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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

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Baltrus?aitis, Andrius

2005-01-01

3

Mechanisms of glutamate transport.  

Science.gov (United States)

L-Glutamate is the predominant excitatory neurotransmitter in the mammalian central nervous system and plays important roles in a wide variety of brain functions, but it is also a key player in the pathogenesis of many neurological disorders. The control of glutamate concentrations is critical to the normal functioning of the central nervous system, and in this review we discuss how glutamate transporters regulate glutamate concentrations to maintain dynamic signaling mechanisms between neurons. In 2004, the crystal structure of a prokaryotic homolog of the mammalian glutamate transporter family of proteins was crystallized and its structure determined. This has paved the way for a better understanding of the structural basis for glutamate transporter function. In this review we provide a broad perspective of this field of research, but focus primarily on the more recent studies with a particular emphasis on how our understanding of the structure of glutamate transporters has generated new insights. PMID:24137018

Vandenberg, Robert J; Ryan, Renae M

2013-10-01

4

Transport mechanisms in the ammonium transporter family.  

Science.gov (United States)

Ammonium transport is mediated by membrane proteins of the ubiquitous Amt/Rh family. Despite the availability of different X-ray structures that provide many insights on the ammonium permeation process, the molecular details of its mechanism remain controversial. The X-ray structures have revealed that the pore of the Amt and Rh proteins is characterized by a hydrophobic portion about 12A long in which electronic density was observed in crystallographic study of AmtB from Escherichia coli. This electronic density was initially only observed when crystals were grown in presence of ammonium salt and was thus attributed to ammonia (NH(3)) molecules, and lead the authors to suggest that the conduction mechanism in the Amt/Rh proteins involves the single-file diffusion of NH(3) molecules. However, other X-ray crystallography results and molecular mechanics simulations suggest that the pore of AmtB could also be filled with water molecules. The possible presence of water molecules in the pore lumen calls for a reassessment of the growing consensus that Amt/Rh proteins work as plain NH(3) channels. Indeed, functional experiments on plant ammonium transporters and rhesus proteins suggest a variety of permeation mechanisms including the passive diffusion of NH(3), the antiport of NH(4)(+)/H(+), the transport of NH(4)(+), or the cotransport of NH(3)/H(+). We discuss these mechanisms in light of some recent functional and simulation studies on the AmtB transporter and illustrate how they can be reconciled with the available high resolution X-ray data. PMID:20674437

Lamoureux, G; Javelle, A; Baday, S; Wang, S; Bernèche, S

2010-09-01

5

Turbulent transport and lithium destruction in main sequence stars  

International Nuclear Information System (INIS)

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

6

Modeling coastal current transport in the Gulf of Maine  

Science.gov (United States)

A numerical simulation of the circulation in the Gulf of Maine is compared with observations taken during the spring and summer of 1994, focusing on two distinct coastal current systems. The eastern Maine coastal current is well mixed out to approximately 50m depth, with the influence of tidal mixing extending to 100m depth. In contrast, the western Maine coastal current consists mainly of a surface-trapped plume emanating from the Kennebec River. Various methods of model/data comparison are discussed, ranging from qualitative comparisons of surface temperature and currents to quantitative measurements of model skill. In particular, one primary metric of comparison is the amount and distribution of fresh water carried within the coastal current systems. In both coastal current systems, fresh-water flux has an approximately self-similar structure so that measurements taken at a single mooring location may be extrapolated to estimate the entire along-shore fresh-water flux. This self-similar structure is shown to be internally consistent within the model, and results in good model/data comparisons. The model has more skill at predicting fresh-water flux than other point-to-point surface property comparisons in all cases except surface salinity in the western Maine coastal current. This suggests fresh-water flux is a robust feature in the model, and a suitable metric for gauging the model ability to reproduce the broad-scale transport of the Maine coastal current system.

Hetland, Robert D.; Signell, Richard P.

2005-09-01

7

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

8

The main aspects of the Vivitron mechanical structure  

International Nuclear Information System (INIS)

The main aspects of the Vivitron mechanical structure are discussed through a description of the tank and the internal structure. The results of the calculated constraints on the structure are presented

9

Membranes, mechanics, and intracellular transport  

Science.gov (United States)

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

Parthasarathy, Raghuveer

2012-10-01

10

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

11

Mechanical Smoke Exhaust in Underground Transport Passage of Hydropower Station  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper, the fire scenario occuring in the main transformer hall of an underground hydropower station is taken as an example of the mechanical smoke exhaust effect in the transport passage when the smoke spilled from the fired main transformer hall is analyzed by means of theoretical analysis, experiment and FDS simulation. Firstly, the mathematic correlations regarding the mechanical exhaust rate are derived through theoretical analysis. Secondly, a series of experiments are conduct...

Jiang Hu; Ran Gao; Jiangyan Ma; Yeqiu Wu; Angui Li

2012-01-01

12

Molecular Mechanisms of Renal Ammonia Transport  

Science.gov (United States)

Acid-base homeostasis to a great extent relies on renal ammonia metabolism. In the past several years, seminal studies have generated important new insights into the mechanisms of renal ammonia transport. In particular, the theory that ammonia transport occurs almost exclusively through nonionic NH3 diffusion and NH4+ trapping has given way to a model postulating that a variety of proteins specifically transport NH3 and NH4+ and that this transport is critical for normal ammonia metabolism. Many of these proteins transport primarily H+ or K+ but also transport NH4+. Nonerythroid Rh glycoproteins transport ammonia and may represent critical facilitators of ammonia transport in the kidney. This review discusses the underlying aspects of renal ammonia transport as well as specific proteins with important roles in renal ammonia transport. PMID:17002591

Weiner, I. David; Hamm, L. Lee

2015-01-01

13

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

14

Application of mechanized material transport in uranium mine  

International Nuclear Information System (INIS)

Mechanisms had to be developed for speeding up the transport of material to the underground while increasing work safety and hygiene, this in view of the continuously growing volume of uranium ore mining in the pit. Attention was concentrated mainly on problems of transporting long material through the pit to the mining face. Three types of mechanisms were developed: a suspended material cage which is used to transport material with a length of up to 4 m, a suspension element for the transport of long flanged tubes and a suspension element for the transport of rails. The previous method of material handling is characterized and the new method using the suspended cage is described in detail. The actual amount of material transported in one year is given as is the time needed for manual transport and for transport using the cage. Annual savings are calculated. The transport of tubes and rails using the two suspension elements is described and 14 photographs are published showing the developed mechanisms and their uses. (A.K.)

15

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

16

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

17

Qinshan CANDU 6 main heat transport system high operational performance  

International Nuclear Information System (INIS)

This paper deals with the Qinshan CANDU 6 Critical Channel Power (CCP) performance up to about 6 years of operation. Operational and aging related changes of the primary Heat Transport System (HTS) throughout its lifetime may lead to restrictions in certain safety system settings and hence some restriction in performance under certain conditions. A step in confirming safe reactor operation is the tracking of relevant data and their corresponding interpretation by the use of appropriate thermalhydraulic analytic models. Based on these analytic models up to 10 years of reactor operation are predicted and presented. These predictions, in association with an optimized parameter tracking and adjustment methodology, confirm continued safe reactor operation. This paper demonstrates that Qinshan CANDU Units 1 and 2, as compared to other CANDU 6 nuclear reactors of earlier design, exhibit significantly improved performance with much reduced plant aging effects. This high performance may, in part, be attributed to design improvements as well as improved operating practices. These performance improvements can also be expected for both new and refurbished CANDU 6 type nuclear reactors. (author)

18

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

CERN Document Server

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

Ludwig, H G; Hauschildt, P H

2006-01-01

19

Bacterial transporters: charge translocation and mechanism.  

Science.gov (United States)

A comparative review of the electrophysiological characterization of selected secondary active transporters from Escherichia coli is presented. In melibiose permease MelB and the Na(+)/proline carrier PutP pre-steady-state charge displacements can be assigned to an electrogenic conformational transition associated with the substrate release process. In both transporters cytoplasmic release of the sugar or the amino acid as well as release of the coupling cation are associated with a charge displacement. This suggests a common transport mechanism for both transporters. In the NhaA Na(+)/H(+) exchanger charge translocation due to its steady-state transport activity is observed. A new model is proposed for pH regulation of NhaA that is based on coupled Na(+) and H(+) equilibrium binding. PMID:19366604

Ganea, Constanta; Fendler, Klaus

2009-06-01

20

Polaron transport mechanism in DNA.  

Science.gov (United States)

A theory of polaron-hopping transport is studied in DNA in the presence of an electric field. The helix structure of DNA consists of a molecule of phosphoric acid, a molecule of sugar and a molecule of a nitrogen compound called a nitrogen base. The charge carriers are localized near the bases. Phonons are created due to internal motions such as changes in winding or the inclination angle of the helix. It is considered that, due to the interaction between a charge carrier and a phonon, a localized polaron is formed in the helix near a base. These internal motions also promote hopping of the localized polarons. By interacting with a phonon, the polaron undergoes a hopping process in the helix structure. We consider that the localized polaron sites are distributed randomly in both space and energy coordinates. A polaron hops from one site to another site in this space. Conduction is a result of many series of hops through this hopping space. This approach differs from the percolation method and others in the calculation of the conductivity. The present theory is used to explain the electric-field- and temperature-dependent conductivity experiments of DNA. A good agreement is found between theory and experiments. PMID:15696798

Singh, Mahi R

2004-01-01

 
 
 
 
21

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)

22

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

International Nuclear Information System (INIS)

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

23

Invasive home mechanical ventilation, mainly focused on neuromuscular disorders  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Introduction and background: Invasive home mechanical ventilation is used for patients with chronic respiratory insufficiency. This elaborate and technology-dependent ventilation is carried out via an artificial airway (tracheal cannula) to the trachea. Exact numbers about the incidence of home mechanical ventilation are not available. Patients with neuromuscular diseases represent a large portion of it. Research questions: Specific research questions are formulated and answered concerning th...

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

2010-01-01

24

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

25

Mechanical systems vibrating longitudinally with the transportation effect  

Directory of Open Access Journals (Sweden)

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

S. ?ó?kiewski

2007-03-01

26

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)

27

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

28

Mechanisms of calcium transport across the placenta: Review  

Directory of Open Access Journals (Sweden)

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

Catarina Tivane

2013-01-01

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

Administrative mechanics of research fuel transportation  

International Nuclear Information System (INIS)

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

32

Interhospital transport of the adult mechanically ventilated patient.  

Science.gov (United States)

Interhospital transport of the adult mechanically ventilated patient may be necessary for those who require specialized care. An experienced medical team can safely transport even the most critically ill patients if the care is optimized before departure. Patients with severe respiratory failure may have to remain on an ICU ventilator throughout the transport period, depending on the specific transport ventilator. Near-terminal ARDS can be treated with ECLS, and these patients also may be safely transported to a regional center. PMID:12184656

Reynolds, H Neal; Habashi, Nader M; Cottingham, Christine A; Frawley, P Milo; McCunn, Maureen

2002-03-01

33

Plant pleiotropic drug resistance transporters: transport mechanism, gene expression, and function.  

Science.gov (United States)

Pleiotropic drug resistance (PDR) transporters belonging to the ABCG subfamily of ATP-binding cassette (ABC) transporters are identified only in fungi and plants. Members of this family are expressed in plants in response to various biotic and abiotic stresses and transport a diverse array of molecules across membranes. Although their detailed transport mechanism is largely unknown, they play important roles in detoxification processes, preventing water loss, transport of phytohormones, and secondary metabolites. This review provides insights into transport mechanisms of plant PDR transporters, their expression profiles, and multitude functions in plants. PMID:24645852

Nuruzzaman, Mohammed; Zhang, Ru; Cao, Hong-Zhe; Luo, Zhi-Yong

2014-08-01

34

Morphodynamics, stratigraphy, and sediment transport patterns of the Kennebec River estuary, Maine, USA  

Science.gov (United States)

Sediment transport and circulation patterns within the lower Kennebec River estuary, Maine (˜20 km) have been investigated over a two year and nine month period using fathometer profiles and side-scan sonograms in conjunction with flow measurements, fresh-water discharge data, and grain-size data. The geologic history of the estuary is inferred from high-resolution seismic profiles and bridge borings. Subbottom data corroborate a five-stage evolutionary history that has been determined for other areas of the west-central Maine coast. Scattered deposits of glacial till (diamict) and stratified drift overly a Precambrian to Paleozoic metasedimentary bedrock basement. The glacio-marine blue clay of the Presumpscot Formation unconformably overlies the diamict and drift and drapes the basement, where till is absent. The clay surface is an erosional unconformity formed during the last sea-level lowstand. During subsequent sea-level rise, a relatively coarse-grained estuarine fill was deposited within a flood-dominated, relatively large paleo-Kennebec River estuary. As the rates of sea-level rise slowed, the system shifted to an ebb-dominated estuary in which the estuarine fill underwent reworking and downstream net transport. Bathymetric data show a hierarchical arrangement of bedforms ranging in size and morphology from well-developed, ebb-oriented transverse bars to superimposed simple, straight-crested megaripples. The transverse bars were stable over the study period. The reworking and migration of the smaller forms are closely linked to seasonal variations in the relative contributions between tidal flow and fresh-water discharge. During the spring, large-magnitude discharge events augment ebb-tidal flows. The ebb-reinforced flows dominate the system and result in a net downstream transport of medium- to coarse-grained sand. Estuarine stratification plays an important role in sediment transport during non-spring months. From mid-summer to fall, salinity gradients enhance flood-tidal flows and result in minor quantities of upstream transport. In addition, bedrock bathymetric highs and abrupt changes in channel geometry may influence sediment transport within the estuary.

Fenster, M. S.; FitzGerald, D. M.

1996-12-01

35

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

36

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

37

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

International Nuclear Information System (INIS)

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

38

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

International Nuclear Information System (INIS)

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

39

Mechanisms of contaminant transport in a multi-basin lake.  

Science.gov (United States)

Tracer studies are combined with a three-dimensional (3-D) numerical modeling study to provide a robust description of hydrodynamic and particle transport in Clear Lake, a multi-basin, polymictic lake in northern California, USA. The focus is on the mechanisms of transport of contaminants away from the vicinity of the Sulphur Bank Mercury Mine and out of the Oaks Arm to the rest of the lake and the hydraulic connection existing among the sub-basins of the lake. Under stratified conditions, the rate of spreading of the tracer was found to be large. In less than a week the tracer spread from the eastern end of the Oaks Arm to the other basins. Under non-stratified conditions, the tracer spread more slowly and had a concentration that gradually diminished with distance from the injection location. The numerical results showed that the mechanisms accounting for these observed patterns occur in pulses, with maximum rates coinciding with the stratified periods. Stratification acts first to enhance the currents by inhibiting vertical momentum mixing and decoupling the surface currents from bottom friction. The diversity of the flow structures that results from the interaction of the wind and the density fields in the lake is responsible for the high dispersion rates. Contaminants originating in the Oaks Arm are shown to be transported into the Lower Arm following the surface currents and into the Upper Arm mainly through the bottom currents. It was also shown that, under stratified conditions, both the baroclinic (density driven) gradients and the wind forcing act jointly to exacerbate the interbasin exchange. PMID:19475919

Rueda, Francisco J; Schladow, S Geoffrey; Clark, Jordan F

2008-12-01

40

On transport mechanisms in solar cells involving organic semiconductors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The knowledge of transport mechanisms in solar cells is useful to determine electrical losses. In my doctoral thesis we studied the transport mechanisms in solar cells involving organic semiconductors. We show that models which have been used to study amorphous inorganic solar cells can be applied on organic ones. We conclude that: multitunelling capture emission and tunelling-enhanced interface recombination mechanisms contribute to the dark current characteristics in P3HT/Si, Pc/C60 and P3H...

Nolasco Montan?o, Jairo Ce?sar

2011-01-01

 
 
 
 
41

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

42

Rupture mechanics of metallic alloys for hydrogen transport  

International Nuclear Information System (INIS)

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

43

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)

44

Far SOL transport and main wall plasma interaction in DIII-D  

International Nuclear Information System (INIS)

Far Scrape-Off Layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross-field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma contact with the low field side (LFS) main chamber wall. In H-mode between edge localized modes (ELMs) the plasma-wall contact is weaker than in L-mode. During ELM fluxes of particles and heat to the LFS wall increase transiently above the L-mode values. Depending on the discharge conditions, ELMs are responsible for 30-90% of the net ion flux to the outboard chamber wall. ELMs in high density discharges feature intermittent transport events similar to those observed in L-mode and attributed to blobs of dense hot plasma formed inside the separatrix and propagating radially outwards. Though the blobs decay with radius, some of them survive long enough to reach the outer wall and possibly cause sputtering. In lower density H-modes, ELMs can feature blobs of pedestal density propagating all the way to the outer wall

45

The Remarkable Transport Mechanism of P-glycoprotein; a Multidrug Transporter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Human P-glycoprotein (ABCB1) is a primary multidrug transporter located in plasma membranes, that, utilizes the energy of ATP hydrolysis to pump toxic xenobiotics out of cells. P-glycoprotein employs a most unusual molecular mechanism to perform this drug transport function. Here we review our work to elucidate the molecular mechanism of drug transport by P-glycoprotein. High level heterologous expression of human P-glycoprotein, in the yeast Saccharomyces cerevisiae, has facilitated biophysi...

Al-shawi, Marwan K.; Omote, Hiroshi

2005-01-01

46

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-06-26

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

A model of volcanic magma transport by fracturing stress mechanisms  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Understanding the mechanisms of magma ascent preceding eruptions, and in particular the subvolcanic system that stores and transports magma to the surface, is of crucial relevance for hazard and risk assessment.We propose here a statistical model describi

Cataudella, Vittorio; Di Maio, Rosa; Milano, Leopoldo; Nicodemi, Mario

2008-01-01

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

Drug Transport Mechanism of Oral Antidiabetic Nanomedicines  

Science.gov (United States)

Context: Over the last few decades, extensive efforts have been made worldwide to develop nanomedicine delivery systems, especially via oral route for antidiabetic drugs. Absorption of insulin is hindered by epithelial cells of gastrointestinal tract, acidic gastric pH and digestive enzymes. Evidence Acquisition: Recent reports have identified and explained the beneficial role of several structural molecules like mucoadhesive polymers (polyacrylic acid, sodium alginate, chitosan) and other copolymers for the efficient transport and release of insulin to its receptors. Results: Insulin nanomedicines based on alginate-dextran sulfate core with a chitosan-polyethylene glycol-albumin shell reduced glycaemia in a dose dependent manner. Orally available exendin-4 formulations exerted their effects in a time dependent manner. Insulin nanoparticles formed by using alginate and dextran sulfate nucleating around calcium and binding to poloxamer, stabilized by chitosan, and subsequently coated with albumin showed a threefold increase of the hypoglycemic effect in comparison to free insulin in animal models. Solid lipid nanoparticles showed an enhancement of the bioavailability of repaglinide (RG) within optimized solid lipid nanoparticle formulations when compared with RG alone. Conclusions: Nanoparticles represent multiparticulate delivery systems designed to obtain prolonged or controlled drug delivery and to improve bioavailability as well as stability. Nanoparticles can also offer advantages like limiting fluctuations within therapeutic range, reducing side effects, protecting drugs from degradation, decreasing dosing frequency, and improving patient compliance and convenience PMID:24696697

Gundogdu, Evren; Yurdasiper, Aysu

2014-01-01

51

Distribution and transport of sedimentary trace metals in the tidal portions of the Kennebec/Androscoggin River system, Maine, USA.  

Science.gov (United States)

Previous investigations suggest that contaminant transport from the large Kennebec/Androscoggin watershed is an important large-scale process in mid-coast Maine. To investigate this phenomenon, we determined the concentrations of Cd, Cr, Cu, Ni, Pb, Sn and Zn in the surface sediments of 47 stations in the tidal Kennebec/Androscoggin system. Most stations exhibited elevated metal concentrations. Highest levels were found in the main stem of the system. Distribution patterns lead to the conclusion that metals enter the system from the watershed and are transported to the nearshore Gulf of Maine. The coarse-grained, ebb tide dominated flow prevents the accumulation of contaminants in the estuary. This supports the hypothesis of Larsen and Gaudette (1995) that the Kennebec and Androscoggin watersheds are sources for contaminants observed in the nearshore Gulf of Maine. PMID:20381095

Larsen, Peter Foster; Gaudette, Henri E

2010-08-01

52

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

53

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

International Nuclear Information System (INIS)

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

54

Mechanical energy transport. [during stellar turbulences  

Science.gov (United States)

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

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

1980-01-01

55

Mechanism of Transport through Wood Cell Wall Polymers  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The movement of chemicals through wood is necessaryfor decay and fastener corrosion to occur in forest products.However, the mechanism responsible for the onset of fastenercorrosion and decay in wood is not known. The onset occursbefore the formation of free water in wood cavities and aqueouschemical transport would be possible. Here, we propose that theonset mechanism is the hemicelluloses going through a moistureinducedglass transition. As nm-scale regions of mechanicallysoftened hemicellul...

Jakes, Joseph E.; Nayomi Plaza; Stone, Donald S.; Hunt, Christopher G.; Glass, Samuel V.; Zelinka, Samuel L.

2013-01-01

56

SUPERCONDUCTING TAPES`CHARACTERISTICS BY TRANSPORT MEASUREMENTS UNDER MECHANICAL STRESS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

SUPERCONDUCTING FILMS ON FLEXIBLE SUBSTRATES OR "COATED CONDUCTORS" ARE THE NEW MATERIALS WITH LARGE INDUSTRIAL POTENTIAL, BUT LITTLE KNOWN BECAUSE OF THEIR RECENT DEVELOPMENT. THE APPLICATIONS BASED ON THE COATED CONDUCTORS INDUCE SOME MECHANICAL STRESSES ON THE MATERIAL, WHICH MAY CAUSE SOME DEGRADATIONS OF ELECTRICAL PROPERTIES.THIS WORK AIMS TO EVALUATE THE MECHANICAL STRESSES INFLUENCE ON TRANSPORT PROPERTIES AND ON MORPHOLOGY OF COATED CONDUCTORS. DIFFERENT TECHNIQUES WERE U...

Antonevici-charrier, Anca

2006-01-01

57

Unveiling the gating mechanism of ECF Transporter RibU  

Science.gov (United States)

Energy-coupling factor (ECF) transporters are responsible for uptake of micronutrients in prokaryotes. The recently reported crystal structure of an ECF transporter RibU provided a foundation for understanding the structure and transport mechanism of ECF transporters. In the present study, molecular dynamics (MD) was carried out to study the conformational changes of the S component RibU upon binding by riboflavin. Our result and analysis revealed a critically important gating mechanism, in which part of loop5 (L5') (eleven residues, missing in the crystal structure) between TM5 and TM6 is dynamically flexible and serves as a gate. Specifically, the L5' opens a large cavity accessible to riboflavin from the extracellular space in Apo-RibU and closes the cavity upon riboflavin binding through hydrophobic packing with riboflavin. Thus, L5'is proposed to be the gate for riboflavin binding. In addition, steered molecular dynamics (SMD) simulation is employed to investigate the translocation dynamics of RibU during riboflavin transport. The simulation result does not show evidence that the S component alone can carry out the transport function. Since loop regions are very flexible and therefore could not be resolved by crystallography, their dynamics are hard to predict based on crystal structure alone.

Song, Jianing; Ji, Changge; Zhang, John Z. H.

2013-12-01

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

Early metabolic effects and mechanism of ammonium transport in yeast  

International Nuclear Information System (INIS)

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

 
 
 
 
61

Emissions of greenhouse gases from the use of transportation fuels and electricity. Volume 1, Main text  

Energy Technology Data Exchange (ETDEWEB)

This report presents estimates of full fuel-cycle emissions of greenhouse gases from using transportation fuels and electricity. The data cover emissions of carbon dioxide (CO{sub 2}), methane, carbon monoxide, nitrous oxide, nitrogen oxides, and nonmethane organic compounds resulting from the end use of fuels, compression or liquefaction of gaseous transportation fuels, fuel distribution, fuel production, feedstock transport, feedstock recovery, manufacture of motor vehicles, maintenance of transportation systems, manufacture of materials used in major energy facilities, and changes in land use that result from using biomass-derived fuels. The results for electricity use are in grams of CO{sub 2}-equivalent emissions per kilowatt-hour of electricity delivered to end users and cover generating plants powered by coal, oil, natural gas, methanol, biomass, and nuclear energy. The transportation analysis compares CO{sub 2}-equivalent emissions, in grams per mile, from base-case gasoline and diesel fuel cycles with emissions from these alternative- fuel cycles: methanol from coal, natural gas, or wood; compressed or liquefied natural gas; synthetic natural gas from wood; ethanol from corn or wood; liquefied petroleum gas from oil or natural gas; hydrogen from nuclear or solar power; electricity from coal, uranium, oil, natural gas, biomass, or solar energy, used in battery-powered electric vehicles; and hydrogen and methanol used in fuel-cell vehicles.

DeLuchi, M.A. [California Univ., Davis, CA (United States)

1991-11-01

62

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

63

Mechanism of Na(+)-dependent citrate transport in Klebsiella pneumoniae.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Citrate transport via CitS of Klebsiella pneumoniae has been shown to depend on the presence of Na+. This transport system has been expressed in Escherichia coli, and uptake of citrate in E. coli membrane vesicles via this uptake system was found to be an electrogenic process, although the pH gradient is the main driving force for citrate uptake (M. E. van der Rest, R. M. Siewe, T. Abee, E. Schwartz, D. Oesterhelt, and W. N. Konings, J. Biol. Chem. 267:8971-8976, 1992). Analysis of the affini...

Rest, M. E.; Molenaar, D.; Konings, W. N.

1992-01-01

64

Mechanism of Transport through Wood Cell Wall Polymers  

Directory of Open Access Journals (Sweden)

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

Joseph E Jakes

2013-11-01

65

Structure and mechanism of ATP-dependent phospholipid transporters  

DEFF Research Database (Denmark)

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

Lopez Marques, Rosa Laura; Poulsen, Lisbeth Rosager

2015-01-01

66

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

CERN Document Server

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

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

2012-01-01

67

Directed transport as a mechanism for protein folding in vivo  

CERN Document Server

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

Gonzalez-Candela, Ernesto

2009-01-01

68

Signatures of Cooperative Effects and Transport Mechanisms in Conductance Histograms  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-01-01

69

Mechanism of regulation of glucose transport in Rhizobium leguminosarum.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1982-01-01

70

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

71

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Pothof, I. W. M.

2011-01-01

72

Small substrate transport and mechanism of a molybdate ATP binding cassette transporter in a lipid environment.  

Science.gov (United States)

Embedded in the plasma membrane of all bacteria, ATP binding cassette (ABC) importers facilitate the uptake of several vital nutrients and cofactors. The ABC transporter, MolBC-A, imports molybdate by passing substrate from the binding protein MolA to a membrane-spanning translocation pathway of MolB. To understand the mechanism of transport in the biological membrane as a whole, the effects of the lipid bilayer on transport needed to be addressed. Continuous wave-electron paramagnetic resonance and in vivo molybdate uptake studies were used to test the impact of the lipid environment on the mechanism and function of MolBC-A. Working with the bacterium Haemophilus influenzae, we found that MolBC-A functions as a low affinity molybdate transporter in its native environment. In periods of high extracellular molybdate concentration, H. influenzae makes use of parallel molybdate transport systems (MolBC-A and ModBC-A) to take up a greater amount of molybdate than a strain with ModBC-A alone. In addition, the movement of the translocation pathway in response to nucleotide binding and hydrolysis in a lipid environment is conserved when compared with in-detergent analysis. However, electron paramagnetic resonance spectroscopy indicates that a lipid environment restricts the flexibility of the MolBC translocation pathway. By combining continuous wave-electron paramagnetic resonance spectroscopy and substrate uptake studies, we reveal details of molybdate transport and the logistics of uptake systems that employ multiple transporters for the same substrate, offering insight into the mechanisms of nutrient uptake in bacteria. PMID:24722984

Rice, Austin J; Harrison, Alistair; Alvarez, Frances J D; Davidson, Amy L; Pinkett, Heather W

2014-05-23

73

Microscopic chaos, fractals and transport in nonequilibrium statistical mechanics  

CERN Document Server

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

Klages, Rainer

2007-01-01

74

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

75

Mechanism of copper transport from plasma to hepatocytes  

International Nuclear Information System (INIS)

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

76

Mechanisms of Carrier Transport Induced by a Microswimmer Bath.  

Science.gov (United States)

Recently, it was found that a wedgelike microparticle (referred to as "carrier") which is only allowed to translate but not to rotate exhibits a directed translational motion along the wedge cusp if it is exposed to a bath of microswimmers. Here we model this effect in detail by resolving the microswimmers explicitly using interaction models with different degrees of mutual alignment. Using computer simulations we study the impact of these interactions on the transport efficiency of a V-shaped carrier. We show that the transport mechanisms itself strongly depends on the degree of alignment embodied in the modelling of the individual swimmer dynamics. For weak alignment, optimal carrier transport occurs in the turbulent microswimmer state and is induced by swirl depletion inside the carrier. For strong aligning interactions, optimal transport occurs already in the dilute regime and is mediated by a polar cloud of swimmers in the carrier wake pushing the wedge-particle forward. We also demonstrate that the optimal shape of the carrier leading to maximal transport speed depends on the kind of interaction model used. PMID:25347885

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

2014-10-20

77

IDDTL: A Novel Identified Internet Data Transport Layer Mechanism  

Directory of Open Access Journals (Sweden)

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

Yangyang Gao

2014-01-01

78

Far SOL Transport and Main Wall Plasma Interaction in DIII-D  

International Nuclear Information System (INIS)

Far scrape-off layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross-field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma-wall contact. In H-mode between edge localized modes (ELMs), plasma-wall contact is generally weaker than in L-mode. During ELMs plasma fluxes to the wall increase to, or above the L-mode levels. Depending on the discharge conditions ELMs are responsible for 30-90% of the ion flux to the outboard chamber wall. Cross-field fluxes in far SOL are dominated by large amplitude intermittent transport events that may propagate all the way to the outer wall and cause sputtering. A Divertor Material Evaluation System (DiMES) probe containing samples of several ITER-relevant materials including carbon, beryllium and tungsten was exposed to a series of upper single null (USN) discharges as a proxy to measure the first wall erosion

79

Far SOL transport and main wall plasma interaction in DIII-D  

International Nuclear Information System (INIS)

Far scrape-off layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross-field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma-wall contact. In H-mode between edge localized modes (ELMs), plasma-wall contact is generally weaker than in L-mode. During ELMs plasma fluxes to the wall increase to, or above the L-mode levels. Depending on the discharge conditions ELMs are responsible for 30-90% of the ion flux to the outboard chamber wall. Cross-field fluxes in far SOL are dominated by large amplitude intermittent transport events that may propagate all the way to the outer wall and cause sputtering. A Divertor Material Evaluation System (DiMES) probe containing samples of several ITER-relevant materials including carbon, beryllium and tungsten was exposed to a series of upper single null (USN) discharges as a proxy to measure the first wall erosion. (author)

80

Far SOL transport and main wall plasma interaction in DIII-D  

International Nuclear Information System (INIS)

Full text: Far scrape-off layer (SOL) and near-wall plasma parameters in DIII-D depend strongly on the discharge parameters and confinement regime. In L-mode discharges cross- field transport increases with the average discharge density and flattens far SOL profiles, thus increasing plasma-wall contact. In H-mode between edge localized modes (ELMs), plasma- wall contact is generally weaker than in L-mode. During ELMs plasma fluxes to the wall increase to, or above the L-mode levels. Depending on the discharge conditions ELMs are responsible for 30%-90% of the total plasma flux to the outer chamber wall. Cross-field fluxes in far SOL are dominated by large amplitude intermittent transport events that may propagate all the way to the outer wall and cause sputtering. High levels of plasma interaction with the outer chamber wall are observed during disruptions. A divertor Material Evaluation System (DiMES) probe containing samples of several ITER-relevant materials was exposed to a series of upper single null (USN) discharges as a proxy to measure the first wall erosion. (author)

 
 
 
 
81

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

Directory of Open Access Journals (Sweden)

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

S. V. Myamlin

2014-01-01

82

Mechanism of electrogenic cation transport by the cloned organic cation transporter 2 from rat.  

Science.gov (United States)

The organic cation transporter 2 (OCT2) is expressed in plasma membranes of kidney and brain. Its transport mechanism and substrates are debated. We studied substrate-induced changes of electrical current with the patch clamp technique after expression of rat OCT2 in oocytes. Activation of current, corresponding to efflux, was observed for small organic cations, e.g. choline. In contrast, the bigger cations quinine and tetrabutylammonium elicited no change in current. However, transport of choline could be inhibited by applying quinine or tetrabutylammonium to the cytoplasmic side. Inhibition of organic cation efflux by quinine was competitive with substrates. Quinine at the inside also inhibited substrate influx from the outside. Current-voltage analysis showed that both maximal turnover and apparent affinity to substrates are voltage-dependent. Substrate-induced currents with organic cations on both membrane sides reversed as predicted from the Nernst potential. Our results clearly identify the electrochemical potential as driving force for transport at neutral pH and exclude an electroneutral H(+)/organic cation(+) exchange. We suggest the existence of an electroneutral organic cation(+) exchange and propose a model for a carrier-type transport mechanism. PMID:10889205

Budiman, T; Bamberg, E; Koepsell, H; Nagel, G

2000-09-22

83

Quantum-mechanical transport equation for atomic systems.  

Science.gov (United States)

A quantum-mechanical transport equation (QMTE) is derived which should be applicable to a wide range of problems involving the interaction of radiation with atoms or molecules which are also subject to collisions with perturber atoms. The equation follows the time evolution of the macroscopic atomic density matrix elements of atoms located at classical position R and moving with classical velocity v. It is quantum mechanical in the sense that all collision kernels or rates which appear have been obtained from a quantum-mechanical theory and, as such, properly take into account the energy-level variations and velocity changes of the active (emitting or absorbing) atom produced in collisions with perturber atoms. The present formulation is better suited to problems involving high-intensity external fields, such as those encountered in laser physics.

Berman, P. R.

1972-01-01

84

PKL small break tests and energy transport mechanisms  

International Nuclear Information System (INIS)

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

85

Elementary derivation of nonlinear transport equations from statistical mechanics  

International Nuclear Information System (INIS)

Exact closed nonlinear transport equations for a set of macroscopic variables a are derived from classical statistical mechanics. The deriviation involves only simple manipulations of the Liouville equation, and makes no use of projection operators or graphical expansions. It is based on the Chapman-Enskog idea of separating the distribution function into a constrained equilibrium part, obtained from information theory, and a small remainder. The resulting exact transport equations involve time convolutions over the past history of both a(t) and a(t). However, if the variables a provide a complete macroscopic description, the equations may be simplified. This is accomplished by a systematic expansion procedure of Chapman--Enskog type, in which the small parameter is the natural parameter of slowness relevant to the problem

86

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

87

Nonlinear charge transport mechanism in periodic and disordered DNA  

CERN Document Server

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

Hennig, D; Agarwal, J P

2003-01-01

88

Transport mechanisms for Mg/Zn3P2 junctions  

International Nuclear Information System (INIS)

The dominant transport mechanisms for Mg/Zn3P2 junctions are shown to depend on the heat treatment in hydrogen of the Zn3P2 prior to Mg deposition. For heat treatments below 300 0C, multistep tunneling via defect centers dominates, whereas for heat treatments between 300 and 500 0C, recombination/generation dominates. Correspondence is observed between the imperfections responsible for the junction transport and previously reported imperfections in bulk Zn3P2 crystals. Enhanced tunneling under solar illumination contributes to the low energy conversion efficiency of thin Mg film Mg/Zn3P2 devices. An estimate of the interface recombination velocity for these junctions yields a value of 1.9 x 107 cm/sec

89

Size related transport mechanisms in hybrid metal-polymer nanowires  

Energy Technology Data Exchange (ETDEWEB)

Electrical transport data for hybrid metal-polypyrrole nanowires of various diameters are presented and analyzed. Measurements were performed on both multiple nanowires - embedded within polycarbonate templates - and single nanowires down to low temperature T=4 K. All samples exhibit symmetrical and linear current-voltage (I-V) characteristics at room temperature. Below 77 K, all samples with diameters above 40 nm present nonlinear I-V characteristics and a zero-current plateau at 4 K. The three-dimensional Mott variable-range-hopping model provides a complete framework for the understanding of their behavior. In contrast, the transport mechanism changes for the 40 nm nanowire samples which exhibit a power-law T -dependence of the resistance, indicative of the critical regime of disorder-induced metal-insulator transitions. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Gence, L.; Faniel, S.; Vlad, A.; Dutu, C.; Melinte, S.; Bayot, V. [DICE Lab., Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium); Callegari, V.; Demoustier-Champagne, S. [POLY Lab., Universite Catholique de Louvain, 1348 Louvain-la-Neuve (Belgium)

2008-06-15

90

Mechanical transport in two-dimensional networks of fractures  

Energy Technology Data Exchange (ETDEWEB)

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.

Endo, H.K.

1984-04-01

91

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

92

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 fut 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

93

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

International Nuclear Information System (INIS)

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

94

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

DEFF Research Database (Denmark)

Introduction: Many drug substances are substrates for membrane transporters, which influence their intestinal absorption. Vigabatrin is a drug substance used in the treatment of epilepsy, mainly for treatment of infantile spasms. Vigabatrin is a substrate for the human proton-coupled amino acid transporter hPAT1. The aim of the project was to identify if transporters are involved in cellular uptake of vigabatrin in Caco-2 cells. Methods: The uptake rate of vigabatrin was measured in Caco-2 cells at pH 6.0 or 7.4 for 15 min after application of 0.1 – 25.0 mM vigabatrin. The inhibitory effect of selected amino acids and -derivatives on the apical vigabatrin uptake in Caco-2 cells was investigated. Vigabatrin samples were analyzed using liquid chromatography (LC) coupled to a mass selective detector (MSD). Results: The uptake rate of vigabatrin in Caco-2 cells was pH-dependent. The uptake of vigabatrin was saturable at pH 6.0 with a Michaelis constant, Km of 12.7 ± 3.7 mM and a maximal flux, Jmax of 3.7 ±0.5 nmol•min-1•cm-2. The presences of hPAT1 ligands significantly inhibited the uptake of vigabatrin in Caco-2 cells at pH 6.0, whereas hPAT1 non-ligands did not. Discussion: The saturability of the uptake at pH 6.0 indicates involvement of a carrier-mediated process in vigabatrin absorption. The pH-dependency of the vigabatrin uptake suggests that the uptake may be driven by a proton-coupled transporter. The Km-value is comparable to Km- values for other hPAT1 substrates (1-20 mM). The interaction of hPAT1 ligands with the uptake is a further indication of hPAT1 involvement in vigabatrin absorption. It is concluded that the proton-coupled amino acid transporter hPAT1 is the main transporter responsible for absorption of vigabatrin in Caco-2 cells.

NØhr, Martha Kampp; Hansen, Steen Honore'

95

[Molecular transport mechanism of pefloxacin mesylate binding with transferrin].  

Science.gov (United States)

The binding mechanism between pefloxacin mesylate (PM) and transferrin (Tf) was explored using spectral experiment combined with molecular modeling techniques. The binding parameters and thermodynamic functions of PM-Tf solution system were measured at different temperatures. The effect of PM on molecular conformation of Tf was investigated and the interaction mechanism was also discussed. The results showed that dynamic quenching mechanism occurs with PM binding to Tf. The value of binding distances (r) is low, which indicates the occurrence of energy transfer. The drug had conformational effect on Tf, which resulted in changes of hydrophobic environment of the binding domain in Tf. According to the obtained thermodynamic parameters, the main interaction force between PM and Tf is attributed to hydrophobic bonding. The results of molecular modeling revealed that hydrophobic and hydrogen bonds are main binding forces in the PM-Tf system. These results were in accordance with spectral experiments. The research results have given a better theoretical reference for the study of pharmacological mechanism between protein and quinolone. PMID:23387084

Guo, Ming; Lu, Xiao-Wang; Ran, Xiao-Yun; Hu, Run-Huai

2012-11-01

96

On the transport mechanisms in simulated heterogeneous rod bundle subchannels  

International Nuclear Information System (INIS)

Experimental results are presented on fully developed turbulent flow through simulated heterogeneous rod bundle subchannels. The emphasis of this study is on the universality of the cross-gap turbulence convection transport with respect to symmetric versus asymmetric subchannels. The flow passage was formed by a rod asymmetrically mounted in a trapezoidal duct. The Reynolds number based on the equivalent hydraulic diameter and bulk average axial velocity is 26 300. The measurements include mean axial velocities, r.m.s. values of the fluctuating velocity components and the energy density spectra. The results demonstrate the existence of an unusual region near the asymmetric rod-to-wall gap characterized by high levels of axial turbulence intensity with a remarkably different type of distribution compared with a normal boundary layer. It is also shown that the strength of the cross-gap transport is subchannel geometry dependent. The distributions of wall shear stress and turbulence kinetic energy indicate that mean convection by secondary flow is also an important transport mechanism that should be taken into account in the analysis of momentum/heat transfer in rod bundle subchannels. (orig.)

97

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1993-03-01

98

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)

99

Electron transport properties of single molecular junctions under mechanical modulations.  

Science.gov (United States)

Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on electron transport through single molecular junctions. PMID:22466314

Zhou, Jianfeng; Guo, Cunlan; Xu, Bingqian

2012-04-25

100

Electron transport properties of single molecular junctions under mechanical modulations  

International Nuclear Information System (INIS)

Electron transport behaviors of single molecular junctions are very sensitive to the atomic scale molecule-metal electrode contact interfaces, which have been difficult to control. We used a modified scanning probe microscope-break junction technique (SPM-BJT) to control the dynamics of the contacts and simultaneously monitor both the conductance and force. First, by fitting the measured data into a modified multiple tunneling barrier model, the static contact resistances, corresponding to the different contact conformations of single alkanedithiol and alkanediamine molecular junctions, were identified. Second, the changes of contact decay constant were measured under mechanical extensions of the molecular junctions, which helped to classify the different single molecular conductance sets into specific microscopic conformations of the molecule-electrode contacts. Third, by monitoring the changes of force and contact decay constant with the mechanical extensions, the changes of conductance were found to be caused by the changes of contact bond length and by the atomic reorganizations near the contact bond. This study provides a new insight into the understanding of the influences of contact conformations, especially the effect of changes of dynamic contact conformation on electron transport through single molecular junctions. (paper)

 
 
 
 
101

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

102

Exciton delocalization and energy transport mechanisms in R-phycoerythrin.  

Science.gov (United States)

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

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

2011-03-31

103

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

International Nuclear Information System (INIS)

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

104

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

105

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

106

New mechanism for the control of sodium transport in wheat  

International Nuclear Information System (INIS)

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

107

Cellular Transport Mechanisms of Cytotoxic Metallodrugs: An Overview beyond Cisplatin  

Directory of Open Access Journals (Sweden)

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

Sarah Spreckelmeyer

2014-09-01

108

Investigation of innovation development of the mechanical engineering enterprises considering the main risk factors  

Directory of Open Access Journals (Sweden)

Full Text Available The main risks occurring while the innovations introducing at the mechanicalengineering enterprises have been analyzed. An innovation production policy of the mechanicalengineering enterprise was determined on the basis of theoretical investigation. The optimalapproach concerning the risk estimation of the enterprise innovation activity is proposed in thearticle.

Halushchak, Olha Yaropolkivna

2012-11-01

109

Investigation of innovation development of the mechanical engineering enterprises considering the main risk factors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main risks occurring while the innovations introducing at the mechanicalengineering enterprises have been analyzed. An innovation production policy of the mechanicalengineering enterprise was determined on the basis of theoretical investigation. The optimalapproach concerning the risk estimation of the enterprise innovation activity is proposed in thearticle.

Halushchak, Olha Yaropolkivna; Zharovska, Nadiya Yuriyivna

2012-01-01

110

Availability and Failure Effects of NLC Main Linac Mechanical Movers(LCC-0141)  

International Nuclear Information System (INIS)

We analyze the probability of failure and the failure effects of the quadrupole and RF girder translation stages (''movers'') in the 500 GeV CM NLC Main Linac. In order to achieve its alignment tolerances, the NLC main linac will require a large installation of remote controlled translation stages with multiple degrees of freedom. In particular, each of the 591 quads in each 250 GeV main linac will be mounted on a magnet mover with 3 degrees of freedom (x, y, roll); each of the 2304 RF structure girders in each linac will be mounted on a girder mover with 5 degrees of freedom (x, y, roll, pitch, yaw). Simulation studies of main linac operation typically assume that all movers are operational at all times, in order to limit the complexity of the simulation. This is obviously not a realistic expectation for a system with so many components, especially when the number of sub-elements of each mover (stepper motors, rotary encoders, position transducers, cabling, control electronics, database, operator) are considered. The unavailability risk of the mover system is of particular concern for the NLC, since very few accelerators have ever been built with such a large fraction of its beamline hardware on remote-controlled translation stages. In order to predict the availability of the movers, it is necessary to estimate a few quantities, specifically: how often will a mover break (mean time between failures, or MTBF); how long will it take to repair a mover (mean time to repa take to repair a mover (mean time to repair, or MTTR); what is the performance ''hit'' which accrues when movers are broken? To answer the first two questions we used historical failure data from the two large mover systems at SLAC, in the arcs of the Stanford Linear Collider (SLC) and in the Final Focus Test Beam (FFTB). For the final question, we can get some estimate from simulation studies of the NLC main linac in normal operation

111

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

Science.gov (United States)

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

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

2014-12-01

112

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

Science.gov (United States)

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

Boano, Fulvio; Harvey, Judson W.; Marion, Andrea; Packman, Aaron I.; Revelli, Roberto; Ridolfi, Luca; Anders, Wörman

2014-01-01

113

Electrical transport through a mechanically gated molecular wire  

Science.gov (United States)

A surface-adsorbed molecule is contacted with the tip of a scanning tunneling microscope (STM) at a predefined atom. On tip retraction, the molecule is peeled off the surface. During this experiment, a two-dimensional differential conductance map is measured on the plane spanned by the bias voltage and the tip-surface distance. The conductance map demonstrates that tip retraction leads to mechanical gating of the molecular wire in the STM junction. The experiments are compared with a detailed ab initio simulation. We find that density functional theory (DFT) in the local density approximation (LDA) describes the tip-molecule contact formation and the geometry of the molecular junction throughout the peeling process with predictive power. However, a DFT-LDA-based transport simulation following the nonequilibrium Green's function (NEGF) formalism fails to describe the behavior of the differential conductance as found in experiment. Further analysis reveals that this failure is due to the mean-field description of electron correlation in the local density approximation. The results presented here are expected to be of general validity and show that, for a wide range of common wire configurations, simulations which go beyond the mean-field level are required to accurately describe current conduction through molecules. Finally, the results of the present study illustrate that well-controlled experiments and concurrent ab initio transport simulations that systematically sample a large configuration space of molecule-electrode couplings allow the unambiguous identification of correlation signatures in experiment.

Toher, C.; Temirov, R.; Greuling, A.; Pump, F.; Kaczmarski, M.; Cuniberti, G.; Rohlfing, M.; Tautz, F. S.

2011-04-01

114

Mechanical reliability of geometrically imperfect tubular oxygen transport membranes  

DEFF Research Database (Denmark)

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

Kwok, Kawai; Frandsen, Henrik Lund

2014-01-01

115

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

116

Diamond-like nanocomposites: electronic transport mechanisms and some applications  

Energy Technology Data Exchange (ETDEWEB)

A new class of electrically conductive diamond-like nanocomposite (DLN) was synthesized in which the conductivity can be varied over 18 orders of magnitude, from 10{sup 14}-10{sup 16} {Omega} cm to 2-4 x 10{sup -4} {Omega} cm. The electron transport mechanisms of the materials as amorphous dielectric, amorphous metal and in an intermediate state were studied. In the highly conducting state, the DLN structure contains a filamentary (on an atomic scale) random metallic network. A variety of metals, including lithium, silver, copper, aluminum, zinc, magnesium, niobium, tantalum, chromium, molybdenum, tungsten, rhenium, iron, cobalt and nickel can be used to form metallic DLN. Conducting DLN materials can be used as Schottky barriers with semiconductors such as silicon and GaAs. Extremely stable metal-dielectric multilayer structures without interfacial structural boundaries were fabricated. The unique combination of diamond-like chemical and mechanical properties and high electrical conductivity opens the possibility for applications of DLN materials in several areas such as microelectronics and stable anode materials for battery technology. (orig.).

Dorfman, V.F.; Skotheim, T.A.; Srivatsa, A.R. (Moltech Corporation, Engineering Building, SUNY, Stony Brook, NY (United States)); Bozhko, A.; Khan, I. (Dept. of Physics, Moscow State Univ. (Russia)); Pypkin, B.N. (Moscow Inst. of Controlling Machines, Moscow (Russia)); Borra, R.T.; Zhang, H. (Dept. of Materials Science and Engineering, SUNY, Stony Brook, NY (United States)); Rodichev, D.; Kirpilenko, G. (Inst. of Physical Problems, Zelenograd (Russia))

1992-05-15

117

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

Science.gov (United States)

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

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

2015-01-01

118

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

Science.gov (United States)

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

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

2013-11-01

119

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

120

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

 
 
 
 
121

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

122

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

123

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

124

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

125

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

Science.gov (United States)

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

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

2012-07-01

126

Differential mechanisms for insulin-induced relaxations in mouse posterior tibial arteries and main mesenteric arteries.  

Science.gov (United States)

The characteristics of endothelium-dependent relaxations in response to insulin and acetylcholine (ACh) in the mouse posterior tibial artery (PTA) were studied on wire myograph, and compared to those in the mouse main mesenteric artery (MMA). Insulin-induced relaxation in PTA was reversed by PI3K and Akt inhibitors, LY294002 and triciribine, but not by nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (L-NAME) or guanylate cyclase inhibitor, ODQ. The relaxation in PTA was also inhibited by apamin (small-conductance Ca(2+)-activated K(+) channel blocker) plus charybdotoxin (intermediate-conductance Ca(2+)-activated K(+) channel blocker), elevated KCl or ouabain (Na(+)-K(+) ATPase inhibitor) plus BaCl2 [inwardly rectifying K(+) (KIR) channel inhibitor]; whereas L-NAME but not triciribine inhibited ACh-induced relaxation in PTA. On the other hand, nitric oxide and endothelium-derived hyperpolarizing factor albeit to a less extent mediated both insulin- and ACh-induced relaxations in MMA. The present study is for the first time dissecting out the components of endothelium-dependent relaxation in mouse PTA and suggesting differential responses to different agonists in distinctive blood vessels. PMID:25446161

Qu, Dan; Liu, Jian; Lau, Chi Wai; Huang, Yu

2014-12-01

127

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

128

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

129

Main trends in heavy ion reaction mechanisms when the energy increases  

International Nuclear Information System (INIS)

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

130

The transport mechanism DC arcs in advanced spectroanalysis  

International Nuclear Information System (INIS)

This report presents some basic investigations concerning the emission spectroanalysis of powder specimens with application of a new type of advanced DC arcs which operate in horizontally arranged graphite cylinders. The extremely low detection limits found by experiment for various elements (Be, Cd, In, Pb, Sn) suggest a beneficial and reflector like effect of the graphite cylinder on the transport process in the arc plasma. Experiments in detail and by using radioactive tracers (Ag-110, Cd-115, Co-56, Fe-59, Zn-65) lead to an element specific modified model of the effective mechanism of the new arc arrangement. Elements of favourable thermochemical properties produce about three times as much of the average particle density in the arc plasma with the effect of the graphite cylinder. Besides these effects the element specific properties of the graphite cylinder are remarkably invariable towards magnetic fields (1,24 . 10-2T bzw. 2,6 . 10-4T) and various additives (Ga2O3, Li2Co3, NaCl) to the test specimens. (orig.)

131

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

132

Hearing molecules, mechanism and transportation: Modeled in Drosophila melanogaster.  

Science.gov (United States)

Mechanosensory transduction underlies the perception of touch, sound and acceleration. The mechanical signals exist in the environment are resensed by the specialized mechanosensory cells, which convert the external forces into the electrical signals. Hearing is a magnificent example that relies on the mechanotransduction mediated by the auditory cells, for example the inner-ear hair cells in vertebrates and the Johnston's organ (JO) in fly. Previous studies have shown the fundamental physiological processes in the fly and vertebrate auditory organs are similar, suggesting that there might be a set of similar molecules underlying these processes. The molecular studies of the fly JO have been shown to be remarkably successful in discovering the developmental and functional genes that provided further implications in vertebrates. Several evolutionarily conserved molecules and signaling pathways have been shown to govern the development of the auditory organs in both vertebrates and invertebrates. The current review describes the similarities and differences between the vertebrate and fly auditory organs at developmental, structural, molecular, and transportation levels. © 2014 Wiley Periodicals, Inc. Develop Neurobiol 75: 109-130, 2015. PMID:25081222

Bokolia, Naveen Prakash; Mishra, Monalisa

2015-02-01

133

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)

134

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

135

Modelling intrinsic defects and transport mechanisms in the bismuth germanate crystalline system  

Science.gov (United States)

In the present work, computer modelling techniques based on energy minimisation were used to study the defect chemistry and physics for the Bi4Ge3O12 scintillator phase. A potential set was derived by fitting to the structure of this material together with the Bi12GeO20 phase and this potential set was then used to: i- calculate the bulk properties of both Bi4Ge3O12 and Bi12GeO20 phases; ii- study the relative stability of the phases; iii- calculate formation energies of intrinsic defects and non-stoichiometry in BGO; and iv- investigate charge transport mechanisms, comparing them to experimental results obtained via Impedance Spectroscopy. The potential parameter set reproduces the lattice parameters of the 4-3-12 and the 12-1-20 phases to within 0.3% and the available elastic and dielectric constants within reasonable accuracy. The main intrinsic disorder in the 4-3-12 phase is predicted to be the Bi/Ge anti-site. Impedance Spectroscopy measurements for the Bi4Ge3O12 phase were also carried out, and the results indicates that the charge transport mechanism would be related to a process with a distribution in activation energies, with mean value of about (1.41 +/- 0.04) eV. The simulations provided an interpretation of those results picturing a model that explain the origin of such distribution.

Valerio, Mário E. G.; Jackson, Robert A.; Macedo, Zélia S.

2005-01-01

136

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...

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

2006-01-01

137

Agmatine is transported into liver mitochondria by a specific electrophoretic mechanism  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Cravanzola, Carlo; Colombatto, Sebastiano

2006-01-01

138

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

International Nuclear Information System (INIS)

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

139

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

140

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

International Nuclear Information System (INIS)

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

 
 
 
 
141

Transport mechanisms in the outer region of RFX-mod  

International Nuclear Information System (INIS)

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

142

Transport mechanisms in the outer region of RFX-mod  

Science.gov (United States)

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

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

2009-04-01

143

Mechanisms Underlying Methamphetamine-Induced Dopamine Transporter Complex Formation  

Science.gov (United States)

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

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

2009-01-01

144

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

145

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

Science.gov (United States)

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

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

2015-01-01

146

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

Directory of Open Access Journals (Sweden)

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

Ilchenko Svetlana V.

2012-01-01

147

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

CERN Document Server

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

Sonoi, Takafumi

2012-01-01

148

The contribution of low affinity transport mechanisms to serotonin clearance in synaptosomes  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although many studies assert that the serotonin (5-HT) transporter (SERT) is the predominant mechanism controlling extracellular 5-HT concentrations, accumulating evidence suggests that low affinity, high capacity transport mechanisms may contribute more to 5-HT clearance than previously thought. The goal of this study was to quantify the contributions of SERT relative to other mechanisms in clearing extracellular 5-HT concentrations ranging from 50 nM to 1 ?M in synaptosomes prepared from w...

Hagan, Catherine E.; Schenk, James O.; Neumaier, John F.

2011-01-01

149

Modelization of the Thermo-Mechanical Structure of the LHC Main Dipole and Influence on Field Quality  

CERN Document Server

The mechanical structure of the main LHC dipole is analysed. A finite element model is used to estimate the loads and the deformations at cryogenic temperature. The correct setting of the model parameters is crucial to obtain a reliable model to forecast the influence of design and tolerances on field quality. We discuss how the prestress loss from room to cryogenic temperature experimentally observed in the prototypes can be predicted using the finite element model. An estimate of the influence on field quality of deformations and tolerances due to manufacturing is given.

Ferracin, P; Todesco, Ezio; Tropea, P; Vanenkov, I

2000-01-01

150

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

International Nuclear Information System (INIS)

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

151

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

International Nuclear Information System (INIS)

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

152

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2014-01-01

153

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.

154

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

155

Mechanisms of anion conduction by coupled glutamate transporters.  

Science.gov (United States)

Excitatory amino acid transporters (EAATs) are essential for terminating glutamatergic synaptic transmission. They are not only coupled glutamate/Na(+)/H(+)/K(+) transporters but also function as anion-selective channels. EAAT anion channels regulate neuronal excitability, and gain-of-function mutations in these proteins result in ataxia and epilepsy. We have combined molecular dynamics simulations with fluorescence spectroscopy of the prokaryotic homolog GltPh and patch-clamp recordings of mammalian EAATs to determine how these transporters conduct anions. Whereas outward- and inward-facing GltPh conformations are nonconductive, lateral movement of the glutamate transport domain from intermediate transporter conformations results in formation of an anion-selective conduction pathway. Fluorescence quenching of inserted tryptophan residues indicated the entry of anions into this pathway, and mutations of homologous pore-forming residues had analogous effects on GltPh simulations and EAAT2/EAAT4 measurements of single-channel currents and anion/cation selectivities. These findings provide a mechanistic framework of how neurotransmitter transporters can operate as anion-selective and ligand-gated ion channels. PMID:25635461

Machtens, Jan-Philipp; Kortzak, Daniel; Lansche, Christine; Leinenweber, Ariane; Kilian, Petra; Begemann, Birgit; Zachariae, Ulrich; Ewers, David; de Groot, Bert L; Briones, Rodolfo; Fahlke, Christoph

2015-01-29

156

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.

157

Method of nuclear reaction product transport by aerosol gas flow. Main features of the method of nuclear reaction product transport by a gas jet  

International Nuclear Information System (INIS)

Review of papers devoted to investigations of a method for nuclear reaction product transport from their formation place (accelerator target chamber) to detection systems is given. The method is based on the fact, that recoil atoms from the target material are slowed-down in gas medium, captured by aerosol particles, presenting in the gas, and move together with gas flow from slowing-down volume to the detection place. Relations, which describe particle transport along capacity, precipitation of aerosol particles in the capillary, absorption of recoil atoms on aerozols in thermolizing volume, time of recoil atom transport by gas flow, are presented. It is shown, that gas transport systems, which operate at low temperatures, may transport recoil atoms at several meters with good effectiveness

158

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2009-01-01

159

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

160

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

 
 
 
 
161

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.

162

Electron transport mechanisms in thin boron-doped diamond films  

International Nuclear Information System (INIS)

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

163

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

164

Motor Coordination Via Tug-Of-War Mechanism Drives Bidirectional Vesicle Transport  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The microtubule motors kinesin and dynein function collectively to drive vesicular transport. High resolution tracking of vesicle motility in the cell indicates that transport is often bidirectional, characterized by frequent directional changes. However, the mechanisms coordinating the collective activities of oppositely-oriented motors bound to the same cargo are not well understood. To examine motor coordination, we purified neuronal transport vesicles and analyzed their motility using aut...

Hendricks, Adam G.; Perlson, Eran; Ross, Jennifer L.; Schroeder, Harry W.; Tokito, Mariko; Holzbaur, Erika L. F.

2010-01-01

165

On the mechanism of fluid transport across corneal endothelium and epithelia in general.  

Science.gov (United States)

The mechanism by which fluid is transported across epithelial layers is still unclear. The prevalent idea is that fluid traverses these layers transcellularly, driven by local osmotic gradients secondary to electrolyte transport and utilizing the high osmotic permeability of aquaporins. However, recent findings that some aquaporin knockout mice epithelia transport fluid sow doubts on local osmosis. This review discusses recent evidence in corneal endothelium that points instead to electro-osmosis as the mechanism underlying fluid transport. In this concept, a local recirculating electrical current would result in electro-osmotic coupling at the level of the intercellular junctions, dragging fluid via the paracellular route. The text also mentions possible mechanisms for apical bicarbonate exit from endothelial cells, and discusses whether electro-osmosis could be a general mechanism. PMID:14598383

Fischbarg, Jorge

2003-11-01

166

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-07-15

167

The GMPLS-based span-ring transport mechanism for multiple resilient packet ring  

Science.gov (United States)

This paper presents a span-ring transport mechanism for multiple resilient packet rings based on GMPLS. The simulation result shows that this approach can be used to achieve transparent and reliable transportation of the span-ring services in the RPR multi-ring network.

Wu, Xiangjun; Yang, Zongkai; Zhang, Jijun

2007-11-01

168

Cellular mechanisms of Cl? transport in trout gill mitochondrion-rich cells  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have studied Cl? transport mechanisms in freshwater rainbow trout gill mitochondrion-rich (MR) cells using intracellular pH (pHi) imaging. Scanning electron microscopy demonstrated maintenance of cellular polarity in isolated MR cells. MR cell subtypes were identified by Na+ introduction to the bath, and Cl? transport mechanisms were subsequently examined. Cl?-free exposure resulted in an alkalinization of pHi in both MR cell subtypes, which was dependent on HCO3? in the bath and i...

Parks, Scott K.; Tresguerres, Martin; Goss, Greg G.

2009-01-01

169

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

170

STUDY OF THE STABILIZATION TO THE NANOMETER LEVEL OF MECHANICAL VIBRATIONS OF THE CLIC MAIN BEAM QUADRUPOLES  

CERN Document Server

To reach the design luminosity of CLIC, the movements of the quadrupoles should be limited to the nanometre level in order to limit the beam size and emittance growth. Below 1 Hz, the movements of the main beam quadrupoles will be corrected by a beambased feedback. But above 1 Hz, the quadrupoles should be mechanically stabilized. A collaboration effort is ongoing between several institutes to study the feasibility of the “nanostabilization” of the CLIC quadrupoles. The study described in this paper covers the characterization of independent measuring techniques including optical methods to detect nanometre sized displacements and analyze the vibrations. Actuators and feedback algorithms for sub-nanometre movements of magnets with a mass of more than 400 kg are being developed and tested. Input is given to the design of the quadrupole magnets, the supports and alignment system in order to limit the amplification of the vibration sources at resonant frequencies. A full scale mock-up integrating all these f...

Artoos, K; Collette, C; Guinchard, M; Hauviller, C; Lackner, F; Pfingstner, J; Schmickler, H; Sylte, M; Fontaine, M; Coe, P; Urner, D; Bolzon, B; Brunetti, L; Deleglise, G; Geffroy, N; Jeremie, A

2009-01-01

171

Study of the Stabilization to the Nanometre Level of Mechanical Vibrations of the CLIC Main Beam Quadrupoles  

CERN Document Server

To reach the design luminosity of CLIC, the movements of the quadrupoles should be limited to the nanometre level in order to limit the beam size and emittance growth. Below 1 Hz, the movements of the main beam quadrupoles will be corrected by a beambased feedback. But above 1 Hz, the quadrupoles should be mechanically stabilized. A collaboration effort is ongoing between several institutes to study the feasibility of the “nanostabilization” of the CLIC quadrupoles. The study described in this paper covers the characterization of independent measuring techniques including optical methods to detect nanometre sized displacements and analyze the vibrations. Actuators and feedback algorithms for sub-nanometre movements of magnets with a mass of more than 400 kg are being developed and tested. Input is given to the design of the quadrupole magnets, the supports and alignment system in order to limit the amplification of the vibration sources at resonant frequencies. A full scale mock-up integrating all these f...

Artoos, K; Collette, C; Guinchard, M; Hauviller, C; Lackner, F; Pfingstner, J; Schmickler, H; Sylte, M; Fontaine, M; Coe, P; Urner, D; Bolzon, B; Brunetti, L; Deleglise, G; Geffroy, N; Jeremie, A

2010-01-01

172

Formation of artificial granules for proving gelation as the main mechanism of aerobic granulation in biological wastewater treatment.  

Science.gov (United States)

In this study, gelation-facilitated biofilm formation as a new mechanism is proposed for the phenomenon of aerobic granulation in biological wastewater treatment. To obtain an experimental proof for the gelation-based theory, the granulation process was simulated in a chemical system using latex particles for bacterial cells and organic polymers (alginate and peptone) for extracellular polymeric substances (EPS) in a solution with the addition of cations (Ca²?, Mg²? and Fe³?). The results showed that at a low alginate content (70 mg g?¹ mixed liquid suspended solids (MLSS)) flocculation was observed in the suspension with loose flocs. At a higher alginate content (180 mg g?¹ MLSS), together with discharge of small flocs, formation of artificial gel granules was successfully achieved leading to granulation. The artificial granules show a morphological property similar to that of actual microbial granules. However, if the protein content increased, granulation became difficult with little gel formation. The experimental work demonstrates the importance of the bonding interactions between EPS functional groups and cations in gel formation and granulation. The laboratory results on the formation of artificial granules provide a sound proof for the theory of gelation-facilitated biofilm formation as the main mechanism for aerobic granulation in sludge suspensions. PMID:25098887

Li, Yun; Yang, Shu-Fang; Zhang, Jian-Jun; Li, Xiao-Yan

2014-01-01

173

Mechanisms Underlying Methamphetamine-Induced Dopamine Transporter Complex Formation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Repeated, high-dose methamphetamine (METH) administrations cause persistent dopaminergic deficits in rodents, nonhuman primates, and humans. In rats, this treatment also causes the formation of high-molecular mass (greater than approximately 120 kDa) dopamine transporter (DAT)-associated complexes, the loss of DAT monomer immunoreactivity, and a decrease in DAT function, as assessed in striatal synaptosomes prepared 24 h after METH treatment. The present study extends ...

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

2009-01-01

174

A molecular mechanism for aberrant CFTR-dependent HCO(3)(-) transport in cystic fibrosis.  

Science.gov (United States)

Aberrant HCO(3)(-) transport is a hallmark of cystic fibrosis (CF) and is associated with aberrant Cl(-)-dependent HCO(3)(-) transport by the cystic fibrosis transmembrane conductance regulator (CFTR). We show here that HCO(3)(-) current by CFTR cannot account for CFTR-activated HCO(3)(-) transport and that CFTR does not activate AE1-AE4. In contrast, CFTR markedly activates Cl(-) and OH(-)/HCO(3)(-) transport by members of the SLC26 family DRA, SLC26A6 and pendrin. Most notably, the SLC26s are electrogenic transporters with isoform-specific stoichiometries. DRA activity occurred at a Cl(-)/HCO(3)(-) ratio > or =2. SLC26A6 activity is voltage regulated and occurred at HCO(3)(-)/Cl(-) > or =2. The physiological significance of these findings is demonstrated by interaction of CFTR and DRA in the mouse pancreas and an altered activation of DRA by the R117H and G551D mutants of CFTR. These findings provide a molecular mechanism for epithelial HCO(3)(-) transport (one SLC26 transporter-electrogenic transport; two SLC26 transporters with opposite stoichiometry in the same membrane domain-electroneutral transport), the CF-associated aberrant HCO(3)(-) transport, and reveal a new function of CFTR with clinical implications for CF and congenital chloride diarrhea. PMID:12411484

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

2002-11-01

175

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

176

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

Science.gov (United States)

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

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

2014-01-01

177

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

International Nuclear Information System (INIS)

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

178

Mechanical properties used for the qualification of transport casks  

International Nuclear Information System (INIS)

The qualification process that should be sufficient for qualification of a specific cask (material/geometry combination) has been examined. The prototype cask should be tested to determine its overall variation in microstructure, chemistry, and mechanical properties. This prototype may also be subjected to 'proof testing' to demonstrate the validity of the design analysis (including the mechanical properties used in the analysis). The complete mechanical property mapping does not necessarily have to precede the proof testing (i.e., portions of the cask which experience only low (elastic) loads during the drop test are suitable for mechanical test specimens). The behavior of the prototype cask and the production casks are linked by assuring that each cask possesses at least the minimum level of one or more critical mechanical properties. This may be done by measuring the properties of interest directly, or by relying on a secondary measurement (such as subsize mechanical test results or microstructure/compositional measurements) which has been statistically correlated to the critical properties. The database required to show the correlation between the secondary measurement and the valid design property may be established by tests on the material from the prototype cask. The production controls must be demonstrated as being adequate to assure that a uniform product is produced. The testing of coring (or test block or prolongation) samples can only be viewed as providing a valid link to the benchmark results provided by the prototype cask if the process used to create follow-on casks remains essentially similar. The MOSAIK Test Program has demonstrated the qualification method through the benchmarking stage. The program did not establish for qualifying serial production casks through, for example, a correlation between small specimen parameters and valid design fracture toughness properties. Such a correlation would require additional experimental work. (J.P.N.)

179

Turbulence elasticity—A new mechanism for transport barrier dynamics  

International Nuclear Information System (INIS)

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

180

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

 
 
 
 
181

Turbulence elasticity—A new mechanism for transport barrier dynamics  

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-09-15

182

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

Science.gov (United States)

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

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

2013-03-01

183

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

Directory of Open Access Journals (Sweden)

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

James Baker-Jarvis

2009-11-01

184

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

185

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2013-01-01

186

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

International Nuclear Information System (INIS)

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

187

Mechanism of P-type ATPase-catalyzed phospholipid transport : tackling the giant substrate problem  

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Mechanism of P-type ATPase-catalyzed phospholipid transport: tackling the giant substrate problem After the initial discovery of an ATP-driven transporter of aminophospholipids as a principal generator of phospholipid asymmetry in the erythrocyte membrane in 1984, it took another 25 years before flippase activity was demonstrated directly by functional reconstitution of the purified enzyme. Surprisingly, the enzymes that catalyze flippase activity belong to the P-type ATPase superfamily of ca...

Puts, C. F.

2010-01-01

188

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1994-01-01

189

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

The esophageal submucosal glands (SMG) secrete HCO3? and mucus into the esophageal lumen, where they contribute to acid clearance and epithelial protection. This study characterized the ion transport mechanisms linked to HCO3? secretion in SMG. We localized ion transporters using immunofluorescence, and we examined their expression by RT-PCR and in situ hybridization. We measured HCO3? secretion by using pH stat and the isolated perfused esophagus. Using double labeling with Na+-K+-ATPa...

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

2011-01-01

190

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

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

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

2001-01-01

191

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

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In this work we monitor the catalytic mechanism of P-glycoprotein (Pgp) using single-molecule fluorescence resonance energy transfer (FRET). Pgp, a member of the ATP binding cassette family of transport proteins, is found in the plasma membrane of animal cells where it is involved in the ATP hydrolysis driven export of hydrophobic molecules. When expressed in the plasma membrane of cancer cells, the transport activity of Pgp can lead to the failure of chemotherapy by excludi...

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

2011-01-01

192

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

International Nuclear Information System (INIS)

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

193

On the mechanism of activated transport in glassy liquids.  

Science.gov (United States)

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

Lubchenko, Vassiliy; Rabochiy, Pyotr

2014-11-26

194

Exploring cargo transport mechanics in the type IV secretion systems.  

Science.gov (United States)

Type IV secretion systems (T4SSs) are used by various bacteria to deliver protein and DNA molecules to a wide range of target cells. These include systems that are directly involved in pathogenesis, such as the secretion of pertussis toxin by Bordetella pertussis into human cells and the delivery of single-stranded DNA (ssDNA) into plants by Agrobacterium. These complex systems are composed of proteins that span the bacterial cytoplasm. The Agrobacterium T4SS is composed of 12 virulence proteins and delivers its transferred ssDNA and several virulence protein substrates to a variety of eukaryotic cells. Recent studies on the Agrobacterium T4SS have revealed new information on the localization and structure of its proteins in the bacteria, the biochemical properties of its transport signal, the route of a DNA substrate through the secretion system, and the initial point of contact of the system with its host. These findings have expanded our knowledge and understanding of the still mostly obscure structure and function of the T4SSs. PMID:15923116

Li, Jianxiong; Wolf, Sharon G; Elbaum, Michael; Tzfira, Tzvi

2005-07-01

195

The direction of water transport on Mars: A possible pumping mechanism  

Science.gov (United States)

It is suggested that an atmospheric pumping mechanism might be at work in which water is preferentially transported into the north by a mass outflow wind (due to sublimation from polar cap) that is stronger during southern spring than it is during northern spring. The mechanism is provided by the asymmetric seasonal temperature distribution produced by the eccentric martial orbit and by the associated seasonal asymmetry in the carbon dioxide cycle. The alternating condensation and sublimation of CO2 at the poles produces condensation winds which, in turn, contribute to the meridional transport of water vapor.

James, P. B.

1987-01-01

196

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

International Nuclear Information System (INIS)

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

197

Sequential mechanism of electron transport in the resonant tunneling diode with thick barriers  

International Nuclear Information System (INIS)

A frequency-dependent impedance analysis (0.1-50 GHz) of an InGaAs/InAlAs-based resonant tunneling diode with a 5-nm-wide well and 5-nm-thick barriers showed that the transport mechanism in such a diode is mostly sequential, rather than coherent, which is consistent with estimates. The possibility of determining the coherent and sequential mechanism fractions in the electron transport through the resonant tunneling diode by its frequency dependence on the impedance is discussed

198

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1989-01-01

199

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

200

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)

 
 
 
 
201

Mechanical damage and transport properties of synthetic argillaceous rocks  

International Nuclear Information System (INIS)

The role of mechanical damage on the evolution of permeability was studied on synthetic argillaceous rocks made of sand, cement and clay. An experimental set-up was developed in order to produce synthetic rock samples made of the above mentioned components in fixed proportions. The mixture is introduced in a tubular mould of internal diameter 20 mm. A uniaxial compression of 10 kN is applied on the mixture to allow better grain contacts and to reduce the residual porosity. In a first step the procedure has been validated on a sand-cement mixture. We measured the uniaxial compressive strength as a function of cement content. The results clearly show a non-linear dependence between both parameters. This can be interpreted as a percolation problem in a medium containing two phases: sand grains and cement matrix. In a second step, the same procedure has been applied on a sand-clay mixture. Again the uniaxial compressive strength was measured as a function of clay content. Like for cement, the results show a non-linear dependence which can be explained as a percolation transition. A second experimental set-up was developed in order to measure the gas (N2) permeability of the synthetic samples. A hydrostatic cell (20 MPa) was designed with water as confining fluid. The sample is isolated from the confining pressure fluid by a Viton jacket clamped on the end pieces connected to the pore circuit. The upstream pore pressure circuit contains the pressurized gas bottlcircuit contains the pressurized gas bottle and a pressure transducer, the gas outflow being measured by a volumetric flowmeter in the downstream portion which is kept at atmospheric pressure. Permeability is measured using the stationary flow method. Confining pressure has been kept constant and equal to 3 MPa. Pore pressure is then changed to allow for Forchheimer and Klinkenberg corrections in order to determine the true permeability of the specimen. The procedure has been validated on samples composed of sand and clay pre-compacted at 10 kN. The results show the drastic decrease of permeability (10-12 to 10-15 m2) as clay content is increased from 10 to 40% ) Next we have checked the residual effect of mechanical damage on pre-compacted samples containing sand, cement and clay. Cement proportion has been kept constant and sand and clay content were varied accordingly. The samples were loaded in a uniaxial press up to increasing stress levels, unloaded, and introduced in the hydrostatic cell. Their apparent gas permeability was measured by keeping the pore pressure constant. The preliminary results show that for low clay content a slight permeability decrease precedes a rapid increase (from 3 10-19 to 2.5 10-18 m2 ) as one approaches the peak stress of the deformation curve. This effect of mechanical damage is less pronounced when increasing clay content. (authors)

202

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

203

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

204

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

2012-11-01

205

Mechanisms Underlying Food-Drug Interactions: Inhibition of Intestinal Metabolism and Transport  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Food-drug interaction studies are critical to evaluate appropriate dosing, timing, and formulation of new drug candidates. These interactions often reflect prandial-associated changes in the extent and/or rate of systemic drug exposure. Physiologic and physicochemical mechanisms underlying food effects on drug disposition are well-characterized. However, biochemical mechanisms involving drug metabolizing enzymes and transport proteins remain underexplored. Several plant-derived beverages have...

Won, Christina S.; Oberlies, Nicholas H.; Paine, Mary F.

2012-01-01

206

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

207

Transport mechanism of doxorubicin loaded chitosan based nanogels across intestinal epithelium.  

Science.gov (United States)

Chitosan/carboxymethyl chitosan nanogels (CS/CMCS-NGs) could enhance the oral bioavailability of doxorubicin hydrochloride (DOX). To identify the mechanisms that support this recent observation, different transport pathways of CS/CMCS-NGs through the small intestine were studied in this work. Transcellular mechanisms were investigated in the presence of different inhibitors of protein-mediated endocytosis. A reduction of 52.32±18% of drug transport was found when clathrin-mediated endocytosis was inhibited, which demonstrated that clathrin-mediated endocytosis played an important role in the transcellular transport of DOX:CS/CMCS-NGs. The paracellular transport results showed that CMCS in NGs could produce a transient and reversible enhancement of paracellular permeability by depriving Ca(2+) from adherens junctions, whose efficacy as an absorption enhancer was about 1.7-3.3 folds higher than CS in NGs in GI tract. Finally, in vivo experiment showed that the transport capacity of DOX:CS/CMCS-NGs was significantly inhibited by extra added Ca(2+), which confirmed that the higher capacity to binding Ca(2+) of CS/CMCS-NGs was beneficial for transport of DOX. PMID:24316340

Feng, Chao; Sun, Guohui; Wang, Zhiguo; Cheng, Xiaojie; Park, Hyunjin; Cha, Dongsu; Kong, Ming; Chen, Xiguang

2014-05-01

208

Pore scale mechanisms for enhanced vapor transport through partially saturated porous media  

Science.gov (United States)

Recent theoretical and experimental studies of vapor transport through porous media question the existence and significance of vapor transport enhancement mechanisms postulated by Philip and de Vries. Several enhancement mechanisms were proposed to rectify shortcomings of continuum models and to reconcile discrepancies between predicted and observed vapor fluxes. The absence of direct experimental and theoretical confirmation of these commonly invoked pore scale mechanisms prompted alternate explanations considering the (often neglected) role of transport via capillary connected pathways. The objective of this work was to quantify the specific roles of liquid bridges and of local thermal and capillary gradients on vapor transport at the pore scale. We considered a mechanistic pore scale model of evaporation and condensation dynamics as a building block for quantifying vapor diffusion through partially saturated porous media. Simulations of vapor diffusion in the presence of isolated liquid phase bridges reveal that the so-called enhanced vapor diffusion under isothermal conditions reflects a reduced gaseous diffusion path length. The presence of a thermal gradient may augment or hinder this effect depending on the direction of thermal relative to capillary gradients. As liquid phase saturation increases, capillary transport becomes significant and pore scale vapor enhancement is limited to low water contents as postulated by Philip and deVries. Calculations show that with assistance of a mild thermal gradient water vapor flux could be doubled relative to diffusion of an inert gas through the same system.

Shahraeeni, Ebrahim; Or, Dani

2012-05-01

209

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

Science.gov (United States)

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

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

2012-12-01

210

Growth mechanism of ZnSe single crystal by chemical vapour transport method  

International Nuclear Information System (INIS)

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

211

The transport mechanisms of polymer nanoparticles in Caco-2 epithelial cells.  

Science.gov (United States)

As the primary physiological barrier, intestinal epithelial cells regulate the transportation of oral therapeutic agents including nanomedicines which significantly improves the bioavailability of many drugs. However, currently there seems in the lack of comprehensive understanding on nanoparticle transport in intestinal epithelial cells as well as the mechanisms related. So, in an attempt to illustrate the profile of nanoparticle transport in intestinal epithelial cells, Caco-2 cells and polymer nanoparticles (PNs) were used as the models to explore the whole transport process including endocytosis, intracellular trafficking, exocytosis and transcytosis. Via various techniques, the transport pathways of PNs in Caco-2 cells and their mechanisms were clarified. Firstly, the transport was characterized by its non-specificity. The co-mediation of clathrin, lipid raft/caveolae and macropinocytosis as well as the co-involvement of different proteins like actins, protein tyrosine kinase (PTK) and cyclooxygenase (COX) were found in the endocytosis of PNs. The endocytosed PNs could transport to apical early endosome (AEE) and then from AEE to lysososmes via AEE/late endosome (LE)/lysosome pathway, as well as to recycling endosome compartment (REC) or endoplasmic reticulum (ER) through AEE/REC and AEE/ER pathways, respectively. Both ER/Golgi and Golgi/REC/plasma membrane (PM) pathways were involved in the exocytosis of PNs. The transcytosis of PNs across the cell monolayer was very low with a ratio less than 0.5%, due to complicated reasons. Secondly, the transport was evidenced by its partial energy-dependency. Beside the energy-dependent transport mediated by some proteins, quantitative study demonstrated the obvious internalization as well as surface binding of PNs at both 37 °C and 4 °C, but significantly higher at 37 °C. Interestingly, the consistency between surface binding and internalization at each temperature was found, suggesting that cell binding was the precondition and key step for the following endocytosis. The involvement of both energy dependent and independent mechanism was also observed in the exocytosis and transcytosis process of PNs. Finally, there were opposite mechanisms found between the exocytosis and endocytosis of PNs, including the regulation role of lipid raft/caveolae, COX and Golgi complex, which also contributed to the fact of "easy entry and hard across" for PNs. Overall, this study depicts a clear picture of nanoparticle transport in Caco-2 epithelial cells characterized by non-specificity, partial energy-dependency and low transcytosis. PMID:23694903

He, Bing; Lin, Ping; Jia, Zengrong; Du, Wenwen; Qu, Wei; Yuan, Lan; Dai, Wenbing; Zhang, Hua; Wang, Xueqing; Wang, Jiancheng; Zhang, Xuan; Zhang, Qiang

2013-08-01

212

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

Science.gov (United States)

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

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

2014-06-01

213

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

International Nuclear Information System (INIS)

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

214

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

215

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.

I J van Rooyen; J H Neethling; J A A Engelbrecht; P M van Rooyen; G Strydom

2012-10-01

216

Structural insights into the mechanisms of Mg2+ uptake, transport, and gating by CorA.  

Science.gov (United States)

Despite the importance of Mg(2+) for numerous cellular activities, the mechanisms underlying its import and homeostasis are poorly understood. The CorA family is ubiquitous and is primarily responsible for Mg(2+) transport. However, the key questions-such as, the ion selectivity, the transport pathway, and the gating mechanism-have remained unanswered for this protein family. We present a 3.2 Å resolution structure of the archaeal CorA from Methanocaldococcus jannaschii, which is a unique complete structure of a CorA protein and reveals the organization of the selectivity filter, which is composed of the signature motif of this family. The structure reveals that polar residues facing the channel coordinate a partially hydrated Mg(2+) during the transport. Based on these findings, we propose a unique gating mechanism involving a helical turn upon the binding of Mg(2+) to the regulatory intracellular binding sites, and thus converting a polar ion passage into a narrow hydrophobic pore. Because the amino acids involved in the uptake, transport, and gating are all conserved within the entire CorA family, we believe this mechanism is general for the whole family including the eukaryotic homologs. PMID:23091000

Guskov, Albert; Nordin, Nurhuda; Reynaud, Aline; Engman, Henrik; Lundbäck, Anna-Karin; Jong, Agnes Jin Oi; Cornvik, Tobias; Phua, Terri; Eshaghi, Said

2012-11-01

217

Tubulin transport by IFT is upregulated during ciliary growth by a cilium-autonomous mechanism.  

Science.gov (United States)

The assembly of the axoneme, the structural scaffold of cilia and flagella, requires translocation of a vast quantity of tubulin into the growing cilium, but the mechanisms that regulate the targeting, quantity, and timing of tubulin transport are largely unknown. In Chlamydomonas, GFP-tagged ?-tubulin enters cilia as an intraflagellar transport (IFT) cargo and by diffusion. IFT-based transport of GFP-tubulin is elevated in growing cilia and IFT trains carry more tubulin. Cells possessing both nongrowing and growing cilia selectively target GFP-tubulin into the latter. The preferential delivery of tubulin boosts the concentration of soluble tubulin in the matrix of growing versus steady-state cilia. Cilia length mutants show abnormal kinetics of tubulin transport. We propose that cells regulate the extent of occupancy of IFT trains by tubulin cargoes. During ciliary growth, IFT concentrates soluble tubulin in cilia and thereby promotes elongation of the axonemal microtubules. PMID:25583998

Craft, Julie M; Harris, J Aaron; Hyman, Sebastian; Kner, Peter; Lechtreck, Karl F

2015-01-19

218

A fully resolved active musculo-mechanical model for esophageal transport  

CERN Document Server

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

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

2015-01-01

219

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

220

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 CSFstudy 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

 
 
 
 
221

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

M.I. Mishchenko

2012-08-01

222

ASSESSMENT OF THE LATERAL DYNAMICS AND THE MECHANISMS OF TRANSPORT IN THE ESTUARY OF CAMBORIÚ RIVER AVALIAÇÃO DA DINÂMICA LATERAL E DOS MECANISMOS DE TRANSPORTE NO ESTUÁRIO DO RIO CAMBORIÚ  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The main objective of this work is evaluate the structure lateral hydrodynamics of the estuary of the Camboriú River, in periods of neap and spring tide, as well as defining the main mechanisms of operating transports in this estuary. In the two carried campaigns, data of speed current and salinity had been acquired to each hour during two complete tide’s cycles (~25 hours). The vertical profiles had been gotten in three stations in the transversal section of the estuary. In the conditions...

Franklin-silva, L. A.; Schettini, C. A.

2003-01-01

223

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

224

A chemical genetic screen for modulators of exocytic transport identifies inhibitors of a transport mechanism linked to GTR2 function.  

Science.gov (United States)

Membrane and protein traffic to the cell surface is mediated by partially redundant pathways that are difficult to perturb in ways that yield a strong phenotype. Such robustness is expected in a fine-tuned process, regulated by environmental cues, that is required for controlled cell surface growth and cell proliferation. Synthetic genetic interaction screens are especially valuable for investigating complex processes involving partially redundant pathways or mechanisms. In a previous study, we used a triple-synthetic-lethal yeast mutant screen to identify a novel component of the late exocytic transport machinery, Avl9. In a chemical-genetic version of the successful mutant screen, we have now identified small molecules that cause a rapid (within 15 min) accumulation of secretory cargo and abnormal Golgi compartment-like membranes at low concentration (pathway that is perturbed by the compounds. Because avl9Delta and gtr mutants share some phenotypes, our results indicate that the small molecules identified by our chemical-genetic strategy are promising tools for understanding Avl9 function and the mechanisms that control late exocytic transport. PMID:19897736

Zhang, Lisha; Huang, Min; Harsay, Edina

2010-01-01

225

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

International Nuclear Information System (INIS)

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

226

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

Energy Technology Data Exchange (ETDEWEB)

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

Kim, Y. H.; Park, B. S.; Jung, J. H.; Yoon, J. S.; Kim, H. D.; Hwang, J. S.; Yoon, K. H. [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2008-08-15

227

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

International Nuclear Information System (INIS)

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

228

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

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

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

2007-01-01

229

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

230

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

231

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

Directory of Open Access Journals (Sweden)

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

L. Slater

1997-01-01

232

Study of hydrological mechanisms for solutes transport in shallow aquifer of watershed with crystalline bedrock  

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In catchments underlaid by shallow hard rock with low permeability, shallow groundwater develops along the hillslopes and plays a major role on discharge control and on solute transport. This groundwater, characterized by large seasonal variations of the water table level, develops in an aquifer mainly constituted by weathered rock and unconsolidated materials whose hydrodynamic properties remain little studied. Understanding the hydrological and hydrochemical functioning of these systems and...

Rouxel, Matthieu

2010-01-01

233

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

Science.gov (United States)

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

Liang, Qing

234

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

Directory of Open Access Journals (Sweden)

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

Nakonechnaya Darina Yu.

2013-05-01

235

A study of the mechanical characteristics of the flywheel as the main component of an inertial mechanical energy storage system on board a space vehicle  

Science.gov (United States)

The mechanical properties of a composite flywheel with compliant spokes are briefly examined as part of research concerned with inertial mechanical energy storage devices for space applications. Results of an experimental study of the stiffness coefficients of the spokes in the radial direction and resonance frequencies of the flywheel provide the basis for formulating material selection criteria and developing technology for fabricating flywheel components.

Golovkin, G. S.; Stepanychev, E. I.; Ruchinskii, V. S.

236

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

Science.gov (United States)

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

Appold, Martin; Joshi, Ajit

2014-05-01

237

Mechanical evaluation of a natural UF6 transport container at high temperature  

International Nuclear Information System (INIS)

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

238

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

International Nuclear Information System (INIS)

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

239

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

240

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

 
 
 
 
241

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

242

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

CERN Document Server

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

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

2011-01-01

243

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

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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 con...

Gusseinov Gassan Ahmad; Bagirov Sahib Abbas

2014-01-01

244

Mechanisms of Laser-Induced Dissection and Transport of Histologic Specimens  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2007-01-01

245

Comparative study of key exchange and authentication methods in application, transport and network level security mechanisms  

Science.gov (United States)

The key-exchange and authentication are two crucial elements of any network security mechanism. IPsec, SSL/TLS, PGP and S/MIME are well-known security approaches in providing security service to network, transport and application layers; these protocols use different methods (based on their requirements) to establish keying materials and authenticates key-negotiation and participated parties. This paper studies and compares the authenticated key negotiation methods in mentioned protocols.

Fathirad, Iraj; Devlin, John; Jiang, Frank

2012-09-01

246

Structural and mechanical feasibility study of a variable camber wing (VCW) for a transport aircraft  

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Aerodynamic investigations have shown' that variable camber wings (VCW) for transport aircraft have considerable potential in terms of improving aircraft performance and enhancing their operational flexibility. In order to justify these benefits it is essential that the camber varying system is structurally and mechanically feasible. This research examined the feasibility of providing variable camber to two supercritical aerofoil sections of different'characteristics. The uniqu...

Macci, S. H. M.

1992-01-01

247

Transport mechanisms for cationic drugs in the hepato-biliary system. A pharmacokinetic and cellbiological study.  

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The liver is an important organ for the clearance of many drugs from the blood stream and thus contributes to the termination of their pharmacological effect. Many drugs in current clinical practice are compounds with one or more quaternary or tertiary ammonium functions, that occur in cationic form. The studies reported in this thesis deal with the hepatic transport mechanisms for organic cations, using the rat as the experimental animal. ... Zie: Summary

Mol, Wilhelmus Everardus Maria

1988-01-01

248

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

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

Myers, Stephen A.; Alex Nield; Mark Myers

2012-01-01

249

Oxygen reduction and transportation mechanisms in solid oxide fuel cell cathodes  

Energy Technology Data Exchange (ETDEWEB)

In recent years, various models have been developed for describing the reaction mechanisms in solid oxide fuel cell (SOFC) especially for the cathode electrode. However, many fundamental issues regarding the transport of oxygen and electrode kinetics have not been fully understood. This review tried to summarize the present status of the SOFC cathode modeling efforts, and associated experimental approaches on this topic. In addition, unsolved problems and possible future research directions for SOFC cathode kinetics had been discussed. (author)

Li, Yihong; Liu, Xingbo [National Energy Technology Laboratory, Morgantown, WV 26507 (United States); Mechanical and Aerospace Engineering Department, West Virginia University, Morgantown, WV 26506 (United States); Gemmen, Randall [National Energy Technology Laboratory, Morgantown, WV 26507 (United States)

2010-06-01

250

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1995-01-01

251

Analysis of alternative tendering mechanisms for transportation Public-Private Partnerships  

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This paper describes a theoretical model based primarily on transaction costs, for comparing the various tendering mechanisms used for transportation Public-Private Partnership (PPP) projects. In particular, the model contrasts negotiated procedures with the open procedure, as defined by the current European Union legislation on public tendering. The model includes both ex ante transaction costs (borne during the tendering stage) and ex post transaction costs (such as enforcement costs, re-ne...

Sanchez Solin?o, Antonio; Gago Santos, Pilar

2013-01-01

252

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1984-01-01

253

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

Science.gov (United States)

A detailed theoretical investigation of the charge transport mechanism in poly(4-vinyl-imidazole) (P4VI), the parent polymer of a series of N-heterocyclic-based membranes used as an electrolyte in proton exchange membrane fuel cells, is presented. In particular, Density Functional Theory (DFT) results obtained for small model systems (protonated imidazole dimers and trimers) suggest that the commonly accepted conduction mechanism, based on a sequential proton transfer between imidazole moieties, could be impeded by the geometrical constraints imposed by the polymeric backbone. Indeed only one kind of proton transfer reaction is energetically allowed between adjacent imidazoles, so that a rotation of the protonated imidazole is required for a second proton transfer. Molecular dynamics simulations on a larger model (15 oligomers with an excess proton) show that the rotation of the imidazole carrying the excess proton is a soft large amplitude motion. These results allow us to propose a new proton conduction mechanism in P4VI, where a frustrated rotation of the protonated imidazole before each proton transfer reaction represents the rate-limiting step. Furthermore, in contrast with the Grotthuss proton transport mechanism in water, our results indicate that here it is the same proton which could be successively transferred. From a chemical point of view, these new insights into the mechanism are relevant for a rational design of modified azole-based systems for Proton Exchange Membrane Fuel Cells. PMID:22706331

Mangiatordi, Giuseppe Felice; Butera, Valeria; Russo, Nino; Laage, Damien; Adamo, Carlo

2012-08-21

254

Theoretical studies on the transport mechanism of 5-fluorouracil through cyclic peptide based nanotubes.  

Science.gov (United States)

Cyclic peptide nanotubes (CPNTs) formed by the self-assembly of cyclic peptides (CPs) with an even number of alternate l/d amino acids are typically used in the field of the transport of ions and drug molecules across the lipid bilayer. This study investigates the transport mechanism of the antitumor drug molecule, 5-fluorouracil (5FU), through the CPNT using classical and steered molecular dynamics simulations combined with umbrella sampling. During the transport of 5FU through the CPNT, 5FU is partially desolvated because the lumen of the CPNT is too small to allow for water molecules solvating it. 5FU forms H-bonding interactions with the backbones of the CPNT and at the same time, also forms hydrophobic contacts with the backbone C? and C atoms of the CPNT. The cooperative breaking of the H-bond and hydrophobic interactions between the CPNT and 5FU increases the pulling force to transport the 5FU from the mid-C? region to the C? one. The calculated free energies of binding reveal that the energy barriers for the transport of 5FU are ?-6.0 and ?-2.0 kcal mol(-1) in the mid-C? and C? plane regions, respectively. PMID:23229174

Vijayaraj, Ramadoss; Van Damme, Sofie; Bultinck, Patrick; Subramanian, Venkatesan

2013-01-28

255

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

256

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

257

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

International Nuclear Information System (INIS)

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

258

Slip rate estimation along the western segment of the Main Marmara Fault over the last 405-490 ka by correlating mass transport deposits  

Science.gov (United States)

3-D seismic data acquired in the Sea of Marmara on the Western High, along the northwestern branch of the North Anatolian Fault (also known as the Main Marmara Fault), shed new light on the evolution of the deformation over the last 500-600 ka. Sedimentary sequences in ponded basins are correlated with glacioeustatic cycles and transitions between marine and low sea/lake environments in the Sea of Marmara. In the 3 × 11 km2 of the 3-D seismic survey, deformation over the last 405-490 ka is localized along the main fault branch and north of it, where N130°-N140° trending normal faults and N40°-N50° folding accommodated strike-slip deformation associated with active argillokinesis. There is some evidence that deformation was more distributed further back in the past, at least over the depth range (survey. A N110° basin and buried ridge system were eventually cut by the presently active fault. The southern part of the basin was then uplifted, while the northern part was folded but continued to subside along the fault. A mass transport deposits complex dated between 405-490 ka shows a lateral displacement of 7.7 ± 0.3 km, corresponding to an estimated slip rate of 15.1-19.7 mm/a. We conclude that this strand of the Main Marmara Fault on the Western High has taken up most of the strike slip motion between the Anatolian and Eurasian plates over the last 405 ka at least.

Grall, C.; Henry, P.; Thomas, Y.; Westbrook, G. K.; ?a?atay, M. N.; Marsset, B.; Saritas, H.; ?ifçi, G.; Géli, L.

2013-12-01

259

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

Science.gov (United States)

We have studied photodarkening in ytterbium-doped fibre preforms with an aluminosilicate glass core. Analysis of their absorption and luminescence spectra indicates the formation of stable Yb2+ ions in the glass network under IR laser pumping at a wavelength ? = 915 nm and under UV irradiation with an excimer laser (? = 193 nm). We have performed comparative studies of the luminescence spectra of the preforms and crystals under excitation at a wavelength of 193 nm. The mechanism behind the formation of Yb2+ ions and aluminium – oxygen hole centres (Al-OHCs), common to ytterbium-doped YAG crystals and aluminosilicate glass, has been identified: photoinduced Yb3+ charge-transfer state excitation.

Bobkov, K. K.; Rybaltovsky, A. A.; Vel'miskin, V. V.; Likhachev, M. E.; Bubnov, M. M.; Dianov, E. M.; Umnikov, A. A.; Gur'yanov, A. N.; Vechkanov, N. N.; Shestakova, I. A.

2014-12-01

260

Coupled mechanical and chemo-transport model for the simulation of cementitious materials subjected to external sulfate attack  

International Nuclear Information System (INIS)

We propose in this study to develop a chemo-transport-mechanical model for the simulation of external sulfate attack in cementitious materials. This degradation mainly consists in the hydrate decalcification/dissolution due to leaching, and in the reaction between the sulfate ions migrating within the material and mono-sulfate initially present to precipitate into ettringite. It may generate macroscopic expansions leading to severe microcracking. The key point in this study is the use of the integration numerical platform ALLIANCES which couples a code solving the chemical equations, the diffusion of ionic species into the porosity and the mechanical problem. The crystallization pressures resulting from the interaction between growing mono-sulfate crystals and the surrounding C-S-H matrix are assumed to cause the observed macroscopic swelling. A macroscopic bulk strain tensor calculated from the volume of formed ettringite is introduced for directly reproducing these expansions. Explicit up-scaling techniques applied on a simplified representation of the materials allow estimating both mechanical and diffusive properties of the evolving microstructure. The calculated macroscopic free expansions are in quite good agreement with experimental data, provided a correct calibration of the parameter involved in the expression of the bulk strain tensor. However, it is asserted that the model would lead to very high stress levels in the structures in the particular case of rese structures in the particular case of restrained displacements at its boundaries

 
 
 
 
261

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

262

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

263

Barotropic Mechanisms of Derivative-based Uncertainty Propagation in Drake Passage Transport Estimation  

Science.gov (United States)

We apply derivative-based uncertainty quantification (UQ) and sensitivity methods to the estimation of Drake Passage transport in a global barotropic configuration of the MIT ocean general circulation model (MITgcm). Sensitivity and uncertainty fields are evaluated via first and second derivative codes of the MITgcm, generated via algorithmic differentiation (AD). Observation uncertainties are projected to uncertainties in the control variables by inversion of the Hessian of the nonlinear least-squares misfit function. Only data-supported components of Hessian information are retained through elimination of the unconstrained uncertainty nullspace. The assimilated observation uncertainty is combined with prior control variable uncertainties to reduce their posterior uncertainty. The spatial patterns of posterior uncertainty reduction and their temporal evolution are explained in terms of barotropic dynamics. Global uncertainty teleconnection mechanisms are identified as barotropic uncertainty waves. Uncertainty coupling across different control fields is demonstrated by assimilation of sea surface height uncertainty. A second step in our UQ scheme consists in propagating prior and posterior uncertainties of the model controls onto model output variables of interest, here Drake Passage transport. Forward uncertainty propagation amounts to matrix transformation of the uncertainty covariances via the model Jacobian and its adjoint. Sources of uncertainties of the transport are revealed through analysis of the adjoint wave dynamics in the model. These adjoint (reversed) mechanisms are associated with the evolution of sensitivity fields and our method formally extends sensitivity analysis to uncertainty quantification. Inverse uncertainty propagation mechanisms can be linked to adjoint dynamics in a similar manner. The posterior correlations of controls are found to dominate the reduction of the transport uncertainty compared to the marginal uncertainty reduction of the posterior diagonal. The time resolving analysis of uncertainty and sensitivity dynamics reveals transient and stationary regimes, associated with different initial and boundary conditions controls.

Kalmikov, A.; Heimbach, P.

2013-12-01

264

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

265

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

Science.gov (United States)

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

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

2011-06-01

266

Hydrogen transport in superionic system Rb3H(SeO4)2: A revised cooperative migration mechanism  

Science.gov (United States)

We performed density functional studies of electronic properties and mechanisms of hydrogen transport in Rb3H(SeO4)2 crystal that represents technologically promising class M3H(XO4)2 of proton conductors (M=Rb, Cs, NH4; X=S,Se). The electronic structure calculations show a decisive role of lattice dynamics in the process of proton migration. In the obtained revised mechanism of proton transport, the strong displacements of the vertex oxygens play a key role in establishing the continuous hydrogen transport and in achieving low activation energies of proton conduction that is in contrast to the standard two-stage Grotthuss mechanism of proton transport. Consequently, any realistic model description of proton transport should inevitably involve the interactions with the sublattice of the XO4 groups.

Pavlenko, N.; Pietraszko, A.; Pawlowski, A.; Polomska, M.; Stasyuk, I. V.; Hilczer, B.

2011-08-01

267

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

International Nuclear Information System (INIS)

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

268

Insights into the mechanism of proton transport in cytochrome c oxidase.  

Science.gov (United States)

Cytochrome c oxidase (CcO), known as complex IV of the electron transport chain, plays several important roles in aerobic cellular respiration. Electrons transferred from cytochrome c to CcO's catalytic site reduce molecular oxygen and produce a water molecule. These electron transfers also drive active proton pumping from the matrix (N-side) to intermembrane region (P-side) in mitochondria; the resultant proton gradient activates ATP synthase to produce ATP from ADP. Although the existence of the coupling between the electron transfer and the proton transport (PT) is established experimentally, its mechanism is not yet fully understood at the molecular level. In this work, it is shown why the reduction of heme a is essential for proton pumping. This is demonstrated via novel reactive molecular dynamics (MD) simulations that can describe the Grotthuss shuttling associated with the PT as well as the dynamic delocalization of the excess proton electronic charge defect. Moreover, the "valve" role of the Glu242 residue (bovine CcO notation) and the gate role of d-propionate of heme a(3) (PRDa3) in the explicit PT are explicitly demonstrated for the first time. These results provide conclusive evidence for the CcO proton transporting mechanism inferred from experiments, while deepening the molecular level understanding of the CcO proton switch. PMID:22191804

Yamashita, Takefumi; Voth, Gregory A

2012-01-18

269

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

270

Mechanism of transport of saquinavir-loaded nanostructured lipid carriers across the intestinal barrier.  

Science.gov (United States)

The aims of this work were (i) to evaluate the potential of nanostructured lipid carriers (NLCs) as a tool to enhance the oral bioavailability of poorly soluble compounds using saquinavir (SQV), a BCS class IV drug and P-gp substrate as a model drug, and (ii) to study NLC transport mechanisms across the intestinal barrier. Three different NLC formulations were evaluated. SQV transport across Caco-2 monolayers was enhanced up to 3.5-fold by NLCs compared to SQV suspension. M cells did not enhance the transport of NLCs loaded with SQV. The size and amount of surfactant in the NLCs influenced SQV's permeability, the transcytosis pathway and the efflux of SQV by P-gp. An NLC of size 247 nm and 1.5% (w/v) surfactant content circumvented P-gp efflux and used both caveolae- and clathrin-mediated transcytosis, in contrast to the other NLC formulations, which used only caveolae-mediated transcytosis. By modifying critical physicochemical parameters of the NLC formulation, we were thus able to overcome the P-gp drug efflux and alter the transcytosis mechanism of the nanoparticles. These findings support the use of NLCs approaches for oral delivery of poorly water-soluble P-gp substrates. PMID:23266764

Beloqui, Ana; Solinís, María Ángeles; Gascón, Alicia R; del Pozo-Rodríguez, Ana; des Rieux, Anne; Préat, Véronique

2013-03-10

271

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

272

The main role of inner histidines in the molecular mechanism of myoglobin oxidation catalyzed by copper compounds.  

Science.gov (United States)

In the presence of Cu(2+) and Cu(Gly)(2), the oxidation of two native MbO(2)'s (Mb = myoglobin), from the sperm whale and horse, and also two chemically modified sperm whale MbO(2)'s alkylated at solvent-accessible histidines by sodium bromoacetate (CM-MbO(2)) and by iodoacetamide (CA-MbO(2)) have been studied at different pH's, ionic strengths, and concentrations of the copper reagent. The influence of competitive redox-inactive zinc ions on the reaction rate is investigated as well. Localization of Cu(Gly)(2) in sperm whale met-Mb and CM-met-Mb has been examined using the high-resolution NMR method. The obtained data suggest that binding of copper compounds to the surface histidines (all of them are 1.8-2.7 nm apart from the heme) has only a minor, no more than 35%, contribution to the overall reaction rate, in particular under a large excess of the reagent (more than 8-10-fold). The noticeable contribution of His113(116), His48, and His81, which have the greatest affinity to copper according to NMR data, is revealed only at small concentrations of copper, less than a 5-fold excess relative to the protein. The main contribution to the reaction rate must be from the binding of copper to the inner histidines, His97 (0.62 nm from the heme), and possibly to the distal His64. Both are inaccessible to the modification by alkylating reagents and have much lower affinity to copper than all surface histidines, because they are hydrogen-bonded, the former with the carboxyl group of the heme propionate and the second with the liganded O(2). PMID:20088488

Postnikova, G B; Moiseeva, S A; Shekhovtsova, E A

2010-02-15

273

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

International Nuclear Information System (INIS)

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

274

Molecular Mechanism of Inhibition of the Mitochondrial Carnitine/Acylcarnitine Transporter by Omeprazole Revealed by Proteoliposome Assay, Mutagenesis and Bioinformatics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The effect of omeprazole on the mitochondrial carnitine/acylcarnitine transporter has been studied in proteoliposomes. Externally added omeprazole inhibited the carnitine/carnitine antiport catalysed by the transporter. The inhibition was partially reversed by DTE indicating that it was caused by the covalent reaction of omeprazole with Cys residue(s). Inhibition of the C-less mutant transporter indicated also the occurrence of an alternative non-covalent mechanism. The IC50 of the inhibition...

Tonazzi, Annamaria; Eberini, Ivano; Indiveri, Cesare

2013-01-01

275

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

276

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)

277

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)

278

Transport of large components form decommissioned nuclear installations. Experience with the mechanical expert evaluation  

International Nuclear Information System (INIS)

In the frame of dismantling projects of decommissioned nuclear installations large components (steam generators, reactor pressure vessels) have to be transported on public traffic routes to the interim storage facility. Due to the surface contamination or neutron activation of these components an expert opinion in the sense o the hazardous material transport regulation is required. For surface contaminated components the IAEA safeguard regulations are the basis for the mechanical expert evaluation. Since the free fall experiments from defined height, including the dependence on the mass of the container, on a firm platform and stacking weight tests according to the IAEA safeguard regulations are not possible, numerical analyses have to be performed. The evaluation on based on stress distributions, taking into account the radiation induced embrittlement. Due to the fact that experimental verification of the modeling is not possible, the assumptions with respect to physical processes and material properties have to be conservative with sufficient safety margins.

279

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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.

Soroka, M. L.; Yaryishkina, L. A.

2011-01-01

280

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

 
 
 
 
281

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

1989-01-01

282

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

283

Physical mechanisms of power fractal asymptotic forms of dispersion transport in disordered media  

Science.gov (United States)

Particle drift in systems with anomalous diffusion is investigated. Physical mechanisms of power fractal asymptotic forms in dispersion transport are established and the physical meaning of the characteristic changeover time for asymptotic forms is clarified. It is shown that long-term power fractal asymptotic forms for particle mobility in subdiffusion problems corresponding to the behavior of transition currents in disordered systems (i.e., having different asymptotic forms for short and long time intervals) are associated with capture in traps (ribs in the comb structure).

Arkhincheev, V. E.

2009-09-01

284

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

285

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

286

Decompaction Weakening and Mechanical Channeling Instability: Implications for Asthenospheric Melt Segregation and Transport (Invited)  

Science.gov (United States)

We propose that a mechanical flow channeling instability, which arises because of rock weakening at high fluid pressure, facilitates segregation and transport of asthenospheric melts. To characterize the weakening effect the ratio of the matrix viscosity during decompaction to that for compaction is treated as a free parameter R in the range 1 to 10-6. Two-dimensional numerical simulations with this rheology reveal that solitary, vertically elongated, porosity waves with spacing on the compaction length scale ? initiate from minuscule porosity perturbations. By analogy with viscous compaction models we infer that in the absence of far-field stress the three-dimensional expression of the waves is as pipe-like structures of radius ?R1/2, a geometry that increases fluid fluxes by a factor of ~1/R. The waves grow by draining fluid from the background porosity, but leave a wake of elevated porosity that localizes subsequent flow. Wave amplitudes grow linearly with time, increasing by a factor of R-3/8 in the time required to drain the porosity a distance of ~?. Dissipation of gravitational potential energy by the waves has the capacity to enhance growth rates through melting. Maximum wave speeds are ~40 times the speed of fluid flow through the unperturbed matrix. Such waves may provoke the elastic response necessary to nucleate, and localize the melt necessary to sustain, more effective transport mechanisms. The numerical results can be understood in the context of an analytical solution of the compaction equations that is completely general with respect to the constitutive relations used to define the matrix rheology and permeability. This solution combines the porosity dependence of the rheology and permeability in a single hydromechanical potential, which can be used to construct phase diagrams depicting the conditions for smooth pervasive flow, wave propagated melt extraction and matrix disaggregation (dike formation). Mechanical channeling instabilities offer a means of enhancing melt flow in environments where reactive transport instabilities are unlikely to be operative, notably in retrograde thermal regimes that are hostile to melt transport such as the upper portion of the mantle wedge or in the lowermost portions of sub-ridge asthenosphere where melt production is controlled by chemical heterogeneity. A parametrization of the model for this latter setting suggests that mechanical channeling instabilities could extract melt on a time scale adequate to explain the 226Ra excesses observed in mid-ocean ridge basalts.

Connolly, J.; Podladchikov, Y.

2009-12-01

287

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

Science.gov (United States)

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

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

2015-01-01

288

Investigation of transport mechanisms and regulation of intracellular Zn2+ in pancreatic alpha-cells.  

Science.gov (United States)

During insulin secretion, pancreatic alpha-cells are exposed to Zn(2+) released from insulin-containing secretory granules. Although maintenance of Zn(2+) homeostasis is critical for cell survival and glucagon secretion, very little is known about Zn(2+)-transporting pathways and the regulation of Zn(2+) in alpha-cells. To examine the effect of Zn(2+) on glucagon secretion and possible mechanisms controlling the intracellular Zn(2+) level ([Zn(2+)](i)), we employed a glucagon-producing cell line (alpha-TC6) and mouse islets where non-beta-cells were identified using islets expressing green fluorescent protein exclusively in beta-cells. In this study, we first confirmed that Zn(2+) treatment resulted in the inhibition of glucagon secretion in alpha-TC6 cells and mouse islets in vitro. The inhibition of secretion was not likely via activation of K(ATP) channels by Zn(2+). We then determined that Zn(2+) was transported into alpha-cells and was able to accumulate under both low and high glucose conditions, as well as upon depolarization of cells with KCl. The nonselective Ca(2+) channel blocker Gd(3+) partially inhibited Zn(2+) influx in alpha-TC cells, whereas the L-type voltage-gated Ca(2+) channel inhibitor nitrendipine failed to block Zn(2+) accumulation. To investigate Zn(2+) transport further, we profiled alpha-cells for Zn(2+) transporter transcripts from the two families that work in opposite directions, SLC39 (ZIP, Zrt/Irt-like protein) and SLC30 (ZnT, Zn(2+) transporter). We observed that Zip1, Zip10, and Zip14 were the most abundantly expressed Zips and ZnT4, ZnT5, and ZnT8 the dominant ZnTs. Because the redox state of cells is also a major regulator of [Zn(2+)](i), we examined the effects of oxidizing agents on Zn(2+) mobilization within alpha-cells. 2,2'-Dithiodipyridine (-SH group oxidant), menadione (superoxide generator), and SIN-1 (3-morpholinosydnonimine) (peroxynitrite generator) all increased [Zn(2+)](i) in alpha-cells. Together these results demonstrate that Zn(2+) inhibits glucagon secretion, and it is transported into alpha-cells in part through Ca(2+) channels. Zn(2+) transporters and the redox state also modulate [Zn(2+)](i). PMID:18250168

Gyulkhandanyan, Armen V; Lu, Hongfang; Lee, Simon C; Bhattacharjee, Alpana; Wijesekara, Nadeeja; Fox, Jocelyn E Manning; MacDonald, Patrick E; Chimienti, Fabrice; Dai, Feihan F; Wheeler, Michael B

2008-04-11

289

Chemokines at large: in-vivo mechanisms of their transport, presentation and clearance.  

Science.gov (United States)

Compelling evidence implicates chemokines in the induction of leukocyte emigration from blood into tissues. This arguably most fundamental effect of chemokines is accomplished by triggering cognate classical G-protein-coupled chemokine receptors on the leukocyte surface. In vitro, these same receptors mediate leukocyte migration; however, the mechanisms of chemokine-induced migration differ between in-vivo and in-vitro settings. Leukocyte egress from blood is greatly influenced by haemodynamic conditions and requires full cooperation of endothelial cells. The behaviour of chemokines in their "native habitat" in vivo is controlled by their interaction with several accessory molecules which influence immobilisation, transport, clearance and degradation of chemokines and thereby determine the sites and duration of their action. Here we discuss peculiarities of the in vivo actions of chemokines, the mechanisms of chemokine interaction with receptors and auxiliary molecules including interceptors, glycosaminoglycans and enzymes and illustrate how these interactions influence the outcome of chemokine activities in vivo. PMID:17479178

Colditz, Ian G; Schneider, Martin A; Pruenster, Monika; Rot, Antal

2007-05-01

290

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

291

Common Evolution of Mechanical and Transport Properties in Thermally Cracked Westerly Granite at Elevated Hydrostatic Pressure  

Science.gov (United States)

Increasing the damage and crack porosity in crustal rocks can result in significant changes to various key physical properties, including mechanical strength, elastic and mechanical anisotropy, and the enhancement of transport properties. Using a Non-Interactive Crack Effective Medium (NIC) theory as a fundamental tool, we show that elastic wave dispersion can be inverted to evaluate crack density as a function of temperature and is compared with optically determined crack density. Further, we show how the existence of embedded microcrack fabrics in rocks also significantly influences the fracture toughness (KIC) of rocks as measured via a suite of tensile failure experiments (chevron cracked notch Brazilian disk). Finally, we include fluid flow in our analysis via the Guéguen and Dienes crack porosity-permeability model. Using the crack density and aspect ratio recovered from the elastic-wave velocity inversion, we successfully compare permeability evolution with pressure with the laboratory measurements of permeability.

Nasseri, M. H. B.; Schubnel, A.; Benson, P. M.; Young, R. P.

2009-07-01

292

Transport mechanisms of uranium released to the coolant from fuel defects  

International Nuclear Information System (INIS)

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

293

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

Science.gov (United States)

Temperature dependent pulsed and ramped substrate bias measurements are used to develop a detailed understanding of the vertical carrier transport in the buffer layers in a carbon doped GaN power heterojunction field effect transistor. Carbon doped GaN and multiple layers of AlGaN alloy are used in these devices to deliver an insulating and strain relieved buffer with high breakdown voltage capability. However, understanding of the detailed physical mechanism for its operation is still lacking. At the lowest electric fields (process. Balancing the onset of these leakage mechanisms is essential to allow the build-up of positive rather than negative space charge, and thus minimize bulk-related current-collapse in these devices.

Uren, Michael J.; Cäsar, Markus; Gajda, Mark A.; Kuball, Martin

2014-06-01

294

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

295

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-04-11

296

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-treatmenclearly observed with rising heat-treatment temperature

297

Molecular mechanism of pH-dependent substrate transport by an arginine-agmatine antiporter.  

Science.gov (United States)

Enteropathogenic bacteria, exemplified by Escherichia coli, rely on acid-resistance systems (ARs) to survive the acidic environment of the stomach. AR3 consumes intracellular protons through decarboxylation of arginine (Arg) in the cytoplasm and exchange of the reaction product agmatine (Agm) with extracellular Arg. The latter process is mediated by the Arg:Agm antiporter AdiC, which is activated in response to acidic pH and remains fully active at pH 6.0 and below. Despite our knowledge of structural information, the molecular mechanism by which AdiC senses acidic pH remains completely unknown. Relying on alanine-scanning mutagenesis and an in vitro proteoliposome-based transport assay, we have identified Tyr74 as a critical pH sensor in AdiC. The AdiC variant Y74A exhibited robust transport activity at all pH values examined while maintaining stringent substrate specificity for Arg:Agm. Replacement of Tyr74 by Phe, but not by any other amino acid, led to the maintenance of pH-dependent substrate transport. These observations, in conjunction with structural information, identify a working model for pH-induced activation of AdiC in which a closed conformation is disrupted by cation-? interactions between proton and the aromatic side chain of Tyr74. PMID:25136114

Wang, Sheng; Yan, Renhong; Zhang, Xi; Chu, Qi; Shi, Yigong

2014-09-01

298

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

Science.gov (United States)

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.

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

2013-04-01

299

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

Science.gov (United States)

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.

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

2012-10-01

300

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

 
 
 
 
301

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

302

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

303

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

Science.gov (United States)

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

Rickman, D.; Gertsch, L.

2014-01-01

304

Carbon dioxide concentrating mechanism in Chlamydomonas reinhardtii: inorganic carbon transport and CO2 recapture.  

Science.gov (United States)

Many microalgae are capable of acclimating to CO(2) limited environments by operating a CO(2) concentrating mechanism (CCM), which is driven by various energy-coupled inorganic carbon (Ci; CO(2) and HCO(3)(-)) uptake systems. Chlamydomonas reinhardtii (hereafter, Chlamydomonas), a versatile genetic model organism, has been used for several decades to exemplify the active Ci transport in eukaryotic algae, but only recently have many molecular details behind these Ci uptake systems emerged. Recent advances in genetic and molecular approaches, combined with the genome sequencing of Chlamydomonas and several other eukaryotic algae have unraveled some unique characteristics associated with the Ci uptake mechanism and the Ci-recapture system in eukaryotic microalgae. Several good candidate genes for Ci transporters in Chlamydomonas have been identified, and a few specific gene products have been linked with the Ci uptake systems associated with the different acclimation states. This review will focus on the latest studies on characterization of functional components involved in the Ci uptake and the Ci-recapture in Chlamydomonas. PMID:21409558

Wang, Yingjun; Duanmu, Deqiang; Spalding, Martin H

2011-09-01

305

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-04-01

306

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

307

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

Science.gov (United States)

In this work we monitor the catalytic mechanism of P-glycoprotein (Pgp) using single-molecule fluorescence resonance energy transfer (FRET). Pgp, a member of the ATP binding cassette family of transport proteins, is found in the plasma membrane of animal cells where it is involved in the ATP hydrolysis driven export of hydrophobic molecules. When expressed in the plasma membrane of cancer cells, the transport activity of Pgp can lead to the failure of chemotherapy by excluding the mostly hydrophobic drugs from the interior of the cell. Despite ongoing effort, the catalytic mechanism by which Pgp couples MgATP binding and hydrolysis to translocation of drug molecules across the lipid bilayer is poorly understood. Using site directed mutagenesis, we have introduced cysteine residues for fluorescence labeling into different regions of the nucleotide binding domains (NBDs) of Pgp. Double-labeled single Pgp molecules showed fluctuating FRET efficiencies during drug stimulated ATP hydrolysis suggesting that the NBDs undergo significant movements during catalysis. Duty cycle-optimized alternating laser excitation (DCO-ALEX) is applied to minimize FRET artifacts and to select the appropriate molecules. The data show that Pgp is a highly dynamic enzyme that appears to fluctuate between at least two major conformations during steady state turnover.

Ernst, S.; Verhalen, B.; Zarrabi, N.; Wilkens, S.; Börsch, M.

2011-03-01

308

Transport  

International Nuclear Information System (INIS)

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

309

Mechanisms underlying food-drug interactions: inhibition of intestinal metabolism and transport.  

Science.gov (United States)

Food-drug interaction studies are critical to evaluate appropriate dosing, timing, and formulation of new drug candidates. These interactions often reflect prandial-associated changes in the extent and/or rate of systemic drug exposure. Physiologic and physicochemical mechanisms underlying food effects on drug disposition are well-characterized. However, biochemical mechanisms involving drug metabolizing enzymes and transport proteins remain underexplored. Several plant-derived beverages have been shown to modulate enzymes and transporters in the intestine, leading to altered pharmacokinetic (PK) and potentially negative pharmacodynamic (PD) outcomes. Commonly consumed fruit juices, teas, and alcoholic drinks contain phytochemicals that inhibit intestinal cytochrome P450 and phase II conjugation enzymes, as well as uptake and efflux transport proteins. Whereas myriad phytochemicals have been shown to inhibit these processes in vitro, translation to the clinic has been deemed insignificant or undetermined. An overlooked prerequisite for elucidating food effects on drug PK is thorough knowledge of causative bioactive ingredients. Substantial variability in bioactive ingredient composition and activity of a given dietary substance poses a challenge in conducting robust food-drug interaction studies. This confounding factor can be addressed by identifying and characterizing specific components, which could be used as marker compounds to improve clinical trial design and quantitatively predict food effects. Interpretation and integration of data from in vitro, in vivo, and in silico studies require collaborative expertise from multiple disciplines, from botany to clinical pharmacology (i.e., plant to patient). Development of more systematic methods and guidelines is needed to address the general lack of information on examining drug-dietary substance interactions prospectively. PMID:22884524

Won, Christina S; Oberlies, Nicholas H; Paine, Mary F

2012-11-01

310

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

311

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

International Nuclear Information System (INIS)

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

312

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

Energy Technology Data Exchange (ETDEWEB)

We have investigated the effect of the Au-diffusion on the mechanical and transport properties of the (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}Oy (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-T{sub c} 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.

Nursoy, M. [Department of Mechanical Engineering, Faculty of Engineering and Architecture, Abant Izzet Baysal University, 14280 Bolu (Turkey); Yilmazlar, M. [Faculty of Education, Sakarya University, 54300 Hendek, Sakarya (Turkey); Terzioglu, C. [Department of Physics, Faculty of Arts and Science, Abant Izzet Baysal University, 14280 Bolu (Turkey)], E-mail: terzioglu_c@ibu.edu.tr; Belenli, I. [Department of Physics, Faculty of Arts and Science, Abant Izzet Baysal University, 14280 Bolu (Turkey)

2008-07-14

313

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

314

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

International Nuclear Information System (INIS)

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

315

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

Energy Technology Data Exchange (ETDEWEB)

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

Isabella Van Rooyen

2014-10-01

316

Sub-continental transport mechanisms and pathways during two ozone episodes in northern Spain  

Directory of Open Access Journals (Sweden)

Full Text Available Two ozone episodes (occurring in June 2001 and June 2003 in the air quality monitoring network of the Basque Country (BC are analyzed. The population information threshold was exceeded in many stations (urban, urban-background and rural. During this type of episodes, forced by a blocking anticyclone over the British Isles, ozone background concentrations over the area increase after the import of pollution from both, the continental Europe and the western Mediterranean areas (Gangoiti et al., 2002. For the present analysis, emphasis is made in the search for transport mechanisms, pathways and area sources contributing to the build-up of the episodes. Contributions from a selection of 17 urban and industrial conglomerates in the western European Atlantic (WEA and the western Mediterranean (WM are shown after the results of a coupled RAMS-HYPACT modelling system. Meteorological simulations are tested against both the high-resolution wind data recorded at the BC coastal area by a boundary layer wind-profiler radar (Alonso et al., 1998 and the wind soundings reported by the National Centres of Meteorology at a selection of European and north-African sites. Results show that during the accumulation phase of the episodes, background ozone concentrations increase in the whole territory as a consequence of transport from the Atlantic coast of France and the British Channel. For the peak phase, intrusions from new sources, located at the Western Mediterranean, Southern France, Ebro Valley, and, occasionally, the area of Madrid are added, resulting in a further increase in the ozone concentrations. Direct day and night transport within the north-easterly winds over the sea from the WEA source region, and night-time transport within the residual layer over continental areas (southern France, the Ebro Valley, and central Iberia modulate the import sequence of pollutants and the local increase of ozone concentrations. The alternative direct use of low resolution meteorological data for the estimation of back-trajectories shows a more simple transport scheme with no contributions neither from the Western Mediterranean nor from the Madrid area.

G. Gangoiti

2006-01-01

317

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

International Nuclear Information System (INIS)

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

318

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

319

Transportation R and D included in thermal and mechanical sciences program  

Science.gov (United States)

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

1995-06-01

320

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

International Nuclear Information System (INIS)

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

 
 
 
 
321

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-06-30

322

Ab initio simulations of the mechanics and electrical transport of Pt nanowires  

Directory of Open Access Journals (Sweden)

Full Text Available Based on first principles, theoretical studies of atomic-scale platinum contacts are presented. A short monatomic wire freely suspended between tips is seen to vibrate as its tensile load increases. The main vibration mode is transversal for lower tensions and longitudinal for higher tensions up to the breaking of the nanowire. The computed conductance exhibits oscillation in the sub-picosecond regime that can be well correlated to the mechanical oscillations of the nanowire. Both the values for the maximum tensile load and the average conductance agree well with available experimental measurements.

Jose A. Torres

2007-01-01

323

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)

324

Tunneling mechanism through the nonlinear electrical transport in Co/CoO particles with core-shell nanostructure  

International Nuclear Information System (INIS)

We investigate the nonlinear electrical transport as a function of temperature in Co/CoO nanoparticles having core-shell nanostructure. Nanoparticle was synthesized by sol-gel citrate precursor technique where core-shell nanostructure is confirmed by the high resolution Transmission Electron Microscopy. Current-voltage (I-V) characteristics are measured over the temperature range 20-295 K. I-V curve exhibits ohmic behaviour at 295 K. Nonlinear electrical transport is observed at low temperature (T) for T?275 K. Electrical transport properties have been interpreted in terms of tunneling mechanism where tunneling between ferromagnetic Co nanoparticles takes place through the antiferromagnetic CoO layer. Analysis of dynamic conductance (G=dI/dV) indicates that the inelastic tunneling via localized states of antiferromagnetic CoO layers is dominant in the transport mechanism at low temperature.

325

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

Science.gov (United States)

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

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

2015-01-01

326

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

Science.gov (United States)

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

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

2011-07-01

327

Mechanisms of photodoping in oxygen-deficient YBa2Cu3Ox films studied by in situ transport measurements  

Science.gov (United States)

In situ studies of the superconducting and normal-state transport properties in partially oxygen-depleted, metallic YBa2Cu3Ox (Tc,mid~52 K) thin films exposed to long-term white-light illumination (photodoping) are reported. We observed that the effects of photoexcitation strongly depended on the temperature at which the photodoping was performed. The Hall number increased during the illumination in the entire tested temperature range from 70 to 290 K, with the strongest increase near room temperature, whereas, the Hall mobility increased steadily only upon low-temperature illumination. At temperatures above 250 K, it showed an abrupt initial increase followed by a long-term decrease. At high temperatures, the Hall quantities react on the impact of light excitation independently from each other, which strongly suggests that both the photoassisted oxygen ordering and charge-transfer mechanisms contribute to photodoping, the former acting mainly on the mobility, while the latter on the density of charge carriers. The photoinduced enhancement of the superconducting transition temperature Tc exhibited essentially the same temperature dependence as the enhancement of the Hall number, being largest (?Tc~2.6 K) for the illumination performed at high temperatures. Thus, the Tc enhancement results from the change of the density more likely than of the mobility of the charge carriers.

Stockinger, C.; Markowitsch, W.; Lang, W.; Kula, W.; Sobolewski, Roman

1998-04-01

328

A study on the mechanism of the proton transport in bacteriorhodopsin: the importance of the water molecule.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The mechanism of proton transport around the Schiff base in bacteriorhodopsin was investigated by ab initio molecular orbital (MO) calculations. Computations were performed for the case where there is a water molecule between the Schiff base and the Asp residue and for the case where there is no water molecule. Changes in the atomic configuration and potential energy through the proton transport process were compared between two cases. In the absence of water, the protonated Schiff base was n...

Murata, K.; Fujii, Y.; Enomoto, N.; Hata, M.; Hoshino, T.; Tsuda, M.

2000-01-01

329

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

330

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

331

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

Energy Technology Data Exchange (ETDEWEB)

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.

Price, S. [Forgemasters Steel and Engineering, Sheffield (United Kingdom); Honeyman, G.A. [Forged Rolls UK Ltd., Sheffield (United Kingdom)

1997-12-31

332

Charge carrier transport mechanisms in perovskite CdTiO3 fibers  

Directory of Open Access Journals (Sweden)

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

Z. Imran

2014-06-01

333

High-forward-bias transport mechanism in a-Si:H/c-Si heterojunction solar cells  

Energy Technology Data Exchange (ETDEWEB)

In order to elucidate the transport mechanism in a-Si:H/c-Si heterojunction solar cells under high forward bias (U > 0.5 V), we conducted temperature-dependent measurements of current-voltage (I-V) curves in the dark and under illumination. ZnO:Al/(p)a-Si:H/(n)c-Si/(n{sup +})a-Si:H cells are compared with inversely doped structures and the impact of thin undoped a-Si:H buffer layers on charge carrier transport is explored. The solar cell I-V curves are analyzed employing a generalized two-diode model which allows fitting I-V data for a broad range of samples. The fitting results are complemented with numerical simulations using AFORS-HET under consideration of microscopic a-Si:H parameters as determined by constant-final-state-yield photoelectron spectroscopy (CFSYS) to identify possible origins for a systematic increase of the high-forward-bias ideality factor along with the open-circuit voltage (V{sub oc}). It is further shown that also for a-Si:H/c-Si heterojunctions, dark I-V curve fit parameters can unequivocally be linked to V{sub oc} under illumination, which may prove helpful for device assessment. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Schulze, T.F.; Korte, L.; Conrad, E.; Schmidt, M.; Rech, B. [Department of Silicon Photovoltaics, Helmholtz-Zentrum Berlin fuer Materialien und Energie, Kekulestrasse 5, 12489 Berlin (Germany)

2010-03-15

334

Charge carrier transport mechanisms in perovskite CdTiO3 fibers  

Science.gov (United States)

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

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

2014-06-01

335

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

Directory of Open Access Journals (Sweden)

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

Huan-Chao Keh

2011-01-01

336

Charge carrier transport mechanisms in perovskite CdTiO3 fibers  

International Nuclear Information System (INIS)

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

337

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

Science.gov (United States)

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

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

1999-01-01

338

K(+) uptake systems in the yeast Hansenula polymorpha. Transcriptional and post-translational mechanisms involved in high-affinity K(+) transporter regulation.  

Science.gov (United States)

We have identified the two main K(+) transporters in the yeast Hansenula polymorpha. So far this is the only yeast with these transporters amenable to molecular genetic analysis. Two ORF-encoding permeases with high similarity to Trk1 and Hak1 are present in the genome of this yeast. Deletion of either of these genes led to defective growth in low K(+). The K(+) and Rb(+) uptake rates showed high affinity of Hak1 for K(+), while the affinity estimated for Trk1 was two orders of magnitude lower. TRK1 was not transcriptionally regulated and HAK1 was strongly induced in response to very low K(+) and down-regulated by the presence of K(+). This process is clearly dependent on calcineurin. The use of a set of strains carrying mutations affecting intracellular protein trafficking revealed that in response to K(+), Hak1 is endocytosed and degraded in the vacuole, this depending on the ubiquitin ligase Rsp5. This is a first insight into the transcriptional and post-translational mechanisms regulating a high-affinity K(+) transporter (HAK-type transporter) that allows cells to respond and adapt to K(+) availability. PMID:22776636

Cabrera, Elisa; Álvarez, María C; Martín, Yusé; Siverio, José M; Ramos, José

2012-09-01

339

Shear induced transport property in impermeable fault rocks and its effect on the mechanical property  

Science.gov (United States)

Transport property in fault zone will change by shear deformation during and after earthquakes, and the change in transport property may lead to the fault strength transition as well. Previous study by Tanikawa et al. (2012) revealed that, for permeable rocks, shear induced permeability in medium to high slip velocity is mainly controlled by the fluid viscosity that changes due to frictional heating. However, impermeable fault rocks may show different evolution process for the fluid transport property compared to permeable fault rock. In this study, rock-to-rock friction tests was conducted on granite samples to see a shear induced transport property in impermeable fault rocks. We measured flow rate during and after friction test using a rotary shear apparatus. Two 20-mm-long hollow cylindrical specimens (outer and inner diameters of 25 and 9.5 mm, respectively) of low permeable Aji Granite (permeability of 10^-19 m^2) were used in all tests. One cylindrical specimen was fixed and the other rotated under a fixed axial stress of 2 MPa. We applied the total slip displacements of 1.5 and 3 m at various constant slip rates from 0.076 to 150 mm/s. To measure shear-induced fluid transport property, radial flow from the inner wall to the outer wall of the specimen was induced by applying a differential pore pressure between the inner and outer walls. Nitrogen gas was used as a pore fluid. Friction coefficient typically decreased from 0.9 to 0.5 with an increase of slip velocity. At the same slip rate, friction coefficient increased with an increase in apparent permeability of specimen. Apparent permeability during and after friction test were over one order of magnitude larger than that of intact granite. At slower slip rate below 0.01 m/s, permeability decreased soon after sliding ceased, though at high slip rate, permeability increased after sliding. By comparing initial permeability and permeability after 10 minutes of friction tests, results show a reduction in permeability that occurred when initial permeability is high. In contrast, permeability increases with sliding when initial permeability is low. This transition transport property is (intrinsic) transmissivity of ~2*10^-21 m3 that is equivalent to fracture aperture of ~0.3 ?m assuming that threshold aperture is equivalent to hydraulic aperture evaluated by cubic law. We assume that the permeability change during sliding is caused by the production of gouge and smoothing of slip surface that changes aperture size and real contact area of specimens. The change of surface property resulted in change of friction property as well. The reduction of permeability immediately after sliding is probably caused by the thermo-elastic effect on aperture due to frictional heating.

Tanikawa, Wataru; Tadai, Osamu; Mukoyoshi, Hideki; Hirose, Takehiro

2013-04-01

340

Evidence for a novel affinity mechanism of motor-assisted transport along microtubules.  

Science.gov (United States)

In microtubule (MT) translocation assays, using colloidal gold particles coupled to monoclonal tubulin antibodies to mark positions along MTs, we found that relative motion is possible between the gold particle and an MT, gliding on dynein or kinesin. Such motion evidently occurred by an affinity release and rebinding mechanism that did not require motor activity on the particle. As the MTs moved, particles drifted to the trailing edge of the MT and then were released. Sometimes the particles transferred from one MT to another, moving orthogonally. Although motion of the particles was uniformly rearward, movement was toward the (-) or (+) end of the MT, depending on whether dynein or kinesin, respectively, was used in the assay. These results open possibilities for physiological mechanisms of organelle and other movement that, although dependent on motor-driven microtubule transport, do not require direct motor attachment between the organelle and the microtubule. Our observations on the direction of particle drift and time of release may also provide confirmation in a dynamic system for the conclusion that beta tubulin is exposed at the (+) end of the MT. PMID:10637299

Wada, Y; Hamasaki, T; Satir, P

2000-01-01

 
 
 
 
341

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

International Nuclear Information System (INIS)

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

342

Contact resistivity and transport mechanisms in W contacts to p- and n-GaN  

Science.gov (United States)

The electrical properties of W contacts to both n- and p-GaN were investigated. W contacts to p-type GaN doped with Mg to a level of 1018cm-3 were annealed for 1 min at temperatures from 350 to 900 °C. The contact resistivity was found to decrease with increasing annealing temperature parallel to an increase in the GaN sheet resistance. The contacts were rectifying after all of the heat treatments. Measurements at higher temperatures (up to 400 °C) resulted in I-V characteristics becoming almost linear and a decrease in contact resistivity with temperature down to 10-2 ? cm2. These results are attributed to the ionization of more Mg acceptors as the temperature increases. In this system thermionic emission combined with tunneling through deep energy levels was found to be the transport mechanism. W contacts to heavily Si implanted (Nd˜1020 cm-3) n-GaN annealed at 750-1050 °C for 10 s produced ohmic behavior with no significant dependence of the contact resistivity on the annealing temperature. The observed weak dependence of the contact resistivity on the measurement temperature is attributed to the dominance of the field emission mechanism.

Zeitouny, A.; Eizenberg, M.; Pearton, S. J.; Ren, F.

2000-08-01

343

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

344

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

International Nuclear Information System (INIS)

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

345

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

346

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

International Nuclear Information System (INIS)

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

347

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

Science.gov (United States)

Selectivity is one of the most fundamental concepts in natural sciences, and it is also critically important in various technological, industrial, and medical applications. Although there are many experimental methods that allow to separate molecules, frequently they are expensive and not efficient. Recently, a new method of separation of chemical mixtures based on utilization of channels and nanopores has been proposed and successfully tested in several systems. However, mechanisms of selectivity in the molecular transport during the translocation are still not well understood. Here, we develop a simple theoretical approach to explain the origin of selectivity in molecular fluxes through channels. Our method utilizes discrete-state stochastic models that take into account all relevant chemical transitions and can be solved analytically. More specifically, we analyze channels with one and two binding sites employed for separating mixtures of two types of molecules. The effects of the symmetry and the strength of the molecular-pore interactions are examined. It is found that for one-site binding channels, the differences in the strength of interactions for two species drive the separation. At the same time, in more realistic two-site systems, the symmetry of interaction potential becomes also important. The most efficient separation is predicted when the specific binding site is located near the entrance to the nanopore. In addition, the selectivity is higher for large entrance rates into the channel. It is also found that the molecular transport is more selective for repulsive interactions than for attractive interactions. The physical-chemical origin of the observed phenomena is discussed. PMID:25638001

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

2015-01-28

348

Investigation of Gas Phase Transport Mechanisms in Unsaturated Zones Under Natural Conditions  

Science.gov (United States)

Diffusive flux is traditionally treated as the dominant mechanism for gas transport in unsaturated zones without active disturbance. However, some researchers have found that the pressure-driven and density-driven advective flux may also be important under certain conditions. This article conducts a comprehensive study of the diffusive, pressure-driven and density-driven advective fluxes of the gas phase volatile organic compounds (VOCs) in the unsaturated zone under various hydrogeological conditions. The presence of a less or more permeable layer at ground surface in a heterogeneous unsaturated zone is investigated for their influence on the time-averaged advective and diffusive fluxes. Our developed numerical solution is applied to interpret a field study of the trichloroethylene contamination in the unsaturated zone at Picatinny Arsenal in Morris County, New Jersey. Results show that under most of the field conditions the time-averaged advective flux is one to three orders of magnitude smaller than the diffusive flux, and the influence of the density-driven flux on the advective flux is undetectable. The time-averaged advective flux is comparable in magnitude with the diffusive flux only in a deep unsaturated zone (thickness greater than 15 m), or when the gas-filled porosity is less than 0.05, or the magnitude of the water table fluctuation is greater than 0.2 m for the default parameters used in this study. A less permeable layer at ground surface increases the total flux of VOCs under it, while a permeable layer at ground surface increases the total flux in it. The error induced by fixing the water table position but allowing the fluctuation of water table moving velocity is negligible for predicting the gas phase VOCs transport in an unsaturated zone at non-coastal sites.

You, K.; Zhan, H.

2012-12-01

349

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-06-15

350

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 speci 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

351

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

352

Computational modelling of thermo-mechanical and transport properties of carbon nanotubes  

International Nuclear Information System (INIS)

Over the recent years, numerical modelling and computer-based simulation of the properties of carbon nanotubes have become the focal points of research in computational nano-science and its associated fields of computational condensed matter physics and materials modelling. Modelling of the mechanical, thermal and transport properties of nanotubes via numerical simulations forms the central part of this research, concerned with the nano-scale mechanics and nano-scale thermodynamics of nanotubes, and nano-scale adsorption, storage and flow properties in nanotubes. A review of these properties, obtained via computational modelling studies, is presented here. We first introduce the physics of carbon nanotubes, and then present the computational simulation tools that are appropriate for conducting a modelling study at the nano-scales. These include the molecular dynamics (MD), the Monte Carlo (MC), and the ab initio MD simulation methods. A complete range of inter-atomic potentials, of two-body and many-body varieties, that underlie all the modelling studies considered in this review is also given. Mechanical models from continuum-based elasticity theory that have been extensively employed in computing the energetics of nanotubes, or interpret the results from atomistic modelling, are presented and discussed. These include models based on the continuum theory of curved plates, shells, vibrating rods and bending beams. The validity of these continuum-based models has also of these continuum-based models has also been examined and the conditions under which they are applicable to nanotube modelling have been listed. Pertinent concepts from continuum theories of stress analysis are included, and the relevant methods for conducting the computation of the stress tensor, elastic constants and elastic modulii at the atomic level are also given. We then survey a comprehensive range of modelling studies concerned with the adsorption and storage of gases, and flow of fluids, in carbon nanotubes of various types. This is then followed by an extensive survey of the numerical modelling investigations that have addressed the mechanical and thermal properties of these structures. The survey of modelling studies is supplemented by reviews of experimental investigations, where appropriate, to help clarify their results

353

Molecular insights into the translocation mechanism for substrates by the serotonin transporter  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The serotonin transporter (SERT) is responsible for regulating the serotonin (5-HT) concentration in the synapse. I used human and Drosophila serotonin transporters (hSERT and dSERT, respectively) to explore differences in substrate recognition. hSERT and dSERT showed similar K m values for 5-HT transport, suggesting similar recognition of 5-HT by the two species variants. Interestingly, another substrate, N-methyl-4-phenylpyridinium (MPP+), was transported only by hSERT. However, MPP + inhib...

Rodriguez, Gustavo J.

2004-01-01

354

Modeling of Glycerol-3-Phosphate Transporter Suggests a Potential ‘Tilt’ Mechanism involved in its Function  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Many major facilitator superfamily (MFS) transporters have similar 12-transmembrane ?-helical topologies with two six-helix halves connected by a long loop. In humans, these transporters participate in key physiological processes and are also, as in the case of members of the organic anion transporter (OAT) family, of pharmaceutical interest. Recently, crystal structures of two bacterial representatives of the MFS family — the glycerol-3-phosphate transporter (GlpT) and lac-permease (LacY)...

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

2008-01-01

355

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Talon, Suzanne; Charbonnel, Corinne

2008-01-01

356

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

DEFF Research Database (Denmark)

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

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

2000-01-01

357

Carrier transport mechanism of Ohmic contact to p-type diamond  

Science.gov (United States)

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

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

1997-05-01

358

Time-local view of nonequilibrium statistical mechanics. I. Linear theory of transport and relaxation  

International Nuclear Information System (INIS)

The aim of this paper is to develop the time-local picture (TLP) of nonequilibrium statistical mechanics on a new footing and to consider its physical implications for topics such as the formulation of irreversible thermodynamics. The most natural approach to TLP is seen to derive from the Fourier-Laplace transform anti C(z) of pertinent time correlation functions, which on the physical sheet typically displays an essential singularity at z = ? and a number of macroscopic and microscopic poles in the lower half-plane corresponding to long- and short-lived modes, respectively, the former giving rise to the autonomous macrodynamics, whereas the latter are interpreted as doorway modes mediating the transfer of information from relevant to irrelevant channels. Possible implications of this doorway mode concept for so-called extended irreversible thermodynamics are briefly discussed. The pole structure is used for deriving new kinds of generalized Green-Kubo relations expressing macroscopic quantities, transport coefficients, e.g., by contour integrals over current-current correlation functions obeying Hamiltonian dynamics, the contour integration replacing projection

359

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

Directory of Open Access Journals (Sweden)

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

Simona TU?KUT?

2013-03-01

360

Carrier transport mechanisms of hybrid ZnO nanorod-polymer LEDs  

Science.gov (United States)

A hybrid polymer-nanorod (NR) light-emitting diode (LED), consisting of a hole-conducting polymer poly (9-vinyl carbazole) (PVK) and ZnO nanorod (NR) composite, with the device structure of glass/indium-tin-oxide (ITO)/PEDOT:PSS/(PVK + ZnO nanorods)/Al is fabricated through a simple spin coating technique. TEM images shows inhomogeneous deposition and the agglomeration of ZnO NRs, which is explained through their low probability of adsorption on PVK due to two-dimensional structural property. In the current-voltage characteristics, negative differential resistance (NDR) phenomenon is observed corresponding to device structure without ZnO NRs. The carrier transport behavior in the LED device is well described by both ohmic and space-chargelimited-current (SCLC) mechanisms. Broad blue electroluminescence (EL) consisting of two sub peaks, are centered at 441 nm and the other at 495 nm, is observed, which indicates that the ZnO nanorod play a role as a recombination center for excitons. The red shift in the position of the EL compared to that photoluminescence is well explained through band offsets at the heterojunction between the PVK and ZnO NRs.

Cho, Sungjae; Lee, Kyu Seung; Son, Dong Ick; Oh, Youngjei; Choi, Won Kook; Angadi, Basavaraj

2014-07-01

 
 
 
 
361

Nurr1 enhances transcription of the human dopamine transporter gene through a novel mechanism.  

Science.gov (United States)

The importance of the nuclear receptor nurr1 for the appropriate development of mesencephalic dopamine-synthesizing neurons has been clearly demonstrated through the targeted disruption of the nurr1 gene. The persistence of nurr1 expression in adult tissue suggests a possible role for this transcription factor in the maintenance, as well as development, of the dopaminergic phenotype. To address this issue, we analyzed the effects of nurr1 on the transcriptional expression of the human dopamine transporter gene (hDAT), one of the most specific phenotypic markers for dopaminergic neurons. Nurr1 enhanced the transcriptional activity of hDAT gene constructs transiently transfected into a newly described cell line (SN4741) that expresses a dopaminergic phenotype, whereas other members of the NGFI-B subfamily of nuclear receptors had lesser or no effects. Nurr1 activation of hDAT was not dependent upon heterodimerization with the retinoid X receptor. Unexpectedly, functional analysis of a series of gene constructs revealed that a region of the hDAT 5'-flanking sequence devoid of NGFI-B response element (NBRE)-like sites mediated nurr1 activation. Additional experiments using a nurr1 mutant construct suggest that nurr1 activates hDAT transcription via a novel NBRE-independent mechanism. PMID:11238740

Sacchetti, P; Mitchell, T R; Granneman, J G; Bannon, M J

2001-03-01

362

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

363

Transport  

Energy Technology Data Exchange (ETDEWEB)

Motorised transport is vital for today's global economy. Currently, the internal combustion engine (ICE) using crude oil based fuels is the prime mover for almost the whole sector. The continuous use of ICE has been possible because the plaguing air polluting emissions have been successfully reduced using catalytic exhaust aftertreatment systems based mostly on platinumgroup noble metals. However, transport is still a major source of air pollution and is responsible for some 30% of global CO{sub 2} emissions. Therefore, as no aftertreatment technology is able to reduce CO{sub 2} emissions, increasing pressure has been applied to drastically improve the energy efficiency of the ICE, or better yet, to replace it with an alternative that is more efficient, non-polluting, and uses renewable energy sources. For global vehicle manufacturers, Finland represents a small market. The emergence of tailormade solutions designed to suit our needs only is therefore unlikely. Moreover, we shall have to settle to adapt mainstream vehicles to our use. To a certain extent, this also includes fuels and energy sources, although in this instance the freedom to make our own choices seems to be larger. This is especially true if renewable energy sources such as biomass are exploited in a growing fashion. As a global trend, use of less carbonaceous fuels like natural gas is increasing slowly but steadily. Right now, we are standing at the gate of a new technology era in terms of vehicle technology and that of their powerplants. Many competing candidates for the replacement of ICE are being developed and evaluated, but it is far too early to judge which ones if any shall survive and become the new mainstream technology. Therefore, devising scenarios for the future is quite difficult. Nevertheless, it is more than likely that diversification in terms of transport-related energy sources and prime movers is going to increase from the present-day oil and ICE-dominated situation.

Laurikko, J.

2002-07-01

364

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)

365

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)

366

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

367

Indomethacin secretion in the isolated perfused proximal straight rabbit tubule. Evidence for two parallel transport mechanisms.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We studied indomethacin as a probe of anion transport across the isolated perfused proximal straight tubule of the rabbit and discovered that a substantial component of transport may occur by anion exchange at the basolateral membrane. Various perturbations involving direct or indirect dissipation of the cellular sodium gradient (ouabain, sodium- or potassium-free solutions, cooling to 18 degrees C) resulted in only a 50% inhibition of indomethacin transport, which raised the question of a co...

Zeeuw, D.; Jacobson, H. R.; Brater, D. C.

1988-01-01

368

Di-tripeptides and oligopeptides are taken up via distinct transport mechanisms in Lactococcus lactis.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Lactococcus lactis ML3 possesses two different peptide transport systems of which the substrate size restriction and specificity have been determined. The first system is the earlier-described proton motive force-dependent di-tripeptide carrier (E. J. Smid, A. J. M. Driessen, and W. N. Konings, J. Bacteriol. 171:292-298, 1989). The second system is a metabolic energy-dependent oligopeptide transport system which transports peptides of four to at least six amino acid residues. The involvement ...

Kunji, E. R.; Smid, E. J.; Plapp, R.; Poolman, B.; Konings, W. N.

1993-01-01

369

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

370

Discovery of an Auto-Regulation Mechanism for the Maltose ABC Transporter MalFGK2  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The maltose transporter MalFGK2, together with the substrate-binding protein MalE, is one of the best-characterized ABC transporters. In the conventional model, MalE captures maltose in the periplasm and delivers the sugar to the transporter. Here, using nanodiscs and proteoliposomes, we instead find that MalE is bound with high-affinity to MalFGK2 to facilitate the acquisition of the sugar. When the maltose concentration exceeds the transport capacity, MalE captures maltose and dissociates f...

Bao, Huan; Duong, Franck

2012-01-01

371

Deposition patterns and transport mechanisms for the endocrine disruptor 4-nonylphenol across the Sierra Nevada Mountains, California.  

Science.gov (United States)

Dust and particulate distribution patterns are shifting as global climate change brings about longer drought periods. Particulates act as vehicles for long range transport of organic pollutants, depositing at locations far from their source. Nonylphenol, a biodegradation product of nonylphenol polyethoxylate, is a known endocrine disruptor. Nonylphenol polyethoxylate enters the environment as an inert ingredient in pesticide sprays, potentially traveling great distances from its application site. This is of concern when a highly agricultural region, California's Central Valley, lies adjacent to sensitive areas like the Eastern Sierra Nevada Mountains. The distribution and transport mechanisms for 4-nonylphenol were investigated in Eastern Sierra Nevada canyons. Regions close to canyon headwalls showed trace amounts of 4-nonylphenol in surface water, snow, and atmospheric deposition. Exposed areas had yearly average concentrations as high as 9 ?g/L. Distribution patterns are consistent with particulate-bound transport. This suggests with increasing drought periods, higher levels of persistent organic pollutants are likely. PMID:25215456

Lyons, Rebecca; Van de Bittner, Kyle; Morgan-Jones, Sean

2014-12-01

372

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)

373

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Zhang, Lisha; Huang, Min; Harsay, Edina

2010-01-01

374

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

International Nuclear Information System (INIS)

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

375

Current bistability and carrier transport mechanisms of organic bistable devices based on hybrid Ag nanoparticle-polymethyl methacrylate polymer nanocomposites  

Science.gov (United States)

The current bistability and the carrier transport mechanisms of organic bistable devices (OBDs) using Ag nanoparticle-polymethyl methacrylate (PMMA) nanocomposites have been investigated. Current-voltage measurements at 300 K on the Al/Ag nanoparticles embedded in the PMMA layer/indium-tin-oxide devices exhibit a current bistability with an ON/OFF ratio of 103. Write-read-erase-read sequence results demonstrate the switching characteristics of the OBD. The cycling endurance number of the ON/OFF switching for the OBD is above 7×104. The current bistability and carrier transport mechanisms of the OBD fabricated utilizing hybrid Ag nanoparticle-PMMA polymer nanocomposites are described on the basis of the experimental data.

Kim, Won Tae; Jung, Jae Hun; Kim, Tae Whan; Son, Dong Ick

2010-06-01

376

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2012-01-01

377

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

378

Seismic pumping and cataclastic flow - important transport mechanisms during hydration and metasomatism of the oceanic lithosphere  

Science.gov (United States)

Transform faults are the locus of earthquakes that extend down to 29 km below the seafloor (Choy and McGarr 2002). These faults are also associated with a mass deficiency (Gregg et al. 2007) possibly caused by extensive serpentinization. The mantle and crustal sections of the Leka ophiolite is characterized by deformation at all scales including faults and shear zones. Ongoing investigations of these structures reveal that olivine is strongly fractured and faulted. Tabular fragments of olivine are rotated relative to each other locally forming bookshelf-like fault pattern. Serpentine and diopside fill the space between the rotated fragments, and the texture suggests that these minerals grew in opening caused by the faults. The growth of secondary minerals indicated high fluid fluxes along these deformation zones. The space created by the faulting is estimated to ca 50 %.The main slip surfaces are decorated by banded serpentine. Each band represents a slip event and more than 10 slip events are recorded across a 1 cm broad fault zone. The faulting and fragmentation of the olivine, the opening of space between the fragments, combined with mineral growth and repeated faulting provides an efficient seismic (?) pumping system. Rodingites with textures indicating cataclastic flow are developed along some of the faults. The rodingites also show evidence of repeated deformations and growth of minerals such as vesuvianite, grossular and diposide. It is suggested that faulting including seismic pumping and cataclastic flow is an efficient mechanism to hydrate the oceanic lithosphere and cause serpentinization and metasomatism along transform/fracture zones. Choy and McGarr 2002. Geophys J. Int 150 506-523 Gregg et al. 2007. Nature 448, 183-187

Austrheim, H.; Jung, H.; Prestvik, T.

2009-04-01

379

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

CERN Document Server

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

Vikhrenko, V S; Groda, Y G

2003-01-01

380

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

 
 
 
 
381

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2011-01-01

382

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2010-01-01

383

Mechanisms to explain the reverse perivascular transport of solutes out of the brain.  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Experimental studies and observations in the human brain indicate that interstitial fluid and solutes, such as amyloid-beta (Abeta), are eliminated from grey matter of the brain along pericapillary and periarterial pathways. It is unclear, however, what constitutes the motive force for such transport within blood vessel walls, which is in the opposite direction to blood flow. In this paper the potential for global pressure differences to achieve such transport are considered. A mathematical m...

Schley, D.; Carare-nnadi, R.; Please, Cp; Perry, VH; Weller, Ro

2006-01-01

384

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Tanford, C.

1982-01-01

385

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Saksena, Seema; Theegala, Saritha; Bansal, Nikhil; Gill, Ravinder K.; Tyagi, Sangeeta; Alrefai, Waddah A.; Ramaswamy, Krishnamurthy; Dudeja, Pradeep K.

2009-01-01

386

SLC5 and SLC2 transporters in epithelia-cellular role and molecular mechanisms.  

Science.gov (United States)

Members of the SLC5 and SLC2 family are prominently involved in epithelial sugar transport. SGLT1 (sodium-glucose transporter) and SGLT2, as representatives of the former, mediate sodium-dependent uptake of sugars into intestinal and renal cells. GLUT2 (glucose transporter), as representative of the latter, facilitates the sodium-independent exit of sugars from cells. SGLT has played a major role in the formulation and experimental proof for the existence of sodium cotransport systems. Based on the sequence data and biochemical and biophysical analyses, the role of extramembranous loops in sugar and inhibitor binding can be delineated. Crystal structures and homology modeling of SGLT reveal that the sugar translocation involves operation of two hydrophobic gates and intermediate exofacial and endofacial occluded states of the carrier in an alternating access model. The same basic model is proposed for GLUT1. Studies on GLUT1 have pioneered the isolation of eukaryotic transporters by biochemical methods and the development of transport kinetics and transporter models. For GLUT1, results from extensive mutagenesis, cysteine substitution and accessibility studies can be incorporated into a homology model with a barrel-like structure in which accessibility to the extracellular and intracellular medium is altered by pinching movements of some of the helices. For SGLT1 and GLUT1, the extensive hydrophilic and hydrophobic interactions between sugars and binding sites of the various intramembrane helices occur and lead to different substrate specificities and inhibitor affinities of the two transporters. A complex network of regulatory steps adapts the transport activity to the needs of the body. PMID:23177983

Raja, Mobeen; Puntheeranurak, Theeraporn; Hinterdorfer, Peter; Kinne, Rolf

2012-01-01

387

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

388

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

International Nuclear Information System (INIS)

In low/intermediate-level waste (L/ILW) repositories, anaerobic corrosion of metals and degradation of organic materials produce hydrogen, methane, and carbon dioxide. Gas accumulation and gas transport in a L/ILW repository is an important component in the safety assessment of proposed deep repositories in low-permeability formations. The dominant gas transport mechanisms are dependent on the gas overpressures as with increasing overpressure the gas transport capacity of the system increases. The dominant gas transport mechanisms occurring with increasing gas pressure within the anticipated pressure ranges are: diffusion of gas dissolved in pore water (1), two phase flow in the host rock and the excavation damaged zone (EDZ) whereby no deformation of the pore space occurs (2), gas migration within parts of the repository (if repository materials are appropriately chosen) (3) and pathway dilation (4). Under no circumstances the gas is expected to induce permanent fractures in the host rock. This paper focuses on the gas migration in parts of the repository whereby materials are chosen aimed at increasing the gas transport capacity of the backfilled underground structures without compromising the radionuclide retention capacity of the engineered barrier system (EBS). These materials with enhanced gas permeability and low water permeability can supplement the gas flow that is expected to occur through the EDZ and the host rock. The impact of the use of adapted backfill The impact of the use of adapted backfill and sealing materials on