one of the key factors of all biomedical applications, and transport mechanisms on a Madin Darby Canine Kidney (MDCK) cell monolayer. The experimental results revealed that under ~300 mg L-1, GQDs were innoxious to MDCK and did not affect the morphology and integrity of the cell monolayer. The Papp values were determined to be 1-3 × 10-6 cm s-1 for the 12 nm GQDs and 0.5-1.5 × 10-5 cm s-1 for the 3 nm GQDs, indicating that the 3 nm GQDs are well-transported species while the 12 nm GQDs have a moderate membrane permeability. The transport and uptake of GQDs by MDCK cells were both time and concentration-dependent. Moreover, the incubation of cells with GQDs enhanced the formation of lipid rafts, while inhibition of lipid rafts with methyl-?-cyclodextrin almost eliminated the membrane transport of GQDs. Overall, the experimental results suggested that GQDs cross the MDCK cell monolayer mainly through a lipid raft-mediated transcytosis. The present work has indicated that GQDs are a novel, low-toxic, highly-efficient general carrier for drugs and/or diagnostic agents in biomedical applications.As an emerging nanomaterial, graphene quantum dots (GQDs) have shown enormous potential in theranostic applications. However, many aspects of the biological properties of GQDs require further clarification. In the present work, we prepared two sizes of GQDs and for the first time investigated their membrane permeabilities, one of the key factors of all biomedical applications, and transport mechanisms on a Madin Darby Canine Kidney (MDCK) cell monolayer. The experimental results revealed that under ~300 mg L-1, GQDs were innoxious to MDCK and did not affect the morphology and integrity of the cell monolayer. The Papp values were determined to be 1-3 × 10-6 cm s-1 for the 12 nm GQDs and 0.5-1.5 × 10-5 cm s-1 for the 3 nm GQDs, indicating that the 3 nm GQDs are well-transported species while the 12 nm GQDs have a moderate membrane permeability. The transport and uptake of GQDs by MDCK cells were both time and concentration-dependent. Moreover, the incubation of cells with GQDs enhanced the formation of lipid rafts, while inhibition of lipid rafts with methyl-?-cyclodextrin almost eliminated the membrane transport of GQDs. Overall, the experimental results suggested that GQDs cross the MDCK cell monolayer mainly through a lipid raft-mediated transcytosis. The present work has indicated that GQDs are a novel, low-toxic, highly-efficient general carrier for drugs and/or diagnostic agents in biomedical applications. Electronic supplementary information (ESI) available: Table S1 and Fig. S1-S3. See DOI: 10.1039/c4nr04136d

Wang, Xin-Yi; Lei, Rong; Huang, Hong-Duang; Wang, Na; Yuan, Lan; Xiao, Ru-Yue; Bai, Li-Dan; Li, Xue; Li, Li-Mei; Yang, Xiao-Da

2015-01-01

158

Mechanism of government management of a transport complex development ??????????????? ????????? ?????????? ????????? ????????????? ?????????  

Directory of Open Access Journals (Sweden)

Full Text Available In the article the expediency of carrying out of different forms of privatization of strategically important transport agencies, presence of different existing approaches in world practice and a substantiation of recommendations concerning development of a transport complex of Ukraine is analyzed.? ?????? ???????????????? ???????????????? ?????????? ?????? ???? ???????????? ????????????? ?????? ???????????? ???????????, ??????? ?????? ???????????? ???????? ? ??????? ???????? ? ??????????? ???????????? ? ????????? ???????? ????????????? ????????? ???????.

Ilchenko Svetlana V.

2012-01-01

159

Atomistic mechanisms of rapid energy transport in light-harvesting molecules  

Energy Technology Data Exchange (ETDEWEB)

Synthetic supermolecules such as ?-conjugated light-harvesting dendrimers efficiently harvest energy from sunlight, which is of significant importance for the global energy problem. Key to their success is rapid transport of electronic excitation energy from peripheral antennas to photochemical reaction cores, the atomistic mechanisms of which remains elusive. Here, quantum-mechanical molecular dynamics simulation incorporating nonadiabatic electronic transitions reveals the key molecular motion that significantly accelerates the energy transport based on the Dexter mechanism.

Ohmura, Satoshi; Koga, Shiro; Akai, Ichiro; Shimojo, Fuyuki; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya

2011-01-01

160

Behavior-Based Transportation Greenhouse Gas Mitigation Under the Clean Development Mechanism Transport-Efficient Development in Nanchang, China  

OpenAIRE

We propose a methodology, consistent with the Kyoto Protocol?s Clean Development Mechanism (CDM), to quantify the greenhouse gas (GHG) emission reduction benefits of transport efficient development (TED). TED aims to reduce transportation GHGs by changing urban development patterns. We use the Nanchang Transit-Oriented Development project in China to demonstrate the methodology and, thus, the possibilities for bringing such projects into the carbon market. The case illustrates the challenge...

Zegras, P. Christopher; Chen, Yang; Grutter, Jurg M.

2009-01-01

161

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)

162

Structural mechanics research and development for main components of Chinese 300 MWe PWR NPPs: from design to life management  

International Nuclear Information System (INIS)

Qinshan Nuclear Power Plant (Unit I), is a 300 MWe prototype PWR independently developed by Chinese own efforts, from design, manufacture, construction, installation, commissioning, to operation, inspection, maintenance, ageing management and lifetime assessment. Shanghai Nuclear Engineering Research and Design Institute (SNERDI) has taken up with and involved in deeply the R and D to tackle problems of this type of reactor since very beginning in early 1970s. Structural mechanics is one of the important aspects to ensure the safety and reliability for NPP components. This paper makes a summary on role of structural mechanics for component safety and reliability assessment in different stages of design, commissioning, operation, as well as lifetime assessment on this type PWR NPPs, including Qinshan-I and Chashma-I, a sister plant in Pakistan designed by SNERDI. The main contents of the paper cover design by analysis for key components of NSSS; mechanical problems relating to safety analysis; special problems relating to pressure retaining components, such as fracture mechanics, sealing analysis and its test verifications, etc.; experimental research on flow-induced vibration; seismic qualification for components; component failure diagnosis and root cause analysis; vibration qualification and diagnosis technique; component online monitoring technique; development of defect assessment; methodology of aging management and lifetime assessment for key components of NPPs,ime assessment for key components of NPPs, etc. (authors)

163

CO2-ECBM related coupled physical and mechanical transport processes  

Science.gov (United States)

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH4, CO2) and inert gases (N2, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected "true" permeability coefficients and the Klinkenberg slip factors were derived. The "true"-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (cf) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (cf) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and "diffusion coefficients" were calculated using several unipore and bidisperse diffusion models. While the CH4 sorption capacity of moisture-equilibrated coals was significantly lower (by 50%) than of dry coals, no hysteresis was observed between sorption and desorption on dry and moisture-equilibrated samples and the sorption isotherms recorded for different particle sizes were essentially identical. The CH4 uptake rates were lower by a factor of two for moist coals than for dry coals. Busch, A., Gensterblum, Y., Krooss, B.M. and Siemons, N., 2006. Investigation of high-pressure selective adsorption/desorption behaviour of CO2 and CH4 on coals: An experimental study. International Journal of Coal Geology, 66(1-2): 53-68. Harpalani, S. and McPherson, M.J., 1985. Effect of stress on permeability of coal. Quarterly Review of methane from coal seams technology, 3(2): 23-29. Seidle, J.P., Jeansonne, M.W. and Erickson, D.J., 1992. Application of Matchstick Geometry to Stress-Dependent Permeability in Coals, SPE Rocky Mountain Regional Meeting, Casper, Wyoming.

Gensterblum, Yves; Satorius, Michael; Busch, Andreas; Krooß, Bernhard

2013-04-01

164

Trypanosoma brucei aquaglyceroporin 2 is a high-affinity transporter for pentamidine and melaminophenyl arsenic drugs and the main genetic determinant of resistance to these drugs  

OpenAIRE

Objectives: Trypanosoma brucei drug transporters include the TbAT1/P2 aminopurine transporter and the high-affinity pentamidine transporter (HAPT1), but the genetic identity of HAPT1 is unknown. We recently reported that loss of T. brucei aquaglyceroporin 2 (TbAQP2) caused melarsoprol/pentamidine cross-resistance (MPXR) in these parasites and the current study aims to delineate the mechanism by which this occurs. Methods: The TbAQP2 loci of isogenic pairs of drug-susceptible and MPXR stra...

Munday, Jane C.; Eze, Anthonius A.; Baker, Nicola; Glover, Lucy; Clucas, Caroline; Aguinaga Andres, David; Natto, Manal J.; Teka, Ibrahim A.; Mcdonald, Jennifer; Lee, Rebecca S.; Graf, Fabrice E.; Ludin, Philipp; Burchmore, Richard J. S.; Turner, C. Michael R.; Tait, Andy

2014-01-01

165

Chemically- and mechanically-mediated influences on the transport and mechanical characteristics of rock fractures  

Energy Technology Data Exchange (ETDEWEB)

A model is presented to represent changes in the mechanical and transport characteristics of fractured rock that result from coupled mechanical and chemical effects. The specific influence is the elevation of dissolution rates on contacting asperities, which results in a stress- and temperature-dependent permanent closure. A model representing this pressure-dissolution-like behavior is adapted to define the threshold and resulting response in terms of fundamental thermodynamic properties of a contacting fracture. These relations are incorporated in a stress-stiffening model of fracture closure to define the stress- and temperature-dependency of aperture loss and behavior during stress and temperature cycling. These models compare well with laboratory and field experiments, representing both decoupled isobaric and isothermal responses. The model was applied to explore the impact of these responses on heated structures in rock. The result showed a reduction in ultimate induced stresses over the case where chemical effects were not incorporated, with permanent reduction in final stresses after cooling to ambient conditions. Similarly, permeabilities may be lower than they were in the case where chemical effects were not considered, with a net reduction apparent even after cooling to ambient temperature. These heretofore-neglected effects may have a correspondingly significant impact on the performance of heated structures in rock, such as repositories for the containment of radioactive wastes.

Min, K.-B.; Rutqvist, J.; Elsworth, D.

2009-02-01

166

FEATURES FOR TRANSPORT AND AIR MECHANICAL SYSTEMS OF DANGEROUS GOODS  

Directory of Open Access Journals (Sweden)

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.

Eugen Dumitru BUSA

2012-05-01

167

Origin of traps and charge transport mechanism in hafnia  

Science.gov (United States)

In this study, we demonstrated experimentally and theoretically that oxygen vacancies are responsible for the charge transport in HfO2. 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 HfO2 was determined based on the charge transport experiments.

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

2014-12-01

168

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

OpenAIRE

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...

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

2009-01-01

169

Osmotic water transport in aquaporins : evidence for a stochastic mechanism  

DEFF Research Database (Denmark)

Abstract? We test a novel, stochastic model of osmotic water transport in aquaporins. A solute molecule present at the pore mouth can either be reflected or permeate the pore. We assume that only reflected solute molecules induce osmotic transport of water through the pore, while permeating solute molecules give rise to no water transport. Accordingly, the rate of water transport is proportional to the reflection coefficient ?, while the solute permeability, P(S), is proportional to 1 - ?. The model was tested in aquaporins heterologously expressed in Xenopus oocytes. A variety of aquaporin channel sizes and geometries were obtained with the two aquaporins AQP1 and AQP9 and mutant versions of these. Osmotic water transport was generated by adding 20 mM of a range of different-sized osmolytes to the outer solution. The osmotic water permeability and the reflection coefficient were measured optically at high resolution and compared to the solute permeability obtained from short-term uptake of radio-labelled solute under isotonic conditions. For each type of aquaporin there was a linear relationship between solute permeability and reflection coefficient, in accordance with the model. We found no evidence for coupling between water and solute fluxes in the pore. In confirmation of molecular dynamic simulations, we conclude that the magnitude of the osmotic water permeability and the reflection coefficient are determined by processes at the arginine selectivity filter located at the outward-facing end of the pore.

Zeuthen, Thomas; Alsterfjord, Magnus

2013-01-01

170

Water transport mechanism through open capillaries analyzed by direct surface modifications on biological surfaces  

OpenAIRE

Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The whar...

Ishii, Daisuke; Horiguchi, Hiroko; Hirai, Yuji; Yabu, Hiroshi; Matsuo, Yasutaka; Ijiro, Kuniharu; Tsujii, Kaoru; Shimozawa, Tateo; Hariyama, Takahiko; Shimomura, Masatsugu

2013-01-01

171

A new transport mechanism of biomass burning from Indochina as identified by modeling studies  

OpenAIRE

Biomass burning in the Indochina Peninsula (Indochina) is one of the important ozone sources in the low troposphere over East Asia in springtime. Moderate Resolution Imaging Spectroradiometer (MODIS) data show that 20 000 or more active fire detections occurred annually in spring only from 2000 to 2007. In our tracer modeling study, we identify a new mechanism transporting the tracer over Indochina that is significantly different from the vertical transport mechanism over the equatorial areas...

-y Lin, C.; Hsu, H. M.; Lee, Y. H.; Kuo, C. H.; -f Sheng, Y.; Chu, D. A.

2009-01-01

172

Water transport mechanisms across inorganic membranes in rad waste treatment by electro dialysis  

International Nuclear Information System (INIS)

The work described in this paper deals with effects and mechanisms of water transport across an inorganic membrane, as related to some studied on the concentration of caesium, strontium, plutonium and other cations of interest to radioactive waste treatment. Several different water transport mechanisms are analysed and assessed as to their individual contribution towards the total transference of water during electro-dialysis using inorganic membranes. Water transfer assisted by proton jump mechanism, water of hydration transferred along with the ions, water related to thermo-osmotic effect, water transferred by concentration gradient and water transferred electrolytically under zeta potential surface charge drive are some of the different mechanism discussed. (author)

173

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

Science.gov (United States)

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. PMID:25010455

Alvarino, T; Suarez, S; Lema, J M; Omil, F

2014-08-15

174

Basic mechanisms for recognition and transport of synaptic cargos  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Synaptic cargo trafficking is essential for synapse formation, function and plasticity. In order to transport synaptic cargo, such as synaptic vesicle precursors, mitochondria, neurotransmitter receptors and signaling proteins to their site of action, neurons make use of molecular motor proteins. These motors operate on the microtubule and actin cytoskeleton and are highly regulated so that different cargos can be transported to distinct synaptic specializations at both pre- and post-synaptic sites. How synaptic cargos achieve specificity, directionality and timing of transport is a developing area of investigation. Recent studies demonstrate that the docking of motors to their cargos is a key control point. Moreover, precise spatial and temporal regulation of motor-cargo interactions is important for transport specificity and cargo recruitment. Local signaling pathways ? Ca2+ influx, CaMKII signaling and Rab GTPase activity ? regulate motor activity and cargo release at synaptic locations. We discuss here how different motors recognize their synaptic cargo and how motor-cargo interactions are regulated by neuronal activity.

Schlager Max A

2009-08-01

175

Benchmark calculations for mechanical stresses upon a transport cask  

International Nuclear Information System (INIS)

Due to the regulations for the safe transport of type B(U) packages, transport casks for spent fuel elements have to prove their ability to withstand a series of tests which simulate various hypothetical incidental drops without loss of leak tightness. According to transport regulations it is permissible to apply analytical methods instead of tests. One of these methods used for transport casks of the CASTOR type is the finite element method. Thus it is possible to calculate displacements and stresses or strains in the time domain. The knowledge of these quantities makes it possible to compare them with allowable values and to establish the safety margin for the various load cases. This method is also of advantage for design calculations as the variation of parameters can be done with a small amount of effort compared to tests. Due to the progress of hardware development, even large finite element models can be analyzed by means of personal computers nowadays, which makes the application of this method even more interesting. Supposition for the use of a certain finite element program, however, is the proof that for the analysis of certain problems the code produces results which approach the actual values as close as possible. This can be verified by benchmark calculations. For the present case it had to be shown that the load due to so-called type B(U) tests can be calculated in a sufficiently accurate manner by means of the finite element program ADINA. Among othersfinite element program ADINA. Among others, the type B(U) test cases are load cases submitting transport casks either to a free drop from a height of 9 meters onto a rigid target or to a penetration test during which the cask drops from a height of I meter onto a defined bar. During the verification calculations, the ability of the code to approach the non-linear processes is verified. Having proved the basic ability of ADINA by means of benchmark calculations of the 9 meter drops for simplified geometries in, some more verifications were made for more complex geometry of a transport cask. The cases analyzed were the 9 meter drop with impact flat onto the cylindrical shell of the shock absorber at the bottom part as well as the 1 meter drop with impact of the bar in the center of the cylinder wall. Having done all the calculations, the measurements were analyzed. It was found that a relatively small number of values were reliable. During the test many of them were destroyed of showed incorrect results. As long as the values were reliable they were used for comparison

176

Aromatic isophthalamides aggregate in lipid bilayers: evidence for a cooperative transport mechanism.  

Science.gov (United States)

The synthesis and anion transport properties of a series of transmembrane anion transporters based on an isophthalamide scaffold with phenyl, naphthyl or anthracenyl central rings are reported. Anion transport studies using POPC vesicles, showed that the compounds have Hill coefficients >1. This is indicative of higher order complex formation, evidence that leads us to suggest that the compounds are not functioning solely as mobile carriers but rather that a cooperative transport mechanism is being observed. Fluorescence spectroscopy was used to show that the compounds aggregate in the phospholipid bilayer, which provides evidence that these compounds function as a self-assembled anion-conducting aggregate. PMID:25633557

Berry, Stuart N; Busschaert, Nathalie; Frankling, Charlotte L; Salter, Dale; Gale, Philip A

2015-02-24

177

Mechanisms of dopamine transporter regulation in normal and disease states  

OpenAIRE

The dopamine transporter (DAT) controls the spatial and temporal dynamics of dopamine (DA) neurotransmission by driving reuptake of extracellular transmitter into presynaptic neurons. Many diseases such as depression, bipolar disorder, Parkinson’s disease, and attention deficit hyperactivity disorder are associated with abnormal DA levels, implicating DAT as a factor in their etiology. Medications used to treat these disorders and many addictive drugs target DAT and enhance dopaminergic sig...

Vaughan, Roxanne A.; Foster, James D.

2013-01-01

178

Mechanisms of electron transport and recombination in ZnO nanostructures for dye-sensitized solar cells.  

Science.gov (United States)

ZnO is an attractive material for applications in dye-sensitized solar cells and related devices. This material has excellent electron-transport properties in the bulk but its electron diffusion coefficient is much smaller in mesoporous films. In this work the electron-transport properties of two different kinds of dye-sensitized ZnO nanostructures are investigated by small-perturbation electrochemical techniques. For nanoparticulate ZnO photoanodes prepared via a wet-chemistry technique, the diffusion coefficient is found to reproduce the typical behavior predicted by the multiple-trapping and the hopping models, with an exponential increase with respect to the applied bias. In contrast, in ZnO nanostructured thin films of controlled texture and crystallinity prepared via a plasma chemical vapor deposition method, the diffusion coefficient is found to be independent of the electrochemical bias. This observation suggests a different transport mechanism not controlled by trapping and electron accumulation. In spite of the quite different transport features, the recombination kinetics, the electron-collection efficiency and the photoconversion efficiency are very similar for both kinds of photoanodes, an observation that indicates that surface properties rather than electron transport is the main efficiency-determining factor in solar cells based on ZnO nanostructured photoanodes. PMID:24729526

Vega-Poot, Alberto G; Macías-Montero, Manuel; Idígoras, Jesus; Borrás, Ana; Barranco, Angel; Gonzalez-Elipe, Agustín R; Lizama-Tzec, Francisco I; Oskam, Gerko; Anta, Juan A

2014-04-14

179

From Mechanical Motion to Brownian Motion, Thermodynamics and Particle Transport Theory  

Science.gov (United States)

The motion of a particle in a medium is dealt with either as a problem of mechanics or as a transport process in non-equilibrium statistical physics. The two kinds of approach are often unrelated as they are taught in different textbooks. The aim of this paper is to highlight the link between the mechanical and statistical treatments of particle…

Bringuier, E.

2008-01-01

180

Mechanism of arsenate inhibition of the glucose active transport system in Neurospora crassa  

International Nuclear Information System (INIS)

The mechanism of arsenate inhibition of the glucose active transport system in wild-type cells of Neurospora crassa has been examined. Arsenate treatment results in approximately 65% inhibition of the glucose active transport system with only a small depression of cellular ATP levels. The transport system is not inhibited in cells treated with sodium arsenate in the presence of sodium azide. The transport inhibition is suppressed when orthophosphate is present during arsenate treatment, but is not reversed by orthophosphate when added after the arsenate treatment. The transport inhibition is completely reversed by treatment of the cells with mercaptoethanol. Gel chromatography of sonicates of intact cells which had been treated with [74As]arsenate reveals three radioactive peaks, one with the elution volume of arsenate, one with the elution volume of arsenite, and in high molecular-weight radioactive fraction. Treatment of the high molecular-weight radioactive fraction with mercaptoethanol results in the production of radioactive arsenite. In view of these findings, it is proposed that arsenate inhibition of the glucose active transport system in Neurospora involves transport of arsenate into the cells, probably via the orthophosphate transport system, reduction of the transported arsenate to arsenite, and interaction of arsenite with some component of the glucose active transport system, presumably via covalent binding with vicinal thiol groups. 15 referending with vicinal thiol groups. 15 references, 4 figures, 2 tables

181

Turbulence elasticity—A new mechanism for transport barrier dynamics  

Energy Technology Data Exchange (ETDEWEB)

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.

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

182

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

Directory of Open Access Journals (Sweden)

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.

James Baker-Jarvis

2009-11-01

183

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

Energy Technology Data Exchange (ETDEWEB)

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.

P Zhang; J Wang; Y Shi

2011-12-31

184

Overview of Erosion Mechanisms, Impurity Transport, and Deposition in TEXTOR and Related Modeling  

International Nuclear Information System (INIS)

This paper gives an overview of the research activities at TEXTOR on impurity production, impurity transport through the plasma, and then deposition. First, laboratory experiments on chemical erosion by hydrogen and oxygen and radiation-enhanced sublimation are described, followed by the main part, which concentrates on the TEXTOR data of impurity release, impurity transport, and redeposition. The differences between the behavior of high-Z and low-Z materials are discussed. Many of the TEXTOR experiments are carried out using special limiter locks, but the overall carbon balance of net erosion sources and net deposition zones are also shown. Finally, modeling of erosion and dedicated transport experiments are addressed

185

Theories of the Charge Transport Mechanism in Ordered Organic Semiconductors  

Science.gov (United States)

The traditional theories of charge transport in ordered organic semiconductors are reviewed and their limitations discussed. The recent contributions of computational chemistry to the understanding of the parameters that determine the charge mobility in bulk semiconductors are analyzed in detail. The effect of thermal motions on the electronic wavefunction and the effect of strong off-diagonal electron-phonon coupling are identified as essential ingredients for the proper description of the charge dynamics. The development of suitable methods to compute the charge mobility taking into account these new computational results is reviewed, with special emphasis on the models that allow the prediction of the structure-property relationship. The available experimental evidence is compared with the predictions made by the most recent models.

Troisi, Alessandro

186

Structure and permeation mechanism of a mammalian urea transporter  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2012-09-17

187

NPC Mimics: Probing the Mechanism of Nucleocytoplasmic Transport  

OpenAIRE

In vitro mimics of cellular machines have been recently engineered and utilized to investigate processes within cells. These devices can provide novel insights into biological mechanisms and have the potential to improve biotechnological processes such as separation. In particular, several devices have been designed to mimic translocation through nuclear pore complexes (NPCs). We describe here the fabrication of a biomimetic NPC using nanoporous filters lined with FG-repeats of proteins that ...

Jovanovic-talisman, Tijana; Chait, Brian T.; Rout, Michael P.

2014-01-01

188

HYDROLOGICAL AND SEDIMENT TRANSPORT SIMULATION TO ASSESS THE IMPACT OF DAM CONSTRUCTION IN THE MEKONG RIVER MAIN CHANNEL  

OpenAIRE

The downstream impact of dams is a complex problem in watershed management. In the upper Mekong River watershed and its main channel, dam construction projects were started in the 1950s to meet increasing demands for energy and food production. Dams called the Mekong Cascade were completed on the Mekong River in China, the Manwan Dam in 1996 and the Dachaoshan Dam in 2003. We evaluated the impact of the Manwan Dam and its related watershed development on seasonal water discharge and suspended...

Satoshi Kameyama; Hiroto Shimazaki; Seiichi Nohara; Tatsuaki Sato; Yoshiaki Fujii; Keita Kudo

2013-01-01

189

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.)

190

Transport mechanisms in the outer region of RFX-mod  

International Nuclear Information System (INIS)

The transport processes taking place in the outer region of fusion-relevant magnetically confined plasmas are generally believed to be driven by the fluctuating electric field associated to plasma microturbulence. The edge plasma of RFX-mod, a large reversed field pinch (RFP) toroidal device, shares many peculiar characteristics of other configurations. The edge turbulence exhibits an intermittent behaviour, associated with blobs, coherent eddies and structures emerging form the turbulent background. Despite the crucial role in the improved confinement regimes of the interaction between the generation/dissipation of the flow and the creation/destruction of turbulent structures, its description is far from being completely understood. RFX-mod is equipped with a full set of edge diagnostic systems with sub-microsecond time resolution: the Gas Puffing Imaging diagnostic which gives great details of the structures and of their dynamics; the Integrated System of Internal Sensors, a distributed system of in-vessel magnetic and electrostatic probes, which can follow the structures in their motion and relate them to large scale instabilities; an insertable 'U-probe' which simultaneously measures local magnetic field, current density, plasma pressure, E x B flow and turbulent particle flux; a 'Gundestrup probe' which provides direct measurements of both parallel and perpendicular flow. Very recently new Thomson scattering and thermal Helium beam spectroscopy diagnostics for meelium beam spectroscopy diagnostics for measurement of edge electron density and temperature profiles have been put into operation. The paper presents the new insights achieved starting from the obtained measurements: the properties of the structures in terms of pressure, flow and current density; an estimation of the diffusivity associated to the coherent structures, found to decrease with increasing n/nGreenwald between 0.1 G < 0.35 with a tendency to saturate at higher values; the analysis of turbulent momentum fluxes, described in terms of the Maxwell and Reynolds stress terms of momentum transport equation, where the Reynolds stress has been found to dominate the process over the Maxwell stress for at least a factor five. (author)

191

Effects of intravenous furosemide on mucociliary transport and rheological properties of patients under mechanical ventilation  

OpenAIRE

The use of intravenous (IV) furosemide is common practice in patients under mechanical ventilation (MV), but its effects on respiratory mucus are largely unknown. Furosemide can affect respiratory mucus either directly through inhibition of the NaK(Cl)2 co-transporter on the basolateral surface of airway epithelium or indirectly through increased diuresis and dehydration. We investigated the physical properties and transportability of respiratory mucus obtained from 26 patients under MV distr...

Kondo, Cla?udia Seiko; Macchionne, Maria?ngela; Nakagawa, Naomi Kondo; Carvalho, Carlos Roberto Ribeiro; King, Malcolm; Saldiva, Paulo Hila?rio Nascimento; Lorenzi-filho, Geraldo

2001-01-01

192

[Helicopter transportation of a sedated, mechanically ventilated patient with cervical cord injury].  

Science.gov (United States)

We report helicopter transportation of a sedated, mechanically ventilated patient with cervical cord injury. A 20-year-old male sustained traumatic injury to the cervical spinal cord during extracurricular activities in a college. On arrival at the hospital, a halo vest was placed on the patient and tracheostomy was performed. On the 38th hospital day, he was transported a distance of 520km by helicopter to a specialized hospital in Fukuoka for medical repatriation. Cabin space was narrow. Since power supply and carrying capacity were limited, battery-driven and portable medical devices were used. In consideration for patient's psychological stress, he was sedated with propofol. RSS (Ramsay sedation scale) scores were recorded to evaluate whether the patient was adequately sedated during helicopter transportation. Prior to transport, we rehearsed the sedation using bispectral index monitoring (BIS) in the hospital to further ensure the patient's safety during the transport. PMID:24063142

Kato, Hideya; Nishiwaki, Yuko; Hosoi, Kunihiko; Shiomi, Naoto; Hirata, Masashi

2013-09-01

193

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

194

Kinetics and mechanism of proton transport across membrane nanopores  

CERN Document Server

We use computer simulations to study the kinetics and mechanism of proton passage through a narrow-pore carbon-nanotube membrane separating reservoirs of liquid water. Free energy and rate constant calculations show that protons move across the membrane diffusively in single-file chains of hydrogen-bonded water molecules. Proton passage through the membrane is opposed by a high barrier along the effective potential, reflecting the large electrostatic penalty for desolvation and reminiscent of charge exclusion in biological water channels. At neutral pH, we estimate a translocation rate of about 1 proton per hour and tube.

Dellago, C; Dellago, Christoph; Hummer, Gerhard

2006-01-01

195

Co-60 transport mechanism under ultra low crud control  

International Nuclear Information System (INIS)

Ni/Fe control had been performed in Japanese low crud BWR plants to reduce cobalt ion, including Co-60 and Co-58 in reactor water (RW). But, Co-60 ion conc. began to increase after the application of new type fuel bundles using high corrosion resistant zircaloy tubes. The behavior was clearly observed in plants where the fuel bundles were initially loaded. It was clarified from the analysis of fuel crud and the laboratory experiments that the cause was due to unstable chromium oxides assisting the release of Co-60 from crud. Another disadvantaged activity buildup behavior was observed. The deposition rates of Co-60 and Co-58 on electro-polished primary recirculation (PLR) pipings in some plants were widely scattered. It was assumed that high deposition was caused by large amount of crud due to deposited crud from RW or thick corrosion oxide films made by corrosion. On the other hand, such a high deposition rate was not observed after water chemistry change from Ni/Fe control to high nickel ion control obtained by ultra low crud control. In this report, a new concept, ultra low crud control substituted Ni/Fe control was introduced. The characteristics of cobalt transport behavior and the applicability to actual BWR plants were clarified. (J.P.N.)

196

On the mechanism of activated transport in glassy liquids.  

Science.gov (United States)

We explore several potential issues that have been raised over the years regarding the "entropic droplet" scenario of activated transport in liquids, due to Wolynes and co-workers, with the aim of clarifying the status of various approximations of the random first-order transition theory (RFOT) of the structural glass transition. In doing so, we estimate the mismatch penalty between alternative aperiodic structures, above the glass transition; the penalty is equal to the typical magnitude of free energy fluctuations in the liquid. The resulting expressions for the activation barrier and the cooperativity length contain exclusively bulk, static properties; in their simplest form they contain only the bulk modulus and the configurational entropy per unit volume. The expressions are universal in that they do not depend explicitly on the molecular detail. The predicted values for the barrier and cooperativity length and, in particular, the temperature dependence of the barrier are in satisfactory agreement with observation. We thus confirm that the entropic droplet picture is indeed not only internally consistent but is also fully constructive, consistent with the apparent success of its many quantitative predictions. A simple view of a glassy liquid as a locally metastable, degenerate pattern of frozen-in stress emerges in the present description. Finally, we derive testable relationships between the bulk modulus and several characteristics of glassy liquids and peculiarities in low-temperature glasses. PMID:25347199

Lubchenko, Vassiliy; Rabochiy, Pyotr

2014-11-26

197

Transportation mechanism for vanillin uptake through fungal plasma membrane.  

Science.gov (United States)

Protoplasts of the basidiomycete, Fomitopsis palustris (formerly Tyromyces palustris), were utilized to study a function of the fungal plasma membrane. Fungal protoplasts exhibited metabolic activities as seen with intact mycelial cells. Furthermore, the uptake of certain compounds into the protoplast cells was quantitatively observed by using non-radioactive compounds. Vanillin was converted to vanillyl alcohol and vanillic acid as major products and to protocatechuic acid and 1,2,4-trihydroxybenzene as trace products by protoplasts prepared from F. palustris. Extracellular culture medium showed no activity responsible for the redox reactions of vanillin. Only vanillic acid was detected in the intracellular fraction of protoplasts. However, the addition of disulfiram, an aldehyde dehydrogenase inhibitor, caused an intracellular accumulation of vanillin, strongly suggesting that vanillin is taken up by the cell, followed by oxidation to vanillic acid. The addition of carbonylcyanide m-chlorophenylhydrazone, which dissipates the pH gradient across the plasma membrane, inhibited the uptake of either vanillin or vanillic acid into the cell. Thus, the fungus seems to possess transporter devices for both vanillin and vanillic acid for their uptake. Since vanillyl alcohol was only observed extracellularly, the reduction of vanillin was thought to be catalyzed by a membrane system. PMID:15868144

Shimizu, Motoyuki; Kobayashi, Yoshinori; Tanaka, Hiroo; Wariishi, Hiroyuki

2005-09-01

198

Mechanism of unassisted ion transport across membrane bilayers  

Science.gov (United States)

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.

Wilson, M. A.; Pohorille, A.

1996-01-01

199

The mechanisms and regulation of placental amino acid transport to the human foetus.  

Science.gov (United States)

The mechanisms by which amino acids are transferred across the human placenta are fundamental to our understanding of foetal nutrition. Amino acid transfer across the human placenta is dependent on transport across both the microvillous and basal plasma membranes of the placental syncytiotrophoblast, and on metabolism within the syncytiotrophoblast. Although the principles underlying uptake of amino acids across the microvillous plasma membrane are well understood, the extent to which amino acids are metabolised within human placenta and the mechanisms by which amino acids are transported out of the placenta across the basal plasma membrane are not well understood. Understanding the mechanisms and regulation of amino acid transport is necessary to understand the causes of intrauterine growth restriction in human pregnancy. PMID:18266945

Cleal, J K; Lewis, R M

2008-04-01

200

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 f/sub> = (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

201

Identification of glucuronidation and biliary excretion as the main mechanisms for gossypol clearance: in vivo and in vitro evidence.  

Science.gov (United States)

1.?The natural polyphenol gossypol possesses many therapeutic benefits. Here we aim to determine the elimination pathways of gossypol in vivo and in vitro. 2.?Metabolite elucidation of gossypol was performed using UPLC-QTOF/MS coupled with Metabolynx analysis. Clearance of gossypol was evaluated in bile duct cannulated rats and in the single-pass perfused rat intestine model. In vitro glucuronidation of gossypol was characterized using liver and intestine microsomes as well as recombinant UDP-glucuronosyltransferase (UGT) enzymes. 3.?Analysis of rat plasma, urine, and feces revealed glucuronidation as the only metabolic pathway for gossypol. In bile duct cannulated rats, considerable amounts of glucuronides (G1, G2 and G3; 58.8-83.2% of dose) and parent compound (5.0-20%) were excreted into bile after IV administration. In the perfused rat intestine model, gossypol was well absorbed with a [Formula: see text] (the dimensionless effective permeability) value of 4.4. Significant amounts of glucuronides (G1, G2 and G3) were excreted into the gut lumen (2.5%) and into the bile (4.8%). Biliary excretion of unchanged gossypol (6.0%) was comparable to that of glucuronides. Further, gossypol was subjected to rapid glucuronidation by liver and intestine microsomes. Reaction phenotyping showed that multiple UGT1A enzymes (including UGT1A1, 1A3, 1A7 and 1A8) are mainly responsible for gossypol metabolism. 4.?In conclusion, glucuronidation was the only metabolic pathway for gossypol in rats. Excretion of unchanged gossypol into bile was also an important clearance mechanism. PMID:24555821

Liu, Hongming; Sun, Hua; Lu, Danyi; Zhang, Yuchen; Zhang, Xingwang; Ma, Zhiguo; Wu, Baojian

2014-08-01

202

Copper transport from ceruloplasmin: characterization of the cellular uptake mechanism.  

Science.gov (United States)

Copper uptake from 67Cu-labeled ceruloplasmin (67CuCp) was studied in K-562 cells, a human erythroleukemic cell line. 67CuCp was prepared by an ascorbate-catalyzed exchange of recrystallized ceruloplasmin with 67CuCl2. The labeled protein was treated with Chelex-100 and gel filtration to ensure that 67Cu was tightly bound to the structure. 67CuCp bound specifically to the K-562 cells at 4 degrees C. The binding was linear with protein in the range of 200-800 nM and in the presence of 3% albumin. In this concentration range, 67CuCl2 showed no binding that could be interpreted as specific; 80-90% of the cell-bound 67Cu was removed by washing the cells with acid buffer. When binding was attempted at 37 degrees C, a significant fraction of the 67Cu resisted acid washing and with time accumulated in the cells. Fractionating the cytosolic components on Percoll gradients located the 67Cu in buoyant fractions of densities 1.030-1.05, with a peak at 1.035. Repeating the experiment with 125I-labeled ceruloplasmin failed to localize any 125I label in Percoll fractions; very little 125I was detected in the cytosol. Double-labeled 67Cu-125I-ceruloplasmin confirmed that copper and not the protein moiety of ceruloplasmin was taken up by the cells. The uptake reaction was inhibited by 1 mM bathocuproine sulfonate and by 1 mM sodium iproniazid. Ascorbate (100 microM) strongly stimulated uptake. These studies provide evidence that K-562 cells are able to extract copper atoms from ceruloplasmin and transport the copper to the cytosol.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2301561

Percival, S S; Harris, E D

1990-01-01

203

A transition in mechanisms of size dependent electrical transport at nanoscale metal-oxide interfaces  

International Nuclear Information System (INIS)

As device miniaturization approaches nanoscale dimensions, interfaces begin to dominate electrical properties. Here the system archetype Au/SrTiO3 is used to examine the origin of size dependent transport properties along metal-oxide interfaces. We demonstrate that a transition between two classes of size dependent electronic transport mechanisms exists, defined by a critical size ?. At sizes larger than ? an edge-related tunneling effect proportional to 1/D (the height of the supported Au nanoparticle) is observed; interfaces with sizes smaller than ? exhibit random fluctuations in current. The ability to distinguish between these mechanisms is important to future developments in nanoscale device design

204

A transition in mechanisms of size dependent electrical transport at nanoscale metal-oxide interfaces  

Energy Technology Data Exchange (ETDEWEB)

As device miniaturization approaches nanoscale dimensions, interfaces begin to dominate electrical properties. Here the system archetype Au/SrTiO{sub 3} is used to examine the origin of size dependent transport properties along metal-oxide interfaces. We demonstrate that a transition between two classes of size dependent electronic transport mechanisms exists, defined by a critical size ?. At sizes larger than ? an edge-related tunneling effect proportional to 1/D (the height of the supported Au nanoparticle) is observed; interfaces with sizes smaller than ? exhibit random fluctuations in current. The ability to distinguish between these mechanisms is important to future developments in nanoscale device design.

Hou, Jiechang; Nonnenmann, Stephen S.; Qin, Wei; Bonnell, Dawn A., E-mail: bonnell@lrsm.seas.upenn.edu [Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)

2013-12-16

205

Oxygen transport mechanisms in REAlO{sub 3} scintillators  

Energy Technology Data Exchange (ETDEWEB)

The performance of oxide scintillators often suffers from phenomena related to the existence of point defects. Thus, if deleterious defects are removed, it follows that scintillator performance will improve. In the case of REAlO{sub 3} perovskites, the oxygen vacancy has been identified as the predominant electron trap site. Previous empirical efforts to minimize the concentration of this particular defect through aliovalent doping have been successful. Here we discuss the results of atomic scale simulations that provide important detail regarding the mechanism by which the oxygen vacancy concentration is reduced. Specifically, we describe the complex mobility of oxygen vacancies and interstitials, which governs the recombination of these defects. The results of these simulations will aid in the synthesis of optimized scintillation materials. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Stanek, C.R.; Uberuaga, B.P.; McClellan, K.J. [Materials Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Levy, M.R.; Grimes, R.W. [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom)

2007-03-15

206

Trypanosoma brucei aquaglyceroporin 2 is a high-affinity transporter for pentamidine and melaminophenyl arsenic drugs and the main genetic determinant of resistance to these drugs  

Science.gov (United States)

Objectives Trypanosoma brucei drug transporters include the TbAT1/P2 aminopurine transporter and the high-affinity pentamidine transporter (HAPT1), but the genetic identity of HAPT1 is unknown. We recently reported that loss of T. brucei aquaglyceroporin 2 (TbAQP2) caused melarsoprol/pentamidine cross-resistance (MPXR) in these parasites and the current study aims to delineate the mechanism by which this occurs. Methods The TbAQP2 loci of isogenic pairs of drug-susceptible and MPXR strains of T. brucei subspecies were sequenced. Drug susceptibility profiles of trypanosome strains were correlated with expression of mutated TbAQP2 alleles. Pentamidine transport was studied in T. brucei subspecies expressing TbAQP2 variants. Results All MPXR strains examined contained TbAQP2 deletions or rearrangements, regardless of whether the strains were originally adapted in vitro or in vivo to arsenicals or to pentamidine. The MPXR strains and AQP2 knockout strains had lost HAPT1 activity. Reintroduction of TbAQP2 in MPXR trypanosomes restored susceptibility to the drugs and reinstated HAPT1 activity, but did not change the activity of TbAT1/P2. Expression of TbAQP2 sensitized Leishmania mexicana promastigotes 40-fold to pentamidine and >1000-fold to melaminophenyl arsenicals and induced a high-affinity pentamidine transport activity indistinguishable from HAPT1 by Km and inhibitor profile. Grafting the TbAQP2 selectivity filter amino acid residues onto a chimeric allele of AQP2 and AQP3 partly restored susceptibility to pentamidine and an arsenical. Conclusions TbAQP2 mediates high-affinity uptake of pentamidine and melaminophenyl arsenicals in trypanosomes and TbAQP2 encodes the previously reported HAPT1 activity. This finding establishes TbAQP2 as an important drug transporter. PMID:24235095

Munday, Jane C.; Eze, Anthonius A.; Baker, Nicola; Glover, Lucy; Clucas, Caroline; Aguinaga Andrés, David; Natto, Manal J.; Teka, Ibrahim A.; McDonald, Jennifer; Lee, Rebecca S.; Graf, Fabrice E.; Ludin, Philipp; Burchmore, Richard J. S.; Turner, C. Michael R.; Tait, Andy; MacLeod, Annette; Mäser, Pascal; Barrett, Michael P.; Horn, David; De Koning, Harry P.

2014-01-01

207

Plutonium Colloid-Facilitated Transport in the Environment - Experimental and Transport Modeling Evidence for Plutonium Migration Mechanisms  

International Nuclear Information System (INIS)

Natural inorganic colloids (< 1 micron particles) found in groundwater can sorb low-solubility actinides and may provide a pathway for transport in the subsurface. For example, Kerting et al found that Pu, associated with colloids fraction of the groundwater, was detected over 1 km away from the underground nuclear test at the Nevada Test Site (NTS) where it was originally deposited 28 years earlier. However, laboratory experiments have not identified the mechanisms by which Pu may sorb to colloids or exist as its own colloid and travel relatively unimpeded in the subsurface. Some data suggest that Pu sorption to colloids is a very fast process while desorption is very slow or simply does not occur. Slow desorption of Pu from colloids could allow Pu sorbed to a colloid to travel much farther than if sorption were an equilibrium process. However, PU sorption (and particularly desorption) data in the literature are scant and sometimes contradictory. In some cases, Pu desorption is rather fast, with rates dependent on colloid mineralogy. Moreover, the effect of sorption and desorption kinetics (as well as other mechanisms) on colloid-facilitated transport at the field scale has not been thoroughly evaluated. This is, in part, due to limitations in colloid transport as well as sorption/desorption models

208

Pultonium Colloid-Facilitated Transport in the Environment - Experimental and Transport Modeling Evidence for Plutonium Migration Mechanisms  

Energy Technology Data Exchange (ETDEWEB)

Natural inorganic colloids (< 1 micron particles) found in groundwater can sorb low-solubility actinides and may provide a pathway for transport in the subsurface. For example, Kerting et al found that Pu, associated with colloids fraction of the groundwater, was detected over 1 km away from the underground nuclear test at the Nevada Test Site (NTS) where it was originally deposited 28 years earlier. However, laboratory experiments have not identified the mechanisms by which Pu may sorb to colloids or exist as its own colloid and travel relatively unimpeded in the subsurface. Some data suggest that Pu sorption to colloids is a very fast process while desorption is very slow or simply does not occur. Slow desorption of Pu from colloids could allow Pu sorbed to a colloid to travel much farther than if sorption were an equilibrium process. However, PU sorption (and particularly desorption) data in the literature are scant and sometimes contradictory. In some cases, Pu desorption is rather fast, with rates dependent on colloid mineralogy. Moreover, the effect of sorption and desorption kinetics (as well as other mechanisms) on colloid-facilitated transport at the field scale has not been thoroughly evaluated. This is, in part, due to limitations in colloid transport as well as sorption/desorption models.

Zavarin, M; Maxwell, R M; Kersting, A B; Zhao, P; Sylwester, E R; Allen, P G; Williams, R W

2003-02-19

209

Mechanism of coupling drug transport reactions located in two different membranes.  

Science.gov (United States)

Gram- negative bacteria utilize a diverse array of multidrug transporters to pump toxic compounds out of the cell. Some transporters, together with periplasmic membrane fusion proteins (MFPs) and outer membrane channels, assemble trans-envelope complexes that expel multiple antibiotics across outer membranes of Gram-negative bacteria and into the external medium. Others further potentiate this efflux by pumping drugs across the inner membrane into the periplasm. Together these transporters create a powerful network of efflux that protects bacteria against a broad range of antimicrobial agents. This review is focused on the mechanism of coupling transport reactions located in two different membranes of Gram-negative bacteria. Using a combination of biochemical, genetic and biophysical approaches we have reconstructed the sequence of events leading to the assembly of trans-envelope drug efflux complexes and characterized the roles of periplasmic and outer membrane proteins in this process. Our recent data suggest a critical step in the activation of intermembrane efflux pumps, which is controlled by MFPs. We propose that the reaction cycles of transporters are tightly coupled to the assembly of the trans-envelope complexes. Transporters and MFPs exist in the inner membrane as dormant complexes. The activation of complexes is triggered by MFP binding to the outer membrane channel, which leads to a conformational change in the membrane proximal domain of MFP needed for stimulation of transporters. The activated MFP-transporter complex engages the outer membrane channel to expel substrates across the outer membrane. The recruitment of the channel is likely triggered by binding of effectors (substrates) to MFP or MFP-transporter complexes. This model together with recent structural and functional advances in the field of drug efflux provides a fairly detailed understanding of the mechanism of drug efflux across the two membranes. PMID:25759685

Zgurskaya, Helen I; Weeks, Jon W; Ntreh, Abigail T; Nickels, Logan M; Wolloscheck, David

2015-01-01

210

Mechanism of coupling drug transport reactions located in two different membranes  

Science.gov (United States)

Gram- negative bacteria utilize a diverse array of multidrug transporters to pump toxic compounds out of the cell. Some transporters, together with periplasmic membrane fusion proteins (MFPs) and outer membrane channels, assemble trans-envelope complexes that expel multiple antibiotics across outer membranes of Gram-negative bacteria and into the external medium. Others further potentiate this efflux by pumping drugs across the inner membrane into the periplasm. Together these transporters create a powerful network of efflux that protects bacteria against a broad range of antimicrobial agents. This review is focused on the mechanism of coupling transport reactions located in two different membranes of Gram-negative bacteria. Using a combination of biochemical, genetic and biophysical approaches we have reconstructed the sequence of events leading to the assembly of trans-envelope drug efflux complexes and characterized the roles of periplasmic and outer membrane proteins in this process. Our recent data suggest a critical step in the activation of intermembrane efflux pumps, which is controlled by MFPs. We propose that the reaction cycles of transporters are tightly coupled to the assembly of the trans-envelope complexes. Transporters and MFPs exist in the inner membrane as dormant complexes. The activation of complexes is triggered by MFP binding to the outer membrane channel, which leads to a conformational change in the membrane proximal domain of MFP needed for stimulation of transporters. The activated MFP-transporter complex engages the outer membrane channel to expel substrates across the outer membrane. The recruitment of the channel is likely triggered by binding of effectors (substrates) to MFP or MFP-transporter complexes. This model together with recent structural and functional advances in the field of drug efflux provides a fairly detailed understanding of the mechanism of drug efflux across the two membranes.

Zgurskaya, Helen I.; Weeks, Jon W.; Ntreh, Abigail T.; Nickels, Logan M.; Wolloscheck, David

2015-01-01

211

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)

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.)

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

212

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

213

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

Energy Technology Data Exchange (ETDEWEB)

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

Svensson, Urban (ed.) (Computer-aided Fluid Engineering AB (CFE AB), SE-602 10 Norrkoeping (Sweden)); Vidstrand, Patrik (Bergab AB, Goeteborg (Sweden)); Neretnieks, Ivars (Dept. of Chemical Engineering and Technology, Royal Inst. of Technology, Stockholm (Sweden)); Wallin, Bill (Geokema, Lidingoe (Sweden))

2008-05-15

214

SUPG and discontinuity-capturing methods for coupled fluid mechanics and electrochemical transport problems  

Science.gov (United States)

Electrophoresis is the motion of charged particles relative to the surrounding liquid under the influence of an external electric field. This electrochemical transport process is used in many scientific and technological areas to separate chemical species. Modeling and simulation of electrophoretic transport enables a better understanding of the physicochemical processes developed during the electrophoretic separations and the optimization of various parameters of the electrophoresis devices and their performance. Electrophoretic transport is a multiphysics and multiscale problem. Mass transport, fluid mechanics, electric problems, and their interactions have to be solved in domains with length scales ranging from nanometers to centimeters. We use a finite element method for the computations. Without proper numerical stabilization, computation of coupled fluid mechanics, electrophoretic transport, and electric problems would suffer from spurious oscillations that are related to the high values of the local Péclet and Reynolds numbers and the nonzero divergence of the migration field. To overcome these computational challenges, we propose a stabilized finite element method based on the Streamline-Upwind/Petrov-Galerkin (SUPG) formulation and discontinuity-capturing techniques. To demonstrate the effectiveness of the stabilized formulation, we present test computations with 1D, 2D, and 3D electrophoretic transport problems of technological interest.

Kler, Pablo A.; Dalcin, Lisandro D.; Paz, Rodrigo R.; Tezduyar, Tayfun E.

2013-02-01

215

14 CFR 29.691 - Autorotation control mechanism.  

Science.gov (United States)

...AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY ROTORCRAFT Design and Construction Control Systems § 29.691 Autorotation control mechanism. Each main rotor blade pitch control mechanism must allow rapid entry into...

2010-01-01

216

Silver (Ag) Transport Mechanisms in TRISO Coated Particles: A Critical Review  

Energy Technology Data Exchange (ETDEWEB)

Transport of 110mAg in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE’s fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified.

IJ van Rooyen; ML Dunzik-Gougar; PM van Rooyen

2014-05-01

217

Silver (Ag) transport mechanisms in TRISO coated particles: A critical review  

International Nuclear Information System (INIS)

Transport of 110mAg in the intact SiC layer of TRISO coated particles has been studied for approximately 30 years without arriving at a satisfactory explanation of the transport mechanism. In this paper the possible mechanisms postulated in previous experimental studies, both in-reactor and out-of reactor research environment studies are critically reviewed and of particular interest are relevance to very high temperature gas reactor operating and accident conditions. Among the factors thought to influence Ag transport are grain boundary stoichiometry, SiC grain size and shape, the presence of free silicon, nano-cracks, thermal decomposition, palladium attack, transmutation products, layer thinning and coated particle shape. Additionally new insight to nature and location of fission products has been gained via recent post irradiation electron microscopy examination of TRISO coated particles from the DOE's fuel development program. The combined effect of critical review and new analyses indicates a direction for investigating possible the Ag transport mechanism including the confidence level with which these mechanisms may be experimentally verified

218

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

219

A fully resolved active musculo-mechanical model for esophageal transport  

CERN Document Server

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...

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

2015-01-01

220

Sensitivity analysis and parameter identification of nonlinear hybrid systems for glycerol transport mechanisms in continuous culture.  

Science.gov (United States)

In this paper, we establish a modified fourteen-dimensional nonlinear hybrid dynamic system with genetic regulation to describe the microbial continuous culture, in which we consider that there are three possible ways for glycerol to pass the cell's membrane and one way for 1,3-PD (passive diffusion and active transport). Then we discuss the existence, uniqueness, continuous dependence of solutions and the compactness of the solution set. We construct a global sensitivity analysis approach to reduce the number of kinetic parameters. In order to infer the most reasonable transport mechanism of glycerol, we propose a parameter identification model aiming at identifying the parameter with higher sensitivity and transport of glycerol, which takes the robustness index of the intracellular substance together with the relative error between the experimental data and the computational values of the extracellular substance as a performance index. Finally, a parallel algorithm is applied to find the optimal transport of glycerol and parameters. PMID:24406809

Gao, Kuikui; Zhang, Xu; Feng, Enmin; Xiu, Zhilong

2014-04-21

221

Polyamine transport is mediated by both endocytic and solute carrier transport mechanisms in the gastrointestinal tract  

OpenAIRE

The polyamines spermidine and spermine, and their precursor putrescine, are required for cell growth and cellular functions. The high levels of tissue polyamines are implicated in carcinogenesis. The major sources of exogenous polyamines are diet and intestinal luminal bacteria in gastrointestinal (GI) tissues. Both endocytic and solute carrier-dependent mechanisms have been described for polyamine uptake. Knocking down of caveolin-1 protein increased polyamine uptake in colon cancer-derived ...

Uemura, Takeshi; Stringer, David E.; Blohm-mangone, Karen A.; Gerner, Eugene W.

2010-01-01

222

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

Energy Technology Data Exchange (ETDEWEB)

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 (/sup 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 (/sup 125/I)iodo-PRL transport from blood to CSF. In contrast, nonlactogenic hormones, viz bovine GH and insulin, had no effect on (/sup 125/I)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 (/sup 125/I)iodo-PRL administered with a range of concentrations of unlabeled oPRL revealed a dose-response inhibition in the transport of (/sup 125/I)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.

Walsh, R.J.; Slaby, F.J.; Posner, B.I.

1987-05-01

223

Deposition, diffusion and transport mechanism of dry powder microparticulate salbutamol, at the respiratory epithelia.  

Science.gov (United States)

The deposition, dissolution and transport of salbutamol base (SB) and salbutamol sulfate (SS) inhalation powders were investigated using the Calu-3 air interface cell culture model and Franz diffusion cell. Drug uptake by cells was studied with respect to deposited dose, drug solubility and hydrophobicity. Furthermore, the role of active transport via organic cationic transporters (OCTs) was studied. SB and SS were processed to have similar diameters (3.09 ± 0.06 ?m and 3.07 ± 0.03 ?m, respectively) and were crystalline in nature. Analysis of drug wetting, dissolution and diffusion using a conventional in vitro Franz cell (incorporating a cell culture support Transwell polyester membrane) showed diffusion of SB to be slower than that of SS (98.57 ± 4.23 ?g after 4 h for SB compared to 98.57 ± 4.01 ?g after 15 min for SS). Such observations suggest dissolution to be the rate-limiting step. In comparison, the percentage transfer rate using the air interface Calu-3 cell model suggested SB transport to be significantly faster than SS transport (92.02 ± 4.47 ?g of SB compared to 63.76 ± 8.84 ?g of SS transported over 4 h), indicating that passive diffusion through the cell plays a role in transport. Furthermore, analysis of SB and SS transport, over a range of deposited doses, suggested the transport rate in the Franz diffusion cell to be limited by wetting of the particle and dissolution into the medium. However, for the cell monolayer, the cell membrane properties regulate the diffusion and transport rate. Analysis of the drug transport in the presence of triethylamine (TEA), a known inhibitor of OCTs, resulted in a significant decrease in drug transport, suggesting an active transport mechanism. The presence of OCTs in this cell line was further validated by Western blot analysis. Finally, the transport of SS from a commercial product (Ventolin Rotacaps) was studied and showed good agreement with the model SS system studied here. PMID:22574661

Haghi, Mehra; Traini, Daniela; Bebawy, Mary; Young, Paul M

2012-06-01

224

Sodium absorption by barley roots: its mediation by mechanism 2 of alkali cation transport.  

Science.gov (United States)

When barley roots absorb Na(+) at concentrations ranging from 1 to 50 mm, in the presence of low concentrations of Ca(2+) and K(+), absorption of Na(+) is mediated by carrier mechanism 2 of alkali cation transport, mechanism 1 being unavailable for Na(+) transport under these conditions. The absorption isotherm depicting the rate of Na(+) absorption as a function of the external Na(+) concentration, over the 1 to 50 mm range of concentrations, shows several inflections. This stepwise response occurs whether Cl(-) or SO(4) (2-) is the counterion, but actual rates of Na(+) absorption are lower in the latter case.When the concentration of Na(+) is 50 mm, and the concentration of either K(+) or Ca(2+) is increased from nil to 50 mm, the rate of absorption of Na(+) is diminished not as a smooth function of increasing concentrations of the interfering ions but stepwise. Similarly, when the concentration of K(+) is 50 mm, and the concentration of either Na(+) or Ca(2+) is increased from nil to 50 mm, the rate of absorption of K(+) is diminished not as a smooth function of increasing concentrations of the interfering ions but stepwise.Together, this evidence supports the previous conclusion to the effect that mechanism 2 of alkali cation transport possesses a spectrum of carrier sites with different ionic affinities.When both K(+) and Na(+) are presented at equivalent concentrations over the 1 to 50 mm range, mechanism 2 transports Na(+) almost exclusively, and mechanism 1 K(+) almost exclusively. These findings support previous conclusions to the effect that the active sites of mechanism 2 have higher affinity for Na(+) than for K(+), whereas the reverse is true for mechanism 1. PMID:16656510

Rains, D W; Epstein, E

1967-03-01

225

About charge-transport mechanisms in mesoporous silicon under adsorption of plant viruses  

Energy Technology Data Exchange (ETDEWEB)

Changes in the electric parameters and the charge-transport mechanism in a mesoporous silicon under adsorption of TORSV (tomato ringspot virus) and GFLV (grapevine fan leaf virus) NEPO-viruses are analyzed. The mechanism influencing the electric characteristics of the mesoporous silicon under adsorption of the plant viruses is related with the changes in parameters of a potential-barrier system due to redistribution of voltages at the silicon structure. The mechanism of charge transport in the mesoporous silicon is more likely connected to the changes in parameters of isotopic heterojunction barriers under small bias voltages, and it can be interpreted as Poole-Frenkel and tunnel conductivity for large bias. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Vashpanov, Yuriy; Kwack, Kae-Dal; Woo, Sun-Bo [Research Institute of Electrical and Computer Engineering, HIT Hanyang University, Seongdong-ku, Seoul (Korea); Son, Jung-Young [School of Computer and Communication Engineering, Daegu University, Kyungsan, Kyungbuk (Korea); Choi, Kyu-Hwan [Physics Department, Korea University, Seoul (Korea)

2009-07-15

226

OPTIMIZATION OF REGULATORY MECHANISMS AS A CONDITION OF COMPETITIVE TRANSPORT COMPLEX  

Directory of Open Access Journals (Sweden)

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.

S. Ilchenko

2012-06-01

227

Engineering design on main mechanism of a high throughput vol-oxidizer for decladding and vol-oxidation of rod-cuts  

International Nuclear Information System (INIS)

In this paper, we designed the main mechanisms for a high throughput device for the rod-cuts of a spent fuel. To design the main mechanisms, we evaluated the current mechanical (slitting, ball mill, roller straightening) and chemical methods (muffle furnace, rotary kiln). As a result, the methods for a ball drop and a rotary drum as concepts were selected at the analysis step. For an enhancement of the oxidation rate, we devised blades for the reactor as a mesh type. Also, for an enhancement of the decladding rate, we designed the ball size and the rotation of the reactor as a mesh type and devised a vacuum system for the fission products. We also designed the main mechanisms devices and tested the capacity of these devices. Mechanisms for the oxidation and recovery can simultaneously handle the rod-cuts of a spent fuel and provide an independent recovery. The results of the mechanisms designs can be used for a scale-up of a high throughput device

228

Improved electron transport mechanics in the PENELOPE Monte-Carlo model  

International Nuclear Information System (INIS)

We describe a new model of electron transport mechanics, the method by which an electron is transported geometrically in an infinite medium as a function of pathlength, s, the accumulated elastic multiple-scattering angular deflection characterized by ?(s), the polar scattering angle, and PHI, a random azimuthal angle. This model requires only one sample of the multiple-scattering angle yet it reproduces exactly the following spatial moments and space-angular correlations: , , , , 2>, 2> and 2>. Moreover, the distributions associated with these moments exhibit a good improvement over the PENELOPE transport mechanics model when compared self-consistently with the results of analog simulations. When we split the transport step into two steps with equal pathlength, we observe excellent agreement with the distributions, indicating that the algorithm nearly matches higher order moments when employed in this way. The equations described herein are relatively inexpensive to employ in an iterative Monte-Carlo code. We have employed the new model to demonstrate the usefulness of the new mechanics for several examples that span the dynamic range of application

229

From mechanical motion to Brownian motion, thermodynamics and particle transport theory  

International Nuclear Information System (INIS)

The motion of a particle in a medium is dealt with either as a problem of mechanics or as a transport process in non-equilibrium statistical physics. The two kinds of approach are often unrelated as they are taught in different textbooks. The aim of this paper is to highlight the link between the mechanical and statistical treatments of particle motion in a medium, starting from the well-studied case of Brownian motion. First, deterministic dynamics is supplemented with stochastic elements accounting for the thermal agitation of the host medium: it is the approach of Langevin, which has been rephrased and extended by Kramers. It handles time-independent and time-dependent stochastic motions as well. In that approach, the host medium is not affected by the guest particles and the latter do not interact with each other. Both limitations are shown to be overcome in thermodynamics, which however is restricted to equilibrium situations, i.e. stochastic motions with no net current. When equilibrium is slightly perturbed, we show how thermodynamic and kinetic concepts supersede mechanical concepts to describe particle transport. The description includes multicomponent transport. The discussions of stochastic dynamics and of thermodynamics are led at the undergraduate level; the treatment of multicomponent transport introduces graduate-level concepts

230

Neuropathy-Induced Spinal GAP-43 Expression Is Not a Main Player in the Onset of Mechanical Pain Hypersensitivity  

OpenAIRE

Structural plasticity within the spinal nociceptive network may be fundamental to the chronic nature of neuropathic pain. In the present study, the spatiotemporal expression of growth-associated protein-43 (GAP-43), a protein which has been traditionally implicated in nerve fiber growth and sprouting, was investigated in relation to mechanical pain hypersensitivity. An L5 spinal nerve transection model was validated by the presence of mechanical pain hypersensitivity and an increase in the ea...

Jaken, Robby J.; Gorp, Sebastiaan; Joosten, Elbert A.; Losen, Mario; Marti?nez-marti?nez, Pilar; Baets, Marc; Marcus, Marco A.; Deumens, Ronald

2011-01-01

231

Mechanism for enhanced glucose transport response to insulin in adipose cells from chronically hyperinsulinemic rats. Increased translocation of glucose transporters from an enlarged intracellular pool.  

OpenAIRE

The mechanism for the increased glucose transport response to insulin in adipose cells from chronically hyperinsulinemic rats was examined. Rats were infused with insulin s.c. for 2 wk. Isolated adipose cells were incubated with and without insulin, 3-O-methylglucose transport was measured, and glucose transporters in subcellular membrane fractions were assessed by cytochalasin B binding. Adipose cells from insulin-treated rats showed no change in basal but a 55% increase in insulin-stimulate...

Kahn, B. B.; Horton, E. S.; Cushman, S. W.

1987-01-01

232

Evidence for an allosteric mechanism of substrate release from membrane-transporter accessory binding proteins.  

Science.gov (United States)

Numerous membrane importers rely on accessory water-soluble proteins to capture their substrates. These substrate-binding proteins (SBP) have a strong affinity for their ligands; yet, substrate release onto the low-affinity membrane transporter must occur for uptake to proceed. It is generally accepted that release is facilitated by the association of SBP and transporter, upon which the SBP adopts a conformation similar to the unliganded state, whose affinity is sufficiently reduced. Despite the appeal of this mechanism, however, direct supporting evidence is lacking. Here, we use experimental and theoretical methods to demonstrate that an allosteric mechanism of enhanced substrate release is indeed plausible. First, we report the atomic-resolution structure of apo TeaA, the SBP of the Na(+)-coupled ectoine TRAP transporter TeaBC from Halomonas elongata DSM2581(T), and compare it with the substrate-bound structure previously reported. Conformational free-energy landscape calculations based upon molecular dynamics simulations are then used to dissect the mechanism that couples ectoine binding to structural change in TeaA. These insights allow us to design a triple mutation that biases TeaA toward apo-like conformations without directly perturbing the binding cleft, thus mimicking the influence of the membrane transporter. Calorimetric measurements demonstrate that the ectoine affinity of the conformationally biased triple mutant is 100-fold weaker than that of the wild type. By contrast, a control mutant predicted to be conformationally unbiased displays wild-type affinity. This work thus demonstrates that substrate release from SBPs onto their membrane transporters can be facilitated by the latter through a mechanism of allosteric modulation of the former. PMID:22084072

Marinelli, Fabrizio; Kuhlmann, Sonja I; Grell, Ernst; Kunte, Hans-Jörg; Ziegler, Christine; Faraldo-Gómez, José D

2011-12-01

233

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

Science.gov (United States)

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.

Agar, Ertan

234

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

Directory of Open Access Journals (Sweden)

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.

Radenovi? ?edomir N.

2005-01-01

235

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

Science.gov (United States)

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.

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

2010-01-01

236

Impacts of transport mechanisms and plume history on tailing of sorbing plumes in heterogeneous porous formations  

Science.gov (United States)

This work investigated the impacts of permeability and sorption heterogeneity on contaminant transport in groundwater using simulation experiments designed to elucidate the causes of tailing. The effects of advection, diffusion and sorption mechanisms and plume history were explored. A simple conceptual model consisting of a single inclusion (heterogeneity) of uniform hydraulic conductivity K and sorption distribution coefficient Kd was adopted. The 3D inclusion, shaped as a horizontal oblate ellipsoid of variable thickness, was placed in a homogeneous anisotropic background of different hydraulic conductivity and sorption distribution coefficient. The background represents average K and Kd of a heterogeneous porous formation. A closed-form analytic flow solution for uniform flow past the inclusion was coupled with a numerical transport solution to simulate contaminant migration for a wide range of transport parameters and two distinct source conditions. Over 2600 numerical simulations were performed in parallel. Transport results were presented in terms of travel time distributions at a control plane downstream of the inclusion and used to quantify tailing for a wide range of transport parameters, in order to separate advection-dominated from diffusion-dominated transport regime and to investigate effects of inclusion shape, diffusion, sorption and plume history on tailing.

Maghrebi, Mahdi; Jankovic, Igor; Allen-King, Richelle M.; Rabideau, Alan J.; Kalinovich, Indra; Weissmann, Gary S.

2014-11-01

237

An autoregulatory mechanism governing mucociliary transport is sensitive to mucus load.  

Science.gov (United States)

Mucociliary clearance, characterized by mucus secretion and its conveyance by ciliary action, is a fundamental physiological process that plays an important role in host defense. Although it is known that ciliary activity changes with chemical and mechanical stimuli, the autoregulatory mechanisms that govern ciliary activity and mucus transport in response to normal and pathophysiological variations in mucus are not clear. We have developed a high-speed, 1-?m-resolution, cross-sectional imaging modality, termed micro-optical coherence tomography (?OCT), which provides the first integrated view of the functional microanatomy of the epithelial surface. We monitored invasion of the periciliary liquid (PCL) layer by mucus in fully differentiated human bronchial epithelial cultures and full thickness swine trachea using ?OCT. We further monitored mucociliary transport (MCT) and intracellular calcium concentration simultaneously during invasion of the PCL layer by mucus using colocalized ?OCT and confocal fluorescence microscopy in cell cultures. Ciliary beating and mucus transport are up-regulated via a calcium-dependent pathway when mucus causes a reduction in the PCL layer and cilia height. When the load exceeds a physiological limit of approximately 2 ?m, this gravity-independent autoregulatory mechanism can no longer compensate, resulting in diminished ciliary motion and abrogation of stimulated MCT. A fundamental integrated mechanism with specific operating limits governs MCT in the lung and fails when periciliary layer compression and mucus viscosity exceeds normal physiologic limits. PMID:24937762

Liu, Linbo; Shastry, Suresh; Byan-Parker, Suzanne; Houser, Grace; K Chu, Kengyeh; Birket, Susan E; Fernandez, Courtney M; Gardecki, Joseph A; Grizzle, William E; Wilsterman, Eric J; Sorscher, Eric J; Rowe, Steven M; Tearney, Guillermo J

2014-10-01

238

The evolvement of the transport mechanism with the ensemble density of Si quantum dots  

Energy Technology Data Exchange (ETDEWEB)

In this review I will try to suggest a comprehensive understanding of the transport mechanisms in three dimensional systems of Si quantum dots (QDs) from the single QD to the very dense ensembles. This understanding is based on our systematic microscopic and macroscopic electrical measurements as a function of the density of Si nanocrystallites. In particular, the role of quantum confinement and Coulomb blockade effects in the transport will be discussed and the concept of QDs' 'touching' will be applied. This consideration will enable to reveal the presence of two transitions, a local carrier deconfinement transition and a percolation transition at which these effects are reminiscent of those found in the single QD. It is hoped that our discussion of the evolvement of the transport with the density of the QDs will provide guidance for the understanding of ensembles of semiconductor QDs in general and ensembles of Si QDs in particular.

Balberg, Isaac [The Racah Institue of Physics, The Hebrew University, Jerusalen 91904 (Israel)

2014-03-31

239

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

240

Neutrino-driven supernovae Boltzmann neutrino transport and the explosion mechanism  

CERN Document Server

Core-collapse supernovae are, despite their spectacular visual display, neutrino events. Virtually all of the 10^53 ergs of gravitational binding energy released in the formation of the nascent neutron star is carried away in the form of neutrinos and antineutrinos of all three flavors, and these neutrinos are primarily responsible for powering the explosion. This mechanism depends sensitively on the neutrino transport between the neutrinospheres and the shock. In light of this, we have performed a comparison of multigroup Boltzmann neutrino transport (MGBT) and multigroup flux-limited diffusion (MGFLD) in post-core bounce environments. Differences in the mean inverse flux factors, luminosities, and RMS energies translate to heating rates that are up to 2 times larger for Boltzmann transport, with net cooling rates below the gain radius that are typically 0.8 times the MGFLD rates. These differences are greatest at earlier postbounce times for a given progenitor mass, and for a given postbounce time, greater ...

Messer, O E B; Bruenn, S W; Guidry, M W

1998-01-01

241

Business Model of an Energy Efficient Company: Main Components and the Mechanism of Influence on Formation of Competitive Advantages ??????-?????? ?????????????????? ???????????: ???????? ???????????? ? ???????? ??????? ?? ???????????? ???????????? ???????????  

Directory of Open Access Journals (Sweden)

Full Text Available The article considers different approaches of scientists in the field of the study of the essence and interpretation of the “business model” notion. It offers a descriptive definition of the “business model of an energy efficient company” term, which takes into account semantics of the “business model” notion and specific features of this phenomenon from the system point of view. It presents main tasks of formalisation and complex presentation of this business model. It identifies and characterises its main structural components for energy intensive company, including ones that deal with cement production, which are: key stakeholders of the company; offer of values for stakeholders; main task of energy saving; direction of formation of additional competitive advantages by means of increase of energy efficiency; criteria of managing energy saving; internal factors of energy saving; barriers of energy effectiveness; conditions of effective management of energy saving; system of management of energy saving; assessment of energy saving and management of it. The article identifies and describes interconnection between the offered structural components and also the system of links with external environment.? ?????? ??????????? ????????? ??????? ?????? ? ??????? ???????????? ???????? ? ????????? ??????? «??????-??????». ?????????? ????????????? ??????????? ??????? «??????-?????? ?????????????????? ???????????», ??????? ????????? ????????? ??????? «??????-??????» ? ??????????? ??????? ??????? ? ????????? ????? ??????. ???????????? ??????? ?????? ???????????? ? ???????????? ????????????? ?????? ??????-??????. ???????????????? ? ???????????????? ?? ???????? ??????????? ?????????? ??? ???????????? ???????????, ? ??? ?????, ????????????? ????????????? ???????, ???????? ????????: ???????? ???????????? ???????????; ??????????? ????????? ??? ?????????????; ??????? ??????? ????????????????; ??????????? ???????????? ?????????????? ???????????? ??????????? ?? ???? ????????? ???????????????????; ???????? ?????????? ?????????????????; ?????????? ??????? ????????????????; ??????? ???????????????????; ??????? ???????????? ?????????? ?????????????????; ??????? ?????????? ?????????????????; ?????????? ???????????????? ? ?????????? ??. ?????????? ? ??????? ??????????? ????? ????????????? ???????????? ????????????, ? ????? ??????? ?????? ? ??????? ??????.

Nakonechnaya Darina Yu.

2013-05-01

242

Solitary waves: a possible mechanism for rapid fluid transport in low permeability porous media  

Science.gov (United States)

Elastic porous media in which the rate of fluid pressure generation is high relative to the rate of fluid pressure diffusion and whose permeabilities are a sensitive function of effective stress may generate solitary waves manifest as discrete pulses of elevated pore pressure and porosity that can travel at velocities that are orders of magnitude greater than the velocities of the pore fluids in the background Darcian flow regime. Solitary waves may thus be important vehicles for fluid transport through porous media whose permeabilities are otherwise too low to allow significant rates of flow. Solitary waves have been hypothesized for diverse geologic settings and processes, including magmatic hydrothermal ore formation, magma transport, fault slip in accretionary wedges and at transform plate boundaries, and primary hydrocarbon migration in sedimentary basins. The present study has focused on solitary waves as agents of oil and methane transport through numerical simulation of their origin and behavior. The results show solitary waves to have limited capacity for transporting oil for several reasons: (1) the rate of fluid pressure generation by typical mechanisms like compaction disequilibrium and hydrocarbon formation is too low to allow solitary waves to form unless permeability is exceptionally low (10-24 to 10-25 m2), (2) solitary waves are only able to ascend no more than 1-2 km before dissipating to ambient pressure and porosity values, (3) the waves are too small and the frequency of their formation is too low to account for the amount of oil observed in the reservoirs that they have been hypothesized to feed. Solitary waves have been found to be more effective at transporting methane because of its lower density and viscosity compared to oil, provided that a mechanism for rapid pressure generation exists and permeabilities are very low. If those conditions exist, then solitary waves can ascend over two kilometers at rates on the order of 100's of meters per year compared to millimeters per year for solitary waves transporting oil.

Appold, Martin; Joshi, Ajit

2014-05-01

243

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-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)

244

A New Human NHERF1 Mutation Decreases Renal Phosphate Transporter NPT2a Expression by a PTH-Independent Mechanism  

Science.gov (United States)

Background The sodium-hydrogen exchanger regulatory factor 1 (NHERF1) binds to the main renal phosphate transporter NPT2a and to the parathyroid hormone (PTH) receptor. We have recently identified mutations in NHERF1 that decrease renal phosphate reabsorption by increasing PTH-induced cAMP production in the renal proximal tubule. Methods We compared relevant parameters of phosphate homeostasis in a patient with a previously undescribed mutation in NHERF1 and in control subjects. We expressed the mutant NHERF1 protein in Xenopus Oocytes and in cultured cells to study its effects on phosphate transport and PTH-induced cAMP production. Results We identified in a patient with inappropriate renal phosphate reabsorption a previously unidentified mutation (E68A) located in the PDZ1 domain of NHERF1.We report the consequences of this mutation on NHERF1 function. E68A mutation did not modify cAMP production in the patient. PTH-induced cAMP synthesis and PKC activity were not altered by E68A mutation in renal cells in culture. In contrast to wild-type NHERF1, expression of the E68A mutant in Xenopus oocytes and in human cells failed to increase phosphate transport. Pull down experiments showed that E68A mutant did not interact with NPT2a, which robustly interacted with wild type NHERF1 and previously identified mutants. Biotinylation studies revealed that E68A mutant was unable to increase cell surface expression of NPT2a. Conclusions Our results indicate that the PDZ1 domain is critical for NHERF1- NPT2a interaction in humans and for the control of NPT2a expression at the plasma membrane. Thus we have identified a new mechanism of renal phosphate loss and shown that different mutations in NHERF1 can alter renal phosphate reabsorption via distinct mechanisms. PMID:22506049

Courbebaisse, Marie; Leroy, Christine; Bakouh, Naziha; Salaün, Christine; Beck, Laurent; Grandchamp, Bernard; Planelles, Gabrielle; Hall, Randy A.; Friedlander, Gérard; Prié, Dominique

2012-01-01

245

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

246

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

247

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

248

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

249

Transport mechanisms of a novel antileukemic and antiviral compound 9-norbornyl-6-chloropurine.  

Science.gov (United States)

6-Chloropurines substituted at the position 9 with variously modified bicyclic skeletons represent promising antiviral and anticancer agents. This work aimed to investigate the transport mechanisms of 9-[(1R*,2R*,4S*)-bicyclo[2.2.1]hept-2-yl]-6-chloro-9H-purine (9-norbornyl-6-chloropurine, NCP) and their relationship to the metabolism and biological activity of the compound. Transport experiments were conducted in CCRF-CEM cells using radiolabeled compound ([(3)H]NCP). The pattern of the intracellular uptake of [(3)H]NCP in CCRF-CEM cells pointed to a combination of passive and facilitated diffusion as prevailing transport mechanisms. NCP intracellular metabolism was found to enhance its uptake by modifying NCP concentration gradient. The transport kinetics reached steady state under the conditions of MRP and MDR proteins blockade, indicating that NCP is a substrate for these efflux pumps. Their inhibition also increased the cytotoxicity of NCP. Our findings suggest that the novel nucleoside analog NCP has potential to become a new orally available antileukemic agent due to its rapid membrane permeation. PMID:24679051

Pla?ková, Pavla; H?ebabecký, Hubert; Šála, Michal; Nencka, Radim; Elbert, Tomáš; Mertlíková-Kaiserová, Helena

2015-02-01

250

Mechanisms of magnetoresistance in variable-range-hopping transport for two-dimensional electron systems  

OpenAIRE

The temperature and magnetic-field dependencies of hopping transport in dilutely doped ? layers have been measured under the conditions for which the variable-range mechanism applies. We trace the transition from negative magnetoresistance in low fields to positive magnetoresistance in high fields. In the range of intermediate fields, the resistance in the perpendicular orientation appears to be several times less than that in the parallel one. It is shown that this ‘‘inverted’’ rela...

Raikh, M. E.; Czingon, J.; Ye, Qiu-yi; Koch, F.; Schoepe, Wilfried; Ploog, K.

1992-01-01

251

Mechanism of electroinduced ionic species transport through a multilamellar lipid system.  

OpenAIRE

A theoretical model for electroporation of multilamellar lipid system due to a series of large electrical pulses is presented and then used to predict the functional dependence of the transport of charged molecules. Previously, electroporation has been considered only for single bilayer systems such as artificial planar bilayer membranes and cell membranes. The former have been extensively studied with respect to electrical and mechanical behavior, and the latter with respect to molecular tra...

Chizmadzhev, Y. A.; Zarnitsin, V. G.; Weaver, J. C.; Potts, R. O.

1995-01-01

252

Study of the charge transport mechanism in pulsed laser deposited AlN:Si films  

International Nuclear Information System (INIS)

AlN films doped with Si (AlN:Si) were synthesized on p-Si(100) substrates by pulsed laser deposition. Al-AlN:Si-Si metal-insulator-silicon (MIS) structures were formed and their current-voltage characteristics measured at 77 K and 290 K were analyzed. The results revealed that the charge transport is carried through the AlN:Si-Si MIS structures by the mechanism of trap space charge limited current.

253

Mechanism of calcium transport stimulated by chlorothiazide in mouse distal convoluted tubule cells.  

OpenAIRE

Thiazide diuretics inhibit Na+ and stimulate Ca2+ absorption in renal distal convoluted tubules. Experiments were performed on immortalized mouse distal convoluted tubule (MDCT) cells to determine the mechanism underlying the dissociation of sodium from calcium transport and the stimulation of calcium absorption induced by thiazide diuretics. Control rates of 22Na+ uptake averaged 272 +/- 35 nmol min-1 mg protein-1 and were inhibited 40% by chlorothiazide (CTZ, 10(-4) M). Control rates of 36C...

Gesek, F. A.; Friedman, P. A.

1992-01-01

254

Potential Role of Epigenetic Mechanisms in the Regulation of Drug Metabolism and Transport  

OpenAIRE

This is a report of a symposium on the potential role of epigenetic mechanisms in the control of drug disposition sponsored by the American Society for Pharmacology and Experimental Therapeutics and held at the Experimental Biology 2013 meeting in Boston, MA, April 21, 2013. Epigenetics is a rapidly evolving area, and recent studies have revealed that expression of drug-metabolizing enzymes and transporters is regulated by epigenetic factors, including histone modification, DNA methylation, a...

Ingelman-sundberg, Magnus; Zhong, Xiao-bo; Hankinson, Oliver; Beedanagari, Sudheer; Yu, Ai-ming; Peng, Lai; Osawa, Yoichi

2013-01-01

255

Validation of a fracture mechanics approach to nuclear transportation cask design through a drop test program  

International Nuclear Information System (INIS)

Sandia National Laboratories (SNL), under contract to the Department of Energy, is conducting a research program to develop and validate a fracture mechanics approach to cask design. A series of drop tests of a transportation cask is planned for the summer of 1986 as the method for benchmarking and, thereby, validating the fracture mechanics approach. This paper presents the drop test plan and background leading to the development of the test plan including structural analyses, material characterization, and non-destructive evaluation (NDE) techniques necessary for defining the test plan properly

256

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

257

Charge compensation mechanism of a Na+-coupled, secondary active glutamate transporter.  

Science.gov (United States)

Forward glutamate transport by the excitatory amino acid carrier EAAC1 is coupled to the inward movement of three Na(+) and one proton and the subsequent outward movement of one K(+) in a separate step. Based on indirect evidence, it was speculated that the cation binding sites bear a negative charge. However, little is known about the electrostatics of the transport process. Valences calculated using the Poisson-Boltzmann equation indicate that negative charge is transferred across the membrane when only one cation is bound. Consistently, transient currents were observed in response to voltage jumps when K(+) was the only cation on both sides of the membrane. Furthermore, rapid extracellular K(+) application to EAAC1 under single turnover conditions (K(+) inside) resulted in outward transient current. We propose a charge compensation mechanism, in which the C-terminal transport domain bears an overall negative charge of -1.23. Charge compensation, together with distribution of charge movement over many steps in the transport cycle, as well as defocusing of the membrane electric field, may be combined strategies used by Na(+)-coupled transporters to avoid prohibitive activation barriers for charge translocation. PMID:22707712

Grewer, Christof; Zhang, Zhou; Mwaura, Juddy; Albers, Thomas; Schwartz, Alexander; Gameiro, Armanda

2012-08-01

258

High-Schmidt-number mass transport mechanisms from a turbulent flow to absorbing sediments  

Science.gov (United States)

We have investigated the mechanisms involved in dissolved oxygen (DO) transfer from a turbulent flow to an underlying organic sediment bed populated with DO-absorbing bacteria. Our numerical study relies on a previously developed and tested computational tool that couples a bio-geochemical model for the sediment layer and large-eddy simulation for transport on the water side. Simulations have been carried out in an open channel configuration for different Reynolds numbers (Re? = 180-1000), Schmidt numbers (Sc = 400-1000), and bacterial populations (?* = 100-700 mg l-1). We show that the average oxygen flux across the sediment-water interface (SWI) changes with Re? and Sc, in good agreement with classic heat-and-mass-transfer parametrizations. Time correlations at the SWI show that intermittent peaks in the wall-shear stress initiate the mass transfer and modulate its distribution in space and time. The diffusive sublayer acts as a de-noising filter with respect to the overlying turbulence; the instantaneous mass flux is not affected by low-amplitude background fluctuations in the wall-shear stress but, on the other hand, it is receptive to energetic and coherent near-wall transport events, in agreement with the surface renewal theory. The three transport processes involved in DO depletion (turbulent transport, molecular transport across the diffusive sublayer, and absorption in the organic sediment layer) exhibit distinct temporal and spatial scales. The rapidly evolving near-wall high-speed streaks transport patches of fluid to the edge of the diffusive sublayer, leaving slowly regenerating elongated patches of positive DO concentration fluctuations and mass flux at the SWI. The sediment surface retains the signature of the overlying turbulent transport over long time scales, allowed by the slow bacterial absorption.

Scalo, Carlo; Piomelli, Ugo; Boegman, Leon

2012-08-01

259

Sodium transport and mechanism(s) of sodium tolerance in Frankia strains.  

Science.gov (United States)

The mechanism(s) underlying differential salt sensitivity/tolerance were investigated in the terms of altered morphological and physiological responses against salinity such as growth, electrolyte leakage, Na? uptake, efflux, accumulation and intracellular concentrations of macronutrients among the Frankia strains newly isolated from Hippöphae salicifolia D. Don. Growth was minimally reduced at 500 and 250?mM NaCl respectively in HsIi10 and rest of the strains (HsIi2, HsIi8, HsIi9) which proved that 500 and 250?mM NaCl are the critical concentrations for the respective strains. The differences in the sodium influx/efflux rate was responsible for the differential amount of remaining sodium among the frankial strains and might be one of the primary determinants for the reestablishment of macronutrients (Mg²?, Ca²? and K?) during salinity. Secondly, the interactive effect of sodium influx/efflux rate, remaining sodium and intracellular macronutrients (Mg²?, Ca²? and K?) concentration has been responsible for the extent of membrane damage and growth sustenance of the tolerant/sensitive frankial strains during salinity. HsIi10 showed better co-regulation of various factors and managed to tolerate salt stress up to considerable extent. Therefore, HsIi10 can serve as a potential biofertilizer in the saline soil. PMID:22733696

Srivastava, Amrita; Singh, Satya Shila; Mishra, Arun Kumar

2013-02-01

260

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.

261

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

Energy Technology Data Exchange (ETDEWEB)

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 YBa{sub 2}Cu{sub 3}O{sub 7} (YBCO) and GdBa{sub 2}Cu{sub 3}O{sub 7} (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.

Nishijima, G., E-mail: nishijima.gen@nims.go.jp [Superconducting Materials Center, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Awaji, S.; Watanabe, K. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Shikimachi, K.; Hirano, N. [Chubu Electric Power Co. Inc., Nagoya 459-8522 (Japan); Nagaya, S. [Superconducting Materials Center, National Institute for Materials Science, Tsukuba 305-0047 (Japan); Ibi, A.; Izumi, T.; Shiohara, Y. [Superconductor Research Laboratory-ISTEC, Tokyo 135-0062 (Japan)

2011-11-15

262

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)

263

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

264

Species transport mechanisms governing capacity loss in vanadium flow batteries: Comparing Nafion® and sulfonated Radel membranes  

International Nuclear Information System (INIS)

Highlights: • Species transport mechanisms are investigated in Nafion® and s-Radel for VRFBs. • Unlike diffusion in Nafion®, crossover in s-Radel is dominated by convection. • In particular, electro-osmotic convection is the dominant mode in s-Radel. • Change in direction of convection causes a lower crossover in s-Radel. • Hydraulic and electrokinetic permeability are as important as vanadium permeability. -- Abstract: In this study, a 2-D, transient vanadium redox flow battery (VRFB) model was used to investigate and compare the ion transport mechanisms responsible for vanadium crossover in Nafion® 117 and sulfonated Radel (s-Radel) membranes. Specifically, the model was used to distinguish the relative contribution of diffusion, migration, osmotic and electro-osmotic convection to the net vanadium crossover in Nafion® and s-Radel. Model simulations indicate that diffusion is the dominant mode of vanadium transport in Nafion®, whereas convection dominates the vanadium transport through s-Radel due to the lower vanadium permeability, and thus diffusivity of s-Radel. Among the convective transport modes, electro-osmotic convection (i.e., electro-osmotic drag) is found to govern the species crossover in s-Radel due to its higher fixed acid concentration and corresponding free ions in the membrane. Simulations also show that vanadium crossover in s-Radel changes direction during charge and discharge due to the change in the direction of electro-osmotic convection. This reversal in the direction of crossover during charge and discharge is found to result in significantly lower “net” crossover for s-Radel when compared to Nafion®. Comparison of these two membranes also provides guidance for minimizing crossover in VRFB systems and underscores the importance of measuring the hydraulic and the electro-kinetic permeability of a membrane in addition to vanadium diffusion characteristics, when evaluating new membranes for VRFB applications

265

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

266

Sensitizing curium luminescence through an antenna protein to investigate biological actinide transport mechanisms.  

Science.gov (United States)

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 biomolecular 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 processes. To start unraveling these pathways, our approach takes advantage of the unique spectroscopic properties of trivalent curium. We clearly show that the human iron transporter transferrin acts as an antenna that sensitizes curium luminescence through intramolecular energy transfer. This behavior has been used to describe the coordination of curium within the two binding sites of the protein and to investigate the recognition of curium-transferrin complexes by the cognate transferrin receptor. In addition to providing the first protein-curium spectroscopic characterization, these studies prove that transferrin receptor-mediated endocytosis is a viable mechanism of intracellular entry for trivalent actinides such as curium and provide a new tool utilizing the specific luminescence of curium for the determination of other biological actinide transport mechanisms. PMID:23363005

Sturzbecher-Hoehne, Manuel; Goujon, Christophe; Deblonde, Gauthier J-P; Mason, Anne B; Abergel, Rebecca J

2013-02-20

267

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.)

268

Defining the Morphology and Mechanism of the Hemoglobin Transport Pathway in Plasmodium falciparum-Infected Erythrocytes.  

Science.gov (United States)

Hemoglobin degradation during the asexual cycle of Plasmodium falciparum is an obligate process for parasite development and survival. It is established that hemoglobin is transported from the host erythrocyte to the parasite digestive vacuole (DV), but this biological process is not well characterized. Three-dimensional reconstructions made from serial thin-section electron micrographs of untreated, trophozoite-stage P. falciparum-infected erythrocytes (IRBC) or IRBC treated with different pharmacological agents provide new insight into the organization and regulation of the hemoglobin transport pathway. Hemoglobin internalization commences with the formation of cytostomes from localized, electron-dense collars at the interface of the parasite plasma and parasitophorous vacuolar membranes. The cytostomal collar does not function as a site of vesicle fission but rather serves to stabilize the maturing cytostome. We provide the first evidence that hemoglobin transport to the DV uses an actin-myosin motor system. Short-lived, hemoglobin-filled vesicles form from the distal end of the cytostomes through actin and dynamin-mediated processes. Results obtained with IRBC treated with N-ethylmaleimide (NEM) suggest that fusion of hemoglobin-containing vesicles with the DV may involve a soluble NEM-sensitive factor attachment protein receptor-dependent mechanism. In this report, we identify new key components of the hemoglobin transport pathway and provide a detailed characterization of its morphological organization and regulation. PMID:25724884

Milani, Katharine J; Schneider, Timothy G; Taraschi, Theodore F

2015-04-01

269

210Pb and 210Po as tracers of particle transport mechanisms on continental margins  

International Nuclear Information System (INIS)

The natural radionuclides 210Po and 210Pb, members of the 238U decay chain, are particularly helpful to the understanding of particle transport processes in the ocean. These isotopes were analysed on sediment trap particles collected during 3 one-year experiments on continental margins. In the Bay of Biscay (Northeastern Atlantic) and in the Gulf of Lion (Northwestern Mediterranean Sea) both as part of the French ECOMARGE programme, and in the Middle Atlantic Bight (Northwestern Atlantic) as part of the SEEP programme. They yielded great insights into scenarios of particle transfer at each site, mainly based on the spatial and temporal distribution of 210Pb particulate concentrations and fluxes. (author)

270

A fracture mechanics approach to spent nuclear fuel transportation cask design  

International Nuclear Information System (INIS)

The Transportation Technology Center at Sandia National Laboratories (SNL/TTC) is assessing the potential of using materials other than stainless steel in the manufacture of nuclear transport cask bodies for service in the United States of America. The programme deals with issues which are of concern from the standpoint of US licensing and design, specifically failure modes at low temperatures with impact loading, fracture mechanics properties and validation of analytic codes which model cask response due to impact loading. Specific materials which will be dealt with in the course of this programme are (i) ductile cast iron (DCI); (ii) low alloy ferritic steel (FS); (iii) depleted uranium (DU). Current efforts are focused on DCI, primarily because this material is of immediate interest to the cask industry and there is an ample supply of material available for testing, while FS will be dealt with in the near future and DU subsequent to FS. (author)

271

Self-induced spontaneous transport of water molecules through a symmetrical nanochannel by ratchetlike mechanism  

CERN Document Server

Gaining work from thermal fluctuations without external input energy is a dream for scientists but is forbidden by the second law of thermodynamics. Feynman proposed a molecular ratchet toward this direction but there are still theoretical arguments against it. Here, we revisit this classical problem by using molecular dynamics simulation to monitor water molecules confined in a carbon nanotube. A spontaneous directional transportation of water molecules was observed in this symmetrical nanochannel by a ratchetlike mechanism. This is the first ratchetlike system without any asymmetrical structure or external field, while the asymmetric ratchetlike potential solely results from the transported water molecules that form hydrogen-bonded chains among themselves. Importantly, the resulting net water fluxes reached the level of biological channel, suggesting possible adoption by life. This effect is ascribed to the exceptive structure of the water molecule; a minute change in hydrogen-bond strength dramatically aff...

Wan, R; Li, J; Bao, J; Hu, J; Fang, H; Wan, Rongzheng; Lu, Hangjun; Li, Jinyuan; Bao, Jingdong; Hu, Jun; Fang, Haiping

2006-01-01

272

Renal brush-border chloride transport mechanisms characterized using a fluorescent indicator  

International Nuclear Information System (INIS)

Cl transport mechanisms in brush-border membrane vesicles (BBMV) isolated from rabbit renal cortex were characterized using the Cl-sensitive fluorescent indicator 6-methoxy-N-[3-sulfopropyl]quinolinium (SPQ). In control experiments using 36Cl, SPQ did not itself alter rates for Cl transport. Cl fluxes (JCl) in nanomoles per second per milligram vesicle protein in response to gradients of Cl and other ions were calculated from the SPQ fluorescence time course, fluorescence vs. [Cl] calibration, and BBMV glucose space. These studies demonstrate the presence of stilbene-inhibitable Cl-OH and Cl-formate exchange, and DPC-inhibitable anion conductance, but absence of Na-Cl and Na-K-Cl cotransport

273

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

274

Mechanism for northward propagation of boreal summer intraseasonal oscillation: Convective momentum transport  

Science.gov (United States)

This study demonstrates that the momentum transport by cumulus convection plays a significant role in the organization and northward propagation of intraseasonal (ISO) convection anomalies over the Indian and western Pacific regions during boreal summer. A version of Seoul National University's atmosphere-ocean coupled general circulation model simulates northward propagation when convective momentum transport (CMT) is implemented; the northward propagation disappears when CMT is disabled. An axially symmetric shallow water model with a parameterized CMT is used to understand the role of CMT in the northward propagation of ISO. The basic mechanism of northward propagation is the lower-level convergence to the north of convection, which is induced by the secondary meridional circulation associated with large momentum mixing by convection in the region of large mean vertical shear. A large mean vertical shear exists in South Asian region during boreal summer.

Kang, In-Sik; Kim, Daehyun; Kug, Jong-Seong

2010-12-01

275

Mechanism of dislocation-governed charge transport in schottky diodes based on gallium nitride  

International Nuclear Information System (INIS)

A mechanism of charge transport in Au-TiBx-n-GaN Schottky diodes with a space charge region considerably exceeding the de Broglie wavelength in GaN is studied. Analysis of temperature dependences of current-voltage (I-V) characteristics of forward-biased Schottky barriers showed that, in the temperature range 80-380 K, the charge transport is performed by tunneling along dislocations intersecting the space charge region. Estimation of dislocation density ? by the I-V characteristics, in accordance with a model of tunneling along the dislocation line, gives the value ? ? 1.7 x 107 cm-2, which is close in magnitude to the dislocation density measured by X-ray diffractometry.

276

Growth dynamics and gas transport mechanism of nanobubbles in graphene liquid cells  

Science.gov (United States)

Formation, evolution and vanishing of bubbles are common phenomena in nature, which can be easily observed in boiling or falling water, carbonated drinks, gas-forming electrochemical reactions and so on. 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 the liquid phase. Here, we demonstrate for the first time that the nanobubbles in water encapsulated by graphene membrane can be visualized by in-situ ultra-high vacuum transmission electron microscopy. Our microscopic results indicate two distinct growth mechanisms of merging nanobubbles and the existence of a critical radius of nanobubbles that determines the unusually long stability of nanobubbles. 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 condensation, transmission and evaporation.

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

2015-02-01

277

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)

278

Molecular characterisation of transport mechanisms at the developing mouse blood-CSF interface : a transcriptome approach  

DEFF Research Database (Denmark)

Exchange mechanisms across the blood-cerebrospinal fluid (CSF) barrier in the choroid plexuses within the cerebral ventricles control access of molecules to the central nervous system, especially in early development when the brain is poorly vascularised. However, little is known about their molecular or developmental characteristics. We examined the transcriptome of lateral ventricular choroid plexus in embryonic day 15 (E15) and adult mice. Numerous genes identified in the adult were expressed at similar levels at E15, indicating substantial plexus maturity early in development. Some genes coding for key functions (intercellular/tight junctions, influx/efflux transporters) changed expression during development and their expression patterns are discussed in the context of available physiological/permeability results in the developing brain. Three genes: Secreted protein acidic and rich in cysteine (Sparc), Glycophorin A (Gypa) and C (Gypc), were identified as those whose gene products are candidates to target plasma proteins to choroid plexus cells. These were investigated using quantitative- and single-cell-PCR on plexus epithelial cells that were albumin- or total plasma protein-immunopositive. Results showed a significant degree of concordance between plasma protein/albumin immunoreactivity and expression of the putative transporters. Immunohistochemistry identified SPARC and GYPA in choroid plexus epithelial cells in the embryo with a subcellular distribution that was consistent with transport of albumin from blood to cerebrospinal fluid. In adult plexus this pattern of immunostaining was absent. We propose a model of the cellular mechanism in which SPARC and GYPA, together with identified vesicle-associated membrane proteins (VAMPs) may act as receptors/transporters in developmentally regulated transfer of plasma proteins at the blood-CSF interface.

Liddelow, Shane A; Temple, Sally

2012-01-01

279

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

Science.gov (United States)

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 (<1h). Additionally, 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

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

2015-05-01

280

Cellular mechanisms of glucose-induced myo-inositol transport upregulation in rat mesangial cells.  

Science.gov (United States)

Uptake of myo-inositol (MI) is necessary to maintain normal cellular phosphoinositide signaling and function. MI transport is up-regulated in the cells of diabetic rat glomeruli compared with normal rat glomeruli [C. I. Whiteside, J. C. Thompson, and J. Ohayon. Am. J. Physiol. 260 (Renal Fluid Electrolyte Physiol. 29): F138-F144, 1991]. To identify mechanisms associated with upregulation of MI transport, rat mesangial cells were cultured in high (25.6 mM) vs. normal (5.6 mM) glucose. Specific Na(+)-dependent [3H]MI uptake (> 97%), using L-[14C]glucose as the nonspecific marker, was linear for 120 min in high and normal glucose. In high glucose, compared with normal glucose, there was no change in Michaelis-Menten constant values [29.1 +/- 0.6 vs. 30.3 +/- 0.7 microM (SE)], whereas maximum velocity (Vmax) was increased (2.024 +/- 52 vs. 1.132 +/- 115 fmol.mg protein-1.min-1, P < 0.001). Mannitol (20.0 mM), used as an osmotic control, had no effect on the upregulation of MI transport. Maximum upregulation of MI transport measured by Vmax (control taken as 100%) was observed after 8 h of exposure to high glucose (222 +/- 6% above control, P < 0.0001) or galactose (20.0 mM) (194 +/- 6%, P < 0.0001) and was sustained for up to 48 h. The protein synthesis inhibitors cycloheximide (20 micrograms/ml) or actinomycin D (5 micrograms/ml), the F-actin depolymerizing agent cytochalasin D (2 micrograms/ml), and the aldose reductase inhibitor Tolrestat (0.3 mM) independently prevented glucose- or galactose-induced upregulation of MI transport.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8092260

Chatzilias, A A; Whiteside, C I

1994-09-01

281

Correlation between the mechanical and magneto-transport properties of cobalt film on semiconducting substrate  

Energy Technology Data Exchange (ETDEWEB)

We have investigated the mechanical and magneto-transport properties of electron beam evaporated Co film on p-Si(1 0 0) substrate. Real time intrinsic stress measurement of the Co film, measured using a cantilever beam technique, shows the evolution of a large tensile stress with the growth of the film on the Si substrate. The analysis of stress reveals a columnar type Volmer-Weber growth which is also confirmed by the atomic force microscopy (AFM) measurements. The Co-film shows high positive (negative) magnetoresistance at all temperatures (below 10 K) on application of out-of-plane (in-plane) magnetic field.

Sarkar, A.; Adhikari, R. [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India); Das, A.K., E-mail: amal@phy.iitkgp.ernet.in [Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur, West Bengal 721302 (India)

2012-11-01

282

Correlation between the mechanical and magneto-transport properties of cobalt film on semiconducting substrate  

International Nuclear Information System (INIS)

We have investigated the mechanical and magneto-transport properties of electron beam evaporated Co film on p-Si(1 0 0) substrate. Real time intrinsic stress measurement of the Co film, measured using a cantilever beam technique, shows the evolution of a large tensile stress with the growth of the film on the Si substrate. The analysis of stress reveals a columnar type Volmer-Weber growth which is also confirmed by the atomic force microscopy (AFM) measurements. The Co-film shows high positive (negative) magnetoresistance at all temperatures (below 10 K) on application of out-of-plane (in-plane) magnetic field.

283

On the binding mechanism of the peptide receptor of the oligopeptide transport system of Lactococcus lactis  

OpenAIRE

Lactococcus lactis degrades exogenous proteins such as ?-casein to peptides of 4–30 amino acids, and uses these as nitrogen sources. The binding protein or receptor (OppALl) of the oligopeptide transport system (Opp) of L.lactis has the unique capacity to bind peptides from five up to at least 20 residues. To study the binding mechanism of OppALl, nonameric peptides were used in which the cysteine at position 1, 3, 4, 5, 6, 7 or 9 was selectively labeled with either bulky and non-fluoresc...

Lanfermeijer, Frank C.; Detmers, Frank J. M.; Konings, Wil N.; Poolman, Bert

2000-01-01

284

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.

285

On the mechanism of electronic transport in polycrystalline CdO thin films  

Science.gov (United States)

Cadmium Oxide (CdO) thin films ( d = 0.16-0.62 ?m) were deposited onto glass substrates by thermal evaporation under vacuum (quasi closed volume technique) of high purity (99.99%) CdO polycrystalline powders. The substrate temperature was 300 and 473 K, respectively. After a post-deposition heat treatment, the temperature dependence of the electrical conductivity becomes reversible. The electronic transport mechanism in studied samples is explained in terms of Seto's model for polycrystalline semiconducting films. The values of optical bandgap have been determined from absorption spectra.

Dantus, C.; Rusu, R. S.; Rusu, G. I.

2011-10-01

286

Identification of current transport mechanism in Al2O3 thin films for memory applications  

Science.gov (United States)

The effect of oxygen anneal on the electrical characteristics, especially on the current transport mechanism, of Al2O3 films in the thickness range of 10-30 nm was examined in detail. The analyses were performed at electric fields of ?2.5 MV/cm to effectively address the reliability of Al2O3-based devices operating in the low electric field regime. The general conduction mechanism equations were used to simulate the expected current density ( J) values for a given electric field ( E) range. The characteristic linear plots of the conduction mechanisms were then used to compare the experimental and simulated data to identify the most probable mechanism occurring in the dielectric. Parameters like barrier height and activation energy were extracted from the fit. It was found that oxygen anneal has profound effects on the electrical properties of Al2O3 films, with annealed films demonstrating a different conduction mechanism than their unannealed counterparts, along with significant improvement in the leakage current and barrier height. This kind of analyses will help optimize the process conditions for Al2O3 deposition and provide an optimal range for device operation, thus improving the reliability of Al2O3 films for applications in CMOS logic and Flash memory.

Ramesh, Sivaramakrishnan; Dutta, Shibesh; Shankar, Balakrishnan; Gopalan, Sundar

2015-01-01

287

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)

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)

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

2009-07-15

288

Main Achievements 2003-2004 - Experimental Nuclear Physics - Mechanisms of nuclear reactions - Mechanism of light-ion scattering to discrete states  

International Nuclear Information System (INIS)

Angular distributions of the 7Li + 11B elastic and inelastic scattering were measured at 44 MeV for the transitions to the ground and excited states of 7Li and 11B. The results were analyzed with the optical model and coupled-reaction channel method. The deformation parameters of 7Li and 11B and energy dependence of 7Li* and 11B* optical potential parameters were obtained. Angular distributions of the 11B + 14C elastic and inelastic scattering were measured at 45 MeV. The mechanism of the 11B + 14C anomalous large angle scattering was determined. Halo properties of the first excited states of 13C and 14C were demonstrated. Angular distributions of the 9Be(11B,10B)10Be were measured. Dominant one- and two-step transfers were found. The isotopic effect for the 9Be + 10B, 9Be + 11B and 10Be + 10B was analyzed. Angular distributions of the 13C + 11B elastic and inelastic scattering were measured at 45 MeV. The mechanism of the 13C + 11B anomalous large angle scattering was identified. The OM potential parameters for the 13C + 11B elastic scattering and deformation parameters of 13C and 11B were deduced. Using light ion beams (up>B were deduced. Using light ion beams (12C, 9B, 11B) of the U200P Warsaw Cyclotron several multistep reactions on light nuclei targets from 9Be to 28Si were studied. The motivation was to study the coupling between various reaction channels and optical potentials of unstable particles showing up in the intermediate states

289

Mechanism of thermal transport in zirconia and yttria-stabilized zirconia by molecular-dynamics simulation  

International Nuclear Information System (INIS)

The authors present results of molecular-dynamics simulations of the thermal conductivity, K, of ZrO2 and Y2O3-stabilized ZrO2 (YSZ). For both pure ZrO2 and YSZ with low concentrations of Y2O3, they find that the high-temeprature K is typical of a crystalline solid, with the dominant mechanism being phonon-phonon scattering. With increasing Y2O3 concentration, however, the mechanism changes to one more typical of an amorphous system. In particular, phononlike vibrational modes with well-defined wave vectors appear only at very low frequencies. As in amorphous materials, the vast majority of vibrational modes, while delocalized, do not propagate like ordinary phonon modes but transport energy in a diffusive manner. The authors also find that the few highest frequency modes are localized and do not contribute to K

290

Influence of surface wettability on transport mechanisms governing water droplet evaporation.  

Science.gov (United States)

Prediction and manipulation of the evaporation of small droplets is a fundamental problem with importance in a variety of microfluidic, microfabrication, and biomedical applications. A vapor-diffusion-based model has been widely employed to predict the interfacial evaporation rate; however, its scope of applicability is limited due to incorporation of a number of simplifying assumptions of the physical behavior. Two key transport mechanisms besides vapor diffusion-evaporative cooling and natural convection in the surrounding gas-are investigated here as a function of the substrate wettability using an augmented droplet evaporation model. Three regimes are distinguished by the instantaneous contact angle (CA). In Regime I (CA ? 60°), the flat droplet shape results in a small thermal resistance between the liquid-vapor interface and substrate, which mitigates the effect of evaporative cooling; upward gas-phase natural convection enhances evaporation. In Regime II (60 ? CA ? 90°), evaporative cooling at the interface suppresses evaporation with increasing contact angle and counterbalances the gas-phase convection enhancement. Because effects of the evaporative cooling and gas-phase convection mechanisms largely neutralize each other, the vapor-diffusion-based model can predict the overall evaporation rates in this regime. In Regime III (CA ? 90°), evaporative cooling suppresses the evaporation rate significantly and reverses entirely the direction of natural convection induced by vapor concentration gradients in the gas phase. Delineation of these counteracting mechanisms reconciles previous debate (founded on single-surface experiments or models that consider only a subset of the governing transport mechanisms) regarding the applicability of the classic vapor-diffusion model. The vapor diffusion-based model cannot predict the local evaporation flux along the interface for high contact angle (CA ? 90°) when evaporative cooling is strong and the temperature gradient along the interface determines the peak local evaporation flux. PMID:25105726

Pan, Zhenhai; Weibel, Justin A; Garimella, Suresh V

2014-08-19

291

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

Directory of Open Access Journals (Sweden)

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.

B. Guenet

2013-04-01

292

The relative importance of decomposition and transport mechanisms in accounting for C profiles  

Directory of Open Access Journals (Sweden)

Full Text Available Soil is the major terrestrial reservoirs 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 test and compare 3 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 named after V.V. Alekhin, in the Kursk Region of Russia. The transport schemes tested are diffusion, advection or both diffusion and advection. They are coupled to two 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 links SOC decomposition rate to the amount of fresh organic matter, representing a "priming effect". 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 optimized using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter. In comparison to the first-order kinetic model, the "priming" model reduces the underestimation of SOC decomposition in the top layers and the over estimation in the deep layers. We also observe that the transport scheme that improved the fit with the data depends on the soil carbon mineralization formulation chosen. When soil carbon decomposition is modelled to depend on the fresh organic matter amount, the transport mechanisms which improves best the fit to the SOC profile data is the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the lesser the need for diffusion is. This suggests that stabilized carbon may not be transported within the profile by the same mechanisms than more labile carbon.

B. Guenet

2012-10-01

293

Spatial variations in deformation mechanisms along the Main Central thrust zone: Implications for the evolution of the MCT in the Darjeeling -Sikkim Himalaya  

Science.gov (United States)

In the Darjeeling-Sikkim Himalaya, we recognize two distinct MCT sheets: the structurally higher MCT1 and the lower MCT2. Microstructural studies from three different segments along the transport direction of the MCT2 fault zone suggest that the fault has undergone strain softening by different mechanisms. The geometry of the tapered crystalline orogenic wedge resulted in variation of overburden along the MCT2. Strain softening by different deformation mechanisms accommodated translation of ?100 km along a thin MCT2 fault zone. As the mylonitic trailing part of the MCT2 in Pelling had the greatest overburden, deformation took place by dislocation creep in quartz and by microfracturing in feldspar. Reaction softening of feldspar produced an intrinsically weak matrix that primarily controlled the deformation, resulting in a strain softening fault zone. At Soreng MCT2 zone, under intermediate crustal conditions, finer-grained recrystallized quartz and micaceous matrix deformed by grain-size sensitive diffusion creep mechanisms resulting in strain softening. The fault rocks at Sivitar had the least overburden and record a prominent mineralogical change from the protolith; strain softening occurred by pressure solution slip, possibly by a combination of grain-size reduction by cataclasis and an increase in fluid activity.

Bhattacharyya, Kathakali; Mitra, Gautam

2014-12-01

294

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

Energy Technology Data Exchange (ETDEWEB)

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.

Zencker, U.; Mueller, K.; Droste, B.; Roedel, R.; Voelzke, H. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany)

2004-07-01

295

Charge trapping and carrier transport mechanism in silicon-rich silicon oxynitride  

International Nuclear Information System (INIS)

The charge-trapping and carrier transport properties of silicon-rich silicon oxynitride (SRO:N) were studied. The SRO:N films were deposited by low pressure chemical vapor deposition. Infrared (IR) and transmission electron microscopic (TEM) measurements were performed to characterize their structural properties. Capacitance versus voltage and current versus voltage measurements (I-V) were used to study the charge-trapping and carrier transport mechanism. IR and TEM measurements revealed the existence of Si nanodots in SRO:N films. I-V measurements revealed that there are two conduction regimes divided by a threshold voltage V T. When the applied voltage is smaller than V T, the current is dominated by the charge transfer between the SRO:N and substrate; and in this regime only dynamic charging/discharging of the SRO:N layer is observed. When the voltage is larger than V T, the current increases rapidly and is dominated by the Poole-Frenkel mechanism; and in this regime, large permanent trapped charge density is obtained. Nitrogen incorporation significantly reduced the silicon nanodots or defects near the SRO:N/Si interface. However, a significant increase of the density of silicon nanodot in the bulk of the SRO:N layer is obtained

296

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

1998-04-01

297

Prestin is an anion transporter dispensable for mechanical feedback amplification in Drosophila hearing.  

Science.gov (United States)

In mammals, the membrane-based protein Prestin confers unique electromotile properties to cochlear outer hair cells, which contribute to the cochlear amplifier. Like mammals, the ears of insects, such as those of Drosophila melanogaster, mechanically amplify sound stimuli and have also been reported to express Prestin homologs. To determine whether the D. melanogaster Prestin homolog (dpres) is required for auditory amplification, we generated and analyzed dpres mutant flies. We found that dpres is robustly expressed in the fly's antennal ear. However, dpres mutant flies show normal auditory nerve responses, and intact non-linear amplification. Thus we conclude that, in D. melanogaster, auditory amplification is independent of Prestin. This finding resonates with prior phylogenetic analyses, which suggest that the derived motor function of mammalian Prestin replaced, or amended, an ancestral transport function. Indeed, we show that dpres encodes a functional anion transporter. Interestingly, the acquired new motor function in the phylogenetic lineage leading to birds and mammals coincides with loss of the mechanotransducer channel NompC (=TRPN1), which has been shown to be required for auditory amplification in flies. The advent of Prestin (or loss of NompC, respectively) may thus mark an evolutionary transition from a transducer-based to a Prestin-based mechanism of auditory amplification. PMID:25412730

Kavlie, Ryan G; Fritz, Janice L; Nies, Florian; Göpfert, Martin C; Oliver, Dominik; Albert, Joerg T; Eberl, Daniel F

2015-01-01

298

Water management in a PEMFC: water transport mechanism and material degradation in gas diffusion layers  

Energy Technology Data Exchange (ETDEWEB)

It has now been well recognized that both the performance and durability of proton exchange membrane fuel cells (PEMFCs) are closely related to the water accumulation and transport inside its porous components, particularly in the gas diffusion layer (GDL), and microporous layer (MPL). In this paper, the key GDL and MPL properties that affect water transport through them are first discussed and a review of GDL degradation mechanisms is presented. An intermittent water drainage mechanism across the GDL is discussed. The capillary breakthrough pressure (CBP) and the dynamic capillary pressure (DCP), or recurrent breakthrough dynamics, have been identified as key GDL properties that affect its water management performance and function as indicators of the degradation of GDL material. This work uses a novel ex situ experiment to degrade a GDL by exposing it to an accelerated stress test (AST) that subjects the GDL to elevated operation conditions seen at the cathode side of a PEMFC for an extended period of time. In turn, the effect of the AST on the CBP and DCP is investigated. As a result, a loss of hydrophobicity occurred on the MPL surface. This altered the CBP and DCP, thus decreasing water management in the GDL. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Kandlikar, S.G.; Garofalo, M.L.; Lu, Z. [Department of Mechanical Engineering, Rochester Institute of Technology, 76 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2011-12-15

299

Current transport mechanism in metal/HfO2/metal structures  

International Nuclear Information System (INIS)

The metal-insulator-metal (MIM) capacitor integration into BiCMOS technology is governed by the efforts toward increasing the capacitance density, reducing the leakage current density and improving the voltage linearity. In particular, achievement of an acceptable leakage current density in BEOL MIM capacitors is still a challenge. To get around this critical problem, high-k dielectrics have been introduced. Among various candidates, HfO2 has been investigated due to its high dielectric constant, low leakage current and chemical stability. Despite the considerable efforts for HfO2, its current transport mechanism in MIM structures needs further investigations. Based on experimental results of the temperature dependence of the leakage current, we studied the current transport mechanism and energy band diagrams. The leakage current was measured in the temperature range of 200-400 K. The slope of an Arrhenius plot yielded activation energies in the range of Ea=0.2 eV. In particular, we obtained a trap level at ?PF=0.4 eV below the HfO2 conduction band which contributes to Poole-Frenkel conduction

300

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

301

Effects of moisture and grain size on the mechanisms of rainsplash transport  

Science.gov (United States)

Desert shrubs accumulate soil mounds beneath their canopies through rainsplash transport. Previous studies of this process have suggested that there is a preferential concentration of smaller grain sizes closer to the base of the shrub, based on the idea that smaller material is more readily splashed inward beneath the shrub. However, our studies have shown that there are two mechanisms of ejection of the grains with moist soil conditions, each preferentially moving either large or small grain sizes. Larger grains tend to be launched from grain-to-grain collisions following drop impact and travel as individual grains. Smaller grains appear to clump together and move as a single large "grain". The medium-sized grains generally had a greater travel distance than the very large or very small grains, potentially because they involve both modes of transport with a greater effective transfer of energy from the raindrop to the grains. The average travel distance is greatest near 100 microns, which is reflected by the data of Leguedois, et al. (2005). Experiments using high-speed imaging reveals that there is a marked difference between the mechanism of transport when the sediment grains are dry versus when they are moist. The dry grains are rapidly deposited about the impact site with a small proportion moving far from the site. However, moist grains tend to clump together to form “blobs” of water and sediment. Immediately after impact, the drop creates a water corona with entrained sediment, which then contracts into water-sediment blobs that are rocketed outwards from the impact, leaving little to no grain mass near the impact site. Varying degrees of moisture content appeared to have little influence on grain dispersal, leading us to believe that once the soil material is moist (but not saturated), its splash behavior is mostly related to details of the drop corona.

Taube, S. R.; Furbish, D. J.

2010-12-01

302

Expression and substrate specificity of betaine/proline transporters suggest a novel choline transport mechanism in sugar beet.  

Science.gov (United States)

Proline transporters (ProTs) originally described as highly selective transporters for proline, have been shown to also transport glycinebetaine (betaine). Here we examined and compared the transport properties of Bet/ProTs from betaine accumulating (sugar beet, Amaranthus, and Atriplex,) and non-accumulating (Arabidopsis) plants. Using a yeast mutant deficient for uptake of proline and betaine, it was shown that all these transporters exhibited higher affinity for betaine than proline. The uptake of betaine and proline was pH-dependent and inhibited by the proton uncoupler carbonylcyanide m-chlorophenylhydrazone (CCCP). We also investigated choline transport by using a choline transport-deficient yeast mutant. Results revealed that these transporters exhibited a higher affinity for choline uptake rather than betaine. Uptake of choline by sugar beet BvBet/ProT1 was independent of the proton gradient and the inhibition by CCCP was reduced compared with that for uptake of betaine, suggesting different proton binding properties between the transport of choline and betaine. Additionally, in situ hybridization experiments revealed the localization of sugar beet BvBet/ProT1 in phloem and xylem parenchyma cells. PMID:21511362

Yamada, Nana; Sakakibara, Shota; Tsutsumi, Koichi; Waditee, Rungaroon; Tanaka, Yoshito; Takabe, Teruhiro

2011-09-15

303

The effects of sediment transport, weathering, and aeolian mechanisms on soil evolution  

Science.gov (United States)

Aeolian-derived soils are found throughout the world. Soil evolution processes in aeolian-dominated landscapes differ from processes in bedrock-weathering landscapes by a number of key aspects including the lack of (1) soil production depth dependency, (2) surface armoring, and (3) grain size self-organization in the soil profile. We use here a soil evolution model (mARM5D) to study the differences between aeolian and bedrock-weathering-dominated landscapes by analyzing soil evolution on a hillslope under various aeolian and bedrock-soil supply settings subject to fluvial and diffusive sediment transport. The model simulates spatial and temporal variation in soil particle size distribution (PSD) and profile depth for each grid cell on the landscape, as a function of physical weathering, aeolian deposition, and diffusive and fluvial sediment transport. Our results indicate that surface armoring plays a major role in soil evolution. Under bedrock-weathering-dominated conditions, armoring reduces soil erosion and in conjunction with depth-dependent soil production, leads to steady state soil grading and depth and a relatively uniform soil distribution. In contrast, aeolian-dominated landscapes tend to have considerable spatial variability in soil depth and PSD. Our results also indicate that in contrast with diffusive transport, which is assumed to be PSD independent, fluvial sediment transport is strongly influenced by the soil production mechanism (aeolian or bedrock weathering). Based on the results presented here, we propose that aeolian-dominated landscapes are more responsive to environmental changes (e.g., climatic and anthropogenic) compared with bedrock-weathering landscapes. We further propose that this sensitivity may help explain the patchy soil distribution that is often observed in aeolian-dominated regions.

Cohen, Sagy; Willgoose, Garry; Svoray, Tal; Hancock, Greg; Sela, Shai

2015-02-01

304

Transport  

International Nuclear Information System (INIS)

Transport is one of the major causes of environmental damage in Austria. Energy consumption, pollutants emissions, noise emissions, use of surfaces, sealing of surfaces, dissection of ecosystems and impact on landscape are the most significant environmental impacts caused by it. An overview of the transport development of passengers and freight in Austria is presented. Especially the energy consumption growth, carbon dioxide and nitrogen oxide emissions by type of transport, and the emissions development (HC, particle and carbon monoxide) of goods and passengers transport are analyzed covering the years 1980 - 1999. The health cost resulting from transport-related air pollution in Austria is given and measures to be taken for an effective control of the transport sector are mentioned. Figs. 8, Table 1. (nevyjel)

305

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

Science.gov (United States)

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.

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

1988-01-01

306

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

Science.gov (United States)

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.

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

2014-10-01

307

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

DEFF Research Database (Denmark)

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.

Dölger, Julia; Rademaker, Hanna

2014-01-01

308

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

DEFF Research Database (Denmark)

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.

Dölger, Julia; Rademaker, Hanna

2014-01-01

309

Transport, microstructure and mechanical properties of Au diffusion-doped Bi-2223 superconductors  

International Nuclear Information System (INIS)

We have investigated the effect of the Au-diffusion on the mechanical and transport properties of the (Bi,Pb)2Sr2Ca2Cu3Oy (Bi-2223) superconducting samples with different annealing times of 10, 20 and 50 h. The samples are prepared by the conventional solid-state reaction method in the polycrystalline bulk form. Doping of Bi-2223 was carried out by means of Au diffusion during sintering from an evaporated Au film on pellets. The experimental works in this study consist of dc electrical resistivity and critical current density measurements for electrical and superconducting properties, microhardness measurements for mechanical properties, powder X-ray diffraction (XRD) for phase analyses (phase ratio) and lattice parameters, and scanning electron microscopy (SEM) for microstructure examination. These measurements showed that Au-doping, in comparison with the undoped samples, increased the critical transition temperature, critical current density and enhanced formation of high-Tc phase. Additionally, microhardness and grain size were also improved with increasing amount of diffusion. Moreover, the diffusion-annealing time decreased the number and size of voids and increased the transition temperature. The experimental results of microhardness measurements were analyzed using the Kick's law, modified proportional specimen resistance (MPSR) model and the Hays-Kendall (HK) approach. Kick's law did not give useful knowloach. Kick's law did not give useful knowledge of the origin of the indentation size effect. It was observed that the load independent microhardness values were determined based on the MPSR and HK models, and found to be similar with each other. The possible reasons for the observed enhancement in transport and mechanical properties due to Au diffusion are discussed

310

A novel hypothesis for the mechanism of action of P-glycoprotein as a multidrug transporter.  

Science.gov (United States)

For years, P-glycoprotein (P-gp) has been purported to be a membrane transporter capable of selectively transporting many (but not all) lipophilic anticancer drugs with diverse chemical structures. Because the alleged functions of P-gp provide a straightforward, near-perfect explanation for the molecular mechanism of multidrug resistance associated with P-gp overexpression. However, the exact molecular mechanism for P-gp's purported function has never been clearly understood since its initial discovery some 20 yr ago. In this paper, I develop a novel working hypothesis regarding the mechanism of P-gp's action and suggest that P-gp is an energy-dependent efflux pump only for certain conjugated metabolites (probably sulfates) of the lipophilic anticancer drugs but not for the parent compounds, as was always claimed. According to this hypothesis, P-gp overexpression in most cases is not the "culprit" but instead an "accomplice" in P-gp-associated multidrug resistance. The culprit is probably the enhanced function of the metabolizing enzymes for the lipophilic anticancer drugs. This hypothesis also predicts that one of the important physiological functions of P-gp is to be part of an intracellular machinery (together with the phase I and II metabolizing enzymes) for the metabolism, detoxification, and disposition of lipophilic endogenous chemicals as well as xenobiotics, including cytotoxic anticancer drugs. There exists a considerable body of circumstantial evidence in the literature that lends strong support to this mechanistic hypothesis of P-gp's action as well as to the predicted physiological functions of P-gp. It will be of considerable interest to examine this novel hypothesis experimentally. PMID:10331739

Zhu, B T

1999-05-01

311

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.

312

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

313

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

Energy Technology Data Exchange (ETDEWEB)

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.

Isabella Van Rooyen

2014-10-01

314

Non-equilibrium statistical mechanics: from a paradigmatic model to biological transport  

International Nuclear Information System (INIS)

Unlike equilibrium statistical mechanics, with its well-established foundations, a similar widely accepted framework for non-equilibrium statistical mechanics (NESM) remains elusive. Here, we review some of the many recent activities on NESM, focusing on some of the fundamental issues and general aspects. Using the language of stochastic Markov processes, we emphasize general properties of the evolution of configurational probabilities, as described by master equations. Of particular interest are systems in which the dynamics violates detailed balance, since such systems serve to model a wide variety of phenomena in nature. We next review two distinct approaches for investigating such problems. One approach focuses on models sufficiently simple to allow us to find exact, analytic, non-trivial results. We provide detailed mathematical analyses of a one-dimensional continuous-time lattice gas, the totally asymmetric exclusion process. It is regarded as a paradigmatic model for NESM, much like the role the Ising model played for equilibrium statistical mechanics. It is also the starting point for the second approach, which attempts to include more realistic ingredients in order to be more applicable to systems in nature. Restricting ourselves to the area of biophysics and cellular biology, we review a number of models that are relevant for transport phenomena. Successes and limitations of these simple models are also highlighted.

315

Transportation R and D included in thermal and mechanical sciences program  

Energy Technology Data Exchange (ETDEWEB)

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, related facilities, and listing, as a contact, the principal investigator, are included.

NONE

1995-03-01

316

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

International Nuclear Information System (INIS)

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.

317

Ricin and Ricin-Containing Immunotoxins: Insights into Intracellular Transport and Mechanism of action in Vitro  

Directory of Open Access Journals (Sweden)

Full Text Available Ricin is a type II ribosome inactivating protein (RIP isolated from castor beans. Its high toxicity classifies it as a possible biological weapon. On the other hand, ricin linked to specific monoclonal antibodies or used in other conjugates has powerful medical applications. Ricin consists of an A-chain (RTA that damages ribosomes and inhibits protein synthesis, and a B-chain that plays a role in binding and cellular uptake. A number of recent studies have demonstrated that ricin-induced inhibition of protein synthesis is not the only mechanism responsible for cell death. It turns out that ricin is able to induce apoptosis in different cell lines and multiple organs in animals. However, the molecular link between protein synthesis inhibition and ricin-dependent triggering of apoptotic cell death is unclear. This review describes the intracellular transport of ricin and ricin-based immunotoxins and their mechanism of action in different non-malignant and cancer cell lines. Moreover, various ricin-containing immunotoxins, their composition, medical applications and side-effects will be described and discussed. Understanding the mechanism of action of ricin-based immunotoxins will facilitate construction of effectively acting immunotoxins that can be used in the clinic for cancer treatment.

Monika S?omi?ska-Wojewódzka

2013-04-01

318

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

319

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

CERN Document Server

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.

Bostan, Mihai

2012-01-01

320

MAINE HYDROGRAPHY  

Science.gov (United States)

Hydronet_me24 and Hydropoly_me24 depict Maine's hydrography data, based on 8-digit hydrological unit codes (HUC's) at the 1:24,000 scale. Some New Hampshire and New Brunswick hydrography data are also included. The NHD hydrography data was compiled from previous ArcIn...

321

Maine Ingredients  

Science.gov (United States)

This article features Maine Learning Technology Initiative (MLTI), the nation's first-ever statewide 1-to-1 laptop program which marks its seventh birthday by expanding into high schools, providing an occasion to celebrate--and to examine the components of its success. The plan to put laptops into the hands of every teacher and student in grades 7…

Waters, John K.

2009-01-01

322

Temperature and gate bias dependence of carrier transport mechanisms in amorphous indium-gallium-zinc oxide thin film transistors  

Science.gov (United States)

The electrical properties of amorphous indium-gallium-zinc oxide thin film transistors are measured in the temperature range from 70 to 300 K. The device shows normal enhancement mode operation with significantly reduced drain current at low temperature. Its turn-on voltage and subthreshold swing decrease as temperature increases. The transport mechanisms of channel electrons are analyzed based on the evolution of field-effect mobility and channel conductance as a function of temperature and gate bias. It is suggested that in low temperature range, the dominant carrier transport mechanism is hopping between localized band-tail states. As temperature increases, multiple trapping and release plays a role in the whole carrier transport process. Meanwhile, in high gate bias range when the Fermi level moves above the mobility edge, band transport starts to dominate.

Huang, Xiaoming; Wu, Chenfei; Lu, Hai; Ren, Fangfang; Chen, Dunjun; Jiang, Rong; Zhang, Rong; Zheng, Youdou; Xu, Qingyu

2013-08-01

323

Mechanical properties of B-SUS304P-1 used for basket of transport and storage cask  

International Nuclear Information System (INIS)

The basket of transport and storage cask must have structural strength, neutron absorption ability and heat dissipation function. Borated stainless steels are suitable for application to baskets in transport and storage casks for spent fuels. In order to use this material for cask basket, it is necessary to be registered to the 'Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)' by the Japan Society of Mechanical Engineers. Therefore, various mechanical properties of B-SUS304P-1 such as tensile strength at elevated temperature, fracture toughness and allowable stress have been evaluated according to the 'Rules on Transport/Storage Packagings for Spent Nuclear Fuel (JSME S FA1-2007)'. (author)

324

In Vitro Transport Mechanism of Psoralen in a Human Placental Cell Line (BeWo Cells).  

Science.gov (United States)

The mechanism by which psoralen is transported across the placenta was investigated in the BeWo human placental cell line derived from choriocarcinoma in a transwell assay system using liquid chromatography-mass spectrometry/mass spectrometry detection. Psoralen uptake by BeWo cells increased linearly over the concentration range of 0.01?µM to 100?µM (r (2)?=?0.997) and was not saturable. Psoralen uptake by BeWo cells was not affected by temperature (4?°C, room temperature, and 37?°C; p?>?0.05). Psoralen transport increased linearly over 180?min (r (2)?=?0.988) with 3.08?±?0.26?%, 5.47?±?0.21?%, 7.54?±?0.06?%, 9.40?±?0.37?%, 11.49?±?0.31?%, and 12.46?±?0.61?% transferred from the apical chamber to the basolateral chamber in the transwell assays at 30, 60, 90, 120, 150, and 180?min, respectively. The rate of transport showed the same tendency, increasing linearly from 0.13?±?0.01?pmol/s to 0.58?±?0.03?pmol/s over the concentration range of 25?µM to 100?µM (r (2)?=?0.989). The apparent permeability coefficient for psoralen (100?µM) was 5.62?±?0.24?×?10(-6)?cm/s and 5.53?±?0.47?×?10(-6)?cm/s before and after treatment with verapamil (100?µM), respectively (p?>?0.05). The efflux value for psoralen was approximately 1. These data show that psoralen is well absorbed and crosses the placental barrier via passive diffusion in the BeWo cell line. PMID:25626141

Guo, Jie; Song, Dianrong; Han, Fang; Zhang, Wei; Wang, Yanan; Wang, Yuhua; Du, Wenxin

2015-01-01

325

Mechanisms of chloride transport across the syncytiotrophoblast basal membrane in the human placenta.  

Science.gov (United States)

Chloride transport mechanisms in isolated plasma membrane vesicles were studied to characterize pathways for transcellular transport of chloride. Microvillous membrane (MVM) and basal membranes (BM) vesicles were isolated from term placentae. Western blot analysis of the anion exchanger isoform 1 (AE1) demonstrated that the density of AE1 was 12-fold higher on the MVM compared to the BM. At 30 sec, the Cl- uptake in the absence of a potential difference (p.d.) was 457.3 +/- 69.7 and 111.0 +/- 29.1 pmol/mg protein in MVM and BM, respectively (mean +/- SEM, n=6). Chloride transport pathways were characterized using diisothiocyano-2'2-disulphonic stilbene. (DIDS, 0.1 mM) and diphenylamine-2-carboxylate (DPC, 0.5 mM) in the absence or presence of inside positive membrane potentials. Anion exchange (DIDS-sensitive uptake at zero mV) was found in the MVM only. Both MVM and BM showed increased chloride uptake in the presence of inside positive potentials, suggesting the presence of chloride conductance pathways. The chloride uptake with a 25-mV inside positive p.d. could be inhibited by both DIDS and DPC in MVM and BM. However greater potentials (50 mV) showed no significant inhibition by DIDS or DPC in BM. In conclusion, the anion exchanger is unlikely to contribute significantly to chloride fluxes across BM. The data also suggest the presence of Cl- conductance pathways in both the MVM and BM which are sensitive to both DIDS and DPC. PMID:9639328

Powell, T L; Lundquist, C; Doughty, I M; Glazier, J D; Jansson, T

1998-05-01

326

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

Science.gov (United States)

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.

Jang, Seon-Ho; Jang, Ja-Soon

2013-03-01

327

Mechanisms of molecular transport through the urea channel of Helicobacter pylori  

Science.gov (United States)

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.

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

2013-12-01

328

Molecular Mechanisms of Ischemic Cerebral Edema: Role of Electroneutral Ion Transport  

Science.gov (United States)

The brain achieves homeostasis of its intracellular and extracellular fluids by precisely regulating the transport of solute and water across its major cellular barriers: endothelia of the blood-brain barrier (BBB), choroid plexus epithelia, and neuroglial cell membranes. Cerebral edema, the pathological accumulation of fluid in the brainÂ?s intracellular and extracellular spaces, is a major cause of morbidity and mortality following stroke and other forms of ischemic brain injury. Until recently, mechanisms of cerebral edema formation have been obscure; consequently, its treatment has been empiric and suboptimal. Here, we provide a paradigm for understanding ischemic cerebral edema, showing that its molecular pathogenesis is a complex yet step-wise process that results largely from impaired astrocytic cell volume regulation and permeability alterations in the cerebral microvasculature, both of which arise from pathological changes in the activities of specific ion channels and transporters. Recent data has implicated the bumetanide-sensitive NKCC1, an electroneutral cotransporter expressed in astrocytes and the BBB, in cerebral edema formation in several different rodent models of stroke. Pharmacological inhibition or genetic deficiency of NKCC1 decreases ischemia-induced cell swelling, BBB breakdown, cerebral edema, and neurotoxicity. Combination pharmacological strategies that include NKCC1 as a target might thus prove beneficial for the treatment of ischemic, and potentially other types of, cerebral edema.

Kristopher Kahle (Massachusetts General Hospital and Harvard Medical School Neurosurgery)

2009-08-01

329

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

Science.gov (United States)

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

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

2014-12-23

330

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

331

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

Directory of Open Access Journals (Sweden)

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.

Huan-Chao Keh

2011-01-01

332

Ovarian hyperstimulation affects fluid transporters in the uterus: a potential mechanism in uterine receptivity.  

Science.gov (United States)

Controlled ovarian hyperstimulation is commonly used in fertility treatment. Evidence suggests that this could alter the endometrial environment and influence implantation rate. However, the mechanisms underlying this disruption are unknown. A recently developed rat ovarian hyperstimulation (OH) model found alterations in the localisation and expression of several molecules associated with implantation, as well as an increase in luminal fluid at the time of implantation. The present study investigated the effects of OH in rats on the expression of fluid-transporting molecules aquaporin 5 (AQP5) and claudin 4. The expression of these proteins was investigated in uterine luminal epithelial cells of rats undergoing OH and compared with normal pregnancy. There was a significant increase in AQP5 protein in OH rats at the time of implantation, along with a loss of the mesometrial staining gradient, which is thought to contribute to implantation position. At the same time, there was a significant decrease in claudin 4 protein. These results suggest that OH in rats causes a dysregulation in uterine fluid dynamics through modifications to fluid-transporting molecules, resulting in an unfavourable implantation environment for the blastocyst. PMID:23886336

Lindsay, Laura A; Murphy, Christopher R

2014-08-01

333

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 22Nadient were assessed using 22Na+ distribution

334

The optimization of mechanical properties for nuclear transportation casks in ASTM A350 LF5  

International Nuclear Information System (INIS)

Transport flasks are required for the movement of spent nuclear fuel. Due to their nature of operation, it is necessary that these flasks are produced from forged steels with exceptional toughness properties. The material specification generally cited for flask manufacture is ASTM A350 Grade LF5 Class 1, a carbon-manganese-nickel alloy. The range of chemical analysis permitted by this specification is very broad and it is the responsibility of the material manufacturer to select a composition within this range which will satisfy all the mechanical properties requirements, and to ensure safe and reliable performance. Forgemasters Steel and Engineering Limited have experience in the manufacture of large high integrity fuel element flask forgings which extend over several decades. This experience and involvement in international standards in US, Europe and Japan has facilitated the development of an optimized analysis with a low carbon content, nickel levels towards the top end of the allowed range, a deliberate aluminum addition to control grain size and strictly controlled residual element levels. The resultant steel has excellent low temperature impact properties which greatly exceed the requirements of the specification. This analysis is now being adopted for the manufacture of all current transport flasks

335

Charge carrier transport mechanisms in perovskite CdTiO3 fibers  

Directory of Open Access Journals (Sweden)

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.

Z. Imran

2014-06-01

336

Transport of prostaglandin F(2alpha) pulses from the uterus to the ovary at the time of luteolysis in ruminants is regulated by prostaglandin transporter-mediated mechanisms.  

Science.gov (United States)

In ruminants, prostaglandin F2alpha (PGF(2alpha)) is the uterine luteolytic hormone. During luteolysis, PGF(2alpha) is synthesized and released from the endometrium in a pulsatile pattern. The unique structure of the vascular utero-ovarian plexus (UOP) allows transport of luteolytic PGF(2alpha) pulses directly from the uterus to the ovary, thus bypassing the systemic circulation. However, the underlying molecular mechanism is not known. The objective of the present study was to determine a role for PG transporter protein (PGT) in the compartmental transport of PGF(2alpha) from uterus to ovary through the UOP at the time of luteolysis using the sheep as a ruminant model. [(3)H]PGF(2alpha), with or without a PGT inhibitor, was infused into UOP, and PGF(2alpha) transport and PGT protein expression were determined. Results indicate that PGT protein is expressed in tunica intima, tunica media, and tunica adventitia of the utero-ovarian vein and the ovarian artery of the UOP, and the expression levels are higher on d 10-15 compared with d 3-6 of the estrous cycle. Pharmacological inhibition of PGT prevented transport of exogenous [(3)H]PGF(2alpha) as well as oxytocin-induced endogenous luteolytic PGF(2alpha) pulse up to 80% from uterine venous blood into ovarian arterial blood through the UOP at the time of luteolysis in sheep. Taken together, these results indicate that at the time of luteolysis, transport of PGF(2alpha) from uterus to ovary through the UOP is regulated by PGT-mediated mechanisms. These findings also suggest that impaired PGT-mediated transport of PGF(2alpha) from the utero-ovarian vein into the ovarian artery could adversely influence luteolysis and thus affect fertility in ruminants. PMID:20410207

Lee, JeHoon; McCracken, John A; Banu, Sakhila K; Rodriguez, Royce; Nithy, Thamizh K; Arosh, Joe A

2010-07-01

337

Ceruloplasmin ferroxidase activity stimulates cellular iron uptake by a trivalent cation-specific transport mechanism  

Science.gov (United States)

The balance required to maintain appropriate cellular and tissue iron levels has led to the evolution of multiple mechanisms to precisely regulate iron uptake from transferrin and low molecular weight iron chelates. A role for ceruloplasmin (Cp) in vertebrate iron metabolism is suggested by its potent ferroxidase activity catalyzing conversion of Fe2+ to Fe3+, by identification of yeast copper oxidases homologous to Cp that facilitate high affinity iron uptake, and by studies of "aceruloplasminemic" patients who have extensive iron deposits in multiple tissues. We have recently shown that Cp increases iron uptake by cultured HepG2 cells. In this report, we investigated the mechanism by which Cp stimulates cellular iron uptake. Cp stimulated the rate of non-transferrin 55Fe uptake by iron-deficient K562 cells by 2-3-fold, using a transferrin receptor-independent pathway. Induction of Cp-stimulated iron uptake by iron deficiency was blocked by actinomycin D and cycloheximide, consistent with a transcriptionally induced or regulated transporter. Cp-stimulated iron uptake was completely blocked by unlabeled Fe3+ and by other trivalent cations including Al3+, Ga3+, and Cr3+, but not by divalent cations. These results indicate that Cp utilizes a trivalent cation-specific transporter. Cp ferroxidase activity was required for iron uptake as shown by the ineffectiveness of two ferroxidase-deficient Cp preparations, copper-deficient Cp and thiomolybdate-treated Cp. We propose a model in which iron reduction and subsequent re-oxidation by Cp are essential for an iron uptake pathway with high ion specificity.

Attieh, Z. K.; Mukhopadhyay, C. K.; Seshadri, V.; Tripoulas, N. A.; Fox, P. L.

1999-01-01

338

Current transport mechanism of AlGaN/GaN Schottky barrier diode with fully recessed Schottky anode  

Science.gov (United States)

Both the forward and reverse-bias current transport mechanisms of an AlGaN/GaN Schottky barrier diode with a fully recessed Schottky anode (recessed-SBD) are investigated for the first time. A two-dimensional (2D) device simulation gives insight into the electronic transport. The difference between the forward and reverse conduction paths enables the reduction in Von without sacrificing the low reverse leakage current properties. The results of temperature-dependent current–voltage (T–I–V) measurements show that thermionic field emission (TFE) is the dominant current transport mechanism for forward bias. In the reverse-bias region above the pinch-off voltage, two mechanisms codetermine leakage currents, which contain Frenkel–Poole emission from the overlapped planar contact and tunneling from the recessed sidewall contact. Below the pinch-off voltage, the leakage currents are observed to have exponential temperature dependence, which may be consistent with trap-assisted tunneling (TAT).

Yao, Yao; Zhong, Jian; Zheng, Yue; Yang, Fan; Ni, Yiqiang; He, Zhiyuan; Shen, Zhen; Zhou, Guilin; Wang, Shuo; Zhang, Jincheng; Li, Jin; Zhou, Deqiu; Wu, Zhisheng; Zhang, Baijun; Liu, Yang

2015-01-01

339

Mechanics of Force Propagation in TonB-Dependent Outer Membrane Transport  

OpenAIRE

For the uptake of scarce yet essential organometallic compounds, outer membrane transporters of Gram-negative bacteria work in concert with an energy-generating inner membrane complex, thus spanning the periplasmic space to drive active transport. Here, we examine the interaction of TonB, an inner membrane protein, with an outer membrane transporter based upon a recent crystal structure of a TonB-transporter complex to characterize two largely unknown steps of the transport cycle: how energy ...

Gumbart, James; Wiener, Michael C.; Tajkhorshid, Emad

2007-01-01

340

Statistical Thermodynamics for Functionally Rotating Mechanism of the Multidrug Efflux Transporter AcrB.  

Science.gov (United States)

AcrB, a homotrimer, is the pivotal part of a multidrug efflux pump. A "functionally rotating" picture has been proposed for the drug transport by AcrB, but its mechanism remains unresolved. Here, we investigate the energetics of the whole functional rotation cycle using our theoretical methods. We find that the packing efficiency of AcrB is ununiform, and this ununiformity plays imperative roles primarily through the solvent-entropy effect. When a proton binds to or dissociates from a protomer, the packing properties of this protomer and its two interfaces are perturbed overall in the direction that the solvent translational entropy is lowered. The packing properties of the other two protomers are then reorganized with the recovery or maintenance of closely packed interfaces, so that the solvent-entropy loss can be compensated. The functional structural change by an isolated protomer would cause a seriously large free-energy increase. By forming a trimer, any free-energy increase caused by a protomer is always canceled out by the free-energy decrease brought by the other two protomers via the mechanism mentioned above. The functional structural rotation is thus accomplished using the free-energy decrease arising from the transfer of only a single proton per cycle. The similarities to F1-ATPase are also discussed. PMID:25633129

Mishima, Hirokazu; Oshima, Hiraku; Yasuda, Satoshi; Kinoshita, Masahiro

2015-02-26

341

Carbon materials with quasi-graphene layers: The dielectric, percolation properties and the electronic transport mechanism  

International Nuclear Information System (INIS)

We investigate the dielectric properties of multi-walled carbon nanotubes (MWCNTs) and graphite filling in SiO2 with the filling concentration of 2–20 wt.% in the frequency range of 102–107 Hz. MWCNTs and graphite have general electrical properties and percolation phenomena owing to their quasi-structure made up of graphene layers. Both permittivity ? and conductivity ? exhibit jumps around the percolation threshold. Variations of dielectric properties of the composites are in agreement with the percolation theory. All the percolation phenomena are determined by hopping and migrating electrons, which are attributed to the special electronic transport mechanism of the fillers in the composites. However, the twin-percolation phenomenon exists when the concentration of MWCNTs is between 5–10 wt.% and 15–20 wt.% in the MWCNTs/SiO2 composites, while in the graphite/SiO2 composites, there is only one percolation phenomenon in the graphite concentration of 10–15 wt.%. The unique twin-percolation phenomenon of MWCNTs/SiO2 is described and attributed to the electronic transfer mechanism, especially the network effect of MWCNTs in the composites. The network formation plays an essential role in determining the second percolation threshold of MWCNTs/SiO2

342

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)

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.

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

2014-12-01

343

Avaliação de mecânica ventilatória por oscilações forçadas: fundamentos e aplicações clínicas Analysis of the ventilatory mechanics by forced oscillations technique: main concepts and clinical applications  

Directory of Open Access Journals (Sweden)

Full Text Available Requerendo apenas cooperação passiva e fornecendo novos parâmetros para análise da mecânica ventilatória, a técnica de oscilações forçadas (TOF apresenta características complementares aos métodos clássicos de avaliação pulmonar. Neste trabalho, inicialmente é apresentada uma revisão dos princípios da técnica juntamente com uma discussão sobre suas vantagens e atuais limitações. A performance da técnica é comparada com a dos métodos clássicos na detecção de afecções respiratórias. As principais aplicações clínicas reportadas anteriormente na literatura, incluindo a avaliação da mecânica ventilatória infantil, estudos em neonatos, monitorização de pacientes sob ventilação mecânica, medicina ocupacional e avaliação de distúrbios no sono, são revisadas e discutidas. Com base na revisão efetuada e nos resultados obtidos em estudos efetuados em laboratório, os autores concluem que a TOF pode contribuir para um exame mais detalhado, assim como para facilitar a realização de testes de função pulmonar em condições nas quais as técnicas tradicionais não são adequadas.Requesting passive cooperation from the patient and supplying new parameters for the analysis of the ventilatory mechanics, the forced oscillations technique (FOT has complementary characteristics to the classical methods of lung evaluation. In this work, a review of the principles of this technique is initially presented together with a discussion about its advantages and present limitations. The performance of the technique is compared to classical methods in the detection of breathing disorders. The main clinical applications reported previously in the literature, including the evaluation of the ventilatory mechanics in children, studies in neonates, monitoring of patients under mechanical ventilation, occupational medicine, and evaluation of respiratory sleep disturbances are reviewed and discussed. Based on this review and on the results obtained in studies made in their laboratory, the authors concluded that FOT could render a more detailed examination and facilitate the accomplishment of lung function tests under conditions in which traditional techniques are not appropriate.

PEDRO LOPES DE MELO

2000-08-01

344

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

Science.gov (United States)

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 (GLT-1), and interactions with ?2? subunits of voltage-gated Ca(2+) channels and endogenous noradrenaline. Basal extracellular concentration and tissue content of glutamate in the LC were greater in SNL rats than normal ones. Intravenously administered and LC-perfused gabapentin increased extracellular glutamate concentration in the LC. The net amount of glutamate increased by gabapentin is larger in SNL rats compared with normal ones, although the percentage increases from the baseline did not differ. The gabapentin-related ?2? ligand pregabalin increased extracellular glutamate concentration in the LC, whereas another ?2? ligand, 3-exo-aminobicyclo [2.2.1] heptane-2-exo-carboxylic acid (ABHCA), did not. Selective blockade by the dihydrokainic acid or knock-down of GLT-1 by the small interfering RNA abolished the gabapentin-induced glutamate increase in the LC, whereas blockade of GABA-B receptors by the CGP-35348 and depletion of noradrenalin by the dopamine-?-hydroxylase antibody conjugated to saporin did not. These results suggest that gabapentin induces glutamate release from astrocytes in the LC via GLT-1-dependent mechanisms to stimulate descending inhibition. The present study also demonstrates that this target of gabapentin in astrocytes does not require interaction with ?2? subunits in neurons. PMID:24495399

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

2014-06-01

345

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

346

Railway Heavy-haul Cargo Distribution and Transportation System Incentive Mechanism based on Principal-agent Theory  

Directory of Open Access Journals (Sweden)

Full Text Available In the railway heavy-haul cargo distribution and transportation system, the partners are confronted with problems such as information asymmetry or conflicts of profits. An effectively designed incentive system is the key to the profit maximization of the integrated cargo distribution and transportation system. While specifying the incentive mechanism of the railway heavy-haul cargo distribution and transportation system, the study has set the incentive goal for cargo distribution and transportation system and further built an incentive model for the cargo distribution and transportation system that involves one principal and multiple agents. Results indicate that the harder the agents work and the higher the risks are, the more outputs will be shared. When the railway companies are delivering services to multiple enterprises or harbors, a more effective incentive mechanism is required to be designed for more important enterprises or harbors that hold more risks. Finally through case studies, it is proved that the proposed incentive mechanism is proper and efficient.

Li Feiran

2012-01-01

347

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)

348

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

Science.gov (United States)

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.

Agah, Shaghayegh; Pasquali, Matteo; Kolomeisky, Anatoly B.

2015-01-01

349

Interchange motion as a transport mechanism for formation of cold-dense plasma sheet  

Science.gov (United States)

To evaluate whether interchange motion can provide the transport for the formation of the cold-dense plasma sheet in the near-Earth region, we present an event of cold-dense plasma sheet observed by five THEMIS probes after the interplanetary magnetic field turned northward, as well as their comparisons with the simulation results from the Rice Convection Model (RCM) combined with a modified Dungey force-balanced magnetic field solver. The observations of cold-dense plasma at different locations show quite different characteristics: (1) closer to the flank, the appearance is more periodic and exhibits larger fluctuations in plasma moments and magnetic field; (2) further away from the flank, the cold plasma appears later; (3) in the mixture with the cold plasma, the decrease in high-energy particle fluxes becomes less significant further away from the flank; (4) there is energy-dispersion in the cold particles at some locations; and (5) near the magnetopause, the fluctuations have the characteristics of the Kelvin-Helmholtz (K-H) vortices and the colder-denser plasma is likely to have lower entropy. In the RCM simulations, lower entropy plasma consisting of colder-denser ions and electrons was periodically released locally at the outer boundary to represent the plasma created within a K-H vortex. This lower entropy perturbation is interchange unstable and the resulting interchange motion through the magnetosphere-ionosphere coupling pushes the colder-denser plasma radially inward. The simulated particle energy spectrums at different locations qualitatively reproduce the observations, strongly suggesting that the seemingly different characteristics of cold-dense plasma observed by different probes are all a result of the same interchange-related transport mechanism.

Wang, Chih-Ping; Gkioulidou, Matina; Lyons, Larry R.; Xing, Xiaoyan; Wolf, Richard A.

2014-10-01

350

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

351

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

DEFF Research Database (Denmark)

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.

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

1992-01-01

352

“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

353

Fibre bundle formulation of nonrelativistic quantum mechanics; 4, Mixed states and evolution transport's curvature  

CERN Document Server

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...

Iliev, Bozhidar Z

1999-01-01

354

Oxygen transport in perovskite-type solid oxide fuel cell materials: insights from quantum mechanics.  

Science.gov (United States)

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

Muñoz-García, Ana B; Ritzmann, Andrew M; Pavone, Michele; Keith, John A; Carter, Emily A

2014-11-18

355

Transport mechanisms of the retinal pigment epithelium to maintain of visual function  

Science.gov (United States)

In the visual process the interaction between the retinal pigment epithelium (RPE) and photoreceptors involves several transport phenomena. Heat from light-absorption is eliminated by blood-flow in the choroid. Transepithelial transport eliminates water from subretinal space for close interaction between photoreceptors and RPE. A recycling transport supplies the chromophore for photoreceptors. Last but not least transmembranal K+ transport maintains excitability of photoreceptors and Ca2+ enables the regulation of RPE function.

Strauß, Olaf

2014-03-01

356

[Anaerobic reduction of humus/Fe (III) and electron transport mechanism of fontibacter sp. SgZ-2].  

Science.gov (United States)

Humus and Fe(III) respiration are important extracellular respiration metabolism. Electron transport pathway is the key issue of extracellular respiration. To understand the electron transport properties and the environmental behavior of a novel Fe(III)- reducing bacterium, Fontibacter sp. SgZ-2, capacities of anaerobic humus/Fe(III) reduction and electron transport mechanisms with four electron acceptors were investigated in this study. The results of anaerobic batch experiments indicated that strain SgZ-2 had the ability to reduce humus analog [ 9,10-anthraquinone-2,6-disulfonic acid (AQDS) and 9,10-anthraquinone-2-sulfonic acid (AQS)], humic acids (HA), soluble Fe(IIl) (Fe-EDTA and Fe-citrate) and Fe(III) oxides [hydrous ferric oxide (HFO)]. Fermentative sugars (glucose and sucrose) were the most effective electron donors in the humus/Fe( III) reduction by strain SgZ-2. Additionally, differences of electron carrier participating in the process of electron transport with different electron acceptors (i. e. , oxygen, AQS, Fe-EDTA and HFO) were investigated using respiratory inhibitors. The results suggested that similar respiratory chain components were involved in the reducing process of oxygen and Fe-EDTA, including dehydrogenase, quinones and cytochromes b-c. In comparison, only dehydrogenase was found to participate in the reduction of AQS and HFO. In conclusion, different electron transport pathways may be employed by strain SgZ-2 between insoluble and soluble electron acceptors or among soluble electron acceptors. Preliminary models of electron transport pathway with four electron acceptors were proposed for strain SgZ-2, and the study of electron transport mechanism was explored to the genus Fontibacter. All the results from this study are expected to help understand the electron transport properties and the environmental behavior of the genus Fontibacter. PMID:25518675

Ma, Chen; Yang, Gui-qin; Lu, Qin; Zhou, Shun-gui

2014-09-01

357

Angular momentum transport by internal gravity waves. IV - Wave generation by surface convection zone, from the pre-main sequence to the early-AGB in intermediate mass stars  

OpenAIRE

This is the fourth in a series of papers that deal with angular momentum transport by internal gravity waves in stellar interiors. Here, we want to examine the potential role of waves in other evolutionary phases than the main sequence. We study the evolution of a 3Msun Population I model from the pre-main sequence to the early-AGB phase and examine whether waves can lead to angular momentum redistribution and/or element diffusion at the external convection zone boundary. We...

Talon, Suzanne; Charbonnel, Corinne

2008-01-01

358

Testing of the mechanical strength of casks for the transport of highly radioactive substances  

International Nuclear Information System (INIS)

The high degree of safety of casks and flasks for highly radioactive substances is achieved by extremely stringent testing requirements, the relevant parameters being selected in such a manner that for specifically light casks normally used for alpha-ray emitters requiring less shielding, a lower degree of safety is achieved than for heavy casks (with thick shielding walls) at comparable potential risks involved. On the basis of an accident analysis carried out in the USA, showing that impacts inducing the can to collapse are the most frequent types of mechanical impacts leading to accidents in road carriage, the BAM has elaborated a special method of testing the collapsible strength of casks; the tests have been carried out on several casks within the framework of two projects, the results being compared with those of tests hitherto used. By support of the repossible German authorities these test results have been taken into account in the current revision of IAEA rules for the shielding and transport of radioactive substances. (orig.)

359

Carrier transport mechanism of Ohmic contact to p-type diamond  

Science.gov (United States)

The carrier transport mechanism through the p-diamond/metal interface was studied by measuring specific contact resistances (?c) using a transmission line method for Ti, Mo, and Cr (carbide forming metals) and Pd and Co (carbon soluble metals) metals contacting to the boron-doped polycrystalline diamond films. Schottky barrier heights (?B) of around 0.5 eV were measured for the annealed contacts. The present result indicates that formation of thermally stable graphite layers at the diamond/metal interfaces upon annealing would pin the Fermi level of the p-diamond. This model led to the preparation of in situ Ohmic contacts by depositing a thin diamondlike carbon on the p-diamond surface prior to metal deposition, and also to excellent Schottky contacts with breakdown voltages higher than 900 V. The present experiment concluded that the existence of a graphite layer at the diamond/metal interface controlled the electrical properties through the p-diamond/metal interface.

Yokoba, M.; Koide, Yasuo; Otsuki, A.; Ako, F.; Oku, T.; Murakami, Masanori

1997-05-01

360

Transport-mechanisms in natural nucleate boiling in absence of external forces  

Science.gov (United States)

In literature it is generally supposed that under terrestrial conditions the driving force in natural, nucleate boiling heat transfer is namely buoyancy caused by earth gravity, which is expressed in the empirical correlations for technical applications. However, experiments in microgravity performed during the past three decades demonstrate unanimously that up to a medium level heat flux the overall heat transfer in pool boiling is nearly independent from gravity. We refer and discuss in this paper on results of experiments performed with various liquids and liquid states and also using various heater geometries on mission platforms which provide low gravity for short and long periods. Beside the measurements of the experimental parameters to determine the heat transfer, we observed the macroscopic boiling process itself with movie films and videos in order to study the bubble dynamics. From these records we learned about the mechanisms of heat and vapour bubble transport, about the interaction between solid heater, superheated liquid, and vapour without gravity or other external force only generated by the bubbles themselves, and we observed significant details about the boiling process not recognized so far. These findings are essential for a better understanding of the complex physical process; and therefore they are important for the formulation of empirical correlations, and in future for numerical simulations to predict properly boiling heat transfer for technical applications.

Straub, Johannes; Zell, Martin

2010-11-01

361

Mechanism of transport of U-Th series radioisotopes from solids into ground water  

International Nuclear Information System (INIS)

A set of experiments conducted to understand the mechanism responsible for release of large quantities of 222Rn from solids into ground water reveals that a major part of Rn moving into the intergranular water comes from within the grains (solids), not by recoil from the outer surface. We have deduced that the solids we have studied are permeated, to a varying degree, with pores having very large wall area but very small volume, i.e. having width of opening of the order of 10 to 20 nm. Recoil from the walls of these openings introduces Rn and other isotopes into the water contained in these openings (nanopores). Radon, an inert gas, is able to diffuse from nanopore water into the intergranular water in substantial quantities. In contrast, nongaseous isotopes of the U-Th series recoiled into the nanopore water in comparable quantities are adsorbed within the nanopores on the large internal area available there. Further, it appears that a large part of the inventory of long-lived isotopes produced by decay of radon in intergranular water is slowly transported to and adsorbed on the large internal area available in the nanopores. (author)

362

Comparison of mechanical and manual ventilation during transport of patients to the intensive care unit after cardiac surgery  

Directory of Open Access Journals (Sweden)

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

Atilla Canbulat

2012-12-01

363

CBM and CO{sub 2}-ECBM related coupled transport- and mechanical properties  

Energy Technology Data Exchange (ETDEWEB)

The interrelation of cleat transport processes and mechanical properties was investigated by permeability tests at different stress levels (60% to 130% of in-situ stress) with sorbing (CH{sub 4}, CO{sub 2}) and inert gases (N{sub 2}, Ar, He) on a sub bituminous A coal from the Surat Basin, Queensland Australia. From the flow tests under controlled triaxial stress conditions the Klinkenberg-corrected 'true' permeability coefficients and the Klinkenberg slip factors were derived. The 'true'-, absolute or Klinkenberg corrected permeability shows a gas type dependence. Following the approach of Seidle et al. (1992) the cleat volume compressibility (c{sub f}) was calculated from observed changes in apparent permeability upon variation of external stress (at equal mean gas pressures). The observed effects also show a clear dependence on gas type. Due to pore or cleat compressibility the cleat aperture decreases with increasing effective stress. Vice versa we observe with increasing mean pressure at lower confining pressure an increase in permeability which we attribute to a cleat aperture widening. The cleat volume compressibility (c{sub f}) also shows a dependence on the mean pore pressure. Non-sorbing gases like helium and argon show higher apparent permeabilities than sorbing gases like methane. Permeability coefficients measured with successively increasing mean gas pressures were consistently lower than those determined at decreasing mean gas pressures. This permeability hysteresis is in accordance with results reported by Harpalani and McPherson (1985). The kinetics of matrix transport processes were studied by sorption tests on different particle sizes at various moisture contents and temperatures (cf. Busch et al., 2006). Methane uptake rates were determined from the pressure decline curves recorded for each particle-size fraction, and 'diffusion coefficients' were calculated using several unipore and bidisperse diffusion models. These observations have been summarised to a best practice for the operation of a CBM reservoir. This contains for instance a permeability development as a function of reservoir pressure. (orig.)

Gensterblum, Y.; Satorius, M.; Krooss, B.M. [RWTH Aachen Univ. (Germany). Energy and Mineral Resources Group (EMR); Busch, A. [Shell Global Solutions International, Rijswijk (Netherlands)

2013-08-01

364

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)

365

An integrated modelling approach to reconstruct complex solute transport mechanisms – Cl and ?37Cl in pore water of sediments from a former brackish lagoon in The Netherlands  

OpenAIRE

A one-dimensional transport model was developed to reconstruct historical conservative transport of chloride and ?37Cl in pore water of sediments from a former brackish lagoon in The Netherlands, an area now covered by the freshwater Lakes IJssel and Marken. Knowledge of the mechanism of historical solute transport in the sediments and environmental conditions during transport is critical in understanding observed pore water chemistry and will form a basis for simulating effects of changing ...

Beekman, H. E.; Eggenkamp, H. G. M.; Appelo, C. A. J.

2011-01-01

366

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)

367

Transportation  

Science.gov (United States)

A unit designed to increase students' knowledge and understanding of diesel and gasoline engines, providing an introduction for students interested in more specialized training in the automobile field and its scientific principles through math, science, and chemistry. It will also help students realize the importance of transportation, and will help them meet their needs in math through problem solving by dealing with materials in their world, letting them develop skills and techniques through hands-on experience. Includes more than 20 problems to solve.

Bryant, Joyce

368

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

369

Regulation and Logistics in Rail Freight Transport  

Science.gov (United States)

The author pays attention to phenomenal importance of regulation in the sector of rail transport. The sector develops thanks to pro-competition regulation of access to the network (the infrastructure of rail transport), and also in consequence of more frequently used logistic solutions. In the second part of the article main assumptions of European Union's transport policy are discussed, which are orientated towards implementation of logistic mechanisms into the development process of freight transport sector.

Antonowicz, Miros?aw

2011-09-01

370

Exact stochastic simulations of intra-cellular transport by mechanically coupled molecular motors  

OpenAIRE

Numerous processes in live cells depend on active, motor-driven transport of cargo and organelles along the filaments of the cytoskeleton. Understanding the resulting dynamics and the underlying biophysical and biochemical processes critically depends on computational models of intra-cellular transport. A number of motor{cargo models have hence been developed to reproduce experimentally observed transport dynamics on various levels of detail. Computer simulations of these models have so far e...

Helmuth, Jo A.; Reboux, Sylvain; Sbalzarini, Ivo F.

2011-01-01

371

Degradation of energy confinement or degradation of plasma-heating. What is the main definite process for Plasma transport in stellarator?  

International Nuclear Information System (INIS)

The analysis of plasma energy balance in stellarators and tokamaks depends on the different assumptions made and may give different and even contradictory results. When assuming full power absorption by thermal plasmas, paradoxical results can be obtained: degradation of the energy confinement time with heating power as well as degradation of plasma thermal conductivity in very short times (t<< tau:E) during power modulation experiments are deduced. On the other hand, assuming that plasma transport characteristics do not change while pain plasma parameters (density and temperature, their gradients, etc.) are kept constant, leads to conclude that heating efficiency is not unity and that it depends on both, plasma parameters and heating power. In this case no contradiction is found when analyzing plasma energy balances. In this paper the results of ECRH experiments on L-2M will be presented. The experiments were aimed to try to answer this important question. Analyses of the fast processes occurring during the switch off phase of the ECR heating, modulation of the heating power, and specific plasma decay phase, have lead to the conclusion that plasma transport characteristics remaining unchanged during fast variations of the heating power is the correct assumption. 2 refs

372

Tasks related to increase of RA reactor exploitation and experimental potential, 04. Device for transport of radioactive reactor channels and semi channels of the RA reactor, design project (I-III) Part II, Vol. II  

International Nuclear Information System (INIS)

This second volume includes calculations of the main components of the transporter, description of the mechanical part of the transporter and the engineering drawing of the device for transport of radioactive reactor channels and semi channels of the RA reactor

373

Correlated small polaron hopping transport in 1D disordered systems at high temperatures: a possible charge transport mechanism in DNA.  

Science.gov (United States)

Based on the generalized molecular crystal model (GMCM) and theoretical percolation arguments we investigate small polaron hopping transport in 1D disordered systems at high temperatures. Correlation (cr) effects are taken into account. An analytical expression for the temperature dependence of the electrical conductivity, ln?(h,cr)?T(-1/2), is obtained. This result reproduces satisfactorily the experimental data reported for ?-DNA and for poly(dA)-poly(dT) DNA, considering DNA as a one-dimensional disordered molecular wire in which small polarons are the charge carriers. ln?(h,cr) versus T(-1/2) plots permit the evaluation of the maximum hopping distance. The results indicate that correlation effects are probably responsible for large hopping distances in DNA samples. PMID:21817272

Triberis, G P; Dimakogianni, M

2009-01-21

374

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 ivity 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

375

Molecular basis for nanoscopic membrane curvature generation from quantum mechanical models and synthetic transporter sequences  

Science.gov (United States)

We investigate the physical origin of peptide-induced membrane curvature by contrasting differences between H-bonding interactions of prototypical cationic amino acids, arginine (Arg) and lysine (Lys), with phosphate groups of phospholipid heads using quantum mechanical (QM) calculations of a minimum model, and test the results via synthetic oxaorbornene-based transporter sequences without the geometric constraints of polypeptide backbones. QM calculations suggest that although individual Lys can in principle coordinate two phosphates, they are not able to do so at small inter-Lys distances without drastic energetic penalties. In contrast, Arg can coordinate two phosphates down to less than 5 Å, where guanidinium groups can stack ‘face to face’. In agreement with these observations, poly-Lys cannot generate the nanoscale positive curvature necessary for inducing negative Gaussian membrane curvature, in contrast to poly-Arg. Also consistent with QM calculations, polyguanidine-oxanorbornene homopolymers (PGONs) showed that curvature generation is exquisitely sensitive to the guanidinium group spacing when the phosphate groups are near close packing. Addition of phenyl or butyl hydrophobic groups into guanidine-oxanorbornene polymers increased the amount of induced saddle-splay membrane curvature, and broadened the range of lipid compositions where saddle-splay curvature was induced. The enhancement of saddle-splay curvature generation and relaxation of lipid composition requirements via addition of hydrophobicity is consistent with activity profiles. While PGON polymers displayed selective antimicrobial activity against prototypical (Gram positive and negative) bacteria, polymers with phenyl and butyl groups were also active against red blood cells. Our results suggest that it is possible to achieve deterministic molecular design of pore forming peptides. PMID:23061419

Schmidt, Nathan W.; Lis, Michael; Zhao, Kun; Lai, Ghee Hwee; Alexandrova, Anastassia; Tew, Gregory N.; Wong, Gerard C. L.

2013-01-01

376

Patterns and mechanisms of heat transport in the northern Denver Basin: Nebraska, South Dakota and Wyoming  

Science.gov (United States)

Finite difference simulations of the hydrothermal system of the northern Denver Basin are suggestive of a correlation between anomalous heat flux and the presence of faults and structural lineaments mapped in the region. Geothermal, hydrogeological, lithological, and structural data available for the northern Denver Basin were compiled and analyzed in an effort to determine the hydrothermal mechanisms responsible for observed heat flow anomalies in the study area. Measurement of thermal conductivity was conducted for 82 solid core samples and 60 unconsolidated samples from drill cuttings, yielding a harmonic mean thermal conductivity value of 1.52 +/- 0.91W m-1 K -1 for the stratigraphic column of the study area. A total of 929 thermal gradient values compiled from several databases were incorporated with thermal conductivity data to produce a heat flow map of the study area, delineating prominent areas of anomalous heat flux. Data was processed using finite difference simulation software (Hydrotherm Interactive) developed by the U.S. Geological Survey for the purposes of modeling and predicting heat and fluid transport in porous media. Two-dimensional cross-sectional models were calibrated using heat flow profiles and available potentiometric surface data for the Madison and Dakota aquifers in the region. Although calibrated models resulted in accurate simulations of non-anomalous heat flow profiles, anomalous heat flow highs were not reproduced. Acknowledging the existence of several major faults and numerous structural lineaments documented in the study area, vertical pathways of fluid flow were added to simulations to recreate the effect of such structural features. Models which incorporated a hypothetical linear fracture sufficiently accounted for previous discrepancies, and indicate probable upward advective flow through existing vertical fractures.

Ochsner, Aaron Thomas

377

Different molecular mechanisms are involved in the multihormonal control of glucose transport in FRTL5 rat thyroid cells.  

Science.gov (United States)

We investigated the molecular mechanisms by which TSH, insulin and IGF-1 modulate the glucose transport system in FRTL5 cells. We found that TSH, insulin and IGF-1 increased the glucose transporter Glut-1 specific mRNA levels 6, 8 and 5 fold over control, respectively. The effect on Glut-1 mRNA was evident after 2 hours, followed by an increased Glut-1 protein expression in whole cells, as judged by western blot analysis, after 5 hours of stimulation with all the hormones studied. In contrast, plasma membrane Glut-1 increased (300-400% over control) after 2 hours of stimulation with TSH (10 mU/ml), dibutyryl-cAMP (1mM), IGF-1 (10 ng/ml) and insulin (10 nM). These data indicate that the glucose transport system is under multihormonal control in FRTL5 cells. Two different mechanisms are involved in TSH, IGF-1 and insulin stimulation of the glucose transport: a) neosynthesis of Glut-1 by activation of gene expression; b) recruitment of carriers from the intracellular pool to the plasma membrane. PMID:8077615

Russo, D; Damante, G; Foti, D; Costante, G; Filetti, S

1994-05-01

378

Mechanism of Polybrominated Diphenyl Ether Uptake into the Liver: PBDE Congeners Are Substrates of Human Hepatic OATP Transporters  

OpenAIRE

Polybrominated diphenyl ethers (PBDEs) are flame-retardants that upon chronic exposure enter the liver where they are biotransformed to potentially toxic metabolites. The mechanism by which PBDEs enter the liver is not known. However, due to their large molecular weights (MWs ?485 to 1000 Da), they cannot enter hepatocytes by simple diffusion. Organic anion–transporting polypeptides (OATPs) are responsible for hepatic uptake of a variety of amphipathic compounds of MWs larger than 350 Da....

Pacyniak, Erik; Roth, Megan; Hagenbuch, Bruno; Guo, Grace L.

2010-01-01

379

Spin transport in self assembled all-metal nanowire spin valves: A study of the pure Elliott-Yafet mechanism  

OpenAIRE

We report experimental study of spin transport in all-metal nanowire spin valve structures. The nanowires have a diameter of 50 nm and consist of three layers - cobalt, copper and nickel. Based on the experimental observations, we conclude that the primary spin relxation mechanism in the paramagnet copper is the Elliott-Yafet mode associated with frequent interface roughness scattering. This mode is overwhelmingly dominant over all other modes, so that we are able to study t...

Pramanik, Sandipan; Stefanita, Carmen Gabriela; Bandyopadhyay, Supriyo

2005-01-01

380

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. Metaiodobenrial 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

381

Metaiodobenzylguanidine (/sup 131/I) scintigraphy detects impaired myocardial sympathetic neuronal transport function of canine mechanical-overload heart failure  

Energy Technology Data Exchange (ETDEWEB)

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 (/sup 131/I) 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 (/sup 131/I) 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 (/sup 131/I) scintigraphic findings reflect the integrity of the cardiac sympathetic neuronal transport system in canine mechanical-overload heart failure. Metaiodobenzylguanidine (/sup 123/I) scintigraphy should be explored as a means of early detection of mechanical-overload heart failure in patients.

Rabinovitch, M.A.; Rose, C.P.; Rouleau, J.L.; Chartrand, C.; Wieland, D.M.; Lepanto, L.; Legault, F.; Suissa, S.; Rosenthall, L.; Burgess, J.H.

1987-12-01

382

Mechanism of maltose transport in Escherichia coli: transmembrane signaling by periplasmic binding proteins.  

OpenAIRE

Maltose transport across the cytoplasmic membrane of Escherichia coli is dependent on the presence of a periplasmic maltose-binding protein (MBP), the product of the malE gene. The products of the malF, malG, and malK genes form a membrane-associated complex that catalyzes the hydrolysis of ATP to provide energy for the transport event. Previously, mutants were isolated that had gained the ability to grow on maltose in the absence of MBP. After reconstitution of the transport complex into pro...

Davidson, A. L.; Shuman, H. A.; Nikaido, H.

1992-01-01

383

AN INNOVATIVE MECHANISM OF ECONOMIC COOPERATION SECTORAL EDUCATION AND TRANSPORT SECTOR  

Directory of Open Access Journals (Sweden)

Full Text Available The problems of increase of functioning quality of the transport high school in view of conformity of the branch education to requirements of the transport complex are investigated. The opportunity of reduction of load on the state budget due to creation of the endowment at the Ministry of Transport and Communications is considered. In doing so, the branch ministries and departments will bear a part (all amount of charges on financing the high school that will lead to saving a significant share of the state budget means for other purposes.

O. O. Kovtun

2010-03-01

384

Transport mechanisms and rates of transport of radionuclides in the geosphere as related to the Swedish KBS concept  

International Nuclear Information System (INIS)

The bedrock investigated in the KBS project has a permeability of less than 10-9m/s at the depths and in the areas of interest for disposal of radioactive waste. The water flow rate will typically be 0.2 ltr/m2 per year in the bedrock surrounding the repository. The diffusion resistances, which have been measured in the buffer material and in the laminar water in the fissures, strongly limit the amount of water which can leach the glass or uranium oxide matrix. They also severely limit the amount of oxidants which can reach a copper capsule in the KBS concept for disposing of unreprocessed fuel. This capsule is nearly 5 m long with a diameter of 0.75 m and it is placed in a hole of diameter 1.5 m. The buffer material is a strongly compacted bentonite clay. The capsule contains about 1.4 tonnes of UO2. Such a capsule will be 'reached' by less than 1 litre of water per year. The time needed to corrode through the 20 cm copper wall is in the range of many millions of years. Similar periods of time are needed to dissolve the uranium oxide matrix in this concept and also to dissolve the glass matrix of reprocessed waste. The bentonite buffer surrounding the canister is a strong cation exchanger. The diffusion of 90Sr, 137Cs and 241Am will be so retarded that they will decay by a factor of more than 10-7 during their transport in the buffer. The rock has also been found to have strong sorbing propeso been found to have strong sorbing properties. Under the reducing conditions in the repository Np, U and Pu will travel 1 mm or less per year in the fissures in the rock. (author)

385

ABC transporters as multidrug resistance mechanisms and the development of chemosensitizers for their reversal  

Directory of Open Access Journals (Sweden)

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.

Choi Cheol-Hee

2005-10-01

386

Evidence for an allosteric mechanism of substrate release from membrane-transporter accessory binding proteins  

OpenAIRE

Numerous membrane importers rely on accessory water-soluble proteins to capture their substrates. These substrate-binding proteins (SBP) have a strong affinity for their ligands; yet, substrate release onto the low-affinity membrane transporter must occur for uptake to proceed. It is generally accepted that release is facilitated by the association of SBP and transporter, upon which the SBP adopts a conformation similar to the unliganded state, whose affinity is sufficiently reduced. Despite ...

Marinelli, Fabrizio; Kuhlmann, Sonja I.; Grell, Ernst; Kunte, Hans-jo?rg; Ziegler, Christine; Faraldo-go?mez, Jose? D.

2011-01-01

387

Introduction of Organic Anion Transporters (SLC22A) and a Regulatory Mechanism by Caveolins  

OpenAIRE

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...

Lee, Woon Kyu; Jung, Sun-mi; Kwak, Jin-oh; Cha, Seok Ho

2006-01-01

388

Membrane trafficking of yeast transporters: mechanisms and physiological control of downregulation  

OpenAIRE

Of the 125 plasma membrane transporters thus far identified in the yeast S. cerevisiae, a growing number is reported to be subject to tight control at membrane trafficking level, in addition to control at transcriptional level. Typical physiological conditions inducing these controls include changes of substrate concentration and availability of alternative nutrients. These changes of conditions often provoke the downregulation of specific transporters eventually accompanied by upregulation o...

Haguenauer-tsapis, Rosine; Andre?, Bruno

2004-01-01

389

Mechanism for Cocaine Blocking the Transport of Dopamine: Insights from Molecular Modeling and Dynamics Simulations  

OpenAIRE

Molecular modeling and dynamics simulations have been performed to study how cocaine inhibits dopamine transporter (DAT) for the transport of dopamine. The computationally determined DAT-ligand binding mode is totally different from previously proposed overlap binding mode in which cocaine- and dopamine-binding sites are the same (Beuming, T. et al. Nature Neurosci. 2008, 11, 780–789). The new cocaine-binding site does not overlap with, but close to, the dopamine-binding site. Analysis of a...

Huang, Xiaoqin; Gu, Howard H.; Zhan, Chang-guo

2009-01-01

390

A physiochemical analysis of the mechanisms for transport and retention of technetium (Tc-99) in unsaturated soils - 59050  

International Nuclear Information System (INIS)

Document available in abstract form only. Full text of publication follows: The transport of technetium (Tc-99), is of interest due to the potential for human exposure and impact on ecosystems. Technetium has been released to the environment through nuclear power production and nuclear fuel processing; as a result, further spreading of Tc-99 is a concern at DOE sites across the US. Specifically, technetium is a contaminant of concern at the Hanford Site in southeastern Washington, due to the magnitude of material that was disposed. The current body of work conducted on Tc- 99 has provided a wealth of information regarding the redox relationships, sorption, solubility, and stability of the mineral phases (Artinger et al., 2003; Beals and Hayes, 1995; Cui and Eriksen, 1996b; Gu and Schulz, 1991; Jaisi et al., 2009; Keith-Roach et al., 2003; Kumar et al., 2007), however little work has been conducted on the transport of technetium in unsaturated soils. Current conceptual models do not explain the persistence and presence of technetium in deep vadose zone environments such as the Hanford site. In an oxic reducing environment with low organic content the residence time of technetium is the soil would be expected to be low, due to its low sorption and high solubility. Surprisingly, nearly 50 years following the release of contamination into the site, much of the element has persisted in the subsurface. Using an integrated testing approach we examined the mechanisms for physproach we examined the mechanisms for physical and chemical retention and transport of technetium. By employing transport and breakthrough curve analysis as well as pore water and sequential extractions, we evaluated transport behavior, technetium mineral association, and technetium leachability with regard to pore size distribution. (authors)

391

Transport mechanisms for synoptic, seasonal and interannual SF6 variations and "age" of air in troposphere  

Directory of Open Access Journals (Sweden)

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.

K. Miyazaki

2009-02-01

392

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)

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

Baltr?nait?, Edita; Baltr?nas, Pranas; Lietuvninkas, Arvydas; Serevi?ien?, Vaida; Zuokait?, Egl?

2014-01-01

393

Intestinal transport of aminopterin enantiomers in dogs and humans with psoriasis is stereoselective: evidence for a mechanism involving the proton-coupled folate transporter.  

Science.gov (United States)

N-[4-[[(2,4-diamino-6-pterdinyl)methyl]amino]benzoyl]-L/D-glutamic acid (L/D-AMT) is an investigational drug in phase 1 clinical development that consists of the L-and D-enantiomers of aminopterin (AMT). L/D-AMT is obtained from a novel process for making the L-enantiomer (L-AMT), a potent oral antiinflammatory agent. The purpose of these studies was to characterize oral uptake and safety in the dog and human of each enantiomer alone and in combination and provide in vitro evidence for a mechanism of intestinal absorption. This is the first report of L /D-AMT in humans. In dogs (n = 40) orally dosed with L-AMT or D-AMT absorption was stereoselective for the L-enantiomer (6- to 12-fold larger peak plasma concentration after oral administration and area under the plasma concentration-time curve at 0-4 h; p < 0.001). D-AMT was not toxic at the maximal dose tested (82.5 mg/kg), which was 100-fold larger than the maximal nonlethal L-AMT dose (0.8 mg/kg). Dogs (n = 10) and humans with psoriasis (n = 21) orally administered L-AMT and L /D-AMT at the same L-enantiomer dose resulted in stereoselective absorption (absent D-enantiomer in plasma), bioequivalent L-enantiomer pharmacokinetics, and equivalent safety. Thus, the D-enantiomer in L/D-AMT did not perturb L-enantiomer absorption or alter the safety of L-AMT. In vitro uptake by the human proton-coupled folate transporter (PCFT) demonstrated minimal transport of D-AMT compared with L-AMT, mirroring the in vivo findings. Enantiomer selectivity by PCFT was attributable almost entirely to decreased binding affinity rather than changes in transport rate. Collectively, our results demonstrate a strong in vitro-in vivo correlation implicating stereoselective transport by PCFT as the mechanism underlying stereoselective absorption observed in vivo. PMID:22653877

Menter, Alan; Thrash, Breck; Cherian, Christina; Matherly, Larry H; Wang, Lei; Gangjee, Aleem; Morgan, Joel R; Maeda, Dean Y; Schuler, Aaron D; Kahn, Stuart J; Zebala, John A

2012-09-01

394

Assessing the gas transport mechanisms in the Swiss L/ILW concept using numerical modeling and supporting experimental work  

International Nuclear Information System (INIS)

In low/intermediate-level waste (L/ILW) repositories, anaerobic corrosion of metals and degradation of organic materials produce hydrogen, methane, and carbon dioxide. Gas accumulation and gas transport in a L/ILW repository is an important component in the safety assessment of proposed deep repositories in low-permeability formations. The dominant gas transport mechanisms are dependent on the gas overpressures as with increasing overpressure the gas transport capacity of the system increases. The dominant gas transport mechanisms occurring with increasing gas pressure within the anticipated pressure ranges are: diffusion of gas dissolved in pore water (1), two phase flow in the host rock and the excavation damaged zone (EDZ) whereby no deformation of the pore space occurs (2), gas migration within parts of the repository (if repository materials are appropriately chosen) (3) and pathway dilation (4). Under no circumstances the gas is expected to induce permanent fractures in the host rock. This paper focuses on the gas migration in parts of the repository whereby materials are chosen aimed at increasing the gas transport capacity of the backfilled underground structures without compromising the radionuclide retention capacity of the engineered barrier system (EBS). These materials with enhanced gas permeability and low water permeability can supplement the gas flow that is expected to occur through the EDZ and the host rock. The impact of the use of adapted backfill The impact of the use of adapted backfill and sealing materials on the gas pressure build-up and the major gas paths were assessed using numerical two-phase flow models on the repository scale. Furthermore, both the gas and water fluxes as a function of time and gas generation rate can be evaluated by varying the physical properties of the materials and hence their transport capacity. Results showed that by introducing seals with higher gas permeability, the modelled gas flow is largely limited to the access tunnels and the excavation disturbed zone for the case of a very low permeability host rock. The bulk of the gas flows through the repository seal and the adjacent EDZ into the tunnel system. In addition to the demonstration of the gas flow in the seal and access tunnel system by numerical models, laboratory results confirm the high gas transport capacity of the sand/bentonite mixtures. In a next step a multi year demonstration scale experiment (GAST) at the Grimsel Test Site is envisioned. (author)

395

Contraction-stimulated glucose transport in muscle is controlled by AMPK and mechanical stress but not sarcoplasmatic reticulum Ca2+ release  

DEFF Research Database (Denmark)

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