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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

2

Sediment transport mechanics  

Science.gov (United States)

The Editor of Acta Geophysica and the Guest Editors wish to dedicate this Topical Issue on Sediment Transport Mechanics to the memory of Stephen Coleman, who died recently. During his career, Stephen had made an outstanding scientific contribution to the topic of Sediment Transport. The level of his contribution is demonstrated in the paper by Aberle, Coleman, and Nikora included in this issue, on which he started working before becoming aware of the illness that led to his untimely death. For scholars and colleagues Stephen remains an example of intellectual honesty and scientific insight.

Ballio, Francesco; Tait, Simon

2012-12-01

3

MEGARA main optics opto-mechanics  

Science.gov (United States)

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

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

2014-08-01

4

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

5

Main gas particle transport in RFP helical equilibria  

Science.gov (United States)

Self organized helical states, where the innermost resonant tearing mode grows to large amplitude, routinely appear in all the RFP machines. With a sufficiently large dominant mode, the plasma's original magnetic axis is replaced with a new helical axis, bringing about the single helical axis (SHAx) state. A 3D magnetic topology can thereby occur in a toroidally axisymmetric device and this topology has been shown in RFX-mod (the Italian RFP) to exhibit improved energy confinement features (?E increases more than a factor 3) and beneficial effects on particle confinement, too. In this work, we will compare the main gas particle transport in SHAx plasmas in RFX-mod and MST. This analysis is based in part on multi-chord measurements of the density profile and modeling with the ASTRA code, accounting for the helical topology of the magnetic surfaces in the core.

Auriemma, Fulvio; Bergeson, William; Chapman, Brett; Ding, Wiexing; Brower, David; Carraro, Lorella; Innocente, Paolo; Lin, Liang; Lorenzini, Rita; Momo, Barbara; Terranova, David

2011-11-01

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)

7

Mechanical Smoke Exhaust in Underground Transport Passage of Hydropower Station  

Directory of Open Access Journals (Sweden)

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

Jiang Hu

2012-09-01

8

Summary on main policies, funding mechanisms, actors and trends  

DEFF Research Database (Denmark)

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

Kressler, Florian; Weiss, Lucas

2014-01-01

9

Investigation into mechanical properties of bone and its main constituents  

Science.gov (United States)

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

Evdokimenko, Ekaterina

10

Main 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

Amino acid secondary transporters: toward a common transport mechanism.  

Science.gov (United States)

Solute carriers (SLC) that transport amino acids are key players in health and diseases in humans. Their prokaryotic relatives are often involved in essential physiological processes in microorganisms, e.g. in homeostasis and acidic/osmotic stress response. High-resolution X-ray structures of the sequence-unrelated amino acid transporters unraveled a striking structural similarity between carriers, which were formerly assigned to different families. The highly conserved fold is characterized by two inverted structural repeats of five transmembrane helices each and indicates common mechanistic transport concepts if not an evolutionary link among a large number of amino acid transporters. Therefore, these transporters are classified now into the structural amino acid-polyamine-organocation superfamily (APCS). The APCS includes among others the mammalian SLC6 transporters and the heterodimeric SLC7/SLC3 transporters. However, it has to be noted that the APCS is not limited entirely to amino acid transporters but contains also transporters for, e.g. amino acid derivatives and sugars. For instance, the betaine-choline-carnitine transporter family of bacterial activity-regulated Na(+)- and H(+)-coupled symporters for glycine betaine and choline is also part of this second largest structural superfamily. The APCS fold provides different possibilities to transport the same amino acid. Arginine can be transported by an H(+)-coupled symport or by antiport mechanism in exchange against agmatine for example. The convergence of the mechanistic concept of transport under comparable physiological conditions allows speculating if structurally unexplored amino acid transporters, e.g. the members of the SLC36 and SLC38 family, belong to the APCS, too. In the kidney, which is an organ that depends critically on the regulated amino acid transport, these different SLC transporters have to work together to account for proper function. Here, we will summarize the basic concepts of Na(+)- and H(+)-coupled amino acid symport and amino acid-product antiport in the light of the respective physiological requirements. PMID:23177982

Schweikhard, Eva S; Ziegler, Christine M

2012-01-01

13

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

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

Charge transport mechanism in transpolyacetylene  

Science.gov (United States)

Both theoretical and experimental studies in the past have indicated that the charge transport in lightly doped polyacetylene is due primarily to traveling charged solitonic waves along the polymer chain backbone accompanied by hopping from one chain to another. The conductivity in this model is still dictated by a bandgap. The nature of the ground and excited states of the doped system, however, is not fully understood. Previous ab initio calculations on polyenes doped by a single iodine atom have brought out the interesting feature that, while calculations at the Hartree- Fock level lead to the charge-transfer state as the ground state, a correlated calculation, on the other hand, shows it to be an excited state with the ground state showing little charge transfer. Since, however, only polyiodide anions I3-, I5-, etc. are found in solution rather than neutral radicals such as I, I3 etc., inferences based on the calculation employing a single iodine atom are not conclusive. We present here a systematic ab initio study in which the nature of the ground and excited states of polyenes, doped with iodine, are investigated.

Das, G. P.; Yeates, A. Todd; Dudis, Douglas S.

1997-12-01

16

Seesaw mechanism in turbulence and turbulent transport  

International Nuclear Information System (INIS)

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

17

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 a 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 Te and ne are found closely coupled, with the temperature decay length two times shorter than the density decay length corresponding to ?e ? 2. The ?e constraint allows us to calculate the electron temperature and density profiles from the pressure profile if the density and temperature values are known at one spatial position. 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)

18

[Advances in plant anthocyanin transport mechanism].  

Science.gov (United States)

Anthocyanin biosynthesis is one of the thoroughly studied enzymatic pathways in biology, but little is known about the molecular mechanisms of its final stage: the transport of the anthocyanins into the vacuole. A clear picture of the dynamic trafficking of flavonoids is only now beginning to emerge. So far four different models have been proposed to explain the transport of anthocyanins from biosynthetic sites to the central vacuole, and four types of transporters have been found associated with the transport of anthocyanins: glutathione S-transferase, multidrug resistance-associated protein, multidrug and toxic compound extrusion, bilitranslocase-homologue. The functions of these proteins and related genes have also been studied. Although different models have been proposed, cellular and subcellular information is still lacking for reconciliation of different lines of evidence in various anthocyanin sequestration studies. According to the information available, through sequence analysis, gene expression analysis, subcellular positioning and complementation experiments, the function and location of these transporters can be explored, and the anthocyanin transport mechanism can be better understood. PMID:25212003

Wang, Lu; Dai, Silan; Jin, Xuehua; Huang, He; Hong, Yan

2014-06-01

19

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

20

A mechanism for offshore initiation of harmful algal blooms in the coastal Gulf of Maine  

Science.gov (United States)

A combination of observations and model results suggest a mechanism by which coastal blooms of the toxic dinoflagellate Alexandrium fundyense can be initiated from dormant cysts located in offshore sediments. The mechanism arises from the joint effects of organism behavior and the wind-driven response of a surface-trapped plume of fresh water originating from riverine sources. During upwelling-favorable winds, the plume thins vertically and extends offshore; downwelling winds thicken the plume and confine it to the nearshore region. In the western Gulf of Maine, the offshore extent of the river plume during upwelling conditions is suffcient to entrain upward-swimming A. fundyense cells germinated from offshore cyst beds. Subsequent downwelling conditions then transport those populations towards the coast.

McGillicuddy, D.J., Jr.; Signell, R.P.; Stock, C.A.; Keafer, B.A.; Keller, M.D.; Hetland, R.D.; Anderson, D.M.

2003-01-01

 
 
 
 
21

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

International Nuclear Information System (INIS)

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

22

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

International Nuclear Information System (INIS)

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

23

Dynamic analysis of the mechanical systems vibrating transversally in transportation  

Directory of Open Access Journals (Sweden)

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

A. Buchacz

2007-01-01

24

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

International Nuclear Information System (INIS)

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

25

Mechanical systems vibrating longitudinally with the transportation effect  

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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

26

Evaporation as the transport mechanism of metals in arid regions.  

Science.gov (United States)

Soils of arid regions are exposed to drought and drastic temperature oscillations throughout the year. Transport mechanisms in these soils are therefore very different from the ones in temperate regions, where rain dictates the fate of most elements in soils. Due to the low rainfall and high evaporation rates in arid regions, groundwater quality is not threatened and all soil contamination issues tend to be overlooked. But if soil contamination happens, where do contaminants go? This study tests the hypothesis of upward metal movement in soils when evaporation is the main transport mechanism. Laboratory evaporation tests were carried out with heavy metal spiked Saudi soil, using circulation of air as the driving force (Fig. 1). Main results show that loamy soil retains heavy metals quite well while evaporation drives heavy metals to the surface of a sandy soil. Evaporation transports heavy metals upward in sandy soils of arid regions, making them accumulate at the soil surface. Sand being the dominating type of soil in arid regions, soils can then be a potential source of contaminated aerosols and atmospheric pollution - a transboundary problem. Some other repercussions for this problem are foreseen, such as the public ingestion or inhalation of dust. PMID:24997976

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

2014-09-01

27

As if Kyoto mattered: The clean development mechanism and transportation  

International Nuclear Information System (INIS)

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

28

Molecular Mechanism of Ochratoxin A Transport in the Kidney  

Directory of Open Access Journals (Sweden)

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

Naohiko Anzai

2010-06-01

29

Molecular Mechanism of Ochratoxin A Transport in the Kidney  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 transport...

Naohiko Anzai; Promsuk Jutabha; Hitoshi Endou

2010-01-01

30

Studies on lipid transport mechanism in the fish  

International Nuclear Information System (INIS)

In mammals, absorbed micelles are resynthesized in the epithelial cells of the intestine and transported as chylomicrons through the lymphatic route, then as various lipoproteins in the circulatory system. It is rather difficult to draw conclusions about the dynamic processes involved in the absorption and transport of lipids, since there are few studies on these processes in fish. From the cannulated tube of a carp, 0.8 ml of blood was collected at various intervals after feeding. The disc electrophoresis pattern of carp blood plasma shows three main lipoprotein bands when prestained with acetylated Suden black B: Band 1 (albumin lipid complex), Band 2 (near alpha2-lipoprotein) and Band 3 (near beta- and pre-beta-lipoproteins of human plasma). Incorporation of palmitic acid into plasma lipid classes in starved fish was markedly characterized by the initial appearance within 1/2-3 hr of FFA associated mainly with Band 1 followed by gradual increase in TG and PL later. Under normal conditions, high levels of FFA appeared; however, TG associated with Band 3 and 1 appeared distinctly only after 6-12 hr. In the case of tripalmitin feeding, FFA appeared first, the incorporation being moderate but constant, followed by TG (after 3 hr) as the major lipid constituent associated first with Band 3 which seemed to be converted to Band 1 after 6 hr. It can be pointed out from these results that the mammalian lipid transport mechanism is not applicable to fish; instead,hanism is not applicable to fish; instead, Band 1 associated mainly with FFA plays an important role in fish lipid transport. (auth.)

31

Mechanisms of the meridional heat transport in the Southern Ocean  

Science.gov (United States)

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

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

2010-08-01

32

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

33

Mechanism of ochratoxin A transport in kidney  

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-08-01

34

Longitudinal vibrations of mechanical systems with the transportation effect  

Directory of Open Access Journals (Sweden)

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

A. Buchacz

2009-01-01

35

Molecular dynamics simulations elucidate the mechanism of proton transport in the glutamate transporter EAAT3.  

Science.gov (United States)

The uptake of glutamate in nerve synapses is carried out by the excitatory amino acid transporters (EAATs), involving the cotransport of a proton and three Na(+) ions and the countertransport of a K(+) ion. In this study, we use an EAAT3 homology model to calculate the pKa of several titratable residues around the glutamate binding site to locate the proton carrier site involved in the translocation of the substrate. After identifying E374 as the main candidate for carrying the proton, we calculate the protonation state of this residue in different conformations of EAAT3 and with different ligands bound. We find that E374 is protonated in the fully bound state, but removing the Na2 ion and the substrate reduces the pKa of this residue and favors the release of the proton to solution. Removing the remaining Na(+) ions again favors the protonation of E374 in both the outward- and inward-facing states, hence the proton is not released in the empty transporter. By calculating the pKa of E374 with a K(+) ion bound in three possible sites, we show that binding of the K(+) ion is necessary for the release of the proton in the inward-facing state. This suggests a mechanism in which a K(+) ion replaces one of the ligands bound to the transporter, which may explain the faster transport rates of the EAATs compared to its archaeal homologs. PMID:24940785

Heinzelmann, Germano; Kuyucak, Serdar

2014-06-17

36

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)

37

Low Energy Reaction Mechanisms In a Transport Approach  

Science.gov (United States)

Starting from Heavy Ion Collisions with exotic nuclear beams at low energy, the reaction path is investigated in a transport theory based on a stochastic mean field approach. We focus on the interplay between reaction mechanisms, fusion vs. break-up in HIC with exotic nuclear beams at low energies. Fusion probabilities for reactions induced by 132Sn on 64,58Ni targets at 10AMeV are evaluated looking at the evolution of the phase-space quadrupole collective modes. The break-up events appear sensitive to the stiffness of the symmetry energy. 197Au + 197Au collisions at 15 and 23 AMeV are simulated to investigate the main modes of re-separation, ternary-quaternary partition, of a heavy nuclear system.

Rizzo, C.; Colonna, M.; Di Toro, M.; Baran, V.

2014-05-01

38

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

International Nuclear Information System (INIS)

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

39

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

40

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

 
 
 
 
41

Jaumann transport in relativistic continuum mechanics  

International Nuclear Information System (INIS)

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

42

Jaumann transport in relativistic continuum mechanics  

Energy Technology Data Exchange (ETDEWEB)

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

Radhakrishna, L.; Katkar, L.N.; Date, T.H. (Shivaji Univ., Kolhapur (India). Dept. of Mathematics)

1981-10-01

43

IMPROVEMENT OF FREIGHT TRANSPORTATION PROCESS AND THEIR MANAGEMENT MECHANISM  

Directory of Open Access Journals (Sweden)

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

L. V. Martsenyuk

2014-03-01

44

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

45

Transport mechanisms of small molecules through polyamide 12/montmorillonite nanocomposites.  

Science.gov (United States)

The aim of this work is to study the transport of small molecules through the hybrid systems polyamide 12 (PA12)/organo-modified montmorillonite (Cloisite 30B, C30B) prepared by melt blending, using two blending conditions. The transport mechanisms were investigated by using three probe molecules: nitrogen, water, and toluene. While a barrier effect appears clearly with nitrogen, this effect changes with the amount of fillers for water and disappears for toluene. The reduction of permeability for nitrogen is mainly due to the increase of tortuosity. For water and toluene, the permeation kinetics reveals many concomitant phenomena responsible for the permeation behavior. Despite the tortuosity effect, the toluene permeability of nanocomposites increases with C30B fraction. The water and toluene molecules interact differently with fillers according to their hydrophilic/hydrophobic character. Moreover, the plasticization effect of water and toluene in the matrix, involving a concentration-dependent diffusion coefficient, is correctly described by the law D = D(0)e(gammaC). On the basis of Nielsen's tortuosity concept, we suggest a new approach for relative permeability modeling, not only based on the geometrical parameters (aspect ratio, orientation, recovery) but also including phenomenological parameters deduced from structural characterization and permeation kinetics. PMID:20568802

Alexandre, B; Colasse, L; Langevin, D; Médéric, P; Aubry, T; Chappey, C; Marais, S

2010-07-15

46

Glutamate, aspartate and nucleotide transporters in the SLC17 family form four main phylogenetic clusters: evolution and tissue expression  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Abstract Background The SLC17 family of transporters transports the amino acids: glutamate and aspartate, and, as shown recently, also nucleotides. Vesicular glutamate transporters are found in distinct species, such as C. elegans, but the evolutionary origin of most of the genes in this family has been obscure. Results Our phylogenetic analysis shows that the SLC17 family consists of four main phylogenetic clades which were all present before the diver...

Levine Allen S; Olszewski Pawel K; Ha, Shaik Jafar; Sreedharan Smitha; Schiöth Helgi B; Fredriksson Robert

2010-01-01

47

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

48

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

49

Charge Transport Mechanism in Thin Cuticles Holding Nandi Flame Seeds  

Directory of Open Access Journals (Sweden)

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

Wycliffe K. Kipnusu

2009-01-01

50

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

International Nuclear Information System (INIS)

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

51

Design and manufacture of main heat transport components of 500 MWe PFBR  

International Nuclear Information System (INIS)

The function of heat transport circuit in Prototype Fast Breeder Reactor (PFBR) is to transport the nuclear heat generated in the core of the reactor to the steam/water circuit meeting safety norms. The design and manufacturing experience of important components of heat transport components are discussed in the 500 MWe PFBR. (author)

52

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

International Nuclear Information System (INIS)

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

53

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

Energy Technology Data Exchange (ETDEWEB)

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

Koppe, Torsten, E-mail: torsten.koppe@ipp.mpg.de [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Cardella, A.; Missal, B.; Hein, B.; Krause, R.; Jenzsch, H. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Wendelsteinstrasse 1, D-17491 Greifswald (Germany); Reich, J. [ITER Organization, CS 90 046, 13067 St Paul lez Durance Cedex (France); Leher, F.; Binni, A.; Segl, J. [MAN DT, GmbH, AB - Plant Construction, Werftstrasse 17, 94469 Deggendorf (Germany); Camin, R. [Equipos Nucleares, S.A., Avda. Juan Carlos 1, 39600 Maliano (Spain); Giordano, L. [ROVERA CM, Via Vecchia di Cuneo 45, 12011 Borgo san Dalmazzo (Italy); Langone, S. [Romabau Gerinox AG, Fohlenweide, Pf 167, CH-8570 Weinfelden (Switzerland); Ridzewski, J. [IMA GmbH, P.O. Box: 80 01 44, D-01101 Dresden (Germany); Corniani, G. [Ettore Zanon s.p.a.,Via Vicenza 113, I-36015 Schio (Italy)

2011-10-15

54

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

55

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.

Santos, Ilmar

2012-01-01

56

Main chamber sources and edge transport of tungsten in H-mode plasmas at ASDEX Upgrade  

International Nuclear Information System (INIS)

In the fully tungsten clad ASDEX Upgrade, the sputtering rates of tungsten have been determined at all relevant plasma facing components using fast spectroscopic measurements with temporal resolution down to 0.5 ms. The sputtering strongly increases during an edge-localized mode (ELM) and the ELMs are often the dominant cause of tungsten sputtering. A modelling approach was employed to calculate the tungsten source at the limiters and the resulting tungsten density at the pedestal top inside the H-mode edge transport barrier (ETB). In the ETB, it is assumed that tungsten transport is collisional, i.e. behaves like other impurities. The collisional transport leads to strong inward drifts and steep density gradients in the ETB, which are flattened during an ELM causing an efflux of tungsten. The collisional transport in the ETB is also calculated for typical ITER conditions and the resulting tungsten density profiles as well as the transport of the helium ash through the ETB are evaluated.

57

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-11-01

58

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

59

On the Electronic Transport Mechanism in Conducting Polymer Nanofibers  

CERN Document Server

Here, we present theoretical analysis of electron transport in polyaniline based (PANi) nanofibers assuming the metalic state of the material. To build up this theory we treat conducting polymers as a special kind of granular metals, and we apply the quantum theory of conduction in mesoscopic systems to describe the transport between metallic-like granules. Our results show that the concept of resonance electron tunneling as the predominating mechanism providing charge transport between the grains is supported with recent experiments on the electrical characterization of single PANi nanofibers. By contacting the proposed theory with the experimental data we estimate some important parameters characterizing the electron transport in these materials. Also, we discuss the origin of rectifying features observed in current-voltage characteristics of fibers with varying cross-sectional areas.

Zimbovskaya, N A; Pinto, N J; Zimbovskaya, Natalya A.; Johnson, Alan T.; Pinto, Nicholas J.

2005-01-01

60

Perturbations to SOC models as a mechanism for transport control  

Energy Technology Data Exchange (ETDEWEB)

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}bursty{close_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.

Chen, Haiyin [Oak Ridge Institute for Science Education, TN (United States); Newman, D.E.; Carreras, B.A. [Oak Ridge National Lab., TN (United States)

1996-12-31

 
 
 
 
61

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

Science.gov (United States)

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

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

2010-12-01

62

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

International Nuclear Information System (INIS)

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

63

Influence of architectural imperfections on the dynamic mechanical response of main-chain smectic elastomers  

Science.gov (United States)

Main-chain liquid crystalline polymers that form low-temperature smectic mesophases are synthesized by linking terephthalic acid, bis-(4-allyloxyphenyl) ester (PPT) mesogens with 1,1,3,3,5,5 hexamethyltrisiloxane (F3) spacers via Pt-catalyzed hydrosilylation. Significant differences in thermal behavior and mesomorphic ordering are found between the polymer having unsubstituted PPT mesogens (F3-PPT-H) and the polymer having methyl substituents on the terminal rings of the mesogens (F3-PPT-CH3). Combined evidence from polarized light optical microscopy, differential scanning calorimetry, and X-ray diffraction reveals SCA ordering in both polymers. To our knowledge, the SCA phase has been reported for the first time in the siloxane containing main-chain liquid crystalline polymers. Smectic elastomers are synthesized by non-linear polymerization of PPT-H or PPT-CH3 mesogens with F3 spacers and a tetrafunctional crosslinker, tetrakis(dimethylsiloxy)silane (A4). The influence of structural imperfections on mechanical damping in polydomain smectic main-chain liquid crystalline elastomers (MCLCE) subjected to small strain oscillatory shear is examined. The mechanical loss factor tan delta = G"(o)/G'(o) exhibits a strong maximum (tan delta ? 1.0) near the smectic-isotropic (clearing) transition. "Optimal" elastomers that exhibit minimal equilibrium swelling in a good solvent are compared to highly swelling "imperfect elastomers" that contain higher concentrations of structural imperfections such as pendant chains. For the imperfect elastomers, tan delta is markedly enhanced in the isotropic state due to relaxation of pendant chains and other imperfections. However, within the smectic state, the magnitude of tan delta and its temperature dependence are similar for optimal and imperfect elastomers at o = 1 Hz. The prominent loss peak near the clearing transition arises from segment-level relaxations that are insensitive to the details of chain connectivity. Smectic MCLCE can be tailored for applications as vibration-damping materials by manipulating the clearing transition temperature through the backbone structure or by deliberate introduction of structural imperfections such as pendant chains. The stress-strain behavior of polydomain smectic main-chain liquid crystalline elastomers (MCLCE) subjected to uniaxial deformation is examined. The stress-strain curves of the MCLCE exhibit three regions. In region I, at low strain, excluded amorphous material and crosslink junctions in between smectic domains deform with minimal disordering of smectic domains. In Region II, characterized by a "plateau" stress, deformation of microdomains takes place by hairpin unfolding, followed by reformation of smectic domains in a globally oriented "monodomain" state. In Region III, at higher strain, hairpins are depleted except for "trapped" hairpins, and as elastic chains can not elongate further, deformation of the "monodomain" takes place by layer buckling.

Patil, Harshad P.

64

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

65

TRANSMISSION OF IMPACTS DURING MECHANICAL GRAPE HARVESTING AND TRANSPORTATION  

Directory of Open Access Journals (Sweden)

Full Text Available 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 was sought between the transmitted stresses and characteristics of the harvested product. The effects on product quality were evaluated by chemical analyses of the musts and sensorial analysis of the end-product, vinified using the same procedure.

Claudio Caprara

2008-09-01

66

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

67

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

68

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

2011-01-01

69

Transportation of radionuclides in Celtic Sea a possible mechanism  

International Nuclear Information System (INIS)

Measurements in the western approaches of the English Channel exhibits a too high level of artificial radioactivity compared to Atlantic background. Despite this activity may appear negligible as regard to the natural one, it is important to explain the source of the contamination. Simultaneous examination of data from different cruises and results of numerical modelling suggest that Irish Sea may be the source. A mechanism for an intermittent southward transportation into the Celtic Sea is proposed. (author)

70

Transportation of radionuclides in Celtic Sea a possible mechanism  

Energy Technology Data Exchange (ETDEWEB)

Measurements in the western approaches of the English Channel exhibits a too high level of artificial radioactivity compared to Atlantic background. Despite this activity may appear negligible as regard to the natural one, it is important to explain the source of the contamination. Simultaneous examination of data from different cruises and results of numerical modelling suggest that Irish Sea may be the source. A mechanism for an intermittent southward transportation into the Celtic Sea is proposed. (author) 5 refs.

Garreau, P. [IFREMER, 29 - Plouzane (France); Bailly Du Bois, P. [CEA Centre de La Hague, 50 - Cherbourg-Octeville (France). Laboratoire de Radioecologie Marine

1997-12-31

71

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

72

Transport mechanisms of uranium and thorium in fractured rock aquifers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The Karoo has been receiving considerable attention since the early 1970s when uranium mining was at its peak, with numerous research studies being instigated to look at all aspects of uranium mining. It has recently been observed that there seems to be resurgence in uranium exploration in and around the town of Beaufort West. A study on the transport mechanisms of uranium and thorium in fractured-rock aquifers, initiated in the hope of understanding the actual processes controlling radionucl...

Wyk, Yazeed

2011-01-01

73

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

Science.gov (United States)

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

Bar, Arie

2009-04-01

74

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

International Nuclear Information System (INIS)

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

75

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

76

Fracture mechanics approach to spent nuclear fuel transportation cask design  

International Nuclear Information System (INIS)

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

77

Mechanical transport in two-dimensional networks of fractures  

International Nuclear Information System (INIS)

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

78

Analysis of mechanical systems with transversal vibrations in transportation  

Directory of Open Access Journals (Sweden)

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

A. Buchacz

2008-12-01

79

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

International Nuclear Information System (INIS)

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

80

Mechanism of travelling-wave transport of particles  

International Nuclear Information System (INIS)

Numerical and experimental investigations have been carried out on transport of particles in an electrostatic travelling field. A three-dimensional hard-sphere model of the distinct element method was developed to simulate the dynamics of particles. Forces applied to particles in the model were the Coulomb force, the dielectrophoresis force on polarized dipole particles in a non-uniform field, the image force, gravity and the air drag. Friction and repulsion between particle-particle and particle-conveyer were included in the model to replace initial conditions after mechanical contacts. Two kinds of experiments were performed to confirm the model. One was the measurement of charge of particles that is indispensable to determine the Coulomb force. Charge distribution was measured from the locus of free-fallen particles in a parallel electrostatic field. The averaged charge of the bulk particle was confirmed by measurement with a Faraday cage. The other experiment was measurements of the differential dynamics of particles on a conveyer consisting of parallel electrodes to which a four-phase travelling electrostatic wave was applied. Calculated results agreed with measurements, and the following characteristics were clarified. (1) The Coulomb force is the predominant force to drive particles compared with the other kinds of forces, (2) the direction of particle transport did not always coincide with that of the travelling wave but changed partially. It depended on the frequency of the travelling wave, the particle diameter and the electric field, (3) although some particles overtook the travelling wave at a very low frequency, the motion of particles was almost synchronized with the wave at the low frequency and (4) the transport of some particles was delayed to the wave at medium frequency; the majority of particles were transported backwards at high frequency and particles were not transported but only vibrated at very high frequency

 
 
 
 
81

Bloom development and transport of toxic Alexandrium fundyense populations within a coastal plume in the Gulf of Maine  

Science.gov (United States)

Toxic Alexandrium fundyense blooms in the western Gulf of Maine (GOM) are a common occurrence, causing paralytic shellfish poisoning (PSP) each spring. In contrast, high A. fundyense abundances and PSP toxicity commonly occur later in the summer in the eastern GOM and the Bay of Fundy. The objective of this study was to determine if the bloom dynamics of the two areas are linked early in the bloom season when initial outbreaks of toxicity are reported. A. fundyense cell abundance and hydrographic data were acquired during three cruises in May and June, 2001 spanning areas of the western and eastern GOM. Surface drifters also were released into the nearshore coastal flow of the eastern GOM. These data provide a coherent view of the springtime evolution of toxic A. fundyense blooms in the GOM and the influence of both small- and large-scale circulation. Early in the bloom season (May), the bulk of the A. fundyense population was consistently observed in an alongshore band of cells in the eastern GOM associated with relatively low-salinity water (outbreaks of nearshore PSP toxicity. The transport is influenced by wind. In particular, some of the cells within the nearshore flow may be lost to the interior GOM when upwelling-favorable winds transport them offshore and into the large-scale circulation dominated by the cyclonic flow of the Jordan Basin Gyre. Downwelling-favorable winds keep the cells close to the coast and rapidly transport them into the western GOM. This study unequivocally demonstrates the linkage between early season A. fundyense bloom formation in the eastern GOM and blooms in the western GOM. It also indicates that the lack of toxicity along the mid-Maine coast commonly referred to as the "PSP sandwich" may be an artifact of the lack of shellfish sampling along the outer remote islands of Penobscot Bay, as populations sufficient to cause toxicity can be found adjacent to the coastline. The association of the A. fundyense populations with low-salinity water near the coast requires a refinement of the terminology for the eastern Maine Coastal Current to distinguish this nearshore water mass from the adjacent, more saline offshore waters. We name this feature the Gulf of Maine Coastal Plume (GOMCP) to reflect the freshwater inputs into the GOM that are critically important in the long-distance transport and growth of A. fundyense populations along the New England coast. The GOMCP is likely to be important for other organisms as well.

Keafer, Bruce A.; Churchill, James H.; McGillicuddy, Dennis J.; Anderson, Donald M.

2005-09-01

82

Internal mode mechanism for collective energy transport in extended systems.  

Science.gov (United States)

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 both on the initial and the relative phases of the two harmonic drivings, even in the presence of noise. PMID:14683187

Morales-Molina, Luis; Quintero, Niurka R; Mertens, Franz G; Sánchez, Angel

2003-12-01

83

Mechanical seals qualification procedure of the main pumps of nuclear power plants in France  

International Nuclear Information System (INIS)

Many important pumps in the nuclear power plants are equipped with mechanical seals. The good behaviour and reliability of mechanical seals depend specially on the quality and the stability of an interface of several microns. Peripheral speed reaches 50 m/s and pressure 5 MPa, shaft diameter may be 200 mm. Any failure of the mechanical seals may stop the production of electricity or may compromise nuclear safety. As far back as 1970, EDF has conducted qualification actions for the most important mechanical seals in terms of availability and safety. A qualification of mechanical seals needs three steps: - constructor test (tuning) at normal conditions, -qualification test on test rig at EDF/DER (semi-industrial) at normal, exceptional and incidental conditions lasting about 1500 h, - industrial qualification test in nuclear power station over one year. Several supplying sources are absolutely necessary. Any pump may receive mechanical seals from at least two different suppliers. A compromise had to be found to restrict the suppliers' number down to three. This choice concerned three high technology suppliers. A consistent modification procedure had been developed (references file procedure). For each power plant series, about ten types of mechanical seals are concerned. The selection criteria are the higher loads factors P, Vg or the safety related importance. This expensive approach is useful for EDF, many functional failures have been detected before the serial mechanical seals installation in the power plants. (authors). 1 annexe

84

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

Science.gov (United States)

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

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

2014-12-01

85

Bidirectional transepithelial water transport: measurement and governing mechanisms.  

Science.gov (United States)

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 than JWB-->L (4.5 microliter/min/cm2, p B = 1.0 x 10(-4) cm/s and PdB-->L = 7.5 x 10(-5) cm/s. The activation energy (Ea) of JWL-->B (11.6 kcal/mol) was larger than the Ea of JWB-->L (6.5 kcal/mol, p JWL-->B from 6.1 to 4.4 microliter/min/cm2 (p JWL-->B from 5.7 to 3.7 microliter/min/cm2 (p L. These data indicate that in tracheal epithelia under homeostatic conditions, JWB-->L was dominated by diffusion (Ea = 4.6 kcal/mol), whereas approximately 30% of JWL-->B was coupled to the active Na+,K+-ATPase pump (Ea = 27 kcal/mol). PMID:9929488

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

1999-02-01

86

Multi-scale mechanical and transport properties of a hydrogel.  

Science.gov (United States)

In this paper, molecular dynamic simulation was used to study the effect of water on the equilibrated structure and mechanical properties of cross-linked hydrogel at multiple scales. The hydrogel consisted of Polyethylene glycol diglycidyl ether (PEGDGE) as epoxy and the Jeffamine, poly-oxy-alkylene-amines, as curing agent. The results for systems with various water contents indicated that the cross-links were more hydrophilic within the hydrogel structure. Effects of cross-linking on the transport properties were also investigated by computing diffusion coefficients of water molecules. A new Coarse-Grained (CG) scheme for hydrogels is proposed, and validated by comparing the transport properties with the all-atom method, demonstrating the capability of the model to capture the correct dynamic evolution of the system. The all-atom model of the hydrogel was mapped to the CG model using the MARTINI force field. This method resulted in a more realistic representation of the stiffness of the system, compared to the previous experimental studies in the literature. The variation of the stiffness of the hydrogel as a function of the water content showed that 40% water content is the optimal value for mechanical performance of the hydrogel. PMID:24967978

Salahshoor, Hossein; Rahbar, Nima

2014-09-01

87

Calcium transport mechanism in molting crayfish revealed by microanalysis  

International Nuclear Information System (INIS)

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

88

Developing Hypothetical Inhibition Mechanism of Novel Urea Transporter B Inhibitor  

Science.gov (United States)

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

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

2014-07-01

89

Mass transport mechanisms during excimer laser nitriding of aluminum  

International Nuclear Information System (INIS)

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

90

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

Science.gov (United States)

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

Zhang, Yongjun

91

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

Science.gov (United States)

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 HCT116 cells. Dietary supplied putrescine was accumulated in GI tissues and liver in caveolin-1 knockout mice more than wild-type mice. Knocking out of nitric oxide synthase (NOS2), which has been implicated in the release of exogenous polyamines from internalized vesicles, abolished the accumulation of dietary putrescine in GI tissues. Under conditions of reduced endogenous tissue putrescine contents, caused by treatment with the polyamine synthesis inhibitor difluoromethylornithine (DFMO), small intestinal and colonic mucosal polyamine contents increased with dietary putrescine levels, even in mice lacking NOS2. Knocking down the solute carrier transporter SLC3A2 in HCT116-derived Hkh2 cells reduced the accumulation of exogenous putrescine and total polyamine contents in DFMO treated cells, relative to non-DFMO-treated cells. These data demonstrate that exogenous putrescine is transported into GI tissues by caveolin-1- and NOS2-dependent mechanisms, but that the solute carrier transporter SLC3A2 can function bidirectionally to import putrescine under conditions of low tissue polyamines. PMID:20522643

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

2010-08-01

92

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

Science.gov (United States)

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

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

2014-11-01

93

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

International Nuclear Information System (INIS)

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)

94

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

95

High-Performance Concurrency Control Mechanisms for Main-Memory Databases  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Larson, Per-a?ke; Blanas, Spyros; Diaconu, Cristian; Freedman, Craig; Patel, Jignesh M.; Zwilling, Mike

2011-01-01

96

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

97

Flexible Mechanical Conveyors for Regolith Extraction and Transport  

Science.gov (United States)

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

Walton, Otis R.; Vollmer, Hubert J.

2013-01-01

98

Transport mechanism in lightly doped hydrogenated microcrystalline silicon thin films  

Science.gov (United States)

Boron-doped microcrystalline silicon films have been deposited in a plasma-enhanced chemical vapor deposition system using silane diluted in hydrogen, and diborane (B2H6) as a dopant gas. The temperature dependence of the dark conductivity has been measured from 120to420K in all samples. In the high-temperature range above room temperature, the carrier transport is found to be thermally activated, with a single activation energy that changes with the B2H6 compensation degree. In the low-temperature range (300-120K), variable range hopping (VRH) was established as a predominant electronic transport mechanism for all samples, with the exception of the sample with a diborane concentration of 12.5ppm. A model for Mott's VRH, referred to as the "diffusional model," which yields a relation between the conductivity and the localized density of gap states, is presented. Using classical equations from the percolation theory and the diffusional model, the density of states near the Fermi level, as well as the hopping parameters, are calculated. A correlation between the hopping parameters for both models is deduced. A numerical factor that improves the value of each parameter is calculated.

Dussan, A.; Buitrago, R. H.

2005-02-01

99

Mechanical reliability of geometrically imperfect tubular oxygen transport membranes  

DEFF Research Database (Denmark)

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

Kwok, Kawai; Frandsen, Henrik Lund

2014-01-01

100

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.

 
 
 
 
101

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

102

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

103

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

104

Fluka and thermo-mechanical studies for the CLIC main dump  

CERN Document Server

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

105

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

CERN Document Server

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

Maharramov, Musa

2013-01-01

106

The IAEA transport regulations: main modifications included in the 1996 edition and the possible impact of its adoption in Argentina  

International Nuclear Information System (INIS)

Full text: This paper points out a comparative analysis between the requirements of the 1985 edition (as Amended 1990), in-force in almost all countries included Argentina, and the 1996 edition, that is foresee to put in-force 1st January 2001, of the Regulations for the safe transport of radioactive material, published by the International Atomic Energy Agency (IAEA). The English version of the 1996 edition was published in December 1996 and the Spanish one in September 1997. Such edition was the culmination of a difficult consensus and harmonisation reached after an analysis process of the-years cycle between the IAEA Member Sates and related international organisations (United Nations, International Civil Aviation Organisation, International Air Transport Association, International Federation of Air Lines Pilots Associations, International Maritime Organisation) as well as regional organisations (Economic Commission for Europe, Commission of the European Communities). Both editions of the Regulations include a set of design, operational and administrative requirements that substantially do not differ as for their safety basic philosophy. However, the 1996 edition introduces numerous modifications of different magnitude, which will derive in technological, economic and operative consequences. Of such modifications the paper only analysed the relevant ones which update the state of art in the subject and allow the Regulations continue maintaining an acceptable level of control of the radiation, criticality and thermal hazards to persons, property and the environment during the transport of radioactive material. In addition, the paper briefly describes the possible impact that the main modifications induced in the 1996 edition of the Regulations should have, depending on the type of user considered either in Argentina or in other Latin America countries. However, it is desirable that the personal of competent authorities of each country involved in transport regulatory activities know in detail all the modifications introduced in the 1996 edition and notify them to the corresponding users. It is advantageous because of changes in structural or thermal requirements should be interesting for designers instead of changes in operative or administrative requirements should be for consignors or carriers concern. (author)

107

CLUB FORMATION MECHANISM FOR TRANSPORT-COMMUNITY CREDIT CARDS  

Science.gov (United States)

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

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

108

Analysis Of Transport Properties of Mechanically Alloyed Lead Tin Telluride  

Science.gov (United States)

The work described in this thesis had two objectives. The first objective was to develop a physically based computational model that could be used to predict the electronic conductivity, Seebeck coefficient, and thermal conductivity of Pb1-xSnxTe alloys over the 400 K to 700 K temperature as a function of Sn content and doping level. The second objective was to determine how the secondary phase inclusions observed in Pb1-xSn xTe alloys made by consolidating mechanically alloyed elemental powders impact the ability of the material to harvest waste heat and generate electricity in the 400 K to 700 K temperature range. The motivation for this work was that though the promise of this alloy as an unusually efficient thermoelectric power generator material in the 400 K to 700 K range had been demonstrated in the literature, methods to reproducibly control and subsequently optimize the materials thermoelectric figure of merit remain elusive. Mechanical alloying, though not typically used to fabricate these alloys, is a potential method for cost-effectively engineering these properties. Given that there are deviations from crystalline perfection in mechanically alloyed material such as secondary phase inclusions, the question arises as to whether these defects are detrimental to thermoelectric function or alternatively, whether they enhance thermoelectric function of the alloy. The hypothesis formed at the onset of this work was that the small secondary phase SnO2inclusions observed to be present in the mechanically alloyed Pb1-xSnxTe would increase the thermoelectric figure of merit of the material over the temperature range of interest. It was proposed that the increase in the figure of merit would arise because the inclusions in the material would not reduce the electrical conductivity to as great an extent as the thermal conductivity. If this were to be true, then the experimentally measured electronic conductivity in mechanically alloyed Pb1-xSnxTe alloys that have these inclusions would not be less than that expected in alloys without these inclusions while the portion of the thermal conductivity that is not due to charge carriers (the lattice thermal conductivity) would be less than what would be expected from alloys that do not have these inclusions. Furthermore, it would be possible to approximate the observed changes in the electrical and thermal transport properties using existing physical models for the scattering of electrons and phonons by small inclusions. The approach taken to investigate this hypothesis was to first experimentally characterize the mobile carrier concentration at room temperature along with the extent and type of secondary phase inclusions present in a series of three mechanically alloyed Pb1-xSnxTe alloys with different Sn content. Second, the physically based computational model was developed. This model was used to determine what the electronic conductivity, Seebeck coefficient, total thermal conductivity, and the portion of the thermal conductivity not due to mobile charge carriers would be in these particular Pb1-x SnxTe alloys if there were to be no secondary phase inclusions. Third, the electronic conductivity, Seebeck coecient and total thermal conductivity was experimentally measured for these three alloys with inclusions present at elevated temperatures. The model predictions for electrical conductivity and Seebeck coefficient were directly compared to the experimental elevated temperature electrical transport measurements. The computational model was then used to extract the lattice thermal conductivity from the experimentally measured total thermal conductivity. This lattice thermal conductivity was then compared to what would be expected from the alloys in the absence of secondary phase inclusions. Secondary phase inclusions were determined by X-ray diraction analysis to be present in all three alloys to a varying extent. The inclusions were found not to significantly degrade electrical conductivity at temperatures above 400 K in these alloys, though they do dramatically impact elect

Krishna, Rajalakshmi

109

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

110

Current Imbalances and Main Adjustment Mechanisms in the European Monetary Union  

Directory of Open Access Journals (Sweden)

Full Text Available The adoption of the euro as a common currency in 17 of the 27 member states of the European Union was achieved in a process that did not strictly observe the recommendations of the economic theory of an optimal monetary area. The elimination of exchange rates before the establishment of European Monetary Union represented the renunciation of an automatic macroeconomic stabilization mechanism and generated major commercial and financial imbalances between the countries in the Eurozone. The emergence of the financial crisis in 2008 combined with the lack of mobility of the labor at European level and the lack of fiscal reforms in the less competitive countries led to the current situation of the unsustainable public debts. The measures envisaged with the purpose to address this crisis are different in terms of level of assistance the competitive countries have to give to the others, the duration and value of wealth transfers that should be made between the states and the limit from which they will affect the fundamental stability and prosperity policy objectives of the European project.

Gheorghe Matei

2013-11-01

111

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

International Nuclear Information System (INIS)

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

112

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

113

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

114

How LeuT shapes our understanding of the mechanisms of sodium-coupled neurotransmitter transporters.  

Science.gov (United States)

Neurotransmitter transporters are ion-coupled symporters that drive the uptake of neurotransmitters from neural synapses. In the past decade, the structure of a bacterial amino acid transporter, leucine transporter (LeuT), has given valuable insights into the understanding of architecture and mechanism of mammalian neurotransmitter transporters. Different conformations of LeuT, including a substrate-free state, inward-open state, and competitive and non-competitive inhibitor-bound states, have revealed a mechanistic framework for the transport and transport inhibition of neurotransmitters. The current review integrates our understanding of the mechanistic and pharmacological properties of eukaryotic neurotransmitter transporters obtained through structural snapshots of LeuT. PMID:23878376

Penmatsa, Aravind; Gouaux, Eric

2014-03-01

115

Active transport of vesicles in neurons is modulated by mechanical tension  

Science.gov (United States)

Effective intracellular transport of proteins and organelles is critical in cells, and is especially important for ensuring proper neuron functionality. In neurons, most proteins are synthesized in the cell body and must be transported through thin structures over long distances where normal diffusion is insufficient. Neurons transport subcellular cargo along axons and neurites through a stochastic interplay of active and passive transport. Mechanical tension is critical in maintaining proper function in neurons, but its role in transport is not well understood. To this end, we investigate the active and passive transport of vesicles in Aplysia neurons while changing neurite tension via applied strain, and quantify the resulting dynamics. We found that tension in neurons modulates active transport of vesicles by increasing the probability of active motion, effective diffusivity, and induces a retrograde bias. We show that mechanical tension modulates active transport processes in neurons and that external forces can couple to internal (subcellular) forces and change the overall transport dynamics.

Ahmed, Wylie W.; Saif, Taher A.

2014-03-01

116

Mechanical transport and porous media equivalence in anisotropic fracture networks  

International Nuclear Information System (INIS)

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

117

Mechanical transport and porous media equivalence in anisotropic fracture networks  

International Nuclear Information System (INIS)

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

118

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

119

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)

120

The single mitochondrial porin of Trypanosoma brucei is the main metabolite transporter in the outer mitochondrial membrane.  

Science.gov (United States)

All mitochondria have integral outer membrane proteins with beta-barrel structures including the conserved metabolite transporter VDAC (voltage dependent anion channel) and the conserved protein import channel Tom40. Bioinformatic searches of the Trypanosoma brucei genome for either VDAC or Tom40 identified a single open reading frame, with sequence analysis suggesting that VDACs and Tom40s are ancestrally related and should be grouped into the same protein family: the mitochondrial porins. The single T. brucei mitochondrial porin is essential only under growth conditions that depend on oxidative phosphorylation. Mitochondria isolated from homozygous knockout cells did not produce adenosine-triphosphate (ATP) in response to added substrates, but ATP production was restored by physical disruption of the outer membrane. These results demonstrate that the mitochondrial porin identified in T. brucei is the main metabolite channel in the outer membrane and therefore the functional orthologue of VDAC. No distinct Tom40 was identified in T. brucei. In addition to mitochondrial proteins, T. brucei imports all mitochondrial tRNAs from the cytosol. Isolated mitochondria from the VDAC knockout cells import tRNA as efficiently as wild-type. Thus, unlike the scenario in plants, VDAC is not required for mitochondrial tRNA import in T. brucei. PMID:19091722

Pusnik, Mascha; Charrière, Fabien; Mäser, Pascal; Waller, Ross F; Dagley, Michael J; Lithgow, Trevor; Schneider, André

2009-03-01

 
 
 
 
121

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

122

Center for low-gravity fluid mechanics and transport phenomena  

Science.gov (United States)

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

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

1991-01-01

123

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

124

Agmatine is transported in liver mitochondria by a specific electrophoretic mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2006-01-01

125

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

Science.gov (United States)

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

Lucy R. Forrest (Max Planck Institute for Biophysics); Gary Rudnick (Yale University School of Medicine)

2009-12-01

126

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

Energy Technology Data Exchange (ETDEWEB)

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 {approx}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 {approx} V{sup m} with m > 2 is consistent with the model of trap-charge limited conduction. The total electron trap density is estimated to be {approx}5 x 10{sup 18} cm{sup -3}. The critical voltage (V{sub c}) is found to be {approx}45 V and is almost independent of the materials.

Khan, M A; Xu Wei; Khizar-ul-Haq; Zhang Xiaowen; Bai Yu; Jiang, X Y; Zhang, Z L; Zhu, W Q [Department of Materials Science, Shanghai University, Jiading 201800 (China)

2008-11-21

127

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.

128

On the Relation Between Quantum Mechanical and Classical Parallel Transport  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We explain how the kind of ``parallel transport'' of a wavefunction used in discussing the Berry or Geometrical phase induces the conventional parallel transport of certain real vectors. These real vectors are associated with operators whose commutators yield diagonal operators; or in Lie algebras those operators whose commutators are in the (diagonal) Cartan subalgebra.

Anandan, J.; Stodolsky, L.

1999-01-01

129

Early metabolic effects and mechanism of ammonium transport in yeast  

International Nuclear Information System (INIS)

nism similar to that of monovalent alkaline cations, driven by a membrane potential. The immediate metabolic effects of this cation seem to be due to an increased [H+]ATPase, to which its transport is coupled. However, the carriers seem to be different. The transport system studied in this work was that of low affinity

130

CO2-ECBM related coupled physical and mechanical transport processes  

Science.gov (United States)

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

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

2013-04-01

131

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

CERN Document Server

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

2003-01-01

132

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

133

The 2-Hydroxycarboxylate Transporter Family: Physiology, Structure, and Mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The 2-hydroxycarboxylate transporter family is a family of secondary transporters found exclusively in the bacterial kingdom. They function in the metabolism of the di- and tricarboxylates malate and citrate, mostly in fermentative pathways involving decarboxylation of malate or oxaloacetate. These pathways are found in the class Bacillales of the low-CG gram-positive bacteria and in the gamma subdivision of the Proteobacteria. The pathways have evolved into a remarkable diversity in terms of...

Sobczak, Iwona; Lolkema, Juke S.

2005-01-01

134

FEATURES FOR TRANSPORT AND AIR MECHANICAL SYSTEMS OF DANGEROUS GOODS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Busa, Eugen Dumitru

2012-01-01

135

FEATURES FOR TRANSPORT AND AIR MECHANICAL SYSTEMS OF DANGEROUS GOODS  

Directory of Open Access Journals (Sweden)

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

Eugen Dumitru BUSA

2012-05-01

136

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

137

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.

138

Osmotic water transport in aquaporins : evidence for a stochastic mechanism  

DEFF Research Database (Denmark)

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

Zeuthen, Thomas; Alsterfjord, Magnus

2013-01-01

139

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

140

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

 
 
 
 
141

Cutting through the noise: the mechanics of intracellular transport.  

Science.gov (United States)

Intracellular transport of organelles and proteins is driven by multiple ATP-dependent processes. Recently in Cell, Guo et al. (2014) developed a technique, force-spectrum microscopy, to measure intracellular forces and demonstrate that large motion of cellular components can be produced by random ATP-dependent fluctuations within the cytoplasm. PMID:25158851

Stam, Samantha; Gardel, Margaret L

2014-08-25

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

143

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.

144

Trafficking of glucose transporters--signals and mechanisms.  

Science.gov (United States)

The uptake of glucose into mammalian cells, catalysed by members of the GLUT family of glucose transporters, is regulated by a variety of hormones, growth factors and other agents. In adipocytes, skeletal muscle and heart the principal regulator is the hormone insulin, which rapidly stimulates glucose uptake by bringing about the translocation of the GLUT4 glucose transporter isoform from an intracellular vesicular compartment to the cell surface. Recent studies have implicated the C-terminal hydrophilic region of this protein as being primarily responsible for its insulin-regulated trafficking. In an attempt to identify the protein machinery involved in this trafficking, we have used glutathione S-transferase fusion proteins bearing hydrophilic domains of various GLUT transporters in affinity purification experiments on detergent-solubilized extracts of 3T3-L1 adipocyte intracellular membranes. The C-terminal region of GLUT4 was found specifically to bind a number of polypeptides in these extracts, which are therefore candidates for components of the trafficking machinery. Although these proteins did not bind to the corresponding region of the more widely-distributed GLUT1 glucose transporter isoform, regulation of this transporter also appears to be of physiological importance in some cell types. To study such regulation we have used as a model system the interleukin-3 (IL-3)-dependent haemopoietic cell line IC.DP. These cells express a temperature sensitive mutane of the v-abl tyrosine kinase, whose activation at the permissive temperature permits cell survival in the absence of IL-3 by suppression of apoptosis, although the growth factor is still required for proliferation. Both IL-3 and activation of the kinase were found to stimulate glucose transport by promoting the translocation of GLUT1 to the cell surface. Moreover, inhibition of glucose uptake by addition of transport inhibitors markedly increased the rate of apoptosis, an effect which could be reversed by the provision of alternative energy sources. These observations suggest that the trafficking of GLUT1, regulated by growth factors or oncogenes, may play an important role in the suppression of apoptosis in haemopoietic cells. PMID:9156573

Baldwin, S A; Barros, L F; Griffiths, M

1995-12-01

145

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.

146

Mechanism of charge transport along zinc porphyrin-based molecular wires.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study charge transport along zinc porphyrin-based molecular wires is simulated, considering both bandlike and hopping mechanisms. It is shown that bandlike transport simulations yield significantly overestimated hole mobility values. On the basis of kinetic and thermodynamic considerations, it is inferred that charge transport along zinc porphyrin-based molecular wires occurs by small polaron hopping. Hole mobility values on the order of 0.1 cm(2) V(-1) s(-1) are found from small pola...

Kocherzhenko, Aa; Patwardhan, S.; Grozema, Fc; Anderson, Hl; Siebbeles, Ld

2009-01-01

147

[New Developments in CKD-MBD. Molecular mechanisms of intestinal and renal phosphate transport].  

Science.gov (United States)

Intestinal inorganic phosphate (Pi) absorption and renal Pi reabsorption are regulated by parathyroid hormone, fibroblast growth factor 23, or 1,25-dihydroxyvitamin D, which modulate the expression of Pi transporters. Identification, functional characterization and analysis of knockout mice of Pi transporters contributed to clarify the role of each transporter in Pi homeostasis. Furthermore, the molecular mechanisms will lead to the development of new pharmaceutical research approaches. PMID:25423924

Segawa, Hiroko; Ikuta, Kayo; Miyamoto, Kenichi

2014-12-01

148

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

Scientific Electronic Library Online (English)

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

Mateo, Martinic B.

2009-07-01

149

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

Scientific Electronic Library Online (English)

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

Mateo, Martinic B.

150

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

Directory of Open Access Journals (Sweden)

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

Mateo Martinic B

2009-07-01

151

Yet Another Possible Mechanism for Anomalous Transport: Theory, Numerical Method, and Experiments  

Science.gov (United States)

A new possible mechanism for anomalous transport is studied and a new numerical approach is presented based on the mechanism. The transport behavior of passive solute in a heterogeneous medium is generally found non-Fickian, and the plume cannot be described by a time-independent center of mass velocity and constant dispersion coefficients. As a result, most of the publications concerning the mechanism for the anomalous transport behavior put their basis on the existence of inhomogeneities. That is, variation in a velocity field is widely considered to be the source of the anomalous transport. In the present study, from the discussion of the general transport equation called continuous time random walk, we show that a transport remains normal even in an existence of a very low conductivity inhomogeneity (highly heterogeneous case) but that only the Newtonian feature of any fluid can make a transport anomalous. The numerical analysis method is developed by transforming the three-dimensional general transport equation to one-dimensional along a streamline. This modification is valid only if a transverse dispersivity is negligible compared to a longitudinal dispersivity. The validity of the theory and the numerical approach is confirmed through three types of tracer experiments. A tracer test through two parallel smooth plastic plates demonstrates that anomalous transport can be observed in a Newtonian fluid without any inhomogeneity. Tracer tests through uniform porous media filled with glass beads and parallel plates with non-permeable zone are compared to the results obtained with the present method.

Inoue, J.; Chun, P.

2005-12-01

152

Carrier transport mechanisms of p-type amorphous-n-type crystalline silicon heterojunctions  

Science.gov (United States)

Measured current-voltage characteristics of undoped and p-type hydrogenated amorphous silicon (a-Si:H)/n-type crystalline silicon (c-Si) heterojunctions are used to discuss the carrier transport mechanisms. The forward current was characterized by two parts: The forward current increased with applied voltage exponentially (region 1), and nonexponentially (region 2). In region 1, it was found that the current was dominated by the tunneling process in which electrons tunneled from the c-Si into gap states in the a-Si:H and recombinated holes captured by the gap states in the a-Si:H. In region 2, the current was found to be a space-charge-limited current due to both electrons injected from the c-Si and holes injected from an ohmic contact. The carrier transport mechanism of reverse currents depended on the magnitude of boron doping in the a-Si:H. The reverse current was considered to be mainly generated in the depletion layer of the a-Si:H for the heterojunction with undoped a-Si:H, generated in the depletion layer of both the a-Si:H and the c-Si for that with boron-doped a-Si:H of B2H6/SiH4=1×10-5, and generated in the depletion layer of the c-Si for that with boron-doped a-Si:H of B2H6/SiH4=1×10-4.

Mimura, Hidenori; Hatanaka, Yoshinori

1992-03-01

153

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

Energy Technology Data Exchange (ETDEWEB)

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

Pandey, R.P.; Singh, Kulbir; Albert, Shaju; Chellapandi, P.; Chetal, S.C.; Raj, Baldev [Indira Gandhi Centre for Atomic Research, Kalpakkam (India)

2010-07-01

154

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

International Nuclear Information System (INIS)

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

155

Main mineral melting behavior and mineral reaction mechanism at molecular level of blended coal ash under gasification condition  

Energy Technology Data Exchange (ETDEWEB)

The main mineral melting behavior and mineral reaction mechanism at molecular level of Chinese blended coal ash under gasification condition (30% H{sub 2}, 66% CO, 4% CO{sub 2}) from 1073 K to 1573 K were studied through the ASTM test, X-ray diffraction (XRD), ternary phase diagram system and quantum chemistry calculation with ab-initio calculations. The results show that with increasing blending mass fraction of low ash fusion temperature (AFT) ash (ash B), the location of blended ash in ternary systems is transferred from the mullite region to the anorthite region, as the dominant crystal mineral of blended ash at around DT (XRD analysis) is also transferred from mullite to anorthite. The calcium-bearing minerals, such as anhydrite, calcite etc., can react with mullite and the precursors of mullite (metakaolinite etc.), which is one of the main refractory minerals in high AFT ash (ash A), and is converted into low-melting minerals (anorthite, gehlenite, and fayalite etc.) in the temperature range between 1273 K and 1403 K. The reaction between mullite and CaO to form anorthite plays a significant role in decreasing AFTs of blended coal ash A/B. It is because the chemical activity of the highest occupied molecular orbits (HOMO) in mullite cluster is stronger than that of the lowest unoccupied molecular orbits (LUMO) in mullite cluster, the Ca{sup 2+} as electron acceptor can easily enter into the crystal lattice of mullite mainly through O (7) and O (12) and cause the rupture of bonds Al (1)-O (13) (in the [AlO{sub 6}]{sup 9-}-octahedron) and Al (8)-O (13) (in the [AlO{sub 4}]{sup 5-}-tetrahedron), which are weaker than any other bonds in crystal lattice of mullite. Finally, the entrance of Ca{sup 2+} can force mullite to transform to anorthite by the effect of Ca{sup 2+}, and the entered Ca{sup 2+} is located in the center of [SiO{sub 4}]{sup 4-}-tetrahedron ring in the anorthite crystal lattice. Taking the [SiO{sub 4}]{sup 4{sup -}}-tetrahedron, which is composed of Si (70), O (78), O (48), O (91), O (86) as an example, the Ca{sup 2+} can capture the partial electronics of O (86) and cause the bond length (B.L.) of bond Si (70)-O (86) to become longer and unstable. (author)

Wu, Xiaojiang; Zhang, Zhongxiao; Chen, Yushuang; Zhou, Tuo; Fan, Junjie; Piao, Guilin; Kobayashi, Nobusuke; Mori, Shigekatsu; Itaya, Yoshinori,

2010-11-15

156

Transport of free surface liquid films and drops by external ratchets and self-ratcheting mechanisms  

Science.gov (United States)

We discuss the usage of ratchet mechanisms to transport a continuous phase in several micro-fluidic settings. In particular, we study the transport of a dielectric liquid in a heterogeneous ratchet capacitor that is periodically switched on and off. The second system consists of drops on a solid substrate that are transported by different types of harmonic substrate vibrations. We argue that the latter can be seen as a self-ratcheting process and discuss analogies between the employed class of thin film equations and Fokker-Planck equations for transport of discrete objects in a 'particle ratchet'.

Thiele, Uwe; John, Karin

2010-10-01

157

Regulation of amniotic fluid volume: mathematical model based on intramembranous transport mechanisms.  

Science.gov (United States)

Experimentation in late-gestation fetal sheep has suggested that regulation of amniotic fluid (AF) volume occurs primarily by modulating the rate of intramembranous transport of water and solutes across the amnion into underlying fetal blood vessels. In order to gain insight into intramembranous transport mechanisms, we developed a computer model that allows simulation of experimentally measured changes in AF volume and composition over time. The model included fetal urine excretion and lung liquid secretion as inflows into the amniotic compartment plus fetal swallowing and intramembranous absorption as outflows. By using experimental flows and solute concentrations for urine, lung liquid, and swallowed fluid in combination with the passive and active transport mechanisms of the intramembranous pathway, we simulated AF responses to basal conditions, intra-amniotic fluid infusions, fetal intravascular infusions, urine replacement, and tracheoesophageal occlusion. The experimental data are consistent with four intramembranous transport mechanisms acting in concert: 1) an active unidirectional bulk transport of AF with all dissolved solutes out of AF into fetal blood presumably by vesicles; 2) passive bidirectional diffusion of solutes, such as sodium and chloride, between fetal blood and AF; 3) passive bidirectional water movement between AF and fetal blood; and 4) unidirectional transport of lactate into the AF. Further, only unidirectional bulk transport is dynamically regulated. The simulations also identified areas for future study: 1) identifying intramembranous stimulators and inhibitors, 2) determining the semipermeability characteristics of the intramembranous pathway, and 3) characterizing the vesicles that are the primary mediators of intramembranous transport. PMID:25186112

Brace, Robert A; Anderson, Debra F; Cheung, Cecilia Y

2014-11-15

158

Angler awareness of aquatic nuisance species and potential transport mechanisms  

Science.gov (United States)

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

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

2009-01-01

159

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

160

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

Science.gov (United States)

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

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

2014-04-14

 
 
 
 
161

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-01-01

162

Transport mechanisms in the outer region of RFX-mod  

International Nuclear Information System (INIS)

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

163

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

Energy Technology Data Exchange (ETDEWEB)

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

P Zhang; J Wang; Y Shi

2011-12-31

164

Current transport mechanisms in the thin oxygen films  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The conduction mechanisms in SiO-Al, Al-SiO2-Al, Al-Al2O3-Al and p/Si-Ta2O5-Al structures has been investigated. In this way there were observed the current dependences of voltages by various temperature values, also the current dependence of temperatures by various valtage values and an activation energy dependence from voltage and temperature. The experimental data have been compared with the teorical tunneling probabilities depending on the strength of the electric field and temperature. T...

S?laic?iu?naite?, Ilona

2007-01-01

165

Oxygen transport mechanisms in REAlO3 scintillators  

International Nuclear Information System (INIS)

The performance of oxide scintillators often suffers from phenomena related to the existence of point defects. Thus, if deleterious defects are removed, it follows that scintillator performance will improve. In the case of REAlO3 perovskites, the oxygen vacancy has been identified as the predominant electron trap site. Previous empirical efforts to minimize the concentration of this particular defect through aliovalent doping have been successful. Here we discuss the results of atomic scale simulations that provide important detail regarding the mechanism by which the oxygen vacancy concentration is reduced. Specifically, we describe the complex mobility of oxygen vacancies and interstitials, which governs the recombination of these defects. The results of these simulations will aid in the synthesis of optimized scintillation materials. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

166

New Method to Detect the Transport Scattering Mechanisms of Graphene Carriers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Detecting the carrier scattering mechanisms in a materials system is important for transport related science and engineering. The approaches of fast laser process and electrical conductivity matching were used in previous literature, which do not give accurate information on scattering relaxation time as a function of carrier energy for intrinsic photon-free transport. Graphene is considered as a model system in materials science studying for its simple atomic and electronic...

Tang, Shuang; Dresselhaus, Mildred S.

2014-01-01

167

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2003-01-01

168

HKT transporter-mediated salinity resistance mechanisms in Arabidopsis and monocot crop plants  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The salinization of irrigated lands is increasingly detrimental to plant biomass production and agricultural productivity as most plant species are sensitive to high concentrations of sodium (Na+), which causes combined Na+ toxicity and osmotic stress. Plants have multiple Na+ transport systems to circumvent Na+ toxicity. Essential physiological functions of major Na+ transporters and their mechanisms mediating salinity resistance have been identified in Arabidopsis, including the SOS1, AtNHX...

Horie, Tomoaki; Hauser, Felix; Schroeder, Julian I.

2009-01-01

169

Transport mechanism of thermohydraulic instability in natural circulation boiling water reactors during startup  

International Nuclear Information System (INIS)

This paper presents experimental study on transport mechanism of thermohydraulic instability, which may occur in natural circulation experimental loop featuring twin parallel boiling water reactor during startup. The research was carried out using a natural circulation experimental loop featuring twin parallel boiling channels with chimney assembly. The experiments were performed with the pressure range of 0.1 to 0.7 MPa and maximum heat flux of 577 kW/m2. The objective of the study is to formulate thermohydraulic stability maps required for determining rational startup procedure of the reactor, in which the instability could be prevented. The study clarified that the flow modes during startup consist of the following sequence: (1) single-phase flow, (2) geysering, (3) oscillation due to hydrostatic head fluctuation. (4) density wave oscillation, (5) transition oscillation, and (6) stable two-phase flow. The main findings of the experiments are as follows: First, low amplitude geysering still occurs at 0.7 MPa under lower heat flux and high inlet subcooling. Second, stable two-phase natural circulation is achieved with system pressure as low as 0.2 MPa, under medium heat flux, and subcooling lower than 5K. Third, oscillation due to hydrostatic head fluctuation only occurs under atmospheric condition. Finally, thermohydraulic stability maps and rational startup procedure are formulated. (author)

170

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

Directory of Open Access Journals (Sweden)

Full Text Available Biomass burning in the Indochina Peninsula (Indochina is one of the important ozone sources in the low troposphere over East Asia in springtime. Moderate Resolution Imaging Spectroradiometer (MODIS data show that 20 000 or more active fire detections occurred annually in spring only from 2000 to 2007. In our tracer modeling study, we identify a new mechanism transporting the tracer over Indochina that is significantly different from the vertical transport mechanism over the equatorial areas such as Indonesia and Malaysia. Simulation results demonstrate that the leeside troughs over Indochina play a dominant role in the uplift of the tracer below 3 km, and that the strong westerlies prevailing above 3 km transport the tracer. These fundamental mechanisms have a major impact on the air quality downwind from Indochina over East Asia. The climatological importance of such a leeside trough is also discussed.

C.-Y. Lin

2009-10-01

171

Mechanism of Cu+-transporting ATPases: Soluble Cu+ chaperones directly transfer Cu+ to transmembrane transport sites  

Digital Repository Infrastructure Vision for European Research (DRIVER)

As in other P-type ATPases, metal binding to transmembrane metal-binding sites (TM-MBS) in Cu+-ATPases is required for enzyme phosphorylation and subsequent transport. However, Cu+ does not access Cu+-ATPases in a free (hydrated) form but is bound to a chaperone protein. Cu+ transfer from Cu+ chaperones to regulatory cytoplasmic metal-binding domains (MBDs) present in these ATPases has been described, but there is no evidence of a proposed subsequent Cu+ movement from the MBDs to the TM-MBS. ...

Gonza?lez-guerrero, Manuel; Argu?ello, Jose? M.

2008-01-01

172

The mechanism of quinonediimine acceptor activity in photosynthetic electron transport.  

Science.gov (United States)

The rates of electron flow catalyzed by a variety of unsubstituted and C- or N-methylated quinonediimine electron acceptors in a reaction requiring photosystem II in KCN-inhibited chloroplasts vary according to the structure of acceptor used. Quinonediimine, but not quinone, electron acceptor activities are inhibited by a variety of uncouplers. Kinetic analysis of this inhibition shows that it is competitive. Low concentrations of aniline also inhibit the activity of C-methylated quinonediimines, but this appears to be due to a chemical reaction between the acceptor and aniline at low pH inside the chloroplast. Light-induced uptake of a quinonediimine, p-phenylenediimine, was shown to occur in a DCMU-sensitive reaction. Methylamine uncoupling inhibits this uptake to the same extent as it inhibits electron flow. Experiments with a lipophobic acceptor, N,N,N',N'-tetramethyl-p-phenylenediimine, indicate that it catalyzes electron flow by the same mechanism as other quinonediimines. A model is proposed to account for quinonediimine-catalyzed electron flow. PMID:1247521

Guikema, J A; Yocum, C F

1976-01-27

173

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

174

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

175

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-12-16

176

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

International Nuclear Information System (INIS)

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

177

Changes of the main parameters of the primary heat transport system of the Embalse NPP after the replacement of the divider plates of the steam generators  

International Nuclear Information System (INIS)

Divider plates of the four steam generators were repaired at Embalse NPP during the outage of 2002. This task led to a reduction of heavy water by-pass from the hot to the cold side. As a consequence of this, some Primary Heat Transport System (PHTS) parameters were affected. The main results of this work are the following: a) Bulk PHTS flow did not change significantly; b) Inlet Header temperature dropped 2,8 C degrees at full power; c) Quality at Outlet Header is now practically negligible. (author)

178

Electron transport across magnetic field in low-temperature plasmas: An alternative approach for obtaining evidence of Bohm mechanism  

International Nuclear Information System (INIS)

A comparative study involving both experimental and numerical investigations was made to resolve a long-standing problem of understanding electron conductivity mechanism across magnetic field in low-temperature plasmas. We have calculated the plasma parameters from experimentally obtained electric field distribution, and then made a 'back' comparison with the distributions of electron energy and plasma density obtained in the experiment. This approach significantly reduces an influence of the assumption about particular phenomenology of the electron conductivity in plasma. The results of the experiment and calculations made by this technique have showed that the classical conductivity is not capable of providing realistic total current and electron energy, whereas the phenomenological anomalous Bohm mobility has demonstrated a very good agreement with the experiment. These results provide an evidence in favor of the Bohm conductivity, thus making it possible to clarify this pressing long-living question about the main driving mechanism responsible for the electron transport in low-temperature plasmas

179

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2008-05-15

180

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

International Nuclear Information System (INIS)

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

 
 
 
 
181

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

182

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

Directory of Open Access Journals (Sweden)

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

Ana Carolina Donofre

2014-01-01

183

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

Science.gov (United States)

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

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

2013-02-01

184

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

185

A quantum mechanical transport approach to simulation of quadruple gate silicon nanowire transistor.  

Science.gov (United States)

In this paper we have used quantum mechanical transport approach to analyse electrical characteristics of silicon nanowire transistor and have compared the results with those obtained using semi classical Boltzmann transport model. The analyse employs a three dimensional simulation of Silicon nanowire transistor based on self consistent solution of Poisson, Schrodinger equations. Quantum mechanical transport model uses the non equilibrium Green's function (NEGF) while the semi classic model doesn't account for tunneling current. The results have shown that Quantum tunneling is significant in inversion condition especially when the channel length is short. For the long devices quantum modeling and semi classical model produce the same result, and tunneling is negligible. PMID:22408929

Karimi, Fatemeh; Fathipour, Morteza; Hosseini, Reza

2011-12-01

186

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

187

Mass transport mechanism in the collision of sulphur on medium-weight nuclei  

International Nuclear Information System (INIS)

The reactions of 32S on 59Co, 65Cu, 74Ge, 79Br, 85Rb, 89Y are studied. An explanation for the specific shape of the double differential cross sections as a function of the scattering angle and the mass asymmetry is given in the framework of a transport model. Conclusions about the reaction mechanism are drawn

188

Quantum heat transport in a spin-boson nanojunction: Coherent and incoherent mechanisms  

Science.gov (United States)

Quantum heat transport in a spin-boson system under nonequilibrium steady state (NESS) is investigated by the nonequilibrium Green's function (NEGF) method. Spin-spin correlators are calculated via the Majorana fermion representation of spin operators, which allows us to make use of Wick's theorem through standard diagrammatic techniques. An analytic formula of heat current is obtained, and numerical results are presented in comparison with those obtained by other methods. Two types of transport mechanisms are identified in high- and low-temperature regions, respectively, which shows a transition from incoherent to coherent transport process with the baths' temperatures decreased. Additionally, a saturation of the heat current is confirmed when increasing the coupling strength between the baths and the intermediate system, which is a sign of quantum Zeno effect (QZE) in the transport process.

Yang, Yue; Wu, Chang-Qin

2014-08-01

189

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

Science.gov (United States)

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

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

2014-04-21

190

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

International Nuclear Information System (INIS)

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

191

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-15

192

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

193

Competitiveness of the railway transportation in the conditions of functioning of the infrastructure new organizational-economic mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The transport infrastructure of railways of the countries of EU-27 in the conditions of functioning new organizational-economic mechanism, and also dynamics of level of competitiveness of a railway transportation as result of reforming of railways of the countries of EU-27, in the conditions of realisation of the European transport legislation is investigated.

Mishchenko, M. I.

2012-01-01

194

Hydraulic mechanism to limit torsional loads between the IUS and space transportation system orbiter  

Science.gov (United States)

The Inertial Upper Stage (IUS) is a two-stage booster used by NASA and the Defense Department to insert payloads into geosynchronous orbit from low-Earth orbit. The hydraulic mechanism discussed here was designed to perform a specific dynamic and static interface function within the Space Transportation System's Orbiter. Requirements, configuration, and application of the hydraulic mechanism with emphasis on performance and methods of achieving zero external hydraulic leakage are discussed. The hydraulic load-leveler mechanism meets the established design requirements for operation in a low-Earth orbit. Considerable testing was conducted to demonstrate system performance and verification that external leakage had been reduced to zero. Following each flight use of an ASE, all hydraulic mechanism components are carefully inspected for leakage. The ASE, including the hydraulic mechanism, has performed without any anomalies during all IUS flights.

Farmer, James R.

1986-01-01

195

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

Science.gov (United States)

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

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

2011-12-01

196

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

197

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

198

Structural basis for dynamic mechanism of proton-coupled symport by the peptide transporter POT  

Science.gov (United States)

Proton-dependent oligopeptide transporters (POTs) are major facilitator superfamily (MFS) proteins that mediate the uptake of peptides and peptide-like molecules, using the inwardly directed H+ gradient across the membrane. The human POT family transporter peptide transporter 1 is present in the brush border membrane of the small intestine and is involved in the uptake of nutrient peptides and drug molecules such as ?-lactam antibiotics. Although previous studies have provided insight into the overall structure of the POT family transporters, the question of how transport is coupled to both peptide and H+ binding remains unanswered. Here we report the high-resolution crystal structures of a bacterial POT family transporter, including its complex with a dipeptide analog, alafosfalin. These structures revealed the key mechanistic and functional roles for a conserved glutamate residue (Glu310) in the peptide binding site. Integrated structural, biochemical, and computational analyses suggested a mechanism for H+-coupled peptide symport in which protonated Glu310 first binds the carboxyl group of the peptide substrate. The deprotonation of Glu310 in the inward open state triggers the release of the bound peptide toward the intracellular space and salt bridge formation between Glu310 and Arg43 to induce the state transition to the occluded conformation. PMID:23798427

Doki, Shintaro; Kato, Hideaki E.; Solcan, Nicolae; Iwaki, Masayo; Koyama, Michio; Hattori, Motoyuki; Iwase, Norihiko; Tsukazaki, Tomoya; Sugita, Yuji; Kandori, Hideki; Newstead, Simon; Ishitani, Ryuichiro; Nureki, Osamu

2013-01-01

199

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

Science.gov (United States)

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

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

2014-11-01

200

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

Science.gov (United States)

Protein transport is an important phenomenon in biological systems. Proteins are transported via several mechanisms to reach their destined compartment of cell for its complete function. One such mechanism is the microtubule mediated protein transport. Up to now, there are no reports on synthetic systems mimicking the biological protein transport mechanism. Here we report a highly efficient method of mimicking the microtubule mediated protein transport using newly designed biotinylated peptides encompassing a microtubule-associated sequence (MTAS) and a nuclear localization signaling (NLS) sequence, and their final conjugation with streptavidin-coated CdSe/ZnS quantum dots (QDs). Our results demonstrate that these novel bio-conjugated QDs enhance the endosomal escape and promote targeted delivery into the nucleus of human mesenchymal stem cells via microtubules. Mimicking the cellular transport mechanism in stem cells is highly desirable for diagnostics, targeting and therapeutic applications, opening up new avenues in the area of drug delivery. PMID:23851637

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

2013-01-01

 
 
 
 
201

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

Science.gov (United States)

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

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

2014-10-01

202

New mechanism for amino acid influx into human epidermal Langerhans cells: L-dopa/proton counter-transport system.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have characterized a stereospecific transport mechanism for L-dopa into human epidermal Langerhans cells (LCs). It is different from any other amino acid transport system. It is highly concentrative, largely pH-independent, and independent of exogenous Na+, glucose and oxygen, and fuelled by a renewable intracellular energy source inhibited by iodoacetate but not by arsenate. We propose that the mechanism is a unidirectional L-dopa/proton counter-transport system. We have recently demonstr...

Falck, Bengt; Bendso?e, Niels; Ronquist, Gunnar

2003-01-01

203

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

204

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

International Nuclear Information System (INIS)

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

205

Ocean heat transport in Simple Ocean Data Assimilation: Structure and mechanisms  

Science.gov (United States)

The trend and variability of global ocean heat transport for the period 1958-2004 are investigated using the Simple Ocean Data Assimilation (SODA) analysis. The ocean model is forced with the European Center for Medium Range Weather Forecast (ECMWF) ERA-40 atmospheric reanalysis winds from 1958 to 2001 and with QuikSCAT winds from 2002 to 2004. The assimilation is based on a sequential estimation algorithm, with observations from the historical archive of hydrographic profiles supplemented by ship intake measurements, moored hydrographic observations and remotely sensed sea surface temperature. Heat transport is calculated using temperature and velocity from the ocean analysis. Mean heat transport from the analysis generally agrees with previously published estimates from observational and modeling studies. Trends of heat transport show a range of behaviors. In the Atlantic and Pacific Oceans there is mostly increasing poleward heat transport with two important exceptions. In the Atlantic Ocean there is decreasing heat transport around 50°N and 60°N, and in both the Atlantic and Pacific Oceans there is decreasing heat transport near 10°S. There is also prominent interannual and decadal variability in all of the ocean basins. The results suggest that ocean heat transport variability is primarily determined by the strength of the meridional overturning circulation (MOC), which is controlled by complex processes governing fresh water flux in the northern North Atlantic and surface wind stress. However, the role of temperature variability increases at high latitude, particularly in the northern North Atlantic Ocean. Eddies play an important role in heat transport in the Gulf Stream and its extension in the Atlantic Ocean, and the Kuroshio and its extension in the Pacific Ocean and enhanced Subtropical cells (STCs) affect heat transport estimates in the tropics. In the northern North Atlantic Ocean, a small increase in meridional heat transport and a slight weakening of MOC are detected. Weakening in the northern North Atlantic MOC mainly arises from a freshening in the Labrador Sea and slowdown of the overflows from the Nordic Seas into the northern North Atlantic Ocean. Trends in North Atlantic surface momentum forcing are uniform across several atmospheric reanalyses, however there is less agreement in the role of precipitation in forcing trends of MOC and this exists as a primary source of uncertainty in our analysis.

Zheng, Yangxing; Giese, Benjamin S.

2009-11-01

206

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

207

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

208

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

International Nuclear Information System (INIS)

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

209

Unconventional mechanisms of protein transport to the cell surface of eukaryotic cells.  

Science.gov (United States)

The classical secretion of soluble proteins and transport of integral membrane proteins to the cell surface require transit into and through the endoplasmic reticulum and the Golgi apparatus. Signal peptides or transmembrane domains target proteins for translocation into the lumen or insertion into the membrane of the endoplasmic reticulum, respectively. Here we discuss two mechanisms of unconventional protein targeting to plasma membranes, i.e., transport processes that are active in the absence of a functional Golgi system. We first focus on integral membrane proteins that are inserted into the endoplasmic reticulum but that, however, are transported to plasma membranes in a Golgi-independent manner. We then discuss soluble secretory proteins that are secreted from cells without any involvement of the endoplasmic reticulum and the Golgi apparatus. PMID:18590485

Nickel, Walter; Seedorf, Matthias

2008-01-01

210

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-03-31

211

Modified random hinge transport mechanics and multiple scattering step-size selection in EGS5  

International Nuclear Information System (INIS)

The new transport mechanics in EGS5 allows for significantly longer electron transport step sizes and hence shorter computation times than required for identical problems in EGS4. But as with all Monte Carlo electron transport algorithms, certain classes of problems exhibit step-size dependencies even when operating within recommended ranges, sometimes making selection of step-sizes a daunting task for novice users. Further contributing to this problem, because of the decoupling of multiple scattering and continuous energy loss in the dual random hinge transport mechanics of EGS5, there are two independent step sizes in EGS5, one for multiple scattering and one for continuous energy loss, each of which influences speed and accuracy in a different manner. Further, whereas EGS4 used a single value of fractional energy loss (ESTEPE) to determine step sizes at all energies, to increase performance by decreasing the amount of effort expended simulating lower energy particles, EGS5 permits the fractional energy loss values which are used to determine both the multiple scattering and continuous energy loss step sizes to vary with energy. This results in requiring the user to specify four fractional energy loss values when optimizing computations for speed. Thus, in order to simplify step-size selection and to mitigate step-size dependencies, a method has been devised to automatically optimize step-size selection based on a single material dependent input related to the size erial dependent input related to the size of problem tally region. In this paper we discuss the new transport mechanics in EGS5 and describe the automatic step-size optimization algorithm. (author)

212

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

213

Mechanical and transport properties of Ag alloy/Bi-2223 superconducting tapes under axial fatigue loading  

International Nuclear Information System (INIS)

For the endurance evaluation of HTS conductors, the mechanical and transport properties of Ag alloy/Bi-2223 superconducting tapes subjected to high cycle axial fatigue loading were investigated at 77 K. The relations between the applied stress amplitude and the fatigue life (S-N curves) were obtained using the Ag alloy/Bi-2223 tapes and their transport properties were evaluated with the increase of repeated cycles at different stress amplitudes. The effect of the stress ratio, R, on the I c degradation behavior under fatigue loading was also examined considering the practical application situation of HTS tapes. Fractographic observation was performed in order to understand the I c degradation mechanism in fatigued Bi-2223 tapes

214

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

International Nuclear Information System (INIS)

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

215

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

International Nuclear Information System (INIS)

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

216

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-01-07

217

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

218

Transport capacity and saturation mechanism in a real-space cellular automaton dune model  

Science.gov (United States)

In a real-space cellular automaton dune model, individual physical processes such as erosion, deposition and transport are implemented by nearest neighbor interactions and a time-dependent stochastic process. Hence, the transport capacity, the saturation mechanism and the characteristic wavelength for the formation of dunes are emergent properties that can only be determined a posteriori from the output of the numerical simulations. Here we propose a simplified version of the model to establish asymptotic relations between the microscopic erosion-deposition-transport rate parameters and the characteristic length and time scales of the flux saturation mechanism. In particular, we show that, in the cellular automaton, the saturation length is a mean transport distance controlled by the deposition of mobile sedimentary cells. Then, we discuss how these results can be used to determine the sediment flux within dune fields and the rate parameters of a new class of discrete models that concentrate on the effect of heterogeneities in grain-size on dune morphodynamics.

Gao, X.; Zhang, D.; Rozier, O.; Narteau, C.

2014-04-01

219

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

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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

220

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

 
 
 
 
221

Transport mechanisms for adenosine and uridine in primary-cultured rat cortical neurons and astrocytes.  

Science.gov (United States)

Endogenous adenosine and uridine are important modulators of neural survival and activity. In the present study, we examined transport mechanisms of adenosine and uridine in primary-cultured rat cortical neurons, and compared the results for neurons with those for astrocytes. Reverse transcription-polymerase chain reaction identified the mRNAs for ENT1, ENT2, and CNT2, but not CNT1 and CNT3, in neurons and astrocytes. [3H]Adenosine and [3H]uridine were time-, temperature-, and concentration-dependently taken up into neurons and astrocytes. In kinetic analyses, the uptake of both substrates by neurons and astrocytes consisted of two and one, respectively, saturable transport components. The uptake clearance for both substrates by neurons was greater than that by astrocytes. The relative contribution of the high-affinity major component of both substrates to total uptake was estimated to be approximately 80% in neurons. The uptake of [3H]adenosine and [3H]uridine by both neurons and astrocytes was almost entirely Na+-independent, and sensitive to micro, but not nano, molar concentrations of nitrobenzylmercaptopurine riboside, which are transport characteristics of ENT2. Therefore, it was indicated that adenosine and uridine are more efficiently taken up into neurons than into astrocytes, and ENT2 may predominantly contribute to the transport of the nucleosides as a high-affinity transport system in neurons, as in the case of astrocytes. PMID:16043124

Nagai, Katsuhito; Nagasawa, Kazuki; Fujimoto, Sadaki

2005-09-01

222

Structural basis of the alternating-access mechanism in a bile acid transporter  

Science.gov (United States)

Bile acids are synthesized from cholesterol in hepatocytes and secreted through the biliary tract into the small intestine, where they aid in absorption of lipids and fat-soluble vitamins. Through a process known as enterohepatic recirculation, more than 90% of secreted bile acids are then retrieved from the intestine and returned to the liver for resecretion. In humans, there are two Na+-dependent bile acid transporters involved in enterohepatic recirculation, the Na+-taurocholate co-transporting polypeptide (NTCP; also known as SLC10A1) expressed in hepatocytes, and the apical sodium-dependent bile acid transporter (ASBT; also known as SLC10A2) expressed on enterocytes in the terminal ileum. In recent years, ASBT has attracted much interest as a potential drug target for treatment of hypercholesterolaemia, because inhibition of ASBT reduces reabsorption of bile acids, thus increasing bile acid synthesis and consequently cholesterol consumption. However, a lack of three-dimensional structures of bile acid transporters hampers our ability to understand the molecular mechanisms of substrate selectivity and transport, and to interpret the wealth of existing functional data. The crystal structure of an ASBT homologue from Neisseria meningitidis (ASBTNM) in detergent was reported recently, showing the protein in an inward-open conformation bound to two Na+ and a taurocholic acid. However, the structural changes that bring bile acid and Na+ across the membrane are difficult to infer from a single structure. To understand the structural changes associated with the coupled transport of Na+ and bile acids, here we solved two structures of an ASBT homologue from Yersinia frederiksenii (ASBTYf) in a lipid environment, which reveal that a large rigid-body rotation of a substrate-binding domain gives the conserved `crossover' region, where two discontinuous helices cross each other, alternating accessibility from either side of the cell membrane. This result has implications for the location and orientation of the bile acid during transport, as well as for the translocation pathway for Na+.

Zhou, Xiaoming; Levin, Elena J.; Pan, Yaping; McCoy, Jason G.; Sharma, Ruchika; Kloss, Brian; Bruni, Renato; Quick, Matthias; Zhou, Ming

2014-01-01

223

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

Science.gov (United States)

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

Scalo, Carlo; Piomelli, Ugo; Boegman, Leon

2012-08-01

224

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

225

Ovariectomy enhances mechanical load-induced solute transport around osteocytes in rat cancellous bone.  

Science.gov (United States)

To test if osteoporosis alters mechanical load-induced interstitial fluid flow in bone, this study examined the combined effect of estrogen deficiency and external loading on solute transport around osteocytes. An in vivo tracer, FITC-labeled bovine serum albumin, was injected into anesthetized ovariectomized and control female Sprague-Dawley rats before the right tibia was subjected to a controlled, physiological, non-invasive sinusoidal load to mimic walking. Tracer movement through the lacunar-canalicular system surrounding osteocytes was quantified in cortical and cancellous bone from the proximal tibia using confocal microscopy, with the non-loaded tibia serving as internal control. Overall, the application of mechanical loading increased the percentage of osteocyte lacunae labeled with injected tracer, and ovariectomy further enhanced movement of tracer. An analysis of separate regions demonstrated that ovariectomy enhanced in vivo transport of the injected tracer in the cancellous bone of the tibial epiphysis and metaphysis but not in the cortical bone of the metaphysis. These findings show that bone changes due to reduced estrogen levels alter convectional transport around osteocytes in cancellous bone and demonstrate a functional difference of interstitial fluid flow around osteocytes in estrogen-deficient rats undergoing the same physical activity as controls. The altered interstitial fluid flow around osteocytes is likely related to nanostructural matrix-mineral level differences recently demonstrated at the lacunar-canalicular surface of estrogen-deficient rats, which could affect the transmission of mechanical loads to the osteocyte. PMID:24316418

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

2014-02-01

226

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)

227

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

228

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

Directory of Open Access Journals (Sweden)

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

P. Zunino

2013-10-01

229

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

230

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

231

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

Scientific Electronic Library Online (English)

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

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

232

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

Scientific Electronic Library Online (English)

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

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

2014-04-01

233

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

International Nuclear Information System (INIS)

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

234

Sensitizing Curium Luminescence through an Antenna Protein to Investigate Biological Actinide Transport Mechanisms  

Science.gov (United States)

Worldwide stocks of actinides and lanthanide fission products produced through conventional nuclear spent fuel are increasing continuously, resulting in a growing risk of environmental and human exposure to these toxic radioactive metal ions. Understanding the bio-molecular pathways involved in mammalian uptake, transport and storage of these f-elements is crucial to the development of new decontamination strategies and could also be beneficial to the design of new containment and separation processes. To start unraveling these pathways, our approach takes advantage of the unique spectroscopic properties of trivalent curium. We clearly show that the human iron transporter transferrin acts as an antenna that sensitizes curium luminescence through intramolecular energy transfer. This behavior has been used to describe the coordination of curium within the two binding sites of the protein and to investigate the recognition of curium-transferrin complexes by the cognate transferrin receptor. In addition to providing the first protein-curium spectroscopic characterization, these studies prove that transferrin receptor-mediated endocytosis is a viable mechanism of intracellular entry for trivalent actinides such as curium and provide a new tool utilizing the specific luminescence of curium for the determination of other biological actinide transport mechanisms. PMID:23363005

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

2013-01-01

235

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

Science.gov (United States)

Worldwide stocks of actinides and lanthanide fission products produced through conventional nuclear spent fuel are increasing continuously, resulting in a growing risk of environmental and human exposure to these toxic radioactive metal ions. Understanding the biomolecular pathways involved in mammalian uptake, transport and storage of these f-elements is crucial to the development of new decontamination strategies and could also be beneficial to the design of new containment and separation processes. To start unraveling these pathways, our approach takes advantage of the unique spectroscopic properties of trivalent curium. We clearly show that the human iron transporter transferrin acts as an antenna that sensitizes curium luminescence through intramolecular energy transfer. This behavior has been used to describe the coordination of curium within the two binding sites of the protein and to investigate the recognition of curium-transferrin complexes by the cognate transferrin receptor. In addition to providing the first protein-curium spectroscopic characterization, these studies prove that transferrin receptor-mediated endocytosis is a viable mechanism of intracellular entry for trivalent actinides such as curium and provide a new tool utilizing the specific luminescence of curium for the determination of other biological actinide transport mechanisms. PMID:23363005

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

2013-02-20

236

Molecular mechanism of ligand recognition by membrane transport protein, Mhp1.  

Science.gov (United States)

The hydantoin transporter Mhp1 is a sodium-coupled secondary active transport protein of the nucleobase-cation-symport family and a member of the widespread 5-helix inverted repeat superfamily of transporters. The structure of Mhp1 was previously solved in three different conformations providing insight into the molecular basis of the alternating access mechanism. Here, we elucidate detailed events of substrate binding, through a combination of crystallography, molecular dynamics, site-directed mutagenesis, biochemical/biophysical assays, and the design and synthesis of novel ligands. We show precisely where 5-substituted hydantoin substrates bind in an extended configuration at the interface of the bundle and hash domains. They are recognised through hydrogen bonds to the hydantoin moiety and the complementarity of the 5-substituent for a hydrophobic pocket in the protein. Furthermore, we describe a novel structure of an intermediate state of the protein with the external thin gate locked open by an inhibitor, 5-(2-naphthylmethyl)-L-hydantoin, which becomes a substrate when leucine 363 is changed to an alanine. We deduce the molecular events that underlie acquisition and transport of a ligand by Mhp1. PMID:24952894

Simmons, Katie J; Jackson, Scott M; Brueckner, Florian; Patching, Simon G; Beckstein, Oliver; Ivanova, Ekaterina; Geng, Tian; Weyand, Simone; Drew, David; Lanigan, Joseph; Sharples, David J; Sansom, Mark S P; Iwata, So; Fishwick, Colin W G; Johnson, A Peter; Cameron, Alexander D; Henderson, Peter J F

2014-08-18

237

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

International Nuclear Information System (INIS)

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

238

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

International Nuclear Information System (INIS)

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

239

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

International Nuclear Information System (INIS)

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

240

Crystal structure of the carnitine transporter and insights into the antiport mechanism.  

Science.gov (United States)

CaiT is a membrane antiporter that catalyzes the exchange of L-carnitine with gamma-butyrobetaine across the Escherichia coli membrane. To obtain structural insights into the antiport mechanism, we solved the crystal structure of CaiT at a resolution of 3.15 A. We crystallized CaiT as a homotrimer complex, in which each protomer contained 12 transmembrane helices and 4 l-carnitine molecules outlining the transport pathway across the membrane. Mutagenesis studies revealed a primary binding site at the center of the protein and a secondary substrate-binding site at the bottom of the intracellular vestibule. These results, together with the insights obtained from structural comparison with structurally homologous transporters, provide mechanistic insights into the association between substrate translocation and the conformational changes of CaiT. PMID:20357772

Tang, Lin; Bai, Lin; Wang, Wen-hua; Jiang, Tao

2010-04-01

 
 
 
 
241

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

Energy Technology Data Exchange (ETDEWEB)

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

Chen, Peiyuan; Illsley, N.P.; Verkman, A.S. (Univ. of California, San Francisco (USA))

1988-01-01

242

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

International Nuclear Information System (INIS)

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

243

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

CERN Document Server

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

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

2006-01-01

244

A fracture mechanics approach to spent nuclear fuel transportation cask design  

International Nuclear Information System (INIS)

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

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)

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

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

DEFF Research Database (Denmark)

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

Liddelow, Shane A; Temple, Sally

2012-01-01

248

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)

249

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

250

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

251

Monte Carlo study in the mechanisms of transport of fast neutrons in various media  

Energy Technology Data Exchange (ETDEWEB)

The life histories of fast neutrons created by the straight Monte Carlo method in various attenuation media were examined. The media studied range from the one with simple, featureless properties (Na) to iron with very complicated cross section structure. The life histories of exceptional neutrons, i.e. those staying very close to the source, or those going very far from the source, were compared with those of the general population. When the exceptional neutrons exploited a particular collision property in a narrow energy band in order to reach a given detector, the method of analyzing Monte Carlo histories was able to provide a clear physical picture and single out the influence of that property on the macroscopic behavior of the neutrons. Two such phenomena were demonstrated by using this technique. In one, transport in a cross section minimum dominates the deep penetration of the neutrons. In such a circumstance most of the spatial transport is accomplished by the traveling at energies in and near the minimum, while little transport occurs at any other energies. The second example involves the effect of inelastic scattering on the low-energy leakage spectra for small bare assemblies. It is shown that, for a small bare iron sphere and for a fission source, the exit current spectrum below 100 keV is extremely sensitive to the details of the inelastic scattering near threshold. It often happened that in some exceptional situations the number of histories available for the analysis was too few to give statistically significant results. The most important conclusion to be drawn here is that the analysis of Monte Carlo histories can provide information on the details of transport mechanisms that is not available through forward or even adjoint deterministic transport calculations. 47 figures, 21 tables. (RWR)

Ku, L.

1976-01-01

252

222Rn fluctuations in thermal spring gases and possible transport mechanism  

International Nuclear Information System (INIS)

The waters of many thermal springs in eastern India contain radon in excess of the surrounding ground waters. The spring waters being deep-seated are also the source of helium bearing terrestrial gases that carry an enhanced 222Rn. Temporal variations in both the helium as well as radon activity have been observed. Sudden changes in radon concentration is related to telluric disturbances. Possible transport mechanism to account for increased radon concentration due to relatively distant seismic activity is discussed. (author). 12 refs., 2 figs., 1 tab

253

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

Energy Technology Data Exchange (ETDEWEB)

We present exemplary results of extensive studies of mechanical, electronic and transport properties of covalent functionalization of graphene monolayers (GML). We report new results of ab initio studies for covalent functionalization of GML with ?NH{sub 2} groups up to 12.5 % concentration. Our studies are performed in the framework of the density functional theory (DFT) and non-equilibrium Green’s function (NEGF). We discuss the stability (adsorption energy), elastic moduli, electronic structure, band gaps, and effective electron masses as a function of the density of the adsorbed molecules. We also show the conductance and current – voltage I(V) characteristics for these systems.

Milowska, Karolina Z.; Birowska, Magdalena; Majewski, Jacek A. [Faculty of Physics, University of Warsaw, ul. Ho?a 69, 00-681 Warszawa (Poland)

2013-12-04

254

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

International Nuclear Information System (INIS)

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

255

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

Science.gov (United States)

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

Milowska, Karolina Z.; Birowska, Magdalena; Majewski, Jacek A.

2013-12-01

256

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-11-01

257

Role of thin descending limb urea transport in renal urea handling and the urine concentrating mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Urea transporters UT-A2 and UT-B are expressed in epithelia of thin descending limb of Henle's loop and in descending vasa recta, respectively. To study their role and possible interaction in the context of the urine concentration mechanism, a UT-A2 and UT-B double knockout (UT-A2/B knockout) mouse model was generated by targeted deletion of the UT-A2 promoter in embryonic stem cells with UT-B gene knockout. The UT-A2/B knockout mice lacked detectable UT-A2 and UT-B transcripts and proteins a...

Lei, Tianluo; Zhou, Lei; Layton, Anita T.; Zhou, Hong; Zhao, Xuejian; Bankir, Lise; Yang, Baoxue

2011-01-01

258

Insights into the ClC-4 Transport Mechanism from Studies of Zn2+ Inhibition  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The CLC family of chloride channels and transporters is a functionally diverse group of proteins important in a wide range of physiological processes. ClC-4 and ClC-5 are localized to endosomes and seem to play roles in the acidification of these compartments. These proteins were recently shown to function as Cl?/H+ antiporters. However, relatively little is known about the detailed mechanism of CLC-mediated Cl?/H+ antiport, especially for mammalian isoforms. We attempted to identify mole...

Osteen, Jeremiah D.; Mindell, Joseph A.

2008-01-01

259

Electron transport mechanism of thermally oxidized ZnO gas sensors  

International Nuclear Information System (INIS)

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

260

Main Facilities  

International Nuclear Information System (INIS)

This chapter discuss on main nuclear facilities available in the Malaysian Institute for Nuclear Technology Research (MINT). As a national research institute whose core activities are nuclear science and technology, MINT are made up of main commercializable radiation irradiators, pilot plant and fully equipped laboratories. Well elaboration on its characteristics and functions explain for RTP (PUPSPATI TRIGA reactors), Cobalt-60 gamma irradiator, electron beam accelerators, and radioactive waste management center

 
 
 
 
261

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

262

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

Energy Technology Data Exchange (ETDEWEB)

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.

Garrison, W.M.

1982-08-01

263

Mechanical and analytical screening of braided composites for transport fuselage applications  

Science.gov (United States)

The mechanics of materials progress in support of the goal of understanding the application of braided composites in a transport aircraft fuselage are summarized. Composites consisting of both 2-D and 3-D braid patterns are investigated. Both consolidation of commingled graphite/PEEK and resin transfer molding of graphite-epoxy braided composite processes are studied. Mechanical tests were used to examine unnotched tension, open hole tension, compression, compression after impact, in-plane shear, out-of-plane tension, bearing, and crippling. Analytical methods are also developed and applied to predict the stiffness and strengths of test specimens. A preliminary study using the test data and analytical results is performed to assess the applicability of braided composites to a commercial aircraft fuselage.

Fedro, Mark J.; Gunther, Christian; Ko, Frank K.

1991-01-01

264

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

Science.gov (United States)

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

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

2014-08-19

265

Conformational cycle and ion-coupling mechanism of the Na+/hydantoin transporter Mhp1.  

Science.gov (United States)

Ion-dependent transporters of the LeuT-fold couple the uptake of physiologically essential molecules to transmembrane ion gradients. Defined by a conserved 5-helix inverted repeat that encodes common principles of ion and substrate binding, the LeuT-fold has been captured in outward-facing, occluded, and inward-facing conformations. However, fundamental questions relating to the structural basis of alternating access and coupling to ion gradients remain unanswered. Here, we used distance measurements between pairs of spin labels to define the conformational cycle of the Na(+)-coupled hydantoin symporter Mhp1 from Microbacterium liquefaciens. Our results reveal that the inward-facing and outward-facing Mhp1 crystal structures represent sampled intermediate states in solution. Here, we provide a mechanistic context for these structures, mapping them into a model of transport based on ion- and substrate-dependent conformational equilibria. In contrast to the Na(+)/leucine transporter LeuT, our results suggest that Na(+) binding at the conserved second Na(+) binding site does not change the energetics of the inward- and outward-facing conformations of Mhp1. Comparative analysis of ligand-dependent alternating access in LeuT and Mhp1 lead us to propose that different coupling schemes to ion gradients may define distinct conformational mechanisms within the LeuT-fold class. PMID:25267652

Kazmier, Kelli; Sharma, Shruti; Islam, Shahidul M; Roux, Benoît; Mchaourab, Hassane S

2014-10-14

266

Identification of p-glycoprotein and transport mechanism of Paclitaxel in syncytiotrophoblast cells.  

Science.gov (United States)

When chemotherapy is administered during pregnancy, it is important to consider the fetus chemotherapy exposure, because it may lead to fetal consequences. Paclitaxel has become widely used in the metastatic and adjuvant settings for woman with cancer including breast and ovarian cancer. Therefore, we attempted to clarify the transport mechanisms of paclitaxel through blood-placenta barrier using rat conditionally immortalized syncytiotrophoblast cell lines (TR-TBTs). The uptake of paclitaxel was time- and temperature-dependent. Paclitaxel was eliminated about 50% from the cells within 30 min. The uptake of paclitaxel was saturable with Km of 168 ?M and 371 ?M in TR-TBT 18d-1 and TR-TBT 18d-2, respectively. [(3)H]Paclitaxel uptake was markedly inhibited by cyclosporine and verapamil, well-known substrates of P-glycoprotein (P-gp) transporter. However, several MRP substrates and organic anions had no effect on [(3)H]paclitaxel uptake in TR-TBT cells. These results suggest that P-gp may be involved in paclitaxel transport at the placenta. TR-TBT cells expressed mRNA of P-gp. These findings are important for therapy of breast and ovarian cancer of pregnant women, and should be useful data in elucidating teratogenicity of paclitaxel during pregnancy. PMID:24596624

Lee, Na-Young; Lee, Ha-Eun; Kang, Young-Sook

2014-01-01

267

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

268

Molecular dynamics simulation of effective thermal conductivity and study of enhanced thermal transport mechanism in nanofluids  

Science.gov (United States)

Nanofluids have been proposed as a route for surpassing the performance of currently available heat transfer liquids in the near future. In this study an equilibrium molecular dynamics simulation was used to model a nanofluid system. The thermal conductivity of the base fluid and nanofluid was computed using the Green-Kubo method for various volume fractions of nanoparticle loadings. This study showed the ability of molecular dynamics to predict the enhanced thermal conductivity of nanofluids. Through molecular dynamics calculation of mean square displacements for liquid phase in base fluid and for liquid and solid phases in nanofluid, this study tried to investigate the mechanisms involved in thermal transport of nanofluids at the atomic level. The result showed that the thermal transport enhancement of nanofluids was mostly due to the increased movement of liquid atoms in the presence of nanoparticle. Diffusion coefficients were also calculated for base fluid and nanofluids. Similarity of enhancement in thermal conductivity and diffusion coefficient for nanofluids indicates similar transport process for mass and heat.

Sarkar, Suranjan; Selvam, R. Panneer

2007-10-01

269

Mechanisms of lithium transport through transition metal oxides studied by analysis of current transients  

Energy Technology Data Exchange (ETDEWEB)

Lithium transport through such transition metal oxides as Li{sub 1+{delta}}[Ti{sub 5/3}]O{sub 4}, Li{sub 1-{delta}}NiO{sub 2} and Li{sub {delta}}V{sub 2}O{sub 5} was investigated by analysis of current transients. All the experimental current transients in shape deviated markedly from the Cottrell character during the whole intercalation/deintercalation, and the initial current level varied linearly with the applied potential step according to Ohm's law. Moreover, it was observed that the current transient during phase transformation is characterised by a 'current plateau'. The current transient was simulated as a function of applied potential by numerical analysis assuming 'cell-impedance-controlled lithium transport. The numerically simulated current transient featured quantitative behaviour characteristic of non-Cottrell behaviour and exhibited a 'current plateau'. The lithium transport mechanism through the oxides is discussed in terms of 'cell-impedance-controlled' intercalation/deintercalation. (Author)

Shin, Heon-Cheol; Pyun, Su-Il; Kim, Sung-Woo; Lee, Min-Hyung [Korea Advanced Inst. of Science and Technology, Taejon (Korea). Dept. of Materials Science and Engineering

2001-07-01

270

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

271

Exploring particulate retention mechanisms through visualization of E. coli transport through a single, saturated fracture  

Science.gov (United States)

Groundwater is an extremely valuable resource; a large body of work has been conducted towards remediating, tracking and reducing its contamination. Even so, there are large gaps within the current understanding of groundwater flow and contaminant transport, particularly within fractured media. Fractured media has the ability transport contaminants over longer distances in less time relative to porous media. Furthermore, colloids display unique transport characteristics in comparison to dissolved constituents, including the fact that they typically exhibit earlier initial arrival times. Of particular concern to human health are pathogenic microorganisms, which often originate from fecal contamination. Escherichia coli is a common indicator for fecal contamination; some strains are pathogenic, causing acute illness and sometimes death, in humans. A comprehensive understanding of the transport and retention of E. coli in fractured media will improve our ability to accurately assess whether a site is at risk of becoming contaminated by pathogenic microorganisms. Therefore, the goal of this work is to expand our mechanistic understanding particulate retention, specifically E. coli, in fractures, and the influence of flow rate on these mechanisms. In order to achieve this goal, clear epoxy casts were fabricated of two dolomitic limestone fractures retrieved from a quarry in Guelph, Ontario. Each aperture field was characterized through hydraulic and tracer tests, and measured directly using the light transmission technique. E. coli RS2-GFP, which is a non-pathogenic strain of E. coli that has been tagged with a green fluorescent protein, was injected into the cast under three separate specific discharges ranging from 5 - 30 m/d. These experiments were conducted on an ultraviolet light source, and a high resolution charged-couple device (CCD) camera was employed to take photos at regular intervals in order to capture the dominant flow paths and the areas of retention within the epoxy fracture. Samples were drawn downstream to obtain the E. coli breakthrough curve and determine the percent retained within the fracture. This paper will present the dominant retention mechanisms of E. coli at various effective flow rates as determined from an analysis of the images showing trapped E. coli, together with the aperture field information from the direct measurement. This information will help to improve the robustness and of contaminant transport models in fractures, and will therefore improve the ability to assess the risk posed by using bedrock aquifers as drinking water sources.

Burke, M. G.; Dickson, S. E.; Schutten, M.

2011-12-01

272

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

Directory of Open Access Journals (Sweden)

Full Text Available Soil is the major terrestrial reservoirs of carbon, and a substantial part of this carbon is stored in deep layers, typically deeper than 50 cm below the surface. Several studies underlined the quantitative importance of this deep Soil Organic Carbon (SOC pool and models are needed to better understand this stock and its evolution under climate and land-uses changes. In this study, we test and compare 3 simple theoretical models of vertical transport for SOC against SOC profiles measurements from a long-term bare fallow experiment carried out by the Central-Chernozem State Natural Biosphere Reserve named after V.V. Alekhin, in the Kursk Region of Russia. The transport schemes tested are diffusion, advection or both diffusion and advection. They are coupled to two different formulations of soil carbon decomposition kinetics. The first formulation is a first order kinetics widely used in global SOC decomposition models; the second one links SOC decomposition rate to the amount of fresh organic matter, representing a "priming effect". Field data are from a set of three bare fallow plots where soil received no input during the past 20, 26 and 58 yr respectively. Parameters of the models were optimized using a Bayesian method. The best results are obtained when SOC decomposition is assumed to be controlled by fresh organic matter. In comparison to the first-order kinetic model, the "priming" model reduces the underestimation of SOC decomposition in the top layers and the over estimation in the deep layers. We also observe that the transport scheme that improved the fit with the data depends on the soil carbon mineralization formulation chosen. When soil carbon decomposition is modelled to depend on the fresh organic matter amount, the transport mechanisms which improves best the fit to the SOC profile data is the model representing both advection and diffusion. Interestingly, the older the bare fallow is, the lesser the need for diffusion is. This suggests that stabilized carbon may not be transported within the profile by the same mechanisms than more labile carbon.

B. Guenet

2012-10-01

273

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

Directory of Open Access Journals (Sweden)

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

B. Guenet

2013-04-01

274

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2004-07-01

275

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

International Nuclear Information System (INIS)

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

276

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-08-15

277

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

International Nuclear Information System (INIS)

BAM is the responsible authority in Germany for the assessment of the mechanical and thermal design safety of packages for the transport of radioactive materials. The assessment has to cover the brittle fracture safety 'proof of package' for components made of potentially brittle materials. This paper gives a survey of the regulatory and technical requirements for such an assessment according to BAM's new 'Guidelines for the application of ductile cast iron for transport and storage casks for radioactive materials'. Based on these guidelines, higher stresses than before will be permissible, but it is necessary to put more effort into the safety assessment procedure. The fundamentals of such a proof using the methods of fracture mechanics are presented. The recommended procedure takes into account the guidelines of the IAEA's advisory material which are based on the prevention of crack initiation. Examples of BAM's research and safety assessment practices are given. Recommendations for further developments towards package designs with higher acceptable stress levels will conclude the paper. (author)

278

Current transport mechanism in metal/HfO2/metal structures  

International Nuclear Information System (INIS)

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

279

Current transport mechanism in metal/HfO{sub 2}/metal structures  

Energy Technology Data Exchange (ETDEWEB)

The metal-insulator-metal (MIM) capacitor integration into BiCMOS technology is governed by the efforts toward increasing the capacitance density, reducing the leakage current density and improving the voltage linearity. In particular, achievement of an acceptable leakage current density in BEOL MIM capacitors is still a challenge. To get around this critical problem, high-k dielectrics have been introduced. Among various candidates, HfO{sub 2} has been investigated due to its high dielectric constant, low leakage current and chemical stability. Despite the considerable efforts for HfO{sub 2}, its current transport mechanism in MIM structures needs further investigations. Based on experimental results of the temperature dependence of the leakage current, we studied the current transport mechanism and energy band diagrams. The leakage current was measured in the temperature range of 200-400 K. The slope of an Arrhenius plot yielded activation energies in the range of E{sub a}=0.2 eV. In particular, we obtained a trap level at {phi}{sub PF}=0.4 eV below the HfO{sub 2} conduction band which contributes to Poole-Frenkel conduction.

Walczyk, Christian; Schroeder, Thomas; Wenger, Christian; Dabrowski, Jaroslaw; Lukosius, Mindaugas [IHP, Frankfurt (Oder) (Germany); Pasko, Sergej; Lohe, Christoph [AIXTRON AG, Aachen (Germany)

2008-07-01

280

Investigation of the energy transport mechanism in the TCA tokamak by studying the plasma dynamical response  

International Nuclear Information System (INIS)

The energy transport mechanisms that govern the electron temperature behaviour of a tokamak remain very badly understood and up to now no proper model has been proposed that can explain experimental observations such as profile consistency or the influence of the density profile. One approach to this problem, extensively used on TCA, is to study the dynamical response of the plasma due to externally imposed modifications of parameters which have an influence on the plasma energy content. The temporal evolution of the electron temperature will closely depend on the type and the characteristics of the implied mechanisms. Thus a detailed measurement of the dynamical response would reveal experimentally the dominant properties that would have to be taken into account in the elaboration of a model of the transport processes. Most of the results presented here were obtained by analysing the electron temperature response inferred from soft X-ray emissivity during modification of the plasma density due to either gas puffing, laser impurity ablation or alfven wave heating on TCA (a = 0.18 m, R = 0.61 m, B? = 1.52 T). 4 refs., 3 figs

 
 
 
 
281

Dependence of spontaneous neuronal firing and depolarisation block on astroglial membrane transport mechanisms.  

Science.gov (United States)

Exposed to a sufficiently high extracellular potassium concentration ([K(?+?)]?), the neuron can fire spontaneous discharges or even become inactivated due to membrane depolarisation ('depolarisation block'). Since these phenomena likely are related to the maintenance and propagation of seizure discharges, it is of considerable importance to understand the conditions under which excess [K(?+?)]? causes them. To address the putative effect of glial buffering on neuronal activity under elevated [K(?+?)](o) conditions, we combined a recently developed dynamical model of glial membrane ion and water transport with a Hodgkin-Huxley type neuron model. In this interconnected glia-neuron model we investigated the effects of natural heterogeneity or pathological changes in glial membrane transporter density by considering a large set of models with different, yet empirically plausible, sets of model parameters. We observed both the high [K(?+?)]?-induced duration of spontaneous neuronal firing and the prevalence of depolarisation block to increase when reducing the magnitudes of the glial transport mechanisms. Further, in some parameter regions an oscillatory bursting spiking pattern due to the dynamical coupling of neurons and glia was observed. Bifurcation analyses of the neuron model and of a simplified version of the neuron-glia model revealed further insights about the underlying mechanism behind these phenomena. The above insights emphasise the importance of combining neuron models with detailed astroglial models when addressing phenomena suspected to be influenced by the astroglia-neuron interaction. To facilitate the use of our neuron-glia model, a CellML version of it is made publicly available. PMID:21667153

Øyehaug, Leiv; Østby, Ivar; Lloyd, Catherine M; Omholt, Stig W; Einevoll, Gaute T

2012-02-01

282

Neuronal and glial glutamate transporters possess an SH-based redox regulatory mechanism.  

Science.gov (United States)

Glutamate uptake into nerve cells and astrocytes via high-affinity transporters controls the extracellular glutamate concentration in the brain, with major implications for physiological excitatory neurotransmission and the prevention of excitotoxicity. We report here that three recently cloned rat glutamate transporter subtypes, viz. EAAC1 (neuronal), GLT1 and GLAST (glial), possess a redox-sensing property, undergoing opposite functional changes in response to oxidation or reduction of reactive sulphydryls present in their structure. In particular, thiol oxidation with 5,5'-dithio-bis(2-nitrobenzoic) acid (DTNB) and disulphide reduction with dithiothreitol (DTT) result, respectively, in reduced and increased uptake capacity by a preparation of partially purified brain transporters as well as by the three recombinant proteins reconstituted into liposomes. In this model system, EAAC1, GLT1 and GLAST react similarly to DTT/DTNB exposures despite their different contents of cysteines, suggesting that only the conserved residues might be involved in redox modulation. Redox sensitivity is a property of the glutamate transporters also when present in their native cell environment. Thus, by using cultured cortical astrocytes and the whole-cell patch-clamp technique we were able to observe dynamic increase and decrease of the glutamate uptake current in response to application of DTT and DTNB in sequence. Moreover, in the same paradigm, DDT-reversible current inhibition was observed with hydrogen peroxide instead of DTNB, indicating that the SH-based redox modulatory site is targeted by endogenous oxidants and might constitute an important physiological or pathophysiological regulatory mechanism of glutamate uptake in vivo. PMID:9215707

Trotti, D; Rizzini, B L; Rossi, D; Haugeto, O; Racagni, G; Danbolt, N C; Volterra, A

1997-06-01

283

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

International Nuclear Information System (INIS)

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

284

Dual mechanisms of metabolite acquisition by the obligate intracytosolic pathogen Rickettsia prowazekii reveal novel aspects of triose phosphate transport.  

Science.gov (United States)

Rickettsia prowazekii is an obligate intracytosolic pathogen and the causative agent of epidemic typhus fever in humans. As an evolutionary model of intracellular pathogenesis, rickettsiae are notorious for their use of transport systems that parasitize eukaryotic host cell biochemical pathways. Rickettsial transport systems for substrates found only in eukaryotic cell cytoplasm are uncommon among free-living microorganisms and often possess distinctive mechanisms. We previously reported that R. prowazekii acquires triose phosphates for phospholipid biosynthesis via the coordinated activities of a novel dihydroxyacetone phosphate transport system and an sn-glycerol-3-phosphate dehydrogenase (K. M. Frohlich et al., J. Bacteriol. 192:4281-4288, 2010). In the present study, we have determined that R. prowazekii utilizes a second, independent triose phosphate acquisition pathway whereby sn-glycerol-3-phosphate is directly transported and incorporated into phospholipids. Herein we describe the sn-glycerol-3-phosphate and dihydroxyacetone phosphate transport systems in isolated R. prowazekii with respect to kinetics, energy coupling, transport mechanisms, and substrate specificity. These data suggest the existence of multiple rickettsial triose phosphate transport systems. Furthermore, the R. prowazekii dihydroxyacetone phosphate transport systems displayed unexpected mechanistic properties compared to well-characterized triose phosphate transport systems from plant plastids. Questions regarding possible roles for dual-substrate acquisition pathways as metabolic virulence factors in the context of a pathogen undergoing reductive evolution are discussed. PMID:23772074

Frohlich, Kyla M; Audia, Jonathon P

2013-08-01

285

THE STRUCTURAL LOGICAL SCHEME OF DEVELOPMENT HYDROCARBONS’ TROUBLE EMISSIONS AND MAIN DEMANDS TO SORBENTS WHICH ARE USED FOR THEIR LIQUIDATION ON THE RAILWAY TRANSPORT  

Directory of Open Access Journals (Sweden)

Full Text Available The processes and factors associated with the development of emergency emissions of hydrocarbons during their transportation by rail are considered in the article. Basic requirements to sorbents used to eliminate emergency emissions of hydrocarbons on railway transport are offered.

M. L. Soroka

2011-01-01

286

Mechanism of carrier transport through a silicon-oxide layer for solar cells  

Science.gov (United States)

The mechanism of carrier transport through a thin silicon-oxide layer for solar cells has been studied by measurements of the dark current density as a function of the thickness of the silicon-oxide layer, together with the observation of transmission electron micrographs. Cross-sectional transmission electron micrography shows that a uniform silicon-oxide layer with the thickness of ˜2 nm is present between ITO and Si when the ITO film is deposited on a flat Si(100) surface at 450 °C. The dark current density under a depletion condition strongly depends on the thickness of the silicon-oxide layer. It is concluded from these results that quantum mechanical tunneling is the dominant mechanism for the charge carrier transport through the silicon-oxide layer. On the other hand, when the ITO film is deposited on a mat-textured Si surface at the same temperature, a nonuniform silicon-oxide layer is formed, with ITO penetrating into the silicon-oxide layer in the top and valley regions of the pyramidal structure. By raising the deposition temperature of the ITO film on the flat Si(100) surface to 500 °C, the silicon-oxide layer becomes also nonuniform. For these diodes with the nonuniform silicon-oxide layer, the carrier transfer probability is less dependent on the thickness of the silicon-oxide layer, leading to the conclusion that minute channels of ITO are present in the silicon-oxide layer and charge carriers transfer through the channels. The photovoltage is decreased by the presence of the minute channels, with its magnitude depending on the density of the channels. The conversion efficiency of the solar cells is unchanged upon illumination for 1000 h. The good cell stability is attributed to the well-crystallized ITO film which effectively suppresses diffusion of oxygen from the air and to low reactivity of ITO with Si at room temperature.

Kobayashi, H.; Ishida, T.; Nakato, Y.; Mori, H.

1995-09-01

287

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

International Nuclear Information System (INIS)

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

288

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

DEFF Research Database (Denmark)

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

Dölger, Julia; Rademaker, Hanna

2014-01-01

289

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

Science.gov (United States)

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

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

2014-10-01

290

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

DEFF Research Database (Denmark)

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

Dölger, Julia; Rademaker, Hanna

2014-01-01

291

Local controlled drug delivery to the brain: mathematical modeling of the underlying mass transport mechanisms.  

Science.gov (United States)

The mass transport mechanisms involved in the controlled delivery of drugs to living brain tissue are complex and yet not fully understood. Often the drug is embedded within a polymeric or lipidic matrix, which is directly administered into the brain tissue, that is, intracranially. Different types of systems, including microparticles and disc- or rod-shaped implants are used to control the release rate and, thus, to optimize the drug concentrations at the site of action in the brain over prolonged periods of time. Most of these dosage forms are biodegradable to avoid the need for the removal of empty remnants after drug exhaustion. Various physical and chemical processes are involved in the control of drug release from these systems, including water penetration, drug dissolution, degradation of the matrix and drug diffusion. Once the drug has been released from the delivery system, it has to be transported through the living brain tissue to the target site(s). Again, a variety of phenomena, including diffusion, drug metabolism and degradation, passive or active uptake into CNS tissue and convection can be of importance for the fate of the drug. An overview is given of the current knowledge of the nature of barriers to free access of drug to tumour sites within the brain and the state of the art of: (i) mathematical modeling approaches describing the physical transport processes and chemical reactions which can occur in different types of intracranially administered drug delivery systems, and of (ii) theories quantifying the mass transport phenomena occurring after drug release in the living tissue. Both, simplified as well as complex mathematical models are presented and their major advantages and shortcomings discussed. Interestingly, there is a significant lack of mechanistically realistic, comprehensive theories describing both parts in detail, namely, drug transport in the dosage form and in the living brain tissue. High quality experimental data on drug concentrations in the brain tissue are difficult to obtain, hence this is itself an issue in testing mathematical approaches. As a future perspective, the potential benefits and limitations of these mathematical theories aiming to facilitate the design of advanced intracranial drug delivery systems and to improve the efficiency of the respective pharmacotherapies are discussed. PMID:16647231

Siepmann, J; Siepmann, F; Florence, A T

2006-05-18

292

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

Directory of Open Access Journals (Sweden)

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

Monika S?omi?ska-Wojewódzka

2013-04-01

293

Mechanics and transport modeling of particulate and fibrous network: Toward design of improved nickel metal hydride and lithium-ion battery technologies  

Science.gov (United States)

The main goals of this work were to gain insight into the transport and mechanical properties of the particulate and fibrous network materials widely used as electrodes in NiMH and Li-Ion batteries. During electrochemical cycling, the networks experience multiaxial loading, resulting in degradation and morphology changes of the electrode materials. A stochastic finite element model was used to investigate the effects of morphologic parameters on material properties. This work comprised two studies, of mechanics and transport, respectively, in porous materials. In a mechanics study, beam elements were used to model segments of the networks; several assumptions were investigated to model bond properties and local failures. In the transport study, another stochastic finite element model was developed, wherein particles were modeled as generalized ellipses. A four-point-probe experimental technique was used to measure electrode conductivity, for validation of the models. In the mechanics study, network simulations and two-beam models showed that use of the Euler beam assumption was adequate for the nickel networks of interest, since the shortest segments in the networks apparently served only as rigid connections; most of the network deformation occurred with bending of the longer aspect ratio segments. A torsion spring bond assumption was found suitable for modeling imperfect bonding and curved fibers in the networks. The scale effect was found to be important; simulations less than one staple length in size resulted in unrealistically stiff networks. In the transport study, simulation results showed moderate increases in fiber or whisker aspect ratio significantly improved conductivity, offering immediately practical advice for manufacturers. Overall, the capability of determining the effect of particle shape on material properties makes the stochastic model superior to continuum approaches for porous media. Further work will include extension to 3D materials, and coupling of models with electrochemical performance.

Wang, Chia-Wei

2002-01-01

294

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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-t...

Burut-Archanai Surachet; Eaton-Rye Julian J; Incharoensakdi Aran

2011-01-01

295

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

CERN Document Server

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

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

2012-01-01

296

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

CERN Document Server

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

Hong, J; Hong, Jongbae; Woo, Wonmyung

2007-01-01

297

Inherited disorders of bilirubin transport and conjugation: new insights into molecular mechanisms and consequences.  

Science.gov (United States)

Inherited disorders of bilirubin metabolism might reduce bilirubin uptake by hepatocytes, bilirubin conjugation, or secretion of bilirubin into bile. Reductions in uptake could increase levels of unconjugated or conjugated bilirubin (Rotor syndrome). Defects in bilirubin conjugation could increase levels of unconjugated bilirubin; the effects can be benign and frequent (Gilbert syndrome) or rare but severe, increasing the risk of bilirubin encephalopathy (Crigler-Najjar syndrome). Impairment of bilirubin secretion leads to accumulation of conjugated bilirubin (Dubin-Johnson syndrome). We review the genetic causes and pathophysiology of disorders of bilirubin transport and conjugation as well as clinical and therapeutic aspects. We also discuss the possible mechanisms by which hyperbilirubinemia protects against cardiovascular disease and the metabolic syndrome and the effects of specific genetic variants on drug metabolism and cancer development. PMID:24704527

Erlinger, Serge; Arias, Irwin M; Dhumeaux, Daniel

2014-06-01

298

Electron transport mechanism of thermally oxidized ZnO gas sensors  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-11-01

299

A novel RAR?/CAR-mediated mechanism for regulation of human organic solute transporter-? gene expression.  

Science.gov (United States)

The organic solute transporter-?/? (OST?/?) is a heteromeric transporter that is essential for bile acid and sterol disposition and for the enterohepatic circulation. To better understand the mechanism underlying OST gene regulation, the effects of retinoic acid (RA) on OST?/? gene expression were investigated. The results show a dose-dependent induction of OST? but not OST? expression in both Huh7 and HepG2 cells by RA treatment. A novel functional RA receptor response element (RARE; so-called DR5) in the promoter of OST? gene was identified. The interaction of RAR?/RXR? with the RARE was verified by electrophoretic mobility shift and chromatin immunoprecipitation assays and its functional importance by hOST? promoter activation in luciferase reporter assays. The studies demonstrated that the RARE is also a constitutive androstane receptor (CAR) binding site for OST? gene regulation. These results suggest that OST? is a target of both FXR-mediated (by binding to IR-1 element) and RAR?- and CAR-mediated (by binding to DR5 element) gene regulation pathways. In summary, this study has uncovered a novel RARE (DR5) element in the promoter of OST? that binds RAR? or CAR heterodimerized with RXR? and appears to function synergistically with the IR-1 element to provide maximal induction of OST? in response to RA. These findings demonstrate a role for RAR? and CAR in controlling OST? expression levels. PMID:24264050

Xu, Shuhua; Sun, An-Qiang; Suchy, Frederick J

2014-01-01

300

Quantum mechanical simulation of hole transport in p-type Si Schottky barrier MOSFETs.  

Science.gov (United States)

A full quantum-mechanical simulation of p-type nanowire Schottky barrier metal oxide silicon field effect transistors (SB-MOSFETs) is performed by solving the three-dimensional Schrödinger and Poisson's equations self-consistently. The non-equilibrium Green's function (NEGF) approach is adopted to treat hole transport, especially quantum tunneling through SB. In this work, p-type nanowire SB-MOSFETs are simulated based on the 3-band k.p method, using the k.p parameters that were tuned by benchmarking against the tight-binding method with sp3s* orbitals. The device shows a strong dependence on the transport direction, due to the orientation-sensitive tunneling effective mass and the confinement energy. With regard to the subthreshold slope, the [110] and [111] oriented devices with long channel show better performance, but they are more vulnerable to the short channel effects than the [100] oriented device. The threshold voltage also shows a greater variation in the [110] and [111] oriented devices with the decrease of the channel length. PMID:22121621

Choi, Wonchul; Shin, Mincheol

2011-07-01

 
 
 
 
301

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

Science.gov (United States)

Helicobacter pylori survival in acidic environments relies on cytoplasmic hydrolysis of gastric urea into ammonia and carbon dioxide, which buffer the pathogen's periplasm. Urea uptake is greatly enhanced and regulated by HpUreI, a proton-gated inner membrane channel protein essential for gastric survival of H. pylori. The crystal structure of HpUreI describes a static snapshot of the channel with two constriction sites near the center of the bilayer that are too narrow to allow passage of urea or even water. Here we describe the urea transport mechanism at atomic resolution, revealed by unrestrained microsecond equilibrium molecular dynamics simulations of the hexameric channel assembly. Two consecutive constrictions open to allow conduction of urea, which is guided through the channel by interplay between conserved residues that determine proton rejection and solute selectivity. Remarkably, HpUreI conducts water at rates equivalent to aquaporins, which might be essential for efficient transport of urea at small concentration gradients. PMID:24305683

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

2013-01-01

302

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

303

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

International Nuclear Information System (INIS)

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

304

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

Science.gov (United States)

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

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

1999-01-01

305

A review of corrosion and mass transport in liquid sodium and the effects on the mechanical properties  

International Nuclear Information System (INIS)

The chemical and metallurgical effects of exposing candidate fast reactor materials to liquid sodium are described. The thermodynamic principles that lead to corrosion and mass transport in liquid sodium are briefly discussed and the factors that interact to affect the kinetics of these processes are reviewed. Experimental observations of corrosion and mass transport are presented and effects on mechanical properties are related to metallurgical changes due to the environment. It is shown that interstitial element transport is the major cause of strength or ductility changes in materials exposed to liquid sodium. The conclusion is reached that mass transport in liquid sodium is a complex phenomenon, the mechanisms of which are not fully understood. Until the observed processes can be accurately quantified large design safety factors will continue to be necessary. (author)

306

Regulation of intestinal serotonin transporter expression via epigenetic mechanisms: role of HDAC2.  

Science.gov (United States)

The serotonin (5-HT) transporter (SERT) facilitates clearance of extracellular 5-HT by its uptake and internalization. Decreased expression of SERT and consequent high 5-HT levels have been implicated in various diarrheal disorders. Thus, appropriate regulation of SERT is critical for maintenance of 5-HT homeostasis in health and disease. Previous studies demonstrated that SERT is regulated via posttranslational and transcriptional mechanisms. However, the role of epigenetic mechanisms in SERT regulation is not known. Current studies investigated the effects of histone deacetylase (HDAC) inhibition on SERT expression and delineated the mechanisms. Treatment of Caco-2 cells with the pan-HDAC inhibitors butyrate (5 mM) and trichostatin (TSA, 1 ?M) decreased SERT mRNA and protein levels. Butyrate- or TSA-induced decrease in SERT was associated with decreased activity of human SERT (hSERT) promoter 1 (upstream of exon 1a), but not hSERT promoter 2 (upstream of exon 2). Butyrate + TSA did not show an additive effect on SERT expression, indicating that mechanisms involving histone hyperacetylation may be involved. Chromatin immunoprecipitation assays demonstrated enrichment of the hSERT promoter 1 (flanking nt -250/+2) with tetra-acetylated histone H3 or H4, which was increased (~3-fold) by butyrate. Interestingly, specific inhibition of HDAC2 (but not HDAC1) utilizing small interfering RNA decreased SERT mRNA and protein levels. The decrease in SERT expression by HDAC inhibition was recapitulated in an in vivo model. SERT mRNA levels were decreased in the ileum and colon of mice fed pectin (increased availability of butyrate) compared with controls fed a fiber-free diet (~50-60%). Our results identify a novel role of HDAC2 as a regulator of SERT gene expression in intestinal epithelial cells. PMID:23195070

Gill, Ravinder K; Kumar, Anoop; Malhotra, Pooja; Maher, Daniel; Singh, Varsha; Dudeja, Pradeep K; Alrefai, Waddah; Saksena, Seema

2013-02-15

307

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

Science.gov (United States)

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

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

2014-12-01

308

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

Scientific Electronic Library Online (English)

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

PEDRO LOPES DE, MELO; MARCELO MARTINS, WERNECK; ANTONIO, GIANNELLA-NETO.

309

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

International Nuclear Information System (INIS)

e expression of amino acid transport system genes. In the in vivo study, H441-cell accumulation of 3H-D-MET was higher than that of 14C-L-MET. Hepatic and renal accumulation of 3H-D-MET was lower than that of 14C-L-MET. Conclusion: The transport mechanism of 3H-D-MET was different from that of 3H-L-MET. Since 3H-D-MET has high metabolic stability, its accumulation reflects the transporter function of system L and ASC.

310

Transport  

...comply with the Carriage of Dangerous Goods and Use of Transportable Pressure...concerning the International Carriage of Dangerous Goods by Road (ADR). Some additional...a Radiation Protection Advisor or Dangerous Goods Safety Advisor to ensure you...

311

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

312

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

313

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

314

Free volume analysis and gas transport mechanisms of aromatic polyimide membranes: a molecular simulation study.  

Science.gov (United States)

Molecular simulation techniques were adopted to investigate membrane free volume morphologies and gas-transport mechanisms in the aromatic polyimide (PI) membranes composed of various diamines and dianhydrides. A molecular dynamics (MD) technique was adopted to analyze the fractional free volume (FFV), fractional accessible volume (FAV), free volume size and shape, and diffusion mechanisms. A Monte Carlo (MC) method was used to analyze the gas sorption behaviors in the membranes. The FFV, FAV, and free volume morphology analyses reveal that bulky groups in the PI membranes contributed to the formation of a larger and more continuous free volume. The thermal motion analysis shows that a greater effective free volume in the membranes promoted effective motion, such as jumping and diffusive motions. The sorption analysis indicates that the larger free volume provides more sites for gas molecule absorption. The MD and MC results provide good agreement with the experimental data from past reports, which validates the feasibility of molecular simulation techniques in gas separation membranes at a molecular scale. PMID:19569642

Chang, Kai-Shiun; Tung, Chieng-Chi; Wang, Ko-Shung; Tung, Kuo-Lun

2009-07-23

315

Critical Evaluation of the determination of the SOL transport mechanism from a statistical examination of experimental data  

International Nuclear Information System (INIS)

A statistical approach originally proposed to determine the underlying transport mechanism from a regression analysis of experimental measurements of the power deposition width at the targets is tested against 2D modelling data. The method is found to be unable to discriminate clearly in favour of the transport mechanism actually used in the modelling. Therefore conclusions based on such an analysis of experimental data may not be warranted. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

316

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

DEFF Research Database (Denmark)

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 mechanism; from predominantly a combination of thermionic emission and field emission to purely thermionic emission.

Clausen, Thomas; Leistiko, Otto

1993-01-01

317

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

318

Structures and properties of sulfonated ionomers probed by transport and mechanical measurements: The role of solute activity  

Science.gov (United States)

This work is focused on advancing the understanding of the structures and properties of sulfonated ionomer membranes in the context of Polymer Electrolyte Membrane Fuel Cell applications by transport and mechanical measurements. Transport and mechanical properties are two critical elements of ionomer membranes that govern the performance and longevity of fuel cells. Additionally, transport and mechanical property measurements can also provide valuable information about the structure of the ionomer membranes. It is essential to develop a comprehensive understanding of them under well controlled environmental conditions. The mechanism of water transport through Nafion membranes was found to be governed by water diffusivity, swelling of the hydrophilic phase and the interfacial transport across membrane/vapor interface. A transport model incorporating these parameters was developed and successfully employed to resolve water activity profiles in the membrane and make quantitative predictions under steady state and dynamic conditions. Experimental results of diffusivity, volume of mixing and tortuosity also provided hints about the hydration shell structure around in the hydrophilic domains of Nafion. The alcohol sorption and transport was found to be qualitatively similar to the behavior of water and the quantitative differences were attributed to the difference in molecular size. The transport of alcohol water mixtures through Nafion displayed significant non-ideality which was connected to the abnormal swelling and incomplete mixing within the hydrophilic domains. The mechanical properties of several perfluoro-sulfonated ionomer (PFSI) membranes were studied as functions of temperature and solute activity. The thermal transition found between 60-100°C was described as an order-disorder transition of the ionic clusters. Water and other polar solutes were found to plasticize PFSI below the transition but stiffen PFSI above the transition. The stiffening effect was attributed to polar solute induced re-clustering of the ionic domains. Two hydrocarbon model ionomer SPS and SPEEK were studied to further understand the structural-property relationships of ionomers. Water sorption and proton conductivity were enhanced with increasing ion content but water content was independent of ion content and proton conductivity scaled with hydrophilic volume fraction. Water transport was dependent on diffusion and interfacial transport, both of which were affected by the size and shape of the hydrophilic domains.

Zhao, Qiao

319

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

Science.gov (United States)

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

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

2014-10-01

320

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.

1992-01-01

 
 
 
 
321

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

322

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

Science.gov (United States)

Conspectus Global advances in industrialization are precipitating increasingly rapid consumption of fossil fuel resources and heightened levels of atmospheric CO2. World sustainability requires viable sources of renewable energy and its efficient use. First-principles quantum mechanics (QM) studies can help guide developments in energy technologies by characterizing complex material properties and predicting reaction mechanisms at the atomic scale. QM can provide unbiased, qualitative guidelines for experimentally tailoring materials for energy applications. This Account primarily reviews our recent QM studies of electrode materials for solid oxide fuel cells (SOFCs), a promising technology for clean, efficient power generation. SOFCs presently must operate at very high temperatures to allow transport of oxygen ions and electrons through solid-state electrolytes and electrodes. High temperatures, however, engender slow startup times and accelerate material degradation. SOFC technologies need cathode and anode materials that function well at lower temperatures, which have been realized with mixed ion-electron conductor (MIEC) materials. Unfortunately, the complexity of MIECs has inhibited the rational tailoring of improved SOFC materials. Here, we gather theoretically obtained insights into oxygen ion conductivity in two classes of perovskite-type materials for SOFC applications: the conventional La1-xSrxMO3 family (M = Cr, Mn, Fe, Co) and the new, promising class of Sr2Fe2-xMoxO6 materials. Using density functional theory + U (DFT+U) with U-J values obtained from ab initio theory, we have characterized the accompanying electronic structures for the two processes that govern ionic diffusion in these materials: (i) oxygen vacancy formation and (ii) vacancy-mediated oxygen migration. We show how the corresponding macroscopic oxygen diffusion coefficient can be accurately obtained in terms of microscopic quantities calculated with first-principles QM. We find that the oxygen vacancy formation energy is a robust descriptor for evaluating oxide ion transport properties. We also find it has a direct relationship with (i) the transition metal-oxygen bond strength and (ii) the extent to which electrons left behind by the departing oxygen delocalize onto the oxygen sublattice. Design principles from our QM results may guide further development of perovskite-based MIEC materials for SOFC applications. PMID:24972154

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

2014-11-18

323

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

Directory of Open Access Journals (Sweden)

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

Li Feiran

2012-01-01

324

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.

2000-01-01

325

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

326

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

327

A Hopping Mechanism for Cargo Transport by Molecular Motors on Crowded Microtubules  

Science.gov (United States)

Most models designed to study the bidirectional movement of cargos as they are driven by molecular motors rely on the idea that motors of different polarities can be coordinated by external agents if arranged into a motor-cargo complex to perform the necessary work Gross, Hither and yon: a review of bidirectional microtubule-based transport (Gross in Phys. Biol. 1:R1-R11, 2004). Although these models have provided us with important insights into these phenomena, there are still many unanswered questions regarding the mechanisms through which the movement of the complex takes place on crowded microtubules. For example (i) how does cargo-binding affect motor motility? and in connection with that - (ii) how does the presence of other motors (and also other cargos) on the microtubule affect the motility of the motor-cargo complex? We discuss these questions from a different perspective. The movement of a cargo is conceived here as a hopping process resulting from the transference of cargo between neighboring motors. In the light of this, we examine the conditions under which cargo might display bidirectional movement even if directed by motors of a single polarity. The global properties of the model in the long-time regime are obtained by mapping the dynamics of the collection of interacting motors and cargos into an asymmetric simple exclusion process (ASEP) which can be resolved using the matrix ansatz introduced by Derrida (Derrida and Evans in Nonequilibrium Statistical Mechanics in One Dimension, pp. 277-304, 1997; Derrida et al. in J. Phys. A 26:1493-1517, 1993).

Goldman, Carla

2010-05-01

328

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

329

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

Energy Technology Data Exchange (ETDEWEB)

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

Straub, Johannes [Technical University Munich, Faculty Mw. Thermodynamic, Garching (Germany); Zell, Martin [ESA-ESTEC, Directorate of Human Spaceflight, Head of ISS Utilisation Department, Noordwijk (Netherlands)

2010-11-15

330

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...

Fach, Andreas

2006-01-01

331

Electrical transport and scattering mechanisms in thin silver films for thermally insulating glazing  

Energy Technology Data Exchange (ETDEWEB)

Thin silver films are widely used in low-emissivity coatings for building glazing due to their high reflectance in the infrared and high transmittance in the visible spectrum. The determining parameter for the infrared reflectance is the electrical conductance of the layer stack - the better the conductance the higher the reflectance. Electrically conductive films of thicknesses smaller than the electron mean free path exhibit a strong increase in the residual resistivity proportional to the inverse of the film thickness. Despite intensive discussions, which have extended over tens of years, it is not understood yet if this conductive behavior originates from electron scattering at interfaces (Fuchs-Sondheimer model) or grain boundaries (Mayadas-Shatzkes model). To achieve a fundamental understanding of the prevailing electron scattering mechanisms, aluminum-doped zinc oxide (ZnO:Al)/Ag /ZnO:Al layer stacks produced by magnetron sputtering were investigated concerning their electronic structure and electrical transport properties. The electronic structure of the layer stacks was probed and analyzed by electron energy-loss spectroscopy. By this technique, plasmonic excitations are observed, which can be categorized into excitations of the electrons in the bulk silver and excitations at the ZnO:Al/Ag interface. The plasmons were analyzed with respect to their dispersion and the peak width, and brought into relation with electrical conductivity measurements by calculating the plasmon lifetime and the electron scattering rate. The difficulty in determining the relative contributions of the interface and grain boundary scattering in experimental conditions is due to the fact that the way in which these scattering mechanisms depend on the film thickness, is very similar. Understanding the electron transport in thin films is of paramount importance, because the differentiation between the scattering mechanisms is a key issue for the improvement of the coatings. In the present work, the solution came from the expected difference in the temperature-dependent behavior of the resistivity between electron scattering at interfaces and electron scattering at grain boundaries. Hence, the resistivity was measured as a function of the temperature on layer stacks with different silver film thickness varying in the range of 4 to 200 nm. The data were analyzed using the extended Mayadas-Shatzkes model involving both electron scattering at interfaces (Fuchs-Sondheimer model), and electron scattering at grain boundaries. The results demonstrate that electron scattering at grain boundaries dominates for all film thicknesses. The basic layer stack was compared to more sophisticated systems, obtained either by adding a thin titanium layer in between silver and ZnO:Al, or by exposing the growing silver film to an oxygen partial pressure (oxidizing the film). Furthermore, the effect of annealing at 250 C was studied for all these systems.

Philipp, Martin

2011-04-21

332

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

International Nuclear Information System (INIS)

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

333

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 perfary. 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)

334

Molecular mechanism of ?-tocopheryl-phosphate transport across the cell membrane  

International Nuclear Information System (INIS)

?-Tocopheryl-phosphate (?-TP) is synthesized and hydrolyzed in animal cells and tissues where it modulates several functions. ?-TP is more potent than ?-T in inhibiting cell proliferation, down-regulating CD36 transcription, inhibiting atherosclerotic plaque formation. Administration of ?-TP to cells or animals requires its transfer through membranes, via a transporter. We show here that ?-TP is passing the plasma membrane via a system that is inhibited by glibenclamide and probenecid, inhibitors of a number of transporters. Glibenclamide and probenecid prevent dose-dependently ?-TP inhibition of cell proliferation. The two inhibitors act on ATP binding cassette (ABC) and organic anion transporters (OAT). Since ABC transporters function to export solutes and ?-TP is transported into cells, it may be concluded that ?-TP transport may occur via an OAT family member. Due to the protection by glibenclamide and probenecid on the ?-TP induced cell growth inhibition it appears that ?-TP acts after its uptake inside cells

335

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)

336

A novel sorbitol transport mechanism in cultured renal papillary epithelial cells  

International Nuclear Information System (INIS)

The renal papillary epithelial cell line, GRB-PAP1, accumulates sorbitol when grown in a hypertonic (500 mosmol/kgH2O) bathing medium. When the cells are returned to a 300 mosmol/kgH2O medium, they lose their sorbitol rapidly to the bath. Sorbitol movement across the membranes of these cells was investigated by studying the uptake of radioactive sorbitol and related compounds. Sorbitol uptake increased 71-fold when cells grown in 500 mosmol/kgH2O medium were exposed to a 300 mosmol/kgH2O test solution. The magnitude of the permeability increase was proportional to the size of the change in the osmolality of the bathing medium and not the absolute osmolality. Sorbitol uptake was a linear function of medium sorbitol concentration with no sign of saturation at sorbitol concentrations up to 315 mM. Although the permeability of other polyols was increased when the osmolality was reduced, competition between sorbitol and related sugars and polyols could not be demonstrated. Both the increased sorbitol uptake after a decrease in medium osmolality and the decrease to control permeability after return to the original osmolality were complete within 30 s. A wide variety of transport inhibitors and ion substitutions failed to alter the magnitude of the sorbitol permeability increase. The most effective inhibitor was quinidine, 1 mM reducing sorbitol uptake by 73%. The sorbitol permeability increase could also be blocked by reducing the temperature to 0 degrees C. Nonspecific uptemperature to 0 degrees C. Nonspecific uptake of sorbitol, such as endocytosis, was shown to be of only minor significance. The large increase in sorbitol permeability and subsequent sorbitol efflux enables these cells to withstand large decreases in osmolality without excessive swelling and consequent damage. A similar compensatory mechanism may operate in vivo in the renal papilla during the onset of diuresis

337

The role of biomembrane lipids in the molecular mechanism of ion transport radiation damage  

International Nuclear Information System (INIS)

Increase in the rate of ATP synthesis (I.4-I.6 times), Ca2+-capacity (I.4-I.8 times), membrane potential (by 20-50 mv) and decrease in K--conductivity (2.5-3 times) in rat liver mitochondria was observed three hours after ?-irradiation at a dose of 1000r. The process of oxidative phosphorylation was normalized 24 hours later, whereas damages of Ca2+-accumulation and K+-conductivity remain. The molecular mechanism of reduction in K+-permeability of mitochondrial membranes has been studied. The endogenous regulators of ionic transport in the lipid phase of mitochondrial biomembranes were investigated before and after ?-irradiation. It was revealed that K+-conductivity of the artificial phospholipid membranes (APM) formed of the phospholipids from irradiated mitochondria was substantially lower than that in the control. Using thin-layer chromatography the minor phospholipid fraction which increases K+-conductivity of APM was isolated from the lipids of unirradiated mitochondria. In the lipid preparations of irradiated mitochondria the minor phospholipid fraction content is sharply lowered (or absent at all). Besides the content of lysoforms of phosphatidylcholine and phosphatidylethanolamine as well as that of fatty acids and cholesterol esters were reduced 24 hours after irradiation. Three compounds with different capability to increase the APM conductivity for monovalent ions were revealed in the composition of the minor fraction. One of these components was shown to be lysopolyglycerophosphatide (lysodiphosphatidylglycerol). The role of the enzyme systems involved in radiational changes of the membrane lipid components and the importance of these phenomena for cell radiosensitivity will be discussed

338

Mechanisms of laser-induced dissection and transport of histologic specimens.  

Science.gov (United States)

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 mum diameter was investigated by means of time-resolved photography. The working mechanism of microdissection was found to be plasma-mediated ablation initiated by linear absorption. Catapulting was driven by plasma formation when tightly focused pulses were used, and by photothermal ablation at the bottom of the sample when defocused pulses producing laser spot diameters larger than 35 microm were used. With focused pulses, driving pressures of several hundred MPa accelerated the specimen to initial velocities of 100-300 m/s before they were rapidly slowed down by air friction. When the laser spot was increased to a size comparable to or larger than the sample diameter, both driving pressure and flight velocity decreased considerably. Based on a characterization of the thermal and optical properties of the histologic specimens and supporting materials used, we calculated the evolution of the heat distribution in the sample. Selected catapulted samples were examined by scanning electron microscopy or analyzed by real-time reverse-transcriptase polymerase chain reaction. We found that catapulting of dissected samples results in little collateral damage when the laser pulses are either tightly focused or when the laser spot size is comparable to the specimen size. By contrast, moderate defocusing with spot sizes up to one-third of the specimen diameter may involve significant heat and ultraviolet exposure. Potential side effects are maximal when samples are catapulted directly from a glass slide without a supporting polymer foil. PMID:17766336

Vogel, Alfred; Lorenz, Kathrin; Horneffer, Verena; Hüttmann, Gereon; von Smolinski, Dorthe; Gebert, Andreas

2007-12-15

339

Cysteine could change the transport mechanism of PVP-coated silver nanoparticles in porous media  

Science.gov (United States)

Silver nanoparticles (AgNPs) can hardly be removed by wastewater treatment plant and have big potential to enter groundwater, jeopardizing the water quality & aquatic ecosystem. Most AgNPs have surface coatings such as polyvinylpyrrolidone (PVP) which dominate their transport in porous media. Our previous study shows that PVP may promote the deposition of AgNPs on silica surface by a bridging mechanism. This study further explored how cysteine, a natural organic matter type, may influence the role of the PVP coating on AgNP translocation. Dynamic Light Scattering (DLS) measurement (Figure 1A) shows that the PVP coating rendered the AgNP dispersion high stability during the measuring period (3hrs). Addition of 100 ppm cysteine to the dispersion resulted in a rapid decrease in particle size from 100nm to 52nm within one hour, following which no further decline in particle size occurred. Column experiment results (Figure 1B) show that corresponding to the particle size change was a substantial decrease in particle deposition rates: introduction of 100 ppm cysteine into the particle dispersion resulted in a decrease in AgNP attenuation by the porous medium from 67% to 26%. The decline in particle size suggested that cysteine may have displaced the macromolecular PVP from the particle surface. Desorption of PVP resulted in a weakening or vanish of polymer bridging effect which in turn lowered the deposition rates substantially. This study demonstrated an implication of environmental transformation of coated AgNPs to their mobility in saturated sand aquifers. Acknowledgment Xinyao Yang appreciates the Natural Science Foundation of China (Grant No.:41101475) for covering the registration fee and traveling costs.igure 1 Particle size measurement (A) and breakthrough curves (B) of PVP-coated silver nanoparticle in the absence and presence of cysteine: pH=7.0, ionic strength=1mM, flow rate=1ml/min.

Yang, X.; Lin, S.; Wiesner, M.

2012-12-01

340

Vertical transport mechanisms of black carbon over East Asia in spring during the A-FORCE aircraft campaign  

Science.gov (United States)

of vertical transport of black carbon (BC) aerosols and their three-dimensional transport pathways over East Asia in spring were examined through numerical simulations for the Aerosol Radiative Forcing in East Asia (A-FORCE) aircraft campaign in March-April 2009 using a modified version of the Community Multiscale Air Quality (CMAQ) modeling system. The simulations reproduced the spatial distributions of mass concentration of BC and its transport efficiency observed by the A-FORCE campaign reasonably well, including its vertical and latitudinal gradients and dependency on precipitation amount that air parcels experienced during the transport. During the A-FORCE period, two types of pronounced upward BC mass fluxes from the planetary boundary layer (PBL) to the free troposphere were found over northeastern and inland-southern China. Over northeastern China, cyclones with modest precipitation were the primary uplifting mechanism of BC. Over inland-southern China, both cumulus convection and orographic uplifting along the slopes of the Tibetan Plateau played important roles in the upward transport of BC, despite its efficient wet deposition due to a large amount of precipitation supported by an abundant moisture supply by the low-level southerlies. In addition to the midlatitude (35-45°N) eastward outflow within the PBL (21% BC removal by precipitation during transport), the uplifting of BC over northeastern and inland-southern China and the subsequent BC transport by the midlatitude lower tropospheric (50% BC removal) and subtropical (25-35°N) midtropospheric westerlies (67% BC removal), respectively, provided the major transport pathways for BC export from continental East Asia to the Pacific.

Oshima, N.; Koike, M.; Kondo, Y.; Nakamura, H.; Moteki, N.; Matsui, H.; Takegawa, N.; Kita, K.

2013-12-01

 
 
 
 
341

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

342

Mechanisms affecting the transport and retention of bacteria, bacteriophage and microspheres in laboratory-scale saturated fractures  

Science.gov (United States)

Groundwater is becoming an increasingly important water source due to the ever-increasing demands from agricultural, residential and industrial consumers. In search of more secure sources, wells are routinely finished over large vertical depths in bedrock aquifers, creating new hydraulic pathways and thus increasing the risk of cross contamination. Moreover, hydraulic pathways are also being altered and created by increasing water withdrawal rates from these wells. Currently, it is not well understood how biological contaminants are transported through, and retained in, fractured media thereby making risk assessment and land use decisions difficult. Colloid transport within fractured rock is a complex process with several mechanisms affecting transport and retention, including: advection, hydrodynamic dispersion, diffusion, size exclusion, adsorption, and decay. Several researchers have investigated the transport of bacteria, bacteriophage, and microspheres (both carboxylated and plain) to evaluate the effects of surface properties and size on transport and retention. These studies have suggested that transport is highly dependent on the physico-chemical properties of the particle, the fracture, and the carrying fluid. However, these studies contain little detail regarding the specific mechanisms responsible for transport beyond speculating about their existence. Further, little work has been done to compare the transport of these particulate materials through the same fracture, allowing for direct observations based on particulate size and surface properties. This research examines the similarities and differences in transport and retention between four different particles through two different laboratory-scale, saturated fractures. This work is designed to explore the effects of particle size, surface properties, ionic strength of the carrying solution, and aperture field characteristics on transport and retention in single, saturated fractures. The particulates chosen for this work include E.coli RS2-GFP, MS2, and carboxylated microspheres with diameters of 0.0425 ?m and 0.525 ?m. The results of this work will contribute to the understanding of risk posed by contaminants to bedrock aquifer sources. Dolomite rock samples were collected from the DoLime quarry in Guelph, Ontario. A single fracture was induced in the sample by applying a uniaxial force. Lengthwise edges were sealed to create no-flow boundaries, and flow cells were fitted on the up- and down-stream ends of the fracture. Aperture size and variability were characterized using hydraulic and solute tracer tests. Particulate tracer tests were conducted by injecting a pulse of particles (E.coli RS2-GFP, MS2, or microspheres) into the upstream flow cell, and measuring the subsequent effluent concentration profile. From these tests, the percent recovery and mean residence time of the particulate were analyzed. Generally, it was found that microspheres are a poor indication of biological particulate transport, likely due to differences in surface properties affecting the retention mechanisms. This talk will provide an analysis of the breakthrough curves, with specific details regarding the transport and retention mechanisms for the various types and sizes of particles employed in these experiments.

Seggewiss, G.; Dickson, S. E.

2013-12-01

343

Description of the transport mechanisms and pathways in the far field of a KBS-3 type repository  

International Nuclear Information System (INIS)

The main purpose of this document is to serve as a reference document for the far field radionuclide transport description within SKB 91. A conceptual description of far field transport in crystalline rock is given together with a discussion of the application of the stream tube concept. In this concept the transport in a complex tree-dimensional flow field is divided into a number of imaginary tubes which are modelled independently. The stream tube concept is used as the basis for the radionuclide calculations in SKB 91. Different mathematical models for calculating the transport of radionuclides in fractured rock are compared: advection dispersion models, channeling models and network models. In the SKB 91 project a dual-porosity continuum model based on the one dimensional advection-dispersion equation taking into account matrix diffusion, sorption in the rock matrix and radioactive chain decay. Furthermore, the data needed for the transport models is discussed and recommended ranges and central values are given. (42 refs.) (au)

344

Different hydration patterns in the pores of AmtB and RhCG could determine their transport mechanisms.  

Science.gov (United States)

The ammonium transporters of the Amt/Rh family facilitate the diffusion of ammonium across cellular membranes. Functional data suggest that Amt proteins, notably found in plants, transport the ammonium ion (NH4(+)), whereas human Rhesus (Rh) proteins transport ammonia (NH3). Comparison between the X-ray structures of the prokaryotic AmtB, assumed to be representative of Amt proteins, and the human RhCG reveals important differences at the level of their pore. Despite these important functional and structural differences between Amt and Rh proteins, studies of the AmtB transporter have led to the suggestion that proteins of both subfamilies work according to the same mechanism and transport ammonia. We performed molecular dynamics simulations of the AmtB and RhCG proteins under different water and ammonia occupancy states of their pore. Free energy calculations suggest that the probability of finding NH3 molecules in the pore of AmtB is negligible in comparison to finding water. The presence of water in the pore of AmtB could support the transport of proton. The pore lumen of RhCG is found to be more hydrophobic due to the presence of a phenylalanine conserved among Rh proteins. Simulations of RhCG also reveal that the signature histidine dyad is occasionally exposed to the extracellular bulk, which is never observed in AmtB. These different hydration patterns are consistent with the idea that Amt and Rh proteins are not functionally equivalent and that permeation takes place according to two distinct mechanisms. PMID:24021113

Baday, Sefer; Wang, Shihao; Lamoureux, Guillaume; Bernèche, Simon

2013-10-01

345

Vasopressin-stimulated electrogenic sodium transport in A6 cells is linked to a Ca(2+)-mobilizing signal mechanism.  

Science.gov (United States)

Vasopressin is known to activate two types of cell surface receptors; V2, coupled to adenylate cyclase, and V1, linked to a Ca(2+)-dependent transduction system. We investigated whether arginine vasopressin (AVP) stimulation of electrogenic sodium transport in A6 cells, derived from Xenopus laevis, is mediated by activation of either one or both types of AVP-specific receptors. AVP caused a rapid increase in electrogenic sodium transport, reflected by the transepithelial potential difference (VT) and equivalent short circuit current (Ieq) measurements. AVP also rapidly increased intracellular Ca2+ (Ca2+i) and total inositol trisphosphate. The increase in Ieq was dependent on the rise in (Ca2+i), because 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) dose-dependently inhibited the Ieq response. There was no evidence, however, that activation of adenylate cyclase mediated AVP-stimulated Ieq; transport was not inhibited after AVP-induced activation of adenylate cyclase was abolished by 2',5'-dideoxyadenosine or when cAMP-dependent protein kinase (PKA) activity was abolished by the specific PKA inhibitor IP20. Further studies showed that although both forskolin and 8-(4-chlorophenylthio)-cAMP stimulated Ieq, this occurred by mechanisms independent of PKA activation. These results indicate that AVP-stimulated Na+ transport is mediated by a V1 receptor and a Ca(2+)-dependent mechanism. PMID:7608170

Hayslett, J P; Macala, L J; Smallwood, J I; Kalghatgi, L; Gassala-Herraiz, J; Isales, C

1995-07-01

346

Study of mechanical and thermal transport properties of Cis- and Trans-polyisoprene blends in low temperature range  

Science.gov (United States)

Measurements of mechanical and thermal transport properties have been carried out on the samples of polyisoprene (Cis and Trans) blends prepared by solution casting, in the temperature range from 173K to 273K using Dynamic Mechanical Analyzer and Transient Plane Source Technique, respectively. Results show that a sudden change is observed in the values of tan ?, storage modulus (G), thermal conductivity (?) and heat capacity per unit volume (?cp) at the glass transition temperature. Also the values of G, ? and ?cp have been observed higher for all the three blends as compared to their pure components. The variation of all these properties has been explained on the basis of crystallinity and crosslink density.

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

2014-10-01

347

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....

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

2010-01-01

348

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

International Nuclear Information System (INIS)

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

349

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. PMID:24733747

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

2014-08-01

350

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

International Nuclear Information System (INIS)

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

351

MECHANISMS OF CONVECTION-INDUCED MODULATION OF PASSIVE TRACER INTERHEMISPHERIC TRANSPORT INTERANNUAL VARIABILITY  

Science.gov (United States)

Interannual variations of tropical convection impact atmospheric circulation and influence year-to-year variations of the transport of trace constituents in the troposphere. This study examines how two modes of convective variability-anomalous intensification and meridional disp...

352

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

Directory of Open Access Journals (Sweden)

Full Text Available Abstract One of the major problems related with anticancer chemotherapy is resistance against anticancer drugs. The ATP-binding cassette (ABC transporters are a family of transporter proteins that are responsible for drug resistance and a low bioavailability of drugs by pumping a variety of drugs out cells at the expense of ATP hydrolysis. One strategy for reversal of the resistance of tumor cells expressing ABC transporters is combined use of anticancer drugs with chemosensitizers. In this review, the physiological functions and structures of ABC transporters, and the development of chemosensitizers are described focusing on well-known proteins including P-glycoprotein, multidrug resistance associated protein, and breast cancer resistance protein.

Choi Cheol-Hee

2005-10-01

353

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

354

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

355

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

356

Integrated evaluation of aerogenic pollution by air-transported heavy metals (Pb, Cd, Ni, Zn, Mn and Cu) in the analysis of the main deposit media.  

Science.gov (United States)

The composition of the ambient air is constantly changing; therefore, the monitoring of ambient air quality to detect the changes caused by aerogenic pollutants makes the essential part of general environmental monitoring. To achieve more effective improvement of the ambient air quality, the Directive 2008/50/EC on 'Ambient Air Quality and Cleaner Air for Europe' was adopted by the European Parliament and the European Council. It informed the public and enterprises about a negative effect of pollution on humans, animals and plants, as well as about the need for monitoring aerogenic pollutants not only at the continuous monitoring stations but also by using indicator methods, i.e. by analysing natural deposit media. The problem of determining the relationship between the accumulation level of pollutants by a deposit medium and the level of air pollution and its risks is constantly growing in importance. The paper presents a comprehensive analysis of the response of the main four deposit media, i.e. snow cover, soil, pine bark and epigeic mosses, to the long-term pollution by aerogenic pollutants which can be observed in the area of oil refinery influence. Based on the quantitative expressions of the amounts of the accumulated pollutants in the deposit media, the territory of the oil refinery investigated in this paper has been referred to the areas of mild or moderate pollution. PMID:23933956

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

2014-01-01

357

On the mechanism of substrate binding to the purine-transport system of Saccharomyces cerevisiae.  

Science.gov (United States)

The yeast Saccharomyces cerevisiae takes up adenine, guanine, hypoxanthine, and cytosine via a common energy-dependent transport system. The apparent affinity of the transport system to these and other purines and pyrimidines is correlated with their capability to be protonated to the positively charged form. Further organic molecules are competitive inhibitors when they are cationic, e.g. guanidine and octylguanidine in contrast to urea, or hexadecyltrimethylammonium in contrast to dodecylsulfate and Triton X-100. The influence of the pH on the kinetic constants of hypoxanthine transport points to a stoichiometry of one proton being associated to the transport system together with one substrate molecule. The pKa values of two ionizable groups that are involved in substrate binding are revealed; one of which (pKa = 1.8) may be attributed to the substrate, the other (pKa = 5.1) to an amino acid residue in the recognition site of the transport system. Studies with group-specific inhibitors indicate that this amino acid residue contains a carboxyl group. The results are in accordance with the assumption that a carboxyl group of the transport system, a proton and a substrate molecule arrange to an uncharged ternary complex. PMID:23293

Forêt, M; Schmidt, R; Reichert, U

1978-01-01

358

Apical and basal membrane ion transport mechanisms in bovine retinal pigment epithelium.  

Science.gov (United States)

1. Intracellular voltage recordings using conventional and double-barrelled chloride-selective microelectrodes have been used to identify several transport mechanisms at the apical and basolateral membranes of the isolated bovine retinal pigment epithelium (RPE)-choroid preparation. Intracellular recordings were obtained from two cell populations, melanotic (pigmented) and amelanotic (non-pigmented). The electrical properties of these two populations are practically identical. For melanotic cells the average apical resting membrane potential (VA) is -61 +/- 2 mV (mean +/- S.E.M., n = 49 cells, thirty-three eyes). For these cells the ratio of apical to basolateral membrane resistance (a) was 0.22 +/- 0.02. The mean transepithelial voltage and resistance were 6 +/- 1 mV and 138 +/- 7 omega cm2, respectively. 2. The apical membrane, which faces the distal retina, contains a Ba(2+)-inhibitable K+ conductance and a ouabain-inhibitable, electrogenic Na(+)-K+ pump. In addition it contains a bumetanide-sensitive mechanism, the putative Na(+)-K(+)-Cl- cotransporter. The basolateral membrane contains a DIDS (4,4'-diisothiocyanostilbene-2,2'-disulphonic acid)-inhibitable chloride channel. The relative conductances of the apical and basolateral membranes to K+ and Cl- are TK approximately 0.9 and TCl approximately 0.7, respectively. 3. The ouabain-induced fast phase of apical membrane depolarization (0-30 s) was used to calculate the equivalent resistances of the apical (RA) and basolateral (RB) cell membranes, as well as the paracellular or shunt resistance (RS). They are: 3190 +/- 400, 17920 +/- 2730 and 2550 +/- 200 omega (mean +/- S.E.M., n = 9 tissues), respectively. From these data the equivalent electromotive forces (EMF) at the apical (EA) and basolateral (EB) membranes were also calculated. They are: -69 +/- 5.0 and -24 +/- 5.0 mV, respectively. 4. Intracellular Cl- activity (aiCl) was measured using double-barreled ion-selective microelectrodes. In the steady state aiCl = 61 +/- 4.0 mM and the Nernst potential ECl = -13.5 +/- 1.5 mV (mean +/- S.E.M., n = 4). 5. In the intact eye or in retina, RPE-choroid preparations it has been shown that the transition between light and dark alters the K+ concentration in the extracellular (or subretinal) space between the photoreceptors and the apical membrane of the RPE. These light-induced changes in subretinal [K+]o were qualitatively simulated in vitro by altering apical K+ between 5 and 2 mM. This produced a sequence of voltage changes at the apical and basolateral membranes that had three operationally distinct phases. Phase 1 is generated by the combination of an apical membrane K+ diffusion potential and inhibition of the electrogenic Na(+)-K+ pump.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1722821

Joseph, D P; Miller, S S

1991-01-01

359

The transport mechanism of the human sodium/myo-inositol transporter 2 (SMIT2/SGLT6), a member of the LeuT structural family.  

Science.gov (United States)

The sodium/myo-inositol transporter 2 (SMIT2) is a member of the SLC5A gene family, which is believed to share the five-transmembrane segment inverted repeat of the LeuT structural family. The two-electrode voltage-clamp (TEVC) technique was used to measure the steady-state and the pre-steady-state currents mediated by human SMIT2 after expression in Xenopus laevis oocytes. Phlorizin is first shown to be a poor inhibitor of pre-steady-state currents for depolarizing voltage pulse. From an up to threefold difference between the apparent ON and OFF transferred charges during a voltage pulse, we also show that a fraction of the transient current recorded for very negative potentials is not a true pre-steady-state current coming from the cotransporter conformational changes. We suggest that this transient current comes from a time-dependent leak current that can reach large amplitudes when external Na(+) concentration is reduced. A kinetic model was generated through a simulated annealing algorithm. This algorithm was used to identify the optimal connectivity among 19 different kinetic models and obtain the numerical values of the associated parameters. The proposed 5-state model includes cooperative binding of Na(+) ions, strong apparent asymmetry of the energy barriers, a rate-limiting step that is likely associated with the translocation of the empty transporter, and a turnover rate of 21 s(-1). The proposed model is a proof of concept for a novel approach to kinetic modeling of electrogenic transporters and allows insight into the transport mechanism of members of the LeuT structural family at the millisecond timescale. PMID:24944204

Sasseville, Louis J; Longpré, Jean-Philippe; Wallendorff, Bernadette; Lapointe, Jean-Yves

2014-09-01

360

Multiple mechanisms of ligand interaction with the human organic cation transporter, OCT2.  

Science.gov (United States)

OCT2 is the entry step for organic cation (OC) secretion by renal proximal tubules. Although many drugs inhibit OCT2 activity, neither the mechanistic basis of their inhibition nor their transport status is generally known. Using representatives of several structural classes of OCT2-inhibitory ligands described recently (Kido Y, Matsson P, Giacomini KM. J Med Chem 54: 4548-4558, 2011), we determined the kinetic basis of their inhibition of 1-methyl-4-phenylpyridinium (MPP) transport into Chinese hamster ovary cells that stably expressed hOCT2. The "cluster II" inhibitors (which contain known OCT2 substrates) metformin and cimetidine interacted competitively with MPP. However, other cluster II compounds, including tetraethylammonium (TEA), diphenidol and phenyltoloxamine, were mixed-type inhibitors of MPP transport (i.e., decreasing J(max) and increasing K(t)). A cluster III (neutral steroid) representative, adrenosterone, and a cluster I (large, flexible cation) representative, carvedilol, displayed noncompetitive inhibitory profiles. Competitive counterflow (CCF) was used to determine whether the inhibitory ligands served as substrates of hOCT2. Carvedilol (cluster I) and adrenosterone (cluster III) did not support CCF, consistent with the prediction that members of these structural classes are likely to be nontransported inhibitors of OCT2. The cluster II representatives MPP, metformin, cimetidine, and TEA all supported CCF, consistent with independent assessments of their OCT2-mediated transport. However, the other cluster II representatives, diphenidol and phenyltoloxamine, failed to support CCF, suggesting that neither compound is transported by OCT2. An independent assessment of diphenidol transport (using liquid chromatography with tandem mass spectroscopy) confirmed this observation. The results underscore the caution required for development of predictive models of ligand interaction with multidrug transporters. PMID:23034939

Harper, Jaclyn N; Wright, Stephen H

2013-01-01

 
 
 
 
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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.

362

EmrE, a model for studying evolution and mechanism of ion-coupled transporters.  

Science.gov (United States)

EmrE is a small (110 residues) SMR transporter from Escherichia coli that extrudes positively charged aromatic drugs in exchange for two protons, thus rendering bacteria resistant to a variety of toxic compounds. Due to its size, stability and retention of its function upon solubilization in detergent, EmrE provides a unique experimental paradigm for the biochemical and biophysical studies of membrane based ion-coupled transporters. In addition, EmrE has been in center stage in the past two years because it provides also a paradigm for the study of the evolution of membrane proteins. Controversy around this topic is still going on and some novel concepts are surfacing that may contribute to our understanding of evolution of topology of membrane proteins. Furthermore, based on the findings that the cell multidrug transporters interact functionally we introduce the concept of a cell Resistosome. PMID:19167526

Schuldiner, Shimon

2009-05-01

363

Polycyclic aromatic hydrocarbons in soils of Beijing and Tianjin region: vertical distribution, correlation with TOC and transport mechanism.  

Science.gov (United States)

The contents and distribution of 20 polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic hydrocarbons (HAHs) were investigated in 16 soil profiles of Beijing and Tianjin region. Transport of high molecular weight PAHs (HMWPAHs) and the correlation between total organic carbon (TOC) and their concentrations were also discussed. The results indicated that highly contaminated sites were located at urban or wastewater irrigation areas and pollutants mainly accumulated in topsoil (soils from Tianjin were markedly greater than those from Beijing. Even the contents at bottoms of soil profiles in Tianjin were higher than those in topsoils of Beijing soil profile. HMWPAHs dominated the PAH profiles, exhibiting a uniform distribution of pyrogenic origin between topsoils and deep layers. Furthermore, the percentages of HMWPAHs remained relative constant with the depth of soil profiles, which were consistent with the distribution of particulate matter-associated PAHs in the local atmospheric environments. Therefore, HMWPAHs transport with particulates might be the predominant source found in soil profiles. PMID:20108671

He, Fengpeng; Zhang, Zhihuan; Wan, Yunyang; Lu, Song; Wang, Liang; Bu, Qingwei

2009-01-01

364