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1

Vacuum and beam transport lines: main principles  

International Nuclear Information System (INIS)

Some details of vacuum system designs of beam transport lines are presented. The effect of gas desorption to vacuum equilibrium and stability and ion-induced pressure instability in the beam transport lines are discussed. Main vacuum relationships are also given as a basis for understanding the vacuum system configuration of beam transport lines. Residual gas spectra together with specific outgassing rates of main materials used for construction of beam transport lines are shown. 13 refs., 13 figs., 2 tabs

1996-01-01

2

Study on the influence of asphalt concrete pavement physical – mechanical and other incices on the transport – operation properties of the main Lithuanian highways  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main aim of this thesis paper is to determine the influence of physical and mechanical indices of asphalt concrete pavement on the operational properties of Lithuanian highway pavement as well as on the functional lifetime of road pavement. The analysis of pavement condition of Lithuanian highways is presented. The classification regarding the damage and deformation of material used for the construction of asphalt concrete pavement and of road pavement structure is provided. The causes of...

2005-01-01

3

Nature and main kinds of psychopathological mechanisms  

Directory of Open Access Journals (Sweden)

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

Panagiotis Oulis

2010-12-01

4

Main aging mechanisms in Li ion batteries  

Energy Technology Data Exchange (ETDEWEB)

Some of the aging mechanisms occurring in Li ion batteries, either on rest or on cycling, are described from long-term storage or cycling data. Generally, the most critical part of the cell is the negative electrode/electrolyte interface. Stability of the solid electrolyte interface (SEI), more generally of the passivating layer, must be insured by proper material choice and additives. Excessive growth induces with time a capacity loss corresponding to the lithium corrosion, and a reduction of power capability of the electrode, from the active surface area degradation. In a worst case, reduction of charge rate capability may lead to local lithium plating during cycling, strongly aggravating the capacity fading. When the SEI is correctly built, with low electronic conductivity, the negative electrode stability can be very stable, as described by long-term aging (more than 4 years) at higher temperature than ambient. Vinylen carbonate is confirmed as outstanding additive. At elevated temperature, high SOC induces side reactions at the positive interface, involving electrolyte components oxidation. The results are an increase of cell impedance, and possible slow CO{sub 2} evolution. Presence of lithium carbonate greatly enhanced the gas formation. The observed impedance increase indicates a reduction of the active surface area, in agreement with solid deposit. When properly designed with an appropriate choice of active materials and electrolyte, the Li ion system can provide a very long service. (author)

Broussely, M. [Saft, BP 1039, 86060 Poitiers (France); Biensan, Ph.; Bonhomme, F.; Blanchard, Ph.; Herreyre, S. [Saft 111 Bvd. A. Daney, 33000 Bordeaux (France); Nechev, K.; Staniewicz, R.J. [Saft America, 107 Beaver Court, Cockeysville, MD (United States)

2005-08-26

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

Inversion mechanisms for OH main lines astrophysical masers  

International Nuclear Information System (INIS)

Excitation processes that can lead to inversion of the main lines of the OH ground state are discussed. Due to the frequency dependence of the emission coefficient of dust, far-IR emitted by warm enough dust can excite the upper halves of the ?-doublets of rotational levels more strongly than the lower halves. The cascade back to the ground state will then invert the main lines and it is shown that this mechanism can explain rather well the main lines emission from OH-IR stars. The main lines masers associated with compact HII regions are discussed extensively. It is argued that the most plausible explanation for them is a model based on the mechanism suggested some time ago by Johnston where the inversion is due to collisional excitation by streams of uni-directional electrons. (author)

1977-01-01

7

Main Components of the Mechanism of Readjustment of Ukrainian Enterprises ???????? ???????????? ????????? ??????? ??????????? ???????  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The article considers importance of theoretical provisions of scientific substantiation of readjustment of an enterprise. It formulates a system of readjustment measures of organisation and legal, production and technical, financial and economic and social character. It studies a structure of organisation and economic mechanism of readjustment. It develops mechanisms of managing the process of readjustment of enterprises. It generalises main goals of readjustment. It establishes stages of per...

Lisnichuk Oksana A.

2013-01-01

8

[Human placental glutathione transport mechanism].  

Science.gov (United States)

The placental transport mechanism of glutathione (GSH) was investigated using microvillous membrane vesicles prepared from human term placenta. Using (3H-glycine)-labeled-GSH, it was clarified that GSH in the extravesicular compartment of placental microvillous membranes was rapidly degraded by gamma-GTP (gamma-glutamyltranspeptidase) and resulting amino acid, and 3H-labeled-glycine was actively transported via a sodium cotransport system. AT-125 treated microvillous membrane vesicles almost entirely lost its gamma-GTP activity, and showed intact GSH transport. Using AT-125 treated microvillous membrane vesicles, it was revealed that GSH was transported across the microvillous membrane as an anion via a membrane potential-dependent mechanism. These results indicated that gamma-GTP which existed in microvillous membrane played a role in GSH metabolism and that intracellular GSH was translocated out of the syncythiotrophoblast cell into the maternal blood space via a specific carrier in microvillous membrane because the GSH concentration was higher in intracellular than extracellular and extracellular membrane potential was positively charged. PMID:2885385

Iioka, H; Moriyama, I; Kyuma, M; Akasaki, M; Katoh, Y; Itoh, K; Saitoh, M; Hino, K; Okamura, Y; Itani, Y

1987-05-01

9

Freight transport in towns. Main report; Godstransport i byer. Hovedrapport  

Energy Technology Data Exchange (ETDEWEB)

The aim was to evaluate a number of possibilities for reducing energy consumption and thus air pollution caused by freight transport in urban areas. The Danish towns of Vejle and Roskilde were taken as examples and the two towns were compared with regard to the town plan, use of land area, the road network, amount of traffic and commercial structure. Economical aspects and the most important initiatives for improvements, including a decrease in traffic accidents, are discussed. These initiatives are coordination of transportation by firms, more drivers using the same vehicles, less frequent deliveries, optimazation of route planning, car sharing, special routes for lorries, traffic and speed control, better siting of new transport functions, re-siting of firms dependent on freight transport, the use of smaller vehicles where possible, no transport of people in trucks or vans, less use of bicycles for transporting messages, more use of underground pipes for transport of materials, lifting equipment for smaller vans and trucks, lifting equipment that is more flexible, motors turned off when loading and loading, reduction of emballage volume, and a more careful way of driving which can help to reduce energy consumption. A computer programme was constructed in order to calculate energy consumption in these relations, emission of hydrocarbons, carbon monoxide, nitrogen oxides and particles, transportation costs and number of traffic accidents. Results are presented in detail and discussed. (AB) (78 refs.).

1992-10-01

10

Main Components of the Mechanism of Readjustment of Ukrainian Enterprises ???????? ???????????? ????????? ??????? ??????????? ???????  

Directory of Open Access Journals (Sweden)

Full Text Available The article considers importance of theoretical provisions of scientific substantiation of readjustment of an enterprise. It formulates a system of readjustment measures of organisation and legal, production and technical, financial and economic and social character. It studies a structure of organisation and economic mechanism of readjustment. It develops mechanisms of managing the process of readjustment of enterprises. It generalises main goals of readjustment. It establishes stages of performance of readjustment and identifies goals of each stage. It identifies the place of readjustment as one of the elements of anti-crisis management of an enterprise. It proves that, at this stage of development of Ukrainian economy, it is necessary to improve the institute of readjustment of bankrupt enterprises, depriving competitive creditors of economic subjects and authorised bodies of a possibility to sell property in parts with the purpose of maximal satisfaction of presented claims.? ?????? ??????????? ?????? ???????? ????????????? ????????? ???????? ??????????? ??????? ???????????. ??????? ???????????? ??????? ??????????? ??????????? ??????????????-?????????, ???????????????-????????????, ?????????-?????????????? ? ??????????? ?????????. ??????????? ????????? ???????????????-?????????????? ????????? ???????. ??????????? ????????? ?????????? ????????? ??????? ???????????. ???????? ???????? ???? ???????. ??????????? ????? ????????????? ??????? ? ?????????? ???? ??????? ?????. ?????????? ????? ??????? ??? ?????? ?? ????????? ?????????????? ?????????? ???????????. ????????, ??? ?? ?????? ????? ???????? ?????????? ????????? ?????????? ????????????????? ???????? ??????? ??????????????? ???????????, ?? ????? ??????????? ?????????? ?????????? ????????? ?????????????? ? ?????????????? ??????? ???????????? ????????? ?? ?????? ? ????? ????????????? ?????????????? ????????????? ??????????.

Lisnichuk Oksana A.

2013-04-01

11

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

12

Ethanol as a Future Fuel for Road Transportation : Main report  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Larsen, Ulrik; Johansen, Troels; Schramm, Jesper

2011-01-01

13

Mechanical Smoke Exhaust in Underground Transport Passage of Hydropower Station  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 conduct...

2012-01-01

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

Nucleocytoplasmic transport: a thermodynamic mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nuclear pore supports molecular communication between cytoplasm and nucleus in eukaryotic cells. Selective transport of proteins is mediated by soluble receptors, whose regulation by the small GTPase Ran leads to cargo accumulation in, or depletion from, the nucleus, i.e., nuclear import or nuclear export. We consider the operation of this transport system by a combined analytical and experimental approach. Provocative predictions of a simple model were tested using cell-free nuclei recon...

2009-01-01

16

Invasive home mechanical ventilation, mainly focused on neuromuscular disorders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

2010-01-01

17

Invasive home mechanical ventilation, mainly focused on neuromuscular disorders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Geiseler, J.; Karg, O.; Bo?rger, S.; Becker, K.; Zimolong, A.

2010-01-01

18

Edge transport and its interconnection with main chamber recycling in ASDEX upgrade  

International Nuclear Information System (INIS)

Edge profiles of electron temperature and density are measured in ASDEX Upgrade with high spatial resolution of 2-3 mm with Thomson scattering. In the region of the edge transport barrier in ELMy H-mode, the gradient lengths of T_e and n_e are found closely coupled, with the temperature profile twice as steep as the density profile corresponding to ?_e ? 2. The edge density in the region of the barrier foot is closely coupled to the main chamber recycling, with no strong dependence on other parameters. In contrast the density rise from the outer barrier foot to the pedestal exhibits pronounced dependence on plasma current and shaping, indicating quite different mechanisms determining the absolute density and its gradient. (author)

2003-09-01

19

Triggering mechanisms for transport barriers  

International Nuclear Information System (INIS)

The radial shear ?ExB of the ExB flow is evaluated with the Monte Carlo orbit following code ASCOT at the onset of the L-H transition and internal transport barriers (ITB) in JET, TFTR, ASDEX Upgrade, TEXTOR, and FT-2 tokamaks. Systematically, a large shear (sufficient for turbulence suppression) is found for local parameters close to the experimental threshold conditions at the barrier location. For L-H transition in JET and ASDEX Upgrade, the large shear is obtained by increasing the edge ion temperature. For TEXTOR, the radial electric field and the electrode current bifurcate at a threshold electrode voltage. In a JET database study, toroidal rotation is found to be dominant in triggering the JET ITB, and an empirical s-?ExB fit is found for the transition threshold. For TFTR and FT-2, in which toroidal rotation does not play a role, ASCOT predicts a significant ?ExB shear for the ITB conditions. The ripple-induced transport is not found to be important here. (author)

2001-05-01

20

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

 
 
 
 
21

Transport mechanism of a bacterial homologue of glutamate transporters.  

Science.gov (United States)

Glutamate transporters are integral membrane proteins that catalyse a thermodynamically uphill uptake of the neurotransmitter glutamate from the synaptic cleft into the cytoplasm of glia and neuronal cells by harnessing the energy of pre-existing electrochemical gradients of ions. Crucial to the reaction is the conformational transition of the transporters between outward and inward facing states, in which the substrate binding sites are accessible from the extracellular space and the cytoplasm, respectively. Here we describe the crystal structure of a double cysteine mutant of a glutamate transporter homologue from Pyrococcus horikoshii, Glt(Ph), which is trapped in the inward facing state by cysteine crosslinking. Together with the previously determined crystal structures of Glt(Ph) in the outward facing state, the structure of the crosslinked mutant allows us to propose a molecular mechanism by which Glt(Ph) and, by analogy, mammalian glutamate transporters mediate sodium-coupled substrate uptake. PMID:19924125

Reyes, Nicolas; Ginter, Christopher; Boudker, Olga

2009-12-17

22

Transport Mechanism of a Bacterial Homologue of Glutamate Transporters  

Energy Technology Data Exchange (ETDEWEB)

Glutamate transporters are integral membrane proteins that catalyse a thermodynamically uphill uptake of the neurotransmitter glutamate from the synaptic cleft into the cytoplasm of glia and neuronal cells by harnessing the energy of pre-existing electrochemical gradients of ions. Crucial to the reaction is the conformational transition of the transporters between outward and inward facing states, in which the substrate binding sites are accessible from the extracellular space and the cytoplasm, respectively. Here we describe the crystal structure of a double cysteine mutant of a glutamate transporter homologue from Pyrococcus horikoshii, GltPh, which is trapped in the inward facing state by cysteine crosslinking. Together with the previously determined crystal structures of Glt{sub Ph} in the outward facing state, the structure of the crosslinked mutant allows us to propose a molecular mechanism by which Glt{sub Ph} and, by analogy, mammalian glutamate transporters mediate sodium-coupled substrate uptake.

Reyes, N.; Ginter, C; Boudker, O

2009-01-01

23

Molecular Mechanism of Biological Proton Transport  

Energy Technology Data Exchange (ETDEWEB)

Proton transport across lipid membranes is a fundamental aspect of biological energy transduction (metabolism). This function is mediated by a Grotthuss mechanism involving proton hopping along hydrogen-bonded networks embedded in membrane-spanning proteins. Using molecular simulations, the authors 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{sup +}-transport devices in biological systems.

Pomes, R.

1998-09-01

24

Flexibility analysis of main primary heat transport system : Narora Atomic Power Project  

International Nuclear Information System (INIS)

The paper presents flexibility analysis problem of main primary heat transport system and the approximate analysis that has been made to estimate the loads coming on major equipments. The primary heat transport system for Narora Atomic Power Project is adopting vertical steam generators and pumps equally divided on either side of the reactor with inter-connecting pipes and feeders. Since the system is mainly spring supported with movement of a few points in certain direction defined but no anchorage, it represents a good problem for flexibility analysis which can only be solved in one step by developing a good computer programme. (author)

1975-03-20

25

The freshwater transport and dynamics of the western Maine coastal current  

Science.gov (United States)

Observations in the Gulf of Maine, USA, were used to characterize the freshwater transport, temporal variability and dynamics of the western Maine coastal current. These observations included moored measurements, multiple hydrographic surveys, and drifter releases during April-July of 1993 and 1994. There is a strong seasonal signal in salinity and along-shore velocity of the coastal current, caused by the freshwater inputs of the rivers entering the western Gulf. Surface salinity within the coastal current during the spring freshet is typically 2psu below ambient, and along-shore currents in the surface layer are directed southwestward at speeds of 0.10-0.20ms-1, occasionally reaching 0.50ms-1. The plume thickness is typically 10-20m in water depths of 50-100m, thus it is well isolated from the bottom over most of its areal extent. The along-coast freshwater transport within the plume varies considerably due to variations in wind stress, but on time scales of weeks to months it follows the variations of riverine input, with a time lag consistent with the advective velocity. Less than half of the transport of the coastal current is explained by the baroclinic gradient; the barotropic forcing associated with the larger-scale dynamics of the Gulf of Maine accounts for about 60% of the transport. The volume of freshwater transport in the coastal current exceeds the local riverine input of fresh water by 30%, suggesting a significant contribution of freshwater transport from the St. John River, 500km northeastward. The measurements within the western Maine coastal current, however, indicate a significant decrease in the baroclinic transport of fresh water along the coast, with an e-folding scale of approximately 200km. ?? 2004 Elsevier Ltd. All rights reserved.

Geyer, W. R.; Signell, R. P.; Fong, D. A.; Wang, J.; Anderson, D. M.; Keafer, B. A.

2004-01-01

26

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

27

Device for transporting mechanized reinforcement sections  

Energy Technology Data Exchange (ETDEWEB)

This device for transporting mechanized reinforcements has a substructure consisting of two runners joined by detachable transverse bonds, clamps used to hold the hydraulic prop sections from both sides and locks. Also, to decrease the number of clamp operations, the clamps are linked to the runners by transverse hinges, the locks are made like stops secured to the runners by longitudinal hinges and like support extensions fastened securely to the runners. The stops are located between the clamps and support extensions and interact with them.

Belov, V.P.; Poleshchuk, B.I.; Semenov, Yu.Ye.; Stolbchenko, V.A.

1980-03-30

28

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

29

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

2007-10-01

30

Los Barrios thermal power station - main features of the mechanical plant and equipment  

Energy Technology Data Exchange (ETDEWEB)

The article covers the mechanical characteristics of the main plant and equipment at the thermal power station: boiler, pre-heating system, precipitator, stack, fuel system, grinding mills, turbines, condenser, circulating water, pumps and demineralized water system.

Garcia Mendez, J.; Sanchez, J.

1984-01-01

31

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

32

Mechanisms of solute transport in extracorporeal therapies.  

Science.gov (United States)

Diffusion and convection are the main mechanisms involved in the membrane separation processes occurring in extracorporeal hemodialysis. Operational parameters should be optimized in hollow fiber hemodialyzers to achieve the maximal efficiency. The nature of blood which is a non Newtonian fluid, requires specific attention in the design of dialyzers to ensure that the blood compartment operates properly. Similar attention must be placed in the design of the dialysate compartment to ensure a homogeneous distribution of the fluid and to prevent blood to dialysate flow mismatch. Finally, the membrane represents the third component of the hemodialyzer. Membrane performance depends on the used biomaterial, its biocompatibility, the thickness, the hydrophilic-hydrophobic mixture, the hydraulic permeability and the number and diameter of the pores. In this setting, diffusion and convection tend to reciprocally interfere, producing a final result that depends on the prevalence of one or the other mechanism for every specific solute. PMID:15876823

Ronco, Claudio; Levin, Nathan W

2005-01-01

33

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

1983-09-01

34

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

1989-01-01

35

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

36

Tellurite enters Escherichia coli mainly through the PitA phosphate transporter.  

Science.gov (United States)

Several transporters suspected to be involved in tellurite uptake in Escherichia coli were analyzed. Results showed that the PitA phosphate transporter was related to tellurite uptake. Escherichia coli ?pitA was approximately four-fold more tolerant to tellurite, and cell viability remained almost unchanged during prolonged exposure to the toxicant as compared with wild type or ?pitB cells. Notably, reduced thiols (toxicant targets) as well as superoxide dismutase, catalase, and fumarase C activities did not change when exposing the ?pitA strain to tellurite, suggesting that tellurite-triggered oxidative damage is attenuated in the absence of PitA. After toxicant exposure, remaining extracellular tellurite was higher in E. coli ?pitA than in control cells. Whereas inductively coupled plasma atomic emission spectrometric studies confirmed that E. coli ?pitA accumulates ?50% less tellurite than the other strains under study, tellurite strongly inhibited (32)P(i) uptake suggesting that the PitA transporter is one of the main responsible for tellurite uptake in this bacterium. PMID:23189244

Elías, Alex O; Abarca, María José; Montes, Rebecca A; Chasteen, Thomas G; Pérez-Donoso, José M; Vásquez, Claudio C

2012-09-01

37

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

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)

1989-12-04

39

Mechanism of ochratoxin A transport in kidney  

International Nuclear Information System (INIS)

The effect of the fungal metabolite (mycotoxin) Ochratoxin A (OTA) on the transport of p-amino[3H]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

1988-01-01

40

Transport mechanism of a bacterial homologue of glutamate transporters  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Glutamate transporters are integral membrane proteins that catalyze a thermodynamically uphill uptake of the neurotransmitter glutamate from the synaptic cleft into the cytoplasm of glial and neuronal cells by harnessing the energy of pre-existing electrochemical gradients of ions. The linchpin of the reaction is the conformational transition of the transporters between outward and inward facing states, in which the substrate binding sites are accessible from the extracellular space and the c...

2009-01-01

 
 
 
 
41

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

42

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

43

Optical design of the National Ignition Facility main laser and switchyard/target area beam transport system  

Energy Technology Data Exchange (ETDEWEB)

The optical design of the main laser and transport mirror sections of the National Ignition Facility are described. For the main laser the configuration, layout constraints, multiple beam arrangement, pinhole layout and beam paths, clear aperture budget, ray trace models, alignment constraints, lens designs, wavefront performance, and pupil aberrations are discussed. For the transport mirror system the layout, alignment controls and clear aperture budget are describe

English, R E; Korniski, R J; Miller, J L; Rodgers, J M

1998-06-26

44

Transport Mechanisms in the Shallow Sedimentary Basin of Thuringia  

Science.gov (United States)

Salty groundwater reaching the surface or coming close to it is a phenomena that can be observed in many places in the Thuringian Basin. By means of numerical investigations we aim to determine the main transport mechanisms of this shallow sedimentary basins. Simulations of fluid flow and mass transport have been carried out in order to understand the role of geological features such as hydraulic parameters, faults and fluid density differences. For this purpose a 2D cross section model representing the geological setting and incorporating major fault structures of the basin has been constructed. Preliminary numerical investigations indicate that the brine migration is mainly determined by the regional groundwater flow, which depends strongly on the local hydraulic parameters. Density effects only play a minor role. With regard to the large uncertainty involved in measurements of hydraulic conductivity a qualitative sensitivity analysis on input parameters for aquifer permeability is performed. Additionally different hydraulic characteristics of the faults - from sealing up to more permeable - are tested. Furthermore heterogeneity is taken into account using geostatistics. Log-normal distributed permeability fields have been applied for every aquifer and aquitard unit. The results underline the findings that hydraulic parameters are the decisive factor for the regional groundwater flow pattern. Relatively small differences in permeability can strongly impact on the development of the local flow regime. Also significant effects for heterogeneous permeability distributions can be observed. With this work we contribute to the understanding of fluid convection processes influenced by density differences and local geological characteristics at basin scale. The described mechanism could develop in any shallow sedimentary basin with conditions comparable to those in the Thuringian basin.

Zech, Alraune; Fischer, Thomas; Zehner, Björn; Attinger, Sabine

2013-04-01

45

Membrane transport mechanism 3D structure and beyond  

CERN Document Server

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

Ziegler, Christine

2014-01-01

46

ANALYSIS OF THE MAIN FACTORS INFLUENCING THE QUALITY OF WINE FROM MECHANICALLY HARVESTED GRAPES  

Directory of Open Access Journals (Sweden)

Full Text Available The present paper consisted in the study of the main factors influencing the quality of wines produced from mechanically harvested grapes. In particular, 8 samples of grape clusters were examined, different for the harvesting technique, grape juice production, time of exposure to the ambient conditions and addition of an antioxidant The results confirm that the control of some parameters such as grape juice production, ambient temperature and time of exposure of the harvested grapes to the ambient conditions is essential in order to obtain wines of quality from mechanically harvested grapes.

Mariangela Vallone

2009-12-01

47

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.)

2007-06-18

48

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.

2010-06-01

49

Bidirectional transepithelial water transport: measurement and governing mechanisms.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the search for the mechanisms whereby water is transported across biological membranes, we hypothesized that in the airways, the hydration of the periciliary fluid layer is regulated by luminal-to-basolateral water transport coupled to active transepithelial sodium transport. The luminal-to-basolateral (JWL-->B) and the basolateral-to-luminal (JWB-->L) transepithelial water fluxes across ovine tracheal epithelia were measured simultaneously. The JWL-->B (6.1 microliter/min/cm2) was larger ...

Phillips, J. E.; Wong, L. B.; Yeates, D. B.

1999-01-01

50

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

51

TRANSMISSION OF IMPACTS DURING MECHANICAL GRAPE HARVESTING AND TRANSPORTATION  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The aim of the research was to study vibrational stress on grapes during mechanical harvesting, transfer and delivery to the winery, in order to identify the most critical stages and the consequent effects on the winemaking. An instrumented sphere was used to evaluate and memorise the impacts in the grape harvester and means of transport. Three treatments, obtained by differing harvesting method (manual and mechanical) and transport type (short and long distance), were compared. A correlation...

Fabio Pezzi; Claudio Caprara; Francesco Bordini

2008-01-01

52

Walking mechanism of the intracellular cargo transporter myosin V  

International Nuclear Information System (INIS)

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

2006-08-23

53

Mechanical verification of a data transport protocol  

Energy Technology Data Exchange (ETDEWEB)

A protocol which models the data transfer functions of TCP has been formally specified and mechanically verified. This paper applies deductive verification techniques to protocol process model and its associated proof techniques. Mechanical theorem proving is used as an integral part of the methodology. Both formal and informal specifications of the protocol are presented as well as a high level overview of the proof. 10 references.

Di Vito, B.L.

1983-03-01

54

Mechanism of isotonic water transport in glands.  

Science.gov (United States)

Since water and electrolytes pass cell membranes via separate channels, there can be no interactions in the membranes, and osmotic interactions between water and solutes can be expressed as the product of solute flux, frictional coefficient of solute, and length of pathway. It becomes clear that isotonic transport via a cell is impossible. In glands, where cation-selective junctions impede anion flux between the cells, isotonic water transport is only possible if sodium, after having passed the junction, is reabsorbed in the acinus and returned to the serosal side. Thus it can be recycled via the cation-selective junction and exert its drag on water more than once. This hypothesis was tested on frog skin glands. Skins were mounted in flux chambers with identical Ringer solutions on both sides. Na channels of the principal cells were closed with amiloride in the outside solution, and secretion stimulated with noradrenaline in the inside solution. Influx and efflux of Na, K and Br (used as tracer for Cl) were measured on paired half-skins during the constant-secretion phase. Flux ratios for both Na and K were higher than expected for electrodiffusion, indicating outgoing solvent drag. Flux ratios for K were much higher than those for Na. This is an agreement with the concept that Na is reabsorbed in the acinus and K is not. Two independent expressions for the degree of sodium recycling are developed. Under all experimental conditions these expressions give values for the recycling which are in good agreement. PMID:2473601

Ussing, H H; Eskesen, K

1989-07-01

55

Tellurite enters Escherichia coli mainly through the PitA phosphate transporter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Several transporters suspected to be involved in tellurite uptake in Escherichia coli were analyzed. Results showed that the PitA phosphate transporter was related to tellurite uptake. Escherichia coli ?pitA was approximately four-fold more tolerant to tellurite, and cell viability remained almost unchanged during prolonged exposure to the toxicant as compared with wild type or ?pitB cells. Notably, reduced thiols (toxicant targets) as well as superoxide dismutase, catalase, and fumarase C ...

Eli?as, Alex O.; Abarca, Mari?a Jose?; Montes, Rebecca A.; Chasteen, Thomas G.; Pe?rez-donoso, Jose? M.; Va?squez, Claudio C.

2012-01-01

56

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

57

Scattering Mechanisms for Semiconductor Transport Calculations.  

Science.gov (United States)

We have applied our Monte Carlo approach to impact ionization to various important semiconductor materials including GaAs, InP and InAs. We find that in all these materials the ionization mechanism is quantitatively different to what has been described in...

J. Bude K. Hess

1991-01-01

58

Closing mechanism for transport containers using the principle of concentric chuck  

International Nuclear Information System (INIS)

A closing mechanism is described based on the principle of the concentric chuck, for containers for the transport of radioactive wastes from nuclear power plants. In the lid of the container is placed a chuck which contains at least two slipper blocks to which are attached catches fitting into a groove in the upper part of the container body. The closing mechanism is suitable mainly for the transport of harmful materials, such as bituminized radioactive wastes. The advantage of the closure is its simple design, ease of handling, reliability and low production costs. (J.B.). 2 figs

1983-07-04

59

Drug Transport Mechanism of Oral Antidiabetic Nanomedicines  

Science.gov (United States)

Context: Over the last few decades, extensive efforts have been made worldwide to develop nanomedicine delivery systems, especially via oral route for antidiabetic drugs. Absorption of insulin is hindered by epithelial cells of gastrointestinal tract, acidic gastric pH and digestive enzymes. Evidence Acquisition: Recent reports have identified and explained the beneficial role of several structural molecules like mucoadhesive polymers (polyacrylic acid, sodium alginate, chitosan) and other copolymers for the efficient transport and release of insulin to its receptors. Results: Insulin nanomedicines based on alginate-dextran sulfate core with a chitosan-polyethylene glycol-albumin shell reduced glycaemia in a dose dependent manner. Orally available exendin-4 formulations exerted their effects in a time dependent manner. Insulin nanoparticles formed by using alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin showed a threefold increase of the hypoglycemic effect in comparison to free insulin in animal models. Solid lipid nanoparticles showed an enhancement of the bioavailability of repaglinide (RG) within optimized solid lipid nanoparticle formulations when compared with RG alone. Conclusions: Nanoparticles represent multiparticulate delivery systems designed to obtain prolonged or controlled drug delivery and to improve bioavailability as well as stability. Nanoparticles can also offer advantages like limiting fluctuations within therapeutic range, reducing side effects, protecting drugs from degradation, decreasing dosing frequency, and improving patient compliance and convenience

Gundogdu, Evren; Yurdasiper, Aysu

2014-01-01

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. 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

1992-07-03

 
 
 
 
61

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

1993-01-01

62

Novel non-conjugated main-chain hole-transporting polymers for organic electronics application.  

Science.gov (United States)

A new class of hole-transporting polymers for use in organic electronic devices such as organic light-emitting diodes (OLEDs) or photorefractive holographic storage devices has been synthesized. The polymers contain tetraarylbenzidines or tetraarylphenylenediamines as charge-transporting units in the polymer backbone and are connected by non-conjugating fluorene bridges. For use in OLEDs the novel polymers were functionalized with oxetane groups that can be cross-linked via a cationic ring opening polymerization to yield insoluble networks. Such insoluble films are necessary for the fabrication of multilayer devices by wet deposition techniques. The novel materials feature improved film-formation properties as demonstrated in green-emitting double-layer OLEDs. PMID:21567567

Schelter, Jürgen; Mielke, Georg Felix; Köhnen, Anne; Wies, Jenna; Köber, Sebastian; Nuyken, Oskar; Meerholz, Klaus

2010-09-01

63

Mass transportation mechanism in electric-biased carbon nanotubes.  

Science.gov (United States)

The mass transportation mechanism in electric-biased carbon nanotubes (CNTs) is investigated experimentally. Except for the widely accepted electromigration mechanism, we find out the thermal effect can also induce the mass transportation in the form of thermomigration or thermal evaporation. Moreover, the convincing in situ transmission electron microscope experiment results show the thermal gradient force overrides the electromigration force in most conditions, according to specific parameters of the CNTs and "cargos". A full analysis on the thermal gradient force and electromigration force imposed on the cargos is given, thus our experimental results are well explained and understood. PMID:20957981

Zhao, Jiong; Huang, Jia-Qi; Wei, Fei; Zhu, Jing

2010-11-10

64

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

65

Intestinal transportations of main chemical compositions of polygoni multiflori radix in caco-2 cell model.  

Science.gov (United States)

Context. Polygoni Multiflori Radix (PMR) is originated from the root of Polygonum multiflorum Thunb. and used in oriental countries for centuries. However, little researches pay close attention to the absorption of its major constituents. Objective. Transepithelial transport of TSG, RL, PL, and four anthraquinones is carried out. Materials and Methods. Caco-2 cell monolayer, which represented a well-established model for the study of intestinal transport of nutrients and xenobiotics, was used in this paper. Results. The apparent permeability coefficients (P app) in the Caco-2 cell monolayers were TSG (2.372 × 10(-9)) < EG (2.391 × 10(-9)) < EN (2.483 × 10(-9)) < PL (4.917 × 10(-9)) < RN (1.707 × 10(-8)) < RL (1.778 × 10(-8)) < AE (1.952 × 10(-8)). Thus, RN, RL, and AE were considered partly absorbed, while other constituents were hardly absorbed. Discussion and Conclusion. Glycosides showed poor permeabilities than aglycones. In the meantime, TSG and EN gave out poor recovery rates in this assay, which indicated that TSG and EN may accumulate or metabolise in the Caco-2 cells. In silico prediction indicated that Gibbs energy (r = 0.751, p < 0.05) and heat of form (r = 0.701, p < 0.05) were strongly positively correlated with P app. PMID:24693324

Yu, Jie; Li, Na; Lin, Pei; Li, Yunfei; Mao, Xiaojian; Bao, Getuzhaori; Gu, Wen; Zhao, Ronghua

2014-01-01

66

Issues in tokamak/stellarator transport and confinement enhancement mechanisms  

Energy Technology Data Exchange (ETDEWEB)

At present, the mechanism for anomalous energy transport in low-{beta} toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E {times} 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.

Perkins, F.W.

1990-08-01

67

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

1990-01-01

68

Perturbations to SOC models as a mechanism for transport control  

International Nuclear Information System (INIS)

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

1996-03-18

69

Procedures for the design of the main mechanical components of a wind system; Dimensionamento dos componentes mecanicos principais de aerogeradores  

Energy Technology Data Exchange (ETDEWEB)

Procedures for the design of the main mechanical components of a wind system were developed. One of the main concerns was related to the possibility of its use in small micro-computers. This goal was reached and an APPLE II computer was used. The resulting algorithm permits a friendly interaction between man and machine. 5 refs., 12 figs

Hirata, M.H.; Marco Filho, F. de [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

1990-12-31

70

Inorganic carbon transporters of the cyanobacterial CO2 concentrating mechanism.  

Science.gov (United States)

Cyanobacteria possess an environmental adaptation known as a CO(2) concentrating mechanism (CCM) that evolved to improve photosynthetic performance, particularly under CO(2)-limiting conditions. The CCM functions to actively transport dissolved inorganic carbon species (Ci; HCO(3)(-) and CO(2)) resulting in accumulation of a pool of HCO(3)(-) within the cell that is then utilised to provide an elevated CO(2) concentration around the primary CO(2) fixing enzyme, ribulose bisphosphate carboxylase-oxygenase (Rubisco). Rubisco is encapsulated in unique micro-compartments known as carboxysomes and also provides the location for elevated CO(2) levels in the cell. Five distinct transport systems for active Ci uptake are known, including two types of Na(+)-dependent HCO(3)(-) transporters (BicA and SbtA), one traffic ATPase (BCT1) for HCO(3)(-) uptake and two CO(2) uptake systems based on modified NADPH dehydrogenase complexes (NDH-I(3) and NDH-I(4)). The genes for a number of these transporters are genetically induced under Ci limitation via transcriptional regulatory processes. The in-membrane topology structures of the BicA and SbtA HCO(3)(-) transporters are now known and this may aid in determining processes related to transporter activation during dark to light transitions or under severe Ci limitation. PMID:21359551

Price, G Dean

2011-09-01

71

Directed transport as a mechanism for protein folding in vivo  

CERN Multimedia

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

72

Signatures of Cooperative Effects and Transport Mechanisms in Conductance Histograms  

Energy Technology Data Exchange (ETDEWEB)

We present a computational investigation into the lineshapes of peaks in conductance histograms, finding that they possess high information content. In particular, the histogram peak associated with conduction through a single molecule elucidates the electron transport mechanism and is generally well-described by beta distributions. A statistical analysis of the peak corresponding to conduction through two molecules reveals the presence of cooperative effects between the molecules and also provides insight into the underlying conduction channels. This work provides tools for extracting additional interpretations from experimental statistical data, helping us better understand electron transport processes.

Reuter, Matthew G [ORNL; Hersam, Mark C. [Northwestern University, Evanston; Seideman, Tamar [Northwestern University, Evanston; Ratner, Mark A. [Northwestern University, Evanston

2012-01-01

73

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)

2001-04-01

74

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)

2001-05-01

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

Configuration evaluation and criteria plan. Volume 2: Evaluation criteria plan (update). Space Transportation Main Engine (STME) configuration study  

Science.gov (United States)

Candidate main engine configurations which enhance vehicle performance, operation and cost are identified. These candidate configurations are evaluated and the configurations which provide significant advantages over existing systems are selected for consideration for the next generation of launch vehicles. The unbiased selection of the Space Transportation Main Engine (STME) configuration requires that the candidate engines be evaluated against a predetermined set of criteria which must be properly weighted to emphasize critical requirements defined prior to the actual evaluation. During a prior study of the STME a Gas Generator Cycle engine was selected for conceptual design, with emphasis on reusability, reliability and low cost while achieving good performance. In this study emphasis is on expendable application of the STME while maintaining low cost and high reliability.

Bair, E. K.

1987-01-01

77

Real versus synthesized fractal surfaces: Contact mechanics and transport properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this work, we analyze diffusion and viscous flow through the aperture field of a contact between rough surfaces pressed against each other. The purpose of our study is to validate the use of synthesized rough surfaces instead of real ones for surfaces exhibiting fractal properties. Models for mechanical deformation of asperities as well as for transport resulting from a pressure gradient or a species concentration gradient are presented. At the macroscopic scale, viscous and diffusive tran...

Vallet, Christophe; Lasseux, Didier; Sainsot, Philippe; Zahouani, H.

2008-01-01

78

Internal mode mechanism for collective energy transport in extended systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study directed energy transport in homogeneous nonlinear extended systems in the presence of homogeneous ac forces and dissipation. We show that the mechanism responsible for unidirectional motion of topological excitations is the coupling of their internal and translation degrees of freedom. Our results lead to a selection rule for the existence of such motion based on resonances that explain earlier symmetry analysis of this phenomenon. The direction of motion is found to depend bo...

Morales-molina, Luis; Quintero, Niurka R.; Mertens, Franz G.

2003-01-01

79

Internal mode mechanism for collective energy transport in extended systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study directed energy transport in homogeneous nonlinear extended systems in the presence of homogeneous ac forces and dissipation. We show that the mechanism responsible for unidirectional motion of topological excitations is the coupling of their internal and translation degrees of freedom. Our results lead to a selection rule for the existence of such motion based on resonances that explains earlier symmetry analysis of this phenomenon. The direction of motion is found...

Morales-molina, Luis; Quintero, Niurka R.; Mertens, Franz G.; Sanchez, Angel

2003-01-01

80

Cell encapsules with tunable transport and mechanical properties  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We utilized a microfluidic device with hydrodynamic flow focusing geometry to produce uniform agarose droplets in the range of 50 to 110 ?m. The transport property of the thermally gelled particles was tailored by layer-by-layer (LBL) polyelectrolytes coating on the surface and was measured via the release rates of Rhodamine B. The mechanical strength of the capsules was further enhanced by a coating of silica nano-particles in addition to polyelectrolyte coatings. We demonstrated that yeast...

Luo, Dawei; Pullela, Srinivasa Rao; Marquez, Manuel; Cheng, Zhengdong

2007-01-01

 
 
 
 
81

Increased coordination in public transport â?? 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

82

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

83

Phloem transport: a review of mechanisms and controls.  

Science.gov (United States)

It is generally believed that an osmotically generated pressure gradient drives the phloem mass flow. So far, this widely accepted Münch theory has required remarkably few adaptations, but the debate on alternative and additional hypotheses is still ongoing. Recently, a possible shortcoming of the Münch theory has been pointed out, suggesting that the Münch pressure flow is more suitable for herbs than for trees. Estimation of the phloem resistance indicates that a point might be reached in long sieve tubes where the pressure required to drive the Münch flow cannot be generated. Therefore, the relay hypothesis regained belief as it implies that the sieve tubes are shorter then the plant's axial axis. In the source phloem, three different loading strategies exist which probably result from evolutionary advantages. Passive diffusion seems to be the most primitive one, whereas active loading strategies substantially increase the growth potential. Along the transport phloem, a leakage-retrieval mechanism is observed. Appreciable amounts of carbohydrates are lost from the sieve tubes to feed the lateral sinks, while a part of these lost carbohydrates is subsequently reloaded into the sieve tubes. This mechanism is probably involved to buffer short-term irregularities in phloem turgor and gradient. In the long term, the mechanism controls the replenishment and remobilization of lateral stem storage tissues. As phloem of higher plants has multiple functions in plant development, reproduction, signalling, and growth, the fundamental understanding of the mechanisms behind phloem transport should be elucidated to increase our ability to influence plant growth and development. PMID:24106290

De Schepper, Veerle; De Swaef, Tom; Bauweraerts, Ingvar; Steppe, Kathy

2013-11-01

84

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

1981-08-01

85

Influence of Mechanical Tolerances on Field Quality in the LHC Main Dipoles  

CERN Document Server

We evaluate the influence of mechanical tolerances on the field quality in the LHC dipoles. We show that the most relevant effect is due to tolerances on the coil and on the internal part of the collars. The sensitivities of the field error multipoles on the mechanical tolerances are worked out using a finite element model of the dipole cross section. A MonteCarlo method is used to simulate the overall effect of both collar and coil tolerances on field quality. Correlation between random multipoles is worked out, and a comparison with the target table of the LHC field errors is given.

Scandale, Walter; Tropea, P

2000-01-01

86

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

87

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

CERN Multimedia

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

Ramos, D

2012-01-01

88

Charge transport through a SET with a mechanically oscillating island  

CERN Document Server

We consider a single-electron transistor (SET) whose central island is a nanomechanical oscillator. The gate capacitance of the SET depends on the mechanical displacement, thus, the vibrations of the island vibrations may strongly influence the current-voltage characteristics, current noise, and higher cumulants of the current. Harmonic oscillations of the island and oscillations with random amplitude (e.g., due to the thermal activation) change the transport characteristics in a different way. The noise spectrum has a peak at the frequency of the island oscillations; when the island oscillates harmonically, the peak reduces to a $\\delta$-peak. We show that knowledge of the SET transport properties helps to determine in what way the island oscillates, to estimate the amplitude, and the frequency of the oscillations.

Chtchelkatchev, N M; Bruder, C

2004-01-01

89

Na+-stimulated phosphate uptake system in Synechocystis sp. PCC 6803 with Pst1 as a main transporter  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract Background Most living cells uptake phosphate, an indispensable nutrient for growth from their natural environment. In Synechocystis sp. PCC 6803, the cells lack phosphate-inorganic transport (Pit system but contain two phosphate-specific transport (Pst systems, Pst1 and Pst2. We investigated the kinetics of Pi uptake of these two Pst systems by constructing the two mutants, ?Pst1 and ?Pst2, and comparing their kinetic properties with those of the wild-type cells under both Pi-sufficient and deficient conditions. The effects of pH and Na+ on the uptake of phosphate in Synechocystis were also studied. Results Growth rates of the two mutants and wild type were similar either under phosphate-sufficient or deficient condition. The Km for phosphate uptake was 6.09 ?M in wild type and this was reduced to 0.13 ?M in ?Pst1 cells and 5.16 ?M in the ?Pst2 strain. The Vmax values of 2.48, 0.22, and 2.17 ?mol • (min • mg of chlorophyll a-1 were obtained for wild type, the ?Pst1 and ?Pst2 strains, respectively. A monophasic phosphate uptake was observed in wild-type cells. The uptake of phosphate was energy and pH-dependent with a broad pH optimum between pH 7-10. Osmolality imposed by NaCl stimulated phosphate uptake whereas that imposed by sorbitol decreased uptake, suggesting stimulation of uptake was dependent upon ionic effects. Conclusion The data demonstrate that Pst2 system of Synechocystis has higher affinity toward phosphate with lower Vmax than Pst1 system. The Pst1 system had similar Km and Vmax values to those of the wild type suggesting that Pst1 is the main phosphate transporter in Synechocystis sp. PCC 6803. The Km of Pst1 of Synechocystis is closer to that of Pit system than to that of the Pst system of E. coli, suggesting that Synechocystis Pst1 is rather a medium/low affinity transporter whereas Pst2 is a high affinity transporter.

Burut-Archanai Surachet

2011-10-01

90

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

1998-01-01

91

Statistical Studies of the Robustness of the LHC Main Dipole Mechanical Structure  

CERN Document Server

This paper describes two methods used to study the effect of the tolerances of the components on the structure of the LHC main dipole. The first method, called semi-statistical, is useful for the study of the effect of single different parameters and allows the determination of the acceptable variance of the dimensions of magnet components. The second one, fully statistical, allows the study of the combined effect of many parameters. The use of these two methods allowed to evaluate with good confidence the robustness of two different dipole cross-section designs, featuring austenitic and aluminium alloy collars, respectively.

Bajko, M; Perini, D

2000-01-01

92

Discovery of a mechanism for oxygen transport during UCG  

Energy Technology Data Exchange (ETDEWEB)

The qualitative study of the flow patterns in a UCG (underground coal gasification) flow model has identified a mechanism for oxygen transport. The injected fluid was found to be drawn directly to the cavity walls in a thin layer along the bottom of the cavity. This stratified flow is caused primarily by the density differences between the injected fluid and the bulk fluid. The flow patterns were qualitatively studied in a laboratory flow model that was made dynamically similar to a UCG system by equating the Grashoff and Reynolds numbers for the two systems. 16 refs.

Massaquoi, J.G.M.; Rohaus, D.M.; Riggs, J.B.

1982-01-01

93

ALMA - Transport container: mechanical impact by accidents; conceptual design  

International Nuclear Information System (INIS)

A recent pilot study of a sea transportation system for the radioactive waste storage project ALMA is continued. The mechanical stresses on special shipping containers (with an internal volume of 25 m"3) were investigated for normal handling and sea going conditions as well as for extreme conditions following free fall in water or air or caused by ship collisions. A non-shielding steel container was designed on the basis of the results obtained. The report contains collision calculations for the proposed vessel and calculations of velocities due to free fall of the container in water and air. (author)

1979-01-01

94

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

95

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

2006-01-01

96

Fluka and thermo-mechanical studies for the CLIC main dump  

CERN Multimedia

In order to best cope with the challenge of absorbing the multi-MW beam, a water beam dump at the end of the CLIC post-collision line has been proposed. The design of the dump for the Conceptual Design Report (CDR) was checked against with a set of FLUKA Monte Carlo simulations, for the estimation of the peak and total power absorbed by the water and the vessel. Fluence spectra of escaping particles and activation rates of radio-nuclides were computed as well. Finally, the thermal transient behavior of the water bath and a thermo-mechanical analysis of the preliminary design of the window were done.

Mereghetti, Alessio; Vlachoudis, Vasilis

2011-01-01

97

The regulation of glycine transporter GLYT1 is mainly mediated by protein kinase Calpha in C6 glioma cells.  

Science.gov (United States)

Glycine has been shown to possess important functions as a bidirectional neurotransmitter. At synaptic clefts, the concentration of glycine is tightly regulated by the uptake of glycine released from nerve terminals into glial cells by the transporter GLYT1. It has been recently demonstrated that protein kinase C (PKC) mediates the downregulation of GLYT1 activity in several cell systems. However, it remains to be elucidated which subtypes of PKC might be important in the regulation of GLYT1 activity. In this study, we attempted to make clear the mechanism of the phorbol 12-myristate 13-acetate (PMA)-suppressed uptake of glycine in C6 glioma cells which have the native expression of GLYT1. In C6 cells, the expression of PKCalpha, PKCdelta, and PKCvarepsilon of the PMA-activated subtypes was detected. The PMA-suppressed action was fully reversed by the removal of both extracellular and intracellular Ca(2+). Furthermore, the inhibitory effects of PMA or thymeleatoxin (THX), which is a selective activator of conventional PKC (cPKC), were blocked by the downregulation of all PKCs expressed in C6 cells by long-term incubation with THX, or pretreatment with GF109203X or Gö6983, which are broad inhibitors of PKC, or Gö6976, a selective inhibitor of cPKC. On the other hand, treatment of C6 cells with ingenol, a selective activator of novel PKCs, especially PKCdelta and PKCvarepsilon, did not affect the transport of glycine. Silencing of PKCdelta expression by using RNA interference or pretreatment with the inhibitor peptide for PKCvarepsilon had no effect on the PMA-suppressed uptake of glycine. Together, these results suggest PKCalpha to be a crucial factor in the regulation of glycine transport in C6 cells. PMID:18778746

Morioka, Norimitsu; Abdin, Joynal Md; Morita, Katsuya; Kitayama, Tomoya; Nakata, Yoshihiro; Dohi, Toshihiro

2008-12-01

98

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

CERN Multimedia

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

99

Mechanically induced chemiluminescence from polymers incorporating a 1,2-dioxetane unit in the main chain  

Science.gov (United States)

Nature uses mechanochemical transduction processes to achieve diverse and vital functions, such as hearing, cellular adhesion and gating of ion channels. One fascinating example of biological mechanotransduction is the emission of light on mechanical stimulation. However, molecular-level transduction of force into luminescence in a synthetic system remains a challenge. Here, we show that bis(adamantyl)-1,2-dioxetane emits visible light when force is applied to a polymer chain or network in which this unit is incorporated. Bright-blue luminescence was observed on sonication of solutions of dioxetane-containing linear polymers and on the straining of polymer networks with dioxetane crosslinkers. Light is emitted from the adamantanone-excited state that forms on opening of the four-membered dioxetane ring. Increased sensitivity and colour tuning were achieved by energy transfer to suitable acceptors. High spatial and temporal resolutions highlight the potential to study the failure of polymeric materials in unprecedented detail.

Chen, Yulan; Spiering, A. J. H.; Karthikeyan, S.; Peters, Gerrit W. M.; Meijer, E. W.; Sijbesma, Rint P.

2012-07-01

100

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

 
 
 
 
101

Mechanisms of episodic acidification in low-order streams in Maine, USA  

Energy Technology Data Exchange (ETDEWEB)

In addition to decreases in base cations associated with increased discharge, four other factors contribute to episodic depressions in pH and acid neutralizing capacity (ANC) in low-order streams in Maine: (1) increases in NO[sub 3] concentrations; (2) increases in organic acidity; (3) increases in anion fraction of SO[sub 4] concentrations; and (4) salt-effect generated acidity from soil solutions. In conjunction with increased discharge, factors 1, 2, or 4 appear necessary to depress pH to less than 5. The chemistry of individual precipitation events is irrelevant to the generation of acidic episodes, except those caused by high loading of neutral salts in coastal regions. Increases in discharge, but not necessarily in dilution of solutes, in combination with the chronically high SO4 from atmospheric deposition, provide the antecedent chemical conditions for episodic acidification. Differences in antecedent moisture conditions determine the processes that control output of either ANC or acidifying agents to aquatic systems.

Kahl, J.S.; Norton, S.A.; Haines, T.A.; Rochette, E.A.; Heath, R.H.

1992-01-01

102

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-07-01

103

New mechanism for the control of sodium transport in wheat  

International Nuclear Information System (INIS)

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

2002-10-03

104

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

105

Spin relaxation mechanism of hopping transport in a 2D asymmetric quantum dot array  

International Nuclear Information System (INIS)

Spin relaxation is studied in the hopping conduction mode in 2D arrays of quantum dots (QDs) with structural asymmetry. It is shown that the absence of the 'up-down' symmetry in a QD leads to the emergence of a new spin relaxation mechanism in tunneling in a 2D QD array. The difference in spin relaxation mechanisms for symmetric and asymmetric QDs is demonstrated on the basis of theoretical analysis of an elementary event (jump between two tunnel-coupled dots). It is shown that spin flip during tunneling between QDs is the main spin relaxation mechanism in the transport in dense arrays of QDs in Ge placed in weak (1-10 T) magnetic fields

2007-08-01

106

Synthesis, characterization and charge transport mechanism of CdZnO nanorods  

International Nuclear Information System (INIS)

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

2009-10-19

107

On the Breakup of Patterened Nanoscale Copper Rings into Nanoparticles: Competing Instability and Transport Mechanisms  

International Nuclear Information System (INIS)

Nanolithographically patterned copper rings were synthesized, and the self-assembly of the rings into ordered nanoparticle/nanodrop arrays was accomplished via nanosecond pulsed laser heating above the melt threshold. The resultant length scale was correlated to the transport and instability growths that occur during the liquid lifetime of the melted copper rings. For 13-nm-thick rings, a change in the nanoparticle spacing with the ring width is attributed to a transition from a Raleigh-Plateau instability to a thin film instability because of competition between the cumulative transport and instability timescales. To explore the competition between instability mechanisms further, we carried out experiments with 7-nm-thick rings. In agreement with the theoretical predictions, these rings break up in both the azimuthal and radial directions, confirming that a simple hydrodynamic model captures the main features of the processes leading to the breakup.

2010-06-01

108

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)

2011-06-05

109

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

110

Configuration evaluation and criteria plan. Volume 2: Evaluation critera plan (preliminary). Space Transportation Main Engine (STME) configuration study  

Science.gov (United States)

The unbiased selection of the Space Transportation Main Engine (STME) configuration requires that the candidate engines be evaluated against a predetermined set of criteria which must be properly weighted to emphasize critical requirements defined prior to the actual evaluation. The evaluation and selection process involves the following functions: (1) determining if a configuration can satisfy basic STME requirements (yes/no); (2) defining the evaluation criteria; (3) selecting the criteria relative importance or weighting; (4) determining the weighting sensitivities; and (5) establishing a baseline for engine evaluation. The criteria weighting and sensitivities are cost related and are based on mission models and vehicle requirements. The evaluation process is used as a coarse screen to determine the candidate engines for the parametric studies and as a fine screen to determine concept(s) for conceptual design. The criteria used for the coarse and fine screen evaluation process is shown. The coarse screen process involves verifying that the candidate engines can meet the yes/no screening requirements and a semi-subjective quantitative evaluation. The fine screen engines have to meet all of the yes/no screening gates and are then subjected to a detailed evaluation or assessment using the quantitative cost evaluation processes. The option exists for re-cycling a concept through the quantitative portion of the screening and allows for some degree of optimization. The basic vehicle is a two stage LOX/HC, LOX/LH2 parallel burn vehicle capable of placing 150,000 lbs in low Earth orbit (LEO).

Bair, E. K.

1986-01-01

111

Mechanisms of calcium transport in small intestine. Final report  

Energy Technology Data Exchange (ETDEWEB)

The vitamin D hormone, 1,25-dihydroxyvitamin D/sub 3/, was demonstrated to be the prime hormonal agent regulating intestinal absorption of divalent cations. Production of the vitamin D hormone is, in turn, regulated by parathyroid hormone, low dietary calcium, low plasma phosphorus, and is suppressed by 1,25-dihydroxyvitamin D/sub 3/, by high plasma phosphorus, high plasma calcium, and the absence of parathyroid hormone. A variety of analogs of the vitamin D hormone were prepared. In addition, the preparation of radiolabeled vitamin D hormone was accomplished using chemical synthesis, and this highly radioactive substance was found to localize in the nuclei of the intestinal villus cells that promote intestinal absorption of calcium. A receptor for the vitamin D hormone was also located, and the general mechanism of response to the vitamin D hormone included the binding to a receptor molecule, transfer to the nucleus, transcription of specific genes followed by translation to transport proteins. Methods were developed for the discovery of the appropriate gene products that play a role in calcium transport.

DeLuca, H.F.

1982-07-01

112

Atomic mechanisms of mass transport in ceramic nuclear fuel materials  

International Nuclear Information System (INIS)

A critical review is given on self-diffusion, impurity diffusion, chemical diffusion, thermal diffusion and radiation-enhanced diffusion in the ceramic nuclear fuels, i.e. oxides, carbides, nitrides and carbonitrides of uranium and plutonium. Atomic transport in ThO2 is also discussed. Besides experimental results on diffusion, calculations of defect energies, diffusion mechanisms, and the relevant data on kinetic processes related to diffusion, ranging from creep, grain growth and sintering to leaching in water are also treated. Furthermore, recent results on damage-induced defects and their thermal behaviour using ion implantation of UO2 and UN with fission products and Rutherford backscattering/channelling techniques are reported and used to discuss the fission product behaviour in these fuels. Finally, suggestions are made for future work. (author)

1990-01-01

113

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

114

[In vitro absorption mechanism of strychnine and the transport interaction with liquiritin in Caco-2 cell monolayer model].  

Science.gov (United States)

To study the effect of liquiritin (Liq) on the transport of strychnine (Str) in Caco-2 cell monolayer model, the transport parameters of Str, such as apparent permeability coefficient (P app (B-->A) and P app (A-->B)) and cumulative transport amount (TRcum), were determined and comparatively analyzed when Str was used solely and co-used with Liq. The effect of drug concentrations, conveying times, P-glycoprotein (P-gp) inhibitor verapamil and conveying liquor pH values on the transport of Str were also investigated. The results indicated that the absorption of Str in Caco-2 cell monolayer model was well and the passive transference was the main intestinal absorption mechanism of Str in the Caco-2 monolayer model, along with the excretion action mediated by P-gp. Liq enhanced the absorption of Str. Meanwhile, conveying liquor pH value had significant influence on the excretion transport of Str. PMID:21351573

Wang, Jun-jun; Liao, Xiao-huan; Ye, Min; Chen, Yong

2010-09-01

115

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 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.

2012-11-01

116

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

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

Vibrational instability of Population III very massive main-sequence stars due to the $\\varepsilon$-mechanism  

CERN Multimedia

Very massive stars are thought to be formed in the early Universe because of a lack of cooling process by heavy elements, and might have been responsible for the later evolution of the Universe. We had an interest in vibrational stability of their evolution and carried out the linear nonadiabatic analysis of radial and nonradial oscillations for population III very massive main-sequence stars with $500-3000M_{\\sun}$. We found that only the radial fundamental mode becomes unstable due to the $\\varepsilon$-mechanism for these stars. The instability appears just after the CNO cycle is activated and the nuclear energy generation rate becomes large enough to stop the pre--main-sequence contraction, and continues during the early stage of the core hydrogen burning. Besides, we roughly estimated amount of mass loss due to the instability to know its significance.

Sonoi, Takafumi

2012-01-01

119

High-speed tracking of intracellular structures: understanding the transport mechanisms in living plant cells  

Science.gov (United States)

Zera® technology offers the possibility to artificially induce the formation of spherical organelles in different kinds of cells. Their large size and high density, compared to the native organelles of the cell, make them good candidates to be used as a handles for the realization of biophysical experiments inside living cells. Furthermore, they present a high signal-to-noise ratio in fluorescence microscopy and small photobleaching. This work focuses mainly on the nature of protein body motion in Nicotiana Benthamiana (tobacco) cells. The high-speed tracking of these structures reveals that they move in a stepwise mode, suggesting that myosin XI motors directly pull these organelles through the cytosol. Our results indicate that these artificially-induced structures are well integrated into the natural processes of the cell so that the technique may be advantageous for the study of the intracellular transport mechanisms. Large forces can be exerted with optical tweezers to mechanically interact with the moving organelles.

López-Quesada, C.; Joseph, M.; Selva, J.; Farré, A.; Egea, G.; Ludevid, M. D.; Martín-Badosa, E.; Montes-Usategui, M.

2011-09-01

120

Mechanism and regulation of phosphate transport in Streptococcus pyogenes  

International Nuclear Information System (INIS)

In contrast to results reported with other bacteria, uptake of "3"2Pi 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 "3"2P/sub i/ in the presence of trans unlabeled P/sub i/ exhibited similar characteristics and were largely eliminated by reduction of the trans P/sub i/ concentration. Neither process was inhibited appreciably by pretreatment of cells with ionophores or metabolic inhibitors, but both processes were abolished by exposure to p-chloromercuribenzoate. Inhibition by both exogenous energy sources resulted in a reduction in the maximal velocity of transport (V/sub max/). Whereas arginine also caused a shift in the apparent Michaelis-Menten constant (K/sub m/) to larger values, glucose did not alter the K/sub m/. On the basis of the results reported, it is proposed that the rate of P/sub i/ exchange is determined positively by the intracellular and extracellular concentrations of P/sub i/ and negatively by ATP or metabolites thereof. The mechanism of ATP action is unknown but could involve either covalent or noncovalent modification of the carrier protein

1987-01-01

 
 
 
 
121

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)

2001-05-01

122

Ion Homeostasis, Channels, and Transporters: An Update on Cellular Mechanisms  

Science.gov (United States)

Discussion of how elucidation of molecular structures, some at the atomic level, of model ion transport proteins and use of the tools of cell biology to explore the cell-specific function or subcellular localization of ion transport proteins have provided new, and sometimes surprising, insights regarding four major questions in current ion transporter research

PhD George R Dubyak (Case Western Reserve University Dept. of Physiology and Biophysics)

2004-12-01

123

The transport mechanism DC arcs in advanced spectroanalysis  

International Nuclear Information System (INIS)

This report presents some basic investigations concerning the emission spectroanalysis of powder specimens with application of a new type of advanced DC arcs which operate in horizontally arranged graphite cylinders. The extremely low detection limits found by experiment for various elements (Be, Cd, In, Pb, Sn) suggest a beneficial and reflector like effect of the graphite cylinder on the transport process in the arc plasma. Experiments in detail and by using radioactive tracers (Ag-110, Cd-115, Co-56, Fe-59, Zn-65) lead to an element specific modified model of the effective mechanism of the new arc arrangement. Elements of favourable thermochemical properties produce about three times as much of the average particle density in the arc plasma with the effect of the graphite cylinder. Besides these effects the element specific properties of the graphite cylinder are remarkably invariable towards magnetic fields (1,24 . 10"-"2T bzw. 2,6 . 10"-"4T) and various additives (Ga_2O_3, Li_2Co_3, NaCl) to the test specimens. (orig.)

1977-01-01

124

Nodal methods for problems in fluid mechanics and neutron transport  

International Nuclear Information System (INIS)

A new high-accuracy, coarse-mesh, nodal integral approach is developed for the efficient numerical solution of linear partial differential equations. It is shown that various special cases of this general nodal integral approach correspond to several high efficiency nodal methods developed recently for the numerical solution of neutron diffusion and neutron transport problems. The new approach is extended to the nonlinear Navier-Stokes equations of fluid mechanics; its extension to these equations leads to a new computational method, the nodal integral method which is implemented for the numerical solution of these equations. Application to several test problems demonstrates the superior computational efficiency of this new method over previously developed methods. The solutions obtained for several driven cavity problems are compared with the available experimental data and are shown to be in very good agreement with experiment. Additional comparisons also show that the coarse-mesh, nodal integral method results agree very well with the results of definitive ultra-fine-mesh, finite-difference calculations for the driven cavity problem up to fairly high Reynolds numbers

1985-01-01

125

Mechanisms and modeling development of water transport/phase change in catalyst layers of portion exchange membrane fuel cells  

Energy Technology Data Exchange (ETDEWEB)

Research on proton exchange membrane fuel cells has shown that incorporation of nanosized catalysts can effectively increase active areas and catalyst activity and make a great contribution to development in performance and catalyst utilization. Multiphase transport processes are as significant and complicated as water generation/transfer processes which occur in nano-structured catalyst layers. A review project has been launched aimed at gaining a comprehensive understanding of the mechanisms of water generation or transport phenomena. It covers catalytic reactions and water-phase change within the catalyst layers. The review proceeds in three main stages: Firstly, it characterizes and reconstructs the nano/micro-structured pores and solid-phases; secondly, it emphasises the importance of sensitive and consistent analysis of various water-phase change and transport schemes; and thirdly, it recommends development of microscopic models for multi-phase transport processes in the pores and the solid phases.

Xiao, Yexiang [Dept. of Thermal Engineering, Tsinghua University Beijing (China)], email: Yexiang.Xiao@energy.lth.se; Yuan, Jinliang; Sunden, Bengt [Dept. of Energy Sciences, Faculty of Engineering, Lund University (Sweden)], email: Jinliang.yuan@energy.lth.se, email: bengt.sunden@energy.lth.se

2011-07-01

126

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.

2012-12-01

127

Ion homeostasis, channels, and transporters: an update on cellular mechanisms.  

Science.gov (United States)

The steady-state maintenance of highly asymmetric concentrations of the major inorganic cations and anions is a major function of both plasma membranes and the membranes of intracellular organelles. Homeostatic regulation of these ionic gradients is critical for most functions. Due to their charge, the movements of ions across biological membranes necessarily involves facilitation by intrinsic membrane transport proteins. The functional characterization and categorization of membrane transport proteins was a major focus of cell physiological research from the 1950s through the 1980s. On the basis of these functional analyses, ion transport proteins were broadly divided into two classes: channels and carrier-type transporters (which include exchangers, cotransporters, and ATP-driven ion pumps). Beginning in the mid-1980s, these functional analyses of ion transport and homeostasis were complemented by the cloning of genes encoding many ion channels and transporter proteins. Comparison of the predicted primary amino acid sequences and structures of functionally similar ion transport proteins facilitated their grouping within families and superfamilies of structurally related membrane proteins. Postgenomics research in ion transport biology increasingly involves two powerful approaches. One involves elucidation of the molecular structures, at the atomic level in some cases, of model ion transport proteins. The second uses the tools of cell biology to explore the cell-specific function or subcellular localization of ion transport proteins. This review will describe how these approaches have provided new, and sometimes surprising, insights regarding four major questions in current ion transporter research. 1) What are the fundamental differences between ion channels and ion transporters? 2) How does the interaction of an ion transport protein with so-called adapter proteins affect its subcellular localization or regulation by various intracellular signal transduction pathways? 3) How does the specific lipid composition of the local membrane microenvironment modulate the function of an ion transport protein? 4) How can the basic functional properties of a ubiquitously expressed ion transport protein vary depending on the cell type in which it is expressed? PMID:15545343

Dubyak, George R

2004-12-01

128

Electronic transport mechanism of CdTe nanocrystalline  

Energy Technology Data Exchange (ETDEWEB)

Highlights: {yields} CdTe nanocrystalline powder was synthesized by chemical process. {yields} The dc and ac electrical conductivities of CdTe nanocrystalline were measured in the temperature range 293-423 K. {yields} The electronic transport and conduction mechanisms of CdTe nanocrystalline were studied. - Abstract: CdTe nanocrystalline powder was synthesized by chemical process. The structure of CdTe nanocrystalline was investigated by means of X-ray diffraction (XRD) technique, energy-dispersive X-ray analysis (EDAX) spectrum and transmission electron microscopy (TEM). The selected area electron diffraction (SAED) study confirms the crystallinity of the CdTe nanocrystalline. Some structural parameters such as the mean crystallite size, the dislocation density and the strain were calculated. The temperature dependence of the dc and ac conductivity was measured in the temperature range 293-423 K. It was found that the dc conductivity is thermally activated type. Values of dc activation energy and the pre-exponential were determined. The ac conductivity was found to increase with increasing both the temperature and frequency and follows the power low. The frequency exponent s was found to decrease with increasing temperature. The correlated barrier hopping (CBH) model was found to be applying to the ac conductivity data. The maximum barrier height W{sub m} and the density of localized states N(E{sub F}) were calculated and equal to 0.47 eV and 8.82 x 10{sup 22} to 1.43 x 10{sup 23} eV{sup -1} cm{sup -3}, respectively. CdTe nanomaterial is a good candidate for semiconductor devices due to its high conductivity.

Abd El-sadek, M.S., E-mail: el_sadek_99@yahoo.com [Nanomaterial Laboratory, Physics Department, Faculty of Science, South Valley University, Qena (Egypt); Yahia, I.S. [Nano-Science Laboratory, Physics Department, Faculty of Education, Ain Shams University, Roxy, Cairo (Egypt); Department of Metallurgical and Materials Science Engineering, Firat University, Elazig (Turkey); Salem, A.M. [Electron Microscopy and Thin Film Department, National Research Center, Dokki, Cairo (Egypt)

2011-10-17

129

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

130

Early metabolic effects and mechanism of ammonium transport in yeast  

International Nuclear Information System (INIS)

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

1987-01-01

131

Electron injection and transport mechanism in organic devices based on electron transport materials  

International Nuclear Information System (INIS)

Electron injection and transport in organic devices based on electron transport (ET) materials, such as 4,7- diphyenyl-1,10-phenanthroline (Bathophenanthroline BPhen), 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (Bathocuproine BCP) and bipyridyl oxadiazole compound 1,3-bis [2-(2,2'-bipyridin-6-yl)-1,3,4-oxadiazol-5-yl]benzene (Bpy-OXD), have been reported. The devices are composed of ITO/ET materials (BPhen, BCP Bpy-OXD)/cathodes, where cathodes = Au, Al and Ca. Current-voltage characteristics of each ET material are performed as a function of cathodes. We have found that Ca and Al exhibit quite different J-V characteristics compared with the gold (Au) cathode. The current is more than one order of magnitude higher for the Al cathode and more than three orders of magnitude higher for Ca compared with that of the Au cathode at ?8 V for all ET materials. This is because of the relatively low energy barrier at the organic/metal interface for Ca and Al cathodes. Electron-only devices with the Au cathode show that the electron transfer limitation is located at the organic/cathode interface and the Fowler-Nordheim mechanism is qualitatively consistent with experimental data at high voltages. With Ca and Al cathodes, electron conduction is preponderant and is bulk limited. A power law dependence J ? Vm with m > 2 is consistent with the model of trap-charge limited conduction. The total electron trap density is estimated to be ?5 x 1018 cm-3. The critical voltage (Vc) is found to be ?45 V and is almost independent of the materials.

2008-11-21

132

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)

1995-11-19

133

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

134

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

135

Regional variation of the dimethyl sulfide oxidation mechanism in the summertime marine boundary layer in the Gulf of Maine  

Science.gov (United States)

Mixing ratios of dimethyl sulfide (DMS) and its nighttime oxidant, the nitrate radical (NO3), were measured in the summertime marine boundary layer (MBL) of the Gulf of Maine during the New England Air Quality Study-International Transport and Chemical Transformation campaign in 2004. DMS fluxes from the ocean were derived from simultaneous measurements of the wind speed and DMS in seawater. Day and night DMS oxidation rates were determined from modeled OH and measured NO3 concentrations. The average DMS lifetime with respect to oxidation by OH at noon was 13.5 ± 3.4 (1?) h, while at night, DMS lifetimes with respect to NO3 oxidation varied by sampling region from 11 min to 28 h. Oxidation by photochemically generated halogen species likely also played a role during the day, although the nature and extent of the halogen species is more difficult to predict due to lack of halogen measurements. Closure of the DMS budget in the MBL required a vertical entrainment velocity of ˜0.4 cm s-1. This study suggests that entrainment of DMS out of the MBL competes with daytime oxidation and that the presence of pollution in the form of NOx and O3 in near-coastal regions at night results in nearly complete DMS oxidation within the MBL via reaction with NO3, with a much smaller contribution from entrainment. One potential implication of near-complete DMS oxidation within the MBL is a reduction of the amount of sulfur available for aerosol formation and growth at higher altitudes in the atmosphere.

Osthoff, Hans D.; Bates, Timothy S.; Johnson, James E.; Kuster, William C.; Goldan, Paul; Sommariva, Roberto; Williams, Eric J.; Lerner, Brian M.; Warneke, Carsten; de Gouw, Joost A.; Pettersson, Anders; Baynard, Tahllee; Meagher, James F.; Fehsenfeld, Frederick C.; Ravishankara, A. R.; Brown, Steven S.

2009-04-01

136

Exciton transport, charge extraction, and loss mechanisms in organic photovoltaics  

Science.gov (United States)

Organic photovoltaics have attracted significant interest over the last decade due to their promise as clean low-cost alternatives to large-scale electric power generation such as coal-fired power, natural gas, and nuclear power. Many believe power conversion efficiency targets of 10-15% must be reached before commercialization is possible. Consequently, understanding the loss mechanisms which currently limit efficiencies to 4-5% is crucial to identify paths to reach higher efficiencies. In this work, we investigate the dominant loss mechanisms in some of the leading organic photovoltaic architectures. In the first class of architectures, which include planar heterojunctions and bulk heterojunctions with large domains, efficiencies are primarily limited by the distance photogenerated excitations (excitons) can be transported (termed the exciton diffusion length) to a heterojunction where the excitons may dissociate. We will discuss how to properly measure the exciton diffusion length focusing on the effects of optical interference and of energy transfer when using fullerenes as quenching layers and show how this explains the variety of diffusion lengths reported for the same material. After understanding that disorder and defects limit exciton diffusion lengths, we suggest some approaches to overcome this. We then extensively investigate the use of long-range resonant energy transfer to increase exciton harvesting. Using simulations and experiments as support, we discuss how energy transfer can be engineered into architectures to increase the distance excitons can be harvested. In an experimental model system, DOW Red/PTPTB, we will show how the distance excitons are harvested can be increased by almost an order of magnitude up to 27 nm from a heterojunction and give design rules and extensions of this concept for future architectures. After understanding exciton harvesting limitations we will look at other losses that are present in planar heterojunctions. One of the primary losses that puts stringent requirements on the charge carrier mobilities in these cells is the recombination losses due to space charge build up at the heterojunction. Because electrons are confined to the acceptor and holes to the donor, net charge density always exists even when mobilities are matched, in contrast to bulk heterojunctions wherein matched mobilities lead to zero net charge. This net charge creates an electric field which opposes the built-in field and limits the current that can be carried away from this heterojunction. Using simulations we show that for relevant current densities charge carrier mobilities must be higher than 10-4 cm2/V.s to avoid significant losses due to space charge formation. In the last part of this work, we will focus on the second class of architectures in which exciton harvesting is efficient. We will present a systematic analysis of one of the leading polymer:fullerene bulk heterojunction cells to show that losses in this architecture are due to charge recombination. Using optical measurements and simulations, exciton harvesting measurements, and device characteristics we will show that the dominant loss is likely due to field-dependent geminate recombination of the electron and hole pair created immediately following exciton dissociation. No losses in this system are seen due to bimolecular recombination or space charge which provides information on charge-carrier mobility targets necessary for the future design of high efficiency organic photovoltaics.

Scully, Shawn Ryan

137

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

Directory of Open Access Journals (Sweden)

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

R Millaleo

2010-01-01

138

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

Scientific Electronic Library Online (English)

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

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

139

Osmotic water transport in aquaporins : evidence for a stochastic mechanism  

DEFF Research Database (Denmark)

Abstractâ?? 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 Ï?, while the solute permeability, P(S), is proportional to 1 - Ï?. 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

140

Osmotic water transport in aquaporins: evidence for a stochastic mechanism.  

Science.gov (United States)

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. PMID:23959676

Zeuthen, Thomas; Alsterfjord, Magnus; Beitz, Eric; MacAulay, Nanna

2013-10-15

 
 
 
 
141

Transport mechanism of MeV protons in tapered glass capillaries  

International Nuclear Information System (INIS)

To investigate the transport mechanism of MeV protons in tapered glass capillaries, spatially resolved energy spectra were measured for proton microbeams focused by 20-?m-outlet capillaries having various taper angles. Three-dimensional Monte Carlo (MC) simulations were also performed to support the experiments and trace each particle in the capillary in more detail. The dependence of the proton energy distribution on the outgoing angle proved that the capillary-focused proton beam consists of two different components, protons traveling straight through the capillary without colliding with the capillary wall and protons scattered by the capillary inner wall. Moreover, the focusing effect of the tapered glass capillary was found to be mainly due to the scattered beam component. The MC simulations well reproduced the experimental results and showed that beam focusing ratios of 1.6-2.4 are possible with capillaries having a convex inner wall. The flight distance of the scattered proton in the capillary glass body was found to play an important role in determining transport efficiency of the protons through the capillary.

2011-08-15

142

Dust transport: Wind-blown and mechanical resuspension  

International Nuclear Information System (INIS)

The purpose of the dust transport study is to understand and quantify the physical processes that lead to the resuspension of soil contaminated with plutonium. The soil in question was contaminated 20 years ago with machining oil containing <3-?m plutonium particles. 10 refs., 15 figs., 4 tabs

1987-05-01

143

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

International Nuclear Information System (INIS)

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

2011-05-17

144

The mechanism of substrate release by the aspartate transporter GltPh: insights from simulations†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Glutamate transporters regulate excitatory amino acid neurotransmission across neuronal and glial cell membranes by coupling the translocation of their substrate (aspartate or glutamate) into the intracellular (IC) medium to the energetically favorable transport of sodium ions or other cations. The first crystallographically resolved structure of this family, the archaeal aspartate transporter, GltPh, has served as a structural paradigm for elucidating the mechanism of substrate translocation...

Dechancie, Jason; Shrivastava, Indira H.; Bahar, Ivet

2011-01-01

145

Fragmentation versus transportation mechanisms in the pyroclastic sequence of Monte Pilato-Rocche Rosse (Lipari, Italy)  

Science.gov (United States)

Monte Pilato is a rhyolitic pumice cone formed about 1400 years ago during the last volcanic activity which occurred at Lipari. Its activity consisted of numerous explosive episodes, ending with the extrusion of the Rocche Rosse obsidian lava flow. We have identified nine different pyroclastic lithofacies, of which four main lithofacies represent 90% of the erupted products; they include: (1) deposits consisting of decimeters- to meters-thick well-sorted, graded beds of pumice lapilli, which are of fall origin; (2) massive deposits consisting of decimeters-thick beds of pumice lapilli in an ash matrix, interpreted as being of pyroclastic flow origin; (3) deposits of centimeters-thick ash beds of surge origin; (4) decimeter-thick fine ash layers with scattered subcentimetric accretionary lapilli of turbulent "flow" origin. The complex grain size distributions of the main lithofacies were distinguished using a multivariate statistic analysis ( R-mode factor analysis). Variations of the grain size characteristics in relation to the distance from the vent area have been investigated in order to discriminate the roles played by fragmentation and transportation processes. In the lithofacies 1 fall deposits, the grain size distribution is always unimodal and varies from a Rosin-type distribution near the vent to a Gaussian one in the distal outcrops. This is caused by the transport process and the different particle trajectories. In lithofacies 2, 3 and 4, the grain size distributions are always polymodal. The polymodality is not caused by preferential processes occurring during transportation, but seems, rather, to be connected with the original fragmentation of the pyroclastic material. The pumice lapilli present both in lithofacies 1 and 2 have mean vesicularity index values always in excess of 65%, and the value is homogeneous throughout the sample. These data suggest that for these two lithofacies, the pumice lapilli originated from exsolution of magmatic gases. In contrast, the fine ash particles in lithofacies 2, and also the main mode of lithofacies 3 and 4 deposits, show typical features of hydromagmatic fragmentation processes. The grain size population is always centered at 4-5 ? (0.032-0.064 mm) and, interestingly, the same grain size has been obtained recently (Zimanowski et al., 1991) for fragments produced by experimental magma/water interaction. Field and laboratory data suggest that during Monte Pilato-Rocche Rosse eruptions magmatic and hydromagmatic mechanisms were frequently operative at the same time.

Dellino, P.; Volpe, L. La

1995-03-01

146

Evaluation of the Use of Capnography during the Transport of Critically Ill Mechanically Ventilated Patients.  

Science.gov (United States)

Critically ill, mechanically ventilated, patients were monitored with manometry, spirometry, and capnography during intrahospital transport out of the ICU. Patients functioned as their own control, and medical personnel were 'blinded' to capnography for 5...

D. P. Stoltzfus

1992-01-01

147

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

International Nuclear Information System (INIS)

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

2005-01-01

148

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

Science.gov (United States)

Abstract 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

149

Development of Micro and Nano Electro-Mechanical Technologies for Space Transportation Systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We review the long-standing activity on Micro Electro Mechanical Systems (MEMS) for application to space transportation and describe recent developments in Nano Electro Mechanical Systems (NEMS) technology with a potential impact on space transport vehicles. We show how NEMS, if implemented into everyday technologies, could reduce the size of modern devices and allow for better performing sensors. Carbon based materials have served as prime materials for NEMS use, because of their highlighted...

Bellucci, S.; Coderoni, L.; Micciulla, F.; Sacco, I.

2011-01-01

150

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)

1992-12-01

151

The mechanism of transmembrane S-nitrosothiol transport  

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S-nitrosothiols have been suggested to play an important role in nitric oxide (NO)-mediated biological events. However, the mechanisms by which an S-nitrosothiol (or the S-nitroso functional group) is transferred across cell membrane are still poorly understood. We have demonstrated previously that the degradation of S-nitrosoglutathione (GSNO) by cells absolutely required the presence of cystine in the extracellular medium and proposed a mechanism that involved the reduction of cystine to cy...

Zhang, Yanhong; Hogg, Neil

2004-01-01

152

The electronic transport mechanism in amorphous tetrahedrally-coordinated carbon films  

Energy Technology Data Exchange (ETDEWEB)

The electronic transport mechanism in tetrahedrally coordinated amorphous carbon was investigated using measurements of stress relaxation, thermal evolution of electrical conductivity, and temperature dependent conductivity measurements. Stress relaxation measurements were used to determine the change in 3-fold coordinated carbon concentration, and the electrical conductivity was correlated to this change. It was found that the conductivity was exponentially proportional to the change in 3-fold concentration, indicating a tunneling or hopping transport mechanism. It was also found that the activation energy for transport decreased with increasing anneal temperature. The decrease in activation energy was responsible for the observed increase in electrical conductivity. A model is described wherein the transport in this material is described by thermally activated conduction along 3-fold linkages or chains with variable range and variable orientation hopping. Thermal annealing leads to chain ripening and a reduction in the activation energy for transport.

Sullivan, J.P.; Friedmann, T.A.; Dunn, R.G.; Stechel, E.B.; Schultz, P.A.

1998-02-01

153

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.

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; MacLeod, Annette; Maser, Pascal; Barrett, Michael P.; Horn, David; De Koning, Harry P.

2014-01-01

154

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

155

Transport mechanisms in high Tc bismuth-based oxide superconductors  

International Nuclear Information System (INIS)

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

2008-01-01

156

What are the main pathways for the cross-tropopause transport of water vapor and CO over the Asian monsoon/Tibetan Plateau?  

Science.gov (United States)

During boreal summer, much of the water vapor and CO entering the global tropical stratosphere is transported over the Asian monsoon/Tibetan Plateau (TP) region. The observed trend of increasing stratosphere water vapor during 1980s and 90s also peaks in this region during boreal fall, highlight the potential importance of this region in understanding the causes of the stratospheric water vapor changes. This study explores the primary pathways for water vapor and CO transport to the lower stratosphere. Previous studies suggest that most of this transport is carried out either by tropical convection over the South Asian monsoon region or by extratropical convection over Southern China. Using measurements from newly available NASA Aura Microwave Limb Sounder along with observations from the Aqua and Tropical Rainfall Measuring Mission satellites, we suggest that the TP provides the main pathway for cross-tropopause transport in this region. Tropospheric moist convection driven by elevated surface heating over the TP is deeper and detrains more water vapor, CO, and ice at the tropopause than over the monsoon area. Warmer tropopause temperatures and slower falling smaller cirrus cloud particles in less saturated ambient air at the tropopause also allow more water vapor to travel into the lower stratosphere over the TP, effectively short- circuiting the slower ascent of water vapor across the cold tropical tropopause over the monsoon area. Air high in water vapor and CO over the Asian monsoon/TP region enters the lower stratosphere primarily over the TP, then it is transported equatorward toward the Asian monsoon area and disperses into the large scale upward motion of the global stratospheric circulation. Thus hydration of the global stratosphere could be especially sensitive to changes of convection over the TP.

Fu, R.; Hu, Y.; Wright, J. S.; Jiang, J. H.

2006-05-01

157

Analysis of physical mechanisms underlying density-dependent transport in porous media:  

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In this thesis, the interaction between (large) density gradients and flow and transport in porous media is studied. Large gradients in the density of groundwater exist for example near deep salt rock formations, which are considered as possible long-term storage sites for radioactive waste. Furthermore, density effects play a role in many other groundwater applications, such as salt water intrusion. Density gradients mainly affect the flow field and mass transport in two ways: by fluid vo...

Landman, A. J.

2005-01-01

158

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

159

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

Science.gov (United States)

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

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

2008-10-01

160

[The transport mechanism of antibiotics using microvillous membrane vesicles (placental transport of fosfomycin)].  

Science.gov (United States)

Using the rapid filtration technique, the uptake of fosfomycin into microvillous membrane vesicles isolated from human term placental trophoblast was investigated. The microvillous membrane vesicles exhibited the uptake of fosfomycin into an osmotically reactive intravesicular space and it was indicated that the uptake of fosfomycin by microvillous membrane vesicles represented transport into membrane vesicles. The uptake of fosfomycin by microvillous membrane vesicles was not dependent on the Na+ electrochemical gradient or membrane potential. The initial uptake of fosfomycin by microvillous membrane vesicles did not exhibit saturation kinetics with respect to fosfomycin concentration, and increased linearly as the fosfomycin concentration increased. These results indicated that fosfomycin was transported across the microvillous membrane by simple diffusion. L-alanine, L-valine, L-lysine, inorganic phosphate or D-glucose did not inhibit the uptake of fosfomycin into microvillous membrane vesicles. On the other hand, fosfomycin did not inhibit the uptake of L-alanine, L-valine, L-lysine inorganic phosphate or D-glucose into microvillous membrane vesicles. These results revealed that fosfomycin did not affect the placental transport activity of other nutrients. PMID:3782953

Iioka, H; Moriyama, I; Kyuma, M; Tsuji, Y; Ichijo, M

1986-10-01

 
 
 
 
161

Mechanisms of along-channel sediment transport in the North Passage of the Yangtze Estuary and their response to large-scale interventions  

Science.gov (United States)

The effects of large-scale interventions in the North Passage of the Yangtze Estuary (the Deep Waterway Project, DWP) on the along-channel flow structure, suspended sediment distribution and its transport along the main channel of this passage are investigated. The focus is explaining the changes in net sediment transport in terms of physical mechanisms. For this, data of flow and suspended sediment concentration (SSC), which were collected simultaneously at several locations and at different depths along the main channel of the North Passage prior to and after the engineering works, were harmonically analyzed to assess the relative importance of the transport components related to residual (time-mean) flow and various tidal pumping mechanisms. Expressions for main residual flow components were derived using theoretical principles. The SSC revealed that the estuarine turbidity maximum (ETM) was intensified due to the interventions, especially in wet seasons, and an upstream shift and extension of the ETM zone occurred. The amplitude of the M 2 tidal current considerably increased, and the residual flow structure was significantly altered by engineering works. Prior to the DWP, the residual flow structure was that of a gravitational circulation in both seasons, while after the DWP, there was seaward flow throughout the channel during the wet season. The analysis of net sediment transport reveals that during wet seasons and prior to the DWP, the sediment trapping was due to asymmetric tidal mixing, gravitational circulation, tidal rectification, and M 2 tidal pumping, while after the DWP, the trapping was primarily due to seaward transport caused by Stokes return flow and fresh water discharge and landward transport due to M 2 tidal pumping and asymmetric tidal mixing. During dry seasons, prior to the DWP, trapping of sediment at the bottom relied on landward transports due to Stokes transport, M 4 tidal pumping, asymmetric tidal mixing, and gravitational circulation, while after the DWP the sediment trapping was caused by M 2 tidal pumping, Stokes transport, asymmetric tidal mixing, tidal rectification, and gravitational circulation.

Jiang, Chenjuan; de Swart, Huib E.; Li, Jiufa; Liu, Gaofeng

2013-03-01

162

[The transport mechanism of polycationic compounds across intestinal and renal cell membrane].  

Science.gov (United States)

This article reviewed the transport mechanism of polycationic compounds across rat intestinal and renal cell membranes. The inside-negative diffusion potential stimulated the initial uptake of dicationic compounds into intestinal brush-border membrane vesicles, and a good correlation was observed between lipophilicity and the amount of diffusion potential-dependent transport of the dications. On the other hand, tri- and tetracationic compounds were not affected by the diffusion potential because of their much lower lipophilicity. The membrane surface potential affected to the transport of polycationic compounds, similar to monocationic compounds. Therefore it appears that the membrane surface potential plays a common role in the transport of mono- and polycationic compounds across cell membranes. On the intestinal basolateral membrane, it was found that there was a Na+/putrescine symporter. This recognized dicationic compounds and transported them from the blood into intestinal cells. This transporter did not recognize spermine and spermidine. Furthermore, we found a novel transport system, a Na+/spermine antiporter, on the rat renal brush-border membrane. This transporter recognized aliphatic polycation, which has more than four amino groups, and actively secreted spermine and trientine into the renal proximal tubules in vitro and in vivo. However, this transporter did not recognize trientine-copper complex. These results are useful for the prediction of the intestinal absorption and renal excretion of polyamine derivatives. PMID:12235852

Kobayashi, Michiya

2002-09-01

163

The fluid mechanics of nutrient transport within biofilms  

Science.gov (United States)

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

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

2011-11-01

164

Super-Diffusive Spin-Transport as a Mechanism of Ultrafast Demagnetization  

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We propose a semi-classical model for femtosecond-laser induced demagnetization due to spin-polarized excited electron diffusion in the super-diffusive regime. Our approach treats the finite elapsed time and transport in space between multiple electronic collisions exactly, as well as the presence of several metal films in the sample. Solving the derived transport equation numerically we show that this mechanism accounts for the experimentally observed demagnetization within...

Battiato, Marco; Carva, Karel; Oppeneer, Peter M.

2011-01-01

165

The mechanism of ferrichrome transport through Arn1p and its metabolism in Saccharomyces cerevisiae  

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Siderophores are low molecular weight compounds, synthesized and secreted by microorganisms, that specifically bind ferric iron with exceptionally high affinity. Microbes capture these compounds and take up the bound iron through specific, high-affinity systems. Saccharomyces cerevisiae can take up iron bound to siderophores through the transporters of the ARN family; however, the mechanism by which the siderophore-bound iron enters the cell via these transporters is not known. Here we descri...

2003-01-01

166

Mechanism of proton/substrate coupling in the heptahelical lysosomal transporter cystinosin  

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Secondary active transporters use electrochemical gradients provided by primary ion pumps to translocate metabolites or drugs “uphill” across membranes. Here we report the ion-coupling mechanism of cystinosin, an unusual eukaryotic, proton-driven transporter distantly related to the proton pump bacteriorhodopsin. In humans, cystinosin exports the proteolysis-derived dimeric amino acid cystine from lysosomes and is impaired in cystinosis. Using voltage-dependence analysis of steady-state a...

2012-01-01

167

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

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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

2002-01-01

168

Calcium and copper transport ATPases: analogies and diversities in transduction and signaling mechanisms  

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The calcium transport ATPase and the copper transport ATPase are members of the P-ATPase family and retain an analogous catalytic mechanism for ATP utilization, including intermediate phosphoryl transfer to a conserved aspartyl residue, vectorial displacement of bound cation, and final hydrolytic cleavage of Pi. Both ATPases undergo protein conformational changes concomitant with catalytic events. Yet, the two ATPases are prototypes of different features with regard to transduction and signal...

Inesi, Giuseppe

2011-01-01

169

Tug-of-war as a cooperative mechanism for bidirectional cargo transport by molecular motors  

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Intracellular transport is based on molecular motors that pull cargos along cytoskeletal filaments. One motor species always moves in one direction, e.g. conventional kinesin moves to the microtubule plus end, while cytoplasmic dynein moves to the microtubule minus end. However, many cellular cargos are observed to move bidirectionally, involving both plus-end and minus-end directed motors. The presumably simplest mechanism for such bidirectional transport is provided by a t...

Mu?ller, Melanie J. I.; Klumpp, Stefan; Lipowsky, Reinhard

2008-01-01

170

Study of the transport mechanism in molecular self-assembling devices  

Science.gov (United States)

This paper focuses on the intrinsic charge transport in self-assembled monolayers (SAMs) and on the nature of transport in organic systems, in which surface and bulk properties are undistinguishable due to scale of consistent materials. Developed SAM-OFETs and photovoltaic (SAM-PVC) devices are characterized independently to study a role of charge delocalization both in electrical and optical manifold. The dynamics of charge transport are determined and used to clarify a transport mechanism. Taken together, these SAM devices provide a unique tool to study the fundamentals of polaronic transport on organic surfaces and to discuss the SAM-OFET and SAM PVC performance. Vapor phase molecular self-assembly of 1, 4, 5, 8-naphthalene-tetracarboxylic diphenylimide (NTCDI) having a rich ?-stacking charge delivery system is used to enhance the performance of SAM-OFET and SAM PVC devices. Charge mobility in SAM-OFET could achieve values of more than 30 cm2 V-1 s-1. The dynamics of charge transport in NTCDI-derived SAM-OFETs were probed using time-resolved measurements in an NTCDI-derived photovoltaic cell device. Time-resolved photovoltaic studies allow us to separate the charge annihilation kinetics in the conductive NTCDI channel from the overall charge kinetic in a SAM-OFET device. It has been demonstrated that tuning of the type of conductivity in NTCDI SAM-OFET devices is possible by changing Si substrate doping. In addition, the possibility of measuring transport in highly ordered SAM structures shines light on the polaron charge transfer in organic materials. Our study proposes that a cation-radical exchange (redox) mechanism is the major transport mechanism in SAM nanodevices. The role and contribution of the transport through delocalized states of redox active surface molecular aggregates of NTCDI are exposed and investigated in this report.

Pakoulev, Andrei V.; Burtman, Vladimir

2010-03-01

171

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

1980-06-06

172

Calcium transport mechanisms in basolateral plasma membrane-enriched vesicles from rat parotid gland.  

Science.gov (United States)

Ca2+ transport was studied by using basolateral plasma membrane vesicles from rat parotid gland prepared by a Percoll gradient centrifugation method. In these membrane vesicles, there were two Ca2+ transport systems; Na+/Ca2+ exchange and ATP-dependent Ca2+ transport. An outwardly directed Na+ gradient increased Ca2+ uptake. Ca2+ efflux from Ca2+-preloaded vesicles was stimulated by an inwardly directed Na+ gradient. However, Na+/Ca2+ exchange did not show any 'uphill' transport of Ca2+ against its own gradient. ATP-dependent Ca2+ transport exhibited 'uphill' transport. An inwardly directed Na+ gradient also decreased Ca2+ accumulation by ATP-dependent Ca2+ uptake. The inhibition of Ca2+ accumulation was proportional to the external Na+ level. Na+/Ca2+ exchange was inhibited by monensin, tetracaine and chlorpromazine, whereas ATP-dependent Ca2+ transport was inhibited by orthovanadate, tetracaine and chlorpromazine. Oligomycin had no effect on either system. These results suggest that in the parotid gland cellular free Ca2+ is extruded mainly by an ATP-dependent Ca2+ transport system, and Na+/Ca2+ exchange may modify the efficacy of that system.

Takuma, T; Kuyatt, B L; Baum, B J

1985-01-01

173

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

Energy Technology Data Exchange (ETDEWEB)

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.

Carreras, B.A.

1993-01-01

174

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

Energy Technology Data Exchange (ETDEWEB)

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.

Carreras, B.A.

1993-01-01

175

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Nakonechnaya Darina Yu.

2013-01-01

176

Telomere Healing Following DNA polymerase Arrest Induced Breakages is likely the Main Mechanism Generating Chromosome 4p Terminal Deletions  

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Abstract Constitutional developmental disorders are frequently caused by terminal chromosomal deletions. The mechanisms and/or architectural features that might underlie those chromosome breakages remain largely unexplored. Since telomeres are the vital DNA protein complexes stabilizing linear chromosomes against chromosome degradation, fusion and incomplete replication, those terminal deleted chromosomes acquired new telomeres either by telomere healing or by telomere capture. To ...

2010-01-01

177

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

178

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

2013-12-16

179

Mechanism of ion transport during anodic oxidation Pf Cdsub(x)Hgsub(1-x)Te  

International Nuclear Information System (INIS)

The mechanism of ion transport during anodic oxidation of Cdsub(x)Hgsub(1-x)Te has been studied by the labelled layer technique with the use of 18O isotope and B) as labels. The label distribution profile in the ox1de has been defined by secondary ion mass-spectrometry. The vacancy oxygen higration is shown to be the determining mechanism in ion transport through the anodic oxide. An assumption is made that the existence of a positive fixed charge in the Cdsub(x)Hsub(1-x)Te anodic oxide is explained by the presence of oxygen vacancies

1984-03-01

180

Mechanism of ion transport during anodic oxidation of Cdsub(x)Hgsub(1-x)Te  

Energy Technology Data Exchange (ETDEWEB)

The mechanism of ion transport during anodic oxidation of Cdsub(x)Hgsub(1-x)Te has been studied by the labelled layer technique with the use of /sup 18/O isotope and B) as labels. The label distribution profile in the oxide has been defined by secondary ion mass-spectrometry. The vacancy oxygen migration is shown to be the determining mechanism in ion transport through the anodic oxide. An assumption is made that the existence of a positive fixed charge in the Cdsub(x)Hsub(1-x)Te anodic oxide is explained by the presence of oxygen vacancies.

Beketov, G.V.; Bibik, V.F.; Matsas, E.P.; Titov, V.A. (AN Ukrainskoj SSR, Kiev. Inst. Fiziki)

1984-03-01

 
 
 
 
181

Qualitative Assessment of Flow and Transport Mechanisms in Bioremediation Processes  

Science.gov (United States)

Recent studies suggest that time-lapse crosshole geophysical methods may be effective in monitoring subsurface hydrological and biochemical mechanisms. These methods have potential to provide a minimally invasive, cost-effective, high resolution, field relevant means to gain information previously limited to wellbore data. Our study area is located at a DOE Hanford site, an area heavily polluted with toxic chromate. Time- lapse crosshole seismic and radar data sets have been collected in order to monitor spatio-temporal responses to these processes. Before using these data for parameter estimation and monitoring hydrobiogeochemical processes, we need to 1) identify the critical parameters involved in these processes; 2) determine the sensitivity of seismic/radar responses to these parameters; and 3) choose the most appropriate forward modeling approach for forward and inverse modeling. In this study, we treat critical parameters (e.g., hydraulic conductivity, flow rate, and the dispersion coefficients) as random variables, which can be described by their probabilistic density distributions. Then we adopt stochastic sampling method within the Minimum relative entropy (MRE) framework to generate many realistic models based on the welllog data. From here, the geophysical (crosshole seismic and radar) responses are computed using different forward models to study the sensitivity of the responses to those aforementioned parameters, and the performances of the different forward modeling approaches are compared. Finally, geophysical data are used for hydrobiogeochemical parameter estimation through Bayesian inverse modeling. Our study provides guidance on favorable situations in which borehole geophysical data can be effectively used for monitoring subsurface hydrobiogeochemical processes.

Terry, N.; Hou, Z.

2008-12-01

182

From statistic mechanic outside equilibrium to transport equations; De la mecanique statistique hors equilibre aux equations de transport  

Energy Technology Data Exchange (ETDEWEB)

This lecture notes give a synthetic view on the foundations of non-equilibrium statistical mechanics. The purpose is to establish the transport equations satisfied by the relevant variables, starting from the microscopic dynamics. The Liouville representation is introduced, and a projection associates with any density operator , for given choice of relevant observables, a reduced density operator. An exact integral-differential equation for the relevant variables is thereby derived. A short-memory approximation then yields the transport equations. A relevant entropy which characterizes the coarseness of the description is associated with each level of description. As an illustration, the classical gas, with its three levels of description and with the Chapman-Enskog method, is discussed. (author). 3 figs., 5 refs.

Balian, R. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Service de Physique Theorique

1995-12-31

183

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

184

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

185

Charge transport in poly-imidazole membranes: a fresh appraisal of the Grotthuss mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A detailed theoretical investigation of the charge transport mechanism in poly(4-vinyl-imidazole) (P4VI), the parent polymer of a series of N-heterocyclic-based membranes used as an electrolyte in proton exchange membrane fuel cells, is presented. In particular, Density Functional Theory (DFT) results obtained for small model systems (protonated imidazole dimers and trimers) suggest that the commonly accepted conduction mechanism, based on a sequential proton transfer between imidazole moieti...

2012-01-01

186

Growth mechanism of ZnSe single crystal by chemical vapour transport method  

International Nuclear Information System (INIS)

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

2006-04-01

187

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

Science.gov (United States)

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

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

2012-12-01

188

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

1988-01-01

189

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

190

Protein transport across nanopores: a statistical mechanical perspective from coarse-grained modeling and approaches.  

Science.gov (United States)

We survey the transport of proteins across nanopores in the framework of coarse-grained modeling. The advantage of a reduced complexity with respect to full-atomistic techniques lies in the possibility of massive sampling of events, thus allowing a statistical mechanical description of translocation in terms of ensemble averages. Often, protein transport through narrow channels tightly couples with unfolding pathways causing a richer phenomenology compared to unstructured polymer translocation. This reflects into a process controlled by the presence of protein-specific free-energy barriers which can be conveniently estimated by statistical mechanical methods implemented in coarse-grained simulations. We illustrate how protein transport dynamics can be characterized by the statistical properties of trajectories and sometimes interpreted as driven diffusion of a single collective coordinate over a free-energy landscape. We also discuss, through selected examples, the connection between reduced-model simulations and recent experimental results. PMID:24370254

Cecconi, Fabio; Bacci, Marco; Chinappi, Mauro

2014-03-01

191

En-route mechanical activation of viscous oil and oil products transported in railroad tank cars  

Directory of Open Access Journals (Sweden)

Full Text Available The authors of this document are aiming to substantiate the advantages of en-route mechanical activation technology as aids for railroad transportation of viscous oil and oil products in tank cars. The conceptual design implies the use of momentum generated by brake action. This document also contains preliminary data of laboratory research confirming the validity of the developed concept.

Yerlan MYRZAKHMETOV

2012-01-01

192

The collective mechanism of mass transport in surface layers of irradiated materials  

International Nuclear Information System (INIS)

The new collective mechanism of mass transport connected with diffusion of submicroscopic dislocation loops (SDL) which can act in surface layers of radiated crystalline materials is proposed and substantiated. It is shown that in real conditions SDL can diffuse essentially faster then point defects

2001-12-01

193

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

194

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

Energy Technology Data Exchange (ETDEWEB)

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.

Azarm, M.A.; Boccio, J.L.; Mitra, S.

1985-12-01

195

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

1985-01-01

196

MAIN FEATURES OF THE MECHANISM OF FORMATION THE SURFACE GRINDING WITH THE PERIPHERY OF A STRAIGHT DISK  

Directory of Open Access Journals (Sweden)

Full Text Available The article deals with the problem of stationary provision of grinding surface by creating the uniform abrasive impact on it. Mechanisms of forming the non-uniform abrasive action on machined surface grinding with the periphery of a start disk have been defined. It was revealed that stationary breaking of micro and macro geometry of grinding surfaces basically occurs in the areas of input of grinding disk in contact with machined surface and output from it and in the areas of configuration changes of machined surface. On the basis of analysis of analytical expressions, a new construction of the grinding disk has been worked out. It was determined that uniform abrasive action on machined surface is being provided at grinding with varied grained disk, therefore high grinding efficiency. It is explained with the concentrating on the operating surface of anisomerous grinding disk of granularity, starting with rough and ending with thin, allows combining the elements of rough and smooth grinding in one processing step. .

Gusseinov Gassan Ahmad

2014-03-01

197

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

198

Quantum mechanics of Dirac particle beam transport through optical elements with straight and curved axes  

CERN Document Server

Classical mechanical treatment of charged particle beam optics is so far very satisfactory from a practical point of view in applications ranging from electron microscopy to accelerator technology. However, it is desirable to understand the underlying quantum mechanics since the classical treatment is only an approximation. Quantum mechanical treatment of spin-1/2 particle beam transport through optical elements with straight optic axes, based on the proper equation, namely, the Dirac equation, has been developed already to some extent. In such a theory the orbital and spin motions are treated within a unified framework. Here, after a brief review of the Dirac spinor beam optics for systems with straight optic axes it is outlined how the application of the formalism of general relativity leads to the use of the Dirac equation for getting a quantum theory of spin-1/2 beam transport through optical elements with curved axes.

Jaganathan, R

2003-01-01

199

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

2001-01-01

200

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

Science.gov (United States)

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

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

2013-12-01

 
 
 
 
201

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

202

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

203

Electrical Imaging of Saline Tracer Migration for the Investigation of Unsaturated Zone Transport Mechanisms  

Directory of Open Access Journals (Sweden)

Full Text Available Abstract: Better understanding of field-scale unsaturated zone transport mechanisms is required if the fate of contaminants released at the surface is to be predicted accurately. Interpretation of results from direct tracer sampling in terms of operative hydraulic processes is often limited by the poor spatial coverage and the invasive nature of such techniques. Cross-borehole electrical imaging during progress of saline tracer migration is proposed to assist investigation of field-scale solute transport in the unsaturated zone. Electrical imaging provides non-destructive, high density and spatially continuous sampling of saline tracer transport injected over an area of the ground surface between two boreholes. The value of electrical imaging was tested at a field site on an interfluve of the UK Chalk aquifer. Improved understanding of active transport mechanisms in the unsaturated zone of the UK Chalk is required to predict its vulnerability to surface pollutants. In a tracer experiment in May 1996, a conductive saline tracer was infiltrated over 18 m2 at an average rate of 47 mm day-1 for 56 hours. Cross-borehole images obtained during and after infiltration show a large, homogenous, resistivity reduction in the top 3 m, no change between 3 m and 6 m depth, and smaller, inhomogeneous, resistivity reductions below 6 m depth. The resistivity has reduced at down to 15 m depth less than 2 days after tracer infiltration began. Hydrological interpretation of a sequence of electrical images obtained prior to, during, and up to three months after tracer injection suggests: (1 rapid tracer entry into the soil zone and upper 2 m of weathered Chalk, (2 intergranular transport of the bulk of the tracer, (3 a significant fissure flow component transporting tracer to at least 15 m depth in 31 hours, and (4 vertical changes in transport mechanisms possibly caused by interception of fissures by marl layers. The results of this experiment suggest that electrical imaging can assist the description of unsaturated zone hydraulic mechanisms through visual identification of spatial and temporal variations in transport processes.

L. Slater

1997-01-01

204

Mechanism of NaCl transport-stimulated prostaglandin formation in MDCK cells  

International Nuclear Information System (INIS)

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

1987-01-01

205

Kinetic Evidence Is Consistent with the Rocker-Switch Mechanism of Membrane Transport by GlpT†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Secondary active transport of substrate across the cell membrane is crucial to many cellular and physiological processes. The crystal structure of one member of the secondary active transporter family, the sn-glycerol-3-phosphate (G3P) transporter (GlpT) of the inner membrane of Escherichia coli, suggests a mechanism for substrate translocation across the membrane that involves a rocker-switch-type movement of the protein. This rocker-switch mechanism makes two specific predictions with respe...

Law, Christopher J.; Yang, Qiang; Soudant, Celine; Maloney, Peter C.; Wang, Da-neng

2007-01-01

206

Neutrino-driven supernovae Boltzmann neutrino transport and the explosion mechanism  

CERN Multimedia

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

207

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

2008-01-01

208

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

209

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

210

Mechanical evaluation of a natural UF{sub 6} transport container at high temperature  

Energy Technology Data Exchange (ETDEWEB)

International Atomic Energy Agency (IAEA) revised the transport regulation for natural uranium hexafluoride (UF{sub 6}) 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 UF{sub 6} 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 UF{sub 6} 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 UF{sub 6} transport container was proposed based on the CRIEPI's material tests and applied to the ABAQUS computer code. According to the mechanical non-linear analysis results, it was found that it is necessary to evaluate the safety margin for the rupture of the 48Y-cylinder because considerable plastic and creep deformations are generated due to the temperature distribution of the cylinder and the inner pressure. This thermal-mechanical behavior of the container will be verified according to the rupture test results of the 48Y-cylinder until the end of 1998. (authors)

Shirai, K.; Wataru, M.; Kosaki, A.; Saegusa, T. [Central Research Inst. of Electric Power Industry, Abiko, Chiba (Japan); Shimamura, K. [Ishikawajima-Harima Heavy Industries Co. Ltd., Tokyo (Japan)

1998-07-01

211

Mechanism of ionophoric transport of indium-111 cations through a lipid bilayer membrane  

International Nuclear Information System (INIS)

The use of mobile ionophores to facilitate the transport of "1"1"1In through a lipid bilayer membrane has broad applications in liposome technology and cell labeling. However, the mechanism of such ionophore-mediated transport of "1"1"1In through a lipid bilayer membrane is not completely clear. The present report describes the correlations of the behaviors of ionophoric loading of "1"1"1In into liposomes with the lipophilicity and the indium-binding affinity of three ionophores, namely, 8-hydroxyquinoline, acetylacetone, and tropolone. Our results suggest that the mechanism of the ionophoric transport of "1"1"1In through a lipid bilayer membrane involves the rapid exchange of "1"1"1In cations among the ionophores in both the aqueous solution and the lipid bilayer. Furthermore, the effectiveness of an ionophore in facilitating the transport of "1"1"1In from the external aqueous compartment to the entrapped nitrilotriacetic acid depends not only on the lipophilicity of the ["1"1"1In]ionophore complex, but also on the lipophilicity of the free ionophore itself and the competition of "1"1"1In between nitrilotriacetic acid inside the inner aqueous compartment of the liposome and the ionophore imbedded in the lipid bilayer membrane of the liposome

1987-01-01

212

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

Energy Technology Data Exchange (ETDEWEB)

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

Overton, W.C. Jr.; Weinstock, H.

1981-01-01

213

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

CERN Document Server

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

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

2004-01-01

214

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

CERN Multimedia

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

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

2011-01-01

215

Mechanism of charge transport in Si/Al2O3/Al structures  

International Nuclear Information System (INIS)

The investigation of current – voltage characteristics of structures Si/Al2O3/Al on the basis of aluminium oxide layers obtained by a method atomic layer deposition is carried out. It is established, that the possible mechanism of charge transport in structure is the space charge limited currents. The charge carrier concentration (Nt), concentration of traps (n0) and electron mobility (?) in Al2O3 layer are calculated

2013-08-28

216

Investigation of Neutrino-Driven Convection and the Core Collapse Supernova Mechanism Using Multigroup Neutrino Transport  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate neutrino-driven convection in core collapse supernovae and its ramifications for the explosion mechanism, for a 15 solar mass model. Our two-dimensional simulation begins at 12 ms after bounce and proceeds for 500 ms. We couple two-dimensional PPM hydrodynamics to precalculated one-dimensional MGFLD neutrino transport. (The accuracy of this approximation is assessed.) For the moment we sacrifice dimensionality for realism in other aspects of our neutrino trans...

Mezzacappa, A.; Calder, A. C.; Bruenn, S. W.; Blondin, J. M.; Guidry, M. W.; Strayer, M. R.; Umar, A. S.

1997-01-01

217

Neutrino-driven supernovae: Boltzmann neutrino transport and the explosion mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 t...

Messer, O. E. B.; Mezzacappa, A.; Bruenn, S. W.; Guidry, M. W.

1998-01-01

218

Fluorescence study of the divalent cation-transport mechanism of ionophore A23187 in phospholipid membranes.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The mechanism for transport of divalent cations across phospholipid bilayers by the ionophore A23187 was investigated. The intrinsic fluorescence of the ionophore was used in equilibrium and rapid-mixing experiments as an indicator of ionophore environment and complexation with divalent cations. The neutral (protonated) form of the ionophore binds strongly to the membrane, with a high quantum yield relative to that in the aqueous phase. The negatively charged form of the ionophore binds somew...

Kolber, M. A.; Haynes, D. H.

1981-01-01

219

Mechanics of transport phenomena in multi-component sessile drops with solidification  

Science.gov (United States)

The mechanics of transport phenomena in multicomponent sessile drops with internal solidification is determined on the basis of an experimental study. A shadowgraph-schlieren system and a microscope-video system are used for the study. It is suggested that present data can be used to enhance the solid or crystal quality in a reduced-gravity environment where both thermo- and diffuso-capillary effects of solidification and crystal growth are dominant.

Su, Yeong-Jen; Yang, Wen-Jei; Liu, Jiaching

1990-01-01

220

Microscale modeling of coupled water transport and mechanical deformation of fruit tissue during dehydration  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Water loss of fruit typically results in fruit tissue deformation and consequent quality loss. To better understand the mechanism of water loss, a model of water transport between cells and intercellular spaces coupled with cell deformation was developed. Pear (Pyrus communis L. cv. Conference) was chosen as a model system as this fruit suffers from shriveling with excessive water loss. A 2D geometric model of cortex tissue was obtained by a virtual fruit tissue generator that is based on cel...

2014-01-01

 
 
 
 
221

Baryogenesis with vector-like quark model in charge transport mechanism  

CERN Multimedia

The electroweak baryogenesis is studied in the charge transport mechanism with the vector-like quark model. Introducing an extra vector-like up-type quark and a singlet Higgs scalar with the mass of the order of a few hundred GeV, the baryon number generation from the bubble wall is estimated. We show that this scenario is consistent with the measurement of the present baryon to entropy ratio of our universe, if the parameters are in the right region.

Uesugi, T; Yamaguchi, A

1997-01-01

222

Charge transport mechanism in intercalated Cu x HfSe2 compounds  

Science.gov (United States)

Alternating current resistivity measurements have been performed for the first time on intercalated Cu x HfSe2 (0 ? x ? 0.18) samples using the impedance spectroscopy technique together with direct current measurements. The results obtained indicate the hopping mechanism of charge transport in Cu x HfSe2 compounds. It has been found that an increase in the copper content in samples enhances relaxation processes. The ac conductivity exhibits frequency dispersion described by the universal dynamic response.

Pleshchev, V. G.; Baranov, N. V.; Melnikova, N. V.; Selezneva, N. V.

2012-07-01

223

Mechanisms of Laser-Induced Dissection and Transport of Histologic Specimens  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Rapid contact- and contamination-free procurement of histologic material for proteomic and genomic analysis can be achieved by laser microdissection of the sample of interest followed by laser-induced transport (laser pressure catapulting). The dynamics of laser microdissection and laser pressure catapulting of histologic samples of 80 ?m diameter was investigated by means of time-resolved photography. The working mechanism of microdissection was found to be plasma-mediated ablation initiate...

Vogel, Alfred; Lorenz, Kathrin; Horneffer, Verena; Hu?ttmann, Gereon; Von Smolinski, Dorthe; Gebert, Andreas

2007-01-01

224

Mechanism of hypercalciuria in genetic hypercalciuric rats. Inherited defect in intestinal calcium transport.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Excessive urine calcium excretion in patients with idiopathic hypercalciuria may involve a primary increase in intestinal calcium absorption, overproduction of 1,25-dihydroxyvitamin D3 or a defect in renal tubular calcium reabsorption. To determine the mechanism of hypercalciuria in an animal model, hypercalciuria was selected for in rats and the most hypercalciuric animals inbred. Animals from the fourth generation were utilized to study mineral balance and intestinal transport in relation t...

Bushinsky, D. A.; Favus, M. J.

1988-01-01

225

Specificity and mechanism of ferrioxamine-mediated iron transport in Streptomyces pilosus.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although the ferrioxamines are an important and well-characterized class of siderophores produced by several species of Nocardia, Streptomyces, Micromonospora, Arthrobacter, Chromobacterium, and Pseudomonas, no studies of the mechanism of ferrioxamine-mediated iron uptake have been performed for an organism which produces the siderophore. This is the first report of metal transport in Streptomyces pilosus mediated by the native ferrioxamines B, D1, D2, and E. 55Fe accumulation in these ferrio...

Mu?ller, G.; Raymond, K. N.

1984-01-01

226

The study of placental L-ascorbate (vitamin C) transport mechanism (using microvillous membrane vesicles).  

Science.gov (United States)

To investigate the placental L-ascorbate (Vitamin C) transport mechanism, the uptake of L-ascorbate into microvillous membrane vesicles prepared from human term placenta was studied using the rapid filtration technique. The uptake of L-ascorbate into microvillous membrane vesicles was osmotically sensitive. This finding indicated that the uptake of L-ascorbate into microvillous membrane vesicles represented transport into the vesicles. The uptake of L-ascorbate into microvillous membrane vesicles was not dependent on sodium electrochemical gradient. The initial rate of uptake was not changed when the intravesicular space was rendered electrically more negative by membrane diffusion potential induced by the use of highly permeant anions. The initial rate of L-ascorbate transport exhibited saturation kinetics with respect to the L-ascorbate concentration; an apparent Km of 1.33 mM and Vmax of 47p mol/mg protein/20 sec was calculated. The uptake of L-ascorbate into microvillous membrane vesicles was competitively inhibited by D-isoascorbate. These results indicated that transport of L-ascorbate across the placental microvillous membrane vesicles was carrier mediated and was passive transport. PMID:3598278

Iioka, H; Moriyama, I; Kyuma, M; Akasaki, M; Katoh, Y; Itoh, K; Hino, K; Okamura, Y; Ninomiya, Y; Kiyozuka, Y

1987-05-01

227

Intramuscular Drug Transport Under Mechanical Loading: Resonance Between Tissue Function and Uptake  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Dynamic architecture and motion in mechanically active target tissues can influence the pharmacokinetics of locally delivered agents. Drug transport in skeletal muscle under controlled mechanical loads was investigated. Static (0–20%) and cyclic (±2.5% amplitude, 0–20% mean, 1–3 Hz) strains and electrically paced isometric contractions (0.1–3 Hz, 0% strain) were applied to rat soleus incubated in 1 mM 20 kDa FITC-dextran. Dextran penetration, tissue porosity, and active force-length ...

Wu, Peter I.; Minisini, Sara; Edelman, Elazer R.

2009-01-01

228

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

1986-01-01

229

Role of osmium in the electrical transport mechanism of polycrystalline tin oxide thin films  

Science.gov (United States)

Undoped and Os-doped SnO2 thin films have been deposited by the sol-gel method. Their electrical properties have been investigated by resistivity and Hall effect measurements in order to understand the role of Os in the electrical transport mechanism. The measurements have been carried out in 100-500 K temperature range both in a vacuum and in air. The experimental results have been analyzed according to the grain-boundary scattering mechanism and they have been used to explain the response toward CH4 of the Os-doped SnO2 thin-film-based gas sensors.

Forleo, A.; Capone, S.; Epifani, M.; Siciliano, P.; Rella, R.

2004-02-01

230

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

231

Multi-scale transport dynamics dominated by multiple dissipation mechanisms near the critical gradient  

International Nuclear Information System (INIS)

We found a new class of transient transport near the critical gradient (CG) referred to as GAM growing intermittency, which is caused by the collision-less GAM damping and leads to dynamical establishment of the Dimits shift. Here, we present a new predator-prey model which includes the effect of anisotropic pressure perturbation (GAM) and parallel ion sound velocity and successfully reproduces the essential features of the growing intermittency. We have also extended the simulation model by taking into account the collisional zonal flow (ZF) damping. Due to the mixture of two kinds of damping mechanisms, i.e., the GAM damping and collisional damping, the growing intermittency is found to recursively appear accompanied with complex envelope modulation to ZFs over collisional (or transport) time scale. Furthermore, we have investigated the effect of zonal pressure (ZP) near the CG, which also works as a dissipation mechanism. The ZP changes the temperature scale length through the coupling with GAMs and causes a sudden termination of the growing intermittency. Thus, the multiple dissipation mechanisms are found to synergetically couple each other and lead plasmas to complex dynamical transport over long time scale. (author)

2008-10-13

232

Variability of the transport of anthropogenic CO2 at the Greenland-Portugal OVIDE section: controlling mechanisms  

Science.gov (United States)

The interannual to decadal variability in the transport of anthropogenic CO2 (Cant) across the subpolar North Atlantic (SPNA) is investigated, using summer data of the FOUREX and OVIDE high-resolution transoceanic sections, from Greenland to Portugal, occupied six times from 1997 to 2010. The transport of Cant across this section, Tcant hereafter, is northward, with a mean value of 254 ± 29 kmol s-1 over the 1997-2010 period. We find that Tcant undergoes interannual variability, masking any trend different from 0 for this period. In order to understand the mechanisms controlling the variability of Tcant across the SPNA, we propose a new method that quantifies the transport of Cant caused by the diapycnal and isopycnal circulation. The diapycnal component yields a large northward transport of Cant (400 ± 29 kmol s-1) that is partially compensated by a southward transport of Cant caused by the isopycnal component (-171 ± 11 kmol s-1), mainly localized in the Irminger Sea. Most importantly, the diapycnal component is found to be the main driver of the variability of Tcant across the SPNA. Both the Meridional Overturning Circulation (computed in density coordinates, MOC?) and the Cant increase in the water column have an important effect on the variability of the diapycnal component and of Tcant itself. Based on this analysis, we propose a simplified estimator for the variability of Tcant based on the intensity of the MOC? and on the difference of Cant between the upper and lower limb of the MOC? (?Cant). This estimator shows a good consistency with the diapycnal component of Tcant, and help to disentangle the effect of the variability of both the circulation and the Cant increase on the Tcant variability. We find that ?Cant keeps increasing over the past decade, and it is very likely that the continuous Cant increase in the water masses will cause an increase in Tcant across the SPNA at long timescale. Nevertheless, at the timescale analyzed here (1997-2010), the MOC? controls the Tcant variability, blurring any Tcant trend. Extrapolating the observed ?Cant increase rate and considering the predicted slow-down of 25% of the MOC?, Tcant across the SPNA is expected to increase by 430 kmol s-1 during the 21st century. Consequently, an increase in the storage rate of Cant in the SPNA could be envisaged.

Zunino, P.; Garcia-Ibañez, M. I.; Lherminier, P.; Mercier, H.; Rios, A. F.; Pérez, F. F.

2014-04-01

233

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

234

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

2013-05-30

235

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

International Nuclear Information System (INIS)

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

1982-01-01

236

The transport mechanism of bacterial Cu+-ATPases: distinct efflux rates adapted to different function.  

Science.gov (United States)

Cu(+)-ATPases play a key role in bacterial Cu(+) homeostasis by participating in Cu(+) detoxification and cuproprotein assembly. Characterization of Archaeoglobus fulgidus CopA, a model protein within the subfamily of P(1B-1) type ATPases, has provided structural and mechanistic details on this group of transporters. Atomic resolution structures of cytoplasmic regulatory metal binding domains (MBDs) and catalytic actuator, phosphorylation, and nucleotide binding domains are available. These, in combination with whole protein structures resulting from cryo-electron microscopy analyses, have enabled the initial modeling of these transporters. Invariant residues in helixes 6, 7 and 8 form two transmembrane metal binding sites (TM-MBSs). These bind Cu(+) with high affinity in a trigonal planar geometry. The cytoplasmic Cu(+) chaperone CopZ transfers the metal directly to the TM-MBSs; however, loading both of the TM-MBSs requires binding of nucleotides to the enzyme. In agreement with the classical transport mechanism of P-type ATPases, occupancy of both transmembrane sites by cytoplasmic Cu(+) is a requirement for enzyme phosphorylation and subsequent transport into the periplasmic or extracellular milieus. Recent transport studies have shown that all Cu(+)-ATPases drive cytoplasmic Cu(+) efflux, albeit with quite different transport rates in tune with their various physiological roles. Archetypical Cu(+)-efflux pumps responsible for Cu(+) tolerance, like the Escherichia coli CopA, have turnover rates ten times higher than those involved in cuproprotein assembly (or alternative functions). This explains the incapability of the latter group to significantly contribute to the metal efflux required for survival in high copper environments. PMID:21210186

Raimunda, Daniel; González-Guerrero, Manuel; Leeber, Blaise W; Argüello, José M

2011-06-01

237

Mechanical and transport properties of IBAD/EDDC-SmBCO coated conductor tapes during fatigue loading  

Science.gov (United States)

In electrical devices like superconducting motor, generator and SMES, HTS coated conductor (CC) tapes will be subjected to alternating stress or strain during manufacturing and operation. The repeated loading will affect the mechanical integrity and eventually the electrical transport property of CC tapes. Therefore in such applications, electro-mechanical property of CC tapes should be evaluated. In this study, the endurance of an IBAD/EDDC-SmBCO CC tape under high-cycle fatigue loading has been evaluated. Applied maximum stress and fatigue life ( S-N) relation was obtained at 77 K. The mechanical properties and the critical current, I c, of the sample under fatigue loading were investigated at 77 K. Considering the practical operating environment, the effect of the stress ratio R, on the degradation behavior of I c under fatigue loading was also examined.

Shin, Hyung-Seop; Dedicatoria, Marlon J.

2011-06-01

238

Mechanisms of 1D crystal growth in reactive vapor transport: indium nitride nanowires.  

Science.gov (United States)

Indium nitride (InN) nanowire synthesis using indium (In) vapor transport in a dissociated ammonia environment (reactive vapor transport) is studied in detail to understand the nucleation and growth mechanisms involved with the so-called "self-catalysis" schemes. The results show that the nucleation of InN crystal occurs first on the substrate. Later, In droplets are formed on top of the InN crystals because of selective wetting of In onto InN crystals. Further growth via liquid-phase epitaxy through In droplets leads the growth in one dimension (1D), resulting in the formation of InN nanowires. The details about the nucleation and growth aspects within these self-catalysis schemes are rationalized further by demonstrating the growth of heteroepitaxially oriented nanowire arrays on single-crystal substrates and "tree-like" morphologies on a variety of substrates. However, the direct nitridation of In droplets using dissociated ammonia results in the spontaneous nucleation and basal growth of nanowires directly from the In melt surface, which is quite different from the above-mentioned nucleation mechanism with the reactive vapor transport case. The InN nanowires exhibit a band gap of 0.8 eV, whereas the mixed phase of InN and In(2)O(3) nanowires exhibit a peak at approximately 1.9 eV in addition to that at 0.8 eV. PMID:16089500

Vaddiraju, Sreeram; Mohite, Aditya; Chin, Alan; Meyyappan, M; Sumanasekera, Gamini; Alphenaar, Bruce W; Sunkara, Mahendra K

2005-08-01

239

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

Energy Technology Data Exchange (ETDEWEB)

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

Subekti, A.; Chin, V. W. L.; Tansley, T. L. [Macquarie University, Sydney, NSW (Australia). Semiconductor Science and Technology Laboratories

1996-12-31

240

Carrier transport mechanism in indium tin oxide (ITO)/silicon heterojunctions: effect of chlorine  

International Nuclear Information System (INIS)

Transparent-conducting-oxide (TCO)-based photovoltaic junctions have shown complexity in the transport phenomena at the interface. The present study is an attempt to understand the effect of chlorine at the interface between indium tin oxide (ITO) and Si. The ITO/Si junctions have been prepared by depositing transparent and conducting tin-doped indium oxide (ITO) thin films on as-cleaned and chlorine-treated single-crystal p-type and n-type silicon substrates using the reactive electron-beam evaporation technique. ITO/n-Si junctions have shown photovoltaic properties. The photoconversion efficiency of these junctions is observed to increase from 2.3% to 5.5% under chlorine treatment. The transport mechanism across these junctions has been studied by current-voltage (I-V, both dark and illuminated) and capacitance-voltage (C-V) characterisation techniques. The carrier transport mechanism is found to be dominated by recombination at the depletion region for the junctions prepared with chlorine treatment, whereas for the other junctions, the thermionic process seems to be prominent. The unrealistic barrier heights observed in these junctions by the C-V technique confirms the complex nature of the interface. (orig.)

2005-02-01

 
 
 
 
241

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.)

1994-01-01

242

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

Energy Technology Data Exchange (ETDEWEB)

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.)

Kerstiens, G. [Inst. of Environmental and Biological Sciences, Div. of Biological Sciences, Lancaster Univ. (United Kingdom)

1994-12-31

243

Toda lattice mass transport in Lagrangian mechanics and in a two-dimensional system  

Science.gov (United States)

This paper explores the connection between the hydrodynamic mass transport description and the thermodynamic description for a nonlinear range of the Toda lattices. Particular attention is paid to the broken isotropy in the KdV and Burgers equations. The flow variable representation is established from the Lagrangian mechanics for hydrodynamic mass transport. Based on the inverse scattering transform, the Gel’fand-Levitan-Marchenko (GLM) equation is formulated from the KdV equation expressed by the flow variable representation. We found that a kernel of the GLM equation is given by the concentration variable Q(x,t). A Lagrangian is formulated for the KdV equation in state space (Q(x,t),K(x,t)). Next, an extension of the flow variable representation is sought in a two-dimensional system. The LHS of the Kadomtsev-Petviashvili (KP) equation takes the same form as in the second formalism of the KdV equation. By setting up the flow variable representation of the KP equation, the Burgers equation in two dimensions is formulated. These results contribute to an understanding of the broken isotropy for the nonlinear mass transport equations. These results provide physical insight into various consequences of the generalized form of the Kawasaki-Ohta equation from the viewpoint of mass transport.

Horii, Zene

2006-03-01

244

Mechanisms of heat transport across a nano-scale gap in heat assisted magnetic recording  

Science.gov (United States)

This paper compares different mechanisms of heat transport across nano-scale gaps and discusses the role of electromagnetic phenomena in heat transport in general nano-scale layered structures. The results of the analysis suggest that heat transfer across sub-5 nm gaps like that appearing in prototypes of heat assisted magnetic recording (HAMR) systems is dominated by direct intermolecular interactions between the separated bodies and is little affected by electromagnetic radiation. The analysis further suggests that local heating for HAMR with sub-5 nm spacing can be more efficiently achieved by a Joule heater that is simpler to fabricate than laser-based optical systems and is less destructive for the nano-scale transducers than laser radiation, which may lead to their structural damage and short duration life of nanoscale transducers.

Budaev, Bair V.; Bogy, David B.

2012-06-01

245

Mechanical properties of ductile cast iron and cast steel for intermediate level waste transport containers  

International Nuclear Information System (INIS)

UK Nirex Ltd is developing Type B re-usable shielded transport containers (RSTCs) in a range of shielding thicknesses to transport intermediate level radioactive waste (ILW) to a deep repository. The designs are of an essentially monolithic construction and rely principally on the plastic flow of their material to absorb the energies involved in impact events. Nirex has investigated the feasibility of manufacturing the RSTCs from ductile cast iron (DCI) or cast steel instead of from forgings, since this would bring advantages of reduced manufacturing time and costs. However, cast materials are perceived to lack toughness and ductility and it is necessary to show that sufficient fracture toughness can be obtained to preclude brittle failure modes, particularly at low temperatures. The mechanical testing carried out as part of that programme is described. It shows how the measured properties have been used to demonstrate avoidance of brittle fracture and provide input to computer modelling of the drop tests. (author)

1994-01-01

246

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

CERN Document Server

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

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

2014-01-01

247

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)

1988-01-01

248

Involvement of organic cation transporter 2 inhibition in potential mechanisms of antidepressant action.  

Science.gov (United States)

Novel antidepressants or treatment strategies that may offer a more rapid onset of action, improved efficacy, and greater tolerability are in desperate need. Because current clinically utilized antidepressants, which target high-affinity transporters for serotonin and norepinephrine, fail to provide satisfactory treatment outcomes for quite a portion of patients. In recent investigations, a low-affinity but high-capacity transporter organic cation transporter 2 (OCT2, SLC22A2) has been proposed as an important postsynaptic determinant of aminergic tonus and mood-related behaviors, a complementary system to the high-affinity transporters. In order to evaluate whether OCT2 inhibition may at least in part contribute to the pharmacological effects of antidepressants, several typical antidepressant compounds of various mechanism categories were employed to inhibit OCT2 activity in cells stably overexpressing OCT2. The tested antidepressant agents included selective serotonin reuptake inhibitors (SSRIs, fluoxetine, sertraline and paroxetine), tricyclic antidepressants (TCAs, amitriptyline, imipramine, desipramine), monoamine oxidase inhibitor (MAOI, moclobemide), serotonin-norepinephrine reuptake inhibitor (SNRI, venlafaxine) and reported antidepressant alkaloid piperine. Piperine was screened through synaptosomes before cell experiments, without the interference of monoamine oxidase. All of the nine antidepressant compounds showed moderate inhibitory effects on OCT2-mediated metformin, serotonin and/or norepinephrine uptake. Sertraline and desipramine tended to inhibit OCT2 activity via a competitive mechanism. The fact could be easily belied, since passive diffusion dominated the influx process. It remains to be seen whether OCT2 inhibition plays a role to the overall therapeutic effects in clinical practice. PMID:24657329

Wang, Kai; Sun, Siyuan; Li, Liping; Tu, Meijuan; Jiang, Huidi

2014-08-01

249

Formation of the mechanism of interaction of the motor transportation enterprise with subjects the market of the international freight traffics  

Directory of Open Access Journals (Sweden)

Full Text Available Takes up a question of formation of the mechanism of interaction of the motor transportation enterprise (MC in the market of the international cargo automobile transportations (ICAT with subjects of the market. Given the characteristic of the basic subjects which operate in market ICAT. The innovation model card clientenoughtable MC in market of ICAT is offered.

A.M.Ponomaryov

2011-12-01

250

The Role of Transport Mechanisms in Mycobacterium Tuberculosis Drug Resistance and Tolerance  

Directory of Open Access Journals (Sweden)

Full Text Available In the fight against tuberculosis, cell wall permeation of chemotherapeutic agents remains a critical but largely unsolved question. Here we review the major mechanisms of small molecule penetration into and efflux from Mycobacterium tuberculosis and other mycobacteria, and outline how these mechanisms may contribute to the development of phenotypic drug tolerance and induction of drug resistance. M. tuberculosis is intrinsically recalcitrant to small molecule permeation thanks to its thick lipid-rich cell wall. Passive diffusion appears to account for only a fraction of total drug permeation. As in other bacterial species, influx of hydrophilic compounds is facilitated by water-filled open channels, or porins, spanning the cell wall. However, the diversity and density of M. tuberculosis porins appears lower than in enterobacteria. Besides, physiological adaptations brought about by unfavorable conditions are thought to reduce the efficacy of porins. While intracellular accumulation of selected drug classes supports the existence of hypothesized active drug influx transporters, efflux pumps contribute to the drug resistant phenotype through their natural abundance and diversity, as well as their highly inducible expression. Modulation of efflux transporter expression has been observed in phagocytosed, non-replicating persistent and multi-drug resistant bacilli. Altogether, M. tuberculosis has evolved both intrinsic properties and acquired mechanisms to increase its level of tolerance towards xenobiotic substances, by preventing or minimizing their entry. Understanding these adaptation mechanisms is critical to counteract the natural mechanisms of defense against toxic compounds and develop new classes of chemotherapeutic agents that positively exploit the influx and efflux pathways of mycobacteria.

Jansy Passiflora Sarathy

2012-11-01

251

The role of transport mechanisms in mycobacterium tuberculosis drug resistance and tolerance.  

Science.gov (United States)

In the fight against tuberculosis, cell wall permeation of chemotherapeutic agents remains a critical but largely unsolved question. Here we review the major mechanisms of small molecule penetration into and efflux from Mycobacterium tuberculosis and other mycobacteria, and outline how these mechanisms may contribute to the development of phenotypic drug tolerance and induction of drug resistance. M. tuberculosis is intrinsically recalcitrant to small molecule permeation thanks to its thick lipid-rich cell wall. Passive diffusion appears to account for only a fraction of total drug permeation. As in other bacterial species, influx of hydrophilic compounds is facilitated by water-filled open channels, or porins, spanning the cell wall. However, the diversity and density of M. tuberculosis porins appears lower than in enterobacteria. Besides, physiological adaptations brought about by unfavorable conditions are thought to reduce the efficacy of porins. While intracellular accumulation of selected drug classes supports the existence of hypothesized active drug influx transporters, efflux pumps contribute to the drug resistant phenotype through their natural abundance and diversity, as well as their highly inducible expression. Modulation of efflux transporter expression has been observed in phagocytosed, non-replicating persistent and multi-drug resistant bacilli. Altogether, M. tuberculosis has evolved both intrinsic properties and acquired mechanisms to increase its level of tolerance towards xenobiotic substances, by preventing or minimizing their entry. Understanding these adaptation mechanisms is critical to counteract the natural mechanisms of defense against toxic compounds and develop new classes of chemotherapeutic agents that positively exploit the influx and efflux pathways of mycobacteria. PMID:24281307

Sarathy, Jansy Passiflora; Dartois, Véronique; Lee, Edmund Jon Deoon

2012-01-01

252

TRANSPORT  

Science.gov (United States)

Presentation outline: transport principles, effective solubility; gasoline composition; and field examples (plume diving). Presentation conclusions: MTBE transport follows from - phyiscal and chemical properties and hydrology. Field examples show: MTBE plumes > benzene plu...

253

Evidence for a carrier-mediated mechanism for thiamine transport to human jejunal basolateral membrane vesicles.  

Science.gov (United States)

Recent studies from our laboratory have demonstrated the presence of a pH-dependent, amiloride-sensitive, electroneutral carrier-mediated exchange for thiamine absorption in the human small intestinal brush-border membrane vesicles. However, the mechanism of thiamine transport across the human small intestinal basolateral membrane is not understood. The present study was aimed to characterize the mechanism of thiamine transport across the basolateral membranes of the human jejunum. Basolateral membrane vesicles (BLMV) were purified from mucosal scrapings of organ donors, utilizing a Percoll continuous density gradient centrifugation technique. The results showed [3H] thiamine uptake into BLMV to be: (1) markedly stimulated in the presence of an outwardly directed H+ gradient (pH 5.5in/7.5out); (2) significantly inhibited by amiloride in a dose-dependent manner; (3) sensitive to temperature and medium osmolarity and insensitive to changes in membrane potential; (4) not influenced by the addition of 1 mM Mg(2+)-ATP, inside and outside the vesicles in the presence of Na+ and K+; (5) inhibited by structural analogs-amprolium, oxythiamin, and unlabeled thiamine (100 microM); (6) not affected by organic cations, eg, TEA, N-methyl-nicotinamide (NMN), and choline; and (7) saturable as a function of concentration (apparent Km of 0.76 +/- 0.21 microM and a V(max) of 1.38 +/- 0.35 pmol/mg protein/10 sec). These results indicate the presence of a proton gradient-dependent specialized carrier-mediated exchange mechanism for thiamine transport across the human jejunum basolateral membranes. PMID:12645798

Dudeja, Pradeep K; Tyagi, Sangeeta; Gill, Ravinder; Said, Hamid M

2003-01-01

254

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.

2012-11-01

255

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

2014-03-01

256

Light-induced trimer to monomer transition in the main light-harvesting antenna complex of plants: thermo-optic mechanism.  

Science.gov (United States)

The main chlorophyll a/b light-harvesting complex of photosystem II, LHCIIb, has earlier been shown to be capable of undergoing light-induced reversible structural changes and chlorophyll a fluorescence quenching in a way resembling those observed in granal thylakoids when exposed to excess light [Barzda, V., et al. (1996) Biochemistry 35, 8981-8985]. The nature and mechanism of this unexpected structural flexibility has not been elucidated. In this work, by using density gradient centrifugation and nondenaturing green gel electrophoresis, as well as absorbance and circular dichroic spectroscopy, we show that light induces a significant degree of monomerization, which is in contrast with the preferentially trimeric organization of the isolated complexes in the dark. Monomerization is accompanied by a reversible release of Mg ions, most likely from the outer loop of the complexes. These data, as well as the built-in thermal and light instability of the trimeric organization, are explained in terms of a simple theoretical model of thermo-optic mechanism, effect of fast thermal transients (local T-jumps) due to dissipated photon energies in the vicinity of the cation binding sites, which lead to thermally assisted elementary structural transitions. Disruption of trimers to monomers by excess light is not confined to isolated trimers and lamellar aggregates of LHCII but occurs in photosystem II-enriched grana membranes, intact thylakoid membranes, and whole plants. As indicated by differences in the quenching capability of trimers and monomers, the appearance of monomers could facilitate the nonphotochemical quenching of the singlet excited state of chlorophyll a. The light-induced formation of monomers may also be important in regulated proteolytic degradation of the complexes. Structural changes driven by thermo-optic mechanisms may therefore provide plants with a novel mechanism for regulation of light harvesting in excess light. PMID:12484748

Garab, Gyozo; Cseh, Zoltán; Kovács, László; Rajagopal, Subramanyam; Várkonyi, Zsuzsanna; Wentworth, Mark; Mustárdy, László; Dér, András; Ruban, Alexander V; Papp, Elemér; Holzenburg, Andreas; Horton, Peter

2002-12-24

257

Palmitate stimulates glucose transport in rat adipocytes by a mechanism involving translocation of the insulin sensitive glucose transporter (GLUT4)  

Science.gov (United States)

In rat adipocytes, palmitate: a) increases basal 2-deoxyglucose transport 129 +/- 27% (p less than 0.02), b) decreases the insulin sensitive glucose transporter (GLUT4) in low density microsomes and increases GLUT4 in plasma membranes and c) increases the activity of the insulin receptor tyrosine kinase. Palmitate-stimulated glucose transport is not additive with the effect of insulin and is not inhibited by the protein kinase C inhibitors staurosporine and sphingosine. In rat muscle, palmitate: a) does not affect basal glucose transport in either the soleus or epitrochlearis and b) inhibits insulin-stimulated glucose transport by 28% (p less than 0.005) in soleus but not in epitrochlearis muscle. These studies demonstrate a potentially important differential role for fatty acids in the regulation of glucose transport in different insulin target tissues.

Hardy, R. W.; Ladenson, J. H.; Henriksen, E. J.; Holloszy, J. O.; McDonald, J. M.

1991-01-01

258

Localization and mechanism of thymidine transport in the central nervous system  

Energy Technology Data Exchange (ETDEWEB)

The localization and mechanism of thymidine and deoxyuridine transport in the central nervous system were studied in vivo and in vitro. Previous studies have shown that thymidine enters brain from blood in part via the CSF. In vitro, isolated adult bovine cerebral microvessels, which readily concentrated and phosphorylated deoxyglucose, were unable to concentrate thymidine and deoxyuridine. In vivo, (/sup 3/H)thymidine (0.2 microM) and (/sup 3/H)deoxyuridine (0.4 microM) were not extracted more readily than (/sup 14/C)sucrose in a single pass through the cerebral circulation of rats. In vivo, (/sup 3/H)thymidine retention in CSF and brain after entry from blood was increased when the efflux of (/sup 3/H)thymidine from CSF and the phosphorylation of (/sup 3/H)thymidine in brain were depressed by the intraventricular injection of unlabeled thymidine. These studies and previous work suggest that the transfer of thymidine (and deoxyuridine) through the blood-brain barrier in either direction must be extremely low. The present studies are consistent with the postulate that thymidine is transported by an active transport system in the choroid plexus that transfers thymidine from blood into the CSF; from the CSF, the thymidine enters brain cells and is phosphorylated.

Spector, R.; Berlinger, W.G.

1982-09-01

259

Transport and mechanical properties of self consolidating concrete with high volume fly ash  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the transport and mechanical properties of self consolidating concrete that contain high percentages of low-lime and high-lime fly ash (FA). Self consolidating concretes (SCC) containing five different contents of high-lime FA and low-lime FA as a replacement of cement (30, 40, 50, 60 and 70 by weight of total cementitious material) are examined. For comparison, a control SCC mixture without any FA was also produced. The fresh properties of the SCCs were observed through, slump flow time and diameter, V-funnel flow time, L-box height ratio, and segregation ratio. The hardened properties included the compressive strength, split tensile strength, drying shrinkage and transport properties (absorption, sorptivity and rapid chloride permeability tests) up to 365 days. Test results confirm that it is possible to produce SCC with a 70% of cement replacement by both types of FA. The use of high volumes of FA in SCC not only improved the workability and transport properties but also made it possible to produce concretes between 33 and 40 MPa compressive strength at 28 days, which exceeds the nominal compressive strength for normal concrete (30 MPa).

Mustafa Sahmaran; Ismail O. Yaman; Mustafa Tokyay [Gaziantep University, Gaziantep (Turkey). Department of Civil Engineering

2009-02-15

260

Mechanism of lithium transport through an MCMB heat-treated at 800-1200 deg. C  

International Nuclear Information System (INIS)

Mechanism of lithium transport through a mesocarbon-microbeads (MCMB) heat-treated at 800-1200 deg. C was elucidated in 1 M LiPF6-ethylene carbonate-diethyl carbonate (50:50 vol.%) solution by the quantitative analysis of potentiostatic current transient considering the difference in the relative amount of lithium deintercalation sites having different activation energies for lithium deintercalation. From the coincidence between the current transients experimentally measured and theoretically calculated based upon the modified McNabb-Foster equation along with 'cell-impedance-controlled' constraint as the governing equation with the boundary condition, respectively, it is suggested that lithium transport through the MCMB electrode is limited by the 'cell-impedance', and at the same time the difference in the kinetics of lithium transport between through the four different lithium deintercalation sites is due to the difference in activation energy for lithium deintercalation between from the four different lithium deintercalation sites present within the MCMB. Moreover, it is realised that since the degree of microcrystallinity of the MCMB is increased with rising heat-treatment temperature, the relative charge amount of lithium deintercalated from the lattice-site is increased, but that amount from the extra-sites is decreased. Thus, the inflexion point, i.e. 'quasi-current plateau' in the current transient is less clearly observed with rising heat-treatment temperature

2002-12-20

 
 
 
 
261

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-04-11

262

A continuum treatment of growth in biological tissue: the coupling of mass transport and mechanics  

Science.gov (United States)

Growth (and resorption) of biological tissue is formulated in the continuum setting. The treatment is macroscopic, rather than cellular or sub-cellular. Certain assumptions that are central to classical continuum mechanics are revisited, the theory is reformulated, and consequences for balance laws and constitutive relations are deduced. The treatment incorporates multiple species. Sources and fluxes of mass, and terms for momentum and energy transfer between species are introduced to enhance the classical balance laws. The transported species include: (i) a fluid phase, and (ii) the precursors and byproducts of the reactions that create and break down tissue. A notable feature is that the full extent of coupling between mass transport and mechanics emerges from the thermodynamics. Contributions to fluxes from the concentration gradient, chemical potential gradient, stress gradient, body force and inertia have not emerged in a unified fashion from previous formulations of the problem. The present work demonstrates these effects via a physically consistent treatment. The presence of multiple, interacting species requires that the formulation be consistent with mixture theory. This requirement has far-reaching consequences. A preliminary numerical example is included to demonstrate some aspects of the coupled formulation.

Garikipati, K.; Arruda, E. M.; Grosh, K.; Narayanan, H.; Calve, S.

2004-07-01

263

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

264

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

265

A coral polyp model of photosynthesis, respiration and calcification incorporating a transcellular ion transport mechanism  

Science.gov (United States)

A numerical simulation model of coral polyp photosynthesis, respiration and calcification was developed. The model is constructed with three components (ambient seawater, coelenteron and calcifying fluid), and incorporates photosynthesis, respiration and calcification processes with transcellular ion transport by Ca-ATPase activity and passive transmembrane CO2 transport and diffusion. The model calculates dissolved inorganic carbon and total alkalinity in the ambient seawater, coelenteron and calcifying fluid, dissolved oxygen (DO) in the seawater and coelenteron and stored organic carbon (CH2O). To reconstruct the drastic variation between light and dark respiration, respiration rate dependency on DO in the coelenteron is incorporated. The calcification rate depends on the aragonite saturation state in the calcifying fluid (? a cal). Our simulation result was a good approximation of "light-enhanced calcification." In our model, the mechanism is expressed as follows: (1) DO in the coelenteron is increased by photosynthesis, (2) respiration is stimulated by increased DO in the light (or respiration is limited by DO depletion in the dark), then (3) calcification increases due to Ca-ATPase, which is driven by the energy generated by respiration. The model simulation results were effective in reproducing the basic responses of the internal CO2 system and DO. The daily calcification rate, the gross photosynthetic rate and the respiration rate under a high-flow condition increased compared to those under the zero-flow condition, but the net photosynthetic rate decreased. The calculated calcification rate responses to variations in the ambient aragonite saturation state (? a amb) were nonlinear, and the responses agreed with experimental results of previous studies. Our model predicted that in response to ocean acidification (1) coral calcification will decrease, but will remain at a higher value until ? a amb decreases to 1, by maintaining a higher ? a cal due to the transcellular ion transport mechanism and (2) the net photosynthetic rate will increase.

Nakamura, T.; Nadaoka, K.; Watanabe, A.

2013-09-01

266

Stucture, Mechanics, and Transport in Block Copolymer-Nanoparticle Composites at the Macroscopic and Nanometer Lengthscales  

Science.gov (United States)

Pluronic triblock copolymers self-assemble in water to form thermoreversible soft solids that comprise of periodically spaced micelles. The interstitial spacings of these micellar crystals are on the order of tens of nanometers, and have been used to template comparably sized nanoparticles with hydrodynamic diameters (Dh) ranging from 4-7 nm. Here, nanoparticle diffusivity is studied and modeled in these self-assembling block copolymers across a range of polymer concentrations. Transport in the disordered micellar solution is described as diffusion through a polymer solution, while diffusive behavior in the structured micellar phase is modeled as an activated hopping process. The effects of protein loading, shear alignment, particle type, and block copolymer composition on particle transport are also examined, and they affect particle diffusivity to varying degrees. Block copolymer architecture influences the micellar structure and dimensions, which in turn affects protein templating and protein aggregation behavior. The overall micellar dimensions are smaller in block copolymers with shorter block lengths, and efforts to template particles which are larger than the interstitial spacings result in changes to the block copolymer structure and mechanics. It is possible, however, for block copolymers to accommodate a limited amount of particles which are larger than the estimated micellar interstitial site. When examining protein aggregation behavior in block copolymers with varying PEO chain lengths, striking differences in aggregation behavior are observed as well. Ultimately, this work underscores the interplay between the structure, mechanics, and transport behavior in nanoparticle-block copolymer composites, and this knowledge can be applied towards the design of self-assembling nanoscale materials.

Cheng, Vicki Alice

2013-08-01

267

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

1995-09-06

268

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

269

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  

CERN Document Server

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 find that, although waves produced by the surface convection zone can be ignored safely for such a star during the main sequence, it is not the case for later evolutionary stages. In particular, angular momentum transport by internal waves could be quite important at the end of the sub-giant branch and during the early-AGB phase. Wave-induced mixing of chemicals is expected during the early-AGB phase.

Talon, Suzanne

2008-01-01

270

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

Energy Technology Data Exchange (ETDEWEB)

The natural radionuclides {sup 210}Po and {sup 210}Pb, members of the {sup 238}U 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 {sup 210}Pb particulate concentrations and fluxes. (author) 11 refs.

Radakovitch, O.; Heussner, S. [Perpignan Univ., 66 (France). Lab. de Sedimentologie et Geochimie Marines; Biscaye, P.; Abassi, A. [Columbia Univ., Palisades, NY (United States). Lamont Doherty Earth Observatory

1997-12-31

271

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

International Nuclear Information System (INIS)

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

2012-06-24

272

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

273

Transport of single-walled carbon nanotubes in porous media: filtration mechanisms and reversibility.  

Science.gov (United States)

Deposition of nanomaterials onto surfaces is a key process governing their transport, fate, and reactivity in aquatic systems. We evaluated the transport and deposition behavior of carboxyl functionalized single-walled carbon nanotubes (SWNTs) in a well-defined porous medium composed of clean quartz sand over a range of solution chemistries. Our results showthat increasing solution ionic strength or addition of calcium ions result in increased SWNT deposition (filtration). This observation is consistent with conventional colloid deposition theories, thereby suggesting that physicochemical filtration plays an important role in SWNT transport. However, the relatively insignificant change of SWNT filtration at low ionic strengths (< or = 3.0 mM KCl) and the incomplete breakthrough of SWNTs in deionized water (C/Co = 0.90) indicate that physical straining also plays a role in the capture of SWNTs within the packed sand column. It is proposed that SWNT shape and structure, particularly the very large aspect ratio and its highly bundled (aggregated) state in aqueous solutions, contribute considerably to straining in flow through porous media. We conclude that both physicochemical filtration and straining play a role at low (< 3.0 mM) ionic strength, while physicochemical filtration is the dominant mechanism of SWNT filtration at higher ionic strengths. Our results further show that deposited SWNTs are mobilized (released) from the quartz sand upon introduction of low ionic strength solution following deposition experiments with monovalent salt (KCl). In contrast, SWNTs deposited in the presence of calcium ions were not released upon introduction of low ionic strength solution to the packed column, even when humic acid was present in solution during SWNT deposition. PMID:19068812

Jaisi, Deb P; Saleh, Navid B; Blake, Ruth E; Elimelech, Menachem

2008-11-15

274

Probing the mechanism of the hamster mitochondrial folate transporter by mutagenesis and homology modeling.  

Science.gov (United States)

The mitochondrial folate transporter (MFT) was previously identified in human and hamster cells. Sequence homology of this protein with the inner mitochondrial membrane transporters suggested a domain structure in which the N- and C-termini of the protein are located on the mitochondrial intermembrane-facing surface, with six membrane-spanning regions interspersed by two intermembrane loops and three matrix-facing loops. We now report the functional significance of insertion of the c-myc epitope into the intermembrane loops and of a series of site-directed mutations at hamster MFT residues highly conserved in orthologues. Insertional mutagenesis in the first predicted intermembrane loop eliminated MFT function, but the introduction of a c-myc peptide into the second loop was without effect. Most of the hamster MFT residues studied by site-directed mutagenesis were remarkably resilient to these mutations, except for R249A and G192E, both of which eliminated folate transport activity. Homology modeling, using the crystal structure of the bovine ADP/ATP carrier (AAC) as a scaffold, suggested a similar three-dimensional structure for the MFT and the AAC. An ion-pair interaction in the AAC thought to be central to the mechanism of membrane penetration by ADP is predicted by this homology model to be replaced by a pi-cation interaction in MFT orthologues and probably also in other members of the family bearing the P(I/L)W motif. This model suggests that the MFT R249A and G192E mutations both modify the base of a basket-shaped structure that appears to constitute a trap door for the flux of folates into the mitochondrial matrix. PMID:17279620

Perchiniak, Erin; Lawrence, Scott A; Kasten, Shane; Woodard, B Ann; Taylor, Shirley M; Moran, Richard G

2007-02-13

275

Electric vehicles and renewable energy in the transport sector - energy system consequences. Main focus: Battery electric vehicles and hydrogen based fuel cell vehicles  

DEFF Research Database (Denmark)

The aim of the project is to analyse energy, environmental and economic aspects of integrating electric vehicles in the future Danish energy system. Consequences of large-scale utilisation of electric vehicles are analysed. The aim is furthermore toillustrate the potential synergistic interplay between the utilisation of electric vehicles and large-scale utilisation of fluctuating renewable energy resources, such as wind power. Economic aspects for electric vehicles interacting with a liberalisedelectricity market are analysed. The project focuses on battery electric vehicles and fuel cell vehicles based on hydrogen. Based on assumptions on the future technical development for battery electric vehicles, fuel cell vehicles on hydrogen, and forthe conventional internal combustion engine vehicles, scenarios are set up to reflect expected options for the long-term development of road transport vehicles. Focus is put on the Danish fleet of passenger cars and delivery vans. The scenario analysisincludes assumptions on market potential developments and market penetration for the alternative vehicles. Vehicle replacement rates in the Danish transport fleet and the size of fleet development are based on data from The Danish Road Directorate. Theelectricity supply system development assumed is based on the Danish energy plan, Energy 21, The Plan scenario. The time horizon of the analysis is year 2030. Results from the scenario analysis include the time scales involved for the potentialtransition towards electricity based vehicles, the fleet composition development, the associated developments in transport fuel consumption and fuel substitution, and the potential CO2-emission reduction achievable in the overall transport and powersupply system. Detailed model simulations, on an hourly basis, have furthermore been carried out for year 2005 that address potential electricity purchase options for electric vehicles in the context of a liberalised electricity market. The baselineelectricity market considered comprises a spot market and a balance market. The structure chosen for the baseline spot market is close to the structure of the Nord Pool electricity market, and the structure of the balance or regulatory market is close tothe Norwegian model.

Nielsen, L.H.; Jørgensen K., no-firstname

2000-01-01

276

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

International Nuclear Information System (INIS)

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

1995-01-01

277

Mechanism of linolenic acid-induced inhibition of photosynthetic electron transport  

Energy Technology Data Exchange (ETDEWEB)

The effect of linolenic acid on photosynthetic electron transport reactions in chloroplasts has been localized at a site on the donor side of photosystem I and at two functionally distinct sites in photosystem II. In photosystem I, an increase in the electron transport rate occurs in the presence of 10 to 100 micromolar linolenic acid, followed by a decline in rate from 100 to 200 micromolar linolenic acid. The increase may result from an alteration of membrane structure that allows greater reactivity of the artificial donors with plastocyanin. The decrease is due to loss of plastocyanin from the membrane. In photosystem II, reversible site and an irreversible site of inhibiton have been located. At the irreversible site, there is a time-dependent loss of the loosely bound pool of Mn implicated in the water-splitting mechanism. At the reversible site, the photochemical charge separation is rapidly inhibited. This reversible inhibition of the photoact is a unique characteristic of linolenic acid and suggests evidence for a new mode of inhibition of photosystem II.

Golbeck, J.H.; Martin, I.F.; Fowler, C.F.

1980-04-01

278

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

279

Plasma transport in the vicinity of the Rings of Saturn: A Siphon flow mechanism  

International Nuclear Information System (INIS)

The unique combination of rapidly rotating ionosphere and meteoroid impact ionization at the rings of Saturn provides the elements of many interesting plasma transport phenomena. One of the most significant processes might be the upward field-aligned flow of the impact plasma at the equatorial region inside 1.6252 R/sub s/. Such a siphoning mechanism limits the efficiency of ring plane matter recycling to a minimum and could lead to appreciable loss of ring mass in this region. At the same time, channeling of the heavy ions into the mid-altitude ionosphere could also cause a large reduction in the ionospheric electron content as observed by the Pioneer 11 and the Voyager radio science experiments. The resulting electrodynamical coupling of the Saturnian rings with the ionosphere thus represents a completely new kind of ionospheric process than studied before

1983-02-01

280

Solid state transport as a mechanism of oxygen thermomigration in (U, Pu)Osub(2+-x)  

International Nuclear Information System (INIS)

A general account is given of the theory of thermomigration as it applies to oxygen redistribution via the solid state in non-stoichiometric mixed-plutonium oxide. This predicts that oxygen redistributes down the temperature gradient in hypostoichiometric material and up in hyperstoichiometric material. Some previous treatments are criticised. The evidence from laboratory experiments suggests that solid state transport is the dominant mechanism. A treatment, such as the cluster model, based on the manner in which oxygen deficiency or excess is accommodated in the structure, accounts naturally for the observed behaviour. The CO2/CO route may be limited because os fluggish transfer of oxygen between the solid and the gas mixture. The H2O/H2 route could be important in reactor fuel pins during service, the behaviour then being different from that found in the out-of-pile work. (Auth.)

1979-01-01

 
 
 
 
281

ATP-binding cassette and multidrug and toxic compound extrusion transporters in plants: a common theme among diverse detoxification mechanisms.  

Science.gov (United States)

Plants have developed elaborate detoxification mechanisms to cope with a large number of potentially toxic compounds, which include exogenous xenobiotics and endogenous metabolites, especially secondary metabolites. After enzymatic modification or synthesis, such compounds are transported and accumulated in apoplastic cell walls or central vacuoles in plant cells. Membrane transporters actively catalyze translocation of a diverse range of these compounds across various membranes within cells. Biochemical, molecular, and genetic studies have begun to reveal functions of a handful of ATP-binding cassette and multidrug and toxic compound extrusion family transporters engaged in transport of organic xenobiotics, heavy metals, metalloids, aluminum, alkaloids, flavonoids, terpenoids, terpenoid-derived phytohormones, cuticle lipids, and monolignols in plants. This detoxification versatility and metabolic diversity may underlie the functional diversification in plants of these families of transporters, which are largely involved in multidrug resistance in microorganisms and animals. PMID:24529726

Shoji, Tsubasa

2014-01-01

282

On the effective contribution of discrete transport factors to the propagation of landfill leachate components in groundwater The Monte Scherbelino landfill near Frankfurt am Main /Germany  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The propagation of a landfill leachate plume was analysed based on gathering long-term groundwater qual ity monitoring data from a landfill site near Frankfurt am Main. On the landfill site Monte Scherbelino 18,3 Mio m3 refuse, debris and industrial waste was deposited be tween 1925 and 1968. Three dumps with a maximum hight of 42 m were built up on a shallow aquifer of fluviatile sediments. The groundwater monitoring data from Monte Scherbelino includes semiannual chemical analyses of main...

2006-01-01

283

Preliminary investigation of gas transport mechanism in a H+ irradiated polyimide-ceramic composite membrane  

International Nuclear Information System (INIS)

Recent research by our group indicated that ion beam irradiation can simultaneously increase the gas permeability and permselectivity of polymeric membrane materials. The temperature dependence of the gas permeation properties of a H+ ion irradiated polyimide-ceramic composite membrane was investigated to address issues of changes in the gas transport mechanism in irradiated polymers. As was seen for glassy polymers, the temperature dependence of the permeation properties of the irradiated membrane followed an Arrhenius type relationship. Both the activation energy (Ep) for gas permeation and the pre-exponential factor (P0) of the irradiated polymer were greater than the values of the unmodified bulk polymer. Large increases in the pre-exponential factor of the irradiated sample for small size gas molecules (He, O2 and CO2) combined with the dominant contribution of the pre-exponential factor to the permselectivity for several gas pairs (He/CH4, O2/N2, and CO2/CH4) implied that the irradiated sample had a different permeation mechanism than the bulk material

1999-05-01

284

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

Energy Technology Data Exchange (ETDEWEB)

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

Snyder, Michelle MV; Um, Wooyong

2014-04-30

285

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

Science.gov (United States)

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

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

2012-12-01

286

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

Directory of Open Access Journals (Sweden)

Full Text Available A procedure for tagging ozone produced from NO sources through updates to an existing chemical mechanism is described, and results from its implementation in the Model for Ozone and Related chemical Tracers (MOZART-4, a global chemical transport model, are presented. Artificial tracers are added to the mechanism, thus not affecting the standard chemistry. The results are linear in the troposphere, i.e., the sum of ozone from individual tagged sources equals the ozone from all sources to within 3% in zonal mean monthly averages. The stratospheric ozone contribution to the troposphere determined from the difference between total ozone and ozone from all tagged sources is significantly less than estimates using a traditional stratospheric ozone tracer (8 vs 20 ppbv at the surface. The commonly used technique of perturbing NO emissions by 20% in a region to determine its ozone contribution is compared to the tagging technique, showing that the tagged ozone is 2–4 times the ozone contribution that was deduced from perturbing emissions.

L. K. Emmons

2012-07-01

287

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

Directory of Open Access Journals (Sweden)

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

L. K. Emmons

2012-12-01

288

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

International Nuclear Information System (INIS)

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

2013-08-21

289

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

Science.gov (United States)

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

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

2013-08-01

290

Flow structure and transport mechanism in lower half heated upper half cooled enclosures in laminar flow regime  

Science.gov (United States)

This paper presents an investigation on the transport mechanism in autoclave/thermosyphon type enclosures. Without a baffle to separate the lower- from the upper-half, the flow structure and the transport mechanisms are the same in rectangular and cylindrical enclosures. Thus, the efficiency of the fluid exchange and heat transfer between the enclosure’s two halves due to wall-layers feeding structure ensures that the center cores have almost uniform temperature. However, when a baffle separates the two halves, the wall layers’ interactions are eliminated and two temperature zones are established.

Li, Hongmin; Braun, Minel J.

2006-07-01

291

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

292

A novel nutrient sensing mechanism underlies substrate-induced regulation of monocarboxylate transporter-1.  

Science.gov (United States)

Monocarboxylate transporter isoform-1 (MCT1) plays an important role in the absorption of short-chain fatty acids (SCFAs) in the colon. Butyrate, a major SCFA, serves as the primary energy source for the colonic mucosa, maintains epithelial integrity, and ameliorates intestinal inflammation. Previous studies have shown substrate (butyrate)-induced upregulation of MCT1 expression and function via transcriptional mechanisms. The present studies provide evidence that short-term MCT1 regulation by substrates could be mediated via a novel nutrient sensing mechanism. Short-term regulation of MCT1 by butyrate was examined in vitro in human intestinal C2BBe1 and rat intestinal IEC-6 cells and ex vivo in rat intestinal mucosa. Effects of pectin feeding on MCT1, in vivo, were determined in rat model. Butyrate treatment (30-120 min) of C2BBe1 cells increased MCT1 function {p-(chloromercuri) benzene sulfonate (PCMBS)-sensitive [(14)C]butyrate uptake} in a pertussis toxin-sensitive manner. The effects were associated with decreased intracellular cAMP levels, increased V(max) of butyrate uptake, and GPR109A-dependent increase in apical membrane MCT1 level. Nicotinic acid, an agonist for the SCFA receptor GPR109A, also increased MCT1 function and decreased intracellular cAMP. Pectin feeding increased apical membrane MCT1 levels and nicotinate-induced transepithelial butyrate flux in rat colon. Our data provide strong evidence for substrate-induced enhancement of MCT1 surface expression and function via a novel nutrient sensing mechanism involving GPR109A as a SCFA sensor. PMID:22982338

Borthakur, Alip; Priyamvada, Shubha; Kumar, Anoop; Natarajan, Arivarasu A; Gill, Ravinder K; Alrefai, Waddah A; Dudeja, Pradeep K

2012-11-15

293

Transportation  

Energy Technology Data Exchange (ETDEWEB)

A brief summary of research over the past five years in the field of climate change, as it relates to key sectors in Canada, is presented in the report entitled: Climate change impacts and adaptation: a Canadian perspective. The emphasis of this chapter is on transportation, the role of adaptation in reducing vulnerabilities, and capitalizing on potential opportunities. Other sectors, such as fisheries, the coastal zone, tourism and human health might be affected by decisions made with regard to transportation. The areas that seem most vulnerable to climate change in transportation include northern ice roads, Great Lakes shipping, coastal infrastructure threatened by sea-level rise, and infrastructure located on permafrost. Most of the attention has been devoted to infrastructure and operations issues in northern Canada, despite most of the transportation activities taking place in southern Canada. Milder and or shorter winters might lead to savings, but additional knowledge is required before quantitative estimates can be made. The changed frequency of extreme climate events, and or changes in precipitation may influence other weather hazards or inefficiencies. If Canadians are prepared to be proactive, the report indicated that the effects of climate change on transportation may be largely manageable. 77 refs., 2 tabs., 3 figs.

NONE

2003-08-01

294

Bundling dynamics regulates the active mechanics and transport in carbon nanotube networks and their nanocomposites  

Science.gov (United States)

High-density carbon nanotube networks (CNNs) continue to attract interest as active elements in nanoelectronic devices, nanoelectromechanical systems (NEMS) and multifunctional nanocomposites. The interplay between the network nanostructure and its properties is crucial, yet current understanding remains limited to the passive response. Here, we employ a novel superstructure consisting of millimeter-long vertically aligned single walled carbon nanotubes (SWCNTs) sandwiched between polydimethylsiloxane (PDMS) layers to quantify the effect of two classes of mechanical stimuli, film densification and stretching, on the electronic and thermal transport across the network. The network deforms easily with an increase in the electrical and thermal conductivities, suggestive of a floppy yet highly reconfigurable network. Insight from atomistically informed coarse-grained simulations uncover an interplay between the extent of lateral assembly of the bundles, modulated by surface zipping/unzipping, and the elastic energy associated with the bent conformations of the nanotubes/bundles. During densification, the network becomes highly interconnected yet we observe a modest increase in bundling primarily due to the reduced spacing between the SWCNTs. The stretching, on the other hand, is characterized by an initial debundling regime as the strain accommodation occurs via unzipping of the branched interconnects, followed by rapid rebundling as the strain transfers to the increasingly aligned bundles. In both cases, the increase in the electrical and thermal conductivity is primarily due to the increase in bundle size; the changes in network connectivity have a minor effect on the transport. Our results have broad implications for filamentous networks of inorganic nanoassemblies composed of interacting tubes, wires and ribbons/belts.High-density carbon nanotube networks (CNNs) continue to attract interest as active elements in nanoelectronic devices, nanoelectromechanical systems (NEMS) and multifunctional nanocomposites. The interplay between the network nanostructure and its properties is crucial, yet current understanding remains limited to the passive response. Here, we employ a novel superstructure consisting of millimeter-long vertically aligned single walled carbon nanotubes (SWCNTs) sandwiched between polydimethylsiloxane (PDMS) layers to quantify the effect of two classes of mechanical stimuli, film densification and stretching, on the electronic and thermal transport across the network. The network deforms easily with an increase in the electrical and thermal conductivities, suggestive of a floppy yet highly reconfigurable network. Insight from atomistically informed coarse-grained simulations uncover an interplay between the extent of lateral assembly of the bundles, modulated by surface zipping/unzipping, and the elastic energy associated with the bent conformations of the nanotubes/bundles. During densification, the network becomes highly interconnected yet we observe a modest increase in bundling primarily due to the reduced spacing between the SWCNTs. The stretching, on the other hand, is characterized by an initial debundling regime as the strain accommodation occurs via unzipping of the branched interconnects, followed by rapid rebundling as the strain transfers to the increasingly aligned bundles. In both cases, the increase in the electrical and thermal conductivity is primarily due to the increase in bundle size; the changes in network connectivity have a minor effect on the transport. Our results have broad implications for filamentous networks of inorganic nanoassemblies composed of interacting tubes, wires and ribbons/belts. Electronic supplementary information (ESI) available: Detailed experimental methods. See DOI: 10.1039/c2nr30254c

Hahm, Myung Gwan; Wang, Hailong; Jung, Hyun Young; Hong, Sanghyun; Lee, Sung-Goo; Kim, Sung-Ryong; Upmanyu, Moneesh; Jung, Yung Joon

2012-05-01

295

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

International Nuclear Information System (INIS)

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

1991-04-01

296

Mechanism of Osmotic Activation of the Quaternary Ammonium Compound Transporter (QacT) of Lactobacillus plantarum  

Science.gov (United States)

The accumulation of quaternary ammonium compounds in Lactobacillus plantarum is mediated via a single transport system with a high affinity for glycine betaine (apparent Km of 18 ?M) and carnitine and a low affinity for proline (apparent Km of 950 ?M) and other analogues. Mutants defective in the uptake of glycine betaine were generated by UV irradiation and selected on the basis of resistance to dehydroproline (DHP), a toxic proline analogue. Three independent DHP-resistant mutants showed reduced glycine betaine uptake rates and accumulation levels but behaved similarly to the wild type in terms of direct activation of uptake by high-osmolality conditions. Kinetic analysis of glycine betaine uptake and efflux in the wild-type and mutant cells is consistent with one uptake system for quaternary ammonium compounds in L. plantarum and a separate system(s) for their excretion. The mechanism of osmotic activation of the quaternary ammonium compound transport system (QacT) was studied. It was observed that the uptake rates were inhibited by the presence of internal substrate. Upon raising of the medium osmolality, the QacT system was rapidly activated (increase in maximal velocity) through a diminished inhibition by trans substrate as well as an effect that is independent of intracellular substrate. We also studied the effects of the cationic amphipath chlorpromazine, which inserts into the cytoplasmic membrane and thereby influences the uptake and efflux of glycine betaine. The results provide further evidence for the notion that the rapid efflux of glycine betaine upon osmotic downshock is mediated by a channel protein that is responding to membrane stretch or tension. The activation of QacT upon osmotic upshock seems to be brought about by a turgor-related parameter other than membrane stretch or tension.

Glaasker, Erwin; Heuberger, Esther H. M. L.; Konings, Wil N.; Poolman, Bert

1998-01-01

297

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

298

Transport Pathways and Enhancement Mechanisms within Localized and Non-Localized Transport Regions in Skin Treated with Low-Frequency Sonophoresis and Sodium Lauryl Sulfate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent advances in transdermal drug delivery utilizing low-frequency sonophoresis (LFS) and sodium lauryl sulfate (SLS) have revealed that skin permeability enhancement is not homogenous across the skin surface. Instead, highly perturbed skin regions, known as localized transport regions (LTRs), exist. Despite these findings, little research has been conducted to identify intrinsic properties and formation mechanisms of LTRs and the surrounding less-perturbed non-LTRs. By independently analyz...

Polat, Baris E.; Figueroa, Pedro L.; Blankschtein, Daniel; Langer, Robert

2011-01-01

299

Transport Pathways and Enhancement Mechanisms within Localized and Non-Localized Transport Regions in Skin Treated with Low-Frequency Sonophoresis and Sodium Lauryl Sulfate  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Recent advances in transdermal drug delivery utilizing low-frequency sonophoresis (LFS) and sodium lauryl sulfate (SLS) have revealed that skin permeability enhancement is not homogenous across the skin surface. Instead, highly perturbed skin regions, known as localized transport regions (LTRs), exist. Despite these findings, little research has been conducted to identify intrinsic properties and formation mechanisms of LTRs and the surrounding less-perturbed non-LTRs. By independently analyz...

Polat, Baris E.; Figueroa, Pedro L.; Blankschtein, Daniel; Langer, Robert

2010-01-01

300

ABC transporters during epilepsy and mechanisms underlying multidrug resistance in refractory epilepsy.  

Science.gov (United States)

It is estimated 20-25% of the epileptic patients fails to achieve good control with the different antiepileptic drugs (AEDs) treatments, developing refractory epilepsy (RE). Discovered first in cancer, the activity of P-glycoprotein (P-gp) and others ABC transporters as multidrug-resistance-associated proteins (MRPs) and breast cancer resistant protein (BCRP) are directly related with the refractoriness. We have observed the overexpression of these all transporters in the brain of patients with RE, and according with other authors, all these data suggests an active drug efflux from brain. Both constitutive and seizure induced brain P-gp overexpression was also suggested. As confirmation of these clinical evidences, different models of experimental epilepsy have demonstrated P-gp overexpression on blood brain barrier (BBB) and brain parenchyma cells, as astrocytes and neurons. In our model, early P-pg detection in vessel-related cells and later additional P-gp detection in neurons, correlated with the gradual loss of protective effect of phenytoin. The progressive neuronal P-gp expression, depending on intensity and time-constancy of seizure-injury, was in agreement with the development of "P-gp-positive seizure-axis" proposed by Kwan & Brodie, who also showed that the development of RE directly correlated with the number and frequency of seizures before initiation of drug therapy. P-gp expression in excretory organs suggests that P-gp have a central role in drug elimination. Persistent low levels of AEDs in plasma and P-gp brain overexpression in several RE pediatric patients were reported. We also observed in adult RE patients, an increased liver clearance of 99mTc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) (a P-gp substrate), and the surgically treated cases showed P-gp brain overexpression. These results suggest the systemic hyperactivity of P-gp in RE patients, including brain P-gp over-expression should be suspected when persistent subtherapeutic levels of AEDs in plasma are detected. P-gp neuronal expression described in both clinical and experimental reports indicates that additional mechanisms could be operative from seizure-affected P-gp-positive neurons, due to AEDs targets are expressed at membrane level. An alternative mechanism was demonstrated in P-gp-expressed cells that exhibit lower membrane potential (Deltapsi(0)=-10 to -20) compared to normal physiological Deltapsi(0) of -60 mV. Under this situation and irrespective to the P-gp pharmacoresistant property or type of drug treatment selected, P-gp-expressed neurons could increase their sensitivity to new seizures perhaps as an epileptogenic mechanism. The understanding of properties of these ABC transporters can offer new tools for better selection of more effective preventive or therapeutic strategies and avoid the invasive surgical treatments for RE. PMID:17910594

Lazarowski, Alberto; Czornyj, Liliana; Lubienieki, Fabiana; Girardi, Elena; Vazquez, Silvia; D'Giano, Carlos

2007-01-01

 
 
 
 
301

Mechanism of lipid mobilization by the small intestine after transport blockade  

International Nuclear Information System (INIS)

The nonionic detergent, Pluronic L-81 (L-81) has been shown to block the transport of intestinal mucosal triacylglycerol (TG) in chylomicrons. This results in large lipid masses within the enterocyte that are greater in diameter than chylomicrons. On removal of L-81, mucosal TG is rapidly mobilized and appears in the lymph. We questioned whether the blocked TG requires partial or complete hydrolysis before its transport. Rats were infused intraduodenally with [3H]glyceryl, [14C]oleoyl trioleate (TO) and 0.5 mg L-81/h for 8 h, followed by 120 mumol/h linoleate for 18 h. Mesenteric lymph was collected and analyzed for TG content and radioactivity. An HPLC method was developed to separate TG on the basis of its acyl group species. The assumed acyl group composition was confirmed by gas liquid chromatography analysis. TG lymphatic output was low for the first 8 h but increased to 52 mumol/h at the 11th h of infusion (3 h after stopping L-81). 38% of the infused TO was retained in the mucosa after the 8-h infusion. 95% of mucosal TG was TO, 92% of the radioactivity was in TG, and 2.4% of the 14C disintegrations per minute was in fatty acid. HPLC analysis of lymph at 6, 10, 12, and 14.5 h of infusion showed a progressive rise in TG composed of one linoleate and two oleates, to 39%; and in TG composed of two linoleates and one oleate to 20% at 14.5 h of infusion. On a mass basis, however, 80% of the TG acyl groups were oleate. 3H/14C ratios in the various TG acyl group species reflected the decrease in oleate. We conclude that first, unlike liver, most mucosal TG is not hydrolyzed before transport. The mechanism of how the large lipid masses present in mucosal cells after L-81 infusion are converted to the much smaller chylomicrons is unknown. Second, the concomitant infusion of linoleate did not impair lymph TG delivery after L-81 blockade

1988-01-01

302

Mechanism of lipid mobilization by the small intestine after transport blockade  

Energy Technology Data Exchange (ETDEWEB)

The nonionic detergent, Pluronic L-81 (L-81) has been shown to block the transport of intestinal mucosal triacylglycerol (TG) in chylomicrons. This results in large lipid masses within the enterocyte that are greater in diameter than chylomicrons. On removal of L-81, mucosal TG is rapidly mobilized and appears in the lymph. We questioned whether the blocked TG requires partial or complete hydrolysis before its transport. Rats were infused intraduodenally with (3H)glyceryl, (14C)oleoyl trioleate (TO) and 0.5 mg L-81/h for 8 h, followed by 120 mumol/h linoleate for 18 h. Mesenteric lymph was collected and analyzed for TG content and radioactivity. An HPLC method was developed to separate TG on the basis of its acyl group species. The assumed acyl group composition was confirmed by gas liquid chromatography analysis. TG lymphatic output was low for the first 8 h but increased to 52 mumol/h at the 11th h of infusion (3 h after stopping L-81). 38% of the infused TO was retained in the mucosa after the 8-h infusion. 95% of mucosal TG was TO, 92% of the radioactivity was in TG, and 2.4% of the 14C disintegrations per minute was in fatty acid. HPLC analysis of lymph at 6, 10, 12, and 14.5 h of infusion showed a progressive rise in TG composed of one linoleate and two oleates, to 39%; and in TG composed of two linoleates and one oleate to 20% at 14.5 h of infusion. On a mass basis, however, 80% of the TG acyl groups were oleate. 3H/14C ratios in the various TG acyl group species reflected the decrease in oleate. We conclude that first, unlike liver, most mucosal TG is not hydrolyzed before transport. The mechanism of how the large lipid masses present in mucosal cells after L-81 infusion are converted to the much smaller chylomicrons is unknown. Second, the concomitant infusion of linoleate did not impair lymph TG delivery after L-81 blockade.

Halpern, J.; Tso, P.; Mansbach, C.M. II

1988-07-01

303

Mechanisms of Bacterial Resistance to Antibiotics: Altering the Membranes and Transport Systems  

Science.gov (United States)

Bacteria may resist antibiotics by altering the membranes and transport systems in order to prevent the entry of the antibiotic into the bacterium and/or actively transport the antibiotic out of the bacterium.

American Society For Microbiology;

2005-03-11

304

Configuration evaluation and criteria plan. Volume 1: System trades study and design methodology plan (preliminary). Space Transportation Main Engine (STME) configuration study  

Science.gov (United States)

The System Trades Study and Design Methodology Plan is used to conduct trade studies to define the combination of Space Shuttle Main Engine features that will optimize candidate engine configurations. This is accomplished by using vehicle sensitivities and engine parametric data to establish engine chamber pressure and area ratio design points for candidate engine configurations. Engineering analyses are to be conducted to refine and optimize the candidate configurations at their design points. The optimized engine data and characteristics are then evaluated and compared against other candidates being considered. The Evaluation Criteria Plan is then used to compare and rank the optimized engine configurations on the basis of cost.

Bair, E. K.

1986-01-01

305

Rate and mechanism of facilitated americium(III) transport through a supported liquid membrane containing a bifunctional organophosphorus mobile carrier  

International Nuclear Information System (INIS)

The facilitated transport of Am(III) from aqueous nitrate solutions to formic acid aqueous solutions through a supported liquid membrane (SLM) is described. The supported liquid membrane consists of a solution of a new (carbamoylmethyl)phosphine oxide in diethylbenzene (DEB) absorbed into a 48 ?m thick microporous polypropylene film. The transport mechanism consists of a diffusion process through an aqueous diffusion film, a fast interfacial chemical reaction, and diffusion through the membrane itself. Equations describing the rate of transport are derived. They correlate the membrane permeability coefficient to diffusional parameters and to the chemical composition of the system. Different rate-controlling processes are shown to control the membrane permeability when the composition of the system is varied and as long as the transport occurs. The experimental data are quantitatively explained with the derived equations. The diffusion coefficient of the permeating species and the equilibrium constant of the fast interfacial reactions are evaluated. 13 figures, 1 table

1983-11-10

306

Indentation: A Simple, Nondestructive Method for Characterizing the Mechanical and Transport Properties of pH-Sensitive Hydrogels.  

Science.gov (United States)

We use instrumented indentation to characterize the mechanical and transport behavior of a pH-sensitive hydrogel in various aqueous buffer solutions. In the measurement an indenter is pressed to a fixed depth into a hydrogel disk and the load on the inden...

D. T. Auguste J. You J. J. Vlassak Y. Hu Z. Suo

2011-01-01

307

Mechanical and Thermal Transport Properties of Suspension Thermal-Sprayed Alumina-Zirconia Composite Coatings  

Science.gov (United States)

Micro-laminates and nanocomposites of Al2O3 and ZrO2 can potentially exhibit higher hardness and fracture toughness and lower thermal conductivity than alumina or zirconia alone. The potential of these improvements for abrasion protection and thermal barrier coatings is generating considerable interest in developing techniques for producing these functional coatings with optimized microstructures. Al2O3-ZrO2 composite coatings were deposited by suspension thermal spraying (APS and HVOF) of submicron feedstock powders. The liquid carrier employed in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to unique and novel fine-scaled microstructures. The suspensions were injected internally using a Mettech Axial III plasma torch and a Sulzer-Metco DJ-2700 HVOF gun. The different spray processes induced a variety of structures ranging from finely segregated ceramic laminates to highly alloyed amorphous composites. Mechanisms leading to these structures are related to the feedstock size and in-flight particle states upon their impact. Mechanical and thermal transport properties of the coatings were compared. Compositionally segregated crystalline coatings, obtained by plasma spraying, showed the highest hardness of up to 1125 VHN3 N, as well as the highest abrasion wear resistance (following ASTM G65). The HVOF coating exhibited the highest erosion wear resistance (following ASTM G75), which was related to the toughening effect of small dispersed zirconia particles in the alumina-zirconia-alloyed matrix. This microstructure also exhibited the lowest thermal diffusivity, which is explained by the amorphous phase content and limited particle bonding, generating local thermal resistances within the structure.

Oberste Berghaus, Jörg; Legoux, Jean-Gabriel; Moreau, Christian; Tarasi, Fariba; Chráska, Tomas

2008-03-01

308

Simulation study of the lithium ion transport mechanism in ternary polymer electrolytes: the critical role of the segmental mobility.  

Science.gov (United States)

We present an extensive molecular dynamics (MD) simulation study of the lithium ion transport in ternary polymer electrolytes consisting of poly(ethylene oxide) (PEO), lithium-bis(trifluoromethane)sulfonimide (LiTFSI), and the ionic liquid N-methyl-N-propylpyrrolidinium bis(trifluoromethane)sulfonimide (PYR13TFSI). In particular, we focus on two different strategies by which the ternary electrolytes can be devised, namely by (a) adding the ionic liquid to PEO20LiTFSI and (b) substituting the PEO chains in PEO20LiTFSI by the ionic liquid. To grasp the changes of the overall lithium transport mechanism, we employ an analytical, Rouse-based cation transport model (Maitra et al. Phys. Rev. Lett. 2007, 98, 227802), which has originally been devised for binary PEO-based electrolytes. This model distinguishes three different microscopic transport mechanisms, each quantified by an individual time scale. In the course of our analysis, we extend this mathematical description to account for an entirely new transport mechanism, namely, the TFSI-supported diffusion of lithium ions decoupled from the PEO chains, which emerges for certain stoichiometries. We find that the segmental mobility plays a decisive role in PEO-based polymer electrolytes. That is, whereas the addition of the ionic liquid to PEO20LiTFSI plasticizes the polymer network and thus also increases the lithium diffusion, the amount of free, mobile ether oxygens reduces when substituting the PEO chains by the ionic liquid, which compensates the plasticizing effect. In total, our observations allow us to formulate some general principles about the lithium ion transport mechanism in ternary polymer electrolytes. Moreover, our insights also shed light on recent experimental observations (Joost et al. Electrochim. Acta 2012, 86, 330). PMID:24383892

Diddens, Diddo; Heuer, Andreas

2014-01-30

309

On the Oxygen Transport Mechanism in Titanium Thin Films under Irradiation by Molecular Water Ions  

Directory of Open Access Journals (Sweden)

Full Text Available The behavior of oxygen atoms in (0.5 – 1.0 mm thick Ti films is investigated under high-flux, low-energy molecular water ion irradiation. The anomalously deep penetration of oxygen without formation of new compounds observable by XRD has been registered after 10 min of irradiation at room temperature using Auger Electron spectroscopy analysis. The mechanism driving oxygen atoms from the surface into the bulk is discussed. It is based on the results of experimental studies of surface topography and assumption that the surface energy increases under ion irradiation, and relaxation processes minimizing the surface energy initiate the atomic redistribution  on the surface and in the bulk. Two processes minimizing the surface free energy are considered: (i the mixing of atoms on the surface, and (ii the annihilation of surface vacancies by the atoms transported from the bulk to the surface.DOI: http://dx.doi.org/10.5755/j01.ms.19.1.3822

Simona TU?KUT?

2013-03-01

310

Mechanism of methane transport from the rhizosphere to the atmosphere through rice plants  

Energy Technology Data Exchange (ETDEWEB)

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths.

Nouchi, Isamu (National Institute of Agro-Environmental Sciences, Ibaraki (Japan)); Mariko, Shigeru (Tokyo Metropolitan Univ. (Japan)); Aoki, Kazuyuki (Tokyo Metropolitan Research Institute for Environmental Protection (Japan))

1990-09-01

311

Dust transport: Wind blown and mechanical resuspension, July 1983 to December 1984  

Energy Technology Data Exchange (ETDEWEB)

This study defines the processes that resuspend plutonium (Pu) particles from Pu-contaminated soil at Rocky Flats. Such knowledge can predict the transport of Pu particles from the site and the population dose. A vertical dust flux tower profiled the plume of Pu particles from the site. The data show a 70% reduction between 1 and 10 m in the concentration of coarse and inhalable Pu particles. The respirable particle concentration remained steady at both heights, slightly above background levels. High winds visually resuspend large amounts of dust for short periods, but we suspected that present sampling devices do not function properly above 50 km/h. During a windstorm reaching 80 km/h, the size-selective sampler used seriously underestimated the dust(Pu) concentration. Wind tunnel studies measured resuspension versus wind speed from our prairie grass covered, arid soil. We failed to find a good correlation between resuspension and wind speed. This led to a search for alternative mechanisms of resuspension besides wind erosion. Resuspension of dust(Pu) from grass proved to be important, as well as resuspension from rain splash.

Langer, G.

1986-09-20

312

Discovery of a mechanism for oxygen transport during UCG. [Underground coal gasification  

Energy Technology Data Exchange (ETDEWEB)

A qualitative study of the flow patterns in an underground-coal-gasification laboratory flow model has identified a mechanism for oxygen transport. The injected fluid is drawn directly to the cavity walls in a thin layer along the cavity's floor, with the difference in density between the injected fluid and the bulk fluid being the primary cause of this stratified flow. The model was made dynamically similar to a UCG system by equating the Grashoff and Reynolds numbers for the two systems. With water as the model fluid, equating the Grashoff numbers resulted in a 0.20 scale factor for the model, while equating the Reynolds numbers set the injection rate for the model. Although the operating conditions were varied over a significant range, the general shape of the flow pattern remained unchanged. The injected fluid impacted the floor of the cavity, flowed radially outward toward the walls in a thin layer on the floor, was drawn up past the cavity walls, and then backmixed in the cavity before being swept out toward the exit. The injected fluid arriving at the cavity wall was thus almost completely undiluted by the bulk fluid.

Massaquoi, J.G.M.; Rohaus, D.M.; Riggs, J.B.

1982-01-01

313

Investigating radionuclide bearing suspended sediment transport mechanisms in the Ribble estuary using airborne remote sensing  

International Nuclear Information System (INIS)

BNFL Sellafield has been authorised to discharge radionuclides to the Irish Sea since 1952. In the aquatic environment the radionuclides are adsorbed by sediments and are thus redistributed by sediment transport mechanisms. This sediment is known to accumulate in the estuaries of the Irish Sea. BNFL Springfields is also licensed to discharge isotopically different radionuclides directly to the Ribble estuary. Thus there is a need to understand the sediment dynamics of the Ribble estuary in order to understand the fate of these radionuclides within the Ribble estuary. Estuaries are highly dynamic environments that are difficult to monitor using the conventional sampling techniques. However, remote sensing provides a potentially powerful tool for monitoring the hydrodynamics of the estuarine environment by providing data that are both spatially and temporally representative. This research develops a methodology for mapping suspended sediment concentration (SSC) in the Ribble estuary using airborne remote sensing. The first hypothesis, that there is a relationship between SSC and 137Cs concentration is proven in-situ (R2=0.94), thus remotely sensed SSC can act as a surrogate for 137Cs concentration. Initial in-situ characterisation of the suspended sediments was investigated to identify spatial and temporal variability in grain size distributions and reflectance characteristics for the Ribble estuary. Laboratory experiments were then performed to clearly define the SSC reflectance relationship, identify the optimum CASI wavelengths for quantifying SSC and to demonstrate the effects on reflectance of the environmental variables of salinity and clay content. Images were corrected for variation in solar elevation and angle to give a ground truth calibration for SSC, with an R2=0.76. The remaining scatter in this relationship was attributed to the differences in spatial and temporal representation between sampling techniques and remote sensing. The second hypothesis assumes that a series of images over a flood tide can be animated to provide information on the hydrodynamic regime, erosion, and deposition. Spatial and temporal data demonstrated the complex controls on sediment transport. The data also showed the importance of microphytobenthos in the stabilisation of intertidal sediments, highlighting their importance in defining sources and sinks of radionuclides in intertidal areas. Water volume data from the VERSE model were combined with SSC from the imagery to calculate the total sediment in suspension for each flight line. This provided the figures used to determine total erosion and deposition, which were then used to derive net suspended sediment and 137Cs influxes of 2.01x106 kg and 604MBq per flood tide. (author)

2000-01-01

314

Main roads to melanoma  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The characterization of the molecular mechanisms involved in development and progression of melanoma could be helpful to identify the molecular profiles underlying aggressiveness, clinical behavior, and response to therapy as well as to better classify the subsets of melanoma patients with different prognosis and/or clinical outcome. Actually, some aspects regarding the main molecular changes responsible for the onset as well as the progression of melanoma toward a more aggressive phenotype h...

Palmieri, Giuseppe; Capone, Mariaelena; Ascierto, Maria Libera; Gentilcore, Giusy; Stroncek, David F.; Casula, Milena; Sini, Maria Cristina; Palla, Marco; Mozzillo, Nicola; Ascierto, Paolo Antonio

2009-01-01

315

Determinación de los principales parámetros de calidad que afectan la cosecha mecanizada de arroz / Determination of the main quality parameters that affect the mechanical harvest of rice  

Scientific Electronic Library Online (English)

Full Text Available SciELO Cuba | Language: Spanish Abstract in spanish El presente trabajo tiene como objetivo analizar la calidad de la cosecha mecanizada de la semilla de arroz, realizada por las cosechadoras de arroz New Holland L521, en las condiciones de trabajo del Complejo Agroindustrial (CAI) Arrocero "Los Palacios". Fueron evaluados los parámetros tecnológicos [...] de la cosechadora en función de la calidad del producto cosechado, tales como: grano entero, pelado y/o quebrado, contenido de impurezas y pérdidas totales. Los resultados obtenidos para los parámetros estudiados indican que para las cosechadoras New Holland L 521 el comportamiento del grano pelado y/o quebrado en los cinco rendimientos agrícolas diferentes observados tomó valores de 5,2-6,4% y el contenido de impurezas estuvo entre 8,3-9,6%, encontrándose ambos parámetros por encima de los límites establecidos, influyendo principalmente en este aspecto la mala regulación de los órganos de trilla, la velocidad trabajo y la mala capacitación de los operadores. La aplicación de estos resultados le permite al CAI Arrocero "Los Palacios" disminuir las pérdidas durante la cosecha se redujeron las pérdidas de 206 kg/ha hasta 85 kg/ha, lo que representa un efecto económico de $ 316 202.04 pesos cubanos y a la vez permite dejar de invertir aproximadamente por la compra del arroz cáscara para ser procesado para la alimentación de nuestra población 184 793.4 USD. Abstract in english The present paper has as objective to analyze quality parameters that affect the mechanical harvest of the seed of rice, carried out by the New Holland L521 rice harvester machine, under the conditions of work of the Rice Enterprise "Los Palacios" the cropper's technological parameters were evaluate [...] d in function of the quality of the harvested product, such as: seed entirely, peeled broken and content of sludges and total losses. The results obtained for the studied parameters indicate that for the New Holland L521 rice harvester machine the behavior of the grain peeled y/o broken in the five observed different agricultural yields took values of 5,2-6,4% and the content of sludges was among 8,3-9,6%, being both parameters above the established limits, influencing mainly in this aspect the bad regulation of the organs of it thrashes, the speed work and the bad training of the operators. The application of these results allows him to the Rice Enterprise "Los Palacios to diminish the losses during the crop decreased the losses of 206 kg/ha up to 85 kg/ha, what represents an economic effect of $316 202.04 Cuban pesos and at the same time allows to stop to invest approximately for the purchase of the rice shell to be processed for our population's feeding 184 793.4 USD.

Alexander, Miranda Caballero; Ciro E, Iglesias Coronel; Erwin, Herrera González; Nathali, Abraham Ferro; Santiago, Castells Hernández.

316

Anterograde Transport of Herpes Simplex Virus Capsids in Neurons by both Separate and Married Mechanisms?†  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Anterograde transport of herpes simplex virus (HSV) from neuronal cell bodies into, and down, axons is a fundamentally important process for spread to other hosts. Different techniques for imaging HSV in axons have produced two models for how virus particles are transported in axons. In the Separate model, viral nucleocapsids devoid of the viral envelope and membrane glycoproteins are transported in axons. In the Married model, enveloped HSV particles (with the viral glycoproteins) encased wi...

Wisner, Todd W.; Sugimoto, Ken; Howard, Paul W.; Kawaguchi, Yasushi; Johnson, David C.

2011-01-01

317

Mg2+-sensing mechanism of Mg2+ transporter MgtE probed by molecular dynamics study  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Proper regulation of the intracellular ion concentration is essential to maintain life and is achieved by ion transporters that transport their substrates across the membrane in a strictly regulated manner. MgtE is a Mg2+ transporter that may function in the homeostasis of the intracellular Mg2+ concentration. A recent crystallographic study revealed that its cytosolic domain undergoes a Mg2+-dependent structural change, which is proposed to gate the ion-conducting pore passing through the tr...

2008-01-01

318

A molecular mechanism for aberrantCFTR-dependent HCO3– transport in cystic fibrosis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Aberrant HCO3– transport is a hallmark of cystic fibrosis (CF) and is associated with aberrant Cl–-dependent HCO3– transport by the cystic fibrosis transmembrane conductance regulator (CFTR). We show here that HCO3– current by CFTR cannot account for CFTR-activated HCO3– transport and that CFTR does not activate AE1–AE4. In contrast, CFTR markedly activates Cl– and OH–/HCO3– transport by members of the SLC26 family DRA, SLC26A6 and pendrin. Most notably, the SLC26s are elect...

Ko, Shigeru B. H.; Shcheynikov, Nikolay; Choi, Joo Young; Luo, Xiang; Ishibashi, Kenichi; Thomas, Philip J.; Kim, Joo Young; Kim, Kyung Hwan; Lee, Min Goo; Naruse, Satoru; Muallem, Shmuel

2002-01-01

319

Retrograde axonal transport of herpes simplex virus: evidence for a single mechanism and a role for tegument.  

Science.gov (United States)

Herpes simplex virus type I (HSV) typically enters peripheral nerve terminals and then travels back along the nerve to reach the neuronal cell body, where it replicates or enters latency. To monitor axoplasmic transport of HSV, we used the giant axon of the squid, Loligo pealei, a well known system for the study of axoplasmic transport. To deliver HSV into the axoplasm, viral particles stripped of their envelopes by detergent were injected into the giant axon, thereby bypassing the infective process. Labeling the viral tegument protein, VP16, with green fluorescent protein allowed viral particles moving inside the axon to be imaged by confocal microscopy. Viral particles moved 2.2 +/- 0.26 micrometer/sec in the retrograde direction, a rate comparable to that of the transport of endogenous organelles and of virus in mammalian neurons in culture. Electron microscopy confirmed that 96% of motile (stripped) viral particles had lost their envelope but retained tegument, and Western blot analysis revealed that these particles had retained protein from capsid but not envelope. We conclude that (i) HSV recruits the squid retrograde transport machinery; (ii) viral tegument and capsid but not envelope are sufficient for this recruitment; and (iii) the giant axon of the squid provides a unique system to dissect the viral components required for transport and to identify the cellular transport mechanisms they recruit. PMID:10884436

Bearer, E L; Breakefield, X O; Schuback, D; Reese, T S; LaVail, J H

2000-07-01

320

Transport mechanisms in low-resistance ohmic contacts to p-InP formed by rapid thermal annealing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermionic emission across a very small effective Schottky barrier (0-0.2 eV) are reported as being the dominant transport process mechanism in very low-resistance ohmic contacts for conventional AuZn(Ni) metallization systems top-InP formed by rapid thermal annealing. The barrier modulation process is related to interdiffusion and compound formation between the metal elements and the InP. The onset of low specific contact resistance is characterized by a change in the dominant transport mech...

Clausen, Thomas; Leistiko, Otto

2009-01-01

 
 
 
 
321

Mechanical design of the high-energy beam-transport line for the FMIT 2-MeV accelerator  

International Nuclear Information System (INIS)

The beam-transport line for the high-power 2-MeV Fusion Materials Irradiation Test (FMIT) accelerator is one of the most heavily instrumented ever designed. A wide variety of diagnostics is required to accurately determine the characteristics of the beam that will ultimately be used. Because the machine is only 2 MeV, the packing factor in the high-energy beam transport (HEBT) is high, especially since full-scale FMIT-grade components are used where possible. The HEBT's mechanical design aspects and its instrumentation are described

1983-08-01

322

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

323

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)

2012-01-01

324

Two-Dimensional Hopping Conductivity: Experimental Evidence for a Novel Electron Transport Mechanism  

International Nuclear Information System (INIS)

Results are presented of measurements of two-dimensional (2D) variable-range-hopping (VRH) conductivity and magnetoresistance (MR) in a delta-doped GaAs/AlGaAs heterostructure. It is shown that at zero magnetic field and low temperatures (T xx(T) exhibits 'Coulomb-gap behavior': ?(T) =: ?0exp(T0/T)1/2 with the pre factor ?0 = (h/e2) which is independent of temperature and electron density. This value of po exactly coincides with that observed by Mason et al. in a different material - Si-MOSFET. Universality of the hopping pre factor is considered as evidence that in some interval of electron densities close to the metal-insulator transition, the 2D VRH is assisted by the electron-electron interaction (EEI), rather than by conventional electron-phonon interaction. Experimental data show that (i) existence of a delta-doped layer in the proximate vicinity of the 2D conducting plane favors EEI-assisted VRH, and (ii) a strong magnetic field parallel to the 2D plane leads to the suppression of the EEI-assistance and the restoration of the conventional phonon-assisted hopping. To interpret these experimental observations, a novel electron transport mechanism is suggested, according to which the current-carrying single electron move via quantum resonant tunneling between localized states, brought into resonance by fast electron hops in their environment. The last hops can be assisted by phonons; however, the phonon frequency does not appear in the final expression for the current-carrying transition rate

1999-03-18

325

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  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

326

A Chemical Genetic Screen for Modulators of Exocytic Transport Identifies Inhibitors of a Transport Mechanism Linked to GTR2 Function?  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Membrane and protein traffic to the cell surface is mediated by partially redundant pathways that are difficult to perturb in ways that yield a strong phenotype. Such robustness is expected in a fine-tuned process, regulated by environmental cues, that is required for controlled cell surface growth and cell proliferation. Synthetic genetic interaction screens are especially valuable for investigating complex processes involving partially redundant pathways or mechanisms. In a previous study, ...

2010-01-01

327

Structure and molecular mechanism of a nucleobase-cation-symport-1 family transporter  

DEFF Research Database (Denmark)

The nucleobase-cation-symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 transmembrane helices, 10 of which are arranged in two inverted repeats of five helices. The structures of the outward-facing open and substrate-bound occluded conformations were solved, showing how the outward-facing cavity closes upon binding of substrate. Comparisons with the leucine transporter LeuT(Aa) and the galactose transporter vSGLT reveal that the outward- and inward-facing cavities are symmetrically arranged on opposite sides of the membrane. The reciprocal opening and closing of these cavities is synchronized by the inverted repeat helices 3 and 8, providing the structural basis of the alternating access model for membrane transport.

Weyand, Simone; Shimamura, Tatsuro

2008-01-01

328

ACIDIFICATION TRENDS AND THE EVOLUTION OF NEUTRALIZATION MECHANISMS THROUGH TIME AT THE BEAR BROOK WATERSHED IN MAINE (BBWM), U.S.A.  

Science.gov (United States)

The paired catchment study at the forested Bear Brook Watershed in Maine (BBWM) U.S.A. documents interactions among short- to long-term processes of acidification. In 1987-1989, runoff from the two catchments was nearly identical in quality and quantity. Ammonium sulfate has been...

329

Field Study of the Mechanics of the Placement of Dredged Material at Open-Water Disposal Sites. Volume I. Main Text and Appendices A-1.  

Science.gov (United States)

A field study has been made of the mechanics of the placement of dredged material at five locations, an estuarine site on the Atlantic and one on the Pacific coast, two sites in the Great Lakes, and one in the open ocean. The objective was to observe all ...

H. J. Bokuniewicz J. Gebert R. B. Gordon J. L. Higgins P. Kaminsky

1978-01-01

330

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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....

2010-01-01

331

An Investigation of Neutrino-Driven Convection and the Core Collapse Supernova Mechanism Using Multigroup Neutrino Transport  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate neutrino-driven convection in core collapse supernovae and its ramifications for the explosion mechanism. We begin with an ``optimistic'' 15 solar mass precollapse model, which is representative of the class of stars with compact iron cores. This model is evolved through core collapse and bounce in one dimension using multigroup (neutrino-energy--dependent) flux-limited diffusion (MGFLD) neutrino transport and Lagrangian hydrodynamics, providing realistic init...

Mezzacappa, A.; Calder, A. C.; Bruenn, S. W.; Blondin, J. M.; Guidry, M. W.; Strayer, M. R.; Umar, A. S.

1996-01-01

332

Mechanical CPR devices compared to manual CPR during out-of-hospital cardiac arrest and ambulance transport: a systematic review  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Aims The aim of this paper was to conduct a systematic review of the published literature to address the question: “In pre-hospital adult cardiac arrest (asystole, pulseless electrical activity, pulseless Ventricular Tachycardia and Ventricular Fibrillation), does the use of mechanical Cardio-Pulmonary Resuscitation (CPR) devices compared to manual CPR during Out-of-Hospital Cardiac Arrest and ambulance transport, improve outcomes (e.g. Quality of CPR, Return Of Sp...

Ong Marcus; Mackey Kevin E; Zhang Zhong; Tanaka Hideharu; Ma Matthew; Swor Robert; Shin Sang

2012-01-01

333

Mechanisms controlling surface ozone over East Asia: a multiscale study coupling regional and global chemical transport models  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Mechanisms controlling surface ozone (O3) over East Asia are examined using the regional Community Multiscale Air Quality (CMAQ) model at two horizontal scales: 81 km and 27 km. Through sensitivity studies and comparison with recently available satellite data and surface measurements in China and Japan, we find that the O3 budget over East Asia shows complex interactions among photochemical production, regional transport, meteorological conditions...

Lin, M.; Holloway, T.; Oki, T.; Streets, D. G.; Richter, A.

2008-01-01

334

P2Y1 receptor inhibits GABA transport through a calcium signalling-dependent mechanism in rat cortical astrocytes.  

Science.gov (United States)

Astrocytes express a variety of purinergic (P2) receptors, involved in astrocytic communication through fast increases in [Ca(2+) ]i . Of these, the metabotropic ATP receptors (P2Y) regulate cytoplasmic Ca(2+) levels through the PLC-PKC pathway. GABA transporters are a substrate for a number of Ca(2+) -related kinases, raising the possibility that calcium signalling in astrocytes impact the control of extracellular levels of the major inhibitory transmitter in the brain. To access this possibility we tested the influence of P2Y receptors upon GABA transport into astrocytes. Mature primary cortical astroglial-enriched cultures expressed functional P2Y receptors, as evaluated through Ca(2+) imaging, being P2Y1 the predominant P2Y receptor subtype. ATP (100 ?M, for 1 min) caused an inhibition of GABA transport through either GAT-1 or GAT-3 transporters, decreasing the Vmax kinetic constant. ATP-induced inhibition of GATs activity was still evident in the presence of adenosine deaminase, precluding an adenosine-mediated effect. This, was mimicked by a specific agonist for the P2Y1,12,13 receptor (2-MeSADP). The effect of 2-MeSADP on GABA transport was blocked by the P2 (PPADS) and P2Y1 selective (MRS2179) receptor antagonists, as well as by the PLC inhibitor (U73122). 2-MeSADP failed to inhibit GABA transport in astrocytes where intracellular calcium had been chelated (BAPTA-AM) or where calcium stores were depleted (?-cyclopiazonic acid, CPA). In conclusion, P2Y1 receptors in astrocytes inhibit GABA transport through a mechanism dependent of P2Y1 -mediated calcium signalling, suggesting that astrocytic calcium signalling, which occurs as a consequence of neuronal firing, may operate a negative feedback loop to enhance extracellular levels of GABA. GLIA 2014;62:1211-1226. PMID:24733747

Jacob, Pedro F; Vaz, Sandra H; Ribeiro, Joaquim A; Sebastião, Ana M

2014-08-01

335

Mechanisms of disease: psychomotor retardation and high T3 levels caused by mutations in monocarboxylate transporter 8.  

Science.gov (United States)

The actions and the metabolism of thyroid hormone are intracellular events that require the transport of iodothyronines across the plasma membrane. It is increasingly clear that this process does not occur by simple diffusion, but is facilitated by transport proteins. Only recently have iodothyronine transporters been identified at the molecular level, of which organic anion transporting polypeptide 1C1 and monocarboxylate transporter 8 (MCT8) deserve special mention, because of their high activity and specificity for iodothyronines. Organic anion transporting polypeptide 1C1 is almost exclusively expressed in brain capillaries, and may be crucial for the transport of the prohormone T4 across the blood-brain barrier. MCT8 is also expressed in the brain--in particular, in neurons--but also in other tissues. MCT8 seems to be especially important for the uptake of active hormone T3 into neurons, which is essential for optimal brain development. T3 is produced from T4 by type 2 deiodinase in neighboring astrocytes. Neurons express type 3 deiodinase, the enzyme that terminates T3 activity. The SLC16A2 (formerly MCT8) gene is located on chromosome Xq13.2 and has recently been associated with a syndrome combining severe, X-linked, psychomotor retardation and high serum T3 levels. In over 20 families, where affected males have developed this syndrome, several mutations in MCT8 have been identified. The disease mechanism is thought to involve a defect in the neuronal entry of T3 and, therefore, in the action and metabolism of T3 in these cells. This defect results in impaired neurological development and a decrease in T3 clearance. PMID:16957765

Friesema, Edith C H; Jansen, Jurgen; Heuer, Heike; Trajkovic, Marija; Bauer, Karl; Visser, Theo J

2006-09-01

336

Metaiodobenzylguanidine [131I] scintigraphy detects impaired myocardial sympathetic neuronal transport function of canine mechanical-overload heart failure  

International Nuclear Information System (INIS)

In heart failure secondary to chronic mechanical overload, cardiac sympathetic neurons demonstrate depressed catecholamine synthetic and transport function. To assess the potential of sympathetic neuronal imaging for detection of depressed transport function, serial scintigrams were acquired after the intravenous administration of metaiodobenzylguanidine [131I] to 13 normal dogs, 3 autotransplanted (denervated) dogs, 5 dogs with left ventricular failure, and 5 dogs with compensated left ventricular hypertrophy due to a surgical arteriovenous shunt. Nine dogs were killed at 14 hours postinjection for determination of metaiodobenzylguanidine [131I] and endogenous norepinephrine content in left atrium, left ventricle, liver, and spleen. By 4 hours postinjection, autotransplanted dogs had a 39% reduction in mean left ventricular tracer accumulation, reflecting an absent intraneuronal tracer pool. Failure dogs demonstrated an accelerated early mean left ventricular tracer efflux rate (26.0%/hour versus 13.7%/hour in normals), reflecting a disproportionately increased extraneuronal tracer pool. They also showed reduced late left ventricular and left atrial concentrations of tracer, consistent with a reduced intraneuronal tracer pool. By contrast, compensated hypertrophy dogs demonstrated a normal early mean left ventricular tracer efflux rate (16.4%/hour) and essentially normal late left ventricular and left atrial concentrations of tracer. Metaiodobenzylguanidine [131I] scintigraphic findings reflect the integrity of the cardiac sympathetic neuronal transport system in canine mechanical-overload heart failure. Metaiodobenzylguanidine [123I] scintigraphy should be explored as a means of early detection of mechanical-overload heart failure in patients

1987-01-01

337

Statistical mechanical theory of transport and relaxation processes in interacting lattice systems  

CERN Multimedia

The dynamics of lattice systems are described by the irreversible Markovian master equation that is used to calculate microscopic particle and energy fluxes. After reduction of the description the deviations of particle and energy densities from their equilibrium values obey a system of non-Markovian equations that allow one to deduce microscopic expressions for different transport coefficients. All the expressions consist of two parts: one proportional to a static correlation function and the other to the time integral of a time correlation function. The relevant or quasi-equilibrium distribution contributes significantly to transport coefficients contrary to systems obeying the reversible, e.g. Hamiltonian dynamics. At some conditions the memory effects can be disregarded. Then the transport coefficients are represented by lattice gas equilibrium characteristics that are calculated within the self-consistent diagram approximation. Transport coefficients depend on thermodynamic conditions (concentration and ...

Vikhrenko, V S; Groda, Y G

2003-01-01

338

A Receptor Mechanism for Methamphetamine Action in Dopamine Transporter Regulation in BrainS?  

Science.gov (United States)

This study reveals a novel receptor mechanism for methamphetamine action in dopamine transporter (DAT) regulation. Trace amine-associated receptor 1 (TAAR1) is expressed in brain dopaminergic nuclei and is activated by methamphetamine in vitro. Here, we show that methamphetamine interaction with TAAR1 inhibits [3H]dopamine uptake, enhances or induces [3H]dopamine efflux, and triggers DAT internalization. In time course assays in which methamphetamine and [3H]dopamine were concurrently loaded into cells or synaptosomes or in pretreatment assays in which methamphetamine was washed away before [3H]dopamine loading, methamphetamine caused a distinct inhibition in [3H]dopamine uptake in TAAR1 + DAT-cotransfected cells and in wild-type mouse and rhesus monkey striatal synaptosomes. This distinct uptake inhibition was not observed in DAT-only transfected cells or in TAAR1 knockout mouse striatal synaptosomes. In [3H]dopamine efflux assays using the same cell and synaptosome preparations, methamphetamine enhanced [3H]dopamine efflux at a high loading concentration of [3H]dopamine (1 ?M) or induced [3H]dopamine efflux at a low loading concentration of [3H]dopamine (10 nM) in a TAAR1-dependent manner. In DAT biotinylation assays using the same cell and synaptosome preparations, we observed that 1 ?M methamphetamine induced DAT internalization in a TAAR1-dependent manner. All these TAAR1-mediated effects of methamphetamine were blocked by the protein kinase inhibitors H89 [N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline] and/or 2-{8-[(dimethylamino) methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-(1-methylindol-3-yl)maleimide (Ro32-0432), suggesting that methamphetamine interaction with TAAR1 triggers cellular phosphorylation cascades and leads to the observed effects of methamphetamine on DAT. These findings demonstrate a mediatory role of TAAR1 in methamphetamine action in DAT regulation and implicate this receptor as a potential target of therapeutics drugs for methamphetamine addiction.

Xie, Zhihua; Miller, Gregory M.

2009-01-01

339

A receptor mechanism for methamphetamine action in dopamine transporter regulation in brain.  

Science.gov (United States)

This study reveals a novel receptor mechanism for methamphetamine action in dopamine transporter (DAT) regulation. Trace amine-associated receptor 1 (TAAR1) is expressed in brain dopaminergic nuclei and is activated by methamphetamine in vitro. Here, we show that methamphetamine interaction with TAAR1 inhibits [(3)H]dopamine uptake, enhances or induces [(3)H]dopamine efflux, and triggers DAT internalization. In time course assays in which methamphetamine and [(3)H]dopamine were concurrently loaded into cells or synaptosomes or in pretreatment assays in which methamphetamine was washed away before [(3)H]dopamine loading, methamphetamine caused a distinct inhibition in [(3)H]dopamine uptake in TAAR1 + DAT-cotransfected cells and in wild-type mouse and rhesus monkey striatal synaptosomes. This distinct uptake inhibition was not observed in DAT-only transfected cells or in TAAR1 knockout mouse striatal synaptosomes. In [(3)H]dopamine efflux assays using the same cell and synaptosome preparations, methamphetamine enhanced [(3)H]dopamine efflux at a high loading concentration of [(3)H]dopamine (1 muM) or induced [(3)H]dopamine efflux at a low loading concentration of [(3)H]dopamine (10 nM) in a TAAR1-dependent manner. In DAT biotinylation assays using the same cell and synaptosome preparations, we observed that 1 muM methamphetamine induced DAT internalization in a TAAR1-dependent manner. All these TAAR1-mediated effects of methamphetamine were blocked by the protein kinase inhibitors H89 [N-[2-(4-bromocinnamylamino)ethyl]-5-isoquinoline] and/or 2-{8-[(dimethylamino) methyl]-6,7,8,9-tetrahydropyrido[1,2-a]indol-3-yl}-3-(1-methylindol-3-yl)maleimide (Ro32-0432), suggesting that methamphetamine interaction with TAAR1 triggers cellular phosphorylation cascades and leads to the observed effects of methamphetamine on DAT. These findings demonstrate a mediatory role of TAAR1 in methamphetamine action in DAT regulation and implicate this receptor as a potential target of therapeutics drugs for methamphetamine addiction. PMID:19364908

Xie, Zhihua; Miller, Gregory M

2009-07-01

340

Mechanism of active transport: free energy dissipation and free energy transduction.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The thermodynamic pathway for "chemiosmotic" free energy transduction in active transport is discussed with an ATP-driven Ca2+ pump as an illustrative example. Two innovations are made in the analysis. (i) Free energy dissipated as heat is rigorously excluded from overall free energy bookkeeping by focusing on the dynamic equilibrium state of the chemiosmotic process. (ii) Separate chemical potential terms for free energy donor and transported ions are used to keep track of the thermo...

1982-01-01

 
 
 
 
341

The Mechanism of Field-Scale Solute Transport: An insight from Numerical Simulations  

Science.gov (United States)

Field-scale transport of conservative (chloride) and reactive (nitrate) solutes was analyzed by means of two different model processes for the local description of the transport. The first is the classical, one-region advection dispersion equation (ADE) model, while the second is the two-region, mobile-immobile (MIM) model. The analyses were performed by means of detailed three-dimensional (3-D), numerical simulations of the flow and the transport considering realistic features of the soil-water-plant-atmosphere system, pertinent to a turf field located in the Glil Yam site, Israel, irrigated with treated waste water (TWW). Simulated water content and concentration profiles were compared with available measurements of their counterparts. Results of the analyses suggest that the behavior of both the conservative and the reactive solutes in the Glil Yam site is quantified better when the transport on the local scale is modeled as a two-region, MIM model, than when a single-region, ADE model is used. Reconstruction of the shape of the measured solute concentration profiles using the MIM transport model, required relatively large immobile water content fraction and relatively small mass transfer coefficient. These results suggest that in the case of initially non-zero solute concentration profile (e.g., chloride and nitrate), the 3-D ADE transport model may significantly overestimate the groundwater contamination hazard posed by the solutes moving through the vadose zone, as compared with the 3-D MIM transport model, while the opposite is true in the case of initially zero solute concentration profile (e.g., carbamazepine). These findings stem from the combination of relatively large immobile water content fraction and relatively small mass transfer coefficient taken into account in the MIM transport model. In the first case, this combination forces a considerable portion of the solute mass to remain in the immobile region of the water-filled pores, while the opposite is true in the second case.

Russo, David

2014-05-01

342

Mechanisms underlying modulation of monocarboxylate transporter 1 (MCT1) by somatostatin in human intestinal epithelial cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Somatostatin (SST), an important neuropeptide of the gastrointestinal tract has been shown to stimulate sodium chloride absorption and inhibit chloride secretion in the intestine. However, the effects of SST on luminal butyrate absorption in the human intestine have not been investigated. Earlier studies from our group and others have shown that monocarboxylate transporter (MCT1) plays an important role in the transport of butyrate in the human intestine. The present studies were undertaken t...

2009-01-01

343

Epidermal growth factor upregulates serotonin transporter in human intestinal epithelial cells via transcriptional mechanisms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Serotonin transporter (SERT) regulates extracellular availability of serotonin and is a potential pharmacological target for gastrointestinal disorders. A decrease in SERT has been implicated in intestinal inflammatory and diarrheal disorders. However, little is known regarding regulation of SERT in the intestine. Epidermal growth factor (EGF) is known to influence intestinal electrolyte and nutrient transport processes and has protective effects on intestinal mucosa. Whether EGF regulates SE...

Gill, Ravinder K.; Anbazhagan, Arivarasu Natarajan; Esmaili, Ali; Kumar, Anoop; Nazir, Saad; Malakooti, Jaleh; Alrefai, Waddah A.; Saksena, Seema

2011-01-01

344

Structure and molecular mechanism of a nucleobase-cation-symport-1 family transporter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The ‘Nucleobase-Cation-Symport-1’, NCS1, transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85 Å resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 transmembrane helices, ten of which are arranged in two inverted repeats of 5 helices. The structures of the outward-facing open and substrate-bound occluded conformations were solved showing how the outwa...

Weyand, Simone; Shimamura, Tatsuro; Yajima, Shunsuke; Suzuki, Shun Ichi; Mirza, Osman; Krusong, Kuakarun; Carpenter, Elisabeth P.; Rutherford, Nicholas G.; Hadden, Jonathan M.; O Reilly, John; Ma, Pikyee; Saidijam, Massoud; Patching, Simon G.; Hope, Ryan J.; Norbertczak, Halina T.

2008-01-01

345

Structure and molecular mechanism of a nucleobase-cation-symport-1 family transporter.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nucleobase-cation-symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 transmembrane helices, 10 of which are arranged in two inverted repeats of five helices. The structures of the outward-facing open and substrate-bound occluded conformations were solved, showing how the ou...

Weyand, S.; Shimamura, T.; Yajima, S.; Suzuki, S.; Mirza, O.; Krusong, K.; Carpenter, Ep; Rutherford, Ng; Hadden, Jm; O Reilly, J.; Ma, P.; Saidijam, M.; Patching, Sg; Hope, Rj; Norbertczak, Ht

2008-01-01

346

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

347

Abnormal expression of dopamine and serotonin transporters associated with the pathophysiologic mechanism of Tourette syndrome  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Background : Tourette syndrome (TS) is a neurobehavioral and neuropsychiatric disorder and its pathophysiology is not well understood. However, recent studies provide evidence implicating metabolic abnormalities of dopamine (DA) and serotonin (5-HT) of the basal ganglia both in TS patients and TS animal models. It is also well known that dopamine and serotonin transporters (DAT and SERT) are monoamine neurotransmitter transporters, which participate in the metabolism of DA and 5-HT, re...

Jijun Li; Zaiwang Li; Anyuan Li; Shuzhen Wang; Fanghua Qi; Lin Zhao; Hong Lv

2010-01-01

348

Mechanisms of cilia-driven transport in the airways in the absence of mucus.  

Science.gov (United States)

Airway mucus is thought to be required for the clearance of inhaled particles by mucociliary transport, but this view has recently been challenged. To test if mucus is necessary for cilia-driven particle transport, we removed mucus from murine and human ex vivo airway preparations by thorough rinsing with buffer with or without additional dithiothreitol washing. The transport of particles with diameters of 4.5 ?m, 200 nm, and 40 nm and of bacteria was analyzed by video microscopy. Complete removal of mucus was verified by wheat germ agglutinin staining and by scanning electron microscopy. In the absence of mucus, we observed efficient transport of particles and bacteria by direct cilia-mediated propulsion or via fluid flow generated by ciliary beating. Virus-sized particles had the tendency to attach to cilia. Because direct contact of particles with ciliated cells occurs in the absence of mucus, we examined if this direct interaction changes epithelial function. Neither bacteria- nor LPS-induced nuclear translocation of NF-?B p65 in ciliated cells occurred, indicating that mere contact between ciliated cells and bacteria during transport does not activate the epithelium. Attachment of virus-sized particles to cilia could induce mucus release and/or increase the ciliary beat frequency. Our results indicate that cilia-driven transport of particles with various sizes is possible in murine and human airways without the presence of mucus. If mucus-free transport fails, the epithelium can react by releasing mucus or increasing the ciliary beat frequency to maintain particle transport. PMID:24467665

Bermbach, Saskia; Weinhold, Karina; Roeder, Thomas; Petersen, Frank; Kugler, Christian; Goldmann, Torsten; Rupp, Jan; König, Peter

2014-07-01

349

Environmental Impact of Flooding in the Main (Smallwood) Reservoir of the Churchill Falls Power Plant, Labrador, Canada. II. Chemical and Mechanical Analysis of Flooded Trees and Shoreline Changes.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Churchill Falls Hydro Project (called the “Upper Churchill Development”) in Labrador, Canada, was initiated in the late 1960s. At that time, in general, not much attention was paid to the impact of such devel-opment on the flooding of vegetation especially forest stands. Both forested and un-forested terrestrial vege-tation types were flooded (244 915 ha). Some islands were created and in addition portions of existing areas were flooded to form islands (74 075 ha) in the Main (Smallwo...

Denes Bajzak; Roberts, Bruce A.

2011-01-01

350

Biogenesis of Tim Proteins of the Mitochondrial Carrier Import Pathway: Differential Targeting Mechanisms and Crossing Over with the Main Import Pathway  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Two major routes of preprotein targeting into mitochondria are known. Preproteins carrying amino-terminal signals mainly use Tom20, the general import pore (GIP) complex and the Tim23–Tim17 complex. Preproteins with internal signals such as inner membrane carriers use Tom70, the GIP complex, and the special Tim pathway, involving small Tims of the intermembrane space and Tim22–Tim54 of the inner membrane. Little is known about the biogenesis and assembly of the Tim proteins of this carrie...

Kurz, Martin; Martin, Heiko; Rassow, Joachim; Pfanner, Nikolaus; Ryan, Michael T.

1999-01-01

351

Mechanical Ventilation in Hypobaric Atmosphere - Aeromedical Transport of Critically Ill Patients.  

Science.gov (United States)

Mechanical ventilation is used in most of the aeroevacuations of critically ill patients. Patients and mechanical ventilators suffer from variations in the environmental pressure, partial pressure of oxygen, humidity, luminosity, accelerations and vibrati...

A. Hernandez Abadia de Barbara A. Gil Heras J. A. Lopez Lopez F. Rios Tejada

2004-01-01

352

Main Achievements 2003-2004 - Interdisciplinary Research - Applications of nuclear methods to biomedical physics, environmental biology, environmental physics, and medical physics - Mechanical properties of living cells  

International Nuclear Information System (INIS)

Mechanical properties of living cells, as potential markers of pathological cell state, were investigated in their native environment by atomic force microscopy. In normal and pathological living cells, local elasticity and the specific binding interactions between biomolecules were measured, showing that the interaction force between lectins (ConA, SNA, PHA-L) and cell surface carbohydrates was altered due to cancerous transformation. In further collaboration with the Collegium Medicum of the Jagiellonian University, the elasticity of large number of blood samples, originated from healthy and hospitalized patients, was studied as a first attempt at applying AFM as a tool in medical diagnostics

2005-01-01

353

Influence of transport mechanisms on nucleation and grain structure formation in DC cast aluminium alloy ingots  

International Nuclear Information System (INIS)

The grain structure formation in direct chill (DC) casting is directly linked to nucleation, which is generally promoted by inoculation. Inoculation prevents defects, but also modifies the physical properties by changing the microstructure. We studied the coupling of the nucleation on inoculant particles and the grain growth in the presence of melt flow induced by thermosolutal convection and of the transport of free-floating equiaxed grains. We used a volume-averaged two-phase multiscale model with a fully coupled description of phenomena on the grain scale (nucleation on grain refiner particles and grain growth) and on the product scale (macroscopic transport). The transport of inoculant particles is also modeled, which accounts for the inhomogeneous distribution of inoculant particles in the melt. The model was applied to an industrial sized (350mm thick) DC cast aluminium alloy ingot. A discretised nuclei size distribution was defined and the impact of different macroscopic phenomena on the grain structure formation was studied: the zone and intensity of nucleation and the resulting grain size distribution. It is shown that nucleation in the presence of macroscopic transport cannot be explained only in terms of cooling rate, but variations of composition, nuclei density and grain density, all affected by transport, must be accounted for.

2012-01-12

354

Environmental Impact of Flooding in the Main (Smallwood Reservoir of the Churchill Falls Power Plant, Labrador, Canada. II. Chemical and Mechanical Analysis of Flooded Trees and Shoreline Changes.  

Directory of Open Access Journals (Sweden)

Full Text Available The Churchill Falls Hydro Project (called the “Upper Churchill Development” in Labrador, Canada, was initiated in the late 1960s. At that time, in general, not much attention was paid to the impact of such devel-opment on the flooding of vegetation especially forest stands. Both forested and un-forested terrestrial vege-tation types were flooded (244 915 ha. Some islands were created and in addition portions of existing areas were flooded to form islands (74 075 ha in the Main (Smallwood Reservoir area. This paper, the second in a series provides the rate of bio-chemical and physical deterioration of flooded trees in typical forest stands. The analysis of samples taken from selected trees indicated that their lignin content slightly increased and their elastic module decreased on the short term (three years after flooded. A model for the new shore line development was developed and illustrated with graphics and with an aerial photographic sterogramm in a typical flooded forest stand. Major changes were taking place within three years after the flooding. The most significant changes had occurred near the edge of the reservoir due to the continuous variation of water level caused by the amount of seasonal precipitation and by the required drawdown of water to operate the power plant. In general the water in the Main Reservoir reaches its maximum elevation in August, after this (from October to May the water level slowly decreases during the ice cover. Ice forms first, when the water level is high, then the water level drops resulting in large vertical forces on the trees trapped in the ice. When the water in the reservoir is at its lowest point (at the spring the ice cruses the trees, and when the water rises (in July the ice up-roots the captured trees.

Bruce A. Roberts

2011-03-01

355

Analysis and further development of fracture mechanics failure concepts. Main topic: Application of the J integral concept and its extensions on component-relevant situations  

International Nuclear Information System (INIS)

In many investigations with increasingly complex conditions of use, the concepts of elastic/plastic fracture mechanics and particularly the J integral concept for the quantitative evaluation of failure behaviour have proved successful. This was proved in this project by largely clearing up the effects of constraint in the environment of cracks and the use of the J integral concept with superimposed thermal and mechanical stresses which can occur in thermal shock transients important for safety analysis. In continuing the investigations of dynamic JR curves, it was confirmed that the tendency to form auxiliary cracks and therefore to raise the crack resistance curve increases with the stress parameters and also with the size of the sample. Here and in investigations on the effect of large crack widths on quickly loaded disks with side cracks caused some difficulties. The improvement of the J integral calculation aimed at by correction terms could not be satisfactorily achieved. One way out is the crack energy to describe great extensions of cracks. (orig.)

1991-01-01

356

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 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)

2010-10-03

357

Vibrational mechanics in an optical lattice: controlling transport via potential renormalization  

CERN Multimedia

We demonstrate theoretically and experimentally the phenomenon of vibrational resonance in a periodic potential, using cold atoms in an optical lattice as a model system. A high-frequency (HF) drive, with frequency much larger than any characteristic frequency of the system, is applied by phase-modulating one of the lattice beams. We show that the HF drive leads to the renormalization of the potential. We used transport measurements as a probe of the potential renormalization. The very same experiments also demonstrate that transport can be controlled by the HF drive via potential renormalization.

Wickenbrock, A; Wahab, N A Abdul; Phoonthong, P; Cubero, D; Renzoni, F

2011-01-01

358

POTENTIAL MECHANISMS INVOLVED IN THE ABSORPTIVE TRANSPORT OF CADMIUM IN ISOLATED PERFUSED RABBIT RENAL PROXIMAL TUBULES  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lumen-to-cell transport, cellular accumulation, and toxicity of cadmium as ionic cadmium (Cd2+) or as the L-cysteine (Cys) or D,L-homocysteine (Hcy) S-conjugate of cadmium (Cys-S-Cd-S-Cys, Hcy-S-Cd-S-Hcy) were studied in isolated, perfused rabbit proximal tubular segments. When Cd2+ (0.73?M) or Cys-S-Cd-S-Cys (0.73?M) was perfused through the lumen of S2 segments of the proximal tubule, no visual evidence of cellular pathological changes was detected during 30 min of study. Cd2+-transport w...

Wang, Yanhua; Zalups, Rudolfs K.; Barfuss, Delon W.

2010-01-01

359

Evidence of transport, sedimentation and coagulation mechanisms in the relaxation of post-volcanic stratospheric aerosols  

Directory of Open Access Journals (Sweden)

Full Text Available Spatio-temporal distributions of stratospheric aerosols, measured by the ORA instrument from August 1992 until May 1993, are presented in the latitude range (40° S–40° N. Particle total number density, mode radius and distribution width are derived and interpreted. The respective roles of advection, sedimentation and coagulation are discussed. We also identify clear transport/sedimentation patterns and we show the enhancement of coagulation in stagnation regions. Efficient transport of aerosol particles up to 50 km is suggested.

Key words. Atmospheric composition and structure (aerosols and particles; middle atmosphere-composition and chemistry; volcanic effects

D. Fussen

360

Interfacial Reduction-Oxidation Mechanisms Governing Fate and Transport of Contaminants in the Vadose Zone  

Energy Technology Data Exchange (ETDEWEB)

There are many soil contamination sites at the Department of Energy (DOE) installations that contain radionuclides and toxic metals such as uranium (U), technetium (Tc), and chromium (Cr). Since these contaminants are the main 'risk drivers' at the Hanford site (WA) and some of them also pose significant risk at other DOE facilities (e.g., Oak Ridge Reservation - TN; Rocky Flats - CO), development of technologies for cost effective site remediation is needed. Current assessment indicates that complete removal of these contaminants for ex-situ disposal is infeasible, thus in-situ stabilization through reduction to insoluble species is considered one of the most important approaches for site remediation. In Situ Gaseous Reduction (ISGR) is a technology developed by Pacific Northwest National Laboratory (PNNL) for vadose zone soil remediation. The ISGR approach uses hydrogen sulfide (H{sub 2}S) for reductive immobilization of contaminants that show substantially lower mobility in their reduced forms (e.g., Tc, U, and Cr). The technology can be applied in two ways: (i) to immobilize or stabilize pre-existing contaminants in the vadose zone soils by direct H{sub 2}S treatment, or (ii) to create a permeable reactive barrier (PRB) that prevents the migration of contaminants. Direct treatment involves reduction of the contaminants by H{sub 2}S to less mobile species. Formation of a PRB is accomplished through reduction of ferric iron species in the vadose zone soils by H{sub 2}S to iron sulfides (e.g., FeS), which provides a means for capturing the contaminants entering the treated zone. Potential future releases may occur during tank closure activities. Thus, the placement of a permeable reactive barrier by ISGR treatment can be part of the leak mitigation program. Deployment of these ISGR approaches, however, requires a better understanding of the immobilization kinetics and mechanisms, and a better assessment of the long-term effectiveness of treatment. The primary objective of this project was to understand the complex interactions among the contaminants (i.e., Cr, Tc, and U), H{sub 2}S, and various soil constituents. The reaction with iron sulfide is also the focus of the research, which could be formed from iron oxide reduction by hydrogen sulfide. Factors controlling the reductive immobilization of these contaminants were identified and quantified. The results and fundamental knowledge obtained from this project shall help better evaluate the potential of in situ gaseous treatment to immobilize toxic and radioactive metals examined.

Principal Investigator: Baolin Deng, University of Missouri, Columbia, MO; Co-Principal Investigator: Silvia Sabine Jurisson, University of Missouri, Columbia, MO; Co-Principal Investigator: Edward C. Thornton, Pacific Northwest National Laboratory Richland, WA; Co-Principal Investigator: Jeff Terry, Illinois Institute of Technology, Chicago, IL

2008-05-12

 
 
 
 
361

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

1963-01-01

362

The secretory intestinal transport of some beta-lactam antibiotics and anionic compounds: a mechanism contributing to poor oral absorption.  

Science.gov (United States)

The mechanisms of intestinal permeation of several beta-lactam antibiotics and anionic compounds were studied in vitro using excised rat intestinal segments. Permeation of cefazolin through jejunum, ileum and colon was highly secretory-oriented; serosal-to-mucosal permeation rates were two- to three-fold greater than mucosal-to-serosal permeation rates. Serosal-to-mucosal permeation decreased in the absence of D-glucose, and mucosal-to-serosal permeation increased, indicating that the preferential secretory transport of cefazolin is energy dependent. Ampicillin permeation across rat jejunum also favored secretion, whereas the permeation of cefaclor and cephradine favored absorption. Because cefazolin is anionic, several structurally unrelated anionic compounds were also tested. Of these only phenol red exhibited preferential serosal-to-mucosal permeation. The intestinal permeation of phenol red was concentration dependent and glucose dependent. Verapamil and a monoclonal antibody to P-glycoprotein only modestly and inconsistently affected the permeation of cefazolin, ampicillin and phenol red. Probenecid and guanidine were much more effective inhibitors of cefazolin and phenol red secretion. Mutual interactions between cefazolin and phenol red were also observed. These results show that the rat intestine has the capability for net secretory transport of some hydrophilic, anionic compounds. Transport of these compounds has some of the characteristics of organic anion and organic cation transport systems. PMID:8764353

Saitoh, H; Gerard, C; Aungst, B J

1996-07-01

363

Ozone-surface interactions: Investigations of mechanisms, kinetics, mass transport, and implications for indoor air quality  

Energy Technology Data Exchange (ETDEWEB)

In this dissertation, results are presented of laboratory investigations and mathematical modeling efforts designed to better understand the interactions of ozone with surfaces. In the laboratory, carpet and duct materials were exposed to ozone and measured ozone uptake kinetics and the ozone induced emissions of volatile organic compounds. To understand the results of the experiments, mathematical methods were developed to describe dynamic indoor aldehyde concentrations, mass transport of reactive species to smooth surfaces, the equivalent reaction probability of whole carpet due to the surface reactivity of fibers and carpet backing, and ozone aging of surfaces. Carpets, separated carpet fibers, and separated carpet backing all tended to release aldehydes when exposed to ozone. Secondary emissions were mostly n-nonanal and several other smaller aldehydes. The pattern of emissions suggested that vegetable oils may be precursors for these oxidized emissions. Several possible precursors and experiments in which linseed and tung oils were tested for their secondary emission potential were discussed. Dynamic emission rates of 2-nonenal from a residential carpet may indicate that intermediate species in the oxidation of conjugated olefins can significantly delay aldehyde emissions and act as reservoir for these compounds. The ozone induced emission rate of 2-nonenal, a very odorous compound, can result in odorous indoor concentrations for several years. Surface ozone reactivity is a key parameter in determining the flux of ozone to a surface, is parameterized by the reaction probability, which is simply the probability that an ozone molecule will be irreversibly consumed when it strikes a surface. In laboratory studies of two residential and two commercial carpets, the ozone reaction probability for carpet fibers, carpet backing and the equivalent reaction probability for whole carpet were determined. Typically reaction probability values for these materials were 10{sup {minus}7}, 10{sup {minus}5}, and 10{sup {minus}5} respectively. To understand how internal surface area influences the equivalent reaction probability of whole carpet, a model of ozone diffusion into and reaction with internal carpet components was developed. This was then used to predict apparent reaction probabilities for carpet. He combines this with a modified model of turbulent mass transfer developed by Liu, et al. to predict deposition rates and indoor ozone concentrations. The model predicts that carpet should have an equivalent reaction probability of about 10{sup {minus}5}, matching laboratory measurements of the reaction probability. For both carpet and duct materials, surfaces become progressively quenched (aging), losing the ability to react or otherwise take up ozone. He evaluated the functional form of aging and find that the reaction probability follows a power function with respect to the cumulative uptake of ozone. To understand ozone aging of surfaces, he developed several mathematical descriptions of aging based on two different mechanisms. The observed functional form of aging is mimicked by a model which describes ozone diffusion with internal reaction in a solid. He shows that the fleecy nature of carpet materials in combination with the model of ozone diffusion below a fiber surface and internal reaction may explain the functional form and the magnitude of power function parameters observed due to ozone interactions with carpet. The ozone induced aldehyde emissions, measured from duct materials, were combined with an indoor air quality model to show that concentrations of aldehydes indoors may approach odorous levels. He shows that ducts are unlikely to be a significant sink for ozone due to the low reaction probability in combination with the short residence time of air in ducts.

Morrison, Glenn C.

1999-12-01

364

Hypolipidaemic effects and mechanisms of the main component of Opuntia dillenii Haw. polysaccharides in high-fat emulsion-induced hyperlipidaemic rats.  

Science.gov (United States)

The antihyperlipidaemic effects of ODP-Ia, one of the main components of Opuntia dillenii Haw. polysaccharides, were studied. Gavage administration of ODP-Ia was observed to significantly decrease serum lipid levels and to increase serum high-density lipoprotein cholesterol level in hyperlipidaemic rats. Similar suppressive patterns were also seen in hepatic total cholesterol and triglyceride levels. Moreover, the ODP-Ia administration significantly increased serum lecithin:cholesterol acyltransferase activity, increased the production of serum NO, inhibited hepatic HMG-CoA reductase activity, augmented serum and hepatic superoxide dismutase activities and decreased the serum and hepatic malondialdehyde contents in hyperlipidaemic rats. In addition, a histopathological examination revealed that ODP-Ia administration significantly suppressed inflammatory cell infiltration and the expression of VCAM-1. Together, these results indicate that ODP-Ia is a potential natural product for the treatment of hyperlipidaemia-related diseases by improving antioxidant levels, modulating the activities of enzymes involved in cholesterol metabolism, promoting the production of NO and suppressing the expression of VCAM-1, thereby suppressing lipid accumulation and inflammatory cell infiltration. PMID:23107714

Zhao, Long-Yan; Huang, Wei; Yuan, Qing-Xia; Cheng, Jie; Huang, Zhen-Chi; Ouyang, Le-Jun; Zeng, Fu-Hua

2012-09-15

365

[Studies on L-glutamate transport mechanism in human placental trophoblast microvilli membrane vesicles].  

Science.gov (United States)

The uptake of L-glutamate in brush border (microvilli) vesicles prepared from human term placenta was studied using the rapid filtration technique. The uptake of L-glutamate into the vesicles occurred osmotically, and preincubation with L-glutamate increased the uptake of amino acid. These findings indicate that the uptake of L-glutamate by placental trophoblast brush border membranes represents the transport into membrane vesicles. A Na+ electrochemical gradient (extravesicular greater than intravesicular) stimulated the initial rate of L-glutamate uptake about three times. The initial rate of transport exhibited saturation kinetics with respect to the L-glutamate concentration; an apparent Km of 0.15 mM and V max of 70 pmol/mg protein in 20 seconds were calculated. The uptake of L-glutamate into the vesicles was competitively inhibited by L-glutamate and L-cysteate (acidic amino acid). These results indicate that a Na-dependent acidic amino acid specific transport system exists in the placental trophoblast microvilli membrane. These results indicate that the transport of L-glutamate across the placental microvilli membrane is sodium-dependent and carrier mediated. PMID:3973444

Iioka, H; Moriyama, I; Kyuma, M; Ito, K; Amasaki, M; Ichijo, M

1985-02-01

366

Modeling of the Electro-Mechanical Response of Carbon Nanotubes: Molecular Dynamics and Transport Calculations  

Science.gov (United States)

This paper presents viewgraphs on the modeling of the electromechanical response of carbon nanotubes, utilizing molecular dynamics and transport calculations. The topics include: 1) Simulations of the experiment; 2) Effect of diameter, length and temperature; and 3) Study of sp3 coordination-"The Table experiment".

Svizhenko, Alexel; Anantram, M. P.; Maiti, Amitesh

2003-01-01

367

Electrochemistry in concentrated organic redox solutions. Unusual reaction mechanisms and transport phenomena  

Energy Technology Data Exchange (ETDEWEB)

This report discusses and gives several examples of voltammetric studies in concentrated organic solutions and show that quantitative measurements can be performed under conditions where redox species is present in molar quantities. A brief description of experimental methods and theory of ultramicroelectrode techniques is presented. Examples of transport phenomena, coupled homogeneous reactions, and magnetic field effects in highly concentrated organic redox solutions are given.

Ragsdale, S.R.; Paulson, S.C.; White, H.S. [Utah Univ., Salt Lake City, UT (United States). Dept. of Chemistry; Feldberg, S.W. [Brookhaven National Lab., Upton, NY (United States)

1997-04-01

368

Somatic spectrum of cancer-associated single basepair substitutions in the TP53 gene is determined mainly by endogenous mechanisms of mutation and by selection.  

Science.gov (United States)

The spectrum of somatic TP53 single basepair substitutions detected in 955 cancers was compared with that of 2,224 different germline mutations in 279 different human genes (other than TP53), reported as the cause of inherited disease. This comparison reveals that, disregarding a relatively small subset (12%) of TP53 mutations that probably result from the action of exogenous mutagens, both the relative rates and the nearest-neighbor spectra of single basepair substitutions are similar in the two datasets. This spectral resemblance suggests that a substantial proportion of cancer-associated somatic TP53 mutations result from endogenous cellular mechanisms. The likelihood of clinical observation of a particular mutation type differs, however, between tumors and genetic diseases, when the chemical properties of the resulting amino acid substitutions are considered. Together with a sixfold higher observation likelihood for mutations at evolutionarily conserved residues, this finding argues that selection is a critical factor in determining which TP53 mutations are found to be associated with human cancer. PMID:7728149

Krawczak, M; Smith-Sorensen, B; Schmidtke, J; Kakkar, V V; Cooper, D N; Hovig, E

1995-01-01

369

The Simulation of a Spherically Symmetric Supernova of a 13 Solar Mass Star with Boltzmann Neutrino Transport, and Its Implications for the Supernova Mechanism  

CERN Document Server

With three-flavor Boltzmann neutrino transport, we obtain a supernova explosion of a 13 solar mass star in spherical symmetry, the Newtonian limit, without invoking convection. In the absence of convection, prior spherically symmetric models, which implemented approximations to Boltzmann neutrino transport, failed to produce explosions. Our results demonstrate the qualitative change in supernova models enabled by exact transport and have significant consequences for the supernova mechanism.

Mezzacappa, A; Bronson-Messer, O E; Hix, W R; Thielemann, F K; Bruenn, S W; Mezzacappa, Anthony; Liebendoerfer, Matthias; Thielemann, Friederich-Karl; Bruenn, Stephen W.

2001-01-01

370

Effects of nonframework metal cations and phonon scattering mechanisms on the thermal transport properties of polycrystalline zeolite LTA films  

Science.gov (United States)

We present a systematic study to investigate the effects of nonframework cations and the role of phonon scattering mechanisms on the thermal transport properties of zeolite LTA, via experiment and semiempirical lattice dynamics calculations. Our study is motivated by the increasing interest in accurate measurements and mechanistic understanding of the thermal transport properties of zeolite materials. The presence of a nanostructured pore network, extra-framework cations, and tunable framework structure and composition confer interesting thermophysical properties to these materials, making them a good model system to investigate thermal transport in complex materials. Continuous films of zeolite LTA with different nonframework cations (Na+, K+, and Ca+2) were synthesized and characterized. The thermal conductivity was measured using the three-omega method over a wide range of temperature (150-450 K). These are the first thermal conductivity measurements performed on bulk LTA, so they are more accurate than previous measurements, which involved the use of compacted zeolite powders. Our data showed significant dependence of the thermal conductivity on the extra-framework cations as well the temperature. The thermal conductivities of the zeolite LTA samples were modeled with the relaxation time approximation to the Boltzmann transport equation. The full phonon spectra for each type of LTA zeolite were calculated and used in conjunction with semiempirical relaxation time expressions to calculate the thermal conductivity. The results both validated, and suggested the limitations of, this modeling approach. Optical phonons dominated the thermal conductivity and boundarylike scattering was found to be the strongest phonon scattering mechanism, as also observed in MFI zeolite.

Greenstein, Abraham; Hudiono, Yeny; Graham, Samuel; Nair, Sankar

2010-03-01

371

Metabolismo do ferro: uma revisão sobre os principais mecanismos envolvidos em sua homeostase Iron metabolism: an overview on the main mechanisms involved in its homeostasis  

Directory of Open Access Journals (Sweden)

Full Text Available Um perfeito sincronismo entre absorção, utilização e estoque de ferro é essencial para a manutenção do equilíbrio desse metal no organismo. Alterações nesses processos podem levar tanto à deficiência como ao seu acúmulo de ferro, duas situações com repercussões clínicas e laboratoriais importantes para o paciente. Essa revisão aborda os diversos aspectos relacionados com a cinética do ferro, descrevendo as proteínas e mediadores nela envolvidos. Apresenta, ainda, como é feita a regulação intracelular e sistêmica do ferro que visa a manutenção de uma quantidade ótima de ferro para o metabolismo das células e, em especial, para uma perfeita hematopoiese.É discutido também o importante papel da hepcidina, como regulador da homeostase sistêmica. Será a apresenta da a relação entre a hepcidina e a resposta de fase aguda, e como as alterações na expressão da hepcidina podem contribuir com a fisiopatogênese da anemia de doença crônica.The perfect synchronism of intestinal absorption, use and storage of iron is critical for maintaining a balance in the organism. Disorders in these processes may lead either to iron deficiency or to iron overload, both of which have important clinical and laboratorial consequences for the patient. This review describes aspects related to iron metabolism and the participation of several proteins and mediators in these mechanisms. Moreover, intracellular and systemic regulation is responsible for providing the optimal iron concentration for cellular metabolism and, in particular, for adequate hematopoiesis. The relationship between hepcidin and acute phase response is presented and how changes in hepcidin expression may be related to the physiopathogenesis of anemia of chronic disease.

Helena Z. W. Grotto

2008-10-01

372

Metabolismo do ferro: uma revisão sobre os principais mecanismos envolvidos em sua homeostase / Iron metabolism: an overview on the main mechanisms involved in its homeostasis  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: Portuguese Abstract in portuguese Um perfeito sincronismo entre absorção, utilização e estoque de ferro é essencial para a manutenção do equilíbrio desse metal no organismo. Alterações nesses processos podem levar tanto à deficiência como ao seu acúmulo de ferro, duas situações com repercussões clínicas e laboratoriais importantes p [...] ara o paciente. Essa revisão aborda os diversos aspectos relacionados com a cinética do ferro, descrevendo as proteínas e mediadores nela envolvidos. Apresenta, ainda, como é feita a regulação intracelular e sistêmica do ferro que visa a manutenção de uma quantidade ótima de ferro para o metabolismo das células e, em especial, para uma perfeita hematopoiese.É discutido também o importante papel da hepcidina, como regulador da homeostase sistêmica. Será a apresenta da a relação entre a hepcidina e a resposta de fase aguda, e como as alterações na expressão da hepcidina podem contribuir com a fisiopatogênese da anemia de doença crônica. Abstract in english The perfect synchronism of intestinal absorption, use and storage of iron is critical for maintaining a balance in the organism. Disorders in these processes may lead either to iron deficiency or to iron overload, both of which have important clinical and laboratorial consequences for the patient. T [...] his review describes aspects related to iron metabolism and the participation of several proteins and mediators in these mechanisms. Moreover, intracellular and systemic regulation is responsible for providing the optimal iron concentration for cellular metabolism and, in particular, for adequate hematopoiesis. The relationship between hepcidin and acute phase response is presented and how changes in hepcidin expression may be related to the physiopathogenesis of anemia of chronic disease.

Grotto, Helena Z. W..

373

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 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)

2011-09-25

374

Noble gases as natural tracers of water circulation in the Paris Basin: 1. Measurements and discussion of their origin and mechanisms of vertical transport in the basin  

Science.gov (United States)

The concentrations and isotopic compositions of helium, neon, and argon were measured in 29 water samples collected from five superposed aquifers in the Paris Basin (Ypresian, Albian, Neocomian, Dogger, and Trias). In all these groundwater flow systems the data showed excesses of 3He, 4He, and 40Ar above the solubility equilibrium with the atmosphere (air saturated water (ASW)), as well as vertical concentration gradients of these isotopes throughout the basin. The water of the Dogger and the Trias formations also had a 21Ne excess above ASW values. The mean rate of radiogenic and nucleogenic isotope production in the entire sedimentary sequence of the basin cannot produce the measured quantities of 3He, 4He, 21Ne, and 40Ar, if reasonable water residence times are considered. The total calculated production is estimated to represent less than about 13% of the measured values for all isotopes. The greater part (>87%) of the radiogenic and nucleogenic noble gas isotopes is thus believed to originate from the bedrock, and the isotopes are transported vertically through the entire basin. Three mechanisms of transport are considered: advection, dispersion, and molecular diffusion. For the Trias the radiogenic/nucleogenic production ratios of 4He/40Ar and 21Ne/40Ar are close to the mean production rate in the crust (4 ± 3 and 0.96 × 10-7, respectively). For the overlying Dogger, however, these ratios are much higher (4He/40Ar: 10 to 70; 21Ne/40Ar: 8 × 10-7 to 23 × 10-7). We suggest that differences in the vertical diffusive flux of 4He, 21Ne, and 40Ar are the reason for the high isotope ratios observed in the Dogger. In the vertical direction, 4He is transported mostly by diffusion, whereas 40Ar is transported mostly by advection. Neon 21 represents an intermediate situation. The distribution of 3He, 4He,21Ne, and 40Ar throughout the basin can be explained by the existence of only two sources: an atmospheric component contributed by recharge water and a radiogenic/nucleogenic component originating mainly in the bedrock. This concept is supported by two-dimensional cross-section modeling of the water flow in the Paris Basin and the advective, dispersive, and diffusive transport of these noble gases in its multiaquifer system presented in part 2 of this study.

Castro, Maria Clara; Jambon, Albert; de Marsily, Ghislain; Schlosser, Peter

1998-10-01

375

Mechanism of molecular transport in novel reverse-selective nanocomposite membranes  

International Nuclear Information System (INIS)

Full text: Polymer nanocomposites continue to receive tremendous attention as organic-inorganic hybrid materials exhibiting a wide range of interesting, as well as technologically relevant, properties. This work reports a novel use of polymer nanocomposites as reverse-selective membranes. We have found that physical dispersion of nonporous fumed silica [FS] into glassy poly(4-methyl-2-pentyne) [PMP] simultaneously enhances membrane permeability (by as much as 240%) and selectivity for large organic molecules over small permanent gases. This surprising observation, in stark contrast to conventional filled polymer systems, reflects silica-induced disruption of local polymer chain packing and, as discerned by positron annihilation lifetime spectroscopy [PALS], a resulting subtle increase in the size of free volume elements through which molecular transport occurs. Such nanoscale hybridization represents an innovative means of tuning the transport properties of glassy polymeric media through control of molecular ordering

2002-02-01

376

Long-range cargo transport on crowded microtubules: The motor jamming mechanism  

Science.gov (United States)

The hopping model for cargo transport by molecular motors introduced in Goldman and Sena (2009), Goldman (2010) is extended here in order to incorporate the movement of cargo-motor complexes (C-MC). Hopping processes in this context express the possibility for cargo to be exchanged between neighboring motors at a microtubule where the transport takes place. Jamming of motors is essential for cargos to execute long-range movement in this way. Results from computer simulations accompanied by a mean-field analysis of the extended model confirm our previous analytical results and suggests that an interplay between cargo hopping and the movement of the C-MC’s would control the efficiency of cargo transfer and cargo delivery in these model systems.

Rossi, Lucas W.; Radtke, Paul K.; Goldman, Carla

2014-05-01

377

Investigation of silicate surface chemistry and reaction mechanisms associated with mass transport in geologic media  

International Nuclear Information System (INIS)

The concentration and rate of transport of radionuclides through geologic media can be strongly influenced by the extent of sorption on aquifer surfaces. Over time intervals relevant to such transport processes, rock and mineral surfaces cannot be considered as inert, unreactive substrates but rather as groundwater/solidphase interfaces which are commonly in a state of natural or artificially induced disequilibrium. The goal of the present research is to define experimentally the type of water/rock interactions that will influence surface chemistry and hence sorption characteristics and capacities of natural aquifers. As wide a range of silicate minerals as possible was selected for study to represent rock-forming minerals in basalt, tuff, and granite. The minerals include K-feldspar, plagioclase feldspar, olivine, hornblende, biotite, and volcanic glass

1982-09-01

378

Structure and mechanism of the ECF-type ABC transporter for thiamin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Guus Erkens’ PhD thesis is about the thiamin (vitamin B1) transport protein ThiT from the bacterium Lactococcus lactis. During his research project he has investigated the recognition of thiamin by ThiT. Also he has determined the three-dimensional structure of ThiT using X-ray crystallography. These results may provide a starting point for the development of antibiotics.

Erkens, Guus Bjorn

2011-01-01

379

Towards the Restructuring and Co-ordination Mechanisms for the Architecture of Chinese Transport Logistics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

With China’s emergence as a global manufacturing centre, reshaping the country’s logistics industry is assuming a global dimension too. The Chinese transport sector, despite its tremendous potential in facilitating the economic development of the country, is plagued with problems of insufficient infrastructure; overlapping regulatory authority; operational inefficiencies and a lack of logistics culture. The thesis shows that China urgently needs to restructure the architecture of its tra...

Yang, J.

2009-01-01

380

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Guenet, B.; Eglin, T.; Vasilyeva, N.; Peylin, P.; Ciais, P.; Chenu, C.

2012-01-01

 
 
 
 
381

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 measure...

Guenet, B.; Eglin, T.; Vasilyeva, N.; Peylin, P.; Ciais, P.; Chenu, C.

2013-01-01

382

Multistep molecular mechanism for Bone morphogenetic protein extracellular transport in the Drosophila embryo  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In the Drosophila embryo, formation of a bone morphogenetic protein (BMP) morphogen gradient requires transport of a heterodimer of the BMPs Decapentaplegic (Dpp) and Screw (Scw) in a protein shuttling complex. Although the core components of the shuttling complex—Short Gastrulation (Sog) and Twisted Gastrulation (Tsg)—have been identified, key aspects of this shuttling system remain mechanistically unresolved. Recently, we discovered that the extracellular matrix protein collagen IV is i...

Sawala, Annick; Sutcliffe, Catherine; Ashe, Hilary L.

2012-01-01

383

A Molecular Mechanism for Copper Transportation to Tyrosinase That Is Assisted by a Metallochaperone, Caddie Protein*  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Cu(II)-soaked crystal structure of tyrosinase that is present in a complex with a protein, designated “caddie,” which we previously determined, possesses two copper ions at its catalytic center. We had identified two copper-binding sites in the caddie protein and speculated that copper bound to caddie may be transported to the tyrosinase catalytic center. In our present study, at a 1.16–1.58 ? resolution, we determined the crystal structures of tyrosinase complexed with caddie pre...

Matoba, Yasuyuki; Bando, Naohiko; Oda, Kosuke; Noda, Masafumi; Higashikawa, Fumiko; Kumagai, Takanori; Sugiyama, Masanori

2011-01-01

384

Synthesis, transport and mechanism of a type I prodrug: L-carnitine ester of prednisolone.  

Science.gov (United States)

Aerosol glucocorticoid medications have become more and more important in treating BA (bronchial asthma). Although these agents are dosed to directly target airway inflammation, adrenocortical suppression and other systematic effects are still seen. To tackle this problem in a novel way, two L-carnitine ester derivatives of prednisolone (as the model drug), namely, PDC and PDSC, were synthesized to increase the absorption of prednisolone across the human bronchial epithelial BEAS-2B cells by the organic cation/carnitine transporter OCTN2 (SLC22A5) and then to slowly and intracellularly release prednisolone. The transport of prednisolone, PDC and PDSC into the human bronchial epithelial BEAS-2B cells was in the order PDSC > prednisolone > PDC at 37 °C. It was found that PDSC displayed 1.79-fold increase of uptake compared to prednisolone. Transport of PDSC by BEAS-2B was temperature-, time-, and Na(+)-dependent and saturable, with an apparent K(m) value of 329.74 ?M, suggesting the involvement of carrier-mediated uptake. An RT-PCR study showed that organic cation/carnitine transporters OCTN1 and OCTN2 are expressed in BEAS-2B cells, but little in HEK293T cells. The order of uptake by HEK293T was prednisolone > PDC > PDSC. In addition, the inhibitory effects of organic cations such as L-carnitine, ergothioneine, TEA(+) and ipratropium on PDSC uptake in BEAS-2B cells were in the order L-carnitine > ipratropium > TEA(+) > ergothioneine, whereas their inhibitory effects on PDSC uptake in HEK293T cells were negligible. Finally, in vitro LPS-induced IL-6 production from BEAS-2B was more and longer suppressed by PDSC than prednisolone and PDC. All of these results suggested PDSC may be an attractive c