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1

Nature and main kinds of psychopathological mechanisms  

Directory of Open Access Journals (Sweden)

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

Panagiotis Oulis

2010-01-01

2

Maine`s electric revenue adjustment mechanism: Why it fizzled  

Energy Technology Data Exchange (ETDEWEB)

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

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

1995-10-01

3

Mechanical conveying, transporting and feeding  

Energy Technology Data Exchange (ETDEWEB)

This publication comprises of 32 technical papers on Mechanical conveying, transporting and feeding which have been selected and reprinted from the Bulk Solids Handling journal 1981-1985. The contents include all aspects of bulk solids transportation written by experts in mechanical conveying and transportation systems. Areas covered consist of vibrating conveyors feeding equipment, bulk elevators and dumping systems. Other fields such as bulk packaging and materials handling are also discussed.

1986-01-01

4

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)

1977-01-01

5

Molecular mechanisms of cystine transport.  

UK PubMed Central (United Kingdom)

The transport of L-cystine into cells of the mammalian brain is an essential step in the supply of cysteine for synthesis of the antioxidant glutathione. Uptake of L-cystine in rat brain synaptosomes occurs by three mechanisms that are distinguishable on the basis of their ionic dependence, kinetics of transport and specificity of inhibitors. Almost 90% of L-cystine transport is by a low-affinity, sodium-dependent mechanism (K(m)=473+/-146 microM), that is mediated by the X(AG)- family of glutamate transporters. Both L-glutamate (IC(50)=9.1+/-0.4 microM) and L-cysteine sulphinate (IC(50)=16.4+/-3.6 microM) are non-competitive inhibitors of sodium-dependent L-[(14)C]cystine transport, whereas L-trans-pyrrolidine-2,4-dicarboxylic acid (IC(50)=5.6+/-2.0 microM), L-serine-O-sulphate (IC(50)=13.2+/-5.4 microM), kainate (IC(50)=215+/-78 microM) and L-cysteine (IC(50)=363+/-63 microM) are competitive inhibitors. L-Cystine has no effect on the sodium-dependent uptake of D-[(3)H]aspartate. These results suggest that L-cystine binds to a site that is different from the L-glutamate recognition site on X(AG)- glutamate transporters. In rat brain slices, sodium-dependent transport of both L-glutamate and L-cystine is necessary for maintaining glutathione levels. Uptake of L-cystine is sensitive to inhibition by an increased extracellular concentration of L-glutamate, which has important implications for understanding conditions that may initiate oxidative stress.

McBean GJ; Flynn J

2001-11-01

6

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

International Nuclear Information System (INIS)

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

2007-10-05

7

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

Energy Technology Data Exchange (ETDEWEB)

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

1992-10-01

8

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.

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

2012-01-01

9

[Calcium transport mechanisms in neuroprotection and neurotoxicity].  

UK PubMed Central (United Kingdom)

INTRODUCTION: Calcium (Ca²(+)) has been found to be involved in neuroprotective processes, by triggering enzymatic cascades that are essential for the synthesis and functioning of the elements that carry out this process. However, it is paradoxical that this ion is one of the main initiators of apoptotic cascades. This difference in its effects is conditioned by differences in the cytoplasmic concentrations. DEVELOPMENT: Ca²(+) plays a role in the activation of antiapoptotic signals in the neuron when its levels rise moderately, but it also starts apoptotic processes that are triggered mainly by its accumulation in mitochondria. This Ca²(+) comes from the outside or from intracellular deposits by means of different types of transporters. In order to assess the role of Ca²(+) in these processes, it is necessary to consider all the means of transport in an integral manner, since manipulating it pharmacologically gives rise to either protective or toxic processes, due to alterations in the intracellular concentrations of the ion. CONCLUSIONS: Notable progress has been made in the understanding of the effects of Ca²(+) on the central nervous system and on the mechanisms for controlling and transporting it. It is important to stress that understanding these physiological processes has led to the development of drugs with protective effects and, although most of them are still in the study phase or display important side effects, it remains a promising field that will help in the development of useful therapeutic strategies in neuroprotection.

Sánchez JC; López-Zapata DF; Romero-Leguizamón CR

2010-11-01

10

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

CERN Multimedia

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

11

Manganese Transport via the Transferrin Mechanism  

Science.gov (United States)

Excessive manganese (Mn) uptake by brain cells, particularly in regions like the basal ganglia, can lead to toxicity. Mn2+ is transported into cells via a number of mechanisms, while Mn3+ is believed to be transported similarly to iron (Fe) via the transferrin (Tf) mechanism. Cellular Mn uptake is therefore determined by the activity of the mechanisms transporting Mn into each type of cell and by the amounts of Mn2+, Mn3+ and their complexes to which these cells are exposed; this complicates understanding the contributions of each transporter to Mn toxicity. While uptake of Fe3+ via the Tf mechanism is well understood, uptake of Mn3+ via this mechanism has not been systematically studied. The stability of the Mn3+Tf complex allowed us to form and purify this complex and label it with a fluorescent (Alexa green) tag. Using purified and labeled Mn3+Tf and biophysical tools, we have developed a novel approach to study Mn3+Tf transport independently of other Mn transport mechanisms. This approach was used to compare the uptake of Mn3+Tf into neuronal cell lines with published descriptions of Fe3+ uptake via the Tf mechanism, and to obtain quantitative information on Mn uptake via the Tf mechanism. Results confirm that in these cell lines significant Mn3+ is transported by the Tf mechanism similarly to Fe3+Tf transport; although Mn3+Tf transport is markedly slower than other Mn transport mechanisms. This novel approach may prove useful for studying Mn toxicity in other systems and cell types.

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

2013-01-01

12

Common folds and transport mechanisms of secondary active transporters.  

UK PubMed Central (United Kingdom)

Secondary active transporters exploit the electrochemical potential of solutes to shuttle specific substrate molecules across biological membranes, usually against their concentration gradient. Transporters of different functional families with little sequence similarity have repeatedly been found to exhibit similar folds, exemplified by the MFS, LeuT, and NhaA folds. Observations of multiple conformational states of the same transporter, represented by the LeuT superfamily members Mhp1, AdiC, vSGLT, and LeuT, led to proposals that structural changes are associated with substrate binding and transport. Despite recent biochemical and structural advances, our understanding of substrate recognition and energy coupling is rather preliminary. This review focuses on the common folds and shared transport mechanisms of secondary active transporters. Available structural information generally supports the alternating access model for substrate transport, with variations and extensions made by emerging structural, biochemical, and computational evidence.

Shi Y

2013-01-01

13

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

International Nuclear Information System (INIS)

[en] 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)

2003-01-01

14

Mitochondrial calcium transport: mechanisms and functions.  

Science.gov (United States)

Ca(2+)transport across the mitochondrial inner membrane is facilitated by transporters having four distinct sets of characteristics as well as through the Ca(2+)-induced mitochondrial permeability transition pore (PTP). There are two modes of inward transport, referred to as the Ca(2+)uniporter and the rapid mode or RaM. There are also two distinct mechanisms mediating outward transport, which are not associated with the PTP, referred to as the Na(+)-dependent and the Na(+)-independent Ca(2+)efflux mechanisms. Several important functions have been proposed for these mechanisms, including control of the metabolic rate for cellular energy (ATP) production, modulation of the amplitude and shape of cytosolic Ca(2+)transients, and induction of apoptosis through release of cytochrome c from the mitochondrial inter membrane space into the cytosolic space. The goals of this review are to survey the literature describing the characteristics of the mechanisms of mitochondrial Ca(2+)transport and their proposed physiological functions, emphasizing the more recent contributions, and to consider how the observed characteristics of the mitochondrial Ca(2+)transport mechanisms affect our understanding of their functions. PMID:11115368

Gunter, T E; Buntinas, L; Sparagna, G; Eliseev, R; Gunter, K

15

THE MECHANISM OF ISOTONIC WATER TRANSPORT.  

UK PubMed Central (United Kingdom)

The mechanism by which active solute transport causes water transport in isotonic proportions across epithelial membranes has been investigated. The principle of the experiments was to measure the osmolarity of the transported fluid when the osmolarity of the bathing solution was varied over an eightfold range by varying the NaCl concentration or by adding impermeant non-electrolytes. An in vitro preparation of rabbit gall bladder was suspended in moist oxygen without an outer bathing solution, and the pure transported fluid was collected as it dripped off the serosal surface. Under all conditions the transported fluid was found to approximate an NaCl solution isotonic to whatever bathing solution used. This finding means that the mechanism of isotonic water transport in the gall bladder is neither the double membrane effect nor co-diffusion but rather local osmosis. In other words, active NaCl transport maintains a locally high concentration of solute in some restricted space in the vicinity of the cell membrane, and water follows NaCl in response to this local osmotic gradient. An equation has been derived enabling one to calculate whether the passive water permeability of an organ is high enough to account for complete osmotic equilibration of actively transported solute. By application of this equation, water transport associated with active NaCl transport in the gall bladder cannot go through the channels for water flow under passive conditions, since these channels are grossly too impermeable. Furthermore, solute-linked water transport fails to produce the streaming potentials expected for water flow through these passive channels. Hence solute-linked water transport does not occur in the passive channels but instead involves special structures in the cell membrane, which remain to be identified.

DIAMOND JM

1964-09-01

16

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 spec

Geiseler, Jens; Karg, Ortrud; Börger, Sandra; Becker, Kurt; Zimolong, Andreas

2010-01-01

17

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

Science.gov (United States)

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

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

2003-01-01

18

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

International Nuclear Information System (INIS)

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

2008-01-01

19

Transport Mechanism of a Bacterial Homologue of Glutamate Transporters  

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-01-01

20

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

International Nuclear Information System (INIS)

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

1975-03-20

 
 
 
 
21

Soil mechanics and transport in porous media  

CERN Document Server

This book contains an overview of the most relevant scientific contributions of Gerard de Josselin de Jong to the development of both Soil Mechanics and Transport in Porous Media. The volume comprises a selection of papers by de Josselin de Jong as they were published in the international scientific literature. In addition, some unpublished, but highly relevant work has been included. Most of the papers by de Josselin de Jong are concerned with issues related to soil mechanics. This is not surprising, considering the fact that he worked at Delft Soil Mechanics Laboratory and given the nature o

Schotting, Ruud J; Verruijt, Arnold

2008-01-01

22

Structure and mechanism of a nitrate transporter.  

UK PubMed Central (United Kingdom)

The nitrate/nitrite transporters NarK and NarU play an important role in nitrogen homeostasis in bacteria and belong to the nitrate/nitrite porter family (NNP) of the major facilitator superfamily (MFS) fold. The structure and functional mechanism of NarK and NarU remain unknown. Here, we report the crystal structure of NarU at a resolution of 3.1 Å and systematic biochemical characterization. The two molecules of NarU in an asymmetric unit exhibit two distinct conformational states: occluded and partially inward-open. The substrate molecule nitrate appears to be coordinated by four highly conserved, charged, or polar amino acids. Structural and biochemical analyses allowed the identification of key amino acids that are involved in substrate gating and transport. The observed conformational differences of NarU, together with unique sequence features of the NNP family transporters, suggest a transport mechanism that might deviate from the canonical rocker-switch model.

Yan H; Huang W; Yan C; Gong X; Jiang S; Zhao Y; Wang J; Shi Y

2013-03-01

23

Dynamic analysis of the mechanical systems vibrating transversally in transportation  

Directory of Open Access Journals (Sweden)

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

A. Buchacz; S. ?ó?kiewski

2007-01-01

24

Mechanisms involved in iontophoretic transport of angiotensin.  

UK PubMed Central (United Kingdom)

PURPOSE: The feasibility of using iontophoresis to enhance the permeation rate of a model peptide was investigated in vitro using hairless mouse skin. METHODS: Angiotensin 2 (AT 2) was employed as a permeant probe, using optimum iontophoresis conditions. A number of physicochemical parameters (donor ionic strength; valence of competitive ions; pH of donor solution) were studied with the aim of exploring the mechanisms involved in the iontophoretic transport through the skin: electrokinetic transport or convective transport. For this purpose, the magnitude of the convective solvent flow was also evaluated by the permeation of (3H) H2O. The interest of pulsed currents for peptide delivery was also investigated and the effect of current density and frequency was studied. RESULTS: AT 2 transport was found to be enhanced 20-fold in comparison to passive permeation and was found to be proportional to the current density with direct currents as with pulsed currents. CONCLUSIONS: Although the flux enhancement of ions during iontophoresis is due principally to the electrical potential gradient, secondary effects such as convective solvent flow contribute also to flux enhancement of peptide delivery. This effect is dependent of physicochemical conditions of formulation.

Clemessy M; Couarraze G; Bevan B; Puisieux F

1995-07-01

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.

A. Buchacz; S. ?ó?kiewski

2007-01-01

26

As if Kyoto mattered: The clean development mechanism and transportation  

International Nuclear Information System (INIS)

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

2007-01-01

27

Molecular Mechanism of Ochratoxin A Transport in the Kidney  

Directory of Open Access Journals (Sweden)

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

Naohiko Anzai; Promsuk Jutabha; Hitoshi Endou

2010-01-01

28

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

Energy Technology Data Exchange (ETDEWEB)

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.

Charbonneau, P.; Michaud, G.; Proffitt, C.R. (Montreal Universite (Canada))

1989-12-01

29

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

Science.gov (United States)

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.

Charbonneau, Paul; Michaud, Georges; Proffitt, Charles R.

1989-12-01

30

Administrative mechanics of research fuel transportation  

International Nuclear Information System (INIS)

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

1983-01-01

31

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; Marcio Nogueira Rodrigues; Phelipe Oliveira Favaron; Antonio Chaves de Assis Neto; Eduardo Harry Birgel Júnior; Maria Angelica Miglino

2013-01-01

32

Studies on lipid transport mechanism in the fish  

International Nuclear Information System (INIS)

[en] 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, Band 1 associated mainly with FFA plays an important role in fish lipid transport. (auth.)

1976-01-01

33

Chemical and mechanical control of corrosion product transport  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-01

34

Current transport mechanisms in ITO/nSi structures  

International Nuclear Information System (INIS)

The state of the semiconductor-insulator interface plays an important role in the process of radiation generated charge carrier separation and, therefore, in conversion efficiency increasing. The information about the state of the semiconductor-insulator interface could be obtained from the investigation of dark current-voltage characteristics and the determination of charge transport mechanisms through this interface what is the main purpose of this communication. In n+ITO/SiO2/nSi structures two mechanisms of the direct current flow are observed: tunneling-recombination at direct voltage less than 0.3 V and over barrier emission at voltages more than 0.3 V. The reduction of the influence of the former will lead to the increase in efficiency of the conversion of the solar energy into electric one by the investigated structures. Further investigations of the interface at various thicknesses of the insulator layer are necessary to clarify the case.

2009-01-01

35

Mechanism of ochratoxin A transport in kidney  

Energy Technology Data Exchange (ETDEWEB)

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

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

1988-08-01

36

Longitudinal vibrations of mechanical systems with the transportation effect  

Directory of Open Access Journals (Sweden)

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

A. Buchacz; S. ?ó?kiewski

2009-01-01

37

H+ transporters in the main excretory duct of the mouse mandibular salivary gland.  

Science.gov (United States)

1. We used microspectrofluorimetry with the pH-sensitive fluoroprobe 2',7'-bis(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF) to study the regulation of cytosolic pH (pHi) in the isolated, perfused main excretory duct of the mouse mandibular gland. 2. In nominally HCO3(-)-free solutions, removal of Na+ from the lumen alone caused pHi to decline whereas removing it from the bath alone did not. 3. Readmission of Na+ to the lumen of ducts studied under zero-Na+ conditions caused pHi to recover fully. This recovery was blocked by 5-(N-ethyl-N-isopropyl)-amiloride (EIPA) with a half-maximum concentration of 0.5 mumol l-1, indicating the presence of an apical Na(+)-H+ exchanger. 4. Readmission of Na+ to the bath of ducts studied under zero-Na+ conditions also caused pHi to recover. This recovery was blocked by 100 mumol l-1 EIPA, indicating the presence of a basolateral Na(+)-H+ exchanger. 5. Measurements of H+ fluxes indicated that the apical Na(+)-H+ exchanger was approximately four times more active than the basolateral Na(+)-H+ exchanger. 6. In three sets of experiments (in the absence of Na+, in the presence of Na+, and in the presence of Na+ plus 100 mumol l-1 EIPA), the effects of changing luminal K+ concentration on pHi were examined. We found no evidence for the presence of K(+)-H+ exchange or Na(+)-coupled K(+)-H+ exchange in the apical membranes of duct cells. 7. pHi recovery under nominally HCO3(-)-free conditions following acidification with an NH4Cl pulse was abolished by removal of Na+ from the bath and luminal solutions, indicating that no Na(+)-independent systems such as H(+)-ATPases were present. 8. A repeat of the above experiments in the presence of 25 mmol l-1 HCO3- plus 5% CO2 did not reveal any additional H+ transport systems. The removal of luminal Cl-, however, caused a small rise in pHi. This latter effect was blocked by 500 mumol l-1 4,4'-diisothiocyanatodihydrostilbene-2,2'-disulphonic acid (H2-DIDS), suggesting that a Cl(-)-HCO3- exchanger in the apical membrane might contribute in a minor way to pHi regulation. 9. We conclude that the predominant H+ transport systems in the mouse mandibular main excretory duct are Na(+)-H+ exchangers in the apical and the basolateral membranes. The model we postulate to account for electrolyte transport across the main duct in the mouse mandibular gland is quite different from that previously developed for the rat duct but is similar to that developed for the rabbit duct. The difference is in concordance with the known ability of the mandibular gland of the rat, but not the rabbit or the mouse, to secrete a HCO3(-)-rich final saliva. PMID:9379413

Chaturapanich, G; Ishibashi, H; Dinudom, A; Young, J A; Cook, D I

1997-09-15

38

Structural insights into ABC transporter mechanism  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-07-27

39

Effect of main technological design parameters of percussion mechanisms for eliminating jamming on their energy characteristics  

Energy Technology Data Exchange (ETDEWEB)

Requirements are examined for the main design and technological parameters (length of the free telescopic stroke of the mechanism, its triggering stress, force of the impact realized by it, features of the layout) of percussion devices used to eliminate jamming and installed in direct proximity to the site of jamming of the elements in layout of the bottom of the drilling string (KNBK). It is indicated that the wave theory of percussion explains fairly simply the physical meaning of the processes occurring, and makes it possible to obtain a relationship which can be used to achieve satisfactory accuracy in planning percussion mechanisms and their operating mode in a well.

Panov, V.N.

1982-01-01

40

[Main influencing factors of functional magnetic resonance imaging for acupuncture mechanism research].  

UK PubMed Central (United Kingdom)

Functional magnetic resonance imaging (fMRI) has been widely used in the research of acupuncture mechanism in recent years. This article analyzes the effect of four main influencing factors, i.e., research subject, selection of acupoints, manipulation of acupuncture and evaluation of Deqi, and examples are given to explain research application of these four aspects. Based on those mentioned above, the authors presumed that removing ex terior and interior factors of research subject, optimizing compatibility of acupoints and manipulations of acupuncture and making use of correct evaluation scale of Deqi can improve the scientificity and objectivity of fMRI for evaluation of acupuncture mechanism research.

Liu ZP; Wu W; Zhang SS

2013-02-01

 
 
 
 
41

The mechanically based non-local elasticity: an overview of main results and future challenges.  

UK PubMed Central (United Kingdom)

The mechanically based non-local elasticity has been used, recently, in wider and wider engineering applications involving small-size devices and/or materials with marked microstructures. The key feature of the model involves the presence of non-local effects as additional body forces acting on material masses and depending on their relative displacements. An overview of the main results of the theory is reported in this paper.

Di Paola M; Failla G; Pirrotta A; Sofi A; Zingales M

2013-06-01

42

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

UK PubMed Central (United Kingdom)

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

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

2010-07-01

43

A Finite Element Model for Mechanical Analysis of LHC Main Dipole Magnet Coils  

CERN Multimedia

After years of studies and observations, the mechanical stability of the LHC main dipole magnets still remains an open issue. The robustness of these magnets has already been asserted and their reliability in operation is not far from being proven. However, anomalous mechanical behaviors sometimes observed are not yet completely understood. A finite element model, which has been recently developed at CERN, aims at providing an instrument for better explaining these anomalies. Cable modeling and contact between elements, friction and mechanical hysteresis are the key features of this model. The simulation of the hysteresis experienced by the coil during collaring, presented here, is the starting point for the representation of the whole life cycle of the dipole coil.

Pojer, Mirko; Scandale, Walter

2007-01-01

44

Grain transport mechanics in shallow overland flow  

Science.gov (United States)

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

45

Grain transport mechanics in shallow flow  

Science.gov (United States)

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

46

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

International Nuclear Information System (INIS)

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

2010-10-01

47

Transport Mechanisms in Polarized Semiconductor Photocathodes  

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-12-18

48

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

UK PubMed Central (United Kingdom)

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.

Larsen PF; Gaudette HE

2010-08-01

49

Molecular mechanism of the Escherichia coli maltose transporter.  

Science.gov (United States)

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

Chen, Jue

2013-04-27

50

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

51

Simulation studies of the mechanism of membrane transporters.  

UK PubMed Central (United Kingdom)

Membrane transporters facilitate active transport of their specific substrates, often against their electrochemical gradients across the membrane, through coupling the process to various sources of cellular energy, for example, ATP binding and hydrolysis in primary transporters, and pre-established electrochemical gradient of molecular species other than the substrate in the case of secondary transporters. In order to provide efficient energy-coupling mechanisms, membrane transporters have evolved into molecular machines in which stepwise binding, translocation, and transformation of various molecular species are closely coupled to protein conformational changes that take the transporter from one functional state to another during the transport cycle. Furthermore, in order to prevent the formation of leaky states and to be able to pump the substrate against its electrochemical gradient, all membrane transporters use the widely-accepted "alternating access mechanism," which ensures that the substrate is only accessible from one side of the membrane at a given time, but relies on complex and usually global protein conformational changes that differ for each family of membrane transporters. Describing the protein conformational changes of different natures and magnitudes is therefore at the heart of mechanistic studies of membrane transporters. Here, using a number of membrane transporters from diverse families, we present common protocols used in setting up and performing molecular dynamics simulations of membrane transporters and in analyzing the results, in order to characterize relevant motions of the system. The emphasis will be on highlighting how optimal design of molecular dynamics simulations combined with mechanistically oriented analysis can shed light onto key functionally relevant protein conformational changes in this family of membrane proteins.

Enkavi G; Li J; Mahinthichaichan P; Wen PC; Huang Z; Shaikh SA; Tajkhorshid E

2013-01-01

52

Determining the transport mechanism of an enzyme-catalytic complex metabolic network based on biological robustness.  

UK PubMed Central (United Kingdom)

Understanding the transport mechanism of 1,3-propanediol (1,3-PD) is of critical importance to do further research on gene regulation. Due to the lack of intracellular information, on the basis of enzyme-catalytic system, using biological robustness as performance index, we present a system identification model to infer the most possible transport mechanism of 1,3-PD, in which the performance index consists of the relative error of the extracellular substance concentrations and biological robustness of the intracellular substance concentrations. We will not use a Boolean framework but prefer a model description based on ordinary differential equations. Among other advantages, this also facilitates the robustness analysis, which is the main goal of this paper. An algorithm is constructed to seek the solution of the identification model. Numerical results show that the most possible transport way is active transport coupled with passive diffusion.

Wang L

2013-04-01

53

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

International Nuclear Information System (INIS)

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

1977-08-19

54

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

55

Production mechanism of the polar wall of the main ionospheric through  

International Nuclear Information System (INIS)

[en] Consideration is given to formation mechanism and dynamics of polar wall of the main ionospheric through electron concentration of ionosphere F region. Model of high-energy electron precipitations in auroral oval, working at any level of geomagnetic activity, has been created. Model calculations of electron concentration in F2 layer maximum at Kp=0 and 5 were conducted. It is shown that increase of geomagnetic activity up to Kp=5 leads to displacement of the polar wall of the through to equator approximately by 7 deg. This is supported by experimental data. Minor changes of electron concentration gradient on polar wall of the through, connected with variation of geomagnetic activity level, are simulated. 34 refs

1993-01-01

56

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

International Nuclear Information System (INIS)

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

1993-01-01

57

The mechanism for thermal decomposition of cellulose and its main products.  

Science.gov (United States)

Experiment is performed to investigate the mechanism of the cellulose pyrolysis and the formation of the main products. The evolution of the gaseous products is examined by the 3-D FTIR spectrogram at the heating rate of 5-60 K/min. A pyrolysis unit, composed of fluidized bed reactor, carbon filter, vapour condensing system and gas storage, is employed to investigate the products of the cellulose pyrolysis under different temperatures (430-730 degrees C) and residence time (0.44-1.32 s). The composition in the bio-oil is characterized by GC-MS while the gases sample is analyzed by GC. The effects of temperature and residence time on the main products in bio-oil (LG, 5-HMF, FF, HAA, HA and PA) are examined thoroughly. Furthermore the possible routes for the formation of the products are developed from the direct conversion of cellulose molecules and the secondary reactions of the fragments. It is found that the formation of CO is enhanced with elevated temperature and residence time, while slight change is observed for the yield of CO(2). PMID:19625184

Shen, D K; Gu, S

2009-07-21

58

The mechanism for thermal decomposition of cellulose and its main products.  

UK PubMed Central (United Kingdom)

Experiment is performed to investigate the mechanism of the cellulose pyrolysis and the formation of the main products. The evolution of the gaseous products is examined by the 3-D FTIR spectrogram at the heating rate of 5-60 K/min. A pyrolysis unit, composed of fluidized bed reactor, carbon filter, vapour condensing system and gas storage, is employed to investigate the products of the cellulose pyrolysis under different temperatures (430-730 degrees C) and residence time (0.44-1.32 s). The composition in the bio-oil is characterized by GC-MS while the gases sample is analyzed by GC. The effects of temperature and residence time on the main products in bio-oil (LG, 5-HMF, FF, HAA, HA and PA) are examined thoroughly. Furthermore the possible routes for the formation of the products are developed from the direct conversion of cellulose molecules and the secondary reactions of the fragments. It is found that the formation of CO is enhanced with elevated temperature and residence time, while slight change is observed for the yield of CO(2).

Shen DK; Gu S

2009-12-01

59

X-ray structure of dopamine transporter elucidates antidepressant mechanism.  

UK PubMed Central (United Kingdom)

Antidepressants targeting Na(+)/Cl(-)-coupled neurotransmitter uptake define a key therapeutic strategy to treat clinical depression and neuropathic pain. However, identifying the molecular interactions that underlie the pharmacological activity of these transport inhibitors, and thus the mechanism by which the inhibitors lead to increased synaptic neurotransmitter levels, has proven elusive. Here we present the crystal structure of the Drosophila melanogaster dopamine transporter at 3.0?Å resolution bound to the tricyclic antidepressant nortriptyline. The transporter is locked in an outward-open conformation with nortriptyline wedged between transmembrane helices 1, 3, 6 and 8, blocking the transporter from binding substrate and from isomerizing to an inward-facing conformation. Although the overall structure of the dopamine transporter is similar to that of its prokaryotic relative LeuT, there are multiple distinctions, including a kink in transmembrane helix 12 halfway across the membrane bilayer, a latch-like carboxy-terminal helix that caps the cytoplasmic gate, and a cholesterol molecule wedged within a groove formed by transmembrane helices 1a, 5 and 7. Taken together, the dopamine transporter structure reveals the molecular basis for antidepressant action on sodium-coupled neurotransmitter symporters and elucidates critical elements of eukaryotic transporter structure and modulation by lipids, thus expanding our understanding of the mechanism and regulation of neurotransmitter uptake at chemical synapses.

Penmatsa A; Wang KH; Gouaux E

2013-09-01

60

Mass transportation mechanism in electric-biased carbon nanotubes.  

UK PubMed Central (United Kingdom)

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

Zhao J; Huang JQ; Wei F; Zhu J

2010-11-01

 
 
 
 
61

Mass transportation mechanism in electric-biased carbon nanotubes.  

Science.gov (United States)

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

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

2010-11-10

62

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

Energy Technology Data Exchange (ETDEWEB)

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.

Rudakov, D L; Boedo, J A; Moyer, R A; Stangeby, P C; Watkins, J G; Whyte, D G; Zeng, L; Brooks, N H; Doerner, R P; Evans, T E; Fenstermacher, M E; Groth, M; Hollmann, E M; . Krasheninnikov, S I; Lasnier, C J; Leonard, A W; Mahdavi, M A; McKee, G R; McLean, A G; Pigarov, A Y; Wampler, W R; Wang, G; West, W P; Wong, C C

2004-10-19

63

On the Electronic Transport Mechanism in Conducting Polymer Nanofibers  

CERN Multimedia

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

64

Early metabolic effects and mechanism of ammonium transport in yeast  

Energy Technology Data Exchange (ETDEWEB)

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-H/sub 2/O/sub 2/ 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 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.

Pena, A.; Pardo, J.P.; Ramirez, J.

1987-03-01

65

Multi-glasshouse group control device based on multiple main communication mechanisms  

UK PubMed Central (United Kingdom)

The utility model belongs to modern agriculture fiel, and especially relates to a multi-glasshouse group control device based on multiple main communication mechanisms, which is composed of a control room, an EC sensor, a greenhouse environmental controller, a greenhouse actuator, a greenhouse environmental sensor, an outdoor weather station, a PH sensor, an irrigation nutrient solution control valve, an irrigation nutrient solution control pump, the control room is composed of a monitoring supervisory computer and an embedded data concentrator which are connected by RS232 data bus, the embedded data concentrator is connected to the EC sensor, the PH sensor and the irrigation nutrient solution control valve by the analogue signal line, and while are connected to the irrigation nutrient solution control pump by the three phase AC contactor, and are connected to the greenhouse environmental controller and the outdoor weather station by RS485 bus the greenhouse environmental controller is connected to the greenhouse environmental sensor by the analogue signal line, and is connected to the greenhouse environmental sensor by the three phase AC contactor. The utility model effectively controls environmental condition in the greenhouse by using environmental control equipment, by the successive production and management mode, without influenced by place and climate, and effectively improves agriculture ecology and production conditions, promotes scientific exploitation and reasonable utilization of agricultural resources, and improves economic benefit.

XU LIHONG WU

66

Modeling Transport and Flow Regulatory Mechanisms of the Kidney.  

UK PubMed Central (United Kingdom)

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

Layton AT

2012-07-01

67

New insights into the transport mechanisms in plant vacuoles.  

UK PubMed Central (United Kingdom)

The vacuole is the largest compartment in plant cells, often occupying more than 80% of the total cell volume. This organelle accumulates a large variety of endogenous ions, metabolites, and xenobiotics. The compartmentation of divergent substances is relevant for a wide range of biological processes, such as the regulation of stomata movement, defense mechanisms against herbivores, flower coloration, etc. Progress in molecular and cellular biology has revealed that a large number of transporters and channels exist at the tonoplast. In recent years, various biochemical and physiological functions of these proteins have been characterized in detail. Some are involved in maintaining the homeostasis of ions and metabolites, whereas others are related to defense mechanisms against biotic and abiotic stresses. In this review, we provide an updated inventory of vacuolar transport mechanisms and a comprehensive summary of their physiological functions.

Shitan N; Yazaki K

2013-01-01

68

Mechanical vibration and sound levels experienced in neonatal transport.  

UK PubMed Central (United Kingdom)

Exposure of neonates to sound and to mechanical vibration was measured while transferring the neonates to a regional referral unit by ambulance and by rotary wing and fixed wing aircraft. Recordings were made during different phases of each type of transportation and were analyzed later. In the nursery, sound levels ranged from 72 to 74 dBA (A-weighted decibel level) (77 to 81 dB), while in transit, levels were higher at 78 to 99 dBA (90 to 110 dB), depending on the means of transport. Vibration was measured in the horizontal and vertical axes relative to the neonate in different frequency ranges. The vibration acceleration magnitude ranged from 0.4 m/sq s to 5.6 m/sq s, depending on the axis and type of transport; the maximum obtained was in rotary wing transport. When compared with adult tolerance levels, both sound and vibration exposure of the neonate are high and potentially hazardous. Further evaluation of vibration stress and means of attenuating sound and vibration in transport infant incubators is desirable to enhance the safety of transported infants.

Campbell AN; Lightstone AD; Smith JM; Kirpalani H; Perlman M

1984-10-01

69

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

70

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

Directory of Open Access Journals (Sweden)

Full Text Available 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 sediment transportation using hydrological simulations of target years 1991 (before dam construction) and 2002 (after dam completion). Our study area was the main channel of the Mekong River in northern Thailand extending about 100 km downstream from the intersection of Myanmar, Thailand and Laos. We used the MIKE SHE and MIKE11 (Enterprise) models to calculate seasonal changes of water discharge and sediment transport at five points 15-35-km apart in this interval. Sediment load was calculated from a regression equation between sediment load and water discharge, using suspended sediment concentrations in monthly river water samples taken between November 2007 and November 2008. Finally we estimated annual sediment load along the study reach using from both of simulated annual hydrograph and the regression equation. Our simulations showed that after construction of the dam, there was a moderate decrease in peak discharge volume and during the rainy season in August and September and a corresponding increase in the subsequent months. Accordingly, sediment transportation budgets were increased in months after the rainy season. The suspended sediment transportation in Chiang Sean was increased from 21.13 to 27.90 (M ton/year) in our model condition.

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

2013-01-01

71

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

International Nuclear Information System (INIS)

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

2003-01-01

72

Transport mechanisms and enhanced confinement studies in RFX  

International Nuclear Information System (INIS)

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

2001-01-01

73

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

UK PubMed Central (United Kingdom)

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

Weyand S; Shimamura T; Beckstein O; Sansom MS; Iwata S; Henderson PJ; Cameron AD

2011-01-01

74

TRANSMISSION OF IMPACTS DURING MECHANICAL GRAPE HARVESTING AND TRANSPORTATION  

Directory of Open Access Journals (Sweden)

Full Text Available The aim of the research was to study vibrational stress on grapes during mechanical harvesting, transfer and delivery to the winery, in order to identify the most critical stages and the consequent effects on the winemaking. An instrumented sphere was used to evaluate and memorise the impacts in the grape harvester and means of transport. Three treatments, obtained by differing harvesting method (manual and mechanical) and transport type (short and long distance), were compared. A correlation was sought between the transmitted stresses and characteristics of the harvested product. The effects on product quality were evaluated by chemical analyses of the musts and sensorial analysis of the end-product, vinified using the same procedure.

Fabio Pezzi; Claudio Caprara; Francesco Bordini

2008-01-01

75

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

Science.gov (United States)

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

Bar, Arie

2008-12-06

76

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

UK PubMed Central (United Kingdom)

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

Bar A

2009-04-01

77

A Quantum Mechanical Approach To The Polarization Transport of Photons  

CERN Multimedia

Based on quantum mechanical approach the polarization transport of photons which propagate in a medium with slow varying refractive index is studied. The photon polarizations are separated in opposite directions normal to the ray which is called "Spin Hall effect" of photons, and also the rotation of polarization plane, a manifestation of the Berry phase, occurs. This approach can be generalized to other spinning particles in inhomogeneous media as a universal approach.

Torabi, Reza

2010-01-01

78

Increased coordination in public transport-which mechanisms are available?  

DEFF Research Database (Denmark)

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

SØrensen, Claus Hedegaard; Longva, Frode

2011-01-01

79

Increased coordination in public transport – which mechanisms are available?  

DEFF Research Database (Denmark)

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

SØrensen, Claus Hedegaard; Longva, Frode

2011-01-01

80

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

 
 
 
 
81

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.

1992-01-01

82

Mechanism of electrochemical charge transport in individual transition metal complexes.  

Science.gov (United States)

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

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

2006-12-27

83

Diffusion and the dislocation sweeping mechanism for hydrogen transport  

International Nuclear Information System (INIS)

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

1975-09-07

84

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

Directory of Open Access Journals (Sweden)

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

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

2011-01-01

85

[Mechanical stress of newborn infants caused by incubator transport  

UK PubMed Central (United Kingdom)

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

Boenisch H; Gaden W; Mau G; Gohrbandt U; Teuteberg HO; Braun H; Beermann HJ

1985-07-01

86

Calcium transport by mammary secretory cells: mechanisms underlying transepithelial movement.  

UK PubMed Central (United Kingdom)

The secretion of calcium into milk by mammary epithelial cells is a fundamentally important process. Despite this, the mechanisms which underlie the movement of calcium across the lactating mammary gland are still poorly understood. There are, however, two models which describe the handling of calcium by mammary epithelial cells. On the one hand, a model which has existed for several decades, suggests that the vast majority of calcium enters milk via the Golgi secretory vesicle route. On the other hand, a new model has recently been proposed which implies that the active transport of calcium across the apical membrane of mammary secretory cells is central to milk calcium secretion. This short review examines the strengths and weaknesses of both models and suggests some experiments which could add to our understanding of mammary calcium transport.

Shennan DB

2008-01-01

87

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.

1984-01-01

88

Analysis of mechanical systems with transversal vibrations in transportation  

Directory of Open Access Journals (Sweden)

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

A. Buchacz; S. ?ó?kiewski

2008-01-01

89

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

International Nuclear Information System (INIS)

A recent pilot study of a sea transportation system for the radioactive waste storage project ALMA is continued. The mechanical stresses on special shipping containers (with an internal volume of 25 m3) were investigated for normal handling and sea going conditions as well as for extreme conditions following free fall in water or air or caused by ship collisions. A non-shielding steel container was designed on the basis of the results obtained. The report contains collision calculations for the proposed vessel and calculations of velocities due to free fall of the container in water and air. (author)

1979-01-01

90

[Dynamic hyperinflation -- the main mechanism of decreased exercise tolerance in patients with COPD].  

UK PubMed Central (United Kingdom)

Decreased exercise tolerance in patients with COPD is the result of involvement in variable proportion of three mechanisms: ventilatory limitation, muscle dysfunction and cardio-vascular involvement (inadequate intake of oxygen at tissue level). Ventilatory limitation is caused by the combination of increased demand and decreased ventilatory capacity Increased ventilatory demand is the result of exercise worsening of ventilation-perfusion imbalance, and decreased ventilatory capacity is the result of decreased elastic recoil and dynamic obstruction. The consequence is the expiratory flowlimitation, leading to inefficientexpiratory muscle activity and dynamic hyperinflation. Dynamic hyperinflation is a result of structural abnormalities in COPD producing mechanical disorders that limit ventilation. Dynamic hyperinflation has some beneficial effects by facilitating maximal exhalation. Negative effects ofhyperinflation are: (1) decreased tidal volume ability to grow properly at exercise, which causes mechanical ventilatorlimitation; (2) decreased functional capacity of inspiratory musles (by increasing elastic load with respiratory muscle fatigue and increase work ofbreathing); (3) exercise hypoxemia and carbon dioxide retention; (4) impairmentof cardiac function during exercise by decreasing venous return and cardiac output. Evaluation of pulmonary hyperinflation is a useful tool for better characterizing the effects of disease and for monitoring the response of therapeutic interventions on exercise tolerance of patients with COPD.

Gologanu D

2013-03-01

91

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

International Nuclear Information System (INIS)

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

2006-01-01

92

Flux-based transport enhancement as a plausible unifying mechanism for auxin transport in meristem development.  

UK PubMed Central (United Kingdom)

Plants continuously generate new organs through the activity of populations of stem cells called meristems. The shoot apical meristem initiates leaves, flowers, and lateral meristems in highly ordered, spiralled, or whorled patterns via a process called phyllotaxis. It is commonly accepted that the active transport of the plant hormone auxin plays a major role in this process. Current hypotheses propose that cellular hormone transporters of the PIN family would create local auxin maxima at precise positions, which in turn would lead to organ initiation. To explain how auxin transporters could create hormone fluxes to distinct regions within the plant, different concepts have been proposed. A major hypothesis, canalization, proposes that the auxin transporters act by amplifying and stabilizing existing fluxes, which could be initiated, for example, by local diffusion. This convincingly explains the organised auxin fluxes during vein formation, but for the shoot apical meristem a second hypothesis was proposed, where the hormone would be systematically transported towards the areas with the highest concentrations. This implies the coexistence of two radically different mechanisms for PIN allocation in the membrane, one based on flux sensing and the other on local concentration sensing. Because these patterning processes require the interaction of hundreds of cells, it is impossible to estimate on a purely intuitive basis if a particular scenario is plausible or not. Therefore, computational modelling provides a powerful means to test this type of complex hypothesis. Here, using a dedicated computer simulation tool, we show that a flux-based polarization hypothesis is able to explain auxin transport at the shoot meristem as well, thus providing a unifying concept for the control of auxin distribution in the plant. Further experiments are now required to distinguish between flux-based polarization and other hypotheses.

Stoma S; Lucas M; Chopard J; Schaedel M; Traas J; Godin C

2008-10-01

93

[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

94

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

UK PubMed Central (United Kingdom)

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.

Guo M; Lu XW; Ran XY; Hu RH

2012-11-01

95

Calcium transport mechanism in molting crayfish revealed by microanalysis  

Energy Technology Data Exchange (ETDEWEB)

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

Mizuhira, V.; Ueno, M.

1983-01-01

96

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

2011-03-07

97

Exciton delocalization and energy transport mechanisms in R-phycoerythrin.  

UK PubMed Central (United Kingdom)

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.

Womick JM; Liu H; Moran AM

2011-03-01

98

Mass transport mechanisms during excimer laser nitriding of aluminum  

International Nuclear Information System (INIS)

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

2002-06-01

99

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

100

Charge transport mechanism in a typical Au/CdTe Schottky diode  

Energy Technology Data Exchange (ETDEWEB)

The charge transport mechanism in a typical Au/CdTe Schottky diode has been investigated. Evidence for different types of charge transport at different temperature regions has been observed. The dominant transport mechanism in the 100-300K region is identified as the Poole-Frenkel type. The activation energy of the trap level detected in the 100-300K temperature range shows a voltage dependence. The transport mechanism changes at a characteristic temperature of about 270K.

Mathew, Xavier; Pantoja Enriquez, J.; Sebastian, P.J.; Pattabi, M.; Sanchez-Juarez, A.; Campos, J. [Solar-Hydrogen-Fuel cell group, Solar Materials Department, Centro de Investigacion en Energia- UNAM 62580, Temixco, Morelos (Mexico); McClure, J.C. [Metallurgical and Materials Engineering Department, University of Texas El Paso, El Paso, TX (United States); Singh, V.P. [Electrical and Computer Engineering Department, University of Kentucky, Lexington, KY (United States)

2000-08-31

 
 
 
 
101

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

International Nuclear Information System (INIS)

[en] 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)

1996-01-01

102

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-07-01

103

Main trends in heavy ion reaction mechanisms when the energy increases  

International Nuclear Information System (INIS)

[en] 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

1985-01-01

104

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

International Nuclear Information System (INIS)

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

1977-08-19

105

Water-soluble main ions in precipitation over the southeastern Adriatic region: chemical composition and long-range transport.  

UK PubMed Central (United Kingdom)

BACKGROUND, AIM AND SCOPE: Precipitation samples collected from 1995 to 2000 at meteorological station in the eastern outskirts of Herceg Novi (Montenegro) were analysed on Na(+), K(+), Mg(2+), Ca(2+), Cl(-), SO(4) (2-), NO(3)(-) and NH(4)(+). Four-day backward trajectory simulations were conducted during the precipitation period to investigate the regional transport of main ions and their deposition in the region of the southeastern Adriatic Sea. The air mass trajectories were classified into six trajectory categories by the origin and direction of their approach to Herceg Novi. MATERIALS AND METHODS: A bottle and funnel with a small net between them was used for sampling at a height of 1.5 m above the ground. The concentrations of Cl(-), NO(3)(-), NH(4)(+) and SO(4)(2-) were determined spectrophotometrically, the concentrations of Na(+) and K(+) were determined by the FAES method and the concentrations of Mg(2+) and Ca(2+) by the FAAS method. The factor analysis technique (PCA analysis) based on the calculation of the factors was employed to differentiate the contribution of emission sources to the content of the main ions in the precipitation. The obtained data sets were processed using the SPSS 11.5 statistical program. The Hybrid Single-Particle Lagrangian Integrated Trajectory model was used to study the air origin for the city of Herceg Novi (42°27'N, 18°33'E), Montenegro. DISCUSSION: The following origins of the air masses were considered: northern Europe (NE), eastern Europe-northeastern Europe (EE-NE); eastern Mediterranean-southeastern Europe (EM-SE); Africa-Central Mediterranean (A-CM); western Mediterranean (WM); western Europe-Central Europe (WE-CE) and undefined. The heights and frequencies of precipitation coming by air masses from northern Europe and eastern-northeastern Europe are the lowest. On the contrary, the heights and frequencies of precipitation coming by air masses from the western Mediterranean (36.6%) and Africa and the Central Mediterranean (30.6%) are the highest. The sea salt components (Na(+), Cl(-), Mg(2+)) are significantly correlated, except for air masses originating from the northern and eastern European regions. Significant correlations between SO(4)(2-) and NO(3)(-) are found in air masses coming from the western Europe and North Africa, over the Mediterranean. CONCLUSIONS: The highest volume-weighted mean (VWM) of: SO(4)(2-), NH(4)(+) and Mg(2+) are for precipitation from EE-NE while the highest values of VWM of Cl(-) are from WM and of K(+) are from WE-CE. Long-range transport of Sahara dust is confirmed. RECOMMENDATIONS AND PERSPECTIVES: For better estimation of origins of water-soluble ions in precipitation expanding list of analysis on anions of organic acids, such as HCOO(-), CH(3)COO(-), and C(2)H(2)COO(-), could be indicative of volatile organic compounds emitted by vegetation but also traffic. The chemical composition of precipitation together with a study of air backward trajectories is the proper tool for tracking the long-range transport of water-soluble ions and estimating transboundary pollution.

Dor?evi? DS; Tosi? I; Unkasevi? M; Duraskovi? P

2010-11-01

106

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

International Nuclear Information System (INIS)

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

2010-06-01

107

Bidirectional transepithelial water transport: measurement and governing mechanisms.  

UK PubMed Central (United Kingdom)

In the search for the mechanisms whereby water is transported across biological membranes, we hypothesized that in the airways, the hydration of the periciliary fluid layer is regulated by luminal-to-basolateral water transport coupled to active transepithelial sodium transport. The luminal-to-basolateral (JWL-->B) and the basolateral-to-luminal (JWB-->L) transepithelial water fluxes across ovine tracheal epithelia were measured simultaneously. The JWL-->B (6.1 microliter/min/cm2) was larger than JWB-->L (4.5 microliter/min/cm2, p < 0.05, n = 30). The corresponding water diffusional permeabilities were PdL-->B = 1.0 x 10(-4) cm/s and PdB-->L = 7.5 x 10(-5) cm/s. The activation energy (Ea) of JWL-->B (11.6 kcal/mol) was larger than the Ea of JWB-->L (6.5 kcal/mol, p < 0.05, n = 5). Acetylstrophanthidin (100 microM basolateral) reduced JWL-->B from 6.1 to 4.4 microliter/min/cm2 (p < 0. 05, n = 5) and abolished the PD. Amiloride (10 microM luminal) reduced JWL-->B from 5.7 to 3.7 microliter/min/cm2 (p < 0.05, n = 5) and reduced PD by 44%. Neither of these agents significantly changed JWB-->L. These data indicate that in tracheal epithelia under homeostatic conditions, JWB-->L was dominated by diffusion (Ea = 4.6 kcal/mol), whereas approximately 30% of JWL-->B was coupled to the active Na+,K+-ATPase pump (Ea = 27 kcal/mol).

Phillips JE; Wong LB; Yeates DB

1999-02-01

108

Mechanisms of calcium transport in small intestine. Final report  

Energy Technology Data Exchange (ETDEWEB)

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

DeLuca, H.F.

1982-07-01

109

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

110

Nanoscale mechanism of molecular transport through the nuclear pore complex as studied by scanning electrochemical microscopy.  

UK PubMed Central (United Kingdom)

The nuclear pore complex (NPC) is the proteinaceous nanopore that solely mediates molecular transport across the nuclear envelope between the nucleus and cytoplasm of a eukaryotic cell. Small molecules (<40 kDa) diffuse through the large pore of this multiprotein complex. A passively impermeable macromolecule tagged with a signal peptide is chaperoned through the nanopore by nuclear transport receptors (e.g., importins) owing to their interactions with barrier-forming proteins. Presently, this bimodal transport mechanism is not well understood and is described by controversial models. Herein, we report on a dynamic and spatially resolved mechanism for NPC-mediated molecular transport through nanoscale central and peripheral routes with distinct permeabilities. Specifically, we develop a nanogap-based approach of scanning electrochemical microscopy to precisely measure the extremely high permeability of the nuclear envelope to a small probe molecule, (ferrocenylmethyl)trimethylammonium. Effective medium theories indicate that the passive permeability of 5.9 × 10(-2) cm/s corresponds to the free diffusion of the probe molecule through ~22 nanopores with a radius of 24 nm and a length of 35 nm. Peripheral routes are blocked by wheat germ agglutinin to yield 2-fold lower permeability for 17 nm-radius central routes. This lectin is also used in fluorescence assays to find that importins facilitate the transport of signal-tagged albumin mainly through the 7 nm-thick peripheral route rather than through the sufficiently large central route. We propose that this spatial selectivity is regulated by the conformational changes in barrier-forming proteins that transiently and locally expand the impermeably thin peripheral route while blocking the central route.

Kim J; Izadyar A; Nioradze N; Amemiya S

2013-02-01

111

Refractory cardiac arrest in a rural area: mechanical chest compression during helicopter transport.  

UK PubMed Central (United Kingdom)

BACKGROUND: Out-of-hospital refractory cardiac arrest patients can be transported to a hospital for extracorporeal life support (ECLS), which can be either therapeutic or performed for organ donation. Early initiation is of vital importance and the main limitation when considering ECLS. This explains that all reported series of cardiac arrest patients referred for ECLS were urban ones. We report a series of rural out-of-hospital non-heart-beating patients transported by helicopter. METHODS: This observational study was performed in two rural districts in France. Data on patients with pre-hospital criteria for ECLS who were transported to the hospital by helicopter, maintained by mechanical chest compression, were recorded over a 2-year period. RESULTS: During the study period, 27 patients were referred for ECLS, of which 14 for therapeutic ECLS and 13 for organ preservation. The median transport distance was 37?km (25th and 75th percentiles: 31-58; range 25 to 94?km). Among the therapeutic ECLS patients, one survived to discharge from the hospital. Liver and kidneys were retrieved in another patient after brain death was ascertained. In the 13 patients referred for organ donation, four were excluded for medical reasons; 18 kidneys were retrieved in nine patients, of which six kidneys were successfully transplanted. CONCLUSION: In this preliminary study, we report the feasibility and the interest of helicopter transport of refractory cardiac arrest patients maintained by mechanical chest compression. Patients with refractory cardiac arrest occurring in rural areas, even at distance from a referral centre, can be candidates for ECLS.

Tazarourte K; Sapir D; Laborne FX; Briole N; Letarnec JY; Atchabahian A; Cornu JF; Monchi M; Jabre P; Combes X

2013-01-01

112

Analysis Of Transport Properties of Mechanically Alloyed Lead Tin Telluride  

Science.gov (United States)

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

Krishna, Rajalakshmi

113

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

International Nuclear Information System (INIS)

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

2001-01-01

114

Mechanical-physical characteristics of main anhydrite and hard salt; Das mechanisch-physikalische Verhalten von Hauptanhydrit und Hartsalz  

Energy Technology Data Exchange (ETDEWEB)

As a component of the zechstein formation, the main anhydrite is an influencing parameter of rock mechanics in mining and tunnelling. It differs from most other rock salts in its relatively high strength and elasticity. The author presents results of an investigation. [German] Als Bestandteil der Zechsteinformation ist der Hauptanhydrit nicht unerheblich an der Gebirgsmechanik in Bergbau und Tunnelbau beteiligt. Die Untersuchung des mechanisch-physikalischen Verhaltens des Hauptanhydrits ist um so mehr von bergbau- und tunnelbausicherheitlicher Bedeutung, als dieses Gestein aufgrund einer relativ hohen Festigkeit und Elastizitaet vom mechanisch-physikalischen Verhalten der meisten anderen Salzgesteine erheblich abweicht. In den folgenden Ausfuehrungen werden Ergebnisse einer gesteinsmechanischen Komplexuntersuchung des Hauptanhydrits bekanntgegeben. (orig.)

Heyne, K.H.

2000-02-01

115

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)

2007-10-05

116

An auxin transport mechanism restricts positive orthogravitropism in lateral roots.  

UK PubMed Central (United Kingdom)

As soon as a seed germinates, plant growth relates to gravity to ensure that the root penetrates the soil and the shoot expands aerially. Whereas mechanisms of positive and negative orthogravitropism of primary roots and shoots are relatively well understood, lateral organs often show more complex growth behavior. Lateral roots (LRs) seemingly suppress positive gravitropic growth and show a defined gravitropic set-point angle (GSA) that allows radial expansion of the root system (plagiotropism). Despite its eminent importance for root architecture, it so far remains completely unknown how lateral organs partially suppress positive orthogravitropism. Here we show that the phytohormone auxin steers GSA formation and limits positive orthogravitropism in LR. Low and high auxin levels/signaling lead to radial or axial root systems, respectively. At a cellular level, it is the auxin transport-dependent regulation of asymmetric growth in the elongation zone that determines GSA. Our data suggest that strong repression of PIN4/PIN7 and transient PIN3 expression limit auxin redistribution in young LR columella cells. We conclude that PIN activity, by temporally limiting the asymmetric auxin fluxes in the tip of LRs, induces transient, differential growth responses in the elongation zone and, consequently, controls root architecture.

Rosquete MR; von Wangenheim D; Marhavý P; Barbez E; Stelzer EH; Benková E; Maizel A; Kleine-Vehn J

2013-05-01

117

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

CERN Multimedia

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

2003-01-01

118

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

International Nuclear Information System (INIS)

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

2012-01-01

119

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

UK PubMed Central (United Kingdom)

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

Penmatsa A; Gouaux E

2013-07-01

120

Molecular mechanisms of urea transport in health and disease.  

UK PubMed Central (United Kingdom)

In the late 1980s, urea permeability measurements produced values that could not be explained by paracellular transport or lipid phase diffusion. The existence of urea transport proteins were thus proposed and less than a decade later, the first urea transporter was cloned. The family of urea transporters has two major subgroups, designated SLC14A1 (or UT-B) and Slc14A2 (or UT-A). UT-B and UT-A gene products are glycoproteins located in various extra-renal tissues however, a majority of the resulting isoforms are found in the kidney. The UT-B (Slc14A1) urea transporter was originally isolated from erythrocytes and two isoforms have been reported. In kidney, UT-B is located primarily in the descending vasa recta. The UT-A (Slc14A2) urea transporter yields six distinct isoforms, of which three are found chiefly in the kidney medulla. UT-A1 and UT-A3 are found in the inner medullary collecting duct (IMCD), while UT-A2 is located in the thin descending limb. These transporters are crucial to the kidney's ability to concentrate urine. The regulation of urea transporter activity in the IMCD involves acute modification through phosphorylation and subsequent movement to the plasma membrane. UT-A1 and UT-A3 accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation of the urea transporters in the IMCD involves altering protein abundance in response to changes in hydration status, low protein diets, or adrenal steroids. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new genetically engineered mouse models are being developed to study these transporters.

Klein JD; Blount MA; Sands JM

2012-12-01

 
 
 
 
121

The transport mechanism DC arcs in advanced spectroanalysis  

International Nuclear Information System (INIS)

[en] 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.)[de] In der vorliegenden Arbeit werden grundlegende Untersuchungen an einem neuartigen Typ fortgeschrittener, in horizontalen Grafitzylindern brennender Gleichstromlichtboegen zur Emissionsspektralanalyse pulverfoermiger Proben dargestellt. Die experimentell erzielten extrem niedrigen Nachweisgrenzen fuer verschiedene Elemente (Be, Cd, In, Pb, Sn) lassen auf einen positiven, reflektoraehnlichen Einfluss des Grafitzylinders auf die Transportprozesse im Bogenplasma schliessen. Detaillierte Untersuchungen mit Hilfe radioaktiver Tracer (Ag-110, Cd-115, Co-56, Fe-59, Zn-65) fuehren zu einer elementspezifisch modifizierten Modellvorstellung ueber den Wirkungsmechanismus dieser neuartigen Bogenanordnung. Fuer Elemente mit guenstigen thermochemischen Eigenschaften wird durch den Einfluss des Grafitzylinders die mittlere Teilchendichte im Bogenplasma etwa verdreifacht. Darueber hinaus zeigen die elementspezifischen Eigenschaften des Grafitzylinders eine weitgehende Invarianz gegenueber den Einfluessen von magnetischen Feldern (1.24 . 10-2T bzw. 2.6 . 20-4T) und verschiedenen Zusaetzen (Ga2O3, Li2CO3, NaCl) zur Probensubstanz. (orig.)

1977-01-01

122

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 transfo...

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

123

[Mechanism of lumen loss of the left circumflex ostium after main vessel stent implantation: observations by intravascular ultrasound].  

UK PubMed Central (United Kingdom)

OBJECTIVE: To explore the mechanism of lumen loss of the left circumflex ostium after main vessel stent implantation. METHODS: Twenty-eight patients undergoing provisional T technique were enrolled in this study. Intravascular ultrasound (IVUS) examination was performed before and after main vessel stenting and kissing balloon post-dilatation to evaluate the geometrical changes of the vessels. RESULTS: The CSA of LCX ostium lumen decreased significantly from 5.9?2 mm(2) to 4.9?1.9 mm(2) (P<0.01) after the procedure, and the CSA of LCX ostium P and M increased from 5.4?2.9 mmmm(2) to 5.7?2.9 mm(2) (P=0.21) after the main vessel stenting. The changes in LCX ostium lumen CSA was correlated with the changes of LCX ostium EEM CSA but not the LCX ostium P and M CSA. After kissing balloon post-dilatation, the CSA of LCX ostium lumen increased from 4.9?1.9 mm(2) to 5.5?1.9 mm(2) (P<0.01) , and the CSA of LCX ostium P and M showed no obvious changes (5.7?2.9 mmmm(2) vs 5.7?2.6 mmmm(2), P=0.89). The changes of LCX ostium lumen CSA were correlated with the those of the LCX ostium EEM CSA (R=0.432, P=0.02). CONCLUSION: After stent implantation from the LMCA to the LAD, most of lumen losses of the LCX are due to carina shift, and in occasional cases, plaque shift occurs from the distal LMCA to the ostium of the LCX. Kissing balloon technique can adjust carina shift but can not improve plaque shift.

Xiu J; Liao W; Liu B; Zhang X; Hou Y; Huang Z; Guo Z; Zhou Z; Cao S; Cui K

2013-07-01

124

Regulation and molecular mechanisms of calcium transport genes: do they play a role in calcium transport in the uterine endometrium?  

Science.gov (United States)

Maintenance of calcium (Ca) balance in the uterus is critically important for many physiological functions, including smooth muscle contraction during embryo implantation. Ca transport genes, i.e., transient receptor potential cation channel subfamily V members 5/6 (TRPV5/6), calbindins, plasma membrane Ca(2+)-ATPase 1 (PMCA1), and NCX1/NCKX3, may play roles in the uterus for Ca transport and reproductive function. Although these Ca transport genes may have a role in Ca metabolism, their role(s) and molecular mechanisms require further elucidation. In this review, we highlight the expression and regulation of Ca transport genes in the uterus to clarify their potential role(s). Since Ca transport genes are abundantly expressed in reproductive tissues in a distinct manner, they may be involved in specific uterine functions including fetal implantation, Ca homeostasis, and endometrial cell production. PMID:22204796

Choi, K C; An, B S; Yang, H; Jeung, E B

2011-10-01

125

Regulation and molecular mechanisms of calcium transport genes: do they play a role in calcium transport in the uterine endometrium?  

UK PubMed Central (United Kingdom)

Maintenance of calcium (Ca) balance in the uterus is critically important for many physiological functions, including smooth muscle contraction during embryo implantation. Ca transport genes, i.e., transient receptor potential cation channel subfamily V members 5/6 (TRPV5/6), calbindins, plasma membrane Ca(2+)-ATPase 1 (PMCA1), and NCX1/NCKX3, may play roles in the uterus for Ca transport and reproductive function. Although these Ca transport genes may have a role in Ca metabolism, their role(s) and molecular mechanisms require further elucidation. In this review, we highlight the expression and regulation of Ca transport genes in the uterus to clarify their potential role(s). Since Ca transport genes are abundantly expressed in reproductive tissues in a distinct manner, they may be involved in specific uterine functions including fetal implantation, Ca homeostasis, and endometrial cell production.

Choi KC; An BS; Yang H; Jeung EB

2011-10-01

126

Proceedings of the Canadian Society for Mechanical Engineers forum 1996: theory of machines and mechanisms; advances in transportation systems  

Energy Technology Data Exchange (ETDEWEB)

Recent developments in the field of the theory of machines and mechanisms and the broadening scope and interdisciplinary nature of transport system technology were the subject of papers presented in these two symposia. The themes covered by the 24 research papers in machines and mechanisms included machine dynamics, robot design and kinematics, CAD, kinematics and geometry, flexible systems, and mechanical and hybrid systems. The 32 research papers on guided, road and off-road transportation systems covered subjects as diverse as advances in vehicle system dynamics, current and future needs for the development of transportation technology, advances in guided transport systems, dynamics of heavy vehicle systems, and driver-vehicle interactions and human factors. refs., tabs., figs.

NONE

1996-09-01

127

On the molecular mechanism of intestinal calcium transport.  

UK PubMed Central (United Kingdom)

The intestinal absorption of calcium is certainly a complex process, dependent on several factors of which vitamin D, via 1,25(OH)2D3, is the major controlling hormone. The efficiency of calcium absorption is a function of calcium status and calcium need. As the body's demand for calcium increases, the process commonly termed, adaptation, is activated in which the synthesis of 1,25(OH)2D3 from precursor is increased, resulting in the stimulation of the rate of calcium absorption. The increased demand for calcium might result from the ingestion of a diet deficient in calcium, from growth, pregnancy, lactation and egg shell formation in the laying hen. Accomapanying the change in calcium absorptive efficiency are molecular modifications of the transporting enterocytes, some mentioned herein and elsewhere (Wasserman & Chandler, 1985; Wasserman, 1980; Wasserman et al., 1984). Highly correlated with the rate of calcium absorption under a wide variety of conditions is the concentration of the vitamin D-induced calcium-binding protein, calbindin-D28K (avian type) and calbindin-D9K (mammalian intestinal type). The role of calbindin-D in this transport process is not precisely known but is considered to act at the present time as a cytosolic facilitator of Ca2+ diffusion from the brush border membrane to the basolateral membrane. In addition to the induction of calbindin-D synthesis, 1,25(OH)2D3 exerts other effects on the intestinal epithelium that can have consequences on the calcium absorptive process. Some of these effects are summarized in Figure 14. Vitamin D-dependent reactions might be either direct effects of 1,25(OH)2D3 or indirect effects due to elevated intracellular Ca2+ concentrations. These include changes in the fluidity of the brush border membrane, an increase in microvillar alkaline phosphatase-low affinity Ca-activated ATPase activity, an association of calmodulin with the 105 kD brush border cytoskeletal protein and, following calbindin D synthesis, the binding of calbindin D to a 60 kD brush border protein and to microtubules. The latter has been suggested to be related to the proposed transfer of Ca2+ by an endocytotic-exocytotic mechanism. In addition, a vitamin D-dependent intestinal membrane calcium-binding protein has been identified (Kowarski & Schachter, 1980). Playing into this multi-component system is a stimulation of cyclic nucleotide synthesis by 1,25(OH)2D3 which, through activation of cyclic nucleotide-dependent protein kinases, might modify membrane Ca2+ "channels" by phosphorylation reactions.4+ Intracellular organelles, i.e., the endoplasmic reticulum, mitochondria, the Golgi apparatus, are potent sequesters of Ca2+ and could contribute to the protection of the cell from excessively high Ca2+ concentrations by transiently storing absorbed Ca2+.

Wasserman RH; Fullmer CS

1989-01-01

128

Insights into the mechanisms of sterol transport between organelles.  

UK PubMed Central (United Kingdom)

In cells, the levels of sterol vary greatly among organelles. This uneven distribution depends largely on non-vesicular routes of transfer, which are mediated by soluble carriers called lipid-transfer proteins (LTPs). These proteins have a domain with a hydrophobic cavity that accommodates one sterol molecule. However, a demonstration of their role in sterol transport in cells remains difficult. Numerous LTPs also contain membrane-binding elements, but it is not clear how these LTPs couple their ability to target organelles with lipid transport activity. This issue appears critical, since many sterol transporters are thought to act at contact sites between two membrane-bound compartments. Here, we emphasize that biochemical and structural studies provide precious insights into the mode of action of sterol-binding proteins. Recent studies on START, Osh/ORP and NPC proteins suggest models on how these proteins could transport sterol between organelles and, thereby, influence cellular functions.

Mesmin B; Antonny B; Drin G

2013-09-01

129

Insights into the mechanisms of sterol transport between organelles.  

Science.gov (United States)

In cells, the levels of sterol vary greatly among organelles. This uneven distribution depends largely on non-vesicular routes of transfer, which are mediated by soluble carriers called lipid-transfer proteins (LTPs). These proteins have a domain with a hydrophobic cavity that accommodates one sterol molecule. However, a demonstration of their role in sterol transport in cells remains difficult. Numerous LTPs also contain membrane-binding elements, but it is not clear how these LTPs couple their ability to target organelles with lipid transport activity. This issue appears critical, since many sterol transporters are thought to act at contact sites between two membrane-bound compartments. Here, we emphasize that biochemical and structural studies provide precious insights into the mode of action of sterol-binding proteins. Recent studies on START, Osh/ORP and NPC proteins suggest models on how these proteins could transport sterol between organelles and, thereby, influence cellular functions. PMID:23283302

Mesmin, Bruno; Antonny, Bruno; Drin, Guillaume

2013-01-03

130

Osmotic water transport in aquaporins. Evidence for a stochastic mechanism.  

UK PubMed Central (United Kingdom)

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, PS, 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-labeled 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 T; Alsterfjord M; Beitz E; Macaulay N

2013-08-01

131

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

Directory of Open Access Journals (Sweden)

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

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

2010-01-01

132

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

Scientific Electronic Library Online (English)

Full Text Available 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, and biochemical disorders such as oxidative stress. Some studies on Mn toxicity and Mn translocation from soil to plant cells in Mn2+ form have demonstrated their importance unde (more) r 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.

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

2010-01-01

133

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

Science.gov (United States)

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

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

2009-01-01

134

The anti-oxidant effects are not the main mechanism for glutamine's protective effects on acute kidney injury in mice.  

Science.gov (United States)

Acute kidney injury (AKI) is a common problem characterized by an inflammatory response in the kidney and oxidative stress. However, there are no interventions to prevent AKI. Glutamine is an important precursor of glutathione and has also been shown to induce heat shock proteins (HSP). Thus, glutamine may affect both oxidative stress and inflammation. This study was to explore the effects of glutamine pretreatment on nephrotoxic AKI and to investigate the underlying mechanisms. First, the effects of alternate doses of glutamine were compared in CD-1 mice with AKI induced with folic acid intra-peritoneal injection. Then the effects of glutamine quercetin (an HSP inhibitor), and quercetin+glutamine, were compared in the same AKI model. AKI were assessed with plasma creatinine, urine neutrophil gelatinase-associated lipocalin, and renal histology. Inflammatory response was monitored with renal tumor necrosis factor (TNF-?), chemkines (CXCL1 and CCL2) contents, and neutrophil infiltration. Oxidative injury was detected with reduced glutathione, malondialdehyde, and protein thiol. Glutamine provided dose-dependent renal protection. Pretreatment with quercetin, which was showed to inhibit HSP-70 expression, abolished glutamine's renal-protective effects. Quercetin also abrogated glutamine's beneficial effects on renal TNF-?, chemokines, and neutrophil infiltration. However, quercetin did not affect glutamine's anti-oxidative effects. These results suggest that glutamine's renal-protective effects are mainly related to its activation of HSP-70, which mitigates inflammatory response, renal neutrophil infiltration and subsequent AKI. Regulating neutrophil infiltration might be a potential therapeutic target for AKI. PMID:23454558

Peng, Zhi-Yong; Zhou, Feihu; Wang, Hong-Zhi; Wen, Xiao-Yan; Nolin, Thomas D; Bishop, Jeffery V; Kellum, John A

2013-02-27

135

The anti-oxidant effects are not the main mechanism for glutamine's protective effects on acute kidney injury in mice.  

UK PubMed Central (United Kingdom)

Acute kidney injury (AKI) is a common problem characterized by an inflammatory response in the kidney and oxidative stress. However, there are no interventions to prevent AKI. Glutamine is an important precursor of glutathione and has also been shown to induce heat shock proteins (HSP). Thus, glutamine may affect both oxidative stress and inflammation. This study was to explore the effects of glutamine pretreatment on nephrotoxic AKI and to investigate the underlying mechanisms. First, the effects of alternate doses of glutamine were compared in CD-1 mice with AKI induced with folic acid intra-peritoneal injection. Then the effects of glutamine quercetin (an HSP inhibitor), and quercetin+glutamine, were compared in the same AKI model. AKI were assessed with plasma creatinine, urine neutrophil gelatinase-associated lipocalin, and renal histology. Inflammatory response was monitored with renal tumor necrosis factor (TNF-?), chemkines (CXCL1 and CCL2) contents, and neutrophil infiltration. Oxidative injury was detected with reduced glutathione, malondialdehyde, and protein thiol. Glutamine provided dose-dependent renal protection. Pretreatment with quercetin, which was showed to inhibit HSP-70 expression, abolished glutamine's renal-protective effects. Quercetin also abrogated glutamine's beneficial effects on renal TNF-?, chemokines, and neutrophil infiltration. However, quercetin did not affect glutamine's anti-oxidative effects. These results suggest that glutamine's renal-protective effects are mainly related to its activation of HSP-70, which mitigates inflammatory response, renal neutrophil infiltration and subsequent AKI. Regulating neutrophil infiltration might be a potential therapeutic target for AKI.

Peng ZY; Zhou F; Wang HZ; Wen XY; Nolin TD; Bishop JV; Kellum JA

2013-04-01

136

Mechanisms of Drug Resistance in Cancer Chemotherapy: Coordinated Role and Regulation of Efflux Transporters and Metabolizing Enzymes.  

UK PubMed Central (United Kingdom)

Cancer remains one of the major leading causes of death worldwide. Acquisition of multidrug resistance (MDR) remains a major impediment to successful chemotherapy. As the name implies, MDR is not limited only to one drug but often associated to structurally and functionally unrelated chemotherapeutics. Extensive research and investigations have identified several mechanisms underlying the development of MDR. This process of drug resistance is considered to be multifactorial including decreased drug accumulation, increased efflux, increased biotransformation, drug compartmentalization, modification of drug targets and defects in cellular pathways. In the first part of the review, these pharmacokinetic and pharmacodynamic mechanisms have been described in brief. Although the pathways can act independently, they are more often intertwined. Of the various mechanisms involved, up-regulation of efflux transporters and metabolizing enzymes constitute a major resistance phenotype. This review also provides a general biological overview of important efflux transporters and metabolizing enzymes involved in MDR. Further, synergistic action between efflux transporters and metabolizing enzymes leading to MDR could possibly arise due to two different factors; overlapping substrate specificity and coordinated regulation of their expression. The expression of efflux transporters and metabolizing enzymes is governed by nuclear receptors, mainly pregnane X receptor (PXR). The pharmacological role of PXR and advances in the development of PXR antagonists to overcome MDR are outlined.

Vadlapatla RK; Vadlapudi AD; Pal D; Mitra AK

2013-07-01

137

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

Science.gov (United States)

Some small animals only use water transport mechanisms passively driven by surface energies. However, little is known about passive water transport mechanisms because it is difficult to measure the wettability of microstructures in small areas and determine the chemistry of biological surfaces. Herein, we developed to directly analyse the structural effects of wettability of chemically modified biological surfaces by using a nanoliter volume water droplet and a hi-speed video system. The wharf roach Ligia exotica transports water only by using open capillaries in its legs containing hair- and paddle-like microstructures. The structural effects of legs chemically modified with a self-assembled monolayer were analysed, so that the wharf roach has a smart water transport system passively driven by differences of wettability between the microstructures. We anticipate that this passive water transport mechanism may inspire novel biomimetic fluid manipulations with or without a gravitational field.

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

2013-01-01

138

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

2009-01-01

139

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 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 mecánica 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 modernization that characterized the upbringing extensive sheep farming, main vertebrate activity of the magellanic economy.

Martinic B, Mateo

2009-07-01

140

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

International Nuclear Information System (INIS)

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

2011-01-01

 
 
 
 
141

High Affinity Ammonium Transporters: Molecular Mechanism of Action  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The importance of the family of high affinity ammonium transporters is demonstrated by the presence of these proteins in all domains of life, including bacteria, archaea, fungi, plants, and humans. The majority of the proteins that have been studied from this family show high affinity and selectivit...

Pantoja, Omar

142

Mechanisms of acetylcholine synthesis: Coupling with choline transport  

International Nuclear Information System (INIS)

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

1983-11-04

143

Electrical transport through carbon nanotube junctions created by mechanical manipulation  

CERN Multimedia

Using an atomic force microscope we have created nanotube junctions such as buckles and crossings within individual single-wall metallic carbon nanotubes connected to metallic electrodes. The electronic transport properties of these manipulated structures show that they form electronic tunnel junctions. The conductance shows power-law behavior as a function of bias voltage and temperature, which can be well modeled by a Luttinger liquid model for tunneling between two nanotube segments separated by the manipulated junction.

Postma, H; Yao, Z; Dekker, C; Postma, Henk W.Ch.; Jonge, Mark de; Yao, Zhen; Dekker, Cees

2000-01-01

144

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

UK PubMed Central (United Kingdom)

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

Karimi F; Fathipour M; Hosseini R

2011-12-01

145

Coupling mechanical forces to electrical signaling: molecular motors and the intracellular transport of ion channels.  

UK PubMed Central (United Kingdom)

Proper localization of various ion channels is fundamental to neuronal functions, including postsynaptic potential plasticity, dendritic integration, action potential initiation and propagation, and neurotransmitter release. Microtubule-based forward transport mediated by kinesin motors plays a key role in placing ion channel proteins to correct subcellular compartments. PDZ- and coiled-coil-domain proteins function as adaptor proteins linking ionotropic glutamate and GABA receptors to various kinesin motors, respectively. Recent studies show that several voltage-gated ion channel/transporter proteins directly bind to kinesins during forward transport. Three major regulatory mechanisms underlying intracellular transport of ion channels are also revealed. These studies contribute to understanding how mechanical forces are coupled to electrical signaling and illuminating pathogenic mechanisms in neurodegenerative diseases.

Barry J; Gu C

2013-04-01

146

Guide to innovative financing mechanisms for mass transportation: an update  

Energy Technology Data Exchange (ETDEWEB)

The document provides an overview of nonstandard techniques currently being used to finance transit capital and operating expenses. An update of a study, the report focused on six types of mechanisms: assessments, taxes and user charges, use of property and property rights, issuance of debt, contracted services, and voluntary participation programs. A new section, Initiatives and Ideas, discusses local funding of community services like Montgomery County, Maryland's Ride On, franchise approaches, and nonsubsidized bus and vanpool services. The report is structured in two independant parts: the first describes the theoretical background of each technique, and is keyed to a second part, which describes typical applications of the mechanism.

1985-12-01

147

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

2008-01-01

148

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

149

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+ chaper...

González-Guerrero, Manuel; Argüello, José M.

150

Transport mechanisms in high Tc bismuth-based oxide superconductors  

International Nuclear Information System (INIS)

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

2008-01-01

151

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1981-01-01

152

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

Science.gov (United States)

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

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

2008-10-01

153

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

UK PubMed Central (United Kingdom)

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

Tsigelny IF; Greenberg J; Kouznetsova V; Nigam SK

2008-10-01

154

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

155

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; Jack Surek

2009-01-01

156

Heat stress increases protein antigen transport across the intestinal epithelium via a mechanism of impairing proteolytic enzymatic activity.  

UK PubMed Central (United Kingdom)

It has not been fully understood how intact protein antigens escape digestion in the course of absorption. The present study was designed to investigate the mechanism that heat stress induced an increase in intact protein antigen absorption. Human colonic cell line Caco-2 cells were treated with high temperature (37 to 43 degrees C) for 60 min. Epithelial permeability was evaluated by horseradish peroxidase (HRP) flux and dextran flux. Activity of the major intracellular proteolytic enzyme, acid phosphatase, in Caco-2 cells was determined. HRP products in Caco-2 cells were observed by electron microscopy (EM) and analyzed with a computerized image processing system. Heat stress significantly increased intact protein HRP transport across Caco-2 monolayers, decreased acid phosphatase activity of the cells, and significantly reduced transepithelial electric resistance of Caco-2 cells. EM results showed that HRP transport across Caco-2 monolayers occurred mainly via the intracellular pathway.

Yang PC; Wang CS

2006-05-01

157

Mechanism of intestinal folate transport during folate deficiency in rodent model.  

UK PubMed Central (United Kingdom)

BACKGROUND & OBJECTIVES: Folate deficiency is a public health problem and is the most notable for its association with neural tube defect in developing embryo, megaloblastic anaemia, cancers and cardiovascular diseases. The mechanisms of the intestinal folate uptake process have been earlier characterized. However, much less is known about regulation. In this study we evaluated the mechanistic insights of folate absorption in an in vivo model of folate deficiency. METHODS: Male Wistar rats were fed folate-containing diet (2 mg/kg folic acid) or a folic acid-free diet over 3 months and folate transport was studied in intestinal brush border membrane vesicles (BBMV). RESULTS: The characterization of the folate transport system in intestinal brush border membrane (BBM) suggested it to be a carrier mediated, acidic pH stimulated, and Na? independent. Folate deficiency increased the folate transport by altering the Vmax without changing the Km of folate transport process. The increased transport efficiency of the BBM was associated with upregulation of folate transporters at both mRNA and protein level. INTERPRETATION & CONCLUSIONS: Folate deficiency resulted in significant upregulation of intestinal folate uptake, by increasing number of transporters without any change in specificity of transporters towards its substrate. The observed upregulation was associated with significant increase in reduced folate carrier (RFC) and proton coupled folate transporter (PCFT) expressions, suggesting the transcriptional and translational regulation of folate uptake during folate deficiency.

Wani NA; Thakur S; Kaur J

2012-11-01

158

Kinetics and mechanism of proton transport across membrane nanopores  

CERN Document Server

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

Dellago, C; Dellago, Christoph; Hummer, Gerhard

2006-01-01

159

Conserved transport mechanisms but distinct auxin responses govern shoot patterning in Selaginella kraussiana.  

UK PubMed Central (United Kingdom)

To provide a comparative framework to understand the evolution of auxin regulation in vascular plants, the effect of perturbed auxin homeostasis was examined in the lycophyte Selaginella kraussiana. Polar auxin transport was measured by tracing tritiated IAA in excised shoots. Shoots were cultured in the presence of auxin efflux inhibitors and exogenous auxin, and developmental abnormalities were documented. Auxin transport in Selaginella shoots is exclusively basipetal, as in angiosperms. Perturbed auxin transport results in the loss of meristem maintenance and abnormal shoot architecture. Dichotomous root branching in Selaginella appears to be regulated by an antagonistic relationship between auxin and cytokinin. The results suggest that basipetal polar auxin transport occurred in the common ancestor of lycophytes and euphyllophytes. Although the mechanisms of auxin transport appear to be conserved across all vascular plants, distinct auxin responses govern shoot growth and development in lycophytes and euphyllophytes.

Sanders HL; Langdale JA

2013-04-01

160

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

Energy Technology Data Exchange (ETDEWEB)

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.

Bell, W.E.; Greenberg, S.; Goodin, D.T.; Langer, S.

1980-05-01

 
 
 
 
161

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

UK PubMed Central (United Kingdom)

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

Kato H; Nishiwaki Y; Hosoi K; Shiomi N; Hirata M

2013-09-01

162

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2006-11-17

163

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

International Nuclear Information System (INIS)

[en] 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.)

1974-06-11

164

Mechanisms and control of K sup + transport in plants and fungi  

Energy Technology Data Exchange (ETDEWEB)

The overall purposes of this study are to provide a detailed functional description of active and passive potassium transport in model plant/fungal cells, to identify and isolate the protein molecules which mediate K+ transport, and ultimately to determine the intramolecular mechanisms which determine ion passage. The two major research lines now being followed are cloning three varieties of K+ transporters in Neurospora crassa, and characterizing potassium channels and proton pumps in Neurospora and Saccharomyces cerevisiae electrophysiologically, largely by means of patch recording.

Slayman, C.L.

1990-01-01

165

Oxygen transport mechanisms in REAlO{sub 3} scintillators  

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-03-15

166

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

Directory of Open Access Journals (Sweden)

Full Text Available Biomass burning in the Indochina Peninsula (Indochina) is one of the important ozone sources in the low troposphere over East Asia in springtime. MODIS data showed that nearly 20 000 fires or more occurred annually in spring only from 2000 to 2007. In our tracer modeling study, we identified a new mechanism transporting the tracer over Indochina that is significantly different from the vertical transport mechanism over the areas around the equator such as Indonesia and Malaysia. Simulation results demonstrate that the leeside trough over Indochina played a dominant role in the uplift of the tracer below 3 km, and that the strong westerlies prevailed above 3 km to transport the tracer. They provided the fundamental mechanisms a major impact on the air quality downwind from Indochina over East Asia. And the climatological importance of such leeside trough is also discussed.

C.-Y. Lin; H. M. Hsu; Y. H. Lee; C. H. Kuo; Y.-F. Sheng; D. A. Chu

2009-01-01

167

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

Directory of Open Access Journals (Sweden)

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

C.-Y. Lin; H.-m. Hsu; Y. H. Lee; C. H. Kuo; Y.-F. Sheng; D. A. Chu

2009-01-01

168

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2003-02-19

169

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

International Nuclear Information System (INIS)

[en] 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

2008-01-01

170

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.

2013-01-01

171

Qualitative Assessment of Flow and Transport Mechanisms in Bioremediation Processes  

Science.gov (United States)

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

Terry, N.; Hou, Z.

2008-12-01

172

Studies on the cerebellar projections from the main and external cuneate nuclei in the cat by means of retrograde axonal transport of horseradish peroxidase.  

UK PubMed Central (United Kingdom)

The cerebellar projections from the main and external cuneate nuclei in the cat have been studied by means of retrograde axonal transport of horseradish peroxidase. The main projection from the external cuneate nucleus (ECN) is to the intermediate and, possibly, the small lateral part of lobule V and to the paramedian lobule on the ipsilateral side. The projection from the ECN to the cerebellar regions mentioned is topographically organized. Cells in the caudal part of the ECN send their axons to the caudal parts of lobule V and to the rostral part of the paramedian lobule. Cells in the rostral part of the ECN project to the rostralmost part of lobule V and to the folia in the caudal part of the paramedian lobule. The experimental study also shows that cells in the main cuneate nucleus (MCN) send their axons to the cerebellum. These axons, like those from the ECN, terminate in the intermediate part of lobule V of the anterior lobe and in the paramedian lobule. However, the axons of the cells in the MCN terminate only in the superficial parts of the folia, whereas those from the ECN terminate in the depth of the folia in these two cerebellar areas. The present study also gives evidence that cells in the ventral part of the gracile nucleus send their axons to lobules I and II of the anterior lobe vermis. The observations referred to here are to our knowledge the first anatomical findings demonstrating a projection from the main cuneate and gracile nuclei onto the cerebellar cortex. The observations confirm previous physiological studies.

Rinvik E; Walberg F

1975-09-01

173

Growth mechanism of ZnSe single crystal by chemical vapour transport method  

International Nuclear Information System (INIS)

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

2006-04-01

174

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

UK PubMed Central (United Kingdom)

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.

Pohl PC; Klafke GM; Júnior JR; Martins JR; da Silva Vaz I Jr; Masuda A

2012-12-01

175

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

UK PubMed Central (United Kingdom)

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.

He B; Lin P; Jia Z; Du W; Qu W; Yuan L; Dai W; Zhang H; Wang X; Wang J; Zhang X; Zhang Q

2013-08-01

176

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

2013-05-18

177

Transport with ongoing resuscitation: a comparison between manual and mechanical compression.  

UK PubMed Central (United Kingdom)

AIM: In special circumstances it may be necessary to transport out-of-hospital cardiac arrest patients with ongoing resuscitation to the hospital. External mechanical chest compression devices could be an alternative for these resuscitations. The study compares manual chest compression with external mechanical devices and a semiautomatic device in transport conditions using a resuscitation manikin. METHODS: Manual chest compressions were compared with LUCAS 2, AutoPulse and animax mono devices using the Ambu Man Wireless MegaCode manikin (10 series each). The measurements were performed in a standard ambulance vehicle during transport on a predefined track of 5.0 km. RESULTS: Mean compression frequencies in the manual group (117 ± 18 min(-1)) and in the animax mono group (115 ± 10 min(-1)) were significantly higher than in the LUCAS 2 group (100 min(-1), p=0.02) and the AutoPulse group (80 min(-1), p<0.01). Both mechanical devices worked absolutely constantly. Only the animax mono group reached with 51.2 mm the recommended compression depth. The quality of manual compressions decreased considerably during braking or change manoeuvres while the mechanical devices continued to work constantly. CONCLUSIONS: During a patient transport with ongoing resuscitation, external mechanical compression devices may be a good alternative to manual compression because they increase the safety of the rescuer and patient. Yet, in this study only animax mono reached the guideline specifications regarding chest compressions' frequency and depth. Concerning constancy, the mechanical devices work reliably and more independently from motion influences. Further studies are necessary to evaluate the effectiveness of these devices in patient transport.

Gässler H; Ventzke MM; Lampl L; Helm M

2013-07-01

178

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-07-01

179

Potassium transport through lipid bilayer membranes facilitated by tentoxin dimers. A new mechanism of ion carrier transport?  

UK PubMed Central (United Kingdom)

The cyclic tetrapeptide tentoxin at concentrations greater than 5 X 10(-7) M selectively increases the ion conductivity for potassium of lipid bilayer membranes, while the naturally occurring derivative dihydrotentoxin has no influence on this property. Current-voltage curves, zero-current potential and charge-pulse measurements were used to characterize the action of tentoxin. The results suggest that a new mechanism of facilitated ion transport operates. The model of tentoxin dimerization and tentoxin-K+ association developed is in contradiction to the model of tentoxin pore formation described recently by Heitz et al. (Biophys. Chem. 23 (1986) 245).

Klotz MG; Müller E; Liebermann B

1987-08-01

180

Potassium transport through lipid bilayer membranes facilitated by tentoxin dimers. A new mechanism of ion carrier transport?  

Science.gov (United States)

The cyclic tetrapeptide tentoxin at concentrations greater than 5 X 10(-7) M selectively increases the ion conductivity for potassium of lipid bilayer membranes, while the naturally occurring derivative dihydrotentoxin has no influence on this property. Current-voltage curves, zero-current potential and charge-pulse measurements were used to characterize the action of tentoxin. The results suggest that a new mechanism of facilitated ion transport operates. The model of tentoxin dimerization and tentoxin-K+ association developed is in contradiction to the model of tentoxin pore formation described recently by Heitz et al. (Biophys. Chem. 23 (1986) 245). PMID:3663841

Klotz, M G; Müller, E; Liebermann, B

1987-08-01

 
 
 
 
181

Acute Mechanical Stretch Promotes eNOS Activation in Venous Endothelial Cells Mainly via PKA and Akt Pathways.  

UK PubMed Central (United Kingdom)

In the vasculature, physiological levels of nitric oxide (NO) protect against various stressors, including mechanical stretch. While endothelial NO production in response to various stimuli has been studied extensively, the precise mechanism underlying stretch-induced NO production in venous endothelial cells remains incompletely understood. Using a model of continuous cellular stretch, we found that stretch promoted phosphorylation of endothelial NO synthase (eNOS) at Ser(1177), Ser(633) and Ser(615) and NO production in human umbilical vein endothelial cells. Although stretch activated the kinases AMPK?, PKA, Akt, and ERK1/2, stretch-induced eNOS activation was only inhibited by kinase-specific inhibitors of PKA and PI3K/Akt, but not of AMPK? and Erk1/2. Similar results were obtained with knockdown by shRNAs targeting the PKA and Akt genes. Furthermore, inhibition of PKA preferentially attenuated eNOS activation in the early phase, while inhibition of the PI3K/Akt pathway reduced eNOS activation in the late phase, suggesting that the PKA and PI3K/Akt pathways play distinct roles in a time-dependent manner. Finally, we investigated the role of these pathways in stretch-induced endothelial exocytosis and leukocyte adhesion. Interestingly, we found that inhibition of the PI3K/Akt pathway increased stretch-induced Weibel-Palade body exocytosis and leukocyte adhesion, while inhibition of the PKA pathway had the opposite effects, suggesting that the exocytosis-promoting effect of PKA overwhelms the inhibitory effect of PKA-mediated NO production. Taken together, the results suggest that PKA and Akt are important regulators of eNOS activation in venous endothelial cells under mechanical stretch, while playing different roles in the regulation of stretch-induced endothelial exocytosis and leukocyte adhesion.

Hu Z; Xiong Y; Han X; Geng C; Jiang B; Huo Y; Luo J

2013-01-01

182

Controlling mechanism for dual-label transport in T-MPLS  

Science.gov (United States)

T-MPLS is a connection-oriented packet switched solution for transport networks. The standardization process is pushed by ITU-T and IETF, many recommendation appeared in these days. T-MPLS is much easier to achieve a convergent packet platform for any L2 protocol. It focuses on the packet transport application that adhere to the standard groups. Although IETF PWE3 WG have already specified the common architecture for L2/L3 service encapsulation, as different service always has different characteristics. So we propose a control mechanism for dual label transport across T-MPLS in this paper, through which we can easily achieve a convergent packet transporting platform for any L2 and L3 protocols, . At last, a flow chart for T-MPLS realization and a FSM structure have been introduced.

Li, Bin; Liu, Kangjian; Huang, Shanguo; Zhang, Yongjun; Gu, Wanyi

2007-12-01

183

Single molecule spectroscopy reveals heterogeneous transport mechanisms for molecular ions in a polyelectrolyte polymer brush.  

UK PubMed Central (United Kingdom)

Single molecule polarization and fluorescence correlation spectroscopy were used to evaluate heterogeneous transport mechanisms of molecular ions within supported polyelectrolyte brushes. Modes of diffusive transport include periods of significantly restricted rotational motion, often maintained over tens of milliseconds; periods of fast molecular rotation; and occasional adsorption of fluorescent probe molecules in the brush. The studies reveal rapid switching between orientational states during each observed mode of motion. Through quantitative analysis of state occupation times, the rate constants for transitions from weakly associated to strongly associated states were extracted. Additionally, the pH dependence of the ion transport rates in the brush exhibits an abrupt, rather than continuous, trend. These single molecule studies demonstrate the presence of dynamic anisotropic interactions between the charged molecular probe and the polymer brush and provide experimental evidence of stimuli responsive switchable transport functionality in the polyelectrolyte brush.

Reznik C; Estillore N; Advincula RC; Landes CF

2009-11-01

184

Single molecule spectroscopy reveals heterogeneous transport mechanisms for molecular ions in a polyelectrolyte polymer brush.  

Science.gov (United States)

Single molecule polarization and fluorescence correlation spectroscopy were used to evaluate heterogeneous transport mechanisms of molecular ions within supported polyelectrolyte brushes. Modes of diffusive transport include periods of significantly restricted rotational motion, often maintained over tens of milliseconds; periods of fast molecular rotation; and occasional adsorption of fluorescent probe molecules in the brush. The studies reveal rapid switching between orientational states during each observed mode of motion. Through quantitative analysis of state occupation times, the rate constants for transitions from weakly associated to strongly associated states were extracted. Additionally, the pH dependence of the ion transport rates in the brush exhibits an abrupt, rather than continuous, trend. These single molecule studies demonstrate the presence of dynamic anisotropic interactions between the charged molecular probe and the polymer brush and provide experimental evidence of stimuli responsive switchable transport functionality in the polyelectrolyte brush. PMID:19813742

Reznik, Carmen; Estillore, Nicel; Advincula, Rigoberto C; Landes, Christy F

2009-11-01

185

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

Science.gov (United States)

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

Karimi, Fatemeh; Fathipour, Morteza; Hosseini, Reza

2011-12-01

186

Transport mechanisms and genesis of limestone clast conglomerates with examples from Cambrian of east Tennessee  

Energy Technology Data Exchange (ETDEWEB)

Limestone clast conglomerates are common sedimentary features of most Cambrian strata. Cambrian researchers have considered many of these conglomeratic deposits to have formed from erosion and redeposition of partially lithified sediments by storm currents in shallow subtidal and intertidal environments. Analysis of conglomeratic beds from the Middle and Late Cambrian (Maryville Limestone and Nolichucky Shale) in east Tennessee suggests that other, more dominant, processes were responsible for their genesis and transport. The proposed processes may serve as an alternative explanation for limestone clast conglomerates deposited elsewhere in Cambrian sequences. As the authors gain a greater understanding of transport mechanisms and their resultant sedimentary features, many of the conglomeratic beds that were once thought to be the result of storms may be reinterpreted as mass-gravity flows. Differentiating between these various types of transport mechanisms may be crucial to paleo-environmental interpretation.

Kozar, M.G.; Weber, L.J.; Walker, K.R.

1986-05-01

187

Mechanisms of transcellular transport of wheat germ agglutinin-functionalized polymeric nanoparticles in Caco-2 cells.  

Science.gov (United States)

Transcellular transport is essential for transmucosal and plasma-to-tissue drug delivery by nanoparticles, whereas its fundamental pathways have not been fully clarified. In this study, an in-depth investigation was conducted into the intracellular itinerary and the transcytosis pathway of wheat germ agglutinin-functionalized nanoparticles (WGA-NP) with various polymer architectures in the Caco-2 cell model. GFP-Rabs, Rab4, Rab5, Rab7, Rab11, GTPases served as key regulators of vesicular transport, and their mutants were transfected to Caco-2 cells respectively to determine the cellular itinerary of WGA-NP and the role of Rabs therein. Transcytosis inhibition experiments indicated that transcellular transport of WGA-NP (PEG(3000)-PLA(40000) formulation) happened in a cytoskeleton-dependent manner and majorly by means of clathrin-mediated mechanism. Intracellular transport, especially the endolysosome pathway was found largely contribute to the transcytosis of WGA-NP. WGA-NP with shorter surface PEG length (2000) resulted in higher cellular association and more colocalization with the clathrin-mediated transport pathway, while that with longer surface PEG length (5000) avoided the clathrin-mediated transport pathway but achieved higher transcytosis after 4 h incubation. WGA-NP with PLGA as the core materials obtained elevated lysosome escape and enhanced transcytosis after 2 h incubation. These findings provided important evidence for the role of polymer architectures in modulating cellular transport of functionalized nanocarriers, and would be helpful in improving carrier design to enhance drug delivery. PMID:22705199

Song, Qingxiang; Yao, Lei; Huang, Meng; Hu, Quanyin; Lu, Qin; Wu, Bingxian; Qi, Hong; Rong, Zhengxing; Jiang, Xinguo; Gao, Xiaoling; Chen, Jun; Chen, Hongzhuan

2012-06-15

188

Mechanisms of transcellular transport of wheat germ agglutinin-functionalized polymeric nanoparticles in Caco-2 cells.  

UK PubMed Central (United Kingdom)

Transcellular transport is essential for transmucosal and plasma-to-tissue drug delivery by nanoparticles, whereas its fundamental pathways have not been fully clarified. In this study, an in-depth investigation was conducted into the intracellular itinerary and the transcytosis pathway of wheat germ agglutinin-functionalized nanoparticles (WGA-NP) with various polymer architectures in the Caco-2 cell model. GFP-Rabs, Rab4, Rab5, Rab7, Rab11, GTPases served as key regulators of vesicular transport, and their mutants were transfected to Caco-2 cells respectively to determine the cellular itinerary of WGA-NP and the role of Rabs therein. Transcytosis inhibition experiments indicated that transcellular transport of WGA-NP (PEG(3000)-PLA(40000) formulation) happened in a cytoskeleton-dependent manner and majorly by means of clathrin-mediated mechanism. Intracellular transport, especially the endolysosome pathway was found largely contribute to the transcytosis of WGA-NP. WGA-NP with shorter surface PEG length (2000) resulted in higher cellular association and more colocalization with the clathrin-mediated transport pathway, while that with longer surface PEG length (5000) avoided the clathrin-mediated transport pathway but achieved higher transcytosis after 4 h incubation. WGA-NP with PLGA as the core materials obtained elevated lysosome escape and enhanced transcytosis after 2 h incubation. These findings provided important evidence for the role of polymer architectures in modulating cellular transport of functionalized nanocarriers, and would be helpful in improving carrier design to enhance drug delivery.

Song Q; Yao L; Huang M; Hu Q; Lu Q; Wu B; Qi H; Rong Z; Jiang X; Gao X; Chen J; Chen H

2012-10-01

189

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

International Nuclear Information System (INIS)

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

1988-01-01

190

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2007-07-15

191

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

International Nuclear Information System (INIS)

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

2007-01-01

192

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

Directory of Open Access Journals (Sweden)

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

Yerlan MYRZAKHMETOV; Aleksander S?ADKOWSKI

2012-01-01

193

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

International Nuclear Information System (INIS)

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

2001-01-01

194

Drug efflux mechanism by a secondary transporter LmrP of Lactococcus lactis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Microorganisms have developed multiple strategies to resist the cytotoxic effects of antimicrobial compounds. These mechanisms include (i) enzymatic degradation or modification of drug; (ii) alteration of drug target; (iii) prevention of drug entry, and (iv) active extrusion of drugs by transport pr...

Mazurkiewicz, Piotr Stanislaw,

195

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

2012-01-01

196

Rituximab reduces the number of peripheral blood B-cells in vitro mainly by effector cell-mediated mechanisms.  

UK PubMed Central (United Kingdom)

BACKGROUND AND OBJECTIVES: The humanized CD20 mono- clonal antibody, rituximab, has significant anti-tumor activity in patients with B-cell non-Hodgkin's lymphoma and induces depletion of B-cells in vivo. It was the objective of this study to define the contribution of the different mechanisms of action of rituximab on primary normal and malignant B-cells. DESIGN AND METHODS: Primary human B-lymphocytes and effector cell fractions were isolated from peripheral blood of normal donors using an immunomagnetic separation technique. Blood samples from 20 patients with chronic lymphocytic leukemia (CLL) were studied and the B-lymphoblastoid Daudi cell line was used as a control. B-cells were cultured in the presence or absence of rituximab adding a secondary hyper-crosslinking antibody, serum as source of complement or different effector cell fractions. The cells were analyzed by immunofluorescence staining and flow cytometry. RESULTS: In contrast to the B-lymphoblastoid Daudi cell line, the number of highly purified normal peripheral blood CD19+ cells was only minimally affected by rituximab in the presence of autologous serum. A significant reduction in the number of B-cells was observed when mononuclear cells from peripheral blood were added back. To identify the cell type which mediates this effect, CD3+ T-cells, CD56+ cells, and CD14+ monocytes were added to selected CD22+ B-cells. A marked B-cell decrease was only observed in the presence of CD56+ and CD14+ cells in an effector to target ratio of 10:1. The experiments with mononuclear cells from patients with CLL showed a B-cell reduction by rituximab, which was significantly enhanced following addition of granulocyte-macrophage colony-stimulating factor (GM-CSF). INTERPRETATION AND CONCLUSIONS: These data support the important role of cell-mediated mechanisms in the B-cell-depleting action of rituximab and suggest that pre-treatment with GM-CSF could improve the response to rituximab in patients with CLL.

Voso MT; Pantel G; Rutella S; Weis M; D'Alò F; Urbano R; Leone G; Haas R; Hohaus S

2002-09-01

197

Two-gate mechanism for phospholipid selection and transport by type IV P-type ATPases.  

UK PubMed Central (United Kingdom)

Most P-type ATPases pump specific cations or heavy metals across a membrane to form ion gradients. However, the type IV P-type ATPases evolved the ability to transport specific phospholipid substrates rather than cations and function to establish plasma membrane asymmetry in eukaryotic cells. The mechanism for how a P-type ATPase, or any other transporter, can recognize and flip a phospholipid substrate is unclear. Here, through a combination of genetic screening and directed mutagenesis with the type IV P-type ATPases Dnf1 and Drs2 from budding yeast, we identify more than a dozen residues that determine headgroup specificity for phospholipid transport. These residues cluster at two interfacial regions flanking transmembrane segments 1-4 and lie outside of the canonical substrate binding site operating in cation pumps. Our data imply the presence of two substrate-selecting gates acting sequentially on opposite sides of the membrane: an entry gate, where phospholipid is initially selected from the extracellular leaflet, and an exit gate at the cytosolic leaflet. The entry and exit gates act cooperatively but imperfectly, with neither being able to restrict phosphatidylserine selection completely when the opposing gate is tuned to permit it. This work describes a unique transport mechanism for a P-type ATPase and provides insight into how integral membrane proteins can recognize and transport phospholipid substrate across a lipid bilayer.

Baldridge RD; Graham TR

2013-01-01

198

Dpp/BMP transport mechanism is required for wing venation in the sawfly Athalia rosae.  

UK PubMed Central (United Kingdom)

The pattern of wing venation varies considerably among different groups of insects and has been used as a means of species-specific identification. However, little is known about how wing venation is established and diversified among insects. The decapentaplegic (Dpp)/bone morphogenetic protein (BMP) signaling pathway plays a critical role in wing vein formation during the pupal stages in Drosophila melanogaster. A key mechanism is BMP transport from the longitudinal veins (LVs) to the posterior crossvein (PCV) by the BMP-binding proteins, short gastrulation (Sog) and twisted gastrulation2/crossveinless (Tsg2/Cv). To investigate whether the BMP transport mechanism is utilized to specify insect wing vein patterns in other than Drosophila, we used the sawfly Athalia rosae as a model, which has distinct venation patterns in the fore- and hindwings. Here, we show that Ar-dpp is ubiquitously expressed in both the fore- and hindwings, but is required for localized BMP signaling that reflects distinct wing vein patterns between the fore- and hindwings. By isolating Ar-tsg/cv in the sawfly, we found that Ar-Tsg/Cv is also required for BMP signaling in wing vein formation and retains the ability to transport Dpp. These data suggest that the BMP transport system is widely used to redistribute Dpp to specify wing venation and may be a basal mechanism underlying diversified wing vein patterns among insects.

Matsuda S; Yoshiyama N; Künnapuu-Vulli J; Hatakeyama M; Shimmi O

2013-05-01

199

Dpp/BMP transport mechanism is required for wing venation in the sawfly Athalia rosae.  

Science.gov (United States)

The pattern of wing venation varies considerably among different groups of insects and has been used as a means of species-specific identification. However, little is known about how wing venation is established and diversified among insects. The decapentaplegic (Dpp)/bone morphogenetic protein (BMP) signaling pathway plays a critical role in wing vein formation during the pupal stages in Drosophila melanogaster. A key mechanism is BMP transport from the longitudinal veins (LVs) to the posterior crossvein (PCV) by the BMP-binding proteins, short gastrulation (Sog) and twisted gastrulation2/crossveinless (Tsg2/Cv). To investigate whether the BMP transport mechanism is utilized to specify insect wing vein patterns in other than Drosophila, we used the sawfly Athalia rosae as a model, which has distinct venation patterns in the fore- and hindwings. Here, we show that Ar-dpp is ubiquitously expressed in both the fore- and hindwings, but is required for localized BMP signaling that reflects distinct wing vein patterns between the fore- and hindwings. By isolating Ar-tsg/cv in the sawfly, we found that Ar-Tsg/Cv is also required for BMP signaling in wing vein formation and retains the ability to transport Dpp. These data suggest that the BMP transport system is widely used to redistribute Dpp to specify wing venation and may be a basal mechanism underlying diversified wing vein patterns among insects. PMID:23499566

Matsuda, Shinya; Yoshiyama, Naotoshi; Künnapuu-Vulli, Jaana; Hatakeyama, Masatsugu; Shimmi, Osamu

2013-03-07

200

Transport mechanisms of flavanone aglycones across Caco-2 cell monolayers and artificial PAMPA membranes.  

UK PubMed Central (United Kingdom)

OBJECTIVES: We recently reported that flavanone aglycones (hesperetin, naringenin and eriodictyol) are efficiently absorbed via proton-coupled active transport, in addition to transcellular passive diffusion, in Caco-2 cells. Here, we aimed to evaluate in detail the absorption mechanisms of these flavanones, as well as homoeriodictyol and sakuranetin. METHODS: We evaluated the absorption mechanisms of the above compounds by means of in vitro studies in Caco-2 cells in parallel with an artificial membrane permeation assay (PAMPA) under pH-gradient and iso-pH conditions. KEY FINDINGS: Comparison of the permeability characteristics of flavanones in Caco-2 cells and in PAMPA under these conditions, as well as a consideration of the physicochemical properties, indicated that hesperetin, naringenin, eriodictyol and homoeriodictyol were efficiently transported by passive diffusion according to the pH-partition hypothesis, except in the case of sakuranetin. However, transport of all flavanones were remarkably temperature-dependent, and was significantly reduced when Caco-2 cells were treated with amino acid-modifying reagents. CONCLUSIONS: Our data confirm that both passive diffusion and an active transport mechanism contribute to flavanone absorption through human intestinal epithelium.

Kobayashi S; Nagai T; Konishi Y; Tanabe S; Morimoto K; Ogihara T

2012-01-01

 
 
 
 
201

Improved electron transport mechanics in the PENELOPE Monte-Carlo model  

International Nuclear Information System (INIS)

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

2001-01-01

202

Improved electron transport mechanics in the PENELOPE Monte-Carlo model  

Science.gov (United States)

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

Bielajew, A. F.; Salvat, F.

2001-01-01

203

Improved electron transport mechanics in the PENELOPE Monte-Carlo model  

Energy Technology Data Exchange (ETDEWEB)

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

Bielajew, A.F. E-mail: bielajew@umich.edu; Salvat, F

2001-01-01

204

Through drying of paper from mechanical and chemical pulp blends: Transport phenomena behavior  

Energy Technology Data Exchange (ETDEWEB)

Printing and heavier grades of paper, often made from pulp blends, are dried by a mature process, cylinder drying, which has a much lower drying rate than through air drying. Analysis of the possible extension of through drying to such semipermeable sheets requires knowledge of the basic characteristics of this process when applied to such grades. Both momentum transport and drying rate aspects of transport phenomena in through air drying were investigated for sheets made from mechanical pulp--chemical pulp blends. The first determination of air permeability for moist paper from TMP and blends of TMP and kraft pulp is reported. The porosity, bulk and specific surface of paper from such blends are also reported. For paper from such blends the mechanical pulp exerts a disproportionate influence through control of the macrostructure by the stiff mechanical pulp fibers and control of the microstructure by its high fines content. Changes in sheet structure affect the momentum transport sensitively but the heat and mass transfer behavior determining drying rate is much less affected. Progress was made on the fundamental Re-{integral}-d{sub p} basis of analysis of through drying. The highly nonlinear dependence of momentum transport properties on pulp blend composition and on moisture content was related to the corresponding changes in the macro-and micro-pore structure available for air through flow.

Hashemi, S.J.; Douglas, W.J.M.

1999-11-01

205

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

UK PubMed Central (United Kingdom)

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

Young RE; Twelkmeyer B; Vitiazeva V; Power PM; Schweda EK; Hood DW

2013-08-01

206

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

UK PubMed Central (United Kingdom)

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

Narayanan K; Yen SK; Dou Q; Padmanabhan P; Sudhaharan T; Ahmed S; Ying JY; Selvan ST

2013-01-01

207

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

Science.gov (United States)

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

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

2013-01-01

208

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.; Beljanski Miloš V.; Maksimov Georgij V.; Kalauzi Aleksandar A.; Draži? Milan D.

2005-01-01

209

Nanoparticle growth and transport mechanisms in capacitively coupled silane discharges: a numerical investigation  

International Nuclear Information System (INIS)

A self-consistent 1D fluid model is used to investigate the formation, growth and transport mechanisms of sub-micrometer particles in a low pressure capacitively coupled radio-frequency silane (SiH4) discharge. In this contribution we analyze the competition between the different forces governing the transport of nanometer-sized particles and the specific role of the thermophoretic force arising from a thermal gradient in gas temperature induced by heating or cooling of the electrodes. Further growth of the nanoparticles due to coagulation is also described by coupling the 1D fluid model with an aerosol dynamics model

2005-10-31

210

Dynamic length-scale characterization and nonequilibrium statistical mechanics of transport in open-cell foams.  

Science.gov (United States)

Nuclear magnetic resonance measurements of scale dependent dynamics in a random solid open-cell foam reveal a characteristic length scale for transport processes in this novel type of porous medium. These measurements and lattice Boltzmann simulations for a model foam structure indicate dynamical behavior analogous to lower porosity consolidated granular porous media, despite extremely high porosity in solid cellular foams. Scaling by the measured characteristic length collapses data for different foam structures as well as consolidated granular media. The nonequilibrium statistical mechanics theory of preasymptotic dispersion, developed for hierarchical porous media, is shown to model the hydrodynamic dispersive transport in a foam structure. PMID:20366068

Brosten, Tyler R; Codd, Sarah L; Maier, Robert S; Seymour, Joseph D

2009-11-20

211

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

2011-11-14

212

Identification of an allosteric modulator of the serotonin transporter with novel mechanism of action.  

Science.gov (United States)

Serotonin transporters (SERTs) play an essential role in the termination and regulation of serotonin signaling in the brain. SERT is also the target of antidepressants and psychostimulants. Molecules with novel activities and modes of interaction with regard to SERT function are of great scientific and clinical interest. We explored structural regions outside the putative serotonin translocation pathway to identify potential binding sites for allosteric transporter modulators (ATMs). Mutational studies revealed a pocket of amino acids outside the orthosteric substrate binding sites located in the interface between extracellular loops 1 and 3 that when mutated affect transporter function. Using the structure of the bacterial transporter homolog leucine transporter as a template, we developed a structural model of SERT. We performed molecular dynamics simulations to further characterize the allosteric pocket that was identified by site-directed mutagenesis studies and employed this pocket in a virtual screen for small-molecule modulators of SERT function. In functional transport assays, we found that one of the identified molecules, ATM7, increased the reuptake of serotonin, possibly by facilitating the interaction of serotonin with transport-ready conformations of SERT when concentrations of serotonin were low and rate limiting. In addition, ATM7 potentiates 3,4-methylenedioxy-N-methylamphetamine (MDMA, "Ecstasy")-induced reversed transport by SERT. Taking advantage of a conformationally sensitive residue in transmembrane domain 6, we demonstrate that ATM7 mechanistically stabilizes an outward-facing conformation of SERT. Taken together these observations demonstrate that ATM7 acts through a novel mechanism that involves allosteric modulation of SERT function. PMID:23632081

Kortagere, Sandhya; Fontana, Andreia Cristina Karklin; Rose, Deja Renée; Mortensen, Ole Valente

2013-04-28

213

Identification of an allosteric modulator of the serotonin transporter with novel mechanism of action.  

UK PubMed Central (United Kingdom)

Serotonin transporters (SERTs) play an essential role in the termination and regulation of serotonin signaling in the brain. SERT is also the target of antidepressants and psychostimulants. Molecules with novel activities and modes of interaction with regard to SERT function are of great scientific and clinical interest. We explored structural regions outside the putative serotonin translocation pathway to identify potential binding sites for allosteric transporter modulators (ATMs). Mutational studies revealed a pocket of amino acids outside the orthosteric substrate binding sites located in the interface between extracellular loops 1 and 3 that when mutated affect transporter function. Using the structure of the bacterial transporter homolog leucine transporter as a template, we developed a structural model of SERT. We performed molecular dynamics simulations to further characterize the allosteric pocket that was identified by site-directed mutagenesis studies and employed this pocket in a virtual screen for small-molecule modulators of SERT function. In functional transport assays, we found that one of the identified molecules, ATM7, increased the reuptake of serotonin, possibly by facilitating the interaction of serotonin with transport-ready conformations of SERT when concentrations of serotonin were low and rate limiting. In addition, ATM7 potentiates 3,4-methylenedioxy-N-methylamphetamine (MDMA, "Ecstasy")-induced reversed transport by SERT. Taking advantage of a conformationally sensitive residue in transmembrane domain 6, we demonstrate that ATM7 mechanistically stabilizes an outward-facing conformation of SERT. Taken together these observations demonstrate that ATM7 acts through a novel mechanism that involves allosteric modulation of SERT function.

Kortagere S; Fontana AC; Rose DR; Mortensen OV

2013-09-01

214

Carrier transport mechanism in the SnO2:F/p-type a-Si:H heterojunction  

Science.gov (United States)

We characterize SnO2:F/p-type a-Si:H/Mo structures by current-voltage (I-V) and capacitance-voltage (C-V) measurements at different temperatures to determine the transport mechanism in the SnO2:F/p-type a-Si:H heterojunction. The experimental I-V curves of these structures, almost symmetric around the origin, are ohmic for |V|SnO2:F/p-type a-Si:H and Mo/p-type a-Si:H junctions. We simulated the reverse I-V curves of the SnO2:F/p-type a-Si:H heterojunction at different temperatures by using the simulation software SCAPS 2.9.03. In the model the main transport mechanism is generation of holes enhanced by tunneling by acceptor-type interface defects with a trap energy of 0.4 eV above the valence bandedge of the p-type a-Si:H layer and with a density of 4.0 × 1013 cm-2. By using I-V simulations and the proposed C-V model the built-in potential (Vbi) of the SnO2:F/p-type a-Si:H (0.16 V) and p-type a-Si:H/Mo (0.14 V) heterojunctions are extracted and a band diagram of the characterized structure is proposed.

Cannella, G.; Principato, F.; Foti, M.; di Marco, S.; Grasso, A.; Lombardo, S.

2011-07-01

215

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

International Nuclear Information System (INIS)

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

2008-01-01

216

Transport properties and mechanism of C60 coupled to carbon nanotube electrode  

International Nuclear Information System (INIS)

By applying non-equilibrium Green's functions in combination with density-functional theory, we investigate electronic transport properties of C60 coupled to carbon nanotubes and Li electrodes. The results show that electronic transport properties of CNT-C60-CNT and Li-C60-Li systems are completely different. Nonlinear I-V characteristic, varistor-type behavior and negative differential resistance (NDR) phenomenon are observed when electrodes are carbon nanotubes. We discuss the mechanism of I-V characteristics of CNT-C60-CNT systems in details. Our results suggest conductance, energy level of Frontier molecular orbitals, energy gap between HOMO and LUMO, the coupling between molecular orbitals and electrodes are all playing critical roles in electronic transport properties.

2011-05-15

217

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

Energy Technology Data Exchange (ETDEWEB)

The use of mobile ionophores to facilitate the transport of /sup 111/In through a lipid bilayer membrane has broad applications in liposome technology and cell labeling. However, the mechanism of such ionophore-mediated transport of /sup 111/In through a lipid bilayer membrane is not completely clear. The present report describes the correlations of the behaviors of ionophoric loading of /sup 111/In into liposomes with the lipophilicity and the indium-binding affinity of three ionophores, namely, 8-hydroxyquinoline, acetylacetone, and tropolone. Our results suggest that the mechanism of the ionophoric transport of /sup 111/In through a lipid bilayer membrane involves the rapid exchange of /sup 111/In cations among the ionophores in both the aqueous solution and the lipid bilayer. Furthermore, the effectiveness of an ionophore in facilitating the transport of /sup 111/In from the external aqueous compartment to the entrapped nitrilotriacetic acid depends not only on the lipophilicity of the (/sup 111/In)ionophore complex, but also on the lipophilicity of the free ionophore itself and the competition of /sup 111/In between nitrilotriacetic acid inside the inner aqueous compartment of the liposome and the ionophore imbedded in the lipid bilayer membrane of the liposome.

Choi, H.O.; Hwang, K.J.

1987-01-01

218

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

International Nuclear Information System (INIS)

The use of mobile ionophores to facilitate the transport of 111In through a lipid bilayer membrane has broad applications in liposome technology and cell labeling. However, the mechanism of such ionophore-mediated transport of 111In through a lipid bilayer membrane is not completely clear. The present report describes the correlations of the behaviors of ionophoric loading of 111In into liposomes with the lipophilicity and the indium-binding affinity of three ionophores, namely, 8-hydroxyquinoline, acetylacetone, and tropolone. Our results suggest that the mechanism of the ionophoric transport of 111In through a lipid bilayer membrane involves the rapid exchange of 111In cations among the ionophores in both the aqueous solution and the lipid bilayer. Furthermore, the effectiveness of an ionophore in facilitating the transport of 111In from the external aqueous compartment to the entrapped nitrilotriacetic acid depends not only on the lipophilicity of the [111In]ionophore complex, but also on the lipophilicity of the free ionophore itself and the competition of 111In between nitrilotriacetic acid inside the inner aqueous compartment of the liposome and the ionophore imbedded in the lipid bilayer membrane of the liposome.

1987-01-01

219

Mechanisms of lipid transport involved in organelle biogenesis in plant cells.  

Science.gov (United States)

Chloroplasts are the defining organelle of photoautotrophic plant cells. Photosynthetic light reactions and electron transport are the functions of an elaborate thylakoid membrane system inside chloroplasts. The lipid composition of photosynthetic membranes is characterized by a substantial fraction of nonphosphorous galactoglycerolipids reflecting the need of sessile plants to conserve phosphorus. Lipid transport and assembly of glycerolipids play an essential role in the biogenesis of the photosynthetic apparatus in developing chloroplasts. During chloroplast biogenesis, fatty acids are synthesized in the plastid and are exported to the endoplasmic reticulum, where they are incorporated into membrane lipids. Alternatively, lipids can also be assembled de novo at the inner envelope membrane of plastids in many plants. A rich repertoire of lipid exchange mechanisms involving the thylakoid membranes, the chloroplast inner and outer envelope membranes, and the endoplasmic reticulum is emerging. Studies of thylakoid biogenesis provide new insights into the general mechanisms of intermembrane lipid transfer. PMID:19572810

Benning, Christoph

2009-01-01

220

Mechanisms of lipid transport involved in organelle biogenesis in plant cells.  

UK PubMed Central (United Kingdom)

Chloroplasts are the defining organelle of photoautotrophic plant cells. Photosynthetic light reactions and electron transport are the functions of an elaborate thylakoid membrane system inside chloroplasts. The lipid composition of photosynthetic membranes is characterized by a substantial fraction of nonphosphorous galactoglycerolipids reflecting the need of sessile plants to conserve phosphorus. Lipid transport and assembly of glycerolipids play an essential role in the biogenesis of the photosynthetic apparatus in developing chloroplasts. During chloroplast biogenesis, fatty acids are synthesized in the plastid and are exported to the endoplasmic reticulum, where they are incorporated into membrane lipids. Alternatively, lipids can also be assembled de novo at the inner envelope membrane of plastids in many plants. A rich repertoire of lipid exchange mechanisms involving the thylakoid membranes, the chloroplast inner and outer envelope membranes, and the endoplasmic reticulum is emerging. Studies of thylakoid biogenesis provide new insights into the general mechanisms of intermembrane lipid transfer.

Benning C

2009-01-01

 
 
 
 
221

Existing and emerging mechanisms for transport of iron and manganese to the brain.  

UK PubMed Central (United Kingdom)

The metals iron (Fe) and manganese (Mn) are essential for normal functioning of the brain. This review focuses on recent developments in the literature pertaining to Fe and Mn transport. These metals are treated together because they appear to share several transport mechanisms. In addition, several neurological diseases such as Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease are all associated with Fe mismanagement in the brain, particularly in the striatum and basal ganglia. Similarly, Mn accumulation in brain also appears to target the same brain regions. Therefore, stringent regulation of the concentration of these metals in the brain is essential. The homeostatic mechanisms for these metals must be understood in order to design neurotoxicity prevention strategies.

Malecki EA; Devenyi AG; Beard JL; Connor JR

1999-04-01

222

Existing and emerging mechanisms for transport of iron and manganese to the brain.  

Science.gov (United States)

The metals iron (Fe) and manganese (Mn) are essential for normal functioning of the brain. This review focuses on recent developments in the literature pertaining to Fe and Mn transport. These metals are treated together because they appear to share several transport mechanisms. In addition, several neurological diseases such as Alzheimer's Disease, Parkinson's Disease, and Huntington's Disease are all associated with Fe mismanagement in the brain, particularly in the striatum and basal ganglia. Similarly, Mn accumulation in brain also appears to target the same brain regions. Therefore, stringent regulation of the concentration of these metals in the brain is essential. The homeostatic mechanisms for these metals must be understood in order to design neurotoxicity prevention strategies. PMID:10777372

Malecki, E A; Devenyi, A G; Beard, J L; Connor, J R

1999-04-15

223

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

International Nuclear Information System (INIS)

[en] 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

1998-01-01

224

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

225

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

Science.gov (United States)

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

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

2012-06-26

226

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2009-07-15

227

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

Energy Technology Data Exchange (ETDEWEB)

Transport of vitamin K into isolated fibroblasts was followed using /sup 3/H vitamin K/sub 1/. The initial rate is saturable by 5 min. at 25..mu..M vitamin K with a Km(app) of 10..mu..M and V/sub max/ of 50 pmols/min/10/sup 6/ cells. Kinetics of uptake are biphasic with a second slower rate ensuing after 10 minutes. Insensitivity of the initial rate of uptake to FCCP or ouabain indicates an ATP-independent transport mechanism. Specificity of transport is shown by competition of uptake of /sup 3/H vitamin K by unlabelled vitamin and strong (>90%) inhibition of the initial rate by equimolar concentrations of the vitamin K analog, Chloro-K. In addition, following uptake, both vitamins K/sub 1/ and K/sub 2/ are metabolized to their respective epoxides. Vitamin K/sub 1/ epoxide is also transported into fibroblasts and metabolized to the parent quinone in a Warfarin-sensitive reaction. Following alkaline hydrolysis of isolated intracellular protein, the vitamin K-dependent amino acid, gamma carboxyglutamic acid (gla) was detected. It is concluded that vitamin K is specifically transported into fibroblasts and metabolized via the classical pathway described in liver with the concomitant production of vitamin K-dependent proteins.

Canfield, L.M.; Townsend, A.F.; Hibbs, D.B.

1986-03-01

228

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

International Nuclear Information System (INIS)

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

1986-03-01

229

Mechanism of energy coupling for transport of D-ribose in Escherichia coli.  

UK PubMed Central (United Kingdom)

In Escherichia coli ML 308-225, d-ribose is transported into the cell by a constitutive active transport system of high activity. The activity of this transport system is severely reduced in cells subjected to osmotic shock, and the system is not present in membrane vesicles. The mechanism by which metabolic energy is coupled to transport of ribose was investigated. Substrates which generate adenosine 5'-triphosphate primarily through oxidative phosphorylation are poor energy sources for ribose uptake in DL-54, a mutant of ML 308-225 which lacks activity for the membrane-bound Ca(2+), Mg(2+)-dependent adenosine triphosphatase required for oxidative phosphorylation. Arsenate severely inhibits ribose uptake, whereas, under the same conditions, uptake of l-proline is relatively insensitive to arsenate. Anaerobiosis does not significantly inhibit ribose uptake in ML 308-225 or DL-54 when glucose is the energy source. A significant amount of ribose uptake is resistant to uncouplers of oxidative phosphorylation such as 2,4-dinitrophenol. These results indicate that the phosphate bond energy of adenosine 5'-triphosphate, rather than an energized membrane state, couples energy to ribose transport in ML 308-225.

Curtis SJ

1974-10-01

230

Is electron transport to oxygen an important mechanism in photoprotection? Contrasting responses from Antarctic vascular plants  

UK PubMed Central (United Kingdom)

Photoreduction of oxygen by the photosynthetic electron transport chain has been suggested to be an important process in protecting leaves from excess light under conditions of stress; however, there is little evidence that this process occurs significantly except when plants are exposed to conditions outside their normal tolerance range. We have examined the oxygen dependency of photosynthetic electron transport in the two vascular plants found growing in Antarctica -Colobanthus quitensis and Deschampsia antarctica. Photosynthetic electron transport in C.quitensis is insensitive to changes in oxygen concentration under non-photorespiratory conditions, indicating that electron transport to oxygen is negligible; however, it has a substantial capacity for non-photochemical quenching (NPQ) of chlorophyll fluorescence. In contrast, D. antarctica has up to 30% of its photosynthetic electron transport being linked to oxygen, but has a substantially lower capacity for NPQ. Thus, these plants rely on contrasting photoprotective mechanisms to cope with the Antarctic environment. Both plants seem to use cyclic electron flow associated with PSI, however, this is activated at a lower irradiance in C.quitensis than in D. antarctica.

Pérez-Torres E; Bravo LA; Corcuera LJ; Johnson GN

2007-06-01

231

Fluid transportation mechanisms by a coupled system of elastic membranes and magnetic fluids  

International Nuclear Information System (INIS)

The basic properties of the fluid transportation mechanism that is produced by the coupled waves propagating along a thin elastic membrane covering a magnetic fluid layer in a shallow and long rectangular vessel are investigated. It is shown that the progressive magnetic field induced by the rectangular pulses generates sinusoidal vibration of the displacement of elastic membrane and makes the system work more efficiently than the magnetic field induced by the pulse-width-modulation method

2002-01-01

232

Inelastic Quantum Transport and Peierls-like Mechanism in Carbon Nanotubes  

CERN Multimedia

We report on a theoretical study of inelastic quantum transport in $(3m,0)$ carbon nanotubes. By using a many-body description of the electron-phonon interaction in Fock space, a novel mechanism involving optical phonon emission (absorption) is shown to induce an unprecedented energy gap opening at half the phonon energy, $\\hbar\\omega_{0}/2$, above (below) the charge neutrality point. This mechanism, which is prevented by Pauli blocking at low bias voltages, is activated at bias voltages in the order of $\\hbar\\omega_{0}$.

Foà-Torres, L E F

2006-01-01

233

Turbulent particle transport in streams: can exponential settling be reconciled with fluid mechanics?  

UK PubMed Central (United Kingdom)

Most ecological studies of particle transport in streams that focus on fine particulate organic matter or benthic invertebrates use the Exponential Settling Model (ESM) to characterize the longitudinal pattern of particle settling on the bed. The ESM predicts that if particles are released into a stream, the proportion that have not yet settled will decline exponentially with transport time or distance and will be independent of the release elevation above the bed. To date, no credible basis in fluid mechanics has been established for this model, nor has it been rigorously tested against more-mechanistic alternative models. One alternative is the Local Exchange Model (LEM), which is a stochastic advection-diffusion model that includes both longitudinal and vertical spatial dimensions and is based on classical fluid mechanics. The LEM predicts that particle settling will be non-exponential in the near field but will become exponential in the far field, providing a new theoretical justification for far-field exponential settling that is based on plausible fluid mechanics. We review properties of the ESM and LEM and compare these with available empirical evidence. Most evidence supports the prediction of both models that settling will be exponential in the far field but contradicts the ESM's prediction that a single exponential distribution will hold for all transport times and distances.

McNair JN; Newbold JD

2012-05-01

234

MAINE HYDROGRAPHY  

Science.gov (United States)

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

235

Separate sites and mechanisms for placental transport of calcium, iron and glucose in the equine placenta.  

Science.gov (United States)

The placenta is the only channel for transport of nutrients to the conceptus and the fetal nutrient demands increase exponentially to term. The 9 kDa calcium binding protein (calbindin, 9CBP) and the iron binding protein uteroferrin (UF) are proving to be reliable markers for epithelia that mediate active transcellular calcium and iron transport and the glucose transporter proteins (GT1 and GT3) for glucose transport by facilitated diffusion. Light and electron microscope immunocytochemistry have been used on perfusion fixed resin embedded material to establish the distribution of 9CBP, UF, GT1 and GT3 in the equine placenta from 100 days of pregnancy to term (336 days). The equine placenta has two main structural components, flat areolae and microcotyledons. From 100 days of pregnancy to term immunoreactive 9CBP is found only in the cytoplasm of the maternal glands and the areolar trophoblast cells with none in the microcotyledons; whereas GT1 is present exclusively in the microcotyledons on the basolateral plasmalemma of both trophoblast and uterine epithelia with GT3 on the apical microvilli. The glands show neither GT1 nor GT3 expression. The areas of both areolae and microcotyledons increase enormously during gestation but there is no indication of increasing amounts of 9CBP, GT1 or GT3 protein per cell. Glucose transport through the placental cell cytoplasm is by diffusion of the free molecule, but calcium ions in transit must be sequestered in some way since the high calcium fluxes needed to support fetal bone growth in later pregnancy would be deleterious to calcium based homeostasis and cellular control systems. Electron microscope immunocytochemistry shows that 9CBP is uniformly distributed in the cytoplasm and nucleoplasm of the areolar trophoblast cells but excluded from all membrane bounded compartments such as mitochondria, Golgi saccules and pinocytotic transport vesicles. Such apical transport vesicles can be identified immunocytochemically by their content of uteroferrin, a component of the secretion from the uterine glands. It is suggested that transcellular calcium transport is therefore based on facilitated diffusion, not the vesicular method followed by the iron in the UF molecules, with 9CBP providing both transfer and sequestration functions for the transient calcium ions. These results show that the equine placenta has transport systems with restricted regional distribution similar to those recently shown for the ruminant placenta. PMID:10985966

Wooding, F B; Morgan, G; Fowden, A L; Allen, W R

2000-09-01

236

Highways versus pipelines: contributions of two fungal transport mechanisms to efficient bioremediation.  

Science.gov (United States)

Based on experimental studies, two different fungus-mediated transport mechanisms have been suggested to facilitate the bacterial degradation of organic soil pollutants: bacteria may use liquid films around fungal hyphae for quick dispersal ('fungal highways'), and fungi may take up and translocate pollutants through their mycelial network ('fungal pipelines'). Both mechanisms are anticipated to enhance the bioavailability of pollutants to degrading bacteria. Using a microbial simulation model, we therefore investigated their respective efficiency in increasing biodegradation performance. We analysed networks that act either as bacterial dispersal vectors or as pollutant translocation vectors or as a combination of both. Our results suggest that each mechanism can improve biodegradation performance. The degree of improvement, however, varies distinctly depending on the environmental conditions, and is even negligible under certain conditions. Mycelial networks acting as 'highways' allow bacteria to overcome motility restrictions and reach remote areas, whereas networks acting as 'pipelines' may initiate degradation by bringing remote pollutants to bacteria. As a consequence, highest biodegradation improvements often emerge from the combination of both mechanisms. We conclude that 'fungal highways' as well as 'fungal pipelines' should be considered for developing novel bioremediation strategies based on fungus-mediated transport in soils. PMID:23584964

Banitz, Thomas; Johst, Karin; Wick, Lukas Y; Schamfuß, Susan; Harms, Hauke; Frank, Karin

2012-10-24

237

Highways versus pipelines: contributions of two fungal transport mechanisms to efficient bioremediation.  

UK PubMed Central (United Kingdom)

Based on experimental studies, two different fungus-mediated transport mechanisms have been suggested to facilitate the bacterial degradation of organic soil pollutants: bacteria may use liquid films around fungal hyphae for quick dispersal ('fungal highways'), and fungi may take up and translocate pollutants through their mycelial network ('fungal pipelines'). Both mechanisms are anticipated to enhance the bioavailability of pollutants to degrading bacteria. Using a microbial simulation model, we therefore investigated their respective efficiency in increasing biodegradation performance. We analysed networks that act either as bacterial dispersal vectors or as pollutant translocation vectors or as a combination of both. Our results suggest that each mechanism can improve biodegradation performance. The degree of improvement, however, varies distinctly depending on the environmental conditions, and is even negligible under certain conditions. Mycelial networks acting as 'highways' allow bacteria to overcome motility restrictions and reach remote areas, whereas networks acting as 'pipelines' may initiate degradation by bringing remote pollutants to bacteria. As a consequence, highest biodegradation improvements often emerge from the combination of both mechanisms. We conclude that 'fungal highways' as well as 'fungal pipelines' should be considered for developing novel bioremediation strategies based on fungus-mediated transport in soils.

Banitz T; Johst K; Wick LY; Schamfuß S; Harms H; Frank K

2013-04-01

238

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

239

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

Science.gov (United States)

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

Horii, Zene

2006-03-01

240

In vivo imaging of oskar mRNA transport reveals the mechanism of posterior localization.  

Science.gov (United States)

oskar mRNA localization to the posterior of the Drosophila oocyte defines where the abdomen and germ cells form in the embryo. Although this localization requires microtubules and the plus end-directed motor, kinesin, its mechanism is controversial and has been proposed to involve active transport to the posterior, diffusion and trapping, or exclusion from the anterior and lateral cortex. By following oskar mRNA particles in living oocytes, we show that the mRNA is actively transported along microtubules in all directions, with a slight bias toward the posterior. This bias is sufficient to localize the mRNA and is reversed in mago, barentsz, and Tropomyosin II mutants, which mislocalize the mRNA anteriorly. Since almost all transport is mediated by kinesin, oskar mRNA localizes by a biased random walk along a weakly polarized cytoskeleton. We also show that each component of the oskar mRNA complex plays a distinct role in particle formation and transport. PMID:18775316

Zimyanin, Vitaly L; Belaya, Katsiaryna; Pecreaux, Jacques; Gilchrist, Michael J; Clark, Alejandra; Davis, Ilan; St Johnston, Daniel

2008-09-01

 
 
 
 
241

In vivo imaging of oskar mRNA transport reveals the mechanism of posterior localization.  

UK PubMed Central (United Kingdom)

oskar mRNA localization to the posterior of the Drosophila oocyte defines where the abdomen and germ cells form in the embryo. Although this localization requires microtubules and the plus end-directed motor, kinesin, its mechanism is controversial and has been proposed to involve active transport to the posterior, diffusion and trapping, or exclusion from the anterior and lateral cortex. By following oskar mRNA particles in living oocytes, we show that the mRNA is actively transported along microtubules in all directions, with a slight bias toward the posterior. This bias is sufficient to localize the mRNA and is reversed in mago, barentsz, and Tropomyosin II mutants, which mislocalize the mRNA anteriorly. Since almost all transport is mediated by kinesin, oskar mRNA localizes by a biased random walk along a weakly polarized cytoskeleton. We also show that each component of the oskar mRNA complex plays a distinct role in particle formation and transport.

Zimyanin VL; Belaya K; Pecreaux J; Gilchrist MJ; Clark A; Davis I; St Johnston D

2008-09-01

242

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1994-12-31

243

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

International Nuclear Information System (INIS)

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

1994-01-01

244

Energetics of sodium-coupled active transport mechanisms in invertebrate epithelia.  

Science.gov (United States)

The Na+ gradient has been implicated as the sole or primary energy source for accumulative transport of organic solutes (e.g., sugars, amino acids) across the mucosal membrane of a variety of epithelial cells. A basic question concerning the Na+-coupled transport process in epithelia is whether the energy available from the transmucosal Na+ electrochemical difference is sufficient to sustain an accumulated organic solute steady-state level. Measurements of Na+ activities, with Na+-sensitive microelectrodes, gave accurate estimates of the Na+ electrochemical potential difference across the mucosal membrane of Aplysia californica gut. The results suggest that the transmucosal Na+ gradient can furnish sufficient energy to sustain the observed intracellular levels of the cotransported species. Many other species sustain large intracellular-extracellular gradients (less than 10(6):1) of free solutes. Theoretical models suggest that secondary active transport mechanisms in these epithelia operate by energetic multiple coupling to the Na+ electrochemical gradient; coupling coefficients of approximately 3 may represent an evolutionary optimization of these epithelial cotransporters. To properly investigate the cotransport mechanisms and energetics in invertebrate membranes, prototype mammalian vesicle experiments should be extended to the invertebrate laboratory. PMID:2675637

Gerencser, G A; Stevens, B R

1989-09-01

245

Energetics of sodium-coupled active transport mechanisms in invertebrate epithelia.  

UK PubMed Central (United Kingdom)

The Na+ gradient has been implicated as the sole or primary energy source for accumulative transport of organic solutes (e.g., sugars, amino acids) across the mucosal membrane of a variety of epithelial cells. A basic question concerning the Na+-coupled transport process in epithelia is whether the energy available from the transmucosal Na+ electrochemical difference is sufficient to sustain an accumulated organic solute steady-state level. Measurements of Na+ activities, with Na+-sensitive microelectrodes, gave accurate estimates of the Na+ electrochemical potential difference across the mucosal membrane of Aplysia californica gut. The results suggest that the transmucosal Na+ gradient can furnish sufficient energy to sustain the observed intracellular levels of the cotransported species. Many other species sustain large intracellular-extracellular gradients (less than 10(6):1) of free solutes. Theoretical models suggest that secondary active transport mechanisms in these epithelia operate by energetic multiple coupling to the Na+ electrochemical gradient; coupling coefficients of approximately 3 may represent an evolutionary optimization of these epithelial cotransporters. To properly investigate the cotransport mechanisms and energetics in invertebrate membranes, prototype mammalian vesicle experiments should be extended to the invertebrate laboratory.

Gerencser GA; Stevens BR

1989-09-01

246

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

International Nuclear Information System (INIS)

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

2005-01-01

247

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

UK PubMed Central (United Kingdom)

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.

Yamashita T; Voth GA

2012-01-01

248

Transport mechanisms in capillary condensation of water at a single-asperity nanoscopic contact.  

UK PubMed Central (United Kingdom)

Transport mechanisms involved in capillary condensation of water menisci in nanoscopic gaps between hydrophilic surfaces are investigated theoretically and experimentally by atomic force microscopy (AFM) measurements of capillary force. The measurements showed an instantaneous formation of a water meniscus by coalescence of the water layers adsorbed on the AFM tip and sample surfaces, followed by a time evolution of meniscus toward a stationary state corresponding to thermodynamic equilibrium. This dynamics of the water meniscus is indicated by time evolution of the meniscus force, which increases with the contact time toward its equilibrium value. Two water transport mechanisms competing in this meniscus dynamics are considered: (1) Knudsen diffusion and condensation of water molecules in the nanoscopic gap and (2) adsorption of water molecules on the surface region around the contact and flow of the surface water toward the meniscus. For the case of very hydrophilic surfaces, the dominant role of surface water transportation on the meniscus dynamics is supported by the results of the AFM measurements of capillary force of water menisci formed at sliding tip-sample contacts. These measurements revealed that fast movement of the contact impedes on the formation of menisci at thermodynamic equilibrium because the flow of the surface water is too slow to reach the moving meniscus.

Sirghi L

2012-02-01

249

Transport mechanisms in capillary condensation of water at a single-asperity nanoscopic contact.  

Science.gov (United States)

Transport mechanisms involved in capillary condensation of water menisci in nanoscopic gaps between hydrophilic surfaces are investigated theoretically and experimentally by atomic force microscopy (AFM) measurements of capillary force. The measurements showed an instantaneous formation of a water meniscus by coalescence of the water layers adsorbed on the AFM tip and sample surfaces, followed by a time evolution of meniscus toward a stationary state corresponding to thermodynamic equilibrium. This dynamics of the water meniscus is indicated by time evolution of the meniscus force, which increases with the contact time toward its equilibrium value. Two water transport mechanisms competing in this meniscus dynamics are considered: (1) Knudsen diffusion and condensation of water molecules in the nanoscopic gap and (2) adsorption of water molecules on the surface region around the contact and flow of the surface water toward the meniscus. For the case of very hydrophilic surfaces, the dominant role of surface water transportation on the meniscus dynamics is supported by the results of the AFM measurements of capillary force of water menisci formed at sliding tip-sample contacts. These measurements revealed that fast movement of the contact impedes on the formation of menisci at thermodynamic equilibrium because the flow of the surface water is too slow to reach the moving meniscus. PMID:22229845

Sirghi, Lucel

2012-01-25

250

Reaction rate modeling in noncatalytic gas-solid systems: Species transport and mechanical stress  

Energy Technology Data Exchange (ETDEWEB)

A detailed model to describe the overall reaction rate of the oxidation of titanium is developed. The mathematical model consists of two facets, the first of which involves a detailed description of species transport that accounts for the formation of charged species. This is augmented by a description of the occurrence of mechanical stress due to a Pilling-Bedworth ratio that differs significantly from 1 as well as differences between precursor and product thermal expansion coefficients. A self-imposed electric field is formed across the oxide layer due to different mobilities of the species considered. This field opposes the transport of electrons and enhances the transport of anion vacancies, thus increasing the overall reaction rate compared to a pure diffusion process, while also ensuring that electrical charge is conserved. Large growth stresses result from the unmatched precursor and product volumes, significantly affecting the overall process. These results show that the incorporation of a consistent treatment of mechanical stress forms a necessary part of any accurate description of the overall behavior of a reacting particle.

Rode, H.; Orlicki, D.; Hlavacek, V. [State Univ. of New York, Buffalo, Amherst, NY (United States)

1995-12-01

251

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-12-31

252

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

International Nuclear Information System (INIS)

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

1996-02-02

253

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

UK PubMed Central (United Kingdom)

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

Sturzbecher-Hoehne M; Goujon C; Deblonde GJ; Mason AB; Abergel RJ

2013-02-01

254

TRANSPORT  

Science.gov (United States)

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

255

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

256

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

CERN Multimedia

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

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

2006-01-01

257

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

Science.gov (United States)

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

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

2010-03-28

258

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

UK PubMed Central (United Kingdom)

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

Tang L; Bai L; Wang WH; Jiang T

2010-04-01

259

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

260

Transport mechanisms and rates for the long-lived Chernobyl deposits  

International Nuclear Information System (INIS)

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

1988-01-01

 
 
 
 
261

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

Directory of Open Access Journals (Sweden)

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

N.M.Ponomaryova; A.M.Ponomaryov

2011-01-01

262

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

Directory of Open Access Journals (Sweden)

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

Jansy Passiflora Sarathy; Véronique Dartois; Edmund Jon Deoon Lee

2012-01-01

263

Two relaxation mechanisms observed in transport between spin-split edge states at high imbalance  

Science.gov (United States)

Using a quasi-Corbino geometry to directly study electron transport between spin-split edge states under high imbalance conditions, we find a pronounced hysteresis in the I-V curves originating from dynamic nuclear polarization near the sample edge. Already in the simplest case of filling factor ?=2 we observe a complicated relaxation, depending on the sign of the electrochemical potential difference. The characteristic relaxation times are about 25 s and 200 s, which points to the presence of two different relaxation mechanisms. The two time constants are ascribed to the formation of a local nuclear polarization due to flip-flop processes and the diffusion of nuclear spins.

Deviatov, E. V.; Würtz, A.; Lorke, A.; Melnikov, M. Yu.; Dolgopolov, V. T.; Reuter, D.; Wieck, A. D.

2004-03-01

264

[Status and prospect of studies on habitat characteristics, parasitic mechanism and nutrient transport of Cistanche deserticola].  

UK PubMed Central (United Kingdom)

Cistanche Herba is one of precious traditional Chinese medicine, which original wild plant resources dropped sharply in recent years. It is urgent to make sustainable utilization. The genus of Cistanche is a total parasitic plant, its physiological ecology and nutrition transfer are very particular. The status of the studies on habitat characteristics, parasitic mechanism and nutrient transport of Cistanche was reviewed, prospect was also given. It can provide reference for the further basic and applied studies on the nutrition transfer, germplasm quality and agriculture practice.

Huang XF; Xu R; Chen J; Yu J; Liu S; Liu TN

2012-10-01

265

[Status and prospect of studies on habitat characteristics, parasitic mechanism and nutrient transport of Cistanche deserticola].  

Science.gov (United States)

Cistanche Herba is one of precious traditional Chinese medicine, which original wild plant resources dropped sharply in recent years. It is urgent to make sustainable utilization. The genus of Cistanche is a total parasitic plant, its physiological ecology and nutrition transfer are very particular. The status of the studies on habitat characteristics, parasitic mechanism and nutrient transport of Cistanche was reviewed, prospect was also given. It can provide reference for the further basic and applied studies on the nutrition transfer, germplasm quality and agriculture practice. PMID:23270217

Huang, Xiao-fang; Xu, Rong; Chen, Jun; Yu, Jing; Liu, Sai; Liu, Tong-ning

2012-10-01

266

Hydrogels as controlled drug delivery systems: Synthesis, crosslinking, water and drug transport mechanism  

Directory of Open Access Journals (Sweden)

Full Text Available Hydrogels are presently under investigation as a delivery system for bioactive molecules, because of their similar physical properties as that of living tissue, which is due to their high water content, soft and rubbery consistency, and low interfacial tension with water or biological fluids. Anionic hydrogels are used in the design of intelligent controlled release devices for site-specific drug delivery of therapeutic proteins to the large intestine, where the biological activity of the proteins are prolonged, and cationic hydrogels are studied for the development of self-regulated insulin delivery system, which releases the insulin in response to changing glucose concentration. The different methods of preparation of hydrogels, novel methods of crosslinking used in the preparation of hydrogels, the mechanism of water transport through the ionic hydrogels, and the release mechanism of the solute from the hydrogels, are discussed in the present article.

Satish C; Satish K; Shivakumar H

2006-01-01

267

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

International Nuclear Information System (INIS)

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

2002-12-20

268

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

269

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

Science.gov (United States)

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

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

2004-11-01

270

To gate, or not to gate: regulatory mechanisms for intercellular protein transport and virus movement in plants.  

UK PubMed Central (United Kingdom)

Cell-to-cell signal transduction is vital for orchestrating the whole-body physiology of multi-cellular organisms, and many endogenous macromolecules, proteins, and nucleic acids function as such transported signals. In plants, many of these molecules are transported through plasmodesmata (Pd), the cell wall-spanning channel structures that interconnect plant cells. Furthermore, Pd also act as conduits for cell-to-cell movement of most plant viruses that have evolved to pirate these channels to spread the infection. Pd transport is presumed to be highly selective, and only a limited repertoire of molecules is transported through these channels. Recent studies have begun to unravel mechanisms that actively regulate the opening of the Pd channel to allow traffic. This macromolecular transport between cells comprises two consecutive steps: intracellular targeting to Pd and translocation through the channel to the adjacent cell. Here, we review the current knowledge of molecular species that are transported though Pd and the mechanisms that control this traffic. Generally, Pd traffic can occur by passive diffusion through the trans-Pd cytoplasm or through the membrane/lumen of the trans-Pd ER, or by active transport that includes protein-protein interactions. It is this latter mode of Pd transport that is involved in intercellular traffic of most signal molecules and is regulated by distinct and sometimes interdependent mechanisms, which represent the focus of this article.

Ueki S; Citovsky V

2011-09-01

271

To gate, or not to gate: regulatory mechanisms for intercellular protein transport and virus movement in plants.  

Science.gov (United States)

Cell-to-cell signal transduction is vital for orchestrating the whole-body physiology of multi-cellular organisms, and many endogenous macromolecules, proteins, and nucleic acids function as such transported signals. In plants, many of these molecules are transported through plasmodesmata (Pd), the cell wall-spanning channel structures that interconnect plant cells. Furthermore, Pd also act as conduits for cell-to-cell movement of most plant viruses that have evolved to pirate these channels to spread the infection. Pd transport is presumed to be highly selective, and only a limited repertoire of molecules is transported through these channels. Recent studies have begun to unravel mechanisms that actively regulate the opening of the Pd channel to allow traffic. This macromolecular transport between cells comprises two consecutive steps: intracellular targeting to Pd and translocation through the channel to the adjacent cell. Here, we review the current knowledge of molecular species that are transported though Pd and the mechanisms that control this traffic. Generally, Pd traffic can occur by passive diffusion through the trans-Pd cytoplasm or through the membrane/lumen of the trans-Pd ER, or by active transport that includes protein-protein interactions. It is this latter mode of Pd transport that is involved in intercellular traffic of most signal molecules and is regulated by distinct and sometimes interdependent mechanisms, which represent the focus of this article. PMID:21746703

Ueki, Shoko; Citovsky, Vitaly

2011-07-10

272

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

International Nuclear Information System (INIS)

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

1995-01-01

273

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

UK PubMed Central (United Kingdom)

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

Frohlich KM; Audia JP

2013-08-01

274

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

Science.gov (United States)

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

Frohlich, Kyla M; Audia, Jonathon P

2013-06-14

275

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

276

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-12-15

277

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

International Nuclear Information System (INIS)

[en] 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

2004-01-01

278

Structural Insight into the Mechanisms of Transport across the Salmonella enterica Pdu Microcompartment Shell*  

Science.gov (United States)

Bacterial microcompartments are a functionally diverse group of proteinaceous organelles that confine specific reaction pathways in the cell within a thin protein-based shell. The propanediol utilizing (Pdu) microcompartment contains the reactions for metabolizing 1,2-propanediol in certain enteric bacteria, including Salmonella. The Pdu shell is assembled from a few thousand protein subunits of several different types. Here we report the crystal structures of two key shell proteins, PduA and PduT. The crystal structures offer insights into the mechanisms of Pdu microcompartment assembly and molecular transport across the shell. PduA forms a symmetric homohexamer whose central pore appears tailored for facilitating transport of the 1,2-propanediol substrate. PduT is a novel, tandem domain shell protein that assembles as a pseudohexameric homotrimer. Its structure reveals an unexpected site for binding an [Fe-S] cluster at the center of the PduT pore. The location of a metal redox cofactor in the pore of a shell protein suggests a novel mechanism for either transferring redox equivalents across the shell or for regenerating luminal [Fe-S] clusters.

Crowley, Christopher S.; Cascio, Duilio; Sawaya, Michael R.; Kopstein, Jeffery S.; Bobik, Thomas A.; Yeates, Todd O.

2010-01-01

279

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

Science.gov (United States)

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

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

2013-09-01

280

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

International Nuclear Information System (INIS)

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

2004-01-01

 
 
 
 
281

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

Scientific Electronic Library Online (English)

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

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

2000-08-01

282

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

Science.gov (United States)

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 °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 °C. The present results are discussed considering that supplying oxygen to the metal/dielectric interface can cause device threshold voltage shifts.

Pezzi, R. P.; Copel, M.; Gordon, M.; Cartier, E.; Baumvol, I. J. R.

2006-06-01

283

Solid lipid nanoparticles as intracellular drug transporters: an investigation of the uptake mechanism and pathway.  

UK PubMed Central (United Kingdom)

The aim of this work was to develop a systematic analysis of the cellular internalisation mechanism and pathway of solid lipid nanoparticles (SLN) internalisation. To evaluate if SLN show cell uptake and to understand the mechanism of internalisation, four human glioma cell lines (A172, U251, U373 and U87) and a human macrophage cell line (THP1) were used. For this purpose rhodamine 123 (R123) was loaded into SLN coated with polysorbate 60 and 80. Fluorescence microscopy and flow cell cytometry techniques were assessed to study internalisation of these systems within the cells. MTT studies were performed to evaluate the cytotoxicity of the R123-loaded SLN. To assess the SLN internalisation mechanism and intracellular pathway, excluding endocytosis mechanisms were applied. Our results revealed that R123-loaded SLN with mean size below 200 nm and slight negative surface charge (around -20 mV) have the ability to be internalised by gliomas in a higher amount than by macrophages. The mechanism of internalisation was found to be mainly through a clathrin-dependent endocytic pathway. In addition, the cytotoxicity of SLN was higher for gliomas than for macrophages. These results suggest that SLN can be a promising alternative in brain tumours treatment.

Martins S; Costa-Lima S; Carneiro T; Cordeiro-da-Silva A; Souto EB; Ferreira DC

2012-07-01

284

Solid lipid nanoparticles as intracellular drug transporters: an investigation of the uptake mechanism and pathway.  

Science.gov (United States)

The aim of this work was to develop a systematic analysis of the cellular internalisation mechanism and pathway of solid lipid nanoparticles (SLN) internalisation. To evaluate if SLN show cell uptake and to understand the mechanism of internalisation, four human glioma cell lines (A172, U251, U373 and U87) and a human macrophage cell line (THP1) were used. For this purpose rhodamine 123 (R123) was loaded into SLN coated with polysorbate 60 and 80. Fluorescence microscopy and flow cell cytometry techniques were assessed to study internalisation of these systems within the cells. MTT studies were performed to evaluate the cytotoxicity of the R123-loaded SLN. To assess the SLN internalisation mechanism and intracellular pathway, excluding endocytosis mechanisms were applied. Our results revealed that R123-loaded SLN with mean size below 200 nm and slight negative surface charge (around -20 mV) have the ability to be internalised by gliomas in a higher amount than by macrophages. The mechanism of internalisation was found to be mainly through a clathrin-dependent endocytic pathway. In addition, the cytotoxicity of SLN was higher for gliomas than for macrophages. These results suggest that SLN can be a promising alternative in brain tumours treatment. PMID:22465548

Martins, S; Costa-Lima, S; Carneiro, T; Cordeiro-da-Silva, A; Souto, E B; Ferreira, D C

2012-03-23

285

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; A. Albizuri; L. Alonso; M. Navazo; M. Matabuena; V. Valdenebro; J. A. García; M. M. Millán

2006-01-01

286

Nanoscale mechanism of molecular transport through the nuclear pore complex as studied by scanning electrochemical microscopy.  

Science.gov (United States)

The nuclear pore complex (NPC) is the proteinaceous nanopore that solely mediates molecular transport across the nuclear envelope between the nucleus and cytoplasm of a eukaryotic cell. Small molecules (nanogap-based approach of scanning electrochemical microscopy to precisely measure the extremely high permeability of the nuclear envelope to a small probe molecule, (ferrocenylmethyl)trimethylammonium. Effective medium theories indicate that the passive permeability of 5.9 × 10(-2) cm/s corresponds to the free diffusion of the probe molecule through ~22 nanopores with a radius of 24 nm and a length of 35 nm. Peripheral routes are blocked by wheat germ agglutinin to yield 2-fold lower permeability for 17 nm-radius central routes. This lectin is also used in fluorescence assays to find that importins facilitate the transport of signal-tagged albumin mainly through the 7 nm-thick peripheral route rather than through the sufficiently large central route. We propose that this spatial selectivity is regulated by the conformational changes in barrier-forming proteins that transiently and locally expand the impermeably thin peripheral route while blocking the central route. PMID:23320434

Kim, Jiyeon; Izadyar, Anahita; Nioradze, Nikoloz; Amemiya, Shigeru

2013-01-30

287

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

International Nuclear Information System (INIS)

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

2009-01-01

288

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

289

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; Kirsten Sandvig

2013-01-01

290

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

Energy Technology Data Exchange (ETDEWEB)

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.

Clarno, Kevin T [ORNL; Hamilton, Steven P [ORNL; Philip, Bobby [ORNL; Sampath, Rahul S [ORNL; Allu, Srikanth [ORNL; Berrill, Mark A [ORNL; Barai, Pallab [ORNL; Banfield, James E [ORNL

2012-01-01

291

Impact of the base doping concentration on the transport mechanisms in n-type a-SiGe:H/p-type c-Silicon Heterojunctions  

Scientific Electronic Library Online (English)

Full Text Available Abstract in spanish Heterouniones de a-SiGe:H tipo-n sobre silicio cristalino tipo-p con cuatro diferentes concentraciones pico en la base (l x lO15, 7 x lO16, 7 x l0(17) y 5 x lO18 cm-3) fueron fabricadas y caracterizadas. Los mecanismos de transporte se determinaron por medio de sus curvas características de corriente vs voltaje en función de la temperatura. El análisis de los resultados muestra que a bajos voltajes de polarización directa (V(more) centración pico la corriente es determinada por la difusión de electrones del a-SiGe:H tipo-n hacia el silicio cristalino tipo-p. Mientras que el multituneleo captura-emisión (MTCE) es el principal mecanismo de transporte en las otras heterouniones. A altos voltajes de polarizacion directa (V> 0.45V) el efecto de corriente limitada por carga espacial (SCLC) es el mecanismo de transporte dominante en todos los dispositivos caracterizados. El incremento en la concentración de dopantes en la base, además, causa un aumento en la corriente inversa. Abstract in english The charge transport mechanisms occurring in n-type a-SiGe:H on p-type c-Si heteroj unctions were determined by analyzing the temperature dependence of the current-voltage characteristics in structures with four different peak base doping concentrations (N B = 1 x 10(15), 7 x 10(16), 7 x l0(17) and 5 x lO18 cm-3). From the experimental results, we observed that at low forward bias (V(more) the p-type c-Si for the heterojunction with N B = 1 x 10(15)cm-3, whereas the Multi-Tunneling Capture Emission (MTCE) was identified as the main transport mechanism for the other base doping concentrations. On the other hand, at high forward bias (V> 0.45V), the space charge limited current effect became the dominant transport mechanism for all the measured devices. Under reverse bias the transport mechanisms depends on the peak base doping, going from carrier generation inside the space charge region for the lowest doping, to hopping and thermionic field emission as the base doping concentration is increased.

Rosales-Quintero, P.; Moreno-Moreno, M.; Torres-Jacome, A.; Hidalga Wade, F.J. De la; Molina-Reyes, J.; Calleja-Arriaga, W.; Zuñiga-Islas, C.

2011-04-01

292

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

2011-04-06

293

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

CERN Document Server

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

Bostan, Mihai

2012-01-01

294

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

295

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.

2009-08-03

296

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

Science.gov (United States)

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

Choi, Wonchul; Shin, Mincheol

2011-07-01

297

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

UK PubMed Central (United Kingdom)

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

Choi W; Shin M

2011-07-01

298

Mechanism of polymeric nanoparticle-based drug transport across the blood-brain barrier (BBB).  

UK PubMed Central (United Kingdom)

In 1995 it was reported for the first time that nanoparticles could be used for the delivery of drugs across the blood-brain barrier (BBB) following intravenous injection. In vitro and in vivo experiments show that the underlying mechanism is receptor-mediated endocytosis followed by transcytosis. No opening of the tight junctions was observed. Due to the overcoating of the nanoparticles with polysorbate 80 or poloxamers 188, apolipoproteins A-I and/or E are adsorbed from the blood on to the particle surface after injection. These apolipoproteins mediate the interaction with LDL or scavenger receptors on the BBB followed by the above brain uptake processes. Likewise, covalent attachment of these apolipoproteins or of transferrin, insulin or antibodies against the respective receptors also enables a similar nanoparticle-mediated drug transport across the BBB. From these results it can be concluded that the nanoparticles act as "Trojan Horses" taking advantage of physiological receptor-mediated transport processes across the BBB.

Kreuter J

2013-01-01

299

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

International Nuclear Information System (INIS)

[en] 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

1997-01-01

300

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.

Steven K.C. Lo; Huan-Chao Keh

2011-01-01

 
 
 
 
301

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

International Nuclear Information System (INIS)

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

1995-01-01

302

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

Energy Technology Data Exchange (ETDEWEB)

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

Moreno, L.; Gylling, B.; Neretniks, I. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Engineering and Technology

1995-06-01

303

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

International Nuclear Information System (INIS)

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

1979-01-01

304

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

CERN Document Server

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

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

2012-01-01

305

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

306

Nonlinear electric transport in graphene: Quantum quench dynamics and the Schwinger mechanism  

Science.gov (United States)

We present a unified view of electric transport in undoped graphene for finite electric field. The weak field results agree with the Kubo approach. For strong electric field, the current increases nonlinearly with the electric field as E3/2 . As the Dirac point is moved around in reciprocal space by the field, excited states are generated. This is analogous to the generation of defects in a finite-rate quench through a quantum-critical point, which we account for in the framework of the Kibble-Zurek mechanism. These results are also recast in terms of Schwinger’s pair production and Landau-Zener tunneling. Other systems exhibiting a band structure with Dirac cones, in particular, cold atoms in optical lattices, should exhibit the same dynamics as well.

Dóra, Balázs; Moessner, Roderich

2010-04-01

307

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

International Nuclear Information System (INIS)

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

2000-01-01

308

Investigating the effects of ABC transporter-based acquired drug resistance mechanisms at the cellular and tissue scale.  

UK PubMed Central (United Kingdom)

In this paper we systematically investigate the effects of acquired drug resistance at the cellular and tissue scale, with a specific focus on ATP-binding cassette (ABC) transporter-based mechanisms and contrast this with other representative intracellular resistance mechanisms. This is done by developing in silico models wherein the drug resistance mechanism is overlaid on a coarse-grained description of apoptosis; these cellular models are coupled with interstitial drug transport, allowing for a transparent examination of the effect of acquired drug resistances at the tissue level. While ABC transporter-mediated resistance mechanisms counteract drug effect at the cellular level, its tissue-level effect is more complicated, revealing unexpected trends in tissue response as drug stimuli are systematically varied. Qualitatively different behaviour is observed in other drug resistance mechanisms. Overall the paper (i) provides insight into the tissue level functioning of a particular resistance mechanism, (ii) shows that this is very different from other resistance mechanisms of an apparently similar type, and (iii) demonstrates a concrete instance of how the functioning of a negative feedback based cellular adaptive mechanism can have unexpected higher scale effects.

Liu C; Krishnan J; Xu XY

2013-03-01

309

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

UK PubMed Central (United Kingdom)

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

Alvaro M; Bonilla LL; Carretero M; Melnik RV; Prabhakar S

2013-08-01

310

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

311

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

Directory of Open Access Journals (Sweden)

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

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

2012-01-01

312

Transport, Growth Mechanisms, and Material Quality in GaN Epitaxial Lateral Overgrowth  

Energy Technology Data Exchange (ETDEWEB)

Growth kinetics, mechanisms, and material quality in GaN epitaxial lateral over-growth (ELO) were examined using a single mask of systematically varied patterns. A 2-D gas phase reaction/diffusion model describes how transport of the Ga precursor to the growth surface enhances the lateral rate in the early stages of growth. In agreement with SEM studies of truncated growth runs, the model also predicts the dramatic decrease in the lateral rate that occurs as GaN over-growth reduces the exposed area of the mask. At the point of convergence, a step-flow coalescence mechanism is observed to fill in the area between lateral growth-fronts. This alternative growth mode in which a secondary growth of GaN is nucleated along a single convergence line, may be responsible for producing smooth films observed to have uniform cathodoluminescence (CL) when using 1{micro}m nucleation zones. Although emission is comprised of both UV ({approximately}365nm) and yellow ({approximately}550nm) components, the spectra suggest these films have reduced concentrations of threading dislocations normally associated with non-radiative recombination centers and defects known to accompany growth-front convergence lines.

Baca, Albert G.; Bartram, M.E.; Coltrin, M.E.; Crawford, M.H.; Han, J.; Missert, N.; Willan, C.C.

1999-01-11

313

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

Science.gov (United States)

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

Li, Hongmin; Braun, Minel J.

2006-07-01

314

p38 MAP kinase activation does not stimulate serotonin transport in rat brain: Implications for sickness behaviour mechanisms.  

UK PubMed Central (United Kingdom)

AIMS: Several studies suggested an association between dysregulation of immune mediators and behavioural, neuroendocrine and neurochemical features of depression. Available data showed that cytokines affect the serotonin transporter (SERT) activity through p38 MAP kinase (MAPK)-dependent mechanisms in some cell lines and mice neurons (Zhu et al., Neuropsychopharmacology, 2006; 31:2121-31). The aim of this study was to investigate the interaction of Interleukin-1? (IL-1?) or p38 MAPK with SERT activity in rat brain and cell lines. MAIN METHODS: Synaptosomes or cells were treated with IL-1? or the p38 MAPK activator anisomycin at different concentrations and end-points and the modulation of SERT activity as Km and Vmax was evaluated. KEY FINDINGS: Treatments with IL-1? or anisomycin did not affect serotonin uptake and p38 MAPK activation in rat synaptosomes, in contrast to reports in mice (Zhu et al., Neuropsychopharmacology, 2010; 35:2510-20). The same treatments activated p38 MAPK phosphorylation in HeLa cells used as positive controls. Similarly, no changes after anisomycin treatment could be detected in [(3)H]serotonin uptake rate in LLC-PK cells expressing human SERT, although phosphorylated p38 MAPK levels augmented significantly. Direct cytokine release in brain was induced by intracerebroventricular administration of bacterial lipopolysaccaride. Although pro-inflammatory cytokines, such as IL-1ß, IL6, and Tumor Necrosis Factor ?, showed significant increases in brain cortex, modulation of SERT activity in term of Km and Vmax was not detected. SIGNIFICANCE: These results imply that the stimulation of serotonin uptake by cytokines may not be a unique and fundamental mechanism in the pathology of depression induced by altered immune response.

Andreetta F; Barnes NM; Wren PB; Carboni L

2013-07-01

315

Inhibition of Glycine Transporter-I as a Novel Mechanism for the Treatment of Depression.  

UK PubMed Central (United Kingdom)

BACKGROUND: Antidepressants, aiming at monoaminergic neurotransmission, exhibit delayed onset of action, limited efficacy, and poor compliance. Glutamatergic neurotransmission is involved in depression. However, it is unclear whether enhancement of the N-methyl-D-aspartate (NMDA) subtype glutamate receptor can be a treatment for depression. METHODS: We studied sarcosine, a glycine transporter-I inhibitor that potentiates NMDA function, in animal models and in depressed patients. We investigated its effects in forced swim test, tail suspension test, elevated plus maze test, novelty-suppressed feeding test, and chronic unpredictable stress test in rats and conducted a 6-week randomized, double-blinded, citalopram-controlled trial in 40 patients with major depressive disorder. Clinical efficacy and side effects were assessed biweekly, with the main outcomes of Hamilton Depression Rating Scale, Global Assessment of Function, and remission rate. The time course of response and dropout rates was also compared. RESULTS: Sarcosine decreased immobility in the forced swim test and tail suspension test, reduced the latency to feed in the novelty-suppressed feeding test, and reversed behavioral deficits caused by chronic unpredictable stress test, which are characteristics for an antidepressant. In the clinical study, sarcosine substantially improved scores of Hamilton Depression Rating Scale, Clinical Global Impression, and Global Assessment of Function more than citalopram treatment. Sarcosine-treated patients were much more likely and quicker to remit and less likely to drop out. Sarcosine was well tolerated without significant side effects. CONCLUSIONS: Our preliminary findings suggest that enhancing NMDA function can improve depression-like behaviors in rodent models and in human depression. Establishment of glycine transporter-I inhibition as a novel treatment for depression waits for confirmation by further proof-of-principle studies.

Huang CC; Wei IH; Huang CL; Chen KT; Tsai MH; Tsai P; Tun R; Huang KH; Chang YC; Lane HY; Tsai GE

2013-04-01

316

Mechanism of transport of riboflavin in rabbit intestinal brush border membrane vesicles.  

Science.gov (United States)

Uptake of luminal riboflavin (RF) into the absorptive cells of rabbit small intestine was examined using purified brush border membrane vesicle (BBMV) preparations. These preparations were used in order to eliminate the interference of intracellular metabolism that occurs to the RF molecule during absorption. Uptake of RF by BBMV was found to be mainly (> 76%) the result of transport of the vitamin into the intracellular space with less binding to membrane surfaces. All 3H radioactivity that appeared in the intravesicular space after incubation with [3H]RF was found to be in the form of intact RF. Uptake of RF with time was independent of the presence or absence of a Na+ or a K+ gradient (out > in) and occurred without transaccumulation of the substrate in the intravesicular space. Furthermore, changing the incubation buffer pH showed minimal effect on RF uptake. When examined as a function of concentration, the initial rate of RF uptake was found to be saturable both in jejunal and ileal BBMV with an apparent Km of 7.24 +/- 1.06 and 8.88 +/- 0.90 microM and Vmax of 24.31 +/- 1.48 and 34.24 +/- 1.55 pmol/mg protein/5 sec, respectively. Unlabeled RF and the related compounds lumiflavin, 8-aminoriboflavin, isoriboflavin, and lumichrome all inhibited (but to different degrees) the uptake of physiologic concentration of [3H]RF. On the other hand, 8-hydroxyriboflavin, lumazine, and D-ribose all failed to inhibit [3H]RF uptake. Similarly, the membrane transport inhibitors DIDS, SITS, and furosemide all failed to inhibit [3H]RF uptake. The uptake of RF was found to be insensitive to changes in the transmembrane electrical potential, as shown by studies with anion substitution and valinomycin K(+)-induced negative or positive intravesicular potential methodologies. These results indicate that RF uptake by rabbit intestinal BBMV occurs via a carrier-mediated system that is Na+ independent in nature and transports the substrate by an electroneutral process. The role of this system in the overall absorption process of RF is discussed. PMID:8456106

Said, H M; Mohammadkhani, R; McCloud, E

1993-04-01

317

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

DEFF Research Database (Denmark)

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

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

1992-01-01

318

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

International Nuclear Information System (INIS)

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

2010-01-01

319

Salt stress in Thellungiella halophila activates Na+ transport mechanisms required for salinity tolerance.  

UK PubMed Central (United Kingdom)

Salinity is considered one of the major limiting factors for plant growth and agricultural productivity. We are using salt cress (Thellungiella halophila) to identify biochemical mechanisms that enable plants to grow in saline conditions. Under salt stress, the major site of Na+ accumulation occurred in old leaves, followed by young leaves and taproots, with the least accumulation occurring in lateral roots. Salt treatment increased both the H+ transport and hydrolytic activity of salt cress tonoplast (TP) and plasma membrane (PM) H(+)-ATPases from leaves and roots. TP Na(+)/H+ exchange was greatly stimulated by growth of the plants in NaCl, both in leaves and roots. Expression of the PM H(+)-ATPase isoform AHA3, the Na+ transporter HKT1, and the Na(+)/H+ exchanger SOS1 were examined in PMs isolated from control and salt-treated salt cress roots and leaves. An increased expression of SOS1, but no changes in levels of AHA3 and HKT1, was observed. NHX1 was only detected in PM fractions of roots, and a salt-induced increase in protein expression was observed. Analysis of the levels of expression of vacuolar H(+)-translocating ATPase subunits showed no major changes in protein expression of subunits VHA-A or VHA-B with salt treatment; however, VHA-E showed an increased expression in leaf tissue, but not in roots, when the plants were treated with NaCl. Salt cress plants were able to distribute and store Na+ by a very strict control of ion movement across both the TP and PM.

Vera-Estrella R; Barkla BJ; García-Ramírez L; Pantoja O

2005-11-01

320

Salt stress in Thellungiella halophila activates Na+ transport mechanisms required for salinity tolerance.  

Science.gov (United States)

Salinity is considered one of the major limiting factors for plant growth and agricultural productivity. We are using salt cress (Thellungiella halophila) to identify biochemical mechanisms that enable plants to grow in saline conditions. Under salt stress, the major site of Na+ accumulation occurred in old leaves, followed by young leaves and taproots, with the least accumulation occurring in lateral roots. Salt treatment increased both the H+ transport and hydrolytic activity of salt cress tonoplast (TP) and plasma membrane (PM) H(+)-ATPases from leaves and roots. TP Na(+)/H+ exchange was greatly stimulated by growth of the plants in NaCl, both in leaves and roots. Expression of the PM H(+)-ATPase isoform AHA3, the Na+ transporter HKT1, and the Na(+)/H+ exchanger SOS1 were examined in PMs isolated from control and salt-treated salt cress roots and leaves. An increased expression of SOS1, but no changes in levels of AHA3 and HKT1, was observed. NHX1 was only detected in PM fractions of roots, and a salt-induced increase in protein expression was observed. Analysis of the levels of expression of vacuolar H(+)-translocating ATPase subunits showed no major changes in protein expression of subunits VHA-A or VHA-B with salt treatment; however, VHA-E showed an increased expression in leaf tissue, but not in roots, when the plants were treated with NaCl. Salt cress plants were able to distribute and store Na+ by a very strict control of ion movement across both the TP and PM. PMID:16244148

Vera-Estrella, Rosario; Barkla, Bronwyn J; García-Ramírez, Liliana; Pantoja, Omar

2005-10-21

 
 
 
 
321

Mechanism of lipid mobilization by the small intestine after transport blockade  

International Nuclear Information System (INIS)

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

1988-01-01

322

Modification of Erythrocyte Membrane Proteins, Enzymes and Transport Mechanisms in Chronic Alcoholics: An In vivo and In vitro Study.  

UK PubMed Central (United Kingdom)

AIM: The aim of the study was to elucidate the molecular mechanisms underlying the alcohol perturbation leading to deleterious effects on erythrocyte membrane transport in chronic alcoholics. METHODS: Membrane bound enzyme activities such as Na(+), K(+)-ATPase, Ca(2+),Mg(2+)-ATPase and acetylcholine esterase and membrane transport analysis by in vitro and erythrocyte membrane profile analysis in controls and chronic alcoholic red cells were analyzed. RESULTS: It was observed that decreased Na(+), K(+)-ATPase enzyme activity and increased activities of Ca(2+),Mg(2+)-ATPase and acetylcholine esterase in chronic alcoholics compared to controls. The in vitro studies of erythrocytes suggested that there is an increased uptake of glucose through chronic alcoholic red cells. However, glucose utilization by chronic alcoholic red cells was decreased. An increased sensitivity of ouabain for its binding site on Na(+), K(+)-ATPase in chronic alcoholic erythrocyte membrane was evident from this study. Though there appears to be an increased Na(+) influx in chronic alcoholic cells, the status of Na(+) transport is not altered much. However, ouabain caused slight disturbances in the transport of sodium, similar disturbances in the potassium transport resulting in much accumulation of potassium in red cells. CONCLUSIONS: It was concluded that chronic alcohol consumption modified certain membrane bound proteins, enzymes and transport mechanisms in chronic alcoholics.

Maturu P; Vaddi DR; Pannuru P; Nallanchakravarthula V

2013-08-01

323

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

Science.gov (United States)

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

American Society For Microbiology;

2005-03-11

324

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

Directory of Open Access Journals (Sweden)

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

Feng Fenling; Li Feiran

2012-01-01

325

Procedure de qualification des garnitures mecaniques des pompes principales des centrales nucleaires Francaises. (Mechanical seals qualification procedure of the main pumps of nuclear power plants in France).  

Science.gov (United States)

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...

D. Buchdahl R. Martin J. M. Girault

1992-01-01

326

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

Science.gov (United States)

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

Goldman, Carla

2010-05-01

327

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1990-09-01

328

Mechanism of carrier transport in highly efficient solar cells having indium tin oxide/Si junctions  

Energy Technology Data Exchange (ETDEWEB)

The carrier transport mechanism of the Si solar cells having {ital n}-Si/indium tin oxide (ITO) junctions has been studied by use of the current-voltage and capacitance-voltage measurements and x-ray photoelectron spectroscopy. An 11-A-thick nonstoichiometric Si oxide layer is formed when ITO is deposited by spray pyrolysis on a Si electrode etched with hydrofluoric acid. In this case, the tunneling probability of majority carriers through the oxide layer is high, and the thermionic emission current over the energy barrier in Si takes a dominant part of the dark current. On the other hand, for a Si electrode where a Si oxide layer is intentionally interposed between ITO and Si, the thermionic emission current is suppressed, and trap-assisted multistep tunneling through the depletion layer becomes dominant. By making a mat-structure treatment on the Si surface, a solar energy conversion efficiency of 13% and the photocurrent density of 42.5 mA cm{sup {minus}2} were attained under AM 1 100 mW cm{sup {minus}2} illumination.

Kobayashi, H.; Ishida, T.; Nakato, Y.; Tsubomura, H. (Laboratory for Chemical Conversion of Solar Energy and Department of Chemistry, Faculty of Engineering Science, Osaka University, Toyonaka, Osaka (Japan))

1991-02-01

329

Mass-transport mechanisms in deforming rocks: Recognition using microstructural and microchemical criteria  

Energy Technology Data Exchange (ETDEWEB)

We establish microstructural and microchemical criteria that can be used to distinguish the extent to which mass transport during deformation occurred by diffusion or fluid infiltration, as well as the extent to which it was pervasive or channelized, continuous or episodic. Diffusive mechanisms are indicated by a small scale of mass transfer and symmetrical patterns of redistribution of chemical components. Infiltration typically leads to asymmetric patterns of chemical variation because of smearing out of chemical anomalies in the direction of fluid movement, and can lead to unpredictable directions of chemical change because of bypassing of layers by permeable pathways and nonpervasive flow. Examples of the use of the criteria include the following: (1) patterns of compositional variation in olivine across the layering in lherzolitic mylonites, (2) detection of microveins containing more calcic plagioclase even where they have been completely recrystallized int he matrix of a granitic mylonite, and (3) complex and variable lengthwise zoning patterns in adjacent plagioclase porphyroblasts in a lithologically complex mylonite, indicating transient, nonpervasive fluid infiltration. Combined microstructural and microchemical studies, coupled with thermodynamic calculations, are essential if the sites of mineral dissolution and growth, together with the direction of chemical change and the likely sources of metasomatic components, are to be defined.

McCaig, A.M.; Knipe, R.J. (Univ. of Leeds (England))

1990-09-01

330

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

UK PubMed Central (United Kingdom)

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

Baltr?nait? E; Baltr?nas P; Lietuvninkas A; Serevi?ien? V; Zuokait? E

2013-08-01

331

Oligomeric status and nucleotide binding properties of the plastid ATP/ADP transporter 1: toward a molecular understanding of the transport mechanism.  

UK PubMed Central (United Kingdom)

BACKGROUND: Chloroplast ATP/ADP transporters are essential to energy homeostasis in plant cells. However, their molecular mechanism remains poorly understood, primarily due to the difficulty of producing and purifying functional recombinant forms of these transporters. METHODOLOGY/PRINCIPAL FINDINGS: In this work, we describe an expression and purification protocol providing good yields and efficient solubilization of NTT1 protein from Arabidopsis thaliana. By biochemical and biophysical analyses, we identified the best detergent for solubilization and purification of functional proteins, LAPAO. Purified NTT1 was found to accumulate as two independent pools of well folded, stable monomers and dimers. ATP and ADP binding properties were determined, and Pi, a co-substrate of ADP, was confirmed to be essential for nucleotide steady-state transport. Nucleotide binding studies and analysis of NTT1 mutants lead us to suggest the existence of two distinct and probably inter-dependent binding sites. Finally, fusion and deletion experiments demonstrated that the C-terminus of NTT1 is not essential for multimerization, but probably plays a regulatory role, controlling the nucleotide exchange rate. CONCLUSIONS/SIGNIFICANCE: Taken together, these data provide a comprehensive molecular characterization of a chloroplast ATP/ADP transporter.

Deniaud A; Panwar P; Frelet-Barrand A; Bernaudat F; Juillan-Binard C; Ebel C; Rolland N; Pebay-Peyroula E

2012-01-01

332

Investigating the mechanism of substrate uptake and release in the glutamate transporter homologue Glt(Ph) through metadynamics simulations.  

UK PubMed Central (United Kingdom)

A homeostatic concentration of glutamate in the synaptic cleft ensures a correct signal transduction along the neuronal network. An unbalance in this concentration can lead to neuronal death and to severe neurodegenerative diseases such as Alzheimer's or Parkinson's. Glutamate transporters play a crucial role in this respect because they are responsible for the reuptake of the neurotransmitter from the synaptic cleft, thus controlling the glutamate concentration. Understanding the molecular mechanism of this transporter can provide the possibility of an exogenous control. Structural studies have shown that this transporter can assume at least three conformations, thus suggesting a pronounced dynamical behavior. However, some intermediate states that lead to the substrate internalization have not been characterized and many aspects of the transporter mechanism still remain unclear. Here, using metadynamics simulations, we investigate the substrate uptake from the synaptic cleft and its release in the intracellular medium. In addition, we focus on the role of ions and substrate during these processes and on the stability of the different conformations assumed by the transporter. The present dynamical results can complement available X-ray data and provide a thorough description of the entire process of substrate uptake, internalization, and release.

Grazioso G; Limongelli V; Branduardi D; Novellino E; De Micheli C; Cavalli A; Parrinello M

2012-01-01

333

Investigating the mechanism of substrate uptake and release in the glutamate transporter homologue Glt(Ph) through metadynamics simulations.  

Science.gov (United States)

A homeostatic concentration of glutamate in the synaptic cleft ensures a correct signal transduction along the neuronal network. An unbalance in this concentration can lead to neuronal death and to severe neurodegenerative diseases such as Alzheimer's or Parkinson's. Glutamate transporters play a crucial role in this respect because they are responsible for the reuptake of the neurotransmitter from the synaptic cleft, thus controlling the glutamate concentration. Understanding the molecular mechanism of this transporter can provide the possibility of an exogenous control. Structural studies have shown that this transporter can assume at least three conformations, thus suggesting a pronounced dynamical behavior. However, some intermediate states that lead to the substrate internalization have not been characterized and many aspects of the transporter mechanism still remain unclear. Here, using metadynamics simulations, we investigate the substrate uptake from the synaptic cleft and its release in the intracellular medium. In addition, we focus on the role of ions and substrate during these processes and on the stability of the different conformations assumed by the transporter. The present dynamical results can complement available X-ray data and provide a thorough description of the entire process of substrate uptake, internalization, and release. PMID:22092197

Grazioso, Giovanni; Limongelli, Vittorio; Branduardi, Davide; Novellino, Ettore; De Micheli, Carlo; Cavalli, Andrea; Parrinello, Michele

2011-12-08

334

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

Energy Technology Data Exchange (ETDEWEB)

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 {sup 137}Cs concentration is proven in-situ (R{sup 2}=0.94), thus remotely sensed SSC can act as a surrogate for {sup 137}Cs concentration. Initial in-situ characterisation of the suspended sediments was investigated to identify spatial and temporal variability in grain size distributions and reflectance characteristics for the Ribble estuary. Laboratory experiments were then performed to clearly define the SSC reflectance relationship, identify the optimum CASI wavelengths for quantifying SSC and to demonstrate the effects on reflectance of the environmental variables of salinity and clay content. Images were corrected for variation in solar elevation and angle to give a ground truth calibration for SSC, with an R{sup 2}=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 {sup 137}Cs influxes of 2.01x10{sup 6} kg and 604MBq per flood tide. (author)

Atkin, P.A

2000-10-01

335

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-08-01

336

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

International Nuclear Information System (INIS)

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

2000-01-01

337

Mechanical seals qualification procedure of the main pumps of nuclear power plants in France; Procedure de qualification des garnitures mecaniques des pompes principales des centrales nucleaires Francaises  

Energy Technology Data Exchange (ETDEWEB)

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.

Buchdahl, D.; Martin, R.; Girault, J.M.

1992-12-01

338

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

Energy Technology Data Exchange (ETDEWEB)

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

Liska, D.; Carlisle, L.; Greenwood, D.; Grieggs, R.; McCormick, J.; Sigler, F.; Uher, J.; Zimmerman, G.

1983-08-01

339

Effects of the diuretics, triamterene and mersalyl on active sodium transport mechanisms in isolated frog skin.  

UK PubMed Central (United Kingdom)

1. Triamterene reduces the rate coefficients for sodium movement into the transporting system of the isolated frog skin. The isotopically measured ;active sodium transport pool' is also reduced.2. Mersalyl reduces the rate coefficient for sodium and the calculated sodium flux from the transporting system to the inner bathing solution. The ;active sodium transport pool' is increased by this diuretic.3. The action of triamterene closely resembles that of amiloride and both reduce the entry of sodium into the system. In contrast, mersalyl limits the exit of sodium ions from the skin.

Salako LA; Smith AJ

1971-03-01

340

Main regularities in variations of mechanical properties and microstructure of fuel element assembly can material (steel EhP-450) irradiated in BN-600 and BN-350 reactors  

International Nuclear Information System (INIS)

[en] The complex of mechanical properties of steel EhP-450 fuel assembly cans irradiated in fast reactors was under study. The steel is shown to possess a high resistance to swelling as well as acceptable values of mechanical properties under tension and impact bending. Based on the results obtained a conclusion is made that in a low-temperature zone of BN-600 reactor fuel assembly cans at 15% burnup the most essential change in mechanical properties should be expected in the vicinity of a lower reactor core boundary at damaging doses of 20-40 dpa[ru] ??????????? ???????? ???????????? ?????? ?????????? ? ??????? ????????? ?????? ??? ?? ????? ??-450. ????????, ??? ????? ???????? ??????? ?????????????? ?????????? ? ??????????? ?????????? ???????????? ??????? ??? ?????????? ? ??????? ??????. ?? ????????? ?????????? ??????????? ?????? ?????, ??? ? ?????????????????? ???? ?????? ??? ???????? ??-600 ??? ????????? ?? 15% ?.?. ???????? ????????????? ????????? ???????????? ??????? ??????? ??????? ? ???? ?????? ??????? ???????? ???? ??? ???????????? ????? 20-40 ???

1996-01-01

 
 
 
 
341

Mechanical, sorption and transport experiments on a German high volatile bituminous coal  

Energy Technology Data Exchange (ETDEWEB)

A high volatile bituminous coal (vitrinite reflectance: 0.93%, carbon content: 83%) from the Prosper-Haniel mine, North Rhine-Westphalia has been studied using a comprehensive set of measurements and experimental procedures at RWTH Aachen University and the University of Queensland. Using the True Triaxial Stress Coal Permeameter (TTSCP) (Massarotto 2003) of the University of Queensland, permeability and gas displacement tests were performed on an 80 mm cube of the Prosper-Haniel coal. Extensive data sets were recorded to assess the effects of stress changes on gas transport and the impact of nitrogen, methane and CO{sub 2} sorption on the mechanical properties. We investigate the permeability coefficients for helium, nitrogen, methane and carbon dioxide measured on this sample as a function of net stress. As expected, permeability values decrease with increasing stress. Methane and nitrogen have nearly identical permeability coefficients throughout the entire net stress range, while permeability coefficients measured with helium are higher and those measured with CO{sub 2} significantly lower. During the permeability measurements with CO{sub 2} an anisotropic swelling of the coal cube by about 0.19% to 0.23% was observed. The volumetric effect (swelling) is 100 times slower than gas displacement. Simultaneous mechanical tests indicated a softening of the coal block upon exposure to CO{sub 2}. Thus, a decrease of Young's modulus (YM) of the coal cube during the CO{sub 2} flow test was observed as compared to the methane and nitrogen tests. High-pressure sorption isotherms with CH{sub 4} and CO{sub 2} were determined on different grain-size fractions of the Prosper-Haniel coal at 318K and different moisture contents. Methane sorption capacity decreases by 29% with increasing moisture content. Also, a decrease of sorption rate was observed with increasing moisture content. While sorption rates are generally faster for CO{sub 2} than for CH{sub 4}, the sorption rates of CH{sub 4} and CO{sub 2} at a moisture content of 1.6 % were nearly identical. The results of this study are compared with those of similar experiments performed on a other sets of coals (Busch and Gensterblum, 2011). Finally several theoretical models to predict the reservoir permeability as a function of reservoir pressure has been tested. (orig.)

Gensterblum, Y.; Krooss, B.M. [RWTH Aachen Univ. (Germany). Inst. of Geology and Geochemistry of Petroleum and Coal; Massarotto, Paul [Queensland Univ., Brisbane, St Lucia, QLD (Australia). School of Engineering

2013-08-01

342

The National Qualifications Framework - an enabling mechanism to build capacity within the transport sector  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Paper presented at the 20th Annual South African Transport Conference 16 - 20 July 2001 "Meeting the transport challenges in Southern Africa", CSIR International Convention Centre, Pretoria, South Africa. , A series of initiatives beginning with the De Lange, Riekert and Wiehahn Commissions in the earl...

Kistan, K.

343

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Choi Cheol-Hee

344

Mechanisms and control of K/sup +/ transport in plants and fungi: Research progress report  

Energy Technology Data Exchange (ETDEWEB)

This report briefly describes experiments on transport responses to long-and short-term temperature changes in Neurospora, preliminary chracterization of potassium channels in the plasma membrane of Arabidopsis protoplasts, and cloning of the gene for high-affinity K/sup +/ transport in Neurospora.

1988-01-01

345

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

DEFF Research Database (Denmark)

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

Weyand, Simone; Shimamura, Tatsuro

2008-01-01

346

Novel insights in transport mechanisms and kinetics of phenylacetic acid and penicillin-G in Penicillium chrysogenum.  

UK PubMed Central (United Kingdom)

Although penicillin-G (PenG) production by the fungus Penicillium chrysogenum is a well-studied process, little is known about the mechanisms of transport of the precursor phenylacetic acid (PAA) and the product PenG over the cell membrane. To obtain more insight in the nature of these mechanisms, in vivo stimulus response experiments were performed with PAA and PenG in chemostat cultures of P. chrysogenum at time scales of seconds to minutes. The results indicated that PAA is able to enter the cell by passive diffusion of the undissociated acid at a high rate, but is at the same time actively excreted, possibly by an ATP-binding cassette transporter. This results in a futile cycle, dissipating a significant amount of metabolic energy, which was confirmed by increased rates of substrate and oxygen consumption, and carbon dioxide production. To estimate the kinetic properties of passive import and active export of PAA over the cell membrane, a dynamic mathematical model was constructed. With this model, a good description of the dynamic data could be obtained. Also, PenG was found to be rapidly taken up by the cells upon extracellular addition, indicating that PenG transport is reversible. The measured concentration gradient of PenG over the cell membrane corresponded well with facilitated transport. Also, for PenG transport, a dynamic model was constructed and validated with experimental data. The outcome of the model simulations was in agreement with the presence of a facilitated transport system for PenG.

Douma RD; Deshmukh AT; de Jonge LP; de Jong BW; Seifar RM; Heijnen JJ; van Gulik WM

2012-03-01

347

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

International Nuclear Information System (INIS)

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

1987-01-01

348

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-12-01

349

An Human Reliability Analysis to Identify Human Error Mechanisms for Reducing the Risks Associated with Human Errors in a Main Control Room of the SMART  

International Nuclear Information System (INIS)

The research results are summarized as followed: (1) The task analysis performed on the EOGs of the SMART MMIS identified seven different human error mechanisms: Perception Error, Decision Error, Control-Identification Error, Control-Selection Error, Control-Execution Error, Communication Error, and Extraneous Error. The human error mechanisms includes 48 different human error types. 2) The design requirements were proposed to prevent 48 different possible human errors while running the HSI of SMART. 3) Sixteen different human errors were found for the SC designed by KAERI. Fifty six PSFs were also identified influencing the initiation of a human error mechanism. 4) Human factors design requirements were developed to hinder the human error mechanisms. CHED in KHU proposed a design alternative of the SC which took into account the human factors design requirements previously identified. 5) An human error quantification technique was applied to compare the CHED design with that the KAERI's in terms of the probabilities of the human errors caused by each design. The comparison showed that the CHD design was more effective than the KAERI's to reduce the human error probability from 0.0108 to 0.00004. It meant that 96.3% of the human error probability in the KAERI's was prevented by introducing the human factors design recommendations on the SC design

2011-01-01

350

An Human Reliability Analysis to Identify Human Error Mechanisms for Reducing the Risks Associated with Human Errors in a Main Control Room of the SMART  

Energy Technology Data Exchange (ETDEWEB)

The research results are summarized as followed: (1) The task analysis performed on the EOGs of the SMART MMIS identified seven different human error mechanisms: Perception Error, Decision Error, Control-Identification Error, Control-Selection Error, Control-Execution Error, Communication Error, and Extraneous Error. The human error mechanisms includes 48 different human error types. 2) The design requirements were proposed to prevent 48 different possible human errors while running the HSI of SMART. 3) Sixteen different human errors were found for the SC designed by KAERI. Fifty six PSFs were also identified influencing the initiation of a human error mechanism. 4) Human factors design requirements were developed to hinder the human error mechanisms. CHED in KHU proposed a design alternative of the SC which took into account the human factors design requirements previously identified. 5) An human error quantification technique was applied to compare the CHED design with that the KAERI's in terms of the probabilities of the human errors caused by each design. The comparison showed that the CHD design was more effective than the KAERI's to reduce the human error probability from 0.0108 to 0.00004. It meant that 96.3% of the human error probability in the KAERI's was prevented by introducing the human factors design recommendations on the SC design

Byeon, S. N.; Kim, J. H.; Hur, E. M.; Park, H. J.; Jeong, K. H.; Kim, H. J.; Park, H. J.; Yoon, S. J.; Park, S. Y. [Kyunghee University, Seoul (Korea, Republic of)

2011-06-15

351

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

2005-01-01

352

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

Science.gov (United States)

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

353

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

UK PubMed Central (United Kingdom)

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.

Raja M; Puntheeranurak T; Hinterdorfer P; Kinne R

2012-01-01

354

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

UK PubMed Central (United Kingdom)

Thiazide diuretics inhibit Na+ and stimulate Ca2+ absorption in renal distal convoluted tubules. Experiments were performed on immortalized mouse distal convoluted tubule (MDCT) cells to determine the mechanism underlying the dissociation of sodium from calcium transport and the stimulation of calcium absorption induced by thiazide diuretics. Control rates of 22Na+ uptake averaged 272 +/- 35 nmol min-1 mg protein-1 and were inhibited 40% by chlorothiazide (CTZ, 10(-4) M). Control rates of 36Cl- uptake averaged 340 +/- 50 nmol min-1 mg protein-1 and were inhibited 50% by CTZ. CTZ stimulated 45Ca2+ uptake by 45% from resting levels of 2.86 +/- 0.26 nmol min-1 mg protein-1. Bumetanide (10(-4) M) had no effect on 22Na+, 36Cl-, or 45Ca2+ uptake. Control levels of intracellular calcium activity ([Ca2+]i) averaged 91 +/- 12 nM. CTZ elicited concentration-dependent increases of [Ca2+]i to a maximum of 654 +/- 31 nM at 10(-4) M. CTZ reduced intracellular chloride activity ([Cl-]i), as determined with the chloride-sensitive fluorescent dye 6-methoxy-N-(3-sulfopropyl)quinolinium. The chloride channel blocker 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, 10(-5) M) abolished the effect of CTZ on [Cl-]i. NPPB also blocked CTZ-induced increases of 45Ca2+. Resting membrane voltage, measured in cells loaded with the potential-sensitive dye 3,3'-dihexyloxacarbocyanine iodide [DiOC6(3)], averaged -72 +/- 2 mV. CTZ hyperpolarized cells in a concentration-dependent and reversible manner. At 10(-4) M, CTZ hyperpolarized MDCT cells by 20.4 +/- 7.2 mV. Reduction of extracellular Cl- or addition of NPPB abolished CTZ-induced hyperpolarization. Direct membrane hyperpolarization increased 45Ca2+ uptake whereas depolarization inhibited 45Ca2+ uptake. CTZ-stimulated 45Ca2+ uptake was inhibited by the Ca2+ channel blocker nifedipine (10(-5) M). We conclude that thiazide diuretics block cellular chloride entry mediated by apical membrane NaCl cotransport. Intracellular chloride, which under control conditions is above its equilibrium value, exits the cell through NPPB-sensitive chloride channels. This decrease of intracellular chloride hyperpolarizes MDCT cells and stimulates Ca2+ entry by apical membrane, dihydropyridine-sensitive Ca2+ channels.

Gesek FA; Friedman PA

1992-08-01

355

High-speed transport and magneto-mechanical resonant sensing of superparamagnetic microbeads using magnetic domain walls  

Science.gov (United States)

Surface-functionalized superparamagnetic (SPM) microbeads are of great interest in biomedical research and diagnostic device engineering for tagging, manipulating, and detecting chemical and biological species in a fluid environment [1-5]. Recent work has shown that magnetic domain walls (DWs) can be used to shuttle individual SPM microbeads and magnetically tagged entities across the surface of a chip [1-5]. This talk will describe the dynamics of SPM microbead transport by nanotrack-guided DWs, and show how these coupled dynamics can be exploited for on-chip digital biosensing applications. Using curvilinear magnetic nanotracks, we demonstrate rapid transport of SPM microbeads at speeds approaching 1000 ?m/s [3], and present a mechanism for selective transport at a junction that allows for the design of complex bead routing networks. We further demonstrate that a SPM bead trapped by a DW exhibits a distinct magneto-mechanical resonance that depends on its hydrodynamic characteristics in the host fluid [4, 5], and that this resonance can be used for robust size-based discrimination of commercial microbead populations. By embedding a spin-valve sensor within a DW transport conduit, we show that the resonance can be detected electrically and on-the-fly [5]. Thus, we demonstrate a complete set of essential bead handling functions, including capture, transport, identification, and release, required for an integrated lab-on-a-chip platform.[4pt] [1] G. Vieira et al., Phys. Rev. Lett. 103, 128101 (2009).[0pt] [2] M. Donolato et al., Lab Chip. 11, 2976--2983 (2011).[0pt] [3] E. Rapoport and G.S.D. Beach, Appl. Phys. Lett. 100, 082401 (2012).[0pt] [4] E. Rapoport and G.S.D. Beach, J. Appl. Phys. 111, 07B310 (2012).[0pt] [5] E. Rapoport, D. Montana, and G.S.D. Beach, Lab Chip. 12, 4433-4440 (2012)

Rapoport, Elizabeth

2013-03-01

356

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

UK PubMed Central (United Kingdom)

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.

Harper JN; Wright SH

2013-01-01

357

Multi-scales modeling of reactive transport mechanisms. Impact on petrophysical properties during CO2 storage  

International Nuclear Information System (INIS)

[en] The geo-sequestration of carbon dioxide (CO2) is an attractive option to reduce the emission of greenhouse gases. Within carbonate reservoirs, acidification of brine in place can occur during CO2 injection. This acidification leads to mineral dissolution which can modify the transport properties of a solute in porous media. The aim of this study is to quantify the impact of reactive transport on a solute distribution and on the structural modification induced by the reaction from the pore to the reservoir scale. This study is focused on reactive transport problem in the case of single phase flow in the limit of long time. To do so, we used a multi-scale up-scaling method that takes into account (i) the local scale, where flow, reaction and transport are known; (ii) the pore scale, where the reactive transport is addressed by using averaged formulation of the local equations; (iii) the Darcy scale (also called core scale), where the structure of the rock is taken into account by using a three-dimensions network of pore-bodies connected by pore-throats; and (iv) the reservoir scale, where physical phenomenon, within each cell of the reservoir model, are taken into account by introducing macroscopic coefficients deduced from the study of these phenomenon at the Darcy scale, such as the permeability, the apparent reaction rate, the solute apparent velocity and dispersion. (author)

2012-01-01

358

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

International Nuclear Information System (INIS)

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

2005-01-01

359

Mechanism of Proton Transport in Proton Exchange Membranes: Insights from Computer Simulation  

Energy Technology Data Exchange (ETDEWEB)

The solvation and transport of hydrated protons in proton exchange membranes (PEMs) such as NafionTM will be described using a novel multi-state reactive molecular dynamics (MD) approach, combined with large scale MD simulation to help probe various PEM morphological models. The multi-state MD methodology allows for the treatment of explicit (Grotthuss) proton shuttling and charge defect delocalization which, in turn, can strongly influence the properties of the hydrated protons in various aqueous and complex environments. A significant extension of the methodology to treat highly acidic (low pH) environments such as the hydrophilic domains of a PEM will be presented. Recent results for proton solvation and transport in NafionTM will be described which reveal the significant role of Grotthuss shuttling and charge defect delocalization on the excess proton solvation structures and transport properties. The role of PEM hydration level and morphology on these properties will also be described.

Gregory A. Voth

2010-11-30

360

Molecular structure and mechanisms of action of cyclic and linear ion transport antibiotics.  

UK PubMed Central (United Kingdom)

As a direct result of the vision, determination, and magnetic personality of Yuri Ovchinnikov a collaboration between the Shemyakin Institute of Bioorganic Chemistry and the Medical Foundation of Buffalo was begun in the early 1970's. The collaboration generated valuable insight into the structural basis for the capture, transport, and release of ions by ion transport antibiotics and the basis for the ion selectivity of these compounds. The collaboration produced dozens of joint publications on the structure and function of cyclic and linear ion transport antibiotics, fostered fruitful exchange visits between scientists in the two Research Institutes and has been a major source of creativity in my scientific career and those of many of my colleagues in Buffalo. This review summarizes major accomplishments of the collaboration.

Duax WL; Langs DA; Smith GD; Grochulski P; Pletnev V; Ivanov V

1992-10-01

 
 
 
 
361

Biosynthetic Mechanism for L-Gulose in Main Polar Lipids of Thermoplasma acidophilum and Possible Resemblance to Plant Ascorbic Acid Biosynthesis.  

UK PubMed Central (United Kingdom)

L-Gulose is a very rare sugar, but appears as a sugar component of the main polar lipids characteristic in such a thermophilic archaeon as Thermoplasma acidophilum that lives without cell walls in a highly acidic environment. The biosynthesis of L-gulose in this thermophilic organism was investigated with deuterium-labeling experiments. L-Gulose was found to be biosynthesized from D-glucose via stepwise stereochemical inversion at C-2 and C-5. The involvement of an epimerase related to GDP-mannose 3,5-epimerase, the key enzyme of plant ascorbate biosynthesis, was also suggested in this C-5 inversion. The resemblance of L-gulose biosynthesis in archaea and plants might be suggested from these results.

Yamauchi N; Nakayama Y

2013-10-01

362

Mechanisms of transjunctional transport of NaCl and water in proximal tubules of mammalian kidneys.  

UK PubMed Central (United Kingdom)

Tight junctions and the intercellular space of proximal tubules are not accessible to direct measurements of fluid composition and transport rates, but morphological and functional data permit analysis of diffusion and osmosis causing transjunctional NaCl and water transport. In the S2 segment NaCl diffuses through tight junctions along a chloride gradient, but against a sodium gradient. Calculation in terms of modified Nernst-Fick diffusion equation after eliminating electrical terms shows that transport rates (300-500 pmol min-1 mm-1 tubule length) and transepithelial voltage of +2 mV are in agreement with observations. Diffusion coefficients are Dtj=1500 microm2 s-1 in the S1 segment, and Dtj=90-100 microm2 s-1 in the S2 segment where apical intercellular NaCl concentration is 132 mM, 1 mM below complete stop (Dtj=0 and Donnan equilibrium). Tight junctions with gap distance 6 A are impermeable to mannitol (effective molecular radius 4 A); reflection coefficients are sigma=0.92 for NaHCO3 and sigma=0.28 for NaCl, because of difference in anion size. The osmotic force is provided by a difference in effective transjunctional osmolality of 10 mOsm kg-1 in the S1 segment and 30 mOsm kg-1 in the S2 segment, where differences in transjunctional concentration contribute with 21 mOsm kg-1 for NaHCO3 and -4 mOsm kg-1 for NaCl. Transjunctional difference of 30 mOsm kg-1 causes a volume flow of 2 nL min-1 mm-1 tubule length. Luminal mannitol concentration of 30 mM stops all volume flow and diffusive and convective transport of NaCl. In conclusion, transjunctional diffusion and osmosis along gradients generated by transcellular transport of other solutes account for all NaCl transport in proximal tubules.

Kiil F

2002-05-01

363

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

Directory of Open Access Journals (Sweden)

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